Evaluating The Effect of Refraction on Underwater Stereo Vision

Underwater binocular stereo vision is a method for the three-dimensional measurement of underwater objects, but its measurement accuracy is affected by the refraction of underwater cameras. The calibration-based refraction compensation method is widely used due to its easy operation and calculation, while the physical model-based method seems to be a higher precision but is not popular enough. In this paper, we propose to compare the calibration-based and the physical model-based refraction correction methods for their best working conditions. We constructed the underwater binocular distance measurement environment and evaluated the calibration-based and the physical model-based method by adjusting the setting of the underwater camera parameters and the calibration mode of the underwater camera. We analyzed the effect of several key factors emphatically, such as the distance between the optical center of the camera and the glass interface (camera-glass distance), the calibration distance of the underwater camera, and the measurement distance of the underwater camera. Results demonstrate that the calibration-based method has smaller errors when the camera-glass distance is smaller, or when the underwater binocular distance measurement is carried out nearby the calibration distance of the underwater camera. In other cases, the physical model method is more suitable.