Virtual and augmented reality systems and methods having improved diffraction grating structures

Abstract

Providing virtual and augmented reality systems and methods having improved diffraction grating structures. [Solution] An improved diffraction structure for a 3D display system is disclosed. The improved diffraction structure includes an intermediate layer between a waveguide substrate and an upper grating surface. The upper grating surface comprises a first material corresponding to a first refractive index value, the lower layer comprises a second material corresponding to a second refractive index value, and the substrate comprises a third material corresponding to a third refractive index value. In one embodiment, the waveguide substrate, the lower layer, and the surface grating all correspond to different refractive index values. In one embodiment, the surface grating corresponds to a surface grating refractive index higher than the lower layer diffraction coefficient, and the lower layer diffraction coefficient is higher than the waveguide refractive index.

Description

Technical Field

[0001] The present disclosure relates to virtual reality and augmented reality imaging and visualization systems.

Background Art

[0002] Modern computing and display technologies have facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images or portions thereof are presented to a user in a manner that appears or can be perceived as being real. Virtual reality, i.e., a "VR" scenario, typically involves the presentation of digital or virtual image information without transparency to other actual real-world visual inputs. Augmented reality, i.e., an "AR" scenario, typically involves the presentation of digital or virtual image information as an extension of the visualization of the actual world surrounding the user. For example, referring to FIG. 1, an augmented reality scene (4) is depicted, and a user of AR technology perceives that a setting (6) such as a real-world park featuring people, trees, buildings as a background, and a concrete platform (1120) is visible. In addition to these items, the user of AR technology also "sees" a robotic image (1110) standing on the real-world platform (1120) and an avatar character (2) in the form of a flying cartoon that appears to be an anthropomorphic hornet, but these elements (2, 1110) do not exist in the real world. In conclusion, the human visual perception system is very complex, and it is difficult to generate VR or AR technologies that facilitate a comfortable and natural-feeling rich presentation of virtual image elements among other virtual or real-world image elements.

[0003] Presenting 3D virtual content to users of AR systems presents numerous challenges. A fundamental prerequisite for presenting 3D content to users is the generation of multiple depth perceptions. In other words, it may be desirable for some virtual content to appear closer to the user, while others appear further away. Therefore, to achieve 3D perception, AR systems should be configured to deliver virtual content to the user at different focal planes.

[0004] It is desirable for 3D displays to generate a distance accommodation response corresponding to the virtual depth of each point within the display's field of view, in order to provide a true sense of depth, or more specifically, a simulated sense of surface depth. If the distance accommodation response for a display point does not correspond to the virtual depth of that point, which is determined by the binocular depth cues for convergence and stereopsis, the human visual system will experience distance accommodation collision, which can result in unstable image formation, harmful eye strain, headaches, and, in the absence of distance accommodation information, a near-complete loss of surface depth.

[0005] Therefore, there is a need for improved techniques to implement 3D displays that solve these and other problems of conventional approaches. The systems and techniques described herein are configured to address these challenges in conjunction with typical human visual constructs. [Overview of the Initiative] [Means for solving the problem]

[0006] Embodiments of the present invention relate to devices, systems, and methods for facilitating virtual reality and / or augmented reality interactions for one or more users.

[0007] An augmented reality (AR) display system for delivering augmented reality content to a user, according to several embodiments, comprises an image 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 a diffractive optical element (DOE) for receiving light associated with one or more frames of image data and directing the light toward the user's eye, wherein the DOE comprises a diffractive structure having a waveguide substrate, a surface grating, and an intermediate layer (also referred to herein as the “underlayer”) disposed between the waveguide substrate and the surface grating, the underlayer having a lower layer diffraction coefficient different from that of the waveguide refractive index.

[0008] According to some embodiments of the present invention, the diffraction structure is employed for DOE, including a lower layer between the waveguide substrate and the upper lattice surface. The upper lattice surface comprises a first material corresponding to a first refractive index value, the lower layer comprises a second material corresponding to a second refractive index value, and the substrate comprises a third material corresponding to a third refractive index value.

[0009] Any combination of identical or different materials may be employed to implement each of these parts of the structure, for example, all three materials may be different (and all three materials may correspond to different refractive index values), or two of the layers may share the same material (for example, two of the three materials may be identical and therefore share a common refractive index value different from that of the third material). Any suitable set of materials may be used to implement any layer of the improved diffraction structure.

[0010] Therefore, various combinations are available, and a lower layer of one refractive index can be combined with a substrate of a third refractive index and an upper grating of another refractive index. Adjusting these relative values ​​provides many variations in the dependence of diffraction efficiency on the angle of incidence. Layered waveguides with layers of different refractive indices are presented. Various combinations and permutations are presented along with relevant performance data to illustrate their functionality. An advantage is the increase in angle, which provides an increase in output angle using the grating and, therefore, an increase in field of view using the eyepiece. Furthermore, the ability to counteract the normal decrease in diffraction efficiency with angle is functionally beneficial.

[0011] In some embodiments, the waveguide substrate, the underlayer, and the surface grating correspond to different refractive index values. For example, the surface grating may correspond to a higher surface grating refractive index compared to the underlayer diffraction coefficient, and the underlayer diffraction coefficient may be higher than the waveguide refractive index.

[0012] In some embodiments, at least two of the waveguide substrate, sublayer, and surface grating correspond to a common refractive index value. For example, the surface grating may correspond to a surface grating refractive index that is identical to the waveguide diffraction coefficient, while the sublayer diffraction coefficient differs from the waveguide refractive index and the surface grating refractive index. In addition, the surface grating may correspond to a surface grating refractive index that is identical to the sublayer diffraction coefficient, while the waveguide diffraction coefficient differs from the sublayer refractive index and the surface grating refractive index.

[0013] In some embodiments, the sublayer has a non-uniform thickness. The non-uniform thickness of the sublayer can vary from relatively thin to relatively thick as the distance from the light source increases. In addition, the sublayer can have a non-uniform sublayer refractive index. For example, the non-uniform sublayer refractive index of the sublayer can vary from being relatively similar to the waveguide refractive index to having an increasing difference from the waveguide refractive index as the distance from the light source increases.

[0014] In some embodiments, the system comprises a stacked waveguide assembly having multiple diffraction structures stacked together. In addition, the DOE is switchable between an on and off state. The system can be implemented as a head-mountable wearable system.

[0015] In at least one embodiment, the diffraction structure comprises an upper layer covering the surface lattice. The upper layer may be used to form an intervening layer for stacking the diffraction structure, and the upper layer has a relatively low refractive index. In addition, the upper layer may also be used to provide a diffraction effect, for example, the upper layer has a relatively high refractive index.

[0016] Additional and other objects, features, and advantages of the present invention are described in the embodiments, drawings, and claims for carrying out the invention. For example, this application provides the following items. (Item 1) An augmented reality (AR) display system for delivering augmented reality content to users, An image source for providing one or more frames of image data, An optical modulator for transmitting light associated with one or more frames of the image data, A diffractive optical element (DOE) for receiving light associated with one or more frames of the image data and directing the light toward the user's eye. Equipped with, The DOE comprises a diffraction structure having a waveguide substrate, a surface grating, and a lower layer disposed between the waveguide substrate and the surface grating, wherein the lower layer corresponds to a lower layer diffraction coefficient different from that of the waveguide. (Item 2) The waveguide substrate, the lower layer, and the surface grid are all of the system described in item 1, corresponding to different refractive index values. (Item 3) The system according to item 2, wherein the surface grating corresponds to a surface grating refractive index higher than the lower layer diffraction coefficient, and the lower layer diffraction coefficient is higher than the waveguide refractive index. (Item 4) The system according to item 1, wherein at least two of the waveguide substrate, the lower layer, and the surface grid correspond to a common refractive index value. (Item 5) The system described in item 4, wherein the surface grid corresponds to a surface grid refractive index that is the same as the waveguide diffraction coefficient, and the lower layer diffraction coefficient is different from the waveguide refractive index and the surface grid refractive index. (Item 6) The system described in item 4, wherein the surface grid corresponds to a surface grid refractive index that is the same as the lower layer diffraction coefficient, and the waveguide diffraction coefficient is different from the lower layer refractive index and the surface grid refractive index. (Item 7) The lower layer has a non-uniform thickness, as described in item 1. (Item 8) The system described in item 7, wherein the non-uniform thickness of the lower layer changes from relatively thin to relatively thick as the distance from the light source increases. (Item 9) The system according to item 1, wherein the lower layer has a non-uniform lower layer refractive index. (Item 10) The system according to item 9, wherein the non-uniform refractive index of the lower layer changes from being relatively similar to the refractive index of the waveguide to having an increasing difference from the refractive index of the waveguide as the distance from the light source increases. (Item 11) The system according to item 1, comprising a stacked waveguide assembly having a plurality of the diffraction structures stacked together. (Item 12) The aforementioned DOE is switchable between an on state and an off state, as described in item 1. (Item 13) The system described in item 1 is embodied as a wearable system that can be mounted on the head. (Item 14) The system according to item 1, wherein the diffraction structure further includes an upper layer covering the surface grating. (Item 15) The system according to item 14, wherein the upper layer forms an intervening layer for stacking the diffraction structure, and the upper layer has a relatively low refractive index. (Item 16) The system according to any one of items 1 to 15, wherein the waveguide substrate, the lower layer, and the surface grating correspond to different materials.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 illustrates a user's view of augmented reality (AR) through a wearable AR user device in one illustrated embodiment.

[0018] [Figure 2] FIG. 2 illustrates a conventional stereoscopic 3D simulation display system.

[0019] [Figure 3] FIG. 3 illustrates an improved approach for implementing a stereoscopic 3D simulation display system according to some embodiments of the present invention.

[0020] [Figure 4A] FIGS. 4A-4D illustrate various systems, subsystems, and components for addressing the purpose of providing a high-quality and comfortably perceivable display system for human VR and / or AR. [Figure 4B] FIGS. 4A-4D illustrate various systems, subsystems, and components for addressing the purpose of providing a high-quality and comfortably perceivable display system for human VR and / or AR. [Figure 4C]Figures 4A-4D illustrate various systems, subsystems, and components to address the objective of providing a high-quality, comfortable-perceiving display system for human VR and / or AR. [Figure 4D] Figures 4A-4D illustrate various systems, subsystems, and components to address the objective of providing a high-quality, comfortable-perceiving display system for human VR and / or AR.

[0021] [Figure 5] Figure 5 illustrates a plan view of an exemplary configuration of a system utilizing an improved diffraction structure.

[0022] [Figure 6] Figure 6 illustrates a stacked waveguide assembly.

[0023] [Figure 7] Figure 7 illustrates the Department of Energy (DOE).

[0024] [Figure 8] Figures 8 and 9 illustrate exemplary diffraction patterns. [Figure 9] Figures 8 and 9 illustrate exemplary diffraction patterns.

[0025] [Figure 10] Figures 10 and 11 illustrate two waveguides into which the beam is injected. [Figure 11] Figures 10 and 11 illustrate two waveguides into which the beam is injected.

[0026] [Figure 12] Figure 12 illustrates a stack of waveguides.

[0027] [Figure 13A] Figure 13A illustrates an exemplary approach for implementing a diffraction structure that has a waveguide substrate and an upper grating surface, but without an underlying layer.

[0028] [Figure 13B] Figure 13B shows a chart of exemplary simulation results.

[0029] [Figure 13C] Figure 13C shows an annotated version of Figure 13A.

[0030] [Figure 14A] Figure 14A illustrates an exemplary approach for implementing a diffraction structure having a waveguide substrate, a lower layer, and an upper lattice surface.

[0031] [Figure 14B] Figure 14B illustrates an exemplary approach for implementing a diffraction structure having a waveguide substrate, a lower layer, a lattice surface, and an upper surface.

[0032] [Figure 14C] Figure 14C illustrates an exemplary approach for implementing a stack of diffraction structures having a waveguide substrate, a lower layer, a lattice surface, and an upper surface.

[0033] [Figure 15A] Figure 15A illustrates an exemplary approach for implementing a diffraction structure having a high refractive index waveguide substrate, a low refractive index underlayer, and a low refractive index upper lattice surface.

[0034] [Figure 15B] Figure 15B shows a chart of exemplary simulation results.

[0035] [Figure 16A] Figure 16A illustrates an exemplary approach for implementing a diffraction structure having a low refractive index waveguide substrate, a high refractive index underlayer, and a low refractive index upper lattice surface.

[0036] [Figure 16B] Figure 16B shows a chart of exemplary simulation results.

[0037] [Figure 17A] Figure 17A illustrates an exemplary approach for implementing a diffraction structure having a low refractive index waveguide substrate, a medium refractive index underlayer, and a high refractive index upper lattice surface.

[0038] [Figure 17B] Figure 17B shows a chart of exemplary simulation results.

[0039] [Figure 18A] Figures 18A-D illustrate the modification of the lower layer characteristics. [Figure 18B] Figures 18A-D illustrate the modification of the lower layer characteristics. [Figure 18C] Figures 18A-D illustrate the modification of the lower layer characteristics. [Figure 18D] Figures 18A-D illustrate the modification of the lower layer characteristics. [Modes for carrying out the invention]

[0040] According to some embodiments of the present invention, a diffraction structure is employed, and the diffraction structure includes a lower / intermediate layer between the waveguide substrate and the upper lattice surface. The upper lattice surface comprises a first material corresponding to a first refractive index value, the lower layer comprises a second material corresponding to a second refractive index value, and the substrate comprises a third material corresponding to a third refractive index value.

[0041] One advantage of this approach is that, by appropriately selecting the relative refractive indices for the three layers, the minimum total internal reflection angle decreases as the refractive index increases, allowing the structure to obtain a wider field of view for a wider range of incident light. Diffraction efficiency can be increased, enabling the output of "brighter" light to the display of an image viewing device.

[0042] Various combinations are available, where a lower layer of one refractive index is combined with a substrate of a third refractive index and an upper grating of another refractive index. Adjusting these relative values ​​provides many variations in the dependence of diffraction efficiency on the angle of incidence. Layered waveguides with layers of different refractive indices are presented. Various combinations and permutations are presented along with relevant performance data to illustrate their functionality. The advantages include an increase in angle, which provides an increase in output angle using the grating and, therefore, an increase in field of view using the eyepiece. Furthermore, the ability to counteract the usual decrease in diffraction efficiency with angle is functionally beneficial.

[0043] (Display systems in several embodiments) This portion of the present disclosure describes an exemplary display system that may be used in conjunction with the improved diffraction structure of the present invention.

[0044] Figure 2 illustrates a conventional stereoscopic 3D simulation display system, typically having 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 fails to account for many of the useful cues utilized by the human eye and brain to detect and interpret depth in three dimensions, including accommodation cues.

[0045] In fact, the typical human eye can interpret numerous depth layers based on radial distance, for example, approximately 12 depth layers. The near field limit of approximately 0.25 meters is the closest depth of focus, and the far field limit of approximately 3 meters means that any item beyond approximately 3 meters from the human eye will appear in infinite focus. The layers of focus become increasingly thin as the object gets closer to the eye. In other words, the eye can perceive very small differences in focal length when the object is relatively close to it, and this effect dissipates as the object moves further away from the eye. At infinite object location, the depth of focus / optical refraction interval value is approximately 1 / 3 diopters.

[0046] Figure 3 illustrates an improved approach to implementing a stereoscopic 3D simulation display system according to several embodiments of the present invention, where two composite images are displayed one for each eye 4 and 6, and various radial depths of focus (12) for various sides (14) of each image can be utilized to provide a perception of three-dimensional depth hierarchies within the image perceived by each eye. Since multiple focal planes (e.g., 12 focal planes) exist between the user's eye and infinity, these focal planes and the data within the relationships depicted can be utilized to position virtual elements within an augmented reality scenario for the user's viewing, because the human eye is constantly moving and uses focal planes to perceive depth. While this figure shows a specific number of focal planes at various depths, it should be noted that implementations of the present invention may use any number of focal planes as needed for a desired specific application, and the present invention is therefore not limited to devices having only the specific number of focal planes shown in any of the figures in this disclosure.

[0047] Referring to Figures 4A-4D, several general component options according to several embodiments of the present invention are illustrated. In part of the detailed description following the discussion of Figures 4A-4D, various systems, subsystems, and components are presented to address the objective of providing a high-quality, comfortable-to-perceive display system for human VR and / or AR.

[0048] As shown in Figure 4A, an AR system user (60) is depicted wearing a frame (64) structure which is coupled to a display system (62) positioned in front of the user's eyes. In the depicted configuration, a speaker (66) is coupled to the frame (64) and 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) by wired or wireless connections, and the data module (70) can be mounted in various configurations, such as being fixedly attached to a frame (64), fixedly attached to a helmet or hat (80) as shown in the embodiment of Figure 4B, embedded in headphones, detachably attached to the user's (60) torso (82) in a backpack configuration as shown in the embodiment of Figure 4C, or detachably attached to the user's (60) waist (84) in a belt-connected configuration as shown in the embodiment of Figure 4D.

[0049] The local processing and data module (70) may comprise a low-power processor or controller and digital memory such as flash memory, both of which may be used to assist in data processing, caching, and storage. The data is a) data captured from sensors that can be operably coupled to the frame (64), such as image capture devices (cameras, etc.), microphones, inertial measurement units, accelerometers, compasses, GPS units, wireless devices, and / or gyroscopes, and / or b) data acquired and / or processed using the remote processing module (72) and / or remote data repository (74) for passing to the display (62) after processing or reading. The local processing and data module (70) may be operably coupled to the remote processing module (72) and remote data repository (74) via wired or wireless link, etc.76, 78), these remote modules (72, 74) are operably coupled to each other and available as resources to the local processing and data module (70).

[0050] In one embodiment, the remote processing module (72) may comprise 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 comprise a relatively large digital data storage facility that may be available through the internet or other networking configurations in a “cloud” resource configuration. In one embodiment, all data is stored and all calculations are performed in the local processing and data modules, enabling fully autonomous use from any remote module.

[0051] The perception of the Z-axis difference (i.e., the straight-line distance from the eye along the optical axis) can be enhanced by using a waveguide in conjunction with a variable-focus optical element configuration. Image information from a display can be collimated and fed into the waveguide and distributed in a large-exit pupil manner using any suitable substrate-guided optics method known to those skilled in the art, and then the variable-focus optical element capability can be used to change the focus of the wavefront of the light emerging from the waveguide, providing the eye with the perception that the light emanating from the waveguide is from a particular focal length. In other words, since the incident light is collimated to avoid the challenges in an all-internal-reflection waveguide configuration, it exits in a collimated manner, requiring the viewer's eye to adjust to the far point and focus it on the retina, and consequently, it will be interpreted as being from optical infinity unless some other intervention is made to refocus the light and make it perceived as being from a different viewing distance. One suitable such intervention is a variable-focus lens.

[0052] In some embodiments, collimated image information is introduced into a piece of glass or other material at an angle such that it undergoes total internal reflection and passes through an adjacent waveguide. The waveguide may be configured such that the collimated light from the display is distributed substantially uniformly along the length of the waveguide, across a distribution of reflectors or diffraction features. Upon emission toward the eye, the emitted light passes through a variable focus lens element, and depending on the controlled focus of the variable focus lens element, the light emitted from the variable focus lens element and incident upon the eye will have varying levels of focus (a collimated flat wavefront represents optical infinity, and a larger beam divergence / wavefront curvature represents a closer viewing distance to the eye 58).

[0053] In a "frame-sequential" configuration, a sequential stack of two-dimensional images is fed sequentially to a display in a manner similar to how a computed tomography system uses stacked image slices to represent a three-dimensional structure, thereby generating three-dimensional perception over time. A series of two-dimensional image slices may be presented to the eye, each at a different focal length relative to the eye, and the eye / brain will integrate such a stack into the perception of a coherent three-dimensional volume. Depending on the display type, ordering by row or even by pixel may be performed to generate the perception of three-dimensional viewing. For example, in a scanning light display (such as a scanning fiber display or scanning mirror display), the display presents one line or one pixel at a time to the waveguide in a sequential manner.

[0054] Referring to Figure 6, a stacked waveguide assembly (178) having multiple waveguides (182, 184, 186, 188, 190) and multiple weak lenses (198, 196, 194, 192) may be used to provide three-dimensional perception to the eye / brain, and the multiple waveguides and multiple weak lenses are configured together to transmit image information to the eye at various levels of wavefront curvature for each waveguide level, indicating the focal length to be perceived relative to that waveguide level. Multiple displays (200, 202, 204, 206, 208), or in another embodiment, a single multiplexed display, may be used to load collimated image information into the waveguides (182, 184, 186, 188, 190), and each waveguide may be configured to distribute the incident light substantially equally across the length of each waveguide for emission to the eye, as described above.

[0055] The waveguide (182) closest to the eye is configured to deliver collimated light to the eye, which, as it is introduced into such waveguide (182), may represent the optical infinity focal plane. The next upward waveguide (184) is configured to transmit collimated light that passes through a first weak lens (192; e.g., a weak negative lens) before it can reach the eye (58). Such a first weak lens (192) may be configured to create a slight convex wavefront curvature so that the eye / brain interprets the light originating from the next upward waveguide (184) as originating from a first focal plane closer to the person and inward from optical infinity. Similarly, the third upward waveguide (186) passes its output light through the first (192) and second (194) lenses before it reaches the eye (58). The combined refractive power of the first (192) and second (194) lenses may be configured to create another incremental wavefront divergence such that the eye / brain interprets the light originating from the third waveguide (186) above it as originating from a second focal plane that is even closer to the person and further from optical infinity than the light from the next upper waveguide (184).

[0056] Other waveguide layers (188, 190) and weak lenses (196, 198) are configured similarly, and the highest waveguide (190) in the stack transmits its output through all the weak lenses between it and the eye for the total focal force representing the focal plane closest to the person. When viewing / interpreting light from the other side of the stacked waveguide assembly (178) from the world (144), a compensating lens layer (180) is placed on top of the stack to compensate for the stack of lenses (198, 196, 194, 192) and to compensate for the total refractive power of the lower lens stack (198, 196, 194, 192). Such a configuration again provides a relatively large exit pupil configuration for the same number of perceived focal planes as the available waveguide / lens pairs, as previously described. Both the reflective side of the waveguide and the focusing side of the lens can be static (i.e., not dynamic or electroactive). In alternative embodiments, the system may be dynamic and, as described above, utilize electroactive features, allowing a small number of waveguides to be multiplexed in a time-series manner to generate a larger number of effective focal planes.

[0057] Various diffraction configurations can be employed 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, i.e., a "Fresnel zone plate," will change the beam's focus. Combined diffraction patterns having both linear and radial elements can be employed to produce both deflection and focusing of a collimated input beam. These deflection and focusing effects can be produced in both reflection and transmission modes.

[0058] These principles can be applied in conjunction with waveguide configurations to allow for additional optical control. As shown in Figure 7, a diffraction pattern (220), i.e., a “diffractive optical element” (or “DOE”), is embedded within the plane waveguide (216) such that it intersects the diffraction pattern (220) at numerous locations as the collimated beam undergoes total internal reflection along the plane waveguide (216). The structure may also include another waveguide (218) into which a beam can be injected (e.g., by a projector or display), and the DOE (221) is embedded within this other waveguide (218).

[0059] Preferably, the DOE(220) has relatively low diffraction efficiency such that only a portion of the beam light is deflected toward the eye (58) using each intersection of the DOE(220), while the remainder continues to travel through the plane waveguide (216) via total internal reflection. The light carrying the image information is therefore split into several related light beams that exit the waveguide at numerous locations, resulting in a very uniform pattern of exit emission toward the eye (58) relative to this particular collimated beam bouncing within the plane waveguide (216), as shown in Figure 8. The exit beam toward the eye (58) is shown in Figure 8 as substantially parallel, since the DOE(220) in this case has only a linear diffraction pattern. However, variations in this linear diffraction pattern pitch can be used to controllably deflect the exit parallel beam, thereby generating scanning or tiling functionality.

[0060] Referring to Figure 9, as the radially symmetric diffraction pattern component of the embedded DOE(220) changes, the emitted beam pattern becomes more divergent, which requires the eye to adjust for closer distances and focus the emitted beam pattern onto the retina, and the brain will interpret the emitted beam pattern as light from a viewing distance closer to the eye than optical infinity.

[0061] Referring to Figure 10, with the addition of other waveguides (218) into which a beam may be injected (e.g., by a projector or display), a DOE (221) embedded in this other waveguide (218), such as a linear diffraction pattern, may function to diffuse light throughout the larger planar waveguide (216), which, according to the specific DOE configuration in operation, functions to provide a very large incident field of incident light emanating from the larger planar waveguide (216), for example, a large eyebox, to the eye (58).

[0062] DOE(220, 221) is depicted as bisecting the associated waveguide(216, 218), but this is not required. They can be positioned closer to or on either side of either waveguide(216, 218) to have identical functionality. Thus, as shown in Figure 11, with the input of a single collimated beam, the entire field of cloned collimated beams can be directed toward the eye(58). In addition, in the combined linear diffraction pattern / radially symmetric diffraction pattern scenarios described above, beam distribution waveguide optics with Z-axis focusing capability are presented (for functionality such as functional extension of the exit pupil, in configurations like those in Figure 11, the exit pupil can be the same size as the optical element itself, which can be a very significant advantage for user comfort and ergonomics), and both the divergence angle of the cloned beam and the wavefront curvature of each beam represent light originating from a point closer than optical infinity.

[0063] In one embodiment, one or more DOEs are 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 comprise a layer of polymer-dispersed liquid crystal, in which microdroplets have a diffraction pattern in the host medium, and the refractive index of the microdroplets can be switched to substantially match the refractive index of the host material (in which case the pattern does not significantly diffract incident light), or the refractive index of the microdroplets can be switched to one that does not match that of the host medium (in which case the pattern actively diffracts incident light). Furthermore, beam scanning or tiling functionality can be achieved with the dynamic change in the diffraction term. As mentioned above, it is desirable that each of the DOEs (220, 221) has a relatively low diffraction grating efficiency. This is because it facilitates the distribution of light, and furthermore, the light passing through the waveguide to which it is desired (for example, in an augmented reality configuration, the light originating from world 144 toward eye 58) is less affected if the diffraction efficiency of the DOE(220) it intersects with is lower, and therefore a better view of the real world is achieved through such a configuration.

[0064] Configurations such as those illustrated herein are preferably driven in conjunction with the input of image information in a time-series approach, with frame-sequential driving being the easiest to implement. For example, an image of the sky at optical infinity may be input at time 1, and a diffraction grating that preserves light collimation may be utilized. Subsequently, an image of a closer tree branch may be input at time 2, while the DOE provides a controllable change in focus, for example, at a distance of 1 diopter or 1 meter, giving the eye / brain the perception that the light information of the branch is coming from a closer focal distance. This type of paradigm can be repeated in a fast time-series manner such that the eye / brain perceives that the input is an entire part of the same image. This is just an example of two focal planes. Preferably, the system would include more focal planes and provide a smoother transition between objects and their focal distances. This type of configuration generally assumes that the DOE is switched relatively slowly (i.e., synchronized with the frame rate of the display inputting images in the range of tens to hundreds of cycles / second).

[0065] The opposite configuration could involve a DOE element that can shift focus at tens to hundreds of MHz or more, facilitating the switching of the DOE element's focus state on a per-pixel basis as the pixel is scanned into the eye (58) using a scanning light display type approach. This is desirable because it means the overall display frame rate can be kept very low (low enough to ensure that "flicker" is not an issue (in the range of approximately 60–120 frames / second)).

[0066] If the DOE can be switched at a kHz rate within these ranges, the focus on each scan line can be adjusted on a line-by-line basis, which can provide the user with a visible advantage, for example, in terms of temporal artifacts in eye movements relative to the display. For example, different focal planes in a given scene can be interleaved in this way to minimize visible artifacts in response to head movements (as will be discussed in detail later in this disclosure). A line-by-line focus modulator can be operably coupled to a line-scanning display, such as a grating-valve display, in which a linear array of pixels is swept to form an image. A line-by-line focus modulator can be operably coupled to scanning light displays, such as fiber-optic scanning displays and mirror-scanning light displays.

[0067] A stacked configuration similar to that in Figure 6 can simultaneously provide multi-plane focusing using dynamic DOE. For example, using three simultaneous focal planes, a primary focal plane (e.g., based on measured orthocular accommodation) may be presented to the user, while + and - margins (i.e., one closer focal plane, one farther focal plane) may be utilized to provide a larger focal range that the user can adjust to before a plane update is required. This increased focal range can provide a time advantage when the user switches to a closer or farther focus (i.e., as determined by the accommodation measurement), with the new focal plane being the central depth of focus, and the + and - margins again prepared for a quick switch to either one while the system catches up.

[0068] Referring to Figure 12, a stack (222) of planar waveguides (244, 246, 248, 250, 252) is shown, each having reflectors (254, 256, 258, 260, 262) at its ends. Collimated image information fed into one end by a display (224, 226, 228, 230, 232) is reflected back by all internal reflections to the reflectors, at which point some or all of the light is reflected toward the eye or another target. Each of the reflectors may have slightly different angles to reflect the outgoing light toward a common destination such as the pupil. Lenses (234, 236, 238, 240, 242) may be inserted between the display and the waveguide for beam steering and / or focusing.

[0069] As mentioned earlier, objects at optical infinity essentially create a plane wavefront, while objects closer to the eye, such as 1 meter away, create a curved wavefront (with a convex radius of curvature of approximately 1 meter). The eye's optical system needs to have sufficient refractive power to bend the incident light rays so that they can ultimately be focused on the retina (the convex wavefront is converted to a concave wavefront, and then to the focal point on the retina). These are the basic functions of the eye.

[0070] In many of the embodiments described above, the light directed towards the eye is treated as part of a single continuous wavefront, some of which will strike the pupil of a particular eye. In an alternative approach, the light directed towards the eye may be effectively discretized or split into multiple beamlets or individual rays, each having a diameter of less than about 0.5 mm and an intrinsic propagation path, as part of a larger aggregate wavefront that can be functionally created by the aggregate of beamlets or rays. For example, a curved wavefront may be approximated by aggregating multiple individual neighbor collimated beams approaching the eye from appropriate angles, each approaching the eye from an origin that coincides with the center of the radius of curvature of the desired aggregate wavefront.

[0071] If the beamlets have a diameter of approximately 0.5 mm or less, they appear as if they are occurring through a pinhole lens configuration, meaning that each individual beamlet is always at a relative focal point on the retina, independent of the eye's accommodative state; however, the trajectory of each beamlet will be influenced by the accommodative state. For example, if the beamlets approach the eye parallel to it and represent a discretized, collimated aggregate wavefront, an eye that is properly accommodated to infinity will deflect the beamlets so that they all converge to the same shared spot on the retina, resulting in a focused appearance. If the eye is accommodated to, for example, 1 m, the beams will converge to a spot directly in front of the retina, crossing paths and hitting multiple neighboring or partially overlapping spots on the retina, resulting in a blurred appearance.

[0072] If a beamlet approaches the eye in a divergent configuration, and the shared origin is 1 meter from the viewer, 1-meter accommodation will direct the beam to a single spot on the retina, resulting in a focused image. If the viewer accommodates to infinity, the beamlet will converge to a spot behind the retina, generating multiple neighboring or partially overlapping spots on the retina, producing a blurred image. More generally, the eye's accommodation determines the degree of overlap of spots on the retina, and given pixels are "in focus" if all spots are directed to the same spot on the retina, and "blurred" if the spots are offset from each other. This concept, that beamlets with a diameter of 0.5 mm or less can all be assembled so that they are always in focus and perceived by the eye / brain as substantially identical to a coherent wavefront, can be used to generate configurations for comfortable three-dimensional virtual or augmented reality perception.

[0073] In other words, a set of multiple narrow beams may be used to mimic a situation using a larger diameter variable focus beam, and if the beamlet diameter is kept to a maximum of approximately 0.5 mm, the beamlet angular trajectory may be selected to create an effect similar to that of a larger defocus beam in order to maintain a relatively static focus level and generate a defocused perception, if necessary (such a defocusing treatment may not be identical to a Gaussian blurring treatment like that for a larger beam, but it will create a multimodal point spreading function that can be interpreted in a manner similar to Gaussian blurring).

[0074] In some embodiments, the beamlets are not mechanically deflected to form this convergence effect; rather, the eye receives a top set of many beamlets, including both numerous incident angles and numerous locations where the beamlets intersect the pupil. To represent a given pixel from a particular viewing distance, a portion of the beamlets from the top set (as if emitted from the same shared origin in space) with appropriate incident angles and intersections with the pupil are turned on with matching color and intensity to represent the convergence wavefront, while beamlets in the top set that are not consistent with the shared origin are not turned on with their color and intensity (although some of them may be turned on at other color and intensity levels, for example, to represent different pixels).

[0075] Referring here to Figure 5, an exemplary embodiment 800 of an AR system using an improved diffraction structure is described here. The AR system generally includes an image generation processor 812, at least one FSD 808 (fiber scanning device), an FSD circuit 810, a coupled optics 832, and at least one optical assembly (DOE assembly 802) having a waveguide stacked together with the improved diffraction structure described below. The system may also include an eye tracking subsystem 806. As shown in Figure 5, the FSD circuit may comprise an image generation processor 812 having a Maxim chip CPU 818, a temperature sensor 820, a piezoelectric driver / converter 822, a red laser 826, a blue laser 828, a green laser 830, and a circuit 810 that communicates with a fiber combiner combining all three lasers 826, 828, and 830. Note that other types of imaging techniques may also be used instead of the FSD device. For example, high-resolution liquid crystal display ("LCD") systems, back-illuminated ferroelectric panel displays, and / or high-frequency DLP systems can all be used in some embodiments of the present invention.

[0076] The image generation processor is involved in generating the virtual content that will ultimately be displayed to the user. The image generation processor can convert images or videos associated with the virtual content into a format that can be projected to the user in 3D. For example, in generating 3D content, the virtual content may need to be formatted so that a portion of a particular image is displayed on a particular depth plane, while the rest is displayed on other depth planes. Alternatively, the entire image may be generated on a particular depth plane. Alternatively, the image generation processor may be programmed to feed slightly different images to the right and left eyes so that, when viewed together, the virtual content appears coherently and comfortably to the user's eyes. In one or more embodiments, the image generation processor 812 delivers the virtual content to the optical assembly in a time-series manner. A first portion of the virtual scene may be delivered first so that the optical assembly projects the first portion on a first depth plane. Then, the image generation processor 812 may deliver another portion of the same virtual scene so that the optical assembly projects the second portion on a second depth plane, and so on. Here, the Alvarez lens assembly can be translated laterally quickly enough to generate multiple lateral translations (corresponding to multiple depth planes) on a frame-by-frame basis.

[0077] The image generation processor 812 may further include memory 814, a CPU 818, a GPU 816, and other circuitry for image generation and processing. The image generation processor may be programmed with 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 within a wearable AR system. In other embodiments, the image generation processor and other circuitry may be housed within a beltpack coupled to a wearable optical system.

[0078] The AR system also includes coupled optics 832 for directing light from the FSD to the optical assembly 802. The coupled optics 832 may refer to one or more conventional lenses used to direct light into the DOE assembly. The AR system also includes an eye-tracking subsystem 806 configured to track the user's eyes and determine the user's focus.

[0079] In one or more embodiments, software blurring may be used to induce blurring as part of a virtual scene. A blurring module may, in one or more embodiments, be part of a processing circuit. The blurring module may blur a portion of one or more frames of image data being fed into the DOE. In such embodiments, the blurring module may completely blur a portion of frames that are not intended to be rendered in a particular depth frame. Exemplary approaches that may be used to implement the aforementioned image display system and its components are described in U.S. Utility Patent Application No. 14 / 555,585, filed November 27, 2014 (which is incorporated herein by reference in its entirety).

[0080] (Improved diffraction structure) As described above, a collimated beam undergoes total internal reflection along a planar waveguide, and diffraction patterns can be formed on the planar waveguide such that the beam intersects diffraction patterns at multiple locations. This array can be stacked to provide image objects at multiple focal planes in a stereoscopic 3D simulation display system according to some embodiments of the present invention.

[0081] Figure 13A illustrates one possible approach to implementing the structure 1300 of the waveguide 1302 (also referred to herein as the “optical guide,” “substrate,” or “waveguide substrate”), in which an outcoupling grating 1304 is formed directly on the upper surface of the waveguide 1302, for example, as a combined monolithic structure, and / or both are formed from the same material (even if not constructed from the same monolithic structure). In this approach, the refractive index of the grating material is the same as the refractive index of the waveguide 1302. The refractive index n (or “refractive index”) of a material describes the degree to which light propagates through its medium, and is defined as n = c / v, where c is the speed of light in a vacuum and v is the phase velocity of light in the medium. The refractive index determines the degree to which light is bent or refracted when it enters the material.

[0082] Figure 13B shows Chart 1320, an exemplary simulation result of the efficiency of light emanating from structure 1300 for single polarization, as a function of the angle at which the light propagates through the waveguide. This chart shows that the diffraction efficiency of out-coupled light to structure 1300 decreases at higher incidence angles. As can be seen from the figure, at an angle of approximately 43 degrees, the efficiency drops relatively sharply on the plotted graph, due to variations in total internal reflectivity based on the incidence angle within a medium with a uniform refractive index.

[0083] Therefore, the usable range of configuration 1300 is somewhat limited and undesirable because the bounce interval may decrease at higher incidence angles, which can further reduce the brightness visible to the observer at those angles. The diffraction efficiency is lower at the shallowest incidence angles, which is undesirable because the bounce interval between interactions with the upper surface (see Figure 13C) is very large and there are very few opportunities for light to externally couple. Thus, a dimming signal with fewer externally coupled samples will result from this arrangement, and this problem will be exacerbated by gratings with lower diffraction efficiency at these high angles using this polarization orientation. Note that, as used herein and in the figures, "1T" refers to the primary transmission diffraction order.

[0084] In some embodiments of waveguide-based optical systems or substrate-guided optical systems, such as those described above, different pixels in a substrate-guided image are represented by beams propagating through the waveguide at different angles, with light propagating along the waveguide by total internal reflection (TIR). The range of beam angles that remain trapped within the waveguide by TIR is a function of the difference in refractive index between the waveguide and the medium outside the waveguide (e.g., air). The greater the difference in refractive index, the greater the number of beam angles. In some embodiments, the range of beam angles propagating along the waveguide correlates with the field of view of the image coupled outward from the waveguide surface by the diffraction element, and also correlates with the image resolution supported by the optical system. In addition, the angular range in which total internal reflection occurs is determined by the refractive index of the waveguide. In some embodiments, this range is approximately 43 degrees at the minimum and approximately 83 degrees at the practical maximum, and therefore in the range of 40 degrees.

[0085] Figure 14A illustrates an approach to address this problem according to several embodiments of the present invention, the structure 1400 including an intermediate layer 1406 (hereinafter referred to as the “lower layer 1406”) between the substrate 1302 and the upper lattice surface 1304. The upper surface 1304 comprises a first material corresponding to a first refractive index value, the lower layer 1406 comprises a second material corresponding to a second refractive index value, and the substrate 1302 comprises a third material corresponding to a third refractive index value. Note that any combination of identical or different materials may be employed to implement each of these parts of the structure 1400, for example, all three materials may be different (and all three materials may correspond to different refractive index values), or two of the layers may share the same material (for example, two of the three materials may be identical and therefore share a common refractive index value different from the refractive index value of the third material). Any combination of refractive index values ​​may be employed. For example, one embodiment includes a low refractive index for the lower layer and uses a higher refractive index for the surface lattice and substrate. Other exemplary configurations with other exemplary combinations of refractive index values ​​are described below. Any suitable set of materials can be used to implement structure 1500. For example, polymers, glass, and sapphire are all examples of materials that can be selected to implement any of the layers of structure 1400.

[0086] As shown in Figure 15A, in some embodiments, it may be desirable to use a substrate with a relatively high refractive index as the waveguide substrate 1302, and to implement the structure 1500 with a relatively lower refractive index underlayer 1406 and a relatively lower refractive index upper lattice surface 1304. This is because, through the relation n1 × sin(θ1) = n2 × sin(θ0), it may be possible to obtain a wider field of view from the fact that as the refractive index increases, the minimum total internal reflection angle decreases. For a substrate with a refractive index of 1.5, the critical angle is 41.8 degrees. However, for a substrate with a refractive index of 1.7, the critical angle is 36 degrees.

[0087] A grating formed on a substrate with a higher refractive index can be used to externally couple light, even if it itself has a lower refractive index, as long as the layers of material constituting the grating are not too thick between the grating and the substrate. This is related to the fact that such a configuration can have a wider angle for total internal reflection ("TIR"). In other words, the TIR angle drops to a lower value using such a configuration. In addition, it should be noted that many current etching processes may not be very suitable for extending to high refractive index glasses. In some embodiments, it is desirable to reliably and inexpensively replicate the external coupling layer.

[0088] The configuration of the lower layer 1406 can be adjusted to modify the performance characteristics of the structure 1500, for example, by changing the thickness of the lower layer 1406. The configuration in Figure 15A (the structure includes a lattice structure 1304 with a relatively low refractive index material at the top, accompanied by an associated lower refractive index lower layer 1406, which also includes an associated high refractive index light induction substrate 1302) can be modeled to yield data such as that depicted in Figure 15B. Referring to this figure, the left plot 1502a relates to a configuration with a zero-thickness lower layer 1502. The middle plot 1502b shows data for a 0.05-micron thick lower layer 1502. The right plot 1502c shows data for a 0.1-micron thick lower layer 1502.

[0089] As the data in these plots show, as the underlayer thickness increases, the diffraction efficiency as a function of the angle of incidence becomes far more nonlinear and is suppressed at high angles, which can be undesirable. Therefore, in this case, controlling the underlayer is an important functional input. However, it should be noted that when using only a zero-thickness underlayer and the lattice features themselves having a lower refractive index, the range of angles supported by the structure is governed by the TIR condition in the higher refractive index base material, rather than the lattice feature material with a lower refractive index.

[0090] Referring to Figure 16A, an embodiment of structure 1600 is illustrated, characterized by a relatively high refractive index lower layer 1406 on a lower refractive index substrate 1302, where the upper surface diffraction grating 1304 has a refractive index lower than, and not necessarily equal to, that of the lower layer 1406, but comparable to that of the substrate 1302. For example, the upper surface grating may correspond to a refractive index of 1.5, the lower layer to a refractive index of 1.84, and the substrate to a refractive index of 1.5. For this example, assume that the period is 0.43 μm and λ corresponds to 0.532 μm.

[0091] Simulations related to such configurations are presented in Figure 16B. As shown in this figure, in Chart 1602a with a 0.3-micron thick underlayer 1406, the diffraction efficiency decreases as in the previously described configuration, but then begins to increase at higher endpoints in the angular range. This is also true for the 0.5-micron thick underlayer 1406 configuration, as shown in Chart 1602b. In each of these (0.3-micron, 0.5-micron) configurations, the relatively high efficiency at higher limits in the angular range is beneficial. Such functionality can tend to counteract the aforementioned concerns about sparser bounce spacing. Furthermore, shown in this figure is Chart 1602c for an embodiment featuring an example of 90-degree rotational polarization, where the diffraction efficiency is low as expected, but exhibits desirable behavior in that it provides better efficiency at steeper angles compared to shallower angles.

[0092] In fact, in some embodiments, the diffraction efficiency-to-angle ratio can increase at higher angles. This can be a desirable feature for some embodiments because it helps compensate for lower bounce intervals that may occur at higher propagation angles. Therefore, the structural configuration of Figure 16A is preferable to the aforementioned monolithic configuration because it facilitates an increase in diffraction efficiency-to-angle ratio at higher angles, thus compensating for lower bounce intervals (which occur using higher propagation angles) is desirable.

[0093] Referring to Figure 17A, another structure 1700 is depicted, where the lower layer 1406 has a substantially higher refractive index than the substrate 1302. The lattice structure 1304 is at the top, and the lattice structure 1304 also has a higher refractive index than the lower layer 1406. For example, the upper surface lattice may correspond to a refractive index of 1.86, the lower layer may correspond to a refractive index of 1.79, and the substrate may correspond to a refractive index of 1.5. As mentioned above, for this example, assume that the period is 0.43 μm and λ corresponds to 0.532 μm.

[0094] Referring to Figure 17B, Chart 1702 shows simulation data illustrated for structure 1700 in Figure 17A. As shown in Chart 1702, the resulting diffraction efficiency versus angle of incidence plot demonstrates desirable overall behavior, which helps compensate for the aforementioned lower bounce interval at relatively high angles of incidence and maintains reasonable diffraction efficiency over a wider range of angles overall.

[0095] It should be noted that the underlayer 1406 does not need to be uniform throughout the entire substrate. Any properties of the underlayer 1406 can be varied at different locations on the substrate, such as differences in the thickness, composition, and / or refractive index of the underlayer 1406. One possible reason for varying the properties of the underlayer 1406 is to promote uniform display characteristics in the presence of known variations in either the display image or the non-uniform light transmission within the display system.

[0096] For example, consider the case where the waveguide structure receives incident light at a single internal coupling site 1802 on the waveguide, as shown in Figure 18A. When incident light is injected into waveguide 1302, less and less light will remain as it propagates along the length of waveguide 1302. This means that the output light near the internal coupling site 1802 may appear "brighter" than the output light further along the length of waveguide 1302. If the underlayer 1406 is uniform along the entire length of waveguide 1302, the optical effect of the underlayer 1406 may enhance this non-uniform brightness level across the substrate.

[0097] The properties of the lower layer 1406 can be tuned across the substrate 1302 to make the output light more uniform. Figure 18B illustrates an approach in which the thickness of the lower layer 1406 is varied over the length of the waveguide substrate 1302, with the lower layer 1406 being thinner near the internal coupling site 1802 and thicker as the distance from site 1802 increases. Thus, the effect of the lower layer 1406 to promote better diffraction efficiency can, at least partially, improve the effect of optical loss along the length of the waveguide substrate 1302, thereby promoting a more uniform optical output throughout the structure.

[0098] Figure 18C illustrates an alternative approach in which the thickness of the underlayer 1406 is not varied, but the refractive index of the underlayer 1406 is varied across the substrate 1302. For example, to address the problem that the output light near location 1802 tends to be brighter at locations further away from location 1802, the refractive index for the underlayer 1406 is configured to be the same as or similar to that of the substrate 1302 near location 1802, but with an increasing difference in their refractive index values ​​at locations further away from location 1802. The composition of the underlayer 1406 material can be varied at different locations, resulting in different refractive index values. Figure 18D illustrates a hybrid approach in which both the thickness and refractive index of the underlayer 1406 are varied across the substrate 1302. Note that this same approach can be performed by varying the thickness and / or refractive index of the upper lattice surface 1304 and / or the substrate 1302, in conjunction with or instead of varying the underlayer 1406.

[0099] Therefore, various combinations are available, and a lower layer 1406 of a certain refractive index can be combined with a substrate 1302 of a third refractive index and an upper grating 1304 of a different refractive index, and adjusting these relative values ​​provides many variations in the dependence of diffraction efficiency on the incident angle. Layered waveguides with layers of different refractive indices are presented. Various combinations and permutations are presented along with relevant performance data to illustrate their functionality. An advantage is the increase in angle, which provides an increase in output angle using the grating 1304, and therefore an increase in field of view using the eyepiece. Furthermore, the ability to counteract the usual decrease in diffraction efficiency with angle is functionally beneficial.

[0100] Figure 14B illustrates an embodiment in which another layer (upper surface) of material 1409 is placed above the lattice layer 1304. Layer 1409 can be configurably implemented to address different design objectives. For example, layer 1409 can form an intervening layer between multiple stacked diffraction structures 1401a and 1401b, as shown in Figure 14C. As shown in Figure 14C, this intervening layer 1409 can be employed to eliminate any gaps / intervals and provide a support structure for the stacked diffraction components. In this use case, layer 1409 can be formed from a material having a relatively low refractive index, e.g., about 1.1 or 1.2. Although not shown in this figure, other layers (e.g., weak lenses) may also be placed between the diffraction structures 1401a and 1401b.

[0101] In addition, layer 1409 can be formed from a material having a relatively high refractive index. In this situation, it is the lattice on layer 1409, rather than the lattice surface 1304, that will provide the diffraction effect for all or a significant amount of the incident light.

[0102] As is evident, in order to achieve the desired optical effect and result, different relative combinations of refractive index values ​​can be selected for different layers, including layer 1409.

[0103] Such structures can be manufactured using any suitable manufacturing technique. Certain high refractive index polymers, such as those known as "MR174," can be directly embossed, printed, or etched to produce desired patterned structures, although challenges exist related to curing shrinkage of such layers. Therefore, in another embodiment, a different material may be transferred, embossed, or etched onto a high refractive index polymer layer (i.e., a layer of MR174, etc.) to produce functionally similar results. State-of-the-art printing, etching (which may include resist removal and patterning steps similar to those used in conventional semiconductor processes), and embossing techniques can be used and / or combined to carry out such printing, embossing, and / or etching steps. For example, molding techniques similar to those used in DVD production can also be used for certain replication steps. Furthermore, certain jetting or deposition techniques used in printing and other deposition processes can also be used to deposit certain layers with precision.

[0104] In the aforementioned specification, the present invention has been described with reference to specific embodiments thereof. However, it will be apparent that various modifications and changes can be made therein without departing from the broader spirit and scope of the invention. For example, the process flow described above is described with reference to a specific sequence of process actions. However, many of the sequences of process actions described can be changed without affecting the scope or operation of the invention. This specification and drawings are therefore to be considered illustrative, not restrictive.

[0105] Various exemplary embodiments of the present invention are described herein. These embodiments are referenced in a non-limiting sense. They are provided to illustrate broader and more applicable aspects of the present invention. Various modifications may be made to the described invention, and equivalents may be substituted without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt specific circumstances, materials, material compositions, processes, process actions, or steps to the object, spirit, or scope of the invention. Furthermore, as will be understood by those skilled in the art, each of the individual modifications described and illustrated herein has discrete components and features that can be readily separated from or combined with features of any of several other embodiments without departing from the scope or spirit of the invention. All such modifications are intended to be within the scope of the claims associated with this disclosure.

[0106] The present invention includes methods that can be performed using the device of interest. The methods may include the act of providing such a suitable device. Such provision may be performed by an end user. In other words, the act of “providing” simply requires the end user to acquire, access, approach, position, configure, activate, power on, or otherwise operate the essential device in the method of interest. The methods described herein may be performed in any logically possible order of the described events, as well as in the order in which the events are described.

[0107] Exemplary aspects of the present invention, along with details relating to material selection and manufacturing, are described above. Further details of the present invention are understood in connection with the patents and publications referenced above and are generally known or understood by those skilled in the art. The same may apply to the method-based aspects of the present invention in terms of additional actions that may be generally or logically adopted.

[0108] In addition, while the present invention is described with reference to several embodiments that optionally incorporate various features, the present invention is not limited to those described and indicated as being considered with respect to each modification of the present invention. Various modifications may be made to the described invention, and equivalents (whether described herein or not for some simplicity) may be substituted without departing from the true spirit and scope of the invention. Furthermore, where a range of values ​​is provided, it should be understood that all intervening values ​​between the upper and lower limits of that range, and any other provisions or intervening values ​​within that defined range, are encompassed within the present invention.

[0109] Any optional feature of the modified versions of the invention described herein may be described and claimed independently or in combination with one or more of the features described herein. References to singular items include the possibility that there are plural identical items. More specifically, as used herein and in the claims associated herein, the singular forms “a,” “an,” “said,” and “the” include plural referents unless otherwise specified. In other words, the use of articles allows for “at least one” of the items of interest in the above description and in the claims associated with this disclosure. Furthermore, it should be noted that such claims may be drafted to exclude any optional elements. Thus, this description is intended to function as an antecedent for the use of exclusive terms such as “simply,” “only,” or for the use of “negative” restrictions in connection with the description of elements of a claim.

[0110] Without using such exclusive terms, the term “equipped with” in the claims relating to this disclosure shall allow for the inclusion of any additional elements, whether a given number of elements are enumerated in such claims or whether the addition of features can be considered a transformation of the properties of the elements described in such claims. Unless specifically defined herein, all technical and scientific terms used herein are given the broadest possible generally understood meaning while maintaining the validity of the claims.

[0111] The scope of the present invention is not limited to the provided examples and / or the subject specification, but rather is limited only by the language of the claims associated with this disclosure.

[0112] The above description of the illustrated embodiments is not intended to be exclusive or to limit embodiments to the precise forms disclosed. Specific embodiments and examples are described herein for illustrative purposes, but various equivalent modifications can be made without departing from the spirit and scope of this disclosure, as will be recognized by those skilled in the art. The teachings provided herein for various embodiments may also be applied to other devices that implement virtual, AR, or hybrid systems and / or employ user interfaces, rather than necessarily the exemplary AR systems described above in general.

[0113] For example, the detailed description above illustrates various embodiments of devices and / or processes through the use of block diagrams, schematic diagrams, and examples. It will be understood by those skilled in the art that, insofar as such block diagrams, schematic diagrams, and examples contain one or more functions and / or operations, each function and / or operation within such block diagrams, flowcharts, or examples can be implemented, individually and / or collectively, by a wide range of hardware, software, firmware, or virtually any combination thereof.

[0114] 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 can be equivalently implemented in a standard integrated circuit, in whole or in part, as one or more computer programs executed by one or more computers (e.g., as one or more programs launched 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 virtually any combination thereof, and that the design of circuits for software and / or firmware and / or the writing of code will be well within the scope of the art in light of the teachings of this disclosure.

[0115] Once logic is implemented as software and stored in memory, the logic or information can be stored on any computer-readable medium for use by or associated with any processor-related system or method. In the context of this disclosure, memory is a computer-readable medium that is an electronic, magnetic, optical, or other physical device or means containing or storing computer and / or processor programs. Logic and / or information can be embodied on any computer-readable medium for use by or associated with instruction execution systems, devices, or other systems, such as computer-based systems, processor-containing systems, or other systems, that can fetch instructions from instruction execution systems, devices, or other devices and execute instructions associated with the logic and / or information.

[0116] In the context of this specification, “computer-readable medium” can be any element capable of storing programs associated with logic and / or information for use by or in connection with instruction execution systems, apparatus, and / or devices. Computer-readable medium can be, for example, but not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices. More specific examples of computer-readable medium (a non-exclusive list) would include portable computer discets (magnetic, CompactFlash® cards, SecureDigital, or equivalents), 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-transient media.

[0117] Many of the methods described herein can be carried out with modifications. For example, many of the methods may include additional actions, omit some actions, and / or be carried out in a different order than those illustrated or described.

[0118] Further embodiments can be provided by combining the various embodiments described above. All U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications, and non-patent publications mentioned herein and / or listed in the application datasheet are incorporated herein by reference in their entirety, provided that they do not conflict with the specific teachings and definitions herein. The aspects of the embodiments may be modified if it is necessary to utilize systems, circuits, and concepts from various patents, applications, and publications in order to provide further embodiments.

[0119] These and other modifications may be made to embodiments in light of the description detailed above. In general, the terms used in the following claims should not be construed to limit the claims to the specific embodiments disclosed herein and herein, but rather to include all possible embodiments, along with the entire scope of equivalents to which such claims are entitled. Thus, the claims are not limited by this disclosure.

[0120] Furthermore, the various embodiments described above can be combined to provide further embodiments. Moreover, aspects of the embodiments can be modified, if necessary, to adopt concepts from various patents, applications, and publications in order to provide even further embodiments.

[0121] These and other modifications may be made to embodiments in light of the description detailed above. In general, the terms used in the following claims should not be construed to limit the claims to the specific embodiments disclosed herein and herein, but rather to include all possible embodiments, along with the entire scope of equivalents to which such claims are entitled. Thus, the claims are not limited by this disclosure.

Claims

1. An augmented reality (AR) display system for delivering augmented reality content to a user, wherein the AR display system is: An image source for providing one or more frames of image data, An optical modulator for transmitting light associated with one or more frames of the image data, A diffractive optical element (DOE) for receiving the light associated with one or more frames of the image data and directing the light toward the user's eye. Equipped with, The DOE comprises a diffraction structure, the diffraction structure having a waveguide substrate, a surface grating, a lower layer disposed between the waveguide substrate and the surface grating, and a light input location at one end of the diffraction structure. The waveguide substrate has a waveguide refractive index, The lower layer has a non-uniform lower layer refractive index that changes from a refractive index relatively similar to the waveguide refractive index to a refractive index where the difference from the waveguide refractive index increases as the distance from the light input point increases, thereby the non-uniform refractive index of the lower layer at least partially compensates for the decrease in the intensity of the light as the light propagates along the length of the diffraction structure from the light input point, in an AR display system.

2. The system according to claim 1, wherein the lower layer has a non-uniform lower layer thickness.

3. The system according to claim 1, wherein the waveguide substrate, the lower layer, and the surface grid are made of a plurality of different materials.

4. The system according to claim 1, wherein at least two of the waveguide substrate, the lower layer, and the surface grid are made of the same material.

5. The system according to claim 1, comprising a stacked waveguide assembly having a plurality of diffraction structures stacked together, wherein the plurality of diffraction structures include the diffraction structures.

6. The system according to claim 5, wherein the plurality of image sources feed the image data into each of the plurality of diffraction structures in the stacked waveguide assembly.

7. The system according to claim 1, wherein the waveguide substrate, the lower layer, and the surface grid are made of at least one of a polymer material, sapphire, or glass.

8. The system according to claim 1, wherein the DOE is switchable between an ON state and an OFF state.

9. The system according to claim 1, wherein the system is embodied as a wearable system that can be mounted on the head.

10. The system according to claim 1, wherein the diffraction structure further comprises an upper layer covering the surface lattice.

11. The system according to claim 10, wherein the upper layer forms an intervening layer for stacking the diffraction structure, and the upper layer has a relatively low refractive index.

12. The system according to claim 1, wherein the surface grid has a surface grid refractive index.

13. The system according to claim 12, wherein the waveguide refractive index, the non-uniform lower layer refractive index, and the surface lattice refractive index are different from each other at all points along the length of the diffraction structure.

14. The system according to claim 12, wherein at least two of the waveguide refractive index, the non-uniform lower layer refractive index, and the surface lattice refractive index are equal to each other at a certain point along the length of the diffraction structure.

15. The system according to claim 12, wherein the surface lattice refractive index is higher than the non-uniform lower layer refractive index at all points along the length of the diffraction structure, and the non-uniform lower layer refractive index is higher than the waveguide refractive index at all points along the length of the diffraction structure.

16. The system according to claim 12, wherein the surface lattice refractive index is the same as the waveguide refractive index, and the non-uniform lower layer refractive index is different at all points along the length of the diffraction structure from the waveguide refractive index and the surface lattice refractive index.

17. The system according to claim 12, wherein the surface lattice refractive index and the waveguide refractive index are lower at all points along the length of the diffraction structure than the non-uniform lower layer refractive index.

18. The system according to claim 12, wherein the surface lattice refractive index and the non-uniform lower layer refractive index are higher than the waveguide refractive index at all points along the length of the diffraction structure.

19. The system according to claim 12, wherein the surface lattice refractive index is the same as the non-uniform lower layer refractive index at a certain point along the length of the diffraction structure, and the waveguide refractive index is different from the non-uniform lower layer refractive index and the surface lattice refractive index at the same point along the length of the diffraction structure.

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