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Fast two-step phase-shifting method for measuring the three-dimensional contour of objects

Abstract. A two-step phase-shifting method is proposed. The method realized the rapid measurement of the three-dimensional (3D) contour of some objects using mean envelope denoising based on the striped structured light. First, Butterworth low-pass pre-filtering in the frequency domain was performed on the two deformed fringe images containing the height information of the objects. It reduced the influence of higher harmonics. Then the peak and valley values of fringes with sub-pixel accuracy were obtained through numerical interpolation and point-by-point comparison. Furthermore, the mean envelope was accurately obtained and removed. After removing the mean envelope, the rectangular low-pass filtering was used to thoroughly filter out the remaining background signal. Finally, the fast reconstructions of the 3D contour of the objects were realized. The 3D contour reconstructions of the objects were simulated and experimentally measured using the method proposed. The calculation speed and accuracy were compared with the traditional four-step phase-shifting method and other two-step phase-shifting methods. The method has the advantages of fast calculation speed and high calculation accuracy. It is a valuable method for quickly measuring the 3D contour of some objects.