Methods and systems for high efficiency eyepiece in augmented reality devices

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.

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.