US Patent 10534176 Waveguide display with gratings for improved diffraction efficiency

A waveguide display is used for presenting media to a user. The waveguide display includes a light source assembly, an output waveguide, and a controller. The light source assembly projects an image light at least along one dimension. The output waveguide includes a waveguide body with two opposite surfaces. The output waveguide includes an input area, an output area, a first diffractive element on the first side, and a second diffractive element on the second side of the output waveguide. The output area is located between the input area and the first and second diffractive elements. The first and second diffractive elements reflect a second portion of the expanded image light back toward the output area for outcoupling to the eyebox. The controller controls the scanning of the light source assembly to form a two-dimensional image.