JP2000231009A5 - - Google Patents

Description

[Claims]
[Claim 1] Optical system including varifocal lens..
2. Characterized by being a retrofocus typeThe optics according to claim 1.system..
3. The above.The power of the liquid crystal layer of the varifocal lens is φ _LC , When the power of the entire optical system is φ
0.005 ≦ ｜ φ _LC / Φ ｜ ≦ 0.4
Characterized by satisfyingClaim 1Or 2Optics described insystem..
4. When the angle formed by the main ray having an image height of 1 in the liquid crystal layer of the varifocal lens and the optical axis is Y.
｜ tanY ｜ ≦ 0.6
The optical system according to any one of claims 1 to 3, wherein the optical system is characterized in that.
5. The focal length of the pre-aperture group is f ₁ , When the focal length of the whole system is f,
0.8 ≦ | f ₁ / F ｜ ≦ ∞
The optical system according to any one of claims 1 to 4, wherein the optical system is characterized in that.
6. The focal length of the pre-aperture group is f ₁ , When the focal length of the whole system is f,
−1.0 ≦ f / f ₁ ≤ ∞
The optical system according to any one of claims 1 to 5, wherein the optical system is characterized in that.
7. The optical system according to any one of claims 1 to 6, wherein the variable focus lens is provided between the pre-aperture group and the post-aperture group.
8. When the distance from the first surface of the lens to the image plane is L and the focal length of the entire system is f.
0.8 ≤ | L / f | ≤ 15
The optical system according to any one of claims 1 to 7, wherein the optical system is characterized in that.
9. The focal length of the group after aperture is f ₂ , When the focal length of the whole system is f,
f ₂ > 0
And
0.3 ≤ | f ₂ / F | ≤4
The optical system according to any one of claims 1 to 8, wherein the optical system is characterized in that.
10. The optical system according to any one of claims 1 to 9, wherein the focal length of the varifocal lens is changed in n steps (where n is an integer of 2 or more).
11. The optical system according to any one of claims 1 to 9, wherein the focal length of the varifocal lens is continuously changed.
12. An imaging device comprising the optical system according to any one of claims 1 to 11.
13. The optical system according to claim 1, wherein the optical system has a symmetrical lens configuration.
14. The optical system according to claim 13, which is a triplet type.
15. An optical system that includes a varifocal lens in which the distance between lenses is invariant.
16. An optical system that includes a varifocal lens that is not a zoom lens.
17. An optical system that is teletype and includes a varifocal lens.
18. An optical system composed of three groups, the first group having convex power, the second group having concave power, and the third group having convex power in order from the object side, and including at least one varifocal lens.
19. It consists of three groups, in order from the object side, the first group has convex power, the second group has concave power, the third group has convex power, and includes at least one varifocal lens, which is the most image side. An optical system in which the lens is a convex lens.
20. The optical system according to claim 1, wherein the optical system includes an aspherical surface.

The optical system according to claim 1 is characterized by including a varifocal lens.

The optical system according to claim 2, in the optical system according to claim 1, is characterized in that a retro-focus type.

Further, the optical system according to claim 3 is the optical system according to claim 1 or 2, when the power of the liquid crystal layer portion of the varifocal lens is φ _LC and the power of the entire optical system is φ.
0.005 ≤ | φ _LC / φ | ≤ 0.4
It is characterized by satisfying.
Further, the optical system according to claim 4 is the angle formed by the main ray having an image height of 1 in the liquid crystal layer of the varifocal lens and the optical axis in the optical system according to any one of claims 1 to 3. When is Y
｜ tanY ｜ ≦ 0.6
It is characterized by satisfying.
Further, the optical system according to claim 5 is the optical system according to any one of claims 1 to 4, when the focal length of the pre-aperture group is f ₁ and the focal length of the entire system is f.
0.8 ≤ | f ₁ / f | ≤ ∞
It is characterized by satisfying.
Further, the optical system according to claim 6 is the optical system according to any one of claims 1 to 5, when the focal length of the pre-aperture group is f ₁ and the focal length of the entire system is f.
−1.0 ≦ f / f ₁ ≦ ∞
It is characterized by satisfying.
The optical system according to claim 7 is characterized in that, in the optical system according to any one of claims 1 to 6, the variable focus lens is provided between the pre-aperture group and the post-aperture group. It is a thing.
Further, in the optical system according to claim 8, in the optical system according to any one of claims 1 to 7, the distance from the first surface of the lens to the image plane is L, and the focal length of the entire system is f. When
0.8 ≤ | L / f | ≤ 15
It is characterized by satisfying.
Further, the optical system according to claim 9 is the optical system according to any one of claims 1 to 8, when the focal length of the group after aperture is f ₂ and the focal length of the entire system is f.
f ₂ > 0
And
0.3 ≤ | f ₂ / f | ≤ 4
It is characterized by satisfying.
Further, the optical system according to claim 10 changes the focal length of the varifocal lens in n steps (where n is an integer of 2 or more) in the optical system according to any one of claims 1 to 9. It is characterized by doing so.
The optical system according to claim 11 is characterized in that, in the optical system according to any one of claims 1 to 9, the focal length of the varifocal lens is continuously changed. is there.
The imaging device according to claim 12 is characterized by including the optical system according to any one of claims 1 to 11.
The optical system according to claim 13 is the optical system according to claim 1, characterized in that it has a symmetrical lens configuration.
The optical system according to claim 14 is the optical system according to claim 13, characterized in that it is a triplet type.
The optical system according to claim 15 is characterized by including a varifocal lens in which the distance between the lenses is invariant.
The optical system according to claim 16 is characterized by including a varifocal lens that is not a zoom lens.
The optical system according to claim 17 is a teletype and includes a varifocal lens.
The optical system according to claim 18 is composed of three groups, in which order from the object side, the first group has a convex power, the second group has a concave power, and the third group has a convex power, and at least one. It is characterized by including a single varifocal lens.
The optical system according to claim 19 is composed of three groups, in which order from the object side, the first group has a convex power, the second group has a concave power, and the third group has a convex power, and at least one. It includes a number of variable focus lenses, and is characterized in that the lens on the image side is a convex lens.
The optical system according to claim 20 is characterized in that the optical system according to claim 1 includes an aspherical surface.

を得る。 Approximating Eq. (4) by considering up to the first order of P / λ, it becomes as follows. That is, in equations (13) to (15), up to the first order of P / λ, that is, from equation (11), leaving up to the first order of Γ / Φ, the second order or higher of P / λ, and the second order of Γ / Φ. If the above is omitted,

To get.

に近づくが、この式は、入射光の偏光方向は（Γ／４）・（Γ／Φ）だけ回転するが、液晶１は等方媒質であると見なせることを意味している。
｜ｉΓ／２Φ｜≒０ （２６）
つまり、
｜Γ／２Φ｜≪１ （２７）
であれば、ボケのない可変焦点レンズが得られる。式（１１）から、

となる。 Therefore, in _{order to consider that the value of W tN} is substantially equal to the Jones matrix of the isotropic medium, | i · Γ / 2Φ | should be close to 0. At this time, W _tN is

However, this equation means that the polarization direction of the incident light rotates by (Γ / 4) and (Γ / Φ), but the liquid crystal 1 can be regarded as an isotropic medium.
｜ iΓ / 2Φ ｜ ≒ 0 (26)
In other words
｜ Γ / 2Φ ｜ ≪1 (27)
If so, a varifocal lens without blurring can be obtained. From equation (11)

Will be.

Further, the variable focus lens of the first optical system may be composed of a liquid crystal lens (second optical system).
As the liquid crystal lens, for example, there is a lens as shown in FIG. 1, and the focal length can be changed by changing the refractive index of the liquid crystal. Since a liquid crystal is used, the applied voltage is generally as small as several V, and the power consumption is also small. Further, the liquid crystal for Ru many types there can be selected a liquid crystal used in accordance with the purpose from a wide range.

As described above, the eighth optical system satisfies the conditional equation (43) when the angle formed by the main ray having an image height of 1 in the liquid crystal layer of the varifocal lens with the optical axis is Y. It is possible to obtain a good image in which there is little blurring at any position of the imaged image and the difference in the amount of blurring is suppressed.
In order to correct distortion and reduce the tilt angle of the main ray in the liquid crystal, -0.7 ≤ f / f ₁ ≤ ∞ _{depending on whether f 1 is positive or negative.}
Is desirable. If f / f ₁ is below the lower limit, strong negative distortion will occur. On the contrary, if f / f ₁ is too large, positive distortion becomes conspicuous, so −0.7 ≦ f / f ₁ ≦ 3.0.
It is even better. To better correct positive distortion -0.7 ≤ f / f ₁ ≤ 1.25
It is good to say.
On the other hand, in an optical system with a wide angle of view, it is _{better if the lower limit of f / f 1} is smaller because tan Y can be made smaller.
-1 ≤ f / f ₁ ≤ ∞
It is good to be. As the upper limit of f / f ₁ is reduced to 3.0 or 1.25 in order to correct the positive distortion and shorten the total length of the lens, the positive distortion correction is also improved and the total length of the lens can be reduced.

The shape of the varifocal lens 11 used in the above description is that the liquid crystal layer 12 has a plano-convex lens shape, but the shape of the liquid crystal layer is not limited to this. Depending on the application, a plano-concave lens shape may be used as shown in FIG. 5, or a biconvex lens shape may be used as shown in FIG. Further, it may have a biconcave lens shape, or one or both surfaces may have an aspherical shape.
Further, when the diameter of the lens is large and the thickness of the liquid crystal layer 12 is large, the liquid crystal layer 12 can be made thin as a Fresnel shape as shown in FIG.
Further, irregularities such as a fine rectangle, a sawtooth shape, a triangular wave shape, and a sine wave shape may be provided on a flat surface or a curved surface to simultaneously have a function as a diffraction grating. For example, as shown in FIG. 8, a triangular wave-shaped diffraction grating can be provided. In this case, changing the refractive index of the liquid crystal layer 12, Ri retardation irregularities I variant, it is possible to change the diffraction efficiency.
Further, the surface of the substrate that sandwiches the liquid crystal layer 12 on the side opposite to the liquid crystal layer 12 may be a spherical surface, an aspherical surface, or a diffraction grating surface instead of a flat surface. For example, as shown in FIG. 9, by making one surface 15a of the plano-convex lens-shaped substrate 15 an aspherical surface, aberration can be satisfactorily corrected.

Eighth Example Next, an example in which an optical system using an optical characteristic variable optical element according to the present invention is applied to an image pickup apparatus will be shown as an eighth embodiment.
FIG. 29 is a schematic configuration diagram of the image pickup apparatus according to this embodiment. This image pickup device is configured by arranging an optical system 20, an individual image pickup device 21, and a signal processing circuit 22 in order from an object side (not shown). As the optical system 20, any of the optical systems shown in the third to seventh embodiments described above may be used. Then, in this optical system 20, in order from the object side, a filter group 26 including a negative lens group 23, an aperture 24, a varifocal lens 11, a positive lens group 25, an infrared cut filter, a low-pass filter, and the like are arranged. It is configured. The aperture 24 and the varifocal lens 11 are in contact with each other. Further, the solid-state image sensor 21 is provided with a mosaic-like color filter of RGB3 primary colors on its photoelectric conversion surface.

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