Optical EngineeringPhase reliability evaluation in phase-shifting method using Fourier transform for shape measurement
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We propose an evaluation method for the reliability of the analyzed phase in a phase-shifting method using a Fourier transform (PSM/FT) for shape measurement by fringe projection method. In PSM/FT, since the initial phase information is determined only from the first frequency of the Fourier spectrum of the phase-shifted intensity values at each point of an object, and the frequency components higher than the first frequency almost depend on noise, experimental noise can almost be eliminated. The phase reliability evaluation value using a Fourier transform (PREV/FT) is, therefore, defined as the ratio of the first frequency component of the Fourier spectrum to the average of the frequency components higher than the first frequency of the Fourier spectrum. PREV/FT is useful to merge data when we change the measurement condition for shape measurement. We apply the PREV/FT to eliminate the halation effect on a metallic object. Shape measurement of an aluminum specimen that is a rotational body produced by a lathe is performed as an experiment. The results show that the halation effect is eliminated successfully by selecting the highest PREV/FT.