JP2022067328A - Image forming optical system - Google Patents

Abstract

To provide an inner focus type image forming optical system that is compact, and that has a wide angle of view, a high photographing magnification, and excellent optical performance obtained by satisfactorily correcting various aberrations.SOLUTION: An image forming optical system consists of, in order from an object side: a first lens group G1 having a positive refractive index; an aperture stop S; a second lens group G2 having positive refractive power; and a third lens group G3 having negative refractive power. The first lens group G1 has a negative meniscus lens that is nearest to the object, and has a convex surface facing the object. During focusing from an object at infinity to an object at a short distance, a specific conditional expression is satisfied when the first lens group G1, the aperture stop S, and the third lens group G3 are fixed, and the second lens group G2 moves along the optical axis toward the object.SELECTED DRAWING: Figure 1

Description

The present invention relates to a photographing lens suitable for an imaging device such as a digital camera, a silver salt camera and a video camera.

In recent years, with the increase in the number of pixels of photographing devices such as digital cameras, there is a demand for an optical system having high optical performance in which various aberrations are sufficiently corrected.

Further, as the miniaturization of the image pickup apparatus progresses, a compact imaging optical system is required. In particular, as the miniaturization of image pickup devices progresses, portability increases, and a wide-angle imaging optical system suitable for snapshots and landscape photographs is required. Further, since the wide-angle lens enables a shooting expression that emphasizes the perspective as the shooting magnification is higher, it is preferable that the maximum shooting magnification is high.

Patent No. 6061187 Patent No. 6597626 Japanese Unexamined Patent Publication No. 2019-74632 Patent No. 3816726

The lenses described in Patent Documents 1 and 2 are small inner focus type wide-angle lenses, but the amount of movement of the image plane with respect to the amount of focus movement is small, and the amount that can be moved at the time of focusing is limited, so that the close-up shooting magnification is sufficient. It has the problem that it is not.

The lenses described in Patent Documents 3 and 4 have a configuration in which the front lens is extended at the time of focusing, and the total optical length changes. When the shooting magnification is high, the subject and the front surface of the lens come into contact with each other, increasing the risk of the subject and the lens becoming dirty. Further, in the configuration in which the front lens is extended, the front lens, which tends to be heavy, is moved, which causes a problem that it is difficult to increase the focus speed.

The present invention has been made in view of such a situation, and provides an inner focus type imaging optical system having a small size, a wide angle, a high shooting magnification, good correction of various aberrations, and high optical performance. With the goal.

The imaging optical system according to the present invention, which is a means for solving the above problems, has a first lens group G1 having a positive refractive index, an aperture aperture S, and a positive refractive force in order from the object side. It is composed of two lens groups G2 and a third lens group G3 having a negative refractive force. When focusing on a short-range object, the first lens group G1, the aperture aperture S, and the third lens G3 are fixed, and the second lens group G2 moves toward the object along the optical axis. However, it is characterized by satisfying the following conditional expression.
(1) -0.70 <f2 / f3 <-0.30
f2: Focal length of the second lens group G2 f3: Focal length of the third lens group G3

Further, the imaging optical system according to the present invention is further characterized in that the first lens group G1 has a negative lens satisfying the following conditional expression.
(2) νd1m <25.00
(3) ΔPgF1m> 0.0150
νd1m: Abbe number of the negative lens ΔPgF1m: Abnormal dispersibility of the negative lens ΔPgF1m = PgF1m + 0.0018 × νd1m ― 0.64833
PgF1m is a partial dispersion ratio PgF with respect to the g-line and F-line of the negative lens.

Further, in the imaging optical system according to the present invention, the first lens group G1 further has an arrangement of a negative lens L1m, a negative lens L2m, and a positive lens L1p in order from the object side, and the positive lens L1p has the following conditions. An imaging optical system characterized by satisfying an equation.
(4) NdL1p> 1.85
NdL1p: Refractive index of the positive lens L1p

Further, the imaging optical system according to the present invention is further characterized by satisfying the following conditional expression.
(5) 1.25 <β3 <2.33
β3: Lateral magnification of the third lens group G3 in the infinity state

Further, the imaging optical system according to the present invention is further characterized by satisfying the following conditions.
(6) 2.50 <LT / Ymax <3.30
LT: Surface spacing from the most object-side surface of the first lens group G1 to the image plane in the infinity-focused state Ymax: Maximum image height of the imaging optical system

Further, the imaging optical system according to the present invention is further characterized by satisfying the following conditions.
(7) 2.50 <β3 ^ 2 * (1-β2 ^ 2) <3.50
β3: Lateral magnification of the third lens group G3 in the infinity state β2: Lateral magnification of the second lens group G2 in the infinity state

According to the present invention, it is possible to obtain an inner focus type imaging optical system having a small size, a wide angle, a high shooting magnification, good correction of various aberrations, and high optical performance.

It is a lens block diagram which concerns on Example 1 of the imaging optical system of this invention. FIG. 3 is a longitudinal aberration diagram of the imaging optical system of Example 1 at an infinity shooting distance. It is a longitudinal aberration diagram at the imaging magnification −0.5 times of the imaging optical system of Example 1. FIG. FIG. 5 is a lateral aberration diagram of the imaging optical system of Example 1 at an infinity shooting distance. It is a lateral aberration diagram at the imaging magnification −0.5 times of the imaging optical system of Example 1. FIG. It is a lens block diagram which concerns on Example 2 of the imaging optical system of this invention. FIG. 3 is a longitudinal aberration diagram of the imaging optical system of the second embodiment at an infinity shooting distance. It is a longitudinal aberration diagram at the imaging magnification −0.5 times of the imaging optical system of Example 2. FIG. FIG. 3 is a lateral aberration diagram of the imaging optical system of the second embodiment at an infinity shooting distance. It is a lateral aberration diagram at the imaging magnification −0.5 times of the imaging optical system of Example 2. FIG. It is a lens block diagram which concerns on Example 3 of the imaging optical system of this invention. FIG. 3 is a longitudinal aberration diagram of the imaging optical system of Example 3 at an infinity shooting distance. It is a longitudinal aberration diagram at the imaging magnification −0.5 times of the imaging optical system of Example 3. FIG. FIG. 3 is a lateral aberration diagram of the imaging optical system of Example 3 at an infinity shooting distance. It is a lateral aberration diagram at the imaging magnification −0.5 times of the imaging optical system of Example 3. FIG. It is a lens block diagram which concerns on Example 4 of the imaging optical system of this invention. FIG. 3 is a longitudinal aberration diagram of the imaging optical system of Example 4 at a shooting distance of infinity. It is a longitudinal aberration diagram at the imaging magnification −0.5 times of the imaging optical system of Example 4. FIG. FIG. 5 is a lateral aberration diagram of the imaging optical system of Example 4 at a shooting distance of infinity. It is a lateral aberration diagram at the imaging magnification −0.5 times of the imaging optical system of Example 4. FIG. It is a lens block diagram which concerns on Example 5 of the imaging optical system of this invention. FIG. 5 is a longitudinal aberration diagram of the imaging optical system of Example 5 at an infinity shooting distance. FIG. 3 is a longitudinal aberration diagram at an imaging magnification of −0.5 times of the imaging optical system of Example 5. FIG. 5 is a lateral aberration diagram of the imaging optical system of Example 5 at a shooting distance of infinity. FIG. 3 is a lateral aberration diagram at an imaging magnification of −0.5 times of the imaging optical system of Example 5. It is a lens block diagram which concerns on Example 6 of the imaging optical system of this invention. 6 is a longitudinal aberration diagram of the imaging optical system of Example 6 at an infinity shooting distance. It is a longitudinal aberration diagram at the imaging magnification −0.5 times of the imaging optical system of Example 6. FIG. 3 is a lateral aberration diagram of the imaging optical system of Example 6 at an infinity shooting distance. FIG. 3 is a lateral aberration diagram at an imaging magnification of −0.5 times of the imaging optical system of Example 6.

Hereinafter, examples of the optical system according to the present invention will be described in detail. It should be noted that the following description of the examples describes an example of the imaging optical system of the present invention, and the present invention is not limited to the present embodiment as long as the gist of the present invention is not deviated.

As can be seen from the lens configuration diagrams shown in FIGS. 1, 6, 11, 16, 21, and 26, the imaging optical system of the embodiment of the present invention has a positive refractive index in order from the object side to the image side. The first lens group G1 is composed of a first lens group G1 having a positive refractive index, a second lens group G2 having a positive refractive index, and a third lens group G3 having a negative refractive index. It has a negative meniscus lens with a convex on the side of the object, and when focusing from an infinity object to a short-range object, the first lens group G1, the aperture aperture S, and the third lens group G3 is fixed, and the second lens group G2 moves toward the object along the optical axis and satisfies the following conditional expression.
(1) -0.70 <f2 / f3 <-0.30
f2: Focal length of the second lens group G2 f3: Focal length of the third lens group G3

By setting the refractive power of the first lens group G1 to be positive, the height of the axial light beam incident on the subsequent second lens group G2 can be lowered, and the weight of the second lens group G2, which is the focus group, can be reduced. Further, by arranging a negative meniscus lens whose convexity is directed toward the object side on the most object side of the first lens group G1, a retrofocus type configuration can be obtained and a wide angle can be achieved.

The conditional expression (1) is a condition for appropriately defining the ratio of the focal lengths of the second lens group G2 and the third lens group G3 and achieving miniaturization.

When the positive refractive power of the second lens group G2, which is the focus group, becomes relatively weak beyond the upper limit of the conditional expression (1), the amount of movement of the focus group increases, so that the entire imaging optical system is compact. It is disadvantageous to the conversion.

If the negative refractive power of the third lens group G3 becomes relatively strong beyond the lower limit of the conditional expression (1), the back focus becomes large, and it becomes difficult to reduce the size of the entire imaging optical system.

By setting the upper limit value of the conditional expression (1) to −0.40 and the lower limit value to −0.65, the above-mentioned effect can be further ensured.

Further, the first lens group G1 is characterized by having a negative lens satisfying the following conditional expression.
(2) νd1m <25.00
(3) ΔPgF1m> 0.0150
νd1m: Abbe number of the negative lens ΔPgF1m: Abnormal dispersibility of the negative lens ΔPgF1m = PgF1m + 0.0018 × νd1m ― 0.64833
PgF1m is a partial dispersion ratio PgF with respect to the g-line and F-line of the negative lens.

The conditional equation (2) and the conditional equation (3) define the Abbe number and the anomalous dispersibility of the negative lens in the first lens group G1 in order to satisfactorily correct the chromatic aberration of magnification.

If the upper limit of the conditional expression (2) is exceeded and the lower limit of the conditional expression (3) is exceeded, the Abbe number increases and the anomalous dispersibility decreases, the correction of chromatic aberration of magnification becomes insufficient.

By setting the upper limit value of the conditional expression (2) to 22.00 and the lower limit value of the conditional expression (3) to 0.0250, the above-mentioned effect can be further ensured.

Further, the first lens group G1 has an arrangement of a negative lens L1m, a negative lens L2m, and a positive lens L1p in order from the object side, and the positive lens L1p satisfies the following conditional expression (4).
(4) NdL1p> 1.85
NdL1p: Refractive index of the positive lens L1p

By having the negative lens L1m, the negative lens L2m, and the positive lens L1p arranged in the first lens group G1 from the object side, the first lens group G1 has a negative refractive power on the object side and a positive refractive power on the image side. It has a retrofocus type configuration to be placed, which is advantageous for widening the angle.

The conditional expression (4) defines the refractive index of the positive lens L1p in the first lens group G1 and is a condition for miniaturization and good correction of curvature of field.

When the refractive index becomes low beyond the lower limit of the conditional expression (4), the Petzval sum increases and the curvature of field is insufficiently corrected. Also, if the same refractive power is to be obtained when the refractive index is low, the radius of curvature becomes smaller and it becomes necessary to secure the thickness of the peripheral portion of the lens, which increases the inner thickness of the lens. It is disadvantageous for miniaturization.

By setting the lower limit of the conditional expression (4) to 1.90, the above-mentioned effect can be further ensured.

Further, by arranging the negative lens L1m, the negative lens L2m, and the positive lens L1p in order from the object side of the first lens group G1 on the object side, the position of the rear principal point can be moved closer to the image side. And the effect can be assured.

Further, it is characterized by satisfying the following conditional expression (5).
(5) 1.25 <β3 <2.33
β3: Lateral magnification of the third lens group G3 in the infinity state

Conditional expression (5) defines the ratio of the combined focal length of the first lens group G1 and the second lens group G2 to the focal length of the entire system, and is a condition for achieving miniaturization and high performance. ..

If the lateral magnification of the third lens group G3 exceeds the upper limit of the conditional expression (5), the residual aberrations of the first lens group G1 and the second lens group G2 will be expanded, and thus the performance will be improved. It will be disadvantageous to.

If the lateral magnification of the third lens group G3 exceeds the lower limit of the conditional expression (5) and the lateral magnification of the third lens group G3 becomes low, the amount of movement of the focus group at the time of focusing to a close distance becomes large, and it becomes difficult to reduce the size of the lens.

By setting the upper limit value of the conditional expression (5) to 2.00 and the lower limit value to 1.47, the above-mentioned effect can be further ensured.

Further, it is characterized by satisfying the following conditional expression (6).
(6) 2.50 <LT / Ymax <3.30
LT: Surface spacing from the most object-side surface of the first lens group G1 to the image plane in the infinity-focused state Ymax: Maximum image height of the imaging optical system

The conditional expression (6) defines the relationship between the total optical length and the maximum image height, and is a condition for achieving both miniaturization and aberration correction.

If the upper limit of the conditional expression (6) is exceeded and the total optical length is longer than the imager size, it cannot be said that the size is small.

If the lower limit of the conditional expression (6) is exceeded and the total optical length is shortened, the correction of various aberrations, particularly the correction of the sagittal coma, becomes insufficient.

By setting the upper limit value 3.15 of the conditional expression (6) to the lower limit value 2.80, the above-mentioned effect can be further ensured.

Further, it is characterized by satisfying the following conditional expression (7).
(7) 2.50 <β3 ^ 2 * (1-β2 ^ 2) <3.50
β3: Lateral magnification of the third lens group G3 in the infinity state β2: Lateral magnification of the second lens group G2 in the infinity state

The conditional expression (7) defines the focus sensitivity of the second lens group G2, and achieves miniaturization and a high shooting magnification.

If the upper limit of the conditional expression (7) is exceeded and the focus sensitivity becomes high, it becomes difficult to secure the focus group stop position accuracy at the time of focusing.

If the lower limit of the conditional expression (7) is exceeded and the focus sensitivity becomes low, the amount of focus movement to obtain a high shooting magnification becomes large, and it is necessary to secure a wider space in the optical axis direction. It is difficult to achieve both high shooting magnification.

By setting the upper limit value of the conditional expression (7) to 3.30 and the lower limit value of 2.70, the above-mentioned effect can be further ensured.

It is desirable that the third lens group G3 has an aspherical lens having a shape such that at least one side of the third lens group G3 is concave and has a shape in which a negative refractive power becomes stronger toward the periphery. By arranging an aspherical lens having such a shape in G3 of the third lens group, it is possible to effectively correct the effect of mainly curvature of field.

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

In [plane data], the surface number is the number of the lens surface or aperture aperture 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 d line (wavelength λ = 587.56 nm). The refractive index, νd is the Abbe number with respect to the d line, and ΔPgF is the anomalous dispersibility.

* (Asterisk) attached to the surface number indicates that the lens surface shape is aspherical. In addition, BF represents back focus.

The radius of curvature ∞ (infinity) with respect to a flat surface or an aperture stop is entered in the area numbered (aperture).

In [Aspherical surface data], each coefficient value that gives the aspherical surface shape of the lens surface marked with * in [Surface data] is shown. The shape of the aspherical surface is y for the displacement in the direction orthogonal to the optical axis, z for the displacement (sag amount) in the optical axis direction from the intersection of the aspherical surface and the optical axis, and K, 4, 6, 8 for the conic coefficient. When the 10th, 12th, 14th, 16th, 18th, and 20th order aspherical coefficients are set as A4, A6, A8, A10, A12, A14, A16, A18, and A20, respectively, the aspherical coordinates are expressed by the following equations. It shall be.
z = (y2 / r) / [1 + {1- (1 + K) (y / r) 2} 1/2] + A4y4 + A6y6 + A8y8 + A10y10 + A12y12 + A14y14 + A16y16 + A18y18 + A20y20

[Various data] shows values such as the focal length when the shooting distance is INF and the shooting magnification is −0.5 times.

[Variable interval data] shows the values of the variable interval and BF (back focus) when the shooting distance is INF and the shooting magnification is −0.5 times.

[Lens group data] shows the surface number on the most object side constituting each lens group, and the combined focal length and refractive power of the entire group. In all the following specification values, the focal length f, the radius of curvature r, the lens surface spacing d, and other length units are described in millimeters (mm) unless otherwise specified, but optics. The system is not limited to this because the same optical performance can be obtained in both proportional expansion and proportional reduction.

Further, in the aberration diagram corresponding to each embodiment, d, g, and C represent the d-line, g-line, and C-line, respectively, and ΔS and ΔM represent the sagittal image plane and the meridional image plane, respectively.
Further, in the lens configuration diagram shown in FIGS. 1, 6, 11, 16, 21, and 26, S is an aperture diaphragm, and the alternate long and short dash line passing through the center is the optical axis.

FIG. 1 is a lens configuration diagram of the imaging optical system according to the first embodiment of the present invention when the lens is in focus at infinity. The imaging optical system of the first embodiment has a first lens group G1 having a positive refractive power, an aperture aperture S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power in order from the object side. It consists of group G3. When focusing from an infinite object to a short-range object, the first lens group G1, the aperture stop S, and the third lens group G3 are fixed to the image plane, and the second lens group G2 is along the optical axis. Move to the object side.

The first lens group G1 includes a negative meniscus lens L11 having an aspherical surface on the object side and a convex surface, a negative meniscus lens L12 having a concave surface on the object side, and a positive meniscus lens L12 having a concave surface on the object side. It is composed of L13, a junction lens composed of a positive meniscus lens L14 having a convex surface facing the object side and a negative meniscus lens L15 having a convex surface facing the object side.

The negative meniscus lens L11 of the first lens group G1 corresponds to the negative lens L1m, the negative meniscus lens L12 corresponds to the negative lens L2m, and the positive meniscus lens L13 corresponds to the positive lens L1p.

The second lens group G2 is composed of a junction lens composed of a biconvex lens L21, a negative meniscus lens L22 with a concave surface facing the object side, and a biconvex lens L23 having aspherical surfaces on both sides.

The third lens group G3 is composed of a biconcave lens L31 having an aspherical surface on the image plane side and a negative meniscus lens L32 with the concave surface facing the object side.

The specification values of the imaging optical system according to the first embodiment are shown below.
Numerical Example 1
Unit: mm
[Surface data]
Surface number rd nd vd ΔPgF
Physical surface ∞ (d0)
1 * 22.3254 1.2000 1.59271 66.97
2 10.3967 8.0142
3 -18.8622 0.8000 1.98613 16.48 0.0469
4 -47.0701 0.1500
5 -393.9653 2.6943 2.05090 26.94
6 -24.8351 0.1500
7 19.1582 2.2297 2.05090 26.94
8 46.2374 0.8000 1.54072 47.20
9 15.3402 3.3618
10 (aperture) ∞ (d10)
11 76.8877 4.1964 1.49700 81.61
12 -11.2104 0.8000 1.84666 23.78
13 -36.9349 1.2958
14 * 132.5036 5.2747 1.85135 40.10
15 * -15.6964 (d15)
16 -565.0813 1.1700 1.69350 53.20
17 * 34.3585 3.2592
18 -31.8250 1.5989 1.51680 64.20
19 -99.3133 (BF)
Image plane ∞

[Aspherical data]
1 side 14 sides
K 0.00000 -1.00000
A4 2.22205E-05 -5.06066E-06
A6 -4.69259E-08 3.02711E-07
A8 8.56143E-10 -5.62626E-09
A10 -2.54125E-12 6.54011E-11
A12 3.90193E-15 -1.85433E-13
A14 0.00000E + 00 -2.87753E-15
A16 0.00000E + 00 2.20828E-17
A18 0.00000E + 00 -4.32346E-20
A20 0.00000E + 00 0.00000E + 00

15 sides 17 sides
K 0.00000 0.00000
A4 5.59739E-05 1.07013E-05
A6 -1.09750E-08 -2.50582E-07
A8 2.66207E-09 1.44276E-08
A10 -8.42405E-11 -2.35199E-10
A12 1.45129E-12 1.81668E-12
A14 -1.07799E-14 -4.10422E-15
A16 2.85320E-17 -3.03923E-17
A18 0.00000E + 00 1.99913E-19
A20 0.00000E + 00 -3.19756E-22

[Various data]
INF -0.5x Focal length 24.00 19.45
F number 3.62 3.92
Full angle of view 2ω 81.27 78.13
Image height Y 21.63 21.63
Lens total length 65.22 65.22

[Variable interval data]
INF -0.5 times
d0 ∞ 40.0680
d10 7.0307 3.1949
d15 1.5000 5.3358
BF 19.6941 19.6941

[Lens group data]
Focal length of group origin
G1 1 340.56
G2 11 17.20
G3 16 -30.27

FIG. 6 is a lens configuration diagram of the imaging optical system according to the second embodiment of the present invention when the lens is focused at infinity. The imaging optical system of the second embodiment has a first lens group G1 having a positive refractive power, an aperture aperture S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power in order from the object side. It consists of group G3. When focusing from an infinite object to a short-range object, the first lens group G1, the aperture stop S, and the third lens group G3 are fixed to the image plane, and the second lens group G2 is along the optical axis. Move to the object side.

The first lens group G1 includes a negative meniscus lens L11 having an aspherical surface on the object side and a convex surface, a biconcave lens L12, a biconvex lens L13, and a positive meniscus lens L14 having a convex surface on the object side. It is composed of a bonded lens made of a negative meniscus lens L15 having a shape with a convex surface facing to the side.

The negative meniscus lens L11 of the first lens group G1 corresponds to the negative lens L1m, the biconcave lens L12 corresponds to the negative lens L2m, and the biconvex lens L13 corresponds to the positive lens L1p.

The second lens group G2 is composed of a junction lens composed of a biconvex lens L21, a negative meniscus lens L22 with a concave surface facing the object side, and a biconvex lens L23 having aspherical surfaces on both sides.

The third lens group G3 is composed of a biconcave lens L31 having an aspherical surface on the image plane side and a biconcave lens L32.

The specification values of the imaging optical system according to the second embodiment are shown below.
Numerical Example 2
Unit: mm
[Surface data]
Surface number rd nd vd ΔPgF
Physical surface ∞ (d0)
1 * 37.1707 1.2000 1.59271 66.97
2 11.9708 4.6706
3 -90.1757 0.8000 1.86966 20.02 0.0312
4 18.0508 0.5946
5 19.3238 4.1893 2.05090 26.94
6 -86.3596 0.1500
7 32.4873 2.2096 2.05090 26.94
8 219.5183 0.8000 1.49700 81.61
9 35.0382 4.7859
10 (aperture) ∞ (d10)
11 80.0108 4.2725 1.49700 81.61
12 -10.7816 0.8000 1.84666 23.78
13 -32.1745 1.6687
14 * 123.4622 5.4645 1.85108 40.12
15 * -15.7000 (d15)
16 -101.3685 1.1700 1.69350 53.20
17 * 51.2172 2.5377
18 -39.5716 0.8000 1.51680 64.20
19 193.3971 (BF)
Image plane ∞

[Aspherical data]
1 side 14 sides
K 0.00000 -1.00000
A4 1.12761E-05 -8.73607E-06
A6 -7.31857E-08 2.30362E-07
A8 1.14060E-09 -4.79714E-09
A10 -6.34786E-12 3.67455E-11
A12 1.46137E-14 -2.67385E-14
A14 0.00000E + 00 -8.73714E-16
A16 0.00000E + 00 -1.63768E-18
A18 0.00000E + 00 2.62737E-20
A20 0.00000E + 00 0.00000E + 00

15 sides 17 sides
K 0.00000 0.00000
A4 5.82134E-05 1.63614E-06
A6 -3.31395E-08 -1.27731E-07
A8 1.91909E-09 9.89556E-09
A10 -9.21090E-11 -1.23776E-10
A12 1.49754E-12 6.35230E-13
A14 -1.03775E-14 -4.80713E-16
A16 2.62651E-17 5.32540E-18
A18 0.00000E + 00 -1.72839E-19
A20 0.00000E + 00 7.96866E-22

[Various data]
INF -0.5x Focal length 24.15 19.22
F number 3.61 3.88
Full angle of view 2ω 80.93 78.73
Image height Y 21.63 21.63
Lens total length 64.56 64.56

[Variable interval data]
INF -0.5 times
d0 ∞ 40.5284
d10 6.9039 3.2274
d15 1.8460 5.5225
BF 19.7011 19.7011

[Lens group data]
Focal length of group origin
G1 1 342.89
G2 11 16.68
G3 16 -26.94

FIG. 11 is a lens configuration diagram of the imaging optical system according to the third embodiment of the present invention when the lens is focused at infinity. The imaging optical system of the third embodiment has a first lens group G1 having a positive refractive power, an aperture aperture S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power in order from the object side. It consists of group G3. When focusing from an infinite object to a short-range object, the first lens group G1 and the aperture stop S, the third lens group G3 are fixed to the image plane, and the second lens group G2 is along the optical axis. Move to the object side.

The first lens group G1 includes a negative meniscus lens L11 having an aspherical surface on the object side and a convex surface, a negative meniscus lens L12 having a concave surface on the object side, and a positive meniscus lens L12 having a concave surface on the object side. It is composed of L13, a junction lens composed of a positive meniscus lens L14 having a convex surface facing the object side and a negative meniscus lens L15 having a convex surface facing the object side.

The negative meniscus lens L11 of the first lens group G1 corresponds to the negative lens L1m, the negative meniscus lens L12 corresponds to the negative lens L2m, and the positive meniscus lens L13 corresponds to the positive lens L1p.

The second lens group G2 is composed of a junction lens composed of a biconvex lens L21, a negative meniscus lens L22 with a concave surface facing the object side, and a biconvex lens L23 having aspherical surfaces on both sides.

The third lens group G3 is composed of a biconcave lens L31 whose surface on the image plane side is an aspherical surface.

The specification values of the imaging optical system according to the third embodiment are shown below.
Numerical Example 3
Unit: mm
[Surface data]
Surface number rd nd vd ΔPgF
Physical surface ∞ (d0)
1 * 19.3403 1.2000 1.59271 66.97
2 10.0501 8.2793
3 -19.0892 0.8000 1.98613 16.48 0.0469
4 -57.5124 0.1500
5 -982.0122 2.6517 2.05090 26.94
6 -25.1961 0.1500
7 20.5762 2.4078 2.05090 26.94
8 85.7147 0.8000 1.54072 47.20
9 15.2057 2.9612
10 (aperture) ∞ (d10)
11 91.7895 4.2738 1.49700 81.61
12 -11.4949 0.8000 1.84666 23.78
13 -40.6182 0.8850
14 * 116.2318 5.6655 1.85135 40.10
15 * -15.7000 (d15)
16 -44.5697 1.1700 1.69350 53.20
17 * 44.1440 (BF)
Image plane ∞

[Aspherical data]
1 side 14 sides
K 0.00000 -1.00000
A4 2.38338E-05 -4.93365E-06
A6 -9.25570E-08 3.33208E-07
A8 1.95066E-09 -5.94861E-09
A10 -1.00902E-11 4.75144E-11
A12 3.10366E-14 -1.17585E-14
A14 0.00000E + 00 -1.76473E-15
A16 0.00000E + 00 2.56093E-18
A18 0.00000E + 00 3.67331E-20
A20 0.00000E + 00 0.00000E + 00

15 sides 17 sides
K 0.00000 0.00000
A4 5.32969E-05 9.69161E-06
A6 -4.54691E-09 -2.95553E-07
A8 4.00931E-09 1.15376E-08
A10 -1.14359E-10 -1.46162E-10
A12 1.52261E-12 7.42590E-13
A14 -9.31630E-15 4.35612E-16
A16 2.19663E-17 -5.70815E-18
A18 0.00000E + 00 -1.49263E-19
A20 0.00000E + 00 8.13616E-22

[Various data]
INF -0.5x Focal length 24.00 19.51
F number 3.61 3.94
Full angle of view 2ω 81.28 77.53
Image height Y 21.63 21.63
Lens total length 64.78 64.78

[Variable interval data]
INF -0.5 times
d0 ∞ 40.1457
d10 7.2895 3.2229
d15 3.0184 7.0850
BF 22.2762 22.2762

[Lens group data]
Focal length of group origin
G1 1 340.79
G2 11 17.52
G3 16 -31.81

FIG. 16 is a lens configuration diagram of the imaging optical system according to the fourth embodiment of the present invention when the lens is focused at infinity. The imaging optical system of the fourth embodiment has a first lens group G1 having a positive refractive power, an aperture aperture S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power in order from the object side. It consists of group G3. When focusing from an infinite object to a short-range object, the first lens group G1 and the aperture stop S, the third lens group G3 are fixed to the image plane, and the second lens group G2 is along the optical axis. Move to the object side.

The first lens group G1 includes a negative meniscus lens L11 having an aspherical surface on the object side and facing a convex surface, a negative meniscus lens L12 having a concave surface facing the object side, a biconvex lens L13, a biconvex lens L14, and a biconcave lens L15. It is composed of a bonded lens made of.

The negative meniscus lens L11 of the first lens group G1 corresponds to the negative lens L1m, the negative meniscus lens L12 corresponds to the negative lens L2m, and the biconvex lens L13 corresponds to the positive lens L1p.

The second lens group G2 is composed of a junction lens composed of a biconvex lens L21, a negative meniscus lens L22 with a concave surface facing the object side, and a biconvex lens L23 having aspherical surfaces on both sides.

The third lens group G3 is composed of a biconcave lens L31 having an aspherical surface on the image plane side and a negative meniscus lens L32 with the concave surface facing the object side.

The specification values of the imaging optical system according to the fourth embodiment are shown below.
Numerical Example 4
Unit: mm
[Surface data]
Surface number rd nd vd ΔPgF
Physical surface ∞ (d0)
1 * 22.7288 1.2000 1.59271 66.97
2 10.3746 6.6313
3 -19.3202 0.8000 1.98613 16.48 0.0469
4 -71.1259 0.1500
5 530.3897 2.5801 2.05090 26.94
6 -25.9928 0.1500
7 26.1508 2.4646 2.05090 26.94
8-476.9596 0.8000 1.54072 47.20
9 23.6409 2.7503
10 (aperture) ∞ (d10)
11 76.9533 3.7681 1.49700 81.61
12 -13.3024 0.8000 1.84666 23.78
13 -116.0370 1.2382
14 * 81.5067 5.6667 1.85135 40.10
15 * -15.7000 (d15)
16 -89.3952 1.1700 1.69350 53.20
17 * 56.9079 3.7384
18 -21.8172 0.8000 1.51680 64.20
19 -33.2026 (BF)
Image plane ∞

[Aspherical data]
1 side 14 sides
K 0.00000 -1.00000
A4 2.37229E-05 -1.25375E-05
A6 -1.73149E-07 6.01878E-07
A8 2.87882E-09 -8.10717E-09
A10 -1.87176E-11 5.33151E-11
A12 5.08950E-14 9.02453E-14
A14 0.00000E + 00 -2.18577E-15
A16 0.00000E + 00 6.91343E-18
A18 0.00000E + 00 -9.36600E-21
A20 0.00000E + 00 0.00000E + 00

15 sides 17 sides
K 0.00000 0.00000
A4 5.08564E-05 6.90067E-06
A6 9.14727E-08 -2.15542E-07
A8 5.46549E-09 8.76352E-09
A10 -1.35814E-10 -1.11219E-10
A12 1.49854E-12 7.43289E-13
A14 -6.62382E-15 -2.52714E-15
A16 9.57636E-18 1.09020E-17
A18 0.00000E + 00 -1.31489E-19
A20 0.00000E + 00 5.84423E-22

[Various data]
INF -0.5x Focal length 24.72 19.96
F number 3.58 3.88
Full angle of view 2ω 80.74 78.79
Image height Y 21.63 21.63
Lens total length 63.50 63.50

[Variable interval data]
INF -0.5 times
d0 ∞ 42.6065
d10 7.5916 3.1877
d15 1.5000 5.9039
BF 19.7007 19.7007

[Lens group data]
Focal length of group origin
G1 1 125.97
G2 11 18.78
G3 16 -35.20

FIG. 21 is a lens configuration diagram of the imaging optical system according to the fifth embodiment of the present invention when the lens is focused at infinity. The imaging optical system of the fifth embodiment has a first lens group G1 having a positive refractive power, an aperture aperture S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power in order from the object side. It consists of group G3. When focusing from an infinite object to a short-range object, the first lens group G1 and the aperture stop S, the third lens group G3 are fixed to the image plane, and the second lens group G2 is along the optical axis. Move to the object side.

The first lens group G1 includes a negative meniscus lens L11 having an aspherical surface on the object side and a convex surface, a negative meniscus lens L12 having a concave surface on the object side, and a positive meniscus lens L12 having a concave surface on the object side. It is composed of L13, a junction lens composed of a biconvex lens L14 and a biconcave lens L15.

The negative meniscus lens L11 of the first lens group G1 corresponds to the negative lens L1m, the negative meniscus lens L12 corresponds to the negative lens L2m, and the positive meniscus lens L13 corresponds to the positive lens L1p.

The second lens group G2 is composed of a junction lens composed of a biconvex lens L21, a negative meniscus lens L22 with a concave surface facing the object side, and a biconvex lens L23 having aspherical surfaces on both sides.

The third lens group G3 is composed of a biconcave lens L31 having an aspherical surface on the image plane side and a biconcave lens L32.

The specification values of the imaging optical system according to the fifth embodiment are shown below.
Numerical Example 5
Unit: mm
[Surface data]
Surface number rd nd vd ΔPgF
Physical surface ∞ (d0)
1 * 25.6184 1.2000 1.59271 66.97
2 11.4333 8.0123
3 -18.1129 0.8000 1.98613 16.48 0.0469
4 -44.1159 0.1971
5 -147.1051 2.6311 1.91082 35.25
6 -22.7900 0.1500
7 31.1944 2.9595 2.05090 26.94
8 -53.7634 0.8000 1.51742 52.15
9 26.1741 2.6500
10 (aperture) ∞ (d10)
11 109.2546 3.6930 1.49700 81.61
12 -12.2532 0.8000 1.84666 23.78
13 -100.9833 1.5488
14 * 77.4354 5.7994 1.85135 40.10
15 * -15.7000 (d15)
16 -160.8924 1.1700 1.69350 53.20
17 * 52.6581 2.3949
18 -47.2602 0.8000 1.51680 64.20
19 177.5154 (BF)
Image plane ∞

[Aspherical data]
1 side 14 sides
K 0.00000 -1.00000
A4 9.06338E-06 -1.01897E-05
A6 -1.12275E-07 4.93656E-07
A8 1.32780E-09 -7.20364E-09
A10 -7.04619E-12 5.54057E-11
A12 1.39247E-14 -5.99477E-15
A14 0.00000E + 00 -1.70460E-15
A16 0.00000E + 00 3.36146E-19
A18 0.00000E + 00 3.83291E-20
A20 0.00000E + 00 0.00000E + 00

15 sides 17 sides
K 0.00000 0.00000
A4 5.53058E-05 1.08652E-05
A6 6.74321E-08 -2.28202E-07
A8 4.13057E-09 1.06980E-08
A10 -1.21125E-10 -1.42735E-10
A12 1.60787E-12 8.63381E-13
A14 -9.27863E-15 -1.83718E-16
A16 1.98182E-17 -1.91254E-17
A18 0.00000E + 00 -1.80352E-20
A20 0.00000E + 00 5.29014E-22

[Various data]
INF -0.5x Focal length 24.72 19.31
F number 3.58 3.77
Full angle of view 2ω 79.61 79.32
Image height Y 21.63 21.63
Lens total length 64.38 64.38

[Variable interval data]
INF -0.5 times
d0 ∞ 40.2578
d10 7.5717 3.2675
d15 1.5000 5.8043
BF 19.7000 19.7000

[Lens group data]
Focal length of group origin
G1 1 71.26
G2 11 19.19
G3 16 -31.22

FIG. 26 is a lens configuration diagram of the imaging optical system according to the sixth embodiment of the present invention when the lens is focused at infinity. The imaging optical system of Example 6 has a first lens group G1 having a positive refractive power, an aperture aperture S, a second lens group G2 having a positive refractive power, and a third lens having a negative refractive power in order from the object side. It consists of group G3. When focusing from an infinite object to a short-range object, the first lens group G1 and the aperture stop S, the third lens group G3 are fixed to the image plane, and the second lens group G2 is along the optical axis. Move to the object side.

The first lens group G1 includes a negative meniscus lens L11 having an aspherical surface on the object side and a convex surface, a negative meniscus lens L12 having a concave surface on the object side, and a positive meniscus lens L12 having a concave surface on the object side. It is composed of L13, a junction lens composed of a biconvex lens L14 and a biconcave lens L15.

The negative meniscus lens L11 of the first lens group G1 corresponds to the negative lens L1m, the negative meniscus lens L12 corresponds to the negative lens L2m, and the positive meniscus lens L13 corresponds to the positive lens L1p.

The second lens group G2 is composed of a junction lens composed of a biconvex lens L21, a negative meniscus lens L22 with a concave surface facing the object side, and a biconvex lens L23 having aspherical surfaces on both sides.

The third lens group G3 is composed of a biconcave lens L31 having an aspherical surface on the image plane side and a biconcave lens L32.

The specification values of the imaging optical system according to the sixth embodiment are shown below.

The values corresponding to the conditional expressions corresponding to each of the above embodiments are shown below.
Numerical Example 6
Unit: mm
[Surface data]
Surface number rd nd vd ΔPgF
Physical surface ∞ (d0)
1 * 22.7667 1.2000 1.59271 66.97
2 10.6074 9.2705
3 -17.9907 0.8000 1.98613 16.48 0.0469
4-41.5064 0.1500
5 -112.4554 2.2169 2.05090 26.94
6 -23.5811 0.1500
7 29.9060 2.1656 2.05090 26.94
8-1274.6856 0.8000 1.54072 47.20
9 24.7640 2.6470
10 (aperture) ∞ (d10)
11 215.5201 4.3408 1.43700 95.10
12 -10.4430 0.8000 1.77047 29.74
13 -32.6126 0.6724
14 * 84.9777 6.7381 1.63858 55.18
15 * -12.8792 (d15)
16 -145.6860 1.1700 1.69350 53.20
17 * 200.0000 2.0402
18 -36.1124 0.8000 1.51680 64.20
19 62.2874 (BF)
Image plane ∞

[Aspherical data]
1 side 14 sides
K 0.00000 -1.00000
A4 1.98159E-05 -7.00733E-06
A6 -5.76599E-08 2.44079E-07
A8 1.25984E-09 -8.49429E-09
A10 -6.54968E-12 1.02991E-10
A12 1.90833E-14 -2.77954E-13
A14 0.00000E + 00 -8.37375E-15
A16 0.00000E + 00 8.67837E-17
A18 0.00000E + 00 -2.37525E-19
A20 0.00000E + 00 0.00000E + 00

15 sides 17 sides
K 0.00000 0.00000
A4 8.51517E-05 -3.26971E-06
A6 1.39981E-07 -2.42596E-07
A8 -2.23789E-09 1.49012E-08
A10 -2.27896E-11 -2.11588E-10
A12 1.18935E-12 1.30844E-12
A14 -1.18526E-14 -1.35166E-16
A16 3.95162E-17 -3.83081E-17
A18 0.00000E + 00 1.14364E-19
A20 0.00000E + 00 1.45352E-22

[Various data]
INF -0.5x Focal length 24.00 19.39
F number 3.61 3.93
Full angle of view 2ω 81.28 78.03
Image height Y 21.63 21.63
Lens total length 67.30 67.30

[Variable interval data]
INF -0.5 times
d0 ∞ 40.1817
d10 7.7041 3.3343
d15 3.9344 8.3042
BF 19.6990 19.6990

[Lens group data]
Focal length of group origin
G1 1 341.01
G2 11 19.42
G3 16 -31.85

The values corresponding to the conditional expressions corresponding to each of the above embodiments are shown below.
[Conditional expression correspondence value]
Conditional expression Example 1 Example 2 Example 3
[1] -0.70 <f2 / f3 <-0.30 -0.57 -0.62 -0.55
[2] νd1m <25.00 16.48 20.02 16.48
[3] ΔPgF1m> 0.0150 0.0469 0.0312 0.0469
[4] NdL1p> 1.85 2.05 2.05 2.05
[5] 1.25 <β3 <2.33 1.76 1.81 1.71
[6] 2.50 <LT / Ymax <3.30 3.02 2.98 2.99
[7] 2.50 <β3 ^ 2 * (1-β2 ^ 2) <3.50 3.10 3.26 2.92

Conditional expression Example 4 Example 5 Example 6
[1] -0.70 <f2 / f3 <-0.30 -0.53 -0.61 -0.61
[2] νd1m <25.00 16.48 16.48 16.48
[3] ΔPgF1m> 0.0150 0.0469 0.0469 0.0469
[4] NdL1p> 1.85 2.05 1.91 2.05
[5] 1.25 <β3 <2.33 1.66 1.69 1.65
[6] 2.50 <LT / Ymax <3.30 2.94 2.98 3.11
[7] 2.50 <β3 ^ 2 * (1-β2 ^ 2) <3.50 2.73 2.74 2.72

G1 1st lens group G2 2nd lens group G3 3rd lens group S Aperture aperture L1m Negative lens L1m
L2m Negative lens L2m
L1p Positive lens L1p

Claims (6)

From the object side, it is composed of a first lens group G1 having a positive refractive index, an aperture aperture S, a second lens group G2 having a positive refractive force, and a third lens group G3 having a negative refractive force. The first lens group G1 has a negative meniscus lens with a convex on the object side on the most object side, and the first lens group G1 and the aperture when focusing from an infinity object to a short-range object. An imaging optical system characterized in that the aperture S and the third lens G3 are fixed, and the second lens group G2 moves toward an object along an optical axis to satisfy the following conditional expression.
(1) -0.70 <f2 / f3 <-0.30
f2: Focal length of the second lens group G2 f3: Focal length of the third lens group G3 The imaging optical system according to claim 1, wherein the first lens group G1 has a negative lens satisfying the following conditional expression.
(2) νd1m <25.00
(3) ΔPgF1m> 0.0150
νd1m: Abbe number of the negative lens ΔPgF1m: Abnormal dispersibility of the negative lens ΔPgF1m = PgF1m + 0.0018 × νd1m ― 0.64833
PgF1m is a partial dispersion ratio PgF with respect to the g-line and F-line of the negative lens. Claim 1 or 2, wherein the first lens group G1 has an arrangement of a negative lens L1m, a negative lens L2m, and a positive lens L1p in order from the object side, and the positive lens L1p satisfies the following conditional expression. The imaging optical system described.
(4) NdL1p> 1.85
NdL1p: Refractive index of the positive lens L1p The imaging optical system according to any one of claims 1 to 3, wherein the imaging optical system satisfies the following conditional expression.
(5) 1.25 <β3 <2.33
β3: Lateral magnification of the third lens group G3 in the infinity state The imaging optical system according to any one of claims 1 to 4, wherein the imaging optical system satisfies the following conditions.
(6) 2.50 <LT / Ymax <3.30
LT: Surface spacing from the most object-side surface of the first lens group G1 to the image plane in the infinity-focused state Ymax: Maximum image height of the imaging optical system The imaging optical system according to any one of claims 1 to 5, wherein the imaging optical system satisfies the following conditions.
(7) 2.50 <β3 ^ 2 * (1-β2 ^ 2) <3.50
β3: Lateral magnification of the third lens group G3 in the infinity state β2: Lateral magnification of the second lens group G2 in the infinity state

Images