BACKLIGHT SYSTEM, DISPLAY SYSTEM, AND METHOD

Abstract

The backlight system, multi-view display system, and method of backlight system operation use light extraction elements to extract waveguided light from a first light guide and provide the extracted light to a second light guide. The backlight system includes a first light guide and light extraction elements spaced along a length of the first light guide. The light extraction elements are configured to extract portions of the waveguided light from the first light guide to form an extracted light portion. The backlight further includes a second light guide configured to combine the extracted light received from the multiple light extraction elements to form a combined waveguided light. The multi-view display system includes a multi-beam element configured to scatter the light out of the multi-view backlight that receives the extracted light, the scattered light comprising a directional light beam having a direction corresponding to a viewing direction of the multi-view display.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS N / A

[0002] STATEMENT REGARDING U.S. GOVERNMENT SPONSORED RESEARCH OR DEVELOPMENT N / A [Background technology]

[0003] Electronic displays are a nearly ubiquitous medium for communicating information to users of a wide variety of devices and products. The most commonly used electronic displays include cathode ray tubes (CRTs), plasma display panels (PDPs), liquid crystal displays (LCDs), electroluminescent displays (ELs), organic light emitting diode (OLED) and active matrix OLED (AMOLED) displays, electrophoretic displays (EPs), and various displays that use electromechanical or electrofluidic light modulation (e.g., digital micromirror devices, electrowetting displays, etc.). In general, electronic displays can be categorized as active displays (i.e., displays that emit light) or passive displays (i.e., displays that modulate light provided by another light source). The most obvious examples of active displays include CRTs, PDPs, and OLED / AMOLEDs. Displays that are typically classified as passive when considering the light emitted include LCD and EP displays. Passive displays often exhibit attractive performance characteristics, including but not limited to, inherently low power consumption, but may be considered somewhat limited in many practical applications due to their lack of ability to emit light. Backlighting using an emissive backlight may allow a variety of passive displays, such as but not limited to LCD and EP displays, to be effectively converted into emissive displays without incurring the increased size, complexity, and power often associated with traditional active display technologies. Summary of the Invention

[0004] Various features of examples and embodiments according to principles described herein can be more readily understood by reference to the following detailed description in conjunction with the accompanying drawings, in which like reference numerals refer to like structural elements and in which: [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a perspective view of a multiple view display in an example according to an embodiment consistent with principles described herein. [Diagram 2] A figure illustrating a graphical representation of the angular components of a light beam having a particular principal angular direction corresponding to the view direction of a multi-view display in one example according to one embodiment consistent with the principles described herein. [Figure 3-1] 3A and 3B are perspective and plan views of an example backlight system according to an embodiment consistent with principles described herein. [Figure 3-2] FIG. 3C is a plan view of an example backlight system according to another embodiment consistent with principles described herein. [Figure 4-1] FIG. 4A is a top view of a portion of an example backlight system according to an embodiment consistent with principles described herein. [Figure 4-2] 4B and 4C are top views of a portion of an example backlight system according to another embodiment and yet another embodiment consistent with principles described herein. [Diagram 5] FIG. 1 is a block diagram of a multi-view display system in one example according to an embodiment consistent with principles described herein. [Figure 6]1 illustrates a method of backlight system operation in one example according to one embodiment consistent with principles described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] Particular examples and embodiments have other features in addition to and in the alternative to those shown in the above-referenced figures, which are described in more detail below with reference to the above-referenced figures.

[0007] Embodiments and examples according to the principles described herein provide backlighting using various light extraction elements to extract light from a first light guide and provide the extracted light to a second light guide that can be used as a backlight in a display. In particular, according to various embodiments of the principles described in the present invention, a backlight system is provided that includes a plurality of light extraction elements distributed along the edge or side of a first light guide to extract portions of the light guided in the first light guide. The extracted portions of light are then directed into a second backlight, where the extracted portions are combined together as a combined guided light to illuminate the second light guide. A light guide is provided that includes a light guide configured to receive light at an end of the light guide and to guide the received light along the length of the light guide as guided light. The combined guided light can be scattered out of the second light guide as emission light for use in a display.

[0008] Compared to a single light guide system that may include a row of discrete light sources (e.g., light emitting diodes) spaced along the edge of the light guide plate, the backlight system described herein may reduce or consolidate several discrete light sources required to fully illuminate the light guide plate. For example, the multiple light sources may be reduced to one or perhaps two discrete light sources. In turn, the power consumption and the complexity of the electrical connections used to power and control the light sources may also be reduced. Furthermore, using the first light guide to distribute light along the edge of the second light guide may help randomize and homogenize the light delivered to the second light guide, which may improve the uniformity of the light in and emitted by the backlight system. For example, using the first light guide to distribute light along the edge of the second light guide may help mask non-uniformities in intensity and / or color temperature that may otherwise cause problems when discrete light sources are used.

[0009] A "two-dimensional display" or "2D display" is defined herein as a display configured to provide a view of an image that is substantially the same regardless of the direction from which the image is viewed (i.e., within the predefined viewing angle or range of the 2D display). A conventional liquid crystal display (LCD) found in many smartphones and computer monitors is an example of a 2D display. In contrast, a "multi-view display" is defined herein as an electronic display or display system configured to provide different views of a multi-view image at or from different viewing directions. In particular, the different views may represent different perspective views of a scene or object of the multi-view image. Uses of the one-sided backlight and one-sided multi-view displays described herein include, but are not limited to, mobile phones (e.g., smartphones), watches, tablet computers, mobile computers (e.g., laptop computers), personal computers and computer monitors, automobile display consoles, camera displays, as well as various other mobile and substantially non-mobile display applications and devices.

[0010] Figure 1 illustrates a perspective view of a multi-view display 10 in one example according to one embodiment consistent with the principles described herein. As illustrated in Figure 1, the multi-view display 10 comprises a screen 12 for visibly displaying a multi-view image. The screen 12 may be, for example, a display screen of a phone (e.g., a mobile phone, a smartphone, etc.), a tablet computer, a laptop computer, a computer monitor of a desktop computer, a camera display, or an electronic display of virtually any other device.

[0011] The multi-view display 10 provides different views 14 of a multi-view 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 frames at the ends of the arrows (i.e., depicting the view directions 16). Only four views 14 and four view directions 16 are illustrated, all by way of example and not limitation. Although the different views 14 are illustrated in FIG. 1 as being above the screen, the views 14 would actually appear on or near the screen 12 when the multi-view image is displayed on the multi-view display 10. Depicting the views 14 above the screen 12 is merely for simplicity of illustration and is intended to represent viewing the multi-view display 10 from each of the view directions 16 corresponding to a particular view 14. The 2D display may be substantially similar to the multi-view display 10, except that the 2D display is typically configured to provide a single view of the displayed image (e.g., one view similar to view 14), as opposed to the different views 14 of the multi-view image provided by the multi-view display 10.

[0012] A light beam having a view direction, or equivalently, a direction corresponding to a view direction of a multi-view display, generally has a principal angular direction given by angular components {θ, φ}, as defined herein. Angular component θ is referred to herein as the "elevation component" or "elevation angle" of the light beam. Angular component φ is referred to herein as the "azimuth component" or "azimuth angle" of the light beam. By definition, elevation angle θ is an angle in a vertical plane (e.g., perpendicular to the plane of the multi-view display screen), while azimuth angle φ is an angle in a horizontal plane (e.g., parallel to the multi-view display screen plane).

[0013] 2 illustrates a graphical representation of the angular components {θ,φ} of a light beam 20 having a particular principal angular direction corresponding to a viewing direction (e.g., viewing direction 16 in FIG. 1) of a multi-view display in one example according to one embodiment consistent with the principles described herein. In addition, light beam 20, as defined herein, is emitted or emanated from a particular point. That is, by definition, light beam 20 has a central ray associated with a particular origin within the multi-view display. FIG. 2 also illustrates light beam (or viewing direction) origin O.

[0014] A "light guide" is defined herein as a structure that uses total internal reflection to guide light within the structure. In particular, a light guide can include a core that is substantially transparent at the operating wavelength of the light guide. The term "light guide" generally refers to a dielectric light guide that uses total internal reflection to guide light at the interface between the dielectric material of the light guide and the material or medium that surrounds the light guide. By definition, the condition for total internal reflection is that the refractive index of the light guide is greater than the refractive index of the surrounding medium adjacent to the surface of the light guide material. In some embodiments, the light guide can include a coating in addition to or as an alternative to the aforementioned refractive index difference to further facilitate total internal reflection. The coating can be, for example, a reflective coating. The light guide can be any one of several light guides, including, but not limited to, plate or slab guides and / or strip guides.

[0015] Additionally, the term "plate" as applied to a light guide, as well as to a "light guide plate," is defined herein as a piecewise or differentially planar layer or sheet, which may be referred to as a "slab" guide. In particular, a light guide plate is defined as a light guide configured to guide light in two substantially orthogonal directions bounded by the top and bottom (i.e., opposing) surfaces of the light guide. Moreover, as defined herein, both the top and bottom surfaces can be separated from each other and at least differentially substantially parallel to each other. That is, within any differentially small section of the light guide plate, the top and bottom surfaces are substantially parallel or coplanar.

[0016] In some embodiments, the light guide plate can be substantially flat (i.e., confined to a plane), and thus the light guide plate is a planar light guide. In other embodiments, the light guide plate can be curved in one or two orthogonal dimensions. For example, the light guide plate can be curved in a single dimension to form a cylindrical light guide plate. However, the radius of curvature of any curvature is large enough to ensure that total internal reflection is maintained within the light guide plate to guide the light.

[0017] Within this specification, a "diffraction grating" is generally defined as a plurality of features (i.e., diffractive features) arranged to provide diffraction of light incident on the diffraction grating. In some examples, the plurality of features may be arranged in a periodic or quasi-periodic manner. For example, a diffraction grating may include a plurality of features (e.g., a plurality of grooves or ridges in a material surface) arranged in a one-dimensional (1D) array. In other examples, a diffraction grating may be a two-dimensional (2D) array of features. A diffraction grating may be, for example, a 2D array of protrusions on a material surface or holes in a material surface.

[0018] As such, and as defined herein, a "diffraction grating" is a structure that provides diffraction of light incident on the grating. When light is incident on the grating from a light guide, a provided diffraction or diffractive scattering may result, which may therefore be referred to as "diffractive coupling" in that the grating may couple light out of the light guide by diffraction. The grating also redirects or changes the angle of the light by diffraction (i.e., the diffraction angle). In particular, as a result of diffraction. The light exiting the grating generally has a propagation direction that is different from the propagation direction of the light incident on the grating (i.e., the incident light). The change in the propagation direction of light by diffraction is referred to herein as "diffractive redirection." Thus, a diffraction grating may be understood to be a structure that includes diffractive features that diffractively redirect light incident on the grating, and when light is incident from a light guide, the grating may also be configured to diffractively couple light out of the light guide.

[0019] Further, as defined herein, features of a diffraction grating are referred to as "diffractive features" and may be at one or more of a material surface, within a material surface, and on a material surface (i.e., at an interface between two materials). The surface may be, for example, a surface of a light guide. Diffractive features may include any of a variety of structures that diffract light, including but not limited to, one or more of grooves, ridges, holes, and protrusions at, within, or on a surface. For example, a diffraction grating may include a plurality of substantially parallel grooves in a material surface. In another example, a diffraction grating may include a plurality of parallel ridges rising from a material surface. Diffractive features (e.g., grooves, ridges, holes, protrusions, etc.) may have any of a variety of cross-sectional shapes or profiles that provide diffraction, including but not limited to, one or more of a sinusoidal profile, a rectangular profile (e.g., a binary diffraction grating), a triangular profile, and a sawtooth profile (e.g., a blazed grating).

[0020] According to various examples described herein, a diffraction grating (e.g., a diffraction grating of a multi-beam element as described below) may be used to diffractively scatter or couple light out of a light guide (e.g., a light guide plate) as a light beam. In particular, the diffraction angle θ of or provided by a locally periodic diffraction grating may be m is given by the following equation (1):

[0021]

number

[0022] As defined herein, a "multibeam element" is a structure or element of a backlight or display that produces light comprising multiple directional light beams. In some embodiments, the multibeam element may be optically coupled to a light guide of a backlight to provide a light beam by coupling out a portion of the light guided within the light guide. Furthermore, the light beams of the multiple light beams produced by the multibeam element have different principal angular directions from each other, as defined herein. In particular, by definition, a light beam of the multiple has a predetermined principal angular direction that is different from another light beam of the multiple light beams. Furthermore, the multiple light beams may represent a light field. For example, the multiple light beams may be constrained to a generally conical region of space or may have a predetermined angular spread that includes different principal angular directions of the light beams within the multiple light beams. As such, the predetermined angular spread of the combined light beam (i.e., the multiple light beams) may represent a light field. According to various embodiments, the different principal angular directions of the various light beams are determined by characteristics including, but not limited to, the size (e.g., length, width, area, etc.) of the multiple light beams. In some embodiments, the multibeam element may be considered an "extended point source," i.e., multiple point sources that are distributed across the extent of the multibeam element, as defined herein.

[0023] As used herein, "size" may be defined in any of a variety of ways, including, but not limited to, length, width, or area. For example, the size of a multibeam element may be the length of the multibeam element. In another example, size may refer to the area of ​​the multibeam element. In some embodiments, the size of the multibeam element is comparable to the size of a light valve used to modulate the directional light beams of the multiple directional light beams. As such, the multibeam element size may be comparable to the light valve size when the multibeam element size is about 25% to about 200% of the light valve size. For example, if the multibeam element size is designated as "s" and the light valve size is designated as "S", the multibeam element size s may be given by the following equation (2):

[0024]

number

[0025] In other examples, the multibeam element size is greater than about 50% of the light valve size, or greater than about 60% of the light valve size, or greater than about 70% of the light valve size, or greater than about 80% of the light valve size, or greater than about 90% of the light valve size, and the multibeam element is less than about 180% of the light valve size, or less than about 160% of the light valve size, or less than about 140% of the light valve size, or less than about 120% of the light valve size. For example, the multibeam element may be comparable in size to the light valve size, and the multibeam element size is between about 75% and about 150% of the light valve size. In another example, the multibeam element and the light valve may be comparable in size, and the multibeam element size is between about 125% and about 85% of the light valve size. According to some embodiments, the comparable sizes of the multi-beam elements and the light valves may be selected to reduce, or in some examples minimize, dark areas between views of the multi-view display, while at the same time reducing, or in some examples minimizing, overlap between the views of the multi-view display.

[0026] As used herein, "collimation factor" is defined as the degree to which light is collimated. In particular, as defined herein, the collimation factor defines the angular spread of rays within a collimated light beam. For example, the collimation factor σ can be specified such that a majority of rays within a collimated beam of light are within a particular angular spread (e.g., ±σ degrees relative to the center or principal angular direction of the collimated light beam). According to some examples, the rays of a collimated light beam can have a Gaussian distribution with respect to angle, and the angular spread can be an angle determined by half the peak intensity of the collimated light beam.

[0027] As used herein, a "light source" is defined as a source of light (e.g., a light emitter configured to generate and emit light). For example, a light source may comprise a light emitter, such as a light emitting diode (LED), that emits light when activated or powered on. In particular, as used herein, a light source may be virtually any light source or may comprise virtually any light 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 light emitter, a fluorescent lamp, an incandescent lamp, and virtually any other light source. The light provided 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, a light source may comprise multiple light emitters. For example, a light source may include a set or group of light emitters, where at least one of the light emitters provides light having a color, or equivalently, a wavelength, that is different from the color or wavelength of light provided by at least one other light emitter in the set or group. The different colors can include, for example, primary colors (eg, red, green, blue).

[0028] As used herein, the article "a" is intended to have its ordinary meaning in the patent art, i.e., "one or more." For example, "a light extraction element" means one or more light extraction elements, and thus, as used herein, "the light extraction element" means "light extraction element(s)." Also, as used herein, any reference to "top," "bottom," "upper," "lower," "upper," "lower," "front," "rear," "first," "second," "left," or "right" is not intended to be limiting of the present specification. As used herein, the term "about" applied to a value generally means within the tolerance of the equipment used to produce that value, unless otherwise expressly stated, or can mean ±10%, or ±5%, or ±1%. Additionally, as used herein, the terms "substantially" and "about" mean a majority, or nearly all, or all, or an amount in the range of about 51% to about 100%. Moreover, the examples herein are intended to be illustrative only and are presented for purposes of discussion and not limitation.

[0029] In some embodiments of the principles described herein, a backlight system is provided. Figure 3A illustrates a perspective view of an example backlight system 100 according to an embodiment consistent with the principles described herein. Figure 3B illustrates a plan view of an example backlight system 100 according to an embodiment consistent with the principles described herein. Figure 3C illustrates a plan view of an example backlight system 100 according to another embodiment consistent with the principles described herein.

[0030] As illustrated, the backlight system 100 comprises a first light guide 110. The first light guide 110 is configured to guide light along a length of the first light guide 110 as guided light 112. According to various embodiments, the guided light 112 is guided according to total internal reflection within the first light guide 110. For example, the first light guide 110 may include a dielectric material configured as a light guide. The dielectric material of the light guide may have a first refractive index greater than a second refractive index of a medium surrounding the dielectric light guide. The refractive index difference is configured to promote total internal reflection of the guided light 112 according to one or more guided modes of the first light guide 110.

[0031] According to various embodiments, the optically transparent dielectric material of the first light guide 110 may include or consist of any of a variety of dielectric materials, including, but not limited to, one or more of various types of glass (e.g., fused silica, alkali aluminosilicate glass, borosilicate glass, etc.), one or more substantially optically transparent plastics or polymers (e.g., poly(methyl methacrylate) or "acrylic glass", polycarbonate, etc.), or combinations thereof. In some embodiments, the first light guide 110 may further include a cladding layer (not illustrated) on at least a portion of a surface of the first light guide 110 (e.g., one or more of the top, side, and bottom surfaces). The cladding layer may be used to further promote total internal reflection, according to some examples.

[0032] In various embodiments, the first light guide 110 is or comprises a bar-shaped cylindrical light guide, for example, as illustrated in Figures 3A-3C. In particular, as illustrated, the first light guide 110 has a bar shape with a length L in the y-direction that is greater than both a width W in the x-direction and a height H in the z-direction (i.e., L>W and L>H). As noted above, the guided light 112 can be guided along the length L and in any direction along that length. For example, the guided light 112 can be guided within the first light guide 110 from a first end towards a second end, or from the second end towards the first end, or from each of the first and second ends, according to various embodiments.

[0033] 3A-3C , the backlight system 100 further comprises a plurality of light extraction elements 120 spaced apart from one another along the length of the first light guide 110. The light extraction elements 120 of the plurality of light extraction elements are each configured to extract a respective portion of the guided light 112 from the first light guide 110 to form an extracted light portion 122. In FIGs. 3A-3C , the extracted light portion 122 is depicted as an arrow, which should be understood to merely represent a light or light beam of the extracted light portion 122. For example, the illustrated arrow may represent a single beam of light of the extracted light portion 122.

[0034] 3A-3C further comprises a second light guide 130. The second light guide 130 is configured to combine the extracted light portions 122 to form a combined guided light 132. The second light guide 130 is further configured to direct the combined guided light 132 away from the plurality of light extraction elements 120 and the first light guide 110 along a length of the second light guide 130. In some embodiments, the second light guide 130 may be further configured to emit the combined guided light 132, or a portion thereof, as emitted light 134, as described further below. For example, the second light guide 130 may be used as a backlight to illuminate a display using the emitted portion of the combined guided light 132.

[0035] According to various embodiments, the second light guide 130 may be substantially similar to the first light guide 110. That is, the second light guide 130 is configured to guide light according to total internal reflection within a light-transmissive dielectric material configured as a light guide. The light-transmissive dielectric material of the second light guide 130 may include or be composed of any of a variety of dielectric materials, including, but not limited to, one or more of various types of glass (e.g., quartz glass, alkali aluminosilicate glass, borosilicate glass, etc.), one or more substantially light-transmissive plastics or polymers (e.g., poly(methyl methacrylate) or "acrylic glass", polycarbonate, etc.), or combinations thereof. In some embodiments, the second light guide 130 may further include a cladding layer (not illustrated) on at least a portion of the surface of the first light guide 110 (e.g., one or more of the top, side, and bottom surfaces). The cladding layer may be used to further promote total internal reflection, according to some examples.

[0036] In some embodiments, the second light guide 130 is planar or nearly planar (i.e., a light guide plate) and extends over a rectangular region. In other embodiments, the second light guide 130 may have a shape other than a rectangle, including, but not limited to, a hexagon and a triangle. In these embodiments, the first light guide 110 may extend along at least a portion of the edge of the second light guide 130, for example, along the edge of a rectangular region or shape of the second light guide 130 as illustrated in Figures 3A-3C.

[0037] In some embodiments, the second light guide 130 may comprise a plurality of scattering features distributed across an area of ​​the second light guide 130. For example, the scattering features may be distributed over a rectangular area of ​​the second light guide 130. The scattering features are configured to scatter a portion of the combined guided light 132 from the second light guide 130 as emitted light. In some embodiments, the scattering features of the plurality of scattering features comprise multi-beam elements. The multi-beam elements are configured to scatter a portion of the combined guided light 132 from the second light guide 130 as a plurality of directional light beams having different principal angular directions corresponding to respective different viewing directions of the multi-view display. In some embodiments, the scattering features comprise an array of multi-beam elements, as described in more detail below.

[0038] According to various embodiments, the light extraction elements 120 of the plurality of light extraction elements 120 include sidewalls 124 configured to reflect the corresponding extracted light portions 122 toward the second light guide 130. In some embodiments, the sidewalls 124 of the light extraction elements 120 have a linear shape or include a linear or nearly linear reflective surface. For example, the light extraction elements 120 illustrated in FIG. 3A and FIG. 3B have sidewalls 124 with a linear shape, i.e., include linear sidewalls 124. In other embodiments, the sidewalls 124 of the light extraction elements have a curved shape. For example, the curved shape of the sidewalls 124 can be circular or semicircular, as illustrated in FIG. 3C. In another example, the curved shape can include a parabolic curve or a hyperbolic curve. In yet other embodiments, the sidewall 124 may have a complex shape, such as, but not limited to, a piecewise linear or piecewise curved shape, i.e., may include multiple straight sections (piecewise linear) or multiple curved sections (piecewise curved) that approximate a curved shape or yet another complex shape.

[0039] According to some embodiments, the sidewalls 124 of the light extraction elements 120 are configured to reflect the extracted light portions 122 according to total internal reflection. That is, the light extraction elements 120 act as light guides to guide the extracted light portions 122 using total internal reflection at the sidewalls 124. In other embodiments, the sidewalls 124 of the light extraction elements 120 comprise a reflective material configured to reflect the extracted light portions 122. In yet other embodiments, the sidewalls 124 are configured to reflect the extracted light portions 122 using both total internal reflection and a reflective material, e.g., a reflective cladding, of the sidewalls 124.

[0040] 4A illustrates a top view of a portion of a backlight system 100 in one example according to an embodiment consistent with principles described herein. As illustrated, the portion of the backlight system 100 includes a first light guide 110, a light extraction element 120, and a second light guide 130. The light extraction element 120 illustrated in FIG. 4A has a sidewall 124 that is straight or nearly straight. In addition, the straight sidewall 124 is angled or tilted with respect to a surface normal of the side of the first light guide 110 and a surface normal of an edge or end of the second light guide 130, as illustrated. That is, the sidewalls 124 are angled or tilted in the y-direction such that the light extraction element 120 has a narrower or smaller aperture at the end adjacent the first light guide 110 and a wider or larger aperture at the end opposite the first light guide adjacent end, e.g., the end adjacent the second light guide 130, as described below. Figure 4A also illustrates the guided light 112 entering the light extraction element 120, being reflected by the sidewalls 124, and exiting the light extraction element 120 as extracted light portion 122. As noted above, Figures 3A-3B also illustrate a light extraction element 120 having curved sidewalls 124.

[0041] FIG. 4B illustrates a top view of a portion of a backlight system 100 in an example according to another embodiment consistent with the principles described herein. The portion of the backlight system 100 illustrated in FIG. 4B includes a first light guide 110, a second light guide 130, and a light extraction element 120 having a curved sidewall 124. According to various embodiments, the curved sidewall 124 can have a semicircular curved shape, for example, as illustrated. As in FIG. 4A, the light extraction element 120 illustrated in FIG. 4B has an aperture adjacent to the first light guide 110 that is smaller than the aperture of the light extraction element 120 at the opposite end of the light extraction element 120. In some embodiments, the aperture adjacent to the first light guide 110 can be or represent a point contact between the first light guide 110 and the light extraction element 120, for example, that meets the semicircular shape of the sidewall 124 at the end of the light extraction element 120, as illustrated. 4B illustrates guided light 112 entering light extraction element 120, being reflected by curved sidewall 124, and exiting light extraction element 120 as extracted light portion 122. FIG. 3C also illustrates a light extraction element 120 having curved sidewall 124, as discussed above.

[0042] FIG. 4C illustrates a top view of a portion of a backlight system 100 in an example according to yet another embodiment consistent with the principles described herein. As in FIGS. 4A-4B, the portion of the backlight system 100 includes a first light guide 110, a light extraction element 120, and a second light guide 130. In FIG. 4C, the light extraction element 120 has a sidewall 124 that is piecewise linear. That is, the piecewise linear sidewall 124 comprises a plurality of straight line segments that join to approximate a curved surface or shape, as illustrated. Again, the aperture of the light extraction element 120 adjacent to the first light guide 110 is smaller than the aperture of the light extraction element 120 at the opposite end of the light extraction element 120, as illustrated in FIG. 4C. The guided light 112 that enters the light extraction element 120 and is reflected by the sidewall 124 to exit the light extraction element 120 as an extracted light portion 122 is also illustrated in FIG. 4C.

[0043] 4A-4C, a portion of the guided light 112 may enter the light extraction element 120 from the first light guide 110 at a first propagation angle. The sidewalls 124 then reflect the portion of the guided light 112 to provide an extracted light portion 122 at a different second propagation angle after reflection. As a result of the angle or curvature of the sidewalls 124, the second propagation angle may be smaller than the first propagation angle relative to a surface normal of an end or edge of the first light guide 110, according to various embodiments (e.g., as illustrated).

[0044] In some embodiments, the light extraction elements 120 may be directly adjacent to one another. That is, there is no or substantially no space between adjacent light extraction elements 120. In other embodiments, adjacent light extraction elements 120 of the plurality of light extraction elements 120 are spaced apart by air gaps along the length of the first light guide 110. According to some embodiments, the size of the individual light extraction elements 120 is between about 5 micrometers (μm) and about 500 micrometers (μm). In other embodiments, the size of the individual light extraction elements 120 is between about 10 micrometers (μm) and about 300 micrometers (μm). Smaller light extraction elements 120, for example, less than about 50 μm or 100 μm, may facilitate a tighter distribution of the light extraction elements 120 along the length of the first light guide 110. A tighter distribution may provide, for example, more uniformity to the combined guided light 132. On the other hand, larger light extraction elements 120, for example, larger than about 200 micrometers (μm), may improve or facilitate manufacturability.

[0045] According to various embodiments, the light extraction elements 120 comprise a dielectric material, such as, but not limited to, a light-transmissive dielectric material. In some embodiments, the light extraction elements 120 of the plurality of light extraction elements 120 are integral with the second light guide 130 while being separate from the first light guide 110. In these embodiments, the light extraction elements 120 may contact an edge of the first light guide 110 to provide light extraction in the area of ​​contact between the light extraction elements 120 and the first light guide 110. In other embodiments, the light extraction elements 120 of the plurality of light extraction elements 120 are integral with the first light guide 110. In these embodiments, an aperture at the input of the light extraction elements 120 is provided to provide light extraction from the first light guide 110. Additionally, the light extraction elements 120 may contact an edge of the second light guide 130 in some embodiments. In yet other embodiments, the light extraction elements 120 are structures that are separate from both the first and second light guides 110, 130. In these embodiments, the light extraction elements 120 may be sandwiched or otherwise positioned between the first light guide 110 and the second light guide 130.

[0046] In some of these embodiments, the combined waveguided light 132 may have a predetermined collimation factor determined by the plurality of light extraction elements 120. In particular, in some embodiments, the plurality of light extraction elements 120 are configured to collimate the extracted light portions 122 and provide the extracted light portions 122 to the second light guide 130 to be guided as the combined waveguided light 132. In some embodiments, the light extraction elements 120 collimate the extracted light portions 122 according to a predetermined collimation factor σ.

[0047] In some embodiments (e.g., as illustrated in FIGS. 3A-3C ), the backlight system 100 further comprises a light source 140. The light source 140 is configured to provide light to the first light guide 110 to be guided as guided light 112. In some embodiments, the light source 140 is disposed at an end of the first light guide 110, and the plurality of light extraction elements 120 are disposed at a side of the first light guide 110 perpendicular to the end. In these embodiments, the light source 140 is configured to provide light through the end of the first light guide 110. In some embodiments, the light source 140 may include two portions, one at each end of the first light guide 110. In these embodiments, the light source 140 may provide light to both ends of the first light guide 110. In some embodiments, the light source 140 may comprise a light emitting diode.

[0048] Embodiments of the principles described herein further provide a display system, and more specifically, a multi-view display system that may employ various portions or elements of the backlight system 100 described above. FIG. 5 illustrates a block diagram of a multi-view display system 200 in an example according to an embodiment consistent with the principles described herein. As illustrated, the multi-view display system 200 comprises a bar light guide 210. The bar light guide 210 is configured to guide light as guided light. In some embodiments, the bar light guide 210 may be substantially similar to the first light guide 110 described above with respect to the backlight system 100.

[0049] 5 further comprises a plurality of light extraction elements 220. The plurality of light extraction elements 220 are disposed along the sides of the bar light guide 210 and spaced apart from one another. According to various embodiments, the plurality of light extraction elements 220 are configured to extract a portion of the waveguided light from the bar light guide 210 to form an extracted light portion 222. In some embodiments, the plurality of light extraction elements 220 may be substantially similar to the plurality of light extraction elements 120 of the backlight system 100 described above.

[0050] In particular, in some embodiments, the light extraction elements 220 of the plurality of light extraction elements 220 may include sidewalls configured to reflect corresponding extracted light portions toward a light guide plate at the output of the light extraction elements 220. For example, the light guide plate may be a light guide plate of a multi-view backlight described below. In various embodiments, the sidewalls may have one of a curved shape and a straight shape, for example, as illustrated above in FIGS. 4A-4C. In various embodiments, the light extraction elements 220 of the plurality of light extraction elements 220 may be one or more of: integral with the light guide plate, integral with the bar light guide 210, and a separate element from both the light guide plate and the bar light guide 210, e.g., sandwiched between the light guide plate and the bar light guide 210.

[0051] 5, the multi-view display system 200 further comprises a multi-view backlight 230. The multi-view backlight 230 comprises a light guide plate 232 and a plurality of multi-beam elements 234. In some embodiments, the light guide plate 232 may be substantially similar to the second light guide 130 of the backlight system 100 described above. In particular, the light guide plate 232 is configured to combine the extracted light portions 222 to form a combined guided light. The plurality of multi-beam elements 234 are in turn configured to scatter the combined guided light from the light guide plate as a directional light beam 202 having a direction corresponding to a view direction of the multi-view display system 200, or equivalently, a view of a multi-view image displayed by the multi-view display system 200.

[0052] According to various embodiments, the multibeam element 234 may comprise any of a number of different structures configured to scatter a portion of the guided light from the light guide plate 232. For example, the different structures may include, but are not limited to, a diffraction grating, a micro-reflective element, a micro-refractive element, or various combinations thereof. In some embodiments, the multibeam element 234 comprising a diffraction grating is configured to diffractively scatter the guided light portion as a plurality of directional light beams 202 having different principal angular directions. In other embodiments, the multibeam element 234 comprising a micro-reflective element is configured to reflectively scatter the guided light portion as a plurality of directional light beams 202, or the multibeam element 234 comprising a micro-refractive element is configured to scatter the guided light portion as a plurality of directional light beams 202 by or using refraction (i.e., refractively scatter the guided light portion). In some embodiments, the multibeam element 234 has a size that is between 25% and 200% of the size of the light valves of the multiview display system 200.

[0053] According to some embodiments (e.g., as illustrated in FIG. 5 ), the multi-view display system 200 further comprises a light source 240. The light source 240 is configured to provide light to be guided by the bar light guide 210. The light source 240 may be substantially similar to the light source 140 of the backlight system 100 described above. In particular, the light source 240 may be disposed at an end of the bar light guide 210. Furthermore, the light source 240 may comprise a light emitting diode in some embodiments.

[0054] The multi-view display system 200 of Figure 5 comprises an array of light valves 250 configured to modulate a directional light beam 202 to provide a multi-view image, according to various embodiments. Dashed arrows are used in Figure 5 to illustrate the modulated directional light beam 202.

[0055] In various embodiments, different types of light valves may be used as the light valves 250 of the light valve array, including, but not limited to, one or more of a liquid crystal light valve, an electrophoretic light valve, and an electrowetting based light valve. In various embodiments, the size of the multi-beam elements 234 may be comparable to the size of the light valves 250. In particular, the multi-beam element size may be about 25% to about 200% or about 50% to 150% of the light valve size.

[0056] According to yet another embodiment of the principles described herein, a method of backlight system operation is provided. Figure 6 illustrates a method 300 of backlight system operation in an example according to an embodiment consistent with the principles described herein. As illustrated, the method 300 of backlight operation includes directing 310 light as guided light along a length of a first light guide. In some embodiments, the first light guide may be substantially similar to the first light guide 110 described above with respect to the backlight system 100. In particular, the first light guide may be a bar-shaped light guide.

[0057] 6 may further include extracting 320 a portion of the waveguided light from the first light guide using light extraction elements spaced along the length of the first light guide to form an extracted light portion. In some embodiments, the light extraction elements used for extracting 320 the portion of the waveguided light may be substantially similar to the light extraction elements 120 of the backlight system 100 described above. In particular, extracting 320 the portion of the waveguided light may, in some embodiments, include reflecting the extracted light portion at a sidewall of the light extraction element using one or both of total internal reflection and a reflective material on the sidewall.

[0058] According to various embodiments, the method 300 further includes providing 330 the extracted light portions to a second light guide and combining the extracted light portions in the second light guide to form a combined waveguided light. According to some embodiments, the second light guide may be substantially similar to the second light guide 130 of the backlight system described above. In particular, the combined waveguided light is guided away from the light extraction element and the first light guide by the second light guide, according to various embodiments. Furthermore, in some embodiments, the combined waveguided light may be collimated according to a collimation factor by the light extraction element.

[0059] In some embodiments, the light extraction elements may be integral with the second light guide and / or integral with the first light guide. The light extraction elements integral with the second light guide may contact an edge of the first light guide to provide light extraction in the area of ​​contact between the light extraction elements and the first light guide. The light extraction elements integral with the first light guide may provide light extraction from the first light guide through an aperture at the input of each of the light extraction elements.

[0060] Thus, examples and embodiments of backlight systems, multi-view display systems, and methods of backlight system operation are described in which light extraction elements are used to extract portions of guided light from a first light guide to form extracted light portions, and the extracted light portions are provided to a second light guide to be combined to form a combined guided light. It should be understood that the foregoing examples are merely illustrative of a few of many specific examples illustrating the principles described herein. It will be apparent to one of ordinary skill in the art that numerous other arrangements can be readily devised without departing from the scope defined in the following claims. [Explanation of symbols]

[0061] 10 Multi-view display 12 screens 14 Views 16 View Directions 20 Light Beam 100 Backlight System 110 First light guide 112 Waveguide Light 120 Light Extraction Elements 122 Extracted light part 124 Side wall 130 Second light guide 132 Combined Waveguide Light 134 Emitted light 140 light source 200 Multi-view Display System 202 directional light beam 210 Bar light guide 220 Light Extraction Elements 222 Extracted light part 230 Multi-view backlight 232 Light guide plate 234 Multi-Beam Element 240 light source 250 Light bulb

Claims

1. 1. A backlight system comprising: a first light guide configured to guide light as guided light along a length of the first light guide; a plurality of light extraction elements spaced along the length of the first light guide, each light extraction element of the plurality of light extraction elements configured to extract a portion of the guided light from the first light guide to form an extracted light portion; a second light guide configured to combine the extracted light portions received from the plurality of light extraction elements to form a combined waveguided light, the second light guide further configured to direct the combined waveguided light along a length of the second light guide away from the plurality of extraction elements and the first light guide; A backlight system comprising:

2. 10. The backlight system of claim 1, wherein the light extraction elements of the plurality of light extraction elements comprise sidewalls configured to reflect the extracted light portions of the waveguiding light towards the second light guide.

3. The backlight system of claim 2 , wherein the sidewalls of the light extraction elements have a curved shape.

4. The backlight system of claim 2 , wherein the sidewalls of the light extraction elements are configured to reflect the extracted light portions of the waveguided light according to total internal reflection.

5. 3. The backlight system of claim 2, wherein the sidewalls of the light extraction elements comprise a reflective material configured to reflect the extracted light portions of the waveguiding light.

6. 10. The backlight system of claim 1, wherein adjacent light extraction elements of the plurality of extraction elements are separated by an air gap along the length of the first light guide.

7. 2. The backlight system of claim 1, wherein the light extraction elements of the plurality of light extraction elements are integral with the second light guide and contact edges of the first light guide to provide light extraction at points of contact between the light extraction elements and the first light guide.

8. 10. The backlight system of claim 1, wherein light extraction elements of the plurality of light extraction elements are integral with the first light guide, and an aperture at an input of the light extraction element provides light extraction from the first light guide.

9. 2. The backlight system of claim 1, further comprising a light emitting diode configured to provide light to the first light guide to be guided as the guided light, the light emitting diode being disposed at an end of the first light guide and positioned to provide light through the end of the first light guide, and the plurality of light extraction elements being disposed on a side of the first light guide perpendicular to the end.

10. 10. The backlight system of claim 1, wherein the second light guide is planar and extends over a rectangular area, and the first light guide extends along and to the edges of the rectangular area of ​​the second light guide.

11. 11. The backlight system of claim 10, wherein the second light guide includes a plurality of scattering features distributed over the rectangular area and configured to scatter a portion of the combined guided light from the second light guide as emitted light.

12. 12. The backlight system of claim 11 , wherein the scattering features of the plurality of scattering features comprise multi-beam elements configured to scatter a portion of the combined guided light from the second light guide as a plurality of directional light beams having different principal angular directions corresponding to respective different view directions of a multi-view display, the combined guided light having a predetermined collimation factor determined by the plurality of light extraction elements.

13. 1. A multi-view display system, comprising: A bar light guide configured to guide light as guided light; a multi-view backlight comprising a light guide plate and a plurality of multi-beam elements; a plurality of light extraction elements spaced apart from one another along a side of the bar light guide and configured to extract portions of the guided light from the bar light guide to constitute extracted light portions and to provide the extracted light portions as combined guided light to the multi-view backlight; a multi-beam element of the plurality of multi-beam elements configured to scatter the combined guided light from the light guide plate as a directional light beam having a direction corresponding to a viewing direction of the multi-view display.

14. 14. The multi-view display system of claim 13, wherein the light extraction elements of the plurality of light extraction elements have sidewalls configured to reflect the extracted light portions of the guided light toward the light guide plate of the multi-view backlight, the sidewalls having one of a curved shape and a sloped straight shape.

15. The multiple view display system of claim 13 , wherein light extraction elements of the plurality of light extraction elements are integral with one or both of the light guide plate and the bar light guide.

16. The multiple view display system of claim 13 , further comprising a light source at an end of the bar light guide, the light source configured to provide light to be guided as the guided light by the bar light guide.

17. 14. The multiple view display system of claim 13, further comprising an array of light valves configured to modulate the directional light beams to provide a multiple view image.

18. 1. A method of backlight system operation, comprising: directing the light as guided light along a length of a first light guide; extracting a portion of the guided light from the first light guide using light extraction elements spaced along a length of the first light guide to form an extracted light portion; providing the extracted light portions to a second light guide and combining the extracted light portions within the second light guide as a combined guided light; The method of backlight system operation, wherein the combined waveguided light is guided away from the light extraction element and the first light guide by the second light guide.

19. 20. The method of operating a backlight system of claim 18, wherein extracting the portion of the guided light includes reflecting the extracted light portion at a sidewall of the light extraction element using one of both total internal reflection and a reflective material on the sidewall.

20. 20. The method of claim 18, wherein light extraction elements are integral with the second light guide and / or the first light guide, the light extraction elements integral with the second light guide contacting edges of the first light guide to provide light extraction at points of contact between the light extraction elements and the first light guide, while the light extraction elements integral with the first light guide provide light extraction from the first light guide through apertures at the inputs of the light extraction elements.

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