Order-Shifting Temporal Phase Unwrapping for High-Fidelity Dynamic 3-D Measurement

Fringe projection profilometry (FPP) has advanced from accurate 3D surface acquisition to achieving real-world sensing. A dynamic 3D measurement method based on order shifting temporal phase unwrapping (OSTPU) is proposed. It integrates true free-space adaptability, true color detection, and true 3D measurement. Unlike conventional phase unwrapping methods, OSTPU encodes fringe order shifts using Gray-coded patterns instead of assigning absolute fringe order values. This approach significantly reduces the number of independent numbers needed for accurate encoding. By encoding only eight unique codewords, both the efficiency and the robustness within a predefined depth range are effectively enhanced. Its transferable encoding strategy reduces complexity and enables plug-and-play. Channel-wise chromatic independence preserves high-fidelity color reproduction. Experimental results show the validity in real-world dynamic 3D measurement scenarios.