Image capture lens and image capture apparatus

Next, a first example (Example 1-1)of the image capture lens 10 according to the embodiment will now be described with reference to FIGS. 3A to 6 C.

FIGS. 3A and 3B are tables of an image capture lens 10 - 1 using specific values according to Example 1-1. In FIG. 3A, a surface number Si denotes the sequence of lens surfaces from the object side. With regard to the refractive index and the Abbe number, values at d-line (wavelength λ=587.6 nm) are shown. The ‘r i ’ represents radius of curvature of the ‘i’th lens surface from the object side similar to the ‘r i ’ shown in FIG. 2 . Similar to the ‘d i ’ as in FIG. 2, the ‘d i ’ represents surface separation between the ‘i’th lens surface S i and the [i+1]th lens surface S i +1 from the object side on the optical axis. The radius of curvature ‘r i ’ and the surface separation ‘d i ’ are expressed in millimeter (mm).

FIG. 3B shows values for the object distance and the image distance at three typical imaging magnification (−0.6×, −1.0× and −1.6×) of the image capture lens 10 - 1 . The object distance d 0 denotes a distance from an object point to a first lens surface S 1 on the optical axis, while the image distance d 15 denotes a distance from a last lens surface S 15 to an image point on the optical axis.

FIG. 4 shows values corresponding to the conditional expressions (1) to (5). With reference to FIG. 3A, in the image capture lens 10 - 1 according to Example 1-1, with respect to the positive lens L 3 in the third lens Group G 3 , the Abbe number ν 3 at d-line is 71.3; the relative partial dispersion θ 3 is 1.243; and the anomalous dispersion δ 3 is 0.0263, which satisfies the conditional expression (1). With respect to the positive lens L 6 in the fourth lens group G 4 , the Abbe number ν 6 at d-line is 71.3; the relative partial dispersion θ 6 is 1.243; and the anomalous dispersion δ 6 is 0.0263, which satisfies the conditional expression (2).

In the image capture lens 10 - 1 , the value for φ 3 *δθ 3 +φ 6 *δθ 6 is 0.122, which satisfies the conditional expression (3). The value for (n 3 *ν 4 )/(n 4 *ν 3 ) is 0.96, which satisfies the conditional expression (4). The value for φT 2 /(φ 3,4 *φ 5,6 ) is ″0.49, which satisfies the conditional expression (5).

FIGS. 5A to 5 C are aberration charts of spherical aberration, astigmatism, distortion and chromatic aberration of magnification at each magnification in the image capture lens 10 - 1 . FIGS. 5A, 5 B and 5 C show aberrations at imaging magnification of −0.6×, −1.0× and −1.6×, respectively. FIGS. 5A to 5 C also show effective F number (Fno) at each magnification. FIGS. 6A to 6 C show coma at each imaging magnification in the image capture lens 10 - 1 . FIGS. 6A, 6 B and 6 C show coma at magnification of −0.6×, −1.0× and −1.6×, respectively. In these aberration charts, ‘H’ represents image height and ‘R’, ‘G’ and ‘B’ represent red, green and blue, respectively. In these aberration charts, C-line, d-line and F-line represent R (red), G (green) and B (blue), respectively. In the aberration charts showing astigmatism, ‘S’ represents the sagittal image surface and ‘T’ represents the meridional (tangential) image surface. Coma of green is shown in the aberration charts of coma.

As apparent from these aberration charts and values for the conditions as in FIG. 4, in the image capture lens 10 - 1 of Example 1-1, various kinds of aberrations are preferably corrected all the area from the center to peripheries of the image at each magnification, thereby exhibiting preferable optical performance suitable for capturing images.

With reference to FIGS. 7 to 11 C, a second example (Example 1-2) of the image capture lens 10 of the embodiment will be described herein below.

FIGS. 8A and 8B are tables of an image capture lens 10 - 2 using specific values according to Example 1-2. FIG. 7 is illustrated corresponding to the values for elements of the image capture lens 10 - 2 as in FIGS. 8A and 8B. Symbols in FIG. 7 and FIGS. 8A and 8B represent the same as those in FIG. 2 and FIGS. 3A and 3B.

FIG. 8B shows values for the object distance and the image distance at three typical imaging magnification (−0.6×, −1.0× and −1.8×) of the image capture lens 10 - 2 . The object distance d 0 denotes a distance from an object point to a first lens surface S 1 on the optical axis, while the image distance d 15 denotes a distance from a last lens surface S 15 to an image point on the optical axis.

FIG. 9 shows values corresponding to the conditional expressions (1) to (5). With reference to FIG. 8A, in the image capture lens 10 - 2 according to Example 1-2, with respect to the positive lens L 3 in the third lens Group G 3 , the Abbe number ν 3 at d-line is 71.3; the relative partial dispersion θ 3 is 1.243; and the anomalous dispersion δ 3 is 0.0263, which satisfies the conditional expression (1). With respect to the positive lens L 6 in the fourth lens group G 4 , the Abbe number ν 6 at d-line is 71.3; the relative partial dispersion θ 6 is 1.243; and the anomalous dispersion δ 6 is 0.0263, which satisfies the conditional expression (2).

In the image capture lens 10 - 2 , the value for φ 3 *δθ 3 +φ 6 *δθ 6 is 0.119, which satisfies the conditional expression (3). The value for (n 3 * ν 4 )/(n 4 *ν 3 ) is 0.86, which satisfies the conditional expression (4). The value for φ T 2 /(φ 3,4 *φ 5,6 ) is −5.29, which satisfies the conditional expression (5).

FIGS. 10A to 10 C are aberration charts of spherical aberration, astigmatism, distortion and chromatic aberration of magnification at each imaging magnification in the image capture lens 10 - 2 . FIGS. 10A, 10 B and 10 C show aberrations at imaging magnification of −0.6×, −1.0× and −1.8×, respectively. FIGS. 10A to 10 C also show effective F number (Fno) at each imaging magnification. FIGS. 11A to 11 C show coma at each magnification in the image capture lens 10 - 2 . FIGS. 11A, 11 B and 11 C show coma at magnification of −0.6×, −1.0× and −1.8×, respectively. Symbols in these aberration charts represent the same as those in FIGS. 5A to 5 C and 6 A to 6 C.

As apparent from these aberration charts and values for the conditions as in FIG. 9, in the image capture lens 10 - 2 of Example 1-2, various kinds of aberrations are preferably corrected all the area from the center to peripheries of the image at each magnification, thereby exhibiting preferable optical performance suitable for capturing images.

With reference to FIGS. 12 to 16 C, a third example (Example 1-3) of the image capture lens 10 of the embodiment will be described herein below.

FIGS. 13A and 13B are tables of an image capture lens 10 - 3 using specific values according to Example 1-3. FIG. 12 is illustrated corresponding to the values for elements of the image capture lens 10 - 3 of the Example 1-3 as in FIGS. 13A and 13B. Symbols in FIG. 12 and FIGS. 13A and 13B represent the same as those in FIG. 2 and FIGS. 3A and 3B.

FIG. 13B shows values for the object distance and the image distance at three typical imaging magnification (−0.6×,−1.0× and −1.6×) of the image capture lens 10 - 3 . The object distance d 0 denotes a distance from an object point to a first lens surface S 1 on the optical axis, while the image distance d 15 denotes a distance from a last lens surface S 15 to an image point on the optical axis.

FIG. 14 shows values corresponding to the conditional expressions (1) to (5). With reference to FIG. 13A, in the image capture lens 10 - 3 according to Example 1-3, with respect to the positive lens L 3 in the third lens group G 3 , the Abbe number ν 3 at d-line is 81.6; the relative partial dispersion θ 3 is 1.232; and the anomalous dispersion δ 3 is 0.0367, which satisfies the conditional expression (1). With respect to the positive lens L 6 in the fourth lens group G 4 , the Abbe number ν 6 at d-line is 71.3; the relative partial dispersion θ 6 is 1.234; and the anomalous dispersion δ 6 is 0.263, which satisfies the conditional expression (2).

In the image capture lens 10 - 3 , the value for φ 3 *δθ 3 +*φ 6 is 0.146, which satisfies the conditional expression (3). The value for (n 3 *ν 4 )/(n 4 *ν 3 ) is 0.80, which satisfies the conditional expression (4). The value for φ T 2 /(φ 3,4 *φ 5,6 ) is −0.51, which satisfies the conditional expression (5).

FIGS. 15A to 15 C are aberration charts of spherical aberration, astigmatism, distortion and chromatic aberration of magnification at each imaging magnification in the image capture lens 10 - 3 . FIGS. 15A, 15 B and 15 C show aberrations at imaging magnification of −0.6×, −1.0× and −1.6×, respectively. FIGS. 15A to 15 C also show effective F number (Fno) at each magnification. FIGS. 16A to 16 C show coma at each imaging magnification in the image capture lens 10 - 3 . FIGS. 16A, 16 B and 16 C show coma at magnification of −0.6×, −1.0× and −1.6×, respectively. Symbols in these aberration charts represent the same as those in FIGS. 5A to 5 C and 6 A to 6 C.

As apparent from these aberration charts and values for the conditions as in FIG. 14, in the image capture lens 10 - 3 of Example 1-3, various kinds of aberrations are preferably corrected all the area from the center to peripheries of the image at each magnification, thereby exhibiting optical performance suitable for capturing images.

Second Embodiment

A second embodiment of the present invention will now be described herein below. The same elements as those of the first embodiment are indicated by the same reference numerals and the description is appropriately omitted.

FIG. 17 is a schematic diagram of the configuration of the image capture lens 20 according to the second embodiment showing each lens element in cross section within a single plane including an optical axis O.

Similar to the image capture lens 10 of the first embodiment, the image capture lens 20 of the second embodiment is applicable to the readout optical system of the image capture apparatus 1 as in FIG. 1 . In the image capture lens 20 successively from the object side provided are a first lens group G 1 including a negative meniscus lens L 1 ,a second lens group G 2 including a positive lens L 2 directing its convex to the object side, a third lens group G 3 including a cemented lens which is composed of a bi-convex positive lens L 3 and a bi-concave negative lens L 4 , the cemented lens having positive refractive power with its convex facing the object side, a fourth lens group G 4 including a cemented lens which is composed of a bi-concave negative lens L 5 and a bi-convex positive lens L 6 , the cemented lens having positive refractive power with its convex facing the image side, a fifth lens group G 5 including a positive lens L 7 directing its convex to the image side and a sixth lens group G 6 including a negative lens L 8 directing a surface thereof whose radius of curvature is small to the objective side.

In addition to these lens groups, the image capture lens 20 further comprises a seventh lens group G 7 including a negative meniscus lens L 9 and a positive lens L 10 . The seventh lens group G 7 is provided on the image side relative to the sixth lens group G 6 . In the seventh lens group G 7 , the meniscus lens L 9 and the positive lens L 10 constitute a cemented lens directing its convex to the object side. Alternatively, the meniscus lens L 9 and the positive lens L 10 may be constituted having a clearance therebetween. Further, in the embodiment, the positive lens L 10 has a meniscus shape directing its convex to the object side as in FIG. 17 but may have a bi-convex shape as shown in Example 2-2 to be described later.

In the embodiment, as shown in FIG. 17 the concave of the negative meniscus lens L 1 in the first lens group G 1 faces the object side, for example. The positive lens L 2 in the second lens group L 2 has a bi-convex shape, for example. The positive lens L 7 in the fifth lens group G 5 has a plano-concave shape, for example. The negative lens L 8 in the sixth lens group G 6 has a meniscus shape, directing its concave to the object side. However, shapes of the lens element are not limited to those illustrated in FIG. 17 . For example, the negative meniscus lens L 1 in the first lens group G 1 have not only a shape such that its concave faces the object side but also the lens L 1 have a shape such that its convex faces the object side as shown in Example 2-2 to be described later. For example, the negative lens L 8 in the sixth lens group G 6 takes not only a meniscus shape but also a bi-concave shape as shown in Example 2-2 to be described later.

Similar to the image capture lens 10 of the first embodiment, preferably the image capture lens 20 of the second embodiment satisfies the conditional expressions (1) to (3). The action and effect brought by satisfying the conditional expressions (1) to (3) are similar to those of the first embodiment.

When ‘ν 9 ’ and ‘ν 10 ’ are the Abbe number at d-line of the negative meniscus lens L 9 and the positive lens L 10 in the seventh lens group G 7 and ‘r 16 ’, ‘r 17 ’ and ‘r 18 ’ are the radius of curvature of lens surfaces of the seventh lens group G 7 from the object side, preferably the image capture lens 20 of the second embodiment satisfies the following conditional expressions (6) to (8). ‘  T ’ in the conditional expression (7) represents the refractive power of the entire lens system including all lens groups.

−0.2<r 16 /r 18 <1.2  (6)

0.35<φ T *r 17 <1.2  (7)

13<ν 9 −ν 10   (8)

The conditional expression (6) provides a condition for preferably correcting curvature of field or coma in a part where field angle is large. In the image capture lens 20 , if a radius of curvature r 16 of a 16th surface becomes large, exceeding the upper limit of the conditional expression (6), a change of an incident angle of a light entering the 16th surface relative to a change of a field angle becomes small, resulting in reducing the effect of correcting curvature of field. If a radius of curvature r 18 of an 18th surface becomes small, exceeding the conditional expression (6), astigmatism or coma flare at peripheries of a flux becomes large. Therefore, it is difficult to perform preferable correction of aberrations which is necessary for obtaining high resolution. If the refractive power of the concave becomes large in the seventh lens group G 7 , exceeding the lower limit of the conditional expression (6), correction to the curvature of field is difficult.

The conditional expression (7) defines the condition for effectively correcting aberration off the optical axis. In the case where the seventh lens group G 7 constitutes the cemented lens, by defining the radius of curvature r 17 of the cemented surface within the range of the conditional expression (7), an influence on correction of the axial aberrations, particularly, spherical aberration is suppressed as well as aberration off the optical axis can be corrected.

The conditional expression (8) defines a condition on the correction of chromatic aberration of magnification. With respect to lenses L 9 and L 10 in the seventh lens group G 7 , by selecting a glass material so as to satisfy the conditional expression (8), obtained is a combination of the Abbe number of the convex lens and the Abbe number of the concave lens with which excess correction of chromatic aberration of magnification is achromatized, the excess correction of chromatic aberration of magnification occurring due to intensive correction of the axial chromatic aberration in the third lens group G 3 and the fourth lens group G 4 .

Similar to the image capture lens 10 according to the first embodiment, the image capture lens 20 of the second embodiment constituted as described above exhibits optical performance such that color images provided by an original such as a negative film or positive film are captured by scaling them up or down crossing over the magnification of the actual size, for example. More specifically, in the image capture lens 20 of the second embodiment, auxiliary lens elements such as the lens L 8 with negative power are added to the Gauss lens system. Thus, with the use of the lens material with high anomalous dispersion, each lens has moderate refractive power, so that bright optical performance in which various aberrations are preferably corrected over a wide magnification range, e.g., −0.6× to −1.6× is obtained. Scaling is performed in a manner that the entire lens system is shifted in accordance with the magnification, thereby changing object distance or image distance, for example.

As has been described in the image capture lens 20 according to the embodiment, optical performance suitable for capturing images is obtained, similar to the image capture lens 10 of the first embodiment.

Next, a first example (Example 2-1)of the image capture lens 20 according to the embodiment will now be described with reference to FIGS. 18A to 21 C.

FIGS. 18A and 18B are tables of an image capture lens 20 - 1 using specific values according to Example 2-1. Symbols used in FIGS. 18A and 18B represent the same as those used in FIGS. 3A and 3B.

FIG. 18B shows values for the object distance and the image distance at three typical imaging magnification (−0.6×, −1.0× and −1.6×) of the image capture lens 20 - 1 . The object distance d 0 denotes a distance from an object point to a first lens surface S 1 on the optical axis, while the image distance d 18 denotes a distance from a last lens surface S 18 to an image point on the optical axis.

FIG. 19 shows values corresponding to the conditional expressions (1) to (3) and (6) to (8). With reference to FIG. 18A, in the image capture lens 20 - 1 of Example 2-1, with respect to the positive lens L 3 in the third lens group G 3 , the Abbe number ν 3 at d-line is 71.3; the relative partial dispersion θ 3 is 1.243; and the anomalous dispersion δ 3 is 0.0263, which satisfies the conditional expression (1). With respect to the positive lens L 6 in the fourth lens group G 4 , the Abbe number ν 6 at d-line is 71.3; the relative partial dispersion θ 6 is 1.243; and the anomalous dispersion δ 6 is 0.0263, which satisfies the conditional expression (2).

In the image capture lens 20 - 1 , the value for φ 3 *δθ 3 +φ 6 *δθ 6 is 0.124, which satisfies the conditional expression (3). The value for r 16 /r 18 is 1.12, which satisfies the conditional expression (6). The value for φ T *r 17 is 0.45, which satisfies the conditional expression (7). The value for ν 9 −ν 10 is 21.0, which satisfies the conditional expression (8).

FIGS. 20A to 20 C are aberration charts of spherical aberration, astigmatism, distortion and chromatic aberration of magnification at each imaging magnification in the image capture lens 20 - 1 . FIGS. 21A, 21 B and 21 C show aberrations at imaging magnification of −0.6×, −1.0× and −1.6×, respectively. FIGS. 20A to 20 C also show effective F number (Fno) at each magnification. FIGS. 21A to 21 C show coma at each imaging magnification in the image capture lens 20 - 1 . FIGS. 21A, 21 B and 21 C show coma at magnification of −0.6×, −1.0× and −1.6×, respectively. Symbols in these aberration charts represent the same in FIGS. 5A to 5 C and 6 A to 6 C.

As apparent from these aberration charts and values for the conditions as in FIG. 19, in the image capture lens 20 - 1 of Example 2-1, various kinds of aberrations are preferably corrected all the area from the center to peripheries of the image at each magnification, thereby exhibiting preferable optical performance suitable for capturing images.

With reference to FIGS. 22 to 26 C, a second example (Example 2-2) of the image capture lens 20 of the embodiment will be described herein below.

FIGS. 23A and 23B are tables of an image capture lens 20 - 2 using specific values according to Example 2-2. FIG. 22 is illustrated corresponding to the values for elements of the image capture lens 20 - 2 as in FIGS. 23A and 23B. Symbols in FIG. 22 and FIGS. 23A and 23B represent the same as those in FIG. 2 and FIGS. 3A and 3B.

FIG. 23B shows values for the object distance and the image distance at three typical imaging magnification (−0.6×, −1.0× and −1.6×) of the image capture lens 20 - 2 . The object distance d 0 denotes a distance from an object point to a first lens surface S 1 on the optical axis, while the image distance d 18 denotes a distance from a last lens surface S 18 to an image point on the optical axis.

FIG. 24 shows values corresponding to the conditional expressions (1) to (3) and (6) to (8). With reference to FIG. 23A, in the image capture lens 20 - 2 of Example 2-2, with respect to the positive lens L 3 in the third lens group G 3 , the Abbe number ν 3 at d-line is 71.3; the relative partial dispersion θ 3 is 1.243; and the anomalous dispersion δ 3 is 0.0263, which satisfies the conditional expression (1). With respect to the positive lens L 6 in the fourth lens group G 4 , the Abbe number ν 6 at d-line is 71.3; the relative partial dispersion θ 6 is 1.243; and the anomalous dispersion δ 6 is 0.0263, which satisfies the conditional expression (2).

In the image capture lens 20 - 2 , the value for φ 3 *δθ 3 +φ 6 *δθ 6 is 0.135, which satisfies the conditional expression (3). The value for r 16 /r 18 is −0.10, which satisfies the conditional expression (6). The value for φ T *r 17 is 1.09, which satisfies the conditional expression (7). The value for ν 9 −ν 10 is 13.8, which satisfies the conditional expression (8).

FIGS. 25A to 25 C are aberration charts of spherical aberration, astigmatism, distortion and chromatic aberration of magnification at each imaging magnification in the image capture lens 20 - 2 . FIGS. 25A, 25 B and 25 C show aberrations at magnification of −0.6×, −1.0× and −1.6×, respectively. FIGS. 25A to 25 C also show effective F number (Fno) at each magnification. FIGS. 26A to 26 C show coma at each imaging magnification in the image capture lens 20 - 2 . FIGS. 26A, 26 B and 26 C show coma at magnification of −0.6×, −1.0× and −1.6×, respectively. Symbols in these aberration charts represent the same as those in FIGS. 5A to 5 C and 6 A to 6 C.

As apparent from these aberration charts and values for the conditions as in FIG. 24, in the image capture lens 20 - 2 of Example 2-2, various kinds of aberrations are preferably corrected all the area from the center to peripheries of the image at each magnification, thereby exhibiting preferable optical performance suitable for capturing images.

The present invention is not limited to the above embodiments and various modifications are possible. For example, values of each lens element such as the radius of curvature r, the surface separation d, the refractive index n and the Abbe number ν are not limited to the values shown in the above examples and may take other values.

According to the image capture lens of the invention, successively from an object side provided are a first lens group including a negative meniscus lens; a second lens group including a positive lens directing its convex to the object side; a third lens group including a first cemented lens composed of a bi-convex positive lens and a bi-concave negative lens, the first cemented lens having positive refractive power and directing its convex to the object side; a fourth lens group including a second cemented lens composed of a bi-concave negative lens and a bi-convex positive lens, the second cemented lens having negative refractive power and directing its convex to an image side; a fifth lens group including a positive lens directing its convex to the image side; and a sixth lens group including a negative lens directing its concave to the object side. Thus, various kinds of aberrations are corrected and optical performance suitable for capturing images is obtained.

According to the image capture lens of another aspect of the invention, successively from an object side provided are a first lens group including a negative meniscus lens; a second lens group including a positive lens directing its convex to the object side; a third lens group including a first cemented lens composed of a bi-convex positive lens and a bi-concave negative lens, the first cemented lens having positive refractive power and directing its convex to an image side; a fourth lens group including a second cemented lens composed of a bi-concave negative lens and a bi-convex positive lens, the second cemented lens directing its convex to the image side; a fifth lens group including a positive lens directing its convex to the image side; a sixth lens group including a negative lens directing a surface thereof to the object side, a radius of the surface being smaller than that of an opposite surface; and a seventh lens group including a negative meniscus lens and a positive lens. Thus, various kinds of aberrations are corrected and high-quality images are read.

According to the image capture lens of still another aspect of the invention, 0.09<(φ 3 *δθ 3 +φ 6 *δθ 6 )/φ T <0.15 is satisfied when the φ 3 and the δθ 3 represent refractive power and anomalous dispersion of the positive lens in the third lens group, respectively, the φ 6 and the δθ 6 represent refractive power and anomalous dispersion of the positive lens in the fourth lens group, respectively, and the φ T represents refractive power of an entire lens system including all the lens groups, for example. Thus, the third lens group and the fourth lens group have moderate refractive power with the use of a lens material having large anomalous dispersion. Accordingly, chromatic aberration is preferably corrected in particular.

According to the image capture apparatus of the invention, in the image capture lens successively from an object side provided are a first lens group including a negative meniscus lens; a second lens group including a positive lens directing its convex to the object side; a third lens group including a first cemented lens composed of a bi-convex positive lens and a bi-concave negative lens, the first cemented lens having positive refractive power and directing its convex to an image side; a fourth lens group including a second cemented lens composed of a bi-concave negative lens and a bi-convex positive lens, the second cemented lens having negative refractive power and directing its convex to the image side; a fifth lens group including a positive lens directing its convex to the image side; and a sixth lens group including a negative lens directing its concave to the object side. Thus, in the image capture lens, various kinds of aberrations are corrected. Accordingly, optical performance suitable for capturing images is obtained and high-quality image capturing is possible.

According to the image capture lens of yet another aspect of the invention, successively from an object side provided are a first lens group including a negative meniscus lens; a second lens group including a positive lens directing its convex to the object side; a third lens group including a first cemented lens composed of a bi-convex positive lens and a bi-concave negative lens, the first cemented lens having positive refractive power and directing its convex to the object side; a fourth lens group including a second cemented lens composed of a bi-concave negative lens and a bi-convex positive lens, the second cemented lens directing its convex to an image side; a fifth lens group including a positive lens directing its convex to the image side; a sixth lens group including a negative lens directing a surface thereof to the object side, a radius of the surface being smaller than that of an opposite surface; and a seventh lens group including a negative meniscus lens and a positive lens. In the image capture lens, various kinds of aberrations are corrected. Thus, optical performance suitable for capturing images is obtained and high-quality image capturing is possible.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.