JP6957174B2 - Attachment optical system, imaging optical system, and imaging device - Google Patents

Description

The present invention relates to a variable field curvature lens, and is particularly suitable for use in an interchangeable lens type single-lens reflex camera, a mirrorless camera, a digital video camera, or the like.

Conventionally, as an attachment lens for a single-lens reflex camera or the like, an optical system that can be attached to a photographing lens to change its optical characteristics has been proposed. Patent Document 1 discloses an aberration variable optical system capable of continuously changing spherical aberration by a converter lens group mounted on the image side of a photographing lens.

Japanese Unexamined Patent Publication No. 10-68880

However, Patent Document 1 does not disclose a method for changing aberrations other than spherical aberration. Of the aberrations other than spherical aberration, especially when curvature of field occurs, the imaging characteristics of the peripheral portion are significantly deteriorated, and it is difficult to correct them by post-processing. Generally, the curvature of field can be continuously changed by changing the lens spacing of a part of the optical system, but other factors (characteristics) such as spherical aberration and the focus position on the axis are also present. It will change a lot.

Therefore, an object of the present invention is to provide an attachment optical system, an imaging optical system, and an imaging device capable of effectively changing the curvature of field.

The attachment optical system as one aspect of the present invention is an attachment optical system that can be attached to and detached from the imaging optical system, and has a front group and a rear group capable of changing the distance between them, and is the most of the front group. The lens surface on the image side and the lens surface on the most object side of the rear group are aspherical surfaces having the same reference numeral , and the refractive index of the material of the lens including the aspherical surface in the front group is N1, and the rear lens surface is N1. When the refractive index of the lens material including the aspherical surface in the group is N2, the minimum distance between the front group and the rear group is Dmin, and the maximum distance is Dmax.
1.00 ≤ N1 / N2 <1.05
0.0 <Dmin / Dmax <0.20
Satisfy the conditions .

The imaging optical system as another aspect of the present invention has a front group and a rear group in which the distance between them can be changed, and the lens surface on the most image side of the front group and the most object side of the rear group. The reference spherical surface of each of the lens surfaces is an aspherical surface having the same reference numeral, the refractive index of the lens material containing the aspherical surface in the front group is N1, and the refractive index of the lens material containing the aspherical surface in the rear group is N1. Is N2, the minimum distance between the front group and the rear group is Dmin, and the maximum distance is Dmax.
1.00 ≤ N1 / N2 <1.05
0.0 <Dmin / Dmax <0.20
Satisfy the conditions .

An imaging device as another aspect of the present invention includes an imaging optical system and an imaging element that receives an optical image formed via the imaging optical system.

Other objects and features of the present invention will be described in the following examples.

According to the present invention, it is possible to provide an attachment optical system, an imaging optical system, and an imaging device capable of effectively changing the curvature of field.

It is sectional drawing (at the time of the minimum effect) at the wide-angle end of the zoom lens which attached the attachment lens in Example 1. It is sectional drawing (at the time of the maximum effect) at the wide-angle end of the zoom lens which attached the attachment lens in Example 1. It is an aberration diagram (at the time of the minimum effect) at the wide-angle end of the zoom lens which attached the attachment lens in Example 1. It is an aberration diagram (at the time of the maximum effect) at the wide-angle end of the zoom lens which attached the attachment lens in Example 1. FIG. 5 is an aberration diagram at a wide-angle end of a zoom lens to which the attachment lens of the first embodiment is not attached. It is an aberration diagram (at the time of the minimum effect) at the telephoto end of the zoom lens which attached the attachment lens in Example 1. It is an aberration diagram (at the time of the maximum effect) at the telephoto end of the zoom lens which attached the attachment lens in Example 1. FIG. 5 is an aberration diagram at the telephoto end of a zoom lens to which the attachment lens of the first embodiment is not attached. It is sectional drawing (at the time of the minimum effect) at the wide-angle end of the zoom lens in Example 2. It is sectional drawing (at the time of the maximum effect) at the wide-angle end of the zoom lens in Example 2. It is an aberration diagram (at the time of the minimum effect) at the wide-angle end of the zoom lens in Example 2. It is an aberration diagram (at the time of the maximum effect) at the wide-angle end of the zoom lens in Example 2. It is an aberration diagram (at the time of the minimum effect) at the telephoto end of the zoom lens in Example 2. It is an aberration diagram (at the time of the maximum effect) at the telephoto end of the zoom lens in Example 2. It is the schematic of the image pickup apparatus in each Example.

Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

First, the attachment lens and the zoom lens according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 8. FIG. 1 is a cross-sectional view (at the minimum effect) of a zoom lens (imaging optical system) equipped with an attachment lens (attachment optical system) at a wide-angle end. FIG. 2 is a cross-sectional view (at the maximum effect) of the zoom lens to which the attachment lens is attached at the wide-angle end.

As shown in FIGS. 1 and 2, the attachment lens AL (attachment optical system) of this embodiment is detachably attached on the image side of the master lens ML (zoom lens as an imaging optical system). However, this embodiment is not limited to this, and the attachment optical system may be configured so as to be attached to the object side of the zoom lens.

The master lens ML has a first lens group L1 with a negative refractive power, a second lens group L2 with a positive refractive power, a third lens group L3 with a negative refractive power, and a positive refractive power in this order from the object side to the image side. It has a fourth lens group L4, a fifth lens group L5 with a negative power, and a sixth lens group L6 with a positive power. Further, the master lens ML has an aperture diaphragm SP and a flare cut diaphragm FS. The master lens ML performs zooming by changing the distance between each lens group in the direction along the optical axis OA (optical axis direction). The IP is an image plane, and when used as an image pickup optical system for a video camera or a digital still camera, an image pickup surface of an image pickup element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor is placed. When used as an imaging optical system for a silver halide film camera, a photosensitive surface corresponding to the film surface is placed.

The attachment lens AL has a front group FU and a rear group RU. The front group FU and the rear group RU can change the distance (relative distance to each other) from each other in the optical axis direction. In this embodiment, the front group FU and the rear group RU of the attachment lens AL each have an infinite focal length on the paraxial axis, and the focus fluctuation does not substantially occur even if the attachment lens AL moves in the optical axis direction.

Further, in this embodiment, the front group FU and the rear group RU of the attachment lens AL each have one or more aspherical surfaces having the same reference spherical surface. Here, the reference spherical surface is a spherical surface that passes through the surface apex on the aspherical lens surface and the point at the effective diameter of the light beam. In such a configuration, if the distance between the front group FU and the rear group RU is reduced, the aspherical effect of the front group FU and the aspherical effect of the rear group RU cancel each other out. On the other hand, when the distance between the front group FU and the rear group RU is increased, the aperture aperture is reduced with respect to the aspherical effect of the front group FU and the aspherical effect of the rear group RU, which is closer to the aperture stop SP. The aspherical effect on the side far from the SP works strongly. Therefore, by attaching the attachment lens AL of the present embodiment to the master lens ML, the curvature of field can be changed arbitrarily and effectively. In the present embodiment, the aspherical surface of the front group FU is the most image-side surface of the front group FU, and the aspherical surface of the rear group RU is the most object-side surface of the rear group RU. However, this embodiment is not limited to this.

Preferably, the attachment lens AL satisfies the following conditional expression (1).

| (Xmax-Xmin) / EA | <0.10 ... (1)
In the conditional expression (1), EA is the effective diameter of the aspherical surface of the rear group RU. Xmax and Xmin are the maximum and minimum values of the distance Xh between the aspherical surface of the front group FU and the aspherical surface of the rear group RU at the height h from the optical axis OA within the range of 0 <h <EA, respectively. Is. The conditional expression (1) defines a preferable relationship between the aspherical shapes of the front group FU and the rear group RU. When the range of the conditional expression (1) is exceeded, even if the distance between the front group FU and the rear group RU is minimized, the canceling effect of the aspherical effect does not work sufficiently, and the aspherical effect cannot be sufficiently weakened.

Preferably, the attachment lens AL satisfies the following conditional expression (2).

| S1 / S2 | <0.01 ... (2)
In the conditional expression (2), S1 and S2 are the amount of change in the on-axis focus position and the amount of off-axis focus position change when the distance between the front group FU and the rear group RU is changed to the maximum, respectively. Is. Conditional expression (2) defines a preferable ratio between the paraxial focus position on the axis and the curvature of field indicating the off-axis focus position when the distance between the front group FU and the rear group RU is changed. doing. If it exceeds the range of the conditional expression (2), the focus position on the axis also fluctuates greatly when the curvature of field is greatly changed. As a result, it is necessary to readjust the focus, or the focus cannot be sufficiently adjusted, which is not preferable.

Preferably, one of the aspherical surface of the front group FU and the aspherical surface of the rear group RU has a shape in which the positive refractive power increases toward the peripheral portion, and the other has a shape in which the negative refractive power decreases toward the peripheral portion. be. Also preferably, the front group FU and the rear group RU each consist of one lens. Further, preferably, the aspherical lens of the front group FU and the aspherical lens of the rear group RU are resin lenses (for example, resin lenses manufactured by injection molding), respectively.

Preferably, the attachment lens AL satisfies the following conditional expression (3).

0.95 <N1 / N2 <1.05 ... (3)
In the conditional expression (3), N1 is the refractive index of the material of the aspherical lens of the front group FU, and N2 is the refractive index of the material of the aspherical lens of the rear group RU. Conditional expression (3) defines a preferable relationship between the refractive indexes of the glass materials of the aspherical lens of the front group FU and the aspherical lens of the rear group RU. If the range of the conditional expression (3) is exceeded, the difference in the refractive index of each aspherical lens becomes too large. Therefore, even if the distance between the aspherical lenses is minimized, the canceling relationship of the aspherical effect does not work, and the aspherical effect is sufficiently satisfied. Can't be weakened.

Preferably, the attachment lens AL satisfies the following conditional expression (4).

0.0 <Dmin / Dmax <0.20 ... (4)
In conditional expression (4), Dmin and Dmax are the minimum and maximum intervals between the front group FU and the rear group RU, respectively. Conditional expression (4) defines the relationship between the minimum interval and the maximum interval between the front group FU and the rear group RU. If the upper limit of the conditional expression (4) is exceeded, the amount of change in the interval between the front group FU and the rear group RU is small, so that the adjustment range of the effect is limited, and it is difficult to sufficiently weaken or strengthen the effect. If it falls below the lower limit of the conditional expression (4), the minimum distance between the front group FU and the rear group RU becomes too small and adjacent lenses come into contact with each other, or the maximum distance becomes too large and the entire lens system becomes large. It is not preferable because it increases the size.

Preferably, the attachment lens AL satisfies the following conditional expression (5).

0.2 << Ls / L | <0.6 ... (5)
In the conditional expression (5), Ls is the distance from the apex of the lens surface farthest from the aperture stop SP of the attachment lens AL (front group FU and rear group RU) to the aperture stop SP, and L is the most object of the master lens ML. It is the distance from the side surface to the image surface IP. The conditional expression (5) defines a preferable distance relationship between the aperture stop SP and the attachment lens AL. If the upper limit of the conditional expression (5) is exceeded, the distance between the aperture stop SP and the attachment lens AL is too large, so it is necessary to increase the distance between the front group FU and the rear group RU in order to obtain a sufficient aspherical effect. Yes, which leads to an increase in the size of the front lens system. On the other hand, if it falls below the lower limit of the conditional equation (5), the attachment lens AL is too close to the aperture stop SP, so that it is difficult to change only the curvature of field due to the aspherical surface, and at the same time, the spherical aberration and the like also change. ..

FIG. 3 is an aberration diagram (at the minimum effect) at the wide-angle end (W) of the zoom lens equipped with the attachment lens AL. FIG. 4 is an aberration diagram (at the maximum effect) at the wide-angle end of the zoom lens equipped with the attachment lens AL. FIG. 5 is an aberration diagram at the wide-angle end of the zoom lens to which the attachment lens AL is not attached. FIG. 6 is an aberration diagram (at the minimum effect) at the telephoto end (T) of the zoom lens equipped with the attachment lens AL. FIG. 7 is an aberration diagram (at the maximum effect) of the zoom lens equipped with the attachment lens AL at the telephoto end. FIG. 8 is an aberration diagram at the telephoto end of a zoom lens to which the attachment lens AL is not attached. In each aberration diagram, M and S are a meridional image plane and a sagittal image plane, respectively, and the chromatic aberration of magnification is represented by a g-line. ω is a half angle of view and Fno is an F number.

In this embodiment, the attachment lens AL is composed of a front group FU and a rear group RU, but is not limited thereto. The attachment lens AL may include other groups other than the front group FU and the rear group RU. That is, the attachment lens AL includes at least two lenses (lens group), and these two lenses (lens group) may function as a front group and a rear group.

According to the attachment lens AL of this embodiment, the curvature of field can be changed by an arbitrary amount.

Next, the zoom lens (imaging lens or imaging optical system) according to the second embodiment of the present invention will be described with reference to FIGS. 9 to 14. FIG. 9 is a cross-sectional view (at the minimum effect) of the zoom lens at the wide-angle end. FIG. 10 is a cross-sectional view (at the maximum effect) of the zoom lens at the wide-angle end.

As shown in FIGS. 9 and 10, the zoom lens (imaging optical system) of this embodiment includes a zoom group ZU and an adjustment group AU. Similar to the zoom lens of the first embodiment, the zoom group ZU has the first lens group L1, the second lens group L2, the third lens group L3, the fourth lens group L4, and the fifth lens in order from the object side to the image side. It has a group L5 and a sixth lens group L6. Further, the zoom group ZU has an aperture diaphragm SP and a flare cut diaphragm FS. The zoom group ZU performs zooming by changing the distance between each lens group in the direction along the optical axis OA (optical axis direction). The adjustment group AU is an image plane curvature adjustment group provided on the most image side of the zoom lens and having a front group FU and a rear group RU capable of changing the distance between them in the optical axis direction. The front group FU and the rear group RU each have one or more aspherical surfaces having the same reference numeral as in the first embodiment. Further, the front group FU and the rear group RU each have a gentle positive refractive power, and are suppressed so that the focus fluctuation when moving in the optical axis direction becomes small. Preferably, the adjustment group AU satisfies at least one of the conditional expressions (1) to (5).

FIG. 11 is an aberration diagram (at the minimum effect) at the wide-angle end (W) of the zoom lens. FIG. 12 is an aberration diagram (at the maximum effect) at the wide-angle end of the zoom lens. FIG. 13 is an aberration diagram (at the minimum effect) at the telephoto end (T) of the zoom lens. FIG. 14 is an aberration diagram (at the maximum effect) at the telephoto end of the zoom lens. In each aberration diagram, M and S are a meridional image plane and a sagittal image plane, respectively, and the chromatic aberration of magnification is represented by a g-line. ω is a half angle of view and Fno is an F number.

Hereinafter, Numerical Example 1 corresponding to Example 1 and Numerical Example 2 corresponding to Example 2 will be shown. In each numerical embodiment, i indicates the order (plane number) of the faces from the object side. Further, ri indicates the radius of curvature of the i-th lens surface (i-plane) in order from the object side, and di indicates the distance between the i-th surface and the (i + 1) surface. ndi and νdi are the refractive index and Abbe number of the lens material with respect to the d-line, respectively. BF is the air equivalent length from the final surface of the lens to the paraxial image plane. The unit of the value related to the length is mm unless otherwise specified. Table 1 is a table showing the values of the conditional expressions (1) to (5) in each numerical example.

(Numerical Example 1)
Unit mm

Surface data (27 to 30 surfaces are removable attachment lenses)
Surface number ri di ndi ν di Effective diameter
1 30.000 1.60 1.77250 49.6 37.45
2 18.850 4.50 31.64
3 * 26.555 2.50 1.53110 55.9 31.50
4 * 22.754 4.00 29.33
5 -586.400 1.25 1.69680 55.5 29.45
6 21.473 0.50 26.46
7 21.403 4.50 1.80809 22.8 26.58
8 43.781 (variable) 25.57
9 * 113.037 2.00 1.53110 55.9 13.30
10 -62.214 (variable) 13.30
11 -25.577 1.00 1.53110 55.9 12.10
12 * 69.090 (variable) 12.48
13 3436.015 2.00 1.53110 55.9 13.25
14 * -32.138 0.15 13.56
15 24.000 4.00 1.60311 60.6 13.96
16 -23.373 0.75 1.84666 23.9 13.86
17 -53.850 1.00 13.91
18 (Aperture) ∞ (Variable) 13.68
19 -775.077 0.60 1.58144 40.8 12.14
20 13.120 2.10 1.80610 33.3 11.79
21 23.477 1.00 11.40
22 ∞ (variable) 11.37
23 1993.370 1.70 1.53110 55.9 16.20
24 * 129.782 0.90 16.95
25 39.224 3.30 1.48749 70.2 18.09
26 -43.398 (variable) 18.47
27 ∞ 1.00 1.53110 55.9 30.00
28 * ∞ (variable) 30.00
29 * ∞ 1.00 1.53110 55.9 30.00
30 ∞ (variable) 30.00
Image plane ∞

Aspherical data third surface
K = 4.32691e-001 A 4 = -2.01075e-005 A 6 = -5.77042e-008 A 8 = 2.18817e-010 A10 = 7.74314e-014

4th side
K = -8.80639e-001 A 4 = -1.89233e-005 A 6 = -8.57520e-008 A 8 = 4.23972e-010 A10 = -5.10133e-014

Side 9
K = 6.06800e + 001 A 4 = -2.73271e-006 A 6 = -9.63836e-008 A 8 = 1.03681e-009

12th page
K = 3.45986e + 001 A 4 = -1.72460e-006 A 6 = -2.27910e-007 A 8 = 2.66175e-009

Page 14
K = 6.16063e + 000 A 4 = 1.73713e-005 A 6 = 1.56379e-007 A 8 = -5.99782e-010

24th page
K = -5.25180e + 001 A 4 = 3.24345e-005 A 6 = 6.21489e-008 A 8 = -4.19270e-010 A10 = 4.06004e-012

28th page
K = 0.00000e + 000 A 4 = -4.91076e-006 A 6 = -1.04975e-008 A 8 = 7.59942e-011 A10 = -9.51763e-014

29th page
K = 0.00000e + 000 A 4 = -4.91076e-006 A 6 = -1.04975e-008 A 8 = 7.59942e-011 A10 = -9.51763e-014

Various data Zoom ratio 2.88

Focal length 18.58 53.49
F number 3.56 5.87
Angle of view 36.32 14.32
Image height 13.66 13.66
Lens total length 126.24 126.06
BF 11.55 11.55

d 8 32.96 1.28
d10 3.15 4.29
d12 2.34 1.20
d18 3.38 12.35
d22 9.42 0.44
<Minimum effect>
d26 22.00 53.50
d28 0.10 0.10
d30 11.55 11.55
<Maximum effect>
d26 2.00 43.50
d28 20.10 10.10
d30 11.55 11.55

Zoom lens group Data group Start surface Focal length
1 1 -29.86
2 9 75.86
3 11 -35.02
4 13 21.61
5 19 -57.76
6 23 50.77
7 27 ∞
8 29 ∞

(Numerical Example 2)
Unit mm

Surface data Surface number ri di ndi νdi Effective diameter
1 30.000 1.60 1.77250 49.6 37.45
2 18.850 4.50 31.64
3 * 26.555 2.50 1.53110 55.9 31.50
4 * 22.754 4.00 29.33
5 -586.400 1.25 1.69680 55.5 29.45
6 21.473 0.50 26.46
7 21.403 4.50 1.80809 22.8 26.58
8 43.781 (variable) 25.57
9 * 113.037 2.00 1.53110 55.9 13.30
10 -62.214 (variable) 13.30
11 -25.577 1.00 1.53110 55.9 12.10
12 * 69.090 (variable) 12.48
13 3436.015 2.00 1.53110 55.9 13.25
14 * -32.138 0.15 13.56
15 24.000 4.00 1.60311 60.6 13.96
16 -23.373 0.75 1.84666 23.9 13.86
17 -53.850 1.00 13.91
18 (Aperture) ∞ (Variable) 13.68
19 -775.077 0.60 1.58144 40.8 12.14
20 13.120 2.10 1.80610 33.3 11.79
21 23.477 1.00 11.40
22 ∞ (variable) 11.37
23 1993.370 1.70 1.53110 55.9 16.20
24 * 129.782 0.90 16.95
25 39.224 3.30 1.48749 70.2 18.09
26 -43.398 (variable) 18.47
27 100.000 1.00 1.62263 58.2 26.00
28 * 100.000 (variable) 26.00
29 * -200.000 1.00 1.58313 59.5 26.00
30 -200.000 (variable) 26.00
Image plane ∞

Aspherical data third surface
K = 4.32691e-001 A 4 = -2.01075e-005 A 6 = -5.77042e-008 A 8 = 2.18817e-010 A10 = 7.74314e-014

4th side
K = -8.80639e-001 A 4 = -1.89233e-005 A 6 = -8.57520e-008 A 8 = 4.23972e-010 A10 = -5.10133e-014

Side 9
K = 6.06800e + 001 A 4 = -2.73271e-006 A 6 = -9.63836e-008 A 8 = 1.03681e-009

12th page
K = 3.45986e + 001 A 4 = -1.72460e-006 A 6 = -2.27910e-007 A 8 = 2.66175e-009

Page 14
K = 6.16063e + 000 A 4 = 1.73713e-005 A 6 = 1.56379e-007 A 8 = -5.99782e-010

24th page
K = -5.25180e + 001 A 4 = 3.24345e-005 A 6 = 6.21489e-008 A 8 = -4.19270e-010 A10 = 4.06004e-012

28th page
K = 0.00000e + 000 A 4 = -1.78817e-005 A 6 = -9.04733e-008 A 8 = 1.55020e-009 A10 = -4.59524e-012

29th page
K = 0.00000e + 000 A 4 = -1.78817e-005 A 6 = -9.04733e-008 A 8 = 1.55020e-009 A10 = -4.59524e-012

Various data Zoom ratio 2.88

Focal length 18.54 53.37
F number 3.55 5.86
Angle of view 36.39 14.36
Image height 13.66 13.66
Lens total length 126.24 126.05
BF 10.14 10.14

d 8 32.96 1.28
d10 3.15 4.29
d12 2.34 1.20
d18 3.38 12.35
d22 9.42 0.44
<Minimum effect>
d26 22.00 53.50
d28 1.50 1.50
d30 10.14 10.14
<Maximum effect>
d26 5.00 30.50
d28 18.50 24.50
d30 9.99 9.94

Zoom lens group Data group Start surface Focal length
1 1 -29.86
2 9 75.86
3 11 -35.02
4 13 21.61
5 19 -57.76
6 23 50.77
7 27 41856.16
8 29 186228.35

Next, with reference to FIG. 15, a digital camera (imaging apparatus) using an imaging optical system (or an imaging optical system including an attachment optical system) in each embodiment will be described. FIG. 15 is a schematic view of the image pickup apparatus 100.

In FIG. 15, 20 is a camera body, and 21 is an imaging optical system (or an imaging optical system including an attachment optical system) of each embodiment. Reference numeral 22 denotes an image pickup element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor, which is built in the camera body 20 and receives an optical image (subject image) formed via the image pickup optical system 21. Reference numeral 23 denotes a storage means (memory) for recording information corresponding to the subject image photoelectrically converted by the image sensor 22, and 24 includes a liquid crystal display panel or the like for observing the subject image formed on the image sensor 22. It is a display element (finder) for this purpose.

According to the present embodiment, it is possible to provide an attachment optical system, an imaging optical system, and an imaging device capable of effectively changing the curvature of field.

Although preferable examples of the present invention have been described above, the present invention is not limited to these examples, and various modifications and changes can be made within the scope of the gist thereof.

AL attachment lens (attachment optical system)
FU front group RU rear group

Claims (13)

An attachment optical system that can be attached to and detached from the imaging optical system.
It has a front group and a rear group that can change the distance from each other,
The lens surface on the most image side of the front group and the lens surface on the most object side of the rear group are aspherical surfaces having the same reference spherical surface, respectively.
The refractive index of the lens material containing the aspherical surface in the front group is N1, the refractive index of the lens material containing the aspherical surface in the rear group is N2, and the minimum distance between the front group and the rear group. When is Dmin and the maximum distance is Dmax,
1.00 ≤ N1 / N2 <1.05
0.0 <Dmin / Dmax <0.20
An attachment optical system characterized by satisfying the above conditions. The distance between the aspherical surface of the front group and the aspherical surface of the rear group at the position where the height from the optical axis is h is Xh, and the effective diameter of the aspherical surface of the rear group is EA, 0 <h <. When the maximum value of the distance Xh in EA is Xmax and the minimum value is Xmin,
| (Xmax-Xmin) / EA | <0.10
The attachment optical system according to claim 1, wherein the above condition is satisfied. When the change amount S1 of the focus position on the axis, the variation of off-axis focus position S2 at the time of interval was maximal change between said rear group and the front group,
| S1 / S2 | <0.01
The attachment optical system according to claim 1 or 2, wherein the above condition is satisfied. One of the aspherical surface of the front group and the aspherical surface of the rear group has a shape in which the positive refractive power increases toward the peripheral portion, and the other has a shape in which the negative refractive power decreases toward the peripheral portion. The attachment optical system according to any one of claims 1 to 3 , wherein the attachment optical system is characterized in that. The attachment optical system according to any one of claims 1 to 4 , wherein each of the front group and the rear group comprises one lens. An attachment optical system that can be attached to and detached from the imaging optical system.
It has a front group and a rear group that can change the distance from each other,
Each of the front group and the rear group is an attachment optical system characterized in that the reference spherical surface is composed of one lens including an aspherical surface having the same reference numeral. It said lens including an aspherical surface, the attachment optical system according to any one of claims 1 to 6, characterized in that a resin lens in each of the front group Contact and the rear group. The attachment optical system according to any one of claims 1 to 7, wherein the imaging optical system can be attached to and detached from the image side. It has a front group and a rear group that can change the distance from each other,
The lens surface on the most image side of the front group and the lens surface on the most object side of the rear group are aspherical surfaces having the same reference spherical surface, respectively.
The refractive index of the lens material containing the aspherical surface in the front group is N1, the refractive index of the lens material containing the aspherical surface in the rear group is N2, and the minimum distance between the front group and the rear group. When is Dmin and the maximum distance is Dmax,
1.00 ≤ N1 / N2 <1.05
0.0 <Dmin / Dmax <0.20
An imaging optical system characterized by satisfying the above conditions. It also has an aperture stop
The distance from the apex of the lens surface farthest from the aperture diaphragm to the aperture diaphragm among the lens surfaces included in the front group and the rear group is Ls, and the distance from the lens surface to the image plane on the object side of the imaging optical system is When the distance is L,
0.2 << Ls / L | <0.6
The imaging optical system according to claim 9 , wherein the imaging optical system satisfies the above-mentioned condition. It has an aperture diaphragm and a front group and a rear group that can change the distance between each other.
The front group and the rear group each include an aspherical surface having the same reference spherical surface as the reference spherical surface.
The distance from the apex of the lens surface farthest from the aperture diaphragm to the aperture diaphragm among the lens surfaces included in the front group and the rear group is Ls, and the distance from the lens surface to the image plane on the object side of the imaging optical system is When the distance is L,
0.2 << Ls / L | <0.6
An imaging optical system characterized by satisfying the above conditions. The imaging optical system according to claim 10 or 11, wherein the front group and the rear group are arranged on the image side of the aperture diaphragm. An imaging optical system according to any one of claims 9 to 12, the image pickup apparatus characterized by comprising an imaging element for receiving an optical image formed through the imaging optical system.

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