Stereoscopic deflectometry with a curved screen

Abstract

Deflectometry has been widely used in topography measurement of specular surface. In deflectometry with a curved screen, the range of the gradient and height field of the measured specular surface can be effectively expanded compared to deflectometry with a plane screen. As stereo deflectometry measures gradient with high accuracy, the specular surface is reconstructed by integrating the gradient. In this paper, a stereo deflectometry with a curved screen is proposed in the aspect of system calibration and measuring principle. A pair of cameras and deflectometric system are calibrated simultaneously to obtain the camera parameters and relationship between two cameras and the curved screen. Then, pairs of rectified fringe patterns are demodulated to obtain two pairs of rectified absolute phase maps and homologous points are searched along epipolar line with the principle of the same normal direction on specular surface. Finally, simulated and actual experiments are carried out and the results show high accuracy and stability.