A zoom lens system according to the present invention, from an object side to an image side, comprises a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power. In zooming, the first to the fourth lens units all move along the optical axis. The conditions (1): 0<âˆš(f 4 Â·f W Â·tan Ï‰)/L W <0.13 and (2): 0.05â‰¦f 3 /f 4 â‰¦0.97 are satisfied (where, 16<f T /f W , Ï‰>35; Ï‰ is a half view angle at a wide-angle limit; L W is an overall optical axial length of the entire system at a wide-angle limit; f 3 is a focal length of the third lens unit; f 4 is a focal length of the fourth lens unit; f T is a focal length of the entire system at a telephoto limit; and f W is a focal length of the entire system at a wide-angle limit). As a result, the zoom lens system has a reduced size and still realizes a wide view angle at a wide-angle limit, as well as a remarkably high zooming ratio and high performance.

Description

66 parts

›TECHNICAL FIELD

The present invention relates to a zoom lens system, an imaging device and a camera. In particular, the present invention relates to: a zoom lens system having a reduced size and still realizing a wide view angle at a wide-angle limit, as well as a remarkably high zooming ratio and high performance; an imaging device employing this zoom lens system; and a thin and compact camera employing this imaging device.

›BACKGROUND ART

Remarkably strong demands are present for improved performance of cameras such as digital still cameras and digital video cameras (simply referred to as digital cameras, hereinafter) provided with an image sensor for performing photoelectric conversion. In particular, in order that a single digital camera should be capable of covering a wide focal length range from a wide-angle condition to a high telephoto condition, cameras employing a zoom lens system having a remarkably high zooming ratio are strongly demanded from a convenience point of view. Further, in recent years, zoom lens systems are also desired that have a wide angle range where the photographing field is wide.

As zoom lens systems having high zooming ratios and suitable for the above-mentioned digital cameras, for example, the following zoom lens systems have been proposed.

For example, Japanese Laid-Open Patent Publication No. 2006-171655 discloses an image-taking optical system at least comprising a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein any of the lens unit intervals is changed so that variable magnification is achieved, and wherein the ratio between the focal length of the third lens unit and the focal length of the fourth lens unit and the ratio between the focal length of the first lens unit and the focal length of the entire optical system at a wide-angle limit are set forth.

Japanese Laid-Open Patent Publication No. 2006-184413 discloses an image-taking optical system at least comprising a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein at least the first lens unit is moved so that variable magnification is achieved, and wherein the ratio between the distance from the surface located on the most image-taking object side in the first lens unit at a wide-angle limit to the image formation surface and the focal length of the entire optical system at a telephoto limit and the ratio between the focal length of the first lens unit and the focal length of the entire optical system at a wide-angle limit are set forth.

Japanese Laid-Open Patent Publication No. 2006-184416 discloses an image-taking optical system at least comprising a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein any of the lens unit intervals is changed so that variable magnification is achieved, and wherein the ratio between the focal length of the first lens unit and the focal length of the entire optical system at a wide-angle limit, the ratio between the ratio of the focal length of the second lens unit at a telephoto limit and at a wide-angle limit and the ratio of the focal length of the entire optical system at a telephoto limit and at a wide-angle limit, and the ratio between the magnification of the third lens unit at a telephoto limit and the magnification of the third lens unit at a wide-angle limit are set forth.

Japanese Laid-Open Patent Publication No. 2006-189598 discloses an image-taking optical system at least comprising a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein the third lens unit at least includes two positive optical power lenses and one negative optical power lens, wherein at least the second, the third, and the fourth lens units are moved so that variable magnification is achieved, and wherein the ratio between the focal length of the first lens unit and the focal length of the entire optical system at a wide-angle limit, the ratio between the focal length of the negative optical power lens in the third lens unit and the focal length of the third lens unit, and the refractive index of the negative optical power lens in the third lens unit are set forth.

Japanese Laid-Open Patent Publication No. 2007-003554 discloses a variable magnification optical system at least comprising a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein at least the first and the third lens units are moved so that variable magnification is achieved, wherein in this magnification change, the first lens unit is moved to the object side, and wherein the ratio between the amount of relative movement of the second lens unit at the time of magnification change and the focal length of the entire optical system at a wide-angle limit, the ratio between the focal length of the first lens unit and the focal length of the entire optical system at a wide-angle limit, and the ratio between the focal length of the third lens unit and the focal length of the entire optical system at a telephoto limit are set forth.

Japanese Laid-Open Patent Publication No. 2007-010695 discloses a variable magnification optical system at least comprising a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein at least the first lens unit is moved so that variable magnification is achieved, and wherein the ratio between the focal length of the first lens unit and the focal length of the entire optical system at a wide-angle limit and the average refractive index to the d-line of all lenses in the second lens unit are set forth.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-171655 Patent Document 2: Japanese Laid-Open Patent Publication No. 2006-184413 Patent Document 3: Japanese Laid-Open Patent Publication No. 2006-184416 Patent Document 4: Japanese Laid-Open Patent Publication No. 2006-189598 Patent Document 5: Japanese Laid-Open Patent Publication No. 2007-003554 Patent Document 6: Japanese Laid-Open Patent Publication No. 2007-010695

›DISCLOSURE OF THE INVENTION · 1 of 4

Problems to be Solved by the Invention

The optical systems disclosed in the above-mentioned publications have high zooming ratios sufficient for application to digital cameras. Nevertheless, width of the view angle at a wide-angle limit and size reduction are not simultaneously realized. In particular, from the viewpoint of size reduction, requirements in digital cameras of recent years are not satisfied.

Objects of the present invention are to provide: a zoom lens system having a reduced size and still realizing a wide view angle at a wide-angle limit, as well as a remarkably high zooming ratio and high performance; an imaging device employing this zoom lens system; and a thin and compact camera employing this imaging device.

Solution to the Problems

(I) One of the above-mentioned objects is achieved by the following zoom lens system. That is, the present invention relates to

a zoom lens system, in order from an object side to an image side, comprising a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein

in zooming from a wide-angle limit to a telephoto limit, all of the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move along an optical axis, and wherein

the following conditions (1) and (2) are satisfied:

0<√( f 4 ·f W ·tan ω)/ L W <0.13 (1)

0.05≦ f 3 /f 4 ≦0.97 (2)

(here, 16<f T /f W and ω>35)

where,

ω is a half view angle (°) at a wide-angle limit,

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface),

f 3 is a focal length of the third lens unit,

f 4 is a focal length of the fourth lens unit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

One of the above-mentioned objects is achieved by the following imaging device. That is, the present invention relates to

an imaging device capable of outputting an optical image of an object as an electric image signal, comprising:

a zoom lens system that forms the optical image of the object; and

an image sensor that converts the optical image formed by the zoom lens system into the electric image signal, wherein

in the zoom lens system,

the zoom lens system, in order from an object side to an image side, comprises a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power, wherein

in zooming from a wide-angle limit to a telephoto limit, all of the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move along an optical axis, and wherein

the following conditions (1) and (2) are satisfied:

0<√( f 4 ·f W ·tan ω)/ L W <0.13 (1)

0.0 5≦ f 3 /f 4 ≦0.97 (2)

(here, 16<f T /f W and ω>35)

where,

ω is a half view angle (°) at a wide-angle limit,

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface),

f 3 is a focal length of the third lens unit,

f 4 is a focal length of the fourth lens unit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

One of the above-mentioned objects is achieved by the following camera. That is, the present invention relates to

a camera for converting an optical image of an object into an electric image signal and then performing at least one of displaying and storing of the converted image signal, comprising

an imaging device including a zoom lens system that forms the optical image of the object and an image sensor that converts the optical image formed by the zoom lens system into the electric image signal, wherein

in the zoom lens system,

in zooming from a wide-angle limit to a telephoto limit, all of the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move along an optical axis, and wherein

the following conditions (1) and (2) are satisfied:

0<√( f 4 ·f W ·tan ω)/ L W <0.13 (1)

0.05≦ f 3 /f 4 ≦0.97 (2)

(here, 16<f T /f W and ω>35)

where,

ω is a half view angle (°) at a wide-angle limit,

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface),

f 3 is a focal length of the third lens unit,

f 4 is a focal length of the fourth lens unit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

(II) One of the above-mentioned objects is achieved by the following zoom lens system. That is, the present invention relates to

in zooming from a wide-angle limit to a telephoto limit, all of the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move along an optical axis, wherein

the second lens unit includes a lens element having negative optical power and being arranged on the most object side and a lens element having positive optical power, and wherein

the following condition (3) is satisfied:

( nd 4 −1)+( nd 6 −1)≦1.8 (3)

(here, 16<f T /f W and ω>35)

where,

nd 4 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the second lens unit,

›DISCLOSURE OF THE INVENTION · 2 of 4

nd 6 is a refractive index to the d-line of a lens element having positive optical power in the second lens unit,

ω is a half view angle (°) at a wide-angle limit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

One of the above-mentioned objects is achieved by the following imaging device. That is, the present invention relates to

an imaging device capable of outputting an optical image of an object as an electric image signal, comprising:

a zoom lens system that forms the optical image of the object; and

an image sensor that converts the optical image formed by the zoom lens system into the electric image signal, wherein

in the zoom lens system,

in zooming from a wide-angle limit to a telephoto limit, all of the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move along an optical axis, wherein

the second lens unit includes a lens element having negative optical power and being arranged on the most object side and a lens element having positive optical power, and wherein

the following condition (3) is satisfied:

( nd 4 −1)+( nd 6 −1)≧1.8 (3)

(here, 16<f T /f W and ω>35)

where,

nd 4 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the second lens unit,

nd 6 is a refractive index to the d-line of a lens element having positive optical power in the second lens unit,

ω is a half view angle (°) at a wide-angle limit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

One of the above-mentioned objects is achieved by the following camera. That is, the present invention relates to

a camera for converting an optical image of an object into an electric image signal and then performing at least one of displaying and storing of the converted image signal, comprising

in the zoom lens system,

in zooming from a wide-angle limit to a telephoto limit, all of the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move along an optical axis, wherein

the second lens unit includes a lens element having negative optical power and being arranged on the most object side and a lens element having positive optical power, and wherein

the following condition (3) is satisfied:

( nd 4 −1)+( nd 6 −1)≧1.8 (3)

(here, 16<f T /f W and ω>35)

where,

nd 4 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the second lens unit,

nd 6 is a refractive index to the d-line of a lens element having positive optical power in the second lens unit,

ω is a half view angle (°) at a wide-angle limit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

(III) One of the above-mentioned objects is achieved by the following zoom lens system. That is, the present invention relates to

in zooming from a wide-angle limit to a telephoto limit, all of the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move along an optical axis, wherein

the first lens unit includes a lens element having negative optical power and being arranged on the most object side, and at least two lens elements having positive optical power that include a lens element having positive optical power and being arranged on the most image side, and wherein

the following conditions (4) and (5) are satisfied:

nd 1 −nd 2 ≧0.5 (4)

( nd 1 −1)+( nd 3 −1)≧1.8 (5)

(here, 16<f T /f W and ω>35)

where,

nd 1 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the first lens unit,

nd 2 is a refractive index to the d-line of a lens element located on the most object side among the lens elements having positive optical power in the first lens unit,

nd 3 is a refractive index to the d-line of a lens element having positive optical power and being arranged on the most image side in the first lens unit,

ω is a half view angle (°) at a wide-angle limit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

One of the above-mentioned objects is achieved by the following imaging device. That is, the present invention relates to

an imaging device capable of outputting an optical image of an object as an electric image signal, comprising:

a zoom lens system that forms the optical image of the object; and

an image sensor that converts the optical image formed by the zoom lens system into the electric image signal, wherein

in the zoom lens system,

›DISCLOSURE OF THE INVENTION · 3 of 4

in zooming from a wide-angle limit to a telephoto limit, all of the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move along an optical axis, wherein

the following conditions (4) and (5) are satisfied:

nd 1 −nd 2 ≧0.5 (4)

( nd 1 −1)+( nd 3 −1)≧1.8 (5)

(here, 16<f T /f W and ω>35)

where,

nd 1 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the first lens unit,

nd 2 is a refractive index to the d-line of a lens element located on the most object side among the lens elements having positive optical power in the first lens unit,

nd 3 is a refractive index to the d-line of a lens element having positive optical power and being arranged on the most image side in the first lens unit,

ω is a half view angle (°) at a wide-angle limit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

One of the above-mentioned objects is achieved by the following camera. That is, the present invention relates to

a camera for converting an optical image of an object into an electric image signal and then performing at least one of displaying and storing of the converted image signal, comprising

in the zoom lens system,

in zooming from a wide-angle limit to a telephoto limit, all of the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move along an optical axis, wherein

the following conditions (4) and (5) are satisfied:

nd 1 −nd 2 ≧0.5 (4)

( nd 1 −1)+( nd 3 −1)≧1.8 (5)

(here, 16<f T /f W and ω>35)

where,

nd 1 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the first lens unit,

nd 2 is a refractive index to the d-line of a lens element located on the most object side among the lens elements having positive optical power in the first lens unit,

nd 3 is a refractive index to the d-line of a lens element having positive optical power and being arranged on the most image side in the first lens unit,

ω is a half view angle (°) at a wide-angle limit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

(IV) One of the above-mentioned objects is achieved by the following zoom lens system. That is, the present invention relates to

a zoom lens system, in order from an object side to an image side, comprising a first lens unit having positive optical power, a second lens unit having negative optical power, and subsequent lens units, wherein

the subsequent lens units include at least a third lens unit having positive optical power and a fourth lens unit having positive optical power, wherein

in zooming from a wide-angle limit to a telephoto limit, at least the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move along an optical axis, and wherein

the following condition (IV-10) is satisfied:

1.95< m 2T /m 34T <3.50 (IV-10)

(here, 16<f T /f W and ω>35)

where,

m 2T is a lateral magnification of the second lens unit at a telephoto limit,

m 34T is a lateral magnification at a telephoto limit of a composite lens unit consisting of all lens units located on the image side relative to the second lens unit,

ω is a half view angle (°) at a wide-angle limit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

One of the above-mentioned objects is achieved by the following imaging device. That is, the present invention relates to

an imaging device capable of outputting an optical image of an object as an electric image signal, comprising:

a zoom lens system that forms the optical image of the object; and

an image sensor that converts the optical image formed by the zoom lens system into the electric image signal, wherein

in the zoom lens system,

the zoom lens system, in order from an object side to an image side, comprises a first lens unit having positive optical power, a second lens unit having negative optical power, and subsequent lens units, wherein

the subsequent lens units include at least a third lens unit having positive optical power and a fourth lens unit having positive optical power, wherein

in zooming from a wide-angle limit to a telephoto limit, at least the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move along an optical axis, and wherein

the following condition (IV-10) is satisfied:

1.95< m 2T /m 34T <3.50 (IV-10)

(here, 16<f T /f W and ω>35)

where,

m 2T is a lateral magnification of the second lens unit at a telephoto limit,

m 34T is a lateral magnification at a telephoto limit of a composite lens unit consisting of all lens units located on the image side relative to the second lens unit,

ω is a half view angle (°) at a wide-angle limit,

f T is a focal length of the entire system at a telephoto limit, and

›DISCLOSURE OF THE INVENTION · 4 of 4

f W is a focal length of the entire system at a wide-angle limit.

One of the above-mentioned objects is achieved by the following camera. That is, the present invention relates to

a camera for converting an optical image of an object into an electric image signal and then performing at least one of displaying and storing of the converted image signal, comprising

in the zoom lens system,

the subsequent lens units include at least a third lens unit having positive optical power and a fourth lens unit having positive optical power, wherein

in zooming from a wide-angle limit to a telephoto limit, at least the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move along an optical axis, and wherein

the following condition (IV-10) is satisfied:

1.95< m 2T /m 34T <3.50 (IV-10)

(here, 16<f T /f W and ω>35)

where,

m 2T is a lateral magnification of the second lens unit at a telephoto limit,

m 34T is a lateral magnification at a telephoto limit of a composite lens unit consisting of all lens units located on the image side relative to the second lens unit,

ω is a half view angle (°) at a wide-angle limit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

Effects of the Invention

The present invention provides a zoom lens system having a reduced size and still realizes a wide view angle at a wide-angle limit, as well as a remarkably high zooming ratio and high performance. Further, according to the present invention, an imaging device employing this zoom lens system and a thin and compact camera employing this imaging device are provided.

›BRIEF DESCRIPTION OF THE DRAWINGS · 1 of 2

FIG. 1 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment I-1 (Example I-1).

FIG. 2 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example I-1.

FIG. 3 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example I-1.

FIG. 4 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment I-2 (Example I-2).

FIG. 5 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example I-2.

FIG. 6 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example I-2.

FIG. 7 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment I-3 (Example I-3).

FIG. 8 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example I-3.

FIG. 9 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example I-3.

FIG. 10 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment I-4 (Example I-4).

FIG. 11 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example I-4.

FIG. 12 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example I-4.

FIG. 13 is a schematic construction diagram of a digital still camera according to Embodiment I-5.

FIG. 14 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment II-1 (Example II-1).

FIG. 15 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example II-1.

FIG. 16 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example II-1.

FIG. 17 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment II-2 (Example II-2).

FIG. 18 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example II-2.

FIG. 19 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example II-2.

FIG. 20 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment II-3 (Example II-3).

FIG. 21 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example II-3.

FIG. 22 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example II-3.

FIG. 23 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment II-4 (Example II-4).

FIG. 24 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example II-4.

FIG. 25 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example II-4.

FIG. 26 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment II-5 (Example II-5).

FIG. 27 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example II-5.

FIG. 28 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example II-5.

FIG. 29 is a schematic construction diagram of a digital still camera according to Embodiment II-6.

FIG. 30 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment III-1 (Example III-1).

FIG. 31 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example III-1.

FIG. 32 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example III-1.

FIG. 33 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment III-2 (Example III-2).

FIG. 34 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example III-2.

FIG. 35 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example III-2.

FIG. 36 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment III-3 (Example III-3).

FIG. 37 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example III-3.

FIG. 38 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example III-3.

FIG. 39 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment III-4 (Example III-4).

›BRIEF DESCRIPTION OF THE DRAWINGS · 2 of 2

FIG. 40 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example III-4.

FIG. 41 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example III-4.

FIG. 42 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment III-5 (Example III-5).

FIG. 43 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example III-5.

FIG. 44 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example III-5.

FIG. 45 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment III-6 (Example III-6).

FIG. 46 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example III-6.

FIG. 47 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example III-6.

FIG. 48 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment III-7 (Example III-7).

FIG. 49 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example III-7.

FIG. 50 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example III-7.

FIG. 51 is a schematic construction diagram of a digital still camera according to Embodiment III-8.

FIG. 52 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment IV-1 (Example IV-1).

FIG. 53 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example IV-1.

FIG. 54 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example IV-1.

FIG. 55 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment IV-2 (Example IV-2).

FIG. 56 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example IV-2.

FIG. 57 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example IV-2.

FIG. 58 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment IV-3 (Example IV-3).

FIG. 59 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example IV-3.

FIG. 60 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example IV-3.

FIG. 61 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment IV-4 (Example IV-4).

FIG. 62 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example IV-4.

FIG. 63 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example IV-4.

FIG. 64 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment IV-5 (Example IV-5).

FIG. 65 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example IV-5.

FIG. 66 is a lateral aberration diagram in a basic state where image blur compensation is not performed and in an image blur compensation state at a telephoto limit of a zoom lens system according to Example IV-5.

FIG. 67 is a schematic construction diagram of a digital still camera according to Embodiment IV-6.

›DESCRIPTION OF THE REFERENCE CHARACTERS

G 1 first lens unit

G 2 second lens unit

G 3 third lens unit

G 4 fourth lens unit

L 1 first lens element

L 2 second lens element

L 3 third lens element

L 4 fourth lens element

L 5 fifth lens element

L 6 sixth lens element

L 7 seventh lens element

L 8 eighth lens element

L 9 ninth lens element

L 10 tenth lens element

L 11 eleventh lens element

L 12 twelfth lens element

L 12 , L 13 plane parallel plate

A diaphragm

S image surface

1 zoom lens system

2 image sensor

3 liquid crystal display monitor

4 body

5 main barrel

6 moving barrel

7 cylindrical cam

›BEST MODE FOR CARRYING OUT THE INVENTION · 1 of 7

Embodiments I-1 to I-4

FIG. 1 is a lens arrangement diagram of a zoom lens system according to Embodiment I-1. FIG. 4 is a lens arrangement diagram of a zoom lens system according to Embodiment I-2. FIG. 7 is a lens arrangement diagram of a zoom lens system according to Embodiment I-3. FIG. 10 is a lens arrangement diagram of a zoom lens system according to Embodiment I-4.

FIGS. 1 , 4 , 7 and 10 show respectively a zoom lens system in an infinity in-focus condition. In each figure, part (a) shows a lens configuration at a wide-angle limit (in the minimum focal length condition: focal length f W ), part (b) shows a lens configuration at a middle position (in an intermediate focal length condition: focal length f M =√(f W *f T )), and part (c) shows a lens configuration at a telephoto limit (in the maximum focal length condition: focal length f T ). Further, in each figure, bent arrows provided between part (a) and part (b) are lines obtained by connecting the positions of the lens units at a wide-angle limit, at a middle position and at a telephoto limit, in order from the top to the bottom. Thus, straight lines are used simply between a wide-angle limit and a middle position and between a middle position and a telephoto limit. That is, these straight lines do not indicate the actual motion of the individual lens units. Moreover, in each figure, an arrow provided to a lens unit indicates focusing from an infinity in-focus condition to a close-object in-focus condition, that is, the moving direction at the time of focusing from an infinity in-focus condition to a close-object in-focus condition.

The zoom lens system according to each embodiment, in order from the object side to the image side, comprises a first lens unit G 1 having positive optical power, a second lens unit G 2 having negative optical power, a third lens unit G 3 having positive optical power, and a fourth lens unit G 4 having positive optical power. Then, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 , the second lens unit G 2 , the third lens unit G 3 and the fourth lens unit G 4 all move along the optical axis (this lens configuration is referred to as the basic configuration I of Embodiments I-1 to I-4, hereinafter). In the zoom lens system according to each embodiment, these lens units are arranged into a desired optical power arrangement, so that a remarkably high zooming ratio exceeding 16 and high optical performance are achieved and still size reduction is realized in the entire lens system.

In FIGS. 1 , 4 , 7 and 10 , an asterisk “*” provided to a particular surface indicates that the surface is aspheric. Further, in each figure, a symbol (+) or (−) provided to the sign of each lens unit corresponds to the sign of optical power of the lens unit. Moreover, in each figure, the straight line located on the most right-hand side indicates the position of an image surface S. On the object side relative to the image surface S (between the image surface S and the most image side lens surface of the fourth lens unit G 4 ), a plane parallel plate such as an optical low-pass filter and a face plate of an image sensor is provided. Moreover, in each figure, a diaphragm A is provided between the most image side lens surface of the second lens unit G 2 and the most object side lens surface of the third lens unit G 3 .

As shown in FIG. 1 , in the zoom lens system according to Embodiment I-1, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a bi-convex second lens element L 2 ; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment I-1, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a bi-concave seventh lens element L 7 . Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment I-1, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus eighth lens element L 8 with the convex surface facing the object side; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment I-1, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

Here, in the zoom lens system according to Embodiment I-1, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment I-1, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 4 , in the zoom lens system according to Embodiment I-2, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a positive meniscus second lens element L 2 with the convex surface facing the object side; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

›BEST MODE FOR CARRYING OUT THE INVENTION · 2 of 7

In the zoom lens system according to Embodiment I-2, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a negative meniscus seventh lens element L 7 with the convex surface facing the image side. Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment I-2, the third lens unit G 3 , in order from the object side to the image side, comprises: a bi-convex eighth lens element L 8 ; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment I-2, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

Here, in the zoom lens system according to Embodiment I-2, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment I-2, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 7 , in the zoom lens system according to Embodiment I-3, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a positive meniscus second lens element L 2 with the convex surface facing the object side; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment I-3, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a bi-concave seventh lens element L 7 . Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment I-3, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus eighth lens element L 8 with the convex surface facing the object side; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment I-3, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

Here, in the zoom lens system according to Embodiment I-3, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment I-3, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 10 , in the zoom lens system according to Embodiment I-4, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a bi-convex second lens element L 2 ; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment I-4, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a bi-concave seventh lens element L 7 . Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment I-4, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus eighth lens element L 8 with the convex surface facing the object side; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment I-4, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

›BEST MODE FOR CARRYING OUT THE INVENTION · 3 of 7

Here, in the zoom lens system according to Embodiment I-4, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment I-4, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

In the zoom lens system according to each embodiment, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 , the second lens unit G 2 , the third lens unit G 3 and the fourth lens unit G 4 all move along the optical axis. Among these lens units, for example, the third lens unit is moved in a direction perpendicular to the optical axis, so that image blur caused by hand blurring, vibration and the like can be compensated optically.

In the present invention, when the image blur is to be compensated optically, the third lens unit moves in a direction perpendicular to the optical axis as described above, so that image blur is compensated in a state that size increase in the entire zoom lens system is suppressed and a compact construction is realized and that excellent imaging characteristics such as small decentering coma aberration and decentering astigmatism are satisfied.

The following description is given for conditions desired to be satisfied by a zoom lens system having the above-mentioned basic configuration I like the zoom lens system according to Embodiments I-1 to I-4. Here, a plurality of preferable conditions are set forth for the zoom lens system according to each embodiment. A construction that satisfies all the plural conditions is most desirable for the zoom lens system. However, when an individual condition is satisfied, a zoom lens system having the corresponding effect can be obtained.

Further, all conditions described below hold only under the following two premise conditions, unless noticed otherwise.

16< f T /f W

ω>35

where,

f T is a focal length of the entire system at a telephoto limit,

f W is a focal length of the entire system at a wide-angle limit, and

ω is a half view angle (°) at a wide-angle limit.

The zoom lens system having the basic configuration I satisfies the following condition (1).

0<√( f 4 ·f W ·tan ω)/ L W <0.13 (1)

where,

ω is a half view angle (°) at a wide-angle limit,

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface),

f 4 is a focal length of the fourth lens unit, and

f W is a focal length of the entire system at a wide-angle limit.

The condition (1) substantially sets forth the focal length of the fourth lens unit. When the value exceeds the upper limit of the condition (1), the optical power of the fourth lens unit is excessively weak, and hence the necessary amount of movement in zooming increases. Thus, it is difficult to achieve a thin lens barrel configuration. Further, when the value exceeds the upper limit of the condition (1), it becomes difficult to achieve a satisfactory peripheral illuminance on the image surface especially at a wide-angle limit.

The zoom lens system having the basic configuration I satisfies the following condition (2) with satisfying the above-mentioned condition (1).

0.05≦ f 3 /f 4 ≦0.97 (2)

where,

f 3 is a focal length of the third lens unit, and

f 4 is a focal length of the fourth lens unit.

The condition (2) sets forth the ratio between the focal length of the third lens unit and the focal length of the fourth lens unit. When the value exceeds the upper limit of the condition (2), the focal length of the third lens unit is excessively long. Thus, the amount of movement of the third lens unit necessary for achieving a high magnification exceeding 16 increases excessively. Further, when the value exceeds the upper limit of the condition (2), a problem arises that it becomes difficult, for example, for the third lens unit to be moved in a direction perpendicular to the optical axis for blur compensation. In contrast, when the value goes below the lower limit of the condition (2), the focal length of the third lens unit is excessively short. Thus, a large aberration fluctuation arises in zooming so as to cause difficulty in compensation. Further, the absolute values of various kinds of aberration generated in the third lens unit increase excessively, and hence compensation cannot be achieved. Moreover, when the value goes below the lower limit of the condition (2), an excessively high error sensitivity to the inclination between the surfaces in the third lens unit is caused. This causes a problem that assembling of the optical system becomes difficult.

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, especially in a case that the second lens unit includes a lens element having negative optical power and being arranged on the most object side and a lens element having positive optical power, it is preferable that the following condition (3) is satisfied.

( nd 4 −1)+( nd 6 −1)≧1.8 (3)

where,

nd 4 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the second lens unit, and

nd 6 is a refractive index to the d-line of a lens element having positive optical power in the second lens unit.

The condition (3) sets forth a condition desired to be satisfied by lens elements contained in the second lens unit. When the value falls outside the range of the condition (3), compensation of distortion and curvature of field is difficult especially at a wide-angle limit. Thus, this situation is not preferable.

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Here, when the following condition (3)′ is satisfied, the above-mentioned effect is achieved more successfully.

( nd 4 −1)+( nd 6 −1)≧1.9 (3)′

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (8) is satisfied.

0.15< dG 3/ dG< 0.27 (8)

where,

dG 3 is an optical axial center thickness of the third lens unit, and

dG is a sum of the optical axial thicknesses of the first lens unit, the second lens unit, the third lens unit and the fourth lens unit.

The condition (8) sets forth the optical axial thickness of the third lens unit. When the value exceeds the upper limit of the condition (8), the thickness of the third lens unit is excessively great, and hence it is difficult in some cases to achieve a compact lens system. Further, when the value exceeds the upper limit of the condition (8), the thickness of the third lens unit is excessively great, and hence it becomes difficult that, for example, the third lens unit is moved in a direction perpendicular to the optical axis for blur compensation. In contrast, when the value goes below the lower limit of the condition (8), difficulty arises in compensating various kinds of aberration to be compensated by the third lens unit, especially in compensating spherical aberration and coma aberration at a wide-angle limit. Thus, this situation is not preferable.

Here, when at least one of the following conditions (8)′ and (8)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.19< dG 3/ dG (8)′

dG 3/ dG< 0.22 (8)′

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (9) is satisfied.

2.7<√( f 3 2 +f 4 2 )/ |f 2 |<3.6 (9)

where,

f 2 is a focal length of the second lens unit,

f 3 is a focal length of the third lens unit, and

f 4 is a focal length of the fourth lens unit.

The condition (9) sets forth the focal lengths of the lens units. When the value exceeds the upper limit of the condition (9), the absolute value of the optical power of the second lens unit is relatively strong excessively. Thus, compensation of various kinds of aberration, especially, compensation of distortion at a wide-angle limit, becomes difficult. Thus, this situation is not preferable. In contrast, when the value goes below the lower limit of the condition (9), the absolute value of the optical power of the second lens unit is relatively weak excessively. Thus, in a case that a zoom lens system having a high magnification is to be achieved, the necessary amount of movement of the second lens unit is excessively great. Thus, this situation is not preferable.

Here, when at least one of the following conditions (9)′ and (9)″ is satisfied, the above-mentioned effect is achieved more successfully.

2.8<√( f 3 2 +f 4 2 )/| f 2 | (9)′

√( f 3 2 +f 4 2 )/| f 2 |<3.5 (9)′

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (I-10) is satisfied.

1.95< m 2T /m 34T <3.47 (I-10)

where,

m 2T is a lateral magnification of the second lens unit at a telephoto limit, and

m 34T is a lateral magnification at a telephoto limit of a composite lens unit consisting of all lens units located on the image side relative to the second lens unit.

The condition (I-10) sets forth the magnification of the lens units at a telephoto limit. When the value exceeds the upper limit of the condition (I-10), the overall length at a telephoto limit is excessively great, and hence difficulty arises in realizing a compact zoom lens system. Further, for example, in a case that the lens units on the image side relative to the second lens unit are moved in a direction perpendicular to the optical axis so that blur compensation is achieved, an excessively large aberration fluctuation is caused. Thus, this situation is not preferable. In contrast, when the value goes below the lower limit of the condition (I-10), similarly, for example, in a case that the lens units on the image side relative to the second lens unit are moved in a direction perpendicular to the optical axis so that blur compensation is achieved, an excessively large aberration fluctuation is caused. Thus, this situation is not preferable.

Here, when at least one of the following conditions (I-10)′ and (I-10)″ is satisfied, the above-mentioned effect is achieved more successfully.

2.2< m 2T /m 34T (I-10)′

m 2T /m 34T <3.2 (I-10)′

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (11) is satisfied.

0.037< d 1 NG/d 1 G< 0.135 (11)

where,

d1NG is an optical axial center thickness of the lens element having negative optical power contained in the first lens unit, and

d1G is an optical axial center thickness of the first lens unit.

The condition (11) sets forth the thickness of the lens element having negative optical power contained in the first lens unit. When the value exceeds the upper limit of the condition (11), the thickness of the entirety of the first lens unit is excessively great, and hence it is difficult to achieve a compact zoom lens system. Thus, this situation is not preferable. In contrast, when the value goes below the lower limit of the condition (11), remarkable difficulty arises in fabricating the lens element having negative optical power contained in the first lens unit. Thus, this situation is not preferable.

Here, when at least one of either condition (11)′ or condition (11)″ and condition (11)′″ is satisfied, the above-mentioned effect is achieved more successfully.

0.075< d 1 NG/d 1 G (11)′

0.100< d 1 NG/d 1 G (11)′

d 1 NG/d 1 G< 0.110 (11)′

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (12) is satisfied.

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0.11< f W ·tan(ω−ω 0 )<0.15 (12)

where,

f W is a focal length of the entire system at a wide-angle limit,

ω is a half view angle (real half view angle (°)) at a wide-angle limit, and

ω is a paraxial half view angle (°) at a wide-angle limit.

The condition (12) sets forth the difference between the real half view angle and the paraxial half view angle at a wide-angle limit. This condition substantially controls distortion. When the value falls outside the range of the condition (12), distortion is excessively great. Thus, this situation is not preferable.

Here, when at least one of the following conditions (12)′ and (12)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.12< f W ·tan(ω−ω 0 ) (12)′

f W ·tan(ω−ω 0 )<0.14 (12)′

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (13) is satisfied.

0.17< f 4 /f T <0.30 (13)

where,

f 4 is a focal length of the fourth lens unit, and

f T is a focal length of the entire system at a telephoto limit.

The condition (13) sets forth the optical power of the fourth lens unit. When the value exceeds the upper limit of the condition (13), the focal length of the fourth lens unit is excessively long, that is, the optical power is excessively weak. Thus, difficulty arises in appropriately controlling the exit pupil position especially at a wide-angle limit. Accordingly, it is difficult in some cases to achieve a satisfactory image surface illuminance In contrast, when the value goes below the lower limit of the condition (13), the focal length of the fourth lens unit is excessively short, that is, the optical power is excessively strong. Thus, it becomes difficult that large aberration generated in the fourth lens unit is compensated by other lens units. Thus, this situation is not preferable.

Here, when at least one of the following conditions (13)′ and (13)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.19< f 4 /f T (13)′

f 4 /f T <0.26 (13)′

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (14) is satisfied.

0.60<| M 1 /M 2 |<1.30 (14)

where,

M 1 is an amount of movement of the first lens unit in the optical axis direction during zooming from a wide-angle limit to a telephoto limit (movement from the image side to the object side is defined to be positive), and

M 2 is an amount of movement of the second lens unit in the optical axis direction during zooming from a wide-angle limit to a telephoto limit (movement from the image side to the object side is defined to be positive).

The condition (14) sets forth the amount of movement of the first lens unit in the optical axis direction. When the value exceeds the upper limit of the condition (14), the amount of movement of the first lens unit is excessively large. Thus, the effective diameter of the first lens unit necessary for achieving a satisfactory F-number at a wide-angle limit increases. This causes difficulty in some cases in achieving a compact zoom lens system. In contrast, when the value goes below the lower limit of the condition (14), the amount of movement of the second lens unit necessary for achieving a satisfactory high magnification is relatively large excessively. Thus, it is difficult in some cases to achieve a compact zoom lens system.

Here, when at least one of the following conditions (14)′ and (14)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.75<| M 1 /M 2 | (14)′

| M 1 /M 2 <1.15 (14)′

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (15) is satisfied.

0.4<| M 3 /M 2 |<1.2 (15)

where,

M 3 is an amount of movement of the third lens unit in the optical axis direction during zooming from a wide-angle limit to a telephoto limit (movement from the image side to the object side is defined to be positive).

The condition (15) sets forth the amount of movement of the third lens unit in the optical axis direction. When the value exceeds the upper limit of the condition (15), the amount of movement of the third lens unit is excessively large. Thus, an excessively large aberration fluctuation is generated in the third lens unit during zooming Accordingly, it is difficult in some cases to compensate this aberration by other lens units. In contrast, when the value goes below the lower limit of the condition (15), the amount of movement of the third lens unit is excessively small. Thus, a relatively excessively large amount of movement of the second lens unit is necessary for achieving a high magnification. Accordingly, it is difficult in some cases to achieve a compact zoom lens system.

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (16) is satisfied.

0.35<( m 2T /m 2W )/( f T /f W )<0.65 (16)

where,

m 2T is a lateral magnification of the second lens unit at a telephoto limit,

m 2W is a lateral magnification of the second lens unit at a wide-angle limit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

The condition (16) sets forth a lateral magnification change in the second lens unit and substantially sets forth the degree of variable magnification load to the second lens unit. When the value exceeds the upper limit of the condition (16), the variable magnification load to the second lens unit is excessive. Thus, it is difficult in some cases to compensate various kinds of off-axial aberration, especially, distortion at a wide-angle limit. In contrast, when the value goes below the lower limit of the condition (16), the variable magnification load to the second lens unit is excessively small. Thus, the amount of movement of the third lens unit during zooming necessary for achieving a satisfactory high magnification becomes relatively large. Accordingly, it is difficult in some cases to achieve size reduction of the entire zoom lens system.

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Here, when at least one of the following conditions (16)′ and (16)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.40<( m 2T /m 2W )/( f T /f W ) (16)′

( m 2T /m 2W )/( f T /f W )<0.50 (16)′

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (17) is satisfied.

1.3< m 3T /m 3W <2.2 (17)

where,

m 3T is a lateral magnification of the third lens unit at a telephoto limit, and

m 3W is a lateral magnification of the third lens unit at a wide-angle limit.

The condition (17) sets forth a lateral magnification change in the third lens unit and substantially sets forth the degree of variable magnification load to the third lens unit. When the value exceeds the upper limit of the condition (17), the variable magnification load to the third lens unit is excessive. Thus, difficulty arises in compensating various kinds of aberration that vary during magnification change, especially, in compensating off-axial aberration. Thus, this situation is not preferable. In contrast, when the value goes below the lower limit of the condition (17), the variable magnification load to the third lens unit is excessively small. Thus, a relatively excessively large amount of movement of the second lens unit is necessary for achieving a high magnification. Accordingly, it is difficult in some cases to achieve a compact zoom lens system.

Here, when at least one of the following conditions (17)′ and (17)″ is satisfied, the above-mentioned effect is achieved more successfully.

1.5< m 3T /m 3W (17)′

m 3T /m 3W <2.0 (17)′

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (18) is satisfied.

5.5<√( f 3 2 +f 4 2 )/( f W ·tan ω)<9.0 (18)

where,

ω is a half view angle (°) at a wide-angle limit,

f 3 is a focal length of the third lens unit,

f 4 is a focal length of the fourth lens unit, and

f W is a focal length of the entire system at a wide-angle limit.

The condition (18) sets forth the focal lengths of the third lens unit and the fourth lens unit. When the value exceeds the upper limit of the condition (18), the focal lengths of the third lens unit and the fourth lens unit are excessively long. This causes difficulty in some cases in achieving a compact zoom lens system. In contrast, when the value goes below the lower limit of the condition (18), the focal lengths of the third lens unit and the fourth lens unit are excessively short. Thus, aberration compensation capability especially of the third lens unit is excessive. Accordingly, it is difficult in some cases to achieve satisfactory balance of aberration compensation in the entire zoom lens system.

Here, when at least one of the following conditions (18)′ and (18)″ is satisfied, the above-mentioned effect is achieved more successfully.

6.8<√( f 3 2 +f 4 2 )/( f W ·tan ω) (18)′

√( f 3 2 +f 4 2 )/( f W ·tan ω)<7.5 (18)′

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (19) is satisfied.

3.0<( L T −L W )/( f w ·tan ω)<6.0 (19)

where,

ω is a half view angle (°) at a wide-angle limit,

L T is an overall optical axial length of the entire system at a telephoto limit (a distance from the most object side surface to the most image side surface),

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface), and

f W is a focal length of the entire system at a wide-angle limit.

The condition (19) sets forth an overall length change during zooming When the value falls outside the range of the condition (19), it is difficult to construct a compact lens barrel mechanism. Thus, this situation is not preferable.

Here, when at least one of the following conditions (19)′ and (19)″ is satisfied, the above-mentioned effect is achieved more successfully.

3.5<( L T −L W )/( f W ·tan ω) (19)′

( L T −L W )/( f W ·tan ω)<4.5 (19)′

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (20) is satisfied.

50<( L T ·f T )/ f 4 ( f W ·tan ω)<150 (20)

where,

ω is a half view angle (°) at a wide-angle limit,

L T is an overall optical axial length of the entire system at a telephoto limit (a distance from the most object side surface to the most image side surface),

f 4 is a focal length of the fourth lens unit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

The condition (20) sets forth a suitable overall length at a telephoto limit. When the value exceeds the upper limit of the condition (20), the overall length at a telephoto limit is excessively long, and hence it is difficult in some cases to achieve a compact zoom lens system having a short overall length. Further, when the value exceeds the upper limit of the condition (20), the overall length at a telephoto limit is excessively long. Thus, it becomes difficult to construct a compact lens barrel mechanism. Accordingly, this situation is not preferable. In contrast, when the value goes below the lower limit of the condition (20), the focal length of the fourth lens unit is, relatively, excessively long. Thus, it becomes difficult to control the exit pupil position at a wide-angle limit. Accordingly, it becomes difficult to maintain an appropriate image surface illuminance. Thus, this situation is not preferable.

Here, when at least one of the following conditions (20)′ and (20)″ is satisfied, the above-mentioned effect is achieved more successfully.

80<( L T ·f T )/ f 4 ( f W ·tan ω) (20)′

( L T ·f T )/ f 4 ( f W ·tan ω)<125 (20)′

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (21) is satisfied.

›BEST MODE FOR CARRYING OUT THE INVENTION · 7 of 7

50<( L W ·f T )/ f 4 ( f W ·tan ω)<125 (21)

where,

ω is a half view angle (°) at a wide-angle limit,

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface),

f 4 is a focal length of the fourth lens unit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

The condition (21) sets forth a suitable overall length at a wide-angle limit. When the value exceeds the upper limit of the condition (21), the overall length at a wide-angle limit is excessively long, and hence it is difficult in some cases to achieve a zoom lens system having a compact accommodation size. In contrast, when the value goes below the lower limit of the condition (21), the focal length of the fourth lens unit is, relatively, excessively long. Thus, it becomes difficult to control the exit pupil position at a wide-angle limit. Accordingly, it becomes difficult to maintain an appropriate image surface illuminance Thus, this situation is not preferable.

Here, when at least one of the following conditions (21)′ and (21)″ is satisfied, the above-mentioned effect is achieved more successfully.

65<( L W ·f T )/ f 4 ( f W ·tan ω) (21)′

( L W ·f T )/ f 4 ( f W ·tan ω)<100 (21)′

In a zoom lens system having the above-mentioned basic configuration I like each zoom lens system according to Embodiments I-1 to I-4, it is preferable that the following condition (22) is satisfied.

4.0< f 3 /f w ·tan ω<5.2 (22)

where,

ω is a half view angle (°) at a wide-angle limit,

f 3 is a focal length of the third lens unit, and

f W is a focal length of the entire system at a wide-angle limit.

The condition (22) sets forth the focal length of the third lens unit. When the value exceeds the upper limit of the condition (22), the focal length of the third lens unit is excessively long. This causes difficulty in some cases in achieving a compact zoom lens system. Further, when the value exceeds the upper limit of the condition (22), the necessary amount of movement in a case that, for example, the third lens unit is moved in a direction perpendicular to the optical axis for blur compensation becomes excessively large. Thus, this situation is not preferable. In contrast, when the value goes below the lower limit of the condition (22), the focal length of the third lens unit is excessively short. Thus, the aberration compensation capability of the third lens unit is excessive, and hence the compensation balance of various kinds of aberration is degraded. This causes difficulty in some cases in achieving a compact zoom lens system.

Here, when at least one of the following conditions (22)′ and (22)″ is satisfied, the above-mentioned effect is achieved more successfully.

4.4< f 3 /f W ·tan ω (22)′

f 3 /f W ·tan ω<4.8 (22)′

Here, the lens units constituting the zoom lens system of each embodiment are composed exclusively of refractive type lenses that deflect the incident light by refraction (that is, lenses of a type in which deflection is achieved at the interface between media each having a distinct refractive index). However, the lens type is not limited to this. For example, the lens units may employ diffractive type lenses that deflect the incident light by diffraction; refractive-diffractive hybrid type lenses that deflect the incident light by a combination of diffraction and refraction; or gradient index type lenses that deflect the incident light by distribution of refractive index in the medium.

Further, in each embodiment, a reflecting surface may be arranged in the optical path so that the optical path may be bent before, after or in the middle of the zoom lens system. The bending position may be set up in accordance with the necessity. When the optical path is bent appropriately, the apparent thickness of a camera can be reduced.

Moreover, each embodiment has been described for the case that a plane parallel plate such as an optical low-pass filter is arranged between the last surface of the zoom lens system (the most image side surface of the fourth lens unit) and the image surface S. This low-pass filter may be: a birefringent type low-pass filter made of, for example, a crystal whose predetermined crystal orientation is adjusted; or a phase type low-pass filter that achieves required characteristics of optical cut-off frequency by diffraction.

›Embodiment I-5 · 1 of 8

FIG. 13 is a schematic construction diagram of a digital still camera according to Embodiment I-5. In FIG. 13 , the digital still camera comprises: an imaging device having a zoom lens system 1 and an image sensor 2 composed of a CCD; a liquid crystal display monitor 3 ; and a body 4 . The employed zoom lens system 1 is a zoom lens system according to Embodiment I-1. In FIG. 13 , the zoom lens system 1 comprises a first lens unit G 1 , a second lens unit G 2 , a diaphragm A, a third lens unit G 3 and a fourth lens unit G 4 . In the body 4 , the zoom lens system 1 is arranged on the front side, while the image sensor 2 is arranged on the rear side of the zoom lens system 1 . On the rear side of the body 4 , the liquid crystal display monitor 3 is arranged, while an optical image of a photographic object generated by the zoom lens system 1 is formed on an image surface S.

The lens barrel comprises a main barrel 5 , a moving barrel 6 and a cylindrical cam 7 . When the cylindrical cam 7 is rotated, the first lens unit G 1 , the second lens unit G 2 , the third lens unit G 3 and the fourth lens unit G 4 move to predetermined positions relative to the image sensor 2 , so that magnification change can be achieved ranging from a wide-angle limit to a telephoto limit. The fourth lens unit G 4 is movable in an optical axis direction by a motor for focus adjustment.

As such, when the zoom lens system according to Embodiment I-1 is employed in a digital still camera, a small digital still camera is obtained that has a high resolution and high capability of compensating the curvature of field and that has a short overall optical length of lens system at the time of non-use. Here, in the digital still camera shown in FIG. 13 , any one of the zoom lens systems according to Embodiments I-2 to I-4 may be employed in place of the zoom lens system according to Embodiment I-1. Further, the optical system of the digital still camera shown in FIG. 13 is applicable also to a digital video camera for moving images. In this case, moving images with high resolution can be acquired in addition to still images.

Further, an imaging device comprising a zoom lens system according to Embodiments I-1 to I-4 described above and an image sensor such as a CCD or a CMOS may be applied to a mobile telephone, a PDA (Personal Digital Assistance), a surveillance camera in a surveillance system, a Web camera, a vehicle-mounted camera or the like.

Embodiments II-1 to II-5

FIG. 14 is a lens arrangement diagram of a zoom lens system according to Embodiment II-1. FIG. 17 is a lens arrangement diagram of a zoom lens system according to Embodiment II-2. FIG. 20 is a lens arrangement diagram of a zoom lens system according to Embodiment II-3. FIG. 23 is a lens arrangement diagram of a zoom lens system according to Embodiment II-4. FIG. 26 is a lens arrangement diagram of a zoom lens system according to Embodiment II-5.

FIGS. 14 , 17 , 20 , 23 and 26 show respectively a zoom lens system in an infinity in-focus condition. In each figure, part (a) shows a lens configuration at a wide-angle limit (in the minimum focal length condition: focal length f W ), part (b) shows a lens configuration at a middle position (in an intermediate focal length condition: focal length f M =√(f W *f T )), and part (c) shows a lens configuration at a telephoto limit (in the maximum focal length condition: focal length f T ). Further, in each figure, bent arrows provided between part (a) and part (b) are lines obtained by connecting the positions of the lens units at a wide-angle limit, at a middle position and at a telephoto limit, in order from the top to the bottom. Thus, straight lines are used simply between a wide-angle limit and a middle position and between a middle position and a telephoto limit. That is, these straight lines do not indicate the actual motion of the individual lens units. Moreover, in each figure, an arrow provided to a lens unit indicates focusing from an infinity in-focus condition to a close-object in-focus condition, that is, the moving direction at the time of focusing from an infinity in-focus condition to a close-object in-focus condition.

The zoom lens system according to each embodiment, in order from the object side to the image side, comprises a first lens unit G 1 having positive optical power, a second lens unit G 2 having negative optical power, a third lens unit G 3 having positive optical power, and a fourth lens unit G 4 having positive optical power. Then, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 , the second lens unit G 2 , the third lens unit G 3 and the fourth lens unit G 4 all move along the optical axis (this lens configuration is referred to as the basic configuration II of Embodiments II-1 to II-5, hereinafter). In the zoom lens system according to each embodiment, these lens units are arranged into a desired optical power arrangement, so that a remarkably high zooming ratio exceeding 16 and high optical performance are achieved and still size reduction is realized in the entire lens system.

In FIGS. 14 , 17 , 20 , 23 and 26 , an asterisk “*” provided to a particular surface indicates that the surface is aspheric. Further, in each figure, a symbol (+) or (−) provided to the sign of each lens unit corresponds to the sign of optical power of the lens unit. Moreover, in each figure, the straight line located on the most right-hand side indicates the position of an image surface S. On the object side relative to the image surface S (between the image surface S and the most image side lens surface of the fourth lens unit G 4 ), a plane parallel plate such as an optical low-pass filter and a face plate of an image sensor is provided. Moreover, in each figure, a diaphragm A is provided between the most image side lens surface of the second lens unit G 2 and the most object side lens surface of the third lens unit G 3 .

As shown in FIG. 14 , in the zoom lens system according to Embodiment II-1, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a bi-convex second lens element L 2 ; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

›Embodiment I-5 · 2 of 8

In the zoom lens system according to Embodiment II-1, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a bi-concave seventh lens element L 7 . Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment II-1, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus eighth lens element L 8 with the convex surface facing the object side; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment II-1, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

Here, in the zoom lens system according to Embodiment II-1, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment II-1, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 17 , in the zoom lens system according to Embodiment II-2, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a planer-convex second lens element L 2 with the convex surface facing the object side; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment II-2, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a bi-concave seventh lens element L 7 . Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment II-2, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus eighth lens element L 8 with the convex surface facing the object side; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment II-2, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

Here, in the zoom lens system according to Embodiment II-2, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment II-2, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 20 , in the zoom lens system according to Embodiment II-3, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a positive meniscus second lens element L 2 with the convex surface facing the object side; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment II-3, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a bi-concave seventh lens element L 7 . Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment II-3, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus eighth lens element L 8 with the convex surface facing the object side; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment II-3, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

›Embodiment I-5 · 3 of 8

Here, in the zoom lens system according to Embodiment II-3, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment II-3, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 23 , in the zoom lens system according to Embodiment II-4, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a positive meniscus second lens element L 2 with the convex surface facing the object side; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment II-4, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; and a bi-convex sixth lens element L 6 .

Further, in the zoom lens system according to Embodiment II-4, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus seventh lens element L 7 with the convex surface facing the object side; a bi-convex eighth lens element L 8 ; and a bi-concave ninth lens element L 9 . Among these, the eighth lens element L 8 and the ninth lens element L 9 are cemented with each other.

Further, in the zoom lens system according to Embodiment II-4, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex tenth lens element L 10 ; and a negative meniscus eleventh lens element L 11 with the convex surface facing the image side. The tenth lens element L 10 and the eleventh lens element L 11 are cemented with each other.

Here, in the zoom lens system according to Embodiment II-4, a plane parallel plate L 12 is provided on the object side relative to the image surface S (between the image surface S and the eleventh lens element L 11 ).

In the zoom lens system according to Embodiment II-4, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 26 , in the zoom lens system according to Embodiment II-5, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a bi-convex second lens element L 2 ; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment II-5, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a bi-concave seventh lens element L 7 . Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment II-5, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus eighth lens element L 8 with the convex surface facing the object side; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment II-5, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

Here, in the zoom lens system according to Embodiment II-5, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment II-5, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

›Embodiment I-5 · 4 of 8

The following description is given for conditions desired to be satisfied by a zoom lens system having the above-mentioned basic configuration II like the zoom lens system according to Embodiments II-1 to II-5. Here, a plurality of preferable conditions are set forth for the zoom lens system according to each embodiment. A construction that satisfies all the plural conditions is most desirable for the zoom lens system. However, when an individual condition is satisfied, a zoom lens system having the corresponding effect can be obtained.

Further, all conditions described below hold only under the following two premise conditions, unless noticed otherwise.

16< f T /f W

ω>35

where,

f T is a focal length of the entire system at a telephoto limit,

f W is a focal length of the entire system at a wide-angle limit, and

ω is a half view angle (°) at a wide-angle limit.

The zoom lens system having the basic configuration II, in which the second lens unit includes a lens element having negative optical power and being arranged on the most object side and a lens element having positive optical power, satisfies the following condition (3).

( nd 4 −1)+( nd 6 −1)≧1.8 (3)

where,

nd 4 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the second lens unit, and

nd 6 is a refractive index to the d-line of a lens element having positive optical power in the second lens unit.

The condition (3) sets forth a condition satisfied by lens elements contained in the second lens unit. When the value falls outside the range of the condition (3), distortion and curvature of field cannot be compensated especially at a wide-angle limit.

Here, when the following condition (3)′ is satisfied, the above-mentioned effect is achieved more successfully.

( nd 4 −1)+( nd 6 −1)≧1.9 (3)′

In a zoom lens system having the above-mentioned basic configuration II like each zoom lens system according to Embodiments II-1 to II-5, it is preferable that the following condition (1) is satisfied.

0<√( f 4 ·f W ·tan ω)/ L W <0.13 (1)

where,

ω is a half view angle (°) at a wide-angle limit,

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface),

f 4 is a focal length of the fourth lens unit, and

f W is a focal length of the entire system at a wide-angle limit.

The condition (1) substantially sets forth the focal length of the fourth lens unit. When the value exceeds the upper limit of the condition (1), the optical power of the fourth lens unit is excessively weak, and hence the necessary amount of movement in zooming increases. Thus, it is difficult in some cases to achieve a thin lens barrel configuration. This situation is not preferable. Further, when the value exceeds the upper limit of the condition (1), it becomes difficult in some cases to achieve a satisfactory peripheral illuminance on the image surface especially at a wide-angle limit.

0.05 ≦f 3 /f 4 ≦0.97 (2)

where,

f 3 is a focal length of the third lens unit, and

f 4 is a focal length of the fourth lens unit.

The condition (2) sets forth the ratio between the focal length of the third lens unit and the focal length of the fourth lens unit. When the value exceeds the upper limit of the condition (2), the focal length of the third lens unit is excessively long. Thus, a possibility arises that the amount of movement of the third lens unit necessary for achieving a high magnification exceeding 16 increases excessively. Further, when the value exceeds the upper limit of the condition (2), in some cases, it becomes difficult that, for example, the third lens unit is moved in a direction perpendicular to the optical axis for blur compensation. In contrast, when the value goes below the lower limit of the condition (2), the focal length of the third lens unit is excessively short. Thus, a large aberration fluctuation arises in zooming so as to cause difficulty in compensation. Further, the absolute values of various kinds of aberration generated in the third lens unit increase excessively, and hence compensation becomes difficult. Thus, this situation is not preferable. Moreover, when the value goes below the lower limit of the condition (2), an excessively high error sensitivity to the inclination between the surfaces in the third lens unit is caused. This causes in some cases difficulty in assembling the optical system.

In a zoom lens system having the above-mentioned basic configuration II like each zoom lens system according to Embodiments II-1 to II-5, especially in a case that the first lens unit includes a lens element having negative optical power and being arranged on the most object side and a lens element having positive optical power, it is preferable that the following condition (4) is satisfied.

nd 1 −nd 2 ≧0.5 (4)

where,

nd 1 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the first lens unit, and

nd 2 is a refractive index to the d-line of a lens element located on the most object side among the lens elements having positive optical power in the first lens unit.

The condition (4) sets forth a condition desired to be satisfied by lens elements contained in the first lens unit. When the value falls outside the range of the condition (4), compensation of chromatic aberration, especially, axial chromatic aberration, at a telephoto limit is difficult. Thus, this situation is not preferable.

›Embodiment I-5 · 5 of 8

Here, when the following condition (4)′ is satisfied, the above-mentioned effect is achieved more successfully.

nd 1 −nd 2 ≧0.6 (4)′

In a zoom lens system having the above-mentioned basic configuration II like each zoom lens system according to Embodiments II-1 to II-5, especially in a case that the first lens unit includes a lens element having negative optical power and being arranged on the most object side and a lens element having positive optical power and being arranged on the most image side, it is preferable that the following condition (5) is satisfied.

( nd 1 −1)+( nd 3 −1)≧1.8 (5)

where,

nd 1 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the first lens unit, and

nd 3 is a refractive index to the d-line of a lens element having positive optical power and being arranged on the most image side in the first lens unit.

The condition (5) sets forth a condition desired to be satisfied by lens elements contained in the first lens unit. When the value falls outside the range of the condition (5), compensation of chromatic aberration, especially, axial chromatic aberration, at a telephoto limit is difficult. Thus, this situation is not preferable.

Here, when the following condition (5)′ is satisfied, the above-mentioned effect is achieved more successfully.

( nd 1 −1)+( nd 3 −1)≧1.9 (5)′

0.15 <dG 3 /dG< 0.27 (8)

where,

dG 3 is an optical axial center thickness of the third lens unit, and

dG is a sum of the optical axial thicknesses of the first lens unit, the second lens unit, the third lens unit and the fourth lens unit.

Here, when at least one of the following conditions (8)′ and (8)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.19 <dG 3 /dG (8)′

dG 3 /dG< 0.22 (8)′

2.7<√( f 3 2 +f 4 2 )/| f 2 |<3.6 (9)

where,

f 2 is a focal length of the second lens unit,

f 3 is a focal length of the third lens unit, and

f 4 is a focal length of the fourth lens unit.

Here, when at least one of the following conditions (9)′ and (9)″ is satisfied, the above-mentioned effect is achieved more successfully.

2.8<√( f 3 2 +f 4 2 )/| f 2 | (9)′

√( f 3 2 +f 4 2 )/| f 2 |<3.5 (9)′

1.95 <m 2T /m 34T <3.47 (II-10)

where,

m 2T is a lateral magnification of the second lens unit at a telephoto limit, and

m 34T is a lateral magnification at a telephoto limit of a composite lens unit consisting of all lens units located on the image side relative to the second lens unit.

The condition (II-10) sets forth the magnification of the lens units at a telephoto limit. When the value exceeds the upper limit of the condition (II-10), the overall length at a telephoto limit is excessively great, and hence difficulty arises in realizing a compact zoom lens system. Further, for example, in a case that the lens units on the image side relative to the second lens unit are moved in a direction perpendicular to the optical axis so that blur compensation is achieved, an excessively large aberration fluctuation is caused. Thus, this situation is not preferable. In contrast, when the value goes below the lower limit of the condition (II-10), similarly, for example, in a case that the lens units on the image side relative to the second lens unit are moved in a direction perpendicular to the optical axis so that blur compensation is achieved, an excessively large aberration fluctuation is caused. Thus, this situation is not preferable.

Here, when at least one of the following conditions (II-10)′ and (II-10)″ is satisfied, the above-mentioned effect is achieved more successfully.

2.2 <m 2T /m 34T (II-10)′

m 2T /m 34T <3.2 (II-10)′

›Embodiment I-5 · 6 of 8

0.037 <d 1 NG/d 1 G <0.135 (11)

where,

d1NG is an optical axial center thickness of the lens element having negative optical power contained in the first lens unit, and

d1G is an optical axial center thickness of the first lens unit.

Here, when at least one of either condition (11)′ or condition (11)″ and condition (11)′″ is satisfied, the above-mentioned effect is achieved more successfully.

0.075< d 1 NG/d 1 G (11)′

0.100 <d 1 NG/d 1 G (11)′

d 1 NG/d 1 G< 0.110 (11)′

0.11 <f W ·tan(ω−ω 0 )<0.15 (12)

where,

f W is a focal length of the entire system at a wide-angle limit,

ω is a half view angle (real half view angle (°)) at a wide-angle limit, and

ω 0 is a paraxial half view angle (°) at a wide-angle limit.

Here, when at least one of the following conditions (12)′ and (12)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.12 <f W ·tan(ω−ω 0 ) (12)′

f W ·tan(ω−ω 0 )<0.14 (12)′

0.17 <f 4 /f T <0.30 (13)

where,

f 4 is a focal length of the fourth lens unit, and

f T is a focal length of the entire system at a telephoto limit.

Here, when at least one of the following conditions (13)′ and (13)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.19 <f 4 /f T (13)′

f 4 /f T <0.26 (13)′

0.60 <|M 1 /M 2 |<1.30 (14)

where,

Here, when at least one of the following conditions (14)′ and (14)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.75 <|M 1 /M 2 | (14)′

| M 1 /M 2 |<1.15 (14)′

0.4 <|M 3 /M 2 |<1.2 (15)

where,

›Embodiment I-5 · 7 of 8

0.35<( m 2T /m 2W )/( f T /f W )<0.65 (16)

where,

m 2T is a lateral magnification of the second lens unit at a telephoto limit,

m 2W is a lateral magnification of the second lens unit at a wide-angle limit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (16)′ and (16)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.40<( m 2T /m 2W )/( f T /f W ) (16)′

( m 2T /m 2W )/( f T /f W )<0.50 (16)′

1.3 <m 3T /m 3W <2.2 (17)

where,

m 3T is a lateral magnification of the third lens unit at a telephoto limit, and

m 3W is a lateral magnification of the third lens unit at a wide-angle limit.

Here, when at least one of the following conditions (17)′ and (17)″ is satisfied, the above-mentioned effect is achieved more successfully.

1.5 <m 3T /m 3W (17)′

m 3T /m 3W <2.0 (17)′

5.5<√( f 3 2 +f 4 2 )/( f W ·tan ω)<9.0 (18)

where,

ω is a half view angle (°) at a wide-angle limit,

f 3 is a focal length of the third lens unit,

f 4 is a focal length of the fourth lens unit, and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (18)′ and (18)″ is satisfied, the above-mentioned effect is achieved more successfully.

6.8<√( f 3 2 +f 4 2 )/( f W ·tan ω) (18)′

√( f 3 2 +f 4 2 )/( f W ·tan ω)<7.5 (18)′

3.0<( L T −L W )/( f W ·tan ω)<6.0 (19)

where,

ω is a half view angle (°) at a wide-angle limit,

L T is an overall optical axial length of the entire system at a telephoto limit (a distance from the most object side surface to the most image side surface),

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface), and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (19)′ and (19)″ is satisfied, the above-mentioned effect is achieved more successfully.

3.5<( L T −L W )/( f W ·tan ω) (19)′

( L T −L W )/( f W ·tan ω)<4.5 (19)′

50<( L T ·f T )/ f 4 ( f W ·tan ω)<150 (20)

where,

ω is a half view angle (°) at a wide-angle limit,

L T is an overall optical axial length of the entire system at a telephoto limit (a distance from the most object side surface to the most image side surface),

›Embodiment I-5 · 8 of 8

f 4 is a focal length of the fourth lens unit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (20)′ and (20)″ is satisfied, the above-mentioned effect is achieved more successfully.

80<( L T −f T )/ f 4 ( f W ·tan ω) (20)′

( L T −f T )/ f 4 ( f W ·tan ω)<125 (20)′

50<( L W ·f T )/ f 4 ( f W ·tan ω)<125 (21)

where,

ω is a half view angle (°) at a wide-angle limit,

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface),

f 4 is a focal length of the fourth lens unit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (21)′ and (21)″ is satisfied, the above-mentioned effect is achieved more successfully.

65<( L W ·f T )/ f 4 ( f W ·tan ω) (21)′

( L W ·f T ) /f 4 ( f W ·tan ω)<100 (21)′

4.0 <f 3 /f W ·tan ω<5.2 (22)

where,

ω is a half view angle (°) at a wide-angle limit,

f 3 is a focal length of the third lens unit, and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (22)′ and (22)″ is satisfied, the above-mentioned effect is achieved more successfully.

4.4 <f 3 /f W ·tan ω (22)′

f 3 /f W ·tan ω<4.8 (22)′

›Embodiment II-6 · 1 of 9

FIG. 29 is a schematic construction diagram of a digital still camera according to Embodiment II-6. In FIG. 29 , the digital still camera comprises: an imaging device having a zoom lens system 1 and an image sensor 2 composed of a CCD; a liquid crystal display monitor 3 ; and a body 4 . The employed zoom lens system 1 is a zoom lens system according to Embodiment II-1. In FIG. 29 , the zoom lens system 1 comprises a first lens unit G 1 , a second lens unit G 2 , a diaphragm A, a third lens unit G 3 and a fourth lens unit G 4 . In the body 4 , the zoom lens system 1 is arranged on the front side, while the image sensor 2 is arranged on the rear side of the zoom lens system 1 . On the rear side of the body 4 , the liquid crystal display monitor 3 is arranged, while an optical image of a photographic object generated by the zoom lens system 1 is formed on an image surface S.

As such, when the zoom lens system according to Embodiment II-1 is employed in a digital still camera, a small digital still camera is obtained that has a high resolution and high capability of compensating the curvature of field and that has a short overall optical length of lens system at the time of non-use. Here, in the digital still camera shown in FIG. 29 , any one of the zoom lens systems according to Embodiments II-2 to II-5 may be employed in place of the zoom lens system according to Embodiment II-1. Further, the optical system of the digital still camera shown in FIG. 29 is applicable also to a digital video camera for moving images. In this case, moving images with high resolution can be acquired in addition to still images.

Further, an imaging device comprising a zoom lens system according to Embodiments II-1 to II-5 described above and an image sensor such as a CCD or a CMOS may be applied to a mobile telephone, a PDA (Personal Digital Assistance), a surveillance camera in a surveillance system, a Web camera, a vehicle-mounted camera or the like.

Embodiments III-1 to III-7

FIG. 30 is a lens arrangement diagram of a zoom lens system according to Embodiment III-1. FIG. 33 is a lens arrangement diagram of a zoom lens system according to Embodiment III-2. FIG. 36 is a lens arrangement diagram of a zoom lens system according to Embodiment III-3. FIG. 39 is a lens arrangement diagram of a zoom lens system according to Embodiment III-4. FIG. 42 is a lens arrangement diagram of a zoom lens system according to Embodiment III-5. FIG. 45 is a lens arrangement diagram of a zoom lens system according to Embodiment III-6. FIG. 48 is a lens arrangement diagram of a zoom lens system according to Embodiment III-7.

FIGS. 30 , 33 , 36 , 39 , 42 , 45 and 48 show respectively a zoom lens system in an infinity in-focus condition. In each figure, part (a) shows a lens configuration at a wide-angle limit (in the minimum focal length condition: focal length f W ), part (b) shows a lens configuration at a middle position (in an intermediate focal length condition: focal length f M =√(f W *f T )), and part (c) shows a lens configuration at a telephoto limit (in the maximum focal length condition: focal length f T ). Further, in each figure, bent arrows provided between part (a) and part (b) are lines obtained by connecting the positions of the lens units at a wide-angle limit, at a middle position and at a telephoto limit, in order from the top to the bottom. Thus, straight lines are used simply between a wide-angle limit and a middle position and between a middle position and a telephoto limit. That is, these straight lines do not indicate the actual motion of the individual lens units. Moreover, in each figure, an arrow provided to a lens unit indicates focusing from an infinity in-focus condition to a close-object in-focus condition, that is, the moving direction at the time of focusing from an infinity in-focus condition to a close-object in-focus condition.

The zoom lens system according to each embodiment, in order from the object side to the image side, comprises a first lens unit G 1 having positive optical power, a second lens unit G 2 having negative optical power, a third lens unit G 3 having positive optical power, and a fourth lens unit G 4 having positive optical power. Then, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 , the second lens unit G 2 , the third lens unit G 3 and the fourth lens unit G 4 all move along the optical axis (this lens configuration is referred to as the basic configuration III of Embodiments III-1 to III-7, hereinafter). In the zoom lens system according to each embodiment, these lens units are arranged into a desired optical power arrangement, so that a remarkably high zooming ratio exceeding 16 and high optical performance are achieved and still size reduction is realized in the entire lens system.

In FIGS. 30 , 33 , 36 , 39 , 42 , 45 and 48 , an asterisk “*” provided to a particular surface indicates that the surface is aspheric. Further, in each figure, a symbol (+) or (−) provided to the sign of each lens unit corresponds to the sign of optical power of the lens unit. Moreover, in each figure, the straight line located on the most right-hand side indicates the position of an image surface S. On the object side relative to the image surface S (between the image surface S and the most image side lens surface of the fourth lens unit G 4 ), a plane parallel plate such as an optical low-pass filter and a face plate of an image sensor is provided. Moreover, in each figure, a diaphragm A is provided between the most image side lens surface of the second lens unit G 2 and the most object side lens surface of the third lens unit G 3 .

›Embodiment II-6 · 2 of 9

As shown in FIG. 30 , in the zoom lens system according to Embodiment III-1, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a bi-convex second lens element L 2 ; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment III-1, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a bi-concave seventh lens element L 7 . Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment III-1, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus eighth lens element L 8 with the convex surface facing the object side; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment III-1, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

Here, in the zoom lens system according to Embodiment III-1, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment III-1, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 33 , in the zoom lens system according to Embodiment III-2, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a positive meniscus second lens element L 2 with the convex surface facing the object side; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment III-2, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; and a bi-convex sixth lens element L 6 .

Further, in the zoom lens system according to Embodiment III-2, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus seventh lens element L 7 with the convex surface facing the object side; a bi-convex eighth lens element L 8 ; and a bi-concave ninth lens element L 9 . Among these, the eighth lens element L 8 and the ninth lens element L 9 are cemented with each other.

Further, in the zoom lens system according to Embodiment III-2, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex tenth lens element L 10 ; and a negative meniscus eleventh lens element L 11 with the convex surface facing the image side. The tenth lens element L 10 and the eleventh lens element L 11 are cemented with each other.

Here, in the zoom lens system according to Embodiment III-2, a plane parallel plate L 12 is provided on the object side relative to the image surface S (between the image surface S and the eleventh lens element L 11 ).

In the zoom lens system according to Embodiment III-2, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 36 , in the zoom lens system according to Embodiment III-3, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a positive meniscus second lens element L 2 with the convex surface facing the object side; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

Further, in the zoom lens system according to Embodiment III-3, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a bi-concave seventh lens element L 7 . Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment III-3, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus eighth lens element L 8 with the convex surface facing the object side; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

›Embodiment II-6 · 3 of 9

Further, in the zoom lens system according to Embodiment III-3, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

Here, in the zoom lens system according to Embodiment III-3, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment III-3, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 39 , in the zoom lens system according to Embodiment III-4, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a bi-convex second lens element L 2 ; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

Further, in the zoom lens system according to Embodiment III-4, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a bi-concave seventh lens element L 7 . Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment III-4, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus eighth lens element L 8 with the convex surface facing the object side; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment III-4, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

Here, in the zoom lens system according to Embodiment III-4, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment III-4, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 42 , in the zoom lens system according to Embodiment III-5, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a bi-convex second lens element L 2 ; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

Further, in the zoom lens system according to Embodiment III-5, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a negative meniscus seventh lens element L 7 with the convex surface facing the image side. Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment III-5, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus eighth lens element L 8 with the convex surface facing the object side; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment III-5, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

Here, in the zoom lens system according to Embodiment III-5, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment III-5, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

›Embodiment II-6 · 4 of 9

As shown in FIG. 45 , in the zoom lens system according to Embodiment III-6, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a bi-convex second lens element L 2 ; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment III-6, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; and a bi-convex sixth lens element L 6 .

Further, in the zoom lens system according to Embodiment III-6, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus seventh lens element L 7 with the convex surface facing the object side; a bi-convex eighth lens element L 8 ; and a bi-concave ninth lens element L 9 . Among these, the eighth lens element L 8 and the ninth lens element L 9 are cemented with each other.

Further, in the zoom lens system according to Embodiment III-6, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex tenth lens element L 10 ; and a negative meniscus eleventh lens element L 11 with the convex surface facing the image side. The tenth lens element L 10 and the eleventh lens element L 11 are cemented with each other.

Here, in the zoom lens system according to Embodiment III-6, a plane parallel plate L 12 is provided on the object side relative to the image surface S (between the image surface S and the eleventh lens element L 11 ).

In the zoom lens system according to Embodiment III-6, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 48 , in the zoom lens system according to Embodiment III-7, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a positive meniscus second lens element L 2 with the convex surface facing the object side; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment III-7, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; and a positive meniscus sixth lens element L 6 with the convex surface facing the object side.

Further, in the zoom lens system according to Embodiment III-7, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus seventh lens element L 7 with the convex surface facing the object side; a bi-convex eighth lens element L 8 ; and a bi-concave ninth lens element L 9 . Among these, the eighth lens element L 8 and the ninth lens element L 9 are cemented with each other.

Further, in the zoom lens system according to Embodiment III-7, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex tenth lens element L 10 ; and a negative meniscus eleventh lens element L 11 with the convex surface facing the image side. The tenth lens element L 10 and the eleventh lens element L 11 are cemented with each other.

Here, in the zoom lens system according to Embodiment III-7, a plane parallel plate L 12 is provided on the object side relative to the image surface S (between the image surface S and the eleventh lens element L 11 ).

In the zoom lens system according to Embodiment III-7, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

The following description is given for conditions desired to be satisfied by a zoom lens system having the above-mentioned basic configuration III like the zoom lens system according to Embodiments III-1 to III-7. Here, a plurality of preferable conditions are set forth for the zoom lens system according to each embodiment. A construction that satisfies all the plural conditions is most desirable for the zoom lens system. However, when an individual condition is satisfied, a zoom lens system having the corresponding effect can be obtained.

›Embodiment II-6 · 5 of 9

Further, all conditions described below hold only under the following two premise conditions, unless noticed otherwise.

16 <f T /f W

ω>35

where,

f T is a focal length of the entire system at a telephoto limit,

f W is a focal length of the entire system at a wide-angle limit, and

ω is a half view angle (°) at a wide-angle limit.

The zoom lens system having the basic configuration III, in which the first lens unit includes a lens element having negative optical power and being arranged on the most object side, and at least two lens elements having positive optical power that include a lens element having positive optical power and being arranged on the most image side, satisfies the following condition (4).

nd 1 −nd 2 ≧0.5 (4)

where,

nd 1 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the first lens unit, and

nd 2 is a refractive index to the d-line of a lens element located on the most object side among the lens elements having positive optical power in the first lens unit.

The condition (4) sets forth a condition satisfied by lens elements contained in the first lens unit. When the value falls outside the range of the condition (4), chromatic aberration, especially, axial chromatic aberration, at a telephoto limit cannot be compensated.

Here, when the following condition (4)′ is satisfied, the above-mentioned effect is achieved more successfully.

nd 1 −nd 2 ≧0.6 (4)′

( nd 1 −1)+( nd 3 −1)≧1.8 (5)

where,

nd 1 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the first lens unit, and

nd 3 is a refractive index to the d-line of a lens element having positive optical power and being arranged on the most image side in the first lens unit.

The condition (5) also sets forth a condition satisfied by lens elements contained in the first lens unit. When the value falls outside the range of the condition (5), chromatic aberration, especially, axial chromatic aberration, at a telephoto limit cannot be compensated.

Here, when the following condition (5)′ is satisfied, the above-mentioned effect is achieved more successfully.

( nd 1 −1)+( nd 3 −1)≧1.9 (5)′

In a zoom lens system having the above-mentioned basic configuration III like each zoom lens system according to Embodiments III-1 to III-7, it is preferable that the following condition (1) is satisfied.

0<√( f 4 ·f W ·tan ω)/ L W <0.13 (1)

where,

ω is a half view angle (°) at a wide-angle limit,

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface),

f 4 is a focal length of the fourth lens unit, and

f W is a focal length of the entire system at a wide-angle limit.

The condition (1) substantially sets forth the focal length of the fourth lens unit. When the value exceeds the upper limit of the condition (1), the optical power of the fourth lens unit is excessively weak, and hence the necessary amount of movement in zooming increases. Thus, it is difficult in some cases to achieve a thin lens barrel configuration. This situation is not preferable. Further, when the value exceeds the upper limit of the condition (1), it becomes difficult in some cases to achieve a satisfactory peripheral illuminance on the image surface especially at a wide-angle limit.

0.05 ≦f 3 /f 4 ≦0.97 (2)

where,

f 3 is a focal length of the third lens unit, and

f 4 is a focal length of the fourth lens unit.

The condition (2) sets forth the ratio between the focal length of the third lens unit and the focal length of the fourth lens unit. When the value exceeds the upper limit of the condition (2), the focal length of the third lens unit is excessively long. Thus, a possibility arises that the amount of movement of the third lens unit necessary for achieving a high magnification exceeding 16 increases excessively. This situation is not preferable. Further, when the value exceeds the upper limit of the condition (2), in some cases, it becomes difficult that, for example, the third lens unit is moved in a direction perpendicular to the optical axis for blur compensation. In contrast, when the value goes below the lower limit of the condition (2), the focal length of the third lens unit is excessively short. Thus, a large aberration fluctuation arises in zooming so as to cause difficulty in compensation. Further, the absolute values of various kinds of aberration generated in the third lens unit increase excessively, and hence compensation becomes difficult. Thus, this situation is not preferable. Moreover, when the value goes below the lower limit of the condition (2), an excessively high error sensitivity to the inclination between the surfaces in the third lens unit is caused. This causes in some cases difficulty in assembling the optical system.

In a zoom lens system having the above-mentioned basic configuration III like each zoom lens system according to Embodiments III-1 to III-7, especially in a case that the second lens unit includes a lens element having negative optical power and being arranged on the most object side and a lens element having positive optical power, it is preferable that the following condition (3) is satisfied.

( nd 4 −1)+( nd 6 −1)≧1.8 (3)

where,

nd 4 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the second lens unit, and

›Embodiment II-6 · 6 of 9

nd 6 is a refractive index to the d-line of a lens element having positive optical power in the second lens unit.

Here, when the following condition (3)′ is satisfied, the above-mentioned effect is achieved more successfully.

( nd 4 −1)+( nd 6 −1)≧1.9 (3)′

0.15 <dG 3 /dG< 0.27 (8)

where,

dG 3 is an optical axial center thickness of the third lens unit, and

dG is a sum of the optical axial thicknesses of the first lens unit, the second lens unit, the third lens unit and the fourth lens unit.

Here, when at least one of the following conditions (8)′ and (8)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.19 <dG 3 /dG (8)′

dG 3 /dG< 0.22 (8)′

2.7<√( f 3 2 +f 4 2 )/| f 2 |<3.6 (9)

where,

f 2 is a focal length of the second lens unit,

f 3 is a focal length of the third lens unit, and

f 4 is a focal length of the fourth lens unit.

Here, when at least one of the following conditions (9)′ and (9)″ is satisfied, the above-mentioned effect is achieved more successfully.

2.8<√( f 3 2 +f 4 2 )/| f 2 | (9)′

√( f 3 2 +f 4 2 )/| f 2 |<3.5 (9)′

1.95 <m 2T /m 34T <3.47 (III-10)

where,

m 2T is a lateral magnification of the second lens unit at a telephoto limit, and

m 34T is a lateral magnification at a telephoto limit of a composite lens unit consisting of all lens units located on the image side relative to the second lens unit.

The condition (III-10) sets forth the magnification of the lens units at a telephoto limit. When the value exceeds the upper limit of the condition (III-10), the overall length at a telephoto limit is excessively great, and hence difficulty arises in realizing a compact zoom lens system. Further, for example, in a case that the lens units on the image side relative to the second lens unit are moved in a direction perpendicular to the optical axis so that blur compensation is achieved, an excessively large aberration fluctuation is caused. Thus, this situation is not preferable. In contrast, when the value goes below the lower limit of the condition (III-10), similarly, for example, in a case that the lens units on the image side relative to the second lens unit are moved in a direction perpendicular to the optical axis so that blur compensation is achieved, an excessively large aberration fluctuation is caused. Thus, this situation is not preferable.

Here, when at least one of the following conditions (III-10)′ and (III-10)″ is satisfied, the above-mentioned effect is achieved more successfully.

2.2 <m 2T /m 34T (III-10)′

m 2T /m 34T <3.2 (III-10)′

0.037 <d 1 NG/d 1 G <0.135 (11)

where,

d1NG is an optical axial center thickness of the lens element having negative optical power contained in the first lens unit, and

d1G is an optical axial center thickness of the first lens unit.

›Embodiment II-6 · 7 of 9

Here, when at least one of either condition (11)′ or condition (11)″ and condition (11)′″ is satisfied, the above-mentioned effect is achieved more successfully.

0.075 <d 1 NG/d 1 G (11)′

0.100 <d 1 NG/d 1 G (11)′

d 1 NG/d 1 G< 0.110 (11)′

0.11 <f W ·tan(ω−ω 0 )<0.15 (12)

where,

f W is a focal length of the entire system at a wide-angle limit,

ω is a half view angle (real half view angle (°)) at a wide-angle limit, and

ω 0 is a paraxial half view angle (°) at a wide-angle limit.

Here, when at least one of the following conditions (12)′ and (12)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.12 <f W ·tan(ω−ω 0 ) (12)′

f W ·tan(ω−ω 0 )<0.14 (12)′

0.17 <f 4 /f T <0.30 (13)

where,

f 4 is a focal length of the fourth lens unit, and

f T is a focal length of the entire system at a telephoto limit.

Here, when at least one of the following conditions (13)′ and (13)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.19 <f 4 /f T (13)′

f 4 /f T <0.26 (13)′

0.06 <|M 1 /M 2 |<1.30 (14)

where,

Here, when at least one of the following conditions (14)′ and (14)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.75 <|M 1 /M 2 | (14)′

| M 1 /M 2 |<1.15 (14)′

0.4 <|M 3 /M 2 |<1.2 (15)

where,

0.35<( m 2T /m 2W )/( f T /f W )<0.65 (16)

where,

m 2T is a lateral magnification of the second lens unit at a telephoto limit,

m 2W is a lateral magnification of the second lens unit at a wide-angle limit,

›Embodiment II-6 · 8 of 9

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (16)′ and (16)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.40<( m 2T /m 2W )/( f T /f W ) (16)′

( m 2T /m 2W )/( f T /f W )<0.50 (16)′

1.3 <m 3T /m 3W <2.2 (17)

where,

m 3T is a lateral magnification of the third lens unit at a telephoto limit, and

m 3W is a lateral magnification of the third lens unit at a wide-angle limit.

Here, when at least one of the following conditions (17)′ and (17)″ is satisfied, the above-mentioned effect is achieved more successfully.

1.5 <m 3T /m 3W (17)′

m 3T /m 3W <2.0 (17)′

5.5<√( f 3 2 +f 4 2 )/( f W ·tan ω)<9.0 (18)

where,

ω is a half view angle (°) at a wide-angle limit,

f 3 is a focal length of the third lens unit,

f 4 is a focal length of the fourth lens unit, and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (18)′ and (18)″ is satisfied, the above-mentioned effect is achieved more successfully.

6.8<√( f 3 2 +f 4 2 )/( f W ·tan ω) (18)′

√( f 3 2 +f 4 2 )/( f W ·tan ω)<7.5 (18)′

3.0<( L T −L W )/( f W ·tan ω)<6.0 (19)

where,

ω is a half view angle (°) at a wide-angle limit,

L T is an overall optical axial length of the entire system at a telephoto limit (a distance from the most object side surface to the most image side surface),

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface), and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (19)′ and (19)″ is satisfied, the above-mentioned effect is achieved more successfully.

3.5<( L T −L W )/( f W ·tan ω) (19)′

( L T −L W )/( f W ·tan ω)<4.5 (19)′

50<( L T ·f T )/ f 4 ( f W ·tan ω)<150 (20)

where,

ω is a half view angle (°) at a wide-angle limit,

L T is an overall optical axial length of the entire system at a telephoto limit (a distance from the most object side surface to the most image side surface),

f 4 is a focal length of the fourth lens unit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

›Embodiment II-6 · 9 of 9

Here, when at least one of the following conditions (20)′ and (20)″ is satisfied, the above-mentioned effect is achieved more successfully.

80<( L T ·f T )/ f 4 ( f W ·tan ω) (20)′

( L T ·f T )/ f 4 ( f W ·tan ω)<125 (20)′

50<( L W ·f T )/ f 4 ( f W ·tan ω)<125 (21)

where,

ω is a half view angle (°) at a wide-angle limit,

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface),

f 4 is a focal length of the fourth lens unit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (21)′ and (21)″ is satisfied, the above-mentioned effect is achieved more successfully.

65<( L W ·f T )/ f 4 ( f W ·tan ω) (21)′

( L W ·f T )/ f 4 ( f W ·tan ω)<100 (21)′

4.0 <f 3 /f W ·tan ω<5.2 (22)

where,

ω is a half view angle (°) at a wide-angle limit,

f 3 is a focal length of the third lens unit, and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (22)′ and (22)″ is satisfied, the above-mentioned effect is achieved more successfully.

4.4 <f 3 /f W ·tan ω (22)′

f 3 /f W ·tan ω<4.8 (22)′

›Embodiment III-8 · 1 of 9

FIG. 51 is a schematic construction diagram of a digital still camera according to Embodiment III-8. In FIG. 51 , the digital still camera comprises: an imaging device having a zoom lens system 1 and an image sensor 2 composed of a CCD; a liquid crystal display monitor 3 ; and a body 4 . The employed zoom lens system 1 is a zoom lens system according to Embodiment III-1. In FIG. 51 , the zoom lens system 1 comprises a first lens unit G 1 , a second lens unit G 2 , a diaphragm A, a third lens unit G 3 and a fourth lens unit G 4 . In the body 4 , the zoom lens system 1 is arranged on the front side, while the image sensor 2 is arranged on the rear side of the zoom lens system 1 . On the rear side of the body 4 , the liquid crystal display monitor 3 is arranged, while an optical image of a photographic object generated by the zoom lens system 1 is formed on an image surface S.

As such, when the zoom lens system according to Embodiment III-1 is employed in a digital still camera, a small digital still camera is obtained that has a high resolution and high capability of compensating the curvature of field and that has a short overall optical length of lens system at the time of non-use. Here, in the digital still camera shown in FIG. 51 , any one of the zoom lens systems according to Embodiments III-2 to III-7 may be employed in place of the zoom lens system according to Embodiment III-1. Further, the optical system of the digital still camera shown in FIG. 51 is applicable also to a digital video camera for moving images. In this case, moving images with high resolution can be acquired in addition to still images.

Further, an imaging device comprising a zoom lens system according to Embodiments III-1 to III-7 described above and an image sensor such as a CCD or a CMOS may be applied to a mobile telephone, a PDA (Personal Digital Assistance), a surveillance camera in a surveillance system, a Web camera, a vehicle-mounted camera or the like.

Embodiments IV-1 to IV-5

FIG. 52 is a lens arrangement diagram of a zoom lens system according to Embodiment IV-1. FIG. 55 is a lens arrangement diagram of a zoom lens system according to Embodiment IV-2. FIG. 58 is a lens arrangement diagram of a zoom lens system according to Embodiment IV-3. FIG. 61 is a lens arrangement diagram of a zoom lens system according to Embodiment IV-4. FIG. 64 is a lens arrangement diagram of a zoom lens system according to Embodiment IV-5.

FIGS. 52 , 55 , 58 , 61 and 64 show respectively a zoom lens system in an infinity in-focus condition. In each figure, part (a) shows a lens configuration at a wide-angle limit (in the minimum focal length condition: focal length f W ), part (b) shows a lens configuration at a middle position (in an intermediate focal length condition: focal length f M =√(f W *f T )), and part (c) shows a lens configuration at a telephoto limit (in the maximum focal length condition: focal length f T ). Further, in each figure, bent arrows provided between part (a) and part (b) are lines obtained by connecting the positions of the lens units at a wide-angle limit, at a middle position and at a telephoto limit, in order from the top to the bottom. Thus, straight lines are used simply between a wide-angle limit and a middle position and between a middle position and a telephoto limit. That is, these straight lines do not indicate the actual motion of the individual lens units. Moreover, in each figure, an arrow provided to a lens unit indicates focusing from an infinity in-focus condition to a close-object in-focus condition, that is, the moving direction at the time of focusing from an infinity in-focus condition to a close-object in-focus condition.

The zoom lens system according to Embodiments IV-1 to IV-4, in order from the object side to the image side, comprises a first lens unit G 1 having positive optical power, a second lens unit G 2 having negative optical power, a third lens unit G 3 having positive optical power, and a fourth lens unit G 4 having positive optical power. Then, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 , the second lens unit G 2 , the third lens unit G 3 and the fourth lens unit G 4 all move along the optical axis. While the zoom lens system according to Embodiment IV-5, in order from the object side to the image side, comprises a first lens unit G 1 having positive optical power, a second lens unit G 2 having negative optical power, a third lens unit G 3 having positive optical power, a fourth lens unit G 4 having positive optical power, and a fifth lens unit G 5 having positive optical power. Then, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 , the second lens unit G 2 , the third lens unit G 3 and the fourth lens unit G 4 among these lens units move along the optical axis (lens configuration, in order from an object side to an image side, comprising a first lens unit having positive optical power, a second lens unit having negative optical power, and subsequent lens units, in which the subsequent lens units include at least a third lens unit having positive optical power and a fourth lens unit having positive optical power, and in which in zooming from a wide-angle limit to a telephoto limit, at least the first lens unit, the second lens unit, the third lens unit and the fourth lens unit move along an optical axis, is referred to as the basic configuration IV of Embodiments IV-1 to IV-5, hereinafter). In the zoom lens system according to each embodiment, these lens units are arranged into a desired optical power arrangement, so that a remarkably high zooming ratio exceeding 16 and high optical performance are achieved and still size reduction is realized in the entire lens system.

›Embodiment III-8 · 2 of 9

In Embodiment IV-5, the fifth lens unit G 5 being a subsequent lens unit has positive optical power. However, the present invention is not limited to this. The fifth lens unit G 5 can have negative optical power. The number of the subsequent lens units is not limited as long as the subsequent lens units include at least the third lens unit having positive optical power and the fourth lens unit having positive optical power. The number of the subsequent lens units can be suitably set with setting positive optical power or negative optical power for each lens unit. Further, in Embodiment IV-5, in zooming from a wide-angle limit to a telephoto limit, the fifth lens unit G 5 being a subsequent lens unit does not move along the optical axis. However, whether the subsequent lens units are moved along the optical axis or not in zooming can be suitably set in accordance with the aimed configuration of the entire zoom lens system and the like.

In FIGS. 52 , 55 , 58 , 61 and 64 , an asterisk “*” provided to a particular surface indicates that the surface is aspheric. Further, in each figure, a symbol (+) or (−) provided to the sign of each lens unit corresponds to the sign of optical power of the lens unit. Moreover, in each figure, the straight line located on the most right-hand side indicates the position of an image surface S. On the object side relative to the image surface S (Embodiments IV-1 to IV-4: between the image surface S and the most image side lens surface of the fourth lens unit G 4 , Embodiment IV-5: between the image surface S and the most image side lens surface of the fifth lens unit G 5 ), a plane parallel plate such as an optical low-pass filter and a face plate of an image sensor is provided. Moreover, in each figure, a diaphragm A is provided between the most image side lens surface of the second lens unit G 2 and the most object side lens surface of the third lens unit G 3 .

As shown in FIG. 52 , in the zoom lens system according to Embodiment IV-1, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a bi-convex second lens element L 2 ; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment IV-1, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a bi-concave seventh lens element L 7 . Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment IV-1, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus eighth lens element L 8 with the convex surface facing the object side; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment IV-1, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

Here, in the zoom lens system according to Embodiment IV-1, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment IV-1, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 55 , in the zoom lens system according to Embodiment IV-2, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a positive meniscus second lens element L 2 with the convex surface facing the object side; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment IV-2, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a bi-concave seventh lens element L 7 . Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment IV-2, the third lens unit G 3 , in order from the object side to the image side, comprises: a bi-convex eighth lens element L 8 ; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment IV-2, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

›Embodiment III-8 · 3 of 9

Here, in the zoom lens system according to Embodiment IV-2, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment IV-2, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 58 , in the zoom lens system according to Embodiment IV-3, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a bi-convex second lens element L 2 ; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment IV-3, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a bi-concave seventh lens element L 7 . Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment IV-3, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus eighth lens element L 8 with the convex surface facing the object side; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment IV-3, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

Here, in the zoom lens system according to Embodiment IV-3, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment IV-3, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 61 , in the zoom lens system according to Embodiment IV-4, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a bi-convex second lens element L 2 ; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

In the zoom lens system according to Embodiment IV-4, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; a bi-convex sixth lens element L 6 ; and a bi-concave seventh lens element L 7 . Among these, the sixth lens element L 6 and the seventh lens element L 7 are cemented with each other.

Further, in the zoom lens system according to Embodiment IV-4, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus eighth lens element L 8 with the convex surface facing the object side; a bi-convex ninth lens element L 9 ; and a bi-concave tenth lens element L 10 . Among these, the ninth lens element L 9 and the tenth lens element L 10 are cemented with each other.

Further, in the zoom lens system according to Embodiment IV-4, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex eleventh lens element L 11 ; and a negative meniscus twelfth lens element L 12 with the convex surface facing the image side. The eleventh lens element L 11 and the twelfth lens element L 12 are cemented with each other.

Here, in the zoom lens system according to Embodiment IV-4, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment IV-4, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. Further, the fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 .

As shown in FIG. 64 , in the zoom lens system according to Embodiment IV-5, the first lens unit G 1 , in order from the object side to the image side, comprises: a negative meniscus first lens element L 1 with the convex surface facing the object side; a bi-convex second lens element L 2 ; and a positive meniscus third lens element L 3 with the convex surface facing the object side. Among these, the first lens element L 1 and the second lens element L 2 are cemented with each other.

›Embodiment III-8 · 4 of 9

In the zoom lens system according to Embodiment IV-5, the second lens unit G 2 , in order from the object side to the image side, comprises: a negative meniscus fourth lens element L 4 with the convex surface facing the object side; a bi-concave fifth lens element L 5 ; and a positive meniscus sixth lens element L 6 with the convex surface facing the object side.

Further, in the zoom lens system according to Embodiment IV-5, the third lens unit G 3 , in order from the object side to the image side, comprises: a positive meniscus seventh lens element L 7 with the convex surface facing the object side; a bi-convex eighth lens element L 8 ; and a bi-concave ninth lens element L 9 . Among these, the eighth lens element L 8 and the ninth lens element L 9 are cemented with each other.

Further, in the zoom lens system according to Embodiment IV-5, the fourth lens unit G 4 , in order from the object side to the image side, comprises: a bi-convex tenth lens element L 10 ; and a negative meniscus eleventh lens element L 11 with the convex surface facing the image side. The tenth lens element L 10 and the eleventh lens element L 11 are cemented with each other.

Further, in the zoom lens system according to Embodiment IV-5, the fifth lens unit G 5 comprises solely a positive meniscus twelfth lens element L 12 with the concave surface facing the object side.

Here, in the zoom lens system according to Embodiment IV-5, a plane parallel plate L 13 is provided on the object side relative to the image surface S (between the image surface S and the twelfth lens element L 12 ).

In the zoom lens system according to Embodiment IV-5, in zooming from a wide-angle limit to a telephoto limit, the first lens unit G 1 and the third lens unit G 3 move to the object side, while the second lens unit G 2 moves to the image side, that is, such that the position at a wide-angle limit should be located on the object side relative to the position at a telephoto limit. The fourth lens unit G 4 moves with locus of a convex to the object side with changing the interval with the third lens unit G 3 . Further, the fifth lens unit G 5 is fixed to the image surface S.

In the zoom lens system according to each embodiment, in zooming from a wide-angle limit to a telephoto limit, at least the first lens unit G 1 , the second lens unit G 2 , the third lens unit G 3 and the fourth lens unit G 4 move along the optical axis. Among these lens units, for example, the third lens unit is moved in a direction perpendicular to the optical axis, so that image blur caused by hand blurring, vibration and the like can be compensated optically.

The following description is given for conditions desired to be satisfied by a zoom lens system having the above-mentioned basic configuration IV like the zoom lens system according to Embodiments IV-1 to IV-5. Here, a plurality of preferable conditions are set forth for the zoom lens system according to each embodiment. A construction that satisfies all the plural conditions is most desirable for the zoom lens system. However, when an individual condition is satisfied, a zoom lens system having the corresponding effect can be obtained.

Further, all conditions described below hold only under the following two premise conditions, unless noticed otherwise.

16< f T /f W

ω>35

where,

f T is a focal length of the entire system at a telephoto limit,

f W is a focal length of the entire system at a wide-angle limit, and

ω is a half view angle (°) at a wide-angle limit.

The zoom lens system having the basic configuration IV satisfies the following condition (IV-10).

1.95< m 2T /m 34T <3.50 (IV-10)

(here, 16<f T /f W and ω>35)

where,

m 2T is a lateral magnification of the second lens unit at a telephoto limit, and

m 34T is a lateral magnification at a telephoto limit of a composite lens unit consisting of all lens units located on the image side relative to the second lens unit.

The condition (IV-10) sets forth the magnification of the lens units at a telephoto limit. When the value exceeds the upper limit of the condition (IV-10), the overall length at a telephoto limit is excessively great, and hence a compact zoom lens system cannot be realized. Further, for example, in a case that the lens units on the image side relative to the second lens unit are moved in a direction perpendicular to the optical axis so that blur compensation is achieved, an excessively large aberration fluctuation is caused. In contrast, when the value goes below the lower limit of the condition (IV-10), similarly, for example, in a case that the lens units on the image side relative to the second lens unit are moved in a direction perpendicular to the optical axis so that blur compensation is achieved, an excessively large aberration fluctuation is caused.

Here, when at least one of condition (IV-10)′ and either condition (IV-10)″ or condition (IV-10)′″ is satisfied, the above-mentioned effect is achieved more successfully.

2.2 0< m 2T /m 34T (IV-10)′

m 2T /m 34T <3.47 (IV-10)′

m 2T /m 34T <3.20 (IV-10)′

In a zoom lens system having the above-mentioned basic configuration IV like each zoom lens system according to Embodiments IV-1 to IV-5, it is preferable that the following condition (1) is satisfied.

0<√( f 4 ·f W ·tan ω)/ L W <0.13 (1)

where,

ω is a half view angle (°) at a wide-angle limit,

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface),

f 4 is a focal length of the fourth lens unit, and

f W is a focal length of the entire system at a wide-angle limit.

›Embodiment III-8 · 5 of 9

The condition (1) substantially sets forth the focal length of the fourth lens unit. When the value exceeds the upper limit of the condition (1), the optical power of the fourth lens unit is excessively weak, and hence the necessary amount of movement in zooming increases. Thus, it is difficult in some cases to achieve a thin lens barrel configuration. This situation is not preferable. Further, when the value exceeds the upper limit of the condition (1), it becomes difficult in some cases to achieve a satisfactory peripheral illuminance on the image surface especially at a wide-angle limit.

0.05 ≦f 3 /f 4 ≦0.97 (2)

where,

f 3 is a focal length of the third lens unit, and

f 4 is a focal length of the fourth lens unit.

The condition (2) sets forth the ratio between the focal length of the third lens unit and the focal length of the fourth lens unit. When the value exceeds the upper limit of the condition (2), the focal length of the third lens unit is excessively long. Thus, a possibility arises that the amount of movement of the third lens unit necessary for achieving a high magnification exceeding 16 increases excessively. Further, when the value exceeds the upper limit of the condition (2), in some cases, it becomes difficult that, for example, the third lens unit is moved in a direction perpendicular to the optical axis for blur compensation. In contrast, when the value goes below the lower limit of the condition (2), the focal length of the third lens unit is excessively short. Thus, a large aberration fluctuation arises in zooming so as to cause difficulty in compensation. Further, the absolute values of various kinds of aberration generated in the third lens unit increase excessively, and hence compensation becomes difficult. Thus, this situation is not preferable. Moreover, when the value goes below the lower limit of the condition (2), an excessively high error sensitivity to the inclination between the surfaces in the third lens unit is caused. This causes in some cases difficulty in assembling the optical system.

In a zoom lens system having the above-mentioned basic configuration IV like each zoom lens system according to Embodiments IV-1 to IV-5, especially in a case that the second lens unit includes a lens element having negative optical power and being arranged on the most object side and a lens element having positive optical power, it is preferable that the following condition (3) is satisfied.

( nd 4 −1)+( nd 6 −1)≧1.8 (3)

where,

nd 4 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the second lens unit, and

nd 6 is a refractive index to the d-line of a lens element having positive optical power in the second lens unit.

Here, when the following condition (3)′ is satisfied, the above-mentioned effect is achieved more successfully.

( nd 4 −1)+( nd 6 −1)≧1.9 (3)′

In a zoom lens system having the above-mentioned basic configuration IV like each zoom lens system according to Embodiments IV-1 to IV-5, especially in a case that the first lens unit includes a lens element having negative optical power and being arranged on the most object side and a lens element having positive optical power, it is preferable that the following condition (4) is satisfied.

nd 1 −nd 2 ≧0.5 (4)

where,

nd 1 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the first lens unit, and

nd 2 is a refractive index to the d-line of a lens element located on the most object side among the lens elements having positive optical power in the first lens unit.

Here, when the following condition (4)′ is satisfied, the above-mentioned effect is achieved more successfully.

nd 1 −nd 2 ≧0.6 (4)′

In a zoom lens system having the above-mentioned basic configuration IV like each zoom lens system according to Embodiments IV-1 to IV-5, especially in a case that the first lens unit includes a lens element having negative optical power and being arranged on the most object side and a lens element having positive optical power and being arranged on the most image side, it is preferable that the following condition (5) is satisfied.

( nd 1 −1)+( nd 3 −1)≧1.8 (5)

where,

nd 1 is a refractive index to the d-line of a lens element having negative optical power and being arranged on the most object side in the first lens unit, and

nd 3 is a refractive index to the d-line of a lens element having positive optical power and being arranged on the most image side in the first lens unit.

Here, when the following condition (5)′ is satisfied, the above-mentioned effect is achieved more successfully.

( nd 1 −1)+( nd 3 −1)≧1.9 (5)′

›Embodiment III-8 · 6 of 9

0.15< dG 3 /dG< 0.27 (8)

where,

dG 3 is an optical axial center thickness of the third lens unit, and

dG is a sum of the optical axial thicknesses of the first lens unit, the second lens unit, the third lens unit and the fourth lens unit.

Here, when at least one of the following conditions (8)′ and (8)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.19< dG 3/ dG (8)′

dG 3/ dG< 0.22 (8)′

2.7<√( f 3 2 +f 4 2 )/| f 2 |<3.6 (9)

where,

f 2 is a focal length of the second lens unit,

f 3 is a focal length of the third lens unit, and

f 4 is a focal length of the fourth lens unit.

Here, when at least one of the following conditions (9)′ and (9)″ is satisfied, the above-mentioned effect is achieved more successfully.

2.8<√( f 3 2 +f 4 2 )/| f 2 | (9)′

√( f 3 2 +f 4 2 )/| f 2 |<3.5 (9)′

0.037< d 1 NG/d 1 G< 0.135 (11)

where,

d1NG is an optical axial center thickness of the lens element having negative optical power contained in the first lens unit, and

d1G is an optical axial center thickness of the first lens unit.

Here, when at least one of either condition (11)′ or condition (11)″ and condition (11)′″ is satisfied, the above-mentioned effect is achieved more successfully.

0.075< d 1 NG/d 1 G (11)′

0.100< d 1 NG/d 1 G (11)′

d 1 NG/d 1 G< 0.110 (11)′

0.11< f W ·tan(ω−ω 0 )<0.15 (12)

where,

f W is a focal length of the entire system at a wide-angle limit,

ω is a half view angle (real half view angle (°)) at a wide-angle limit, and

ω 0 is a paraxial half view angle (°) at a wide-angle limit.

Here, when at least one of the following conditions (12)′ and (12)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.12< f W ·tan(ω−ω 0 ) (12)′

f W ·tan(ω−ω 0 )<0.14 (12)′

0.17< f 4 /f T <0.30 (13)

where,

f 4 is a focal length of the fourth lens unit, and

f T is a focal length of the entire system at a telephoto limit.

›Embodiment III-8 · 7 of 9

Here, when at least one of the following conditions (13)′ and (13)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.19 <f 4 /f T (13)′

f 4 /f T <0.26 (13)′

0.60< |M 1 /M 2 |<1.30 (14)

where,

Here, when at least one of the following conditions (14)′ and (14)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.75<| M 1 /M 2 | (14)′

| M 1 /M 2 |<1.15 (14)′

0.4<| M 3 /M 2 |<1.2 (15)

where,

0.35<( m 2T /m 2W )/( f T /f W )<0.65 (16)

where,

m 2T is a lateral magnification of the second lens unit at a telephoto limit,

m 2W is a lateral magnification of the second lens unit at a wide-angle limit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (16)′ and (16)″ is satisfied, the above-mentioned effect is achieved more successfully.

0.40<( m 2T /m 2W )/( f T /f W ) (16)′

( m 2T /m 2W )/( f T /f W )<0.50 (16)′

1.3< m 3T /m 3W <2.2 (17)

where,

m 3T is a lateral magnification of the third lens unit at a telephoto limit, and

m 3W is a lateral magnification of the third lens unit at a wide-angle limit.

›Embodiment III-8 · 8 of 9

Here, when at least one of the following conditions (17)′ and (17)″ is satisfied, the above-mentioned effect is achieved more successfully.

1.5< m 3T /m 3W (17)′

m 3T /m 3W <2.0 (17)′

5.5<√( f 3 2 +f 4 2 )/( f W ·tan ω)<9.0 (18)

where,

ω is a half view angle (°) at a wide-angle limit,

f 3 is a focal length of the third lens unit,

f 4 is a focal length of the fourth lens unit, and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (18)′ and (18)″ is satisfied, the above-mentioned effect is achieved more successfully.

6.8<√( f 3 2 +f 4 2 )/( f W ·tan ω) (18)′

√( f 3 2 +f 4 2 )/( f W ·tan ω)<7.5 (18)′

3.0<( L T −L W )/( f W ·tan ω)<6.0 (19)

where,

ω is a half view angle (°) at a wide-angle limit,

L T is an overall optical axial length of the entire system at a telephoto limit (a distance from the most object side surface to the most image side surface),

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface), and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (19)′ and (19)″ is satisfied, the above-mentioned effect is achieved more successfully.

3.5<( L T −L W )/( f W ·tan ω) (19)′

( L T −L W )/( f W ·tan ω)<4.5 (19)′

50<( L T ·f T )/ f 4 ( f W ·tan ω)<150 (20)

where,

ω is a half view angle (°) at a wide-angle limit,

L T is an overall optical axial length of the entire system at a telephoto limit (a distance from the most object side surface to the most image side surface),

f 4 is a focal length of the fourth lens unit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (20)′ and (20)″ is satisfied, the above-mentioned effect is achieved more successfully.

80<( L T −f T )/ f 4 ( f W ·tan ω) (20)′

( L T ·f T )/ f 4 ( f W ·tan ω)<125 (20)′

50<( L W ·f T )/ f 4 ( f W ·tan ω)<125 (21)

where,

ω is a half view angle (° at a wide-angle limit,

L W is an overall optical axial length of the entire system at a wide-angle limit (a distance from the most object side surface to the most image side surface),

f 4 is a focal length of the fourth lens unit,

f T is a focal length of the entire system at a telephoto limit, and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (21)′ and (21)″ is satisfied, the above-mentioned effect is achieved more successfully.

65<( L W ·f T )/ f 4 ( f W ·tan ω) (21)′

( L W ·f T )/ f 4 ( f W ·tan ω)<100 (21)′

›Embodiment III-8 · 9 of 9

4.0< f 3 /f W ·tan ω<5.2 (22)

where,

ω is a half view angle (°) at a wide-angle limit,

f 3 is a focal length of the third lens unit, and

f W is a focal length of the entire system at a wide-angle limit.

Here, when at least one of the following conditions (22)′ and (22)″ is satisfied, the above-mentioned effect is achieved more successfully.

4.4< f 3 /f W ·tan ω (22)′

f 3 /f W ·tan ω<4.8 (22)′

Moreover, each embodiment has been described for the case that a plane parallel plate such as an optical low-pass filter is arranged between the last surface of the zoom lens system (Embodiments IV-1 to IV-4: the most image side surface of the fourth lens unit, Embodiment IV-5: the most image side surface of the fifth lens unit) and the image surface S. This low-pass filter may be: a birefringent type low-pass filter made of, for example, a crystal—whose predetermined crystal orientation is adjusted; or a phase type low-pass filter that achieves required characteristics of optical cut-off frequency by diffraction.

›Embodiment IV-6 · 1 of 2

FIG. 67 is a schematic construction diagram of a digital still camera according to Embodiment IV-6. In FIG. 67 , the digital still camera comprises: an imaging device having a zoom lens system 1 and an image sensor 2 composed of a CCD; a liquid crystal display monitor 3 ; and a body 4 . The employed zoom lens system 1 is a zoom lens system according to Embodiment IV-1. In FIG. 67 , the zoom lens system 1 comprises a first lens unit G 1 , a second lens unit G 2 , a diaphragm A, a third lens unit G 3 and a fourth lens unit G 4 . In the body 4 , the zoom lens system 1 is arranged on the front side, while the image sensor 2 is arranged on the rear side of the zoom lens system 1 . On the rear side of the body 4 , the liquid crystal display monitor 3 is arranged, while an optical image of a photographic object generated by the zoom lens system 1 is formed on an image surface S.

As such, when the zoom lens system according to Embodiment IV-1 is employed in a digital still camera, a small digital still camera is obtained that has a high resolution and high capability of compensating the curvature of field and that has a short overall optical length of lens system at the time of non-use. Here, in the digital still camera shown in FIG. 67 , any one of the zoom lens systems according to Embodiments IV-2 to IV-5 may be employed in place of the zoom lens system according to Embodiment IV-1. Further, the optical system of the digital still camera shown in FIG. 67 is applicable also to a digital video camera for moving images. In this case, moving images with high resolution can be acquired in addition to still images.

Further, an imaging device comprising a zoom lens system according to Embodiments IV-1 to IV-5 described above and an image sensor such as a CCD or a CMOS may be applied to a mobile telephone, a PDA (Personal Digital Assistance), a surveillance camera in a surveillance system, a Web camera, a vehicle-mounted camera or the like.

Numerical examples are described below in which the zoom lens systems according to Embodiments I-1 to I-4, II-1 to II-5, III-1 to III-7 and IV-1 to IV-5 are implemented. In the numerical examples, the units of the length in the tables are all “mm”, while the units of the view angle are all “°”. Moreover, in the numerical examples, r is the radius of curvature, d is the axial distance, nd is the refractive index to the d-line, and vd is the Abbe number to the d-line. In the numerical examples, the surfaces marked with * are aspheric surfaces, and the aspheric surface configuration is defined by the following expression.

Z = h 2 / r 1 + 1 - ( 1 + κ ) ⁢ ( h / r ) 2 + A ⁢ ⁢ 4 ⁢ h 4 + A ⁢ ⁢ 6 ⁢ h 6 + A ⁢ ⁢ 8 ⁢ h 8 + A ⁢ ⁢ 10 ⁢ h 10 + A ⁢ ⁢ 12 ⁢ h 12

Here, κ is the conic constant, and A4, A6, A8, A10 and A12 are a fourth-order, sixth-order, eighth-order, tenth-order and twelfth-order aspherical coefficients, respectively.

FIG. 2 is a longitudinal aberration diagram of a zoom lens system according to Example I-1. FIG. 5 is a longitudinal aberration diagram of a zoom lens system according to Example I-2. FIG. 8 is a longitudinal aberration diagram of a zoom lens system according to Example I-3. FIG. 11 is a longitudinal aberration diagram of a zoom lens system according to Example I-4.

FIG. 15 is a longitudinal aberration diagram of a zoom lens system according to Example II-1. FIG. 18 is a longitudinal aberration diagram of a zoom lens system according to Example II-2. FIG. 21 is a longitudinal aberration diagram of a zoom lens system according to Example II-3. FIG. 24 is a longitudinal aberration diagram of a zoom lens system according to Example II-4. FIG. 27 is a longitudinal aberration diagram of a zoom lens system according to Example II-5.

FIG. 31 is a longitudinal aberration diagram of a zoom lens system according to Example III-1. FIG. 34 is a longitudinal aberration diagram of a zoom lens system according to Example III-2. FIG. 37 is a longitudinal aberration diagram of a zoom lens system according to Example III-3. FIG. 40 is a longitudinal aberration diagram of a zoom lens system according to Example III-4. FIG. 43 is a longitudinal aberration diagram of a zoom lens system according to Example III-5. FIG. 46 is a longitudinal aberration diagram of a zoom lens system according to Example III-6. FIG. 49 is a longitudinal aberration diagram of a zoom lens system according to Example III-7.

FIG. 53 is a longitudinal aberration diagram of a zoom lens system according to Example IV-1. FIG. 56 is a longitudinal aberration diagram of a zoom lens system according to Example IV-2. FIG. 59 is a longitudinal aberration diagram of a zoom lens system according to Example IV-3. FIG. 62 is a longitudinal aberration diagram of a zoom lens system according to Example IV-4. FIG. 65 is a longitudinal aberration diagram of a zoom lens system according to Example IV-5.

In each longitudinal aberration diagram, part (a) shows the aberration at a wide-angle limit, part (b) shows the aberration at a middle position, and part (c) shows the aberration at a telephoto limit. Each longitudinal aberration diagram, in order from the left-hand side, shows the spherical aberration (SA (mm)), the astigmatism (AST (mm)) and the distortion (DIS (%)). In each spherical aberration diagram, the vertical axis indicates the F-number (in each FIG., indicated as F), and the solid line, the short dash line and the long dash line indicate the characteristics to the d-line, the F-line and the C-line, respectively. In each astigmatism diagram, the vertical axis indicates the image height (in each FIG, indicated as H), and the solid line and the dash line indicate the characteristics to the sagittal plane (in each FIG., indicated as “s”) and the meridional plane (in each FIG, indicated as “m”), respectively. In each distortion diagram, the vertical axis indicates the image height (in each FIG., indicated as H).

›Embodiment IV-6 · 2 of 2

Further, FIG. 3 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example I-1. FIG. 6 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example I-2. FIG. 9 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example I-3. FIG. 12 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example I-4.

Further, FIG. 16 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example II-1. FIG. 19 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example II-2. FIG. 22 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example II-3. FIG. 25 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example II-4. FIG. 28 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example II-5.

Further, FIG. 32 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example III-1. FIG. 35 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example III-2. FIG. 38 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example III-3. FIG. 41 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example III-4. FIG. 44 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example III-5. FIG. 47 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example III-6. FIG. 50 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example III-7.

Further, FIG. 54 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example IV-1. FIG. 57 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example IV-2. FIG. 60 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example IV-3. FIG. 63 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example IV-4. FIG. 66 is a lateral aberration diagram at a telephoto limit of a zoom lens system according to Example IV-5.

In each lateral aberration diagram, the upper three aberration diagrams correspond to a basic state where image blur compensation is not performed at a telephoto limit, while the lower three aberration diagrams correspond to an image blur compensation state where the entire third lens unit G 3 is moved by a predetermined amount in a direction perpendicular to the optical axis at a telephoto limit. Among the lateral aberration diagrams of the basic state, the upper one shows the lateral aberration at an image point of 70% of the maximum image height, the middle one shows the lateral aberration at the axial image point, and the lower one shows the lateral aberration at an image point of −70% of the maximum image height. Among the lateral aberration diagrams of an image blur compensation state, the upper one shows the lateral aberration at an image point of 70% of the maximum image height, the middle one shows the lateral aberration at the axial image point, and the lower one shows the lateral aberration at an image point of −70% of the maximum image height. In each lateral aberration diagram, the horizontal axis indicates the distance from the principal ray on the pupil surface. The solid line indicates the characteristics to the d-line, the short dash line indicates the characteristics to the F-line, and the long dash line indicates the characteristics to the C-line. In each lateral aberration diagram, the meridional plane is adopted as the plane containing the optical axis of the first lens unit G 1 and the optical axis of the third lens unit G 3 .

The amount of movement of the third lens unit G 3 in a direction perpendicular to the optical axis in the image blur compensation state at a telephoto limit is as follows.

Example I-1 0.300 mm

Example I-2 0.268 mm

Example I-3 0.269 mm

Example I-4 0.295 mm

Example II-1 0.323 mm

Example II-2 0.320 mm

Example II-3 0.276 mm

Example II-4 0.264 mm

Example II-5 0.295 mm

Example III-1 0.323 mm

Example III-2 0.268 mm

Example III-3 0.300 mm

Example III-4 0.302 mm

Example III-5 0.300 mm

Example III-6 0.298 mm

Example III-7 0.333 mm

Example IV-1 0.321 mm

Example IV-2 0.263 mm

Example IV-3 0.295 mm

Example IV-4 0.287 mm

›Example IV-5 0.300 mm · 1 of 2

When the shooting distance is infinity, at a telephoto limit, the amount of image decentering in a case that the zoom lens system inclines by 0.3° is equal to the amount of image decentering in a case that the entire third lens unit G 3 displaces in parallel by each of the above-mentioned values in a direction perpendicular to the optical axis.

As seen from the lateral aberration diagrams, satisfactory symmetry is obtained in the lateral aberration at the axial image point. Further, when the lateral aberration at the +70% image point and the lateral aberration at the −70% image point are compared with each other in the basic state, all have a small degree of curvature and almost the same inclination in the aberration curve. Thus, decentering coma aberration and decentering astigmatism are small. This indicates that sufficient imaging performance is obtained even in the image blur compensation state. Further, when the image blur compensation angle of a zoom lens system is the same, the amount of parallel translation required for image blur compensation decreases with decreasing focal length of the entire zoom lens system. Thus, at arbitrary zoom positions, sufficient image blur compensation can be performed for image blur compensation angles up to 0.3° without degrading the imaging characteristics.

Numerical Example I-1

The zoom lens system of Numerical Example I-1 corresponds to Embodiment I-1 shown in FIG. 1 . Table I-1 shows the surface data of the zoom lens systems of Numerical Example I-1. Table I-2 shows the aspherical data. Table I-3 shows various data.

Numerical Example I-2

The zoom lens system of Numerical Example I-2 corresponds to Embodiment I-2 shown in FIG. 4 . Table I-4 shows the surface data of the zoom lens systems of Numerical Example I-2. Table I-5 shows the aspherical data. Table I-6 shows various data.

Numerical Example I-3

The zoom lens system of Numerical Example I-3 corresponds to Embodiment I-3 shown in FIG. 7 . Table I-7 shows the surface data of the zoom lens systems of Numerical Example I-3. Table I-8 shows the aspherical data. Table I-9 shows various data.

Numerical Example I-4

The zoom lens system of Numerical Example I-4 corresponds to Embodiment I-4 shown in FIG. 10 . Table I-10 shows the surface data of the zoom lens systems of Numerical Example I-4. Table I-11 shows the aspherical data. Table I-12 shows various data.

The following Table I-13 shows the corresponding values to the individual conditions in the zoom lens system of the numerical examples.

Numerical Example II-1

The zoom lens system of Numerical Example II-1 corresponds to Embodiment II-1 shown in FIG. 14 . Table II-1 shows the surface data of the zoom lens systems of Numerical Example II-1. Table II-2 shows the aspherical data. Table II-3 shows various data.

Numerical Example II-2

The zoom lens system of Numerical Example II-2 corresponds to Embodiment II-2 shown in FIG. 17 . Table II-4 shows the surface data of the zoom lens systems of Numerical Example II-2. Table II-5 shows the aspherical data. Table II-6 shows various data.

Numerical Example II-3

The zoom lens system of Numerical Example II-3 corresponds to Embodiment II-3 shown in FIG. 20 . Table II-7 shows the surface data of the zoom lens systems of Numerical Example II-3. Table II-8 shows the aspherical data. Table II-9 shows various data.

Numerical Example II-4

The zoom lens system of Numerical Example II-4 corresponds to Embodiment II-4 shown in FIG. 23 . Table II-10 shows the surface data of the zoom lens systems of Numerical Example II-4. Table II-11 shows the aspherical data. Table II-12 shows various data.

Numerical Example II-5

The zoom lens system of Numerical Example II-5 corresponds to Embodiment II-5 shown in FIG. 26 . Table II-13 shows the surface data of the zoom lens systems of Numerical Example II-5. Table II-14 shows the aspherical data. Table II-15 shows various data.

The following Table II-16 shows the corresponding values to the individual conditions in the zoom lens system of the numerical examples.

Numerical Example III-1

The zoom lens system of Numerical Example III-1 corresponds to Embodiment III-1 shown in FIG. 30 . Table III-1 shows the surface data of the zoom lens system of Numerical Example III-1. Table III-2 shows the aspherical data. Table III-3 shows various data.

Numerical Example III-2

The zoom lens system of Numerical Example III-2 corresponds to Embodiment III-2 shown in FIG. 33 . Table III-4 shows the surface data of the zoom lens system of Numerical Example III-2. Table III-5 shows the aspherical data. Table III-6 shows various data.

Numerical Example III-3

The zoom lens system of Numerical Example III-3 corresponds to Embodiment III-3 shown in FIG. 36 . Table III-7 shows the surface data of the zoom lens system of Numerical Example III-3. Table III-8 shows the aspherical data. Table III-9 shows various data.

Numerical Example III-4

The zoom lens system of Numerical Example III-4 corresponds to Embodiment III-4 shown in FIG. 39 . Table III-10 shows the surface data of the zoom lens system of Numerical Example III-4. Table III-11 shows the aspherical data. Table III-12 shows various data.

Numerical Example III-5

The zoom lens system of Numerical Example III-5 corresponds to Embodiment III-5 shown in FIG. 42 . Table III-13 shows the surface data of the zoom lens system of Numerical Example III-5. Table III-14 shows the aspherical data. Table III-15 shows various data.

Numerical Example III-6

The zoom lens system of Numerical Example III-6 corresponds to Embodiment III-6 shown in FIG. 45 . Table III-16 shows the surface data of the zoom lens system of Numerical Example III-6. Table III-17 shows the aspherical data. Table III-18 shows various data.

Numerical Example III-7

The zoom lens system of Numerical Example III-7 corresponds to Embodiment III-7 shown in FIG. 48 . Table III-19 shows the surface data of the zoom lens system of Numerical Example III-7. Table III-20 shows the aspherical data. Table III-21 shows various data.

The following Table III-22 shows the corresponding values to the individual conditions in the zoom lens systems of the numerical examples.

›Example IV-5 0.300 mm · 2 of 2

Numerical Example IV-1

The zoom lens system of Numerical Example IV-1 corresponds to Embodiment IV-1 shown in FIG. 52 . Table IV-1 shows the surface data of the zoom lens systems of Numerical Example IV-1. Table IV-2 shows the aspherical data. Table IV-3 shows various data.

Numerical Example IV-2

The zoom lens system of Numerical Example IV-2 corresponds to Embodiment IV-2 shown in FIG. 55 . Table IV-4 shows the surface data of the zoom lens systems of Numerical Example IV-2. Table IV-5 shows the aspherical data. Table IV-6 shows various data.

Numerical Example IV-3

The zoom lens system of Numerical Example IV-3 corresponds to Embodiment IV-3 shown in FIG. 58 . Table IV-7 shows the surface data of the zoom lens systems of Numerical Example IV-3. Table IV-8 shows the aspherical data. Table IV-9 shows various data.

Numerical Example IV-4

The zoom lens system of Numerical Example IV-4 corresponds to Embodiment IV-4 shown in FIG. 61 . Table IV-10 shows the surface data of the zoom lens systems of Numerical Example IV-4. Table IV-11 shows the aspherical data. Table IV-12 shows various data.

Numerical Example IV-5

The zoom lens system of Numerical Example IV-5 corresponds to Embodiment IV-5 shown in FIG. 64 . Table IV-13 shows the surface data of the zoom lens systems of Numerical Example IV-5. Table IV-14 shows the aspherical data. Table IV-15 shows various data.

The following Table IV-16 shows the corresponding values to the individual conditions in the zoom lens system of the numerical examples.

The zoom lens system according to the present invention is applicable to a digital input device such as a digital still camera, a digital video camera, a mobile telephone, a PDA (Personal Digital Assistance), a surveillance camera in a surveillance system, a Web camera or a vehicle-mounted camera. In particular, the zoom lens system according to the present invention is suitable for a photographing optical system where high image quality is required like in a digital still camera, a digital video camera or the like.

›Tables in the description — 46

TABLE I — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	46.64325	1.00000	1.84666	23.8
2	31.58521	5.26100	1.49700	81.6
3	−1061.17596	0.15000
4	29.08415	3.12090	1.62299	58.1
5	72.43838	Variable
6	59.37976	0.70000	1.88300	40.8
7	7.29817	4.30280
8*	−21.73416	0.55000	1.66547	55.2
9*	21.59312	0.83340
10	16.27273	2.00000	1.84700	23.8
11	−94.63452	0.55000	1.67839	56.4
12	150.58846	Variable
13(Diaphragm)	∞	0.96250
14	8.63264	1.75910	1.69680	55.5
15	79.68736	2.50380
16*	10.86684	1.45760	1.66547	55.2
17	−34.20392	0.44920	1.71736	29.5
18	7.06860	Variable
19*	14.22294	2.88740	1.60602	57.4
20	−10.49120	0.54980	1.68893	31.2
21	−38.38846	Variable
22	∞	1.46600	1.51680	64.2
23	∞	0.87000
24	∞	(BF)
Image surface	∞

TABLE I — (Various data) Zooming ratio 17.35545

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7534	33.0021	82.4966
F-number	2.92069	3.36750	4.53189
View angle	38.5536	6.2800	2.4683
Image height	3.6000	3.6000	3.6000
Overall length	73.9139	78.5518	89.0406
of lens system
BF	0.01387	0.01204	0.04062
d5	0.6000	25.2043	31.3189
d12	29.4567	3.5367	2.1000
d18	7.5290	7.2346	21.4185
d21	4.9408	11.1907	2.7891

TABLE I — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	45.58027	0.29880	1.84666	23.8
2	29.13959	4.64030	1.49700	81.6
3	3144.16519	0.15000
4	26.07049	3.15470	1.72500	54.0
5	64.13617	Variable
6*	113.44694	1.40000	1.80470	41.0
7*	6.91788	5.01430
8	−14.58562	0.30000	1.71891	54.3
9	50.43219	0.30640
10	20.56042	1.77880	1.84700	23.8
11	−25.90405	0.55000	1.72500	54.0
12	−284.10307	Variable
13(Diaphragm)	∞	1.20000
14*	10.21465	2.87650	1.59050	61.9
15	−29.79241	2.19600
16	10.32052	1.11950	1.66979	56.9
17	−41.94030	0.44920	1.71166	31.8
18	6.68552	Variable
19*	14.65464	2.88740	1.60602	57.4
20	−16.44133	0.54980	1.84704	23.8
21	−37.86003	Variable
22	∞	0.78000	1.51680	64.2
23	∞	0.87000
24	∞	(BF)
Image surface	∞

TABLE I — (Various data) Zooming ratio 17.66807

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7532	32.9970	83.9796
F-number	2.92135	3.38151	5.08174
View angle	38.6042	6.2756	2.4298
Image height	3.6000	3.6000	3.6000
Overall length	70.6847	72.7597	88.0179
of lens system
BF	0.30730	0.00395	0.02751
d5	0.6000	21.7525	26.3849
d12	26.7016	3.2299	2.1000
d18	6.5447	4.4121	25.5257
d21	6.0094	12.8395	3.4581
Entrance pupil	17.8051	111.6713	199.0761
position
Exit pupil	−35.8564	−33.6208	57.2096
position
Front principal	21.9335	112.2873	406.3912
points position
Back principal	65.9315	39.7627	4.0383
points position

TABLE I — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	48.62133	1.15000	1.84666	23.8
2	30.94094	4.74580	1.49700	81.6
3	2563.71125	0.15000
4	27.26452	3.08400	1.74676	49.5
5	59.74032	Variable
6	31.36034	0.70000	2.00060	25.5
7	7.63968	4.39930
8*	−19.60369	0.80000	1.72500	54.0
9*	21.36682	1.15400
10	17.76074	2.31890	1.92286	20.9
11	−29.71350	0.45000	1.80530	41.1
12	131.71172	Variable
13(Diaphragm)	∞	1.20000
14	8.93187	1.79410	1.68441	56.0
15	215.91767	2.54290
16*	10.91837	2.04160	1.66942	46.6
17	−8.73541	0.52350	1.72812	29.5
18	7.07039	Variable
19*	13.42970	3.19330	1.57066	61.6
20	−15.40937	0.45000	1.84700	23.8
21	−32.10015	Variable
22	∞	0.78000	1.51680	64.2
23	∞	0.87000
24	∞	(BF)
Image surface	∞

TABLE I — (Various data) Zooming ratio 17.66993

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7527	33.0026	83.9794
F-number	2.91865	3.30336	5.03762
View angle	38.5658	6.2940	2.4278
Image height	3.6000	3.6000	3.6000
Overall length	73.9045	74.8731	89.0062
of lens system
BF	0.00441	0.00419	0.00621
d5	0.6000	24.4631	29.3748
d12	29.4831	3.3553	2.1000
d18	6.5761	3.4161	23.0855
d21	4.8935	11.2870	2.0923
Entrance pupil	18.2746	123.8854	216.8370
position
Exit pupil	−35.0856	−28.7658	64.5383
position
Front principal	22.3836	119.0301	410.1036
points position
Back principal	69.1518	41.8705	5.0268
points position

TABLE I — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	45.32568	1.30000	1.84666	23.8
2	31.96732	6.00000	1.49700	81.6
3	−465.95760	0.15000
4	31.02235	3.20000	1.60311	60.7
5	70.61610	Variable
6	101.53090	0.70000	1.90366	31.3
7	7.86890	4.70000
8*	−20.55497	0.80000	1.66547	55.2
9*	31.47034	0.85000
10	20.42499	2.45000	1.92286	20.9
11	−33.42648	0.60000	1.83481	42.7
12	140.41630	Variable
13(Diaphragm)	∞	2.30000
14	8.34831	1.90000	1.69680	55.5
15	53.23219	2.25000
16*	10.01290	1.58000	1.66547	55.2
17	−22.10466	0.50000	1.71736	29.5
18	6.46268	Variable
19*	13.27992	3.80000	1.60602	57.4
20	−10.79685	0.60000	1.68893	31.2
21	−52.08229	Variable
22	∞	1.50000	1.51633	64.0
23	∞	0.37000
24	∞	(BF)
Image surface	∞

TABLE I — (Various data) Zooming ratio 22.24156

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7300	32.3327	105.2017
F-number	2.93911	3.38403	5.23447
View angle	39.1735	6.3700	1.9176
Image height	3.6000	3.6000	3.6000
Overall length	77.0121	82.2972	96.7586
of lens system
BF	0.00000	−0.00001	−0.00002
d5	0.6545	25.5975	32.6534
d12	28.6039	3.0484	1.3091
d18	6.5672	6.0613	26.5797
d21	5.6364	12.0401	0.6665
Entrance pupil	19.6238	126.0506	272.8794
position
Exit pupil	−38.9910	−42.4432	48.0752
position
Front principal	23.7800	133.7527	608.2910
points position
Back principal	72.2821	49.9646	−8.4431
points position

TABLE I — (Corresponding values to conditions) Numerical Example

	Condition	I-1	I-2	I-3	I-4
(1)	(f 4 · f W · tanω)/L W	0.116	0.125	0.118	0.114
(2)	f 3 /f 4	0.927	0.851	0.866	0.941
(3)	(nd 4 − 1) + (nd 6 − 1)	1.730	1.652	1.923	1.827
(8)	dG3/dG	0.220	0.240	0.234	0.199
(9)	(f 3 2 + f 4 2 )/\|f 2 \|	3.02	3.44	3.05	3.15
(I-10)	m 2T /m 34T	2.845	2.121	2.182	2.598
(11)	d1NG/d1G	0.10491	0.03625	0.12596	0.12207
(12)	f W · tan(ω − ω 0 )	0.11742	0.12152	0.11808	0.15681
(13)	f 4 /f T	0.235	0.246	0.238	0.189
(14)	\|M 1 /M 2 \|	0.758	0.909	0.660	1.005
(15)	\|M 3 /M 2 \|	0.589	0.847	0.599	0.765
(16)	(m 2T /m 2W )/(f T /f W )	0.502	0.432	0.427	0.431
(17)	m 3T /m 3W	1.667	1.849	1.896	1.572
(18)	(f 3 2 + f 4 2 )/(f W · tanω)	6.97	7.16	6.97	7.07
(19)	(L T − L W )/(f W · tanω)	3.99	4.57	3.99	5.12
(20)	(L T · f T )/f 4 (f W · tanω)	100.2	94.1	98.7	133.1
(21)	(L W · f T )/f 4 (f W · tanω)	83.2	75.6	82.0	106.0
(22)	f 3 /f W · tanω	4.74	4.64	4.56	4.85

TABLE II — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	54.67874	1.15000	2.20000	24.0
2	36.43543	5.05340	1.49700	81.6
3	−416.24419	0.15000
4	31.15733	3.57660	1.75161	48.6
5	85.40205	Variable
6	41.03425	0.70000	2.00000	40.0
7	7.60737	4.29990
8*	−19.89329	0.80000	1.72500	54.0
9*	32.70363	0.99640
10	22.93899	1.67400	2.20000	24.0
11	−97.37342	0.45000	1.79999	41.7
12	111.71189	Variable
13(Diaphragm)	∞	1.20000
14	7.49994	1.92750	1.63645	59.1
15	215.91767	1.69790
16*	9.43190	1.90840	1.69652	42.0
17	−11.33555	0.45000	1.80595	30.0
18	5.99424	Variable
19*	12.22671	2.80000	1.50044	69.0
20	−14.83348	0.45000	1.84700	23.8
21	−22.64524	Variable
22	∞	0.78000	1.51680	64.2
23	∞	(BF)
Image surface	∞

TABLE II — (Various data) Zooming ratio 17.36563

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7524	33.0049	82.5290
F-number	2.91648	3.48271	4.34807
View angle	38.5456	6.2523	2.4721
Image height	3.6000	3.6000	3.6000
Overall length	73.9059	79.1817	89.0086
of lens system
BF	0.87587	0.87107	0.87851
d5	0.6000	26.5565	33.9577
d12	30.3658	3.5702	2.1000
d18	6.4260	6.1225	18.5502
d21	5.5741	11.9973	3.4581
Entrance pupil	18.0226	120.2230	262.6229
position
Exit pupil	−32.7172	−37.5269	95.6119
position
Front principal	22.1027	124.8587	417.0488
points position
Back principal	69.1534	46.1768	6.4796
points position

TABLE II — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	46.13135	1.15000	1.84666	23.8
2	31.95861	4.81240	1.49700	81.6
3	∞	0.15000
4	30.38811	2.88740	1.62299	58.1
5	73.04390	Variable
6	42.17330	0.70000	1.90366	31.3
7	7.26077	4.30280
8*	−27.15662	0.55000	1.66547	55.2
9*	23.12958	0.83340
10	16.95297	2.00000	1.92286	20.9
11	−63.29959	0.55000	1.83481	42.7
12	68.72884	Variable
13(Diaphragm)	∞	0.96250
14	8.08916	1.89830	1.69680	55.5
15	45.65310	2.29140
16*	10.08033	1.48290	1.66547	55.2
17	−24.83782	0.44920	1.71736	29.5
18	6.71627	Variable
19*	13.92874	2.88740	1.60602	57.4
20	−9.81032	0.54980	1.68893	31.2
21	−37.66450	Variable
22	∞	1.46600	1.51680	64.2
23	∞	(BF)
Image surface	∞

TABLE II — (Various data) Zooming ratio 17.41973

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7498	32.8767	82.7408
F-number	2.91629	3.58178	4.52707
View angle	38.5639	6.2772	2.4613
Image height	3.6000	3.6000	3.6000
Overall length	70.5088	77.2641	88.3592
of lens system
BF	0.87879	0.91012	1.22909
d5	0.6000	25.7365	33.3146
d12	28.1433	2.8125	1.2833
d18	5.2303	5.9886	19.6030
d21	5.7329	11.8929	3.0057
Entrance pupil	18.2388	114.1817	247.1346
position
Exit pupil	−28.3925	−38.0080	85.7657
position
Front principal	22.2179	119.2853	410.8586
points position
Back principal	65.7590	44.3874	5.6184
points position

TABLE II — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	47.62460	0.30000	1.84666	23.8
2	31.25260	4.32160	1.49700	81.6
3	4446.75167	0.15000
4	27.48777	2.72000	1.73593	51.6
5	60.21619	Variable
6	28.96503	0.70000	2.00060	25.5
7	7.24362	4.31700
8*	−19.98426	0.30000	1.71386	54.5
9*	22.37765	0.93660
10	17.60080	2.05760	1.92286	20.9
11	−28.82319	0.30000	1.77494	44.9
12	130.30430	Variable
13(Diaphragm)	∞	1.20000
14	8.76142	1.26280	1.69188	52.1
15	163.49317	2.64960
16*	10.57314	1.76360	1.66903	56.9
17	−8.70263	0.46440	1.72619	32.7
18	6.87850	Variable
19*	13.99649	3.42470	1.59108	61.9
20	−14.99712	0.30000	1.84700	23.8
21	−31.04929	Variable
22	∞	0.78000	1.51680	64.2
23	∞	(BF)
Image surface	∞

TABLE II — (Various data) Zooming ratio 17.67030

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7529	33.0026	83.9855
F-number	2.91500	3.35985	5.03984
View angle	38.5682	6.2836	2.4305
Image height	3.6000	3.6000	3.6000
Overall length	70.5087	73.1298	88.0019
of lens system
BF	0.87863	0.87057	0.87191
d5	0.6000	24.4540	29.7149
d12	28.9912	3.3558	2.1000
d18	6.7130	4.7082	24.3615
d21	5.3780	11.7933	3.0057
Entrance pupil	16.6380	114.3202	205.3061
position
Exit pupil	−35.6369	−32.5596	53.2942
position
Front principal	20.7723	114.7423	423.8446
points position
Back principal	65.7558	40.1272	4.0164
points position

TABLE II — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	48.02764	0.30000	1.84666	23.8
2	30.28906	4.34950	1.49700	81.6
3	926.55115	0.15000
4	27.23869	2.93200	1.75057	48.8
5	60.38189	Variable
6	31.30607	0.70000	2.08000	30.4
7*	7.50435	4.46510
8	−19.17689	0.30050	1.68940	40.4
9	17.63798	0.74070
10	17.62356	1.63770	1.94595	18.0
11	−93.47757	Variable
12(Diaphragm)	∞	1.20000
13	8.63828	2.20100	1.69210	55.6
14	169.54109	2.10550
15*	10.35891	1.89040	1.66924	56.9
16	−8.02287	0.38850	1.73281	34.1
17	6.70746	Variable
18*	13.99824	2.50000	1.58820	59.0
19	−15.33828	0.30000	1.84700	23.8
20	−31.91402	Variable
21	∞	0.78000	1.51680	64.2
22	∞	(BF)
Image surface	∞

TABLE II — (Various data) Zooming ratio 17.67152

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7193	33.0029	83.3978
F-number	2.91879	3.39129	5.24705
View angle	38.7672	6.3037	2.4484
Image height	3.6000	3.6000	3.6000
Overall length	70.4623	72.8612	87.9819
of lens system
BF	0.88094	0.87175	0.85191
d5	0.6000	24.8701	29.9169
d11	29.9112	3.5832	2.4032
d17	6.5299	4.6973	24.8633
d20	5.5994	11.8980	3.0057
Entrance pupil	16.5711	115.0052	198.8555
position
Exit pupil	−32.9498	−31.2896	54.1261
position
Front principal	20.6321	114.1417	412.8081
points position
Back principal	65.7430	39.8584	4.5841
points position

TABLE II — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	45.52425	1.30000	1.84666	23.8
2	32.16757	6.00000	1.49700	81.6
3	−474.36440	0.15000
4	31.42311	3.20000	1.60311	60.7
5	71.93247	Variable
6	85.97154	0.70000	1.90366	31.3
7	7.78750	4.70000
8*	−20.49027	0.80000	1.66547	55.2
9*	31.55131	0.85000
10	20.49610	2.45000	1.92286	20.9
11	−33.70458	0.60000	1.83481	42.7
12	150.07760	Variable
13(Diaphragm)	∞	2.30000
14	8.35327	1.90000	1.69680	55.5
15	53.32427	2.25000
16*	9.98413	1.58000	1.66547	55.2
17	−21.94441	0.50000	1.71736	29.5
18	6.46504	Variable
19*	13.63884	3.80000	1.60602	57.4
20	−10.92392	0.60000	1.68893	31.2
21	−48.40053	Variable
22	∞	1.50000	1.51633	64.0
23	∞	(BF)
Image surface	∞

TABLE II — (Various data) Zooming ratio 20.73116

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7135	32.2077	97.7165
F-number	2.90061	3.42257	5.05142
View angle	39.0553	6.3899	2.0709
Image height	3.6000	3.6000	3.6000
Overall length	76.3557	83.2004	97.3161
of lens system
BF	0.36998	0.36997	0.36990
d5	0.6545	25.5533	32.6164
d12	28.3328	3.0495	1.3091
d18	5.9770	6.9976	25.9569
d21	5.8414	12.0500	1.8838
Entrance pupil	19.6265	123.7296	262.6743
position
Exit pupil	−35.5639	−48.0276	49.4999
position
Front principal	23.7217	134.5036	554.7428
points position
Back principal	71.6422	50.9927	−0.4004
points position

TABLE II — (Corresponding values to conditions) Numerical Example

	Condition	II-1	II-2	II-3	II-4	II-5
(3)	(nd 4 − 1) + (nd 6 − 1)	2.200	1.827	1.923	2.026	1.827
(1)	(f 4 · f W · tanω)/L W	0.114	0.121	0.122	0.122	0.114
(2)	f 3 /f 4	0.965	0.939	0.910	0.890	0.935
(4)	nd 1 − nd 2	0.703	0.350	0.350	0.350	0.350
(5)	(nd 1 − 1) + (nd 3 − 1)	1.952	1.470	1.583	1.597	1.450
(8)	dG3/dG	0.213	0.223	0.236	0.264	0.199
(9)	(f 3 2 + f 4 2 )/\|f 2 \|	2.81	2.88	3.02	2.95	3.13
(II-10)	m 2T /m 34T	3.470	3.130	2.154	1.952	2.421
(11)	d1NG/d1G	0.1158	0.1278	0.0400	0.0388	0.1221
(12)	f W · tan(ω − ω 0 )	0.1163	0.1165	0.1184	0.1178	0.1386
(13)	f 4 /f T	0.226	0.231	0.232	0.235	0.204
(14)	\|M 1 /M 2 \|	0.730	0.971	0.824	0.801	1.161
(15)	\|M 3 /M 2 \|	0.484	0.653	0.719	0.718	0.887
(16)	(m 2T /m 2W )/(f T /f W )	0.550	0.521	0.428	0.401	0.429
(17)	m 3T /m 3W	1.504	1.545	1.914	2.022	1.687
(18)	(f 3 2 + f 4 2 )/(f W · tanω)	6.83	6.92	6.94	6.94	7.13
(19)	(L T − L W )/(f W · tanω)	3.99	4.71	4.62	4.62	5.48
(20)	(L T · f T )/f4(f W · tanω)	104.2	101.1	100.2	98.6	124.8
(21)	(L W · f T )/f 4 (f W · tanω)	86.5	80.7	80.3	79.0	97.9
(22)	f 3 /f W · tanω	4.75	4.73	4.67	4.61	4.87

TABLE III — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	54.67874	1.15000	2.20000	24.0
2	36.43543	5.05340	1.49700	81.6
3	−416.24419	0.15000
4	31.15733	3.57660	1.75161	48.6
5	85.40205	Variable
6	41.03425	0.70000	2.00000	40.0
7	7.60737	4.29990
8*	−19.89329	0.80000	1.72500	54.0
9*	32.70363	0.99640
10	22.93899	1.67400	2.20000	24.0
11	−97.37342	0.45000	1.79999	41.7
12	111.71189	Variable
13(Diaphragm)	∞	1.20000
14	7.49994	1.92750	1.63645	59.1
15	215.91767	1.69790
16*	9.43190	1.90840	1.69652	42.0
17	−11.33555	0.45000	1.80595	30.0
18	5.99424	Variable
19*	12.22671	2.80000	1.50044	69.0
20	−14.83348	0.45000	1.84700	23.8
21	−22.64524	Variable
22	∞	0.78000	1.51680	64.2
23	∞	(BF)
Image surface	∞

TABLE III — (Various data) Zooming ratio 17.36563

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7524	33.0049	82.5290
F-number	2.91648	3.48271	4.34807
View angle	38.5456	6.2523	2.4721
Image height	3.6000	3.6000	3.6000
Overall length	73.9059	79.1817	89.0086
of lens system
BF	0.87587	0.87107	0.87851
d5	0.6000	26.5565	33.9577
d12	30.3658	3.5702	2.1000
d18	6.4260	6.1225	18.5502
d21	5.5741	11.9973	3.4581
Entrance pupil	18.0226	120.2230	262.6229
position
Exit pupil	−32.7172	−37.5269	95.6119
position
Front principal	22.1027	124.8587	417.0488
points position
Back principal	69.1534	46.1768	6.4796
points position

TABLE III — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	42.26228	1.15000	2.20000	24.0
2	29.58825	5.27660	1.49700	81.6
3	409.30698	0.15000
4	27.49451	3.87240	1.75375	48.2
5	73.18604	Variable
6	29.00749	0.70000	2.00000	40.0
7	8.51750	4.40000
8	−21.83943	0.80000	1.78385	43.7
9	13.18575	1.39670
10	18.56196	1.67600	1.99537	20.7
11*	−290.97026	Variable
12(Diaphragm)	∞	1.20000
13	8.73101	1.54910	1.70451	55.0
14	134.42539	1.91660
15*	10.87085	1.89830	1.73241	52.3
16	−9.41755	0.45000	1.74673	33.9
17	6.48549	Variable
18*	13.62788	2.50000	1.48700	70.4
19	−12.50777	0.45000	1.83294	27.9
20	−20.88993	Variable
21	∞	0.78000	1.51680	64.2
22	∞	(BF)
Image surface	∞

TABLE III — (Various data) Zooming ratio 17.35610

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7567	33.0001	82.5572
F-number	2.91683	3.47905	5.06796
View angle	38.5428	6.2844	2.4795
Image height	3.6000	3.6000	3.6000
Overall length	73.2152	73.7541	88.9890
of lens system
BF	0.87956	0.86395	0.85904
d5	0.6000	23.2693	28.7251
d11	29.5598	3.4821	2.4000
d17	5.7531	2.9568	23.3811
d20	6.2570	13.0162	3.4581
Entrance pupil	19.9956	117.0099	215.4939
position
Exit pupil	−28.0466	−26.4238	83.2517
position
Front principal	23.9701	110.1017	380.7733
points position
Back principal	68.4585	40.7539	6.4318
points position

TABLE III — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	47.40168	1.15000	2.20000	24.0
2	32.73210	4.60560	1.49700	81.6
3	1811.82817	0.15000
4	29.28012	3.25450	1.77209	45.3
5	73.51295	Variable
6	23.77851	0.70000	2.20000	24.0
7	9.42084	4.40000
8	−22.78173	0.80000	1.72500	54.0
9	13.93477	1.72500
10*	16.62157	2.14990	1.92286	20.9
11	−62.38542	0.45000	1.72500	54.0
12	60.02022	Variable
13(Diaphragm)	∞	1.20000
14	8.88082	1.65680	1.81328	37.1
15	227.60274	0.93430
16*	9.98408	2.13640	1.73182	52.5
17	−10.72168	0.45000	1.82217	27.4
18	5.77290	Variable
19*	12.46093	2.50000	1.49190	69.9
20	−13.24787	0.45000	1.84700	23.8
21	−20.44955	Variable
22	∞	0.78000	1.51680	64.2
23	∞	(BF)
Image surface	∞

TABLE III — (Various data) Zooming ratio 17.36185

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7532	33.0062	82.5250
F-number	2.91537	3.36011	4.67079
View angle	38.5791	6.3085	2.4788
Image height	3.6000	3.6000	3.6000
Overall length	73.9109	76.2516	89.0354
of lens system
BF	0.88092	0.87773	0.90550
d5	0.6000	25.8935	31.8378
d12	30.3595	3.6537	2.1000
d18	6.9274	4.6762	21.2415
d21	5.6506	11.6580	3.4581
Entrance pupil	19.1833	128.4786	242.8861
position
Exit pupil	−31.8559	−28.5804	72.2290
position
Front principal	23.2464	124.5032	420.8967
points position
Back principal	69.1577	43.2454	6.5104
points position

TABLE III — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	52.59842	1.15000	2.20000	24.0
2	34.47960	5.15820	1.49700	81.6
3	−352.90042	0.15000
4	29.63743	3.73150	1.75367	48.2
5	86.50685	Variable
6*	93.63364	1.40000	1.80470	41.0
7*	7.29761	4.40000
8	−18.62041	0.80000	1.72500	54.0
9	17.24130	0.98650
10	19.33656	1.45870	2.20000	24.0
11	−363.93562	0.55000	1.72500	54.0
12	151.08215	Variable
13(Diaphragm)	∞	1.20000
14	7.20848	1.92400	1.53675	65.6
15	361.36121	2.51630
16*	10.86800	1.95560	1.71566	49.0
17	−8.08887	0.44920	1.79373	34.4
18	7.66859	Variable
19*	11.95119	2.88740	1.49620	69.4
20	−13.35872	0.54980	1.84700	23.8
21	−21.36569	Variable
22	∞	0.78000	1.51680	64.2
23	∞	(BF)
Image surface	∞

TABLE III — (Various data) Zooming ratio 17.36759

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7520	32.9986	82.5303
F-number	2.91585	3.31180	4.44405
View angle	38.5721	6.2679	2.4663
Image height	3.6000	3.6000	3.6000
Overall length	73.6402	79.3682	89.0155
of lens system
BF	0.88071	0.87501	0.88538
d5	0.6000	25.1697	30.7096
d12	28.0698	4.0584	2.1000
d18	6.7990	6.1143	19.8152
d21	5.2435	11.1036	3.4581
Entrance pupil	18.8106	131.3413	248.3168
position
Exit pupil	−40.8957	−41.8915	67.8163
position
Front principal	23.0220	138.8782	432.6125
points position
Back principal	68.8882	46.3696	6.4851
points position

TABLE III — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	52.01477	1.15000	2.20000	24.0
2	33.82397	4.88700	1.49700	81.6
3	−974.87570	0.15000
4	30.09110	3.63300	1.77160	45.4
5	87.92091	Variable
6	24.93959	0.70000	2.00000	40.0
7	8.51943	4.25400
8	−18.76832	0.80000	2.00000	40.0
9	19.54481	1.44980
10*	24.04482	1.72800	1.99537	20.7
11	−51.31582	0.45000	1.49804	69.2
12	−55.39576	Variable
13(Diaphragm)	∞	1.20000
14	8.62229	1.67300	1.72630	53.7
15	227.60274	1.55540
16*	9.82918	2.04910	1.75148	48.6
17	−9.91647	0.65880	1.82007	32.2
18	5.88545	Variable
19*	12.29900	2.50000	1.48872	70.2
20	−14.71787	0.45000	1.82329	24.4
21	−22.92614	Variable
22	∞	0.78000	1.51680	64.2
23	∞	(BF)
Image surface	∞

TABLE III — (Various data) Zooming ratio 17.36516

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7536	33.0039	82.5469
F-number	2.91683	3.46510	4.56445
View angle	38.5704	6.2589	2.4724
Image height	3.6000	3.6000	3.6000
Overall length	73.9106	77.3048	88.6624
of lens system
BF	0.88083	0.87197	0.88744
d5	0.6000	25.4734	32.0380
d12	30.2400	3.6628	2.1000
d18	6.6650	5.1475	20.0598
d21	5.4567	12.0810	3.5091
Entrance pupil	18.8477	121.3455	245.7974
position
Exit pupil	−31.5429	−31.6131	90.5731
position
Front principal	22.9043	120.8183	404.3206
points position
Back principal	69.1570	44.3008	6.1156
points position

TABLE III — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	49.86175	1.15000	2.20000	24.0
2	33.58480	4.77490	1.49700	81.6
3	−1440.30841	0.15000
4	29.61518	3.44680	1.75740	47.6
5	80.22125	Variable
6	25.61075	0.70000	2.00000	40.0
7	8.56646	4.27940
8	−19.98111	0.80000	2.00000	40.0
9	18.92597	1.44940
10*	23.39905	1.73930	1.99537	20.7
11	−57.02638	0.30000
12	∞	Variable
13(Diaphragm)	∞	1.20000
14	8.66667	1.86200	1.74753	49.3
15	227.60274	0.98860
16*	10.56566	2.07070	1.77152	45.4
17	−10.79646	0.61100	1.80912	30.5
18	5.83639	Variable
19*	12.75563	2.50000	1.48700	70.4
20	−13.32082	0.45000	1.84700	23.8
21	−20.84567	Variable
22	∞	0.78000	1.51680	64.2
23	∞	(BF)
Image surface	∞

TABLE III — (Various data) Zooming ratio 17.36511

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.7535	33.0068	82.5448
F-number	2.91632	3.40741	4.58326
View angle	38.5729	6.2793	2.4761
Image height	3.6000	3.6000	3.6000
Overall length	73.9117	76.9123	88.5409
of lens system
BF	0.88178	0.87739	0.90246
d5	0.6000	25.7167	31.9840
d12	30.4225	3.7366	2.1000
d18	7.1164	5.2988	20.8442
d21	5.6389	12.0307	3.4581
Entrance pupil	18.8077	124.7143	244.6411
position
Exit pupil	−32.4442	−31.1059	91.2447
position
Front principal	22.8831	123.6580	402.6062
points position
Back principal	69.1582	43.9055	5.9961
points position

TABLE III — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	43.82438	1.15000	2.20000	24.0
2	31.02039	5.27900	1.49700	81.6
3	658.44950	0.15000
4	28.52422	3.61590	1.75034	48.7
5	68.48960	Variable
6	29.56473	0.70000	2.00000	40.0
7	8.61895	3.90870
8	−51.68615	0.80000	2.00000	40.0
9	11.64585	1.11860
10*	14.40520	1.99730	1.99537	20.7
11	499.61576	0.30000
12	∞	Variable
13(Diaphragm)	∞	1.20000
14	8.59978	1.74890	1.74441	49.9
15	227.60274	0.79490
16*	10.68361	2.20130	1.76720	46.0
17	−8.54791	0.52740	1.80467	31.9
18	5.91886	Variable
19*	13.47020	2.50000	1.49264	69.8
20	−13.34321	0.45000	1.83850	24.0
21	−19.19175	Variable
22	∞	0.78000	1.51680	64.2
23	∞	(BF)
Image surface	∞

TABLE III — (Various data) Zooming ratio 19.25092

	Wide-angle	Middle	Telephoto
limit	position	limit
Focal length	4.6667	30.0051	89.8390
F-number	2.91703	3.53914	4.75267
View angle	39.0420	6.9132	2.2857
Image height	3.6000	3.6000	3.6000
Overall length	71.0108	73.8911	88.8837
of lens system
BF	0.88090	0.87889	0.90694
d5	0.6000	24.2513	32.4604
d12	28.5134	4.2216	2.1880
d18	5.0635	2.2496	20.6447
d21	6.7310	13.0677	3.4617
Entrance pupil	19.4202	112.7683	269.9674
position
Exit pupil	−25.5549	−23.9178	75.6116
position
Front principal	23.2631	106.4658	467.8458
points position
Back principal	66.3441	43.8859	−0.9553
points position

TABLE III — (Corresponding values to conditions) Numerical Example

	Condition	III-1	III-2	III-3	III-4	III-5	III-6	III-7
(4)	nd 1 − nd 2	0.703	0.703	0.703	0.703	0.703	0.703	0.703
(5)	(nd 1 − 1) + (nd 3 − 1)	1.952	1.954	1.972	1.954	1.972	1.957	1.950
(1)	(f 4 · f W · tanω)/L W	0.114	0.122	0.114	0.114	0.116	0.117	0.119
(2)	f 3 /f 4	0.965	0.819	0.937	0.933	0.906	0.896	0.942
(3)	(nd 4 − 1) + (nd 6 − 1)	2.200	1.995	2.123	2.005	1.995	1.995	1.995
(8)	dG3/dG	0.213	0.206	0.188	0.228	0.211	0.203	0.194
(9)	(f 3 2 + f 4 2 )/\|f 2 \|	2.81	3.18	2.85	3.05	2.91	2.94	2.97
(III-10)	m 2T /m 34T	3.470	2.125	2.772	2.851	2.803	2.800	3.275
(11)	d1NG/d1G	0.1158	0.1101	0.1255	0.1129	0.1171	0.1208	0.1128
(12)	f W · tan(ω − ω 0 )	0.1163	0.1182	0.1194	0.1183	0.1189	0.1191	0.1136
(13)	f 4 /f T	0.226	0.257	0.229	0.226	0.234	0.239	0.210
(14)	\|M 1 /M 2 \|	0.730	0.713	0.659	0.816	0.687	0.661	0.860
(15)	\|M 3 /M 2 \|	0.484	0.669	0.529	0.596	0.533	0.523	0.594
(16)	(m 2T /m 2W )/(f T /f W )	0.550	0.418	0.480	0.518	0.493	0.490	0.511
(17)	m 3T /m 3W	1.504	1.942	1.726	1.648	1.725	1.715	1.457
(18)	(f 3 2 + f 4 2 )/(f W · tanω)	6.83	7.24	6.82	6.73	6.86	6.97	6.83
(19)	(L T − L W )/(f W · tanω)	3.99	4.16	3.99	4.06	3.89	3.86	4.72
(20)	(L T · f T )/f4(f W · tanω)	104.2	91.4	102.7	104.0	100.1	97.9	112.1
(21)	(L W · f T )/f 4 (f W · tanω)	86.5	75.2	85.2	86.0	83.5	81.7	89.5
(22)	f 3 /f W · tanω	4.75	4.59	4.67	4.59	4.61	4.65	4.68

TABLE IV — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	47.86281	1.15000	1.84666	23.8
2	33.24858	5.16480	1.49700	81.6
3	−658.43417	0.15000
4	31.59626	3.24500	1.62299	58.1
5	73.16804	Variable
6	62.19494	0.70000	1.90366	31.3
7	7.68819	4.30280
8*	−25.45386	0.80000	1.66547	55.2
9*	27.04745	0.98370
10	17.54224	2.11960	1.92286	20.9
11	−63.29959	0.55000	1.83481	42.7
12	63.67954	Variable
13(Diaphragm)	∞	1.20000
14	8.17821	1.54460	1.69680	55.5
15	50.15175	2.85270
16*	10.58685	1.58080	1.66547	55.2
17	−17.29764	0.44920	1.71736	29.5
18	6.92061	Variable
19*	14.42090	2.88740	1.60602	57.4
20	−11.35612	0.54980	1.68893	31.2
21	−38.87902	Variable
22	∞	0.78000	1.51680	64.2
23	∞	(BF)
Image surface	∞

TABLE IV — (Various data) Zooming ratio 17.66940

		Wide-angle	Middle	Telephoto
		limit	position	limit
	Focal length	4.7524	33.0032	83.9726
	F-number	2.91562	3.50436	4.37235
	View angle	38.5454	6.2547	2.4246
	Image height	3.6000	3.6000	3.6000
	Overall length	73.9020	81.0698	88.9967
	of lens system
	BF	0.87187	0.84904	0.86742
	d5	0.6000	26.3784	33.7301
	d12	29.6525	3.5682	1.2833
	d18	6.2287	7.7696	18.7938
	d21	5.5385	11.4942	3.3117
	Entrance pupil	18.9310	124.2208	262.3059
	position
	Exit pupil	−34.1059	−50.5829	101.4202
	position
	Front principal	23.0377	136.0463	416.4049
	points position
	Back principal	69.1495	48.0667	5.0241
	points position
Magnification of zoom lens unit
Lens	Initial	Wide-angle	Middle	Telephoto
unit	surface No.	limit	position	limit
1	1	0.00000	0.00000	0.00000
2	6	−0.24575	−0.80741	−2.31871
3	13	−0.66906	−3.13122	−1.03875
4	19	0.55668	0.25142	0.67148

TABLE IV — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	49.37395	1.15000	1.84666	23.8
2	30.08727	5.26460	1.49700	81.6
3	1248.31339	0.15000
4	26.60463	3.53600	1.76586	46.2
5	58.56231	Variable
6	29.85248	0.70000	2.00060	25.5
7	8.29795	4.27210
8*	−25.68526	0.80000	1.75605	47.8
9*	14.59270	1.59880
10	16.76461	1.94270	1.94595	18.0
11	−103.02313	0.45000	1.80800	40.8
12	77.76048	Variable
13(Diaphragm)	∞	1.20000
14	8.81557	1.68470	1.69600	48.5
15	−551.81799	1.85500
16*	10.46051	2.17960	1.67502	56.6
17	−8.55000	0.45000	1.74705	30.9
18	6.49452	Variable
19*	13.09103	2.50000	1.51357	67.7
20	−12.56166	0.45000	1.82925	29.2
21	−22.44559	Variable
22	∞	0.78000	1.51680	64.2
23	∞	(BF)
Image surface	∞

TABLE IV — (Various data) Zooming ratio 17.67150

		Wide-angle	Middle	Telephoto
		limit	position	limit
	Focal length	4.7526	33.0026	83.9848
	F-number	2.91908	3.31384	5.12330
	View angle	38.5676	6.3193	2.4326
	Image height	3.6000	3.6000	3.6000
	Overall length	73.9064	74.1462	89.0002
	of lens system
	BF	0.87620	0.87195	0.87010
	d5	0.6000	23.7546	28.3353
	d12	29.5571	3.7147	2.1000
	d18	6.7252	3.1728	23.7256
	d21	5.1844	11.6686	3.0057
	Entrance pupil	19.6512	126.1606	211.1312
	position
	Exit pupil	−32.3397	−25.8180	63.5563
	position
	Front principal	23.7238	118.3550	407.6359
	points position
	Back principal	69.1538	41.1436	5.0154
	points position
Magnification of zoom lens unit
Lens	Initial	Wide-angle	Middle	Telephoto
unit	surface No.	limit	position	limit
1	1	0.00000	0.00000	0.00000
2	6	−0.26292	−0.93147	−1.87436
3	13	−0.64138	−2.73265	−1.34499
4	19	0.60169	0.27681	0.71123

TABLE IV — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	45.32568	1.30000	1.84666	23.8
2	31.96732	6.00000	1.49700	81.6
3	−465.95760	0.15000
4	31.02235	3.20000	1.60311	60.7
5	70.61610	Variable
6	101.53090	0.70000	1.90366	31.3
7	7.86890	4.70000
8*	−20.55497	0.80000	1.66547	55.2
9*	31.47034	0.85000
10	20.42499	2.45000	1.92286	20.9
11	−33.42648	0.60000	1.83481	42.7
12	140.41630	Variable
13(Diaphragm)	∞	2.30000
14	8.34831	1.90000	1.69680	55.5
15	53.23219	2.25000
16*	10.01290	1.58000	1.66547	55.2
17	−22.10466	0.50000	1.71736	29.5
18	6.46268	Variable
19*	13.27992	3.80000	1.60602	57.4
20	−10.79685	0.60000	1.68893	31.2
21	−52.08229	Variable
22	∞	1.50000	1.51633	64.0
23	∞	(BF)
Image surface	∞

TABLE IV — (Various data) Zooming ratio 22.24156

		Wide-angle	Middle	Telephoto
		limit	position	limit
	Focal length	4.7300	32.3327	105.2017
	F-number	2.93911	3.38403	5.23447
	View angle	39.1735	6.3700	1.9176
	Image height	3.6000	3.6000	3.6000
	Overall length	77.0121	82.2972	96.7586
	of lens system
	BF	0.37000	0.36999	0.36998
	d5	0.6545	25.5975	32.6534
	d12	28.6039	3.0484	1.3091
	d18	6.5672	6.0613	26.5797
	d21	5.6364	12.0401	0.6665
	Entrance pupil	19.6238	126.0506	272.8794
	position
	Exit pupil	−38.6210	−42.0732	48.4452
	position
	Front principal	23.7800	133.7527	608.2910
	points position
	Back principal	72.2821	49.9646	−8.4431
	points position
Magnification of zoom lens unit
Lens	Initial	Wide-angle	Middle	Telephoto
unit	surface No.	limit	position	limit
1	1	0.00000	0.00000	0.00000
2	6	−0.24250	−0.80342	−2.32434
3	13	−0.73360	−3.92128	−1.15289
4	19	0.52565	0.20290	0.77615

TABLE IV — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	46.44500	1.30000	1.84666	23.8
2	32.72500	6.00000	1.49700	81.6
3	−982.64300	0.15000
4	31.73700	3.20000	1.60311	60.7
5	80.08200	Variable
6	67.96500	0.70000	1.90366	31.3
7	7.58200	4.70000
8*	−19.90900	0.80000	1.66547	55.2
9*	30.64300	0.85000
10	20.43900	2.45000	1.92286	20.9
11	−35.61000	0.60000	1.83481	42.7
12	205.15200	Variable
13(Diaphragm)	∞	2.30000
14	8.34800	1.90000	1.69680	55.5
15	53.88700	2.25000
16*	9.73700	1.58000	1.66547	55.2
17	−19.97400	0.50000	1.71736	29.5
18	6.45700	Variable
19*	13.57200	3.80000	1.60602	57.4
20	−11.07700	0.60000	1.68893	31.2
21	−48.33800	Variable
22	∞	1.50000	1.51633	64.0
23	∞	(BF)
Image surface	∞

TABLE IV — (Various data) Zooming ratio 16.56444

		Wide-angle	Middle	Telephoto
		limit	position	limit
	Focal length	4.5227	32.1468	74.9158
	F-number	2.67412	3.40666	4.20747
	View angle	40.1340	6.4020	2.7184
	Image height	3.6000	3.6000	3.6000
	Overall length	75.6478	82.5569	94.6221
	of lens system
	BF	4.61064	2.39245	4.30248
	d5	0.6545	25.5587	32.3597
	d12	28.4185	2.2206	1.3091
	d18	5.4751	7.2857	20.7204
	d21	1.3091	9.9194	0.7504
	Entrance pupil	19.4978	118.9789	242.2873
	position
	Exit pupil	−28.7952	−48.5941	77.6649
	position
	Front principal	23.4081	130.8573	393.7053
	points position
	Back principal	71.1252	50.4101	19.7062
	points position
Magnification of zoom lens unit
Lens	Initial	Wide-angle	Middle	Telephoto
unit	surface No.	limit	position	limit
1	1	0.00000	0.00000	0.00000
2	6	−0.24005	−0.75819	−1.84676
3	13	−0.69140	−3.95981	−1.37544
4	19	0.53187	0.20899	0.57566

TABLE IV — (Surface data)

Surface number	r	d	nd	vd
Object surface	∞	∞
1	54.67900	1.15000	1.84666	23.8
2	33.85830	5.33100	1.49700	81.6
3	−520.75630	0.14000
4	29.06920	3.40000	1.72916	54.7
5	69.94080	Variable
6*	205.67640	1.40000	1.80470	41.0
7*	7.60550	4.02000
8	−29.09410	0.80000	1.77250	49.6
9	13.88200	0.89110
10	14.69180	2.10000	1.92286	20.9
11	247.18480	Variable
12(Diaphragm)	∞	1.20000
13	6.84270	2.00000	1.49700	81.6
14	161.71140	2.60000
15*	12.86980	1.70000	1.74993	45.4
16	−12.17790	0.45000	1.80610	33.3
17	9.02040	Variable
18*	17.70450	2.60000	1.60602	57.4
19	−14.33780	0.55000	1.68893	31.2
20	−57.21160	Variable
21	−10.27770	0.95000	1.53116	56.0
22*	−6.68700	0.60000
23	∞	0.90000	1.51633	64.0
24	∞	(BF)
Image surface	∞

TABLE IV — (Various data) Zooming ratio 17.99125

		Wide-angle	Middle	Telephoto
		limit	position	limit
	Focal length	4.7492	26.3755	85.4432
	F-number	2.92218	3.78528	4.58117
	View angle	38.8061	7.5754	2.3477
	Image height	3.6000	3.6000	3.6000
	Overall length	72.8284	78.9426	90.7245
	of lens system
	BF	0.88377	0.82371	0.81765
	d5	0.4000	20.5746	30.2663
	d11	27.7989	6.0791	2.0000
	d17	4.6967	4.7259	20.5759
	d20	6.2669	13.9571	4.2825
	Entrance pupil	18.4983	89.1638	241.3789
	position
	Exit pupil	−117.9857	2018.0953	31.6340
	position
	Front principal	23.0577	115.8841	563.7262
	points position
	Back principal	68.0793	52.5671	5.2813
	points position
Magnification of zoom lens unit
Lens	Initial	Wide-angle	Middle	Telephoto
unit	surface No.	limit	position	limit
1	1	0.00000	0.00000	0.00000
2	6	−0.24154	−0.60078	−2.10398
3	12	−0.73957	−3.49902	−1.33427
4	18	0.57716	0.27188	0.65940
5	21	0.96913	0.97095	0.97113

TABLE IV — (Corresponding values to conditions) INDUSTRIAL APPLICABILITY Numerical Example

	Condition	IV-1	IV-2	IV-3	IV-4	IV-5
(IV-10)	m 2T /m 34T	3.470	1.964	2.598	2.332	2.457
(1)	(f 4 · f W · tanω)/L W	0.114	0.118	0.114	0.110	0.134
(2)	f 3 /f 4	0.965	0.848	0.941	0.917	0.704
(3)	(nd 4 − 1) + (nd 6 − 1)	2.200	1.947	1.827	1.827	1.728
(4)	nd 1 − nd 2	0.703	0.350	0.350	0.350	0.350
(5)	(nd 1 − 1) + (nd 3 − 1)	1.952	1.613	1.450	1.450	1.576
(8)	dG3/dG	0.213	0.213	0.199	0.199	0.243
(9)	(f 3 2 + f 4 2 )/\|f 2 \|	2.81	3.08	3.15	3.07	3.750
(11)	d1NG/d1G	0.11581	0.11385	0.12207	0.12207	0.11464
(12)	f W · tan(ω − ω 0 )	0.1163	0.1182	0.1568	0.1275	0.1376
(13)	f 4 /f T	0.226	0.237	0.189	0.264	0.292
(14)	\|M 1 /M 2 \|	0.730	1.194	1.005	1.490	1.269
(15)	\|M 3 /M 2 \|	0.484	1.172	0.765	1.129	0.980
(16)	(m 2T /m 2W )/(f T /f W )	0.550	0.404	0.431	0.464	0.483
(17)	m 3T /m 3W	1.504	2.093	1.572	1.990	1.802
(18)	(f 3 2 + f 4 2 )/(f W · tanω)	6.83	6.90	7.07	7.04	8.00
(19)	(L T − L W )/(f W · tanω)	3.99	3.98	5.12	4.98	4.70
(20)	(L T · f T )/f4(f W · tanω)	104.2	98.9	133.1	97.2	81.5
(21)	(L W · f T )/f 4 (f W · tanω)	86.5	82.1	106.0	78.3	65.4
(22)	f 3 /f W · tanω	4.75	4.46	4.85	4.76	4.60

Claims as granted

4 claims

Classifications

4 codes

IPC · International Patent Classification

Section H — Electricity

H04N5/225

USPC · US Patent Classification

348/335348/240.99348/360

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Tuan Ho

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