Matching photometric-stereo images

Abstract

We introduce a new process of shape estimation through the matching of photometric-stereo images, which are monocular images obtained under different illuminations. If the illumination directions are not far apart, and if the imaged surface is smooth, so that a linear approximation to the reflectance map is applicable, the disparities produced by the matching process can be related to the depth function of the imaged surface through a differential equation whose approximate solution is easily found. We thus obtain a closed-form expression for surface depth, depending only on the coefficients of the linear-reflectance-map function. If those coefficients are not available, a simple iterative scheme still allows the recovery of depth, up to an overall scale factor.