Waveguide manufactuing process and apparatus for manufacturing waveguides including different interpupillary distance and different eye relief

Abstract

Disclosed herein are systems and methods for recording a waveguide device. In various embodiments a master grating is used to fabricate multiple waveguide devices. Some embodiments a grating is recorded with a holographic exposure system.

Description

WAVEGUIDE MANUFACTUING PROCESS AND APPARATUS FOR MANUFACTURING WAVEGUIDES INCLUDING DIFFERENT INTERPUPILLARY DISTANCE AND DIFFERENT EYE RELIEFCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The current application claims the benefit of U.S. Provisional Patent Application No. 63 / 627,406 entitled “Waveguide Manufacturing Process and Apparatus for Manufacturing Waveguides Including Different Interpupillary Distance and Different Eye Relief’ filed January 31 , 2024. The disclosure of U.S. Provisional Patent Application No. 63 / 627,406 is hereby incorporated by reference in its entirety for all purposes.FIELD OF THE INVENTION

[0002] The present invention generally relates to waveguides and methods for fabricating waveguides and more specifically to waveguide displays containing a grating structure comprising of one or more gratings.BACKGROUND

[0003] Waveguides can be referred to as structures with the capability of confining and guiding waves (i.e., restricting the spatial region in which waves can propagate). One subclass includes optical waveguides, which are structures that can guide electromagnetic waves, typically those in the visible spectrum. Waveguide structures can be designed to control the propagation path of waves using a number of different mechanisms. For example, planar waveguides can be designed to utilize diffraction gratings to diffract and couple incident light into the waveguide structure such that the incoupled light can proceed to travel within the planar structure via total internal reflection (TIR).

[0004] Fabrication of waveguides can include the use of material systems that allow for the recording of holographic optical elements within the waveguides. One class of such material includes polymer dispersed liquid crystal (PDLC) mixtures, which are mixtures containing photopolymerizable monomers and liquid crystals. A further subclass of such mixtures includes holographic polymer dispersed liquid crystal (HPDLC) mixtures.Holographic optical elements, such as volume phase gratings, can be recorded in such a liquid mixture by illuminating the material with two mutually coherent laser beams. During the recording process, the monomers polymerize, and the mixture undergoes a photopolymerization-induced phase separation, creating regions densely populated by liquid crystal micro-droplets, interspersed with regions of clear polymer. The alternating liquid crystal-rich and liquid crystal-depleted regions form the fringe planes of the grating. The resulting grating, which is commonly referred to as a switchable Bragg grating (SBG), has all the properties normally associated with volume or Bragg gratings but with much higher refractive index modulation ranges combined with the ability to electrically tune the grating over a continuous range of diffraction efficiency (the proportion of incident light diffracted into a desired direction). The latter can extend from non-diffracting (cleared) to diffracting with close to 100% efficiency.

[0005] Waveguide optics, such as those described above, can be considered for a range of display and sensor applications. In many applications, waveguides containing one or more grating layers encoding multiple optical functions can be realized using various waveguide architectures and material systems, enabling new innovations in neareye displays for augmented reality (AR) and virtual reality (VR), compact head-up displays (HLIDs) and helmet-mounted displays or head-mounted displays (HMDs) for road transport, aviation, and military applications, and sensors for biometric and laser radar (LIDAR) applications.SUMMARY OF THE INVENTION

[0006] Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the disclosure. A further understanding of the nature and advantages of the present disclosure may be realized by reference to the remaining portions of the specification and the drawings, which forms a part of this disclosure.

[0007] In some embodiments, the techniques described herein relate to a method for recording a waveguide device, the method including the steps of: providing a set of master gratings including an input grating master; a fold grating master, and an output gratingmaster; positioning the set of master gratings in a first configuration; providing a first substrate coated with a first holographic mixture of monomer and inert material; exposing the first holographic mixture through the set of master gratings in the first configuration to form a first grating configuration for providing a first user prescription, the first grating configuration including an input grating formed over a first substrate area with a first clock angle, a fold grating formed over a second substrate area with a second clock angle, and an output grating over a third substrate area with a third clock angle; providing a second substrate coated with a second holographic mixture of monomer and inert material; positioning the set of master gratings in a second configuration; and exposing the second holographic mixture through the set of master gratings in the second configuration to form a second grating configuration for providing a second user prescription, the second grating configuration including an input grating formed over a fourth substrate area with a fourth clock angle; a fold grating formed over a fifth substrate portion with a fifth clock angle and an output grating over a sixth substrate portion with a sixth clock angle.

[0008] In some embodiments, the techniques described herein relate to a method, wherein the first user prescription and the second user prescription each include at least one selected from the group of: interpupillary distance, exit pupil, eye relief and rake angle.

[0009] In some embodiments, the techniques described herein relate to a method, wherein the first and second substrates are components of different waveguide devices.

[0010] In some embodiments, the techniques described herein relate to a method, wherein the first and second substrates are components of the same waveguide device.

[0011] In some embodiments, the techniques described herein relate to a method, wherein the set of master gratings forms at least one multiplexed grating.

[0012] In some embodiments, the techniques described herein relate to a method, wherein the set of master gratings forms at least one overlapping pair of gratings.

[0013] In some embodiments, the techniques described herein relate to a method, wherein the substrate areas over which the gratings are formed are specified for different eye relief.

[0014] In some embodiments, the techniques described herein relate to a method, wherein the substate areas over which the gratings are formed are specified for different eye relief in the range of approximately 15-30mm.

[0015] In some embodiments, the techniques described herein relate to a method, wherein the first grating configuration and a laterally inverted version of the first grating configuration provide eye pieces of a first eyeglass display, wherein the position of the input grating relative to the propagation axis of input light in each eyepiece is such that an IPD of approximately 110 mm is provided, wherein the second grating configuration and a laterally inverted version of the second grating configuration provide eye pieces of a second eyeglass display, wherein the position of the input grating relative to the propagation axis of input light in each eyepiece is such that an IPD of approximately 140 mm is provided.

[0016] In some embodiments, the techniques described herein relate to a method, wherein the steps of recording of the first and second grating configurations involve a holographic phase separation process.

[0017] In some embodiments, the techniques described herein relate to a method, further including at least one step selected from the group of inert component removal, etching of residual polymer, backfilling and coating.

[0018] In some embodiments, the techniques described herein relate to a method, wherein the waveguide device is a display.

[0019] In some embodiments, the techniques described herein relate to a method, wherein at least two of the input grating master, fold grating master, and output grating master have identical Bragg fringe spacings and modulations.

[0020] In some embodiments, the techniques described herein relate to a method, wherein a grating recorded from a master grating has a slant angle determined by the angle of a recording beam incident at the master grating.

[0021] In some embodiments, the techniques described herein relate to a method, wherein the diffraction efficiency across a grating recorded from a master has a spatial variation determined by the spatial variation of the mixture concentration across the substrate.

[0022] In some embodiments, the techniques described herein relate to a holographic exposure system including: a layer of holographic recording material; a first aperture plate including a first aperture and a second aperture located on a plane parallel to the layer of holographic recording material, wherein the first aperture and the second aperture have geometry and center separation distances that vary beam cross sections at the surface of the holographic recording material; a first light source configured to direct a first portion of light through the first aperture as a zero order recording beam and a second portion of light through the second aperture as a first order recording beam, wherein the first portion of light and the second portion of light interfere to form an interference pattern which exposes the layer of holographic recording material to form a first grating of a predefined K-vector within the layer of holographic recording material.

[0023] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the layer of holographic recording material is positioned on a substrate.

[0024] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the layer of holographic recording material is encapsulated between a first substrate and a second substrate.

[0025] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the first substrate supports a mask.

[0026] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the first substrate includes a release layer.

[0027] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the first light source includes one or more mirrors to direct light that forms the first portion of light towards the first aperture and light that forms the second portion of light towards the second aperture.

[0028] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the one or more mirrors includes a single mirror which is mounted on a track that is translatable along a direction parallel to a principal grating direction of the grating formed within the layer of holographic recording material.

[0029] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the one or more mirrors are configured to direct light at predefined angles for recording specific K-vectors.

[0030] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein beams transmitted by the first aperture and the second aperture include skew rays.

[0031] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the first aperture plate is rotatable and / or translatable relative to the layer of holographic recording material.

[0032] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the first aperture plate includes a single film with openings that form the first aperture and the second aperture.

[0033] In some embodiments, the techniques described herein relate to a holographic exposure system, further including a top plate, a middle plate, and a bottom plate, wherein the top plate supports the layer of holographic recording material, the middle plate supports the first aperture plate, and the bottom plate supports the light source.

[0034] In some embodiments, the techniques described herein relate to a holographic exposure system, further including an aperture frame which houses the aperture plate.

[0035] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the aperture frame includes a top aperture frame and a bottom aperture frame which surround the aperture plate.

[0036] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the first aperture plate includes a first slot in which a first post extends through and a second slot in which a second post extends through.

[0037] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the first post and the second post are positioned on opposite portions of the bottom aperture frame.

[0038] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the top aperture frame includes a first hole and a second hole positioned on opposite portions of the top frame.

[0039] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the first post extends through the first hole and cooperates with a first nut to use the top aperture frame to apply pressure to the first aperture plate such that the first aperture plate is held in place between the top aperture frame and the bottom aperture frame.

[0040] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the second post extends through the second hole and cooperates with a second nut to use the top aperture frame to apply pressure to the first aperture plate such that the first aperture plate is held in place between the top aperture frame and the bottom aperture frame.

[0041] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the first slot and the second slot are elongated in an extending direction to allow the first aperture plate to translate along the first slot and the second slot.

[0042] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein aperture frame is positioned in a slot located on a middle plate.

[0043] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the slot is configured to have multiple positions along a first direction in which to accommodate the aperture frame, wherein the first slot and the second slot extend along a second direction, wherein the first direction is different than the second direction.

[0044] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the first direction is substantially perpendicular to the second direction.

[0045] In some embodiments, the techniques described herein relate to a holographic exposure system, further including: a second aperture plate including a third aperture and a fourth aperture located on a plane parallel to the layer of holographic recording material, wherein the third aperture and the fourth aperture have geometry and center separation distances that vary beam cross sections at the surface of the holographic recording material; a second light source configured to direct a third portion of light through the third aperture a zero order recording beam and a fourth portion of light through the fourthaperture as a first order recording beam, wherein the third portion of light and the fourth portion of light interfere to form an interference pattern which exposes the layer of holographic recording material to form a second grating of a predefined K-vector within the layer of holographic recording material.

[0046] In some embodiments, the techniques described herein relate to a holographic exposure system, further including: a third aperture plate including a fifth aperture and a sixth aperture located on a plane parallel to the layer of holographic recording material, wherein the fifth aperture and the sixth aperture have geometry and center separation distances that vary beam cross sections at the surface of the holographic recording material; a third light source configured to direct a fifth portion of light through the fifth aperture a zero order recording beam and a sixth portion of light through the sixth aperture as a first order recording beam, wherein the fifth portion of light and the sixth portion of light interfere to form an interference pattern which exposes the layer of holographic recording material to form a third grating of a predefined K-vector within the layer of holographic recording material.

[0047] In some embodiments, the techniques described herein relate to a holographic exposure system, wherein the first grating includes an input grating, the second grating includes a fold grating, and the third grating includes an output grating.BRIEF DESCRIPTION OF THE FIGURES

[0048] The description will be more fully understood with reference to the following figures, which are presented as embodiments of the invention and should not be construed as a complete recitation of the scope of the invention, wherein:

[0049] Figure 1 illustrates a grating structure comprising multiple gratings to form a waveguide display.

[0050] Figure 2 illustrates a grating structure comprising multiple gratings to form a waveguide display.

[0051] Figure 3 illustrates two grating structures comprising multiple gratings to form a pair of waveguides displays.

[0052] Figure 4 illustrates two grating structures comprising multiple gratings to form a pair of waveguides displays.

[0053] Figure 5 schematically illustrates a cross-sectional view of a waveguide display.

[0054] Figure 6 schematically illustrates a cross-sectional view of a waveguide display.

[0055] Figure 7 schematically illustrates a graph of a waveguide display incorporated into a user device.

[0056] Figure 8 illustrates a process for fabricating a waveguide display.

[0057] Figure 9 illustrates a cross sectional view of a portion of an example waveguide display illustrating output grating size, eye relief (ER), exit pupil (EP), and field of view (FoV).

[0058] Figure 10 schematically illustrates a system for manufacturing waveguide gratings.

[0059] Figure 11 schematically illustrates a three tier system for manufacturing waveguide gratings.

[0060] Figure 12A schematically illustrates a close up view of a middle plate of a three tier system for manufacturing waveguide gratings.

[0061] Figure 12B schematically illustrates a top down view of a middle plate of a three tier system for manufacturing waveguide gratings.

[0062] Figure 13 schematically illustrates a close up view of a top plate of a three tier system for manufacturing waveguide gratings.

[0063] Figures 14A to 14C schematically illustrate an exploded view of an aperture that may be incorporated into a system for manufacturing waveguide gratings.

[0064] Figure 15 schematically illustrates a middle plate without an aperture.

[0065] Figures 16A to 16C illustrate the geometry of the input, output, and fold apertures.

[0066] Figure 17 schematically illustrates an aperture mask.DETAILED DESCRIPTION

[0067] Waveguide displays are manufactured with specific exit pupils, interpupillary distances (IPDs), and eye reliefs. However, different applications may benefit from different exit pupils, IPDs, and / or eye reliefs. Thus, it may be advantageous to be able to customize the exit pupils, the IPDs, and / or eye reliefs of different waveguides. The disclosed techniques include methods and apparatuses for producing waveguidedisplays with different exit pupils, IPDs, and / or eye reliefs. In some examples, the various waveguide displays have a range of different IPDs and / or eye reliefs (ERs) which can be provided using a set of common input, fold and output grating masters, each having a defined Bragg fringe spacing and slant angle. The locations, areas, shapes and clock angles of the recorded gratings may be adjusted prior to exposure to control ER and IPD. The waveguide displays may be near to eye displays. In many embodiments, the above grating configuration parameters may also be used to control the exit pupil. In some embodiments the grating configuration parameters may be used to compensate for rake angles. In some cases, the grating configurations parameters may provide at least partial control of eyeglow.

[0068] The process and apparatus for fabricating multiple holographic waveguide configurations may include using a common set of master gratings. The master gratings may include one or more masters for recording one or more of an input grating, a fold grating, and / or an output grating. The one or more masters may be used to record gratings into one or more holographic recording material layers supported by one or more substrates. For example, a holographic recording layer may be positioned between two substrates. The holographic recording layer may be exposed to create an input grating, a fold grating, and an output grating when an input grating master, a fold grating master, and an output grating master are in a first configuration. The input grating master, the fold grating master, and the output grating master may be reconfigurable into a second configuration different from the first configuration. The input grating master, the fold grating master, and the output grating master may then be utilized to expose a second holographic recording layer for use in the same waveguide, or for use in another waveguide. A given set of master gratings with suitable adjustments (e.g., clock angle) may be used record more than one grating type, depending on the waveguide specification.

[0069] In some embodiments, at least two of the input grating master, the fold grating master, and the output grating master have identical Bragg fringe spacing and modulations. In some embodiments, a grating recorded from a master grating has a slant angle determined by the angle of a recording beam incident at the master grating. In some embodiments, the diffraction efficiency across a grating recorded from a master has aspatial variation determined by the spatial variation of the mixture concentration prior to recording of the grating. In many embodiments, the holographic mixture may be coated using an inkjet printing method. In many embodiments, the spatial concentration variation results from the use of an inkjet bit map specific to the grating application. Various masking techniques may be used to alter the shape and area of gratings for different waveguide applications.

[0070] In some examples, different recording layers may be positioned between different substrates. In some embodiments, the different recording layers include components of different waveguide devices. In many embodiments, the gratings may be recorded onto substrates that are components of the same waveguide device. In many cases, multiple grating layers may be formed on a single substrate. In some embodiments, the gratings may be formed on substrates that are configured with air gaps as part of a single waveguide. In many embodiments, the set of master gratings may be used to form multiplexed gratings. The multiplexed grating may be formed using successive or simultaneous exposures from one or more masters of the gratings to be combined in the recorded multiplexed grating. In some cases, the master could be a multiplexed grating. The master may be subject to the clock angle, area, spatial position adjustments for different waveguide applications.

[0071] In many embodiments, the set of master gratings may be used to form overlapping pairs of gratings with the gratings formed on separate substrates or gratings stacked on a single substrate. For example, different waveguides may each have partial overlap of the fold and output grating. The masters may be configured such that the overlap is provided by first recording the fold grating, removing the fold grating master, introducing the output grating master and recording the overlapping output grating. The latter may be achieved using various processes including applying a substrate over the cured fold grating, coating the substrate and exposing the fold grating using the fold grating master. Alternatively, the cured grating may be coated and exposed. Alternatively, the overlapping gratings may be recorded as multiplexed gratings.

[0072] Turning to the drawings, Fig. 1 is an example of a grating structure 100 recorded onto a substrate 101. The grating structure 100 includes a recorded grating configuration including an input grating 102 for coupling light from an external imageprojector into a total internal reflection (TIR) path inside a waveguide. The input grating 102 has a grating pattern 102A characterized by a Bragg fringe spacing and slant angle (e.g. a grating vector or K-vector). The grating pattern 102A includes a grating vector component 102B in the plane of the substrate 101 which defines a clock angle of the input grating 102. The recorded grating configuration further includes a fold grating 103 with a grating pattern 103A and a clock angle 103B and an output grating 104 with a grating pattern 104A and clock angle 104B.

[0073] Each of the input grating 102, the fold grating 103, and the output grating 104 are fabricated using a set of master gratings including a master input grating, a master fold grating, and a master output grating. The set of master gratings may be in a first configuration when recording the grating structure 100 of Fig. 1. The same set of master gratings may be used to produce different waveguides with different configurations. The master gratings may be rotated from one exposure to another. The grating sizes and orientations change from one design to the other, where the grating apertures are resized and rotated with respect to the master gratings to keep the gratings in a preferred orientation with the respect to the master. In some embodiments, portions of the master may be masking off which may reduce its aperture to create a recorded grating of a specified area / shape. The master may have a shape / area that can accommodate the ranges of gratings required in various waveguide applications (for example, as determined by glasses form factors).

[0074] The set of master gratings may be positioned in different configurations which may include different positioning and / or different clocking. The same master is used for different waveguides. The gratings all rotate together from one exposure to another. The grating sizes and orientations change from one design to the other, wherein the grating apertures are resized and rotated with respect to the master to keep the gratings in a preferred orientation with the respect to the master.

[0075] The slant angles of the master gratings may change which may optimize diffraction efficiency. The slant angles of the master gratings may change by changing the beam angle illumination of the master grating. Aperture changes are usually slightly modified also. The material concentration of the holographic mixture before exposure on the film plane may be modified to change diffraction efficiency. This is implemented withinkjet printing a different bitmap for the constituent material.

[0076] Fig. 2 is an example of a waveguide grating configuration that is fabricated from the same master grating set however in a different configuration from Fig. 1 . The grating fringe spacings and slant angles may remain the same, but the grating locations areas shapes and clock angles have been adjusted. The grating configuration includes an input grating with a grating pattern 112A and a clock angle 112B, a fold grating 113 with a grating pattern 113A and clock angle 113B, and an output grating 114 with a grating pattern 114A and clock angle 114B. The output grating is closer to the top of the waveguide when compared to the configuration of Fig. 1 . Grating areas may be adjusted to provide different eye relief values. Typically, eye reliefs are in the range of approximately 15-30mm to meet a wide range of form factors.

[0077] Fig. 3 is a layout of a waveguide display 120 based on the configuration of Fig. 1. The waveguide display 120 has a left eyepiece including a waveguide substrate 121 supporting an input grating 122, a fold grating 123, and an output grating 124. The waveguide display 120 has a right eyepiece including a waveguide substrate 125 supporting an input grating 126, a fold grating 127, and an output grating 128. In this example, the position of the input grating relative to the propagation axis of input light in each eyepiece is such that an IPD 129 of approximately 110 mm may be provided.

[0078] As discussed above, different configurations may be manufactured using the same set of master gratings. For example, using the same set of master gratings, a wider IPD can be achieved. Fig. 4 is a layout of a waveguide display 130 based on the configuration of Fig. 2. The waveguide display 130 includes a left eyepiece including a waveguide substrate 131 supporting a input grating 132, a fold grating 133, and an output grating 134. The waveguide display further includes a right eyepiece including a waveguide substrate 135 supporting a input grating 136, a fold grating 137, and an output grating 138. In this case an IPD 139 of approximately 140 mm may be provided. Utilizing the same set of master gratings, the implemented techniques may provide a wide range of IPDs. This range of IPDs may accommodate a wide range of temple-to-temple variations for different users.

[0079] For example, for each new waveguide application, the grating clock angle, area, location within the waveguide substrate may be adjusted. The recording beamincidence angle at the masters may be adjusted to control the slant angles. Other process components may include, masks, rotation stages, beam steering optics etc.

[0080] Figs. 5-6 show example schematics waveguide structures to which the above described processes may be applied. Fig. 5 is a cross-sectional view of a waveguide display in accordance with an embodiment of the invention. The waveguide display includes a substrate 141 supporting an input grating 143, a fold grating 142, and an output grating 145. The input grating 143 and the fold grating 142 are on one layer and the output grating 145 are on a separate layer. An isolation material 146, 147 surrounds the output grating 145. The output grating 145 is positioned between a bottom substrate 144 and a top substrate 141 . The output grating 145 at least partially overlaps the input grating 143 and the fold grating 142. The input grating 143 and the fold grating 142 are positioned on the top substrate 141 .

[0081] Fig. 6 is a cross-sectional view of a waveguide display in accordance with an embodiment of the invention. The waveguide display shares many identically labelled features with the waveguide display described in connection with Fig. 5. The description of these features is applicable to this waveguide display and the description will not be repeated. The waveguide display of Fig. 6 only includes a single substrate 151. The output grating 145 is positioned on one surface of the substrate 151 and the input grating 143 and the fold grating 142 are positioned on an opposite surface of the substrate 151. The location of the various grating types within the stacks of Figs. 5-6 may be varied. In some embodiments, the input grating 143, the fold grating 142, and / or the output grating 145 may be a volume phased grating (e.g. a volume Bragg grating) or a surface relief grating (SRG). The SRG may be a deep SRG which may be created using an evacuation process to create an evacuated periodic structure. Examples of EPSs and processes of making EPSs are described in U.S. Pat. App. Pub. No. 2021 / 0063634, filed on Aug. 28, 2020 and U.S. Pat. App. Pub. No. 2022 / 0283376, filed on Mar. 7, 2022 which are hereby incorporated by reference in their entirety. In some examples, the gratings may be formed using a holographic phase separation process. Such processes may further include at least some of the steps of inert component removal, etching of residual polymer, backfilling and coating of the etched structure. In many cases, the inert material used in the recording mixtures is liquid crystal.

[0082] In some embodiments, the field of view of the waveguide display may be 50 degrees diagonal with a luminous efficiency of greater than 400 nits / lumen at the eye box and better that 30% uniformity. The thicknesses of the waveguide stacks shown in Figs. 5-6 may be in the range 1 .5-1 .8 mm.

[0083] FIG. 7 is a graphical representation of the embodiments described in connection with Figs. 3-4. A top waveguide display 702 has a IPD 702a of about 112mm and a bottom waveguide display 704 has a IPD 704a of about 140mm. Each of these waveguide displays may be produced using the same set of master gratings in different configurations. Thus, the process has high flexibility in the number of possible configurations. While these IPDs are illustrated, it is understood that many other IPDs may be produced using the same set of master gratings.

[0084] FIG. 8 is a flow chart of a method of fabricating a waveguide device in accordance with many embodiments. The method 800 includes providing (802) a set of master gratings including an input grating master, a fold grating master, and an output grating master. The method 800 further includes positioning (804) the set of master gratings in a first configuration. The method 800 further includes providing (806) a first substrate coated with a first holographic mixture of a monomer and an inert material. The method 800 further includes exposing (808) the first holographic mixture through the set of master gratings in the first configuration. The exposing may record, using the set of master gratings, a grating configuration including an input grating formed over a first substrate area with a first clock angle; a fold grating formed over a second substrate area with a second clock angle, and an output grating over a third substrate area with a third clock angle. The method 800 further includes positioning (810) the set of master gratings in a second configuration. The method 800 further includes providing (812) a second substrate coated with a second holographic mixture of a monomer and an inert material. The method 800 further includes exposing (814) the second holographic mixture through the set of master gratings in the second configuration. Exposing the second mixture records a second grating configuration for providing a second user prescription using the set of master gratings. The second grating configuration includes an input grating formed over a fourth substrate area with a fourth clock angle; a fold grating formed over a fifth substrate portion with a fifth clock angle; and an output grating over a sixth substrateportion with a sixth clock angle.

[0085] In the case of the first waveguide a process for positioning, rotation, slant angle adjustment (using the recording beam angle), and masking of the gratings may be of similar complexity may be similar to that required in any waveguide process. Advantageously the same masters for recording a different waveguide (with suitable adjustment of position, grating area and clock angle) may result in significant savings in master tooling. The first configuration and second configuration may be separate. For example, they may be used in different eyeglass displays.

[0086] For a given waveguide application, a set of master gratings may be exposed through with a certain clocking, masking, and / or slant angle adjustment grating locations. Depending on the application, the exposure may be done in separate stages. For example, separate recording rigs may be used for recording the input, fold and output gratings onto the substrate. In other embodiments all three master gratings may be set up and illuminated with recording beams one at a time. In yet another set up all three masters may be illuminated at the same time for simultaneous grating exposure. Different exposure techniques may be selected based on process throughput, cost and plant scale, and automation considerations. Examples of different exposure techniques are discussed in U.S. Pat. App. Pub. No. 2019 / 0212588, filed on Nov. 28, 2018, U.S. Pat. App. Pub. No. 2019 / 0212698, filed on Aug. 29, 2018, and U.S. Pat. App. Pub. No. 2019 / 0212588, filed on Nov. 28, 2018, which are hereby incorporated by reference in their entirety.

[0087] Fig. 9 is a cross sectional view of a portion of an example waveguide display illustrating output grating size, eye relief (ER), exit pupil (EP), and field of view (FoV). The portion 820 of the waveguide 821 contains an output grating 822 of dimension D. The propagating TIR rays 823 are diffracted 824 out of the waveguide towards an exit pupil 825 of dimension EP with an eye relief ER. The eye relief is the distance from the last surface of an eyepiece within which the full field of view is visible. The parameters are related by the equation D= EP + 2*ER*tan(FoV / 2). In practice, the determination of eye relief and exit pupil may be trade-offs between the grating size and location of all the gratings in the system and light efficiency, FoV etc.Example Systems for Reconfigurable Manufacturing of Holographic Waveguides

[0088] The present disclosure includes a process for fabricating multiple holographic waveguide configuration using a reconfigurable holographic recording apparatus. A versatile process for fabricating holographic waveguides using reconfigurable free space recording apparatus is described. The apparatus includes variable apertures for control beam cross sections and mirrors mounted on translation and rotation stages for controlling beam directions for recording gratings of defined grating spatial frequencies and K-vectors. Starting from a given waveguide prescription including gratings for input coupling and beam expansion, and outcoupling, different variants of the waveguide for providing FoV, eyebox, eye relief, IPD and tern ple-to-tem pie distance, styling can be provided by making changes to the sizing, position and clocking and positioning of the gratings and the print profiles used in the deposition of the recording material used in the grating recording.

[0089] A master grating may include a recording stack including a layer of holographic recording material for recording gratings of a particular size, shape, clock angle, relative position and a print profile for depositing specified composition, thickness (which may vary spatially) for each grating. The disclosed system is based on the conventional understanding of holographic mastering in which holograms are recorded by contact copying from an amplitude grating master using the diffracted 0thand 1storder diffracted beams.

[0090] Flexible manufacturing may be a process for fabricating holographic waveguides of a range of capabilities by controlling each of: glass shape, beam angles, apertures grating orientation, grating lateral offset, rotation of the substrate with respect to the gratings and printing profiles for depositing of the recording material prescription. A variety of different FoVs for different applications may be provided using a common master. For example, a master designed, for example, for a 30° FoV can also produce a 20° waveguide by resizing the gratings and adjusting the printing profiles.

[0091] The processes for controlling print profiles in the recording of waveguide gratings are described in U.S. Pat. App. Pub. No. 2019 / 0212588, entitled “Systems and Methods for Manufacturing Waveguide Cells” and filed Nov. 28, 2018 which is hereby incorporated by reference in its entirety for all purposes. Different compositions of optical recording material can be deposited over different substrate regions using one or moredeposition heads. Refractive index modulation, average refractive index, birefringence, liquid crystal director alignment, grating layer thickness, and spatial variations of any of these parameters can be controlled at the print head. The flexible manufacture process may be integrated in the high volume waveguide manufacturing processes described in U.S. Pat. App. Pub. No. 2019 / 0212698, entitled “Systems and Methods for High- Throughput Recording of Holographic Gratings in Waveguide Cells” and filed Aug. 29, 2018 which is hereby incorporated by reference in its entirety for all purposes.

[0092] Flexible manufacture offers many benefits in waveguide fabrication. For example, in wearable display applications, waveguides can be tailored to different user head sizes by adjustment of the grating input to output coupler position. The ability to reconfigure the recording beams for different glasses shapes on the exposure plane may be beneficial in different fashion applications. A further benefit of flexible manufacture may be the ability to place the gratings within the display for comfortable viewing, ergonomics, and / or to meet requirements of augmented reality (AR) data presentation. For example, relative vertical positional of the input coupler relative to output coupler may be adjusted. In many cases, gratings can be rotated as a group, while maintaining the clocking alignment of the gratings relative to each other. Various aperture rotations and relative displacements can also be performed as ensemble operations. Eye relief may also be tailored to the needs of specific waveguide display applications in association with aperture rotation, translation, and sizing. In many such applications, a closer eye relief will typically include smaller gratings, which may be provided by aperture resizing and relocation.

[0093] The scope of flexible manufacture may be very broad: the master / master stack as defined above can be easily modified or replaced entirely if needed, mirrors can be repositioned, and apertures can be replaced. In this context the entire fabrication apparatus can be flexible, allowing a manufacturing line to be quickly modified from one master system to a completely different product variant.

[0094] The following description and accompanying drawings disclose a waveguide grating exposure system for waveguide displays. Fig. 10 is a schematic of a system for manufacturing waveguide gratings in accordance with an embodiment of the invention. In the physical exposure module, 3 beams enter the structure (which may be enclosed insheet metal) horizontally, reflect off mirrors, pass thru aperture & waveplate components, and strike the bottom of a glass-stack / master. All mirrors, apertures, and waveplates translate along slots, which correspond to k-vector planes, allowing accommodation of a large range of beam angles.

[0095] The system includes a base plate 1002, a mid-plate 1004, and a top-plate 1006. The mid-plate 1004 is positioned between the base plate 1002 and the top-plate 1006. The base plate 1002 may include a first mirror 1008a, a second mirror 1008b, and a third mirror 1008c. Each of these mirrors 1008a, 1008b, 1008c may be utilized to provide a first beam and a second beam to expose an input grating, an output grating, and a fold grating. The mid-plate 1004 includes a first aperture 1010a, a second aperture 1010b, and a third aperture 1010c. The first aperture 1010a may receive a first beam and a second beam from the first mirror 1008a. The second aperture 1010b may receive a first beam and a second beam from the second mirror 1008b. The third aperture 1010c may receive a first beam and a second beam from the third mirror 1008c. A first waveplate 1012a and a second waveplate 1012b may be positioned in front of one of the first beam or second beam of the first aperture 1010a, the second aperture 1010b, or the third aperture 1010c. For example, the first waveplate 1012a may be positioned in front of the first beam of the first aperture 1010a and the second waveplate 1012b may be positioned in front of the first beam of the second aperture 1010b.

[0096] The top plate 1006 supports a master 1014 which supports a first master grating 1016a, a second master grating 1016b, and a third master grating 1016c. The first mirror 1008a, the first aperture 1010a, and the first master grating 1016a may be associated with the exposure of an input grating. The second mirror 1008b, the second aperture 1010b, and the second master grating 1016b may be associated with the exposure of a fold grating. The third mirror 1008c, the third aperture 1010c, and the third master grating 1016c may be associated with the exposure of an output grating. Each first beam may be first order light and each second beam may be zero order light.

[0097] A substrate supporting a layer of holographic recording material may be positioned over the master 1014 such that the beams that are diffracted through the first master grating 1016a, the second master grating 1016b, and the third master grating 1016c record a first grating, a second grating, and a third grating into the layer ofholographic recording material. The first grating may be an input grating, the second grating may be a fold grating, and a third grating may be an output grating.

[0098] Fig. 11 is an example of a system for manufacturing waveguide gratings in accordance with an embodiment of the invention. As with the system of Fig. 10, the system includes three stacked parallel plates. A top plate 1006 supports a housing containing a recording substrate or cell. A middle plate 1004 supports apertures. A bottom plate 1002 supports the mirror assemblies. The bottom plate supports the illumination optics comprising tiltable mirrors on mounts configured to be linearly translated along tracks formed in the plate.

[0099] Fig. 12A is a close up view of the middle plate 1004 of Fig. 11 . Fig. 12B is a top down view of the middle plate 1004 of Fig. 11. As illustrated the middle plate supports a first aperture 1202a, a second aperture 1202b, and a third aperture 1202c. As discussed below, each of the apertures may translated. In many cases mirrors may be provide above the middle plate 1004. The number, location and tilt angles of the mirrors depend on the waveguide configuration.

[0100] Fig. 13 is an exploded view of the top plate 1006 of Fig. 11. The top plate includes a waveguide grating substrate clamping assembly.

[0101] Fig. 14A illustrates a close up view of an aperture in accordance with an embodiment of the invention. The aperture may be the first aperture 1202a, the second aperture 1202b, and / or the third aperture 1202c of Fig. 11. The aperture includes an aperture film 1402 which may be a replaceable precut aperture lamina. The aperture film 1402 may be positioned between an upper frame 1404 and a lower frame 1406. The geometry of the aperture film 1402 may be computed from the projection of the incident beam by determining the projection coordinates of the exposure beams on the recording material surface using ray tracing software such as ZEMAX or by some other methods. The upper frame 1404 may be held together with the lower frame 1406 by a nut 1408. The nut 1408 may be a thumb nut 1408. Fig. 14B shows the lower portion of the aperture illustrated in Fig. 14A without the upper frame 1404. Fig. 14C is an exploded view of the aperture illustrated in Fig. 14C. As illustrated, the aperture film 1402 may include translation slots 1402a, 1402b. The translation slots 1402a, 1402b may allow the aperture film 1402 to be translated which allows the aperture film 1402 to be moveable. Theaperture film 1402 may be placed onto the lower frame 1406 and the upper frame 1404 replaced such that the aperture film 1402 is free to translate left and right in the completed frame. The aperture film 1402 can translate in the lower frame 1406 and the upper frame 1404 perpendicular to the k-vector to allow for accurate beam placement on the cell. The aperture film 1402 can also be configured for rotational displacement in a plane parallel to the recording material layer. As illustrated, the aperture film 1402 may include two translation slots 1412a, 1412b for enabling linear translation of the film prior to securing the upper frame 1404 and the lower frame 1406. In some embodiments, the translation along the k-vector and can in many cases be used with exposure beams including skew rays to form gratings slanted in more than one plane.

[0102] The aperture film may include a first slot 1412a in which a first post 1410a extends through and a second slot 1412b in which a second post extends through 1410b. The first post 1410a and the second post 1410b are positioned on opposite portions of the lower frame 1406. The upper frame 1404 includes a first hole 1414a and a second hole 1414b positioned on opposite portions of the upper frame 1404.

[0103] The first post 1410a extends through the first hole 1414a and cooperates with a first nut 1408 to use the upper frame 1404 to apply pressure to the aperture film 1402 such that the aperture film 1402 is held in place between the upper frame 1404 and the lower frame 1406. The second post 1410b extends through the second hole 1414b and cooperates with a second nut to use the upper frame 1404 to apply pressure to the aperture film 1402 such that the aperture film 1402 is held in place between the upper frame 1404 and the lower frame 1406. The first slot 1412a and the second slot 1412b are elongated in an extending direction to allow the aperture film 1402 to translate along the extending direction of the first slot 1412a and the second slot 1412b.

[0104] The aperture is positioned in a slot located on a middle plate. The slot is configured to have multiple positions along a first direction in which to accommodate the aperture. The first slot 1412a and the second slot 1412b extend along a second direction. The first direction is different than the second direction. The first direction may be substantially perpendicular to the second direction.

[0105] Fig. 15 is a plan view of an unpopulated aperture plate in accordance with an embodiment of the invention. The unpopulated aperture plate includes an input slot 1501for placing an aperture for exposing the input grating. The unpopulated aperture plate includes an output slot 1502 for placing an aperture for exposing the output grating. The unpopulated aperture plate includes a fold slot 1503 for placing an aperture for exposing the fold grating. The unpopulated aperture plate may be on the middle plate. The slots are configured to align with principal grating directions of the input, fold and output gratings. In many cases, the slots are aligned to run along each grating’s k-vector. This allows considerable flexibility in the placement and translation of input, fold, and output aperture films to accommodate various incident beam angles. In some embodiments, all mirrors may be mounted on bases that translate in slots along the grating k-vector on the bottom baseplate for further fabrication flexibility.

[0106] During alignment, the assembled aperture frame can be placed in the appropriate slot and translated along the slot until both zeroth and first order beams can be observed on the intended grating region on recording material. In some embodiments, one of the two apertures may be blocked to observe if both zeroth and first order beams are incident on the intended region.

[0107] The grating shape and configuration which are specific to a particular grating prescription may be determined accurately using coordinates calculated using ray tracking and / or CAD projection or using some other means. Rays are positioned so that a zeroth and first order pair intersects at the holographic recording plane at the vertices of the nominal grating locations for each of the input, output, and fold gratings.

[0108] Two sets of rays may be provided for each of the input, fold, and output gratings. Rays are positioned so that a zeroth and first order pair intersects at the exposure plane at the vertices of the nominal grating locations. The calculation takes into account the intended incident angle and target grating locations.

[0109] Beams that are incident on the recording material directly from a mirror on the baseplate have center separation distances that can be determined directly using ray tracing.

[0110] Beams that are incident on a mirror above the middle plate may experience compression in the grating k-vector direction that depends on the cosine of the incident angle beam. This may apply in the case of fold grating recording. Using the above described methods, apertures may be designed according to the desired modelparameters and the mirrors and apertures positioned without replacing any of the fixturing. The above described approach offers significant advantages in fabrication with target grating parameters (e.g., peak angle) being met without the need to measure mirror angle or location, glass stack parallelism to the module baseplate / optical table, or account for miscellaneous beam alignment errors since we are only concerned with overlapping the zeroth and first order beams at the material plane.

[0111] In many cases, the exposure module may have removable bottom / mid / top plates such that a change in k-vector can be accommodated without replacing the entire stack. All the mirrors and fixtures can then be reused with the new plates using various configuration of the illustrated slot schemes.

[0112] Figs.16A-16C illustrate the geometry of the input, output and fold apertures. In the case of the output apertures (Fig. 16A), the endpoints of each apertures’ long straight components can be connected to create an intersection points (A1 , A2). The midpoint of the connecting line can be used to determine the center of the aperture pair. In the case of the input aperture (Fig. 16B), the midpoint (A3) of a connecting line the points of minimum separation of the aperture pair may be used to determine aperture center. In the case of the fold, apertures (Fig. 16C), the center (A4) of the aperture pair is determined by first construct the vertical and horizonal lines linking the furthest extremities of the apertures and then determining the intersection point of the vertical and horizontal lines lying midway between the extremity lines. Fig. 17 is a plan view of mask with input apertures configured according to Fig. 16B overlaid.DOCTRINE OF EQUIVALENTS

[0113] This description of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the teaching above. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications. This description will enable others skilled in the art to best utilize and practice the invention in various embodiments and with various modifications as are suited to a particular use. The scope of the invention is defined by the following claims.

[0114] As used herein, the singular terms “a,” “an,” and “the,” may include plural referents unless the context clearly dictates otherwise. Reference to an object in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.”

[0115] As used herein, the terms “approximately” and “about” are used to describe and account for small variations. When used in conjunction with an event or circumstance, the terms can refer to instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs to a close approximation. When used in conjunction with a numerical value, the terms can refer to a range of variation of less than or equal to ± 10% of that numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1 %, less than or equal to ±0.5%, less than or equal to ±0.1 %, or less than or equal to ±0.05%.

[0116] Additionally, amounts, ratios, and other numerical values may sometimes be presented herein in a range format. It is to be understood that such range format is used for convenience and brevity and should be understood flexibly to include numerical values explicitly specified as limits of a range, but also to include all individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly specified. Where ranges are described, the range should be understood to include the endpoints of the ranges, and the endpoints of such ranges are also contemplated to stand on their own as inventive, individual data points and to form the endpoints of other ranges. For example, a ratio in the range of about 1 to about 200 should be understood to include the explicitly recited limits of about 1 and about 200, but also to include individual ratios such as about 2, about 3, and about 4, sub-ranges such as about 1 to about 10, about 10 to about 50, about 20 to about 100, about 100 to about 200, and so forth, and related ranges such as greater than about 1 or less than about 200.

Claims

WHAT IS CLAIMED IS:1 . A method for recording a waveguide device, the method comprising the steps of: providing a set of master gratings comprising an input grating master; a fold grating master, and an output grating master; positioning the set of master gratings in a first configuration; providing a first substrate coated with a first holographic mixture of monomer and inert material; exposing the first holographic mixture through the set of master gratings in the first configuration to form a first grating configuration for providing a first user prescription, the first grating configuration comprising an input grating formed over a first substrate area with a first clock angle, a fold grating formed over a second substrate area with a second clock angle, and an output grating over a third substrate area with a third clock angle; providing a second substrate coated with a second holographic mixture of monomer and inert material; positioning the set of master gratings in a second configuration; and exposing the second holographic mixture through the set of master gratings in the second configuration to form a second grating configuration for providing a second user prescription, the second grating configuration comprising an input grating formed over a fourth substrate area with a fourth clock angle; a fold grating formed over a fifth substrate portion with a fifth clock angle and an output grating over a sixth substrate portion with a sixth clock angle.

2. The method of claim 1 , wherein the first user prescription and the second user prescription each comprise at least one selected from the group of: interpupillary distance, exit pupil, eye relief and rake angle.

3. The method of claim 1 , wherein the first and second substrates are components of different waveguide devices.

4. The method of claim 1 , wherein the first and second substrates are components of the same waveguide device.

5. The method of claim 1 , wherein the set of master gratings forms at least one multiplexed grating.

6. The method of claim 1 , wherein the set of master gratings forms at least one overlapping pair of gratings.

7. The method of claim 1 , wherein the substrate areas over which the gratings are formed are specified for different eye relief.

8. The method of claim 1 , wherein the substate areas over which the gratings are formed are specified for different eye relief in the range of approximately 15-30mm.

9. The method of claim 1 , wherein the first grating configuration and a laterally inverted version of the first grating configuration provide eye pieces of a first eyeglass display, wherein the position of the input grating relative to the propagation axis of input light in each eyepiece is such that an IPD of approximately 110 mm is provided, wherein the second grating configuration and a laterally inverted version of the second grating configuration provide eye pieces of a second eyeglass display, wherein the position of the input grating relative to the propagation axis of input light in each eyepiece is such that an IPD of approximately 140 mm is provided.

10. The method of claim 1 , wherein the steps of recording of the first and second grating configurations involves a holographic phase separation process.

11. The method of claim 1 , further comprising at least one step selected from the group of inert component removal, etching of residual polymer, backfilling and coating.

12. The method of claim 1 , wherein the waveguide device is a display.

13. The method of claim 1 , wherein at least two of the input grating master, fold grating master, and output grating master have identical Bragg fringe spacings and modulations.

14. The method of claim 1 , wherein a grating recorded from a master grating has a slant angle determined by the angle of a recording beam incident at the master grating.

15. The method of claim 1 , wherein the diffraction efficiency across a grating recorded from a master has a spatial variation determined by the spatial variation of the mixture concentration across the substrate.

16. A holographic exposure system comprising: a layer of holographic recording material; a first aperture plate including a first aperture and a second aperture located on a plane parallel to the layer of holographic recording material, wherein the first aperture and the second aperture have geometry and center separation distances that vary beam cross sections at the surface of the holographic recording material; a first light source configured to direct a first portion of light through the first aperture as a zero order recording beam and a second portion of light through the second aperture as a first order recording beam, wherein the first portion of light and the second portion of light interfere to form an interference pattern which exposes the layer of holographic recording material to form a first grating of a predefined K-vector within the layer of holographic recording material.

17. The holographic exposure system of claim 16, wherein the layer of holographic recording material is positioned on a substrate.

18. The holographic exposure system of claim 16, wherein the layer of holographic recording material is encapsulated between a first substrate and a second substrate.

19. The holographic exposure system of claim 18, wherein the first substrate supports a mask.

20. The holographic exposure system of claim 18, wherein the first substrate comprises a release layer.

21. The holographic exposure system of claim 16, wherein the first light source comprises one or more mirrors to direct light that forms the first portion of light towards the first aperture and light that forms the second portion of light towards the second aperture.

22. The holographic exposure system of claim 21 , wherein the one or more mirrors comprises a single mirror which is mounted on a track that is translatable along a direction parallel to a principal grating direction of the grating formed within the layer of holographic recording material.

23. The holographic exposure system of claim 22, wherein the one or more mirrors are configured to direct light at predefined angles for recording specific K-vectors.

24. The holographic exposure system of claim 16, wherein beams transmitted by the first aperture and the second aperture include skew rays.

25. The holographic exposure system of claim 16, wherein the first aperture plate is rotatable and / or translatable relative to the layer of holographic recording material.

26. The holographic exposure system of claim 25, wherein the first aperture plate comprises a single film with openings that form the first aperture and the second aperture.

27. The holographic exposure system of claim 16, further comprising a top plate, a middle plate, and a bottom plate, wherein the top plate supports the layer of holographic recording material, the middle plate supports the first aperture plate, and the bottom plate supports the light source.

28. The holographic exposure system of claim 16, further comprising an aperture frame which houses the aperture plate.

29. The holographic exposure system of claim 28, wherein the aperture frame comprises a top aperture frame and a bottom aperture frame which surround the aperture plate.

30. The holographic exposure system of claim 29, wherein the first aperture plate comprises a first slot in which a first post extends through and a second slot in which a second post extends through.

31. The holographic exposure system of claim 30, wherein the first post and the second post are positioned on opposite portions of the bottom aperture frame.

32. The holographic exposure system of claim 31 , wherein the top aperture frame comprises a first hole and a second hole positioned on opposite portions of the top frame.

33. The holographic exposure system of claim 32, wherein the first post extends through the first hole and cooperates with a first nut to use the top aperture frame to apply pressure to the first aperture plate such that the first aperture plate is held in place between the top aperture frame and the bottom aperture frame.

34. The holographic exposure system of claim 33, wherein the second post extends through the second hole and cooperates with a second nut to use the top aperture frame to apply pressure to the first aperture plate such that the first aperture plate is held in place between the top aperture frame and the bottom aperture frame.

35. The holographic exposure system of claim 31 , wherein the first slot and the second slot are elongated in an extending direction to allow the first aperture plate to translate along the first slot and the second slot.

36. The holographic exposure system of claim 35, wherein aperture frame is positioned in a slot located on a middle plate.

37. The holographic exposure system of claim 36, wherein the slot is configured to have multiple positions along a first direction in which to accommodate the aperture frame, wherein the first slot and the second slot extend along a second direction, wherein the first direction is different than the second direction.

38. The holographic exposure system of claim 37, wherein the first direction is substantially perpendicular to the second direction.

39. The holographic exposure system of claim 16, further comprising: a second aperture plate comprising a third aperture and a fourth aperture located on a plane parallel to the layer of holographic recording material, wherein the third aperture and the fourth aperture have geometry and center separation distances that vary beam cross sections at the surface of the holographic recording material; a second light source configured to direct a third portion of light through the third aperture a zero order recording beam and a fourth portion of light through the fourth aperture as a first order recording beam, wherein the third portion of light and the fourth portion of light interfere to form an interference pattern which exposes the layer of holographic recording material to form a second grating of a predefined K-vector within the layer of holographic recording material.

40. The holographic exposure system of claim 39, further comprising: a third aperture plate comprising a fifth aperture and a sixth aperture located on a plane parallel to the layer of holographic recording material, wherein the fifth aperture and the sixth aperture have geometry and center separation distances that vary beam cross sections at the surface of the holographic recording material; a third light source configured to direct a fifth portion of light through the fifth aperture a zero order recording beam and a sixth portion of light through the sixth aperture as a first order recording beam,-SO-wherein the fifth portion of light and the sixth portion of light interfere to form an interference pattern which exposes the layer of holographic recording material to form a third grating of a predefined K-vector within the layer of holographic recording material.

41. The holographic exposure system of claim 40, wherein the first grating comprises an input grating, the second grating comprises a fold grating, and the third grating comprises an output grating.

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