Manufacturing of patterned polymer disc stacks

Abstract

To provide a method of aligning a stencil to an eyepiece wafer.SOLUTION: A method includes determining locations of at least two stencil apertures 402. The method also includes providing an eyepiece wafer 302. The eyepiece wafer 302 includes at least two eyepiece waveguides, each eyepiece waveguide including an incoupling grating 606 and a corresponding diffraction pattern 622. The method further includes directing second light from one or more light sources to impinge on each of the corresponding diffraction patterns 622, imaging light diffracted from each incoupling grating 606, determining locations of at least two incoupling grating 606, determining offsets between corresponding stencil 402 aperture locations and incoupling grating 606 locations, and aligning the stencil 402 to the eyepiece wafer 302 on the basis of the determined offsets.SELECTED DRAWING: Figure 6C

Description

Technical Field

[0001] (Cross-Reference to Related Applications) The present application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 865,715, entitled "POLYMER PATTERNED DISK STACK MANUFACTURING", filed on June 24, 2019, and U.S. Provisional Patent Application No. 62 / 892,427, entitled "POLYMER PATTERNED DISK STACK MANUFACTURING", filed on August 27, 2019, the entire contents of which are incorporated herein by reference for all purposes.

Background Art

[0002] (Background of the Invention) Modern computing and display technologies have promoted the development of systems for "virtual reality" or "augmented reality" experiences. Digitally reproduced images, or portions thereof, are presented to a viewer in a manner that makes them appear to be real, or can be perceived as real. A virtual reality, or "VR", scenario typically involves presentation of digital or virtual image information without transparency to other actual real-world visual input, whereas an augmented reality, or "AR", scenario typically involves presentation of digital or virtual image information as an augmentation to the visualization of the real world surrounding the viewer.

[0003] Notwithstanding the progress that has been made in these display technologies, a need exists in the art for improved methods and systems related to augmented reality systems.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Patent Document 2

[0005] (Summary of the invention) Embodiments of the present invention relate to assembly tools and methods for fabricating and assembling multilayer eyepieces.

[0006] A system and method for manufacturing a multilayer polymer eyepiece stack is described. Specifically, a retractable tool for performing one or more fabrication and / or assembly steps is described. In some embodiments, the retractable tool is configured to manufacture a multilayer polymer eyepiece. The retractable tool may include equipment or stations used to perform fabrication and assembly steps related to casting, curing, coating, aligning, stacking, singulation, and / or finishing the edges of the multilayer polymer eyepiece stack. Performing multiple fabrication steps within the retractable tool can improve the output quality of the multilayer polymer eyepiece stack by limiting contamination of the eyepiece by dust or other particles in the fabrication area. A further advantage of an integrated retractable tool is that throughput can be increased by synchronizing the fabrication and assembly steps. Cost savings can be achieved by using the retractable tool by eliminating the need for a cleanroom fabrication and assembly environment.

[0007] A method for aligning a stencil on an eyepiece wafer is provided according to embodiments of the present invention. The method includes providing a stencil, positioning the stencil with respect to a first light source, and determining the locations of at least two holes in the stencil. The method also includes providing an eyepiece wafer, the eyepiece wafer comprising at least two eyepiece waveguides, each eyepiece waveguide comprising an input coupling grating and a corresponding diffraction pattern. The method further includes directing light from one or more second light sources to collide with each of the corresponding diffraction patterns, imaging the light diffracted from each input coupling grating, determining the locations of at least two input coupling gratings, determining the shift between the locations of the corresponding stencil holes and the locations of the input coupling gratings, and aligning the stencil on the eyepiece wafer based on the determined shift.

[0008] A system is provided according to another embodiment of the present invention. The system includes a first chuck operable to support a stencil containing a plurality of holes, a wafer chuck operable to support and move a wafer containing a plurality of input coupling gratings, and a first light source operable to direct light to strike a first surface of the stencil. The system also includes one or more second light sources operable to direct light to strike the wafer, and one or more lens and camera assemblies. One or more camera assemblies operable to receive light from the first light sources that has passed through the plurality of holes in the stencil and to receive light from one or more second light sources diffracted from the plurality of input coupling gratings in the wafer. The system further includes an alignment system operable to move the wafer relative to the stencil and to reduce the misalignment between the locations of the holes and the locations of the input coupling gratings.

[0009] An assembly system is provided according to a particular embodiment of the present invention. The assembly system includes a wafer casting station, a stencil setting station, and a deposition station. The assembly system also includes a stencil separation station, a first inspection station, a layer assembly station, and a second inspection station. In one embodiment, the stencil setting station includes a first chuck operable to support a stencil having a plurality of holes, a wafer chuck operable to support and move a wafer having a plurality of input coupling gratings, a first light source operable to direct light to strike a first surface of the stencil, and one or more second light sources operable to direct light to strike the wafer. The stencil setting station also includes one or more lens and camera assemblies operable to receive light from the first light sources that have passed through the plurality of holes in the stencil and to receive light from one or more second light sources diffracted from the plurality of input coupling gratings in the wafer. The stencil setting station further includes an alignment system operable to move the wafer relative to the stencil and to reduce the misalignment between the locations of the holes and the locations of the input coupling gratings.

[0010] Numerous advantages are achieved by the methods of the present invention, which surpass the conventional art. For example, embodiments of the present invention provide methods and systems that enable the fabrication of multilayer eyepieces with high precision, specifically high precision related to the alignment of layers. Furthermore, embodiments of the present invention utilize the optical diffraction structure present within the eyepiece to enable a self-aligning assembly process. These embodiments of the present invention, along with other embodiments, which embody many of the advantages and features of the present invention, are described in more detail below with accompanying text and drawings. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 shows an illustrative diagram of the internal equipment of a retractable manufacturing and assembly tool according to an embodiment of the present invention.

[0012] [Figure 2] Figure 2 shows a cross-sectional view of a polymer wafer casting station according to an embodiment of the present invention.

[0013] [Figure 3] Figure 3 shows a plan view of an exemplary polymer wafer according to an embodiment of the present invention, the polymer wafer having an eyepiece molded therein.

[0014] [Figure 4] Figure 4 shows a plan view of an exemplary coating stencil according to an embodiment of the present invention.

[0015] [Figure 5] Figure 5 shows an exemplary process flow relating to stencil alignment according to an embodiment of the present invention.

[0016] [Figure 6A] Figure 6A shows a cross-sectional view of an alignment station in a first process step according to an embodiment of the present invention.

[0017] [Figure 6B] Figure 6B shows an exemplary image of cutouts in a backlit stencil according to an embodiment of the present invention.

[0018] [Figure 6C] Figure 6C shows a cross-sectional view of an alignment station in a second process step according to an embodiment of the present invention.

[0019] [Figure 6D] Figure 6D shows an exemplary image of an illuminated input coupling grating illustrated in accordance with an embodiment of the present invention.

[0020] [Figure 6E] Figure 6E shows a cross-sectional view of an alignment station in a second process step according to another embodiment of the present invention.

[0021] [Figure 6F] Figure 6F is an exploded perspective view of a clamping system according to an embodiment of the present invention.

[0022] [Figure 7] Figure 7 shows a cross-sectional view of an exemplary stencil and wafer assembly in a coating deposition station according to an embodiment of the present invention.

[0023] [Figure 8] Figure 8 shows a plan view of a coated polymer wafer according to an embodiment of the present invention.

[0024] [Figure 9] Figure 9 shows a cross-sectional view of the coated polymer wafer shown in Figure 8.

[0025] [Figure 10] Figure 10 shows a plan view of an exemplary spacer according to an embodiment of the present invention.

[0026] [Figure 11] Figure 11 shows a plan view of an exemplary multilayer polymer wafer stack according to an embodiment of the present invention.

[0027] [Figure 12] Figure 12 shows a cross-sectional view of the multilayer polymer wafer stack shown in Figure 11. [Modes for carrying out the invention]

[0028] (Detailed description of specific embodiments) Embodiments of the present invention relate to assembly tools and methods for fabricating and assembling multilayer eyepieces.

[0029] Figure 1 shows an exemplary schematic of the equipment inside a retractable fabrication and assembly tool according to an embodiment of the present invention. Referring to Figure 1, an exemplary retractable multilayer polymer eyepiece fabrication and assembly tool 110 is shown. The tool 110 includes an enclosure 112 that houses equipment for fabricating and assembling polymer eyepiece stacks. In some embodiments, the enclosure 112 is sealed to prevent particles and contaminants from entering the interior where fabrication and assembly take place. The enclosure 112 can house machines that perform various fabrication and assembly steps. For example, the enclosure 112 may include one or more of the following: a wafer casting station 200, an annealing station 120, a stencil setting station 125, a metal deposition station 130, a stencil separation station 135, a layer assembly station 145, and an inspection station 140. Although each of those steps is represented as a separate station, it is possible to combine multiple tasks or functions into a single station, or to subdivide tasks into one or more steps.

[0030] Figure 2 shows a cross-sectional view of a polymer wafer casting station according to an embodiment of the present invention. The wafer casting station 200 receives a curable polymer resin material from a polymer material supply 101 (illustrated in Figure 1) located either inside or outside the enclosure 112. The casting station 200 produces a patterned polymer wafer. The curable polymer resin can be a multi-part (e.g., two-part or three-part or more) polymer mixture that is cured in a mold using at least one of UV light and / or thermal energy.

[0031] The wafer casting station 200 includes two mold structures 204a and 204b (also referred to as “optical flats”), which are clamped to actuating stages 212a and 212b, respectively (e.g., through clamps 202a and 202b). In some cases, the clamps 202a and 202b may be magnetic (e.g., electromagnets) and / or pneumatic clamps, which allow the mold structures 204a and 204b to be reversibly mounted on and removed from the actuating stages 212a and 212b. In some cases, the clamps 202a and 202b may be controlled by switches and / or by a control module 210 (e.g., by selectively applying electricity to the electromagnets of the clamps 202a and 202b, and / or by selectively operating a pneumatic mechanism to engage or disengage the mold structures).

[0032] A curable polymer 214 (e.g., a photopolymer, or a photoactivating resin that hardens when exposed to light) is deposited on mold structure 204b within an opening 216 between mold structure 204a and mold structure 204b. In some embodiments, the polymer material to be cured may have a refractive index higher than about 1.5 (e.g., about 1.65 or higher). Mold structures 204a and 204b are moved toward each other (e.g., by moving the actuated stages 212a and / or 212b vertically along the support frame 208 using a motor assembly 218), and the curable material 214 is surrounded by the surface 220a of mold structure 204a and the surface 220b of mold structure 204b. To provide a predetermined gap between mold structure 204a and mold structure 204b, a spacer 224 may be used, the top surface 226 of the spacer 224 in contact with the surface 220a of mold structure 204a when in the position to form the mold. The curable material 214 is then cured (for example, by exposing the curable material 214 to light from light sources 206a and / or 206b) to form a thin film having one or more features defined by mold structures 204a and 204b. After the curable material 214 has cured, the mold structures 204a and 204b are separated from each other (for example, by moving the actuated stages 212a and / or 212b vertically along the support frame 208) and the film is removed. In some embodiments, the thin film may be a polymer wafer 302 as shown in Figure 3, and the polymer wafer 302 has one or more eyepieces 304a, 304b, 304c, and 304d molded therein. The eyepieces 304a, 304b, 304c, and 304d may be referred to as eyepiece waveguides. More than four or fewer than four eyepieces may be molded in the wafer. For example, six eyepieces adapted at 60° angular intervals may be used in the same manner as four eyepieces 304a, 304b, 304c, and 304d adapted at 90° angular intervals as shown in Figure 3.Accordingly, embodiments of the present invention are not limited to this specific implementation, and a number of other eyepieces can be fabricated on the polymer wafer 302. Alternatively, in some embodiments, a single polymer eyepiece layer can be produced by a cast-to-shape method, and the subsequent singulation step can be omitted. Additional information on casting equipment and methods is available in U.S. Patent Application Publication 2019 / 0111642 (Patent Document 1), filed on 17 October 2018, which is incorporated herein by reference in its entirety.

[0033] In some embodiments, two, three, or more casting stations 200 can be included within the enclosure 112 of the tool 110. Such a configuration allows for increased wafer production and can also enable each casting station to produce polymer wafers from different polymer chemistrys. For example, a first casting station can produce wafers from a first polymer formulation, and a second casting station can produce wafers from a second polymer formulation different from the first, and so on.

[0034] After the molded polymer wafer is removed from the casting station, the polymer wafer is optionally moved to the annealing station 120, where it is heated to reduce material stress within the wafer, increase the thermal stability of the polymer material, and / or fine-tune the wafer's contour or flatness. In some embodiments, the polymer wafer is placed on a substrate (e.g., a thermally conductive plate such as aluminum) having a surface roughness of 100 nm or higher to prevent the polymer material from sticking to the substrate. It is desirable that the polymer wafer be able to freely stretch and / or shrink during the annealing process so that it can conform to the shape of the substrate. In some embodiments, the substrate is flat and has low local thickness variation (LTV) and low total thickness variation (TTV). Alternatively, at least a portion of the substrate may include a concave or convex curved surface, which is imparted to the polymer wafer during annealing.

[0035] During annealing, gravity may be sufficient to cause the polymer wafer to conform to the shape of the annealing substrate; however, to increase the degree of shape conformity, a second substrate can be used as a weight on top of the polymer wafer, with the wafer sandwiched between the two substrates. The second substrate may be a thermally conductive plate, or it may be an optical flat of fused silica coated with a conductive metal layer or a mixed layer of metal / metal oxide.

[0036] The specific annealing method may depend on the specific polymer material. In some embodiments, the annealing step may include exposing the polymer wafer to a temperature higher than the wafer's glass transition temperature (e.g., about 100°C for some materials). The temperature decrease to room temperature may occur slowly near the glass transition temperature (e.g., at a rate lower than about 2°C per minute), which can reduce the risk of warping or distortion of the polymer wafer.

[0037] The annealing step can be performed at a dedicated annealing station 120, but annealing can also be performed in which the cast polymer wafer moves between the casting station 200 and the stencil placement station 125 (for example, moving on a moving conveyor belt or other transfer mechanism).

[0038] Figure 3 shows a plan view of an exemplary polymer wafer according to an embodiment of the present invention, the polymer wafer having an eyepiece molded therein. Figure 4 shows a plan view of an exemplary coating stencil according to an embodiment of the present invention.

[0039] Referring here to Figures 3 and 4, the stencil placement station 125 receives the polymer wafer 302 directly or indirectly from the casting station 200, and also receives the stencil 402 from the stencil supply 103, which is located either inside or outside the enclosure. An alignment step is performed at the stencil placement station 125 to determine the adaptation of the stencil 402 to the wafer 302 by rotation or translation. In some embodiments, alignment is performed using a computer vision algorithm that references reference markers and features on the wafer and on the stencil. Precise alignment between the stencil and the wafer causes certain portions of the wafer 302 to remain exposed after the stencil is placed on the wafer. For example, a specific pattern or part of a pattern (e.g., a diffraction grating) molded within each eyepiece 304a, 304b, 304c, 304d is aligned with the holes 404 in the stencil and exposed by the holes 404. The rest of the wafer 302 is covered by the stencil.

[0040] In some embodiments, each hole 404 on the stencil is aligned with a set of input coupling grids (ICGs) molded within each eyepiece 304 on the polymer wafer 302. In some embodiments, the holes 404 are smaller than the ICG area, and only a portion of the ICG area is exposed. Once aligned, the stencil 402 is removably bonded to the wafer 302 using any suitable means to prevent movement between the stencil and the wafer. As is discussed more in relation to Figure 6F, in some embodiments, the stencil is clamped to the wafer using a magnetic clamp. Although four holes 404 are illustrated in Figure 4 in relation to the four eyepieces 304a, 304b, 304c, and 304d shown in Figure 3, embodiments of the present invention are not limited to this specific implementation, and other numbers of hole / eyepiece pairs can be utilized, for example, six hole / eyepiece pairs can be utilized. While some embodiments consider aligning a wafer onto a stencil, in other embodiments, the wafer can be aligned first, and then the stencil can be aligned onto the wafer. Those skilled in the art will recognize many variations, modifications, and substitutions.

[0041] Figure 5 shows an exemplary process flow for stencil alignment according to an embodiment of the present invention. Figure 6A shows a cross-sectional view of the alignment station in the first process step according to an embodiment of the present invention. Figure 6B shows an exemplary image of a backlit stencil cutout according to an embodiment of the present invention. Figure 6C shows a cross-sectional view of the alignment station in the second process step according to an embodiment of the present invention. Figure 6D shows an exemplary image of an illuminated input coupling grid illustrated according to an embodiment of the present invention.

[0042] Referring to Figure 5, an example of the alignment process flow 500 is shown in relation to an exemplary stencil placement station 125, which is shown in two process steps in Figures 6A and 6C. In process 500, the stencil 402 is received by the stencil placement station 125 (502 in Figure 5). The stencil is made of a ferromagnetic metal or may otherwise contain portions of ferromagnetic metal and is configured to attract magnetic material. The stencil 402 is opaque, and light does not pass through the stencil material. The stencil 402 includes at least one hole 404, also referred to as a cutout. In some embodiments, the stencil 402 includes at least one hole 404 for each input coupling grid formed on each of the eyepieces 304a / 304b / 304c / 304d on the wafer 302.

[0043] The stencil 402 is positioned to cover the first light source 610 (504 in Figure 5), and the apparatus shown in Figure 6A is used to determine the location of the holes 404 within the stencil 402. In some embodiments, a screen 612 is positioned between the first light source 610 and the stencil 402 to diffuse the light from the first light source 610. Thus, the first light source 610 combined with the screen 612 provides a diffused image of the holes 404. The first light source 610 can be implemented as an LED, an LED array, or other preferred light source, and the first light source 610 can be turned on (510 in Figure 5) to illuminate at least one lens and camera assembly 614 / 615 through holes 604a and 604b, which may also be referred to as cutouts, toward the stencil 402. Referring to Figures 4 and 6A, the holes 604a and 604b shown in Figure 6A correspond to two of the holes 404 shown in Figure 4. Since Figure 6A is a cross-sectional view, the other two holes 404 shown in Figure 4 are positioned such that one hole is in front of the plane of the figure and the other is behind the plane of the figure. As is more fully described in relation to Figure 6C, in some configurations, the wafer 302 containing the input coupling gratings 606a and 606b is positioned above the stencil 402 during imaging of holes 604a and 604, however, the inventors have determined that the presence of the input coupling gratings 606a and 606b positioned between the holes 604a and 604b and the lens and camera assembly 614 / 615 does not interfere with imaging of the holes. In some configurations, the wafer 302 can be positioned as shown in Figure 6C after imaging of holes 404. Those skilled in the art will recognize many variations, modifications, and substitutions.

[0044] Referring to Figure 4, the hole 404 illustrated in Figure 4 is shown as holes 604 and 604b in Figure 6A. To obtain the positions of at least two stencil holes, light from a first light source passing through the stencil holes can be imaged using one or more cameras (512 in Figure 5). Some configurations include a single camera that can capture light illuminating through multiple cutouts, while other configurations may include two or more cameras, each of which may be configured by lens and camera assemblies 614 and 615 to separately capture light from each cutout as shown in Figure 6A. An exemplary image of the backlight captured by the lens and camera assembly through the stencil cutouts is shown in Figure 6B. Once the cutout images are captured by the cameras, the first light source can be turned off (514 in Figure 5).

[0045] Images from lens and camera assemblies 614 and 615 are provided as input to an alignment system 616, which may include an alignment algorithm that identifies the center of each imaged illuminated portion corresponding to the center of each imaged stencil cutout in coordinate points. For example, the alignment algorithm can calculate the center of each cutout in x, y, and theta coordinates. In other embodiments, the shape of the imaged holes is characterized by width and height, which can then be used to calculate the center. In some embodiments, in addition to the two holes 604a and 604b shown in Figure 6A, additional cutouts (not shown) are used to improve the accuracy of the alignment. For example, four cutouts, six cutouts, etc., can be used in the alignment process. As will be more fully described herein, the hole locations will be used, for example, to align the stencil 402 to the wafer 302 by minimizing the misalignment between the corresponding holes and the input coupling grid. For example, the location of each hole (e.g., its location in xy coordinates or pixel coordinates) can be compared to the location of the corresponding input coupled grid, and the average distance between the location of each hole and the location of the corresponding input coupled grid can be minimized.

[0046] Referring to Figure 6C, the wafer is received (506 in Figure 5), positioned over the stencil, and the diffraction grating intended to be coated or metallized is adapted to be present within the wafer and facing the stencil (508 in Figure 5). A small gap (e.g., on the order of several hundred microns to several millimeters) is provided between the wafer 302 and the stencil 402, thereby allowing the wafer position to be adjusted without damaging the surface of the wafer or the grating placed on it. The wafer is roughly aligned with the stencil along the longitudinal axis 618. To ensure that the input coupled grating 606a / 606b is aligned with the opening in the stencil, one or more second light sources 620 / 621, such as red, green, or blue LED light, illuminate the wafer within the region of the diffraction pattern 622a / 622b (516 in Figure 5). The diffraction pattern 622a can be, for example, a diffraction grating, which is configured to directly or indirectly diffract the incident light from the second light source 620 to the input coupled grating 606a (for example, via internal total internal reflection within the wafer). The diffraction pattern 622b can be, for example, a diffraction grating, which is configured to directly or indirectly diffract the incident light from the second light source 621 to the input coupled grating 606b (for example, via internal total internal reflection within the wafer). Thus, the input coupled grating 606a and the diffraction pattern 622a can be considered to correspond to each other, and the input coupled grating 606b and the diffraction pattern 622b can be considered to correspond to each other.

[0047] When in use, each of the diffraction patterns 622a and 622b can be a composite pupil expander (CPE) that forms an output coupled grating, and the output coupled grating can be used to direct the image light generated in the projector and diffracted into the plane of the eyepiece waveguide placed in the wafer to the user's eye via the corresponding input coupled gratings 606a / 606b. As will be apparent to those skilled in the art, illumination of diffraction patterns 622a / 622b using a second light source 620 / 621, propagation to input coupling gratings 606a / 606b via TIR, and diffraction of light from the second light source to the lens and camera assembly 614 / 615 utilize the propagation of light along an optical path, which is opposite to the optical path used when using an eyepiece waveguide (when using an eyepiece waveguide, input coupling to the eyepiece waveguide occurs at diffraction gratings 622a / 622b used for output coupling to the user, and output coupling occurs at input coupling gratings 606a / 606b used for input coupling from the projector). Those skilled in the art will recognize many variations, modifications, and substitutions.

[0048] When light from diffraction patterns 622a / 622b reaches the input coupled gratings 606a / 606b, at least some of the light exits the input coupled gratings 606a / 606b toward the lens and camera assembly 614 / 615, where an image of the input coupled gratings 606a / 606b is captured (518 in Figure 5). An exemplary image of the illuminated input coupled grating is shown in Figure 6D. It should be noted that the lens and camera assembly 614 / 615 has sufficient depth of field to image both the stencil 402 and the wafer 302, regardless of the gaps between their elements during the alignment process. Although separate lens and camera assemblies 614 and 615 are illustrated in Figure 6A, embodiments of the present invention are not limited to the use of multiple cameras, and a single lens and camera assembly having a field of view including the elements to be imaged can be used as an alternative to the separate lens and camera assemblies 614 and 615 shown.

[0049] Once the illuminated ICG image is captured, the second light source 620 / 621 may be turned off. At least one captured image of the illuminated input coupled gratings 606a / 606b is provided to the alignment algorithm 616, and the center of each input coupled grating 606a / 606b is identified at a coordinate point. For example, the alignment algorithm can calculate the center of each input coupled grating in x, y, and theta coordinates. The coordinates of the input coupled gratings can be compared to the coordinates of the cutout to determine the relative position between the stencil and the wafer (520 in Figure 5). Any misalignment between the center of the input coupled grating and the center of the corresponding stencil cutout can be calculated and used as a reference for adjusting the position of the wafer in the x, y, and / or theta direction via the actuated wafer chuck 624, which holds the wafer at its periphery (e.g., using a vacuum ground in contact with the outer edge of the wafer) and adjusts the position of the wafer 302 (522 in Figure 5). One or more of the above alignment steps can be repeated when necessary to achieve a relative position between the stencil and the wafer that is within a predetermined tolerance.

[0050] In some embodiments, a portion of the number of holes 604a / 604b and input coupling grids 606a / 606b may be used in the alignment process. For example, captured images of two illuminated holes 604a / 604b and two illuminated input coupling grids 606a / 606b may be used in the x, y, θ alignment of the wafer relative to the stencil. In other embodiments, all (e.g., four or six) of the holes 604a / 604b and input coupling grids 606a / 606b may be used in the alignment process. The use of a larger number of holes and input coupling grids may be advantageous when the input coupling grids are misaligned from their intended positions, resulting in registration errors between the misaligned input coupling grids(s) and the corresponding holes(s) in the stencil. The use of a larger number of holes and input coupling grids will allow global adjustments to address such registration errors, as the best fit among a group of holes and input coupling grids can be used in the alignment process.

[0051] In specific embodiments of the present invention, the alignment algorithm utilizes the central positions of some or all of the holes and some or all of the input coupling grids. When utilizing precise relative position measurements of the holes / input coupling grids, the hole / input coupling grid positions measured using the lens and camera assembly are used in a best-fit algorithm that minimizes the positional difference between each hole and the corresponding input coupling grid. For example, the center of the best-fit circle passing through all the holes being measured can be matched to the center of the best-fit circle passing through all the input coupling grids being measured. Thus, the minimum average positional difference can be used to adjust the wafer position in x, y, and θ coordinates.

[0052] When the alignment is within an acceptable tolerance, the wafer is moved to contact the stencil, and a plate made of magnetic material, or a plate separately housing one or more magnets, is placed on the top of the wafer to create a magnetic clamp (524 in Figure 5). In some mounting configurations, the stencil can be positioned relative to a reference plane (e.g., a vacuum chuck) using a vacuum. As considered in relation to Figure 6F, the magnets on the top plate attract the ferromagnetic stencil, holding the wafer in place and preserving the alignment. The assembly can then be moved to other areas of the tool or repositioned without disrupting the precise alignment between the stencil and the wafer.

[0053] In some embodiments, the alignment of the stencil and the wafer is confirmed after a magnetic clamp is used to clamp the wafer to the stencil. Thus, it can be confirmed that no movement of the wafer relative to the stencil occurred during the clamping process.

[0054] Figure 6E shows a cross-sectional view of the alignment station in a second process step according to another embodiment of the present invention. Rather than injecting light directly into the wafer via diffraction gratings 622a / 622b as illustrated in Figure 6E, in the embodiment illustrated in Figure 6E, light from the second light source 640 / 641 is reflected from mirrors 636 / 637, coupled to the wafer, and propagates to each input coupling grating 606 via internal total internal reflection so that the light propagates within the eyepiece waveguide. By injecting light into wafer 302 as illustrated in Figure 6E, the second light source 640 / 641 can be positioned on both sides of wafer 302 at locations outside the periphery of wafer 302, allowing other system elements, including lens and camera assembly 614 / 615, to be positioned closer to wafer 302 along the z-axis, etc.

[0055] In specific embodiments, mirrors 636 / 637 can be implemented as prisms, but other reflective structures can be utilized. In addition, in some embodiments, light from a second light source 640 / 641 can be injected into the wafer 302 via grazing incidence, eliminating the need for mirrors 636 / 637. Thus, embodiments of the present invention can couple light to the wafer using diffraction gratings 622a / 622b as illustrated in Figure 6C, or embodiments of the present invention can provide light that can be output coupled from the input coupling grating 606 by utilizing other methods of injecting light into the wafer as illustrated in Figure 6E. Those skilled in the art will recognize numerous variations, modifications, and substitutions.

[0056] Figure 6F is an exploded perspective view of a clamping system according to an embodiment of the present invention. As shown in Figure 6F, a magnetic clamp 650 is used with a wafer 652 and a stencil 654 to magnetically clamp the wafer to the stencil using magnetic force. The magnetic clamp 650 includes a plurality of magnets 651, which are arranged or positioned at various locations on the upper surface of the magnetic clamp. In the illustrated example, 12 magnets 651 are used, but the present invention is not limited to this specific number, and other numbers may be used according to other embodiments. The stencil 654 is made of a magnetic material such as stainless steel, but other suitable materials may be used.

[0057] While the magnetic clamp 650 is positioned adjacent to the stencil 654, the wafer 652 is clamped between the magnetic clamp and the stencil, allowing the alignment achieved, as discussed in relation to Figure 5, to be maintained during subsequent processing operations.

[0058] Figure 7 shows a cross-sectional view of an exemplary stencil and wafer assembly in a coating deposition station according to an embodiment of the present invention. As illustrated in Figure 7, an assembly 702 is shown, which includes a stencil 402 detachably bonded to a wafer 302. The assembly 702 can be moved to a deposition station 130, where a coating material 704, such as a metal or a high refractive index inorganic material, is deposited over the stencil 402 and through the holes 404 onto the exposed portion of the polymer wafer 302. The coating deposition process can be carried out in a vacuum deposition chamber within the deposition station 130 (illustrated in Figure 1).

[0059] The coating material to be deposited is received by the deposition station 130 from the coating material supply 104 (illustrated in Figure 1), deposited over the stencil, and forms a layer 706 on one or more areas of the polymer wafer 302 (for example, forming a layer 706 on at least a portion of the ICG area of ​​each eyepiece). The size and shape of the layer 706 are limited by the size and shape of the holes 404 in the stencil 402. Although circular holes 404 are shown, holes of other shapes such as square, elliptical, rectangular, polygonal, or other shapes can also be used. The coating material can be aluminum, silver, titanium dioxide, zirconium dioxide, or other suitable reflective materials.

[0060] After the coating deposition step is complete, the stencil 402 is removed from the wafer 302 by lifting the stencil upward in a direction substantially perpendicular to the wafer surface coated with layer 706. Such a stencil removal technique can minimize damage to layer 706. The used stencil can be discarded in a used stencil bin 105 (illustrated in Figure 1), which is located inside or outside the enclosure 112 of the tool 110. Stencil separation can be performed in a stencil separation station 135 (illustrated in Figure 1).

[0061] Methods for depositing alternative coating materials and fluid coating materials can be used instead of, or in addition to, the deposition techniques discussed above. Such techniques are described in U.S. Patent No. 10,436,968, filed April 16, 2018, and U.S. Patent Application Publication No. 2018 / 0329132, filed July 23, 2018 (Patent Document 2), each of which is incorporated herein by reference in whole.

[0062] Although not shown in Figure 7, embodiments of the present invention can utilize a magnetic clamp 650 as shown in Figure 6F. In this embodiment, the magnetic clamp is positioned below the wafer 302 and applies a force perpendicular to the wafer 302, pushing the wafer toward the stencil 402, thereby maintaining alignment between the wafer and the stencil.

[0063] Figure 8 shows a plan view of a coated polymer wafer according to an embodiment of the present invention. Figure 9 shows a cross-sectional view of the coated polymer wafer of Figure 8. An exemplary coated wafer 802 is shown following the removal of the stencil, as illustrated in Figures 8 and 9. Each of the eyepieces 804a, 804b, 804c, and 804d molded within the coated wafer 802 has a coating layer 706 placed on it. Although one layer 706 is shown for each eyepiece 804, it is possible that multiple layers 706 are deposited on each eyepiece 804, depending on the stencil design. In addition, although multiple eyepieces 804 are shown arranged in a windmill configuration, other configurations are possible depending on the size and shape of the eyepieces and wafer. The stencil can be designed accordingly so that a desired area of ​​the wafer is exposed when the stencil is placed on the wafer.

[0064] Referring again to Figure 1, the tool 110 may include an inspection station 140, which, after the removal of the stencil, evaluates the coated wafer 802 according to various metrics and qualifies the coated wafer 802 to proceed with stack assembly. In some embodiments, the inspection unit may perform checks to ensure that the wafer shape, grid shape, grid position, deposited layer shape, deposited layer position, and deposited layer adhesion are within selected tolerances. In some embodiments, a computer vision system or other suitable measuring tool may be used to obtain those measurements. If the inspection station 140 determines that the coated wafer 802 does not pass the quality criteria, the wafer may be removed from the assembly line and placed in a wafer waste bin 106 (illustrated in Figure 1), which is either inside or outside the enclosure 112 of the tool 110. Wafers that pass the inspection can proceed further in the tool's workflow.

[0065] The coated wafer is transferred to the layer assembly station 145. The first coated wafer is received at the layer assembly station 145 to begin the assembly of the multilayer polymer stack. As discussed in more detail below, the layer assembly station 145 also receives the first spacers, such as spacer 1002, from the spacer preparation station 150, spacer 1002 is shown in the plan view in Figure 10.

[0066] Figure 10 shows a plan view of an exemplary spacer according to an embodiment of the present invention. The spacer 1002 may be similar in shape to a cast polymer wafer, however, the spacer includes cutouts 1004a / 1004b / 1004c / 1004d configured to align with an eyepiece molded in the polymer wafer. The cutouts 1004 are generally slightly smaller than the outer boundary of the eyepiece 804, and the spacer overlaps with the periphery of the eyepiece molded in the wafer in an overlapping region 1008. In some embodiments, the overlapping region may be less than 1 mm wide, or it may be between approximately 1 mm and approximately 5 mm wide. Depending on the desired amount of edge reinforcement in the multilayer stack, other overlapping region widths are possible.

[0067] Using a computer vision system that recognizes various features or markers on one or more of the spacers and coated wafers, the spacer 1002 is aligned on the coated wafer. In embodiments in which at least a portion of the spacers is a transparent substrate, the alignment method may be one such as that discussed in International Patent Application PCT / US2019 / 036380, filed June 10, 2019, which is incorporated herein by reference in its entirety.

[0068] Spacer 1002 includes an adhesive material on a first surface (e.g., the bottom surface), the first surface facing the coated wafer. Once the spacer is adapted and aligned on the wafer, the adhesive on the first surface of the spacer is pressed into contact with the wafer, fixing the spacer to the wafer. A second wafer can be bonded to the second surface (e.g., the top surface) of the first spacer using the same method, which involves pressing the adhesive layer on the spacer into contact with the second wafer, allowing the adhesive to harden. Additional layers can be added to the stack in the same manner.

[0069] In some embodiments, the adhesive is a high refractive index adhesive and can be formed as a double-sided adhesive tape. The adhesive can be a UV-curable material and the step of exposing the adhesive to UV light while the spacer and wafer are in contact can be utilized. The adhesive material can be transparent, or the adhesive material can contain carbon or coloring additives to make the adhesive layer optically opaque or translucent. The carbon or coloring additives can give the adhesive a dark color, such as dark gray or black. The adhesive layer can be present on the top and / or bottom of the spacer, thereby allowing the wafer to be bonded to the top and / or bottom of the spacer during the stacking assembly process at the layer assembly station 145.

[0070] When the spacer is housed in the spacer supply bin 108 (illustrated in Figure 1) prior to assembly with the wafer, a protective film may be removably bonded to the adhesive layer on the top and / or bottom surface of the spacer to prevent contaminants from adhering to the adhesive of the spacer. The spacer preparation station 150 is configured to remove the first protective film from the first surface (e.g., the bottom) of the spacer, exposing the first layer of adhesive prior to delivery of the spacer to the layer assembly station 145 (both the spacer preparation station 150 and the layer assembly station 145 are illustrated in Figure 1). In some embodiments, the second protective film remains in place on the second surface (e.g., the top) of the spacer during transfer to and assembly with the first wafer. Once the spacer is aligned on the previously exposed adhesive surface and secured to the first wafer, the layer assembly station may remove the second protective film from the second surface (e.g., the top) in preparation for bonding the second wafer onto the top of the spacer. Minimizing the time between the step of removing the protective film and the step of bonding the exposed adhesive to the wafer may be advantageous in reducing the risk of contamination or other damage to the adhesive layer.

[0071] When using adhesives that require a UV or thermal curing step, UV or thermal exposure may be performed after each step in which the wafer and spacer are pressed together and come into contact. Alternatively, the complete stack of wafer and spacer layers may be assembled prior to the delivery of the UV and / or thermal curing amount.

[0072] Referring to Figure 1, a separate spacer preparation station 150 is shown, but it is also possible to integrate the functions of the spacer preparation station 150 into the layer assembly station 145 by having the layer assembly station 145 remove the protective film from the spacer layer and discard it.

[0073] A multilayer polymer eyepiece is assembled by alternately stacking layers of wafers and layers of spacers. In some embodiments, the stack includes at least three wafers and at least two spacers.

[0074] Figure 11 shows a plan view of an exemplary multilayer polymer wafer stack according to an embodiment of the present invention. Figure 12 shows a cross-sectional view of the multilayer polymer wafer stack of Figure 11. Thus, Figure 12 illustrates a multilayer polymer wafer stack 1102 including a plurality of wafers 802 and spacers 1002. In some embodiments, the multilayer polymer wafer stack 1102, which may also be referred to as a stack, includes at least six wafers and at least five spacers. Stacks with any number of layers can be assembled. Once the stack is complete, the layer assembly station 145 can optionally cover the top surface 1104 and bottom surface 1206 with protective films to reduce the risk of damage to the completed stack.

[0075] To provide alignment between wafer 802 and spacer 1002, references are placed on wafer 802 and spacer 1002 to facilitate interlayer alignment within the multilayer polymer wafer stack 1102. For example, referring to Figure 10, a reference 1010 fabricated on spacer 1002 may be used together with a corresponding reference 810 (shown in Figure 8) fabricated on wafer 802. In the illustrated example, reference 810 has a smaller diameter than reference 1010, enabling alignment of wafer 802 onto spacer 1002. While circular references are illustrated, it will be understood that other shapes, dimensions, positions, and numbers of references are available according to embodiments of the present invention.

[0076] As the thickness of the multilayer polymer wafer stack 1102 increases, an alignment camera with a large depth of field may be used to image a reference at various depths within the stack. Alternatively, as the stack is assembled, the position of the alignment camera may be modified to provide imaging of a reference on the wafers and spacers. Those skilled in the art will recognize many modifications, modifications, and substitutions. In an alternative embodiment, a cover plate is used to maintain the perfect condition of the top surface 1104 of wafer 802a and the bottom surface 1206 of wafer 802c, and is attached to wafers 802a and 802c using appropriate spacers (not shown). As will be apparent to those skilled in the art, the use of a cover plate allows voids to be provided adjacent to the input coupling gratings 606a / 606b and diffraction patterns 622a / 622b, thereby promoting internal total internal reflection and preventing dust and debris from accumulating on the optical surface.

[0077] In the embodiment shown in Figure 12, each example of the input coupling grid and the aligned layer 706 in each eyepiece waveguide is aligned along a single axis aligned with the z-axis. In other embodiments, for example, to implement a subpupil design, the input coupling grid and the corresponding layer 706 can be spatially shifted, i.e., literally laterally shifted in the xy-plane. In those embodiments, spatially shifted references can be used per wafer and per spacer in a predetermined manner to achieve the desired positioning between adjacent input coupling grids, which is suitable for a specific subpupil design. Those skilled in the art will recognize many variations, modifications, and substitutions.

[0078] After the stack assembly is complete, the stack can be optionally moved to the stack inspection station 155 (illustrated in Figure 1). Stack inspection may include steps of measuring the alignment between layers, and / or checking light output metrics such as contrast, uniformity, and / or brightness of the image projected through the stack. Stacks whose measurements fall within threshold tolerances can proceed to the completed stack collection bin 109, while stacks that do not pass the quality standards can be moved to the waste bin 911 (both the completed stack collection bin 109 and the waste bin 911 are illustrated in Figure 1). The stack collection bin 109 and the stack waste bin 111 may be located inside or outside the enclosure 112 of the tool 110.

[0079] Several stations are discussed above by describing the various manufacturing or assembly steps performed at each station. Transfer of components between stations can be achieved using conveyors, transfer arms with vacuum attachments, mobile stages, or other component transfer means. Components can be moved individually between stations, or components can be collected as a batch at one station and moved to another. Intermediate storage areas are provided between any of the described stations to temporarily hold wafers, spacers, and / or assemblies for later batch transfers.

[0080] The completed stack can exit the enclosure 112 of tool 110, and further processing steps may be performed, such as milling, laser cutting, waterjet, die-cutting (i.e., cutting the stacked wafers into individual eyepieces), or other means of singulation. The edges of the singulated eyepiece stack can be coated with an adhesive material such as a high refractive index UV-curable adhesive doped with carbon nanopowder, mesoporous carbon, carbon black, various dyes, or a combination thereof.

[0081] The singulation and edge coating steps can be performed outside the enclosure 112 of the tool 110, thereby preventing debris created by the singulation process from contaminating other processes performed inside the enclosure 112. However, it is also possible to create one or more containment areas inside the enclosure 112, in which the singulation and / or edge coating steps can be performed in isolation from other fabrication and assembly steps. Such isolation areas can prevent the transfer of debris, vibration, or fumes to other areas of the enclosure 112. In some embodiments, the enclosure 112 is substantially similar to a cleanroom environment. In some embodiments, providing vents to the enclosure 112 and / or isolation areas inside the enclosure 112 outside the tool 110 allows for a controlled circulation of filtered air to remove contaminants and / or fumes from inside the enclosure 112.

[0082] While several examples of fabrication and assembly steps for creating multilayer polymer eyepieces within a retractable tool are discussed herein, instrumentation stations and process steps can be added or removed to optimize the tool and construct a specific product. It will be apparent to those skilled in the art that a great many changes, modifications, deformations, substitutions, and equivalents will not deviate from the spirit and scope of this disclosure. Examples of the present invention are shown below. (Example 1) A method for aligning a stencil on an eyepiece wafer, the method being: To provide the stencil, Positioning the stencil relative to the first light source, Determine the location of at least two stencil holes, To provide an eyepiece wafer, the eyepiece wafer includes at least two eyepiece waveguides, each eyepiece waveguide includes an input coupling grating and a corresponding diffraction pattern. Directing light from one or more second light sources to collide with each of the corresponding diffraction patterns, To image the light diffracted from each input coupled grating, Determine the locations of at least two input coupled grids, Determining the shift between the location of the corresponding stencil holes and the location of the input coupling grid, Aligning the stencil on the eyepiece wafer based on the determined misalignment, Methods that include... (Example 2) The method according to Example 1, wherein the locations of at least two of the stencil holes include locations for four holes or six holes. (Example 3) Determining the location of the holes in the at least two stencils is After the light from the first light source passes through the first of the holes in the at least two stencils, the light from the first light source is imaged using the first camera. After the light from the first light source passes through the second of the at least two holes in the stencil, the light from the first light source is imaged using a second camera. The method described in Example 1, including the method described in Example 1. (Example 4) Determining the location of the holes in the at least two stencils is After the light from the first light source passes through the first of the holes in the at least two stencils, the light from the first light source is imaged using a camera. After the light from the first light source passes through the second of the at least two holes in the stencil, the camera is used to image the light from the first light source. The method described in Example 1, including the method described in Example 1. (Example 5) The method according to Example 1, further comprising directing light from each of the one or more second light sources to collide with the corresponding diffraction pattern, and then redirecting at least a portion of the light from each of the one or more second light sources to each of the input coupled gratings via internal total internal reflection. (Example 6) Imaging the light diffracted from each input coupled grating is After light from one or more second light sources is diffracted from the first input coupling grating of the input coupling grating, the light from the first light source is imaged using the first camera. After light from one or more second light sources passes through the second input coupling grid of the input coupling grid, the light from the second light source is imaged using a second camera. The method described in Example 1, including the method described in Example 1. (Example 7) Imaging the light diffracted from each input coupled grating is After light from one or more second light sources is diffracted from the first input coupling grating of the input coupling grating, the light from the primary light source is imaged using a camera. After light from one or more secondary light sources is diffracted from the second input coupling grating of the input coupling grating, the camera is used to image the light from the secondary light sources. The method described in Example 1, including the method described in Example 1. (Example 8) The method according to Example 1, wherein aligning the stencil with the eyepiece wafer includes moving the eyepiece wafer relative to the stencil to reduce the determined misalignment. (Example 9) The method according to Example 8, wherein moving the eyepiece wafer includes rotating and translating the eyepiece wafer, and reducing the determined misalignment includes minimizing the determined misalignment. (Example 10) A system, said system A first chuck that is operable to support a stencil containing multiple holes, A wafer chuck that supports a wafer containing multiple input coupling grids and is operable to move the wafer, A first light source that is operable to direct light so as to strike the first surface of the stencil, One or more second light sources that are operable to direct light so as to collide with the wafer, One or more lenses and camera assemblies, the one or more lenses and camera assemblies are Receiving light from the first light source that has passed through the multiple holes in the stencil, Receiving light from one or more second light sources diffracted from the plurality of input coupled gratings within the wafer. One or more lens and camera assemblies capable of performing the following actions: An alignment system that can move the wafer relative to the stencil and reduce the misalignment between the hole locations and the input coupling grid locations, A system equipped with these features. (Example 11) The one or more lenses and camera assemblies are, A first camera capable of detecting the position of a first hole among the plurality of holes, A second camera capable of detecting the position of the second hole among the plurality of holes, The system described in Example 10, which includes the above features. (Example 12) The method according to Example 10, wherein the one or more lens and camera assemblies comprises a single camera capable of detecting the position of a first hole among the plurality of holes and the position of a second hole among the plurality of holes. (Example 13) The system according to Example 10, wherein the light from one or more second light sources diffracted from the input coupling grating within the wafer propagates by internal total internal reflection before being diffracted out of the wafer from the input coupling grating. (Example 14) Moving the wafer relative to the stencil is, Rotating and translating the wafer, Subsequently, the wafer is brought into contact with the stencil. The system described in Example 10, including the system described in Example 10. (Example 15) The system according to Example 10, wherein the first light source and the one or more second light sources are located on opposite sides of the wafer. (Example 16) An assembly system, wherein the assembly system is Wafer casting station and Stencil installation station and Deposition station and Stencil separation station, The first inspection station, Layer assembly station, Second testing station and An assembly system equipped with these features. (Example 17) The aforementioned stencil installation station is A first chuck that is operable to support a stencil containing multiple holes, A wafer chuck that supports a wafer containing multiple input coupling grids and is operable to move the wafer, A first light source that is operable to direct light so as to strike the first surface of the stencil, One or more second light sources that are operable to direct light so as to collide with the wafer, One or more lenses and camera assemblies, the one or more lenses and camera assemblies are Receiving light from the first light source that has passed through the multiple holes in the stencil, Receiving light from one or more second light sources diffracted from the plurality of input coupled gratings within the wafer. One or more lens and camera assemblies capable of performing the following actions: An alignment system that can move the wafer relative to the stencil and reduce the misalignment between the hole locations and the input coupling grid locations, The assembly system described in Example 16, which includes the following features. (Example 18) The one or more lenses and camera assemblies are, A first camera capable of detecting the position of a first hole among the plurality of holes, A second camera capable of detecting the position of the second hole among the plurality of holes, The assembly system described in Example 17, which includes the following features. (Example 19) The method according to Example 17, wherein the one or more lens and camera assemblies comprises a single camera capable of detecting the position of a first hole among the plurality of holes and the position of a second hole among the plurality of holes. (Example 20) The system according to Example 17, wherein the light from one or more second light sources diffracted from the input coupling grating in the wafer propagates by internal total internal reflection before being diffracted out of the wafer from the input coupling grating.

Claims

1. A system, wherein the system is A first chuck that is operable to support a stencil containing multiple holes, A wafer chuck that supports a wafer containing multiple input coupling grids and is operable to move the wafer, A first light source that is operable to direct light so as to strike the first surface of the stencil, One or more second light sources that are operable to direct light so as to collide with the wafer, One or more lenses and camera assemblies, the one or more lenses and camera assemblies are Receiving light from the first light source that has passed through the plurality of holes in the stencil, One or more lens and camera assemblies, operable to receive light from one or more second light sources diffracted from the plurality of input coupling gratings in the wafer, An alignment system that operates to move the wafer relative to the stencil and adjust the positions of the plurality of holes and the plurality of input coupling grids based on the light from the first light source and the light from the second light source received by the one or more lens and camera assemblies, A system equipped with these features.

2. The one or more lenses and camera assemblies are, A first camera capable of detecting the position of a first hole among the plurality of holes, A second camera capable of detecting the position of the second hole among the plurality of holes, The system according to claim 1, comprising:

3. The system according to claim 1, wherein the one or more lens and camera assemblies comprises a single camera capable of detecting the position of a first hole among the plurality of holes and the position of a second hole among the plurality of holes.

4. The system according to claim 1, wherein the light from one or more second light sources diffracted from the input coupling grating in the wafer propagates by internal total internal reflection before being diffracted out of the wafer from the input coupling grating.

5. Moving the wafer relative to the stencil is, Rotating and translating the wafer, Subsequently, the wafer is brought into contact with the stencil. The system according to claim 1, including the following:

6. The system according to claim 1, wherein the first light source and the one or more second light sources are located on opposite sides of the wafer.

7. The system according to claim 1, wherein the wafer is arranged in a transverse plane and includes at least two eyepiece waveguides, the plurality of input coupling gratings include a first input coupling grating and a second input coupling grating, the first eyepiece waveguide includes a first diffraction pattern and the first input coupling grating, and the second eyepiece waveguide includes a second diffraction pattern and the second input coupling grating.

8. The system according to claim 7, wherein the first input coupling grid is positioned at a first transverse position in the transverse plane, the first diffraction pattern is positioned at a second transverse position laterally shifted from the first transverse position in the transverse plane, the second input coupling grid is positioned at a third transverse position in the transverse plane, and the second diffraction pattern is positioned at a fourth transverse position laterally shifted from the third transverse position in the transverse plane.

9. An assembly system, wherein the assembly system is Wafer casting station and Stencil installation station and Deposition station and Stencil separation station, The first inspection station, Layer assembly station, Second testing station and Equipped with, The aforementioned stencil installation station is A first chuck that is operable to support a stencil containing multiple holes, A wafer chuck that supports a wafer containing multiple input coupling grids and is operable to move the wafer, A first light source that is operable to direct light so as to strike the first surface of the stencil, One or more second light sources that are operable to direct light so as to collide with the wafer, One or more lenses and camera assemblies, the one or more lenses and camera assemblies are Receiving light from the first light source that has passed through the plurality of holes in the stencil, Receiving light from one or more second light sources diffracted from the plurality of input coupling gratings within the wafer. One or more lens and camera assemblies that are operable to perform the following: An alignment system that operates to move the wafer relative to the stencil and adjust the positions of the plurality of holes and the plurality of input coupling grids based on the light from the first light source and the light from the second light source received by the one or more lens and camera assemblies, An assembly system equipped with these features.

10. The one or more lenses and camera assemblies are, A first camera capable of detecting the position of a first hole among the plurality of holes, A second camera capable of detecting the position of the second hole among the plurality of holes, The assembly system according to claim 9, comprising:

11. The assembly system according to claim 9, wherein the one or more lens and camera assemblies comprises a single camera capable of detecting the position of a first hole among the plurality of holes and the position of a second hole among the plurality of holes.

12. The assembly system according to claim 9, wherein the light from one or more second light sources diffracted from the input coupling grating in the wafer propagates by internal total internal reflection before being diffracted out of the wafer from the input coupling grating.

13. Moving the wafer relative to the stencil is, Rotating and translating the wafer, Subsequently, the wafer is brought into contact with the stencil. The assembly system according to claim 9, including the assembly system according to claim 9.

14. The assembly system according to claim 9, wherein the wafer is arranged in a transverse plane and includes at least two eyepiece waveguides, the plurality of input coupling gratings include a first input coupling grating and a second input coupling grating, the first eyepiece waveguide includes a first diffraction pattern and the first input coupling grating, and the second eyepiece waveguide includes a second diffraction pattern and the second input coupling grating.

15. The assembly system according to claim 14, wherein the first input coupling grid is positioned at a first transverse position in the transverse plane, the first diffraction pattern is positioned at a second transverse position laterally shifted from the first transverse position in the transverse plane, the second input coupling grid is positioned at a third transverse position in the transverse plane, and the second diffraction pattern is positioned at a fourth transverse position laterally shifted from the third transverse position in the transverse plane.

16. The alignment system according to claim 1, wherein the alignment system is positioned to align the center of at least one hole among the plurality of holes with the center of at least one input bonding grid among the plurality of input bonding grids.

17. The assembly system according to claim 9, wherein the alignment system is positioned to align the center of at least one of the plurality of holes with the center of at least one of the plurality of input bonding grids.

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