Methods and systems for high efficiency eyepiece in augmented reality devices

Patent metadata

Field	Value
Publication number	US-2021356748-A1
Application number	US-202117332373-A
Country	US
Kind code	A1
Filing date	May 27, 2021
Priority date	Nov 30, 2018
Publication date	Nov 18, 2021
Grant date	—

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.

First claim

What is claimed is:

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.

2 . 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.

3 . The display system of claim 1 further comprising a projection display configured to direct the beam of light to the projection optics.

4 . The display system of claim 1 wherein the beam of light comprises a plurality of colors projected sequentially.

5 . The display system of claim 1 wherein the second direction is parallel to the first lateral plane.

6 . The display system of claim 1 wherein the retroreflector is disposed on the opposing surface.

7 . The display system of claim 1 wherein the retroreflector is disposed parallel to the opposing surface at a predetermined distance from the opposing surface.

8 . 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.

9 . 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.

10 . 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.

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.

12 . The eyepiece unit of claim 11 , wherein the second incoupling diffractive optical element comprises a metallized retroreflector.

13 . The eyepiece unit of claim 11 , wherein the first incoupling diffractive optical element is configured to incouple light in a first spectral band.

14 . 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.

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.

16 . 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.

17 . 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.

18 . The method of claim 15 wherein the first diffractive optical element is disposed on the incident light surface.

19 . 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.

20 . 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.

Assignees

• Magic Leap Inc

Inventors

• Cheng Hui-Chuan

Classifications

• G02B6/0076

  Stacked arrangements of multiple light guides of the same or different cross-sectional area · CPC title

• G02B27/0081 Primary

  with means for altering, e.g. enlarging, the entrance or exit pupil · CPC title

• G02B6/0023

  provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source · CPC title

• G02B2005/1804

  Transmission gratings · CPC title

• G02B5/122

  cube corner, trihedral or triple reflector type · CPC title