Waveguide display with gaze tracking

A display system comprising:

• a waveguide configured to direct image light;
• a surface relief grating structure on the waveguide, wherein the surface relief grating structure is configured to:
• receive reflected infrared light,
• couple the reflected infrared light into the waveguide, and
• couple the reflected infrared light out of the waveguide after the reflected infrared light has reflected at least once off of a surface of the waveguide;
• an image sensor configured to generate image sensor data based on the reflected infrared light coupled out of the waveguide by the surface relief grating structure;
• and
• control circuitry configured to perform gaze tracking operations based at least in part on the image sensor data.

A display system for displaying image light, the display system comprising:

• a waveguide;
• a light source configured to generate infrared light;
• an input coupler configured to couple the image light into the waveguide;
• an output coupler on the waveguide and configured to couple the image light out of the waveguide;
• and
• a diffractive grating on the waveguide, wherein the diffractive grating is configured to direct the image light towards the output coupler, is configured to diffract the infrared light into the waveguide at a first angle within a total internal reflection (TIR) range of the waveguide, and is configured to diffract, out of the waveguide and at a second angle outside the TIR range of the waveguide, the infrared light diffracted into the waveguide by the diffractive grating after the infrared light diffracted into the waveguide by the diffractive grating has reflected off a surface of the waveguide via TIR.