Photometric stereo using point light sources

Practical lamps for undersea illumination are closely approximated by point sources, the light from which diverges and also attenuates due to scattering and absorption by the water. The objective is to determine the error introduced by these departures from the usual lighting assumptions of photometric stereo and to find an approach to solution of the brightness equations. It is demonstrated that an iterative approach to photometric stereo, plus a sparse range map containing as little as one range datum for each object in the scene, is sufficient to permit determination of the surface gradients. Simulation indicated that the method improves accuracy and was robust with respect to measurement error in both sparse range data and attenuation length