JP2010121935A - Polarized image picking-up device and image processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarized image picking-up apparatus which is small-sized and low-cost. <P>SOLUTION: The polarized image picking-up apparatus 10 includes a light source 16 for emitting light; a first polarizer 18, which is constituted statically in terms of the structure and on which the emission light from the light source 16 is incident; a first conversion part 24, which is constituted statically in terms of the structure and which changes the direction of polarization of the emission light from the first polarizer 18 and radiates it onto an object; a second conversion part 30, which is constituted statically in terms of the structure and changes the direction of polarization of the emission light from the object; a second polarizer 32, which is statically constituted, in terms of the structure and on which the emission light from the second conversion part 30 is made incident; an image picking-up part 34, which picks up an image formed by the emission light from the second polarizer 32; and a control part which controls the changes in the directions of polarization in the first converting part 24 and the second converting part 30, independently respectively and variably electrically. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polarization image capturing technique for capturing an image by polarized light and an image processing technique related to the technique.

  Conventionally, for example, an apparatus described in Patent Document 1 is known as an apparatus for observing the polarization state of light. The apparatus described in Patent Document 1 has a configuration in which a polarizer made of a birefringent material having the same size as a pixel is spread on the front surface of an image sensor such as a CCD. Then, by performing calculation processing of luminance information received by using four adjacent pixels having different polarization axes as one unit, the polarization state of light can be observed as image information.

  Moreover, there exist some which were described in patent document 2, and nonpatent literature 1, 2 as a liquid-crystal filter for removing reflected light and imaging using a TN cell, and an imaging device using the same.

Patent Document 3 discloses an apparatus for irradiating a liquid crystal cell, which is a measurement object, with polarized light whose polarization direction is controlled, and measuring the light intensity of polarized light in a specific polarization direction with respect to light emitted from the measurement object. ing.
International Publication No. 04/008196 Pamphlet Japanese Patent Laid-Open No. 10-108065 JP 2000-241292 A Hideo Fujikake, Kuniharu Takizawa, Michio Kobayashi, Toshihiro Negishi, “Development of a reflected light suppression camera using a liquid crystal polarizing filter”, Movie TV Technology, 1998/6 (550), p. 32-34 Hiroto Sato, Hideo Fujikake, Masahiro Kawakita, Hiroshi Kikuchi, Shiro Sato, “Development of an automatic reflected light suppression system using a liquid crystal polarizing filter”, IEICE Transactions C, 2003/3, Vol. J86-C, no. 3, p. 244-251

  However, in the case of the apparatus disclosed in Patent Document 3, it is necessary to provide a mechanism for mechanically rotating optical elements such as a polarizer and an analyzer in order to adjust the polarization direction of irradiated light and the polarization direction of receiving light. . For this reason, the apparatus configuration becomes relatively large, which may be a factor that increases costs.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a polarization image capturing technique that enables a compact and inexpensive configuration and an image processing technique using the technique.

  In order to solve the above-described problems, a polarization image capturing apparatus according to an aspect of the present invention includes a light source that emits light, a first polarizer that is statically configured in structure and receives light emitted from the light source, and a structure. A first conversion unit configured to statically convert the polarization direction of the outgoing light from the first polarizer and irradiate the target; and a polarization direction of the outgoing light from the target configured statically on the structure A second converter that converts the light, a second polarizer that is configured statically and that receives light emitted from the second converter, and an imaging unit that captures an image of the light emitted from the second polarizer And a control unit that electrically and variably controls the conversion of the polarization direction in the first conversion unit and the second conversion unit.

  According to this aspect, it is possible to irradiate the object with polarized light having an arbitrary polarization direction, and it is possible to extract polarized light with an arbitrary polarization direction from the light emitted from the object and to capture an image with the polarized light. Since the optical elements such as the first polarizer, the first conversion unit, the second polarizer, and the second conversion unit can be configured statically, a mechanism for rotating the optical element is not necessary. Therefore, it is easy to configure the apparatus in a small size and at a low cost.

  The first conversion unit and / or the second conversion unit may include a phase control element that changes the phase difference of the polarization components orthogonal to each other of incident light on the first conversion unit and / or the second conversion unit.

  The first conversion unit and / or the second conversion unit includes a first phase control element that receives light incident on the first conversion unit and / or a second phase control element that receives light emitted from the first phase control element. The main axis of the phase control element and the main axis of the second phase control element may be shifted by 45 degrees.

  The first conversion unit and / or the second conversion unit may include an optical rotation element that rotates the plane of polarization by rotating the incident light on itself by electrical control.

  The imaging unit may capture an image of light emitted from the second polarizer in synchronization with switching of polarization direction conversion in the first conversion unit and / or the second conversion unit. The control unit may synchronize the switching of the polarization direction conversion between the first conversion unit and the second conversion unit.

  Another aspect of the present invention is an image processing apparatus. This apparatus includes the above-described polarization image capturing apparatus, an original image holding unit that stores a plurality of images captured by the polarization image capturing apparatus as original images for subsequent processing, and a function determined according to the processing purpose. An image generation unit that generates a final image by acting on a plurality of original images.

  According to this aspect, it is possible to generate a final image that has been subjected to image processing in accordance with the processing purpose, from a plurality of images captured by the polarization image capturing apparatus described above.

  The image generation unit may generate a final image for the purpose of displaying on the display device. The imaging unit uses a sampling clock having a frequency n times higher than the display frequency of the display device (n is an integer of 2 or more) and captures and stores a plurality of original images for each display period in a time-sharing manner. The image generation unit may generate one final image from the stored n original images.

  The image generation unit may use a function represented by a linear linear sum of a plurality of original images as a function. The image generation unit may use a function in which the coefficient of any original image is zero among the linear linear sums. The image generation unit may use a function in which the coefficient of the original image in a predetermined polarization direction is zero. Further, the image generation unit may use a function in which the coefficient of the original image in which the luminance of at least some of the pixels is equal to or higher than a predetermined value is zero.

  The image generation unit may generate a final image for the purpose of issuing an alarm. In addition, a determination unit that determines whether or not a pixel having a luminance equal to or higher than a predetermined value exists in the final image, and an alarm is issued when the determination unit determines that a pixel having a luminance equal to or higher than the predetermined value exists. You may further provide an alarm issuing part.

  It should be noted that any combination of the above-described constituent elements and a representation of the present invention converted between a method, an apparatus, a system, etc. are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the polarization image imaging technique which enables a small and cheap structure and the image processing technique using the technique can be provided.

  The polarization image capturing apparatus according to the present embodiment irradiates a target with polarized light having an arbitrary polarization direction, and outputs polarized light having an arbitrary polarization direction out of light (transmitted light or reflected light) emitted from the target object. It is possible to extract and take an image of the polarized light. For example, this apparatus is used to irradiate the glass with polarized light having various polarization directions, and to extract a plurality of images by extracting the polarized light with various polarization directions from the light transmitted through the glass. By observing and analyzing the plurality of captured images, it is possible to detect residual strain (hereinafter simply referred to as “strain”) and defects of the glass. The defect of glass is a general term for unevenness and scratches existing on the surface, foreign matter, foreign matter existing inside, compositional unevenness and the like.

  FIG. 1 is a diagram illustrating a configuration of a polarization image capturing apparatus according to the present embodiment. The polarization image capturing apparatus 10 can receive the polarized light in any polarization direction out of the light transmitted through the glass 80 and the irradiation unit 12 that can irradiate the glass 80 as a measurement object with polarized light in any polarization direction. A light receiving unit 14 is provided.

  The irradiation unit 12 includes a light source 16, a first polarizer 18, and a first conversion unit 24. Here, at least the first polarizer 18 and the first converter 24 are structurally statically configured. That is, the first polarizer 18 and the first conversion unit 24 are fixedly provided structurally or at least relatively. Therefore, the irradiation unit 12 of the polarization image capturing apparatus 10 according to the present embodiment has the polarization direction of the emitted light by a mechanical operation in which one of the first polarizer 18 or the first conversion unit 24 rotates. It does not change.

  The light source 16 emits outgoing light 50 toward the first polarizer 18. As the light source 16, a natural light source such as a light bulb or a fluorescent lamp that outputs non-polarized light, a laser that outputs random polarized light, or the like can be used.

  The first polarizer 18 receives the outgoing light 50 from the light source 16, transmits only linearly polarized light in the direction of the polarization axis 18 a, and emits outgoing light 52 to the first conversion unit 24. In the present embodiment, the first polarizer 18 is provided such that the polarization axis 18a is in the horizontal direction. Accordingly, horizontal polarized light is extracted from the light 50 emitted from the light source 16 and is output to the first converter 24. Here, in this embodiment, the x-axis direction of the orthogonal coordinate system is the horizontal direction, and the y-axis direction is the vertical direction. If a light source 16 having a strong specific linearly polarized light component is used, a configuration in which the first polarizer 18 is omitted is possible. As a light source having a specific linearly polarized light component, an edge-emitting laser diode element can be exemplified.

  The 1st conversion part 24 converts the polarization direction of the emitted light 52 radiate | emitted from the 1st polarizer 18, and irradiates the irradiation light 56 to the glass 80 which is a measuring object. The first converter 24 includes a first phase control element 20 that receives the emitted light 52 from the first polarizer 18 and a second phase control element 22 that receives the emitted light 54 from the first phase control element 20.

The first phase control element 20 is provided with a first variable power supply 36 that changes an applied voltage V ₁ to the first phase control element 20 (hereinafter referred to as a first applied voltage V ₁ ). Is provided with a second variable power supply 38 for changing the applied voltage V ₂ to the second phase control element 22 (hereinafter, the second applied voltage V ₂ ). Hereinafter, the first phase control element 20, the second phase control element 22, the third phase control element 26 and the fourth phase control element 28, which will be described later, are simply referred to as “phase control elements”.

  The phase control element is an optical element that electrically changes the phase difference of polarized light components of incident light that are orthogonal to each other by using the birefringence of a substance having optical anisotropy. The structure of the phase control element is such that a spacer with a thickness of several microns is inserted between two parallel-treated ITO glasses and nematic liquid crystal is sealed between the ITO glasses. The alignment state when no voltage is applied to the phase control element is a homogeneous alignment in which molecules are aligned parallel to the glass. The phase control element configured as described above is also called a π cell. It is known that the π cell has a response speed of about several milliseconds.

  The phase control element has a fast axis that is an azimuth with a fast phase velocity and a slow axis that is an azimuth with a slow phase velocity among two polarized components of incident light that are orthogonal to each other. The fast axis and the slow axis are collectively referred to as “main axis”. By adjusting the voltage applied to the phase control element, the phase of the polarization component in the slow axis direction is delayed, and the phase difference between the polarization component of the fast axis and the polarization component of the slow axis is changed from 0 degrees to 180 degrees. Can be made.

  The first phase control element 20 is provided with its slow axis 20a inclined at a predetermined angle, here 45 degrees, from the polarization axis 18a of the first polarizer 18. Further, the second phase control element 22 is provided such that its slow axis 22a is inclined 45 degrees from the slow axis 20a of the first phase control element 20 and is in the same direction as the polarization axis 18a of the first polarizer 18. It is done. In other words, the main axis of the first phase control element 20 and the main axis of the second phase control element 22 are arranged so as to be shifted by 45 degrees.

By arranging the first phase control element 20 and the second phase control element 22 in this way, the first applied voltage V ₁ and the second applied voltage V ₂ are adjusted, and the outgoing light 52 from the first polarizer 18 is adjusted. Can be converted to a desired polarization direction. The conversion of the polarization direction will be described in detail with reference to FIG.

  The irradiation light 56 emitted from the second phase control element 22 is applied to the glass 80. The transmitted light 58 transmitted through the glass 80 is incident on the light receiving unit 14.

  The light receiving unit 14 includes a second conversion unit 30, a second polarizer 32, and an imaging unit 34. Here, at least the second conversion unit 30 and the second polarizer 32 are structurally statically configured. That is, the second conversion unit 30 and the second polarizer 32 are fixedly provided structurally or at least relatively. Therefore, the light receiving unit 14 of the polarization image capturing apparatus 10 according to the present embodiment displays a plurality of images to be described later by a mechanical operation in which one of the second conversion unit 30 or the second polarizer 32 rotates. It is not something to be imaged.

  The second conversion unit 30 converts the polarization direction of the transmitted light 58 from the glass 80. The second conversion unit 30 includes a third phase control element 26 that receives the transmitted light 58 and a fourth phase control element 28 that receives the outgoing light 60 from the third phase control element 26. The third phase control element 26 and the fourth phase control element 28 are incident using the birefringence of a material having optical anisotropy, similar to the first phase control element 20 and the second phase control element 22 described above. It is an optical element that electrically changes the phase difference of polarized light components orthogonal to each other.

The third phase control element 26 is provided with a third variable power source 40 that changes an applied voltage V ₃ to the third phase control element 26 (hereinafter, third applied voltage V ₃ ). Is provided with a fourth variable power source 42 that changes an applied voltage V ₄ (hereinafter, a fourth applied voltage V ₄ ) to the fourth phase control element 28.

  In the present embodiment, the slow axis 26a of the third phase control element 26 is provided to be horizontal. Further, the fourth phase control element 28 is provided such that its slow axis 28a is inclined at a predetermined angle, here 45 degrees, from the slow axis 26a of the third phase control element 26. In other words, the main axis of the third phase control element 26 and the main axis of the fourth phase control element 28 are arranged so as to be shifted by 45 degrees.

By arranging the third phase control element 26 and the fourth phase control element 28 in this way, the third applied voltage V ₃ and the fourth applied voltage V ₄ are adjusted, and the polarization direction of the transmitted light 58 from the glass 80 is adjusted. Can be converted into a desired polarization direction. In the present embodiment, the third applied voltage V ₃ and the fourth applied voltage V ₄ are controlled so that polarized light in a desired polarization direction to be extracted from the transmitted light 58 from the glass 80 is converted into horizontal polarized light. The conversion of the polarization direction will be described in detail with reference to FIG.

  The second polarizer 32 receives the outgoing light 62 from the fourth phase control element 28, transmits only linearly polarized light in the direction of the polarization axis 32 a, and outputs the linearly polarized light to the imaging unit 34. In the present embodiment, the second polarizer 32 is provided such that its polarization axis 32a is in the horizontal direction. Accordingly, only the polarized light in the desired polarization direction among the transmitted light 58 from the glass 80 can pass through the second polarizer 32.

  The imaging unit 34 has a plurality of light receiving elements 70 arranged in a matrix. As the imaging unit 34, a CCD image sensor, a CMOS image sensor, or the like can be used. The plurality of light receiving elements 70 receive the emitted light 64 from the second polarizer 32, so that it is possible to take an image of polarized light in a desired polarization direction among the transmitted light 58 from the glass 80.

  FIG. 2 is a diagram illustrating a Poincare sphere for explaining the conversion of the polarization direction by the first conversion unit 24 and the second conversion unit 30. In general, a polarization component in an arbitrary polarization direction can be represented as a point on the spherical surface of the Poincare sphere. When the Poincare sphere is viewed as the earth, a point on the northern hemisphere represents clockwise elliptically polarized light, and a point on the southern hemisphere represents counterclockwise elliptically polarized light. The equator represents linearly polarized light, the north pole L represents clockwise circularly polarized light, and the south pole R represents counterclockwise circularly polarized light. In the figure, the point H on the equator represents horizontal polarization, and the point V represents vertical polarization.

  Here, as an example showing that an arbitrary polarization state can be converted into another arbitrary polarization state by the first conversion unit 24 or the second conversion unit 30, a first clockwise elliptical polarization is converted by the first conversion unit 24. It can be converted to horizontal polarization. In order to show this, it is only necessary to show that a point 150 representing a clockwise clockwise polarized light can move to a point H representing a horizontally polarized light on the Poincare sphere. First, by applying a predetermined voltage to the first phase control element 20, the point 150 can be rotated around the S1 axis and moved to a point 152 on a circle perpendicular to the S2 axis. Next, by applying a predetermined voltage to the second phase control element 22, the point 152 can be rotated around the S2 axis and moved to a point H representing horizontal polarization. The same applies to other polarization directions, such as circularly polarized light and linearly polarized light.

  Thus, according to the 1st conversion part 24 of this Embodiment, the polarization direction (horizontal polarization | polarized-light) of the emitted light 52 from the 1st polarizer 18 can be converted into a desired polarization direction. Therefore, according to the irradiation unit 12 of the polarization image capturing apparatus 10 according to the present embodiment, it is possible to irradiate the irradiation light 56 in an arbitrary polarization direction onto the glass 80 that is the measurement object.

  Similarly, according to the second conversion unit 30 of the present embodiment, of the transmitted light 58 from the glass 80, the polarization component in an arbitrary polarization direction is converted into linear polarization in the desired polarization direction, here horizontal polarization. Can be converted. Since the converted horizontal polarized light can pass through the second polarizer 32 and is received by the imaging unit 34, according to the light receiving unit 14 according to the present embodiment, any polarized light among the transmitted light 58 from the glass 80. An image with a polarization component in the direction can be captured.

The applied voltage-phase difference characteristics of the first phase control element 20 and the second phase control element 22 of the first conversion unit 24 and the third phase control element 26 and the fourth phase control element 28 of the second conversion unit 30 are known. Therefore, a combination of the first applied voltage V ₁ and the second applied voltage V _2, a combination of the third applied voltage V ₃ and the fourth applied voltage V ₄ necessary for converting the incident light into a desired polarization direction. Can be determined by experimentation or simulation. When capturing images of various polarization directions, the image capturing unit 34 may capture images in synchronization with switching of polarization direction conversion in the first conversion unit 24 and / or the second conversion unit 30.

As described above, according to the polarization image capturing apparatus 10 according to the present embodiment, the first phase control element 20 and the second phase control element 22 of the first conversion unit 24, the third phase control element 26 of the second conversion unit 30, and By independently controlling the voltage applied to the fourth phase control element 28, it is possible to irradiate the glass 80 with the irradiation light 56 having an arbitrary polarization direction, and the polarized light having an arbitrary polarization direction among the transmitted light 58 from the glass 80. Ingredients can be extracted. A plurality of different images corresponding to the degree of conversion of the polarization direction can be captured in a time division manner by capturing an image with the image capturing unit 34 in synchronization with the timing of changing the voltage applied to each phase control element. Since it is known that the π cells used in the first conversion unit 24 and the second conversion unit 30 can operate at a response speed of about several milliseconds, a plurality of polarization directions having different polarization directions within one frame period _{Tf of} moving image display. These images can be taken in a time-sharing manner, and a plurality of images can be processed to generate a single image that can be displayed as a moving image.

  Further, the polarization image capturing apparatus 10 can structurally and statically configure the first polarizer 18 and the first conversion unit 24 of the irradiation unit 12 and the second conversion unit 30 and the second polarizer 32 of the light receiving unit 14. Therefore, a mechanism such as rotating the polarizer becomes unnecessary. Therefore, the apparatus can be made small and inexpensive, and the service life of the apparatus is improved.

  Further, in the polarization image capturing apparatus 10, it is not necessary to arrange a minute polarizer according to each of the light receiving elements 70 of the image capturing unit 34, and the second conversion unit 30 and the second polarizer 32 are aligned with respect to the image capturing unit 34. Not so high accuracy is required. Therefore, the device can be easily manufactured and the manufacturing cost can be reduced. Further, since each of the light receiving elements 70 in the imaging unit 34 can be used as a pixel, an image having a resolution that takes advantage of the number of pixels inherent to the imaging unit 34 can be obtained.

FIG. 3 is a diagram illustrating an image display apparatus using the polarization image capturing apparatus according to the present embodiment. The image display device 100 includes a display device 200 such as an LCD, a display device control unit 202 that controls the display device 200, the polarization image capturing device 10 illustrated in FIG. 1, and a final image _If displayed on the display device 200. An image processing apparatus 110 is provided.

Although this image display device 100 can be used in various ways, in this embodiment, a case where the image display device 100 is used as a strain measurement device that measures strain of a transparent material such as glass will be described. A glass 80 as a measurement object is disposed between the irradiation unit 12 and the light receiving unit 14 of the polarization image capturing apparatus 10, and the switching of the polarization direction conversion in the first conversion unit 24 and the second conversion unit 30 is performed in synchronization. However, the imaging unit 34 captures a plurality of images. The image captured by the polarization image capturing device 10 is subjected to image processing by the image processing device 110 to generate a final image _If . As the image processing performed here, for example, there is processing for displaying distortion in the glass 80 without omission. The final image _If is displayed on the display device 200.

  The irradiation unit 12 of the polarization imaging apparatus 10 irradiates the glass 80 with the irradiation light 56 having ten different polarization directions in a predetermined cycle in order. The ten types of polarization directions are (1) horizontal polarization (0 degree polarization), (2) 22.5 degree polarization, (3) 45 degree polarization, (4) 67.5 degree polarization, and (5) vertical polarization ( 90 degree polarized light), (6) 112.5 degree polarized light, (7) 135 degree polarized light, (8) 157.5 degree polarized light, (9) clockwise circularly polarized light, and (10) counterclockwise circularly polarized light. Here, for example, 45-degree polarized light is linearly polarized light that is rotated 45 degrees counterclockwise from the horizontal direction on a plane perpendicular to the traveling direction of light.

  In addition, the light receiving unit 14 of the polarization image capturing apparatus 10 extracts polarized light in a polarization direction having a relationship of orthogonal Nicols with the polarization direction of the irradiation light 56 from the transmitted light 58 transmitted through the glass 80, and captures an image based on the polarization. To do. Switching of the polarization direction to be extracted in the light receiving unit 14 and imaging of polarized light in the polarization direction are performed in synchronization with switching of the polarization direction of the irradiation light 56 in the irradiation unit 12. That is, for example, when the irradiation unit 12 is irradiating the glass 80 with the horizontally polarized irradiation light 56, the light receiving unit 14 extracts the vertically polarized light having the relationship of the horizontal polarized light and the orthogonal Nicols from the transmitted light 58, and depends on the polarization. Take an image. For example, when the irradiation unit 12 switches the polarization direction and irradiates the glass 80 with the 22.5 degree polarized light, the light receiving unit 14 has a relationship of 22.5 degree polarized light and orthogonal Nicols from the transmitted light 58. 5 degree polarized light is extracted, and an image by the polarized light is captured. In this way, ten images of ten different polarization directions are picked up in time division by the light receiving unit 14. Since these ten images are images that are the basis of subsequent processing, the respective images are also referred to as “original images”.

  As described above, when the polarization direction of the irradiation light 56 irradiated by the irradiation unit 12 and the polarization direction extracted by the light receiving unit 14 are in a relationship of orthogonal Nicols, if the glass 80 is not distorted, the image is captured. The image captured by the unit 34 becomes dark. On the other hand, when a part of the glass 80 is distorted, a bright and dark pattern appears in the image captured by the imaging unit 34 due to the photoelastic effect of the glass. Therefore, it is possible to measure whether or not there is distortion in the glass 80 by observing an image captured by the imaging unit 34.

  However, when the main stress direction of the distortion of the glass 80 is inclined by 45 degrees with respect to the polarization direction of the irradiating unit 12, a bright and dark pattern does not appear in the captured image, and the distortion cannot be observed. Therefore, in the present embodiment, the polarization direction of the irradiation light 56 and the polarization direction captured by the light receiving unit 14 are variably configured, and by capturing ten images with different polarization directions, a specific direction in which distortion cannot be observed. Is prevented from occurring.

In the image display device 100 according to the present embodiment, processing is performed on the ten original images captured by the imaging unit 34, and one final image _{If that} is finally displayed on the display device 200 is obtained. Generated. In order to display an image as a moving image on the display device 200, processing from capturing of ten original images to generation of the final image _If is performed during one frame period _Tf of moving image display.

The image processing apparatus 110 includes the polarization image capturing apparatus 10 illustrated in FIG. 1, a memory 130 that stores an image, a memory controller 132 that controls read / write of the image to the memory 130, and a first image of the polarization image capturing apparatus 10. An applied voltage control unit 134 that independently controls voltages applied to the phase control element 20, the second phase control element 22, the third phase control element 26, and the fourth phase control element 28, and an image that generates the final image _If. A generation unit 136 and a function holding unit 138 that holds a function that defines processing performed by the image generation unit 136 are provided.

The applied voltage control unit 134 includes a first variable power source 36, a second variable power source 38, a third variable power source 40, a fourth variable power source 42, a voltage instruction unit 140, and a table holding unit 142. The conversion of the polarization direction in the conversion unit 24 and the second conversion unit 30 is independently and electrically variably controlled. Table holding unit 142, a combination of the first 10 Street applied voltages V ₁ and the second applied voltage V ₂ required to image the 10 kinds of the original image described above, the third applied voltage V ₃ 4 applied the combination of 10 kinds of voltage V _4, is stored as a table.

The voltage instruction unit 140 synchronizes with the sampling clock SCLK and captures the first applied voltage V ₁ , the second applied voltage V ₂ , the third applied voltage V ₃ , and the fourth each time each original image is captured from the table holding unit 142. reading the applied voltage V _4, the first variable power source 36 to generate their voltage, the second variable power source 38, the third variable power source 40, it instructs the fourth variable power supply 42. The first variable power supply 36, the second variable power supply 38, the third variable power supply 40, and the fourth variable power supply 42 are respectively designated as the first applied voltage V ₁ , the second applied voltage V ₂ , the third applied voltage V ₃ , A fourth applied voltage V ₄ is generated and applied to the first phase control element 20, the second phase control element 22, the third phase control element 26, and the fourth phase control element 28. Techniques for generating a desired voltage from a digital voltage indication are known as various regulator circuits or elements.

The sampling clock SCLK is set to a frequency n times (n is an integer of 2 or more) higher than the display frequency DCLK of the display device 200. Since the polarization image capturing apparatus 10 according to the present embodiment captures 10 original images during one frame period _Tf , the sampling clock SCLK is set to a frequency that is 10 times higher than the display frequency DCLK.

  The imaging unit 34 of the polarization image capturing apparatus 10 images light emitted from the second polarizer 32 in synchronization with the sampling clock SCLK. Since the polarization direction of the light emitted from the second polarizer 32 changes in synchronization with the sampling clock SCLK, 10 types of images having different polarization directions are obtained by capturing 10 images in synchronization with the sampling clock SCLK. An original image is taken in a time division manner.

The memory 130 includes an original image holding unit 144 that stores a plurality of original images captured by the polarization image capturing device 10 and a final image holding unit 146 that stores a final image _If generated by an image generation unit 136 described later. Have. The final image holding unit 146 functions as a frame memory related to the display device 200.

The original image captured by the polarization image capturing apparatus 10 is sequentially stored in the original image holding unit 144 in synchronization with the sampling clock SCLK by the memory controller 132. That is, the image when the glass 80 is irradiated with the horizontally polarized light is the original image I ₀ , the image when the 22.5 degree polarized light is irradiated is the original image I ₁ , and the image when the 45 degree polarized light is irradiated is the original image. As I ₂ , an image when irradiated with 67.5 degrees of polarized light is an original image I ₃ , an image when irradiated with vertically polarized light is an original image I ₄ , and an image when irradiated with 112.5 degrees of polarized light is an original image an image I _5, as the image is the original image I ₆ when irradiated with 135 degree polarization, as the image is the original image I ₇ when irradiated with 157.5 degree polarization, image when irradiated with right-handed circularly polarized light As the original image I ₈ , an image when the counterclockwise circularly polarized light is irradiated is sequentially stored in the original image holding unit 144 as the original image I ₉ is captured.

The image generation unit 136 applies a function determined according to the processing purpose to the ten original images I _{0 to} I ₉ stored in the original image holding unit 144 to generate one final image _If . This function is held in the function holding unit 138 and is expressed by a linear linear sum of a plurality of original images. That is, in this embodiment, the function F is
F = a ₀ I ₀ + a ₁ I ₁ + a ₂ I ₂ +... + A ₉ I ₉ (Formula 1)
It is represented by a _{0 to} a ₉ are coefficients for adding the original images I _{0 to} I ₉ . The coefficients a _{0 to} a ₉ are set so that the final image _If has sufficient luminance when the original images I _{0 to} I ₉ are combined. For example, if the exposure time for each original image is sufficient, the coefficients a _{0 to} a ₉ are set to 1/10. If the exposure time is insufficient, a value larger than 1/10 is set and adjustment is performed so as to obtain a necessary luminance. The relationship between the exposure time and the coefficient is determined in advance from experiments, simulations, specifications of the imaging unit 34, or the like. In addition, the function holding unit 138 stores various other functions according to the processing purpose.

Now, it is assumed that the processing purpose is “displaying an image representing all strains in the stress direction in the glass 80”. In this case, since it is only necessary to synthesize 10 captured original images, in Equation 1, a function in which the coefficients a _{0 to} a ₉ are uniformly 1/10, that is,
_{F = I 0/10 + I} 1/10 + I 2/10 + ··· + I 9/10 ( Equation 2)
Is stored in the function holding unit 138 in advance. The image generation unit 136 uses this function to synthesize the original images I _{0 to} I ₉ . As a result, a final image _If representing the strain in all the stress directions in the glass 80 is generated.

The final image I _f generated by the image generating unit 136 is stored in the final image holding unit 146 to be used as a frame memory. This final image _If is read by the display device control unit 202 in synchronization with the display frequency DCLK of the display device 200 and output to the display device 200.

FIG. 4 is a timing chart conceptually showing the time division processing of the image display apparatus 100. Here, one frame period T _f of the display device 200 is represented. The one frame period _Tf of the display device 200 is about 33 milliseconds when the frame rate is 30 fps.

In one frame period _Tf , first, the original images I _{0 to} I ₉ are sequentially captured by the polarization image capturing device 10. The captured images are sequentially stored in the original image holding unit 144. If the response time of the π cell is 2 milliseconds, the sampling period Ts for capturing 10 original images I _{0 to} I ₉ is 20 milliseconds.

Thereafter, the image generation unit 136 determines which function is selected according to the processing purpose in the determination period T _j . As described above, when displaying an image representing all strains in the stress direction in the glass 80, the image generation unit 136 reads and uses the function of Expression 2.

Image generating unit 136 Subsequently, in the image combining period _{T a,} and calculates the first-order linear sum of the original image _I 0 ~I ₉ synthesizes the original image _I 0 ~I _9, to produce the final image _{I f.} At this point, a final image _If representing the strain in all stress directions in the glass 80 is generated.

Finally, in the writing period _Tw , the memory controller 132 writes the final image _If generated by the image generation unit 136 to the final image holding unit 146. The final image _{I f} written to the final image holding unit 146, a display device control unit 202, during the next frame period _{T f,} is displayed on the display device 200. Thereafter, the moving image can be displayed on the display device 200 by performing the time-sharing process in each frame period _Tf . By configuring the display device 200 to display a moving image in this manner, for example, when the glass 80 is large and the entire image cannot be captured at once, distortion can be observed while the glass 80 is moved.

  The image processing apparatus 110 can achieve various other processing purposes. For example, when an image having extremely high luminance is included in the original image, the lightness and darkness of the imaged distortion may be buried in another image. In such a case, if the processing purpose is “to make it easy to observe the distortion of the glass”, the image generation unit 136 uses the coefficient of the original image with the maximum average image brightness as zero in Equation 1. Here, the average luminance of the image is obtained by averaging the luminance of all pixels in the image. By removing such an original image, obstructive light is removed and the distortion of the glass is easily observed.

  It should be noted that in this case, the coefficient of Equation 1 is not fixedly fixed in advance. Therefore, the image generation unit 136 performs necessary processing as appropriate, and adaptively determines the coefficient. For this reason, the function holding unit 138 records a process such as an operation for determining a coefficient as a program in association with the processing purpose. This program is also a broad function. Thereafter, the same processing is performed when the coefficient is adaptively determined.

  In this case, the image generation unit 136 may use the coefficient of the original image in which the average luminance of the image is equal to or greater than a predetermined value in Equation 1 as zero. By doing so, it becomes easy to observe the distortion of the glass even if, for example, two original images with extremely high luminance are included. As another method, in Equation 1, an original image coefficient including zero or more pixels having a luminance of a predetermined value or more may be set to zero.

  Also, if it is known in advance that the brightness of an image in a specific polarization direction becomes extremely high due to the characteristics of the glass, for example, due to the characteristics of the glass, the count of the original image in that polarization direction is zero in Equation 1. Function is used. This removes disturbing light and makes it easier to observe the distortion of the glass.

In the above-described image display apparatus 100 is used to display the final image I _f formed by the image processing apparatus 110 to the display device 200, the final image I _f, the final for the purpose of issuing an alarm to the user The image _If may be used.

In this case, the image processing apparatus 110 determines whether or not there is a pixel having a luminance equal to or higher than the predetermined value in the final image _If , and the determination unit determines that there is a pixel whose luminance is equal to or higher than the predetermined value. An alarm issuing unit for issuing an alarm when the alarm is issued. When there is distortion in the glass, a bright and dark pattern appears in the image as described above. Therefore, by configuring in this way, it is possible to configure a distortion determination device that determines whether there is distortion in the glass. The alarm issuing unit may be configured to issue an alarm by sound or light.

  In addition, with respect to the arbitrarily selected polarization direction of the irradiating unit 12, the polarization direction captured by the light receiving unit 14 is changed to capture a plurality of original images, and the change in luminance of the original image is measured. Can be measured quantitatively.

  FIG. 5 is a diagram showing another embodiment of the polarization image capturing apparatus. The polarization image capturing apparatus 500 illustrated in FIG. 5 is, like the polarization image capturing apparatus 10 illustrated in FIG. 1, a first irradiation unit 502 that can irradiate the glass 580 serving as a measurement target with polarized light having an arbitrary polarization direction. And a light receiving unit 506 capable of receiving polarized light in an arbitrary polarization direction out of the light emitted from the glass 580. Furthermore, the polarization image capturing apparatus 500 includes a second irradiation unit 504 that can irradiate the glass 580 with polarized light in an arbitrary polarization direction.

  The first irradiation unit 502 includes a first light source 508, a first polarizer 510, a first phase control element 512, and a second phase control element 514. The second irradiation unit 504 includes a second light source 516, a second polarizer 518, a third phase control element 520, and a fourth phase control element 522. The light receiving unit 506 includes a fifth phase control element 524, a sixth phase control element 526, a third polarizer 528, and an imaging unit 530. The configuration of the first irradiation unit 502 and the second irradiation unit 504 is the same as the configuration of the irradiation unit 12 in FIG. 1, and the configuration of the light receiving unit 506 is the same as the configuration of the light receiving unit 14 in FIG.

  In the polarization image capturing apparatus 500, the first irradiation unit 502 is applied to the light receiving unit 506 provided on the one surface 580 a side of the glass 580 and the irradiated light is transmitted through the glass 580 and is provided on the other surface 580 b side of the glass 580. It is provided to receive light. The second irradiation unit 504 is provided on the same surface 580 b side of the glass 580 as the light receiving unit 506 so that the irradiated light is reflected by the glass 580 and received by the light receiving unit 506.

In the polarization imaging apparatus 500 configured as described above, the first irradiation unit 502 and the second irradiation unit 504 each emit polarized light in a predetermined polarization direction. The polarization direction is switched at a predetermined cycle. The imaging unit 530 extracts polarized light in a predetermined polarization direction in synchronization with switching of the polarization directions of the first irradiation unit 502 and the second irradiation unit 504, and the imaging unit 530 captures an image. A plurality of original images captured in this way are subjected to image processing according to the processing purpose as described above to generate a final image _If and display it on the display device, thereby observing the distortion of the glass 580. can do.

  In the polarization image capturing apparatus 500, two irradiation units that irradiate polarized light are provided, and an image of the transmitted light and reflected light from the glass 580 can be captured. Thereby, for example, as shown in FIG. 1, distortion that cannot be observed only by imaging transmitted light can be observed, and the accuracy of distortion observation can be improved. As described above, by using the polarization imaging apparatus shown in FIG. 1 or 5 and analyzing using the polarization information in addition to the light intensity information of the image, it is possible to perform a more precise analysis.

  FIG. 6 is a diagram for explaining an example in which the image display device according to the present embodiment is used in a vehicle night vision system. The night vision system is a driving assistance device for expanding a driver's view at night and improving driving visibility.

  An image display device 600 used as a night vision system includes, for example, a display device 602 installed on a dashboard of a vehicle 610, an irradiation unit 604 provided as a headlight of the vehicle 610, and a front bumper or a hood in front of the vehicle 610, for example. The light-receiving part 606 provided in is provided. The irradiation unit 604 has the same configuration as the irradiation unit 12 shown in FIG. 1, and the light receiving unit 606 has the same configuration as the light receiving unit 14 shown in FIG. The image display device 600 includes the image processing device and the display device control unit described in FIG.

In the image display device 600, the irradiation unit 604 emits polarized light in a predetermined polarization direction to the front of the vehicle 610. Of the light emitted from the irradiation unit 604 and reflected by the road sign 620, for example, polarized light in a predetermined polarization direction is received by the light receiving unit 606, and an image is captured. The image picked up by the light receiving unit 606 is subjected to image processing by an image processing device, and a final image _If is generated. The generated final image _If is displayed on the display device 602.

  An example of detailed operation of the image display apparatus 600 will be described. The example described here is an effective operation when it is difficult to see the road sign 620 in front of the vehicle due to the headlight of the oncoming vehicle.

  In the image display device 600, the irradiating unit 604 is polarized in 10 types of polarization directions, that is, (1) horizontal polarized light (0 degree polarized light), and (2) 22.5 degrees, like the irradiating unit 12 in FIG. Polarized light, (3) 45 degree polarized light, (4) 67.5 degree polarized light, (5) vertical polarized light (90 degree polarized light), (6) 112.5 degree polarized light, (7) 135 degree polarized light, (8) 157. It is configured to irradiate the front of the vehicle with 5 degree polarized light, (9) clockwise circularly polarized light and (10) counterclockwise circularly polarized light.

At time t _1, a voltage is applied to the irradiation unit 604 so that the horizontally polarized light is irradiated toward the front of the vehicle. From the road sign 620 located in front of the vehicle 610, polarized light having a polarization direction orthogonal to horizontal polarized light, that is, vertically polarized light is reflected. Also, at the same time t _1, a voltage is applied to the light receiving portion 606 so that it can receive the vertically polarized light, capturing an image by the vertical polarization. Captured image is displayed on the display device 602 until the next time t _2.

Then, at time _{t 2,} 22.5 degree polarization applies a voltage to the irradiation unit 604 so as to be irradiated. Further, the time _{t 2, the} 112.5-degree polarized light reflected from road signs 620 by applying a voltage to the light receiving portion 606 to allow light, capturing an image by 112.5 degrees polarization. Captured image is displayed on the display device 602 until the next time t _3. Similarly, the polarization direction of irradiation and the polarization direction of imaging are changed with a predetermined period, and images in the respective polarization directions are captured and displayed on the display device 602.

  By operating the image display device 600 in this manner, an image from which most of the light from the headlight of the oncoming vehicle is removed can be displayed on the display device 602, so that the S / N ratio of the image is increased, The visibility of the road sign 620 can be improved.

  In the operation example of the image display device 600 described above, the polarization directions of the irradiation unit 604 and the light receiving unit 606 are changed in synchronization, but the polarization in the polarization direction by the phase control element and the imaging by the imaging unit can be performed at a sufficiently high speed. If possible, the light receiving unit 606 captures, for example, ten images with the above-described ten types of polarization directions while the irradiation unit 604 is irradiating polarized light of one polarization direction, and the average luminance of the image is the highest. An image having a high value may be extracted and displayed on the display device 602. In this case, a function in which the coefficient of the image with the highest average luminance of the image is set to 1 and the coefficient of the other image is set to zero may be applied.

Another example of detailed operation of the image display device 600 will be described. In this example, the irradiation unit 604 is configured to emit alternately right-handed circularly polarized light and left-handed circularly polarized light with a predetermined period T _1. The light receiving unit 606 alternately receives clockwise circularly polarized light and counterclockwise circularly polarized light at the timing T ₂ (n times the cycle T ₁ , where n is an integer equal to or greater than 2) at the timing of the irradiation unit 604, and performs imaging To do.

  When clockwise circularly polarized light is emitted from the irradiating unit 604 and reflected by the road sign 620 that has not been subjected to retroreflection processing and received by the light receiving unit 606, the direction of the circularly polarized light is reversed. Thus, it becomes counterclockwise circularly polarized light. When counterclockwise circularly polarized light is emitted and reflected only once by the road sign 620, the light received by the light receiving unit 606 becomes clockwise circularly polarized light. When the road sign 620 is subjected to retroreflection, the direction of the received circularly polarized light does not change, right-handed circularly polarized light is right-handed circularly polarized light, and left-handed circularly polarized light is left-handed circularly polarized light. Received light.

Thus, for example, during the period T _2, which received the right-handed circularly polarized light, road sign 620 is displayed on the display device 602 when irradiated with left-handed circularly polarized light, appear when irradiated with right-handed circularly polarized light If not, it can be determined that the road sign 620 has not been subjected to retroreflection processing. Between the period T _2, which received the right-handed circularly polarized light, if the road sign 620 when irradiated with left-handed circularly polarized light is not displayed, is displayed when irradiated with right-handed circularly polarized light, It can be determined that the road sign 620 has undergone retroreflection processing.

  In this way, it is possible to determine whether or not the road sign 620 has been subjected to retroreflection processing by alternately irradiating clockwise circularly polarized light and counterclockwise circularly polarized light and analyzing the captured image. . In many cases, the retroreflective processing is performed mainly in places where special attention should be given to driving, such as road signs and shoulder displays.Therefore, the retroreflective process is performed as in this operation example. By displaying the portion in red, it is possible to effectively recognize the portion to be noted by the driver.

  FIG. 7 is a diagram showing still another embodiment of the polarization image capturing apparatus. As illustrated in FIG. 7, the polarization image capturing apparatus 700 includes an irradiation unit 712 that can irradiate glass 780 serving as a measurement target with horizontal or vertical polarization, and horizontal polarization or vertical light out of the light transmitted through the glass 780. A light receiving unit 714 capable of receiving polarized light is provided.

  The irradiation unit 712 includes a light source 716, a first polarizer 718, and a first TN cell 724 (Twisted Nematic cell). In the irradiation unit 712, at least the first polarizer 718 and the first TN cell 724 are structurally statically configured. That is, the first polarizer 718 and the first TN cell 724 are each or at least relatively fixed in structure.

  The light source 716 emits outgoing light 750 toward the first polarizer 718. As the light source 716, a natural light source such as a light bulb or a fluorescent lamp that outputs non-polarized light, a laser that outputs random polarized light, or the like can be used.

  The first polarizer 718 receives the emitted light 750 from the light source 716, transmits only linearly polarized light in the direction of the polarization axis 718 a, and emits the emitted light 752 to the first TN cell 724. The first polarizer 718 is provided such that the polarization axis 718a is in the horizontal direction. Accordingly, horizontal polarized light is extracted from the light 750 emitted from the light source 716 and emitted to the first TN cell 724. Here, in this embodiment, the x-axis direction of the orthogonal coordinate system is the horizontal direction, and the y-axis direction is the vertical direction. Note that if the light source 716 has a strong specific linearly polarized light component, a configuration in which the first polarizer 718 is omitted is also possible. As a light source having a specific linearly polarized light component, an edge-emitting laser diode element can be exemplified.

  The first TN cell 724 converts the polarization direction of the emitted light 752 emitted from the first polarizer 718, and irradiates the glass 780, which is a measurement object, with the irradiation light 754. The first TN cell 724 is provided with a first variable power source 738 that controls the voltage applied to the first TN cell 724.

  The first TN cell 724 is an example of an optical rotator that rotates incident light by rotating incident light. The first TN cell 724 is configured such that the incident side is vertically aligned and the output side is horizontally aligned. The first TN cell 724 converts the polarization direction of the outgoing light 752 by 90 degrees when no voltage is applied. Also, when a voltage is applied, the polarization direction is not converted. Thus, by controlling the voltage applied to the first TN cell 724, the polarization direction of the irradiation light 754 can be variably converted.

  The light receiving unit 714 includes a second TN cell 730, a second polarizer 732, and an imaging unit 734. In the light receiving unit 714, at least the second TN cell 730 and the second polarizer 732 are structurally statically configured. That is, the second TN cell 730 and the second polarizer 732 are each or at least relatively fixed in structure.

  Second TN cell 730 converts the polarization direction of transmitted light 756 from glass 780. The second TN cell 730 is provided with a second variable power source 740 that controls the voltage applied to the second TN cell 730.

  The second TN cell 730 is an example of an optical rotator that rotates incident light by rotating incident light. The second TN cell 730 is configured such that the incident side is vertically aligned and the output side is horizontally aligned. The second TN cell 730 converts the polarization direction by 90 degrees when no voltage is applied. Also, when a voltage is applied, the polarization direction is not converted. Thus, by controlling the voltage applied to the second TN cell 730, the polarization direction of the transmitted light 756 can be variably converted.

  The second polarizer 732 is disposed such that the polarization axis 732a is in the horizontal direction. Thereby, only the horizontally polarized light out of the emitted light 758 emitted from the second TN cell 730 passes through the second polarizer 732 and is received by the imaging unit 734.

  The imaging unit 734 includes a plurality of light receiving elements 770 arranged in a matrix. As the imaging unit 734, a CCD image sensor, a CMOS image sensor, or the like can be used. The plurality of light receiving elements 770 receive the emitted light 760 from the second polarizer 732, so that an image by horizontal polarization or vertical polarization of the transmitted light 756 from the glass 780 can be captured.

  The operation of the polarization imaging apparatus 700 configured as described above will be described by taking as an example the case of observing the distortion of the glass 780. The light source 716 continues to emit non-polarized outgoing light 750.

When the voltage applied to the first variable power supply 738 is turned off at time t ₁ , the TN cell 724 converts the emitted light 752 that is horizontally polarized light that has passed through the first polarizer 718 into irradiation light 754 that is vertically polarized light. The irradiation light 754 passes through the glass 780 and enters the second TN cell 730 as transmitted light 756.

Here, when there is no distortion in the glass 780, the polarization direction is not converted by the glass 780, so that the transmitted light 756 is also vertically polarized. When the voltage applied to the second TN cell 730 is turned on at time t ₁ , the transmitted light 756 is transmitted through the second TN cell 730 without changing the polarization direction and is incident on the second polarizer 732. Since the second polarizer 732 transmits only horizontal polarized light, the outgoing light 758 that is vertically polarized light cannot pass through the second polarizer 732, and a dark image is captured by the imaging unit 734. On the other hand, in the case where strain exists in a part of the glass 780, the polarization direction of the light transmitted through the strained portion is changed, so that the transmitted light 756 has a horizontally polarized polarization component. In this case, since the horizontally polarized light can pass through the second polarizer 732 in the portion where the distortion exists, a bright and dark pattern is formed in the image picked up by the image pickup unit 734.

Next, when the voltage applied to the first TN cell 724 is turned on at time t ₂ , the first TN cell 724 irradiates the glass 780 with irradiation light 754 that is horizontally polarized light without changing the polarization direction of the emitted light 752. To do. When the glass 780 is not distorted, the transmitted light 756 that is horizontally polarized light is incident on the second TN cell 730. When the voltage applied to the second TN cell 730 is turned off at time t ₂ , the transmitted light 756 is converted into vertical polarization by the second polarizer 732, and therefore cannot be transmitted through the second polarizer 732, and the imaging unit 734 has a dark image. Is imaged. On the other hand, when a part of the glass 780 is distorted, the polarization direction of the light transmitted through the distorted part is changed, so that the transmitted light 756 has a vertically polarized polarization component. In this case, since the vertically polarized light is converted into the horizontally polarized light in the portion where the distortion exists, light can be transmitted through the second polarizer 732, and a light and dark pattern is formed in the image captured by the image capturing unit 734.

  As described above, when the first variable power supply 738 and the second variable power supply 740 are repeatedly turned on and off, and an image is captured in synchronization with the on / off switching, the distortion of the glass 780 can be observed. When the polarization direction of the light applied to the glass 780 is only one direction, the strain may not be detected depending on the strain direction of the strain. However, by using the polarization imaging device 700, the light in two orthogonal polarization directions can be detected. Therefore, the accuracy of strain observation can be improved. Since the response speed of the TN cell is usually about 10 milliseconds and can be operated at a frequency faster than the display frequency of the display device, a moving image can be generated.

  Since the polarization imaging apparatus 700 can structurally statically configure the first polarizer 718 and the first TN cell 724 in the irradiation unit 712 and the second TN cell 730 and the second polarizer 732 in the light receiving unit 714, the polarizer A mechanism such as rotating is not necessary. Moreover, the conversion part which converts a polarization direction is comprised only with one TN cell. Therefore, the apparatus can be made small and inexpensive, and the service life of the apparatus can be improved. The ease of manufacturing the device, the reduction in manufacturing cost, and ensuring the image resolution are the same as in the case of FIG.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

In the polarization imaging apparatus of FIG. 1, the π cell is exemplified as the phase control element, but the phase control element is not limited to the π cell, such as PLZT crystal (lead lanthanum zirconate titanate titanate), LiNbO ₃ crystal, and the like. It may be.

  In the polarization imaging apparatus of FIG. 1, two phase control elements are provided in each of the first conversion unit 24 of the irradiation unit 12 and the second conversion unit 30 of the light receiving unit 14, but the conversion unit is configured by one phase control element. May be. In this case, although it is impossible to irradiate light with an arbitrary polarization direction or to image light with an arbitrary polarization direction, it is possible to irradiate or image, for example, horizontally polarized light and vertically polarized light.

  In FIG. 1, the irradiation unit 12 in a state where the first polarizer 18, the first phase control element 20, and the second phase control element 22 are separated from each other, the third phase control element 26, the fourth phase control element 28, and the second phase control element 22. Although the light receiving unit 14 is shown in which the polarizer 32 and the imaging unit 34 are separated from each other, it is of course possible to configure the light receiving unit 14 to be in contact with each other, which can contribute to the downsizing of the apparatus. This also applies to the polarization image capturing apparatus 700 shown in FIG.

  In the image display apparatus of FIG. 3, the memory is depicted as an integrated memory of the original image holding unit 144 and the final image holding unit 146, but of course may be separate. In that case, a memory suitable for each process can be selected, and the processing speed and cost can be easily optimized.

It is a figure which shows the structure of the polarization | polarized-light imaging device which concerns on this Embodiment. It is a figure which shows the Poincare sphere for demonstrating conversion of the polarization direction by a 1st conversion part and a 2nd conversion part. It is a figure which shows the image display apparatus using the polarization | polarized-light imaging device which concerns on this Embodiment. It is a timing chart which shows notionally the time division processing of an image display device. It is a figure which shows another embodiment of a polarized image imaging device. It is a figure for demonstrating the example which uses the image display apparatus which concerns on this Embodiment for the night vision system of a vehicle. It is a figure which shows another embodiment of a polarization | polarized-light imaging device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Polarization image pick-up device, 16 Light source, 18 1st polarizer, 20 1st phase control element, 22 2nd phase control element, 24 1st conversion part, 26 3rd phase control element, 28 4th phase control element, 30 2nd conversion part, 32 2nd polarizer, 34 Imaging part, 110 Image processing apparatus, 136 Image generation part, 200 Display apparatus.

Claims (15)

A light source that emits light;
A first polarizer that is statically configured and that receives light emitted from the light source;
A first converter configured statically in structure and converting the polarization direction of the outgoing light from the first polarizer to irradiate the object;
A second converter configured statically in structure and converting a polarization direction of light emitted from the object;
A second polarizer that is configured statically in structure and receives light emitted from the second converter;
An imaging unit that captures an image of light emitted from the second polarizer;
A control unit that electrically and variably controls the conversion of the polarization direction in the first conversion unit and the second conversion unit;
A polarization image capturing apparatus comprising:   The first conversion unit and / or the second conversion unit includes a phase control element that changes a phase difference of polarization components orthogonal to each other of incident light on the first conversion unit and / or the second conversion unit. The polarized image capturing apparatus according to 1.   The first conversion unit and / or the second conversion unit includes a first phase control element that receives light incident on itself and a second phase control element that receives light emitted from the first phase control element. The polarization image capturing apparatus according to claim 2, wherein the main axis of the first phase control element and the main axis of the second phase control element are arranged to be shifted by 45 degrees.   The said 1st conversion part and / or the said 2nd conversion part are equipped with the optical rotator which rotates the polarization plane by rotating the incident light to self by electrical control. Polarized imaging device.   The imaging unit captures an image of light emitted from the second polarizer in synchronization with switching of polarization direction conversion in the first conversion unit and / or the second conversion unit. The polarized image capturing apparatus according to any one of 1 to 4.   The polarization image capturing apparatus according to claim 1, wherein the control unit synchronizes switching of polarization direction conversion between the first conversion unit and the second conversion unit. The polarization image capturing apparatus according to any one of claims 1 to 6,
An original image holding unit that stores a plurality of images captured by the polarization image capturing device as original images for subsequent processing;
An image generation unit that generates a final image by causing a function determined according to a processing purpose to act on the plurality of original images;
An image processing apparatus comprising:   The image processing apparatus according to claim 7, wherein the image generation unit generates the final image for the purpose of displaying on a display device. The imaging unit uses a sampling clock having a frequency n times (n is an integer of 2 or more) higher than the display frequency of the display device, and captures and stores the plurality of original images for each display cycle in a time-sharing manner. n times,
The image processing apparatus according to claim 8, wherein the image generation unit generates one final image from the stored n original images.   The image processing apparatus according to claim 7, wherein the image generation unit uses a function represented by a linear linear sum of the plurality of original images as the function.   The image processing apparatus according to claim 10, wherein the image generation unit uses a function in which a coefficient of any original image is zero among the linear linear sums.   The image processing apparatus according to claim 11, wherein the image generation unit uses a function in which a coefficient of an original image in a predetermined polarization direction is zero.   The image processing apparatus according to claim 11, wherein the image generation unit uses a function in which a coefficient of an original image in which the luminance of at least some of the pixels is equal to or higher than a predetermined value is set to zero.   The image processing apparatus according to claim 7, wherein the image generation unit generates the final image for the purpose of issuing an alarm.   A determination unit that determines whether or not there is a pixel having a luminance greater than or equal to a predetermined value in the final image, and an alarm is issued when the determination unit determines that there is a pixel that has a luminance greater than or equal to the predetermined value The image processing apparatus according to claim 14, further comprising an alarm issuing unit.

Images