ROTATED SUBWAVELENGTH GRATING FOR HIGH EFFICIENCY THIN WAVEGUIDE

摘要

An apparatus includes a waveguide, a first diffraction grating on a front side of the waveguide and a second diffraction grating on a back side of the waveguide. The small period back side gratings, rotated around the propagation direction, will rotate the state of polarization of an incoming light beam after a first Total Internal reflection (TIR). The back side diffraction grating is designed such that it does not change the propagation direction of the guiding light and will reduce backcoupling from the incoupler, hence increasing the net guided energy towards the user' s eye. The back side diffraction grating of the disclosed embodiments will help to increase the guiding efficiency and thereby result in a brighter augmented reality image.