Defocused projection model for phase-shifting profilometry with a large depth range

Phase-shifting 3D profilometry is widely combined with defocused projection, but the accuracy of defocused projection could be far below expectations especially in the case of large depth range measurement. In this paper, a new defocus-induced error related to the shape of the measured object is pinpointed and a novel defocused projection model is established to cope with such a error to improve the accuracy of defocusing phase-shifting profilometry. Supplemented with a specialized calibration and reconstruction procedure, the phase is well corrected to obtain accurate measurement results. Furthermore, the impact of the defocus-induced error is analyzed through simulations, and the feasibility of our method is verified by experiments. Faced with issues involving a large measurement range, the proposed method is expected to give a competitive performance.