Design of a dual-focal geometrical waveguide near-eye see-through display

Abstract

Vergence-accommodation conflict (VAC) is an obstacle in approaching the natural visual perception in near-eye see-through display. Conventional stereoscopic displays provide virtual images in a single focal plane, which are unable to satisfy the accommodative perception of the human eyes. The geometrical waveguide can be employed to achieve a larger field of view (FOV), larger exit pupil area, lower thickness and lighter weight, thus providing the possibility to offer multiple focal planes in a compact design. In this paper, we propose a wide-FOV dual-focal geometrical waveguide see-through display with a relatively thin structure. The causes of stray light in the dual-focal model are systematically analyzed based on the non-sequential ray tracing. Correspondingly, a solution is presented to eliminate the stray light and reach uniform illumination at the entire exit pupil area. The achieved illumination uniformity of the dual-depth system reaches 0.83 and the intensity uniformity is over 0.7. The depth cues of the optimized design are infinity and 100 mm with 35° FOV, 38.46 mm eye box and 20 mm eye relief, which greatly improves the optical performance and reduces the dizziness caused by the VAC problem. The total internal reflection (TIR) collimator greatly improves the uniformity of the virtual images from the projector.