# US 2019/0377183 A1 · Reverse-order crossed pancake lens with a shaped polarizer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0377183 A1 - Document ID: US20190377183A1 - Status: Published application - Kind: A1 - Application number: 16/159,752 - Filed: 2018-10-15 - Published: 2019-12-12 - Earliest claimed: 2018-06-07 - Assignees: Facebook Technologies, LLC - Applicants: Facebook Technologies, LLC - Inventors: Gary Dean Sharp - Web page: https://patentgrep.com/patent/US20190377183A1 ## CPC - G02B 27/0018: {with means for preventing ghost images (anti-reflection coatings G02B1/11)} - G02B 5/3016: {involving passive liquid crystal elements (optical properties of liquid crystals G02F1/0063; polarising elements associated with active liquid crystal devices G02F1/133528)} - G02B 5/3058: {comprising electrically conductive elements, e.g. wire grids, conductive particles} - G02B 5/3066: {involving the reflection of light at a particular angle of incidence, e.g. Brewster's angle} - G02B 5/3083: {Birefringent or phase retarding elements (G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001)} - G02B 27/0025: {for optical correction, e.g. distorsion, aberration} - G02B 27/0037: {with diffracting elements (G02B27/0056 takes precedence; holographic optical elements G02B5/32; zone systems G02B5/1876)} - G02B 27/0093: {with means for monitoring data relating to the user, e.g. head-tracking, eye-tracking} - G02B 27/0172: {characterised by optical features} - G02B 27/0983: {being curved} - G02B 27/283: {used for beam splitting or combining} - G02B 27/286: {for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another (G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34)} - G02B 2027/012: {comprising devices for attenuating parasitic image effects} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract In various embodiments, a pancake lens block including a shaped reflective polarizer is described. In an embodiment, the shaped reflective polarizer may include an optical element that may be configured to transmit at least a portion of light from a light source. Further, the shaped reflective polarizer may include a wire-grid polarizer that comprises (i) a bolstering substrate, (ii) a wire-grid substrate coupled to the bolstering substrate, and (iii) wire-grids disposed on the wire-grid substrate. The shaped reflective polarizer may be spaced from the optical element by a distance, which may include a cavity filled with a material (such as air or a nanovoided material). ## Claims ### Claim 1 A pancake lens block, comprising: an optical element configured to transmit at least a portion of radiation from a radiation source; and a shaped reflective polarizer spaced at a distance from the optical element; wherein the shaped reflective polarizer is configured to provide achromatic optical power to the pancake lens block. ### Claim 2 (depends on 1) The pancake lens block of claim 1, wherein the optical element comprises: a first retarder having a first axis of orientation, where the first retarder is configured to selectively transmit a portion of the radiation from the radiation source; a partial reflector that receives the portion of radiation from the first retarder and transmits the portion of radiation; and a second retarder having a surface at a distance from the shaped reflective polarizer, where the second retarder is oriented to a second axis of orientation that is substantially orthogonal to the first axis of orientation, and where the second retarder transmits the portion of radiation from the partial reflector. ### Claim 3 (depends on 2) The pancake lens block of claim 2, wherein the shaped reflective polarizer is configured to reflect the portion of radiation transmitted by the second retarder back to the partial reflector through the second retarder, where the partial reflector reflects a second portion of the radiation from the second retarder back to the shaped reflective polarizer. ### Claim 4 (depends on 2) The pancake lens block of claim 2, wherein the shaped reflective polarizer comprises a wire-grid polarizer that comprises: (i) a bolstering substrate, (ii) a wire-grid substrate coupled to the bolstering substrate, and (iii) wire-grids disposed on the wire-grid substrate. ### Claim 5 (depends on 4) The pancake lens block of claim 4, wherein the bolstering substrate provides mechanical support to the wire-grid polarizer and maintains the polarization state of the portion of radiation transmitted by the second retarder. ### Claim 6 (depends on 4) The pancake lens block of claim 4, wherein the bolstering substrate comprises a tri-acetyl cellulose (TAC) material or a poly-methyl methacrylate (PMMA) material. ### Claim 7 (depends on 4) The pancake lens block of claim 4, wherein the wire-grid polarizer is disposed on a lens having a radius of curvature, and the thickness of the bolstering substrate is at least partially based on the radius of curvature. ### Claim 8 (depends on 4) The pancake lens block of claim 4, wherein the wire-grid polarizer is thermoformed and the bolstering substrate has a glass transition temperature characterized by an associated rate of change with temperature being below a threshold. ### Claim 9 (depends on 4) The pancake lens block of claim 4, wherein the wire-grid substrate comprises a TAC material or a PMMA material. ### Claim 10 (depends on 4) The pancake lens block of claim 4, wherein the wire-grids comprise a TAC material. ### Claim 11 (depends on 1) The pancake lens block of claim 1, wherein the shaped reflective polarizer has a surface that is convex, concave, flat, or irregular. ### Claim 12 (depends on 1) The pancake lens block of claim 1, wherein: the distance is configured to provide additional optical path length in the pancake lens block; and the distance is provided by at least one of an air gap or a material. ### Claim 13 A head mounted display (HMD) comprising: an electronic display configured to emit light; and a pancake lens block comprising: an optical element configured to transmit at least a portion of the light emitted by the electronic display; and a shaped reflective polarizer spaced at a distance from the optical element; wherein the shaped reflective polarizer is configured to provide achromatic optical power to the pancake lens block. ### Claim 14 (depends on 13) The HMD of claim 13, wherein the optical element comprises: a first retarder having a first axis of orientation, where the first retarder is configured to selectively transmit a portion of the light emitted by the electronic display; a partial reflector that receives the portion of light from the first retarder and transmits the portion of light; and a second retarder having a surface at a distance from the shaped reflective polarizer, and where the second retarder is oriented to a second axis of orientation that is substantially orthogonal to the first axis of orientation, and where the second retarder transmits the portion of light from the partial reflector. ### Claim 15 (depends on 14) The HMD of claim 14, wherein the shaped reflective polarizer is configured to reflect the portion of light transmitted by the second retarder back to the partial reflector through the second retarder, where the partial reflector reflects a second portion of the light from the second retarder back to the shaped reflective polarizer. ### Claim 16 (depends on 13) The HMD of claim 13, wherein the shaped reflective polarizer comprises a wire-grid polarizer that comprises (i) a bolstering substrate, (ii) a wire-grid substrate coupled to the bolstering substrate, and (iii) wire-grids disposed on the wire-grid substrate. ### Claim 17 (depends on 16) The HMD of claim 16, wherein the bolstering substrate comprises a tri-acetyl cellulose (TAC) material or a poly-methyl methacrylate (PMMA) material. ### Claim 18 (depends on 16) The HMD of claim 16, wherein the wire-grid polarizer is disposed on a lens having a radius of curvature, and the thickness of the bolstering substrate is at least partially based on the radius of curvature. ### Claim 19 A method of assembling a pancake lens block, the method comprising: configurating an optical element to transmit at least a portion of radiation from a radiation source; and spacing a shaped reflective polarizer from the optical element by a distance; wherein the shaped reflective polarizer is configured to provide achromatic optical power to the pancake lens block. ### Claim 20 (depends on 19) The method of claim 19, wherein the shaped reflective polarizer comprises a wire-grid polarizer that comprises (i) a bolstering substrate, (ii) a wire-grid substrate coupled to the bolstering substrate, and (iii) wire-grids disposed on the wire-grid substrate.