Three-color waveguide exit pupil expansion system with optical power

Abstract

A system for displaying a virtual image (310) to a user comprises a light engine (111) that generates display light (290) representing the virtual image, a diffractive waveguide (335) that focuses a first component light of the generated display light at a first focal distance from an eye of the user and focuses one or more additional component lights of the generated display light at one or more different other focal distances from the eye of the user, and one or more processors (1002) communicatively coupled to the light engine and configured to modify the virtual image to correct for a perceived distortion of at least one of the one or more additional component lights.

Description

[Background technology]

[0001] The present disclosure generally relates to augmented reality (AR) eyewear that blends real-world views with a head-up display overlay. A wearable head-up display (WHUD) is a wearable electronic device that uses an optical combiner to combine the real world with a virtual image. The optical combiner may be integrated with one or more lenses to provide a combiner lens that can be incorporated into the support frame of the WHUD. In operation, the combiner lens provides a virtual display that the user can see when the WHUD is worn on the user's head. Some optical combiners transmit light using a waveguide (also called a light guide). Generally, light from a projector of the WHUD enters the combiner's waveguide through an in-coupler, propagates along the waveguide via total internal reflection (TIR), and exits the waveguide through an out-coupler. When the pupil of the eye is aligned with one or more exit pupils provided by the out-coupler, at least a portion of the light exiting the out-coupler enters the pupil of the eye, thereby allowing the user to see the virtual image. The combiner lens is transparent so the user can still see the real world. Summary of the Invention

[0002] Described herein are embodiments in which a virtual image (a projected image of a virtual object) is displayed to a user via a light engine that generates display light representative of the virtual image, a diffractive waveguide, and one or more processors communicatively coupled to the light engine. A first component light of the generated display light is focused via the diffractive waveguide at a first focal distance from the user's eye, and one or more additional component lights of the generated display light are focused at one or more different other focal distances from the user's eye. The virtual image is modified to correct a perceived distortion of at least one component light of the virtual image resulting from the different focal distances.

[0003] In certain embodiments, a system for displaying a virtual image to a user includes a light engine that generates display light representing the virtual image, a diffractive waveguide that focuses a first component light of the generated display light at a first focal distance from an eye of a user and focuses one or more additional component lights of the generated display light at one or more different other focal distances from the eye of the user, and one or more processors communicatively coupled to the light engine and configured to modify the virtual image to correct for a perceived distortion of at least one of the one or more additional component lights.

[0004] The first component light of the generated display light may include a first color component light, and the one or more additional component lights may include at least one of a group including a second color component light of the generated display light, or a third color component light of the generated display light.

[0005] The first color component light of the generated display light may include green component light having a wavelength of 495 nm to 570 nm.

[0006] Modifying the virtual image may include performing one or more deconvolution operations on the virtual image. The one or more deconvolution operations may be performed utilizing a blur kernel associated with the at least one additional component light. The blur kernel may be generated based on one or more measurements of an angular spread of the at least one additional component light at the first focal length. The blur kernel may be generated based on modeling an angular spread of the at least one additional component light at the first focal length.

[0007] The one or more additional component lights may include blue component light and red component light, whereby a first blur kernel may be generated based on an angular spread of the blue component light at the first focal length and a second blur kernel may be generated based on a second angular spread of the red component light at the first focal length.

[0008] The system may further include an in-coupler optically coupled to the diffractive waveguide, the in-coupler receiving the display light from the light engine and directing the received display light to the diffractive waveguide, and the system may further include an out-coupler optically coupled to the diffractive waveguide, the out-coupler directing at least a portion of the display light from the diffractive waveguide to a user's eye.

[0009] The system may further comprise a memory storing instructions that, when executed by the one or more processors, cause the one or more processors to modify the virtual image before the light engine generates the display light.

[0010] In certain embodiments, the system may be included within a wearable head-up display (WHUD).

[0011] In certain embodiments, a method of displaying a virtual image to a user may include receiving a virtual image by one or more processors, modifying, by the one or more processors, the virtual image via one or more pre-processing operations to generate a modified virtual image, generating, by a light engine, display light representative of the modified virtual image, receiving the display light from the light engine and directing the received display light to a diffractive waveguide, and directing at least a portion of the display light from the diffractive waveguide to an eye of the user. Directing the portion of the display light may include focusing a first component light of the generated display light at a first focal distance away from the eye of the user and focusing one or more additional component lights of the generated display light at one or more different other focal distances away from the eye of the user.

[0012] The first component light of the generated display light may include a first color component light, whereby the one or more additional component lights include at least one of a group including a second color component light of the generated display light, or a third color component light of the generated display light. The first color component light of the generated display light may include a green component light having a wavelength of 495 nm to 570 nm.

[0013] Modifying the virtual image via the one or more pre-processing operations may include performing one or more deconvolution operations on the virtual image. Performing the one or more deconvolution operations may include utilizing a blur kernel associated with the at least one additional component light.

[0014] The method may further include generating a blur kernel based on one or more measurements of an angular spread of the at least one additional component light at the first focal length.

[0015] The method may further include generating a blur kernel based on modeling an angular spread of the at least one additional component light at the first focal length.

[0016] The one or more additional component lights may include blue component light and red component light, whereby the method further includes generating a first blur kernel based on an angular spread of the blue component light at the first focal length and generating a second blur kernel based on the angular spread of the red component light at the first focal length.

[0017] The method may further include receiving the display light from the light engine at an in-coupler optically coupled to the diffractive waveguide, directing the received display light to the diffractive waveguide, and directing at least a portion of the display light from the diffractive waveguide to a user's eye via an out-coupler optically coupled to the diffractive waveguide.

[0018] The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art, by referring to the accompanying drawings. The use of the same reference symbols in different drawings indicates similar or identical items. It is understood that, unless specifically stated otherwise, aspects of the accompanying drawings are not, and are not to be assumed as being, presented to scale. [Brief description of the drawings]

[0019] [Figure 1]1 illustrates an example of a wearable display device according to some embodiments. [Diagram 2] 1 shows a diagram of a wearable display device according to some embodiments. [Diagram 3] FIG. 1 shows a diagram of an augmented reality environment including multiple optical components of a wearable display device. [Figure 4] 1 shows a partial cross-sectional view of a diffractive waveguide surface grating. [Diagram 5] 1 illustrates a partial cross-sectional view of a diffractive waveguide surface grating according to some embodiments. [Figure 6] 1 illustrates a diagram of an augmented reality environment including multiple optical components of a wearable display device according to some embodiments. [Figure 7] 1 illustrates aspects of a virtual image provided by optical components of a wearable display device according to some embodiments. [Figure 8] 1 illustrates aspects of a virtual image provided by optical components of a wearable display device according to some embodiments. [Figure 9] 4 illustrates an operational routine of a display device according to some embodiments. [Figure 10] FIG. 1 is an element-level block diagram illustrating an example of a WHUD computing system suitable for implementing one or more embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] At least in part, because diffractive waveguide architectures typically rely on the light entering and exiting the waveguide being collimated, WHUDs using such waveguides are typically designed to display images that appear to the user's eye to be at an infinite distance from the user (as opposed to real-world objects that are closer to the user), such as the way stars appear when looking at the night sky. While this is a relaxed position for the eye, infinite distance presents a problem when attempting to overlay a virtual image onto a real-world image of the user's perceived surroundings, as the eye simultaneously attempts to focus on and interpret real-world objects perceived at a finite distance and virtual images presented at infinite distance.

[0021] Previous attempts to solve this problem involve displaying an image at a finite distance, typically around 2 meters, by placing a physical lens with positive refractive power between the eye and the waveguide. (As used herein, refractive power refers to the degree to which a lens, mirror, or other optical system converges or diverges light.) However, to ensure that the perceived image of the real world is not affected by the corresponding distortion, an additional corrective physical lens (identical to the first lens but with the opposite refractive power) may be placed on the other side of the waveguide. The resulting architecture is usually successful in "distance shifting" the virtual display, but utilizes correspondingly larger and heavier components, making it typically unsuitable for wearable devices such as WHUDs.

[0022] Alternatively, the refractive power may be applied directly via the diffractive out-coupler of the waveguide exit pupil expander. In certain scenarios and embodiments, such a refractive power may be applied to the out-coupling grating by introducing a slight curvature to the otherwise rectilinear grating. However, due to the way in which the grating interacts with and affects the light exiting the out-coupler, the resulting refractive power does not affect different wavelengths of light equally. In particular, the curvature of such an out-coupler grating affects the angles at which the individual red, green, and blue (RGB) components of the displayed virtual image exit the out-coupler quite differently, such that the components will be perceived by the user's eye as occurring at different focal lengths unless the incorporated device includes multiple different waveguides (e.g., one or more per red, green, and blue spectrum). As with approaches that utilize multiple physical lenses to achieve a desired distance shift of the virtual display, incorporating multiple different waveguides generally corresponds to a larger and heavier device, which, as mentioned above, is not suitable for wearable devices.

[0023] Embodiments of the techniques presented herein provide optical power (such as distance shifting or other purposes) via an out-coupler grating of only a single waveguide. In certain embodiments, the parameters of such an out-coupler grating can be selected to tune the focal length of a full-color virtual image (an image that includes red, green, and blue components) specifically to the peak of human photopic vision, which is typically centered around green light, which has a wavelength of about 555 nm (the wavelength of light that the human visual system primarily uses to perceive image detail).

[0024] From a radiometric perspective, the red and blue light components of the virtual image provided through the single waveguide tuned in this way may appear out of focus or blurred. However, when considering the entire human visual system (including the brain's cognitive image processing), the image will often appear sharp because the human visual system relies primarily on green light to judge sharpness and resolve details. Thus, in this way, refractive power can be applied to the output coupling region of the single waveguide extended-pupil system while maintaining a high degree of visual acuity for the user to perceive the resulting virtual image. Furthermore, embodiments of the techniques described herein can provide a digital pre-processing operation to at least reduce the perceived distortion resulting from the red and blue light components of the virtual image being focused at different focal lengths. For example, the degree of defocus can be determined and used as a basis for generating one or more blur kernels for each of the red and blue light components. As used herein, blur kernel refers to a two- or three-dimensional diffraction pattern generated by a collimated light source passing through an optical path of a display system. The generated blur kernel(s) may then be used to modify the red and / or blue light components of the virtual image before it is provided to the user via the light engine and waveguide.

[0025] FIG. 1 illustrates an example of a wearable display device 100 according to various embodiments. The wearable display device 100 includes a support structure including a first arm 110, a second arm 120, and a front frame 130 physically coupled to the first arm 110 and the second arm 120. When worn by a user, the first arm 110 may be positioned on a first side of the user's head, the second arm 120 may be positioned on a second side of the user's head opposite the first side, and the front frame 130 may be positioned on a front side of the user's head. The first arm 110 is equipped with a light engine 111 that outputs light representing an augmented reality (AR) content to be viewed by the user. The first arm 110 may also optionally be equipped with some additional components of the wearable display device 100, such as a processor, a non-transitory processor-readable storage medium, or a power supply circuit, among other examples. The front frame 130 carries a lens structure 135 with display optics 131 (including a diffractive waveguide (not shown)) within the user's field of view to receive light output from the light engine 111 and redirect the light to form AR content to be seen by the user in combination with a view of the real world (the physical world as seen by the user and that physically exists beyond the display assembly).

[0026] In the example of FIG. 1, the display is a monocular display visible to the right eye of the user. The second arm 120 shown in FIG. 1 carries a power source 121 that provides power to the components of the wearable display device 100. The front frame 130 carries a series of conductive current paths 140 that provide electrical coupling between the power source 121 and the light engine 111 and other electrical components carried by the first arm 110. The term power source as used herein refers to a component that provides power, which may include a storage source such as a battery (e.g., chemical battery, mechanical battery), or a power generation system such as a piezoelectric element, solar cell, or the like. A series of conductive current paths as used herein refers to a single conductive current path, such as a wire or conductive trace on a printed circuit board, and multiple conductive current paths, such as multiple wires or multiple conductive traces on a printed circuit board.

[0027] In various embodiments, aspects of the exemplary wearable display device may be modified in various ways from the illustrated example. For example, in certain embodiments, the orientation of the wearable display device 100 may be reversed so that the display is presented to the user's left eye instead of the right eye. The second arm 120 may carry a light engine similar to the light engine 111 carried by the first arm 110, and the front frame 130 may also carry another lens structure similar to the lens structure 135, such that the wearable display device 100 presents a binocular display to both the user's right and left eyes.

[0028] The light engine 111 and the display optics 131 include any suitable display architecture for outputting light and redirecting the light to form a display seen by a user. For example, in some embodiments, the light engine 111, and any of the light engines described herein, include at least one or more examples of components selected from the group including one of a projector, a scanning laser projector, a microdisplay, a white light source, or any other display technology suitable for a given application. The display optics 131 include at least one or more examples of optical components selected from the group including a wave guide (as used herein, a reference that includes and encompasses both light guides and wave guides), a holographic optical element, a prism, a diffraction grating, an optical reflector, an optical reflector array, an optical refractor, an optical refractor array, or any other light redirection technology suitable for a given application, positioned and oriented to redirect the AR content from the light engine 111 toward the user's eyes.

[0029] The lens structure 135 may include multiple lens layers, each of which may be located closer to the user's eyes (eye side) than the display optics 131 or farther from the user's eyes (world side) than the display optics 131. The lens layers may be molded or cast, may include thin films or coatings, and may include one or more transparent carriers, for example. A transparent carrier as described herein may refer to a material that serves to hold or support the light redirector. As an example, the transparent carrier may be a spectacle lens or lens assembly. Additionally, in certain embodiments, one or more of the lens layers may be implemented as a contact lens.

[0030] Non-limiting example display architectures include a combination of a scanning laser projector and a holographic optical element, a side-illuminated optical light guide display, a pinlight display, or any other wearable head-up display technology suitable for a given application. Various example display architectures are described at least in U.S. Provisional Patent Application No. 62 / 754,339, U.S. Provisional Patent Application No. 62 / 782,918, U.S. Provisional Patent Application No. 62 / 789,908, U.S. Provisional Patent Application No. 62 / 845,956, and U.S. Provisional Patent Application No. 62 / 791,514. The term "light engine" as used herein is not limited to referring to a single light source, but may also refer to multiple light sources and may also refer to a light engine assembly. The light engine assembly may include several components that enable the light engine to function or improve the operation of the light engine. As an example, the light engine may include a light source such as a laser or multiple lasers. The light engine assembly may further include electrical components such as driver circuit wiring that provides power to at least one light source. The light engine assembly may include additional optical elements such as collimation lenses, beam combiners, or beam shaping optics. The light engine assembly may further include beam redirecting optics such as at least one MEMS mirror, which may be operated to scan light from at least one laser light source, such as a scanning laser projector. In the above example, the light engine assembly includes a light source and also includes components that receive the output from the at least one light source and generate a conditioned display light to convey the AR content. All components in the light engine assembly may be included in the light engine assembly housing, may be fixed to a substrate of the light engine assembly, such as a printed circuit board or the like, or may be separately attached as components of a wearable head-up display (WHUD). A specific light engine assembly is described in U.S. Provisional Patent Application No. 62 / 916,297.

[0031] 2 shows a diagram of a wearable display device 200 according to some embodiments. In some embodiments, the wearable display device 200 may implement or be implemented by aspects of the wearable display device 100. For example, the wearable display device 200 may include a first arm 210, a second arm 220, and a front frame 230. The first arm 210 may be coupled to the front frame 230 by a hinge 219, which allows the first arm 210 to rotate relative to the front frame 230. The second arm 220 may be coupled to the front frame 230 by a hinge 229, which allows the second arm 220 to rotate relative to the front frame 230.

[0032] In the example of FIG. 2, the wearable display device 200 may be in an unfolded configuration with the first arm 210 positioned on a first side of the user's head, the second arm 220 positioned on a second side of the user's head opposite the first side, and the front frame 230 positioned in front of the user's head, with the first arm 210 and the second arm 220 rotated so that the wearable display device 200 can be worn on the user's head. The first arm 210 and the second arm 220 can be rotated toward the front frame 230 until both the first arm 210 and the second arm 220 are approximately parallel to the front frame 230, which allows the wearable display device 200 to assume a compact shape that conveniently fits into a rectangular, cylindrical, or oval case. Alternatively, the first arm 210 and the second arm 220 may be fixedly attached to the front frame 230, such that the wearable display device 200 cannot be folded.

[0033] In FIG. 2, the first arm 210 carries a light engine 211. The second arm 220 carries a power source 221. The front frame 230 carries an input coupling light redirector (incoupler) 231, an output coupling light redirector (outcoupler) 233, and a diffractive waveguide 235 including at least one set of conductive current paths, thereby providing electrical coupling between the power source 221 and the electrical components carried by the first arm 210 (such as the light engine 211). Such electrical coupling may be provided indirectly, such as through a power supply circuit, or directly from the power source 221 to each electrical component in the first arm 210. As used herein, the terms "carry," "carries," or similar terms do not necessarily imply that one component physically supports another component. For example, the first arm 210 was described above as carrying the light engine 211. This may mean that the light engine 211 is mounted to or within the first arm 210, such that the first arm 210 physically supports the light engine 211. However, it may also be the case that the first arm 210 does not necessarily physically support the light engine 211, but still represents a direct or indirect coupling relationship.

[0034] The light engine 211 can output a display light 290 (simplified in this example) representing AR content or other display content to be viewed by a user. The display light 290 can be redirected by the diffractive waveguide 235 towards the user's eye 291 so that the user can view the AR content. The display light 290 from the light engine 211 hits the in-coupler 231 and is redirected to travel within the volume of the diffractive waveguide 235, where the display light 290 is guided through the light guide, such as by total internal reflection (TIR) ​​or a surface treatment such as a hologram or reflective coating. The display light 290 traveling within the volume of the diffractive waveguide 235 then hits the out-coupler 233, which redirects the display light 290 from the light guide redirector towards the user's eye 291. Exemplary WHUD display architectures are described at least in U.S. Provisional Patent Application No. 62 / 754,339, U.S. Provisional Patent Application No. 62 / 782,918, U.S. Provisional Patent Application No. 62 / 789,908, U.S. Provisional Patent Application No. 62 / 845,956, and U.S. Provisional Patent Application No. 62 / 791,514.

[0035] The wearable display device 200 may include a processor (not shown) communicatively coupled to each electrical component in the wearable display device 200, including but not limited to the light engine 211. The processor may be any suitable component capable of executing instructions or logic, including but not limited to a microcontroller, a microprocessor, a multi-core processor, an integrated circuit, an ASIC, an FPGA, a programmable logic device, or any suitable combination of these components. The wearable display device 200 may include a processor-readable non-transitory storage medium that may store processor-readable instructions that, when executed by the processor, may cause the processor to perform any number of functions, including causing the light engine 211 to output light 290 representing display content to be viewed by a user, receiving user input, managing a user interface, generating display content to be presented to a user, receiving and managing data from any sensors mounted on the wearable display device 200, receiving and processing external data and messages, and any other functions suitable for a given application. The non-transitory processor-readable storage medium may be any suitable component that can store instructions, logic, or programs, including, but not limited to, non-volatile or volatile memory, read-only memory (ROM), random access memory (RAM), flash memory, registers, a magnetic hard disk, an optical disk, or any combination of these components.

[0036] As noted elsewhere herein, additional waveguides may entail generally undesirable increases in mass, size, and manufacturing complexity associated with including a WHUD device. However, in certain embodiments, it may be useful to include multiple waveguides tuned in the manner described above for the green light component of the virtual image. For example, the WHUD device 200 may, in certain embodiments, include a single separate waveguide for each of multiple focal planes desired to be viewed by a user of the WHUD device, such as providing a first virtual image at a first focal distance from the user, providing a second virtual image at a different second focal distance from the user, and so on. Thus, although various examples are described herein with respect to a single waveguide and outcoupler grating for providing a virtual image at a single focal distance, it will be understood that in various embodiments multiple waveguides (and corresponding outcoupler gratings) may be utilized, such as each corresponding to a different focal distance.

[0037] FIG. 3 shows a diagram of optical components of a wearable display device in an augmented reality environment. Specifically, a light engine 311 is positioned to provide in-coupled display light 389 representing a virtual image 310 to a user's eye 291, which is positioned to receive out-coupled display light 390 via an in-coupler 331 and an out-coupler 333 of a diffractive waveguide 335. In the depicted environment, a real-world object (a tree) 301 appears at a finite distance from the user. However, in this example, the diffractive waveguide 335 is a "straight" diffractive waveguide with no grating curvature to provide refractive power via the out-coupler 333, so the virtual image 310 appears to the user at an infinite focal distance. This arrangement can confuse the user because the virtual image 310 is effectively superimposed in front of the perceived tree 301, even though the tree is focally closer than the infinitely distant virtual image.

[0038] 4 shows a partial cross-sectional view of the surface of a diffractive waveguide outcoupler grating 401. In the illustrated example, the surface of the outcoupler grating 401 includes etched vertical channels 405 that are approximately 20 nm deep and spaced apart approximately 350 nm apart. Notably, the vertical channels 405 are substantially perpendicular to the surface of the outcoupler grating 401, indicating that the outcoupler grating 401 is a "straight" outcoupler grating that does not provide any optical power that would affect the resulting virtual image's perceived infinite distance by the user. As a result, although the focal plane of the resulting virtual image is at infinity, all optical components of the virtual image are directed to the same focal plane.

[0039] 5 illustrates a partial cross-sectional view of a surface of a diffractive waveguide outcoupler grating 501 in accordance with one or more embodiments. In the illustrated example, the surface of the outcoupler grating 501 includes etched channels 505 that are approximately 20 nm deep and spaced apart approximately 350 nm apart. In contrast to the example outcoupler grating 401 of FIG. 4, the etched channels 505 of the outcoupler grating 501 are tilted and curved (sometimes referred to as "blazed") to provide a degree of optical power that affects the perceived focal length of the resulting virtual image. In certain embodiments, the etched channels may be "chirped," providing an additional aspect of optical power by varying the pitch (lateral spacing) of the etched channels along the surface of the outcoupler grating 501.

[0040] In contrast to the outcoupler grating 401 of FIG. 4, which does not have any refractive power to converge or diverge the outcoupled display light, the same physical properties of the outcoupler grating 501 that allow such a refractive power also affect the angle at which the outcoupled display light exits the corresponding outcoupler, depending on the wavelength of its incident light. Thus, the provision of this refractive power means that the red, green, and blue components of the resulting virtual image appear at different focal lengths. In various embodiments, the refractive power provided by the outcoupler grating 501, and the resulting perceived focal length of the resulting virtual image, can be configured by one or more physical parameters of the outcoupler grating itself. For example, the refractive power can be configured by selecting one or more parameters from a set of parameters including the depth of the grating channels, the lateral spacing of the grating channels, the curvature of the grating channels, and the angle of the grating channels. In various embodiments, such parameters are held substantially constant throughout the outcoupler grating, but in certain embodiments, the physical parameters of the outcoupler grating may be varied (commonly referred to as "chirping") across one or more dimensions of the outcoupler grating, e.g., to gradually increase or decrease the lateral spacing of the grating channels to provide a non-planar perceived focal length for a virtual image displayed through the outcoupler grating. It will be understood that the actual channel angles and / or curvatures are exaggerated. At the scale of such elements, the associated angles and / or curvatures are likely to be imperceptible to a human observer, even when the depiction of the associated outcoupler grating is enlarged, as illustrated in FIG. 5.

[0041] 6 shows a diagram of optical components of a wearable display device in an augmented reality environment according to some embodiments. A light engine 611 is arranged to provide in-coupled display light 689 representing a virtual image 610 to a user's eye 291, which is arranged to receive out-coupled display light 690 via an in-coupler 631 and an out-coupler 633 of a diffractive waveguide 635. In the illustrated embodiment, the diffractive waveguide 635 provides a sufficient degree of refractive power to affect the focal length of the virtual image 610 via the surface grating of the out-coupler 633, such that the virtual image appears to the user at a focal plane 710 and is perceived at a focal length of approximately 2 m. Such an arrangement is intuitively convincing to a user, as the virtual image 610 is expectedly perceived as closer than the tree 301 on which it is superimposed, thereby reducing potential user confusion as described with respect to the augmented reality environment of FIG.

[0042] FIG. 7 illustrates aspects of a virtual image provided by optical components of a wearable display device according to some embodiments. In particular, the embodiment of FIG. 7 illustrates the mismatch of focal planes associated with the respective red, green, and blue light components of a virtual image 610 presented to a user's eye. As in the example of FIG. 6, the light engine 611 provides in-coupled display light 689 to the user's eye 291, which receives out-coupled display light 690 via the in-coupler 631 and out-coupler 633 of the diffractive waveguide 635. The out-coupler 633 includes a surface grating similar to the out-coupler grating 501 (see FIG. 5), thereby providing a degree of refractive power to focus the green component of the virtual image 610 to the focal plane 710 perceived by the user's eye 291. However, that surface grating affects the angle at which the incident light exits the out-coupler 633 differently depending on the wavelength of the incident light. Thus, the green light component of the virtual image 610 is focused at a focal plane 710 perceived by the user's eye 291, while the red light component of the virtual image 610, having a longer wavelength, is focused at a different focal plane 705; similarly, the blue light component of the virtual image, having a shorter wavelength, is focused at focal plane 715. Due to the wavelengths associated with the blue light component of the virtual image (shorter than those associated with the green light component) and similarly the wavelengths associated with the red light component (longer than those associated with the green light component), the respective focal planes 705 and 715 of these components are perceived to be on either side of the green light focal plane 710. That is, the focal plane 705 of the red light component is perceived to be located slightly in front of the green light focal plane 710, and the focal plane 715 of the blue light component is perceived to be located slightly behind the green light focal plane 710.

[0043] FIG. 8 illustrates aspects of a virtual image provided by optical components of a wearable display device according to some embodiments. In particular, the example of FIG. 8 further illustrates the result of providing a single waveguide and a corresponding out-coupler associated with sufficient refractive power to shift the focal length at which the green light component of the virtual image is focused as it exits the out-coupler. As seen in the illustrated embodiment, the green light component 810 is perceived as being in focus and having a focal length 890 of approximately 2 meters. However, as a result of the different focal lengths of the focal planes 705 and 715 (see FIG. 7) of the blue and red light components, respectively, the red light component 805 (having a focal length 885 that is shorter than the focal length of the green light component, which is 2 meters) and the blue light component 815 (having a focal length 895 that is greater than the focal length of the green light component, which is 2 meters) are each perceived as blurry by the user. As shown in the example of FIG. 8, this perceived blurring of the red light component 805 and blue light component 815 can, in certain circumstances, result in components that have a larger perceived profile and / or area than the green light component 810, which is sharply focused at the focal plane 710.

[0044] It will be appreciated that the red and blue light components of virtual image 610 are not actually blurred or otherwise distorted, but are merely perceived as blurred (out of focus) due to the photopic adaptation of the human visual system, which relies primarily on green light to detect detail and therefore automatically focuses on the focal plane where the green light component of the virtual image appears. Thus, the focal distance at which the resulting virtual image is perceived typically coincides with the focal plane where the green light component appears sharpest.

[0045] In certain embodiments, the perceived blurring or other distortion of red and blue light components of a virtual image tuned for green light wavelengths may be mitigated or effectively eliminated using image pre-processing techniques. As a non-limiting example, a processor of an incorporated WHUD device may compensate for the larger perceptual profile of one or more objects in a virtual image that includes red and blue components by effectively modifying the size of the object(s) before the light engine 611 provides the in-coupled display light 689 to the incoupler 631 (see FIGS. 6 and 7).

[0046] The degree to which a user of a display system (such as the wearable display device 100 of FIG. 1 or the wearable display device 200 of FIG. 2) perceives blurring of the red light component 805 and / or the blue light component 815 may be determined or estimated in a variety of ways. For example, the degree of defocus may be characterized by optical modeling, measurement, or a combination thereof. Based on such modeling and / or measurement, a blur kernel may be generated.

[0047] A perfectly focused waveguide for a collimated light source would have no angular spread for that collimated light source. That is, optimally, there would be no difference between the angular width of the source light component entering the in-coupler of the waveguide and the angular width of the light component exiting the out-coupler of the waveguide. Thus, in certain embodiments, by measuring the respective angular spreads associated with each of the red and blue light components at the green light focal length 890, component-specific blur kernels can be generated for each of the red and blue light components 805 and 815 for a particular waveguide (e.g., diffractive waveguide 235). In other embodiments, similar component-specific blur kernels can be generated by modeling for each of the red and blue light components 805 and 815, allowing the angular spread of those light components to be estimated based on the physical parameters of the diffractive waveguide 235.

[0048] The generated blur kernel can be used to establish a deconvolution algorithm to apply to some or all of the red light component 805 and / or blue light component 815 of any AR content presented to the user. By applying this deconvolution algorithm, based on the generated blur kernel, to a virtual image to be projected by the light engine, the resulting modified virtual image pre-compensates for the degree of defocus corresponding to the red light component and / or the blue light component, respectively.

[0049] The generation of the blur kernel and the application of the resulting deconvolution algorithm may be performed as at least part of a digital pre-processing operation, such as to at least partially correct for perceived distortions of red and / or blue light components. Such digital pre-processing operations may be performed at any time before the AR content is presented to the user. For example, a digital pre-processing operation to correct for perceived distortions of red and / or blue light components may be performed via software instructions of one or more general-purpose processors (such as hardware processor 1002 of FIG. 10), via instructions of one or more shaders of a graphics processing unit (such as GPU 1006 of FIG. 10), or via a combination thereof, as part of specifying what a user of a display system should perceive as AR content.

[0050] As an example, the AR content presented to the user may include a geometric line with a finite width. As previously described, the different focal lengths (and resulting angular spread) associated with each of the red light component 805, green light component 810, and blue light component 815 cause the line to appear wider than originally intended for the AR content. However, as a result of the digital pre-processing operations described above, the geometric line may be modified to be correspondingly narrower. In this way, the line appears closer to its originally intended width, despite the perceived distortion caused by the focal lengths 885 and 895 associated with each of the red light component 805 and / or blue light component 815.

[0051] Furthermore, in certain scenarios, the perceived distortion of the red light component 805 and / or the blue light component 815 may be perceived by a user as color distortion rather than loss of detail. Thus, in certain scenarios and embodiments, the generated blur kernel may provide not only blur correction, but also one or more aspects of color correction.

[0052] FIG. 9 illustrates an operational routine 900 for a display device (eg, the wearable display device 200 of FIG. 2 and / or the WHUD computing system 1000 of FIG. 10) according to some embodiments.

[0053] The routine begins at block 905, where the angular spread for each of one or more light components (e.g., red light component 805 and / or blue light component 815 of FIG. 8) is determined based on physical parameters 901 of the waveguide (such as through modeling of diffractive waveguide 235 of FIGS. 2 and 8), based on measurements 902, or based on some combination thereof. The routine then proceeds to block 910.

[0054] At block 910, a blur kernel is generated for each of one or more light components of the virtual image based on the determined angular spread of those light components and the respective focal lengths at which the individual light components of the virtual image are focused. The routine then proceeds to block 915.

[0055] At block 915, the display device receives the virtual image for display to the user. The routine proceeds to block 920, where the display device modifies the received virtual image based on the generated blur kernel. In certain embodiments, for example, modifying the virtual image may include one or more pre-processing operations (e.g., one or more deconvolution operations) that utilize the generated blur kernel.

[0056] After block 920, the routine proceeds to block 925, where a display light representative of the modified virtual image is generated by a light engine of the display device (e.g., light engine 211 of FIGS. 2 and 8). The routine then proceeds to block 930.

[0057] In block 930, the generated display light is directed to the user's eye via a waveguide (e.g., diffractive waveguide 235 of FIGS. 2 and 8). As part of directing the generated display light to the user's eye, a first component light (e.g., green light component 810) is focused at a first focal length, as shown in block 935, while one or more other component lights (e.g., red light component 805 and / or blue light component 815) are focused at one or more other focal lengths, as shown in block 940. The pre-processing operations used to modify the virtual image in block 920 reduce or eliminate perceived distortions of the other component lights caused by focusing at focal lengths other than the first component light.

[0058] FIG. 10 is an element-level block diagram illustrating an example of a WHUD Computing System 1000 suitable for implementing one or more embodiments. In alternative embodiments, the WHUD Computing System 1000 may operate as a standalone device or may be connected (e.g., networked) to other systems. In various embodiments, one or more components of the WHUD Computing System 1000 may be incorporated as or within one or more server computing systems to provide, by way of example and not limitation, graphics rendering for display to users via the incorporated WHUD devices. It will be understood that the associated server computing devices may include some, but not necessarily all, components of the WHUD Computing System 1000. In a networked deployment, the WHUD Computing System 1000 may operate as a server machine, a client machine, or both, in a server-client network environment. In at least one example, the WHUD Computing System 1000 may function as a peer system in a peer-to-peer (P2P) (or other distributed) network environment. Thus, WHUD computing system 1000 may operate, in certain embodiments, as a server computer, a personal computer (PC), a tablet PC, a set-top box (STB), a mobile computing device, a web appliance, a network router, a switch or bridge, or any system capable of executing instructions (sequential or otherwise) that specify actions to be performed by the system. Additionally, although only a single system is illustrated, the term "system" is also intended to include any collection of systems that individually or collectively execute a set (or sets) of instructions to perform any one or more of the methodologies discussed herein, such as cloud computing, software as a service (SaaS), other computer cluster configurations, etc.

[0059] Examples described herein may include or may operate with logic or several components or mechanisms. Circuit wiring is a collection of circuits implemented in a tangible entity that includes hardware (e.g., simple circuits, gates, logic, etc.). All components of the circuit wiring may be flexible over time and variations in the underlying hardware. Circuit wiring includes components that can be used alone or in combination to perform a specific operation when in operation. In one example, the hardware of the circuit wiring may be immutably designed (e.g., hardwired) to perform a specific operation. In one example, the hardware of the circuit wiring may include variably connected physical components (e.g., execution units, transistors, simple circuits, etc.) that include computer-readable media that are physically modified (e.g., magnetic, electrical, movable arrangements of immutable mass particles, etc.) to encode instructions for a specific operation. Connecting the physical components changes the underlying electrical properties of the hardware components, for example, from an insulator to a conductor or vice versa. The instructions cause the embedded hardware (e.g., an execution unit or loading mechanism) to create, in operation, members of the circuit wiring within the hardware via variable connections to perform some of the specific operations. Thus, the computer-readable medium is communicatively coupled to other components of the circuit wiring when the device is operating. In one example, any of the physical components may be used in multiple members of multiple circuit wirings. For example, during operation, the execution unit may be used in a first circuit of a first circuit wiring at one time and reused by a second circuit of the first circuit wiring or reused by a third circuit of the second circuit wiring at another time.

[0060] The WHUD computing system 1000 may include one or more hardware processors 1002 (e.g., a central processing unit (CPU), a hardware processor core, or any combination thereof), a main memory 1004, and a graphics processing unit (GPU) 1006, some or all of which may communicate with each other via an interlink (e.g., a bus) 1008. The WHUD computing system 1000 may further include a display unit 1010 (such as a display monitor or other display device), an alphanumeric input device 1012 (e.g., a keyboard or other physical or touch-based actuator), and a user interface (UI) navigation device 1014 (e.g., a mouse or other pointing device, such as a touch-based interface). In one example, the display unit 1010, the input device 1012, and the UI navigation device 1014 may include a touch screen display. The WHUD computing system 1000 may further include a storage device (e.g., a drive unit) 1016, a signal generating device 1018 (e.g., a speaker), a network interface device 1020, and one or more sensors 1021 (such as a Global Positioning System (GPS) sensor, a compass, an accelerometer, or other sensor). The WHUD computing system 1000 may include an output controller 1028, such as a serial (e.g., Universal Serial Bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection, for communicating with or controlling one or more peripheral devices (e.g., a printer, a card reader, etc.).

[0061] The storage device 1016 may include a computer-readable medium 1022 having stored thereon one or more data structures or a set of instructions 1024 (e.g., software) that embody or utilize any one or more of the techniques or functions described herein. The instructions 1024 may also reside, completely or at least partially, within the main memory 1004, within the GPU 1006, or within the hardware processor 1002 during its execution by the WHUD computing system 1000. In one example, one or any combination of the hardware processor 1002, the main memory 1004, the GPU 1006, or the storage device 1016 may constitute a computer-readable medium.

[0062] Although the computer-readable medium 1022 is depicted as a single medium, the term “computer-readable medium” may include a single medium or multiple media (e.g., a centralized or distributed database, and / or associated caches and servers) configured to store one or more instructions 1024.

[0063] The term "computer-readable medium" may include any medium capable of storing, encoding, or carrying instructions executed by the WHUD computing system 1000, causing the WHUD computing system 1000 to perform one or more of the techniques of the present disclosure, or capable of storing, encoding, or carrying data structures used by or associated with such instructions. Non-limiting examples of computer-readable media may include solid-state memory, as well as optical and magnetic media. In one example, a large-capacity computer-readable medium includes a computer-readable medium that includes a plurality of particles with an unchanging (e.g., stationary) mass. Thus, a large-capacity computer-readable medium is not a signal that propagates temporarily. Specific examples of large-capacity computer-readable media include non-volatile memories such as semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)) and flash memory devices, magnetic disks such as internal hard disks and removable disks, magneto-optical disks, and CD-ROM and DVD-ROM disks.

[0064] The instructions 1024 may further be transmitted or received over a communications network 1026 using a transmission medium via a network interface device 1020 utilizing any one of a number of transport protocols (e.g., Frame Relay, Internet Protocol (IP), Transmission Control Protocol (TCP), User Datagram Protocol (UDP), Hypertext Transfer Protocol (HTTP), etc.). Examples of communications networks may include local area networks (LANs), wide area networks (WANs), packet data networks (e.g., the Internet), mobile telephone networks (e.g., cellular networks), plain old telephone (POTS) networks, and wireless data networks (e.g., the Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards known as Wi-Fi®, the IEEE 802.16 family of standards known as WiMax®), the IEEE 802.15.4 family of standards, peer-to-peer (P2P) networks, etc., among others. In one example, the network interface device 1020 may include one or more physical jacks (e.g., Ethernet™, coaxial, or phone jacks) or one or more antennas for connecting to the communications network 1026. In one example, the network interface device 1020 may include multiple antennas for wireless communication using at least one of single-input multiple-output (SIMO), multiple-input multiple-output (MIMO), or multiple-input single-output (MISO) techniques. The term "transmission medium" is intended to include intangible media capable of storing, encoding, or carrying instructions executed by the WHUD computing system 1000, including digital or analog communications signals or other intangible media that facilitate communication of such software.

[0065] As disclosed herein, in some embodiments, a system for displaying a virtual image to a user comprises a light engine that generates a display light representing the virtual image, a diffractive waveguide that focuses a first component light of the generated display light at a first focal distance from an eye of the user and focuses one or more additional component lights of the generated display light at one or more different other focal distances from the eye of the user, and one or more processors communicatively coupled to the light engine and configured to modify the virtual image to correct a perceived distortion of at least one of the one or more additional component lights. In one aspect, the first component light of the generated display light includes a first color component light, and the one or more additional component lights include at least one of the group including a second color component light of the generated display light, or a third color component light of the generated display light. In another aspect, the first color component light of the generated display light includes a green component light having a wavelength between 495 nm and 570 nm. In yet another aspect, modifying the virtual image includes performing one or more deconvolution operations on the virtual image.

[0066] In one embodiment, the one or more deconvolution operations are performed utilizing a blur kernel associated with the at least one additional component light. In another embodiment, the blur kernel is generated based on one or more measurements of an angular spread of the at least one additional component light at a first focal length. In yet another embodiment, the blur kernel is generated based on modeling an angular spread of the at least one additional component light at a first focal length. In yet another embodiment, the one or more additional component lights include a blue component light and a red component light, and a first blur kernel is generated based on an angular spread of the blue component light at the first focal length and a second blur kernel is generated based on a second angular spread of the red component light at the first focal length.

[0067] In one aspect, the system comprises an in-coupler optically coupled to the diffractive waveguide, the in-coupler receiving the display light from the light engine and directing the received display light to the diffractive waveguide, and an out-coupler optically coupled to the diffractive waveguide, the out-coupler directing at least a portion of the display light from the diffractive waveguide to an eye of a user. In another aspect, the system comprises a memory storing instructions, the instructions when executed by the one or more processors, causing the one or more processors to modify the virtual image before the light engine generates the display light.

[0068] In some embodiments, a wearable head-up display (WHUD) includes any of the above systems.

[0069] In some embodiments, a method of displaying a virtual image to a user includes receiving the virtual image by one or more processors, modifying the virtual image by the one or more processors via one or more pre-processing operations to generate a modified virtual image, generating display light representative of the modified virtual image by a light engine, receiving the display light from the light engine and directing the received display light to a diffractive waveguide, and directing at least a portion of the display light from the diffractive waveguide to an eye of a user, where directing includes focusing a first component light of the generated display light at a first focal distance from the eye of the user and focusing one or more additional component lights of the generated display light at one or more different other focal distances from the eye of the user. In one aspect, the first component light of the generated display light includes a first color component light and the one or more additional component lights include at least one of a group including a second color component light of the generated display light or a third color component light of the generated display light.

[0070] In one aspect, the first color component light of the generated display light includes a green component light having a wavelength between 495 nm and 570 nm. In another aspect, modifying the virtual image via the one or more pre-processing operations includes performing one or more deconvolution operations on the virtual image. In yet another aspect, performing the one or more deconvolution operations includes utilizing a blur kernel associated with one additional component light of the one or more additional component lights. In yet another aspect, the method includes generating the blur kernel based on one or more measurements of an angular spread of the one additional component light at the first focal length.

[0071] In one aspect, the method includes generating a blur kernel based on modeling an angular spread of one additional component light at a first focal length. In another aspect, the one or more additional component lights include a blue component light and a red component light, and the method further includes generating a first blur kernel based on an angular spread of the blue component light at the first focal length and generating a second blur kernel based on an angular spread of the red component light at the first focal length. In yet another aspect, the method includes receiving display light from the light engine at an in-coupler optically coupled to the diffractive waveguide, directing the received display light to the diffractive waveguide, and directing at least a portion of the display light from the diffractive waveguide to an eye of a user via an out-coupler optically coupled to the diffractive waveguide.

[0072] In some embodiments, certain aspects of the techniques described above may be implemented by one or more processors of a processing system executing software. The software includes one or more sets of executable instructions stored or otherwise tangibly embodied on a non-transitory computer-readable storage medium. The software may include instructions and specific data that, when executed by one or more processors, operate the one or more processors to perform one or more aspects of the techniques described above. Non-transitory computer-readable storage media may include, for example, magnetic or optical disk storage devices, solid-state storage devices such as flash memory, caches, random access memory (RAM) or other non-volatile memory devices or devices, and the like. The executable instructions stored on the non-transitory computer-readable storage medium may be in source code, assembly language code, object code, or other instruction formats that are interpreted or otherwise executable by one or more processors.

[0073] A computer-readable storage medium may include any storage medium, or combination of storage media, that is accessible by a computer system during use to provide instructions and / or data to the computer system. Such storage media may include, but are not limited to, optical media (e.g., compact discs (CDs), digital versatile discs (DVDs), Blu-ray discs), magnetic media (e.g., floppy disks, magnetic tapes, or magnetic hard drives), volatile memory (e.g., random access memory (RAM) or cache), non-volatile memory (e.g., read-only memory (ROM) or flash memory), or microelectromechanical systems (MEMS)-based storage media. A computer-readable storage medium may be incorporated into a computing system (e.g., system RAM or ROM), fixedly attached to a computing system (e.g., a magnetic hard drive), removably attached to a computing system (e.g., an optical disk or a universal serial bus (USB)-based flash memory), or coupled to a computer system via a wired or wireless network (e.g., network-accessible storage (NAS)).

[0074] In addition to those described, it is noted that not all activities or elements described above in the general description are required, and that certain activities or parts of devices may not be required, and that one or more additional activities can be performed or one or more additional elements can 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 certain 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. For example, in certain embodiments, some of the above routine 900 may be performed outside of a display device, such as when the determination of an angular spread associated with one or more light components and / or the generation of blur kernels associated with those light components are performed as part of the initialization or configuration of the display device (e.g., as part of the manufacturing or initial configuration). Thus, the present specification and drawings should be considered in an illustrative and not a limiting sense, and all such modifications are intended to be included within the scope of the present disclosure.

[0075] 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 can 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 can 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. 1. A system for displaying a virtual image to a user, comprising: a light engine for generating display light representative of the virtual image; a diffractive waveguide that focuses a first component light of the generated display light at a first focal distance from the eye of the user and focuses one or more additional component lights of the generated display light at one or more other different focal distances from the eye of the user; one or more processors communicatively coupled to the light engine and configured to modify the virtual image to correct for a perceived distortion of at least one of the one or more additional component lights; A system comprising:

2. the first component light of the generated display light includes a first color component light; The system of claim 1 , wherein the one or more additional component lights include at least one of a group including a second color component light of the generated display light or a third color component light of the generated display light.

3. The system of claim 2 , wherein the first color component light of the generated display light comprises a green component light having a wavelength between 495 nm and 570 nm.

4. The system of any of claims 1 to 3, wherein modifying the virtual image comprises performing one or more deconvolution operations on the virtual image.

5. The system of claim 4 , wherein the one or more deconvolution operations are performed utilizing a blur kernel associated with the at least one additional component light.

6. The system of claim 5 , wherein the blur kernel is generated based on one or more measurements of an angular spread of the at least one additional component light at the first focal length.

7. The system of claim 5 , wherein the blur kernel is generated based on modeling an angular spread of the at least one additional component light at the first focal length.

8. the one or more additional component lights include a blue component light and a red component light; a first blur kernel is generated based on an angular spread of the blue component light at the first focal length; The system of claim 5 , wherein a second blur kernel is generated based on a second angular spread of the red component light at the first focal length.

9. The system comprises: The optical system further includes an in-coupler optically coupled to the diffractive waveguide, the in-coupler receiving the display light from the optical engine and directing the received display light to the diffractive waveguide; The system of any one of claims 1 to 8, further comprising an out-coupler optically coupled to the diffractive waveguide, the out-coupler directing at least a portion of the display light from the diffractive waveguide to an eye of the user.

10. A system as described in any one of claims 1 to 9, further comprising a memory for storing instructions, which when executed by the one or more processors, cause the one or more processors to modify the virtual image before the light engine generates the display light.

11. A wearable head-up display (WHUD) comprising a system according to any one of claims 1 to 10.

12. 1. A method of displaying a virtual image to a user, comprising: receiving the virtual image by one or more processors; modifying, by the one or more processors, the virtual image via one or more pre-processing operations to generate a modified virtual image; generating, by a light engine, a display light representative of the modified virtual image; receiving the display light from the light engine and directing the received display light to a diffractive waveguide; directing at least a portion of the display light from the diffractive waveguide to an eye of the user, the directing comprising: converging a first component light of the generated display light at a first focal distance from the eye of the user; focusing one or more additional component lights of the generated display light at one or more different other focal distances from the eye of the user; A method comprising:

13. the first component light of the generated display light includes a first color component light; The method of claim 12 , wherein the one or more additional component lights include at least one of a group including a second color component light of the generated display light or a third color component light of the generated display light.

14. The method of claim 13, wherein the first color component light of the generated display light comprises a green component light having a wavelength between 495 nm and 570 nm.

15. The method of any of claims 12 to 14, wherein modifying the virtual image through one or more pre-processing operations comprises performing one or more deconvolution operations on the virtual image.

16. The method of claim 15 , wherein performing the one or more deconvolution operations comprises utilizing a blur kernel associated with one of the one or more additional component lights.

17. The method of claim 16 , further comprising generating the blur kernel based on one or more measurements of an angular spread of the one additional component light at the first focal length.

18. 17. The method of claim 16, further comprising generating the blur kernel based on modeling an angular spread of the one additional component light at the first focal length.

19. the one or more additional component lights include a blue component light and a red component light; generating a first blur kernel based on an angular spread of the blue component light at the first focal length; generating a second blur kernel based on an angular spread of the red component light at the first focal length; The method of any of claims 12 to 18, further comprising:

20. receiving, at an in-coupler optically coupled to the diffractive waveguide, a display light from the optical engine and directing the received display light to the diffractive waveguide; directing at least a portion of the display light from the diffractive waveguide to an eye of the user via an out-coupler optically coupled to the diffractive waveguide; The method of any one of claims 12 to 19, further comprising:

Images