On the Estimation of the Luminance Distribution by the Diffuse Reflection Component of an Object's Surface and Shape Measurement-Analysis by the Numerical Experiment-

A method is described for estimating three-dimensional(3D) shapes from two-dimensional(2-D) shading information in gray-level images that uses the diffuse reflection components in a luminance distribution with diffuse and specular reflection components. It overcomes the problem of highlights caused by the specular reflection components that occurs when multiple fixed light sources are used, which is a drawback to the “photometric stereo” method proposed by Woodham. First, the bi-directional reflectance distribution function is estimated for the detected area of a gray-level image with highlights. Then, the luminance distribution caused by the diffuse reflection components in the detected area is estimated based on the luminance distribution in a gray-level image without highlights. Numerical shape-measurement experiments using mixed diffuse-specular objects with different characteristic reflectances and shapes showed that the proposed method can accurately measure the 3-D shape of mixed diffuse-specular objects.