Combination of air- and water-calibration for a fringe projection based underwater 3D-scanner

A new calibration methodology for photogrammetric underwater stereo scanners is presented. By combination with a complete air calibration, the water part of the calibration can be performed with low expenditure. This leads to an easy handling of the whole procedure. In this paper an underwater camera model is described which considers the refraction effects at the interfaces of the different media air, glass, and water, leading to a ray based presentation. In order to facilitate the calibration procedure and to increase robustness, some simplifications concerning the sensor geometry were made. First results obtained with a new fringe projection based underwater 3D scanner are presented which show the effectiveness of the new calibration strategy.