Waveguides having integral spacers and related systems and methods

Abstract

To provide a head-mounted near-eye display system.SOLUTION: A head-mounted near-eye display system comprises a stack of waveguides with integrated spacers 1120b separating the waveguides 1100. Each of the waveguides may include diffractive optical elements that are formed simultaneously with the spacers by imprinting or casting. The spacers are disposed on one or more major surfaces of the waveguides, and define a distance between immediately adjacent waveguides. The adjacent waveguides may be bonded using adhesives on the spacers. The spacer may fit within indentations of overlying waveguides. The spacers may form one or more walls of material substantially around a periphery of an associated waveguide. Vent holes may be provided in the walls to allow gas to flow into and out from an internal volume defined by the spacers. Debris trapping structures may be provided between two walls of the spacers to trap and prevent debris from entering into the internal volume.SELECTED DRAWING: Figure 11C

Description

[Technical field]

[0001] (Priority Claim) This application claims the benefit of priority to U.S. Provisional Application No. 62 / 865,689, filed June 24, 2019, and U.S. Provisional Application No. 62 / 908,247, filed September 30, 2019, each of which is incorporated herein by reference.

[0002] (Incorporated by reference) This application is incorporated by reference into the following patent applications: PCT Application No. PCT / US2019 / 025224, filed April 1, 2019, and entitled "HYBRID POLYMER WAVEGUIDE AND METHODS FOR MAKING THE SAME"; U.S. Patent Application No. 14 / 555,585, filed November 27, 2014, and published on July 23, 2015 as U.S. Patent Publication No. 2015 / 0205126; U.S. Patent Application No. 2015 / 0302652, filed April 18, 2015, and published on October 22, 2015 as U.S. Patent Publication No. This application incorporates in its entirety each of U.S. Patent Application No. 14 / 690,401, U.S. Patent Application No. 14 / 212,961, filed March 14, 2014 and issued August 16, 2016, now U.S. Patent No. 9,417,452, and U.S. Patent Application No. 14 / 331,218, filed July 14, 2014 and published on October 29, 2015 as U.S. Patent Publication No. 2015 / 0309263.

[0003] (Field) The present disclosure relates to display systems, and more particularly to augmented reality display systems. [Background technology]

[0004] Description of Related Art Modern computing and display technologies have facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences, in which digitally reproduced images or portions thereof are presented to a user in a manner that appears or may be perceived as real. Virtual reality, or "VR", scenarios typically involve the presentation of digital or virtual image information without transparency to other actual real-world visual inputs, and augmented reality, or "AR", scenarios typically involve the presentation of digital or virtual image information as an extension to the visualization of the real world around the user. Mixed reality, or "MR", scenarios are a type of AR scenario that typically involve virtual objects that are integrated into and responsive to the natural world. For example, in MR scenarios, AR image content may be perceived as being occluded by or otherwise interacting with objects in the real world.

[0005] 1, an augmented reality scene 10 is depicted in which a user of the AR technology sees a real-world park-like setting 20 featuring people, trees, buildings in the background, and a concrete platform 30. In addition to these items, the user of the AR technology also perceives that they "see" "virtual content," such as a robotic figure 40 standing on the real-world platform 30 and a flying cartoon-like avatar character 50 that appears to be an anthropomorphic bumblebee, even though these elements 40, 50 do not exist in the real world. The human visual perception system is complex, and it is difficult to produce AR technology that facilitates a pleasant, natural-feeling, and rich presentation of virtual image elements among other virtual or real-world image elements.

[0006] The systems and methods disclosed herein address various challenges associated with AR and VR technologies. Summary of the Invention [Means for solving the problem]

[0007] (summary) Some aspects relate to a display system comprising a stack of waveguides, the first waveguide comprising an optically transmissive body, a first major surface, and a spacer integral with the optically transmissive body, the spacer extending perpendicularly from the first major surface, the second waveguide comprising an optically transmissive body and a second major surface, the second major surface facing the first major surface of the first waveguide and spaced therefrom by the spacer, and an adhesive provided on a top surface of the spacer, the adhesive attaching the spacer to the second major surface of the second waveguide, the adhesive having an as-deposited viscosity of 10 mPa·s to 100 mPa·s. In some embodiments, the spacer extends along a periphery of the first waveguide. In some embodiments, the spacer defines an edge of the waveguide. In some embodiments, the adhesive comprises a first adhesive, and the stack of waveguides further comprises a second adhesive forming an adhesive mass extending between and attaching the first major surface of the first waveguide and the second major surface of the second waveguide. In some embodiments, the first adhesive and the second adhesive have different viscosities. In some embodiments, the second adhesive has an as-deposited viscosity of 10,000 mPa·s to 50,000 mPa·s. In some embodiments, the adhesive is located at the periphery of a spacer on the first major surface of the first waveguide. In some embodiments, the first waveguide further comprises one or more diffractive optical elements within an area within the first major surface of the spacer. In some embodiments, the first major surface of the first waveguide further comprises an adhesive capture recess between the one or more diffractive optical elements and the adhesive. In some embodiments, the adhesive is disposed on a top surface and a lateral surface of the spacer. In some embodiments, the first waveguide comprises a plurality of spacers. In some embodiments, one or more surfaces in contact with the adhesive have a texture that is rough or not smooth. In some embodiments, the spacer comprises one or more vent holes extending laterally through the spacer. In some embodiments, the first waveguide comprises a plurality of spacers, each spacer comprising one or more vent holes.In some embodiments, the spacers of a pair of spacers of the plurality of spacers are laterally extended alongside one another, and the stack of waveguides further comprises one or more debris capture structures located within a volume between the spacers of an adjacent pair of the plurality of spacers. In some embodiments, the spacers are located within an interior area of ​​a first major surface of the first waveguide. In some embodiments, the spacers comprise single point contact spacers having a maximum lateral cross-sectional dimension of 500 μm or less. In some embodiments, the second major surface of the second waveguide comprises a recess that houses the spacer within the recess. In some embodiments, the stack of waveguides comprises a plurality of waveguides, two or more of the plurality of waveguides comprise a spacer and a recess, and the recess houses the spacer of the underlying waveguide. In some embodiments, the spacer comprises a shape selected from the group consisting of a square prism, a square pyramid, a triangular prism, a triangular pyramid, a cylinder, and a cone. In some embodiments, the adhesive comprises a light absorber. In some embodiments, the adhesive is doped with a black colorant. In some embodiments, the first and second waveguides are separated by an air gap having a size defined by the spacer and the adhesive.

[0008] In some embodiments, the adhesive has a refractive index greater than 1.65. In some embodiments, the first and second waveguides each comprise an in-coupling optical element configured to in-couple the incident image light and an out-coupling optical element configured to out-couple the in-coupled image light. In some embodiments, the display system further comprises a light projector system configured to project the image light onto the in-coupling optical element. In some embodiments, the spacer comprises a light absorbing material.

[0009] Some aspects relate to a display system comprising an eyepiece comprising: a waveguide, an optically transmissive body comprising at least one spacer integral with the optically transmissive body; an outcoupling optical element configured to outcouple light propagating within the optically transmissive body; an overlying waveguide spaced from the waveguide by the at least one spacer; and a post formed of an adhesive that attaches the optically transmissive body to a surface of the waveguide. In some embodiments, the outcoupling optical element comprises a plurality of protrusions and intervening recesses on a major surface of the optically transmissive body, the at least one spacer extending from the major surface to a height that exceeds a height of the plurality of protrusions. In some embodiments, the adhesive has an as-deposited viscosity of 10,000 mPa·s to 50,000 mPa·s. In some embodiments, the waveguide comprises a pair of integral spacers, the adhesive being located between the pair of integral spacers. In some embodiments, the adhesive is doped with a black colorant. In some embodiments, the adhesive has a refractive index greater than 1.65. In some embodiments, the adhesive is located on a surface of the optically transparent body between the outcoupling optical element and the at least one spacer. In some embodiments, the surface of the optically transparent body comprises an adhesive capture recess between the outcoupling optical element and the adhesive. In some embodiments, the adhesive is located adjacent to a periphery of the optically transparent body. In some embodiments, the at least one spacer is positioned between the outcoupling optical element and the adhesive. In some embodiments, the adhesive constitutes a first adhesive, and the eyepiece comprises a second adhesive bonded to the at least one spacer and a surface of the upper waveguide. In some embodiments, the optically transparent body comprises a plurality of spacers.Some aspects relate to a display system comprising an eyepiece comprising a waveguide, the eyepiece comprising an outcoupling optical element configured to outcouple light propagating within the optically transparent body, an overlying waveguide spaced from the waveguide, and a pillar formed of an adhesive extending from the waveguide to the overlying waveguide, the adhesive having an as-deposited viscosity of 10,000 mPa·s to 50,000 mPa·s. In some embodiments, the height is between 30 μm and 200 μm. In some embodiments, the waveguide comprises an integral spacer extending adjacent to the pillar, the spacer extending perpendicularly and contacting the waveguide. In some embodiments, the adhesive is doped with a black colorant. In some embodiments, the adhesive has a refractive index greater than 1.65. In some embodiments, the adhesive defines edges of the waveguide and the overlying waveguide. In some embodiments, the waveguide comprises an adhesive capture recess on a surface of the waveguide between the external coupling optical element and the post. In some embodiments, the recess has a width of 50 μm to 2 mm. In some embodiments, the recess has a depth of 50 μm to 0.4 mm.

[0010] Some aspects relate to a method for making a waveguide stack, the method comprising forming a lower waveguide, the forming the lower waveguide comprising defining an integral outcoupling optical element and an integral spacer on a major surface of the lower waveguide, the integral spacer being spaced from the outcoupling optical element and extending to a height above the outcoupling optical element, providing an adhesive on the major surface of the lower waveguide, and attaching an upper waveguide to the lower waveguide using the adhesive, the integral spacer defining a gap between a major surface of the lower waveguide and a bottom surface of the upper waveguide. In some embodiments, the integral outcoupling optical element and the integral spacer are formed simultaneously. In some embodiments, the method further comprises curing the adhesive after attaching the upper waveguide to the lower waveguide. In some embodiments, the method further comprises singulating the lower waveguide and the upper waveguide. In some embodiments, the singulating step includes cutting the lower waveguide and the upper waveguide along a singulation path. In some embodiments, the cutting the lower waveguide includes cutting the lower waveguide with a laser. In some embodiments, the singulating step includes removing at least a portion of the integral spacer. In some embodiments, the singulating step includes removing at least a portion of the adhesive. In some embodiments, the singulating step includes removing the entire integral spacer. In some embodiments, the adhesive comprises a first adhesive and a second adhesive is provided on a top surface of the integral spacer. In some embodiments, the second adhesive has a deposition viscosity of 10 mPa·s to 100 mPa·s. In some embodiments, the first adhesive has a deposition viscosity of 10,000 mPa·s to 50,000 mPa·s. In some embodiments, the adhesive is provided adjacent to the integral spacer. In some embodiments, the adhesive is provided around the periphery of the integral spacer on a major surface of the lower waveguide. In some embodiments, an adhesive is provided between the outcoupling optical element and the integral spacer on a major surface of the underlying waveguide.In some embodiments, a plurality of integral spacers are defined on a major surface of the lower waveguide. In some embodiments, the adhesive fills a volume between two spacers of the plurality of spacers. In some embodiments, the method further comprises roughening one or more surfaces of the lower waveguide and the upper waveguide prior to attaching the upper waveguide to the lower waveguide, the one or more surfaces comprising a surface in contact with the adhesive. In some embodiments, the method further comprises forming one or more vent holes extending laterally through the integral spacer.

[0011] Some aspects relate to a display system comprising an eyepiece comprising a waveguide, the eyepiece comprising an outcoupling optical element configured to outcouple light propagating within the optically transmissive body, and an upper waveguide spaced from the waveguide, and an adhesive attaching the waveguide to the upper waveguide, wherein a surface of the optically transmissive body and the upper waveguide in contact with the adhesive is roughened. In some embodiments, the roughened surface comprises nanostructures for increasing adhesiveness of the adhesive. In some embodiments, the waveguide comprises an integral spacer, the spacer separating the waveguide and the upper waveguide. In some embodiments, the display system further comprises a pair of integral spacers extending along a circumference of the waveguide. In some embodiments, each spacer of the pair of integral spacers comprises a vent hole extending laterally through the spacer. In some embodiments, the adhesive is disposed on an upper surface of the spacer, the upper surface being one of the roughened surfaces. In some embodiments, the adhesive has an as-deposited viscosity of 10,000 mPa·s to 50,000 mPa·s and forms pillars having a height of 10 μm to 200 μm. In some embodiments, the display system further comprises an adhesive capture recess on a major surface of the waveguide between the outcoupling optical element and the adhesive.

[0012] Some aspects relate to a display system comprising an eyepiece comprising a waveguide, a light outcoupling optical element, a spacer integral with the waveguide, the spacer extending along a circumference of the waveguide, and one or more vent holes formed in the spacer, the one or more vent holes having a width of 100 μm or less, the one or more vent holes having a through opening extending laterally through the spacer. In some embodiments, the integral spacer defines an edge of the waveguide. In some embodiments, the display system further comprises an adhesive attaching the waveguide to the upper waveguide, the adhesive having an as-deposited viscosity of 10,000 mPa·s to 50,000 mPa·s, forming a pillar having a height of 10 μm to 200 μm extending from the waveguide to the upper waveguide. In some embodiments, the display system further comprises an adhesive on a top surface of the spacer, attaching the waveguide to the overlying waveguide, the adhesive having an as-deposited viscosity of 10 mPa·s to 100 mPa·s.

[0013] Some aspects relate to a display system comprising an eyepiece comprising a waveguide, a light outcoupling optical element, a pair of spacers integral with the waveguide, the spacers extending around a circumference of the waveguide, extending alongside one another and defining a channel therebetween, and one or more laterally extending vent holes in each of the spacers, and an overlying waveguide attached to the waveguide, the overlying waveguide being spaced from the waveguide by the pair of spacers. In some embodiments, the one or more vent holes in a first one of the spacers are located remotely from the one or more vent holes formed in a second one of the spacers. In some embodiments, the display system further comprises a debris capture structure formed between adjacent walls of the spacer of a plurality of walls of the spacer. In some embodiments, the debris capture structure comprises a physical barrier configured to capture debris flowing through the channel between the pair of spacers. In some embodiments, the debris capture structure comprises an angled extension of the spacer that extends into the channel. In some embodiments, the pair of spacers extend parallel to one another. In some embodiments, the waveguide further comprises one or more additional integral spacers that extend around a circumference of the waveguide. In some embodiments, the one or more additional integral spacers define a volume with another of the integral spacers, further comprising an adhesive within the volume, the adhesive attaching the waveguide to the overlying waveguide.

[0014] Some aspects relate to a display system comprising an eyepiece lens, a waveguide comprising a light extraction optical element on an active area of ​​a major surface of the waveguide, and a plurality of spacers within the active area, the spacers separating the waveguide and the upper layer waveguide, the spacers being approximately 0.1 mm in diameter. 2The display system includes an eyepiece having an areal density of one spacer per eyepiece or less. In some embodiments, the spacer has a cross-sectional shape in a plane transverse to the height of the spacer, the cross-sectional shape having a maximum dimension of 300 μm or less. In some embodiments, the display system further includes one or more integral spacers extending along a periphery of the waveguide. In some embodiments, the display system further includes an adhesive that attaches the integral spacer extending along a periphery of the waveguide to the upper waveguide, the adhesive having a deposited viscosity of 10 mPa·s to 100 mPa·s. In some embodiments, the display system further includes an adhesive that attaches the waveguide to the upper waveguide, the adhesive having a deposited viscosity of 10,000 mPa·s to 50,000 mPa·s, forming a pillar having a height of 10 μm to 200 μm.

[0015] Some aspects relate to a method for making a waveguide stack, the method comprising forming a lower waveguide, the forming the lower waveguide comprising defining an integral outcoupling optical element and an integral spacer on a major surface of the lower waveguide, the integral spacer being spaced from the diffractive optical element and extending to a height above the diffractive optical element, providing an adhesive on the upper waveguide, and attaching the upper waveguide to the lower waveguide using the adhesive provided on the upper waveguide, the integral spacer defining a gap between a major surface of the lower waveguide and a bottom surface of the upper waveguide. In some embodiments, the defining the integral outcoupling optical element and the integral spacer comprises casting the waveguide in a mold. In some embodiments, the defining the integral outcoupling optical element comprises forming a diffraction grating. In some embodiments, the providing the adhesive comprises depositing an adhesive having a viscosity of 10 mPa·s to 100 mPa·s.

[0016] In some embodiments, a display system includes an eyepiece comprising a stack of waveguides. The stack of waveguides includes a first waveguide comprising an optically transmissive body and a spacer integral with the optically transmissive body, the spacer having an end, the end comprising one or more ridges extending across the end. The stack of waveguides also includes an adhesive disposed within a volume defined by the one or more ridges, and a second waveguide overlying the first waveguide and in contact with the adhesive. The one or more ridges may comprise a plurality of ridges forming a grating. The one or more ridges may extend around a perimeter of the end of the spacer and enclose the volume. The adhesive may have a maximum thickness of 1 μm or greater. The maximum thickness may also be 35 μm or less. A surface of the second waveguide in contact with the adhesive may have a roughened texture. The first and second waveguides may each comprise an optical in-coupling optical element and an optical out-coupling optical element. The optical out-coupling optical elements of the first and second waveguides may be configured to output light with different amounts of wavefront divergence.

[0017] In some other embodiments, a method for making an eyepiece is provided. The method includes forming a waveguide stack. The forming of the waveguide stack includes providing a waveguide having an integral spacer, the spacer having one or more ridges extending across an end of the spacer, providing an adhesive on the one or more ridges and in a volume between the one or more ridges of the spacer, and contacting the adhesive with the other waveguide to bond the integral spacer to the other waveguide. The providing of the adhesive may include squirting-depositing the adhesive on and between the one or more ridges. The providing of the adhesive may include depositing a layer of adhesive having a maximum thickness of 1-35 μm. The one or more ridges comprise a plurality of ridges forming a lattice. The one or more ridges may extend around a perimeter of the end of the spacer and enclose a volume.

[0018] In some embodiments, a display system is provided. The display system includes an eyepiece comprising a stack of waveguides. The stack of waveguides includes a first waveguide formed from a polymer, a second waveguide formed from a polymer, and a spacer separating and extending between the first and second waveguides. The spacer is formed from a polymer, and the first waveguide, the spacer, and the second waveguide form a continuous mass of polymer. The first and second waveguides may comprise parallel sheets of polymer. The first and second waveguides may each comprise an optical in-coupling optical element and an optical out-coupling optical element. The optical in-coupling optical element and the optical out-coupling optical element may comprise a diffraction grating formed from a polymer. The optical out-coupling optical element of the first waveguide and the optical out-coupling optical element of the second waveguide may be configured to output light with different amounts of wavefront divergence.

[0019] In some embodiments, a method for making an eyepiece is provided. The method includes forming a waveguide stack. The forming of the waveguide stack includes providing a waveguide having an integral spacer, the waveguide being formed from a polymer, providing an adhesive solution on an end of the spacer, the adhesive solution comprising a chemical species for forming a polymer, contacting the solution with the other waveguides, and solidifying the solution to form a monolithic mass comprising the integral spacer, the waveguide, and the other waveguides. The providing of the solution may include jet-depositing the solution on the end of the spacer. The providing of the waveguide may include depositing a waveguide-forming solution comprising a chemical species for forming a polymer into a mold. The adhesive solution may have a lower viscosity than the waveguide-forming solution. The end of the spacer may include one or more ridges that define a volume, and the providing of the adhesive solution may include providing the adhesive solution within the volume. The one or more ridges may include a plurality of ridges that form a grating. The one or more ridges may extend around the periphery of the end of the spacer and enclose a portion of the volume. The present invention provides, for example, the following: (Item 1) 1. A display system, comprising: Waveguide Stack the waveguide stack comprising: a first waveguide comprising an optically transmissive body, a first major surface, and a spacer integral with the optically transmissive body, the spacer extending perpendicularly from the first major surface; a second waveguide comprising an optically transparent body and a second major surface facing the first major surface of the first waveguide and spaced therefrom by the spacer; an adhesive provided on a top surface of the spacer, the adhesive attaching the spacer to a second major surface of the second waveguide; Equipped with The adhesive has an as-deposited viscosity of 10 mPa·s to 100 mPa·s. (Item 2) Item 2. The display system of item 1, wherein the spacer extends along a circumference of the first waveguide. (Item 3) Item 2. The display system of item 1, wherein the spacer defines an edge of the waveguide. (Item 4) 2. The display system of claim 1, wherein the adhesive constitutes a first adhesive and the waveguide stack further comprises a second adhesive extending between and forming an adhesive mass attaching a first major surface of the first waveguide and a second major surface of the second waveguide. (Item 5) Item 5. The display system of item 4, wherein the first adhesive and the second adhesive have different viscosities. (Item 6) 6. The display system of claim 5, wherein the second adhesive has an as-deposited viscosity of 10,000 mPa·s to 50,000 mPa·s. (Item 7) 5. The display system of claim 4, wherein the second adhesive is located around a periphery of a spacer on the first major surface of the first waveguide. (Item 8) Item 2. The display system of item 1, wherein the first waveguide further comprises one or more diffractive optical elements within an area within the first major surface of the spacer. (Item 9) 9. The display system of claim 8, wherein the first major surface of the first waveguide further comprises an adhesive-capturing recess between the one or more diffractive optical elements and the adhesive. (Item 10) Item 2. The display system of item 1, wherein the adhesive is disposed on a top surface and a side surface of the spacer. (Item 11) Item 13. The display system of item 1, wherein the first waveguide comprises a plurality of spacers. (Item 12) Item 11. The display system of item 1, wherein one or more surfaces in contact with the adhesive are rough. (Item 13) Item 13. The display system of item 12, wherein the one or more surfaces are nano-textured. (Item 14) Item 13. The display system of item 12, further comprising an adhesive flow barrier extending along two or more sides of the top surface, the adhesive flow barrier defining a central volume occupied by the adhesive. (Item 15) Item 2. The display system of item 1, wherein the spacer comprises one or more ventilation holes extending laterally through the spacer. (Item 16) Item 16. The display system of item 15, wherein the first waveguide comprises a plurality of spacers, each spacer comprising one or more ventilation holes. (Item 17) 17. The display system of claim 16, wherein the spacers of a pair of spacers of the plurality of spacers extend laterally alongside each other, and the waveguide stack further comprises one or more debris capture structures located within a volume between adjacent pairs of spacers of the plurality of spacers. (Item 18) 2. The display system of claim 1, wherein the spacer is located within an interior area of ​​a first major surface of the first waveguide. (Item 19) Item 19. The display system of item 18, wherein the spacers comprise single point contact spacers having a maximum lateral cross-sectional dimension of 500 μm or less. (Item 20) Item 2. The display system of item 1, wherein a second major surface of the second waveguide comprises a recess that receives the spacer within the recess. (Item 21) 21. The display system of claim 20, wherein the waveguide stack comprises a plurality of waveguides, two or more of the plurality of waveguides comprising a spacer and a recess, the recess accommodating a spacer of an underlying waveguide. (Item 22) Item 2. The display system of item 1, wherein the spacer has a shape selected from the group consisting of a rectangular prism, a rectangular pyramid, a triangular prism, a triangular pyramid, a cylinder, and a cone. (Item 23) Item 13. The display system of item 1, wherein the adhesive comprises a light absorber. (Item 24) Item 24. The display system of item 23, wherein the adhesive is doped with a black colorant. (Item 25) Item 2. The display system of item 1, wherein the first and second waveguides are separated by a gap having a size defined by the spacer and adhesive. (Item 26) Item 13. The display system of item 1, wherein the adhesive has a refractive index greater than 1.65. (Item 27) Each of the first and second waveguides comprises: an incoupling optical element configured to incoupling the incident image light; an outcoupling optical element configured to outcoupling the incoupled image light; Item 2. The display system of item 1, comprising: (Item 28) Item 28. The display system of item 27, further comprising a light projector system configured to project the image light onto the internal coupling optical element. (Item 29) Item 13. The display system of item 1, wherein the spacer comprises a light absorbing material. (Item 30) 1. A display system, comprising: Eyepiece The eyepiece comprises: A waveguide comprising: an optically transmissive body comprising at least one spacer integral with said optically transmissive body; an outcoupling optical element, the outcoupling optical element configured to outcouple light propagating within the optically transmissive body; a waveguide comprising: an upper layer waveguide, the upper layer waveguide being spaced from the waveguide by the at least one spacer; and a pillar, the pillar being formed from an adhesive that attaches the optically transparent body to a surface of an upper layer waveguide; A display system comprising: (Item 31) 31. The display system of claim 30, wherein the external coupling optical element comprises a plurality of protrusions and intervening recesses on a major surface of the optically transparent body, and the at least one spacer extends from the major surface to a height greater than a height of the plurality of protrusions. (Item 32) 31. The display system of claim 30, wherein the adhesive has an as-deposited viscosity of 10,000 mPa·s to 50,000 mPa·s. (Item 33) Item 31. The display system of item 30, wherein the waveguide comprises a pair of integral spacers, and the adhesive is located between the pair of integral spacers. (Item 34) Item 31. The display system of item 30, wherein the adhesive is doped with a black colorant. (Item 35) Item 31. The display system of item 30, wherein the adhesive has a refractive index greater than 1.65. (Item 36) Item 31. The display system of item 30, wherein the adhesive is located on a surface of the optically transparent body between the outcoupling optical element and the at least one spacer. (Item 37) Item 31. The display system of item 30, wherein a surface of the optically transmissive body includes an adhesive capture recess between the outcoupling optical element and the adhesive. (Item 38) Item 31. The display system of item 30, wherein the adhesive is located adjacent a periphery of the optically transmissive body. (Item 39) Item 39. The display system of item 38, wherein the at least one spacer is positioned between the outcoupling optical element and the adhesive. (Item 40) 31. A display system as described in item 30, wherein the adhesive constitutes a first adhesive and the eyepiece lens comprises a second adhesive bonded to a surface of the at least one spacer and the upper layer waveguide. (Item 41) Item 31. The display system of item 30, wherein the optically transmissive body comprises a plurality of spacers. (Item 42) 1. A display system, comprising: Eyepiece The eyepiece comprises: a waveguide, the waveguide comprising an outcoupling optical element configured to outcouple light propagating within an optically transmissive body; an upper waveguide spaced apart from the waveguide; a pillar, the pillar being formed from an adhesive extending from the waveguide to the overlying waveguide, the adhesive having an as-deposited viscosity of 10,000 mPa·s to 50,000 mPa·s; A display system comprising: (Item 43) Item 43. The display system of item 42, wherein the height is between 30 μm and 200 μm. (Item 44) Item 43. The display system of item 42, wherein the waveguide comprises an integral spacer extending adjacent to the post, the spacer extending vertically and contacting the waveguide. (Item 45) Item 43. The display system of item 42, wherein the adhesive is doped with a black colorant. (Item 46) Item 43. The display system of item 42, wherein the adhesive has a refractive index greater than 1.65. (Item 47) Item 43. The display system of item 42, wherein the adhesive defines edges of the waveguide and the upper waveguide. (Item 48) Item 43. The display system of item 42, wherein the waveguide comprises an adhesive capture recess on a surface of the waveguide between the outcoupling optical element and the post. (Item 49) Item 49. The display system of item 48, wherein the recess has a width of 50 μm to 2 mm. (Item 50) Item 50. The display system of item 49, wherein the recess has a depth of 50 μm to 0.4 mm. (Item 51) 1. A method for making a waveguide stack, the method comprising: Forming the underlying waveguide forming the underlying waveguide comprises: defining an integral outcoupling optical element and an integral spacer on a major surface of the underlying waveguide, the integral spacer being spaced from the outcoupling optical element and extending to a height above the outcoupling optical element; providing an adhesive on a major surface of the underlying waveguide; attaching an upper waveguide to the lower waveguide using said adhesive; Including, The method of claim 1, wherein the integral spacer defines a gap between a major surface of the lower waveguide and a bottom surface of the upper waveguide. (Item 52) Item 52. The method of item 51, wherein the integral outcoupling optical element and the integral spacer are formed simultaneously. (Item 53) 52. The method of claim 51, further comprising curing the adhesive after attaching the upper waveguide to the lower waveguide. (Item 54) 52. The method of claim 51, further comprising singulating the lower waveguide and the upper waveguide. (Item 55) 55. The method of claim 54, wherein the singulating comprises cutting the lower waveguide and the upper waveguide along a singulation path. (Item 56) Item 56. The method of item 55, wherein cutting the underlying waveguide comprises cutting the underlying waveguide with a laser. (Item 57) Item 55. The method of item 54, wherein the singulating comprises removing at least a portion of the integral spacer. (Item 58) 55. The method of claim 54, wherein the singulating comprises removing at least a portion of the adhesive. (Item 59) Item 55. The method of item 54, wherein the singulating comprises removing the entire unitary spacer. (Item 60) Item 52. The method of item 51, wherein the adhesive comprises a first adhesive and a second adhesive is provided on an upper surface of the integral spacer. (Item 61) Item 61. The method of item 60, wherein the second adhesive has an as-deposited viscosity of 10 mPa·s to 100 mPa·s. (Item 62) Item 61. The method of item 60, wherein the first adhesive has an as-deposited viscosity of 10,000 mPa·s to 50,000 mPa·s. (Item 63) Item 52. The method of item 51, wherein the adhesive is provided adjacent the integral spacer. (Item 64) Item 64. The method of item 63, wherein the adhesive is provided around an integral spacer on a major surface of the underlying waveguide. (Item 65) Item 52. The method of item 51, wherein the adhesive is provided between the outcoupling optical element and an integral spacer on a major surface of the underlying waveguide. (Item 66) Item 52. The method of item 51, wherein a plurality of integral spacers are defined on a major surface of the underlying waveguide. (Item 67) Item 67. The method of item 66, wherein the adhesive fills a volume between two spacers of the plurality of spacers. (Item 68) 52. The method of claim 51, further comprising roughening one or more surfaces of the lower waveguide and the upper waveguide prior to attaching the upper waveguide to the lower waveguide, the one or more surfaces comprising a surface in contact with the adhesive. (Item 69) 52. The method of claim 51, further comprising forming one or more vent holes extending laterally through the integral spacer. (Item 70) 1. A display system, comprising: An eyepiece, a waveguide, the waveguide comprising an outcoupling optical element configured to outcouple light propagating within an optically transmissive body; an upper waveguide spaced apart from the waveguide; an eyepiece comprising: an adhesive for attaching the waveguide to the upper layer waveguide; Equipped with A display system, wherein the surfaces of the optically transmissive body and the upper waveguide in contact with the adhesive are roughened. (Item 71) Item 71. The display system of item 70, wherein the rough surface comprises nanostructures to increase adhesion of the adhesive. (Item 72) Item 71. The display system of item 70, wherein the waveguide comprises an integral spacer, the spacer separating the waveguide and the upper layer waveguide. (Item 73) Item 73. The display system of item 72, further comprising a pair of integral spacers extending around the periphery of the waveguide. (Item 74) Item 74. The display system of item 73, wherein each spacer of the pair of integral spacers includes a ventilation hole extending laterally through the spacer. (Item 75) Item 73. The display system of item 72, wherein the adhesive is disposed on an upper surface of the spacer, the upper surface being one of the roughened surfaces. (Item 76) Item 71. The display system of item 70, wherein the adhesive has an as-deposited viscosity of 10,000 mPa·s to 50,000 mPa·s and forms pillars having heights of 10 μm to 200 μm. (Item 77) Item 71. The display system of item 70, further comprising an adhesive capture recess on a major surface of the waveguide between the outcoupling optical element and the adhesive. (Item 78) 1. A display system, comprising: Eyepiece with Waveguide The waveguide comprises: a light outcoupling optical element; a spacer integral with the waveguide, the spacer extending around a circumference of the waveguide; one or more vent holes formed in the spacer, the one or more vent holes comprising through openings extending laterally through the spacer; Equipped with A display system wherein the vent hole has a width of 100 μm or less. (Item 79) Item 79. The display system of item 78, wherein the integral spacer defines an edge of the waveguide. (Item 80) Item 79. The display system of item 78, further comprising an adhesive attaching the waveguide to an upper waveguide, the adhesive having an as-deposited viscosity of 10,000 mPa·s to 50,000 mPa·s and forming a pillar having a height of 10 μm to 200 μm extending from the waveguide to the upper waveguide. (Item 81) Item 79. The display system of item 78, further comprising an adhesive on a top surface of the spacer, the adhesive attaching the waveguide to an overlying waveguide, the adhesive having an as-deposited viscosity of 10 mPa·s to 100 mPa·s. (Item 82) 1. A display system, comprising: Eyepiece The eyepiece comprises: A waveguide comprising: a light outcoupling optical element; a pair of spacers integral with the waveguide, the spacers extending around a circumference of the waveguide, the spacers extending alongside one another and defining a channel therebetween; one or more laterally extending vent holes in each of said spacers; a waveguide comprising: an upper layer waveguide attached to the waveguide, the upper layer waveguide being spaced from the waveguide by the pair of spacers; A display system comprising: (Item 83) Item 83. The display system of item 82, wherein the one or more ventilation holes in a first one of the spacers are located remotely from the one or more ventilation holes formed in a second one of the spacers. (Item 84) Item 83. The display system of item 82, further comprising a debris capture structure formed between adjacent walls of the spacer of the plurality of walls of the spacer. (Item 85) Item 85. The display system of item 84, wherein the debris capture structure comprises a physical barrier configured to capture debris flowing through the channel between the pair of spacers. (Item 86) Item 86. The display system of item 85, wherein the debris capture structure comprises an angled extension of the spacer, the angled extension extending into the channel. (Item 87) Item 83. The display system of item 82, wherein the pair of spacers extend parallel to each other. (Item 88) Item 83. The display system of item 82, wherein the waveguide further comprises one or more additional integral spacers extending along a periphery of the waveguide. (Item 89) 89. The display system of claim 88, wherein the one or more additional integral spacers define a volume with another of the integral spacers and further comprise an adhesive within the volume, the adhesive attaching the waveguide to the upper layer waveguide. (Item 90) 1. A display system, comprising: Eyepiece The eyepiece comprises: A waveguide comprising: a light extraction optical element on an active area of ​​a major surface of the waveguide; a plurality of spacers within the active area; a waveguide comprising: Upper waveguide and Equipped with the spacer separates the waveguide and the upper waveguide; The spacer is mm 2 A display system having an areal density of one spacer per pixel or less. (Item 91) Item 91. The display system of item 90, wherein the spacer has a cross-sectional shape on a plane transverse to the height of the spacer, the maximum dimension of the cross-sectional shape being 300 μm or less. (Item 92) Item 91. The display system of item 90, further comprising one or more integral spacers extending around a periphery of the waveguide. (Item 93) 93. The display system of any one of claims 92, further comprising an adhesive attaching the integral spacer extending around a circumference of the waveguide to the upper layer waveguide, the adhesive having an as-deposited viscosity of 10 mPa·s to 100 mPa·s. (Item 94) Item 91. The display system of item 90, further comprising an adhesive attaching the waveguide to the overlying waveguide, the adhesive having an as-deposited viscosity of 10,000 mPa·s to 50,000 mPa·s and forming pillars having a height of 10 μm to 200 μm. (Item 95) 1. A method for making a waveguide stack, the method comprising: forming an underlying waveguide, the forming of the underlying waveguide comprising: defining an integral outcoupling optical element and an integral spacer on a major surface of the underlying waveguide, the integral spacer being spaced from and extending to a height above the diffractive optical element; and providing an adhesive on the upper waveguide; attaching the upper layer waveguide to the lower layer waveguide using the adhesive provided on the upper layer waveguide; Including, The method of claim 1, wherein the integral spacer defines a gap between a major surface of the lower waveguide and a bottom surface of the upper waveguide. (Item 96) Item 96. The method of item 95, wherein defining an integral outcoupling optical element and the integral spacer comprises casting the waveguide in a mold. (Item 97) Item 96. The method of item 95, wherein defining the integral outcoupling optical element includes forming a diffraction grating. (Item 98) 96. The method of claim 95, wherein providing the adhesive comprises depositing an adhesive having a viscosity of 10 mPa·s to 100 mPa·s. (Item 99) 1. A display system, comprising: Eyepiece with Waveguide Stack the waveguide stack comprising: a first waveguide comprising an optically transmissive body and a spacer integral with the optically transmissive body, the spacer having an end, the end comprising one or more ridges extending across the end; an adhesive, the adhesive being disposed within a volume defined by the one or more ridges; a second waveguide, the second waveguide being on top of the first waveguide and in contact with the adhesive; A display system comprising: (Item 100) 99. The display system of claim 99, wherein the one or more ridges comprise a plurality of ridges forming a grid. (Item 101) 100. The display system of claim 99, wherein the one or more ridges extend around a perimeter of an end of the spacer and enclose the volume. (Item 102) 99. The display system of claim 99, wherein the adhesive has a maximum thickness of 1 μm or more. (Item 103) Item 103. The display system of item 102, wherein the maximum thickness is 35 μm or less. (Item 104) Item 100. The display system of item 99, wherein the surface of the second waveguide in contact with the adhesive has a rough texture. (Item 105) Item 100. The display system of item 99, wherein the first waveguide and the second waveguide each comprise a light in-coupling optical element and a light out-coupling optical element. (Item 106) 100. The display system of claim 99, wherein the light outcoupling optical elements of the first waveguide and the second waveguide are configured to output light with different amounts of wavefront divergence. (Item 107) 1. A method for making an eyepiece lens, the method comprising: Forming a Waveguide Stack forming the waveguide stack comprises: providing a waveguide having an integral spacer, the spacer having one or more ridges extending across an end of the spacer; providing an adhesive onto the one or more ridges and within a volume between the one or more ridges of the spacer; contacting the adhesive with another waveguide and adhering the integral spacer to the other waveguide; A method comprising: (Item 108) Item 108. The method of item 107, wherein providing the adhesive comprises squirting-depositing the adhesive onto and between the one or more ridges. (Item 109) Item 108. The method of item 107, wherein providing the adhesive comprises depositing a layer of adhesive having a maximum thickness of 1 to 35 μm. (Item 110) Item 108. The display system of item 107, wherein the one or more ridges comprise a plurality of ridges forming a grid. (Item 111) Item 108. The display system of item 107, wherein the one or more ridges extend around a perimeter of an end of the spacer and enclose the volume. (Item 112) 1. A display system, comprising: Eyepiece with Waveguide Stack the waveguide stack comprising: a first waveguide formed from a polymer; a second waveguide formed from the polymer; and a spacer separating and extending between the first and second waveguides, the spacer being formed from the polymer; Equipped with The display system, wherein the first waveguide, the spacer, and the second waveguide form a continuous mass of polymer. (Item 113) Item 113. The display system of item 112, wherein the first and second waveguides comprise parallel sheets of the polymer. (Item 114) Item 113. The display system of item 112, wherein the first and second waveguides each comprise a light in-coupling optical element and a light out-coupling optical element. (Item 115) Item 113. The display system of item 112, wherein the light in-coupling optical elements and the light out-coupling optical elements comprise diffraction gratings formed from the polymer. (Item 116) Item 113. The display system of item 112, wherein the light outcoupling optical element of the first waveguide and the light outcoupling optical element of the second waveguide are configured to output light with different amounts of wavefront divergence. (Item 117) 1. A method for making an eyepiece lens, the method comprising: Forming a Waveguide Stack forming the waveguide stack comprises: providing a waveguide having an integral spacer, said waveguide being formed from a polymer; providing an adhesive solution on the end of the spacer, the adhesive solution comprising a chemical species for forming the polymer; contacting the solution with another waveguide; allowing the solution to solidify to form a monolithic mass comprising the integral spacer, the waveguide, and the other waveguide; A method comprising: (Item 118) Item 118. The method of item 117, wherein providing the solution includes jet-depositing the solution onto the ends of the spacers. (Item 119) Item 118. The method of item 117, wherein providing the waveguide comprises depositing into the mold a waveguide-forming solution comprising chemical species for forming the polymer. (Item 120) Item 120. The method of item 119, wherein the adhesive solution has a lower viscosity than the waveguide forming solution. (Item 121) Item 118. The method of item 117, wherein an end of the spacer comprises one or more ridges defining a volume, and providing the adhesive solution comprises providing the adhesive solution within the volume. (Item 122) Item 118. The display system of item 117, wherein the one or more ridges comprise a plurality of ridges forming a grid. (Item 123) Item 118. The display system of item 117, wherein the one or more ridges extend around a perimeter of an end of the spacer and enclose a portion of the volume. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 illustrates a user's view of an augmented reality (AR) device.

[0021] [Diagram 2] FIG. 2 illustrates a conventional display system for simulating a three-dimensional image for a user.

[0022] [Diagram 3] 3A-3C illustrate the relationship between the radius of curvature and the radius of focus.

[0023] [Figure 4A] Figure 4A illustrates a representation of the accommodation-vergence-divergence motor response of the human visual system.

[0024] [Figure 4B] FIG. 4B illustrates examples of different accommodation and convergence states of a pair of eyes of a user.

[0025] [Figure 4C] FIG. 4C illustrates an example of a top-down view representation of a user viewing content through a display system.

[0026] [Figure 4D] FIG. 4D illustrates another example of a top-down view representation of a user viewing content through a display system.

[0027] [Diagram 5] FIG. 5 illustrates aspects of an approach for simulating a three-dimensional image by modifying wavefront divergence.

[0028] [Figure 6] FIG. 6 illustrates an embodiment of a waveguide stack for outputting image information to a user.

[0029] [Figure 7] FIG. 7 illustrates an example of an output beam output by a waveguide.

[0030] [Figure 8]FIG. 8 illustrates an example of a stacked waveguide assembly in which each depth plane contains an image formed using multiple different primary colors.

[0031] [Figure 9A] FIG. 9A illustrates a cross-sectional side view of an example of a set of stacked waveguides, each of which includes an internal coupling optical element.

[0032] [Figure 9B] FIG. 9B illustrates a perspective view of the multiple stacked waveguide embodiment of FIG. 9A.

[0033] [Figure 9C] FIG. 9C illustrates a top-down plan view of the multiple stacked waveguide embodiment of FIGS. 9A and 9B.

[0034] [Figure 9D] FIG. 9D illustrates an example of a wearable display system.

[0035] [Figure 10A] FIG. 10A illustrates an embodiment of a waveguide with a spacer.

[0036] [Figure 10B] FIG. 10B illustrates an example of a three-dimensional shape for a spacer and a recess for receiving the spacer.

[0037] [Figure 10C] FIG. 10C illustrates an example of a stack of waveguides with spacers.

[0038] [Figure 11A] FIG. 11A illustrates an example of a stack of waveguides comprising spacers with light scattering features.

[0039] [Figure 11B]FIG. 11B illustrates an example of a stack of waveguides with spacers and anti-light leakage material at the interfaces between the spacers and the adjacent waveguides.

[0040] [Figure 11C] FIG. 11C illustrates an example of a stack of waveguides with adhesive at the interface between the spacer and the adjacent waveguide.

[0041] [Figure 11D] FIG. 11D illustrates an example of a stack of waveguides with adhesive both at the interface between the spacer and the nearest waveguide and on the vertical sides of the spacer.

[0042] [Figure 11E] FIG. 11E illustrates an example of a waveguide stack with adhesive forming posts adjacent to the spacers.

[0043] [Figure 11F] FIG. 11F illustrates an example of a stack of waveguides with a first adhesive at the interface between the spacer and the adjacent waveguide and a second adhesive forming a post adjacent the spacer.

[0044] [Figure 11G] FIG. 11G illustrates an example of a stack of waveguides with multiple spacers forming a volume therebetween that holds an adhesive that extends to the nearest waveguide.

[0045] [Figure 11H] FIG. 11H illustrates an embodiment of a stack of waveguides with adhesive-capturing recesses on the major surfaces of the waveguides between the adhesive and the active areas of the waveguides.

[0046] [Figure 11I] FIG. 11I illustrates an example of a waveguide stack with a roughened surface in the area where the adhesive is applied.

[0047] [Figure 11J] FIG. 11J illustrates an example of a stack of waveguides similar to that of FIG. 11G, but in which at least one of the waveguides includes an adhesive capture recess on a major surface of the waveguide between the adhesive and the active area of ​​the waveguide.

[0048] [Figure 11K] FIG. 11K illustrates an example of a waveguide stack with multiple spacers, where adhesive is applied within a volume between two adjacent spacers and an additional spacer that forms an adhesive capture volume adjacent to the adhesive fill volume.

[0049] [Figure 11L] 11L-11M illustrate cross-sectional side and top-down view embodiments of a spacer, respectively, having ridges for retaining adhesive. [Figure 11M] 11L-11M illustrate cross-sectional side and top-down view embodiments of a spacer, respectively, having ridges for retaining adhesive.

[0050] [Figure 11N] 11N-11O illustrate cross-sectional side and top-down views, respectively, of another embodiment of a spacer having ridges for retaining adhesive. [Figure 11O] 11N-11O illustrate cross-sectional side and top-down views, respectively, of another embodiment of a spacer having ridges for retaining adhesive.

[0051] [Figure 12A] 12A-12C illustrate an embodiment of a method for forming a waveguide with a spacer. [Figure 12B] 12A-12C illustrate an embodiment of a method for forming a waveguide with a spacer. [Figure 12C] 12A-12C illustrate an embodiment of a method for forming a waveguide with a spacer.

[0052] [Figure 13A]13A-13B illustrate an example of a top-down plan view of a waveguide with a spacer. [Figure 13B] 13A-13B illustrate an example of a top-down plan view of a waveguide with a spacer.

[0053] [Figure 13C] FIG. 13C illustrates an example of a top-down plan view of a waveguide comprising a spacer defining walls with vent holes therein.

[0054] [Figure 13D] FIG. 13D illustrates an example of a top-down plan view of a waveguide comprising multiple walls of a spacer with vent holes in the walls and a debris capture structure in the volume between the walls.

[0055] [Figure 13E] FIG. 13E illustrates an example of a top-down plan view of a waveguide with spacers within the interior area of ​​the major surfaces of the waveguide.

[0056] [Figure 14] FIG. 14 illustrates an embodiment of a waveguide with spacers and recesses of variable dimensions.

[0057] [Figure 15A] 15A-15G illustrate an embodiment of a method for forming a hybrid waveguide with a spacer. [Figure 15B] 15A-15G illustrate an embodiment of a method for forming a hybrid waveguide with a spacer. [Figure 15C] 15A-15G illustrate an embodiment of a method for forming a hybrid waveguide with a spacer. [Figure 15D] 15A-15G illustrate an embodiment of a method for forming a hybrid waveguide with a spacer. [Figure 15E] 15A-15G illustrate an embodiment of a method for forming a hybrid waveguide with a spacer. [Figure 15F]15A-15G illustrate an embodiment of a method for forming a hybrid waveguide with a spacer. [Figure 15G] 15A-15G illustrate an embodiment of a method for forming a hybrid waveguide with a spacer.

[0058] [Figure 16] FIG. 16 illustrates an embodiment of a waveguide having edges that are coated with an absorbing material.

[0059] [Figure 17] 17-18 illustrate examples of waveguides having light absorbing material extending over portions of the top and bottom major surfaces of the waveguide. [Figure 18] 17-18 illustrate examples of waveguides having light absorbing material extending over portions of the top and bottom major surfaces of the waveguide.

[0060] [Figure 19] 19-20 illustrate simulation results of extinction as a function of incidence angle for different absorbing materials. [Figure 20] 19-20 illustrate simulation results of extinction as a function of incidence angle for different absorbing materials.

[0061] [Figure 21] FIG. 21 illustrates an example of a waveguide having roughened edges that may be coated with an absorbing material.

[0062] [Figure 22A] FIG. 22A illustrates an example of a waveguide having edges with an external coupling grating and an absorbing material.

[0063] [Figure 22B] 22B-22C illustrate an embodiment of a waveguide having edges with light trapping structures and light absorbing materials. [Figure 22C] 22B-22C illustrate an embodiment of a waveguide having edges with light trapping structures and light absorbing materials.

[0064] [Figure 23] FIG. 23 illustrates an example edge of an embodiment of the placement of light absorbing material along the edge of a waveguide.

[0065] [Figure 24] FIG. 24 illustrates a stack of waveguides with integral spacers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0066] Detailed Description (Detailed Description) The eyepiece augmentation and virtual reality display system may include an eyepiece for directing image information into a viewer's eye. The eyepiece may be formed from a stack of waveguides spaced apart by intervening beads of glue. It should be understood that the size of the beads and the separation between the waveguides provided by the beads may affect the optical performance of the eyepiece and the perceived image quality of the display system. For example, the beads may be formed in a specific location, and then an upper waveguide may press the beads at a specific pressure, after which the beads may be solidified by curing. As a result, the formation of the beads may require precise alignment and controlled pressure to maintain a constant separation distance between the waveguides throughout the entire stack of waveguides. Providing such precise alignment and pressure control may be difficult.

[0067] Additionally, complications can arise when dispensing liquid adhesives: air bubbles and gaps can be present during adhesive dispensing. Solid adhesives, on the other hand, can have difficulties in bubble-free application and precise adhesive registration.

[0068] Also, when the waveguides are formed from a polymer, the polymer waveguides may be flexible, and utilizing beads of material alone to separate the waveguides may not provide sufficient mechanical or structural stability to maintain the desired separation between the waveguides. For example, some stacking systems may use a liquid adhesive mixed with microspheres that are intended to set the gap between adjacent layers. However, the microspheres almost always contain some size variation, resulting in inconsistent separation between the layers, regardless of other factors. Additionally, the viscosity of the adhesive may prevent a uniform press onto the adhesive throughout the entire surface area of ​​the eyepiece.

[0069] In some embodiments, one or more of the waveguides that may be used to form a stack of waveguides may include an integral spacer to provide a desired separation from an overlying or underlying structure, such as another waveguide. The waveguide may form an eyepiece that is part of a display system (e.g., an AR or VR headset) with a waveguide having a light outcoupling optical element for directing image light to a user's eye. In some embodiments, the light outcoupling optical element may be a surface relief feature, e.g., a diffractive optical element, formed simultaneously with the integral spacer. In addition to display systems, the various embodiments described herein may generally be applied to stacks of polymer layers where a fixed distance is required between the layers.

[0070] In some embodiments, the spacer and the main body of the waveguide form a monolithic structure, and such a spacer may be referred to as an integral spacer. In some embodiments, the waveguide may be a hybrid waveguide, comprising multiple layers, one of which may include the spacer and the external coupling optical element. In some embodiments, the spacer and the main body of the waveguide (or layers of the hybrid waveguide) may be formed from the same material, which extends continuously and homogeneously from the main body (or layers of the hybrid waveguide) and defines the spacer.

[0071] In some embodiments, the outcoupling optical elements may be located within the active area of ​​the waveguide, while the spacers may be located within a non-active area of ​​the waveguide (e.g., an area of ​​the waveguide spaced from an area having a diffractive optical element) such that the spacers do not interfere with the line of sight of a user of a display system comprising the waveguide. For example, the spacers may extend along substantially the entire circumference of the waveguide. In some embodiments, contact spacers may be located within the active area of ​​the waveguide, but the contact spacers may be sized and shaped such that they are substantially invisible to the user (e.g., such that interference with the user's line of sight can be eliminated or sufficiently reduced to provide good display quality).

[0072] It should be appreciated that the one or more spacers of the waveguide provide the desired spacing between the waveguide and the overlying waveguide. Preferably, the spacers attach or bond the waveguides together using an adhesive. In some embodiments, a low viscosity adhesive may be utilized on a surface of the spacer, which contacts the overlying waveguide and bonds the spacer (and integral waveguide) to the overlying waveguide. Advantageously, the low viscosity adhesive may provide good wetting and gap-filling properties for excellent adhesion to the spacer and overlying waveguide. In some embodiments, the low viscosity adhesive may have a viscosity of 5 mPa·s to 100 mPa·s.

[0073] In some other embodiments, one or more spacers may be used to space the waveguides from the overlying waveguide, while the adhesive bonding the waveguides together may extend directly from the surface of the waveguide to the overlying waveguide such that the adhesive forms pillars that extend vertically substantially the entire height of the spacer. These pillars may advantageously provide additional mechanical support to the waveguide stack and / or allow for subsequent removal of the spacer. In such embodiments, the adhesive is preferably a high viscosity adhesive, e.g., having a viscosity in the range of 10,000 mPa·s to 50,000 mPa·s. In some embodiments, regardless of whether the adhesive is a high or low viscosity adhesive, an adhesive capture structure may be provided between the active area of ​​the waveguide (e.g., the area containing the optical outcoupling optical elements) and the adhesive.

[0074] In some embodiments, the upper end of the spacer for interfacing with the upper waveguide may comprise a ridge that acts as a barrier and prevents unwanted bleeding or flow of adhesive. For example, the ridge may encapsulate a volume into which the adhesive is deposited, or may form a lattice structure with a volume for receiving adhesive, the volume being elongated in a direction that directs the adhesive away from the optical structure or other structures of the waveguide that are desired to be free of adhesive.

[0075] In some embodiments, the adhesive that joins the spacer and the upper waveguide together may be formed from the same polymer as the spacer and the waveguide. For example, an adhesive solution containing the same chemical species to form the polymer may be applied to the end of the spacer, the spacer with the adhesive solution may be joined to the upper waveguide, and the adhesive solution may then be solidified (e.g., by curing). Advantageously, a monolithic stack of waveguides may thus be formed using the same polymer material that extends from the waveguide to the spacer to the upper waveguide.

[0076] It should be understood that in a stack of waveguides, the spacer may enclose a volume that separates two adjacent waveguides. One or more vent holes in the spacer may be provided to allow gas flow in and out of that volume. The vent holes in the integral spacer may be formed during casting of the polymer eyepiece. Alternatively, the vent holes may be created by contacting the surface of the eyepiece with a milling nozzle or laser light from the side and / or top of the waveguide stack. If a milling nozzle or laser is to be used, the integral spacer may be cast as a closed loop around the periphery of the waveguides, and the vent holes may be subsequently formed during the milling step.

[0077] In some embodiments, a waveguide may comprise two or more walls formed from integral spacers around the periphery of the waveguide. In some embodiments, vent holes can be formed in each wall formed from the integral spacer. To prevent debris from flowing into the active area of ​​the waveguide during singulation (e.g., when dicing or cutting a portion of a large sheet of optically transparent material into individual waveguides), vent holes may be formed at different locations in each wall formed from the integral spacer. It should further be understood that a pair of integral spacers may define channels between them, and debris capture structures may be formed in these channels (e.g., near the vent holes) to prevent debris from traveling through the channels and entering the active area through the vent holes in the inner spacer.

[0078] In some embodiments, singulation may be performed along a contour that extends through one or more spacers. In such cases, the spacers themselves may define one or more edges of the singulated waveguides. In some other embodiments, as described herein, the singulation path may result in total removal of the spacers, thereby leaving behind, for example, pillars formed from the adhesive to join and space adjacent waveguides.

[0079] In some embodiments, a spacer is disposed on one major surface of the waveguide, and a recess is provided on the opposing major surface of the waveguide. The recess is sized and positioned to align with the spacer of the immediately adjacent waveguide, thereby forming a self-aligned stack of waveguides. The top of the spacer may comprise light scattering features and / or a light leakage prevention material (e.g., an anti-reflective coating and / or a light absorbing material) to prevent light leakage between the waveguides. In some embodiments, an adhesive (e.g., a bead of glue) may be used to align and adhere the spacer (of another waveguide) to the opposing major surface of the waveguide. The adhesive may be used alone or may be utilized in combination with the recess to align and adhere the spacer, improving adhesion and mechanical stability of the waveguide stack. Additionally, the spacer may comprise a roughened non-uniform or irregular surface to provide small structures that increase the contact area and improve adhesion between the spacer and the opposing major surface of the waveguide.

[0080] In some embodiments, the spacers and / or depressions may have variable sizes (e.g., widths), orientations, locations, and / or multiple spacers and / or depressions may be formed in adjacent groups of spacers and / or depressions. For example, both major surfaces of a waveguide may include spacers and depressions, thereby forming an interlocking system of spacers and depressions with underlying and / or overlying matching waveguides to form a stack of waveguides. Advantageously, the variable sizes and / or adjacent groups of spacers and / or depressions may increase the mechanical and structural stability of a single waveguide and / or a stack of waveguides.

[0081] In some embodiments, where the waveguides form an eyepiece for a display system, different waveguides of a stack of waveguides may be configured to in-couple and / or out-couple light of different colors, e.g., different primary colors to form a full-color image. Additionally or alternatively, different waveguides of a stack of waveguides may be configured to output light with different amounts of wavefront divergence to display image content at different apparent distances from a viewer.

[0082] Advantageously, the spacers that are integral with the waveguides provide a rigid structure for easy and reproducible separation of the spacers of a stack of spacers. In addition, providing matching recesses in the waveguides further facilitates the creation of a consistent stack of spacers by providing a self-aligned stack. Consistent separation between spacers can provide consistent optical performance by consistently preventing light from leaking between the waveguides in addition to promoting total internal reflection of light through the individual waveguides. Furthermore, the manufacturing process can be simplified by eliminating a separate step for depositing a bead of material, precisely applying pressure to the waveguides, and then solidifying the glue material. Rather, if the waveguide comprises a light outcoupling optical element that is a surface feature, the spacers may be formed simultaneously with the outcoupling optical element. In some embodiments, the spacers may be provided without the use of any adhesive. However, even when spacers are used in combination with beads of glue or other adhesive material, the presence of the spacers may reduce the precision required when applying pressure because the spacers provide a fixed physical barrier between adjacent waveguides, preventing the waveguides from advancing closer to each other beyond the spacers.

[0083] The advantage of polymer eyepieces is that they can be cast as monolithic pieces with integral spacers and nanostructures for light propagation. The built-in spacers can be cast with a highly consistent height, which contributes to creating consistent air gaps between adjacent layers and improves the performance of the overall layered structure. These eyepieces can be stacked by utilizing these integral spacers to form more functional and complex display assemblies.

[0084] The methodology discussed herein simplifies the polymer layer assembly process and can significantly improve the performance of, for example, waveguide-based polymer eyepieces for AR or VR applications. The assembly methods described herein can produce robust polymer eyepiece (e.g., waveguide) stacks with consistent gaps throughout the stack, resulting in display devices with consistent and increased performance.

[0085] As discussed herein, the waveguide with integrated spacer may form an eyepiece for an augmented and virtual reality display system. The waveguide may be configured to output light and display image content for a viewer. It should be understood that some light beams in the waveguide may proceed through the waveguide without being outcoupled for the viewer. Such light may be referred to herein as "unused light." Unused light may, in some circumstances, reflect off the edge of the waveguide and propagate back through the waveguide, where the light may propagate out of the waveguide (e.g., be outcoupled by an external coupling element in the waveguide, or escape from total internal reflection due to the angle at which the light reflects off the edge). Undesirably, this propagation of unused light out of the waveguide may cause visual artifacts, such as residual images and / or a reduction in the contrast of the display system.

[0086] In some embodiments, one or more of the waveguides that may be used to form a stack of waveguides (which may include integral spacers to separate adjacent waveguides) may include an edge treatment to reduce or mitigate unwanted reflection and propagation of unused light out of the waveguide, thus improving image quality. Edge treatments may include, by way of example, light absorbing materials applied to one or more edges of the waveguides, and / or anti-reflective structures formed on those edges. In some embodiments, edge treatments may include black oxide treatment materials, black inks, light absorbing materials, edge roughening, outcoupling gratings, light trapping structures, absorbing polymers, and combinations of these and other treatments.

[0087] Advantageously, in some embodiments, various edge treatments may be formed simultaneously with the formation of the spacers and / or diffractive optical elements. For example, the imprint mold may include a pattern to define the edge treatments (e.g., the pattern may define a roughened texture, an outcoupling optical element, and / or a light trapping microstructure).

[0088] In some embodiments, the waveguide with integral spacer disclosed herein may be formed using an imprinting or casting process. For example, the integral spacer and the waveguide may be formed simultaneously by a casting process in which the waveguide material in a liquid state is flowed onto or into a mold containing a negative of the features (e.g., spacers and / or optical elements such as gratings) desired to be formed on the surface of the waveguide. The material is then solidified and the mold is removed, leaving the waveguide with the integral spacer (and possibly other features such as optical elements).

[0089] Reference will now be made to the drawings in which like reference numbers refer to like parts throughout. Unless otherwise indicated, the drawings are schematic and are not necessarily drawn to scale. Exemplary Display Systems

[0090] FIG. 2 illustrates a conventional display system for simulating a three-dimensional image for a user. It should be understood that when a user's eyes are spaced apart and viewing a real object in space, each eye may have a slightly different view of the object and form an image of the object at a different location on each eye's retina. This may be referred to as binocular disparity and may be exploited by the human visual system to provide a perception of depth. Conventional display systems simulate binocular disparity by presenting two distinctly different images 190, 200 with slightly different views of the same virtual object, one for each eye 210, 220, corresponding to the view of the virtual object as it would appear by each eye as if the virtual object were a real object at a desired depth. These images provide binocular cues that the user's visual system may interpret to derive a perception of depth.

[0091] Continuing with reference to FIG. 2, the images 190, 200 are spaced from the eyes 210, 220 by a distance 230 on the z-axis, which is parallel to the optical axis of the viewer when that eye is fixating on an object at optical infinity directly in front of the viewer. The images 190, 200 are flat and at a fixed distance from the eyes 210, 220. Based on slightly different views of the virtual object in the images presented to the eyes 210, 220, respectively, the eyes may necessarily rotate such that the image of the object falls on a corresponding point on the eye's respective retina to maintain single binocular vision. This rotation may cause the line of sight of each of the eyes 210, 220 to converge on a point in space where the virtual object is perceived to reside. As a result, providing three-dimensional images traditionally involves manipulating the convergence and divergence movements of the user's eyes 210, 220 to provide binocular cues that the human visual system interprets to provide the perception of depth.

[0092] However, creating a realistic and comfortable perception of depth is difficult. It should be understood that light from an object at different distances from the eye has a wavefront with different amounts of divergence. Figures 3A-3C illustrate the relationship between distance and divergence of light rays. The distance between the object and the eye 210 is represented in the order of decreasing distances R1, R2, and R3. As shown in Figures 3A-3C, the light rays become more divergent as the distance to the object decreases. Conversely, as the distance increases, the light rays become more collimated. In other words, the light field generated by a point (an object or part of an object) can be said to have a spherical wavefront curvature that is a function of the distance the point is away from the user's eye. The curvature increases with decreasing distance between the object and the eye 210. Although only a single eye 210 is illustrated in Figures 3A-3C and other figures herein for clarity of illustration, the discussion regarding the eye 210 may apply to both eyes 210 and 220 of a viewer.

[0093] 3A-3C, light from an object that a viewer's eye is fixating on may have different wavefront divergences. Due to the different wavefront divergences, the light may be focused differently by the eye's lens, which in turn may require the lens to assume a different shape and form a focused image on the eye's retina. If a focused image is not formed on the retina, the resulting retinal blur acts as an accommodative cue, causing the shape of the eye's lens to change until a focused image is formed on the retina. For example, the accommodative cue may induce relaxation or contraction of the ciliary muscle surrounding the eye's lens, thereby modulating the force applied to the suspensory ligament that holds the lens, thus changing the shape of the eye's lens, thereby forming a focused image of the fixated object on the eye's retina (e.g., fovea) until retinal blur of the fixated object is eliminated or minimized. The process by which the eye lens changes shape may be referred to as accommodation, and the shape of the eye lens required to form a focused image of a fixated object on the eye's retina (e.g., the fovea) may be referred to as the state of accommodation.

[0094] Referring now to FIG. 4A, a representation of the accommodation-vergence response of the human visual system is illustrated. A movement of the eye to fixate an object causes the eye to receive light from the object, which forms an image on each of the eye's retinas. The presence of retinal blur in the image formed on the retina may provide a cue for accommodation, and the relative location of the image on the retina may provide a cue for vergence. The cue for accommodation causes the lens of the eye to assume a particular accommodation state that creates accommodation and forms a focused image of the object on the retina of the eye (e.g., the fovea). On the other hand, the cue for vergence causes a vergence movement (eye rotation) such that the image formed on each retina of each eye is at a corresponding retinal point that maintains single binocular vision. In these positions, the eyes may be said to be in a particular vergence state. Continuing with reference to FIG. 4A, accommodation can be understood to be the process by which the eye achieves a particular accommodation state, and convergence can be understood to be the process by which the eye achieves a particular convergence state. As shown in FIG. 4A, the accommodation and convergence state of the eye can change when the user fixates a different object. For example, the accommodated state can change when the user fixates a new object at a different depth on the z-axis.

[0095] Without being limited by theory, it is believed that a viewer of an object may perceive the object as "three-dimensional" due to a combination of vergence-divergence and accommodation. As noted above, vergence-divergence of the two eyes relative to one another (e.g., rotation of the eyes such that the pupils move toward or away from one another, converging the gaze of the eyes to fixate on the object) is closely coupled to accommodation of the eye's lenses. Under normal conditions, a change in the shape of the eye's lenses to change focus from one object to another at a different distance will automatically produce a corresponding change in vergence-divergence to the same distance, a relationship known as the "accommodation-vergence-divergence reflex." Similarly, a change in vergence-divergence will induce a corresponding change in lens shape under normal conditions.

[0096] 4B, an example of different accommodation and convergence states of the eyes is illustrated. The pair of eyes 222a fixates an object at optical infinity, while the pair of eyes 222b fixates an object 221 at less than optical infinity. Notably, the convergence states of each pair of eyes are different, with the pair of eyes 222a pointing straight ahead, while the pair of eyes 222 converge on the object 221. The accommodation states of the eyes forming each pair of eyes 222a and 222b are also different, as represented by the different shapes of the lenses 210a, 220a.

[0097] Unfortunately, many users of conventional "3-D" display systems may find such conventional systems uncomfortable or may not perceive any depth sensation due to a mismatch between accommodation and vergence states in these displays. As noted above, many stereoscopic or "3-D" display systems display a scene by providing a slightly different image to each eye. Such systems are uncomfortable for many viewers because, among other things, they simply provide different presentations of a scene, causing changes in the vergence states of the eyes, but without a corresponding change in the accommodation states of those eyes. Rather, images are presented by the display at a fixed distance from the eyes, such that the eyes view all image information in a single accommodation state. Such an arrangement counters the "accommodation-vergence-divergence reflex" by causing changes in vergence states without a corresponding change in accommodation state. This mismatch is believed to cause viewer discomfort. Display systems that provide a better match between accommodation and convergence-divergence movements may produce a more realistic and comfortable simulation of a three-dimensional image.

[0098] Without being limited by theory, it is believed that the human eye may typically interpret a finite number of depth planes to provide depth perception. As a result, a highly realistic simulation of perceived depth may be achieved by providing the eye with different presentations of images corresponding to each of these limited number of depth planes. In some embodiments, the different presentations may provide both vergence cues and matching cues for accommodation, thereby providing a physiologically correct accommodation-vergence divergence match.

[0099] 4B, two depth planes 240 are illustrated, corresponding to different distances in space from the eyes 210, 220. For a given depth plane 240, vergence-divergence cues may be provided by displaying appropriately different perspective images for each eye 210, 220. In addition, for a given depth plane 240, the light forming the image provided to each eye 210, 220 may have a wavefront divergence corresponding to the light field generated by a point at the distance of that depth plane 240.

[0100] In the illustrated embodiment, the distance along the z-axis of the depth plane 240 containing the point 221 is 1 m. As used herein, the distance or depth along the z-axis may be measured with the zero point located at the exit pupil of the user's eye. Thus, the depth plane 240 located at a depth of 1 m corresponds to a distance of 1 m away from the exit pupil of the user's eye on the optical axis of those eyes with the eyes pointed towards optical infinity. As an approximation, the depth or distance along the z-axis may be measured from the display in front of the user's eye (e.g., from the surface of the waveguide) and a value for the distance between the device and the exit pupil of the user's eye may be added. That value may be referred to as the pupil distance and corresponds to the distance between the exit pupil of the user's eye and the display worn by the user in front of the eye. In practice, the value for the pupil distance may be a normalized value that is generally used for all viewers. For example, the pupil distance may be assumed to be 20 mm and the depth plane at a depth of 1 m may be at a distance of 980 mm in front of the display.

[0101] 4C and 4D, examples of matched accommodation-vergence-divergence distances and mismatched accommodation-vergence-divergence distances are illustrated, respectively. As illustrated in FIG. 4C, the display system may provide an image of a virtual object to each eye 210, 220. The image may cause the eyes 210, 220 to assume a convergence-divergence state in which the eyes converge on point 15 on the depth plane 240. In addition, the image may be formed by light having a wavefront curvature corresponding to a real object in that depth plane 240. As a result, the eyes 210, 220 assume an accommodation state in which the image focuses on the retinas of those eyes. Thus, the user may perceive the virtual object as being at point 15 on the depth plane 240.

[0102] It should be appreciated that each of the accommodation and convergence states of the eyes 210, 220 is associated with a particular distance on the z-axis. For example, an object at a particular distance from the eyes 210, 220 will cause those eyes to assume a particular accommodation state based on the distance of the object. The distance associated with a particular accommodation state is referred to as the accommodation distance A. d Similarly, a particular convergence-divergence distance V associated with the eyes in a particular convergence-divergence state or position relative to one another may be referred to as d If the accommodation distance and the vergence distance match, the relationship between accommodation and vergence is said to be physiologically correct. This is considered to be the most comfortable scenario for the viewer.

[0103] However, in a stereoscopic display, the accommodation distance and the vergence distance may not always coincide. For example, as illustrated in FIG. 4D, the image displayed to the eyes 210, 220 may be displayed with a wavefront divergence corresponding to the depth plane 240, and the eyes 210, 220 may be in a particular accommodation state in which the points 15a, 15b on that depth plane are in focus. However, the image displayed to the eyes 210, 220 may provide a cue for vergence that causes the eyes 210, 220 to converge on a point 15 that is not located on the depth plane 240. As a result, the accommodation distance corresponds in some embodiments to the distance from the exit pupils of the eyes 210, 220 to the depth plane 240, while the vergence distance corresponds to a larger distance from the exit pupils of the eyes 210, 220 to the point 15. The accommodation distance is different from the vergence distance. As a result, there is an accommodation-vergence-divergence mismatch. Such a mismatch may be considered undesirable and may cause discomfort to the user. The mismatch may be related to the distance (e.g., V d -A d ) and can be characterized in terms of diopters.

[0104] It should be understood that in some embodiments, reference points other than the exit pupils of the eyes 210, 220 may be utilized to determine distances for determining accommodation-vergence mismatch, so long as the same reference points are utilized for accommodation distance and vergence distance. For example, distances may be measured from the cornea to the depth plane, from the retina to the depth plane, from the ocular lens (e.g., a waveguide in a display device) to the depth plane, from the center of rotation of the eye, etc.

[0105] Without being limited by theory, it is believed that a user may still perceive an accommodation-vergence-divergence mismatch of up to about 0.25 diopters, up to about 0.33 diopters, and up to about 0.5 diopters as physiologically correct, without the mismatch itself causing significant discomfort. In some embodiments, a display system disclosed herein (e.g., display system 250, FIG. 6) presents an image to a viewer having an accommodation-vergence-divergence mismatch of about 0.5 diopters or less. In some other embodiments, the accommodation-vergence-divergence mismatch of the image provided by the display system is about 0.33 diopters or less. In still other embodiments, the accommodation-vergence-divergence mismatch of the image provided by the display system is about 0.25 diopters or less, including about 0.1 diopters or less.

[0106] FIG. 5 illustrates aspects of an approach for simulating a three-dimensional image by modifying the wavefront divergence. The display system includes a waveguide 270 configured to receive light 770 encoded with image information and output the light to a user's eye 210. The waveguide 270 may output light 650 with a defined amount of wavefront divergence that corresponds to the wavefront divergence of a light field generated by a point on a desired depth plane 240. In some embodiments, the same amount of wavefront divergence is provided for all objects presented on that depth plane. In addition, it will be illustrated that the user's other eye may be provided with image information from a similar waveguide.

[0107] In some embodiments, a single waveguide may be configured to output light with a set wavefront divergence corresponding to a single or limited number of depth planes, and / or the waveguide may be configured to output light of a limited range of wavelengths. As a result, in some embodiments, multiple or stacked waveguides may be utilized to provide different wavefront divergence for different depth planes and / or output light of different ranges of wavelengths. As used herein, it should be understood that a depth plane may follow the contour of a flat or curved surface. In some embodiments, advantageously and for simplicity, a depth plane may follow the contour of a flat surface.

[0108] 6 illustrates an example of a waveguide stack for outputting image information to a user. The display system 250 includes a stack of waveguides or a stacked waveguide assembly 260 that can be utilized to provide a three-dimensional perception to the eye / brain using multiple waveguides 270, 280, 290, 300, 310. It should be understood that the display system 250 can be considered a light field display in some embodiments. Additionally, the waveguide assembly 260 can also be referred to as an eyepiece.

[0109] In some embodiments, the display system 250 may be configured to provide a substantially continuous cue for convergence and multiple discrete cues for accommodation. The cues for convergence may be provided by displaying different images to each of the user's eyes, and the cues for accommodation may be provided by outputting light forming images with selectable discrete amounts of wavefront divergence. In other words, the display system 250 may be configured to output light with variable levels of wavefront divergence. In some embodiments, each discrete level of wavefront divergence corresponds to a particular depth plane and may be provided by a particular one of the waveguides 270, 280, 290, 300, 310.

[0110] Continuing with reference to FIG. 6, the waveguide assembly 260 may also include a number of features 320, 330, 340, 350 between the waveguides. In some embodiments, the features 320, 330, 340, 350 may be one or more lenses. The waveguides 270, 280, 290, 300, 310 and / or the number of lenses 320, 330, 340, 350 may be configured to transmit image information to the eye with various levels of wavefront curvature or light beam divergence. Each waveguide level may be associated with a particular depth plane and may be configured to output image information corresponding to that depth plane. The image input devices 360, 370, 380, 390, 400 may act as light sources for the waveguides and may be utilized to input image information into the waveguides 270, 280, 290, 300, 310, which may each be configured to disperse incident light across each individual waveguide for output towards the eye 210, as described herein. Light exits output surfaces 410, 420, 430, 440, 450 of the image input devices 360, 370, 380, 390, 400 and is input into corresponding input surfaces 460, 470, 480, 490, 500 of the waveguides 270, 280, 290, 300, 310. In some embodiments, each of the input surfaces 460, 470, 480, 490, 500 may be an edge of the corresponding waveguide or a portion of the major surface of the corresponding waveguide (i.e., one of the waveguide surfaces that directly faces the world 510 or the viewer's eye 210). It should be understood that the major surface of a waveguide corresponds to the surface of the waveguide between which the thickness of the waveguide extends. In some embodiments, a single beam of light (e.g., a collimated beam) may be launched into each waveguide and output an entire field of cloned collimated beams that are directed toward the eye 210 at a particular angle (and divergence) corresponding to the depth plane associated with the particular waveguide. In some embodiments, a single one of the image launch devices 360, 370, 380, 390, 400 may be associated with and launch light into multiple (e.g., three) waveguides 270, 280, 290, 300, 310.

[0111] In some embodiments, the image input devices 360, 370, 380, 390, 400 are discrete displays that each generate image information for input into a corresponding waveguide 270, 280, 290, 300, 310. In some other embodiments, the image input devices 360, 370, 380, 390, 400 are outputs of a single multiplexed display that may send image information to each of the image input devices 360, 370, 380, 390, 400, for example, via one or more optical conduits (such as fiber optic cables). It should be understood that the image information provided by the image input devices 360, 370, 380, 390, 400 may include light of different wavelengths or colors (e.g., different primary colors as discussed herein).

[0112] In some embodiments, the light injected into the waveguides 270, 280, 290, 300, 310 is provided by a light projector system 520 comprising a light module 530, which may include light emitters such as light emitting diodes (LEDs). Light from the light module 530 may be directed through a beam splitter 550 to and modified by a light modulator 540, e.g., a spatial light modulator. The light modulator 540 may be configured to vary the perceived intensity of the light injected into the waveguides 270, 280, 290, 300, 310 and encode the light with image information. Examples of spatial light modulators include liquid crystal displays (LCDs), including liquid crystal on silicon (LCOS) displays. It should be understood that image injection devices 360, 370, 380, 390, 400 are illustrated diagrammatically and in some embodiments these image injection devices may represent different light paths and locations within a common projection system configured to output light into associated ones of waveguides 270, 280, 290, 300, 310. In some embodiments, the waveguides of the waveguide assembly 260 may act as ideal lenses, relaying light injected into the waveguides to the user's eye. In this concept, the object may be a spatial light modulator 540 and the image may be an image on a depth plane.

[0113] In some embodiments, the display system 250 may be a scanning fiber display comprising one or more scanning fibers configured to project light in various patterns (e.g., raster scan, spiral scan, Lissajous pattern, etc.) into one or more waveguides 270, 280, 290, 300, 310 and ultimately to the viewer's eye 210. In some embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may represent diagrammatically a single scanning fiber or a bundle of scanning fibers configured to inject light into one or more waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may represent diagrammatically multiple scanning fibers or multiple bundles of scanning fibers configured to inject light into associated ones of the waveguides 270, 280, 290, 300, 310, respectively. It should be understood that one or more optical fibers may be configured to transmit light from the optical module 530 to one or more of the waveguides 270, 280, 290, 300, 310. It should be understood that one or more intervening optical structures may be provided between the scanning fiber or fibers and one or more of the waveguides 270, 280, 290, 300, 310, for example, to redirect light exiting the scanning fiber into one or more of the waveguides 270, 280, 290, 300, 310.

[0114] The controller 560 controls the operation of one or more of the stacked waveguide assemblies 260, including the operation of the image input devices 360, 370, 380, 390, 400, the light source 530, and the light modulator 540. In some embodiments, the controller 560 is part of the local data processing module 140. The controller 560 includes programming (e.g., instructions in a non-transient medium) that coordinates the timing and provision of image information to the waveguides 270, 280, 290, 300, 310, for example, according to any of the various schemes disclosed herein. In some embodiments, the controller may be a single integrated device or a distributed system connected by wired or wireless communication channels. The controller 560 may be part of the processing module 140 or 150 (FIG. 9D) in some embodiments.

[0115] Continuing with reference to FIG. 6, the waveguides 270, 280, 290, 300, 310 may be configured to propagate light within each individual waveguide by total internal reflection (TIR). Each of the waveguides 270, 280, 290, 300, 310 may be planar or have another shape (e.g., curved) with major top and bottom surfaces and edges extending between their major top and bottom surfaces. In the illustrated configuration, each of the waveguides 270, 280, 290, 300, 310 may include an out-coupling optical element 570, 580, 590, 600, 610 configured to extract light from the waveguide by redirecting light propagating within each individual waveguide out of the waveguide and outputting image information to the eye 210. The extracted light may also be referred to as out-coupled light, and the out-coupling optical element may also be referred to as a light extraction optical element. The extracted beam of light may be output by the waveguide at a location where the light propagating within the waveguide strikes the light extraction optical element. The outcoupling optical element 570, 580, 590, 600, 610 may be a grating, for example, including diffractive optical features as further discussed herein. Although shown disposed on the bottom major surface of the waveguide 270, 280, 290, 300, 310 for ease of explanation and clarity of drawing, in some embodiments the outcoupling optical element 570, 580, 590, 600, 610 may be disposed on the top and / or bottom major surfaces and / or directly within the volume of the waveguide 270, 280, 290, 300, 310, as further discussed herein. In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 may be formed within a layer of material that is attached to a transparent substrate and forms the waveguide 270, 280, 290, 300, 310. In some other embodiments, the waveguide 270, 280, 290, 300, 310 may be a monolithic piece of material and the outcoupling optical elements 570, 580, 590, 600, 610 may be formed on and / or within that piece of material.

[0116] With continued reference to FIG. 6, as discussed herein, each waveguide 270, 280, 290, 300, 310 is configured to output light and form an image corresponding to a particular depth plane. For example, the waveguide 270 closest to the eye may be configured to deliver collimated light (injected into such waveguide 270) to the eye 210. The collimated light may represent an optical infinity focal plane. The next upper waveguide 280 may be configured to send collimated light that passes through a first lens 350 (e.g., a negative lens) before it can reach the eye 210. Such first lens 350 may be configured to generate a slight convex wavefront curvature such that the eye / brain interprets the light originating from the next upper waveguide 280 as originating from a first focal plane closer inward from optical infinity toward the eye 210. Similarly, the third upper waveguide 290 passes its output light through both the first lens 350 and the second lens 340 before reaching the eye 210. The combined refractive powers of the first lens 350 and the second lens 340 may be configured to produce another incremental amount of wavefront curvature such that the eye / brain interprets the light originating from the third upper waveguide 290 as originating from a second focal plane that is closer inward from optical infinity towards the person than was the light from the next upper waveguide 280.

[0117] The other waveguide layers 300, 310 and lenses 330, 320 are similarly configured, with the highest waveguide 310 in the stack sending its output through all of the lenses between it and the eye for an aggregate focal force that represents the focal plane closest to the person. To compensate the stack of lenses 320, 330, 340, 350 when viewing / interpreting light originating from the world 510 on the other side of the stacked waveguide assembly 260, a compensating lens layer 620 may be placed on top of the stack to compensate for the aggregate force of the lens stacks 320, 330, 340, 350 below. Such a configuration provides as many perceived focal planes as there are waveguide / lens pairs available. Both the outcoupling optical elements of the waveguides and the focusing sides of the lenses may be static (i.e., not dynamic or electroactive). In some alternative embodiments, one or both may be dynamic using electroactive features.

[0118] In some embodiments, two or more of the waveguides 270, 280, 290, 300, 310 may have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, 310 may be configured to output images set at the same depth plane, or multiple subsets of the waveguides 270, 280, 290, 300, 310 may be configured to output images set at the same depth planes, with one set per depth plane. This may provide an advantage for forming tiled images to provide an extended field of view at those depth planes.

[0119] Continuing with reference to FIG. 6, the outcoupling optical elements 570, 580, 590, 600, 610 may be configured to redirect light out of their respective waveguides and output the light with an appropriate amount of divergence or collimation for the particular depth plane associated with the waveguides. As a result, waveguides with different associated depth planes may have different configurations of outcoupling optical elements 570, 580, 590, 600, 610 that output light with different amounts of divergence depending on the associated depth plane. In some embodiments, the light extraction optical elements 570, 580, 590, 600, 610 may be solid or surface features that may be configured to output light at specific angles. For example, the light extraction optical elements 570, 580, 590, 600, 610 may be solid holograms, surface holograms, and / or diffraction gratings. In some embodiments, the features 320, 330, 340, 350 may not be lenses. Rather, they may simply be spacers (eg, cladding layers and / or structures to form an air gap).

[0120] In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 are diffractive features or "diffractive optical elements" (also referred to herein as "DOEs") that form a diffraction pattern. Preferably, the DOEs have a sufficiently low diffraction efficiency so that only a portion of the light in the beam is deflected toward the eye 210 at each intersection of the DOE, while the remainder continues traveling through the waveguide via TIR. The light carrying the image information is thus split into several related exit beams that exit the waveguide at multiple locations, resulting in a very uniform pattern of exit emission toward the eye 210 for this particular collimated beam bouncing within the waveguide.

[0121] In some embodiments, one or more DOEs may be switchable between an "on" state in which they actively diffract and an "off" state in which they do not significantly diffract. For example, a switchable DOE may comprise a layer of polymer dispersed liquid crystal in which the microdroplets comprise a diffractive pattern within a host medium, and the refractive index of the microdroplets may be switched to substantially match the refractive index of the host material (in which case the pattern does not significantly diffract incident light), or the microdroplets may be switched to a refractive index that does not match that of the host medium (in which case the pattern actively diffracts incident light).

[0122] In some embodiments, a camera assembly 630 (e.g., a digital camera, including visible and infrared light cameras) may be provided to capture images of the eye 210 and / or tissues surrounding the eye 210, for example, to detect user input and / or monitor a physiological condition of the user. As used herein, a camera may be any image capture device. In some embodiments, the camera assembly 630 may include an image capture device and a light source that projects light (e.g., infrared light) onto the eye, which may then be reflected by the eye and detected by the image capture device. In some embodiments, the camera assembly 630 may be mounted to the frame 80 (FIG. 9D) and may be in electrical communication with the processing modules 140 and / or 150, which may process image information from the camera assembly 630. In some embodiments, one camera assembly 630 may be utilized per eye, monitoring each eye separately.

[0123] 7, an example of an output beam output by a waveguide is shown. Although one waveguide is shown, it should be understood that other waveguides in the waveguide assembly 260 (FIG. 6) may function similarly and that the waveguide assembly 260 includes multiple waveguides. Light 640 is launched into the waveguide 270 at the input surface 460 of the waveguide 270 and propagates within the waveguide 270 by TIR. At the point where the light 640 impinges on the DOE 570, a portion of the light exits the waveguide as an output beam 650. The output beams 650 are shown as approximately parallel, but as discussed herein, they may also be redirected to propagate to the eye 210 at an angle (e.g., to form a diverging output beam) depending on the depth plane associated with the waveguide 270. It should be understood that a nearly collimated exit beam may refer to a waveguide with outcoupling optics that outcouples light to form an image that appears to be set on a depth plane at a large distance (e.g., optical infinity) from the eye 210. Other waveguides or other sets of outcoupling optics may output a more divergent exit beam pattern, which would require the eye 210 to accommodate to a closer distance and focus on the retina, and would be interpreted by the brain as light from a distance closer to the eye 210 than optical infinity.

[0124] In some embodiments, a full color image may be formed at each depth plane by overlaying an image on each of the primary colors, for example, three or more primary colors. FIG. 8 illustrates an example of a stacked waveguide assembly in which each depth plane includes an image formed using multiple different primary colors. The illustrated embodiment shows depth planes 240a-240f, but more or less depths are also contemplated. Each depth plane may have three or more primary color images associated with it, including a first image of a first color G, a second image of a second color R, and a third image of a third color B. The different depth planes are indicated in the figure by different numbers for diopters (dpt) following the letters G, R, and B. By way of example only, the numbers following each of these letters indicate the diopters (1 / m), i.e., the inverse distance of the depth plane from the viewer, and each box in the figure represents an individual primary color image. In some embodiments, the exact placement of the depth planes for the different primary colors may be varied to account for differences in the eye's focusing of different wavelengths of light. For example, different primary color images for a given depth plane may be placed on depth planes corresponding to different distances from the user. Such an arrangement may increase visual acuity and user comfort and / or reduce chromatic aberration.

[0125] In some embodiments, light of each primary color may be output by a single dedicated waveguide, such that each depth plane may have multiple waveguides associated with it. In such embodiments, each box in the figure containing the letter G, R, or B may be understood to represent an individual waveguide, and three waveguides may be provided per depth plane, with three primary color images provided per depth plane. The waveguides associated with each depth plane are shown adjacent to each other in this drawing for ease of illustration, but it should be understood that in a physical device, the waveguides may all be arranged in a stack with one waveguide per level. In some other embodiments, multiple primary colors may be output by the same waveguide, such that, for example, only a single waveguide may be provided per depth plane.

[0126] 8, in some embodiments, G is green, R is red, and B is blue. In some other embodiments, other colors associated with other wavelengths of light, including magenta and cyan, may be used in addition to or in place of one or more of red, green, or blue.

[0127] It should be understood that references throughout this disclosure to a given color of light will be understood to encompass one or more wavelengths of light within the range of wavelengths of light that are perceived by a viewer as being of that given color. For example, red light may include one or more wavelengths of light within a range of about 620-780 nm, green light may include one or more wavelengths of light within a range of about 492-577 nm, and blue light may include one or more wavelengths of light within a range of about 435-493 nm.

[0128] In some embodiments, the light source 530 (FIG. 6) may be configured to emit light at one or more wavelengths outside the range of visual perception of a viewer, e.g., infrared and / or ultraviolet wavelengths. Additionally, the waveguide in-coupling, out-coupling, and other light redirecting structures of the display 250 may be configured to direct and emit this light from the display toward the user's eye 210, e.g., for imaging and / or user stimulation applications.

[0129] 9A, in some embodiments, light impinging on a waveguide may need to be redirected to in-couple the light into the waveguide. An in-coupling optical element may be used to redirect and in-couple the light into its corresponding waveguide. FIG. 9A illustrates a cross-sectional side view of an example of a plurality or set 660 of stacked waveguides, each including an in-coupling optical element. The waveguides may each be configured to output light of one or more different wavelengths or one or more different wavelength ranges. It should be understood that the stack 660 may correspond to the stack 260 (FIG. 6), and that the illustrated waveguides of the stack 660 may correspond to a portion of the plurality of waveguides 270, 280, 290, 300, 310, except that light from one or more of the image input devices 360, 370, 380, 390, 400 is input into the waveguide from a position that requires the light to be redirected for in-coupling.

[0130] The illustrated set 660 of stacked waveguides includes waveguides 670, 680, and 690. Each waveguide includes an associated incoupling optical element (which may also be referred to as the light input area on the waveguide), for example, incoupling optical element 700 is disposed on a major surface (e.g., the top major surface) of waveguide 670, incoupling optical element 710 is disposed on a major surface (e.g., the top major surface) of waveguide 680, and incoupling optical element 720 is disposed on a major surface (e.g., the top major surface) of waveguide 690. In some embodiments, one or more of the incoupling optical elements 700, 710, 720 may be disposed on a bottom major surface of an individual waveguide 670, 680, 690 (particularly if one or more of the incoupling optical elements is a reflective turning optical element). As shown, the incoupling optical elements 700, 710, 720 may be disposed on the upper major surfaces of the respective waveguides 670, 680, 690 (or on top of the next lower waveguide), particularly if the incoupling optical elements are transmissive deflecting optical elements. In some embodiments, the incoupling optical elements 700, 710, 720 may be disposed within the body of the respective waveguides 670, 680, 690. In some embodiments, as discussed herein, the incoupling optical elements 700, 710, 720 are wavelength selective, such that they selectively redirect one or more wavelengths of light while transmitting other wavelengths of light. Although illustrated on one side or corner of the respective waveguides 670, 680, 690, it should be understood that the incoupling optical elements 700, 710, 720 may be disposed within other areas of the respective waveguides 670, 680, 690 in some embodiments.

[0131] As shown, the in-coupling optical elements 700, 710, 720 may be laterally offset from one another. In some embodiments, each in-coupling optical element may be offset to receive light without that light passing through another in-coupling optical element. For example, each in-coupling optical element 700, 710, 720 may be configured to receive light from a different image input device 360, 370, 380, 390, and 400, as shown in FIG. 6, and may be separated (e.g., laterally spaced) from the other in-coupling optical elements 700, 710, 720 such that it does not receive substantially any light from others of the in-coupling optical elements 700, 710, 720.

[0132] Each waveguide also includes an associated optically dispersive element, for example, optically dispersive element 730 is disposed on a major surface (e.g., a top major surface) of waveguide 670, optically dispersive element 740 is disposed on a major surface (e.g., a top major surface) of waveguide 680, and optically dispersive element 750 is disposed on a major surface (e.g., a top major surface) of waveguide 690. In some other embodiments, optically dispersive elements 730, 740, 750 may be disposed on the bottom major surfaces of associated waveguides 670, 680, 690, respectively. In some other embodiments, optically dispersive elements 730, 740, 750 may be disposed on both the top and bottom major surfaces of associated waveguides 670, 680, 690, respectively, or optically dispersive elements 730, 740, 750 may be disposed on different ones of the top and bottom major surfaces in different associated waveguides 670, 680, 690, respectively.

[0133] The waveguides 670, 680, 690 may be spaced apart and separated by, for example, gas, liquid, and / or solid layers of material. For example, as shown, layer 760a may separate the waveguides 670 and 680, and layer 760b may separate the waveguides 680 and 690. In some embodiments, layers 760a and 760b are formed from a low index material (i.e., a material having a lower index of refraction than the material forming the immediately adjacent ones of the waveguides 670, 680, 690). Preferably, the index of refraction of the material forming layers 760a, 760b is 0.05 or 0.10 or less than the index of refraction of the material forming the waveguides 670, 680, 690. Advantageously, the lower refractive index layers 760a, 760b may act as cladding layers to promote total internal reflection (TIR) ​​of light through the waveguides 670, 680, 690 (e.g., TIR between the top and bottom major surfaces of each waveguide). In some embodiments, the layers 760a, 760b are formed from air. Although not shown, it should be understood that the top and bottom of the illustrated set of waveguides 660 may include adjacent cladding layers.

[0134] Preferably, for ease of manufacturing and other considerations, the materials forming the waveguides 670, 680, 690 are similar or the same, and the materials forming the layers 760a, 760b are similar or the same. In some embodiments, the materials forming the waveguides 670, 680, 690 may vary between one or more of the waveguides, and / or the materials forming the layers 760a, 760b may differ while still maintaining the various refractive index relationships described above.

[0135] 9A, light rays 770, 780, 790 are incident on the set of waveguides 660. It should be understood that light rays 770, 780, 790 may be injected into the waveguides 670, 680, 690 by one or more image injection devices 360, 370, 380, 390, 400 (FIG. 6).

[0136] In some embodiments, the light beams 770, 780, 790 have different properties, e.g., different wavelengths or different wavelength ranges, that may correspond to different colors. Each of the incoupling optical elements 700, 710, 720 deflects the incident light such that the light propagates through a respective one of the waveguides 670, 680, 690 by TIR. In some embodiments, each of the incoupling optical elements 700, 710, 720 selectively deflects one or more particular wavelengths of light while transmitting other wavelengths to the underlying waveguide and associated incoupling optical element.

[0137] For example, incoupling optical element 700 may be configured to selectively deflect light beam 770 having a first wavelength or wavelength range while transmitting light beams 780 and 790 having different second and third wavelengths or wavelength ranges, respectively. The transmitted light beam 780 impinges on and is deflected by incoupling optical element 710, which is configured to deflect light of the second wavelength or wavelength range. Light beam 790 is deflected by incoupling optical element 720, which is configured to selectively deflect light of the third wavelength or wavelength range.

[0138] 9A, the deflected light rays 770, 780, 790 are deflected to propagate through the corresponding waveguides 670, 680, 690. That is, the incoupling optical element 700, 710, 720 of each waveguide deflects the light into its corresponding waveguide 670, 680, 690 and incouplings the light into the corresponding waveguide. The light rays 770, 780, 790 are deflected at an angle that causes the light to propagate through the respective waveguides 670, 680, 690 by TIR. The light rays 770, 780, 790 propagate through the respective waveguides 670, 680, 690 by TIR until they impinge on the corresponding optical dispersive element 730, 740, 750 of the waveguide.

[0139]

[0046] Referring now to Figure 9B, a perspective view of the multiple stacked waveguide embodiment of Figure 9A is illustrated. As described above, the in-coupled light rays 770, 780, 790 are deflected by the in-coupling optical elements 700, 710, 720, respectively, and then propagate by TIR within the waveguides 670, 680, 690, respectively. The light rays 770, 780, 790 then impinge on the optically dispersive elements 730, 740, 750, respectively. The optically dispersive elements 730, 740, 750 deflect the light rays 770, 780, 790 to propagate towards the out-coupling optical elements 800, 810, 820, respectively.

[0140] In some embodiments, the optically dispersive elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPEs deflect or disperse the light to the out-coupling optical elements 800, 810, 820, and in some embodiments may also increase the beam or spot size of this light as it propagates to the out-coupling optical elements. In some embodiments, the optically dispersive elements 730, 740, 750 may be omitted and the in-coupling optical elements 700, 710, 720 may be configured to deflect the light directly to the out-coupling optical elements 800, 810, 820. For example, referring to FIG. 9A, the optically dispersive elements 730, 740, 750 may be replaced with the out-coupling optical elements 800, 810, 820, respectively. In some embodiments, the outcoupling optical elements 800, 810, 820 are exit pupils (EPs) or exit pupil expanders (EPEs) that direct light into the viewer's eye 210 (FIG. 7). It should be understood that an OPE may be configured to increase the size of the eyebox in at least one axis, and an EPE may increase the eyebox in an axis that intersects, e.g., perpendicular to, the axis of the OPE. For example, each OPE may be configured to redirect a portion of the light striking the OPE to an EPE of the same waveguide, while allowing the remaining portion of the light to continue propagating down the waveguide. Again, in response to striking the OPE, another portion of the remaining light is redirected to the EPE, which continues to propagate further down the waveguide, and so on. Similarly, in response to striking the EPE, a portion of the impinging light is directed out of the waveguide towards the user, which continues to propagate through the waveguide until it again strikes the EP, at which point another portion of the impinging light is directed out of the waveguide, and so on. As a result, a single beam of internally coupled light may be "replicated" each time a portion of that light is redirected by an OPE or EPE, thereby forming a cloned beam field of light, as shown in Figure 6. In some embodiments, the OPE and / or EPE may be configured to modify the size of the beam of light.

[0141] Thus, referring to Figures 9A and 9B, in some embodiments, a set of waveguides 660 includes, for each primary color, a waveguide 670, 680, 690, an in-coupling optical element 700, 710, 720, an optical dispersion element (e.g., OPE) 730, 740, 750, and an out-coupling optical element (e.g., EP) 800, 810, 820. The waveguides 670, 680, 690 may be stacked with an air gap / cladding layer between each one. The in-coupling optical element 700, 710, 720 redirects or deflects the incoming light into its waveguide (with different in-coupling optical elements receiving different wavelengths of light). The light then propagates at an angle that will result in TIR within the individual waveguides 670, 680, 690. In the illustrated embodiment, light ray 770 (e.g., blue light) is deflected by the first in-coupling optical element 700 in the manner previously described, then continues to bounce back down the waveguide, interacting with the optically dispersive element (e.g., OPE) 730 and then the out-coupling optical element (e.g., EP) 800. Light rays 780 and 790 (e.g., green and red light, respectively) pass through the waveguide 670, where light ray 780 impinges on and is deflected by the in-coupling optical element 710. Light ray 780 then proceeds via TIR back down the waveguide 680, to its optically dispersive element (e.g., OPE) 740 and then to the out-coupling optical element (e.g., EP) 810. Finally, light ray 790 (e.g., red light) passes through the waveguide 690 and impinges on the optically in-coupling optical element 720 of the waveguide 690. The light in-coupling optical element 720 deflects the light beam 790 such that it propagates by TIR to a light dispersive element (e.g., OPE) 750 and then by TIR to an out-coupling optical element (e.g., EP) 820. The out-coupling optical element 820 then finally out-couples the light beam 790 to a viewer, who also receives the out-coupled light from the other waveguides 670, 680.

[0142] FIG. 9C illustrates a top-down plan view of an example of the multiple stacked waveguides of FIGS. 9A and 9B. As shown, the waveguides 670, 680, 690 may be vertically aligned with each waveguide's associated light dispersive element 730, 740, 750 and associated out-coupling optical elements 800, 810, 820. However, as discussed herein, the in-coupling optical elements 700, 710, 720 are not vertically aligned. Rather, the in-coupling optical elements are preferably non-overlapping (e.g., laterally spaced apart, as seen in the top-down view). As discussed further herein, this non-overlapping spatial arrangement facilitates the injection of light from different sources into different waveguides on a one-to-one basis, thereby allowing a specific light source to be uniquely coupled to a specific waveguide. In some embodiments, an arrangement including non-overlapping spatially separated in-coupling optical elements may be referred to as a shifted pupil system, and the in-coupling optical elements in these arrangements may correspond to sub-pupils.

[0143] 9D illustrates an example of a wearable display system 60 into which the various waveguide and associated systems disclosed herein may be integrated. In some embodiments, the display system 60 is the system 250 of FIG. 6, which diagrammatically illustrates some portions of the system 60 in greater detail. For example, the waveguide assembly 260 of FIG. 6 may be part of the display 70.

[0144] 9D, the display system 60 includes a display 70 and various mechanical and electronic modules and systems to support the functionality of the display 70. The display 70 may be coupled to a frame 80 that is wearable by a display system user or viewer 90 and configured to position the display 70 in front of the eye of the user 90. The display 70 may be considered an eyepiece in some embodiments. In some embodiments, a speaker 100 is coupled to the frame 80 and configured to be positioned adjacent to the ear canal of the user 90 (in some embodiments, another speaker, not shown, may optionally be positioned adjacent the user's other ear canal to provide stereo / shapeable sound control). The display system 60 may also include one or more microphones 110 or other devices to detect sound. In some embodiments, the microphones may be configured to allow the user to provide input or commands (e.g., voice menu command selections, natural language questions, etc.) to the system 60 and / or enable audio communication with other persons (e.g., other users of a similar display system). The microphone may further be configured as an ambient sensor to collect audio data (e.g., sounds from the user and / or the environment). In some embodiments, the display system 60 may further include one or more outwardly directed environmental sensors 112 configured to detect objects, stimuli, people, animals, places, or other aspects of the world around the user. For example, the environmental sensors 112 may include, for example, one or more cameras that may be positioned facing outward to capture images similar to at least a portion of the user 90's normal field of view. In some embodiments, the display system may also include an ambient sensor 120a that is separate from the frame 80 and may be attached to the body of the user 90 (e.g., on the user 90's head, torso, limbs, etc.). The ambient sensor 120a may, in some embodiments, be configured to obtain data that characterizes the physiological state of the user 90. For example, the sensor 120a may be an electrode.

[0145] 9D, the display 70 is operably coupled by a communication link 130, such as wired or wireless connectivity, to a local data processing module 140, which may be mounted in a variety of configurations, such as fixedly attached to the frame 80, fixedly attached to a helmet or hat worn by the user, built into headphones, or otherwise removably attached to the user 90 (e.g., in a backpack configuration, in a belt-connected configuration). Similarly, the sensor 120a may be operably coupled to the local processor and data module 140 by a communication link 120b, such as wired or wireless connectivity. The local processing and data module 140 may comprise a hardware processor and digital memory, such as non-volatile memory (e.g., flash memory or hard disk drive), both of which may be utilized to aid in processing, caching, and storing data. Optionally, the local processor and data module 140 may include one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, and the like. The data may include (a) data captured from sensors (e.g., which may be operatively coupled to the frame 80 or otherwise attached to the user 90), such as image capture devices (such as cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, wireless devices, gyroscopes, and / or other sensors disclosed herein, and / or (b) data obtained and / or processed using the remote processing module 150 and / or remote data repository 160 (including data related to virtual content), possibly for passing to the display 70 after processing or retrieval. The local processing and data module 140 may be operatively coupled to the remote processing module 150 and the remote data repository 160 by communication links 170, 180, such as via wired or wireless communication links, such that these remote modules 150, 160 are operatively coupled to each other and available as resources to the local processing and data module 140.In some embodiments, local processing and data module 140 may include one or more of an image capture device, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope. In some other embodiments, one or more of these sensors may be mounted to frame 80 or may be a stand-alone structure that communicates with local processing and data module 140 by a wired or wireless communication path.

[0146] 9D , in some embodiments, remote processing module 150 may comprise one or more processors configured to analyze and process data and / or image information, including, for example, one or more central processing units (CPUs), graphics processing units (GPUs), dedicated processing hardware, etc. In some embodiments, remote data repository 160 may comprise a digital data storage facility, which may be available through the Internet or other networking configurations in a "cloud" resource configuration. In some embodiments, remote data repository 160 may include one or more remote servers that provide information, for example, information for generating augmented reality content to local processing and data module 140 and / or remote processing module 150. In some embodiments, all data is stored and all calculations are performed in the local processing and data module, allowing for fully autonomous use from the remote modules. Optionally, an external system (e.g., one or more processors, one or more computer systems), including a CPU, GPU, etc., may perform at least a portion of the processing (e.g., generating image information, processing data) and provide information to and receive information from modules 140, 150, 160, e.g., via a wireless or wired connection. Exemplary Waveguide Structures

[0147] 10A, an embodiment of a waveguide comprising a spacer is illustrated. The waveguide 1000 comprises a main optically transparent body 1010 and a spacer 1020 extending perpendicularly from a major surface 1022 of the main body 1010. Preferably, the spacer 1020 is integral with the waveguide 1000 and forms a monolithic structure with at least a portion of the waveguide that defines the major surface 1022. More preferably, the spacer 1020 forms a monolithic structure with the entire waveguide 1000, with the material of the waveguide 1000 extending perpendicularly to form the spacer 1020. As a result, the spacer 1020 and the main body 1010 may be formed from the same material with no intervening boundary.

[0148] In some embodiments, the spacers 1020 may be formed from a different material than the main body 1010 such that an intervening boundary exists at the interface of the spacers 1020 and the main body 1010. For example, the spacers 1020 may include a locally deposited material that is then imprinted to form the spacers 1020.

[0149] In some embodiments, a recess 1030 is provided that extends into a major surface 1032 of the waveguide 1000. As shown, the major surface 1032, and therefore the recess 1030, is disposed on the side of the waveguide 1000 opposite the major surface 1022. As discussed further herein, the recesses 1030 are preferably positioned, shaped, and sized such that spacers of an underlying waveguide (not shown) can be received within their recesses 1030. Similarly, the spacers 1020 are preferably positioned, shaped, and sized such that they can be received within the recesses of an upper waveguide (not shown). In some embodiments, the waveguide 1000 may be provided without the recess 1030, and any underlying spacers may simply contact the major surface 1032. Further, in some embodiments, a spacer 1020 may be provided on major surface 1032 and a recess 1030 may be provided on major surface 1022 such that the spacer 1020 extends to the underlying waveguide and is received by the recess 1030 on the underlying waveguide's major surface 1022. In some embodiments, a recess 1030 is not provided on either major surface 1022 or major surface 1032 such that the spacer 1020 disposed on major surface 1022 extends to and directly contacts major surface 1032 (or major surface 1022 when the spacer is disposed on the upper waveguide's major surface 1032).

[0150] Continuing with reference to FIG. 10A, in some embodiments, the major surface 1022 may comprise a surface relief feature 1040. As shown, the spacer 1020 extends vertically to a height above the top of the surface relief feature 1040. Preferably, the spacer 1020 has a height sufficient to space the waveguide 1000 from the upper or lower waveguide by a desired separation distance, for example, 10 μm or more, or 30 μm or more, or between 10 μm and 200 μm. In some embodiments, the spacer 1020 has a height of 30 μm or more. As discussed herein, the spacer 1020 may, in some embodiments, fit within a recess 1030 in the upper or lower waveguide. In such embodiments, the height of the spacer 1020 may be equal to the desired separation between the waveguides (e.g., 30 μm) plus the height of the recess into which the spacer is inserted. If the recess 1030 is not provided, the height of the spacer 1020 may be equal to the desired separation between the waveguides (eg, 30 μm).

[0151] In addition to or as an alternative to the surface relief features 1040, in some embodiments, the opposing major surface 1032 may include surface relief features 1050. In some embodiments, one or both of the surface relief features 1040 and 1050 may include a pattern of protrusions and depressions that are sized and arranged to form a diffractive optical element, such as a diffraction grating. It should be understood that such a diffractive optical element may correspond to one or more of the in-coupling optical elements 700, 710, 720, the light dispersing elements 730, 740, 750, or the out-coupling optical elements 800, 810, 820 of FIGS. 9A-9C. In some embodiments, the waveguide 1000 may omit one or both of the surface relief features 1040, 1050 such that the major surfaces 1022, 1032 may be smooth, except for the spacers 1020, 1030, respectively. Further, it should be understood that the surface relief features 1040 and 1050 may vary in size, number, location, and / or orientation from the illustrated embodiment. For example, the surface relief features 1040, 1050 may comprise multiple diffraction gratings (e.g., for optical incoupling) positioned away from the center of the waveguide 1000 along the major surfaces 1022, 1032.

[0152] In some embodiments, the surface relief features 1040, 1050 may be the same, which may advantageously increase the density of the surface relief features across a given extension of the waveguide 1000. In some other embodiments, the surface relief features 1040, 1050 may be different. For example, the surface relief feature 1040 may be configured to diffract light of different wavelengths and / or different angles of incidence and / or output light from the surface relief feature 1050 at different angles.

[0153] Continuing with reference to FIG. 10A, the waveguide 1000 is formed from an optically transmissive material, e.g., a highly transparent material. Preferably, the material has a high refractive index, which may provide an advantage for providing a wide field of view. In some embodiments, the material has a refractive index greater than 1.5, or greater than 1.65. The material forming the waveguide 1000 may be a highly transparent polymeric material, e.g., an organic polymeric material. Examples of high refractive index materials include polyimide-based high refractive index resins, halogen-containing (e.g., bromine- or iodine-containing) polymers, phosphorus-containing polymers, thiol-ene-based polymers, and high refractive index resin materials. Examples of high refractive index resin materials include those commercially available from NTT-AT (Kawasaki-shi, Kanagawa, Japan), such as high refractive index resins sold under the designations #565 and #566, and high refractive index resin materials commercially available from Akron Polymer System (Akron, Ohio, USA), such as high refractive index resins sold under the designations APS-1000, APS2004, APS-4001, and as part of the APS3000 series.

[0154] 10B, examples of three-dimensional shapes for spacers and recesses for accommodating the spacers are illustrated. In some embodiments, the spacer 1020 and corresponding recess 1030 may be laterally extended three-dimensional volumes. It should be understood that such laterally extended volumes may provide advantages for structural stability and mechanical strength, especially when the waveguide is utilized to form a stack of similar waveguides. An example of such a laterally extended three-dimensional volume is a square prism of shape A. In some embodiments, the spacer 1020 and corresponding recess 1030 may have other shapes, including a square prism (shape B), a cylinder (shape C), a square pyramid (shape D), a triangular pyramid (shape E), and a cone (shape F). It should be understood that multiple different shapes may be utilized in some embodiments within a single waveguide and / or a stack of waveguides. In some embodiments, the top of the spacer 1020, having a sharp shape (e.g., a square pyramid (shape D), a triangular pyramid (shape E), or a cone (shape F)) may be rounded or flattened to reduce stress at the contact point with an overlying structure, such as another waveguide. If the spacer 1020 is formed by imprinting, the desired rounding or flattening of the top of the shape may be formed by an appropriately shaped mold or imprint reticle. It should be understood that the sides and top of the spacer 1020 may comprise other shapes according to the requirements and specifications of the optical device comprising the stack of waveguides.

[0155] 10C, an example of a stack of waveguides with spacers is illustrated. The stack of waveguides 1100 comprises individual waveguides 1000a, 1000b, and 1000c. Each of the individual waveguides 1000a, 1000b, and 1000c comprises an optically transparent body 1010a, 1010b, and 1010c, respectively. Each waveguide further comprises a spacer 1020a, 1020b, and 1020c, respectively. Preferably, each waveguide also comprises a recess 1030a, 1030b, and 1030c, respectively, for receiving the spacer of the immediately underlying waveguide. It should be understood that the spacer has a height that exceeds the depth of the recess such that once received in the recess, the spacer separates the waveguides by a gap (e.g., an air gap). As shown, spacer 1020b fits within recess 1030a and spacer 1020c fits within recess 1030b.

[0156] In some embodiments, one or more of the waveguides 1000a, 1000b, 1000c may include surface relief features on one or more major surfaces of the waveguides. For example, the waveguides may include surface relief features 1040a, 1050b, respectively, corresponding to surface relief features 1040, 1050 (FIG. 10A) of the waveguide 1000. In some embodiments, different ones of the waveguides 1000a, 1000b, 1000c may include diffractive optical elements configured to in-couple and / or out-couple different wavelengths of light, e.g., corresponding to different primary colors to form a full-color image. For example, the waveguides 1000a, 1000b, 1000c may correspond to the waveguides 670, 680, 690 of FIGS. 9A-9C.

[0157] It should be understood that light may propagate, for example, from the in-coupling optical element to the out-coupling optical element through the waveguides 1000a, 1000b, 1000c by total internal reflection. In addition, light leakage between the waveguides may degrade image quality. To reduce the likelihood that the spacers 1020, 1020a, 1020b, 1020c may be conduits for light leakage between the waveguides, the spacers 1020, 1020a, 1020b, 1020c are preferably positioned at locations that are out of the path of light propagation between the in-coupling optical element and the out-coupling optical element. Furthermore, the spacers 1020, 1020a, 1020b, 1020c may be preferably positioned at locations that are out of the path of light between the image injection devices, such as the image injection devices 360, 370, 380, 390, 400 of FIG. 6, and the in-coupling optical element. Additionally, the spacers 1020, 1020a, 1020b, 1020c may be positioned at locations that are preferably out of the path of light between the outcoupling optics and the eye of a user of the display device. For example, the spacers 1020, 1020a, 1020b, 1020c may be located along the periphery of their respective waveguides.

[0158] In some embodiments, light leakage between the waveguides may be mitigated using one or both of light scattering features and light leakage prevention materials at the interfaces between the spacers 1020, 1020a, 1020b, 1020c and the immediately adjacent waveguides. Examples of light leakage prevention materials include layers of light absorbing materials and materials that form anti-reflective coatings. FIG. 11A illustrates an example of a waveguide comprising a spacer 1020 with light scattering features 1060 on a surface of the spacer configured to interface with an overlying waveguide. In some embodiments, the light scattering features 1060 may take the form of peaks and valleys (e.g., irregularly oriented peaks and valleys) on the surface of the spacer 1020. In some embodiments, the light scattering features 1060 may be provided only on the top surface of the spacer. In some other embodiments, the light scattering features 1060 may also extend on the sides of the spacer 1020. It should be understood that the light scattering features 1060 may be formed by roughening the surface of the spacer 1020, for example, by polishing. In some embodiments, roughening the spacer 1020 may prevent light leakage and also improve adhesion of the bond between directly adjacent waveguide layers. In some embodiments, the light scattering features 1060 may be formed during the formation of the spacer 1020. For example, the spacer 1020 may be formed by imprinting, where a mold used to form the spacer 1020 may include a pattern for forming the light scattering features 1060 on top of the spacer 1020, thereby advantageously allowing for simultaneous formation of the waveguide features (e.g., diffractive optical element 1040), the spacer 1020, and the light scattering features 1060. Thus, the light scattering features 1060 may comprise regularly or irregularly shaped features, and in some embodiments may take the form of a nanotextured surface, such as a grating (e.g., a nanograting). It should be understood that conventional waveguide materials such as glass are generally considered incompatible with such simultaneous formation due to concerns regarding breakage of discrete integral protrusions such as spacers and the inability to accurately reproduce the constituent features that form the diffractive optical element 1040 and light scattering features 1060.

[0159] As mentioned above, in some embodiments, one or more layers of material may be utilized to prevent light leakage between the spacer and the waveguide. FIG. 11B illustrates an example of a stack of waveguides 1100 comprising spacers 1020a, 1020b, 1020c and a light leakage prevention material 1070 at the interface between the spacers and the immediate ones of the waveguides 1000a, 1000b, 1000c. For example, the light leakage prevention material 1070 may be one or more layers of a material forming a light absorbing material and / or an anti-reflective coating. The light leakage prevention material 1070 may be provided between the spacer 1020b and the waveguide 1000a. The light leakage prevention material 1070 may also be provided between the spacer 1020c and the waveguide 1000b. The light leakage prevention material 1070 may also be provided on the spacer 1020a and on the recess 1030c. In some embodiments, the light leakage prevention material 1070 may be applied to the spacer before attaching the spacer to another waveguide. For example, the light leakage prevention material 1070 may be deposited on a surface of the spacer before inserting the spacer into a matching recess in the upper waveguide. Examples of light absorbing materials to serve as the light leakage prevention material 1070 include carbon black, mesoporous carbon, and carbon nanotubes (single-walled and multi-walled nanotubes). Examples of carbon nanotubes include single-atom carbon nanotubes, such as those sold under the name VANTA BLACK® and available from Surrey NanoSystems (Newhaven, the United Kingdom). In some embodiments, the light leakage prevention material 1070 may be a light absorbing adhesive, which may be used to bond the spacer to the upper waveguide. In some embodiments, the spacer may include light scattering features and a light leakage prevention material at the interface between the spacer and the upper waveguide.

[0160] In some embodiments, the spacer 1020a may be formed from the light absorbing material itself. For example, a light absorbing resin can be provided to form the spacer 1020a. Alternatively, the light absorbing material (e.g., resin) may be doped with some light absorbing material, such as carbon black, mesoporous carbon, carbon nanotubes (single-walled and multi-walled nanotubes), etc. Examples of carbon nanotubes include single-atom carbon nanotubes, such as nanotubes sold under the name VANTA BLACK® and available from Surrey NanoSystems (Newhaven, the United Kingdom). In some embodiments, doping the resin may include mixing the light absorbing material while it is in liquid form. In some embodiments, the light absorbing material may be doped with the light absorbing material prior to casting the light absorbing material and forming the spacer 1020a. In some embodiments, the spacer with the light absorbing material may be formed by depositing the light absorbing material into a mold to form the spacer, followed by adding an optically transparent material to the mold to form the remainder of the waveguide.

[0161] 11B, the light leakage prevention material 1070 may form an anti-reflective coating. Examples of anti-reflective coatings include single-layer and multi-layer anti-reflective coatings formed from partially reflective and partially transmissive layers of material.

[0162] As discussed herein, an adhesive may be used to adhere the integral spacers disclosed herein to the adjacent waveguides. Preferably, the adhesive is a light absorbing adhesive, as discussed herein, to reduce or prevent light leakage. In some other embodiments, the adhesive may be a non-light absorbing adhesive. In some embodiments, an adhesive may be used alone or in combination with a recess to bond the spacer to the adjacent waveguide.

[0163] In some embodiments, a low viscosity adhesive may be utilized to attach the spacer to the adjacent waveguide. In some other embodiments, a medium or high viscosity adhesive (which may simply be referred to herein as a high viscosity adhesive) may be utilized to form a pillar that extends substantially the height of the spacer, which pillar attaches the waveguide to the adjacent waveguide. Thus, an adhesive may be provided to bond a major surface of the spacer and / or the lower waveguide to a surface of the upper waveguide.

[0164] For example, adhesive may be provided on the bottom surface of the upper waveguide or in a depression on the bottom surface of the upper waveguide. For example, adhesive may be dispensed into a depression on the bottom surface of the waveguide while the bottom surface faces up. The waveguide may then be inverted and placed on top of the lower waveguide along with a spacer, and adhesive may be used to bond the upper and lower waveguides. This method may be preferred when using a low viscosity adhesive, which may be more difficult to keep localized than a high viscosity adhesive. In some embodiments, an adhesive (e.g., a high viscosity adhesive) may be used for bonding and applied to the top surface of the integral spacer, and then the upper waveguide is placed on top of the spacer and adhesive to attach the upper waveguide to the lower waveguide.

[0165] The use of solid integral spacers that define the separation distance between adjacent waveguides, as discussed herein, provides one or more advantages. Using the assemblies and methods described herein, less precision may be required in controlling adhesive dispensing parameters (e.g., pressure, presence of bubbles, etc.) and alignment. The integral spacers provide a fixed gap between the upper surface of the lower layer waveguide and the bottom surface of the upper layer waveguide, such that precise application of adhesive may not be required to maintain a consistent gap between layers of the waveguide stack. The built-in spacers can be cast with a very consistent height, which, as discussed herein, can provide a consistent gap (e.g., air gap) between adjacent layers, increasing the performance of the display device.

[0166] 11C illustrates an example of a stack of waveguides 1100 with adhesive 1180 at the interface between integral spacer 1120b and the adjacent waveguide 1110a. It should be understood that spacers 1120x (number 1120 followed by various letters) may correspond to spacers 1020. Spacer 1120b is integral with waveguide 1100b. Spacers 1120a on waveguide 1100a and spacers 1120b on waveguide 1100b preferably have a width of about 10 μm to about 2000 μm in some embodiments. As an example, the width of the spacers 1120a, 1120b may be about 10 μm, about 20 μm, about 30 μm, about 40 μm, about 50 μm, about 100 μm, about 200 μm, about 300 μm, about 400 μm, about 500 μm, about 750 μm, about 1000 μm, about 1250, about 1500 μm, about 17500 μm, about 2000 μm, or any value between any two of the aforementioned values. Furthermore, the width of the spacers may be reduced if multiple spacers, forming a sequence of walls, are provided on a single waveguide. The spacers are preferably located on the periphery of the major surface of the associated waveguide to avoid interference with the light propagation in the waveguide and the user's line of sight. However, as discussed below, the spacers may be located across the entire area of ​​the major surface of the waveguide in some embodiments. The height of the spacers may vary depending on the desired distance between adjacent waveguides 1100a and 1100b, but generally may be in the range of about 10 μm to about 200 μm. By way of example, the height of spacers 1120a, 1120b may be about 10 μm, about 15 μm, about 20 μm, about 25 μm, about 30 μm, about 35 μm, about 40 μm, about 45 μm, about 50 μm, about 60 μm, about 70 μm, about 80 μm, about 90 μm, about 100 μm, about 110 μm, about 120 μm, about 130 μm, about 140 μm, about 150 μm, about 160 μm, about 170 μm, about 180 μm, about 190 μm, about 200 μm, or any value between any two of the foregoing values.

[0167] 11C, the waveguides 1100a, 1100b further comprise surface relief features 1140a, 1140b and 1140c, 1140d, respectively. The surface relief features 1140a, 1140b, 1140c, 1140d may comprise a pattern of protrusions and depressions sized and arranged to form a diffractive optical element, such as a diffraction grating. It should be understood that such a diffractive optical element may correspond to one or more of the incoupling optical elements 700, 710, 720, the light dispersive elements 730, 740, 750, or the outcoupling optical elements 800, 810, 820 of FIGS. 9A-9C.

[0168] In some embodiments, the waveguides 1100a, 1100b may omit some or all of the surface relief features 1140a, 1140b, 1140c, 1140d such that the major surfaces of the waveguides 1100a, 1100b may be smooth except for the spacers 1120a, 1120b, respectively. Additionally, it should be understood that the surface relief features 1140a, 1140b, 1140c, 1140d may vary in size, number, location, and / or orientation from the illustrated embodiment.

[0169] In some embodiments, adhesive 1180 may be disposed on spacer 1120b. In some embodiments, adhesive 1180 may be a low viscosity adhesive. The low viscosity adhesive may include, for example, one or more of the following: epoxy, silicone, polyurethane, cyanoacrylate, methyl-cyanoacrylate, ethyl-cyanoacrylate, elastomeric contact cement, UV curable adhesive, fast curing adhesive, low viscosity glue, and adhesive resin, among others. Adhesive 1180 preferably has an as-deposited viscosity (viscosity of the adhesive before it is cured) in the range of about 5 mPa·s to about 100 mPa·s. As examples, the adhesive 1180 may have a viscosity of about 5 mPa·s, about 10 mPa·s, about 15 mPa·s, about 20 mPa·s, about 25 mPa·s, about 30 mPa·s, about 35 mPa·s, about 40 mPa·s, about 45 mPa·s, about 50 mPa·s, about 55 mPa·s, about 60 mPa·s, about 65 mPa·s, about 70 mPa·s, about 75 mPa·s, about 80 mPa·s, about 85 mPa·s, about 90 mPa·s, about 95 mPa·s, about 100 mPa·s, or any value between any two of the aforementioned values. In some embodiments, the low viscosity adhesive may be deposited by jet deposition (e.g., inkjet deposition), where the low viscosity of the adhesive may facilitate the deposition of the adhesive. In some other embodiments, the adhesive may be applied to the spacer by contacting an open reservoir of adhesive with the spacer. It should be understood that after being deposited, the adhesive may become solidified, i.e., change from a flowable liquid form to a solid form (e.g., by curing, such as by exposure to UV and / or heat).

[0170] The adhesive 1180 may be applied during a stacking process, where two or more waveguides are bonded and stacked to form a stacked waveguide assembly or a waveguide stack, such as stacked waveguide assembly 260 of FIG. 6. In some embodiments, after stacking two adjacent waveguides, or after stacking the entire waveguide assembly, the adhesive 1180 may undergo a curing process, where the adhesive 1180 may be solidified, for example, by exposure to heat, light, air, etc. Once cured, the adhesive 1180 may provide a high strength and flexible or rigid bond between adjacent waveguides. After curing, the adhesive 1180 may be resistant to changes in temperature or humidity, such that the adhesive is capable of maintaining a strong bond despite exposure to temperature changes or humidity inside the display device.

[0171] In some embodiments, the adhesive may have a thickness defined by the distance between the top surface of the spacer 1120b and the underlying surface of the waveguide 1100a. In some embodiments, the thickness of the adhesive 1180 after curing may range from about 2 μm to about 20 μm. By way of example, the thickness of the adhesive 1180 may range from about 2.0 μm, about 2.5 μm, about 3.0 μm, about 3.5 μm, about 4.0 μm, about 4.5 μm, about 5.0 μm, about 5.5 μm, about 6.0 μm, about 6.5 μm, about 7.0 μm, about 7.5 μm, about 8.0 μm, about 8.5 μm, about 9.0 μm, about 9.5 μm, about 10.0 μm, about 10.5 μm, about 11.0 μm, about 11.5 μm, about 12.0 μm, about 13.0 μm, about 14.0 μm, about 15.0 μm, about 16.0 μm, about 17.0 μm, about 18.0 μm, about 19.0 μm, about 20.0 μm, about 21.0 μm, about 22.0 μm, about 23.0 μm, about 24.0 μm, about 25.0 μm, about 26.0 μm, about 27.0 μm, about 28.0 μm, about 29.0 μm, about 30.0 μm, about 31.0 μm, about 32.0 μm, about 33.0 μm, about 34.0 μm, about 35.0 μm, about 36.0 μm, about 37.0 μm, about 38.0 μm, about 39.0 μm, about The thickness of the adhesive may be 2.0 μm, about 12.5 μm, about 13.0 μm, about 13.5 μm, about 14.0 μm, about 14.5 μm, about 15.0 μm, about 15.5 μm, about 16.0 μm, about 16.5 μm, about 17.0 μm, about 17.5 μm, about 18.0 μm, about 18.5 μm, about 19.0 μm, about 19.5 μm, about 20.0 μm, or any value between any two of the aforementioned values. Preferably, the adhesive has a high refractive index. For example, the adhesive 1180 may have a refractive index greater than 1.65 and can be doped with a black colorant or a light absorbing material (e.g., a light absorbing dye). As discussed in more detail below, if unused light is not absorbed in the adhesive or the edges of the waveguide, it could potentially reflect back into the active display area, creating undesirable residual images or stray light, thus degrading image quality. A high refractive index and black dopant can advantageously reduce or eliminate reflection of unused light from the adhesive 1180 into the active display area.

[0172] It should be understood that in some embodiments, each of the waveguides 1100a, 1100b may be part of a larger sheet of optically transparent material that may then be cut or singulated to form multiple discrete stacks of waveguides, each forming an individual eyepiece for a display device. Thus, after stacking the waveguides and curing the adhesive 1180, excess peripheral areas of the stack of waveguides 1100 may be removed as part of the singulation process. During singulation, excess material may be removed from the waveguide stack 1100, for example, along the singulation path 1185. Singulation may be performed, for example, using a laser cutting device. In embodiments where the singulation path runs along the length of the spacer, the edge of the waveguide and the spacer are substantially coextensive, so the spacer may be understood to define the edge of the waveguide. In some embodiments, the waveguides disclosed herein may be understood as sheets of optically transparent material that are singulated from a larger sheet of optically transparent material. Preferably, in some embodiments, the waveguides forming the stack of waveguides are generally parallel to each other.

[0173] It should be understood that the location of the singulation path 1185 may be modified depending on the location, number, orientation, and size of the spacers 1120a, 1120b, and the location, thickness, type, and physical properties of the adhesive 1185. As illustrated in FIG. 11C, the singulation path 1185 may be located such that singulation results in the removal of a portion of the spacers 1120a, 1120b. In some embodiments, such as that illustrated in FIG. 11E, the singulation path 1185 may be located such that singulation results in the complete removal of the spacers 1120a, 1120b. In embodiments in which singulation completely removes the spacers 1120a, 1120b from the waveguide stack 1100, as will be discussed further below with respect to FIG. 11E, a relatively large amount of adhesive, forming one or more columns, may be provided between the upper surface of the waveguide 1100b and the lower surface of the waveguide 1100a to maintain a consistent separation between the waveguides. In some embodiments, the singulation path 1185 may be located such that the peripheral side of the spacer 1120b is removed. As a result, after singulation, the waveguide stack 1100 may comprise a straight peripheral edge. However, in some embodiments, various edge treatments may be applied to the waveguides 1100a, 1100b to increase the performance of the waveguide stack 1100, as described in more detail below.

[0174] 11D, an example of a stack of waveguides is illustrated that includes adhesive both at the interface between the spacer and the adjacent waveguide and on the vertical sides of the spacer. In some embodiments, adhesive 1180 may be applied to the top of the spacer 1120b first and then flow down the sides of the spacer 1120b. This may occur, for example, when adhesive 1180 includes a low viscosity adhesive, as a less viscous adhesive may flow easily from the top surface to the sides of the spacer 1120b. As will be described in more detail below with respect to FIG. 11H, in some embodiments, one or more hollow recesses may be provided on the upper major surface of the waveguide 1100b to prevent further flow of adhesive 1180 onto the active areas, particularly the active areas defined by surface features 1140c, 1104d.

[0175] In some embodiments, a relatively large amount of adhesive 1180 may be provided in contact with and extending directly between the upper and lower major surfaces of the waveguides 1100b. Such a large amount of adhesive 1180 may be understood to form a pillar extending between those major surfaces. Advantageously, the pillar may increase the stability of the waveguide stack 1100. In some embodiments, the adhesive 1180 may be provided adjacent the spacer 1120b. FIG. 11E illustrates an example of a waveguide stack with adhesive forming a pillar adjacent the spacer. In some embodiments, an integral spacer 1120b may be formed during casting of the waveguide 1100b and may be used to set the distance or gap between the waveguides 1120a and 1120b during the waveguide stack. Prior to singulation, the adhesive 1180 may be applied directly onto the upper major surface of the waveguide 1100b adjacent the spacer 1120b. Adhesive 1180 may be used to bond the lower surface of waveguide 1100a to the upper surface of waveguide 1120b.

[0176] Advantageously, the use of adhesive 1180 in combination with spacer 1120b reduces the precision required when applying adhesive 1180. During stacking of waveguides 1100a, 1100b, spacer 1120b provides a physical barrier between the waveguides, preventing the lower surface of waveguide 1100a from advancing closer to the upper surface of waveguide 1100b. As a result, adhesive 1180 is not necessarily required to maintain the distance between waveguides 1100a, 1120b prior to singulation. Adhesive 1180 may be used to secure waveguide 1100a to waveguide 1100b and may be compressed until spacer 1120b prevents further compression. As a result, the requirements for high precision and accuracy in the amount of adhesive dispensed may be reduced. Rather, an excess amount of adhesive may be applied and spacers 1120b may be utilized to provide consistent separation between waveguides 1100b and 1100a. Note that in some embodiments, the volume of adhesive 1180 applied is precisely controlled such that the adhesive is prevented from flowing into the active area of ​​waveguide 1100b during stacking of waveguides 1100a, 1100b. Utilizing an integral spacer and adhesive in combination may thus enable the creation of a consistent gap between two adjacent waveguides in a waveguide stack, increasing performance.

[0177] In some embodiments where the adhesive 1180 forms a pillar and bonds two adjacent waveguides together, the adhesive 1180 preferably comprises a medium or high viscosity adhesive. When the adhesive 1180 is applied or deposited adjacent to and within the spacer 1120b (inside the spacer 1120b within the volume defined by the spacer 1120b and encompassing the features 1140c, 1140d), it may be preferable for the medium or high viscosity adhesive to limit or prevent flow of the adhesive into the active area of ​​the waveguide 1100b, and in particular to prevent flow into the surface features 1140c, 1140d. When the adhesive 1180 is applied adjacent to and within the spacer 1120b, the adhesive 1180 preferably has an as-deposited viscosity (viscosity before curing or solidifying) in the range of about 10,000 mPa·s to about 50,000 mPa·s. In examples, the adhesive may have a viscosity of about 10,000 mPa·s, about 12,000 mPa·s, about 14,000 mPa·s, about 16,000 mPa·s, about 18,000 mPa·s, about 20,000 mPa·s, about 22,000 mPa·s, about 24,000 mPa·s, about 26,000 mPa·s, about 28,000 mPa·s, about 30,000 mPa·s, about 31,000 mPa·s, about 32,000 mPa·s, about 33,000 mPa·s, about 34,000 mPa·s, about 35,000 mPa·s, about 36,000 mPa·s, about 37,000 mPa·s, about 38,000 mPa·s, about 39,000 mPa·s, about 40,000 mPa·s, about 41,000 mPa·s, about 42,000 mPa·s, about 43,000 mPa·s, about 44,000 mPa·s, about 45,000 mPa·s, about 46,000 mPa·s, about 47,000 mPa·s, about 48,000 mPa·s, about 49,000 mPa·s, about 50,000 mPa·s, about 51,000 mPa·s, about 52,000 mPa·s, about 53,000 mPa·s, about 54,000 mPa·s, about 55,000 mPa·s, about 56,000 mPa·s, about 57,000 mPa·s, about 58,00 The adhesive may have a viscosity of about 2,000 mPa·s, about 34,000 mPa·s, about 36,000 mPa·s, about 38,000 mPa·s, about 40,000 mPa·s, about 42,000 mPa·s, about 44,000 mPa·s, about 46,000 mPa·s, about 48,000 mPa·s, about 50,000 mPa·s, or any value between any two of the aforementioned values. It is to be understood that after being deposited, the adhesive may be in a solidified state (e.g., by curing).

[0178] High viscosity adhesives include one or more of the following: epoxy, silicone, polyurethane, cyanoacrylate, methyl-cyanoacrylate, ethyl-cyanoacrylate, elastomeric contact cement, UV curable adhesive, fast curing adhesive, medium or high viscosity glue, and adhesive resin, among others. Preferably, adhesive 1180 has a high refractive index. For example, adhesive 1180 may have a refractive index greater than 1.65. Additionally, adhesive 1180 may be doped with a black colorant or a light absorbing material (e.g., a light absorbing dye) to aid in the absorption of underutilized light.

[0179] After the stacking process is completed, the entire integral spacers 1120a, 1120b may be removed during singulation. As illustrated in FIG. 11E, a singulation path 1185 may be along the inside of the spacers 1120a, 1120b such that the spacers 1120a, 1120b are removed from the waveguide stack 1100 while the adhesive 1180 remains intact as part of the final waveguide stack 1100. During singulation, the adhesive 1180 may be pre-cured and hardened such that the distance between the waveguides 1100a, 1100b remains substantially constant despite the removal of the spacers 1120b. Thus, in some embodiments, after singulation, the waveguide stack 1100 may not include the spacers 1120a, 1120b and the gap between adjacent waveguides, e.g., waveguides 1100a and 1100b, is maintained by the cured adhesive 1180.

[0180] In some embodiments, two or more adhesives may be provided on the waveguide 1100b to further improve the bond strength and mechanical stability of the waveguide stack 1100. FIG. 11F illustrates an example of a waveguide stack comprising a first adhesive at the interface between the spacer and the immediately adjacent waveguide and a second adhesive adjacent the spacer. In some embodiments, the waveguide stack 1100 may comprise both a low viscosity adhesive 1180a and a medium or high viscosity adhesive 1180b. The low viscosity adhesive 1180a may be dispensed and adhered onto the top surface of the spacer 1120b, while the medium or high viscosity adhesive 1180b may be dispensed and adhered onto the upper major surface of the waveguide 1100b adjacent the spacer 1120b. As illustrated in FIG. 11F, prior to curing, the low viscosity adhesive 1180a and the medium to high viscosity adhesive 1180b may flow and form a mixed adhesive 1180c. In some other embodiments, adhesive 1180c may be understood to be a single adhesive (e.g., a medium or high viscosity adhesive) that extends to the sides and top of the spacer. It should also be understood that in some embodiments, adhesives 1180a and 1180b may remain distinctly different such that both the left and right sides have similar but distinctly different arrangements of adhesive on the top and sides of adjacent spacers. In some other embodiments, adhesive 1180c may be understood to be present on both the left and right sides of the illustrated waveguide stack 1100.

[0181] The low viscosity adhesive 1180a may comprise any of the low viscosity adhesives described above with respect to FIG. 11C. The medium or high viscosity adhesive may comprise any of the medium or high viscosity adhesives described above with respect to FIG. 11E. Both the low viscosity adhesive 1180a and the medium or high viscosity adhesive 1180b preferably have a high refractive index. For example, the refractive index of both the low viscosity adhesive 1180a and the medium or high viscosity adhesive 1180b may be greater than 1.65 in some embodiments. Additionally, both the low viscosity adhesive 1180a and the medium or high viscosity adhesive 1180b may be doped with a black colorant or light absorbing material (e.g., a light absorbing dye) to facilitate light absorption and, for example, prevent light leakage.

[0182] It should be appreciated that the use of multiple adhesives can increase adhesion between the waveguide 1100a and the waveguide 1100b and improve the robustness of the waveguide stack 1100. In some embodiments, the medium or high viscosity adhesive 1180b may be provided on the periphery of the waveguide 1100b outside the spacer 1120b, as illustrated in FIG. 11F. Providing the medium or high viscosity adhesive 1180b on the periphery of the waveguide 1100b beyond the spacer 1120b allows the spacer 11029b to act as a physical barrier between the adhesive 1180b and the active area of ​​the waveguide 1100b, particularly the surface features 1140c, 1140d. It should be appreciated that the medium to high viscosity adhesive 1180b may be provided on the interior of the spacer 1120b, as described with respect to FIG. 11E. In some embodiments, the medium to high viscosity adhesive 1180b may be provided on both sides of the spacer 1120b. Providing a medium to high viscosity adhesive 1180b on both sides of the spacer 1120b may further increase the bond strength between the waveguides 1100a and 1100b.

[0183] 11F, singulation path 1185 may be positioned such that at least a portion of medium-high viscosity adhesive 1180b is removed in response to singulation. Removal of peripheral portions of medium-high viscosity adhesive 1180b may result in a straightened periphery of waveguide stack 1100. In some embodiments, various edge treatments may be applied to waveguides 1100a, 1100b to increase performance of waveguide stack 1100, as described in further detail below.

[0184] In some embodiments, multiple spacers may be provided to extend along the periphery of each of the waveguides 1100a, 1100b. For example, the spacers may extend alongside one another along the periphery of the waveguides 1100a, 1100b. FIG. 11G illustrates an example of a waveguide stack comprising multiple spacers and one or more adhesives both in the volume formed between the spacers and at the interface between the top surface of the spacer and the immediately adjacent waveguide. Although the example waveguide stack 1100 of FIG. 11G illustrates only the waveguide 1100b with multiple spacers 1120b, 1120c, it should be understood that some or all of the waveguides of the waveguide stack assembly may comprise multiple spacers on each periphery. In some embodiments, the spacers 1120b, 1120c may extend alongside one another, e.g., may be extended parallel to one another.

[0185] Continuing with reference to FIG. 11G, two or more integral spacers may be created during the casting of the polymer eyepiece. The spacers 1120b, 1120c may each have the same height, which may advantageously provide an additional physical barrier between adhesive or external debris and the active area of ​​the waveguide 1100b. Furthermore, one or more waveguides with multiple spacers may provide additional stability to the waveguide stack 1100 during the stacking and singulation process. In addition, providing multiple spacers on the waveguides may ensure that a consistent gap is created between the entire bottom surface of the upper waveguide and the upper surface of the lower waveguide by providing multiple contact points with the same height. In some embodiments, the waveguide 1100b may include multiple spacers to increase the bonding area and strength.

[0186] In some embodiments, as illustrated on the left side of the waveguide stack 1100 in FIG. 11G, the spacer 1120c may have a different height than the spacer 1120b. For example, the height of the spacer 1120c may be less than or greater than the height of the spacer 1120b. The height of the spacer 1120c and the additional spacers may be varied to trap adhesive between the walls of the spacers, prevent external contaminants such as debris from entering the active area of ​​the waveguide 1100b, and provide additional stability. In some embodiments, the outer spacer 1120c has a lower height than the inner spacer 1120b. This configuration may encourage an outward flow of the adhesive 1180 away from the central active area of ​​the waveguide 1100b and toward the periphery of the waveguide 1100b. Additionally, in any of the configurations described herein, the adhesive may be applied to the edges of the waveguide 1100b to reduce the spread of the adhesive to the central area of ​​the waveguide 1100b.

[0187] In some embodiments, adhesive 1180 may be provided between spacers 1120b and 1120c, on the top surfaces of spacers 1120b, 1120c, and on the outside of spacer 1120c, as illustrated in FIG. 11G. Alternatively, in some embodiments, adhesive 1180 may be provided only on the top surfaces of spacers 1120b, 1120c, and between spacers 1120b and 1120c. In some embodiments, adhesive 1180 may be provided only on the top surface of spacer 1120b and / or the top surface of spacer 1120c. Additionally, any of the adhesive types, arrangements, and placement locations described above with respect to FIGS. 11C-11F may be utilized with multiple spacers on a single waveguide. For example, low, medium, or high viscosity adhesives may be used alone or in any combination. Adhesive can be provided anywhere on the waveguide 1100b, but is preferably not provided on the active area, particularly on the surface features 1140c, 1140d. In some embodiments, the space between adjacent walls of the spacer, for example the space between spacers 1120b and 1120c, may be devoid of adhesive 1180 to improve ease of singulation through that area. For example, an area of ​​singulation path 1185 may be provided without adhesive 1180 to reduce simulation difficulty and reduce debris creation. In some embodiments, spaces between adjacent walls of the spacer may be left devoid of adhesive 1180.

[0188] During singulation, one or more walls of the spacer may be removed from the waveguide stack 1100. For example, at least a portion of the spacer 1120c may be removed during singulation. Prior to removal, the spacer 1120c may confine the adhesive 1180 from entering the central active area of ​​the waveguide 1100b.

[0189] In some embodiments, one or more recesses 1190 may be formed between the surface features 1140c, 1140d and the spacer 1120c. FIG. 11H illustrates an example of a stack of waveguides with a groove or recess on the major surface of the waveguide between the adhesive and the active area of ​​the waveguide. Even when a medium or high viscosity adhesive is used, some adhesive may flow from the periphery of the waveguide 1100b toward the active area, including the surface features 1140c, 1140d. A recess 1190 may thus be provided on the upper major surface of the waveguide 1100b to capture and prevent flow of adhesive 1180 into the active area, particularly onto the surface features 1140c, 1140d. In some embodiments, the recess may have a width in the range of 50 μm to 2 mm and a depth in the range of 50 μm to 0.4 mm. Recesses 1190 can be utilized in any of the configurations previously described, including, for example, the configurations of Figures 11C-11G. Recesses may also be provided between adjacent walls of a spacer, such as between spacer 1120b and spacer 1120c in Figure 11G.

[0190] One or more recesses 1190 may also be provided on a major surface of the waveguide that includes a plurality of spacers. For example, FIG. 11J illustrates an example waveguide 1100b that includes a plurality of spacers 1120b, 1120c and an adhesive capture recess 1190 provided between the adhesive 1180 and the active areas 1140c, 1140d. In some embodiments, the spacers 1120b, 1120c and the recesses 1190 can both act as physical obstacles to the flow of the adhesive 1180 into the active areas that include features 1140c, 1140d.

[0191] To further reduce adhesive flow into the active areas of the waveguides and increase adhesive bond strength of the waveguide stack 1100, some or all of the surfaces of the waveguides 1100a, 1100b may be roughened (e.g., textured and non-smooth). FIG. 11I illustrates an example of a stack of waveguides with roughened surfaces in the areas where the adhesive is applied. In some embodiments, the surfaces to which the adhesive 1180, 1180a, 1180b will be applied may be roughened, for example, by physical abrasion and / or by nanostructures formed during casting of the waveguides and spacers, to improve adhesion of the adhesive 1180, 1180a, 1180b. For example, roughened surface areas 1195 may be provided along the top and sides of the spacer 1120b, along the bottom major surface of the waveguide 1100a, and / or along the upper major surface of the waveguide 1100b.

[0192] It should be understood that in embodiments where the roughened surface is formed in a mold, the mold would typically need to be separated from the waveguide with the roughened surface formed in the mold. As a result, forming a roughened vertical surface may be difficult because the vertical surface may be parallel to the direction of relative movement of the mold within the waveguide during manufacturing, i.e., having a roughened vertical surface may cause the waveguide and integral spacer to "stick" in the mold. For ease of manufacturing, in some embodiments, the roughened surface area 1195 may be present on the top surface of the spacer 1120b and / or the bottom surface of the waveguide 1100a, and / or along the upper surface of the waveguide 1100b.

[0193] In some embodiments, the roughened surface area 1195 may include random peaks and valleys (e.g., resulting from physical abrasion, etc.) or may include regularly repeating peaks and valleys (e.g., nano-lattices, etc.). It should be understood that the roughened surface area 1195 effectively increases the surface area in contact with the adhesive, thereby improving adhesion. The roughened surface area 1195 provided on any spacer and waveguide surface disclosed herein may include, for example, any of the configurations shown in Figures 10C-11H and 11J-11K.

[0194] As described above, the waveguide may comprise a plurality of spacers, for example forming concentric or coaxial walls of the spacers, and adhesive may be applied in a volume formed between a pair of immediately adjacent spacers. FIG. 11K illustrates an example of a stack of waveguides comprising a plurality of spacers, in which adhesive is applied in a volume between two adjacent spacers and an additional spacer that forms an adhesive capture volume near the adhesive fill volume. In some embodiments, spaces between adjacent spacers, such as the space between adjacent spacers 1120b and 1120c or the space between adjacent spacers 1120d and 1120e, may be left devoid of adhesive, allowing those volumes to capture excess adhesive that may escape from the volume between spacers 1120c and 1120d. In some embodiments, as illustrated, the volume between two adjacent spacers in the center of the plurality of spacers (i.e., not adjacent to the periphery of waveguide 1100b and not adjacent to surface features 1140c, 1140d) may comprise adhesive. In some embodiments, the spacer 1120b and / or additional spacers may provide a physical barrier between the adhesive 1180 and the active area, including the surface features 1140c, 1140d. Similarly, the spacer 1120e and / or additional walls of the spacer may act as a physical barrier between the adhesive 1180 and the periphery of the waveguide 1100b. When multiple spacers are provided, the singulation path 1185 may intersect the waveguide 1120b at any point between the adhesive 1180 and the periphery of the waveguide 1100b.

[0195] As discussed herein, in some embodiments, the adhesive joining the spacer to the adjacent waveguide may be a low viscosity adhesive. Such low viscosity adhesives offer advantages for ease of dispensing (e.g., by jet deposition, such as inkjet deposition), but may be susceptible to running off the surface of the spacer onto which it is deposited. As a result, it may be difficult to deposit a thick adhesive layer using such low viscosity adhesives. It should be appreciated that a relatively thick adhesive layer may provide better adhesion between the spacer and the overlying waveguide.

[0196] In addition to or as an alternative to forming an adhesive capture volume adjacent the spacer (e.g., as shown in Figures 11G-11K), the top or ends of the spacer may be shaped to protect against undesired adhesive migration. In some embodiments, the ends of the spacer may include structure to localize the adhesive on the ends, reducing adhesive migration from the ends of the spacer and promoting adhesion between the spacer and the overlying waveguide.

[0197] 11L-11M respectively illustrate cross-sectional side and top-down view examples of a spacer having ridges for retaining adhesive. These figures show integral spacer 1120 in isolation. It should be understood that spacer 1120 may be any of the integral spacers disclosed herein and may correspond, for example, to spacer 1020 and spacer 1120x (where x is a letter as used in the various figures herein).

[0198] 11L, the integral spacer 1120 has an end 1121 for receiving adhesive. In some embodiments, the end 1121 includes one or more ridges 1122, which act as a physical barrier to adhesive migration. The ridges 1122 may be elevated portions of the end 1121 and may extend across the end 1121 to define a volume 1123. In some embodiments, as illustrated in FIG. 11M, the one or more ridges 1122 may form a single continuous barrier structure that surrounds the volume 1123 and limits lateral migration of adhesive deposited within the volume 1123. While the depicted cross-sectional view is shown to have a stepped profile for ease of illustration, it should be understood that the ridges 1122 may have a curved or multi-sided profile, and the bottom of the volume 1123 may also be curved (e.g., curved outward) or have an irregular profile (e.g., a multi-sided profile).

[0199] In some embodiments, the volume 1123 has a depth 1124 sufficient to support an adhesive layer having a thickness of 1 μm or more, 5 μm or more, 10 μm or more, including 1-35 μm and 5-10 μm, measured at the thickest portion of the adhesive layer. It should be understood that the thickness of the adhesive layer typically exceeds the depth 1124 of the volume 1123 to allow for desired contact between the adhesive and the overlying waveguide. However, as an approximation, in some embodiments, the maximum depth 1124 of the volume 1123 (i.e., the depth of the volume at its lowest point) may be understood to be about 1 μm or more, 5 μm or more, 10 μm or more, including 1-35 μm and 5-10 μm.

[0200] It should be appreciated that the end 1121 of the spacer 1120 may include a plurality of ridges 1122. FIGS. 11N-11O illustrate examples of cross-sectional side and top-down views of a spacer having a plurality of ridges 1122 for retaining adhesive, respectively. The ridges 1122 define volumes 1123 between pairs of ridges 1122 into which adhesive may be applied. In some embodiments, the volumes 1123 may have a depth of 1 μm or more, 5 μm or more, 10 μm or more, including 1-35 μm and 5-10 μm. As discussed herein, the thickness of the adhesive layer occupying the volume 1123 may exceed the depth of the volume 1123. In some embodiments, the ridges 1122 may form a lattice, having regularly spaced ridges 1122 separated by regularly spaced volumes 1123.

[0201] 11O, the ridge 1122 may extend transversely to the direction in which adhesive would flow from the spacer 1120 to the optical structures of the waveguide stack. For example, the external coupling optical structures may be seen to be on the left side of the drawing, and the ridge 1122 may be oriented to block the flow of adhesive toward that left side. Thus, the ridge 1122 may be seen to be generally transverse to an axis extending from the spacer 1120 to the optical structures of the waveguide, such as the external coupling optical elements or the internal coupling optical elements. Viewed another way, the volume 1123 may be seen as a channel that diverts adhesive away from the optical structures of the waveguide.

[0202] While shown as having a stepped profile for ease of illustration, it should be understood that the ridges 1122 may have other cross-sectional shapes. For example, in addition to the square shape shown in FIG. 11N, the ridges 1122 may each have rounded edges, may be multi-sided, etc. Additionally, in some embodiments, rather than multiple steps, the multiple ridges 1122 may collectively form a sawtooth profile.

[0203] 11L-11O, end 1121 may have an adhesive applied thereon, as discussed herein. The adhesive may be applied by jet deposition (e.g., inkjet deposition), in some embodiments. In some other embodiments, end 1121 may be provided with adhesive by touching the end to a reservoir containing the adhesive. The adhesive may be a high, medium, or low viscosity adhesive, as discussed herein. In some embodiments, the adhesive is a low viscosity adhesive, which may have manufacturing efficiency advantages, such as with high speed dispensing systems, such as jet deposition systems.

[0204] After applying the adhesive to the end 1121, the adhesive may be contacted with another waveguide to adhere the spacer 1121 to the other waveguide. In some embodiments, the contact point may simply be a major surface of the other waveguide. In some other embodiments, the contact point may be a recess in the other waveguide, which is sized and shaped to accommodate the end 1121. Also, as discussed herein, in some embodiments, the contact point may also be a roughened or textured surface, which may have the advantage of increasing the surface area in contact with the adhesive and increasing the strength of the bond between the spacer and the waveguide.

[0205] 12A-12C, an example of a method for forming a waveguide with a spacer is illustrated. Referring to FIG. 12A, a pair of molds 1200, 1202 are provided. The mold 1202 includes a pattern of elevated features 1250, which may be a negative of a desired pattern to be defined in the waveguide to be formed. In some embodiments, the mold 1202 includes one or more of the elevated features 1230 for forming recesses in the waveguide to be formed. A mass of material 1012 for forming the waveguide is deposited on the mold 1202.

[0206] 12B, molds 1200, 1202 are brought together to compress material 1012 (FIG. 12A). The compressed material may undergo a curing process (e.g., exposure to UV light) to solidify the material and form waveguide 1010. As shown, negative pattern 1250 defines patterned structure 1050, which may comprise a diffractive optical element. It should be understood that additional negative patterns may be provided on mold 1202, as desired, to form additional structures, including diffractive optical elements.

[0207] 12C, molds 1200, 1202 are moved away from each other. Waveguide 1010 is released from the mold, thereby forming waveguide 1000.

[0208] 12A-12C, it should be understood that in some other embodiments, the elevated features 1230 are omitted, such that the resulting waveguide 1000 does not include the depression 1030. Instead, in some embodiments, the spacers of the lower waveguide simply rest on the bottom major surface of the upper waveguide.

[0209] 11C-11O, as discussed herein, the adhesive that bonds the spacer 1120 to the overlying waveguide (e.g., adhesives 1180, 1180a, 1180b) may be one or more of a variety of low, medium, and / or high viscosity adhesives. In some embodiments, the adhesive may be formed from a solution containing the same chemical species (e.g., the same monomer or partially formed polymer) used to form the polymer waveguide of which the integral spacer 1120 is a component part. As discussed herein, the waveguide and integral spacer 1120 may be formed by applying a solution containing the chemical species to form the polymer of the polymer waveguide on or in a mold and / or pressing the mold into the solution. In some embodiments, an adhesive solution containing the same chemical species may be utilized as one or more of the adhesives that bond the spacer to the adjacent waveguide.

[0210] In some embodiments, the adhesive solution may comprise a chemical species along with other constituent chemical species to provide a lower viscosity solution than that used to form the main body of the polymeric waveguide. For example, the adhesive solution may comprise a lower concentration of polymer-forming chemical species and a larger amount of solvent than the solution used to form the polymeric waveguide. In another example, the adhesive solution may have a higher or similar viscosity than the solution used to form the polymeric waveguide. Such a high viscosity solution may be utilized to form the high viscosity adhesive structure 1180b.

[0211] An adhesive solution may be deposited on or adjacent to the spacer 1120 as discussed herein. The adhesive solution is then contacted with another waveguide to provide adhesion to the other waveguide. The adhesive solution may then be solidified to form a monolithic mass comprising the integral spacer 1120, the waveguide, and the other waveguide. The solidifying step may be accomplished, for example, by curing through the application of energy (e.g., UV light and / or heat). Advantageously, the resulting monolithic structure may be formed from a single polymer that extends continuously from the waveguide, through the integral spacer, to the other waveguide. This may have the advantage of providing a structure with index-matched structure and high mechanical stability.

[0212] As discussed herein, the spacers 1020, 1120 are preferably formed away from the path of light propagation between the in-coupling and out-coupling optical elements of the waveguide. Figures 13A-13E illustrate examples of top-down plan views of a waveguide including spacers. As shown in Figure 13A, the spacers 1020 are preferably positioned along the periphery of the waveguide 1000. It should be understood that the spacers 1020 may thus surround an area within which diffractive optical elements, such as the in-coupling and out-coupling optical elements, are disposed.

[0213] In some embodiments, referring to FIG. 13B, the spacer 1020 may be elongated along the same axis 1042 as the surface relief feature 1040. In such embodiments, the spacer 1020 may include a spacer having a relatively long extension along the axis 1042 and a plurality of other spacers 1020' having a relatively shorter extension. For example, these other spacers 1020' may be spaced apart and arrayed in groups 1024, the groups of spacers being spaced apart along an axis that intersects the axis 1042. Advantageously, having the spacers 1020, 1020' elongated along the same axis 1042 as the surface relief feature 1040 can facilitate consistent manufacturing of the spacers and the surface relief features. For example, in some embodiments, the spacers and the surface relief features may be formed by imprinting using a mold that is subsequently removed by peeling the mold and the waveguide away from one another. It should be understood that this release may be performed along axis 1042, and that spacers or surface relief features that are elongated along a different axis may face an increased likelihood of breakage or deformation upon removal of the mold.

[0214] In some embodiments, referring to FIG. 13C, one or more vent holes 1330 may be provided extending laterally through the spacer 1320. FIG. 13C illustrates an example of a top-down plan view of a waveguide comprising a spacer 1320 with vent holes 1330. As described above, the spacer 1320 may be cast as part of a monolithic waveguide 1300 comprising an optically transparent body 1310 in which the spacer 1320 extends along the circumference of the waveguide 1300. The vent holes 1330 may be created in the spacer 1320 during or after casting of the waveguide 1300. In some embodiments, the spacer 1320 is cast with the vent holes 1330 formed in the mold used for casting. Alternatively, the vent holes 1330 may be created after casting by removing a portion of the spacer 1320, for example, using a milling nozzle or laser. A milling nozzle may contact the surface of the waveguide 1300 from either the side or the top of the waveguide 1300 to create the vent holes 1330. If the vent holes 1330 are to be formed after casting, the spacer 1320 may be cast as a closed loop and the vent holes may be created during a separate milling step, either before or after stacking multiple waveguides together. Multiple vent holes 1330 in the spacer 1320 may be preferred because one or more of the vent holes 1330 may be blocked during processing, for example, due to application of adhesive, debris from singulation, etc. It should be understood that the spacer 1320 in which the vent holes 1330 are formed may be understood as a single spacer in which material has been removed to form the vent holes 1330. In some other embodiments, the spacer 1320 may be understood to refer to multiple distinct (but still tracing a loop around the waveguide 1300) spacer structures.

[0215] The vent holes 1330 may provide one or more advantages, including allowing gas to flow in and out of the interior volume enclosed by the spacer 1320 in which the vent holes are formed. In some embodiments, about 1 to 10 vent holes 1330 may be provided. Preferably, multiple small vent holes 1330 may be utilized to reduce the ingress of debris into the active area of ​​the waveguide 1300, rather than a single large vent hole, which may allow contamination of the interior volume by external particulates or debris. For example, vent holes up to 100 μm in diameter may be provided, but the vent holes 1330 are preferably about 1 μm to about 10 μm in diameter to prevent particles and debris from ingressing into the active area through the vent holes 1330. As an example, the diameter of the vent hole 1330 may be about 1.0 μm, about 1.5 μm, about 2.0 μm, about 2.5 μm, about 3.0 μm, about 3.5 μm, about 4.0 μm, about 4.5 μm, about 5.0 μm, about 5.5 μm, about 6.0 μm, about 6.5 μm, about 7.0 μm, about 7.5 μm, about 8.0 μm, about 8.5 μm, about 9.0 μm, about 9.5 μm, about 10.0 μm, about 15.0 μm, about 20 μm, about 30 μm, about 40 μm, about 40 μm, about 50 μm, about 60 μm, about 70 μm, about 80 μm, about 90 μm, about 100 μm, about 110 μm, about 120 μm, about 130 μm, about 140 μm, about 150 μm, about 160 μm, about 170 μm, about 180 μm, about 190 μm, about 200 μm, about 210 μm, about 220 μm, about 230 μm, about 240 μm, about 250 μm, about 260 μm, about 270 μm, about 280 μm, about 290 μm, about 300 μm, about 310 μm, about 320 μm, about 330 μm, about 340 μm, about 350 μm, about 360 μm, about 370 μm, about 380 μm, about 390 μm, about 400 μm, about 400 μm, about 400 μm, about 41 0.0 μm, about 25.0 μm, about 30.0 μm, about 35.0 μm, about 40.0 μm, about 45.0 μm, about 50.0 μm, about 55.0 μm, about 60.0 μm, about 65.0 μm, about 70.0 μm, about 75.0 μm, about 80.0 μm, about 85.0 μm, about 90.0 μm, about 95.0 μm, about 100.0 μm, or any value between any two of the aforementioned values.

[0216] As discussed with reference to FIG. 11G, in some embodiments, multiple spacers are provided to extend around the periphery of the waveguide. FIG. 13D illustrates an example of a top-down plan view of a waveguide with multiple walls of the spacer with vent holes and debris capture structures. In some embodiments, the spacers 1320a, 1320b may each include vent holes 1320a, 1330b, respectively. Vent holes may be required in each wall of the spacers 1320a, 1320b to facilitate gas flow in and out of the interior area outlined by the spacers 1320a, 1320b. The vent holes 1330a in the spacer 1320a may be located remotely from the vent holes 1330b in the spacer 1330b to prevent particles or debris created during singulation from entering the active area of ​​the waveguide 1330. For example, vent holes 1330a, 1330b may be located on different sides of the waveguide 1300. Thus, if debris enters through vent hole 1330a, it must travel an increased distance in the channel formed between spacers 1320a and 1320b to reach vent hole 1330b and ultimately the active area of ​​the waveguide 1300.

[0217] To further protect against debris from entering the active area, one or more debris capture structures 1340 may be provided in the space between adjacent spacers. For example, one or more debris capture structures 1340 may be provided in a volume or channel formed between spacers 1320a and 1320b. The debris capture structures 1340 may comprise angled features or walls that physically block or capture debris as it flows, for example, from vent holes 1330a to vent holes 1330b. For example, the debris capture structures 1340 may include angled extensions of the spacers that protrude into the channel formed between spacers 1320a and 1320b. The debris capture structures 1340 are preferably located near the vent holes 1330a, 1330b to block debris from entering therethrough. However, it should be understood that the debris capture structure 1340 may be provided at multiple locations within the channel between adjacent spacers 1320a and 1320b. If multiple spacers are provided as part of the waveguide 1300, the debris capture structure 1340 may be located between some or all of the adjacent spacers.

[0218] The integral spacers are preferably located on the periphery of the waveguide 1300, but in some embodiments, the spacers may be provided at any point within the area of ​​the major surface of the waveguide 1300, including the active area. FIG. 13E illustrates an example of a top-down plan view of a waveguide with a single-point contact spacer within the active area. In some embodiments, the single-point contact spacer 1350 may be provided anywhere on the major surface of the waveguide 1300, including the center of the active area. The single-point contact spacer 1350 may help maintain a consistent gap between adjacent waveguides across the entire area of ​​the adjacent waveguides.

[0219] The single-point contact spacer 1350 may comprise any of the shapes discussed with reference to FIG. 10B. It should be appreciated that such a three-dimensional volume may provide advantages in structural stability and mechanical strength, particularly when the waveguide is utilized to form a stack of similar waveguides. It should be appreciated that for single waveguides and / or stacks of waveguides, a number of different shapes for the single-point contact spacer 1350 may be utilized in some embodiments. In some embodiments, the top of the single-point contact spacer 1350 may have a pointed shape (e.g., a square pyramid (shape D), a triangular pyramid (shape E), or a cone (shape F)) and may be rounded or flattened at the point of contact with an overlying structure, such as another waveguide. If the single-point contact spacer 1350 is formed by imprinting, the desired rounding or flattening of the top of the shape may be formed by an appropriately shaped mold or imprint reticle. It should be understood that the sides and top of the single point contact spacer 1350 may have one or more cross-sectional shapes (with the cross section taken transverse to the long vertical axis of the spacer) that may comprise any shape according to the requirements and specifications of the optical device comprising the stack of waveguides.

[0220] The spacers 1350 may be referred to as single point contact spacers because they contact the overlying waveguide at a single point, which may be sized and shaped to be substantially imperceptible to the human eye. For example, the longest lateral dimension of the cross-sectional shape of the single point contact spacers 1350 may be in the range of about 10 μm to about 500 μm. Preferably, the longest lateral dimension is less than 300 μm. More preferably, the longest lateral dimension is less than 250 μm. By way of example, the longest lateral dimension may be about 10 μm, about 15 μm, about 20 μm, about 25 μm, about 30 μm, about 35 μm, about 40 μm, about 45 μm, about 50 μm, about 60 μm, about 70 μm, about 80 μm, about 90 μm, about 100 μm, about 110 μm, about 120 μm, about 130 μm, about 140 μm, about 150 μm, about 160 μm, about 170 μm, about 180 μm, about 190 μm, about 200 μm, about 210 μm, about 220 μm, about 230 μm, about 240 μm, about 250 μm, The spacer may be about 260 μm, about 270 μm, about 280 μm, about 290 μm, about 300 μm, about 310 μm, about 320 μm, about 330 μm, about 340 μm, about 350 μm, about 360 μm, about 370 μm, about 380 μm, about 390 μm, about 400 μm, about 410 μm, about 420 μm, about 430 μm, about 440 μm, about 450 μm, about 460 μm, about 470 μm, about 480 μm, about 490 μm, about 500 μm, or any value between any two of the aforementioned values. In some embodiments, the spacer is approximately symmetrical about the longest lateral dimension described above. Forming a smaller single-point contact spacer 1350 (having a smaller cross-sectional area) may not be as optically objectionable as a larger single-point contact spacer 1350. Similarly, to further reduce the perceptibility of multiple spacers 1350 and reduce interference with the user's line of sight, the single point contact spacers 1350 are preferably spaced at one or fewer spacers / mm on the major surface of the waveguide. 2 As an example, the single point contact spacers 1350 are provided at a density of about 0.05 spacers / mm 2 , about 0.10 spacer / mm 2 , about 0.15 spacer / mm 2 , about 0.20 spacers / mm 2 , approximately 0.25 spacers / mm 2 , about 0.30 spacers / mm2 , approximately 0.35 spacers / mm 2 , about 0.40 spacers / mm 2 , approximately 0.45 spacers / mm 2 , approximately 0.50 spacer / mm 2 , approximately 0.55 spacers / mm 2 , about 0.60 spacers / mm 2 , approximately 0.65 spacers / mm 2 , about 0.70 spacers / mm 2 , about 0.75 spacers / mm 2 , about 0.80 spacers / mm 2 , approximately 0.85 spacers / mm 2 , approximately 0.90 spacers / mm 2 , approximately 0.95 spacers / mm 2 , approximately 1.00 spacer / mm 2 , or any value between any two of the aforementioned values.

[0221] The single point contact spacers 1350 may be provided in any pattern, orientation, location, geometry, or number, and anywhere on the major surface of the waveguide 1350, including the active area. In some embodiments, the single point contact spacers 1350 may be provided centrally on the waveguide 1300, but away from various surface features, including the in-coupling and out-coupling optical elements.

[0222] 14, an example of a waveguide is shown with spacers 1020 and depressions 1030 of varying dimensions. It should be understood that some spacers 1020 may be wider than others. The width of the spacer 1020 may vary depending on its location on the waveguide 1000. For example, a spacer 1020 in a location that is less likely to interact with light may be wider than a spacer 1020 in a location where the spacer 1020 is more likely to receive light and unintentionally leak that light into a nearby waveguide.

[0223] With continued reference to FIG. 14, in some embodiments, multiple juxtaposed spacers 1020 and / or multiple juxtaposed recesses 1030 may be provided in place of the single one of the spacers 1020 and recesses 1030 illustrated in FIG. 10A. For example, as illustrated, two juxtaposed spacers 1020 and two corresponding juxtaposed recesses 1030 may be provided in place of the single one of the spacers 1020 and 1030 of FIG. 10A. In some embodiments, the juxtaposed spacers and recesses may have different widths. In some embodiments, spacers may be provided on both the top and bottom major surfaces of the waveguide 1000. In such embodiments, the spacers and recesses may interlock when forming a stack, thereby advantageously increasing the stability and mechanical strength of a stack of waveguides formed using these waveguides. In some embodiments, each one of the spacers 1020 may include multiple tiers that decrease in width with distance from the major surface of the waveguide.

[0224] In some embodiments, the waveguide 1000 may be a hybrid waveguide formed by multiple layers of different materials. For example, the hybrid waveguide may include a core layer and at least one auxiliary layer. Preferably, the core layer is formed from a highly transparent material and the auxiliary layer is formed from a thinner layer of material in which a surface relief structure, such as a diffractive optical element, is provided. In some embodiments, the material forming the core layer is a highly transparent polymer, for example having a transparency relay transmission of greater than 85%, greater than 90%, or greater than 96% in the visible light spectrum across the thickness of the core layer. The material may be a flowable material (e.g., a flowable polymer) that can be flowed onto the surface and subsequently hardened, for example, by curing. The auxiliary layer may be thinner than the core layer and is preferably formed from a different material than the core layer. In some embodiments, the auxiliary layer is formed from a polymer (e.g., an organic polymer), an inorganic material, a hybrid organic / inorganic material, or a combination thereof. In some embodiments, for a given thickness, the auxiliary layer may have a lower transparency in the visible spectrum and / or a lower homogeneity (in optical properties such as composition and / or transparency) than the core layer, however, this lower transparency and / or lower homogeneity may be ameliorated by the relative thinness of the auxiliary layer compared to the core layer.

[0225] Preferably, the core layer is formed from a material with a high refractive index, which may advantageously provide a wide field of view for a display device utilizing the core layer in a waveguide. In some embodiments, the material forming the core layer may have a refractive index of about 1.65 or more, about 1.70 or more, or about 1.80 or more. In addition, the auxiliary layer may be formed from a material with a different refractive index than the core layer. It should be understood that the difference in refractive index at the interface with the nanophotonic structure can facilitate the ability of the diffractive optical elements in that layer to redirect light. In some embodiments, the material forming the auxiliary layer has a refractive index that differs from the refractive index of the material forming the core layer by about 0.05 or more, about 0.1 or more, or about 0.2 or more. In some embodiments, the waveguide may include an additional auxiliary layer in which recesses and / or additional surface relief features (e.g., diffractive optical elements) are formed. Additional details regarding hybrid waveguides are disclosed in U.S. Patent Application No. 62 / 651,507, filed April 2, 2018, and entitled "HYBRID POLYMER WAVEGUIDE AND METHODS FOR MAKING THE SAME," which is incorporated by reference in its entirety.

[0226] In some embodiments, the core and auxiliary layers may be formed using flowable materials without deposition. The core layer may be formed from a relatively high refractive index material as described above with respect to the waveguide 1000, and the auxiliary layers may be formed from a lower refractive index material. Examples of low refractive index materials (e.g., having a refractive index lower than 1.65) include organic polymer materials, low refractive index resins, sol-gel based hybrid polymers (e.g., TiO2, ZrO2, and ITO sol-gel materials), polymers doped with nanoparticles (TiO2, ZrO2, etc.), and active materials (e.g., polymers doped with quantum dots). Examples of low refractive index organic polymeric materials include those commercially available from Sigma-Aldrich (St. Louis, Missouri, USA), such as polymeric materials sold under the names CPS1040UV, CPS1040UV-A, CPS1030, CPS1020UV, CPS1040UV-VIS, CPS1030UV-VIS, and CPS1020UV-VIS. Examples of low refractive index resins include those commercially available from Miwon (Nagase Group, Osaka, Japan).

[0227] In some embodiments, the pattern (e.g., the pattern defining the diffractive optical element) may be formed during formation of the core and / or auxiliary layer without a separate patterning and etching process. For example, the pattern may be formed by imprinting followed by solidification or curing of the imprinted material.

[0228] 15A-15G illustrate a method of forming a hybrid waveguide with a core layer and upper and lower auxiliary layers. Referring to FIG. 15A, a pair of molds 1201, 1202 are provided, with the mold 1202 having a pattern of elevated features 1250 for forming surface relief features in the auxiliary layer to be formed. A mass of material 1300 for forming the auxiliary layer is then deposited on the mold 1202. Referring to FIG. 15B, the molds 1201, 1202 are moved closer together to compress the mass of material 1300 (FIG. 16A). The compressed material 1300 may undergo a curing process (e.g., by exposure to UV light), which solidifies the materials and forms a solid auxiliary layer 1031. Referring to FIG. 15C, the mold 1201 is separated from the auxiliary layer 1031, and a mass of core layer material 1310 is deposited on the auxiliary layer 1031. Referring to FIG. 15D, the molds 1201, 1202 are moved closer together to compress the mass of material 1310, thereby forming the core layer 1010. The compressed material may undergo a curing process (e.g., by exposure to UV light), which solidifies the material and forms the solid core layer 1010. Referring to FIG. 15E, the mold 1201 is separated from the core layer 1010 and replaced with the mold 1200. The mold 1200 includes a pattern of protrusions 1240 for defining surface relief features in the additional auxiliary layer. An additional mass of material 1320 for forming the additional auxiliary layer is deposited on the core layer 1010. Referring to FIG. 15F, the molds 1200, 1202 are moved closer together to compress the mass of material 1320 (FIG. 16E) and define the auxiliary layer 1021. It should be appreciated that the pattern of features 1240 imprints the desired surface relief features 1040 into the help layer 1021. The compressed material forming the help layer 1021 may undergo a curing process to solidify the material and form a solid help layer 1020. Referring to Figure 15G, the molds 1200, 1202 are moved apart and the hybrid waveguide, comprising the core layer 1010 and the help layers 1031, 1021, is released from the mold.

[0229] In some other embodiments, the core and auxiliary layers may be formed from different flowable materials that are immiscible. These materials may be deposited on top of one another and then subsequently compressed and solidified. Further details regarding such processes can be found in U.S. Patent Application No. 62 / 651,507, filed April 2, 2018, and entitled "HYBRID POLYMER WAVEGUIDE AND METHODS FOR MAKING THE SAME."

[0230] 12A-12C and 15A-15G, it should be understood that the molds 1200, 1201, 1202 may be patterned with a negative of the spacer and surface relief features to be formed. In addition, the molds preferably have sufficient rigidity to imprint features into the various flowable materials used to form the waveguides. Examples of materials for forming the molds include glass, fused silica, quartz, silicon, and metals.

[0231] The negative form of the spacers may be defined in these materials using various processes depending on whether the spacers have vertical or gradient sidewalls. For spacers with vertical sidewalls, the spacers as seen in the top and bottom diagrams may first be patterned using lithography, for example, by patterning a photoresist that is deposited on the material to be patterned, and then etched through the patterned photoresist using a directional etch. Examples of directional etches include dry etches such as RIE, ICP, sputter etches, etc. In some other embodiments, a wet etch (e.g., including HF) may be utilized.

[0232] For spacers with gradient sidewalls, the negative of the spacer may be formed by patterning a three-dimensional shape into a resist layer as a mask using grayscale lithography, and the geometry of the shape is transferred into the underlying substrate (mold material) by one or more dry etching techniques such as RIE, ICP, and sputter etching, or by wet etching. For silicon substrates, gradient sidewall surfaces may also be fabricated using wet chemical etching. In some embodiments, the top-bottom view shape / geometry may be patterned into a resist layer first using lithography, and then the substrate (mold) is etched first using dry etching and then wet etching. For silicon molds, the silicon wet etch may include KOH and TMAH. Exemplary Waveguide Structures for Reducing Propagation of Unused Light Out of the Waveguide

[0233] As discussed herein, not all of the light that propagates through a waveguide may be outcoupled as the light makes a single pass across the waveguide. Light that remains after propagating across the waveguide to the edge of the waveguide may be referred to as unused light. Also, as discussed herein, optical artifacts may occur if this unused light were to propagate out of the waveguide. Various embodiments disclosed herein provide edge treatments that reduce the recirculation of light within the waveguide after contacting the edge or an area near the edge, thereby reducing the likelihood that unused light will propagate out of the waveguide.

[0234] In some embodiments, the edge treatment may comprise a light absorbing material that coats one or more edges of the waveguide. Referring now to FIG. 16, an example of a waveguide 1602 having edges that are coated with a light absorbing material is illustrated. The waveguide 1602 has a top major surface 1601, a bottom major surface 1603, and an edge 1605. The edge 1605 is coated with a light absorbing material 1604. The light absorbing material 1604 may in some embodiments be a layer of light absorbing material applied onto the edge of the waveguide 1602 and may absorb the unused light beams, and thus the light beams 1606 and 1608 that travel toward the edge. The unused light beams may include light beams that are not coupled out of the waveguide 1602 to a viewer. The unused light beam may reflect off the edge 1605 of the waveguide 1602, propagate back through the waveguide 1602, and then be coupled out of the waveguide 1602 (e.g., via an external coupling element such as the external coupling optical elements 800, 810, 820 of FIG. 9B) as residual images and / or stray light, which reduces image quality.

[0235] 16, without the light absorbing material 1604, a light beam, such as light beam 1608, striking an edge of the waveguide 1602 with a relatively large angle of incidence may reflect back from the edge, reducing contrast (e.g., by impinging on the top major surface 1601 of the waveguide at an angle such that the light escapes total internal reflection and propagates out of the waveguide 1602). Similarly, a light beam with a relatively small angle of incidence, such as light beam 1606, exiting the waveguide 1602 will still reflect the refractive index (Δn=n waveguide -n ink ), may cause some of the light, such as reflection 1607, to be reflected back into the waveguide.

[0236] Without being limited by theory, it has been found that the refractive index (n) and extinction coefficient (k) of an absorbing material applied to an edge, such as material 1604 applied to waveguide 1602, affect the degree to which the absorbing material extracts and absorbs light from the waveguide. Simulations were performed for absorption versus reflection for a light beam striking an absorbing material applied to the edge as a function of the extinction coefficient (k) of the absorbing material and as a function of incidence angle (e.g., measured with respect to a vector normal to the plane of the waveguide edge shown as Θ in FIG. 16, light beam 1606 having a larger angle of incidence than light beam 1608). Simulations were performed for absorption of s-polarized light (e.g., transverse electric TE polarized light) and absorption of p-polarized light (e.g., transverse magnetic TM polarized light) and an average was taken to determine the absorption average for s-polarized light and p-polarized light. The simulations assumed a waveguide with an index of refraction of 1.73. Some of the simulations assumed an absorbing material with a refractive index of 1.55, while some of the simulations assumed an absorbing material with a refractive index of 1.65. The simulation results showed that light beams with higher incidence angles (e.g., light beams that strike the absorbing material 1604 relatively directly, instead of in an oblique manner) may not be fully absorbed and may be reflected. In particular, as the incidence angle increases beyond about 65 degrees, absorption drops and light begins to reflect off the edge 1605 (e.g., due to the difference in refractive index between the waveguide 1602 and the absorbing material 1604). The simulation results also show that increasing the extinction coefficient k of the absorbing material 1604 increases the absorption of higher incidence angle light beams, but the increase is relatively limited (e.g., the absorption at k=0.05 is only about 50% higher than the absorption at k=0.005, assuming all other factors are constant).

[0237] Again, without being limited by theory, the simulation results show that an absorbing material with a refractive index of 1.65 is significantly superior to an absorbing material with a refractive index of 1.55. This is believed to be due to the lower difference in refractive index between the waveguide and the absorbing material. Thus, the simulation results illustrate that in order to improve absorption by the absorbing material 1604, it is useful to reduce the difference in refractive index of the waveguide 1602 and the absorbing material 1604, and to a lesser extent, to utilize an absorbing material 1604 with a high extinction coefficient (k). In some embodiments, the difference in refractive index of the waveguide 1602 and the absorbing material 1604 is 0.2 or less. Additionally, in some embodiments, the absorbing material 1604 has an extinction coefficient (k) of at least 0.02.

[0238] It should be understood that the above discussion pertains to a single interaction of the light beam with edge 1605 and light absorbing material 1604. To further improve absorption of the light beam into the light absorbing material, the coverage area of ​​the light absorbing material may be increased as illustrated in Figures 17 and 18, where the light absorbing material extends over a larger portion of the waveguide.

[0239] 17-18 illustrate an example of a waveguide having light absorbing material extending over a portion of the top and bottom major surfaces 1801, 1803 of the waveguide 1802. As shown, the light absorbing material 1804 covers at least one edge 1805 of the waveguide 1802 and also extends over portions adjacent the edges of the top and bottom major surfaces 1801, 1803 of the waveguide. In particular, the light absorbing material 1804 may be formed on a portion of the waveguide 1802 that extends a particular distance, illustrated as a length of blackening 1806 away from the edge 1805 of the waveguide 1802.

[0240] As shown in Figure 18, extending the light absorbing material 1804 over a length 1806 can create multiple interactions between the propagating light beam and the light absorbing material 1804, thus increasing the absorption of the unused light beam. In particular, Figure 18 illustrates how a particular light beam 1808 propagating within the waveguide 1802 via total internal reflection (TIR) ​​can interact with the light absorbing material 1804 at point 1810a and also at point 1810b.

[0241] In general, the length 1806 required to ensure that the propagating light interacts with the light absorbing material 1804 multiple times may vary depending on the difference in refractive index between the waveguide 1802 and the adjacent material (which may be air), the thickness of the waveguide 1802, the wavelength of the light passing through the waveguide 1802, the grating design (e.g., the design of the outcoupling elements such as the outcoupling optical elements 800, 810, 820 of FIG. 9B), the field of view of the waveguide 1802, among other possible factors. FIG. 18 illustrates a specific example of blue light propagating via TIR inside glass having a refractive index of 1.8 with air as the adjacent material, where a length of blackening of at least about 1.87 mm of black ink (with n=1.73) is sufficient to ensure multiple interactions. In some embodiments, the length 1806 may extend from the waveguide edge about 2 mm, about 5 mm, or about 2-5 mm to effectively absorb most of the propagating light that reaches the edge of the waveguide.

[0242] It has been determined that the thickness of light absorbing material applied to the edges, such as material 1604 applied to waveguide 1602 and material 1804 applied to waveguide 1802, affects the degree to which the material extracts and absorbs light from the waveguide. A study of the absorption of light by a light absorbing material, such as black ink, was performed for materials with three different refractive indices (n=1.55, n=1.65, and n=1.73). Various simulations were performed as a function of the angle of incidence and for materials with an extinction coefficient of approximately 7×10 -3 ~About 10×10 -3The simulations also showed that a material thickness of about 20 μm advantageously provided a range of simulated angles of incidence (e.g., about 20 degrees from normal to about 70 degrees from normal) and simulated extinction coefficients (e.g., about 7×10) over a range of simulated angles of incidence (e.g., about 20 degrees from normal to about 70 degrees from normal) and simulated extinction coefficients (e.g., about 7×10). -3 ~About 10×10 -3 It has been shown that light absorbing materials can be utilized to achieve high levels of absorption for a desired range of wavelengths. In some embodiments, the light absorbing material has a thickness of 20 μm or greater.

[0243] Any suitable material may be used as the light absorbing or blackening material applied to the edges (e.g., material 1604 applied to waveguide 1602 and material 1804 applied to waveguide 1802). By way of example, light absorbing or blackening materials applied to the edges may include thin film materials such as fullerenes, graphene, amorphous silicon, germanium, etc., that may be deposited on the waveguide surface by physical or chemical vapor deposition or via other suitable process deposition processes; black inks, including low viscosity black inks such as inkjet black available from Nazdar (Shawnee, KS), that may be applied by inkjet printing or other suitable methods; and light absorbing additives dispersed or dissolved in a polymer (e.g., a UV curable polymer resin), such as carbon black, carbon nanopowder, carbon nanotubes, metal nanoparticles, color dyes, pigments, phosphors, etc.

[0244] Simulation results of the reflectance of various different light absorbing materials are shown in graph 2000 of Figure 19 and graph 2050 of Figure 20. The simulations of Figures 19 and 20 involve a single interaction of a light beam with a light absorbing material.

[0245] The different light absorbing materials simulated for FIG. 19 include plot 2002 for black ink and plots 2004, 2006, 2008, 2010, 2012, 2014 for varying concentrations of carbon nanopowder dispersed or dissolved in resin. As shown by plot 2002 in FIG. 19, black ink has low reflectivity (e.g., reflectivity below 10%, and therefore at least 90% absorptivity) for angles of incidence below about 55 degrees. However, the reflectivity of black ink increases substantially above 55 degrees. As shown by plots 2004, 2006, 2008, 2010, 2012, and 2014, increasing the concentration of carbon in the light absorbing material tends to decrease the reflectivity, and therefore increase the absorptivity of the light absorbing material. However, once a certain concentration of carbon is reached, the performance of the light absorbing material plateaus and further increases in carbon concentration do not further decrease the reflectivity. In particular, FIG. 19 illustrates that concentrations of approximately 1.56% carbon (plot 2010), 6.25% carbon (plot 2012), and 25% carbon (plot 2014) have relatively similar reflective and absorptive performance across the simulated angles of incidence.

[0246] The different light absorbing materials simulated for FIG. 20 include plot 2052 for Etercure 6948.8B.28 (e.g., blue dye), plot 2054 for orange LPB (e.g., orange dye), plot 2056 for red LPB (e.g., red dye), and plot 2058 for RS1813 Jet Black (e.g., black dye). As shown in FIG. 20, the orange and red dyes are able to maintain reflectance below 10% over the entire range of simulated angles of incidence, as seen in plots 2056 and 2058. In contrast, the blue dye has reflectance below 10% only for simulated angles of incidence below about 53 degrees, as seen in plot 2054, and the black dye has reflectance below 10% only for simulated angles of incidence below about 63 degrees, as seen in plot 2052.

[0247] Another technique for preventing absorptance and / or reflection of the light beam at the edges of the waveguide is roughening of the waveguide edges, as shown in FIG. 21. The waveguide 2100 may be roughened to provide a rough texture to the edges 2105. In some embodiments, the edges 2105 are coated with a light absorbing material 2104. The waveguide 2102 may be roughened along its edges and over the top and bottom major surfaces 2101, 2103 that extend away from the edges for a length of roughening 2110, which may be less than the length of the blackening treatment 2112 over which the light absorbing material 2104 is applied. In some embodiments, the length of the roughening 2110 may be 2mm to 5mm from the edge of the waveguide 2100, and the length of the blackening treatment 2112 may extend from the waveguide edge 2mm to 5mm beyond the roughened area. Roughening the waveguide 2100 in this manner may serve to diffuse the propagating light, as shown by the scattering of light beam 2106 when it strikes the roughened area of ​​the waveguide 2100 to which the light absorbing material 2104 is applied. Without being limited by theory, the diffusion of a light beam, such as light beam 2106, may increase the interaction between the light beam and the light absorbing material 2104, leading to an increase in the overall absorption rate.

[0248] The edges and adjacent surfaces of the waveguide 2100 (extending inward from the waveguide edge over the length of the roughening 2110) may be roughened by grinding the waveguide, by forming the waveguide with a mold having a rough texture, or by other methods. Different grit sizes may be used in grinding the waveguide to different roughnesses. As an example, a grit size having P150-100 μm grains or a grit size having P2500-8.4 μm grains may be used in grinding the waveguide to the desired roughness. The waveguide may be formed, ground, or otherwise treated to have a surface roughness (Sa) of at least 1 in some embodiments. In some embodiments, the surface roughness (Sa) is in the range of 1 to 100. In some embodiments, the waveguide may be radially roughened such that less light is backscattered toward the active eyepiece area (e.g., away from the edge).

[0249] Additional techniques for improving the absorption of the light beam at the edges of the waveguide include forming a diffraction grating, as shown in FIG. 22A, or a light trapping structure, as shown in FIGS. 22B and 22C, along the edges of the waveguide.

[0250] 22A illustrates a waveguide 2200a whose edges 2205 are coated with a light absorbing material 2204 that extends over the area of ​​the black oxide treatment 2212 on the top and bottom major surfaces 2201, 2203, and the waveguide 2202a includes an outcoupling optical element 2220 over the area of ​​the grating 2210a that extends over the top and bottom major surfaces 2201, 2203 of the waveguide 2202a. In some embodiments, the outcoupling optical element 2220 is a diffraction grating. In some embodiments, the waveguide 2202a may have such a grating on its edges in addition to or instead of having outcoupling optical elements on the top and bottom major surfaces 2201, 2203 adjacent the edges. In some embodiments, the light absorbing material 2204 may be omitted.

[0251] The outcoupling optical element 2220 may be, as an example, an outcoupling grating configured to outcouple light propagating in the waveguide 2202a, such as light beams 2206 and 2208, into the light absorbing material 2204, where the light is absorbed. As an example, the area of ​​the grating 2210a may extend 2-5 mm out from the edge of the waveguide 2202a (e.g., to ensure that any light beams propagating in the waveguide interact with the grating), and the area of ​​the black oxide treatment 2212 may also extend 2-5 mm out from the area of ​​the grating 2210a (e.g., to promote absorption by the light absorbing material 2204 of light scattered by the grating). The design of the grating 2220 may vary depending on the refractive indices of the waveguide 2202a and the light absorbing material 2204, the wavelength of the light propagating through the waveguide 2202a, among other possible factors. In some embodiments, the diffraction grating 2220 may be formed in the waveguide 2202a by patterning a mold in which the waveguide 2202a is formed. The diffraction grating 2200 may be formed in some embodiments as part of and / or using the same processing techniques used in forming the outcoupling optical elements 800, 810, and 820 of FIG. 9B and other diffractive elements disclosed herein, such as integral spacers as disclosed herein.

[0252] 22B illustrates a waveguide 2202a whose edge 2205 is similarly coated with a light absorbing material 2204 extending across the area of ​​the black oxide treatment 2212 on the top and bottom major surfaces 2201, 2203, and the top and bottom major surfaces 2201, 2203 of the waveguide 2202a include light capture structures 2230a and / or 2230b across the light capture area 2210b extending from the edge 2205. In some embodiments, the waveguide 2202b may have light capture structures on its edges in addition to or instead of having such structures on the top and bottom major surfaces 2201, 2203 adjacent the edges. In some embodiments, the light absorbing material 2204 may be omitted. The light capture structures 2230a and 2230b may be microstructures, by way of example. As shown in Figure 22C, a simulated light beam 2232 incident on the edge region of the waveguide 2202b does not escape the edge region without multiple interactions due to the shape and size of the light trapping structures 2230a and 2230b. As shown, during one of these interactions, the light may escape the waveguide and propagate into the light absorbing material 2204 (Figure 22B). Without being limited by theory, the light trapping structures 2230a and 2230b may advantageously increase the absorption of light.

[0253] In some embodiments, the area of ​​light trapping 2210b may be 2-5 mm from the edge of waveguide 2202b (e.g., may increase the likelihood that a light beam propagating in the waveguide will interact with the light trapping structure), and the area of ​​black oxide treatment 2212 may extend 2-5 mm from the area of ​​light trapping 2210b (e.g., may increase the likelihood that any light scattered by the light trapping structure will be absorbed by light absorbing material 2204). In some embodiments, light trapping structures such as structures 2230a and 2230b may be formed in waveguide 2202b by patterning a mold in which waveguide 2202b is formed. Light trapping structures 2230a and 2230b may be formed in some embodiments as part of and / or using the same fabrication techniques used in forming diffractive elements disclosed herein, such as outcoupling optical elements 800, 810, and 820 of FIG. 9B and integral spacers as disclosed herein.

[0254] The design of the light trapping structures 2230a and 2230b may vary depending on the refractive index of the waveguide 2202b and the light absorbing material 2204, the wavelength of light propagating through the waveguide 2202b, among other factors. In some embodiments, the width and height of the light trapping structures 2230a and 2230b range from 0.5 μm to 100 μm. By way of example, the width and height of the light trapping structures 2230a and 2230b may be about 0.5 μm, about 1.0 μm, about 2.0 μm, about 4.0 μm, about 10.0 μm, about 20.0 μm, about 50 μm, about 75 μm, or about 100 μm, where "about" is understood to be within 0.4 μm.

[0255] It should be understood that any of the strategies for improving light absorption at the edges of the waveguide may be combined together. As an example, the waveguide may include light absorbing material on the edges and extending inward from the waveguide edges (as disclosed in Figures 17 and 18), with either a roughening of the waveguide surface (as disclosed in Figure 21), a diffraction grating (as disclosed in Figure 22A), and / or light trapping structures (as disclosed in Figures 22B and 22C) made from materials at least as disclosed in Figures 19 and 20 having a sufficient thickness for the desired level of light absorption.

[0256] FIG. 23 illustrates edges 2404a, 2404b of a waveguide 2400 that have a higher level of unused light. The strategies disclosed herein for improving light absorption at the edges of a waveguide may be applied to all of the edges of the waveguide, or in some embodiments, only to areas of the waveguide that are expected to have a higher level of unused light relative to other areas of the waveguide. For example, edges 2404a, 2404b in FIG. 23 may be considered to have a high level of unused light. Areas with high levels of unused light may be areas of the waveguide in which a relatively large amount of light reaches the waveguide edges without being outcoupled. Such unused light, if not absorbed at the edges, may potentially reflect back into the active display area, creating undesirable residual images or stray light, thus reducing image quality. In some embodiments, areas of the waveguide 2400 with high levels of unused light include edges 2404a adjacent to the incoupling optical elements 700, 710, 720. The edge 2404a is on the side of the in-coupling optical element 700, 710, 720 that faces the direction in which the light is directed by the in-coupling optical element 700, 710, 720 for eventual outcoupling. Another area with a high level of unused light includes the edge 2404b adjacent to the outcoupling optical element 800, 810, 820. The light in this area includes light that propagated across the outcoupling optical element 800, 810, 820 without being outcoupled. It should be understood that the light incident on these edges is unused because the light was not outcoupled after passing through those optical elements that are intended for outcoupling. In contrast, the edges adjacent to the light dispersing elements 730, 740, 750 may have a relatively low level of unused light and therefore may not benefit much from the light absorption strategies described herein.

[0257] It should be understood that, as described herein, the various waveguides 1602, 1802, 2102, 2202a, and 2202b of Figures 16-18 and 21-23 may include one or more integral spacers and / or recesses for accommodating spacers. Additionally, in some embodiments, the waveguides 1602, 1802, 2102, 2202a, and 2202b may be part of a stack of waveguides, each of which may include an integral spacer and a recess for accommodating an underlying spacer from an underlying waveguide that also includes an integral spacer.

[0258] FIG. 24 illustrates a stack of waveguides with integral spacers. The individual waveguides shown may be any of the waveguides 1602, 1802, 2102, 2202a, 2202b, also shown in FIGS. 16-18 and 21-23. It should be understood that only the portions of the waveguides 1602, 1802, 2102, 2202a, 2202b that have integral spacers 1020 and / or recesses 1030 are shown in this figure for clarity. The remainder of the waveguides 1602, 1802, 2102, 2202a, and 2202b may include various edge treatments (e.g., light absorbing materials, roughened textures, outcoupling optical elements, light trapping microstructures) as shown in the corresponding ones of FIGS. 16-18 and 21-23 and disclosed herein. In some embodiments, each of the waveguides 1602, 1802, 2102, 2202a, 2202b has one or more integral spacers 1020 configured to provide isolation between the waveguide and an immediately adjacent overlying waveguide. Thus, as shown, the waveguides 1602, 1802, 2102, 2202a, 2202b with their integral spacers may form a waveguide stack (e.g., corresponding to the waveguide stack 660 of FIGS. 9A-9C). In some embodiments, each of the waveguides 1602, 1802, 2102, 2202a, 2202b of the waveguide stack may be similar (e.g., have similar edge treatments). In some other embodiments, the waveguides forming the waveguide stack may have different edge treatments (e.g., different ones of the waveguides 1602, 1802, 2102, 2202a, 2202b from Figures 16-18 and 21-23 may be utilized at different locations within the waveguide stack).

[0259] It should be understood that the integral spacers 1020 and / or recesses 1030 of the waveguides 1602, 1802, 2102, 2202a, and 2202b may be formed to have shapes and orientations as described above with respect to Figures 10A-15G. For example, in some embodiments, the waveguides 1602, 1802, 2102, 2202a, 2202b and the integral spacers 1020 may be formed from a polymeric material that may be molded (e.g., using an imprint mold) to define the integral spacers 1020. In addition, as discussed herein, the mold may include relief features to define one or more of the internal coupling optical element, the external coupling optical element, the roughened surface texture 2105 on and adjacent to the edge (Figure 21), the external coupling optical element 2220 (Figure 22A), and the light capture structures 2230a and / or 2230b (Figures 22B and 22C).

[0260] In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be apparent that various modifications and changes can be made therein without departing from the broader spirit and scope of the invention. The specification and drawings are, therefore, to be regarded in an illustrative rather than a restrictive sense.

[0261] Indeed, it should be understood that the systems and methods of the present disclosure each have several innovative aspects, none of which is solely responsible for or required for the desirable attributes disclosed herein. The various features and processes described above may be used independently of one another or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of the present disclosure.

[0262] Certain features described herein in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, although features may be described above as acting in a combination and may even be initially claimed as such, one or more features from the claimed combination may, in some cases, be deleted from the combination, and the claimed combination may be directed to a subcombination or variation of the subcombination. No single feature or group of features is necessary or essential to every embodiment.

[0263] In particular, conditional statements used herein, such as "can," "could," "might," "may," "eg," and the like, unless specifically stated otherwise or understood otherwise within the context as used, should be understood to be generally intended to convey that certain embodiments include certain features, elements, and / or steps, while other embodiments do not include them. Thus, such conditional statements are generally not intended to imply that features, elements, and / or steps are in any way required for one or more embodiments, or that one or more embodiments necessarily include logic for determining whether those features, elements, and / or steps should be included or performed in any particular embodiment, with or without authorial input or prompting. The terms "comprising," "including," "having," and the like, are synonymous and used inclusively in a non-limiting manner and do not exclude additional elements, features, acts, operations, etc. Also, the term "or," for example, when used to connect a list of elements, is used in its inclusive sense (and not its exclusive sense) so that the term "or" means one, some, or all of the elements in the list. In addition, the articles "a," "an," and "the," as used in this application and the appended claims, should be interpreted to mean "one or more" or "at least one," unless otherwise specified. Similarly, although operations may be depicted in the figures in a particular order, it should be recognized that such operations need not be performed in the particular order depicted, or in sequential order, or that all of the illustrated operations need not be performed to achieve desirable results. Additionally, the figures may diagrammatically depict one or more exemplary processes in the form of a flow chart. However, other operations not depicted may also be incorporated within the diagrammatically illustrated exemplary methods and processes. For example, one or more additional operations may be performed before, after, simultaneously with, or during any of the illustrated operations.In addition, operations may be rearranged or reordered in other embodiments. In some situations, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the program components and systems described may generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.

[0264] Thus, the claims are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the present disclosure, the principles and novel features disclosed herein.

Claims

[Claim 1] The invention described in this specification.

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