A fast underwater calibration method based on vanishing point optimization of two orthogonal parallel lines

Abstract This paper proposes a fast underwater calibration method based on vanishing point optimization of two orthogonal parallel lines. Based on the distance optimization, two sets of precise vanishing points corresponding to orthogonal parallel lines are constructed, and then after getting the underwater camera focal length and the equivalent image in air of the underwater image, the camera's external parameters are obtained. This underwater calibration method is easy to operate, which needs only two sets of mutually orthogonal parallel lines from one image, reducing the restriction requirements of underwater camera calibration on scene. In addition, the calibration time is about 2 s. Compared with the classic vanishing point method and the Matlab toolbox, the speed is increased by 231.61% and 387.80%, respectively. The accuracy error of reconstruction model is kept within 2.5%. Results show that the method has enhancement speed while ensuring accuracies, and can be used for underwater robot manipulation.