CROSS-REFERENCE TO RELATED APPLICATION

[0001] N/A

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] N/A

BACKGROUND

[0003] 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). Examples of active displays include CRTs, PDPs and OLEDs/ AMOLED s. Example of passive displays include 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.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] 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.

[0005] Figure 1 illustrates a perspective view of a multiview display in an example according to an embodiment consistent with the principles described herein. [0006] Figure 2 illustrates a graphical representation of the angular components of a light beam having a particular principal angular direction corresponding to a view direction of a multiview display in an example, according to an embodiment consistent with the principles described herein.

[0007] Figure 3 A illustrates a cross sectional view of a multiview backlight in an example, according to an embodiment consistent with the principles described herein. [0008] Figure 3B illustrates a plan view of a multiview backlight in an example, according to an embodiment consistent with the principles described herein.

[0009] Figure 3C illustrates a perspective view of a multiview backlight in an example, according to an embodiment consistent with the principles described herein. [0010] Figure 4 illustrates a graphical representation of tailored, off-axis luminance profiles in an example, according to an embodiment consistent with the principles described herein.

[0011] Figure 5 A illustrates a cross-sectional view of a portion of a multiview backlight including a multibeam element in an example, according to an embodiment consistent with the principles described herein.

[0012] Figure 5B illustrates a cross-sectional view of a portion of a multiview backlight including a multibeam element in an example, according to another embodiment consistent with the principles described herein.

[0013] Figure 6 illustrates a cross-sectional view of a portion of a multiview backlight including a multibeam element in an example, according to another embodiment consistent with the principles described herein.

[0014] Figure 7 illustrates a cross-sectional view of a portion of a multiview backlight including a multibeam element in an example, according to another embodiment consistent with the principles described herein.

[0015] Figure 8 illustrates a cross-sectional view of a portion of a multiview backlight including a multibeam element in an example, according to another embodiment consistent with the principles described herein.

[0016] Figure 9 illustrates a plan view of a multibeam element in an example, according to an embodiment consistent with the principles described herein. [0017] Figure 10 illustrates a block diagram of a multiview display in an example, according to an embodiment consistent with the principles described herein.

[0018] Figure 11 illustrates a flow chart of a method of multiview display operation in an example, according to an embodiment consistent with the principles described herein.

[0019] Certain examples and embodiments 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 detailed below with reference to the above-referenced figures.

DETAILED DESCRIPTION

[0020] Examples and embodiments in accordance with the principles described herein provide multiview backlighting having applications to a multiview or three- dimensional (3D) display. In particular, embodiments consistent with the principles described herein provide a multiview backlight and display that have an off-axis luminance profile that is tailored to a particular use or application. In various embodiments, the tailored, off-axis luminance profile of the emitted light has a lower luminance in an on-axis direction that is perpendicular to a surface of the multiview backlight and a higher luminance in off-axis directions away from the on-axis direction. Multiview displays that employ the multiview backlight described herein may be used in a variety of applications including, but are not limited to, mobile telephones (e.g., smart phones), watches, tablet computers, mobile computers (e.g., laptop computers), personal computers and computer monitors, cameras displays, and various other mobile as well as substantially non-mobile display applications and devices. Notably however, the tailored, off-axis luminance profile may provide particular utility when the multiview display is employed in automobile display consoles where optimal viewing locations relative to the multiview display are typically off-axis as opposed to on-axis.

[0021] In some embodiments, a multiview backlight comprising an array of multibeam elements configured to emit light as a plurality of directional light beams exhibiting the tailored, off-axis luminance profile and having different directions corresponding to view directions of a multiview image. In other embodiments, a multiview display comprise an array of light valves configured to modulate the directional light beams of the emitted light from the multiview backlight to provide view pixels of the multiview image.

[0022] Herein a ‘two-dimensional display’ or ‘2D display’ is defined as a display configured to provide a view of an image that is substantially the same regardless of a direction from which the image is viewed (i.e., within a predefined viewing angle or range of the 2D display). A conventional liquid crystal display (LCD) found in many smart phones and computer monitors are examples of 2D displays. In contrast herein, a ‘multiview display’ is defined as an electronic display or display system configured to provide different views of a multiview image in or from different view directions. In particular, the different views may represent different perspective views of a scene or object of the multiview image, according to some embodiments.

[0023] Figure 1 illustrates a perspective view of a multiview display 10 in an example, according to an embodiment consistent with the principles described herein. As illustrated in Figure 1, the multiview display 10 comprises a screen 12 to display a multiview image to be viewed. The screen 12 may be a display screen of a telephone (e.g., mobile telephone, smart phone, etc.), a tablet computer, a laptop computer, a computer monitor of a desktop computer, a camera display, or an electronic display of substantially any other device, for example. The multiview display 10 provides different views 14 of the multiview image in different view directions 16 relative to the screen 12. The view directions 16 are illustrated as arrows extending from the screen 12 in various different principal angular directions; the different views 14 are illustrated as shaded polygonal boxes at the termination of the arrows (i.e., depicting the view directions 16); and only four views 14 and four view directions 16 are illustrated, all by way of example and not limitation. Note that while the different views 14 are illustrated in Figure 1 as being above the screen, the views 14 actually appear on or in a vicinity of the screen 12 when the multiview image is displayed on the multiview display 10. Depicting the views 14 above the screen 12 is only for simplicity of illustration and is meant to represent viewing the multiview display 10 from a respective one of the view directions 16 corresponding to a particular view 14. A 2D display may be substantially similar to the multiview display 10, except that the 2D display is generally configured to provide a single view (e.g., one view similar to view 14) of a displayed image as opposed to the different views 14 of the multiview image provided by the multiview display 10.

[0024] 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 or simply a ‘direction’ given by angular components {6, </)}, by definition herein. The angular component is referred to herein as the ‘elevation component’ or ‘elevation angle’ of the light beam. The angular component ^is referred to as the ‘azimuth component’ or ‘azimuth angle’ of the light beam. By definition, the elevation angle #is an angle in a vertical plane (e.g., perpendicular to a plane of the multiview display screen while the azimuth angle ^is an angle in a horizontal plane (e.g., parallel to the multi view display screen plane).

[0025] Figure 2 illustrates a graphical representation of the angular components { 6, (f>} of a light beam 20 having a particular principal angular direction corresponding to a view direction (e.g., view direction 16 in Figure 1) of a multiview display in an example, according to an embodiment consistent with the principles described herein. In addition, the light beam 20 is emitted or emanates from a particular point, by definition herein. That is, by definition, the light beam 20 has a central ray associated with a particular point of origin within the multiview display. Figure 2 also illustrates the light beam (or view direction) point of origin O.

[0026] Herein, the term ‘multiview’ as used in the terms ‘multiview image’ and ‘multiview display’ is defined as a plurality of views representing different perspectives or including angular disparity between views of the view plurality. In addition, herein the term ‘multiview’ may explicitly include more than two different views (i.e., a minimum of three views and generally more than three views). As such, ‘multiview display’ as employed herein may be explicitly distinguished from a stereoscopic display that includes only two different views to represent a scene or an image. Note however, while multiview images and multiview displays include more than two views, by definition herein, 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). [0027] A ‘multiview pixel’ is defined herein as a set of pixels representing ‘view’ pixels in each of a similar plurality of different views of a multiview display. In particular, a multiview pixel may have an individual pixel or set of pixels corresponding to or representing a view pixel in each of the different views of the multiview image. By definition herein therefore, a ‘view pixel’ is a pixel or set of pixels corresponding to a view in a multiview pixel of a multiview display. In some embodiments, a view pixel may include one or more color sub-pixels. Moreover, the view pixels of the multiview pixel are so-called ‘directional pixels’ in that each of the view pixels is associated with a predetermined view direction of a corresponding one of the different views, by definition herein. Further, according to various examples and embodiments, the different view pixels 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 view pixels located at {xl, y 1 } in each of the different views of a multiview image, while a second multiview pixel may have individual view pixels located at {x2, y2] in each of the different views, and so on.

[0028] Herein, a ‘light guide’ is defined as a structure that guides light within the structure using total internal reflection. In particular, the light guide may include a core that is substantially transparent at an operational wavelength of the light guide. The term Tight guide’ generally refers to a dielectric optical waveguide that employs total internal reflection to guide light at an interface between a dielectric material of the light guide and a material or medium that surrounds that light guide. By definition, a condition for total internal reflection is that a refractive index of the light guide is greater than a refractive index of a surrounding medium adjacent to a surface of the light guide material. In some embodiments, the light guide may include a coating in addition to or instead of the aforementioned refractive index difference to further facilitate the total internal reflection. The coating may be a reflective coating, for example. The light guide may be any of several light guides including, but not limited to, one or both of a plate or slab guide and a strip guide.

[0029] Further herein, the term ‘plate’ when applied to a light guide as in a ‘plate light guide’ is defined as a piece-wise or differentially planar layer or sheet, which is sometimes referred to as a ‘slab’ guide. In particular, a plate light guide is defined as a light guide configured to guide light in two substantially orthogonal directions bounded by a top surface and a bottom surface (i.e., opposite surfaces) of the light guide. Further, by definition herein, the top and bottom surfaces are both separated from one another and may be substantially parallel to one another in at least a differential sense. That is, within any differentially small section of the plate light guide, the top and bottom surfaces are substantially parallel or co-planar. In some embodiments, the plate light guide may be substantially flat (i.e., confined to a plane) and therefore, the plate light guide is a planar light guide. In other embodiments, the plate light guide may be curved in one or two orthogonal dimensions. For example, the plate light guide may be curved in a single dimension to form a cylindrical shaped plate light guide. However, any curvature has a radius of curvature sufficiently large to ensure that total internal reflection is maintained within the plate light guide to guide light.

[0030] By definition herein, a ‘multibeam element’ is a structure or element of a backlight or a display that produces emitted light that includes a plurality of directional light beams. In some embodiments, the multibeam element may be optically coupled to a light guide of a backlight to provide the plurality of light beams by coupling or scattering out a portion of light guided in the light guide. In other embodiments, the multibeam element may generate light emitted as the directional light beams (e.g., may comprise a light source). Further, the directional light beams of the plurality of directional light beams produced by a multibeam element have different principal angular directions from one another, by definition herein. In particular, by definition, a directional light beam of the plurality has a predetermined principal angular direction that is different from another directional light beam of the directional light beam plurality. Furthermore, the directional light beam plurality may represent a light field. For example, the directional light beam plurality may be confined to a substantially conical region of space or have a predetermined angular spread that includes the different principal angular directions of the directional light beams in the light beam plurality. As such, the predetermined angular spread of the directional light beams in combination (i.e., the light beam plurality) may represent the light field.

[0031] According to various embodiments, the different principal angular directions of the various directional light beams of the plurality are determined by a characteristic including, but not limited to, a size (e.g., length, width, area, etc.) and an orientation or rotation of the multibeam element. In some embodiments, the multibeam element may be considered an ‘extended point light source’, i.e., a plurality of point light sources distributed across an extent of the multibeam element, by definition herein. Further, a directional light beam produced by the multibeam element has a principal angular direction given by angular components {6, </)}, by definition herein, and as described above with respect to Figure 2.

[0032] Herein a ‘collimator’ is defined as substantially any optical device or apparatus that is configured to collimate light. According to various embodiments, an amount of collimation provided by the collimator may vary in a predetermined degree or amount from one embodiment to another. Further, the collimator may be configured to provide collimation in one or both of two orthogonal directions (e.g., a vertical direction and a horizontal direction). That is, the collimator may include a shape in one or both of two orthogonal directions that provides light collimation, according to some embodiments.

[0033] Herein, a ‘collimation factor’ is defined as a degree to which light is collimated. In particular, a collimation factor defines an angular spread of light rays within a collimated beam of light, by definition herein. For example, a collimation factor <5 may specify that a majority of light rays in a beam of collimated light is within a particular angular spread (e.g., +/- <5 degrees about a central or principal angular direction of the collimated light beam). The light rays of the collimated light beam 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 beam, according to some examples.

[0034] Herein, a Tight source’ is defined as a source of light (e.g., an optical emitter configured to produce and emit light). For example, the light source may comprise an optical emitter such as a light emitting diode (LED) that emits light when activated or turned on. In particular, herein the light source may be substantially any source of light or comprise substantially any optical emitter including, but not limited to, one or more of 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 virtually any other source of light. The light produced by the light source may have a color (i.e., may include a particular wavelength of light), or may be a range of wavelengths (e.g., white light). In some embodiments, the light source may comprise a plurality of optical emitters. For example, the light source may include a set or group of optical emitters in which at least one of the optical emitters produces light having a color, or equivalently a wavelength, that differs from a color or wavelength of light produced by at least one other optical emitter of the set or group. The different colors may include primary colors (e.g., red, green, blue) for example.

[0035] As used herein, the article ‘a’ is intended to have its ordinary meaning in the patent arts, namely ‘one or more’. For example, ‘a multibeam element’ means one or more multibeam element and as such, ‘the multibeam element’ means ‘multibeam element(s)’ herein. Also, any reference herein to ‘top’, ‘bottom’, ‘upper’, Tower’, ‘up’, ‘down’, ‘front’, back’, ‘first’, ‘second’, ‘left’ or ‘right’ is not intended to be a limitation herein. Herein, the term ‘about’ when applied to a value generally means within the tolerance range of the equipment used to produce the value, or may mean plus or minus 10%, or plus or minus 5%, or plus or minus 1%, unless otherwise expressly specified. Further, the term ‘substantially’ as used herein means a majority, or almost all, or all, or an amount within a range of about 51% to about 100%. Moreover, examples herein are intended to be illustrative only and are presented for discussion purposes and not by way of limitation.

[0036] According to some embodiments of the principles described herein, a multiview backlight is provided. Figure 3 A illustrates a cross sectional view of a multiview backlight 100 in an example, according to an embodiment consistent with the principles described herein. Figure 3B illustrates a plan view of a multiview backlight 100 in an example, according to an embodiment consistent with the principles described herein. Figure 3C illustrates a perspective view of a multiview backlight 100 in an example, according to an embodiment consistent with the principles described herein. The perspective view in Figure 3C is illustrated with a partial cut-away to facilitate discussion herein only.

[0037] The multiview backlight 100 illustrated in Figures 3A-3C is configured to provide emitted light 102 having a tailored, off-axis luminance profile and comprising a plurality of directional light beams having different directions corresponding to view directions of a multiview image (e.g., as or representing a light field). In particular, the directional light beams of the emitted light 102 are scattered out of the multiview backlight 100 and directed away from the multiview backlight 100 in different directions corresponding to respective view directions of the multiview image or equivalently of a multiview display configured to display the multiview image. That is, in some embodiments the directional light beams of the emitted light 102 may be modulated (e.g., using light valves, as described below) to facilitate the display of information having multiview content, e.g., as the multiview image. The multiview image may represent or include three-dimensional (3D) content, for example. Figures 3A-3C also illustrate a multiview pixel 106 comprising an array or set of light valves 108, by way of example and not limitation. In various embodiments, any of a variety of different types of light valves may be employed as the light valves 108 of the light valve array including, but not limited to, one or more of liquid crystal light valves, electrophoretic light valves, and light valves based on or employing electrowetting. A surface of the multiview backlight 100 through which the directional light beams of the emitted light 102 are scattered out of and toward the light valves 108 may be referred to as an ‘emission surface’ of the multiview backlight 100.

[0038] According to various embodiments, the tailored, off-axis luminance profile of the emitted light 102 may be tailored to a particular application or use of the multiview backlight 100. In particular, the tailored, off-axis luminance profile may have a lower luminance in an on-axis direction that is perpendicular to a surface of the multiview backlight and a higher luminance in off-axis directions away from the on-axis direction, according to various embodiments. For example, the off-axis luminance profile may be used to preferentially direct the emitted light 102 in an oblique direction to the on-axis direction such as toward a driver or a passenger when the multiview backlight 100 is used in a central information display of an automobile, for example. In another embodiment, the tailored, off-axis luminance profile may have a higher luminance in off-axis directions corresponding angles both less than and greater than the on-axis direction. When used in a central information display of an automobile or similar application, these embodiments may be particularly useful in directing the emitted light 102 toward both the driver and the passenger, for example. In either of these examples, the off-axis luminance profile may minimize ‘wasted’ light directed in the on-axis direction perpendicular between the driver and passenger.

[0039] Figure 4 illustrates a graphical representation of tailored, off-axis luminance profiles in an example, according to an embodiment consistent with the principles described herein. In particular, Figure 4 provides luminance (Relative Luminance) as a function of angle. A first curve A illustrated in Figure 4 depicts a tailored, off-axis luminance profile having a lower luminance in an on-axis direction that is perpendicular to a surface of the multiview backlight and a higher luminance in off-axis directions away from the on-axis direction. As illustrated, the first curve A has a maximum luminance A _max around one hundred thirty degrees (130°) and a lower luminance at ninety degrees (90°) representing the on-axis direction. As illustrated, the tailored, off-axis luminance profile represented by the first curve A has a higher luminance in off-axis directions corresponding to angles greater than the on-axis direction. In an automobile application in which the multiview backlight is employed in a central information display, the higher luminance angle greater than the on-axis direction may direct more emitted light 102 toward a passenger than toward a driver, for example. [0040] Another tailored, off-axis luminance profile represented by a second curve B in Figure 4 has a pair of maxima B _ma x,i, B _ma x,2, one at about fifty-five degrees (55°) and another at about one hundred twenty-five degrees (125°). The tailored, off-axis luminance profile second curve may represent a tailored, off-axis luminance profile having a higher luminance in off-axis directions corresponding angles both less than and greater than the on-axis direction, for example. In a central information display of an automobile, a first maximum B _ma x,i the second curve B representing luminance may be directed toward a driver, while the second maximum B _ma x,2 of the second curve B representing luminance may be directed toward a passenger, for example.

[0041] Referring back to Figures 3A-3C, the multiview backlight 100 comprises a light guide 110. The light guide 110 is configured to guide light in a first propagation direction 103 as guided light 104. For example, the light guide 110 may include a dielectric material configured as an optical waveguide. The dielectric material may have a first refractive index that is greater than a second refractive index of a medium surrounding the dielectric optical waveguide. The difference in refractive indices may be configured to facilitate total internal reflection of the guided light 104 according to one or more guided modes of the light guide 110. According to some embodiments, the guided light 104 may be guided having or according to a predetermined collimation factor <5. The predetermined collimation factor may be selected to determine or control an overall spread angle of the plurality of directional light beams, in some embodiments.

[0042] In particular, in some embodiments, the light guide 110 may be a slab or plate optical waveguide (i.e., a plate light guide) comprising an extended, substantially planar sheet of optically transparent, dielectric material. The substantially planar sheet of dielectric material is configured to guide the guided light 104 using total internal reflection. According to various examples, the optically transparent material of the light guide 110 may include or be made up of any of a variety of dielectric materials including, but not limited to, one or more of various types of glass (e.g., silica glass, alkalialuminosilicate glass, borosilicate glass, etc.) and substantially optically transparent plastics or polymers (e.g., poly(m ethyl methacrylate) or 'acrylic glass', polycarbonate, and others). In some embodiments, the light guide 110 may further include a cladding layer (not illustrated) on at least a portion of a surface (e.g., one or both of the top surface and the bottom surface) of the light guide 110. The cladding layer may be used to further facilitate total internal reflection, according to some examples. In particular, the cladding may comprise a material having an index of refraction that is greater than an index of refraction of the light guide material.

[0043] Further, according to some embodiments, the light guide 110 is configured to guide the guided light 104 according to total internal reflection at a non-zero propagation angle between a first surface 110' (e.g., ‘front’ or ‘top’ surface or side) and a second surface 110" (e.g., ‘back’ or ‘bottom’ surface or side) of the light guide 110. In particular, the guided light 104 propagates as a guided light beam by reflecting or ‘bouncing’ between the first surface 110' and the second surface 110" of the light guide 110 at the non-zero propagation angle. Note, the non-zero propagation angle is not illustrated in Figures 3 A-3C for simplicity of illustration. However, a bold arrow representing the first propagation direction 103 depicts a general propagation direction of the guided light 104 along the light guide length in Figure 3 A. [0044] As defined herein, a ‘non-zero propagation angle’ is an angle relative to a surface (e.g., the first surface 110' or the second surface 110") of the light guide 110. Further, the non-zero propagation angle is both greater than zero and less than a critical angle of total internal reflection within the light guide 110, according to various embodiments. For example, the non-zero propagation angle of the guided light 104 may be between about ten degrees (10°) and about fifty degrees (50°) or, between about twenty degrees (20°) and about forty degrees (40°), or between about twenty-five degrees (25°) and about thirty -five degrees (35°). For example, the non-zero propagation angle may be about thirty degrees (30°). In other examples, the non-zero propagation angle may be about 20°, or about 25°, or about 35°. Moreover, a specific non-zero propagation angle may be chosen (e.g., arbitrarily) for a particular implementation as long as the specific non-zero propagation angle is chosen to be less than the critical angle of total internal reflection within the light guide 110.

[0045] The guided light 104 in the light guide 110 may be introduced or directed into the light guide 110 at the non-zero propagation angle (e.g., about 30-35 degrees). In some embodiments, a structure such as, but not limited to, a lens, a mirror or similar reflector (e.g., a tilted collimating reflector), a diffraction grating, and a prism (not illustrated) as well as various combinations thereof may be employed to introduce light into the light guide 110 as the guided light 104. In other examples, light may be introduced directly into the input end of the light guide 110 either without or substantially without the use of a structure (i.e., direct or ‘butt’ coupling may be employed). Once directed into the light guide 110, the guided light 104 is configured to propagate along the light guide 110 in the first propagation direction 103 that is generally away from the input end.

[0046] Further, the guided light 104 having the predetermined collimation factor <j may be referred to as a ‘collimated light beam’ or ‘collimated guided light.’ Herein, a ‘collimated light’ or a 'collimated light beam' is generally defined as a beam of light in which rays of the light beam are substantially parallel to one another within the light beam (e.g., the guided light beam), except as allowed by the collimation factor c.

Further, rays of light that diverge or are scattered from the collimated light beam are not considered to be part of the collimated light beam, by definition herein. [0047] As illustrated in Figures 3A-3C, the multiview backlight 100 further comprises an array of multibeam elements 120 spaced apart from one another across the light guide 110. According to various embodiments, each multibeam element 120 of the multibeam element array is configured to scatter out a portion of the guided light 104 as the emitted light 102 having the tailored, off-axis luminance profile and comprising the plurality of directional light beams. In Figures 3 A and 3C, the directional light beams of the emitted light 102 are depicted as arrows directed away from individual multibeam elements 120 of the multibeam element array.

[0048] According to some embodiments (e.g., as illustrated in Figures 3A-3C), multibeam elements 120 of the multibeam element array may be disposed at or adjacent to the first surface 110' of the light guide 110 or equivalently adjacent to a first surface of the multiview backlight 100. In other embodiments (not illustrated in Figures 3A-3C), the multibeam elements 120 may be located within the light guide 110. In yet other embodiments (also not illustrated), the multibeam elements 120 may be located at or on the second surface 110" of the light guide 110 or equivalently adjacent to a second surface of the multiview backlight 100. Further, a size of the multibeam element 120 may be comparable to a size of a light valve of a multiview display configured to display the multiview image, e.g., the light valve 108 illustrated in Figures 3A-3C. That is, the multibeam element size is comparable to a light valve size of the light valve array as illustrated.

[0049] Herein, the ‘size’ may be defined in any of a variety of manners to include, but not be limited to, a length, a width or an area. For example, the size of a light valve may be a length thereof and the comparable size of the multibeam element 120 may also be a length of the multibeam element 120. In another example, size may refer to an area such that an area of the multibeam element 120 may be comparable to an area of the light valve. In some embodiments, the size of the multibeam element 120 is comparable to the light valve size such that the multibeam element size is between about twenty-five percent (25%) of and about two hundred percent (200%) of the light valve size. For example, if the multibeam element size is denoted A’ and the light valve size of the light valve 108 is denoted ‘5’ (e.g., as illustrated in Figure 3 A), then the multibeam element size 5 may be given by equation (1) as is < s < 2S (2)

[0050] In other examples, the multibeam element size is greater than about fifty percent (50%) of the light valve size, or 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 percent (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 120 may be comparable in size to the light valve 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 120 and the light valve may be chosen to reduce, or in some examples to minimize, dark zones between views of the multiview display, while at the same time reducing, or in some examples minimizing, an overlap between views of the multiview display or equivalent of the multiview image.

[0051] In some embodiments, a relationship between the multibeam elements 120 of the plurality and corresponding multiview pixels 106 (e.g., sets of light valves 108) may be a one-to-one relationship. That is, there may be an equal number of multiview pixels 106 and multibeam elements 120. Figure 3C explicitly illustrates by way of example the one-to-one relationship where each multiview pixel 106 comprising a different set of light valves 108 is illustrated as surrounded by a dashed line. In other embodiments (not illustrated), the number of multiview pixels 106 and multibeam elements 120 may differ from one another.

[0052] In some embodiments, an inter-element distance (e.g., center-to-center distance) between a pair of adjacent multibeam elements 120 of the array of multibeam elements 120 may be equal to an inter-pixel distance (e.g., a center-to-center distance) between a corresponding adjacent pair of multiview pixels 106, e.g., represented by light valve sets. In other embodiments (not illustrated), the relative center-to-center distances of pairs of multibeam elements 120 and corresponding light valve sets may differ, e.g., the multibeam elements 120 may have an inter-element spacing (i.e., center-to-center distance) that is one of greater than or less than a spacing (i.e., center-to-center distance) between light valve sets representing multiview pixels 106.

[0053] In some embodiments, a shape of the multibeam element 120 is analogous to a shape of the multiview pixel 106 or equivalently, a shape of a set of the light valves 108 corresponding to the multiview pixel 106. For example, the multibeam element 120 may have a square shape and the multiview pixel 106 (or an arrangement of a corresponding set of light valves 108) may be substantially square. In another example, the multibeam element 120 may have a rectangular shape, i.e., may have a length or longitudinal dimension that is greater than a width or transverse dimension. In this example, the multiview pixel 106 (or equivalently the arrangement of the set of light valves 108) corresponding to the multibeam element 120 may have an analogous rectangular shape. Figure 3C illustrates a perspective view of square-shaped multibeam elements 120 and corresponding square-shaped multiview pixels 106 comprising square sets of light valves 108. In yet other examples (not illustrated), the multibeam elements 120 and the corresponding multiview pixels 106 have various shapes including or at least approximated by, but not limited to, a triangular shape, a hexagonal shape, and a circular shape.

[0054] In some embodiments, a multibeam element 120 of the multibeam element array may comprise a diffraction grating configured to diffractively scatter out the guided light portion as the directional light beam plurality of the emitted light 102. In some embodiments, a multibeam element 120 of the multibeam element array may comprise a micro-reflective element configured to reflectively scatter out the guided light portion as the directional light beam plurality. In some embodiments, a multibeam element 120 of the multibeam element array may comprise a micro-refractive element configured to refractively scatter out the guided light portion as the directional light beam plurality. In some embodiments, the multibeam element 120 may comprise one or more of a diffraction grating, a micro-reflective element, and a micro-refracting element.

[0055] According to various embodiments, characteristics of the multibeam element 120 such as, but not limited to, scattering efficiency and scattering orientation of the multibeam element 120 may be configured to determine or control the tailored, off- axis luminance profile provided by each multibeam element 120 of the multibeam element array. For example, in a multibeam element 120 comprising a diffraction grating, a depth or height of various diffractive features of the diffraction grating (i.e., diffraction grating depth), an orientation of the various diffractive features as well as a pitch or spacing of the diffractive features may be used to control diffractive scattering of light to determine or control the tailored, off-axis luminance profile of the emitted light 102. Similarly for example, the tailored, off-axis luminance profile provided by multibeam elements 120 comprising micro-reflective elements may be determined or provide by a slope and orientation of a reflective surface of the micro-reflective element along with or as well as an overall reflectivity of the reflective surface. In a multibeam element 120 comprising a micro-refractive element, the off-axis luminance profile may be determined or controlled by a refractive index and an orientation of the micro-reflective element, for example.

[0056] Figure 5A illustrates a cross-sectional view of a portion of a multiview backlight 100 including a multibeam element 120 in an example, according to an embodiment consistent with the principles described herein. Figure 5B illustrates a cross- sectional view of a portion of a multiview backlight 100 including a multibeam element 120 in an example, according to another embodiment consistent with the principles described herein. In particular, Figures 5A-5B illustrate the multibeam element 120 of the multiview backlight 100 comprising a diffraction grating 122. The diffraction grating 122 is configured to diffractively couple or scatter out a portion of the guided light 104 as the plurality of directional light beams of the emitted light 102. The diffraction grating 122 comprises a plurality of diffractive features spaced apart from one another by a diffractive feature spacing (or a diffractive feature pitch or grating pitch) configured to provide diffractive scattering out of the guided light portion. According to various embodiments, the spacing or grating pitch of the diffractive features in the diffraction grating 122 may be sub -wavelength (i.e., less than a wavelength of the guided light 104). [0057] In some embodiments, the diffraction grating 122 of the multibeam element 120 may be located at or adjacent to a surface of the light guide 110. For example, the diffraction grating 122 may be at or adjacent to the first surface 110' of the light guide 110, as illustrated in Figure 5A. The diffraction grating 122 at the first surface 110' of the light guide 110 may be a transmission mode diffraction grating configured to diffractively scatter out the guided light portion through the first surface 110' as the directional light beams of the emitted light 102. In another example, as illustrated in Figure 5B, the diffraction grating 122 may be located at or adjacent to the second surface 110" of the light guide 110. When located at the second surface 110", the diffraction grating 122 may be a reflection mode diffraction grating. As a reflection mode diffraction grating, the diffraction grating 122 is configured to both diffract the guided light portion and reflect the diffracted guided light portion toward the first surface 110' to exit through the first surface 110' as the directional light beams of the emitted light 102. In other embodiments (not illustrated), the diffraction grating may be located between the surfaces of the light guide 110, e.g., as one or both of a transmission mode diffraction grating and a reflection mode diffraction grating. Note that, in some embodiments described herein, the principal angular directions of the directional light beams of the emitted light 102 may include an effect of refraction due to the directional light beams exiting the light guide 110 at a light guide surface. For example, Figure 5B illustrates refraction (i.e., bending) of the directional light beams due to a change in refractive index as the emitted light 102 crosses the first surface 110', by way of example and not limitation. Also see Figures 6 and 7, described below.

[0058] According to some embodiments, the diffractive features of the diffraction grating 122 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 light guide 110, e.g., may be formed in a surface of the light guide 110. In another example, the grooves or the ridges may be formed from a material other than the light guide material, e.g., a film or a layer of another material on a surface of the light guide 110.

[0059] In some embodiments, the diffraction grating 122 of the multibeam element 120 is a uniform diffraction grating in which the diffractive feature spacing is substantially constant or unvarying throughout the diffraction grating 122. In other embodiments, the diffraction grating 122 may be a chirped diffraction grating. By definition, the ‘chirped’ diffraction grating is a diffraction grating exhibiting or having a diffraction spacing of the diffractive features (i.e., the grating pitch) that varies across an extent or length of the chirped diffraction grating. In some embodiments, the chirped diffraction grating may have or exhibit a ‘chirp’ of or change in the diffractive feature spacing that varies linearly with distance. As such, the chirped diffraction grating is a ‘linearly chirped’ diffraction grating, by definition. In other embodiments, the chirped diffraction grating of the multibeam element 120 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 or sawtooth chirp, may also be employed. Combinations of any of these types of chirps may also be employed.

[0060] Figure 6 illustrates a cross-sectional view of a portion of a multiview backlight 100 including a multibeam element 120 in an example, according to another embodiment consistent with the principles described herein. Figure 7 illustrates a cross- sectional view of a portion of a multiview backlight 100 including a multibeam element 120 in an example, according to another embodiment consistent with the principles described herein. In particular, Figures 6 and 7 illustrate various embodiments of the multibeam element 120 comprising a micro-reflective element 124. Micro-reflective elements used as or in the multibeam element 120 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 total internal reflection (TIR). According to some embodiments (e.g., as illustrated in Figures 6-7), the multibeam element 120 comprising the micro-reflective element 124 may be located at or adjacent to a surface (e.g., the second surface 110") of the light guide 110. In other embodiments (not illustrated), the micro-reflective element 124 may be located either within the light guide 110 between the first and second surfaces 110', 110". In yet other embodiments (not illustrated), the micro-reflective element 124 may be disposed at or within the first surface 110' of the light guide 110, e.g., the micro- reflective element 124 may comprise a reflective slot in the first surface 110'. In some embodiments, micro-reflective element 124 of the multibeam element 120 may be configured to scatter guided light 104 incident from different directions, as illustrated in Figures 6 and 7 by a pair of arrows representing a first propagation direction 103 and a second propagation direction 103' of the guided light 104. [0061] Figure 8 illustrates a cross-sectional view of a portion of a multiview backlight 100 including a multibeam element 120 in an example, according to another embodiment consistent with the principles described herein. In particular, Figure 8 illustrates a multibeam element 120 comprising a micro-refractive element 126. According to various embodiments, the micro-refractive element 126 is configured to refractively couple or scatter out a portion of the guided light 104 from the light guide 110. That is, the micro-refractive element 126 is configured to employ refraction (e.g., as opposed to diffraction or reflection) to couple or scatter out the guided light portion from the light guide 110 as the emitted light 102 comprising the directional light beams, as illustrated in Figure 8. The micro-refractive element 126 may have various shapes including, but not limited to, a semi-spherical shape, a rectangular shape or a prismatic or an inverted prismatic shape (i.e., a shape having sloped facets). According to various embodiments, the micro-refractive element 126 may extend or protrude out of a surface (e.g., the first surface 110') of the light guide 110, as illustrated, or may be a cavity in the surface (not illustrated). Further, the micro-refractive element 126 may comprise a material of the light guide 110, in some embodiments. In other embodiments, the micro- refractive element 126 may comprise another material adjacent to, and in some examples, in contact with the light guide surface.

[0062] In some embodiments, a multibeam element 120 of the multibeam element array may comprise a plurality of sub-elements configured to scatter out the guided light portion and collectively provide the plurality of directional light beam having the intensities configured to provide the tailored, off-axis luminance profile and the directions corresponding to the view directions. That is, sub-elements of the sub-element plurality may have different scattering characteristics that are tuned or otherwise configured to collectively provide the tailored, off-axis luminance profile.

[0063] For example, the plurality of sub-elements of the multibeam element 120 may comprise a plurality of diffraction grating sub-elements, an orientation, a grating pitch, and a grating scattering efficiency of different diffraction grating sub-elements being configured to collectively contribute to both the direction and intensity of directional light beams to provide the tailored, off-axis luminance profile. In some embodiments, differential grating depths of the different diffraction grating sub-elements may be configured to determine the grating scattering efficiency that provides or contributes to the tailored, off-axis luminance profile.

[0064] In other examples, the plurality of sub-elements of the multibeam element 120 may comprise a plurality of reflective sub-elements, an orientation and reflectivity characteristics of different diffraction grating sub-elements of the reflective sub-element plurality being configured to collectively contribute to both the direction and intensity of directional light beams to provide the tailored, off-axis luminance profile. In yet other example, the plurality of sub-elements of the multibeam element 120 may comprise refractive sub-elements having different refraction characteristics and orientations configured to collectively contribute to both the direction and intensity of directional light beams to provide the tailored, off-axis luminance profile.

[0065] In some embodiments, the multibeam element 120 comprising diffraction grating sub-elements is a diffraction grating 122 comprises a plurality or an array of subgratings. Further, according to some embodiments, a differential density of sub-gratings within the diffraction grating 122 between different multibeam elements 120 of the multibeam element array may be configured to control a relative intensity of the plurality of directional light beams of the emitted light 102 that is diffractively scattered out by respective different multibeam elements 120. In other words, the multibeam elements 120 may have different densities of sub-gratings within the diffraction gratings 122, respectively, and the different sub-grating densities may be configured to control the relative intensity of the plurality of directional light beams. In particular, a multibeam element 120 having fewer sub-gratings within the diffraction grating 122 may produce a plurality of directional light beams of the emitted light 102 having a lower intensity (or beam density) than another multibeam element 120 having relatively more sub-gratings. Further, selective density differences of sub-gratings may be employed to control or determine the tailored, off-axis luminance profile. That is, different sub-gratings having different scattering directions may be included or omitted from the diffraction grating to provide a particular tailored, off-axis luminance profile of the particular multibeam element 120.

[0066] Figure 9 illustrates a plan view of a multibeam element 120 in an example, according to an embodiment consistent with the principles described herein. As illustrated, the multibeam element 120 comprises a diffraction grating 122 having a plurality of sub-gratings 128. In addition, the diffraction grating 122 has locations 129 without a sub-grating to facilitate control of a density of sub-gratings and, in turn, control a relative intensity of scattering as well as the tailored, off-axis luminance profile provided by the diffraction grating 122, as illustrated in Figure 9. Figure 9 also illustrates a size 5 of the multibeam element 120 to emphasize that the sub-gratings are all contained within the diffraction grating 122 having the size 5. Note that while Figure 9 illustrates an embodiment of a multibeam element 120 comprising a diffraction grating 122 having sub-gratings, a multibeam element 120 having reflective sub-elements or refractive subelements would be conceptually similar to that illustrated in Figure 9, however with reflective sub-elements or refractive sub-elements replacing the sub-gratings (or equivalently diffractive sub-elements).

[0067] Referring again to Figures 3A-3C, the multiview backlight 100 may further comprise a light source 130, according to some embodiments. As such, the multiview backlight 100 may be an edge-lit backlight, for example. According to various embodiments, the light source 130 is configured to provide the light to be guided within light guide 110 as the guided light 104. In particular, the light source 130 may be located adjacent to an entrance surface or end (input end) of the light guide 110. In various embodiments, the light source 130 may comprise substantially any source of light (e.g., optical emitter) including, but not limited to, one or more light emitting diodes (LEDs) or a laser (e.g., laser diode). In some embodiments, the light source 130 may comprise an optical emitter configured produce a substantially monochromatic light having a narrowband spectrum denoted by a particular color. In particular, the color of the monochromatic light may be a primary color of a particular color space or color model (e.g., a red-green-blue (RGB) color model). In other examples, the light source 130 may be a substantially broadband light source configured to provide substantially broadband or polychromatic light. For example, the light source 130 may provide white light. In some embodiments, the light source 130 may comprise a plurality of different optical emitters configured to provide different colors of light. The different optical emitters may be configured to provide light having different, color-specific, non-zero propagation angles of the guided light corresponding to each of the different colors of light. [0068] In some embodiments, the light source 130 may further comprise a collimator (not illustrated). The collimator may be configured to receive substantially uncollimated light from one or more of the optical emitters of the light source 130. The collimator is further configured to convert the substantially uncollimated light into collimated light. In particular, the collimator may provide collimated light having the non-zero propagation angle and being collimated according to a predetermined collimation factor G, according to some embodiments. Moreover, when optical emitters of different colors are employed, the collimator may be configured to provide the collimated light having one or both of different, color-specific, non-zero propagation angles and having different color-specific collimation factors. The collimator is further configured to communicate the collimated light to the light guide 110 to propagate as the guided light 104, described above. According to various embodiments, wherein the predetermined collimation factor G may be selected to determine an overall spread angle of the plurality of directional light beams of the emitted light 102.

[0069] According to some embodiments of the principles described herein, a multiview display is provided. Figure 10 illustrates a block diagram of a multiview display 200 in an example, according to an embodiment consistent with the principles described herein. As illustrated, the multiview display 200 comprises a multiview backlight 210 having an array of multibeam elements spaced apart from one another. According to various embodiments, each multibeam element of the multibeam element array is configured to provide directional light beams 202 having intensities configured to provide a tailored, off-axis luminance profile and directions corresponding to view directions of the multiview display 200. The multiview display 200 illustrated in Figure 10 further comprises an array of light valves 220 configured to modulate the directional light beams 202 to provide view pixels of a multiview image displayed by the multiview display. According to various embodiments, a size of each multibeam element is between one quarter and two times a size of a light valve of the light valve array. Further, the tailored, off-axis luminance profile has a lower luminance in an on-axis direction and a higher luminance in off-axis directions away from the on-axis direction, according to various embodiments. [0070] In some embodiments, the multiview backlight 210 may be substantially similar to the multiview backlight 100 described above. In particular, the directional light beams 202 may be substantially similar to the directional light beams of the emitted light 102 of the above-described multiview backlight 100. Additionally, in some embodiments the multiview backlight 210 may further comprise a light guide configured to guide light as guided light. In these embodiments, multibeam elements of the multibeam element array are configured to being configured to scatter out a portion of the guided light to provide the directional light beams 202. In some embodiments, the light valves 220 of the light valve array may be substantially similar to the light valves 108 described above with respect to the multiview backlight 100.

[0071] In some embodiments, multibeam elements of the multiview backlight 210 may be substantially similar to multibeam elements 120 of the multiview backlight 100. For example, a multibeam element of the multibeam element array of the multiview backlight 210 may comprise one or more of a diffraction grating configured to diffractively scatter out the guided light portion as the directional light beams, a micro- reflective element configured to reflectively scatter out the guided light portion as the directional light beams, and a micro-refractive element configured to refractively scatter out the guided light portion as the directional light beams. Also, a multibeam element of the multibeam element array may comprise a plurality of sub-elements configured to scatter out the guided light portion and collectively provide the directional light beams having the intensities configured to provide the tailored, off-axis luminance profile and the directions corresponding to the view directions, in some embodiments.

[0072] In other embodiments, the multiview backlight further comprises a substrate, multibeam elements of the multibeam element array comprising active emitters mounted on and spaced apart across the substrate. In some embodiments, the tailored, off-axis luminance profile has a higher luminance in off-axis directions corresponding to angles greater than the on-axis direction. In some embodiments, the tailored, off-axis luminance profile has a higher luminance in off-axis directions corresponding angles both less than and greater than the on-axis direction. In some embodiments, the multiview display 200 may be configured to be used in an automobile, the off-axis directions having the higher luminance of the tailored, off-axis luminance profile corresponding to a direction of a driver and a direction of a passenger of the automobile.

[0073] In accordance with other embodiments of the principles described herein, a method of multiview display operation is provided. The method of multiview display operation may be used to generate a multiview image using or on a multiview display characterized by a tailored, off-axis luminance profile that is tailored to particular uses or applications of the multiview display. In particular, tailored, off-axis luminance profile may be tailored to particular uses or applications of the multiview display such as, but not limited to, providing multiview images to one or both of a driver and a passenger of an automobile, for example.

[0074] Figure 11 illustrates a flow chart of a method 300 of multiview display operation in an example, according to an embodiment consistent with the principles described herein. As illustrated, the method 300 of multiview display operation comprises emitting 310 directional light beams using an array of multibeam elements. In various embodiments, the emitted directional light beams have intensities configured to provide a tailored, off-axis luminance profile along with directions corresponding to different views of a multiview image displayed by the multiview display. In particular, the tailored, off-axis luminance profile may have a lower luminance in an on-axis direction and a higher luminance in off-axis directions away from the on-axis direction. In some embodiments, the tailored, off-axis luminance profile may have either a higher luminance in off-axis directions corresponding to angles greater than the on-axis direction or a higher luminance in off-axis directions corresponding angles both less than and greater than the on-axis direction, the on-axis direction being perpendicular to a surface of the multi view display

[0075] The method 300 of multiview display operation illustrated in Figure 11 further comprises modulating 320 the directional light beams using an array of light valves to provide view pixels of the multiview image. In various embodiments, a size of each multibeam element of the multibeam element array is between one quarter and two times a size of a light valve of the light valve array. In some embodiments, the light valves of the light valve array may be substantially similar to either the light valves 108 of the above-described multiview backlight 100 or the light valves 220 of the multiview display 200, described above.

[0076] In some embodiments (not illustrated), the method 300 of multiview display operation further comprises guiding light in a light guide as guided light. In some embodiments, the light guide may be substantially similar to the light guide 110 described above with respect to the multiview backlight 100.

[0077] In some embodiments, the array of multibeam elements used in emitting 310 directional light beams may be substantially similar to the array of multibeam elements 120 of the multiview backlight 100, described above. In addition, the emitted directional light beams may be substantially similar to the plurality of directional light beams of the emitted light 102 described above with respect to the multiview backlight 100. In particular, multibeam elements of the multibeam element array may comprise one or more of a diffraction grating that diffractively scatters out a portion of the guided light as the directional light beams, a micro-reflective element that reflectively scatters out a portion of the guided light as the directional light beams, and a micro-refractive element that refractively scatters out a portion of the guided light as the directional light beams. In addition, multibeam elements may each comprise a plurality of sub-elements that collectively scatter out the guided light portion and provide the directional light beams having the intensities that provide the tailored, off-axis luminance profile and the directions corresponding to the view directions, according to some embodiments.

[0078] Thus, there have been described examples and embodiments of a multiview backlight, a multiview display, and a method of multiview display operation that provide emitted light having a tailored, off-axis luminance profile. It should be understood that the above-described examples are merely illustrative of some of the many specific examples and embodiments that represent the principles described herein. Clearly, those skilled in the art can readily devise numerous other arrangements without departing from the scope as defined by the following claims.