Numerical analysis of eyeglow reduction in AR near eye display using holographic optical element

Abstract

Many architectures of near eye display (NED) using a holographic optical element (HOE) come on the market. HOE has already been successfully industrialized due to its easy manufacturing process and small form factor. However, many studies are being conducted to solve degradation effect by the eye glow that the visibility of the user decreases occurred to external light. HOE is generally used as an element of NED for its good angular and wavelength selectivity characteristics. The parameters controlling those characteristics are the refractive index change and the thickness of HOE. Although the selectivity characteristics are optimized by regulating the two parameters, the eye glow occurs because the HOE reacts in parts other than the desired characteristics for sunlight and white light sources. For a fundamental reason, eye glow is further caused by a sudden refractive index change in boundary condition when incident into the HOE from the air. In this study, we figure out that the boundary condition changes continuously by apodization of the refractive index of HOE for eye glow reduction. Also, we calculate the angular and wavelength selectivity efficiency using scalar Fourier modal method (sFMM) based on rigorous coupled-wave analysis (RCWA) according to the thickness and refractive index change, and investigate the relationship between those parameters.