Design and fabrication of a freeform optical engine for full-color geometric waveguide augmented reality glasses

Abstract

One-dimensional (1D) geometric waveguide displays are well suited for full-color augmented reality (AR) glasses because they provide higher optical efficiency and require lower source radiance than two-dimensional pupil-expanding architectures. However, the highly asymmetric shape of waveguide input pupil poses a great challenge for the design of optical engine. In this work, we propose a novel compact 1D freeform optical engine architecture for the 1D geometric waveguide. The pupil-splitting design methodology is developed to map the eyebox constraint into a tractable multi-configuration optimization problem. Based on this method, a freeform optical engine composed of only two optical elements is realized, achieving substantial reductions in optical weight and element count while preserving imaging performance. The stray light associated with the folded freeform architecture is further analyzed and suppressed by corresponding structural modification strategies. A prototype of optical engine is fabricated and integrated with a 1D geometric waveguide. The developed optical engine achieves a 28° field of view and an optics weight of 0.77 g. The final display prototype achieves a high luminance efficiency of 5700 nits/lm. These results demonstrate that the proposed waveguide-eyebox-driven pupil-splitting methodology is effective for realizing compact and lightweight full-color AR projection optics.