# US 12,222,499 B2 · Eye glow suppression in waveguide based displays > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,222,499 B2 - Document ID: US12222499B2 - Status: Granted - Kind: B2 - Application number: 17/645,212 - Filed: 2021-12-20 - Published: 2022-06-23 - Granted: 2025-02-11 - Earliest claimed: 2020-12-21 - Assignees: DigiLens Inc. - Applicants: DigiLens Inc. - Inventors: Alastair John Grant; Richard E. Bergstrom, Jr.; Roger Allen Conley Smith; Michiel Koen Callens; Nicholas Sherwood; Nima Shams; Milan Momcilo Popovich - Web page: https://patentgrep.com/patent/US12222499B2 ## CPC - G02B 6/0043: {provided on the surface of the light guide} - G02B 27/0101: {characterised by optical features (G02B27/0172 takes precedence)} - G02B 6/0036: {2-D arrangement of prisms, protrusions, indentations or roughened surfaces} - G02B 27/0018: {with means for preventing ghost images (anti-reflection coatings G02B1/11)} - G02B 2027/0118: {comprising devices for improving the contrast of the display / brillance control visibility} - G02B 2027/0174: {holographic} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract Methods and apparatus for eye-glow suppression in waveguide systems is disclosed herein. Some embodiments of the methods and the apparatus include a source of image modulated light; a waveguide having an eye-facing surface and an external surface facing the outside world; an input coupler for coupling the light into a total reflection internal path in the waveguide; at least one grating for providing beam expansion and extracting light from the waveguide towards an eyebox; a polymer grating structure comprising a modulation depth and a grating pitch. The modulation depth is greater than the grating pitch across at least a portion of the polymer grating structure. Advantageously, the polymer grating structure is configured to diffract light entering the waveguide from the outside world or stray light generated within the waveguide away from optical paths that are refracted through the external surface into the outside world. ## Claims ### Claim 1 A waveguide display comprising: a source of image modulated light; a waveguide having an eye-facing surface and an external surface facing the outside world; an input coupler for coupling the light into a total reflection internal path in the waveguide; at least one grating for providing beam expansion and extracting light from the waveguide towards an eyebox; a surface relief reflection grating comprising a modulation depth and a grating pitch, wherein the modulation depth is greater than the grating pitch across at least a portion of the polymer grating structure, wherein the surface relief reflection grating is positioned on the external surface of the waveguide, wherein the surface relief reflection grating is configured to redirect stray light generated within the waveguide away from optical paths that are refracted through the external surface into the outside world and back out of the waveguide through the eye-facing surface, wherein the surface relief reflection grating does not disturb the propagation of image modulated light within the waveguide and the extraction of the image modulated light towards the eyebox, wherein the stray light generated within the waveguide comprises at least one selected from the group consisting of: light scattered from the grating material; zero order diffracted image modulated light; and image modulated light propagating along optical paths that are not extracted from the waveguide towards the eyebox. ### Claim 2 (depends on 1) The waveguide display of claim 1, wherein the surface relief reflection grating further comprises a backfill material between adjacent polymer regions, wherein the backfill material has a refractive index higher or lower than the refractive index of the polymer regions. ### Claim 3 (depends on 2) The waveguide display of claim 2, wherein the backfill material occupies a space at a bottom portion of the space between adjacent portions of the polymer grating structure and the air occupies the space from above the top surface of the backfill material to the modulation depth. ### Claim 4 (depends on 2) The waveguide display of claim 2, wherein the backfill comprises a birefringent material. ### Claim 5 (depends on 4) The waveguide display of claim 4, wherein the birefringent material comprises a liquid crystal material. ### Claim 6 (depends on 4) The waveguide display of claim 4, wherein the refractive index difference between the polymer regions and the birefringent material is 0.01 to 0.2. ### Claim 7 (depends on 1) The waveguide display of claim 1, wherein a modulation depth of the surface relief reflection grating is greater than a wavelength of visible light. ### Claim 8 (depends on 1) The waveguide display of claim 1, wherein the grating pitch is the spacing of diffractive features of the surface relief reflection grating and the modulation depth is the depth of the surface relief reflection grating. ### Claim 9 (depends on 1) The waveguide display of claim 1, wherein the surface relief reflection grating further comprises alternating polymer regions and air gap regions and the refractive index difference between the polymer regions and the air gap regions is in the range from 1.4 to 1.9. ### Claim 10 (depends on 1) The waveguide display of claim 1, wherein the surface relief reflection grating comprises: polymer diffracting features; and a birefringent material between adjacent polymer diffracting features, wherein the birefringent material has a higher or lower refractive index than the polymer diffracting features. ### Claim 11 (depends on 1) The waveguide display of claim 1, wherein the modulation depth of the surface relief reflection grating varies across the waveguide to provide a spatially varying polarization-dependent or angle-dependent diffraction efficiency characteristic. ### Claim 12 (depends on 1) The waveguide display of claim 1, wherein the surface relief reflection grating at least partially overlaps the input coupler and/or the at least one grating for providing beam expansion and extracting light from the waveguide. ### Claim 13 (depends on 1) The waveguide display of claim 1, the surface relief reflection grating comprises regions including a Bragg grating, a Raman-Nath grating, and no grating, wherein the regions at least partially cover the input coupler and the at least one grating for providing beam expansion and extracting light. ### Claim 14 (depends on 13) The waveguide display of claim 13, further comprising a light control layer overlapping regions of the surface relief reflection grating containing no grating. ### Claim 15 (depends on 14) The waveguide display of claim 14, wherein the light control layer provides at least one selected from the group consisting of: polarization rotation, polarization-selective absorption, polarization-selective transmission, polarization-selective diffraction, angle-selective transmission, angle selective absorption, anti-reflectivity, and transmission within a defined spectral bandwidth. ### Claim 16 (depends on 1) The waveguide display of claim 1, wherein the surface relief reflection grating includes a rolled K-vector grating with slant angles varying continuously or in piecewise steps. ### Claim 17 (depends on 1) The waveguide display of claim 1, wherein the surface relief reflection grating includes a grating with spatially varying pitch. ### Claim 18 (depends on 1) The waveguide display of claim 1, wherein the surface relief reflection grating is a composite of at least one type of polymer and at least one other material. ### Claim 19 (depends on 18) The waveguide display of claim 18, wherein the at least one other material comprises nanoparticles. ### Claim 20 (depends on 1) The waveguide display of claim 1, wherein the surface relief reflection grating is coated with an optical material with an effective index up to 2.5. ### Claim 21 (depends on 1) The waveguide display of claim 1, wherein the surface relief reflection grating is coated with a first material and the coated grating is backfilled with a second material of refractive index higher or lower than the refractive index of the first material. ### Claim 22 (depends on 1) The waveguide display of claim 1, wherein the surface relief reflection grating comprises a first grating structure positioned on the external surface of the waveguide and a second grating structure positioned on the eye-facing surface of the waveguide. ### Claim 23 (depends on 22) The waveguide display of claim 22, wherein the first grating structure and the second grating structure have different grating periods.