Estimation of Illuminant Direction and Intensity of Multiple Light Sources

Abstract

This paper presents a novel scheme for locating multiple light sources and estimating their intensities from a pair of stereo images of a sphere. No prior knowledge of the location and radius of the sphere is necessary. The sphere surface is not assumed to be a pure Lambertian surface, instead, it has both Lambertian and specular properties. The light source locating algorithm is based on the fact that the Lambertian intensity is not dependent on the direction of view point, while the specular intensity is highly dependent on the direction of the view point. From this fact, we can use a pair of stereo images whose view point changes can be utilized to separate the image of the sphere into two images, one with Lambertian intensities, and the other with specular intensities. The specular image is used to find the directions of the light sources, and then Lambertian image model is used to find the intensities of the light sources. Experiments on both synthetic and real images show that the scheme is successful and robust in finding the directions of the light sources accurately with accurate intensity estimation.