Nonlinear errors correction based on trapezoidal plus sinusoidal phase shifting algorithm

The phase shifting profilometry (PSP) is a widely used optical three-dimensional measurement method. Its accuracy is affected not only by the phase unwrapping algorithm, but also by the nonlinearity of the projector and camera in the measurement system. Theoretically, the effect of nonlinear errors can be reduced by projecting more fringes, but definitely increases the measuring time. To improve the efficiency of errors correction, a measurement method based on trapezoidal plus sinusoidal phase shifting was proposed. This method required two groups of improved trapezoidal phase shifting fringes and only one sinusoidal fringe. The trapezoidal fringe provided the information of image intensity and fringe order. The image intensity information could be used to obtain the nonlinear response curve of the system and further eliminate the nonlinearity of the system. The sinusoidal fringe could obtain the additional fringe by Hilbert transform to calculate the truncated phase information, and the corrected truncated phase information could be used to obtain the three-dimensional information with higher precision. Compared with the previous trapezoidal plus sinusoidal errors correction method, the measurement efficiency of proposed method increased by 28%.