Method and arrangement for bonding transparent plates and manufacturing light-guided optical elements

Abstract

Methods for joining parallel-faced transparent plates are provided. The plates are arranged in a stack having a lateral offset between one or more pairs of adjacent plates to define plate steps. An adhesive is applied to the interfaces between adjacent plates of the stack, and a coating is applied to one side of each interface. In one set of methods, the stack is placed between a pair of pressurizing members, and a compensating member is provided in a stepped configuration corresponding to the plate steps. Then, pressure is applied to the plates through the pressurizing members. In another set of methods, the stack is placed in a flexible container having an opening, and gas is removed from the container through the opening, causing the container to deform around the stack, which applies pressure to the sides of the stack and causes redistribution of excess adhesive from the interfaces.

Description

Technology Field

[0001] Cross-reference regarding related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 621,601 filed January 17, 2024 and U.S. Provisional Application No. 63 / 636,889 filed April 22, 2024, the disclosures of which are incorporated herein by reference in their entirety.

[0003] Technology field

[0004] The present disclosure relates to optical systems, and in particular, to methods and arrays for bonding transparent plates, and methods for manufacturing light-guiding optical elements (LOEs) from bonded transparent plates. Background Technology

[0005] Various types of displays, such as near-eye displays, require a large aperture to cover the area where the observer's (i.e., user, viewer's) eye is located (typically referred to as the eye-motion box—or EMB). To implement a compact device, the image to be projected onto the observer's eye is generated by a small optical image generator (projector) having a small optical aperture. Optical arrays for displays may employ light-guiding optical elements (LOEs) to expand the input image into one or more dimensions. Particularly related to the present disclosure is a reflective LOE, which is implemented as a transparent substrate bounded by two parallel main outer surfaces configured to support the propagation of light between them through (total) internal reflection, and image expansion is performed by a set of mutually parallel partial reflective inner surfaces (or "facets") located between the main outer surfaces. The collimated image propagating within the LOE is progressively partially deflected by the set of facets, thereby achieving aperture expansion.

[0006] Conventional LOE manufacturing methods rely on stacking and bonding parallel-faced transparent plates, at least partially provided with a reflective coating at the interface between the plates. The bonded stack is cut along parallel cutting planes inclined obliquely to the faces of the transparent plates so that the interface forms a facet. Bonding of the stack is achieved by an optical adhesive provided between adjacent plates. FIG. 1 illustrates a conventional stack (1) of transparent plates showing parallel cutting planes (15) inclined obliquely to the plate faces. The stack (1) is shown topped off (at the top and bottom) with additional transparent plates having a thickness several times greater than that of the other plates. For the final LOE product to have optimal mechanical and optical properties, the adhesive layer between the plates must be as thin as possible. This can be achieved by using a press mechanism to apply pressure to the stack through the top and bottom plates of the stack. However, conventional pressing techniques can cause warping or deformation of the plates if uniform pressure is not applied. Additionally, to reduce the amount of scrap, the stack is typically arranged as a staggered stack (1') as shown in FIG. 2. However, optimal mechanical and optical properties may not be achievable using conventional pressurization techniques on a staggered stack. means of solving the problem

[0007] The present disclosure provides a method and an array for bonding transparent plates, and a method and an array for manufacturing light-guided optical elements (LOEs) from bonded transparent plates.

[0008] According to the teaching of an embodiment of the present disclosure, a method is provided comprising the steps of: arranging a plurality of parallel-faced transparent plates in a stack having a lateral offset between one or more adjacent pairs of transparent plates to define one or more plate steps—wherein an optical adhesive is provided at an interface between adjacent transparent plates of the stack, and a coating is provided on one face of each interface, and the stack is disposed between first and second pressure members—; providing a plurality of compensation members in a stepped configuration between the first and second pressure members—wherein the one or more plate steps and the stepped configuration are correspondingly configured so that the compensation members compensate for the offset between one or more adjacent pairs of transparent plates—; and applying pressure to the plurality of transparent plates through the first and second pressure members.

[0009] Optionally, the stepped configuration of the compensation members is provided at least partially by the dimensions of the compensation members.

[0010] Optionally, at least some of the compensation members have an adjustable height, and the height is measured along a dimension perpendicular to the parallel planes of the transparent plates.

[0011] Optionally, a plurality of compensation members include a first compensation member set associated with a first pressure member and a second compensation member set associated with a second pressure member.

[0012] Optionally, a plurality of compensation members include a first compensation member set and a second compensation member set, wherein the first compensation member set is associated with a first end region of the stack and compensates for an offset between one or more adjacent pairs of transparent plates in the first end region of the stack, and the second compensation member set is associated with a second end region of the stack and compensates for an offset between one or more adjacent pairs of transparent plates in the second end region of the stack.

[0013] Optionally, the stack is positioned between the first pressure member and the second pressure member such that the first block member is positioned between the first pressure member and the first transparent plate at the top of the stack, and the second block member is positioned between the second pressure member and the second transparent plate at the bottom of the stack.

[0014] Optionally, the method further comprises the step of deploying a first insulating member between a first block member and a first pressurizing member; and the step of deploying a second insulating member between a second block member and a second pressurizing member.

[0015] Optionally, the coating provides partial reflection optical properties.

[0016] Optionally, the method further comprises the step of solidifying an adhesive so that the stack forms a bonded stack; and the step of cutting the bonded stack along at least two parallel cutting planes inclined obliquely with respect to the faces of the transparent plates to extract one or more parallel-faced substrates having a plurality of mutually parallel partial-reflective inner surfaces formed from the interface.

[0017] Optionally, the method further comprises the steps of: placing a stack in a flexible container having an opening; and removing gas from the container through the opening so that the container deforms around the stack, thereby applying pressure on the sides of the stack and generating differential pressures in regions around the stack within the container—the applied pressure and differential pressures cause excess adhesive to be redistributed from the interfaces to the regions.

[0018] Additionally, according to the teaching of an embodiment of the present disclosure, a press array is provided comprising: a first press member; a second press member facing the first press member—the first and second press members are spaced apart to accommodate a stack of parallel-facing transparent plates, and the transparent plates are arranged in a stack having a lateral offset between one or more pairs of adjacent transparent plates to define one or more plate steps, an optical adhesive is provided at an interface between adjacent transparent plates of the stack, and a coating is provided on one side of each interface—; a plurality of compensation members provided in a stepped configuration between the first and second press members—one or more plate steps and the stepped configuration are correspondingly configured so that the compensation members compensate for an offset between one or more pairs of adjacent transparent plates—; and an actuator associated with at least one of the first or second press members—the actuator is configured to move at least one of the first or second press members to apply pressure to the plurality of transparent plates.

[0019] Additionally, according to the teaching of the embodiments of the present disclosure, the method comprises the steps of: arranging a plurality of parallel-facing transparent plates into a staggered stack—whereby an optical adhesive is provided at the interfaces between adjacent transparent plates of the stack, and a coating is provided on one side of each of the interfaces—; placing the stack in a flexible container having an opening; and removing gas from the container through the opening so that the container deforms around the stack, thereby applying pressure on the sides of the stack and generating differential pressures in regions around the stack within the container—whereby the applied pressure and differential pressures cause excess adhesive from the interfaces to be redistributed to the regions.

[0020] Optionally, the method further includes the step of expanding the container; and the step of removing at least a portion of the redistributed excess adhesive.

[0021] Optionally, the method further comprises the steps of repeatedly removing gas from a container until a stopping condition is satisfied, expanding the container, and removing at least some of the redistributed excess adhesive.

[0022] Optionally, the method further includes the step of thinning the adhesive provided at the interface by diluting the adhesive with an additive to reduce the viscosity of the adhesive.

[0023] Optionally, the additive includes a solvent.

[0024] Optionally, the method further comprises the steps of: cutting a stack along at least two parallel cutting planes inclined obliquely with respect to the faces of the transparent plates to extract at least one parallel-faced substrate having a plurality of mutually parallel internal surfaces formed from the interfaces; and placing at least one substrate in a chamber to rapidly evaporate the solvent.

[0025] Optionally, the method further includes a step of solidifying the adhesive so that the stack forms a bonded stack.

[0026] Optionally, the step of solidifying the adhesive is performed while the container deforms around the stack.

[0027] Optionally, the coating provides partial reflection optical properties.

[0028] Optionally, the method further includes the step of cutting the stack along at least two parallel cutting planes inclined obliquely with respect to the faces of the transparent plates to extract at least one parallel-faced substrate having a plurality of mutually parallel partial-reflective internal surfaces formed from the interfaces.

[0029] Optionally, the applied pressure is substantially uniform across all sides of the stack, thereby mitigating distortion at the edges of the transparent plates.

[0030] Optionally, the stack is topped off at the top and bottom with high-rigidity plates having sufficient rigidity to resist bending of the remaining plates of the stack under applied pressure.

[0031] Optionally, the method further includes a step of heating the container while the container is deforming around the stack.

[0032] Optionally, the method further includes the step of applying external pressure to the container while the container is being heated.

[0033] Optionally, the staggered stack has a lateral offset between one or more pairs of adjacent transparent plates defining one or more plate steps, and the method further comprises the steps of: placing the stack between first and second pressing members; providing a plurality of compensation members in a stepped configuration between the first and second pressing members, wherein one or more plate steps and the stepped configuration are configured correspondingly so that the compensation members compensate for the offset between one or more pairs of adjacent transparent plates; and applying pressure to the plurality of transparent plates through the first and second pressing members.

[0034] Unless otherwise defined in this specification, all technical and / or scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Methods and materials similar or equivalent to those described herein may be used to carry out or test embodiments of the invention, but exemplary methods and / or materials are described below. In the event of a conflict, this specification, including definitions, will control it. Furthermore, materials, methods, and examples are merely illustrative and are not intended to be limiting. Brief explanation of the drawing

[0035] Some embodiments of the present disclosure are described merely by way of example with reference to the drawings attached herein. With specific reference to the drawings, it is emphasized that the details depicted are by way of example and for the exemplary discussion of embodiments of the present disclosure. In this regard, the description taken together with the drawings makes it clear to those skilled in the art how embodiments of the present disclosure may be practiced. Now, attention is paid to drawings in which the same reference numerals or characters correspond to or represent the same components. In the drawings, FIG. 1 is a schematic diagram of a parallel-faced transparent plate stack that can be cut along a parallel cutting plane to create one or more LOEs. FIG. 2 is a schematic diagram of a staggered stack of parallel-faced transparent plates that can be cut along parallel cutting planes to create one or more LOEs. FIG. 3 is a schematic diagram of a parallel-faced transparent plate staggered stack similar to the staggered stack exemplified in FIG. 2, illustrating the plate step defined by the interface between adjacent pairs of transparent plates and the lateral offset between one or more adjacent pairs of transparent plates. FIG. 4 is a schematic diagram of an exemplary interface between the transparent plates of the staggered stack of FIG. 3, showing an optical adhesive provided at the interface. FIG. 5a is a schematic diagram of a press array having a compensation array having independently adjustable compensation members arranged in a stepped configuration corresponding to the plate steps of the staggered stack of FIG. 3, according to embodiments of the present disclosure, and illustrates the staggered stack of FIG. 3 disposed between the press members and interfacing with the compensation array. Figure 5b is an enlarged view of the V region of Figure 5a. FIG. 6 is a schematic diagram of a compensation array and a staggered stack according to embodiments of the present disclosure, illustrating a compensation array and a staggered stack that are spatially separated from each other to more clearly illustrate the relationship between the stepped configuration and the step configuration and the plate steps. FIG. 7 is a schematic diagram of an embodiment similar to the embodiment illustrated in FIG. 5a and FIG. 5b, but in which an insulating member is provided to the pressurizing member and there is no independent control of the compensating member. FIG. 8 is a schematic diagram of an LOE having a pair of mutually parallel main outer surfaces and a set of mutually parallel partial-reflective inner surfaces inclined obliquely with respect to the main outer surfaces, which can be manufactured from a staggered stack of plates joined together according to embodiments of the present disclosure. FIG. 9 is an alternative example of a staggered stack that can be processed using a press array according to embodiments of the present disclosure. FIG. 10 is another alternative example of a staggered stack that can be processed using a press array according to embodiments of the present disclosure. FIG. 11 is another alternative example of a staggered stack that can be processed using a press array according to embodiments of the present disclosure. FIG. 12 is a flowchart of a method for bonding transparent plates and selectively manufacturing one or more LOEs from the bonded plates, according to embodiments of the present disclosure. FIG. 13 is a schematic diagram of a staggered stack of transparent plates, showing the interfaces between the transparent plates and the optical adhesive provided at the interfaces. FIG. 14 is a schematic diagram of the staggered stack of FIG. 13 disposed in a flexible container having an opening and containing a large amount of gas, according to embodiments of the present disclosure. FIG. 15 is a schematic diagram of a flexible container having the staggered stack of FIG. 14, illustrating that, according to embodiments of the present disclosure, the removal of gas from inside the container causes the container to deform around the stack to thin the adhesive at the interfaces between the transparent plates and redistribute the excess adhesive into the pocket regions of the container. FIG. 16 is a schematic diagram of a flexible container having the staggered stack of FIG. 14 and FIG. 15, illustrating the container expansion and redistributed excess adhesive in exposed areas of the staggered stack according to embodiments of the present disclosure. Figure 17 is a schematic diagram of the staggered stack of Figure 16 with the redistributed excess adhesive removed. FIG. 18 is a schematic diagram of the staggered stack of FIG. 17, illustrating a pair of parallel cutting planes that can be cut to create LOE. FIG. 19 is a schematic diagram of a plurality of LOEs that can be extracted from a staggered stack of FIG. 17, illustrating LOEs spread out in a vacuum chamber to rapidly evaporate additives added to an optical adhesive according to embodiments of the present disclosure. FIG. 20 is a schematic diagram of a flexible vessel having a staggered stack similar to FIG. 14, but in which the stack is topped off at the top and bottom of a high-rigidity plate to provide structural support to the stack under high pressure. FIG. 21 is a flowchart of a method for bonding transparent plates and selectively manufacturing one or more LOEs from the bonded plates, according to embodiments of the present disclosure. Specific details for implementing the invention

[0036] Embodiments of the present disclosure provide methods and arrangements for bonding transparent plates and for manufacturing light-guided optical elements (LOEs) from bonded transparent plates.

[0037] The principles of the methods and arrangements according to the present disclosure can be better understood by referring to the accompanying drawings.

[0038] Before describing at least one embodiment of the present disclosure in detail, it should be understood that the present disclosure is not necessarily limited to the application of details regarding the structure and arrangement of configurations and / or methods described in the following description and / or illustrated in the drawings and / or examples. The embodiments of the present disclosure may be implemented or performed in various ways, or other embodiments are possible. Initially, throughout this specification, references are made to directions such as left and right, top and bottom, upper and lower, etc. These directional references are merely illustrative and are used only for ease of presentation and refer to any direction as illustrated in the drawings.

[0039] Embodiments according to the first aspect of the present disclosure provide a method for bonding transparent plates arranged in a staggered stack, which can be used to manufacture a light-guided optical element (LOE). The method comprises various steps (stages), at least some of which are schematically illustrated in FIGS. 3 through 7 and illustrated in the flowchart of FIG. 12. An array and parts thereof for carrying out at least some of the method stages are also schematically illustrated in FIGS. 5a through 7.

[0040] First, looking at FIG. 3, similar to FIG. 2, a plurality of parallel-faced transparent plates (12) are arranged in a staggered stack (10). For clarity, only some of the plates (12) are specified in FIG. 3. The plates can be manufactured from any suitable optically transparent material, typically glass (e.g., BK7), but other transparent materials such as plastic may also be used. The staggering of the transparent plates (12) is to cause a lateral offset to exist between one or more adjacent pairs of transparent plates. The lateral offset between the plates defines one or more plate steps (14) formed from the exposed portions of the parallel faces and the edges of the plates. The staggering of the plates can be performed on groups of plates, for example, as shown in FIG. 3, where four groups of plates are aligned (not staggered) and laterally offset from four adjacent aligned groups of plates. The stack (10) illustrated in FIG. 3 comprises these five aligned thin plate groups and is also depicted as being topped off at the top and bottom by transparent plates (12T and 12B) having a thickness several times that of the other plates (12). Within the context of this specification, the transparent plates (12) are alternatively referred to as “thin plates”, and the transparent plates (12T and 12B) are alternatively referred to as “thick plates”.

[0041] In FIG. 3, the thick plates (12T and 12B) are also laterally offset from adjacent thin plates (12). As a result of the offset of the thick plates combined with the offset of the five aligned thin plate groups, the stack (10) shown in FIG. 3 has a plurality of steps (14), in particular six steps (14), at each end (left end and right end) of the stack (10).

[0042] As an insertion, the offset between adjacent plates typically follows a first dimension (a horizontal dimension in the drawing) that follows the elongation direction of the plates (12). In a second dimension that is perpendicular to the first dimension and in a plane parallel to the plane of the plates' faces (i.e., going in / out in the drawing), there may be no offset (i.e., the plates may be aligned to the second dimension).

[0043] Each of the steps (14) has a height dimension and a width dimension. For most steps, the height dimension, which is vertical in the drawing, generally corresponds to the combined thickness of the aligned group of plates, and the width dimension, which is horizontal in the drawing, generally corresponds to the amount of lateral offset between the two aligned plate groups forming the step. For the top-right and bottom-left steps, the height dimension corresponds to the thickness of the back plates (12T and 12B), respectively, by being combined with part or all of the thickness of the support surface on which the back plates (12T and 12B) are placed. For the top-left and bottom-right steps, the width dimension corresponds to the amount of lateral offset between the back plates (12T and 12B) and their adjacent thin plate groups.

[0044] Generally, staggering between adjacent plates may be uniform or non-uniform. For example, each pair of laterally offset plates does not necessarily have to be offset by the same amount, and the number of plates within each alignment plate group does not necessarily have to be the same. Thus, the steps (14) may have uniform dimensions (uniform width and / or uniform height) across the steps, or different variable dimensions (variable width and / or variable height) for each step. The uniformity or variability of the step dimensions is a function of various parameters including the dimensions of the thin plates (12) (and thick plates (12T and 12B)), the amount of lateral offset between adjacent plate pairs, and / or the number of alignment plates within the group.

[0045] An optical adhesive, which may be a liquid optically curable adhesive, is provided at each of the interfaces (17) between adjacent plates (12) of the stack (10). The interfaces (17) are located between adjacent faces (parallel faces) of the adjacent plates. For clarity, only some of the interfaces (17) are specified in the drawing. Additionally, the optical adhesive at the interface (17) is not shown in FIG. 3, but is schematically illustrated in FIG. 4 for an exemplary one of the interfaces (17). In FIG. 4, the optical adhesive is exaggerated for clarity and is represented by an elongated rectangular dotted pattern fill shape designated as (13). As shown in FIG. 4, the interface (17) is located between the lower face (11L) of the upper plate and the upper face (11U) of the lower plate.

[0046] An adhesive is also provided at the interface between the upper transparent back plate (12T) and its adjacent thin plate (12) and at the interface between the lower transparent back plate (12B) and its adjacent thin plate (12).

[0047] An optical coating is provided on one side (but in certain cases, both sides) at each interface (17) between the thin plates (12). In embodiments where the laminated plates are used to manufacture the LOE, the optical coating is at least a partially reflective coating that provides partially reflective optical properties. However, it should be noted that the methods according to the embodiments described herein may be used to produce other types of optical devices other than LOEs, including optical elements having fully reflective internal surfaces. Accordingly, other types of coatings, such as a fully reflective coating, may be provided at the interface (17) between the plates (12).

[0048] Typically, a stack can be constructed by alternately stacking plates and adhesive. For example, a back plate (12B) can be placed on a surface such as a carrier surface or a carrier plate, and then an optical adhesive can be applied to the exposed surface of the back plate (12B). Then, a first thin plate (12) can be placed on top of the back plate (12B). Then, an optical adhesive is applied to the exposed surface of the first thin plate (12), and then a second thin plate (12) is placed on top of the first thin plate (12) so that the surfaces of the two thin plates in contact with the adhesive form an interface (17). This process can be repeated until the stack (10) is fully constructed, and optionally, the stack is topped off with a back plate (12T). To achieve staggering of the plates, the plates can be placed one on top of another plate with an offset as needed.

[0049] Now, referring to FIGS. 5A and 5B, a stack (10) is positioned between an opposing upper pressurizing member (22) and a lower pressurizing member (24), which are shown as being part of a press device (20). As illustrated, the stack (10) is positioned in the space (26) between the pressurizing members (22 and 24). The stack (10) is positioned such that a thin plate (12) facing the upper (top) of the stack (10) is associated with the upper pressurizing member (22), and a thin plate (12) facing the lower (bottom) of the stack (10) is associated with the lower pressurizing member (24). In an embodiment where the stack is topped off with rear plates (12T and 12B), this arrangement of the stack (10) causes the transparent plate (12T) at the top of the stack (10) to be close to the upper pressure member (22) and the transparent plate (12B) at the bottom of the stack (10) to be close to the lower pressure member (24B).

[0050] The operation of the press device (20) can be achieved through an actuator (28) that may be associated with an upper press member (22) and / or a lower press member (24). The actuator (28) is configured to drive the upper press member (22) and / or the lower press member (24) to move the press members (22 and 24) relative to each other in order to apply pressure to the transparent plate of the stack. The actuator (28) may also be configured to move the upper press member (22) and / or the lower press member (24) to separate the press members (22 and 24) from each other in order to create a space (26) so that the stack can be accommodated in the space (260). The actuator (28) may be, for example, a pneumatic actuator, a hydraulic actuator, or any other suitable actuating device. Alternatively, the actuator (28) may be a user-action mechanical actuator such as a hand crank or lever.

[0051] In the illustrated embodiment, the stack (10) is positioned between block members (34 and 36) configured to contact upper and lower pressure members (22 and 24), respectively. The block members (34 and 36) are dense solid members, for example, dense metal members (e.g., dense metal blocks or anvils). A lower block member (36) is positioned on the exposed pressure surface (25) of the lower pressure member (24). A transparent back plate (12B) is positioned, for example, aligned on the exposed (upper) surface of the block member (36). An upper block member (34) is positioned, for example, aligned on the exposed surface of the transparent back plate (12T).

[0052] In a specific embodiment, the stack (10) may be constructed on a carrier surface located in association with the lower pressurizing member (24) of the press device (20). An example of such a carrier surface is a block member (36). In another embodiment, the stack (10) may be constructed on a carrier surface away from the press device (20), and the carrier surface may be transferred to the lower pressurizing member (24) after the stack (10) is constructed. In yet another embodiment, the stack (10) may be constructed on a carrier surface away from the press device and then transferred to the block member (36).

[0053] As mentioned in the background section, the adhesive layer(s) between the plates (12) should be as thin as possible. For example, in the case of an LOE, the thickness of the adhesive layer(s) is preferably in the range of approximately 0.3 microns to 2 microns. However, the thickness of the adhesive layer(s) may vary depending on the final optical product and / or the optical requirements of the final optical product. The desired thickness of the adhesive layer(s) can be achieved by applying pressure to the plates (12) through upper and lower pressing members. Typically, at least 95% of the adhesive is compressed / expelled from the interface using a pressing technique. However, conventional presses cannot generate uniform pressure across all adhesive layers (interfaces), resulting in non-uniformity of adhesive thickness, which negatively affects the optical performance of the final optical product (e.g., LOE). To generate uniform pressure across each adhesive layer, all areas of the plates must be pressed.

[0054] According to specific embodiments of the first aspect of the present disclosure, a uniform (or approximately uniform) pressure is achieved by using compensation members (42). The compensation member (42) is part of a compensation array (40) that forms a press array together with a press device (20). The compensation member (42) is provided between an upper press member (22) and a lower press member (24) in a stepped configuration (44). The plate steps (14) and the stepped configuration (44) of the compensation member (42) have complementary features so that the compensation member (42) is configured to correspondly compensate for offset(s) between one or more adjacent pairs of transparent plates (12, 12T, and 12B). This correspondence between the plate steps (14) and the stepped configuration (44) of the compensation members (42) allows the contact surfaces of the compensation members (42) to come into contact with the exposed portions of the parallel faces (and preferably the edges) of the plates (12, 12T, and 12B) forming the steps (14), particularly when the press device (20) is operated (i.e., when the pressurizing members (22) apply pressure to the stack (100)). That is, the complementary features between the plate steps (14) and the step-shaped configuration of the compensation members (42) facilitate interlocking or alignment between the compensation members (42) and the stack (10), which allows the compensation members (42) to smoothly interface with the offset portions of the plates (12, 12T, and 12B) and, in particular, fill the voids created by the lateral offset(s) when the press device (20) is operated.

[0055] The stepped configuration of the compensation member (42) can be achieved by staggering the compensation members at different heights and optionally different thicknesses adjacent to each other. In principle, the dimensions of the compensation member (42) (e.g., height and width) can be designed according to the dimensions of the step (14). For example, for a step of uniform height (measured in a direction perpendicular to the surface of the plate (12)) and width, a compensation member having a uniform thickness (width) and a constant height difference may be used. However, it should be noted that a plurality of compensation sub-member groups of smaller widths (the widths of the sub-members may be uniform or non-uniform) may be placed adjacent to each other to form the compensation member, so that the combined total widths of the sub-members correspond to the width of the corresponding step. Similarly, a plurality of compensation sub-member groups of smaller heights (the heights of the sub-members may be uniform or non-uniform) may be placed on top of each other such that the combined total height of the sub-members corresponds to the height of the corresponding step.

[0056] FIG. 6 illustrates an enlarged view of a compensation array (40) spaced apart from a stack (10) to more clearly illustrate the step-shaped configuration (44) of the compensation member (42) and the correspondence between the step-shaped configuration (44) and the plate steps (14). Large block arrows in FIG. 6 are used to indicate how the compensation array (400) and the stack (10) can be interlocked together at the steps (14) and the step-shaped configuration (44). As illustrated, the height difference between adjacent compensation members (vertical direction in the drawing) corresponds to the height of the step (14), and the width of the compensation members (horizontal direction in the drawing) corresponds to the width of the step (14). This stepped configuration (44) allows for a contact surface (43) of the compensation member (42), which is the exposed vertical and horizontal surfaces shown in FIG. 6 to smoothly fill the gap created by the lateral offset(s) by contacting the exposed portions of the parallel faces (and preferably the edges) of the plates (12, 12T, and 12B) forming the step (14) when the press device (20) is operated. As shown in FIG. 6, a portion of one of the contact surfaces (43) of the shortest compensation member (42) is also configured to contact the sides (37 and 39) of the upper and lower block members (34 and 36), respectively. This is because the rear plates (12T and 12B) are aligned with the block members (34 and 36), respectively, to create a portion of the additional step.

[0057] The compensation provided by the compensation member (42) causes the press device (20) to apply uniform pressure across all plates (12, 12T and 12B) within the stack (10). This pressure can be applied by operating the press device (20) to reduce the distance between the press members (22 and 24) so ​​that the press members (22 and 24) provide an inward force on the plates (12) toward the center of the stack (10). Specifically, when the press device (20) is operated, the pressurizing members (22 and 24) apply pressure to the upper and lower block members (34 and 36), respectively, and the upper and lower block members (34 and 36) in turn apply pressure to the transparent back plates (12T and 12B), respectively, and the transparent back plates (12T and 12B) in turn apply pressure to the inner plates (12) of the stack (100), and at the same time, all offset (stepped) regions of the stack (100) are supported by the compensation array (400) (from below and above). The applied pressure is approximately uniform on each adhesive layer, which consequently compresses excess adhesive from the interfaces and redistributes the excess adhesive to the exposed regions of the stack (10) (e.g., outer faces, sides, etc.). The redistributed excess adhesive can then be removed from the exposed regions of the stack (10).

[0058] To achieve a desirable result, the press array is preferably configured to apply pressure such that the pressure on the adhesive between the plates is in the range of approximately 0.2 MPa to 1 MPa. This desirable pressure range compresses a significant amount of adhesive (more than 95%) from the interface between the plates to achieve a suitably thin adhesive layer without damaging the plates (e.g., cracking or destruction). Typically, a pressure (load) in the range of approximately 140 kilogram-force and 700 kilogram-force (for plates with interface dimensions of approximately 70 mm x 100 mm) will achieve the pressure required to sufficiently thin the adhesive layer without damaging the plates.

[0059] The compensation member (42) is preferably a member in the shape of a rectangular cuboid and is composed of a material that is sufficiently dense and compact to apply appropriate pressure to the plate, typically a metal material. Examples of suitable metal materials in which the compensation member (42) may be formed include, but are not limited to, titanium, cast iron, stainless steel (e.g., Grade 410). In certain embodiments, the compensation member (42) and the block members (34 and 36) are composed of the same material. In certain embodiments, the contact surface (43) of the compensation member (42) is formed of a polished glass plate that is bonded to or otherwise attached to the compensation member (42). The compensation member (42) and the polished glass plate forming the contact surface (43) preferably have similar coefficients of thermal expansion.

[0060] In the illustrated embodiment, there are two sets of compensation members (42), one of which is located at each end of the stack (10). This is due to the staggering of the stack, which creates a set of steps in the two end regions of the stack (i.e., each step at one end of the stack has a stack corresponding to the other end of the stack). The first set of compensation members (left side of the related drawing) is deployed in association with the lower pressure member (22), and the second set of compensation members (right side of the related drawing) is deployed in association with the upper pressure member (24). The first set of compensation members (42) is located in the first (left) end region of the stack (10) (associated therewith) and compensates for the offset between one or more pairs of adjacent plates (12, 12T and 12B) in the left end region of the stack (10). A second set of compensation members (42) is located in the second (right) end region of the stack (10) (associated therewith) and compensates for an offset between one or more pairs of adjacent plates (12, 12T and 12B) in the right end region of the stack (10).

[0061] In certain embodiments, part or all of the compensation member (42) may have an adjustable height measured along a dimension perpendicular to the parallel planes of the plates (12) of the stack. Adjustment of the height of the compensation member may provide additional control of the pressure applied by the compensation member. Control of the height adjustment may be provided by an actuator (48), which may be a pneumatic actuator, a hydraulic actuator, or any other suitable operating mechanism. In the embodiments illustrated in FIGS. 5a and 5b, each compensation member (42) has an associated actuator that is height-adjustable and implemented as a pneumatically driven piston. This allows the pressure applied by each compensation member to be controlled independently. The actuator (28), as well as the actuator (48), may be electrically connected to a computerized control system (not shown) to enable computerized control of the operating mechanism.

[0062] FIG. 7 illustrates another embodiment in which a pair of insulating members (50 and 52) are deployed. The insulating members (50 and 52) increase the uniformity of pressure applied to each of the block members (34 and 36). Between the upper block member (34) and the upper pressurizing member (22), an upper insulating member (50) is deployed, which can be implemented as a cushion, for example, an air cushion. The deployment of the upper insulating member (50) can be achieved by attaching the upper insulating member (50) to the pressurizing surface (23) of the upper pressurizing member (22), for example, through an adhesive bond. The upper insulating member (50) can be positioned so that during the operation of the press device (20), a portion of the insulating member (50) comes into contact with most of and preferably the entire upper surface area (35) of the upper block member (34). In exemplary embodiments where the compensation members do not have height-control adjustment, it is desirable that a portion of the upper insulating member (50) also contacts most of and more preferably the entire upper surface area (45) of the adjacent (right) compensation members during the operation of the press device (20).

[0063] The lower insulating member (52) is positioned between the lower block member (36) and the lower pressurizing member (24) and may be implemented as a cushion (e.g., an air cushion). The insulating member (52) may be bonded to the pressurizing surface (25) of the lower pressurizing member (24), for example, through adhesive bonding. The lower insulating member (52) may be positioned relative to the lower block member (36) and the adjacent (left) compensation member in the same or similar manner as the positioning of the upper insulating member (50) relative to the upper block member (34) and the right compensation member.

[0064] The insulating member may also be placed on the contact surface of the compensating member (42) to provide insulation between the compensating member (42) and the plates (12) in order to increase the uniformity of pressure on the plates (12) in the area of ​​the step (14).

[0065] Although the embodiment illustrated in FIG. 7 is shown without height adjustment control (e.g., actuator (48)) of the compensation member (42), it should be easily apparent that the compensation member (42) in the embodiment of FIG. 7 may also be provided with adjustable height and height adjustment control.

[0066] According to a specific embodiment, after the staggered stack (10) of plates (12) is successfully pressed using the techniques described above, at least a portion (preferably most, though not all) of the excess adhesive redistributed (i.e., pressed from the interface) to the exposed area (e.g., outer face, side, etc.) of the stack (10) can be removed from the exposed area. Subsequently, the remaining optical adhesive at the interface (17) can be solidified (cured) using, for example, UV curing or thermal curing, so that the stack (10) becomes a bonded stack.

[0067] In certain embodiments, the bonded stack may then be further processed, for example, to produce one or more LOEs by slicing the stack along a series of parallel cutting planes inclined obliquely to the faces of the plates of the stack (e.g., as illustrated in FIG. 2). Then, the LOEs may be polished on the main outer surfaces created at the cutting planes. Optionally, one or more of the LOEs extracted from the bonded stack may be further sliced ​​along cutting planes perpendicular to the main outer surfaces to cut the LOEs into smaller / shorter LOEs. FIG. 8 illustrates one such exemplary LOE designated as (60). The LOE (60) has a pair of mutually parallel main outer surfaces (62) created by cutting the bonded stack at a pair of parallel cutting planes, and a plurality of mutually parallel partial reflective inner surfaces (facets) (64) formed from interfaces (17) (provided with a partial reflective coating) inclined obliquely to the main outer surfaces (62).

[0068] As another non-limiting example of further processing of a bonding stack, the bonding stack may be cut as part of a two-dimensional (2D) expanded LOE manufacturing process. These 2D expanded LOEs include two aperture expanded regions, each having a set of mutually parallel facets that are not parallel to each other. Details of an exemplary 2D expanded LOE may be found, for example, in the generally owned U.S. Patent No. 10,739,512. By one exemplary use of a bonding stack to produce a 2D expanded LOE, the bonding stack may be cut along two planes to form an optical block having a plurality of partial reflection facets (formed from an interface (17)) that can be used to form a first aperture expanded region of the 2D LOE (represented as region (16) in the aforementioned patent).

[0069] In an embodiment where the coating is a fully reflective coating, slicing the bonding stack along parallel cutting planes produces one or more substrates, each substrate having a pair of mutually parallel main outer surfaces and a plurality of mutually parallel fully reflective inner surfaces inclined obliquely with respect to the main outer surfaces. In these embodiments, one or more of the substrates may be further sliced ​​along a series of parallel cutting planes in which the cutting planes are spaced apart such that one or more of the substrates are perpendicular to the main outer surfaces and each fully reflective inner surface is bounded by a pair of cutting planes. Such slicing along the series of parallel cutting planes cuts the substrates into smaller substrates, each of which has a single fully reflective inner surface embedded therein.

[0070] Note that while the illustrated embodiments show multiple compensation members subdivided into two sets of compensation members (each set itself has multiple compensation members), the arrangement of these compensation members is based on the parameters (e.g., the number of steps and the dimensions of the steps) of the non-limiting exemplary staggered stack (10) illustrated in FIG. 3. In principle, for any staggered stack configuration, a corresponding suitable arrangement of compensation members can be deployed to provide compensation for the offsets (steps) of the staggered stack.

[0071] Some extreme examples of staggered stack configurations are illustrated in FIGS. 9 through 11. First, looking at FIG. 9, a staggered stack configuration consisting only of pairs of thin plates (12) offset from each other is shown, in which the plates (12T and 12B) are provided without offset so that a single step (14) is formed at each end of the stack. In this configuration, a single compensation member may be deployed at each end of the stack to compensate for the single step. The compensation member at the left end of the stack may be compensated by providing pressure from below, and the compensation member at the right end of the stack may be compensated by providing pressure from above.

[0072] Another, more extreme example is illustrated in FIG. 10. In this specification, the staggered stack configuration may consist only of pairs of thin plates of unequal lengths, with one of the plates overhanging the other plate at both ends of the stack. In this specification, the plates (12T and 12B) are provided without offset so that a single step (14) is formed at each end of the stack, but in contrast to the steps in the configuration of FIG. 9, the steps in the configuration of FIG. 10 have the same orientation. In this configuration, a single compensation member may be deployed at each end of the stack to compensate for the single step. The compensation member at the left end of the stack may be compensated by providing pressure from below, and the compensation member at the right end of the stack may also be compensated by providing pressure from below.

[0073] A much more extreme example of a staggered stack configuration is illustrated in FIG. 11. Here, the stack consists only of pairs (12) of unequal lengths, one of the sheets overhangs the other sheet only at the first (left) end of the stack. At the other (right) end of the stack, the sheets (12) are aligned. This results in the formation of a single step (14) located at the left end of the stack. In this configuration, a single compensating member may be deployed at the left end of the stack to compensate for the single step by applying pressure from below. No compensating member is required at the right end of the stack.

[0074] Now, referring to FIG. 12, a flowchart of a process (method) (1200) having a plurality of stages for bonding transparent plates and selectively manufacturing one or more LOEs from the bonded plates, according to embodiments of the first aspect of the above-described disclosure, is shown. Refer also to FIG. 3 through 8.

[0075] In stage (1202), a plurality of parallel-faced transparent plates (12) are arranged in a staggered stack (10), having a lateral offset between one or more adjacent pairs of transparent plates (12) to define one or more plate steps (14). As part of stage (1202) or as part of a separate stage, an optical adhesive (13) is provided at the interface (17) between adjacent transparent plates (12, 12T, and 12B) of the stack (100). As part of stage (1202) or as part of a separate stage, the staggered stack (10) is placed between pairs of pressing members (22 and 24) of the press device (20) as described above. An optical coating (e.g., a partial reflective coating) is provided on one side (or in some cases, both sides) at each of the interfaces (17) between the thin plates (12). It should be noted that providing an optical coating to the required surfaces of the plates (12) is typically performed before the execution of the stage (1202), but can also be performed during the construction of the stack and can be performed using any suitable plate coating technique known in the art.

[0076] In the stage (1204), a plurality of compensation members (42) are provided between the pressurizing members (22 and 24). The compensation member (42) is a stepped configuration (44), and the plate steps (14) and the stepped configuration (44) are configured correspondingly so that the compensation member (42) compensates for a lateral offset between one or more pairs of adjacent transparent plates (12).

[0077] It will be understood that the stages (1202 and 1204) may be performed simultaneously or concurrently, or in a different order than illustrated in FIG. 12. For example, the compensation member (42) may be provided before the plates (12) are arranged in a stack (10). In a particular embodiment, the compensation member (42) may be part of the press device (20).

[0078] In stage (1206), as described above, pressure is applied to the plates (12, 12T and 12B) through the pressurizing members (22 and 24), for example, through the operation of the press device (20).

[0079] In stage (1208), the optical adhesive is solidified, for example, through UV or thermal curing, so that the pressurized stack becomes a bonded stack. Solidification may be performed before the pressurized stack (10) is removed from between the pressurized members (22 and 24), or after the pressurized stack is removed from between the pressurized members (22 and 24).

[0080] At stage (1210), the bonding stack (10) may be further processed, for example, by cutting the bonding stack (10) along parallel cutting planes inclined obliquely to the faces of the plates (12) to create one or more LOEs (60) in LOE manufacturing processing, for example, or by trimming the bonding stack (10) to form an optical block having internal facets for use in 2D LOE manufacturing. Further additional processing steps may include polishing steps, for example, polishing the surfaces of the bonding stack or the surfaces of the LOE(s) extracted from the bonding stack or the surfaces of the optical block extracted from the bonding stack.

[0081] As discussed in the background section, in order for optical products composed of bonded transparent product stacks to have optimal mechanical and optical properties, the adhesive layer between the plates must be as thin as possible. One method to achieve thinning of the adhesive layers is to apply pressure to the stack, as discussed above. However, the pressure must be applied without twisting or deformation of the plates, particularly at the edges of the plates. The following sections of this specification provide embodiments according to a second aspect of the present disclosure, which provide another method for bonding transparent plates that can be used to manufacture light-guided optical elements (LOE). The method comprises, among other things, a step for applying pressure without twisting or deforming the plates. At least some of the steps of the method are schematically illustrated in FIGS. 13 through 19 and are illustrated in the flowchart of FIG. 20. An arrangement for carrying out at least some of the method steps is also schematically illustrated in FIGS. 13 through 19.

[0082] First, referring to FIG. 13, a plurality of parallel-faced transparent (thin) plates (12) are arranged in a stack (70). Although the stack (70) is depicted as a staggered stack in which each single thin plate is offset relative to its neighboring plate, the methods according to this set of embodiments may be used for more complex staggered stack configurations, including configurations in which the staggering is on a plurality of groups of plates (e.g., as illustrated in FIG. 3) and there are back plates that top off the stack (at the top and bottom). Additionally, the methods according to this set of embodiments may be used for less complex stack configurations, such as the configurations illustrated in FIG. 9 through 11. Furthermore, the methods according to this set of embodiments may be used for non-staggered stacks of plates.

[0083] Similar to the embodiment according to the first aspect of the present disclosure, an optical adhesive, which may be a liquid optically curable adhesive, is provided at each of the interfaces (17) between adjacent sheets (12) of the stack (70).

[0084] The adhesive layer is exaggerated for clarity in FIG. 13 and is represented by an elongated rectangular dotted pattern filling shape designated as (13) in the drawing. In an embodiment where laminated plates are used to manufacture the LOE, at least a partially reflective coating providing partially reflective optical properties is provided on one surface at each of the interfaces (17). However, it should be noted that the bonding methods described herein may be used to produce optical devices of other types other than LOEs, including optical elements having fully reflective inner surfaces. Accordingly, other types of coatings, such as a fully reflective coating, may be provided at the interfaces (17).

[0085] As illustrated in FIG. 14, the stack (70) may be placed inside a flexible container (80) having a side wall (84) and an opening (82) within the side wall (84) (typically a small opening whose size is exaggerated in the drawing for clarity of the drawing). The inner surface of the side wall (84) defines the internal volume (86) of the container (80), into which the stack (70) may be placed. In certain embodiments, the inner surface of the side wall (84) may be uneven or grooved (i.e., may have uneven areas / zones or may have grooves in one or more areas / zones of the inner surface).

[0086] To apply pressure to the stack, gas (typically air) inside the internal volume (86) is removed (sucked) from the container (80) through the opening (82). This gas removal can be achieved, for example, by using a gas removal mechanism (89) that forms a pressure array with the container (80). The gas removal mechanism (89) can be implemented as a vacuum or suction pump mechanism fluidly coupled to the opening (82). The gas removal mechanism (89) can create a temporary seal of the opening (82) during the gas removal process. The removal of gas (the flow of gas represented by the thick black arrow in FIG. 14) causes the size of the internal volume (86) to decrease and causes the container (80) (i.e., the side wall (84)) to deform around the stack (70) as illustrated in FIG. 15. This pressure deformation of the container (80) (sidewall (84)) around the stack (70) applies pressure applied to the sides of the stack (70) and creates differential pressures in the regions (88) around the stack (70) within the container (80) (within the internal volume (86)). These applied pressures and differential pressures cause excess adhesive (13') from the interfaces (17) between adjacent plates (12) to be redistributed to the regions (88). In a specific embodiment, excess adhesive may also accumulate in uneven or grooved regions / areas of the inner surface of the sidewall (84).

[0087] More specifically, and with reference to FIG. 15, most of the outer surface area of ​​the vessel (80) is pushed inward by external air pressure during the gas removal process (and optionally reinforced by external pressure applied from the outside). The flow of gas from the opening (82) is represented in the drawing by thick black arrows, and the pushing of the outer surface area inward is represented in the drawing by large block arrows. The pushing of the outer surface area inward applies pressure applied to all sides of the stack (70). The characteristics of the vessel sidewalls (84) cause zones (88) to be formed within the vessel (80) when gas is removed from the inner volume (86) (i.e., when the outer surface area is pushed inward). These zones (88) are in the form of pockets (or folds or creases) of small inner volume combined by the deformed parts of the sidewalls (84). These pocket areas (88) formed in small areas around the stack (70), for example, close to some of the steps (defined by offsets between the plates) and / or close to the top and / or bottom faces of the stack (70), have lower pressure in the small areas around the stack (70), which consequently causes excess adhesive (13') to be compressed between the plates (12) (i.e., from the interfaces) to fill the internal volumes of the areas (88).

[0088] During this process, approximately uniform pressure is applied to all sides of the stack (70) to relieve distortion at the edges of the plates (12). In most practical cases, no distortion, or a negligible amount of distortion, is expected at the edges of the plates (12).

[0089] To achieve a desirable result, the approximately uniform pressure applied to the stack (70) is preferably such that the pressure on the adhesive between the plates is in the range of approximately 0.2 MPa to 1 MPa, which can be achieved by providing the plates with a load force in the range of approximately 140 kilogram-force to 700 kilogram-force (for plates with an interfacial dimension of approximately 70 mm to 100 mm).

[0090] In a specific embodiment, the vessel (80) is heated while deforming under pressure around the stack (70), which advantageously thins the adhesive at the interface between the plates, thereby increasing the flow rate of excess adhesive from the interface during the pressure application process. The temperature at which the vessel (80) is heated can be selected so that sufficient thinning of the adhesive is achieved. This temperature is typically in the range of approximately 60°C to 80°C (depending on the type of adhesive). The vessel (80) may be heated using any suitable mechanism or heating array. In one non-limiting example, an autoclave is used to apply both heat and external pressure to the vessel (80). In another non-limiting example, the vessel (80) may be placed in a water bath, and an immersion circulation device may be used to heat the water temperature and the vessel (80) accordingly. Autoclaves and immersion circulation may be particularly advantageous when precise temperature control is required. As another non-limiting example, a heat source such as a heat lamp may be employed to heat the container (80).

[0091] In a specific embodiment, preferably while the vessel (80) is heated, an external pressure may be applied in combination with the pressure applied through the gas removal process.

[0092] The container (80) may be implemented, for example, as a tube or bladder having flexible but preferably semi-rigid sidewalls (84). The sidewalls (84) must have material properties and an appropriate thickness that enable the formation of regions (88) when the sidewalls (84) deform around the stack (70). In particular, the sidewalls (84) must be sufficiently flexible to deform around the stack and at the same time sufficiently rigid to induce the formation of regions (88). The properties of the sidewalls (84) preferably also provide uneven or grooved regions of the inner surface to the sidewalls (84). Certain types of thermoplastic plastics provide suitable properties (including thermoforming with excellent transparency). Examples of suitable thermoplastic materials in which the sidewalls (84) of the container (80) can be formed include, but are not limited to, polyethylene (PET), polypropylene (PP), etc. Preferably, the sidewall (84) has a thickness in the range of approximately 0.1 mm to 0.6 mm.

[0093] Now, referring to FIG. 16, in a specific embodiment, after pressure is applied and excess adhesive (13') is successfully redistributed into area (88) (and optionally also an uneven or grooved area / zone of the inner surface of the sidewall (84), the vessel (80) may be expanded by introducing gas (e.g., air) into the vessel (80), for example, through an opening (82). In a specific embodiment, a gas removal mechanism (89) may also be configured to introduce gas into the vessel (82). In another embodiment, a separate expansion mechanism, such as a pressurized gas tank having a control-release valve connected to an output nozzle, may be used. The flow of gas into the vessel (80) is indicated in the drawing by a thick black arrow. The introduction of gas causes the sidewall (84) to expand, thereby increasing the size of the internal volume (86). Now, at least some (preferably most, though not all) of the excess adhesive (13') attached to the inner surface of the side wall (84) and / or the outer / exposed surface of the plates (12) can be removed.

[0094] To achieve effective plate stacking with minimal excess adhesive between the plates, the stages of removing gas from the container, expanding the container, and removing excess adhesive may be repeated as needed (until a stopping condition is satisfied). FIG. 17 illustrates the stack (70) after removing gas from the container, expanding the container, and removing excess adhesive, which results in minimal adhesive at the interface (17) between the plates (12).

[0095] After pressurizing the stack, the optical adhesive remaining at the interface (17) can be solidified (cured) using, for example, UV curing or heat curing, so that the stack (70) becomes a bonded stack. In certain embodiments, the adhesive solidifies before the expansion of the container (80) (i.e., while the container is still under pressurization). In certain embodiments, the bonded stack may then be further processed to manufacture one or more LOEs, for example, by slicing the stack (70) along oblique parallel cutting planes (92) with respect to the plate faces as shown in FIG. 18, or may be processed as part of 2D expanded LOE manufacturing processes, similar to those described in the embodiments according to the first aspect. Note that the techniques described above with reference to FIG. 15 and FIG. 16 may be used with LOEs instead of plates to form a bonded stack of LOEs. A bonded stack of these LOEs can be used in 2D extended LOE manufacturing processes, for example, as described in the commonly owned U.S. Patent No. 11,886,008. In these embodiments, each plate, as an LOE, has a plurality of mutually parallel partial-reflective internal surfaces inclined obliquely with respect to the parallel faces of the plate.

[0096] According to certain embodiments, the density of the adhesive layers provided at the interfaces (17) may be reduced (thinning) prior to the pressure application step to reduce the viscosity of the adhesive at the interfaces. This can preferably be achieved by diluting the adhesive with an additive that may be a solvent (diluent) before providing the adhesive to the surfaces of the plates. The reduced adhesive viscosity increases the flow rate of excess adhesive from the interfaces during the pressure application process, which can reduce the total pressure required to sufficiently redistribute the adhesive to the regions (88).

[0097] Subsequently, the solvent within the adhesive may be evaporated as part of further processing of the stack. Evaporation of the solvent may be performed at the stack-level or the slice-level, but there are advantages to performing evaporation at the slice-level. Specifically, because the surface area of ​​the slices is substantially larger than the surface area of ​​the stack, solvent evaporation at the slice-level is significantly faster. To accelerate solvent evaporation, the slices (or stack) may be placed inside a vacuum chamber. FIG. 19 illustrates a plurality of slices (94) extracted from, for example, a stack (70), placed inside a vacuum chamber (100). The evaporation of the solvent is indicated by a curved arrow in FIG. 19.

[0098] After the evaporation of the solvent, additional solidification of the adhesive may be considered because the adhesive is more sensitive to chemical bonding in the absence of the solvent.

[0099] Although optional steps of diluting the adhesive with an additive (e.g., a solvent) and evaporating the additive have been described in the context of the embodiments according to the second aspect of the present disclosure, it should be understood that these optional steps are also applicable for use with the embodiments according to the first aspect as well as with conventional LOE manufacturing processes.

[0100] In the configuration illustrated in FIG. 14, pressure applied to the corners of the staggered stack (70) can bend the sheets (12) at the top and bottom of the stack and deform the stack due to the lack of symmetry of the stack (i.e., due to the staggered plate structure). To mitigate the deformation of the stack under pressure, the stack can be topped off at the top and bottom with high-rigidity plates (i.e., plates having sufficient rigidity to resist bending of the sheets (12). FIG. 20 schematically illustrates this embodiment in which the stack (70) is topped off at the top and bottom with additional plates (12S) having high rigidity. These plates (12S) have sufficient rigidity to resist bending of the sheets (12), thereby improving the flatness of the entire stack structure under pressure.

[0101] Now, referring to FIG. 21, a flowchart of a process (method) (2100) having a plurality of stages for bonding transparent plates and selectively manufacturing LOE from the bonded plates according to the second embodiment of the present disclosure described above is illustrated. Refer also to FIG. 13 through 20.

[0102] In an optional stage (2102), the density of the optical adhesive is reduced by diluting the adhesive with an additive (e.g., a solvent) to reduce the viscosity of the adhesive.

[0103] In stage (2104), a plurality of parallel-faced transparent plates (12) are arranged in a stack (70), which may be a staggered stack having a lateral offset between one or more adjacent pairs of transparent plates (12) to define one or more plate steps. As part of stage (2104) or as part of a separate stage, an optical adhesive (13) is applied to the interface (17) between adjacent transparent plates (12) of the stack (70). An optical coating (e.g., a partial reflective coating) is also applied to one side (or in some cases, both sides) at each interface (17). It should be noted that applying the optical coating to the required sides of the plates (12) is typically performed before the execution of stage (2104) and can be performed using any suitable plate coating technique known in the art.

[0104] In stage (2106), the staggered stack (70) is placed in a flexible container (80) having an opening (82).

[0105] In stage (2108), gas is removed from the container (80) through the opening (82), thereby causing the container (80) to deform around the stack, applying pressure to the side of the stack and creating a differential pressure in the area (88) around the stack (70) within the container (80). The applied pressure and differential pressure cause excess adhesive from the interfaces (17) to be redistributed to the areas (88).

[0106] In stage (2110), the container (80) is expanded, and excess adhesive is removed from the stack and / or the inner surface of the container sidewall.

[0107] Optionally, the stages (2108 and 2110) can be repeated as needed, as indicated by the feedback arrow (2111).

[0108] In stage (2112), the optical adhesive is solidified, for example, through UV or heat curing, so that the stack becomes a bonded stack. As discussed above, this stage is preferably performed while the container is deformed around the container (80) (i.e., immediately after the execution of stage (2108)).

[0109] In stage (2114), the bonding stack may be further processed. This is represented in FIG. 20, for example, as part of the LOE manufacturing process, as a slicing stage for extracting slices (e.g., as shown in FIG. 18). However, note that other processing stages may be executed instead of or in addition to the slicing, including polishing (and optionally additional cutting) and 2D LOE manufacturing processing stages. When stage (2102) is executed, polishing (and additional cutting) is typically performed as a separate subsequent stage, as shown in FIG. 20 as stage (2118).

[0110] When stage (2102) is executed, stage (2116) may also be executed, and the additives in the adhesive are evaporated, for example, by the arrangement of slices in the vacuum chamber (100). As previously mentioned, the evaporation stage may be performed at the stack level instead of the slice level. After stage (2116), grinding (and further cutting) of the slices may be performed at stage (2118). Between stages (2116 and 2118), stage (2112) may be re-executed (i.e., further solidification).

[0111] It should be noted that since the two embodiments of the disclosure presented herein are independent utilities, an embodiment according to the first embodiment and an embodiment according to the second embodiment may each be practiced by their own right. Notwithstanding the foregoing, embodiments using both embodiments together are considered. An embodiment using both embodiments together has specific advantages including reduced processing (bonding) time, because using both embodiments in combination will reduce the amount of time required to achieve the desired thinning of the adhesive layer. These embodiments involve performing at least the following steps: 1) placing a staggered stack of plates (having plate steps) within a flexible container; 2) placing a flexible container (with the stack inside) between a pair of opposing pressure members having a compensation array having compensation members arranged in a stepped configuration corresponding to the steps of the stack; 3) removing gas from the container to apply pressure to the stack; and 4) applying pressure to the plates through the pressure members.

[0112] It will be understood that the step of removing gas from the vessel may be performed before placing the vessel between the pressurizing members. Many variations of such combined embodiments are considered herein, including variations in which the gas removal stage is performed concurrently or simultaneously with the stage of applying pressure through the pressurizing members, and subsequently in certain cases.

[0113] Despite the advantages of such combined embodiments, specific modifications of the first or second embodiments may be required to implement embodiments using both aspects together. For example, the sidewalls of the vessel at the plate steps may alter the geometry of the steps as "shown" by the compensating members. Specifically, the thickness of the sidewalls at the plate steps may lead to non-uniformity of the plate steps and non-planarity of the horizontal and / or vertical portions of the steps. Accordingly, the geometry of the compensating members may require adjustment to account for the sidewalls of the vessel.

[0114] It will be understood that the positioning of plates relative to one another (to achieve offset and / or alignment) can be performed using any suitable optical alignment device(s) / tool(s) that performs suitable optical alignment techniques / methods. Such suitable optical alignment device(s) / tool(s) may include, for example, one or more computerized control devices, one or more computerized processing devices, for example, one or more optical subsystems having one or more light sources, one or more photodetectors / sensors (including optical sensors), one or more optical components (e.g., one or more lenses, one or more foldable optical systems, one or more prisms, etc.), automatic collimators, etc. Details of non-limiting examples of suitable optical alignment devices / device(s) / tool(s) / method(s) that can be used to align the various optical structures described herein may be found in various publications by Lumus Ltd. (Israel), including, for example, International Patent Application No. PCT / IL2021 / 051377 and International Patent Application No. PCT / IL2021 / 051378.

[0115] The present disclosure describes various cutting and slicing stages in which optical structures are cut along cutting lines and / or planes to produce various other optical structures or optical products. In certain embodiments, some or all of the surfaces of these optical structures, including these cutting stages and particularly surfaces resulting from these cutting stages, may be polished, for example, to increase optical quality. In certain embodiments, polishing may be performed as part of or following these cutting stages and prior to subsequent optical joining stages. In the manufacturing methods described above, the cutting or slicing of the various optical structures described herein may be performed by any suitable cutting device / device / tool, as should be understood by those skilled in the art. The polishing of the faces and surfaces of the various optical structures described herein may be performed by any suitable polishing device / device / tool, as should be understood by those skilled in the art.

[0116] The descriptions of the various embodiments of this disclosure are provided for illustrative purposes only, but are not intended to be comprehensive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terms used herein have been chosen to best describe the principles of the invention, practical applications or technical improvements to technologies found in the market, or to enable those skilled in the art to understand the embodiments disclosed herein.

[0117] As used herein, the singular forms “a,” “an,” and “the” include plural references unless the context clearly indicates otherwise.

[0118] The word “exemplary” is used herein to mean “functioning as an example, instance, or example.” Any embodiment described as “exemplary” is not to be interpreted as being preferred or advantageous over other embodiments and / or as excluding the integration of features from other embodiments.

[0119] For clarity, it is understood that specific features of the invention described in the context of individual embodiments may also be provided in combination in a single embodiment. Conversely, for brevity, various features of the invention described in the context of a single embodiment may also be provided individually, in any suitable sub-combination, or as suitable in any other described embodiment of the invention. Specific features described in the context of various embodiments are not considered essential features of such embodiments unless the embodiment would not operate without such elements.

[0120] Although the present invention has been described with its specific embodiments, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to accommodate all such alternatives, modifications, and variations that fall within the spirit and broad scope of the appended claims.

Claims

Claim 1 A method comprising the steps of: arranging a plurality of parallel-faced transparent plates in a stack having a lateral offset between one or more adjacent pairs of transparent plates to define one or more plate steps—wherein an optical adhesive is provided at an interface between adjacent transparent plates of the stack, and a coating is provided on one face of each of the interface, and the stack is disposed between first and second pressing members—; providing a plurality of compensation members in a stepped configuration between the first and second pressing members—wherein the one or more plate steps and the stepped configuration are correspondingly configured so that the compensation members compensate for the offset between the one or more adjacent pairs of transparent plates—; and applying pressure to the plurality of transparent plates through the first and second pressing members. Claim 2 A method according to claim 1, wherein the stepped configuration of the compensation members is provided at least partially by the dimensions of the compensation members. Claim 3 A method according to claim 1, wherein at least some of the compensation members have an adjustable height, and the height is measured along a dimension perpendicular to the parallel planes of the transparent plates. Claim 4 In claim 1, the plurality of compensation members comprises a first compensation member set associated with the first pressurizing member and a second compensation member set associated with the second pressurizing member, a method Claim 5 A method according to claim 1, wherein the plurality of compensation members include a first compensation member set and a second compensation member set, wherein the first compensation member set is associated with a first end region of the stack and compensates for the offset between one or more adjacent pairs of transparent plates in the first end region of the stack, and the second compensation member set is associated with a second end region of the stack and compensates for the offset between one or more adjacent pairs of transparent plates in the second end region of the stack. Claim 6 A method according to claim 1, wherein the stack is positioned between a first pressure member and a second pressure member such that a first block member is positioned between a first pressure member and a first transparent plate at the top of the stack, and a second block member is positioned between a second pressure member and a second transparent plate at the bottom of the stack. Claim 7 A method according to claim 6, further comprising the step of deploying a first insulating member between the first block member and the first pressing member; and the step of deploying a second insulating member between the second block member and the second pressing member. Claim 8 A method according to claim 1, wherein the coating provides partial reflection optical properties. Claim 9 A method according to claim 8, further comprising: a step of solidifying the adhesive so that the stack forms a bonding stack; and a step of cutting the bonding stack along at least two parallel cutting planes inclined obliquely with respect to the faces of the transparent plates to extract one or more parallel-faced substrates having a plurality of mutually parallel partial-reflective inner surfaces formed from the interface. Claim 10 The method of claim 1 further comprises the steps of: placing a stack in a flexible container having an opening; and removing gas from the container through the opening so that the container deforms around the stack, thereby applying pressure on the sides of the stack and generating differential pressures in regions around the stack within the container—the applied pressure and differential pressures cause excess adhesive from the interfaces to be redistributed to said regions. Claim 11 A press array comprising: a first press member; a second press member facing the first press member - the first and second press members are spaced apart to accommodate a stack of parallel-facing transparent plates, the transparent plates are arranged in a stack having a lateral offset between one or more pairs of adjacent transparent plates to define one or more plate steps, an optical adhesive is provided at an interface between adjacent transparent plates of the stack, and a coating is provided on one side of each of the interfaces -; a plurality of compensation members provided in a stepped configuration between the first and second press members - the one or more plate steps and the stepped configuration are configured correspondingly so that the compensation members compensate for the offset between the one or more pairs of adjacent transparent plates -; and an actuator associated with at least one of the first or second press member - the actuator is configured to move at least one of the first or second press member to apply pressure to the plurality of transparent plates. Claim 12 A method comprising the steps of: arranging a plurality of parallel-facing transparent plates in a staggered stack—whereby an optical adhesive is provided at the interfaces between adjacent transparent plates of the stack, and a coating is provided on one side of each of the interfaces—; placing the stack in a flexible container having an opening; and removing gas from the container through the opening so that the container deforms around the stack, thereby applying pressure on the sides of the stack and generating differential pressures in regions around the stack within the container—whereby the applied pressure and differential pressures cause excess adhesive from the interfaces to be redistributed to the regions. Claim 13 A method according to claim 12, further comprising the step of expanding the container; and the step of removing at least a portion of the redistributed excess adhesive. Claim 14 A method according to claim 13, further comprising the step of removing gas from the container, the step of expanding the container, and the step of removing at least some of the redistributed excess adhesive until a stopping condition is satisfied. Claim 15 A method according to claim 12, further comprising the step of thinning the adhesive provided at the interface by diluting the adhesive with an additive to reduce the viscosity of the adhesive. Claim 16 In paragraph 15, the method wherein the above additive comprises a solvent. Claim 17 A method according to claim 15, further comprising: cutting the stack along at least two parallel cutting planes inclined obliquely with respect to the faces of the transparent plates to extract at least one parallel-faced substrate having a plurality of mutually parallel internal surfaces formed from the interfaces; and placing one or more of the at least one substrate in a chamber to rapidly evaporate the solvent. Claim 18 A method according to claim 12, further comprising the step of solidifying the adhesive so that the stack forms a bonded stack. Claim 19 In paragraph 18, the step of solidifying the adhesive is performed while the container is deformed around the stack, a method. Claim 20 In paragraph 12, the method wherein the coating provides partial reflection optical properties. Claim 21 A method according to claim 20, further comprising the step of cutting the stack along at least two parallel cutting planes inclined obliquely with respect to the faces of the transparent plates to extract at least one parallel-faced substrate having a plurality of mutually parallel partial-reflective internal surfaces formed from the interfaces. Claim 22 A method according to claim 12, wherein the applied pressure is substantially uniform on all sides of the stack, thereby mitigating distortion at the edges of the transparent plates. Claim 23 In paragraph 12, the stack is topped off at the top and bottom with high-rigidity plates having sufficient rigidity to resist bending of the remaining plates of the stack under the applied pressure. Claim 24 A method according to claim 12, further comprising the step of heating the container while the container is deformed around the stack. Claim 25 A method according to claim 24, further comprising the step of applying external pressure to the container while the container is receiving the heating. Claim 26 In claim 12, the staggered stack is configured such that a lateral offset exists between one or more adjacent pairs of transparent plates defining one or more plate steps, and the method further comprises the steps of: placing the stack between first and second pressing members; providing a plurality of compensation members in a stepped configuration between the first and second pressing members, wherein the one or more plate steps and the stepped configuration are configured to correspond so that the compensation members compensate for the offset between the one or more adjacent pairs of transparent plates; and applying pressure to the plurality of transparent plates through the first and second pressing members.

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