JP2008176082A - Optical element, photographing optical system, imaging method and photographing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element capable of further widening the range of variable focal distance. <P>SOLUTION: An optical element 10 includes a liquid lens that is formed by sealing a first liquid 20 and a second liquid 19, which does not mix with the first liquid 20, in a container 12 and capable of changing the shape of a boundary surface 21 between the first liquid 20 and second liquid 19 by changing a voltage (physical quantity) applied to the inside of the container 12. The optical element 10 has: half prisms 16 which are located on the first liquid 20 side and through which the optical axis X of the liquid lens passes so as to pass through the boundary surface between the first and second liquids 20 and 19; and an optical member 17 located on the second liquid 19 side and through which the optical axis X of the liquid lens passes so as to pass through the boundary surface between the first and second liquids 20 and 19. The half prisms 16 are provided with a selective light ray transmission/reflection face 16a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical element, a photographing optical system including the optical element, and an imaging method and a photographing method using the optical element.

  Conventionally, in an optical system that performs focusing, zooming, and the like, focusing and zooming have been performed by moving a fixed focal length lens in the optical axis direction. In order to move the fixed focal length lens, there is a power source such as a motor and a mechanical mechanism such as a gear or a cam for converting the driving force from the power source into movement of the fixed focal length lens in the optical axis direction. Although necessary, these mechanical mechanisms have problems such as an increase in the size of a camera and the like, and generation of driving sound.

  As a method to solve these problems, a variable focal length lens using electrowetting phenomenon, a variable shape mirror that can change the focal length by changing the surface shape, etc. are used electrically without a power source or mechanical mechanism. In recent years, many optical systems capable of performing focusing, zooming, diopter adjustment, and the like have been proposed (see, for example, Patent Document 1 or 2).

JP 2001-249282 A

JP 2004-198636 A

  However, the conventional optical element has a problem that a variable focal length range cannot be made large due to limitations of each liquid material and applied voltage. Further, when the shape change is performed on the reflecting surface, there is a problem that the influence on the optical aberration due to the shape error of the variable reflecting surface becomes large. Furthermore, in an optical system using a variable focal length element, there is a close relationship between the variable range of the variable focal length element and the optical path length, and it is necessary to increase the optical path length in order to narrow the variable range of the variable focal length element. there were.

  The present invention has been made in view of such problems, and it is possible to further widen the variable focal length range, to reduce the influence on the optical aberration due to the variable surface shape error, and to make the external dimensions too large. It is an object of the present invention to provide an optical element capable of making the optical path length longer and a photographing optical system having the optical element, and an imaging method and a photographing method using the optical element.

  In order to solve the above-described problem, an optical element according to the present application includes a first liquid and a second liquid that is not mixed with the first liquid and encloses the container in a container, and changes a physical quantity applied to the container. Thus, a liquid lens that can change the shape of the boundary surface between the first liquid and the second liquid is provided. The optical element is located on the first liquid side, and a first optical member (for example, the half prism 16 in the embodiment) through which the optical axis of the liquid lens passes through the boundary surface between the first liquid and the second liquid. A second optical member (for example, the optical member 17 in the embodiment) that is located on the second liquid side and that penetrates the optical axis of the liquid lens that penetrates the boundary surface between the first liquid and the second liquid. The optical member is provided with a selective light transmission / reflection surface.

  In this optical element, the second optical member is provided with a reflecting surface, and the incident light beam is reflected by the reflecting surface after passing through the first liquid and the second liquid in the order in which the light travels, and again the second liquid and the first liquid. And is preferably configured to be injected through.

  Moreover, it is preferable that either one of the first liquid and the second liquid is conductive and the other is insulating. Furthermore, the quantity is preferably a voltage.

  In the optical element, it is preferable that the first optical member is configured by joining at least two or more prisms.

  Furthermore, it is preferable that the selective light transmitting / reflecting surface is disposed on the joint surface of the two prisms. Or it is preferable that the optical member which has a selective light transmissive reflective surface is comprised with the polarizing beam splitter.

  The optical element is preferably configured such that the inner wall surface of the liquid lens is in contact with the boundary surface at the entire circumference around the optical axis of the liquid lens. In this case, an electrode (for example, the second electrode 13 in the embodiment) provided on a member that forms the inner wall surface of the liquid lens, and the electrode is provided between the first liquid and the second liquid. It is preferable to have an insulating means (for example, the second insulator 15 in the embodiment) and to change the shape of the boundary surface by applying a voltage between the conductive liquid and the electrode.

  At this time, it is preferable that the first liquid and the second liquid have substantially the same density.

  In the optical element, the first liquid and the second liquid are preferably configured to have different refractive indexes.

  In the optical element, it is preferable that the inner wall surface of the liquid lens is formed rotationally symmetric with respect to the optical axis of the liquid lens.

  In addition, the photographing optical system according to the present application has a positive refractive power as a whole, and includes any of the optical elements described above in the optical path. At this time, the photographing optical system has a first refractive focal length lens (for example, the negative meniscus lens 31 in the embodiment), the above-described optical element, and a positive refractive power in order from the object side along the optical axis. It is preferable to have a plurality of lenses.

  Furthermore, the imaging method according to the present application is a method of forming an image using any of the above-described optical elements, and the imaging method according to the present application is a method of imaging with the above-described imaging optical system.

  When the optical element according to the present application, the photographing optical system using the optical element, and the imaging method and the photographing method using the optical element are configured as described above, the variable focal length range can be further expanded, and the variable surface It is possible to provide an optical element that has a small influence on optical aberration due to shape error and can increase the optical path length without enlarging the external dimensions, and a photographing optical system using this optical element, and using these An imaging method and an imaging method can be provided.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. First, the optical element according to the present invention will be described with reference to FIG. The optical element 10 includes a first electrode 11 in which a conductive material is formed in a cylindrical bowl shape, a container 12 in which an insulating material such as plastic is formed in a cylindrical shape, and a conductive material in a double cylindrical shape. The second electrode 13 formed, the first insulator 14 in which the insulating material is formed in a cylindrical shape, the second insulator 15 in which the insulating material that transmits light is formed in a cylindrical bowl shape, and transmits light. Two prisms made of material are joined, and a half-prism 16 that is a first optical member having a selective light transmitting / reflecting surface 16a formed on the joined surface, and a material that transmits light in a disc shape. The second optical member 17 is formed. The selective light transmitting / reflecting surface 16 a is a surface that transmits a part of the light and reflects the rest, and a polarizing beam splitter can be used instead of the half prism 16.

  The second electrode 13 has a U-shaped cross section and is attached so as to cover the inner peripheral surface, the lower surface, and the outer peripheral surface of the container 12. Further, the outer diameter of the first insulator 14 is formed to be approximately the same as the inner diameter of the second electrode 13 and the container 12, and the first insulating body 14 has the first insulation with respect to the inner peripheral surfaces of the second electrode 13 and the container 12. A body 14 is inserted and attached. Further, the outer diameter of the second insulator 15 is formed to be approximately the same as the inner diameter of the first insulator 14, and the first insulating member 15 has an opening 15 a facing upward. It is inserted into the body 14 and attached.

  With the second electrode 13, the first insulator 14, and the second insulator 15 attached to the container 12, the lower surfaces thereof are located on substantially the same plane, and the half prism is disposed on the lower surface. 16 is joined. Further, the top surfaces of the container 12, the first insulator 14, and the second insulator 15 are also located on substantially the same plane, and the bottom portion 11b so that the opening portion 11a of the first electrode 11 faces upward with respect to the top surface. Are joined. The bottom 11b of the first electrode 11 is provided with a circular opening window 11c. The inner diameter of the opening window 11c is slightly smaller than the inner diameter of the opening 15a of the second insulator 15, and the opening window 11c and the opening 15a have the same rotational symmetry axis (the optical axis X of the liquid lens described later). Further, the inner diameter of the first electrode 11 and the outer shape of the second optical member 17 are formed to be substantially the same size, and the second optical member 17 is inserted into the first electrode 11 from the opening 11a. The second optical member 17 closes the opening window 11c. Note that a reflective layer 18 on which a highly reflective material is deposited is formed on the upper end surface of the second optical member 17 and functions as the reflective surface 18a.

  In a space surrounded by the second insulator 15, the first electrode 11, and the second optical member 17, a conductive lithium chloride aqueous solution (referred to as “second liquid 19”) and the second liquid 19 And filled with insulating silicon oil having the same density (referred to as “first liquid 20”). At this time, the second liquid 19 and the first liquid 20 are not mixed, and a boundary surface 21 is formed by surface tension (in FIG. 1, the second liquid 19 is located on the second optical member 17 side above the boundary surface 21. The first liquid 20 is located on the half prism 16 side which is the first optical member below the boundary surface 21), and the liquids 19 and 20 are arranged with the boundary surface 21 as a boundary to form a liquid lens. Yes. In addition, since the first liquid 20 and the second liquid 19 are configured to have the same density, gravity does not affect the boundary surface 21 at all. Therefore, the influence of the gravity direction on the boundary surface 21 can be avoided. In addition, mixing by vibration can be avoided.

  In FIG. 1, the inner wall surface 15b of the second insulator 15 is formed rotationally symmetrical, the rotational symmetry axis with respect to the inner wall surface 15b coincides with the optical axis X of the liquid lens, and the optical axis X of the liquid lens is It passes through the half prism 16, the boundary surface 21, and the second optical member 17. A part of the light beam incident from the left side of the half prism 16 is reflected upward by the selective light transmission / reflection surface 16a and is incident on the second insulator 15 with the optical axis X of the liquid lens as the optical axis. That is, the incident light optical axis I is substantially coincident with the optical axis X of the liquid lens in a state where it is bent by the half prism 16. Then, the light beam that has passed through the second insulator passes through the first liquid 20, the second liquid 19, and the second optical member 17, and is reflected by the lower surface (reflecting surface 18a) of the reflective layer 18, and again the second optical. The member 17, the second liquid 19, and the first liquid 20 are transmitted and enter the half prism 16, and a part of the light beam is transmitted through the selective light transmission / reflection surface 16 a and coincides with the optical axis X of the liquid lens. It is emitted as a light beam on the optical axis. That is, the optical axis X of the liquid lens coincides with the optical axis of the outgoing light beam O emitted from the upper side to the lower side.

  In the optical element 10, the boundary surface 21 between the first liquid 20 and the second liquid 19 is in contact with the inner wall surface 15 b on the entire circumference around the optical axis X of the liquid lens. The second electrode 13 is insulated from the first liquid 20 and the second liquid 19 by the first and second insulators 14 and 15, while the opening 11 c of the first electrode 11 is not connected to the second liquid 19. It is in contact and electrically connected. Therefore, by applying a voltage which is a physical quantity to the first electrode 11 and the second electrode 13, the surface tension between the boundary surface 21 and the inner wall surface 15b can be changed. The configuration can be changed. Here, the refractive index of the second liquid 19 at the d-line is n = 1.41, and the refractive index of the first liquid 20 at the d-line is n = 1.55. Thus, the focal length of the entire optical element 10 can be changed. In addition, the light beam passes through the boundary surface 21 twice, so that it is possible to obtain approximately twice the refractive power as compared with the case of passing through the boundary surface 21 once, and the variable focal length range can be further expanded. Possible optical elements can be provided.

  At this time, since the variable focal plane (boundary plane 21) is a refracting plane, it is less affected by the variable plane shape error compared to the case where the reflecting surface is used as the variable focal plane, and the optical aberration due to the variable plane shape error is reduced. An optical element with little influence can be provided. Furthermore, since the light beam passes through the distance from the selective light transmitting / reflecting surface 16a to the reflecting surface 18a twice, the optical path length can be efficiently extended, and the optical path length can be increased without increasing the external dimensions. The optical element which can lengthen can be provided.

  In the above description, the case where the inner wall surface 15b of the second insulator 15 is formed rotationally symmetrical has been described. However, the present embodiment is not limited to this shape. For example, the shape of the inner wall surface 15b is It is also possible to configure a plane symmetry including the optical axis X of the liquid lens. Alternatively, the inner wall surface 15b may be asymmetric. Further, by using two liquids having substantially the same refractive index and different Abbe numbers as the first liquid 20 and the second liquid 19, the chromatic aberration of the entire optical element 10 is caused by a change in the boundary surface shape accompanying a voltage change. Can be configured to be changeable. Moreover, you may comprise the 1st insulator 14 and the 2nd insulator 15 with a transparent integrated insulator. Or the 1st insulator 14 and the 2nd insulator 15 can also be comprised with a transparent insulating thin film.

  Next, a case where the above-described optical element is applied to the photographing optical system will be described with reference to FIG. The photographing optical system 30 includes, in order from the object side, a negative meniscus lens 31 having a convex surface directed toward the object side, a first lens group 33 including the optical element 10 and the biconvex lens 32, a biconcave lens, a biconcave lens, and a biconvex lens. A second lens group 34 having a negative refractive power, a third lens group 35 having a positive refractive power made up of a biconvex lens, a biconvex lens and a biconcave lens, and a positive lens comprising a biconvex lens, a biconvex lens and a biconcave lens. The lens unit 36 includes a fourth lens group 36 having a refractive power, an optical low-pass filter 37, and an image sensor 38. 2 that the imaging optical system 30 is provided with four lenses having positive refractive power.

  A light ray incident on the first lens group 33 from the left side of FIG. 2 is incident on the negative meniscus lens 31 which is the first fixed focal length lens, and further incident on the half prism 16, and a part of the light beam is selectively selected. The light is reflected upward by the light transmitting / reflecting surface 16a, passes through the first liquid 20, the second liquid 19, and the second optical member 17, and is reflected by the reflecting surface 18a. Then, the light passes through the same optical path again and enters the half prism 16 again. A part of the light passes through the selective light transmitting / reflecting surface 16a and is emitted from below the half prism 16, and the convex lens 32, second to fourth. The light passes through the lens groups 34 to 36 and the optical low-pass filter 37 and forms an image on the image sensor 38. For this reason, in this photographing optical system 30, the optical element 10 changes the incident light to the second lens group 34 by the focal length conversion function, and makes the compensator and focus of the zoom lens.

  When the optical element and the photographing optical system shown in the present embodiment are configured as described above and the imaging method and the photographing method using these optical elements are used, the variable focal length can be further increased, and the variable surface shape error can be increased. It is possible to provide an optical element that can increase the optical path length without significantly increasing the external dimensions, and to provide an imaging optical system using the optical element, and imaging using the optical element. A method and an imaging method can be provided.

  The optical element according to the present embodiment can also be used for an optical switch using a focal length conversion means, an NA conversion function of an optical disk pickup lens optical system, and the like. Further, the form of the liquid container of the present invention is not limited to the examples shown in the present specification as long as they have the same function. Further, the liquid material (first and second liquids) is not limited to the examples shown in the present specification as long as they have the same function.

It is a sectional side view of the optical element which concerns on this invention. It is a sectional side view of the imaging optical system using the said optical element.

Explanation of symbols

10 optical element 12 container 13 second electrode (electrode)
DESCRIPTION OF SYMBOLS 15 2nd insulator (insulating means) 15b Inner wall surface 16 Half prism (1st optical member) 16a Selective light transmissive reflective surface 17 2nd optical member 18a Reflecting surface 19 2nd liquid 20 1st liquid 21 Boundary surface 30 Imaging optics System 31 Negative meniscus lens (first fixed focal length lens)
X Optical axis of liquid lens

Claims (16)

A first liquid and a second liquid that is not mixed with the first liquid are sealed in a container, and a physical quantity applied to the container is changed, thereby changing a boundary surface between the first liquid and the second liquid. An optical element having a liquid lens capable of changing its shape,
A first optical member located on the first liquid side and penetrating an optical axis of the liquid lens penetrating a boundary surface between the first liquid and the second liquid;
A second optical member located on the second liquid side and penetrating an optical axis of the liquid lens penetrating a boundary surface between the first liquid and the second liquid;
An optical element in which the first optical member is provided with a selective light transmitting / reflecting surface. A reflective surface is provided on the second optical member;
An incident light beam is configured to pass through the first liquid and the second liquid in the order in which the light travels, then be reflected by the reflecting surface, and then pass through the second liquid and the first liquid again to be emitted. The optical element according to claim 1.   The optical element according to claim 1, wherein one of the first liquid and the second liquid is conductive, and the other is insulating.   The optical element according to claim 1, wherein the physical quantity is a voltage.   The optical element according to claim 1, wherein the first optical member is configured by joining at least two or more prisms.   The optical element according to claim 5, wherein the selective light transmission / reflection surface is disposed on a joint surface between the two prisms.   The optical element according to any one of claims 1 to 4, wherein the optical member having the selective light transmission / reflection surface is configured by a polarization beam splitter.   The optical element according to any one of claims 1 to 7, wherein an inner wall surface of the liquid lens is in contact with the boundary surface at an entire circumference around an optical axis of the liquid lens. An electrode provided on a member forming an inner wall surface of the liquid lens;
Having an insulating means provided between the electrode and the first liquid and the second liquid;
The optical element according to claim 8, wherein the interface shape is changed by applying a voltage between the conductive liquid and the electrode.   The optical element according to claim 1, wherein the first liquid and the second liquid have substantially the same density.   The optical element according to claim 1, wherein the first liquid and the second liquid are configured to have different refractive indexes.   The optical element according to claim 1, wherein an inner wall surface of the liquid lens is formed rotationally symmetrical with respect to an optical axis of the liquid lens. An imaging optical system having a positive refractive power as a whole,
A photographic optical system comprising the optical element according to any one of claims 1 to 12 in an optical path. In order from the object side along the optical axis,
A first fixed focal length lens;
The optical element;
The photographing optical system according to claim 13, further comprising a plurality of lenses having a positive refractive power.   An imaging method for forming an image using the optical element according to claim 1.   A photographing method for photographing with the photographing optical system according to claim 13 or 14.

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