ABSTRACT Augmented reality (AR) displays require lightweight, transparent optical combiners, making diffractive waveguides a leading solution. However, achieving both high system optical efficiency and excellent eyebox uniformity remains a fundamental challenge, as these metrics are inherently subject to a trade‐off in conventional waveguides based solely on either polarization volume gratings (PVGs) or surface relief gratings (SRGs). To overcome this limitation, we propose a hybrid waveguide architecture that synergistically combines a high‐efficiency PVG as the input coupler with a custom‐designed two‐dimensional SRG (2D‐SRG) as the output coupler. The PVG maximizes light injection, while the 2D‐SRG enables precise control of out‐coupling efficiency at each total internal reflection (TIR) for uniform eyebox illumination. We introduce a k‐vector matching error model to quantify fabrication tolerances and guide the design. A 4.65‐inch prototype demonstrates an eightfold enhancement in in‐coupling diffraction efficiency compared with a conventional SRG‐based design. The full system achieves a system optical efficiency of 5% (approximately five times that of a standard all‐SRG waveguide) while maintaining an eyebox uniformity of 45%. This work demonstrates a practical co‐design strategy that effectively mitigates the intrinsic efficiency–uniformity trade‐off, advancing the development of high‐performance AR displays.
Wang et al. (Thu,) studied this question.