US Patent 9791696 Waveguide gratings to improve intensity distributions

An apparatus for use in replicating an image associated with an input-pupil to an output-pupil includes a planar optical waveguide including a bulk-substrate, and also including an input-coupler, an intermediate-component and an output-coupler. The input-coupler couples light corresponding to the image into the bulk-substrate and towards the intermediate-component. The intermediate-component performs horizontal or vertical pupil expansion and directs the light corresponding to the image towards the output-coupler. The output-coupler performs the other one of horizontal or vertical pupil expansion and couples light corresponding to the image, which travels from the input-coupler to the output-coupler, out of the waveguide. In certain embodiments, one or more of the input-coupler, the intermediate-component or the output-coupler comprises a liquid crystal polymer (LCP) based surface relief grating (SRG) or a double-side diffractive optical element (DOE), each of which can be used to improve an intensity distribution of light output by the output-coupler.