Underwater television

(communications) The technique of using remotely controlled television equipment under the surface of the water.

Any type of electronic camera that is located underwater in order to collect and display images. It must be packaged in a waterproof housing. The underwater camera may be packaged with its own recording device, or it can be attached to a television that is located on a ship, in a laboratory, or at a remote site. In the latter case, the images by the camera are real-time images. An underwater television may be used for sport, ocean exploration, industrial applications, or military purposes. Common imaged subjects are animals, coral reefs, underwater shipwrecks, and underwater structures such as piers, bridges, and offshore oil platforms.

During the daytime and at minimal depths, underwater television can be used to view objects illuminated with natural sunlight. For nighttime viewing or at very deep depths, artificial lights must be used. Light in the ocean is reduced in intensity quite severely: even in the clearest natural waters, a beam of blue or green light will be reduced in intensity by approximately 67% every 230 ft (70 m). Light that is propagating through an aqueous medium such as seawater or lake water will also be selectively reduced in intensity, based on wavelength. In most situations, the extreme reds and blues will be most severely attenuated, with the region of highest clarity being the yellow to blue-green wavelengths. See also Electromagnetic radiation.

Modern advances in television cameras have opened up a host of applications for underwater viewing, such as of standard-video, charge-injection-device, silicon-intensified-target, or charge-coupled-device cameras. These cameras can be adapted for high frame rate, low light level, or underwater color imaging. Computer modeling of underwater images can be used to predict the performance of an underwater imaging system in terms of range of viewing and quality of images as a function of the clarity of the water. See also Charge-coupled devices; Underwater photography.