Optical systems with partial reflectors on waveguides for maximizing pupil size coupling

An electronic device comprising:

• a projector configured to generate light;
• a waveguide;
• a prism on the waveguide and configured to couple the light into the waveguide;
• and
• a partial reflector between the prism and the waveguide, wherein the partial reflector comprises:
• a reflective polarizer;
• and
• a quarter waveplate on the reflective polarizer and interposed between the reflective polarizer and the waveguide.

An electronic device comprising:

• a waveguide;
• a prism on the waveguide and configured to receive a pupil of image light;
• and
• a partial mirror between the prism and the waveguide, wherein the partial mirror has an edge region and has a tapered thickness in the edge region, and wherein the prism is configured to direct a first portion of the pupil and a second portion of the pupil into the waveguide and wherein the partial mirror is configured to receive, from within the waveguide, the second portion but not the first portion of the pupil.