# US 11,115,647 B2 · Privacy display apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,115,647 B2 - Document ID: US11115647B2 - Status: Granted - Kind: B2 - Application number: 16/181,157 - Filed: 2018-11-05 - Published: 2019-07-11 - Granted: 2021-09-07 - Earliest claimed: 2017-11-06 - Assignees: RealD Spark, LLC - Applicants: RealD Spark, LLC - Inventors: Graham J. Woodgate; Jonathan Harrold; Michael G. Robinson; Robert Ramsey - Web page: https://patentgrep.com/patent/US11115647B2 ## CPC - 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)} - H04N 13/30: Image reproducers (optical systems for producing stereoscopic or other three-dimensional [3D] effects G02B30/00) - G02B 5/02: Diffusing elements; Afocal elements - G02B 6/0048: {with stepwise taper} - G02B 6/0068: {Arrangements of plural sources, e.g. multi-colour light sources} - G02F 1/13: based on liquid crystals, e.g. single liquid crystal display cells - G02F 1/1323: {Arrangements for providing a switchable viewing angle} - G02F 1/133524: {Light-guides, e.g. fibre-optic bundles, louvered or jalousie light-guides} - G02F 1/133528: {Polarisers} - G02F 1/133536: {Reflective polarizers (G02F1/13362 takes precedence)} - G02F 1/133615: {Edge-illuminating devices, i.e. illuminating from the side} - G02F 1/13363: Birefringent elements, e.g. for optical compensation - G02F 1/1337: Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers - G02F 1/133753: {with different alignment orientations or pretilt angles on a same surface, e.g. for grey scale or improved viewing angle} - G02F 1/1347: Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells - G02F 1/137: characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering - G02F 1/295: {Analog deflection from or} in an optical waveguide structure] - G02F 1/365: in an optical waveguide structure (G02F1/377, {G02F1/395} take precedence) - G02B 6/0011: {the light guides being planar or of plate-like form} - G02F 1/133562: {on the viewer side} - G02F 1/133567: {on the back side} - G02F 1/133638: {Waveplates, i.e. plates with a retardation value of lambda/n} - G02F 1/133738: {for homogeneous alignment} - G02F 1/133742: {for homeotropic alignment} - G02F 1/13478: {based on selective reflection} - G02F 1/13706: {the liquid crystal having positive dielectric anisotropy} - G02F 1/13712: {the liquid crystal having negative dielectric anisotropy} - G02F 2203/12: spatial light modulator - H04N 2013/403: {the images being monoscopic} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS ## Abstract An imaging directional backlight apparatus including a waveguide, a light source array, for providing large area directed illumination from localized light sources. The waveguide may include a stepped structure, in which the steps may further include extraction features optically hidden to guided light, propagating in a first forward direction. Returning light propagating in a second backward direction may be refracted, diffracted, or reflected by the features to provide discrete illumination beams exiting from the top surface of the waveguide. The directional backlight may be arranged to switch between at least a first wide angular luminance profile mode and a second narrow angular luminance profile mode. The directional backlight is arranged to illuminate an LCD with a bias electrode arranged to switch liquid crystal directors in black state pixels between a first wide angular contrast profile mode and a second narrow angular contrast profile mode. Performance of privacy operation for off-axis snoopers is enhanced in comparison to displays with only directional backlights or switchable contrast properties. ## Claims ### Claim 1 A privacy display device comprising: a directional backlight arranged to output light, wherein the directional backlight is arranged to provide switching between at least two different angular luminance profiles; and a transmissive spatial light modulator arranged to receive output light from the backlight, wherein the spatial light modulator is arranged to modulate the output light from the backlight to provide an image that may be switched between at least two different angular contrast profiles, wherein the spatial light modulator comprises a pixelated liquid crystal display comprising a liquid crystal pixel layer and pixel addressing electrodes arranged to provide in-plane electric fields to pixels of the pixelated liquid crystal display, and wherein the spatial light modulator further comprises a liquid crystal bias layer arranged between the input polariser and output polariser of the pixelated liquid crystal display; and bias layer electrodes arranged to provide out-of-plane bias electric fields to the liquid crystal bias layer. ### Claim 2 (depends on 1) A privacy display device according to claim 1 wherein the pixelated liquid crystal display further comprises pixel bias electrodes arranged to provide out-of-plane bias electric fields to the liquid crystal pixel layer. ### Claim 3 (depends on 1) A privacy display device according to claim 1 wherein the bias electric fields are time varying. ### Claim 4 (depends on 3) A privacy display device according to claim 3 wherein the bias layer electrodes are patterned to provide at least two pattern regions. ### Claim 5 (depends on 4) A privacy display device according to claim 4 wherein the pattern regions are camouflage patterns. ### Claim 6 (depends on 4) A privacy display device according to claim 4 wherein at least one of the pattern regions is individually addressable. ### Claim 7 (depends on 6) A privacy display device according to claim 6, wherein the first guide surface is arranged to guide light by total internal reflection, and the second guide surface comprises light extraction features and intermediate regions between the light extraction features, the light extraction features being oriented to deflect the reflected input light through the first guide surface as output light and the intermediate regions being arranged to direct light through the waveguide without extracting it. ### Claim 8 (depends on 1) A privacy display device according to claim 1, wherein the directional backlight comprises: an array of light sources; a waveguide arranged to receive input light from the light sources at different input positions and comprising first and second, opposed guide surfaces for guiding the input light along the waveguide, sides that extend between the first and second guide surfaces and a reflective end for reflecting the input light back along the waveguide, wherein the second guide surface is arranged to deflect the reflected input light through the first guide surface as output light, and the waveguide is arranged to image the light sources in a lateral direction between the sides of the waveguide so that the output light from the light sources is directed into respective optical windows in output directions that are distributed in dependence on input positions of the light sources. ### Claim 9 (depends on 8) A privacy display device according to claim 8, wherein the light extraction features are curved and have positive optical power in the lateral direction between sides of the waveguide that extend between the first and second guide surfaces. ### Claim 10 (depends on 8) A privacy display device according to claim 8, wherein the reflective end has positive optical power in the lateral direction extending between sides of the waveguide that extend between the first and second guide surfaces. ### Claim 11 (depends on 8) A privacy display device according to claim 8, wherein the waveguide comprises an input end opposite to the reflective end and the light sources are arranged to input light into the waveguide through the input end. ### Claim 12 (depends on 8) A privacy display device according to claim 8, wherein the light sources are arranged to input light into the waveguide through the sides of the waveguide. ### Claim 13 (depends on 1) A privacy display device according to claim 1 wherein the angular luminance profiles from the directional backlight may be controlled in the lateral direction; and wherein the out of plane bias electric fields are arranged to tilt the respective liquid crystal layer about an axis parallel to the lateral direction. ### Claim 14 (depends on 1) A privacy display device according to claim 1, further comprising at least one additional polariser arranged on the input side of the input polariser between the input polariser and the backlight or on the output side of the output polariser; and at least one retarder arranged between the at least one additional polariser and the input polariser in the case that the additional polariser is arranged on the input side of the input polariser or between the additional polariser and the output polariser in the case that the additional polariser is arranged on the output side of the input polariser. ### Claim 15 (depends on 14) A privacy display device according to claim 14, wherein the additional polariser is arranged on the input side of the input polariser and said at least one retarder is arranged between the additional polariser and the input polariser. ### Claim 16 (depends on 15) A privacy display device according to claim 15, wherein the additional polariser is a reflective polariser. ### Claim 17 (depends on 14) A privacy display device according to claim 14, wherein the additional polariser has an electric vector transmission direction that is parallel to the electric vector transmission of the input polariser in the case that the additional polariser is arranged on the input side of the input polariser or is parallel to the electric vector transmission of the output polariser in the case that the additional polariser is arranged on the output side of the input polariser. ### Claim 18 (depends on 14) A privacy display device according to claim 14, wherein the additional polariser is arranged on the output side of the output polariser and said at least one retarder is arranged between the additional polariser and the output polariser. ### Claim 19 (depends on 14) A privacy display device according to claim 14, wherein the at least one retarder comprises a retarder having a slow axis perpendicular to the plane of the retarder. ### Claim 20 (depends on 19) A privacy display device according to claim 19, wherein the retarder having a slow axis perpendicular to the plane of the retarder comprises a C-plate. ### Claim 21 (depends on 14) A privacy display device according to claim 14, wherein the at least one retarder comprises a retarder having a slow axis orientation with a component perpendicular to the plane of the retarder, and at least one component in the plane of the retarder. ### Claim 22 (depends on 14) A privacy display device according to claim 14, wherein the at least one retarder comprises a retarder having a slow axis orientation with a component perpendicular to the plane of the retarder, a component that is orthogonal in the plane of the retarder to the electric vector transmission direction of the input polariser and substantially no component that is parallel in the plane of the retarder to the electric vector transmission direction of the input polariser. ### Claim 23 (depends on 14) A privacy display device according to claim 14, wherein the at least one retarder comprises a retarder having a slow axis orientation with a component perpendicular to the plane of the retarder, a component that is parallel in the plane of the retarder to the electric vector transmission direction of the input polariser and substantially no component that is orthogonal in the plane of the retarder to the electric vector transmission direction of the input polariser. ### Claim 24 (depends on 14) A privacy display device according to claim 14, wherein the retarder comprises an O-plate. ### Claim 25 (depends on 14) A privacy display device according to claim 14, wherein the retarder comprises a switchable liquid crystal retarder that is switchable between an O-plate retarder and an A-plate retarder by means of an applied voltage across the switchable liquid crystal retarder. ### Claim 26 (depends on 25) A privacy display device according to claim 25, wherein the switchable liquid crystal retarder comprises at least one homeotropic alignment layer. ### Claim 27 (depends on 26) A privacy display device according to claim 26 further comprising at least one compensation retarder arranged between the at least one additional polariser and the input polariser in the case that the additional polariser is arranged on the input side of the input polariser or between the additional polariser and the output polariser in the case that the additional polariser is arranged on the output side of the input polariser. ### Claim 28 (depends on 27) A privacy display device according to claim 27 wherein the compensating retarder comprises a negative C-plate or crossed positive A-plates. ### Claim 29 (depends on 14) A privacy display device according to claim 14, wherein the at least one retarder comprises a first O-plate retarder and a second O-plate retarder that is switchable. ### Claim 30 (depends on 1) A privacy display device according to claim 1, wherein the at least one retarder comprises a pair of retarders which have slow axes in the plane of the retarders that are crossed. ### Claim 31 (depends on 30) A privacy display device according to claim 30, wherein the pair of retarders have slow axes that each extend at 45° with respect to an electric vector transmission direction that is parallel to the electric vector transmission of the input polariser in the case that the additional polariser is arranged on the input side of the input polariser or is parallel to the electric vector transmission of the output polariser in the case that the additional polariser is arranged on the output side of the input polariser. ### Claim 32 (depends on 30) A privacy display device according to claim 30, wherein the pair of retarders each comprise a single A-plate. ### Claim 33 (depends on 30) A privacy display device according to claim 30, wherein the pair of retarders each comprise plural A-plates having respective slow axes aligned at different angles from each other. ### Claim 34 (depends on 33) A privacy display device according to claim 33, wherein the at least one retarder further comprises a pair of retarders which have slow axes in the plane of the retarders that are crossed. ### Claim 35 (depends on 30) A privacy display device according to claim 30, wherein the pair of retarders have slow axes that each extend at 0° and 90°, respectively, with respect to an electric vector transmission direction that is parallel to the electric vector transmission of the input polariser in the case that the additional polariser is arranged on the input side of the input polariser or is parallel to the electric vector transmission of the output polariser in the case that the additional polariser is arranged on the output side of the input polariser. ### Claim 36 (depends on 1) A privacy display device according to claim 1, wherein the switchable liquid crystal retarder comprises at least first and second regions that are independently addressable with first and second applied voltages. ### Claim 37 (depends on 4) A privacy display system comprising the privacy display device according to claim 4 and a control system arranged to switch the directional backlight between a first mode arranged to switch the directional backlight to a first angular luminance profile and to switch the spatial light modulator to a first angular contrast profile; and a second mode arranged to switch the directional backlight to a second angular luminance profile and to switch the spatial light modulator to a second angular contrast profile, wherein the first angular luminance profile and the first angular contrast profile have half maximum widths that are larger than the half maximum widths of the second angular luminance profile and the second angular contrast profile. ### Claim 38 (depends on 37) A privacy display system according to claim 37 wherein the switching between the at least first and second angular luminance profiles is provided by control of luminous flux distributions across the array of input light sources. ### Claim 39 (depends on 37) A privacy display system according to claim 37 wherein the switching between the at least first and second angular contrast profiles is provided by control of the bias electric field. ### Claim 40 (depends on 38) A privacy display system according to claim 38 wherein in the second mode for a nominal viewing angle there is provided an invisibility function of image contrast against image luminance on which an operating point is selected by control of (i) angular luminance profile and (ii) angular contrast profile. ### Claim 41 (depends on 40) A privacy display system according to claim 40 further comprising an ambient light control system arranged to control the operating point of the invisibility function in response to the ambient illuminance.