Underwater stereo using natural flickering illumination

Computer vision is challenged by the underwater environment. Poor visibility, geometrical distortions and non-uniform illumination typically make underwater vision less trivial than open air vision. One effect which can be rather strong in this domain is sunlight flicker. Here, submerged objects and the water volume itself are illuminated in a natural random pattern, which is spatially and temporally varying. This phenomenon has been considered mainly as a significant disturbance to vision. We show that the spatiotemporal variations of flicker can actually be beneficial to underwater vision. Specifically, flicker disambiguates stereo correspondence. This disambiguation is very simple, yet it yields accurate results. Under flickering illumination, each object point in the scene has a unique, unambiguous temporal signature. This temporal signature enables us to find dense and accurate correspondence underwater. This process may be enhanced by involving the spatial variability of the flicker field in the solution. The method is demonstrated underwater by in-situ experiments. This method may be useful to a wide range of shallow underwater applications.