Nonlinear Error Compensation Method for 3D Sensing System Based on Grating Image Projection

Correcting the sensing error caused by the gamma nonlinear response of the three-dimensional (3D) sensing system (SS) is a key factor in improving the accuracy of sensing. To deal with the nonlinear error of the SS, we propose a sub-area Hilbert transform (SA-HT) method. First, we employ Hilbert transform (HT) on the grating image captured by the camera sensor. Then the coefficient of the nonlinear error model can be fitted in the reference area. Second, the phase disturbance (PD) area is detected. We calculate the phase maps in spatial domain and in HT domain. Then the PD area can be detected according to the absolute phase difference in the two domains. Finally, the Newton iteration method is adopted to obtain the truth-phase in the PD area. In addition, the phase values in spatial domain and in HT domain are averaged outside of the PD area. The results of experiments show that the proposed method can avoid the influence of non-smooth reflectively (NSR) when performing nonlinear error compensation on 3D sensing.