Integral lens assembly and optical system including same

Abstract

An integral lens assembly includes a curved integral optical film assembly including a polymeric reflective polarizer bonded to a polymeric first optical film by a first optical adhesive layer. The curved integral optical film assembly has opposing outermost first and second major surfaces that each has a radius of curvature of less than about 500 mm along each of two mutually orthogonal directions. The integral lens assembly includes a molded first optical lens molded directly onto, and substantially conforming to, the outermost first major surface of the curved integral optical film assembly. The first optical adhesive layer is thinner at or closer to a peripheral edge of the film assembly and thicker at or closer to a central portion of the film assembly. The first optical film can be an absorbing polarizer.

Description

[0001] INTEGRAL LENS ASSEMBLY AND OPTICAL SYSTEM INCLUDING SAME

[0002] TECHNICAL FIELD

[0003] The present description relates generally to integral lens assemblies useful in optical systems.

[0004] BACKGROUND

[0005] An optical system can include a reflective polarizer disposed on a lens. The optical system may be a folded optical system that includes a partial reflector and a retarder layer disposed between the partial reflector and the reflective polarizer.

[0006] SUMMARY

[0007] In some aspects, the present description provides an integral lens assembly including a curved integral optical film assembly including a polymeric reflective polarizer bonded to a polymeric first optical film by a first optical adhesive layer. The curved integral optical film assembly has opposing outermost first and second major surfaces that each has a radius of curvature of less than about 500 mm along each of two mutually orthogonal directions. The integral lens assembly includes a molded first optical lens molded directly onto, and substantially conforming to, the outermost first major surface of the curved integral optical film assembly. The first optical adhesive layer is thinner at or closer to a peripheral edge of the film assembly and thicker at or closer to a central portion of the film assembly.

[0008] In some aspects, the present description provides an integral lens assembly for use in an optical system configured to display a magnified virtual image of an image formed by a display to a viewer. The integral lens assembly includes a curved integral optical film assembly including a polymeric reflective polarizer bonded to a polymeric absorbing polarizer by a first optical adhesive layer. The curved integral optical film assembly has opposing outermost first and second major surfaces. Each of the outermost first and second major surfaces can have a radius of curvature of less than about 500 mm along each of two mutually orthogonal directions. The integral lens assembly includes a molded first optical lens molded directly onto, and substantially conforming to, the outermost first major surface of the curved integral optical film assembly. The first optical adhesive layer has a thickness tl at a first location closer to a first peripheral edge of the film assembly, a thickness t2 at a second location between the first location and a center location of the film assembly, and a thickness t3 at the center location, where t2 is greater than each oftl and t3.

[0009] In some aspects, the present description provides an integral lens assembly for use in an optical system configured to display a magnified virtual image of an image formed by a display to a viewer. The integral lens assembly is substantially centered on an optical axis and includes a curved integral optical film assembly comprising a polymeric reflective polarizer bonded to a polymeric absorbing polarizer by a first optical adhesive layer. The curved integral optical film assembly includes opposing outermost first and second major surfaces. Each of the outermost first and second major surfaces can have a radius of

[0010] -1- curvature of less than about 500 mm along each of two mutually orthogonal directions. The integral lens assembly includes a molded first optical lens molded directly onto, and substantially conforming to, the outermost first major surface of the curved integral optical film assembly. The molding causes the first optical adhesive layer to be thinner at or closer to a peripheral edge of the film assembly and thicker at or closer to a central portion of the film assembly.

[0011] In some aspects, the present description provides an integral lens assembly for use in an optical system configured to display a magnified virtual image of an image formed by a display to a viewer. The integral lens assembly is substantially centered on an optical axis and includes a curved integral optical film assembly including a polymeric reflective polarizer bonded to a polymeric first optical film by a first optical adhesive layer. The curved integral optical film assembly has opposing outermost first and second major surfaces. Each of the outermost first and second major surfaces can have a radius of curvature of less than about 500 mm along each of two mutually orthogonal directions. The integral lens assembly includes a molded first optical lens molded directly onto, and substantially conforming to, the outermost first major surface of the curved integral optical film assembly. The molding causes the first optical adhesive layer to have a thickness variation including a thickness tl at a first location closer to a first peripheral edge of the film assembly, a thickness t2 at a second location between the first location and a center location of the film assembly, and a thickness t3 at the center location, where t2 is greater than each oftl and t3.

[0012] These and other aspects will be apparent from the following detailed description. In no event, however, should this brief summary be construed to limit the claimable subject matter.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIGS. 1-4 are schematic cross-sectional views of optical systems including integral lens assemblies, according to some embodiments.

[0015] FIG. 5 is a schematic cross-section view of optical lenses and a partial reflector, according to some embodiments.

[0016] FIGS. 6-7 are plots of thicknesses of adhesive layers of integral optical assemblies, according to some embodiments.

[0017] FIG. 8 is a schematic cross-sectional view of a multilayer reflective polarizer, according to some embodiments.

[0018] FIG. 9 is a schematic cross-sectional view of an absorbing polarizer, according to some embodiments.

[0019] FIG. 10 is a schematic cross-sectional view of a light beam incident on an integral lens assembly, according to some embodiments.

[0020] FIG. 11 is a plot of modulation transfer function (MTF) of lens assemblies as a function of spatial frequency, according to some embodiments. DETAILED DESCRIPTION

[0021] In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. The following detailed description, therefore, is not to be taken in a limiting sense.

[0022] Optical system useful for virtual or augmented reality systems can include a reflective polarizer, a partial reflector, and a retarder disposed therebetween as generally described in U.S. Pat. No. 10,678,052 (Ouderkirk et al.), for example. In some cases, the reflective polarizer is disposed directly on an optical lens of the optical system to form a lens assembly. The optical lens can be insert molded directly onto the reflective polarizer as generally described in U.S. Pat. Nos. 11,693,168 (Ambur et al.) and 11,630,291 (Etter et al.), for example. Other fdms can be included in the lens assembly as generally described in U.S. Pat. Appl. Pub. No. 2024 / 0004117 (Le et al.), for example.

[0023] The reflective polarizer can be a multilayer optical film. As is known in the art, multilayer optical films including alternating first and second polymeric layers, for example, can be used to provide desired reflection and transmission in desired wavelength ranges by suitable selection of layer thicknesses and refractive index differences. Multilayer optical films and methods of making multilayer optical films are described in U.S. Pat. Nos. 5,882,774 (Jonza et al.); 6,783,349 (Neavin et al.); 6,949,212 (Merrill et al.); 6,967,778 (Wheatley et al.); 9,162,406 (Neavin et al.); and 11,493,677 (Haag et al.), for example.

[0024] A lens assembly can include an optical lens and an optical film assembly disposed on a major surface of the optical lens where the optical film assembly includes a reflective polarizer and optionally one or more optical films. According to some embodiments of the present description, a curved integral optical film assembly includes a polymeric reflective polarizer bonded to a polymeric first optical film (e.g., an absorbing polarizer or a retarder) by a first optical adhesive layer 70 where the adhesive layer has a thickness variation as described further elsewhere herein. It has been found that forming an integral optical film assembly including a polymeric reflective polarizer, an adhesive layer and a polymeric first optical film, thermoforming the integral optical film assembly into a curved shape, and then molding an optical lens directly onto an outermost first major surface of the curved integral optical film assembly, can result in an adhesive layer having a thickness variation described further elsewhere herein and can result in a reflective polarizer having low waviness or orange peel. Waviness and orange peel are terms describing variation in height of a surface that result in distorted wavefronts upon reflection or transmission. Waviness can be described as a surface roughness generally on a length scale (e.g., average distance between peaks) that is typically greater than about 0.1 mm and often less than 10 mm, but a precise definition of length scale may be dependent on the specific application. The terms waviness and orange peel may be used interchangeably herein. Previously it was believed that a uniform thickness of the adhesive layer would have been desired, but it has now been found, according to some embodiments, that that the reduced waviness or orange peel results in optical improvements (e.g., reduced scattering from surface roughness) that more than compensate for any optical defects that may result from the adhesive thickness variation. In some embodiments, the adhesive thickness variation results primarily from the molding step where the adhesive can be thinner near a gate where resin flows into the mold than near a center of the mold. The pattern of adhesive thickness may be affected, for example, by changing the gate geometry (e.g., a wider gate or changing gate type to modify pressure, shear rate and fdl pattern) and / or changing the gate position (e.g., positioning the gate near a thin edge of the part may have a different effect than placement near a thick edge). For example, it has been found that using a gate near an edge of a lens with a gate width several times larger than an edge thickness of the lens can result in an adhesive thickness that is thinner near the gate than at a center location and thicker at a location between the center location and the gate. Other variables that can affect the thickness distribution (e.g., via affecting the distribution of pressure and / or shear during molding) include, for example, the flow rate of the resin (e.g., a higher flow rate can result in higher temperatures and shear rates) and / or the resin temperature (e.g., a higher temperature can reduce resin viscosity and decrease injection pressure to fill the part).

[0025] FIGS. 1-4 are schematic cross-sectional views of optical systems 400, 400', 400", 400"' including respective integral lens assemblies 300, 300', 300", 300'", according to some embodiments. In some embodiments, the integral lens assembly 300, 300', 300", 300'" is for use in an optical system 400, 400', 400", 400'" configured to display a magnified virtual image 12 of an image 11 formed by a display 10 to a viewer 13. The integral lens assembly 300, 300', 300", 300'" incudes a curved integral optical film assembly 40, 40', 40", 40'" including a polymeric reflective polarizer 50 bonded to a polymeric first optical film 60 or 120 by a first optical adhesive layer 70. The polymeric first optical film can be or include a polymeric absorbing polarizer (e.g., 60 in FIGS. 1-2) or a retarder layer (e.g., 120 in FIGS. 3-4), for example. The curved integral optical film assembly 40, 40', 40", 40'" has opposing outermost first and second major surfaces 41 and 42. Each of the outermost first and second major surfaces 41 and 42 can have a radius of curvature of less than about 500, 400, 300, 200, 150, or 100 mm along each of two mutually orthogonal directions (e.g., x- and y-axes referring to the illustrated x-y-z coordinate system). For each of the outermost first and second major surfaces 41 and 42, the radius of curvature can be at least about 20, 25, or 30 mm along each of the two mutually orthogonal directions. The integral lens assembly 300, 300', 300", 300'" includes a molded first optical lens 30 molded directly onto, and substantially conforming to, the outermost first major surface 41 (e.g., conforming, or nominally conforming, or conforming up to deviations small (e.g., less than 10%) compared to a maximum sag of the first major surface 41) of the curved integral optical film assembly 40, 40', 40", 40'". The curved integral optical film assembly 40, 40', 40", 40'" can be formed (e.g., thermoformed) into a curved shape prior to the first optical lens 30 being molded onto the curved integral optical film assembly. The integral film assembly can be provided as a laminate of the polymeric reflective polarizer 50 and the polymeric first optical film 60 or 120 prior to the film assembly being formed into the curved shape. The film assembly can be formed into a desired curved shape using the thermoforming methods of U.S. Pat. No. 11,543,572 (Jennings et al.), for example.

[0026] The lens 30 can be disposed between the viewer 13 and the optical fdm assembly 40, 40"' (see, e.g., FIGS. 1 and 4) or the optical fdm assembly 40', 40" can be disposed between the viewer 13 and the lens 30 (see, e.g., FIGS. 2 and 3). In some embodiments, the lens 30 has opposing major surfaces 31 and 32 where at least one of the major surfaces 31 and 32 is curved. In some embodiments, the optical fdm assembly is disposed on, and substantially conforms to, a curved major surface 31 of the lens 30.

[0027] In some embodiments, the first optical fdm is a polymeric absorbing polarizer 60. The absorbing polarizer 60 is typically disposed between the viewer 13 and the reflective polarizer 50. The absorbing polarizer 60 can be included as a clean-up polarizer to absorb block state light that might have leaked through the reflective polarizer and / or can be included to reduce reflections from the viewer side of the reflective polarizer. In some embodiments, the absorbing polarizer 60 comprises the outermost first major surface 41 of the curved integral optical fdm assembly 40 (see, e.g. FIG. 1).

[0028] In some embodiments, the first optical fdm is a retarder 120. In some embodiments, the retarder 120 comprises the outermost first major surface 41 of the curved integral optical fdm assembly 40" (see, e.g. FIG. 3). In some embodiments, the reflective polarizer 50 comprises the outermost first major surface

[0029] 41 of the curved integral optical fdm assembly 40', 40'" (see, e.g., FIGS. 2 and 4).

[0030] In some embodiments, the reflective polarizer 50 comprises the outermost second major surface

[0031] 42 of the curved integral optical fdm assembly 40, 40". It has been found that the configurations (see, e.g., FIGS. 1 and 3) where the reflective polarizer 50 comprises the outermost second major surface 42 of the curved integral optical fdm assembly 40, 40", and / or where the first optical fdm 60, 120 comprises the outermost first major surface 41 of the curved integral optical fdm assembly 40, 40", results in lower waviness or orange peel (e.g., as indicated by higher MTF for these configurations) compared to the configurations (see, e.g., FIGS. 2 and 4) where the reflective polarizer 50 comprises the outermost first major surface 41, and so may be preferred, according to some embodiments.

[0032] In some embodiments, the optical system 400, 400', 400", 400'" includes the integral lens assembly 300, 300', 300", 300'" and the display 10, where the polymeric reflective polarizer 50 is configured to transmit an image light ray 111 emitted by the display 10 after first reflecting the image light ray 111. In some embodiments, the optical system 400, 400', 400", 400'" is a virtual reality system. In some embodiments, the optical system 400, 400', 400", 400'" is an augmented reality system configured to permit the viewer 13 to see a real-world object 14 in a real-world scene through the augmented reality system. In some embodiments, the optical system 400, 400', 400", 400'" further includes a partial reflector 110 having an average optical reflectance for substantially normally incident (e.g., within about 20, 15, 10, or 5 degrees of normally incident) light 84 in a predetermined wavelength range of about 25% to about 75%, or about 30% to about 70%, or about 35% to about 65%, or about 40% to about 60%, or about 45% to about 55%. The predetermined wavelength range may be from about 400 nm to about 700 nm or about 420 nm to about 680 nm, for example. The partial reflector may be a half- silvered mirror, for example, or may be a multilayer reflector, for example, with a total number of layers and refractive index differences between layers selected to result in a desired reflectance and transmittance in the predetermined wavelength range. The substantially normally incident light 84 can be unpolarized light.

[0033] In some embodiments, the optical system 400, 400' further includes a retarder layer 120 disposed between the partial reflector 110 and the polymeric reflective polarizer 50 (see, e.g., FIGS. 1 and 2). In some embodiments, the first optical film of the curved integral optical film assembly 40", 40"' of the optical system 400", 400'" is a retarder layer 120 (see, e.g., FIGS. 3 and 4). In some embodiments, for at least one wavelength in the predetermined wavelength range, the retarder layer 120 has retardance of about ! of the wavelength. Suitable retarders include, for example, oriented polymeric materials, such as polycarbonate, polyethylene terephthalate or polyvinyl alcohol, and coated liquid crystal materials. Suitable liquid crystal materials include, for example, linear photopolymerizable polymer (LPP) materials and the liquid crystal polymer (LCP) materials described in US Pat. App. Pub. Nos. US 2002 / 0180916 (Schadt et al.); US 2003 / 028048 (Cherkaoui et al.); and US 2005 / 0072959 (Moia et al.), for example. Suitable UPP materials include ROP-131 EXP 306 EPP and suitable LCP materials include ROF-5185 EXP 410 LCP, both available from Rolic Technologies, Allschwil, Switzerland.

[0034] The partial reflector 110 and / or the retarder layer 120 may be disposed on optical lens(es). FIG. 5 is a schematic cross-section view of optical lenses 100 and a partial reflector 110, according to some embodiments. In some embodiments, an optical system 400, 400', 400", 400'" includes a display 10 configured to form an image 11, where the optical system is configured to display a magnified virtual image 12 of the image 11 formed by the display to a viewer 13; the integral lens assembly 300, 300', 300", 300'"; one or more second optical lenses 100 disposed between the integral lens assembly 300, 300', 300", 300'" and the display 10; and a partial reflector 110 disposed on, and substantially conforming to, a major surface 101 of the one or more second optical lenses 100, such that for a substantially normally incident light 84, for at least one wavelength in wavelength range extending from about 400 nm to about 700 nm, and for each of mutually orthogonal polarization states (e.g., light polarized along x-axis and light polarized along y-axis), the partial reflector reflects at least 25% of the incident light 84 and transmits at least 25% of the incident light 84. In some embodiments, the partial reflector reflects at least 30%, or 35%, or 40%, or 45% of the incident light 84. In some embodiments, the partial reflector transmits at least 30%, or 35%, or 40%, or 45% of the incident light. In some embodiments, the optical system 400, 400', 400", 400'" includes a retarder layer 120 disposed between the partial reflector 110 and the polymeric reflective polarizer 50.

[0035] The first optical adhesive layer 70 can have a thickness variation (e.g., thicker at a center of the adhesive layer than a peripheral edge of the layer) which may result primarily from the flow pattern of resin through a mold during molding of the first optical lens 30 onto the optical film assembly 40, 40', 40", 40'". The flow pattern of resin can be adjusted by suitable selection of gate geometry, gate position, resin flow rate, and resin temperature, for example, as described further elsewhere herein. FIGS. 6-7 are plots of thicknesses of adhesive layers of integral optical assemblies, according to some embodiments. The adhesive thicknesses shown in these plots were measured by cutting the integral optical assembly through a center of the lens (e.g., in a plane parallel to the xy-plane) and the thickness of the adhesive was measured in the cross-section at positions from a side (side near location of 0 mm) of the lens opposite the gate used in the molding of the lens to the side adjacent the gate. As can be seen in FIGS. 6-7, the adhesive layer used in the sample of FIG. 6 was thicker than the adhesive layer used in the sample of FIG. 7. The molding for these samples used polymethylmethacrylate (PMMA) resin with a resin temperature of about 485 deg. F and a mold temperature of about 200 deg. F. The resin flow rate varied from about 0.394 to 0.710 in3 / second during the fdling stage where the flow rate was reduced around the time that the resin met the gate so that most of the flow through the mold cavity was at about 0.394 in3 / second. The fan gate used in making these samples was disposed adjacent an edge of the mold cavity and had a thickness of approximately 0.88 times the part edge thickness and a gate width of approximately 4.44 times the part edge thickness. In some embodiments, the gate is positioned adjacent to an edge of the lens mold with a gate thickness in a range of about 0.8 to 1 times an edge thickness of the lens and with a gate width of about 4 to 5 times the edge thickness.

[0036] In some embodiments, the first optical adhesive layer 70 has a thickness tl at a first location dl closer to a first peripheral edge (e.g., 43) of the film assembly, a thickness t2 at a second location d2 between the first location dl and a center location d3 of the film assembly, and a thickness t3 at the center location, where t2 is greater than each of tl and t3. In some embodiments, the lens assembly 300, 300', 300", 300"' includes a molded first optical lens 30 molded directly onto, and substantially conforming to, the outermost first major surface 41 of the curved integral optical film assembly 40, 40', 40", 40'", where the molding causes the first optical adhesive layer to be thinner (e.g., thickness tl) at or closer to a peripheral edge 43 (e.g., at location dl) of the film assembly and thicker (e.g., thickness t2 or t3) at or closer to a central portion 44 (e.g., at location d2 or d3) of the film assembly 40, 40', 40", 40'". In some embodiments, the molding causes the first optical adhesive layer 70 to have a thickness tl at a first location dl closer to the peripheral edge 43, a thickness t2 at a second location d2 between the first location dl and a center location (e.g., d3) of the film assembly, and a thickness t3 at the center location, where t2 is greater than each of tl and t3.

[0037] In some embodiments, t2 is greater than tl by at least about 5, 10, 15, 20, 25 or 30 micrometers. In some embodiments, t2 is greater than each of tl and t3 by at least about 5, 10, 15, or 20 micrometers. In some embodiments, each of tl, t2, and t3 is in a range of about 5 micrometers to about 100 micrometers, or about 6 micrometers to about 80 micrometers, or about 7 micrometers to about 60 micrometers.

[0038] FIG. 8 is a schematic cross-sectional view of a multilayer polymeric reflective polarizer 50, according to some embodiments. In some embodiments, the polymeric reflective polarizer 50 includes a plurality of polymeric layers 51, 52, 53. In some embodiments, the polymeric reflective polarizer 50 includes a plurality of alternating first and second polymeric layers 51, 52, where each first and second polymeric layer 51, 52 has an average thickness of less than about 500, 450, 400, 350, or 300 nm. In some embodiments, the average thickness of each of the first and second polymeric layers 51, 52 is at least 5, 10, 20, 30, 40, or 50 nm. In some embodiments, the plurality of alternating first and second polymeric layers 51, 52 number at least 10, 20, 30, 40, or 50 in total. In some embodiments, the total number of first and second polymeric layers 51, 52 is no more than 3000, 2000, or 1000. In some embodiments, the plurality of alternating first and second polymeric layers 51, 52 is disposed between skin layers 53. In some embodiments, each skin layer 53 has an average thickness greater than about 500, 750, 1000, or 1500 nm. The average thickness of the skin layer 53 may be up to about 50, 40, 30, 20, or 10 micrometers, for example. In some embodiments, the first layers 51 are substantially optically isotropic, and the second layers 52 are birefringent. For example, for at least one wavelength in a wavelength range from about 400 nm to about 700 nm, a maximum birefringence of the first layers 51 can be less than about 0.03, 0.025, 0.02, 0.015, or 0.01 while the maximum birefringence of the second layers 52 can be greater than about 0.05, 0.075, 0.1, 0.125, or 0.15. In some embodiments, for a substantially normally incident light 84 and a predetermined wavelength range (e.g., about 400 nm to about 700 nm or about 420 nm to about 680 nm), the reflective polarizer 50 substantially reflects (e.g., average optical reflectance greater than about 60, 70, 80, or 90 percent) the incident light for a first polarization state (e.g., polarized along the x-axis) and substantially transmits (e.g., average optical transmittance greater than about 60, 70, 80, or 85 percent) the incident light for an orthogonal second polarization state (e.g., polarized along the y-axis).

[0039] FIG. 9 is a schematic cross-sectional view of an absorbing polarizer 60, according to some embodiments. The absorbing polarizer 60 include an inner layer 71 disposed between outer layers 72 and 73. In some embodiments, the absorbing polarizer 60 includes an iodine -stained polyvinyl alcohol layer. For example, layer 71 may be an iodine-stained polyvinyl alcohol layer (in which case, optional oriented dye molecules 74 may be omitted from the volume of the layer and oriented iodine molecules may be present at or near a major surface of the layer) while layers 72 and 73 may be protective layers. Absorbing polarizers including an iodine-stained polyvinyl alcohol layer are known in the art and include those available from Sanritz Corporation (Tokyo, Japan). An alternative to utilizing a polyvinyl alcohol layer is to use an extruded polymer layer that includes a dye (e.g., 74) dispersed therein and that is stretched to orient the polymer molecules and the dye. The polymer may be any strain hardening polymer (e.g., polyester polymers or copolymers) such as those commonly used for the birefringent layers of a multilayer optical film. The polymer is typically a thermoplastic and is typically water insoluble, in contrast to polyvinyl alcohol which is water soluble. A polymer with a water solubility so low at room temperature (e.g., about 23 deg. C) that a film cannot practically be formed from the polymer via deposition from a water-based solution of the polymer will be considered to be water insoluble. The dye can be dichroic dye such as those described in U.S. Pat. Appl. Pub. No. 2021 / 0033766 (Haag et al.), for example, and those available from Mitsui Fine Chemicals, Inc. (Tokyo, Japan), for example. In some embodiments, the absorbing polarizer 60 includes a water-insoluble thermoplastic polymer layer 71 comprising substantially uniaxially oriented (e.g., nominally uniaxially oriented or oriented more or substantially more along a same first axis than along any other axis) optically absorptive dye 74 dispersed therein. In some embodiments, the absorbing polarizer 60 includes co-extruded and costretched first and second polymeric outer layers 72 and 73 and a polymeric inner layer 71 disposed therebetween, where the inner layer 71 includes substantially uniaxially oriented optically absorptive dye 74 dispersed therein. In some embodiments, each of the first and second polymeric outer layers 72 and 73 and the polymeric inner layer 71 comprises water-insoluble thermoplastic polymer. In some embodiments, each of the first and second polymeric outer layers 72 and 73 comprise a substantially optically isotropic polyester and the polymeric inner layer comprises a birefringent polyester. In some embodiments, each of the first and second polymeric outer layers 72 and 73 comprise respective first and second polymers having respective first and second compositions, and the polymeric inner layer 71 comprises a third polymer having a third composition different from each of the first and second compositions. In some embodiments, the first and second compositions are substantially same compositions (e.g., nominally the same or the same up to minor variations that do not substantially affect the physical or optical properties of the layers).

[0040] In some embodiments, for a substantially normally incident light 84 and a predetermined wavelength range (e.g., about 420 nm to about 680 nm), the absorbing polarizer 60 substantially absorbs (e.g., average optical absorption greater than about 60, 70, 80, or 85 percent) the incident light for a first polarization state (e.g., polarized along the x-axis) and substantially transmits (e.g., average optical transmittance greater than about 60, 70, 80, or 85 percent) the incident light for an orthogonal second polarization state (e.g., polarized along the y-axis).

[0041] In some embodiments, for each of the absorbing and reflective polarizers, the first polarization state is along a block axis (e.g., x-axis). In some embodiments, the block axes of the absorbing and reflective polarizers are substantially aligned (e.g., aligned to within about 15, 10, 5, or 3 degrees). FIG. 10 is a schematic cross-sectional view of a light beam 80 incident on an integral lens assembly 300, according to some embodiments. The light beam 80 could alternatively be incident on any of integral lens assemblies 300', 300", 300"'. The light beam 80 can be substantially collimated (e.g., having a convergence or divergence angle less than about 15, 10, 5, or 3 degrees) and can be substantially centered on an optical axis 20. The integral lens assembly 300, 300', 300", 300'" may be incorporated into a folded optical system (e.g., 400, 400', 400", 400'" which may include elements such as a partial reflector and a retarder that are not shown in FIG. 10) that transmits and focuses the incident light to a focal spot 82. A modulation transfer function (MTF) may be determined as a function of spatial frequency which is commonly expressed in terms of line pairs per millimeter (Ip / mm).

[0042] FIG. 11 is a plot of modulation transfer function (MTF) of lens assemblies as a function of spatial frequency, according to some embodiments. The MTF was measured in an optical system including the lens assembly, a beam-splitter lens including a partial reflector on a curved surface of the lens, and a quarter-wave retarder on an opposite major surface of the lens. The MTF was measured using a collimated light beam having a diameter of about 5 mm using a LENSCHECK system from Optikos Corporation (Wakefield, MA). The lens assembly samples A-l and A-2 included a reflective polarizer only with no absorbing polarizer and with side 1 or side 2 of the reflective polarizer, respectively, facing the molding tool surface (i.e., facing away from the lens molded onto the reflective polarizer). The lens assembly samples B-l and B-2 included a reflective polarizer and an absorbing polarizer including an extruded polymer (e.g., a water-insoluble thermoplastic polymer) including substantially uniaxially oriented optically absorptive dye dispersed therein with the reflective polarizer (B-l) or absorbing polarizer (B-2) facing the molding tool surface, respectively. The lens assembly samples C-l and C-2 included a reflective polarizer and a conventional absorbing polarizer including iodine stained polyvinyl alcohol with the reflective polarizer (C-l) or absorbing polarizer (C-2) facing the molding tool surface, respectively. The samples B-l and C-l showed better (larger) MTF than the respective samples B-2 and C-2. The samples A-l and A-2 showed even larger MTF through much of the spatial frequency range but did not include the absorbing polarizer that is desired for some applications (e.g., to reduce eye-side reflections in a near-eye display).

[0043] In some embodiments, the integral lens assembly 300, 300', 300", 300"' is substantially centered on an optical axis 20. An item maybe described as substantially centered on an optical axis when a center or centroid of the item is displaced from the optical axis by less than about 20, 15, 10, or 5 percent of a diameter of the item, for example. In some embodiments, when a substantially collimated light beam 80 that is substantially centered on the optical axis 20 and has a beam diameter D of no less than about 1 mm and no greater than about 10 mm propagates along the optical axis 20 and is incident on the integral optical film assembly side 301 of a first folded optical system (e.g., 400, 400', 400", 400'") incorporating the integral lens assembly 300, 300', 300", 300'" and centered on the optical axis 20 such that the first folded optical system transmits and focuses the incident light to a focal spot 82, a modulation transfer function (MTF) of the integral lens assembly for the incident light beam at the focal spot is greater than about 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, or 0.9 at a spatial frequency of no less than about 3 line pairs per millimeter and no greater than about 25 line pairs per millimeter. Note that an MTF of 0.8, for example, can equivalently be expressed as an MTF of 80%. In some such embodiments, or in other embodiments, the beam diameter D is no less than about 1.5, 2, 2.5, 3, 3.5, or 4 mm. In some such embodiments, or in other embodiments, the beam diameter D is no greater than about 9.5, 9, 8.5, 8, 7.5, or 7 mm. In some such embodiments, or in other embodiments, the spatial frequency is no less than about 3.5, 4, 4.5, 5 line pairs per millimeter. In some such embodiments, or in other embodiments, the spatial frequency is no greater than about 24, 23, 22, 21, or 20 line pairs per millimeter. For example, in some embodiments, the modulation transfer function (MTF) of the integral lens assembly for the incident light beam at the focal spot is greater than about 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, 0.81, 0.82, 0.83, 0.84, or 0.85 at a spatial frequency of about 20 line pairs per millimeter. As another example, in some embodiments, the modulation transfer function (MTF) of the integral lens assembly for the incident light beam at the focal spot is greater than about 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, or 0.9 at a spatial frequency of about 10 line pairs per millimeter.

[0044] Terms such as “about” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “about” as applied to quantities expressing feature sizes, amounts, and physical properties is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “about” will be understood to mean within 10 percent of the specified value. A quantity given as about a specified value can be precisely the specified value. For example, if it is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, a quantity having a value of about 1, means that the quantity has a value between 0.9 and 1. 1, and that the value could be 1.

[0045] Terms such as “substantially” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “substantially” with reference to a property or characteristic is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description and when it would be clear to one of ordinary skill in the art what is meant by an opposite of that property or characteristic, the term “substantially” will be understood to mean that the property or characteristic is exhibited to a greater extent than the opposite of that property or characteristic is exhibited.

[0046] All references, patents, and patent applications referenced in the foregoing are hereby incorporated herein by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control.

[0047] Descriptions for elements in figures should be understood to apply equally to corresponding elements in other figures, unless indicated otherwise. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations, or variations, or combinations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

What is claimed is:

1. An integral lens assembly for use in an optical system configured to display a magnified virtual image of an image formed by a display to a viewer, the integral lens assembly comprising: a curved integral optical film assembly comprising a polymeric reflective polarizer bonded to a polymeric absorbing polarizer by a first optical adhesive layer, the curved integral optical film assembly comprising opposing outermost first and second major surfaces, each of the outermost first and second major surfaces having a radius of curvature of less than about 500 mm along each of two mutually orthogonal directions; and a molded first optical lens molded directly onto, and substantially conforming to, the outermost first major surface of the curved integral optical film assembly, wherein the first optical adhesive layer has a thickness tl at a first location closer to a first peripheral edge of the film assembly, a thickness t2 at a second location between the first location and a center location of the film assembly, and a thickness t3 at the center location, wherein t2 is greater than each oftl and t3.

2. The integral lens assembly of claim 1 being substantially centered on an optical axis, wherein when a substantially collimated light beam that is substantially centered on the optical axis and has a beam diameter of no less than about 1 mm and no greater than about 10 mm propagates along the optical axis and is incident on the integral optical film assembly side of a first folded optical system incorporating the integral lens assembly and centered on the optical axis such that the first folded optical system transmits and focuses the incident light to a focal spot, a modulation transfer function (MTF) of the integral lens assembly for the incident light beam at the focal spot is greater than about 0.4 at a spatial frequency of no less than about 3 line pairs per millimeter and no greater than about 25 line pairs per millimeter.

3. The integral lens assembly of claim 1, wherein the polymeric absorbing polarizer comprises a waterinsoluble thermoplastic polymer layer comprising substantially uniaxially oriented optically absorptive dye dispersed therein.

4. The integral lens assembly of claim 1, wherein the polymeric absorbing polarizer comprises an iodine- stained polyvinyl alcohol layer.

5. The integral lens assembly of claim 1, wherein the polymeric reflective polarizer comprises a plurality of polymeric layers.

6. The integral lens assembly of claim 1, wherein the polymeric reflective polarizer comprises a plurality of alternating first and second polymeric layers, each first and second polymeric layer having an average thickness of less than about 500 nm.

7. The integral lens assembly of claim 1, wherein the polymeric absorbing polarizer comprises the outermost first major surface of the curved integral optical film assembly.

8. The integral lens assembly of claim 1, wherein the polymeric reflective polarizer comprises the outermost first major surface of the curved integral optical film assembly.

9. An integral lens assembly for use in an optical system configured to display a magnified virtual image of an image formed by a display to a viewer, the integral lens assembly substantially centered on an optical axis and comprising: a curved integral optical film assembly comprising a polymeric reflective polarizer bonded to a polymeric absorbing polarizer by a first optical adhesive layer, the curved integral optical film assembly comprising opposing outermost first and second major surfaces, each of the outermost first and second major surfaces having a radius of curvature of less than about 500 mm along each of two mutually orthogonal directions; and a molded first optical lens molded directly onto, and substantially conforming to, the outermost first major surface of the curved integral optical film assembly, the molding causing the first optical adhesive layer to be thinner at or closer to a peripheral edge of the film assembly and thicker at or closer to a central portion of the film assembly.

10. The integral lens assembly of claim 9, wherein the molding causes the first optical adhesive layer to have a thickness tl at a first location closer to the peripheral edge, a thickness t2 at a second location between the first location and a center location of the film assembly, and a thickness t3 at the center location, wherein t2 is greater than each of tl and t3.

11. An optical system, comprising: a display configured to form an image, the optical system configured to display a magnified virtual image of the image formed by the display to a viewer; the integral lens assembly of any one of claims 1 to 10; one or more second optical lenses disposed between the integral lens assembly and the display; and a partial reflector disposed on, and substantially conforming to, a major surface of the one or more second optical lenses, such that for a substantially normally incident light, for at least one wavelength in wavelength range extending from about 400 nm to about 700 nm, and for each of mutuallyorthogonal polarization states, the partial reflector reflects at least 25% of the incident light and transmits at least 25% of the incident light.

12. The optical system of claim 11 further comprising a retarder layer disposed between the partial reflector and the polymeric reflective polarizer.

13. An integral lens assembly for use in an optical system configured to display a magnified virtual image of an image formed by a display to a viewer, the integral lens assembly substantially centered on an optical axis and comprising: a curved integral optical film assembly comprising a polymeric reflective polarizer bonded to a polymeric first optical film by a first optical adhesive layer, the curved integral optical film assembly comprising opposing outermost first and second major surfaces, each of the outermost first and second major surfaces having a radius of curvature of less than about 500 mm along each of two mutually orthogonal directions; and a molded first optical lens molded directly onto, and substantially conforming to, the outermost first major surface of the curved integral optical film assembly, the molding causing the first optical adhesive layer to have a thickness variation comprising a thickness tl at a first location closer to a first peripheral edge of the film assembly, a thickness t2 at a second location between the first location and a center location of the film assembly, and a thickness t3 at the center location, wherein t2 is greater than each oftl and t3.

14. The integral lens assembly of claim 13, wherein the first optical film comprises an absorbing polarizer.

15. The integral lens assembly of claim 13, wherein the first optical film comprises a retarder layer.

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