Wide-conversion lens

1. Technical Field

The disclosure relates to a lens system and, particularly, to a wide-conversion lens having a small number of lens components and a short overall length.

2. Description of Related Art

A short overall length is demanded for use in wide-conversion lens for image acquisition. The wide-conversion lens is mounted in relatively thin equipment, such as simple digital cameras, webcams for personal computers, and portable imaging systems in general. In order to satisfy this demand of compact wide-conversion lens, conventional wide-conversion lens reduce the number of lenses to shorten the overall length, but this will decrease the resolution. Increasing the number of lenses can increase resolution, but will also increase the overall length of the wide-conversion lens.

What is needed, therefore, is a wide-conversion lens to overcome the limitations described above.

Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure.

FIG. 1 is a schematic view of a wide-conversion lens of the present disclosure.

FIG. 2 is a graph showing characteristic curves of axes spherical aberration of the wide-conversion lens of FIG. 1 in accordance with a first embodiment.

FIG. 3 is a graph showing characteristic curves of vertical axes spherical aberration of the wide-conversion lens of FIG. 1 in accordance with the first embodiment.

FIG. 4 is a graph showing characteristic curves of axial spherical aberration of the wide-conversion lens of FIG. 1 in accordance with a second embodiment.

FIG. 5 is a graph showing characteristic curves of vertical axial spherical aberration of the wide-conversion lens of FIG. 1 in accordance with the second embodiment.

Embodiments of the disclosure will now be described in detail below, with reference to the accompanying drawings.

FIG. 1 , is a wide-conversion lens 100 including, in order from the object-side to the image-side, a first lens L 1 with negative refraction power, a second lens L 2 with negative refraction power, a third lens L 3 with positive refraction power, a fourth lens L 4 with positive refraction power, and a fifth lens L 5 with negative refraction power. In the embodiment, a total length of the wide-conversion lens 100 is 43.7 mm, and a zoom magnification is 0.66.

The first lens L 1 is glass lens having biconcave shape. The first lens L 1 includes, in order from the object-side to the image-side of the wide-conversion lens 100 , a first surface S 1 facing the object side and a second surface S 2 facing the image side.

The second lens L 2 is glass lens having biconcave shape. The second lens L 2 includes, in order from the object-side to the image-side of the wide-conversion lens 100 , a third surface S 3 facing the object side and a fourth surface S 4 facing the image side.

The third lens L 3 and the second lens L 2 are attached together to form a single unit. The third lens L 3 is glass lens having biconvex shape. The third lens L 3 includes, in order from the object-side to the image-side of the wide-conversion lens 100 , the fourth surface S 4 and a fifth surface S 5 facing the image side.

The fourth lens L 4 is glass lens having biconvex shape. The fourth lens L 4 includes, in order from the object-side to the image-side of the wide-conversion lens 100 , a sixth surface S 6 and a seventh surface S 7 facing the image side.

The fifth lens L 5 and the fourth lens L 4 are attached together to form a single unit. The fifth lens L 5 is glass lens having meniscus shape. The fifth lens L 5 includes, in order from the object-side to the image-side of the wide-conversion lens 100 , the seventh surface S 7 and a convex eighth surface S 8 facing the image side.

In order to obtain low distortion, good imaging quality, a compact configuration, and wide angle view, the wide-conversion lens 100 satisfies the following conditions:

R 1<0;  (1)

V d 2 −V d1 ≧19;  (2)

V d2 −V d3 ≧35;  (3)

wherein, R1 is the curvature radius of the first surface S 1 of the first lens L 1 ; V d1 is the Abbe number of the first lens L 1 ; V d2 is the Abbe number of the second lens L 2 ; V d3 is the Abbe number of the third lens L 3 .

The conditions (1)-(3) can favorably limit the relation between the focal length of every lens group and the focal length of the lens system 100 to obtain a high resolution. When the conditions V d 2 −V d1 ≧19 and V d2 −V d3 ≧35 are met, chromatic aberrations are effectively reduced and imaging performance is improved.

In one embodiment, the wide-conversion lens 100 further satisfies the following condition:

0.5 ≦f 1 /f 2 ≦1;  (4)

wherein, f 1 is a focal length of the first lens L 1 ; f 2 is a focal length of the second lens L 2 . The condition (4) can reduce the aberration of the field curvature and spherical aberration in the wide-conversion lens 100 .

In the embodiment, the first, second, third, fourth, fifth, sixth, seventh, eighth surfaces S 1 , S 2 , S 3 , S 4 , S 5 , S 6 , S 7 and S 8 all are spherical.

Example diagrams of the wide-conversion lens 100 will be described below with reference to FIGS. 2-5 . The disclosure is not limited to these examples. The following are symbols used in each exemplary embodiment.

ri: radius of curvature of the surface Si;

Di: distance between surfaces on the optical axis of the surface Si and the surface Si+1;

Ni: refractive index of the surface Si;

Vi: Abbe constant of the surface Si; and

Table 1 shows the specifications of a first embodiment of the wide-conversion lens 100 .

In the embodiment, the focal length f 1 of the first lens L 1 is −58.6 mm, the focal length f 2 of the second lens L 2 is −75.78 mm.

FIGS. 2-3 , are graphs of aberration (spherical aberration) of the wide-conversion lens 100 . In FIG. 2 , curves are spherical aberration characteristic curves of a1 light (wavelength: 436 nm), a2 light (wavelength: 486 nm), a3 light (wavelength: 546 nm), a4 light (wavelength: 588 nm), and a5 light (wavelength: 588 nm) of the lens system 100 . The axes spherical aberration of wide-conversion lens 100 of the first exemplary embodiment is from −0.002 mm to 0.002 mm. As illustrated in FIG. 3 , the vertical axes spherical aberration of wide-conversion lens 100 of the first exemplary embodiment is from −0.005 mm to 0.005 mm.

Aberrations occurring in the wide-conversion lens 100 are controlled/corrected to an acceptable level, and changes in aberrations are reduced to acceptable levels as well, accordingly, a high resolution of the wide-conversion lens 100 is obtained, and wide angle view of the wide-conversion lens 100 is also obtained.

Table 2 shows the specifications of a second embodiment of the wide-conversion lens 100 .

In the embodiment, the focal length f 1 of the first lens L 1 is −66.52 mm, the focal length f 2 of the second lens L 2 is −87.05 mm.

FIGS. 4-5 , are graphs of aberration (spherical aberration) of the wide-conversion lens 100 . In FIG. 4 , curves are spherical aberration characteristic curves of a1 light (wavelength: 436 nm), a2 light (wavelength: 486 nm), a3 light (wavelength: 546 nm), a4 light (wavelength: 588 nm), and a5 light (wavelength: 588 nm) of the lens system 100 . The axes spherical aberration of wide-conversion lens 100 of the second exemplary embodiment is from −0.002 mm to 0.002 mm. As illustrated in FIG. 5 , the vertical axes spherical aberration of wide-conversion lens 100 of the second exemplary embodiment is from −0.005 mm to 0.005 mm.

While certain embodiments have been described and exemplified above, various other embodiments will be apparent to those skilled in the art from the foregoing disclosure. The disclosure is not limited to the particular embodiments described and exemplified, and the embodiments are capable of considerable variation and modification without departure from the scope of the appended claims.