Double N-step phase-shifting profilometry using color-encoded grating projection

Although double N-step phase-shifting profilometry can greatly reduce phase error caused by the non-sinusoidal nature of grating fringes, its number of the projection fringes doubles and its measurement efficiency is reduced. In this paper, a double N-step phase-shifting profilometry using color-encoded grating projection is proposed. It encodes the original phase-shifting fringes and the additional phase-shifting fringes into two colored fringes and fuses them into one color-encoded grating fringe projection. Then, the phase information of two sets of fringes is extracted from the captured color-encoded fringes. After calculating their wrapped phases, the two wrapped phases are fused to reduce phase error. In order to verify the effectivity of the proposed method, we combine the proposed method with two typical phase unwrapping algorithms to carry out experiments. The experimental results show that the proposed method can effectively reduce the phase error without adding any additional grating fringes and that its measurement efficiency is enhanced by 46%