The Irradiance Error and its Effect in Photometric Stereo

This paper discusses some essential aspects on evaluating the three-source photometric stereo method (PSM). PSM is a shading based 3D shape recovery approach that calculates a dense set of surface orientations from three input images taken by changing the illumination direction without moving the optical sensor. A subsequent step can be used to convert the surface gradients into a dense height map by means of an integration method. In a previous paper [2] we carried out evaluations of integration approaches. Here we show how the resolution of surface orientations depends on perturbations in the image irradiances (intensities). Previous methods considered only single light source configurations or particular image irradiance triples, hence no general predictions could be made. We give a simple geometrical interpretation to estimate upper bounds of angular deviations with respect to expected errors in image irradiances. Such predictions are necessary for the practical application of the photometric stereo method. * The University of Auckland, Tamaki Campus, Computing and Information Technology Research, Computer Vision Unit, Auckland, New Zealand The Irradiance Error and its Effect in Photometric Stereo Karsten Schluns Computing and Information Technology Research – CITR Computer Science Department, Tamaki Campus University of Auckland New Zealand E-mail: karsten@cs.auckland. ac.nz Abstract This paper discusses some essential aspects on evaluating the three-source photometric stereo method (PSM). PSM is a shading based 3D shape recovery approach that calculates a dense set of surface orientations from three input images taken by changing the illumination direction without moving the optical sensor. A subsequent step can be used to convert the surface gradients into a dense height map by means of an integration method. In a previous paper [2] we carried out evaluations of integration approaches. Here we show how the resolution of surface orientations depends on perturbations in the image irradiances (intensities). Previous methods considered only single light source configurations or particular image irradiance triples, hence no general predictions could be made. We give a simple geometrical interpretation to estimate upper bounds of angular deviations with respect to expected errors in image irradiances. Such predictions are necessary for the practical application of the photometric stereo method.This paper discusses some essential aspects on evaluating the three-source photometric stereo method (PSM). PSM is a shading based 3D shape recovery approach that calculates a dense set of surface orientations from three input images taken by changing the illumination direction without moving the optical sensor. A subsequent step can be used to convert the surface gradients into a dense height map by means of an integration method. In a previous paper [2] we carried out evaluations of integration approaches. Here we show how the resolution of surface orientations depends on perturbations in the image irradiances (intensities). Previous methods considered only single light source configurations or particular image irradiance triples, hence no general predictions could be made. We give a simple geometrical interpretation to estimate upper bounds of angular deviations with respect to expected errors in image irradiances. Such predictions are necessary for the practical application of the photometric stereo method.