A novel projector calibration method based on improved two-frequency grating projection

System calibration is crucial for any structured light-based 3D shape mea surement system. To address the instability of the unwrapping process during the procedure of the projector calibration, an improved two-frequency grating projection method based on the phase-shifting method is proposed. To avoid the complicated phase error compensation, a simple and robust nonlinear regression model is used to t the coordinates in the projector image which vary with the coordinates in the camera image. The reprojection errors of the checkerboard corners for the projector images are no more than ±1 pixels. The proposed scheme is more accurate than the three-step phase-shifting method for estimating the intrinsic projector parameters.