Underwater Radiance Scanner.
NAVAL ELECTRONICS LAB CENTER SAN DIEGO CALIF
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The Underwater Radiance Scanner was developed to measure radiance distributions of natural light fields underwater. It was deployed in a series of experiments designed to validate a model describing propagation of optical energy from a satellite to an underwater terminal. In addition to measuring radiance distribution, the instrument is required to rapidly sample the solar energy distributions found just below the surface at an adequate rate to define the sea surface wave slope statistics. A Radiance Camera system was designed around the Nikkor fisheye lens, which has a nominal field of 180 degrees. Since an entire hemisphere is projected onto a photographic film in the focal plane of the fisheye lens, it became practicable for the first time to acquire data of high resolution rapidly. Two such cameras were mounted together, one covering the upper hemisphere, the other the lower, to obtain complete radiance distributions. The usual problems of using film to make photometric measurements are encountered in the radiance camera. It is necessary to take two frames at differing exposure values to accommodate the dynamic range of the scene. Data reduction is accomplished after careful film processing using an automatic scanning microdensitometer coupled to a computer.