High-accuracy projector calibration method for fringe projection profilometry considering perspective transformation.

Camera and projector are the key components of structured light three-dimensional (3-D) measurements, and Digital Light Processing (DLP) projector has been widely used for projecting digital structured light patterns for the measurement. The light projecting of projectors can be modeled as the inverse procedures of camera imaging, and its high-accuracy calibration is still a remaining challenge. Therefore, this paper proposes a novel projector calibration method to improve the calibration accuracy of DLP projector. By fixing the position of the camera and calibration board, this method essentially eliminates the perspective transformation error and effectively avoids the distortion of the extracted marker points. The proposed projector calibration procedures are given as follows: Firstly, the optical axis of the camera is adjusted parallel to the normal of the hollow ring calibration board, and a texture image is captured by the camera; Secondly, the horizontal and vertical fringe patterns with nine different positions and directions are projected onto the calibration board, and nine sets of projected images are taken; Finally, a one-to-one correspondence between the camera and the projector is established, and the projector is accurately calibrated using the phase equivalence. The experimental results show that the proposed projector calibration method is feasible and easy to operate, which can essentially eliminate the perspective transformation error and ensure the competitive accuracy.