Study on ray-tracing-based 3D reconstruction method for underwater measurement in glass-flume experiments

Stereo-vision-based measurement is affected by refraction of light in hydrodynamics and ocean-engineering experiments that are performed in glass flumes. Using the conventional 3D reconstruction strategy in measurement of underwater objects will lead to considerable errors. In this paper, a new reconstruction method based on ray tracing is proposed for measurement in the flume experiments. The refractive interfaces of the experiments are estimated by a robust algorithm, so that light rays corresponding to the image points can be recovered reliably. In the estimation algorithm, differential evolution is employed to compute globally optimal parameters from general image correspondences. To determine the more reasonable reconstructed points, a modified triangulation approach is also developed. The intersection of the back-projected rays is computed by correcting the corresponding image points. Experiments are conducted with synthetic data and real underwater objects. The results demonstrate the effectiveness and convenience of the proposed method in such underwater measurement tasks.