Experiments using a 525 nm time-of-flight camera for object imagining and ranging in clear and turbid water

This paper presents experiments using a time of flight (ToF) camera modified to use 525 nm green laser illumination to capture amplitude and depth images of an underwater scene. Experiments in object imaging and ranging were conducted in both clear and turbid water. 3D imaging using flood illumination was successfully performed in clear water and in some turbid water conditions. Ranging using collimated laser beams was performed in turbid water. Several major error sources were observed, including low illumination levels, fixed pattern noise, and backscatter contribution to the phase measurement. To attempt to address these concerns, multiple lasers were used to improve illumination levels and spatial frequency domain filtering was performed to mitigate fixed pattern noise. Additionally, experiments with using multiple modulation frequencies suggested that there may be potential for discriminating backscatter from object reflection.