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| {{SI}}
| | #REDIRECT [[Thermography (Sympathetic galvonic skin studies)]] |
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| ==Overivew==
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| [[Image:Infrared dog.jpg|thumb|left|332px|Image of a small dog taken in mid-[[infrared]] ("thermal") light (false color)]] | |
| [[Image:wiki ostrich.jpg|thumb|left|Thermographic image of two ostriches]]
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| [[Image:wiki stranglesnake.jpg|thumb|left|Thermographic image of a snake held by a human]]
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| [[Image:wiki lion.jpg|thumb|left|Thermographic image of a lion]]
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| [[Image:Passivhaus thermogram gedaemmt ungedaemmt.png|thumb|left|Thermographic image of a traditional building in the background and a 'passive house' in the foreground]]
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| [[Image:electrical_fault.jpg|thumb|left|This thermograph shows a fault with an industrial electrical fuse block.]]
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| '''Thermography''', '''thermal imaging''', or '''thermal video''', is a type of [[infrared]] imaging. Thermographic cameras detect [[electromagnetic radiation|radiation]] in the [[infrared]] range of the [[electromagnetic spectrum]] (roughly 900–14,000 [[nanometer]]s or 0.9–14 [[µm]]) and produce images of that radiation. Since infrared radiation is emitted by all objects based on their temperatures, according to the [[black body]] [[Planck's law of black-body radiation|radiation law]], thermography makes it possible to "see" one's environment with or without [[optical spectrum|visible]] illumination. The amount of radiation emitted by an object increases with temperature, therefore thermography allows one to see variations in temperature (hence the name). When viewed by thermographic camera, warm objects stand out well against cooler backgrounds; humans and other warm-blooded animals become easily visible against the environment, day or night. As a result, thermography's extensive use can historically be ascribed to the military and security services.
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| Thermal imaging photography finds many other uses. For example, [[firefighter]]s use it to see through [[smoke]], find persons, and localize the base of a fire. With thermal imaging, [[electric power transmission|power line]]s maintenance technicians locate overheating joints and parts, a telltale sign of their failure, to eliminate potential hazards. Where [[thermal insulation]] becomes faulty, building construction technicians can see heat leaks to improve the efficiencies of cooling or heating air-conditioning. Thermal imaging cameras are also installed in some luxury cars to aid the driver, the first being the 2000 Cadillac DeVille. Some physiological activities, particularly responses, in human beings and other warm-blooded animals can also be monitored with thermographic imaging.
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| [http://www.sadcom.com/night/night1.htm]
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| The appearance and operation of a modern [[infrared camera|thermographic camera]] is often similar to a [[camcorder]]. Enabling the user to see in the infrared spectrum is a function so useful that ability to record their output is often optional. A recording module is therefore not always built-in.
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| Instead of [[charge coupled device|CCD]] sensors, most thermal imaging cameras use [[CMOS]] Focal Plane Array ([[FPA]]). The most common types are [[InSb]], [[InGaAs]], [[QWIP]] FPA. The newest technologies are using low cost and uncooled [[microbolometer]]s FPA sensors. Their resolution is considerably lower than of optical cameras, mostly 160x120 or 320x240 [[pixels]], up to 640x512 for the most expensive models. Thermographic cameras are much more expensive than their visible-spectrum counterparts, and higher-end models are often export-restricted. Older [[bolometer]]s or more sensitive models as InSB require cryogenic cooling, usually by a miniature [[Stirling cycle]] refrigerator or [[liquid nitrogen]].
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| ==Difference between IR film and thermography==
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| IR film is sensitive to temperatures between 250 °[[Celsius|C]] and 500 °C while thermography is sensitive to approximately -50 °C to over 2,000 °C. So for a IR film to show something it must be over 250 °C or be reflecting infrared radiation from something that is at least that hot. Night vision goggles normally just amplify the small amount of [[light]] that is available outside like starlight or moon light and can't see heat or work in complete darkness.
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| ==Advantages of Thermography==
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| * You get a visual picture so that you can compare temperatures over a large area
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| * It is real time capable of catching moving targets
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| * Able to find deteriorating components prior to failure
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| * Measurement in areas inaccessible or hazardous for other methods
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| ==Limitations & disadvantages of thermography==
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| * Quality cameras are expensive and are easily damaged
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| * Images can be hard to interpret accurately even with experience
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| * Accurate temperature measurements are very hard to make because of emissivities
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| * Most cameras have ±2% or worse accuracy (not as accurate as contact)
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| * Training and staying proficient in IR scanning is time consuming
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| ==Applications==
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| * Condition monitoring
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| * Medical imaging
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| * Research
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| * Process control
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| * Non destructive testing
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| * [[Chemical imaging]]
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| Thermal infrared imagers convert the [[energy]] in the infrared wavelength into a visible light [[video]] display. All objects above 0 [[kelvin]]s emit thermal infrared energy so thermal imagers can passively see all objects regardless of ambient light. However, most thermal imagers only see objects warmer than -50 °C.
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| The [[Thermal radiation#Properties|spectrum and amount of thermal radiation]] depend strongly on an object's surface temperature. This makes it possible for a thermal camera to display an object's temperature. However, other factors also influence the radiation, which limits the accuracy of this technique. For example, the radiation depends not only on the temperature of the object, but is also a function of the [[emissivity]] of the object. Also, radiation also originates from the surroundings and is reflected in the object, and the radiation from the object and the reflected radiation will also be influenced by the [[absorption]] of the [[atmosphere]].
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| ==See also==
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| * [[Infrared camera]]
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| * [[Infrared thermometer]]
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| * [[Infrared detector]]
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| * [[Chemical Imaging]]
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| ==External links==
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| *[http://www.goinfrared.com/success/image_gallery.asp Good examples of FLIR thermographic images broken down by industry application]
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| *[http://www.irinfo.org/ IrInfo.org, online resource for infrared thermography]
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| *[http://www.infratec.de/en/infratec/submenu/theory/basics.html Physical basics]
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| *[http://www.radio101.info/thermographie/pictures.htm various examples of thermographic images]
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| *[http://vzone.virgin.net/ljmayes.mal/pubs/uncooled.htm Uncooled Thermal Imaging]
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| [[Category:Thermodynamics]]
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| [[Category:Measurement]]
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| [[ca:Termografia]]
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| [[de:Thermografie]]
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| [[fr:Thermographie]]
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| [[it:Termografia]]
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| [[he:תרמוגרפיה]]
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| [[nl:Thermografie]]
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| [[ja:サーモグラフィー]]
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| [[pl:Termografia]]
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| [[pt:Termografia]]
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| [[ur:حراری تخطیط]]
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| {{WH}}
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| {{WikiDoc Sources}}
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