Patent Publication Number: US-11048036-B2

Title: Multiview displays having a reflective support structure

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation patent application of and claims the benefit of priority to International Application No. PCT/US2016/068935, filed Dec. 28, 2016, which is incorporated by reference herein in its entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     N/A 
     BACKGROUND 
     Electronic displays are a nearly ubiquitous medium for communicating information to users of a wide variety of devices and products. Most commonly employed electronic displays include the cathode ray tube (CRT), plasma display panels (PDP), liquid crystal displays (LCD), electroluminescent displays (EL), organic light emitting diode (OLED) and active matrix OLEDs (AMOLED) displays, electrophoretic displays (EP) and various displays that employ electromechanical or electrofluidic light modulation (e.g., digital micromirror devices, electrowetting displays, etc.). Generally, electronic displays may be categorized as either active displays (i.e., displays that emit light) or passive displays (i.e., displays that modulate light provided by another source). Among the most obvious examples of active displays are CRTs, PDPs and OLEDs/AMOLEDs. Displays that are typically classified as passive when considering emitted light are LCDs and EP displays. Passive displays, while often exhibiting attractive performance characteristics including, but not limited to, inherently low power consumption, may find somewhat limited use in many practical applications given the lack of an ability to emit light. 
     In order to overcome the limitations of passive displays associated with emitted light, many passive displays are coupled to an external light source. The coupled light source may allow these otherwise passive displays to emit light and function substantially as an active display. Examples of such coupled light sources are backlights. A backlight may serve as a source of light (often a panel backlight) that is placed behind an otherwise passive display to illuminate the passive display. For example, a backlight may be coupled to an LCD or an EP display. The backlight emits light that passes through the LCD or the EP display. The light emitted is modulated by the LCD or the EP display and the modulated light is then emitted, in turn, from the LCD or the EP display. Often backlights are configured to emit white light. Color filters are then used to transform the white light into various colors used in the display. The color filters may be placed at an output of the LCD or the EP display (less common) or between the backlight and the LCD or the EP display, for example. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Various features of examples and embodiments in accordance with the principles described herein may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, where like reference numerals designate like structural elements, and in which: 
         FIG. 1A  illustrates a perspective view of a multiview image produced by an example multiview display. 
         FIG. 1B  illustrates a graphical representation of angular components of a light beam emanating from a point of a multiview display. 
         FIG. 2A  illustrates an isometric view of an example multiview display. 
         FIG. 2B  illustrates a cross-sectional view of the multiview display illustrated in  FIG. 2A . 
         FIG. 2C  shows an exploded isometric view of the multiview display illustrated in  FIG. 2A . 
         FIG. 3  illustrates a cross-sectional view of light coupled into a plate light guide of a multiview display. 
         FIG. 4  illustrates total internal reflection at a surface of a plate light guide. 
         FIG. 5  illustrates a cross-sectional view of a support layer, a reflective layer, and a plate light guide. 
         FIG. 6A  illustrates an exploded isometric view of an example multiview display configured with a segmented reflective layer. 
         FIG. 6B  illustrates an exploded isometric view of an example multiview display configured with a segmented reflective layer. 
         FIG. 7  illustrates a cross-sectional view of an example multiview display configured with a reflective support layer. 
         FIG. 8A  illustrates a cross-sectional view of an example multibeam element of a plate light guide configured as a transmittable diffraction grating. 
         FIG. 8B  illustrates a cross-sectional view of an example multibeam element of a plate light guide configured as a reflective diffraction grating. 
         FIG. 9  illustrates a cross-sectional view of an example multibeam element of a plate light guide configured as a micro-refractive element. 
         FIG. 10A  illustrates a cross-sectional view of an example multibeam element of a plate light guide configured as a prismatic-shaped micro-reflective element. 
         FIG. 10B  illustrates a cross-sectional view of an example multibeam element of a plate light guide configured as a semi-spherical micro-refractive element. 
         FIG. 11  illustrates a flow diagram of a method to display multiview images. 
     
    
    
     Certain examples and embodiments may have other features that are one of in addition to and in lieu of the features illustrated in the above-referenced figures. These and other features are described below with reference to the above-referenced figures. 
     DETAILED DESCRIPTION 
     Examples and embodiments in accordance with the principles described herein provide a multiview display comprising a reflective support structure located between a backlight and a screen. The reflective support structure is configured to maintain a substantially uniform separation distance between the screen and the backlight and to adhere or affix the screen to the backlight. In addition, reflective properties of the reflective support may ‘recycle’ light propagating within the backlight, according to some embodiments. In particular, the reflective support may recycle light by substantially reflecting light incident on the reflective support back into the light guide. Recycling light in this manner may prevent leakage or unwanted transmission of light from the light guide, according to various embodiments as described below. 
     A multiview display is an electronic display or display system configured to provide a plurality or number of different views of a multiview image in different view directions. The term ‘multiview’ as used in the terms ‘multiview image’ refers to a plurality or a number of views representing different perspective views or including angular disparity between views of the many different views. In addition, the term ‘multiview’ includes more than two different views (i.e., a minimum of three views and generally more than three views). As such, a ‘multiview display’ is distinguished from a stereoscopic display. A stereoscopic display displays only two different views to represent a scene or an image. Note however, while multiview images and multiview displays include more than two views, multiview images may be viewed (e.g., on a multiview display) as a stereoscopic pair of images by selecting only two of the multiview views to view at a time (e.g., one view per eye). 
     A multiview display comprises a screen with a plurality of multiview pixels. Each multiview pixel comprises a plurality of sets of light valves. The multiview display includes a backlight that comprises a light source optically coupled to a plate light guide that is configured with a plurality of multibeam elements. Each multibeam element corresponds to a set of light valves. Further, each multibeam element is spatially offset with respect to a center of each corresponding set of light valves toward a center of the multiview pixel. The sets of light valves modulate the light diffractively coupled out of the corresponding multibeam elements. The spatial offset of the multibeam elements creates an angular offset in modulated light beams emerging from the sets of light valves. The modulated light beams that emerge from the sets of light valves associated with each multiview pixel interleave to create multiview images at a viewing distance from the screen. 
       FIG. 1A  illustrates a perspective view of a multiview image produced by an example multiview display  100 . As illustrated in  FIG. 1A , the multiview display  100  may simultaneously display multiple images. Each image provides a different view of a scene or object from a different view direction. In  FIG. 1A , the view directions are illustrated as arrows extending from the multiview display  100  in various different principal angular directions. The different views are illustrated as shaded polygonal panels at the termination of the arrows. For example, in  FIG. 1A , four polygonal panels  102 - 105  represent four different views of a multiview image from different corresponding view directions  106 - 109 . Suppose the multiview display  100  is used to display a multiview image of an object (e.g., a three-dimensional object within a scene). When an observer views the multiview display  100  in the direction  106 , the observer sees the view  102  of the object. However, when the observer views the multiview display  100  from the view direction  109 , the observer sees a different view  105  of the same object. Note that for simplicity of illustration the different views are illustrated in  FIG. 1A  as being above the multiview display  100 . In practice, the different views are actually simultaneously displayed on a screen of the multiview display  100 , enabling an observer to view an object or scene from different view directions by simply changing the observer&#39;s view direction of the multiview display  100 . 
     A view direction or equivalently a light beam having a direction corresponding to a view direction of a multiview display generally has a principal angular direction given by angular components (α,β). The angular component α is referred to as the ‘elevation component’ or ‘elevation angle’ of the light beam. The angular component β is referred to as the ‘azimuth component’ or ‘azimuth angle’ of the light beam. The elevation angle α is an angle in a vertical plane (e.g., perpendicular to a plane of the screen of the multiview display) while the azimuth angle β is an angle in a horizontal plane (e.g., parallel to the plane of the screen of the multiview display). 
       FIG. 1B  illustrates a graphical representation of the angular components (α,β) of a light beam  110  emitted or emanating from a point of the multiview display  100  with a particular principal angular direction corresponding to a view direction, such as the view direction  108  in  FIG. 1A . The light beam  110  has a central ray associated with a particular point of origin ‘O’ within the multiview display  100 . 
     The backlight of the multiview display is configured with a plate light guide that diffractively couples out light that propagates within the plate light guide through multibeam elements of the plate light guide. The reflective support structure located between the backlight and the screen abuts a portion of the surface of the plate light guide and is configured to allow transmission of the light diffractively coupled out by way of the multibeam elements. The reflective support structure is configured to recycle light propagating within the plate light guide by reflecting light incident on the portion of the surface that abuts the reflective support structure back into the plate light guide. 
       FIG. 2A  illustrates an isometric view of an example multiview display  200 .  FIG. 2B  illustrates a cross-sectional view of the multiview display  200  along a line I-I in  FIG. 2A .  FIG. 2C  illustrates an exploded isometric view of the multiview display  200 . As illustrated in  FIGS. 2A-2C , the multiview display  200  comprises a multiview backlight  202 , a reflective layer  204 , a support layer  206 , and a screen  208 . The multiview backlight  202  comprises a plate light guide  210  and a light source  212  optically coupled to an edge of the plate light guide  210 . The plate light guide  210  is configured to guide light generated by the light source  212  between a first surface  214  and a second surface  216  of the plate light guide  210 . 
     In  FIGS. 2B and 2C , the plate light guide  210  may be a plate optical waveguide having substantially planar, parallel first and second surfaces  214 ,  216 . The first surface  214  of the plate light guide  210  may be configured with a number of multibeam elements  220 . In  FIGS. 2B and 2C , the reflective layer  204  has a rectangular shape with an opening  222 . In  FIG. 2C , the support layer  206  also has a rectangular shape with an opening  224 . In  FIG. 2B , the support layer  206  is located on a surface of the reflective layer  204 . Widths of the straight sections of the reflective layer  204 , denoted by W r , are greater than the widths of the straight sections of the support layer  206 . In other embodiments, the width of the straight sections of the reflective layer  204  may be approximately equal to the widths of the straight sections of the support layer  206 . 
     In  FIGS. 2A-2C , the screen  208  comprises a light valve array  226  surrounded by a screen border  228 . The light valve array  226  comprises separate and individually operable light valves  230  that may be selectively switched from opaque to transparent. The light valves  230  may be liquid crystal light valves, electrophoretic light valves, and light valves based on electrowetting. Each of the light valves  230  may be separately modulated to display images on the light valve array  226 . As illustrated in  FIG. 2B , the screen border  228  is placed on and abuts the support layer  206 . The support layer  206  and the reflective layer  204  form a reflective support structure that separates the screen from the plate light guide  210  by a substantially uniform distance D. The support layer  206  may be configured with a thickness, T s , and the reflective layer  204  may be configured with a thickness, T r , that combine to separate the screen  208  from the first surface  214  of the plate light guide  210  by the distance D=T s +T r . The support layer  206  and the reflective layer  204  may include adhesives that adhere (affix) the screen to the plate light guide  210  The openings  222  and  224  in the corresponding reflective and support layers  204 ,  206  create an unobstructed space between the light valve array  226  of the screen  208  and the multibeam elements  220  of the first surface  214  of the plate light guide  210 . In other words, the openings  222  and  224  are created in order to not block or obstruct light diffractively couple out of the plate light guide  210  toward the light valve array  226 . 
     The plate light guide  210  may comprise any one of a number of different optically transparent materials or comprise any of a variety of dielectric materials including, but not limited to, one or more of various types of glass, such as silica glass, alkali-aluminosilicate glass, borosilicate glass, and substantially optically transparent plastics or polymers, such as poly(methyl methacrylate) or acrylic glass, and polycarbonate. In some embodiments, the plate light guide  210  may include a cladding layer on at least a portion of a surface of the plate light guide  210  (not illustrated) to facilitate total internal reflection (TIR). 
     The light source  212  may comprise one or more optical emitters. An optical emitter may be a light-emitting diode (LED), a laser, an organic light-emitting diode (OLED), a polymer light-emitting diode, a plasma-based optical emitter, a fluorescent lamp, an incandescent lamp, and any other source of light. The light produced by the light source  212  may be of a particular wavelength (i.e., may be of a particular color), or may be over a range of wavelengths (e.g., white light). In some embodiments, the light source  212  may include sets of optical emitters in which each set of optical emitters produces light of a particular wavelength or a range of wavelengths that is different from the wavelength or range of wavelengths produced by the other sets of optical emitters. For example, the light source  212  may comprise sets of optical emitters in which each set of one or more optical emitters produces one of the primary colors (e.g., red, green, and blue). 
     As illustrated in  FIGS. 2A-2C , the light valve array  226  comprises separate light valves  230  that may be modulated to display images on the light valve array. A multiview pixel comprises an array of two or more light valves. In  FIGS. 2A-2C , the light valves of the light valve array  226  are partitioned to create eight multiview pixels. Each multiview pixel comprises a 7×7 array of light valves  230 . Each 7×7 array of light valves that forms a multiview pixel is demarcated by a dashed-line square. For example, light valve  230  is one of forty-nine (49) light valves of a multiview pixel  232  demarcated in  FIGS. 2A and 2C . A multiview pixel is a set of light valves that represent ‘view’ pixels in each of a similar number of different views of a multiview display. In particular, a multiview pixel may have an individual light valve corresponding to, or representing, a view pixel in each of the different views of a multiview image. In addition, the light valves of the multiview pixel are also called ‘directional pixels’ in that each of the light valves is associated with a predetermined view direction of one of the different views. Furthermore, according to various examples and embodiments, the different view pixels represented by the light valves of a multiview pixel may have equivalent or at least substantially similar locations or coordinates in each of the different views. For example, a first multiview pixel may have individual light valves corresponding to view pixels located at {x 1 , y 1 } in each of the different views of a multiview image, while a second multiview pixel may have individual light valves corresponding to view pixels located at {x 2 , y 2 } in each of the different views, and so on. 
     In some embodiments, a number of light valves in a multiview pixel may be equal to a number of views of the multiview display. For example, a multiview pixel may comprise an array of sixty-four (64) light valves that may be used to create a multiview display having 64 different views. In another example, a multiview display may provide an eight by four array of views (i.e., 32 views) and the multiview pixel may include thirty-two (32) light valves (i.e., one for each view). For example, each different light valve may have an associated direction (e.g., light beam principal angular direction) that corresponds to a different one of the view directions corresponding to the 64 different views. In addition, according to some embodiments, a number of the multiview pixels of the multiview display may be substantially equal to a number of ‘view’ pixels (i.e., pixels that make up a selected view) in the multiview display views. For example, if a view includes six hundred forty by four hundred eighty view pixels (i.e., a 640×480 view resolution), the multiview display may have three hundred seven thousand two hundred (307, 200) multiview pixels. In another example, when the views include one hundred by one hundred pixels, the multiview display may include a total of ten thousand (i.e., 100×100=10,000) multiview pixels. 
     According to some embodiments, the multibeam elements  220  may be arranged in either a one-dimensional (1D) array or two-dimensional (2D) array. For example, the multibeam elements  220  may be arranged as a linear 1D array. In another example, the multibeam elements  220  may be arranged as a rectangular 2D array as illustrated in  FIG. 2C . In other example, the multibeam elements may be arranged in a circular or elliptical 2D array. In other examples, arrays of multibeam elements (i.e., 1D or 2D array) may be regular or uniformly spaced multibeam elements. In particular, an inter-element distance (e.g., center-to-center distance or spacing) between the multibeam elements  220  may be substantially uniform or constant across the array of multibeam elements. In still other examples, the inter-element distance between the multibeam elements  220  may be varied in one or both of x and y directions. 
     As illustrated in  FIG. 2B , the size of a multibeam element  220 , denoted by s, is comparable to the size of the light valve  230 , denoted by S, of the light valve array  226 . The ‘size’ may be, but is not limited to, a length, a width or an area of a light valve. For example, the size of a light valve  230  may be a length of the light valve and the comparable size of the multibeam element  220  may also be a length of the multibeam element  220 . In another example, size may refer to an area, such as area of the multibeam element  220 , comparable to an area of the light valve  230 . 
     In some embodiments, the size of the multibeam element  220  is comparable to the size of a light valve such that the size of the multibeam element is between about fifty percent (50%) and about two hundred percent (200%) of the size of the light valve. For example, the size s of the multibeam element satisfies the following condition:
 
½S≤s≤2S  (1)
 
In other examples, the multibeam element size is greater than about sixty percent (60%) of the light valve size, or about seventy percent (70%) of the light valve size, or greater than about eighty percent (80%) of the light valve size, or greater than about ninety percent (90%) of the light valve size, and the multibeam element is less than about one hundred eighty percent (180%) of the light valve size, or less than about one hundred sixty percent (160%) of the light valve size, or less than about one hundred forty (140%) of the light valve size, or less than about one hundred twenty percent (120%) of the light valve size. For example, by ‘comparable size,’ the multibeam element size may be between about seventy-five percent (75%) and about one hundred fifty (150%) of the light valve size. In another example, the multibeam element  220  may be comparable in size to the light valve  230  where the multibeam element size is between about one hundred twenty-five percent (125%) and about eighty-five percent (85%) of the light valve size. According to some embodiments, the comparable sizes of the multibeam element  220  and the light valve  230  may be chosen to reduce, or in some examples to minimize, dark zones between views of the multiview display  200 , while at the same time reducing, or in some examples minimizing, an overlap between views of the multiview display  200 .
 
       FIG. 3  illustrates a cross-sectional view of the multiview display  200  in which light produced by the light source  212  is input to, or coupled into, the plate light guide  210  as light  302 . The light  302  is coupled into the plate light guide  210  at a non-zero propagation angle (e.g., about 30-35 degrees) with respect to the first and second surfaces  214 ,  216  of the plate light guide  210 . One or more lenses, prisms, mirrors or similar reflectors (e.g., a tilted collimating reflector) (not illustrated) may be used to couple light produced by the light source  212  into the plate light guide  210  at the non-zero propagation angle. The light  302  may be input to the plate light guide  210  as collimated light. The degree to which the light  302  is collimated is represented by a collimation factor denoted by σ. The collimation factor defines an angular spread of light rays within the collimated light. For example, a collimation factor σ may specify that a majority of light rays of collimated light  302  is within a particular angular spread (e.g., +/−σ degrees about a central or principal angular direction of the collimated light). The light rays of the collimated light  302  may have a Gaussian distribution in terms of angle and the angular spread may be an angle determined by at one-half of a peak intensity of the collimated light. 
     In  FIG. 3 , the plate light guide  210  guides the light  302  according to TIR at the non-zero propagation angle between the first surface  214  and the second surface  216  of the plate light guide  210 .  FIG. 4  illustrates trajectories of two rays of light that propagate within the plate light guide  210  and are incident on the same point of a surface  402  (e.g., the first surface  214  or the second surface  216 ) of the plate light guide  210 . The surface  402  is a boundary between the plate light guide  210  and air  404 , which has a lower refractive index than the plate light guide  210 . Dot-dash line  406  represents a normal and θ c  denotes a critical angle with respect to the normal. The angle of incidence is measured with respect to the normal. The light incidence on the surface  402  at angles greater than the critical angle θ c  experiences TIR. For example, because the light represented by directional arrow  408  is incident on the surface  402  at an angle greater than the critical angle θ c , the light is internally reflected as represented by directional arrow  410 . Light incident on the surface  402  at an angle less than the critical angle θ c , as represented by directional arrow  412 , is transmitted as represented by directional arrow  414 . 
     The reflective layer  204  comprises a reflective material, such as, but not limited to, silver or aluminum, located on the first surface  214  of the plate light guide  210 . The reflective layer  204  may be pre-formed and deposited as a film or reflective tape around the border of the first surface  214 . Alternatively, the reflective layer  204  may be formed by first depositing the reflective material using chemical or physical vapor deposition on the first surface  214  followed by forming the opening  222  using any one or more of wet etching, ion milling, photolithography, anisotropic etching, and plasma etching. The reflective layer  204  reflects light that propagates within the plate light guide  210  and is incident on the first surface  214  beneath the reflective layer  204  back into the plate light guide  210 . 
       FIG. 5  illustrates a cross-sectional view of a portion of the support layer  206 , the reflective layer  204 , and the plate light guide  210 . Dot-dash line  502  represents a normal to the first surface  214  of the plate light guide  210 . Directional arrow  504  represents light that is incident on the first surface  214  adjacent to the reflective layer  204 . The reflective layer  204  reflects the light back into the plate light guide  110  as represented by directional arrow  506 . According to some embodiments, the reflective layer  204  may serve as a nearly perfect specular reflector by reflecting light that is incident on any portion of the first surface  214  that abuts the reflective layer  204  back into the plate light guide  210 . The light reflected back into the plate light guide  210  may be recycled by TIR from other surfaces of the plate light guide  210 . 
     The reflective properties of the reflective layer  204  prevents light incident on the first surface  214  adjacent to the support layer  206  from leaking into the support layer  206 . Consider, for example, multiview displays configured as described above but without the reflective layer  204 . Such multiview displays would have the support layer  206  placed directly against the first surface  214  of the plate light guide  210 . As a result, at least a portion of light incident on the first surface  214  adjacent to the support layer  206  leaks into the support layer  206 , creating an optical drain into the support layer  206  through which light is lost. 
     Returning to  FIG. 3 , each multibeam element  220  is configured to couple out a portion of light as coupled-out light into a corresponding multiview pixel  232 . For example, in  FIG. 3 , a portion of the light  302  incident on multibeam element  220  produces coupled-out light represented by diverging directional arrows  238  that pass through the light valves of the multiview pixel  232 . The plate light guide  210  may include a reflector (not illustrated) at an end of the plate light guide  210  opposite the edge along which light is input to the plate light guide  210 . The reflector reflects the light  302  back into the plate light guide  210  to recycle light, as represented by an arrow  306  in  FIG. 3 . Recycling light in this manner may increase brightness of the multiview backlight  202  (e.g., an intensity of the coupled-out light) by making light available more than once. 
     In the example illustrated in  FIGS. 2B-2C , the reflective layer  204  of the multiview display  200  described above is a continuous rectangular-shaped object placed on the first surface  214  of the plate light guide  210 . In other embodiments, a reflective layer of the multiview display  200  may comprise reflective segments disposed on the first surface  214  of the plate light guide  210 . 
       FIG. 6A  illustrates an exploded isometric view of a display  600  that is similar to the multiview display  200  but the reflective layer  204  and the support layer  206  of the multiview display  200  are replaced by a segmented reflective layer  602  and a segmented support layer  604 . As illustrated in  FIG. 6 , the display  600  includes the multiview backlight  202  and the screen  208  described above with reference to  FIGS. 2A-2C . The reflective layer  602  comprises straight reflective segments  606 - 609 . The support layer  604  comprises straight support segments  610 - 613 . When the display  600  is assembled, the reflective segments  606 - 609  are located near edges of the first surface  214  and the support segments  610 - 613  are located on the corresponding reflective segments  606 - 609 . The segmented reflective layer  602  and the segmented support layer  604  form a reflective support structure that separates the screen  208  from the plate light guide  210 . 
       FIG. 6B  illustrates an exploded isometric view of a display  620  that is similar to the multiview display  200  but the reflective layer  204  and the support layer  206  of the multiview display  200  are replaced by a segmented reflective layer  622  and a segmented support layer  624 . As illustrated in  FIG. 6B , the display  620  includes the multiview backlight  202  and the screen  208  described above with reference to  FIGS. 2A-2C . The reflective layer  622  comprises bent reflective segments  626 - 629 . The support layer  624  comprises bent support segments  630 - 633 . When the display  620  is assembled, the bent reflective segments  626 - 629  are located near the corners of the first surface  214  and the support segments are located on the corresponding bent reflective segments  606 - 609 . The segmented reflective layer  622  and the segmented support layer  624  form a reflective support structure that separates the screen  208  from the plate light guide  210 . 
     In other embodiments, a reflective support structure that separates the screen  208  from the plate light guide  210  may be comprised of a reflective material.  FIG. 7  shows a cross-sectional view of an example display  700  that is similar to the multiview display  200  except the reflective support structure of the multiview display  200  (i.e., the reflective layer  204  and the support layer  206 ) are replaced with a reflective support structure  702  that separates the screen  208  from the first surface  214  of the plate light guide  210  by the distance D. The reflective support structure  702  is located near the edges of the first surface  214  of the plate light guide  210 . The reflective support structure  702  may be an adhesive that adheres and affixes the screen  208  to the plate light guide  210  and also comprises a reflective material, such as silver or aluminum. The reflective support structure  702  may have a continuous rectangular shape with an opening  704  the enables diffractively coupled-out light from the diffraction grating to propagate unblocked to the light valve array  226 . In other embodiments, the reflective support structure  702  may be a segmented reflective support structure with segments located near the edges and corners of the first surface  214 . The reflective support structure  702  serves as a nearly perfect specular reflector by reflecting light that is incident on any portion of the first surface  214  that abuts the reflective support structure  702  back into the plate light guide  210  in the same manner as the reflective layer  204  described above with reference to  FIG. 5 . 
     According to various embodiments, the multibeam elements  220  may comprise any of a number of different structures configured to couple out a portion of the light  302 . For example, the different structures may include, but are not limited to, diffraction gratings, micro-reflective elements, micro-refractive elements, or various combinations thereof. According to some embodiments, diffractive features of the diffraction grating may comprise one or both of grooves and ridges that are spaced apart from one another. The grooves or the ridges may comprise a material of the plate light guide  210 , e.g., the grooves and ridges may be formed in a surface of the plate light guide  210 . In another example, the grooves or the ridges may be formed from a material other than the plate light guide material, e.g., a film or a layer of another material on a surface of the plate light guide  210 . 
       FIG. 8A  illustrates a cross-sectional view a multibeam element  220  of the plate light guide  210  configured as a diffraction grating  802  in the first surface  214  of the plate light guide  210 . The diffraction grating  802  comprises diffractive features with spacing between diffractive features represented by d, which is wider than one or more wavelengths of the light  302 . Consider light of a particular wavelength λ interacting with the diffraction grating  802 . The light is transmitted and scattered in different directions by the diffractive features. Waves of the light emerge from the diffraction grating  802  with different phases. As a result, the waves constructively and destructively interfere to create beams of light where the waves constructively interfere. For example, when the path difference between the waves of the light emerging from adjacent diffractive features is half the wavelength (i.e., λ/2), the waves emerge out of phase and may be cancelled through destructive interference. On the other hand, when the path difference between the waves emerging from adjacent diffractive features equals the wavelength λ, the waves constructively interfere creating light with maximum intensity. Beams of light that emerges with maxima intensity from the diffraction grating are represented by directional arrows  804  and the diffraction angles at which light emerges from the diffraction grating  802  with respect to a normal  806  to the first surface  214  may be calculated according to the diffraction equation: 
     
       
         
           
             
               
                 
                   
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                             m 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             λ 
                           
                           d 
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
     where
         m is the diffraction order (i.e., m= . . . , −2, −1, 0, 1, 2, . . . );   n is the refractive index of the plate light guide  210 ;   θ i  is the angle of incidence of light  302  with respect to the normal  806 ; and   θ m  is the diffraction angle with respect to the normal  806  of the m-th beam of light diffractively coupled out from the plate light guide  210 .       

     In another example, as illustrated in  FIG. 8B , the multibeam element  220  is a diffraction grating  810  located at or adjacent to the second surface  216  of the plate light guide  210 . The multibeam element includes a reflective coating  812  that fills the diffractive features of the diffraction grating  810  to create a reflective diffraction grating. The reflective coating  812  reflects the diffracted light toward the first surface  214  to exit through the first surface  214  as the diffractively coupled-out light  814 . The diffractively coupled-out light  814  that emerges from the plate light guide  210  along the first surface  214  is refracted as a result of traveling from the higher refractive index material of the plate light guide  210  into the lower refractive index of air, which causes the diffractively coupled-out light  814  to spread. The spacing of the diffractive features of the diffraction grating  810  may be selected to account for spreading of the light emerging from the plate light guide  210 . 
     In other embodiments (not illustrated), the multibeam elements  220  may be diffraction gratings located between the first and second surfaces  214 ,  216  of the plate light guide  210 . Note that, in some embodiments, the principal angular directions of the coupled-out light created by the multibeam elements  220  may include an effect of refraction due to the coupled-out light exiting the plate light guide  210  into air. 
     In some embodiments, the diffraction gratings of the multibeam elements may be uniform diffraction gratings in which the diffractive feature spacing is substantially constant or unvarying throughout the diffraction grating. In other embodiments, the multibeam elements may be chirped diffraction gratings. The diffractive feature spacing of a chirped diffraction grating varies across an extent or length of the chirped diffraction grating. In some embodiments, a chirped diffraction grating may have or exhibit a chirp of the diffractive feature spacing that varies linearly with distance. As such, the chirped diffraction grating is a ‘linearly chirped’ diffraction grating. In other embodiments, the chirped diffraction grating may exhibit a non-linear chirp of the diffractive feature spacing. Various non-linear chirps may be used including, but not limited to, an exponential chirp, a logarithmic chirp or a chirp that varies in another, substantially non-uniform or random but still monotonic manner. Non-monotonic chirps such as, but not limited to, a sinusoidal chirp or a triangle chirp or sawtooth chirp, may also be employed. Combinations of any of non-linear chirps may also be employed. 
     In other embodiments, the multibeam elements  220  may comprise micro-refractive elements configured to refractively couple out portions of the light  302  as the coupled-out light.  FIG. 9  illustrates a cross-sectional view of the plate light guide  210  in which a multibeam element  220  comprises a micro-refractive element  902 . According to various embodiments, the micro-refractive element  902  is configured to refractively couple out a portion of the light  302  from the plate light guide  210  as the coupled-out light  904 . The micro-refractive element  902  may have various shapes including, but not limited to, a semi-spherical shape, a rectangular shape or a prismatic shape (i.e., a shape having sloped facets). According to various embodiments, the micro-refractive element  902  may extend or protrude out of the first surface  214  of the plate light guide  210 , as illustrated, or may be a cavity or recess in the first surface  214  (not illustrated). In some embodiments, the micro-refractive element  902  may comprise a material of the plate light guide  210 . In other embodiments, the micro-refractive element  902  may comprise another material adjacent to, and in some examples, in contact with the first surface  214 . 
     In other embodiments, the multibeam elements  220  may comprise micro-reflective elements configured to reflectively couple out portions of the light  302  as the coupled-out light.  FIG. 10A  illustrates a cross-sectional view of the plate light guide  210  in which a multibeam element  220  comprises a prismatic-shaped micro-reflective element  1002  located along the second surface  216 .  FIG. 10B  illustrates a cross-sectional view of the plate light guide  210  in which a multibeam element  220  comprises a semi-spherical micro-refractive element  1004  located along the second surface  216 . The micro-reflective elements  1002  and  1004  may include, but are not limited to, a reflector that employs a reflective material or layer thereof (e.g., a reflective metal) or a reflector based on TIR. In other embodiments (not illustrated), the micro-reflective element may be located within the plate light guide  210  between the first and second surfaces  214 ,  216 . In  FIG. 10A , the prismatic-shaped micro-reflective element  1002  has reflective facets located adjacent to the second surface  216  of the plate light guide  210 . The facets of the prismatic micro-reflective element  1002  are configured to reflect (i.e., reflectively couple) a portion of the light  302  out of the plate light guide  210 . The facets may be slanted or tilted (i.e., have a tilt angle) relative to a propagation direction of the light  302  to reflect the light portion out of plate light guide  210 , for example. The facets may be formed using a reflective material within the plate light guide  210  (e.g., as illustrated in  FIG. 10A ) or may be surfaces of a prismatic cavity in the second surface  216 , according to various embodiments. When a prismatic cavity is employed, either a refractive index change at the cavity surfaces may provide reflection (e.g., TIR) or the cavity surfaces that form the facets may be coated with a reflective material to provide reflection, in some embodiments. In  FIG. 10B , the semi-spherical micro-reflective element  1004  has a substantially smooth, curved surface. The surface curvature of the semi-spherical micro-reflective element  1004  reflects the portion of the light  302  depending on a point of incidence the light  302  makes with the curved surface. The semi-spherical micro-reflective element  1004  in  FIG. 10B  may be either a reflective material within the plate light guide  210  or a cavity (e.g., a semi-circular cavity) formed in the second surface  216 , as illustrated in  FIG. 10B . Note that, in  FIGS. 10A and 10B , the principal angular directions of the coupled-out light  1006  and  1008  are refracted due to a change in refractive index as the coupled-out light  1006  and  1008  cross the first surface  214  into air. 
       FIG. 11  illustrates a flow diagram of a method to operate a multiview display. In block  1101 , light generated by a light source is optically coupled into a plate light guide to create light that propagates within the plate light guide, as described above with reference to  FIGS. 2A-2C . In block  1102 , a portion of the light is coupled out of the plate light guide through multibeam elements as described above with reference to  FIG. 3 . In block  1103 , light that is incident on a portion of the surface that abuts a reflective support structure is reflected back into the plate light guide, as described above with reference to  FIG. 5 . The reflective support structure is configured to allow transmission of the light coupled out light from the multibeam elements. In block  1104 , the coupled out light is modulated using multiview pixels of a light valve array located on the reflective support structure to create an image. 
     It is appreciated that the previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments illustrated herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.