A simple method to estimate surface reflectance parameters for three light photometric stereo

摘要

A complete procedure to reconstruct part shape using a 3-light photometric stereo technique is investigated and experimentally verified. The part reflectance parameters are initially estimated and then the photometric stereo technique is applied at selected illumination directions. Finally, the recovered surface normals are integrated to reconstruct the part shape.The light sources are placed at 120° azimuth angle spacing while the slant angle is optimized according to the range of slopes found in the part surface. For a free form surface with small radii of curvature, a 45° light source slant angle is found to give better results on the global scale, with relatively lower accuracy. For a near-flat surface, a light source slant angle of 25° may be used to attain more accurate results. For surfaces having slopes less than 40° the mean surface normal recovery error is experimentally found to be less than 5°.