Super Wide-view Optical See-through Head Mounted Displays with Per-pixel Occlusion Capability

Augmented reality (AR) has been widely used that combines human with the digital world tightly at an unprecedented level, and various types of optical see-through head-mounted displays (OSTHMDs) have been actively developed to meet the requirement of everyday AR use. Correct mutual occlusion between real and virtual objects is often necessary for displaying realistic virtual images for users in the AR application scenarios. Some optical designs have been proposed to realize mutual occlusion by means of an OSTHMD in recent years. However, all of them support a limited field of view (FOV) that is much narrower than that of a natural human. The main limiting factor of the FOV of general OSTHMDs is the limited numerical aperture (NA) of the lenses. To address the problem, we propose an OSTHMD based on the double ellipsoidal mirror structure to avoid a stack of lenses and to achieve a wide FOV close to that of the naked eye with small distortion. A pair of imaging lenses are carefully arranged, then assembled between the two ellipsoidal mirrors with a pinhole mask to improve image quality.An experiment using a monocular prototype shows that a sharp see-through view is achieved which remains clear regardless of the focus of the eye-simulating camera. An image undistortion algorithm is also developed to obtain a full-view display, enabling a virtual image to be displayed spanning a super wide FOV of H160^{\circ}\times V74^{\circ}. Finally, per-pixel mutual occlusion of a wide FOV of H122^{\circ}\times V74^{\circ} is realized by placing a spatial light modulator (SLM) in front of the entrance pupil.