Analysis of pupil aiming illumination scheme for AR waveguide combiner

Exit pupil expansion (EPE) is commonly used in AR waveguide combiners to create an eyebox large enough to accommodate variations in human pupil size and interpupillary distance (IPD). However, EPE suffers from poor light-transfer efficiency, wasting a significant fraction of the display's output. Here, we propose a novel pupil-aiming illumination scheme that in theory directs substantial higher amount of light radiating from light engine into the user's eye pupil. We develop a 1st order theoretical model of its light-transfer efficiency and show that, in principle, it can approach 25% utilization—dramatically outperforming traditional EPE that is on the order of only a coupler of percentage. Our analysis underscores the urgent need to adopt pupil-aiming illumination as a new architectural paradigm for high-efficiency AR waveguide combiners.