An Iterative Deflectometry Method of Reconstruction of Separated Specular Surfaces

Phase measuring deflectometry (PMD) plays a more and more significant role in the measurement of specular surfaces. However, most of the deflectometric methods are only suitable for continuous specular surfaces, but not for the discontinuous surfaces. In this work, with the hardware of stereoscopic PMD, a mechanism is introduced that a specular surface can be reconstructed iteratively with the pre-known coordinate of a reflecting point. Based on the mechanism and the excellent local properties of the B-spline surface, a reconstruction method suitable for the both kinds of specular surfaces is proposed. Meanwhile, to resist the noise of the single point, this work mathematically analyses the mechanism of the method. With the mathematical conclusion, the sparse point cloud solved by stereoscopic PMD is employed to scale the B-spline surfaces, improving the accuracy of reconstruction. Simulated and actual experiments are carried out and the results show high accuracy and robustness of the PMD system and the reconstruction method.