Patent Description:
Electronic displays are a nearly ubiquitous medium for communicating information to users of a wide variety of devices and products. Among the most commonly found electronic displays are the cathode ray tube (CRT), plasma display panels (PDP), liquid crystal displays (LCD), electroluminescent displays (EL), organic light emitting diode (OLED) and active matrix OLEDs (AMOLED) displays, electrophoretic displays (EP) and various displays that employ electromechanical or electrofluidic light modulation (e.g., digital micromirror devices, electrowetting displays, etc.). In general, electronic displays may be categorized as either active displays (i.e., displays that emit light) or passive displays (i.e., displays that modulate light provided by another source). Among the most obvious examples of active displays are CRTs, PDPs and OLEDs/AMOLEDs. Displays that are typically classified as passive when considering emitted light are LCDs and EP displays. Passive displays, while often exhibiting attractive performance characteristics including, but not limited to, inherently low power consumption, may find somewhat limited use in many practical applications given the lack of an ability to emit light.

To overcome the limitations of passive displays associated with emitted light, many passive displays are coupled to an external light source. The coupled light source may allow these otherwise passive displays to emit light and function substantially as an active display. Examples of such coupled light sources are backlights. A backlight may serve as a source of light (often a panel backlight) that is placed behind an otherwise passive display to illuminate the passive display. For example, a backlight may be coupled to an LCD or an EP display. The backlight emits light that passes through the LCD or the EP display. The light emitted is modulated by the LCD or the EP display and the modulated light is then emitted, in turn, from the LCD or the EP display. Often backlights are configured to emit white light. Color filters are then used to transform the white light into various colors used in the display. The color filters may be placed at an output of the LCD or the EP display (less common) or between the backlight and the LCD or the EP display, for example.

<CIT> describes a thin film type controlled viewing window back light unit. <CIT> describes an illumination device for illuminating at least one spatial light modulator device.

A time-multiplexed backlight in accordance with the invention is defined in claim <NUM>. A method of time-multiplexed backlight operation in accordance with the invention is defined in claim <NUM>. A multiview electronic display comprising the time-multiplexed backlight of claim <NUM> is defined in claim <NUM>. Various features in accordance with the principles described herein may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, where like reference numerals designate like structural elements, and in which:.

The present disclosure relates to time-multiplexed display backlighting. In particular, backlighting of a display (e.g., an electronic display) employs a time-multiplexed light source to provide a light beam having different angles of propagation during different intervals of time. Light of the light beam may be coupled-out of a backlight as an emitted or coupled-out light beam that is directed in a viewing direction of the display. According to various embodiments, the
coupled-out light beam has a principal angular direction corresponding to or that is determined by the light beam propagation angle. As such, the coupled-out light beam has different, albeit predetermined, principal angular directions in the different time intervals. Time multiplexing enables switching between the different principal angular directions as a function of time.

A plurality of coupled-out light beams is provided by the backlight from the light beam of the time-multiplexed light source. Coupled-out light beams of the plurality have different principal angular directions from one another. The coupled-out light beams having the different principal angular directions (also referred to as 'the differently directed light beams') may be employed to display information including three-dimensional (3D) or multiview information. In particular, the different principal angular directions of the coupled-out light beam plurality may correspond to various view directions of different views of a 3D or multiview display (e.g., a 'glasses free' or autostereoscopic electronic display). Further, the differently directed coupled-out light beams may be modulated and serve as pixels of the different views of the multiview display.

Moreover, the plurality of coupled-out light beams and different views corresponding thereto provided from the light beam of the time-multiplexed light source have different directions in different time intervals. In particular, sets of coupled-out light beams of the plurality and corresponding sets of different views provided during the different time intervals according to time multiplexing of the light source may be angularly interleaved with one another, in some embodiments. Angular interleaving of coupled-out light beams and different views of the sets may effectively increase one or both of a pixel resolution and a view resolution of the display, according to various embodiments.

Herein, a 3D or multiview display is defined as an electronic display or display system configured to provide different views of a multiview image in different view directions. <FIG> illustrates a perspective view of a multiview display <NUM>. As illustrated in <FIG>, the multiview display <NUM> comprises a screen <NUM> that is viewed in order to see a
3D or multiview image. The multiview display <NUM> provides different views <NUM> of the multiview image in different view directions <NUM> relative to the screen <NUM>. The view directions <NUM> are illustrated as arrows extending from the screen <NUM> in various different principal angular directions; the different views <NUM> are illustrated as shaded polygonal boxes at the termination of the arrows (i.e., depicting the view directions <NUM>); and only four views <NUM> and four view directions <NUM> are illustrated, all by way of example and not limitation. Note that while the different views <NUM> are illustrated in <FIG> as being above the screen, the views <NUM> actually appear on or in a vicinity of the screen <NUM> when the multiview image is displayed on the multiview display <NUM>. Depicting the views <NUM> above the screen <NUM> is only for simplicity of illustration meant to represent viewing the multiview display <NUM> from a respective one of the view directions <NUM> corresponding to a particular view <NUM>.

A view direction or equivalently a light beam having a direction corresponding to a view direction of a multiview display generally has a principal angular direction given by angular components {θ, φ}, by 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 `azimuth component' or `azimuth angle' of the light beam. By definition, the elevation angle θ is an angle in a vertical plane (e.g., perpendicular to a plane of the multiview display screen while the azimuth angle φ is an angle in a horizontal plane (e.g., parallel to the multiview display screen plane). <FIG> illustrates a graphical representation of the angular components {θ, φ} of a light beam <NUM> having a particular principal angular direction corresponding to a view direction of a multiview display. In addition, the light beam <NUM> is emitted or emanates from a particular point, by definition herein. That is, by definition, the light beam <NUM> has a central ray associated with a particular point of origin within the multiview display. <FIG> also illustrates the light beam (or view direction) point of origin O.

Referring again to <FIG>, also illustrated are other views <NUM>' (e.g., a second set of views) with corresponding view directions <NUM>'. The other views <NUM>' are polygonal boxes shaded with dashed-dot shading at the end of the dashed-line corresponding view direction <NUM>' arrows to further distinguish from the first mentioned views <NUM>. The other views <NUM>' may be views of the multiview display provided during a second time interval, while the views <NUM> (e.g., a first set of views) may be views of multiview display provided during a first time interval, for example. Further, as illustrated, the other views <NUM>' and the other view directions <NUM>' are angularly interleaved with the views <NUM> and the corresponding view directions <NUM>. Note that in <FIG>, solid lines illustrating the views <NUM> and the view directions <NUM> represent these elements during the first time interval, while dashed lines of the other views <NUM>' and the other view directions <NUM>' represent these elements during the second time interval. Note that while reference is made herein to a 'first' time interval and a 'second' time interval, in general any number of time intervals may be used. As such, there may also be a third time interval, a fourth time interval and so on. Herein, reference is confined to 'first' and 'second' for ease of discussion and not by way of limitation.

Herein, 'multiview' as used in the terms 'multiview image' and 'multiview display' is defined as a plurality of views representing different perspectives or including angular disparity between views of the view plurality. Further, the term 'multiview' by definition explicitly includes more than two different views (i.e., a minimum of three views and generally more than three views). As such, 'multiview' as employed herein is explicitly distinguished from stereoscopic views that include only two different views to represent a scene. Note however, while multiview images and multiview displays include more than two views, by definition herein, multiview images may be viewed (e.g., on a multiview display) as a stereoscopic pair of images by selecting only two of the multiview views to view at a time (e.g., one view per eye).

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

Further herein, the term 'plate' when applied to a light guide as in a `plate light guide' is defined as a piece-wise or differentially planar layer or sheet, which is sometimes referred to as a 'slab' guide. In particular, a plate light guide is defined as a light guide configured to guide light in two substantially orthogonal directions bounded by a top surface and a bottom surface (i.e., opposite surfaces) of the light guide. Further, by definition herein, the top and bottom surfaces are both separated from one another and may be substantially parallel to one another in at least a differential sense. That is, within any differentially small section of the plate light guide, the top and bottom surfaces are substantially parallel or co-planar.

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

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. For example, the diffraction grating may include a plurality of features (e.g., a plurality of grooves or ridges in a material surface) arranged in a one-dimensional (1D) array. In other examples, the diffraction grating may be a two-dimensional (2D) array of features. The diffraction grating may be a 2D array of bumps on or holes in a material surface, for example.

As such, and by definition herein, the 'diffraction grating' is a structure that provides diffraction of light incident on the diffraction grating. If the light is incident on the diffraction grating from a light guide, the provided diffraction or diffractive scattering may result in, and thus be referred to as, 'diffractive coupling' in that the diffraction grating may couple light out of the light guide by diffraction. The diffraction grating also redirects or changes an angle of the light by diffraction (i.e., at a diffractive angle). In particular, as a result of diffraction, light leaving the diffraction grating generally has a different propagation direction than a propagation direction of the light incident on the diffraction grating (i.e., incident light). The change in the propagation direction of the light by diffraction is referred to as 'diffractive redirection' herein. Hence, the diffraction grating may be understood to be a structure including diffractive features that diffractively redirects light incident on the diffraction grating and, if the light is incident from a light guide, the diffraction grating may also diffractively couple out the light from the light guide.

Further, by definition herein, the features of a diffraction grating are referred to as 'diffractive features' and may be one or more of at, in and on a material surface (i.e., a boundary between two materials). The surface may be a surface of a light guide, for example. 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 bumps at, in or on the surface. For example, the diffraction grating may include a plurality of substantially parallel grooves in the material surface. In another example, the diffraction grating may include a plurality of parallel ridges rising out of the material surface. The diffractive features (e.g., grooves, ridges, holes, bumps, etc.) may have any of a variety of cross sectional shapes or profiles that provide diffraction including, but not limited to, one or more of a sinusoidal profile, a rectangular profile (e.g., a binary diffraction grating), a triangular profile and a saw tooth profile (e.g., a blazed grating).

By definition herein, a 'multibeam diffraction grating' is a diffraction grating that produces diffractively redirected light (e.g., diffractively coupled-out light) that includes a plurality of light beams. The light beams of the plurality produced by a multibeam diffraction grating have different principal angular directions from one another, by definition herein. In particular, by definition, a light beam of the plurality has a predetermined principal angular direction that is different from another light beam of the light beam plurality as a result of diffractive coupling and diffractive redirection of incident light by the multibeam diffraction grating. The light beam plurality may represent a light field. For example, the light beam plurality may include eight light beams that have eight different principal angular directions. The eight light beams in combination (i.e., the light beam plurality) may represent the light field, for example. According to various embodiments, the different principal angular directions of the various light beams are determined by a combination of a grating pitch or spacing and an orientation or rotation of the diffractive features of the multibeam diffraction grating at points of origin of the respective light beams relative to a propagation direction or angle of the light incident on the multibeam diffraction grating.

A diffraction grating (e.g., a multibeam diffraction grating) may be employed to produce coupled-out light that represents pixels of an electronic display or simply a 'display. ' In particular, the light guide having a multibeam diffraction grating to produce the light beams of the plurality having different principal angular directions may be part of a backlight of or used in conjunction with a display such as, but not limited to, a 'glasses free' multiview display (also sometimes referred to as a 'holographic' display or an autostereoscopic display). As such, the differently directed light beams produced by coupling out guided light from the light guide using the multibeam diffractive grating may be or represent 'pixels' of the multiview display. Moreover, as described above, the differently directed light beams may form a light field including directions corresponding to view directions of the multiview display.

A multibeam diffraction grating may be employed to diffractively couple light out of a light guide (e.g., a plate light guide) as a light beam. In particular, a diffraction angle θm of or provided by a locally periodic diffraction grating may be given by equation (<NUM>) as: <MAT> where λ is a wavelength of the light, m is a diffraction order, n is an index of refraction of a light guide, d is a distance between features of the diffraction grating, θi is an angle of incidence of light on the diffraction grating. For simplicity, equation (<NUM>) assumes that the diffraction grating is adjacent to a surface of the light guide and a refractive index of a material outside of the light guide is equal to one (i.e., nout = <NUM>). In general, the diffraction order m is given by an integer. According to various examples, a diffraction angle θm of a light beam produced by the diffraction grating may be given by equation (<NUM>) where the diffraction order is positive (e.g., m > <NUM>). For example, first-order diffraction is provided when the diffraction order m is equal to one (i.e., m = <NUM>).

<FIG> illustrates a cross sectional view of a diffraction grating <NUM>. For example, the diffraction grating <NUM> may be located on a surface of a light guide <NUM>. In addition, <FIG> illustrates a light beam <NUM> incident on the diffraction grating <NUM> at an incident angle θi. The light beam <NUM> is a guided time-multiplexed light beam within the light guide <NUM>. Also illustrated in <FIG> is a coupled-out light beam <NUM> diffractively produced and coupled-out by the diffraction grating <NUM> as a result of the incident light beam <NUM>. The coupled-out light beam <NUM> has a diffraction angle θm (or principal angular direction) as given by equation (<NUM>). The coupled-out light beam <NUM> may correspond to a diffraction order 'm' of the diffraction grating <NUM>, for example.

Herein a 'collimator' is defined as substantially any optical device or apparatus that is configured to collimate light. For example, a collimator may include, but is not limited to, a collimating mirror or reflector, a collimating lens, and various combinations thereof. In some embodiments, the collimator comprising a collimating reflector may have a reflecting surface characterized by a parabolic curve or shape. In another example, the collimating reflector may comprise a shaped parabolic reflector. By 'shaped parabolic' it is meant that a curved reflecting surface of the shaped parabolic reflector deviates from a 'true' parabolic curve in a manner determined to achieve a predetermined reflection characteristic (e.g., a degree of collimation). Similarly, a collimating lens may comprise a spherically shaped surface (e.g., a biconvex spherical lens).

In some embodiments, the collimator may be a continuous reflector or a continuous lens (i.e., a reflector or a lens having a substantially smooth, continuous surface). In other embodiments, the collimating reflector or the collimating lens may comprise a substantially discontinuous surface such as, but not limited to, a Fresnel reflector or a Fresnel lens that provides light collimation. According to various embodiments, an amount of collimation provided by the collimator may vary in a predetermined degree or amount from one embodiment to another. Further, the predetermined degree or amount from one embodiment to another. Further, the collimator may be configured to provide collimation in one or both of two orthogonal directions (e.g., a vertical direction and a horizontal direction). That is, the collimator may include a shape or shaped surface in one or both of two orthogonal directions that provides light collimation, according to some embodiments.

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

Further, as used herein, the article 'a' is intended to have its ordinary meaning in the patent arts, namely `one or more'. For example, 'a grating' means one or more gratings and as such, 'the grating' means 'the grating(s)' herein. Also, any reference herein to 'top', 'bottom', 'upper', 'lower', 'up', 'down', 'front', back', 'first', 'second', 'left' or 'right' is not intended to be a limitation herein. Herein, the term 'about' when applied to a value generally means within the tolerance range of equipment used to produce the value, or may mean plus or minus <NUM>%, or plus or minus <NUM>%, or plus or minus <NUM>%, unless otherwise expressly specified. Further, the term `substantially' as used herein means a majority, or almost all, or all, or an amount within a range of about <NUM>% to about <NUM>%. Moreover, examples herein are intended to be illustrative only and are presented for discussion purposes and not by way of limitation.

In accordance with the invention and as defined in claim <NUM>, a time-multiplexed backlight is provided. <FIG> illustrates a cross sectional view of a time-multiplexed backlight <NUM> in an example, according to an embodiment consistent with the principles described herein. <FIG> illustrates a cross sectional view of a portion of a time-multiplexed backlight <NUM>. <FIG> illustrates a cross sectional view of another portion of a time-multiplexed backlight <NUM>.

Light coupled out from the time-multiplexed backlight <NUM> forms or provides an emitted or 'coupled-out' light beam <NUM> directed away from a surface of the time-multiplexed backlight <NUM>. Moreover, the coupled-out light beam <NUM> is directed away from the surface in different principal angular directions during different time intervals. Thus, the coupled-out light beam <NUM> is time-multiplexed to have a first principal angular direction in or during a first time interval and a second principal angular direction during a second time interval. In particular, the principal angular direction of the coupled-out light beam <NUM> is time-multiplexed.

<FIG> and <FIG> depicts the coupled-out light beam <NUM> during a first time interval using a solid arrow, while a dashed arrow depicts the coupled-out light beam <NUM> during a second time interval. In particular, <FIG> illustrates a plurality of coupled-out light beams <NUM>, where the coupled-out light beams <NUM> in the first time interval are angularly interleaved with the coupled-out light beams <NUM> in the second time interval. <FIG> illustrates a single coupled-out light beam <NUM> having a different principal angular direction in each of the first time interval and the second time interval.

Note that while specific reference is made above to a 'first' non-time interval and a 'second' time interval, in general there may be a plurality of time intervals and corresponding different coupled-out light beams <NUM> in different time intervals of the plurality. As such, for example, there may also be a third time interval, a fourth time interval and so on with corresponding coupled-out light beams <NUM>. Herein, reference is confined to 'first' and 'second' for ease of discussion and not by way of limitation.

The time-multiplexed backlight <NUM> is based on an array of multibeam diffraction gratings, as is defined in claim <NUM>.

The plurality of coupled-out light beams <NUM> may be configured to form a light field. The light field may have different characteristics or different angular components during different time intervals as a function of or as provided by time multiplexing. The different sets of coupled-out light beams <NUM> having corresponding different sets of principal angular directions are provided in different time intervals by the time multiplexed backlight <NUM>, as a result of time multiplexing.

According to various embodiments, the coupled-out light of the coupled-out light beam <NUM> includes a portion of light within the time-multiplexed backlight <NUM>. The light is guided light or equivalently a guided light beam <NUM> within the time-multiplexed backlight <NUM> (i.e. in a light guide, as described below). As illustrated in <FIG>, a general propagation direction of the guided light beam <NUM> is illustrated as horizontal bold arrows <NUM> for simplicity of illustration and not by way of limitation. Further, time multiplexing of the principal angular direction of the coupled-out light beam <NUM> is provided through time multiplexing of a non-zero propagation angle of the guided light <NUM>, as is described below in more detail.

In some embodiments, the time-multiplexed backlight <NUM> may be a source of light or a 'backlight' of a display (e.g., an electronic display). In particular, according to some embodiments where a light field is produced by the plurality of coupled-out light beams <NUM>, the electronic display may be a so-called 'glasses free' multiview electronic display (e.g., a 3D display or autostereoscopic display) in which the various coupled-out light beams <NUM> correspond to or represent pixels associated with different 'views' of the multiview display. Further, the coupled-out light beams <NUM> may be modulated (e.g., by a light valve, as described below). For example, a light valve may be employed to modulate the coupled-out light beam <NUM>. Modulation of different sets of coupled-out light beams <NUM> directed in different angular directions away from the time-multiplexed backlight <NUM> may be particularly useful for dynamic multiview electronic display applications. That is, the different sets of modulated coupled-out light beams <NUM> directed in particular view directions may represent dynamic pixels of the multiview electronic display corresponding to the particular view directions thereof.

The time-multiplexed backlight <NUM> illustrated in <FIG> comprises a light guide <NUM>. In some embodiments, the light guide <NUM> may be a plate light guide. The light guide <NUM> is configured to guide light as a guided beam of light (i.e., a guided light beam <NUM>). For example, the light guide <NUM> may include a dielectric material configured as an optical waveguide. The dielectric material may have a first refractive index that is greater than a second refractive index of a medium surrounding the dielectric optical waveguide. The difference in refractive indices is configured to facilitate total internal reflection of the guided light according to one or more guided modes of the light guide <NUM>, for example. In some embodiments, the guided light beam <NUM> may be collimated (i.e., a collimated guided light beam <NUM>).

According to various embodiments, the guided light beam <NUM> is guided by and along a length of the light guide <NUM> (e.g., the general direction as illustrated by the bold arrows <NUM> in <FIG>). Further, the light guide <NUM> is configured to guide the guided light beam <NUM> at a non-zero propagation angle between a first surface <NUM>' (e.g., 'front' surface or side) and a second surface <NUM>" (e.g., 'back' surface or side) of the light guide <NUM> using total internal reflection. In particular, the guided light beam <NUM> propagates by reflecting or 'bouncing' between the first surface <NUM>' and the second surface <NUM>" of the light guide <NUM> at the non-zero propagation angle.

As defined herein, a 'non-zero propagation angle' is an angle relative to a surface (e.g., the first surface <NUM>' or the second surface <NUM>") of the light guide <NUM>. Further, when referring to light (e.g., the guided light beam <NUM>) guided by the light guide <NUM>, the non-zero propagation angle is, by definition herein, both greater than zero and less than a critical angle of total internal reflection within the light guide <NUM>. Moreover, a specific non-zero propagation angle may be chosen (e.g., arbitrarily) for a particular implementation as long as the specific non-zero propagation angle is chosen to be less than the critical angle of total internal reflection within the light guide <NUM>.

In some examples, the light guide <NUM> (e.g., as a plate light guide) may be a slab or plate optical waveguide comprising an extended, substantially planar sheet of optically transparent, dielectric material. The substantially planar sheet of dielectric material is configured to guide the guided light beam <NUM> using total internal reflection. According to various examples, the optically transparent material of the light guide <NUM> may include or be made up of any of a variety of dielectric materials including, but not limited to, one or more of various types of glass (e.g., silica glass, alkali-aluminosilicate glass, borosilicate glass, etc.) and substantially optically transparent plastics or polymers (e.g., poly(methyl methacrylate) or `acrylic glass', polycarbonate, etc.). In some examples, the light guide <NUM> may further include a cladding layer (not illustrated) on at least a portion of a surface (e.g., one or both of the top surface and the bottom surface) of the light guide <NUM>. The cladding layer may be used to further facilitate total internal reflection, according to some embodiments.

Light of the guided light beam <NUM> in the light guide <NUM> is introduced or coupled into the light guide <NUM> at the non-zero propagation angle. One or more of a lens, a mirror or similar reflector (e.g., a tilted collimating reflector), and a prism (not illustrated) may facilitate coupling light into an input end of the light guide <NUM> as the guided light beam <NUM> at the non-zero propagation angle, for example. Once coupled into the light guide <NUM>, the guided light beam <NUM> propagates along the light guide <NUM> in a direction that is generally away from the input end (e.g., illustrated by bold arrows <NUM> pointing along an x-axis in <FIG>).

Further, the guided light beam <NUM> produced by coupling light into the light guide <NUM> may be a collimated light beam, according to various embodiments. Herein, a 'collimated light' or 'collimated light beam' is defined as a beam of light in which rays of the light beam are substantially parallel to one another within the light beam (e.g., the guided light beam <NUM>). Further, rays of light that diverge or are scattered from the collimated light beam are not considered to be part of the collimated light beam, by definition herein. Collimation of the light to produce the collimated guided light beam <NUM> may be provided by a collimator including, but not limited to, the lens or mirror (e.g., tilted collimating reflector, etc.).

As illustrated in <FIG> and <FIG>, the time-multiplexed backlight <NUM> further comprises a time-multiplexed light source <NUM>. The time-multiplexed light source <NUM> is configured to provide light as a light beam to the light guide <NUM>. For example, the time-multiplexed light source <NUM> may be optically coupled to an input end of the light guide <NUM> such that the provided light is communicated to the light guide <NUM> through the input end. Further, the time-multiplexed light source <NUM> is configured to provide the light to the light guide <NUM> as the guided light beam <NUM> (respective light beams <NUM>' and <NUM>") at a first non-zero propagation angle during a first time interval and at a second non-zero propagation angle during a second time interval, wherein the first non-zero propagation angle and the second non-zero propagation angle are different from one another.

Note that while specific reference is made herein to a 'first' non-zero propagation angle and a 'second' non-zero propagation angle corresponding to the first and second time intervals, respectively, in general there may a plurality of different non-zero propagation angles. In particular, the time-multiplexed light source <NUM> may be configured to provide the guided light beam <NUM> at different non-zero propagation angles of the plurality corresponding to respective different time intervals of the plurality of time intervals.

In particular, in <FIG>, the guided light beam <NUM>' provided by the time-multiplexed light source <NUM> during the first time interval is illustrated using a solid extended arrow. Similarly, the guided light beam <NUM>" provided by the time-multiplexed light source <NUM> during the second time interval is depicted by a dashed extended arrow. Further, <FIG> illustrate the first non-zero propagation angle γ' and the second non-zero propagation angle γ" of the guided light beams <NUM>', <NUM>" provided respectively in each of the first and second time intervals by the time-multiplexed light source <NUM>.

In some embodiments, the first and second time intervals may be non-overlapping intervals of time. That is, the respective guided light beam <NUM> may have at any point in time either, but not both, of the first non-zero propagation angle or the second non-zero propagation angle. In other embodiments, the first and second time intervals may overlap such that both propagation angles exist simultaneously within the light guide <NUM> for a period of time corresponding to the overlap in time intervals. Note that <FIG> illustrates the guided light beam <NUM>', <NUM>" having both the first non-zero propagation angle γ' and the second non-zero propagation angle γ" simultaneously incident on the diffraction grating <NUM>, for simplicity of illustration not by way of limitation.

The time-multiplexed light source <NUM> may be realized using any of variety of different configurations, according to various embodiments. For example, the time-multiplexed light source <NUM> may include a plurality of optical emitters having locations or positions configured to provide light at different angles to the light guide <NUM>. Selectively switching the optical emitters of the plurality on and off may provide time multiplexing of the non-zero propagation angle of the guided light beam, according to some embodiments. In other examples, an optical element of the time-multiplexed light source <NUM> such as, but not limited to, a tilted reflector or a collimator (e.g., collimating reflector or collimating lens) may be configured to selectively change an angle of light from an optical emitter as a function of time in order to effect time multiplexing of the non-zero propagation angle. In yet other examples, the time-multiplexed light source <NUM> may include an optical emitter that is selectively movable or that may be selectively tilted to provide the different angles of light at an input of the light guide <NUM>. For example, a mounting structure of the optical emitter may be mechanically shifted or moved relative to the input end of the light guide <NUM>. In another example, the optical emitter may be gimbal-mounted allowing selective tilting of the optical emitter to provide time multiplexing of the non-zero propagation angle of the guided light beam <NUM>.

<FIG> illustrates a time-multiplexed light source <NUM>. As illustrated in <FIG>, the time-multiplexed light source <NUM> comprises a pair of time-multiplexed optical emitters <NUM>', <NUM>". A first optical emitter <NUM>' of the pair is configured to provide the guided light beam <NUM>' at the first non-zero propagation angle and a second optical emitter <NUM>" of the pair is configured to provide the guided light beam <NUM>" at the second non-zero propagation angle. The different propagation angles of the guided light beam <NUM>', <NUM>" may result from a difference in a relative location of the first and second optical emitters <NUM>', <NUM>" relative to a tilted reflector <NUM>, as illustrated for example. The tilted reflector <NUM> may be a tilted collimating reflector, for example. Switching between (i.e., selective turning on and off) the first optical emitter <NUM>' and the second optical emitter <NUM>" as a function of time may be configured to provide the guided light beam <NUM>', <NUM>" during respective first and second time intervals, according to various embodiments. As illustrated in <FIG>, a solid line represents the guided light beam <NUM>' during the first time interval from the first optical emitter <NUM>', while a dashed line represents the guided light beam <NUM>" during the second time interval from the second optical emitter <NUM>", by way of example.

In some embodiments, the optical emitter <NUM> of the time-multiplexed light source <NUM> may include, but is not limited to, a light emitting diode (LED) and a laser. For example, the first and second optical emitters <NUM>', <NUM>" may include an LED of a particular color (e.g., red, green, blue) to provide monochromatic light. In some embodiments, an optical emitter <NUM> of the pair may comprise a plurality of optical emitters configured to provide a plurality of different colors of light. For example, the optical emitter <NUM> may comprise a first LED configured to provide red light, a second LED configured to provide green light, and a third LED configured to provide blue light. According to some embodiments in which different colors of light are provided by the optical emitters <NUM> of the time-multiplexed light source <NUM>, the light guide <NUM> may be further configured to guide light beams representing the different colors of light at different color-specific, non-zero propagation angles (e.g., in addition to the first and second non-zero propagation angles associated with the time multiplexing). For example, when the time-multiplexed light source <NUM> is configured to provide red light, green light and blue light, each of the red light, the green light and the blue light may be provided as a different color, collimated light beam. Further, the light guide <NUM> may be configured to guide each of the different color collimated light beams at a respective different color-specific, non-zero propagation angle. In other embodiments, the time-multiplexed light source <NUM> may be a broadband light source such as, but not limited to, a fluorescent light and a white LED or more generally a polychromatic LED configured to provide broadband light (e.g., white or polychromatic light).

<FIG> illustrates a time-multiplexed light source <NUM>. In particular, as illustrated in <FIG>, the time-multiplexed light source <NUM> comprises the optical emitter <NUM> configured to emit light. The time-multiplexed light source <NUM> of <FIG> further comprises a time-multiplexed collimator <NUM>. The time-multiplexed collimator <NUM> is configured to collimate the emitted light and to provide the collimated emitted light as the guided light beam <NUM>. According to various embodiments, the time-multiplexed collimator <NUM> has a first collimation state configured to provide the collimated emitted light at the first non-zero propagation angle during the first time interval. Further, the time-multiplexed collimator <NUM> has a second collimation state configured to provide the collimated emitted light at the second non-zero propagation angle during the second time interval. The first and second collimation states may be provided by mechanical motion of the time-multiplexed collimator <NUM>, according to some embodiments. For example, the time-multiplexed collimator <NUM> may comprise a tilted collimating reflector (e.g., as illustrated in <FIG>) having a tilt angle that is variable to provide first and second collimation states.

Referring again to <FIG> and <FIG>, the time-multiplexed backlight <NUM> further comprises a diffraction grating <NUM>. The diffraction grating <NUM> is a member of a plurality or array of diffraction gratings <NUM> spaced apart from one another in the direction of propagation (bold arrows <NUM>) of the guided light beam <NUM>, e.g., as illustrated in <FIG>. The diffraction grating <NUM> is configured to diffractively couple out a portion of the guided light beam <NUM> as a coupled-out light beam <NUM>. According to the invention, the coupled-out light beam <NUM> has a different principal angular direction in each of the first time interval and the second time interval. Moreover, the time interval-based different principal angular directions of the coupled-out light beam <NUM> in the first time interval and the second time interval correspond to respective ones of the first non-zero propagation angle and the second non-zero propagation angle of the guided light beam <NUM>, e.g., according to equation (<NUM>) above.

Further, the diffraction gratings <NUM> are optically coupled to the light guide <NUM>. In particular, by definition, the diffraction grating <NUM> is located within an optical field of the guided light beam <NUM> within the light guide <NUM> to enable diffractive coupling out of the guided light beam portion. According to some embodiments, the diffraction grating <NUM> may be located at (e.g., on, in or otherwise adjacent to) a surface of the light guide <NUM>. At the surface, the diffraction grating <NUM> is within an evanescent portion of the optical field of the guided light beam <NUM> enabling diffractive coupling out. For example, the diffraction grating <NUM> may be located on the first surface <NUM>' of the light guide <NUM>, as illustrated in <FIG>. In another example (not illustrated), the diffraction grating <NUM> may be adjacent to the second surface <NUM>" of the light guide <NUM>. In other embodiments (also not illustrated), the diffraction grating <NUM> may be located within the light guide <NUM>; that is, the diffraction grating <NUM> may be located between the first and second surfaces <NUM>', <NUM>" of the light guide) to provide diffractive coupling out of the guided time-multiplexed light beam portion.

Referring to <FIG>, an extended arrow (solid line) depicts or represents the guided light beam <NUM>' propagating in the light guide <NUM> during the first time interval. Another extended arrow (dashed line) in <FIG> depicts the guided light beam <NUM>" propagating in the light guide <NUM> during the second time interval. During the first time interval, the guided light beam <NUM>' is illustrated as having the first non-zero propagation angle γ' and during the second time interval, the guided light beam <NUM>" is illustrated as having the second non-zero propagation angle γ". Further, both of the first and second time interval guided light beams <NUM>', <NUM>" are illustrated incident on the diffraction grating <NUM> from their respective different propagation angles γ', γ". Also illustrated in <FIG> is a first coupled-out light beam <NUM>' (solid line) corresponding to the guided light beam <NUM>' during the first time interval and a second coupled-out light beam <NUM>" (dashed line) corresponding to the guided light beam <NUM>" in the second time interval. The first coupled-out light beam <NUM>' has a different principal angular direction than a principal angular direction of the second coupled-out light beam <NUM>", as illustrated.

According to the invention, an array of an array of multibeam diffraction gratings <NUM> is proivded. The multibeam diffraction grating <NUM> is configured to diffractively couple out the portion of the guided light beam <NUM> as a plurality of coupled-out light beams <NUM> (e.g., as illustrated in <FIG>). Further, the coupled-out light beams <NUM> diffractively coupled out by the multibeam diffraction grating <NUM> have different principal angular directions from one another (as illustrated in <FIG>). In particular, the multibeam diffraction grating <NUM> is configured to provide a first plurality of coupled-out light beams <NUM> having a first set of different principal angular directions during the first time interval. Further, the multibeam diffraction grating <NUM> is configured to provide a second plurality of coupled-out light beams <NUM> having a second set of different principal angular directions during the second time interval.

<FIG> illustrates the first plurality of coupled out light beams <NUM> comprising coupled-out light beams <NUM>' (solid lines) during the first time interval and the second plurality of coupled-out light beams <NUM> comprising second coupled-out light beams <NUM>" (dashed lines) during the second time interval provided by the multibeam diffraction grating <NUM>. Further, as illustrated in <FIG>, the coupled-out light beams <NUM>', <NUM>" of the first and second pluralities are angularly interleaved with one another, by way of example and not limitation. The first and second sets of different principal angular directions are a function, respectively, of the first and second non-zero propagation angles of the corresponding guided light beams <NUM>' and <NUM>", according to various embodiments.

<FIG> illustrates a cross sectional view of a multibeam diffraction grating <NUM>. <FIG> illustrates a perspective view of a multibeam diffraction grating <NUM>. The multibeam diffraction grating <NUM> illustrated in <FIG> may represent the diffraction grating <NUM> of <FIG> and <FIG>, for example. In particular, the illustrated multibeam diffraction grating <NUM> may be optically coupled to a light guide <NUM> with an incident guided time-multiplexed light beam <NUM>, as illustrated. The light guide <NUM> and an incident guided time-multiplexed light beam <NUM> may be substantially similar to the light guide <NUM> and the guided light beam <NUM>, for example.

Further, as illustrated, the multibeam diffraction grating <NUM> may be configured to diffractively couple out a portion of the guided time-multiplexed light beam <NUM> provided by a time-multiplexed light source (e.g., the time-multiplexed light source <NUM>) as a plurality of coupled-out light beams <NUM> directed away from the multibeam diffraction grating <NUM>, as illustrated in <FIG>. The plurality of coupled-out light beams <NUM> may be substantially similar to the plurality of coupled-out light beams <NUM>, described above for example. In particular, a coupled-out light beam <NUM> of the plurality may have principal angular direction that differs from principal angular directions of other coupled-out light beams <NUM> of the plurality.

The multibeam diffraction grating <NUM> illustrated in <FIG> comprises a plurality of diffractive features <NUM> that may represent one or both of grooves and ridges spaced apart from one another, for example. Further, each of the coupled-out light beams <NUM> of the plurality may have a different principal angular direction determined by characteristics of the diffractive features <NUM> of the multibeam diffraction grating <NUM>. Moreover, the different principal angular directions of the coupled-out light beams <NUM> may correspond to different view directions of a multiview display, for example.

In particular, the diffractive features <NUM> of the multibeam diffraction grating <NUM> are configured to provide diffraction. The provided diffraction is responsible for the diffractive coupling of the portion of the guided time-multiplexed light beam <NUM> out of the light guide <NUM>. According to some embodiments, the multibeam diffraction grating <NUM> may be or comprise a chirped diffraction grating. By definition, the 'chirped' diffraction grating is a diffraction grating exhibiting or having a diffraction spacing d of or between the diffractive features (i.e., a diffraction pitch) that varies across an extent or length of the chirped diffraction grating, e.g., as illustrated in <FIG> (and also in <FIG>, for example). Herein, the varying diffraction spacing d is defined and referred to as a 'chirp'. As a result of the chirp, the portion of the guided time-multiplexed light beam that is diffractively coupled out propagates away from the chirped diffraction grating at different diffraction angles corresponding to different points of origin across the chirped diffraction grating of the multibeam diffraction grating <NUM>. By virtue of a predefined chirp, the chirped diffraction grating is responsible for the predetermined and different principal angular directions of the coupled-out light beams <NUM> of the light beam plurality.

In some examples, the chirped diffraction grating of the multibeam diffraction grating <NUM> may have or exhibit a chirp of the diffractive spacing d that varies linearly with distance. As such, the chirped diffraction grating is a 'linearly chirped' diffraction grating, by definition. <FIG> illustrate the multibeam diffraction grating <NUM> as a linearly chirped diffraction grating, by way of example and not limitation. In particular, as illustrated therein, the diffractive features <NUM> are closer together at a first end of the multibeam diffraction grating <NUM> than at a second end. Further, the diffractive spacing d of the illustrated diffractive features <NUM> varies linearly from the first end to the second end, as illustrated therein.

In another example (not illustrated), the chirped diffraction grating of the multibeam diffraction grating <NUM> may exhibit a non-linear chirp of the diffractive spacing. Various non-linear chirps that may be used to realize the multibeam diffraction grating <NUM> include, but are not limited to, an exponential chirp, a logarithmic chirp or a chirp that varies in another, substantially non-uniform or random but still monotonic manner. Non-monotonic chirps such as, but not limited to, a sinusoidal chirp or a triangle or sawtooth chirp, may also be employed. Combinations of any of these types of chirps may also be employed.

The multibeam diffraction grating <NUM> may comprise diffractive features <NUM> that are one or both of curved and chirped. For example, as illustrated in <FIG>, the multibeam diffraction grating <NUM> comprises diffractive features <NUM> that are both curved and chirped (i.e., the multibeam diffraction grating <NUM> in <FIG> is a curved, chirped diffraction grating). Further illustrated in <FIG>, the guided time-multiplexed light beam <NUM> is represented by a bold arrow pointing in an incident direction relative to the multibeam diffraction grating <NUM> at a first end of the multibeam diffraction grating <NUM>. Also illustrated is the plurality of coupled-out light beams <NUM> represented by arrows pointing away from the light-incident side the multibeam diffraction grating <NUM>. The coupled-out light beams <NUM> propagate away from the multibeam diffraction grating <NUM> in a plurality of different predetermined principal angular directions. In particular, the predetermined different principal angular directions of the coupled-out light beams <NUM> are different from one another in both azimuth and elevation, as illustrated therein. According to various examples, both the predefined chirp of the diffractive features <NUM> and the curve of the diffractive features <NUM> may be responsible for the different predetermined principal angular directions of the coupled-out light beams <NUM>.

According to an embodiment, a multiview electronic display as defined by claim <NUM> is provided. The display is configured to emit modulated light beams as pixels of the display. A plurality of pixels, in turn, represents or provides a view of the display. The emitted modulated light beams are preferentially directed toward a viewing direction of the display. Different ones of the modulated, differently directed light beams may correspond to different 'views' associated with the multiview electronic display. The different views may provide a 'glasses free' (e.g., autostereoscopic) representation of information being displayed by the multiview electronic display, for example.

<FIG> illustrates a block diagram of a multiview display <NUM>. The multiview display <NUM> may also be referred to as a multiview electronic display. As illustrated, the multiview display <NUM> is configured to emit light beams <NUM> representing pixels corresponding to different views associated with different view directions of the multiview display <NUM>. Further, a plurality of emitted or 'coupled-out' light beams <NUM> may be emitted during a corresponding plurality of different time intervals. In particular, first emitted or coupled-out light beams <NUM>' may be emitted during a first time interval, and second emitted or coupled-out light beams <NUM>" may be emitted during a second time interval. The emitted or coupled-out light beams <NUM> may be modulated emitted or coupled-out light beams <NUM>, e.g., as described below.

As illustrated in <FIG>, the multiview display <NUM> comprises a time-multiplexed light source <NUM>. The time-multiplexed light source <NUM> is configured to provide a light beam having a first non-zero propagation angle during a first time interval and a second non-zero propagation angle during a second time interval. The first non-zero propagation angle is different the second non-zero propagation angle. The time-multiplexed light source <NUM> may be substantially similar to the time-multiplexed light source <NUM> described above with respect to the time-multiplexed backlight <NUM>.

For example, the time-multiplexed light source <NUM> may comprise a pair of time-multiplexed optical emitters. A first optical emitter of the pair may be configured to provide the light beam <NUM> at the first non-zero propagation angle during the first time interval (depicted as a solid-line arrow) and a second optical emitter of the pair being configured to provide the light beam <NUM> (depicted as a dashed-line arrow) at the second non-zero propagation angle during the second time interval. The time-multiplexed light source <NUM> may be substantially similar to the time-multiplexed light source <NUM> illustrated in above-described <FIG>, for example.

In another example, the time-multiplexed light source <NUM> may comprise a time-multiplexed collimator configured to provide the light beam as a collimated light beam. The time-multiplexed collimator has a first collimation state configured to provide the collimated light beam at the first non-zero propagation angle and a second collimation state configured to provide the collimator light beam at the second non-zero propagation angle. For example, the time-multiplexed light source <NUM> may be substantially similar to the time-multiplexed light source <NUM> illustrated in <FIG>, described above.

The multiview display <NUM> illustrated in <FIG> further comprises a multibeam backlight <NUM>. The multibeam backlight <NUM> is configured to emit a portion of the light beam <NUM> from the time-multiplexed light source <NUM> as a first plurality of coupled-out light beams <NUM> (e.g., solid line arrows) during the first time interval and as a second plurality of coupled-out light beams <NUM> (e.g., dashed line arrows) during the second time interval, respectively. Further, the first and second coupled-out light beam pluralities have corresponding first and second sets of principal angular directions determined respectively by the first and second non-zero propagation angles of the light beam from the time-multiplexed light source <NUM>. The principal angular directions are or correspond to view directions of different views of the multiview display. The coupled-out light beams <NUM> of the first and second pluralities of coupled-out light beams may be angularly interleaved with one another. Similarly, the different views of the multiview display <NUM> in each of the first and second time intervals may be angularly interleaved, in some embodiments.

In some embodiments, the multibeam backlight <NUM> may comprise a plate light guide configured to guide the light beam <NUM> from the time-multiplexed light source <NUM>. The light beam <NUM> is guided at the first non-zero propagation angle during the first time interval and at the second non-zero propagation angle during a second time interval. Further, the time-multiplexed light source <NUM> is optically coupled to an input of the plate light guide. The plate light guide may be substantially similar to the light guide <NUM> of the time-multiplexed backlight <NUM>, described above.

For example, the plate light guide may be a slab optical waveguide that is a planar sheet of dielectric material configured to guide light by total internal reflection. The guided light beam <NUM> may be guided at either the first or second non-zero propagation angles as a beam of light. Thus, the guided light beam <NUM> guided by the plate light guide may be substantially similar to the guided light beam <NUM> of the time-multiplexed backlight <NUM>. For example, the guided light beam <NUM> may be a collimated light beam.

The multibeam backlight <NUM> may further comprise an array of multibeam diffraction gratings optically coupled to the plate light guide. A multibeam diffraction grating of the array may be configured to diffractively couple out a portion of the guided light beam <NUM> as the first plurality of coupled-out light beams <NUM> during the first time interval (e.g., solid line arrows <NUM>) and as the second plurality of coupled-out light beams <NUM> during the second time interval (e.g., dashed line arrows <NUM>). The multibeam diffraction grating of the array may be substantially similar to the multibeam diffraction grating <NUM> of the time-multiplexed backlight <NUM> as well as the multibeam diffraction grating <NUM> (<FIG>), described above. For example, a multibeam diffraction grating of the array of multibeam diffraction gratings may comprise a chirped diffraction grating or a chirped diffraction grating having curved diffractive features.

As e.g. illustrated in <FIG>, the multiview display <NUM> may further comprise a light valve array <NUM>. The light valve array <NUM> is configured to modulate the coupled-out light beams <NUM> of the first and second pluralities to produce respective modulated coupled-out light beams <NUM>', <NUM>". The modulated coupled-out light beams <NUM> represent pixels of the different views of the multiview display <NUM>. The different views are divided into a first set of views corresponding to the first time interval and a second set of views corresponding to the second time interval. Further, the view directions of the first and second sets of views may be angularly interleaved with one another, according to some embodiments. In various examples, different types of light valves in the light valve array <NUM> may be employed including, but not limited to, one or more of liquid crystal (LC) light valves, electrowetting light valves, and electrophoretic light valves. In <FIG>, the arrows associated with modulated coupled-out light beams <NUM> with dashed lines depict modulated coupled-out light beams <NUM>" of the second plurality and the arrows associated with modulated coupled-out light beams <NUM> with solid lines represent the modulated coupled-out light beams <NUM>' of the first plurality.

Some coupled-out light beams <NUM> of the first and second pluralities may be configured to pass through the same light valves (not illustrated) of the light valve array <NUM>. For example, a coupled-out light beam <NUM> of the first plurality and another coupled-out light beam <NUM> of the second plurality may be configured to pass through or 'share' the same light valve, even though the coupled-out light beams <NUM> have different principal angular directions. The light valve may modulate the first plurality coupled-out light beam <NUM> during the first time interval differently from the second plurality coupled-out light beam <NUM>. Such time-interval dependent modulation may facilitate time-multiplexed representation of different views of the multiview display <NUM>, for example. Moreover, light valve sharing between coupled-out light beams <NUM> of the first and second pluralities may increase (e.g., substantially double) a resolution of the multiview display <NUM> for a given light valve resolution.

According to principles described herein, a method of time-multiplexed backlight operation is provided. <FIG> illustrates a flow chart of a method <NUM> of time-multiplexed backlight operation. As is illustrated in <FIG>, the method <NUM> of time-multiplexed backlight operation comprises providing <NUM> a time-multiplexed light beam in a light guide of a backlight where the provided <NUM> light beam is guided. Providing <NUM> a time-multiplexed light beam comprises introducing a first light beam into the light guide using a time-multiplexed light source to propagate at a first non-zero propagation angle during a first time interval; and introducing a second light beam into the light guide using the time-multiplexed light source to propagate at a second non-zero propagation angle during a second time interval. The first and second time intervals are different from one another. Moreover, the first and second non-zero propagation angles are different from one another.

The time-multiplexed light beam may be provided <NUM> using a time-multiplexed light source substantially similar to the time-multiplexed light source <NUM> described above with respect to the time-multiplexed backlight <NUM>, according to some embodiments. For example, the time-multiplexed light source may be implemented using a time-multiplexed optical emitters as illustrated in <FIG> or with a time-multiplexed collimator as illustrated in <FIG>. Further, the light guide and the guided time-multiplexed light beam may be substantially similar to the light guide <NUM> and the guided light beam <NUM>, described above with respect to the time-multiplexed backlight <NUM>. In particular, the light guide may guide the guided light according to total internal reflection (e.g., as a collimated beam of light). Further, the provided <NUM> light beam may be guided at the first and second non-zero propagation angles between a first surface and a second surface of the light guide. The light guide may be a substantially planar dielectric optical waveguide (e.g., a plate light guide).

The method <NUM> of time-multiplexed backlight operation further comprises diffractively coupling out <NUM> a portion of the guided time-multiplexed light beam as a coupled-out light beam using a diffraction grating. In particular, the portion is diffractively coupled out <NUM> during the first time interval and the second time interval using the diffraction grating. The coupled-out light beam is directed away from a surface of the light guide at time interval-based different predetermined principal angular directions. Further, the predetermined principal angular direction in each of the first time interval and the second time interval corresponds to a respective one of the first non-zero propagation angle and the second non-zero propagation angle of the guided time-multiplexed light beam.

Diffractively coupling out <NUM> a portion of the guided time-multiplexed light beam comprises using a diffraction grating, for example, a diffraction grating that is substantially similar to the diffraction grating <NUM> described above with respect to the time-multiplexed backlight <NUM>. Further, the coupled-out light beam may be substantially similar to the coupled-out light beam <NUM> (i.e., light beams <NUM>', <NUM>"), also described above. The diffraction grating may comprise a multibeam diffraction grating. The multibeam diffraction grating may be substantially similar to the multibeam diffraction grating <NUM> described above. In particular, the multibeam diffraction grating may be configured to diffractively couple out <NUM> the portion of the guided time-multiplexed light beam as a plurality of coupled-out light beams. The coupled-out light beams of the coupled-out light beam plurality may have different principal angular directions from one another. Also, the coupled-out light beams in the first time interval generally have different principal angular directions from the coupled-out light beams during the second time interval. Further, the different principal angular directions of the coupled-out light beams may correspond to respective view directions of different views of a multiview electronic display.

As e.g. illustrated in <FIG>, the method <NUM> of time-multiplexed backlight operation further includes modulating <NUM> the coupled-out light beam using a light valve. The modulated <NUM> coupled-out light beam may form a pixel of an electronic display. Where e.g. a multibeam diffraction grating is used, modulating <NUM> the coupled-out light beam may provide modulation of a plurality of differently directed coupled-out light beams using a plurality of light valves. Moreover, the modulated <NUM> differently directed coupled-out light beams may be directed in different ones of various view directions of the multiview electronic display, for example. Further, the different views may comprise a first set of views during the first time interval and a second set of views in the second time interval. In addition, the first set of views may be angularly interleaved with the second set of views.

The light valve used in modulating <NUM> the coupled-out light beam may be substantially similar to a light valve of the light valve array <NUM>. For example, the light valve may include a liquid crystal light valve. In another example, the light valve may be another type of light valve including, but not limited to, one or both of an electrowetting light valve and an electrophoretic light valve, or combinations thereof with liquid crystal light valves or other light valve types.

Claim 1:
A time-multiplexed backlight (<NUM>) comprising:
a light guide (<NUM>) configured to guide a beam of light as a guided light beam (<NUM>);
a time-multiplexed light source (<NUM>) configured to provide to the light guide the light beam at a first non-zero propagation angle during a first time interval and at a second non-zero propagation angle during a second time interval, wherein the first non-zero propagation angle and the second non-zero propagation angle are different from one another, and each of the first and
second non-zero propagation angle being an angle relative to a surface of the light guide which is greater than zero and less than a critical angle of total internal reflection within the light guide; and
further comprising:
an array of multibeam diffraction gratings spaced apart from one another in the direction of propagation of the light beam,
wherein each multibeam grating of the array is a multibeam diffraction grating (<NUM>) configured to diffractively couple out of the light guide a portion of the guided light beam as a plurality of coupled-out light beams (<NUM>), coupled-out light beams of the coupled-out light beam plurality having different principal angular directions from one another, wherein the multibeam diffraction grating is configured to diffractively coupled out a first plurality of coupled-out light beams having a first set (<NUM>') of different principal angular directions in the first time interval and a second plurality of coupled-out light beams having a second set (<NUM>") of different principal angular directions in the second time interval, the first set and the second set being different and corresponding to respective ones of the first non-zero propagation angle and the second non-zero propagation angle of the guided light beam.