Realizing mutual occlusion in a wide field-of-view for optical see-through augmented reality displays based on a paired-ellipsoidal-mirror structure

Mutual occlusion is an essential feature for augmented reality (AR) displays for allowing the virtual content to be clearly perceived under an excessively illuminated environment. Although a few works have been done to facilitate the performance of occlusion-capable optical see-through augmented reality (OC-OST-AR) displays, the realization of mutual occlusion in a wide field-of-view (FOV) is still challenging. Divergent from typical hard-edge occlusion and soft edge-occlusion designs, we propose the paired-ellipsoidal-mirror (PEM) structure. The proposed system is allowed to support either hard-edge occlusion or enhanced soft-edge occlusion in a wide FOV by optionally fixing a spatial light modulator (SLM) before the entrance pupil or at an inner focal plane. The numerical aperture (NA) of the system is efficiently increased by the combination of paired ellipsoidal mirror imaging and aperture stop restriction. With proof-of-concept prototypes built, virtual display in a FOV of H160°×V74° and mutual occlusion in a FOV of H122°×V74° are demonstrated with a basic design, respectively. Furthermore, a mixed FOV of H95.3°×V52.9° is demonstrated by an optimized design with vertical parallax reduction and virtual display improvement.