JP2008309900A - Liquid crystal optical element, optical system equipped with liquid crystal optical element, and image acquiring device equipped with optical system equipped with liquid crystal optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal optical element which brings about no loss of light quantity and which has high image-forming performance, an optical system equipped with the same, and an image acquiring device equipped with them. <P>SOLUTION: The liquid crystal optical element has a first liquid crystal lens 11 and a second liquid crystal lens 12, wherein the first liquid crystal lens 11 and the second liquid crystal lens 12 are placed opposite to each other in such a way that their alignment directions vertically intersect each other in a plane vertical to the optical axis, and a focal length of the second liquid crystal lens 12 with respect to incident light of one polarization direction to receive a light polarizing action in the second liquid crystal lens 12 is made shorter compared with a focal length of the first liquid crystal lens 11 with respect to incident light of the other polarization direction vertical to the one polarization direction to receive a light polarizing action in the first liquid crystal lens 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging optical system, and more particularly to a liquid crystal optical element as an optical characteristic variable optical element, an optical system including the same, and an image acquisition apparatus including them.

The focusing of the imaging optical system is usually performed by moving the lens in the optical axis direction. However, a space and an actuator for moving the whole or a part of the lens system are required, which is not preferable for downsizing the optical system. Therefore, as means for solving these problems, an optical system is generally known in which a variable focus lens using a liquid crystal lens is used for zooming and focusing without moving the lens system. However, since such a liquid crystal lens requires a polarizing plate, there has been a problem that the light amount loss increases. Therefore, as means for solving such a problem, the first diffractive liquid crystal lens and the second diffractive liquid crystal lens are arranged to face each other so that the alignment directions are orthogonal to each other in a plane perpendicular to the optical axis. Thus, an imaging optical system that realizes a variable focus mechanism that does not require a polarizing plate is known (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-73758

  However, the optical system described in Patent Document 1 has a problem that the imaging position of P-polarized light and the imaging position of S-polarized light in the entire lens system are different, and sufficient imaging performance cannot be obtained.

  The present invention has been made in view of the above-described conventional problems, and provides a liquid crystal optical element having no loss of light amount and high imaging performance, an optical system including the same, and an image acquisition apparatus including them. For the purpose.

  In order to achieve the above object, a liquid crystal optical element according to the present invention includes a first liquid crystal lens and a second liquid crystal lens, and the first liquid crystal lens and the second liquid crystal lens are aligned with each other. Compared to the focal length of the first liquid crystal lens with respect to incident light in one polarization direction that is subjected to a light beam deflection action in the first liquid crystal lens, while being opposed to each other in a plane perpendicular to the optical axis, The second liquid crystal lens is characterized in that a focal length of the second liquid crystal lens with respect to incident light in the other polarization direction orthogonal to the one polarization direction, which is subjected to a light beam deflection action in the second liquid crystal lens, is shortened.

In the liquid crystal optical element of the present invention, it is preferable that the following conditional expression (1) is satisfied.
0 <| (f1-f2) /f1|≦0.5 (1)
However, f1 is the focal length of the first liquid crystal lens with respect to the incident light in the one polarization direction that receives the light beam deflection action in the first liquid crystal lens, and f2 is subjected to the light beam deflection action in the second liquid crystal lens. The focal length of the second liquid crystal lens with respect to incident light in the other polarization direction orthogonal to the one polarization direction.

  An optical system according to the present invention includes any one of the liquid crystal optical elements according to the present invention described above, and has a focal position with respect to incident light in the one polarization direction that undergoes a light beam deflection action in the first liquid crystal lens, and the first The second liquid crystal lens is characterized in that the focal position with respect to the incident light in the other polarization direction orthogonal to the one polarization direction, which is subjected to the light beam deflection action, substantially coincides.

  An optical system according to the present invention includes any one of the liquid crystal optical elements according to the present invention, and controls a voltage applied to the liquid crystal optical element to correct a focal position shift with respect to incident light from different object points. It is characterized by performing.

  In the optical system of the present invention, the light beam incident on the liquid crystal optical element is transmitted without being diffracted or refracted so that the liquid crystal optical element acts as a parallel plate when focusing on an object point at infinity. Is preferable.

  In the optical system of the present invention, the far-point object point is focused when the liquid crystal optical element has no light beam deflection function, and the near-point object point is focused when the liquid crystal optical element has a light beam deflection function. It is preferable to focus.

In the optical system of the present invention, it is preferable that the following conditional expression (2) is satisfied.
| Δ / f | ≦ 0.6 (2)
Where Δ is the distance between the first liquid crystal lens and the second liquid crystal lens, and f is the focal length of the optical system.

  In addition, an image acquisition apparatus according to the present invention includes any one of the optical systems according to the present invention, an image sensor, and a zoom optical system.

  According to the present invention, it is possible to obtain a liquid crystal optical element having no loss of light amount and high imaging performance, an optical system including the same, and an image acquisition apparatus including them.

  Prior to the description of the embodiments, the effects of the present invention will be described. For convenience of explanation, in the following explanation, out of two linearly polarized light having polarization planes orthogonal to each other, linearly polarized light in one polarization direction is P-polarized light, and linearly polarized light in the other polarization direction is S-polarized light.

FIG. 1 is a conceptual diagram showing the basic configuration and operation principle of a liquid crystal optical element according to the first embodiment of the present invention. FIG. 1A shows a state in which no voltage is applied to the liquid crystal lens, and FIG. 2 shows the effect of incident light upon application of, respectively.
The liquid crystal optical element 1 of the present embodiment includes a first diffractive liquid crystal lens 11 and a second diffractive liquid crystal lens 12. In the example of FIG. 1, the liquid crystal optical element 1 is integrated by laminating a first diffractive liquid crystal lens 11 and a second diffractive liquid crystal lens 12 between substrates 13a, 13b, and 13c. ing.

  For example, as shown in FIG. 16, the first diffractive liquid crystal lens 11 and the second diffractive liquid crystal lens 12 are formed on a substrate 11a (12a) having a predetermined serrated relief 11a1 (12a1) on a thin film transparent electrode. The liquid crystal 11d (12d) is sandwiched between 11b (12b) and the counter electrode 11c (12c). Then, by applying a desired voltage via the electrode lead wire between the thin film transparent electrode 11b (12b) and the counter electrode 11c (12c), the refractive index of the liquid crystal 11d (12d) is changed, and the liquid crystal 11d ( 12d) The phase distribution of the layer is changed to change the diffraction order of the liquid crystal lens.

The liquid crystal optical element of this embodiment includes the two diffractive liquid crystal lenses 11 and 12 configured as described above, and the light distribution directions of the liquid crystal optical elements are opposed to each other so as to be orthogonal to each other in a plane perpendicular to the optical axis. Has been placed. Therefore, the polarization direction in which the first diffractive liquid crystal lens 11 has a light beam deflecting action and the polarization direction in which the second diffractive liquid crystal lens 12 has a light beam deflecting action are orthogonal to each other.
For example, when a voltage is applied to the liquid crystal 11d of the first diffractive liquid crystal lens 11, the first diffractive liquid crystal lens 11 has a light beam deflecting action on incident light of P-polarized light (or S-polarized light). In other words, by applying a voltage to the liquid crystal 12d of the second diffractive liquid crystal lens 12, the second diffractive liquid crystal lens 12 has a light beam deflecting action on incident light of S-polarized light (or P-polarized light). In the example of FIG. 1, by applying a voltage to each of the liquid crystals, the first diffractive liquid crystal lens 11 has a light beam deflecting action on the incident light of P-polarized light, and the second diffractive liquid crystal lens 12 has It has a light beam deflecting action with respect to S-polarized incident light. Further, the refractive index of the substrate in each of the diffractive liquid crystal lenses 11 and 12 is set to be equal to the ordinary light refractive index of the liquid crystals 11d and 12d.

The liquid crystal optical element 1 of the present embodiment configured as described above operates as follows.
First, when no voltage is applied to either the liquid crystal 11d of the first diffractive liquid crystal lens 11 or the liquid crystal 12d of the second diffractive liquid crystal lens 12, the liquid crystals 11d and 12d are polarized in the direction of polarization of incident light (that is, P Regardless of the direction of polarization or S-polarization), it acts as an ordinary light refractive index. Since the refractive index of the substrate in each of the diffractive liquid crystal lenses 11 and 12 and the ordinary light refractive index of the liquid crystals 11d and 12d are equal, each diffractive liquid crystal lens 11 and 12 deflects light regardless of the polarization direction of the incident light. It has no effect and acts as a parallel plate. That is, the light rays incident on the respective diffractive liquid crystal lenses 11 and 12 are each subjected to the action as the 0th-order diffracted light at each diffractive liquid crystal lens 11 and 12 regardless of the polarization direction (P-polarized light and S-polarized light).

  On the other hand, when a voltage is applied to the liquid crystal 11d of the first diffractive liquid crystal lens 11, the liquid crystal 11d acts as an extraordinary refractive index with respect to P-polarized light, and the first diffractive liquid crystal lens 11 is P It functions as a diffractive optical element blazed with the first-order diffracted light with respect to polarized light. For this reason, the P-polarized light is subjected to a light beam deflection action as first-order diffracted light. On the other hand, the liquid crystal 11d acts as an ordinary refractive index distribution for S-polarized light. For this reason, the first diffractive liquid crystal lens 11 acts as a parallel plate with respect to the S-polarized light, and the S-polarized light is not subjected to the light beam deflecting action.

  Further, when a voltage is applied to the liquid crystal 12d of the second diffractive liquid crystal lens 12, the liquid crystal 12d acts as an extraordinary refractive index with respect to S-polarized light, and the second diffractive liquid crystal lens 12 changes to S-polarized light. On the other hand, it functions as a diffractive optical element blazed with first-order diffracted light. For this reason, S-polarized light is subjected to a light beam deflection action as first-order diffracted light. On the other hand, the liquid crystal 12d acts as an ordinary refractive index distribution for P-polarized light. For this reason, the second diffractive liquid crystal lens 12 acts as a parallel plate with respect to the P-polarized light, and the P-polarized light is not subjected to the light beam deflection action.

  For this reason, when a voltage is applied to both the liquid crystal 11d and the liquid crystal 12d in the liquid crystal optical element 1 of the present embodiment, the incident light is subjected to the light deflection effect on the P-polarized light in the first diffractive liquid crystal lens 11. While being deflected in a predetermined direction with respect to the optical axis, the S-polarized light is emitted without being subjected to a light beam deflection action, and enters the second diffractive liquid crystal lens 12. In the second diffractive liquid crystal lens 12, the S-polarized light is deflected in a predetermined direction with respect to the optical axis by being subjected to the light beam deflecting action, and the P-polarized light is not subjected to the light deflecting action. 11 is emitted in a deflected direction.

  Therefore, according to the liquid crystal optical element 1 of the present embodiment, the incident light beam has the P-polarized light beam deflected by the first diffractive liquid crystal lens 11 and the S-polarized light beam beamed by the second diffractive liquid crystal lens 12. Since the diffractive liquid crystal lens receives the light beam deflecting action regardless of the polarization directions of the P direction and the S direction, such as receiving the deflecting action, the light quantity loss is eliminated.

  Further, the liquid crystal optical element 1 of the present embodiment is configured using a diffractive liquid crystal lens, and the diffractive liquid crystal lens can reduce the liquid crystal thickness. Therefore, according to the liquid crystal optical element 1 of the present embodiment, the liquid crystal lens can be driven at a high speed with a low voltage. Further, the distance between the first diffractive liquid crystal lens 11 and the second diffractive liquid crystal lens 12 can be reduced. As a result, as will be described later, the P-polarized light deflected by the light beam deflection action through the first diffractive liquid crystal lens 11 and the light beam deflection action through the second diffractive liquid crystal lens 12 are deflected. In the case where the deviation of the image formation position of the S-polarized light is eliminated, it becomes easy to reduce the asymmetry of the image formation between the P-polarized light and the S-polarized light.

  In the liquid crystal optical element 1 of the present embodiment, the first diffractive liquid crystal lens 11 and the second diffractive liquid crystal lens 12 are integrated as a laminated structure as shown in FIG. It is preferable in terms of holding. Of course, it may be provided separately.

  In the example of FIG. 1, the configuration that acts as the first-order diffracted light has been described. However, the configuration is not limited to this, and a configuration that acts as the second-order diffracted light and the third-order diffracted light may be used.

  Further, the liquid crystal optical element 1 of the present embodiment is subjected to a light beam deflection action in the first diffractive liquid crystal lens 11 (of two linearly polarized light having polarization planes orthogonal to each other) (here, P One polarized light that is subjected to a light beam deflection action in the second diffractive liquid crystal lens 12 compared to the focal length of the first diffractive liquid crystal lens 11 with a predetermined order light (for example, primary light) with respect to the incident light of the polarized light) The focal length at the same order light as the predetermined order light of the second diffractive liquid crystal lens 12 with respect to incident light in the other polarization direction (here, S-polarized light) orthogonal to the direction is shortened.

As shown in FIG. 1, when the first diffractive liquid crystal lens 11 and the second diffractive liquid crystal lens 12 are laminated, the diffractive surface of the first diffractive liquid crystal lens 11 and the second diffractive liquid crystal lens 12 are stacked. The diffractive surfaces are separated.
Therefore, when the focal length of the first diffractive liquid crystal lens 11 and the focal length of the second diffractive liquid crystal lens 12 are equal, one of P-polarized light and S-polarized light is in focus, and the other is out of focus. In this state, the light is incident on the imaging surface, resulting in a double image on the imaging surface.
Therefore, in the liquid crystal optical element 1 of the present embodiment, the polarized light (here, P-polarized light) subjected to the light beam deflection action by the first diffractive liquid crystal lens 11 and the polarized light (here, the P-polarized light) subjected to the light beam deflection action (second polarization liquid crystal lens 12). Here, the focal lengths of the first diffractive liquid crystal lens 11 and the second diffractive liquid crystal lens 12 are made different so that the imaging positions (focal positions) of the same-order light in S-polarized light substantially coincide with each other. That is, the other polarization direction orthogonal to one polarization direction in the second diffractive liquid crystal lens 12 than the focal length of incident light in one polarization direction (here P-polarized light) in the first diffractive liquid crystal lens 11. The focal length of the same order with respect to incident light (here, S-polarized light) is configured to be short.
In this way, double images can be prevented.

In this case, it is preferable that the following conditional expression (1) is satisfied.
0 <| (f1-f2) /f1|≦0.5 (1)
Here, f1 is the focal length of the first diffractive liquid crystal lens 11, and f2 is the focal length of the second diffractive liquid crystal lens 12.

  If the upper limit of the conditional expression (1) is exceeded, the difference in focal length between the first diffractive liquid crystal lens 11 and the second diffractive liquid crystal lens 12 increases, and the first diffractive liquid crystal lens 11 exerts a light beam deflection action. Asymmetry of imaging is increased between the received polarized light and the polarized light subjected to the light beam deflection action by the second diffractive liquid crystal lens 12.

Preferably, the following conditional expression (1 ′) should be satisfied.
0 <| (f1-f2) /f1|≦0.4 (1 ′)
Here, f1 is the focal length of the first diffractive liquid crystal lens 11, and f2 is the focal length of the second diffractive liquid crystal lens 12.

Furthermore, it is preferable that the following conditional expression (1 ″) is satisfied.
0 <| (f1-f2) /f1|≦0.3 (1 ″)
Here, f1 is the focal length of the first diffractive liquid crystal lens 11, and f2 is the focal length of the second diffractive liquid crystal lens 12.

In the optical system of the present invention, the entire optical system receives polarized light (here, P-polarized light) that is subjected to the light deflection action by the first diffractive liquid crystal lens 11 and light deflection action by the second diffractive liquid crystal lens 12. The focal lengths of the respective liquid crystal lenses are set so that the imaging positions (focal positions) of the same-order light in polarized light (here, S-polarized light) substantially coincide.
Here, it is desirable that the imaging positions (focal positions) substantially coincide with each other. Ideally, it is desirable that the imaging positions in the respective polarization directions completely coincide with each other. This means that the imaging positions may be different to the extent that the performance is not affected. For example, the degree of displacement of the imaging position in a range that cannot be recognized as a double image by the optical system can be mentioned.

Further, the optical system of the present invention has any one of the liquid crystal optical elements 1 described as the present embodiment and at least one lens, and controls the voltage applied to the liquid crystal optical element 1 from different points. The focus position shift with respect to the incident light is corrected (focused).
If it does in this way, the effect of liquid crystal optical element 1 of this embodiment mentioned above in an optical system will be acquired.

Further, in the optical system of the present invention, when the liquid crystal optical element 1 of the present embodiment described above does not have a light beam deflection action, the far point object point is focused, and when the liquid crystal optical element 1 has a light beam deflection action. It is preferable to focus on near object points.
When the liquid crystal lens used for the liquid crystal optical element 1 has a large manufacturing error, there is a possibility that the performance deterioration due to the light beam deflection error of the liquid crystal lens becomes a problem.
However, if the liquid crystal lens is configured not to have a light beam deflecting action with respect to the far point object point as in the optical system of the present invention, the far point object point that requires higher imaging performance than the near point object point is required. It is possible to avoid performance degradation with respect to.

In the optical system of the present invention, it is preferable that the following conditional expression (2) is satisfied.
| Δ / f | ≦ 0.6 (2)
However, (DELTA) is the space | interval of the 1st diffractive liquid crystal lens 11 and the 2nd diffractive liquid crystal lens 12, and f is the focal distance of this optical system.

If the upper limit value of conditional expression (2) is exceeded, the non-imaging of the polarized light that is subjected to the light deflection action by the first diffractive liquid crystal lens 11 and the polarized light that is subject to the light deflection action by the second diffractive liquid crystal lens 12 will be described. Subjectivity becomes too large.
Preferably, the following conditional expression (2 ′) should be satisfied,
0.0001 ≦ | Δ / f | ≦ 0.4 (2 ′)
However, (DELTA) is the space | interval of the 1st diffractive liquid crystal lens 11 and the 2nd diffractive liquid crystal lens 12, and f is the focal distance of this optical system.
Furthermore, preferably, the following conditional expression (2 ″) should be satisfied,
0.0001 ≦ | Δ / f | ≦ 0.2 (2 ″)
However, (DELTA) is the space | interval of the 1st diffractive liquid crystal lens 11 and the 2nd diffractive liquid crystal lens 12, and f is the focal distance of this optical system.

The camera of the present invention includes any one of the optical systems of the present invention, an image sensor, and a zoom optical system.
If it does in this way, the effect of the liquid crystal optical element of this embodiment mentioned above in a camera will be acquired.

  The liquid crystal optical element 1 of the present embodiment has been described by taking a diffractive liquid crystal lens as an example, but is not limited thereto, and may be, for example, a liquid crystal lens having a zone plate shape, a plano-convex shape, and a plano-concave lens shape. Further, it may be a gradient index lens in which a liquid crystal layer is formed concentrically.

Examples 1 to 3 of the optical system according to the present invention will be described below with reference to the drawings.
Optical path diagrams are shown in FIGS.

Example 1
2 is a sectional view along the optical axis showing the optical configuration of the optical system according to the first embodiment using the liquid crystal optical element of the present invention in the state of focusing on an object point at infinity, and FIG. 3 shows the optical system of FIG. It is explanatory drawing which shows the structure of the used liquid crystal optical element. 4 is a lateral aberration diagram when focusing on an object at infinity in the optical system of Example 1, and FIG. 5 is a lateral aberration when focusing on a near point in the optical system of Example 1 (only the liquid crystal lens for P-polarization operates). FIGS. 6A and 6B are lateral aberration diagrams when focusing on the near point in the optical system of Example 1 (only the S-polarized liquid crystal lens operates).
The optical system of Example 1 includes, in order from the object side, a negative meniscus lens L1, a biconvex lens L2, a liquid crystal optical element 1 ′ having a convex surface facing the object side, a cemented lens of a biconcave lens L3 and a biconvex lens L4, and a biconvex lens L5. And a biconcave lens L6, a positive meniscus lens L7 having a concave surface facing the object side, a parallel plate P1, and a parallel plate P2.

₂ , the numbers r ₁ , r ₂ ,... And d ₁ , d ₂ ,... In the lens cross-sectional view correspond to the surface numbers 1, 2,. Further, S represents an aperture stop, and IM represents an imaging surface of the image sensor. In the following numerical data, the refractive index and the Abbe number are values at the d-line (hereinafter, the same applies to other examples).

Since the liquid crystal optical element 1 ′ has the same structure as the liquid crystal optical element 1 of the embodiment shown in FIG. 1, the same members are denoted by the same reference numerals and description thereof is omitted.
In the optical system according to the first embodiment, as a whole optical system, the first diffractive liquid crystal lens 11 receives the light deflecting action (P-polarized light) and the second diffractive liquid crystal lens 12 receives the light deflecting action. The focal lengths of the respective liquid crystal lenses are set so that the imaging positions (focal positions) of the same-order light in polarized light (here, S-polarized light) substantially coincide.

  In the optical system of Example 1, the diffractive liquid crystal lens used as the first diffractive liquid crystal lens 11 and the second diffractive liquid crystal lens 12 in the liquid crystal optical element 1 ′ applies a voltage to the liquid crystals 11d and 12d, respectively. Otherwise, the incident light is acted as zero-order light to focus on an object point at infinity without having a light beam deflecting action, and when a voltage is applied to the liquid crystal, the primary light is incident on the incident light. Thus, it is configured to focus on an object point of 300 mm from the front surface of the lens.

  When the first and second diffractive liquid crystal lenses 11 and 12 are arranged in the vicinity of the aperture stop S as in the optical system of Example 1, the effective diameters of the first and second diffractive liquid crystal lenses 11 and 12 are reduced. can do.

Further, when the diffractive liquid crystal lenses 11 and 12 used in the liquid crystal optical element 1 ′ are arranged in the vicinity of the aperture stop S as in the optical system of the first embodiment, chromatic aberration centered on axial chromatic aberration due to the change of the object point position. Can also be corrected effectively. At this time, it is desirable that the following conditional expression (3) is satisfied.
| Y / sd | ≦ 0.8 (3)
Where y is the height of the most off-axis principal ray in the liquid crystal lens, and sd is the effective radius of the liquid crystal lens.

Further, it is preferable that the following conditional expression (3 ′) is satisfied, because the above-described effect is further increased.
Where y is the height of the most off-axis principal ray in the liquid crystal lens, and sd is the effective radius of the liquid crystal lens.
| Y / sd | ≦ 0.7 (3 ′)

Furthermore, it is preferable that the following conditional expression (3 ′) is satisfied, because the above-described effect is further increased.
| Y / sd | ≦ 0.6 (3 ″)
Where y is the height of the most off-axis principal ray in the liquid crystal lens, and sd is the effective radius of the liquid crystal lens.

  Further, if a lens having positive refraction and a lens having negative refraction are arranged before and after the liquid crystal optical element 1 ′ having a liquid crystal lens as in the optical system of the first embodiment, it is easy to correct chromatic aberration. Therefore, it is preferable.

2 shows numerical data of an optical member constituting an optical system including the liquid crystal optical element 1 ′ according to the first embodiment.
In addition, the rotationally symmetric aspheric surface shown in the following numerical data is shown according to the definition of the following equation.
Z = ch ² / [1 + √ {1− (1 + k) c ² h ² }] + A4h ⁴ + A6h ⁶ + A8h ⁸ + A10h ¹⁰ +.
Where c is the curvature of the vertex, k is the conic coefficient, A4 is the fourth-order aspheric coefficient, A6 is the sixth-order aspheric coefficient, A8 is the eighth-order aspheric coefficient, and A10 is the tenth-order aspheric coefficient. Further, h is a distance from the optical axis, and is represented by h ² = x ² + y ² where x is a horizontal direction and y is a vertical direction in a plane perpendicular to the optical axis.

In addition, as a design method of the diffractive liquid crystal lens shown as numerical data below, the sweat method (ultra-high refractive index method) shown in the following document was used.
Literature: WCSweatt, “Mathematical equivalence between a holographic optical element and an ultra-high index lens”, J.Opt.Soc.Am, Vol.69, No.3 (1979)
In the following numerical data, the refractive index of the ultra-high refractive index lens at the reference wavelength of 587.56 nm is 588.56.

  In the optical system of Example 1, the refractive index (ordinary refractive index) of the liquid crystal when the voltage is OFF is 1.458467, the Abbe number ν is 65.0, the refractive index (abnormal refractive index) of the liquid crystal when the voltage is ON is 1.708467, and the Abbe number ν. 30 and the thickness of the liquid crystal is 0.005mm. These are the same in the following embodiments. [1-1: Object point at infinity], [1-2: Near point (for P-polarized light)] and [1-3: Near point (for S-polarized light)] in numerical examples will be described below. This description is the same in other embodiments.

  In the optical system of Example 1, the 5th to 12th surfaces are liquid crystal lenses, the 7th to 8th surfaces, and the 10th to 11th surfaces are liquid crystal layers.

  Here, for the object point at infinity, the diffraction surface (DOE [1]) of the P-polarization liquid crystal lens and the diffraction surface (DOE [2]) of the S-polarization liquid crystal lens are not operating. That is, among the following numerical data, as shown in the numerical data of [1-1: object point at infinity], the refractive index and the Abbe number (1.4585, 65.0) of the liquid crystal are diffractive surfaces (1.4585, 65.0). ). As for the refractive index, the refractive index of the liquid crystal, the refractive index of the diffractive surface, and the refractive index of the substrate are all the same, 1.4585. For this reason, the diffractive surface physically exists but no optical action (light deflection action) occurs.

  Next, for the near point, both the P-polarization liquid crystal lens and the S-polarization liquid crystal lens are operating. However, for P-polarized light, only the P-polarized liquid crystal lens produces a deflection action, and for S-polarized light, only the S-polarized liquid crystal lens produces a deflection action. Therefore, regarding the near point, two numerical data of [1-2: Near point (for P-polarized light)] and [1-3: Near point (for S-polarized light)] are used.

  [1-2: Near point (for P-polarized light)] is numerical data regarding P-polarized light. For P-polarized light, the diffractive surface (DOE [1]) of the P-polarized liquid crystal lens produces a deflection action, and the diffractive surface (DOE [2]) of the S-polarized liquid crystal lens does not produce a deflection action. Therefore, in the numerical data of [1-2: Near point (for P-polarized light)], the refractive index of the liquid crystal on the 7th to 8th surfaces is changed from 1.4585 to 1.7085. On the other hand, the refractive index of the liquid crystal in the 10th to 11th surfaces remains 1.4585.

  Further, since the refractive index of the liquid crystal from the 7th surface to the 8th surface is 1.7085, the diffractive surface (DOE [1]) of the liquid crystal lens for P-polarization has a deflecting action. Therefore, the refractive index of the diffractive surface (DOE [1]) of the P-polarized liquid crystal lens is also changed from 1.4585 to 588.56.

  [1-3: Near point (for S-polarized light)] is numerical data regarding S-polarized light. For S-polarized light, the diffractive surface (DOE [1]) of the P-polarized liquid crystal lens does not produce a deflection effect, but the diffractive surface (DOE [2]) of the S-polarized liquid crystal lens has a deflection effect. Arise. Therefore, in the numerical data of [1-3: Near point (for S-polarized light)], the refractive index of the liquid crystals on the 7th to 8th surfaces remains 1.4585. On the other hand, the refractive index of the liquid crystal on the 10th to 11th surfaces is changed from 1.4585 to 1.7085.

  Further, since the refractive index of the 10th to 11th liquid crystals is 1.7085, the diffractive surface (DOE [2]) of the S-polarized liquid crystal lens has a deflecting action. Therefore, the refractive index of the diffractive surface (DOE [2]) of the liquid crystal lens for S polarization is also changed from 1.4585 to 588.56.

Numerical data 1 (Example 1)
[1-1: Object point at infinity]
Unit mm Surface data surface number Curvature radius Surface spacing Refractive index Abbe number Object surface ∞ ∞
1 105.00 1.20 1.5182 58.9
2 5.09 1.24
3 38.32 1.50 1.7440 44.8
4 -11.49 0.50
5 ∞ 0.30 1.4585 67.8
6 ∞ 0.00 1.4585 65.0
7 (Diffraction surface) -233418.48 (DOE [1]) 0.005 1.4585 65.0
8 ∞ 0.30 1.4585 67.8
9 ∞ 0.00 1.4585 65.0
10 (Diffraction surface) -237164.15 (DOE [2]) 0.005 1.4585 65.0
11 ∞ 0.30 1.4585 67.8
12 ∞ 0.67
13 -10.80 0.28 1.7620 40.1
14 4.90 1.20 1.7282 28.5
15 -8.47 0.50
16 (diaphragm surface) 0.40
17 5.58 1.95 1.8 160 46.6
18 -4.08 0.01 1.5638 60.7
19 -4.08 0.50 1.8052 25.4
20 4.08 1.87
21 ^* Aspherical surface [1] 2.40 1.8061 40.9
22 -5.66 4.13
23 ∞ 0.50 1.5163 64.1
24 ∞ 2.26
25 ∞ 0.50 1.5163 64.1
26 ∞ 0.49
Image plane ∞ 0.00

Aspheric data surface number 21st surface (Aspherical surface [1])
Radius of curvature -36.45
k = 1.2194E-007
A4 = -7.9872E-004 A6 = 1.0007E-004 A8 = -8.1194E-006
A10 = 5.4486E-007

[1-2: Near point (for P-polarized light)]
Unit mm
Surface data surface number Curvature radius Surface spacing Refractive index Abbe number Object surface ∞ 300.00
1 105.00 1.20 1.5182 58.9
2 5.09 1.24
3 38.32 1.50 1.7440 44.8
4 -11.49 0.50
5 ∞ 0.30 1.4585 67.8
6 ∞ 0.00 588.5 600 -3.5
7 (Diffraction surface) -233418.48 (DOE [1]) 0.005 1.7085 30.0
8 ∞ 0.30 1.4585 67.8
9 ∞ 0.00 1.4585 65.0
10 (Diffraction surface) -237164.15 (DOE [2]) 0.005 1.4585 65.0
11 ∞ 0.30 1.4585 67.8
12 ∞ 0.67
13 -10.80 0.28 1.7620 40.1
14 4.90 1.20 1.7282 28.5
15 -8.47 0.50
16 (diaphragm surface) 0.40
17 5.58 1.95 1.8 160 46.6
18 -4.08 0.01 1.5638 60.7
19 -4.08 0.50 1.8052 25.4
20 4.08 1.87
21 ^* Aspherical surface [1] 2.40 1.8061 40.9
22 -5.66 4.13
23 ∞ 0.50 1.5163 64.1
24 ∞ 2.26
25 ∞ 0.50 1.5163 64.1
26 ∞ 0.49
Image plane ∞ 0.00

Diffraction surface data surface number 7th surface (DOE [1])
Radius of curvature -233418.48
k = 0.0000E + 000
A4 = -2.4691E-008 A6 = 4.1725E-008 A8 = -9.1727E-009

Aspheric data surface number 21st surface (Aspherical surface [1])
Radius of curvature -36.45
k = 1.2194E-007
A4 = -7.9872E-004 A6 = 1.0007E-004 A8 = -8.1194E-006
A10 = 5.4486E-007

[1-3: Near point (for S-polarized light)]
Unit mm
Surface data surface number Curvature radius Surface spacing Refractive index Abbe number Object surface ∞ 300.00
1 105.00 1.20 1.5182 58.9
2 5.09 1.24
3 38.32 1.50 1.7440 44.8
4 -11.49 0.50
5 ∞ 0.30 1.4585 67.8
6 ∞ 0.00 1.4585 65.0
7 (Diffraction surface) -233418.48 (DOE [1]) 0.005 1.4585 65.0
8 ∞ 0.30 1.4585 67.8
9 ∞ 0.00 588.5 600 -3.5
10 (Diffraction surface) -237164.15 (DOE [2]) 0.005 1.7085 30.0
11 ∞ 0.30 1.4585 67.8
12 ∞ 0.67
13 -10.80 0.28 1.7620 40.1
14 4.90 1.20 1.7282 28.5
15 -8.47 0.50
16 (diaphragm surface) 0.40
17 5.58 1.95 1.8 160 46.6
18 -4.08 0.01 1.5638 60.7
19 -4.08 0.50 1.8052 25.4
20 4.08 1.87
21 ^* Aspherical surface [1] 2.40 1.8061 40.9
22 -5.66 4.13
23 ∞ 0.50 1.5163 64.1
24 ∞ 2.26
25 ∞ 0.50 1.5163 64.1
26 ∞ 0.49
Image plane ∞ 0.00

Diffraction surface data surface number 10th surface (DOE [2])
Radius of curvature -237164.15
k = 0.0000E + 000
A4 = -8.7050E-008 A6 = 7.4874E-008 A8 = -1.4487E-008

Aspheric data surface number 21st surface (Aspherical surface [1])
Radius of curvature -36.45
k = 1.2194E-007
A4 = -7.9872E-004 A6 = 1.0007E-004 A8 = -8.1194E-006
A10 = 5.4486E-007

Example 2
FIG. 7 is a sectional view along the optical axis showing the optical configuration of the optical system according to the second embodiment using the liquid crystal optical element of the present invention in the state of focusing on an object point at infinity, and FIG. 8 is the optical system of the second embodiment. 9 is a lateral aberration diagram when focusing on an object at infinity, FIG. 9 is a lateral aberration diagram when focusing on a near point (only the liquid crystal lens for P-polarization operates) in the optical system of Example 2, and FIG. It is a lateral aberration diagram at the time of focusing on the near point in the optical system (only the liquid crystal lens for S polarization is operated).
The optical system of Example 2 is the same as that of Example 1 except for the configuration of the diffractive liquid crystal lens used as the first diffractive liquid crystal lens 11 and the second diffractive liquid crystal lens 12 in the liquid crystal optical element 1 ′. Is different.

In the optical system of Example 2, the diffractive liquid crystal lens used as the first diffractive liquid crystal lens 11 and the second diffractive liquid crystal lens 12 in the liquid crystal optical element 1 ′ does not apply a voltage to the liquid crystals 11 d and 12 d, respectively. When the incident light is acted as zero-order light, focused on an object point at infinity without having a light beam deflection action, and a voltage is applied to the liquid crystal, It is configured to focus on an object point of 200 mm from the front surface of the lens.
Other configurations are substantially the same as those of the optical system of the first embodiment.
The liquid crystal optical element 1 ′ of Example 2 has a diffractive type at a position where the power of the diffractive liquid crystal lens for focusing on the same near point position (200 mm) can be reduced compared to the liquid crystal optical element of Example 3 described later. Since the liquid crystal lens is disposed, the diffractive liquid crystal lens can be easily manufactured.

Next, numerical data of an optical member constituting an optical system including the liquid crystal optical element 1 ′ of Example 2 are shown.
In the optical system of Example 2, as in the optical system of Example 1, the 5th to 12th surfaces are liquid crystal lenses, the 7th to 8th surfaces, the 10th to 11th surfaces are liquid crystal layers, respectively. is there.
Numerical data 2 (Example 2)
[2-1: Infinite object point]
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number Object surface ∞ ∞
1 105.00 1.20 1.5182 58.9
2 5.09 1.24
3 38.32 1.50 1.7440 44.8
4 -11.49 0.50
5 ∞ 0.30 1.4585 67.8
6 ∞ 0.00 1.4585 65.0
7 (Diffraction surface) -158686.60 (DOE [3]) 0.005 1.4585 65.0
8 ∞ 0.30 1.4585 67.8
9 ∞ 0.00 1.4585 65.0
10 (Diffraction surface) -161088.47 (DOE [4]) 0.005 1.4585 65.0
11 ∞ 0.30 1.4585 67.8
12 ∞ 0.67
13 -10.80 0.28 1.7620 40.1
14 4.90 1.20 1.7282 28.5
15 -8.47 0.50
16 (diaphragm surface) 0.40
17 5.58 1.95 1.8 160 46.6
18 -4.08 0.01 1.5638 60.7
19 -4.08 0.50 1.8052 25.4
20 4.08 1.87
21 ^* Aspherical surface [2] 2.40 1.8061 40.9
22 -5.66 4.13
23 ∞ 0.50 1.5163 64.1
24 ∞ 2.26
25 ∞ 0.50 1.5163 64.1
26 ∞ 0.49
Image plane ∞ 0.00

Aspheric data surface number 21st surface (Aspherical surface [2])
Radius of curvature -36.45
k = 1.2194E-007
A4 = -7.9872E-004 A6 = 1.0007E-004 A8 = -8.1194E-006
A10 = 5.4486E-007

[2-2: Near point (for P-polarized light)]
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number Object surface ∞ 200.00
1 105.00 1.20 1.5182 58.9
2 5.09 1.24
3 38.32 1.50 1.7440 44.8
4 -11.49 0.50
5 ∞ 0.30 1.4585 67.8
6 ∞ 0.00 588.5 600 -3.5
7 (Diffraction surface) -158686.60 (DOE [3]) 0.005 1.7085 30.0
8 ∞ 0.30 1.4585 67.8
9 ∞ 0.00 1.4585 65.0
10 (Diffraction surface) -161088.47 (DOE [4]) 0.005 1.4585 65.0
11 ∞ 0.30 1.4585 67.8
12 ∞ 0.67
13 -10.80 0.28 1.7620 40.1
14 4.90 1.20 1.7282 28.5
15 -8.47 0.50
16 (diaphragm surface) 0.40
17 5.58 1.95 1.8 160 46.6
18 -4.08 0.01 1.5638 60.7
19 -4.08 0.50 1.8052 25.4
20 4.08 1.87
21 ^* Aspherical surface [2] 2.40 1.8061 40.9
22 -5.66 4.13
23 ∞ 0.50 1.5163 64.1
24 ∞ 2.26
25 ∞ 0.50 1.5163 64.1
26 ∞ 0.49
Image plane ∞ 0.00

Diffraction surface data surface number 7th surface (DOE [3])
Radius of curvature -158686.60
k = 0.0000E + 000
A4 = -2.6651E-008 A6 = 3.2511E-008 A8 = -7.9738E-009

Aspheric data surface number 21st surface (Aspherical surface [2])
Radius of curvature -36.45
k = 1.2194E-007
A4 = -7.9872E-004 A6 = 1.0007E-004 A8 = -8.1194E-006
A10 = 5.4486E-007

[2-3: Near point (for S-polarized light)]
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number Object surface ∞ 200.00
1 105.00 1.20 1.5182 58.9
2 5.09 1.24
3 38.32 1.50 1.7440 44.8
4 -11.49 0.50
5 ∞ 0.30 1.4585 67.8
6 ∞ 0.00 1.4585 65.0
7 (Diffraction surface) -158686.60 (DOE [3]) 0.005 1.4585 65.0
8 ∞ 0.30 1.4585 67.8
9 ∞ 0.00 588.5 600 -3.5
10 (Diffraction surface) -161088.47 (DOE [4]) 0.005 1.7085 30.0
11 ∞ 0.30 1.4585 67.8
12 ∞ 0.67
13 -10.80 0.28 1.7620 40.1
14 4.90 1.20 1.7282 28.5
15 -8.47 0.50
16 (diaphragm surface) 0.40
17 5.58 1.95 1.8 160 46.6
18 -4.08 0.01 1.5638 60.7
19 -4.08 0.50 1.8052 25.4
20 4.08 1.87
21 ^* Aspherical surface [2] 2.40 1.8061 40.9
22 -5.66 4.13
23 ∞ 0.50 1.5163 64.1
24 ∞ 2.26
25 ∞ 0.50 1.5163 64.1
26 ∞ 0.49
Image plane ∞ 0.00

Diffraction surface data surface number 10th surface (DOE [4])
Radius of curvature -161088.47
k = 0.0000E + 000
A4 = -1.0564E-007 A6 = 7.1812E-008 A8 = -1.3925E-008

Aspheric data surface number 21st surface (Aspherical surface [2])
Radius of curvature -36.45
k = 1.2194E-007
A4 = -7.9872E-004 A6 = 1.0007E-004 A8 = -8.1194E-006
A10 = 5.4486E-007

Example 3
FIG. 11 is a cross-sectional view along the optical axis showing the optical configuration of the optical system according to Example 3 using the liquid crystal optical element of the present invention in the state of focusing on an object point at infinity, and FIG. 12 shows the optical system of FIG. It is explanatory drawing which shows the structure of the used liquid crystal optical element. FIG. 13 is a lateral aberration diagram when focusing on an object at infinity in the optical system of Example 3, and FIG. 14 is a lateral aberration when focusing on a near point in the optical system of Example 3 (only the liquid crystal lens for P-polarization operates). FIGS. 15A and 15B are lateral aberration diagrams when focusing on the near point in the optical system of Example 3 (only the S-polarized liquid crystal lens operates).
The optical system of Example 3 has a configuration in which a liquid crystal lens is disposed on the most object side of the imaging optical system.
Specifically, in order from the object side, the liquid crystal optical element 1 ″, the biconcave lens L1 ′, the biconvex lens L2, the cemented lens of the biconvex lens L3 ′ and the biconcave lens L4 ′, a positive meniscus lens L5 ′ having a concave surface facing the object side, 11 includes a parallel plate P1 and a parallel plate P2. In Fig. 11, S denotes an aperture stop, and IM denotes an image pickup surface of the image pickup device.

  Since the liquid crystal optical element 1 ″ has the same structure as the liquid crystal optical element 1 of the embodiment shown in FIG. 1, the same members are denoted by the same reference numerals and description thereof is omitted.

In the optical system of the third embodiment, the diffractive liquid crystal lens used as the first diffractive liquid crystal lens 11 and the second diffractive liquid crystal lens 12 in the liquid crystal optical element 1 ″ has voltages applied to the liquid crystals 11d and 12d, respectively. Is applied to the incident light as zero-order light to focus on an object point at infinity without having a light beam deflecting action, and when a voltage is applied to the liquid crystal, 1 is applied to the incident light. It is configured to focus on an object point of 200 mm from the front surface of the lens by giving an effect as the next light.
The other configuration of the liquid crystal optical element 1 ″ is substantially the same as that of the liquid crystal optical element 1 ′ in the first and second embodiments.

  According to the optical system of Example 3, when the focal length of the liquid crystal lens is 204 mm, the near point is focused to 200 mm. For this reason, the power of the liquid crystal lens is stronger than that of the optical systems of the first and second embodiments. However, since the liquid crystal lens is provided at the head of the lens system, it is preferable in terms of wiring processing and mechanical mechanism of the liquid crystal lens.

Next, numerical data of optical members constituting an optical system including the liquid crystal optical element 1 ″ of Example 3 are shown.
In the optical system of Example 3, the first to eighth surfaces are liquid crystal lenses, the third to fourth surfaces, and the sixth to seventh surfaces are liquid crystal layers, respectively.

Numerical data 3 (Example 3)
[3-1: Object point at infinity]
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number Object surface ∞ ∞
1 ∞ 0.30 1.4585 67.8
2 ∞ 0.00 1.4585 65.0
3 (Diffraction surface) -119457.53 (DOE [5]) 0.005 1.4585 65.0
4 ∞ 0.30 1.4585 67.8
5 ∞ 0.00 1.4585 65.0
6 (Diffraction surface) -119939.41 (DOE [6]) 0.005 1.4585 65.0
7 ∞ 0.30 1.4585 67.8
8 ∞ 1.00
9 -13.34 0.55 1.5163 64.1
10 5.74 0.99
11 17.40 1.12 2.0033 28.3
12 -12.42 0.60
13 (diaphragm surface) 0.40
14 5.58 1.95 1.8 160 46.6
15 -4.08 0.01 1.5638 60.7
16 -4.08 0.50 1.8052 25.4
17 4.08 1.87
18 ^* Aspherical surface [3] 2.40 1.8061 40.9
19 -5.66 3.05
20 ∞ 0.50 1.5163 64.1
21 ∞ 2.26
22 ∞ 0.50 1.5163 64.1
23 ∞ 0.48
Image plane ∞ 0.00

Aspheric data surface number 18th surface (Aspherical surface [3])
Radius of curvature -36.45
k = 1.2194E-007
A4 = -7.9872E-004 A6 = 1.0007E-004 A8 = -8.1194E-006
A10 = 5.4486E-007

[3-2: Near point (for P-polarized light)]
Unit: mm Surface data surface number Curvature radius Surface spacing Refractive index Abbe number Object surface ∞ 200.00
1 ∞ 0.30 1.4585 67.8
2 ∞ 0.00 588.5 600 -3.5
3 (Diffraction surface) -119457.53 (DOE [5]) 0.005 1.7085 30.0
4 ∞ 0.30 1.4585 67.8
5 ∞ 0.00 1.4585 65.0
6 (Diffraction surface) -119939.41 (DOE [6]) 0.005 1.4585 65.0
7 ∞ 0.30 1.4585 67.8
8 ∞ 1.00
9 -13.34 0.55 1.5163 64.1
10 5.74 0.99
11 17.40 1.12 2.0033 28.3
12 -12.42 0.60
13 (diaphragm surface) 0.40
14 5.58 1.95 1.8 160 46.6
15 -4.08 0.01 1.5638 60.7
16 -4.08 0.50 1.8052 25.4
17 4.08 1.87
18 ^* Aspherical surface [3] 2.40 1.8061 40.9
19 -5.66 3.05
20 ∞ 0.50 1.5163 64.1
21 ∞ 2.26
22 ∞ 0.50 1.5163 64.1
23 ∞ 0.48
Image plane ∞ 0.00

Diffraction surface data surface number 3rd surface (DOE [5])
Radius of curvature -119457.53
k = 0.0000E + 000
A4 = 6.2474E-008 A6 = -4.9008E-009

Aspheric data surface number 18th surface (Aspherical surface [3])
Radius of curvature -36.45
k = 1.2194E-007
A4 = -7.9872E-004 A6 = 1.0007E-004 A8 = -8.1194E-006
A10 = 5.4486E-007

[3-3: Near point (for S-polarized light)]
Unit mm
Surface data Surface number Curvature radius Surface spacing Refractive index Abbe number Object surface ∞ 200.00
1 ∞ 0.30 1.4585 67.8
2 ∞ 0.00 1.4585 65.0
3 (Diffraction surface) -119457.53 (DOE [5]) 0.005 1.4585 65.0
4 ∞ 0.30 1.4585 67.8
5 ∞ 0.00 588.5 600 -3.5
6 (Diffraction surface) -119939.41 (DOE [6]) 0.005 1.7085 30.0
7 ∞ 0.30 1.4585 67.8
8 ∞ 1.00
9 -13.34 0.55 1.5163 64.1
10 5.74 0.99
11 17.40 1.12 2.0033 28.3
12 -12.42 0.60
13 (diaphragm surface) 0.40
14 5.58 1.95 1.8 160 46.6
15 -4.08 0.01 1.5638 60.7
16 -4.08 0.50 1.8052 25.4
17 4.08 1.87
18 ^* Aspherical surface [3] 2.40 1.8061 40.9
19 -5.66 3.05
20 ∞ 0.50 1.5163 64.1
21 ∞ 2.26
22 ∞ 0.50 1.5163 64.1
23 ∞ 0.48
Image plane ∞ 0.00

Diffraction surface data surface number 6th surface (DOE [6])
Radius of curvature -119939.41
k = 0.0000E + 000
A4 = 5.4913E-008 A6 = -4.5332E-009

Aspheric data surface number 18th surface (Aspherical surface [3])
Radius of curvature -36.45
k = 1.2194E-007
A4 = -7.9872E-004 A6 = 1.0007E-004 A8 = -8.1194E-006
A10 = 5.4486E-007

表２

なお、レンズ全長は先頭面から近軸像面までの距離、BFはレンズ最終面から近軸像面までの距離である。 Next, Table 1 and Table 2 show conditional expression parameter corresponding values and various optical system data in the optical systems of Examples 1 to 3.
Table 1

Table 2

The total lens length is the distance from the front surface to the paraxial image surface, and BF is the distance from the last lens surface to the paraxial image surface.

  The present invention is useful in a field in which it is required to use a small and quick image acquisition apparatus. The image acquisition apparatus according to the present invention includes a device that captures a still image, a moving image, or the like with an optical device such as a camera, a microscope, an endoscope, a telescope, and a scanner.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual diagram showing a basic configuration and an operating principle of a liquid crystal optical element according to a first embodiment of the present invention, where (a) is a voltage applied to a liquid crystal lens and (b) is a voltage applied to a liquid crystal lens. The effect | action which incident light receives is shown. It is sectional drawing which follows the optical axis which shows the optical structure of the optical system concerning Example 1 using the liquid crystal optical element of this invention in the state at the time of infinity object point focusing. It is explanatory drawing which shows the structure of the liquid crystal optical element used for the optical system of FIG. FIG. 3 is a lateral aberration diagram when focusing on an object at infinity in the optical system according to Example 1. FIG. 6 is a lateral aberration diagram when focusing on a near point (only the P-polarized liquid crystal lens operates) in the optical system of Example 1. 6 is a lateral aberration diagram when focusing on a near point (only the liquid crystal lens for S polarization is operated) in the optical system of Example 1. FIG. It is sectional drawing which follows the optical axis which shows the optical structure of the optical system concerning Example 2 using the liquid crystal optical element of this invention in the state at the time of infinity object point focusing. 6 is a lateral aberration diagram when focusing on an object at infinity in the optical system of Example 2. FIG. FIG. 7 is a lateral aberration diagram when focusing on a near point (only the P-polarized liquid crystal lens operates) in the optical system of Example 2. FIG. 10 is a lateral aberration diagram when focusing on a near point (only the liquid crystal lens for S polarization is operated) in the optical system of Example 2. It is sectional drawing which follows the optical axis which shows the optical structure of the optical system concerning Example 3 using the liquid crystal optical element of this invention in the state at the time of infinity object point focusing. It is explanatory drawing which shows the structure of the liquid crystal optical element used for the optical system of FIG. FIG. 10 is a lateral aberration diagram when focusing on an object at infinity in the optical system according to Example 3. FIG. 10 is a lateral aberration diagram when focusing on a near point (only the P-polarized liquid crystal lens operates) in the optical system of Example 3. FIG. 10 is a lateral aberration diagram when focusing on a near point (only the liquid crystal lens for S polarization operates) in the optical system of Example 3. It is sectional drawing which shows the example of 1 structure of the diffraction type liquid crystal lens applicable to the liquid crystal optical element of FIG.

Explanation of symbols

1, 1 ′, 1 ″ Liquid crystal optical element 11 First diffractive liquid crystal lens 11a, 12a Substrate 11a1, 12a1 Serrated relief 11b, 12b Thin film transparent electrode 11c, 12c Counter electrode 11d, 12d Liquid crystal 12 Second diffractive liquid crystal Lens 13a, 13b, 13c Substrate L1 Negative meniscus lens with convex surface facing the object side L2, L4, L5, L3 ′ Biconvex lens L3, L6, L1 ′, L4 ′ Biconcave lens L7, L5 ′ With concave surface facing the object side Positive meniscus lens P1, P2 Parallel plate S Aperture stop IM Image sensor surface

Claims (8)

A first liquid crystal lens and a second liquid crystal lens;
The first liquid crystal lens and the second liquid crystal lens are arranged to face each other so that the alignment directions are orthogonal to each other in a plane perpendicular to the optical axis,
The one polarized light that is subjected to the light deflection action in the second liquid crystal lens as compared to the focal length of the first liquid crystal lens with respect to incident light in one polarization direction that is subjected to the light deflection action in the first liquid crystal lens. A liquid crystal optical element characterized in that the focal length of the second liquid crystal lens with respect to incident light in the other polarization direction orthogonal to the direction is shortened. The liquid crystal optical element according to claim 1, wherein the following conditional expression (1) is satisfied.
0 <| (f1-f2) /f1|≦0.5 (1)
However, f1 is the focal length of the first liquid crystal lens with respect to the incident light in the one polarization direction that receives the light beam deflection action in the first liquid crystal lens, and f2 is subjected to the light beam deflection action in the second liquid crystal lens. The focal length of the second liquid crystal lens with respect to incident light in the other polarization direction orthogonal to the one polarization direction.   3. A liquid crystal optical element according to claim 1 or 2, wherein the first liquid crystal lens receives a light beam deflection action, the focal position with respect to incident light in the one polarization direction, and the second liquid crystal lens light beam deflection action. The optical system is characterized in that the focal position with respect to incident light in the other polarization direction orthogonal to the one polarization direction substantially coincides. The liquid crystal optical element according to claim 1 or 2,
An optical system, wherein a voltage applied to the liquid crystal optical element is controlled to correct a focal position shift with respect to incident light from different object points.   5. The light beam incident on the liquid crystal optical element is transmitted without being diffracted or refracted so that the liquid crystal optical element acts as a parallel plate when focusing on an object point at infinity. The optical system described in 1.   The far-point object point is focused when the liquid crystal optical element has no light beam deflection action, and the near-point object point is focused when the liquid crystal optical element has a light beam deflection action. The optical system according to claim 4 or 5. The optical system according to claim 3, wherein the following conditional expression (2) is satisfied.
| Δ / f | ≦ 0.6 (2)
Where Δ is the distance between the first liquid crystal lens and the second liquid crystal lens, and f is the focal length of the optical system. An optical system according to any one of claims 3 to 7,
An image sensor;
Zoom optics,
An image acquisition apparatus comprising:

Images