# US 2018/0024289 A1 · Dual light guide grating-based backlight and electronic display using same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0024289 A1 - Document ID: US20180024289A1 - Status: Published application - Kind: A1 - Application number: 15/724,209 - Filed: 2017-10-03 - Published: 2018-01-25 - Earliest claimed: 2015-04-23 - Assignees: Leia Inc. - Applicants: Leia Inc. - Inventors: David A. Fattal - Web page: https://patentgrep.com/patent/US20180024289A1 ## CPC - G02B 6/0076: {Stacked arrangements of multiple light guides of the same or different cross-sectional area} - G02B 6/0028: {Light guide, e.g. taper} - G02B 6/0031: {Reflecting element, sheet or layer} - G02B 6/0036: {2-D arrangement of prisms, protrusions, indentations or roughened surfaces} - G02B 6/0038: {Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide} - G02B 6/0016: {Grooves, prisms, gratings, scattering particles or rough surfaces} - G02B 6/002: {by shaping at least a portion of the light guide, e.g. with collimating, focussing or diverging surfaces} - G02B 6/0045: {by shaping at least a portion of the light guide} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract Dual light guide, grating-based backlighting redirects light guided in a first light guide in a first direction into a second light guide in a second direction of a grating-based backlight. A dual light guide, grating-based backlight includes the first light guide, the second light guide and a redirection coupler configured to redirect the guided light beam from the first light guide into the second light guide in the second direction. The dual light guide, grating-based backlight further includes a diffraction grating configured to diffractively couple out a portion of the redirected light beam from the second light guide as a coupled-out light beam directed away from a surface of the second light guide at a predetermined principal angular direction. ## Claims ### Claim 1 A dual light guide, grating-based backlight comprising: a first plate light guide configured to guide a light beam in a first direction and at a non-zero propagation angle; a second plate light guide configured to receive and guide a redirected light beam in a second direction; a redirection coupler configured to redirect the guided light beam of the first plate light guide into the second plate light guide as the redirected light beam in the second direction; and a diffraction grating configured to diffractively couple out a portion of the redirected light beam from the second plate light guide as a coupled-out light beam directed away from a surface of the second plate light guide at predetermined principal angular direction. ### Claim 2 (depends on 1) The dual light guide, grating-based backlight of claim 1, wherein the guided light beam is collimated in a plane perpendicular to a plane of the first plate light guide. ### Claim 3 (depends on 1) The dual light guide, grating-based backlight of claim 1, wherein the first plate light guide and the second plate light guide are substantially parallel to one another, and wherein the first direction of the guided light beam is substantially opposite to the second direction of the redirected light beam. ### Claim 4 (depends on 1) The dual light guide, grating-based backlight of claim 1, wherein the redirection coupler comprises a corner reflector at an output end of the first plate light guide and at an input end of the second plate light guide. ### Claim 5 (depends on 1) The dual light guide, grating-based backlight of claim 1, wherein the redirection coupler comprises a tilted mirror and a grating coupler, the tilted mirror being configured to reflect the guided light beam received from the first plate light guide toward the grating coupler, the grating coupler being configured to diffract the reflected light beam from the tilted mirror into the second direction as the redirected light beam to be guided in the second plate light guide. ### Claim 6 (depends on 5) The dual light guide, grating-based backlight of claim 5, wherein the redirection coupler further comprises a second mirror configured to reflect and redirect light of a secondary diffraction product from the grating coupler into the second direction to augment the redirected light beam within the second plate light guide. ### Claim 7 (depends on 5) The dual light guide, grating-based backlight of claim 5, wherein the tilted mirror is configured to reflect the guided light beam from the first plate light guide toward the grating coupler to provide a substantially normal angle of incidence of the reflected light beam at the grating coupler. ### Claim 8 (depends on 5) The dual light guide, grating-based backlight of claim 5, wherein the grating coupler comprises a reflective diffraction grating. ### Claim 9 (depends on 1) The dual light guide, grating-based backlight of claim 1, wherein the redirection coupler comprises a collimating mirror. ### Claim 10 (depends on 1) The dual light guide, grating-based backlight of claim 1, wherein the diffraction grating comprises a multibeam diffraction grating configured to couple out the portion of the redirected light beam as a plurality of coupled-out light beams, a light beam of the coupled-out light beam plurality having a different principal angular direction from other light beams of the coupled-out light beam plurality. ### Claim 11 (depends on 10) The dual light guide, grating-based backlight of claim 10, wherein the multibeam diffraction grating is a linearly chirped diffraction grating. ### Claim 12 (depends on 10) The dual light guide, grating-based backlight of claim 10, wherein the plurality of coupled-out light beams having different principal angular directions form a light field configured to provide pixels corresponding to different views of a three dimensional (3D) electronic display. ### Claim 13 (depends on 1) The dual light guide, grating-based backlight of claim 1, further comprising a light source coupled to an input end of the first plate light guide opposite an output end adjacent to the redirection coupler, the light source to provide a plurality of different colors of light to be guided as a plurality of different color light beams. ### Claim 14 (depends on 13) The dual light guide, grating-based backlight of claim 13, wherein the different color light beams are guided within the first plate light guide at different, color-specific, non-zero propagation angles. ### Claim 15 (depends on 13) The dual light guide, grating-based backlight of claim 13, wherein the redirection coupler comprises a grating coupler configured to redirect the different color light beams in the second direction, each of the different color light beams being redirected at a different, color-specific, non-zero propagation angle into the second plate light guide by the grating coupler. ### Claim 16 (depends on 1) An electronic display comprising the dual light guide, grating-based backlight of claim 1, the electronic display further comprising a light valve configured to modulate the coupled-out light beam, the diffraction grating being at the surface of the second plate light guide that is adjacent to the light valve, wherein the modulated, coupled-out light beam corresponds to a pixel of the electronic display. ### Claim 17 A three-dimensional (3D) electronic display comprising: a first light guide and a second light guide; a redirection coupler configured to couple and redirect a guided light beam from the first light guide into the second light guide; an array of multibeam diffraction gratings at a surface of the second light guide, a multibeam diffraction grating of the array being configured to diffractively couple out a portion of the redirected light beam guided within the second light guide as plurality of coupled-out light beams having different principal angular directions representing different views of the 3D electronic display; and a light valve array configured to modulate the coupled-out light beams, the modulated coupled-out light beams representing pixels corresponding to the different views. ### Claim 18 (depends on 17) The 3D electronic display of claim 17, wherein one or both of the first light guide and the second light guide comprise a plate light guide, the first and second light guides being arranged substantially co-planar to one another, and wherein the first and second light guides are configured to guide light as a collimated light beam at a non-zero propagation angle. ### Claim 19 (depends on 17) The 3D electronic display of claim 17, wherein the redirection coupler comprises a tilted mirror and a reflective grating coupler, the tilted mirror being configured to reflect the guided light beam from the first light guide toward the reflective grating coupler, the reflective grating coupler being configured to diffract the reflected guided light beam from the tilted mirror into the second light guide as a redirected guided light beam within the second light guide. ### Claim 20 (depends on 17) The 3D electronic display of claim 17, wherein the multibeam diffraction grating is a chirped diffraction grating comprising one of curved grooves and curved ridges that are spaced apart from one another. ### Claim 21 (depends on 17) The 3D electronic display of claim 17, further comprising a light source optically coupled to an input end of the first light guide opposite an output end of the first light guide adjacent to the redirection coupler, the light source comprising a plurality of optical emitters arranged along the input end of the first light guide to provide a corresponding plurality of light beams guided in substantially parallel bands by the first light guide. ### Claim 22 (depends on 21) The 3D electronic display of claim 21, wherein an optical length of the first light guide in a propagation direction of the guided light beams is greater than a distance along the first light guide at which the guided light beams of the plurality spread by about one half of a spacing between individual ones of the substantially parallel bands. ### Claim 23 (depends on 21) The 3D electronic display of claim 21, wherein the optical emitters of the plurality corresponding to each of the substantially parallel bands comprise a first optical emitter configured to emit red light, a second optical emitter configured to emit green light, and a third optical emitter configured to emit blue light, the 3D electronic display being a 3D color electronic display. ### Claim 24 (depends on 23) The 3D electronic display of claim 23, wherein the first optical emitter is a red light-emitting diode (LED), the second optical emitter is a green LED, and the third optical emitter is a blue LED. ### Claim 25 (depends on 23) The 3D electronic display of claim 23, wherein the redirection coupler comprises a grating coupler configured to couple and redirect different color guided light beams into the second light guide at corresponding different, color-specific, non-zero propagation angles, the different color-specific, the multibeam diffraction grating being configured to diffractively couple out portions of the redirected different color guided light beams at the corresponding different color-specific, propagation angles as corresponding different color-specific light fields, the different color-specific light fields being configured to provide color pixels corresponding to different views of the 3D electronic display, the color-specific light fields having substantially similar cone angles to one another and producing color-specific pixels representing substantially similar 3D electronic display views to one another in the different colors. ### Claim 26 A method of grating-based backlight operation employing dual light guides, the method comprising: guiding light in a first plate light guide at a non-zero propagation angle as a guided light beam, the guided light beam being collimated; redirecting the guided light beam using a redirection coupler into a second plate light guide as a redirected guided light beam; and diffractively coupling out a portion of the redirected guided light beam using a diffraction grating at a surface of the second plate light guide to produce a coupled-out light beam directed away from the second plate light guide at a predetermined principal angular direction. ### Claim 27 (depends on 26) The method of grating-based backlight operation of claim 26, wherein redirecting the guided light beam comprises: reflecting the guided light beam from the first plate light guide toward a grating coupler; and diffractively redirecting the reflected light beam into the second plate light guide as the redirected guided light beam using the grating coupler. ### Claim 28 (depends on 26) The method of grating-based backlight operation of claim 26, wherein the guided light beam is a plurality of different color light beams, the different color light beams being guided in the first plate light guide at corresponding different, color-specific non-zero propagation angles, and wherein redirecting the guided light beam comprises employing a grating coupler to diffractively redirect the different color light beams into the second plate light guide at the corresponding different, color-specific, non-zero propagation angles. ### Claim 29 (depends on 26) The method of grating-based backlight operation of claim 26, wherein diffractively coupling out a portion of the redirected guided light beam comprises employing a multibeam diffraction grating to produce a plurality of coupled-out light beams that are directed away from the second plate light guide in a plurality of different principal angular directions corresponding to different views of a 3D electronic display. ### Claim 30 (depends on 29) The method of grating-based backlight operation of claim 29, wherein the multibeam diffraction grating is a linearly chirped diffraction grating comprising one of curved grooves and curved ridges that are spaced apart from one another. ### Claim 31 (depends on 29) The method of grating-based backlight operation of claim 29, further comprising modulating the plurality of coupled-out light beams using a plurality of light valves, modulated light beams of the coupled-out light beam plurality forming pixels of the 3D electronic display corresponding to the different views.