Patent Publication Number: US-2016249044-A1

Title: Display device and display method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Japanese Application No. 2015-034056, filed on Feb. 24, 2015, the contents of which are incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a display device and a display method. 
     2. Description of the Related Art 
     A display device is known which displays a stereoscopic image or a multi-view image using an image separator (see Japanese Patent Application Laid-open Publication No. 2013-125042). A parallax barrier or a lenticular lens is used as the image separator. 
     In such a display device, when a relative position of the image separator and a viewer is shifted, a stereoscopic image or a multi-view image is not correctly displayed. Accordingly, the position of a viewer is fixed. As a result, plural viewers cannot view a stereoscopic image or a multi-view image at various positions. 
     SUMMARY 
     According to an aspect, a display device includes: a position information acquiring unit that acquires position information on positions of plural viewers; a separation unit that sequentially changes a position of an image separator based on the position information; an illumination unit that sequentially changes a direction of an optical axis of illumination light based on the position information in synchronization with a timing at which the position of the image separator is changed; and a display unit that modulates the illumination light and displays an image including plural viewpoint images for the plural viewers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a display device according to a first embodiment; 
         FIG. 2  is a cross-sectional view schematically illustrating a configuration of an image forming unit; 
         FIG. 3  is a cross-sectional view illustrating a configuration of a principal part of an illumination unit; 
         FIG. 4  is a schematic diagram illustrating a configuration of a light source disposed in the illumination unit; 
         FIG. 5  is a view of a light source substrate disposed in the illumination unit when viewed from the front side; 
         FIG. 6  is a diagram illustrating a relationship between lighting positions of light sources and an optical axis direction of illumination light; 
         FIG. 7  is a diagram illustrating a relationship between lighting positions of light sources and an optical axis direction of illumination light; 
         FIG. 8  is a diagram illustrating a relationship between lighting positions of light sources and an optical axis direction of illumination light; 
         FIG. 9  is a diagram illustrating a method of setting an optical axis direction and a spread angle of illumination light; 
         FIG. 10  is a diagram illustrating a method of setting an optical axis direction and a spread angle of illumination light; 
         FIG. 11  is a diagram illustrating a method of setting an optical axis direction and a spread angle of illumination light; 
         FIG. 12  is a diagram illustrating a relationship between the number of light sources turned on and a spread angle of illumination light; 
         FIG. 13  is a diagram illustrating a relationship between the number of light sources turned on and a spread angle of illumination light; 
         FIG. 14  is a diagram illustrating a relationship between the number of light sources turned on and a spread angle of illumination light; 
         FIG. 15  is a diagram illustrating a relationship between a distance between a viewer and a display unit and an optimal number of light sources turned on; 
         FIG. 16  is a diagram illustrating a display method when a display is performed in a multi-view mode; 
         FIG. 17  is a diagram illustrating a display method when a display is performed in a multi-view mode; 
         FIG. 18  is a timing chart illustrating various signals; 
         FIG. 19  is a diagram illustrating a display method when a display is performed in a multi-view mode in a display device according to a second embodiment; 
         FIG. 20  is a diagram illustrating a display method when a display is performed in a multi-view mode in the display device according to the second embodiment; 
         FIG. 21  is a timing chart illustrating various signals; 
         FIG. 22  is a diagram illustrating a display method when a display is performed in a multi-view mode in a display device according to a third embodiment; 
         FIG. 23  is a diagram illustrating a display method when a display is performed in a multi-view mode in the display device according to the third embodiment; 
         FIG. 24  is a timing chart illustrating various signals; 
         FIG. 25  is a diagram illustrating an example of a shape of image areas and shutter areas; and 
         FIG. 26  is a diagram illustrating an example of a shape of image areas and shutter areas. 
     
    
    
     DETAILED DESCRIPTION 
     Modes (embodiments) for carrying out the invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to details described in the following embodiments. Elements described below include elements which can be easily thought out by those skilled in the art and elements substantially identical thereto. Elements described below can be appropriately combined. This disclosure is merely an example, and appropriate modifications without departing from the gist of the invention which can be easily thought out by those skilled in the art belong to the scope of the present invention. In order to make description more clear, the drawings schematically illustrate widths, thicknesses, shapes, and the like of elements unlike actual values, which are only an example and do not limit interpretation of the present invention. In this specification and the drawings, the same elements as described with reference to an existing drawing will be referenced by the same reference numerals and signs and detailed description thereof will not be repeated. 
     First Embodiment 
       FIG. 1  is a schematic view of a display device  1  according to a first embodiment. 
     The display device  1  includes an image forming unit  100 , a control unit  200 , and a detection unit  300 . 
     The image forming unit  100  includes a display unit  110 , a separation unit  120 , and an illumination unit  130 . The image forming unit  100  forms an image by causing the display unit  110  to modulate illumination light emitted from the illumination unit  130 . Plural viewers U view the image displayed on the display unit  110  via the separation unit  120 . In  FIG. 1 , two viewers (a first viewer U 1  and a second viewer U 2 ) are illustrated, but the number of viewers U is not limited to two. The image forming unit  100  has a multi-view mode in which plural viewpoint images are displayed and a single-view mode in which a single viewpoint image is displayed. When a display is performed in the multi-view mode, an image separator B is formed in the separation unit  120  and an image (a multi-view mode image) including plural viewpoint images for plural viewers U (a first viewpoint image P 1  for the first viewer U 1  and a second viewpoint image P 2  for the second viewer U 2 ) is displayed on the display unit  110 . When a display is performed in the single-view mode, an image separator B is not formed in the separation unit  120  and an image (a single-view mode image) including only a single viewpoint image is displayed on the display unit  110 . Details of the image forming unit  100  will be described later. 
     The control unit  200  includes a display control unit  210 , a separator control unit  220 , and an illumination control unit  230 . The display control unit  210  controls the display unit  110  so as to display a multi-view mode image or a single-view mode image on the display unit  110 . The separator control unit  220  controls the separation unit  120  so as to form an image separator B in the separation unit  120  in the multi-view mode. The separator control unit  220  controls a position at which the image separator B is formed, a timing at which the image separator B is formed, and the like. The illumination control unit  230  controls the illumination unit  130  so as to irradiate the display unit  110  with illumination light from the illumination unit  130 . The illumination control unit  230  controls a direction of an optical axis of illumination light (a center line of illumination light), a spread angle of illumination light, a timing at which illumination light is emitted, and the like. 
     The detection unit  300  detects position information on positions of plural viewers U and supplies the position information to a position information acquiring unit  240 . The position information acquiring unit  240  is, for example, a connector which is electrically coupled to the control unit  200 . The detection unit  300  includes an imaging unit  310  that images plural viewers U and an image analyzing unit  320  that analyzes an image of plural viewers U captured by the imaging unit  310  and detects the position information. The position information acquiring unit  240  acquires the position information on the positions of the plural viewers U from the image analyzing unit  320 . 
     The control unit  200  controls the display unit  110 , the separation unit  120 , and the illumination unit  130  based on the position information of the plural viewers U. When a display is performed in the multi-view mode, the separation unit  120  sequentially changes the position of the image separator B based on the position information. The illumination unit  130  sequentially changes the direction of the optical axis of illumination light based on the position information in synchronization with the timing at which the position of the image separator B is changed. The display unit  110  modulates illumination light and displays an image (multi-view mode image) including plural viewpoint images for the plural viewers U. When a display is performed in the single-view mode, the separation unit  120  does not form the image separator B and the illumination unit  130  sequentially changes the direction of the optical axis of illumination light based on the position information. The display unit  110  modulates the illumination light and displays a single-view mode image. 
       FIG. 2  is a cross-sectional view schematically illustrating a configuration of the image forming unit  100 . 
     The image forming unit  100  includes the display unit  110 , the separation unit  120 , and the illumination unit  130 . In the following description, configurations of elements will be described based on definitions that a side on which a viewer U views an image is defined as a “front side” and a side opposite to the side on which a viewer U views an image is defined as a “rear side”. 
     The display unit  110  includes a first substrate  111 , a second substrate  112 , a liquid crystal layer  113 , a first polarizing plate  114 , and a second polarizing plate  115 . Illumination light emitted from the illumination unit  130  is transmitted by the second polarizing plate  115 , is incident on the liquid crystal layer  113 , and is modulated by the liquid crystal layer  113 . The illumination light modulated by the liquid crystal layer  113  is transmitted by the first polarizing plate  114  and is displayed as an image. The display mode of the display unit  110  is not particularly limited, and known display modes such as an electrically controlled birefringence (ECB) mode and a twisted nematic (TN) mode are employed. A vertical electric field mode using a vertical (the thickness direction of the liquid crystal layer  113 ) electric field such as a vertical alignment (VA) mode or a horizontal electric field mode using a horizontal (the direction perpendicular to the thickness direction of the liquid crystal layer  113 ) electric field such as an in-plane switching (IPS) mode can be employed as an ECB mode. 
     The display unit  110  is provided with plural pixels arranged in a matrix shape. One pixel includes plural subpixels displaying different colors. A combination of colors which is displayed by plural subpixels is arbitrary. For example, one pixel may include three subpixels displaying three colors of red, green, and blue. One pixel may include three subpixels displaying three colors of cyan, yellow, and magenta. In order to enlarge a color gamut, one pixel may include four or more subpixels. 
     When a display is performed in the single-view mode, a single-view mode image is displayed on the display unit  110  by plural pixels. When a display is performed in the multi-view mode, a multi-view mode image including plural viewpoint images is displayed on the display unit  110  by plural pixels. When a display is performed in the multi-view mode, plural image areas  116  corresponding to the plural viewpoint images are alternately arranged in one direction on the display unit  110 . 
     The plural image areas  116  may be formed in a stripe shape along one side of a rectangular pixel, or may be formed in a step shape or a delta shape along two sides of a rectangular pixel. For example,  FIG. 25  illustrates an example in which the plural image areas  116  (first viewpoint image areas  116 P 1  and second viewpoint image areas  116 P 2 ) are formed in a stripe shape along one side of a rectangular pixel or subpixel PX, and  FIG. 26  illustrates an example in which the plural image areas  116  are formed in a step shape along two sides of a rectangular pixel or subpixel PX. When the image areas  116  are formed in a stripe shape, each image area  116  has a length direction which is a direction parallel to one side of a pixel. When the image areas  116  are formed in a step shape or a delta shape, each image area  116  has a length direction which is a direction (a direction in which the step shape or the delta shape are continuously arranged in a direction intersecting one side of a pixel) obliquely intersecting one side of a pixel. The plural image areas  116  are alternately arranged in one direction perpendicular to the length direction of the image area  116 . 
     Each of the plural image areas  116  is formed by plural pixels or plural subpixels which are arranged in a stripe shape, step shape, or delta shape. For example, in  FIG. 2 , plural first viewpoint image areas  116 P 1  and plural second viewpoint image areas  116 P 2  are alternately arranged in one direction. A first viewpoint image P 1  is displayed by the plural first viewpoint image areas  116 P 1 R and a second viewpoint image P 2  is displayed by the plural second viewpoint image areas  116 P 2 . 
     The separation unit  120  is disposed on the front side of the display unit  110  with an adhesive layer  125  interposed therebetween. The separation unit  120  includes a first substrate  121 , a second substrate  122 , a liquid crystal layer  123 , the first polarizing plate  114 , and a third polarizing plate  124 . The first polarizing plate  114  is also used as the first polarizing plate  114  of the display unit  110 . Illumination light passing through the first polarizing plate  114  is modulated by the liquid crystal layer  123 . The illumination light modulated by the liquid crystal layer  123  is transmitted by the third polarizing plate  124  and is observed by a viewer. The display mode of the separation unit  120  is not particularly limited, and known display modes such as an ECB mode and a TN mode are employed. A vertical electric field mode such as a VA mode or a horizontal electric field mode such as an IPS mode can be employed as an ECB mode. 
     The separation unit  120  includes plural shutter areas  126  of which light transmittance can be controlled. The transmittance of each of the plural shutter areas  126  is controlled based on a separator control signal input to the separation unit  120 . A voltage applied to the liquid crystal layer  123  of each of the shutter areas  126  is controlled based on the separator control signal and thus a degree of modulation of the liquid crystal layer  123  of each of the plural shutter areas  126  is controlled. 
     For example, each of the plural shutter areas  126  is controlled to one of an ON state in which a voltage is applied to the liquid crystal layer  123  and an OFF state in which a voltage is not applied to the liquid crystal layer  123  based on the separator control signal. When the shutter area  126  is in the ON state, the polarization direction of illumination light incident on the shutter area  126  is adjusted to a direction in which the illumination light is absorbed by the third polarizing plate  124 . Accordingly, the transmittance of the shutter area  126  decreases. When the shutter area  126  is in the OFF state, the polarization direction of illumination light incident on the shutter area  126  is adjusted to a direction in which the illumination light is transmitted by the third polarizing plate  124 . Accordingly, the transmittance of the shutter area  126  increases. 
     As illustrated in  FIG. 2 , when a display is performed in the multi-view mode, the separation unit  120  decreases the transmittance of the shutter areas  126 S located at positions at which the image separator B should be formed among the plural shutter areas  126 . Accordingly, the image separator B as a parallax barrier is formed. The image separator B is formed by the shutter areas  126 S of which the transmittance has decreased. The shutter areas  126 P located at positions at which the image separator B is not formed have high transmittance. When a display is performed in the single-view mode, the transmittance of all the shutter areas  126  is kept high. By electrically controlling the transmittance of the plural shutter areas  126 , the position of the image separator B is controlled at a high speed and with high precision. Accordingly, the position of the image separator B can be switched at a high speed depending on the positions of the viewers U. 
     The shape of the shutter areas  126  is arbitrary. In the separation unit  120 , plural rectangular shutter areas  126  may be arranged in a matrix shape. In the separation unit  120 , plural shutter areas  126  having a stripe shape, a step shape, or delta shape corresponding to the shape of the image areas  116  may be arranged in one direction or in two directions. For example,  FIG. 25  illustrates an example in which the plural shutter areas  126  (shutter areas  126 S and shutter areas  126 P) are formed in a stripe shape in parallel to the length direction of the plural image areas  116 , and  FIG. 26  illustrates an example in which the plural shutter areas  126  are formed in a step shape along the length direction (the direction obliquely intersecting one side of a pixel or subpixel PX) of the plural image areas  116 . The pitch of the shutter areas  126  in the arrangement direction of the image areas  116  (the direction perpendicular to the length direction of the image areas  116 ) is preferably smaller than the pitch of the image areas  116 . Accordingly, the position of the image separator B can be finely adjusted depending on the position of a viewer U. 
     The illumination unit  130  is disposed on the rear side of the display unit  110 . The illumination unit  130  illuminates the display unit  110  from the rear side. Illumination light emitted from the illumination unit  130  is transmitted by the display unit  110  and the separation unit  120  and is observed by plural viewers U. The illumination light transmitted by the display unit  110  is displayed as an image. When a display is performed in the multi-view mode, the illumination light transmitted by the display unit  110  is displayed as an image including plural viewpoint images (first viewpoint images P 1  and second viewpoint images P 2 ). The viewpoint images included in the image are separated by the image separator B formed in the separation unit  120  and are incident on the viewers U, respectively. Accordingly, plural viewpoint images are observed by the corresponding viewers U. 
       FIG. 3  is a cross-sectional view illustrating the configuration of a principal part of the illumination unit  130 .  FIG. 4  is a diagram schematically illustrating the configuration of a light source  145  disposed in the illumination unit  130 .  FIG. 5  is a view of a light source substrate  140  disposed in the illumination unit  130  when viewed from the front side. 
     As illustrated in  FIG. 3 , the illumination unit  130  includes the light source substrate  140  and a light adjustment substrate  150 . The light source substrate  140  and the light adjustment substrate  150  are disposed to face the second polarizing plate  115  (see  FIG. 2 ) of the display unit  110 . The light adjustment substrate  150  and the light source substrate  140  are arranged in this order from the display unit  110  side. 
     The light source substrate  140  includes a substrate  141  and plural light sources  145  arranged on the substrate  141 . As illustrated in  FIG. 4 , each light source  145  is, for example, an organic EL element in which a positive electrode  142 , an organic light-emitting layer  143 , and a negative electrode  144  are sequentially stacked from the substrate  141  side. If necessary, a hole injection layer and a hole transport layer are disposed between the organic light-emitting layer  143  and the positive electrode  142 . If necessary, an electron injection layer and an electron transport layer are disposed between the organic light-emitting layer  143  and the negative electrode  144 . 
     As illustrated in  FIG. 5 , the light sources  145  are formed in a stripe shape. Each light source  145  extends in parallel to the length direction of the image area  116  (see  FIG. 2 ). The light sources  145  are arranged in a direction parallel to the arrangement direction of the image areas  116 . Plural wirings  147  extending in the direction intersecting the light sources  145  are disposed on one end side of the light sources  145 . In  FIG. 5 , the number of wirings  147  is six, but the number of wirings  147  is not limited to six. 
     Every six light sources  145  are electrically coupled to the same wiring  147 . Accordingly, the light sources  145  are grouped into six groups. The light sources  145  included in each group are simultaneously driven by the same wiring  147 . Six neighboring light sources  145  are electrically coupled to different wirings  147  and driving thereof is independently controlled. The light sources  145  having the same relative position in each light adjustment set among the light sources  145  disposed in the illumination unit  130  are electrically coupled by the common wiring  147  and are subjected to the same control by the control unit  200 . The six neighboring light sources  145  constitute one light source group  146 . On the substrate  141 , plural light source groups  146  are arranged in the arrangement direction of the light sources  145 . 
     The number of light sources  145  included in each light source group  146  can be increased or decreased depending on the number of wirings  147 . When the number of wirings  147  is n (where n is an integer equal to or greater than  2 ), every n light sources  145  are electrically coupled to the same wiring  147 . Accordingly, the light sources  145  are grouped into n groups. The light sources  145  included in each group are simultaneously driven by the same wiring  147 . The n neighboring light sources  145  are electrically coupled to different wirings  147  and driving thereof is independently controlled. The n neighboring light sources  145  constitute one light source group  146 . 
     When the wirings  147  are distinguished from each other, numerals are added to heads of names of the wirings  147  and the numerals are also added to tails of reference signs thereof. When the light sources  145  which are independently driven by the wirings  147  are distinguished from each other, numerals are added to heads of names of the light sources  145  and the numerals are also added to tails of reference signs thereof. 
     As illustrated in  FIG. 3 , the light adjustment substrate  150  includes a substrate  151  and plural light adjustment layers  152  disposed on the substrate  151 . The light adjustment layers  152  extend in parallel to the length direction of the light sources  145 . The light adjustment layers  152  are disposed in one-to-one correspondence with the light source groups  146 . The light adjustment layers  152  are disposed to face the light sources  145  included in the corresponding light source groups  146  and adjust light L 1  emitted from the light sources  145  such that the optical axes thereof have different directions. One light adjustment set is constituted by one light adjustment layer  152  and plural light sources  145  facing the light adjustment layer  152 . The illumination unit  130  includes plural light adjustment sets which are arranged in a direction parallel to the arrangement direction of the image areas  116 . For example, the light adjustment layer  152  is a lens in which a cross-section parallel to the arrangement direction of the light sources  145  is convex to the display unit  110 . 
       FIG. 3  illustrates an example in which each light adjustment layer  152  is formed of a plano-convex lens, but the lens only has to change the direction of transmitted light depending on the positions of the light sources. One of a plano-convex lens and a Fresnel lens may be used as the lens. That is, the light adjustment layer  152  may be a spherical lens having a spherical surface such as a plano-convex lens or may be an aspherical lens having an aspherical surface such as a Fresnel lens. 
     The illumination unit  130  irradiates the display unit  110  with light L 1  emitted from one or more light sources  145  turned on in each light source group  146  as illumination light L 2 . The illumination unit  130  sequentially changes the lighting position of the light sources  145  based on the position information of the viewers in synchronization with the timing at which the position of the image separator B (see  FIG. 2 ) is changed. 
       FIGS. 6 to 8  are diagrams illustrating a relationship between the lighting positions of the light sources  145  and the direction of the optical axis AX of illumination light L 2 . 
     As illustrated in  FIG. 6 , when a first light source  145 - 1  disposed to face the left end of the light adjustment layer  152  is turned on, light L 1  emitted from the first light source  145 - 1  is converted into illumination light L 2  having an optical axis AX in a direction greatly inclined to the right side by the light adjustment layer  152 . The illumination light L 2  is incident on the display unit at a large angle θa to a normal direction of the display unit or the separation unit. The illumination light L 2  is efficiently emitted to a viewer who views an image from the right side. 
     As illustrated in  FIG. 7 , when a fourth light source  145 - 4  disposed to face the center of the light adjustment layer  152  is turned on, light L 1  emitted from the fourth light source  145 - 4  is converted into illumination light L 2  having an optical axis AX in a direction slightly inclined to the left side by the light adjustment layer  152 . The illumination light L 2  is incident on the display unit at a small angle θb to a normal direction of the display unit or the separation unit. The illumination light L 2  is efficiently emitted to a viewer who views an image from the center or a slightly left side. 
     As illustrated in  FIG. 8 , when a sixth light source  145 - 6  disposed to face the right end of the light adjustment layer  152  is turned on, light L 1  emitted from the sixth light source  145 - 6  is converted into illumination light L 2  having an optical axis AX in a direction greatly inclined to the left side by the light adjustment layer  152 . The illumination light L 2  is incident on the display unit at a large angle θc to a normal direction of the display unit or the separation unit. The illumination light L 2  is efficiently emitted to a viewer who views an image from the left side. 
       FIGS. 9 to 11  are diagrams illustrating a method of setting the direction of the optical axis AX of illumination light L 2  and the spread angle Θ of the illumination light L 2 . In  FIGS. 9 to 11 , the separation unit and the like are not illustrated. 
     As illustrated in  FIG. 9 , the direction of the optical axis AX of illumination light L 2  is controlled based on the position of a viewer U. The illumination unit  130  emits illumination light L 2  in a direction in which a viewer U views an image on the display unit  110 . The detection unit  300  illustrated in  FIG. 1  detects, for example, an angle (hereinafter, referred to as an “observation angle”) α at which a viewer U views the display unit  110 . The observation angle α is, for example, an angle which is formed by a virtual line TL connecting a reference position SP set on a display surface  110   a  of the display unit  110  to a viewer U and a normal line NL of the display surface  110   a . The illumination unit  130  sets the direction of the optical axis AX of illumination light L 2 , for example, such that an incidence angle θ of the illumination light L 2  incident on the display unit  110  is equal to the observation angle α. The position set as the reference position SP is arbitrary. For example, the reference position SP is set to the center of the display surface  110   a , but the position set as the reference position SP is not limited to this example. 
     The spread angle e of illumination light L 2  is controlled based on a distance VR between the viewer U and the display unit  110  (the position information of a viewer U). The distance VR may be a distance D between the viewer U and the reference position SP or may be a distance H between the viewer U and the reference position SP in a direction parallel to the normal line NL of the display surface  110   a . When the distance VR is large, the illumination unit  130  sets the spread angle Θ of the illumination light L 2  to be small. When the distance VR is small, the illumination unit  130  sets the spread angle Θ of the illumination light L 2  to be large. 
     For example, as illustrated in  FIG. 10 , when the distance VR 1  increases, an angle (hereinafter, referred to as an “interocular angle”) EA 1  which is formed by the direction in which the right eye of a viewer U views an image and the direction in which the left eye of the viewer U views the image decreases. Accordingly, the spread angle Θa of the illumination light L 2  can be set to decrease similarly to the interocular angle EA 1 . When the spread angle Θa of the illumination light L 2  is excessively larger than the interocular angle EA 1 , an amount of light emitted to a position which is not viewed by the viewer U increases. Accordingly, the spread angle Θa of the illumination light L 2  is set to the same magnitude as the interocular angle EA 1 . 
     For example, as illustrated in  FIG. 11 , when the distance VR 2  decreases, the interocular angle EA 2  increases. Accordingly, the spread angle Θb of the illumination light L 2  needs to increase similarly to the interocular angle EA 2 . When the spread angle Θb of the illumination light L 2  is excessively larger than the interocular angle EA 2 , an amount of light emitted to a position which is not viewed by the viewer U increases. Accordingly, the spread angle Θb of the illumination light L 2  is set to the same magnitude as the interocular angle EA 2 . 
     The spread angle Θ of the illumination light L 2  can be controlled by controlling the number of light sources  145  turned on in each light source group  146  (see  FIG. 3 ). The illumination unit  130  changes the number of light sources  145  turned on based on the distance VR between the viewer U and the display unit  110 . 
       FIGS. 12 to 14  are diagrams illustrating a relationship between the number of light sources  145  turned on and the spread angle of illumination light. In  FIGS. 12 to 14 , the horizontal axis represents an irradiation angle DA of illumination light and the vertical axis represents brightness BR of illumination light. In  FIGS. 12 to 14 , the number of light sources  145  constituting one light source group  146  is 10. Hereinafter, when the ten light sources  145  are distinguished from each other, numerals are added to heads of names of the light sources  145  and the numerals are also added to tails of reference signs thereof. 
     As illustrated in  FIG. 12 , the optical axes of ten illumination light components which are obtained when the ten light sources  145  are independently turned on are different from each other by 4°. The angle distribution of the illumination light components is a Gaussian distribution. The spread angle of each illumination light component is 8° and each illumination light component is emitted to a range of about 8° with respect to the optical axis thereof. Accordingly, by increasing the number of light sources  145  turned on, the spread angle of the illumination light can be increased. By changing the lighting positions of the light sources  145 , it is possible to change the direction of the optical axis of the illumination light (incidence angle on the display unit). 
     For example, as illustrated in  FIG. 13 , when two light sources  145  (the fifth light source  145 - 5  and the sixth light source  145 - 6 ) located at the center of the light source group are simultaneously turned on, the spread angle of the illumination light is 12° and the incidence angle of the illumination light on the display unit is 0°. As illustrated in  FIG. 14 , when four light sources  145  (the fourth light source  145 - 4 , the fifth light source  145 - 5 , the sixth light source  145 - 6 , and the seventh light source  145 - 7 ) located at the center of the light source group are simultaneously turned on, the spread angle of the illumination light is 20° and the incidence angle of the illumination light on the display unit is 0°. 
       FIG. 15  is a diagram illustrating a relation between the distance VR between a viewer and the display unit and the optimal number N of light sources turned on. In  FIG. 15 , the horizontal axis represents the distance VR, the right vertical axis represents the optimal number N of light sources turned on, and the left vertical axis represents the interocular angle EA. 
     As illustrated in  FIG. 15 , the optimal number N of light sources turned on increases as the distance VR decreases. For example, when the distance VR is equal to or less than 30 cm, the interocular angle EA is equal to or more than 12° and the optimal number N of light sources turned on is 8. When the distance VR is equal to or less than 46 cm, the interocular angle EA is equal to or more than 8° and the optimal number N of light sources turned on is 6. When the distance VR is equal to or less than 92 cm, the interocular angle EA is equal to or more than 4° and the optimal number N of light sources turned on is 4. Accordingly, in comparison with a case in which ten light sources are always turned on, the power consumption decreases by 20% when the distance VR is equal to or less than 30 cm, the power consumption decreases by 40% when the distance VR is equal to or less than 46 cm, and the power consumption decreases by 60% when the distance VR is equal to or less than 92 cm. 
     In this case, the display becomes brighter as the viewer becomes closer to the display unit and the display becomes darker as the viewer becomes farther from the display unit. Accordingly, the illumination unit  130  may change the brightness of the light sources  145  to be turned on based on the distance VR between the viewer and the display unit. For example, when the brightness of the light source to be turned on becomes less as the distance VR becomes less, a large variation of the brightness depending on the distance VR is suppressed. 
       FIGS. 16 and 17  are diagrams illustrating a display method when a display is performed in the multi-view mode.  FIG. 18  is a timing chart illustrating various signals when a display is performed in the multi-view mode. In  FIG. 18 , sign PDS represents a signal on the position information of a viewer which is supplied to the control unit  200  by the image analyzing unit  320  illustrated in  FIG. 1 , sign BDS represents the separator control signal which is supplied to the separation unit  120  by the separator control unit  220 , sign TR represents the transmittance of a specific shutter area  126 - 1  (see  FIGS. 16 and 17 ) disposed in the separation unit  120 , and sign LDS represents the illumination control signal which is supplied to the illumination unit  130  by the illumination control unit  230 . In  FIG. 18 , the horizontal axis represents the time. 
     The operations of the control unit  200  and the detection unit  300  will be described below with reference to  FIGS. 1, 2, and 18 . 
     The image analyzing unit  320  supplies a signal PDS on the position information of plural viewers U to the control unit  200  every predetermined time. The position information acquiring unit  240  acquires the position information on the positions of the viewers U every predetermined time (position information acquiring step). The position information acquired by the position information acquiring unit  240  is supplied to the control unit  200 . The timing at which the signal PDS is supplied to the control unit  200  matches the timing at which the viewer U is switched. For example, when an image of 60 Hz is displayed for two viewers U, the frequency of the signal PDS is 120 Hz. For example, the position information acquiring unit acquires first position information corresponding to a first viewer U 1  and second position information corresponding to a second viewer U 2 . The signal PDS on the position information of the first viewer U 1  and the signal PDS on the position information of the second viewer U 2  are alternately supplied to the control unit  200 . 
     The separator control unit  220  supplies the separator control signal BDS to the separation unit  120  in synchronization with the timing at which the signal PDS is supplied. The transmittance of the shutter areas  126  disposed in the separation unit  120  is controlled based on the position information of the viewers U in accordance with the separator control signal BDS. Accordingly, the separation unit  120  sequentially changes the position of the image separator B based on the position information of the viewers U (separator control step). For example, the separation unit  120  changes the position of the image separator B based on the first position information at a first timing and changes the position of the image separator B based on the second position information at a second timing. 
     The illumination control unit  230  supplies the illumination control signal LDS to the illumination unit  130  in synchronization with the timing at which the signal PDS is supplied. The lighting positions of the light sources  145  disposed in the illumination unit  130  are controlled based on the position information of the viewers U in accordance with the illumination control signal LDS. For example, the illumination unit  130  irradiates the display unit  110  with the illumination light L 2  after the changing of the transmittance TR of the shutter areas  126  located at the positions at which the image separator B should be formed is completed. Accordingly, the illumination unit  130  sequentially changes the direction of the optical axis AX of the illumination light L 2  based on the position information of the viewers U in synchronization with the timing at which the position of the image separator B is changed (illumination control step). For example, the illumination unit  130  changes the direction of the optical axis AX of the illumination light L 2  based on the first position information in synchronization with the timing at which the position of the image separator B is changed at the first timing, and changes the direction of the optical axis AX of the illumination light L 2  based on the second position information in synchronization with the timing at which the position of the image separator B is changed at the second timing. Here, the illumination unit  130  may change the direction of the optical axis AX of the illumination light L 2  by switching the light sources  145  in a state in which the illumination light L 2  is emitted. 
     The display unit  110  modulates the illumination light L 2  and displays an image including plural viewpoint images for plural viewers U (display step). In this embodiment, since two viewers (a first viewer U 1  and a second viewer U 2 ) view the display unit  110 , an image including the first viewpoint image P 1  for the first viewer U 1  and the second viewpoint image P 2  for the second viewer U 2  is displayed on the display unit  110 . When three or more viewers U view the display unit  110 , an image including three or more viewpoint images is displayed on the display unit  110 . 
     The operations of the separation unit  120  and the illumination unit  130  will be described below with reference to  FIGS. 16 and 17 . The times t illustrated in  FIGS. 16 and 17  correspond to time t illustrated in  FIG. 18 . 
     As illustrated in  FIG. 16 , when time t is t 1 , the first viewer U 1  views the first viewpoint image P 1  displayed on the display unit  110  from a first position. The first position is a position which is shifted in a first direction D 1  (for example, the rightward direction in  FIG. 16 ) in the arrangement direction of the light sources  145  from the position facing the reference position SP. The observation angle of the first viewer U 1  is α. 
     The separation unit  120  increases the transmittance of two shutter areas  126  (the shutter area  126 - 2  and the shutter area  126 - 3 ) located in the first direction D 1  side from the boundary between the first viewpoint image P 1  and the second viewpoint image P 2  and decreases the transmittance of the shutter areas  126  adjacent to the two shutter areas  126 , such that the first viewer U 1  can appropriately view the first viewpoint image P 1 . The image separator B is formed by the shutter areas  126  of which transmittance is decreased. 
     The illumination unit  130  turns on the light source  145 - 1  located at the left end of the light source group  146  and causes the illumination light L 2  to be obliquely incident on the display unit  110  at an incidence angle θ 1  so as to apply the illumination light L 2  to the first viewer U 1 . The illumination unit  130  changes the number of light sources  145  turned on based on the distance between the first viewer U 1  and the display unit  110  and controls the spread angle Θ 1  of the illumination light L 2 . 
     As illustrated in  FIG. 17 , when time t is t 2 , the second viewer U 2  views the second viewpoint image P 2  displayed on the display unit  110  from a second position. The second position is a position which is shifted in a second direction D 2  (for example, the leftward direction in  FIG. 17 ) in the arrangement direction of the light sources  145  from the position facing the reference position SP. The observation angle of the second viewer U 2  is β. 
     The separation unit  120  increases the transmittance of two shutter areas  126  (the shutter area  126 - 1  and the shutter area  126 - 4 ) located in the second direction D 2  side from the boundary between the first viewpoint image P 1  and the second viewpoint image P 2  and decreases the transmittance of the shutter areas  126  adjacent to the two shutter areas  126 , such that the second viewer U 2  can appropriately view the second viewpoint image P 2 . The image separator B is formed by the shutter areas  126  of which transmittance is decreased. 
     The illumination unit  130  changes the direction of the optical axis AX of the illumination light L 2  from the first viewer U 1  to the second viewer U 2 . The illumination unit  130  moves the lighting positions of the light sources  145  in a direction directed from the second position to the first position when the position to which the optical axis AX of the illumination light L 2  is directed is changed from the first position to the second position, where the first position and the second position are separated from each other in the arrangement direction of the light sources  145 . 
     For example, the illumination unit  130  turns on the light source  145 - 3  located at the right end of the light source group  146  and turns off the light source  145 - 1  located at the left end and turned on already. Accordingly, the illumination unit  130  causes the illumination light L 2  to be obliquely incident on the display unit  110  at an incidence angle θ 2  to correspond to the observation angle β of the second viewer U 2 . The illumination unit  130  changes the number of light sources  145  turned on based on the distance between the second viewer U 2  and the display unit  110  and controls the spread angle Θ 2  of the illumination light L 2 . As illustrated in  FIG. 18 , the transmittance of the shutter areas  126  is slowly changed. Accordingly, the illumination unit  130  irradiates the display unit  110  with the illumination light L 2  after the changing of the transmittance of the shutter area  126 - 1  and the shutter area  126 - 4  is completed. 
     As described above, in the display device  1  according to this embodiment, the position of the image separator B, the direction of the optical axis AX of the illumination light L 2 , and the spread angle Θ of the illumination light L 2  are changed based on the positions of the viewers U. Accordingly, plural viewers U can view a multi-view image at various positions. 
     Second Embodiment 
       FIGS. 19 and 20  are schematic views of a display device  2  according to a second embodiment of the present invention. 
     This embodiment is different from the first embodiment, in that the image forming unit  100  has a 3D multi-view mode in which a stereoscopic image is displayed for plural viewers U. The image forming unit  100 , the detection unit  300  (see  FIG. 1 ), and the control unit  200  (see  FIG. 1 ) have the same configurations as in the first embodiment. The method of controlling the image forming unit  100  using the control unit  200  is different from that in the first embodiment. Accordingly, the difference from the first embodiment will be described in priority below. In this embodiment, the elements common to the first embodiment will be referenced by the same reference numerals and signs and detailed description thereof will not be repeated. If necessary, the drawings used to describe the first embodiment will also be used. 
     The image forming unit  100  has a 3D multi-view mode in which a stereoscopic image is displayed for plural viewers U and a 2D multi-view mode in which a two-dimensional image is displayed for plural viewers U. When a display is performed in the 3D multi-view mode, plural viewpoint images including plural parallax images are displayed on the display unit  110 . When a display is performed in the 2D multi-view mode, plural viewpoint images not including parallax images are displayed on the display unit  110 . The 2D multi-view mode is the same as the multi-view mode described in the first embodiment. Accordingly, the 3D multi-view mode will be described below. 
     For example,  FIGS. 19 and 20  illustrate an example in which the display unit  110  is viewed by two viewers U (a first viewer U 1  and a second viewer U 2 ). In this example, in the display unit  110 , a first viewpoint image P 1  including a first right-eye image P 1 R and a first left-eye image P 1 L and a second viewpoint image P 2  including a second right-eye image P 2 R and a second left-eye image P 2 L are displayed on the same screen. When the number of viewers U is three or more, the number of viewpoint images displayed on the display unit  110  is three or more. The first right-eye image P 1 R is formed by image areas  116 P 1 R, the first left-eye image P 1 L is formed by image areas  116 P 1 L, the second right-eye image P 2 R is formed by image areas  116 P 2 R, and the second left-eye image P 2 L is formed by image areas  116 P 2 L. 
       FIG. 21  is a timing chart illustrating various signals when a display is performed in the multi-view mode. In  FIG. 21 , sign TR represents the transmittance of a specific shutter area  126 - 3  (see  FIG. 20 ) disposed in the separation unit  120 . The operations of the control unit  200  and the detection unit  300  will be described below with reference to  FIGS. 1, 19, 20, and 21 . 
     The image analyzing unit  320  supplies a signal PDS on the position information of plural viewers U to the control unit  200  every predetermined time. The position information acquiring unit  240  acquires the position information on the positions of the viewers U every predetermined time (position information acquiring step). The position information acquired by the position information acquiring unit  240  is supplied to the control unit  200 . For example, the frequency of the signal PDS is 120 Hz. The signal PDS on the position information of the first viewer U 1  and the signal PDS on the position information of the second viewer U 2  are simultaneously supplied to the control unit  200 . 
     The separator control unit  220  supplies the separator control signal BDS to the separation unit  120  in synchronization with the timing at which the signal PDS is supplied. The transmittance of the shutter areas  126  disposed in the separation unit  120  is controlled based on the position information of the viewers U in accordance with the separator control signal BDS. Accordingly, the separation unit  120  sequentially changes the position of the image separator B based on the position information of the viewers U (separator control step). 
     The illumination control unit  230  supplies the illumination control signal LDS to the illumination unit  130  in synchronization with the timing at which the signal PDS is supplied. The lighting positions of the light sources  145  disposed in the illumination unit  130  are controlled based on the position information of the viewers U in accordance with the illumination control signal LDS. For example, the illumination unit  130  irradiates the display unit  110  with the illumination light L 2  after the changing of the transmittance TR of the shutter areas  126  located at the positions at which the image separator B should be formed is completed. Accordingly, the illumination unit  130  sequentially changes the direction of the optical axis AX of the illumination light L 2  based on the position information of the viewers U in synchronization with the timing at which the position of the image separator B is changed (illumination control step). Here, the illumination unit  130  may change the direction of the optical axis AX of the illumination light L 2  by switching the light sources  145  in a state in which the illumination light L 2  is emitted. 
     The display unit  110  modulates the illumination light L 2  and displays an image (3D multi-view mode image) including plural viewpoint images for plural viewers U (display step). In this embodiment, since two viewers (a first viewer U 1  and a second viewer U 2 ) view the display unit  110 , an image including the first viewpoint image P 1  for the first viewer U 1  and the second viewpoint image P 2  for the second viewer U 2  is displayed on the display unit  110 . When three or more viewers U view the display unit  110 , an image including three or more viewpoint images is displayed on the display unit  110 . 
     The operations of the separation unit  120  and the illumination unit  130  will be described below with reference to  FIGS. 19 and 20 . The times t illustrated in  FIGS. 19 and 20  correspond to time t illustrated in  FIG. 21 . 
     As illustrated in  FIG. 19 , when time t is t 1 , the first viewer U 1  views the first viewpoint image P 1  displayed on the display unit  110  from a first position. The first position is a position which is shifted in a first direction D 1  (for example, the rightward direction in  FIG. 19 ) in the arrangement direction of the light sources  145  from the position facing the reference position SP. The observation angle of the first viewer U 1  is α. 
     The separation unit  120  increases the transmittance of two shutter areas  126  (the shutter area  126 - 1  and the shutter area  126 - 2 ) located in the first direction D 1  side from the boundary between the first right-eye image P 1 R and the first left-eye image P 1 L and decreases the transmittance of the shutter areas  126  adjacent to the two shutter areas  126 , such that the first viewer U 1  can appropriately view the first right-eye image P 1 R and the first left-eye image P 1 L included in the first viewpoint image P 1 . The image separator B is formed by the shutter areas  126  of which transmittance is decreased. 
     The illumination unit  130  turns on the light source  145 - 1  located at the left end of the light source group  146  and causes the illumination light L 2  to be obliquely incident on the display unit  110  at an incidence angle θ 1  so as to apply the illumination light L 2  to the first viewer U 1 . The illumination unit  130  changes the number of light sources  145  turned on based on the distance between the first viewer U 1  and the display unit  110  and controls the spread angle Θ 1  of the illumination light L 2 . 
     As illustrated in  FIG. 20 , when time t is t 2 , the second viewer U 2  views the second viewpoint image P 2  displayed on the display unit  110  from a second position. The second position is a position which is shifted in a second direction D 2  (for example, the leftward direction in  FIG. 20 ) in the arrangement direction of the light sources  145  from the position facing the reference position SP. The observation angle of the second viewer U 2  is β. 
     The separation unit  120  increases the transmittance of two shutter areas  126  (the shutter area  126 - 3  and the shutter area  126 - 4 ) located in the second direction D 2  side from the boundary between the second right-eye image P 2 R and the second left-eye image P 2 L and decreases the transmittance of the shutter areas  126  adjacent to the two shutter areas  126 , such that the second viewer U 2  can appropriately view the second right-eye image P 2 R and the second left-eye image P 2 L included in the second viewpoint image P 2 . The image separator B is formed by the shutter areas  126  of which transmittance is decreased. 
     The illumination unit  130  changes the direction of the optical axis AX of the illumination light L 2  from the first viewer U 1  to the second viewer U 2 . The illumination unit  130  moves the lighting positions of the light sources  145  in a direction directed from the second position to the first position when the position to which the optical axis AX of the illumination light L 2  is directed is changed from the first position to the second position, where the first position and the second position are separated from each other in the arrangement direction of the light sources  145 . 
     For example, the illumination unit  130  turns on the light source  145 - 3  located at the right end of the light source group  146  and turns off the light source  145 - 1  located at the left end and turned on already. Accordingly, the illumination unit  130  causes the illumination light L 2  to be obliquely incident on the display unit  110  at an incidence angle θ 2  to correspond to the observation angle β of the second viewer U 2 . The illumination unit  130  changes the number of light sources  145  turned on based on the distance between the second viewer U 2  and the display unit  110  and controls the spread angle Θ 2  of the illumination light L 2 . As illustrated in  FIG. 21 , the transmittance of the shutter areas  126  is slowly changed. Accordingly, the illumination unit  130  irradiates the display unit  110  with the illumination light L 2  after the changing of the transmittance of the shutter area  126 - 3  and the shutter area  126 - 4  is completed. 
     As described above, in the display device  2  according to this embodiment, plural viewers U can view a stereoscopic image at various positions. 
     Third Embodiment 
       FIGS. 22 and 23  are schematic views of a display device  3  according to a third embodiment of the present invention. 
     This embodiment is different from the second embodiment, in that plural viewpoint images for plural viewers U are alternately displayed every predetermined time. The image forming unit  100 , the detection unit  300  (see  FIG. 1 ), and the control unit  200  (see  FIG. 1 ) have the same configurations as in the second embodiment. The method of controlling the image forming unit  100  using the control unit  200  is different from that in the second embodiment. Accordingly, the difference from the second embodiment will be described in priority below. In this embodiment, the elements common to the second embodiment will be referenced by the same reference numerals and signs and detailed description thereof will not be repeated. If necessary, the drawings used to describe the first embodiment will also be used. 
     The image forming unit  100  has a 3D multi-view mode in which a stereoscopic image is displayed for plural viewers U and a 2D multi-view mode in which a two-dimensional image is displayed for plural viewers U. When a display is performed in the 3D multi-view mode, plural viewpoint images including plural parallax images (right-eye images and left-eye images) are sequentially displayed on the display unit  110 . When a display is performed in the 2D multi-view mode, plural viewpoint images not including parallax images are sequentially displayed on the display unit  110 . Hereinafter, the 3D multi-view mode will be described below. 
     For example,  FIGS. 22 and 23  illustrate an example in which the display unit  110  is viewed by two viewers U (a first viewer U 1  and a second viewer U 2 ). In this example, in the display unit  110 , a first viewpoint image P 1  including a first right-eye image P 1 R and a first left-eye image P 1 L and a second viewpoint image P 2  including a second right-eye image P 2 R and a second left-eye image P 2 L are alternately displayed every predetermined time. When the number of viewers U is three or more, the number of viewpoint images alternately displayed on the display unit  110  is three or more. 
       FIG. 24  is a timing chart illustrating various signals when a display is performed in the multi-view mode. In  FIG. 24 , sign TR represents the transmittance of a specific shutter area  126 - 3  (see  FIGS. 22 and 23 ) disposed in the separation unit  120 . The operations of the control unit  200  and the detection unit  300  will be described below with reference to  FIGS. 1, 22, 23, and 24 . 
     The image analyzing unit  320  supplies a signal PDS on the position information of plural viewers U to the control unit  200  every predetermined time. The position information acquiring unit  240  acquires the position information on the positions of the viewers U every predetermined time (position information acquiring step). The position information acquired by the position information acquiring unit  240  is supplied to the control unit  200 . For example, the frequency of the signal PDS is 120 Hz. The signal PDS on the position information of the first viewer U 1  and the signal PDS on the position information of the second viewer U 2  are alternately supplied to the control unit  200 . 
     The separator control unit  220  supplies the separator control signal BDS to the separation unit  120  in synchronization with the timing at which the signal PDS is supplied. The transmittance of the shutter areas  126  disposed in the separation unit  120  is controlled based on the position information of the viewers U in accordance with the separator control signal BDS. Accordingly, the separation unit  120  sequentially changes the position of the image separator B based on the position information of the viewers U (separator control step). 
     The illumination control unit  230  supplies the illumination control signal LDS to the illumination unit  130  in synchronization with the timing at which the signal PDS is supplied. The lighting positions of the light sources  145  disposed in the illumination unit  130  are controlled based on the position information of the viewers U in accordance with the illumination control signal LDS. For example, the illumination unit  130  irradiates the display unit  110  with the illumination light L 2  after the changing of the transmittance TR of the shutter areas  126  located at the positions at which the image separator B should be formed is completed. Accordingly, the illumination unit  130  sequentially changes the direction of the optical axis AX of the illumination light L 2  based on the position information of the viewers U in synchronization with the timing at which the position of the image separator B is changed (illumination control step). Here, the illumination unit  130  may change the direction of the optical axis AX of the illumination light L 2  by switching the light sources  145  in a state in which the illumination light L 2  is emitted. 
     The display unit  110  modulates the illumination light L 2  and sequentially displays plural viewpoint images including plural parallax images (display step). In this embodiment, since two viewers (a first viewer U 1  and a second viewer U 2 ) view the display unit  110 , the first viewpoint image P 1  for the first viewer U 1  and the second viewpoint image P 2  for the second viewer U 2  are sequentially displayed on the display unit  110 . When three or more viewers U view the display unit  110 , three or more viewpoint images are sequentially displayed on the display unit  110 . 
     The operations of the separation unit  120  and the illumination unit  130  will be described below with reference to  FIGS. 22 and 23 . The times t illustrated in  FIGS. 22 and 23  correspond to time t illustrated in  FIG. 24 . 
     As illustrated in  FIG. 22 , when time t is t 1 , the first viewer U 1  views the first viewpoint image P 1  displayed on the display unit  110  from a first position. The first position is a position which is shifted in a first direction D 1  (for example, the rightward direction in  FIG. 22 ) in the arrangement direction of the light sources  145  from the position facing the reference position SP. The observation angle of the first viewer U 1  is α. 
     The separation unit  120  increases the transmittance of two shutter areas  126  (the shutter area  126 - 2  and the shutter area  126 - 3 ) located in the first direction D 1  side from the boundary between the first right-eye image P 1 R and the first left-eye image P 1 L and decreases the transmittance of the shutter areas  126  adjacent to the two shutter areas  126 , such that the first viewer U 1  can appropriately view the first right-eye image P 1 R and the first left-eye image P 1 L included in the first viewpoint image P 1 . The image separator B is formed by the shutter areas  126  of which transmittance is decreased. 
     The illumination unit  130  turns on the light source  145 - 1  located at the left end of the light source group  146  and causes the illumination light L 2  to be obliquely incident on the display unit  110  at an incidence angle θ 1  so as to apply the illumination light L 2  to the first viewer U 1 . The illumination unit  130  changes the number of light sources  145  turned on based on the distance between the first viewer U 1  and the display unit  110  and controls the spread angle Θ 1  of the illumination light L 2 . 
     As illustrated in  FIG. 23 , when time t is t 2 , the second viewer U 2  views the second viewpoint image P 2  displayed on the display unit  110  from a second position. The second position is a position which is shifted in a second direction D 2  (for example, the leftward direction in  FIG. 23 ) in the arrangement direction of the light sources  145  from the position facing the reference position SP. The observation angle of the second viewer U 2  is β. 
     The separation unit  120  increases the transmittance of two shutter areas  126  (the shutter area  126 - 1  and the shutter area  126 - 4 ) located in the second direction D 2  side from the boundary between the second right-eye image P 2 R and the second left-eye image P 2 L and decreases the transmittance of the shutter areas  126  adjacent to the two shutter areas  126 , such that the second viewer U 2  can appropriately view the second right-eye image P 2 R and the second left-eye image P 2 L included in the second viewpoint image P 2 . The image separator B is formed by the shutter areas  126  of which transmittance is decreased. 
     The illumination unit  130  changes the direction of the optical axis AX of the illumination light L 2  from the first viewer U 1  to the second viewer U 2 . The illumination unit  130  moves the lighting positions of the light sources  145  in a direction directed from the second position to the first position when the position to which the optical axis AX of the illumination light L 2  is directed is changed from the first position to the second position, where the first position and the second position are separated from each other in the arrangement direction of the light sources  145 . 
     For example, the illumination unit  130  turns on the light source  145 - 3  located at the right end of the light source group  146  and turns off the light source  145 - 1  located at the left end and turned on already. Accordingly, the illumination unit  130  causes the illumination light L 2  to be obliquely incident on the display unit  110  at an incidence angle  02  to correspond to the observation angle β of the second viewer U 2 . The illumination unit  130  changes the number of light sources  145  turned on based on the distance between the second viewer U 2  and the display unit  110  and controls the spread angle Θ 2  of the illumination light L 2 . As illustrated in  FIG. 24 , the transmittance of the shutter areas  126  is slowly changed. Accordingly, the illumination unit  130  irradiates the display unit  110  with the illumination light L 2  after the changing of the transmittance of the shutter area  126 - 1  and the shutter area  126 - 4  is completed. 
     As described above, in the display device  3  according to this embodiment, plural viewers U can view a stereoscopic image at various positions without greatly lowering the resolution of an image. 
     While exemplary embodiments of the present invention have been described above, the present invention is not limited to the embodiments. Details disclosed in the embodiments are merely an example and can be modified in various forms without departing from the gist of the present invention. Appropriate modifications made without departing from the gist of the present invention will belong to the technical scope of the present invention. 
     For example, in the above-mentioned embodiments, a connector is exemplified as the position information acquiring unit  240 , but the position information acquiring unit  240  is not limited to the connector. A flexible printed circuit board, an input terminal, or the like may be used as the position information acquiring unit. A liquid crystal panel is exemplified as the separation unit  120 , but the separation unit  120  is not limited to the liquid crystal panel. A light blocking plate having an opening formed therein may be used as the separation unit  120 . In this case, a moving unit that mechanically moves the light blocking plate based on the position of a viewer U is disposed in the display device  1 . A lens (refractive element) is exemplified as the light adjustment layer  152 , but the light adjustment layer  152  is not limited to the lens. A diffractive element that adjusts an optical axis using a diffraction phenomenon such as a hologram element may be used as the light adjustment layer  152 . 
     In the above-mentioned embodiment, the detection unit  300  includes the imaging unit  310  and the image analyzing unit  320 , but the configuration of the detection unit  300  is not limited to this configuration. For example, the detection unit  300  may convert a time until a reflected wave of an infrared ray or an ultrasonic wave emitted to a viewer U is received into a distance to detect the position information of the viewer U. The detection unit  300  may detect information (position information) on the relative position between the viewer U and the display unit  110  using a global positioning system (GPS). 
     In the above-mentioned embodiment, a parallax barrier is exemplified as the image separator B, but the configuration of the image separator is not limited to this configuration. The image separator B may be a lenticular lens. In this case, the separation unit  120  includes plural shutter areas  126  of which a refractive index distribution can be controlled. The separation unit  120  forms the image separator B by controlling the refractive index distribution of the plural shutter areas  126 . The image separator B includes plural lens portions serving as a convex lens (a plano-convex lens or a Fresnel lens). Each lens portion includes plural shutter areas  126 . Plural parallax images displayed on the display unit  110  are separated by the image separator B. The refractive index distribution of the shutter areas  126  is controlled based on an orientation distribution of the liquid crystal layer  123  (an electric field distribution in the liquid crystal layer  123 ). In the separation unit  120 , a refractive index distribution of a convex lens shape over plural shutter areas  126  is realized by controlling the voltage applied to the liquid crystal layer  123  of the shutter areas  126  in accordance with the separator control signal. 
     In the above-mentioned embodiment, the light source  145  is constituted by an organic EL element, but the configuration of the light source  145  is not limited to this configuration. The light source  145  may be constituted by a light emitter and a light guide member. For example, in the light source substrate  140 , plural stripe-shaped first light guide members are arranged in the arrangement area of the plural light sources  145  illustrated in  FIG. 5  and plural (six in the example illustrated in  FIG. 5 ) stripe-shaped second light guide members are arranged in the arrangement area of the plural wirings  147 . Every six first light guide members are coupled to the same second light guide member. A light emitter is disposed at an end of each of the second light guide members. The light emitters are driven independently of each other. In this configuration, the plural first light guide members are grouped into six groups. Light from the light emitters is simultaneously incident on the first light guide members included in each group via the common second light guide member and light propagating in the first light guide members is emitted to the display unit  110 . 
     In the above-mentioned embodiment, it has been exemplified that the position information on the positions of viewers U is acquired and the separation unit  120  or the illumination unit  130  is controlled based on the position information. However, the method of controlling the separation unit  120  or the illumination unit  130  is not limited to this method. 
     For example, the position information of the viewers U may be external information input from the outside via the position information acquiring unit  240  and is not limited to the information directly indicating positional coordinates of the viewers U. For example, the position information of the viewers U may be control information of the separation unit  120  or the illumination unit  130  corresponding to the positional coordinates of the viewers U. The position information of the viewers U may include position information of the image separator B. The position information of the viewers U may include information of the lighting positions of the illumination unit  130  corresponding to the position of the image separator B or information of the number of light sources turned on. 
     The position information of a viewer U is not limited to the position information of an actual viewer U acquired by analyzing an image of the viewer U. The position information of a viewer U may be position information set by an input from a viewer U. For example, even when the actual distance between a viewer U and the display unit  110  is X (cm), Y (cm) other than X (cm) may be input as the position information of the viewer U by an input from the viewer U using buttons or the like. In this case, the separation unit  120  or the illumination unit  130  may be controlled based on position information corresponding to Y (cm).