Active camouflage

[1] Active camouflage is used in several groups of animals, including reptiles on land, and cephalopod molluscs and flatfish in the sea.

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.

[2] Bioluminescence is common among marine animals, so counter-illumination may be widespread, though light has other functions, including attracting prey and signaling.

The first of these was the so-called diffused lighting camouflage tested on Canadian Navy corvettes including HMCS Rimouski.

Active camouflage may now develop using organic light-emitting diodes and other technologies which allow for images to be projected onto irregularly shaped surfaces.

Using visual data from a camera, an object could perhaps be camouflaged well enough to avoid detection by the human eye and optical sensors when stationary.

However, active camouflage works best in one direction at a time, requiring knowledge of the relative positions of the observer and the concealed object.

[1] In 2003 researchers at the University of Tokyo under Susumu Tachi created a prototype active camouflage system using material impregnated with retroreflective glass beads.

The panels are rapidly heated and cooled to match either the temperature of the vehicle's surroundings, or one of the objects in the thermal cloaking system's "library" such as a truck, car or large rock.

Photograph of a camouflaged cuttlefish
Cephalopod molluscs such as this cuttlefish can change color rapidly for signaling or to match their backgrounds .
Drawing showing principle of squid counter-illumination camouflage
Counter-illumination camouflage of the firefly squid, Watasenia scintillans uses bioluminescence to match brightness and color of the sea surface above.
Photographs of a fish changing its coloration to match background
Four frames of a peacock flounder show its ability to match its coloration to the sea bed around and beneath it.
Illustration of principle of Yehudi lights, Second World War active aircraft camouflage using forward-pointing lamps of variable brightness
Yehudi lights prototype raised the average brightness of a Grumman Avenger from a dark shape to the same as the sky.
Illustration of principle of illusory transparency camouflage
An invisibility cloak using active camouflage by Susumu Tachi. Left: The cloth seen without a special device. Right: The same cloth seen through the half-mirror projector part of the Retro-Reflective Projection Technology
Photographs of an armoured vehicle through an infra-red night sight, purportedly showing active camouflage panels in use
An armoured vehicle fitted with Adaptiv infrared side panels, switched off (left), and on to simulate a large car (right) [ 15 ]