Photometric Stereo beyond Glass: Active Separation of Transparent Layer and Five-Light Photometric Stereo with M-Estimator Using Laplace Distribution for a Virtual Museum

One of the necessary techniques for constructing a virtual museum is to digitize the artwork arranged inside a glass or acrylic display case without bringing the artwork out of the display case. By using photometric stereo, we estimate the shape (surface normal) and the reflectance (albedo) of the artwork arranged inside a transparent display case. If we illuminate the display case, the light will reflect at its surface; thus, we cannot apply conventional photometric stereo as is. In this paper, we propose a fivelight photometric stereo that estimates the shape and the reflectance of an object that has specularities under the circumstances that the light is reflected at the surface of the display case.