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.
Active camouflage may now develop using organic light-emitting diodes (OLEDs) 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. Camouflage is weakened by motion, but active camouflage could still make moving targets more difficult to see. However, active camouflage works best in one direction at a time, requiring knowledge of the relative positions of the observer and the concealed object.
Active camouflage technology exists only in theory and proof-of-concept prototypes. 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 viewer stands in front of the cloth viewing the cloth through a transparent glass plate. A video camera behind the cloth captures the background behind the cloth. A video projector projects this image on to the glass plate which is angled so that it acts as a partial mirror reflecting a small portion of the projected light onto the cloth. The retroreflectors in the cloth reflect the image back towards the glass plate which being only weakly reflecting allows most of the retroreflected light to pass through to be seen by the viewer. The system only works when seen from a certain angle.
Phased array optics (PAO) would implement active camouflage, not by producing a two-dimensional image of background scenery on an object, but by computational holography to produce a three-dimensional hologram of background scenery on an object to be concealed. Unlike a two-dimensional image, the holographic image would appear to be the actual scenery behind the object independent of viewer distance or view angle.
In 2011, BAE Systems announced their Adaptiv infrared camouflage technology. It uses about 1000 hexagonal Peltier panels to cover the sides of a tank. 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.
Active camouflage is used in several groups of animals including cephalopod molluscs, fish, and reptiles. There are two mechanisms of active camouflage in animals: Counterillumination camouflage, and color change.
Counterillumination camouflage is the production of light to blend in against a lit background. In the sea, light comes down from 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 camouflage 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 only camouflage.
Active camouflage by color change is used by many bottom-living flatfish such as plaice, sole, and flounder that actively copy the patterns and colors of the seafloor below them. For example, the tropical flounder Bothus ocellatus can match its pattern to "a wide range of background textures" in 2–8 seconds. Similarly, the coral reef fish, the seaweed blenny can match its coloration to its surroundings.
- The eponymous antagonists in the Predator films use active camouflage.
- In the video game series Halo, active camouflage is an alien light-bending technology.
- In the video game Deus Ex: Human Revolution, the Glass Shield Cloaking System is a sub-epidermic, neurally controlled system able to bend light with an electromagnetic field, acting as an active camouflage.
- In the video game series Crysis, the CryNet Nanosuit powered exoskeleton is equipped with active camouflage.
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In-game menu: The Glass-Shield Cloaking System is composed of a grid of fine induction wires connected to a deep-tissue control implant (typically located in the back or ribcage) which, in turn, is linked to the brain. The matrix can be layered directly beneath the surface of the epidermis or over the plating of cybernetic limbs; when activated, it generates a tuned, fixed-focus electromagnetic field that temporarily adjusts the frequency of EM radiation around the user. The net effect is a 'cloak of invisibility' which appears near-perfect. […] Experienced users can learn to adeptly and efficiently enhance the shield's functionality while expending even less bio-energy, thus significantly extending operational time to 7 seconds per energy cell.
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CLOAK ENGAGED: Vanish in broad daylight with active camouflage.
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