High-Contrast Half-Period Fringe Projection Profilometry for High-Robust 3-D Reconstruction

In fringe projection profilometry (FPP), measuring accuracy is closely related to the fringe contrast ratio (CR). Especially for low-reflective scenes, fringe contrast being compressed seriously may inevitably lead to an accuracy decrease. Therefore, a novel high-contrast half-period fringe encoding strategy is developed for the first time. Three half-period fringes generated by folding and fully amplifying three pure sinusoidal fringes with equal phase shifts perform stronger noise resistance than conventional sinusoidal fringes. Due to the folding operation, each half-period fringe naturally has three subregions that map different phase shift amounts, so we especially designed the matching phase extraction algorithm. The algorithm can accurately segment the fringe subregions and then extract the phase from each subregion in a point-to-point manner. Three extracted phase segments with head-to-tail features can be connected seamlessly to produce the final wrapped phase. Experiments compare our method with various advanced encoded fringes and traditional sine fringes across different experimental variables. The results demonstrate that the proposed method exhibits high noise resistance and low-modulation adaptability, resulting in high accuracy, which can be attributed to its superior fringe contrast. Besides, not limited to three-step fringes, the method can be extended to multistep fringes, demonstrating strong flexibility to meet different 3-D measuring requirements.