Optical systems with light-expanding couplers

A display system comprising:

• a waveguide comprising a waveguide substrate with first and second opposing surfaces;
• an input coupler configured to couple light into the waveguide, wherein the input coupler is mounted to the first surface of the waveguide substrate;
• a cross coupler on the waveguide, wherein the cross coupler is configured to diffract the light coupled into the waveguide by the input coupler and wherein the cross coupler comprises a surface relief grating structure in a surface relief grating substrate;
• an output coupler on the waveguide, wherein the output coupler is configured to receive the light diffracted by the cross coupler and couple the light out of the waveguide, wherein the output coupler comprises a set of volume holograms recorded in a grating medium, wherein the grating medium is layered on the second surface of the waveguide substrate, and wherein the grating medium is interposed between the waveguide substrate and the surface relief grating substrate.

An optical system that redirects light produced by a projector towards an eye box, the optical system comprising:

• a waveguide comprising a waveguide substrate and configured to propagate the light via total internal reflection;
• an input coupler configured to couple the light produced by the projector into the waveguide;
• a cross coupler configured to diffract the light coupled into the waveguide by the input coupler, wherein the cross coupler comprises a surface relief grating structure with troughs and ridges formed in a surface relief grating substrate and wherein the troughs extend in a first direction;
• an output coupler formed in an output coupler substrate and configured to couple the light out of the waveguide, wherein the output coupler substrate overlaps the surface relief grating substrate in a second direction orthogonal to the first direction, wherein the waveguide substrate overlaps the output coupler substrate in the second direction, and wherein the output coupler substrate is interposed between the waveguide substrate and the surface relief grating substrate.