Methods and systems for an augmented reality display with a dynamic field of view

Abstract

A dynamic eyepiece for projecting an image to a viewer's eye 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.

Description

Background Art

[0001] (Cross - reference to related applications) This application claims the benefit of priority of U.S. Provisional Patent Application No. 62 / 873,720, filed on 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 on 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 technologies have facilitated the development of systems for so - called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images or portions thereof are presented to a viewer in a manner that appears or can be perceived as being real. Virtual reality, i.e., the "VR" scenario, typically involves the presentation of digital or virtual image information without transparency to other actual real - world visual inputs, and augmented reality, i.e., the "AR" scenario, typically involves the presentation of digital or virtual image information as an augmentation to the visualization of the actual world around the viewer.

[0003] Despite the progress made in these display technologies, there is a need in the art for improved methods and systems related to augmented reality systems.

Summary of the Invention

Means for Solving the Problems

[0004] The present invention generally relates to methods and systems for “virtual reality” or “augmented reality” displays, e.g., displays with a dynamic field of view. More specifically, embodiments of the present invention provide methods and systems related to a flexible waveguide layer for refractive power adjustment.

[0005] In certain embodiments, a dynamic eyepiece lens including a plurality of 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 a plurality of depth planes where the depth can vary continuously or digitally. The present invention is applicable to various applications in computer vision and three-dimensional (3D) reconstruction.

[0006] According to embodiments of the present invention, a dynamic eyepiece lens for projecting an image onto a viewer's eye is provided. The dynamic eyepiece lens 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 therein. The dynamic eyepiece lens 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 provide a first surface profile 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 provide a second surface profile different from the first surface profile on the output surface of the waveguide layer.

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

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

[0009] In one embodiment, a method of forming an eyepiece lens for use in an AR headset is provided. The method includes casting a polymeric waveguide having a light input surface and a light output surface, placing the cast polymeric waveguide on a first mold having a uniformly spherical portion and a locally flat portion, and placing a second mold thereon. The second mold is configured over the polymeric waveguide and includes an opening defined by a first section surrounding 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 surrounding at least half of the flat portion and the light input surface. A thermal process is applied to deform the polymeric 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 may include casting a polymeric waveguide configured to propagate light therein, the polymeric 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 polymeric waveguide, and a light output surface in a second region of the polymeric waveguide. In some aspects, the light input surface and the light output surface are separated by at least a distance D. The method may further include placing the cast polymeric waveguide on a first mold including a uniformly spherical portion having a circular base and a flat portion. In some embodiments, the polymeric waveguide is configured on the first mold such that the first region is perpendicularly aligned with the flat portion and the second region is perpendicularly aligned with the uniformly spherical portion of the first mold. The method may further include placing a second mold on the polymeric waveguide, the second mold being perpendicularly aligned with the polymeric waveguide and the first mold, the second mold being configured across the polymeric waveguide and defined by a first segment of an opening surrounding at least half of the circular base of the uniformly spherical portion of the first mold and the light output surface, and a second segment of the opening surrounding at least half of the flat portion and the light input surface. In one implementation, the method may further include applying a thermal cycling process such that the polymeric waveguide is flat in the first region, the polymeric waveguide is uniformly spherical in the second region, and a curvature / flatness transition between the first region and the second region is shorter than the distance D, and heating the first and second molds to a threshold temperature to deform the polymeric waveguide into the shape defined by the first and second molds.

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

[0012] In some embodiments, the method may further include applying a uniform surface coating of an anti-sticking compound to the polymer waveguide after casting, which operates to prevent 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 microparticles 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. Alternatively, or in addition, the method may include inserting one or more fabrics between the polymer waveguide and the first and / or second molds, wherein the one or more fabrics are 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 can be made of either a 1.72 polymer or a 1.75 polymer and may be a single layer of a multi-layered eyepiece.

[0013] In a further embodiment, the method still further comprises applying a rigid bonding material around at least a portion of the second section, surrounding the light input surface, wherein the rigid bonding material joins the second section to one or more structures adjacent to a polymer waveguide, including one or more of the adjacent polymer waveguides of the multi-layer eyepiece stack or the projector, and the rigid bonding material prevents or reduces movement of the light input surface as the polymer waveguide is dynamically deflected.

[0014] In one embodiment, the method comprises placing a polymer waveguide on a first mold having a uniformly spherical portion with a circular base and a flat portion, wherein the polymer waveguide includes a light input surface in a first region and a light output surface in a second region, and the light input surface and the light output surface are separated by a distance D; placing a second mold on the polymer waveguide, wherein the second mold is vertically aligned with the polymer waveguide and the first mold, and the second mold is configured across the polymer waveguide and includes an opening defined by a first section of the opening surrounding at least half of the circular base of the uniformly spherical portion of the first mold and the light output surface, and a second section of the opening surrounding at least half of the flat portion and the light input surface; and applying a thermal cycling process to heat the first and second molds to a threshold temperature to deform the polymer waveguide into the 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 curvature / flat transition between the first and second regions is shorter than the distance D. Optionally, the polymer waveguide may initially have a substantially flat surface topology or a substantially spherical surface topology. The light input surface can be ICG, and the light output surface can be CPE. In one aspect, the method further comprises applying a uniform surface coating of an anti-sticking compound to the polymer waveguide after casting, which operates to prevent the polymer waveguide from sticking to the first and second molds during the thermal cycling process.

[0015] A number of advantages over conventional techniques are achieved by the method of the present invention. For example, embodiments of the present invention provide a method and system for two-mode or continuous variation in the surface profile of one or more waveguide layers within an eyepiece, thereby enabling a plurality of radii of curvature to be achieved. Further, embodiments of the present invention provide a method and system that provide a variable depth anamorphic imaging system that is characterized by a lighter weight and higher efficiency than conventional systems.

[0016] Furthermore, previous processing techniques for manufacturing polymer waveguides in the configurations described herein often suffer from poor yields or cover a fragile / damaged transition area between curved regions (e.g., combined pupil expanders) and flat regions (e.g., internal coupling gratings), where the curved / flat waveguide transition is processed very short or the curved / flat transition can be processed very long, and both scenarios can introduce detrimental effects (e.g., image distortion) on the waveguide performance characteristics. Various embodiments of the present invention may provide a more reliable and high-yield processing method with shorter curved / flat transitions with consistent and high-performance waveguide performance characteristics, as further described with respect to the various embodiments presented below. These and other embodiments of the present invention will be described in further detail in conjunction with the following text and the accompanying figures, along with many of their advantages and features. The present invention provides, for example, the following. (Item 1) A dynamic eyepiece for projecting an image onto the eyes of a viewer, the dynamic eyepiece comprising: A waveguide layer having an input surface, an output surface facing the input surface, and a periphery, the waveguide layer being configured to propagate light therein; A mechanical structure coupled to at least a part of the periphery of the waveguide layer, the mechanical structure being Operable to apply a first mechanical force to at least a part of the periphery of the waveguide layer and provide a first surface profile on the output surface of the waveguide layer; Operable to apply a second mechanical force to at least a part of the periphery of the waveguide layer and provide a second surface profile different from the first surface profile on the output surface of the waveguide layer And a mechanical structure. A dynamic eyepiece comprising. (Item 2) The dynamic eyepiece according to Item 1, wherein the first surface profile is a plane and the second curvature of the second surface profile is negative or positive. (Item 3) The dynamic eyepiece according to Item 1, wherein the first curvature of the first surface profile is positive and the second curvature of the second surface profile is negative. (Item 4) The dynamic eyepiece according to Item 1, further comprising a projector optically coupled to the dynamic eyepiece. (Item 5) A second waveguide layer having a second input surface, a second output surface facing the second input surface, and a second periphery, the second waveguide layer being configured to propagate light therein; A second mechanical structure coupled to at least a second part of the second periphery of the waveguide layer, the second mechanical structure being Operable to apply a third mechanical force to at least a second part of the second periphery of the second waveguide layer and provide a third surface profile on the second output surface of the second waveguide layer; Operable to apply a fourth mechanical force to at least a second part of the second periphery of the second waveguide layer and provide a fourth surface profile different from the fourth surface profile on the second output surface of the second waveguide layer And a second mechanical structure. The dynamic eyepiece according to Item 1, further comprising. (Item 6) The dynamic eyepiece according to Item 5, further comprising one or more mechanically movable joints between the waveguide layer and the second waveguide layer. (Item 7) The first mechanical force and the second mechanical force are continuously applied to the waveguide layer, thereby providing a range of surface profiles between the first surface profile and the second surface profile, the dynamic eyepiece according to item 1. (Item 8) The mechanical structure is operable to apply shear strain to the waveguide layer, the dynamic eyepiece according to item 1. (Item 9) The mechanical structure is operable to apply tensile and / or compressive forces to the waveguide layer, the dynamic eyepiece according to item 1. (Item 10) The mechanical structure includes a fixed frame and an actuator, the dynamic eyepiece according to item 1. (Item 11) A method of operating a dynamic eyepiece in an augmented reality headset, the method comprising: producing first virtual content associated with a first depth plane; combining the first virtual content into the dynamic eyepiece; projecting the first virtual content through one or more waveguide layers of the dynamic eyepiece onto the viewer's eye, the one or more waveguide layers being characterized by a first surface profile; modifying the one or more waveguide layers to be characterized by a second surface profile different from the first surface profile; producing second virtual content associated with a second depth plane; combining the second virtual content into the dynamic eyepiece; projecting the second virtual content through one or more waveguide layers of the dynamic eyepiece onto the viewer's eye and including. (Item 12) producing third virtual content associated with the first depth plane; modifying the one or more waveguide layers to be characterized by the first surface profile; combining the third virtual content into the dynamic eyepiece; projecting the third virtual content through the one or more waveguide layers onto the viewer's eye further including the method according to item 11. (Item 13) 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, the method according to item 11. (Item 14) Modifying the one or more waveguide layers includes applying shear strain to a peripheral portion of the one or more waveguide layers, the method according to item 11. (Item 15) The method according to item 11, wherein modifying the one or more waveguide layers includes applying a stretching and / or compressing force to a peripheral portion of the one or more waveguide layers. (Item 16) The method according to item 11, wherein modifying the one or more waveguide layers includes moving an actuator towards a fixed frame. (Item 17) A foveated display, a first projector, a dynamic eyepiece optically coupled to the first projector, the dynamic eyepiece comprising a waveguide having a variable surface profile, a second projector, and a fixed depth plano-eyepiece optically coupled to the second projector comprising a foveated display. (Item 18) The foveated display according to item 17, characterized by a field of view, the dynamic eyepiece overlapping a central portion of the field of view, and the fixed depth plano-eyepiece overlapping a peripheral portion of the field of view. (Item 19) The dynamic eyepiece, 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 the periphery of the waveguide layer, the mechanical structure being operable to apply a first mechanical force to at least a portion of the periphery of the waveguide layer and modify a surface profile of the output surface of the waveguide layer, comprising a foveated display according to item 17. (Item 20) The foveated display according to item 19, wherein the mechanical structure is operable to modify an angle associated with the periphery of the waveguide layer. (Item 21) 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 in 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, including, placing the cast polymer waveguide on a first mold, the first mold having 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 aligned perpendicular to the flat portion of the first mold and the second region is aligned perpendicular to the uniformly spherical portion, flat portion including, and placing a second mold on the polymer waveguide, wherein the second mold is aligned perpendicular to the polymer waveguide and the first mold, and the second mold includes an opening defined by at least half of the circular base of the uniformly spherical portion of the first mold and a first section of the opening surrounding the light output surface, and at least half of the flat portion and a second section of the opening surrounding the light input surface including an opening configured across the polymer waveguide defined by, and applying a thermal cycling process to heat the first and second molds to a threshold temperature at which the polymer waveguide is deformed into the 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 curvature / flat transition between the first region and the second region is shorter than the distance D to make, and including, a method. (Item 22) The method according to item 21, wherein the substantially uniform surface topology is a flat surface topology. (Item 23) The method according to item 21, wherein the substantially uniform surface topology is an omnipresently spherical surface topology. (Item 24) The method according to item 21, wherein the polymer waveguide is in a teardrop shape. (Item 25) The method according to item 21, wherein the thermal cycling process is a post-annealing process and the threshold temperature is 120°C. (Item 26) The method according to item 21, wherein the light input surface is an internal coupling grating (ICG). (Item 27) The method according to item 21, wherein the light output surface is a combined pupil expander (CPE). (Item 28) The method according to item 21, wherein the flat portion is a portion where the polymer waveguide has a warp of less than 20 μm, a deflection of less than 20 μm, and a total thickness variation value of less than 1 μm. (Item 29) The method according to item 21, further including applying a uniform surface coating of an anti-adhesion compound to the polymer waveguide after casting, which operates to prevent the polymer waveguide from adhering to the first and second molds during the thermal cycling process. (Item 30) Applying raw material microparticles to one or more surfaces of the 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 adhering to the first and second molds during the thermal cycling process; The method according to item 21, further comprising. (Item 31) Inserting one or more fabrics between the polymer waveguide and the first and / or second molds, wherein the one or more fabrics are configured to prevent the polymer waveguide from adhering to the first and second molds during the thermal cycling process; The method according to item 21, further comprising. (Item 32) The method according to item 21, wherein the polymer waveguide is made of either a 1.72 polymer or a 1.75 polymer. (Item 33) The method according to item 21, wherein the polymer waveguide is a single layer of a multilayer eyepiece. (Item 34) Applying a rigid bonding material around at least a part of the second section to surround the light input surface, wherein the rigid bonding material bonds 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; further comprising, The method according to item 21, wherein the rigid bonding material prevents or reduces the movement of the light input surface as the polymer waveguide is dynamically deflected. (Item 35) A method, 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 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 are separated by a distance D; Placing a second mold on the polymer waveguide, wherein the second mold is vertically aligned with the polymer waveguide and the first mold, and the second mold includes an opening configured over the polymer waveguide defined by at least half of the circular base of the uniformly spherical portion of the first mold and a first section of the opening surrounding the light output surface; at least half of the flat portion and a second section of the opening surrounding the light input surface; and including an opening configured over the polymer waveguide defined thereby. Applying a thermal cycling process and heating to a threshold temperature to deform the first and second molds to the shape defined by the first and second molds for deforming the polymer waveguide, whereby, the polymer waveguide is flat in the first region, the polymer waveguide is uniformly spherical in the second region, the curvature / flatness transition between the first region and the second region is shorter than the distance D to be such that, A method comprising. (Item 36) The method according to item 35, wherein the polymer waveguide initially has a substantially flat surface topology. (Item 37) The method according to item 35, wherein the polymer waveguide initially has a substantially spherical surface topology. (Item 38) The method according to item 35, wherein the light input surface is an internal coupling grating (ICG). (Item 39) The method according to item 35, wherein the light output surface is a combined pupil expander (CPE). (Item 40) The method according to item 35, further comprising applying a uniform surface coating of an anti-sticking compound that operates to prevent the polymer waveguide from sticking to the first and second molds during the thermal cycling process to the polymer waveguide after casting.

Brief Description of the Drawings

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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 refractive power adjustment. The waveguide can propagate light towards the user's eye and simulate a light source at a distance from the user. Modifying the curvature of the flexible waveguide can enable two-mode or continuous simulations of various light sources at variable depths from the user's eye. Thus, the flexible waveguide can be used to propagate light towards the user's eye and simulate an image or object within a three-dimensional space in a VR or AR system.

[0081] As described herein, embodiments of the present invention are also referred to as polymer waveguides (implemented either as 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 to various continuous or discrete depth planes (e.g., distances from 0.2 m to infinity) without any refractive power, and providing various architectures for dynamically changing the curvature of the waveguide layer. In certain embodiments, different types of actuators are utilized as needed for a particular implementation to induce uniform stress and loading forces on the waveguide layer and provide a modification of the radius of curvature with high fidelity to the spherical surface.

[0082] In the embodiments described herein, an eyepiece lens characterized by an adjustable refractive power is achieved by curving the exit pupil expander (EPE) area of the eyepiece lens, and the radius of curvature is proportional to the focal length of the virtual image. By utilizing a polymer-based eyepiece lens having a Young's modulus value that is significantly lower than that of a glass-based eyepiece lens, some embodiments use reasonable and manageable forces / loads (e.g., <25 N) to induce a spherical curved surface (e.g., a radius of curvature of 0.3 m over an area of up to φ50 mm) within a flat polymer substrate (e.g., up to 0.5 mm thick). As described herein, when the force / load is released, the polymer substrate can restore its shape (e.g., to its original shape, to a curved shape, to a combination thereof, which can be a flat shape) by relaxing the stored strain energy. This mechanism is utilized to dynamically modulate the curvature of a waveguide layer (e.g., one or more polymer waveguide layers) between a first curvature state and a second curvature state (in either a continuous or discrete manner). 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 equivalent. 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. A 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 either increases or decreases. However, the present invention is not limited to this condition. For example, as more fully described 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 the actuation against the mechanical force can be utilized to achieve the full range of radius curvatures. As will be apparent to those skilled in the art, these embodiments will reduce or minimize the optical errors that typically accumulate as the waveguide layer is modified away from its nominal state.

[0084] Embodiments provide two-mode or continuous operation of one or more layers of a waveguide. The two-mode operation of a dynamic waveguide system can be interpreted to mean that the waveguide can transition between two discrete states: a static 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 modified 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, the two-mode operation can be implemented to cause two light sources to appear to the user simultaneously, with the distance of each light source defined by the radius of curvature of the waveguide in the two states. By refreshing or toggling the waveguide between two two-mode states at a rate faster than what can be perceived by the human eye (e.g., faster than a 60 Hz refresh rate), embodiments can enable the 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 depths greater than two. Instead of a "full or nothing" two-mode operation where the waveguide can exhibit one of two radius-of-curvature values corresponding to two discrete predetermined distances to the user's eye, the continuous operation of the waveguide can exhibit more than two radius-of-curvature values. The continuous operation of the dynamic waveguide system can implement a state between the natural rest state of the waveguide and the fully compressed or extended state of the waveguide, enabling the light source to be rendered at distances greater than two. For example, multiple light sources can be projected onto the user's eye, and they can appear to be projected simultaneously. A first light source can appear at 0.2 meters from the user's eye, a second light source can appear at 0.5 meters, and a third light source can appear at 1 meter. Each distance can correspond to a different radius-of-curvature value obtained by dynamically adjusting the waveguide between multiple states. In a similar way that the two-mode operation of the dynamic waveguide system can appear to render two light sources to the user in real time, the continuous operation of the dynamic waveguide system can render more than two light sources to the user in real time by toggling between each waveguide state at a rate faster than what the human eye can perceive.

[0086] Figure 1 schematically illustrates the optical path within a Visual Optical Assembly (VOA) that can be used to present a digital or virtual image to a viewer, according to an embodiment of the present invention. The VOA includes a projector 101 and an eyepiece 100 that can 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, namely, one set of eyepiece layers for each of the three primary colors configured to form a virtual image on one depth plane and another set of eyepiece layers for each of the three primary colors configured to form a virtual image on 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 may include 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 Figure 1, the projector 101 projects image light onto the internal coupling grating 107 within the eyepiece layer 100. The internal coupling grating 107 couples the image light from the projector 101 into a planar waveguide that propagates the image light in the direction towards 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 within the waveguide and redirects it towards the EPE region 109. The EPE region 109 includes a diffractive element that couples a portion of the image light propagating within the waveguide and directs it towards the viewer's eye 102 in a direction substantially perpendicular to the plane of the eyepiece layer 100. In this manner, the image projected by the projector 101 can be viewed by the viewer's eye 102.

[0088] The diffractive elements within the EPE region 109 of the eyepiece lens layer 100 typically comprise a grating, e.g., a periodic structure formed on the surface of a planar waveguide within the eyepiece lens. As a light beam 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 closely spaced output beams. The relative refractive power directed to each of the diffracted orders is determined by the shape and nature of the surface profile of a single grating period.

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

[0090] The internally coupled light 222 can be diffracted in a certain direction within the waveguide not only in the range depicted by the fan pattern 224 that travels from the ICG 220 towards the OPE 230 in the approximate +x direction, but also in the range extending to the fan pattern 226 that moves away from the OPE 230 in the approximate -x direction. Other optical paths extending to other fan patterns are, of course, also conceivable as possibilities and depend on the specific grating and diffraction pattern constituted 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, the sampling of the gradual dispersion of a portion of the image light can create a distribution pattern of beamlets that gradually expands across the eyepiece lens. The internally coupled light 222 diffracted within the depicted fan pattern 224 generally follows the optical path 228, enters the OPE 230, traverses in the +x direction, and as it impinges on the diffraction grating constituting the OPE 230, it is accompanied by parasitic dispersion sampling through the OPE 230, and a portion can be directed downward towards the EPE 240 and traverse in the -y direction before being externally coupled in the -z direction towards the user's eye periodically.

[0091] As depicted in FIG. 2, much of the light within the wavelength corresponding to the waveguide 212 can be lost either due to directivity losses such as light diffracted into the fan pattern 226 or due to capture losses resulting from the OPE 230 being improperly positioned or sized to capture all the light within the fan pattern 224. A detailed description of the eyepiece lens is provided in U.S. Patent Application Publication No. 15 / 683,624, the content of which is incorporated by reference for all purposes.

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

[0093] Figure 3B illustrates an example of an optical path 328 within a waveguide 300, according to an embodiment of the present invention. The optical path 328 includes incident light (shown as 328A) that is coupled into the substrate 302 at the ICG 320. The internally coupled light (shown as 328B) propagates towards 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 (shown as 328C), and subsequently diffracted by the EPE grating 353 from the waveguide 300 towards the user's eye in the -z direction (shown as 328D). Similarly, the internally coupled light (shown as 328B) may alternatively encounter the second OPE grating 352 and be diffracted in the -y direction (shown as 328E). The light diffracted in the -y direction (shown as 328E) may be diffracted by the EPE grating 353 from the waveguide 300 towards 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 controlled 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% probability 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] The waveguide 300 is illustrated as having only a single ICG 320, but in some embodiments, the waveguide 300 may preferably include a second ICG on the combined OPE / EPE region 350 opposite the ICG 320. The second ICG may be the same in form and function as the ICG 320, or may be a mirrored version of the ICG 320. For example, while the ICG 320 is configured to diffract internally coupled light related to the projected image into the substrate 302, the second ICG 320 may be configured to diffract internally coupled light related to a mirrored version of the projected image (e.g., inverted in the x direction). In contrast to the optical path 328 associated with the ICG 320, the optical path associated with the second ICG may include incident light that is coupled into the substrate 302 at the second ICG. The internally coupled light propagates towards the 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 subsequently diffracted by the EPE grating 353 from the waveguide 300 towards the user's eye in the -z direction. Similarly, the internally coupled 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 from the waveguide 300 towards the user's eye.

[0095] Further details regarding other waveguide topologies are described in U.S. Patent Application No. 15 / 683,623, which is incorporated by reference above.

[0096] FIG. 4 is a simplified cross-sectional view of a waveguide layer of an eyepiece lens 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 be incident on 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 towards a user's eye 410. As shown in FIG. 4, a certain surface profile is provided on the waveguide layer 404. In some embodiments, the surface profile forms a curve, which can be defined by a radius of curvature for a certain spherical curvature. In other embodiments, the surface profile 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 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 the output light ray 403. For low levels of curvature, the input surface 406 and the output surface 408 are parallel to each other at positions across the waveguide layer. Thus, as light propagates through the waveguide layer by TIR, the parallel nature of the waveguide surface preserves the reflection angle during TIR such that the angle between the output light ray and the output surface is preserved across the waveguide layer. Since the surface normal varies slowly across the output surface of the curved waveguide layer, the output light ray also varies slowly, producing the divergence illustrated in FIG. 4.

[0098] The divergence of the output light ray 403 resulting from the curvature of the output surface 408 can have the effect of rendering the input light beam 402 such that it appears to originate from a point source located at a specific distance behind the waveguide layer 404. Thus, the surface profile or curvature provided on the waveguide layer 404 produces light divergence towards the user's or viewer's eye 410 and effectively renders the light as originating from a depth plane located behind the waveguide layer.

[0099] The distance from the waveguide layer at which the input optical beam appears to originate can be associated with the radius of curvature of the waveguide layer 404. Waveguides with higher radii of curvature can render the light source to appear to emit at a greater distance from the waveguide layer than waveguides with lower radii 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 flexure of the waveguide layer 404 up to 0.4 mm across an EPE having a lateral dimension (e.g., length or width) of 40 mm. Assuming the native curvature of the waveguide layer 404, the input optical beam 402 appears to originate at a distance of 0.5 m from the waveguide layer 404. As another example, another waveguide layer can be operated to render a light source that appears to the user to emit at a distance of 0.2 meters from the waveguide layer and has a radius of curvature of 0.2 m. Thus, by taking advantage of a small amount of curvature, i.e., a fraction of a millimeter of flexure, across a waveguide layer of tens of millimeters in length / depth that is compatible with the waveguide layer material, functionality in the depth plane can be implemented for a two-dimensional extended waveguide, also referred to as a two-dimensional waveguide. The curvature utilized in accordance with embodiments of the present invention generally has a flexure of a few millimeters (e.g., 1-5 mm) and is used within various commercial products including sunglasses, vehicle windshields, and the like. Thus, the small amount of curvature utilized in various embodiments of the present invention does not degrade the optical performance of the eyepiece, introducing, for example, less than 0.1 arc minute of blur into the central field of view and less than 2 arc minutes of blur across the field of view of an eyepiece with a 0.5 m radius of curvature.

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

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

[0102] In some embodiments, the radius of curvature of the waveguide layer, which can 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 lens (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 depth planes from 0.1 m to infinity, including all depth planes typically utilized in extended or mixed reality applications. The surface profile of the waveguide layer, e.g., a flexible polymer waveguide layer, can be adjusted using various methodologies and mechanisms, as will be described in more detail throughout this specification.

[0103] In some of the embodiments described below, a dynamic eyepiece lens is provided, in which the depth plane of the eyepiece lens can be varied to display virtual content on different depth planes, for example, in time-varying as a function of time. Thus, subsequent frames of the virtual content can be displayed to appear to originate from different depth planes. However, static implementations are also included within the scope of the present invention. In these static implementations, a fixed and predetermined surface profile or curvature is provided on the waveguide layer of the eyepiece lens, thereby presenting the virtual content on a fixed depth plane. In contrast to systems that utilize external lenses, diffractive lenses, or other optical elements, embodiments that utilize static implementations can implement the depth plane through the curvature of the waveguide layer, reducing system complexity and improving optical quality. Further, some embodiments can implement a set of eyepiece lenses, each eyepiece lens including a stack of curved waveguide layers that provide two static depth planes. As an example, a first stack of three curved waveguide layers can implement a three-color scene on a depth plane positioned at 1 m using a deflection of 0.2 mm across the width / length of the waveguide stack, and a second stack of three curved waveguide layers can implement a second three-color scene on a depth plane positioned at 0.5 m using a deflection 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 profile 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, effect a crimping on the waveguide layer that results in an adjustment to the surface profile 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 mechanisms, namely, an upper crimping mechanism 602 and a bottom crimping mechanism 604. In FIG. 6A, the two ring-shaped crimping mechanisms are positioned in a non-actuated configuration, thereby enabling the waveguide layer 606 to assume a first surface profile, e.g., a planar surface profile or a surface profile with a small intrinsic curvature. The periphery of the waveguide layer 606 can be positioned or otherwise aligned between the bottom surface of the upper crimping mechanism 602 and the upper surface of the bottom crimping mechanism 604. The bottom surface of the upper crimping mechanism 602 and the upper surface of the bottom crimping mechanism 604 can be angled complementary to each other. Additional explanations of the crimping mechanism are provided in connection with FIGS. 6C and 6D.

[0105] FIG. 6B illustrates a cross-sectional view of a second configuration of a system for dynamically adjusting the surface profile of the waveguide layer illustrated in FIG. 6A. As shown in FIG. 6B, the upper crimping mechanism 602 and the bottom crimping mechanism 604 can be actuated to apply mechanical force against the periphery of the waveguide layer 606. As shown in FIG. 6B, the actuation of the two ring-shaped crimping mechanisms applies mechanical force to the periphery of the waveguide layer 606, which bends in response to the mechanical force at an angle equal to the angle defined by the complementary shapes of the upper crimping mechanism 602 and the bottom crimping mechanism 604. Thus, adjusting the waveguide layer 606, for example, from a planar surface profile to a curved surface profile by applying mechanical force to the periphery of the waveguide layer can adjust the radius of curvature of the waveguide layer. The angles defined by the upper crimping mechanism 602 and the bottom crimping mechanism 604 can be predefined by the structures of the upper crimping mechanism 602 and the bottom crimping mechanism 604 such that different structures that can provide different surface profiles resulting in the production of different depth planes can be machined for various applications. The 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 profile, for example, a plane as illustrated in FIG. 6A.

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

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

[0108] Utilizing a variable surface profile structure as shown in FIGS. 6A and 6B provides a dynamic eyepiece lens in which the depth plane of the eyepiece lens can be varied such that virtual content is displayed on different depth planes. Thus, for example, a time-division multiplexing technique can be utilized to display virtual content that appears to originate from different depth planes using a single eyepiece lens containing three waveguide layers, each associated with a primary color. The embodiments shown in FIGS. 6A and 6B provide two different depth planes, but other implementations allow for continuous variation in the surface profile, thereby providing a dynamic eyepiece lens with continuous depth plane variation. Additionally, the virtual content can be shifted to different depth planes as a function of user movement, such as when the user blinks or the equivalent. Since the current depth plane associated with the eyepiece lens can be correlated with the virtual content to be displayed, 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] Referring again to FIG. 6C, mechanical force can be uniformly applied to the periphery of the waveguide layer 606 through the operation of the upper crimping mechanism 602 and the lower crimping mechanism 604 (not shown). In this embodiment, the annular shape of the two ring-shaped crimping mechanisms conforms to the shape of the waveguide layer 606. In other embodiments, the crimping mechanism can be shaped to conform to a waveguide layer having a shape other than circular.

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

[0111] The fixed portion 612 of the waveguide layer can be attached to a part of the waveguide layer 610 or otherwise held in place adjacent to 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 profile of the waveguide layer in the vicinity of the ICG 613, the fixed portion 612 is utilized to maintain the surface profile of the main portion of the waveguide layer within the fixed surface profile. In other embodiments, the fixed portion, as will be discussed in more detail in relation to FIG. 16, for example, utilizes one or more shims between the waveguide layers such that a part of the waveguide layer 610 adjacent to the fixed portion 612 can bend or remain in its original condition without interference from the fixed portion 612, thereby loosely holding the waveguide layer 610 in place.

[0112] The upper 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 upper C-shaped crimping mechanism 608 can adjust the surface profile 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 example. The use of a C-shaped crimping mechanism as shown in FIG. 6D allows a sufficient portion of the periphery of the waveguide layer to be oriented at a predetermined angle such that, independent of the operation of the profile crimping system, while a part of the waveguide layer is maintained on the fixed surface, the viewing area of the eyepiece is characterized by a surface profile or curvature that is uniform across the width / length of the viewing area. In embodiments utilizing multiple waveguide layers, the C-shaped crimping mechanism 608 can incorporate shims or other flexible meshing surfaces to allow adjacent waveguide layers to slide and / or rotate independently of each other, as will be described in more detail in relation to FIG. 16.

[0113] In some embodiments, a portion of the crimping mechanism can be segmented so that variable mechanical forces can be applied to different portions along the periphery of the waveguide layer. For example, an annular-shaped crimping mechanism can be branched and separated into quadrants, or any number of segments having the same or different crimping angles. The various segments 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 the 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 be less curved or bent into a planar state. FIG. 6E illustrates a cross-sectional view of a third configuration of a system for dynamically adjusting the surface profile 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 profile of the waveguide layer shown in FIG. 6E. As shown in FIGS. 6E and 6F, the waveguide layer 618 can be curved with a predetermined surface profile, for example, a predetermined radius of curvature. The waveguide layer can then be positioned between two ring-shaped crimping mechanisms, namely, an upper crimping mechanism 614 and a bottom crimping mechanism 616, in a manner similar to the embodiments described in connection with FIGS. 6A-6B. In FIG. 6E, the two ring-shaped crimping mechanisms are positioned in a non-operating configuration, thereby allowing the waveguide layer 618 to take on a curved surface profile associated with a first surface profile, for example, 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 upper crimping mechanism 614 and the upper surface of the bottom crimping mechanism 616. The periphery of the waveguide layer 618 can contact the annular-shaped upper crimping mechanism 614 or the complementary-shaped bottom crimping mechanism 616. The bottom surface of the upper crimping mechanism 614 and the upper surface of the bottom crimping mechanism 616 can be angled complementary to each other. These complementary surfaces of the crimping mechanism are 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 examples, the complementary surfaces can be angled to bend the waveguide layer 618 at an angle smaller than the predetermined surface profile of the waveguide layer 618 to produce a reduced radius of curvature. As shown in FIG. 6F, the actuation of the two ring-shaped crimping mechanisms 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 upper crimping mechanism 614 and the bottom crimping mechanism 616. Thus, by applying a mechanical force to the periphery of the waveguide layer, the waveguide layer 618 can be adjusted, for example, from a curved surface profile to a planar surface profile, which can adjust the radius of curvature of the waveguide layer.The angles defined by the upper crimping mechanism 614 and the bottom crimping mechanism 616 can be pre-defined by the structure of the upper crimping mechanism 614 and the bottom crimping mechanism 616 such that different structures, which can provide different surface profiles resulting in the production of different depth planes, can be processed for various applications. The release of the operation of the two ring-shaped crimping mechanisms removes the mechanical force at the periphery of the waveguide layer, which returns to the original surface profile, for example, the curvature shown in FIG. 6E.

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

[0116] Figure 7A illustrates a cross-sectional view of a first configuration of a system for dynamically adjusting the surface profile of a waveguide layer, according to some embodiments. As shown in Figure 7A, a vacuum chuck system is utilized to dynamically adjust the surface profile or curvature of the waveguide layer. The discussions provided in relation to Figures 6A-6F are applicable, as necessary, to the embodiments illustrated in Figures 7A-7D. For example, the bonding mechanism illustrated in Figure 6A is replaced with a vacuum chuck system as illustrated in Figure 7A. In the embodiments illustrated in Figures 7A-7D, the waveguide layer is positioned or otherwise installed on top of the vacuum chuck mechanism.

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

[0118] The upper surface of the fixed portion 706 is inclined at a predetermined angle similar to the upper surface of the bottom bonding mechanism 604 illustrated in Figure 6A. Prior to operation, the outer periphery of the waveguide layer 702 is positioned above the outer periphery of the upper surface of the fixed portion 706, as illustrated by the vertical gap between these portions in Figure 7A. The inner periphery of the waveguide layer 702 contacts the upper 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] Figure 7B illustrates a cross-sectional view of a second configuration of a system for dynamically adjusting the surface profile of the waveguide layer illustrated in Figure 7A. In Figure 7B, a vacuum force is applied to the periphery of the waveguide layer 702 in response to the operation of the vacuum chuck mechanism 704. In response to the vacuum force, the outer periphery of the waveguide layer 702 is brought into contact with the outer periphery of the upper 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 in the fixed portion 706 applies a mechanical force to the periphery of the waveguide layer 702, which, in response to the mechanical force, bends at an angle equal to the angle defined by the shape of the upper surface of the fixed portion 706. Thus, by applying a mechanical force to the periphery of the waveguide layer, the waveguide layer 702 can be adjusted, for example, from a planar surface profile to a curved surface profile, which can adjust the radius of curvature of the waveguide layer. The angle defined by the upper surface of the fixed portion 706 can be predefined by the structure of the vacuum chuck mechanism 704 such that different structures that can provide different surface profiles that result in the production of different depth planes can be machined for various applications. Releasing the vacuum chuck mechanism 704 removes the mechanical force at the periphery of the waveguide layer, which returns to its original surface profile, for example, a plane as illustrated in Figure 7A.

[0120] The vacuum chuck mechanism 704 illustrated in Figures 7A and 7B can bend a planar waveguide layer such that it is characterized by a surface profile 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 profile 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 profile of the waveguide layer illustrated in FIG. 7C. As illustrated in FIG. 7C, the waveguide layer 708 can have an original, i.e., stationary, 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 circumference of the waveguide layer 708 is positioned above the inner circumference of the upper surface of the fixed portion 712, as illustrated by the vertical gap between these portions in FIG. 7C. The outer circumference of the waveguide layer 708 contacts the upper surface of the fixed portion 712. Thus, in this third configuration, the curved waveguide layer can be supported by the vacuum chuck mechanism 710 and maintain its curved surface profile.

[0122] As illustrated in FIG. 7D, when the vacuum chuck mechanism 710 is actuated, the 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 substantially planar shape. According to an embodiment of the present invention, the application of a bending moment at the periphery of the waveguide layer results in a uniform modulation of the surface profile or curvature of the waveguide layer across the width / length of the waveguide layer and the aperture area of the associated eyepiece lens.

[0123] The vacuum chuck mechanism 704 can be in an annular shape so as 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 chuck mechanism 704 can be in a C shape around a teardrop-shaped waveguide, similar to the C-shaped crimping mechanism illustrated in FIG. 6D. Further, in an alternative embodiment, a portion of the vacuum chuck mechanism can be segmented or divided such that variable mechanical forces can be applied to different portions along the periphery of the waveguide layer. For example, an annular-shaped vacuum chuck mechanism can be branched and separated into quadrants, or any number of segments having the same or different angles, and accordingly, the periphery of the waveguide is bent. The various segments of the vacuum chuck mechanism can be activated simultaneously, alternately, or in combination such that some portions of the periphery of the waveguide layer can be vacuum chucked and some portions can remain unchucked. This can enable the movement or positioning of virtual content across a range at different depth planes from the user's line of sight.

[0124] The embodiments illustrated by FIGS. 7A-7D can provide operation in a two-mode fashion, meaning that the vacuum chuck mechanism can switch the waveguide layer between two discrete states, thereby rendering the 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, i.e., "flat", mode and can then be bent 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 can then be bent to operate in a planar, i.e., "flat", mode, and vice versa. In other examples, the waveguide can have a predetermined radius of curvature and can be bent to have a different radius of curvature, either lower or higher, depending on a predetermined angle of the vacuum chuck mechanism.

[0125] FIG. 8A illustrates a cross-sectional view of a first configuration of a pneumatic bladder system for dynamically adjusting the surface profile of a waveguide layer, according to some embodiments. As shown in FIG. 8A, the pneumatic system includes a pneumatic chamber 802 and lenses L1, L2. The pneumatic chamber 802 includes a left chamber portion 804, a right chamber portion 806, and a waveguide layer 810, shown as a pre-curved polymer waveguide layer. The waveguide layer 810 is sealed within an airtight enclosure of the pneumatic chamber 802. The left chamber portion 804 and the right chamber portion 806 are sealed from each other, and thus, different pressures can be applied within each chamber portion. The waveguide layer 810 is substantially rigid, but can be inverted to substantially equal and opposite curvatures. Increasing or decreasing the pressure within the left chamber portion 804 or the right chamber portion 806, depending on the level of the pressure pre-existing within each chamber portion, inverts the waveguide layer 810 and reverses the curvature of the waveguide layer 810, as will be explained below in connection with FIG. 8B. The pressures within the left chamber portion 804 and the 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 profile of the waveguide layer illustrated in FIG. 8A. To toggle the waveguide layer 810 from the first configuration as illustrated in FIG. 8A to the second configuration as illustrated in FIG. 8B, a pressure change can be induced within either the left chamber portion 804 and / or the right chamber portion 806. For example, the pressure within the right chamber portion 806 can be increased to invert the curvature of the waveguide layer 810 to that illustrated in FIG. 8B. Alternatively, the pressure within the left chamber portion 804 can be decreased to invert the curvature of the waveguide layer 810 to that illustrated in FIG. 8B. As another example, the pressure values within the left chamber portion 804 and the right chamber portion 806 can be modified simultaneously and in reverse to toggle the states illustrated by FIGS. 8A and 8B. The embodiments illustrated in FIGS. 8A and 8B are energy efficient as a result of power being utilized only during the state change of the waveguide layer 810.

[0127] In an exemplary embodiment, the lenses L1, L2 have complementary lens functions that are used to achieve two depth planes without affecting the 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 the 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 that appears to originate at infinity (i.e., the far plane). Referring to FIG. 8A, world light passes through the lens L2, which has a refractive power of +0.75D, with little or no perturbation as discussed in relation to FIG. 5, and is focused as it passes through the curved surface of the waveguide layer 810 and defocused as it passes through the lens L1, which has a refractive power of -0.75D. Thus, the combination of the lens L2, the waveguide layer 810, and the lens L1 enables world light to be viewed by the user without refractive power.

[0128] Referring to FIG. 8B, when the waveguide layer 810 is inverted to the second configuration illustrated in FIG. 8B, the waveguide layer 810 has a refractive power of -0.75D. In this second configuration, the virtual content is projected from the waveguide layer 810 and is defocused as it 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 proximity plane). Therefore, the virtual content is presented at infinity in the first configuration and at 0.67 m in the second configuration. As discussed above, since the world light passes through the curved surface of the waveguide layer 810 with little or no disturbance in the second configuration, as discussed in relation to FIG. 5 for the first configuration, the world light is presented to the user without the refractive power applied thereto.

[0129] The embodiments described in connection with FIGS. 8A and 8B can provide operation in a two-mode or bistable mode by varying the pressure value in the pneumatic chamber 802, which means that the waveguide layer can be switched between two discrete states, thereby rendering the projected virtual content at two different discrete depths from the user's line of sight. For example, as illustrated in FIGS. 8A and 8B, the waveguide layer 810 can operate in a curved mode and then be inverted and operate in an inverted curved mode. As discussed in relation to 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 attached to a layer formed using an electroactive polymer (EAP). The EAP can be joined to the waveguide layer by an 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 ionomers such as Nafion, Flemion, polyvinyl alcohol (PVA) gels, acrylamide and vinyl derivative copolymers, copoly(Aam / vdMG) gels, ProDOT-(CH3), polyacrylamide gels, polypyrrole (PPy), and polyaniline (PANI). The EAP can have an original non-expanded state having a certain width. Subsequently, the EAP can expand when a voltage is applied to the EAP. Varying the applied voltage can enable 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 more fully described below, applying a variable voltage to the EAP attached to the waveguide layer can cause the waveguide to bend to a predetermined curvature or surface profile 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 profile of a waveguide layer, according to some embodiments. As shown in FIG. 9A, the periphery of the waveguide layer 902 is positioned on, joined to, or otherwise attached to one side of an EAP film 906, which can be a pre-stretched EAP film. The opposite side of the EAP film 906 is attached to a fixed frame structure 904. In the embodiment shown in FIG. 9A, the waveguide layer 902 has a curved or substantially planar surface profile, whereby it can be characterized by a large radius of curvature (e.g., 2.0 meters), which is typically suitable for providing acceptable focus adjustment. Generally, a certain curvature is desirable in this configuration to achieve predictable bending of the waveguide layer, as more fully described below.

[0132] Figure 9B shows a cross-sectional view of a second configuration of an EAP system for dynamically adjusting the surface profile of the waveguide layer illustrated in Figure 9A. In the second configuration illustrated in Figure 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 the voltage across the EAP film 906 linearly expands the EAP film 906 volumetrically inwardly toward the center of the waveguide layer 902. Thus, expanding the EAP film 906 inwardly compresses the waveguide layer 902, which is joined to the EAP film 906, 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 embodiment). When the applied voltage from the voltage source 908 is removed, the EAP film 906 contracts to return to its original state, thereby returning the waveguide layer 902 to its original uncompressed state as a result of the natural tensile strength of the waveguide layer 902.

[0133] In some exemplary embodiments, the applied voltage provided by voltage source 908 can be reduced or modified from the maximum applied voltage. Varying the voltage applied to EAP film 906 can compress waveguide layer 902 into a plurality of configurations corresponding to variable radius-of-curvature values such that each voltage level applied to EAP film 906 results in a different radius-of-curvature value presented by waveguide layer 902. Varying the voltage applied to EAP film 906 can thus enable continuous modulation of the curvature of waveguide layer 902. As a result, waveguide layer 902 is continuously modified through the structural operation of EAP film 906 and can project virtual content to the user at multiple depth planes. For example, the natural state of waveguide layer 902 can have a radius-of-curvature value appropriate for projecting virtual content emitted at a distance of 2 m from the eyepiece. A small voltage value can then be applied to EAP film 906 using voltage source 908 to slightly compress waveguide layer 902. This slight compression that reduces the radius of curvature of waveguide layer 902 can correspond to virtual content projected to occur at a distance closer to the user than 2 m (e.g., 1 m). A higher voltage can then be applied to EAP film 906 using voltage source 908 to compress waveguide layer 902 by a further amount. Further compressing waveguide layer 902 further reduces the radius-of-curvature value, which can be used to render virtual content emitted at a distance closer to the user than 1 m (e.g., 0.5 m). Continuously applying no voltage, a small voltage, and a higher voltage to the EAP film, for example, at a refresh rate of 90 Hz, enables the display of virtual content at three depth planes corresponding to 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 an applied voltage. Similarly, the decrease in the curvature of the waveguide layer can also be a linear function of the 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, the compression of the waveguide layer initially results in a linear decrease in the radius of curvature with an applied voltage, but then will become non-linear as the waveguide layer is further compressed. Accordingly, embodiments of the present invention can map the radius of curvature to the applied voltage and account for any non-linearity 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. When attached to the EAP film, the waveguide layer is stretched such that the radius of curvature is 2 m, partially flattening the waveguide layer. During operation, the first meter of variation in the radius of curvature is provided 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 profile of the waveguide layer shown in FIGS. 9A and 9B. As shown in FIG. 9C, the waveguide layer 902 is attached to an EAP film 906 that surrounds the waveguide layer 902 at a peripheral location and is attached to a fixed frame structure 904. The periphery of the waveguide layer 902 is circular in shape and is joined to an annular-shaped EAP film 906 that is joined to the fixed frame structure 904 in FIG. 9C, but embodiments of the present invention are not limited to this implementation. Although not shown 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, expanding the EAP film 906 inwardly from the fixed frame structure 904, thereby compressing the waveguide layer 902 inwardly toward the center of the system and continuously varying the radius of curvature of the waveguide layer 902 as shown in FIG. 9C.

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

[0138] Figure 9E illustrates a plan view of the components of an alternative EAP system for dynamically adjusting the surface profile of an alternative waveguide layer, according to some embodiments. Figure 9E illustrates a teardrop-shaped waveguide 914 that is joined to a circular-shaped EAP film 918 whose periphery is attached to a circular-shaped fixed frame structure 916. A voltage can be applied to the EAP film 918 in Figure 9E in the same manner as described with respect to Figure 9C, causing the EAP film to expand linearly and the waveguide layer to be compressed inwardly. Varying the width of the EAP film as a function of the 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 the radial position. Thus, a more uniform spherical curvature can be provided by embodiments of the present invention through the selection of the EAP film width. As will be apparent to those skilled in the art, the various shapes utilized for the EPA film and / or the fixed frame structure can affect the way in which the EAP film expands and applies different forces across the variable portion of the waveguide layer.

[0139] In some embodiments, a portion of the EAP film can be segmented so that variable mechanical forces 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 branched and separated into quadrants, or any number of segments. Each segment can be connected to one or more voltage sources, and in a given case, variable levels of voltage can be applied to different segments of the EAP film. The various segments of the EAP film can be actuated simultaneously, alternately, or in combination so that a portion of the EAP film can expand more or less inwards towards the waveguide than other portions of the EAP film. This can account for an EAP system with a component shape that varies in relation to the shape of the waveguide and reduces the focusing error. Varying the resistivity of a portion of the EAP film can produce a similar effect of 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 profile of a waveguide layer, according to some embodiments. As shown in FIGS. 10A-10B, the radial extension is used to dynamically adjust the surface profile, 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, joined to, or otherwise attached to the viscoelastic polymer layer 1006. The viscoelastic polymer layer 1006 can absorb energy and relieve stress and can be repeatedly stretched and relaxed for continuous operation. Examples of such viscoelastic polymer films include, but are not limited to, acrylic foams, PDMS, PVC, polyolefins, and polyethylene. The viscoelastic polymer layer 1006 can be joined to the waveguide layer 1002, which can be a polymer waveguide layer, by an adhesive or can be molded as an element of the waveguide layer 1002 directly during a casting process. The viscoelastic polymer layer 1006 can be attached to the support struts 1004 / 1009 and 1005 / 1007, which are mechanically coupled to a slotted disk, as will be more fully described below in connection with FIG. 10C.

[0141] The waveguide layer 1002 can be processed in a manner characterized by an initial curvature in the surface profile, e.g., having a predetermined radius of curvature, e.g., 0.3 m.

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

[0143] Figure 10C illustrates a plan view of the components of a mechanical system for dynamically adjusting the surface profile of the waveguide layer shown in FIGS. 10A and 10B. As shown in FIG. 10C, the radial extension of the viscoelastic polymer layer is implemented using a pair of disks, including an upper disk 1010 and a corresponding bottom disk (not shown). These disks have slots through which support struts 1004 / 1009 and 1005 / 1007 pass, respectively. The upper disk 1010 and the bottom disk (not shown) can rotate relative to each other around the center of the waveguide layer 1002. For example, the upper disk 1010 can rotate clockwise, and the bottom disk can rotate counterclockwise simultaneously, shifting the support struts from the first configuration shown in FIG. 10A to the second fully extended configuration shown in FIG. 10B. For example, as the upper disk 1010 and the bottom disk rotate relative to each other, the support strut 1005 can move along the slot 1012, and the support strut 1007 can move along the slot 1014. This mechanism is sometimes also referred to as a Longworth chuck. The mechanical force applied to the support struts by the rotating disks can move the support struts along the slots, which can increase the distance between the support struts and the center of the waveguide layer 1002. An increase in the distance from the center of the system to the support struts can radially extend the viscoelastic polymer layer 1006 and, thus, increase the radius of curvature of the waveguide layer 1002.

[0144] The mechanical (i.e., radial stretcher) system illustrated in FIGS. 10A - 10C can include any number of support struts and corresponding slots, depending on the application. For example, if the support struts are connected directly to the waveguide layer, more (e.g., greater than or equal to 8) support struts may be utilized to achieve uniform radial stretching, which can result in spherical curvature of the waveguide layer because the waveguide layer may not be as flexible as the viscoelastic polymer layer. When the mechanical (i.e., radial stretcher) 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 over the polymer waveguide.

[0145] In some implementations, along with the corresponding support struts, the stretching force applied by the rotational movement of the upper disk 1010 and the bottom disk can be applied at different force values in continuous operation, producing a plurality of waveguide configurations. Thus, the upper 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 static state) and the second configuration illustrated in FIG. 10B (i.e., the waveguide is stretched to a maximum value as the support strut reaches the end of the slot and positions the support strut at the maximum distance farthest from the center of the system). Varying the position of the support strut along the slot, which results in different stretching distances for the viscoelastic polymer layer, can stretch the waveguide layer into a plurality of states corresponding to variable surface profiles or radius of curvature values. As a result, the surface profile of the waveguide layer 1002 is continuously modified, and virtual content can be projected to the user at multiple depth planes. Releasing the force utilized to rotate the upper disk 1010 and the bottom disk can enable the viscoelastic polymer layer 1006 to contract via its tensile strength to return to its original configuration, which can return the waveguide layer 1002 to the first configuration illustrated in FIG. 10A. In an example where the waveguide layer is directly connected to the support strut without the use of a viscoelastic polymer layer, after releasing the stretching force generated by the rotating disk mechanism, the tensile force of the waveguide layer can contract the waveguide layer to its original state and pull the support strut back to the first non-stretched configuration. When all the support struts gradually move inwardly, both the viscoelastic polymer layer 1006 and the waveguide layer 1002 can be gradually restored to their original configurations.

[0146] In some embodiments, the slots in the top and bottom disks can be of different lengths and shapes such that the slots that run towards one side of the radial expander system are gradually longer than the slots that run towards the opposite side. Varying the slot size allows the waveguide and / or viscoelastic polymer layer to be non-circular in design and for certain portions of the waveguide and viscoelastic polymer layer to be stretched more than other portions, thereby enabling a uniform stress distribution to be achieved and used in applications. Note that an alternative embodiment can also be implemented where a first configuration is characterized by a larger radius of curvature, a second configuration is characterized by a smaller radius of curvature, and the mechanical system compresses the waveguide layer during a 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 profile of a waveguide layer, according to some embodiments. As will be apparent to those skilled in the art, the system that utilizes the stretching of the 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 necessary. As illustrated in FIG. 11A, the periphery of the waveguide layer 1102 can be positioned, joined to, or otherwise attached to the 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 profile of the waveguide layer illustrated in FIG. 11A. A fixed frame 1106, which can have an annular or ring shape and has a diameter smaller than that of the actuator 1108, can be positioned under the waveguide layer 1102. The waveguide layer 1102 can be fabricated in a manner characterized by an initial curvature in the surface profile having, for example, a predetermined radius of curvature, for example, 0.3 m. Referring to FIG. 11B, as the actuator 1108 moves coaxially with respect to the fixed frame 1106, the viscoelastic polymer layer 1104 uniformly stretches around and beyond the edge of, for example, the fixed frame 1106, thereby stretching the waveguide layer 1102 radially outward into a planar, substantially planar, or less curved configuration. Thus, by pulling the actuator 1108 downward, continuous variation of the surface profile of the waveguide layer 1102 can be achieved. To decrease the radius of curvature, upward movement of the actuator 1108 enables 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 can be used in these and similar embodiments can include, but are not limited to, voice - coil actuators, piezoelectric actuators, air cylinders, and the like. Embodiments of the present invention thus enable a compact design where vertical movement of the actuator results in horizontal stretching of the waveguide layer.

[0149] FIG. 11C illustrates a plan view of components of an alternative mechanical system for dynamically adjusting the surface profile of the waveguide layer illustrated in FIGS. 11A and 11B. As illustrated in FIG. 11C, the waveguide layer 1102 is attached to an annular-shaped viscoelastic polymer layer 1104 that surrounds the waveguide layer 1102 and is attached to an actuator 1108 at a peripheral location. The periphery of the waveguide layer 1102 is circular in shape and, in FIG. 11C, is joined to the annular-shaped viscoelastic polymer layer 1104 that is joined 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 varying the radius of curvature of the waveguide layer 102 as illustrated.

[0150] FIG. 11D illustrates a plan view of components of another alternative mechanical system for dynamically adjusting the surface profile 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 that is joined to a corresponding teardrop-shaped viscoelastic polymer layer 1112 that is attached to a teardrop-shaped actuator 1114. In a manner similar to that discussed in relation to FIG. 11C, actuation of the actuator results in compression of the waveguide layer and modification of the surface profile of the waveguide layer.

[0151] FIG. 11E illustrates a plan view of components of yet another alternative mechanical system for dynamically adjusting the surface profile of an alternative waveguide layer, according to some embodiments. FIG. 11E illustrates a teardrop-shaped waveguide 1116 joined to a circular-shaped viscoelastic polymer layer 1118 whose periphery is attached to a circular-shaped actuator 1108. As illustrated in FIG. 11B, actuation of actuator 1108 linearly expands the viscoelastic polymer layer and stretches the waveguide layer outwardly. 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 those skilled in the art, the various shapes utilized for the viscoelastic polymer layer and / or the fixed frame / actuator structure can affect the way in which the viscoelastic polymer layer expands and applies different forces across the variable portion of the waveguide layer.

[0152] In some examples, a portion 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, an annular-shaped or teardrop-shaped viscoelastic polymer layer can be branched and separated into quadrants, or any number of segments. Each segment is connected to one or more actuators and, in a given case, a variable level of tension can be applied to different segments of the viscoelastic polymer layer. The various segments of the viscoelastic polymer can be actuated simultaneously, alternately, or in combination so that a portion of the viscoelastic polymer layer expands outwardly such that it is more or less away from the waveguide layer than other portions of the viscoelastic polymer layer. This can account for focusing errors and a viscoelastic polymer layer system with component shapes that vary in relation to the shape of the waveguide layer.

[0153] The waveguide layer can be continuously extended to a planar or substantially planar position to achieve a plurality of states having various radius-of-curvature values. In some implementations, the extension force applied by the movement of actuator 1108 can be applied at different force values in a continuous operation to produce a plurality of waveguide configurations. Thus, actuator 1108 can be positioned at any position between a first configuration illustrated in FIG. 11A (i.e., the waveguide layer 1102 is in a stationary state) and a second configuration illustrated in FIG. 11B (i.e., the waveguide is extended to a maximum value as the actuator reaches its final position). Varying the position of the actuator along its range of motion, which results in different extension distances for the viscoelastic polymer layer, can extend the waveguide layer to a plurality of states corresponding to variable surface profiles or radius-of-curvature values. As a result, the surface profile of the waveguide layer 1102 is continuously modified, and virtual content can be projected to the user at a plurality of depth planes. Releasing the force utilized to pull actuator 1108 downward can, through its tensile strength, enable the viscoelastic polymer layer 1104 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 profile of a waveguide layer, according to some embodiments. As illustrated in FIG. 12A, the periphery of the waveguide layer 1202 is positioned against, joined to, or otherwise attached to the inner portion of a ring actuator 1204. In the embodiment illustrated in FIG. 12A, the waveguide layer 1202 has a curved or substantially planar surface profile, and thereby can be characterized by a large radius of curvature (e.g., 2.0 meters), which is typically suitable for providing acceptable depth-of-field adjustment. Generally, a certain curvature is desirable in this configuration to achieve predictable bending of the waveguide layer, as more fully explained below.

[0155] The outer portion of the ring actuator 1024 is attached to the fixed frame structure 1208. The ring actuator 1204 can be radially, repeatedly expanded or contracted for continuous modulation of the surface profile 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 the sake of clarity. The waveguide layer and the ring actuator can be processed separately and then joined together or processed as a single unit depending on the particular fabrication process utilized.

[0156] Referring to FIG. 12A, the outer portion of the ring actuator 1204 is attached or pinned to the fixed frame structure 1208 via a rotating mechanism 1206 (e.g., a hinge) that acts as a support collar. Thus, the ring actuator 1204 can rotate about the rotating 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 substantially 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 be more substantially curved than when the ring actuator is not contracted as much. As shown in FIG. 12A, the dashed lines represent the possible configurations of the waveguide layer 1202 when the ring actuator 1204 is in various expanded or contracted states.

[0157] FIG. 12B illustrates a plan view of components of a lateral actuation system for dynamically adjusting the surface profile of the waveguide layer illustrated in FIG. 12A. In the embodiment illustrated in FIG. 12B, the circular waveguide layer 1202 is positioned with respect to and bonded to a ring actuator 1204 that is in an annular shape. The ring actuator 1204 can expand toward the center of the waveguide layer 1202 to reduce the radius of curvature of the waveguide layer 1202, and contract outward from the center of the waveguide layer 1202 to flatten the waveguide layer 1202 and increase the radius of curvature. Thus, the waveguide layer 1202 can be continuously flattened to a planar or substantially planar position, or induced to curve at various radius of curvature values by lateral or radial movement of the ring actuator 1204, thereby achieving a plurality of waveguide configurations in continuous operation. Varying the contraction / expansion of the ring actuator along its range of motion can stretch the waveguide layer into a plurality of states corresponding to variable surface profiles or radius of curvature values. As a result, the surface profile of the waveguide layer 1202 is continuously modified, and virtual content can 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 segmented into a plurality of segmented sections such that variable mechanical forces can be applied to different portions along the periphery of the waveguide layer. In some embodiments, different materials or actuator types can be used in any combination for each of the segmented sections for a given application. The various sections of the ring actuator can be actuated simultaneously, alternately, or in combination such that a portion of the ring actuator can expand further or less away from the waveguide layer than another portion of the ring actuator. This can account for ring actuator systems with component shapes that vary in relation to the shape of the waveguide layer to reduce focusing errors.

[0159] FIG. 13A illustrates a cross-sectional view of a first configuration of a plurality of ring systems for dynamically adjusting the surface profile of a waveguide layer, according to some embodiments. As shown 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 will be fully described below. The plurality of ring systems shown in FIGS. 13A and 13B may also be referred to as an on-ring ring system. The inner circumference of the waveguide layer 1302 can be positioned relative to the surface of an extending portion 1305 of the actuator 1304, and the outer circumference of the waveguide layer 1302 can be positioned relative to the surface of the fixed frame 1306, e.g., the bottom surface 1307 of the fixed frame 1306. In the embodiment shown in FIG. 13A, the waveguide layer 1302 has a planar or substantially planar surface profile, whereby it can be characterized by a large radius of curvature (e.g., 2.0 meters), which is typically suitable for providing acceptable range adjustment. The actuator 1304 can be coupled to the fixed frame 1306 through a positioning mechanism that can 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] FIG. 13B illustrates a cross-sectional view of a second configuration of a plurality of ring systems for dynamically adjusting the surface profile 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 the 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 extending portion 1305 of the actuator 1304 applies a mechanical force in an opposing direction to the inner periphery of the waveguide layer 1302. This angularly positions 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 extending 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 reduced 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 the gradually increasing distance between the actuator 1304 and the fixed frame 1306, the waveguide layer 1302 can gradually return to its original planar or substantially planar state as illustrated in FIG. 13A by releasing its stored strain energy. In some exemplary embodiments, the waveguide can be pre-curved, and the actuator and the fixed frame can apply mechanical forces to the outer and inner peripheries of the waveguide, similar to that described, to reduce the angle at which the waveguide is bent and to flatten the waveguide to a planar or more substantially planar state.

[0161] As an example, sometimes, the extending portion 1305 of the actuator 1304, also sometimes referred to as a lever arm, has a length of 0.8 mm, extends outwardly from the upper surface 1303 of the actuator 1304, and can contact the inner circumference of the waveguide layer 1302. An operating stroke of about 65 μm and an operating force of 22 N of the positioning mechanism can be used to flatten the 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 can be any suitable type of 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 circumferences of waveguide layer 1302 by actuator 1304 and fixed frame 1306 can be reduced or modified from a maximum applied force, which induces a minimum radius of curvature. Varying the distance between actuator 1304 and fixed frame 1306 can bend waveguide layer 1302 into a plurality of configurations corresponding to variable radius of curvature values such that each actuator / fixed frame distance results in a different radius of curvature value presented by waveguide layer 1302. Varying the actuator / fixed frame distance, which affects the forces applied to the inner and outer circumferences of waveguide layer 1302, can thus enable continuous modulation of the curvature of waveguide layer 1302. As a result, waveguide layer 1302 can be continuously modified through the operation of actuator 1304 to project virtual content to the user at multiple depth planes. For example, the natural state of waveguide layer 1302 can have a radius of curvature value appropriate for projecting virtual content emitted at a distance of 2 m from the eyepiece. The distance between actuator 1304 and fixed frame 1306 can be reduced to increase the bending moment at the periphery of waveguide layer 1302, thereby increasing the curvature of waveguide layer 1302. The increased bending moment that reduces the radius of curvature of waveguide layer 1302 can correspond to virtual content projected to occur at a distance closer to the user than 2 m (e.g., 1 m). The actuator / fixed frame distance can be further reduced to further bend waveguide layer 1302. Further bending of waveguide layer 1302 reduces the radius of curvature value, which can be used to render virtual content emitted at a distance closer to the user than 1 m (e.g., 0.3 m). Releasing the actuator and returning the distance between actuator 1304 and fixed frame 1306 to its first stationary configuration returns the stress energy of waveguide 1302 to its stationary configuration.For example, at a refresh rate of 90 Hz, continuously 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 enables the display of virtual content on three depth planes corresponding to three radii of curvature, which is achieved using the compression of an actuator against a fixed frame for angling the waveguide layer. Of course, these values are merely illustrative, and other depth planes can also be achieved using embodiments of the present invention.

[0163] FIG. 13C illustrates a plan view of components of a plurality of ring systems for dynamically adjusting the surface profile of the waveguide layer illustrated in FIGS. 13A and 13B. As illustrated in FIG. 13C, the fixed frame 1306 is positioned around the waveguide layer 1302 and contacts an outer portion of the periphery of the waveguide layer 1302. In FIG. 13C, a portion of the actuator 1304 is visible surrounding the periphery of the fixed frame 1306, but this is not required by the present invention, and a laterally compact design in which the outer perimeters of the actuator 1304 and the fixed frame 1306 are vertically aligned can also be utilized. The periphery of the waveguide layer 1302 is circular in shape and contacts an annular-shaped fixed frame 1306 that is coupled to the annular-shaped actuator 1304 in FIG. 13C, but embodiments of the present invention are not limited to this implementation. Although not illustrated in FIG. 13C, the fixed frame 1306 is coupled to the actuator 1304 by a positioning mechanism. The annular-shaped actuator 1304 and the fixed frame 1306 are ring-shaped and can be proportional to each other such that at least a portion of the actuator 1304 overlaps a portion of the fixed frame 1306.

[0164] Figure 13D illustrates a plan view of components of a plurality of ring systems for dynamically adjusting the surface profile of an alternative waveguide layer, according to some embodiments. As illustrated in Figure 13D, the waveguide layer 1308, which can be included in the eyepiece, can be characterized by a teardrop shape in plan view. Although the teardrop shape is illustrated in Figure 13D, embodiments of the present invention are not limited to this particular shape, and other shapes are also included within the scope of the present invention.

[0165] The fixed portion 1312 of the waveguide layer can be attached to a portion of the waveguide layer 1308 or otherwise held in place 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 profile of the waveguide layer in the vicinity of the ICG 1314, the fixed portion 1312 is utilized to maintain the surface profile of this portion of the waveguide layer within the fixed surface profile. In other embodiments, the fixed portion can, for example, utilize one or more shims between the waveguide layers to allow a portion of the waveguide layer 1308 adjacent to the fixed portion 1312 to bend or remain in its original condition without interference from the fixed portion 1312, thereby loosely holding the waveguide layer 1308 in place. The C-shaped actuator 1310 can then be coupled to the fixed portion 1312 and can completely surround the waveguide layer 1308 along the periphery of the waveguide layer. The C-shaped actuator 1310 can adjust the surface profile 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), as described in the previous example. The use of 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, independent of the operation of the system, while maintaining a portion of the waveguide layer in a fixed surface profile, the viewing area of the eyepiece is characterized by a surface profile or curvature that is uniform across the width / length of the viewing area.

[0166] In some exemplary embodiments, a portion of the fixed frame / actuator mechanism can be segmented such that variable mechanical forces can be applied to different portions along the periphery of the waveguide layer. For example, an annular-shaped actuator and fixed frame mechanism can be branched and separated into quadrants, or any number of segments having the same or different dimensions, which define the angle at which the periphery of the waveguide is bent. The various segments of the actuator and fixed frame mechanism can be activated simultaneously, alternately, or in combination such 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 profile of a waveguide layer, according to some embodiments. In some embodiments, the waveguide layer can be positioned between multiple sets of mating roller mechanisms that can operate to flatten or curve the waveguide layer and effect the adjustment on the radius of curvature of the waveguide layer. In FIG. 14A, the waveguide layer 1402, which can be a planar or relatively planar polymeric waveguide layer, is positioned between some mating cylindrical roll mechanisms, namely, between an upper roll mechanism 1404 mated with a bottom roll mechanism 1406 and between an upper roll mechanism 1408 mated with a bottom roll mechanism 1410. In FIG. 14A, the upper roll mechanisms 1404 / 1408 and the bottom roll mechanisms 1406 / 1410 are positioned in a non-operating configuration, thereby enabling the waveguide layer 1402 to take on a first surface profile, e.g., a planar surface profile or a surface profile with a small intrinsic curvature. The periphery of the waveguide layer 1402 can be positioned, clamped, or otherwise aligned between the upper roll mechanism 1404 and the bottom roll mechanism 1406 and between the upper roll mechanism 1408 and the bottom roll mechanism 1410. Additional explanation of the roller system is provided in connection with FIG. 14C.

[0168] FIG. 14B illustrates a cross-sectional view of a second configuration of a roller system for dynamically adjusting the surface profile of the waveguide layer illustrated in FIG. 14A. As shown in FIG. 14B, the upper roll mechanisms 1404 / 1408 and the bottom roll mechanisms 1406 / 1410 can be actuated to apply a lateral mechanical force to the periphery of the waveguide layer 1402. The upper roll mechanism 1404 and the bottom roll mechanism 1406 are operated to reverse direction in opposite directions such that a portion of the periphery of the waveguide layer 1402 is passed between or drawn through the upper roll mechanism 1404 and the bottom roll mechanism 1406 in response to the rotation of the upper roll mechanism 1404 and the bottom roll mechanism 1406. The upper roll mechanism 1408 and the bottom roll mechanism 1410 can be actuated to operate in a manner similar to the upper roll mechanism 1404 and the bottom roll mechanism 1406. The upper roll mechanisms 1404 / 1408 and the bottom roll mechanisms 1406 / 1410 can grip the waveguide 1402 by friction and / or "teeth" or grooves, grip the periphery of the waveguide 1402, or otherwise move it laterally. 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 mechanism.

[0169] As shown in FIG. 14B, actuation of the mated upper roll mechanisms 1404 / 1408 and the bottom roll mechanisms 1406 / 1410 rolls the length of the periphery of the waveguide layer 1402 inwardly toward the center of the waveguide 1402, which bends in response to the mechanical force and radially inwardly offsets the periphery of the waveguide 1402. Thus, by applying a lateral mechanical force to the periphery of the waveguide layer, the waveguide layer 1402 can be adjusted, for example, from a planar surface profile to a curved surface profile, which can adjust the radius of curvature of the waveguide layer. The resulting changes in the bending and radius of curvature values of the waveguide 1402 are a function of the length of the periphery of the displaced waveguide 1402. De-actuation of the upper roll mechanisms 1404 / 1408 and the bottom roll mechanisms 1406 / 1410 removes the mechanical force at the periphery of the waveguide layer, which returns to its original surface profile, e.g., the planar or substantially planar one illustrated in FIG. 14A.

[0170] According to an embodiment of the present invention, the application of a bending moment caused by a roll mechanism at the periphery of the waveguide layer results in a uniform modulation of the surface profile or curvature of the waveguide layer across the width / length of the waveguide layer and the aperture area of the associated eyepiece lens. In some exemplary embodiments, a portion of the roll mechanism can be actuated to flatten or curve the waveguide. For example, the upper roll mechanisms 1404 / 1408 can be actuated, while the bottom roll mechanisms 1406 / 1410 can be independently and freely moved or replaced with pins or wheels without an actuation mechanism. Conversely, the bottom roll mechanisms 1406 / 1410 can be actuated, while the upper roll mechanisms 1404 / 1408 can be independently and freely moved or replaced with pins or wheels 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 planar configuration. Varying the length of the periphery displaced by the roll mechanism can bend the waveguide layer into a plurality of configurations corresponding to variable radius-of-curvature values such that each amount of displaced length corresponds to a different resulting radius-of-curvature value presented by the waveguide layer. Varying the length of the periphery of the displaced waveguide can thus enable continuous modulation of the curvature of the waveguide layer. As a result, the waveguide layer can be continuously modified through the operation of the engaged roll mechanisms to project virtual content to the user at multiple depth planes.

[0172] For example, the natural state of the waveguide layer 1402 can have a radius of curvature value suitable for projecting virtual content emitted at a distance of 2 m from the eyepiece. The periphery 1402 of the waveguide layer is offset radially inwards towards the center of the waveguide layer 1402, which can increase the curvature of the waveguide layer 1402. The increased bending of the waveguide layer that reduces the radius of curvature of the waveguide layer 1402 can correspond to virtual content projected to occur at a distance closer to the user than 2 m (e.g., 1 m). The periphery of the waveguide layer 1402 can be further offset radially inwards to further bend the waveguide layer 1402. The further bending of the waveguide layer 1402 further reduces the radius of curvature value, which can be used to render virtual content emitted 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 stationary configuration returns the waveguide 1402 to its stationary configuration. For example, at a refresh rate of 90 Hz, continuously alternating between the first stationary configuration, a second configuration in which the waveguide is bent, and a third configuration in which the waveguide is further bent enables the display of virtual content on three depth planes corresponding to three radii of curvature, achieved using the roll mechanism to angle the waveguide layer. Of course, these values are merely illustrative, and other depth planes can also be achieved using embodiments of the present invention.

[0173] Figure 14C illustrates a plan view of the components of a roller system for dynamically adjusting the surface profile of the waveguide layer illustrated in Figures 14A and 14B. As illustrated in Figure 14C, the periphery of the waveguide layer 1402 contacts upper roll mechanisms 1404 / 1408 and a bottom roll mechanism (not shown). Additional upper roll mechanisms are illustrated as being uniformly dispersed along the periphery of the waveguide 1402. For example, eight upper roll mechanisms are illustrated and, when mated with and actuated by eight corresponding bottom roll mechanisms (not shown), induce a uniform stress on the waveguide 1402. The additional roll mechanisms uniformly dispersed 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. A circular shape is illustrated in Figure 14C, but embodiments of the present invention are not limited to this particular shape and other shapes are also included within the scope of the present invention. In other embodiments, the roll mechanisms can be positioned to conform to a waveguide layer having a shape other than a circular shape (e.g., a teardrop shape).

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

[0175] In some embodiments, the waveguide is pre-curved and can then be less curved or bent flat 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 profile 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 profile of the waveguide layer shown in FIG. 14D. As shown in FIGS. 14D and 14E, the waveguide layer 1412 can be curved with a predetermined surface profile, e.g., a predetermined radius of curvature. The waveguide layer 1412 can then be positioned between an upper roll mechanism 1414 and a bottom roll mechanism 1416 and between an upper roll mechanism 1418 and a bottom roll mechanism 1420 in a manner similar to the embodiments described in connection with FIGS. 14A and 14B. In FIG. 14D, the upper roll mechanisms 1414 / 1418 and the bottom roll mechanisms 1416 / 1420 are positioned in a non-operating configuration, thereby allowing the waveguide layer 1412 to take on a curved surface profile associated with a first surface profile, e.g., a display of a first depth plane.

[0176] As shown in FIG. 14E, the operation of the upper roll mechanisms 1414 / 1418 and the bottom roll mechanisms 1416 / 1420 applies a mechanical force to the periphery of the waveguide layer 1412, which flattens and radially outwardly displaces the periphery of the waveguide 1412 in response to the mechanical force. Thus, by applying a lateral mechanical force to the periphery of the waveguide layer, the waveguide layer 1412 can be adjusted from, e.g., a curved surface profile to a planar or substantially planar surface profile, which 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 displaced waveguide 1412. The deactivation of the upper roll mechanisms 1414 / 1418 and the bottom roll mechanisms 1416 / 1420 removes the mechanical force at the periphery of the waveguide layer, which returns to its original surface profile, e.g., the curvature shown in FIG. 14D.

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

[0178] FIG. 15 illustrates a cross-sectional view of a pneumatic system for dynamically adjusting the surface profile of a waveguide layer according to some embodiments. As shown in FIG. 15, the pneumatic system includes a waveguide layer 1502 (e.g., a pre-curved polymer waveguide layer with a radius of curvature of 2.0 m), a continuous pressure regulator 1510, and lenses L1, L2. The waveguide layer 1502 is positioned or otherwise joined to a flat, transparent, and rigid base of the lens L2 such that a pressurized cavity 1504 is encapsulated between the waveguide layer 1502 and the lens L2, and an airtight seal 1506 can be created along the periphery of the waveguide layer 1502. In some exemplary embodiments, the flat, transparent, and rigid base can be a component that is distinct from and joined to the lens L2. In a section with the airtight seal 1506, the 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 is operated 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 a change in the curvature of the waveguide layer 1502. A pressure regulator 1510, which is one pressure-inducing device, is shown, but the exemplary embodiments allow for the use of one or more pressure adjustment 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, in a first default configuration, the waveguide layer 1502 can be planar or substantially planar with little or no pressure applied to the waveguide layer 1502 being associated with the pressurized cavity 1504. The continuous pressure regulator 1510 can operate to increase the pressure in the pressurized cavity 1504 and distribute a uniform load over the waveguide layer 1502, thereby modifying the surface profile. The pressure in the pressurized cavity 1504 can be increased to cause 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 the strain energy stored 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 substantially curved shape. The continuous pressure regulator 1510 can operate to decrease the pressure in the pressurized cavity 1504 (i.e., either create a vacuum using a negative pressure value or reduce a positive existing pressure value), thereby uniformly inverting the surface profile of the waveguide layer 1502 inwardly towards the lens L2. The pressure in the pressurized cavity 1504 can be decreased 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 substantially curved shape.

[0181] In a further embodiment, the waveguide layer 1502 can be in a third default configuration and have an existing curvature between planar and substantially curved (i.e., between the first and second default configurations described above). The continuous pressure regulator 1510 can operate to reduce the pressure within the pressurized cavity 1504 (i.e., either create a vacuum using a negative pressure value or reduce a positive existing pressure value), thereby uniformly inverting the surface profile of the waveguide layer 1502 inwardly towards the lens L2. The pressure within the pressurized cavity 1504 can be reduced to cause the waveguide layer 1502 to assume a configuration in which the waveguide layer 1502 has a reduced curvature. Increasing the pressure within 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 within the pressurized cavity 1504, disperse a uniform load over the waveguide layer 1502, and modify the surface profile. The pressure within the pressurized cavity 1504 can be increased to cause the waveguide layer 1502 to assume a configuration in which the waveguide layer 1502 has an increased curvature. Reducing or releasing the pressure within the pressurized cavity 1504 can release the strain energy stored in the waveguide layer 1502 and return the waveguide layer 1502 to the third default configuration.

[0182] In an exemplary embodiment, similar to that discussed in FIGS. 8A and 8B, the lenses L1, L2 are used to achieve two depth planes without affecting the real-world light as perceived by the user's eye 1514 and have complementary lens functions. Thus, the combination of the lens L2, the waveguide layer 1502, and the lens L1 enables world light to be viewed by the user without refractive power. As discussed above, world light passes through the curved surface of the waveguide layer 1502 with little or no perturbation, as discussed in relation to FIG. 5, for any waveguide layer 1502 configuration, and is presented to the user without the refractive power applied to the world light.

[0183] In some exemplary embodiments, the force of the pressure induced within the cavity 1504 pressurized by the pressure regulator 1510 can be modulated to induce the waveguide 1502 to assume a fully curved configuration and a fully planar configuration. Varying the pressure value can cause the waveguide layer 1502 to curve or flatten into a plurality of configurations corresponding to variable radius of curvature values such that each pressure value corresponds to a different resulting radius of curvature presented 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 the 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 emitted at a distance of 2 m from the eyepiece. The pressure value inside the pressurized cavity 1504 can be increased to cause the waveguide layer 1502 to exhibit an increase in curvature. The increased flexure of the waveguide layer 1502, reducing the radius of curvature of the waveguide layer 1502, can correspond to virtual content projected to occur 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 to further flex the waveguide layer 1502. The further flexure of the waveguide layer 1502 further reduces the radius of curvature value, which can be used to render virtual content emitted at a distance closer to the user than 1 m (e.g., 0.3 m). Releasing the pressure returns the waveguide 1502 to its resting configuration. As an alternative to fully releasing the pressure, instead, the pressure can 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, continuously alternating between a first resting configuration, a second configuration where the waveguide is flexed, and a third configuration where the waveguide is further more flexed enables the display of virtual content at three depth planes corresponding to three radii of curvature achieved using the pressure regulator 1510 to adjust the curve of the waveguide layer 1502.Of course, these values are merely illustrative, and other depth planes can also be achieved using embodiments of the present invention.

[0184] The inventors have determined that during the modification of the curvature of a multi-layered eye lens stack including a plurality of waveguide layers, the mechanical relationship between adjacent waveguide layers within the multi-layer stack can affect performance. In particular, when the peripheries of adjacent waveguide layers are joined using a rigid intermediate layer adhesive, it is conceivable that significant errors can be introduced into the curvature between the layers.

[0185] FIG. 16 is a simplified schematic illustration showing a cross-sectional view of the peripheral portions of three waveguide layers within a multi-layered eye lens stack according to some embodiments. As shown in FIG. 16, the fixed frame 1610 supports the outer peripheries of the multi-layered eye lens stack 1620 and the actuator 1612 that contact the inner periphery of the multi-layered eye lens stack 1620. The fixed frame 1610 and the actuator 1612 are shown in FIG. 16 as applying mechanical force to the inner / outer periphery of the multi-layered eye lens stack 1620, thereby angling the periphery of the multi-layered eye lens stack 1620. However, the discussion provided in relation to FIG. 16 is applicable to various embodiments of the present invention as described herein where the angling of the periphery results in a modification to the surface profile or curvature of the waveguide layer or the multi-layered eye lens stack.

[0186] Referring to FIG. 16, a first mechanical movable joint 1622 and a second mechanical movable joint 1624 are positioned between waveguide layers 1626 and 1628 and between waveguide layers 1628 and 1630, respectively. The presence of the mechanical movable joints 1622 and 1624, which may also be referred to as shims or shim layers, allows each of the waveguide layers 1626, 1628, and 1630 to rotate independently of each other, which can result in the production of a more uniform curvature between the waveguide layers. The mechanical movable joints 1622 and 1624 prevent compression in the upper waveguide layer and tension in the bottom waveguide layer that can result from a solid or rigid intermediate layer bond between adjacent layers by allowing the waveguide layers to slide relative to each other within a predetermined range. The mechanical movable joints can be machined to conform to a part or all of the outer periphery of the waveguide layer and assembled in a manner similar to a gasket between adjacent waveguide layers. As shown in FIG. 6D, a part of the periphery (e.g., the C-shaped crimping mechanism 608) can utilize a shim, while another part of the periphery (e.g., the fixed part 612) can utilize a solid or rigid bond between adjacent waveguide layers.

[0187] By utilizing the mechanical movable joints shown in FIG. 16, the curvature of individual eye lenses can be independently controlled, enabling the machining of eye lenses that include both one or more dynamic waveguide layers and one or more static waveguide layers.

[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 lens 1710 and a peripheral eyepiece lens 1720. The central eyepiece lens 1710 includes an internal coupled diffractive optical element 1712 and a central combined OPE / EPE 1714. The central eyepiece lens 1710 receives a display signal from a first projector (not shown). In the illustrated embodiment, the central eyepiece lens 1710 is utilized to provide content for a central portion of the viewer's visual field, e.g., a 40°×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 lens 1710 can be operated to implement a variable curvature that will provide a dynamic depth plane eyepiece lens.

[0189] In addition to the central eyepiece lens 1710, the foveated display system 1705 includes a peripheral eyepiece lens 1720, which includes an internal coupled diffractive optical element 1722 and a peripheral combined OPE / EPE 1724. The peripheral eyepiece lens 1720 receives a display signal from a second projector (not shown). In the illustrated embodiment, the peripheral eyepiece lens 1720 is utilized to provide content for a peripheral portion of the viewer's visual field, e.g., a 50°×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 lens 1720 is operated with a fixed planar geometry, thereby providing a fixed depth plane eyepiece lens.

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

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

[0192] As shown in FIG. 17B, the waveguide layer 1730 of the central eyepiece lens 1714 is characterized by a first curvature (R1). Similarly, the waveguide layer 1740 of the peripheral eyepiece lens 1724 is also shown and has a planar outer shape, i.e., an infinite radius of curvature. Due to the different radii of curvature, the content for the central portion of the viewer's visual field is displayed at a predetermined depth plane, e.g., 3 m, while the 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 schematic view illustrating the waveguide layer of the foveated display system shown in FIG. 17A in a second configuration. Referring to FIG. 17C, the waveguide layer 1730 of the central eyepiece lens 1714 is characterized by a second curvature (R2). As in FIG. 17B, the waveguide layer 1740 of the peripheral eyepiece lens 1724 is also shown and has a planar outer shape, i.e., an infinite radius of curvature. Due to the different radii of curvature, the content for the central portion of the viewer's visual field is displayed at a predetermined depth plane, e.g., 1 m, while the 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 shown 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 a first projector, the virtual content can be displayed at an appropriate depth plane by modifying the radius of curvature of one or more waveguide layers of the central eyepiece lens 1714.

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

[0195] FIG. 18 is a flowchart illustrating a method of operating a dynamic eyepiece within 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 one or more waveguide layers of the dynamic eyepiece onto the viewer's eye. The one or more waveguide layers are characterized by a first surface profile.

[0196] The method also includes a step (1816) of modifying one or more waveguide layers to be characterized by a second surface profile different from the first surface profile. The step of modifying one or more waveguide layers can include a step of applying shear strain to a peripheral portion of the waveguide layer. Additionally, the step of modifying one or more waveguide layers can include a step of applying tensile and / or compressive forces to a peripheral portion of the waveguide layer. Further, the step of modifying one or more waveguide layers can include a step of moving an actuator towards a fixed frame.

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

[0198] In another embodiment, the method includes a step of producing third virtual content associated with a first depth plane, a step of modifying the waveguide layer to be characterized by the first surface profile, a step of coupling the third virtual content into the dynamic eyepiece, and a step of projecting the third virtual content through one or more waveguide layers onto the 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 according to an embodiment of the present invention. Other sequences of steps may also be implemented according to alternative embodiments. For example, alternative embodiments of the present invention may perform the steps outlined above in a different order. Further, the individual steps illustrated in FIG. 18 may include multiple sub-steps that can be implemented in various sequences depending on the requirements of the individual steps. Additionally, additional steps may be added or removed depending on a 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 forming a curved waveguide layer according to an embodiment of the present invention. Referring to FIG. 19, a formed curved polymer layer, or a waveguide layer 1910, which can be a plurality of waveguide layers, each of which can be a formed curved polymer layer, is positioned between two molds 1920 and 1922. The molds 1920 and 1922, which can be made of glass, are characterized by a predetermined curvature, for example, a spherical curvature (e.g., radius > 0.1 m), and are used to form the waveguide layer 1910 such that the waveguide layer has a predetermined curvature, for example, a spherical curvature, on each of the surfaces of the waveguide layer 1910. In some embodiments, the surface 1912 has a first predetermined curvature and the surface 1914 has a second predetermined curvature. The first predetermined curvature and the second predetermined curvature can be the same curvature or different curvatures.

[0201] To form the molds 1920 and 1922, patterning, imprinting, or other techniques, such as patterning on a curved template, can be used. Regarding an 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 can be referred to as a bottom mold and an upper mold, are aligned with high accuracy to obtain a desired total thickness variation (TTV) value. As an example, any of additional marks, such as the edge of the curved surface of the mold or a reference point on the flat portion of the mold, can be utilized to align the molds. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0202] FIG. 20A is a simplified schematic diagram illustrating a pre-annealed planar waveguide layer according to an embodiment of the present invention. FIG. 20B is a simplified schematic diagram illustrating a pre-annealed curved waveguide layer according to an embodiment of the present invention. FIG. 20C is a simplified schematic diagram illustrating a post-annealed curved waveguide layer according to an embodiment of the present invention.

[0203] In FIGS. 20A - 20C, a process of post - annealing the waveguide layer on a curved substrate (referred to as post - annealing process) is utilized to form a curved waveguide layer. In addition to the name of the post - annealing process, this process can also be referred to as "under the action of heat" since this process does not necessarily need to be implemented as a post - annealing process step. Referring to FIG. 20A, this process can utilize a planar waveguide layer 2010 positioned on a curved substrate 2012. As discussed in relation to FIG. 19, the curved surface 1912 (and the curved surface 1922 discussed below) has a predetermined curvature and can be utilized as the curved substrate 2012.

[0204] In addition, as shown in FIG. 20B, this process can utilize a pre - curved waveguide layer 2020 positioned on a curved substrate 2012. Thus, for example, after the initial forming of the waveguide layer to form a planar waveguide layer or a curved waveguide layer using the forming process shown in FIG. 19, the waveguide layer is positioned on a curved substrate or otherwise installed in preparation for the post - annealing process.

[0205] In an embodiment, the waveguide layer (e.g., the planar waveguide layer 2010 or the pre - curved waveguide layer 2020) and the curved substrate 2012 are heated to an annealing temperature (T g ) that is above the glass transition temperature (T ann ) of the material used to fabricate the waveguide layer. As an example, for a polymer waveguide layer, the annealing temperature can be T ann = 120 °C with respect to LPB - 1102. The waveguide layer and the curved substrate are held at a temperature above the annealing temperature for a given time period (typically 10 - 20 minutes) and then cooled, for example, at a low speed such as < 2 °C / min. The waveguide layer (e.g., polymer material) is at T gAs the waveguide layer 2030 is softened at a temperature above, it is formed into the shape of the curved substrate 2012 during the annealing process, including a cooling phase, as shown in FIG. 20C. In some implementations, a curved template with a size smaller than the waveguide layer is utilized to reduce or minimize unwanted flexure / warp in the final waveguide layer. Further, in some embodiments, the surface of the curved substrate is prevented from adhering or otherwise bonding to the waveguide layer material (e.g., polymer) so that the waveguide layer material can freely expand and contract during thermal cycling. To prevent bonding, one of several techniques can be utilized, including the use of a curved substrate having 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. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0206] 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. Referring to FIG. 21, a method of curving a set of waveguide layers that can form an eyepiece element between the stacks of the set of waveguide layers is shown. As shown in FIG. 21, the waveguide layer (e.g., a polymer waveguide layer) can be either flat or curved after either a casting / molding process and / or a post-annealing process is performed.

[0207] Referring to FIG. 21, the curvature of the first waveguide layer 2110 and the second waveguide layer 2112 is determined by using a curved vacuum chuck 2120 for holding the first eyepiece lens layer 2110 and a curved vacuum nozzle 2122 for installing or positioning 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 using an adhesive material 2130 at the peripheral portions of the first waveguide layer 2110 and the second waveguide layer 2112. The adhesive material 2130 applies stress to the first waveguide layer 2110 and the second waveguide layer 2112 and maintains the curved shape resulting from the processing process. Typically, the adhesive material 2130 is characterized by strong adhesion to the waveguide layer material (e.g., a polymer layer). In one implementation, the adhesive material 2130 is either a UV curable adhesive or a pressure sensitive adhesive. In an embodiment where a UV curable adhesive is utilized, the curved nozzle 2122 can be transparent and allow UV light to impinge on the UV curable adhesive.

[0208] FIG. 22 shows a simplified method 2200 of a processing flow for a polymer waveguide according to an embodiment. In operation 2210, method 2200 can include the step of casting a polymer waveguide according to an embodiment. Polymer casting can include the step of forming a polymer waveguide 2280 using an upper mold 2270 and a bottom mold 2260. The polymer waveguide 2280 is shown as a single linear eyepiece lens for ease of explanation, however, such a waveguide is typically a three-dimensional structure as further described herein, for example, as shown in FIGS. 10A - 10C. During casting, the upper mold 2270 and the bottom mold 2260 provide heat and pressure to form and shape the polymer waveguide 2280. Generally, the casting temperature can typically range from room temperature (e.g., 20°C - 22°C) to 120°C, and the casting time can range from 5 seconds to 10 minutes depending on the composition and UV power. In a typical process, casting is performed at room temperature to 40°C for 25 seconds to 1 minute.

[0209] In operation 2220, method 2200 can include, according to certain embodiments, a release process. The release can occur when one of the molds is released from the polymer waveguide. The release process typically occurs at room temperature, although other temperatures are also conceivably possible, as would be understood by one of ordinary skill in the art with the advantages of the present disclosure, and can include various different mechanisms (e.g., mechanical force, pressure differential, adhesion modulation, etc.) for separating the first mold from the cast polymer.

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

[0211] In operation 2240, method 2200 can include, according to certain embodiments, a post - processing annealing process. Annealing is typically a process in which a material is subjected to a heat treatment up to a certain temperature, maintained for a certain time, and then cooled to room temperature in order to modify the material properties. The annealing process is typically time - and temperature - dependent. For polymers (e.g., waveguide polymers), the annealing process can include heating of the polymer portion up to above its glass transition temperature to relieve internal stresses that can be introduced during its processing (e.g., molding, post - molding cooling, machining, welding, etc.). In some cases, annealing can also include a process of heating the plastic portion below its glass transition temperature for a short time period before cooling the plastic, which can act to "relax" the material and reduce the molding stress. Typically, these stresses can typically include tension or compression (e.g., embedded stress or molding stress). The annealed polymer / plastic is likely to have better mechanical and thermal properties because there are likely to be fewer locations that can propagate cracks within the polymer (due to the annealing process) or modify the shape of the device (e.g., waveguide).

[0212] Referring back to operation 2240, the polymer waveguide is formed on a flat template 2275 or a curved template 2277, causing the polymer waveguide 2280 to adopt the form of the template. An annealing process (the "post-annealing process") after processing 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 of the post-annealing process, this process may also be referred to as "under the action of heat" since the process does not necessarily need to be implemented as a post-annealing process step. It should be noted 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, the waveguide layer (e.g., a planar waveguide layer or a pre-curved waveguide layer) and the curved substrate (e.g., curved substrates 2420, 2440, 2460 as shown in FIGS. 24A - 24C) can be heated to an annealing temperature (T g ) that exceeds the glass transition temperature (T ann ) of the material constituting the waveguide layer. As an example, for a polymer waveguide layer, the annealing temperature can be T ann = 120 °C for a 1.72 polymer. The waveguide layer and the curved substrate are held at a temperature above the annealing temperature for a given time period (typically 10 - 20 minutes) and then cooled, for example, at a low rate such as <2 °C / min. The waveguide layer (e.g., a polymer material) is at T gAs the waveguide layer softens at a temperature above this, it is formed into the shape of the curved substrate during an annealing process that includes a cooling phase (operation 2250). Further, in some embodiments, the surface of the curved substrate is prevented from adhering or otherwise bonding to the waveguide layer material (e.g., a polymer) such that the waveguide layer material can freely expand and contract during thermal cycling. To prevent bonding, one of several techniques can be utilized, including the use of a curved substrate having 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 example hydrophobic material is Teflon®. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0214] In operation 2260, method 2200 can include a back-end-of-line (BEOL) process according to certain embodiments. Some examples of BEOL processes can include metallization, stacking, laminating, singulating, integrating, and more, as will be understood by those skilled in the art with the advantages of the present disclosure.

[0215] It should be understood that the specific steps illustrated in FIG. 22 provide a particular method for a processing flow for a polymer waveguide according to certain embodiments. Other sequences of steps may also be performed according to alternative embodiments. Further, additional steps may be added or removed depending on the particular application. For example, the method shows a processing flow for a single polymer waveguide. Some embodiments may employ a multi-template vertical “stack” that incorporates multiple templates (post-annealing molds) for simultaneously forming multiple polymer waveguides in a particular shape (e.g., a combination of curved and flat regions). Any combination can be used, and those skilled in the art with the advantages of the present disclosure will understand many 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 features of a "flat" substrate or polymer waveguide (or a wafer that is cut to form a polymer waveguide) during the manufacturing process. However, "flat" can be more appropriately defined by certain parameters that are frequently associated with the processing process. For example, the terms "warp" and "bow" typically refer to the shape of the wafer when it is left in its natural state without any vacuum suction (from the chuck) or other forces that can deform the wafer. Warp is typically the distance between the best-fit plane at the center of the wafer that is not in contact with the surface. Bow is typically the sum of the maximum positive and negative deviations from the best-fit plane, usually in a state where the wafer is not bonded (there is no external force deforming the wafer at rest). The global backside reference flatness (GBIR) and total thickness variation (TTV) of the wafer are the differences between the maximum and minimum values of the wafer thickness (typically in a state where the wafer is bonded in a fixed position). GBIR (TTV) can also be measured on the front and back surfaces of the wafer when it is in its natural state (not bonded).

[0217] Returning to FIG. 23, for the purposes of this disclosure, a "flat" substrate will typically refer to a wafer 2300 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 from a reference plane 2310. Ideally, the radius of curvature of a flat substrate is infinite. For the purpose of presenting the novel concepts described herein, a wafer (and the corresponding polymer waveguide) can be considered to have a radius of curvature equal to infinity (i.e., a radius of ∞) with a tolerance equal to or better than the limits defined here. This should not be considered limiting, and those skilled in the art with the advantages of this disclosure will generally understand many modifications, variations, and alternative embodiments that would be considered "flat" by industry standards.

[0218] Figures 24A-24C show cross-sections of various custom molds with freeform surfaces for curving polymer waveguides, according to an embodiment. These three examples show various topologies that produce specific shapes in different regions of the polymer waveguide. The freeform surface can be flat, spherical, and aspherical surfaces or combinations of more complex shapes, as would be understood by those skilled in the art with the advantages of the present disclosure, and is not limited to the examples presented here, depending on the desired optical function and application.

[0219] FIG. 24A shows an example of a freeform surface 2420 that operates to introduce omnipresent curvature along a polymer waveguide. The polymer waveguide can be said to have an omnipresent curve because the entire length of the polymer waveguide (also referred to as the lateral extent) is characterized by a constant curvature as a function of the lateral position (i.e., in the x-y plane). The polymer waveguide 2410 is raised to an annealing temperature (e.g., 120° C.) over a certain time period (e.g., 10-20 minutes), and a cooling period (e.g., <2° C. / min) can follow. In some embodiments, the polymer waveguide can consist of a 1.72 polymer (e.g., an annealing temperature range of 90° C. to 120° C.) or a 1.75 polymer (e.g., an annealing temperature range of 80° C. to 100° C.). During the post-annealing process, the waveguide deforms to the shape of the lower surface of the mold 2420. Referring to FIG. 24A, a spherical curvature is formed along the length (omnipresent curvature) or a portion thereof of the polymer waveguide 2410. The curved regions can be very suitable for OPE, EPE, or CPE regions, but as will be understood by those skilled in the art with the advantages of the present disclosure, they can pose problems with respect to the ICG region and can be susceptible to harmful imaging effects such as image floating and distortion during the dynamic modulation of the curvature of the polymer waveguide, and the flat regions help to better align the image projector with the ICG. Note that the terms "freeform surface", "template", and "mold" can be used to refer to the same processing tool structure. For example, the freeform surface 2420 can be referred to as the mold 2420 or the 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] FIG. 24B shows, according to one embodiment, the local curvature of the polymer waveguide 2430 across the spherical region 2434 of the lower surface of the mold 2440 and the flat portion of the waveguide across the flat region 2432 of the lower surface 2440. The locally curved portion may correspond to the CPE region of the polymer waveguide 2430, while the flat region may be highly suitable for installing the ICG, as shown above.

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

[0222] In some embodiments, the lower custom mold (e.g., as shown in FIGS. 24A - 24C) may have anti - adhesive properties such that the polymer waveguide does not adhere to its surface and moves freely during the thermal cycling of the bending process. There are several methods for adopting anti - adhesive properties. For example, as would be understood by those skilled in the art with the advantages of the present disclosure, a uniform surface coating of an anti - adhesive compound such as polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), or other suitable non - stick coatings. In some cases, the free - form surface can be machined directly onto a non - adhesive block (e.g., PTFE).

[0223] The surface of the freeform custom mold can be particle - free after the curving process to maintain the cleanliness of the polymer waveguide. In some aspects, the surface can have some roughness (e.g., 10 nm - 10 μm RMS) so that the waveguide polymer moves freely (e.g., via optical bonding) without sticking to the surface during the thermal cycling of the curving process. This is accomplished by machining (e.g., diamond turning, molding, casting) the raw material (e.g., glass, fused silica, metal, etc.), and surface polishing or etching may follow to achieve the desired roughness while still maintaining a particle - free surface. In cases where the thresholds for roughness or cleanliness are not met, a clean and flexible fabric (e.g., a cleanroom wipe made from synthetic polyester) can be placed between the polymer sample and the freeform surface during the curving process to improve non - stick properties.

[0224] Figures 25A and 25B show aspects of a polymer curving method and corresponding problems that can occur. In some cases, the polymer waveguide may not conform precisely to the underlying surface contour 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 curve / flat transition length, such as when the spherical portion (e.g., CPE) of the polymer waveguide transitions to a flat portion where an ICG cannot be formed. Depending on the polymer thickness and the curved surface area, the transition length can increase and include image distortion at the edge of the eye box. Referring to Figure 25A, an extended curve / flat transition of the polymer waveguide 2510 over the freeform custom mold 2520 occurs, which can cause image distortion across the area of the polymer waveguide at or near the transition 2522. In particular, a longer extension can enter or intrude into the flat area where an ICG can be located, which can further introduce detrimental image effects into the waveguide. Note that the polymer waveguide 2510 does not contact the transition 2522, leaving a gap, thereby contributing to the extension of the curve / flat transition.

[0225] FIG. 25B shows a simplified schematic of the method of curving a “pinched” polymer and the corresponding problems that can arise therefrom. Polymer waveguide 2510 rests on a free-form surface mold 2520 (“bottom mold”), and a second mold 2530 (“top mold”) is placed thereon, “pinching” the polymer waveguide 2510 and applying an additional force to better conform the polymer waveguide 2510 to the contour of the underlying bottom mold. Such methods can operate to incorporate a sharper curve / flattening transition, however, they are susceptible to damage to the polymer waveguide such as scratching, denting, and the like at the sharp transition points, for example, due to misalignment of the top and bottom molds. Referring to FIG. 25B, the polymer waveguide 2510 can be damaged at location 2540 due to inappropriate misalignment, which can be difficult to reliably control. In some cases, the damage can also affect the active lattice (e.g., ICG) when it is in hard contact with the top and / or bottom mold.

[0226] In the following embodiments, various high-fidelity curving techniques are introduced and improved polymer waveguides are produced. These embodiments and methods reduce the extended curve / flattening transitions described above while avoiding damage to the polymer waveguide, allow for improved top and bottom mold alignment during the post-annealing process / curving process, and can help prevent the active lattice (e.g., ICG) from being damaged during the curving process, as further described below.

[0227] FIGS. 26A-26C are simplified schematics showing a side view of a high-fidelity curving process for a polymer waveguide 2600 according to an embodiment. FIG. 26A shows a plan view of a polymer waveguide 2600 including circular and spherical CPE regions 2630 and an ICG region 2650. As shown in FIG. 26A, the waveguide layer can include an eyepiece lens characterized by a teardrop shape in plan view. Although the teardrop shape is shown in FIG. 26A, embodiments of the present invention are not limited to this particular shape, and other shapes are also included within the scope of the present invention.

[0228] The polymer waveguide 2600 is sandwiched between a bottom mold 2610 (not visible from this figure) and an upper mold 2620. The upper mold 2620 defines a desired transition length without inducing damage on a sensitive optical propagation area (e.g., the transition between a curved area and a flat area), enables upper and bottom mold alignment during the post-annealing / curving process, and can operate to prevent damage to the active grating (e.g., ICG 2650) during the curving process, and can have a predetermined cutout area. FIG. 26B shows a side cutaway view of the polymer waveguide 2600 from 26B-26B' (see FIG. 26A) during the curving process. The relationship between the bottom mold 2610, the upper mold 2620, and the polymer waveguide 2600 sandwiched therebetween is more readily visible from this perspective view. From the 26B-26B' perspective view, the upper mold 2620 is positioned at or near the curvature / flat transition of the bottom mold 2610 (e.g., where the locally curved portion 2635 transitions to the flat portion 2640) on both the 26B and 26B' sides, and is aligned (2660), thereby causing a short corresponding transition for the polymer waveguide 2600 while avoiding any damage that could still affect TIR or other optical parameters. That is, the curvature / flat transition along the 26B-26B' cross-section can be abrupt (e.g., ideally as small as or as small as practicable compared to a transition length of 0 mm) because light does not propagate along this direction, and thus this region does not experience harmful optical coupling effects (e.g., distortion).

[0229] FIG. 26C shows a side cut-away view from 26C-26C' of FIG. 26A during the bending process. On the 26C' side, the upper mold 2620 is positioned and aligned near or at the curvature / 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 upper 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 upper mold 2620 is positioned on top of the ICG 2650), but the polymer waveguide 2600 still defines the desired transition length so as to be flat at the ICG 2650 location and maintain good optical performance. That is, the curvature / flat transition along the 26C-26C' cross-section is short enough to ensure that the ICG 2650 is flat (e.g., the curvature / flat transition does not overlap or penetrate too close to the ICG 2650), and as described above, has a transition that is long enough to avoid damage in the curvature / flat transition. For evaluation criteria, some embodiments may have a transition length D2 of about 9 mm without the upper mold 2620, which will not penetrate into the ICG area. With the upper mold 2620, D2 can be reduced to about 6 mm with the upper mold 2620 configured to be about 5 mm from the ICG 2650. The upper mold 2620 can be configured as close as possible (e.g., to the edge of the ICG 2650) without touching the ICG 2650, and generally, the closer the upper mold 2620 is to the ICG 2650, the shorter the transition length D2 can be.

[0230] Figures 26A - 26C illustrate the formation of a single polymer waveguide using a template, but it should be understood that multiple polymer waveguides can be processed using a stacked implementation. Thus, the techniques described herein are applicable to multiple waveguide processing processes. Those skilled in the art will recognize many variations, modifications, and alternatives. In a typical 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 the ICG (e.g., shown as D) can be 10 - 15 mm. Other dimensions and scales are also conceivable, as will be understood by those skilled in the art with the advantages of the present disclosure.

[0231] Figure 27A is a simplified cross - sectional schematic view showing an example of an omnidirectionally flat multi - layer eyepiece stack (the "eyepiece", the "eyepiece stack", the "polymer waveguide stack") 2700 with a locally curved CPE according to an embodiment. In some embodiments, the 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). The projector 2710 may be a split - pupil projector, covering the flat regions of each polymer waveguide and configured to enable optical input of RGB colors at the same angle for proper mixing of the RGB images for each polymer waveguide (ICG 2755). The flat ICG is typically preferred for in - line ICG, which can provide an increased field of view through intermediate - layer crosstalk. In some aspects, coatings 2725, 2735, and 2745 can be added to the ICG, as will be understood by those skilled in the art with the advantages of the present disclosure.

[0232] The shims can each be configured under each polymer waveguide 2720, 2730, 2740 (see FIG. 27B). Typically, each shim is joined to one waveguide layer, which operates to separate the waveguide layers by a distance and allow each layer to rotate independently of each other and adapt to a uniform curvature deformation within each waveguide layer during dynamic bending. The shim may typically consist of a low friction (<0.5) carrier film (e.g., PTFE, PET + hard coating, etc.) with an adhesive on one side. The low friction surface can allow for uniform deformation of all layers. The shim thickness can range from about 20 μm to 500 μm, although other uniform or non-uniform thicknesses are also possible as considerations.

[0233] FIG. 27B is a plan view illustrating an example of an omnidirectionally flat eyepiece lens 2700 with a locally curved CPE within a dynamically curved eyepiece lens, according to an embodiment. With respect to the dynamically curved eyepiece lens, stationary and flat ICGs may be used to minimize image float and distortion during dynamic modulation of the curvature of the eyepiece lens (e.g., polymer waveguides 2720, 2730, 2740). As can be better seen in FIG. 27A, by using a locally curved CPE on an otherwise omnidirectionally flat eyepiece lens, the position and flatness of the ICG 2755 can be well maintained through an increased flexural rigidity inherent in the shape of the eyepiece lens 2700. In some implementations, a rigid adhesive 2750 can be coupled around the ICG to join different layers together and / or the frame and the projector, further minimizing movement of the ICG 2755 and creating a fixed (non-movable) portion 2760 of the eyepiece lens stack 2700. The rigid adhesive 2750 may be configured (e.g., joined thereto) around the perimeter of the eyepiece lens 2700 within an area that does not interfere with the optical path from the projector 2710 or the light propagating through the eyepiece lens 2700. Typically, the bonding length of the rigid adhesive can be configured to maintain the flatness of the ICG area and minimize spherical aberration of the eyepiece lens curvature during dynamic modulation. As an example, the bonding length is typically about 10 - 30 mm, as shown in FIG. 27B, which can result in good optical performance characteristics. In some aspects, the region 2765 around the locally spherical area (e.g., CPE) may be configured with shims placed between vertically adjacent layers of the eyepiece lens 2700, allowing each layer to rotate independently for uniform curvature deformation within each eyepiece lens layer during dynamic bending.

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

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

[0236] A waveguide structure with a variable surface profile as presented herein provides a dynamic eyepiece lens in which the depth plane of the eyepiece lens can be varied such that virtual content is displayed at different depth planes. Thus, for example, a time-division multiplexing technique can be utilized to display virtual content that appears to originate from different depth planes using a single eyepiece lens (e.g., eyepiece lens stack 2700) containing three waveguide layers, each associated with a primary color. The embodiments generally illustrated herein provide two different depth planes, but other implementations also allow for continuous variation in the surface profile, thereby providing a dynamic eyepiece lens with continuous depth plane variation. Additionally, virtual content can be shifted to different depth planes as a function of user movement, such as when the user blinks or the equivalent. Since the current depth plane associated with the eyepiece lens can be correlated with the virtual content to be displayed, 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 attached to a portion of the waveguide layer or otherwise held in place adjacent to 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 profile of the waveguide layer in the vicinity of the ICG 2755, the fixed portion 2760 is utilized to maintain the surface profile of the main portion of the waveguide layer within the fixed surface profile. In other embodiments, the fixed portion can utilize, for example, one or more shims between waveguide layers to allow a portion of the waveguide layer adjacent to the fixed portion 2760 to bend or remain in its original condition without interference by the fixed portion 2760, as will be discussed in more detail in connection with FIG. 16, thereby loosely holding a plurality of waveguide layers (e.g., 2720, 2730, 2740) in place.

[0238] As described above, the periphery of the eyepiece stack 2700 can be positioned, joined to, or otherwise attached to the inner portion of the ring actuator 2770. The outer portion of the ring actuator 2770 may be attached to a fixed frame structure as further described herein. The ring actuator 2770 can be radially, repeatedly expanded or contracted for continuous modulation of the surface profile 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 prevent obscuring the novel concepts described herein. The waveguide layer and the ring actuator can be processed separately and then joined together or processed as a single unit, depending on the particular manufacturing process utilized.

[0239] Referring to FIG. 27B, the outer portion of the ring actuator 2770 can be attached or pinned to the fixed frame structure via a rotating mechanism (e.g., a 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 substantially 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 be more substantially curved than when the ring actuator is not contracted as much. In other words, the ring actuator 2770 can expand towards the center of the waveguide layer and decrease the radius of curvature of the waveguide layer, and contract outwardly from the center of the waveguide layer to flatten the waveguide layer and increase the radius of curvature. Thus, the waveguide layers (e.g., waveguides 2720, 2730, 2740) can be continuously flattened to a planar or substantially planar position or induced to curve at various radius of curvature values by lateral or radial movement of the ring actuator 2770, 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 a plurality of states corresponding to variable surface profiles or radius of curvature values. As a result, the surface profile of each waveguide layer within the eyepiece stack 2700 is continuously modified, and virtual content can 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, as shown, for example, in FIG. 27B. In some embodiments, a portion of the ring actuator can be segmented into a plurality of segmented sections such that variable mechanical forces can be applied to different portions along the periphery of the waveguide layer. In some embodiments, different materials or actuator types can be used in any combination for a given application for each of the segmented sections. The various sections of the ring actuator can be actuated simultaneously, alternately, or in combination such that a portion of the ring actuator can expand so that it is further or less far outward from the waveguide layer than a portion of another ring actuator. This can account for a ring actuator system with component shapes that vary in relation to the shape of the waveguide layer and reduce the focusing error.

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

[0242] Figure 28B is a plan view illustrating an example of a locally flat ICG within an omnidirectionally curved dynamic eyepiece lens 2800, according to an embodiment. With respect to the dynamic curved eyepiece lens, stationary and flat ICGs may be used to minimize image float and distortion during dynamic modulation of the curvature of the eyepiece lens (e.g., polymer waveguides 2820, 2830, 2840). As can be better seen in Figure 28A, by using a locally flat ICG on an omnidirectionally spherical eyepiece lens, the position and flatness of the ICG 2855 can be well maintained through an increased flexural rigidity inherent to the shape of the eyepiece lens 2800. In some implementations, a rigid adhesive 2850 may be coupled around the ICG to join different layers together and / or join the frame and the projector, further minimizing movement of the ICG 2855 and creating a fixed (non-movable) portion 2860 of the eyepiece lens stack 2800, as further described above with respect to Figures 27A - 27B. In some aspects, the region 2860 around the spherical area (e.g., CPE), or in some cases near the rigid area near the ICG 2855, is placed between vertically adjacent layers of the eyepiece lens 2800 and may be configured with shims that allow each layer to rotate independently for uniform curvature deformation within each eyepiece lens layer during dynamic curvature. The shims are typically configured around the area of the CPE since the area of the CPE undergoes movement due to, for example, polymer waveguide deformation as further described above. The shims are typically not configured within these areas since the fixed areas (e.g., ICG) 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 is coupled to the local spherical area and may be configured in any suitable shape, but is typically configured in a circular or C shape to minimize any interference with the light propagating through the eyepiece lens 2800.

[0243] Those skilled in the art will understand that the designs illustrated in FIGS. 27A-27B and 28A-28B can be utilized in conjunction with a system for dynamically adjusting the surface profile of the waveguide layer illustrated in FIGS. 6A-16, as needed. Merely by way of example, considering FIGS. 6E-6F, as illustrated in FIGS. 27A and 28A, a waveguide layer that has been pre-determined and machined with a curved surface profile, e.g., with a predetermined radius of curvature, will then bend in response to a mechanical force, resulting in the radius of curvature of the waveguide layer being modified to, e.g., a planar surface profile or a larger radius of curvature. To apply the mechanical force to the periphery of the waveguide layer, two ring-shaped crimping mechanisms shown in FIGS. 6E and 6F can be operated using. Thus, various devices processed using the processing methods described herein can be integrated with the various dynamic adjustment systems described herein. Although FIGS. 6E-6F are discussed as an example, other systems illustrated in FIGS. 6A-16 can also be utilized as needed. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0244] FIG. 29 is a simplified flowchart showing a side view of a method 2900 for forming a polymeric waveguide for use in an extended reality headset, according to an embodiment. In one embodiment, the side view of method 2900 can be implemented using casting and molding processes and equipment. Method 2900 describes a method for forming a single layer of high-fidelity polymeric waveguides, but the polymeric waveguides described herein may be part of a multi-layered eyepiece, as will be understood by those skilled in the art with the advantages of the present disclosure, and it should be understood that multiple layers may be processed in a multi-stack process (e.g., multiple molds stacked to create multiple waveguides simultaneously).

[0245] In operation 2910, method 2900 can cast a polymer waveguide 2600 configured to propagate light therethrough, 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) eyepiece lens. The polymer waveguide may have a substantially uniform topology. For example, after casting, the polymer waveguide may be flat or curved, either partially or ubiquitously. The polymer waveguide 2600 can include a light input surface (e.g., ICG2650) in a first region and a light output surface (e.g., CPE2630) in a second region, and the light input surface and the light output surface are separated by a predetermined distance. The casting may be performed using a plurality of molds, typically an upper mold and a bottom mold, with the casting temperature further described above, into which the polymer waveguide is narrowly inserted. The casting molds described herein should not be confused with the post - annealing treatment molds (also referred to as templates, free - form surfaces, etc.) described above.

[0246] In operation 2920, method 2900 can include the step of removing the polymer waveguide from the mold, as shown, for example, in FIG. 22. The step of removing the polymer waveguide includes a demolding process in which the bottom mold is separated from the polymer waveguide, and a separation process (e.g., a peeling process) for separating the polymer waveguide from the upper mold may follow. Alternatively, the demolding process may start with the step of first removing the upper mold, followed by the step of removing the bottom mold. Those skilled in the art with the advantages of the present disclosure will understand many modifications, variations, and alternative embodiments thereof.

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

[0248] In operation 2940, method 2900 can include, according to an embodiment, placing a second mold (upper mold 2620) on the polymer waveguide. The second mold can be vertically aligned 2660 with the polymer waveguide 2600 and the first mold 2610. The second mold 2620 can be configured across the polymer waveguide 2600 and include an opening defined by a first section of the opening that surrounds at least half of the circular base of the uniformly 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. For example, referring to FIG. 27B, the second mold can have an opening (also referred to as a "cutout area" or "void") 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 joins both of the enclosed areas (e.g., linearly or with any suitable curved topology). The second mold (upper mold 2620) is further described above in the cross-sections A-A' and B-B' in FIGS. 26A-26C, where the upper mold is configured around the outer edge of the ICG without contacting the ICG, but in close proximity to the curvature / flattening transition, and still defines a desired transition length (e.g., reduces the transition length) without inducing damage (e.g., affecting TIR or other optical parameters) on the sensitive optical propagation area, enables upper and bottom mold alignment during the post-annealing process / curvature process, and can operate to prevent damage to the active grating (e.g., ICG 2650) during the curvature process.

[0249] In operation 2950, method 2900 applies a thermal cycling process (e.g., a post - annealing process) such that the polymer waveguide is flat in a first region, the polymer waveguide is uniformly spherical in a second region, and the curvature / flatness transition between the first and second regions is such that, as shown in FIG. 26C, the active grating does not contact the second mold and the polymer waveguide is deformed into a shape defined by the first and second molds to be shorter than a predetermined distance, resulting in a high - fidelity polymer waveguide. The method can include heating the first and second molds to a threshold temperature. In some aspects, the threshold temperature (e.g., for a 1.72 polymer) can be 120 °C, although lower or higher threshold temperatures are also conceivably possible depending on the type of polymer used. For example, a 1.75 polymer can have a threshold temperature ranging 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 can include applying a uniform surface coating of an anti - sticking compound to the polymer waveguide after casting, 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 can include applying raw material microparticles 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 can include inserting one or more fabrics between the polymer waveguide and the first and / or second molds, where the one or more fabrics are configured to prevent the polymer waveguide from sticking to the first and second molds during the thermal cycling process. Those skilled in the art with the benefits of this disclosure will understand many modifications, variations, and alternative embodiments.

[0251] In some embodiments, method 2900 may include applying, according to an embodiment, a rigid bonding material around at least a portion of a second section, surrounding an optical input surface, wherein the rigid bonding material bonds the second section to one or more structures adjacent to a polymer waveguide, including one or more of adjacent polymer waveguides of a multilayer eyepiece stack or a projector. In some aspects, the rigid bonding material may prevent or reduce movement of the optical 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 an embodiment. Other sequences of steps may also be performed according to alternative embodiments. Additionally, additional steps may be added or removed depending on the particular application. For example, the method may further include machining, disposing, and / or implementing shims, ring actuators, or other elements as further described above with respect to FIGS. 27A-28B. Any combination of modifications may be used, and those skilled in the art with the benefit of this disclosure will understand many variations, modifications, and alternative embodiments.

[0253] Also, it should be understood that the examples and embodiments described herein are for illustrative purposes only, and in light of which, various modifications or changes may be suggested to those skilled in the art and should be included within the spirit and scope of this application and the appended claims. Examples of the present invention are shown below. (Example 1) A dynamic eyepiece for projecting an image onto the eye of a viewer, the dynamic eyepiece comprising a waveguide layer having an input surface, an output surface facing the input surface, and a periphery, the waveguide layer being configured to propagate light therein, a waveguide layer, A mechanical structure in contact with at least a part of the periphery of the waveguide layer, wherein the mechanical structure applies a first mechanical force to at least a part of the periphery of the waveguide layer to provide a first surface profile on the output surface of the waveguide layer, and applies a second mechanical force to at least a part of the periphery of the waveguide layer to provide a second surface profile different from the first surface profile on the output surface of the waveguide layer and is operable to perform, the mechanical structure and a dynamic eyepiece lens comprising the same. (Example 2) The dynamic eyepiece lens according to Example 1, wherein the first surface profile is planar and the second curvature of the second surface profile is negative or positive. (Example 3) The dynamic eyepiece lens according to Example 1, wherein the first curvature of the first surface profile is positive and the second curvature of the second surface profile is negative. (Example 4) The dynamic eyepiece lens according to Example 1, further comprising a projector optically coupled to the dynamic eyepiece lens. (Example 5) A second waveguide layer having a second input surface, a second output surface opposite the second input surface, and a second periphery, wherein the second waveguide layer is configured to propagate light therein, the second waveguide layer, and a second mechanical structure in contact with at least a second part of the second periphery of the waveguide layer, wherein the second mechanical structure applies a third mechanical force to at least the second part of the second periphery of the second waveguide layer to provide a third surface profile on the second output surface of the second waveguide layer, and applies a fourth mechanical force to at least the second part of the second periphery of the second waveguide layer to provide a fourth surface profile different from the fourth surface profile on the second output surface of the second waveguide layer and is operable to perform, the second mechanical structure and the dynamic eyepiece lens according to Example 1 further comprising the same. (Example 6) The dynamic eyepiece lens according to Example 5, further comprising one or more mechanical movable joints between the waveguide layer and the second waveguide layer. (Example 7) The dynamic eyepiece lens according to Example 1, wherein the first mechanical force and the second mechanical force are continuously applied to the waveguide layer, thereby providing a range of surface profiles between the first surface profile and the second surface profile. (Example 8) The dynamic eyepiece lens according to Example 1, wherein the mechanical structure is operable to apply shear strain to the waveguide layer. (Example 9) The dynamic eyepiece according to Example 1, wherein the mechanical structure is operable to apply a stretching and / or compressive force to the waveguide layer. (Example 10) The dynamic eyepiece according to Example 1, wherein the mechanical structure includes a fixed frame and an actuator. (Example 11) A method of operating a dynamic eyepiece in an augmented reality headset, the method comprising: producing first virtual content associated with a first depth plane; combining the first virtual content into the dynamic eyepiece; projecting the first virtual content onto a viewer's eye through one or more waveguide layers of the dynamic eyepiece, wherein the one or more waveguide layers are characterized by a first surface profile; modifying the one or more waveguide layers to be characterized by a second surface profile different from the first surface profile; producing second virtual content associated with a second depth plane; combining the second virtual content into the dynamic eyepiece; projecting the second virtual content onto the viewer's eye through one or more waveguide layers of the dynamic eyepiece and including. (Example 12) producing third virtual content associated with the first depth plane; modifying the one or more waveguide layers to be characterized by the first surface profile; combining the third virtual content into the dynamic eyepiece; projecting the third virtual content onto the viewer's eye through the one or more waveguide layers and further including the method according to Example 11. (Example 13) The method according to Example 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. (Example 14) The method according to Example 11, wherein modifying the one or more waveguide layers includes applying shear distortion to a peripheral portion of the one or more waveguide layers. (Example 15) The method according to Example 11, wherein modifying the one or more waveguide layers includes applying a stretching and / or compressive force to a peripheral portion of the one or more waveguide layers. (Example 16) The method according to Example 11, wherein modifying the one or more waveguide layers includes moving an actuator towards a fixed frame. (Example 17) 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 profile, and a second projector, and a fixed depth planar eyepiece optically coupled to the second projector comprising a foveated display. (Example 18) The foveated display according to Example 17, characterized by a field of view, the dynamic eyepiece overlapping the central part of the field of view, and the fixed depth planar eyepiece overlapping the peripheral part of the field of view. (Example 19) The dynamic eyepiece is a waveguide layer having an input surface, an output surface opposite the input surface, and a periphery, and a mechanical structure coupled to at least a part of the periphery of the waveguide layer, the mechanical structure being operable to apply a first mechanical force to at least a part of the periphery of the waveguide layer and modify the surface profile of the output surface of the waveguide layer, comprising the foveated display according to Example 17. (Example 20) The foveated display according to Example 19, wherein the mechanical structure is operable to modify an angle associated with the periphery of the waveguide layer. (Example 21) 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 in a first region of the polymer waveguide, and 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, including, placing the cast polymer waveguide on a first mold, the first mold comprising a uniformly spherical portion having a circular base, and a flat portion, the polymer waveguide being configured on the first mold such that the first region is aligned perpendicular to the flat portion of the first mold and the second region is aligned perpendicular to the uniformly spherical portion, including, placing a second mold on the polymer waveguide, the second mold being aligned perpendicular to the polymer waveguide and the first mold, and the second mold at least half of the circular base of the uniformly spherical portion of the first mold and a first section of the opening surrounding the light output surface; at least half of the flat portion and a second section of the opening surrounding the light input surface; including an opening configured across the polymer waveguide defined by the first and second sections; applying a thermal cycling process and heating the first and second molds to a threshold temperature at which the polymer waveguide is deformed into the 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 curvature / flatness transition between the first and second regions is shorter than the distance D; such that; a method including. (Example 22) The method according to Example 21, wherein the substantially uniform surface topology is a flat surface topology. (Example 23) The method according to Example 21, wherein the substantially uniform surface topology is an omnipresently spherical surface topology. (Example 24) The method according to Example 21, wherein the polymer waveguide is in a teardrop shape. (Example 25) The method according to Example 21, wherein the thermal cycling process is a post-annealing process and the threshold temperature is 120°C. (Example 26) The method according to Example 21, wherein the light input surface is an internal coupling grating (ICG). (Example 27) The method according to Example 21, wherein the light output surface is a combined pupil expander (CPE). (Example 28) The method according to Example 21, wherein the flat portion is a portion where the polymer waveguide has a warp of less than 20 μm, a deflection of less than 20 μm, and a total thickness variation value of less than 1 μm. (Example 29) The method according to Example 21, further including applying a uniform surface coating of an anti-sticking compound to the polymer waveguide after casting, which operates to prevent the polymer waveguide from sticking to the first and second molds during the thermal cycling process. (Example 30) applying raw material microparticles to one or more surfaces of the polymer waveguide; 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; The method according to Example 21, further including. (Example 31) Inserting one or more fabrics between the polymer waveguide and the first and / or second mold, wherein the one or more fabrics are configured to prevent the polymer waveguide from sticking to the first and second molds during the thermal cycling process The method according to Example 21, further comprising (Example 32) The method according to Example 21, wherein the polymer waveguide is made of either a 1.72 polymer or a 1.75 polymer (Example 33) The method according to Example 21, wherein the polymer waveguide is a single layer of a multilayer eye lens (Example 34) Applying a rigid bonding material around at least a portion of the second section to surround the light input surface, wherein the rigid bonding material joins 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 eye lens stack or a projector further comprising The method according to Example 21, wherein the rigid bonding material prevents or reduces movement of the light input surface as the polymer waveguide is dynamically deflected (Example 35) A method comprising Placing a polymer waveguide on a first mold having a uniformly spherical portion with a circular base and a flat portion, wherein the polymer waveguide includes 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 are separated by a distance D, and Placing a second mold on the polymer waveguide, the second mold being vertically aligned with the polymer waveguide and the first mold, and the second mold includes an opening defined by at least half of the circular base of the uniformly spherical portion of the first mold and a first section of the opening surrounding the light output surface, and at least half of the flat portion and a second section of the opening surrounding the light input surface across the polymer waveguide, and Applying a thermal cycling process to heat the first and second molds to a threshold temperature 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 curvature / flatness transition between the first region and the second region is shorter than the distance D such that The method comprising (Example 36) The polymer waveguide is first formed by the method described in Example 35, which has a substantially flat surface topology. (Example 37) The polymer waveguide is first formed by the method described in Example 35, which has a substantially spherical surface topology. (Example 38) The optical input surface is an internal coupling grating (ICG) as described in Example 35. (Example 39) The optical output surface is a combined pupil expander (CPE) as described in Example 35. (Example 40) The method further includes applying a uniform surface coating of an anti-sticking compound to the polymer waveguide after casting, which operates to prevent the polymer waveguide from sticking to the first and second molds during the thermal cycling process, as described in Example 35.

Claims

1. A dynamic eyepiece for projecting an image onto the eyes of a viewer, wherein the dynamic eyepiece comprises: A waveguide layer having an input surface, an output surface facing the input surface, and a periphery, the waveguide layer being configured to propagate light therein; A mechanical structure having a first portion in contact with a first portion of the periphery of the waveguide layer and a second portion in contact with a second portion of the periphery of the waveguide layer, the mechanical structure being operable to: Apply a first mechanical force to the first and second portions of the periphery of the waveguide layer, impart a first shear strain to the waveguide layer, and impart a first surface profile having a first two-dimensional curvature to the output surface of the waveguide layer; Apply a second mechanical force to the first and second portions of the periphery of the waveguide layer, impart a second shear strain to the waveguide layer, and impart a second surface profile having a second two-dimensional curvature different from the first surface profile to the output surface of the waveguide layer; A mechanical structure operable to perform the above; A dynamic eyepiece comprising the above.

2. The dynamic eyepiece according to claim 1, wherein the first surface profile is planar and the second two-dimensional curvature of the second surface profile is negative or positive.

3. The dynamic eyepiece according to claim 1, wherein the first two-dimensional curvature of the first surface profile is positive and the second two-dimensional curvature of the second surface profile is negative.

4. The dynamic eyepiece according to 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 facing the second input surface, and a second periphery, the second waveguide layer being configured to propagate light therein; A second mechanical structure in contact with at least a second portion of the second periphery of the second waveguide layer, the second mechanical structure being operable to: Apply a third mechanical force to the at least second portion of the second periphery of the second waveguide layer and impart a third surface profile to the second output surface of the second waveguide layer; Apply a fourth mechanical force to the at least second portion of the second periphery of the second waveguide layer and impart a fourth surface profile different from the fourth surface profile to the second output surface of the second waveguide layer; operable to perform, a second mechanical structure and The dynamic eyepiece according to claim 1, further comprising

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

7. The first mechanical force and the second mechanical force are continuously applied to the waveguide layer, thereby providing a range of surface profiles between the first surface profile and the second surface profile. The dynamic eyepiece according to claim 1.

8. The dynamic eyepiece according to claim 1, wherein the mechanical structure comprises a fixed frame and an actuator.

9. A method of operating a dynamic eyepiece in an extended reality headset, the method comprising: producing first virtual content associated with a first depth plane; combining the first virtual content into the dynamic eyepiece; projecting the first virtual content onto the viewer's eye through one or more waveguide layers of the dynamic eyepiece, wherein the one or more waveguide layers are characterized by a first surface profile; coupling a mechanical structure to the one or more waveguide layers, wherein the mechanical structure contacts a periphery of the one or more waveguide layers; applying shear strain to the periphery of the one or more waveguide layers using the mechanical structure to modify the one or more waveguide layers to be characterized by a second surface profile different from the first surface profile, wherein changes in the first surface profile and the second surface profile occur two-dimensionally; producing second virtual content associated with a second depth plane; combining the second virtual content into the dynamic eyepiece; projecting the second virtual content onto the viewer's eye through one or more waveguide layers of the dynamic eyepiece A method comprising.

10. producing third virtual content associated with the first depth plane; modifying the one or more waveguide layers to be characterized by the first surface profile; combining the third virtual content into the dynamic eyepiece; projecting the third virtual content onto the viewer's eye through the one or more waveguide layers The method according to claim 9, further comprising.

11. The method according to claim 9, 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.

12. The method according to claim 9, wherein modifying the one or more waveguide layers comprises moving an actuator towards a fixed frame.

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