Reducing stray light transmission in near eye display using resonant grating filter

Abstract

A near eye optical display system comprising a waveguide and diffractive optical elements (DOEs) for in-coupling, exit pupil expansion, and out-coupling reduces the transmission of stray light in the system using a doubly-periodic surface relief microstructure that combines a guided-mode resonant filter with Bragg reflectance. Such resonant grating filter may be configured with grooves and/or ridges of different widths that are located on the waveguide that have respective sub-periods that match Bragg reflectance periods for particular wavelengths. The interaction of the sub-periods gives rise to a photonic band gap effect in which the resonant grating's effective refractive index is modulated to increase angular sensitivity and wavelength bandwidth of the resonant grating filter. The sub-periods define an overall period (i.e., a super period) for the resonant grating filter by which incident light is coupled into the waveguide, guided, and then coupled out of the waveguide at the side of incidence.