Patent Publication Number: US-2012026417-A1

Title: Imaging device

Description:
TECHNICAL FIELD 
     The present invention relates to an imaging device suitable for obtaining parallax images used for three-dimensional display, for example. 
     BACKGROUND ART 
     In the related art, various imaging devices have been proposed and developed. In addition, imaging devices that subject imaging data obtained by imaging to predetermined image processing and output the result have been proposed. 
     Patent Document 1, for example, proposes an imaging device with an electronic optical shutter using a liquid crystal (which shutter will hereinafter be referred to simply as a liquid crystal shutter). This imaging device includes an imaging lens, a liquid crystal shutter, an imaging element, and an image processing section. The light transmitting region (open region) of the liquid crystal shutter can be changed on a time division basis. Thereby, images are obtained on the basis of a light beam transmitted by each transmitting region of the liquid crystal shutter. The images are generated on the basis of the light beam transmitted by different regions of the liquid crystal shutter, and are thus parallax images having a parallax with respect to each other. Two such parallax images are each displayed by using a special display device, and are separately observed by the right eye and the left eye of an observer. Thereby a stereoscopy can be realized. 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Laid-Open No. 2001-61165 
       
    
     SUMMARY OF INVENTION 
     Incidentally, the liquid crystal shutter as described above includes for example a polarizer, a liquid crystal, and an analyzer. Thereby, only polarized light of light from an object which polarized light coincides with the direction of polarization of the polarizer is transmitted, and switching between the transmission and blockage of the polarized light is performed by the liquid crystal and the analyzer. By performing such switching in each region, the liquid crystal shutter can change the light transmitting region on a time division basis. 
     However, the light incident on the inside of the liquid crystal shutter is light transmitted by the polarizer, that is, polarized light dependent on the direction of polarization of the polarizer. Thus, when the transmitting region of the liquid crystal shutter is changed on a time division basis as described above, light beam information dependent on the direction of polarization of the polarizer in the transmitting region at a certain time is obtained. Thus, an image obtained becomes an image as if taken via a polarizing filter. 
     On the other hand, two images taken by changing the transmitting region are based on the light beam transmitted by different transmitting regions, and are thus parallax images having a parallax with respect to each other. When two such parallax images are viewed by a right eye and a left eye, for example, and the two parallax images are based on same polarized light, the parallax images are viewed as images as if through a same polarizing filter. Alternatively, when the two parallax images are based on different pieces of polarized light from each other, the parallax images are viewed as images as if through different polarizing filters from each other. That is, being affected by limitation of polarization, the parallax images are unnatural. 
     The present embodiment has been made in view of such problems. It is an object to provide an imaging device that can obtain natural parallax images with reduced limitation of polarization. 
     A first imaging device according to one embodiment of the present invention includes: an imaging lens; an imaging element for obtaining imaging data on a basis of received light; a liquid crystal shutter capable of controlling transmittance of a light beam directed to the imaging element in each of a plurality of regions different from each other, the plurality of regions each including a first sub-region selectively transmitting first polarized light and a second sub-region selectively transmitting second polarized light having a different direction of polarization from the first polarized light; and a liquid crystal shutter driving section for driving the liquid crystal shutter by performing switching between transmission and blockage in the plurality of regions in the liquid crystal shutter on a time division basis. 
     The first imaging device according to one embodiment of the present invention performs switching between transmission and blockage in the plurality of regions of the liquid crystal shutter by the driving of the liquid crystal shutter driving section. The imaging element thereby obtains imaging data based on received light beam in each region. Because the plurality of regions in the liquid crystal shutter are different regions from each other, light beams transmitted by the respective regions have a parallax with respect to each other. At this time, because each region is divided into a first sub-region transmitting first polarized light and a second sub-region transmitting second polarized light, the light beams in the imaging element are each based on both the first polarized light and the second polarized light. 
     A second imaging device according to one embodiment of the present invention includes: an imaging lens; an imaging element for obtaining imaging data on a basis of received light; a liquid crystal shutter capable of controlling transmittance of a light beam going toward the imaging element in each of a plurality of regions different from each other, and having a polarizer on a light incidence side; a quarter-wave plate disposed on an imaging object side of the liquid crystal shutter; and a liquid crystal shutter driving section for performing driving by switching between transmission and blockage in the liquid crystal shutter on a time division basis in the plurality of regions. An optical axis of the quarter-wave plate is at 45° with respect to an axis of polarization of the polarizer of the liquid crystal shutter. 
     In the second imaging device according to one embodiment of the present invention, switching between transmission and blockage is performed in the plurality of regions of the liquid crystal shutter by the driving of the liquid crystal shutter driving section, whereby the imaging element obtains imaging data based on the received light beam in each region. Because the plurality of regions in the liquid crystal shutter are regions different from each other, light beams transmitted by the respective regions mutually have a parallax. At this time, the quarter-wave plate is disposed on the imaging object side of the liquid crystal shutter, and the optical axis of the quarter-wave plate is at 45° with respect to the axis of polarization of the polarizer in the liquid crystal shutter, whereby the light incident on the liquid crystal shutter is circularly polarized light including two polarized light components different from each other. 
     According to the first imaging device according to one embodiment of the present invention, the light beam directed to the imaging element is changed and transmitted in each of the plurality of regions of the liquid crystal shutter, and each region is divided into the first and second sub-regions transmitting the first polarized light and the second polarized light. Therefore parallax image data based on both the first polarized light and the second polarized light can be obtained. Thus, natural parallax images with reduced limitation of polarization can be obtained. 
     In accordance with the second imaging device according to one embodiment of the present invention, the light beam going toward the imaging element is switched and transmitted in each of the plurality of regions of the liquid crystal shutter, and the quarter-wave plate is disposed on the imaging object side of the liquid crystal shutter. Thus, the light incident on the liquid crystal shutter can be made to be circularly polarized light including two polarized light components different from each other. Hence, a natural parallax image can be obtained with less limitation due to polarized light. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram showing a configuration of an imaging device according to a first embodiment of the present invention. 
         FIG. 2  shows schematic plan views showing region division and directions of polarization of a liquid crystal shutter shown in  FIG. 1 . 
         FIG. 3  is a sectional view of a boundary between sub-regions and the vicinity thereof in the liquid crystal shutter shown in  FIG. 1 . 
         FIG. 4  is a schematic diagram showing respective plane configurations of a polarizer, sub-electrodes, and an analyzer shown in  FIG. 3 . 
         FIG. 5  is a schematic plan view showing another example of the polarizer shown in  FIG. 4 . 
         FIG. 6  is a diagram showing a sectional configuration of a liquid crystal shutter according to a first comparative example and plane configurations of a polarizer, an electrode, and an analyzer of the liquid crystal shutter. 
         FIG. 7  is a schematic diagram of assistance in explaining action of the liquid crystal shutter shown in  FIG. 6 . 
         FIG. 8  is a diagram showing plane configurations of a polarizer, an electrode, and an analyzer of a liquid crystal shutter according to a second comparative example. 
         FIG. 9  is a schematic diagram of assistance in explaining action of the liquid crystal shutter shown in  FIG. 8 . 
         FIG. 10  shows schematic diagrams of assistance in explaining an example of application of the imaging device shown in  FIG. 1 . 
         FIG. 11  is a sectional view of a schematic configuration of a liquid crystal shutter according to a second embodiment of the present invention. 
         FIG. 12  is a schematic diagram showing respective plane configurations of a polarizer, sub-electrodes, and an analyzer shown in  FIG. 11 . 
         FIG. 13  is a schematic plan view of another example of a polarizer shown in  FIG. 12 . 
         FIG. 14  shows schematic plan views showing region division and directions of polarization of a liquid crystal shutter according to a first example of modification. 
         FIG. 15  shows schematic plan views showing region division and directions of polarization of a liquid crystal shutter according to a second example of modification. 
         FIG. 16  is a schematic diagram showing the respective constitutions of a quarter-wave plate and a liquid crystal shutter in an imaging device according to a third example of modification and their arrangement relation. 
         FIG. 17  is a schematic diagram of assistance in explaining a passing light beam in relation to incident light (polarized light in a 0° direction) in a comparative example. 
         FIG. 18  is a schematic diagram of assistance in explaining a passing light beam in relation to incident light (polarized light in a 90° direction) in a comparative example. 
         FIG. 19  is a schematic diagram of assistance in explaining a passing light beam in relation to incident light (polarized light in a 0° direction) in the arrangement relation of the quarter-wave plate and the liquid crystal shutter shown in  FIG. 16 . 
         FIG. 20  is a schematic diagram of assistance in explaining a passing light beam in relation to incident light (polarized light in a 90° direction) in the arrangement relation of the quarter-wave plate and the liquid crystal shutter shown in  FIG. 16 . 
         FIG. 21  shows diagrams of assistance in explaining an example of use in which switching between transmission and blockage of a light beam is performed in two upper and lower regions. 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
     Preferred embodiments of the present invention will hereinafter be described in detail with reference to the drawings. Incidentally, description will be made in the following order. 
     1. First Embodiment: Example of Dividing Each Region of Liquid Crystal Shutter by Sub-Electrode Formation (Electrode Division) 
     2. Second Embodiment: Example of Dividing Each Region of Liquid Crystal Shutter by Polarizing Region Division in Analyzer (Second Polarizer) 
     3. First Example of Modification: Example of Dividing Each Region into Four Sub-Regions
 
4. Second Example of Modification: Another Example of Dividing Each Region into Four Sub-Regions
 
5. Third Example of Modification: Example in which Quarter-Wave Plate is Disposed on Imaging Object Side of Liquid Crystal Shutter
 
     First Embodiment 
     Configuration of Imaging Device  1   
       FIG. 1  shows a general configuration of an imaging device (imaging device  1 ) according to a first embodiment of the present invention. The imaging device  1  images an image of an imaging object  2 , and outputs imaging data Dout. The imaging device  1  includes an imaging lens  11 , a liquid crystal shutter  12 , an imaging element  13 , a liquid crystal shutter driving section  14 , an imaging element driving section  15 , and a controlling section  16 . Incidentally, the imaging device  1  may have an image processing section not shown in the figure. 
     The imaging lens  11  is a main lens for imaging an image of the imaging object  2 . For example an ordinary imaging lens used in a video camera, a still camera or the like is used as the imaging lens  11 . 
     The liquid crystal shutter  12  is to control the transmittance of a light beam directed to the imaging element  13 . The liquid crystal shutter  12  is disposed on the light incidence side or the light emission side (light emission side in this case) of the imaging lens  11 . A detailed configuration of the liquid crystal shutter  12  will be described later. 
     The imaging element  13  obtains imaging data by receiving the light from the imaging lens  11 . The imaging element  13  is disposed in the focal plane of the imaging lens  11 . The imaging element  13  is for example formed by arranging a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor) or the like in the form of a matrix. Color filters of R, G, and B (not shown) which color filters have a predetermined color arrangement, for example, are disposed on the light receiving surface of the imaging element  13 . 
     The liquid crystal shutter driving section  14  drives the liquid crystal shutter  12  to perform control for switching between transmission (open) and blockage (close) in two regions of the liquid crystal shutter  12  on a time division basis. The switching operation of the liquid crystal shutter driving section  14 , which switching operation will be described later in detail, is performed by changing a voltage supplied to the liquid crystal shutter  12 . 
     The imaging element driving section  15  drives the imaging element  13  to control the light receiving operation of the imaging element  13 . 
     The controlling section  16  controls the operation of the liquid crystal shutter driving section  14  and the imaging element driving section  15 . For example a microcomputer is used as the controlling section  16 . 
     (Detailed Configuration of Liquid Crystal Shutter  12 ) 
     First, an outline of region divisions in the liquid crystal shutter  12  will be described with reference to  FIGS. 2(A) and 2(B) .  FIGS. 2(A) and 2(B)  schematically show region divisions and directions of polarization in the liquid crystal shutter  12 . Each of arrows in respective sub-regions schematically indicates a direction of polarization. The liquid crystal shutter  12  has two regions different from each other (two left and right regions in this case)  12 L and  12 R. The regions  12 L and  12 R are provided so as to be symmetric with respect to an optical axis, for example so as to divide a circular plane shape into two left and right parts. Such a liquid crystal shutter  12  can control the transmittance of a light beam (specifically switch between transmission and blockage) in each of the regions  12 L and  12 R ( FIG. 2(B) ). In  FIG. 2(B) , hatched parts indicate that the light beam is blocked (close). That is, the region  12 L is open on the left (L) of the figure, and the region  12 R is open on the right (R) of the figure. 
     The regions  12 L and  12 R are divided into sub-regions that respectively transmit polarized light in different directions of polarization from each other. For example, the region  12 L is divided into equal sub-regions  12 L 1  and  12 L 2 . Of the regions  12 L 1  and  12 L 2 , the region  12 L 1  selectively transmits first polarized light (solid line arrow, which will be similarly used in the following), and the region  12 L 2  selectively transmits second polarized light (dotted line arrow, which will be similarly used in the following). The region  12 R is similarly divided into equal sub-regions  12 R 1  and  12 R 2 , the sub-region  12 R 1  transmitting the second polarized light, and the sub-region  12 R 2  transmitting the first polarized light. However, in the present specification, the “first polarized light” and the “second polarized light” are linearly polarized light whose directions of polarization are orthogonal to each other (pieces of light that vibrate in a 0° direction and a 90° direction, respectively), and for example one of the “first polarized light” and the “second polarized light” is p-polarized light, and the other is s-polarized light. 
     In the liquid crystal shutter  12 , the region division as described above is performed by dividing a polarizer and an electrode. A concrete configuration of the liquid crystal shutter  12  will hereinafter be described with reference to  FIG. 3  and  FIG. 4 .  FIG. 3  shows a sectional configuration around a boundary between the sub-regions  12 L 1  and  12 L 2  in the liquid crystal shutter  12 .  FIG. 4  schematically shows respective plane configurations of a polarizer, a sub-electrode, and an analyzer.  FIG. 5  shows another example of plane configuration of the polarizer. 
     The liquid crystal shutter  12  has a liquid crystal layer  104  sealed in between a pair of substrates  101  and  106 , has a polarizer  107 A (first polarizer) laminated to the light incidence side of the substrate  101 , and has an analyzer  107 B (second polarizer) laminated to the light emission side of the substrate  106 . The substrates  101  and  106  are each a transparent substrate such for example as a glass substrate, and are able to transmit an incident light beam. 
     An electrode is formed between the substrate  101  and the liquid crystal layer  104 , and the electrode in the present embodiment is divided into a plurality of sub-electrodes (four sub-electrodes in this case)  102 A. The four sub-electrodes  102 A are formed so as to divide the plane shape of the liquid crystal shutter  12  into equal parts radially. The four sub-electrodes  102 A correspond to the sub-regions  12 L 1 ,  12 L 2 ,  12 R 1 , and  12 R 2  in the liquid crystal shutter  12 . Such an electrode division enables transmittance control in each of the regions  12 L and  12 R. 
     On the other hand, an electrode  105  common to the sub-regions  12 L 1 ,  12 L 2 ,  12 R 1 , and  12 R 2  is formed on the substrate  106  opposed to the substrate  101 . An alignment film  103 A is formed between the sub-electrodes  102 A and the liquid crystal layer  104 , and an alignment film  103 B is formed between the electrode  105  and the liquid crystal layer  104 . 
     The sub-electrodes  102 A and the electrode  105  are each formed by a transparent electrode such for example as an ITO (Indium Tin Oxide), and are able to transmit an incident light beam as with the substrates  101  and  106 . The alignment films  103 A and  103 B are to align liquid crystal molecules within the liquid crystal layer  104  in a desired direction. In the present embodiment, respective alignment control directions of the alignment film  103 A and the alignment film  103 B in alignment control on the liquid crystal molecules are orthogonal to each other. The liquid crystal layer  104  is formed by a liquid crystal material such for example as a nematic liquid crystal. A state of alignment of the liquid crystal molecules in the liquid crystal layer  104  is changed according to the magnitude of a voltage applied through the sub-electrodes  102 A and the electrode  105 . Thereby transmittance control is performed. 
     Each of the polarizer  107 A and the analyzer  107 B selectively transmits polarized light in a direction along a predetermined axis of polarization, which polarized light is included in the incident light beam. In the present embodiment, as shown in  FIG. 4 , the polarizer  107 A is divided into polarized light transmitting regions  107 A 1  to  107 A 4  in such a manner as to divide the plane shape of the polarizer  107 A into four equal parts. An axis of polarization is formed in the polarized light transmitting regions  107 A 1  and  107 A 4  among the polarized light transmitting regions  107 A 1  to  107 A 4  so as to selectively transmit the first polarized light. An axis of polarization is formed in the polarized light transmitting regions  107 A 2  and  107 A 3  among the polarized light transmitting regions  107 A 1  to  107 A 4  so as to selectively transmit the second polarized light. The polarized light transmitting regions  107 A 1  to  107 A 4  are provided so as to correspond to the sub-electrodes  102 A. It suffices for the analyzer  107 B in the present embodiment to selectively transmit one of the first polarized light and the second polarized light, or for example the second polarized light, and the analyzer  107 B in the present embodiment does not need to have different axes of polarization in the respective sub-regions  12 L 1 ,  12 L 2 ,  12 R 1 , and  12 R 2 . 
     Incidentally, the respective directions of polarization in the four polarized light transmitting regions of the polarizer  107 A are not limited to the above-described combination. A polarizer  108 A as shown in  FIG. 5 , for example, may also be used. Specifically, polarized light transmitting regions  108 A 1  and  108 A 3  corresponding to the sub-regions  12 L 1  and  12 R 1  may be made to selectively transmit the first polarized light, and polarized light transmitting regions  108 A 2  and  108 A 4  corresponding to the sub-regions  12 L 2  and  12 R 2  may be made to selectively transmit the second polarized light. That is, the region ( 12 L) composed of the sub-regions  12 L 1  and  12 L 2  and the region ( 12 R) composed of the sub-regions  12 R 1  and  12 R 2  may be bilaterally symmetric. 
     Action and Effect of First Embodiment 
     Basic Operation of Imaging Device  1   
     In the imaging device  1 , a light beam of light from the imaging object  2  which light beam has passed through the imaging lens  11  is transmitted by a predetermined region of the liquid crystal shutter  12 , and then reaches the imaging element  13 . The imaging element  13  obtains imaging data Dout (parallax images DR and DL) based on the received light beam according to the driving operation of the imaging element driving section  15 . An image processing section not shown in the figure subjects the parallax images DR and DL to predetermined image processing in the image processing section. Performed as the image processing are temporal rearrangement processing on the parallax images DR and DL, color interpolation processing such as demosaicing, and the like. 
     At this time, the liquid crystal shutter driving section  14  performs switching to open or close the regions  12 L and  12 R of the liquid crystal shutter  12  on a time division basis. Specifically, switching is performed such that the light beam directed to the imaging element  13  is transmitted in the region  12 L of the liquid crystal shutter  12  and blocked in the region  12 R of the liquid crystal shutter  12  in certain timing, and the light beam is blocked in the region  12 L and transmitted in the region  12 R in next timing. At this time, in the present embodiment, transmittance in each of the regions  12 L and  12 R is controlled according to the magnitude of the voltage supplied to each of the sub-electrodes  102 A and the electrode  105 . In this case, because the regions  12 L and  12 R are regions different from each other, the light beams transmitted by the respective regions  12 L and  12 R have a parallax with respect to each other. Thus, the switching operation of the liquid crystal shutter driving section  14  provides two parallax images DL and DR as if taken from two left and right viewpoints as imaging data Dout. 
     Liquid crystal shutters according to comparative examples (first and second comparative examples) will be described in the following with reference to  FIGS. 6 to 9 .  FIG. 6  shows a sectional configuration of a liquid crystal shutter  110  according to the first comparative example and plane configurations of a polarizer, an electrode, and an analyzer in the liquid crystal shutter  110 .  FIG. 8  shows plane configurations of a polarizer, an electrode, and an analyzer according to the second comparative example. 
     First Comparative Example 
     The liquid crystal shutter  110  has a liquid crystal layer  113  sealed in between a pair of substrates  111  and  115 , has a polarizer  116 A laminated to the side of the substrate  111 , and has an analyzer  116 B laminated to the side of the substrate  115 . Electrodes  112  and  114  are formed between the substrates  111  and  115  and the liquid crystal layer  113 . Of the electrodes, for example the electrode  112  formed on the side of the substrate  111  is divided into two sub-electrodes  112 A in such a manner as to divide the electrode  112  into two left and right parts. The polarizer  116 A and the analyzer  116 B are each formed uniformly with an axis of polarization of each of the polarizer  116 A and the analyzer  116 B along one direction, and the polarizer  116 A and the analyzer  116 B are arranged such that the axes of polarization of the polarizer  116 A and the analyzer  116 B are orthogonal to each other. In the first comparative example, transmittance is controlled in each of a left region and a right region corresponding to the two sub-electrodes  112 A, and thereby driving for switching between the opening and closing of these regions is performed. 
     Second Comparative Example 
     Alternatively, as shown in  FIG. 8 , the directions of polarization of the two left and right regions may be different from each other. In this case, in a configuration similar to that of the liquid crystal shutter  110  according to the first comparative example, a polarizer  116  is divided into polarized light transmitting regions  116 A 1  and  116 A 2  transmitting respective pieces of polarized light that are orthogonal to each other. An electrode  112  is not divided, and an analyzer  116 B is similar to that of the first comparative example. 
     However, in the first and second comparative examples, when switching is performed between transmission and blockage in the two left and right regions, as shown in  FIG. 7 , imaging data dependent on polarized light is obtained because the direction of polarization of the polarizer  116 A is uniform even if either of the left and right regions is opened. At this time, in the first comparative example, imaging data dependent on polarized light in an identical direction of polarization is obtained in each region. Thus, parallax images D 110 L and D 110 R are images as if observed via an identical polarizing filter, and are therefore unnatural images. In the second comparative example, as shown in  FIG. 9 , a left and a right parallax image D 111 L and D 111 R are images as if observed via respective polarizing filters having different directions of polarization, and are therefore more unnatural images than in the first comparative example. Incidentally, when an object is observed via a polarizing filter, an observed image is easily affected by light having great polarization dependence, for example light reflected on a water surface or light reflected on a glass surface, and thus becomes unnatural. 
     (Characteristic Operation of Imaging Device  1 ) 
     On the other hand, in the present embodiment, the regions  12 L and  12 R in the liquid crystal shutter  12  are each divided into the sub-region ( 12 L 1  and  12 R 2 ) that selectively transmits the first polarized light and the sub-region ( 12 L 2  and  12 R 1 ) that selectively transmits the second polarized light. The region division into such sub-regions is realized by dividing the polarizer  107 A into polarized light transmitting regions different from each other and performing individual driving based on electrode division (formation of four sub-electrodes  102 A). 
     For example, when the liquid crystal shutter driving section  14  opens the region  12 L according to the above-described switching operation, the liquid crystal shutter driving section  14  supplies a predetermined voltage to each of the sub-electrodes  102 A and the electrode  105  in each of the sub-regions  12 L 1  and  12 L 2 . Thereby, the liquid crystal shutter  12  is driven so as to make each of the light beams (the first polarized light and the second polarized light) transmitted by the polarized light transmitting regions  107 A 1  and  107 A 2  of the polarizer  107 A pass through the liquid crystal layer  104  and the analyzer  107 B. The same is true for a case of opening the region  12 R. That is, the light beams received on the imaging element  13  through each of the regions  12 L and  12 R are each based on both the first polarized light and the second polarized light. Thus, the two parallax images DL and DR obtained are reduced in polarization dependence as compared with the parallax images dependent on only one piece of polarized light as in the first and second comparative examples. Thus, natural parallax images not easily affected by light having great polarization dependence are obtained. When an image of a fish or the like in a water is imaged through the water surface, for example, a polarized light component different from reflected light from the water surface can be detected. Thereby a natural observed image of a state in the water can be obtained with the reflected light component removed. 
     As described above, in the present embodiment, the light beam directed to the imaging element  13  is changed and transmitted by each of the left and right regions  12 L and  12 R of the liquid crystal shutter  12 , so that two left and right parallax images can be obtained. In addition, because the regions  12 L and  12 R are each divided into sub-regions that transmit the first polarized light and the second polarized light, respectively, imaging data can be obtained on the basis of both the first polarized light and the second polarized light. Hence, natural parallax images with reduced limitation of polarization can be obtained. 
     (Example of Application) 
     Such an imaging device  1  is used in a state of being mounted in a camera  3  as shown in  FIG. 10(A) , for example. The camera  3  includes the imaging device  1  inside a casing  30 , and has mechanisms of a finder  31 , a shutter button  32 , and the like. In addition, two parallax images DL and DR ( FIG. 10(B) ) taken by the camera  3  are displayed as an image for a right eye and an image for a left eye by using a 3D display device  4  for three-dimensional display as shown in  FIG. 10(C) , for example. A stereoscopy can be realized by observing the displayed image for a right eye by a right eye and the displayed image for a left eye by a left eye separately. 
     Second Embodiment 
       FIG. 11  shows a sectional configuration of a liquid crystal shutter (liquid crystal shutter  20 ) according to a second embodiment of the present invention.  FIG. 12  schematically shows respective plane configurations of a polarizer, an electrode, and an analyzer.  FIG. 13  shows another example of plane configuration of a polarizer and an analyzer. 
     (Configuration of Liquid Crystal Shutter  20 ) 
     As with the liquid crystal shutter  12  according to the foregoing first embodiment, the liquid crystal shutter  20  is provided to control the transmittance of a light beam directed to an imaging element  13  according to the driving of a liquid crystal shutter driving section  14  in an imaging device  1 . In addition, as with the liquid crystal shutter  12  according to the foregoing first embodiment, the liquid crystal shutter  20  has two left and right regions  12 L and  12 R that can perform transmittance controls different from each other. Further, the regions  12 L and  12 R are divided into sub-regions  12 L 1 ,  12 L 2 ,  12 R 1 , and  12 R 2  that respectively transmit first polarized light and second polarized light. However, in the present embodiment, region division in such a liquid crystal shutter  20  is performed by division into polarized light transmitting regions in the polarizer and the analyzer. In the following, similar constituent elements to those of the foregoing first embodiment are identified by the same reference symbols, and description thereof will be omitted as appropriate. 
     Specifically, the liquid crystal shutter  20  is formed by sealing in a liquid crystal layer  104  between substrates  101  and  106 , and laminating a polarizer  107 A to the side of the substrate  101  and laminating an analyzer  117 B (second polarizer) to the side of the substrate  106 . Electrodes  102  and  105  and alignment films  103 A and  103 B are respectively formed between the substrates  101  and  106  and the liquid crystal layer  104 . 
     In the present embodiment, unlike the foregoing first embodiment, the electrode  102  does not need to be divided into sub-electrodes. The analyzer  117 B selectively transmits polarized light in a direction along a predetermined axis of polarization, which polarized light is included in an incident light beam. However, the analyzer  117 B in this case is divided into polarized light transmitting regions  117 B 1  to  117 B 4  so as to correspond to the polarized light transmitting regions  107 A 1  to  107 A 4  of the polarizer  107 A. An axis of polarization is formed in the polarized light transmitting regions  117 B 1  and  117 B 3  among the polarized light transmitting regions  117 B 1  to  117 B 4  so as to selectively transmit the first polarized light. An axis of polarization is formed in the polarized light transmitting regions  117 B 2  and  117 B 4  among the polarized light transmitting regions  117 B 1  to  117 B 4  so as to selectively transmit the second polarized light. That is, in the present embodiment, transmittance control in each of the regions  12 L and  12 R is made possible by a combination of the polarizer  107 A and the analyzer  117 B. 
     Incidentally, the combination of respective directions of polarization of the four polarized light transmitting regions of the polarizer  107 A and the four polarized light transmitting regions of the analyzer  117 B is not limited to the above-described configuration. A polarizer  108 A and an analyzer  118 B as shown in  FIG. 13 , for example, may also be used. In this case, in the polarizer  108 A, polarized light transmitting regions  108 A 1  and  108 A 3  corresponding to sub-regions  12 L 1  and  12 R 1  are made to selectively transmit the first polarized light, and polarized light transmitting regions  108 A 2  and  108 A 4  corresponding to sub-regions  12 L 2  and  12 R 2  are made to selectively transmit the second polarized light. That is, a region ( 12 L) composed of the sub-regions  12 L 1  and  12 L 2  and a region ( 12 R) composed of the sub-regions  12 R 1  and  12 R 2  may be bilaterally symmetric. As for the analyzer  118 B, polarized light transmitting regions  118 B 1  and  118 B 4  corresponding to the sub-regions  12 L 1  and  12 R 2  are made to selectively transmit the first polarized light, and polarized light transmitting regions  118 B 2  and  118 B 3  corresponding to the sub-regions  12 L 2  and  12 R 1  are made to selectively transmit the second polarized light. 
     Action and Effect of Second Embodiment 
     Also in the present embodiment, as in the foregoing first embodiment, switching is performed to open and close the regions  12 L and  12 R of the liquid crystal shutter  20  by the driving operation of the liquid crystal shutter driving section  14 . The imaging element  13  thereby obtains imaging data Dout (DR and DL) based on a received light beam in each of the regions  12 L and  12 R. 
     In this case, in the liquid crystal shutter  20 , the analyzer  117 B is divided into the polarized light transmitting regions  117 B 1  to  117 B 4  so as to correspond to the polarized light transmitting regions  107 A 1  to  107 A 4  of the polarizer  107 A. In such a configuration, the liquid crystal shutter driving section  14  performs switching to open and close the regions  12 L and  12 R of the liquid crystal shutter  20  according to the magnitude of a voltage supplied to the electrodes  102  and  105 . For example, when the region  12 L is opened, the voltage is supplied so as to make the light beam (the first polarized light and the second polarized light) transmitted by the polarized light transmitting regions  107 A 1  and  107 A 2  of the polarizer  107 A pass through the liquid crystal layer  104  and the polarized light transmitting regions  117 B 1  and  117 B 2  of the analyzer  117 B. 
     Thus, as in the liquid crystal shutter  12  according to the foregoing first embodiment, the received light beams in each of the regions  12 L and  12 R are each based on both the first polarized light and the second polarized light. Hence, equal effects to those of the foregoing first embodiment can be obtained. 
     Examples of modification (a first to a third example of modification) of the liquid crystal shutters according to the foregoing first and second embodiments will next be described. In the following, similar constituent elements to those of the foregoing first embodiment are identified by the same reference symbols, and description thereof will be omitted as appropriate. 
     First Example of Modification 
       FIGS. 14(A) and 14(B)  schematically show region division and directions of polarization (solid line arrows and dotted line arrows) of a liquid crystal shutter  30  according to the first example of modification. The present example of modification is an example of region division of a liquid crystal shutter. The region division in the present example of modification is applicable to both of the foregoing first embodiment (electrode division) and the foregoing second embodiment (region division of an analyzer). 
     As in the case of the regions  12 L and  12 R of the foregoing first embodiment, the liquid crystal shutter  30  has two left and right regions  30 L and  30 R that can perform transmittance controls different from each other. In addition, the regions  30 L and  30 R are radially divided into equal sub-regions (sub-regions  30 L 1 ,  30 L 2 ,  30 R 1 , and  30 R 2 ) that respectively transmit first polarized light and second polarized light. An axis of polarization is formed in the sub-regions  30 L 1  and  30 R 2  among these sub-regions so as to selectively transmit the first polarized light. An axis of polarization is formed in the sub-regions  30 L 2  and  30 R 1  so as to selectively transmit the second polarized light. In  FIG. 14(B) , hatched parts indicate that a light beam is blocked (close). That is, the region  30 L is open on the left (L) of the figure, and the region  30 R is open on the right (R) of the figure. 
     However, in the present example of modification, these sub-regions  30 L 1 ,  30 L 2 ,  30 R 1 , and  30 R 2  are each provided plurally in each of the regions  30 L and  30 R. Specifically, two sub-regions  30 L 1  and two sub-regions  30 L 2  are provided in the region  30 L, and the sub-regions  30 L 1  and the sub-regions  30 L 2  are arranged alternately. Also in the region  30 R, two sub-regions  30 R 1  and two sub-regions  30 R 2  are provided, and the sub-regions  30 R 1  and the sub-regions  30 R 2  are arranged alternately. That is, each of the regions  30 L and  30 R is divided into four equal sub-regions, and the liquid crystal shutter  30  as a whole is divided into eight equal sub-regions. 
     Thus, the sub-regions  30 L 1 ,  30 L 2 ,  30 R 1 , and  30 R 2  respectively dividing the regions  30 L and  30 R in the liquid crystal shutter  30  may be each provided plurally. That is, the number of divisions of the regions  30 L and  30 R is not particularly limited, but may be two as in the foregoing first and second embodiments or may be four as in the present example of modification. This is because equal effects to those of the foregoing first embodiment can be obtained when regions respectively transmitting the first polarized light and the second polarized light are included. In addition, polarization dependence can be further reduced by increasing the number of divisions of each of the regions  30 L and  30 R and alternately arranging the sub-regions  30 L 1  and  30 R 2  transmitting the first polarized light and the sub-regions  30 L 2  and  30 R 1  transmitting the second polarized light. Thus, more natural parallax images than in the foregoing first and second embodiments can be obtained. 
     Second Example of Modification 
       FIGS. 15(A) and 15(B)  schematically show region division and directions of polarization (solid line arrows and dotted line arrows) of a liquid crystal shutter  40  according to the second example of modification. The present example of modification is an example of region division of a liquid crystal shutter. The region division in the present example of modification is applicable to both of the foregoing first embodiment (electrode division) and the foregoing second embodiment (region division of an analyzer). 
     As in the case of the regions  12 L and  12 R of the foregoing first embodiment, the liquid crystal shutter  40  has two left and right regions  40 L and  40 R that can perform transmittance controls different from each other. In addition, the regions  40 L and  40 R are divided into sub-regions (sub-regions  40 L 1 ,  40 L 2 ,  40 R 1 , and  40 R 2 ) that respectively transmit first polarized light and second polarized light. An axis of polarization is formed in the sub-regions  40 L 2  and  40 R 1  among these sub-regions so as to selectively transmit the first polarized light. An axis of polarization is formed in the sub-regions  40 L 1  and  40 R 2  so as to selectively transmit the second polarized light. In the present example of modification, as in the foregoing first example of modification, these sub-regions  40 L 1 ,  40 L 2 ,  40 R 1 , and  40 R 2  are each provided plurally (specifically two each) in each of the regions  40 L and  40 R. In  FIG. 15(B) , hatched parts indicate that a light beam is blocked. That is, the region  40 L is open on the left (L) of the figure, and the region  40 R is open on the right (R) of the figure. 
     However, in the present example of modification, the liquid crystal shutter  40  is divided into regions such that the plane shape (circle) of the liquid crystal shutter  40  is radially divided into four equal parts and concentrically divided into two equal parts. That is, the liquid crystal shutter  40  is divided along a O-direction and an arc R-direction in the circle of the liquid crystal shutter  40 . In the region  40 L, the sub-regions  40 L 1  and the sub-regions  40 L 2  are arranged alternately (so as not to be adjacent to each other). Also in the region  40 R, the sub-regions  40 R 1  and the sub-regions  40 R 2  are arranged alternately. That is, each of the regions  40 L and  40 R is divided into four equal sub-regions, and the liquid crystal shutter  40  as a whole is divided into eight equal sub-regions. 
     Thus, the divided shapes of the sub-regions  40 L 1 ,  40 L 2 ,  40 R 1 , and  40 R 2  in the regions  40 L and  40 R of the liquid crystal shutter  40  are not limited to radial shapes as described above, but may be concentric shapes. Alternatively, the radial shapes and the concentric shapes may be combined with each other. Equal effects to those of the first embodiment and the first example of modification described above can be obtained also in this case. 
     Third Example of Modification 
       FIG. 16  schematically shows the respective constitutions of a quarter-wave plate (quarter-wave plate  17 ) and a liquid crystal shutter (liquid crystal shutter  18 ) in an imaging device according to a third example of modification and their arrangement relation. In the present example of modification, the quarter-wave plate  17  is disposed on the imaging object  2  side of the liquid crystal shutter  18 . Incidentally, constituent elements of the imaging device other than the quarter-wave plate and the liquid crystal shutter  18  (an imaging element  13 , a liquid crystal shutter driving section  14 , an imaging element driving section  15 , and a controlling section  16 ) are similar to those of the foregoing first embodiment. 
     As with the liquid crystal shutter  12  described above, the liquid crystal shutter  18  is to control the transmittance of a light beam going toward the imaging element  13  in each of a plurality of regions (two regions in this case). The liquid crystal shutter  18  is formed by sealing a liquid crystal layer (not shown in  FIG. 16 ) between a pair of substrates. In addition, a polarizer  109 A is laminated on the light incidence side of the liquid crystal shutter  18 , and an analyzer  107 B is laminated on the light emission side of the liquid crystal shutter  18 . Further, electrodes are provided on the liquid crystal layer sides of the respective substrates, and at least one of the electrodes (one electrode  122  in this case) is divided into a plurality of sub-electrodes. However, unlike the first and second embodiments in which the polarizer and the electrode (or the analyzer) are divided into four regions, or the like, in the present example of modification, the polarizer may be divided or may not be divided, and it suffices for the number of divisions of the electrode to be at least two. Incidentally, description in the following will be made by taking as an example a case in which the polarizer  109 A not divided into regions is used and the electrode  122  is divided into two sub-electrodes  122 A. Of course, also in the present example of modification, the electrode  122  may be divided into four or more regions, and the polarizer  109 A may be divided into a plurality of regions that transmit pieces of polarized light different from each other. Further, the analyzer may be divided into a plurality of regions, as described in the foregoing second embodiment. 
     The quarter-wave plate  17  is disposed such that the optical axis  17   a  of the quarter-wave plate  17  is at 45° with respect to an axis of polarization in the polarizer  109 A of the liquid crystal shutter  18 . In this case, as an example, the optical axis  17   a  is disposed at 45° with respect to the axis of polarization in the polarizer  109 A (suppose that the axis of polarization is a 90° direction). Incidentally, the axis of polarization in the polarizer  109 A may be a 0° direction, or the polarizer may be divided into regions as described above, so that the region of the 90° direction and the region of the 0° direction are mixed with each other. In either case, however, the polarizer and the quarter-wave plate are disposed such that the axis of polarization of the polarizer and the optical axis  17   a  of the quarter-wave plate are at 45° with respect to each other. 
     Here,  FIG. 17  and  FIG. 18  schematically show, as comparative examples for the present example of modification, states of passage of a light beam in a case in which the optical axis  17   a  of the quarter-wave plate  17  and the axis of polarization of the polarizer  109 A are made orthogonal to each other (case in which the optical axis  17   a  is in the 0° direction). However,  FIG. 17  shows polarized light in the 0° direction which polarized light is included in light incident on the quarter-wave plate  17 , and  FIG. 18  shows polarized light in the 90° direction which polarized light is included in the light incident on the quarter-wave plate  17 . As shown in  FIG. 17 , when the optical axis  17   a  of the quarter-wave plate  17  is orthogonal to the axis of polarization of the polarizer  109 A, the polarized light in the 0° direction which polarized light is incident on the quarter-wave plate  17  is emitted from the quarter-wave plate  17  as it is without changing a direction of polarization. Therefore, the polarized light in the 0° direction does not pass through the polarizer  109 A having the axis of polarization in the 90° direction, and is not emitted from the liquid crystal shutter  18 . 
     On the other hand, as shown in  FIG. 18 , the polarized light in the 90° direction which polarized light is incident on the quarter-wave plate  17  is emitted from the quarter-wave plate  17  as it is without changing a direction of polarization. Therefore, the polarized light in the 90° direction passes through the polarizer  109 A having the axis of polarization in the 90° direction, and is emitted from the liquid crystal shutter  18 . 
     Thus, in the case in which the quarter-wave plate  17  is disposed such that the optical axis  17   a  of the quarter-wave plate  17  is orthogonal to the axis of polarization of the polarizer  109 A, each of the polarized light components incident on the quarter-wave plate  17  varies in transmittance in the liquid crystal shutter  18 . That is, natural photographing not dependent on polarized light becomes difficult. This is also true for a case where the optical axis  17   a  of the quarter-wave plate  17  is made to coincide with the axis of polarization of the polarizer  109 A. 
     On the other hand, in the present example of modification, the quarter-wave plate  17  is disposed such that the optical axis  17   a  of the quarter-wave plate  17  is at 45° with respect to the axis of polarization of the polarizer  109 A. The polarized light in the 0° direction which polarized light is incident on the quarter-wave plate  17  is thereby emitted from the quarter-wave plate  17  as circularly polarized light ( FIG. 19 ). The polarized light in the 90° direction which polarized light is incident on the quarter-wave plate  17  is similarly emitted from the quarter-wave plate  17  as circularly polarized light ( FIG. 20 ). Thus, the respective pieces of polarized light in the 0° direction and the 90° direction which pieces of polarized light are incident on the quarter-wave plate  17  both become circularly polarized light (however, the directions of rotation of the pieces of polarized light are opposite from each other). 
     Then, only polarized light coinciding with the axis of polarization of the polarizer  109 A, which polarized light is included in the circularly polarized light emitted from the quarter-wave plate  17 , passes through the polarizer  109 A. Thus, in either of the case where the light incident on the quarter-wave plate  17  is polarized light in the 0° direction and the case where the light incident on the quarter-wave plate  17  is polarized light in the 90° direction, substantially half light passes through the liquid crystal shutter  18 . That is, an image can be obtained with less polarized light limitation. Hence, similar effects to those of the foregoing first embodiment can be obtained. In addition, because the polarizer and the analyzer do not necessarily need to be divided, the liquid crystal shutter  18  can be manufactured easily as compared with the foregoing first and second embodiments. 
     The present invention has been described above by citing embodiments and examples of modification. However, the present invention is not limited to these embodiments and the like, but is susceptible of various modifications. For example, in the foregoing embodiments and the like, description has been made by taking as an example a case where sub-regions are formed by dividing two left and right regions in a liquid crystal shutter into equal parts radially or concentrically. However, the divided shapes of the sub-regions are not limited to these. For example, each region may be divided into sub-regions in the form of a lattice (in the form of a matrix), and sub-regions transmitting first polarized light and sub-regions transmitting second polarized light may be formed alternately (for example in a checkered form). In addition, the regions do not necessarily need to be “divided into equal parts.” Equal effects to those of the present embodiment can be obtained as long as each region has sub-regions that respectively transmit first polarized light and second polarized light. Further, the number of divisions is not particularly limited. The larger the number, the more easily polarization dependence is reduced. However, when the number of divisions is increased, region division is desirably performed by the electrode division described in the foregoing first embodiment. Subdivision can be performed by using various kinds of lithography or the like. On the other hand, it is difficult to increase the number of divisions of a polarizer and an analyzer from a viewpoint of processes. Thus, from the viewpoint of processes, a small number of divisions is desirable. A minimum number of divisions is four (two on each of the left and the right). 
     In addition, the directions of polarization in the respective polarized light transmitting regions in the polarizer and the analyzer in the foregoing embodiments and the like are not limited to the directions of polarization described above; various combinations can be set according to a liquid crystal layer driving mode or the like. In addition, while the first polarized light and the second polarized light have been described as pieces of polarized light whose directions of polarization are orthogonal to each other, the directions of polarization do not necessarily need to be orthogonal to each other. 
     Further, in the foregoing embodiments and the like, a case of dividing each region of a liquid crystal shutter into two kinds of sub-regions that respectively transmit the first polarized light and the second polarized light has been taken as an example. However, sub-regions may include another sub-region that selectively transmits another polarized light component. 
     In addition, while an example in which one electrode  102  of the pair of electrodes  102  and  105  in the liquid crystal shutter  12  is divided into a plurality of sub-electrodes is cited as a method of electrode division in the foregoing embodiments, the electrode  105  on the opposite side may be divided, or both electrodes may be divided. 
     In addition, the foregoing embodiments and the like have been described by taking as an example a case where switching is performed between the opening and closing of two left and right regions in a liquid crystal shutter. However, switching may be performed in two upper and lower regions. For example, when a camera  3  including an imaging device is used in a state of being tilted by 90 degrees from a horizontal position as shown in  FIG. 21(A) , switching is performed between transmission and blockage in two upper and lower regions as shown in  FIG. 21(B) . Thereby two vertically long parallax images can be obtained as shown in  FIG. 21(C) . However, in a case in which the camera  3  is thus inclined according to use conditions so that visual point images can be obtained in both of two directions orthogonal to each other, that is, a left-to-right direction (horizontal direction) and a top-to-bottom direction (vertical direction), region division in the liquid crystal shutter is made by electrode division. 
     In addition, the foregoing embodiments have been described by taking as an example a case where switching between opening and closing is performed in two regions in a liquid crystal shutter. However, the number of regions in which the switching is performed is not limited to two, but may be three or more. In this case, the plane shape of the liquid crystal shutter is desirably divided into a radial form or a lattice form, for example. Thereby, three or more parallax images can be obtained, and thus parallax images at a desired viewpoint are obtained easily. 
     Further, the foregoing embodiments have been described by taking as an example a case of using two parallax images obtained for stereoscopy. However, the two parallax images obtained can be used for another purpose. For example, when the two parallax images are subjected to stereo matching image processing, and a phase difference between the parallax images is obtained, a distance to an imaging object can be calculated on the basis of the phase difference.