JP2019008147A - Optical device - Google Patents

Abstract

To provide an imaging lens that can reduce degradation of a taken image by dust on the top surface of a lens in which the distance between the imaged surface and the exchange lens is short.SOLUTION: The optical device includes: an optical surface having an antistatic film formed; and a ground part for making the antistatic film grounded, the optical surface satisfying the conditional expression of L/H<0.85 in which L denotes the length on the optical axis from the optical surface to the image surface and H denotes the size of an image.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical device. For example, the present invention relates to an imaging lens that is detachably attached to a camera device having a short flange back, and a camera device that includes a filter and an extender that can be inserted into and removed from an optical path.

  Patent Document 1 discloses an imaging apparatus in which a charged layer is prevented from adhering to a surface by disposing a hydrophilic layer on the surface of the solid-state image sensor on which light flux is incident.

JP 2006-243694 A

  For example, in the case of an interchangeable lens, even if dust is attached to the lens, if the lens has a relatively long distance from the imaging surface to the lens, the impact of dust on the image quality of the photographed image is negligible. As the distance decreases, the effect may not be minor. For example, dust is easily reflected in a captured image.

  Also, in the case of the imaging device disclosed in Patent Document 1, if the distance from the imaging surface to the lens is shortened, there is a high possibility that dust that has not adhered to the surface of the solid-state imaging element will adhere to the lens.

  An object of the present invention is to provide an optical device that is advantageous for reducing the influence of dust, for example.

In order to achieve the above object, an optical device of the present invention has an optical surface on which an antistatic film is formed, and a grounding portion that grounds the antistatic film, and the optical surface is separated from the optical surface. The length on the optical axis to the image plane is L and the image size is H.
L / H <0.85
The following conditional expression is satisfied.

  According to the present invention, for example, it is possible to provide an optical device that is advantageous in reducing the influence of dust.

Schematic configuration diagram of an imaging lens in Embodiment 1 Schematic configuration of multilayer film in Example 1 Reflectivity characteristics of multilayer film in Example 1 Schematic configuration diagram of an imaging lens in Embodiment 2

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

Hereinafter, an imaging lens (optical apparatus) according to a first embodiment of the present invention will be described with reference to FIG.
The imaging lens in the present embodiment is a lens interchangeable type that is detachable from the camera device, and is used by being detachably attached to the camera device at the time of use.

When the maximum F number of the imaging lens of the present invention is Fmax, the length on the optical axis from the optical surface to the imaging surface is L, and the image size (diameter of the image circle) is H,
0 ≦ L / Fmax <2.5 (1)
L / H <0.85 (2)
An antistatic coat (antistatic film) is formed on the optical surface that satisfies the conditional expression, and has means for flowing charges generated on the surface to the casing of the imaging lens. Here, when the aperture is closed, Fmax = ∞.

  In the imaging lens of this example, a multilayer film is formed on the optical surface 101 on the image side of the lens (optical element) arranged closest to the image side, and an ITO film having conductivity is formed in the multilayer film. Yes. The maximum F number Fmax of the imaging lens in the present embodiment is 16, and the optical path length L from the optical surface 101 on which the multilayer film including the conductive ITO film is formed to the imaging surface 102 is 16.44 mm. It is. The diameter (image size) H of the image circle is 43.28 mm. Therefore, since L / Fmax is 1.03, the conditional expression (1) is satisfied. If the optical path length from the optical surface to the imaging surface becomes far away or the maximum F-number becomes smaller and exceeds the upper limit of the conditional expression (1), dust will hardly appear in the captured image in any case. Since L / H is 0.38, the conditional expression (2) is satisfied. If the optical path length from the optical surface to the imaging surface becomes far and exceeds the upper limit of the conditional expression (2), it becomes difficult for dust to be reflected in the captured image. Therefore, in a range where the conditional expressions (1) and (2) are satisfied, dust is liable to cause deterioration of the image quality of the photographed image, and the conditions of the present invention are remarkably exhibited.

Each of the conditional expressions (1) and (2) is preferable because the effect appears more clearly under the conditions satisfying the following conditional expressions.
0 ≦ L / Fmax <2.3 (1a)
L / H <0.82 (2b)

FIG. 2 shows a schematic diagram of a multilayer film structure formed on the optical surface 101 in this embodiment, and Table 2 shows a layer structure such as an optical film thickness and a refractive index. The multilayer film is formed by laminating films of Al ₂ O ₃ , ZrO ₂ , Al ₂ O ₃ , ITO, Al ₂ O ₃ , ZrO ₂ , and MgF ₂ in order from the lens surface side. Here, the design dominant wavelength is 580 nm. As shown in FIG. 3, the spectral reflectance in the above film configuration is that of the optical surface in the wavelength region of 430 to 670 nm, which almost covers the visible light wavelength range, using the high refractive index ITO by the film configuration of FIG. 2. The reflectance can be suppressed to 0.2% or less.

  The final lens including the optical surface 101 is installed on the imaging lens with a conductive stainless steel lens barrel. By depositing a conductive thin film on the lens surface and further using a lens barrel that supports the lens as a conductive material, charging on the lens surface can be prevented (reduced). Thereby, it is possible to reduce adhesion of charged dust to the lens surface. Instead of using a conductive material (grounding) for the lens barrel, an electrode for releasing charge (grounding) may be provided so as to be in contact with the conductive film ITO in the thin film formed on the lens surface.

  Further, by performing centering (forming the lens outer diameter by grinding) after film formation on the optical surface 101, the ITO layer is exposed (exposed) on the surface of the edge and touches the conductive lens barrel (grounding) To have a grounding part. Thereby, the electrical conductivity can be further increased and the charging on the lens surface can be reduced.

  Furthermore, a member (for example, an adhesive member) that captures dust such as dust that has not adhered to the lens surface is provided in a lens peripheral portion (inside the lens barrel) such as a lens barrel that holds the lens. As a result, it is possible to more reliably reduce the adhesion of dust to the lens surface.

  The imaging lens (optical device) according to the second embodiment of the present invention will be described below with reference to FIG. The optical path length L from the optical surface 401 to the imaging surface 402 is different from that of the first embodiment, but the other configurations are the same as those of the first embodiment. In this embodiment, the optical path length L is 34.22 mm, and the maximum F number is 16. The diameter H of the image circle (diagonal length of the image size) H is 43.28 mm as in the example.

  Therefore, since L / Fmax is 2.14, the conditional expression (1) is satisfied, and since L / H is 0.79, the conditional expression (2) is satisfied.

  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.

  In the illustrated embodiment, the optical surface on which the multilayer film including the conductive ITO film is configured is the most optical surface on the image side that is most frequently in contact with the outside air and touches dust. Although illustrated, the present invention is not limited to this configuration. If the optical surface is in a position that satisfies the conditional expression (2), it has an effect of suppressing deterioration of the image quality of the photographed image due to adhesion of dust or the like to the optical surface.

  In the illustrated embodiment, the case where the formation of the conductive multilayer film of the present invention is configured as an imaging lens that can be attached to and detached from the camera apparatus is illustrated, but the present invention is not limited to this. The same applies to a camera device (optical device) that is detachably mounted on a lens device and in which an optical system such as an extender or a filter can be inserted into and removed from the optical path. Applicable. By configuring the multilayer film on the optical surface that satisfies the conditional expressions of optical elements such as lenses and filters that form the extender, the same effect can be obtained. In that case, the image size H in conditional expression (2) is the diagonal length of the image sensor.

Next, numerical examples 1 and 2 corresponding to the first and second embodiments of the present invention will be described. In each numerical example, i indicates the order of surfaces (optical surfaces) from the object side, and ri is the radius of curvature of the i-th optical surface from the object side. di is an axial distance between the i-th optical surface and the (i + 1) -th optical surface from the object side. ndi and νdi are the refractive index and the Abbe number for the d-line of the medium (optical member) between the i-th optical surface and the (i + 1) -th optical surface, respectively. An aspherical surface is marked with * next to the surface number. The paraxial radius of curvature is R, the eccentricity is K, and the aspheric coefficients are A4, A6, A8, A10, and A12. When the displacement in the optical axis direction at the position of the height h from the optical axis is x with respect to the surface vertex, the aspherical shape is
X = (h ² / R) / [1+ {1− (1 + K) (h / R) ² } ^1/2 ] + A4h ⁴ + A6h ⁶ + A8h ⁸ + A10h ¹⁰ + A12h ¹²
It is represented by Note that “E ± XX” in each aspheric coefficient means “× 10 ^{± XX} ”. Table 1 shows the correspondence with the above-described conditional expressions in each numerical example.

(Numerical example 1)
Unit mm

Surface data surface number i ri di ndi vdi
1 ∞ 1.00
2 * -1131.690 2.70 1.59522 67.7
3 31.420 20.29
4 * 1551.909 2.00 1.76385 48.5
5 * 33.027 13.21
6 -78.000 1.50 1.43875 94.7
7 92.253 0.25
8 83.942 8.99 1.72047 34.7
9 -101.185 1.44
10 -277.435 4.82 1.49700 81.5
11 -78.762 40.40
12 53.661 1.80 1.83481 42.7
13 42.337 2.42
14 48.693 10.05 1.49700 81.5
15 -184.474 1.44
16 130.661 1.00 2.00069 25.5
17 49.810 12.72 1.59522 67.7
18 -69.113 1.72
19 (Aperture) ∞ 7.29
20 -50.774 1.00 1.83481 42.7
21 154.583 5.16 1.85478 24.8
22 -144.528 0.20
23 40.497 3.50 1.72047 34.7
24 53.317 17.20
25 37.240 5.58 1.69680 55.5
26 7770.823 0.18
27 40.086 1.00 2.00 100 29.1
28 26.081 5.68 1.49700 81.5
29 96.751 8.23
30 190.651 6.31 1.43875 94.7
31 -30.564 1.00 2.00330 28.3
32 * -106.779 16.44
Image plane ∞

Aspheric data 2nd surface
K = 0.00000e + 000 A 4 = 5.68409e-006 A 6 = -4.26817e-009 A 8 = 2.69205e-012 A10 = -9.63497e-016 A12 = 1.60310e-019

4th page
K = 0.00000e + 000 A 4 = -2.32989e-006 A 6 = -1.65965e-009 A 8 = 1.45223e-012

5th page
K = 0.00000e + 000 A 4 = 2.23324e-007 A 6 = -9.73277e-009 A 8 = 4.16561e-012

32nd page
K = 0.00000e + 000 A 4 = 1.48109e-005 A 6 = 1.39561e-008

Various data

Focal length 14.00
F number 1.40
Angle of view 57.09
Statue height 21.64
Total lens length 206.52
BF 16.44

(Numerical example 2)
Unit mm

Surface data surface number i ri di ndi vdi
1 ∞ 0.80
2 * 88.644 2.50 1.59522 67.7
3 26.014 16.83
4 * 109.841 2.00 1.76385 48.5
5 28.949 11.61
6 -71.253 1.20 1.59522 67.7
7 112.140 1.19
8 59.819 5.60 1.65412 39.7
9 -1297.881 3.34
10 -98.905 4.23 1.49700 81.5
11 -47.790 33.85
12 126.050 1.44 1.80610 40.9
13 31.072 6.36 1.49700 81.5
14 -275.109 0.20
15 60.649 3.20 1.59522 67.7
16 -264.023 2.66
17 -80.117 3.78 1.59522 67.7
18 -40.686 1.77
19 (Aperture) ∞ 2.93
20 -43.442 0.80 1.83481 42.7
21 53.876 3.98 1.85478 24.8
22 -240.138 23.41
23 38.119 4.24 1.69680 55.5
24 77.468 5.02
25 34.058 0.80 2.00 100 29.1
26 28.391 9.50 1.49700 81.5
27 -83.375 5.48
28 206.314 10.47 1.43875 94.7
29 -26.251 0.80 2.00330 28.3
30 * -101.678 34.22
Image plane ∞

Aspheric data 2nd surface
K = 0.00000e + 000 A 4 = 3.90487e-006 A 6 = -1.13688e-009 A 8 = 7.52886e-013

4th page
K = 0.00000e + 000 A 4 = -1.91463e-006 A 6 = 8.02932e-010 A 8 = 5.86504e-013

30th page
K = 0.00000e + 000 A 4 = 8.60947e-006 A 6 = 6.05598e-009

Various data

Focal length 16.00
F number 2.80
Angle of view 53.52
Statue height 21.64
Total lens length 204.22
BF 34.22

101, 401 Optical surfaces 102, 402 for providing a conductive film in a multilayer film Imaging surfaces 201-207 Each thin film layer constituting the multilayer film

Claims (8)

An optical surface on which an antistatic film is formed;
A grounding portion for grounding the antistatic film,
The optical surface has a length on the optical axis from the optical surface to the image surface as L, and an image size as H.
L / H <0.85
An optical device that satisfies the following conditional expression: The optical device is an imaging lens, and the image size is a diameter of an image circle of the imaging lens;
When the maximum F number of the imaging lens is Fmax, and Fmax = ∞ when the aperture of the imaging lens is closed, 0 ≦ L / Fmax <2.5
The optical apparatus according to claim 1, wherein the following conditional expression is satisfied. The optical device is a camera device in which an imaging lens is detachable and has an imaging element,
The image size is a diagonal length of the image sensor,
The optical surface is an optical surface of an optical element that is provided in the camera device and is detachably inserted into an optical path.
The optical apparatus according to claim 1.   The optical device according to claim 3, wherein the optical element is a filter or an extender.   The optical device according to claim 1, further comprising a member that captures dust instead of the optical surface.   The optical device according to claim 5, wherein the member that captures dust is an adhesive member.   The optical apparatus according to claim 1, wherein the antistatic film includes a multilayer film including a highly conductive layer.   The optical apparatus according to claim 1, wherein the optical surface is an optical surface located closest to the image side.

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