JP5719220B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus having a lens apparatus and a camera apparatus having an optical element that is detachable from the lens apparatus and that can be inserted into and removed from an optical path.

  2. Description of the Related Art Conventionally, there has been known an imaging apparatus that suppresses fluctuations in an image formation position due to insertion / extraction by applying refractive power to an optical element inserted into an optical path.

  For example, Patent Document 1 discloses an invention in which an optical element to be inserted has a refractive power in order to correct a change in imaging position when the optical element is inserted. When a parallel plate optical element is inserted between the imaging lens and the imaging surface or in the lens system of the imaging lens, the imaging position is shifted to the over side (that is, the side opposite to the object side). In Patent Document 1, a positive refractive power is applied to an optical element to be inserted so as to cancel the movement of the imaging position.

JP-A 63-25612

  However, in the prior art disclosed in Patent Document 1, a change in optical characteristics due to insertion / extraction of an optical element occurs. For example, if refractive power is applied to an optical element to be inserted as in Patent Document 1 to cancel the shift of the imaging position, an under-side spherical aberration occurs when the optical element is inserted. FIG. 8 shows a schematic diagram of spherical aberration when the shift of the imaging position is canceled as in Patent Document 1. In FIG. In FIG. 8, an alternate long and short dash line 802 indicates an aberration when the optical element is not inserted in the optical path, a dashed line 801 indicates an aberration when the optical element is inserted in the optical path, and SA indicates an imaging surface position. Due to this spherical aberration, the quality of the obtained image is deteriorated, and the best focus position (803, 804) that can be expressed as a position where the mean square deviation (RMS) of the spot diameter in the spot diagram of the axial light beam is minimized. ) Does not fall within the depth of focus (803), the influence on the image due to the insertion / extraction of the optical element becomes more significant, and the obtained image changes greatly.

  In addition, when the optical element to be inserted does not have a positive refractive power and is a parallel plate as in Patent Document 1, when the optical element is inserted, the imaging position changes to the over side, and the over side Spherical aberration occurs. A schematic diagram of spherical aberration when a parallel plate is inserted is shown in FIG. In FIG. 9, an alternate long and short dash line 902 indicates an aberration when an optical element is not inserted in the optical path, a dashed line 901 indicates an aberration when an optical element that is a parallel plate is inserted in the optical path, and SA indicates an imaging surface position. . The paraxial focusing position is a figure adjusted by moving the lens unit in the optical axis direction or moving the imaging surface so that it is on the imaging surface with respect to the paraxial ray, but as is clear from this figure It can be seen that, among the best focus positions 903 and 904, the best focus position 903 when the optical element is inserted is not within the depth of focus, and this spherical aberration causes an image change due to insertion / extraction. In particular, it changes significantly in an optical system with a small F number.

Therefore, an imaging object of the present invention, when the optical element having a thickness is inserted in the optical path, that satisfactorily correct spherical aberration, even when the optical element is insertion made it possible to suppress the variation of the spherical aberration Is to provide a device.

を満たすことを特徴とする。ただし、Ｒは、ｄを減光フィルターの厚み、Ｎを減光フィルターのｄ線における屈折率、Ｋを撮像素子の撮像面から正の屈折力を有する面の光軸上の空気換算長、Ｆを撮像装置の光学系全体のＦナンバー、とすると、以下の式で表される。 To achieve the above object, an imaging apparatus of the present invention includes a lens device, a camera device detachable to the lens apparatus, and the camera apparatus includes an imaging device, insertable dimming the light path It has a filter, and the extinction filter has a surface having a positive refractive power, the radius of curvature r of the surface having a refractive power of the positive can,

It is characterized by satisfying. Where R is the thickness of the neutral density filter , N is the refractive index at the d line of the neutral density filter , K is the air equivalent length on the optical axis of the surface having positive refractive power from the imaging surface of the image sensor, F whole optical system F-number of the imaging device, and when expressed by the following equation.

  According to the present invention, it is possible to provide an imaging apparatus capable of suppressing deterioration in image quality even when an optical element having a thickness is inserted or removed.

Schematic diagram of a configuration of an imaging apparatus according to the present invention Schematic diagram of a configuration of an imaging apparatus according to the present invention Schematic diagram of apparent exit pupil position and apparent image plane relationship Lens cross-sectional view of the taking optical system of Example 1 Longitudinal aberration diagrams in the photographing optical system of Example 1, (A) At the time of removal of the optical element, (B) At the time of insertion of the optical element Lens sectional view of the taking optical system of Example 2 Longitudinal aberration diagrams in the photographing optical system of Example 2, (A) At the time of removal of the optical element, (B) At the time of insertion of the optical element Schematic diagram of longitudinal aberration during insertion / extraction of an optical element having refractive power in a conventional example Schematic diagram of longitudinal aberration during insertion / extraction of parallel plate optical element in the conventional example

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

  FIG. 1 is a schematic diagram illustrating a configuration of an imaging apparatus according to an embodiment of the present invention. The imaging device of the present invention includes lens devices 101 and 105 and a camera device that can be attached to and detached from the lens device. The camera device has an optical element that can be inserted into and removed from the optical path. FIG. 1A shows a configuration in which the optical element 103 is inserted in the optical path, and FIG. The imaging apparatus of the present invention includes interchangeable imaging lenses 101 and 105, a camera optical system (for example, a color separation optical system and a special effect filter) 102, an imaging element 104, and an optical element 103 to be inserted and removed. The optical element 103 is, for example, an optical characteristic conversion filter such as a neutral density filter, a color temperature conversion filter, a cross screen filter, a soft focus filter, or an infrared cut filter. In the imaging optical system of the present invention, the optical element 103 to be inserted / extracted has a positive refractive power, and the radius of curvature r giving the positive refractive power satisfies the following conditional expression.

なお、条件式内のＲは、３次収差論において補正したい球面収差量ＳＡを補正するのに必要な曲率半径であって、以下の式から求める。

Note that R in the conditional expression is a radius of curvature necessary for correcting the spherical aberration amount SA to be corrected in the third-order aberration theory, and is obtained from the following expression.

この条件式（１）さらに好ましくは（７）を満たすことによって、特にＦナンバーが小さい（Ｆ＜２．０）光学系においても良好な球面収差補正を行うことができる。 Here, d is the thickness of the optical element, N is the refractive index with respect to the d-line of the optical element, K is the air equivalent length on the optical axis from the imaging surface of the imaging element to the surface having the positive refractive power of the optical element, F is the F number of the entire optical system of the image pickup apparatus. By satisfying this conditional expression, it is possible to satisfactorily correct spherical aberration due to insertion of an optical element. More preferably, it is desirable to satisfy the following conditional expression.

By satisfying this conditional expression (1), more preferably (7), it is possible to perform a good spherical aberration correction even in an optical system having a particularly small F number (F <2.0).

  Furthermore, the imaging apparatus of the present invention is characterized by having means for correcting the movement of the imaging position caused by the optical element 103 being inserted into and extracted from the camera optical system. As shown in FIG. 1, the surface 106 of the optical element 103 to be inserted / extracted has a positive refractive power, thereby suppressing the occurrence of spherical aberration due to the insertion of the optical element. As an image position correcting means for correcting the movement of the image position, an optical system 105 is configured in the imaging lens. By shifting the optical system 105 in the imaging lens in the optical axis direction, the movement of the imaging position due to the insertion of the optical element 103 is corrected.

  FIG. 2 shows an example in which means for correcting the movement of the imaging position due to insertion / extraction of the optical element 203 is configured in the camera optical system 202. In this figure, the imaging element 204 is moved in the optical axis direction to correspond to the movement of the imaging position by the insertion and removal of the optical element 203. The image position correcting means is not limited to the movement of the image sensor, and the optical system may be designed to have a lens for correction in the camera optical system, for example. In this case, the imaging position is corrected by shifting the correction lens in the optical axis direction in accordance with the insertion / extraction of the optical element.

  Referring to FIG. 3, a convex surface (a surface having a positive refractive power) for correcting spherical aberration, which is formed in an optical element that is inserted into and removed from the camera optical system, is provided on the object side surface of the optical element and the imaging element. Think about which side to configure. FIG. 3 shows an apparent exit pupil for the surface 106 having positive refractive power in the optical system of the imaging optical system 301, a part 302 of the camera optical system in the imaging camera, the optical element 303 that can be inserted and removed, and the imaging surface 304. 6 is a schematic diagram illustrating the relationship between the distance X on the optical axis and the distance Y on the optical axis to the apparent image plane with respect to the surface 106. FIG. In FIG. 3, 305 represents an on-axis marginal ray, 306 represents an off-axis principal ray, and the signs of the distances X and Y are positive on the image side and negative on the object side from the surface having the curvature of the optical element 303. Show.

  FIG. 3A shows the case where the apparent image plane and the apparent exit pupil position are both on the image side from the optical element (X / Y ≧ 0). When the convex surface of the optical element faces the object side, the incident angle to the convex surface is smaller for both the on-axis light beam and the off-axis light beam than when it faces the image side. it can. Therefore, when X / Y ≧ 0, it is desirable to form a convex surface on the object side of the optical element.

  FIG. 3B shows the case where the apparent image plane is on the image side, the apparent exit pupil is on the object side (X / Y <0), and | X | ≧ | Y | Is the case. In this case, when the convex surface of the optical element faces the object side, the incident angle of the axial ray on the convex surface can be made smaller than when the convex surface faces the image side. For off-axis rays, the incident angle is slightly tight, but the influence is small because the exit pupil position is sufficiently far away. Therefore, when X / Y <0 and | X | ≧ | Y |, the generated aberration can be reduced by forming a convex surface on the object side surface of the optical element.

  FIG. 3C shows the case where the apparent image plane is closer to the image side than the optical element, the apparent exit pupil is present on the object side (X / Y <0), and | X | <| This is the case when Y |. In this case, when the convex surface of the optical element faces the image side, the incident angle of the off-axis light beam on the convex surface can be made smaller than when the convex surface faces the object side. Although the incident angle is slightly tight with respect to the axial ray, the influence is small because the image plane is sufficiently separated. Accordingly, in the case of X / Y <0 and | X | <| Y |, the generated aberration can be reduced by forming a convex surface on the image side surface of the optical element.

  In the case of an interchangeable lens type imaging apparatus, changes in image quality due to insertion / extraction of optical elements can be suppressed by considering these conditions and optimizing according to the specifications of the interchangeable lens.

  The imaging apparatus according to the first embodiment of the present invention will be described below with reference to FIGS. 4 is a lens cross-sectional view of Example 1. FIG. A camera optical system 402 configured in the imaging camera is disposed on the imaging surface side of the zoom lens 401. The camera optical system 402 includes a color separation optical system, an ND filter, and an optical characteristic conversion filter such as a CC filter. The optical element 404 that can be inserted and removed is configured in the camera optical system. The object-side surface 405 of the optical element 404 is convex so as to have a positive refractive power, and is configured so that the spherical aberration is not deteriorated by the insertion of the optical element 404. In this embodiment, the radius of curvature of the surface 405 is 700 mm, the thickness of the optical element 404 is 2 mm, and the d-line refractive index N is 1.51633. The air-converted length X on the optical axis from the surface 405 having positive refractive power to the imaging surface is 19.01 mm, and the open F number is 1.85.

  Table 1 shows numerical values related to the equations (1) to (7). It can be seen that conditional expression (1) and (7) are satisfied. Furthermore, X / Y = 11.4.

  In addition, an image position correction unit 403 that corrects the movement of the imaging position when the optical element is inserted is configured in the imaging lens. When the optical element 404 is inserted in the optical path, the optical element 403 is shifted 0.41 mm toward the object side. As a result, fluctuations in the imaging position due to insertion of the optical element 404 are suppressed. In the configuration of this embodiment, the optical element 404 has a control unit that detects the state of the optical element 404 in accordance with the insertion / extraction in the optical path and drives the image position correction unit in the imaging lens device. The image position correction corresponding to the insertion / extraction of the optical element can be realized without being aware of the driving of the means.

  In this embodiment, since X / Y = 11.4, the convex surface of the optical element to be inserted / extracted is a surface facing the object side.

    Numerical data of the optical system of this example is described in (Numerical Example 1). FIG. 5 is a longitudinal aberration diagram in the optical system of the present example, and shows (A) when the optical element is removed and (B) when the optical element is inserted. The solid line of astigmatism represents a sagittal section, and the broken line represents a meridional section. The lateral chromatic aberration indicates the aberration with respect to the g-line. The surfaces 39 and 40 in the optical data at the time of removing the optical element are only described for easy comparison with the insertion / extraction optical element at the time of inserting the optical element, and nothing exists at the positions of the surfaces 39 and 40. do not do. That is, the space between the surface 38 and the surface 41 is air, and the distance d between them is 4.0 mm.

By forming the surface 405 that is the object side surface of the optical element 404 to be inserted as a convex surface and imparting positive refractive power, the radius of curvature thereof satisfies the conditional expressions (1) and (7). Changes in spherical aberration due to insertion / extraction of optical elements are suppressed.

  Hereinafter, an image pickup apparatus according to a second embodiment of the present invention will be described with reference to FIGS. 6 is a lens cross-sectional view of Example 2. FIG. A camera optical system 602 configured in the imaging camera is disposed on the imaging surface side of the zoom lens 601. The camera optical system 602 includes an optical characteristic conversion filter such as a color separation optical system, an ND filter, and a CC filter. The optical element 603 that can be inserted and removed is configured in the camera optical system. The object-side surface 604 of the optical element 603 is convex so as to have a positive refractive index, and is configured so that spherical aberration is not deteriorated by the insertion of the optical element 603. In this embodiment, the radius of curvature of the surface 604 is 700 mm, the thickness of the optical element 603 is 2 mm, and the d-line refractive index N is 1.51633. The air-converted length X on the optical axis from the surface 604 having positive refractive power to the imaging surface is 19.01 mm, and the open F number is 1.85.

  Table 1 shows various numerical values related to the expressions (1) to (7). It can be seen that conditional expression (1) and (7) are satisfied. In this embodiment, X / Y = 11.4.

  In addition, an image sensor 605 is configured in the camera optical system as an image position correction unit that corrects the movement of the imaging position when the optical element is inserted. When the optical element 603 is inserted in the optical path, the optical element 603 is shifted 0.4 mm toward the image side. Thereby, the fluctuation | variation of the image formation position by optical element 603 insertion is suppressed. In the configuration of the present embodiment, the optical element 404 has a control unit that detects the state of the optical element 404 in accordance with the insertion / extraction in the optical path and drives the image position correction unit in the camera device. The image position correction corresponding to the insertion / extraction of the optical element can be realized without being conscious of the driving of the optical element.

  In this embodiment, X / Y = 11.4, and the convex surface of the optical element to be inserted / extracted faces the object side.

  Numerical data of the optical system of this example is described in (Numerical Example 2). FIG. 7 is a longitudinal aberration diagram in the optical system of the present example, and shows (A) when the optical element is removed and (B) when the optical element is inserted. The surfaces 39 and 40 in the optical data at the time of removing the optical element are only described for easy comparison with the insertion / extraction optical element at the time of inserting the optical element, and nothing exists at the positions of the surfaces 39 and 40. do not do. That is, the space between the surface 38 and the surface 41 is air, and the distance d between them is 4.0 mm.

By forming the surface 604 that is the object-side surface of the optical element 603 to be inserted as a convex surface and imparting positive refractive power, the radius of curvature thereof satisfies the conditional expressions (1) and (7), Changes in spherical aberration due to insertion / extraction of optical elements are suppressed.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

(Numerical example 1)
Unit mm

Surface data (when the optical element is removed)
Surface number rd nd vd
1 600.261 2.20 1.75520 27.5
2 81.461 11.42 1.49700 81.6
3 -290.956 7.63
4 86.701 7.86 1.62041 60.3
5 3044.710 0.15
6 66.016 6.01 1.72916 54.7
7 145.708 (variable)
8 111.445 0.80 1.88300 40.8
9 16.812 4.65
10 -47.842 0.70 1.81600 46.6
11 33.779 2.24
12 28.944 5.20 1.80518 25.4
13 -29.192 0.54
14 -24.664 0.70 1.78800 47.4
15 132.572 (variable)
16 -28.806 0.75 1.74320 49.3
17 37.218 3.81 1.84666 23.9
18 449.023 (variable)
19 (Aperture) ∞ 1.80
20 -231.233 3.33 1.67003 47.2
21 -49.133 0.20
22 -170.365 4.05 1.51742 52.4
23 -38.625 0.20
24 36.315 10.16 1.48749 70.2
25 -35.564 1.66 1.83400 37.2
26 ∞ 36.00
27 97.385 6.35 1.50137 56.4
28 -44.438 0.20
29 -535.653 1.40 1.83400 37.2
30 21.016 7.22 1.50137 56.4
31 -424.093 1.50
32 38.505 8.29 1.51823 58.9
33 -27.482 1.40 1.77250 49.6
34 91.360 0.30
35 38.442 6.84 1.53172 48.8
36 -52.407 5.00
37 ∞ 30.00 1.60342 38.0
38 ∞ 1.00
39 ∞ 2.00
40 ∞ 1.00
41 ∞ 16.20 1.51633 64.2
42 ∞ (variable)
Image plane ∞

Surface data (when optical element is inserted)
Surface number rd nd vd
1 600.261 2.20 1.75520 27.5
2 81.461 11.42 1.49700 81.6
3 -290.956 7.63
4 86.701 7.86 1.62041 60.3
5 3044.710 0.15
6 66.016 6.01 1.72916 54.7
7 145.708 (variable)
8 111.445 0.80 1.88300 40.8
9 16.812 4.65
10 -47.842 0.70 1.81600 46.6
11 33.779 2.24
12 28.944 5.20 1.80518 25.4
13 -29.192 0.54
14 -24.664 0.70 1.78800 47.4
15 132.572 (variable)
16 -28.806 0.75 1.74320 49.3
17 37.218 3.81 1.84666 23.9
18 449.023 (variable)
19 (Aperture) ∞ 1.80
20 -231.233 3.33 1.67003 47.2
21 -49.133 0.20
22 -170.365 4.05 1.51742 52.4
23 -38.625 0.20
24 36.315 10.16 1.48749 70.2
25 -35.564 1.66 1.83400 37.2
26 ∞ 35.59
27 97.385 6.35 1.50137 56.4
28 -44.438 0.20
29 -535.653 1.40 1.83400 37.2
30 21.016 7.22 1.50137 56.4
31 -424.093 1.50
32 38.505 8.29 1.51823 58.9
33 -27.482 1.40 1.77250 49.6
34 91.360 0.30
35 38.442 6.84 1.53172 48.8
36 -52.407 5.41
37 ∞ 30.00 1.60342 38.0
38 ∞ 1.00
39 * 700.000 2.00 1.51633 64.2
40 * ∞ 1.00
41 ∞ 16.20 1.51633 64.2
42 ∞ (variable)
Image plane ∞

* 39 and 40 are insertion / extraction optical elements

Various data Zoom ratio 19.50

Focal length (when optical element is removed) 9.50 15.20 38.86 91.50 185.29
Focal length (with optical element inserted) 9.37 14.99 38.31 90.20 182.65
F number (when the optical element is removed) 1.85 1.85 1.85 1.85 2.85
F number (with optical element inserted) 1.85 1.85 1.85 1.85 2.81
Angle of view (when the optical element is removed) 30.06 19.89 8.06 3.44 1.70
Angle of view (with optical element inserted) 30.42 20.15 8.17 3.49 1.72
Image height 5.50 5.50 5.50 5.50 5.50
Total lens length 266.06 266.06 266.06 266.06 266.06
BF 6.02 6.02 6.02 6.02 6.02

d 7 0.65 15.69 35.96 46.91 52.03
d15 53.75 36.74 13.38 3.88 6.32
d18 5.10 7.07 10.15 8.71 1.15

(Numerical example 2)
Unit mm

Surface data (when the optical element is removed)
Surface number rd nd vd
1 600.261 2.20 1.75520 27.5
2 81.461 11.42 1.49700 81.6
3 -290.956 7.63
4 86.701 7.86 1.62041 60.3
5 3044.710 0.15
6 66.016 6.01 1.72916 54.7
7 145.708 (variable)
8 111.445 0.80 1.88300 40.8
9 16.812 4.65
10 -47.842 0.70 1.81600 46.6
11 33.779 2.24
12 28.944 5.20 1.80518 25.4
13 -29.192 0.54
14 -24.664 0.70 1.78800 47.4
15 132.572 (variable)
16 -28.806 0.75 1.74320 49.3
17 37.218 3.81 1.84666 23.9
18 449.023 (variable)
19 (Aperture) ∞ 1.80
20 -231.233 3.33 1.67003 47.2
21 -49.133 0.20
22 -170.365 4.05 1.51742 52.4
23 -38.625 0.20
24 36.315 10.16 1.48749 70.2
25 -35.564 1.66 1.83400 37.2
26 ∞ 36.00
27 97.385 6.35 1.50137 56.4
28 -44.438 0.20
29 -535.653 1.40 1.83400 37.2
30 21.016 7.22 1.50137 56.4
31 -424.093 1.50
32 38.505 8.29 1.51823 58.9
33 -27.482 1.40 1.77250 49.6
34 91.360 0.30
35 38.442 6.84 1.53172 48.8
36 -52.407 5.00
37 ∞ 30.00 1.60342 38.0
38 ∞ 1.00
39 ∞ 2.00
40 ∞ 1.00
41 ∞ 16.20 1.51633 64.2
42 ∞ (variable)
Image plane ∞

Surface data (when camera optics and optical elements are inserted)
Surface number rd nd vd
1 600.261 2.20 1.75520 27.5
2 81.461 11.42 1.49700 81.6
3 -290.956 7.63
4 86.701 7.86 1.62041 60.3
5 3044.710 0.15
6 66.016 6.01 1.72916 54.7
7 145.708 (variable)
8 111.445 0.80 1.88300 40.8
9 16.812 4.65
10 -47.842 0.70 1.81600 46.6
11 33.779 2.24
12 28.944 5.20 1.80518 25.4
13 -29.192 0.54
14 -24.664 0.70 1.78800 47.4
15 132.572 (variable)
16 -28.806 0.75 1.74320 49.3
17 37.218 3.81 1.84666 23.9
18 449.023 (variable)
19 (Aperture) ∞ 1.80
20 -231.233 3.33 1.67003 47.2
21 -49.133 0.20
22 -170.365 4.05 1.51742 52.4
23 -38.625 0.20
24 36.315 10.16 1.48749 70.2
25 -35.564 1.66 1.83400 37.2
26 ∞ 36.00
27 97.385 6.35 1.50137 56.4
28 -44.438 0.20
29 -535.653 1.40 1.83400 37.2
30 21.016 7.22 1.50137 56.4
31 -424.093 1.50
32 38.505 8.29 1.51823 58.9
33 -27.482 1.40 1.77250 49.6
34 91.360 0.30
35 38.442 6.84 1.53172 48.8
36 -52.407 5.00
37 ∞ 30.00 1.60342 38.0
38 ∞ 1.00
39 * 700.000 2.00 1.51633 64.2
40 * ∞ 1.00
41 ∞ 16.20 1.51633 64.2
42 ∞ (variable)
Image plane ∞

* 39 and 40 are insertion / extraction optical elements

Various data Zoom ratio 19.50

Focal length (when optical element is removed) 9.50 15.20 38.86 91.50 185.29
Focal length (with optical element inserted) 9.37 14.98 38.30 90.19 182.62
F number (when the optical element is removed) 1.85 1.85 1.85 1.85 2.85
F number (with optical element inserted) 1.85 1.85 1.85 1.85 2.81
Angle of view (when the optical element is removed) 30.06 19.89 8.06 3.44 1.70
Angle of view (with optical element inserted) 30.42 20.16 8.17 3.49 1.73
Image height 5.50 5.50 5.50 5.50 5.50
Total lens length 266.06 266.06 266.06 266.06 266.06
BF (when optical element is removed) 6.02 6.02 6.02 6.02 6.02
BF (when optical element is inserted) 6.42 6.42 6.42 6.42 6.42

d 7 0.65 15.69 35.96 46.91 52.03
d15 53.75 36.74 13.38 3.88 6.32
d18 5.10 7.07 10.15 8.71 1.15

101, 105, 301 Imaging lens 102, 302, 402 Camera optical system (configured in the imaging camera)
103, 303 Optical elements 104, 304 to be inserted / removed Imaging surface 106 Surface having positive refractive power

Claims (5)

An imaging device having a lens device and a camera device detachable from the lens device,
The camera device includes an imaging device and a neutral density filter that can be inserted into and removed from the optical path.
The darkening filter has a surface having a positive refractive power, the radius of curvature r of the surface having a refractive power of the positive can,

An imaging device characterized by satisfying the above. Here, R is the air on the optical axis of the d to the surface having a positive refractive power from the imaging surface of the refractive index, the image sensor of K the dimming filter thickness, the N at the d-line of the dimming filter When the conversion length, F, is the F number of the entire optical system of the imaging apparatus, it is expressed by the following equation.

The imaging apparatus has an image position correction unit for correcting the movement of the imaging position due to insertion / extraction of the neutral density filter into the optical path,
The image position correcting means is configured in the lens device.
The imaging apparatus according to claim 1. The imaging apparatus has an image position correction unit for correcting the movement of the imaging position due to insertion / extraction of the neutral density filter into the optical path,
The image position correcting means is configured in the camera device.
The imaging apparatus according to claim 1. The distance on the optical axis to the exit pupil apparent from a surface having a positive refractive power of the neutral density filter X, the optical axis to the image plane of the apparent from the surface having the positive refractive power of the dimming filter when the distance of the upper Y, and a surface having a positive refractive power of the dimming filter,
(X / Y) ≧ 0
Or
(X / Y) <0 and | X | ≧ | Y |
Is configured on the object side,
(X / Y) <0 and | X | <| Y |
Imaging apparatus described in any one of claims 1 to 3, characterized in that it is constituted on the image side when the. However, the image-side positive and negative object side to the dimming filter. The imaging apparatus according to claim 2, further comprising a control unit that drives the image position correcting unit when the neutral density filter is inserted into an optical path.

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