Optical layer for improving performance of eyepieces for use with virtual and augmented reality display systems

Abstract

An improved diffractive optical element for use in an eyepiece of an augmented reality system. The diffractive optical element includes a diffractive structure having a waveguide substrate, a surface grating positioned on a first side of the waveguide substrate, and one or more pairs of optical layers disposed between the waveguide substrate and the surface grating. Each optical layer pair includes a low refractive index layer and a high refractive index layer disposed directly on an outer side of the low refractive index layer.

Description

Technical Field

[0001] The present disclosure relates to virtual reality and augmented reality imaging and visualization systems, and more particularly, to improved eyepiece designs for display systems of virtual reality and / or augmented reality systems. Background Art

[0002] Modern computing and display technologies have facilitated the development of systems for so-called "virtual reality" (VR) or "augmented reality" (AR) and / or "mixed reality" (MR) experiences, in which digitally reproduced images or portions thereof are presented to users in a manner that they appear to be real or can be perceived as real. Virtual reality or "VR" scenes generally involve the presentation of digital or virtual image information without transparency to actual real-world visual input. Augmented reality or "AR" scenes generally involve presenting digital or virtual image information as an enhancement to the visualization of the actual world around the user. Mixed reality scenes are a version of AR scenes, except for a broader fusion of the real world and the virtual world, in which physical objects and virtual objects in the real world can coexist and interact in real time. As used herein, the terms "extended reality" and "XR" are used to collectively refer to any one of VR, AR and / or MR. In addition, the term "AR" refers to one or both of AR and MR.

[0003] For example, refer to Figure 1 , depicting an augmented reality scene (4) in which a user of AR technology sees a real-world park-like setting (6) featuring people, trees, buildings in the background, and a concrete platform (1120). In addition to these items, the user of AR technology also perceives that he "sees" a robotic statue (1110) standing on the real-world platform (1120), as well as a flying cartoon-like avatar character (2) that appears to be an anthropomorphism of a bumblebee, even though these elements (2, 1110) do not exist in the real world. The results show that the human visual perception system is very complex, and it is challenging to produce VR or AR technology that facilitates comfortable, natural, and rich presentation of virtual image elements among other virtual or real-world image elements.

[0004] There are many challenges when it comes to presenting 3D virtual content to users of XR systems. A central premise of presenting 3D content to users involves creating the perception of multiple depths. In other words, it may be desirable for some virtual content to appear closer to the user, while other virtual content appears to be moving away from the user. Therefore, in order to achieve 3D perception, the XR system should be configured to deliver virtual content at different focal planes relative to the user.

[0005] In order for a 3D display to produce a realistic sense of depth, and more specifically, a simulated sense of surface depth, it is desirable for each point in the display's field of view to produce an accommodation response that corresponds to its virtual depth. If the accommodation response to a displayed point does not correspond to the point's virtual depth, as determined by convergence and binocular depth cues of stereopsis, the human visual system may experience accommodation conflict, resulting in unstable imaging, detrimental eye strain, headaches, and, in the absence of accommodation information, an almost complete lack of surface depth.

[0006] Therefore, improved techniques are needed to implement 3D displays that address these and other issues of conventional approaches. The systems and techniques described herein are configured to work with a typical human visual configuration to address these challenges. Summary of the invention

[0007] Embodiments of the present invention relate to apparatus, systems, and methods for facilitating XR interactions for one or more users. More specifically, disclosed herein are improved eyepiece designs for virtual reality and / or augmented reality display systems having improved performance over previous eyepiece designs. The eyepiece designs now disclosed include innovative coatings of optical elements of the display system that improve the functional performance of the eyepiece, such as selectively adjusting the diffraction efficiency for certain colors, increasing the magnitude and uniformity of the diffraction efficiency of the eyepiece, increasing the combined exit pupil expander (CPE) efficiency of the eyepiece, and / or increasing the input coupling grating (ICG) emission efficiency of the eyepiece.

[0008] Therefore, one embodiment disclosed herein is an eyepiece for an XR display system for delivering XR content to a user. The eyepiece includes a diffractive optical element (DOE) for receiving light associated with one or more frames of image data and directing the light to the user's eyes. The DOE includes a diffractive structure having a waveguide substrate, a surface grating positioned on a first side of the waveguide substrate, and one or more optical layer pairs disposed between the waveguide substrate and the surface grating. The optical layer pair may be disposed directly on the first side of the waveguide substrate, or there may be one or more intermediate layers (also referred to herein as "lining layers") disposed between the optical layer pair and the waveguide substrate. Each optical layer pair includes a low refractive index layer and a high refractive index layer disposed directly on the outside of the low refractive index layer. The terms "inside" and "outside" are relative to a plane passing through the middle of the thickness of the waveguide substrate, wherein the plane is the innermost position. The high refractive index layer has a higher refractive index than the low refractive index layer. The use of innovative optical layer pairs is adjusted to improve the uniformity of certain colors displayed by the eyepiece by better matching the DOE's diffraction efficiency with the bounce spacing (outcoupled beam density) and the ICG emission efficiency, both of which depend on the incident angle of the light entering the eyepiece.

[0009] In another aspect, a DOE for an eyepiece may include a first optical layer pair on a first side of a waveguide substrate, and a second optical layer pair on a second side (i.e., a side opposite to the first side) of the waveguide substrate. The DOE may also include a second surface grating on the second side of the waveguide substrate, such that the second optical layer pair is between the waveguide substrate and the second surface grating. In yet another aspect, the eyepiece may further include an input coupling grating disposed on the waveguide substrate.

[0010] In yet another aspect, the DOE may include: a first optical layer pair on a first side of a waveguide substrate, and a second optical layer pair disposed directly outside of the first optical layer pair. In this way, the second optical layer pair can amplify the performance improvements of the first optical layer pair. One or more additional optical layer pairs can be stacked onto the other optical layer pairs to match the diffraction efficiency of the DOE to the reflection-transmission spacing, or to adjust any other desired optical parameter of the eyepiece.

[0011] In another aspect, the waveguide substrate has a higher refractive index than the low refractive index layer. In yet another aspect, the waveguide substrate is formed of TAFD55 glass having a higher refractive index (about 2.0) than the low refractive index layer. In yet another aspect, the surface grating has a high refractive index greater than about 1.7. As used herein, the term "about" refers to plus or minus 10%.

[0012] In additional aspects of the eyepiece, the high refractive index layer can be formed of Si3N4, ZrO2, TiO2, SiC, ZnTe, GP, BP and / or similar materials having a high refractive index (greater than 1.7) and low absorption (k<0.001). In another aspect, the high refractive index layer can be applied to the DOE by any suitable method, such as spray deposition, application of a film, etc. The high refractive index layer can also include organic filler-based materials, such as organic UV and / or thermally curable resin composites composed of sulfur, aromatic groups and high refractive index nanoparticles (e.g., ZrO2, TiO2). The low refractive index layer can be formed of inorganic materials, such as MgF, SiO2, etc., and can also be formed of organic materials, such as ordinary UV and thermally curable resins with a refractive index of about 1.53, and Teflon-type materials with a refractive index of about 1.3. The low refractive index coating can be applied to the DOE by any suitable method, such as spray deposition, application of a film, etc.

[0013] In other aspects, the surface grating has a low refractive index (i.e., lower than the refractive index of the high refractive index layer), and the surface grating can be applied to the DOE using lithography or imprint lithography with ultra-thin RLT (~20nm) using a pattern of organic material on the high refractive index layer of the optical coating. A top surface layer, also having a high refractive index higher than the low refractive index layer, can be disposed on top of the top surface layer grating. The top surface layer can form an interstitial layer between multiple stacked diffractive structures, which removes any air gaps and provides a support structure for the stacked diffractive components.

[0014] Another embodiment disclosed herein relates to an XR display system for delivering extended reality content to a user. The XR display system includes an image generation source that provides one or more frames of image data, an optical modulator that emits light associated with one or more frames of image data, and an eyepiece having a DOE for receiving light associated with one or more frames of image data and directing the light to the user's eyes. The DOE can be any of the DOEs described herein, including the DOE described above for one embodiment disclosed herein. Similarly, a DOE with an innovative pair of optical layers can be adjusted to improve the uniformity of the eyepiece display of certain colors by better matching the diffraction efficiency of the DOE with the reflection transmission interval (outcoupled beam density) and the ICG emission efficiency, where both the reflection transmission interval and the ICG emission efficiency depend on the incident angle of the light entering the eyepiece.

[0015] In additional aspects, the XR display system may include any combination of one or more of the additional aspects and features of the eyepiece embodiments as described herein.

[0016] Another embodiment disclosed herein relates to an XR system for generating XR content and displaying it to a user. The XR system includes a computer having a computer processor, a memory, a storage device, and a software application stored on the storage device and executable to program the computer to perform operations that enable an augmented reality system. The XR system includes an XR display system. The XR display system can be any suitable display system, such as an XR headset with a display for displaying a 3D virtual image (i.e., an XR image). For example, the XR headset may include a frame structure configured to be worn on the user's head. The frame structure carries an image generation source for providing one or more frames of image data, an optical modulator for transmitting light associated with one or more frames of image data, and an eyepiece with a DOE, the DOE being used to receive light associated with one or more frames of image data and directing the light to the user's eyes. The DOE can be any of the DOEs described herein, including the DOE described above for one embodiment disclosed herein. Similarly, a DOE with an innovative pair of optical layers can be tuned to improve the uniformity of certain colors displayed by the eyepiece by better matching the DOE's diffraction efficiency with the reflection-transmission spacing (outcoupled beam density) and the ICG emission efficiency, both of which depend on the incident angle of the light entering the eyepiece.

[0017] In additional aspects, the XR headset may include one or more outward-facing image sensors (e.g., cameras or other computer vision devices) for capturing images of the user's surroundings. The XR headset may also include one or more other sensors, such as an inward-facing camera (e.g., for eye tracking, etc.), and one or more kinematic sensors (e.g., inertial measurement unit (IMU), accelerometer, orientation sensor, compass, gyroscope, GPS sensor, camera, and / or computer vision, etc.).

[0018] In additional aspects, the XR display system may include any combination of one or more of the additional aspects and features of the eyepiece embodiments as described herein.

[0019] Additional and other objects, features and advantages of the present invention will be described in the detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings illustrate the design and utility of various embodiments of the present disclosure. Note that the drawings are not drawn to scale and that elements of similar structure or function are represented by similar reference numerals throughout the drawings. In order to better understand how the above and other advantages and objects of the various embodiments of the present disclosure are obtained, a more detailed description of the present disclosure briefly described above will be presented by reference to specific embodiments of the present disclosure shown in the accompanying drawings. It should be understood that these drawings depict only typical embodiments of the present disclosure and, therefore, should not be considered limiting of its scope. The present disclosure will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:

[0021] Figure 1 In one illustrated embodiment, a user's view of augmented reality (AR) viewing through a wearable AR user device is shown.

[0022] Figure 2 A conventional stereoscopic 3-D simulation display system for an XR system is shown.

[0023] Figure 3 An improved method of implementing a stereoscopic 3-D simulation display system for an XR system according to some embodiments disclosed herein is shown.

[0024] Figures 4A-4D Various systems, subsystems, and components are shown for addressing the goal of providing a high-quality, perceptually comfortable display system for human XR.

[0025] Figure 5 A plan view of an example configuration of an XR system utilizing an improved diffractive structure according to some embodiments disclosed herein is shown.

[0026] Figure 6 A stacked waveguide assembly for use in an XR display system is shown.

[0027] Figure 7 A DOE for a display system according to some embodiments disclosed herein is shown.

[0028] Figure 8 and 9 Example diffraction patterns of a DOE according to some embodiments are shown, resulting in different exit beams directed toward the eye.

[0029] Fig.10 and 11 Shown are two waveguides into which the light beam is injected.

[0030] Fig.12 A stack of waveguides is shown.

[0031] Figures 13A-13H Several exemplary embodiments of diffractive structures for improved eyepieces for XR display systems are shown.

[0032] Fig.14A and 14B Corresponding graphs of diffraction efficiency versus angle of incidence are depicted to compare a diffractive structure without optical layer pairs and a diffractive structure with optical layer pairs.

[0033] Fig. 14C is used to generate Fig. 14B Schematic diagram of the resulting diffraction structure of a single optical layer pair.

[0034] Fig.15A and 15B It is shown that in the use of ( Fig. 15B ) and not using ( Fig.15A )Comparison of the color responses of a single diffractive structure in the three primary colors (red, blue, green, RGB) in the case of optical layer pairs.

[0035] Fig.16A is a schematic diagram of a substrate structure with ICG and CPE.

[0036] Fig. 16B yes Fig.16A Momentum space diagram of the substrate structure, where each incident angle is mapped to the momentum of the light, as shown in the right box.

[0037] Fig. 16C Shown for Fig.16A A typical example of the variation in emission efficiency of a substrate structure depending on the incident angle.

[0038] Fig.16D Shown in Fig.16A Diffraction efficiency of s-polarized light undergoing CPE diffraction in the substrate structure shown.

[0039] Fig.16E Describes the Fig. 16B Momentum profile of the light inside the waveguide in the middle left frame, and the number of collisions with the surface grating for a propagation distance of 2 mm.

[0040] Fig.16F Schematically shows Fig.16A Simulated light distribution at the center of the CPE for the substrate structure.

[0041] Fig.17A and 17B The diffractive structure without optical layer pairs ( Fig.17A ) and the diffractive structure 1300 ( Fig. 17B )’s diffraction efficiency uniformity. DETAILED DESCRIPTION

[0042] Described below are various embodiments of an improved eyepiece design for an extended reality (XR) display system and an XR system for delivering extended reality content to a user. The improved eyepiece utilizes an additional optical layer on a diffractive optical element (DOE) of an eyepiece of an XR display system for receiving light associated with an image data frame displayed on the XR display system. The disclosed eyepiece improves functional performance of the eyepiece, such as selectively adjusting diffraction efficiency for specific colors, increasing the magnitude and uniformity of the diffraction efficiency of the eyepiece, increasing the combined exit pupil expander (CPE) efficiency of the eyepiece, and / or increasing the input coupling grating (ICG) emission efficiency of the eyepiece.

[0043] According to some embodiments of the present invention, a DOE having a diffractive structure is employed, the diffractive structure comprising one or more optical layer pairs disposed between a waveguide substrate and a top grating surface. Typically, the waveguide substrate has a high refractive index, and the top grating surface also has a high refractive index. One or more optical layer pairs are disposed between the waveguide substrate and the surface grating. Each optical layer pair comprises a low refractive index layer and a high refractive index layer disposed directly on the outside of the low refractive index layer. As described herein, the optical layer pairs having a high refractive index layer and a low refractive index layer can be tuned to improve the performance of the DOE, including improving the diffraction efficiency and uniformity of the display of discrete colors, increasing the magnitude and uniformity of the diffraction efficiency of the eyepiece, increasing the CPE efficiency of the eyepiece, and / or increasing the ICG emission efficiency of the eyepiece. Improving the diffraction efficiency has the benefit of allowing "brighter" light to be output to the XR display.

[0044] Display systems according to some embodiments

[0045] This section of the disclosure describes example display systems that may be used in conjunction with the improved diffractive structures disclosed herein.

[0046] Figure 2 A conventional stereoscopic 3-D simulation display system for an XR system is shown. The display system typically has separate displays 74 and 76 for each eye 4 and 6, respectively, at a fixed radial focal distance 10 from the eye. This conventional approach does not take into account the many valuable cues that the human eye and brain use to detect and interpret three-dimensional depth, including accommodation cues.

[0047] In fact, the typical human eye is able to interpret multiple depth layers based on radial distance, for example, the human eye is able to interpret about 12 depth layers. The near field limit of about 0.25 meters is about the closest depth of focus; the far field limit of about 3 meters means that anything farther than about 3 meters from the human eye receives infinity focus. The focused layers become thinner and thinner as they get closer to the eye; in other words, the eye is able to perceive a fairly small focus difference relatively close to the eye, and the effect disappears as the object moves away from the eye. At the infinite object position, the depth of focus / diopter interval value is about 1 / 3 diopter.

[0048] Figure 3 An improved method of implementing a stereoscopic 3-D simulation display system for an AR system according to some embodiments of the present invention is shown, wherein two complex images are displayed, one for each eye 4 and 6, using respective radial focal depths (12) of various aspects (14) of each image to provide each eye with a perception of three-dimensional depth layering within the perceived image. Since there are multiple focal planes (e.g., 12 focal planes) between the user's eyes and infinity, these focal planes and data within the depicted relationships can be used to position virtual elements within an augmented reality scene for the user to view, as the human eye constantly scans around to perceive depth using the focal planes. Although the figure shows a specific number of focal planes at various depths, it should be noted that embodiments of the present invention may use any number of focal planes as desired for the particular application desired, and thus the present invention is not limited to devices having only the specific number of focal planes shown in any figure of the present disclosure.

[0049] refer to Figures 4A-4D , shows some general component options for an XR system according to some embodiments of the present invention. Figures 4A-4D In the sections of the detailed description that follow the discussion of the present invention, various systems, subsystems, and components are presented to address the goal of providing a high-quality, perceptually comfortable display system for human XR experience.

[0050] like Figure 4A As shown, an XR system user (60) is depicted as wearing a frame (64) structure coupled to a display system (62) located in front of the user's eyes. A speaker (66) is coupled to the frame (64) in the depicted configuration and is positioned adjacent to the user's ear canal (in one embodiment, another speaker, not shown, is positioned adjacent to the user's other ear canal to provide stereo / shapeable sound control). The display (62) is operably coupled (68) to a local processing and data module (70), such as by a wired conductor or a wireless connection, which can be mounted in a variety of configurations, such as fixedly attached to the frame (64), fixedly attached to a helmet or hat (80) (such as Figure 4B ), embedded in a headset, removably attached to the torso (82) of the user (60) in a backpack-type configuration (as shown in the embodiment of Figure 4C ), or removably attached to the hip (84) of the user (60) in a belt-coupled configuration (as shown in the embodiment of Figure 4D ).

[0051] The local processing and data module (70) may include a power efficient processor or controller, and digital memory, such as flash memory, both of which may be used to facilitate processing, caching and storing a) data captured from sensors that may be operatively coupled to the frame (64), such as image capture devices (such as cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, radios and / or gyroscopes; and / or b) data acquired and / or processed using a remote processing module (72) and / or a remote data repository (74), possibly for transmission to the display (62) after such processing or retrieval. The local processing and data module (70) may be operatively coupled (76, 78) to the remote processing module (72) and the remote data repository (74), such as via a wired or wireless communication link, such that these remote modules (72, 74) are operatively coupled to each other and may serve as resources for the local processing and data module (70).

[0052] In one embodiment, the remote processing module (72) may include one or more relatively powerful processors or controllers configured to analyze and process data and / or image information. In one embodiment, the remote data repository (74) may include a relatively large-scale digital data storage facility that may be available via the Internet or other networking configuration in a "cloud" resource configuration. In one embodiment, all data is stored and all computations are performed in the local processing and data module, thereby allowing full autonomous use from any remote module.

[0053] The perception of Z-axis differences (i.e., the distance straight out from the eye along the optical axis) can be facilitated by using a waveguide in conjunction with a variable focus optical element configuration. Image information from a display can be collimated and injected into the waveguide, and distributed in a large exit pupil manner using any suitable substrate-directed optical method known to those skilled in the art, and the variable focus optical element capability can then be used to change the focus of the wavefront of the light exiting the waveguide and provide the eye with the perception that the light from the waveguide is from a specific focal distance. In other words, since the incident light has been collimated to avoid the challenges in the total internal reflection waveguide configuration, it will exit in a collimated manner, requiring the observer's eye to accommodate to a far point to focus it on the retina, and naturally be interpreted as coming from optical infinity, unless some other intervention causes the light to be refocused and perceived as coming from a different viewing distance; one suitable such intervention is a variable focus lens.

[0054] In some embodiments, collimated image information is injected into a piece of glass or other material at an angle such that it is totally internally reflected and passed into an adjacent waveguide. The waveguide can be configured so that the collimated light from the display is distributed to exit somewhat uniformly over a distribution of reflectors or diffractive features along the length of the waveguide. On exiting toward the eye, the exiting light passes through a variable focus lens element, where the light exiting the variable focus lens element and entering the eye will have various focus levels (representing a collimated flat wavefront at optical infinity, representing increasing beam divergence / wavefront curvature for closer viewing distances relative to the eye 58 (see Figure 5-12 ).

[0055] In a "frame sequential" configuration, a stack of sequential two-dimensional images may be fed sequentially to a display to produce a three-dimensional perception over time in a manner similar to how a computed tomography system uses stacked image slices to represent a three-dimensional structure. A series of two-dimensional image slices, each at a different focal distance from the eye, may be presented to the eye, and the eye / brain integrates such a stack into the perception of a coherent three-dimensional volume. Depending on the display type, the sequencing may be done line by line or even pixel by pixel to produce the perception of three-dimensional viewing. For example, for a scanned light display (such as a scanning fiber display or a scanning mirror display), the display presents the waveguide with one line or pixel at a time in a sequential manner.

[0056] refer to Figure 6 , the stacked waveguide assembly 178 can be used to provide a three-dimensional perception to the eye / brain by having multiple waveguides 182, 184, 186, 188, 190 and multiple weak lenses 198, 196, 194, 192, which are configured together to send image information to the eye, where the various wavefront curvature levels for each waveguide level indicate the focal length to be perceived for that waveguide level. Multiple displays (200, 202, 204, 206, 208) or in another embodiment a single multiplexed display can be used to inject collimated image information into the waveguides 182, 184, 186, 188, 190, as described above, each waveguide can be configured to distribute the incident light substantially equally across the length of each waveguide so as to exit downwardly toward the eye.

[0057] The waveguide 182 closest to the eye is configured to deliver collimated light as injected into such waveguide 182 to the eye, which collimated light can represent an optical infinity focal plane. The next up waveguide (184) is configured to send out collimated light that passes through a first weak lens (192; e.g., a weak negative lens) before being able to reach the eye (58). The first weak lens (192) can be configured to produce a slightly convex wavefront curvature so that the eye / brain interprets light from one up waveguide (184) as coming from a first focal plane that is closer to the person from optical infinity inward. Similarly, the third up waveguide (186) passes its output light through both the first lens (192) and the second lens (194) before its output light reaches the eye (58). The combined optical power of the first lens (192) and the second lens (194) can be configured to produce another incremental wavefront divergence so that the eye / brain interprets light from the third upstream waveguide (186) as coming from a second focal plane that is closer to the person from optical infinity inward than the light from the next upstream waveguide (184).

[0058] The other waveguide layers (188, 190) and weak lenses (196, 198) are similarly configured, with the highest waveguide (190) in the stack sending its output through all weak lenses between it and the eye for an aggregated focal power that represents the focal plane closest to the person. To compensate for the lens stack (198, 196, 194, 192) when viewing / interpreting light from the world (144) on the other side of the stacked waveguide assembly (178), a compensating lens layer (180) is provided at the top of the stack to compensate for the aggregated power of the lens stack (198, 196, 194, 192) below. This configuration provides as many perceived focal planes as there are available waveguide / lens pairs, again with a relatively large exit pupil configuration as described above. The reflective aspects of the waveguides and the focusing aspects of the lenses can be static (i.e., not dynamic or electrically activated). In alternative embodiments, they may be dynamic, using electrically activated features as described above, thereby enabling a small number of waveguides to be multiplexed in a timed manner to produce a greater number of effective focal planes.

[0059] Various diffraction structures can be used to focus and / or redirect a collimated beam. For example, passing a collimated beam through a linear diffraction pattern, such as a Bragg grating, will deflect or "steer" the beam. Passing a collimated beam through a radially symmetric diffraction pattern or "Fresnel zone plate" will change the focus of the beam. A combined diffraction pattern with both linear and radial elements can be employed that produces both deflection and focusing of the collimated input beam. These deflection and focusing effects can be produced in reflection as well as transmission mode.

[0060] These principles can be applied to waveguide configurations to allow additional control of optical systems. Figure 7 As shown, a diffraction pattern (220) or "diffractive optical element" (or "DOE") has been embedded in a planar waveguide (216) so that when a collimated light beam is totally internally reflected along the planar waveguide (216), it intersects the diffraction pattern (220) at multiple locations. The structure may also include another waveguide (218) into which the light beam can be injected (e.g., by a projector or display), and in which the DOE (221) is embedded.

[0061] Preferably, the DOE (220) has a relatively low diffraction efficiency so that only a portion of the light beam is deflected toward the eye (58) at each intersection with the DOE (220), while the remainder of the light continues to move through the planar waveguide (216) via total internal reflection; the light carrying the image information is thus split into a plurality of related light beams that exit the waveguide at a plurality of locations, and the result is a fairly uniform pattern of outgoing emission toward the eye (58) for that particular collimated light beam reflected and transmitted within the planar waveguide (216), such as Figure 8 As shown. Figure 8 The outgoing beam directed toward the eye (58) is shown as being substantially parallel because in this case the DOE (220) has only a linear diffraction pattern. However, changes in the pitch of the linear diffraction pattern can be used to controllably deflect the outgoing parallel beam, thereby producing a scanning or tiling function.

[0062] refer to Fig. 9 , as the radially symmetric diffraction pattern component of the embedded DOE (220) changes, the outgoing beam pattern is more divergent, which will require the eye to accommodate to a closer distance to focus it on the retina and will be interpreted by the brain as light from a viewing distance closer to the eye than optical infinity.

[0063] refer to Fig.10 , by adding another waveguide (218) into which a light beam can be injected (e.g., by a projector or display), a DOE (221) embedded in the other waveguide (218), such as a linear diffraction pattern, can be used to disperse light across the entire larger planar waveguide (216), which is used to provide a very large incident field of incident light exiting the larger planar waveguide (216) to the eye (58), for example, a large eye box, depending on the particular DOE configuration at work.

[0064] The DOEs (220, 221) are described as bisecting the associated waveguides (216, 218), but this is not necessarily the case; they can be placed closer to either side of or on either of the waveguides (216, 218) to have the same functionality. Fig.11As shown, by injecting a single collimated beam, the entire field of cloned collimated beams can be directed to the eye (58). In addition, using a combined linear diffraction pattern / radially symmetric diffraction pattern scheme such as discussed above, a beam distribution waveguide optical device with Z-axis focusing capability is provided (for functions such as exit pupil function expansion; using a combination such as Fig.11 configuration, the exit pupil can be as large as the optic itself, which can be a significant advantage for user comfort and ergonomics), where the divergence angle of the cloned beams and the wavefront curvature of each beam represent light coming from a point closer than optical infinity.

[0065] In one embodiment, one or more DOEs may be switchable between an "on" state, in which they actively diffract, and an "off" state, in which they do not significantly diffract. For example, a switchable DOE may include a polymer dispersed liquid crystal layer, wherein droplets include a diffraction pattern in a host medium, and the refractive index of the droplets may be switched to substantially match that of the host material (in which case the pattern does not significantly diffract incident light), or the droplets may be switched to a refractive index that does not match that of the host medium (in which case the pattern actively diffracts incident light). In addition, by dynamically changing the diffraction terms, beam scanning or tiling functionality may be achieved. As described above, it is desirable to have a relatively low diffraction grating efficiency in each DOE (220, 221) because it aids in the distribution of light, and also because light transmitted through the waveguide (e.g., light from the world 144 to the eye 58 in an augmented reality configuration) is expected to be less affected when the diffraction efficiency of the DOE (220) that the light intersects is low, thereby achieving a better view of the real world through such a configuration.

[0066] Configurations such as that shown herein are preferably driven by injecting image information in a time sequential approach, with frame sequential drive being the most straightforward to implement. For example, at time 1 an image of the sky at optical infinity may be injected, and a diffraction grating may be utilized to maintain light collimation. Thereafter, at time 2 an image of a closer tree branch may be injected, with the DOE controllably imparting a focus change, such as one diopter or 1 meter away, in order to provide the eye / brain with the perception that the branch light information is from a closer focal range. This paradigm may be repeated in a rapid time sequential manner so that the eye / brain perceives the input as all parts of the same image. This is just an example of two focal planes, and preferably the system will include more focal planes to provide smoother transitions between objects and their focal distances. This configuration typically assumes that the DOE switches at a relatively low rate (i.e., in the tens to hundreds of cycles / second range, synchronized with the frame rate of the display into which the image is being injected).

[0067] The opposite extreme could be a configuration where the DOE element can move focus at frequencies of tens to hundreds of MHz or more, which facilitates switching the focus state of the DOE element on a pixel-by-pixel basis when scanning pixels into the eye (58) using a scanning light display type approach. This is desirable because it means that the overall display frame rate can be kept fairly low; just low enough to ensure that "flicker" is not an issue (in the range of about 60-120 frames / second).

[0068] Between these ranges, if the DOE can be switched at a KHz rate, the focus on each scan line can be adjusted line by line, which can provide a visible benefit to the user in terms of temporal artifacts, for example, during eye movement relative to the display. For example, different focal planes in a scene can be staggered in this way to minimize visible artifacts in response to head movement (as discussed in more detail later in this disclosure). The progressive focus modulator can be operably coupled to a line scan display, such as a grating light valve display, in which a linear array of pixels is scanned to form an image; and can be operably coupled to a scanned light display, such as a fiber scanned display and a mirror scanned light display.

[0069] Similar to Figure 6 With a stacked configuration, a dynamic DOE can be used to provide multi-plane focus simultaneously. For example, with three simultaneous focal planes, a primary focal plane can be presented to the user (e.g., based on measured eye accommodation), and a large focal range can be provided with + and - margins (i.e., one focal plane closer, one farther away) that the user can adjust before the plane needs to be updated. This increased focal range can provide a time advantage if the user switches to a closer or farther focus (i.e., as determined by accommodation measurements); the new focal plane can then be made to an intermediate focal depth, with + and - margins again ready to quickly switch to either while the system catches up.

[0070] refer to Fig.12 , a stack (222) of planar waveguides (244, 246, 248, 250, 252) is shown, each planar waveguide having a reflector (254, 256, 258, 260, 262) at an end and configured so that collimated image information injected into one end by a display (224, 226, 228, 230, 232) is reflected downwardly by total internal reflection to the reflector, at which point some or all of the light is reflected out toward the eye or other target. Each reflector can have a slightly different angle so that they all reflect the outgoing light toward a common destination (such as the pupil). A lens (234, 236, 238, 240, 242) can be inserted between the display and the waveguide for beam steering and / or focusing.

[0071] As mentioned above, objects at optical infinity produce essentially planar wavefronts, while closer objects, such as 1 m from the eye, produce curved wavefronts (with a convex radius of curvature of about 1 m). The optical system of the eye needs to have sufficient refractive power to bend the incident light rays so that they are ultimately focused on the retina (the convex wavefront becomes concave and then goes down to a focal point on the retina). These are the basic functions of the eye.

[0072] In many of the embodiments described above, the light directed to the eye has been considered as parts of one continuous wavefront, some subset of which will hit the pupil of a particular eye. In another approach, the light directed to the eye can be effectively discretized or decomposed into a plurality of beamlets or individual rays, each of which has a diameter of less than about 0.5 mm and a unique propagation path as part of a larger aggregate wavefront that can be functionally generated by the aggregation of beamlets or rays. For example, a curved wavefront can be approximated by aggregating a plurality of discrete adjacent collimated beams, each of which approaches the eye from an appropriate angle to represent an origin that matches the center of the radius of curvature of the desired aggregate wavefront.

[0073] When the sub-beams have a diameter of about 0.5 mm or less, it is as if it comes from a pinhole lens configuration, which means that each individual sub-beam is always relatively focused on the retina, regardless of the eye's accommodation state, however, the trajectory of each sub-beam will be affected by the accommodation state. For example, if the sub-beams approach the eye in parallel, representing a discretized collimated convergent wavefront, then the eye properly accommodated to infinity will deflect the sub-beams to all converge on the same shared spot on the retina, and will appear in focus. If the eye accommodates to the so-called 1 m, the beams will converge to a spot in front of the retina, cross the path, and land on multiple adjacent or partially overlapping spots on the retina - appearing blurred.

[0074] If the sub-beams approach the eye in a diverging configuration with the shared origin 1 meter away from the observer, then 1m of accommodation will steer the beams to a single spot on the retina and will appear in focus; if the observer accommodates to infinity, the sub-beams will converge to a spot behind the retina and produce multiple adjacent or partially overlapping spots on the retina, resulting in a blurred image. More generally, the accommodation of the eye determines the degree of overlap of the spots on the retina, and a given pixel is "in focus" when all spots are directed to the same spot on the retina, and "defocused" when the spots are offset from each other. The concept that all sub-beams of 0.5mm diameter or less are always in focus, and that they can be aggregated to be perceived by the eye / brain as if they were essentially the same as a coherent wavefront, can be used to produce configurations for comfortable three-dimensional virtual or augmented reality perception.

[0075] In other words, a set of multiple narrow beams can be used to simulate what a larger diameter variable focus beam is doing, and if the sub-beam diameters are kept at a maximum of about 0.5mm, they maintain a relatively static focus level, and in order to create the perception of defocus when desired, the sub-beam angular trajectories can be chosen to produce an effect very similar to that of the larger defocused beam (such a defocusing process may be different from the Gaussian blur process used for the larger beam, but will produce a multimodal point spread function that can be interpreted in a manner similar to a Gaussian blur).

[0076] In some embodiments, the sub-beams are not mechanically deflected to form this aggregate focusing effect, but instead the eye receives a superset of many sub-beams, including multiple angles of incidence and multiple locations where the sub-beams intersect the pupil; to represent a given pixel from a particular viewing distance, a subset of the sub-beams from the superset is turned on with a matching color and intensity, which subset includes the appropriate angles of incidence and intersections with the pupil (as if they were emanating from the same shared origin in space) to represent the aggregate wavefront, while the sub-beams in the superset that are not consistent with the shared origin are not turned on with this color and intensity (but some of them may be turned on with some other color and intensity levels to represent, for example, different pixels).

[0077] Reference now Figure 5, an example embodiment of an XR system 800 using an improved eyepiece with an improved diffractive structure will now be described. The XR system generally includes an image generation processor 812, at least one FSD 808 (fiber scanning device), an FSD circuit 810, a coupling optical device 832, and a pair of eyepieces 804 (one for each eye 58). Each eyepiece 804 includes an optical device assembly 802 (also referred to as a "DOE assembly 802"). The DOE assembly 802 includes a plurality of stacked DOEs 1300 having a diffractive structure that includes a waveguide with an improved diffractive structure, as described herein. The system 800 may also include an eye tracking subsystem 806. As Figure 5 As shown, the FSD circuit may include a circuit 810 in communication with an image generation processor 812, the circuit 810 having a Maxim chip CPU 818, a temperature sensor 820, a piezoelectric drive / transducer 822, a red laser 826, a blue laser 828, and a green laser 830, and a fiber combiner that combines all three lasers 826, 828, and 830. Note that other types of imaging technologies may also be used in place of the FSD device. For example, a high-resolution liquid crystal display ("LCD") system, a backlit ferroelectric panel display, and / or a high-frequency DLP system may all be used in some embodiments of the present invention.

[0078] The image generation processor 812 is responsible for generating virtual content that is ultimately displayed to the user. The image generation processor 812 can convert images or videos associated with the virtual content into a format that can be projected to the user in 3D. For example, when generating 3D content, the virtual content may need to be formatted so that parts of a specific image are displayed on a specific depth plane, while other parts are displayed at other depth planes. Alternatively, all images can be generated at a specific depth plane. Alternatively, the image generation processor can be programmed to feed slightly different images to the right eye and the left eye so that when viewed together, the virtual content appears coherent and comfortable to the user's eyes. In one or more embodiments, the image generation processor 812 delivers the virtual content to the optical component in a time-sequential manner. The first part of the virtual scene can be delivered first, so that the optical component projects the first part at a first depth plane. Then, the image generation processor 812 can deliver another part of the same virtual scene, so that the optical component projects the second part at a second depth plane, and so on. Here, the Alvarez lens assembly can be translated laterally fast enough to produce multiple lateral translations (corresponding to multiple depth planes) on a frame-to-frame basis.

[0079] The image generation processor 812 may also include a memory 814, a CPU 818, a GPU 816, and other circuits for image generation and processing. The image generation processor 812 may be programmed with the desired virtual content to be presented to the user of the AR system. It should be understood that in some embodiments, the image generation processor may be housed in a wearable XR system. In other embodiments, the image generation processor and other circuits may be housed in a belt pack coupled to the wearable optical device.

[0080] The XR system 800 also includes coupling optics 832 to direct light from the FSD to the optics assembly 802. The coupling optics 832 may refer to one or more conventional lenses for directing light into the DOE assembly. The XR system 800 also includes an eye tracking subsystem 806 configured to track the user's eyes and determine the user's focus.

[0081] In one or more embodiments, software blur can be used to cause blur as part of a virtual scene. In one or more embodiments, the blur module can be part of the processing circuit. The blur module can blur a portion of one or more frames of image data fed into the DOE. In such an embodiment, the blur module can blur portions of the frame that are not intended to be rendered at a particular depth frame. Example methods that can be used to implement the above-described image display system and components therein are described in U.S. utility patent application serial number 14 / 555,585 filed on November 27, 2014, which is incorporated herein by reference in its entirety.

[0082] Improved diffraction structure

[0083] As described above, a diffraction pattern can be formed on a planar waveguide so that when a collimated light beam is totally internally reflected along the planar waveguide, the light beam intersects the diffraction pattern at multiple locations. According to some embodiments of the present invention, this arrangement can be stacked to provide image objects at multiple focal planes within a stereoscopic 3-D simulation display system.

[0084] Figures 13A-13H Several exemplary embodiments of a diffractive structure 1300 for a DOE 804 are shown, which utilizes optical layer pairs to improve the performance of the eyepiece of the XR display system 800. Figures 13A-13H Different embodiments of have various configurations of the surface grating 1304, the input coupling grating 1310 (also referred to as "ICG" or "in-coupling grating"), the first reflector element 1308, and the optical layer pair 1306 relative to each other and the waveguide substrate 1302, as described herein. For example, Figures 13A-13D The embodiment ("double-sided") has surface gratings 1304 and optical layer pairs 1306 on both sides of the waveguide substrate 1302, while Figures 13E-13HAn embodiment (“single-sided”) has a surface grating 1304 and an optical layer pair 1306 on only a first side of a waveguide substrate 1302.

[0085] Fig.13A A diffractive structure 1300a (i.e., DOE 804) is depicted in which a surface grating 1304, an input coupling grating 1310, and a first reflector element 1308 are all disposed (e.g., formed, deposited, or placed) on a surface of one of the optical layer pairs 1306. The diffractive structure 1300a includes a waveguide substrate 1302 (also referred to herein as a "lightguide," "substrate," or "waveguide substrate"). The waveguide substrate 1302 has a high refractive index relative to the low refractive index elements of the diffractive structure 1300a. For example, the waveguide substrate 1302 can be formed of TAFD55 glass having a refractive index of approximately 2.0.

[0086] The top optical layer pair 1306a (also referred to as the "first optical layer pair 1306a") is disposed on the first side ( Fig.13A 1302 in the orientation shown), while the bottom optical layer pair 1306b (also referred to as the "second optical layer pair 1306b") is disposed on the second side ( Fig.13A 1306a). As used herein, the terms "top" and "bottom" are used only to distinguish elements from one another and provide a reference to their relative positions, and do not refer to the vertical relationship or orientation of any element of the present invention. Although only one top optical layer pair 1306a is shown for the diffractive structure 1300a, additional top optical layer pairs 1306a, such as a second top optical layer pair 1306a, may be stacked on the first optical layer pair 1306a. Similarly, only one bottom optical layer pair 1306b is shown for the diffractive structure 1300a, but additional bottom optical layer pairs 1306b, such as a second bottom optical layer pair 1306b, may be stacked on the top optical layer pair 1306b. For example, Fig.13I A diffractive structure 1300i is shown having two top optical layer pairs 1306a stacked on top of each other and two bottom optical layer pairs 1306b stacked on top of each other. In other embodiments, there may be a different number of stacked optical layer pairs 1306 at the top of the waveguide substrate 1302 than at the bottom (e.g., one top optical layer pair 1306a and two bottom optical layer pairs 1306b). In practice, Figures 13A-13G Any exemplary embodiment of the diffractive structure 1300 shown in FIG. 1 may have multiple optical layer pairs 1306 stacked on top of each other. As another example, Fig.13J A single-sided diffractive structure 1300j is shown having a plurality of optical layer pairs 1306a, in this case two optical layer pairs 1306a.

[0087] Each optical layer pair 1306a, 1036b includes a low refractive index layer 1305a, 1035b and a high refractive index layer 1307a, 1307b disposed directly on the outer side of the low refractive index layer 1305. As defined above, the terms "inside" and "outside" are relative to a plane 1311 passing through the middle of the thickness of the waveguide substrate 1302, wherein the plane 1311 is the innermost position. In other words, if an element is closer to the plane 1311, the element is "inside" of the other element. The high refractive index layer 1307 has a higher refractive index than the low refractive index layer 1305. The relative refractive indices of the high refractive index layer 1307 and the low refractive index layer 1305 are adjusted to selectively improve the uniformity of certain colors of the diffraction efficiency for certain colors, increase the magnitude and uniformity of the diffraction efficiency of the eyepiece, increase the (CPE) efficiency of the eyepiece, and / or increase the input coupling grating (ICG) emission efficiency of the eyepiece. The optical layer pairs 1306 may be disposed directly on a surface of the waveguide substrate 1302 , or there may be one or more intermediate layers (as described herein, and also referred to herein as “liners”) disposed between the optical layer pairs 1306 and the waveguide substrate 1302 .

[0088] like Fig.13A As shown, the input coupling grating 1306 is disposed on the outer surface of the first optical layer pair 1306a. The diffraction structure 1300a has a top surface grating 1304a disposed on the outer surface of the top optical layer pair 1306a disposed on the first side of the waveguide substrate 1302, and a bottom surface grating 1304b disposed on the outer surface of the bottom optical layer pair 1306b disposed on the second side of the waveguide substrate 1302. Therefore, the top optical layer pair 1306a is disposed between the waveguide substrate 1302 and the top surface grating 1304a, and the bottom optical layer pair 1306b is disposed between the waveguide substrate 1302 and the bottom surface grating 1304b. The top surface grating 1304a and the bottom surface grating 1304b have a low refractive index relative to the high refractive index element. As some non-limiting examples, the diffraction grating 1304 can be formed of KT21 material or the like. KT21 has a refractive index of about 1.5.

[0089] A first reflector element 1308 is disposed on an outer surface of the top optical layer pair 1306a. A surface input coupling grating 1306 is disposed on an outer surface of the second optical layer pair 1306a. Light beam 1310 illustrates an example of the path of an input light beam when the light is processed by the diffractive structure 1300a to provide image objects at multiple focal planes within a stereoscopic 3-D simulation display system. Fig.13A Also shown in FIG. 13 is the incident angle 1316 of the light beam as it travels through the diffractive structure 1300 .

[0090] Go to Fig. 13B, the diffraction structure 1300B is the same as the diffraction structure 1300a, except that the first reflector element 1308 is disposed on a surface of the first side (ie, the top surface) of the waveguide substrate 1302.

[0091] Fig. 13C A diffractive structure 1300c is shown that is identical to the diffractive structure 1300b, except that the ICG 1310 is disposed on the outer surface of the low refractive index layer 1305b of the bottom optical layer pair 1306b.

[0092] Fig.13D The diffractive structure 1300d shown is the same as the diffractive structure 1300b, except that the ICG 1310 is directly disposed on the bottom surface of the waveguide substrate 1302. In fact, this configuration in which the ICG 1310 is directly disposed on the surface of the waveguide substrate 1302, without any optical layer of the optical layer pair between the ICG 1310 and the waveguide substrate 1302, can be used in Figure 13A-1 In all embodiments shown in 313H, the performance of DOE 1300 is degraded due to the intermediate layer.

[0093] refer to Fig.13E , the diffractive structure 1300e is similar to the diffractive structure 1300a, except that it has an optical layer pair 1306 and a surface grating 1304 only on the top side of the waveguide substrate 1302. Therefore, the ICG 1310 is directly disposed on the bottom surface of the waveguide substrate 1302. In addition, the surface grating 1304 is formed by rastering etching into both the high refractive index layer 1307 of the top optical layer pair 1306 and the cover layer 1312 (which may be a low refractive index layer).

[0094] Go to Fig.13F , diffractive structure 1300f is identical to diffractive structure 1300e, except that the surface grating 1304a is formed only by etching into the high refractive index layer 1307a of the top optical layer pair 1306a.

[0095] Figure 13G The diffractive structure 1300g shown is identical to the diffractive structure 1300a, except that the surface grating 1304a is formed only in the low refractive index cover layer 1312 on the top side of the waveguide substrate 1302.

[0096] like Fig.13H As shown, the diffractive structure 1300h is the same as the diffractive structure 1300g, except that the diffractive structure 1300g also includes a high refractive index layer 1314 (e.g., a top surface layer or coating) on ​​top of the surface grating 1304a. The high refractive index layer 1314 on top of the surface grating 1304 can be added to any of the embodiments 1300a to 1300f.

[0097] As explained herein, the addition of an optical layer pair 1306 between the surface grating 1304 and the waveguide substrate 1302 improves the performance of the eyepiece. The added optical layer pair 1306 provides an increased degree of freedom to adjust the diffraction efficiency ratio (vs.) incident angle and wavelength behavior. This effect may be the result of a combination of thin film interference effects and changing the direction of light when it is incident on the surface grating 1304 through Snell's law. The ability to adjust the diffraction efficiency ratio vs. incident angle and wavelength potentially allows the following:

[0098] a. Selectively adjust the diffraction efficiency for certain colors in a single substrate eyepiece, where all colors (e.g., three primary colors) share a single waveguide and propagate in different angular ranges of incident angles 1316, resulting in better color uniformity; and

[0099] b. Improve uniformity across the field of view by better matching the diffraction efficiency and reflection transmission spacing (outcoupled beam density) and ICG emission efficiency, which also depends on the incident angle 1316.

[0100] Go to Fig.14A and 14B , the corresponding graph shows that, compared with the diffractive structure with a single optical layer pair 1306 ( Fig. 14B ) compared to a square diffraction structure ( Fig.14A ), diffraction efficiency versus angle of incidence. Fig. 14C A diffractive structure 1300 having a single optical layer pair 1306 is schematically shown in FIG. Fig. 14C The diffractive structure in includes an optical layer pair 1306 having a low refractive index layer 1305 including a coating / film of SiO2 and a high refractive index layer 1306 including a coating / film of TiO2. Fig.14A and 14B The graph of shows that the diffraction efficiency of the diffractive structure 1300 with the optical layer pair 1306 increases at higher incident angles 1316, where the reflection transmission spacing decreases, helping to compensate for the lower outcoupled power.

[0101] Fig.15A and 15B It is shown that in the use of ( Fig. 15B ) and not using ( Fig.15A ) Comparison of the response of the optical layer to a single diffractive structure in the three primary colors (red, blue, green, RGB) in the case of 1306. Fig. 15BThe diffraction structure of the image includes a 2-side surface grating embossed with a honeycomb structure, a waveguide substrate formed of TAFD55 glass and coated with an optical layer pair 1306 under the embossed grating. The optical layer pair 1306 includes a high refractive index layer 1307 and a low refractive index layer 1305, the high refractive index layer includes a 100nm thick TiO2 layer, and the low refractive index layer includes a 10nm thick SiO2 layer. Fig.15A As shown, the blue light has the brightest blue area 1502 and the less bright blue area 1504, the green light has the brightest green area 1506 and the less bright green area 1508, and the red light has the brightest red area 1510 and the less bright red area 1512.

[0102] The goal of the color response is to obtain the maximum overlap of all three colors. Fig.15A and 15B As shown, this occurs near the center. Red and blue are usually displayed on opposite sides of the field of view. Extending either of these colors toward the center will help provide a larger area in which there is proper color overlap and a properly colored image is possible. By comparing Fig.15A and 15B It can be seen that the use of optical layer pair 1306 causes the red color to be extended in the center of the image, which is what this particular optical layer pair 1306 is designed to enhance. Fig. 15B In the example, red is present in 3 / 4 of the image in the eyepiece with the optical layer pair 1306 coating, while in Fig.15A Without optical layer pair 1306, red is present in only approximately half of the image. In general, combinations of higher index coatings and multiple index coatings will produce larger and more complex swings in diffraction efficiency. For a three-layer eyepiece stack, where each layer is individually optimized for red, green, and blue wavelengths, the addition of optical layer pair 1306 coatings affects diffraction efficiency as described above, which in turn also affects overall optical performance, as further explained below.

[0103] Fig.16A Schematically, a substrate structure 1300 is shown with an ICG 1310 and a CPE 1318. Fig.16A As shown, CPE 1318 is a variable height grating structure. A display engine (e.g., a projector) couples light into the waveguide substrate 1302 via ICG 1310. For example, the display engine can be a liquid crystal on silicon (LCOS) display. Each LCOS pixel is mapped to a specific angle of incidence at the location of ICG 1310.

[0104] Fig. 16B yes Fig.16AFigure 13 shows a momentum space diagram of the substrate structure 1300, where each incident angle is mapped to the momentum of the light indicated by the right box 1320. The light within the waveguide propagating toward the CPE 1318 consists of rays whose momentum is shifted by the ICG grating vector (2π / lattice period). The corresponding momentum of the incoupled light is located in the left box 1322. All of these rays interact with the grating areas in the CPE 1318, experiencing the appropriate shifts in momentum space (top box 1324 and bottom box 1326). The CPE grating 1318 is designed to diffuse the light as well as couple it out. Fig. 16C A typical example of the variation of the emission efficiency according to the incident angle for the substrate structure 1300 is shown. Fig. 16B The diffraction efficiency of s-polarized light diffracted by the CPE shown in Fig.16D This is confirmed in Fig. 16C and 16D As is evident from Figure 1, the emission efficiency and diffraction efficiency of the grating, and therefore the display pixel, is highly non-uniform depending on the incident angle or momentum of the light. Another factor that increases the non-uniformity is the non-uniformity in the amount of interaction of the light within the waveguide 1302 with the diffraction grating 1304. Fig. 16B The left box 1322 shows the momentum of the light within the waveguide, Fig.16E The number of collisions with the surface grating 1304 for a propagation distance of 2 mm is shown in . This illustrates that the light rays corresponding to the left portion of the field of view interact more strongly than the light rays corresponding to the right portion of the field of view. As a result, the location of the strongest emission from a particular display pixel varies greatly within the area of ​​the CPE 1318, resulting in a non-uniform luminous emission distribution at a given location. This is schematically shown in , together with a simulated light distribution at the center of the CPE 1318. Fig.16F Ideally, the distribution shown in the top schematic should be uniform across the field of view.

[0105] Ideally, the distribution shown in the top schematic should be uniform across the field of view.

[0106] To capture the contribution of diffraction efficiency, the CPE efficiency over the entire field of view is defined as the product of the diffraction efficiency, the number of collisions with the grating, and the ICG emission efficiency (normalized by an appropriate factor). This quantification is represented by the following equation:

[0107] CPE efficiency(θx，θy) = diffraction efficiency × (number of collisions within 2 mm) / 10 × ICG emission efficiency

[0108] Fig.17A and 17B The diffraction structure without the optical layer pair 1306 is shown ( Fig.17A ) and the diffractive structure 1300 having a single optical layer pair 1306 ( Fig. 17B)’s diffraction efficiency uniformity. Fig.17A Corresponding to a single-layer design consisting of a TAFD55 glass waveguide substrate 1302 and a surface grating 1304 of a 20 nm thick layer of KT21 material. Fig. 17B Corresponding to Fig. 17B The same design, but with the addition of a single optical pair 1306, having a high refractive index layer 1307 comprising a 90 nm thick TiO2 layer and a low refractive index layer 1305 comprising a 10 nm thick SiO2 layer, inserted between the waveguide substrate 1302 and the surface grating layer 1304. Fig.17A and 17B The left 2d plot shows the diffraction efficiency variation, the middle 2d plot shows the CPE efficiency defined above, and the right 2d plot shows the normalized emission distribution within a 4 mm square box located at the center of the CPE. Simulations were performed using in-house ray tracing software.

[0109] For an ideal uniform light emission near the center of the CPE (where the human eye would be located), the CPE efficiency should be uniform across the entire field of view. Engineering the diffraction efficiency of 1306 by adding optical layers reduces CPE efficiency non-uniformity, such as Fig.17A and 17B The uniformity gain is noted with full ray tracing simulations. The uniformity is characterized by a typical 8020 uniformity over the inner 80% of the field of view (the difference between the 80th and 20th percentile values ​​divided by the medium 50th percentile value). Lower values ​​of the 8020 uniformity score mean better uniformity. While this is an example, additional optimizations can be performed based on different combinations of coatings and cover layers to optimize the CPE efficiency uniformity, and therefore the uniformity of the extended reality (XR) waveguide display over the field of view.

[0110] In addition to the above Figures 13A-13G , 14C and 16, these structures are possible with patterns in organic materials on the high refractive index layer 1305 using lithography or imprint lithography with ultra-thin RLT (~20nm, such as using ML's J-FILTM), and these structures should perform similarly to the angles considered in the following cases:

[0111] 1) A high refractive index grating can be etched using pattern definition from an organic layer (reactive ion etching "RIE", inductively coupled plasma etching "ICP", ion beam etching "IBE", etc.);

[0112] 2) A high refractive index layer may be further deposited on the organic pattern using a PVD (sputtering, evaporation) or "CVD" (low pressure plasma enhanced CVD "LPPECVD", atomic layer deposition "ALD", "atmospheric pressure plasma enhanced" APPECVD) process, which then defines a pattern for the capping high refractive index layer;

[0113] 3) depositing a second low refractive index layer on the first high refractive index layer (which is on the first low refractive index layer), and etching the second low refractive index layer using a patterned resist (RIE, ICP, IBE);

[0114] 4) Similarly, the patterned second low refractive index layer can be deposited using PVD (sputtering, evaporation) or CVD (PPPECVD, ALD, APPECVD) processes to obtain a high refractive index capping layer that defines a high refractive index pattern.

[0115] The high refractive index layer 1307 can be a film or coating applied as described herein. The high refractive index layer 1307 can include various inorganic materials, such as Si3N4, ZrO2, TiO2, SiC, ZnTe, GP, BP and / or similar materials with high refractive index (greater than 1.7), and low absorption (k<0.001) type materials, which have a high refractive index greater than 1.7 and low absorption (k<0.001). The high refractive index layer 1307 can also include any suitable organic filler-based materials, such as organic UV and / or thermal curable resin composites composed of sulfur, aromatic groups (which maintain the high refractive index of the aggregate base material>1.6) and high refractive index nanoparticles (e.g., ZrO2, TiO2), which have functional surfaces to prevent particle agglomeration and maintain uniform particle dispersion in the composite resin solution (which causes internal scattering of light in TIR on a uniform homogenous high refractive index film).

[0116] The low refractive index layer 1305 may also be a film or coating applied as described herein. The low refractive index layer 1305 may include, but is not limited to, any suitable inorganic material, such as MgF, SiO2, etc., and organic materials, such as common UV and heat curable resins, which typically have a refractive index of about 1.53, and Teflon type materials, which have a refractive index of about 1.3. Sol-gel methods can be used to prepare porous materials with a refractive index of up to 1.1-1.2 (which will cause the light in TIR to be internally scattered on a uniform and homogeneous low refractive index film). Figures 13A-13G As shown, the surface grating 1304 pattern and the optical layer pair 1306 of the diffractive structure 1300 can be on the same side, opposite sides, or both sides of the waveguide substrate 1302.

[0117] Any suitable manufacturing technique may be used to manufacture the diffractive structure 1300 disclosed herein. Certain high refractive index aggregates, such as one known as "MR 174", can be directly embossed, stamped or etched to produce the desired patterned structure, although there may be challenges associated with the curing shrinkage of such layers, etc. Therefore, in another embodiment, another material may be stamped, stamped or etched on a high refractive index aggregate layer (i.e., such as an MR 174 layer) to produce a functionally similar result. The current state of the art of stamping, etching (i.e., which may include resist removal and patterning steps similar to those utilized in conventional semiconductor processes) and embossing techniques may be utilized and / or combined to achieve such stamping, stamping and / or etching steps. Molding techniques similar to those used, for example, in the production of DVDs may also be used for certain replication steps. In addition, certain spraying or deposition techniques used in stamping and other deposition processes may also be used to precisely deposit certain layers.

[0118] In the foregoing description, the present invention has been described with reference to specific embodiments of the present invention. However, it will be apparent that various modifications and changes may be made thereto without departing from the broader spirit and scope of the present invention. For example, the above process flow is described with reference to a specific sequence of process actions. However, the sequence of many of the described process actions may be changed without affecting the scope or operation of the present invention. Therefore, the description and drawings should be considered illustrative rather than restrictive.

[0119] Various exemplary embodiments of the present invention are described herein. Reference is made to these examples in a non-limiting sense. They are provided to illustrate the more extensive applicable aspects of the present invention. Various changes may be made to the described invention and may be replaced with equivalents without departing from the true spirit and scope of the present invention. In addition, many modifications may be made to adapt specific situations, materials, compositions of matter, processes, process actions or steps to the purpose, spirit or scope of the present invention. In addition, it will be appreciated by those skilled in the art that each individual variation described and illustrated herein has discrete components and features that may be easily separated or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present invention. All of these modifications are intended to fall within the scope of the claims associated with the present disclosure.

[0120] The present invention includes methods that can be performed using subject devices. The methods may include an action of providing such suitable devices. Such providing may be performed by an end user. In other words, the "providing" action merely requires the end user to obtain, access, approach, locate, set up, activate, power on, or otherwise act to provide the necessary devices in the method. The methods described herein may be performed in any order of the events described that is logically possible and in the order of the events described.

[0121] The exemplary aspects of the present invention and the details about material selection and manufacturing have been described above. As for other details of the present invention, these can be understood in conjunction with the above-mentioned patents and publications and what is known or understood by those skilled in the art. The same is true for the method-based aspects of the present invention in terms of additional actions that are usually or logically adopted.

[0122] In addition, although the present invention has been described with reference to several examples optionally incorporating various features, the present invention is not limited to those described or indicated as expected with respect to each variation of the present invention. Various changes may be made to the described present invention, and equivalents may be substituted (whether enumerated herein or not included for brevity) without departing from the true spirit and scope of the present invention. In addition, where a range of values ​​is provided, it is to be understood that each intermediate value between the upper and lower limits of the range and any other specified or intermediate values ​​within the specified range are included in the present invention.

[0123] Moreover, it is contemplated that any optional features of the described variations of the invention may be set forth and claimed independently or in combination with any one or more of the features described herein. References to singular items include the possibility of the presence of a plurality of identical items. More specifically, as used herein and in the claims associated therewith, the singular forms "one", "an", "said", and "the" include plural referents unless otherwise specifically stated. In other words, the use of articles allows for "at least one" of the subject items in the above description and in the claims associated with the present disclosure. It should also be noted that such claims can be written to exclude any optional elements. Therefore, this statement is intended to be used as an antecedent basis for the use of exclusive terms such as "solely", "only", etc., or the use of "negative" limitations related to the narration of the claim elements.

[0124] Without using such exclusive terms, the term "comprising" in the claims associated with the present disclosure will allow for the inclusion of any additional elements - regardless of whether a given number of elements are recited in such claims, or the addition of features can be considered to transform the nature of the elements recited in such claims. Unless otherwise expressly defined herein, all technical and scientific terms used herein shall be given the broadest commonly understood meaning possible while maintaining claim validity.

[0125] The scope of the present invention is not limited to the examples provided and / or subject description, but is limited only by the scope of the claim language associated with the present disclosure.

[0126] The above description of the illustrated embodiments is not intended to be exhaustive, nor is it intended to limit the embodiments to the precise form disclosed. Although specific embodiments and examples are described herein for illustrative purposes, various equivalent modifications may be made without departing from the spirit and scope of the present disclosure, as will be appreciated by those skilled in the relevant art. The teachings of the various embodiments provided herein may be applied to other devices that implement virtual or AR or hybrid systems and / or employ user interfaces, not necessarily the example AR systems generally described above.

[0127] For example, the foregoing detailed description has described various embodiments of the apparatus and / or method by using block diagrams, schematic diagrams, and examples. To the extent that these block diagrams, schematic diagrams, and examples contain one or more functions and / or operations, those skilled in the art will appreciate that each function and / or operation in these block diagrams, flow charts, or examples may be implemented individually and / or collectively by a variety of hardware, software, firmware, or indeed any combination thereof.

[0128] In one embodiment, the subject matter may be implemented via an application specific integrated circuit (ASIC). However, those skilled in the art will recognize that the embodiments disclosed herein may be equivalently implemented in whole or in part in a standard integrated circuit as one or more computer programs executed by one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs executed by one or more controllers (e.g., microcontrollers), as one or more programs executed by one or more processors (e.g., microprocessors), as firmware, or as nearly any combination thereof, and that designing circuits and / or writing code for software and / or firmware is well within the skill of those of ordinary skill in the art in light of the teachings of the present disclosure.

[0129] When logic is implemented as software and stored in memory, the logic or information may be stored on any computer-readable medium for use by or in combination with any processor-related system or method. In the context of the present disclosure, memory is a computer-readable medium, which is an electronic, magnetic, optical or other physical device or component that contains or stores a computer and / or processor program. Logic and / or information may be embodied in any computer-readable medium for use by or in combination with an instruction execution system, device or apparatus, such as a computer-based system, a system containing a processor, or other systems that can obtain instructions from an instruction execution system, device or apparatus and execute instructions associated with logic and / or information.

[0130] In the context of this specification, a "computer-readable medium" can be any element capable of storing a program associated with logic and / or information for use by or in conjunction with an instruction execution system, device, and / or apparatus. A computer-readable medium can be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or apparatus. More specific examples (a non-exhaustive list) of computer-readable media would include the following: portable computer disks (magnetic, compact flash cards, secure digital, etc.), random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM, EEPROM, or flash memory), portable compact disk read-only memory (CDROM), digital tape, and other non-permanent media.

[0131] Any method described herein may be varied. For example, many methods may include additional actions, omit some actions, and / or perform actions in a different order than that illustrated or described.

[0132] The various embodiments described above may be combined to provide further embodiments. To the extent not inconsistent with the specific teachings and definitions herein, all U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications, and non-patent publications mentioned in this specification and / or listed in the Application Data Sheet. If necessary, various aspects of the embodiments may be modified to provide additional embodiments using systems, circuits, and concepts from various patents, applications, and publications.

[0133] These and other changes can be made to the embodiments in light of the above detailed description. Generally, in the appended claims, the terms used should not be interpreted as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be interpreted as including all possible embodiments and the full range of equivalents authorized by these claims. Therefore, the claims are not limited by the present disclosure.

[0134] Furthermore, the various embodiments described above can be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary, to employ concepts of the various patents, applications and publications to provide further embodiments.

[0135] These and other changes can be made to the embodiments in light of the above detailed description. Generally, in the appended claims, the terms used should not be interpreted as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be interpreted as including all possible embodiments and the full range of equivalents authorized by these claims. Therefore, the claims are not limited by the present disclosure.

Claims

1. An eyepiece for an XR display system, comprising: a diffractive optical element (DOE) for receiving light associated with one or more frames of image data and directing the light to an eye of a user, the DOE comprising a diffractive structure having a waveguide substrate, a surface grating, and one or more optical layer pairs, the waveguide substrate having a first side and a second side opposite the first side, the surface grating being positioned on the first side of the waveguide substrate, and the one or more optical layer pairs being disposed between the waveguide substrate and the surface grating; as well as Each optical layer pair includes a low refractive index layer and a high refractive index layer directly disposed on an outer side of the low refractive index layer, wherein the high refractive index layer has a higher refractive index than the low refractive index layer.

2. The eyepiece according to claim 1, wherein: The one or more optical layer pairs are disposed directly on the first side of the waveguide substrate.

3. The eyepiece of claim 1 , further comprising one or more intermediate layers disposed between the pair of optical layers and the waveguide substrate.

4. The eyepiece according to any one of claims 1 to 3, wherein: The one or more optical layer pairs include: a first optical layer pair on the first side of the waveguide substrate; and A second optical layer pair is provided on the second side of the waveguide substrate.

5. The eyepiece according to any one of claims 1 to 4, further comprising: A second surface grating on the second side of the waveguide substrate, wherein the second optical layer pair is between the waveguide substrate and the second surface grating.

6. The eyepiece according to any one of claims 1 to 5, further comprising: an input coupling grating disposed on said first side of said waveguide substrate; as well as A first reflector is disposed on the second side of the waveguide substrate.

7. The eyepiece according to any one of claims 1 to 6, wherein: The waveguide substrate has a refractive index higher than that of the low refractive index layer.

8. The eyepiece according to any one of claims 1 to 7, wherein: The high refractive index layer comprises a material selected from the group consisting of Si3N4, ZrO2, TiO2, SiC, ZnTe, GP, and BP, and the high refractive index layer has a refractive index greater than about 1.7; and The low refractive index layer includes a material selected from the group consisting of MgF, SiO2, a UV curable resin, and a thermal curable resin, and has a refractive index of less than about 1.

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9. The eyepiece according to any one of claims 1 to 8, wherein: The grating surface has a lower refractive index than the high refractive index layer.

10. The eyepiece according to any one of claims 1 to 9, further comprising: A top surface layer is disposed on an outer surface of the surface grating, the top surface layer having a refractive index higher than that of the low refractive index layer.

11. An extended reality (XR) display system for delivering extended reality content to a user, comprising: An image generation source, used for providing one or more frames of image data; a light modulator for transmitting light associated with the one or more frames of image data; as well as a diffractive optical element (DOE) for receiving light associated with the one or more frames of image data and directing the light to an eye of a user, the DOE comprising a diffractive structure having a waveguide substrate, a surface grating, and one or more optical layer pairs, the waveguide substrate having a first side and a second side opposite to the first side, the surface grating being positioned on the first side of the waveguide substrate, and the one or more optical layer pairs being disposed between the waveguide substrate and the surface grating; as well as Each optical layer pair includes a low refractive index layer and a high refractive index layer directly disposed on an outer side of the low refractive index layer, wherein the high refractive index layer has a higher refractive index than the low refractive index layer.

12. The system according to claim 11, wherein: The one or more optical layer pairs are disposed directly on the first side of the waveguide substrate.

13. The system according to claim 11, wherein: The diffractive structure further includes one or more intermediate layers disposed between the pair of optical layers and the waveguide substrate.

14. A system according to any one of claims 11 to 13, wherein: The one or more optical layer pairs include: a first optical layer pair on the first side of the waveguide substrate; and A second optical layer pair is provided on the second side of the waveguide substrate.

15. A system according to any one of claims 11 to 14, wherein: The diffractive structure further comprises: A second surface grating on the second side of the waveguide substrate, wherein the second optical layer pair is between the waveguide substrate and the second surface grating.

16. The system according to any one of claims 11 to 15, further comprising: an input coupling grating disposed on said first side of said waveguide substrate; as well as A first reflector is disposed on the second side of the waveguide substrate.

17. A system according to any one of claims 11 to 16, wherein: The waveguide substrate has a refractive index higher than that of the low refractive index layer.

18. A system according to any one of claims 11 to 17, wherein: The high refractive index layer comprises a material selected from the group consisting of Si3N4, ZrO2, TiO2, SiC, ZnTe, GP, and BP, and the high refractive index layer has a refractive index greater than about 1.7; and The low refractive index layer includes a material selected from the group consisting of MgF, SiO2, a UV curable resin, and a thermal curable resin, and has a refractive index of less than about 1.

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19. A system according to any one of claims 11 to 18, wherein: The grating surface has a lower refractive index than the high refractive index layer.

20. The system according to any one of claims 11 to 19, wherein: The diffractive structure further comprises: A top surface layer is disposed on an outer surface of the surface grating, the top surface layer having a refractive index higher than that of the low refractive index layer.

21. A system according to any one of claims 11 to 19, wherein: The DOE includes a stacked waveguide assembly having a plurality of diffractive structures stacked together, the plurality of diffractive structures including the diffractive structure.

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