Wave optics analysis of corner-cube retro-reflectors in near-to-eye displays based on scanning laser projectors

In near to eye displays based on scanning laser projectors, retro-reflectors seem as convenient image relay components since they can ideally be placed at any location on the scanned beam path. In case of practical retro reflectors though, such as corner cube retro-reflectors (CCRs), the relayed image suffers from loss in quality and resolution due to the positional shift in the retro-reflected rays and the diffraction effects. We perform a wave optics simulation to analyze the image relay performance of a CCR. Our model assumes that the scanned spot of the projector is imaged by the CCR into an array of spots, which superpose and interfere to yield the effective scan spot seen by an eye looking at the CCR. The results indicate that the CCR results in a significant broadened spot size. Experimental results verify the simulation model in terms of achievable resolution and image quality.