# US 11,307,343 B2 · Backlight unit and holographic display apparatus including the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,307,343 B2 - Document ID: US11307343B2 - Status: Granted - Kind: B2 - Application number: 16/675,387 - Filed: 2019-11-06 - Published: 2020-11-19 - Granted: 2022-04-19 - Earliest claimed: 2019-05-17 - Assignees: Samsung Electronics Co., Ltd. - Applicants: Samsung Electronics Co., Ltd. - Inventors: Chilsung Choi; Hoon Song; Jungkwuen An; Hongseok Lee - Web page: https://patentgrep.com/patent/US11307343B2 ## CPC - G02B 6/0026: {Wavelength selective element, sheet or layer, e.g. filter or grating} - G02B 6/0016: {Grooves, prisms, gratings, scattering particles or rough surfaces} - G02B 6/0035: {provided on the surface of the light guide or in the bulk of it} - G02B 6/005: {provided by one optical element, or plurality thereof, placed on the light output side of the light guide} - G02B 6/0066: {characterised by the light source being coupled to the light guide} - G02B 6/0068: {Arrangements of plural sources, e.g. multi-colour light sources} - G02B 6/0076: {Stacked arrangements of multiple light guides of the same or different cross-sectional area} - G02B 30/25: using polarisation techniques - G03H 1/0866: {Digital holographic imaging, i.e. synthesizing holobjects from holograms} - G03H 1/2286: {Particular reconstruction light (G03H1/24 takes precedence); Beam properties} - G03H 1/2294: {Addressing the hologram to an active spatial light modulator} - G03H 2001/2226: {Edge lit holograms} - G03H 2222/34: Multiple light sources - G03H 2223/16: Optical waveguide, e.g. optical fibre, rod - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G03H: HOLOGRAPHIC PROCESSES OR APPARATUS (holograms, e.g. point holograms, used as ordinary optical elements G02B5/32; producing stereoscopic or other three-dimensional effects G02B30/00; diffraction-grating systems G02B27/44; systems using moiré fringes G02B27/60; optical logic elements G02F3/00; stereo-photography G03B35/00; photosensitive materials or processes for photographic purposes G03C; {stereo-photographic or similar processes G03C9/00}; apparatus for processing exposed photographic materials G03D; analogue computers performing mathematical operations with the aid of optical elements G06E3/00; authentication by radiation, of concealed information carried by holograms or diffraction gratings G06K19/16; holographic storage G11B7/0065, G11C13/04; {stereoscopic or other three dimensional effects in television systems H04N13/00}) ## Abstract A backlight unit may include: a light source providing coherent light; a light guide plate having a light entrance surface on which light from the light source is incident and a light exit surface through which the light is output; a plurality of diffraction gratings (for example, a first input grating, a second input grating, and a third input grating) that are arranged in different regions of the light guide plate to sequentially diffract the light from the light source such that that the beam width of the light may increase as the light propagates in the light guide plate; and a diffraction grating (for example, an output grating) that diffracts and outputs the light having an increased beam width in a direction toward the outside of the light guide plate. ## Claims ### Claim 1 A backlight unit comprising: a light source configured to provide coherent light; a light guide plate comprising a light entrance surface on which the light is incident from the light source and a light exit surface through which the light is output; a first input grating provided on the light guide plate and configured to diffract the light from the light source in a first direction, such that the light diffracted by the first input grating propagates in the first direction while being totally reflected in the light guide plate; a second input grating provided on the light guide plate and configured to diffract the light that is diffracted by the first input grating in a second direction orthogonal to the first direction, such that the light diffracted by the second input grating propagates in the second direction different from the first direction while being totally reflected in the light guide plate, wherein beam width of the light propagating in the second direction increases as the light propagates in the light guide in the second direction; a third input grating provided on the light guide plate and configured to diffract the light diffracted by the second input grating in a third direction orthogonal to the second direction, and parallel to the first direction, such that the light diffracted by the third input grating propagates in the third direction different from the second direction, wherein beam width of the light propagating in the third direction increases as the light propagates in the light guide in the third direction; and an output grating provided on the light guide plate and configured to diffract the light diffracted by the third input grating in a fourth direction orthogonal to the first direction, the second direction and the third direction, such that the light is output in a fourth direction toward an outside of the light guide plate. ### Claim 2 (depends on 1) The backlight unit of claim 1, wherein the first input grating, the second input grating, the third input grating, and the output grating are provided on the light exit surface of the light guide plate. ### Claim 3 (depends on 1) The backlight unit of claim 1, wherein an area of the second input grating is larger than an area of the first input grating. ### Claim 4 (depends on 1) The backlight unit of claim 1, wherein the second input grating is configured to collimate the light diffracted by the first input grating. ### Claim 5 (depends on 1) The backlight unit of claim 1, wherein a length of the third input grating in the second direction is larger than a length of the second input grating in the second direction. ### Claim 6 (depends on 1) The backlight unit of claim 1, wherein a length of the output grating in the third direction is larger than a length of the third input grating in the third direction. ### Claim 7 (depends on 1) The backlight unit of claim 1, wherein the third direction is opposite of the first direction.