Active camouflage#In animals

File:Squid Counterillumination.png 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, fish, and reptiles. There are two mechanisms of active camouflage in animals: color change and 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 eye-flash squid and the firefly squid, produce light in photophores on their undersides to match the background.{{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}} Bioluminescence is common among marine animals, so counter-illumination may be widespread, though light has other functions, including attracting prey and signaling.{{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}}{{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}}

File:Peacock Flounder Bothus mancus in Kona.jpg 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 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 signaling, not only camouflage.{{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}}{{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}} Cephalopod active camouflage has stimulated military research in the United States.{{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.}}

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.{{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}} For example, the tropical flounder Bothus ocellatus can match its pattern to "a wide range of background textures" in 2–8 seconds.{{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}} Similarly, the coral reef fish, the seaweed blenny can match its coloration to its surroundings.{{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}}

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.

File:Principle of Yehudi Lights with Avenger head-on view.jpg 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 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.{{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 }} 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.{{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}}

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.

Active camouflage may now develop using organic light-emitting diodes 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.

File:An invisibility cloak using optical camouflage by Susumu Tachi.jpg 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 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.{{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}}

Phased-array optics 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.{{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}}

File:Adaptiv infrared camouflage demo hiding tank as car.jpg infrared side panels, switched off (left), and on to simulate a large car (right)|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 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.{{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}}{{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}}{{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}}

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.{{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}} The eponymous antagonists in the Predator films also use active camouflage.{{cite news |last1=Robley |first1=Les Paul |date=December 1987 |title=Predator: Special Visual Effects |publisher=Cinefantastique}} In many video games, such as the Halo series,{{cite book |date=2013 |title=Halo 4: The Essential Visual Guide |publisher=Dorling Kindersley |page=136 |isbn=978-1-4654-1159-4}}{{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}}{{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}} Deus Ex: Human Revolution,{{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}} and the Crysis series,{{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}} players can obtain and use cloaking devices. In the 2002 James Bond film Die Another Day, Bond's Aston Martin V12 Vanquish is fitted with an active camouflage system.{{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}}

• Cloaking device
• Cloak of invisibility
• Penetration aid
• Snow camouflage – color change with the seasons
• Stealth technology

{{Reflist|30em}}

• "[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