Eyebox enlargement in holographic AR glasses

Abstract

Despite the high output characteristics of holographic optical elements (HOEs), there are still no affordable holographic AR glasses that combine qualities such as a wide field of view (FOV) and a large eyebox (EB). In this study, we propose an architecture for holographic augmented reality glasses that covers both needs. Our solution is based on the combination of an axial HOE with a directional holographic diffuser (DHD) illuminated by a projector. A transparent-type DHD redirects the light from the projector, increasing the angular aperture of the image beams and providing a large EB. A reflection-type axial HOE redirects the light, transforming the spherical beams into parallel ones and providing a wide FOV for the system. The main feature of our system is the coincidence of the DHD position with the planar intermediate image of the axial HOE. This unique condition makes the system free of off-axial aberrations and ensures high output characteristics. The proposed system has a horizontal FOV of 60 deg and an EB width of 10 mm. We used modeling and a prototype to prove our investigations.