HK1250863B - Multibeam diffraction grating-based near-eye display - Google Patents

Description

Near-eye display based on multi-beam diffraction grating

Cross-application of related applications

This application claims priority to U.S. Provisional Patent Application Serial No. 62/242,980, filed October 16, 2015, which is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

N/A

Background Art

Electronic displays are an almost ubiquitous medium for communicating information to users of a variety of devices and products. The most commonly used electronic displays include cathode ray tubes (CRTs), plasma display panels (PDPs), liquid crystal displays (LCDs), electroluminescent displays (ELs), organic light emitting diodes (OLEDs) and active matrix OLED (AMOLED) displays, electrophoretic displays (EPs), and various displays that employ electromechanical or electrofluidic light modulation (e.g., digital micromirror devices, electrowetting displays, etc.). Generally, electronic displays can be classified as 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 CRTs, PDPs, and OLED/AMOLEDs. When considering emitted light, displays that are typically classified as passive are LCDs and EP displays. While passive displays often exhibit attractive performance characteristics including, but not limited to, inherent low power consumption, they may find some limited use in many practical applications due to their lack of ability to emit light.

In addition to being classified as active or passive, electronic displays can also be characterized according to the expected viewing distance of the electronic display. For example, the vast majority of electronic displays are intended to be located at a distance within the normal or "natural" adaptation range of the human eye. In this way, the electronic display can be viewed directly and naturally without the need for additional optics. On the other hand, some displays are specifically designed to be closer to the user's eyes than the normal adaptation range. These electronic displays are generally referred to as "near-eye" displays and typically include some form of optical device for easy viewing. For example, even if the physical electronic display itself may not be directly viewable, the optical device can provide a virtual image of the physical electronic display within the normal adaptation range so that it can be viewed comfortably. Examples of applications that use near-eye displays include, but are not limited to, head-mounted displays (HMDs) and similar wearable displays, as well as some head-up displays. Various virtual reality systems and augmented reality systems often include near-eye displays because in such applications near-eye displays can provide a more immersive experience than conventional displays.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 1 shows a graphical view of the angular components {θ, φ} of a light beam having a particular primary angular direction, according to an example of the principles described herein.

FIG. 2 shows a block diagram of a near-eye display in an example of an embodiment according to the principles described herein.

3 shows a schematic diagram of optics for a near-eye display, according to an example of an embodiment consistent with the principles described herein.

4 shows a cross-sectional view of a near-eye display having an optical system including freeform prisms, according to an example of an embodiment consistent with the principles described herein.

5A shows a cross-sectional view of a multi-beam diffraction grating-based display in an example of an embodiment consistent with the principles described herein.

5B shows a cross-sectional view of a multi-beam diffraction grating-based display in an example according to another embodiment consistent with the principles described herein.

5C shows a perspective view of a multi-beam diffraction grating in an example of an embodiment consistent with the principles described herein.

6 shows a block diagram of a near-eye binocular display system in an example, according to an embodiment consistent with the principles described herein.

7 shows a flow diagram of a method of near-eye display operation in an example of an embodiment consistent with the principles described herein.

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

DETAILED DESCRIPTION

Embodiments and examples according to the principles described herein provide near-eye image displays that provide adaptation support. In particular, according to various embodiments of the principles described herein, the near-eye display employs a multi-view display to generate multiple different views of an image. The multiple different views are projected or mapped to different locations within the eye box where the near-eye displayed image is to be viewed. According to various embodiments, the different views at different locations can support adaptation with respect to the displayed image (i.e., support focusing the eye on an object).

According to various embodiments, a multi-view display includes a multi-beam diffraction grating-based backlight. The multi-beam diffraction grating-based backlight employs multi-beam diffraction coupling of light from a light guide using the multi-beam diffraction grating to generate light beams corresponding to a plurality of different views. In some embodiments, the different views may be substantially similar to the different views generated by a three-dimensional (3D) electronic display (e.g., an autostereoscopic or "glasses-free" 3D electronic display) based on a multi-beam diffraction grating-based backlight. As such, the multi-view display may be referred to as a multi-beam diffraction grating-based display.

According to various embodiments, a multi-beam diffraction grating-based display includes an array of multi-beam diffraction gratings. The multi-beam diffraction grating is used to couple light from a light guide and provide outcoupled beams corresponding to pixels of the multi-beam diffraction grating-based display or equivalent pixels of different views of a displayed image. In particular, according to various embodiments, the outcoupled beams have different primary angular directions from one another. Furthermore, in some embodiments, these differently directed beams generated by the multi-beam diffraction grating can be modulated into and used as pixels corresponding to different views of a displayed image.

Herein, a "lightguide" is defined as a structure that guides light within the structure using total internal reflection. In particular, a lightguide may include a core that is substantially transparent at the operating wavelength of the lightguide. The term "lightguide" generally refers to a dielectric optical waveguide that uses total internal reflection to guide light at the interface between the dielectric material of the lightguide and the material or medium surrounding the lightguide. By definition, the condition for total internal reflection is that the refractive index of the lightguide is greater than the refractive index of the surrounding medium adjacent to the surface of the lightguide material. In some embodiments, the lightguide may include a coating in addition to or instead of the above-mentioned refractive index difference to further promote total internal reflection. For example, the coating may be a reflective coating. The lightguide may be any one of a plurality of lightguides, including but not limited to one or both of a plate or slab guide and a strip guide.

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

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

As used herein, a "diffraction grating," and more specifically, a "multi-beam diffraction grating," is generally defined as a plurality of features (i.e., diffraction features) arranged to provide diffraction of light incident on the diffraction grating. In some examples, the plurality of features may be arranged in a periodic or quasi-periodic manner. For example, the plurality of features of the diffraction grating (e.g., a plurality of grooves in a material surface) may be arranged in a one-dimensional (1-D) array. In other examples, the diffraction grating may be a two-dimensional (2-D) array of features. For example, the diffraction grating may be a 2-D array of bumps on a material surface or holes in a material surface.

As such, and in accordance with the definitions herein, a "diffraction grating" is a structure that provides diffraction of light incident on the diffraction grating. If light is incident on the diffraction grating from a lightguide, the diffraction or diffraction scattering provided can result in and is therefore referred to as "diffraction coupling", because the diffraction grating can couple light out of the lightguide by diffraction. The diffraction grating also redirects or changes the angle of the light by diffraction (i.e. at a diffraction angle). In particular, as a result of diffraction, the light leaving the diffraction grating (i.e. the diffracted light) typically has a propagation direction that is different from the propagation direction of the light incident on the diffraction grating (i.e. the incident light). The change in the propagation direction of light by diffraction is referred to herein as "diffraction redirection". Thus, a diffraction grating can be understood as a structure that includes diffraction features that diffractively redirect light incident on the diffraction grating and, if the light is incident from the lightguide, can also diffractively couple light out of the lightguide.

Further, according to the definitions herein, the features of a diffraction grating are referred to as "diffraction features" and can be one or more of at a surface, in a surface, and on a surface (i.e., where "surface" refers to a boundary between two materials). The surface can be a surface of a plate light guide. The diffraction 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, and these structures can be one or more of at a surface, in a surface, and on a surface. For example, a diffraction grating can include a plurality of parallel grooves in the surface of a material. In another example, a diffraction grating can include a plurality of parallel ridges rising from the surface of a material. The diffraction features (grooves, ridges, holes, 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 a sinusoidal profile, a rectangular profile (e.g., a binary diffraction grating), a triangular profile, and a sawtooth profile (e.g., a blazed grating).

As defined herein, a "multi-beam diffraction grating" is a diffraction grating that produces outcoupled light comprising a plurality of light beams. Further, as defined herein, the plurality of light beams produced by the multi-beam diffraction grating have different principal angular directions from one another. In particular, as defined herein, one of the plurality of light beams has a predetermined principal angular direction that is different from another of the plurality of light beams due to diffraction coupling and diffraction redirection of incident light through the multi-beam diffraction grating. The plurality of light beams may represent a light field. For example, the plurality of light beams may include eight light beams having eight different principal angular directions. For example, the combined eight light beams (i.e., the plurality of light beams) may represent a light field. According to various 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 diffraction features of the multi-beam diffraction grating at the origin of each light beam relative to the propagation direction of light incident on the multi-beam diffraction grating.

In particular, according to the definitions herein, a light beam generated by a multi-beam diffraction grating has a primary angular direction given by angular components {θ, φ}. 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 the plane of the multi-beam diffraction grating), while the azimuth angle φ is an angle in a horizontal plane (e.g., parallel to the plane of the multi-beam diffraction grating). FIG1 illustrates the angular components {θ, φ} of a light beam 10 having a particular primary angular direction, according to an example of the principles described herein. Additionally, according to the definitions herein, the light beam 10 is emitted or emanates from a particular point. That is, by definition, the light beam 10 has a central ray associated with a particular origin within the multi-beam diffraction grating. FIG1 also illustrates the origin O of the light beam. An example of the propagation direction of the incident light is illustrated in FIG1 using a bold arrow 12 pointing to the origin O.

According to various embodiments, properties of a multi-beam diffraction grating and its characteristics (i.e., diffraction characteristics) can be used to control one or both of the angular directionality of the beam with respect to one or more light beams and the wavelength or color selectivity of the multi-beam diffraction grating. Characteristics that can be used to control angular directionality and wavelength selectivity include, but are not limited to, grating length, grating pitch (feature spacing), feature shape, feature size (e.g., groove width or ridge width), and grating orientation. In some examples, the various characteristics used for control can be local characteristics near the origin of the light beam.

Further in accordance with various embodiments described herein, light coupled out of a light guide by a diffraction grating (e.g., a multi-beam diffraction grating) represents pixels of an electronic display. In particular, a light guide having a multi-beam diffraction grating to generate multiple light beams having different primary angular directions can be part of a backlight for, or used in conjunction with, an electronic display, such as, but not limited to, a multi-view display, a "glasses-free" three-dimensional (3D) electronic display (also known as a "holographic" electronic display or an autostereoscopic display). In this manner, the differently directed light beams generated by coupling the guided light from the light guide using the multi-beam diffraction grating can be or represent different views of an image being displayed (e.g., a 3D image). Further, the differently directed light beams have directions corresponding to different viewing angles of the image.

Herein, a "collimator" is defined as substantially any optical device or apparatus 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, a collimator comprising a collimating reflector may have a reflective surface characterized by a parabolic curve or shape. In another example, the collimating reflector may comprise a shaped parabolic reflector. "Shaped parabola" means that the curved reflective surface of the shaped parabolic reflector deviates from a "true" parabolic curve in a manner determined to achieve predetermined reflective characteristics (e.g., collimation). Similarly, a collimating lens may comprise a spherical surface (e.g., a biconvex spherical lens).

In some embodiments, the collimator can be a continuous reflector or a continuous lens (i.e., a reflector or lens having a substantially smooth, continuous surface). In other embodiments, the collimating reflector or collimating lens may include 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, the amount of collimation provided by the collimator can vary from one embodiment to another by a predetermined degree or amount. Further, the collimator can 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 include a shape in one or both of the two orthogonal directions that provide light collimation.

As used herein, a "light source" is defined as a source of light (e.g., a device or apparatus that emits light). For example, a light source can be a light emitting diode (LED) that emits light when activated. A light source can be essentially any light source or 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 a light source can have a color or can include light of a particular wavelength. Thus, a "plurality of different-color light sources" is expressly defined herein as a set or group of light sources, wherein at least one light source generates light of a color that is different from, or of a wavelength that is equivalent to, the color and wavelength of light generated by at least one other light source of the plurality of light sources. Furthermore, a "plurality of different-color light sources" can include more than one light source of the same or substantially similar color, as long as at least two of the plurality of light sources are different-color light sources (i.e., at least two light sources generate light of different colors). Thus, according to the definition herein, a plurality of different-color light sources can include a first light source that generates light of a first color and a second light source that generates light of a second color, where the second color is different from the first color.

As used herein, the term "accommodation" refers to the process of focusing on an object or image element by changing the optical power of the eye. In other words, accommodation is the ability of the eye to focus. An "accommodation range" or equivalently an "accommodation distance" is defined herein as the range of distances from the eye over which focusing can be achieved. Although the accommodation range may vary from person to person, a minimum "normal" accommodation distance of approximately twenty-five (25) centimeters (cm) is assumed herein by way of example and for simplicity. Thus, for an object to be within the so-called "normal accommodation range", the object is generally understood to be located greater than approximately 25 cm from the eye. Further, according to the definition herein, a near-eye display is a display having at least a portion of the display located closer than 25 cm from the eyes of a user of the near-eye display.

Herein, an "eyebox" is defined as an area or volume of space in which an image formed by a display or other optical system (e.g., a lens system) can be viewed. In other words, the eyebox defines the spatial location in which a user's eyes can be placed in order to view the image produced by the display system. In some embodiments, the eyebox can represent a two-dimensional area of space (e.g., an area having length and width but no substantial depth), while in other embodiments, the eyebox can include a three-dimensional area of space (e.g., an area having length, width, and depth). Further, although referred to as a "box," the eyebox may not be limited to a rectangular box. For example, in some embodiments, the eyebox may include a cylindrical area of space.

Further, as used herein, the articles "a" and "an" are intended to have their ordinary meaning in the patent art, i.e., "one or more". For example, "a grating" refers to one or more gratings, and thus, "the grating" herein refers to "(multiple) gratings". Further, any reference herein to "top", "bottom", "upper", "lower", "up", "down", "front", "back", "first", "second", "left", or "right" is not meant to be limiting herein. Here, unless otherwise expressly provided, the term "about" when applied to a value generally means within the tolerance range 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%. In addition, the term "substantially" as used herein refers to most, or almost all, or all, or an amount in the range of about 51% to about 100%. Moreover, the examples herein are merely illustrative and are for discussion purposes only and not for limitation.

In accordance with some embodiments of the principles described herein, a near-eye display is provided. FIG2 shows a block diagram of a near-eye display 100 in an example of an embodiment according to the principles described herein. The near-eye display 100 is configured to provide an image (i.e., a displayed image) at an eye box 102 of the near-eye display 100. In particular, the near-eye display 100 can be configured to provide a plurality of different views 104 of the displayed image. Further, the different views 104 can be provided at different locations within the eye box 102. In accordance with various embodiments, the different views 104 provided at different locations within the eye box 102 are configured to provide a focus depth cue to a user of the near-eye display 100, in accordance with various embodiments. For example, the focus depth cue can enable the user to perceive depth or distance within the displayed image based on the focus depth cue. The focus depth cues provided to the user by the near-eye display 100 can include, but are not limited to, accommodation and retinal blur.

As shown in FIG2 , the near-eye display 100 includes a multi-beam diffraction grating-based display 110. The multi-beam diffraction grating-based display 110 is configured to provide a plurality of different views 104 of a displayed image. According to various embodiments, substantially any number of different views may be provided as the plurality of different views 104. For example, the plurality of different views 104 of the displayed image may include two, three, four, five, six, seven, eight, or more different views. In other examples, the plurality of different views 104 of the displayed image includes a relatively large number of different views, up to and including, but not limited to, sixteen (16), thirty-two (32), sixty-four (64), one hundred twenty-eight (128), or two hundred and fifty-six (256) different views. In some embodiments, the plurality of different views 104 includes at least four different views.

In some embodiments, the image provided or displayed by the near-eye display 100 includes a three-dimensional (3D) image or a portion thereof. For example, the displayed image can be a full 3D or "multi-view" image. In another example, the displayed image can include a 3D image portion as well as a 2D image portion. When the displayed image includes a 3D image, the multiple different views 104 can represent different perspectives of the 3D image (i.e., "3D views"). According to the principles described herein, for example, the different views (e.g., 3D views) can enhance the user's perception of depth within the displayed image through one or both of retinal blurring and accommodation. In some examples (e.g., in the near-eye binocular display system described below), accommodation can mitigate the effects of the so-called accommodation-convergence discrepancy often encountered in 3D images and 3D displays.

The near-eye display 100 shown in FIG2 further includes an optical system 120. According to various embodiments, the optical system 120 is configured to relay a displayed image to the eyebox 102 of the near-eye display 100. In particular, according to various embodiments, the optical system 120 is configured to relay a plurality of different views 104 of the displayed image to a corresponding plurality of different locations within the eyebox 102. According to various embodiments, relaying the different views 104 to different locations 102 within the eyebox is configured to provide a focal depth cue to a user of the near-eye display 100. For example, a first view of the displayed image may be relayed by the optical system 120 to a first location, while a second view may be relayed by the optical system 120 to a second location within the eyebox 102 that is separate from the first location. For example, the first and second locations may be laterally separated from each other. For example, the separation of the first and second views at the corresponding first and second locations may enable a user to adapt differently within the displayed image to the two views of the displayed image.

According to some embodiments, the total angular range of the plurality of different views 104 provided by the multi-beam diffraction grating-based display 110 at the input aperture of the optical system 120 is configured to correspond to the size of the input aperture. In particular, the angles subtended by the combination of the plurality of different views 104 are configured such that a majority of any different view 104 is not outside or beyond the input aperture. In other words, according to some embodiments, substantially all output beams of the multi-beam diffraction grating-based display 110 associated with the different views 104 are configured to be received within the input aperture of the optical system 120. In some examples, the total angular range (i.e., the subtended angles) of the plurality of different views 104 can be configured to substantially correspond to an input aperture size of one or both of a predetermined distance between the multi-beam diffraction grating-based display 110 and the optical system input aperture and a predetermined angular spread of the different views 104 provided by the multi-beam diffraction grating-based display 110.

According to some embodiments, optical system 120 includes a magnifier. In some embodiments, the magnifier includes a simple magnifier. The simple magnifier is configured to provide a virtual image of the displayed image located at a distance from eye box 102 corresponding to the normal accommodation range of the user's eyes. Further, according to various embodiments, the virtual image provided by the simple magnifier includes multiple different views 104 of the displayed image. In other embodiments, the magnifier may be a composite magnifier (e.g., multiple lenses configured to provide magnification).

As used herein, a "simple magnifier" is defined as a lens or similar optical device that forms a magnified or enlarged virtual image of a smaller object or image (i.e., the simple magnifier provides angular magnification). The virtual image formed by the simple magnifier can be formed at the output of the simple magnifier or equivalently located at the output aperture or iris of the simple magnifier (e.g., at the eye box 102). Further, according to the definition herein, the simple magnifier can form an enlarged virtual image at a visible or virtual distance greater than the actual distance of the object. In this way, a simple magnifier can be used to provide a user or "viewer" with the ability to focus on objects located less than the normal accommodation range or distance from the user's eyes. Here, according to some embodiments, "normal accommodation" is generally achievable and is therefore defined herein as a distance greater than approximately twenty-five (25) centimeters (cm) from the user's eyes. As a result, even if the multi-beam diffraction grating-based display 110 providing the displayed image is closer than the normal accommodation distance of the user's eyes (i.e., or equivalently, the eye box 102 of the near-eye display 100) (i.e., closer than about 25 centimeters), a simple magnification of the optical system 120 can allow the user to comfortably focus on viewing multiple different views 104 of the displayed image (i.e., the "object").

FIG3 illustrates a schematic diagram of the optics of a near-eye display 100 according to an example of an embodiment consistent with the principles described herein. As shown, the optical system 120 includes a simple magnifier 122 having a focal length f. By way of example and not limitation, the simple magnifier 122 in FIG3 is illustrated as a biconvex lens. The simple magnifier 122 can be positioned at a distance from the eyebox 102 corresponding to the focal length f of the simple magnifier 122 (e.g., as shown in FIG3 ). Further, the simple magnifier 122 is positioned between the multi-beam diffraction grating-based display 110 and the eyebox 102. The simple magnifier 122 is configured to provide a virtual image 106 (i.e., as seen at the eyebox 102 when viewed through the simple magnifier 122) of a displayed image formed from a plurality of different views (e.g., the different views 104 in FIG2 ) from the multi-beam diffraction grating-based display 110. Due to the magnification provided by the simple magnifier 122, the virtual image 106 is located (or at least appears to be located) at a greater distance from the eye box 102 than from the actual or physical image (i.e., the displayed image) produced by the multi-beam diffraction grating-based display 110. In particular, according to some embodiments, the virtual image 106 may be located within the normal accommodation range or distance d _a of the human eye when viewed from the eye box 102, while the multi-beam diffraction grating-based display 110 (or, equivalently, the image produced or displayed by the multi-beam diffraction grating-based display 110) may be closer to the eye box 102 than the normal accommodation range. Thus, for example, the simple magnifier 122 may facilitate comfortable viewing of the multi-beam diffraction grating-based display 110 (or, equivalently, the output of the multi-beam diffraction grating-based display 110 or the virtual image 106) at the eye box 102.

As further shown in FIG3 , solid and dashed lines are rays 108 (rays of light) emanating from a multi-beam diffraction grating-based display 110, as further described below. The solid lines depict actual rays 108 associated with different views 104 of a displayed image provided by the multi-beam diffraction grating-based display 110, while the dashed lines depict ray projections corresponding to virtual images 106. The rays 108 shown in FIG3 may, for example, correspond to various outcoupled beams (i.e., rays of light) generated by the multi-beam diffraction grating-based display 110, as described below. Further, the rays 108 depicted as converging at different points within the eye box 102 may represent different views of a displayed image provided by the multi-beam diffraction grating-based display 110 after the different views have been relayed to different locations within the eye box 102.

According to some embodiments, both the multi-beam diffraction grating-based display 110 and the optical system 120 are located within a portion of the user's field of view (FOV) and substantially block that portion. In these embodiments, the near-eye display 100 can be a virtual reality display. In particular, the near-eye display 100 can be configured to replace or at least substantially replace the view of the physical environment (i.e., the real-world view) with the near-eye display image within the blocked FOV portion. That is, the near-eye display image can substantially replace the view of the physical environment with the blocked FOV portion. According to various embodiments, the blocked FOV portion can include some or all of the user's FOV. By replacing the view of the physical environment, the user is provided with a virtual reality view provided by the near-eye display image (and the associated multiple different views) rather than a view of the physical environment.

A "view of the physical environment" or "physical environment view" is defined herein as the view a user would have in the absence of the near-eye display 100. Equivalently, the physical environment is any object beyond the near-eye display 100 that may be visible to the user, and a "view" of the physical environment is any object within the user's FOV, excluding any influence that the near-eye display 100 may have on the user's view, as defined herein.

In other embodiments, the multi-beam diffraction grating-based display 110 is located outside the user's FOV, while the optical system 120, or a portion thereof, is located within the FOV. In these embodiments, the near-eye display 100 can be an augmented reality display. In particular, the near-eye display 100 can be configured to use the near-eye display image (and the plurality of associated different views 104) to augment the view of the physical environment. Furthermore, as an augmented reality display, the near-eye display 100 is configured to provide the user with a superimposed or combined view of the near-eye display image and a view of the physical environment beyond the near-eye display 100.

In some embodiments, the optical system 120 of the near-eye display 100 configured as an augmented reality display includes a freeform prism. The freeform prism is configured to relay a displayed image comprising a plurality of different views 104 from a multi-beam diffraction grating-based display 110 to an eyebox 102 for viewing by a user. Furthermore, the freeform prism is configured to relay displayed images from a multi-beam diffraction grating-based display 110 that is located beyond or outside the user's FOV. According to various embodiments, the freeform prism relays the displayed image using total internal reflection between two surfaces (e.g., a front surface and a back surface) of the freeform prism. In some embodiments, the freeform prism is or can function as a simple magnifier (e.g., a simple magnifier 122).

In some embodiments, the optical system 120 configured as an augmented reality display may further include a freeform compensating lens. The freeform compensating lens may also be referred to as a freeform corrector. In particular, the freeform compensating lens is configured to compensate for or correct the effects of the freeform prism on light passing through the optical system 120 from the physical environment beyond the optical system 120 to the eye box 102. That is, according to various embodiments, the freeform compensating lens enables the user to clearly view the physical environment (i.e., within the user's FOV) without the substantial distortion that may be introduced by the freeform prism.

FIG4 shows a cross-sectional view of a near-eye display 100 having an optical system 120 including a freeform prism 124, according to an example of an embodiment consistent with the principles described herein. As shown in FIG4 , the freeform prism 124 of the optical system 120 is positioned between the multi-beam diffraction grating-based display 110 and the eyebox 102 (i.e., exit pupil) of the near-eye display 100. Light representing a displayed image comprising multiple different views 104 provided by the multi-beam diffraction grating-based display 110 is relayed from its input aperture to the eyebox 102 by the freeform prism 124. Light from the multi-beam diffraction grating-based display 110 is shown as ray 108 in FIG4 . According to various embodiments, the relaying of ray 108 from the input end of the freeform prism 124 to its output end can be provided by total internal reflection within the freeform prism 124.

FIG4 also illustrates the user's field of view (FOV). Virtual image 106 is within the FOV to provide an overlay of virtual image 106 with a view of the physical environment within the FOV. Furthermore, as shown in FIG4 , multi-beam diffraction grating-based display 110 is outside the FOV. Thus, for example, FIG4 may illustrate an augmented reality display embodiment of near-eye display 100.

The optical system 120 shown in FIG4 further includes a freeform compensating lens 126. According to various embodiments, the freeform compensating lens 126 can be provided in the optical path between the physical environment (e.g., to be viewed by a user) and the eyebox 102. In particular, as shown, the freeform compensating lens 126 is located adjacent to the freeform prism 124 and between the physical environment and the freeform prism 124. The freeform compensating lens 126 is configured to correct for the effects of the freeform prism 124 so that light rays (not shown) pass from objects in the physical environment to the eyebox 102 according to a substantially straight path (i.e., the light rays are substantially undistorted). In some embodiments (as shown), a partial reflector or partially reflective surface 128 can be provided between the freeform compensating lens 126 and the freeform prism 124. The partially reflective surface 128 is configured to reflect light incident on the partially reflective surface 128 from within the freeform prism 124, and also to allow light from the physical environment to pass through the partially reflective surface 128.

Referring again to FIG2 , in some embodiments, the multi-beam diffraction grating-based display 110 includes a plate light guide configured to guide a collimated light beam at a non-zero propagation angle. In some embodiments, the multi-beam diffraction grating-based display 110 further includes an array of multi-beam diffraction gratings at or near a surface of the plate light guide. According to various embodiments, the multi-beam diffraction gratings of the array are configured to diffractively outcouple portions of the guided collimated light beam as a plurality of outcoupled light beams having different primary angular directions corresponding to viewing directions of the plurality of different views 104 of the displayed image.

Figure 5A shows a cross-sectional view of a multi-beam diffraction grating-based display 110 in an example of an embodiment consistent with the principles described herein. Figure 5B shows a cross-sectional view of a multi-beam diffraction grating-based display 110 in an example of another embodiment consistent with the principles described herein. According to various embodiments, the multi-beam diffraction grating-based display 110 shown in Figures 5A-5B is configured to generate "directional" light, i.e., light that includes beams or rays of light having different primary angular directions.

For example, as shown in Figures 5A-5B, a multi-beam diffraction grating-based display 110 is configured to provide or generate multiple light beams (e.g., as a light field), which are shown as arrows that emanate from the multi-beam diffraction grating-based display 110 and exit the multi-beam diffraction grating-based display 110 at different predetermined primary angular directions. Subsequently, as described below, the multiple light beams can be modulated to facilitate the display of information, i.e., different views of an image (e.g., a displayed image). In some embodiments, the light beams having different predetermined primary angular directions form multiple 3D views of a 3D image displayed by the multi-beam diffraction grating-based display 110. Further, according to some embodiments, the multi-beam diffraction grating-based display 110 can be a so-called "glasses-free" 3D electronic display (e.g., a multi-view, "holographic," or autostereoscopic display). In particular, with respect to the near-eye display 100, the different predetermined primary angular directions form multiple different views of the displayed image (e.g., the different views 104 shown in Figure 2). Thus, the modulated light beams may be the rays or lightrays 108 mentioned above.

As shown in Figures 5A and 5B, a multi-beam diffraction grating-based display 110 includes a plate light guide 112. The plate light guide 112 is configured to guide light as guided light beams (shown as extended arrows propagating within the plate light guide 112, as further described below). For example, the plate light guide 112 may include a dielectric material configured as an optical waveguide. The dielectric material may have a first refractive index greater than a second refractive index 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 according to one or more guided modes of the plate light guide 112.

According to various embodiments, light is guided through and along the length of the plate light guide 112. Further, the plate light guide 112 is configured to guide the light as a guided light beam at a non-zero propagation angle. For example, the guided light beam can be guided at a non-zero propagation angle within the plate light guide 112 using total internal reflection. In particular, the guided light beam propagates by reflecting or "bouncing back and forth" between the top and bottom surfaces of the plate light guide 112 at a non-zero propagation angle (e.g., as shown by the extended, angled arrows representing light rays of the guided light beam).

As defined herein, a "non-zero propagation angle" is an angle relative to a surface (e.g., a top surface or a bottom surface) of the plate light guide 112. 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 plate light guide. For example, the non-zero propagation angle of the guided light beam can be between about ten (10) degrees and about fifty (50) degrees, or in some examples, between about twenty (20) degrees and about forty (40) degrees, or between about twenty-five (25) degrees and about thirty-five (35) degrees. For example, the non-zero propagation angle can be about thirty (30) degrees. In other examples, the non-zero propagation angle can be about 20 degrees, or about 25 degrees, or about 35 degrees.

Light directed as a guided light beam in the plate light guide 112 may be introduced or coupled into the plate light guide 112 at a non-zero propagation angle (e.g., approximately 30-35 degrees). For example, one or more of a lens, a mirror, or similar reflector (e.g., a tilted collimating reflector), and a prism (not shown) may facilitate coupling the light into the input end of the plate light guide 112 as a light beam at a non-zero propagation angle. Once coupled into the plate light guide 112, the guided light beam propagates along the plate light guide 112 in a direction generally away from the input end (e.g., as shown by the bold arrow pointing along the x-axis in Figures 5A-5B).

Further, according to various embodiments, the guided light beam produced by coupling light into the plate light guide 112 can be a collimated light beam. In particular, a "collimated light beam" refers to a light beam in which light rays in the guided light beam are substantially parallel to other light rays in the guided light beam. Light rays that diverge or scatter from the collimated beam of the guided light beam are not considered to be part of the collimated light beam according to the definition herein. The collimation of the light to produce the collimated guided light beam can be provided by a collimator including, but not limited to, the lenses or reflectors (e.g., tilted collimating reflectors, etc.) described above for coupling light into the plate light guide 112.

In some embodiments, the plate light guide 112 can be a plate or slab light waveguide comprising an extended, substantially flat sheet of optically transparent dielectric material. The substantially flat sheet of optically transparent dielectric material is configured to guide the guided light beam using total internal reflection. According to various embodiments, the optically transparent material of the plate light guide 112 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., 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 embodiments, the plate light guide 112 can further include a cladding (not shown) located on at least a portion of a surface (e.g., one or both of the top and bottom surfaces) of the plate light guide 112. According to some examples, the cladding can be used to further promote total internal reflection.

In Figures 5A and 5B, the multi-beam diffraction grating-based display 110 also includes an array of multi-beam diffraction gratings 114. As shown in Figures 5A-5B, the multi-beam diffraction gratings 114 are located on a surface (e.g., the top or front surface) of the plate light guide 112. In other examples (not shown), one or more of the multi-beam diffraction gratings 114 can be located within the plate light guide 112. In other examples (not shown), one or more of the multi-beam diffraction gratings 114 can be located on or on the bottom or back side of the plate light guide 112 (i.e., the surface opposite the surface where the multi-beam diffraction gratings 114 are shown). In combination, the plate light guide 112 and the array of multi-beam diffraction gratings 114 provide or serve as a multi-beam grating-based backlight for the multi-beam diffraction grating-based display 110.

According to various embodiments, the array of multi-beam diffraction gratings 114 is configured to scatter or diffractively couple out portions of the guided light beams as multiple light beams having different principal angular directions corresponding to different views of the display 110 based on the multi-beam diffraction grating. For example, the portion of the guided light beams can be diffractively coupled out by the multi-beam diffraction grating 114 through a plate light guide surface (e.g., through a top surface of the plate light guide 112). Further, the multi-beam diffraction grating 114 is configured to diffractively couple out portions of the guided light beams as outcoupled light beams and diffractively redirect the outcoupled light beams away from the plate light guide surface. As described above, each of the multiple outcoupled light beams can have a different predetermined principal angular direction determined by the characteristics of the diffraction signature of the multi-beam diffraction grating 114.

In particular, the array of multi-beam diffraction gratings 114 includes a plurality of diffraction features that provide diffraction. The diffraction provided is responsible for diffractively coupling a portion of the guided light beams out of the plate light guide 112. For example, the multi-beam diffraction grating 114 may include one or both of grooves in the surface of the plate light guide 112 and ridges protruding from the surface of the plate light guide as diffraction features. The grooves and ridges may be arranged parallel to each other and, at least at some points along the diffraction features, perpendicular to the propagation direction of the guided light beams to be coupled out by the multi-beam diffraction grating 114.

In some examples, grooves or ridges can be etched, milled, or molded into the surface of the plate light guide. Thus, the material of the multi-beam diffraction grating 114 can comprise the material of the plate light guide 112. As shown in FIG5A , for example, the multi-beam diffraction grating 114 comprises substantially parallel grooves extending through the surface of the plate light guide 112. In FIG5B , the multi-beam diffraction grating 114 comprises substantially parallel ridges protruding from the surface of the plate light guide 112. In other examples (not shown), the multi-beam diffraction grating 114 can comprise a film or layer applied to or affixed to the surface of the plate light guide.

According to some embodiments, the multi-beam diffraction grating 114 may be or include a chirped diffraction grating. By definition, a "chirped" diffraction grating is a diffraction grating that exhibits or has a diffraction spacing that varies over the range or length of the chirped diffraction grating (i.e., the diffraction pitch), as shown, for example, in Figures 5A-5B. Herein, the varying diffraction spacing is defined and referred to as "chirp." As a result of the chirp, the partially guided light beams of the plate light guide 112 that are diffractively outcoupled exit the chirped diffraction grating or are emitted from the chirped diffraction grating as outcoupled beams at different diffraction angles corresponding to different origins of the chirped diffraction grating across the multi-beam diffraction grating 114. Due to the predefined chirp, the chirped diffraction grating is responsible for the predetermined and different primary angular directions of the outcoupled beams of the multiple light beams.

In some examples, the chirped diffraction grating of the multi-beam diffraction grating 114 can have or exhibit a chirp with a diffraction spacing that varies linearly with distance. Thus, by definition, a chirped diffraction grating is a "linearly chirped" diffraction grating. By way of example and not limitation, Figures 5A-5B illustrate the multi-beam diffraction grating 114 as a linearly chirped diffraction grating. In particular, as shown, the diffraction features are closer together at a first end of the multi-beam diffraction grating 114 than at a second end. Further, the diffraction spacing of the illustrated diffraction features varies linearly from the first end to the second end (i.e., in the direction of the bold arrows), as shown.

In another example (not shown), the chirped diffraction grating of the multi-beam diffraction grating 114 can exhibit a nonlinear chirp of the diffraction spacing. Various nonlinear chirps that can be used to implement the multi-beam diffraction grating 114 include, but are not limited to, exponential chirp, logarithmic chirp, or chirp that varies in another substantially non-uniform or random but still monotonic manner. Non-monotonic chirps can also be used, such as, but not limited to, sinusoidal chirp or triangular or sawtooth chirp. Combinations of any of these types of chirps can also be used.

According to some embodiments, the multi-beam diffraction grating 114 can include one or both of curved and chirped diffraction features. FIG5C shows a perspective view of the multi-beam diffraction grating 114 in an example according to an embodiment consistent with the principles described herein. As shown in FIG5C , the multi-beam diffraction grating 114 is located in, at, or on a surface of the plate light guide 112. Further, the multi-beam diffraction grating 114 shown includes both curved and chirped diffraction features (i.e., the multi-beam diffraction grating 114 in FIG5C is a curved, chirped diffraction grating).

As shown in FIG5C , the guided light beams have incident directions relative to multi-beam diffraction grating 114, indicated by bold arrows at a first end of multi-beam diffraction grating 114. Also shown are multiple outcoupled or emitted light beams, indicated by arrows pointing away from multi-beam diffraction grating 114 at the surface of plate light guide 112. The light beams are emitted in a plurality of predetermined different principal angular directions. In particular, as shown, the predetermined different principal angular directions of the emitted light beams differ from one another in azimuth and elevation. According to various examples, both the predefined chirp of the diffraction signature and the curve of the diffraction signature are responsible for the predetermined different principal angular directions of the emitted light beams.

In particular, the "underlying diffraction grating" of the multi-beam diffraction grating 114 associated with the curved diffraction feature has different azimuthal orientation angles at different points along the curve of the diffraction feature. The "underlying diffraction grating" refers to a diffraction grating comprising multiple uncurved diffraction gratings that, when superimposed, produce the curved diffraction feature of the multi-beam diffraction grating 114. At a given point along the curved diffraction feature, the curve has a particular azimuthal orientation angle that is generally different from the azimuthal orientation angle at another point along the curved diffraction feature. Further, the particular azimuthal orientation angle results in a corresponding azimuthal angle component in the primary angular direction of the light beam emitted from the given point. In some examples, the curve of the diffraction feature (e.g., groove, ridge, etc.) can represent a portion of a circle. The circle can be coplanar with the lightguide surface. In other examples, the curve can represent a portion of an ellipse or another curved shape, for example, coplanar with the lightguide surface.

According to some embodiments, the multi-beam diffraction grating-based display 110 further includes an array of light valves, or light valve array 116. The light valve array 116 can be configured to selectively modulate the outcoupled light beams into a plurality of pixels corresponding to pixels of different views of the displayed image (i.e., modulate the pixels). For example, referring to Figures 5A-5B, the light valve array 116 is shown adjacent to the panel light guide surface. According to various embodiments, the light valve array 116 is configured to modulate differently directed light beams corresponding to different views of the displayed image (i.e., a plurality of light beams having different predetermined primary angular directions from the multi-beam diffraction grating 114). In particular, light beams of the plurality of light beams pass through and are modulated by a single light valve of the light valve array 116. According to various embodiments, the modulated, differently directed light beams (i.e., light rays 108) can represent pixels of different views of the displayed image based on the different directions of the outcoupled light beams. In various embodiments, different types of light valves can be employed in the light valve array 116, including but not limited to one or more of liquid crystal light valves, electrophoretic light valves, and light valves based on electrowetting.

According to some embodiments (e.g., as shown in Figures 5A-5B), the multi-beam diffraction grating-based display 110 may further include a light source 118. The light source 118 is configured to provide a collimated light beam to the plate light guide 112. In particular, the light source 118 may be located near the entrance surface or end (input end) of the plate light guide 112. In various embodiments, the light source 118 may include substantially any light source (e.g., a light emitter), including but not limited to one or more light emitting diodes (LEDs) or lasers (e.g., laser diodes). In some embodiments, the light source 118 may include a light emitter configured to generate substantially monochromatic light having a narrowband spectrum represented by a specific color. In particular, the color of the monochromatic light may be a primary color of a specific color space or color model (e.g., a red-green-blue (RGB) color model). In some embodiments, the light source 118 may include a plurality of different light emitters configured to provide light of different colors. The different light emitters may be configured to provide light having different, color-specific, non-zero propagation angles of the collimated light beam corresponding to each of the different colors of light.

In some embodiments, the light source 118 may further include a collimator (shown as a shaded area in Figures 5A-5B). The collimator can be configured to receive substantially uncollimated light from one or more light emitters of the light source 118. The collimator is further configured to convert the substantially uncollimated light into a collimated light beam. In particular, according to some embodiments, the collimator can provide a collimated light beam that is collimated in two substantially orthogonal directions. In addition, when light emitters of different colors are employed, the collimator can be configured to provide collimated light beams with different, color-specific, non-zero propagation angles. The collimator is further configured to communicate the collimated light beam to the plate light guide 112 to propagate as a collimated, guided light beam with a non-zero propagation angle as described above.

In accordance with some embodiments of the principles described herein, a near-eye binocular display system is provided. FIG6 shows a block diagram of a near-eye binocular display system 200 in an example according to an embodiment consistent with the principles described herein. The near-eye binocular display system 200 is configured to provide a pair of stereo images 202 of a three-dimensional (3D) scene and relay the pair of stereo images 202 to a corresponding pair of eye boxes 204 for viewing by a user. In accordance with various embodiments, the eye boxes 204 in the pair are laterally displaced from each other to correspond to the position of the user's eyes. In particular, the user can comfortably and naturally view the pair of stereo images 202 at the pair of laterally displaced eye boxes 204. Further, in accordance with some embodiments, the pair of stereo images 202 can both provide a 3D experience and solve various convergence-accommodation problems often associated with near-eye displays.

As shown in FIG6 , a near-eye binocular display system 200 includes a pair of multi-beam diffraction grating-based displays 210. According to various embodiments, each multi-beam diffraction grating-based display 210 is configured to provide a different image 202 from the image 202 provided by the other multi-beam diffraction grating-based display 210 in the pair. The different images 202 of the pair are stereoscopic images 202 of a 3D scene. In some embodiments, one or both of the multi-beam diffraction grating-based displays 210 in the pair can be substantially similar to the multi-beam diffraction grating-based display 110 described above with respect to the near-eye display 100.

In particular, as shown, each multi-beam diffraction grating-based display 210 includes a plate light guide 212 and an array of multi-beam diffraction gratings 214, or simply "multi-beam gratings 214" (e.g., as shown). In some embodiments, the plate light guide 212 can be substantially similar to the plate light guide 112, and the array of multi-beam diffraction gratings 214 can be substantially similar to the array of multi-beam diffraction gratings 114 of the multi-beam diffraction grating-based display 110. In particular, the multi-beam diffraction gratings 214 can be located on or near a surface of the plate light guide 212. Further, in some embodiments, the array of multi-beam diffraction gratings 214 can be configured to diffractively couple guided light from the plate light guide 212 as a plurality of outcoupled beams. In some embodiments, the multi-beam diffraction gratings 214 include chirped diffraction gratings having curved diffraction features. In some embodiments, the chirp of the chirped diffraction grating is a linear chirp.

According to some embodiments, each provided image 202 of the stereoscopic image pair provided by the pair of multi-beam diffraction grating-based displays 210 includes a plurality of different views of a 3D scene. For example, the different views may represent different perspectives of the 3D scene. Further, in various embodiments, the plurality of outcoupled light beams may have different primary angular directions corresponding to 3D view directions of different views of the plurality of different views (i.e., 3D perspective views) of the 3D scene.

The near-eye binocular display system 200 shown in FIG6 further includes a binocular optical system 220. The binocular optical system 220 is configured to respectively relay different images 202 of the stereoscopic image pair provided by the pair of multi-beam diffraction grating-based displays 210 to corresponding pairs of eye boxes 204. According to various embodiments, the eye boxes 204 are laterally displaced relative to each other. As described above, for example, the lateral displacement of the eye boxes 204 can facilitate viewing for the user. The vertical dashed lines between the eye boxes 204 shown in FIG6 depict the lateral displacement.

In some embodiments, the binocular optical system 220 can be substantially similar to the optical system 120 of the near-eye display 100, albeit arranged in a binocular configuration. In particular, the binocular optical system 220 can be configured to relay a plurality of different views (e.g., 3D views) to a corresponding plurality of different locations within the eye box 204. Additionally, the different locations within the eye box 204 are configured to provide depth focus cues to a user of the near-eye binocular display system 200. In particular, according to various embodiments, the depth focus cues can correspond to binocular disparity between the provided images 202 of the stereoscopic image pair.

Further, according to some embodiments, the binocular optical system 220 can include a first free-form prism and a second free-form prism (not shown in FIG6 ). The first free-form prism can be configured to relay the image 202 provided by the first multi-beam diffraction grating-based display 210 of the multi-beam diffraction grating-based display pair to the first eyebox 204 of the eyebox pair. Similarly, the second free-form prism can be configured to relay the image 202 provided by the second multi-beam diffraction grating-based display 210 of the multi-beam diffraction grating-based display pair to the second eyebox 204 of the eyebox pair. In other embodiments (not shown), the binocular optical system 220 can include a pair of magnifying glasses (e.g., a pair of simple magnifying glasses substantially similar to the simple magnifying glasses 122 described above).

In some embodiments, the near-eye binocular display system 200 is configured as a virtual reality display system. Specifically, the different images 202 provided by the stereo pair can be configured to replace the binocular view of the physical environment, at least within the eye box 204. In other embodiments, the near-eye binocular display system 200 shown in FIG. 6 can be configured as an augmented reality display system. For example, when configured as an augmented reality display system, the different images 202 provided by the stereo pair can augment, but generally do not replace, the view of the physical environment within the eye box 204. In other words, the near-eye binocular display system 200 configured as an augmented reality display system provides the user with an optical overlay of the stereo image pair and the view of the physical environment. Furthermore, when configured as an augmented reality display system, the binocular optical system 220 can further include a pair of free-form compensating lenses. According to various embodiments, the free-form compensating lenses can be configured to provide an image of the physical environment to the eye box 204 pair.

According to some embodiments, the multi-beam diffraction grating-based display 210 may further include an array of light valves 216 and a light source 218. In some embodiments, the array of light valves 216 may be substantially similar to the light valve array 116 described above with respect to the multi-beam diffraction grating-based display 110 of the near-eye display 100. For example, the array of light valves 216 may be located near the surface of the plate light guide 212. According to various embodiments, the light valves 216 are configured to selectively modulate the outcoupled light beams from the multi-beam diffraction grating 214 into a plurality of pixels or modulated light beams corresponding to pixels of the provided image 202 of the stereoscopic image pair. In some embodiments, the light valves 216 of the array include liquid crystal light valves. In other embodiments, for example, the light valves 216 of the light valve array may include another type of light valve, including but not limited to an electrowetting light valve, an electrophoretic light valve, a combination thereof, or a combination of a liquid crystal light valve and another type of light valve.

According to some embodiments, the multi-beam diffraction grating-based display 210 may further include a light source 218. The light source 218 is configured to provide light to the plate light guide 212. In some embodiments, the light source 218 may include an optical collimator configured to collimate the light provided by the light source 218. According to various embodiments, the plate light guide 212 of the multi-beam diffraction grating-based display 210 may be configured to guide the collimated light as a collimated light beam at a non-zero propagation angle. According to some embodiments, the light source 218 may be substantially similar to the light source 118 of the multi-beam diffraction grating-based display 110 described above with respect to the near-eye display 100.

In some embodiments, the light source 218 may include a plurality of different light emitting diodes (LEDs) configured to provide light of different colors (referred to as "different color LEDs" for simplicity of discussion). In some embodiments, the different color LEDs may be offset from one another (e.g., laterally offset) or otherwise configured in conjunction with a collimator to provide different, color-specific, non-zero propagation angles of the collimated light beam within the plate light guide 212. Further, the different, color-specific, non-zero propagation angles may correspond to each of the different colors of light provided by the light source 218.

In some embodiments (not shown), the different colors of light may include red, green, and blue of a red-green-blue (RGB) color model. Further, the plate light guide 212 may be configured to direct the different colors as collimated light beams at different, color-dependent, non-zero propagation angles within the plate light guide 212. For example, according to some embodiments, a first directed color light beam (e.g., a red light beam) may be directed at a first, color-dependent, non-zero propagation angle, a second directed color light beam (e.g., a green light beam) may be directed at a second, color-dependent, non-zero propagation angle, and a third directed color light beam (e.g., a blue light beam) may be directed at a third, color-dependent, non-zero propagation angle.

According to other embodiments of the principles described herein, methods of near-eye display operation are provided. FIG7 illustrates a flow chart of a method 300 of near-eye display operation in an example of an embodiment consistent with the principles described herein. As shown in FIG7 , the method 300 of near-eye display operation includes directing 310 a collimated light beam in a light guide at a non-zero propagation angle. According to various embodiments, the collimated light beam can be directed in a plate light guide substantially similar to the plate light guide 112 described above with respect to the near-eye display 100. Furthermore, the collimated light beam can be directed 310 at the non-zero propagation angle as described above with respect to the near-eye display 100.

The method 300 of near-eye display operation further includes diffractively outcoupling 320 a portion of the guided collimated light beam from the light guide using a multi-beam diffraction grating to produce a plurality of outcoupled light beams at different principal angular directions away from the light guide to form a light field. According to various embodiments, the light field provides a plurality of different views of an image (e.g., a displayed image) corresponding to the different principal angular directions of the outcoupled light beams. In some embodiments, the multi-beam diffraction grating is substantially similar to the multi-beam diffraction grating 114 described above with respect to the near-eye display 100. In particular, the light guide for guiding 310 the collimated light beam and the multi-beam diffraction grating for diffractively outcoupling 320 a portion of the collimated light beam can be part of a multi-beam diffraction grating-based display that is substantially similar to the multi-beam diffraction grating-based display 110 of the near-eye display 100.

As shown in FIG7 , the method 300 of near-eye display operation further includes relaying 330 the multiple different views of the image to the eye box using an optical system. In some embodiments, the optical system can be substantially similar to the optical system 120 of the near-eye display 100 described above. In particular, according to some embodiments, relaying 330 the multiple different views of the image refers to relaying different ones of the different views to different locations within the eye box to provide a depth focus cue to a user viewing the image in the eye box. For example, the depth focus cue can facilitate image adaptation for the user's eyes.

In some embodiments, the relayed image may include a three-dimensional (3D) image, and different views of the multiple different views may represent different perspectives of the 3D image. In some embodiments, the relayed image is an image of a stereoscopic image pair. Further, in some examples, the multiple different views of the image may include at least four different views. In some embodiments, relaying 330 the multiple different views of the image includes magnifying the image to provide a virtual image located at a distance from the eye box corresponding to the normal accommodation range of the user's eyes. In some embodiments, relaying 330 the multiple different views provides one or both of an augmented reality display and a virtual reality display of the image.

Thus, examples and embodiments of near-eye displays, binocular near-eye display systems, and methods of near-eye display operation that employ multi-beam diffraction grating-based displays to provide multiple different views of an image have been described. It should be understood that the above examples are merely illustrative of some of the many specific examples that demonstrate the principles described herein. Clearly, those skilled in the art can readily devise numerous other arrangements without departing from the scope of the appended claims.

Claims (19)

1. A near-eye display, comprising: a multi-beam diffraction grating-based display configured to provide multiple different views of an image; and an optical system configured to relay the plurality of different views of the image to a corresponding plurality of different locations within an eye box at an output of the near-eye display, the corresponding plurality of different locations within the eye box being configured to provide focus depth cues to a user of the near-eye display, wherein the optical system comprises a free-form prism, a free-form compensating lens, and a partially reflective surface, the partially reflective surface being disposed between the free-form compensating lens and the free-form prism, The multi-beam diffraction grating-based display comprises: a plate light guide configured to guide a collimated light beam at a non-zero propagation angle; and an array of multi-beam diffraction gratings at a surface of the plate light guide, the multi-beam diffraction gratings of the array being configured to diffractively couple out portions of the guided collimated light beam as a plurality of outcoupled light beams having different principal angular directions corresponding to viewing directions of the plurality of different views of the image, and Wherein the plurality of different views has a total angular range, and the optical system has an input aperture, the total angular range is configured to correspond to a size of the input aperture. 2. The near-eye display of claim 1, wherein the image comprises a three-dimensional (3D) image, and wherein different views of the plurality of different views represent different perspectives of the 3D image. 3. The near-eye display of claim 1 , wherein the plurality of different views of the image comprises at least four different views. 4. The near-eye display of claim 1 , wherein the optical system comprises a simple magnifier configured to provide a virtual image of the image located at a distance from the eye box corresponding to a normal range of accommodation of the user's eyes. 5. The near-eye display of claim 1 , wherein the multi-beam diffraction grating-based display and the optical system are both located within a user's field of view (FOV) to substantially block a portion of the FOV, the near-eye display being a virtual reality display configured to replace a view of a physical environment with an image within the blocked portion of the FOV. 6. The near-eye display of claim 1 , wherein the multi-beam diffraction grating-based display is located outside a user's field of view (FOV), the optical system is located within the FOV, and the near-eye display is an augmented reality display configured to use the image to enhance a view of a physical environment within the FOV. 7. The near-eye display of claim 1, wherein the multi-beam diffraction grating is a linear chirped diffraction grating. 8. The near-eye display of claim 1 , wherein the multi-beam diffraction grating-based display further comprises: a light source configured to provide the collimated light beam to the plate light guide; and A light valve array is adjacent to a surface of the plate light guide, the light valve array being configured to selectively modulate the outcoupled light beam into a plurality of pixels corresponding to pixels of the plurality of different views of the image. 9. A near-eye display as described in claim 8, wherein the light source includes a plurality of different light sources configured to provide light of different colors, and the different light sources are configured to provide different, color-specific, non-zero propagation angles of the collimated guided light beam corresponding to each of the different colors of light. 10. A near-eye binocular display system comprising a pair of near-eye displays as described in claim 1, wherein a first near-eye display of the pair is configured to provide a first plurality of different views of a first image to a first eyebox, and a second near-eye display of the pair is configured to provide a second plurality of different views of a second image to a second eyebox, the second eyebox being laterally offset from the first eyebox, the first image and the second image representing a stereoscopic image pair. 11. A near-eye binocular display system comprising: a pair of multi-beam diffraction grating-based displays, each multi-beam diffraction grating-based display configured to provide a different image of a pair of stereoscopic images representing a three-dimensional (3D) scene; and a binocular optical system configured to respectively relay said different images of said stereoscopic image pair to a corresponding pair of eye boxes, said eye boxes being laterally displaced from each other, wherein the multi-beam diffraction grating-based display of the display pair comprises a plate light guide and an array of multi-beam diffraction gratings, the multi-beam diffraction gratings of the array being configured to diffractively couple guided light from within the plate light guide as a plurality of outcoupled beams, the plurality of outcoupled beams being configured to provide the different images of the stereoscopic image pair, each of the different images of the stereoscopic image pair comprising a plurality of different views of the 3D scene, the outcoupled beams of the plurality of outcoupled beams having different principal angular directions corresponding to 3D view directions of the different views of the plurality of outcoupled beams, the binocular optical system being configured to relay the plurality of different views to a corresponding plurality of different positions within an eye box, the different positions of the different views within the eye box being configured to provide depth focus cues to a user of the near-eye binocular display system, wherein the binocular optical system comprises a first freeform prism and a second freeform prism, a freeform compensating lens pair, and a partially reflective surface pair disposed between the freeform compensating lens pair and the first freeform prism and the second freeform prism, and Wherein the plurality of different views has a total angular range and the binocular optical system has an input aperture, the total angular range is configured to correspond to a size of the input aperture. 12. The near-eye binocular display system of claim 11, wherein the depth focus cue corresponds to binocular disparity between the different images of the stereoscopic image pair. 13. The near-eye binocular display system of claim 11 , wherein the first freeform prism is configured to relay an image provided by a first multi-beam diffraction grating-based display of the multi-beam diffraction grating-based display pair to a first eyebox of the eyebox pair, and the second freeform prism is configured to relay an image provided by a second multi-beam diffraction grating-based display of the multi-beam diffraction grating-based display pair to a second eyebox of the eyebox pair. 14. The near-eye binocular display system of claim 13, wherein the pair of freeform compensating lenses is configured to provide different images of a physical environment to the pair of eye boxes, the near-eye binocular display system being an augmented reality display system. 15. The near-eye binocular display system of claim 11 , wherein the different images provided by the stereoscopic image pair are configured to replace a binocular view of a physical environment within an eye box, the near-eye binocular display system being configured as a virtual reality display system. 16. The near-eye binocular display system of claim 11 , wherein the multi-beam diffraction grating-based display further comprises: a light source configured to provide light; an optical collimator configured to collimate light provided by the light source; and a light valve array adjacent to the plate light guide, the light valve array being configured to selectively modulate the outcoupled light beam into a plurality of pixels corresponding to pixels of the provided image of the stereoscopic image pair, Wherein the plate light guide is configured to guide the collimated light as a collimated light beam at a non-zero propagation angle. 17. A method for near-eye display operation, the method comprising: guiding a collimated light beam in a light guide at a non-zero propagation angle; diffractively outcoupling a portion of the guided collimated light beam from the light guide using a multi-beam diffraction grating for generating a plurality of outcoupled light beams away from the light guide at different principal angular directions to form a light field providing a plurality of different views of the image corresponding to the different principal angular directions of the outcoupled light beams; and relaying the plurality of different views of the image to an eyebox using an optical system, wherein relaying the plurality of different views relays different ones of the different views to different positions within the eyebox, the different positions of the different views providing depth focus cues to a user viewing the image in the eyebox, wherein the optical system comprises a free-form prism, a free-form compensating lens, and a partially reflective surface, the partially reflective surface being disposed between the free-form compensating lens and the free-form prism, and Wherein the plurality of different views has a total angular range, and the optical system has an input aperture, the total angular range is configured to correspond to a size of the input aperture. 18. The method of near-eye display operation of claim 17, wherein relaying the multiple different views of the image comprises magnifying the image to provide a virtual image located at a distance from the eye box corresponding to a normal range of accommodation of the user's eyes. 19. The method of near-eye display operation of claim 17, wherein relaying the plurality of different views of the image provides one or both of an augmented reality display and a virtual reality display of the image.