“3-2-1” PMP: Adding an Extra Pattern to Dual-Band Phase-Shift Profilometry for Higher Precision 3D Imaging

Phase measurement profilometry, or PMP, is undergoing rapid development at present. Combined with defocused projection and advanced multi-band phase-shift algorithms, such as heterodyne and number theory, PMP with over thousand framerates has shown great potential in three-dimensional dynamic scene monitoring, e.g., manufacturing process monitoring and industrial digital twins. PMP’s outstanding advantages include a combination of high lateral resolution, axial precision, and speed; however, the widely used dual-band phase-shift algorithms have limited axial precision compared to low-efficiency tri-band algorithms. In this paper, we propose “3-2-1” PMP, which optimizes the existing dual-band approach by adding an extra fringe pattern for projection acquisition to achieve similar precision performance as tri-band PMP. Associated stabilization algorithms in dealing with fringe blur, nonlinear camera responses, phase-jump errors, and related impact factors have also been investigated. Comparative simulation and experiments show that the “3-2-1” approach produces higher precision performance, with a 42%-85% root-mean-square error lower than general dual-band phase-shift methods and famous μFTP, but using an equivalent projection pattern number of 6 or less.