HK1241471B - Two-dimensional/three-dimensional (2d/3d) switchable display backlight and electronic display - Google Patents

Description

Two-dimensional/three-dimensional (2D/3D) switchable display backlights and electronic displays

CROSS-REFERENCE TO RELATED APPLICATIONS

not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

not applicable.

Background Art

Electronic displays are a nearly ubiquitous medium for conveying information to users of a wide variety of devices and products. The most common electronic displays include cathode ray tubes (CRTs), plasma display panels (PDPs), liquid crystal displays (LCDs), electroluminescent displays (EL), organic light-emitting diode (OLED) and active-matrix OLED (AMOLED) displays, electrophoretic displays (EPs), and various displays that employ electromechanical or current light modulation (e.g., digital micromirror devices, electrowetting displays, etc.). Generally, electronic displays can be categorized as either active (i.e., displays that emit light) or passive (i.e., displays that modulate light provided by another source). The most obvious examples of active displays are CRTs, PDPs, and OLEDs/AMOLEDs. Displays that are typically classified as passive when considering light emission are, for example, LCDs and EPs. Passive displays often have attractive performance characteristics, including, but not limited to, inherently low power consumption. However, passive displays can find somewhat limited use in many practical applications due to their inherent inability to emit light. To overcome this inability, backlights are often used with passive displays to provide light emission from these displays.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features of examples and embodiments according to the principles described herein may be more readily understood by reference to the following detailed description taken in conjunction with the accompanying drawings, wherein like reference numerals represent like structural elements, and wherein:

1A shows a cross-sectional view of a two-dimensional/three-dimensional (2D/3D) switchable display backlight, according to an example consistent with the principles described herein.

1B shows a cross-sectional view of a two-dimensional/three-dimensional (2D/3D) switchable display backlight, according to another example consistent with the principles described herein.

2 illustrates a perspective view of a multi-beam diffraction grating, according to an example consistent with the principles described herein.

3 shows a block diagram of a 2D/3D switchable electronic display, according to an example consistent with the principles described herein.

4A illustrates a cross-sectional view of a 2D/3D switchable electronic display, according to an example consistent with the principles described herein.

4B shows a cross-sectional view of a 2D/3D switchable electronic display, according to another example consistent with the principles described herein.

Figure 4C illustrates a plan view of a 2D/3D switchable electronic display having multiple distinct regions, according to an example consistent with the principles described herein. Figure 5 illustrates a flow chart of a method of operating a 2D/3D switchable electronic display consistent with the principles described herein.

Certain examples and embodiments have other features in addition to and instead of the features shown in the above-mentioned reference figures. These and other features are described in detail below with reference to the above-mentioned reference figures.

DETAILED DESCRIPTION

Examples according to the principles described herein provide information displays that support switching between the display of two-dimensional (2-D) data and three-dimensional (3-D) data. In particular, according to the principles described herein, information can be selectively displayed in either a 2-D mode or a 3-D mode. The 3-D mode can be used to present images and similar information in conjunction with so-called "glasses-free" or autostereoscopic display systems, while the 2-D mode can be used to present information that lacks, or at least does not benefit from, a third dimension (e.g., information such as text, 2-D images, etc.). Furthermore, according to various examples of the principles described herein, switchable 2-D and 3-D modes are provided on the same display unit or system. A switchable display system capable of selectively displaying both 2-D information and 3-D information on the same display system can help adapt a single display system to a wider range of different data presentation needs than would be possible with either 2-D display or 3-D display alone.

According to various examples, a variable or switchable diffuser is used in conjunction with a directional or multi-view display to facilitate switching between the display of 2-D and 3-D information. Specifically, when the switchable diffuser is in a condition or state that scatters or diffuses light passing through the diffuser, a 2-D mode of display operation is provided. Alternatively, when the switchable diffuser is in a condition or state that passes (i.e., does not diffuse) light, a 3-D mode of display operation is provided.

In some examples, the 2-D mode generated by the scattering or diffusing state of the switchable diffuser provides (or is) a high-resolution 2-D mode having a higher resolution than that provided by the 3-D operating mode. For example, the native resolution of the light valve array can be supported in the high-resolution 2-D mode, while the 3-D mode may support a lower resolution due to the multiple views or beam angles used to present the 3-D information. The use of a switchable diffuser also facilitates switching between the 2-D mode and the 3-D mode as needed. Furthermore, according to some examples, the switchable diffuser can provide substantially independent portions, segments, or regions of the display with switchable diffusion to allow for simultaneous display of 2-D information and 3-D information in different areas of the display system.

As used herein, a "lightguide" is defined as a structure that uses total internal reflection to guide light within an optical structure. In particular, a lightguide may include a core that is substantially transparent at the operating wavelength of the lightguide. In various examples, the term "lightguide" generally refers to a dielectric optical waveguide that uses total internal reflection to guide light at an interface between the dielectric material of the lightguide and the material or medium surrounding the lightguide. By definition, a condition for total internal reflection is that the refractive index of the lightguide is greater than the refractive index of the surrounding medium adjacent to the surface of the lightguide material. In some examples, the lightguide may include a coating in addition to or in place of the above-mentioned refractive index difference to further promote total internal reflection. The coating may be, for example, a reflective coating. According to various examples, the lightguide may be any of several types of lightguides, including but not limited to one or both of a plate or guide plate and a guide bar.

Furthermore, when applied to light guides, the term "plate" as in "plate light guide" is defined as a segmented or differentially planar layer or sheet. In particular, a plate light guide is defined as a light guide configured to guide light in two substantially orthogonal directions defined by the top and bottom surfaces (i.e., opposing surfaces) of the light guide. Furthermore, according to the definitions herein, the top and bottom surfaces are both separated from one another and can be substantially parallel to one another, at least in terms of their differences. That is, within any region of the plate light guide where the differences are small, the top and bottom surfaces are substantially parallel or coplanar. In some examples, the plate light guide can be substantially flat (e.g., defining a flat surface), and thus the plate light guide is a planar light guide. In other examples, the plate light guide can be curved in one or two orthogonal dimensions. For example, the plate light guide can be curved in a single dimension to form a cylindrical plate light guide. However, in various examples, any curvature has a sufficiently large radius of curvature to ensure that total internal reflection is maintained in the plate light guide to guide light.

According to various examples described herein, a diffraction grating (e.g., a multi-beam diffraction grating) is used to scatter or couple light out of a plate light guide. As used herein, a "diffraction grating" is generally defined as a plurality of features (i.e., diffraction features) arranged to provide diffraction of light incident on the diffraction grating. In some examples, the plurality of features can be arranged in a periodic or quasi-periodic manner. For example, the diffraction grating can include a plurality of features arranged in a one-dimensional (1-D) array (e.g., a plurality of grooves in a surface of a material). In other examples, the diffraction grating can be a two-dimensional (2-D) feature array of features. For example, the diffraction grating can be a 2-D array of protrusions or holes on a surface of a material.

Thus, according to the definitions herein, a "diffraction grating" is a structure that provides diffraction of light incident on the diffraction grating. If light is incident on the diffraction grating from a light guide, the diffraction or diffraction scattering provided can result in, and is therefore referred to as, "diffractive coupling," since the diffraction grating can couple light out of the light guide by diffraction. A diffraction grating also redirects or changes the angle of light by diffraction (i.e., the diffraction angle). In particular, as a result of diffraction, the light exiting the diffraction grating (i.e., the diffracted light) typically has a propagation direction that is different from the propagation direction of the light incident on the diffraction grating (i.e., the incident light). This change in the propagation direction of light by diffraction is referred to herein as "diffractive redirection." Thus, a diffraction grating can be understood as a structure that includes diffraction features that diffractively redirect light incident on the diffraction grating and, if the light is incident from a light guide, can also diffractively couple light out of the light guide.

Furthermore, as defined herein, the features of a diffraction grating are referred to as "diffractive features" and may be one or more in, in, or on a surface (or a boundary between two materials). For example, the surface may be the surface of a plate light guide. The 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, in, or on the surface. For example, a diffraction grating may include a plurality of parallel grooves in the surface of a material. In another example, a diffraction grating may include a plurality of parallel ridges rising from the surface of a material. The 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 curve, a rectangular profile (e.g., a binary diffraction grating), a triangular profile, and a sawtooth profile (e.g., a blazed grating).

As defined herein, a "multibeam diffraction grating" is a diffraction grating that produces coupled-out light comprising a plurality of light beams. Furthermore, as defined herein, the plurality of light beams produced by the multibeam diffraction grating have different principal angular directions from one another. In particular, as defined herein, one of the plurality of light beams has a predetermined principal angular direction that is different from another of the plurality of light beams due to diffractive coupling and diffractive redirection of incident light by the multibeam diffraction grating. For example, the plurality of light beams may include eight light beams having eight different principal angular directions. For example, the combined eight light beams (i.e., the plurality of light beams) may represent a light field. According to various examples, the different principal angular directions of the various light beams are determined by a combination of an orientation or rotation of the diffraction features of the multibeam diffraction grating at the origin of the respective light beams relative to the propagation direction of light incident on the multibeam diffraction grating and a grating pitch or spacing.

According to various examples described herein, a multi-beam diffraction grating is employed to couple light out of a plate light guide, for example, as pixels of an electronic display. In particular, a plate light guide having a multi-beam diffraction grating to generate multiple light beams having different angular orientations can be part of a backlight for an electronic display or used with an electronic display, such as, but not limited to, a "glasses-free" three-dimensional (3-D) electronic display (e.g., also known as a multi-view or "holographic" electronic display or an autostereoscopic display). Thus, the differently oriented light beams generated by coupling the guided light out of the light guide using the multi-beam diffraction grating can be or represent "pixels" of the 3-D electronic display.

As used herein, a "light source" is defined as a source of light (e.g., a device or apparatus that generates and emits light). For example, a light source can be a light emitting diode (LED) that emits light when activated. As used herein, a light source can be substantially any light source or light emitting source, including but not limited to light emitting diodes (LEDs), lasers, organic light emitting diodes (OLEDs), polymer light emitting diodes, plasma-based light emitters, fluorescent lamps, incandescent lamps, and virtually any other light source. The light generated by a light source can have a color (i.e., can include light of a specific wavelength) or can be a range of wavelengths (e.g., white light).

In addition, as used herein, the article "a" is intended to have its ordinary meaning in the patent art, that is, "one or more". For example, "a grating" refers to one or more gratings, and therefore, "grating" refers to "grating(s)" in this article. In addition, "top", "bottom", "above", "below", "up", "down", "front", "back", "first", "second", "left" or "right" mentioned herein are not used as limitations in this article. In this article, unless otherwise expressly stated, the term "about" when applied to a value generally means within the tolerance range of the equipment used to produce the value, or in some examples, means plus or minus 10%, or plus or minus 5%, or plus or minus 1%. In addition, the term "substantially" used herein means, for example, most, or almost all, or all, or an amount in the range of about 51% to about 100%. In addition, the examples herein are intended to be illustrative only and are for discussion purposes only and not for limitation.

According to some examples of the principles described herein, a two-dimensional/three-dimensional (2D/3D) switchable display backlight is provided. FIG1A shows a cross-sectional view of a two-dimensional/three-dimensional (2D/3D) switchable display backlight 100 according to an example consistent with the principles described herein. FIG1B shows a cross-sectional view of a 2D/3D switchable display backlight 100 according to another example consistent with the principles described herein. According to various examples, the 2D/3D switchable display backlight 100 is configured to generate “directional” light, i.e., light including light beams 102 with different main angular directions. For example, the 2D/3D switchable display backlight 100 can be used as a backlight based on a multi-beam grating, which is configured to provide or generate multiple light beams 102 pointing outward and away from the 2D/3D switchable display backlight 100. In addition, according to various examples, as directional light, the multiple light beams 102 are directed outward and away at different predefined main angular directions.

In some examples, as described below, multiple light beams 102 having different predetermined principal angular directions form multiple pixels of an electronic display. Furthermore, an electronic display using the 2D/3D switchable display backlight 100 can switch between a 2-D electronic display (e.g., a conventional display) and a so-called "glasses-free" 3-D electronic display (e.g., a multi-view, "holographic," or autostereoscopic display). Specifically, according to various examples, the 2D/3D switchable display backlight 100 employs controllable or selectable scattering of the light beams 102 to switch between a 2-D mode of operation and a 3-D mode of operation. For example, when the light beams 102 are selectively scattered, a 2-D mode of operation is supported. Alternatively, without selective scattering, a 3-D mode of operation is supported. Selecting either the 2-D mode of operation or the 3-D mode of operation can facilitate switching the electronic display between displaying 2-D data and 3D data, according to various examples (e.g., as described below).

As shown in Figures 1A-1B, a 2D/3D switchable display backlight 100 includes a light guide 110. In particular, according to various examples, the light guide 110 can be a plate light guide 110. The plate light guide 110 is configured to guide light from a light source (not shown in Figures 1A-1B). In some examples, the light from the light source is guided as a light beam 104 along the length of the plate light guide 110. Furthermore, the plate light guide 110 is configured to guide the light (i.e., guided light beam 104) at a non-zero propagation angle. For example, the guided light beam 104 can be guided at a non-zero propagation angle within the plate light guide 110 using total internal reflection.

As defined herein, a non-zero propagation angle is an angle relative to a surface (e.g., a top surface or a bottom surface) of the plate light guide 110. In some examples, the non-zero propagation angle of the guided light beam can be between about ten (10) degrees and about fifty (50) degrees, or in some examples between about twenty (20) degrees and about forty (40) degrees, or between about twenty-five (25) degrees and about thirty-five (35) degrees. For example, the non-zero propagation angle can be about thirty (30) degrees. In other examples, the non-zero propagation angle can be about 20 degrees, or about 25 degrees, or about 35 degrees.

In some examples, light from a light source is introduced or coupled into the plate light guide 110 at a non-zero propagation angle (e.g., approximately 30-35 degrees). One or more of a lens, mirror, or similar reflector (e.g., a tilted collimating reflector), and a prism (not shown) can assist in coupling the light into the input end, e.g., the plate light guide 110, as a light beam 104 at a non-zero propagation angle. Once coupled into the plate light guide 110, the guided light beam 104 propagates along the plate light guide 110 in a direction generally away from the input end (e.g., as shown by the thick arrow along the x-axis in Figures 1A and 1B). Furthermore, the guided light beam 104 propagates by reflecting or "bouncing" between the top and bottom surfaces of the plate light guide 110 at the non-zero propagation angle (e.g., as shown, the rays of the guided light 104 are represented by the extended angled arrows).

Furthermore, according to various examples, the guided light beam 104 generated by coupling light into the plate light guide 110 can be a collimated light beam. In particular, by "collimated light beam," it is meant that the light rays within the guided light beam 104 are substantially parallel to one another within the guided light beam 104. Light rays emanating from or scattered from the collimated beam of the guided light beam 104 are not considered part of the collimated light beam as defined herein. For example, the collimation of the light used to generate the collimated guided light beam can be provided by a lens or mirror (e.g., a tilted collimating reflector, etc.) used to couple the light into the plate light guide 110.

In some examples, the plate light guide 110 can be a sheet or plate light waveguide comprising an extended, substantially flat, optically transparent dielectric material. The substantially flat sheet of dielectric material is configured to guide the guided light beam 104 using total internal reflection. According to various examples, the optically transparent material of the plate light guide 110 can include or be made 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.) and substantially optically transparent plastics or polymers (e.g., poly(methyl methacrylate) or "acrylic glass," polycarbonate, etc.). In some examples, the plate light guide 110 can also include a cladding layer on at least a portion of a surface (e.g., one or both of the top and bottom surfaces) of the plate light guide 110 (not shown). According to some examples, the cladding layer can be used to further promote total internal reflection.

As shown in Figures 1A-1B, the 2D/3D switchable display backlight 100 also includes a multi-beam diffraction grating 120. According to various examples (e.g., as shown in Figures 1A-1B), the multi-beam diffraction grating 120 is located on a surface (e.g., the top or front surface) of the plate light guide 110. In other examples (not shown), the multi-beam diffraction grating 120 can be located within the plate light guide 110. The multi-beam diffraction grating 120 is configured to couple a portion of the guided light beam 104 out of the plate light guide 110 by or using diffraction coupling. In particular, the outcoupled portion of the guided light beam 104 is diffractively redirected out of the surface of the plate light guide as coupled-out light comprising the plurality of light beams 102. As described above, each of the plurality of light beams 102 has a different predetermined principal angular direction. In addition, the light beams 102 are directed out of the plate light guide 110. For example, according to various examples, the light beam 102 may be directed to exit from a plate light guide surface where, in, or on which the multi-beam diffraction grating 120 is located.

In general, according to various examples, the light beams 102 generated by the multibeam diffraction grating 120 can be diverging (e.g., as shown) or converging (not shown). In particular, Figures 1A-1B illustrate a plurality of diverging light beams 102. Whether the light beams 102 diverge or converge is determined by the propagation direction of the guided light beams 104 relative to a characteristic of the multibeam diffraction grating 120 (e.g., the "chirp" direction). In some examples where the light beams 102 diverge, the diverging light beams 102 may appear to diverge from a "virtual" point (not shown) located a distance below or behind the multibeam diffraction grating 120. Similarly, according to some examples, the converging light beams may converge or intersect at a virtual point (not shown) above or in front of the multibeam diffraction grating 120 (e.g., the front surface of the plate light guide).

As further shown in Figures 1A-1B, the multibeam diffraction grating 120 includes a plurality of diffractive features 122 configured to provide diffraction. The diffraction provided is responsible for diffractively coupling a portion of the guided light beam 104 out of the plate light guide 110. For example, the multibeam diffraction grating 120 can include one or two grooves in the surface of the plate light guide 110 (e.g., as shown in Figure 1B) and ridges protruding from the surface of the plate light guide that serve as the diffractive features 122 (e.g., as shown in Figure 1A). The grooves and ridges can be arranged parallel to each other and, at least at some point along the diffractive features 122, the grooves and ridges are perpendicular to the propagation direction of the guided light beam 104 coupled out of the multibeam diffraction grating 120.

In some examples, the grooves or ridges can be etched, milled, or molded into or applied to the surface of the plate light guide. Thus, the material of the multibeam diffraction grating 120 can include the material of the plate light guide 110. For example, as shown in FIG1A , the multibeam diffraction grating 120 includes substantially parallel ridges protruding from the surface of the plate light guide. In FIG1B , the multibeam diffraction grating 120 includes substantially parallel grooves 122 that penetrate the surface of the plate light guide 110. In other examples (not shown), the multibeam diffraction grating 120 can be a film or layer applied or affixed to the surface of the light guide.

According to various examples, the multibeam diffraction grating 120 can be arranged in, on, or at the surface of the plate light guide 110 in various configurations. For example, the multibeam diffraction grating 120 can be a member of a plurality of gratings (e.g., multibeam diffraction gratings) arranged in columns and rows across the light guide surface. For example, the rows and columns of the multibeam diffraction gratings 120 can represent a rectangular array of the multibeam diffraction gratings 120. In another example, the plurality of multibeam diffraction gratings 120 can be arranged in other arrays, including but not limited to a circular array. In yet another example, the plurality of multibeam diffraction gratings 120 can be substantially randomly distributed on the surface of the plate light guide 110.

According to some examples, the multibeam diffraction grating 120 can be a chirped diffraction grating 120. By definition, a "chirped" diffraction grating 120 is a diffraction grating that exhibits or has a diffraction spacing, or spacing d, of diffraction features 122 that varies across the extent or length of the chirped diffraction grating 120, as shown, for example, in Figures 1A-1B. The varying diffraction spacing d is referred to herein as "chirp." Thus, as described herein, the guided light beams 104 diffractively coupled out of the plate light guide 110 exit or are emitted from the chirped diffraction grating 120 as outcoupled light comprising a plurality of light beams 102. Furthermore, the light beams are coupled out at different diffraction angles, corresponding to the different origins of the respective light beams 102 that passed through the chirped diffraction grating 120. Through the predefined chirp, the chirped diffraction grating 120 is responsible for the predetermined and different primary angular directions of the plurality of light beams 102.

In some examples, the chirped diffraction grating 120 can have or exhibit a chirp with a diffraction spacing d that varies linearly with distance. As such, the chirped diffraction grating 120 can be referred to as a "linearly chirped" diffraction grating. For example, Figures 1A-1B illustrate a multibeam diffraction grating 120 that is a linearly chirped diffraction grating. Specifically, as shown, the diffraction features 122 are closer together at a first end 120' of the multibeam diffraction grating 120 than at a second end 120". Furthermore, by way of example, the diffraction spacing d of the diffraction features 122 is shown to vary linearly from the first end 120' to the second end 120".

In some examples, as described above, the light beam 102 generated by coupling the guided light beam 104 out of the plate light guide 110 using the multibeam diffraction grating 120 can diverge (i.e., a diverging light beam 102), for example, when the guided light beam 104 propagates in a direction from the first end 120' to the second end 120" of the multibeam diffraction grating 120 (e.g., as shown in Figures 1A-1B). Alternatively, according to other examples, a converging light beam 102 (not shown) can be generated when the guided light beam 104 propagates from the second end 120" to the first end 120' of the multibeam diffraction grating 120.

In another example (not shown), the chirped diffraction grating 120 can exhibit a nonlinear chirp of the diffraction spacing d. Various nonlinear chirps that can be used to implement the chirped diffraction grating 120 include, but are not limited to, exponential chirps, logarithmic chirs, or chirps that vary in another substantially non-uniform or random, but still monotonic, manner. Non-monotonic chirps can also be used, such as, but not limited to, sinusoidal chirps or triangular (or sawtooth) chirps. Combinations of any of these types of chirps can also be used.

FIG2 shows a perspective view of a multibeam diffraction grating, according to an example consistent with the principles described herein. As shown, the multibeam diffraction grating 120 includes curved and chirped diffraction features 122 (e.g., grooves or ridges) at, in, or on the surface of the plate light guide 110 (i.e., the multibeam diffraction grating 120 is a curved, chirped diffraction grating). A guided light beam 104 has an incident direction relative to the multibeam diffraction grating 120 and the plate light guide 110, as indicated by the thick arrow labeled 104 in FIG2 . A plurality of outcoupled or emitted light beams 102 are also shown directed away from the multibeam diffraction grating 120 at the surface of the plate light guide 110. As shown, the light beams 102 are emitted at a plurality of predetermined different principal angular directions. In particular, as shown, the predetermined different principal angular directions of the emitted light beams 102 differ in both azimuth and elevation. According to various examples, both the predetermined chirp of the diffractive features 122 and the curvature of the diffractive features 122 can be responsible for the predetermined different primary angular directions of the emitted light beam 102 .

Referring again to Figures 1A-1B, the 2D/3D switchable display backlight 100 further includes a switchable diffuser 130 that can be positioned to intercept the plurality of light beams 102. According to various examples, the switchable diffuser 130 has or provides a selectable first condition or state in which it is configured to pass light from the plurality of light beams 102. Additionally, the switchable diffuser 130 has or provides a selectable second condition or state in which it is configured to scatter light from the light beams 102. Figure 1A shows the switchable diffuser 130 configured to pass light in the selectable first state, while Figure 1B shows the switchable diffuser 130 configured to scatter light in the selectable second state. According to some examples, in the selectable second state, one or more of the degree of scattering, the scattering cone angle, and the scattering type can also be controlled.

For example, in a selectable first state, the switchable diffuser 130 can be substantially transparent to light of the light beam 102 (e.g., as shown in FIG1A ). Thus, according to various examples, upon exiting the switchable diffuser 130 in the selectable first state, the light beam 102 can still have a primary angular direction that is related to, or in some examples substantially similar to, the primary angular direction of the light beam incident upon the switchable diffuser 130. Furthermore, according to some examples, the light beam 102 exiting the switchable diffuser 130 can be substantially similar to the light beam 102 that entered the switchable diffuser 130 in the selectable first state at one or both intensities and directions. To simplify the discussion herein, as shown in FIG1A , no distinction is made between the light beam 102 incident upon and exiting the switchable diffuser 130 when the first state is selected.

On the other hand, as shown in FIG1B , in the selectable second state, the light beam 102 or its light is scattered, or at least substantially scattered, by the switchable diffuser 130. Thus, the light 102′ that exits the switchable diffuser 130 when the second state is selected no longer has the primary angular direction of the light beam 102 incident on or entering the switchable diffuser 130. Instead, according to various examples, the light 102′ that exits the switchable diffuser 130 in the second state (the scattering state) is scattered in a plurality of different directions (e.g., within scattering cone angles or diffusion angles). Furthermore, according to some examples, the plurality of different directions of the scattered light 102′ resulting from the selectable second state can be substantially independent of the primary angular direction of the light beam 102 incident on the switchable diffuser 130. FIG1B illustrates the scattered light 102′ and its scattering cone angle γ by way of example and not limitation.

In some examples, the switchable diffuser 130 can provide substantially isotropic scattering of the incident light beam 102 that is close to Lambertian scattering (e.g., "near-Lambertian") into a scattering cone angle γ. In other examples, the scattering can have a substantially Gaussian scattering profile, for example, or can have another scattering profile. In some examples, the scattering cone angle γ can be controllable from a relatively narrow cone angle (e.g., less than about ten degrees) to a relatively wide cone angle (e.g., greater than about forty degrees). For example, the scattering cone angle γ can be between about sixty (60) degrees and ninety (90) degrees. In another example, the scattering cone angle γ can be between about eighty (80) degrees and about one hundred and eighty (180) degrees. As shown in FIG. 1B , the scattering cone angle γ is about one hundred and twenty (120) degrees.

According to various examples, essentially any switchable or variable diffuser that provides scattering of light in multiple different (e.g., random or arbitrary) directions can be used as the switchable diffuser 130. For example, in some examples, the switchable diffuser 130 can be based on a volume or body diffuser, where scattering is provided by embedded scattering centers having variable properties (e.g., but not limited to, one or more of scattering center density, scattering center size, and scattering center distribution). In other examples, the switchable diffuser 130 can be a surface diffuser configured to provide scattering or diffusion based on variable surface roughness. In some examples, the switchable diffuser 130 is an electronically switchable diffuser. For example, the switchable diffuser 130 can be a polymer dispersed liquid crystal (PDLC) diffuser. In other examples, the switchable diffuser 130 can be based on another technology including, but not limited to, electrophoresis or electrowetting.

In other examples, switchable diffuser 130 can employ electromechanical means to switch between selectable first and second states. For example, switchable diffuser 130 can include a movable diffuser screen having a plurality of apertures. When the apertures are aligned with light beam 102, the light beam passes through switchable diffuser 130 without being scattered (i.e., the selectable first state). On the other hand, when the screen is moved so that light beam 102 passes through a scattering portion of the movable diffuser screen adjacent to the apertures, light beam 102 is scattered, and switchable diffuser 130 provides the selectable second state. Switchable diffuser 130 can be implemented as a microelectromechanical system (MEMS) variable diffuser. A MEMS variable diffuser can implement, for example, a movable diffuser screen or a variable diffuser employing an electromechanically variable surface roughness.

According to various examples, the selection between a selectable first state (non-scattering state) and a selectable second state (scattering state) or a selection thereof can be provided by a control input of the switchable diffuser 130. For example, the switchable diffuser 130 can be an electronically switchable or variable diffuser (e.g., a PDLC), wherein a first control input to the electronically switchable diffuser is configured to provide the first state and pass the light beam 102, and a second control input is configured to provide the second state and scatter the light beam. For example, the first control input can be a first voltage, and the second control input can be a second voltage.

According to some examples of the principles described herein, a 2D/3D switchable electronic display is provided. The 2D/3D switchable electronic display is configured to emit modulated light as pixels. Furthermore, the 2D/3D switchable electronic display can be selectively configured to provide or switch between a first or three-dimensional (3-D) mode and a second or two-dimensional (2-D) operating mode. In particular, in 3-D mode, a modulated light beam can be preferably directed in a plurality of different orientations toward the viewing direction of the 2D/3D switchable electronic display, the modulated light beam having a predetermined primary angular direction and corresponding to different 3-D views. In particular, the 2D/3D switchable electronic display in 3-D mode is a 3-D electronic display (e.g., a glasses-free 3-D electronic display). According to various examples, different beams of the modulated light beams in different orientations correspond to different "views" associated with the 2D/3D switchable electronic display in 3D mode. For example, the different "views" can provide a "glasses-free" (e.g., autostereoscopic or holographic) representation of 3-D information displayed by the 3D/3D switchable electronic display in 3-D mode. On the other hand, in the 2-D mode, for example, the modulated light beam is scattered in a plurality of arbitrary different directions representing diffuse light to serve as a 2-D pixel to display 2-D information.

FIG3 shows a block diagram of a 2D/3D switchable electronic display 200 according to an example consistent with the principles described herein. The 2D/3D switchable electronic display 200 shown in FIG3 includes a plate light guide 210 for guiding light (e.g., as a light beam). The guided light can be collimated and thus guided as, for example, a collimated light beam. The light guided in the plate light guide 210 is a light source that becomes a modulated light beam 202 or diffuse light emitted by the 2D/3D switchable electronic display 200 (e.g., in 3-D mode or 2-D mode, respectively). According to some examples, the plate light guide 210 can be substantially similar to the plate light guide 110 described above with respect to the 2D/3D switchable display backlight 100. For example, the plate light guide 210 can be a flat plate optical waveguide, which is a planar sheet of dielectric material configured to guide light by total internal reflection.

As further shown in FIG3 , the 2D/3D switchable electronic display 200 includes a multi-beam diffraction grating array 220. The multi-beam diffraction grating array 220 is located on or adjacent to a surface of the plate light guide 210. In some examples, the multi-beam diffraction gratings 220 of the array can be substantially similar to the multi-beam diffraction grating 120 of the 2D/3D switchable display backlight 100 described above. In particular, the multi-beam diffraction grating 220 is configured to couple out light guided as part of the plate light guide 210 as a plurality of light beams 204. Furthermore, the multi-beam diffraction grating 220 is configured to guide the light beams 204 into a corresponding plurality of predetermined different principal angular directions.

In some examples, the multibeam diffraction grating 220 comprises a chirped diffraction grating. In some examples, the diffraction features (e.g., grooves, ridges, etc.) of the multibeam diffraction grating 220 are curved diffraction features. In other examples, the array of multibeam diffraction gratings 220 comprises a chirped diffraction grating having curved diffraction features. For example, the curved diffraction features can include curved (i.e., continuously curved or segmented) ridges or grooves. Furthermore, the curved diffraction features can be spaced apart from each other by a spacing between the curved diffraction features that varies as a function of distance across the multibeam diffraction grating 220 (e.g., a "chirped" spacing).

3 , the 2D/3D switchable electronic display 200 further includes a light valve array 230. According to various examples, the light valve array 230 includes a plurality of light valves configured to modulate light 204′ corresponding to the plurality of light beams 204. For example, the plurality of light valves of the light valve array 230 can be substantially similar to the plurality of light beams 204. In particular, the light valves of the light valve array 230 modulate the light beams 204, or light 204′ corresponding to the light beams 204, to provide pixels of the 2D/3D switchable electronic display 200.

For example, when the 2D/3D switchable electronic display 200 is switched to or operates in 3-D mode, the pixels may be 3-D pixels corresponding to different views of the 3-D electronic display. Alternatively, when the 2D/3D switchable electronic display 200 is operated in, for example, 2-D mode, the pixels may be 2-D pixels. In some examples, the display resolution, or equivalently, the pixel density, may be the native resolution or density of the light valve array 230 in 2-D mode, while the display resolution or pixel density in 3D mode may be lower than the native resolution/density. In various examples, different types of light valves may be employed in the light valve array 230, including, but not limited to, one or both of liquid crystal light valves and electrophoretic light valves.

According to various examples, the 2D/3D switchable electronic display 200 further includes a switchable diffuser 240. The switchable diffuser 240 is configured to selectively pass the plurality of light beams 204 or to selectively scatter the light beams 204. Thus, the switchable diffuser 240 outputs light 204' corresponding to the light beams 204, which is either passed (i.e., substantially similar to the light beams 204) or scattered (e.g., into a scattering cone angle). According to various examples, switching the switchable diffuser 240 between passing and scattering the light beams 204 corresponds to switching the 2D/3D switchable electronic display between a 3-D operating mode and a 2-D operating mode.

According to some examples, the switchable diffuser 240 can be substantially similar to the switchable diffuser 130 described above with respect to the 2D/3D switchable display backlight 100. In particular, when configured to pass the light beam 204, the switchable diffuser 240 can be substantially similar to the switchable diffuser 130 having a first state selected, and when configured to scatter the light beam, the switchable diffuser 240 can be substantially similar to the switchable diffuser 130 having a second state. Furthermore, in some examples, the switchable diffuser 240 can be an electronically switchable or variable diffuser, such as, but not limited to, one or more of a PDLC diffuser, an electrophoretic variable diffuser, and an electrowetting-based variable diffuser. In other examples, a mechanical or electromechanical variable diffuser (e.g., a movable diffuser screen, a MEMS diffuser, etc.) can be used as the switchable diffuser 240.

According to some examples (e.g., as shown in FIG3 ), the switchable diffuser 240 is positioned between the light valve array 230 and the multi-beam diffraction grating array 220. When positioned between the light valve array 230 and the multi-beam diffraction grating array 220, the switchable diffuser 240 intercepts and selectively passes or scatters the light beam 204 before being modulated by the light valves of the light valve array 230. For example, when the switchable diffuser 240 is configured to pass the light beam 204 from the multi-beam diffraction grating 220, the light valve array 230 modulates light 204′ corresponding to the light beam 204, which can then continue to be viewed as a 3-D pixel of the modulated light beam 202. Alternatively, when the switchable diffuser 240 is configured to scatter the light beam 204, the scattered light 204′ corresponding to the light beam 204 is modulated by the light valve array 230 to generate a 2-D pixel (not shown). As an example, modulated light (e.g., as modulated light beam 202) is shown as dashed arrows emanating from light valve array 230 in FIG. 3 .

In other examples (not shown in FIG. 3 ), a switchable diffuser 240 is located at the output of the light valve array 230 to selectively pass or scatter the plurality of light beams 204. See, for example, FIG. 4B and the description below. Thus, the light beams 204 are modulated by the light valves of the light valve array 230 before being selectively passed or scattered by the switchable diffuser 240. However, according to various examples, whether located between the multi-beam diffraction grating 220 and the light valve array 230 or at the output of the light valve array 230, the switchable diffuser 240 provides a selectable 2-D or 3-D view from the 2D/3D switchable electronic display 200.

In other examples (not shown), the switchable diffuser can be substantially located within the light valve array. For example, when implementing the light valve array using liquid crystal light valves, the switchable diffuser can be located between the input polarizer and the liquid crystal cell containing the liquid crystal material. In another example, the switchable diffuser can be located between the liquid crystal cell and the output polarizer. According to various examples, it should be noted that when located between the liquid crystal cell and the polarizer of the liquid crystal light valve, a switchable diffuser that does not affect the polarization of light can be used.

FIG4A shows a cross-sectional view of a 2D/3D switchable electronic display 200, according to an example consistent with the principles described herein. FIG4B shows a cross-sectional view of a 2D/3D switchable electronic display 200, according to another example consistent with the principles described herein. Specifically, FIG4A shows a switchable diffuser 240 (e.g., as shown in FIG3 ) positioned between the multibeam diffraction grating array 220 and the light valve array 230. FIG4B shows the switchable diffuser 240 at the output (i.e., adjacent the output side) of the light valve array 230. Thus, as shown, the light valve array 230 is positioned between the multibeam diffraction grating array 220 and the switchable diffuser 240. Furthermore, the surface of the plate light guide 210 in FIG4A and 4B shows the multibeam diffraction grating array 220.

Referring to FIG4A , light, as indicated by the various arrows in FIG4A , is emitted by the multi-beam diffraction grating 220 and corresponds to a light beam 204, which is intercepted by the switchable diffuser 240 and optionally passed or scattered. In particular, the light beam 204, which optionally passes through the switchable diffuser 240, can continue to the light valve array 230 to be modulated into a light beam 202. For example, the modulated light beam 202 can represent a 3-D pixel 206 of the 2D/3D switchable electronic display 200 operating in a 3-D mode. The light beam 204, which is optionally scattered by the switchable diffuser 240, becomes scattered or diffused light 204″, as indicated by the plurality of short arrows. According to various examples, the scattered light 204″ can continue to the light valve array 230 to be modulated and represent a 2-D pixel 208 of the 2D/3D switchable electronic display 200 operating in a 2-D mode.

Referring to FIG4B , light emitted by the multi-beam diffraction grating 220 and corresponding to the light beam 204 is first modulated by the light valve array 230 and then intercepted by the switchable diffuser 240 and selectively passed or scattered. In the 3-D operating mode, the light beam 204 is first modulated by the light valve array 230 and then optionally passed through the switchable diffuser 240, still continuing and representing a 3-D pixel 206 of the 2D/3D switchable electronic display 200. In the 2-D operating mode, the modulated light beam 204, which is selectively scattered by the switchable diffuser 240, becomes light 204″ scattered or diffused at the output side of the switchable diffuser 240, for example, as shown as a plurality of short arrows. For example, in FIG4A and FIG4B , the plurality of short arrows illustrating the scattered light 204″ are arranged to represent the scattering cone angle of the switchable diffuser 240. In FIG. 4B , scattered light 204 ″ originates from the modulated light beam 204 output by the light valve array 230 , and therefore, represents a 2-D pixel 208 of the 2D/3D switchable electronic display 200 operating in a 2-D mode, according to various approaches.

As shown in Figures 4A and 4B, according to various examples, the resolution of the 2-D pixels 208 can be the same as or substantially similar to the native resolution of the light valve array 230, while the resolution of the 3-D pixels 206 can be lower than the native resolution. For example, the 3-D pixel resolution can be determined by the number of 3-D views, while the 2-D resolution can be determined by the number of light valves in the light valve array 230 (e.g., the number of light valves per inch or "native" resolution). For example, when the 2D/3D switchable electronic display 200 supports sixty-four (64) 3-D views, the 2-D resolution can be 64 times the 3-D resolution. In other examples, the 2-D resolution can be two, four, eight, or more times the 3-D resolution.

Note that, according to some examples, the switchable diffuser 240 can be configured to selectively pass the light beam 204 in certain areas of the 2D/3D switchable electronic display 200 while selectively scattering the light beam 204 in other areas (e.g., as shown in Figures 4A and 4B). By selectively passing and scattering the light beam 204 in different areas, the switchable diffuser 240 can facilitate the simultaneous display of 2-D information and 3-D information (e.g., in different areas) using the 2D/3D switchable electronic display 200. In particular, the switchable diffuser 240 can include multiple different areas across the display area of the 2D/3D switchable electronic display 200. The switchable diffuser 240 can be individually configured to selectively pass or scatter the light beam 204 in a first area of the multiple different areas, and selectively pass or scatter the light beam 204 in a second area. In the area where the switchable diffuser 240 is configured to selectively scatter the light beam 204, the pixel can be or represent a 2-D pixel 208 for displaying 2-D information (e.g., text). Alternatively, the pixel may be a 3-D pixel 206 for displaying 3-D information in an area of the 2D/3D switchable electronic display 200 corresponding to an area of the switchable diffuser configured to selectively pass the light beam 204 .

FIG4C illustrates a plan view of a 2D/3D switchable electronic display 200 having multiple distinct regions, according to an example consistent with the principles described herein. Specifically, according to various examples, the illustrated 2D/3D switchable electronic display 200 has distinct regions that can be individually configured to display either 3D information or 2D information using a switchable diffuser 240. As shown, the 2D/3D switchable electronic display 200 includes a switchable diffuser 240 that includes a first region 242 and a second region 244. For example, the first and second regions 242, 244 can be regions of the switchable diffuser 240 that are individually or separately controllable.

In some examples, the first region 242 can be configured to selectively pass the light beam 204 through the first region 242, while the second region 244 is configured to selectively scatter the light beam 204 within the second region 244. In these examples, the first region 242 is configured to display 3-D information, and the second region 244 is configured to display 2-D information (e.g., text, etc.). For example, the second region 244 can be used to display a text-based menu, and the first region 242 can be used to display a 3-D image. The second region 244 can then be reconfigured to selectively pass the light beam 204, so that the first and second regions 242, 244 can be used for 3-D information display. Furthermore, both the first and second regions 242, 244 can be reconfigured to selectively scatter the light beam 204, so that the 2D/3D switchable electronic display 200 can be used for 2-D information display.

In other examples (not shown), a region of a 2D/3D switchable electronic display may include a fixed or non-switchable diffuser, and another region may include a switchable diffuser 240 as described above, or may not include a diffuser. In these examples, the region with the fixed diffuser is dedicated to 2-D information display. When the switchable diffuser is present, the additional region can be used to selectively display both 2-D information and 3-D information. Alternatively, for example, when the diffuser is not present, the other region can be dedicated to 3-D information display.

Referring again to FIG. 3 , in some examples, the 2D/3D switchable electronic display 200 may further include a light source 250. The light source 250 is configured to provide light that propagates within the plate light guide 210 as guided light. Specifically, according to some examples, the guided light is light from the light source 250 coupled to an edge (or input end) of the plate light guide 210. For example, a lens, a collimating reflector, or the like (not shown) may facilitate coupling the light into the plate light guide 110 at its input end or edge. In various examples, the light source 250 may be substantially any light source, including, but not limited to, one or more of a light emitting diode (LED), a fluorescent lamp, and a laser. In some examples, the light source 250 may generate substantially monochromatic light having a narrowband spectrum represented by a specific color. In particular, the color of the monochromatic light may be a primary color of a specific color gamut or color model (e.g., a red-green-blue (RGB) color model). In some examples, the light source 250 may include multiple light sources of different colors.

In some examples, the 2D/3D switchable electronic display 200 may experience so-called "walk-off" of pixels. Specifically, if the switchable diffuser 240 is sufficiently far away from the multi-beam diffraction grating array 220, walk-off may occur. The term "walk-off" as used herein for a pixel is defined as a pixel that is out of sequence or out of position relative to the other pixels of the display. Specifically, a pixel may be out of sequence and, therefore, cause walk-off when the light beams 204 generated by the multi-beam diffraction grating array 220 cross one another. The switchable diffuser 240 may be spaced apart from the multi-beam diffraction grating array 220 to an extent that causes walk-off due to the respective thicknesses of various elements of the 2D/3D switchable electronic display, e.g., the thickness of the light valve array 230, the thickness of the switchable diffuser 240, etc.

According to various examples, walk-off can be mitigated by positioning the switchable diffuser 240 at a distance from the multi-beam diffraction grating array 220 corresponding to an intersection of the light beams 204. For example, the switchable diffuser 240 can be spaced apart from the multi-beam diffraction grating array 220 at a distance where the first light beam 204 intersects or crosses over the second light beam 204 in the plurality of light beams to mitigate walk-off. The intersection can be the first intersection or another intersection (e.g., a second, third, etc. intersection that is further from the multi-beam diffraction grating 220).

According to some examples of the principles described herein, a method of 2D/3D switchable electronic display operation is provided. FIG5 shows a flow chart of a method 300 of 2D/3D switchable electronic display operation consistent with the principles described herein. As shown in FIG5 , the method 300 of 2D/3D switchable electronic display operation includes guiding light in a plate light guide into a beam 310 having a non-zero propagation angle. In some examples, the plate light guide and the guided light can be substantially similar to the plate light guide 110 and the guided light beam 104 described above with respect to the 2D/3D switchable display backlight 100. In particular, the plate light guide guides the guided light beam according to total internal reflection, and in some examples, the guided light beam can be collimated 310. Furthermore, in some examples, the plate light guide can be a substantially planar dielectric optical waveguide or a slab waveguide (e.g., a planar dielectric slab).

As shown in FIG5 , method 300 of operating a 2D/3D switchable electronic display further includes coupling out a portion of the guided light 320. Specifically, the portion of the guided light coupled out of the plate light guide may include a plurality of light beams 320. Light beams in the plurality of light beams are directed away from the surface of the plate light guide. Furthermore, light beams in the plurality of light beams directed away from the surface of the plate light guide have a different primary angular direction than other light beams in the plurality of light beams. In some examples, each light beam in the plurality of light beams has a different primary angular direction relative to the other light beams.

In some examples, coupling out a portion of the guided light 320 includes diffractively coupling out the portion of the guided light using a multi-beam diffraction grating. According to some examples, the multi-beam diffraction grating can be located on or adjacent to a surface of the plate light guide. For example, the multi-beam diffraction grating can be formed as grooves, ridges, etc. on or at a surface (e.g., a top surface) of the plate light guide and can be formed from the material of the plate light guide. In other examples, the multi-beam diffraction grating can include a film on the surface of the plate light guide. In some examples, the multi-beam diffraction grating is substantially similar to the multi-beam diffraction grating 120 described above with respect to the 2D/3D switchable display backlight 100.

The method 300 for a 2D/3D switchable electronic display shown in FIG5 further includes selectively passing or scattering a plurality of light beams 330 using a switchable diffuser. When selectively passed 330 by the switchable diffuser, the plurality of light beams can represent three-dimensional (3-D) pixels of the 2D/3D switchable electronic display, and when selectively scattered 330 by the switchable diffuser, the plurality of light beams can represent two-dimensional (2-D) pixels of the 2D/3D switchable electronic display. According to some examples, the switchable diffuser 330 for selectively passing or scattering the light beams can be substantially similar to the switchable diffuser 130 of the 2D/3D switchable display backlight 100 described above. In particular, the switchable diffuser can include one or both of an electrically variable diffuser and a mechanical/electromechanically variable diffuser. Electrically variable diffusers may include, but are not limited to, polymer dispersed liquid crystal diffusers, electrophoretic-based diffusers, or electrowetting-based variable diffusers, while mechanical/electromechanically variable diffusers may include, but are not limited to, one or both of one or more movable diffuser screens and variable diffusers employing electromechanically variable surface roughness (e.g., MEMS variable diffusers).

According to some examples (not shown in FIG. 5 ), the method 300 for 2D/3D switchable electronic display further includes modulating the plurality of light beams using a plurality of light valves. According to some examples, the plurality of light valves can be substantially similar to the light valve array 230 described above with respect to the 2D/3D switchable electronic display 200. For example, the plurality of light valves can include a plurality of liquid crystal light valves. In some examples, after the plurality of light beams are modulated (e.g., as shown in FIG. 4B ), a switchable diffuser is used to selectively pass or scatter the plurality of light beams 330. In other examples, before the light beams are modulated (e.g., as shown in FIG. 4A ), a switchable diffuser is used to selectively pass or scatter the plurality of light beams 330.

Thus, examples of 2D/3D switchable display backlights, 2D/3D switchable electronic displays, and methods of 2D/3D switchable electronic display operation employing switchable diffusers have been described. It should be understood that the above examples are merely illustrative of some of the many specific examples of the principles described herein. Clearly, those skilled in the art can readily devise numerous other arrangements without departing from the scope of the appended claims.

Claims (19)

1. A 2D/3D switchable display backlight, comprising: A plate light guide, which is configured to guide light from a light source as a guided beam; A multi-beam diffraction grating configured to couple out a portion of a guided beam and guide the coupled portion away from the plate optical guide, the coupled portion comprising multiple beams with different principal angles, wherein the multi-beam diffraction grating comprises a chirped diffraction grating having curved diffraction characteristics; and A switchable diffuser is positioned to intercept the plurality of light beams, the switchable diffuser being configured to selectively allow light from one of the plurality of light beams to pass through to provide three-dimensional 3D pixels, or to scatter the light beams to provide two-dimensional 2D pixels. 2. The 2D/3D switchable display backlight as described in claim 1, wherein the chirped diffraction grating is a linear chirped diffraction grating. 3. The 2D/3D switchable display backlight as claimed in claim 1, wherein the multi-beam diffraction grating is located on the surface of the plate light guide, the multi-beam diffraction grating has diffraction features, the diffraction features including one or two of a curved groove within the surface of the plate light guide and a curved ridge on the surface of the plate light guide, the diffraction features being spaced apart from each other. 4. The 2D/3D switchable display backlight as claimed in claim 1, wherein the switchable diffuser has an electronically controlled selectable state including a first state of passing through the light beam and a second state of scattering the light beam. 5. The 2D/3D switchable display backlight as claimed in claim 1, wherein the switchable diffuser comprises a polymer-dispersed liquid crystal electronic diffuser. 6. An electronic display comprising a 2D/3D switchable display backlight as claimed in claim 1, wherein the coupled portion of the guided light beam is light corresponding to a pixel of the electronic display, and the pixel can be switched to a three-dimensional 3D pixel or a two-dimensional 2D electronic display pixel of the electronic display using the switchable diffuser. 7. The electronic display of claim 6, further comprising a light valve configured to modulate one of the plurality of light beams, wherein the multibeam diffraction grating is located between the light valve and the plate light guide. 8. The electronic display of claim 7, wherein the switchable diffuser is between the multibeam diffraction grating and the optical valve. 9. A 2D/3D switchable electronic display, comprising: A plate light guide, which is configured to guide light from a light source as a guided beam; A multi-beam diffraction grating array on the surface of a plate light guide is configured to couple a portion of the guided beam as multiple beams having corresponding multiple different principal angle directions, wherein the multi-beam diffraction grating of the multi-beam diffraction grating array is a chirped diffraction grating with curved diffraction characteristics. An array of light valves configured to modulate light corresponding to one of the plurality of light beams; and A switchable diffuser is configured to selectively pass one of the plurality of beams through to provide three-dimensional 3D pixels or scatter the beams to provide two-dimensional 2D pixels for a 2D/3D switchable electronic display. 10. The 2D/3D switchable electronic display of claim 9, wherein the light valve array comprises a plurality of liquid crystal light valves. 11. The 2D/3D switchable electronic display of claim 9, wherein the switchable diffuser is located between the light valve array and the multibeam diffraction grating array. 12. The 2D/3D switchable electronic display of claim 9, wherein the switchable diffuser is located near the output of the light valve array to optionally transmit or scatter modulated light. 13. The 2D/3D switchable electronic display of claim 9, wherein the switchable diffuser is spaced apart from the multi-beam diffraction grating array at a distance where one beam of the plurality of beams intersects with another beam of the plurality of beams to mitigate drift. 14. The 2D/3D switchable electronic display of claim 9, wherein the switchable diffuser comprises a plurality of different regions spanning the display area of the 2D/3D switchable electronic display, the switchable diffuser being individually configured to selectively pass through or scatter the light beam in a first region of the plurality of regions, and selectively pass through or scatter the light beam in a second region of the plurality of regions. 15. A method for operating a 2D/3D switchable electronic display, the method comprising: The light in the plate light guide is used as a beam with a non-zero propagation angle; A portion of the guided beam is coupled out using a multi-beam diffraction grating to generate multiple beams guided away from the plate light guide in corresponding multiple different principal angle directions, wherein the multi-beam diffraction grating comprises a chirped diffraction grating having curved diffraction characteristics; and A switchable diffuser can be used to selectively pass through or scatter the beams from the plurality of beams. The selectively passing beams of the plurality of beams represent three-dimensional 3D pixels of the 2D/3D switchable electronic display, and the selectively scattered beams of the plurality of beams represent two-dimensional 2D pixels of the 2D/3D switchable electronic display. 16. The 2D/3D switchable electronic display operation method as described in claim 15, further comprising using a plurality of light valves to modulate the light in the plurality of light beams. 17. The 2D/3D switchable electronic display operation method of claim 16, wherein after modulating the light in the plurality of light beams, passing through or scattering the plurality of light beams can be selectively performed. 18. The 2D/3D switchable electronic display operation method as described in claim 16, wherein the plurality of light valves includes a plurality of liquid crystal light valves. 19. The method of operating a 2D/3D switchable electronic display as described in claim 15, wherein the switchable diffuser is an electronic variable diffuser selected from polymer-dispersed liquid crystal diffusers, electrophoretic diffusers, or electrowetting-based variable diffusers.