Active camouflage the surface, so when marine animals are seen from below, they appear darker than the background. Some species of cephalopod, such as the eye-flash squid and the firefly squid, produce light in photophores on their undersides to match the background. Bioluminescence is common among marine animals, so counterillumination may be widespread, though light has other functions, including attracting prey and signalling. Color change permits camouflage against different backgrounds. Many cephalopods including octopuses, cuttlefish, and squids, and some terrestrial amphibians and reptiles including chameleons and anoles can rapidly change color and pattern, though the major reasons for this include signalling, not
Active camouflage 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 with "illusory transparency" 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