Manufacturing method for a waveguide

Abstract

A method for manufacturing a waveguide for a head-mounted display may include: bonding a first set of waveguide elements using one or more adhesives sensitive to heat or chemical removal, and bonding a second set of waveguide elements using one or more adhesives insensitive to heat or chemical removal to form a waveguide stack; cutting the waveguide stack to form a waveguide structure with embedded facets or diffractive elements; and using heat or chemical removal to remove portions corresponding to the first set of waveguide elements while portions corresponding to the second set of waveguide elements remain bonded.

Description

Manufacturing Method for Waveguide The present invention relates to the field of near-eye display systems such as head-mounted displays. More specifically, the present invention relates to a manufacturing method for waveguides for near-eye displays (NEDs). Consumer demand for improved human-machine interfaces has led to increased interest in high-quality image head-mounted displays (HMDs) or near-eye displays commonly referred to as smart glasses. These devices can provide virtual reality (VR) experiences or augmented reality (AR) experiences, enhancing the way users interact with digital content and their surrounding environment. Consumers seek better image quality, immersive experiences, and greater comfort when using HMDs. Consumers expect displays to have high resolution, vivid colors, and minimal distortion to create a realistic and enjoyable viewing experience. Since users often wear these devices for long periods, comfort is also a key factor. Consumers expect lightweight, stylish designs that are less obtrusive and more convenient to wear in various scenarios. Smaller devices also offer improved portability, making these devices easier to carry and use in different environments. Therefore, the demand for higher-performance but smaller and more compact HMDs is growing. A key component in near-eye display systems is the waveguide. A waveguide is a device that guides light from the system's image projector to the user's eyes. Waveguides rely on total internal reflection along the main surface within the device to propagate light. Improving the performance of miniaturized waveguides poses certain challenges. As the performance of waveguides increases, the waveguides and their manufacturing processes become more complex. Part of this complexity arises because the features that improve performance also increase the complexity of the waveguides. In addition, making waveguides smaller often complicates their production. Smaller components are more difficult to manage and more difficult to reliably reproduce. The increased manufacturing complexity often leads to lower yields and higher costs, which tend to reduce adoption rates. Therefore, innovative waveguide manufacturing processes are needed that will reduce manufacturing complexity while maintaining or improving performance and compactness. The present invention relates to a method for manufacturing a waveguide for a head-mounted display. The novel method may include: using one or more adhesives sensitive to thermal or chemical removal to bond a first set of waveguide elements, and using one or more adhesives insensitive to thermal or chemical removal to bond a second set of waveguide elements to form a waveguide stack, cutting the waveguide stack to form a waveguide structure having an embedded facet or diffraction element, and using thermal or chemical removal to remove the portion corresponding to the first set of waveguide elements while the portion corresponding to the second set of waveguide elements remains bonded to form the desired waveguide. The drawings incorporated herein and forming a part of the specification illustrate various example systems, methods, etc., which illustrate various example embodiments of aspects of the present invention. It will be understood that the element boundaries shown in the figures (e.g., boxes, groups of boxes, or other shapes) represent one example of a boundary. One of ordinary skill 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, the elements may not be drawn to scale. 10, 11c: Waveguide 100, 500, 800: Waveguide stack 101, 112: Plate 101a, 115, 201a, 301a, 41a, 410a: Top surface 101b, 116, 201b, 301b, 41b, 410b: Bottom surface 102, 300, 310: Waveguide block 103, 114, 204, 302, 303, 603, 803, xy, xz, yz: Plane 10a, 10b, 10c, 10d: Waveguide system 11, 810: Waveguide slice 111: Block 113: Second block 117: Occupancy slice 118: Spacing slice 11a, 11b, 21a, 21b, 31a, 31b: Waveguide substrate 12, 32: Diffraction element 13, 14: Main surface 15, 35: Partially reflective surface (facet) 1a, 1c: Prior art waveguide system 1b, 1d: Prior art alternative waveguide system 200: Coupling-in stack segment 201: Coupling-in plate 202: Sacrificial plate 203: Coupling-in stack 250: Waveguide structure 260: Waveguide structure segment 2a, 2b: Configuration 30, 33: Coupling-in prism 301: First waveguide plate 40: Collimated field ray 400: Mixer block 410: Third waveguide plate 41a: Image 41b: Conjugate image 42, 50a, 50b: Light rays 440: Mixer surface (homogenizer) 5: Eye 50a', 50b', X, Z: Directions 51: Projector 52: Collimating lens 600: Composite waveguide block 700: Second waveguide stack 710: Spacer plate 810: Lightguide optical element (LOE) Figure 1A shows a prior art waveguide system with reflective facets. Figure 1B shows a prior art waveguide system with refractive elements. Figure 1C shows a prior art waveguide system with reflective facets and a mirror input. Figure 1D shows a prior art waveguide system with refractive elements and a mirror input. Figure 2A shows a prior art two - dimensional waveguide system with reflective facets. Figure 2B shows a prior art two - dimensional waveguide system with refractive elements. Figures 3A to 3E show a manufacturing method for a waveguide stack. Figures 4A and 4B show a manufacturing method for a mirror coupling section. Figures 5A to 5C show a manufacturing method for a waveguide. Figure 6 shows an alternative manufacturing method for a waveguide. Figures 7A to 7I show a manufacturing method for a two - dimensional waveguide. FIG. 1A shows a prior art waveguide system 1a, which includes a projector 51, a collimating lens 52, and a waveguide system 10a. The waveguide system 10a includes an input prism 30, a waveguide substrate 11a having a first major surface 13 and a second major surface 14, and a partially reflective surface or facet 15 disposed within the waveguide substrate 11a. In the prior art waveguide system 1a, the projector 51 projects light corresponding to an image, and the light is collimated by the lens 52 before entering the waveguide system 10a through the input prism 30. Light rays describing an exemplary field are shown in FIG. 1A. The collimated field light rays 40 are coupled into the waveguide substrate 11a such that the image 41a and the conjugate image 41b are captured between the two major surfaces 13, 14 of the waveguide substrate 11a by total internal reflection (TIR). The light rays 41a and 41b propagate through the waveguide substrate 11a until they interact with one of a set of co-parallel partially reflective surfaces 15 embedded within the waveguide substrate 11a. The embedded partially reflective surface 15 is an output coupler that couples the light rays 41a, 41b out of the waveguide substrate 11a as light rays 42 and projects the image onto the user's eye 5 located within a predetermined eye box. FIG. 1B shows a prior art alternative waveguide system 1b, which includes a projector 51, a collimating lens 52, and a waveguide system 10b. The waveguide system 10b includes an input prism 30, a waveguide substrate 11b having a first major surface 13 and a second major surface 14, and a diffraction element 12 disposed within the waveguide substrate 11b. In the prior art alternative waveguide system 1b, the projector 51 projects light corresponding to an image, and the light is collimated by the lens 52 before entering the waveguide system 10b through the input prism 30. Light rays describing an exemplary field are shown in FIG. 1B. The collimated field light rays 40 are coupled into the waveguide substrate 11b such that the image 41a and the conjugate image 41b are captured by total internal reflection (TIR) between the two major surfaces 13, 14 of the waveguide substrate 11b. The light rays 41a and 41b propagate through the waveguide substrate 11b until they interact with the diffraction element 12 embedded within the waveguide substrate 11b. The embedded diffraction element 12 is an output coupler that couples the light ray 41a out of the waveguide as the light ray 42 and projects the image onto the user's eye 5 located within a predetermined eye box. As shown in FIGS. 1C and 1D, in order to minimize the size of the underlying near-eye display, it is generally necessary to place the projector at a specific position relative to the waveguide. This can be achieved by coating the input prism 33 with a reflective coating and arranging the components as shown. Figure 1C shows a prior art waveguide system 1c, which includes a projector 51, a collimating lens 52, and a waveguide system 10c. The waveguide system 10c includes an input prism 33, a waveguide substrate 11a having a first major surface 13 and a second major surface 14, and a partially reflective surface or facet 15 disposed in the waveguide substrate 11a. In the prior art waveguide system 1c, the projector 51 projects light corresponding to an image, which is collimated by the lens 52 before being reflected by the input prism 33 into the waveguide system 10c. Light rays describing an exemplary field are shown in Figure 1C. The collimated field rays 40 are coupled into the waveguide substrate 11a such that the image 41a and the conjugate image 41b are captured between the two major surfaces 13, 14 of the waveguide substrate 11a by total internal reflection (TIR). The rays 41a and 41b propagate through the waveguide substrate 11a until they interact with one of a set of co-parallel partially reflective surfaces 15 embedded within the waveguide substrate 11a. The embedded partially reflective surface 15 is an output coupling element that couples the rays 41a, 41b out of the waveguide substrate 11a as rays 42 and projects the image onto the user's eye 5 located within a predetermined eye box. Figure 1D shows a prior art alternative waveguide system 1d, which includes a projector 51, a collimating lens 52, and a waveguide system 10d. The waveguide system 10d includes an input prism 33, a waveguide substrate 11b having a first major surface 13 and a second major surface 14, and a diffraction element 12 disposed in the waveguide substrate 11b. In the prior art alternative waveguide system 1d, the projector 51 projects light corresponding to an image, which is collimated by the lens 52 before being reflected by the input prism 33 into the waveguide system 10d. Light rays describing an exemplary field are shown in Figure 1D. The collimated field rays 40 are coupled into the waveguide substrate 11b such that the image 41a and the conjugate image 41b are captured between the two major surfaces 13, 14 of the waveguide substrate 11b by total internal reflection (TIR). The rays 41a and 41b propagate through the waveguide substrate 11b until they interact with the diffraction element 12 embedded within the waveguide substrate 11b. The embedded diffraction element 12 is an output coupling element that couples the ray 41a out of the waveguide as ray 42 and projects the image onto the user's eye 5 located within a predetermined eye box. Figures 1A through 1D show a simple case using only a single set of embedded output coupling elements 15. However, more advanced structures with multiple sets of output coupling elements can also be used. Examples of such advanced structures are shown in Figures 2A and 2B. Figure 2A shows configuration 2a as viewed from three different directions (xy plane, xz plane, and yz plane), where two sets of mutually parallel partial reflection surfaces or facets 15, 35 are used, each set being embedded in corresponding waveguide substrates 21a, 31a that have mutually parallel major surfaces. Light is coupled into waveguide substrate 21a through prism 40 and is captured in waveguide substrate 21a by TIR and propagates according to ray 50a until the light interacts with facet 15 and is redirected in direction 50a'. Then, the light propagates in waveguide substrate 31a by TIR until the light interacts with facet 35 and is coupled out of waveguide substrate 31a and to the user's eye 5. Figure 2B shows configuration 2b as viewed from three different directions (xy plane, xz plane, and yz plane), where two sets of diffraction elements 12, 32 are used, each set being embedded in corresponding waveguide substrates 21b, 31b that have mutually parallel major surfaces. Light is coupled into waveguide substrate 21b through prism 40 and is captured in waveguide substrate 21b by TIR and propagates according to ray 50b until the light interacts with diffraction element 12 and is redirected in direction 50b'. Then, the light propagates in waveguide substrate 31b by TIR until the light interacts with diffraction element 32 and is coupled out of waveguide substrate 31b and to the user's eye 5. Referring to WO2021 / 152602 (the entire content of which is incorporated herein by reference), a method for manufacturing structures 1a, 1b, 2a, and 2b including coupling elements is described. The basic concept is based on an adhesive that is sensitive to chemical reactions or heating of materials and can thus be easily removed without damaging the joined optical components. The method is described below in the context of configurations having reflective elements (e.g., configuration 1c and configuration 2a), but the method is also applicable to waveguides based on diffraction elements or combinations of reflective elements and diffraction elements. Heating for removing adhesives involves applying heat to the adhesive joint to soften or melt the adhesive, making it easier to remove. Heating in the context of the present invention may involve, but is not limited to, placing the joined structure in a heating chamber (i.e., an oven). This method is particularly useful for adhesives that are highly thermosensitive or lose their adhesive properties at high temperatures. Examples of adhesives that are susceptible to heating as a means of breaking the joint include: ultraviolet (UV) curable adhesives such as Loctite 3492 and Dymax OP-24, cyanoacrylate adhesives such as Loctite 401 and Permaband 910, and acrylic adhesives such as 3M DP810 and Loctite 315. (Note: Some acrylic adhesives may have moderate temperature resistance, but they generally have poorer tolerance to high temperatures compared to silicone or certain epoxy resins.) In contrast, some adhesives are designed to withstand higher temperatures, making them suitable for maintaining a strong bond even when exposed to high temperatures. Examples of adhesives that are not susceptible to heating as a means of breaking the joint include: epoxy adhesives such as EPO-TEK 301 and Araldite 2021, and silicone adhesives such as Dow Corning 3145 RTV and Momentive TSE392-C. Chemical etching for removing adhesives involves using chemical solutions to break the bond of the adhesive, either by dissolving the adhesive or weakening its structure so that the adhesive can be easily wiped or rinsed off. This process is particularly useful when mechanical removal methods, such as scraping or peeling, are impractical or may damage the bonding surface. The choice of chemicals used in chemical etching depends on the type of adhesive and the material of the waveguide component involved. Example chemicals that can be used for etching include: acetone (effective for many types of adhesives, especially for acrylics and some epoxies as well as cyanoacrylate adhesives), isopropyl alcohol (IPA) (suitable for removing less aggressive adhesives), and specialized adhesive removers (these removers are formulated to remove specific types of adhesives without damaging the underlying material). Depending on the size of the area and the type of adhesive, the chemicals can be applied to the adhesive using a brush, cloth, or by dipping the object into a chemical bath. Depending on the strength of the adhesive and the chemicals used, the reaction time required for the chemicals to interact with the adhesive can vary from a few minutes to several hours. These chemicals work by weakening or dissolving the molecular bonds that make up the adhesive. This process causes the adhesive to swell, soften, or decompose, making it easier to remove. Once the adhesive has been sufficiently decomposed, it can be wiped, scraped, or rinsed off the surface of the waveguide component. In some cases, gentle scrubbing may be required to remove all the residues. After removing the adhesive, the surface can be rinsed to remove any remaining chemical residues. Then the surface is allowed to dry. Certain adhesives used in optical glass applications may be more susceptible to chemical etching than others, especially when removing the adhesive. Examples of adhesives that are susceptible to chemical etching as a means of removal include: acrylic-based adhesives (usually susceptible to solvents such as acetone or isopropyl alcohol (IPA)), e.g., 3M DP810 and Loctite 315; cyanoacrylate adhesives (usually can also be removed using acetone), e.g., Loctite 401 and Permabond 910; UV-curing adhesives (certain formulations may be susceptible to specific solvents such as acetone or specialized adhesive removers), e.g., Loctite 3492 and Dymax OP-24; certain epoxies (some specific formulations, especially those not designed for high chemical resistance, can be softened or removed with specific solvents or chemical etchants), e.g., EPO-TEK 301 and Araldite 2021. In contrast, some adhesives for optical glass applications are generally resistant to chemical etching and are designed to provide a strong, durable bond that maintains its integrity even in the presence of solvents. Examples of adhesives resistant to chemical etching include: high-performance epoxies such as EPO-TEK 353ND and Master Bond EP30-2; silicone adhesives such as Dow Corning 3145 RTV and Momentive RTV108; modified acrylic resins such as 3M Scotch-Weld AC77 and Loctite 3301 light-curing adhesives; and specialty UV-curing adhesives such as Norland Optical Adhesive 61 and Dymax 3099. "Chemical etching" as used herein may also include water dissolution. Certain adhesives can be used in optical glass applications and are more susceptible to water dissolution, particularly when removing the adhesive. Examples of adhesives susceptible to chemical etching in the form of water dissolution as a means of removal 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 machine PVA; cellulose ethers such as methyl cellulose; specialty removable adhesives such as 3M Removable Repositionable Tape 665 (although not a traditional adhesive in liquid form, the tape uses a water-soluble adhesive that can be used for the temporary positioning of optical components); and hydroxypropyl cellulose (HPC) such as Klucel TM G. Thus, adhesives can be used in pairs or groups. The second member in a pair or group is more easily removable than the first member in the pair or group. In this way, a stack of elements joined with the first member adhesive can remain joined, while elements joined with the second member adhesive can be removed by exposing the stack to removal conditions such as chemical etching (including water dissolution), heating, etc. As described above, adhesives can be characterized as belonging to a first group, which are less easily removable by chemical etching or heating compared to corresponding adhesives in a second group that are more easily removable by chemical etching or heating. A method of manufacturing a waveguide for a head-mounted display may include: joining a first set of waveguide elements with one or more adhesives from a first set (adhesives insensitive to thermal or chemical removal), and joining a second set of waveguide elements with one or more adhesives from a second set (adhesives sensitive to thermal or chemical removal) to form a waveguide stack. The waveguide stack may then be cut to form a waveguide structure having embedded facets or diffractive elements. Portions corresponding to the second set of waveguide elements (joined with adhesives sensitive to removal) may be removed from the waveguide structure using thermal or chemical removal, leaving only the desired first set of waveguide elements. Figures 3A through 3E illustrate the manufacture of waveguide stack 100. In Figure 3A, plate 101 is processed (e.g., coated) such that its top surface 101a or bottom surface 101b is capable of partial reflection or diffraction. Then, as shown in Figure 3A, plates 101 are joined together at top surface 101a or bottom surface 101b to form waveguide block 102. The plates 101 are joined to each other using an adhesive selected from a first set of adhesives (i.e., adhesives insensitive to thermal or chemical removal). The waveguide block 102 may then be cut along a plane 103 that is at an acute angle relative to top surface 101a and bottom surface 101b. As shown in Figure 3B, each of the resulting waveguide slices 11 (similar to waveguide substrate 11a of Figure 1C) has a top surface 13, a bottom surface 14, and an internal facet 15. The resulting slices may also be cut along a plane perpendicular to plane 103 to obtain a cuboid shape as shown in Figure 3B. In Figures 3C through 3D, block 111 and plate 112 may be joined together using an adhesive selected from a second set of adhesives (i.e., adhesives sensitive to thermal or chemical removal) to form a second block 113 having a top surface 115 and a bottom surface 116. Plate 112 may be selected to be relatively thin to minimize portions of plate 112 that may be retained with the final waveguide or that may need to be polished off of the final waveguide. The second block 113 may then be cut along a plane 114 (e.g., parallel to top surface 115 and bottom surface 116) to form placeholder slices 117. In Figure 3E, waveguide slices 11 and placeholder slices 117 are alternated and joined together to form an intermediate waveguide stack 100. The waveguide slices 11 and placeholder slices 117 are joined using an adhesive selected from the second set (i.e., adhesives sensitive to chemical etching or heating removal) and can thus be easily removed and separated from each other at a later time. Figures 4A and 4B illustrate the manufacture of coupled-in stack segment 200. In FIG. 4A, the input plate 201 is processed (e.g., coated) such that its top surface 201a can reflect or diffract to act like a mirror. Then, the top (i.e., mirror) surface 201a of the input plate 201 can be bonded to the first surface of the sacrificial plate 202 and the bottom surface 201b of the input plate 201 can be bonded to the second surface of the sacrificial plate 202 to form an input stack 203 having a top surface 201a and a bottom surface 201b. To allow for subsequent removal of the sacrificial plate portion, an adhesive selected from the second group of adhesives (i.e., an adhesive sensitive to chemical etching or heating removal) can be used to perform one or both of the following: bond the top (i.e., mirror) surface 201a of the input plate 201 to the first surface of the sacrificial plate 202, or bond the bottom surface 201b of the input plate 201 to the second surface of the sacrificial plate 202. In another embodiment, the input plates 201 can be bonded to each other using an adhesive selected from the second group of adhesives (i.e., an adhesive sensitive to chemical etching or heating removal) to form the input stack 203. Then, the input stack 203 can be cut along a plane 204 that is at an acute angle with respect to the top surface 201 and the bottom surface 201b. As shown in FIG. 4B, each of the resulting input stack segments 200 includes a plurality of input plane segments that will become the input prism 33. FIGS. 5A-5C illustrate the fabrication of a waveguide 10 similar to the waveguide system 10c described above. In FIG. 5A, the waveguide stack 100 is bonded to the input stack segment 200 to form a waveguide structure 250. Specifically, the input prism 33 in the input stack segment 200 is aligned and bonded to the corresponding waveguide slice 11 in the waveguide stack 100 using an adhesive selected from the first group of adhesives (i.e., an adhesive insensitive to chemical etching or heating removal). The input prism 33 can also be permanently bonded to the placeholder plate portion 112 of the placeholder slice 117, but most of the placeholder material will be removed in the form of the placeholder block portion 111. Then, the waveguide structure 250 can be cut along a plane 253 that generally follows the bottom surface 14. As shown in FIG. 5B, the plane 253 is thus substantially parallel to the top surface 13 and the bottom surface 14 to form a waveguide structure segment 260. In FIG. 5C, portions corresponding to the placeholder slice 117 and the sacrificial plate 202 (i.e., any portion joined using an adhesive selected from the second group of adhesives) have been removed from the waveguide structure segment 260 by chemical etching or heating to obtain the waveguide system 10c. Any remaining unwanted material (e.g., the remaining portion of the plate 112) can be left in place because its relatively small size will not significantly affect the performance of the resulting waveguide system 10c. Alternatively, for example, during the process of polishing the bottom surface 14 of the polished waveguide 11c, the unwanted material can be polished. Since the size of this portion 112 is not very large compared to the entire waveguide, the main surface 14 of the waveguide 11c dominates during the polishing process, and the main surface 14 will be uniform and co-parallel with the top main surface 13 with high precision. FIG. 6 shows an alternative embodiment of the embodiments of FIGS. 5A to 5C. In the arrangement of FIG. 6, the spacer slice 118 is retained as part of the final waveguide system 10d. If the spacer slice 118 is manufactured to have highly precise co-parallel surfaces, the joining between the spacer slice 118 and the waveguide 11c can be performed using an adhesive in the first group having a sufficiently low refractive index (i.e., an adhesive insensitive to the removal process), so that light can be confined (TIR) within the waveguide 11c. In this case, it is not necessary to form the spacer slice 118 from two different parts 111 and 112 (such as the placeholder slice 117 in FIG. 3C), because the spacer slice 118 remains intact in the final waveguide system 10d and can thus be made of a single part. The novel techniques disclosed herein can also be applied to more advanced configurations, as shown in FIGS. 7A to 7I with reference to WO2023026266A1 (the entire content of which is incorporated herein by reference). In FIG. 7A, the top surface 301a or the bottom surface 301b of the first waveguide plate 301 is processed (e.g., coated) to enable partial reflection or diffraction of the top surface 301a or the bottom surface 301b. Then, the first waveguide plate 301 can be joined at the top surface 301a or the bottom surface 301b using an adhesive selected from the first group of adhesives (i.e., an adhesive insensitive to removal by chemical etching or heating) to form the first waveguide block 300. Then, the first waveguide block 300 can be cut along a first plane 303 that is at an acute angle with respect to the top surface 301a and the bottom surface 301b. The resulting one or more first waveguide blocks 310 have internal facets 15. The resulting one or more waveguide blocks 310 can also be cut along a plane perpendicular to the plane 303 to obtain the cuboid shape shown in FIG. 7B. In FIG. 7C, the structure of the waveguide slice 11 is similar to that described above with reference to FIGS. 3A and 3B, and is joined together using an adhesive selected from the first group of adhesives (i.e., an adhesive insensitive to chemical etching or removal by heating) to form a waveguide stack 500. The top surface 41a or the bottom surface 41b of the third waveguide plate 410 can be processed so that the top surface 410a or the bottom surface 410b can perform partial reflection or diffraction. In the embodiment shown in FIG. 7C, the thicknesses of the top third waveguide plate 410 and the bottom third waveguide plate 410 are half of the thickness of the third waveguide plate 410 between the top and the bottom. The top third waveguide plate 410 and the bottom third waveguide plate 410 can be prefabricated to be thinner, or more practically, as described above with reference to FIG. 7E, when cut along the plane 603, the top third waveguide plate and the bottom third waveguide plate become thinner. Then, an adhesive selected from the first group of adhesives (i.e., an adhesive insensitive to chemical etching or removal by heating) can be used to join the third waveguide plate 410 at the top surface 410a or the bottom surface 410b to form a mixer block 400. As shown in FIG. 7D, an adhesive selected from the first group of adhesives (i.e., an adhesive insensitive to chemical etching or removal by heating) can be used to join the first waveguide block 310 to the mixer block 400 and join the mixer block 400 to the waveguide stack 500 to form a composite waveguide block 600. Then, as shown in FIG. 7E, the composite waveguide block 600 can be cut along a plane 603 corresponding to the top surface 13 and the bottom surface 14 of the second waveguide slice 11 to form a third waveguide slice as shown in FIG. 7F. As shown in FIG. 7F, the mixer block 400 is aligned with the waveguide stack 500 such that the mixer surface or homogenizer 440 appears to be embedded approximately half (in the Z direction) relative to the waveguide slice 11. Generally, an optical mixer or homogenizer such as the 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 located inside the resulting light-guide optical element (LOE) 810 and is parallel to the main surface 13 and the main surface 14. Examples of optical mixers or homogenizers such as the homogenizer 440 are described in great detail, for example, in U.S. Patent Application No. 17 / 420,675 to Ronen et al. (published as Publication No. US 2022 / 0099885). Therefore, optical mixers such as the homogenizer 440 are not described in additional detail here. At this stage, the individual waveguide slices 11 can be finely polished so that the main surface 13 and the main surface 14 of each waveguide slice 11 are parallel to each other with high precision. Next, as shown in FIG. 7F, the waveguide slices 11 can be joined with the alternating placeholder plates 710 using an adhesive selected from the second group (i.e., an adhesive sensitive to chemical etching or heat removal) to form a stack to form a second waveguide stack 700. Then, the second waveguide stack 700 can be cut to form an aperture for coupling into the stack segment 200. FIG. 7G shows a top view of the second waveguide stack 700 (i.e., a view rotated 90 degrees from the view of FIG. 7F). As shown in FIG. 7H, the first waveguide stack 310 of the second waveguide stack 700 is cut along a plane 302 to form an aperture surface 301, the plane 302 being perpendicular to the top surface 13 and the bottom surface 14 of the third waveguide slice 11 and intersecting the edge 303 of the first waveguide stack 310 joining the mixer block 400, to which the coupling stack segment 200 can be joined. The coupling stack segment 200 is joined to the aperture surface 301 using an adhesive selected from the first group (i.e., an adhesive insensitive to chemical etching or heat removal) to form a third waveguide stack 800. As shown in FIG. 7I, the waveguide stack 800 can be cut along a plane 803 corresponding to the bottom surface 14 of the second waveguide slice 11 to form waveguide slices 810. The portions of the waveguide slices 810 corresponding to the placeholder plates 710 or the sacrificial plates 202 (i.e., any portion joined using an adhesive selected from the second group of adhesives) can be removed by at least one of chemical etching or heating. The resulting waveguide structure corresponds to the structure 2a of FIG. 2A. Definitions 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 terms and can be used in implementations. The examples are not intended to be limiting. Both the singular and plural forms of the terms can be within the definitions. An "operably connected" connection, or by which an entity is "operably connected", is a connection through which signals, physical communication, or logical communication can be sent or received. Generally, an operably connected connection includes a physical interface, an electrical interface, or a data interface, but it should be noted that an operably connected connection can include different combinations of these or other types of connections sufficient to allow operable control. For example, two entities can be operably connected by being able to pass signals directly to each other or through one or more intermediate entities such as a processor, an operating system, logic, software, or other entities. A logical or physical communication channel can be used to create an operably connected connection. As used in the detailed description or claims, the terms "include" or "including" are intended to be inclusive in a manner similar to the way the term "comprising" is construed when used as a transitional word in a claim. Further, as used in the specification or claims, the term "or" (e.g., A or B) is intended to mean "A or B or both." When the applicant intends to indicate "only A or B but not both," then the term "only A or B but not both" will be used. Thus, the use of the term "or" herein is inclusive and not exclusive. See Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d ed. 1995). Although example systems, methods, etc. have been illustrated by way of example and, although the examples have been described in considerable detail, the applicant's intention is not to limit or in any way restrict the scope to such details. Of course, it is not possible to describe every conceivable combination of components or methods in order to describe the systems, methods, etc. described herein. Additional advantages and modifications will be apparent to those skilled in the art. Accordingly, the invention is not limited to the specific details, representative apparatus, and illustrative examples shown and described. Thus, the invention is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims. Further, the foregoing description is not intended to limit the scope of the invention. Rather, the scope of the invention is defined by the appended claims and their equivalents. 101: Plate 101a: Top surface 101b: Bottom surface 102: Waveguide block 103: Plane X, Z: Directions

Claims

1. A method for manufacturing a waveguide, the method comprising: The top or bottom surface of the waveguide plate is processed to enable partial reflection or diffraction. The waveguide plate is bonded at the top or bottom surface using an adhesive selected from the first group of adhesives to form a waveguide block having a top surface and a bottom surface; the waveguide block is cut along a plane forming an acute angle with respect to the top and bottom surfaces of the waveguide block to form a waveguide slice having an internal facet; the first plate is bonded to the front surface of the first block to form a second block having a top surface and a bottom surface. The second piece is cut to form a placeholder slice; The waveguide slices and the placeholder slices are alternately bonded using an adhesive selected from the second group of adhesives to form a waveguide stack, wherein the second group of adhesives consists of adhesives that are more susceptible to chemical etching or heat removal compared to the corresponding adhesives in the first group of adhesives.

2. The method as described in claim 1, comprising: The top surface of the coupling plate is treated to enable reflection or diffraction; the coupling plates are bonded together using an adhesive selected from the second group of adhesives to form a coupling stack having a top surface and a bottom surface. And cut the coupling stack along a plane at an acute angle to the top and bottom surfaces of the coupling stack to form one or more coupling stack segments including coupling plane segments.

3. The method as described in claim 1, comprising: The top surface of the coupling plate is treated to enable reflection or diffraction. The top surface of the coupling plate is bonded to the first surface of the sacrificial plate using an adhesive selected from the first group of adhesives, and the bottom surface of the coupling plate is bonded to the second surface of the sacrificial plate using an adhesive selected from the second group of adhesives, to form a coupling stack having a top surface and a bottom surface. And cut the coupling stack along a plane at an acute angle to the top and bottom surfaces of the coupling stack to form one or more coupling stack segments including coupling plane segments.

4. The method as described in claim 2 or claim 3, comprising: The coupling planar segment is bonded to a corresponding waveguide slice in the waveguide stack using an adhesive selected from the first group of adhesives to form a waveguide structure.

5. The method as described in claim 4, comprising: The waveguide structure is cut along a plane parallel to the top and bottom surfaces of the waveguide structure to form one or more waveguide structure segments.

6. The method as described in claim 5, comprising: By means of at least one of chemical etching or heating, portions of the waveguide structure segments bonded with adhesives selected from the second group of adhesives are removed.

7. A method for manufacturing a waveguide, the method comprising: A waveguide stack is generated, in which at least some elements are bonded using an adhesive selected from a first group of adhesives; The top surface of the coupling plate is treated to enable reflection or diffraction; the coupling plates are bonded together or bonded to a sacrificial plate using an adhesive selected from the second group of adhesives to form a coupling stack having a top surface and a bottom surface; the coupling stack is cut along a plane at an acute angle to the top and bottom surfaces of the coupling stack to form one or more coupling stack segments including coupling plane segments; the coupling plane segments are bonded to corresponding waveguide slices in the waveguide stack using an adhesive selected from the first group of adhesives to form a waveguide structure; wherein the second group of adhesives consists of adhesives more susceptible to chemical etching or thermal removal compared to the corresponding adhesives in the first group of adhesives; the waveguide structure is cut along a plane parallel to the top and bottom surfaces of the waveguide structure to form waveguide structure segments; And by at least one of chemical etching or heating, removing portions of the waveguide structure segments bonded with adhesives selected from the second group of adhesives.

8. The method as described in request item 7, wherein, The generation of the waveguide stack includes: processing the top or bottom surface of a waveguide plate to enable partial reflection or diffraction; bonding the waveguide plate at the top or bottom surface using an adhesive selected from a first group of adhesives to form a first block having a top and bottom surface; cutting the first block along a plane at an acute angle relative to the top and bottom surfaces of the first block to form the waveguide slice having an internal facet; cutting a second block to form a spacer slice; and alternating and bonding the waveguide slice with the spacer slice to form the waveguide stack.

9. The method as described in claim 8, comprising: Polishing the top and bottom surfaces of the waveguide slice includes removing a portion of the first plate that remains adhered to the top surface.

10. A method for manufacturing a waveguide, the method comprising: The top or bottom surface of the first waveguide plate is processed so that the top or bottom surface of the first waveguide plate can partially reflect or diffract. The first waveguide plate is bonded at its top or bottom surface using an adhesive selected from the first group of adhesives to form a first waveguide block; the first waveguide block is cut along a first plane at an acute angle relative to the top and bottom surfaces to form one or more first waveguide slices with internal facets; the top or bottom surface of the second waveguide plate is treated to enable partial reflection or diffraction; the second waveguide plate is bonded at its top or bottom surface using an adhesive selected from the first group of adhesives to form a second waveguide block having a top and bottom surface; the second waveguide block is cut along a third plane at an acute angle relative to the top and bottom surfaces of the second waveguide block to form one or more second waveguide slices with internal facets; the waveguide slices are bonded using an adhesive selected from the first group of adhesives to form a waveguide stack; the top or bottom surface of the third waveguide plate is treated to enable partial reflection or diffraction. The third waveguide plate is bonded at its top or bottom surface using an adhesive selected from the first group of adhesives to form a mixer block having a top and bottom surface; at least one of the first waveguide slices is bonded to the mixer block, and the mixer block is bonded to the waveguide stack to form a composite waveguide block; the composite waveguide block is cut along a plane corresponding to the top or bottom surface of the second waveguide slice to form a third waveguide slice; and the third waveguide slice is alternately bonded to a placeholder plate using an adhesive selected from the second group of adhesives to form a second waveguide stack, wherein the second group of adhesives consists of adhesives more susceptible to chemical etching or thermal removal compared to the corresponding adhesives in the first group of adhesives.

11. The method as described in claim 10, comprising: At least one of the first waveguide slices is cut along a plane to form an aperture surface, the plane being perpendicular to the top and bottom surfaces of the third waveguide slice and intersecting the edge of the mixer block joined to at least one of the first waveguide slices.

12. The method as described in claim 11, comprising: The top surface of the coupling plate is treated to enable reflection or diffraction; the top surfaces of the coupling plates are bonded together using an adhesive selected from the second group of adhesives to form a coupling stack having a top surface and a bottom surface. And cut the coupling stack along a plane at an acute angle to the top and bottom surfaces of the coupling stack to form one or more coupling stack segments including coupling plane segments.

13. The method as described in claim 11, comprising: The top surface of the coupling plate is treated to enable reflection or diffraction; the top surface of the coupling plate is bonded to the first surface of the sacrificial plate using an adhesive selected from the first group of adhesives, and the bottom surface of the coupling plate is bonded to the second surface of the sacrificial plate using an adhesive selected from the second group of adhesives, to form a coupling stack having a top surface and a bottom surface; And cut the coupling stack along a plane at an acute angle to the top and bottom surfaces of the coupling stack to form one or more coupling stack segments including coupling plane segments.

14. The method as described in claim 12 or claim 13, comprising: The coupled stack segments are bonded to the aperture surface using an adhesive selected from the first group of adhesives to form a third waveguide stack; The third waveguide stack is cut along a plane corresponding to the bottom surface of the second waveguide slice to form a fourth waveguide slice; And to remove portions bonded with adhesives selected from the second group of adhesives by at least one of chemical etching or heating.

15. A method for manufacturing a waveguide for a head-mounted display, comprising: A first set of waveguide elements is bonded using one or more adhesives that are sensitive to heat or chemical removal, and a second set of waveguide elements is bonded using one or more adhesives that are not sensitive to heat or chemical removal, to form a waveguide stack; the waveguide stack is then cut to form a waveguide structure with embedded facets or diffractive elements. And use thermal or chemical removal to remove the portion corresponding to the first set of waveguide elements, while the portion corresponding to the second set of waveguide elements remains engaged.

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