A simple and practical jump error removal method for fringe projection profilometry based on self-alignment technique

The code-based method is one of the frequently adopted fringe projection profilometry techniques because of its robustness and high speed. However, the abnormal jump errors caused by the misalignment between the wrapped phase and the fringe order impact the phase unwrapping quality and are more serious in binary defocusing measurement with significant defocusing. This paper proposes a self-alignment technique (SAT) with high speed, no additional patterns, and no accuracy loss to eliminate such jump errors. After analyzing the relation between the grating changes and the misalignment, we designed an assist-code that can perfectly align with the wrapped phase even in significant defocusing. After that, this assist-code is used to adjust the misalignment and eliminate the jump errors. The comparison between the median filter and the proposed SAT method in simulations and experiments demonstrates that the proposed SAT method has the ability to completely remove jump errors for complex textures and step-height objects, even in significant defocusing, indicating its potential to be applied to other phase unwrapping fields, e.g., color-based methods with color coupling problems.