Optical waveguide having multiple optical paths

Abstract

Systems and methods are provided that include a waveguide including an in-coupler and an out-coupler. The in-coupler is configured to receive display light representing an image for display and to direct a first portion of the display light to propagate in the waveguide along a first optical path and to direct a second portion of the display light to propagate in the waveguide along a second optical path, the first optical path and the second optical path having substantially non-overlapping propagation angles. The out-coupler is configured to combine the first portion of the display light and the second portion of the display light to display a representation of the image.

Description

[Background technology]

[0001] Some display systems use a projector that projects or shines a pattern of light onto another object (e.g., onto a surface of another object, such as onto a projection screen or onto the retina) to display an image or video on or through the other object. In a conventional projection system, light is modulated in time to provide a spatially distributed pattern of light across a two-dimensional display area. The spatial distribution of the modulated light pattern produces an image in the display area. Summary of the Invention

[0002] In one embodiment, the waveguide includes an in-coupler configured to receive display light representative of an image for display, and an out-coupler, the in-coupler configured to direct a first portion of the display light to propagate within the waveguide along a first optical path and direct a second portion of the display light to propagate within the waveguide along a second optical path, the first optical path and the second optical path having substantially non-overlapping propagation angles, and the out-coupler configured to combine the first portion of the display light and the second portion of the display light to display a representation of the image.

[0003] The first portion of the display light may correspond to a first spatial portion of the image, and the second portion of the display light may correspond to a second spatial portion of the image. The first spatial portion of the image and the second spatial portion of the image may partially overlap.

[0004] The first portion of the display light may include a first set of wavelengths, and the second portion of the display light includes a second set of wavelengths different from the first set of wavelengths.

[0005] The waveguide may include a first exit pupil expander disposed in the first optical path and configured to redirect a first portion of the display light towards the outcoupler, and a second exit pupil expander disposed in the first optical path and configured to redirect a second portion of the display light towards the outcoupler.

[0006] The out-coupler may be configured to combine the first portion of the display light and the second portion of the display light to display the representation.

[0007] The incoupler may be further configured to receive the display light from the optical engine, split the display light into at least a first portion of the display light and a second portion of the display light, redirect the first portion of the display light to propagate in the waveguide along a first optical path, and redirect the second portion of the display light to propagate in the waveguide along a second optical path. The incoupler may be further configured to split the display light into a third portion of the display light and direct the third portion of the display light to propagate along a third optical path different from the first optical path and the second optical path. The representation may be a combination of the first portion of the image, the second portion of the image, and the third portion of the image.

[0008] In one embodiment, a method comprises receiving display light representing an image for display; directing a first portion of the display light to propagate in a waveguide along a first optical path and directing a second portion of the display light to propagate in the waveguide along a second optical path, the first optical path and the second optical path each having a non-overlapping propagation angle, and the method further includes combining the first portion of the display light and the second portion of the display light to display a representation of the image.

[0009] A first portion of the display light may transmit a first spatial portion of the image and a second portion of the display light transmits a second spatial portion of the image, and the first spatial portion of the image and the second spatial portion of the image may partially overlap.

[0010] Directing a first portion of the display light along a first optical path may include directing a first set of wavelengths of the display light along the first optical path, and directing a second portion of the display light along a second optical path includes directing a second set of wavelengths of the display light along the second optical path, whereby the second set of wavelengths is different from the first set.

[0011] The method may further include redirecting a first portion of the display light toward an out-coupler of the waveguide with a first exit pupil expander disposed in the first optical path and redirecting a second portion of the display light toward the out-coupler with a second exit pupil expander disposed in the second optical path. The method may further include combining the first portion of the display light and the second portion of the display light with the out-coupler to display the representation.

[0012] The method may further include receiving the display light from the optical engine using a waveguide incoupler, splitting the display light into at least a first portion of the display light and a second portion of the display light by the incoupler, redirecting the first portion of the display light by the incoupler to propagate within the waveguide along a first optical path, and redirecting the second portion of the display light by the incoupler to propagate within the waveguide along a second optical path.

[0013] The method may further include splitting the display light into a third portion and directing the third portion of the display light to propagate along a third optical path distinct from the first optical path and the second optical path. The method may further include displaying the representation by combining the first portion of the display light, the second portion of the display light, and the third portion of the display light.

[0014] In one embodiment, the projection system includes an optical engine and a waveguide, the waveguide configured to receive display light representing an image for display, and configured to direct a first portion of the display light to propagate within the waveguide along a first optical path and direct a second portion of the display light to propagate within the waveguide along a second optical path, the first optical path and the second optical path each having a non-overlapping propagation angle, the waveguide further configured to combine the first portion of the display light and the second portion of the display light to display a representation of the image. The waveguide may be further configured to split the display light into a third portion and direct the third portion of the display light to propagate along a third optical path different from the first optical path and the second optical path.

[0015] The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by reference to the accompanying drawings, in which: The use of the same reference symbols in different drawings indicates similar or identical items. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 illustrates a display system having an integrated laser projector according to some embodiments. [Diagram 2] FIG. 2 illustrates a partially transparent view of a display system including a projection system, according to some embodiments. [Diagram 3] FIG. 1 illustrates an isometric view of a waveguide with an in-coupler, an out-coupler, and an exit pupil expander. [Figure 4] 4 is a chart showing the propagation of display light through the waveguide of FIG. 3 relative to k-space. [Diagram 5] FIG. 1 illustrates an isometric view of a waveguide having an in-coupler, an out-coupler, and two exit pupil expanders disposed on either side of the in-coupler, in accordance with some embodiments, where the waveguide is configured to propagate light along two optical paths. [Figure 6] 5 is a chart illustrating propagation of display light through the waveguide of FIG. 4 relative to k-space in accordance with some embodiments. [Figure 7] FIG. 1 illustrates an isometric view of a waveguide having an in-coupler, an out-coupler, and two exit pupil expanders in accordance with some embodiments, the waveguide being configured to propagate light along two optical paths, and the in-coupler being configured to redirect first and second portions of the display light along the first and second optical paths toward the exit pupil expanders to shift the corresponding image in both the kx and ky dimensions. [Figure 8] 8 is a chart illustrating propagation of display light through the waveguide of FIG. 7 relative to k-space, according to some embodiments. [Figure 9]FIG. 1 illustrates an isometric view of a waveguide having an in-coupler, an out-coupler, and two exit pupil expanders disposed on either side of the in-coupler, according to some embodiments, the waveguide being configured to propagate display light along three optical paths. [Figure 10] 10 is a chart illustrating propagation of display light through the waveguide of FIG. 9 relative to k-space, according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] 1-10 illustrate embodiments for compactly arranging a near-eye display system (e.g., a wearable head-up display (WHUD)) or other display system while improving the spatial or angular resolution of the displayed image. While certain embodiments described herein involve utilizing optical or other components as part of a wearable display device, it should be understood that additional embodiments may utilize such components via various other types of devices in accordance with the techniques described herein.

[0018] According to embodiments described herein, the projection system of the display system includes a waveguide that propagates the received display light along multiple optical paths between a waveguide in-coupler and a waveguide out-coupler. Each optical path along which the waveguide propagates the received display light corresponds to a different position in k-space (k is the reciprocal of the wavelength such that k=1 / λ), and therefore each optical path has a different propagation angle. Because light can only propagate through the waveguide via total internal reflection (TIR) ​​at a limited number of discrete propagation angles (i.e., polar angles), only a portion of each image conveyed through the display light can be successfully propagated through the waveguide and output to a user's eye. In some embodiments, at least a portion of the different optical paths through the waveguide have non-overlapping propagation angles, thereby allowing different portions of each image to be successfully conveyed through the waveguide. In certain embodiments, the waveguide is configured to propagate light along different optical paths, each having a different (non-overlapping) propagation angle, such that the density of optical modes utilized by the image-carrying display light as it propagates through the waveguide, and the spatial or angular resolution of the image output by the waveguide, is increased compared to corresponding aspects of conventional waveguides that provide a single optical path or multiple optical paths with similar or substantially overlapping propagation angles. As used herein, an optical mode is a set of guided optical propagation paths through the waveguide for a wavelength of the image-carrying display light.

[0019] In some embodiments, the waveguide includes a first exit pupil expander and a second exit pupil expander, each disposed on either side of a waveguide in-coupler. Display light corresponding to an original image for display is received at the waveguide in-coupler. The waveguide is configured to propagate a first portion of the display light along a first optical path including the first exit pupil expander and to propagate a second portion of the display light along a second optical path including the second exit pupil expander. For example, the in-coupler redirects the first portion of the display light toward the first exit pupil expander (to display a first image carried by or otherwise corresponding to the first portion of the display light) at a positive k-space relative to k-space. ydimension) and redirecting a second portion of the received display light toward a second exit pupil expander (transmitting a second image conveyed by or otherwise corresponding to the second portion of the display light into k-space at a negative k-shift. y It should be understood that a subsequent representation of the original image or portions thereof based on transforming or redirecting the display light as described herein may be referred to herein as the image itself.

[0020] The first exit pupil expander redirects a first portion of the display light toward an outcoupler of the waveguide (a first image carried by the first portion of the display light is a negative k-space image). x Dimension and negative k y The second exit pupil expander is configured to redirect a second portion of the display light toward the outcoupler of the waveguide (to shift a second image carried by the second portion of the display light in a negative k dimension relative to k-space). x Dimension and positive k y The out-coupler is configured to output the first and second portions of the display light toward the user's eye at an angle that is the same as or substantially similar (e.g., within about 5%) to the angle at which the display light was input at the in-coupler (the first and second images conveyed by the first and second portions of the display light are shifted in the positive k dimension relative to k-space). x The first and second images are combined at an outcoupler to form a final image. The final image includes a first portion of the original image and a second portion of the original image, where the first portion of the original image corresponds to the first portion of the display light and is transmitted via the first portion of the display light along a first optical path, and the second portion corresponds to the second portion of the display light and is transmitted via the second portion of the display light along a second optical path.

[0021] In some embodiments, a first portion of the original image conveyed by a first portion of the display light normally propagating through the waveguide via TIR along a first optical path is different (e.g., at least partially spatially distinct with respect to the second portion of the original image) from a second portion of the original image conveyed by a second portion of the display light normally propagating through the waveguide via TIR along a second optical path. In some embodiments, the first portion of the display light conveying the first image utilizes a first set of optical modes, and the second portion of the display light conveying the second image utilizes a second set of optical modes, and the first portion of the display light and the second portion of the display light traverse spatially distinct paths. The first set of optical modes and the second set of optical modes are non-overlapping or partially non-overlapping with each other, and each of the first set of optical modes and the second set of optical modes corresponds to a different portion of the original image. In this manner, the density of light modes utilized to convey the final representation is increased compared to the density of light modes utilized to convey the first or second images alone (e.g., compared to a waveguide including only one of the first or second optical paths).By propagating the first and second portions of the display light through two distinct, spatially distinct paths, the spatial or angular resolution of the final image is improved.

[0022] In some embodiments, the first image and the second image are each a representation of the original image presented for display. In some embodiments, the first image corresponds to a first spatial portion of the original image, and the second image corresponds to a second portion of the original image. In certain embodiments, the first and second portions of the original image partially overlap. In some embodiments, the first image corresponds to a first representation of the original image that includes only a first set of wavelengths of light (i.e., colors) of the original image, and the second image corresponds to a second representation of the original image that includes only a second set of wavelengths of light (i.e., colors) of the original image, where the first set of wavelengths of light is at least partially different from the second set of wavelengths of light.

[0023] In some embodiments, the in-coupler is further configured to redirect a third portion of the display light from the in-coupler through the TIR to the out-coupler along a third optical path, carrying a third image, without the third portion of the display light entering an intervening exit pupil expander. The third image is combined with the first and second images to form a final image that is output by the waveguide through the out-coupler. By redirecting the third portion of the display light from the in-coupler through the TIR to the out-coupler without an intervening redirection (e.g., by an exit pupil expander), the third image is k x The third image is shifted only along the first dimension, such that a continuous range of viewing angles (corresponding to the arcs defined by the discrete propagation angles where TIR is enabled in the waveguide) is included in the final image, thereby increasing the density of optical modes utilized in the waveguide and improving the spatial or angular resolution of the final image. In some embodiments, the third image corresponds to only a portion of the original image, and the geometry of the third image is not expanded by the exit pupil expander in the same way that the geometries of the first and second images are expanded by the first and second image pupil expanders, resulting in an improvement in the spatial or angular resolution of only a portion of the final image. In some embodiments, because the propagation length along the third optical path is shorter than either of the propagation lengths along the first and second optical paths, the third portion of the display light propagating along the third optical path experiences less scattering (e.g., due to surface or bulk material features or non-idealities) than the first and second portions of the display light propagating along the first and second optical paths, thereby further improving the spatial or angular resolution of the corresponding portions of the third image and the final image, respectively. In some embodiments, such a configuration improves the spatial or angular resolution of a target region of the field of view (FOV) of the display device that corresponds to a portion of the final image output by the waveguide.

[0024] In some embodiments, the waveguide includes a first exit pupil expander and a second exit pupil expander, and the incoupler is configured to redirect first and second portions of the display light toward the first and second exit pupil expanders, respectively, such that corresponding first and second images conveyed by the first and second portions of the display light are represented, with respect to k-space, as k x Dimension and k y The light carrying the original image is received at an incoupler of the waveguide. The waveguide is configured to propagate a first portion of the display light along a first optical path including a first exit pupil expander and to propagate a second portion of the display light along a second optical path including a second exit pupil expander. For example, the waveguide may redirect the first portion of the display light toward the first exit pupil expander (to position the first image carried by the first portion of the display light at a positive k-axis relative to k-space). y Dimension and negative k x dimension) and redirecting a second portion of the received display light toward a second exit pupil expander (shifting a second image conveyed by the second portion of the display light relative to k-space in a negative k dimension). y Dimension and negative k x The first exit pupil expander is configured to redirect the first portion of the display light toward the outcoupler of the waveguide (to shift the first image carried by the first portion of the display light in the negative k dimension relative to k-space). x Dimension and negative k y The second exit pupil expander is configured to redirect a second portion of the display light toward the outcoupler of the waveguide (to shift a second image carried by the second portion of the display light in a negative k dimension relative to k-space). x Dimension and positive k y The out-coupler is configured to output the first and second portions of the display light toward the user's eye at an angle that is the same as or substantially similar (e.g., within about 5%) to the angle at which the display light was input at the in-coupler (the first and second images conveyed by the first and second portions of the display light are shifted in the positive k dimension relative to k-space). xIn some embodiments, the first image and the second image are each a representation of the original image. In some embodiments, the first image corresponds to a first portion of the original image and the second image corresponds to a second portion of the original image. In certain embodiments, the first and second spatial portions of the original image partially overlap. In some embodiments, the first image corresponds to a first representation of the original image that includes only a first set of wavelengths of light (i.e., colors) of the original image and the second image corresponds to a second representation of the original image that includes only a second set of wavelengths of light (i.e., colors) of the original image, where the first set of wavelengths of light is different from the second set of wavelengths of light.

[0025] The first and second images are combined at an out-coupler to form a final image including a first portion and a second portion of the original image, the first portion of the original image being transmitted via a first portion of the display light transmitting the first image via a first optical path, and the second portion being transmitted via a second portion of the display light transmitting the second image via a second optical path. The first portion of the original image transmitted by the first portion of the display light normally propagating through the waveguide via TIR along the first optical path is different (at least partially spatially distinct with respect to the second portion of the original image) from the second portion of the original image transmitted by the second portion of the display light normally propagating through the waveguide via TIR along the second optical path. In some embodiments, the first portion of the display light transmitting the first image utilizes a first set of optical modes, and the second portion of the display light transmitting the second image utilizes a second set of optical modes, and the first portion of the display light and the second portion of the display light traverse spatially distinct paths. That is, the first set of light modes and the second set of light modes are non-overlapping or partially non-overlapping with each other, and each of the first and second sets of light modes corresponds to a different portion of the original image. In this way, the density of light modes utilized to convey the final image is increased compared to the density of light modes utilized to convey the first image alone and the second image alone (e.g., compared to a waveguide including only one of the first or second optical paths). By causing the first and second portions of the display light to pass through two different, spatially distinct paths, the spatial or angular resolution of the final image is improved. Upon redirection of the first and second portions of the display light by the incoupler (k y (not just dimension)k x Dimension and k yBy shifting the first and second images in both dimensions, in some implementations, the efficiency, uniformity, and eyebox size of the corresponding display are improved while reducing the size of the waveguide. In some embodiments, the first and second exit pupil expanders are aligned such that at least one dimension of each of the first and second exit pupil expanders is non-parallel with respect to a corresponding dimension of the waveguide outcoupler.

[0026] Although some embodiments of the present disclosure are described and illustrated with reference to a particular exemplary near-eye display system in the form of a WHUD, it should be understood that the apparatus and techniques of the present disclosure are not limited to this particular example, but instead may be implemented in any of a variety of display systems using the guidance provided herein.

[0027] 1 illustrates an exemplary display system 100 using a scanning-based optical system according to some embodiments. The display system 100 has a support structure 102 including an arm 104 that houses a projector (e.g., a laser projector, a micro LED projector, a liquid crystal on silicon (LCOS) projector, etc.). The projector is configured to project an image toward a user's eye via a waveguide, so that the user perceives the projected image as being displayed within a field of view (FOV) region 106 of the display at one or both of the lens elements 108, 110. In the illustrated embodiment, the display system 100 is a near-eye display system in the form of a WHUD, where the support structure 102 is configured to be worn on the user's head and has the general shape and appearance (i.e., form factor) of a frame of eyeglasses (e.g., sunglasses).

[0028] The support structure 102 houses or otherwise includes various components to facilitate the projection of such images toward the user's eyes, such as a projector and a waveguide. In some embodiments, the support structure 102 further includes various sensors, such as one or more front-facing cameras, rear-facing cameras, other light sensors, motion sensors, accelerometers, etc. In some embodiments, the support structure 102 includes one or more radio frequency (RF) interfaces or other wireless interfaces, such as a Bluetooth™ interface, a WiFi interface, etc. Additionally, in some embodiments, the support structure 102 further includes one or more batteries or other portable power sources for powering the electrical components of the display system 100. In some embodiments, some or all of these components of the display system 100 are housed completely or partially within an interior volume of the support structure 102, such as within the arms 104 of the region 112 of the support structure 102. It should be noted that while an exemplary form factor is shown, in other embodiments, the display system 100 may have a different shape and appearance than the eyeglass frames shown in FIG. 1. Unless otherwise indicated, instances of the term "or" herein should be understood to refer to a non-exclusive definition of "or." For example, the phrase "X or Y" herein means "either X or Y, or both."

[0029] One or both of lens elements 108, 110 may be used by display system 100 to provide an augmented reality (AR) display in which rendered graphical content may be overlaid on or otherwise combined with a view of the real world perceived by a user through lens elements 108, 110. For example, the projection system of display system 100 may, according to various embodiments, form a perceivable image or series of images using light by projecting display light to a user's eye via a projector of the projection system, a waveguide formed at least partially within the corresponding lens element 108 or 110, and one or more optical elements (e.g., one or more scanning mirrors, one or more optical relays, or one or more collimation lenses disposed between the projector and the waveguide or integrated with the waveguide).

[0030] One or both of the lens elements 108, 110 include at least a portion of a waveguide that transmits display light received by a waveguide in-coupler to a waveguide out-coupler that outputs the display light toward an eye of a user of the display system 100. The display light is modulated and projected to the user's eye such that the user perceives the light as an image. Additionally, each of the lens elements 108, 110 is sufficiently transparent to allow the user to see through the lens element and provide a view of the user's real-world environment, with the image being displayed overlaid on at least a portion of the real-world environment.

[0031] In some embodiments, the projector of the projection system of the display 100 is a digital light processing based projector, a scanning laser projector, or any combination of a modulated light source, such as a laser or one or more light emitting diodes (LEDs), and a dynamic reflection mechanism, such as one or more dynamic scanners, a reflection panel, or a digital light processor (DLP). In some embodiments, the projector includes a micro display panel, such as a micro LED display panel (e.g., a micro AMOLED display panel, or a micro inorganic LED (i-LED) display panel), or a micro liquid crystal display (LCD) display panel (e.g., a low temperature polysilicon (LTPS) LCD display panel, a high temperature polysilicon (HTPS) LCD display panel, or an in-plane switching (IPS) LCD display panel). In some embodiments, the projector includes a liquid crystal on silicon (LCOS) display panel. Such a display panel is considered herein to be part of the optical engine (e.g., the optical engine 208 of FIG. 2) of the corresponding projection system. In some embodiments, the display panel of the projector is configured to output light (representing an image or a portion of an image for display) to the projector's waveguide. The waveguide expands the display light and outputs the display light through an out-coupler towards the user's eye.

[0032] The projector is communicatively coupled to a controller and a non-transitory processor-readable storage medium or memory that stores processor-executable instructions and other data that, when executed by the controller, cause the controller to control the operation of the projector. In some embodiments, the controller controls the projector to selectively set the position and size of the FOV region 106. In some embodiments, the controller is communicatively coupled to one or more processors (not shown) that generate content to be displayed on the display system 100. The projector outputs display light via a waveguide toward the FOV region 106 of the display system 100. In some embodiments, at least a portion of the out-coupler of the waveguide overlaps with the FOV region 106. The range of different user eye positions from which a display can be viewed is referred to herein as the eyebox of the display.

[0033] 2 shows a portion of a display system 200 including a projection system having a projector 206 and a waveguide 212 having multiple optical paths between an in-coupler 214 and an out-coupler 216 of the waveguide 212. In some embodiments, the display system 200 represents the display system 100 of FIG. 1. In this example, the arm 204 of the display system 200 houses the projector 206, which includes an optical engine 208 (e.g., a display panel), one or more optical elements 210, the in-coupler 214, and a portion of the waveguide 212.

[0034] The display system 200 includes an optical combiner lens 218 including a first lens 220, a second lens 222, and a waveguide 212, the waveguide 212 being embedded or otherwise disposed between the first lens 220 and the second lens 222. Light exiting the outcoupler 216 passes through the first lens 220 (e.g., corresponding to an embodiment of the lens element 110 of the display system 100). In use, the display light exiting the first lens 220 enters the pupil of an eye 224 of a user wearing the display system 200, causing the user to perceive a display image carried by the display light output from the optical engine 208. Because the optical combiner lens 218 is substantially transparent, light from a real-world scene corresponding to the environment around the display system 200 passes through the first lens 220, the second lens 222, and the waveguide 212 to reach the user's eye 224. In this manner, images or other graphical content output by projector 206, when projected to the user's eye 224, are combined (e.g., overlaid) with real-world images of the user's environment to provide the user with an AR experience.

[0035] The waveguide 212 of the display system 200 includes an in-coupler 214 and an out-coupler 216. In some embodiments, one or more exit pupil expanders, such as a diffraction grating, are disposed at an intermediate stage between the in-coupler 214 and the out-coupler 216 to receive light coupled into the waveguide 212 by the in-coupler 214, expand the received display light at each exit pupil expander, and redirect the light toward the out-coupler 216, which then couples the display light out of the waveguide 212 (e.g., toward the user's eye 224). In some embodiments, the waveguide 212 is configured to have a peak frequency response at a wavelength of green light, such as about 575 nm, which enhances the perceptibility of the projected image output by the waveguide 212.

[0036] As used herein, the term "waveguide" is understood to mean a combiner that transfers light from an incoupler (such as incoupler 214) to an outcoupler (such as outcoupler 216) using one or more of total internal reflection (TIR), special filters, or reflective surfaces. In some display applications, the display light is a collimated image, and the waveguide transfers and replicates the collimated image to the eye. In general, the terms "incoupler" and "outcoupler" are understood to refer to any type of optical grating structure, including, but not limited to, a diffraction grating, a hologram, a holographic optical element (e.g., an optical element that uses one or more holograms), a volume diffraction grating, a volume hologram, a surface relief diffraction grating, or a surface relief hologram. In some embodiments, a given incoupler or outcoupler is configured as a transmission grating (e.g., a transmission diffraction grating or a transmission holographic grating) that transmits light through the incoupler or outcoupler and applies an optical function(s) to the display light during transmission. In some embodiments, a given in-coupler or out-coupler is configured as a reflective grating (e.g., a reflective diffraction grating or a reflective holographic grating) that reflects light to the in-coupler or out-coupler and applies an optical function(s) to the display light during reflection. In this example, the in-coupler 214 relays the received display light to the out-coupler 216 via multiple optical paths through the waveguide. In some embodiments, the in-coupler 214 redirects a first portion of the display light to the out-coupler 216 via a first optical path in which a first exit pupil expander (not shown, implemented as a folding grating in some embodiments) is located, and redirects a second portion of the display light towards the out-coupler 216 via a second optical path in which a second exit pupil expander (not shown, implemented as a folding grating in some embodiments) is located. The display light propagates through the waveguide 212 via the TIR. The out-coupler 216 then outputs the display light to the user's eye 224.

[0037] In some embodiments, the projector 206 is coupled to a driver or other controller (not shown) that controls the timing of emission of display light from the light sources (e.g., LEDs) of the optical engine 208 according to instructions received by the controller or driver from a computer processor (not shown) coupled to the controller, to modulate the output light such that it is perceived as an image when output to the retina of the user's eye 224. For example, during operation of the display system 200, the light sources of the optical engine 208 output light of selected wavelengths, and the output light is directed to the user's eye 224 via the optical elements 210 and the waveguide 212. The optical engine 208 modulates the intensity of each of the light sources of the optical engine 208 such that the output light represents a pixel of the image. For example, the intensity of a given light source or group of light sources of the optical engine 208 corresponds to the brightness of a corresponding pixel of an image projected by the projector 206 of the display system 200.

[0038] FIG. 3 illustrates a partially transparent perspective view ("front" view) of a waveguide 300 (e.g., an embodiment of the waveguide 212 of the display system 200 of FIG. 2) according to some embodiments. A light source, such as an embodiment of the optical engine 208 of FIG. 2, outputs a display light 304 into the waveguide 300 along a first trajectory 306. As shown, the in-coupler 214 redirects the display light 304 towards the exit pupil expander 302 along a second trajectory 308. In this example, the second trajectory 308 extends in the negative y dimension. It should be noted that the trajectories described herein may be described with reference to the illustrated Cartesian coordinate system (e.g., with reference to the illustrated x-, y-, and z-axes). The exit pupil expander 302 redirects the display light 304 along a third trajectory 310 to the out-coupler 216. In this example, the third trajectory 310 extends in the negative x dimension. The out-coupler redirects the display light 304 such that the display light 304 is output along a fourth trajectory 312 toward a user's eye 314. In some embodiments, the first trajectory 306 and the fourth trajectory 312 are parallel or substantially (e.g., within about 5%) parallel to one another.

[0039] In some embodiments, the exit pupil expander 302 is an optical grating, such as a diffraction grating or a holographic grating, that is configured to redirect the display light 304 along the third trajectory 310 and expands one or more dimensions of the eyebox of a display system that includes the waveguide 300 (e.g., display system 100 of FIG. 1 , display system 200 of FIG. 2 ) (e.g., with respect to what the dimensions of the eyebox of the display would be in the absence of the exit pupil expander 302).

[0040] 4 illustrates a normalized k-space chart 400 representing the propagation of display light through the waveguide 300 of FIG. 3 relative to k-space. That is, the chart 400 is a k-space chart that corresponds to a two-dimensional (2D) generalization of the waveguide 300. Accordingly, certain aspects of the present example are described with respect to the waveguide 300 of FIG. 3 and its elements.

[0041] For light of a given wavelength λ in a material with bulk refractive index n, the total luminous intensity of the light's propagation vector through the waveguide 300 is k=(2πn) / λ. The variable k is sometimes called the wave number, and as used herein, is defined as the inverse of the wavelength, k=1 / λ. A given propagation angle in 2D k-space is represented as a circle, and k 2 =k x 2 +k y 2 Only light traveling at propagation angles between first boundary angle 402 and second boundary angle 404 can propagate along waveguide 300 via TIR. Furthermore, only light traveling at discrete propagation angles (i.e., discrete polar angles) represented by line 406 (the dashed circle located between first boundary angle 402 and second boundary angle 404) can propagate along waveguide 300 via TIR.

[0042] Initially, the display light 304 entering the waveguide 300 at the incoupler 214 is centered at or around the origin of the chart 400. Here, an image 408 represents the image carried by the display light 304. The image 408 is initially located at a first position 410 relative to k-space. Upon redirection of the display light 304 by the incoupler 214, the image 408 is shifted in k-space to a second position 412, resulting in a negative k-space image. y When the display light 304 is redirected by the first exit pupil expander 302, the image 408 is shifted in k-space to a third position 414, corresponding to a shift in the positive k-dimension. y Dimension, and negative k x When the display light 304 is redirected by the outcoupler 216, the image 408 is shifted in k-space to a first position 410, corresponding to a shift in the positive k xThis corresponds to a shift in dimension. In this example, it is assumed that the angle at which the display light 304 enters the waveguide 300 via the in-coupler 214 is the same as or is substantially the same (e.g., within 5%) as the angle at which the display light 304 exits the waveguide 300 via the out-coupler 216. In a waveguide such as the waveguide 300, only portions of the light traveling at certain propagation angles (e.g., corresponding to the lines 406 in this example) can propagate successfully through the waveguide, and as a result, the image information conveyed by the portions of the display light that do not travel at those propagation angles is at least partially lost. This process is sometimes referred to as discretization. For example, at the second position 412, only portions of the display light conveying portions of the image 408 where the lines 416 (corresponding to a portion of the subset of the lines 406) overlap can propagate successfully through the waveguide 300 via TIR. At the third position 414, only the portion of the display light conveying the portion of the image 408 overlapped by the line 418 (corresponding to a portion of the subset of the lines 406) can propagate normally along the waveguide 300. Thus, when the image 408 is redirected out of the waveguide 300 and back to the position 410, only the portion of the image 408 corresponding to the discrete intersection 420 of the line 416 and the line 418 (the point where the lines 416 and 418 would intersect if they overlapped as shown) is preserved. Here, the portion of the image that was preserved because the corresponding light propagated normally through the waveguide 212 is considered to suffer less loss of image information from the discretization. The portion of the display light conveying the portion of the image 408 that does not correspond to the discrete intersection 420 is not propagated completely through the waveguide 300, and the corresponding image information is at least partially lost (e.g., suffers more loss of image information from the discretization than the portion of the image that corresponds to the discrete intersection 420). The spatial or angular resolution of the image 408 carried by the display light 304 exiting the waveguide 300 corresponds, at least in part, to the quantity and density of the discrete intersection points 420. Each intersection point 420 corresponds to a respective portion of the image 408 and a respective set of viewing angles. The spatial or angular resolution of the output image 408 corresponds to how well the image 408 is preserved after the corresponding display light 304 propagates through the waveguide 300.

[0043] 5 illustrates a partially transparent perspective ("front" view) view of a waveguide 500 (e.g., one embodiment of waveguide 212 of display system 200 of FIG. 2) according to some embodiments. Waveguide 500 includes in-coupler 214, first exit pupil expander 502, second exit pupil expander 504, and out-coupler 216. In some embodiments, first exit pupil expander 502 and second exit pupil expander 504 each include an optical grating, such as a diffraction grating or a holographic grating, configured to redirect and expand received display light, thereby expanding one or more dimensions of the eyebox of a display system including waveguide 500 (e.g., display system 100 of FIG. 1, display system 200 of FIG. 2).

[0044] In operation, a light source, such as an embodiment of the optical engine 208 of FIG. 2, outputs a display light 506 into the waveguide 500 along a first trajectory 508. The in-coupler 214 splits the display light 506 into a first portion 511 (sometimes referred to herein as the “first portion of the display light 511”) and a second portion 515 (sometimes referred to herein as the “second portion of the display light 515”). In some embodiments, the display light 506 conveys an image, sometimes referred to herein as the “original” image, the first portion of the display light 511 conveys the first image, the second portion of the display light 515 conveys the second image, and the combined first and second portions of the display light 511 and 515 output via the out-coupler 216 convey a “final” image, which is a combination of the first and second images. In some embodiments, each of the first image and the second image corresponds to an original image, but due to discretization as the first portion of display light 511 and the second portion of display light 515 pass through waveguide 500 along different optical paths, different portions of the original image are not preserved in each of the first image and the second image (i.e., suffer a loss of image information that is much greater than the preserved portions of the original image).

[0045] The in-coupler 214 redirects a first portion of the display light 511 toward the first exit pupil expander 502 along a second trajectory 510. In this example, the second trajectory 510 extends in a positive y dimension and a negative x dimension. The first exit pupil expander 502 redirects the first portion of the display light 511 toward the out-coupler 216 along a third trajectory 512. In this example, the third trajectory 512 extends in a negative x dimension and a negative y dimension. The out-coupler redirects the first portion of the display light 511 out of the waveguide 500 such that the first portion of the display light 511 is output toward the user's eye 522 along a fourth trajectory 514. The in-coupler 214 redirects a second portion of the display light 515 toward the second exit pupil expander 504 along a fifth trajectory 516. In this example, the fifth trajectory 516 extends in the negative y dimension and the negative x dimension. The second exit pupil expander 504 redirects a second portion of the display light 515 towards the out-coupler 216 via a sixth trajectory 518. In this example, the sixth trajectory 518 extends in the positive y dimension and the negative x dimension. The out-coupler 216 redirects the second portion of the display light 515 out of the waveguide 500 towards the user's eye 522 via a seventh trajectory 520. The first trajectory 508, the fourth trajectory 514, and the seventh trajectory 520 are, in some embodiments, parallel or substantially (e.g., within about 5%) parallel to one another.

[0046] In this example, the second trajectory 510, the third trajectory 512, and the fourth trajectory 514 are considered to be first optical paths through the waveguide 500, and the fifth trajectory 516, the sixth trajectory 518, and the seventh trajectory 520 are considered to be second optical paths through the waveguide 500, the first optical paths being different from the second optical paths. For example, at least a portion of the propagation angle of the first portion of the display light 511 as it travels along the first optical path trajectory is different from an otherwise corresponding propagation angle of the second portion of the second display light 515 as it travels along the second optical path trajectory. Each time the trajectory of the light (e.g., display light 506, first portion of display light 511, second portion of display light 515) in the waveguide 500 is changed (e.g., due to incidence on a diffraction grating, such as in-coupler 214, first exit pupil expander 502, second exit pupil expander 504, or out-coupler 216), a portion of the image conveyed by that light will suffer a greater loss of image information, while the remaining portion of the image will be preserved (i.e., will not suffer as great a loss of image information). For example, the portion of the image that is preserved corresponds to the portion of the display light propagating at a propagation angle at which TIR is achievable through the waveguide 500, while the portion of the image that will suffer a relatively greater loss of image information corresponds to the portion of the display light propagating at any other propagation angle. Because the first portion of display light 511, as it travels along the second optical path, travels along a first optical path having a different propagation angle than the propagation angle of the second portion of display light 515, the preserved portion of the original image carried by the first portion of display light 511 differs from the preserved portion of the original image carried by the second portion of display light 515. Thus, the final image output via outcoupler 216 has a higher spatial or angular resolution than either the first image or the second image alone.

[0047] In some embodiments, a first portion of the display light 511 conveying a first image utilizes a first set of light modes, and a second portion of the display light 515 conveying a second image utilizes a second set of light modes, and the first portion of the display light 511 and the second portion of the display light 515 traverse spatially distinct paths. That is, the first set of light modes and the second set of light modes are non-overlapping or partially non-overlapping with each other, and each of the first set of light modes and the second set of light modes correspond to a different portion of the original image. In this manner, the density of light modes utilized to convey the final image is increased compared to the density of light modes utilized to convey the first image alone and the second image alone (e.g., compared to a waveguide that includes only one of the first or second light paths). By redirecting the display light 506 through the waveguide 500 through multiple light paths, the spatial or angular resolution of the image conveyed through the waveguide 500 is advantageously increased.

[0048] Figure 6 shows a chart 600 representing the propagation of display light through the waveguide 500 of Figure 5 relative to k-space. That is, chart 600 is a k-space chart corresponding to a two-dimensional (2D) generalization of the waveguide 500. Accordingly, some aspects of the present example are described with respect to the waveguide 500 and its elements.

[0049] For light of a given wavelength λ in a material with bulk refractive index n, the total luminous intensity of the light's propagation vector through the waveguide 500 is k=(2πn) / λ. A given propagation angle in 2D k-space can be represented as a circle, and k 2 =k x 2 +k y 26. Only light traveling at propagation angles between first boundary angle 602 and second boundary angle 604 can propagate along waveguide 500 via TIR. Furthermore, only light traveling at discrete propagation angles (i.e., discrete polar angles) represented by line 606 (the dashed circle located between first boundary angle 602 and second boundary angle 604) can travel along waveguide 500 via TIR. Line 606 may be referred to herein as "propagation angle 606."

[0050] Initially, the display light 506 entering the waveguide 500 at the incoupler 214 is centered at or around the origin of the chart 600. Here, an original image 608 represents the image carried by the display light 506. The original image 608 is initially located at a first location 610 relative to k-space as it enters the waveguide 500 along a first trajectory 508. When the display light 506 is redirected by the incoupler 214, the original image 608 is split into a first image 617 carried by a first portion of the display light 511 and a second image 613 carried by a second portion of the display light 515. When the first portion of the display light 511 is redirected by the incoupler 214, the first image 617 is shifted in k-space to a second location 616, resulting in a positive k-space image. y When the second portion of the display light 515 is redirected by the intercoupler 214, the second image 613 is shifted in k-space to a third location 612, corresponding to a negative k y When the first portion of the display light 511 is redirected by the first exit pupil expander 502, the first image 617 is shifted in k-space to a fourth position 614, corresponding to a negative k y Dimension, and negative k x When the second portion of the display light 515 is redirected by the second exit pupil expander 504, the second image 613 is shifted in k-space to a fourth position 614, corresponding to a shift in the positive k-dimension. y Dimension, and negative k xWhen the first portion of display light 511 and the second portion of display light 515 are redirected by outcoupler 216, first image 617 and second image 613 are combined to form final image 624, which is returned to first location 610 in k-space and shifted to positive k x This corresponds to a dimensional shift.

[0051] In some embodiments, the first image 617 and the second image 613 are each a representation of the original image 608. In some embodiments, the first image 617 corresponds to a first spatial portion of the original image 608 and the second image 613 corresponds to a second spatial portion of the original image 608. In certain embodiments, the first and second portions of the original image 608 partially overlap. In some embodiments, the first image 617 corresponds to a first representation of the original image 608 that includes only a first set of wavelengths (i.e., colors) of light of the original image 608 and the second image 613 corresponds to a second representation of the original image 608 that includes only a second set of wavelengths (i.e., colors) of light of the original image 608, where the first set of wavelengths of light is different from the second set of wavelengths of light.

[0052] In this example, it is assumed that the angle at which the display light 506 enters the waveguide 500 via the in-coupler 214 is the same or substantially the same (e.g., within 5%) as the angles at which the first and second portions of the display light 511 and the display light 515 exit the waveguide 500 via the out-coupler 216. In the second position 616, only light carrying the portion of the first image 617 where the lines 622 (corresponding to a portion of the subset of the lines 606) overlap can propagate along the waveguide 500 via TIR. In the third position 612, only the portion of the second image 613 where the lines 618 (corresponding to a portion of the subset of the lines 606) overlap can propagate along the waveguide 500 via TIR. In the fourth position 614, only the portion of the first image 617 and the second image 613 where the lines 620 (corresponding to a portion of the subset of the lines 606) overlap can propagate along the waveguide 500. Thus, when the final image 624 is redirected out of the waveguide 500, it returns to the first location 610 (due to the shifting and combining of the first image 617 and the second image 613 at the outcoupler 216).

[0053] Only the portions of the original image 608 that correspond to the discrete intersections 626 are preserved in the final image 624. For example, the intersections 626 include the portions of the first image 617 where the intersections of lines 622 and 620 overlap, and the portions of the second image 613 where the intersections of lines 618 and 620 overlap (these intersections correspond to the points where the corresponding lines would intersect if they overlapped as shown). At least some of the image information corresponding to the portions of the original image 608 that are not located at the intersections 626 suffer a greater loss of image information than those portions that are located at the intersections 626 because the corresponding light does not propagate normally through the waveguide 500 via TIR. In some embodiments, the spatial or angular resolution of the final image 624 corresponds to the quantity and density of the discrete intersections 626. That is, the spatial or angular resolution of the final image 624 corresponds to how much of the original image 608 is preserved after the corresponding light propagates through the waveguide 500.

[0054] A first set of intersections 626 correspond to the intersections of lines 622 and 620 from the first image 617, and a second set of intersections 626 correspond to the intersections of lines 618 and 620 from the second image 613. As shown, the first set of intersections is spatially separated from the second set of intersections, such that the final image 624 includes a greater quantity of intersections 626 than are included individually in either the first image 617 or the second image 613. Thus, by splitting the display light 506 into first and second portions 511 and 515 and propagating the first and second portions 511 and 515 through the waveguide 500 via two different optical paths having different propagation angles, the spatial or angular resolution of the final image 624 is advantageously increased, resulting in an improved spatial or angular resolution of the final image 624 (e.g., compared to the output image 408 of FIG. 4 ).

[0055] It should be noted that the number of propagation angles 606 that allow light to successfully propagate through the waveguide 500 via TIR will typically be greater than the number shown in this example, and thus the number of discrete intersection points 626 in the final image 624 will be greater than the number shown in such example. That is, for ease of illustration, a reduced number of propagation angles 606 and intersection points 626 are shown in this example.

[0056] 7 illustrates a partially transparent perspective ("front" view) view of a waveguide 700 (e.g., one embodiment of waveguide 212 of display system 200 of FIG. 2) according to some embodiments. Waveguide 700 includes in-coupler 214, first exit pupil expander 702, second exit pupil expander 704, and out-coupler 216. In some embodiments, each of first exit pupil expander 702 and second exit pupil expander 704 includes an optical grating, such as a diffraction grating or a holographic grating, configured to redirect and expand received display light, thereby expanding one or more dimensions of the eyebox of a display system that includes waveguide 700 (e.g., display system 100 of FIG. 1, display system 200 of FIG. 2). As shown, a first exit pupil expander 702 is positioned with a primary dimension that extends away from the in-coupler 214 in both the negative x-dimension and the positive y-dimension, and a second exit pupil expander 704 is positioned with a primary dimension that extends away from the in-coupler 214 in both the negative x-dimension and the negative y-dimension. In some embodiments, the amount that the first and second exit pupil expanders 702 and 704 extend in the x-dimension (either the positive x-dimension or the negative x-dimension, according to various embodiments) differs from the amount shown, so that the amount that the first and second exit pupil expanders 702 and 704 are bent towards or away from the out-coupler 216 differs from the amount shown. The dimensions of the first exit pupil expander 702 and the second exit pupil expander 704 cause the incoming light to bend in k-space to a k-space position. x Dimension and k y Shifting in both dimensions.

[0057] In operation, a light source, such as an embodiment of the optical engine 208 of FIG. 2, outputs display light 706 into the waveguide 700 along a first trajectory 708. The in-coupler 214 splits the display light 706 into a first portion 711 (sometimes referred to herein as the “first portion of the display light 711”) and a second portion 715 (sometimes referred to herein as the “second portion” of the display light 715). In some embodiments, the in-coupler 214 includes a two-dimensional grating. In some embodiments, the in-coupler 214 includes two one-dimensional gratings. In some embodiments, the display light 706 conveys an image, sometimes referred to herein as the “original” image, the first portion of the display light 711 conveys the first image, the second portion of the display light 715 conveys the second image, and the combined first and second portions of the display light 711 and 715 output via the out-coupler 216 convey a “final” image that is a combination of the first and second images.

[0058] In some embodiments, each of the first image and the second image corresponds to an original image, but due to discretization as the first portion of the display light 711 and the second portion of the display light 715 pass through the waveguide 700 along different optical paths, each different portion of the original image suffers from a more significant loss of image information in each of the first image and the second image. The in-coupler 214 redirects the first portion of the display light 711 along a second trajectory 710 toward the first exit pupil expander 702. In this example, the second trajectory 710 extends in a positive y dimension and a negative x dimension. The first exit pupil expander 702 redirects the first portion of the display light 711 along a third trajectory 712 to the out-coupler 216. In this example, the third trajectory 712 extends in a negative x dimension and a negative y dimension. The out-coupler redirects the first portion of the display light 711 out of the waveguide 700 such that the first portion of the display light 711 is output along a fourth trajectory 714 toward the user's eye 722. The in-coupler 214 redirects the second portion of the display light 715 along a fifth trajectory 716 toward the second exit pupil expander 704. In this example, the fifth trajectory 716 extends in the negative y dimension and the negative x dimension. The second exit pupil expander 704 redirects the second portion of the display light 715 toward the out-coupler 216 via a sixth trajectory 718. In this example, the sixth trajectory 718 extends in the positive y dimension and the negative x dimension. The out-coupler 216 redirects the second portion of the display light 715 out of the waveguide 700 toward the user's eye 722 via a seventh trajectory 720. The first trajectory 708, the fourth trajectory 714, and the seventh trajectory 720, in some embodiments, are parallel or substantially (eg, within about 7%) parallel to one another.

[0059] In this example, the second trajectory 710, the third trajectory 712, and the fourth trajectory 714 are considered to be first optical paths through the waveguide 700, and the fifth trajectory 716, the sixth trajectory 718, and the seventh trajectory 720 are considered to be second optical paths through the waveguide 700, where the first optical paths are different from the second optical paths. For example, at least a portion of the propagation angle of the first portion of the display light 711 as it travels along the first optical path trajectory is different from an otherwise corresponding propagation angle of the second portion of the second display light 715 as it travels along the second optical path.

[0060] Each time the trajectory of the display light (e.g., display light 706, first portion of display light 711, second portion of display light 715) in the waveguide 700 is changed (e.g., due to incidence on a diffraction grating such as in-coupler 214, first exit pupil expander 702, second exit pupil expander 704, or out-coupler 216), a portion of the image information of the image conveyed by that light will suffer a larger loss, while the remaining portion of the image will suffer a lesser loss. For example, the portion of the image that is preserved (i.e., the portion having image information that does not suffer a large loss) corresponds to the portion of the display light propagating at a propagation angle at which TIR is achievable through the waveguide 700, while the portion of the light that is not preserved (i.e., the portion having image information that suffers a larger loss) corresponds to the portion of the display light propagating at any other propagation angle. The first image conveyed by the first portion of display light 711 and the second image conveyed by the second portion of display light 715 each correspond to at least a portion of the original image. Because the first portion of display light 711, as it travels along the second optical path, travels along a first optical path having a propagation angle different from the propagation angle of the second portion of display light 715, the preserved portion of the original image carried by the first portion of display light 711 differs from the preserved portion of the original image carried by the second portion of display light 715.

[0061] In some embodiments, a first portion of the display light 711 that conveys a first image utilizes a first set of light modes, and a second portion of the display light 715 that conveys a second image utilizes a second set of light modes, and the first portion of the display light 711 and the second portion of the display light 715 traverse spatially distinct paths. That is, the first set of light modes and the second set of light modes are non-overlapping or partially non-overlapping with each other, and each of the first set of light modes and the second set of light modes correspond to a different portion of the original image. In this way, the density of light modes utilized to convey the final image is increased compared to the density of light modes utilized to convey the first image alone and the second image alone (e.g., compared to a waveguide that includes only one of the first or second light paths).

[0062] Thus, the final image output via the out-coupler 216 has a higher spatial or angular resolution than either the first image or the second image alone. By redirecting the display light 706 through the waveguide 700 via multiple optical paths, the spatial or angular resolution of the image transmitted via the waveguide 700 is therefore advantageously improved. Furthermore, because the first and second exit pupil expanders 702 and 704 are not required to extend away from the in-coupler 214 in this example only in the positive and negative y dimensions, the alignment of the first and second exit pupil expanders 702 and 704 becomes essentially a free variable that can be adjusted to improve the efficiency, uniformity, and eyebox size of the display and reduce the size of the waveguide 700.

[0063] Figure 8 shows a chart 800 representing the propagation of display light through the waveguide 700 of Figure 7 relative to k-space. That is, chart 800 is a k-space chart corresponding to a two-dimensional (2D) generalization of the waveguide 700. Accordingly, some aspects of the present example are described with respect to the waveguide 700 and its elements.

[0064] For light of a given wavelength λ in a material with bulk refractive index n, the total luminous intensity of the light's propagation vector through the waveguide 700 is k=(2πn) / λ. A given propagation angle in 2D k-space can be represented as a circle, and k 2 =k x 2 +k y 2 8. Only light traveling at propagation angles between first boundary angle 802 and second boundary angle 804 can propagate along waveguide 700 via TIR. Furthermore, only light traveling at discrete propagation angles (i.e., discrete polar angles) represented by line 806 (the dashed circle located between first boundary angle 802 and second boundary angle 804) can travel along waveguide 700 via TIR. Line 806 may be referred to herein as "propagation angle 806."

[0065] Initially, the display light 706 entering the waveguide 700 at the incoupler 214 is centered at or around the origin of the chart 800. Here, an original image 808 represents the image carried by the display light 706. The original image 808 is initially located at a first location 810 relative to k-space as it enters the waveguide 700 along a first trajectory 708. When the display light 706 is redirected by the incoupler 214, the original image is split into a first image 817 carried by a first portion of the display light 711 and a second image 813 carried by a second portion of the display light 715. When the first portion of the display light 711 is redirected by the incoupler 214, the first image 817 is shifted in k-space to a second location 816, resulting in a positive k-space image. y Dimension and negative k x When the second portion of the display light 715 is redirected by the intercoupler 214, the second image 813 is shifted in k-space to a third location 812, corresponding to a negative k y Dimension and negative k x When the first portion of the display light 711 is redirected by the first exit pupil expander 702, the first image 817 is shifted in k-space to a fourth position 814, corresponding to a negative k y Dimension, and negative k xWhen the second portion of the display light 715 is redirected by the second exit pupil expander 704, the second image 813 is shifted in k-space to a fourth position 814, corresponding to a shift in the positive k dimension. y Dimension, and negative k x When the first portion of display light 711 and the second portion of display light 715 are redirected by outcoupler 216, first image 817 and second image 813 are combined to form final image 824, which is returned to first location 810 in k-space and shifted to positive k x Upon redirection of the first and second portions of the display lights 711 and 715 by the intercoupler 214, (k y (not just dimension)k x Dimension and k y By shifting the first and second images 817 and 813 in both dimensions, in some embodiments, the efficiency, uniformity, and eyebox size of the corresponding display are improved while reducing the size of the waveguide 700.

[0066] In some embodiments, the first image 817 and the second image 813 are each a representation of the original image 808. In some embodiments, the first image 817 corresponds to a first spatial portion of the original image 808, and the second image 813 corresponds to a second spatial portion of the original image 808. In certain embodiments, the first and second portions of the original image 808 partially overlap. In some embodiments, the first image 817 corresponds to a first representation of the original image 808 that includes only a first set of wavelengths of light (i.e., colors) of the original image 808, and the second image 813 corresponds to a second representation of the original image 808 that includes only a second set of wavelengths of light (i.e., colors) of the original image 808, where the first set of wavelengths of light is at least partially different from the second set of wavelengths of light.

[0067] In this example, it is assumed that the angle at which the display light 706 enters the waveguide 700 via the in-coupler 214 is the same or substantially the same (e.g., within 5%) as the angles at which the first and second portions of the display light 711 and the display light 715 exit the waveguide 700 via the out-coupler 216. In the second position 816, only light carrying portions of the first image 817 where the lines 822 (corresponding to a portion of the subset of the lines 806) overlap can propagate along the waveguide 700 via TIR. In the third position 812, only light carrying portions of the second image 813 where the lines 818 (corresponding to a portion of the subset of the lines 806) overlap can propagate along the waveguide 700 via TIR. In the fourth position 814, only light carrying portions of the first image 817 and the second image 813 where the lines 820 (corresponding to a portion of the subset of the lines 806) overlap can propagate along the waveguide 700. Thus, when the final image 824 is redirected out of the waveguide 700, it returns to the first location 810 (due to the shifting and combining of the first image 817 and the second image 813 at the outcoupler 216).

[0068] Only the portions of the original image 808 that correspond to the discrete intersections 826 are preserved in the final image 824. For example, the intersections 826 include portions of the first image 817 where the intersections of lines 822 and 820 overlap, and portions of the second image 813 where the intersections of lines 818 and 820 overlap (these intersections correspond to the points where the corresponding lines would intersect if they were to overlap as shown). At least some of the image information corresponding to portions of the original image 808 that are not located at the intersections 826 is lost because the corresponding light does not propagate normally through the waveguide 700 via TIR. In some embodiments, the spatial or angular resolution of the final image 824 corresponds to the quantity and density of the discrete intersections 826. That is, the spatial or angular resolution of the final image 824 corresponds to how much of the original image 808 is preserved after the corresponding light propagates through the waveguide 700.

[0069] A first set of intersections 826 correspond to the intersections of lines 822 and 820 from the first image 817, and a second set of intersections 826 correspond to the intersections of lines 818 and 820 from the second image 813. As shown, the first set of intersections is spatially separated from the second set of intersections, such that the final image 824 includes a greater quantity of intersections 826 than the quantity of such intersections included individually in either the first image 817 or the second image 813. Thus, by splitting the display light 706 into first and second portions 711 and 715 and propagating the first and second portions 711 and 715 through the waveguide 700 via two different optical paths having different propagation angles, the spatial or angular resolution of the final image 824 is advantageously increased, resulting in an improved spatial or angular resolution of the final image 824 (e.g., compared to the output image 408 of FIG. 4 ).

[0070] It should be noted that the number of propagation angles 806 that allow light to successfully propagate through the waveguide 700 via TIR will typically be greater than the number shown in this example, and thus the number of discrete intersection points 826 in the final image 824 will be greater than the number shown in such example. That is, for ease of illustration, a reduced number of propagation angles 806 and intersection points 826 are shown in this example.

[0071] 9 illustrates a partially transparent perspective ("front" view) view of a waveguide 900 (e.g., one embodiment of waveguide 212 of display system 200 of FIG. 2) according to some embodiments. Waveguide 900 includes in-coupler 214, first exit pupil expander 902, second exit pupil expander 904, and out-coupler 216. In some embodiments, each of first exit pupil expander 902 and second exit pupil expander 904 includes an optical grating, such as a diffraction grating or a holographic grating, configured to redirect and expand received display light, thereby expanding one or more dimensions of the eyebox of a display system that includes waveguide 900 (e.g., display system 100 of FIG. 1, display system 200 of FIG. 2).

[0072] 2 outputs display light 906 into waveguide 900 along a first trajectory 908. In-coupler 214 splits display light 906 into a first portion 911 (sometimes referred to herein as the “first portion of display light 911”), a second portion 915 (sometimes referred to herein as the “second portion” of display light 915), and a third portion 925 (sometimes referred to herein as the “third portion” of display light 925). In some embodiments, the display light 906 conveys an image referred to herein as the “original” image, the first portion of the display light 911 conveys the first image, the second portion of the display light 915 conveys the second image, the third portion of the display light 925 conveys the third image, and the combined first portion of the display light 911, the second portion of the display light 915, and the third portion of the display light 925 output via the outcoupler 216 convey a “final” image that is a combination of the first and second images. In some embodiments, each of the first image, the second image, and the third image corresponds to the original image, but due to discretization as the first portion of the display light 911, the second portion of the display light 915, and the third portion of the display light 925 each travel along a different optical path through the waveguide 900, image information corresponding to different portions of the original image is at least partially lost in each of the first image, the second image, and the third image. In some embodiments, the third image represents only a portion of the original image and the geometry of the third image is not expanded by the exit pupil expander in the same way that the geometry of the first and second images is expanded by the first and second image pupil expanders 902 and 904, resulting in an improvement in the spatial or angular resolution of only a portion of the final image.

[0073] The in-coupler 214 redirects a first portion of the display light 911 toward the first exit pupil expander 902 along a second trajectory 910. In this example, the second trajectory 910 extends in a positive y dimension and a negative x dimension. The first exit pupil expander 902 redirects the first portion of the display light 911 toward the out-coupler 216 along a third trajectory 912. In this example, the third trajectory 912 extends in a negative x dimension and a negative y dimension. The out-coupler redirects the first portion of the display light 911 out of the waveguide 900 such that the first portion of the display light 911 is output toward the user's eye 922 along a fourth trajectory 914. The in-coupler 214 redirects a second portion of the display light 915 toward the second exit pupil expander 904 along a fifth trajectory 916. In this example, the fifth trajectory 916 extends in the negative y dimension and the negative x dimension. The second exit pupil expander 904 redirects a second portion of the display light 915 towards the out-coupler 216 via a sixth trajectory 918. In this example, the sixth trajectory 918 extends in the positive y dimension and the negative x dimension. The out-coupler 216 redirects a second portion of the display light 915 out of the waveguide 900 towards the user's eye 922 via a seventh trajectory 920. The in-coupler 214 redirects a third portion of the display light 925 towards the out-coupler 216 via an eighth trajectory 924. In this example, the ninth trajectory 924 extends in the negative x dimension. The out-coupler 216 redirects a third portion of the display light 926 out of the waveguide 900 towards the user's eye 922 via a ninth trajectory 926. The first trajectory 908, the fourth trajectory 914, the seventh trajectory 920, and the ninth trajectory 926, in some embodiments, are parallel or substantially (e.g., within about 5%) parallel to one another.

[0074] In this example, the second trajectory 910, the third trajectory 912, and the fourth trajectory 914 are considered to be a first optical path through the waveguide 900, the fifth trajectory 916, the sixth trajectory 918, and the seventh trajectory 920 are considered to be a second optical path through the waveguide 900, and the eighth trajectory 924 and the ninth trajectory 926 are considered to be a third path through the waveguide 900, where the first optical path, the second optical path, and the third optical path are each different from each other. For example, at least a portion of the propagation angle of the first portion of the display light 911 when traveling along the first optical path trajectory is different from the corresponding propagation angle of the second portion of the second display light 915 when traveling along the second optical path, and is different from the otherwise corresponding propagation angle of the third display light 925 when traveling along the third optical path trajectory.

[0075] Each time the trajectory of the display light (e.g., display light 906, first portion of display light 911, second portion of display light 915, third portion of display light 925) within the waveguide 900 is changed (e.g., due to incidence on a diffraction grating, such as in-coupler 214, first exit pupil expander 902, second exit pupil expander 904, or out-coupler 216), at least a portion of the image information of a portion of the image conveyed by that light is lost, while the remaining portion of the image is substantially preserved. For example, the portion of the image that is preserved corresponds to the portion of the display light propagating at a propagation angle at which TIR is achievable through the waveguide 900, while the portion of the image that is not fully preserved (i.e., image information is partially lost) corresponds to the portion of the display light propagating at any other propagation angle. Because the first portion of display light 911, the second portion of display light 915, and the third portion of display light 925 each travel through the waveguide 900 along a different optical path having a different propagation angle, the stored portion of the first image carried by the first portion of display light 911, the stored portion of the second image carried by the second portion of display light 915, and the stored portion of the third image carried by the third portion of display light 925 are each different from one another. Thus, in some embodiments, the final image output via outcoupler 216 has a higher spatial or angular resolution than any one of the first image, the second image, or the third image alone.

[0076] In some embodiments, the first portion of the display light 911 conveying the first image utilizes a first set of light modes, the second portion of the display light 915 conveying the second image utilizes a second set of light modes, and the third portion of the display light 925 utilizes a third set of light modes. The first portion of the display light 911, the second portion of the display light 915, and the third portion of the display light 925 traverse spatially distinct paths. That is, the first set of light modes and the second set of light modes are non-overlapping or partially non-overlapping with each other, and each of the first set of light modes and the second set of light modes correspond to a different portion of the original image. In this way, the density of light modes utilized to convey the final image is increased compared to the density of light modes utilized to convey the first image alone or the second image alone (e.g., compared to a waveguide including only one of the first or second light paths).

[0077] By redirecting the display light 906 through the waveguide 900 via multiple optical paths, therefore, the spatial or angular resolution of the image transmitted through the waveguide 900 is advantageously increased. Furthermore, by providing the third portion of the display light 925 directly from the in-coupler 214 to the out-coupler 216 without an intervening structure (e.g., an exit pupil expander or other analysis grating), the change in propagation angle of the third portion of the display light 925 as it traverses the waveguide 900 is less, resulting in less shift of the third image in k-space and a larger portion of the original image (or, in some embodiments, a larger portion of the region of the original image to which the third image corresponds) being retained in the third image than the first and second images.

[0078] In some embodiments, because the propagation length along the third optical path is shorter than both the propagation lengths along the first and second optical paths, the third portion of the display light 925 propagating along the third optical path experiences less scattering (e.g., due to surface or bulk material features or non-idealities) than the first and second portions of the display light 911 and 915 propagating along the first and second optical paths, thereby further improving the spatial or angular resolution of the third image and the corresponding portions of the final image, respectively. In some embodiments, this example configuration improves the spatial or angular resolution of a target region of the field of view (FOV) of the display device that corresponds to a portion of the final image output by the waveguide.

[0079] Figure 10 shows a chart 1000 representing the propagation of display light through the waveguide 900 of Figure 9 relative to k-space. That is, chart 1000 is a k-space chart corresponding to a two-dimensional (2D) generalization of the waveguide 900. Accordingly, some aspects of the present example are described with respect to the waveguide 900 and its elements.

[0080] For light of a given wavelength λ in a material with bulk refractive index n, the total luminous intensity of the light's propagation vector through the waveguide 900 is k=(2πn) / λ. A given propagation angle in 2D k-space can be represented as a circle, k 2 =k x 2 +k y 2 10. Only light traveling at propagation angles between the first boundary angle 1002 and the second boundary angle 1004 can propagate along the waveguide 900 via TIR. Furthermore, only light traveling at discrete propagation angles (i.e., discrete polar angles) represented by line 1006 (the dashed circle located between the first boundary angle 1002 and the second boundary angle 1004) can propagate along the waveguide 900 via TIR. Line 1006 may be referred to herein as "propagation angle 1006."

[0081] Initially, the display light 906 entering the waveguide 900 at the incoupler 214 is centered at or around the origin of the chart 1000. Here, an original image 1008 represents the image carried by the display light 906. The original image 1008 is initially located at a first location 1010 relative to k-space as it enters the waveguide 900 along a first trajectory 908. When the display light 906 is redirected by the incoupler 214, the original image is split into a first image 1017 carried by a first portion of the display light 911, a second image 1013 carried by a second portion of the display light 915, and a third image 1021 carried by a third portion of the display light 925. When the first portion of the display light 911 is redirected by the incoupler 214, the first image 1017 is shifted in k-space to a second location 1016, resulting in a positive k-space image. y When the second portion of the display light 915 is redirected by the intercoupler 214, the second image 1013 is shifted in k-space to a third location 1012, corresponding to a negative k y When the third portion of the display light 925 is redirected by the intercoupler 214, the third image 1021 is shifted in k-space to a fourth location 1014, corresponding to a negative k x When the first portion of the display light 911 is redirected by the first exit pupil expander 902, the first image 1017 is shifted in k-space to a fourth position 1014, corresponding to a negative k y Dimension, and negative k x When the second portion of the display light 915 is redirected by the second exit pupil expander 904, the second image 1013 is shifted in k-space to a fourth position 1014, corresponding to a shift in the positive k-dimension. y Dimension, and negative k x When the first portion of display light 911, the second portion of display light 915, and the third portion of display light 925 are redirected by outcoupler 216, first image 1017, second image 1013, and third image 1021 are combined to form final image 1024, which is returned to first location 1010 in k-space and is aligned with positive k x This corresponds to a dimensional shift.

[0082] In some embodiments, the first image 1017 and the second image 1013 are each a representation of the original image 1008. In some embodiments, the first image 1017 corresponds to a first spatial portion of the original image 1008, and the second image 1013 corresponds to a second spatial portion of the original image 1008. In certain embodiments, the first and second portions of the original image 1008 partially overlap. In some embodiments, the first image 1017 corresponds to a first representation of the original image 1008 that includes only a first set of wavelengths (i.e., colors) of display light for the original image 1008, and the second image 1013 corresponds to a second representation of the original image 1008 that includes only a second set of wavelengths (i.e., colors) of display light for the original image 1008, where the first set of wavelengths of display light is at least partially different from the second set of wavelengths of display light.

[0083] In this example, it is assumed that the angle at which the display light 906 enters the waveguide 900 via the in-coupler 214 is the same or substantially the same (e.g., within 5%) as the angle at which the first portion of the display light 911, the second portion of the display light 915, and the third portion of the display light 925 exit the waveguide 900 via the out-coupler 216. In the second position 1016, only light conveying a portion of the first image 1017 where the lines 1022 (corresponding to a portion of the subset of the lines 1006) overlap can propagate normally along the waveguide 900 via TIR. In the third position 1012, only light conveying a portion of the second image 1013 where the lines 1018 (corresponding to a portion of the subset of the lines 1006) overlap can propagate normally along the waveguide 900 via TIR. At the fourth position 1014, only light carrying portions of the first image 1017, the second image 1013, and the third image 1021 where the lines 1020 (corresponding to a portion of the subset of lines 1006) overlap can propagate normally along the waveguide 900. Thus, the final image 1024, upon being redirected out of the waveguide 900, returns to the first position 1010 (due to the shifting and combining of the first image 1017, the second image 1013, and the third image 1021 at the outcoupler 216).

[0084] In this example, only those portions of the original image 1008 that correspond to the discrete intersection points 1026 and those portions that correspond to the lines 1028 (e.g., corresponding to the line 1020) are preserved (i.e., the light carrying the first and second images 1017 and 1013 propagates normally through the waveguide 900). For example, the intersection points 1026 include the intersection points of the lines 1022 and 1020 from the first image 1017 and the intersection points of the lines 1018 and 1020 from the second image 1013 (these intersection points correspond to points where the corresponding lines would intersect if they were to overlap as shown). The line 1028 corresponds to the portion of the third image 1021 where the line 1020 overlaps. Other portions of the original image 1008 that do not correspond to the discrete intersection points 1026 or the lines 1028 are not fully propagated through the waveguide 900 and the corresponding image information is at least partially lost. Each of the lines 1028 represents a different region of the viewing angle, with the shape of a given region of the viewing angle corresponding to the region of the third image 1021 where the lines 1020 overlap at the fourth location 1014. In some embodiments, each of the intersections 1026 corresponds to a different sub-region of one of the regions of the viewing angle represented by the lines 1028.

[0085] The third portion of the display light 925 carrying the third image 1021 travels directly from the in-coupler 214 to the out-coupler 216 via TIR without being incident on an intervening diffraction grating (e.g., an exit pupil expander), so that the portion of the third image 1021 where the lines 1020 overlap is preserved. For example, when the third portion of the display light 925 propagates through the waveguide 900 along the third optical path, a greater amount of the third image 1021 is preserved than the amount of the first image 1017 and the second image 1013 that is preserved due to the absence of an intervening diffraction grating (e.g., an exit pupil expander) in the optical path of the third portion of the display light 925 between the in-coupler 214 and the out-coupler 216. Because the display light carrying the unstored image portions does not propagate normally through the waveguide 900 via TIR, the image information of the original image 1008 corresponding to the first image 1017, the second image 1013, and the third image 1021 that are not stored suffers from a greater loss than the image information of the original image 1008 corresponding to the portions of the first image 1017, the second image 1013, and the third image 1021 that are stored. The spatial or angular resolution of the final image 1024 corresponds to the quantity and density of the discrete intersections 1026 and lines 1028. That is, the spatial or angular resolution of the final image 1024 corresponds to how much of the original image 1008 is preserved after the corresponding light (e.g., the first portion of the display light 911, the second portion of the display light 915, and the third portion of the display light 925) propagates through the waveguide 900.

[0086] A first set of intersections of the intersections 1026 correspond to the intersections of the lines 1022 and 1020 from the first image 1017, and a second set of intersections of the intersections 1026 correspond to the intersections of the lines 1018 and 1020 from the second image 1013. As shown, the first set of intersections is spatially separated from the second set of intersections. In some embodiments, the final image 1024 includes a greater amount of the original image 1008 than is included individually in either the first image 1017 or the second image 1013. In some embodiments, the brightness of the final image 1024 is greater at the intersections 1026 than at the corresponding locations of the third image 1021 (corresponding portions of the lines 1028). Therefore, by splitting display light 906 into a first portion of display light 911, a second portion of display light 915, and a third portion of display light 925, and propagating the first portion of display light 911, the second portion of display light 915, and the third portion of display light 925 through waveguide 900 via three different optical paths having different propagation angles, the density and quantity of intersection points / optical modes in final image 1024 is advantageously increased, and as a result, the spatial or angular resolution of final image 1024 is increased (e.g., compared to output image 408 in FIG. 4 ).

[0087] It should be noted that the number of propagation angles 1006 that allow light to successfully propagate through the waveguide 900 via TIR will typically be greater than the number shown in this example, and thus the number of discrete intersection points 1026 and lines 1028 in the final image 1024 will be greater than the number shown in such example. That is, for ease of illustration, a reduced number of propagation angles 1006, intersection points 1026, and lines 1028 are shown in this example.

[0088] In addition to what is described, it should be noted that not all activities or elements described above in the general description are required, and that some of the specific activities or devices may not be required, and that one or more additional activities may be performed or elements may be included. Furthermore, the order in which the activities are listed is not necessarily the order in which they are performed. Also, the concepts have been described with reference to specific embodiments. However, those skilled in the art will appreciate that various modifications and variations can be made without departing from the scope of the present disclosure, as set forth in the following claims. Thus, the specification and drawings should be regarded in an illustrative rather than restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure.

[0089] Benefits, other advantages, and solutions to problems have been described above with respect to specific embodiments. However, the benefits, advantages, and solutions to problems, as well as any features that may give rise to or make more pronounced any benefit, advantage, or solution, are not to be construed as critical, necessary, or essential features of any or all claims. Moreover, the specific embodiments disclosed above are illustrative only, as the disclosed inventive subject matter may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. No limitations to the details of construction or design shown herein are intended, other than as set forth in the claims that follow. It is therefore apparent that the specific embodiments disclosed above may be altered or modified, and all such variations are contemplated within the scope of the disclosed inventive subject matter. Accordingly, the protection sought herein is as set forth in the claims that follow.

Claims

1. A waveguide comprising: receiving a display light representative of an image for display; and directing a first portion of the display light to propagate within the waveguide along a first optical path and directing a second portion of the display light to propagate within the waveguide along a second optical path, the first optical path and the second optical path having substantially non-overlapping propagation angles, the waveguide further comprising: a waveguide comprising an outcoupler configured to combine the first portion of the display light and the second portion of the display light to display a representation of the image.

2. the first portion of the display light corresponds to a first spatial portion of the image; The waveguide of claim 1 , wherein the second portion of the display light corresponds to a second spatial portion of the image.

3. The waveguide of claim 2 , wherein the first spatial portion of the image and the second spatial portion of the image partially overlap.

4. the first portion of the display light comprises a first set of wavelengths; The waveguide of claim 1 , wherein the second portion of the display light comprises a second set of wavelengths different from the first set.

5. The waveguide is a first exit pupil expander disposed in the first optical path and configured to redirect the first portion of the display light towards the outcoupler; a second exit pupil expander disposed in the first optical path and configured to redirect the second portion of the display light towards the out-coupler; The waveguide of claim 1 , comprising:

6. The waveguide of claim 1 , wherein the outcoupler is configured to combine the first portion of the display light with the second portion of the display light to display the representation.

7. The inter-coupler includes: receiving the display light from an optical engine; splitting the display light into at least the first portion of the display light and the second portion of the display light; redirecting the first portion of the display light to propagate within the waveguide along the first optical path; redirecting the second portion of the display light to propagate within the waveguide along the second optical path; The waveguide of claim 1 , further configured to:

8. 8. The waveguide of claim 7, wherein the inter-coupler is further configured to split the display light into a third portion of the display light and to guide the third portion of the display light to propagate along a third optical path different from the first optical path and the second optical path.

9. The waveguide of claim 8 , wherein the representation is a combination of the first portion of the image, the second portion of the image, and the third portion of the image.

10. 1. A method comprising: receiving a display light representative of an image for display; directing a first portion of the display light to propagate within a waveguide along a first optical path and directing a second portion of the display light to propagate within the waveguide along a second optical path, the first optical path and the second optical path having respective non-overlapping propagation angles, the method further comprising: combining the first portion of the display light with the second portion of the display light to display a representation of the image.

11. the first portion of the display light conveys a first spatial portion of the image; The method of claim 10 , wherein the second portion of the display light propagates to a second spatial portion of the image.

12. The method of claim 11 , wherein the first spatial portion of the image and the second spatial portion of the image partially overlap.

13. directing the first portion of the display light along the first optical path includes directing a first set of wavelengths of the display light along the first optical path; directing the second portion of the display light along the second optical path includes directing a second set of wavelengths of the display light along the second optical path; The method of claim 10 , wherein the second set of wavelengths is different from the first set.

14. redirecting the first portion of the display light toward an outcoupler of the waveguide using a first exit pupil expander disposed in the first optical path; redirecting the second portion of the display light toward the out-coupler with a second exit pupil expander disposed in the second optical path; The method of claim 10 further comprising:

15. The method of claim 14 , further comprising combining, with the outcoupler, the first portion of the display light and the second portion of the display light to display the representation.

16. receiving the display light from an optical engine using a waveguide in-coupler; splitting the display light into at least the first portion of the display light and the second portion of the display light by the in-coupler; redirecting, by the in-coupler, the first portion of the display light to propagate within the waveguide along the first optical path; redirecting, by the in-coupler, the second portion of the display light to propagate within the waveguide along the second optical path; The method of claim 10, comprising:

17. splitting the display light into a third portion; directing the third portion of the display light to propagate along a third optical path different from the first optical path and the second optical path; The method of claim 10 further comprising:

18. 20. The method of claim 17, further comprising displaying the representation by combining the first portion of the display light, the second portion of the display light, and the third portion of the display light.

19. An optical engine; a waveguide; The waveguide is configured to receive display light representative of an image for display; configured to direct a first portion of the display light for propagation within the waveguide along a first optical path and direct a second portion of the display light for propagation within the waveguide along a second optical path, the first optical path and the second optical path having respective non-overlapping propagation angles, the waveguide further comprising: a projection system configured to combine the first portion of the display light and the second portion of the display light to display a representation of the image.

20. 20. The projection system of claim 19, wherein the waveguide is further configured to split the display light into a third portion and to guide the third portion of the display light to propagate along a third optical path distinct from the first optical path and the second optical path.

Images