Diffractive optical waveguide device for enlarging the exit pupil

摘要

An optical device for enlarging input light in two dimensions in an augmented reality display is disclosed. The device comprises a waveguide (12) and three linear diffraction gratings H0, H1, H2. Incident light from the projector illuminates the input grating H0 with polychromatic light, which is coupled into the waveguide (12). The other two lattices H1 and H2 overlap each other. The light can be diffracted by the one grating H1 to the first diffraction order and directed to the other grating H2, which can decouple the light from the waveguide (12) to the viewer. In another configuration, the cross gratings H1, H2 can be replaced by a photonic crystal (19) having a regular row of cylinders (20) that produces a plurality of effective diffraction gratings.