FIELD OF THE DISCLOSURE

[0001] The present disclosure is in the field of holography, and more specifically, relates to a system for manufacturing custom fit holographic elements for optical combiners.

BACKGROUND

[0002] In an augmented reality (AR) head- mounted display (HMD) system, the exit pupil (or “eyebox”) defines the volume over which the display image is visible to the eye. Eyewear with a large eyebox can accommodate many wearers with different face shapes and eye positions, while units with a small eyebox can only be used by a limited number of individuals, such as those whose interpupillary distance corresponds to the locations of the eyebox when using the display.

[0003] Two main approaches to creating the optical combiner in an AR HMD include waveguides and free space combiners. Waveguide-based HMD systems typically suffer from very low efficiency. They commonly show poor aesthetics originating from the constraints that the waveguide be flat and surrounded by a medium of lower refractive index (typically air) which gives rise to additional optical surfaces inside the lens. Accommodating these constraints can be challenging to combine with prescription constraints, expensive, and generally leads to bulky lenses. Realizations using surface relief gratings (SRGs) can additionally suffer from flare and other optical artifacts. However, waveguide approaches tend to offer larger eyeboxes than free space combiners due to pupil replication.

[0004] On the other hand, free space combiners using holographic optical elements (HOEs) can provide optical efficiency, aesthetics, best form prescription compatibility, and low cost controlled optical artifacts. However, such free space combiners have a small eyebox which is a drawback.

[0005] Despite the benefits of the free space approach, most commercial AR HMD systems (e.g., Hololens, Vuzix, Digilens, Magic Leap) have adopted waveguides for the combiner because the large eyebox accommodates a larger variety of users. Additionally, free space combiners have not gained wide commercial acceptance because of problems relating to manufacturability: the small eyebox should be fit to an individual user to align the eyebox to the user’s eyes. This requires a manufacturer or distributor to stock or otherwise supply many different configurations to satisfy the target market.

[0006] Previous attempts at commercializing free space combiners (e.g., North) used a small number of HOE stock keeping units (SKUs) to accommodate the range of variability in user’s interpupillary distance, vertex distance, prescription constraints, face size, frame position of wear, and differences in optical characteristics of the projector. However, a small number of HOE SKUs limits the degree of customization that is possible and, for non-optimal fit, degrades the device’s performance compared to the peak potential for a user. The small number of HOE SKUs is due to existing commercial-scale manufacturing approaches to HOEs that rely on copying a master hologram. In such approaches, a single master hologram (e.g., an amplitude grating, SRG, or volume holographic grating) is optically replicated through a serial exposure process into many copied HOEs that are all duplicates of the original. Each copy is integrated into a lens and assembled into an HMD unit. Producing a new master is generally complicated and expensive, and exchanging masters in the copying system is similarly time consuming and wasteful, so there is a motivation to reduce the number of masters.

[0007] Thus, what is needed are improved manufacturing methods for individualized HOEs which allow flexibility in the optical design of the HOE and combiner lens.

SUMMARY

[0008] It has been discovered that custom holographic optical elements for optical combiners suitable for individualized head mounted displays can be manufactured based on anthropometric and/or ophthalmic prescription data for the individual user in an economical manner.

[0009] This discovery has been exploited to develop the present disclosure, which, in part, is directed to a process of preparing an optical combiner, the method including: acquiring human subject data including anthropometric data and/or ophthalmic prescription (Rx) data for a human subject; calculating a lens shape for the human subject using the human subject data, the calculated lens shape: correcting refractive error of the human subject’s vision according to the Rx data; and being combinable with a holographic optical element (HOE) in the optical combiner in a head mounted display (HMD) for use by the human subject; calculating a custom HOE optical function using the calculated lens shape, the custom HOE optical function defining a custom HOE for the optical combiner customized for the human subject; calculating one or more compensation factors, the compensation factors including parameters of the HOE that account for changes in a recorded HOE while forming optical combiner using the recorded HOE, parameters of the HOE that account for how the HOE is combined with a lens having the calculated lens shape, and parameters of the HMD that account for the position of a light source in the HMD and/or a position of the user’s eye when the user wears the HMD, the compensation factors being calculated so that the recorded HOE has the custom HOE optical function after the optical combiner is formed; calculating a configuration of a recording tool based on the compensation factors and the custom HOE optical function; setting the recording tool to the calculated configuration; recording a hologram with the recording tool to provide the recorded HOE; and forming the optical combiner using the recorded HOE including combining the recorded HOE and the lens having the calculated lens shape, the recorded HOE having the custom HOE optical function after forming the optical combiner.

[0010] Examples of the process can include one or more of the following features, alone or in any combination. For example, acquiring the human subject data comprises selecting frames for the optical combiner.

[0011] Acquiring the human subject data can include gathering fitting data from the anthropometric data and frame geometry data, the frame geometry data being determined based on the frame selection. The lens shape can be calculated based on the fitting data and the Rx data.

[0012] The anthropometric data can include a pupillary position of the human subject, a topographic map of the human subject's face, the human subject’s ear positions, and/or the human subject’s nose geometry

[0013] In some examples, the custom HOE optical function is calculated based on light source data characterizing the light source used with the optical combiner in the HMD.

[0014] In some examples, recording the hologram includes exposing a hologram-forming material to illumination using the recording tool in the calculated configuration.

[0015] Forming the optical combiner can include post-processing the recorded HOE.

[0016] Forming the optical combiner can include embedding the recorded HOE in the lens.

[0017] Forming the optical combiner can include laminating the recorded HOE to a surface of the lens.

[0018] Forming the optical combiner can include shaping a surface of the lens according to the Rx data.

[0019] Forming the optical combiner can include coating a surface of the lens and/or a surface of the recorded HOE. [0020] In some examples, forming the optical combiner includes edging the lens.

[0021] Forming the optical combiner can include installing the lens in frames.

[0022] In certain aspects, the disclosure is directed to an optical combiner for a head mounted display, the optical combiner including: a custom holographic optical element (HOE) for a human subject formed using a process of the preceding aspect; and a lens having a lens shape for the human subject.

[0023] In a further aspect, the disclosure is directed to a head mounted display including: eyeglass frames; an optical combiner according to the prior aspect mounted in the eyeglass frames; and a light source attached to the eyeglass frames and arranged to direct light along a path that intersects the optical combiner.

[0024] Among other advantages, implementations of the manufacturing processes, process flows, and associated tools can allow manufacturing of HOE based, free space optical combiners that are optimally customized for the individual wearer. The overall production model can enable custom manufacturing of head mounted displays, on demand, to the individual user’s requirements.

[0025] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description below, the figures, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The foregoing and other objects of the present disclosure, the various features thereof, as well as the disclosure itself may be more fully understood from the following description, when read together with the accompanying drawings in which:

[0027] FIG. 1 is a schematic representation of a retinal projection head-mounted display including a custom holographic optical element in accordance with examples of the disclosure;

[0028] FIG. 2A is a flowchart of an exemplary process of making custom fit holographic optical elements suitable for use in the example optical combiners of FIG. 1 in accordance with examples of the disclosure; and

[0029] FIG. 2B is a schematic representation of an exemplary tool suitable for use in the example process of FIG. 2A in accordance with examples of the disclosure; and

[0030] FIG. 2C is a schematic representation of a portion of an exemplary tool suitable for use in the example of process of FIG. 2 A. [0031] In the figures, like reference numerals indicate like elements.

DESCRIPTION

[0032] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The initial definition provided for a group or term herein applies to that group or term throughout the present specification individually or as part of another group, unless otherwise indicated.

[0033] As used herein, the articles “a” and “an” refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element. Furthermore, use of the term “including” as well as other forms, such as “include,” “includes,” and “included,” is not limiting.

[0034] As used herein, the term “about” will be understood by persons of ordinary skill in the art and will vary to some extent on the context in which it is used. As used herein when referring to a measurable value such as an amount, a temporal duration, and the like, the term “about” is meant to encompass variations of ±20% or ±10%, including ±5%, ±1%, and ±0.1% from the specified value, as such variations are appropriate to perform the disclosed methods.

[0035] The present disclosure relates to manufacturing processes, process flows, and to associated tools to allow high speed manufacturing of HOE based, free space optical combiners that are customized for the individual wearer. The processes include use of an HOE exposure tool (e.g., a masterless HOE exposure tool) that can be reconfigured (e.g., but not limited to, between recording every hologram), so that the exposure tool can form customized HOEs with different holograms corresponding to the calculated lens shape of the combiner in which the custom HOE will be installed and the HMD in which the combiner will be used.

An example tool is described below.

[0036] The processes can also include use of the algorithms and datasets to calculate: the hologram optical constraints in use, including the HOE optical function; corrections to compensate for optical changes that occur to the HOE after recording during, e.g., postprocessing and integration into the HMD; and/or how to configure the recording tool to achieve the desired final HOE optical function in the HOE.

[0037] The present disclosure provides a HMD including a custom HOE which adjusts light from a source point to correct for the individual lens shape of a free-space optical combiner. The custom HOE is characterized by a HOE optical function, which includes one or more functions that characterize optical and/or physical characteristics of the hologram and can be used to relate these characteristics to parameters associated with recording the hologram (e.g., but not limited to, beam geometry, beam size, exposure time, etc.).

[0038] The optical combiner in a free space approach generally includes two subcomponents that are integrated together as a monolithic optical device. These two components are a HOE and a transparent optical lens. The lens may be a piano lens or may have optical power to meet the wearer’s prescription. The HOE is a volume holographic grating (VHG) that diffracts light from a projector picture generation unit (PGU) into the wearer’s eye, while at the same time being highly transparent to pass light from the real world. A well fit free space design has a lens and an HOE with optical functions that match the needs of the wearer, and those optical functions can be different for different wearers.

[0039] An exemplary display device 150 using a free space optical combiner 152 is shown in FIG. 1. The display combiner 152 includes a custom HOE 154 and a lens 156. The lens 156 may be piano (i.e., no optical power) or may include optical power to meet a specified Rx (e.g., but not limited to, a spherical correction and/or correction for astigmatism). Rx lenses can be single vision or multi vision lenses (e.g., but not limited to, bifocal lenses, progressive lenses). This can include, but is not limited to, spherical power, cylindrical power, cylinder axis, add power, and prism. This data can be obtained as a prescription, for example, from an optometrist, ophthalmologist, or other eye care professional.

[0040] The display device 150 includes an adapter element 162 located close to and within the projection path of light from the projector 158. The adapter element 162 is small compared to the combiner 152 (e.g., but not limited to, having a largest dimension of about 5 mm or less) and is commonly a refractive freeform lens or mirror, or a multi-facet prism without a diffraction grating. As described herein, in some implementations, the adapter element 162 is a holographic grating encapsulated in, or laminated to, a substrate, such as a refractive slab, prism, or lens.

[0041] In operation, the projector 158 emits a light beam 160 which forms an image for viewing when received by the eye 140. The point of emission of the light beam 160 from projector 158 is the source point (SP). The adapter element 162 is arranged in the path of the light beam 160 from the projector 158 and reflects the beam 160 toward the HOE 154, shaping the beam for reflection by the HOE. The HOE 154, in turn, reflects the light beam 160 towards the eye 140. The light beam 160 forms an image in the eye 140 which combines with (e.g., but not limited to, augments) light from the world side of the display device 150 thereby providing an augmented reality when received by the eye 140 of the user by overlaying displayed imagery with the user’s field of view of the world. Non-limiting examples of the projector 158 include projectors using a micro-electro-mechanical systems (MEMS) mirror projector (e.g., but not limited to, a single-, or two-mirror MEMS system or an oscillating fiber projector). While adapter element 162 is composed of a reflective HOE in the example illustrated, in certain examples transmissive HOEs can be used.

[0042] The custom HOE 154, in this non-limiting example, is a volume holographic grating (VHG) that diffracts light from a projector 158 into an eye 140 of a user (a “wearer”). The display combiner 152 and the custom HOE 154 are sufficiently transparent (e.g., greater than about 80% transmission for operative wavelengths in a wavelength range of about 380 nm to about 750 nm) to pass light from a world side to a user side ( to the eye 140). The design of the display device 150 is such that the display combiner 152 (here, lens 156 and HOE 154), can have a custom optical function that matches the needs of the user. Such optical functions may be different for different users.

[0043] In general, the lens 156 can have a lens shape according to an ophthalmic prescription (Rx) which corrects the refractive error of a human subject’s vision. Correcting the refractive error may reduce distortion when environment light passing through the display combiner 152 from the world side reaches the eye 140. The refractive errors that may be corrected by the display combiner 152 may include astigmatism, hyperopia, myopia, or presbyopia.

[0044] The HOE 154 is a reflective optical element which diffracts light from projector 158 and adapter 162. The HOE is holographically recorded by interfering laser beams within a holographic recording medium, e.g., but not limited to, a photopolymer layer. The HOE 154 is cured/processed and may be combined with other layers to form an HOE stack. In some implementations, the HOE 154 or the stack is thermoformed. The HOE may be embedded into the lens 156 by casting the lens around the HOE 154. Alternatively, the HOE 154 or the stack may be laminated onto a surface of the lens, or the lens 156 injection molded around the HOE 154.

[0045] The HOE 154 is a custom HOE which has an optical function recorded into the holographic recording medium. The optical function as recorded is done so in a manner that reduces (e.g., but not limited to, eliminates) deviations from a final HOE optical function. The final-state HOE optical function refers to a desired optical performance of the HOE for the end user of the HMD once installed in the custom HMD for the user. These deviations can be introduced by the recording tool and/or post-processing of the HOE 154 to the reflected wavefront. The final-state HOE optical function is also determined to account for any effect on the performance of the HMD due to the shape of the lens 156 in which the custom HOE 154 is installed (e.g., due to the Rx of the end user), the frames and/or other hardware associated with the HMD, and/or the anthropometric data of the end user (e.g., the interpupillary distance for the user).

[0046] An exemplary process 100 for calculating a lens shape and HOE optical function which defines a custom HOE is shown schematically in the flowchart in FIG. 2A. The process starts (102) with gathering of information from the user about fitting data like frame style choice (104) and a collection of facial anthropometric data (106), and vision correction prescription (108), if any. The process determines a geometry of the selected frame (110) and the user’s anthropometric information is used to define the position of wear or frame fitting information (112). The data collected/determined in steps 104, 106, 108, 110, and 112 are unique to a user, and as a result, all subsequent steps involve a degree of adjustment based on the data from these prior steps.

[0047] The fitting data combined with any ophthalmic prescription information determines the lens shape, or form, of the correction lens. The following description is made in terms of correction lenses, but it will be understood that the disclosure is equally applicable to piano lenses when no correction is desired or needed, in which case features relating to vision correction are omitted.

[0048] As noted above, anthropometric data is obtained (106). Such data includes, but is not limited to, pupillary positions, and topographic maps of the user's face, ear positions and nose geometry. These data are used with the 3D geometry of the selected frame to identify the position of wear or fitting data for the chosen frame on the user’s face. This data can be collected through, e.g., but not limited to, dedicated anthropometric measurement tools or smartphone- based apps that conduct facial scanning and mapping. The position of wear data include, but are not limited to monocular pupillary distances, vertex distance, temple height and width, and nasal bridge position.

[0049] The user ophthalmic prescription (Rx) is also obtained (108). This can include, but is not limited to, values for spherical power, cylindrical power, cylinder axis, add power, and prism. This data can be obtained as a prescription, from an optometrist, ophthalmologist, or other eye care professional.

[0050] The prescription lens shape is then calculated (116). This involves translating the user’s prescription data into a lens shape. This takes into account both the prescription data and the position of wear data. This can be done in any way known in the art, e.g., using commercially available lens shape calculation packages. The calculated lens shape corresponds to a lens shape that corrects refractive error of the human subject’s vision with minimal distortion, and is combinable with a holographic optical element (HOE) in an optical combiner, such as combiner 152. In other words, the calculated lens shape accounts for the variations in an optical function of the HOE when the HOE is integrated with the lens, e.g., but not limited to, by laminating the HOE to a lens surface or embedding the HOE in the lens material. This ensures the lens provides the intended optical function (e.g., but not limited to, the correct prescription) after being combined with the HOE. Lens shape can be calculated using commercial optical design software, which can account for an embedded or laminated element associate with the lens.

[0051] Data that describe the projector characteristics are also collected (114). This can include, but is not limited, to emission wavelengths of the three color channels (R, G, and B channels), beam profile, and beam divergence or convergence characteristics. The final-state HOE optical function is then calculated (118). This is based on factors including, but not limited to, the position of wear, pupil location, base curvature of the lens, eye-side form of the lens, projector wavelengths, projector position and angle (e.g., relative to the combiner and/or user’s eye). Light source (i.e., projector) and eyepoint vertex locations are also considered. These factors determine the optical characteristics of the HOE so that the HOE diffracts light from the display’s projector into the user’s eye. In other words, these factors determine, at least in part, the final-state HOE optical function. This step defines the customized combiner’s function. Characteristics of the HOE optical function that can be varied based on the finalstate HOE optical function can include, but are not limited to, peak diffraction wavelengths, diffraction efficiency, , active area, optical power, astigmatism, higher order aberrations, and grating orientation within the recording medium.

[0052] These characteristics define the function of the combiner in its final state, as used in the display device, after it has been subjected to various post-recording processing steps that may change the HOE’s optical function after it has been recorded.

[0053] The distortions induced by post-recording processing (e.g., but not limited to, steps 126, 128, 130, 132) can be predicted and accounted for when determining the HOE’s optical function to be recorded in the holographic medium at step 124 such that the HOE’s final state optical function after the post-recording process and integration into the optical combiner is as specified at step 118. Thus, the distortions can be compensated by calculating a HOE optical function that compensates for distortions introduced by the post-recording processing subsequent to the HOE being recorded, so that the final state HOE optical function after postprocessing is as specified at step 118. [0054] For example, based on an understanding of how the post-recording processing steps cause deviations in the intended HOE optical function, the effect of the post-recording processing steps on geometrical distortion, optical distortion, and/or wavelength shifts can be determined. A pre-compensated HOE that accounts for these changes and based on one or more compensation factors is calculated to establish an HOE optical function which compensates for post-recording changes such that the optical function defined in step 118 is achieved (120). Compensation factors can be configured to compensate for changes due to, but not limited to, an amount of volume change (e.g., shrinkage or expansion) of the HOE, a change in grating orientation, a change in grating period, a change in grating amplitude, a change in curvature of the grating, a change in the refractive index of the HOE, etc. Compensation factors can also include adjustments to parameter values for forming the HOE that account for specific features of the custom combiner and user, including lens surface curvature, light source (e.g., projector) location and orientation, and pupil position. Compensation factors can account for whether the HOE is embedded in the lens or laminated onto a surface of the lens. For example, where the HOE is embedded in the lens, this step should account for the refraction of light from the projector when it is incident on and when it exits the eye side surface of the lens. Where HOE is laminated on the eye side surface, this step should account for the curvature of the lens surface as adopted by the HOE.

[0055] The exposure tool configuration for recording the custom HOE is calculated (122). Raytracing simulations may be used to calculate how the recording tool is reconfigured so that the recorded HOE has the desired as-recorded optical function, including the compensation discussed above. The exposure tool is then reconfigured, and the HOE recorded (124). The degrees of freedom of the recording tool may include, but are not limited to, object beam orientation in two dimensions, reference beam orientation in two dimensions, object beam focal length and astigmatism, reference beam focal length and astigmatism, object beam axial position, reference beam axial position, active area aperture position and orientation, exposure irradiance, exposure dose, and exposure wavelengths. One, some or all of these degrees of freedom are adjusted to record an HOE that has the desired as-recorded optical function.

[0056] The HOE can then be further processed by conducting a combination of, e.g., but not limited to, optical, thermal, chemical, pressure, and/ or other processes to convert, enhance, adhere, stabilize, deform, shape, and/or modify the HOE and prepare it to be combined with the lens (step 126). These processes induce changes in the optical function of the HOE that are predicted in advance to ensure that they are correctly compensated for in step 120. [0057] The predictions can be based on simulations and/or empirical studies, e.g., of hologram formation, HOE post-processing, integration of the HOE with the lens, and/or installation of the lens in the frames. Computer simulations can be performed, for example, using commercial optical design software for simulation light propagation through the optical system constituting the HMD. An example of this is simulating how light refracts at the lens surface nearest the user when light from the projector enters and exits the lens. Empirical studies of the HOE formation process and/or post-processing can be used to predict changes to the HOE and/or combiner during these processes. For instance, in examples where a HOE is embedded in a lens by a casting process, changes to the HOE due to stress induced during casting can be predicted by empirical studies of the casting process.

[0058] The custom HOE is then combined with a lens by e.g., but not limited to, resin casting, injection molding, lamination, or other known of embedding the HOE in the lens (step 128).

[0059] The lens is ground and surface finished to the prescription form determined based on the anthropometric data and/or ophthalmic prescription (step 130). Grinding and finishing includes removing material from the surface of the lens to provide the spherical power, and cylindrical power desired to meet the user’s prescription.

[0060] The lens is optionally coated (e.g., but not limited to, with a hard coat and/or spectral filter), edged and installed in a frame (step 132).

[0061] The process may additionally contain one or more in-line and end of line inspection and measurement steps to ensure that the HOE and lens meets the established requirements. [0062] An exemplary tool 200 useful for forming the HOEs, such as custom HOE 154, described above is shown in FIG. 2B. The tool 200 includes an exposure module 210 and an electronic control module 220 (e.g., but not limited to, a computer or other device or devices including one or more electronic processors). The electronic control module 220 stores, or calculates, the HOE optical function to be recorded in an HOE medium. The HOE optical function is based on information related to the lens shape. In other words, the HOE optical function accounts for the optical power and surface shape of the lens. For example, where the HOE is embedded in a lens, the light from the projector will be refracted by a surface of the lens before being incident on the HOE. The HOE optical function therefore accounts for the effect of this refraction on the beam both before incidence on the HOE and after as the light leaves the lens for the user’s eye. In examples where the HOE is laminated onto a surface of the lens, the HOE optical function can account for a curvature of the HOE as it conforms to the shape of the lens surface. [0063] In general, the configuration of the tool 200 is set according to the calculated configuration which includes one or more compensation factors. The electronic control module 220 stores, or calculates, the configuration and controls the components of the exemplary tool 200 to achieve the configuration. The compensation factors correspond to adjustments in the tool 200 reduce one or more deviations of the custom HOE from satisfying the final HOE optical function once processing of the custom HOE is complete. As described above, the deviations can arise from one or more steps occurring after the recording of the custom HOE (e.g., but not limited to, steps 126, 128, 130, 132 of the process 100).

[0064] The recording tool 200 uses the exposure module 210 to focus light diverging from a desired eye-point location toward a recording material 201 with recording light 215. The recording tool 200 can direct recording light beams from multiple locations at which the eye may be located (eye points) for replication of an eye-box by recording a multiplexed hologram. The location of the light beams are chosen such that the light emanating from different eye-points are recorded in the HOE.

[0065] Exposure module 210 includes a light source 212 (e.g., but not limited to, a laser or lasers) and a light shaping module 214 which includes one or more optical elements arranged to shape the light emitted by the exposure module 210. The light is generated from a source (e.g., but not limited to, a laser source) and light shaping module 214 (e.g., but not limited to, one or more lenses and/or mirrors) with a focusing lens which shapes the recording light to provide a divergent (e.g., but not limited to, spherical) wavefront at light shaping module 214. Generally, the optical elements of the light shaping module 214 can include active (e.g., but not limited to, adjustable) and/or passive optical elements. The optical elements can include beamsplitters, polarizers, waveplates, refractive optical elements (e.g., but not limited to, lenses and prisms), reflective optical elements (e.g., but not limited to, mirrors), and/or diffractive optical elements (e.g., but not limited to, gratings). Active optical elements can include, e.g., but not limited to, adaptive optical elements, spatial light modulators (SLM), and MEMS-based active optical elements, such as digital micro mirror devices (DMD). Passive optical elements can be reconfigured with, e.g., translating, and rotating positioners. The recording light emanates from a focal point which corresponds to an eye point (EP) of the HMD.

[0066] During operation, the electronic control module 220 controls the exposure module 210 to expose a hologram forming material 201 with a light 215 to record the HOE in the hologram forming material 201. The recording tool 200 can include mounting fixtures for the hologram forming material 201. The hologram forming material 201 can be a light-sensitive film. Non-limiting examples of the material 201 include a photopolymer blank, di chromated gelatine, silver-halide layers, and holographic polymer-dispersed liquid crystals (H-PDLC). In some non-limiting examples, the recording blank is or hosts an unrecorded holographic medium into which the HOE is recorded. Commercially available hologram forming materials can be used.

[0067] Light 215 is composed of a light pattern shaped so that the hologram formed in the hologram forming material 201 can be used for the custom HOE described above, e.g., the light 215 is modulated to record the calculated HOE optical function into the material 201 such that the custom HOE is created. Shaping the light pattern can include varying either or both the intensity and phase of light across an area of the light forming material 201.

[0068] In some embodiments, the optical elements in the light shaping module 214 include a beamsplitter which divides light from a coherent light source 212 into two or more beams and directs each of the beams so that they overlap, and interfere, at hologram forming material 201.

[0069] The intensity and spectral composition of the light source 212 is selected in accordance with the hologram forming material 201. UV and/or visible light can be used. [0070] Once recorded, the custom HOE is incorporated into a lens through processes described herein to create a combiner 152. In this manner, a combiner for use in an HMD which is specific to a subject’s fitting data and may correct for a subject’s Rx is formed. [0071] A portion 214’ of an example light shaping module for tool 200 is shown in FIG. 2C. Portion 214’ includes a beamsplitters 220, mirrors 230b and 230c, and a stage 204 supporting hologram forming material 201. Actuators 202, 222, and 232b and 232c are coupled (e.g., but not limited to, attached directly or indirectly) to stage 204, beamsplitters 220, and mirrors 230b and 230c, respectively. The actuators are configured to vary the location and/or angular orientation of the respective component to which they are coupled relative to beam 215a from the coherent light source and/or relative to other components in light shaping module. Beamsplitter 220 receives beam 215a from the light source (not shown in FIG. 2C) and splits the beam into two beams 215b and 215c. Mirrors 230b and 230c direct beams 215b and 215c to overlap at the hologram forming material 201, where they form an interference pattern that forms a volume hologram in the hologram forming material 201.

[0072] The custom optical combiners can be integrated into augmented reality (AR) head mounted displays. For example, the combiners may be used in AR HMDs suitable for all-day wearable products where the benefits of efficiency, high brightness, light weight, long battery life, aesthetics, and best-form prescription compatibility are most valuable. The disclosure also relates to enterprise applications where immersion and interchangeability are important, and aesthetics may not be.

EQUIVALENTS

[0073] It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other implementations will be apparent to those of skill in the art upon reading and understanding the above description. Although the present disclosure has been described with reference to specific example implementations, it will be recognized that the disclosure is not limited to the implementations described but can be practiced with modification and alteration within the scope of the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense. Although various features of the approach of the present disclosure have been presented separately the skilled person will understand that, unless they are presented as mutually exclusive, they may each be combined with any other feature or combination of features of the present disclosure

[0074] While this specification contains many details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular examples. Certain features that are described in this specification in the context of separate implementations can also be combined. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple examples separately or in any suitable sub-combination.

[0075] Those skilled in the art will recognize, or be able to ascertain, using no more than routine experimentation, numerous equivalents to the specific embodiments described specifically herein. Such equivalents are intended to be encompassed in the scope of the following claims.