Editing Active camouflage

{{Short description|Camouflage changing continually to match background}}
{{Good article}}
[[File:Cuttlefish color.jpg|thumb|[[Cephalopod]] molluscs such as this [[cuttlefish]] can change color rapidly for [[signalling theory|signaling]] or to [[camouflage|match their backgrounds]].|alt=Photograph of a camouflaged cuttlefish]]
'''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.<ref name="McKee Tack 2007">{{cite report |last1=McKee |first1=Kent W. |last2=Tack |first2=David W. |date=February 2007 |title=Active Camouflage for Infantry Headwear Applications |url=https://apps.dtic.mil/sti/pdfs/ADA477147.pdf |publisher=Humansystems |pages=iii |archive-url=https://web.archive.org/web/20121007125730/http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA477147 |url-status=live |archive-date=October 7, 2012}}</ref>

Active camouflage occurs in several groups of animals, including [[reptile]]s on land, and [[cephalopod]] [[mollusc]]s and [[flatfish]] in the sea. Animals achieve active camouflage both by [[Camouflage#Changeable skin coloration|color change]] and (among marine animals such as squid) by [[counter-illumination]], with the use of [[bioluminescence]].

Military counter-illumination 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 systems that can vary their appearance, such as coatings, or variable temperature [[infrared]] panels using the [[Peltier effect]].

==In animals==

[[File:Squid Counterillumination.png|thumb|[[Counter-illumination]] [[camouflage]] of the firefly squid, ''[[Watasenia scintillans]]'' uses [[bioluminescence]] to match brightness and color of the sea surface above.|alt=Drawing showing principle of squid counter-illumination camouflage]]
{{See also|List of camouflage methods|Animals that can change color}}

Active camouflage is used in several groups of animals including cephalopod molluscs,<ref name="Abralia with photo"/> fish,<ref name="Sumner"/> and reptiles.<ref name="Wallin"/> There are two mechanisms of active camouflage in animals: [[Camouflage#Changeable skin coloration|color change]]<ref name="Wallin"/> and [[counter-illumination]].<ref name="Abralia with photo"/>

===Counter-illumination===
{{Further|Counter-illumination}}

Counter-illumination is camouflage using 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 [[Abralia veranyi|eye-flash squid]] and the [[firefly squid]], produce light in [[photophores]] on their undersides to match the background.<ref name="Abralia with photo">{{cite web |url=http://ocean.si.edu/ocean-photos/midwater-squid-abralia-veranyi |title=Midwater Squid, Abralia veranyi |publisher=Smithsonian National Museum of Natural History |access-date=28 November 2011}}</ref> [[Bioluminescence]] is common among marine animals, so counter-illumination may be widespread, though light has other functions, including attracting prey and signaling.<ref name="Young">{{Cite journal |last1=Young |first1=R.E. |last2=Roper |first2=C.F. |year=1976 |title=Bioluminescent countershading in midwater animals: evidence from living squid |journal=Science |volume=191 |issue=4231 |pages=1046–1048 |doi=10.1126/science.1251214 |pmid=1251214 |bibcode=1976Sci...191.1046Y}}</ref><ref name=Haddock>{{cite journal |last1=Haddock |first1=S. H. D. |author1-link=Steven Haddock |display-authors=etal |date=2010 |title=Bioluminescence in the Sea |journal=Annual Review of Marine Science |volume=2 |pages=443–493 |doi=10.1146/annurev-marine-120308-081028 |pmid=21141672|bibcode=2010ARMS....2..443H}}</ref>

===Color change===

[[File:Peacock Flounder Bothus mancus in Kona.jpg|thumb|Four frames of a [[peacock flounder]] show its ability to match its coloration to the sea bed around and beneath it.|alt=Photographs of a fish changing its coloration to match background]]
{{Further|Chromatophore}}

Color change permits camouflage against different backgrounds. Many cephalopods including [[octopus]]es, [[cuttlefish]], and [[squid]]s, and some terrestrial amphibians and reptiles including [[chameleon]]s and [[Dactyloidae|anole]]s can rapidly change color and pattern, though the major reasons for this include [[Signalling theory|signaling]], not only camouflage.<ref>{{cite book |last1=Forbes |first1=Peter |date=2009 |title=[[Dazzled and Deceived]]: Mimicry and Camouflage |publisher=[[Yale University Press]] |isbn=978-0-300-17896-8}}</ref><ref name="Wallin">{{cite book |last1=Wallin |first1=Margareta |year=2002 |url=http://bioenv.gu.se/digitalAssets/1566/1566454_palettse.pdf |language=sv |title=Naturens palett: Hur djur och människor får färg |trans-title=Nature's Palette: How animals, including humans, produce colors |publisher=Bioscience-explained.org |volume=1 |issue=2 |pages=1–12 |place=Sweden |access-date=9 January 2017 |archive-date=24 June 2020 |archive-url=https://web.archive.org/web/20200624183925/http://bioenv.gu.se/digitalAssets/1566/1566454_palettse.pdf |url-status=dead}}</ref> Cephalopod active camouflage has stimulated military research in the United States.<ref>{{cite book |last1=Reid |first1=Amanda |year=2016 |title=Cephalopods of Australia and Sub-Antarctic Territories |publisher=CSIRO |page=7 |isbn=978-1-486-30393-9 |url=https://books.google.com/books?id=-3-NDAAAQBAJ&pg=PA7 |quote=Not surprisingly, this aspect of cephalopod biology has become the subject of US military research with millions of dollars currently being poured into studies on cephalopod camouflage.}}</ref>

Active camouflage by color change is used by many bottom-living [[flatfish]] such as [[plaice]], [[Sole (fish)|sole]], and [[flounder]] that actively copy the patterns and colors of the seafloor below them.<ref name="Sumner">{{cite journal |last1=Sumner |first1=Francis B. |date=May 1911 |title=The adjustment of flatfishes to various backgrounds: A study of adaptive color change |journal=Journal of Experimental Zoology |volume=10 |issue=4 |pages=409–506 |doi=10.1002/jez.1400100405 |url=https://zenodo.org/record/1426860}}</ref> For example, the tropical flounder ''[[Bothus|Bothus ocellatus]]'' can match its pattern to "a wide range of background textures"<ref name="Ramachandran"/> in 2–8 seconds.<ref name="Ramachandran">{{cite journal |last1=Ramachandran |first1=V. S. |last2=Tyler |first2=C. W. |last3=Gregory |first3=R. L. |last4=Rogers-Ramachandran |first4=D. |last5=Duensing |first5=S. |last6=Pillsbury |first6=C. |last7=Ramachandran |first7=C. |date=29 February 1996 |title=Rapid Adaptive Camouflage in Tropical Flounders |journal=Letters to Nature |volume=379 |issue=6568 |pages=815–818 |doi=10.1038/379815a0 |pmid=8587602 |bibcode=1996Natur.379..815R |s2cid=4304531}}</ref> Similarly, the [[coral reef]] fish, the [[seaweed blenny]] can match its coloration to its surroundings.<ref name=FMNH>{{cite web |last1=Bester |first1=Cathleen |title=Seaweed blenny |work=Ichthyology |publisher=Florida Museum of Natural History |url=http://www.flmnh.ufl.edu/fish/Gallery/Descript/SeaweedBlenny/SeaweedBlenny.html |access-date=6 January 2015 |archive-date=20 September 2015 |archive-url=https://web.archive.org/web/20150920190426/http://www.flmnh.ufl.edu/fish/Gallery/Descript/SeaweedBlenny/SeaweedBlenny.html |url-status=dead}}</ref>

==In research==

Active camouflage provides concealment by making an object not merely generally similar to its surroundings, but effectively [[invisibility|invisible]] with "illusory transparency" through accurate [[mimicry]], and by changing the appearance of the object as changes occur in its background.<ref name="McKee Tack 2007"/>

===Early research===

[[File:Principle of Yehudi Lights with Avenger head-on view.jpg|thumb|[[Yehudi lights]] prototype raised the average brightness of a [[Grumman Avenger]] from a dark shape to the same as the sky.|alt=Illustration of principle of Yehudi lights, Second World War active aircraft camouflage using forward-pointing lamps of variable brightness]]
{{Further|Diffused lighting camouflage|Yehudi lights}}

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 Forces Maritime Command|Canadian Navy]] [[corvettes]] including {{HMCS|Rimouski|K121|6}}. This was followed in the [[United States Army Air Forces]] with the airborne [[Yehudi lights]] project, and trials in ships of the [[Royal Navy]] and the [[US Navy]].<ref name="NavalMuseumQuebec">{{cite web |url=http://www.navy.forces.gc.ca/navres/NMQ_MNQ/researches_recherches/diffusedLighting_camouflageLumineux/index-eng.asp |title=Naval Museum of Quebec |publisher=Royal Canadian Navy |work=Diffused Lighting and its use in the Chaleur Bay |access-date=19 January 2012 |url-status=dead |archive-url=https://web.archive.org/web/20130522231113/http://www.navy.forces.gc.ca/navres/NMQ_MNQ/researches_recherches/diffusedLighting_camouflageLumineux/index-eng.asp |archive-date=22 May 2013 }}</ref> The Yehudi lights project placed low-intensity blue lights on aircraft. As skies are bright, 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 sky, and the aircraft is able to fly closer to its target before being detected.<ref name=NDRC>{{cite report |last1=Bush |first1=Vannevar |author1-link=Vannevar Bush |last2=Conant |first2=James |last3=Harrison |first3=George |date=1946 |url=http://www.dtic.mil/dtic/tr/fulltext/u2/221102.pdf |archive-url=https://web.archive.org/web/20131023061821/http://www.dtic.mil/dtic/tr/fulltext/u2/221102.pdf |url-status=dead |archive-date=October 23, 2013 |work=Visibility Studies and Some Applications in the Field of Camouflage |publisher=Office of Scientific Research and Development, National Defence Research Committee |title=Camouflage of Sea-Search Aircraft |access-date=12 February 2013 |pages=225–240}}</ref>
Bell Textron filed for a patent on 1/28/2021, # 17/161075 Active Aircraft Visual Cloaking System, that proposes using electroluminescent paint along with an active camera system to project and control a luminescent paint scheme to blend the aircraft exterior structure with the sky.

===Possible technologies===

Active camouflage may now develop using [[organic light-emitting diode]]s and other technologies which allow 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.<ref name="McKee Tack 2007"/>

[[File:An invisibility cloak using optical camouflage by Susumu Tachi.jpg|thumb|An [[cloaking device|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|alt=Illustration of principle of illusory transparency camouflage]]

In 2003 researchers at the [[University of Tokyo]] under [[Susumu Tachi]] created a prototype active camouflage system using material impregnated with [[Retroreflector|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 [[Pepper's ghost|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.<ref>{{cite web |title=Light and Dark: The Invisible Man |url=http://www.time.com/time/2003/inventions/invinvisible.html |publisher=Time magazine |date=18 November 2003 |access-date=8 January 2022 |archive-url=https://web.archive.org/web/20031118181052/http://www.time.com/time/2003/inventions/invinvisible.html |archive-date=18 November 2003 |url-status=dead}}</ref>

[[Phased-array optics]] would implement active camouflage, not by producing a two-dimensional image of background scenery on an object, but by [[Computer-generated holography|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.<ref>{{cite book |last1=Wowk |first1=Brian |author1-link=Brian Wowk |year=1996 |chapter=Phased Array Optics |title=Molecular Speculations on Global Abundance |editor1-last=Crandall |editor1-first=B.C. |publisher=[[MIT Press]] |pages=[https://archive.org/details/nanotechnology00bccr/page/147 147–160] |isbn=978-0-262-03237-7 |chapter-url=http://www.phased-array.com/1996-Book-Chapter.html |access-date=18 February 2007 |url-access=registration |url=https://archive.org/details/nanotechnology00bccr/page/147}}</ref>

===Military prototypes===
[[File:Adaptiv infrared camouflage demo hiding tank as car.jpg|thumb|upright=1.4|An armoured vehicle fitted with ''[[Adaptiv]]'' [[infrared]] side panels, switched off (left), and on to simulate a large car (right)<ref name=Adaptiv-Cloak/>|alt=Photographs of an armoured vehicle through an infrared night sight, purportedly showing active camouflage panels in use]]

In 2010, the Israeli company Eltics created an early prototype of a system of tiles for infrared camouflage of vehicles. In 2011, [[BAE Systems]] announced its ''[[Adaptiv]]'' [[infrared]] camouflage technology. Adaptiv uses about 1000 hexagonal [[Peltier panel]]s 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.<ref name=Schechter>{{cite magazine |last1=Schechter |first1=Erik |date=1 July 2013 |title=Whatever Happened to Counter-Infrared Camouflage? |url=http://www.popularmechanics.com/military/research/a9172/whatever-happened-to-counter-infrared-camouflage-15648261/ |magazine=Popular Mechanics |access-date=19 February 2017}}</ref><ref name=Adaptiv-Cloak>{{cite web |url=http://www.baesystems.com/magazine/BAES_019786/adaptiv--a-cloak-of-invisibility |title=Adaptiv-A Cloak of Invisibility |publisher=BAE Systems |year=2011 |access-date=13 June 2012}}</ref><ref>{{cite web |url=https://www.bbc.co.uk/news/technology-14788009 |title=BBC News Technology |publisher=BBC |work=Tanks test infrared invisibility cloak |date=5 September 2011 |access-date=27 March 2012}}</ref>

== In fiction ==

Active camouflage technology, both visual and otherwise, is a commonly used plot device in [[science fiction]] stories. The ''[[Star Trek]]'' franchise incorporated the concept ("cloaking device"), and ''[[Star Trek: Voyager]]'' depicts humans using "bio-dampeners" to infiltrate a [[Borg Cube]] without the antagonists realizing they are there.<ref>{{Cite book |last1=Lasbury |first1=Mark E. |date=24 August 2016 |url=https://www.worldcat.org/oclc/950954032 |title=The realization of Star Trek technologies: the science, not fiction, behind brain implants, plasma shields, quantum computing, and more |publisher=Springer International Publishing |isbn=978-3-319-40912-2 |location=Switzerland |pages=39 |oclc=950954032 |access-date=30 May 2021}}</ref> The eponymous antagonists in the [[Predator (franchise)|''Predator'' films]] also use active camouflage.<ref name="robley">{{cite news |last1=Robley |first1=Les Paul |date=December 1987 |title=''Predator'': Special Visual Effects |publisher=[[Cinefantastique]]}}</ref> In many video games, such as the ''[[Halo (video game series)|Halo]]'' series,<ref>{{cite book |date=2013 |title=Halo 4: The Essential Visual Guide |publisher=[[Dorling Kindersley]] |page=136 |isbn=978-1-4654-1159-4}}</ref><ref>{{cite book |last1=Radcliffe |first1=Doug |date=2003 |title=Halo: Combat Evolved, Sybex official strategies & secrets |publisher=[[Sybex]] |page=27 |isbn=978-0-7821-4236-5}}</ref><ref>{{cite book |last1=Walsh |first1=Doug |last2=Marcus |first2=Phillip |last3=Hunsinger |first3=Rich |author4=Sea Snipers |date=2010 |title=Halo: Reach, Signature Series Guide |publisher=[[BradyGames]] |pages=20, 253 |isbn=978-0744012323}}</ref> ''[[Deus Ex: Human Revolution]]'',<ref>{{cite video game |title=[[Deus Ex: Human Revolution]] |developer=[[Eidos Montréal]] |publisher=[[Square Enix]] |date=23 August 2011 |platform=[[Windows]], [[PlayStation 3]], [[Xbox 360]], [[Wii U]], [[macOS]]}}</ref> and the ''[[Crysis (series)|Crysis]]'' series,<ref name=Crysis>{{cite web |url=http://www.crysis.com/au/crysis-3/adaptive-warfare |title=Crysis 3: Adaptive Warfare |website=Crysis.com |publisher=[[Crytek]] |access-date=28 July 2016 |quote=Cloak Engaged: Vanish in broad daylight with active camouflage. |archive-url=https://web.archive.org/web/20160813030615/http://www.crysis.com/au/crysis-3/adaptive-warfare |archive-date=13 August 2016 |url-status=dead}}</ref> players can obtain and use cloaking devices.<ref name=Crysis/> In the 2002 James Bond film ''[[Die Another Day]]'', Bond's [[Aston Martin V12 Vanquish]] is fitted with an active camouflage system.<ref>{{cite journal |title=Technology in the James Bond Universe |journal=Today's Engineer |date=2006 |issue=January |url=https://ethw.org/Technology_in_the_James_Bond_Universe?veaction=edit |access-date=14 December 2021}}</ref>
<!-- Do not add anything here without a reliable source as a reference, please. -->

== See also ==
* [[Cloaking device]]
* [[Cloak of invisibility]]
* [[Penetration aid]]
* [[Snow camouflage]] – color change with the seasons
* [[Stealth technology]]

== References ==

{{Reflist|30em}}

== External links ==
* "[http://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=1&f=G&l=50&d=PG01&p=1&S1=20020090131.PGNR.&OS=DN/20020090131&RS=DN/20020090131 Multi-perspective background simulation cloaking process and apparatus]", [[United States Patent & Trademark Office]]
* [http://www.smh.com.au/articles/2003/03/29/1048653907088.html?oneclick=true "Scientist show off 'invisible coat'"], ''[[The Sydney Morning Herald]]'', 30 March 2003
* [http://www.phased-array.com/1996-Book-Chapter.html Phased Array Optics]
* [http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&co1=AND&d=PTXT&s1=%22thermal+visual+camouflage%22&OS= "Thermal and Visual Camouflage System Patent No 6,338,292] {{Webarchive|url=https://web.archive.org/web/20190814095255/http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&co1=AND&d=PTXT&s1=%22thermal+visual+camouflage%22&OS= |date=2019-08-14}}", [[United States Patent & Trademark Office]]

{{Camouflage}}

{{DEFAULTSORT:Active Camouflage}}
[[Category:Military camouflage types]]
[[Category:Military electronics]]
[[Category:Camouflage mechanisms]]

[[fr:Camouflage (militaire)#Camouflage optique]]