TW202344657A - Low stress loca additive and loca processing for bonding optical substrates - Google Patents

Abstract

A liquid optically clear adhesive (LOCA) for bonding optical substrates includes siloxane and epoxy-containing oligomers, a UV-activated photo-acid generator, a cross-linker additive, a solvent; and a reactive plasticizer, such as an additive of Structure 1. In one example, the additive of Structure 1 constitutes about 1-7% of a total mass of the LOCA excluding the solvent. R1, R2, and R3 of Structure 1 include methoxide, ethoxide, propoxide, or a combination thereof. R4 of Structure 1 includes an alkyl chain that is linear or branched and includes 2-8 carbons. The LOCA material is characterized by a refractive index equal to or greater than about 1.6 at 450 nm and an optical absorption below about 0.1% per micrometer of a thickness of the LOCA material.

Description

Low-stress LOCA additives and LOCA treatments for joining optical substrates

This invention relates to low stress LOCA additives and LOCA treatments for joining optical substrates. Related applications

This application refers to U.S. Provisional Application No. 63 titled "LOW LOCA ADDITIVE AND LOCA PROCESSING FOR BONDING OPTICAL SUBSTRATES" filed on April 21, 2022. /The interests and priorities of No. 333,243.

Artificial reality systems, such as head-mounted display (HMD) or heads-up display (HUD) systems, often include near-eye displays (e.g., in the form of a head-mounted device or a pair of glasses), It is configured to present content to a user via an electronic or optical display, for example within about 10 to 20 mm in front of the user's eyes. Near-eye displays can display virtual objects or images that combine real objects and virtual objects, such as in virtual reality (VR), augmented reality (AR) or mixed reality (MR) applications. . For example, in an AR system, users can view virtual objects (e.g., computer-generated images (CGI)) and their surroundings through, for example, see-through transparent display glass or lenses (commonly referred to as optical see-through). The image of both environment.

One example of an optical see-through AR system may use a waveguide-based optical display, where the light of the projected image may be coupled into the waveguide (eg, a transparent substrate), propagate within the waveguide, and couple out of the waveguide at various locations. In some embodiments, the light of the projected image may be coupled into or out of the waveguide using diffractive optical elements such as surface-relief gratings (SRG) or volume Bragg gratings (VBG). . Light from the surrounding environment can pass through the see-through area of the waveguide and also reach the user's eyes.

In a waveguide-based optical display system, several optical components (eg, a substrate on which optical elements such as light sources, gratings, microlenses, or liquid crystal structures are formed) can be linked together to form a waveguide display. To achieve the desired performance, the flatness of the tie layers and tie structures may need to be precisely controlled. For example, two opposing outer surfaces of a layer stack including two or more planar substrates joined together may need to maintain a high degree of parallelism, and the layer stack may need to have minimal total thickness variation. variation; TTV) and low curvature.

The present invention generally relates to techniques for joining optical components. More specifically, this article discloses techniques for using liquid optically clear adhesives (LOCA) to join optical substrates (with or without optical components formed thereon) to achieve controlled thickness and low bending of the joined devices. Various inventive embodiments are described herein, including devices, systems, methods, procedures, materials, mixtures, compositions, and the like.

The present invention relates to a liquid optically clear adhesive as in technical claim 1, a method as in technical claim 7, and a device as in technical claim 12. Advantageous embodiments may include features of the patent claims of the appended claims.

Therefore, according to a first aspect of the present invention, a liquid optically clear adhesive (LOCA) for connecting optical substrates is provided, wherein LOCA includes: oligomers containing siloxane and epoxy groups, UV-activated photoacid Generating agent, cross-linking agent additives, solvents and additives of structure 1: The additives of structure 1 constitute 1% to 7% of the total mass of LOCA excluding solvent.

In some specific examples, R ₁ , R ₂ and R ₃ may include methoxide, ethoxide, propoxide or combinations thereof.

In some specific examples, R ₄ may include an alkyl chain that is straight or branched and includes 2 to 8 carbons.

In some specific examples, R ₄ may include linear C ₆ H ₁₂ .

In some embodiments, when cured, the LOCA can have a refractive index equal to or greater than 1.6 at 450 nm and a light absorption of less than 0.1% per micron of thickness of the LOCA.

In some embodiments, LOCA can be cured by UV light, heat, or both.

In some embodiments, LOCA is applied to two 4- to 8-inch substrates and cured to produce a joined stack with a curvature of less than 20 microns.

In some embodiments, LOCA is applied to two glass substrates and when cured, can produce a stack of joined substrates with a lap shear strength greater than 1.5 MPa.

In addition, according to a second aspect of the present invention, a method is provided, wherein the method includes: coating a layer of liquid optically clear adhesive including a solvent and additives of the structure 1 as described above on the first transparent substrate. (LOCA) material; bonding a second transparent substrate to the LOCA material layer (e.g., preferably by compression) to form a substrate stack; curing the substrate stack using ultraviolet (UV) light to cross-link the LOCA material; and The substrate stack is thermally cured to convert the LOCA material into a thermoset state.

In some embodiments, the LOCA material may include a siloxane-containing epoxy adhesive.

In some specific examples, the additives of structure 1 may constitute 1% to 7% of the total mass of the LOCA material; and/or R ₁ , R ₂ and R ₃ may include methoxide, ethoxide, propoxide or combinations thereof ; and/or R ₄ may include an alkyl chain that is straight or branched and includes 2 to 8 carbons.

In some embodiments, the thickness of the LOCA material layer can be between 1 and 100 microns.

In some embodiments, after thermally curing the substrate stack, the LOCA material layer can be characterized by a refractive index equal to or greater than 1.6 at 450 nm and a light absorption of less than 0.1% per micron of thickness of the LOCA material layer, and /Or the substrate stack may be characterized by a lap shear strength greater than 1.5 MPa.

In some specific examples, the first transparent substrate and the second transparent substrate may be substrates with a diameter between 4 and 8 inches, and after the substrate stack is thermally cured, the curvature of the substrate stack may be less than 20 μm.

Furthermore, according to a third aspect of the present invention, there is provided a device, wherein the device includes: a layer stack including two transparent substrates joined together by a siloxane-containing epoxy adhesive layer, wherein the siloxane-containing epoxy adhesive layer contains siloxane. The alkane epoxy adhesive layer includes additives of structure 1 as described above, wherein the additives of structure 1 constitute 1% to 7% of the total mass of the siloxane-containing epoxy adhesive layer.

In some specific examples, R ₁ , R ₂ and R ₃ may include methoxide, ethoxide, propoxide or combinations thereof.

In some specific examples, R ₄ may include an alkyl chain that is straight or branched and includes 2 to 8 carbons.

In some embodiments, the siloxane-containing epoxy adhesive layer may be characterized by a refractive index at 450 nm equal to or greater than 1.6 and a thickness of less than 0.1% per micron of the siloxane-containing epoxy adhesive layer. of light absorption.

In some embodiments, the thickness of the silicone-containing epoxy adhesive layer can be between 1 and 100 microns, and/or the layer stack can be characterized by a lap shear strength greater than 1.5 MPa.

In some embodiments, the two transparent substrates can be substrates with a diameter between 4 and 8 inches; and the curvature of the layer stack is less than 20 μm.

In some embodiments, at least one of the two transparent substrates can be a lens of any shape with a length of 1 to 4 inches, and the curvature of the layer stack can be less than 10 μm.

It will be understood that any feature described herein as suitable for incorporation into one or more aspects or embodiments of the invention is intended to be generally applicable throughout any and all aspects and embodiments of the invention. Other aspects of the present invention can be understood by those with ordinary skill in the art based on the description, patent scope and drawings of the present invention. The foregoing general description and the following detailed description are only illustrative and explanatory, and do not limit the scope of the patent application.

This summary is neither intended to identify key or essential features of the claimed subject matter, nor is it intended to be used alone to determine the scope of the claimed subject matter. The subject matter should be understood by reference to the appropriate portions of the entire specification of the invention, any or all of the drawings, and the patent claims of each claim. The foregoing, along with other features and examples, are described in greater detail below in the following specification, claims, and accompanying drawings. In some embodiments, dimensions, sizes, configurations, parameters, shapes or other quantities or characteristics may be "about" or "approximately" whether or not so expressly stated.

The present invention generally relates to techniques for joining optical components. More specifically, this article discloses techniques for using liquid optically clear adhesives (LOCA) to join optical substrates (with or without optical components formed thereon) to achieve controlled thickness and low bending of the joined devices. Various inventive embodiments are described herein, including devices, systems, methods, procedures, materials, mixtures, compositions, and the like.

In a waveguide-based near-eye display system, the light of the projected image can be coupled into the waveguide (e.g., a substrate) using an input coupler (e.g., a grating coupler formed on the waveguide) via total internal reflection. Propagate within the waveguide and couple out of the waveguide at various locations using an output coupler (e.g., grating coupler) to replicate the exit pupil and expand the orbit. Two or more gratings can be used to expand the orbit in two dimensions. Light from the surrounding environment can pass through at least one see-through zone of the waveguide and reach the user's eyes. In some waveguide-based near-eye display systems, optical components (eg, substrates on which optical elements such as light sources, gratings, microlenses, or liquid crystal structures are formed) may be linked together to form a waveguide display. For example, some input/output couplers implemented using diffractive optical elements (e.g., volume Bragg gratings or polarized volume holograms) may operate only within a narrow range of wavelengths (e.g., light of a certain color) and/or Diffracted light within a small field of view (e.g., light within a certain range of incident angles) and may have limited coupling efficiency. Therefore, in some waveguide display systems, multiple grating couplers (eg, for diffracting light of different colors and from different fields of view) can be formed in multiple grating layers on multiple substrates, and then Multiple substrates including multiple grating couplers can be joined together to form a waveguide including multiple grating couplers.

In some near-eye display systems based on reflective/refractive/polarizing optical elements, such as some folded optics (e.g., pie lenses) or AR/VR systems based on free optics, multilayer waveguides, planar substrates, partially reflective mirrors, Free lenses, wave plates, liquid crystal devices, and/or other components may need to be connected or otherwise integrated to form a near-eye display system, where the thickness and curvature of the connected devices may need to be precisely controlled to achieve desired system performance.

In some display panels (for example, liquid crystal display (LCD), light emitting diode (LED) display, organic light emitting diode (OLED) display or flexible display) , with or without other structures formed thereon (e.g., backlight, touch panel with capacitive touch sensor, transparent conductive oxide layer, polarizer, diffuser, anti-reflective coating, for Optical substrates (microlenses for light collimation, and protective covers) may also need to be connected to form a display panel.

Joining two optical substrates (for example, including one or more optical waveguide layers or other substrates) can be accomplished by using a liquid optically clear adhesive (LOCA). Generally speaking, a LOCA coating can be applied to at least one first substrate, a second substrate can be placed over the LOCA coating, and the substrate stack can undergo thermal drying of the solvent, any partial curing, or catalyst activation (e.g., UV activation) and/or compression bonding, and the LOCA coating can then be cured via UV cure, thermal cure, or a combination. Any or all of the curing steps can be performed under compression. The curing process can transform LOCA from its initial liquid state to an intermediate thermoplastic state, and subsequently to a final thermoset state, where the adhesive strength of the joined stacks can be maximized and the LOCA mechanical properties can be stable against other heat treatments. At the molecular level, the curing process can lead to polymerization and cross-linking of LOCA. In order for LOCA to be compatible with optical substrates for waveguide display applications, LOCA needs to be transparent to visible light (e.g., have an absorption of less than about 0.1%/µm), have a high refractive index (e.g., at 450 nm greater than about 1.6) and can be fully cross-linked upon curing without inducing large internal stresses. High transparency and high refractive index can be achieved by using, for example, siloxane-containing epoxy LOCA. These materials may have a refractive index of about 1.6 or higher at 450 nm, their absorptivity may be less than about 0.1%/µm LOCA materials, and their adhesion strength to glass may typically be greater than 1.5 MPa. Therefore, these LOCA materials can be used to form a permanent connection between two optical substrates, and the connection can withstand device handling and reliability testing.

To achieve the desired performance, thickness variations and bending of the joined substrate stacks may need to be precisely controlled. For example, a substrate stack including two planar substrates joined together may need to maintain a high degree of parallelism between two opposing outer surfaces, and the substrate stack may need to have minimal total thickness variation (TTV) and low Curved (e.g., with minimal wedge angle). Existing joining processes and materials may not allow TTV and/or flex to be low enough for some applications, such as high-end AV/VR applications. For example, cross-linking methods for siloxane epoxy LOCA, which has high transparency and high refractive index, can often result in significant shrinkage that can build up internal stress within the LOCA layer. If the internal stress is too high, the accumulation of internal stress can lead to deformation (eg, bending) or even delamination of the joined substrate stack during normal handling and/or reliability testing. In situations where LOCA can be thermally cured and the two optical substrates can have different thermal expansion coefficients (CTE), the connected substrate stack can be mismatched and heated/cooled due to the CTE of the connected substrate stack. Upon further deformation, it can increase the bending of the connected substrate stack and even cause penetrating deformation of the connected substrate stack. When at least one of the joined optical substrates is used as an optical waveguide, deformation of the substrate stack due to internal stresses in LOCA can lead to distortion and other optical artifacts, such as chief ray angular shifts, modulation transfer function degradation, Lateral chromatic aberration, pupil swim, text breakage, and double images degrade the optical performance of waveguide displays. When a 6-inch wafer is used as the substrate and the curvature of the connected substrate stack is greater than about 20 µm, the optical performance of the waveguide display may be unacceptable. Therefore, it is expected that LOCA materials (e.g., siloxane epoxy LOCA with high refractive index and low light absorption) used in methods of joining two optical substrates for waveguide displays will react during curing and cross-linking and during After heat treatment, no large amount of internal stress is generated that can deform the connected substrate stack through bending.

According to certain embodiments, two optical substrates, at least one of which may serve as an optical waveguide layer, may use a siloxane epoxy that also includes a reactive plasticizer, such as the siloxane additive of Structure 1. Base LOCA link: wherein R ₁ , R ₂ and R ₃ may include methoxide, ethoxide, propoxide or a mixture of these materials, and R ₄ may be a straight or branched alkyl chain composed of 2 to 8 carbons, Such as linear C ₆ H ₁₂ . R ₁ , R ₂ and R ₃ can improve the adhesive strength of LOCA, while R ₄ can help reduce the stress of LOCA during curing and heat treatment. Therefore, the siloxane addition of Structure 1 may allow LOCA to reduce internal stresses so that bending of the connected substrate stack may be minimized and the optical performance of the waveguide display may not be compromised. For example, when the optical substrate includes a 6-inch wafer, the curvature of the joined substrate stack may be less than about 20 µm, and the performance of the waveguide display may not be degraded or may be only minimally degraded. After curing, mixtures of LOCA and the siloxane additive of Structure 1 can produce stable mechanical properties, a refractive index at 450 nm of about 1.6 or higher, an absorbance of less than about 0.1%/µm and greater than about 1.5 MPa permanent bonding layer with adhesive strength to glass.

According to certain embodiments, an optically clear siloxane-containing epoxy adhesive mixture used to join two optical substrates can be cured via UV, heat, or both UV and heat treatment to produce high refractive index, high transparency and low A curved tie layer that provides high adhesion to the stack of joined substrates. The adhesive mixture may include, for example, siloxane- and epoxy-containing oligomers, UV-activated photoacid generators, cross-linker additives, solvents, and additives of structure 1, wherein the additives of structure 1 may constitute the adhesive. Approximately 1% to 7% of the total mass of the mixture (excluding solvent). In the additives of structure 1, R ₁ , R ₂ and R ₃ may include methoxide, ethoxide, propoxide or mixtures of these materials, and R ₄ may be linear or branched and include 2 to 8 carbon alkyl chain. The adhesive mixture, when cured, may have a refractive index between about 1.6 and about 1.7 at 450 nm and a light absorbance of less than 0.1% per micron of the adhesive mixture. The adhesive mixture, when applied to a 4- to 8-inch wafer and cured, produces a stack of connected wafers with a curvature of less than about 20 microns.

According to some specific examples, the method of joining two optical substrates may include spin coating, spraying, inkjet printing, screen printing, dot drop coating or The adhesive layer is otherwise dispensed onto the first substrate, and the adhesive layer is bonded to the second substrate by curing the adhesive mixture through a combination of UV curing and thermal curing. The adhesive mixture may include additives of structure 1, wherein the additives of structure 1 may constitute about 1% to 7% of the total mass of the mixture (excluding solvent). The adhesive mixture can be applied to the first substrate to form an adhesive layer having a thickness of about 1 to 100 microns. The adhesive mixture can be cured to produce a mechanically stable adhesive layer having a refractive index between about 1.6 and about 1.7 at 450 nm and a light absorption of less than about 0.1% per micron of the adhesive mixture. The joined substrate stack may have a lap shear strength of at least 2.0 MPa and a relatively low degree of bending. In some embodiments, the first substrate and the second substrate can be transparent substrates having a diameter of about 4 to 8 inches, and the connected substrate stack can have a curvature of less than 20 microns. In some embodiments, at least one of the first substrate or the second substrate can be a lens of any shape and a length of about 1 to 4 inches, and the joined substrate stack can have a curvature of less than about 10 microns. .

According to some embodiments, two transparent substrates may be joined together by a siloxane-containing epoxy adhesive layer formed from a mixture of additives of Structure 1, wherein the additives of Structure 1 may constitute a solvent-free About 1% to 7% of the total mass of the mixture. The adhesive layer can be mechanically stable and can have a refractive index between about 1.6 and about 1.7 at 450 nm and a light absorption of less than about 0.1% per micron of the adhesive layer. The stack of substrates connected by the adhesive layer can have a lap shear strength of at least 2.0 MPa and can have a low degree of bending. In one example, the two transparent substrates can be wafers approximately 4 to 8 inches in diameter, and the connected substrate stack can have a curvature of less than 20 microns. In some embodiments, at least one of the two transparent substrates is a lens having a random shape and a length of about 1 to 4 inches, and the joined substrate stack has a curvature of less than 10 microns.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

As used herein, the term "about" means that dimensions, sizes, configurations, parameters, shapes and other quantities and characteristics are not precise and need not be precise, but may be approximate and/or greater or smaller as appropriate, This reflects tolerances, conversion factors, rounding, measurement errors and the like, as well as other factors known to those of ordinary skill in the art. Generally speaking, dimensions, sizes, configurations, parameters, shapes or other quantities or characteristics are "about" or "approximately" whether or not so expressly stated. It should be noted that embodiments of widely varying sizes, shapes, and dimensions may employ the described arrangements.

In the following description, for purposes of explanation, specific details are set forth in order to provide a thorough understanding of examples of the invention. However, it is understood that various examples may be practiced without such specific details. For example, devices, systems, structures, assemblies, methods, and other components may be shown as components in block diagram form so as not to obscure the examples with unnecessary detail. In other cases, well-known devices, processes, systems, structures, and techniques may be shown without necessary detail to avoid obscuring the examples. The drawings and descriptions are not intended to be limiting. The terms and expressions which have been used in this invention are terms of description and not of limitation, and in the use of such terms and expressions there is no intention to exclude any equivalents of the features shown and described, or parts thereof. The word "example" is used in this article to mean "to serve as an example, instance, or illustration." Any specific example or design described herein as an "example" is not necessarily to be construed as better or advantageous over other specific examples or designs.

1 is a simplified block diagram of an example of an artificial reality system environment 100 including a near-eye display 120 , according to certain embodiments. The artificial reality system environment 100 shown in Figure 1 may include a near-eye display 120, an optional external imaging device 150, and an optional input/output interface 140, each of which may be coupled to an optional console. 110. Although FIG. 1 shows an example of an artificial reality system environment 100 that includes a near-eye display 120, an external imaging device 150, and an input/output interface 140, any number of these components may be included in the artificial reality system environment 100. Either of these components may be omitted. For example, there may be multiple near-eye displays 120 monitored by one or more external imaging devices 150 in communication with console 110 . In some configurations, the artificial reality system environment 100 may not include the external imaging device 150, the optional input/output interface 140, and the optional console 110. In alternative configurations, different components or additional components may be included in artificial reality system environment 100 .

The near-eye display 120 may be a head-mounted display that presents content to the user. Examples of content presented by the near-eye display 120 include one or more of images, video, audio, or any combination thereof. In some embodiments, audio may be presented via an external device (eg, speakers and/or headphones) that receives audio information from near-eye display 120 , console 110 , or both, and is presented based on the audio information. Audio data. Near-eye display 120 may include one or more rigid bodies, which may be rigidly or non-rigidly coupled to each other. Rigid couplings between rigid bodies cause the coupled rigid bodies to act as a single rigid entity. Non-rigid couplings between rigid bodies may allow the rigid bodies to move relative to each other. In various embodiments, the near-eye display 120 may be implemented in any suitable appearance size including a pair of glasses. Some specific examples of near-eye display 120 are further described below with respect to FIGS. 2 and 3 . Additionally, in various embodiments, the functionality described herein may be used in head-mounted devices that combine images of the environment external to near-eye display 120 with artificial reality content (eg, computer-generated images). Therefore, the near-eye display 120 can amplify the image of the physical real-world environment outside the near-eye display 120 by generating content (eg, images, videos, sounds, etc.) to present an augmented reality to the user.

In various embodiments, near-eye display 120 may include one or more of display electronics 122 , display optics 124 , and eye tracking unit 130 . In some specific examples, the near-eye display 120 may also include one or more locators 126 , one or more position sensors 128 and an inertial measurement unit (IMU) 132 . Near-eye display 120 may omit any of eye tracking unit 130, locator 126, position sensor 128, and IMU 132, or include additional components in various embodiments. Additionally, in some embodiments, near-eye display 120 may include elements that combine the functionality of the various elements described in conjunction with FIG. 1 .

Display electronics 122 may display or facilitate the display of images to the user based on data received from, for example, console 110 . In various embodiments, display electronics 122 may include one or more display panels, such as a liquid crystal display (LCD), an organic light emitting diode (OLED) display, an inorganic light emitting diode (ILED) display, a micro light emitting diode volume (μLED) display, active matrix OLED display (AMOLED), transparent OLED display (TOLED) or some other display. For example, in one implementation of near-eye display 120 , display electronics 122 may include a front TOLED panel, a rear display panel, and optical components (e.g., attenuators, polarizers, or diffractive or spectral films). Display electronics 122 may include pixels to emit light in a primary color such as red, green, blue, white, or yellow. In some embodiments, the display electronics 122 can display a three-dimensional (3D) image through a stereoscopic effect produced by a two-dimensional panel to create a subjective perception of image depth. For example, display electronics 122 may include left and right displays positioned in front of the user's left and right eyes, respectively. The left and right monitors may present copies of the image that are displaced horizontally relative to each other to create a stereoscopic effect (ie, the perception of depth of the image by the user viewing the image).

In some embodiments, display optics 124 can optically display image content (for example, using optical waveguides and couplers), or amplify image light received from display electronics 122 to correct optical errors associated with the image light. , and present the corrected image light to the user of the near-eye display 120 . In various embodiments, display optics 124 may include one or more optical elements, such as a substrate, an optical waveguide, an aperture, a Fresnel lens, a convex lens, a concave lens, a filter, an input/output coupler , or any other suitable optical element that may affect the image light emitted from the display electronics 122 . Display optics 124 may include a combination of different optical elements and mechanical couplers to maintain the relative spacing and orientation of the optical elements in the combination. One or more optical elements in display optics 124 may have an optical coating such as an anti-reflective coating, a reflective coating, a filter coating, or a combination of different optical coatings.

Amplification of image light by display optics 124 may allow display electronics 122 to be physically smaller, lighter weight, and consume less power than larger displays. Additionally, zooming in increases the field of view of the displayed content. The amount that display optics 124 amplifies image light can be changed by adjusting, adding optical elements, or removing optical elements from display optics 124 . In some embodiments, display optics 124 may project the displayed image to one or more image planes that may be farther from the user's eyes than near-eye display 120 .

Display optics 124 may also be designed to correct for one or more types of optical errors, such as two-dimensional optical errors, three-dimensional optical errors, or any combination thereof. Two-dimensional errors may include optical aberrations occurring in two dimensions. Example types of two-dimensional errors may include barrel distortion, pincushion distortion, longitudinal chromatic aberration, and lateral chromatic aberration. Three-dimensional errors may include optical errors that appear in three dimensions. Example types of three-dimensional errors may include spherical aberration, coma aberration, field curvature, and astigmatism.

Locator 126 may be an object located in a specific location on near-eye display 120 relative to each other and relative to a reference point on near-eye display 120 . In some implementations, console 110 may identify locator 126 in images captured by external imaging device 150 to determine the location, orientation, or both of the artificial reality headset. The locator 126 may be a light-emitting diode (LED), a corner cube reflector, a reflective sign, a type of light source that contrasts with the environment in which the near-eye display 120 operates, or any of them. combination. In specific examples where the locator 126 is an active component (eg, an LED or other type of light-emitting device), the locator 126 may emit in a visible light band (eg, approximately 380 nm to 750 nm), an infrared (IR) band ( For example, light in the ultraviolet band (eg, from about 750 nm to about 1 mm), in the ultraviolet band (eg, from about 10 nm to about 380 nm), another portion of the electromagnetic spectrum, or any combination of portions of the electromagnetic spectrum.

External imaging device 150 may include one or more cameras, one or more video cameras, any other device capable of capturing images including one or more of locators 126 , or any combination thereof. Additionally, external imaging device 150 may include one or more optical filters (eg, to increase signal-to-noise ratio). External imaging device 150 may be configured to detect light emitted or reflected from locator 126 in the field of view of external imaging device 150 . In embodiments in which positioners 126 include passive elements (eg, retroreflectors), external imaging device 150 may include light sources illuminating some or all of positioners 126 that may retroreflect light to the external imaging device 150 light sources. Slow calibration data may be communicated from the external imaging device 150 to the console 110, and the external imaging device 150 may receive one or more calibration parameters from the console 110 to adjust one or more imaging parameters (eg, focal length, focal point, frame rate , sensor temperature, shutter speed, aperture, etc.).

Position sensor 128 may generate one or more measurement signals in response to movement of near-eye display 120 . Examples of position sensors 128 may include accelerometers, gyroscopes, magnetometers, other motion detection or error correction sensors, or any combination thereof. For example, in some embodiments, position sensor 128 may include a plurality of accelerometers to measure translational motion (eg, forward/backward, up/down, or left/right) and to Multiple gyroscopes that measure rotational motion (such as pitch, yaw, or roll). In some embodiments, individual position sensors may be oriented orthogonally to each other.

IMU 132 may be an electronic device that generates fast calibration data based on measurement signals received from one or more of position sensors 128 . Position sensor 128 may be located external to IMU 132, internal to IMU 132, or any combination thereof. Based on one or more measurement signals from one or more position sensors 128 , the IMU 132 may generate fast calibration data indicating an estimated position of the near-eye display 120 relative to an initial position of the near-eye display 120 . For example, IMU 132 may integrate measurement signals received from accelerometers over time to estimate a velocity vector, and integrate the velocity vector over time to determine an estimated position of a reference point on near-eye display 120 . Alternatively, IMU 132 can provide sampled measurement signals to console 110, which can determine fast calibration data. Although the reference point may generally be defined as a point in space, in various embodiments, the reference point may also be defined as a point within the near-eye display 120 (eg, the center of the IMU 132).

Eye tracking unit 130 may include one or more eye tracking systems. Eye tracking may refer to determining the position of the eyes relative to the near-eye display 120, including the orientation and position of the eyes. An eye tracking system may include an imaging system to image one or more eyes, and optionally include a light emitter that may generate light directed to the eye such that light reflected by the eye may be captured by the imaging system. For example, the eye tracking unit 130 may include a non-coherent or coherent light source (eg, a laser diode) that emits light in the visible or infrared spectrum, and a camera that captures the light reflected by the user's eyes. As another example, eye tracking unit 130 may capture reflected radio waves emitted by a small radar unit. Eye tracking unit 130 may use low-power light emitters that emit light at frequencies and intensities that will not damage the eyes or cause physical discomfort. Eye tracking unit 130 may be configured to increase the contrast of eye images captured by eye tracking unit 130 while reducing the total power consumed by eye tracking unit 130 (e.g., by reducing the amount of power consumed by the light emitters included in eye tracking unit 130 and power consumed by the imaging system). For example, in some implementations, eye tracking unit 130 may consume less than 100 milliwatts of power.

Near-eye display 120 may use eye orientation to, for example, determine the user's inter-pupillary distance (IPD), determine gaze direction, introduce depth cues (e.g., blurred images outside the user's primary line of sight), collect information about Heuristic information about user interaction in VR media (e.g., time spent with any particular individual, object, or frame, which varies depending on the stimulus to which it is exposed), based in part on the orientation of at least one of the user's eyes some other functionality, or any combination thereof. Because the position of the user's two eyes can be determined, the eye tracking unit 130 may be able to determine where the user is looking. For example, determining the user's gaze direction may include determining the convergence point based on the determined orientations of the user's left and right eyes. The convergence point may be the point where the two foveal axes of the user's eyes intersect. The user's gaze direction may be the direction of a line passing through the midpoint between the convergence point and the pupil of the user's eye.

The input/output interface 140 may be a device that allows the user to send action requests to the console 110 . An action request may be a request to perform a specific action. For example, an action request may be to start or end an application or to perform a specific action within the application. Input/output interface 140 may include one or more input devices. Example input devices may include keyboards, mice, game controllers, gloves, buttons, touch screens, or any other suitable device for receiving action requests and communicating the received action requests to console 110 . Action requests received by input/output interface 140 may be communicated to console 110 which may perform an action corresponding to the requested action. In some examples, the input/output interface 140 may provide tactile feedback to the user according to instructions received from the console 110 . For example, the input/output interface 140 may provide tactile feedback when an action request is received or when the console 110 has performed the requested action and communicated instructions to the input/output interface 140 . In some embodiments, the external imaging device 150 may be used to track the input/output interface 140, such as a tracking controller (which may include, for example, an IR light source) or the location or position of the user's hand to determine the user's movement. In some embodiments, the near-eye display 120 may include one or more imaging devices to track the input/output interface 140, such as tracking the location or position of a controller or a user's hand to determine the user's movements.

The console 110 may provide content to the near-eye display 120 for presentation to the user based on information received from one or more of the external imaging device 150 , the near-eye display 120 , and the input/output interface 140 . In the example shown in FIG. 1 , console 110 may include an app store 112 , a headset tracking module 114 , an artificial reality engine 116 , and an eye tracking module 118 . Some embodiments of console 110 may include different modules or additional modules than those described in conjunction with FIG. 1 . Functionality, described further below, may be distributed among the components of console 110 in different ways than described herein.

In some embodiments, console 110 may include a processor and a non-transitory computer-readable storage medium that stores instructions executable by the processor. A processor may include multiple processing units that execute instructions simultaneously. The non-transitory computer-readable storage medium can be any memory, such as a hard drive, removable memory, or a solid-state drive (eg, flash memory or dynamic random access memory (DRAM)). In various embodiments, the modules of the console 110 described in conjunction with FIG. 1 may be encoded as instructions in a non-transitory computer-readable storage medium that, when executed by a processor, cause the processor to perform the functions described further below. .

Application store 112 may store one or more applications for execution by console 110 . An application may include a set of instructions that, when executed by a processor, generate content for presentation to a user. Content generated by the application may respond to input received from the user through movement of the user's eyes, or input received from the input/output interface 140 . Examples of applications include: gaming applications, conferencing applications, video playback applications, or other suitable applications.

The headset tracking module 114 may use slow calibration information from the external imaging device 150 to track the movement of the near-eye display 120 . For example, the headset tracking module 114 may use the localizer and the model of the near-eye display 120 observed from the slow calibration information to determine the location of the reference point of the near-eye display 120 . The head mounted device tracking module 114 may also use position information from the fast calibration information to determine the position of the reference point of the near-eye display 120 . Additionally, in some embodiments, headset tracking module 114 may use portions of fast calibration information, slow calibration information, or any combination thereof to predict future locations of near-eye display 120 . The head mounted device tracking module 114 may provide the estimated or predicted future position of the near-eye display 120 to the artificial reality engine 116 .

The artificial reality engine 116 can execute applications in the artificial reality system environment 100 and receive the position information of the near-eye display 120, the acceleration information of the near-eye display 120, and the speed information of the near-eye display 120 from the head-mounted device tracking module 114. Predicted future position of near-eye display 120 or any combination thereof. Artificial reality engine 116 may also receive estimated eye position and orientation information from eye tracking module 118 . Based on the received information, the artificial reality engine 116 may determine content to provide to the near-eye display 120 for presentation to the user. For example, if the received information indicates that the user has looked to the left, the artificial reality engine 116 may generate content for the near-eye display 120 that reflects the user's eye movements in the virtual environment. Additionally, the artificial reality engine 116 may perform actions within the application executing on the console 110 in response to action requests received from the input/output interface 140 and provide feedback to the user indicating that the action has been performed. The feedback may be visual or auditory feedback via the near-eye display 120 , or tactile feedback via the input/output interface 140 .

The eye tracking module 118 may receive eye tracking data from the eye tracking unit 130 and determine the position of the user's eyes based on the eye tracking data. The position of the eye may include the orientation, orientation, or both of the eye relative to the near-eye display 120 or any element thereof. Because the eye's axis of rotation changes depending on the eye's orientation in its eye socket, determining the eye's orientation in its eye socket may allow the eye tracking module 118 to more accurately determine the eye's orientation.

2 is a perspective view of an example of a near - eye display in the form of an HMD device 200 for implementing some of the examples disclosed herein. HMD device 200 may be, for example, part of a VR system, AR system, MR system, or any combination thereof. The HMD device 200 may include a body 220 and a head strap 230. Figure 2 shows the bottom side 223, the front side 225 and the left side 227 of the body 220 in a perspective view. The head strap 230 may have an adjustable or extendable length. There may be enough space between the body 220 of the HMD device 200 and the head strap 230 to allow the user to install the HMD device 200 on the user's head. In various embodiments, HMD device 200 may include additional components, fewer components, or different components. For example, in some embodiments, the HMD device 200 may include eyeglass temples and temple tips, as shown, for example, in FIG. 3 below, instead of the headband 230 .

HMD device 200 may present media to a user that includes virtual and/or augmented views of a physical real-world environment with computer-generated elements. Examples of media presented by HMD device 200 may include images (eg, two-dimensional (2D) or three-dimensional (3D) images), video (eg, 2D or 3D video), audio, or any combination thereof. Images and videos may be presented to each eye of the user by one or more display assemblies (not shown in FIG. 2 ) enclosed in the main body 220 of the HMD device 200 . In various embodiments, the one or more display assemblies may include a single electronic display panel or multiple electronic display panels (eg, one display panel for each eye of the user). Examples of electronic display panels may include, for example, LCDs, OLED displays, ILED displays, μLED displays, AMOLEDs, TOLEDs, some other displays, or any combination thereof. The HMD device 200 may include two eye frame areas.

In some implementations, the HMD device 200 may include various sensors (not shown), such as depth sensors, motion sensors, position sensors, and eye tracking sensors. Some of these sensors may use structured light patterns for sensing. In some implementations, HMD device 200 may include an input/output interface for communicating with a console. In some embodiments, the HMD device 200 may include a virtual reality engine (not shown in the figure). The virtual reality engine may execute applications in the HMD device 200 and receive depth information of the HMD device 200 from various sensors. , position information, acceleration information, velocity information, predicted future position, or any combination thereof. In some implementations, information received by the virtual reality engine may be used to generate signals (eg, display commands) for one or more display assemblies. In some embodiments, HMD device 200 may include positioners (not shown, such as positioner 126 ) in fixed positions on body 220 relative to each other and relative to a reference point. Each of the locators can emit light that can be detected by an external imaging device.

3 is a perspective view of an example of a near-eye display 300 in the form of a pair of glasses for implementing some of the examples disclosed herein. Near-eye display 300 may be a particular implementation of near-eye display 120 of FIG. 1 and may be configured to operate as a virtual reality display, an augmented reality display, and/or a mixed reality display. The near-eye display 300 includes a frame 305 and a display 310. Display 310 may be configured to present content to a user. In some examples, display 310 may include display electronics and/or display optics. For example, as described above with respect to near-eye display 120 of FIG. 1 , display 310 may include an LCD display panel, an LED display panel, or an optical display panel (eg, a waveguide display assembly).

Near-eye display 300 may further include various sensors 350a, 350b, 350c, 350d, and 350e on or within frame 305. In some embodiments, sensors 350a to 350e may include one or more depth sensors, motion sensors, position sensors, inertial sensors, or ambient light sensors. In some embodiments, sensors 350a-350e may include one or more image sensors configured to generate image data representing different fields of view in different directions. In some embodiments, the sensors 350a to 350e may be used as input devices to control or influence the displayed content of the near-eye display 300 and/or provide an interactive VR/AR/MR experience to the user of the near-eye display 300. In some specific examples, sensors 350a to 350e may also be used for stereoscopic imaging.

In some embodiments, the near-eye display 300 may further include one or more illuminators 330 to project light into the physical environment. The projected light can be associated with different frequency bands (eg, visible light, infrared light, ultraviolet light, etc.) and can be used for various purposes. For example, one or more illuminators 330 can project light into a dark environment (or an environment with low intensity infrared light, ultraviolet light, etc.) to assist the sensors 350a to 350e in capturing the differences in the dark environment. Image of the object. In some embodiments, one or more illuminators 330 may be used to project certain light patterns onto objects within the environment. In some embodiments, one or more illuminators 330 may serve as locators, such as locator 126 described above with respect to FIG. 1 .

In some specific examples, the near-eye display 300 may also include a high-resolution camera 340. The high-resolution camera 340 can capture images of the physical environment in the field of view. The captured image may be processed, for example, by a virtual reality engine (eg, artificial reality engine 116 of FIG. 1 ) to add virtual objects to the captured image or modify physical objects in the captured image, and the processed image may be displayed by display 310 Displayed to the user for use in AR or MR applications.

4 illustrates an example of an optical see-through augmented reality system 400 including a waveguide display , according to certain embodiments. Augmented reality system 400 may include projector 410 and combiner 415 . Projector 410 may include a light or image source 412 and projector optics 414. In some embodiments, light or image source 412 may include one or more micro-LED devices as described above. In some specific examples, the image source 412 may include a plurality of pixels that display virtual objects, such as an LCD display panel or an LED display panel. In some embodiments, image source 412 may include a light source that generates coherent or partially coherent light. For example, the image source 412 may include a laser diode, a vertical cavity surface emitting laser, an LED, and/or a micro-LED as described above. In some embodiments, image source 412 may include a plurality of light sources (eg, the micro-LED arrays described above) that each emit monochromatic image light corresponding to a primary color (eg, red, green, or blue). In some embodiments, image source 412 may include three two-dimensional arrays of micro-LEDs, where each two-dimensional array of micro-LEDs may include an array of micro-LEDs configured to emit light having a primary color (eg, red, green, or blue). Micro LED. In some embodiments, image source 412 may include an optical pattern generator, such as a spatial light modulator. Projector optics 414 may include one or more optical components that can modulate light from image source 412 , such as expanding, collimating, scanning, or projecting light from image source 412 to combiner 415 . The one or more optical components may include, for example, one or more lenses, liquid lenses, mirrors, apertures, and/or gratings. For example, in some embodiments, image source 412 may include one or more one-dimensional arrays or elongated two-dimensional arrays of micro-LEDs, and projector optics 414 may include a one-dimensional array configured to scan the micro-LEDs. or an elongated two-dimensional array of one or more one-dimensional scanners (e.g., micromirrors or scanners) that produce image frames. In some examples, projector optics 414 may include a liquid lens (eg, a liquid crystal lens) with a plurality of electrodes that allows scanning of light from image source 412 .

The combiner 415 may include an input coupler 430 for coupling light from the projector 410 into the substrate 420 of the combiner 415 . The input coupler 430 may include a volume Bragg grating (VBG), a diffractive optical element (DOE) (eg, a surface relief grating (SRG)), a sloped surface of the substrate 420, or a refractive coupler (eg, a wedge or beam). . For example, input coupler 430 may include a reflective volume Bragg grating or a transmissive volume Bragg grating. For visible light, the input coupler 430 may have a coupling efficiency greater than 30%, 50%, 75%, 90%, or higher. Light coupled into substrate 420 may propagate within substrate 420 via, for example, total internal reflection (TIR). Substrate 420 may be in the form of a lens of a pair of glasses. Substrate 420 may have a flat or curved surface, and may include one or more types of dielectric materials, such as glass, quartz, plastic, polymer, poly(methyl methacrylate) (PMMA), crystal, or ceramic. The thickness of the substrate may range, for example, from less than about 1 mm to about 10 mm or more. Substrate 420 may be transparent to visible light.

Substrate 420 may include or may be coupled to a plurality of output couplers 440 each configured to extract from substrate 420 at least a portion of the light directed by and propagating within substrate 420 , and The extracted light 460 is directed to the orbit 495 where the user's eyes 490 of the augmented reality system 400 may be located when the augmented reality system 400 is in use. Multiple output couplers 440 can replicate the exit pupil to increase the size of the orbit 495 so that the displayed image is visible over a larger area. Like input coupler 430, output coupler 440 may include a grating coupler (eg, a volume holographic grating or a surface relief grating), other diffractive optical elements, mirrors, and the like. For example, output coupler 440 may include a reflective volume Bragg grating or a transmissive volume Bragg grating. Output coupler 440 may have different coupling (eg, diffraction) efficiencies at different locations. The substrate 420 may also allow light 450 from the environment in front of the combiner 415 to pass through with little or no loss. Output coupler 440 may also allow light 450 to pass through with minimal loss. For example, in some implementations, output coupler 440 may have extremely low diffraction efficiency for light 450 such that light 450 may refract or otherwise pass through output coupler 440 with minimal loss, and thus may Has an intensity higher than the extracted light 460. In some implementations, output coupler 440 can have high diffraction efficiency for light 450 and can diffract light 450 in certain desired directions (ie, diffraction angles) with minimal losses. Thus, the user may be able to view a combined image of the environment in front of the combiner 415 and the image of the virtual object projected by the projector 410 .

In some embodiments, projector 410, input coupler 430, and output coupler 440 may be on either side of substrate 420. The input coupler 430 and the output coupler 440 may be a reflective grating (also known as a reflection grating) or a transmission grating (also known as a transmission grating) to couple the display light into or out of the substrate 420 .

Figure 5 illustrates an example of an optical see-through augmented reality system 500 including a waveguide display for exit pupil expansion, according to certain embodiments. Augmented reality system 500 may be similar to augmented reality system 500 and may include a waveguide display and a projector, which may include a light or image source 510 and projector optics 520 . The waveguide display may include a substrate 530, an input coupler 540, and a plurality of output couplers 550 as described above with respect to the augmented reality system 500. Although Figure 5 only shows the propagation of light from a single field of view, Figure 5 shows the propagation of light from multiple fields of view.

Figure 5 shows that the exit pupil is replicated by output coupler 550 to form a focused exit pupil or orbit, where different regions in the field of view (e.g., different pixels on image source 510) can be associated with different individual propagation directions toward the orbit. are coupled, and light from the same field of view (eg, the same pixel on image source 510) can have the same propagation direction for different respective exit pupils. Thus, a single image of image source 510 can be formed by the user's eye positioned anywhere in the orbit, where light from different individual exit pupils traveling in the same direction can come from the same pixel on image source 510 and can be focused to at the same location on the retina of the user's eye. Figure 5 shows that even if the user's eyes move to different parts of the eye socket, the image of the image source is still visible to the user's eyes.

Figure 6A illustrates an example of a waveguide display 600 including a volume Bragg grating coupler. Waveguide display 600 may include a VBG layer 620 within substrate 610 or between two substrates joined together. For example, VBG layer 620 can be formed on one substrate and the substrate with VBG layer 620 can be bonded to another substrate such that VBG layer 620 can be sandwiched by the two substrates to form a waveguide display in which light is displayed. Can be reflected from top surface 612 and bottom surface 614. VBG layer 620 may include input VBG 622 and output VBG 624. In the illustrated example, input VBG 622 can reflectively diffract incident light, and thus can function as a reflective VBG. Output VBG 624 may partially reflectively diffract light from input VBG 622 out of substrate 610 toward the orbit of waveguide display 600 . Input VBG 622 and output VBG 624 may act as multiple reflectors that strongly reflect light with specific wavelengths and/or from specific angles that satisfy the Bragg condition. In various embodiments, depending on the tilt angle of the plurality of reflectors in the VBG, the input VBG 622 and the output VBG 624 may be a transmissive VBG or a reflective VBG, where the reflected light may or may not pass through the VBG such that the VBG is transmissive or Reflectively diffracts incident light. The reflectivity of each of the plurality of reflectors can be determined by the polarization state, wavelength, and angle of incidence of the incident light, as well as the period of VBG, the base refractive index, and the refractive index modulation (Δn).

Figure 6B illustrates an example of a grating-based waveguide display 602 including multiple grating layers for different fields of view, according to certain embodiments. In waveguide display 602, gratings may be spatially multiplexed along the Z direction. For example, waveguide display 602 may include multiple substrates, such as substrates 630, 632, 634, and the like. The substrate may include materials of the same material or of similar refractive index. One or more gratings 640, 642, 644, and the like (eg, VBG or SRG) may be formed on each substrate, such as recorded in a layer of holographic material formed on the substrate or etched into the substrate. The grating can be a reflective grating or a transmissive grating. Substrates with these gratings can be arranged in a substrate stack along the z-direction for spatial multiplexing. In some embodiments, each grating 640, 642, or 644 may be a multiplexed VBG that is designed for different Bragg conditions to couple display light of different wavelength ranges and/or different FOVs into or into the waveguide display 602. multiple rasters. In the example shown in Figure 6B, grating 640 can couple light 654 from the front field of view into the waveguide, as shown by ray 664 within the waveguide. Grating 642 can couple light 650 from an approximately 0° field of view into the waveguide, as illustrated by ray 660 within the waveguide. Grating 644 can couple light 652 from the negative field of view into the waveguide, as illustrated by light 662 within the waveguide.

In many waveguide-based near-eye display systems, to expand the orbit of the waveguide-based near-eye display in two dimensions, two or more output gratings can be used to expand the display light in two dimensions or along two axes (which can called biaxial pupillary dilation). Two gratings can have different grating parameters, such that one grating can be used to replicate the exit pupil in one direction and another grating can be used to replicate the exit pupil in another direction.

7A is a top view of an example of a grating - based (eg, volume Bragg grating or surface relief grating)-based waveguide display 700 with exit pupil expansion and reduced dispersion according to certain embodiments. Waveguide display 700 may be an example of augmented reality system 400 or 500 and may include waveguide 705 , input grating 710 , first intermediate grating 720 , second intermediate grating 730 , and output grating 740 formed on or in waveguide 705 . Each of the input grating 710, the first intermediate grating 720, the second intermediate grating 730, and the output grating 740 may be a transmissive grating or a reflective grating. Display light from a light source (eg, one or more micro-LED arrays) may be coupled into waveguide 705 by input grating 710 . The incoupled display light may be reflected from the surface of the waveguide 705 via total internal reflection as shown in FIG. 4 so that the display light may propagate within the waveguide 705 . Input raster 710 may include VBG or SRGS. In one example, the input grating 710 may include multiplexed VBGs and may couple display light with different colors and from different fields of view into the waveguide 705 corresponding to the diffraction angle.

The first intermediate grating 720 and the second intermediate grating 730 may be in different regions of the same holographic material layer or may be on different holographic material layers. In some embodiments, first intermediate grating 720 may be spatially separated from second intermediate grating 730. The first intermediate grating 720 and the second intermediate grating 730 may each include multiplexed VBG or SRG. In some embodiments, the first intermediate grating 720 and the second intermediate grating 730 can be recorded in the same number of exposures and under similar recording conditions, such that each VBG in the first intermediate grating 720 can match that in the second intermediate grating 730 corresponding VBG (e.g., have the same grating vector in the x-y plane and have the same and/or opposite grating vector in the z direction). For example, in some specific examples, the VBG in the first intermediate grating 720 and the corresponding VBG in the second intermediate grating 730 may have the same grating period and the same grating tilt angle (and therefore the same grating vector), and the same thickness. In one example, first intermediate grating 720 and second intermediate grating 730 may have a thickness of about 20 μm and may each include about 20 or more VBGs recorded over about 20 or more exposures.

Output grating 740 may be formed in a see-through region of waveguide display 700 and may include an exit region 750 when viewed in the z-direction (e.g., at a distance of approximately 18 mm from output grating 740 in the +z or -z direction) , the exit area overlaps with the orbit of the waveguide display 700 . Output grating 740 may include an SRG including many VBGs or a multiplexed VBG grating. In some embodiments, the output grating 740 and the second intermediate grating 730 may at least partially overlap in the x-y plane, thereby reducing the appearance size of the waveguide display 700. The output grating 740 in combination with the first intermediate grating 720 and the second intermediate grating 730 can perform the biaxial pupil expansion described above, thereby expanding the incident display beam in two dimensions to fill the eye socket with display light.

Input grating 710 couples display light from the light source into waveguide 705 . The display light may directly reach the first intermediate grating 720 or may be reflected from the surface of the waveguide 705 to the first intermediate grating 720 , where the size of the display light beam may be slightly larger than the size of the display light beam at the input grating 710 . Each VBG in the first intermediate grating 720 can diffract a part of the display light to the second intermediate grating 730 within the FOV range and the wavelength range that substantially satisfies the Bragg condition of the VBG. Although the display light diffracted by the VBG in the first intermediate grating 720 propagates within the waveguide 705 via total internal reflection (eg, along the direction shown by line 722), whenever the display light propagating within the waveguide 705 reaches the With two intermediate gratings 730 , a portion of the display light may be diffracted by the corresponding VBG in the second intermediate grating 730 toward the output grating 740 , as shown by line 732 . Whenever the display light propagating within the waveguide 705 reaches the exit region 750 of the output grating 740, the output grating 740 can then expand the display from the second intermediate grating 730 in different directions by diffracting a portion of the display light into the orbit. Light.

As described above, each VBG in first intermediate grating 720 may match a corresponding VBG in second intermediate grating 730 (e.g., have the same grating vector in the x-y plane, and have the same and/or opposing grating vector in the z direction ). Due to the opposite propagation directions of the display light at the two matched VBGs, the two matched VBGs can operate under opposite Bragg conditions (for example, +1st order diffraction and -1st order diffraction). For example, as shown in FIG. 7A , the VBG in the first intermediate grating 720 can change the propagation direction of the display light from the downward direction to the right direction, and the matching VBG in the second intermediate grating 730 can change the propagation direction of the display light. The propagation direction changes from rightward to downward. Therefore, the dispersion caused by the second intermediate grating 730 may be opposite to the dispersion caused by the first intermediate grating 720, thereby reducing or minimizing the overall dispersion.

Similarly, each VBG in input grating 710 may match a corresponding VBG in output grating 740 (eg, have the same grating vector in the x-y plane, and have the same and/or opposing grating vector in the z direction). Due to the opposite propagation directions of the displayed light at the two matched VBGs (e.g., into waveguide 705 and out of waveguide 705 ), the two matched VBGs can also operate under opposite Bragg conditions (e.g., +1 order diffraction vs. -1st order diffraction). Therefore, the dispersion caused by the input grating 710 can be opposite to the dispersion caused by the output grating 740, thereby reducing or minimizing the overall dispersion.

Figure 7B is a side view of an example of a waveguide display 700 including a grating coupler. As illustrated, waveguide display 700 may include first assembly 760 and second assembly 770 that are separable by spacers 780 . The first assembly 760 may include a first substrate 762 , a second substrate 766 , and one or more grating layers 764 between the first substrate 762 and the second substrate 766 . The first substrate 762 and the second substrate 766 may each be a thin transparent substrate, such as a glass substrate having a thickness of approximately 100 μm or several hundred microns. Grating layer 764 may include multiplexed reflective VBG, transmissive VBG, SRG, or a combination. Similarly, the second assembly 770 may include a first substrate 772 , a second substrate 776 , and one or more grating layers 774 between the first substrate 772 and the second substrate 776 . Grating layer 774 may include multiplexed reflective VBG, transmissive VBG, SRG, or a combination. In one example, a first assembly 760 can be used to couple red, green, and blue display light from certain fields of view to the user's eyes, and a second assembly 770 can be used to couple display light from other fields of view. Red, green and blue display lights are coupled to the user's eyes.

Figure 8A illustrates an example of a layer stack 800 formed by joining two substrates 810 and 820 using a tie layer 830. Layer stack 800 may function as a waveguide for directing display light, and may include one or more optical elements formed on one or two substrates, as described above. In the illustrated example, output grating coupler 840 may be formed on substrate 820 . Substrate 810 may or may not include a grating formed thereon. A light beam 850 coupled into the waveguide may propagate within the waveguide via total internal reflection. Whenever the guided beam reaches the output grating coupler 840, a portion 860 of the guided beam may be coupled out of the waveguide by the output grating coupler 840. In layer stack 800, the top surface of substrate 820 and the bottom surface of substrate 810 may be parallel to each other. Therefore, the angle of incidence of the guided beam incident on the top surface of substrate 820 and the angle of incidence of the guided beam incident on the bottom surface of substrate 810 can be kept constant and coupled out of the waveguide at different locations. A portion 860 of the directed beams may have the same diffraction angle.

Figure 8B illustrates another example of a waveguide display 802. Waveguide display 802 may include substrate 812, which may be similar to substrate 420 or 530. Substrate 812 may include, for example, glass, silicon, silicon nitride, silicon carbide, LiNbO ₃ , TiO ₂ , GaN, AIN, SiC, CVD diamond, ZnS, or any other suitable material. Input grating 822 and one or more output gratings 832 and 842 may be etched into substrate 812 or etched into a layer of grating material formed on substrate 812 . In some embodiments, input grating 822 and output gratings 832 and 842 may be holographic gratings recorded in a layer of holographic material coated on substrate 812 . In some embodiments, input grating 822 and output gratings 832 and 842 may include tilted or vertical surface relief gratings etched into substrate 812 or imprinted into a layer of nanoimprint material deposited on substrate 812. And may include an overcoat that fills the grating grooves. Output gratings 832 and 842 may be etched on opposing surfaces of substrate 812. In some specific examples, only one output grating 832 or 842 may be used. The input grating 822 can couple display light of different colors (eg, red, green, and blue) from different viewing angles (or within different fields of view (FOV)) into the substrate 812 , which can be directed via total internal reflection. Internally coupled display light. Whenever incoupled display light reaches output grating 832 or 842, a portion of the incoupled display light propagating within substrate 812 may be coupled out of substrate 812 by output grating 832 or 842 toward the orbit of waveguide display 802.

In order to satisfy the grating equation, a diffraction grating can diffract incident light with different colors (wavelengths) and/or from different viewing angles to different diffraction angles. For example, in the example shown in FIG. 8B , two light beams with different colors (eg, red and blue) and the same incident angle (eg, approximately 0°) may be diffracted by the input grating 822 to the substrate 812 different directions within. More specifically, light beams with shorter wavelengths (eg, blue light) may have smaller diffraction angles. Two light beams with the same color but different incident angles can also be diffracted by the input grating 822 to two different directions within the substrate 812 . Due to different propagation directions, the two incoupled beams can reach the surface of the substrate 812 and propagate for different distances in the x-direction before being diffracted outside the substrate 812 . A light beam with a smaller angle relative to the surface normal direction of the substrate 812 may reach the output grating 832 or 842 more times than a light beam with a larger angle relative to the surface normal direction of the substrate 812 . In addition, the grating may not have smooth diffraction efficiency for incident light of different colors or different incident angles. For at least these reasons, display lights with different colors or different FOVs can be directed to the eye sockets with different densities and can also form ghost images on the retina of the user's eyes.

Figure 8C illustrates an example of a multilayer waveguide display 804 according to certain embodiments. Multilayer waveguide display 804 may include a first waveguide layer 814 including one or more input gratings 824 and 826 and one or two output gratings 834 and 844 formed thereon, like waveguide display 802 described above. The first waveguide layer 814 may include, for example, glass, silicon, silicon nitride, silicon carbide, LiNbO ₃ , TiO ₂ , GaN, AIN, CVD diamond, ZnS, and the like. Input gratings 824 and 826 and output gratings 834 and 844 may be tilted or vertical full image or surface relief gratings and may include fill grating trench overcoats. In some embodiments, one or more of input gratings 824 and 826 and output gratings 834 and 844 may each have variable grating period, variable duty cycle, variable tilt angle, and/or variable etching. depth. In some specific examples, one or more of the input grating and the output grating may each include a two-dimensional grating with a variable grating period, a variable duty cycle, and a variable tilt angle along two directions of the two-dimensional grating. and/or variable etch depth.

Multilayer waveguide display 804 may include second waveguide layer 854 and third waveguide layer 864 on opposite sides of first waveguide layer 814 . The second waveguide layer 854 and the third waveguide layer 864 may each be a thin layer of a transparent material having a lower refractive index than the first waveguide layer 814 (eg, a few hundred microns, such as between about 100 μm and about 600 μm). μm). For example, the difference between the refractive index of the first waveguide layer 814 and the refractive index of the second waveguide layer 854 or the third waveguide layer 864 may be about 0.01, 0.02, 0.05, 0.1, 0.2, 0.25, 0.3, or greater. . The second waveguide layer 854 and the third waveguide layer 864 may have the same refractive index or different refractive indices.

In addition, the fourth waveguide layer 870 may be formed on the second waveguide layer 854, and the fifth waveguide layer 880 may be formed on the third waveguide layer 864. The fourth waveguide layer 870 and the fifth waveguide layer 880 may each be a thin layer (e.g., several hundred micrometers) of a transparent material having a lower refractive index than the respective refractive index of the second waveguide layer 854 and the third waveguide layer 864 . such as between about 100 μm and about 600 μm). For example, the difference between the refractive index of the second waveguide layer 854 and the refractive index of the fourth waveguide layer 870 and the difference between the refractive index of the third waveguide layer 864 and the refractive index of the fifth waveguide layer 880 may be about 0.01, 0.02, 0.05, 0.1, 0.2, 0.25, 0.3 or greater. The fourth waveguide layer 870 and the fifth waveguide layer 880 may have the same refractive index or different refractive indices.

Multilayer waveguide display 804 allows for more uniform reproduction of light with different colors and from different FOVs. For example, a first beam 890 (eg, having a longer wavelength or coming from a larger viewing angle) can be coupled into the first waveguide layer 814 via the input grating 824 and can be oriented relative to a surface normal to the first waveguide layer 814 propagates within the first waveguide layer 814. Therefore, due to the larger incident angle and the refractive index difference between the first waveguide layer 814 and the second waveguide layer 854, the first light beam 890 can be totally internally reflected between the first waveguide layer 814 and the second waveguide layer 854. Reflection at the interface.

The second beam 892 (eg, having a shorter wavelength and/or coming from a smaller viewing angle) may be coupled into the first waveguide layer 814 via the input grating 824 and may be smaller relative to the surface normal direction of the first waveguide layer 814 The angle propagates within the first waveguide layer 814. Therefore, the second beam 892 may not be reflected via total internal reflection at the interface between the first waveguide layer 814 and the second waveguide layer 854 since the incident angle may be less than the critical angle at the interface. Therefore, the second light beam 892 may actually be refracted into the second waveguide layer 854 with a larger refraction angle at the interface, and due to the increase in the incident angle and the difference in refractive index between the second waveguide layer 854 and the fourth waveguide layer 870, It is then reflected at the bottom surface of the second waveguide layer 854 via total internal reflection. Therefore, even though the second beam 892 may have a smaller propagation angle relative to the surface normal direction of the first waveguide layer 814 than the first beam 890 , the second beam 892 may travel in the z direction before being reflected via total internal reflection. travels a longer distance, and therefore may travel a similar distance in the x-direction as the first beam 890 before being reflected via total internal reflection. In this manner, the first beam 890 and the second beam 892 may be diffracted by the output grating 834 or 844 at approximately the same location (or at the same intervals) and/or approximately the same number of times.

Similarly, a third beam 894 (eg, having an even shorter wavelength and/or an even smaller viewing angle) may be coupled into the first waveguide layer 814 by the input grating 824 and may be relatively oriented relative to the surface normal of the first waveguide layer 814 . Small angles propagate within the first waveguide layer 814. The third light beam 894 may be refracted at the interface between the first waveguide layer 814 and the second waveguide layer 854 and the interface between the second waveguide layer 854 and the fourth waveguide layer 870, but due to the increased angle of incidence and the The difference in refractive index between the fourth waveguide layer 870 and air can be reflected at the bottom surface of the fourth waveguide layer 870 through total internal reflection. Therefore, even though the third beam 894 may have a smaller propagation angle relative to the surface normal direction of the first waveguide layer 814 than the first beam 890 , the third beam 894 may have a smaller propagation angle in the z direction before being reflected via total internal reflection. travels a longer distance, and therefore may travel a similar distance in the x-direction as the first beam 890 before being reflected via total internal reflection. In this manner, the first beam 890 and the third beam 894 may be diffracted by the output grating 834 or 844 at approximately the same location (or at the same intervals) and/or approximately the same number of times.

The thickness and refractive index of the first waveguide layer 814, the second waveguide layer 854, the third waveguide layer 864, the fourth waveguide layer 870, and the fifth waveguide layer 880 can be selected based on the desired performance. In various embodiments, multilayer waveguide displays herein may include two or more waveguide layers, such as three, four, five or more layers. In some embodiments, the low refractive index waveguide layers can be on the same side of the input and output gratings, and the refractive index of the two or more waveguide layers can be highest on one side of the layer stack and then toward the other side of the layer stack. Taper off one side. In some embodiments, the low refractive index waveguide layers can be on opposite sides of the input and output gratings, and the refractive index of the two or more waveguide layers can be highest at the center of the layer stack and can be toward both of the layer stacks. It gradually decreases on the opposite side. In some embodiments, the refractive index profile of the waveguide layer stack may be symmetrical and have a highest value at the center as shown in Figure 8C. In some specific examples, the refractive index profile of the waveguide layer stack may not be symmetrical with respect to the center of the waveguide layer stack. In some embodiments, one or more gratings or other optical elements may be formed in or on waveguide layer 854, 864, 870, or 880.

In some embodiments, optical substrates (eg, including one or more optical waveguide layers, such as waveguide layers 814, 854, 864, 870, or 880) may be joined using a liquid optically clear adhesive (LOCA). In order for LOCA to be compatible with optical substrates for waveguide display applications, LOCA needs to be transparent to visible light (e.g., have an absorption of less than about 0.1%/µm) and have a high refractive index (e.g., greater than about 1.6) , and can be completely cross-linked through curing without inducing large internal stresses. High transparency and high refractive index can be achieved by using, for example, siloxane-containing epoxy LOCA. These materials may have a refractive index of about 1.6 or higher at 450 nm, their absorptivity may be less than about 0.1%/µm LOCA materials, and their adhesion strength to glass may typically be greater than 1.5 MPa. Therefore, these LOCA materials can be used to form a permanent connection between two optical substrates, and the connection can withstand device handling and reliability testing.

Figure 9A illustrates an example of a method 900 of using a LOCA layer to join two optical substrates. As illustrated, LOCA layer 920 (e.g., including siloxane-containing epoxy LOCA) may be applied to the first optical substrate by, for example, spin coating, spray coating, inkjet printing, screen printing, or other dispensing techniques. Material 910. Any residual solvent can be evaporated, for example by applying post bake (PAB) heat. LOCA can be partially cured via UV treatment. The second optical substrate 930 can then be placed over the LOCA layer 920 and the first optical substrate 910, and the substrate stack can optionally be compressed and joined using a compressor. The substrate stack including the LOCA layer 920 between the first optical substrate 910 and the second optical substrate 930 can be cured via UV curing and/or thermal curing (eg, post-exposure bake (PEB)), which can cure the LOCA material Converts from its initial liquid state to an intermediate thermoplastic state. The substrate stack can then be baked or otherwise thermally cured to convert the LOCA material from a thermoplastic state to a final thermoset state, where the adhesive strength of the joined stacks can be maximized and the LOCA mechanical properties can be stable against other heat treatments. Compression can be applied to the optical substrate during any or all of the curing steps.

Figure 9B illustrates an example of polymerization of LOCA material after UV curing. LOCA materials may include monomers or oligomers 950, such as siloxane- and epoxy-containing oligomers, which may be small molecules. LOCA materials may also include UV-activated photoacid generators, cross-linker additives and solvents. At a molecular level, the curing process can lead to polymerization and cross-linking of LOCA materials. More specifically, upon exposure to UV light, a UV-activated photoacid generator can generate photoacid, which can cause cross-linking of oligomer 950. Any heat treatment may subsequently produce further cross-linking of the adhesive components. Cross-linked oligomer 950 can form polymer 960. Polymer 960 may include long chains of oligomers or polymers and thus may have a large molecular weight. As the chain grows, the LOCA layer can shrink. As shown in Figure 9B, polymer 960 may include some sites 970 that are not fully reacted. Thus, polymer 960 can continue to grow at site 970, which can cross-link the chains and create bridges between chains. The cross-linking process of siloxane epoxy LOCA can cause significant shrinkage, which can build up internal stress within the LOCA layer because macromolecules have difficulty rearranging and relaxing as the LOCA layer shrinks and contracts. The build-up of internal stresses can lead to deformation (eg, bending) of the joined substrate stack, as shown in Figure 9A. If internal stresses are too high, delamination can occur during normal handling and/or reliability testing.

During thermal curing, the LOCA material may continue to polymerize and cross-link to form larger molecules with atomically long chains, and therefore LOCA layer 920 may continue to shrink during thermal curing. For example, polymer 960 can continue to grow at site 970, which can cross-link the chains and create bridges between chains to form larger molecules, and thus can cause further shrinkage of the LOCA layer. Large molecules can require large amounts of energy to rearrange and relax as the LOCA layer contracts and tightens. Therefore, as the LOCA layer continues to cross-link and shrink, internal stress can continue to accumulate. The more cross-links between chains, the more difficult it is for the macromolecules to rearrange and fully relax, reducing internal stress as the LOCA layer shrinks. Therefore, the internal stress in the LOCA layer and the bending of the attached substrate stack may increase during thermal curing as shown in Figure 9A. In cases where the two optical substrates may have different coefficients of thermal expansion (CTE), the joined substrate stack may undergo further deformation due to CTE mismatch and heating/cooling of the joined substrate stack, which may increase the The stack bends and even causes penetrating deformation of the joined substrate stacks.

When at least one of the joined optical substrates is used as an optical waveguide, deformation of the substrate stack due to internal stresses in LOCA can lead to distortion and other optical artifacts, such as chief ray angular shifts, modulation transfer function degradation, Lateral chromatic aberration, pupil movement, text breakage, and double images degrade the optical performance of waveguide displays. When a 6-inch wafer is used as the substrate and the curvature of the connected substrate stack is higher than 20 µm, the optical performance of the waveguide display may be unacceptable.

Figure 10A illustrates an example of a waveguide display 1000 that includes a waveguide layer 1030 having a wedge shape due to fundamental stress caused, for example, by bonding the waveguide layer 1030 to the waveguide layer 1010 using a LOCA material (not shown in Figure 10A). The material bends. Waveguide layer 1010 may include one or more input gratings 1020 and 1022, and one or more output gratings 1024 and 1026 to form waveguide display 1000. In the example shown in FIG. 10A , a first beam 1040 (eg, having a longer wavelength or coming from a larger viewing angle) may be coupled to the waveguide layer 1010 at a larger angle relative to the surface normal direction of the waveguide layer 1010 by the input grating 1022 . in the waveguide layer 1010. Therefore, due to the larger incident angle and the refractive index difference between the waveguide layer 1010 and the waveguide layer 1030, the first beam 1040 may be reflected at the interface between the waveguide layer 1010 and the waveguide layer 1030 via total internal reflection. The second light beam 1042 (eg, having a shorter wavelength and/or coming from a smaller viewing angle) may be coupled into the waveguide layer 1010 via the input grating 1022 and may pass through the waveguide layer at a smaller angle relative to the surface normal direction of the waveguide layer 1010 Spread within 1010. Therefore, the second beam 1042 may not be reflected via total internal reflection at the interface between the waveguide layer 1010 and the waveguide layer 1030 because the incident angle may be smaller than the critical angle at the interface. Therefore, the second beam 1042 may actually be refracted into the waveguide layer 1030 at the interface with a larger refraction angle, and due to the increased angle of incidence and the larger difference in refractive index between the waveguide layer 1030 and air (eg, about 0.5), It may then be reflected at the top surface of waveguide layer 1030 via total internal reflection. When waveguide layer 1030 has a low (eg, near zero) TTV or small wedge angle (eg, has a perfectly flat top surface as shown by plane 1034 ), second beam 1042 may proceed at plane 1034 as shown by ray 1043 reflection. Even though the second beam 1042 may have a smaller propagation angle relative to the surface normal direction of the waveguide layer 1010 than the first beam 1040 , the second beam 1042 may travel a longer distance in the z-direction before being reflected via total internal reflection. And thus may travel a similar distance in the x-direction as first beam 1040 before being reflected via total internal reflection (eg, as shown by ray 1043). In this manner, the first beam 1040 and the second beam 1042 may be diffracted by the output grating 1024 or 1026 at approximately the same location (or at approximately the same intervals) and/or diffracted approximately the same number of times. The thickness and refractive index of waveguide layer 1010 and waveguide layer 1030 can be selected based on desired performance.

However, the waveguide layer 1030 may have a wedge shape (eg, with a wedge angle greater than 1 arcsec) due to substrate bending caused by curing the LOCA tie layer using UV light and/or heat. Due to the wedge shape, the angle of incidence of the second beam 1042 (after being refracted into the waveguide layer 1030) on the top surface 1032 of the waveguide layer 1030 and the angle of incidence of the guided beam on the bottom surface of the waveguide layer 1010 can be gradually change (e.g., gradually decrease in the illustrated example). For example, due to the non-uniformity of the waveguide layer 1030, the second beam 1042 may actually be reflected from the top surface 1032 of the waveguide layer 1030 into the direction shown by ray 1045. Accordingly, first beam 1040 and second beam 1042 may be coupled out of waveguide display 1000 at different locations (eg, diffracted by output grating 1024 or 1026). Additionally, the distance between two adjacent reflective locations at top surface 1032 may gradually decrease. Therefore, the exit pupil may be reproduced unevenly.

Since the incident angles of the light beams incident on different positions of the output gratings 1024 and 1026 may be different, the diffraction angles of the light beams diffracted at different positions of the output gratings 1024 and 1026 may also be different. Therefore, display light from the same FOV angle can be diffracted in different directions at different positions of the output grating. As a result, optical artifacts such as double images may occur and the quality of the displayed image may be poor. In some cases, due to the angle of incidence of the second beam 1042 on the top surface 1032 and the angle of incidence of the second beam 1042 on the bottom surface of the waveguide layer 1010 , the second beam 1042 propagates in the waveguide display 1000 . Gradually, at some locations, the angle of incidence of the second beam 1042 on the top surface 1032 or the angle of incidence of the second beam 1042 on the bottom surface of the waveguide layer 1010 may be less than the critical angle, and therefore may no longer pass through the entire Internal reflections are guided in the waveguide display 1000.

Figure 10B illustrates an example of a layer stack 1005 formed by joining two planar substrates 1050 and 1060 using a liquid optically clear adhesive. In the illustrated example, output grating coupler 1062 may be formed on substrate 1060 . LOCA layer 1070 may be disposed between substrate 1050 and substrate 1060. Substrates 1050 and 1060 may be pushed together by applying pressure (eg, mechanical pressure or vacuum pressure) to the bottom surface of substrate 1050 and/or the top surface of substrate 1060. The LOCA material in LOCA layer 1070 may be allowed to flow without pressure or in response to pressure. After applying pressure for a certain period of time, the LOCA material can be cured using, for example, UV light and/or heat (eg, exposure to UV light in a chamber or baking in an oven), as described above.

Due to the bending of the substrate caused by curing the LOCA layer 1070 using UV light and/or heat, the layer stack 1005 may have a wedge shape. The angle of the wedge may not be precisely controlled and may be larger, such as greater than about 1×10 ⁻⁴ radians. A light beam 1080 coupled into a waveguide formed by connecting layer stack 1005 may need to propagate within the waveguide via total internal reflection. Whenever a guided beam reaches the output grating coupler 1062, a portion 1082 of the guided beam may be coupled out of the waveguide by the output grating coupler 1062. Because the layer stack 1005 may have a wedge shape, the angle of incidence of the directed beam on the top surface of the substrate 1060 and the angle of incidence of the directed beam on the bottom surface of the substrate 1050 may vary gradually (e.g., at gradually decrease in the examples shown). For example, if the top surface of substrate 1060 is parallel to the bottom surface of substrate 1050 , the directed light beam may be reflected (eg, via TIR) from the top surface of substrate 1060 to the direction shown by ray 1084 . Due to the wedge shape of layer stack 1005, the directed beam may actually be reflected from the top surface of substrate 1060 into the direction shown by ray 1086. Accordingly, the direction in which the guided beam is coupled to the portion 1082 outside the waveguide may be different at different locations, as shown in Figure 10B. Additionally, the distance between two adjacent reflective locations at the top surface of the substrate 1060 may gradually decrease. Therefore, the exit pupil may be reproduced unevenly.

In addition, since the angle of incidence of the guided beam on the top surface of the substrate 1060 and the angle of incidence of the guided beam on the bottom surface of the substrate 1050 may gradually decrease as the guided beam propagates in the waveguide, Small, at some locations, the angle of incidence of the guided beam on the top surface of substrate 1060 or the angle of incidence of the guided beam on the bottom surface of substrate 1050 may be less than the critical angle, and thus may no longer pass through Total internal reflection is guided in the waveguide. In fact, as shown by ray 1090, the guided beam may be refracted out of the waveguide.

Therefore, changes in the thickness of the waveguide in a waveguide display can cause distortion and other optical artifacts, such as chief ray angle shift, modulation transfer function degradation, lateral chromatic aberration, pupil movement, and text breakage double images, thereby making the waveguide display The optical performance is degraded. To achieve better optical performance, a waveguide including two or more waveguide layers joined together may need to be flat, such as have low TTV and low surface roughness. For example, the two opposing outer surfaces of a substrate stack including two substrates joined together may need to maintain a high degree of parallelism, and the substrate stack may need to have minimal total thickness variation (TTV) and curvature ( For example, with a very small wedge angle). Therefore, it is expected that LOCA materials (e.g., siloxane epoxy LOCA with high refractive index and low light absorption) used in methods of joining two optical substrates for waveguide displays will react during curing and cross-linking and during After heat treatment, no large amount of internal stress is generated that can deform the connected substrate stack through bending.

According to certain embodiments, two optical substrates, at least one of which may serve as an optical waveguide layer, may use a siloxane epoxy that also includes a reactive plasticizer, such as the siloxane additive of Structure 1. Base LOCA link: wherein R ₁ , R ₂ and R ₃ may include methoxide, ethoxide, propoxide or a mixture of these materials, and R ₄ may be a straight or branched alkyl chain consisting of 2 to 8 carbons, Such as linear C ₆ H ₁₂ . R ₁ , R ₂ and R ₃ can improve the adhesive strength of LOCA, while R ₄ can help reduce the stress of LOCA during curing and heat treatment. Therefore, the siloxane addition of Structure 1 may allow LOCA to reduce internal stresses so that bending of the connected substrate stack may be minimized and the optical performance of the waveguide display may not be compromised. For example, when the optical substrate includes a 6-inch wafer, the curvature of the joined substrate stack may be less than about 20 µm, and the performance of the waveguide display may not be degraded or may be only minimally degraded. After curing, mixtures of LOCA and the siloxane additive of Structure 1 can produce stable mechanical properties, a refractive index at 450 nm of about 1.6 or higher, an absorbance of less than about 0.1%/µm and greater than about 1.5 MPa permanent bonding layer with adhesive strength to glass.

According to certain embodiments, an optically clear siloxane-containing epoxy adhesive mixture used to join two optical substrates can be cured via UV, heat, or both UV and heat treatment to produce high refractive index, high transparency and low A curved tie layer that provides high adhesion to the stack of joined substrates. The adhesive mixture may include, for example, siloxane- and epoxy-containing oligomers, UV-activated photoacid generators, cross-linker additives, solvents, and additives of structure 1, wherein the additives of structure 1 may constitute the adhesive. Approximately 1% to 7% of the total mass of the mixture (excluding solvent). In the additives of structure 1, R ₁ , R ₂ and R ₃ may include methoxide, ethoxide, propoxide or mixtures of these materials, and R4 may be linear or branched and include 2 to 8 carbon alkyl chain. The adhesive mixture may have a refractive index between about 1.6 and about 1.7 when cured, with a light absorbance of less than 0.1% per micron of the adhesive mixture. The adhesive mixture, when applied to a 4- to 8-inch wafer and cured, produces a stack of connected wafers with a curvature of less than about 20 microns.

According to some specific examples, the method of joining two optical substrates may include spin coating, spraying, inkjet printing, screen printing, or otherwise dispensing an adhesive layer including a silicone-containing epoxy adhesive mixture. On the first substrate, the adhesive layer is bonded to the second substrate by curing the adhesive mixture through a combination of UV curing and thermal curing. The adhesive mixture may include additives of structure 1, wherein the additives of structure 1 may constitute about 1% to 7% of the total mass of the mixture (excluding solvent). The adhesive mixture can be applied to the first substrate to form an adhesive layer having a thickness of about 1 to 100 microns. The adhesive mixture can be cured to produce a mechanically stable adhesive layer having a refractive index between about 1.6 and about 1.7 at 450 nm and a light absorption of less than about 0.1% per micron of the adhesive mixture. The joined substrate stack may have a lap shear strength of at least 2.0 MPa and a relatively low degree of bending. The first substrate and the second substrate can be transparent substrates having a diameter of about 4 to 8 inches, and the connected substrate stack can have a curvature of less than 20 microns. At least one of the first substrate or the second substrate can be a lens of any shape and length of about 1 to 4 inches, and the curvature of the joined substrate stack can be less than about 10 microns.

Figure 11A illustrates an example of a method 1100 of using a LOCA layer to join two optical substrates according to certain embodiments. As illustrated, LOCA layer 1120 (e.g., including siloxane-containing epoxy LOCA and the additives of Structure 1) may be applied by, for example, spin coating, spray coating, inkjet printing, screen printing, or other dispensing techniques. on the first optical substrate 1110. Any residual solvent can then evaporate, for example by applying post bake (PAB) heat. LOCA can optionally be partially cured via UV treatment. The second optical substrate 1130 can then be placed over the LOCA layer 1120 and the first optical substrate 1110, and the substrate stack can be compressed and bonded using a compressor. The substrate stack including the LOCA layer 1120 between the first optical substrate 1110 and the second optical substrate 1130 can be cured via UV curing and/or thermal curing (eg, PEB), which can convert the LOCA material from its initial liquid state to an intermediate thermoplastic state. The substrate stack can then be baked or otherwise thermally cured to convert the LOCA material from a thermoplastic state to a final thermoset state, where the adhesive strength of the joined stacks can be maximized and the LOCA mechanical properties can be stable against other heat treatments. Compression bonds can be applied during any or all of the curing steps.

Figure 11B illustrates an example of polymerization of LOCA material including reactive plasticizer 1152 after UV curing. LOCA materials may include monomers or oligomers 1150, such as siloxane- and epoxy-containing oligomers, which may be small molecules. LOCA materials may also include UV activated photoacid generators, cross-linker additives, solvents and reactive plasticizers 1152. Reactive plasticizer 1152 may have a structure as shown by Structure 1. At a molecular level, the curing process can lead to polymerization and cross-linking of LOCA materials. More specifically, upon exposure to UV light, the UV-activated photoacid generator can generate photoacid, which can cause cross-linking of oligomer 1150. Cross-linked oligomers 1150 can form polymer 1160. Polymer 1160 may comprise long chains of oligomers and therefore may have a large molecular weight. As the chain grows, the LOCA layer can shrink. As shown in Figure 11B, polymer 1160 may include incompletely reacted sites 1170. Thus, polymer 1160 can continue to grow at site 1170, which can cross-link the chains and create bridges between chains. The cross-linking process of siloxane-epoxy LOCA can cause significant shrinkage, which can additionally build up internal stress within the LOCA layer. However, the reactive plasticizer 1152 can participate in the polymerization and/or cross-linking process and become covalently linked to the chain through covalent bonds, and can have flexible chains that can adopt a variety of stabilization methods when relaxed. configuration. In other words, the flexible chains of reactive plasticizer 1152 can relax in many ways, and thus can become more relaxed when they assume an unfavorable configuration rather than remain in an unfavorable configuration. Thus, reactive plasticizer 1152 may allow macromolecules in the LOCA layer to rearrange and relax as the LOCA layer shrinks during UV curing. Therefore, stress within the LOCA layer can be reduced during UV curing. Therefore, the bending of the joined substrate stack can be low during UV curing, as shown in Figure 11A.

Similarly, during thermal curing, the LOCA layer 1120 may continue to shrink as the LOCA material continues to polymerize and cross-link (e.g., at site 1170 ) to form large molecules with atomically long chains, and the reactive plasticizer 1152 Molecules may be allowed to rearrange and relax as the LOCA layer 1120 contracts. Therefore, there may be little or no internal stress build-up in LOCA layer 1120. Therefore, the bending of the joined substrate stack can be low during thermal curing, as shown in Figure 11A. Additionally, incorporation of an appropriate amount (eg, an appropriate range) of a reactive plasticizer will not alter the refractive index and absorption characteristics of the siloxane-containing epoxy polymer.

According to some embodiments, two transparent substrates may be joined together by a siloxane-containing epoxy adhesive layer formed from a mixture of additives of Structure 1, wherein the additives of Structure 1 may constitute a solvent-free About 1% to 7% of the total mass of the mixture. The adhesive layer can be mechanically stable and can have a refractive index between about 1.6 and about 1.7 at 450 nm and a light absorption of less than about 0.1% per micron of the adhesive layer. The stack of substrates connected by the adhesive layer can have a lap shear strength of at least 2.0 MPa and can have a low degree of bending. In one example, the two transparent substrates can be wafers approximately 4 to 8 inches in diameter, and the connected substrate stack can have a curvature of less than 20 microns. In some embodiments, at least one of the two transparent substrates is a lens having a random shape and a length of about 1 to 4 inches, and the joined substrate stack has a curvature of less than 10 microns. Example

In all examples described below, a siloxane-containing epoxy adhesive as described above was used. The adhesive includes a mixture of methyl and phenylsiloxane oligomers terminated with epoxy functional groups. Adhesives also include UV-activated photoacid generators and cross-linker additives. The siloxane-containing epoxy LOCA was dissolved in propylene glycol methyl ether acetate (PGMEA) solvent and the solution was spin-coated on a 6-inch optical substrate. The siloxane-containing epoxy adhesive used in embodiments 1 to 12 may not include a reactive plasticizer, and the siloxane-containing epoxy adhesive used in embodiments 13 to 24 may include a reactive plasticizer. chemical agent. A. Comparative Examples 1 to 3

Figure 12A shows the substrate bending of Examples 1-3 using LOCA-joined substrate stacks cured by different curing methods. In the embodiment shown in Figure 12A, a solution including siloxane-containing epoxy LOCA was spin-coated onto a first optical substrate having a diameter of about 6 inches and a CTE of about 8 ppm. The solvent was removed from the LOCA by baking the first optical substrate at about 90°C for about 2 minutes. A second optical substrate with a diameter of about 6 inches and a CTE of about 8 ppm was placed on the LOCA coated on the first optical substrate. Before joining, the two optical substrates to be joined have a substrate bend of less than 5 µm. The substrate stack is compression joined as described above with respect to, for example, Figures 9A and 11A. The substrate stack was ^subsequently exposed to a UV excitation source with a power of 30 mW/cm, allowing the LOCA material to be cross-linked. The refractive index of the LOCA layer is 1.6 at 450 nm (as measured by ellipsometry techniques), and the LOCA absorption is <0.1%/µm.

In Example 1, the curvature of the joined substrate stack increased to 25 µm after UV curing, even in the absence of any thermal curing. This demonstrates that LOCA coating and initial cross-linking via UV curing can increase the bending of the joined substrate stack. Since heat curing was not performed, the substrate bending can be attributed to increased internal stress caused by the drying and shrinkage of the LOCA material during UV curing. Examples 2 to 3 demonstrate that further cross-linking via thermal curing (eg, at 100° C.) can cause a significant increase in substrate bowing due to further LOCA shrinkage and internal stress build-up. Since both substrates have the same CTE, LOCA internal stress can be a major contributor to base material buckling after the joining method is completed. B. Comparative Examples 4 to 6

Figure 12B shows the substrate bending of Examples 4-6 using LOCA-joined substrate stacks cured by different curing methods. Examples 4 to 6 were prepared using a method similar to that used to prepare Examples 1 to 3 described above, but using two 6-inch optical substrates with different CTEs joined by LOCA. As shown by Figure 12B, UV curing results in higher substrate bending (eg, approximately 116 μm) in the joined substrate stack, and further thermal curing results in a further increase in substrate bending. When compared to Examples 1 to 3, the CTE mismatch and lower CTE of the first optical substrate may contribute to the difference in base material bow values. As shown by Example 4, the fact that the substrate bends significantly above 20 µm even when no thermal curing is applied shows that the contribution of the LOCA internal stress to the substrate bending is significant. C. Comparative Examples 7 to 12

Figure 12C shows the substrate bending of Examples 7-12 with substrates having LOCA coatings cured by different curing methods. In Examples 7 to 12, a solution including a siloxane-containing epoxy LOCA was spin-coated onto a first optical substrate having a diameter of about 6 inches and a CTE of about 4 ppm. The solvent was removed from the LOCA by baking the first optical substrate at about 90°C for about 2 minutes. The first optical substrate with the LOCA coating was then exposed to a UV excitation source with a power of 30 mW/cm so that the LOCA material could be ^cross -linked. The first optical substrate with the LOCA coating is not bonded to the second optical substrate. Substrate curvature was measured before coating and after LOCA treatment, and changes in substrate curvature are shown in Figure 12C. As shown by Examples 7 to 12, substrate bending increased after LOCA coating and UV curing. Substrate bending can further increase with increasing heat curing temperature and time. These examples demonstrate that complete curing and cross-linking of LOCA can result in increased substrate bending. The absence of a second optical substrate indicates that substrate bending occurs even when the CTE mismatch between the two substrates is not a contributor to deformation during LOCA cure. D. Working Examples 13 to 18

Figure 12D shows substrate bending of Examples 13-18 of substrates having a LOCA coating including a reactive plasticizer, according to certain embodiments. In Examples 13 to 18, the siloxane-containing epoxy LOCA was mixed with the additive of structure 1 and dissolved in the PGMEA solvent to form a solution. The ratio of LOCA to additives is 95:5 by weight. In all cases, the incorporation of additives does not alter the LOCA optical properties (e.g., refractive index of 1.6 RI, and LOCA absorption of <0.1%/µm LOCA thickness, as measured by ellipsometry techniques). The solution can be spin-coated onto a first optical substrate having a diameter of approximately 6 inches and a CTE of approximately 4 ppm. The solvent was removed from the LOCA by baking the first optical substrate at about 90°C for about 2 minutes. The first optical substrate with the LOCA coating was then exposed to a UV excitation source with a power of 30 mW/cm so that the LOCA material could be ^cross -linked. The LOCA curing conditions in Examples 13 to 18 are the same as those in Examples 7 to 12. The first optical substrate with the LOCA coating is not bonded to the second optical substrate. Substrate curvature was measured before coating and after LOCA treatment, and changes in substrate curvature are shown in Figure 12D. Figure 12D shows that the use of additives in Structure 1 significantly reduces the change in substrate curvature during thermal curing. Additionally, as shown by Example 18, a long thermal cure method can be applied to reduce internal stress via film relaxation. These examples demonstrate that when the additive of Structure 1 is used in the mixture, the internal stress within the siloxane epoxy LOCA can be reduced during thermal cure without affecting the optical properties. E. Working Examples 19 to 21

Figure 12E shows the substrate bending of Examples 19-21 using a LOCA bonded substrate stack including a reactive plasticizer according to certain embodiments. In Examples 19 to 21, the siloxane-containing epoxy LOCA was mixed with the additive of structure 1 and dissolved in the PGMEA solvent to form a solution. The ratio of LOCA to additives is 95:5 by weight. The solution can be spin-coated onto a first optical substrate having a diameter of about 6 inches and a CTE of about 8 ppm. The solvent can be removed from the LOCA, for example, by baking the first optical substrate at about 90°C for about 2 minutes. A second optical substrate with a diameter of about 6 inches and a CTE of about 8 ppm was placed on the LOCA coated on the first optical substrate. Before joining, the two optical substrates to be joined have a substrate bend of less than 5 µm. The substrate stack is compression joined as described above with respect to, for example, Figures 9A and 11A. The substrate stack was ^subsequently exposed to a UV excitation source with a power of 30 mW/cm, allowing the LOCA material to be cross-linked. The substrate stack can also be thermally cured. The incorporation of additives does not alter the optical properties of LOCA (e.g., refractive index of 1.6 RI, and LOCA absorption of <0.1%/µm LOCA thickness, as measured by ellipsometry techniques). Figure 12E shows that the additives cause minimal changes in the bending of the joined stack after thermal curing. In addition, the adhesive strength between the two substrates in Examples 20 to 21 was 4.0 MPa, as measured by lap shear. This demonstrates that two optical substrates can be joined with a siloxane mixture and a thermal curing process can be performed without increasing the bending of the joined stack above 20 µm. F. Working Examples 22 to 24

Figure 12F shows substrate bending of Examples 22-24 using a LOCA-linked substrate stack including a reactive plasticizer, according to certain embodiments. Examples 22 to 24 were prepared using a method similar to that used to prepare Examples 19 to 21 described above, but using two 6-inch optical substrates with different CTEs joined by LOCA. The siloxane-containing epoxy LOCA is mixed with the additive of structure 1 and dissolved in PGMEA solvent to form a solution. The ratio of LOCA to additives is 95:5 by weight. Figure 12F shows that even when there is a CTE mismatch between the two optical substrates, the additives cause minimal changes in the bending of the joined stack after thermal curing. Furthermore, LOCA optical properties were found to be unchanged by the incorporation of stress-reducing additives: LOCA has a refractive index of 1.6, as measured by ellipsometry techniques, and LOCA absorption is less than 0.1%/µm LOCA thickness. This further demonstrates that using a siloxane-containing epoxy LOCA with an additive of Structure 1, two optical substrates can be joined with a siloxane mixture and can be thermally cured without increasing the curvature of the joined stack above 20 µm.

Figure 13A includes a flowchart 1300 illustrating an example of a method of joining an optical substrate that is transparent to visible light according to certain embodiments. It should be noted that the specific operations illustrated in Figure 13A provide specific methods of joining optical substrates. Other sequences of operations may also be performed according to alternative embodiments. Furthermore, the individual operations illustrated in Figure 13A may include multiple sub-steps, which may be performed in various sequences as appropriate for the individual operations. Additionally, depending on the specific application, additional operations may be added, or some operations may not be performed. Many variations, modifications, and substitutions will be apparent to those of ordinary skill in the art.

Operations in block 1310 may include coating a layer of LOCA material on the first transparent substrate, the LOCA material including the solvent and additives of Structure 1: Wherein R ₁ , R ₂ and R ₃ include methoxide, ethoxide, propoxide or combinations thereof, and R ₄ includes an alkyl chain that is linear or branched and includes 2 to 8 carbons (for example, linear C ₆ H ₁₂ ), and the additives of structure 1 constitute 1% to 7% of the total mass of the LOCA material excluding solvent. Solvents may include PGMEA, dipropylene glycol methyl ether (DPGME)/tripropylene glycol monomethyl ether (TPM), or combinations. LOCA materials may also include siloxane- and epoxy-containing oligomers, UV-activated photoacid generators, and cross-linker additives. Applying the layer of LOCA material may include spin coating, spray coating, inkjet printing, screen printing, or drop coating. The thickness of the LOCA material layer can be between 1 and 100 microns.

Operations in block 1320 may include joining the second transparent substrate to the layer of LOCA material (eg, by compression) to form a substrate stack. Operations in block 1330 may include curing the LOCA material layer using ultraviolet (UV) light to cross-link the LOCA material. Operations in block 1340 may include thermosetting the substrate stack to convert the LOCA material to a thermoset state. In some embodiments, compression can be applied to the substrate stack in any or all curing operations. After thermally curing the substrate stack, the LOCA material layer can be characterized by a refractive index greater than 1.6 at 450 nm and a light absorption of less than 0.1% per micron of thickness of the LOCA material layer, and the substrate stack can be characterized by a refractive index greater than 1.5 MPa or greater than about 2 MPa, such as a lap shear strength of about 4 MPa. In some specific examples, the first transparent substrate and the second transparent substrate are substrates with a diameter between 4 and 8 inches, and after the thermal curing of the substrate stack, the curvature of the substrate stack is less than 20 μm. In some embodiments, at least one of the first transparent substrate or the second transparent substrate is a lens having an arbitrary shape and a length of 1 to 4 inches, and after thermally curing the substrate stack, the curvature of the substrate stack Less than 10 μm.

13B includes a flowchart 1305 illustrating another example of a method of joining an optical substrate that is transparent to visible light according to certain embodiments. The operations in block 1315 may include coating a layer of LOCA material on the first transparent substrate, the LOCA material including the solvent and the additives of Structure 1, wherein the additives of Structure 1 may constitute the total mass of the LOCA material excluding the solvent. 1% to 7%. Solvents may include PGMEA, DPGME/TPM, or combinations. LOCA materials may also include siloxane- and epoxy-containing oligomers, UV-activated photoacid generators, and cross-linker additives. Applying the layer of LOCA material may include spin coating, spray coating, inkjet printing, screen printing, or drop coating. The thickness of the LOCA material layer can be between 1 and 100 microns.

Operations in block 1325 may include curing the LOCA material layer using UV light to cross-link the LOCA material. Operations in block 1335 may include joining the second transparent substrate to the layer of LOCA material (eg, by compression) to form a substrate stack. Operations in block 1345 may include thermosetting the substrate stack to convert the LOCA material to a thermoset state. In some embodiments, compression may be applied for any or all curing operations. After thermally curing the substrate stack, the LOCA material layer can be characterized by a refractive index greater than 1.6 at 450 nm and a light absorption of less than 0.1% per micron of thickness of the LOCA material layer, and the substrate stack can be characterized by a refractive index greater than 1.5 MPa or greater than about 2 MPa, such as a lap shear strength of about 4 MPa. In some specific examples, the first transparent substrate and the second transparent substrate are substrates with a diameter between 4 and 8 inches, and after the thermal curing of the substrate stack, the curvature of the substrate stack is less than 20 μm. In some embodiments, at least one of the first transparent substrate or the second transparent substrate is a lens having an arbitrary shape and a length of 1 to 4 inches, and after thermally curing the substrate stack, the curvature of the substrate stack Less than 10 μm.

Specific examples of the invention may include or be implemented in conjunction with artificial reality systems. Artificial reality is a form of reality that has been adjusted in some way before being presented to the user. It can include, for example, virtual reality (VR), augmented reality (AR), mixed reality (MR), and hybrid reality. or a combination and/or derivative thereof. Artificial reality content may include fully generated content or generated content combined with captured (eg, real-world) content. Artificial reality content may include video, audio, haptic feedback, or some combination thereof, and any of these may be presented in a single channel or in multiple channels (such as stereoscopic video that produces a three-dimensional effect on the viewer). In addition, in some specific examples, artificial reality may also be related to applications, products, such as those used to generate content in the artificial reality and/or otherwise used in the artificial reality (e.g., performing activities in the artificial reality). accessories, services, or some combination thereof. Artificial reality systems that provide artificial reality content can be implemented on a variety of platforms, including head-mounted displays (HMDs) connected to host computer systems, stand-alone HMDs, mobile devices or computing systems, or capable of providing Any other hardware platform that provides artificial reality content to one or more viewers.

14 is a simplified block diagram of an example of an electronic system 1400 for a near-eye display (eg, an HMD device) implementing some of the embodiments disclosed herein. Electronic system 1400 may be used as an electronic system for an HMD device or other near-eye display as described above. In this embodiment, electronic system 1400 may include one or more processors 1410 and memory 1420. Processor 1410 may be configured to execute instructions for performing operations at several components, and may be, for example, a general purpose processor or a microprocessor suitable for implementation within a portable electronic device. One or more processors 1410 may be communicatively coupled with a plurality of components within electronic system 1400. To achieve this communication coupling, one or more processors 1410 may communicate across bus 1440 with other illustrated components. Bus 1440 may be any subsystem suitable for moving data within electronic system 1400. Bus 1440 may include a plurality of computer buses and additional circuits to move data.

Memory 1420 may be coupled to processor 1410. In some embodiments, memory 1420 may provide both short-term storage and long-term storage, and may be divided into units. Memory 1420 may be volatile, such as static random access memory (SRAM) and/or dynamic random access memory (DRAM), and/or non-volatile, such as read-only memory. (read-only memory; ROM), flash memory and the like. Additionally, memory 1420 may include a removable storage device, such as a secure digital (SD) card. Memory 1420 may provide storage of computer-readable instructions, data structures, program modules, and other data for electronic system 1400 . In some embodiments, memory 1420 may be distributed among different hardware modules. A set of instructions and/or program code may be stored in memory 1420. The instructions may be in the form of executable code executable by the electronic system 1400, and/or may be in the form of source code and/or installable code that is stored in the electronic system 1400. It can be in the form of executable code when compiled and/or installed on the 1400 (e.g., using any of a variety of commonly used compilers, installers, compression/decompression utilities, etc.).

In some embodiments, memory 1420 may store a plurality of application modules 1422 to 1424, and the plurality of application modules may include any number of applications. Examples of applications may include gaming applications, conferencing applications, video playback applications, or other suitable applications. Apps can include depth-sensing capabilities or eye-tracking capabilities. Application modules 1422 - 1424 may include specific instructions to be executed by one or more processors 1410 . In some embodiments, certain applications or portions of application modules 1422 - 1424 may be executed by other hardware modules 1480 . In some embodiments, memory 1420 may additionally include secure memory, which may include additional security controls to prevent copying or other unauthorized access to secure information.

In some embodiments, memory 1420 may include operating system 1425 loaded therein. Operating system 1425 is operable to initiate execution of instructions provided by application modules 1422 - 1424 and/or manage other hardware modules 1480 and interface with a wireless communications subsystem 1430 that may include one or more wireless transceivers. . Operating system 1425 may be adapted to perform other operations across components of electronic system 1400, including threading, resource management, data storage control, and other similar functionality.

Wireless communications subsystem 1430 may include, for example, infrared communications devices, wireless communications devices and/or chipsets (such as Bluetooth® devices, IEEE 802.11 devices, Wi-Fi devices, WiMax devices, cellular communications infrastructure, etc.) and/or similar communications interface. Electronic system 1400 may include one or more antennas 1434 for wireless communications, as part of wireless communications subsystem 1430 or as a separate component coupled to any portion of the system. Depending on the desired functionality, wireless communications subsystem 1430 may include individual transceivers to communicate with base transceiver stations and other wireless devices and access points, which may include communications with, for example, a wireless wide-area network (WWAN). , wireless local area network (WLAN) or wireless personal area network (wireless personal area network; WPAN) different data networks and/or network types for communication. A WWAN may be a WiMax (IEEE 802.16) network, for example. A WLAN may be, for example, an IEEE 802.11x network. A WPAN can be, for example, a Bluetooth network, IEEE 802.15x, or some other type of network. The techniques described herein may also be used with any combination of WWAN, WLAN, and/or WPAN. Wireless communications subsystem 1430 may permit the exchange of data with networks, other computer systems, and/or any other devices described herein. Wireless communications subsystem 1430 may include components for transmitting or receiving data such as identifiers of HMD devices, location data, geographic maps, heat maps, photos, or videos using antennas 1434 and wireless links 1432 .

Examples of electronic system 1400 may also include one or more sensors 1490 . Sensors 1490 may include, for example, image sensors, accelerometers, pressure sensors, temperature sensors, proximity sensors, magnetometers, gyroscopes, inertial sensors (e.g., a combination of accelerometers and gyroscopes). module), an ambient light sensor, or any other similar module operable to provide sensing output and/or receive sensing input, such as a depth sensor or a position sensor. For example, in some implementations, one or more sensors 1490 may include one or more inertial measurement units (IMUs) and/or one or more position sensors. The IMU may generate calibration data based on measurement signals received from one or more of the position sensors, the calibration data indicating an estimated position of the HMD device relative to an initial position of the HMD device. The position sensor may generate one or more measurement signals in response to movement of the HMD device. Examples of position sensors may include, but are not limited to, one or more accelerometers, one or more gyroscopes, one or more magnetometers, another suitable type of sensor that detects motion, errors for IMUs A type of calibrated sensor, or a combination thereof. The position sensors can be located outside the IMU, inside the IMU, or some combination thereof. At least some sensors may use structured light patterns for sensing.

Electronic system 1400 may include display module 1460. The display module 1460 can be a near-eye display, and can graphically present information (such as images, videos, and various instructions) from the electronic system 1400 to the user. Such information may originate from one or more application modules 1422-1424, the virtual reality engine 1426, one or more other hardware modules 1480, combinations thereof, or be used to parse graphical content for the user (e.g., By any other suitable component of the operating system 1425). Display module 1460 may use liquid crystal display (LCD) technology, light emitting diode (LED) technology (including, for example, OLED, ILED, μLED, AMOLED, TOLED, etc.), light emitting polymer display (LPD) technology, or some other Display technology.

Electronic system 1400 may include user input/output module 1470. The user input/output module 1470 may allow the user to send action requests to the electronic system 1400 . An action request may be a request to perform a specific action. For example, an action request may be to start or end an application or to perform a specific action within the application. User input/output module 1470 may include one or more input devices. Exemplary input devices may include a touch screen, a trackpad, one or more microphones, one or more buttons, one or more dials, one or more switches, a keyboard, a mouse, a game controller, or a user interface. Any other suitable device for receiving the action request and communicating the received action request to the electronic system 1400 . In some embodiments, the user input/output module 1470 can provide tactile feedback to the user according to instructions received from the electronic system 1400 . For example, tactile feedback can be provided when an action request is received or performed.

The electronic system 1400 may include a camera 1450 that may be used to take photos or videos of the user, for example, to track the position of the user's eyes. The camera 1450 can also be used to capture photos or videos of the environment, such as for VR, AR or MR applications. Camera 1450 may include, for example, a complementary metal oxide semiconductor (CMOS) image sensor with millions or tens of millions of pixels. In some implementations, camera 1450 may include two or more cameras that may be used to capture 3D images.

In some embodiments, electronic system 1400 may include a plurality of other hardware modules 1480 . Each of the other hardware modules 1480 may be a physical module within the electronic system 1400 . Although each of the other hardware modules 1480 may be permanently configured as an architecture, some of the other hardware modules 1480 may be temporarily configured to perform specific functions or to be activated temporarily. Examples of other hardware modules 1480 may include, for example, audio output and/or input modules (eg, microphones or speakers), near field communication (NFC) modules, rechargeable batteries, battery management systems, wired /Wireless battery charging system, etc. In some embodiments, one or more functions of other hardware modules 1480 may be implemented in software.

In some specific examples, the memory 1420 of the electronic system 1400 may also store the virtual reality engine 1426. The virtual reality engine 1426 can execute applications within the electronic system 1400 and receive position information, acceleration information, speed information, predicted future position, or some combination thereof of the HMD device from various sensors. In some embodiments, information received by the virtual reality engine 1426 may be used to generate signals (eg, display commands) to the display module 1460 . For example, if the information received indicates that the user has looked to the left, the virtual reality engine 1426 can generate content for the HMD device that reflects the user's movement in the virtual environment. Additionally, the virtual reality engine 1426 may perform actions within the application in response to action requests received from the user input/output module 1470 and provide feedback to the user. The feedback provided may be visual feedback, auditory feedback or tactile feedback. In some implementations, one or more processors 1410 may include one or more GPUs executable by a virtual reality engine 1426 .

In various implementations, the hardware and modules described above may be implemented on a single device or on multiple devices that may communicate with each other using wired or wireless connections. For example, in some implementations, some components or modules, such as the GPU, virtual reality engine 1426, and applications (e.g., tracking applications) may be implemented on a console that interfaces with the head mounted display device Separate. In some implementations, one console may be connected to or support more than one HMD.

In alternative configurations, different and/or additional components may be included in electronic system 1400 . Similarly, the functionality of one or more of the components may be distributed among the components in a manner different from that described above. For example, in some embodiments, electronic system 1400 may be modified to include other system environments, such as AR system environments and/or MR environments.

The methods, systems, and devices discussed above are examples. Various embodiments may omit, substitute, or add various procedures or components as appropriate. For example, in alternative configurations, the described methods may be performed in an order different from that described, and/or various stages may be added, omitted, and/or combined. Likewise, features described with respect to certain embodiments may be combined in various other embodiments. Different aspects and elements of specific embodiments may be combined in similar ways. Also, technology evolves, and thus many elements are examples that do not limit the scope of the invention to those specific examples.

Specific details are given in this description to provide a thorough understanding of specific examples. However, specific examples may be practiced without such specific details. For example, well-known circuits, processes, systems, structures, and techniques have been shown without unnecessary detail in order to avoid obscuring the specific examples. This description provides illustrative specific examples only, and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the foregoing description of specific examples will provide those of ordinary skill in the art with an enlightening description for implementing various specific examples. Various changes may be made in the function and arrangement of components without departing from the scope of the invention.

Additionally, some specific examples are described as procedures depicted as flowcharts or block diagrams. Although each may describe operations as a sequential process, many of the operations may be performed in parallel or simultaneously. Additionally, the order of operations can be reconfigured. The procedures may have additional steps not included in the figures. Furthermore, specific examples of methods may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware or microcode, the code or code segments used to perform the associated tasks may be stored in a computer-readable medium such as a storage medium. The processor can perform associated tasks.

Substantial variations may be made to suit specific requirements as will be apparent to those of ordinary skill in the art. For example, custom or specialized hardware may also be used, and/or specific elements may be implemented in hardware, software (including portable software such as applets, etc.), or both. Additionally, connections to other computing devices, such as network input/output devices, may be used.

Referring to the figures, components that may include memory may include non-transitory machine-readable media. As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any storage medium that participates in providing data that causes a machine to operate in a particular way. In the specific examples provided above, various machine-readable media may be involved in providing instructions/code to a processing unit and/or other device for execution. Additionally or alternatively, machine-readable media may be used to store and/or carry such instructions/code. In many implementations, computer-readable media are physical and/or tangible storage media. This media can take many forms, including, but not limited to, non-volatile media, volatile media, and transmission media. Common forms of computer-readable media include, for example, magnetic and/or optical media such as compact disk (CD) or digital versatile disk (DVD); punched cards; paper tape; anything with a pattern of holes Other physical media; RAM; programmable read-only memory (PROM); erasable programmable read-only memory (EPROM); FLASH-EPROM; any other A memory chip or cartridge; a carrier wave as described below; or any other medium that allows a computer to read instructions and/or program code. A computer program product may include program code and/or machine-executable instructions, which code and/or machine-executable instructions may represent a program, function, subroutine, program, routine, application (App), subroutine , module, package, class, or any combination of instructions, data structures, or program statements.

Those of ordinary skill in the art will appreciate that the information and signals used to convey the messages described herein may be represented using any of a variety of different techniques and techniques. For example, the data, instructions, commands, information, signals, bits, symbols and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, light fields or light particles, or any combination thereof.

As used herein, the terms "and" and "or" may include a variety of meanings, which meanings are also intended to depend, at least in part, on the context in which such terms are used. Typically, "or" when used in relation to a list, such as A, B, or C, is intended to mean A, B, and C (here used in an inclusive sense), as well as A, B, or C (here used in an exclusive sense) . Furthermore, the term "one or more" as used herein may be used to describe any feature, structure or characteristic in the singular, or may be used to describe some combination of features, structures or characteristics. However, it should be noted that this is merely an illustrative example and claimed subject matter is not limited to this example. Furthermore, the term "at least one of" when used in connection with a list such as A, B or C may be interpreted to mean A, B, C or a combination of A, B and/or C such as AB, AC , BC, AA, ABC, AAB, ACC, AABBCCC or the like.

Additionally, although certain specific examples have been described using specific combinations of hardware and software, it should be recognized that other combinations of hardware and software are possible. Certain embodiments may be implemented in hardware only or in software only, or using a combination thereof. In one example, the software may be implemented by a computer program product containing computer code or instructions executable by one or more processors for performing the tasks described in this disclosure. Any or all of the steps, operations or processes, in which the computer program may be stored on a non-transitory computer-readable medium. The various processes described herein may be implemented in any combination on the same processor or on different processors.

Where a device, system, component or module is described as being configured to perform certain operations or functions, the electronic circuit may be programmed, for example, by designing the electronic circuit to perform the operation, by programming the programmable electronic circuit, such as a microprocessor, Processor) to perform operations (such as by executing computer instructions or code, or a processor or core programmed to execute code or instructions stored on non-transitory memory media) or any combination thereof this configuration. Handlers may communicate using a variety of technologies, including but not limited to conventional techniques for inter-handler communication, and different pairs of handlers may use different technologies, or the same pair of handlers may use different technologies at different times.

Therefore, the description and drawings should be viewed in an illustrative rather than a restrictive sense. However, it will be apparent that additions, subtractions, deletions, and other modifications and changes may be made to the present disclosure without departing from the broader scope as set forth in the patent claims. Therefore, although specific examples have been described, these examples are not intended to be limiting. Various modifications and equivalents are within the scope of the following patent applications.

100: Artificial reality system environment 110:Console 112: App Store 114:Head mounted device tracking module 116:Artificial Reality Engine 118: Eye tracking module 120: Near-eye display 122: Display electronics 124: Display optics 126:Locator 128: Position sensor 130: Eye tracking unit 132:Inertial measurement unit 140:Input/output interface 150:External imaging device 200:HMD device 220:Ontology 223:The bottom side of the body 225: Front side of body 227:Left side of body 230:Head strap 300: Near-eye display 305:Frame 310:Display 330:Illuminator 340:Camera 350a: Sensor 350b: Sensor 350c: Sensor 350d: Sensor 350e: Sensor 400:Augmented Reality System 410:Projector 412:Light source or image source 414:Projector optical parts 415:Combiner 420: Base material of combiner 430:Input coupler 440:Output coupler 450:Light 460:Extracted light 490:eyes 495:Eye socket 500:Augmented reality system 510:Light source or image source 520:Projector optical parts 530:Substrate 540:Input coupler 550:Output coupler 600:Waveguide display 602:Waveguide Display 610:Substrate 612: Top surface 614: Bottom surface 620:VBG layer 622: Enter VBG 624: Output VBG 630:Substrate 632:Substrate 634:Substrate 640:Grating 642:Grating 644:Grating 650:Light 652:Light 654:Light 660:Light 662:Light 664:Light 700:Waveguide Display 705:Waveguide 710:Input raster 720: First intermediate grating 722: line 730: Second intermediate grating 732: line 740: Output raster 750:Exit area 760:First assembly 762:First base material 764:Grating layer 766: Second base material 770:Second assembly 772:First base material 774:Grating layer 776:Second base material 780: spacer 800: layer stacking 802:Waveguide Display 804:Multilayer waveguide display 810:Substrate 812:Substrate 814: First waveguide layer 820:Substrate 822:Input raster 824:Input raster 826:Input raster 830:Connection layer 832: Output raster 834: Output raster 840: Output grating coupler 842: Output raster 844: Output raster 850:Beam 854: Second waveguide layer 864: The third waveguide layer 860:Part of the beam 870: The fourth waveguide layer 880: The fifth waveguide layer 890:First beam 892:Second Beam 894:The third beam 900:Method 910:The first optical substrate 920:LOCA layer 930: Second optical substrate 950: Monomer or oligomer 960:Polymer 970: Site of incomplete reaction 1000:Waveguide display 1005:Layer stacking 1010: Waveguide layer 1020:Input raster 1022:Input raster 1024: Output raster 1026: Output raster 1030: Waveguide layer 1032:Top surface 1034:Plane 1040:First beam 1042:Second beam 1043:Light 1045:Plane 1050:Substrate 1060:Substrate 1062: Output grating coupler 1070:LOCA layer 1080:Beam 1082: Part of the guided beam 1084:Light 1086:Light 1090:Light 1100:Method 1110:The first optical substrate 1120:LOCA layer 1130: Second optical substrate 1150: Monomer or oligomer 1152:Reactive plasticizer 1160:Polymer 1170: Site of incomplete reaction 1300:Flowchart 1305:Flowchart 1310:block 1315:block 1320:block 1325:block 1330:block 1335:block 1340:block 1345:block 1400: Electronic systems 1410: One or more processors 1420:Memory 1422:Application module 1424:Application module 1425:Operating system 1426:Virtual Reality Engine 1430: Wireless communication subsystem 1432: One or more links 1434: One or more antennas 1440:Bus 1450:Camera 1460:Display module 1470:User input/output module 1480:Other hardware modules 1490: One or more sensors

Illustrative specific examples are described in detail below with reference to the following drawings. [FIG. 1] is a simplified block diagram of an example of an artificial reality system environment including a near-eye display, according to certain embodiments. [FIG. 2] is a perspective view of an example of a near-eye display in the form of a head-mounted display (HMD) device for implementing some examples disclosed herein. [FIG. 3] is a perspective view of an example of a near-eye display in the form of a pair of glasses for implementing some of the examples disclosed herein. [FIG. 4] illustrates an example of an optical see-through augmented reality system including a waveguide display according to certain embodiments. [FIG. 5] illustrates an example of an optical see-through augmented reality system including a waveguide display for exit pupil expansion, according to certain embodiments. [Fig. 6A] illustrates an example of a waveguide display including a grating coupler. [Figure 6B] illustrates an example of a grating-based waveguide display including multiple grating layers for different fields of view. [FIG. 7A] is a top view of an example of a grating-based waveguide display with exit pupil expansion and dispersion reduction. [FIG. 7B] is a side view of an example of the waveguide display of FIG. 7A. [Fig. 8A] illustrates an example of a layer stack formed by connecting two substrates using a connecting layer. [Fig. 8B] illustrates another example of the waveguide display. [Fig. 8C] illustrates an example of a multilayer waveguide display. [Figure 9A] illustrates an example of a method of joining two optical substrates using a liquid optically clear adhesive (LOCA) layer. [Fig. 9B] illustrates an example of polymerization of LOCA material after UV curing. [Fig. 10A] illustrates an example of a waveguide display including a waveguide layer having a wedge shape. [Figure 10B] illustrates an example of a layer stack formed by joining two planar substrates using a liquid optically clear adhesive. [FIG. 11A] illustrates an example of a method of joining two optical substrates using a LOCA layer according to certain embodiments. [Fig. 11B] illustrates an example of polymerization of a LOCA material including a reactive plasticizer after UV curing. [Figure 12A] Substrate bending showing an example of a substrate stack using LOCA-joined substrates cured by different curing methods. [Figure 12B] Substrate bending showing an example of a substrate stack using LOCA-joined substrates cured by different curing methods. [Figure 12C] Substrate bending showing examples of substrates with LOCA coatings cured by different curing methods. [Fig. 12D] Shows substrate bending of an example of a substrate having a LOCA coating including a reactive plasticizer according to certain embodiments. [FIG. 12E] Demonstrates substrate bending for an example of a substrate stack using LOCA-linked substrates including a reactive plasticizer according to certain embodiments. [FIG. 12F] Demonstrates substrate bending for an example of a substrate stack using LOCA-linked substrates including a reactive plasticizer according to certain embodiments. [FIG. 13A] Includes a flow chart illustrating an example of a method of joining an optical substrate that is transparent to visible light according to certain embodiments. [FIG. 13B] Includes a flow chart illustrating another example of a method of joining an optical substrate that is transparent to visible light according to certain embodiments. [FIG. 14] is a simplified block diagram of an electronic system for implementing an example of a near-eye display of some of the examples disclosed herein. The drawings depict specific examples of the disclosure for illustrative purposes only. Those skilled in the art will readily recognize from the following description that alternative embodiments of the illustrated structures and methods may be employed without departing from the principles or claimed benefits of the invention. In the drawings, similar components and/or features may have the same reference numbers. Additionally, various components of the same type may be distinguished by using a dash after the reference mark and a second mark that distinguishes among similar components. If only a first reference number is used in the specification, the description applies to any of the similar components having the same first reference number regardless of the second reference number.

100: Artificial reality system environment

110:Console

112: App Store

114:Head mounted device tracking module

116:Artificial Reality Engine

118: Eye tracking module

120: Near-eye display

122: Display electronics

124: Display optics

126:Locator

128: Position sensor

130: Eye tracking unit

132:Inertial measurement unit

140:Input/output interface

150:External imaging device

Claims (15)

A liquid optically clear adhesive (LOCA) used to connect optical substrates. The LOCA contains: oligomers containing siloxane and epoxy groups; UV-activated photoacid generator; cross-linking agent addition substance; solvent; and additives of structure 1: The additives of structure 1 constitute 1% to 7% of the total mass of the LOCA excluding the solvent. Such as the LOCA of claim 1, wherein R ₁ , R ₂ and R ₃ include methoxide, ethoxide, propoxide or combinations thereof. Such as the LOCA of claim 1 or claim 2, wherein R ₄ includes an alkyl chain that is a linear or branched chain and includes 2 to 8 carbons; and/or wherein R ₄ includes a linear C ₆ H ₁₂ . The LOCA of any one of the preceding claims, wherein when cured, the LOCA has a refractive index equal to or greater than 1.6 at 450 nm and a light absorption of less than 0.1% per micron thickness of the LOCA; and/or wherein the LOCA LOCA can be cured by UV light, heat, or both. The LOCA of any one of the preceding claims, wherein the LOCA results in a connected stack with a curvature of less than 20 microns when applied to two 4 to 8 inch substrates and cured. The LOCA of any one of the preceding claims, wherein the LOCA, when applied to two glass substrates and cured, results in a stack of connected substrates with a lap shear strength greater than 1.5 MPa. A method, which includes: coating a layer of liquid optically clear adhesive (LOCA) material on a first transparent substrate, the LOCA material including a solvent and an additive of structure 1: attaching a second transparent substrate to the LOCA material layer by compression to form a substrate stack; curing the substrate stack using ultraviolet (UV) light to cross-link the LOCA material; and thermally curing the substrate stack to The LOCA material is converted into a thermoset state. The method of claim 7, wherein the LOCA material includes a siloxane-containing epoxy adhesive. Such as the method of claim 7 or claim 8, wherein: the additive of structure 1 constitutes 1% to 7% of the total mass of the LOCA material; R ₁ , R ₂ and R ₃ include methoxide, ethoxide, and propanol salts or combinations thereof; and R ₄ includes an alkyl chain that is straight or branched and includes 2 to 8 carbons. The method of any one of claims 7 to 9, wherein after thermally curing the substrate stack: the LOCA material layer is characterized by a refractive index at 450 nm equal to or greater than 1.6 and a thickness per micron of the LOCA material layer Less than 0.1% light absorption, and The substrate stack is characterized by a lap shear strength greater than 1.5 MPa. Such as requesting the method of any one of items 7 to 10, wherein: The first transparent substrate and the second transparent substrate are substrates with a diameter between 4 and 8 inches; and After thermally curing the substrate stack, the curvature of the substrate stack is less than 20 μm. A device comprising: a layer stack comprising two transparent substrates joined together by a silicone-containing epoxy adhesive layer, wherein the silicone-containing epoxy adhesive layer includes the additive of Structure 1 : The additives of structure 1 constitute 1% to 7% of the total mass of the siloxane-containing epoxy adhesive layer. The device of claim 12, wherein R ₁ , R ₂ and R ₃ include methoxide, ethoxide, propoxide or a combination thereof; and/or wherein R ₄ is a linear or branched chain and includes 2 to 8 carbons. alkyl chain. The device of claim 12 or claim 13, wherein the siloxane-containing epoxy adhesive layer is characterized by a refractive index equal to or greater than 1.6 at 450 nm and a refractive index of the siloxane-containing epoxy adhesive layer. Less than 0.1% light absorption per micron of thickness; and/or where: The thickness of the silicone-containing epoxy adhesive layer is between 1 and 100 microns; and This layer stack is characterized by a lap shear strength greater than 1.5 MPa. Such as requesting the device of any one of items 12 to 14, wherein: The two transparent substrates are substrates with a diameter between 4 and 8 inches; and the curvature of the layer stack is less than 20 μm; and/or wherein: At least one of the two transparent substrates is a lens of any shape and a length of 1 to 4 inches; and The curvature of this layer stack is less than 10 μm.