Optical waveguide for augmented reality display

Patent metadata

Field	Value
Publication number	US-12360305-B2
Application number	US-202118246147-A
Country	US
Kind code	B2
Filing date	Sep 20, 2021
Priority date	Sep 23, 2020
Publication date	Jul 15, 2025
Grant date	Jul 15, 2025

Abstract

This document discloses a solution for an optical waveguide for an augmented reality display device. According to an aspect, the optical waveguide comprises: a substrate arranged to guide an optical image inside the substrate from an inlet to an outlet of the optical waveguide via a plurality of reflections; a surface relief grating at the inlet or the outlet of the optical waveguide, the surface relief grating guiding the image in the optical waveguide via diffraction and comprising a plurality of grooves; a coating disposed on the surface relief grating and filling at least partially at least one groove disposed at an edge of the surface relief grating where the image is coincident with the at least one groove after a first reflection of the image inside the substrate, the coating having optical characteristics convergent with optical characteristics of the substrate.

First claim

The invention claimed is:

1. An optical waveguide for an augmented reality display device, comprising:
a substrate arranged to guide an optical image inside the substrate from an inlet to an outlet of the optical waveguide via a plurality of reflections;
a surface relief grating at the inlet or the outlet of the optical waveguide, the surface relief grating guiding the image in the optical waveguide via diffraction and comprising a plurality of grooves; and
a coating disposed directly on the surface relief grating and filling at least partially at least an edge-most groove of the surface relief grating where a first order diffraction of the image is coincident with the at least edge-most groove, the coating having a refractive index convergent with a refractive index of the substrate, wherein the coating fills a plurality of grooves of the surface relief grating unevenly such that the coating completely fills at least a first groove of the surface relief grating and partially fills at least a second groove of the surface relief grating, wherein the first groove is closer to the edge of the surface relief grating than the second groove, and wherein the second groove is wider than the first groove, wherein the coating together with groove widths of the surface relief grating cause the grooves of the surface relief grating to provide a gradually narrowing optical groove widths towards the edge of the surface relief grating.

2. The optical waveguide of claim 1 , wherein the coating has at least one layer having the refractive index substantially equal to the refractive index of the substrate.

3. The optical waveguide of claim 2 , wherein the coating comprises first coating material having a first refractive index and second coating material having a second refractive index different from the first refractive index where neither the first refractive index nor the second refractive index is substantially equal to the refractive index of the substrate but that the first coating material together with the second coating material provide the refractive index substantially equal to the refractive index of the substrate.

4. The optical waveguide of claim 1 , wherein the coating completely fills said at least the edge-most groove.

5. The optical waveguide of claim 1 , comprising surface relief gratings at the inlet and the outlet of the optical waveguide, both surface relief gratings guiding the image in the optical waveguide via diffraction and comprising a plurality of grooves, wherein the coating is disposed on at least the edge-most grooves of said both surface relief gratings and filling at least partially the edge-most grooves of the surface relief gratings where the first order diffraction of the image is coincident with the edge-most grooves.

6. The optical waveguide of claim 1 , wherein the coating ( 106 ) disposed directly on the surface relief grating at the inlet and filling at least partially the at least one groove disposed at an edge-most groove of the inlet surface relief grating where a first order diffraction of the image is coincident with the at least one groove, the edge being towards the outlet.

7. The optical waveguide of claim 1 , wherein said outlet is a first outlet and the optical waveguide further comprises a second outlet at an opposite direction from the inlet than the first outlet, the second outlet also provided with a surface relief grating, wherein the coating fills at least partially at least the edge-most groove at both edges of the surface relief grating at the inlet, where the first order diffraction of the image at the inlet towards the first outlet and the second outlet is coincident with the edge-most grooves at the edges of the inlet surface relief grating.

8. An augmented reality eyewear, comprising:
the optical waveguide according to claim 1 ;
a projector configured to output an optical image; and
a lens configured to relay the optical image to the surface relief grating at the inlet of the optical waveguide.

9. A method for manufacturing an optical wave guide, comprising:
forming a substrate arranged to guide an optical image inside the substrate from an inlet to an outlet of the optical waveguide via a plurality of reflections;
forming a surface relief grating to the inlet or the outlet of the optical waveguide, the surface relief grating guiding the image to the substrate via diffraction and comprising a plurality of grooves; and
filling with a coating at least partially at least the edge-most groove of the surface relief grating where a first order diffraction of the image is coincident with the at least one groove, the coating having a refractive index that optically narrows said at least the edge-most groove and thus reduces scattering of the image incident on said at least the edge-most groove incident with the first order diffraction, wherein the coating fills a plurality of grooves of the surface relief grating unevenly such that the coating completely fills at least a first groove of the surface relief grating and partially fills at least a second groove of the surface relief grating, wherein the first groove is closer to the edge of the surface relief grating than the second groove, and wherein the second groove is wider than the first groove, wherein the coating together with groove widths of the surface relief grating cause the grooves of the surface relief grating to provide a gradually narrowing optical groove widths towards the edge of the surface relief grating.

10. The method of claim 9 , wherein the surface relief grating is formed by using lithography.

11. The method of claim 9 , wherein said filling is performed such that the coating completely fills the at least edge-most groove.

Assignees

• Dispelix Oy

Inventors

• Stenberg Petri

Classifications

• G02B27/0172

  characterised by optical features · CPC title

• G02B6/0038

  Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide · CPC title

• G02B5/1857

  using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams · CPC title

• G02B1/10

  Optical coatings produced by application to, or surface treatment of, optical elements (G02B1/08 takes precedence) · CPC title

• G02B27/0103 Primary

  comprising holographic elements · CPC title