An approximation technique for photometric stereo

Photometric stereo is a technique to determine the orientation of an object. It takes at least three images corresponding to three different light sources to determine the orientation and to eliminate the ambiguities which will arise if only two light sources are used. In this report we show that a plausible shape can be obtained based only on two light sources. The method is based on the approximation of a surface patch by a spherical patch. Two real images and one synthetic image are used to illustrate the method.