JP2009031699A - Polarization imaging element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a compact polarization imaging element capable of highly accurately imaging the surface and the inner part of an observation object. <P>SOLUTION: The polarization imaging element has a liquid crystal lens 1 and a TN liquid crystal element 2 as an integral structure using a common substrate. The liquid crystal lens 1 is provided with first, second and third electrodes 21, 22 and 23, respectively, driven by independently variable two voltages and capable of electrically and variably controlling the focal length of a convex lens as well as a concave lens. The TN liquid crystal element 2 electrically performs control of 90° rotation of the polarization direction of illumination light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

In the present invention, a liquid crystal optical element having a function of rotating and controlling the polarization direction of illumination light by 90 degrees and a liquid crystal lens capable of changing a focal length by an applied voltage are miniaturized as an integrated structure, and not only the surface of an observation object but also an internal The present invention relates to a polarization imaging element capable of observing the shape, composition, and the like.

An endoscope is widely used for observing the inside of a living body or the inside of a narrow space. When observing a living body or a narrow space using an endoscope, illumination light is introduced into the interior by a light guide such as an optical fiber bundle or a relay lens from an external light source to illuminate the observation section. The light reflected from the observation unit can be received by an imaging device arranged at the distal end of the endoscope or an imaging device arranged outside by the light guide or the like to obtain an image as an electric signal. .

In general, an imaging lens for objectives having a relatively wide field of view is used in an endoscope, and as a result, the depth of field is widened, and observation is performed with a fixed focus type that does not have a focus adjustment function. There are many things that can be done, but in order to accurately diagnose and determine the affected part or defective part, etc., it is necessary to examine the observation object in detail at a narrow angle or close to it, It may be necessary to examine as a simple image.

In order to perform narrow-angle observation and wide-angle observation, it is necessary to use a zoom lens as an imaging lens, and at least a part of the lens must be mechanically moved. As a method of solving these problems, there is a method of using a liquid crystal lens that electrically changes the focal length of the lens without requiring a mechanical moving means of the lens. This is proposed in Patent Document 1.

Further, Patent Document 2 discloses a method of using a liquid crystal lens that can electrically change the focal length without mechanically moving the objective lens when the distance from the observation object is changed.

The liquid crystal lenses disclosed in Patent Document 1 and Patent Document 2 are superior to other optical materials in that an effective refractive index can be continuously varied from a value for almost extraordinary light to a value for ordinary light by applying a voltage. The liquid crystal device has the excellent characteristics that the focal length can be varied by the applied voltage by utilizing the electro-optic effect in the nematic liquid crystal. This variable-focus lens using liquid crystal has a structure in which a glass substrate with a transparent electrode is curved and the liquid crystal layer itself has a lens shape. By applying a voltage between the electrodes, the alignment of liquid crystal molecules is controlled and effective. This is a lens that changes the refractive index, and is disclosed in Patent Document 3 and Non-Patent Document 1.

In addition, methods utilizing the effect of electrically controlling the focal position by incorporating a liquid crystal lens into an endoscope have been reported in Patent Document 4, Patent Document 5, Patent Document 6, and the like, and the observation optical system In addition to adjusting the focal length of the light, it may be used to change the orientation angle of the illumination light.

In a nematic liquid crystal cell based on the same principle as a method of obtaining a lens effect by giving a spatial parabolic refractive index distribution to an optical medium as a method of variably controlling a focal length by a voltage using a liquid crystal, Some use the property of aligning liquid crystal molecules in the direction of the electric field. This has been reported as a method for obtaining a liquid crystal lens having a spatial refractive index distribution characteristic by using an electrode having a circular hole pattern and utilizing the effect of liquid crystal molecule alignment by an axially symmetric non-uniform electric field. (Patent Document 7, Patent Document 8, Non-Patent Documents 2 and 3).

  In the liquid crystal microlens structure proposed in Patent Document 7, Patent Document 8, Non-Patent Document 2, and Non-Patent Document 3, the diameter of the opening portion of the electrode is increased while the thickness of the liquid crystal layer is constant. When the aperture diameter is increased, an axially symmetric non-uniform electric field does not act up to the vicinity of the center of the opening, and there is a problem that good lens characteristics cannot be obtained. As a method of increasing the effective aperture diameter, an electrode having an opening with a structure similar to the liquid crystal microlens proposed in Patent Document 7, Patent Document 8, Non-Patent Document 2, and Non-Patent Document 3 is used as a liquid crystal layer. Even if the diameter of the electrode opening is increased, the molecular alignment effect due to the axially symmetric non-uniform electric field is near the center of the opening. Can occur. Based on this principle, a method has been proposed in which an insulating layer is inserted between a liquid crystal layer and a circular hole pattern electrode to maintain a distance from the liquid crystal layer to the circular hole electrode (Patent Document). 9, Non-Patent Documents 4 and 5), there is a condition that the ratio of the diameter of the circular hole pattern and the thickness of the liquid crystal layer that provides the best characteristics in the liquid crystal microlens needs to be about 2: 1 to 3: 1 It has been shown that liquid crystal lenses that are relaxed and have a large diameter can be constructed.

On the other hand, in a liquid crystal lens in which an insulating layer is inserted between the liquid crystal layer and the circular hole pattern electrode, a transparent third electrode is disposed outside the circular hole pattern electrode and driven with two voltages. There has been reported a liquid crystal lens capable of changing a focal length over a wide range from a concave lens characteristic to a convex lens characteristic while maintaining good optical characteristics (Patent Document 10).

Unlike ordinary passive optical devices, these optical devices using liquid crystals are optically controlled by applying a voltage between the electrodes to variably control the spatial distribution of the effective refractive index of the liquid crystal medium. A lens capable of adjusting the characteristics and aberration of the optical system is realized.

When observing using an endoscope, the focal length can be changed electrically without having a mechanical moving part by using the liquid crystal lens having the above-described variable focus function. It is possible to configure a small imaging element that can obtain a clear image with high accuracy.

Patent Document 11 discloses a catheter imaging method using near infrared light or infrared light in addition to visible light.

When the object is irradiated with polarized illumination light, the reflected light usually consists of the same polarization component as the illumination light.Therefore, when the polarizing filter is observed so as to transmit only the polarization component perpendicular to the polarization direction, The reflected light component can be removed. Since the polarization component of the light scattered and reflected inside the object includes a polarization component other than the polarization component of the polarized irradiation light, only the polarization component perpendicular to the polarization direction of the polarized irradiation light is transmitted. When a polarizing filter is placed on the surface of the object, an image of light scattered and reflected inside the object can be obtained.

There is a method for using the polarization characteristics of the reflected light so that the illumination light reflected from the inner surface of the transparent sheath does not interfere with the observation of the endoscope and can be favorably observed with the endoscope. It is reported in Patent Document 12.

In addition, a polarizer is disposed at the distal end of the endoscope, and a polarization selection liquid crystal element having a function of switching the polarization direction of incident light to 90 degrees, that is, a vertical direction on the light receiving optical path is provided. A method of switching so as to transmit a polarization component perpendicular to the direction is reported in Patent Document 13.

As an element having a function of switching the polarization direction of incident light to 90 degrees, that is, a vertical direction, the director alignment direction corresponding to the major axis direction of the liquid crystal molecules is between one substrate surface and the other substrate surface constituting the liquid crystal cell. There is known a twisted nematic liquid crystal cell, that is, a TN liquid crystal cell twisted by 90 degrees (Non-Patent Document 6). The TN liquid crystal cell has optical rotation when no voltage is applied, and incident polarized light is emitted by rotating its polarization direction by 90 degrees. On the other hand, when a voltage higher than the threshold value is applied, the optical rotation is lost, and the incident light is emitted as it is. In Patent Document 13, a TN liquid crystal cell is used as a liquid crystal optical element having a function of rotating and controlling the polarization direction by 90 degrees, that is, a polarization selection element, so that the polarization state can be easily switched only by voltage control. We are downsizing.

By receiving light in the same polarization state as the illumination light using a liquid crystal lens, the image can be obtained by focusing on the surface of the object to be observed. In addition, the liquid crystal optical element rotates the polarization direction of the illumination light by 90 degrees, and only the polarized light perpendicular to the polarization direction of the illumination light is received so as to focus on the inside of the object, thereby removing the influence of surface reflection. A polarization imaging element that obtains an image in the state can be configured. In order to attach such a liquid crystal lens and a liquid crystal optical element to the distal end portion of the endoscope, it is necessary to make the structural dimensions of each element as small as possible. Particularly in medical endoscopes and ultra-fine industrial endoscopes, the outer diameter of the distal end portion is required to be several mm or less. As a liquid crystal optical element having a function of rotating the liquid crystal lens and the polarization direction by 90 degrees, for example, a TN liquid crystal cell can be used as an individual element to constitute a polarization imaging element having the above function. By combining a liquid crystal lens and a liquid crystal optical element each having an extremely small structural dimension, it is difficult in terms of manufacturing technology to form an element of several millimeters or less as a whole, and the manufacturing cost is high. is there.
JP-A-61-103116 JP-A-10-73758 JP 54-151854 A JP 2000-197604 A JP2001-154085A JP 2006-181387 A JP-A-11-109303 JP-A-11-109304 JP2004-4616 JP 2006-91826 A Special table 2005-503203 JP 2004-73647 A JP-A-11-19026 S. Sato, “Liquid-crystal lens-cell with variable focal length”, Japanese Journal of Applied Physics, 1979, Vol. 18, P. 1679-1683 Toshiaki Nose, Susumu Sato (T. Nose and S. Sato), “Liquid-crystal micro lens obtained with a non uniform electric field”, Liquid Crystals, 1989, P. 1425 -1433 Susumu Sato, “The World of Liquid Crystals”, Sangyo Tosho Co., Ltd., April 15, 1994, p. 186-189 Hajime, Susumu Sato (M. Ye and S. Sato), "Optical properties of liquid crystal lens of any size", Proceedings of the 49th Joint Conference on Applied Physics , March 2002, 28p-X-10, P.M. 1277 M. Ye and S. Sato, “Optical properties of liquid crystal lens of any size”, Japanese Journal of Applied Physics, May 2002, Vol. 41, No. 5, P. L571-L5733 Susumu Sato, “Liquid Crystal World”, Sangyo Tosho Co., Ltd., April 15, 1994, P.104-107

The liquid crystal lens and the liquid crystal optical element having the function of rotating the polarization direction by 90, such as a TN liquid crystal cell, are combined and attached to the tip of an endoscope or the like so as to focus not only on the surface of the object but also inside the object. In order to construct a polarization imaging element that obtains each image, it is necessary to make the structural dimensions of the polarization imaging element by a liquid crystal lens and a liquid crystal optical element as small as possible, but each element is manufactured and combined individually. Thus, there is a problem in manufacturing a very small polarization imaging element in terms of manufacturing technology, and the manufacturing cost is high.

  Accordingly, an object of the present invention is to solve the above-mentioned problem and to manufacture a liquid crystal lens and a liquid crystal optical element having a function of rotating the polarization direction by 90 degrees, without requiring a manufacturing process of combining individual elements. An object of the present invention is to provide a polarization imaging element capable of reducing the cost, and to provide a polarization imaging element having a very small overall structural dimension because the liquid crystal lens and the liquid crystal optical element are integrated.

In order to solve the above problems, the present invention basically includes a liquid crystal optical element having a function of rotating the polarization direction of polarized illumination light by 90 degrees and a liquid crystal lens capable of changing a focal length by a voltage. The liquid crystal optical element and the substrate constituting the liquid crystal lens have an integral structure.

In addition, the liquid crystal lens includes a first substrate having a transparent first electrode, a second electrode having a hole, and the first electrode between the first substrate and the second electrode. Unlike the alignment film portion, the first liquid crystal layer, which is accommodated so as to face each other and aligns liquid crystal molecules in one direction, is provided between the second electrode and the first liquid crystal layer. A transparent insulating layer for setting a distance between the second electrode and the first liquid crystal layer, and applying a voltage between the first and second electrodes to control alignment of liquid crystal molecules. In the liquid crystal lens that operates, a third electrode substrate is disposed outside the second electrode via an insulating layer, or the third electrode is formed on the second substrate on the second electrode. The third electrode is provided with a second voltage independent of the first voltage. And either one of the first voltage or the second voltage value is fixed, and the second voltage or the second voltage is set to the first voltage. On the other hand, the focal length can be variably controlled by changing one of the first voltages.

Further, the liquid crystal optical element having a function of rotating the polarization direction of the polarized illumination light by 90 degrees includes a second liquid crystal layer sealed between the second substrate and the third substrate of the liquid crystal lens. Alignment that is characterized or that has been subjected to an alignment treatment in which a region that does not constitute a liquid crystal lens on the first liquid crystal layer side of the second substrate is aligned in a direction that is 90 degrees different from the first electrode side Rotating and controlling the polarization direction of polarized illumination light by 90 degrees by arranging a transparent fourth electrode with a layer and changing the voltage applied between the first electrode and the fourth electrode It is characterized by.

According to an embodiment of the present invention, the first stage or the second voltage value is fixed, and the first stage optical characteristic with the lens power substantially maximized is obtained. As an optical characteristic of the first lens, the lens is operated as a convex lens by changing the second voltage with respect to the first voltage, or is operated as a concave lens by changing the first voltage with respect to the second voltage. And means for operating a liquid crystal optical element having a function of rotating and controlling the polarization direction of polarized illumination light by 90 degrees.

  By the above means, the rotation state of the polarization state can be controlled at a low voltage, and the focal length can be greatly varied by the electric control, and the voltage driving of the surface and the inside of the observation object can be imaged. A small polarization imaging element can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, the basic configuration will be described.

  FIG. 1A shows a basic configuration of a polarization imaging element according to an embodiment of the present invention. FIG. 1B is a plan view of the polarization imaging element of FIG. 1, and relates to the second electrode 22 having a circular hole 22 a and a gap 40 separated by a partition wall 50. In FIGS. 1A and 1B, a liquid crystal optical element having a function of rotating the polarization direction of illumination light whose right side is the liquid crystal lens 1 and whose left side is polarized with the broken line 100 as a boundary, that is, the left side is polarized, This is a TN liquid crystal cell 2. The transparent first electrode 21 is formed on the transparent first substrate 11. The transparent second substrate 12 has a transparent second electrode 22, and the circular hole 22 a described above is formed in the second electrode 22. Between the 1st board | substrate 11 and the said 2nd board | substrate 12, the 1st liquid crystal layer 31 accommodated so that it may oppose the 1st electrode 21 and orientates a liquid crystal molecule to one direction is provided. A transparent third substrate 13 having a transparent third electrode 23 a and a fourth electrode 23 b is disposed with respect to the second electrode 22 through a gap 40. The third electrode 23a and the fourth electrode 23b are formed on the transparent third substrate 13, and are separated by a slit (not shown) to electrically insulate each other.

Here, the first voltage V1 can be applied between the first electrode 21 and the second electrode 22 to control the alignment of the liquid crystal molecules, and the first voltage V1 is applied to the third electrode 23a. It is configured to be able to apply an independent second voltage V2. The liquid crystal lens 1 is configured to obtain the first stage optical characteristics based on the first voltage V1 and the second stage optical characteristics based on the second voltage V2. Details of the operation principle of the liquid crystal lens 1 are disclosed in Patent Document 10. According to the liquid crystal lens 1, functions as a convex lens and a concave lens can be obtained.

Further, by using the fourth electrode 23b provided on the third substrate, a TN liquid crystal cell serving as a liquid crystal optical element having a function of rotating and controlling the polarization direction of polarized illumination light, which will be described below, will be described below. 2 can be configured using the same substrate, so that a small polarization imaging element can be configured.

That is, in order to apply a voltage different from that of the liquid crystal lens 1, the third electrode 23a and the fourth electrode 23b are separated and insulated by a slit (not shown) so as not to be electrically connected to each other. The liquid crystal lens side of the gap 40 is an air layer, but the liquid crystal optical element that performs polarization control, that is, the portion that becomes the TN liquid crystal cell 2 shown on the left side of the broken line 100 is separated by the liquid crystal lens unit 1 and the partition unit 50. A second liquid crystal layer 32 is disposed. Processing is performed on the second electrode side and the third electrode side of the liquid crystal layer 32 so that the alignment direction of the liquid crystal molecules is twisted by 90 degrees. By applying a third voltage V3 larger than the threshold value between the second electrode 22 and the fourth electrode 23b, the 90 degree twist in the molecular orientation state of the second liquid crystal layer 32 is eliminated, and polarized illumination. Switching of the polarization direction of light by 90 degrees can be performed. Unlike the transparent electrode 23b formed on the third substrate 13 and separated by the slit, the second electrode 22 formed on the second substrate 12 is formed by the slit as an electrode for constituting the TN liquid crystal cell. It is also possible to use it with electrical isolation. In this case, it is necessary to set the position of the slit for separating and insulating so as not to affect the axisymmetric non-uniform electric field due to the hole 22a provided in the second electrode 22.

In FIG. 1A, reference numeral 11 denotes a first substrate (transparent glass), and a transparent first electrode 21 made of an indium-tin oxide (ITO) is formed on the inner surface side. An ITO electrode 22 is formed on the surface of the second substrate 12 opposite to the first liquid crystal layer 31. A circular hole 22a (for example, 2 mm in diameter) is formed in the region that becomes the liquid crystal lens portion of the second electrode 22 as shown in FIG.

Here, a first liquid crystal layer 31 (for example, a thickness of 20 μm) in which liquid crystal molecules are aligned in one direction is sealed between the first electrode 21 and the second substrate 12. E44 (manufactured by Merck) was used as the liquid crystal material. Although not shown, the spacer for obtaining the first liquid crystal layer 31 and the peripheral portion of the substrate are sealed with liquid crystal with an adhesive. Further, the surface of the electrode or substrate sandwiching the liquid crystal layer is coated with polyimide as an alignment film and rubbed in one direction.

Although the thickness of the second substrate 12 depends on the size of the circular hole 22a and the structure of the liquid crystal cell, it is 800 μm here. A third substrate 13 is disposed on the second substrate 12 with a gap 40 therebetween. The thickness of the gap 40 is the thickness of the third liquid crystal layer 32, and is 20 μm here. An ITO transparent electrode is formed on the lower surface of the third substrate, and a third electrode 23a and a fourth electrode 23b are formed by being separated by a slit for electrical insulation. A second liquid crystal layer 32 having a thickness of 20 μm is formed on the side of the TN liquid crystal cell to be the liquid crystal optical element 2 that controls the polarization of the gap 40 by a partition wall 50 and a spacer (not shown). The E44 was used as the liquid crystal material. A polyimide alignment film is coated on the surfaces of the electrode 22 and the electrode 23b, and the alignment directions of the liquid crystal molecules are twisted by 90 degrees between the two electrodes by rubbing treatment.

In a state where no voltage is applied between the second electrode 22 and the fourth electrode 23b, the alignment direction of the liquid crystal molecules is twisted by 90 degrees between the two electrodes. The direction is twisted 90 degrees and emitted. On the other hand, when a sine wave (1 kHz) voltage of 10 Vrms is applied as the third voltage V3, the liquid crystal molecules of the second liquid crystal layer 32 are aligned in the direction perpendicular to the electrode substrate, thereby eliminating the twist of 90 degrees. The polarization direction of the polarized illumination light is transmitted through the second liquid crystal layer without changing. That is, the polarization direction of the illumination light can be switched by 90 degrees by applying the third voltage.

In a liquid crystal lens manufactured using E44 (manufactured by Merck) as the liquid crystal material, the diameter of the circular hole 22a is 2 mm, the thickness of the first liquid crystal layer 31 is 20 μm, and the first voltage and the second voltage are In addition, a lens power variable effect of about 7 diopters (1 / m) was obtained between the convex lens and the concave lens.

The liquid crystal lens shown in FIG. 1 has an effective refractive index change with respect to incident light polarized in the alignment direction of the liquid crystal molecules in the first liquid crystal layer, that is, an extraordinary light component. It has a feature that it exhibits a lens effect such as condensing and divergence only in the polarized light component. Therefore, when the effective polarization direction in the liquid crystal lens 1, that is, the alignment direction of the liquid crystal molecules in the first liquid crystal layer is configured to be orthogonal to the polarization direction of the illumination light (different by 90 degrees), the third voltage V3 is not applied. In this case, the lens effect is exhibited with respect to light having the same polarization component as that of the illumination light. By appropriately setting the first voltage and the second voltage applied to the liquid crystal lens, the surface of the observation object is focused. In addition, an image of the surface can be obtained by focusing the light reflected from the surface on the image sensor.

As the third voltage V3, when a voltage higher than the threshold value in the TN liquid crystal cell composed of the second liquid crystal layer 32, for example, 10 Vrms, is applied, the polarization direction of the illumination light is changed even after passing through the second liquid crystal layer 32. Since there is no change, the polarization component of the reflected light from the surface of the observation object is 90 degrees different from the effective polarization component showing the lens effect in the liquid crystal lens, so that no lens effect occurs. On the other hand, light that has undergone effects such as scattering and reflection inside the observation object contains various polarization components, so there is an effective polarization component in the liquid crystal lens, and effects such as focus movement on the polarization component. Can be exerted. That is, an image can be obtained by focusing on the inside of the observation object.

FIG. 2 shows a structure of a polarization imaging element as another embodiment according to the present invention. In this embodiment, the third electrode 23 a is provided in the circular hole 22 a of the second electrode 22 on the right side of the broken line 100 constituting the liquid crystal lens. In this structure, unlike the structure of FIG. 1, it is not necessary to provide a gap 40 that separates the second electrode 22 and the third electrode 23 a (including the fourth electrode 23 b in FIG. 1). The structure can be simplified. On the other hand, since a gap for forming the second liquid crystal layer cannot be provided, the TN liquid crystal cell 2 serving as a liquid crystal optical element having a function of rotating the polarization direction of polarized illumination light by 90 degrees is used as the first liquid crystal. It is configured using the layer 31. That is, an ITO electrode 25 serving as 23b in FIG. 1 is formed as a fourth electrode on a portion constituting the TN liquid crystal cell on the surface in contact with the first liquid crystal layer of the second substrate 12, and the first electrode 21 is formed. A third voltage V 3 is applied between the first electrode 25 and the fourth electrode 25. Note that an alignment film made of polyimide is formed on the liquid crystal side surface of the second substrate 12, and the alignment direction of the liquid crystal molecules in the liquid crystal lens 1 corresponds to the portion constituting the TN liquid crystal cell 2 corresponding to the left side of the broken line 100. By rubbing in an orthogonal direction, the molecular alignment state of the liquid crystal phase 31 is TN alignment twisted 90 degrees.

In the liquid crystal cell having the structure shown in FIG. 1A, the second liquid crystal layer 32 is not formed between the second substrate 12 and the third substrate 13, and the first liquid crystal cell shown in FIG. A liquid crystal optical element that performs polarization rotation control, that is, a TN liquid crystal element, may be configured using the liquid crystal layer 31 between the substrate 11 and the second substrate 12. In this case, it is not necessary to form the second liquid crystal layer 32, but the ITO electrode 25 instead of the ITO electrode 23b is formed as the fourth electrode on the second substrate 12 corresponding to the left side of the broken line 100, It is necessary to perform the liquid crystal molecular alignment treatment so that the two sides of the broken line 100, that is, the regions of the liquid crystal lens 1 and the TN liquid crystal cell 2 are different by 90 degrees.

In the liquid crystal cell shown in FIGS. 1 and 2, the first liquid crystal layer 31 may have a structure in which the liquid crystal layer is divided into two or more layers and bonded together. When the liquid crystal layer is divided into two layers and the thickness thereof is halved, the response time to the applied voltage can be shortened to ¼. On the other hand, by using a liquid crystal layer having a structure in which two liquid crystal layers having the same thickness are stacked, the variable range of power as a lens can be doubled.

Since the liquid crystal lens having the configuration shown in FIG. 1 or 2 can change the optical characteristics from a convex lens to a concave lens, it is usually used as a compound lens with another imaging lens. By reducing the depth of focus of the compound lens system, an internal image of a living body or the like can be observed with high positional accuracy.

As the polarized irradiation light, in addition to normal white visible light, light that is monochromatic by a filter or the like, near infrared light, or infrared light in a wavelength band where the liquid crystal material has no absorption effect can be used. . Near-infrared rays and infrared rays have better transmission characteristics in living organisms than visible rays, so by using light of these wavelengths, an image of the affected area in the deep part and its structure can be obtained in living organisms. be able to.

Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine the component covering different embodiment suitably.

The polarization imaging element of the present invention does not have a mechanical movable part, and has a function of electrically moving a focal length and a function of switching polarization. Therefore, it can be applied not only to the surface but also to medical and industrial endoscopes that can obtain an image inside the observation object.

FIG. 1A is a configuration explanatory view showing an embodiment of a polarization imaging element according to the present invention, and FIG. 1B is a plan view of FIG. It is a structure explanatory drawing which shows other embodiment of the polarization imaging element concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal lens, 2 ... TN liquid crystal cell as an optical element which carries out 90 degree rotation control of the polarization direction of polarized illumination light, 11, 12, 13 ... Substrate, 21, 22, 23, 24 ... Electrodes 31, 32 ... liquid crystal layer, 40 ... gap, 50 ... partition, 100 ... broken line separating liquid crystal lens and TN liquid crystal cell.

Claims (5)

It consists of a liquid crystal optical element having a function of rotating and controlling the polarization direction of polarized illumination light by 90 degrees and a liquid crystal lens whose focal length can be changed by voltage, and the liquid crystal optical element and the substrate constituting the liquid crystal lens have an integrated structure. A polarization imaging element characterized by comprising: A liquid crystal lens faces the first electrode between the first substrate having a transparent first electrode, the second electrode having a hole, and the first substrate and the second electrode. A first liquid crystal layer that aligns liquid crystal molecules in one direction, and the second electrode and the first liquid crystal are interposed between the second electrode and the first liquid crystal layer. A second substrate serving as a transparent insulating layer that sets the distance between the layers is disposed, and a voltage is applied between the first and second electrodes to control the alignment of liquid crystal molecules. In the liquid crystal lens, a third electrode substrate is disposed outside the second electrode, or the third electrode is spaced apart in the hole of the second electrode on the second substrate. The second voltage independent from the first voltage can be applied to the electrode on the third electrode substrate surface. And either the first voltage or the second voltage value is fixed, and the second voltage with respect to the first voltage or the first with respect to the second voltage. The polarization imaging element according to claim 1, wherein the focal length can be variably controlled by changing any one of the voltages. The liquid crystal optical element having a function of rotating the polarization direction of polarized illumination light according to claim 1 by 90 degrees is enclosed between the second substrate and the third substrate of the polarization imaging element according to claim 2. The polarization imaging element according to claim 2, comprising the second liquid crystal layer. 3. The polarization imaging element according to claim 2, further comprising an alignment layer subjected to an alignment process in a direction different from the first electrode side by 90 degrees in a region where the liquid crystal lens is not formed on the first liquid crystal layer side of the second substrate. The transparent fourth electrode is arranged, and the voltage applied between the first electrode and the fourth electrode is varied to control the polarization direction of the polarized illumination light by 90 degrees. Polarization imaging element. 5. The polarization imaging element according to claim 2, claim 3, or claim 4, wherein the first voltage or the second voltage value is fixed, and the lens power is substantially maximized. In addition to obtaining the optical characteristics of the stage, the optical characteristics of the second stage can be operated as a convex lens by varying the second voltage with respect to the first voltage, or the first with respect to the second voltage. The liquid crystal optical element is operated by changing the voltage applied to the liquid crystal optical element having a function of rotating the polarization direction of the polarized illumination light by 90 degrees, and means for operating as a concave lens by changing the voltage of the liquid crystal And a polarization imaging element having means for switching polarization.

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