Fabrication method for a waveguide

Abstract

A method of fabricating a waveguide for a head mounted display may include attaching a first set of waveguide elements with one or more adhesives that are sensitive to thermal or chemical removal and attaching a second set of waveguide elements with one or more adhesives that are not sensitive to thermal or chemical removal to form a waveguide stack, cutting the waveguide stack to form waveguide structures with embedded facets or diffractive elements, and removing portions corresponding to the first set of waveguide elements using thermal or chemical removal while portions corresponding to the second set of waveguide elements remain attached.

Description

[Technical Field]

[0001] The present disclosure relates to the field of near-eye display systems, such as head-mounted displays. More particularly, the present disclosure relates to manufacturing methods for waveguides for near-eye displays (NEDs). [Background technology]

[0002] Consumer demand for improved human-computer interfaces has led to increased interest in high-quality imaging head-mounted displays (HMDs) or near-eye displays (NEDs), commonly known as smart glasses. These devices can provide virtual reality (VR) or augmented reality (AR) experiences, enhancing the way users interact with digital content and their surroundings.

[0003] Consumers are demanding better image quality, a more immersive experience, and more comfort when using HMDs. Consumers expect displays with high resolution, vibrant colors, and minimal distortion, which create a realistic and enjoyable viewing experience. Comfort is also a critical factor, as users often wear these devices for extended periods of time. Consumers desire lightweight, sleek designs that are less intrusive and more convenient to wear in a variety of scenarios. Additionally, smaller devices result in improved portability, making them easier to carry and use in different environments. This has led to an increasing demand for smaller, more compact HMDs with higher performance.

[0004] A key element in near-eye display systems is the waveguide, a device that directs light from the system image projector to the user's eye. Waveguides rely on total internal reflection along major surfaces within the device to propagate light. Improving the performance of miniaturized waveguides presents particular challenges. As waveguide performance is enhanced, the waveguides and their manufacturing processes become more complex. This complexity arises, in part, because the features that enhance performance also add to the complexity of the waveguide. Additionally, making waveguides smaller tends to complicate their production. The smaller the components, the more difficult they are to manage and reliably reproduce. This increased complexity in manufacturing tends to lead to reduced throughput and increased costs, which tends to reduce adoption.

[0005] Therefore, there is a need for innovative waveguide manufacturing processes that reduce manufacturing complexity while maintaining or improving performance and compactness. Summary of the Invention

[0006] The present disclosure is directed to a method of fabricating a waveguide for a head mounted display. The novel method may include attaching a first set of waveguide elements with one or more adhesives that are sensitive to thermal or chemical removal and attaching a second set of waveguide elements with one or more adhesives that are not sensitive to thermal or chemical removal to form a waveguide stack, cutting the waveguide stack to form waveguide structures with embedded facets or diffractive elements, and removing portions corresponding to the first set of waveguide elements using thermal or chemical removal while portions corresponding to the second set of waveguide elements remain attached to form the desired waveguide.

[0007] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various example systems, methods, etc., illustrating various example embodiments of aspects of the present invention. It is understood that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) represent one example of a boundary. Those skilled in the art will understand that one element may be designed as multiple elements, or multiple elements may be designed as one element. An element shown as an internal component of another element may be implemented as an external component, and vice versa. Additionally, elements may not be drawn to scale. [Brief explanation of the drawings]

[0008] [Figure 1A] 1 illustrates a prior art waveguide system with reflective facets. [Figure 1B] 1 illustrates a prior art waveguide system having a refractive element. [Figure 1C] 1 illustrates a prior art waveguide system with a reflective facet and a mirror input. [Figure 1D] 1 illustrates a prior art waveguide system with a refractive element and a mirror input. [Figure 2A] 1 illustrates a prior art two-dimensional waveguide system with reflective facets. [Figure 2B] 1 illustrates a prior art two-dimensional waveguide system having refractive elements. [Figure 3A] Illustrates a manufacturing method for a waveguide stack. [Figure 3B] Illustrates a manufacturing method for a waveguide stack. [Figure 3C] Illustrates a manufacturing method for a waveguide stack. [Figure 3D] Illustrates a manufacturing method for a waveguide stack. [Figure 3E] Illustrates a manufacturing method for a waveguide stack. [Figure 4A] Illustrates a manufacturing method for a mirror coupling-in segment. [Figure 4B]Illustrates a manufacturing method for a mirror coupling-in segment. [Figure 5A] Illustrates a manufacturing method for a waveguide. [Figure 5B] Illustrates a manufacturing method for a waveguide. [Figure 5C] Illustrates a manufacturing method for a waveguide. [Figure 6] 1 illustrates an alternative manufacturing method for a waveguide. [Figure 7A] A fabrication method for a two-dimensional waveguide is illustrated. [Figure 7B] A fabrication method for a two-dimensional waveguide is illustrated. [Figure 7C] A fabrication method for a two-dimensional waveguide is illustrated. [Figure 7D] A fabrication method for a two-dimensional waveguide is illustrated. [Figure 7E] A fabrication method for a two-dimensional waveguide is illustrated. [Figure 7F] A fabrication method for a two-dimensional waveguide is illustrated. [Figure 7G] A fabrication method for a two-dimensional waveguide is illustrated. [Figure 7H] A fabrication method for a two-dimensional waveguide is illustrated. [Figure 7I] A fabrication method for a two-dimensional waveguide is illustrated. DETAILED DESCRIPTION OF THE INVENTION

[0009] FIG. 1A illustrates a prior art waveguide system 1a including a projector 51, a collimating lens 52, and a waveguide system 10a. The waveguide system 10a includes a coupling-in prism 30 and a waveguide substrate 11a having a first major surface 13 and a second major surface 14, and an internally disposed partially reflective surface or facet 15. In system 1a, projector 51 projects light corresponding to an image that is collimated by lens 52 before entering waveguide 10a through coupling-in prism 30. Light rays illustrating an exemplary field are shown in FIG. 1A. Collimated field light rays 40 are coupled into waveguide 11a such that image 41a and conjugate image 41b are captured between the two major surfaces 13, 14 of waveguide 11a by total internal reflection (TIR). Light rays 41 a and 41 b propagate through waveguide 11 a until they interact with one of a set of co-parallel partially reflective surfaces 15 embedded within waveguide substrate 11 a. The embedded partially reflective surfaces 15 are coupling-out elements that couple light rays 41 a, 41 b out of waveguide 11 a as light ray 42 and project an image towards a user's eye 5 located within a predetermined eye motion box.

[0010] FIG. 1B illustrates an alternative prior art waveguide system 1b including a projector 51, a collimating lens 52, and a waveguide system 10b. The waveguide system 10b includes a coupling-in prism 30 and a waveguide substrate 11b having a first major surface 13 and a second major surface 14, and a diffractive element 12 disposed therein. In system 1b, a projector 51 projects light corresponding to an image that is collimated by a lens 52 before entering the waveguide 10b through the coupling-in prism 30. Rays illustrating an exemplary field are shown in FIG. 1B. Collimated field rays 40 are coupled into the waveguide 11b such that an image 41a and a conjugate image 41b are captured between the two major surfaces 13, 14 of the waveguide 11b by total internal reflection (TIR). Light rays 41 a and 41 b propagate through waveguide 11 b until they interact with a diffractive element 12 embedded within the waveguide substrate 11 b. The embedded diffractive element 12 is a coupling-out element that couples light ray 41 a from the waveguide into light ray 42 and projects an image towards the user's eye 5 located within a predetermined eye motion box.

[0011] To minimize the size of the underlying near-eye display, it is often desirable to position the projector at a specific location relative to the waveguide, as shown in Figures 1C and 1D. This can be achieved by coating the coupling-in prism 33 with a reflective coating and positioning the element as shown.

[0012] FIG. 1C illustrates a prior art waveguide system 1c including a projector 51, a collimating lens 52, and a waveguide system 10c. The waveguide system 10c includes a coupling-in prism 33 and a waveguide substrate 11a having first and second major surfaces 13 and 14 and an internally disposed partially reflective surface or facet 15. In system 1c, the projector 51 projects light corresponding to an image that is collimated by a lens 52 before being reflected by the coupling-in prism 33 into the waveguide 10c. Light rays illustrating an exemplary field are shown in FIG. 1C. Collimated field light rays 40 are coupled into the waveguide 11a such that an image 41a and a conjugate image 41b are captured between the two major surfaces 13, 14 of the waveguide 11a by total internal reflection (TIR). Light rays 41 a and 41 b propagate through waveguide 11 a until they interact with one of a set of co-parallel partially reflective surfaces 15 embedded within waveguide substrate 11 a. The embedded partially reflective surfaces 15 are coupling-out elements that couple light rays 41 a, 41 b out of waveguide 11 a as light ray 42 and project an image towards a user's eye 5 located within a predetermined eye motion box.

[0013] FIG. 1D illustrates an alternative prior art waveguide system 1d including a projector 51, a collimating lens 52, and a waveguide system 10d. The waveguide system 10d includes a coupling-in prism 33 and a waveguide substrate 11b having a first major surface 13 and a second major surface 14, and a diffractive element 12 disposed therein. In system 1d, the projector 51 projects light corresponding to an image that is collimated by a lens 52 before being reflected by the coupling-in prism 33 into the waveguide 10d. Rays illustrating an exemplary field are shown in FIG. 1D. Collimated field rays 40 are coupled into the waveguide 11b such that an image 41a and a conjugate image 41b are captured between the two major surfaces 13, 14 of the waveguide 11b by total internal reflection (TIR). Light rays 41 a and 41 b propagate through waveguide 11 b until they interact with a diffractive element 12 embedded within the waveguide substrate 11 b. The embedded diffractive element 12 is a coupling-out element that couples light ray 41 a from the waveguide into light ray 42 and projects an image towards the user's eye 5 located within a predetermined eye motion box.

[0014] Figures 1A-1D show a simple case in which only a single set of embedded coupling-out elements 15 is used. However, more advanced structures with several sets of coupling-out elements can also be used. Examples of such advanced structures are shown in Figures 2A and 2B.

[0015] 2A shows configuration 2a viewed from three different directions (xy-plane, xz-plane, and yz-plane), in which two sets of coparallel partially reflective surfaces or facets 15, 35 are used, each set embedded within a respective waveguide substrate 21a, 31a, with mutually coparallel major surfaces. Light is coupled into waveguide portion 21a by prism 40, is trapped within waveguide 21a by TIR, and propagates along ray 50a until it interacts with facet 15 and is redirected in direction 50a'. The light then propagates within waveguide 31a by TIR until it interacts with facet 35 and is coupled out of waveguide portion 31a toward the user's eye 5.

[0016] 2B shows configuration 2b viewed from three different directions (xy-plane, xz-plane, and yz-plane), in which two sets of diffractive elements 12, 32 are used, each set embedded in a respective waveguide substrate 21b, 31b, with mutually co-parallel major surfaces. Light is coupled into waveguide portion 21b by prism 40, is trapped within waveguide 21b by TIR, and propagates along ray 50b until it interacts with element 12 and is redirected in direction 50b'. The light then propagates within waveguide 31b by TIR until it interacts with element 32 and is coupled out of waveguide portion 31b toward the user's eye 5.

[0017] WO 2021 / 152602, incorporated herein by reference in its entirety, describes a method for manufacturing structures 1a, 1b, 2a, and 2b that include coupling-in elements. The basic concept is based on an adhesive that is sensitive to chemical reactions or heating of the material and can therefore be easily removed without damaging the attached optical components. While the method is described below in the context of structures with reflective elements (e.g., structures 1c and 2a), the method also applies to waveguides based on diffractive elements or a combination of reflective and diffractive elements.

[0018] Heating to remove adhesive involves applying heat to the adhesive bond to soften or melt the adhesive, making it easier to remove. Heating in the context of this disclosure can involve, but is not limited to, placing the attached structure in a heating chamber (i.e., oven). This method is particularly useful for adhesives that have high heat sensitivity or that lose their adhesive properties at high temperatures. Examples of adhesives that are susceptible to heating as a means of breaking the bond include UV-curable adhesives such as Loctite 3492 and Dymax OP-24, cyanoacrylate adhesives such as Loctite 401 and Permabond 910, and acrylic adhesives such as 3M DP810 and Loctite 315. (Note: Some acrylic adhesives may have moderate heat resistance, but generally have lower resistance to high temperatures compared to silicones or certain epoxies.)

[0019] In contrast, some adhesives are designed to withstand higher temperatures, making them suitable for remaining strongly attached even when exposed to high temperatures. Examples of adhesives that are not susceptible to heat as a means of breaking the bond include epoxy adhesives such as EPO-TEK301 and Araldite 2021, and silicone adhesives such as Dow Corning 3145 RTV and Momentive TSE392-C.

[0020] Chemical etching for adhesive removal involves using chemical solutions to break down adhesive bonds by dissolving the adhesive or weakening its structure so that it can be easily wiped or washed away. This process is particularly useful when mechanical removal methods (such as scraping or peeling) are impractical or may damage the adhesive surface. The choice of chemical used in chemical etching depends on the type of adhesive and the material of the associated waveguide element. Exemplary chemicals that can be used for etching include acetone (effective for many types of adhesives, particularly acrylic, some epoxy, and cyanoacrylate adhesives), isopropyl alcohol (IPA) (suitable for less invasive adhesive removal), and specialized adhesive removers (which are formulated to accommodate specific types of adhesives without damaging the underlying material). Depending on the size of the area and the type of adhesive, chemicals can be applied to the adhesive using a brush, cloth, or by immersing the object in a chemical bath. The reaction time required for the chemical to interact with the adhesive can vary from minutes to hours, depending on the strength of the adhesive and the chemical used. These chemicals work by weakening or dissolving the molecular bonds that make up the adhesive. This process can cause the adhesive to swell, soften, or disintegrate, making it easier to remove. Once the adhesive has been sufficiently broken down, the surface of the waveguide element can be wiped, scraped, or washed away. In some cases, gentle scrubbing may be necessary to remove all residue. After the adhesive is removed, the surface can be washed to remove any remaining chemical residue. The surface is then allowed to dry.

[0021] Certain adhesives used for optical glass applications may be more susceptible to chemical etching than others, particularly when it comes to their removal. Examples of adhesives that are susceptible to chemical etching as a means of removal include acrylic adhesives such as 3M DP810 and Loctite 315 (typically susceptible to solvents such as acetone or isopropyl alcohol (IPA)), cyanoacrylate adhesives such as Loctite 401 and Permabond 910 (typically removable with acetone), UV-curable adhesives such as Loctite 3492 and Dymax OP-24 (certain formulations may be susceptible to certain solvents such as acetone or specialized adhesive removers), and certain epoxy resins such as EPO-TEK301 and Araldite 2021 (some specific formulations, especially those not designed for high chemical resistance, can be softened or removed with certain solvents or chemical etchants).

[0022] In contrast, some adhesives used for optical glass applications are typically designed to resist chemical etching, providing strong, durable adhesion and maintaining adhesive integrity even in the presence of solvents. Examples of adhesives that resist chemical etching include high-performance epoxy resins such as EPO-TEK 353ND and MasterBond EP30-2, silicone adhesives such as Dow Corning 3145 RTV and Momentive RTV108, modified acrylics such as 3M Scotch-Weld AC77 and Loctite 3301 Light Cure Adhesive, and specialty UV-curable adhesives such as Norland Optical Adhesive 61 and Dymax 3099.

[0023] "Chemical etching" in this context can also include water dissolution. Certain adhesives may be used for optical glass applications and may be more susceptible to water dissolution than other adhesives, particularly when it comes to their removal. Examples of adhesives that are susceptible to chemical etching in a water-dissolvable form as a removal means include water-soluble gums and resins, such as gum arabic and dextrin-based adhesives; polyvinyl alcohol (PVA)-based adhesives, such as Elmer's glue and bookbinding PVA; cellulose ethers, such as methylcellulose; special removable adhesives, such as 3M Removable Repositionable Tape 665 (which, while not a conventional adhesive in liquid form, uses a water-soluble adhesive that can be used for temporary positioning of optical components); and hydroxypropyl cellulose (HPC), such as Klucel™ G.

[0024] Thus, adhesives may be used in pairs or sets, with the second member of the pair or set being more susceptible to removal than the first member of the pair or set. In this manner, a stack including elements attached using the adhesive of the first member may remain attached, while elements attached using the adhesive of the second member may be removed by exposing the stack to removal conditions (e.g., chemical etching (including aqueous dissolution), heating, etc.). Adhesives may be characterized as being in a first group that are less susceptible to removal by chemical etching or heating than their counterparts in a second group that are more susceptible to removal by chemical etching or heating, as described above.

[0025] A method of fabricating a waveguide for a head-mounted display may include attaching a first set of waveguide elements with one or more adhesives from a first group (adhesives that are not sensitive to thermal or chemical removal) and attaching a second set of waveguide elements with one or more adhesives from a second group (adhesives that are sensitive to thermal or chemical removal) to form a waveguide stack. The waveguide stack may then be cut to form a waveguide structure with embedded facets or diffractive elements. Portions corresponding to the second set of waveguide elements (attached using removal-sensitive adhesives) may be removed from the waveguide structure using thermal or chemical removal, leaving only the desired first set of waveguide elements.

[0026] 3A-3E illustrate the fabrication of the waveguide stack 100. FIG.

[0027] In FIG. 3A, plates 101 are treated (e.g., coated) to make their upper or lower surfaces 101a, 101b partially reflective or diffractive. Plates 101 are then attached together at their upper or lower surfaces 101a, 101b, as shown in FIG. 3A, to form waveguide block 102. Plates 101 are attached to each other using an adhesive selected from a first group of adhesives (i.e., an adhesive that is insensitive to thermal or chemical removal). Waveguide block 102 may then be cut along plane 103 at an acute angle to upper and lower surfaces 101a, 101b. As shown in FIG. 3B, the resulting waveguide slices 11 (similar to waveguide structure 11a in FIG. 1C) each have an upper surface 13, a lower surface 14, and an internal facet 15. The resulting slices may also be cut along a plane perpendicular to plane 103 to yield the rectangular parallelepiped shape shown in FIG. 3B.

[0028] 3C-3D, block 111 and plate 112 may be attached together using an adhesive selected from a second group of adhesives (i.e., an adhesive sensitive to thermal or chemical removal) to form second block 113 having top surface 115 and bottom surface 116. Plate 112 may be selected to be relatively thin to minimize the portion of plate 112 that may remain with the final waveguide or that may need to be polished away from the final waveguide. Second block 113 may then be cut along plane 114 (e.g., parallel to top surface 115 and bottom surface 116) to form placeholder slices 117.

[0029] 3E, the waveguide slices 11 and placeholder slices 117 are alternated and attached together to form the intermediate waveguide stack 100. The waveguide slices 11 and placeholder slices 117 are attached using an adhesive selected from a second group (i.e., an adhesive that is sensitive to chemical etching or thermal removal) and therefore can be easily removed and detached from one another later.

[0030] 4A and 4B illustrate the fabrication of the mirror coupling-in segment 200. FIG.

[0031] 4A , coupling-in plates 201 are treated (e.g., coated) to make their upper surfaces 201 a reflective or diffractive, acting like mirrors. The upper (i.e., mirror) surfaces 201 a of coupling-in plates 201 can then be attached to a first surface of a sacrificial plate 202, and the lower surfaces 201 b of coupling-in plates 201 can be attached to a second surface of the sacrificial plate 202 to form a coupling-in stack 203 having upper and lower surfaces 201 a and 201 b. To enable later removal of portions of the sacrificial plate, one or both of the attachment of the upper (i.e., mirror) surfaces 201 a of coupling-in plates 201 to the first surface of the sacrificial plate 202 or the attachment of the lower surfaces 201 b of coupling-in plates 201 to the second surface of the sacrificial plate 202 can be performed using an adhesive selected from a second adhesive group (i.e., an adhesive that is sensitive to chemical etching or thermal removal). In another embodiment, the coupling-in plates 201 may be attached to one another using an adhesive selected from a second group of adhesives (i.e., an adhesive that is sensitive to chemical etching or thermal removal) to form the coupling-in stack 203. The coupling-in stack 203 may then be cut along a plane 204 at an acute angle to the upper and lower surfaces 201b, 201b. As shown in FIG. 4B, the resulting coupling-in stack segment 200 includes multiple coupling-in plane segments that each become a prism 33.

[0032] 5A-5C illustrate the fabrication of a waveguide 10 similar to waveguide 10c described above.

[0033] In FIG. 5A , the waveguide stack 100 is attached to a coupling-in stack segment 200 to form a waveguide structure 250. Specifically, the coupling-in planar segments 33 in the coupling-in stack segment 200 are aligned with and attached to each waveguide slice 10 in the waveguide stack 100 using an adhesive selected from a first group of adhesives (i.e., an adhesive that is insensitive to chemical etching or thermal removal). The coupling-in planar segments 33 may also be permanently attached to the placeholder plate portion 112 of the plate holder slice 117, but most of the placeholder material is removed in the form of the placeholder block portion 111. The waveguide structure 250 may then be cut along a plane 253 that generally continues through the lower surface 14. Therefore, the plane 253 is substantially parallel to the upper and lower surfaces 13 and 14 to form a waveguide structure segment 260, as shown in FIG. 5B .

[0034] 5C, the portions corresponding to the placeholder slice 117 and the sacrificial plate 202 (i.e., any portions attached using an adhesive selected from the second adhesive group) are removed from the segment 260 by chemical etching or heating to reach the waveguide 10c. Any remaining unwanted material, such as the remaining portion of the plate 112, can be left in place because its relatively small size does not significantly affect the performance of the resulting waveguide 10c. Alternatively, the unwanted material can be polished away, for example, in the process of polishing the lower surface 14 of the waveguide 11c. Because the size of this portion 112 is not very large compared to the entire waveguide, the main surface 14 of the waveguide 11c dominates the polishing process, and the main surface 14 is uniform and co-parallel with the upper main surface 13 with high precision.

[0035] FIG. 6 illustrates an alternative embodiment to the embodiment of FIGS. 5A-5C. In the arrangement of FIG. 6, spacer slice 118 remains as part of final waveguide 10d. If spacer slice 118 is fabricated to have coparallel surfaces with very high precision, the attachment between spacer slice 118 and waveguide 11c can be made with an adhesive in the first group (i.e., an adhesive that is not sensitive to the removal process) that has a sufficiently low refractive index so that light can bounce (TIR) ​​within waveguide 11c. In this case, forming spacer slice 118 from two different parts 111 and 112 (as placeholder slice 117 in FIG. 3C) is unnecessary because spacer slice 118 remains entirely within final waveguide 10d and can be fabricated from a single part.

[0036] The novel techniques disclosed herein may also be applied to more advanced configurations, as illustrated in Figures 7A-7J with reference to WO2023 / 026266A1, the entire contents of which are incorporated herein by reference.

[0037] In FIG. 7A , the top surface 301 a or the bottom surface 301 b of the first waveguide plate 301 is treated (e.g., coated) to make the top surface 301 a or the bottom surface 301 b partially reflective or diffractive. The first waveguide plate 301 may then be attached at the top surface 301 a or the bottom surface 301 b using an adhesive selected from a first adhesive group (i.e., an adhesive that is insensitive to chemical etching or thermal removal) to form the first waveguide block 300. The first waveguide block 300 may then be cut along a first plane 303 at an acute angle to the top surface 301 a and the bottom surface 301 b. The resulting one or more first waveguide blocks 310 have internal facets 15. The resulting one or more waveguide blocks 310 may also be cut along a plane perpendicular to the plane 303 to produce the cubic shape shown in FIG. 7B .

[0038] In Figure 7C, the waveguide slices 11 are configured similarly to those described above with reference to Figures 3A and 3B and are attached together using an adhesive selected from a first group of adhesives (i.e., an adhesive that is not sensitive to chemical etching or thermal removal) to form a waveguide stack 500.

[0039] The top surface 41 a or the bottom surface 41 b of the third waveguide plate 410 can be treated to make the top surface 410 a or the bottom surface 410 b partially reflective or diffractive. In the illustrated embodiment of FIG. 7C , the top and bottom third waveguide plates 410 are half the thickness of the third waveguide plate 410 between the top and bottom. The top and bottom third waveguide plates 410 can be prefabricated to be thinner, or more practically, the top and bottom third waveguide plates will be thinner when cut along plane 603, as described above with reference to FIG. 7E . The third waveguide plate 410 can then be attached at the top surface 410 a or the bottom surface 410 b using an adhesive selected from a first adhesive group (i.e., an adhesive that is not susceptible to chemical etching or thermal removal) to form the mixer block 400.

[0040] The first waveguide block 310 can be attached to the mixer block 400, which is attached to the waveguide stack 500, using an adhesive selected from a first group of adhesives (i.e., an adhesive that is insensitive to chemical etching or thermal removal), to form a composite waveguide block 600, as shown in FIG. 7D. As illustrated in FIG. 7E, the composite waveguide block 600 can be cut along a plane 603 corresponding to the top and bottom surfaces 13 and 14 of the second waveguide slice 11 to form a third waveguide slice as shown in FIG. 7F. The mixer block 400 is aligned with the waveguide stack 500 so that the mixer surface or homogenizer 440 appears to be approximately half-recessed (in the Z direction) relative to the waveguide slice 11, as shown in FIG. 7F. Generally, an optical mixer or homogenizer such as homogenizer 440 corresponds to a symmetric beam multiplier region having n internal planar beam splitters, where n is a positive integer. Each beam splitter is internal to the resulting LOE 810 and parallel to the major surfaces 13, 14. Examples of optical mixers or homogenizers such as homogenizer 440 are described in detail, for example, in U.S. Patent Application No. 17 / 420,675 to Ronen et al. (published as Application No. US2022 / 0099885). Accordingly, optical mixers such as homogenizer 440 will not be described in further detail herein. The individual slices 11 can be finely polished at this stage so that the major surfaces 13 and 14 of each waveguide slice 11 are parallel to one another with high precision.

[0041] 7F, the waveguide slices 11 may then be attached in a stack with alternating placeholder plates 710 using an adhesive selected from a second group (i.e., an adhesive that is sensitive to chemical etching or thermal removal) to form a second waveguide stack 700. The second waveguide stack 700 may then be cut to form openings for the coupling-in stack segments 200.

[0042] 7G illustrates a top view (i.e., a view rotated 90 degrees from the view of FIG. 7F) of the second waveguide stack 700. The first waveguide stack 310 of the stack 700 is cut along a plane 302 that is perpendicular to the upper and lower surfaces 13, 14 of the third waveguide slice 11, as shown in FIG. 7H, and intersects with an edge 303 where the first waveguide stack 310 joins with the mixer block 400 to form an aperture surface 301 to which the coupling-in stack segment 200 can be attached. The coupling-in stack segment 200 is attached to the aperture surface 301 with an adhesive selected from a first group (i.e., an adhesive that is insensitive to chemical etching or thermal removal) to form the third waveguide stack 800.

[0043] 7J, waveguide stack 800 may be cut along plane 803 corresponding to bottom surface 14 of second waveguide slice 11 to form waveguide slice 810. Portions of waveguide slice 810 corresponding to placeholder plate 710 or sacrificial plate 202 (i.e., any portions attached using an adhesive selected from the second group of adhesives) may be removed by at least one of chemical etching or heating. The resulting waveguide structure corresponds to structure 2a of FIG. 2A.

[0044] definition The following includes definitions of selected terms used herein. The definitions include various examples or forms of components that fall within the scope of the term and that may be used for implementation. The examples are not intended to be limiting. Both singular and plural forms of a term may be within the scope of the definition.

[0045] An "operable connection," or a connection in which entities are "operably connected," is a connection in which signals, physical communications, or logical communications may be sent or received. Typically, an operable connection includes a physical interface, an electrical interface, or a data interface; however, it should be noted that an operable connection may include different combinations of these or other types of connections sufficient to enable operable control. For example, two entities may be operably connected by being able to communicate signals directly with each other or through one or more intermediary entities, such as processors, operating systems, logic, software, or other entities. An operable connection may be created using a logical or physical communication channel.

[0046] The terms "includes" or "including," to the extent that they are used in the detailed description or the claims, are intended to be inclusive in the same manner as the term "comprising," as that term is interpreted when used as a transitional term in a claim. Furthermore, the term "or," to the extent that they are used in the detailed description or the claims (e.g., A or B), is intended to mean "A or B, or both." Where applicant intends to indicate "A or B only, but not both," the term "A or B only, but not both" is used. Accordingly, use of the term "or" herein is inclusive, not exclusive. See Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995).

[0047] While exemplary systems, methods, etc. have been illustrated by way of setting forth examples, and the examples have been described in considerable detail, it is not the applicant's intention to limit the scope to such details, or to be limiting in any way. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the systems, methods, etc. described herein. Additional advantages and modifications will be readily apparent to those skilled in the art. Accordingly, the present invention is not limited to the specific details, representative apparatus, and illustrative examples shown and described. Accordingly, the present application is intended to cover such alterations, modifications, and variations as fall within the scope of the appended claims. Moreover, the foregoing description is not intended to limit the scope of the present invention. Rather, the scope of the present invention is to be determined by the appended claims and their equivalents.

Claims

1. 1. A method for fabricating a waveguide, comprising: treating a top or bottom surface of a waveguide plate to make said top or bottom surface partially reflective or diffractive; attaching the waveguide plate at the top surface or the bottom surface using an adhesive selected from a first group of adhesives to form a waveguide block having top and bottom surfaces; cutting the waveguide block along a plane at an acute angle to the top and bottom surfaces of the waveguide block to form a waveguide slice having an internal facet; attaching a first plate to a front surface of the first block to form a second block having an upper surface and a lower surface; cutting the second block to form placeholder slices; alternating the waveguide slices and attaching them to the placeholder slices using an adhesive selected from a second group of adhesives to form a waveguide stack; The method, wherein the second group of adhesives comprises adhesives that are more susceptible to chemical etching or thermal removal than each adhesive in the first group of adhesives.

2. treating a top surface of a coupling-in plate to make the top surface of the coupling-in plate reflective or diffractive; adhering the coupling-in plates together using an adhesive selected from the second group of adhesives to form a coupling-in stack having an upper surface and a lower surface; 2. The method of claim 1, comprising: cutting the coupling-in stack along a plane at an acute angle to the upper and lower surfaces of the coupling-in stack to form one or more coupling-in stack segments including a coupling-in plane segment.

3. treating a top surface of a coupling-in plate to make the top surface of the coupling-in plate reflective or diffractive; adhering the upper surface of the coupling-in plate to a first surface of a sacrificial plate using an adhesive selected from the first group of adhesives and adhering the lower surface of the coupling-in plate to a second surface of the sacrificial plate using an adhesive selected from the second group of adhesives to form a coupling-in stack having an upper surface and a lower surface; 2. The method of claim 1, comprising: cutting the coupling-in stack along a plane at an acute angle to the upper and lower surfaces of the coupling-in stack to form one or more coupling-in stack segments including a coupling-in plane segment.

4. 4. The method of claim 2 or 3, comprising attaching the coupling-in planar segments to respective waveguide slices in the waveguide stack using an adhesive selected from the first group of adhesives to form a waveguide structure.

5. The method of claim 4 , comprising cutting the waveguide structure along planes parallel to the top and bottom surfaces of the waveguide structure to form one or more waveguide structure segments.

6. 6. The method of claim 5, comprising removing from one or more of the waveguide structure segment portions attached using an adhesive selected from the second group of adhesives by at least one of chemical etching or heating.

7. 1. A method for fabricating a waveguide, comprising: creating a waveguide stack in which at least some elements are attached using an adhesive selected from a first group of adhesives; treating a top surface of a coupling-in plate to make the top surface of the coupling-in plate reflective or diffractive; adhering the coupling-in plates together or to a sacrificial plate using an adhesive selected from a second group of adhesives to form a coupling-in stack having an upper surface and a lower surface; cutting the coupling-in stack along a plane at an acute angle to the top and bottom surfaces of the coupling-in stack to form one or more coupling-in stack segments including a coupling-in plane segment; attaching the coupling-in planar segments to respective waveguide slices in the waveguide stack using an adhesive selected from the first group of adhesives to form a waveguide structure; forming the second group of adhesives comprising adhesives that are more susceptible to chemical etching or thermal removal than each adhesive in the first group of adhesives; cutting the waveguide structure along planes parallel to the top and bottom surfaces of the waveguide structure to form waveguide structure segments; and removing from one or more of the waveguide structure segment portions attached using an adhesive selected from the second group of adhesives by at least one of chemical etching or heating.

8. said generating said waveguide stack further comprising: treating a top or bottom surface of a waveguide plate to make said top or bottom surface partially reflective or diffractive; attaching the waveguide plate at the top surface or the bottom surface using the adhesive selected from a first group of adhesives to form a first block having a top surface and a bottom surface; cutting the first block along a plane at an acute angle to the top and bottom surfaces of the first block to form a waveguide slice having an internal facet; cutting the second block to form spacer slices; and c. alternating the waveguide slices and attaching them to the spacer slices to form the waveguide stack.

9. 9. The method of claim 8, further comprising polishing the top and bottom surfaces of the waveguide slice, the polishing comprising removing a portion of the first plate that remains adhered to the top surface.

10. 1. A method for fabricating a waveguide, comprising: treating a top or bottom surface of a first waveguide plate to make the top or bottom surface of the first waveguide plate partially reflective or diffractive; attaching the first waveguide plate at the top surface or the bottom surface using an adhesive selected from a first group of adhesives to form a first waveguide block; cutting the first waveguide block along a first plane at an acute angle to the top and bottom surfaces to form one or more first waveguide slices having internal facets; treating a top or bottom surface of a second waveguide plate to make the top or bottom surface of the second waveguide plate partially reflective or diffractive; attaching the second waveguide plate at the top surface or the bottom surface using an adhesive selected from the first group of adhesives to form a second waveguide block having top and bottom surfaces; cutting the second waveguide block along a third plane at an acute angle to the top and bottom surfaces of the second waveguide block to form one or more second waveguide slices having internal facets; adhering the waveguide slices using an adhesive selected from the first group of adhesives to form a waveguide stack; treating a top or bottom surface of a third waveguide plate to make the top or bottom surface of the third waveguide plate partially reflective or diffractive; attaching the third waveguide plate at the top surface or the bottom surface using an adhesive selected from the first group of adhesives to form a mixer block having top and bottom surfaces; attaching at least one of the first waveguide slices to the mixer block and attaching the mixer block to the waveguide stack to form a composite waveguide block; cutting the composite waveguide block along a plane corresponding to the top surface or the bottom surface of the second waveguide slice to form a third waveguide slice; and alternating the third waveguide slices and adhering them to a placeholder plate using an adhesive selected from a second group of adhesives to form a second waveguide stack, the second group of adhesives being comprised of adhesives that are more susceptible to chemical etching or thermal removal than each adhesive in the first group of adhesives.

11. 11. The method of claim 10, comprising cutting the at least one of the first waveguide slices along a plane that is perpendicular to a top surface and a bottom surface of the third waveguide slice and that intersects an edge where the at least one of the first waveguide slices joins the mixer block to form an aperture surface.

12. treating a top surface of a coupling-in plate to make the top surface of the coupling-in plate reflective or diffractive; adhering the upper surfaces of the coupling-in plates together using an adhesive selected from the second group of adhesives to form a coupling-in stack having an upper surface and a lower surface; 12. The method of claim 11, comprising: cutting the coupling-in stack along a plane at an acute angle to the top and bottom surfaces of the coupling-in stack to form one or more coupling-in stack segments including a coupling-in plane segment.

13. treating a top surface of a coupling-in plate to make the top surface of the coupling-in plate reflective or diffractive; adhering the upper surface of the coupling-in plate to a first surface of a sacrificial plate using an adhesive selected from the first group of adhesives and adhering the lower surface of the coupling-in plate to a second surface of the sacrificial plate using an adhesive selected from the second group of adhesives to form a coupling-in stack having an upper surface and a lower surface; 12. The method of claim 11, comprising: cutting the coupling-in stack along a plane at an acute angle to the top and bottom surfaces of the coupling-in stack to form one or more coupling-in stack segments including a coupling-in plane segment.

14. attaching a coupling-in stack segment to the aperture surface with an adhesive selected from the first group to form a third waveguide stack; cutting the third waveguide stack along a plane corresponding to the bottom surface of the second waveguide slice to form a fourth waveguide slice; and removing the portion attached using an adhesive selected from the second group of adhesives by at least one of chemical etching or heating.

15. 1. A method of manufacturing a waveguide for a head mounted display, comprising: attaching a first set of waveguide elements with one or more adhesives that are sensitive to thermal or chemical removal and attaching a second set of waveguide elements with one or more adhesives that are not sensitive to thermal or chemical removal to form a waveguide stack; cutting the waveguide stack to form a waveguide structure with embedded facets or diffractive elements; and removing portions corresponding to the first set of waveguide elements using thermal or chemical removal, while portions corresponding to the second set of waveguide elements remain attached.

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