Laser systems and structured illumination for quantitative undersea imaging

This paper describes several recently developed approaches that are being used by underwater scientists and technologists to improve the amount and quality of quantitative data that can be obtained from conventional film-recording and video cameras. The use of parallel lasers, which produce a pair of small light spots of known separation on film and video images, provides direct scale information on the images. Additional lasers allow calculations of range, orientation, area-of-coverage and feature size to be made. Structured or non uniform illumination techniques provide vision systems with perspective data, and collimated illuminators facilitate photographic recording of particles within a known water volume. These recently developed illumination techniques are gaining increased acceptance for quantitative undersea imaging applications.