Slanted surface relief grating replication by optical proximity recording

Abstract

Slanted surface relief gratings for use in an optical display system in an HMD device are replicated in a manufacturing process that utilizes non-contact optical proximity recording into a specialized photo-sensitive resin that is disposed over a waveguide substrate. The recording process comprises selective resin exposure to ultraviolet light through a mask to spatially record grating structures by interferential exposure and polymerization. Subsequent resin development evacuates unexposed resin down to the waveguide substrate to remove flat surfaces, referred to as a bias layer, that remain in the grating trenches after exposure. The resin development reduces Fresnel reflections that could otherwise be induced at the media interface between the bias layer and the waveguide substrate. Fresnel reflections may cause a loss of diffraction efficiency and thereby reduce the field of view that may be guided by the SRGs in the optical display system.