The path of light is influenced by refraction at transitions between media with different refractive indices. This results in non-linear distortions for image recording under water, which are a major problem for many tasks of the computer vision.
Fraunhofer IGD developed an interactive 3D model that physically correctly represents the path of light from a point of view in the water, through a protective, flat boundary surface (eg glass) to the image sensor of a camera. The simulation of the beam path in 3D is an aid for understanding the processes of image formation in single and stereo camera systems. Based on the concept of the “apparent depth” of an object point, a novel model of a virtual camera could be developed. This allows the media transitions to be virtually eliminated. This is also illustrated by a 3D modeling.
A further model could be derived from the concept of the “apparent depth”. With this model for virtual object points different adapted algorithms for computer vision disciplines under water - like calibration of the system and 3D-reconstruction - could be developed. This makes the correct calibration of an underwater stereo camera system considerably easier.