T. Bell, J. Xu, and S. Zhang, “Method for out-of-focus camera calibration,” Appl. Opt., 55(14), 2016; doi: 10.1364/AO.55.002346
State-of-the-art camera calibration methods assume that the camera is at least nearly in focus, and thus fail if the camera is substantially defocused. This paper presents a method which enables the accurate calibration of an out-of-focus camera. Specifically, the proposed method uses a digital display (e.g., liquid crystal display monitor) to generate fringe patterns which encode feature points into the carrier phase; these feature points can be accurately recovered even if the fringe patterns are substantially blurred (i.e., the camera is substantially defocused). Experiments demonstrated that the proposed method can accurately calibrate a camera regardless of the amounts of defocusing: the focal length difference is approximately 0.2% when the camera is focused compared to when the camera is substantially defocused.