Study of algorithm in phase-shifting profilometry

In phase-shifting measurement, the phase shift fringe image received by CCD must go through the image process, including smoothing filter and phase retrieve. Generally smoothing filter is done before phase retrieve (SAR). We draw a conclusion that, phase retrieve and smoothing filter (RAS) has slightly better noise reduction effect than SAR; RAS needs shorter processing time than SAR, according to their mean and variance as criteria. An algorithm combined with Fourier transform profilometry(FTP) and phase-shifting profilometry is also presented. The algorithm FTP is used to measure accurate phase shift in each step and according to the phase shift value distribution, it can get the object surface 3D datum. When the accurate phase shift is obtained, accurate phase measurement can be accomplished using only three frames. Experiments are carried out to verify its effectiveness. The results show that the algorithms can accurately measure the phase-shift and improve phase measurement accuracy.