JP7247018B2 - Optical system and imaging device having the same - Google Patents

Description

The present invention relates to an optical system, and is suitable for digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, and the like.

Conventionally, focusing in an optical system is performed by moving the entire optical system or by moving some lenses of the optical system. A telephoto lens with a long focal length optical system is large and heavy, and it is difficult to move the entire optical system for focusing. For this reason, telephoto lenses employ a so-called inner focus system in which focusing is performed by moving a relatively small and lightweight lens group other than the heavy front lens group. An inner focus type telephoto lens has a first lens group with a positive refractive index, a second lens group with a positive or negative refractive index, and a third lens group with a positive or negative refractive index, which are arranged in order from the object side to the image side. It has three lens groups, and the second lens group performs focusing.

Further, conventionally, an optical system has been proposed in which part or all of a lens is driven in the direction perpendicular to the optical axis in order to correct image blurring due to vibration. A telephoto lens with a long focal length optical system is large and heavy, so all or part of the relatively small and lightweight rear lens group is driven in the direction perpendicular to the optical axis to reduce vibration. is adopted.

In Patent Document 1, a first lens group with positive refractive power, a second lens group with positive refractive power, and a third lens group with negative refractive power are arranged in order from the object side to the image side, A telephoto lens is disclosed in which image stabilization correction is performed in the middle group of the third lens group.

Further, in Patent Document 2, there is a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, which are arranged in order from the object side to the image side. However, a telephoto lens is disclosed in which the middle group of the third lens group performs vibration reduction correction.

JP 2012-242504 A JP 2014-211496 A

In the inner focus optical system, high-speed focusing is possible by moving the compact and lightweight lens group. Performance is subject to change. In particular, in a telephoto lens having a first lens group with a positive refractive index and a second lens group with a negative refractive index arranged in order from the object side to the image side, focusing is performed by the second lens group. Aberrations such as spherical aberration and coma aberration, which are largely generated in the group, are canceled by the aberration of the second lens group. Therefore, it is necessary to generate a large aberration in the second lens group, and the deterioration of optical performance due to focusing becomes large. Moreover, since the change in optical performance due to eccentricity becomes large, it is difficult to achieve high optical performance during manufacturing.

In addition, it is necessary to reduce the weight of the telephoto lens, which is a heavy weight, and to shorten the total lens length of the optical system.

Patent Documents 1 and 2 do not disclose a method for shortening the total lens length while reducing the deterioration of optical performance due to focusing with a small number of lenses in order to reduce the weight of the optical system.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a compact, lightweight optical system capable of reducing changes in optical performance due to focusing, and an imaging apparatus having the same.

An optical system as one aspect of the present invention comprises a first lens group with positive refractive power, a second lens group with positive refractive power, and a third lens with negative refractive power, which are arranged in order from the object side to the image side. An optical system in which the distance between adjacent lens groups changes during focusing, wherein the third lens group comprises a first subgroup, a second subgroup, and a third subgroup arranged in order from the object side to the image side. The second lens group moves during focusing, moves in a direction including a component in the direction perpendicular to the optical axis during image blur correction, and is the focal point of the optical system when focusing at infinity. When the distance is f, the focal length of the third lens group is f3, the lateral magnification of the second subgroup is β3B, the lateral magnification of the third subgroup is β3C , and the focal length of the first subgroup is f3A ,
-0.32<f3/f<-0.05
−4.00<(1−β3B)×β3C<−2.00
-1.20<f3A/f<-0.40
It is characterized by satisfying the following conditional expression.

Advantageous Effects of Invention According to the present invention, it is possible to provide an optical system that is compact and lightweight and capable of reducing changes in optical performance due to focusing, and an imaging apparatus having the same.

2 is a cross-sectional view of the lens in Example 1 when focusing on infinity. FIG. (A) and (B) are aberration diagrams when focusing on infinity in Example 1, and aberration diagrams when focusing on an object distance of 4.5 m. FIG. 11 is a cross-sectional view of the lens of Example 2 when focusing at infinity; (A) and (B) are aberration diagrams when focusing on infinity in Example 2, and aberration diagrams when focusing on an object distance of 6 m. FIG. 11 is a cross-sectional view of the lens in Example 3 when focusing at infinity; (A) and (B) are aberration diagrams when focusing on infinity in Example 3, and aberration diagrams when focusing on an object distance of 4.5 m. FIG. 12 is a cross-sectional view of the lens of Example 4 when focusing at infinity. (A) and (B) are aberration diagrams when focusing on infinity in Example 4, and aberration diagrams when focusing on an object distance of 4.5 m. 1 is a schematic diagram of a main part of an imaging device of the present invention; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same reference numerals are given to the same members, and overlapping descriptions are omitted.

FIG. 1 is a sectional view of the lens of Example 1 when focusing on infinity. FIGS. 2A and 2B are aberration diagrams of Example 1 when focusing on an object at infinity and when focusing on an object distance of 4.5 m, respectively. The optical system of Example 1 has a focal length of 582 mm and an F number of 11.3.

FIG. 3 is a cross-sectional view of the lens of Example 2 when focusing on infinity. 4A and 4B are aberration diagrams of Example 2 when focusing on infinity and when focusing on an object distance of 6 m, respectively. The optical system of Example 2 has a focal length of 776 mm and an F number of 11.3.

FIG. 5 is a cross-sectional view of the lens when focusing on infinity in Example 3. FIG. 6A and 6B are aberration diagrams of Example 3 when focusing on infinity and when focusing on an object distance of 4.5 m, respectively. The optical system of Example 3 has a focal length of 582 mm and an F number of 11.3.

FIG. 7 is a sectional view of the lens of Example 4 when focusing on infinity. 8A and 8B are aberration diagrams of Example 4 when focusing on infinity and when focusing on an object distance of 4.5 m, respectively. The optical system of Example 4 has a focal length of 582 mm and an F number of 8.2.

The optical system of each embodiment is an optical system used in an imaging apparatus such as a digital video camera, a digital still camera, a broadcast camera, a silver halide film camera, a surveillance camera, and the like. The optical system of each numerical example can also be used as a projection optical system for a projection device (projector).

In each lens sectional view, the left side is the object side (front), and the right side is the image side (rear side). The optical system of each embodiment is configured with a plurality of lens groups. In the present specification, a lens group is a group of lenses that move together or stay still during focusing. That is, in the optical system of each embodiment, the distance between adjacent lens groups changes during focusing from infinity to a short distance. Note that the lens group may be composed of one lens, or may be composed of a plurality of lenses. Also, the lens group may include an aperture stop.

In each lens sectional view, Li indicates the i-th lens group, where i is the order of the lens groups from the object side. SP is the aperture stop. IP is the image plane, and when the optical system of each embodiment is used as the optical system of a digital still camera or a digital video camera, the imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is arranged. be done. When the optical system of each embodiment is used as the optical system of a silver salt film camera, a photosensitive surface corresponding to the film surface is placed on the image plane IP. An optical block corresponding to an optical filter, a face plate, a low-pass filter, an infrared cut filter, etc. can also be arranged on the object side of the image plane IP.

In the spherical aberration diagrams, Fno is the F-number and indicates the amount of spherical aberration for the d-line (wavelength 587.6 nm) and g-line (wavelength 435.8 nm). In the astigmatism diagrams, S indicates the amount of astigmatism on the sagittal image plane for the d-line, and M indicates the amount of astigmatism on the meridional image plane for the d-line. The distortion diagram shows the amount of distortion with respect to the d-line. The chromatic aberration diagram shows the amount of chromatic aberration at the g-line. ω is a half angle of view.

The optical system of the present invention includes a first lens group L1 with positive refractive power, a second lens group L2 with positive refractive power, and a third lens group L3 with negative refractive power, which are arranged in order from the object side to the image side. A diaphragm SP is provided between the second lens group L2 and the third lens group L3. By moving the second lens unit L2 toward the object side, focusing from an infinity object to a short distance object is performed.

In the optical system of the present invention, the composite refractive power of the first lens group L1 with positive refractive power and the second lens group L2 with positive refractive power is the front group with positive refractive power and the third lens group with negative refractive power as the rear group. It has a telephoto type refractive power arrangement that shortens the total lens length (optical total length).

In addition, by sharing the refractive power of the first lens unit L1, in which paraxial axial rays are high and large spherical aberration, coma aberration, axial chromatic aberration, etc. occur, to the second lens unit L2 with positive refractive power, It is possible to reduce the occurrence of high-order aberrations.

In addition, it is possible to reduce the change in optical performance at the time of eccentricity, and to improve the ease of manufacture.

In addition, since the refractive power of the first lens group L1 is smaller than that of the refractive power arrangement in which the second lens group has a negative refractive power, the angle of incidence of light rays on the second lens group L2, which is the focus lens group, becomes moderate. Become. Therefore, since the variation in the height of light rays passing through the second lens unit L2 during focusing is reduced, it is possible to reduce the variation in optical performance due to focusing.

Further, in the optical system of the present invention, the lens closest to the image side in the first lens unit L1 is composed of a negative lens. By arranging a lens with negative refractive power on the object side of the focus lens group, it is possible to further moderate the angle of incidence of light rays on the focus lens group and reduce changes in optical performance due to focusing.

Further, the refractive power arrangement in the first lens unit L1 can be a telephoto type arrangement, and the size of the lens can be reduced.

Further, the optical system of the present invention satisfies the following conditional expression (1), where f is the focal length of the optical system at infinity and f3 is the focal length of the third lens unit L3.

-0.32<f3/f<-0.05 (1)
Conditional expression (1) is a conditional expression for maintaining good optical performance while shortening the total lens length. If the refractive power of the third lens unit L3 becomes too large beyond the upper limit of conditional expression (1), the telephoto-type refractive power arrangement that is asymmetrical with respect to the stop SP becomes too strong, resulting in curvature of field and distortion. Such an off-axis aberration becomes worse. Conversely, when the lower limit of conditional expression (1) is not reached and the refractive power of the third lens unit L3 becomes small, the telephoto-type refractive power arrangement is weakened and the overall lens length becomes long.

In each numerical example, the third lens group L3 is arranged in order from the object side to the image side, namely, the first subgroup 3A with negative refracting power, the second subgroup 3B with negative refracting power, and the third subgroup 3B with positive refracting power. It consists of three subgroups 3C. During vibration reduction (image blur correction), the second subgroup 3B moves in a direction including a component in the direction perpendicular to the optical axis.

By setting the first partial group 3A to have a negative refractive power, the front principal point of the third lens group L3 is positioned on the object side, making it possible to shorten the overall lens length.

Further, the optical system of the present invention preferably satisfies the following conditional expression (2), where D3A is the air space on the optical axis between the first partial group 3A and the second partial group 3B.

0.01<D3A/f<0.05 (2)
Conditional expression (2) is a conditional expression for maintaining an appropriate vibration reduction sensitivity while shortening the total length of the lens. If the air gap D3A on the optical axis between the first subgroup 3A and the second subgroup 3B becomes too long beyond the upper limit of the conditional expression (2), the overall lens length becomes long. In addition, the closer the distance between the third subgroup 3C and the image plane, the smaller the lateral magnification of the third subgroup 3C, and the lower the vibration isolation sensitivity. In addition, since the second subgroup 3B is arranged at the rear, the lens diameter becomes too large to take in the peripheral light flux, resulting in an increase in weight and making it difficult to drive during image stabilization. Conversely, if the air gap D3A on the optical axis between the first lens group 3A and the second subgroup 3B becomes short below the lower limit of conditional expression (2), the distance between the third lens group L3 and the image plane becomes long. As a result, the lateral magnification of the third subgroup 3C becomes too large. As a result, the vibration reduction sensitivity is too high, and the second subgroup 3B moves slightly due to minute vibrations such as shutter shocks during photography, causing image blurring.

Further, the optical system of the present invention preferably satisfies the following conditional expression (3), where f3B is the focal length of the second subgroup 3B.

-0.30<f3B/f<-0.05 (3)
Conditional expression (3) is a conditional expression for shortening the total length of the lens while appropriately setting the vibration reduction sensitivity. If the upper limit of conditional expression (3) is exceeded and the refracting power of the second subgroup 3B becomes too weak, the lens must be moved in the direction of the optical axis greatly during image stabilizing. As a result, the lens drive mechanism becomes large, and as a result, the optical system becomes large. Conversely, if the lower limit of conditional expression (3) is exceeded and the refracting power of the second sub-group 3B becomes too strong, various aberrations cannot be corrected in the third lens group L3, and astigmatism in particular will not be corrected. It gets worse.

Further, the optical system of the present invention preferably satisfies the following conditional expression (4), where L is the total lens length of the optical system when focusing on infinity.

0.40<L/f<0.70 (4)
Conditional expression (4) is a conditional expression for maintaining good optical performance while shortening the total lens length. If the upper limit of conditional expression (4) is exceeded, the total length of the lens becomes too long, resulting in an increase in the size of the optical system. Conversely, if the total lens length becomes too small below the lower limit of conditional expression (4), the spherical aberration, coma, axial chromatic aberration, and chromatic aberration of magnification generated in the first lens unit L1 become too large, and each aberration is reduced. Since it cannot be sufficiently corrected, it becomes difficult to achieve high optical performance. In order to achieve high optical performance, it is necessary to increase the number of lenses in the first lens unit L1, so the weight cannot be reduced.

Further, the optical system of the present invention preferably satisfies the following conditional expression (5), where f3A is the focal length of the first partial group 3A.

-1.20<f3A/f<-0.20 (5)
Conditional expression (5) is a conditional expression for maintaining good optical image performance while shortening the total lens length. If the power of the first partial group 3A becomes too strong beyond the upper limit of conditional expression (5), the curvature of field worsens, and the optical performance deteriorates. Conversely, if the lower limit of conditional expression (5) is not reached and the power of the first subgroup 3A becomes too weak, the power of the third lens group L3 will become too weak. As a result, the effect of the telephoto type is weakened, making it difficult to shorten the total length of the lens.

Further, the optical system of the present invention preferably satisfies the following conditional expression (6), where β3B is the lateral magnification of the second subgroup 3B and β3C is the lateral magnification of the third subgroup 3C.

-4.00<(1-β3B)×β3C<-2.00 (6)
Conditional expression (6) is a conditional expression for appropriately setting the combination of the lateral magnification of the second subgroup 3B, which is the anti-vibration group, and the lateral magnification of the third subgroup 3C arranged on the image side thereof. be. Exceeding the upper limit of conditional expression (6) is not preferable because the amount of movement of the second subgroup 3B during image stabilization correction increases and the diameter of the optical system increases. Conversely, if the lower limit of conditional expression (6) is exceeded, aberration fluctuations increase during image stabilizing correction, which is not preferable. Further, when the lower limit of conditional expression (6) is exceeded, the image stabilization sensitivity becomes too sensitive, and image blur occurs when the image stabilization group moves for purposes other than image blur correction.

Further, it is preferable that the numerical ranges of the conditional expressions (1) to (6) are set to the ranges of the following conditional expressions (1a) to (6a), respectively.

-0.260<f3/f<-0.075 (1a)
0.0125<D3A/f<0.0375 (2a)
-0.200<f3B/f<-0.055 (3a)
0.43<L/f<0.65 (4a)
-1.15<f3A/f<-0.30 (5a)
-3.50<(1-β3B)×β3C<-2.20 (6a)
Further, it is more preferable to set the numerical ranges of the conditional expressions (1) to (6) to the ranges of the following conditional expressions (1b) to (6b), respectively.

-0.20<f3/f<-0.10 (1b)
0.015<D3A/f<0.025 (2b)
-0.15<f3B/f<-0.05 (3b)
0.46<L/f<0.60 (4b)
-1.10<f3A/f<-0.40 (5b)
-3.00<(1-β3B)×β3C<-2.40 (6b)
In the optical systems of Examples 1, 2, and 4, in order to further reduce the number of lenses, a diffractive optical element is provided in the positive lens unit closest to the object side where the most paraxial on-axis ray and pupil paraxial ray are at a high position in the optical system. By arranging the Since the diffractive optical element has a negative Abbe number (νd=-3.453), it is possible to correct axial chromatic aberration and lateral chromatic aberration occurring in the first lens unit L1 by giving positive refractive power to the diffractive surface. Become. Since the diffraction surface has a positive refractive power, the positive refractive power of the first lens unit L1 can be shared by the diffraction surface, so that spherical aberration and coma can be corrected. Furthermore, in combination with the aspherical effect obtained by changing the periodic structure of the diffractive optical element, it is possible to construct the first lens unit L1 with a minimum number of positive lenses, and weight reduction can be achieved.

Next, the configuration of each lens group will be described. In Examples 1 and 4, the first lens unit L1 is composed of a cemented lens of a biconvex lens cemented with a negative meniscus lens having a concave surface on the object side, and a negative meniscus lens having a concave surface on the object side, which are arranged in order from the object side to the image side. . The cemented surface of the cemented lens has a diffractive surface. Methods for reducing axial chromatic aberration, lateral chromatic aberration, and variations in optical performance due to focus are as described above. In Example 2, the first lens unit L1 is composed of a positive meniscus lens with a convex surface on the object side, a cemented lens of a biconvex lens and a biconcave lens, and a negative meniscus lens with a concave surface on the object side, which are arranged in order from the object side to the image side. be. The cemented surface of the cemented lens has a diffractive surface. In Example 3, the first lens unit L1 is composed of a positive meniscus lens with a convex surface on the object side, a biconvex lens, a positive meniscus lens with a convex surface on the object side, and a biconcave lens, which are arranged in order from the object side to the image side.

Further, in Example 1, the second lens group L2 is composed only of a biconvex lens. In Examples 2 to 4, the second lens unit L2 is composed only of a positive meniscus lens having a convex surface on the object side. By constructing the second lens unit L2 with a single positive lens, the weight of the lens can be reduced and high-speed focusing is possible. In each embodiment, the second lens group L2 is composed of one element in order to reduce the weight of the lens and improve the focusing speed. is.

In Examples 1, 2, and 4, the third lens group L3 is composed of a first partial group 3A composed of a cemented lens of a biconcave lens and a biconvex lens, and a cemented lens of a biconvex lens and a biconcave lens, and a biconcave lens. It consists of a second subgroup 3B and a third subgroup 3C of a biconvex lens. In Example 3, the third lens group L3 includes a first subgroup 3A composed of a cemented lens of a biconcave lens and a biconvex lens, and a second subgroup 3B composed of a cemented lens of a biconvex lens and a biconcave lens, and a biconcave lens. , and a third subgroup 3C of a positive meniscus lens convex to the image side.

In all the examples, vibration isolation is performed by moving the second subgroup 3B perpendicularly to the optical axis. Further, although the second partial group 3B is composed of three lenses in each embodiment, it is desirable to be composed of two or more lenses in order to suppress variations in chromatic aberration during image stabilization.

Numerical Examples 1 to 4 corresponding to Examples 1 to 4, respectively, are shown below. In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the axial distance (distance on the optical axis) between the m-th surface and the (m+1)-th surface. . However, m is the surface number counted from the light incident side. Also, nd represents the refractive index for the d-line of each optical member, and νd represents the Abbe number of the optical member. Note that the Abbe number νd of a certain material is defined by Nd , NF, NC,
νd = (Nd-1)/(NF-NC)
is represented by

In each numerical example, d, focal length (mm), F-number, and half angle of view (degrees) are all values when the optical system of each example is focused on an infinite object. The back focus (BF) is the distance on the optical axis from the final lens surface (lens surface closest to the image side) to the paraxial image surface expressed in air conversion length. The “total length of the lens” is the length obtained by adding the back focus to the distance on the optical axis from the front surface (lens surface closest to the object side) of the optical system to the final surface. The term "lens group" is not limited to the case of being composed of a plurality of lenses, but also includes the case of being composed of one lens.

The phase shape ψ of the diffraction grating is defined by m as the diffraction order of diffracted light, λ0 as the design wavelength, h as the height from the optical axis in the direction orthogonal to the optical axis, and Ci as the phase coefficient (i=1, 2, 3...), it is represented by the following equation.

ψ(h,m)=(2π/mλ0)×(C1·h2+C2·h4+C3·h6+...)
When the optical surface is an aspherical surface, (diffraction) is displayed on the right side of the surface number. The aspherical shape has X as the displacement amount from the surface vertex in the optical axis direction, h as the height from the optical axis in the direction perpendicular to the optical axis, R as the paraxial radius of curvature, k as the conic constant, A4, A6, When A8 and A10 are aspheric coefficients of each order,
x=(h ² /R)/[1+{1−(1+k)(h/R) ² } ^1/2 +A4×h ⁴ +A6×h ⁶
+A8× ^h8 +A10× ^h10
is represented by "e±XX" in each aspheric coefficient means "×10± ^XX ".

Table 1 shows the relationship between each conditional expression and numerical examples.
[Numerical Example 1]
unit mm

Surface data surface number rd nd νd
1 58.978 11.86 1.48749 70.2
2 (Diffraction) -205.536 2.70 1.91082 35.3
3 -776.181 61.26
4 -46.263 1.30 1.83481 42.7
5 -112.060 (variable)
6 120.340 2.08 1.48749 70.2
7 -488.018 (Variable)
8 (Aperture) ∞ 6.43
9 -43.031 1.00 1.90043 37.4
10 43.031 3.82 1.65412 39.7
11 -29.498 12.32
12 107.096 3.70 1.65412 39.7
13 -22.333 0.80 1.59282 68.6
14 293.053 0.63
15 -76.788 0.80 1.80400 46.5
16 54.248 1.33
17 63.147 2.07 1.59551 39.2
18 -767.459 138.29
Image plane ∞

Aspheric data 2nd surface (diffractive surface)
A2=-4.47403e-005 A4=1.03980e-008 A6=-5.47538e-012 A8=2.97170e-015
A10=-1.66936e-018

Various data Zoom ratio 1.00

Focal length 582.00
F number 11.31
Half angle of view (degrees) 2.13
Image height 21.64
Lens length 287.05
BF 138.29

When focusing on infinity When focusing on an object distance of 4.5m
d5 17.42 2.51
d7 19.23 34.14


Lens group data group Starting surface Focal length
1 1 386.12
2 6 198.25
3 8 -86.66

3A 8-342.02
3B 12 -55.81
3C17 98.07

[Numerical Example 2]
unit mm

Surface data surface number rd nd νd
1 81.395 9.89 1.48749 70.2
2 767.797 30.35
3 83.964 9.43 1.48749 70.2
4 (Diffraction) -277.706 2.70 1.80400 46.5
5 113.168 85.76
6 -49.232 1.30 1.74400 44.8
7 -95.332 (variable)
8 67.893 2.25 1.51633 64.1
9 448.372 (variable)
10 (Aperture) ∞ 6.43
11 -43.031 1.00 1.90043 37.4
12 43.031 3.82 1.65412 39.7
13 -29.498 12.32
14 107.096 3.70 1.65412 39.7
15 -22.333 0.80 1.59282 68.6
16 293.053 0.63
17 -76.788 0.80 1.80400 46.5
18 54.248 1.33
19 63.147 2.07 1.59551 39.2
20 -767.459 138.10
Image plane ∞

Aspheric surface data 4th surface (diffraction surface)
A2=-4.52286e-005 A4=6.40571e-009 A6=-8.87101e-013 A8=-7.49305e-016
A10= 5.24559e-019

Various data Zoom ratio 1.00

Focal length 775.99
F number 11.31
Half angle of view (degrees) 1.60
Image height 21.64
Lens length 365.39
BF 138.10

When focusing on infinity When focusing on an object distance of 6m
d7 32.49 16.04
d9 20.22 36.67

Lens group data group Starting surface Focal length
1 1 686.23
2 8 154.64
3 10 -86.66

3A 10 -342.02
3B 14 -55.81
3C 19 98.07

[Numerical Example 3]
unit mm

Surface data surface number rd nd νd
1 133.448 4.39 1.59349 67.0
2 245.324 9.88
3 54.814 10.00 1.43875 94.7
4 -294.426 8.61
5 59.825 5.12 1.43875 94.7
6 631.348 1.04
7 -254.244 1.30 1.74100 52.6
8 50.472 (variable)
9 64.215 1.81 1.49700 81.5
10 103.624 (variable)
11 (Aperture) ∞ 5.00
12 -63.723 1.00 1.91082 35.3
13 87.812 3.00 1.73800 32.3
14 -56.968 11.15
15 115.364 3.17 1.73800 32.3
16 -37.330 2.45 1.49700 81.5
17 180.804 0.79
18 -66.872 1.38 1.91082 35.3
19 79.176 2.11
20 -814.769 1.89 1.48749 70.2
21 -67.269 178.41
Image plane ∞

Various data Zoom ratio 1.00

Focal length 582.00
F number 11.31
Half angle of view (degrees) 2.13
Image height 21.64
Lens length 328.50
BF 178.41

When focusing on infinity When focusing on an object distance of 4.5m
d8 73.90 55.33

d10 2.10 20.67


Lens group data group Starting surface Focal length
1 1 255.94
2 9 334.63
3 11 -92.66

3A 11 -349.57
3B 15 -71.37
3C20 150.28

[Numerical Example 4]
unit mm

Surface data surface number rd nd νd
1 87.387 12.85 1.48749 70.2
2 (Diffraction) -334.980 3.00 1.83400 37.2
3 -2900.216 93.84
4 -68.593 1.30 1.80100 35.0
5 -132.015 (variable)
6 89.303 3.07 1.48749 70.2
7 417.857 (variable)
8 (Aperture) ∞ 4.99
9 -91.716 0.99 1.90043 37.4
10 30.296 4.42 1.65412 39.7
11 -42.133 9.99
12 63.149 4.36 1.65412 39.7
13 -22.130 1.75 1.59282 68.6
14 65.686 1.09
15 -76.612 0.70 1.80400 46.5
16 42.003 3.01
17 42.568 3.31 1.51742 52.4
18 -273.996 105.35
Image plane ∞

Aspheric data 2nd surface (diffraction surface)
A2=-3.30742e-005 A4=3.39180e-009 A6=-3.87395e-013 A8=-4.34279e-016
A10= 1.36105e-019

Various data Zoom ratio 1.00

Focal length 582.00
F number 8.20
Half angle of view (degrees) 2.13
Image height 21.64
Lens length 314.65
BF 105.35

When focusing on infinity When focusing on an object distance of 4.5m
d5 21.82 2.50
d7 38.83 58.15

Lens group data group Starting surface Focal length
1 1 448.61
2 6 232.27
3 8 -84.76

3A 8-610.16
3B 12 -41.84
3C17 71.46

[Imaging device]
Next, an embodiment of a digital still camera (imaging device) using the optical system of the present invention as an imaging optical system will be described with reference to FIG. FIG. 9 is a schematic diagram of the main part of the imaging device of the present invention. In FIG. 9, 10 is a camera body, and 11 is an imaging optical system configured by any one of the optical systems described in the first to fourth embodiments. Reference numeral 12 denotes a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or CMOS sensor, which is built in the camera body and receives and photoelectrically converts an optical image formed by the imaging optical system 11 . The camera body 10 may be a so-called single-lens reflex camera having a quick turn mirror, or a so-called mirrorless camera without a quick turn mirror.

By applying the optical system of the present invention to an imaging apparatus such as a digital still camera in this way, it is possible to obtain an imaging apparatus having a small overall length and a small lens system and having high focusing performance.

L1 First lens group L2 Second lens group L3 Third lens group

Claims (7)

It consists of a first lens group with positive refractive power, a second lens group with positive refractive power, and a third lens group with negative refractive power, arranged in order from the object side to the image side. An optical system with varying spacing,
the third lens group comprises a first subgroup, a second subgroup, and a third subgroup arranged in order from the object side to the image side;
the second lens group moves during focusing,
When correcting image blur, the second subgroup moves in a direction including a component in a direction perpendicular to the optical axis,
f is the focal length of the optical system when focused on infinity; f3 is the focal length of the third lens group; β3B is the lateral magnification of the second subgroup; β3C is the lateral magnification of the third subgroup ; When the focal length of one subgroup is f3A ,
-0.32<f3/f<-0.05
−4.00<(1−β3B)×β3C<−2.00
-1.20<f3A/f<-0.40
An optical system characterized by satisfying the following conditional expression: 2. The method of claim 1, wherein the first subgroup has negative refractive power, the second subgroup has negative refractive power, and the third subgroup has positive refractive power. optics. When the distance on the optical axis between the first partial group and the second partial group is D3A,
0.01<D3A/f<0.05
3. The optical system according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the second subgroup is f3B,
-0.30<f3B/f<-0.05
4. The optical system according to any one of claims 1 to 3, wherein the following conditional expression is satisfied. 5. The optical system according to any one of claims 1 to 4 , wherein said second subgroup comprises at least one positive lens and at least one negative lens. When the total lens length of the optical system when focusing on infinity is L,
0.40<L/f<0.70
6. The optical system according to any one of claims 1 to 5 , wherein the following conditional expression is satisfied. An imaging apparatus, comprising: the optical system according to any one of claims 1 to 6 ; and an imaging device for receiving an image formed by the optical system.

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