Novel pancake-based HMD optics to improve light efficiency.

Recently, compactness of head-mounted display (HMD) products have been strongly required to improve comfortableness of user. The folded optics, socalled "Pancake optics", is suitable for realizing compact HMD, but there is a big drawback of lowering light efficiency. To overcome this problem, we propose a novel pancake-based HMD optics named "Double path pancake optics" using two light paths. The optical simulation is performed to find highly optimized optical properties such as thickness, and field of view (FOV). As a result of the simulation, we fixed the appropriate design. From our simple evaluation of both brightness and transmittance, we conclude that light efficiency of "Double path pancake optics" becomes 1.8 times higher than conventional pancake optics. We made the prototype using 1200 ppi high resolution liquid crystal display (LCD) and confirmed that the high image quality can be displayed. [ABSTRACT FROM AUTHOR]