Optical See-Through Head-Mounted Display with Deep Depth of Field Using Pinhole Polarizing Plates

Abstract

Optical See-Through Head-Mounted Displays (OST-HMDs) have attracted much attention as augmented reality (AR) devices. Depth of field (DoF) is a key parameter for OST-HMDs because a shallow DoF often yields focal point gaps between computer-generated graphics (CGs) and real scenes forcing users to re-adjust their focus. However, it is difficult to achieve a deep DoF for CGs over real scenes in compact and low-cost devices because laser projectors or complicated optics are needed. In this paper, we propose an OST-HMD that uses polarizing plates with a pinhole to achieve a deep DoF. The optics of the proposed device comprises two polarizing plates and a beam splitter. The polarization planes of the plates are orthogonal and one of the plates has a pinhole. The key idea of the proposal is the pinhole effect using polarizing plates to achieve a deep DoF without any influence to the field of view (FoV) for real scenes. This method can be implemented at significantly low cost and ease in compact thanks to its simple optics and is applicable to OST-HMDs that employ smartphones. In addition, we confirm that CGs are clearly seen whatever the focal point by constructing a prototype.