Optical camouflage

Active camouflage or adaptive camouflage is camouflage that adapts, often rapidly, to the surroundings of an object such as an animal or military vehicle. In theory, active camouflage could provide perfect concealment from visual detection.

Active camouflage is used in several groups of animals, including reptiles on land, and cephalopod molluscs and flatfish in the sea. Animals achieve active camouflage both by color change and (among marine animals such as squid) by counterillumination, with the use of bioluminescence.

Military counterillumination camouflage was first investigated during World War II for marine use. More recent research has aimed to achieve crypsis by using cameras to sense the visible background, and by controlling Peltier panels or coatings that can vary their appearance.

Active camouflage provides concealment by making an object not merely generally similar to its surroundings, but effectively invisible through accurate mimicry, and by changing the appearance of the object as changes occur in its background.

Military interest in active camouflage has its origins in Second World War studies of counter-illumination. The first of these was the so-called diffused lighting camouflage tested on Canadian Navy corvettes including HMCS Rimouski. This was followed in the armed forces of the United States of America with the airborne Yehudi lights project, and trials in ships of the Royal Navy and the US Navy. The Yehudi lights project placed low-intensity blue lights on aircraft. As night skies are not pitch black, an unilluminated aircraft (of any color) might be rendered visible. By emitting a small, measured amount of blue light, the aircraft's average brightness better matches that of the night sky, and the aircraft is able to fly closer to its target before being detected.

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