Method and system for augmented reality display with dynamic field of view

Abstract

To provide methods and systems that relate to flexible waveguide layers for optical power adjustment.SOLUTION: A dynamic eyepiece for projecting an image to an eye of a viewer includes a waveguide layer having an input surface, an output surface opposing the input surface, and a periphery. The waveguide layer is configured to propagate light therein. The dynamic eyepiece also includes a mechanical structure coupled to at least a portion of the periphery of the waveguide layer. The mechanical structure is operable to apply a first mechanical force to the at least a portion of the periphery of the waveguide layer to impose a first surface profile on the output surface of the waveguide layer and apply a second mechanical force to the at least a portion of the periphery of the waveguide layer to impose a second surface profile different from the first surface profile on the output surface of the waveguide layer.SELECTED DRAWING: Figure 27A

Description

[Background technology]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 873,720, filed July 12, 2019, entitled "METHODS AND SYSTEMS FOR AUGMENTED REALITY DISPLAY WITH DYNAMIC FIELD OF VIEW," and U.S. Provisional Patent Application No. 62 / 959,076, filed January 9, 2020, entitled "METHODS AND SYSTEMS FOR FABRICATING A HIGH FIDELITY POLYMER WAVEGUIDE FOR AN AUGMENTED REALITY DISPLAY," the entire contents of which are incorporated herein by reference for all purposes.

[0002] Modern computing and display technology has 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 viewer in a manner that appears or can be perceived as real. Virtual reality, or "VR," scenarios typically involve the presentation of digital or virtual image information without transparency to other actual, real-world visual input, while augmented reality, or "AR," scenarios typically involve the presentation of digital or virtual image information as an extension to the viewer's visualization of the real world around them.

[0003] Despite the advances made in these display technologies, there remains a need in the art for improved methods and systems related to augmented reality systems. Summary of the Invention [Means for solving the problem]

[0004] The present invention relates generally to methods and systems for "virtual reality" or "augmented reality" displays, e.g., displays with dynamic field of view. More specifically, embodiments of the present invention provide methods and systems relating to flexible waveguide layers for optical power adjustment.

[0005] In certain embodiments, a dynamic eyepiece including multiple waveguide layers (e.g., each associated with a primary color) is utilized in conjunction with a projector to display virtual content to a user at multiple depth planes, which may be continuously or digitally depth-varying. The present invention is applicable to a variety of applications in computer vision and three-dimensional (3D) reconstruction.

[0006] According to an embodiment of the present invention, a dynamic eyepiece for projecting an image to a viewer's eye is provided. The dynamic eyepiece includes a waveguide layer having an input surface, an output surface opposite the input surface, and a periphery. The waveguide layer is configured to propagate light therethrough. The dynamic eyepiece also includes a mechanical structure coupled to at least a portion of the periphery of the waveguide layer. The mechanical structure is operable to apply a first mechanical force to at least a portion of the periphery of the waveguide layer to impart a first surface contour on the output surface of the waveguide layer and to apply a second mechanical force to at least a portion of the periphery of the waveguide layer to impart a second surface contour on the output surface of the waveguide layer that is different from the first surface contour.

[0007] According to another embodiment of the present invention, a method for operating a dynamic eyepiece in an augmented reality headset is provided. The method includes producing first virtual content associated with a first depth plane, coupling the first virtual content into the dynamic eyepiece, and projecting the first virtual content to a viewer's eye through one or more waveguide layers of the dynamic eyepiece. The one or more waveguide layers are characterized by a first surface contour. The method also includes modifying the one or more waveguide layers to be characterized by a second surface contour different from the first surface contour, producing second virtual content associated with a second depth plane, coupling the second virtual content into the dynamic eyepiece, and projecting the second virtual content to the viewer's eye through the one or more waveguide layers of the dynamic eyepiece.

[0008] According to a specific embodiment of the present invention, a foveated display is provided. The foveated display includes a first projector and a dynamic eyepiece optically coupled to the first projector. The dynamic eyepiece comprises a waveguide having a variable surface contour. The foveated display also includes a second projector and a fixed depth eyepiece optically coupled to the second projector.

[0009] In one embodiment, a method for forming an eyepiece for use in an AR headset is provided. The method includes the steps of: casting a polymer waveguide with a light input surface and a light output surface; placing the cast polymer waveguide on a first mold with a uniformly spherical portion and locally flat portions; and placing a second mold thereon. The second mold includes an opening across the polymer waveguide, the opening being defined by a first section that surrounds at least half of the circular base of the spherical portion of the first mold and the light output surface, and a second section of the opening that surrounds at least half of the flat portion and the light input surface. A thermal process is applied to deform the polymer waveguide into the shape defined by the first and second molds.

[0010] In some embodiments, a method of forming an eyepiece for use in an augmented reality headset can include casting a polymer waveguide configured to propagate light therethrough, the polymer waveguide forming a single layer of the eyepiece and including a substantially uniform surface topology, a light input surface in a first region of the polymer waveguide, and a light output surface in a second region of the polymer waveguide. In some aspects, the light input and output surfaces are separated by at least a distance D. The method can further include placing the cast polymer waveguide on a first mold including a uniformly spherical portion having a circular base and a flat portion. In some embodiments, the polymer waveguide is configured on the first mold such that the first region is vertically aligned with the flat portion and the second region is vertically aligned with the uniformly spherical portion of the first mold. The method can further include placing a second mold over the polymer waveguide, the second mold being vertically aligned with the polymer waveguide and the first mold, the second mold including an aperture across the polymer waveguide defined by a first segment of the aperture surrounding at least half of the circular base and the light output surface of the uniformly spherical portion of the first mold and a second segment of the aperture surrounding at least half of the flat portion and the light input surface. In one implementation, the method can further include applying a thermal cycling process to heat the first and second molds to a threshold temperature that transforms the polymer waveguide into the shape defined by the first and second molds, such that the polymer waveguide is flat in the first region and the polymer waveguide is uniformly spherical in the second region, and the curved / flat transition between the first and second regions is less than a distance D.

[0011] In some embodiments, the substantially uniform surface topology can be a flat surface topology or a ubiquitously spherical surface topology. In some cases, the polymer waveguide is teardrop-shaped. The thermal cycling process can be a post-annealing process, and the threshold temperature can be 120°C. The light input surface can be an internal coupling grating (ICG), and the light output surface can be a combined pupil expander (CPE). The flat portion can be a portion where the polymer waveguide has a bow less than 20 μm, a deflection less than 20 μm, and a total thickness variation less than 1 μm.

[0012] In some embodiments, the method may further include applying a uniform surface coating of an anti-stick compound to the molded polymer waveguide, which prevents the polymer waveguide from sticking to the first and second molds during the thermal cycling process. Alternatively, or in addition, the method may include applying raw material particulates to the surface of the polymer waveguide and polishing or etching the polymer waveguide to achieve a surface roughness of 10 nm to 10 μm RMS, which prevents the polymer waveguide from sticking to the first and second molds during the thermal cycling process. Alternatively, or in addition, the method may include inserting one or more woven fabrics between the polymer waveguide and the first and / or second molds, the one or more woven fabrics configured to prevent the polymer waveguide from sticking to the first and second molds during the thermal cycling process. In some embodiments, the polymer waveguide may be comprised of either a 1.72 polymer or a 1.75 polymer and may be a single layer of a multi-layer eyepiece.

[0013] In a further embodiment, the method may still further include applying a rigid bonding material around at least a portion of the second section to surround the light input surface, the rigid bonding material bonding the second section to one or more structures adjacent to the polymer waveguide, including one or more of the adjacent polymer waveguides of a multilayer eyepiece stack or a projector, the rigid bonding material preventing or reducing movement of the light input surface as the polymer waveguide is dynamically deflected.

[0014] In one embodiment, the method includes the steps of: placing a polymer waveguide on a first mold having a uniformly spherical portion with a circular base and a flat portion, the polymer waveguide including a light input surface in a first region and a light output surface in a second region, the light input surface and the light output surface being separated by a distance D; and placing a second mold over the polymer waveguide, the second mold being vertically aligned with the polymer waveguide and the first mold, the second mold including an opening across the polymer waveguide defined by a first segment of the opening surrounding at least half of the circular base and the light output surface of the uniformly spherical portion of the first mold, and a second segment of the opening surrounding at least half of the flat portion and the light input surface. The method may further include applying a thermal cycling process to heat the first and second molds to a threshold temperature such that the polymer waveguide is flat in the first region and uniformly spherical in the second region, with the curved-to-flat transition between the first and second regions being less than a distance D, deforming the polymer waveguide into a shape defined by the first and second molds. In some cases, the polymer waveguide may initially have a substantially flat or substantially spherical surface topology. The light input surface may be an ICG, and the light output surface may be a CPE. In one aspect, the method may further include applying a uniform surface coating of an anti-stick compound to the molded polymer waveguide during the thermal cycling process, the uniform surface coating operating to prevent the polymer waveguide from sticking to the first and second molds.

[0015] Numerous advantages over conventional techniques are achieved by the methods of the present invention. For example, embodiments of the present invention provide methods and systems for bimodal or continuous variation in the surface contour of one or more waveguide layers within an eyepiece, thereby allowing multiple radii of curvature to be achieved. Furthermore, embodiments of the present invention provide methods and systems that provide a variable depth plane imaging system characterized by lighter weight and higher efficiency than conventional systems.

[0016] Furthermore, previous processing techniques for fabricating polymer waveguides in the configurations described herein often suffered from poor yield or weak / damaged transition areas between curved regions (e.g., combined pupil expanders) and flat regions (e.g., internal coupling gratings), resulting in the curved / flat waveguide transition being fabricated too short, or the curved / flat transition being fabricated too long, both scenarios that can introduce deleterious effects in waveguide performance characteristics (e.g., image distortion). Various embodiments of the present invention provide more reliable, high-yield processing methods that can offer the benefits of shorter curved / flat transitions with consistent and high-performance waveguide performance characteristics, as further described with respect to various embodiments presented below. These and other embodiments of the present invention, along with many of their advantages and features, are described in further detail in the following text and in conjunction with the accompanying figures. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 diagrammatically illustrates light paths within a viewing optical assembly (VOA) that may be used to present a digital or virtual image to a viewer, according to an embodiment of the present invention.

[0018] [Figure 2] FIG. 2 illustrates an example of the path of a single beamlet of light that is incoupled into the waveguide of the eyepiece, according to one embodiment of the present invention.

[0019] [Figure 3A] FIG. 3A illustrates an example of a waveguide having an orthogonal pupil expander region (OPE) and an exit pupil expander (EPE) region combined in a single-sided configuration, according to one embodiment of the present invention.

[0020] [Figure 3B] FIG. 3B illustrates an example of an optical path within a waveguide, according to one embodiment of the present invention.

[0021] [Figure 4] FIG. 4 is a simplified cross-sectional view of a waveguide layer of an eyepiece and light projected from the waveguide layer when the waveguide layer is characterized by a predetermined curvature.

[0022] [Figure 5] FIG. 5 is a simplified cross-sectional view of a waveguide layer of an eyepiece and light passing through the waveguide layer when the waveguide layer is characterized by a predetermined curvature.

[0023] [Figure 6A] FIG. 6A illustrates a cross-sectional view of a first configuration of a system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments.

[0024] [Figure 6B] FIG. 6B illustrates a cross-sectional view of a second configuration of the system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 6A.

[0025] [Figure 6C] FIG. 6C illustrates a plan view of a system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIGS. 6A and 6B.

[0026] [Figure 6D] FIG. 6D illustrates a plan view of an alternative system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIGS. 6A and 6B.

[0027] [Figure 6E] FIG. 6E illustrates a cross-sectional view of a third configuration of a system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments.

[0028] [Figure 6F] FIG. 6F illustrates a cross-sectional view of a fourth configuration of the system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 6E.

[0029] [Figure 7A] FIG. 7A illustrates a cross-sectional view of a first configuration of a system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments.

[0030] [Figure 7B] FIG. 7B illustrates a cross-sectional view of a second configuration of the system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 7A.

[0031] [Figure 7C] FIG. 7C illustrates a cross-sectional view of a third configuration of a system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments.

[0032] [Figure 7D] FIG. 7D illustrates a cross-sectional view of a fourth configuration of the system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 7C.

[0033] [Figure 8A] FIG. 8A illustrates a cross-sectional view of a first configuration of a pneumatic bladder system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments.

[0034] [Figure 8B] FIG. 8B illustrates a cross-sectional view of a second configuration of a pneumatic bladder system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 8A.

[0035] [Figure 9A]FIG. 9A illustrates a cross-sectional view of a first configuration of an electroactive polymer (EAP) system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments.

[0036] [Figure 9B] FIG. 9B illustrates a cross-sectional view of a second configuration of an EAP system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 9A.

[0037] [Figure 9C] FIG. 9C illustrates a plan view of the components of an EAP system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIGS. 9A and 9B.

[0038] [Figure 9D] FIG. 9D illustrates a plan view of components of an EAP system for dynamically adjusting the surface contour of an alternative waveguide layer, according to some embodiments.

[0039] [Figure 9E] FIG. 9E illustrates a plan view of components of an alternative EAP system for dynamically adjusting the surface contour of an alternative waveguide layer, according to some embodiments.

[0040] [Figure 10A] FIG. 10A illustrates a cross-sectional view of a first configuration of a mechanical system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments.

[0041] [Figure 10B] FIG. 10B illustrates a cross-sectional view of a second configuration of a mechanical system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 10A.

[0042] [Figure 10C] FIG. 10C illustrates a plan view of the components of a mechanical system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIGS. 10A and 10B.

[0043] [Figure 11A] FIG. 11A illustrates a cross-sectional view of a first configuration of an alternative mechanical system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments.

[0044] [Figure 11B] FIG. 11B illustrates a cross-sectional view of a second configuration of an alternative mechanical system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 11A.

[0045] [Figure 11C] FIG. 11C illustrates a plan view of components of an alternative mechanical system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIGS. 11A and 11B.

[0046] [Figure 11D] FIG. 11D illustrates a plan view of components of another alternative mechanical system for dynamically adjusting the surface contour of an alternative waveguide layer, according to some embodiments.

[0047] [Figure 11E] FIG. 11E illustrates a plan view of components of yet another alternative mechanical system for dynamically adjusting the surface contour of an alternative waveguide layer, according to some embodiments.

[0048] [Figure 12A] FIG. 12A illustrates a cross-sectional view of a lateral actuation system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments.

[0049] [Figure 12B] FIG. 12B illustrates a plan view of the components of a lateral actuation system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 12A.

[0050] [Figure 13A]FIG. 13A illustrates a cross-sectional view of a first configuration of a multiple ring system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments.

[0051] [Figure 13B] FIG. 13B illustrates a cross-sectional view of a second configuration of a multiple ring system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 13A.

[0052] [Figure 13C] FIG. 13C illustrates a plan view of components of a multiple ring system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIGS. 13A and 13B.

[0053] [Figure 13D] FIG. 13D illustrates a plan view of components of a multiple ring system for dynamically adjusting the surface contour of an alternative waveguide layer, according to some embodiments.

[0054] [Figure 14A] FIG. 14A illustrates a cross-sectional view of a first configuration of a roller system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments.

[0055] [Figure 14B] FIG. 14B illustrates a cross-sectional view of a second configuration of a roller system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 14A.

[0056] [Figure 14C] FIG. 14C illustrates a plan view of the components of a roller system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIGS. 14A and 14B.

[0057] [Figure 14D] FIG. 14D illustrates a cross-sectional view of a third configuration of a roller system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments.

[0058] [Figure 14E] FIG. 14E illustrates a cross-sectional view of a fourth configuration of a roller system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 14D.

[0059] [Figure 15] FIG. 15 illustrates a cross-sectional view of a pneumatic system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments.

[0060] [Figure 16] FIG. 16 is a simplified schematic diagram illustrating a cross-sectional view of a peripheral portion of three waveguide layers in a multi-layer eyepiece lens stack according to some embodiments.

[0061] [Figure 17A] FIG. 17A is a simplified schematic diagram illustrating a foveated display system, according to an embodiment of the present invention.

[0062] [Figure 17B] FIG. 17B is a simplified cross-sectional diagram illustrating the waveguide layer of the foveated display system shown in FIG. 17A in a first configuration.

[0063] [Figure 17C] FIG. 17C is a simplified cross-sectional diagram illustrating the waveguide layer of the foveated display system shown in FIG. 17A in a second configuration.

[0064] [Figure 18] FIG. 18 is a flowchart illustrating a method for operating a dynamic eyepiece in an augmented reality headset according to an embodiment of the present invention.

[0065] [Figure 19] FIG. 19 is a simplified schematic diagram illustrating an apparatus for molding a curved waveguide layer, according to an embodiment of the present invention.

[0066] [Figure 20A] FIG. 20A is a simplified schematic diagram illustrating a pre-annealed planar waveguide layer according to an embodiment of the present invention.

[0067] [Figure 20B] FIG. 20B is a simplified schematic diagram illustrating a pre-annealed curved waveguide layer according to an embodiment of the present invention.

[0068] [Figure 20C] FIG. 20C is a simplified schematic diagram illustrating a post-annealed curved waveguide layer according to an embodiment of the present invention.

[0069] [Figure 21] FIG. 21 is a simplified schematic diagram illustrating an apparatus for forming a set of curved waveguide layers, according to an embodiment of the present invention.

[0070] [Figure 22] FIG. 22 shows a simplified method of fabrication process flow for polymer waveguides, according to one embodiment.

[0071] [Figure 23] FIG. 23 shows a simplified diagram illustrating a side view of a flat substrate, according to an embodiment.

[0072] [Figure 24] 24A-24C show cross sections of various custom molds with freeform surfaces for bending polymer waveguides, according to one embodiment.

[0073] [Figure 25] 25A and 25B show aspects of one polymer bending method and corresponding problems that can arise.

[0074] [Figure 26]26A-26C are simplified diagrams illustrating aspects of a high-fidelity bending process for polymer waveguides, according to one embodiment.

[0075] [Figure 27A] FIG. 27A is a simplified cross-sectional diagram showing an example of a ubiquitously flat multi-layer eyepiece stack with a locally curved CPE, according to one embodiment.

[0076] [Figure 27B] FIG. 27B is a plan view illustrating an example of a ubiquitously flat eyepiece with a locally curved CPE within the dynamic curve eyepiece, according to one embodiment.

[0077] [Figure 28A] FIG. 28A is a simplified cross-sectional diagram showing an example of a locally flat ICG within a ubiquitously curved eyepiece stack, according to one embodiment.

[0078] [Figure 28B] FIG. 28B is a plan view illustrating an example of a locally flat ICG within a ubiquitously curved dynamic eyepiece, according to one embodiment.

[0079] [Figure 29] FIG. 29 is a simplified flowchart illustrating aspects of a method for forming a polymer waveguide for use in an augmented reality headset, according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0080] The present disclosure generally relates to methods and systems for "virtual reality" (VR) or "augmented reality" (AR) displays with dynamic fields of view. More specifically, embodiments relate to a flexible waveguide layer for optical power adjustment. The waveguide can propagate light toward a user's eye and simulate a light source at a distance from the user. Varying the curvature of the flexible waveguide can enable bi-modal or continuous simulation of various light sources at variable depths from the user's eye. Thus, the flexible waveguide can be used to propagate light toward a user's eye and simulate images or objects in three-dimensional space within a VR or AR system.

[0081] As described herein, embodiments of the present invention provide various architectures for dynamically varying the curvature of a waveguide layer, also referred to as a polymer waveguide (implemented as either a single layer or a multi-layer stack), at least a portion of which has a substantially spherical surface, thereby providing a projected image projected from a polymer eyepiece at various continuous or discrete depth planes (e.g., from a distance of 0.2 m to infinity) without any optical power. In particular embodiments, different types of actuators can be utilized as needed for the particular implementation to induce uniform stresses and load forces on the waveguide layer, resulting in high-fidelity modifications of the radius of curvature of the spherical surface.

[0082] In the embodiments described herein, eyepieces characterized by adjustable optical power are achieved by curving the eyepiece's exit pupil expander (EPE) area, with the radius of curvature proportional to the focal length of the virtual image. By utilizing polymer-based eyepieces with Young's modulus values ​​well below those of glass-based eyepieces, some embodiments induce a spherically curved surface (e.g., a radius of curvature of 0.3 mm over an area of ​​up to φ50 mm) in a flat polymer substrate (e.g., up to 0.5 mm thick) using reasonable and manageable forces / loads (e.g., <25 N). As described herein, when the force / load is released, the polymer substrate is able to restore its shape (e.g., to its original shape, which may be flat, curved, or a combination thereof) by relaxing the stored strain energy. The mechanism is utilized to dynamically modulate (either continuously or discretely) the curvature of a waveguide layer (e.g., one or more polymeric waveguide layers) between a first curvature state and a second curvature state, for example, from a flat state to a curved state, from a curved state to a flat state, from a curved state to another curved state with a smaller or larger radius of curvature, or the like. In one particular example, a flat state (or a large radius of curvature, e.g., 2.0 m) may be dynamically modulated to a curved state (e.g., a radius of curvature of 0.1 m), or vice versa. Continuous variation in the radius of curvature is thereby provided for radii of curvature from 0.1 m to infinity.

[0083] In some of the embodiments described herein, the curvature modulation is performed in only one direction, i.e., the radius of curvature is either increasing or decreasing. However, the invention is not limited to this condition. For example, as described more fully herein, some embodiments utilize a waveguide layer that is fabricated to have an intermediate curvature, e.g., a radius of curvature of 650 mm. In this example, a mechanical force, e.g., a spring, can be used to bias the waveguide layer in one direction, and then actuation on the mechanical force can be used to achieve the full range of radius curvature. As will be apparent to those skilled in the art, these embodiments will reduce or minimize optical errors that typically accumulate as the waveguide layer is modified away from the nominal state.

[0084] Embodiments provide bi-mode or continuous operation of one or more layers of the waveguide. Bi-mode operation of a dynamic waveguide system may be interpreted to mean that the waveguide can be transitioned into one of two discrete states: a resting state, in which the waveguide exhibits its natural radius of curvature when no external force is applied, and a forced state, in which the radius of curvature of the waveguide is altered through radial compression or expansion by an external mechanical force. Switching to one state can cause the light source to appear at a certain distance from the user's eye. Switching to the other state can cause the light source to appear at a different distance from the user's eye. In some examples, bi-mode operation can be implemented to simultaneously cause two light sources to appear to the user, with the distance of each light source being determined by the radius of curvature of the waveguide in the two states. By refreshing or toggling the waveguide between the two bi-mode states at a rate faster than what the human eye can perceive (e.g., faster than a 60 Hz refresh rate), embodiments can enable a user to perceive multiple light sources at different distances in real time.

[0085] Embodiments that enable continuous operation of the waveguide can render light sources at more than two depths. Instead of an “all-or-none” bimodal operation in which the waveguide can assume one of two radius of curvature values ​​corresponding to two discrete, predetermined distances to the user's eye, continuous operation of the waveguide can assume two or more radius of curvature values. Continuous operation of a dynamic waveguide system can implement states between the waveguide's natural rest state and its fully compressed or expanded state, allowing light sources to be rendered at more than two distances. For example, multiple light sources can be projected onto the user's eye, and the light sources can appear to be projected simultaneously. A first light source can appear 0.2 meters from the user's eye, a second light source can appear 0.5 meters, and a third light source can appear 1 meter. Each distance can correspond to a different radius of curvature value obtained by dynamically adjusting the waveguide between multiple states. In the same way that the two-mode operation of a dynamic waveguide system can appear to render two light sources to a user in real time, the continuous operation of a dynamic waveguide system can render two or more light sources to a user in real time by toggling between each waveguide state at a rate faster than what the human eye can perceive.

[0086] FIG. 1 diagrammatically illustrates the optical paths within a viewing optical assembly (VOA) that may be used to present a digital or virtual image to a viewer, according to one embodiment of the present invention. The VOA includes a projector 101 and an eyepiece 100 that may be worn around the viewer's eye. The eyepiece 100 may include one or more eyepiece layers. In one embodiment, the eyepiece 100 includes three eyepiece layers, one for each of the three primary colors: red, green, and blue. In another embodiment, the eyepiece 100 may include six eyepiece layers, i.e., one set of eyepiece layers for each of the three primary colors configured to form a virtual image in one depth plane and another set of eyepiece layers for each of the three primary colors configured to form a virtual image in another depth plane. In other embodiments, the eyepiece 100 may include three or more eyepiece layers for each of the three primary colors for three or more different depth planes. Each eyepiece layer comprises a planar waveguide and may include an internal coupling grating 107, an orthogonal pupil expander (OPE) region 108, and an exit pupil expander (EPE) region 109.

[0087] Still referring to FIG. 1 , the projector 101 projects image light onto an internal coupling grating 107 in the eyepiece layer 100. The internal coupling grating 107 couples the image light from the projector 101 into a planar waveguide that propagates in a direction toward the OPE region 108. The waveguide propagates the image light horizontally by total internal reflection (TIR). The OPE region 108 of the eyepiece layer 100 also includes a diffractive element that couples a portion of the image light propagating in the waveguide and redirects it toward the EPE region 109. The EPE region 109 includes a diffractive element that couples a portion of the image light propagating in the waveguide and directs it in a direction generally perpendicular to the plane of the eyepiece layer 100 toward the viewer's eye 102. In this manner, the image projected by the projector 101 can be viewed by the viewer's eye 102.

[0088] The diffractive elements in the EPE region 109 of the eyepiece layer 100 typically comprise gratings, periodic structures formed on the surface of, for example, a planar waveguide within the eyepiece. When a beam of light passes through the periodic structure, it will be diffracted into multiple orders. The period of the repeating structure determines the angular separation between the orders. A small period creates a large angular separation, while a large period results in a closely spaced output beam. The relative optical power directed to each of the diffracted orders is dictated by the shape and nature of the surface profile of a single grating period.

[0089] FIG. 2 illustrates an example path of a single beamlet of light internally coupled into a waveguide 212 of an eyepiece 200, according to one embodiment of the present invention. The waveguide 212 may include an ICG 220, an OPE 230, and an EPE 240, each disposed on or within a substrate 202 made of a material capable of guiding optical waves by total internal reflection (typically a dielectric material with a high dielectric constant). In some embodiments, the eyepiece 200 may include three waveguides 212, 214, and 216, each corresponding to a specific wavelength of light. Additional or fewer waveguides are also possible. Waveguides 214 and 216 may each include an ICG, an OPE, and an EPE, similar to the waveguide 212. In some embodiments, injected light 222 may enter the eyepiece 200 at the ICG 220 in the z-direction, orthogonal to the depiction of FIG. 2. The injected light 222 can enter the ICG 220, and the gratings within the ICG 220 can diffract certain wavelengths of light within the incoupled light 222, while other wavelengths of the incoupled light 222 continue through subsequent waveguide layers of the eyepiece 2310. In some embodiments, the ICG 220 is a plurality of separate gratings specific to particular wavelengths.

[0090] The internally coupled light 222 can be diffracted by the ICG 220 in certain directions within the waveguide, ranging not only as depicted by fan-shaped pattern 224 toward the OPE 230 in approximately the +x direction, but also extending into fan-shaped pattern 226 away from the OPE 230 in approximately the −x direction. Other light paths extending into other fan-shaped patterns are, of course, possible and depend on the particular grating and diffraction pattern configured by the projection optics and the ICG 220. That is, the light does not diffract into the waveguide as a diverging beam, and in some embodiments, a gradually dispersed sampling of portions of the image light may create a distribution pattern of gradually expanding beamlets across the eyepiece. The internally coupled light 222 diffracted within the depicted fan-shaped pattern 224 generally follows light path 228, entering OPE 230, traversing in the +x direction, with attendant distributed sampling through OPE 230 as it strikes the diffraction grating that makes up OPE 230, and some may be periodically directed downward to EPE 240 and traversing in the -y direction before being externally coupled in the -z direction towards the user's eye.

[0091] 2 depicts, much of the light in the wavelengths corresponding to waveguide 212 may be lost either due to directional losses, such as light diffracted into fan pattern 226, or due to capture losses caused by OPE 230 being improperly positioned or sized to capture all of the light in fan pattern 224. A detailed description of eyepieces is provided in U.S. Patent Application Publication No. 15 / 683,624, the contents of which are incorporated by reference for all purposes.

[0092] 3A illustrates an example of a waveguide 300 having a combined OPE / EPE region 350 in a single-sided configuration, also referred to as a combined pupil expander (CPE), in accordance with another embodiment of the present invention. The combined OPE / EPE region 350 includes gratings corresponding to both the OPE and the EPE that spatially overlap in the x and y directions. In some embodiments, the gratings corresponding to both the OPE and the EPE are located on the same side of the substrate 302, such that the OPE grating is overlaid on the EPE grating or the EPE grating is overlaid on the OPE grating (or both). In other embodiments, the OPE grating is located on the opposite side of the substrate 302 from the EPE grating, such that the gratings spatially overlap in the x and y directions but are separated from each other in the z direction (i.e., in different planes). Thus, the combined OPE / EPE region 350 can be implemented in either a single-sided or double-sided configuration.

[0093] 3B illustrates an example of a light path 328 within waveguide 300, according to one embodiment of the present invention. Light path 328 includes incident light (shown as 328A) that is coupled into substrate 302 at ICG 320. The internally coupled light (shown as 328B) propagates toward gratings 351, 352, and 353 by total internal reflection. When these light rays encounter first OPE grating 351, the light is diffracted in the +y direction (shown as 328C) and subsequently diffracted by EPE grating 353 in the -z direction out of waveguide 300 toward the user's eye (shown as 328D). Similarly, internally coupled light (shown as 328B) may alternatively encounter second OPE grating 352 and be diffracted in the -y direction (shown as 328E). Light diffracted in the -y direction (shown as 328E) may be diffracted by the EPE grating 353 out of the waveguide 300 toward the user's eye. Whether the light is diffracted in the +y direction (by the first OPE grating 351) or the -y direction (by the second OPE grating 352) is probabilistic and governed by the grating structure. Generally, the performance of the combined OPE / EPE region 350 is improved when the internally coupled light (shown as 328B) has a 50% chance of diffracting in either the +y or -y direction. In some cases, this is achieved when the first OPE grating 351 and the second OPE grating 352 are perpendicular to each other.

[0094] Although waveguide 300 is illustrated as having only a single ICG 320, in some embodiments, it may be preferable for waveguide 300 to include a second ICG on the combined OPE / EPE region 350 opposite ICG 320. The second ICG may be identical in form and function to ICG 320 or may be a mirrored version of ICG 320. For example, ICG 320 may be configured to diffract internally coupled light associated with a projected image into substrate 302, while the second ICG 320 may be configured to diffract internally coupled light associated with a mirrored version (e.g., flipped in the x-direction) of the projected image. In contrast to light path 328 associated with ICG 320, the light path associated with the second ICG may include incident light that is coupled into substrate 302 at the second ICG. The internally coupled light propagates toward gratings 351, 352, and 353 by total internal reflection. When these light rays encounter the first OPE grating 351, the light is diffracted in the -y direction and then diffracted in the -z direction by the EPE grating 353 out of the waveguide 300 toward the user's eye. Similarly, the incoupled light may alternatively encounter the second OPE grating 352 and be diffracted in the +y direction. The light diffracted in the +y direction may be diffracted by the EPE grating 353 out of the waveguide 300 toward the user's eye.

[0095] Further details regarding other waveguide topologies are described in US patent application Ser. No. 15 / 683,623, previously incorporated by reference.

[0096] FIG. 4 is a simplified cross-sectional view of a waveguide layer of an eyepiece and light projected from the waveguide layer when the waveguide layer is characterized by a predetermined curvature, according to some embodiments. An input light beam 402 from a light source, such as a projector (not shown), can enter the waveguide layer 404 through an input surface 406 (e.g., by diffraction from an internal coupling element (not shown)) and exit through an output surface 408 toward a user's eye 410. As illustrated in FIG. 4 , a surface contour is provided on the waveguide layer 404. In some embodiments, the surface contour forms a curve, which can be defined by a radius of curvature for a spherical curvature. In other embodiments, the surface contour is aspherical but can be approximated by a spherical surface shape. Due to the structure of the waveguide layer 404, the input surface 406 can be parallel to the output surface 408 throughout the entire length of the waveguide layer 404.

[0097] As light propagates through the waveguide layer 404 by TIR, as discussed above, the output light is diffracted out of the waveguide layer 404, as illustrated by output ray 403. For low levels of curvature, the input surface 406 and output surface 408 are parallel to one another across the waveguide layer. Thus, as light propagates through the waveguide layer by TIR, the parallel nature of the waveguide surfaces preserves the reflection angle during TIR, such that the angle between the output ray and the output surface is preserved across the waveguide layer. Because the surface normal varies slowly across the output surface of a curved waveguide layer, the output ray also varies slowly, producing the divergence illustrated in FIG. 4.

[0098] The divergence of output light rays 403 resulting from the curvature of output surface 408 can have the effect of rendering input light beam 402 such that the light appears to originate from a point source located at a particular distance behind waveguide layer 404. Thus, the surface contour or curvature imparted on waveguide layer 404 produces a divergence of light toward the user's or viewer's eye 410, effectively rendering the light to originate from a depth plane located behind the waveguide layer.

[0099] The distance from the waveguide layer that the input light beam appears to occur can be related to the radius of curvature of the waveguide layer 404. A waveguide with a higher radius of curvature can render the light source to emanate at a greater distance from the waveguide layer than a waveguide with a lower radius of curvature. For example, as shown in FIG. 4 , the waveguide layer 404 has a radius of curvature of 0.5 m, which can be achieved by deflecting the waveguide layer 404 by up to 0.4 mm across an EPE having a lateral dimension (e.g., length or width) of 40 mm. Given this curvature of the waveguide layer 404, the input light beam 402 appears to occur at a distance of 0.5 m from the waveguide layer 404. As another example, another waveguide layer can be operated to have a radius of curvature of 0.2 m, rendering the light source to appear to the user to emanate at a distance of 0.2 meters from the waveguide layer. Thus, by utilizing a small amount of curvature, i.e., a fraction of a millimeter of deflection, across a waveguide layer of tens of millimeters in length / depth that is compatible with the waveguide layer material, depth-plane functionality can be implemented for two-dimensional extended waveguides, also referred to as two-dimensional waveguides. The curvature utilized in accordance with embodiments of the present invention is commonly used in various commercial products, including sunglasses, vehicle windshields, and the like, which may have a deflection of a few millimeters (e.g., 1-5 mm). Thus, the small amount of curvature utilized in various embodiments of the present invention will not degrade the optical performance of the eyepiece, for example, introducing less than 0.1 arc minutes of blur in the central field and less than 2 arc minutes of blur across the field of view of an eyepiece with a 0.5 mm radius of curvature.

[0100] FIG. 4 illustrates only a one-dimensional cross-section of the waveguide layer 404, an element of the eyepiece. However, it should be understood that the surface contours provided on the waveguide layer can also be provided in a direction perpendicular to the plane of the figure, resulting in two-dimensional curvature of the waveguide layer. Embodiments of the present invention therefore provide depth surface functionality to the structure of the eyepiece, and in particular to the waveguide layer of the eyepiece. As described herein, the depth surface functionality can be bimodal or continuous, depending on the particular implementation.

[0101] FIG. 5 is a simplified cross-sectional view of a waveguide layer of an eyepiece and light passing through the waveguide layer when the waveguide layer is characterized by a predetermined curvature, according to some embodiments. As illustrated in FIG. 4, light projected from the waveguide layer 404 can cause a light source to appear to a user's eye in three-dimensional space. Real-world light 502, i.e., light not projected through the waveguide layer 404 for VR or AR purposes, can pass through the input surface 406 and output surface 408 of the waveguide layer 404 toward the user's eye 410. A waveguide with low thickness variation (e.g., less than 1.0 μm) can have negligible optical power, allowing real-world light 502 to pass through the curved surface of the waveguide layer 404 with little or no disturbance. In some embodiments, no correction of the real-world light is required, and there is little or no off-axis degradation of the real-world light caused by the surface contour of the waveguide layer 404. Thus, imparting a certain surface contour or curvature onto the waveguide layer allows for the projection of virtual content from a position at a certain distance from the eyepiece while maintaining the integrity of the real-world light, thereby allowing both the real-world light to be seen by the user and the virtual content to be rendered for the user in real-time in three-dimensional space.

[0102] In some embodiments, the radius of curvature of the waveguide layer, which may be a polymer waveguide layer, can be dynamically varied from 0.1 m to infinity, which can similarly dynamically vary the depth plane of the eyepiece (i.e., the distance at which the projected light source appears to be rendered) from 0.1 m to infinity. Thus, embodiments of the present invention enable variation of the depth plane from 0.1 m to infinity, including all depth planes typically utilized in augmented or mixed reality applications. The surface contour of the waveguide layer, for example, a flexible polymer waveguide layer, can be adjusted using various methodologies and mechanisms, as described in further detail throughout this specification.

[0103] In some of the embodiments described below, dynamic eyepieces are provided, in which the depth plane of the eyepiece can be varied, e.g., in a time-varying manner as a function of time, to display virtual content at different depth planes. Thus, subsequent frames of virtual content can be displayed to appear to originate from different depth planes. However, static implementations are also within the scope of the present invention. In these static implementations, a fixed and predetermined surface contour or curvature is imparted to the waveguide layer of the eyepiece, thereby presenting virtual content at a fixed depth plane. In contrast to systems utilizing external lenses, diffractive lenses, or other optical elements, embodiments utilizing static implementations can implement depth planes through the curvature of the waveguide layer, reducing system complexity and improving optical quality. Furthermore, some embodiments can implement a set of eyepieces, each of which includes a stack of curved waveguide layers and providing two static depth planes. As an example, a first stack of three curved waveguide layers may implement a three-color scene at a depth plane positioned at 1 m, utilizing a flexure of 0.2 mm across the width / length of the waveguide stack, and a second stack of three curved waveguide layers may implement a second three-color scene at a depth plane positioned at 0.5 m, utilizing a flexure of 0.4 mm across the width / length of the waveguide stack.

[0104] FIG. 6A illustrates a cross-sectional view of a first configuration of a system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments. In some embodiments, the waveguide layer can be positioned between two angled rigid surfaces that, when actuated, act as crimps on the waveguide layer, resulting in an adjustment to the surface contour or curvature of the waveguide layer. In FIG. 6A, a waveguide layer 606, which can be a planar or relatively planar polymeric waveguide layer, is positioned between two ring-shaped crimping features: a top crimping feature 602 and a bottom crimping feature 604. In FIG. 6A, the two ring-shaped crimping features are positioned in an unactuated configuration, thereby allowing the waveguide layer 606 to assume a first surface contour, e.g., a planar surface contour or a surface contour with a small intrinsic curvature. The periphery of the waveguide layer 606 can be positioned or otherwise aligned between the bottom surface of the top crimping feature 602 and the top surface of the bottom crimping feature 604. The bottom surface of the top crimping mechanism 602 and the top surface of the bottom crimping mechanism 604 can be angled to complement one another. Additional description of the crimping mechanisms is provided in connection with Figures 6C and 6D.

[0105] 6B illustrates a cross-sectional view of a second configuration of the system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 6A. As illustrated in FIG. 6B, top crimping mechanism 602 and bottom crimping mechanism 604 can be actuated to apply a mechanical force to the periphery of waveguide layer 606. As shown in FIG. 6B, actuation of the two ring-shaped crimping mechanisms applies a mechanical force to the periphery of waveguide layer 606, which bends in response to the mechanical force at an angle equal to the angle defined by the complementary shapes of top crimping mechanism 602 and bottom crimping mechanism 604. Thus, adjusting waveguide layer 606, for example, from a planar surface contour to a curved surface contour by applying a mechanical force to the periphery of the waveguide layer, can adjust the radius of curvature of the waveguide layer. The angle defined by the top crimping mechanism 602 and the bottom crimping mechanism 604 can be predefined by the structure of the top crimping mechanism 602 and the bottom crimping mechanism 604 so that different structures capable of imparting different surface contours can be fabricated for various applications, resulting in the production of different depth planes. Deactivation of the two ring-shaped crimping mechanisms removes the mechanical force at the periphery of the waveguide layer, which returns to its original surface contour, e.g., a flat surface as illustrated in FIG. 6A.

[0106] According to an embodiment of the present invention, application of a bending moment at the periphery of the waveguide layer results in a modulation of the surface contour or curvature of the waveguide layer uniformly across the width / length of the waveguide layer and the aperture area of ​​the associated eyepiece.

[0107] Figure 6C illustrates a plan view of a system for dynamically adjusting the surface contour of the waveguide layer illustrated in Figures 6A and 6B. As illustrated in Figure 6C, the periphery of the waveguide layer 606 contacts an annular-shaped top crimping feature 602 and a complementary-shaped bottom crimping feature 604 (not shown).

[0108] Utilizing a variable surface contour structure such as that illustrated in FIGS. 6A and 6B provides a dynamic eyepiece in which the depth plane of the eyepiece can be varied to display virtual content at different depth planes. Thus, for example, using a single eyepiece containing three waveguide layers, each associated with a primary color, a time-division multiplexing technique can be utilized to display virtual content that appears to originate from different depth planes. While the embodiment illustrated in FIGS. 6A and 6B provides two different depth planes, other implementations enable continuous variation in the surface contour, thereby providing a dynamic eyepiece with continuous depth plane variation. Additionally, virtual content can be shifted to different depth planes as a function of user movement, when the user blinks, or the like. The current depth plane associated with the eyepiece can be correlated with the virtual content to be displayed, so that the depth plane can be adjusted as a function of the virtual content. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0109] 6C, mechanical force can be applied uniformly to the periphery of waveguide layer 606 through actuation of top crimping mechanism 602 and bottom crimping mechanism 604 (not shown). In this embodiment, the annular shapes of the two ring-shaped crimping mechanisms conform to the shape of waveguide layer 606. In other embodiments, the crimping mechanisms can be shaped to conform to waveguide layers having shapes other than circular.

[0110] Figure 6D illustrates a plan view of an alternative system for dynamically adjusting the surface contour of the waveguide layer illustrated in Figures 6A and 6B. As illustrated in Figure 6D, the eyepiece can include a waveguide layer 610 characterized by a teardrop shape in plan view. Although a teardrop shape is illustrated in Figure 6D, embodiments of the present invention are not limited to this particular shape, and other shapes are within the scope of the present invention.

[0111] The fixed portion 612 of the waveguide layer can be affixed to a portion of the waveguide layer 610 or otherwise hold it in place adjacent the fixed portion. As an example, the ICG 613 can be positioned near the center of the fixed portion 612. To prevent modification of the surface contour of the waveguide layer in the vicinity of the ICG 613, the fixed portion 612 is utilized to maintain the surface contour of this portion of the waveguide layer within the fixed surface contour. In other embodiments, the fixed portion can loosely hold the waveguide layer 610 in place, for example, by utilizing one or more shims between the waveguide layers to allow the portion of the waveguide layer 610 adjacent the fixed portion 612 to bend or remain in its original condition without interference from the fixed portion 612, as discussed in more detail in connection with FIG. 16 .

[0112] A top C-shaped crimping mechanism 608 can then be coupled to the fixed portion 612 and completely surround the waveguide layer 610 along the periphery of the waveguide layer. The top C-shaped crimping mechanism 608 can adjust the surface contour of most of the waveguide layer 610 by crimping the waveguide layer 610 against a complementary bottom C-shaped crimping mechanism (not shown in this plan view), as described in the previous embodiment. Utilizing a C-shaped crimping mechanism as illustrated in FIG. 6D allows a sufficient portion of the periphery of the waveguide layer to be oriented at a predetermined angle such that the viewing area of ​​the eyepiece is characterized by a uniform surface contour or curvature across the width / length of the viewing area, while maintaining a portion of the waveguide layer at a fixed surface, independent of the actuation of the contour crimping system. In embodiments utilizing multiple waveguide layers, the C-shaped crimping mechanism 608 may incorporate shims or other flexible mating surfaces, as described in further detail in connection with FIG. 16, to allow adjacent waveguide layers to slide and / or rotate independently of one another.

[0113] In some examples, portions of the crimping mechanism can be decoupled so that variable mechanical forces can be applied to different portions along the periphery of the waveguide layer. For example, a ring-shaped crimping mechanism can be bifurcated and separated into quadrants, or any number of sections with the same or different crimping angles. Various sections of the crimping mechanism can be activated simultaneously, alternately, or in combination so that some portions of the periphery of the waveguide can be crimped and some portions can remain uncrimped. This can enable movement or positioning of virtual content across a range at different depth planes from the user's line of sight.

[0114] In some embodiments, the waveguide can be pre-curved and then crimped to bend into a less curved or planar state. FIG. 6E illustrates a cross-sectional view of a third configuration of a system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments. FIG. 6F illustrates a cross-sectional view of a fourth configuration of a system for dynamically adjusting the surface contour of a waveguide layer shown in FIG. 6E. As shown in FIGS. 6E and 6F, the waveguide layer 618 can be curved with a predetermined surface contour, e.g., a predetermined radius of curvature. The waveguide layer can then be positioned between two ring-shaped crimping mechanisms, i.e., top crimping mechanism 614 and bottom crimping mechanism 616, in a manner similar to the embodiment described in connection with FIGS. 6A-6B. In FIG. 6E, the two ring-shaped crimping mechanisms are positioned in an unactuated configuration, thereby allowing the waveguide layer 618 to assume a first surface contour, e.g., a curved surface contour associated with a display of a first depth plane. The periphery of the waveguide layer 618 can be positioned or otherwise aligned between the bottom surface of the top crimping feature 614 and the top surface of the bottom crimping feature 616. The periphery of the waveguide layer 618 can contact the annular-shaped top crimping feature 614 or the complementary-shaped bottom crimping feature 616. The bottom surface of the top crimping feature 614 and the top surface of the bottom crimping feature 616 can be angled complementary to one another. These complementary surfaces of the crimping features can be flat, i.e., planar, and can bend the waveguide layer 618 from a predetermined curvature to a planar state or a state with a reduced curvature. In some embodiments, the complementary surfaces can be angled to bend the waveguide layer 618 at an angle less than the predetermined surface profile of the waveguide layer 618, producing a reduced radius of curvature. 6F, actuation of the two ring-shaped crimping features applies a mechanical force to the periphery of the waveguide layer 618, which bends in response to the mechanical force at an angle equal to the angle defined by the complementary shapes of the top crimping feature 614 and the bottom crimping feature 616. Thus, adjusting the waveguide layer 618, for example, from a curved to a planar surface contour by applying a mechanical force to the periphery of the waveguide layer, can adjust the radius of curvature of the waveguide layer.The angles defined by the top crimping mechanism 614 and the bottom crimping mechanism 616 can be predefined by the structure of the top crimping mechanism 614 and the bottom crimping mechanism 616 so that different structures capable of imparting different surface contours can be fabricated for various applications, resulting in the production of different depth planes. Deactivation of the two ring-shaped crimping mechanisms removes the mechanical force at the periphery of the waveguide layer, which returns to its original surface contour, for example, the curvature illustrated in FIG. 6E.

[0115] The embodiments described in connection with FIGS. 6A-6F can provide operation in a bimodal manner, meaning that a crimping mechanism can switch the waveguide layer between two discrete states, thereby rendering projected virtual content at two different discrete depths from the user's eyes. For example, as illustrated in FIGS. 6A and 6B , the waveguide layer 606 can operate in a planar, or “flat,” mode and then bend to operate in a curved mode. The waveguide layer can be continuously transitioned between these two states. As another example of bimodal operation, as described in connection with FIGS. 6E and 6F , the waveguide layer 616 can operate in a curved mode and then bend to operate in a planar, or “flat,” mode, or vice versa. In other examples, the waveguide can have a predetermined radius of curvature and be bent to have a different radius of curvature, either lower or higher, depending on a predetermined angle of the crimping mechanism.

[0116] FIG. 7A illustrates a cross-sectional view of a first configuration of a system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments. As illustrated in FIG. 7A, a vacuum chuck system is utilized to dynamically adjust the surface contour or curvature of the waveguide layer. The discussion provided in connection with FIGS. 6A-6F is applicable to the embodiments illustrated in FIGS. 7A-7D, where appropriate, e.g., the crimping mechanism illustrated in FIG. 6A is replaced with a vacuum chuck system as illustrated in FIG. 7A. In the embodiments illustrated in FIGS. 7A-7D, the waveguide layer is positioned or otherwise mounted on top of the vacuum chuck mechanism.

[0117] 7A, a planar or relatively planar waveguide layer 702, which may be a flexible polymer waveguide, may be positioned against a vacuum chuck mechanism 704, which may have an annular or ring-based shape as discussed in connection with FIGS. 6C and 6D. The periphery of the waveguide layer 702 is positioned with or otherwise aligned with the vacuum chuck mechanism 704. The vacuum chuck mechanism 704 may include a fixed portion 706 that may also house components used to apply a vacuum force within the vacuum chuck mechanism 704.

[0118] The top surface of the fixed portion 706 is inclined at a predetermined angle, similar to the top surface of the bottom crimping mechanism 604 illustrated in FIG. 6A. Prior to actuation, the outer periphery of the waveguide layer 702 is positioned above the outer periphery of the top surface of the fixed portion 706, illustrated by the vertical gap between these portions in FIG. 7A. The inner periphery of the waveguide layer 702 contacts the top surface of the fixed portion 706. Thus, in this first configuration, the planar waveguide layer is supported by the vacuum chuck mechanism 704 and can maintain a planar surface profile.

[0119] FIG. 7B illustrates a cross-sectional view of a second configuration of the system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 7A . In FIG. 7B , a vacuum force is applied to the periphery of the waveguide layer 702 in response to actuation of the vacuum chuck mechanism 704. In response to the vacuum force, the periphery of the waveguide layer 702 is brought into contact with the periphery of the top surface of the fixed portion 706 such that the entire periphery of the waveguide layer 702 contacts the fixed portion 706. Thus, when the vacuum chuck mechanism 704 is actuated, the generation of the vacuum force at the fixed portion 706 applies a mechanical force to the periphery of the waveguide layer 702, which bends in response to the mechanical force at an angle equal to the angle defined by the shape of the top surface of the fixed portion 706. Thus, adjusting the waveguide layer 702, for example, from a planar surface contour to a curved surface contour by applying a mechanical force to the periphery of the waveguide layer, can adjust the radius of curvature of the waveguide layer. The angle defined by the top surface of the fixed portion 706 can be predefined by the structure of the vacuum chuck mechanism 704 so that different structures capable of providing different surface contours can be fabricated for various applications, resulting in the production of different depth planes. Deactivation of the vacuum chuck mechanism 704 removes the mechanical force at the periphery of the waveguide layer, which returns to its original surface contour, e.g., a flat surface as illustrated in FIG. 7A.

[0120] 7A and 7B can bend a planar waveguide layer in a manner characterized by a surface contour defined by the angle of the structure of the vacuum chuck mechanism 704. In other embodiments, the waveguide layer can have an initial predetermined curvature and can be transitioned to a planar state.

[0121] FIG. 7C illustrates a cross-sectional view of a third configuration of a system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments. FIG. 7D illustrates a cross-sectional view of a fourth configuration of a system for dynamically adjusting the surface contour of a waveguide layer, as illustrated in FIG. 7C. As illustrated in FIG. 7C, the waveguide layer 708 can have an original, or resting, state with a predetermined curvature. The vacuum chuck mechanism 710 can have a flat surface on which a portion of the periphery of the waveguide layer 708 can be positioned or otherwise mounted. Due to the predetermined curvature of the waveguide layer 708, the inner periphery of the waveguide layer 708 is positioned above the inner periphery of the top surface of the fixed portion 712, as illustrated by the vertical gap between these portions in FIG. 7C. The outer periphery of the waveguide layer 708 contacts the top surface of the fixed portion 712. Thus, in this third configuration, the curved waveguide layer is supported by vacuum chuck mechanism 710 and is able to maintain its curved surface profile.

[0122] 7D , when the vacuum chuck mechanism 710 is actuated, a vacuum force pulls the curved periphery of the waveguide layer 708 against the flat surface of the fixed portion 712 of the vacuum chuck mechanism 710, uniformly bending the waveguide layer into a planar or near-planar shape. According to an embodiment of the invention, the application of a bending moment at the periphery of the waveguide layer results in a modulation of the surface contour or curvature of the waveguide layer uniformly across the width / length of the waveguide layer and the aperture area of ​​the associated eyepiece.

[0123] The vacuum chucking mechanism 704 can be annular-shaped to conform to the entire periphery of the waveguide layer 702, similar to the crimping mechanism illustrated in FIG. 6C . In other embodiments, the vacuum chucking mechanism 704 can be C-shaped around a teardrop-shaped waveguide, similar to the C-shaped crimping mechanism illustrated in FIG. 6D . Furthermore, in alternative embodiments, portions of the vacuum chucking mechanism can be segmented or broken so that variable mechanical forces can be applied to different portions along the periphery of the waveguide layer. For example, a ring-shaped vacuum chucking mechanism can be bifurcated and separated into quadrants, or any number of sections with the same or different angles, and the periphery of the waveguide is bent accordingly. Various sections of the vacuum chucking mechanism can be activated simultaneously, alternately, or in combination so that some portions of the periphery of the waveguide layer can be vacuum-chucked and some portions can remain unchucked. This can enable movement or positioning of virtual content across a range at different depth planes from the user's line of sight.

[0124] The embodiment described by FIGS. 7A-7D can provide operation in a two-mode manner, meaning that a vacuum chucking mechanism can switch the waveguide layer between two discrete states, thereby rendering projected virtual content at two different discrete depths from the user's eye. For example, as illustrated in FIGS. 7A and 7B , the waveguide layer 702 can operate in a planar, or “flat,” mode and then bend to operate in a curved mode. The waveguide can be continuously transitioned between these two states. As another example of two-mode operation, as illustrated in FIGS. 7C and 7D , the waveguide layer 708 can operate in a curved mode and then bend to operate in a planar, or “flat,” mode, or vice versa. In other examples, the waveguide can have a predetermined radius of curvature and be bent to have a different radius of curvature, either lower or higher, depending on a predetermined angle of the vacuum chucking mechanism.

[0125] FIG. 8A illustrates a cross-sectional view of a first configuration of a pneumatic bladder system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments. As illustrated in FIG. 8A, the pneumatic system includes a pneumatic chamber 802 and lenses L1 and L2. The pneumatic chamber 802 includes a left chamber portion 804, a right chamber portion 806, and a waveguide layer 810, illustrated as a pre-curved polymer waveguide layer. The waveguide layer 810 is sealed within the airtight enclosure of the pneumatic chamber 802. The left and right chamber portions 804 and 806 are sealed from each other, so that different pressures can be applied within each chamber portion. The waveguide layer 810 is substantially rigid but can be flipped to substantially equal and opposite curvatures. Depending on the level of pre-existing pressure in each chamber portion, increasing or decreasing the pressure in left chamber portion 804 or right chamber portion 806 inverts waveguide layer 810 and reverses the curvature of waveguide layer 810, as described below in connection with Figure 8B. The pressure in left chamber portion 804 and right chamber portion 806 can be adjusted using one or more pneumatic devices (e.g., positive pressure / negative pressure, e.g., vacuum devices) (not shown).

[0126] FIG. 8B illustrates a cross-sectional view of a second configuration of a pneumatic bladder system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 8A. To toggle the waveguide layer 810 from a first configuration as illustrated in FIG. 8A to a second configuration as illustrated in FIG. 8B, a pressure change can be induced in either the left chamber portion 804 and / or the right chamber portion 806. For example, the pressure in the right chamber portion 806 can be increased, causing the waveguide layer 810 to reverse its curvature to that illustrated in FIG. 8B. Alternatively, the pressure in the left chamber portion 804 can be decreased, causing the waveguide layer 810 to reverse its curvature to that illustrated in FIG. 8B. As another example, the pressure values ​​in the left chamber portion 804 and the right chamber portion 806 can be simultaneously and inversely altered to toggle between the states illustrated by FIGS. 8A and 8B. The embodiment illustrated in Figures 8A and 8B is energy efficient as a result of power being utilized only during state changes in the waveguide layer 810.

[0127] In an exemplary embodiment, lenses L1, L2 have complementary lens functions used to achieve two depth planes without affecting real-world light as perceived by the user's eye 808. For example, considering the waveguide layer 810 in the first configuration illustrated in FIG. 8A and lens L1 positioned between the eye 808 and the waveguide layer 810, the waveguide layer 810 has a refractive power of +0.75D and L1 has a refractive power of −0.75D, which results in virtual content appearing to occur at infinity (i.e., the far plane). Referring to FIG. 8A, world light passes with little or no disturbance through lens L2, which has a refractive power of +0.75D, and is focused as it passes through the curved surface of the waveguide layer 810, as discussed in connection with FIG. 5, and is defocused as it passes through lens L1, which has a refractive power of −0.75D. Thus, the combination of lens L2, waveguide layer 810, and lens L1 allows world light to be seen by the user without any refractive power.

[0128] Referring to FIG. 8B , when the waveguide layer 810 is flipped to the second configuration shown in FIG. 8B , the waveguide layer 810 has a refractive power of −0.75D. In this second configuration, virtual content is defocused as it projects from the waveguide layer 810 and passes through L1, which has a refractive power of −0.75D. Thus, the combination of the waveguide layer and L1 in the second configuration results in a refractive power of −1.5D (i.e., the near plane). Thus, virtual content is presented at infinity in the first configuration and at 0.67 m in the second configuration. As discussed above, world light is presented to the user with no refractive power applied to the world light because, in the second configuration, as in the first configuration, the world light passes through the curved surface of the waveguide layer 810 with little or no disturbance, as discussed in connection with FIG. 5 .

[0129] 8A and 8B can provide operation in a bi-modal or bistable manner, meaning that varying the pressure value in pneumatic chamber 802 causes the waveguide layer to switch between two discrete states, thereby rendering projected virtual content at two different discrete depths from the user's line of sight. For example, as illustrated in FIGS. 8A and 8B, waveguide layer 810 can operate in a curved mode, then be inverted, and operate in the inverted curved mode. As discussed in connection with FIG. 6C, the shape of the waveguide layer can be circular, although this is not required by embodiments of the present invention.

[0130] In some embodiments, the waveguide layer can be positioned on, mounted to, or otherwise affixed to a layer formed using an electroactive polymer (EAP). The EAP can be bonded to the waveguide layer by adhesive or molded as an element of the waveguide layer during a casting process. Some examples of EAPs include, but are not limited to, dielectric elastomers and ionic polymers, such as Nafion, Flemion, polyvinyl alcohol (PVA) gel, acrylamide and vinyl derivative copolymers, copoly(Aam / vdMG) gel, ProDOT-(CH3), polyacrylamide gel, polypyrrole (PPy), and polyaniline (PANI). The EAP can have an original, unextended state with a certain width. The EAP can then expand when a voltage is applied to the EAP. Varying the applied voltage can allow the EAP to expand to different lengths. A higher applied voltage can result in the EAP expanding to a longer distance than the expansion distance associated with a lower applied voltage. As explained more fully below, applying a variable voltage to an EAP affixed to the waveguide layer can cause the waveguide to bend to a predetermined curvature or surface contour based on the applied voltage.

[0131] FIG. 9A illustrates a cross-sectional view of a first configuration of an electroactive polymer (EAP) system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments. As illustrated in FIG. 9A, the periphery of the waveguide layer 902 is positioned against, bonded to, or otherwise affixed to one side of an EAP film 906, which may be a pre-stretched EAP film. The opposite side of the EAP film 906 is affixed to a fixed frame structure 904. In the embodiment illustrated in FIG. 9A, the waveguide layer 902 has a curved or generally planar surface contour, thereby being characterized by a large radius of curvature (e.g., 2.0 meters), which is typically suitable for providing acceptable accommodation. Generally, a certain curvature is desirable in this configuration to achieve predictable bending of the waveguide layer, as described more fully below.

[0132] FIG. 9B illustrates a cross-sectional view of a second configuration of the EAP system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 9A. In the second configuration illustrated in FIG. 9B, a voltage source 908 is electrically coupled to the EAP film 906. A voltage can be applied to the EAP film 906 by the voltage source 908. Applying a voltage across the EAP film 906 causes the EAP film 906 to expand linearly within the volume inward toward the center of the waveguide layer 902. Thus, expanding the EAP film 906 inward causes the waveguide layer 902, which is bonded to the EAP film 906, to compress uniformly and radially in all directions, increasing the curvature of the waveguide layer 902 and resulting in a reduced radius of curvature (e.g., 0.3 m in this example). When the applied voltage from voltage source 908 is removed, EAP film 906 contracts back to its original state, thereby causing waveguide layer 902 to return to its original, uncompressed state as a result of the natural tensile strength of waveguide layer 902.

[0133] In some exemplary embodiments, the applied voltage provided by the voltage source 908 can be reduced or modified from a maximum applied voltage. Varying the voltage applied to the EAP film 906 can cause the waveguide layer 902 to compress into multiple configurations corresponding to varying radius of curvature values, such that each voltage level applied to the EAP film 906 corresponds to a different resulting radius of curvature value exhibited by the waveguide layer 902. Varying the voltage applied to the EAP film 906 can thus enable continuous modulation of the curvature of the waveguide layer 902. As a result, the waveguide layer 902 can be continuously modified through structural manipulation of the EAP film 906 to project virtual content to a user at multiple depth planes. For example, the natural state of the waveguide layer 902 can have a radius of curvature value appropriate for projecting virtual content emanating at a distance of 2 meters from the eyepiece. A small voltage value can then be applied to the EAP film 906 using the voltage source 908, causing the waveguide layer 902 to compress slightly. This slight compression, which reduces the radius of curvature of the waveguide layer 902, may correspond to projected virtual content occurring at a distance closer to the user than 2 meters (e.g., 1 meter). A higher voltage can then be applied to the EAP film 906 using voltage source 908, causing the waveguide layer 902 to compress by an additional amount. Further compressing the waveguide layer 902 further reduces the radius of curvature value, which can be used to render virtual content emanating at a distance closer to the user than 1 meter (e.g., 0.5 meters). Sequentially applying no voltage, a small voltage, and a higher voltage to the EAP film, for example at a 90 Hz refresh rate, allows the display of virtual content at three depth planes, corresponding to the three radii of curvature achieved using the expansion of the EAP film and the resulting compression of the waveguide layer.

[0134] Generally, the EAP film extends linearly in length with applied voltage. Similarly, the decrease in curvature of the waveguide layer can also be a linear function of applied voltage. For many of the operating conditions described herein, this linear behavior is applicable. However, this is not required by the present invention. In some embodiments, compression of the waveguide layer will initially result in a linear decrease in radius of curvature with applied voltage, but then become nonlinear as the waveguide layer further compresses. Thus, embodiments of the present invention can map the radius of curvature to applied voltage and account for any nonlinearity in the response of the waveguide layer. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0135] In an alternative embodiment, the waveguide layer is fabricated with a radius of curvature of 1 m. Once attached to the EAP film, the waveguide layer is stretched to partially flatten the waveguide layer so that the radius of curvature is 2 m. During operation, the first meter of variation in the radius of curvature is accommodated by a restoring force built into the system. To reduce the radius of curvature to a value less than 1 m, an applied voltage is utilized to extend the length of the EAP film.

[0136] FIG. 9C illustrates a plan view of the components of an EAP system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIGS. 9A and 9B. As illustrated in FIG. 9C, the waveguide layer 902 is attached at peripheral locations to an EAP film 906 that surrounds the waveguide layer 902 and is attached to a fixed frame structure 904. The periphery of the waveguide layer 902 is bonded to an annular-shaped EAP film 906 that is circular in shape and bonded to the fixed frame structure 904 in FIG. 9C, although embodiments of the present invention are not limited to this implementation. Although not illustrated in FIG. 9C, the EAP film 906 is electrically coupled to a voltage source. The voltage source applies one or more voltage values ​​to the EAP film 906, causing the EAP film 906 to expand inward from the fixed frame structure 904, thereby compressing the waveguide layer 902 inward toward the center of the system and continuously changing the radius of curvature of the waveguide layer 902, as illustrated in FIG. 9C.

[0137] 9D illustrates a plan view of components of an EAP system for dynamically adjusting the surface contour of an alternative waveguide layer, according to some embodiments. In the embodiment illustrated in FIG. 9D, the waveguide layer is implemented as a teardrop-shaped waveguide layer 908 bonded to a corresponding teardrop-shaped EAP film 912, which is affixed to a teardrop-shaped fixed frame structure 910. In a manner similar to that discussed in connection with FIG. 9C, actuation of the EAP film results in compression of the waveguide layer and modification of the surface contour of the waveguide layer.

[0138] FIG. 9E illustrates a plan view of components of an alternative EAP system for dynamically adjusting the surface contour of an alternative waveguide layer, according to some embodiments. FIG. 9E illustrates a teardrop-shaped waveguide 914 whose periphery is bonded to a circular-shaped EAP film 918, which is affixed to a circular-shaped fixed frame structure 916. A voltage can be applied to the EAP film 918 in FIG. 9E , similar to that described with respect to FIG. 9C , causing the EAP film to expand linearly and compress the waveguide layer inward. Varying the width of the EAP film as a function of radial position allows for different expansion lengths and resulting forces, thereby allowing different compression values ​​to be applied to the waveguide layer as a function of radial position. Thus, a more uniform spherical curvature can be provided by embodiments of the present invention through selection of the EAP film width. As will be apparent to one skilled in the art, various shapes utilized for the EAP film and / or fixed frame structure can affect how the EAP film expands and imparts different forces across varying portions of the waveguide layer.

[0139] In some embodiments, portions of the EAP film can be segmented so that a variable mechanical force can be applied to different portions along the periphery of the waveguide layer. For example, an annular-shaped or teardrop-shaped EAP film can be bifurcated and separated into quadrants, or any number of sections. Each section can be connected to one or more voltage sources, allowing for variable levels of voltage to be applied to different sections of the EAP film in a given instance. Various sections of the EAP film can be actuated simultaneously, alternately, or in combination so that some portions of the EAP film can expand inward toward the waveguide more or less than other portions of the EAP film. This can reduce focusing errors and allow for EAP systems with component geometries that vary relative to the waveguide geometry. Varying the resistivity of portions of the EAP film can produce a similar effect to varying the compressive force applied to the periphery of the waveguide when a single voltage value is applied to the EAP film.

[0140] FIG. 10A illustrates a cross-sectional view of a first configuration of a mechanical system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments. As illustrated in FIGS. 10A-10B, radial stretching is used to dynamically adjust the surface contour, e.g., the radius of curvature, of the waveguide layer. Referring to FIG. 10A, the periphery of the waveguide layer 1002 can be positioned against, bonded to, or otherwise affixed to a viscoelastic polymer layer 1006. The viscoelastic polymer layer 1006 can absorb energy, relieve stress, and be repeatedly stretched and relaxed for continuous operation. Examples of such viscoelastic polymer films include, but are not limited to, acrylic foam, PDMS, PVC, polyolefin, and polyethylene. The viscoelastic polymer layer 1006 can be bonded to the waveguide layer 1002, which can be a polymer waveguide layer, by adhesive, or can be molded as an element of the waveguide layer 1002 directly during a molding process. A viscoelastic polymer layer 1006 may be affixed to support posts 1004 / 1009 and 1005 / 1007, which are mechanically coupled to the slotted disc, as described more fully below in connection with FIG. 10C.

[0141] The waveguide layer 1002 can be fabricated in such a manner that it is characterized by an initial curvature in the surface profile, for example, having a predetermined radius of curvature, for example, 0.3 m.

[0142] FIG. 10B illustrates a cross-sectional view of a second configuration of the mechanical system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 10A. In FIG. 10B, a mechanical force is applied to support posts 1004 / 1009 and 1005 / 1007, pulling viscoelastic polymer layer 1006 radially outward, which stretches waveguide layer 1002 radially outward and reduces the radius of curvature of waveguide layer 1002, for example, to 2 m. By utilizing the embodiment illustrated in FIGS. 10A-10C, waveguide layer 1002 can be continuously stretched to a planar or near-planar surface contour, thereby achieving multiple configurations with a range of radius of curvature values. In some implementations, the periphery of waveguide layer 1002 can be formed with a flat surface contour to facilitate bonding to support posts 1004 / 1009 and 1005 / 1007.

[0143] FIG. 10C illustrates a plan view of components of a mechanical system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIGS. 10A and 10B. As illustrated in FIG. 10C, radial expansion of the viscoelastic polymer layer is implemented using a pair of disks, including a top disk 1010 and a corresponding bottom disk (not shown). These disks have slots through which support posts 1004 / 1009 and 1005 / 1007, respectively, pass. The top disk 1010 and the bottom disk (not shown) can rotate relative to one another about the center of the waveguide layer 1002. For example, the top disk 1010 can rotate clockwise and the bottom disk can simultaneously rotate counterclockwise, causing the support posts to shift from a first configuration illustrated in FIG. 10A to a second, fully expanded configuration illustrated in FIG. 10B. For example, as the top disk 1010 and the bottom disk rotate relative to one another, support post 1005 can move along slot 1012, and support post 1007 can move along slot 1014. This mechanism is sometimes referred to as a Longworth chuck. Mechanical forces applied to the support posts by the rotating disks can cause the support posts to move along the slots, which can increase the distance between the support posts and the center of the waveguide layer 1002. The increase in the distance from the center of the system to the support posts can stretch the viscoelastic polymer layer 1006 radially outward, which in turn can increase the radius of curvature of the waveguide layer 1002.

[0144] The mechanical (i.e., radial extensor) system illustrated in Figures 10A-10C can include any number of support struts and corresponding slots, depending on the application. For example, if the support struts are directly connected to the waveguide layer, more support struts (e.g., greater than or equal to eight) may be utilized to achieve uniform radial stretching, which can result in a spherical curvature of the waveguide layer because the waveguide layer may not be as flexible as the viscoelastic polymer layer. If the mechanical (i.e., radial extensor) system is connected to the polymer waveguide through another layer of viscoelastic "memory" polymer, the number of support struts can be reduced because the viscoelastic film will redistribute the stress. Nevertheless, in some embodiments, increasing the number of support struts can produce a more uniform stress distribution on the polymer waveguide.

[0145] In some implementations, the extension force applied by the rotational movement of the top disk 1010 and the bottom disk along with the corresponding support posts can be applied at different force values ​​in a continuous motion to produce multiple waveguide configurations. Thus, the top disk 1010 and the bottom disk can be rotated to any configuration between the first configuration illustrated in FIG. 10A (i.e., the waveguide layer 1002 is in a resting state) and the second configuration illustrated in FIG. 10B (i.e., the waveguide is extended to its maximum extent as the support posts reach the ends of the slots, positioning the support posts at the furthest distance from the center of the system). Varying the position of the support posts along the slots, which results in different extension distances for the viscoelastic polymer layer, can extend the waveguide layer to multiple states corresponding to variable surface contours or radius of curvature values. As a result, the surface contour of the waveguide layer 1002 is continuously altered, allowing virtual content to be projected to the user in multiple depth planes. Releasing the force utilized to rotate the top disk 1010 and the bottom disk can allow the viscoelastic polymer layer 1006 to contract back to its original configuration through its tensile strength, which can return the waveguide layer 1002 to the first configuration illustrated in FIG. 10A. In embodiments in which the waveguide layer is directly connected to the support posts without the use of a viscoelastic polymer layer, after releasing the extensional force generated by the rotating disk mechanism, the tensile force of the waveguide layer can cause the waveguide layer to contract back to its original state and pull the support posts back to the first, unextended configuration. As all of the support posts gradually move inward, both the viscoelastic polymer layer 1006 and the waveguide layer 1002 can be gradually restored to their original configurations.

[0146] In some examples, the slots in the top and bottom disks can be of different lengths and shapes, such that the slots toward one side of the radial extensor system are gradually longer than the slots toward the opposite side. Varying slot sizes can be used in applications where the waveguide and / or viscoelastic polymer layer are not circular in design, allowing some portions of the waveguide and viscoelastic polymer layer to be stretched more than others, thereby achieving a uniform stress distribution. Note that alternative embodiments can also be implemented in which a first configuration is characterized by a larger radius of curvature and a second configuration is characterized by a smaller radius of curvature, and a mechanical system compresses the waveguide layer during the continuous transition from the first configuration to the second configuration. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0147] FIG. 11A illustrates a cross-sectional view of a first configuration of an alternative mechanical system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments. As will be apparent to one skilled in the art, the system utilizing the stretching of a viscoelastic polymer film illustrated in FIGS. 11A-11E shares common elements with the system illustrated in FIGS. 10A-10C, and the description provided in connection with FIGS. 10A-10C is applicable to FIGS. 11A-11E, as appropriate. As illustrated in FIG. 11A, the periphery of the waveguide layer 1102 can be positioned against, bonded to, or otherwise affixed to a viscoelastic polymer layer 1104. The viscoelastic polymer layer 1104 can be attached to an actuator 1108, which can be shaped as an annular or ring-shaped element.

[0148] FIG. 11B illustrates a cross-sectional view of a second configuration of an alternative mechanical system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 11A. A fixture frame 1106, which may also have an annular or ring shape with a smaller diameter than the actuator 1108, can be positioned below the waveguide layer 1102. The waveguide layer 1102 can be fabricated in a manner characterized by an initial curvature in the surface contour, for example, having a predetermined radius of curvature, e.g., 0.3 m. Referring to FIG. 11B, as the actuator 1108 moves coaxially relative to the fixture frame 1106, the viscoelastic polymer layer 1104 stretches uniformly, for example, around and beyond the edges of the fixture frame 1106, thereby stretching the waveguide layer 1102 radially outward into a planar, near-planar, or less curved configuration. Thus, by pulling the actuator 1108 downward, continuous variation in the surface contour of the waveguide layer 1102 can be achieved. To reduce the radius of curvature, upward movement of the actuator 1108 allows the tensile strength of the viscoelastic polymer layer 1104 and the waveguide layer 1102 to be restored to the first configuration illustrated in FIG. 11A. Exemplary types of actuators that may be used in these and similar embodiments include, but are not limited to, voice coil actuators, piezoelectric actuators, air cylinders, and the like. Embodiments of the present invention thus enable compact designs in which vertical movement of the actuator results in horizontal extension of the waveguide layer.

[0149] 11A and 11B. As shown in FIG. 11C, the waveguide layer 1102 is attached at peripheral locations to an annular-shaped viscoelastic polymer layer 1104, which surrounds the waveguide layer 1102 and is attached to an actuator 1108. The periphery of the waveguide layer 1102 is bonded to the annular-shaped viscoelastic polymer layer 1104, which in FIG. 11C is bonded to the actuator 1108. Although embodiments of the present invention are not limited to this implementation, as described above, the actuator 1108 moves in a direction perpendicular to the fixed frame 1106, stretching the viscoelastic polymer layer 1104 and the waveguide layer 1102 laterally, thereby continuously changing the radius of curvature of the waveguide layer 1102, as shown.

[0150] 11D illustrates a plan view of components of another alternative mechanical system for dynamically adjusting the surface contour of an alternative waveguide layer, according to some embodiments. In the embodiment illustrated in FIG. 11D, the waveguide layer is implemented as a teardrop-shaped waveguide layer 1110 bonded to a corresponding teardrop-shaped viscoelastic polymer layer 1112, which is affixed to a teardrop-shaped actuator 1114. In a manner similar to that discussed in connection with FIG. 11C, actuation of the actuator results in compression of the waveguide layer and modification of the surface contour of the waveguide layer.

[0151] FIG. 11E illustrates a plan view of components of yet another alternative mechanical system for dynamically adjusting the surface contour of an alternative waveguide layer, according to some embodiments. FIG. 11E illustrates a teardrop-shaped waveguide 1116 whose periphery is bonded to a circular-shaped viscoelastic polymer layer 1118, which is affixed to a circular-shaped actuator 1108. As illustrated in FIG. 11B, actuation of the actuator 1108 linearly expands the viscoelastic polymer layer, stretching the waveguide layer outward. Varying the width of the viscoelastic polymer layer as a function of radial position allows for different expansion lengths and resulting forces, thereby allowing different expansion values ​​to be applied to the waveguide layer as a function of radial position. Thus, a more uniform spherical curvature can be provided by embodiments of the present invention through selection of the viscoelastic polymer layer width. As will be apparent to one skilled in the art, various geometries utilized for the viscoelastic polymer layer and / or the fixed frame / actuator structure can affect how the viscoelastic polymer layer expands and imparts different forces across varying portions of the waveguide layer.

[0152] In some embodiments, portions of the viscoelastic polymer layer can be segmented so that variable mechanical forces can be applied to different portions along the periphery of the waveguide layer. For example, a ring-shaped or teardrop-shaped viscoelastic polymer layer can be branched and separated into quadrants, or any number of sections. Each section can be connected to one or more actuators to apply variable levels of tension to different sections of the viscoelastic polymer layer in a given instance. Various sections of the viscoelastic polymer can be actuated simultaneously, alternately, or in combination so that portions of the viscoelastic polymer layer can expand outward more or less away from the waveguide layer than other portions of the viscoelastic polymer layer. This reduces focusing errors and allows for viscoelastic polymer layer systems with varying component geometries relative to the geometry of the waveguide layer.

[0153] The waveguide layer can be continuously stretched to a planar or near-planar position to achieve multiple states with various radius of curvature values. In some implementations, the stretching force applied by movement of the actuator 1108 can be applied at different force values ​​in a continuous motion to produce multiple waveguide configurations. Thus, the actuator 1108 can be positioned anywhere between the first configuration illustrated in FIG. 11A (i.e., the waveguide layer 1102 is at rest) and the second configuration illustrated in FIG. 11B (i.e., the waveguide is stretched to a maximum value as the actuator reaches its final position). Varying the position of the actuator along its range of motion, resulting in different stretch distances for the viscoelastic polymer layer, can stretch the waveguide layer to multiple states corresponding to variable surface contours or radius of curvature values. As a result, the surface contour of the waveguide layer 1102 is continuously altered, allowing virtual content to be projected to the user in multiple depth planes. Releasing the force utilized to pull the actuator 1108 downward can allow the viscoelastic polymer layer 1104, through its tensile strength, to contract back to its original configuration, which can return the waveguide layer 1102 to the first configuration illustrated in FIG. 11A.

[0154] FIG. 12A illustrates a cross-sectional view of a lateral actuation system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments. As illustrated in FIG. 12A, the periphery of the waveguide layer 1202 is positioned against, bonded to, or otherwise affixed to an inner portion of a ring actuator 1204. In the embodiment illustrated in FIG. 12A, the waveguide layer 1202 has a curved or generally planar surface contour, thereby being characterized by a large radius of curvature (e.g., 2.0 meters), which is typically suitable for providing acceptable accommodation. Generally, a certain curvature is desirable in this configuration to achieve predictable bending of the waveguide layer, as described more fully below.

[0155] An outer portion of the ring actuator 1024 is affixed to a fixed frame structure 1208. The ring actuator 1204 can be repeatedly expanded or contracted radially for continuous modulation of the surface contour of the waveguide layer 1202. Examples of ring actuators include, but are not limited to, piezoelectric actuators, electrothermal actuators, magnetostrictive actuators, and the like. The voltage source utilized to drive the ring actuator is not shown for purposes of clarity. The waveguide layer and ring actuator can be fabricated separately and then bonded together, or fabricated as a single unit, depending on the particular fabrication process utilized.

[0156] Referring to FIG. 12A , an outer portion of the ring actuator 1204 is affixed or pinned to a fixed frame structure 1208 via a rotation mechanism 1206 (e.g., a hinge), which acts as a support collar. Thus, the ring actuator 1204 can rotate about the rotation mechanism 1206, perpendicular to the radial lateral expansion and contraction of the ring actuator 1204. The ring actuator 1204 can expand laterally, and the boundary conditions of the ring actuator can flatten the waveguide layer 1202 into a planar or nearly planar configuration. Conversely, the ring actuator 1204 can contract laterally, and the boundary conditions of the ring actuator can cause the waveguide layer 1202 to curve more substantially than when the ring actuator is less contracted. As illustrated in FIG. 12A , dashed lines represent possible configurations of the waveguide layer 1202 when the ring actuator 1204 is in various states of expansion or contraction.

[0157] FIG. 12B illustrates a plan view of the components of a lateral actuation system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 12A. In the embodiment illustrated in FIG. 12B, a circular waveguide layer 1202 is positioned relative to and joined to a ring actuator 1204, which is annular in shape. The ring actuator 1204 can expand toward the center of the waveguide layer 1202, causing the waveguide layer 1202 to decrease its radius of curvature, and can contract outward from the center of the waveguide layer 1202, causing the waveguide layer 1202 to flatten and increase its radius of curvature. Thus, the waveguide layer 1202 can be continuously flattened to a planar or near-planar position or induced to bend at various radius of curvature values ​​by lateral or radial movement of the ring actuator 1204, thereby achieving multiple waveguide configurations in continuous operation. Varying the contraction / expansion of the ring actuator along its range of motion can stretch the waveguide layer into multiple states corresponding to variable surface contours or radius of curvature values. As a result, the surface contour of the waveguide layer 1202 can be continuously modified, allowing virtual content to be projected to the user at multiple depth planes.

[0158] The ring actuator 1204 can be a continuous ring or loop that completely surrounds the entire periphery of the waveguide layer 1202. In some embodiments, a portion of the ring actuator can be divided into multiple segmented sections so that a variable mechanical force can be applied to different portions along the periphery of the waveguide layer. In some embodiments, different materials or actuator types may be used for each segmented section, in any combination, in a given application. Various sections of the ring actuator can be actuated simultaneously, alternately, or in combination so that some portions of the ring actuator can expand outwardly away from the waveguide layer more or less than other portions of the ring actuator. This reduces focusing errors and allows for ring actuator systems with varying component geometries relative to the geometry of the waveguide layer.

[0159] FIG. 13A illustrates a cross-sectional view of a first configuration of a multiple ring system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments. As illustrated in FIG. 13A , the periphery of a planar or substantially planar waveguide layer 1302 is positioned between an actuator 1304 and a fixed frame 1306. The actuator 1304 and the fixed frame 1306 are joined by a mechanical connection, as described more fully below. The multiple ring system illustrated in FIGS. 13A and 13B may also be referred to as a ring-on-ring system. The inner periphery of the waveguide layer 1302 can be positioned against a surface of an extended portion 1305 of the actuator 1304, and the outer periphery of the waveguide layer 1302 can be positioned against a surface of the fixed frame 1306, for example, a bottom surface 1307 of the fixed frame 1306. 13A, the waveguide layer 1302 has a planar or nearly planar surface profile, which may be characterized by a large radius of curvature (e.g., 2.0 meters), which is typically suitable for providing acceptable accommodation. The actuator 1304 may be coupled to the fixed frame 1306 through a positioning mechanism that may be used to position the fixed frame 1306 at an adjustable distance from the actuator 1304 in response to actuation of the actuator 1304.

[0160] 13B illustrates a cross-sectional view of a second configuration of the multiple ring system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 13A. In the second configuration illustrated in FIG. 13B, the actuator 1304 is actuated to reduce the distance between the actuator 1304 and the fixed frame 1306 in response to movement of the actuator 1304 toward the fixed frame 1306. As the distance between the fixed frame 1306 and the actuator 1304 is reduced, the fixed frame 1306 applies a mechanical force to the outer periphery of the waveguide layer 1302, while the surface of the extension portion 1305 of the actuator 1304 applies a mechanical force in an opposing direction to the inner periphery of the waveguide layer 1302. This angles the periphery of the waveguide layer 1302 at an angle defined as a function of one or more of the distance between the actuator 1304 and the fixed frame 1306, the distance between the mechanical forces applied at the outer and inner peripheries of the waveguide layer 1302, and the length of the extension portion 1305 of the actuator 1304. As the actuator 1304 is positioned closer to the fixed frame 1306, the waveguide layer 1302 is caused to bend at an increased angle, resulting in a decreased radius of curvature, as illustrated in FIG. 13B. Conversely, the actuator 1304 can be actuated to increase the distance between the actuator 1304 and the fixed frame 1306, thereby transitioning the waveguide layer 1302 to any configuration between the first configuration illustrated in FIG. 13A and the second configuration illustrated in FIG. 13B. In response to a gradually increasing distance between the actuator 1304 and the fixed frame 1306, the waveguide layer 1302 can gradually return to its original planar or near-planar state, as illustrated in Figure 13A, by releasing its stored strain energy. In some exemplary embodiments, the waveguide can be pre-curved, and the actuator and fixed frame can apply mechanical forces to the outer and inner peripheries of the waveguide, similar to those described, to reduce the angle at which the waveguide is bent and cause the waveguide to become planar or more substantially planar.

[0161] As an example, the extension portion 1305 of the actuator 1304, sometimes referred to as a lever arm, may be 0.8 mm long and extend outward from the top surface 1303 of the actuator 1304 to contact the inner periphery of the waveguide layer 1302. An actuation stroke of approximately 65 μm and an actuation force of 22 N of the positioning mechanism may be used to flatten a 330 μm polymer waveguide from a state characterized by a 0.3 m radius of curvature to a state characterized by a 2.0 m radius of curvature. The actuator 1304 may be any type of suitable actuator, including, but not limited to, an air cylinder, a piezoelectric actuator, a linear electromechanical actuator, a magnetic actuator, or the like.

[0162] In some exemplary embodiments, the forces applied to the outer and inner peripheries of the waveguide layer 1302 by the actuators 1304 and fixed frame 1306 can be reduced or modified from a maximum applied force that induces a minimum radius of curvature. Varying the distance between the actuators 1304 and the fixed frame 1306 can bend the waveguide layer 1302 into multiple configurations corresponding to variable radius of curvature values, such that each actuator / fixed frame distance corresponds to a different resulting radius of curvature value exhibited by the waveguide layer 1302. Varying the actuator / fixed frame distance, which affects the forces applied to the inner and outer peripheries of the waveguide layer 1302, can therefore enable continuous modulation of the curvature of the waveguide layer 1302. As a result, the waveguide layer 1302 can be continuously modified through manipulation of the actuators 1304 to project virtual content to a user in multiple depth planes. For example, the natural state of the waveguide layer 1302 may have a radius of curvature value appropriate for projecting virtual content emanating at a distance of 2 m from the eyepiece. The distance between the actuator 1304 and the fixed frame 1306 may be reduced to increase the bending moment at the periphery of the waveguide layer 1302, thereby increasing the curvature of the waveguide layer 1302. The increased bending moment, which reduces the radius of curvature of the waveguide layer 1302, may correspond to projected virtual content occurring at a distance closer to the user than 2 m (e.g., 1 m). The actuator / fixed frame distance may be further reduced to further bend the waveguide layer 1302. Further bending of the waveguide layer 1302 further reduces the radius of curvature value, which may be used to render virtual content emanating at a distance closer to the user than 1 m (e.g., 0.3 m). Releasing the actuator and restoring the distance between the actuator 1304 and the stationary frame 1306 back to the first rest configuration restores the stress energy in the waveguide 1302 to its rest configuration.For example, at a 90 Hz refresh rate, successively alternating between a first, stationary configuration, a second configuration in which the waveguide is bent, and a third configuration in which the waveguide is bent even more allows for the display of virtual content in three depth planes, corresponding to three radii of curvature achieved using compression of the actuators relative to a fixed frame to angle the waveguide layer. Of course, these values ​​are merely exemplary, and other depth planes can be achieved using embodiments of the present invention.

[0163] FIG. 13C illustrates a plan view of components of a multiple ring system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIGS. 13A and 13B. As illustrated in FIG. 13C, a fixture frame 1306 is positioned around the waveguide layer 1302 and contacts an outer portion of the periphery of the waveguide layer 1302. While a portion of the actuator 1304 is visible surrounding the periphery of the fixture frame 1306 in FIG. 13C, this is not required by the present invention; a laterally compact design in which the peripheries of the actuator 1304 and fixture frame 1306 are vertically aligned can also be utilized. The periphery of the waveguide layer 1302 contacts an annular-shaped fixture frame 1306, which is circular in shape and coupled to the annular-shaped actuator 1304 in FIG. 13C, although embodiments of the present invention are not limited to this implementation. Although not illustrated in FIG. 13C, the fixture frame 1306 is coupled to the actuator 1304 by a positioning mechanism. The annular shaped actuator 1304 and stationary frame 1306 may be ring shaped and proportional to one another such that at least a portion of the actuator 1304 overlaps a portion of the stationary frame 1306 .

[0164] 13D illustrates a plan view of components of a multiple ring system for dynamically adjusting the surface contour of an alternative waveguide layer, according to some embodiments. As illustrated in FIG. 13D, the eyepiece can include a waveguide layer 1308 characterized by a teardrop shape in plan view. Although a teardrop shape is illustrated in FIG. 13D, embodiments of the present invention are not limited to this particular shape, and other shapes are within the scope of the present invention.

[0165] The fixed portion 1312 of the waveguide layer can be affixed to or otherwise hold in place a portion of the waveguide layer 1308 adjacent to the fixed portion 1312. As an example, the ICG 1314 can be positioned near the center of the fixed portion 1312. To prevent modification of the surface contour of the waveguide layer near the ICG 1314, the fixed portion 1312 is utilized to maintain the surface contour of this portion of the waveguide layer within a fixed surface contour. In other embodiments, the fixed portion can loosely hold the waveguide layer 1308 in place, for example, by utilizing one or more shims between the waveguide layers to allow the portion of the waveguide layer 1308 adjacent the fixed portion 1312 to bend or remain in its original condition without obstruction by the fixed portion 1312. A C-shaped actuator 1310 can then be coupled to the fixed portion 1312 and completely surround the waveguide layer 1308 along the periphery of the waveguide layer. A C-shaped actuator 1310, as described in the previous embodiment, can adjust the surface contour of most of the waveguide layer 1308 by pressing the periphery of the waveguide layer 1308 against a complementary C-shaped fixed frame (not shown in this plan view). Utilizing a C-shaped actuator as illustrated in Figure 13D allows a sufficient portion of the periphery of the waveguide layer to be oriented at a predetermined angle such that the viewing area of ​​the eyepiece is characterized by a surface contour or curvature that is uniform across the width / length of the viewing area, while maintaining a portion of the waveguide layer at a fixed surface contour, independent of system actuation.

[0166] In some exemplary embodiments, portions of the fixture frame / actuator mechanism can be decoupled so that variable mechanical forces can be applied to different portions along the periphery of the waveguide layer. For example, a ring-shaped actuator and fixture frame mechanism can be bifurcated and separated into quadrants, or any number of sections with the same or different dimensions, which define the angle at which the periphery of the waveguide is bent. Various sections of the actuator and fixture frame mechanism can be activated simultaneously, alternately, or in combination so that some portions of the periphery of the waveguide can be bent at different angles than other portions of the periphery of the waveguide. This can enable movement or positioning of the light source across a range at different depths from the user's line of sight.

[0167] FIG. 14A illustrates a cross-sectional view of a first configuration of a roller system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments. In some embodiments, the waveguide layer can be positioned between multiple sets of paired roller mechanisms that can operate to flatten or curve the waveguide layer and effect adjustment to the radius of curvature of the waveguide layer. In FIG. 14A, a waveguide layer 1402, which can be a planar or relatively planar polymeric waveguide layer, is positioned between several paired cylindrical roll mechanisms, namely, between a bottom roll mechanism 1406 and a paired top roll mechanism 1404, and between a bottom roll mechanism 1410 and a paired top roll mechanism 1408. In FIG. 14A, the top roll mechanisms 1404 / 1408 and the bottom roll mechanisms 1406 / 1410 are positioned in an unactuated configuration, thereby allowing the waveguide layer 1402 to assume a first surface contour, for example, a planar surface contour or a surface contour with a small intrinsic curvature. The periphery of waveguide layer 1402 can be positioned, sandwiched, or otherwise aligned between top roll mechanism 1404 and bottom roll mechanism 1406 and between top roll mechanism 1408 and bottom roll mechanism 1410. Additional description of the roll systems is provided in connection with Figure 14C.

[0168] FIG. 14B illustrates a cross-sectional view of a second configuration of a roller system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIG. 14A. As illustrated in FIG. 14B, the top roll mechanisms 1404 / 1408 and the bottom roll mechanisms 1406 / 1410 can be actuated to apply lateral mechanical forces to the periphery of the waveguide layer 1402. The top roll mechanism 1404 and the bottom roll mechanism 1406 can be actuated to reverse direction relative to one another such that a portion of the periphery of the waveguide layer 1402 is passed between or pulled through the top roll mechanism 1404 and the bottom roll mechanism 1406 in response to rotation of the top roll mechanism 1404 and the bottom roll mechanism 1406. The top roll mechanism 1408 and the bottom roll mechanism 1410 can be actuated to operate in a similar manner to the top roll mechanism 1404 and the bottom roll mechanism 1406. The top roll mechanisms 1404 / 1408 and bottom roll mechanisms 1406 / 1410 can grip or otherwise move laterally around the periphery of the waveguide 1402 by frictional forces and / or "teeth" or grooves that allow the roll mechanisms to grip the waveguide 1402. In some exemplary embodiments, the periphery of the waveguide 1402 can have "teeth" or grooves that are compatible with corresponding "teeth" or grooves located on the roll mechanisms.

[0169] 14B , actuation of the mated top roll mechanisms 1404 / 1408 and bottom roll mechanisms 1406 / 1410 causes the peripheral length of the waveguide layer 1402 to roll inward toward the center of the waveguide 1402, which, in response to a mechanical force, bends and deflects the peripheral edge of the waveguide 1402 radially inward. Thus, adjusting the waveguide layer 1402, for example, from a planar surface contour to a curved surface contour, by applying a lateral mechanical force to the peripheral edge of the waveguide layer can adjust the radius of curvature of the waveguide layer. The bending of the waveguide 1402 and the resulting change in the value of the radius of curvature are functions of the peripheral length of the waveguide 1402 that is displaced. Deactivation of the top roll mechanisms 1404 / 1408 and bottom roll mechanisms 1406 / 1410 removes the mechanical force at the periphery of the waveguide layer, which returns to its original surface profile, eg, planar or nearly planar as illustrated in FIG. 14A.

[0170] According to embodiments of the present invention, the application of a bending moment caused by the roll mechanism at the periphery of the waveguide layer uniformly modulates the surface contour or curvature of the waveguide layer across the width / length of the waveguide layer and the associated eyepiece aperture area. In some exemplary embodiments, portions of the roll mechanism can be actuated to flatten or curve the waveguide. For example, the top roll mechanism 1404 / 1408 can be actuated, while the bottom roll mechanism 1406 / 1410 can be enabled to move independently and freely, or be replaced with a pin or wheel without an actuation mechanism. Conversely, the bottom roll mechanism 1406 / 1410 can be actuated, while the top roll mechanism 1404 / 1408 can be enabled to move independently and freely, or be replaced with a pin or wheel without an actuation mechanism.

[0171] In some exemplary embodiments, the mechanical force applied to the periphery of the waveguide layer by the roll mechanism can be modulated between a fully curved configuration and a fully flat configuration. Varying the length of the periphery shifted by the roll mechanism can bend the waveguide layer into multiple configurations corresponding to variable radius of curvature values, with each amount of shifted length corresponding to a different resulting radius of curvature value exhibited by the waveguide layer. Varying the length of the periphery of the shifted waveguide can thus enable continuous modulation of the curvature of the waveguide layer. As a result, the waveguide layer can be continuously altered through operation of the paired roll mechanism to project virtual content to a user in multiple depth planes.

[0172] For example, the natural state of the waveguide layer 1402 may have a radius of curvature appropriate for projecting virtual content emanating at a distance of 2 m from the eyepiece. The periphery 1402 of the waveguide layer may be shifted radially inward toward the center of the waveguide layer 1402, increasing the curvature of the waveguide layer 1402. Increased bending of the waveguide layer, which reduces the radius of curvature of the waveguide layer 1402, may correspond to projected virtual content occurring at a distance closer to the user than 2 m (e.g., 1 m). The periphery of the waveguide layer 1402 may be shifted further radially inward, further bending the waveguide layer 1402. Further bending of the waveguide layer 1402 further reduces the radius of curvature, which may be used to render virtual content emanating at a distance closer to the user than 1 m (e.g., 0.3 m). Releasing the holding force of the roll mechanism to return to the first rest configuration returns the waveguide 1402 to its rest configuration. For example, at a 90 Hz refresh rate, sequentially alternating between a first, stationary configuration, a second configuration in which the waveguide is bent, and a third configuration in which the waveguide is bent even more allows for the display of virtual content in three depth planes, corresponding to three radii of curvature achieved using a roll mechanism to angle the waveguide layer. Of course, these values ​​are merely exemplary, and other depth planes can be achieved using embodiments of the present invention.

[0173] FIG. 14C illustrates a plan view of the components of a roller system for dynamically adjusting the surface contour of the waveguide layer illustrated in FIGS. 14A and 14B. As illustrated in FIG. 14C, the periphery of the waveguide layer 1402 contacts the top roll mechanisms 1404 / 1408 and the bottom roll mechanism (not shown). Additional top roll mechanisms are illustrated as being uniformly distributed along the periphery of the waveguide 1402. For example, eight top roll mechanisms are illustrated, mated with eight corresponding bottom roll mechanisms (not shown), and when actuated, induce a uniform stress on the waveguide 1402. Additional roll mechanisms uniformly distributed along the periphery of the waveguide 1402 can be used to more precisely induce a uniform stress on the waveguide 1402. In this embodiment, the annular positioning of the roll mechanisms conforms to the shape of the waveguide layer 1402. Although a circular shape is illustrated in Figure 14C, embodiments of the present invention are not limited to this particular shape and other shapes are within the scope of the present invention. In other embodiments, the roll mechanism can be positioned to conform to a waveguide layer having a shape other than a circular shape (e.g., a teardrop shape).

[0174] 14C , due to the decoupled nature of the paired roll mechanisms distributed along the periphery of the waveguide 1402, a variable mechanical force can be applied to different portions along the periphery of the waveguide layer 1402. The various paired roll mechanisms can be activated simultaneously, alternately, partially, or in combination such that some portions of the periphery of the waveguide 1402 can be deflected, some portions can remain undeflected, and other portions can be deflected more or less. This can enable movement or positioning of the light source across a range at different depths from the user's line of sight.

[0175] In some embodiments, the waveguide can be pre-curved and then bent to a less curved or flat state using the roll mechanisms shown. FIG. 14D illustrates a cross-sectional view of a third configuration of a roller system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments. FIG. 14E illustrates a cross-sectional view of a fourth configuration of a roller system for dynamically adjusting the surface contour of a waveguide layer, as shown in FIG. 14D. As shown in FIGS. 14D and 14E, the waveguide layer 1412 can be curved with a predetermined surface contour, e.g., a predetermined radius of curvature. The waveguide layer 1412 can then be positioned between the top roll mechanism 1414 and the bottom roll mechanism 1416 and between the top roll mechanism 1418 and the bottom roll mechanism 1420, in a manner similar to the embodiment described in connection with FIGS. 14A and 14B. In FIG. 14D, the top roll mechanism 1414 / 1418 and the bottom roll mechanism 1416 / 1420 are positioned in an unactuated configuration, thereby allowing the waveguide layer 1412 to assume a first surface contour, e.g., a curved surface contour associated with a display of a first depth plane.

[0176] As shown in FIG. 14E , actuation of the top roll mechanisms 1414 / 1418 and bottom roll mechanisms 1416 / 1420 applies a mechanical force to the periphery of the waveguide layer 1412, which flattens and deflects the periphery of the waveguide 1412 radially outward in response to the mechanical force. Thus, adjusting the waveguide layer 1412, for example, from a curved surface profile to a planar or nearly planar surface profile by applying a lateral mechanical force to the periphery of the waveguide layer, can adjust the radius of curvature of the waveguide layer. The bending of the waveguide 1412 and the resulting radius of curvature value are a function of the length of the periphery of the waveguide 1412 that is displaced. Deactuating the top roll mechanisms 1414 / 1418 and bottom roll mechanisms 1416 / 1420 removes the mechanical force at the periphery of the waveguide layer, which returns to its original surface profile, for example, the curvature illustrated in FIG. 14D .

[0177] Various methods can be utilized to form curved waveguide layers, i.e., waveguide layers defined by a predetermined curvature in the rest position. As explained below, these methods include the use of a curved mold, the use of a post-fabrication annealing step to curve an initially flat waveguide layer, or the like.

[0178] FIG. 15 illustrates a cross-sectional view of a pneumatic system for dynamically adjusting the surface contour of a waveguide layer, according to some embodiments. As illustrated in FIG. 15, the pneumatic system includes a waveguide layer 1502 (e.g., a pre-curved polymer waveguide layer with a 2.0 m radius of curvature), a continuous pressure regulator 1510, and lenses L1 and L2. The waveguide layer 1502 can be positioned against or otherwise bonded to a flat, transparent, and rigid base of lens L2, creating an airtight seal 1506 along the periphery of the waveguide layer 1502 such that a pressurized cavity 1504 is enclosed between the waveguide layer 1502 and lens L2. In some exemplary embodiments, the flat, transparent, and rigid base can be a component distinct from and bonded to lens L2. At a section of the airtight seal 1506, a continuous pressure regulator 1510 can be coupled to the airtight seal 1506 via an entry point 1508. The continuous pressure regulator 1510 can operate to transmit pressure changes within the pressurized cavity 1504 via a path 1512 coupled to the entry point 1508. As the continuous pressure regulator 1510 operates to transmit pressure changes within the pressurized cavity 1504, pressure changes are induced on the waveguide layer 1502. The pressure changes in the pressurized cavity 1504 can induce changes in the curvature of the waveguide layer 1502. While one pressure-inducing device, the pressure regulator 1510, is illustrated, exemplary embodiments allow for the use of one or more pressure regulating devices. As discussed in connection with FIG. 6C , the shape of the waveguide layer can be circular, although this is not required by embodiments of the present invention.

[0179] In an exemplary embodiment, the waveguide layer 1502 can be planar or substantially planar in a first default configuration, with little or no pressure in the pressurized cavity 1504 exerting a force on the waveguide layer 1502. The continuous pressure regulator 1510 can operate to increase the pressure in the pressurized cavity 1504, distributing a uniform load on the waveguide layer 1502 and thereby modifying the surface contour. The pressure in the pressurized cavity 1504 can be increased, causing the waveguide layer 1502 to modify its configuration and increase the curvature of the waveguide layer. Reducing or releasing the pressure in the pressurized cavity 1504 can release stored strain energy in the waveguide layer 1502, thereby returning the waveguide layer 1502 to the first default configuration having a planar or substantially planar shape.

[0180] In other embodiments, the waveguide layer 1502 can be in a second default configuration and have a generally curved shape. The continuous pressure regulator 1510 can operate to reduce the pressure in the pressurized cavity 1504 (i.e., either create a vacuum using a negative pressure value or reduce an existing positive pressure value), thereby uniformly inverting the surface profile of the waveguide layer 1502 inward toward the lens L2. The pressure in the pressurized cavity 1504 can be reduced to transition the waveguide layer 1502 to a configuration characterized by a reduced curvature. Increasing the pressure in the pressurized cavity 1504 can return the waveguide layer 1502 to the second default configuration having a generally curved shape.

[0181] In a further embodiment, the waveguide layer 1502 can be in a third default configuration and have a pre-existing curvature between planar and generally curved (i.e., between the first and second default configurations described above). The continuous pressure regulator 1510 can operate to reduce the pressure in the pressurized cavity 1504 (i.e., either create a vacuum using a negative pressure value or reduce a pre-existing positive pressure value), thereby uniformly inverting the surface contour of the waveguide layer 1502 inward toward the lens L2. The pressure in the pressurized cavity 1504 can be reduced to force the waveguide layer 1502 into a configuration in which the waveguide layer 1502 exhibits a reduced curvature. Increasing the pressure in the pressurized cavity 1504 can return the waveguide layer 1502 to the third default configuration. Alternatively, the continuous pressure regulator 1510 can also operate to increase the pressure in the pressurized cavity 1504, distributing a uniform load on the waveguide layer 1502 and modifying the surface contour. The pressure in the pressurized cavity 1504 can be increased to force the waveguide layer 1502 into a configuration in which the waveguide layer 1502 exhibits an increased curvature. Reducing or releasing the pressure in the pressurized cavity 1504 can release the strain energy stored in the waveguide layer 1502, returning the waveguide layer 1502 to the third, default configuration.

[0182] 8A and 8B, lenses L1, L2 have complementary lens functions used to achieve two depth planes without affecting real-world light as perceived by the user's eye 1514. Thus, the combination of lens L2, waveguide layer 1502, and lens L1 allows world light to be viewed by the user without any refractive power. As discussed above, world light is presented to the user without any refractive power applied to it because the world light in any waveguide layer 1502 configuration passes through the curved surface of the waveguide layer 1502 with little or no disturbance, as discussed in connection with FIG.

[0183] In some exemplary embodiments, the pressure force induced within the pressurized cavity 1504 by the pressure regulator 1510 can be modulated to induce the waveguide 1502 into fully curved and fully flat configurations. Varying the pressure value can cause the waveguide layer 1502 to bend or flatten into multiple configurations corresponding to variable radius of curvature values, with each pressure value corresponding to a different resulting radius of curvature value exhibited by the waveguide layer 1502. Varying the pressure value within the pressurized cavity 1504 can thus enable continuous modulation of the curvature of the waveguide layer. As a result, the waveguide layer 1502 can be continuously modified through modulation of the pressure value via the pressure regulator 1510 to project virtual content to a user at multiple depth planes. For example, the natural state of the waveguide layer 1502 can have a radius of curvature value appropriate for projecting virtual content emanating at a distance of 2 m from the eyepiece. The pressure value inside the pressurized cavity 1504 can be increased, causing the waveguide layer 1502 to assume an increased curvature. The increased bending of the waveguide layer 1502, which reduces the radius of curvature of the waveguide layer 1502, may correspond to projected virtual content occurring at a distance closer to the user than 2 m (e.g., 1 m). The pressure value inside the pressurized cavity 1504 can be further increased, causing the waveguide layer 1502 to bend further. Further bending of the waveguide layer 1502 further reduces the radius of curvature value, which may be used to render virtual content emanating at a distance closer to the user than 1 m (e.g., 0.3 m). Releasing the pressure returns the waveguide 1502 to its rest configuration. As an alternative to completely releasing the pressure, the pressure can instead be reduced or increased to achieve any other radius of curvature value determined by the configuration of the waveguide 1502. For example, at a refresh rate of 90 Hz, successively alternating between a first, static configuration, a second configuration in which the waveguide is bent, and a third configuration in which the waveguide is even more bent allows the display of virtual content in three depth planes corresponding to three radii of curvature, achieved using pressure regulator 1510 to adjust the curve of waveguide layer 1502.Of course, these values ​​are merely exemplary and other depth planes can be achieved using embodiments of the present invention.

[0184] The inventors have determined that during curvature modification of a multi-layer eyepiece stack, including multiple waveguide layers, the mechanical relationship between adjacent waveguide layers in the multi-layer stack can affect performance. In particular, when the peripheral edges of adjacent waveguide layers are bonded using a rigid interlayer adhesive, it is possible to introduce significant error into the curvature between the layers.

[0185]

[0013] Figure 16 is a simplified schematic diagram illustrating a cross-sectional view of a peripheral portion of three waveguide layers in a multi-layer ocular stack, according to some embodiments. As shown in Figure 16, a stationary frame 1610 supports the outer periphery of the multi-layer ocular stack 1620 and an actuator 1612, which contacts the inner periphery of the multi-layer ocular stack 1620. While the stationary frame 1610 and actuator 1612 are illustrated in Figure 16 as applying a mechanical force to the inner / outer periphery of the multi-layer ocular stack 1620, thereby angling the periphery of the multi-layer ocular stack 1620, the discussion provided in connection with Figure 16 is applicable to various embodiments of the invention as described herein in which the angling of the periphery results in a modification to the surface contour or curvature of the waveguide layers or the multi-layer ocular stack.

[0186] Referring to FIG. 16 , first and second mechanical movable joints 1622 and 1624 are positioned between waveguide layers 1626 and 1628 and between waveguide layers 1628 and 1630, respectively. The presence of mechanical movable joints 1622 and 1624, which may also be referred to as shims or shim layers, allows each of waveguide layers 1626, 1628, and 1630 to rotate independently of one another, which may result in the production of a more uniform curvature between the waveguide layers. Mechanical movable joints 1622 and 1624 allow the waveguide layers to slide relative to one another within a predetermined range, preventing compression in the top waveguide layer and tension in the bottom waveguide layer that may result from solid or rigid interlayer bonds between adjacent layers. The mechanical movable joints can be fabricated to conform to some or all of the periphery of the waveguide layers and assemble in a manner similar to a gasket between adjacent waveguide layers. As illustrated in FIG. 6D, a portion of the periphery (e.g., C-shaped crimping feature 608) can utilize a shim, while another portion of the periphery (e.g., fixed portion 612) can utilize a solid or rigid bond between adjacent waveguide layers.

[0187] By utilizing the mechanical moveable joints illustrated in FIG. 16, it is possible to fabricate eyepieces that include both one or more dynamic waveguide layers and one or more static waveguide layers, since the curvature of each eyepiece can be controlled independently.

[0188] FIG. 17A is a simplified schematic diagram illustrating a foveated display system according to an embodiment of the present invention. Referring to FIG. 17A, the foveated display system 1705 includes a central eyepiece 1710 and peripheral eyepieces 1720. The central eyepiece 1710 includes an internally coupled diffractive optical element 1712 and a central combined OPE / EPE 1714. The central eyepiece 1710 receives a display signal from a first projector (not shown). In the illustrated embodiment, the central eyepiece 1710 is utilized to provide content for a central portion of a viewer's visual field, e.g., a 40° x 40° field of view at the center of the viewer's visual field. As discussed in connection with FIGS. 17B and 17C, the waveguide layer utilized within the central eyepiece 1710 can be operated to implement a variable curvature, which would provide a dynamic depth-of-field eyepiece.

[0189] In addition to the central eyepiece 1710, the foveated display system 1705 includes a peripheral eyepiece 1720, which includes an internally coupled diffractive optical element 1722 and a peripheral combined OPE / EPE 1724. The peripheral eyepiece 1720 receives a display signal from a second projector (not shown). In the illustrated embodiment, the peripheral eyepiece 1720 is utilized to provide content for a peripheral portion of the viewer's visual field, e.g., a 50° x 50° field of view at the periphery of the viewer's visual field. As discussed in connection with FIGS. 17B and 17C , the waveguide layer utilized within the peripheral eyepiece 1720 can be operated with a fixed planar geometry, thereby providing a fixed depth of field of view.

[0190] Although the peripheral eyepiece 1720 is illustrated to the left of the central eyepiece 1710, this is not required by the present invention, and other geometric arrangements are within the scope of the present invention, including multiple peripheral eyepieces, peripheral eyepieces abutting and thereby at least partially surrounding the central eyepiece 1710 on more than one side, and the like. Furthermore, the fields of view associated with the central and peripheral eyepieces are not limited to the specific fields of view provided above, but may vary according to the particular application. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0191] 17B is a simplified cross-sectional diagram illustrating the waveguide layers of the foveated display system shown in FIG. 17A in a first configuration. For purposes of clarity, only a single waveguide layer for each individual eyepiece is shown in FIG. 17B, but it should be understood that, for example, three waveguide layers, each associated with a primary color, could be utilized to implement a multicolor display. Thus, implementations in which multiple waveguide layers implement the illustrated curvatures are also within the scope of the present invention.

[0192] 17B, ​​the waveguide layer 1730 of the central eyepiece 1714 is characterized by a first curvature (R1). Similarly, the waveguide layer 1740 of the peripheral eyepiece 1724 is also shown, with a planar profile, i.e., an infinite radius of curvature. Due to the different radii of curvature, content for the central portion of the viewer's visual field is displayed at a predetermined depth plane, e.g., 3 m, while content for the peripheral portion of the viewer's visual field is displayed at a greater distance, e.g., infinity.

[0193] FIG. 17C is a simplified cross-sectional diagram illustrating the waveguide layer of the foveated display system illustrated in FIG. 17A in a second configuration. Referring to FIG. 17C, the waveguide layer 1730 of the central eyepiece 1714 is characterized by a second curvature (R2). As in FIG. 17B, the waveguide layer 1740 of the peripheral eyepiece 1724 is also illustrated, with a planar profile, i.e., an infinite radius of curvature. Due to the different radii of curvature, content for the central portion of the viewer's visual field is displayed at a predetermined depth plane, e.g., 1 m, while content for the peripheral portion of the viewer's visual field is displayed at a greater distance, e.g., infinity. In addition to the two radii of curvature R1 and R2 illustrated in FIGS. 17B and 17C, respectively, other radii of curvature can also be produced using the various systems described herein to achieve continuously varying radii of curvature, as described throughout this specification. Thus, in some embodiments, as virtual content associated with a variable depth plane is produced by the first projector, the virtual content can be displayed at the appropriate depth plane by modifying the radius of curvature of one or more waveguide layers of the central eyepiece 1714.

[0194] Thus, embodiments of the present invention provide a foveated display system in which a first projector provides content to a dynamic depth lens optically coupled to the first projector. The dynamic depth lens includes a waveguide layer that can be operated to have different radii of curvature, i.e., variable curvature. In some embodiments, the dynamic depth lens is the central eyepiece of the foveated display, providing variable depth content to a central portion of a user's or viewer's field of view. A second projector is utilized in conjunction with a fixed depth lens optically coupled to the second projector. Thus, the foveated display includes a second region of the field of view characterized by a fixed depth lens. In some embodiments, the fixed depth lens is utilized for content in a peripheral portion of the user's or viewer's field of view. Thus, embodiments of the present invention provide a foveated display characterized by a field of view, including a dynamic depth lens overlapping the central portion of the field of view and a fixed depth lens overlapping the peripheral portion of the field of view. In addition to the eyepieces differing in terms of variable or fixed depth planes, other characteristics of the eyepieces may also vary, such as resolution, with lower resolution eyepieces being utilized for peripheral eyepieces 1724.

[0195] 18 is a flowchart illustrating a method of operating a dynamic eyepiece in an augmented reality headset according to an embodiment of the present invention. The method includes producing (1810) first virtual content associated with a first depth plane. The virtual content can include three colors, and one or more waveguide layers can include three waveguide layers, each associated with one of the three colors. Additionally, the method includes coupling (1812) the first virtual content into the dynamic eyepiece and projecting (1814) the first virtual content through the one or more waveguide layers of the dynamic eyepiece to the viewer's eye. The one or more waveguide layers are characterized by a first surface contour.

[0196] The method also includes modifying (1816) one or more waveguide layers to be characterized by a second surface contour different from the first surface contour. Modifying the one or more waveguide layers can include applying a shear strain to a peripheral portion of the waveguide layer. Additionally, modifying the one or more waveguide layers can include applying a stretching and / or compressive force to a peripheral portion of the waveguide layer. Further, modifying the one or more waveguide layers can include moving an actuator toward a stationary frame.

[0197] The method further includes producing (1818) second virtual content associated with the second depth plane, coupling (1820) the second virtual content into the dynamic eyepiece, and projecting (1822) the second virtual content through one or more waveguide layers of the dynamic eyepiece to the viewer's eye.

[0198] In another embodiment, the method includes producing third virtual content associated with the first depth plane, modifying a waveguide layer to be characterized by a first surface contour, coupling the third virtual content into a dynamic eyepiece, and projecting the third virtual content through the one or more waveguide layers to a viewer's eye.

[0199] It should be understood that the specific steps illustrated in FIG. 18 provide a particular method of operating a dynamic eyepiece in accordance with an embodiment of the present invention. Other sequences of steps may also be implemented in accordance with alternative embodiments. For example, alternative embodiments of the present invention may implement the steps outlined above in a different order. Furthermore, individual steps illustrated in FIG. 18 may include multiple sub-steps that may be implemented in various sequences, depending on the needs of the individual step. Furthermore, additional steps may be added or removed depending on the particular application. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0200] FIG. 19 is a simplified schematic diagram illustrating an apparatus for molding a curved waveguide layer, according to an embodiment of the present invention. Referring to FIG. 19 , a waveguide layer 1910, which may be a molded curved polymer layer or multiple waveguide layers, each of which may be a molded curved polymer layer, is positioned between two molds 1920 and 1922. Molds 1920 and 1922, which may be made of glass, are characterized by a predetermined curvature, e.g., a spherical curvature (e.g., a radius >0.1 m), and are used to mold waveguide layer 1910 such that the waveguide layer has a predetermined curvature, e.g., a spherical curvature, on each of its surfaces. In some embodiments, surface 1912 has a first predetermined curvature, and surface 1914 has a second predetermined curvature. The first and second predetermined curvatures can be the same or different curvatures.

[0201] Patterning, imprinting, or other techniques, such as patterning on a curved template, can be used to form the molds 1920 and 1922. For the example of patterning on a curved template, the curvature of the template corresponds to the curvature of the final desired or predetermined waveguide layer. In some implementations, the molds 1920 and 1922, which may be referred to as the bottom mold and top mold, are aligned with high precision to obtain the desired total thickness variation (TTV). As an example, either the edges of the curved surfaces of the molds or additional marks, such as fiducials on the flat portions of the molds, can be utilized to align the molds. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0202] Figures 20A, 20B, and 20C are simplified schematic diagrams illustrating a pre-annealed planar waveguide layer, a pre-annealed curved waveguide layer, and a post-annealed curved waveguide layer, respectively, according to an embodiment of the present invention.

[0203] 20A-20C, a process of post-fabrication annealing (referred to as post-annealing) of a waveguide layer on a curved substrate is utilized to form a curved waveguide layer. In addition to the name post-annealing, the process may also be referred to as "under the action of heat," as the process need not be performed as a post-annealing process step. With reference to FIG. 20A, the process may utilize a planar waveguide layer 2010 positioned on a curved substrate 2012. As discussed in connection with FIG. 19, curved surface 1912 (and curved surface 1922, discussed below) has a predetermined curvature and may be utilized as the curved substrate 2012.

[0204] Additionally, as illustrated in Figure 20B, the process can utilize a pre-curved waveguide layer 2020 positioned on a curved substrate 2012. Thus, after initial molding of the waveguide layer to form a planar or curved waveguide layer, for example, using the molding process illustrated in Figure 19, the waveguide layer is positioned or otherwise mounted on a curved substrate in preparation for a post-annealing treatment process.

[0205] In some embodiments, the waveguide layer (e.g., the planar waveguide layer 2010 or the pre-curved waveguide layer 2020) and the curved substrate 2012 are formed at a temperature above the glass transition temperature (T g ) above the annealing temperature (T ann As an example, for the polymer waveguide layer, the annealing temperature is T ann = 120°C. The waveguide layer and curved substrate are held at or above the annealing temperature for a given period of time (typically 10-20 minutes), and then cooled at a slow rate, e.g., < 2°C / min. The waveguide layer (e.g., polymer material) can be cooled at T gAs the waveguide layer 2030 softens at temperatures above 1000 K, it forms to the shape of the curved substrate 2012 during the annealing process, including the cooling phase, as illustrated in FIG. 20C. In some implementations, a curved template with a smaller size than the waveguide layer is utilized to reduce or minimize unwanted bowing / warping in the final waveguide layer. Furthermore, in some embodiments, the surface of the curved substrate is prevented from sticking or otherwise adhering to the waveguide layer material (e.g., a polymer) so that the waveguide layer material can freely expand and contract during thermal cycling. To prevent adhesion, one of several techniques can be utilized, including utilizing a curved substrate with a predetermined roughness (e.g., a roughness of 10 nm to 1,000 nm) or coating the curved substrate with a material that provides hydrophobic and / or superhydrophobic properties. An exemplary hydrophobic material is Teflon. As discussed above, the process illustrated in FIG. 20B can be utilized in conjunction with the process illustrated in FIG. 19. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0206] 21 is a simplified schematic diagram illustrating an apparatus for forming a set of curved waveguide layers, according to an embodiment of the present invention. Refer to FIG. 21 for a method of curving a set of waveguide layers, which may form elements of an eyepiece lens, during stacking of the set of waveguide layers. As illustrated in FIG. 21, the waveguide layers (e.g., polymeric waveguide layers) can be either flat or curved after either the casting / molding process and / or post-annealing process is performed.

[0207] 21 , the curvature of the first waveguide layer 2110 and the second waveguide layer 2112 is determined by using a curved vacuum chuck 2120 to hold the first ocular layer 2110 and a curved vacuum nozzle 2122 to install or position the second waveguide layer 2112 adjacent to the first waveguide layer 2110. A gap may be formed between the first waveguide layer 2110 and the second waveguide layer 2112 by the use of a glue material 2130 at the peripheral portions of the first waveguide layer 2110 and the second waveguide layer 2112. The glue material 2130 imparts stress to the first waveguide layer 2110 and the second waveguide layer 2112 to maintain the curved shape resulting from the fabrication process. Typically, the glue material 2130 is characterized by strong adhesion to the waveguide layer material (e.g., a polymer layer). In some implementations, the glue material 2130 is either a UV-curable adhesive or a pressure-sensitive adhesive. In embodiments where a UV-curable adhesive is utilized, the curved nozzle 2122 can be transparent to allow UV light to impinge on the UV-curable adhesive.

[0208] FIG. 22 shows a simplified method 2200 of a fabrication process flow for a polymer waveguide, according to an embodiment. In operation 2210, method 2200 can include casting a polymer waveguide, according to an embodiment. Polymer casting can include utilizing a top mold 2270 and a bottom mold 2260 to form a polymer waveguide 2280. The polymer waveguide 2280 is shown as a single linear eyepiece for ease of illustration; however, such waveguides are typically three-dimensional structures, as illustrated in FIGS. 10A-10C, for example. During casting, the top mold 2270 and the bottom mold 2260 provide heat and pressure to form and shape the polymer waveguide 2280. Generally, casting temperatures typically range from room temperature (e.g., 20°C to 22°C) to 120°C, and casting times can range from 5 seconds to 10 minutes, depending on the composition and UV power. In a typical process, casting is carried out at room temperature to 40°C for 25 seconds to 1 minute.

[0209] In operation 2220, method 2200 can include a demolding process, according to an embodiment. Demolding can occur when one of the molds is released from the polymer waveguide. The demolding process typically occurs at room temperature, although other temperatures are possible, as would be understood by one of ordinary skill in the art with the benefit of this disclosure, and can include a variety of different mechanisms (e.g., mechanical force, pressure differential, adhesive modulation, etc.) for separating the first mold from the cast polymer.

[0210] In operation 2230 (step 3 in FIG. 22), method 2200 can include a separation process, according to an embodiment. The "peel" or separation process occurs when top mold 2270 is removed from polymer waveguide 2280.

[0211] In operation 2240, method 2200 can include a post-fabrication annealing process according to an embodiment. Annealing is typically a process in which a material undergoes heat treatment to a certain temperature, which is held for a certain period of time, and then cooled to room temperature to modify the material properties. The annealing process is typically time and temperature dependent. For polymers (e.g., waveguide polymers), the annealing process involves heating a polymer part above its glass transition temperature to relieve internal stresses that may have been introduced during the fabrication process (e.g., molding, post-molding cooling, machining, welding, etc.). In some cases, annealing may involve heating a plastic part below its glass transition temperature for a short period of time before allowing the plastic to cool, which can act to "relax" the material and reduce molding stresses. Typically, these stresses may include tension or compression (e.g., embedding stresses or molding stresses). Annealed polymers / plastics may have better mechanical and thermal properties because there are likely fewer points in the polymer where cracks can propagate (due to the annealing process) or alter the shape of the device (e.g., a waveguide).

[0212] Referring back to operation 2240, a polymer waveguide is constructed on a flat template 2275 or a curved template 2277, causing the polymer waveguide 2280 to adopt the shape of the template. A post-fabrication annealing ("post-annealing") of the waveguide layer on the curved substrate or template 2277 may be utilized to form the curved waveguide layer. In addition to the name post-annealing, the process may also be referred to as "under the action of heat," as the process need not be performed as a post-annealing process step. Note that the templates described herein may be referred to as molds, with the understanding that the casting mold and the post-annealing mold are different tools and perform different operations, as described herein.

[0213] As an example, a waveguide layer (e.g., a planar waveguide layer or a pre-curved waveguide layer) and a curved substrate (e.g., curved substrates 2420, 2440, 2460 as illustrated in Figures 24A-24C) may be formed at a temperature above the glass transition temperature (T g ) above the annealing temperature (T ann ) for a polymer waveguide layer. As an example, the annealing temperature may be T for a 1.72 polymer. ann = 120°C. The waveguide layer and curved substrate are held at or above the annealing temperature for a given period of time (typically 10-20 minutes), and then cooled at a slow rate, e.g., < 2°C / min. The waveguide layer (e.g., polymer material) can be cooled at T gAs the waveguide layer softens above a temperature above 1000 K, it forms to the shape of the curved substrate during an annealing process, including a cooling phase (operation 2250). Additionally, in some embodiments, the surface of the curved substrate is prevented from sticking or otherwise adhering to the waveguide layer material (e.g., a polymer) so that the waveguide layer material can freely expand and contract during thermal cycling. To prevent adhesion, one of several techniques can be utilized, including utilizing a curved substrate with a predetermined roughness (e.g., a roughness of 10 nm to 1,000 nm) or coating the curved substrate with a material that provides hydrophobic and / or ultra-hydrophobic properties. An example hydrophobic material is Teflon. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0214] At operation 2260, method 2200 may include back-of-the-line (BEOL) processing, according to an embodiment. Some examples of BEOL processing may include metallization, stacking, laminating, singulating, integrating, and more, as would be understood by one of ordinary skill in the art with the benefit of this disclosure.

[0215] It should be understood that the specific steps illustrated in FIG. 22 provide a particular method for a fabrication process flow for a polymer waveguide, according to certain embodiments. Other sequences of steps may also be performed according to alternative embodiments. Furthermore, additional steps may be added or removed depending on the particular application. For example, the present method illustrates a fabrication process for a single polymer waveguide. Some embodiments may employ a multi-template vertical "stack" incorporating multiple templates (post-annealing molds) that can be used to simultaneously form multiple polymer waveguides in a particular shape (e.g., a combination of curved and flat regions). Any combination may be used, and those skilled in the art with the benefit of this disclosure will recognize numerous variations, modifications, and alternative embodiments thereof.

[0216] FIG. 23 shows a simplified schematic diagram illustrating a side view of a flat substrate 2300, according to an embodiment. This application frequently refers to the flat characteristics of a “flat” substrate or polymer waveguide (or wafer that is cut to form the polymer waveguide) during the manufacturing process. However, “flat” can be better defined by certain parameters frequently associated with the fabrication process. For example, the terms “sag” and “warp” refer to the shape of a wafer when it is at rest in its natural state, typically without any vacuum (from a chuck) or other forces that may deform the wafer. Sag is typically the distance between the surface and the best-fit plane at the center of an unpressed wafer. Bow is typically the sum of the maximum positive and negative deviations from the best-fit plane when the wafer is unpressed (no external forces deforming the wafer at rest). The backside-based whole-wafer flatness (GBIR) and total thickness variation (TTV) are the difference between the maximum and minimum wafer thickness (typically with the wafer pressed in place). GBIR (TTV) can also be measured on the front and back surfaces of the wafer when in its native state (unbonded).

[0217] Referring back to FIG. 23 , for purposes of this disclosure, a “flat” substrate will typically refer to a wafer 2300 having less than 20 μm of bow from the reference plane 2310, less than 20 μm of deflection, and less than 1 μm of total thickness variation. Ideally, the radius of curvature in a flat substrate is infinite. For purposes of presenting the novel concepts described herein, the wafer (and corresponding polymer waveguide) may be considered to have a radius of curvature equal to infinity (i.e., a radius of ∞), with tolerances equal to or better than the limits defined herein. This should not be considered limiting, and one of ordinary skill in the art with the benefit of this disclosure will generally recognize many modifications, variations, and alternative embodiments of what would be considered “flat” by industry standards.

[0218] 24A-24C show cross sections of various custom molds with freeform surfaces for curving polymer waveguides, according to certain embodiments. These three examples illustrate various topologies for producing specific shapes in different regions of a polymer waveguide. The freeform surfaces can be combinations of flat, spherical, and aspherical surfaces or more complex shapes, depending on the desired optical function and application, as would be understood by one of ordinary skill in the art with the benefit of this disclosure, and are not limited to the examples presented here.

[0219] FIG. 24A shows an example of a freeform surface 2420 that operates to introduce a ubiquitous curvature along a polymer waveguide, according to one embodiment. The polymer waveguide may be referred to as having a ubiquitous curvature because the entire length (also referred to as the lateral extent) of the polymer waveguide is characterized by a constant curvature as a function of lateral position (i.e., in the x-y plane). The polymer waveguide 2410 may be raised to an annealing temperature (e.g., 120°C) over a period of time (e.g., 10-20 minutes), followed by a cooling period (e.g., <2°C / min). In some embodiments, the polymer waveguide may be comprised of a 1.72 polymer (e.g., annealing temperature range of 90°C-120°C) or a 1.75 polymer (e.g., annealing temperature range of 80°C-100°C). During the post-annealing process, the waveguide deforms to the shape of the underlying surface of the mold 2420. Referring to FIG. 24A, a spherical curvature is formed along the length (ubiquitous curvature) or a portion thereof of polymer waveguide 2410. While curved regions may be highly suitable for OPE, EPE, or CPE regions, they may be problematic for ICG regions, as will be understood by those skilled in the art with the benefit of this disclosure, and may be prone to deleterious imaging effects such as image drift and distortion during dynamic modulation of the polymer waveguide curvature, while flat regions help better align the image projector to the ICG. Note that the terms “freeform surface,” “template,” and “mold” may be used to refer to the same fabrication tool structure. For example, freeform surface 2420 may be referred to as mold 2420 or template 2420, as will be done in subsequent embodiments. However, the use of the term “mold” in the post-annealing process should not be confused with the type of mold used when initially casting the waveguide.

[0220] 24B shows a local curvature of polymer waveguide 2430 over a spherical region 2434 of the underlying surface of mold 2440 and a flat portion of the waveguide over a flat region 2432 of the underlying surface 2440, according to an embodiment. The locally curved portion may correspond to a CPE region of polymer waveguide 2430, while the flat region may be well suited for placing ICG, as shown above.

[0221] FIG. 24C illustrates a local curvature of polymer waveguide 2450 over a spherical region 2454 of underlying surface 2460 and a flat portion of the waveguide over a flat region 2452 of underlying surface 2460, according to an embodiment. The locally curved portion may correspond to a CPE region of polymer waveguide 2430, while flat region 2452 may be a preferred location for projector integration (e.g., ICG) or an area more easily handled in BEOL processes (including metallization, stacking, and singulation). In each of the examples, the curved region can be either spherical (e.g., R0.1 m to R20.0 m) or aspherical, as would be understood by one of ordinary skill in the art with the benefit of this disclosure. Furthermore, while a constant radius of curvature is illustrated in the local areas of curvature in FIGS. 24B and 24C, this is not required, and different curvatures can be utilized at different lateral locations of the local areas of curvature.

[0222] In some embodiments, the underlying custom mold (e.g., as illustrated in Figures 24A-24C) may have anti-stick properties so that the polymer waveguide does not stick to its surface and moves freely during the thermal cycling of the bending process. Several methods exist for employing anti-stick properties. For example, a uniform surface coating of an anti-stick compound such as polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), or other suitable non-stick coating, as will be understood by those of ordinary skill in the art with the benefit of this disclosure. In some cases, the freeform surface can be machined directly onto a non-stick block (e.g., PTFE).

[0223] The surface of the freeform custom mold can be particle-free to maintain the cleanliness of the polymer waveguide after the bending process. In some aspects, the surface can have some roughness (e.g., 10 nm to 10 μm RMS) so that the waveguide polymer does not stick to the surface (e.g., via optical bonding) and moves freely during the thermal cycling of the bending process. This can be accomplished by machining (e.g., diamond turning, molding, casting) the raw material (e.g., glass, fused silica, metal, etc.), followed by surface polishing or etching to achieve the desired roughness while still maintaining a particle-free surface. In cases where the roughness or cleanliness threshold is not met, a clean, flexible fabric (e.g., a cleanroom wipe made from synthetic polyester) can be placed between the polymer sample and the freeform surface during the bending process to improve non-stick properties.

[0224] Figures 25A and 25B illustrate aspects of one polymer bending method and corresponding issues that can arise. In some cases, the polymer waveguide may not conform closely to the underlying surface contours of the freeform custom mold during the post-annealing thermal cycling process when no additional forces other than gravity are applied. This can result in a long curved / flat transition length, such as when a spherical portion of the polymer waveguide (e.g., CPE) transitions into a flat portion where ICG cannot be configured. Depending on the polymer thickness and curve area, the transition length can increase and cause image distortion at the edge of the eyebox. Referring to Figure 25A, an extended curved / flat transition of polymer waveguide 2510 across freeform custom mold 2520 can occur and cause image distortion over the area of ​​the polymer waveguide at or near transition 2522; in particular, longer extensions may encroach or intrude into flat areas where ICG may be located, which can further introduce deleterious image effects into the waveguide. Note that polymer waveguide 2510 does not contact transition 2522, leaving a gap, thereby contributing to the extension of the curved / flat transition.

[0225] FIG. 25B shows a simplified schematic of a "squeezed" polymer bending method and the corresponding problems that can arise therefrom. A polymer waveguide 2510 rests on a freeform surface mold 2520 (the "bottom mold"), and a second mold 2530 (the "top mold") is placed on top of it, "squeezing" the polymer waveguide 2510 and applying additional force to cause the polymer waveguide 2510 to better conform to the contours of the underlying bottom mold. Such methods may work to incorporate a sharper curved / flat transition; however, they are prone to damage to the polymer waveguide, such as scratches, dents, and the like, at the sharp transition point due to, for example, misalignment of the top and bottom molds. Referring to FIG. 25B, the polymer waveguide 2510 may suffer damage at location 2540 due to improper misalignment, which can be difficult to reliably control. In some cases, damage can also affect the active grating (e.g., ICG) when it is subjected to hard contact with the top and / or bottom molds.

[0226] In subsequent embodiments, various high-fidelity bending techniques are introduced to produce improved polymer waveguides. These embodiments and methods mitigate the extended curve / flat transition described above while avoiding damage to the polymer waveguide, allow for improved top and bottom mold alignment during the post-annealing / bending process, and may help prevent active gratings (e.g., ICGs) from being damaged during the bending process, as further described below.

[0227] 26A-26C are simplified diagrams showing aspects of a high-fidelity bending process for a polymer waveguide 2600, according to one embodiment. FIG. 26A shows a plan view of a polymer waveguide 2600 including a circular and spherical CPE region 2630 and an ICG region 2650. As illustrated in FIG. 26A, an eyepiece can include a waveguide layer characterized by a teardrop shape in plan view. While a teardrop shape is illustrated in FIG. 26A, embodiments of the present invention are not limited to this particular shape, and other shapes are within the scope of the present invention.

[0228] The polymer waveguide 2600 is sandwiched between a bottom mold 2610 (not visible in this view) and a top mold 2620. The top mold 2620 can have a predetermined cutout area that can operate to define a desired transition length without inducing damage to sensitive light-transmitting areas (e.g., the transition between the curved and flat areas), allow for top and bottom mold alignment during the post-annealing / bending process, and prevent the active grating (e.g., ICG 2650) from being damaged during the bending process. Figure 26B shows a side cutaway view from 26B-26B' (see Figure 26A) of the polymer waveguide 2600 during the bending process. The relationship between the bottom mold 2610, the top mold 2620, and the polymer waveguide 2600 sandwiched therebetween is more easily visible from this perspective view. From the 26B-26B' perspective view, the top mold 2620 is positioned and aligned (2660) on both the 26B and 26B' ​​sides at or near the curved / flat transition of the bottom mold 2610 (e.g., where the locally curved portion 2635 transitions to the flat portion 2640), thereby creating a short corresponding transition for the polymer waveguide 2600 while still avoiding any damage that may affect TIR or other optical parameters. That is, the curved / flat transition along the 26B-26B' cross section can be abrupt (e.g., ideally as small as a transition length of 0 mm or as small as practical) because light does not propagate along this direction and therefore this region does not experience deleterious optical coupling effects (e.g., distortion).

[0229] Figure 26C shows a side cutaway view from 26C-26C' of Figure 26A during the bending process. On the 26C' side, the top mold 2620 is positioned and aligned at or near the curved / flat transition of the bottom mold 2610, thereby causing a short corresponding transition length D1 for the polymer waveguide 2600. On the 26C side, the top mold 2620 is positioned outside the ICG 2650. In this configuration, the desired transition length D2 can be defined without inducing damage to the ICG 2650 (e.g., when the top mold 2620 is positioned on top of the ICG 2650), yet still define the desired transition length so that the polymer waveguide 2600 is flat at the ICG 2650 and maintains good optical performance. That is, the curved / flat transition along cross section 26C-26C′ is short enough to ensure that the ICG 2650 is flat (e.g., the curved / flat transition does not overlap or encroach too closely on the ICG 2650), and also has a transition long enough to avoid damage at the curved / flat transition, as described above. For evaluation criteria, some embodiments may have a transition length D2 of about 9 mm without the top mold 2620, which would not encroach on the ICG area. With the top mold 2620, D2 may be reduced to about 6 mm with the top mold 2620 configured about 5 mm from the ICG 2650. The top mold 2620 can be configured as close as possible to the ICG 2650 without touching it (e.g., to the edge of the ICG 2650); generally, the closer the top mold 2620 is to the ICG 2650, the shorter the transition length D2 may be.

[0230] While Figures 26A-26C illustrate the formation of a single polymer waveguide using a template, it should be understood that multiple polymer waveguides can be fabricated using stacked packaging. Thus, the techniques described herein are applicable to multiple waveguide fabrication processes. Those skilled in the art will recognize many variations, modifications, and alternatives. In an exemplary embodiment, the CPE may have a diameter of 35-40 mm, the ICG may have a diameter of 1-3 mm, and the distance between the CPE and ICG (e.g., shown as D) can be 10-15 mm. Other dimensions and scales are also possible, as would be understood by one of ordinary skill in the art with the benefit of this disclosure.

[0231] FIG. 27A is a simplified cross-sectional schematic diagram showing an example of a ubiquitously flat multilayer eyepiece stack ("eyepiece," "eyepiece stack," "polymer waveguide stack") 2700 with a locally curved CPE, according to an embodiment. In some embodiments, eyepiece stack 2700 may include three or more polymer waveguides for RGB color imaging, such as polymer waveguides 2720 (e.g., green), 2730 (e.g., blue), and 2740 (e.g., red). Projector 2710 may be a split-pupil projector, configured to cover the flat region of each polymer waveguide and allow optical injection of RGB colors at the same angle per polymer waveguide (ICG 2755) for proper mixing of the RGB image. A flat ICG is typically preferred for in-line ICG, which may result in an increased field of view via interlayer crosstalk. In some aspects, coatings 2725, 2735, and 2745 can be added to the ICG, as would be understood by one of ordinary skill in the art with the benefit of this disclosure.

[0232] Shims can be configured beneath each polymer waveguide 2720, 2730, 2740, respectively (see FIG. 27B). Typically, each shim is bonded to one waveguide layer, which separates each waveguide layer by a distance and can operate to allow each layer to rotate independently of one another and accommodate uniform curvature deformation within each waveguide layer during dynamic bending. Shims may typically be made of a low-friction (<0.5) carrier film (e.g., PTFE, PET + hard coating, etc.) with adhesive on one side. The low-friction surface can allow uniform deformation of all layers. Shim thickness can range from approximately 20 μm to 500 μm, although other uniform or non-uniform thicknesses are also possible.

[0233] FIG. 27B is a plan view illustrating an example of a ubiquitously flat eyepiece 2700 with a locally curved CPE within the dynamically curved eyepiece, according to an embodiment. For dynamically curved eyepieces, a constant and flat ICG may be used to minimize image drift and distortion during dynamic modulation of the curvature of the eyepiece (e.g., polymer waveguides 2720, 2730, 2740). As better seen in FIG. 27A , using locally curved CPEs on an otherwise ubiquitously flat eyepiece allows the position and flatness of the ICG 2755 to be better maintained through the increased bending stiffness inherent in the shape of the eyepiece 2700. In some implementations, a rigid adhesive 2750 can be bonded around the ICG to bond different layers together and / or the frame and projector, further minimizing movement of the ICG 2755 and creating a fixed (non-moving) portion 2760 of the eyepiece stack 2700. Rigid adhesive 2750 may be configured around (e.g., bonded to) eyepiece 2700 in an area that does not interfere with the optical path from projector 2710 or light propagating through eyepiece 2700. Typically, the bond length of the rigid adhesive can be configured to maintain flatness of the ICG area and minimize spherical curvature aberrations of the eyepiece during dynamic modulation. As an example, the bond length is typically about 10-30 mm, as shown in FIG. 27B, which may result in good optical performance characteristics. In some aspects, region 2765 around the local spherical area (e.g., CPE) may be configured with shims placed between vertically adjacent layers of eyepiece 2700 to allow each layer to rotate independently for uniform curvature deformation within each eyepiece layer during dynamic bending.

[0234] The ring actuator 2770, as further described below, may be coupled to a localized spherical area and configured in any suitable shape, but typically circular or C-shaped, to minimize any interference with light propagating through the eyepiece 2700.

[0235] According to embodiments of the present invention, application of a bending moment at the periphery of the waveguide layer (e.g., via a ring actuator) can result in modulation of the surface contour or curvature of the waveguide layer uniformly across the width / length of the waveguide layer and the associated eyepiece aperture area to achieve the various depth planes described above.

[0236] A waveguide structure with a variable surface contour structure as presented herein provides a dynamic eyepiece in which the depth plane of the eyepiece can be varied to display virtual content at different depth planes. Thus, for example, using a single eyepiece (e.g., eyepiece stack 2700) containing three waveguide layers, each associated with a primary color, a time-division multiplexing technique can be utilized to display virtual content that appears to originate from different depth planes. While the embodiment generally illustrated herein provides two different depth planes, other implementations also enable continuous variation in surface contour, thereby providing a dynamic eyepiece with continuous depth plane variation. Additionally, virtual content can be shifted to different depth planes as a function of user movement, when the user blinks, or the like. The current depth plane associated with the eyepiece can be correlated with the virtual content to be displayed, so that the depth plane can be adjusted as a function of the virtual content. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0237] In some aspects, the fixed portion 2760 of the waveguide layer can be affixed to or otherwise hold a portion of the waveguide layer in place adjacent the fixed portion. As an example, the ICG 2755 can be positioned near the center of the fixed portion 2760. To prevent modification of the surface contour of the waveguide layer in the vicinity of the ICG 2755, the fixed portion 2760 is utilized to maintain the surface contour of this portion of the waveguide layer within the fixed surface contour. In other embodiments, the fixed portion can loosely hold multiple waveguide layers (e.g., 2720, 2730, 2740) in place, for example, by utilizing one or more shims between the waveguide layers to allow the portion of the waveguide layer adjacent the fixed portion 2760 to bend or remain in its original condition without obstruction by the fixed portion 2760, as discussed in further detail in connection with FIG. 16 .

[0238] As described above, the periphery of the eyepiece stack 2700 can be positioned against, bonded to, or otherwise affixed to an inner portion of the ring actuator 2770. The outer portion of the ring actuator 2770 may be affixed to a fixed frame structure, as further described herein. The ring actuator 2770 can be repeatedly expanded or contracted radially for continuous modulation of the surface contour of the waveguide layer (e.g., 2720) of the eyepiece 2700. Examples of ring actuators include, but are not limited to, piezoelectric actuators, electrothermal actuators, magnetostrictive actuators, and the like. The voltage source utilized to drive the ring actuator is not shown to avoid obscuring the novel concepts described herein. The waveguide layer and ring actuator can be fabricated separately and then bonded together, or fabricated as a single unit, depending on the particular fabrication process utilized.

[0239] Referring to FIG. 27B , the outer portion of the ring actuator 2770 can be affixed or pinned to a fixed frame structure via a rotational mechanism (e.g., hinge) that acts as a support collar. The ring actuator 2770 can expand laterally, and the boundary conditions of the ring actuator can flatten the waveguide layer 2700 into a planar or nearly planar configuration. Conversely, the ring actuator 2770 can contract laterally, and the boundary conditions of the ring actuator can cause the waveguide layer (e.g., 2720) to curve more substantially than when the ring actuator is less contracted. In other words, the ring actuator 2770 can expand toward the center of the waveguide layer, causing the waveguide layer to decrease its radius of curvature, and can contract outward from the center of the waveguide layer, causing the waveguide layer to flatten and increase its radius of curvature. Thus, the waveguide layers (e.g., waveguides 2720, 2730, 2740) can be continuously flattened into a planar or near-planar position or induced to curve at various radius of curvature values ​​by lateral or radial movement of ring actuator 2770, thereby achieving multiple waveguide configurations in continuous motion. Varying the contraction / expansion of the ring actuator along its range of motion can stretch the waveguide layers into multiple states corresponding to variable surface profiles or radius of curvature values. As a result, the surface profile of each waveguide layer in eyepiece stack 2700 can be continuously altered, allowing virtual content to be projected to the user at multiple depth planes.

[0240] The ring actuator 2770 can be a ring or loop that surrounds a portion of the periphery of the CPE, for example, as shown in FIG. 27B. In some embodiments, a portion of the ring actuator can be divided into multiple segmented sections so that a variable mechanical force can be applied to different portions along the periphery of the waveguide layer. In some embodiments, different materials or actuator types may be used for each segmented section, in any combination, in a given application. Various sections of the ring actuator can be actuated simultaneously, alternately, or in combination so that some portions of the ring actuator can expand outwardly away from the waveguide layer more or less than other portions of the ring actuator. This reduces focusing errors and can allow for ring actuator systems with varying component geometries relative to the geometry of the waveguide layer.

[0241] FIG. 28A is a simplified cross-sectional schematic diagram showing an example of a locally flat ICG in a ubiquitously curved eyepiece stack 2800, according to an embodiment. In some embodiments, eyepiece stack 2800 may include three or more polymer waveguides for RGB color imaging, such as polymer waveguides 2820 (e.g., green), 2830 (e.g., blue), and 2840 (e.g., red). Projector 2810 may be a split-pupil projector, configured across the flat region of each polymer waveguide, allowing optical injection of RGB colors at the same angle for each polymer waveguide (ICG 2855) for proper mixing of the RGB image. Shims may be configured under each polymer waveguide 2820, 2830, 2840, respectively. Typically, each shim is bonded to one waveguide layer, which, as further described above and with respect to FIG. 16, can operate to separate each waveguide layer by a distance, allowing each layer to rotate independently of each other during dynamic bending and accommodate uniform curvature deformation within each waveguide layer. Integration of a locally flat ICG into a curved eyepiece stack allows for a smoother flat / curved transition region from the locally flat ICG to the curved eyepiece waveguide region, thereby reducing damage to the polymer waveguide and improving optical coupling efficiency between the ICG and the curved eyepiece waveguide region.

[0242] Figure 28B is a plan view illustrating an example of a locally flat ICG within a ubiquitously curved dynamic eyepiece 2800, according to one embodiment. With a dynamically curved eyepiece, a constant and flat ICG may be used to minimize image drift and distortion during dynamic modulation of the curvature of the eyepiece (e.g., polymer waveguides 2820, 2830, 2840). As better seen in Figure 28A, by using a locally flat ICG on a ubiquitously spherical eyepiece, the position and flatness of the ICG 2855 can be well maintained via the increased bending stiffness inherent in the shape of the eyepiece 2800. In some implementations, a rigid adhesive 2850 can be bonded around the periphery of the ICG to bond different layers together and / or the frame and projector, as further described above with respect to Figures 27A-27B, to further minimize movement of the ICG 2855 and create a fixed (non-moving) portion 2860 of the eyepiece stack 2800. In some aspects, the region 2860 around the spherical area (e.g., CPE) (or in some cases, around a rigid area near the ICG 2855) may be configured with shims placed between vertically adjacent layers of the eyepiece 2800 to allow each layer to rotate independently due to uniform curvature deformation within each eyepiece layer during dynamic bending. Shims are typically configured around the area of ​​the CPE because this area undergoes movement due to polymer waveguide deformation, etc., as further described above. Shims are typically not configured within fixed areas (e.g., ICG) because these areas are typically configured to be rigid with little or no movement of the layers (polymer waveguides) individually or relative to each other. A ring actuator 2870, as further described above, is coupled to the local spherical area and may be configured in any suitable shape, but is typically configured as a circle or C-shape, to minimize any interference with light propagating through the eyepiece 2800.

[0243] Those skilled in the art will understand that the designs illustrated in Figures 27A-27B and 28A-28B can be utilized in conjunction with the systems for dynamically adjusting the surface contour of a waveguide layer illustrated in Figures 6A-16, if desired. By way of example only, considering Figures 6E-6F, a waveguide layer fabricated with a predetermined curved surface contour, e.g., a predetermined radius of curvature, as illustrated in Figures 27A and 28A, can then be operated using two ring-shaped crimping mechanisms shown in Figures 6E and 6F to apply a mechanical force to the periphery of the waveguide layer, which will result in the waveguide layer bending in response to a mechanical force and the radius of curvature being modified, e.g., to a planar surface contour or a larger radius of curvature. Thus, various devices fabricated using the fabrication methods described herein can be integrated with the various dynamic adjustment systems described herein. While Figures 6E-6F are discussed as examples, the other systems illustrated in Figures 6A-16 can also be utilized, if desired. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0244] 29 is a simplified flowchart illustrating aspects of a method 2900 for forming a polymer waveguide for use in an augmented reality headset, according to an embodiment. In an embodiment, aspects of method 2900 can be implemented utilizing casting and molding processes and equipment. While method 2900 describes a method for forming a single-layer high-fidelity polymer waveguide, it should be understood that the polymer waveguides described herein may be part of a multi-layer eyepiece, and multiple layers may be fabricated in a multi-stack process (e.g., multiple molds stacked to create multiple waveguides simultaneously), as would be understood by one of ordinary skill in the art with the benefit of this disclosure.

[0245] In operation 2910, method 2900 can cast a polymer waveguide 2600 configured to propagate light therein, as illustrated in FIGS. 26A-26C , according to an embodiment. In some aspects, the polymer waveguide is a single layer of a multi-layer (e.g., multi-polymer waveguide) ocular. The polymer waveguide may have a substantially uniform topology. For example, after casting, the polymer waveguide may be partially or entirely flat or curved. The polymer waveguide 2600 can include a light input surface (e.g., ICG 2650) in a first region and a light output surface (e.g., CPE 2630) in a second region, the light input surface and the light output surface being separated by a predetermined distance. Casting can be performed using multiple molds, typically a top mold and a bottom mold, with the polymer waveguide sandwiched between them, with the casting temperature further described above. The casting molds described herein should not be confused with the post-annealing molds (also referred to as templates, freeform surfaces, etc.) described above.

[0246] In operation 2920, method 2900 may include removing the polymer waveguide from the mold, for example, as shown in FIG. 22. Removing the polymer waveguide may include a demolding process in which the bottom mold is separated from the polymer waveguide, followed by a separation process (e.g., a peel process) that separates the polymer waveguide from the top mold. Alternatively, the demolding process may begin with removing the top mold first, followed by removing the bottom mold. Those skilled in the art with the benefit of this disclosure will recognize numerous modifications, variations, and alternative embodiments thereof.

[0247] In operation 2930, the method 2900 may include placing a molded polymer waveguide on a first mold (e.g., bottom mold 2610), which may include a uniformly spherical portion 2635 having a circular base and a flat portion 2640. The polymer waveguide may be configured on the first mold such that a first region is vertically aligned 2660 with the flat portion of the first mold and a second region is vertically aligned with the uniformly spherical portion.

[0248] In operation 2940, method 2900 can include placing a second mold (top mold 2620) over the polymer waveguide, according to an embodiment. The second mold can be vertically aligned 2660 with polymer waveguide 2600 and first mold 2610. Second mold 2620 can include an opening configured across polymer waveguide 2600 defined by a first segment of the opening surrounding at least half of the circular base and light output surface of the uniformly spherical portion of the first mold, and a second segment of the opening surrounding at least half of the flat portion and light input surface. For example, referring to FIG. 27B, the second mold can have an opening (also referred to as a "cutout area" or "cavity") that is teardrop-shaped (or wedge-shaped), where area 2765 surrounds at least half of the CPE section, area 2760 surrounds at least half of the ICG section, and area 2785 connects both of the surrounded areas (e.g., linearly or with any suitable curved topology). The second mold (top mold 2620), as further described above in the A-A' and B-B' cross sections in Figures 26A-26C, is configured around the outer edge of the ICG without contacting it, but sufficiently close to the curved / flat transition, so as to still reduce the transition length to a desired amount, thereby defining the desired transition length (e.g., reducing the transition length) without inducing damage to sensitive light-propagating areas (e.g., affecting TIR or other optical parameters), and can operate to enable top and bottom mold alignment during the post-annealing / bending process and prevent the active grating (e.g., ICG 2650) from being damaged during the bending process.

[0249] In operation 2950, ​​method 2900 may include heating the first and second molds to a threshold temperature, applying a thermal cycling process (e.g., a post-annealing process) to deform the polymer waveguide into a shape defined by the first and second molds such that the polymer waveguide is flat in the first region, the polymer waveguide is uniformly spherical in the second region, and the curved / flat transition between the first and second regions is shorter than a predetermined distance, as shown in FIG. 26C, such that the active grating does not contact the second mold, resulting in a high-fidelity polymer waveguide. In some aspects, the threshold temperature (e.g., for a 1.72 polymer) may be 120°C, although lower or higher threshold temperatures are possible, depending on the type of polymer used. For example, a 1.75 polymer may have a threshold temperature that may range from 80°C to 100°C.

[0250] In some embodiments, method 2900 may further include a process for preventing the polymer waveguide from sticking during the thermal cycling process. For example, method 2900 may include applying a uniform surface coating of an anti-stick compound to the cast polymer waveguide, which operates to prevent the polymer waveguide from sticking to the first and second molds during the thermal cycling process. Alternatively, or in addition, method 2900 may include applying raw material particulates to the surface of the polymer waveguide and surface polishing or etching the polymer waveguide to achieve a surface roughness of 10 nm to 10 μm RMS, which operates to prevent the polymer waveguide from sticking to the first and second molds during the thermal cycling process. In some implementations, method 2900 may include inserting one or more woven fabrics between the polymer waveguide and the first and / or second molds, the one or more woven fabrics configured to prevent the polymer waveguide from sticking to the first and second molds during the thermal cycling process. Those skilled in the art, having the benefit of this disclosure, will recognize many modifications, variations, and alternative embodiments thereof.

[0251] In some embodiments, method 2900 may include applying a rigid bonding material around at least a portion of the second section to surround the light input surface, the rigid bonding material bonding the second section to one or more structures adjacent to the polymer waveguide, including one or more of a multi-layer eyepiece stack or an adjacent polymer waveguide of a projector. In some aspects, the rigid bonding material may prevent or reduce movement of the light input surface as the polymer waveguide is dynamically deflected.

[0252] It should be understood that the specific steps illustrated in FIG. 29 provide a particular method for forming a polymer waveguide for use in an augmented reality headset, according to one embodiment. Other sequences of steps may also be performed according to alternative embodiments. Furthermore, additional steps may be added or removed depending on the particular application. For example, the method may further include fabricating, arranging, and / or mounting shims, ring actuators, or other elements, as further described above with respect to FIGS. 27A-28B. Any combination of variations may be used, and those skilled in the art with the benefit of this disclosure will recognize numerous variations, modifications, and alternative embodiments thereof.

[0253] It should also be understood that the examples and embodiments described herein are for illustrative purposes only, and that various modifications or changes in light thereof will be suggested to those skilled in the art and are to be included within the spirit and scope of the present application and the appended claims.

Claims

1. 1. A dynamic eyepiece for projecting an image onto a viewer's eye, said dynamic eyepiece comprising: a waveguide layer having an input surface, an output surface opposite the input surface, and a periphery, the waveguide layer configured to propagate light therein; a mechanical structure coupled to at least a portion of a periphery of the waveguide layer, the mechanical structure comprising: applying a first mechanical force to at least a portion of a periphery of the waveguide layer to impart a first surface contour on an output surface of the waveguide layer; applying a second mechanical force to at least a portion of a periphery of the waveguide layer to impart a second surface contour on an output surface of the waveguide layer that differs from the first surface contour; a mechanical structure operable to A dynamic eyepiece comprising:

2. The dynamic eyepiece of claim 1 , wherein the first surface contour is planar and the second curvature of the second surface contour is negative or positive.

3. The dynamic eyepiece of claim 1 , wherein the first curvature of the first surface contour is positive and the second curvature of the second surface contour is negative.

4. The dynamic eyepiece of claim 1 , further comprising a projector optically coupled to the dynamic eyepiece.

5. a second waveguide layer having a second input surface, a second output surface opposite the second input surface, and a second periphery, the second waveguide layer configured to propagate light therein; a second mechanical structure coupled to at least a second portion of a second periphery of the waveguide layer, the second mechanical structure comprising: applying a third mechanical force to at least a second portion of a second periphery of the second waveguide layer to impart a third surface contour onto a second output surface of the second waveguide layer; applying a fourth mechanical force to at least a second portion of a second periphery of the second waveguide layer to impart a fourth surface contour on a second output surface of the second waveguide layer, the fourth surface contour being different from the fourth surface contour; a second mechanical structure operable to The dynamic eyepiece of claim 1 further comprising:

6. The dynamic eyepiece of claim 5 , further comprising one or more movable mechanical joints between the waveguide layer and the second waveguide layer.

7. The dynamic eyepiece of claim 1 , wherein the first mechanical force and the second mechanical force are applied sequentially to the waveguide layer, thereby providing a range of surface contours between the first surface contour and the second surface contour.

8. The dynamic eyepiece of claim 1 , wherein the mechanical structure is operable to apply a shear strain to the waveguide layer.

9. The dynamic eyepiece of claim 1 , wherein the mechanical structure is operable to apply a tension and / or compression force to the waveguide layer.

10. The dynamic eyepiece of claim 1 , wherein the mechanical structure comprises a stationary frame and an actuator.

11. 1. A method of operating a dynamic eyepiece in an augmented reality headset, the method comprising: producing a first virtual content associated with a first depth plane; Coupling the first virtual content into the dynamic eyepiece; projecting the first virtual content to an eye of a viewer through one or more waveguide layers of the dynamic eyepiece, the one or more waveguide layers characterized by a first surface contour; modifying the one or more waveguide layers to be characterized by a second surface contour different from the first surface contour; producing second virtual content associated with the second depth plane; coupling the second virtual content into the dynamic eyepiece; projecting the second virtual content to the viewer's eye through one or more waveguide layers of the dynamic eyepiece; A method comprising:

12. producing a third virtual content associated with the first depth plane; modifying the one or more waveguide layers to be characterized by the first surface contour; Integrating the third virtual content into the dynamic eyepiece; projecting the third virtual content through the one or more waveguide layers to the viewer's eye; The method of claim 11 further comprising:

13. 12. The method of claim 11, wherein the first virtual content comprises three colors and the one or more waveguide layers comprise three waveguide layers, each associated with one of the three colors.

14. The method of claim 11 , wherein modifying the one or more waveguide layers comprises applying a shear strain to a peripheral portion of the one or more waveguide layers.

15. The method of claim 11 , wherein modifying the one or more waveguide layers comprises applying a stretching and / or compressive force to a peripheral portion of the one or more waveguide layers.

16. The method of claim 11 , wherein modifying the one or more waveguide layers comprises moving an actuator toward a stationary frame.

17. 1. A foveated display, comprising: a first projector; a dynamic eyepiece optically coupled to the first projector, the dynamic eyepiece comprising a waveguide having a variable surface contour; a second projector; and a fixed depth eyepiece optically coupled to the second projector; 1. A foveated display comprising:

18. 18. The foveated display of claim 17, characterized by a field of view, the dynamic eyepieces overlapping a central portion of the field of view, and the fixed depth eyepieces overlapping a peripheral portion of the field of view.

19. The dynamic eyepiece comprises: a waveguide layer having an input surface, an output surface opposite the input surface, and a periphery; a mechanical structure coupled to at least a portion of a periphery of the waveguide layer, the mechanical structure operable to apply a first mechanical force to at least a portion of a periphery of the waveguide layer to modify a surface contour of an output surface of the waveguide layer; 18. The foveated display of claim 17, comprising:

20. 20. The foveated display of claim 19, wherein the mechanical structure is operable to modify an angle associated with a periphery of the waveguide layer.

21. 1. A method of forming an eyepiece for use in an augmented reality headset, the method comprising: casting a polymer waveguide configured to propagate light therein, the polymer waveguide forming a single layer of the eyepiece; a substantially uniform surface topology; a light input surface at a first region of the polymer waveguide; a light output surface in a second region of the polymer waveguide, the light input surface and the light output surface being separated by at least a distance D; and placing the molded polymer waveguide on a first mold, the first mold comprising: a uniformly spherical portion having a circular base; a flat portion, wherein the polymer waveguide is configured on the first mold such that the first region is vertically aligned with the flat portion of the first mold and the second region is vertically aligned with the uniformly spherical portion; and placing a second mold over the polymer waveguide, the second mold being vertically aligned with the polymer waveguide and the first mold, the second mold comprising: a first section of the opening surrounding at least half of a circular base of the uniformly spherical portion of the first mold and the light output surface; a second section of the opening surrounding at least half of the flat portion and the light input surface; and and an opening configured across the polymer waveguide defined by: applying a thermal cycling process to heat the first and second molds to a threshold temperature that causes the polymer waveguide to deform into a shape defined by the first and second molds, such that: the polymer waveguide is flat in the first region; the polymer waveguide is uniformly spherical in the second region; The curved / flat transition between the first and second regions is less than the distance D. To do so, and A method comprising:

22. The method of claim 21 , wherein the substantially uniform surface topology is a flat surface topology.

23. The method of claim 21 , wherein the substantially uniform surface topology is a ubiquitously spherical surface topology.

24. The method of claim 21 , wherein the polymer waveguide is teardrop shaped.

25. 22. The method of claim 21, wherein the thermal cycling process is a post-annealing process and the threshold temperature is 120°C.

26. 22. The method of claim 21, wherein the light input surface is an internal coupling grating (ICG).

27. 22. The method of claim 21, wherein the light output surface is a combined pupil expander (CPE).

28. 22. The method of claim 21, wherein the flat portion is a portion of the polymer waveguide having a warp of less than 20 μm, a bow of less than 20 μm, and a total thickness variation of less than 1 μm.

29. 22. The method of claim 21, further comprising applying a uniform surface coating of an anti-stick compound to the cast polymeric waveguide, the anti-stick compound operative to prevent the polymeric waveguide from sticking to the first and second molds during the thermal cycling process.

30. applying raw material particulates to one or more surfaces of said polymer waveguide; surface polishing or etching the polymer waveguide to achieve a surface roughness of 10 nm to 10 μm RMS that operates to prevent the polymer waveguide from sticking to the first and second molds during the thermal cycling process; 22. The method of claim 21 further comprising:

31. inserting one or more fabrics between the polymer waveguide and the first and / or second molds, the one or more fabrics being configured to prevent the polymer waveguide from sticking to the first and second molds during the thermal cycling process; 22. The method of claim 21 further comprising:

32. 22. The method of claim 21, wherein the polymer waveguide is comprised of either a 1.72 polymer or a 1.75 polymer.

33. The method of claim 21 , wherein the polymer waveguide is a single layer of a multi-layer eyepiece.

34. applying a rigid bonding material around at least a portion of the second section to surround the light input surface, the rigid bonding material bonding the second section to one or more structures adjacent to the polymer waveguide, including one or more of a multi-layer eyepiece stack or adjacent polymer waveguides of a projector; further comprising 22. The method of claim 21, wherein the rigid bonding material prevents or reduces movement of the light input surface as the polymer waveguide is dynamically deflected.

35. 1. A method comprising: placing a polymer waveguide on a first mold having a uniformly spherical portion with a circular base and a flat portion; the polymer waveguide includes an optical input surface in a first region and an optical output surface in a second region; the light input surface and the light output surface are separated by a distance D; and placing a second mold over the polymer waveguide, the second mold being vertically aligned with the polymer waveguide and the first mold, the second mold comprising: a first section of the opening surrounding at least half of a circular base of the uniformly spherical portion of the first mold and the light output surface; a second section of the opening surrounding at least half of the flat portion and the light input surface; and and an opening configured across the polymer waveguide defined by: applying a thermal cycling process to heat the first and second molds to a threshold temperature that causes the polymer waveguide to deform into a shape defined by the first and second molds, such that: the polymer waveguide is flat in the first region; the polymer waveguide is uniformly spherical in the second region; The curved / flat transition between the first and second regions is less than the distance D. To do so, and A method comprising:

36. 36. The method of claim 35, wherein the polymer waveguide initially has a substantially flat surface topology.

37. 36. The method of claim 35, wherein the polymer waveguide initially has a substantially spherical surface topology.

38. 36. The method of claim 35, wherein the light input surface is an internal coupling grating (ICG).

39. 36. The method of claim 35, wherein the light output surface is a combined pupil expander (CPE).

40. 36. The method of claim 35, further comprising applying a uniform surface coating of an anti-stick compound to the cast polymeric waveguide, the anti-stick compound operative to prevent the polymeric waveguide from sticking to the first and second molds during the thermal cycling process.

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