CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priority to U.S. Provisional Patent Application Serial No. 62/964,589, filed January 22, 2020, the entirety of which is incorporated by reference herein.

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/ AMOLEDs. 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. 2

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[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 reflective microprism scattering element based backlight in an example, according to an embodiment consistent with the principles described herein.

[0008] Figure 3B illustrates a plan view of a reflective microprism scattering element based backlight in an example, according to an embodiment consistent with the principles described herein.

[0009] Figure 3C illustrates a perspective view of a reflective microprism scattering element based backlight in an example, according to an embodiment consistent with the principles described herein.

[0010] Figure 3D illustrates a perspective view of a reflective microprism scattering element based backlight in an example, according to another embodiment consistent with the principles described herein.

[0011] Figure 4A illustrates a perspective view of a portion of a reflective microprism scattering element based backlight in an example, according to an embodiment consistent with the principles described herein.

[0012] Figure 4B illustrates a perspective view of a portion of a reflective microprism scattering element based backlight in an example, according to another embodiment of the principles described herein.

[0013] Figure 4C illustrates a perspective view of a portion of a reflective microprism scattering element based backlight in an example, according to another embodiment of the principles described herein.

[0014] Figure 5A illustrates a perspective view of a portion of a reflective microprism scattering element based backlight in an example, according to an embodiment of the principles described herein. LI-162

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[0015] Figure 5B illustrates a perspective view of a portion of a reflective microprism scattering element based backlight in an example, according to another embodiment of the principles described herein.

[0016] Figure 6A illustrates a cross-sectional view of a multiview display in an example, according to an embodiment consistent with the principles described herein. [0017] Figure 6B illustrates a plan view of a multiview display in an example, according to an embodiment consistent with the principles described herein.

[0018] Figure 6C illustrates a perspective view of a multiview display in an example, according to an embodiment consistent with the principles described herein. [0019] Figure 7 illustrates a flow chart of a method of backlight operation in an example, according to an embodiment consistent with the principles described herein. [0020] 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

[0021] Examples and embodiments in accordance with the principles described herein provide backlighting that provides emitted light with an emission pattern having a predetermined light exclusion zone. The backlighting may be used as an illumination source in displays, including multiview displays, according to various embodiments. In particular, embodiments consistent with the principles described herein provide a reflective microprism scattering element based backlight comprises a plurality or array of reflective microprism scattering elements configured to scatter light out of a light guide as emitted light. The emitted light is preferentially provided within an emission zone, while being excluded from the predetermined exclusion zone by scattering. According to various embodiments, reflective microprism scattering elements of the reflective microprism scattering element plurality comprise a sloped reflective sidewall having a slope angle to control the emission pattern and specifically to provide the predetermined exclusion zone of the emitted light. Uses of displays that employ the reflective microprism scattering element based backlight described herein include, but are not limited to, mobile telephones (e.g., smart phones), watches, tablet computes, mobile computers (e.g., laptop computers), personal computers and computer monitors, automobile display consoles, cameras displays, and various other mobile as well as substantially non-mobile display applications and devices.

[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 {q, f), 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

{ q, 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). 6

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[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, 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 LI-162

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WO 2021/151009 PCT/US2021/014776 by a top surface and a bottom surface (i.e., opposite surfaces) of the light guide. Further, by definition herein, the top and bottom or ‘guiding’ surfaces of the light guide 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. 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 LI-162 8

WO 2021/151009 PCT/US2021/014776 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 {q, f), by definition herein, and as described above with respect to Figure 2.

[0032] Herein, an ‘angle-preserving scattering feature’ or equivalently an ‘angle preserving scatterer’ is defined as any feature or scatterer configured to scatter light in a manner that substantially preserves in scattered light an angular spread of light incident on the feature or scatterer. In particular, by definition, an angular spread o _s of light scattered by an angle-preserving scattering feature is a function of an angular spread s of the incident light (i.e., o _s = /(s) ). In some embodiments, the angular spread o _s of the scattered light is a linear function of the angular spread or collimation factor s of the incident light (e.g., o _s = a s, where a is an integer). That is, the angular spread s _L of light scattered by an angle-preserving scattering feature may be substantially proportional to the angular spread or collimation factor s of the incident light. For example, the angular spread s _L of the scattered light may be substantially equal to the incident light angular spread s (e.g., s _L ~ s). A uniform diffraction grating (i.e., a diffraction grating having a substantially uniform or constant diffractive feature spacing or grating pitch) is an example of an angle-preserving scattering feature. In contrast, a Lambertian scatterer or reflector as well as a general diffuser (e.g., having or approximating Lambertian scattering) are not angle-preserving scatterers, by definition herein.

[0033] 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.

[0034] 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 LI-162

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WO 2021/151009 PCT/US2021/014776 within a collimated beam of light, by definition herein. For example, a collimation factor s may specify that a majority of light rays in a beam of collimated light is within a particular angular spread (e.g., +/- s 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.

[0035] 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.

[0036] As used herein, the article ‘a’ is intended to have its ordinary meaning in the patent arts, namely ‘one or more’. For example, ‘a reflective microprism scattering element’ means one or more reflective microprism scattering elements and as such, ‘the reflective microprism scattering element’ means ‘the reflective microprism scattering element(s)’ herein. Also, any reference herein to ‘top’, ‘bottom’, ‘upper’, ‘lower’, ‘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. LI-162 10

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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.

[0037] According to some embodiments of the principles described herein, a reflective microprism scattering element based backlight is provided. Figure 3 A illustrates a cross-sectional view of a reflective microprism scattering element based backlight 100 in an example, according to an embodiment consistent with the principles described herein. Figure 3B illustrates a plan view of a reflective microprism scattering element based backlight 100 in an example, according to an embodiment consistent with the principles described herein. Figure 3C illustrates a perspective view of a reflective microprism scattering element based backlight 100 in an example, according to an embodiment consistent with the principles described herein. Figure 3D illustrates a perspective view of a reflective microprism scattering element based backlight 100 in an example, according to another embodiment consistent with the principles described herein.

[0038] The reflective microprism scattering element based backlight 100 illustrated in Figures 3A-3D is configured to provide emitted light 102 with an emission pattern having a predetermined light exclusion zone. In particular, as illustrated in Figure 3 A the reflective microprism scattering element based backlight 100 preferentially provides emitted light 102 within an emission zone /, while emitted light 102 is not provided within the predetermined light exclusion zone II. As a result, if the reflective microprism scattering element based backlight 100 is viewed in an angular range representing or encompassing the emission zone /, emitted light 102 may be visible. Alternatively, emitted light 102 may not be visible when the reflective microprism scattering element based backlight 100 is viewed in a range of angles representing or encompassing the predetermined light exclusion zone II.

[0039] The predetermined light exclusion zone II may provide privacy viewing of a display that incorporates the reflective microprism scattering element based backlight 100 as an illumination source, for example. In particular, the emitted light 102 may be modulated to facilitate the display of information on the display that is illuminated by or LI-162 11

WO 2021/151009 PCT/US2021/014776 using the reflective microprism scattering element based backlight 100, in some embodiments. For example, the emitted light 102 may be reflectively scattered out of an ‘emission surface’ of the reflective microprism scattering element based backlight 100 and toward an array of light valves (e.g., an array of light valves 230, described below). The emitted light 102 may then be modulated using the array of light valves to provide an image displayed by or on the display. However, as a result of the predetermined light exclusion zone //provided by the reflective microprism scattering element based backlight 100, the image display be the display may visible exclusively in the emission zone I. Thus, the reflective microprism scattering element based backlight 100 provides privacy viewing the prevents a viewer from seeing the image in the predetermined light exclusion zone II (i.e., the display may appear black or OFF’ when viewed in the predetermined light exclusion zone IT).

[0040] In some embodiments (e.g., as described below with respect to a multiview display), the emitted light 102 may comprise directional light beams having different principal angular directions from one another (e.g., as or representing a light field). Further, the directional light beams of the emitted light 102 are directed away from the reflective microprism scattering element based backlight 100 in different directions corresponding to respective view directions of a multiview display or equivalently different view directions of a multiview image displayed by the multiview display, according to these embodiments. In some embodiments, the directional light beams of the emitted light 102 may be modulated an array of light valves to facilitate the display of information having multiview content, e.g., a multiview image. The multiview image may represent or include three-dimensional (3D) content, for example.

[0041] As illustrated in Figures 3 A-3D, the reflective microprism scattering element based backlight 100 comprises a light guide 110. The light guide 110 is configured to guide light in a propagation direction 103 as guided light 104. Further, the guided light 104 may have or be guided according to a predetermined collimation factor s, in various embodiments. 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 LI-162 12

WO 2021/151009 PCT/US2021/014776 facilitate total internal reflection of the guided light 104 according to one or more guided modes of the light guide 110.

[0042] 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, alkali -aluminosilicate 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. In some embodiments, the guided light 104 may include a plurality of guided light beams representing different colors of light. The different colors of light may be guided by the light guide 110 at respective ones of different color-specific, nonzero propagation angles. Note, the non-zero propagation angle is not illustrated in Figures 3 A-3D for simplicity of illustration. However, a bold arrow representing the propagation direction 103 depicts a general propagation direction of the guided light 104 along the light guide length in Figure 3 A. LI-162

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[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 (35°) degrees. For example, the non-zero propagation angle may be about thirty (30°) degrees. 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 propagation direction 103 that is generally away from the input end. [0046] Further, the guided light 104, having the predetermined collimation factor s 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 s.

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 3 A-3D, the reflective microprism scattering element based backlight 100 further comprises an plurality of reflective microprism scattering elements 120 distributed across the light guide 110. In some embodiments, the reflective microprism scattering elements 120 may be distributed in a random or at least substantially random pattern across the light guide 110, e.g., as illustrated in Figures 3B- 3D. In other embodiments, reflective microprism scattering elements 120 of the reflective microprism scattering element plurality may be arranged in either a one dimensional (ID) arrangement (not illustrated) or a two-dimensional (2D) arrangement (e.g., as illustrated). For example (not illustrated), the reflective microprism scattering elements may be arranged as a linear ID array (e.g., a plurality of lines comprising staggered lines of reflective microprism scattering elements 120). In another example (not illustrated), the reflective microprism scattering elements 120 may be arranged as 2D array such as, but not limited to, a rectangular 2D array or as a circular 2D array. In some embodiments, the reflective microprism scattering elements 120 be distributed in a regular or constant manner across the light guide 110, while in other embodiments the distribution may vary across the light guide 110. For example, a density of the reflective microprism scattering elements 120 may increase as a function of distance across the light guide 110.

[0048] In various embodiments, reflective microprism scattering element 120 of the reflective microprism scattering element plurality may have different cross-sectional profiles. For example, the cross-sectional profiles may exhibit a variety of reflective scattering surfaces with one or both of various slope angles and various surface curvatures to control an emission pattern of the reflective microprism scattering element 120. In particular, reflective microprism scattering elements 120 of the reflective microprism scattering element plurality each comprise a sloped reflective sidewall 122. The sloped reflective sidewall 122 is configured to reflectively scatter out a portion of the guided light 104 as the emitted light 102. Further, the sloped reflective sidewall 122 of the reflective microprism scattering element 120 has a slope angle tilted away from the propagation direction 103 of the guided light 104. According to various embodiments, a slope angle of the sloped reflective sidewall 122 is configured to provide or determine the predetermined light exclusion zone //in an emission pattern of the emitted light 102. That is, an angular range of the predetermined light exclusion zone //is a function of or determined by the slope angle.

[0049] In some embodiments, the sloped reflective sidewall 122 may be a substantially flat or faceted surface having the slope angle (e.g., as illustrated in Figures 3B-3C). In other embodiments (e.g., as illustrated in Figure 3D), the sloped reflective sidewall 122 may be or comprise a surface having a curve, i.e., a curved surface. The slope angle may be defined as an angle of a tangent to the curved surface (e.g., at a center of the curved surface), in these embodiments. Alternatively, the slope angle may be defined as an average slope of the curved surface, e.g., measured at a center point of the curved surface. According to some embodiments, the curved shape may be configured to control emission pattern of scattered light, e.g., by spreading or concentrating the scattered light.

[0050] In some embodiments, a microprism scattering element 120 of the reflective microprism scattering element plurality may extend into an interior of the light guide 110. In other embodiments, a reflective microprism scattering element 120 of the reflective microprism scattering element plurality may protrude from a surface of the light guide and away from an interior of the light guide 110. In yet other embodiments, the reflective microprism scattering elements 120 of the reflective microprism scattering element plurality may both extend into and protrude from the light guide surface. In some embodiments the slope angle may be between about ten degrees (10°) and about fifty degrees (50°) or between about twenty-five degrees (25°) and about forty-five degrees (45°) relative to the light guide surface.

[0051] Figure 4A illustrates a perspective view of a portion of a reflective microprism scattering element based backlight 100 in an example, according to an embodiment of the principles described herein. As illustrated in Figure 4A, the reflective microprism scattering element based backlight 100 comprises the light guide 110 with a reflective microprism scattering element 120 disposed on the second surface 110" of the light guide 110. The reflective microprism scattering element 120 illustrated in Figure 4A extends into an interior of the light guide 110. Guided light 104 may be reflected by the reflective microprism scattering element 120 to exit an emission surface of the light -16-

WO 2021/151009 PCT/US2021/014776 guide 110 (first surface 110') as the emitted light 102 having the predetermined exclusion zone II along with the emission zone I.

[0052] Figure 4B illustrates a perspective view of a portion of a reflective microprism scattering element based backlight 100 in an example, according to another embodiment of the principles described herein. As was illustrated in Figure 4A, the reflective microprism scattering element based backlight 100 illustrated in Figure 4B also comprises the light guide 110 with a reflective microprism scattering element 120 disposed on the second surface 110" of the light guide 110. However, in Figure 4B, the illustrated reflective microprism scattering element 120 protrudes from the light guide surface and away from the interior of the light guide 110. As illustrated, guided light 104 may be reflected by the reflective microprism scattering element 120 to exit an emission surface of the light guide 110 (first surface 110') as the emitted light 102 having the predetermined exclusion zone II along with the emission zone I.

[0053] In Figures 4A-4B, the sloped reflective sidewall 122 comprises a reflective facet or substantially flat surface, as illustrated. The sloped reflective sidewall 122 in each of Figure 4A and Figure 4B is configured to reflect the guided light 104 having the predetermined collimation factor s, as described above. The sloped reflective sidewall 122 may have a slope angle of about thirty -five degrees (35°) relative to the light guide surface, by way of example and not limitation. In some embodiments, the slope angle of about thirty-five degrees may provide an angular range of the predetermined exclusion zone II that is also about thirty-five degree (35°), when measured up from the light guide surface.

[0054] As mentioned above and illustrated Figure 3D, for example, a reflective microprism scattering element 120 of the reflective microprism scattering element plurality may have a curved shape. In various embodiments, the curved shape may be in a direction that is orthogonal to the guided light propagation direction 103. For example, the curved shape may be in a direction that is orthogonal to the propagation direction 103 and also in a plane parallel to a surface of the light guide 110. In other examples, the curved shape may be in a direction that is perpendicular to the surface of the light guide 110. According to some embodiments, the curved shape may be configured to control emission pattern of emitted light 102 one or both of in a plane orthogonal to and a plane LI-162

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WO 2021/151009 PCT/US2021/014776 parallel to the guided light propagation direction, e.g., in one or both of an y-z plane and an x-z plane. For example, controlling the emission pattern in the y-z plane may help to spread or concentrate the emitted light 102 in that plane.

[0055] Figure 4C illustrates a perspective view of a portion of a reflective microprism scattering element based backlight 100 in an example, according to an embodiment of the principles described herein. Figure 4D illustrates a perspective view of a portion of a reflective microprism scattering element based backlight 100 in an example, according to another embodiment of the principles described herein. Figure 4C illustrates the reflective microprism scattering element 120 extending into the interior of the light guide 110 similar to that illustrated in Figure 4A, while Figure 4D illustrates the reflective microprism scattering element 120 protruding from the light guide surface and away from the light guide interior, as was illustrated in Figure 4B. However, in each of Figures 4C and 4D, the reflective microprism scattering element 120 has a sloped reflective sidewall 122 that is curved, i.e., a curved sloped reflective sidewall 122. In particular, both Figures 4C and 4D illustrate a curvature of the curved sloped reflective sidewall 122 that is in an x-z plane, i.e., a plane that is parallel to the propagation direction. A curvature of the curved sloped reflective sidewall 122 in the x-z plane (i.e., length direction) may be configured to control an emission pattern of the emitted light 102 by either concentrating or spreading out an angular spread of the emitted light 102 within the emission zone /, according to various embodiments.

[0056] Figure 5A illustrates a perspective view of a portion of a reflective microprism scattering element based backlight 100 in an example, according to an embodiment of the principles described herein. Figure 5B illustrates a perspective view of a portion of a reflective microprism scattering element based backlight 100 in an example, according to another embodiment of the principles described herein. Both Figures 5A and 5B illustrate the reflective microprism scattering element 120 having a curved sloped reflective sidewall 122. Figure 5A illustrates the reflective microprism scattering element 120 and extending into the interior of the light guide 110, while Figure 5B illustrates the reflective microprism scattering element 120 protruding from the light guide surface and away from the light guide interior. Further, in each of Figures 5 A and 5B, the curved sloped reflective sidewall 122 has a curved shape or curvature in an y-z LI-162

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WO 2021/151009 PCT/US2021/014776 plane, i.e., in a plane that is perpendicular to the guided light propagation direction. The illustrated curvature of the curved sloped reflective sidewall 122 may be configured to control an emission pattern of the emitted light 102 by either concentrating or spreading out an angular spread of the emitted light 102 in the y-z plane (i.e., width direction), according to various embodiments.

[0057] In some embodiments (not illustrated), a reflective microprism scattering element 120 of the reflective microprism scattering element plurality may comprise a reflective material adjacent to and coating reflective surfaces of the reflective microprism scattering element 120. In some embodiments, an extent of the reflective material may be confined to or substantially confined to an extent or boundary of the reflective multibeam element 120 to form a reflective island. In some embodiments, the reflective material may fill or substantially fill the reflective microprism scattering element 120, e.g., when the reflective microprism scattering element 120 extends into an interior of the light guide 110, e.g., as illustrated in Figures 4A, 4C, and 5 A. In other embodiments (not illustrated), the reflective material layer may be configured to coat reflective surfaces of but not fill or substantially fill the reflective microprism scattering element 120.

[0058] In various embodiments, any of a number of reflective materials such as, but not limited to, reflective metals (e.g., aluminum, nickel, silver, gold, etc.) and various reflective-metal polymers (e.g., polymer-aluminum) may be employed as the reflective material. The reflective material may be applied by a variety of methods including, but not limited to, spin coating, evaporative deposition, and sputtering, for example. Photolithography or similar lithographic methods may be employed to define an extent of the reflective material layer after deposition to confine the reflective material to an extent of the reflective microprism scattering element 120 and form the reflective island, according to some embodiments.

[0059] According to various embodiments, the light exclusion zone II has an angular range that corresponds with (e.g., is about equal to) the slope angle of the sloped reflective sidewall 122. That is, the angular range of the predetermined light exclusion zone II is determined by the slope angle and extends from a plane parallel to the light guide surface to an angle g. The angle g of the predetermined light exclusion zone II is equal to ninety degrees (90°) minus the slope angle of the sloped reflective sidewall 122. LI-162

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[0060] Note that while each of the reflective microprism scattering elements 120 illustrated in Figures 3 A-3D are of similar in size and shape, in some embodiments (not illustrated) the reflective microprism scattering element 120 may differ from one another across the light guide surface. For example, the reflective microprism scattering elements 120 may have one or more of different sizes, different cross-sectional profiles, and even different orientations (e.g., a rotation relative to the guided light propagation directions) across the light guide 110. In particular, at least two reflective microprism scattering elements 120 may have different reflective scattering profiles from one another within the emitted light 102, according to some embodiments.

[0061] According to some embodiments, the sloped reflective sidewall 122 of the reflective microprism scattering element 120 is configured to reflectively scatter out a portion of the guided light 104 according to total internal reflection (i.e., due to a difference between a refractive index of materials on either side of the sloped reflective sidewall 122). That is, the guided light 104 having an incident angle of less than a critical angle at the sloped reflective sidewall 122 is reflected by the sloped reflective sidewall 122 to become the emitted light 102.

[0062] According to various embodiments, the slope angle is selected in conjunction with the non-zero propagation angle of the guided light 104 to provide one or both of a target angle of the emitted light 102 and the angular range of the predetermined light exclusion zone II. Further, the selected slope angle may be configured to preferentially scatter light in a direction of the emission surface of the light guide 110 (e.g., the first surface 110') and away from a surface of the light guide 110 opposite to the emission surface (e.g., the second surface 110"). That is, the sloped reflective sidewall 122 may provide little or substantially no scattering of the guided light 104 in a direction away from the emission surface, in some embodiments.

[0063] In some embodiments (e.g., as illustrated in Figures 4A-4D), a second sidewall of a reflective microprism scattering element 120 has a slope angle that is substantially similar to the slope angle of a first sidewall (e.g., the slope angle of the sloped reflective sidewall 122) of the reflective microprism scattering element 120. In other embodiments (not illustrated), the second sidewall of a reflective microprism LI-162 20

WO 2021/151009 PCT/US2021/014776 scattering element 120 may have a slope angle that differs from slope angle of the first sidewall, the first sidewall being the sloped reflective sidewall 122.

[0064] Referring again to Figure 3 A-3D, the reflective microprism scattering element based backlight 100 may further comprise a light source 130. According to various embodiments, the light source 130 is configured to provide the light to light guide 110 to be guided as the guided light 104. In particular, the light source 130 may be located adjacent to an input edge of the light guide 110, as illustrated. In some embodiments, the light source 130 may comprise a plurality of optical emitters spaced apart from one another along the input edge of the light guide 110.

[0065] 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. In accordance with some embodiments of the principles described herein, an electron display is provided. In particular, the electronic display may comprise the reflective microprism scattering element based backlight 100 and an array of light valves. According to these embodiments (not illustrated), array of light valves is configured to modulate the emitted light 102 having the predetermined light exclusion zone //provided by the reflective microprism scattering element based backlight 100. Modulation of the emitted light 102 using the light valve array may provide an image in the emission zone / outside of the predetermined light exclusion zone II. That is, the emitted light 102 illuminates the light valve array enabling display and viewing of the LI-162 21

WO 2021/151009 PCT/US2021/014776 image within the emission zone I. Alternatively, substantially nothing may be displayed within the predetermined light exclusion zone II. As such, the electronic display may appear to be ‘off when viewed from within the predetermined light exclusion zone II. In some embodiment, the electronic display that includes the reflective microprism scattering element based backlight 100 may represent a ‘privacy display’ given the ability to view the displayed image exclusively within the emission zone /, while simultaneously excluding viewing of the image within the predetermined light exclusion zone II.

[0066] In some embodiments, reflective micro-scattering elements of a reflective microprism scattering element backlight may be arranged as an array of reflective microprism multibeam elements. When so arranged, the electronic display may be a multiview display. In particular, each reflective microprism multibeam element of the reflective microprism multibeam element array may comprise a subset of reflective microprism scattering elements of the reflective microprism scattering element plurality. According to various embodiments, the reflective microprism multibeam elements comprising the reflective microprism scattering element subset are configured to reflectively scatter out a portion of the guided light as the emitted light comprising directional light beams having directions corresponding to respective view directions of the multiview display. Further, the directional light beams are confined to an emission zone and excluded from a predetermined exclusion zone within an emission pattern of the emitted light, according to various embodiments.

[0067] Figure 6A illustrates a cross-sectional view of a multiview display 200 in an example, according to an embodiment consistent with the principles described herein. Figure 6B illustrates a plan view of a multiview display 200 in an example, according to an embodiment consistent with the principles described herein. Figure 6C illustrates a perspective view of a multiview display 200 in an example, according to an embodiment consistent with the principles described herein. The perspective view in Figure 6C is depicted with a partial cut-away to facilitate discussion herein only.

[0068] As illustrated, the multiview display 200 comprises a light guide 210. In some embodiments, the light guide 210 may be substantially similar to the light guide 110 of the reflective microprism scattering element based backlight 100, described above. In particular, the light guide 210 is configured to guide light in a propagation direction 203 LI-162 22

WO 2021/151009 PCT/US2021/014776 as guided light 204. As illustrated, the guided light 204 is guided by and between a first surface 210' and a second surface 210" (i.e., guiding surfaces) of the light guide 210. [0069] The multiview display 200 illustrated in Figures 6A-6C further comprises an array of reflective microprism multibeam elements 220 spaced apart from one another across the light guide 210. According to various embodiments, a reflective microprism multibeam element 220 of the reflective microprism multibeam element array comprises a subset of reflective microprism scattering elements 222 of a plurality of reflective microprism scattering elements 222. Further, each reflective microprism scattering element 222 comprises a sloped reflective sidewall. Collectively, the sloped reflective sidewalls of the reflective microprism scattering elements 222 within the reflective microprism multibeam element 220 are configured to reflectively scatter out the guided light 204 (or at least a portion thereof) as emitted light 202 comprising directional light beams having directions corresponding to respective view directions of a multiview image displayed by the multiview display 200. Further, the emitted light 202 has a predetermined light exclusion zone II that is a function of a slope angle of the sloped reflective sidewalls, according to various embodiments. In particular, reflective scattering is configured to occur at or is provided by the sloped reflective sidewalls of the reflective microprism scattering elements 222 of the reflective microprism multibeam element 220. However, the emitted light 202 is preferentially confined to an emission zone / and excluded from the predetermined light exclusion zone II of the emitted light 202, according to various embodiments. Figures 6A and 6C illustrate the directional light beams of the emitted light 202 as a plurality of diverging arrows directed way from the first surface 210' (i.e., emission surface) of the light guide 210 within the emission zone I. The emission zone / and predetermined light exclusion zone II illustrated in Figures 6A and 6C may be substantially similar to the respective emission zone / and predetermined light exclusion zone //, illustrated in Figure 3 A, according to some embodiments.

[0070] In some embodiments, the reflective microprism scattering elements 222 of the reflective microprism multibeam element 220 may be substantially similar to the reflective microprism scattering elements 120 of the above-described reflective microprism scattering element backlight 100. As such, in some embodiments, the light guide 210 and array of reflective microprism multibeam elements 220 may be essentially LI-162

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WO 2021/151009 PCT/US2021/014776 similar to the reflective microprism scattering element based backlight 100 having the plurality of reflective microprism scattering elements 120 arranged as an array of reflective microprism multibeam elements. In some embodiments, a depth of the reflective microprism scattering elements 222 of a reflective microprism multibeam element 220 may be about equal to an average pitch of (or spacing between) adjacent reflective microprism scattering elements 222 within the reflective microprism multibeam element 220.

[0071] As illustrated, the multiview display further comprises an array of light valves 230. The array of light valves 230 is configured to modulate the directional light beams to provide the multiview image. In various embodiments, different types of light valves may be employed as the light valves 230 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 electrowetting.

[0072] According to various embodiments, a size of each of the reflective microprism multibeam elements 220 that includes within the size the subset of reflective microprism scattering elements 222 (e.g., as illustrated a lower-case A’ in Figure 6A) is comparable to a size of a light valve 230 (e.g., as illustrated by an upper-case ‘A in Figure 6A) in the multiview display 200. 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 230 may be a length thereof and the comparable size of the reflective microprism multibeam element 220 may also be a length of the reflective microprism multibeam element 220. In another example, the size may refer to an area such that an area of the reflective microprism multibeam element 220 may be comparable to an area of the light valve 230.

[0073] In some embodiments, a size of each reflective microprism multibeam element 220 is between about twenty-five percent (25%) and about two hundred percent (200%) of a size of a light valve 230 in light valve array of the multiview display 200. In other examples, the reflective microprism multibeam element size is greater than about fifty percent (50%) of the light valve size, or greater than about sixty percent (60%) of the light valve size, or greater than about seventy percent (70%) of the light valve size, or greater than about seventy-five percent (75%) of the light valve size, or greater than about LI-162

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WO 2021/151009 PCT/US2021/014776 eighty percent (80%) of the light valve size, or greater than about eighty -five percent (85%) of the light valve size, or greater than about ninety percent (90%) of the light valve size. In other examples, the reflective microprism multibeam element size 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. According to some embodiments, the comparable sizes of the reflective microprism multibeam element 220 and the light valve 230 may be chosen to reduce, or in some embodiments to minimize, dark zones between views of the multiview display. Moreover, the comparable sizes of the reflective microprism multibeam element 220 and the light valve 230 may be chosen to reduce, and in some embodiments to minimize, an overlap between views (or view pixels) of the multiview display.

[0074] As illustrated in Figures 6A and 6C, different ones of the directional light beams within the emission zone of the emitted light 202 having different principal angular directions pass through and may be modulated by different ones of the light valves 230 in the light valve array. Further, as illustrated, a set of the light valves 230 may correspond to a multiview pixel 206 and a light valve 230 of the array may correspond to a sub-pixel of the multiview pixel 206, and of the multiview display 200.

In particular, in some embodiments, a different set of light valves 230 of the light valve array is configured to receive and modulate the directional light beams of the emitted light 202 within the emission zone / provided by or from a corresponding one of the reflective microprism multibeam elements 220, i.e., there is one unique set of light valves 230 for each reflective microprism multibeam element 220, as illustrated.

[0075] In some embodiments, a relationship between the reflective microprism multibeam elements 220 and corresponding multiview pixels 206 (i.e., sets of sub-pixels and corresponding sets of light valves 230) may be a one-to-one relationship or correspondence. That is, there may be an equal number of multiview pixels 206 and reflective microprism multibeam elements 220. Figure 6B explicitly illustrates by way of example the one-to-one relationship where each multiview pixel 206 comprising a different set of light valves 230 is illustrated as surrounded by a dashed line. In other LI-162

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WO 2021/151009 PCT/US2021/014776 embodiments (not illustrated), the number of multiview pixels 206 and the number of reflective microprism multibeam elements 220 may differ from one another.

[0076] In some embodiments, an inter-element distance (e.g., center-to-center distance) between a pair of reflective microprism multibeam elements 220 of the plurality may be equal to an inter-pixel distance (e.g., a center-to-center distance) between a corresponding pair of multiview pixels 206, e.g., represented by light valve sets. For example, as illustrated in Figure 6A, a center-to-center distance between the first reflective microprism multibeam element 220a and the second reflective microprism multibeam element 220b is substantially equal to a center-to-center distance between the first light valve set 230a and the second light valve set 230b. In other embodiments (not illustrated), the relative center-to-center distances of pairs of reflective microprism multibeam elements 220 and corresponding light valve sets may differ, e.g., the reflective microprism multibeam elements 220 may have an inter-element spacing that is one of greater than or less than a spacing between light valve sets representing multiview pixels 206.

[0077] Further (e.g., as illustrated in Figures 6A and 6C), each reflective microprism multibeam element 220 may be configured to provide directional light beams of the emitted light 202 to one and only one multiview pixel 206, according to some embodiments. In particular, for a given one of the reflective microprism multibeam elements 220, the directional light beams having different principal angular directions corresponding to the different views of the multiview display may be substantially confined to a single corresponding multiview pixel 206 and the sub-pixels thereof, i.e., a single set of light valves 230, corresponding to the reflective microprism multibeam element 220. As such, each reflective microprism multibeam element 220 of the provides a corresponding set of directional light beams of the emitted light 202 within the emission zone that has a set of the different principal angular directions corresponding to the different views of the multiview display (i.e., the set of directional light beams contains a light beam having a direction corresponding to each of the different view directions). [0078] In some embodiments, emitted, modulated light beams provided by the multiview display 200 within the emission zone may be preferentially directed toward a plurality of viewing directions or views of the multiview display or equivalent of the LI-162

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WO 2021/151009 PCT/US2021/014776 multiview image. In non-limiting examples, the multiview image may include one-by- four (1x4), one-by-eight (1x8), two-by-two (2x2), four-by-eight (4x8) or eight-by-eight (8x8) views with a corresponding number of view directions. The multiview display 200 that includes a plurality of views in a one direction but not in another (e.g., 1x4 and 1x8 views) may be referred to as a ‘horizontal parallax only’ multiview display in that these configurations may provide views representing different view or scene parallax in one direction (e.g., a horizontal direction as horizontal parallax), but not in an orthogonal direction (e.g., a vertical direction with no parallax). The multiview display 200 that includes more than one scene in two orthogonal directions may be referred to a full- parallax multiview display in that view or scene parallax may vary on both orthogonal directions (e.g., both horizontal parallax and vertical parallax). In some embodiments, the multiview display 200 is configured to provide a multiview display having three- dimensional (3D) content or information. The different views of the multiview display or multiview image may provide a ‘glasses free’ (e.g., autostereoscopic) representation of information in the multiview image being displayed by the multiview display.

[0079] In some embodiments, the guided light 204 within the light guide 210 of the multiview display 200 may be collimated according to a predetermined collimation factor. In some embodiments, an emission pattern of the emitted light 202 within the emission zone is a function of the predetermined collimation factor of the guided light.

For example, predetermined collimation factor may be substantially similar to the predetermined collimation factor s, described above with respect to the reflective microprism scattering element based backlight 100.

[0080] In some of these embodiments (e.g., as illustrated in Figures 6A-6C), the multi view display 200 may further comprise a light source 240. The light source 240 may be configured to provide the light to the light guide 210 with a non-zero propagation angle and, in some embodiments, is collimated according to a predetermined collimation factor to provide a predetermined angular spread of the guided light 204 within the light guide 210. According to some embodiments, the light source 240 may be substantially similar to the light source 130, described above with respect to the reflective microprism scattering element based backlight 100. LI-162

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[0081] In accordance with some embodiments of the principles described herein, a method of backlight operation is provided. Figure 7 illustrates a flow chart of a method 300 of backlight operation in an example, according to an embodiment consistent with the principles described herein. As illustrated in Figure 7, the method 300 of backlight operation comprises guiding 310 light in a propagation direction along a length of a light guide as guided light. In some embodiments, the light may be guided 310 at a non-zero propagation angle. Further, the guided light may be collimated. In particular, the guided light may be collimated according to a predetermined collimation factor. According to some embodiments, the light guide may be substantially similar to the light guide 110 described above with respect to the reflective microprism scattering element based backlight 100. In particular, the light may be guided according to total internal reflection within the light guide, according to various embodiments. Similarly, the predetermined collimation factor and non-zero propagation angle may be substantially similar to the predetermined collimation factor s and non-zero propagation angle described above with respect to the light guide 110 of the reflective microprism scattering element based backlight 100.

[0082] As illustrated in Figure 7, the method 300 of backlight operation further comprises reflecting 320 a portion of the guided light out of the light guide using a plurality of reflective microprism scattering elements to provide emitted light having a predetermined light exclusion zone. In various embodiments, a sloped reflective sidewall of a reflective microprism scattering element of the reflective microprism scattering element plurality has a slope angle tilted away from the propagation direction of the guided light, the predetermined light exclusion zone of the emitted light being determined by the slope angle of the sloped reflective sidewall.

[0083] In some embodiments, the reflective microprism scattering element may be substantially similar to the reflective microprism scattering element 120 of the reflective microprism scattering element based backlight 100, described above. In particular, the sloped reflective sidewall may reflectively scatter light according to total internal reflection to reflect the portion of the guided out of the light guide and provide the emitted light. In some embodiments, a reflective microprism scattering element of the reflective microprism scattering element plurality may be disposed on a surface of the LI-162

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WO 2021/151009 PCT/US2021/014776 light guide, e.g., either an emission surface or a surface opposite the emission surface of the light guide. In other embodiments, the reflective microprism scattering element may be located between and spaced apart from opposing light guide surfaces. According to various embodiments, an emission pattern of the emitted light may be a function, at least in part, of the predetermined collimation factor of the guided light.

[0084] In some embodiments, the slope angle the sloped reflective sidewall is between zero degrees (0°) and about forty -five degrees (45°) relative to a surface normal of an emission surface of the light guide and the predetermined exclusion zone is between ninety degrees (90°) and the slope angle. According to various embodiments, the slope angle is chosen in conjunction with the non-zero propagation angle of the guided light to preferentially scatter light in a direction of the emission surface of the light guide and away from a surface of the light guide opposite to the emission surface. Further, the slope angle is chosen to determine an angular range of the predetermined light exclusion zone. [0085] In some embodiments (not illustrated), the method of backlight operation further comprises providing light to the light guide using a light source. The provided light one or both of may have a non-zero propagation angle within the light guide and may be collimated within the light guide according to a collimation factor to provide a predetermined angular spread of the guided light within the light guide. In some embodiments, the light source may be substantially similar to the light source 130 of the reflective microprism scattering element based backlight 100, described above.

[0086] In some embodiments (e.g., as illustrated in Figure 7), the method 300 of backlight operation further comprises modulating 330 the emitted light reflectively scattered out by the reflective microprism scattering elements using light valves to provide an image. According to various embodiments, the image is visible exclusively within the emission zone and not visible within the predetermined exclusion zone.

[0087] In some embodiments, the plurality of reflective microprism scattering elements are arranged as an array of reflective microprism multibeam elements, each reflective microprism multibeam element of the reflective microprism multibeam element array comprising a subset of reflective microprism scattering elements of the reflective microprism scattering element plurality. Further, reflective microprism multibeam elements of the reflective microprism multibeam element array may be spaced apart from LI-162

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WO 2021/151009 PCT/US2021/014776 one another across the light guide to reflectively scatter out the guided light as the emitted light comprising directional light beams having directions corresponding to respective view directions of a multiview image. The multibeam image when displayed is visible only within the emission zone and not in the predetermined light exclusion zone. In some embodiments, a size of the reflective microprism multibeam element may be between twenty-five percent (25%) and two hundred percent (200%) of a size of a light valve of the light valve array.

[0088] Thus, there have been described examples and embodiments of a reflective microprism scattering element based backlight, a method of backlight operation, and a multiview display that employs reflective microprism scattering elements to provide emitted light having a predetermined light exclusion zone. It should be understood that the above-described examples are merely illustrative of some of the many specific examples 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.