# US 11,994,680 B2 · Methods and systems for high efficiency eyepiece in augmented reality devices > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,994,680 B2 - Document ID: US11994680B2 - Status: Granted - Kind: B2 - Application number: 17/332,373 - Filed: 2021-05-27 - Published: 2021-11-18 - Granted: 2024-05-28 - Earliest claimed: 2018-11-30 - Assignees: Magic Leap, Inc. - Applicants: Magic Leap, Inc. - Inventors: Hui-Chuan Cheng - Web page: https://patentgrep.com/patent/US11994680B2 ## CPC - G02B 27/0172: {characterised by optical features} - G02B 5/122: cube corner, trihedral or triple reflector type - G02B 6/0023: {provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source} - G02B 6/0076: {Stacked arrangements of multiple light guides of the same or different cross-sectional area} - G02B 25/001: {Eyepieces} - G02B 27/0081: {with means for altering, e.g. enlarging, the entrance or exit pupil} - G02B 2005/1804: {Transmission gratings} - G02B 2027/0178: {Eyeglass type (eyeglass details G02C)} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A display system includes projection optics configured to project a beam of light in a first direction and an eyepiece unit including a first waveguide layer disposed in a first lateral plane and including an incident light surface and an opposing surface opposite the incident light surface and an incoupling diffractive optical element disposed on the incident light surface. The incoupling diffractive optical element is configured to incouple a first portion of the beam of light and to propagate the first portion of the beam of light by total internal reflection in a second direction and transmit a second portion of the beam of light along the first direction. The eyepiece also includes a retroreflector disposed adjacent the opposing surface. The retroreflector is configured to retroreflect the second portion of the beam of light along a reflected direction opposite to the first direction. ## Claims ### Claim 1 A display system comprising: projection optics configured to project a beam of light in a first direction; an eyepiece unit including: a first waveguide layer disposed in a first lateral plane and including an incident light surface and an opposing surface opposite the incident light surface; an incoupling diffractive optical element disposed on the incident light surface, wherein the incoupling diffractive optical element is configured to: incouple a first portion of the beam of light and to propagate the first portion of the beam of light by total internal reflection in a second direction; and transmit a second portion of the beam of light along the first direction; and a retroreflector disposed adjacent the opposing surface, wherein the retroreflector is configured to retroreflect the second portion of the beam of light along a reflected direction opposite to the first direction. ### Claim 2 (depends on 1) The display system of claim 1 wherein the eyepiece unit further comprises: an orthogonal pupil expander region laterally displaced from the incoupling diffractive optical element; and an exit pupil expander (EPE) region laterally displaced from the incoupling diffractive optical element. ### Claim 3 (depends on 1) The display system of claim 1 further comprising a projection display configured to direct the beam of light to the projection optics. ### Claim 4 (depends on 1) The display system of claim 1 wherein the beam of light comprises a plurality of colors projected sequentially. ### Claim 5 (depends on 1) The display system of claim 1 wherein the second direction is parallel to the first lateral plane. ### Claim 6 (depends on 1) The display system of claim 1 wherein the retroreflector is disposed on the opposing surface. ### Claim 7 (depends on 1) The display system of claim 1 wherein the retroreflector is disposed parallel to the opposing surface at a predetermined distance from the opposing surface. ### Claim 8 (depends on 1) The display system of claim 1 wherein the incoupling diffractive optical element is further configured to: incouple a third portion of the second portion of the beam of light and to propagate the third portion by total internal reflection in the second direction; and transmit a fourth portion of the beam of light along the reflected direction. ### Claim 9 (depends on 1) The display system of claim 1, further comprising: a second waveguide layer disposed in a second lateral plane adjacent to the first lateral plane and including a second incoupling diffractive optical element disposed at a second lateral position, a second waveguide optically coupled to the second incoupling diffractive optical element, and a second outcoupling diffractive optical element optically coupled to the second waveguide; and a third waveguide layer disposed in a third lateral plane and including a third incoupling diffractive optical element disposed at a third lateral position, a third waveguide optically coupled to the third incoupling diffractive optical element, and a third outcoupling diffractive optical element optically coupled to the third waveguide. ### Claim 10 (depends on 9) The display system of claim 9, wherein the incoupling diffractive optical element is disposed at a first lateral position and the first lateral position and the second lateral position are a same lateral position. ### Claim 11 An eyepiece unit comprising: a waveguide layer disposed in a lateral plane and including an incident light surface and an opposing surface opposite the incident light surface; a first incoupling diffractive optical element disposed on the incident light surface, wherein the first incoupling diffractive optical element is configured to: incouple a first portion of a beam of light propagating in a first direction and to propagate the first portion of the beam of light by total internal reflection in a second direction; and transmit a second portion of the beam of light along the first direction; a second incoupling diffractive optical element disposed on the opposing surface, wherein the second incoupling diffractive optical element is configured to: receive the second portion of the beam of light along the first direction; incouple a third portion of the beam of light and to propagate the third portion of the beam of light by total internal reflection in a third direction; and transmit a fourth portion of the beam of light along the first direction; and a retroreflector disposed adjacent the opposing surface, wherein the retroreflector is configured to retroreflect the fourth portion of the beam of light along a reflected direction opposite to the first direction. ### Claim 12 (depends on 11) The eyepiece unit of claim 11, wherein the second incoupling diffractive optical element comprises a metallized retroreflector. ### Claim 13 (depends on 11) The eyepiece unit of claim 11, wherein the first incoupling diffractive optical element is configured to incouple light in a first spectral band. ### Claim 14 (depends on 13) The eyepiece unit of claim 13 wherein: the second incoupling diffractive optical element is configured to incouple light in a second spectral band; the first spectral band includes red wavelengths; and the second spectral band includes green wavelengths. ### Claim 15 A method of operating a display system, the method comprising: directing a beam of light in a first direction; receiving the beam of light at an incident light surface of a waveguide layer having an opposing surface opposite the incident light surface; propagating, at a first diffractive optical element, a first portion of the beam of light into the waveguide layer in a second direction; transmitting, at the first diffractive optical element, a second portion of the beam of light toward the opposing surface; and retroreflecting the second portion of the beam of light along a reflected direction opposite to the first direction. ### Claim 16 (depends on 15) The method of claim 15 further comprising: propagating, at the first diffractive optical element, a first fraction of the second portion of the beam of light into the waveguide layer in the second direction; and transmitting, at the first diffractive optical element, a second fraction of the second portion of the beam of light along the reflected direction. ### Claim 17 (depends on 16) The method of claim 16 further comprising: reflecting at least a portion of the second fraction in the first direction toward the waveguide layer; receiving the reflected portion at the incident light surface of the waveguide layer; and propagating, at the first diffractive optical element, a portion of the reflected portion into the waveguide layer in the second direction. ### Claim 18 (depends on 15) The method of claim 15 wherein the first diffractive optical element is disposed on the incident light surface. ### Claim 19 (depends on 15) The method of claim 15 wherein retroreflecting the second portion of the beam of light comprises retroreflecting light along a reflected direction opposite to the first direction. ### Claim 20 (depends on 15) The method of claim 15 wherein directing the beam of light in the first direction comprises reflecting a time sequential color beam from a display element.