HK40011704A - Unilateral backlight, multiview display, and method employing slanted diffraction gratings - Google Patents

Description

Single sided backlight, multiview display and method employing tilted diffraction grating

Cross reference to related applications

This application claims priority from U.S. provisional patent application serial No. 62/481,625, filed on 4/2017, which is incorporated herein by reference in its entirety.

Statement regarding federally sponsored research or development

N/A

Background

Electronic displays are a nearly ubiquitous medium for conveying information to users of a variety of devices and products. The most commonly employed electronic displays include Cathode Ray Tubes (CRTs), Plasma Display Panels (PDPs), Liquid Crystal Displays (LCDs), electroluminescent displays (ELs), Organic Light Emitting Diodes (OLEDs) and active matrix OLED (amoled) displays, electrophoretic displays (EPs) and various displays employing electromechanical or electrofluidic light modulation (e.g., digital micromirror devices, electrowetting displays, etc.). In general, electronic displays can be classified as either active displays (i.e., displays that emit light) or passive displays (i.e., displays that modulate light provided by another source). The most obvious examples of active displays are CRT, PDP and OLED/AMOLED. Displays which are generally classified as passive when considering the emitted light are LCD and EP displays. Passive displays, while often exhibiting attractive performance characteristics, including but not limited to inherently low power consumption, may find limited use in many practical applications in view of the lack of light-emitting capabilities.

To overcome the limitations of passive displays associated with emitting light, many passive displays are coupled to an external light source. The coupled light sources may allow these otherwise passive displays to emit light and function substantially as active displays. An example of such a coupled light source is a backlight. The backlight may be used as a light source (typically a panel backlight) that is placed behind an otherwise passive display to illuminate the passive display. For example, the backlight may be coupled to an LCD or EP display. Backlights emit light through an LCD or EP display. The emitted light is modulated by the LCD or EP display and the modulated light is then emitted from the LCD or EP display in turn. Typically the backlight is configured to emit white light. The white light is then converted to the various colors used in the display using color filters. For example, a color filter may be placed at the output (less common) of an LCD or EP display or between a backlight and an LCD or EP display.

Drawings

Various features of examples and embodiments in accordance with the principles described herein may be more readily understood by reference to the following detailed description in conjunction with the accompanying drawings, in which like reference numerals designate like structural elements, and in which:

fig. 1A illustrates a perspective view of a multi-view display in an example in accordance with an embodiment consistent with principles described herein.

Fig. 1B illustrates a graphical representation of angular components of light beams having a particular principal angular direction corresponding to a view direction of a multi-view display in an example according to an embodiment consistent with principles described herein.

Figure 2A illustrates a cross-sectional view of a diffraction grating in an example according to an embodiment consistent with principles described herein.

Figure 2B illustrates a cross-sectional view of a tilted diffraction grating in an example according to an embodiment consistent with principles described herein.

Fig. 3 illustrates a cross-sectional view of a single sided backlight in an example in accordance with an embodiment consistent with principles described herein.

Fig. 4A illustrates a cross-sectional view of a single-sided multiview display in an example in accordance with an embodiment consistent with principles described herein.

Fig. 4B illustrates a plan view of a single-sided multiview display in an example in accordance with an embodiment consistent with principles described herein.

Fig. 4C illustrates a perspective view of a single-sided multiview display in an example in accordance with an embodiment consistent with principles described herein.

FIG. 5 illustrates a block diagram of a dual mode display in an example in accordance with an implementation consistent with principles described herein.

Fig. 6 illustrates a flow chart of a method of single sided backlight operation in an example in accordance with an embodiment consistent with the principles described herein.

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

Detailed Description

Examples and embodiments in accordance with the principles described herein provide single-sided backlighting (unilaterally backlighting) as well as single-sided multi-view displays and dual-mode displays employing single-sided backlighting. In particular, embodiments consistent with principles described herein provide a single-sided backlight (backlight) employing a single-sided diffractive element including an inclined diffraction grating. The single-sided diffractive element is configured to scatter light out of the single-sided backlight as a directional beam of light having a single-sided direction. That is, according to various embodiments, the slanted diffraction grating of the one-sided diffractive element preferably directs or scatters light out of only one side of the backlight. In some embodiments, a single-sided diffractive element may be used as a single-sided multi-beam element configured to scatter light out as a plurality of directional light beams having different principal angular directions in a single-sided or "one-sided" direction. For example, the plurality of directional light beams may have directions corresponding to various view directions of a multi-sided multi-view display.

Herein, a "two-dimensional display" or a "2D display" is defined as a display in which: which is configured to provide a view of substantially the same image regardless of the direction from which the image is viewed (i.e., within a predetermined viewing angle or range of the 2D display). Conventional Liquid Crystal Displays (LCDs) that may be found in smart phones and computer monitors are examples of 2D displays. In contrast, a "multi-view display" is defined as an electronic display or display system configured to provide different views of a multi-view image in or from different view directions. In particular, the different views may represent different perspective views of a scene or object of the multi-view image. Uses of the single-sided backlit and single-sided multiview displays described herein include, but are not limited to, mobile phones (e.g., smart phones), watches, tablet computers, mobile computers (e.g., laptop computers), personal computers and computer monitors, automotive display consoles, camera displays, and various other mobile and substantially non-mobile display applications and devices.

Fig. 1A illustrates a perspective view of a multi-view display 10 in an example according to an embodiment consistent with principles described herein. As shown in fig. 1A, the multi-view display 10 includes a screen 12 to display a multi-view image to be viewed. For example, the screen 12 may be a display screen of a telephone (e.g., a mobile phone, a smart phone, etc.), a computer display of a tablet computer, a laptop computer, a desktop computer, a camera display, or an electronic display of substantially any other device.

The multi-view display 10 provides different views 14 of the multi-view image in different view directions 16 relative to the screen 12. View direction 16 is shown as an arrow extending from screen 12 in various principal angular directions; the different views 14 are shown as shaded polygonal boxes at the ends of the arrows (i.e., depicting view direction 16); and only four views 14 and four view directions 16 are shown, all by way of example and not limitation. Note that although the different views 14 are shown above the screen in fig. 1A, when the multi-view image is displayed on the multi-view display 10, the views 14 actually appear on the screen 12 or near the screen 12. The depiction of the views 14 above the screen 12 is for simplicity of illustration only and is intended to represent viewing of the multi-view display 10 from a respective one 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) instead of a different view 14 of the multi-view image provided by the multi-view display 10.

A view direction or equivalent light beam having a direction corresponding to the view direction of a multi-view display typically has a principal angular direction given by the angular components theta, phi, according to the definition herein. The angular component θ is referred to herein as the "elevation component" or "elevation angle" of the light beam. The angular component φ is referred to as the "azimuthal component" or "azimuth" of the beam. By definition, the elevation angle θ is an angle in a vertical plane (e.g., a plane perpendicular to the multi-view display screen), and the azimuth angle φ is an angle in a horizontal plane (e.g., a plane parallel to the multi-view display screen).

Fig. 1B illustrates a graphical representation of angular components θ, φ of a light beam 20 having a particular principal angular direction corresponding to a view direction (e.g., view direction 16 in fig. 1A) of a multi-view display in an example according to an embodiment consistent with principles described herein. Further, the light beam 20 is emitted or emitted from a particular point, as defined herein. That is, by definition, the light beam 20 has a central ray associated with a particular origin within the multi-view display. Fig. 1B also shows the beam (or view direction) point of origin O.

Further, herein, the term "multi-view" as used in the terms "multi-view image" and "multi-view display" is defined as a plurality of views representing different viewing angles or angular differences between views comprising a plurality of views. In addition, the term "multi-view" herein expressly includes more than two different views (i.e., a minimum of three views and often more than three views), as defined herein. As such, a "multi-view display" as used herein is clearly distinguished from a stereoscopic display that includes only two different views to represent a scene or image. Note, however, that while the multi-view image and multi-view display may include more than two views, the multi-view image may be viewed as a stereoscopic image pair (e.g., on the multi-view display) by selecting only two of the multi-view views to be viewed simultaneously (e.g., one view per eye), as defined herein.

A "multi-view pixel" is defined herein as a group of pixels representing a "view" pixel in each of a plurality of different views of a multi-view display. In particular, the multi-view pixels may have respective pixels corresponding to or representing view pixels in each different view of the multi-view image. Further, by definition herein, a pixel of a multiview pixel is a so-called "directional pixel",this is because each pixel is associated with a predetermined view direction of a corresponding one of the different views. Furthermore, according to various examples and embodiments, the different view pixels represented by the pixels of the multi-view pixel may have equivalent or at least substantially similar positions or coordinates in each of the different views. For example, the first multi-view pixel may have a position equal to { x } in each of the different views of the multi-view image₁，y₁The respective pixels corresponding to the view pixels at, and the second multi-view pixels may have, in each of the different views, a position corresponding to the position x₂，y₂The respective pixels corresponding to the view pixels at, etc.

In some embodiments, the number of pixels in a multiview pixel may be equal to the number of different views of the multiview display. For example, a multi-view pixel may provide sixty-four (64) pixels associated with a multi-view display having 64 different views. In another example, a multiview display may provide an eight-by-four view array (i.e., 32 views), and the multiview pixels may include thirty-two (32) pixels (i.e., one for each view). Additionally, for example, each different pixel may have an associated direction (e.g., a principal angular direction of the light beam) corresponding to a different one of the view directions corresponding to the 64 different views. Furthermore, according to some embodiments, the number of multiview pixels of the multiview display may be substantially equal to the number of "view" pixels (i.e. pixels making up the selected view) in the multiview display view. For example, if a view includes six hundred forty by four hundred eighty view pixels (i.e., 640 x 480 view resolution), a multi-view display may have thirty-zero seven thousand two hundred (307,200) multi-view pixels. In another example, when a view includes one hundred by one hundred pixels, the multi-view display may include a total of ten thousand (i.e., 100 × 100 ═ 10,000) multi-view pixels.

In this context, a "light guide" is defined as a structure that uses total internal reflection to guide light within the structure. In particular, the light guide may comprise a core that is substantially transparent at the operating wavelength of the light guide. In various examples, the term "light guide" generally refers to a dielectric optical waveguide that employs total internal reflection to guide light at an interface between a dielectric material of the light guide and a material or medium surrounding 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 may include a coating in addition to or in place of the above-described refractive index difference to further promote total internal reflection. For example, the coating may be a reflective coating. The light guide may be any one of several light guides including, but not limited to, one or both of a plate light guide or a sheet light guide and a strip light guide.

Further, herein, the term "plate" when applied to a light guide, as in a "plate light guide," is defined as a layer or sheet of segments or different planes, which is sometimes referred to as a "sheet" light guide. In particular, a plate light guide is defined as a light guide configured to guide light in two substantially orthogonal directions bounded by a top surface and a bottom surface (i.e., opposing surfaces) of the light guide. Further, as defined herein, both the top and bottom surfaces are separate from each other and may be substantially parallel to each other in at least a differential sense. That is, the top and bottom surfaces are substantially parallel or coplanar within any differential small portion of the plate light guide.

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

Herein, an "angle-preserving scattering feature" or, equivalently, an "angle-preserving diffuser" is any feature or diffuser configured to scatter light in a manner that substantially preserves the angular spread of light incident on the feature or diffuser in the scattered light. In particular, by definition, the angular spread σ of the light scattered by the angle-preserving scattering feature_sIs a function of the angular spread σ of the incident light (i.e., σ)_sF (σ)). In some embodiments, the angular spread σ of the scattered light_sIs the angular spread of incident lightLinear function of degree or collimation factor sigma (e.g. sigma)_sα · σ, where α is an integer). That is, the angular spread σ of light scattered by the angle-preserving scattering feature_sMay be substantially proportional to the angular spread or collimation factor sigma of the incident light. For example, the angular spread σ of the scattered light_sMay be substantially equal to the incident optical angular spread σ (e.g., σ)_sσ). A uniform diffraction grating (i.e., a diffraction grating having a substantially uniform or constant diffraction feature spacing or grating pitch) is one example of an angle-preserving scattering feature. In contrast, Lambertian diffusers or Lambertian reflectors, as well as ordinary diffusers (e.g., with Lambertian scattering or near-Lambertian scattering), are not angle-preserving diffusers, as defined herein.

Herein, a "polarization-maintaining scattering feature" or, equivalently, a "polarization-maintaining scatterer" is any feature or scatterer configured to scatter light in a manner that substantially preserves the polarization, or at least the degree of polarization, of the light incident on the feature or scatterer in the scattered light. Thus, a "polarization preserving scattering feature" is any feature or scatterer that has a degree of polarization of light incident on the feature or scatterer that is substantially equal to the degree of polarization of the scattered light. Further, by definition, "polarization-preserving scattering" is scattering (e.g., of guided light) that preserves or substantially preserves a predetermined polarization of the scattered light. For example, the scattered light may be polarized light provided by a polarized light source.

The term "single-sided" in "single-sided backlight", "single-sided diffractive scattering element" and "single-sided multi-beam element" is defined herein to mean "one side" or "preferentially in a direction" corresponding to a first side opposite to another direction corresponding to a second side. In particular, a "single-sided backlight" is defined as a backlight that emits light from a first side rather than from a second side opposite the first side. For example, a single-sided backlight may emit light into a first (e.g., positive) half-space, but not into a corresponding second (e.g., negative) half-space. The first half space may be above the single-sided backlight and the second half space may be below the single-sided backlight. Thus, for example, a single-sided backlight may emit light into a region above the single-sided backlight or toward that direction, and emit little or no light to another region below the single-sided backlight or toward another direction. Similarly, a "single-sided diffuser," such as, but not limited to, a single-sided diffractive scattering element or a single-sided multi-beam element, is configured to scatter light and scatter light out toward a first surface, but not a second surface opposite the first surface, as defined herein.

Herein, 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. In other examples, the diffraction grating may be a mixed-period diffraction grating comprising a plurality of diffraction gratings, each of the plurality of diffraction gratings having a different arrangement of periodic features. Further, the diffraction grating may include a plurality of features (e.g., a plurality of grooves or ridges on the surface of the material) arranged in a one-dimensional (1D) array. Alternatively, the diffraction grating may comprise a two-dimensional (2D) array of features or an array of features defined in two dimensions. For example, the diffraction grating may be a 2D array of bumps on the surface of the material or holes in the surface of the material. In some examples, the diffraction grating may be substantially periodic in a first direction or dimension and substantially non-periodic (e.g., constant, random, etc.) in another direction across or along the diffraction grating.

As such, and in accordance with the definition 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 the light guide, this may result in diffraction or diffraction scattering being provided and is therefore referred to as "diffractive coupling" because the diffraction grating may couple light out of the light guide by diffraction. Diffraction gratings also redirect or change the angle of light by diffraction (i.e., at diffraction angles). In particular, as a result of diffraction, light exiting a diffraction grating typically has a propagation direction that is different from the propagation direction of light incident on the diffraction grating (i.e., the incident light). Changing the propagation direction of light by diffraction is referred to herein as "diffractive redirection". Thus, a diffraction grating may be understood as a structure comprising diffractive features that diffractively redirect light incident on the diffraction grating, and if light is incident from the light guide, the diffraction grating may also diffractively couple light out of the light guide.

Further, features of a diffraction grating are referred to as "diffractive features" according to the definitions herein, and may be one or more of at a material surface (i.e., a boundary between two materials), in a material surface, and on a material surface. For example, the surface may be a surface of a light guide. The diffractive features can include any of a variety of structures that diffract light, including, but not limited to, one or more of grooves, ridges, holes, and bumps at, in, or on the surface. For example, the diffraction grating may comprise a plurality of substantially parallel grooves in the surface of the material. In another example, the diffraction grating may include a plurality of parallel ridges rising from the surface of the material. The diffractive features (e.g., grooves, ridges, apertures, bumps, etc.) can have any of a variety of cross-sectional shapes or profiles that provide diffraction, including but not limited to one or more of sinusoidal profiles, rectangular profiles (e.g., binary diffraction gratings), triangular profiles, and sawtooth profiles (e.g., blazed gratings).

According to various examples described herein, a diffraction grating (e.g., of a diffractive element as described below) may be employed to diffractively scatter or couple light out of a light guide (e.g., a plate light guide) as a light beam. In particular, the diffraction angle θ of the locally periodic diffraction grating_mOr diffraction angle theta provided by a locally periodic diffraction grating_mCan be given by equation (1):

where λ is the wavelength of the light, m is the diffraction order, n is the index of refraction of the light guide, d is the distance or spacing between the features of the diffraction grating, and θ_iIs the angle of incidence of the light on the diffraction grating. For simplicity, equation (1) assumes that the diffraction grating is adjacent to the surface of the light guide and that the refractive index of the material outside the light guide is equal to 1(i.e., n)_out1). Typically, the number of diffraction orders m is given by an integer (i.e., m ═ 1, ± 2, …). Diffraction angle theta of light beam generated by diffraction grating_mCan be given by equation (1). For example, a first order diffraction or more specifically a first order diffraction angle θ is provided when the number of diffraction orders m is equal to one (i.e., m is 1)_m。

Figure 2A illustrates a cross-sectional view of a diffraction grating 30 in an example according to an embodiment consistent with principles described herein. For example, the diffraction grating 30 may be located on a surface of the light guide 40. In addition, fig. 2A shows the angle of incidence θ_iA light beam 50 incident on the diffraction grating 30. Incident light beam 50 may be a beam of guided light (i.e., a guided light beam) within light guide 40. Also shown in fig. 2A is a directional beam 60 diffractively generated and coupled out by the diffraction grating 30 as a result of diffraction of the incident beam 50. The directed beam 60 has a diffraction angle θ given by equation (1)_m(or "principal angular direction" herein). Diffraction angle theta_mMay correspond to the diffraction order "m" of the diffraction grating 30, e.g., the diffraction order m is 1 (i.e., the first diffraction order).

Herein, by definition, a "tilted" diffraction grating is a diffraction grating having diffractive features with a tilt angle with respect to a surface normal of the diffraction grating surface. According to various embodiments, the tilted diffraction grating may provide single-sided scattering by diffraction of incident light.

Figure 2B illustrates a cross-sectional view of a tilted diffraction grating 80 in an example, according to an embodiment consistent with principles described herein. As shown, the tilted diffraction grating 80 is a binary diffraction grating located at the surface of the light guide 40, similar to the diffraction grating 30 shown in FIG. 2A. However, the tilted diffraction grating 80 shown in FIG. 2B includes diffractive features 82 having a tilt angle γ and a grating height, depth, or thickness t relative to a surface normal (shown by the dashed lines), as shown. Also shown is an incident beam 50 and a directed beam 60 representing a single-sided diffraction scattering of the incident beam 50 by the tilted diffraction grating 80. Note that according to various embodiments, the diffraction scattering of light in the secondary direction (second direction) by the inclined diffraction grating 80 is suppressed by the one-sided diffraction scattering. In fig. 2B, a dashed arrow 90 indicates suppressed diffraction scattering in the secondary direction by the tilted diffraction grating 80.

According to various embodiments, the tilt angle γ of the diffractive features 82 may be selected to control the one-sided diffraction characteristics of the tilted diffraction grating 80, including the degree of suppression of diffraction scattering in the secondary direction. For example, the tilt angle γ may be selected between about twenty degrees (20 °) and about sixty degrees (60 °), or between about thirty degrees (30 °) and about fifty degrees (50 °), or between about forty degrees (40 °) and about fifty-five degrees (55 °). For example, a tilt angle γ in the range of about 30 ° -60 ° may provide about forty times (40x) better suppression of diffraction scattering in the secondary direction compared to the single-sided direction provided by the tilted diffraction grating 80. According to some embodiments, the thickness t of the diffractive features 82 may be between about one hundred nanometers (100nm) and about four hundred nanometers (400 nm). For example, for a grating period p in the range from about 300nm and about 500 nanometers (500nm), the thickness t may be between about 150 nanometers (150nm) and about 300 nanometers (300 nm).

Further, according to some embodiments, the diffractive features may be curved and may also have a predetermined orientation (e.g., rotation) relative to the direction of propagation of the light. For example, one or both of the curvature of the diffractive feature and the orientation of the diffractive feature may be configured to control the direction of light coupled out by the diffraction grating. For example, the principal angular direction of the coupled-out light may be a function of the angle of the diffractive features at the point where the light is incident on the diffraction grating relative to the direction of propagation of the incident light.

A "multi-beam element," as defined herein, is a structure or element of a backlight or display that produces light comprising a plurality of light beams. By definition, a "diffractive" multi-beam element is a multi-beam element that produces multiple beams of light by or using diffractive coupling. In particular, in some embodiments, a diffractive multibeam element may be optically coupled to a light guide of a backlight to provide a plurality of light beams by diffractively coupling out a portion of light guided in the light guide. Further, a diffractive multibeam element, as defined herein, includes a plurality of diffraction gratings within a boundary or extent of the multibeam element. The light beams of the plurality of light beams (or "light beam plurality") produced by the multi-beam element have different principal angular directions from one another, as defined herein. In particular, by definition, one of the plurality of beams has a predetermined principal angular direction that is different from another of the plurality of beams. According to various embodiments, the spacing or grating pitch of the diffractive features in the diffraction grating of the diffractive multibeam element may be sub-wavelength (i.e., less than the wavelength of the guided light).

According to various embodiments, the plurality of light beams may represent a light field. For example, the plurality of light beams may be confined in a substantially conical spatial area or have a predetermined angular spread comprising different principal angular directions of the light beams of the plurality of light beams. In this way, the predetermined angular spread of the combined light beam (i.e., the plurality of light beams) may represent the light field.

According to various embodiments, the different principal angular directions of the various ones of the plurality of light beams are determined by characteristics including, but not limited to, the size (e.g., one or more of length, width, area, etc.) of the diffractive multibeam element and the "grating spacing" or diffractive feature spacing and orientation of the diffraction gratings within the diffractive multibeam element. In some embodiments, a diffractive multi-beam element may be considered as an "extended point source", i.e., a plurality of point sources distributed across the range of the diffractive multi-beam element, according to the definitions herein. Further, the light beam produced by the diffractive multi-beam element has a principal angular direction given by the angular components { θ, φ }, as defined herein, and described above with respect to FIG. 1B.

Herein, a "collimator" is defined as essentially any optical device or apparatus configured to collimate light. For example, the collimator may include, but is not limited to, a collimating mirror or reflector, a collimating lens, a diffraction grating, a tapered light guide, and various combinations thereof. According to various embodiments, the amount of collimation provided by the collimator may vary by a predetermined degree or amount from one embodiment to another. Further, the collimator may be configured to provide collimation in one or both of two orthogonal directions (e.g., a vertical direction and a horizontal direction). That is, according to some embodiments, the collimator may comprise a shape or similar collimating characteristic in one or both of the two orthogonal directions providing light collimation.

Herein, the "collimation factor", denoted as σ, is defined as the degree to which light is collimated. In particular, the collimation factor, as defined herein, defines the angular spread of rays within the collimated beam. For example, the collimation factor σ may specify that a majority of the rays in the collimated beam are within a particular angular spread (e.g., +/- σ degrees about the center or a particular principal angular direction of the collimated beam). According to some examples, the rays of the collimated light beam may have a gaussian distribution in terms of angle, and the angular spread may be an angle determined by half the peak intensity of the collimated light beam.

Herein, a "light source" is defined as a source of light (e.g., a light emitter configured to generate and emit light). For example, the light source may comprise a light emitter, such as a Light Emitting Diode (LED) that emits light when activated or turned on. In particular, the light source herein may be substantially any light source, or substantially include 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 generated by the light source may be of a color (i.e., may include light of a particular wavelength), or may be a range of wavelengths (e.g., white light). In some embodiments, the light source may comprise a plurality of light emitters. For example, the light source may comprise a set or group of light emitters, wherein at least one light emitter produces light having a color or equivalent wavelength different from the color or wavelength of light produced by at least one other light emitter in the set or group. For example, the different colors may include primary colors (e.g., red, green, blue).

By definition, "wide-angle" emitted light is defined as light having a cone angle that is greater than the cone angle of the multi-view image or multi-view display viewing angle. In particular, in some embodiments, the wide-angle emitted light may have a cone angle greater than about 20 degrees (e.g., > ± 20 °). In other embodiments, the wide-angle emitted light cone angle may be greater than about 30 degrees (e.g., > ± 30 °), or greater than about 40 degrees (e.g., > ± 40 °), or greater than 50 degrees (e.g., > ± 50 °). For example, the cone angle of the wide-angle emitted light may be about 60 degrees (e.g., > ± 60 °).

In some embodiments, the wide angle emission cone angle may be defined as approximately the same as the viewing angle of an LCD computer monitor, LCD tablet, LCD television, or similar digital display device for wide angle (e.g., about ± 40-65 °) viewing. In other embodiments, the wide-angle emission provided by the backlight may also be characterized or described as diffuse light, substantially diffuse light, non-directional light (i.e., lacking any particular or defined directionality), or light having a single or substantially uniform direction, for example.

In addition, as used herein, the articles "a" and "an" are intended to have their ordinary meaning in the patent arts, i.e., "one or more". For example, "an element" refers to one or more elements, and as such, "an element" refers herein to "the element(s)". Moreover, any reference herein to "top," "bottom," "above," "below," "upper," "lower," "front," "back," "first," "second," "left," or "right" is not intended to be limiting herein. As used herein, the term "about" when applied to a value generally means within the tolerance of the device used to produce the value, or may mean plus or minus 10%, or plus or minus 5%, or plus or minus 1%, unless expressly specified otherwise. Further, the term "substantially" as used herein refers to an amount in the range of most, or almost all, or about 51% to about 100%. Furthermore, the examples herein are intended to be illustrative only and for purposes of discussion and not as a limitation.

According to some embodiments of the principles described herein, a single sided backlight is provided. Fig. 3 illustrates a cross-sectional view of a single sided backlight 100 in an example in accordance with some embodiments consistent with principles described herein. As shown, the single-sided backlight is configured to provide emitted light as a directed light beam 102 having a single-sided direction. In fig. 3, the unilateral direction of the directional lightbeam 102 is a direction corresponding to a half-space above the surface of the unilateral backlight 100.

The single-sided backlight 100 shown in fig. 3 includes a light guide 110. According to some embodiments, the light guide 110 may be a plate light guide. The light guide 110 is configured to guide light along a length of the light guide 110 as guided light 104. For example, the light guide 110 may include a dielectric material configured as an optical waveguide. The dielectric material may have a first index of refraction that is greater than a second index of refraction of a medium surrounding the dielectric optical waveguide. For example, the difference in refractive index is configured to promote total internal reflection of the guided light 104, according to one or more guided modes of the light guide 110.

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

Further, according to some embodiments, the light guide 110 is configured to guide the guided light 104 at a non-zero propagation angle between a first surface 110' (e.g., a "front" surface or side) and a second surface 110 "(e.g., a" back "surface or side) of the light guide 110 according to total internal reflection. In particular, the guided light 104 propagates by reflecting or "bouncing" between the first surface 110' and the second surface 110 "of the light guide 110 at a non-zero propagation angle. In some embodiments, the guided light 104 includes multiple guided light beams of different colors of light. The light beams of the multiple guided light beams may be guided by the light guide 110 at respective ones of different color-specific non-zero propagation angles. Note that for simplicity of illustration, non-zero propagation angles are not shown. However, the bold arrows depicted in fig. 3 as propagation directions 103 show the general propagation directions of guided light 104 along the length of the light guide.

As defined herein, a "non-zero propagation angle" is an angle relative to a surface of the light guide 110 (e.g., the first surface 110' or the second surface 110 "). Further, according to various embodiments, the non-zero propagation angle is greater than zero and less than the critical angle for total internal reflection within the light guide 110. For example, the non-zero propagation angle of the guided light 104 may be between about ten degrees (10 °) and about fifty degrees (50 °), or in some examples, between about twenty degrees (20 °) and about forty degrees (40 °), or between about twenty-five degrees (25 °) and about thirty-five degrees (35 °). For example, the non-zero propagation angle may be about thirty degrees (30 °). In other examples, the non-zero propagation angle may be about 20 °, or about 25 °, or about 35 °. Further, the particular non-zero propagation angle may be selected (e.g., arbitrarily) for a particular implementation as long as the particular non-zero propagation angle is less than the critical angle for total internal reflection within the light guide 110.

The guided light 104 in the light guide 110 may be introduced or coupled into the light guide 110 at a non-zero propagation angle (e.g., about 30-35 degrees). For example, one or more of a lens, mirror, or similar reflector (e.g., a tilted collimating reflector), a diffraction grating, and a prism (not shown) may facilitate coupling light into the input end of light guide 110 as guided light 104 at a non-zero propagation angle. Once coupled into the light guide 110, the guided light 104 propagates along the light guide 110 in a direction that may be generally away from the input end (e.g., as shown by the thick arrow pointing along the x-axis in fig. 3).

Further, according to various embodiments, the guided light 104 may be collimated. Herein, "collimated light" or "collimated light beam" is generally defined as a light beam in which the rays of the light beam are substantially parallel to each other within the light beam (e.g., guided light 104). Further, light rays that diverge or scatter from the collimated beam are not considered part of the collimated beam, as defined herein. In some embodiments, the single-sided backlight 100 may include a collimator, such as, but not limited to, a lens, reflector or mirror, diffraction grating, or tapered light guide, configured to collimate light from a light source, for example. In some embodiments, the light source comprises a collimator. The collimated light provided to the light guide 110 is collimated guided light 104. In various embodiments, the guided light 104 may be collimated according to or with a collimation factor σ.

As shown in fig. 3, the single-sided backlight 100 also includes an array of single-sided diffractive elements 120 spaced apart from each other along the length of the light guide. In particular, the single-sided diffractive elements 120 of the array are separated from each other by finite intervals along the length of the light guide and represent separate distinct elements. That is, the single-sided diffractive elements 120 are spaced apart from one another according to a finite (i.e., non-zero) inter-element distance (e.g., a finite center-to-center distance), as defined herein. Furthermore, according to some embodiments, the plurality of single-sided diffractive elements 120 do not generally intersect, overlap, or otherwise contact each other. Thus, each one-sided diffractive element 120 of the one-sided diffractive element array is typically distinct and separate from the other one-sided diffractive elements 120 in the one-sided diffractive element 120.

According to some embodiments, the single-sided diffractive elements 120 of the single-sided diffractive element array may be arranged in a one-dimensional (ID) array or a two-dimensional (2D) array. For example, the single-sided diffractive elements 120 may be arranged as a linear ID array. In another example, the single-sided diffractive elements 120 may be arranged as a rectangular 2D array or a circular 2D array. Further, in some examples, the array (i.e., ID or 2D array) may be a regular or uniform array. In particular, the inter-element distance (e.g., center-to-center distance or spacing) between the single-sided diffractive elements 120 may be substantially uniform or constant across the array. In other examples, the inter-element distance between the single-sided diffractive elements 120 may vary one or both across the array and along the length of the light guide 110.

According to various embodiments, the single-sided diffractive elements 120 in the array of single-sided diffractive elements 120 comprise a tilted diffraction grating 122. According to some embodiments (e.g., as shown), all of the single-sided diffractive elements 120 may be or include a tilted diffraction grating 122. The one-sided diffractive element 120 comprising the tilted diffraction grating 122 is configured to scatter a portion of the guided light 104 out of the light guide 110 as a directed light beam 102 having a one-sided direction. In particular, according to various embodiments, a portion of the guided light 104 is scattered out by the plurality of single-sided diffractive elements 120 by diffractive scattering. For example, fig. 3 shows the directional light beam 102 being emitted from the first surface 110 'of the light guide 110 in a single-sided direction corresponding to a half-space above the first surface 110'.

In some embodiments, the tilted diffraction grating 122 of the single-sided diffractive element 120 may be substantially similar to the tilted diffraction grating 80 shown in fig. 2B. For example, in some embodiments, the tilt angle of the tilted diffraction grating 122, corresponding to the tilt angle γ shown in fig. 2B, may be between about thirty degrees (30 °) and about fifty degrees (50 °) relative to the surface normal of the light guide 110. Further, in some embodiments (not shown), the tilted diffraction grating 122 may include a plurality of sub-gratings, each sub-grating being a tilted diffraction grating.

In some embodiments, a single-sided diffractive element may be configured to scatter a portion of guided light 104 out as a plurality of directional light beams 102 having different principal angular directions in a single-sided direction. Furthermore, in some embodiments, the different principal angular directions of the plurality of directional light beams may correspond to respective view directions of a single-sided multiview display. In particular, the one-sided diffractive element 120 comprising an inclined diffraction grating may be a multibeam element and may therefore be referred to as a one-sided multibeam element. In some embodiments, the size of the single-sided diffractive element is comparable (comparable) to the size of the pixels (or equivalently, the size of the light valves) in the multiview pixels of the single-sided multiview display.

Fig. 4A illustrates a cross-sectional view of a single-sided multiview display 200 in an example according to an embodiment consistent with principles described herein. Fig. 4B illustrates a plan view of a single-sided multiview display 200 in an example according to an embodiment consistent with principles described herein. Fig. 4C illustrates a perspective view of a single-sided multiview display 200 in an example according to an embodiment consistent with principles described herein. The perspective view in fig. 4C is shown in partial cross-sectional view to facilitate discussion only herein. The single-sided multi-view display 200 shown in fig. 4A-4C is configured to provide a plurality of directional light beams 202 (e.g., as a light field) having different principal angular directions from one another. In some embodiments, a directional light beam 202 of the plurality of directional light beams may be modulated (e.g., using a light valve described below) to facilitate displaying information having three-dimensional (3D) content.

As shown in fig. 4A-4C, the single-sided multiview display 200 includes a light guide 210 and an array of single-sided diffractive elements 220 spaced apart from each other along the length of the light guide 210. According to various embodiments, the light guide 210 is configured to guide light along the light guide length as guided light 204. According to various embodiments, the single-sided diffractive elements 220 (or equivalent single-sided multi-beam elements) of the single-sided diffractive element array are configured to provide a plurality of directional light beams 202 having different principal angular directions corresponding to respective different view directions of the single-sided multi-view display 200. In some embodiments, the array of one-sided diffractive elements 220 may be substantially similar to the array of one-sided diffractive elements 120, as described above with respect to the one-sided backlight 100. In particular, the single-sided diffractive element 220 of the single-sided diffractive element array includes a tilted diffraction grating 222, which may be substantially similar to the tilted diffraction grating 122 described above. Further, in some embodiments, the light guide 210 and the array of single-sided diffractive elements 220 of the single-sided multiview display 200, when combined, may be substantially similar to the single-sided backlight 100 described above.

Fig. 4A and 4C illustrate the directional light beam 202 as depicted as a plurality of diverging arrows directed away from the first (or front) surface 210' of the light guide 210. Furthermore, according to various embodiments, the dimensions of the single-sided diffractive element 220 are comparable (compatible) to the dimensions of the pixels in the multiview pixels 206 of the multiview display 100, as described below and further described below. As used herein, "dimension" may be defined in any of a variety of ways to include, but is not limited to, length, width, or area. For example, the size of a pixel may be its length, and the equivalent size of the one-sided diffractive element 220 may also be the length of the one-sided diffractive element 220. In another example, the size may refer to an area, such that the area of the one-sided diffractive element 220 may be comparable to the area of a pixel.

In some embodiments, the size of the one-sided diffractive element 220 is comparable to the pixel size, such that the one-sided diffractive element size is between about fifty percent (50%) and about two hundred percent (200%) of the pixel size. For example, if the single-sided diffractive element size is denoted as "S" and the pixel size is denoted as "S" (e.g., as shown in fig. 4A), the single-sided diffractive element size S can be given as:

in other examples, the single-sided diffractive element size is in a range greater than about sixty percent (60%) of the pixel size, or greater than about seventy percent (70%) of the pixel size, or greater than about eighty percent (80%) of the pixel size, or greater than about ninety percent (90%) of the pixel size, and less than about one-hundred eighty percent (180%) of the pixel size, or less than about one-hundred sixty percent (160%) of the pixel size, or less than about one-hundred forty percent (140%) of the pixel size, or less than about one-hundred twenty percent (120%) of the pixel size. For example, by "comparable size," the single-sided diffractive element size may be between about seventy-five percent (75%) and about one-hundred fifty percent (150%) of the pixel size. In another example, the single-sided diffractive element 220 may be comparable in size to a pixel, with the single-sided diffractive element size being between about one hundred twenty five percent (125%) and about eighty five percent (85%) of the pixel size. According to some embodiments, the equivalent sizes of the single-sided diffractive elements 220 and pixels may be selected to reduce or in some examples minimize dark regions between views of the single-sided multiview display 200. Furthermore, the equivalent sizes of the single-sided diffractive elements 220 and pixels may be selected to reduce or, in some examples, minimize overlap between views (or view pixels) of the single-sided multiview display 200.

As shown in fig. 4A-4C, the single-sided multiview display 200 further comprises an array of light valves 230. The array of light valves 230 is configured to modulate a directional beam 202 of the plurality of directional beams. As shown in fig. 4A-4C, different directed light beams 202 having different principal angular directions pass through and may be modulated by different light valves 230 in the array of light valves. Further, as shown, the light valves 230 of the array correspond to pixels of the multiview pixels 206, and one set of light valves 230 corresponds to the multiview pixels 206 of the single-sided multiview display 200. In particular, different sets of light valves 230 of the light valve array are configured to receive and modulate the directed light beams 202 from a respective different one of the single-sided diffractive elements 220, i.e., there is a unique set of light valves 230 for each single-sided diffractive element 220, as shown. In various embodiments, different types of light valves may be employed as the light valves 230 of the light valve array, including but not limited to one or more of liquid crystal light valves, electrophoretic light valves, and electrowetting-based light valves.

As shown in fig. 4A, first set of light valves 230a is configured to receive and modulate directional light beam 202 from first single-sided diffractive element 220 a. Further, second set of light valves 230b is configured to receive and modulate directional light beam 202 from second single-sided diffractive element 220 b. Thus, as shown in fig. 4A, each set of light valves (e.g., first and second sets of light valves 230a, 230b) in the array of light valves corresponds to a different one-sided diffractive element 220 (e.g., elements 220a, 220b), respectively, and also to a different multi-view pixel 206, where each light valve 230 of the set of light valves corresponds to a pixel of the corresponding multi-view pixel 206.

Note that as shown in fig. 4A, the size of the pixels of the multiview pixel 206 may correspond to the size of the light valves 230 in the light valve array. In other examples, the pixel size may be defined as the distance (e.g., center-to-center distance) between adjacent light valves 230 of the array of light valves. For example, the light valves 230 may be smaller than the center-to-center distance between the light valves 230 in the array of light valves. For example, the pixel size may be defined as the size of the light valves 230 or a size corresponding to the center-to-center distance between the light valves 230.

In some embodiments, the relationship between the single-sided diffractive element 220 and the corresponding multiview pixel 206 (i.e., the group of pixels and the corresponding group of light valves 230) may be a one-to-one relationship. That is, there may be an equal number of multiview pixels 206 and single-sided diffractive elements 220. Fig. 4B explicitly shows, by way of example, a one-to-one relationship in which each multi-view pixel 206 including a different set of light valves 230 (and corresponding pixels) is shown enclosed with a dashed line. In other embodiments (not shown), the number of multi-view pixels 206 and the number of single-sided diffractive elements 120 may be different from each other.

In some embodiments, the inter-element distance (e.g., center-to-center distance) between a pair of single-sided diffractive elements 220 may be equal to the inter-pixel distance (e.g., center-to-center distance) between a corresponding pair of multi-view pixels 206, e.g., represented by a set of light valves. For example, as shown in fig. 4A, the center-to-center distance D between the first single-sided diffractive element 220a and the second single-sided diffractive element 220b is substantially equal to the center-to-center distance D between the first and second valve sets 230a and 230 b. In other embodiments (not shown), the relative center-to-center distances of the pairs of single-sided diffractive elements 220 and the corresponding sets of valve optics may be different, e.g., the single-sided diffractive elements 220 may have an inter-element spacing (i.e., center-to-center distance D) that is greater than or less than one of the spacings between the sets of valve optics (i.e., center-to-center distance D) representing the multiview pixels 206.

In some embodiments, the shape of the single-sided diffractive element 120 is similar to the shape of the multiview pixel 206 or equivalent to the shape of the group (or "sub-array") of light valves 230 corresponding to the multiview pixel 206. For example, the single-sided diffractive element 220 may have a square shape, and the multiview pixels 206 (or the corresponding arrangement of groups of light valves 230) may be substantially square. In another example, the single-sided diffractive element 220 may have a rectangular shape, i.e., may have a length or longitudinal dimension that is greater than a width or lateral dimension. In this example, the multiview pixels 206 (or equivalently, the arrangement of the groups of light valves 230) corresponding to the one-sided diffractive element 220 may have a rectangular-like shape. Fig. 4B shows a top or plan view of a square-shaped one-sided diffractive element 220 and a corresponding square-shaped multiview pixel 206 comprising a square group of light valves 230. In yet another example (not shown), the single-sided diffractive element 220 and the corresponding multi-view pixel 206 have various shapes, including or at least approximating, but not limited to, triangular, hexagonal, and circular.

Further (e.g., as shown in fig. 4A), according to some embodiments, each single-sided diffractive element 220 is configured to provide a directional light beam 202 to one and only one multi-view pixel 206. In particular, for a given one of the one-sided diffractive elements 220, the directed light beams 202 having different principal angular directions corresponding to different views of the one-sided multiview display 200 are substantially limited to a single corresponding multiview pixel 206 and its pixels, i.e. a single group of light valves 230 corresponding to the one-sided diffractive element 220, as shown in fig. 4A. In this way, each one-sided diffractive element 220 of the one-sided multi-view display 200 provides a corresponding set of directed light beams 202, the set of directed light beams 202 having a different set of principal angular directions corresponding to different views of the one-sided multi-view display 200 (i.e., the set of directed light beams 202 includes light beams having directions corresponding to each of the different view directions).

According to some embodiments, the diffractive features of the tilted diffraction gratings 122, 222 of the single-sided diffractive element array in the single-sided backlight 100 or the single-sided multiview display 200 may comprise one or both of tilted grooves and tilted ridges spaced apart from each other. The slanted groove or slanted ridge may comprise, for example, the material of the light guide 110 which may be formed in the surface of the light guide 110. In another example, the slanted grooves or slanted ridges may be formed of a material other than the light guide material, e.g., a layer or film of another material on the surface of the light guide 110.

In some embodiments, the tilted diffraction grating 122, 222 is a uniform diffraction grating in which the diffractive feature spacing is substantially constant or constant throughout the tilted diffraction grating 122. In other embodiments, the tilted diffraction grating 122 is a chirped diffraction grating. By definition, a "chirped" diffraction grating is a diffraction grating that exhibits or has a diffraction spacing of diffractive features (i.e., grating pitch) that varies across the range or length of the chirped diffraction grating. In some embodiments, a chirped diffraction grating may have or exhibit a chirp of the diffractive feature spacing that varies linearly with distance. Thus, by definition, a chirped diffraction grating is a "linearly chirped" diffraction grating. In other embodiments, the chirped diffraction grating may exhibit a non-linear chirp of the diffractive feature spacing. Various non-linear chirps may be used, including but not limited to exponential chirps, logarithmic chirps, or chirps that vary in another, substantially non-uniform, or random but still monotonic manner. Non-monotonic chirps may also be employed, such as but not limited to sinusoidal chirps or triangular or saw tooth chirps. Combinations of any of these types of chirps may also be employed. Further, the tilt angle of the tilted diffraction grating 122 may vary within the length, width, or range of the tilted diffraction grating 122. In some embodiments, the tilted diffraction grating 122, 222 may include a plurality of sub-gratings, each sub-grating being a tilted diffraction grating.

Referring again to fig. 3, the single-sided backlight 100 may further include a light source 130. Similarly, the single-sided multi-view display 200 shown in FIGS. 4A-4C may also include a light source 240. As shown, the light source 130, 240 is configured to provide light to be guided within the light guide 110, 210. In particular, the light source 130, 240 may be located adjacent an entrance surface or end (input end) of the light guide 110, 210.

In various embodiments, the light sources 130, 240 may include substantially any source of light (e.g., an optical emitter), including but not limited to a Light Emitting Diode (LED), a laser (e.g., a laser diode), or a combination thereof. In some embodiments, the light source 130, 240 may include an optical emitter configured to produce substantially monochromatic light having a narrow-band spectrum represented by a particular color. In particular, the color of the monochromatic light may be a primary color of a particular color space or color model (e.g., a red-green-blue (RGB) color model). In other examples, the light sources 130, 240 may be substantially broadband light sources configured to provide substantially broadband or polychromatic light. For example, the light sources 130, 240 may provide white light. In some embodiments, the light sources 130, 240 may include a plurality of different optical emitters configured to provide different colors of light. The different optical emitters may be configured to provide light having different, color-specific, non-zero propagation angles of the guided light corresponding to each of the different colors of light. According to various embodiments, diffractive feature spacing and other diffraction grating characteristics (e.g., diffraction period) and grating orientation relative to the direction of propagation of the guided light 104, 204 may correspond to different colors of light. In other words, for example, the single-sided diffractive element 120 may comprise different slanted diffraction gratings 122 that may be adapted to different colors of the guided light 104. Likewise, the single-sided diffractive element 220 of the single-sided multiview display 200 may comprise a plurality of slanted gratings, each adapted to a different color of the guided light 204.

In some embodiments, the light source 130, 240 may also include a collimator. The collimator may be configured to receive substantially uncollimated light from one or more optical emitters of the light source 130, 240. The collimator is further configured to convert the substantially uncollimated light into collimated light. In particular, according to some embodiments, the collimator may provide collimated light having a non-zero propagation angle or being collimated according to a predetermined collimation factor, or provide collimated light having a non-zero propagation angle and being collimated according to a predetermined collimation factor. Further, when different color optical emitters are employed, the collimator may be configured to provide collimated light having different color-specific non-zero propagation angles or having different color-specific collimation factors, or to provide collimated light having different color-specific non-zero propagation angles and having different color-specific collimation factors. As described above, the collimator is further configured to transmit the collimated light beam to the light guide 110, 210 to propagate as the guided light 104, 204.

In some embodiments, the single-sided backlight 100 may be configured to be substantially transparent to light in a direction through the light guide 110 that is orthogonal (or substantially orthogonal) to the propagation direction 103 of the guided light 104. In particular, in some embodiments, the light guide 110 and the spaced apart single sided diffractive elements 120 allow light to pass through the light guide 110 through the first surface 110' and the second surface 110 ″. In some embodiments, transparency may be facilitated, at least in part, due to the relatively small size of the single-sided diffractive elements 120 and the relatively large inter-element spacing of the single-sided diffractive elements 120. Furthermore, according to some embodiments, the slanted diffraction grating 122 of the single-sided diffractive element 120 may also be substantially transparent to light propagating orthogonal to the light guide surfaces 110', 110 ″. For example, the combination of the light guide 210 and the array of single-sided diffractive elements 220 of the single-sided multiview display 200 may similarly be configured to be transparent to light in a direction orthogonal (or substantially orthogonal) to the propagation direction of the guided light 204.

According to some embodiments of the principles described herein, a dual mode display is provided. According to various embodiments, the dual mode display is configured to provide a multi-view image during a first mode and a display image comprising a single view (e.g., a 2D image) during a second mode. FIG. 5 illustrates a block diagram of a dual mode display 300 in an example in accordance with an implementation consistent with principles described herein. The operation of the dual mode display 300 in the first mode (mode 1) is shown in the left half of fig. 5, while the right half shows operation in the second mode (mode 2).

The dual mode display 300 shown in fig. 5 includes a single-sided multiview display 310 configured to provide multiview images during a first mode (mode 1). As shown, the single-sided multiview display 310 includes a light guide 312 and an array of single-sided diffractive elements 314. The single-sided diffractive elements 314 of the single-sided diffractive element array each include one or more slanted diffraction gratings. During the first mode, the array of single-sided diffractive elements 314 is configured to provide a plurality of directional light beams having a direction corresponding to the view direction of the multi-view image by diffractively scattering out the light guided in the light guide 312. In some embodiments, the single-sided multiview display 310 may be substantially similar to the single-sided multiview display 200 described above. In particular, the light guide 312 may be substantially similar to the light guide 210, and the array of one-sided diffractive elements may be substantially similar to the array of one-sided diffractive elements 220, as described above with respect to the one-sided multiview display 200.

Further, the single-sided multiview display 310 includes an array of light valves 316 configured to modulate a directional beam of the plurality of directional beams into a multiview image. According to some embodiments, the array of light valves 316 may be substantially similar to the array of light valves 230 of the single-sided multiview display 200 described above. In particular, the modulated directional light beams 302 emitted by the single-sided multiview display 310 are used to display multiview images and may correspond to pixels of different views (i.e., view pixels). The modulated light beam 302 is shown as a directional arrow emanating from a single-sided multiview display 310 in fig. 5.

As shown in fig. 5, the dual mode display 300 also includes a wide angle backlight 320 configured to provide wide angle light 304 during the second mode (mode 2). In fig. 5, the wide-angle backlight 320 is shown adjacent to a surface (e.g., a back surface) of the single-sided multiview display 310 such that the light guide 312 and the array of single-sided diffractive elements 314 are located between the wide-angle backlight 320 and the array of light valves 316. According to various embodiments, the array of light valves 316 is configured to modulate the wide-angle light 304 during the second mode to provide a display image having a single view. In particular, the array of light valves 316 is configured to modulate the wide-angle light 304 after the wide-angle light 304 has passed through the light guide 312 and the array of single-sided diffractive elements 314 (e.g., as shown in the right half of fig. 5). As such, according to various embodiments, the light guide 312 and the array of single-sided diffractive elements 314 are transparent to the wide-angle light 304. Further, according to various embodiments, the light valves 316 of the light valve array of the single-sided multiview display 310 are configured to provide a modulation that results in both the multiview image during the first mode and the display image during the second mode.

According to other embodiments of the principles described herein, methods of single-sided backlight operation are provided.

Fig. 6 illustrates a flow chart of a method 400 of single-sided backlight operation in an example in accordance with an embodiment consistent with principles described herein. As shown in fig. 6, a method 400 of single-sided backlight operation includes directing 410 light along a length of a light guide. In some embodiments, the light may be directed 410 at a non-zero propagation angle. In some embodiments, the guided light may be collimated, for example, according to a predetermined collimation factor. According to some embodiments, the light guide may be substantially similar to the light guide 110 described above with respect to the single-sided backlight 100. In particular, according to various embodiments, light may be guided within the light guide according to total internal reflection.

As shown in fig. 6, the method 400 of single-sided backlight operation further includes diffractively scattering 420 a portion of the guided light out of the light guide using an array of single-sided diffractive elements to provide a plurality of directional light beams having a single-sided direction. According to various embodiments, a single-sided diffractive element of the plurality of single-sided diffractive elements comprises a tilted diffraction grating. In some embodiments, the array of one-sided diffractive elements may be substantially similar to the array of one-sided diffractive elements 120 of the one-sided backlight 100 described above. In particular, the tilted diffraction grating may be substantially similar to the tilted diffraction grating 122 described above.

In some embodiments, a single-sided diffractive element in the array of single-sided diffractive elements provides a plurality of directional light beams having different principal angular directions in a single-sided direction. Furthermore, in some embodiments, different cardinal directions may correspond to respective view directions of the multi-view display. Furthermore, the size of the single-sided diffractive elements may be comparable to the size of the pixels in the multi-view pixels of the multi-view display. For example, the single-sided diffractive element size may be greater than half the pixel size and less than twice the pixel size. Further, according to various embodiments, the single-sided diffractive elements of the array may include a plurality of slanted diffraction gratings. Thus, in some embodiments, a single-sided diffractive element may be a single-sided multi-beam element.

In some embodiments (not shown), the method 400 of single-sided backlight operation further includes providing light to the light guide using a light source. The provided light may have a non-zero propagation angle within the light guide or may be collimated within the light guide according to a collimation factor, or may have a non-zero propagation angle within the light guide and may be collimated within the light guide according to a collimation factor to provide a predetermined angular spread of the guided light within the light guide. In some embodiments, the light source may be substantially similar to the light source 130 of the single-sided backlight 100 described above.

In some embodiments, the method 400 of single-sided backlight operation further includes modulating 430 the plurality of directional light beams using a plurality of light valves to display an image in a single-sided direction. In some embodiments, the plurality of light valves may be substantially similar to the array of light valves 230 described above with respect to the single-sided multiview display 200. In particular, according to some embodiments, a light valve of the plurality of light valves may correspond to a pixel of a multiview pixel. That is, for example, the light valve may have a size comparable to the size of a pixel or a size comparable to the center-to-center spacing between pixels of a multiview pixel. Furthermore, different groups of light valves may correspond to different multi-view pixels in a manner similar to the correspondence of the first and second groups of light valves 230a, 230b to the different multi-view pixels 206, as described above.

Thus, examples and embodiments of a single-sided backlight, a method of single-sided backlight operation, and a single-sided multiview display using single-sided diffractive elements employing tilted diffraction gratings have been described. It should be understood that the above-described examples are merely illustrative of some of the many specific examples that represent the principles described herein. It is clear that a person skilled in the art can easily devise many other arrangements without departing from the scope defined by the following claims.

Claims (20)

1. A single-sided backlight, comprising:

a light guide configured to guide light in a propagation direction along a length of the light guide; and

an array of one-sided diffractive elements spaced apart from one another along the light guide length, the one-sided diffractive elements of the array of one-sided diffractive elements comprising a tilted diffraction grating configured to scatter a portion of guided light out of the light guide as a directed light beam having a one-sided direction.

2. The single-sided backlight of claim 1, wherein a tilt angle of the tilted diffraction grating relative to a surface normal of the light guide is between thirty degrees and sixty degrees.

3. The single sided backlight of claim 1, wherein the tilted diffraction grating comprises a plurality of sub-gratings, each sub-grating being a tilted diffraction grating.

4. The single-sided backlight of claim 1, wherein the single-sided diffractive element is configured to scatter a portion of the guided light out as a plurality of directional light beams having different principal angular directions in a single-sided direction corresponding to respective different view directions of a single-sided multiview display, the single-sided diffractive element having a size comparable to a pixel size in a multiview pixel of the single-sided multiview display.

5. The single-sided backlight of claim 4, wherein the size of the single-sided diffractive element is between fifty percent and two hundred percent of the pixel size.

6. The single-sided backlight of claim 4, wherein a shape of the single-sided diffractive element is similar to a shape of the multiview pixel.

7. The single sided backlight of claim 1, wherein the single sided diffractive element is located at one of a first surface and a second surface of the light guide, the single sided diffractive element configured to scatter a portion of the guided light in the single sided direction out through the first surface.

8. The single-sided backlight of claim 1, further comprising a light source optically coupled to an input of the light guide, the light source configured to provide light to the light guide, the guided light being collimated according to a predetermined collimation factor.

9. The single-sided backlight of claim 1, wherein the combination of the light guide and the array of single-sided diffractive elements is configured to be optically transparent in a direction orthogonal to a propagation direction of the guided light.

10. A display comprising the single-sided backlight of claim 1, the display further comprising an array of light valves configured to modulate a plurality of directional light beams scattered out by the array of single-sided diffractive elements into a display image.

11. The display of claim 10, wherein the single-sided diffractive elements of the array of single-sided diffractive elements are configured as single-sided multi-beam elements to scatter a portion of the guided light out as a plurality of directional light beams having different principal angular directions in the single-sided direction corresponding to respective view directions of a multi-view display, the display image being a multi-view image.

12. A single-sided multiview display comprising:

a light guide configured to guide light along a length of the light guide as guided light;

an array of one-sided multibeam elements spaced apart from each other along the light guide length, a one-sided multibeam element of the array of multibeam elements comprising a tilted diffraction grating configured to scatter a portion of guided light in a one-sided direction as a plurality of directed light beams having principal angular directions corresponding to respective view directions of a multiview image; and

an array of light valves configured to modulate the plurality of directional beams into the multi-view image.

13. The single-sided multiview display of claim 12, wherein the size of the single-sided multibeam element is greater than half the size of a light valve in the array of light valves and less than twice the size of the light valve.

14. The single-sided multiview display of claim 12, wherein a shape of the single-sided multi-beam element is similar to a shape of a set of light valves representing multiview pixels of the multiview display.

15. The single-sided multiview display of claim 12, wherein the tilted diffraction grating has a tilt angle between thirty and sixty degrees relative to a surface normal of the light guide.

16. The single-sided multiview display of claim 12, further comprising a light source configured to provide light to the light guide, the guided light being collimated according to a collimation factor to provide a predetermined angular spread of the guided light within the light guide.

17. A dual mode display comprising the single-sided multiview display of claim 12, further comprising a wide-angle backlight configured to provide wide-angle light during a second mode, the light guide and the array of single-sided multibeam elements being between the wide-angle backlight and the array of light valves, wherein the array of light valves is configured to modulate the plurality of directional light beams into the multiview image during a first mode and the array of light valves is configured to modulate the wide-angle light to provide a display image having a single view during the second mode.

18. A method of single-sided backlight operation, the method comprising:

directing light in a propagation direction along a length of the light guide; and

diffractively scattering a portion of the guided light out of the light guide using an array of single sided diffractive elements spaced apart from each other along the light guide length to provide a plurality of directed light beams having a single sided direction,

wherein a single-sided diffractive element of the array of single-sided diffractive elements comprises a slanted diffraction grating.

19. The method of single-sided backlight operation of claim 18, wherein the single-sided diffractive elements of the array of single-sided diffractive elements provide a plurality of directional light beams having different principal angular directions in the single-sided direction, the different principal angular directions corresponding to respective view directions of a multi-view display, the single-sided diffractive elements having dimensions comparable to dimensions of pixels of multi-view pixels of the multi-view display.

20. The method of single-sided backlight operation of claim 18, further comprising modulating the plurality of directional beams using a plurality of light valves to display an image in the single-sided direction.