EP4705812A1 - Optical films for curved lamination - Google Patents

Abstract

Example apparatus may include a head-mounted device, such as an augmented reality and/or virtual reality device. Example apparatus may include a display and an optical configuration configured to form an image of the display, for example, at an eye of a user when the user wears the head-mounted device. The optical configuration may include a lens assembly, which may include a lens having a curved surface and a multilayer film supported by the curved surface of the lens. The multilayer film may include a polarizer layer and an optical retarder layer. The optical retarder layer may have a molecular alignment based on a liquid crystal phase, such as a nematic phase. In some examples, the optical retarder layer may have an optical retarder layer thickness of between 1 micron and 10 microns. Other devices, methods, systems, and computer-readable media are also disclosed.

Description

OPTICAL FILMS FOR CURVED LAMINATION

SUMMARY OF THE INVENTION

[0001] According to the present invention there is provided an apparatus comprising a display; and an optical configuration configured to form an image of the display, wherein the optical configuration comprises a lens assembly; the lens assembly comprises a lens having a curved surface and a multilayer film supported by the curved surface of the lens; the multilayer film comprises a polarizer layer and an optical retarder layer; the optical retarder layer has a molecular alignment based on a liquid crystal phase; the optical retarder layer has an optical retarder layer thickness of between 1 micron and 10 microns; and the apparatus comprises a head-mounted device.

[0002] Optionally the polarizer layer is a linear polarizer.

[0003] Optionally the optical retarder layer thickness is between 1 micron and 5 microns.

[0004] Optionally, the polarizer layer has a polarizer layer thickness of between 1 microns and 10 microns.

[0005] Optionally the polarizer layer has a polarizer layer thickness of between 2 microns and 8 microns.

[0006] Optionally the curved surface of the lens has a magnitude of radius of curvature of less than 200 mm.

[0007] Optionally the curved surface of the lens has a magnitude of radius of curvature of between 50 mm and 100 mm.

[0008] Optionally, the lens assembly has a magnitude of optical retardance uniformity equal to or better than 0.5 nm (+/- 0.5 nm) over a field of view of the lens assembly.

[0009] Optionally the optical retarder layer is a quarter-wave plate.

[0010] Optionally the multilayer film further comprises an adhesive layer, and the adhesive layer has an elastic modulus less than 1 MPa.

[0011] Optionally the multilayer film further comprises: an antireflection layer; a reflective polarizer; an optically clear adhesive layer located between the antireflection layer and the reflective polarizer; and a pressure sensitive adhesive layer located between the reflective polarizer and the optical retarder layer.

[0012] Optionally the display comprises a liquid crystal display. [0013] Optionally the head-mounted device is a virtual reality device.

[0014] Optionally the head-mounted device is an augmented reality device.

[0015] Optionally the optical configuration is configured to form an image of the display at an eyebox, the eyebox being a location at which a user may view the image of the display when the user wears the head-mounted device.

[0016] Optionally the multilayer film has a multilayer film thickness of between 50 microns and 200 microns.

[0017] According to the present invention there is further provided a method comprising: forming a multilayer film comprising at least one liquid crystal based optical retarder and at least one polarizer; laminating the multilayer film to a curved surface of a lens to form a lens assembly; and fabricating a device comprising a display and an optical configuration comprising the lens assembly configured to form an image of the display at an eye of a user when the user wears the device; wherein the device comprises an augmented reality device, a virtual reality device, or a combination thereof.

[0018] Optionally the at least one polarizer comprises an ultrathin polarizer having a thickness of between 0.5 microns and 10 microns, and the at least one liquid crystal based optical retarder comprises an optical retarder having a thickness of between 0.5 microns and 10 microns.

[0019] Optionally the at least one liquid crystal based optical retarder comprises at least one quarter wave plate.

[0020] According to the present invention there is yet further provided a method comprising: forming a multilayer film comprising a liquid crystal based optical retarder and an ultrathin polarizer; laminating the multilayer film to a curved surface of a lens to form a lens assembly; and fabricating a device comprising a display and an optical configuration comprising the lens assembly configured to form an image of the display at an eye of a user when the user wears the device, wherein: the device comprises an augmented reality device, a virtual reality device, or a combination thereof; the ultrathin polarizer has a thickness between 1 micron and 10 microns; and laminating the multilayer film to a curved surface of a lens to form a lens assembly comprises plasma treatment of the multilayer film.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings illustrate a number of exemplary embodiments and are a part of the specification. Together with the following description, these drawings demonstrate and explain various principles of the present disclosure.

[0022] FIGS. 1A and IB show pancake lens configurations according to some examples.

[0023] FIGS. 2A and 2B show further example pancake lens configurations according to some examples, where the example shown in FIG. 2B shows a curved multilayer film.

[0024] FIGS. 3A and 3B show example multilayer film configurations, according to some examples.

[0025] FIGS. 4A - 4C show an example lenses according to some examples.

[0026] FIG. 5 shows retardation non-uniformity over the aperture of an example lens.

[0027] FIGS. 6A and 6B show example lenses according to some examples.

[0028] FIGS. 7A and 7B show further example lenses according to some examples.

[0029] FIGS. 8A and 8B show further example lenses according to some examples.

[0030] FIGS. 9A - 9C show further example lenses according to some examples.

[0031] FIGS. 10A - 10D illustrate film behavior according to some examples.

[0032] FIGS. 11A - 11C show an example optical system for evaluating lenses having multilayer coatings and the optical evaluation of example lenses.

[0033] FIG. 12 shows tabulated data for different lens configurations.

[0034] FIG. 13 illustrates reduction of the dimensional variance of standard and ultra-thin polarizers according to some embodiments.

[0035] FIG. 14 illustrates an example multilayer configuration.

[0036] FIGS. 15A - 15C show further example multilayer configurations.

[0037] FIGS. 16A - 16C show example optical properties.

[0038] FIGS. 17A - 17C show further example optical properties.

[0039] FIGS. 18A and 18B show further example multilayer configurations.

[0040] FIGS. 19A and 19B show further example multilayer configurations.

[0041] FIG. 20 shows a further example multilayer configuration.

[0042] FIG. 21 shows a method according to some examples.

[0043] FIG. 22 illustrates a further method according to some examples.

[0044] FIG. 23 illustrates a further method according to some examples.

[0045] FIG. 24 is an illustration of exemplary augmented-reality glasses that may be used in connection with examples of this disclosure.

[0046] FIG. 25 is an illustration of an exemplary virtual-reality headset that may be used in connection with examples of this disclosure.

[0047] Throughout the drawings, identical reference characters and descriptions indicate similar, but not necessarily identical, elements. While the exemplary embodiments described herein are susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail herein. However, the exemplary embodiments described herein are not intended to be limited to the particular forms disclosed. Rather, the present disclosure further covers all modifications, equivalents, and alternatives falling within the scope of the appended claims.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0048] The present disclosure is directed to apparatus and methods relating to AR/VR devices, which may include at least one of an augmented reality (AR) and/or a virtual reality (VR) device. The AR/VR device may include a display configured to provide virtual or augmented reality elements to the user at a location termed the eyebox. In augmented reality (AR), the AR image elements may be combined with light from an external environment.

[0049] FIGS. 1A and IB show example optical configurations including lenses, according to some examples.

[0050] FIG. 1A shows an example pancake lens assembly 100 including a first lens 120 and a second lens 110. The first lens 120 supports a first coating 122 and the second lens 110 supports a second coating 112. The pancake lens assembly 100 may be used to form an image of a light source, such as images of portions of the display 126 at locations such as 102, 104, and 106. The image may be formed within an eyebox of a device, where an eyebox is a location where a user may view the display. In some examples, the device may be an AR/VR device and a user may view an image of the display within the eyebox when the user wears the AR/VR device. For example, locations 102, 104, and 106 may represent images of different portions of the display 126. In some examples, the first coating 122 and/or the second coating 112 may include a multilayer film that may be laminated to a surface of the respective lens.

[0051] FIG. IB shows an example pancake lens assembly 150 that may be similar to the pancake lens assembly 100 discussed above. The pancake lens assembly includes a first lens 140 supporting a first multilayer film 154 and a second lens 130 supporting a second multilayer film 152. The first and second multilayer films are shown in exploded form for clarity. The first multilayer film 154, supported by the first lens 140 (labeled LI) includes an antireflection layer 142 (labeled AR) and an optical retarder layer 144 (labeled QWP, quarterwave plate). The second multilayer film 152 supported by the second lens 130 includes an optical retarder layer 132, a linear polarizer layer 134 (labeled LP), a reflective polarizer layer 136 (labeled RP) and an antireflection layer 138 (labeled AR). The arrows indicate the directions that respective exploded layer representations may be collapsed to provide a more accurate representation.

[0052] In FIGS. 1A and IB, the multilayer films are shown supported by (e.g., laminated to) a planar surface of a plano-convex lens. If only planar lamination is used, lenses are restricted to planar-convex or planar-concave lenses. To further improve the performance of a pancake lens in an AR/VR device, it would be useful to not be restricted to lenses having a planar surface. This may be achieved using multilayer films that may be laminated to curved surfaces as described further below.

[0053] The lens separation (124) between the first lens and the second lens may be referred to as a pancake cavity. In some examples, the dimensions of the pancake cavity may be appreciably reduced or substantially eliminated using one or more multilayer films supported by the respective surface(s) of a single lens.

[0054] FIGS. 2A and 2B show further example pancake lens configurations according to some examples, where the example shown in FIG. 2B shows a curved multilayer film.

[0055] FIG. 2A shows an optical configuration 200 including a display 226, first lens 220 and second lens 210. The first lens 220 and second lens 210 cooperatively provide a pancake lens configured to provide an image of the display 226. The dashed lines illustrate exemplary light beams from different portions of the display focused at first location 202, second location 204, and third location 206. A multilayer film 222 is formed on a curved surface of the first lens 220.

[0056] FIG. 2B shows an example multilayer film in more detail within a pancake lens configuration 270 (that may be similar to that shown in FIG. 2A) including first lens 240 and second lens 230. The multilayer film 260 (shown in exploded form) may include an antireflection film 242 (denoted AR), first optical retarder 246 (denoted QWP, quarter wave plate), polarizer 248 (denoted LP, linear polarizer), reflective polarizer 250 (denoted RP), and second optical retarder 252. The multilayer film is supported by a first curved surface 254 of first lens 240. The first curved surface 254 is illustrated as a concave surface, though other lens configurations may be used. First lens 240 has a second curved surface 256. Second curved surface 256 may support an additional single layer or multilayer film, such as a film including a reflective polarizer, beamsplitter, or other optical layer. For illustrative clarity, the multilayer film 260 is shown in an exploded form, but in a device the layers may be adjacent to each other and located on the first curved surface 254 of the first lens 240. The arrow indicates a direction that respective layer representations may be collapsed to provide a better representation.

[0057] FIGS. 3A and 3B show an example layer arrangement within a multilayer film 312 supported by a curved surface 314 of a lens 310. The combination of the lens 310 and the multilayer film 312 may be referred to as a lens assembly 300. The multilayer film 312 may be supported by the curved surface 314 of the lens 310, for example, after lamination of the multilayer film to the curved surface. The lens may have a second curved surface 316 which may support additional layers (not shown in the figure), such as a beam splitter or a reflective polarizer.

[0058] FIG. 3B shows the layer configuration of the multilayer film in more detail. The cross-section detail 320 shows an example layer arrangement within the multilayer film 312 shown in FIG. 3A. In some examples, the multilayer film 312 includes an antireflection (AR) layer 322 (denoted AR-CAT), first pressure-sensitive adhesive (PSA) layer 324, first layer 326 (denoted LC +C), first adhesive (or glue) layer (328), first optical retarder layer 330 (in this example, N-QWP or quarter-wave plate), second pressure-sensitive adhesive layer 332, triacetyl cellulose (TAC) polymer layer (334), linear polarizer (LP) layer 336, cyclic olefin polymer (COP) layer (338), third pressure-sensitive adhesive layer 340, reflective polarizer (RP) layer 342, fourth pressure-sensitive adhesive layer 344, second optical retarder layer 346, second adhesive layer 348, positive C plate layer (350, denoted LC +C), and hard optically clear adhesive (OCA) layer 352.

[0059] In some examples, a pancake multilayer film was developed having a configuration that effectively combines the function of the first and second lenses of a two- lens pancake lens configuration when applied to a curved surface of the first lens. In some approaches, the pancake film had a relatively high modulus. For example, an optically clear adhesive layer may have a relatively high modulus to obtain a higher thermal or mechanical stability. In some examples, polymers having higher glass transition temperatures were used in order to obtain higher mechanical stability, for example, using polycarbonate (PC) or triacetyl cellulose (TAC) polymers. The use of high modulus layers and thicker layers appears attractive to obtain improved mechanical stability. However, a high modulus layer and/or a relatively thick film may result in relatively high out-of-plane stresses when the film is laminated to a curved surface. In some examples, fabricated lenses showed various visually- discernable defects such as crack, delamination, and poor optical uniformity.

[0060] FIGS. 4A - 4C show example lenses having variously visually-discernable defects. FIG. 4A shows a lens (410) having an inner bubble (412) and a line bubble (414). FIG. 4B shows a lens (420) having areas of delamination (422). FIG. 4C shows a lens (430) that, on inspection, included a crack in the optical retarder layer.

[0061] FIG. 5 shows the retardation non-uniformity (500) over the aperture of an example lens. The optical retardation non-uniformity may be induced by stresses within layers in lenses fabricated using conventional approaches. This aspect is discussed in more detail below, such as in relation to FIGS. 11A - 11C.

[0062] I mproved performance of multilayer films supported by a curved surface (e.g., a lens surface) would be useful to reduce layer stress and formation of visually- discernable defects. Examples include multilayer films, lenses, and optical assemblies having improve stress relaxation, optical performance, and reliability.

[0063] In some examples, a multilayer film may include an adhesive layer (e.g., an OCA layer) that may have a relatively high modulus for higher thermal stability. This approach may be reasonable for lamination of planar surfaces but may lead to problems when laminating a curved surface. Cracks, delamination, and poor optical retardance uniformity were frequently observed when a relatively high modulus adhesive layer was used. Further, a relatively thick multilayer film may deliver high out-of-plane stresses after curved lamination if the multilayer film has a high modulus or includes high modulus layers. In some examples, a high modulus may be associated with a high glass transition temperature (e.g., for a multilayer film including one or more PC and/or TAC layers).

[0064] In some examples, a multilayer film may provide improved lamination to a curved surface for one or more of the following aspects: a reduced overall thickness (e.g., less than 200 microns), inclusion of polymer layers with a lower lass transition temperature (e.g., less than 20 degrees C, such as less than 0 degrees C), relatively low modulus adhesive layers, liquid crystal based optical retarders, and/or ultrathin polarizers. These aspects are discussed in more detail below. Example multilayer films may provide stress relaxation (e.g., after lamination, possibly due to reduced elastic modulus), improved optical performance, and/or improved reliability.

[0065] Example multilayer films allow support by curved surfaces, such as a lens surface, and provide improvements for a magnitude of radius of curvature of less than 200 mm, such as less than 150 mm, for example, less than 100 mm. In some examples, a multilayer film was supported by a curved surface having a magnitude of radius of curvature between 50 mm and 100 mm, such as between 60 mm and 90 mm. In some examples, improved optical and/or mechanical multilayer film performance was observed when the multilayer film was laminated to a curved lens surface having a magnitude of radius of curvature in the range 50 mm to 100 mm, such as the range 60 mm - 90 mm, such as the range 70 mm - 80 mm.

[0066] Crack or delamination of one or more component films of a multilayer film may arise due to support by (e.g., lamination to) a surface having a three-dimensional curvature, such as a spherical surface or other curved surface. Out-of-plane stresses, for example, due to bending stiffness, may result in increased prevalence of crack or delamination defects.

[0067] In some examples, lamination of a multilayer film to a curved surface may induce stresses within the multilayer film. Stress modes may include shrinkage stress, which may be proportional to the cross-sectional area and the elastic modulus of the multilayer film or component layer thereof. Stress modes may also include bending stiffness that may be proportional to the elastic modulus and layer inertia.

[0068] Optical uniformity of a multilayer film may be improved by lowering the stress within a film. In some examples, stress may be reduced using thin layers. For example, a polycarbonate based optical retarder (e.g., a QWP) having a layer thickness of approximately 50 microns may be replaced by a liquid crystal based optical retarder having a layer thickness of between 0.5 microns and 10 microns, such as between 0.5 microns and 5 microns.

[0069] In some examples, uniform optical properties of a multilayer film were obtained using a liquid crystal based optical retarder having a layer thickness of between 0.5 microns and 20 microns, for example, between 1 micron and 10 microns, such as between 1 micron and 5 microns, for example, between 2 microns and 4 microns. In some examples, dimensional stability may be improved (e.g., shrinkage reduced) using an ultra-thin polarizer. In this context, an ultra-thin polarizer may have a thickness of approximately 10 microns or less, such as a thickness of between 1 micron and 10 microns, such as a thickness of between 2 microns and 8 microns, for example, a thickness of approximately 5 microns (e.g., between 4 microns and 6 microns). Example layers may include lower shrinkage layers, such as crosslinked polymer layers. In some examples, a polarizer may be a component of a multilayer film, such as an outer layer or an inner layer of a multilayer film, and may be referred to as a coating polarizer.

[0070] In some examples, an optical retarder may have an optical anisotropy due to stretching, such as stretching of a polymer layer. However, as discussed in more detail below, stretched layers may introduced non-uniformities after lamination. In some examples, a multilayer film may include no stretched polymer films. In some examples, a multilayer film may include an anisotropic film, such as an optical retarder, having an optical anisotropy arising from formation of a liquid crystal phase, such as a nematic phase. For example, the optical retarder layer may have a molecular alignment based on a liquid crystal phase, such as a nematic phase. The liquid crystal order (e.g., molecular alignment) may be locked in by one or more of polymerization (including polymerization of unpolymerized or partially polymerized states), cross-linking (e.g., UV photo-crosslinking), formation of network polymers, or other process that forms a solid layer having liquid crystal like order).

[0071] In some examples, thermal and hygroscopic stability may be improved by removing a TAC layer from the multilayer film, for example, a TAC layer used for the polarizer layer. An example multilayer film may include no polymer layers having a glass transition temperature above 80 degrees C, such as greater than 40 degrees C, such as greater than 30 degrees C.

[0072] In some examples, the thickness of the multilayer film may be reduced (e.g., from approximately 300 microns) to a multilayer film thickness of less than 250 microns, for example, between 50 microns and 200 microns, such as between 100 microns and 200 microns.

[0073] In some examples, the multilayer film may include an adhesive layer, such as an optically clear adhesive (OCA) and/or pressure-sensitive adhesive (PSA), that provides improved adhesion and/or improved stress release. In some examples, plasma treatment of a multilayer film or a component thereof (e.g., an adhesive layer) may improve adhesion. For example, a surface (e.g., a surface of a lens, mirror, or other optical element) may be treated with a hydrogen, oxygen, and/or nitrogen based plasma. In some examples, an adhesive layer with a lower elastic modulus (e.g., compared to a typical adhesive layer) may allow relief of some or all of a stress within a layer. For example, a relatively soft adhesive layer may be used. The mechanical properties of the adhesive layer may be adjusted to allow relief of most (or all) of a layer stress while providing sufficient adhesive strength. In some examples, a pressure sensitive adhesive (PSA) may have a layer thickness of between 5 and 12 microns. The limits of this range (and of other ranges described herein) may be approximate and/or may be inclusive.

[0074] In some examples, a multilayer film may include film components having a reduced film thickness and/or lower modulus film components. In some examples, polymer components may have a glass transition temperature less than a typical operating temperature. For example, an optically clear adhesive (OCA) layer may have a relatively low elastic modulus (e.g., in comparison with other materials used). In some examples, polarization layers may be ultra-thin, for example, including layers having a layer thickness of less than 10 microns. In some examples, polarization components may include liquid crystal layers, such as cholesteric (e.g., chiral nematic) liquid crystal layers. In this context, a liquid crystal layer may have molecular orientations similar to or based on liquid crystal molecular orientations, but the layer may be a solid layer or a layer with a flow viscosity sufficiently high at typical operating temperatures that no appreciable layer flow is expected within the device lifetime. Example liquid crystal layers may include polymer layers such as cross-linked polymer layers. Example polarization layers may include linear polarizers and/or circular polarizers, optical retarders, and +C plates. In some examples, the function of a circular polarizer (CP) may be provided by a linear polarizer (LP) in combination with a quarter-wave plate (QWP) or a half-wave plate (HWP). In some examples, a multilayer film may include a +C plate (e.g., a positive C plate or film) that may be used as an optical compensation film, for example, to improve color uniformity of a displayed image.

[0075] FIGS. 6A and 6B show example lenses having a pancake-side optical retarder layer crack. FIG. 6A shows a lens 600 having a central region 602 including a plurality of generally parallel cracks. FIG. 6B shows a lens 620 having a field of view 630 including a plurality of cracks.

[0076] FIGS. 7A and 7B further illustrate delamination in example lenses. FIG. 7A shows a lens 700 showing evidence of delamination 702 in a peripheral portion 704 of the lens 700. FIG. 7B shows a lens 720 showing visual evidence of delamination in a peripheral portion 730 of the lens 720.

[0077] FIGS. 8A and 8B show further example lenses according to some examples obtained using an example process. FIG. 8A shows cracks in a peripheral portion 810 of a lens 800 fabricated using a QWP/+C configuration. FIG. 8B shows a lens 830 fabricated using a liquid crystal based optical retarder (e.g., QWP) that shows no evidence of cracks. Replacement of a stretched polymer based optical retarder with a liquid crystal based optical retarder gave improved mechanical and/or optical properties.

[0078] FIGS. 9A - 9C show further example lenses according to some examples. FIG. 9A shows a lens 900 that had improved resistance to delamination, at least in part due to the use of layers having a reduced layer thickness, showing slight defects in a peripheral portion 902. FIG. 9B shows a lens profile 920 showing reduced delamination 922 in a portion of the lens 924 due to an optically clear adhesive (OCA) layer having a reduced elastic modulus. FIG. 9C shows a view of an example lens 940 also having reduced delamination in a peripheral portion 942 due to an OCA layer having a reduced elastic modulus.

[0079] FIGS. 10A - 10D illustrates film behavior according to some examples. FIG. IDA shows an example multilayer film 1000. FIG. 10B shows an example curved surface 1010 to which the multilayer film 1000 may be laminated. FIG. 10C shows a crack 1022 formed in a multilayer film 1020 due to an attempt to conform the multilayer film 1020 to a curved surface. FIG. 10D shows further growth of a crack 1032 in a multilayer film 1030 due to an attempt to conform the multilayer film 1020 to a curved surface having a lower magnitude of radius of curvature than the case discussed above in relation to FIG. 10D.

[0080] Stress modes within an example multilayer film may include in-plane stresses and out-of-plane stresses. In -plane stresses may result from shrinkage forces (e.g., scaled by LP/RP). Stresses may be proportional to thickness and/or modulus. Out-of-plane stresses may result from bending stiffness which may be proportional to E* l/L, where E is an elastic modulus, I represents inertia, and L represents length. The moment of inertia (I) may be proportional to the third power of thickness. Bending stiffness may be an extra force present in a curved lamination process and may be affected by temperature, thickness, or elastic modulus (which may be, e.g., proportional to the reciprocal of temperature).

[0081] Using conventional fabrication methods, the optical retardation of example multilayer films was non-uniform across the lens aperture, for example, as discussed above in relation to FIG. 5.

[0082] Stretching may be used to introduce optical retardance in a polymer film. Polymer based optical retarder films may be subject to high ratio TD stretching. The stretched polymer films may then have different mechanical properties, such as elastic modulus, along different directions. For example, the elastic modulus along the direction of stretching may be appreciably different from the elastic modulus perpendicular to the direction of stretching. This may lead to changes in optical properties and increased optical non-uniformities after lamination of the multilayer film (including a stretched polymer film) to the lens. The nonuniformities may be greater for three-dimensional lamination (e.g., lamination to a curved surface such as a convex or concave surface) than for lamination to a planar surface.

[0083] As noted above, for a polymer based film (such as a polycarbonate based film) optical retardation may be introduced by stretching the film. Further stretching may occur during thermal lamination, for example, to a lens surface. The stretching may introduce anisotropic mechanical properties that may lead to additional optical retardation nonuniformity. For example, there may be differences in optical retardation along the slow axis compared with along the fast axis. The optical retardation non-uniformity may reduce the contrast ratio of the image displayed to a user, and may lead to ghost images. Similarly, optical retardation non-uniformity may lead to a reduction in luminance uniformity and color uniformity over the field of view.

[0084] Data analysis and simulations were used to determine changes in optical retardation uniformity in an optical retardance film. Optical retarder films based on alternative film materials, such as liquid crystal (LC) based materials, were found to give improved optical performance.

[0085] An improved multilayer film may include one or more liquid crystal (LC) based polarization components, such as one or more LC based optical retarder layers. An LC based optical retarder layer may have an optical retardance that has a relatively low sensitivity to strain compared to that of a polymer film that has optical retardance introduced by stretching.

[0086] FIGS. 11A - 11C show an example optical apparatus for the optical evaluation of lenses, for example, lenses having at least one curved surface supporting a multilayer film.

[0087] FIG. 11A shows an apparatus 1100 including a light source 1102, an optical film 1104 and a camera 1110. A lens 1106 supporting a multilayer film 1108 may be placed in the light path between the light source 1102 and the camera 1110. In this example, the light source includes a backlight unit (BLU), for example, a BLU for a liquid crystal display used in an AR/VR device.

[0088] FIG. 11B shows luminance variations 1120 in a multilayer film including a stretched polymer based optical retarder film. In some examples, red and blue optical mura were observed. FIG. 11C shows optical retardance non-uniformity 1140 in a multilayer film including a stretched polymer based optical retarder film. The non-uniformities appeared to be based on the direction of stretching as discussed above. The results qualitatively agreed with numerical simulations based on the expected performance of stretched polymer films.

[0089] FIG. 12 shows tabulated illustrations of different lens configurations including a multilayer film laminated to the curved surface of a lens. The figure shows the multilayer film configuration (for lenses having curved multilayer film lamination) and associated retardation mura that may indicate optical non-uniformities.

[0090] A converging lens 1200 has a convex upper surface (as illustrated) and a concave lower surface that may support a multilayer film. For illustrative clarity, the multilayer films are shown with planar layers having a greatly exaggerated thickness. Multilayer films were laminated to the concave surface of the lens at 110 degrees C, though this and other ranges are exemplary and not limiting. Layer thicknesses of the posi-C layer and the adhesive layer may be between 0.5 and 10 microns. The optical retarder layer (e.g., a quarter wave plate, QWP) may have a layer thickness between 1 micron and 100 microns, such as between 1 and 60 microns.

[0091] Lens 1204 supports a multilayer film 1202 and may be referred to as a lens assembly 1210. The multilayer film 1202 may include an optically clear adhesive (OCA) layer, a posi-C layer (e.g., a positive C plate), an adhesive layer, an optical retarder layer (e.g., a QWP), a PSA layer, and an acrylic polymer layer. In some examples, the optical retarder layer may have a thickness between 30 microns and 70 microns, such as approximately 50 microns. The mura 1208 indicates an optical non-uniformity.

[0092] Lens 1234 supports a multilayer film 1232 and may be referred to as a coated lens 1230. The multilayer film may have a similar structure to the multilayer film 1202 discussed above. The multilayer film may include an optical retarder layer having a thickness between 30 microns and 40 microns, such as 37 microns. The mura 1238 indicates an optical non-uniformity.

[0093] Lens 1254 supports a multilayer film 1252 and may be referred to as a coated lens 1250. The multilayer film may have a similar structure to the multilayer film 1202 discussed above. An optical retarder layer may have a thickness between 50 microns and 60 microns, such as 57 microns. The mura 1258 indicates an optical non-uniformity but increasing the thickness of the optical retarder layer has slightly reduced the optical non- uniformity. This may be due to the thicker film allowing stresses to relax.

[0094] Lens 1274 supports a multilayer film in a similar manner to that of lens 1254 and may be referred to as a lens assembly. The multilayer film may have a similar structure to the multilayer film 1202 discussed above. In this example, the optical retarder includes a liquid crystal based material, such as a liquid crystal quarter wave plate (LC-QWP). The optical retarder layer 1276 may have a thickness between 0.5 microns and 10 microns, such as between 1 micron and 5 microns, such as approximately 3 microns. The mura 1278 indicates an optically uniform multilayer film. The scale 1290 illustrates how the mura shading may relate to optical retardance expressed in nm. In some examples, optical retardance may be measured at 450 nm, 525 nm, or 625 nm. The retardance in nm may refer to 525 nm measurements.

[0095] In some examples, a lens includes a curved surface supporting a multilayer film. The multilayer film may include an optical retarder layer and the optical retarder layer may include a liquid crystal based layer. In some examples, the liquid crystal based layer may have nematic-like order of molecules and/or molecular moieties. A liquid crystal based layer may include, for example, a solid layer of a material that may have a higher temperature nematic phase, or which may be cross-linked after formation of nematic-like order.

[0096] FIG. 13 illustrates a chart 1300 showing reduction of the dimensional variance of standard and ultra-thin polarizers. The figure shows that the dimensional stability of a multilayer film including an ultra-thin polarizer (1304) is reduced by 60% compared to the dimensional stability of a standard polarizer (1302).

[0097] FIG. 14 illustrates an example multilayer film configuration with exemplary film thicknesses in microns shown in parentheses. The multilayer film (1400) includes an antireflection (AR) layer 1410 that may include an acrylic polymer, G-PSA layer (1412), posi-C layer (1414, e.g., a positive C plate), adhesive layer (1416), optical retarder layer (1418), second G-PSA layer (1420), triacetyl cellulose (TAC) layer (1422), GRT polarizer layer (1424, e.g, including a grating), cyclo-olefin polymer (COP) layer (1426), optically clear adhesive (OCA) layer (1428), a reflective polarizer layer (1430, denoted IQP-E or image quality polarizer - enhanced), a third G-PSA layer (1432), a second optical retarder layer (1434), a second adhesive layer (1436), and a second posi-C layer (1438).

[0098] FIGS. ISA - 15C show further example multilayer configurations. Layer compositions may be similar to those discussed above and are not discussed here in detail.

[0099] FIG. 15A shows a multilayer film 1500 including a first liquid crystal based optical retarder layer 1502, a second liquid crystal based optical retarder layer 1506, and an ultrathin polarizer 1504. Other layers may be as discussed above. The use of liquid crystal based optical retarders may provide appreciable improvement in optical uniformity as discussed above in relation to FIG. 12. The inclusion of an ultrathin polarizer layer may provide appreciable improvement in dimensional stability of the multilayer film as discussed in relation to FIGS. 16A - 16C below. A lens assembly including a lens and a multilayer film such as multilayer film 1500 may provide improved performance in, for example, an AR/VR device.

[0100] FIG. 15B shows a multilayer film 1540 including a liquid crystal based optical retarder layer 1542, for example, a liquid crystal based quarter wave plate (QWP) layer. Other layers may be as discussed above, for example, in relation to FIG. 14. In some examples, a multilayer film may include a liquid crystal based optical retarder layer, an adhesive layer, a TAC layer, a GRT (grating) polarizer layer, a COP layer, a PSA layer, and an antireflection layer.

[0101] FIG. 15C shows a multilayer film 1570 including a liquid crystal based optical retarder layer 1572, for example, a liquid crystal based quarter wave plate (QWP) layer. Other layers may be as discussed above, for example, in relation to FIG. 14. In some examples, a multilayer film may include an antireflection layer, an optically clear adhesive (OCA) layer, a reflective polarizer layer, a pressure-sensitive adhesive layer, a liquid crystal based optical retarder layer, and a posi-C (e.g., a positive C plate) layer. A C-plate optical retarder may be termed a positive C plate retarder if the extraordinary refractive index is larger than the ordinary index of refraction for the C plate.

[0102] Retardance uniformity was determined using a radiant camera test and a polarimeter. The results were generally consistent regarding retardance uniformity but occasionally the sign of retardance error was different.

[0103] FIGS. 16A - 16C show example optical properties. The graphs show optical retardance (nm, ordinate) against spatial location (arbitrary units) as determined using a radiant camera.

[0104] FIG. 16A shows results for a multilayer film including a liquid crystal based optical retarder and one TAC layer. The optical uniformity was good with a retardance uniformity of 0.5 nm (+/- 1.5 nm) within 30 mm of the film center (illustrated by the dashed line 1612) and a retardance uniformity of 1 nm (+/- 2 nm) for the entire field of view (illustrated by the solid line 1610).

[0105] FIG. 16B shows that removal of the TAC layer further improves the optical retardance uniformity of the multilayer film. The multilayer film includes a liquid crystal based optical retarder and no TAC layers. The optical retardance uniformity is 0.5 nm (+/- 0.5 nm) for the entire field of view. Curves 1620, 1622, 1624, and 1626 show optical retardance uniformity for various spatial portions of the multilayer film.

[0106] FIG. 16C shows optical retardance uniformity for a multilayer film including a liquid crystal based optical retarder and two TAC layers. The retardance uniformity was 3 nm (+/- 5 nm) within 30 mm of the film center (illustrated by the dashed line 1632) and 3 nm (+/- 9 nm) for the entire field of view (illustrated by the solid line 1630). The results further illustrate that the removal of TAC layers improved the optical retardance uniformity.

[0107] FIGS. 17A - 17C show further example optical properties. The graphs show optical retardance (nm, ordinate) against spatial location (arbitrary units) as determined using a polarimeter. FIG. 17A shows a uniformity of 3 nm (+/- 3 nm) over the full field as shown by dashed line 1710. FIG. 17B shows a uniformity of -0.5 nm (+/- 1.5 nm) over the full field as shown by dashed line 1720. FIG. 17C shows a uniformity of 2 nm (+/- 8 nm) over the full field as shown by dashed line 1730. FIGS. 17A - 17C were obtained for the same samples discussed above in relation to FIGS. 16A - 16C, respectively.

[0108] FIGS. 18A and 18B show further example multilayer configurations.

[0109] FIG. 18A shows a multilayer film 1810 including anti-reflection layer (1812), pressure sensitive adhesive layer (1814), first liquid crystal based optical retarder layer (1816, in this example a quarter-wave plate), second pressure sensitive adhesive layer (1818), triacetyl cellulose (TAC) layer (1820), linear polarizer (LP) layer (1822), cyclo-olefin polymer (COP) layer (1824), optically clear adhesive (OCA) layer (1826), RP (e.g., a reflective polarizer) layer (1828), third pressure sensitive adhesive layer (1830), second liquid crystal based optical retarder layer (1832, in this example a quarter-wave plate), adhesive layer (1832), and LC +C layer (1834). In some examples, the linear polarizer layer (1822) may be a polarizer layer having a thickness of between 1 micron and 20 microns, such as between 2 microns and 20 microns, and may include an arrangement of anisotropic electrically conductive elements such as microwires, nanowires, or molecular moieties.

[0110] FIG. 18B shows a further multilayer film 1840 having a similar structure to that of FIG. 18A. Many layers are similar to those discussed above in relation to FIG. 18A and are not discussed again here for conciseness. Similar to the multilayer film 1810, the multilayer film 1840 includes a first liquid crystal based optical retarder layer 1842 and a liquid crystal based optical retarder layer 1844. Unlike the multilayer film 1810, the multilayer film 1840 does not include a TAC layer. The multilayer film 1840 includes an ultra-thin polarizer layer 1846 and an acrylate polymer layer 1848. The polymer layer 1848 may be selected to have an elastic modulus significantly less than the TAC layer, for example, by using a polymer having an appreciably lower glass transition temperature.

[0111] The multilayer film 1810 showed reasonable optical uniformity, but the optical properties may be further improved in the multilayer film 1840. For example, the inclusion of the ultra-thin polarizer layer improves the dimensional stability of the multilayer film, and the removal of the TAC layer further increases optical retardance uniformity.

[0112] FIGS. 19A and 19B show further example multilayer configurations.

[0113] FIG. 19A shows a multilayer film (1910) including an ultrathin polarizer

(1920) and a liquid crystal based optical retarder (1922). Other layers are similar to those discussed above in relation to FIG. 18A. The multilayer film 1910 may provide enhanced optical uniformity and/or dimensional stability when supported by a curved or planar lens surface (e.g., following a lamination process). An ultrathin polarizer may have a thickness of between approximately 1 micron and approximately 10 microns, such as approximately 5 microns.

[0114] FIG. 19B shows a multilayer film 1940 including first liquid crystal based optical retarder (1942), a coating polarizer (1944), and second liquid crystal based optical retarder (1946). Other layers may be similar to those discussed above in relation to FIG. 18A. The multilayer film 1940 may provide enhanced optical uniformity and/or dimensional stability when supported by a curved or planar lens surface. A coating polarizer may have a thickness of between approximately 1 micron and approximately 10 microns, such as approximately 5 microns. [0115] FIG. 20 shows a multilayer film 2010 including a coating polarizer (2012) and liquid crystal based optical retarder (2014). Other layers are similar to those discussed above in relation to FIG. 18A. The multilayer film 2010 may provide enhanced optical uniformity and/or dimensional stability when supported by a curved or planar lens surface.

[0116] The thickness of an example multilayer film may be less than 200 microns, for example, in the range 140 microns to 200 microns. The ultra-thin polarizer may allow a reduction of the multilayer film thickness. High elastic modulus layers, such as one or more TAC layers, may not be included. In some examples, a lower magnitude of radius of curvature (ROC) may be used, such as a ROC magnitude less than 100 mm, such as in the range 20 mm -80 mm, such as 30 mm - 70 mm, such as approximately 50 mm. The reduced layer thickness of liquid crystal based polarization components (such as liquid crystal based optical retarders) may allow a reduction in multilayer film thickness and/or allow fabrication of a relatively low elastic modulus multilayerfilm. In some examples, an optically clear adhesive (OCA) layer may have a layer thickness between 20 microns and 80 microns, such as approximately 50 microns. In some examples, an OCA layer may have an elastic modulus of less than 1 MPa, such as less than 0.5 MPa, and in some examples, less than 0.25 MPa. In some examples, an OCA layer may have an elastic modulus of between 0.5 and 0.25 MPa. In this example, and other examples described herein, an elastic modulus may be determined at 25 degrees C.

[0117] In some examples, an AR/VR device may include a lens (e.g., a pancake lens and/or a lens assembly including a multilayer film) that allows a reduced value of pixels per degree (e.g., a PPD of between 20 and 30) and/or a reduced focal length (e.g., a magnitude of focal length (f) of between 20 mm and 40 mm). These value ranges (and othervalue ranges in this specification) are exemplary and not restrictive, and may be inclusive.

[0118] FIG. 21 shows an example method according to some examples. The method 2100 includes forming a multilayer film including at least one liquid crystal based optical retarder and at least one polarizer (2110), laminating the multilayer film to a curved surface of a lens (2120), and fabricating an AR/VR device including a display and an optical configuration configured to form an image of the display (2130) where the optical configuration includes the multilayer film. In some examples, the at least one polarizer may include an ultrathin polarizer having a thickness of between 0.5 microns and 10 microns. In some examples, the at least one liquid crystal based optical retarder may include an optical retarder having a thickness of between 0.5 microns and 10 microns. In some examples, the at least one liquid crystal based optical retarder may include at least one quarter wave plate (QWP).

[0119] FIG. 22 illustrates a further method according to some examples. The method 2200 includes forming a multilayer film that includes at least one liquid crystal based optical retarder, at least one ultrathin polarizer, and at least one optically clear adhesive (OCA) layer having an elastic modulus less than 1 MPa (2210), laminating the multilayer film to a curved surface of a lens to form a lens assembly (2220), and fabricating a head-mounted device including a display and an optical configuration configured to form an image of the display (2230), where the optical configuration includes the lens assembly.

[0120] FIG. 23 illustrates a further method according to some examples. The method 2300 includes forming a multilayer film including an optical retarder and an ultrathin polarizer (2310), laminating the multilayer film to a curved surface of a lens (2320) or other optical component such as a reflective and/or diffractive component, and fabricating a headmounted device including a display and an optical configuration configured to form an image of the display (2330) where the optical configuration includes the multilayer film. In some examples, the multilayer film may be laminated to a surface (e.g., a curved surface) of a lens to form a lens assembly and/or laminated to a surface of another optical component (e.g., laminated to a surface of a window, prism, beamsplitter, polarizer, optical retarder, or polarized reflector).

[0121] In some examples, a multilayer film may include a polarizer, an optical retarder, and an adhesive layer. In some examples, the polarizer may include an ultrathin polarizer (e.g., a coating polarizer or other polarizer) having a thickness of between 0.5 microns and 10 microns. The polarizer may be a linear polarizer or a circular polarizer. In some examples, a liquid crystal based optical retarder may include an optical retarder having a thickness of between 0.5 microns and 10 microns. In some examples, a liquid crystal based optical retarder may include at least one quarter wave plate (QWP). In some examples, a multilayer film may be laminated to (or otherwise supported by) a surface (e.g., a curved surface) of a lens, mirror, or other optical component. In some examples, a multilayer film may be laminated to (or otherwise supported by) at least part of a reflective surface of a mirror, such as a planar mirror, a concave mirror, or a convex mirror. A curved surface (of, e.g., a lens or mirror) may be a spherical surface (or a portion of a sphere, such as a hemisphere or lens or mirror surface), or a non-spherical surface such as a parabolic surface or a freeform surface.

[0122] In some examples, a multilayer film may be configured as an optical film for lamination to a curved surface. An example multilayer film may be laminated to a surface having a radius having a magnitude of radius of curvature between approximately 50 mm to approximately 100 mm, for example, between approximately 70 mm and approximately 80 mm. An example multilayer film may also include a lower glass transition temperature (T_g) material (such as a polymer having a glass transition temperature of approximately equal to or greater than 25 degrees C. An example multilayer film may include a lower modulus optical clear adhesive (OCA), a LC type polarization component such as a coating polarizer, QWP, +C plate, or ultra-thin polarizer. An example LC type optical (e.g., polarization) component may have low strain sensitivity, for example, compared to stretched polymer based optical component. In some examples, a multilayer film may have a total thickness between approximately 100 microns and 250 microns, for example, between approximately 139 microns and approximately 192 microns. In some examples, an optical element (e.g., a reflective, refractive, and/or diffractive component) may have a curved surface supporting a multilayer film as described herein, and a fabrication process may include plasma treatment of the curved surface before lamination of the multilayer film (or otherwise supporting or depositing the multilayer film on the curved surface). In some examples, a multilayer film may be deposited on a planar surface and the properties of multilayer films as described herein may reduce the effects of due thermal stresses, mechanical stresses, or other effects.

[0123] Example methods may include computer-implemented methods for operating or fabricating an apparatus, such as an apparatus as described herein. The steps of an example method, such as adhering components together, may be performed by any suitable computer-executable code and/or computing system. In some examples, one or more of the steps of an example method may represent an algorithm whose structure includes and/or may be represented by multiple sub-steps. In some examples, a method for assembling an optical device such as an AR/VR device may include computer control of an apparatus, for example, to fabricate an optical element including a multilayer film.

[0124] In some examples, an apparatus may include at least one physical processor and physical memory including computer-executable instructions that, when executed by the physical processor, cause the physical processor to control an apparatus, for example, using a method such as described herein. In some examples, an apparatus may include a microcontroller which may be pre-programmed with firmware. The firmware may be updated based on device performance, for example, based on device performance for a particular user.

[0125] In some examples, a non-transitory computer-readable medium may include one or more computer-executable instructions that, when executed by at least one processor of an apparatus, cause the apparatus to at least partially assemble an optical device, for example, using a method such as described herein.

[0126] Example apparatus and methods may relate to a head-mounted device, such as an augmented reality and/or virtual reality device. Example apparatus may include a display and an optical configuration configured to form an image of the display, for example, at an eye of a user when the user wears the head-mounted device. The optical configuration may include a lens assembly, which may include a lens having a curved surface and a multilayer film supported by the curved surface of the lens. The multilayer film may include a polarizer and an optical retarder layer. The optical retarder layer may have a molecular alignment based on a liquid crystal phase, such as a nematic phase. In some examples, the optical retarder layer (or other layer, such as a polarizer layer) may include an optically anisotropic layer that has not been appreciably stretched. The polarizer may be an ultrathin polarizer having a thickness of between approximately 0.5 microns and approximately 20 microns, such as between approximately 1 micron and approximately 10 microns. In some examples, the optical retarder layer may have a layer thickness of between 1 micron and 10 microns. Other devices, methods, systems, and computer-readable media are also disclosed herein.

[0127] E mbodiments of the present disclosure may include or be implemented in

-conjunction with various types of artificial reality systems. Artificial reality is a form of reality that has been adjusted in some manner before presentation to a user, which may include, for example, a virtual reality, an augmented reality, a mixed reality, a hybrid reality, or some combination and/or derivative thereof. Artificial-reality content may include completely computer-generated content or computer-generated content combined with captured (e.g., real-world) content. The artificial-reality content may include video, audio, haptic feedback, or some combination thereof, anyof which may be presented in a single channel or in multiple channels (such as stereo video that produces a three-dimensional (3D) effect to the viewer). Additionally, in some embodiments, artificial reality may also be associated with applications, products, accessories, services, or some combination thereof, that are used to, for example, create content in an artificial reality and/or are otherwise used in (e.g., to perform activities in) an artificial reality.

[0128] Artificial-reality systems may be implemented in a variety of different form factors and configurations. Some artificial reality systems may be designed to work without near-eye displays (NEDs). Other artificial reality systems may include an NED that also provides visibility into the real world (such as, e.g., augmented-reality system 2400 in FIG. 24) or that visually immerses a user in an artificial reality (such as, e.g., virtual-reality system 2500 in FIG. 25). While some artificial-reality systems may be self-contained systems, other artificial-reality systems may communicate and/or coordinate with external devices to provide an artificial-reality experience to a user. Examples of such external devices include handheld controllers, mobile devices, desktop computers, devices worn by a user, devices worn by one or more other users, and/or any other suitable external system.

[0129] Turning to FIG. 24, augmented-reality system 2400 may include an eyewear device 2402 with a frame 2410 configured to hold a left display device 2415(A) and a right display device 2415(B) in front of a user's eyes. Display devices 2415(A) and 2415(B) may act together or independently to present an image or series of images to a user. While augmented-reality system 2400 includes two displays, embodiments of this disclosure may be implemented in augmented-reality systems with a single NED or more than two NEDs.

[0130] In some embodiments, augmented-reality system 2400 may include one or more sensors, such as sensor 2440. Sensor 2440 may generate measurement signals in response to motion of augmented-reality system 2400 and may be located on substantially any portion of frame 2410. Sensor 2440 may represent one or more of a variety of different sensing mechanisms, such as a position sensor, an inertial measurement unit (IMU), a depth camera assembly, a structured light emitter and/or detector, or any combination thereof. In some embodiments, augmented-reality system 2400 may or may not include sensor 2440 or may include more than one sensor. In embodiments in which sensor 2440 includes an IMU, the IMU may generate calibration data based on measurement signals from sensor 2440. Examples of sensor 2440 may include, without limitation, accelerometers, gyroscopes, magnetometers, other suitable types of sensors that detect motion, sensors used for error correction of the IMU, or some combination thereof.

[0131] In some examples, augmented-reality system 2400 may also include a microphone array with a plurality of acoustic transducers 2420(A)-2420(J), referred to collectively as acoustic transducers 2420. Acoustic transducers 2420 may represent transducers that detect air pressure variations induced by sound waves. Each acoustic transducer 2420 may be configured to detect sound and convert the detected sound into an electronic format (e.g., an analog or digital format). The microphone array in FIG. 24 may include, for example, ten acoustic transducers: 2420(A) and 2420(B), which may be designed to be placed inside a corresponding ear of the user, acoustic transducers 2420(C), 2420(D), 2420(E), 2420(F), 2420(G), and 2420(H), which may be positioned at various locations on frame 2410, and/or acoustic transducers 2420(1) and 2420(J), which may be positioned on a corresponding neckband 2405.

[0132] In some embodiments, one or more of acoustic transducers 2420(A)-(J) may be used as output transducers (e.g., speakers). For example, acoustic transducers 2420(A) and/or 2420(B) may be earbuds or any other suitable type of headphone or speaker.

[0133] The configuration of acoustic transducers 2420 of the microphone array may vary. While augmented-reality system 2400 is shown in FIG. 24 as having ten acoustic transducers 2420, the number of acoustic transducers 2420 may be greater or less than ten. In some embodiments, using higher numbers of acoustic transducers 2420 may increase the amount of audio information collected and/or the sensitivity and accuracy of the audio information. In contrast, using a lower number of acoustic transducers 2420 may decrease the computing power required by an associated controller 2450 to process the collected audio information. In addition, the position of each acoustic transducer 2420 of the microphone array may vary. For example, the position of an acoustic transducer 2420 may include a defined position on the user, a defined coordinate on frame 2410, an orientation associated with each acoustic transducer 2420, or some combination thereof.

[0134] Acoustic transducers 2420(A) and 2420(B) may be positioned on different parts of the user's ear, such as behind the pinna, behind the tragus, and/or within the auricle or fossa. Or, there may be additional acoustic transducers 2420 on or surrounding the ear in addition to acoustic transducers 2420 inside the ear canal. Having an acoustic transducer 2420 positioned next to an ear canal of a user may enable the microphone array to collect information on how sounds arrive at the ear canal. By positioning at least two of acoustic transducers 2420 on either side of a user's head (e.g., as binaural microphones), augmented- reality system 2400 may simulate binaural hearing and capture a 3D stereo sound field around about a user's head. In some embodiments, acoustic transducers 2420(A) and 2420(B) may be connected to augmented-reality system 2400 via a wired connection 2430, and in other embodiments acoustic transducers 2420(A) and 2420(B) may be connected to augmented- reality system 2400 via a wireless connection (e.g., a BLUETOOTH connection). In still other embodiments, acoustic transducers 2420(A) and 2420(B) may not be used at all in conjunction with augmented-reality system 2400.

[0135] Acoustic transducers 2420 on frame 2410 may be positioned in a variety of different ways, including along the length of the temples, across the bridge, above or below display devices 2415(A) and 2415(B), or some combination thereof. Acoustic transducers 2420 may also be oriented such that the microphone array is able to detect sounds in a wide range of directions surrounding the user wearing the augmented-reality system 2400. In some embodiments, an optimization process may be performed during manufacturing of augmented-reality system 2400 to determine relative positioning of each acoustic transducer 2420 in the microphone array.

[0136] In some examples, augmented-reality system 2400 may include or be connected to an external device (e.g., a paired device), such as neckband 2405. Neckband 2405 generally represents any type or form of paired device. Thus, the following discussion of neckband 2405 may also apply to various other paired devices, such as charging cases, smart watches, smart phones, wrist bands, other wearable devices, hand-held controllers, tablet computers, laptop computers, other external compute devices, etc.

[0137] As shown, neckband 2405 may be coupled to eyewear device 2402 via one or more connectors. The connectors may be wired or wireless and may include electrical and/or non-electrical (e.g., structural) components. In some cases, eyewear device 2402 and neckband 2405 may operate independently without any wired or wireless connection between them. While FIG. 24 illustrates the components of eyewear device 2402 and neckband 2405 in example locations on eyewear device 2402 and neckband 2405, the components may be located elsewhere and/or distributed differently on eyewear device 2402 and/or neckband 2405. In some embodiments, the components of eyewear device 2402 and neckband 2405 may be located on one or more additional peripheral devices paired with eyewear device 2402, neckband 2405, or some combination thereof.

[0138] Pairing external devices, such as neckband 2405, with augmented-reality eyewear devices may enable the eyewear devices to achieve the form factor of a pair of glasses while still providing sufficient battery and computation power for expanded capabilities. Some or all of the battery power, computational resources, and/or additional features of augmented-reality system 2400 may be provided by a paired device or shared between a paired device and an eyewear device, thus reducing the weight, heat profile, and form factor of the eyewear device overall while still retaining desired functionality. For example, neckband 2405 may allow components that would otherwise be included on an eyewear device to be included in neckband 2405 since users may tolerate a heavier weight load on their shoulders than they would tolerate on their heads. Neckband 2405 may also have a larger surface area over which to diffuse and disperse heat to the ambient environment. Thus, neckband 2405 may allow for greater battery and computation capacity than might otherwise have been possible on a stand-alone eyewear device. Since weight carried in neckband 2405 may be less invasive to a userthan weight carried in eyewear device 2402, a user may tolerate wearing a lighter eyewear device and carrying or wearing the paired device for greater lengths of time than a user would tolerate wearing a heavy standalone eyewear device, thereby enabling users to more fully incorporate artificial reality environments into their day-to-day activities.

[0139] Neckband 2405 may be communicatively coupled with eyewear device 2402 and/or to other devices. These other devices may provide certain functions (e.g., tracking, localizing, depth mapping, processing, storage, etc.) to augmented-reality system 2400. In the embodiment of FIG. 24, neckband 2405 may include two acoustic transducers (e.g., 2420(1) and 2420(J)) that are part of the microphone array (or potentially form their own microphone subarray). Neckband 2405 may also include a controller 2425 and a power source 2435.

[0140] Acoustic transducers 2420(1) and 2420(1) of neckband 2405 may be configured to detect sound and convert the detected sound into an electronic format (analog or digital). In the embodiment of FIG. 24, acoustic transducers 2420(1) and 2420(J) may be positioned on neckband 2405, thereby increasing the distance between the neckband acoustic transducers 2420(1) and 2420(J) and other acoustic transducers 2420 positioned on eyewear device 2402. In some cases, increasing the distance between acoustic transducers 2420 of the microphone array may improve the accuracy of beamforming performed via the microphone array. For example, if a sound is detected by acoustic transducers 2420(C) and 2420(D) and the distance between acoustic transducers 2420(C) and 2420(D) is greater than, e.g., the distance between acoustic transducers 2420(D) and 2420(E), the determined source location of the detected sound may be more accurate than if the sound had been detected by acoustic transducers 2420(D) and 2420(E).

[0141] Controller 2425 of neckband 2405 may process information generated by the sensors on neckband 2405 and/or augmented-reality system 2400. For example, controller 2425 may process information from the microphone array that describes sounds detected by the microphone array. For each detected sound, controller 2425 may perform a direction-of-arrival (DOA) estimation to estimate a direction from which the detected sound arrived at the microphone array. As the microphone array detects sounds, controller 2425 may populate an audio data set with the information. In embodiments in which augmented- reality system 2400 includes an inertial measurement unit, controller 2425 may compute all inertial and spatial calculations from the IMU located on eyewear device 2402. A connector may convey information between augmented-reality system 2400 and neckband 2405 and between augmented-reality system 2400 and controller 2425. The information may be in the form of optical data, electrical data, wireless data, or any other transmittable data form. Moving the processing of information generated by augmented-reality system 2400 to neckband 2405 may reduce weight and heat in eyewear device 2402, making it more comfortable to the user.

[0142] Power source 2435 in neckband 2405 may provide power to eyewear device 2402 and/or to neckband 2405. Power source 2435 may include, without limitation, lithium ion batteries, lithium-polymer batteries, primary lithium batteries, alkaline batteries, or any other form of power storage. In some cases, power source 2435 may be a wired power source. Including power source 2435 on neckband 2405 instead of on eyewear device 2402 may help better distribute the weight and heat generated by power source 2435.

[0143] As noted, some artificial reality systems may, instead of blending an artificial reality with actual reality, substantially replace one or more of a user's sensory perceptions of the real world with a virtual experience. One example of this type of system is a head-worn display system, such as virtual-reality system 2500 in FIG. 25, that mostly or completely covers a user's field of view. Virtual-reality system 2500 may include a front rigid body 2502 and a band 2504 shaped to fit around a user's head. Virtual-reality system 2500 may also include output audio transducers 2506(A) and 2506(B). Furthermore, while not shown in FIG. 25, front rigid body 2502 may include one or more electronic elements, including one or more electronic displays, one or more inertial measurement units (IMUs), one or more tracking emitters or detectors, and/or any other suitable device or system for creating an artificial-reality experience.

[0144] Artificial reality systems may include a variety of types of visual feedback mechanisms. For example, display devices in augmented-reality system 2400 and/or virtual- reality system 2500 may include one or more liquid crystal displays (LCDs), light emitting diode (LED) displays, microLED displays, organic LED (OLED) displays, digital light project (DLP) micro-displays, liquid crystal on silicon (LCoS) micro-displays, and/or any other suitable type of display screen. These artificial reality systems may include a single display screen for both eyes or may provide a display screen for each eye, which may allow for additional flexibility for varifocal adjustments or for correcting a user's refractive error. Some of these artificial reality systems may also include optical subsystems having one or more lenses (e.g., concave or convex lenses, Fresnel lenses, adjustable liquid lenses, etc.) through which a user may view a display screen. These optical subsystems may serve a variety of purposes, including to collimate (e.g., make an object appear at a greater distance than its physical distance), to magnify (e.g., make an object appear larger than its actual size), and/or to relay (to, e.g., the viewer's eyes) light. These optical subsystems may be used in a non-pupil-forming architecture (such as a single lens configuration that directly collimates light but results in so- called pincushion distortion) and/or a pupil-forming architecture (such as a multi-lens configuration that produces so-called barrel distortion to nullify pincushion distortion).

[0145] In addition to or instead of using display screens, some of the artificial reality systems described herein may include one or more projection systems. For example, display devices in augmented-reality system 2400 and/or virtual-reality system 2500 may include micro-LED projectors that project light (using, e.g., a waveguide) into display devices, such as clear combiner lenses that allow ambient light to pass through. The display devices may refract the projected light toward a user's pupil and may enable a user to simultaneously view both artificial reality content and the real world. The display devices may accomplish this using any of a variety of different optical components, including waveguide components (e.g., holographic, planar, diffractive, polarized, and/or reflective waveguide elements), lightmanipulation surfaces and elements (such as diffractive, reflective, and refractive elements and gratings), coupling elements, etc. Artificial reality systems may also be configured with any other suitable type or form of image projection system, such as retinal projectors used in virtual retina displays.

[0146] The artificial reality systems described herein may also include various types of computer vision components and subsystems. For example, augmented-reality system 2400 and/or virtual-reality system 2500 may include one or more optical sensors, such as two-dimensional (2D) or 3D cameras, structured light transmitters and detectors, time-of- flight depth sensors, single-beam or sweeping laser rangefinders, 3D LiDAR sensors, and/or any other suitable type or form of optical sensor. An artificial reality system may process data from one or more of these sensors to identify a location of a user, to map the real world, to provide a user with context about real-world surroundings, and/or to perform a variety of other functions.

[0147] The artificial reality systems described herein may also include one or more input and/or output audio transducers. Output audio transducers may include voice coil speakers, ribbon speakers, electrostatic speakers, piezoelectric speakers, bone conduction transducers, cartilage conduction transducers, tragus-vibration transducers, and/or any other suitable type or form of audio transducer. Similarly, input audio transducers may include condenser microphones, dynamic microphones, ribbon microphones, and/or any other type or form of input transducer. In some embodiments, a single transducer may be used for both audio input and audio output.

[0148] In some embodiments, the artificial reality systems described herein may also include tactile (i.e., haptic) feedback systems, which may be incorporated into headwear, gloves, body suits, handheld controllers, environmental devices (e.g., chairs, floormats, etc.), and/or any other type of device or system. Haptic feedback systems may provide various types of cutaneous feedback, including vibration, force, traction, texture, and/or temperature. Haptic feedback systems may also provide various types of kinesthetic feedback, such as motion and compliance. Haptic feedback may be implemented using motors, piezoelectric actuators, fluidic systems, and/or a variety of other types of feedback mechanisms. Haptic feedback systems may be implemented independent of other artificial reality devices, within other artificial reality devices, and/or in conjunction with other artificial reality devices.

[0149] By providing haptic sensations, audible content, and/or visual content, artificial reality systems may create an entire virtual experience or enhance a user's real-world experience in a variety of contexts and environments. For instance, artificial reality systems may assist or extend a user's perception, memory, or cognition within a particular environment. Some systems may enhance a user's interactions with other people in the real world or may enable more immersive interactions with other people in a virtual world. Artificial reality systems may also be used for educational purposes (e.g., for teaching or training in schools, universities, hospitals, business enterprises, etc.), entertainment purposes (e.g., for playing video games, listening to music, watching video content, etc.), and/or for accessibility purposes (e.g., as hearing aids, visual aids, etc.). The embodiments disclosed herein may enable or enhance a user's artificial reality experience in one or more of these contexts and environments and/or in other contexts and environments.

[0150] The process parameters and sequence of the steps described and/or illustrated herein are given by way of example only and can be varied as desired. For example, while the steps illustrated and/or described herein may be shown or discussed in a particular order, these steps do not necessarily need to be performed in the order illustrated or discussed. The various exemplary methods described and/or illustrated herein may also omit one or more of the steps described or illustrated herein or include additional steps in addition to those disclosed.

[0151] The preceding description has been provided to enable others skilled in the art to best utilize various aspects of the exemplary embodiments disclosed herein. This exemplary description is not intended to be exhaustive or to be limited to any precise form disclosed. Many modifications and variations are possible without departing from the scope of the present disclosure as defined by the claims. The embodiments disclosed herein should be considered in all respects illustrative and not restrictive. Reference may be made to any claims appended hereto and their equivalents in determining the scope of the present disclosure.

[0152] Uni ess otherwise noted, the terms "connected to" and "coupled to" (and their derivatives), as used in the specification and/or claims, are to be construed as permitting both direct and indirect (i.e., via other elements or components) connection. In addition, the terms "a" or "an," as used in the specification and/or claims, are to be construed as meaning "at least one of." Finally, for ease of use, the terms "including" and "having" (and their derivatives), as used in the specification and/or claims, are interchangeable with and have the same meaning as the word "comprising."

Claims

WHAT IS CLAIMED IS:

1. An apparatus comprising: a display; and an optical configuration configured to form an image of the display, wherein: the optical configuration comprises a lens assembly; the lens assembly comprises a lens having a curved surface and a multilayer film supported by the curved surface of the lens; the multilayer film comprises a polarizer layer and an optical retarder layer; the optical retarder layer has a molecular alignment based on a liquid crystal phase; the optical retarder layer has an optical retarder layer thickness of between 1 micron and 10 microns; and the apparatus comprises a head-mounted device.

2. The apparatus of claim 1, wherein the polarizer layer is a linear polarizer.

3. The apparatus of claim 1, wherein the optical retarder layer thickness is between 1 micron and 5 microns; and/or wherein the optical retarder layer is a quarter-wave plate.

4. The apparatus of claim 1, wherein the polarizer layer has a polarizer layer thickness of between 1 microns and 10 microns.

5. The apparatus of claim 1, wherein the curved surface of the lens has a magnitude of radius of curvature of less than 200 mm.

6. The apparatus of claim 1, wherein the lens assembly has a magnitude of optical retardance uniformity equal to or better than 0.5 nm (+/- 0.5 nm) over a field of view of the lens assembly.

7. The apparatus of claim 1, wherein: the multilayer film further comprises an adhesive layer; and the adhesive layer has an elastic modulus less than 1 MPa.

8. The apparatus of claim 1, wherein the multilayer film further comprises: an antireflection layer; a reflective polarizer; an optically clear adhesive layer located between the antireflection layer and the reflective polarizer; and a pressure sensitive adhesive layer located between the reflective polarizer and the optical retarder layer.

9. The apparatus of claim 1, wherein the display comprises a liquid crystal display.

10. The apparatus of claim 1, wherein the head-mounted device is a virtual reality device; and/or wherein the head-mounted device is an augmented reality device.

11. The apparatus of claim 1, wherein the optical configuration is configured to form an image of the display at an eyebox, the eyebox being a location at which a user may view the image of the display when the user wears the head-mounted device.

12. The apparatus of claim 1, wherein the multilayer film has a multilayer film thickness of between 50 microns and 200 microns.

13. A method, comprising: forming a multilayer film comprising at least one liquid crystal based optical retarder and at least one polarizer; laminating the multilayer film to a curved surface of a lens to form a lens assembly; and fabricating a device comprising a display and an optical configuration comprising the lens assembly configured to form an image of the display at an eye of a user when the user wears the device, wherein: the device comprises an augmented reality device, a virtual reality device, or a combination thereof.

14. The method of claim 13, wherein: the at least one polarizer comprises an ultrathin polarizer having a thickness of between 0.5 microns and 10 microns; and the at least one liquid crystal based optical retarder comprises an optical retarder having a thickness of between 0.5 microns and 10 microns; and/or wherein the at least one liquid crystal based optical retarder comprises at least one quarter wave plate.

15. A method, comprising: forming a multilayer film comprising a liquid crystal based optical retarder and an ultrathin polarizer; laminating the multilayer film to a curved surface of a lens to form a lens assembly; and fabricating a device comprising a display and an optical configuration comprising the lens assembly configured to form an image of the display at an eye of a user when the user wears the device, wherein: the device comprises an augmented reality device, a virtual reality device, or a combination thereof; the ultrathin polarizer has a thickness between 1 micron and 10 microns; and laminating the multilayer film to a curved surface of a lens to form a lens assembly comprises plasma treatment of the multilayer film.