A Practical Calibration Method for Cameras and Multiple Line-Lasers in Light Sectioning Systems for Underwater Environments

In recent years, the increasing demand for underwater 3D measurement for various applications has brought about challenges such as low accuracy in 3D shape acquisition and difficulties in localizing sensor positions. This paper introduces a robust calibration method for underwater 3D sensors, comprising line lasers and cameras, utilizing a physically accurate model. Specifically, our proposed line laser calibration method estimates laser plane parameters using two types of planar constraints, avoiding the need for the costly process of backward-projection of refraction for optimization. For camera calibration, we advocate a two-step approach incorporating a simple yet effective deep-learning-based marker detection algorithm to estimate parameters of refraction, representing a physically correct lens model. Through experiments, we validate the superior performance of our methods over previous approximation-based approaches, as demonstrated in simulations and actual experiments conducted in a swimming pool.