JP6540052B2 - Imaging optical system - Google Patents

Description

  The present invention relates to an imaging optical system suitable for a photographing lens used for a digital camera, a video camera and the like.

  Heretofore, in a lens-interchangeable photographing apparatus, it has been common to have an optical finder. Therefore, a long back focus is necessary because it is necessary to arrange a mirror for guiding a light beam to the finder optical system between the imaging optical system and the imaging device. Therefore, in a wide-angle lens, as described in Patent Document 1, a retrofocus type in which a back focus longer than the focal length can be secured is generally used.

  However, in recent years, a so-called mirrorless camera capable of lens exchange employing an electronic finder has become available which can transfer an image directly from an imaging device to a finder. Since a mirrorless camera can omit a mirror for guiding a light beam to a finder optical system, it is possible to shorten the back focus of the photographing lens, and even in a wide-angle lens, it is necessary to use an extreme retrofocus type. Absent. In addition, the focal length can be further shortened. (For example, patent document 2 is mentioned.)

JP-A-8-110467 JP, 2012-173435, A

  It is known that in a retrofocus type imaging optical system, it is difficult to correct distortion properly. In the image forming optical system described in Patent Document 1, in order to secure a long back focus, the tendency of the retrofocus type becomes strong. Therefore, there is a problem that the correction of distortion is insufficient.

  Although the imaging optical system of Patent Document 2 does not secure a long back focus, it still has insufficient correction of distortion, and if it is attempted to shorten the focal length while maintaining the current back focus, the retro There is a problem that the tendency of the focus type has to be strengthened, and further deterioration of distortion is inevitable. Furthermore, in the imaging optical system of Patent Document 2, the first lens group having negative refractive power is configured of a negative lens and a positive lens, and has an effect of canceling the chromatic aberration with only the first lens group. Even in the group, it is necessary to have the effect of canceling the chromatic aberration only with the third lens group, and it is necessary to increase the refractive power of each positive and negative lens for achromatization, so the choice of glass material is limited and so on Was a difficult task.

  The present invention has been made in view of such a situation, and it has an extremely small distortion, a half angle of view of 43 degrees or more, and an optical system having a back focus of 1.2 to 1.4 times the focal length. An object of the present invention is to provide an imaging optical system that has good performance and can perform rapid focusing.

In the first invention, which is a means for solving the above problems, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having negative refractive power, and an aperture stop S The second lens group G2 is moved to the object side along the optical axis at the time of focusing from infinity to near distance, and the first lens group G1 is composed of the third lens group G3 having a positive refractive power. An imaging optical system characterized by satisfying the following conditional expression, which is composed of two negative meniscus lenses having a convex surface facing the object side .
(1) vdLA> 80.0
(2) 0.80 <| f12 / f | <1.40
vdLA: Abbe number maximum for the d-line of the negative meniscus lens constituting the first lens group G1 f12: Combined focal length f of the first lens group G1 and the second lens group G2 at infinity: all lenses Focal length at infinity in the system

  A second invention as a means for solving the above-mentioned problems is the imaging optical system according to the first invention, and the second lens group G2 is a single lens or a set of units. It is an imaging optical system comprised.

  According to the present invention, distortion is extremely small, and furthermore, optical performance with a half angle of view of 43 degrees or more and a back focus of about 1.2 to 1.4 times the focal length is good, and rapid focusing is possible. Imaging optical system can be provided.

It is a lens block diagram in infinite distance which concerns on Example 1 of the imaging optical system of this invention. 5 is a longitudinal aberration diagram of the imaging optical system of Example 1 at an infinite shooting distance. FIG. 5 is a longitudinal aberration diagram of the imaging optical system of Example 1 at a shooting distance of 200 mm. FIG. 5 is a lateral aberration diagram of the image forming optical system of Example 1 at an infinite shooting distance. FIG. 5 is a lateral aberration diagram at a shooting distance of 200 mm of the imaging optical system of Example 1. FIG. It is a lens block diagram in infinite distance which concerns on Example 2 of the imaging optical system of this invention. FIG. 6 is a longitudinal aberration diagram of the imaging optical system of Example 2 at a shooting distance of infinity. 5 is a longitudinal aberration diagram of the imaging optical system of Example 2 at a shooting distance of 200 mm. FIG. 5 is a lateral aberration diagram of the imaging optical system of Example 2 at a shooting distance of infinity. FIG. FIG. 7 is a lateral aberration diagram at a shooting distance of 200 mm of the imaging optical system of Example 2. It is a lens block diagram in infinite distance which concerns on Example 3 of the imaging optical system of this invention. FIG. 16 is a longitudinal aberration diagram of the imaging optical system of Example 3 at an imaging distance of infinity. FIG. 16 is a longitudinal aberration diagram of the imaging optical system of Example 3 at a shooting distance of 200 mm. FIG. 7 is a lateral aberration diagram of the imaging optical system of Example 3 at infinity of shooting distances. FIG. 7 is a lateral aberration diagram of the imaging optical system of Example 3 at a shooting distance of 200 mm. It is a lens block diagram in infinite distance which concerns on Example 4 of the imaging optical system of this invention. FIG. 16 is a longitudinal aberration diagram of the imaging optical system of Example 4 at a shooting distance of infinity. FIG. 16 is a longitudinal aberration diagram of the imaging optical system of Example 4 at a shooting distance of 200 mm. FIG. 16 is a lateral aberration diagram of the imaging optical system of Example 4 at a shooting distance of infinity. FIG. 16 is a lateral aberration diagram at a photographing distance of 200 mm of the imaging optical system of Example 4.

The imaging optical system according to the present invention, as a first invention, has negative refraction in order from the object side, as can be seen from the lens configuration diagram of the embodiment of the present invention shown in FIG. 1, FIG. 6, FIG. It is composed of a first lens group G1 having a power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power including an aperture stop S, and from infinity to a short distance. An imaging optical system characterized in that the second lens group G2 is moved to the object side along the optical axis during focusing, and the following conditional expression is satisfied.
(1) vdLA> 70.0
(2) 0.80 <| f12 / f | <1.40
vdLA: Abbe number maximum for the d-line of the negative meniscus lens constituting the first lens group G1 f12: Combined focal length f of the first lens group G1 and the second lens group G2 at infinity: all lenses Focal length at infinity in the system

  First, the refractive power arrangement of the first lens group G1, the second lens group G2, and the third lens group G3 will be described. The imaging optical system of the present invention comprises a first lens group G1 having negative refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. The retrofocus type refracting power arrangement made up of these lenses makes it possible to support an interchangeable lens camera while using a wide-angle lens with a half angle of view of 43 degrees or more.

  Further, in the image forming optical system according to the present invention, since the first lens group G1 has negative refracting power, distortion aberration which occurs largely under may be peripheral compared to the lens center in the first lens group G1. The correction is properly performed by arranging a negative meniscus aspheric lens in which the refracting power is weakened.

In the present invention, distortion at the time of shooting at infinity is expressed by a calculation formula (A). In the present invention, it is assumed that the difference between the maximum value and the minimum value of the distortion aberration D from the optical axis to the maximum image height is properly corrected within 1%.
(A) D = (Y-y0) / y0 * 100 [%]
D: distortion Y: actual image height y0: ideal image height

  Conditional expression (1) defines the maximum value of the Abbe number for the d-line of the negative meniscus lens that constitutes the first lens group G1. By defining the maximum value of the Abbe number for the d-line of the negative meniscus lens constituting the first lens group G1, a preferable range for suppressing lateral chromatic aberration is defined.

  When the lower limit value of the conditional expression (1) is exceeded, the refractive index difference of each wavelength of the negative meniscus lens becomes large. That is, the dispersion becomes large, and it becomes difficult to correct the lateral chromatic aberration well.

  In addition, about the conditional expression (1) mentioned above, the effect mentioned above is made more reliable by limiting the lower limit to 80.0, and it is effective also in the chromatic aberration correction of a secondary spectrum.

  Conditional expression (2) defines the ratio of the combined focal length f12 of the first lens group G1 and the second lens group G2 at infinity, and the focal length f at infinity of the entire lens system. . By satisfying the conditional expression (2), the length of the back focus and the distance between the second lens group G2 and the third lens group G3 become appropriate, and maintaining an appropriate distortion while preventing the overall lens length from becoming too long. Is possible.

  If the upper limit value of the conditional expression (2) is exceeded, the back focus becomes short, but the focal length f3 of the third lens group G3 becomes long and the distance between the second lens group G2 and the third lens group G3 becomes long. Induces an increase in overall length.

  If the lower limit value of the conditional expression (2) is exceeded, the refractive power of the combined focal length f12 of the first lens group G1 and the second lens group G2 becomes strong, and the occurrence of distortion becomes large. As a result, it becomes difficult to correct distortion.

  In the conditional expression (2) described above, a more preferable effect can be expected by further limiting the lower limit value to 0.90 and the upper limit value to 1.30.

  Furthermore, with the conditional expression (2) described above, by further limiting the lower limit value to 0.95 and the upper limit value to 1.10, the above-mentioned effect can be made more reliable.

  The imaging optical system according to the second aspect of the present invention is the first aspect, and the second lens group G2 is desirably configured of a single lens or a set of units. However, a unit refers to a lens group that performs the same movement during focusing.

  Since the second lens group G2 is configured to move to the object side along the optical axis during focusing from infinity to near distance, it is desirable that the focus group be lightweight. If the focus group is lightweight, rapid focusing can be achieved, and an actuator for moving the focus lens can be made smaller.

  The imaging optical system according to the third invention is the first or second invention, and it is preferable that the first lens group G1 is configured only by a negative meniscus lens having a convex surface facing the object side. .

  In the case of the retrofocus type wide-angle lens, the height of the off-axis light beam incident on the first lens group is much higher than the height of the on-axis light beam. Therefore, the rays of the off-axis light beam are strongly affected by being bent downward, so that the occurrence of negative distortion is increased. Therefore, in consideration of the incident angle of the off-axis ray to the first lens group and the lens shape so as to reduce the declination of the first lens group, the first lens group is only a negative meniscus lens having a convex surface facing the object side. The configuration is optimum, and generation of aberrations including distortion can be suppressed, which contributes to optical performance.

  An imaging optical system according to a fourth invention is any one of the first to third inventions, and the first lens group G1 is composed of two negative meniscus lenses having a convex surface facing the object side. It is desirable to be done.

  Further, by forming two negative meniscus lenses, the incidence angle of the off-axis ray to the first lens group and the deflection angle of the first lens group are further optimized, thereby further suppressing the occurrence of distortion. it can. Although it is possible to reduce the occurrence of distortion by inserting a positive lens closer to the image plane than the negative meniscus lens in the first lens group G1, the height of the off-axis light beam and the on-axis light beam entering the positive lens The difference between the heights of light rays is smaller than the difference between the height of the off-axis light beam incident on the negative meniscus lens and the height of the light beam on the on-axis light beam, so the negative lens produces negative distortion of the off-axis light beam. When the lens size is reduced, the effect of the positive lens is stronger than the effect of the negative meniscus lens in the light flux near the center, and positive distortion occurs largely at an intermediate angle of view. Therefore, it is not preferable to put a positive lens in the first lens group G1 for the purpose of suppressing the occurrence of distortion.

  Next, the lens configuration of an embodiment according to the image forming optical system of the present invention will be described. In the following description, lens configurations are described in order from the object side to the image side.

  In [Surface Data], the surface number is the lens surface number or aperture stop number counted from the object side, r is the radius of curvature of each surface, d is the distance between each surface, and nd is the refractive index for d line (wavelength 587.56 nm) And vd indicate the Abbe number of the d-line, and the effective radius indicates the ray height.

  The * (asterisk) attached to the surface number indicates that the lens surface shape is aspheric. Further, BF indicates the back focus, and the distance on the object plane indicates the distance from the subject to the first lens surface.

  The (diaphragm) attached to the surface number indicates that the aperture stop S is positioned at that position, and (flare cut) indicates that the flare cut F is positioned at that position. Further, the radius of curvature for the plane, the aperture stop S or the flare cut F is filled with ∞ (infinity).

[Aspheric surface data] indicates an aspheric coefficient that gives the aspheric shape of the lens surface marked with * in [Surface data]. The shape of the aspheric surface is y from the optical axis in the direction orthogonal to the optical axis, z from the intersection of the aspheric surface and the optical axis toward the optical axis (sag amount), r the radius of curvature of the reference spherical surface When the K, 4, 6, 8, 10th-order aspheric coefficients are set as A4, A6, A8, A10, the coordinates of the aspheric surface are represented by the following equation.

  [Various data] show values such as focal length in each focal length state.

  [Variable distance data] indicates values of variable distance and BF (back focus) in each focal length state.

  [Lens group data] indicates the surface number closest to the object side constituting each lens group and the combined focal length of the entire group.

  Further, in the aberration diagrams corresponding to the respective examples, d, g and C respectively represent d line, g line and C line, and ΔS and ΔM respectively represent a sagittal image plane and a meridional image plane. .

  Further, in the lens configuration diagrams shown in FIGS. 1, 6, 11 and 16, I is an image plane, and an alternate long and short dash line passing through the center is an optical axis.

  In all the following specification values, the unit of focal length f, radius of curvature r, inter-lens surface distance d, and other lengths described is millimeter (mm) unless otherwise specified. The system is not limited to this, as the same optical performance can be obtained in the proportional expansion and the proportional reduction.

  FIG. 1 is a lens configuration diagram of an image forming optical system according to a first embodiment of the present invention. The first lens group G1 has a negative refracting power as a whole, and the first lens group G1 comprises a first lens group G1, a second lens group G2, and a third lens group G3 in order from the object side. The negative meniscus lens L1a has a convex surface on the object side, and the negative meniscus lens L1b has a convex surface on the object side. Both lens surfaces of the negative meniscus lens L1a have a predetermined aspheric shape.

  The second lens group G2 has a negative refractive power as a whole, and is composed of a biconcave negative lens L2a.

  The third lens group G3 has a positive refractive power as a whole, and includes two lenses of an aperture stop S, a negative meniscus lens L3a having a convex surface facing the object side, and a biconvex positive lens L3b. A cemented lens consisting of a cemented lens, a flared cut F, a biconvex positive lens L3c, a negative meniscus lens L3d with a convex surface facing the object side, and a biconvex positive lens L3e, and both The negative meniscus lens L3h is composed of a cemented lens consisting of two lenses of a convex positive lens L3f and a negative meniscus lens L3g concave on the object side, and a negative meniscus lens L3h concave on the object side The lens surface on the image side of the lens has a predetermined aspheric shape.

  The second lens group G2 moves to the object side along the optical axis at the time of focusing from infinity to near distance.

Subsequently, specification values of the imaging optical system according to Example 1 will be shown below.
Numerical embodiment 1
Unit: mm
[Plane data]
Face number rd nd vd
Object surface ((d0)
1 * 24.3233 2.0000 1.5891 3 61.25
2 * 10.8623 5.5093
3 20.9206 1.2000 1.49700 81.60
4 11.4711 (d4)
5 -68.6637 1.0000 1.43700 95.10
6 316.0852 (d6)
7 (F-stop) 2.6 2.6501
8 37.9119 0.8000 1.59282 68.62
9 10.6710 3.8497 1.51680 64.19
10-36.941 2.3000
11 (flare cut) 2.4 2.4648
12 22.5426 3.4623 1.43700 95.10
13-728.6284 3.1921
14 106.0910 2.0067 1.58144 40.89
15 20.7523 5.9354 1.43700 95.10
16-20. 523 2.5 257
17 38.7382 5.5152 1.43700 95.10
18-15.5752 0.7500 1.88300 40.80
19-70.3393 2.5105
20-31.8947 1.1000 1.80610 40.73
21 * -57.6037 (BF)
Image plane ∞

[Aspheric surface data]
One side Two sides 21 sides
K 0.00000 -1.00000 0.00000
A4-3.75518E-05 5.90593E-07 3.90101E-05
A6 4.36935E-08 -9.34038E-08 2.80426E-08
A8 -5.91274E-11 -3.08947E-11 5.22392E-10
A10 0.00000E + 00 0.00000E + 00 1.35285E-13

[Various data]
INF 200 mm
Focal length 13.98 13.28
F number 3.53 3.54
Total angle of view 2 ω 90.74 92.90
Image height Y 14.20 14.20
Lens total length 89.25 89.25

[Variable interval data]
INF 200 mm
d0 110.7500
d4 17.5523 13.0242
d6 4.3541 8.8822
BF 17.5750 17.5750

[Lens group data]
Group start focal length
G1 1-19.82
G2 5-128.98
G12 1-15.13
G3 7 20.57

  FIG. 6 is a lens configuration diagram of an image forming optical system according to a second embodiment of the present invention. The first lens group G1 has a negative refracting power as a whole, and the first lens group G1 comprises a first lens group G1, a second lens group G2, and a third lens group G3 in order from the object side. The negative meniscus lens L1a has a convex surface on the object side, and the negative meniscus lens L1b has a convex surface on the object side. Both lens surfaces of the negative meniscus lens L1a have a predetermined aspheric shape.

  The second lens group G2 has a negative refractive power as a whole, and is composed of a biconcave negative lens L2a.

  The third lens group G3 has a positive refractive power as a whole, and includes two lenses of an aperture stop S, a negative meniscus lens L3a having a convex surface facing the object side, and a biconvex positive lens L3b. A cemented lens consisting of two lenses: a cemented lens, a flare cut F, a positive meniscus lens L3c with a convex surface facing the object side, and a negative meniscus lens L3d with a convex surface facing the object side and a biconvex positive lens L3e A cemented lens consisting of a lens, a biconvex positive lens L3f, and a negative meniscus lens L3g having a concave surface facing the object side, and a negative meniscus lens L3h having a concave surface facing the object side, The lens surface on the image side of the negative meniscus lens L3h has a predetermined aspheric shape.

  The second lens group G2 moves to the object side along the optical axis at the time of focusing from infinity to near distance.

Subsequently, specification values of the imaging optical system according to Example 2 will be shown below.
Numerical embodiment 2
Unit: mm
[Plane data]
Face number rd nd vd
Object surface ((d0)
1 * 23.0837 2.0000 1.58313 59.46
2 * 9.0102 3.1875
3 16.1661 1.2000 1.49700 81.60
4 10.5125 (d4)
5-200.0000 1.0000 1.43700 95.10
6 77.0603 (d6)
7 (F-stop) 2.6 2.6974
8 33.1050 0.8000 1.59282 68.62
9 9.9000 3.5521 1.51680 64.19
10-29.6381 3.3000
11 (flare cut) 1.4 1.4753
12 18.5751 3.1373 1.43700 95.10
13 202.4366 3.3777
14 68. 6065 1. 4048 1. 83481 42. 72
15 18.8114 4.7258 1.43700 95.10
16 -18.8114 2.6357
17 40.1618 4.7212 1.43700 95.10
18-15.6140 0.7500 1.88300 40.80
19 -62.2753 2.5693
20-27.7936 1.1000 1.80610 40.73
21 * -47.8074 (BF)
Image plane ∞

[Aspheric surface data]
One side Two sides 21 sides
K 0.00000 -1.00000 0.00000
A4 -3.96887E-05 3.35668E-05 4.27783E-05
A6 2.94290E-08 -1.00793E-07 8.80624E-08
A8-5.15347E-11-1.13985E-09 3.92712E-10
A10 0.00000E + 00 0.00000E + 00 2.22145E-12


[Various data]
INF 200 mm
Focal length 13.97 13.28
F number 4.13 4.13
Total angle of view 2 ω 90.90 92.68
Image height Y 14.20 14.20
Lens total length 82.60 82.60

[Variable interval data]
INF 200 mm
d0 117.4043
d4 16.7970 12.9201
d6 4.4772 8.3541
BF 17.6874 17.6874

[Lens group data]
Group start focal length
G1 1-18.01
G2 5 -127.16
G12 1 -13.96
G3 7 19.33

  FIG. 11 is a lens configuration diagram of an image forming optical system according to a third embodiment of the present invention. The first lens group G1 has a negative refracting power as a whole, and the first lens group G1 comprises a first lens group G1, a second lens group G2, and a third lens group G3 in order from the object side. The negative meniscus lens L1a has a convex surface on the object side, and the negative meniscus lens L1b has a convex surface on the object side. Both lens surfaces of the negative meniscus lens L1a have a predetermined aspheric shape.

  The second lens group G2 has a negative refractive power as a whole, and is composed of a negative meniscus lens L2a having a concave surface facing the object side.

  The third lens group G3 has a positive refracting power as a whole, and 2 of a flare cut F, an aperture stop S, a negative meniscus lens L3a having a convex surface facing the object side, and a biconvex positive lens L3b. A cemented lens consisting of two lenses: a cemented lens consisting of two lenses, a positive meniscus lens L3c with a concave surface facing the object side, and a negative meniscus lens L3d with a convex surface facing the object side and a biconvex positive lens L3e An image of a biconvex positive lens L3b comprising a lens and a cemented lens consisting of a positive meniscus lens L3f concave on the object side and a negative meniscus lens L3g concave on the object side The side lens surface has a predetermined aspheric shape.

  The second lens group G2 moves to the object side along the optical axis at the time of focusing from infinity to near distance.

Subsequently, specification values of the imaging optical system according to Example 3 will be shown below.
Numerical embodiment 3
Unit: mm
[Plane data]
Face number rd nd vd
Object surface ((d0)
1 * 23.0082 2.0000 1.5891 3 61.25
2 * 10.5500 3.5667
3 20.5747 1.2000 1.49700 81.60
4 11.2177 (d4)
5 -48.2096 0.8000 1.49700 81.60
6-643.3350 (d6)
7 (flare cut) 3. 3.7000
8 (F-stop) 0.8 0.8327
9 16.4396 1.5000 1.77250 49.62
10 12.2389 2.7713 1.59201 67.02
11 * -129.3729 4.2553
12 -68.5672 2.4013 1.72916 54.67
13 -18.8724 2.6683
14 104.2574 0.8500 1.88300 40.80
15 13.9002 4.3051 1.43700 95.10
16-29.9419 4.2847
17-229.8410 5.1989 1.43700 95.10
18-11.2967 0.8500 1.80611 40.73
19 -28.7754 (BF)
Image plane ∞

[Aspheric surface data]
1 face 2 faces 11 faces
K 0.00000 -1.00000 0.00000
A4 6.16610E-06 6.15401E-05 9.16687E-05
A6 -1.46961E-07 -1.04199E-07 9.47152E-09
A8 3.79843E-10 -1.18186E-09 3.67952E-09
A10 -5.81863E-13 0.00000E + 00 0.00000E + 00
A12

[Various data]
INF 200 mm
Focal length 14.07 13.46
F number 3.97 3.97
Total angle of view 2 ω 90.50 91.83
Image height Y 14.20 14.20
Lens total length 82.08 82.08

[Variable interval data]
INF 200 mm
d0 117.9197
d4 11.9058 7.5487
d6 10.3918 14.7490
BF 18.5984 18.5984

[Lens group data]
Group start focal length
G1 1 -19.97
G2 5 -104.91
G12 1 -15.16
G3 7 20.48

  FIG. 16 is a lens configuration diagram of an image forming optical system according to a fourth embodiment of the present invention. The first lens group G1 has a negative refracting power as a whole, and the first lens group G1 comprises a first lens group G1, a second lens group G2, and a third lens group G3 in order from the object side. The negative meniscus lens L1a has a convex surface on the object side, and the negative meniscus lens L1b has a convex surface on the object side. Both lens surfaces of the negative meniscus lens L1a have a predetermined aspheric shape.

  The second lens group G2 has a negative refractive power as a whole, and is constituted by a cemented lens consisting of two lenses of a positive meniscus lens L2a having a concave surface facing the object side and a biconcave negative lens L2b. ing.

  The third lens group G3 has a positive refractive power as a whole, and includes two lenses of an aperture stop S, a negative meniscus lens L3a having a convex surface facing the object side, and a biconvex positive lens L3b. A cemented lens consisting of a cemented lens, a flared cut F, a biconvex positive lens L3c, a negative meniscus lens L3d with a convex surface facing the object side, and a biconvex positive lens L3e, and both The negative meniscus lens L3h is composed of a cemented lens consisting of two lenses of a convex positive lens L3f and a negative meniscus lens L3g concave on the object side, and a negative meniscus lens L3h concave on the object side The lens surface on the image side of the lens has a predetermined aspheric shape.

  The second lens group G2 moves to the object side along the optical axis at the time of focusing from infinity to near distance.

Subsequently, specification values of the imaging optical system according to Example 4 will be shown below.
Numerical embodiment 4
Unit: mm
[Plane data]
Face number rd nd vd
Object surface ((d0)
1 * 24.4914 2.0000 1.58313 59.46
2 * 10.1923 5.0443
3 20.5045 1.2000 1.49700 81.60
4 11.1542 (d4)
5 -163.0811 1.2922 1.83481 42.72
6-70.0000 0.8000 1.49700 81.60
7 80.2887 (d7)
8 (F-stop) 1.1 1.1651
9 31.5920 0.8000 1.59282 68.62
10 10.9270 3.4846 1.48749 70.44
11-31.9827 3.3000
12 (flare cut) 4.6 4.6 359
13 23.7463 3.6743 1.43700 95.10
14 -97.6865 2.8555
15 132.4828 0.7500 1.83481 42.72
16 28.9897 4.8214 1.43700 95.10
17 -20.7481 3.6788
18 36.5138 5.5079 1.43700 95.10
19-15.7784 0.7500 1.88300 40.80
20-70.9689 2.6458
21 -32.6440 1.1000 1.80610 40.73
22 * -60.9047 (BF)
Image plane ∞

[Aspheric surface data]
1 side 2 side 22
K 0.00000 -1.00000 0.00000
A4-3.88749E-05 7.20337E-06 3.61522E-05
A6 4.44487E-08 -1.17461E-07 4.09738E-08
A8-6.25055E-11-2.24384E-10 3.21264E-10
A10 0.00000E + 00 0.00000E + 00 5.62204E-13
A12

[Various data]
INF 200 mm
Focal length 13.97 13.28
F number 3.99 3.99
Total angle of view 2 ω 90.89 92.62
Image height Y 14.20 14.20
Lens total length 89.15 89.15

[Variable interval data]
INF 200 mm
d0 110.8529
d4 17.8172 12.9513
d7 4.4872 9.3531
BF 17.3369 17.3369

[Lens group data]
Group start focal length
G1 1 -18.25
G2 5-154.10
G12 1-14.55
G3 7 20.56

  Moreover, the corresponding value list of the conditional expression in each of these Examples is shown.

[Conditional expression corresponding value]
Conditional Expression / Example 1 2 3 4
(1) vdLA> 70.0 81.6 81.6 81.6 81.6
(2) 0.80 <| f12 / f | <1.40 1.08 1.00 1.08 1.04

G1 First lens group G2 Second lens group G3 Third lens group G12 Compound S of first lens group and second lens group S Aperture stop F Flare cut

Claims (2)

From the object side, the first lens group G1 having negative refractive power, the second lens group G2 having negative refractive power, and the third lens group G3 having positive refractive power including an aperture stop S The second lens group G2 is moved to the object side along the optical axis during focusing from infinity to near distance, and the first lens group G1 comprises two negative meniscus lenses with convex surfaces facing the object side. has become configuration, the imaging optical system satisfies the following conditional expression.
(1) vdLA> 80.0
(2) 0.80 <| f12 / f | <1.40
vdLA: Abbe number maximum for the d-line of the negative meniscus lens constituting the first lens group G1 f12: Combined focal length f of the first lens group G1 and the second lens group G2 at infinity: all lenses Focal length at infinity in the system   The imaging optical system according to claim 1, wherein the second lens group G <b> 2 is configured of a single lens or a set of units.

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