Abstract:
Lenticles of a lenticular array can be electronically controlled to be optically equivalent to either of two sets of virtual lenticles having two distinct physical characteristics. Each of the lenticles is in sufficiently close proximity to one or more switchable prisms to optically combine with therewith. The switchable optical elements can be switchable columnar prisms for example. In a first state, the switchable prisms optically combine with the lenticles such that the combination is optically equivalent to a first set of virtual lenticles. In a second, different state, the switchable prisms optically combine with the lenticles such that the combination is optically equivalent to a second, different set of virtual lenticles. Accordingly, the lenticular array can switch between two distinct configurations with the flip of a switch.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of U.S. Provisional Patent Application S/N 61/696,718 filed Sep. 4, 2012 entitled “Autostereoscopic Video Display” by Neal Weinstock and Richard A. Muller. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to autostereoscopic displays, and, more particularly, to a lenticular array that can be switched between two different configurations. 
       BACKGROUND OF THE INVENTION 
       [0003]    Conventional autostereoscopic displays use arrays of lenses or parallax barriers or other view selectors to make a number of pixels of the display visible to one eye of a viewing person and to make a number of other pixels of the display visible to the other eye of the viewing person. By isolating the pixels of the display visible to each eye, the two components of a stereoscopic image can be presented on the display. 
         [0004]    Since an ordinary viewer&#39;s eyes are side-by-side and aligned horizontally, the array of lenses makes pixels visible according to horizontal orientation. As a result, corresponding pixels for the left and right eyes are located in the same scanline and displaced from one another horizontally. 
         [0005]    Each eye of the viewer therefore sees an image whose horizontal resolution is halved in an autostereoscopic displays having only two views. In most autostereoscopic displays, field of view is improved by having more than just two views. In attempts to provide greater perceived depths of projection, many more views—e.g., 24 views—are required. A typical LCD display screen has a pixel density of about 200 pixels per inch, though some have densities approaching 300 pixels per inch or more. That&#39;s approximately 6 pixels per millimeter, i.e., sufficient resolution to provide 24 views in a 4 mm space. 
         [0006]    For some stereoscopic video content, perceived pixels that are 4 mm wide might be adequate. However, not all video content is the same. For some stereoscopic video content, it may be preferred to have fewer views but to have finer horizontal display resolution. In particular, if the display is to also sometimes display video content that is not stereoscopic, it would be preferable that the lenticular array not group views in groups that are 24 pixels and 4 mm wide but instead provide full horizontal resolution or as near to full horizontal resolution as possible. 
         [0007]    In conventional autostereoscopic displays, such reconfiguration is only achievable, if at all, by physical removal of the lenticular array and perhaps replacement with a different lenticular array. 
       SUMMARY OF THE INVENTION 
       [0008]    In accordance with the present invention, lenticles—i.e., columnar lenses—of a lenticular array can be electronically controlled to be optically equivalent to either of two sets of virtual lenticles having two distinct physical characteristics. Each of the lenticles is in sufficiently close proximity to one or more switchable optical elements to optically combine with the switchable optical elements. The switchable optical elements can be switchable columnar prisms for example. 
         [0009]    In a first state, the switchable prisms optically combine with the lenticles such that the combination is optically equivalent to a first set of virtual lenticles. For example, the switchable prisms in the first state can have a refraction index substantially equivalent to the refraction index of a surrounding material such that the switchable prisms essentially have no optical effect. In such a case, the first set of virtual lenticles would be optically equivalent to the lenticles of the lenticular array alone. 
         [0010]    In a second, different state, the switchable prisms optically combine with the lenticles such that the combination is optically equivalent to a second, different set of virtual lenticles. For example, the switchable prisms in the second state can have a refraction index substantially equivalent to the refraction index of the lenticles such that the optical combination of the switchable prisms with the lenticles is significantly different, optically speaking, than the lenticles alone. Each of the switchable prisms combine with only a part of the lenticle such that the remainder of the lenticle does not combine optically with the switchable prism. The remainder can optically combine with another switchable prism that deflects light at a significantly different angle in the second state or no switchable prism at all. The result is that the part of the lenticle that combines optically with a switchable prism is optically different in a significant way from the remainder of the lenticle that does not optically combine with the switchable prism. In effect, the prism is split into two virtual prisms. Additional switchable prisms can be used with a lenticle to effectively split the lenticle into three or more virtual lenticles. 
         [0011]    Using birefringent material for the switchable optical elements, the refraction index—and therefore the state—of the switchable optical elements can be controlled electrically. Accordingly, the lenticular array can switch between two distinct configurations with the flip of a switch. 
     
    
     
       A BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a plan view of a viewer and an autostereoscopic display in accordance with the present invention. 
           [0013]      FIG. 2  is a plan view of a lenticular array of the autostereoscopic display of  FIG. 1  in greater detail. 
           [0014]      FIGS. 3-5  are plan views of the lenticular array that illustrate how the lenticular array is switchable between two alternative configurations in accordance with the present invention. 
           [0015]      FIGS. 6 and 7  are plan views of an alternative lenticular array, illustrating how the alternative lenticular array is switchable between two alternative configurations in accordance with the present invention. 
           [0016]      FIG. 8  is a plan view of switchable prisms of the lenticular arrays of  FIGS. 2-7  in greater detail. 
           [0017]      FIG. 9  is a plan view of alternative switchable prisms of the lenticular arrays of  FIGS. 2-7  in greater detail. 
           [0018]      FIG. 10  is a plan view of the lenticular array of  FIGS. 2-5  and a front view of a pixel array positioned behind the lenticular array to illustrate two distinct modes of operation in accordance with the present invention. 
           [0019]      FIG. 11  is a plan view of the lenticular array of  FIG. 10  in the state illustrated by  FIG. 3  and a front view of the pixel array of  FIG. 10 . 
           [0020]      FIG. 12  is a plan view of the lenticular array of  FIG. 10  in the state illustrated by  FIG. 5  and a front view of the pixel array of  FIG. 10 . 
           [0021]      FIGS. 13  are  14  are each a plan view of an alternative lenticular array. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    In accordance with the present invention, lenticles  202 A-D ( FIG. 3 ) of a lenticular array  100  can be electronically controlled to act optically as shown in  FIG. 3  or to act optically as shown by lenticles  502 A-H ( FIG. 5 ). Lenticular array  100  ( FIG. 1 ) presents an autostereoscopic view to a human viewer  10  and the view has a perceived width  120  and a perceived depth  130 . 
         [0023]    Lenticular array  100  ( FIGS. 1-3 ) includes switchable prisms  204 A-H ( FIG. 2 ) that can be switched between a state in which lenticles  202 A-D optically behave in one way and a second state in which lenticles  202 A-D optically behave in a second, different way. As described more completely below in conjunction with  FIG. 8 , switchable prisms  204 A-H are made of birefringent material such as liquid crystal and can be electronically switched between two different refraction indices. In this illustrative embodiment, one of the refraction indices is that of lenticles  202 A-D and the other is that of transparent layer  206  in which switchable prisms  204 A-H are formed. In addition, switchable prisms  204 A-H have a right triangle cross section in which angle  208  is 16 degrees in this illustrative embodiment. Switchable prisms  204 A-H can also be designed as Fresnel type prisms. 
         [0024]    In an “off” state in which switchable prisms  204 A-H have no optical effect, the refraction index of switchable prisms  204 A-H is set to be effectively the same as that of transparent layer  206 . In this “oft” state, the optical behavior of lenticular array  100  is as shown in  FIG. 3 . Switchable prisms  204 A-H, having the same refraction index as transparent layer  206 , are optically indistinguishable from transparent layer  206 . 
         [0025]    In an “on” state in which switchable prisms  204 A-H have an optical effect, the refraction index of switchable prisms  204 A-H is set to be significantly different from that of transparent layer  206 . In one embodiment, the refraction index of switchable prisms  204 A-H in this “on” state is set to be the same as that of lenticles  202 A-D. In this “on” state, switchable prisms  204 A-H, being optically distinguishable from transparent layer  206 , optically combine with lenticles  202 A-D to affect their optical behavior. 
         [0026]      FIG. 4  shows a lenticular array that is optically equivalent to that of lenticular array  100  in the on state. For example, lenticle  202 A ( FIG. 2 ) combined with switchable prisms  204 A-B are optically equivalent to lenticle  402 A ( FIG. 4 ) combined with element  404 A and lenticle  40213  combined with element  404 B. For thin lenses, lenticles  402 A-H combined with elements  404 A-H are optically equivalent to lenticles  502 A-H ( FIG. 5 ) combined with elements  504 A-H. While lenticular array  100  is still physically configured as shown in  FIG. 2 , lenticular array  100  in this “on” state is optically equivalent to the state shown in  FIG. 5 . 
         [0027]    Since lenticles  502 A-H combined with elements  504 A-H represent the effective optical behavior of lenticular array  100  in this “on” state, lenticles  502 A-H are referred to herein as virtual lenticles of lenticular array  100 . In other words, virtual lenticles of lenticular array  100  are lenticles that are optically equivalent to lenticular array  100  in a given state. Thus, lenticular array  100  is switchable between at least two states that have virtual lenticles of different optical behavior. 
         [0028]    Lenticles  502 A-H have half the width of lenticles  202 A-D. Thus, by electronically controlling the refraction index of switchable prisms  204 A-H, lenticular array  100  can be switched between a state in which lenticular array  100  behaves optically as if lenticles  202 A-D have their physical dimensions and a state in which lenticular array  100  behaves optically as if lenticles  202 A-D are twice as many in number and have half their physical width. 
         [0029]    The electrical division of lenticles is not limited to halving of lenticles. Lenticular array  100 B ( FIG. 6 ) includes lenticles  602 A-B, each of which is positioned in front of four (4) switchable prisms, i.e., switchable prisms  604 A-D and  604 E-H, respectively. When switchable prisms  604 A-H are in the “off” state described above, lenticular array  100 B optically behaves as shown in  FIG. 7 . 
         [0030]    When switchable prisms  604 A-H are in the “on” state described above, lenticular array  100 B optically behaves as shown in  FIG. 5 . In particular, lenticle  602 A ( FIG. 6 ) combines with switchable prisms  604 A-D to optically behave as illustrated by lenticles  402 A-D ( FIG. 4 ) combined with elements  404 A-D. As described above, for thin lenses, lenticles  402 A-D ( FIG. 4 ) combined with elements  404 A-D are optically equivalent to lenticles  502 A-D ( FIG. 5 ) combined with elements  504 A-D. 
         [0031]    It should be appreciated that the number of virtual lenticles into which a lenticle can be divided can be other than the embodiments described herein in which lenticles are divided into two (2) and four (4) virtual lenticles. For example, lenticles can be divided into three, five, or more virtual pixels. In addition, while lenticles are described herein as being divided into virtual lenticles of equal width, the division of lenticles can be into virtual lenticles of varying widths. What is important is that, in the “on” state, each switchable prisms deflects light through the lenticle at an angle substantially different from angles of deflection of light through adjacent portions of the lenticle. 
         [0032]    While switchable prisms are shown in the Figures to be arranged in pairs of reversed but otherwise identical configurations, it should be appreciated that lenticles such as lenticles  202 A-D can be divided so long as adjacent switchable prisms deflect light passing through the lenticles at different angles. For example, switchable prisms  204 A,  204 C,  204 E, and  204 G can be omitted completely as shown by lentic lenticles ular array  100 C ( FIG. 13 ) and, with the exception of a small net deflection of lenticular array  100 C, function as described above with respect to  FIGS. 2-5 . Similarly, lenticular array  100 D ( FIG. 14 ) replaces switchable prisms  204 A,  204 C,  204 E, and  204 G with switchable prisms  1404 A,  1404 C,  1404 E, and  1404 G that, in the “on” state, reflect light at a significantly different angle than do switchable prisms  204 B,  204 D,  204 F, and  204 H. Switchable prisms  1404 A,  1404 C,  1404 E, and  1404 G can differ from switchable prisms  204 B,  204 D,  204 F, and  204 H in physical dimension and/or in refraction index in the “on” state to achieve the significant difference in angle of deflection of light. 
         [0033]    Switchable prisms  204 A-C are shown in greater detail in  FIG. 8  in cross-section view from above. Unless otherwise noted herein, the following description of switchable prisms  204 A-C in conjunction with  FIG. 8  is equally applicable to switchable prisms  204 D-H,  602 A-H,  1404 A,  1404 C,  1404 E, and  1404 G. Each of switchable prisms  204 A-C is a triangular column of birefringent material such as liquid crystal. Switchable prisms  204 A-C are positioned between a layer  802  of transparent plastic or glass and a grooved layer  806  of transparent plastic or glass into which triangular grooves are made to provide space for the triangular columns of switchable prisms  204 A-C. 
         [0034]    Behind layer  806  is a switch layer  810  of liquid crystal between electrode layers  808  and  812 . By selectively applying a charge to electrode layers  808  and  812 , polarization of light passing through switch layer  810  can be switched, e.g., between parallel and perpendicular orientations relative to the birefringent material of switchable prisms  204 A-C. 
         [0035]    The birefringent material, its orientation set at manufacture, and the size and shape of switchable prisms  204 A-C are selected to provide one amount of light deflection with one polarization orientation of switch layer  810  and a different amount of deflection with the other polarization orientation of switch layer  810 . In effect, the birefringent material in the triangular columns of switchable prisms  204 A-C is formed into prisms whose degree of light deflection vary according to the state of switch layer  810 . 
         [0036]    In this illustrative embodiment, the birefringent material is selected to have one refraction index substantially equal to the refraction index of the transparent material of layers  802  and  806 , and therefore provides no deflection of light as shown by arrow  814 A, for one polarization orientation of switch layer  810 . In effect, switchable prisms  204 A-C disappear into layers  802  and  806 , and switchable prisms  204 A-C and layers  802  and  806  appear to be a single, flat layer of transparent material. For the other polarization orientation of switch layer  810 , the birefringent material of switchable prisms  204 A-C, its orientation set at manufacture, is selected to have a refraction index substantially equivalent to that of lenticles  202 A-D in the embodiment of  FIG. 2  or that of lenticles  602 A-B in the embodiment of  FIG. 6 . In this alternative state of switchable prisms  204 A-C ( FIG. 8 ), switchable prisms  204 A-C deflect light passing through transparent layers  802  and  806  as shown by arrow  814 B. 
         [0037]      FIG. 9  shows switchable prisms  904 A-C, which are an alternative embodiment of switchable prisms  204 A-C ( FIG. 8 ). Unless otherwise noted herein, the following description of switchable prisms  904 A-C is equally applicable to an alternative embodiment of switchable prisms  204 A-H,  602 A-H,  1404 A,  1404 C,  1404 E, and  1404 G. Switchable prisms  904 A-C are triangular columns of a material whose refraction index is controllable, e.g., by an electrical field. An example of such a material is liquid crystal. Switchable prisms  904 A-C are positioned between a layer  906  of transparent plastic or glass and a grooved layer  910  of transparent plastic or glass into which triangular grooves are made to provide space for the triangular columns of switchable prisms  904 A-C. 
         [0038]    In front of layer  906  is an electrode layer  902 . Behind layer  910  is an electrode layer  912 . By selectively applying a charge to electrode layers  902  and  912 , the refraction index of the material in switchable prisms  904 A-C can be varied. 
         [0039]    The material within switchable prisms  904 A-C, its orientation set at manufacture, and the size and shape of switchable prisms  904 A-C are selected to provide desired refraction indices for the two states of switchable prisms  904 A-C in response to electrical fields that can be produced across electrode layers  902  and  912 . In effect, the material in switchable prisms  904 A-C is formed into prisms whose degree of light deflection vary according to the electrical field between electrode layers  902  and  912 . 
         [0040]      FIG. 10  shows lenticular array  100  of  FIG. 2  positioned in front of a pixel array  1002  in which sub-pixels are arranged in a mosaic arrangement as shown. For clarity of explanation, lenticular array  100  is shown in cross-section view from above and pixel array  1002  is shown in a front view as facing human viewer  10  ( FIG. 1 ). Lenticular array  100  and pixel array  1002  are switchable between an autostereoscopic three-dimensional display and a two-dimensional display with full resolution. 
         [0041]    In this illustrative embodiment, pixel array  1002  is part of a 1080p video display having a native resolution of 1920×1080. Each of lenticles  202 A-D is positioned in front of six (6) sub-pixel columns, having 960 lenticles in lenticular array  100 . 
         [0042]    In the 3D mode of operation, lenticular array  100  is in the “off” state shown in  FIGS. 3 and 11 . Furthermore, lenticular array  100  ( FIG. 11 ) and pixel array  1002  maximize horizontal resolution at the expense of vertical resolution. One of the advantages of the mosaic arrangement of sub-pixels of pixel array  1002  is that the sub-pixels of pixel array  1002  can be logically grouped to form pixels horizontally or vertically. Consider 3-by-3 sub-pixel matrix  1004 . Each row of sub-pixels of matrix  1004  collectively represents a color of a pixel. However, by transposing matrix  1004 , each column of sub-pixels of matrix  1004  collectively represents a color of a pixel. Such transposition of each 3-by-3 sub-pixel array can be accomplished by swapping sub-pixel values in the pixel data representing video content to be displayed. 
         [0043]    As noted above, each of lenticles  202 A-D is positioned in front of six (6) columns of sub-pixels of pixel array  1002 . In ordinary grouping of sub-pixels, that&#39;s two columns of pixels. However, after sub-pixel matrix transposition, that&#39;s six (6) columns of pixels but the rows of pixels are reduced by a third. In effect, the 1920×1080 display is now a 5,760×360 display, and the 960 lenticles of lenticular array  100  group the 5,760 columns into six (6) views under each lenticle. 
         [0044]    To further increase the number of views for autostereoscopic display, pixel array  1002  is time mulitplexed by a factor of four (4) in the manner described in Appendix A of U.S. Provisional Patent Application 61/696,718 and that description is incorporated herein by reference. Thus, each of the pixel columns behind lenticles  202 A-D can present four (4) virtual pixels side-by-side in the area of a single sub-pixel column. As a result, behind each of lenticles  202 A-D are 24 views, providing good quality autostereoscopic effect to human viewer  10  ( FIG. 1 ). In effect, the 1920×1080 display is now a 23,040×360 display, and the 960 lenticles of lenticular array  100  group the 23,040 columns into 24 views under each lenticle. Since only one of the 24 views will appear to fill each of lenticles  202 A-D completely when viewed by either eye of human viewer  10 , the perception of human viewer  10  is a stereoscopic image with a resolution of 960×360. 
         [0045]    In the 2D mode of operation, lenticular array  100  is in the “on” state shown in  FIGS. 5 and 12 . Accordingly, lenticles  502 A-H ( FIG. 12 ) are each in front of three (3) sub-pixel columns. Sub-pixel array  1004  is not transposed such that sub-pixel array  1004  represents a single column of three pixels. The time multiplexing of each sub-pixel column is disabled or nullified by making all four (4) time multiplexed pixels be the same. Without transposition of sub-pixel matrix  1004  and without time multiplexing, the result of the display remains the original 1920×1080. 
         [0046]    The result is that each of lenticles  502 A-H is positioned in front of a single column of pixels. Without transposition of sub-pixel matrix  1004  and without time multiplexing, the result of the display remains the original 1920×1080. In addition, lenticles  502 A-H number 1,920, keeping the perceived resolution at 1920×1080. 
         [0047]    Thus, lenticular array  100  and pixel array  1002  are switchable between a two-dimensional display at full 1080p resolution and a three-dimensional display with 24 views at a resolution of 960×360. 
         [0048]    The above description is illustrative only and is not limiting. The present invention is defined solely by the claims which follow and their full range of equivalents. It is intended that the following appended claims be interpreted as including all such alterations, modifications, permutations, and substitute equivalents as fall within the true spirit and scope of the present invention.