Normal Direction Measurement Method for Glossy Surface with Holographic Optical Element

Abstract

We propose a brand-new measurement method for glossy surfaces by the unique lighting module with a transmission type holographic optical element (HOE). Since the diffracted lights from HOE has large chromatic dispersion, the diffraction direction is determined by colors. This characteristic means that light ray directions from glossy surfaces can be analyzed using chromatic property in captured image. In our method, hue value is treated as a function of light ray direction. Therefore, normal direction on a surface in each pixel can be estimated by using hue value in the same pixel. In this paper, relations between hue values and light ray directions are estimated using approximated formula and we discuss the calculation result for sample objects.