Camera-projector calibration using Double N-Step phase shift profilometry and circle grid calibration pattern

Abstract

Accurate calibration of the camera-projector setup is necessary to obtain accurate 3D world coordinates from phase shift profilometry (PSP). In this paper, a camera-projector calibration method using the Double N-Step PSP and a circle grid pattern is presented. The temporal phase unwrapping (TPU) technique was used to obtain phase maps from a set of 4-step phase shifted sinusoidal images. The camera-projector response function is known to be nonlinear, and thus the Double N-Step method is utilized to minimize nonlinearity and phase errors. Circle grid patterns were used for feature point detection to exclude regions with low signal-to-noise ratio (SNR) to minimize phase errors from propagating during the calibration. We observed phase errors which may have been caused by jump errors during TPU. We estimated the camera-projector stereo parameters with a reprojection error of 1.61 pixels. After 3D reconstruction using the triangulation method, we observed a mean error of 1.13(2) mm in the Z_w axis of the recovered world coordinates of the feature points.