High-quality 3D shape measurement with binary half truncated sinusoidal fringe pattern

Abstract

Digital fringe projection (DFP) with defocused binary fringe patterns could overcome the projector nonlinearity and achieve a high-speed 3D measurement. Most of the binary defocusing techniques take sinusoidal fringe as the target of binarization, hoping the binary fringes can become “quasi-sinusoidal” after defocusing. However, considering that the phase-shifting algorithm (PSA) has an inherent resistance to certain order harmonics components, it is not the best choice to make the defocused binary fringe become more sinusoidal. This paper proposed a new kind of fringe called half truncated sinusoidal (ht-sinusoidal) fringe, which has the same phase result as the sinusoidal fringe with 4-step PSA theoretically. And this kind of fringe is easier to be binarized for the reason that half of it has 0 intensity values already. Therefore it can achieve significant phase quality improvements compared with the binary sinusoidal fringe. We mainly verified that the ht-sinusoidal fringe will help substantially improve the measurement accuracy of different error diffusion methods through both simulations and experiments.