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| | I'm Hunter and I live in Vancouver. <br>I'm interested in Engineering, Skydiving and Chinese art. I like to travel and reading fantasy.<br><br>Feel free to visit my weblog; [https://www.facebook.com/consolidatedcreditcanada Consolidated Credit] |
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| [[File:Ir girl.png|thumb|right|A [[false color]] image of two people taken in long-wavelength infrared (body-temperature thermal) light. ]]
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| [[File:Wide-field Infrared Survey Explorer first-light image.jpg|thumb|right|This infrared space telescope image has (false color) blue, green and red corresponding to 3.4, 4.6, and 12 [[µm]] wavelengths, respectively.]]
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| '''Infrared''' ('''IR''') light is [[electromagnetic radiation]] with longer [[wavelength]]s than those of [[Light|visible light]], extending from the nominal [[red]] edge of the [[visible spectrum]] at 700 [[nanometre|nanometers]] (nm) to 1 mm. This range of wavelengths corresponds to a [[Frequency spectrum|frequency]] range of approximately 430 [[THz]] down to 300 [[GHz]].<ref>{{cite web|author=Liew, S. C. |url=http://www.crisp.nus.edu.sg/~research/tutorial/em.htm |title=Electromagnetic Waves |publisher=Centre for Remote Imaging, Sensing and Processing |accessdate=2006-10-27}}</ref> Most of the [[thermal radiation]] emitted by objects near room temperature is infrared. | |
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| Infrared radiation was discovered in 1800 by astronomer [[William Herschel]], who discovered a type of invisible radiation in the light spectrum beyond red light, by means of its effect upon a thermometer. Slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has a critical effect on Earth's [[climate]].
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| Infrared light is emitted or absorbed by [[molecule]]s when they change their [[Infrared spectroscopy|rotational-vibrational]] movements. Infrared energy elicits [[vibration]]al modes in a [[molecule]] through a change in the [[Molecular dipole moment|dipole moment]], making it a useful frequency range for study of these energy states for molecules of the proper symmetry. [[Infrared spectroscopy]] examines absorption and transmission of [[photon]]s in the infrared energy range.<ref>{{cite web|last=Reusch |first=William |year=1999 |url=http://www.cem.msu.edu/~reusch/VirtualText/Spectrpy/InfraRed/infrared.htm |title=Infrared Spectroscopy |publisher=Michigan State University |accessdate=2006-10-27}}</ref>
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| Infrared light is used in industrial, scientific, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected. [[Infrared astronomy]] uses sensor-equipped [[telescopes]] to penetrate dusty regions of space, such as [[molecular cloud]]s; detect objects such as [[planet]]s, and to view highly [[Redshift|red-shifted]] objects from the early days of the [[universe]].<ref name="ir_astronomy">{{cite web|url=http://www.ipac.caltech.edu/Outreach/Edu/importance.html |title=IR Astronomy: Overview |publisher=NASA Infrared Astronomy and Processing Center |accessdate=2006-10-30}}</ref> Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, and to detect overheating of electrical apparatus.
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| Thermal-infrared imaging is used extensively for military and civilian purposes. Military applications include [[target acquisition]], surveillance, [[night vision]], homing and tracking. Humans at normal body temperature radiate chiefly at wavelengths around 10 μm (micrometers). Non-military uses include [[thermal efficiency]] analysis, environmental monitoring, industrial facility inspections, remote temperature sensing, short-ranged [[wireless communication]], [[spectroscopy]], and [[weather forecasting]].
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| ==Definition and relationship to the electromagnetic spectrum==
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| Infrared light extends from the nominal [[red]] edge of the [[visible spectrum]] at 700 [[nanometre|nanometers]] (nm) to 1 mm. This range of wavelengths corresponds to a [[Frequency spectrum|frequency]] range of approximately 430 [[THz]] down to 300 [[GHz]]. Below infrared is the microwave portion of the electromagnetic spectrum.
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| [[File:ElectromagneticSpectrum5.png|500px|thumb|Infrared in relation to Electromagnetic spectrum]]
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| {| class=wikitable style="text-align:center; font-size:12px; float:center; margin:2px"
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| |- bgcolor= style="font-size: smaller;"
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| | colspan="8" style="text-align:center;"|'''[[Electromagnetic spectrum|Light comparison]]'''<ref>{{cite book|ref=Haynes|editor=Haynes, William M.|year=2011|title= CRC Handbook of Chemistry and Physics |edition=92nd ed.|publisher= CRC Press|isbn=1439855110|page=10.233}}</ref>
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| ! Name || [[Wavelength]] || [[Millihertz|Frequency (Hz)]] || [[Electronvolt#Properties|Photon Energy (eV)]]
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| | [[Gamma ray]] || less than 0.01 nm || more than 30 EHz || 124 keV – 300+ GeV
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| | [[X-Ray]] || 0.01 nm – 10 nm || 30 EHz – 30 PHz || 124 eV – 124 keV
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| | [[Ultraviolet]] || 10 nm – 380 nm || 30 PHz – 790 THz || 3.3 eV – 124 eV
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| |-
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| | [[Visible light|Visible]] || 380 nm–700 nm || 790 THz – 430 THz || 1.7 eV – 3.3 eV
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| |- style="background:#FFE8E8;"
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| | '''Infrared''' || 700 nm – 1 mm || 430 THz – 300 GHz || 1.24 [[milli|m]]eV – 1.7 eV
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| |-
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| | [[Microwave]] || 1 mm – 1 meter || 300 GHz – 300 MHz ||1.24 [[Micro-|µ]]eV – 1.24 meV
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| |-
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| <!-- radio waves _include_ microwaves, so following ranges overlap those above -->
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| | [[Radio waves|Radio]] ||1 mm – 100,000 km || [[Extremely high frequency|300 GHz]] – [[Extremely low frequency|3 Hz]] ||12.4 [[Femto-|f]]eV – 1.24 meV
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| |}
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| ==Natural infrared==
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| Sunlight, at an effective temperature of 5,780 kelvins, is composed of nearly thermal-spectrum radiation that is slightly more than half infrared. At zenith, sunlight provides an [[irradiance]] of just over 1 [[kilowatts]] per square meter at sea level. Of this energy, 527 watts is infrared radiation, 445 watts is [[visible light]], and 32 watts is [[ultraviolet]] radiation.<ref>{{cite web|url=http://rredc.nrel.gov/solar/spectra/am1.5/ |title=Reference Solar Spectral Irradiance: Air Mass 1.5|accessdate=2009-11-12}}</ref>
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| On the surface of Earth, at far lower temperatures than the surface of the Sun, almost all thermal radiation consists of infrared in various wavelengths. Of these natural thermal radiation processes only lightning and natural fires are hot enough to produce much visible energy, and fires produce far more infrared than visible-light energy.
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| ==Regions within the infrared==
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| {{refimprove section|date=July 2006}}
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| In general, objects emit infrared radiation across a spectrum of wavelengths, but sometimes only a limited region of the spectrum is of interest because sensors usually collect radiation only within a specific bandwidth. Thermal infrared radiation also has a maximum emission wavelength, which is inversely proportional to the absolute temperature of object, in accordance with [[Wien's displacement law]].
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| Therefore, the infrared band is often subdivided into smaller sections.
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| === Commonly used sub-division scheme ===
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| A commonly used sub-division scheme is:<ref name="Byrnes">{{Cite book|last=Byrnes |first=James |title=Unexploded Ordnance Detection and Mitigation |publisher=Springer |year=2009 |pages=21–22 |isbn=978-1-4020-9252-7}}</ref>
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| {| class="wikitable"
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| |'''Division Name'''
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| |'''Abbreviation'''
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| |'''Wavelength'''
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| |'''Frequency'''
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| |'''Photon Energy'''
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| |'''Characteristics'''
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| |'''Near-infrared'''
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| |NIR, IR-A ''[[DIN]]''
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| |0.75–1.4 µm
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| | 0.9–1.7 [[Electronvolt|eV]]
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| | Defined by the water absorption, and commonly used in [[fiber optic]] telecommunication because of low attenuation losses in the SiO<sub>2</sub> glass ([[silica]]) medium. [[image intensifier|Image intensifiers]] are sensitive to this area of the spectrum. Examples include [[night vision]] devices such as night vision goggles.
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| |'''Short-wavelength infrared'''
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| | SWIR, IR-B ''DIN''
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| | 1.4-3 µm
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| |.
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| | 0.4–0.9 eV
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| | Water absorption increases significantly at 1,450 nm. The 1,530 to 1,560 nm range is the dominant spectral region for long-distance telecommunications.
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| |{{anchor|MidIR|MWIR|IIR|IR-C}}'''Mid-wavelength infrared'''
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| |MWIR, IR-C ''DIN''; MidIR.<ref name=rdmag20120908>{{Cite news |publication-date=August 14, 2012 |title=Photoacoustic technique 'hears' the sound of dangerous chemical agents |periodical=[[R&D Magazine]] |at=rdmag.com |url=http://www.rdmag.com/News/2012/08/Chemistry-Test-Measurement-Photonics-Photoacoustic-technique-hears-the-sound-of-dangerous-chemical-agents/?et_cid=2797047&et_rid=54719290&linkid=http%3a%2f%2fwww.rdmag.com%2fNews%2f2012%2f08%2fChemistry-Test-Measurement-Photonics-Photoacoustic-technique-hears-the-sound-of-dangerous-chemical-agents |accessdate=September 8, 2012 }}</ref> Also called intermediate infrared (IIR)
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| | 3–8 µm
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| | 150–400 meV
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| | In guided missile technology the 3–5 µm portion of this band is the atmospheric window in which the homing heads of passive IR 'heat seeking' missiles are designed to work, homing on to the [[Infrared signature]] of the target aircraft, typically the jet engine exhaust plume. This region is known as thermal infrared, but it detects only temperatures somewhat above body temperature.
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| | '''Long-wavelength infrared'''
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| | LWIR, IR-C ''DIN''
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| | 8–15 µm
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| | 80–150 meV
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| | The "thermal imaging" region, in which sensors can obtain a completely passive image of objects only slightly higher in temperature than room temperature, (for example, the human body), based on thermal emissions only and requiring no illumination such as the sun, moon, or infrared illuminator. This region is also called the "thermal infrared."
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| |'''Far-infrared'''
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| | FIR
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| | 15–1,000 µm
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| | 1.2–80 meV
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| | (see also [[far-infrared laser]] and [[far infrared]]).
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| |}
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| NIR and SWIR is sometimes called "reflected infrared," whereas MWIR and LWIR is sometimes referred to as "thermal infrared." Due to the nature of the blackbody radiation curves, typical 'hot' objects, such as exhaust pipes, often appear brighter in the MW compared to the same object viewed in the LW.
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| ===CIE division scheme===
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| The [[International Commission on Illumination]] (CIE) recommended the division of infrared radiation into the following three bands:<ref>{{cite web|last=Henderson |first=Roy |url=http://info.tuwien.ac.at/iflt/safety/section1/1_1_1.htm |title=Wavelength considerations |publisher=Instituts für Umform- und Hochleistungs |accessdate=2007-10-18 |archiveurl = http://web.archive.org/web/20071028072110/http://info.tuwien.ac.at/iflt/safety/section1/1_1_1.htm <!-- Bot retrieved archive --> |archivedate = 2007-10-28}}</ref>
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| * IR-A: 700 nm – 1400 nm (0.7 µm – 1.4 µm, 215 THz – 430 THz)
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| * IR-B: 1400 nm – 3000 nm (1.4 µm – 3 µm, 100 THz – 215 THz)
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| * IR-C: 3000 nm – 1 mm (3 µm – 1000 µm, 300 GHz – 100 THz)
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| ===ISO 20473 scheme===
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| [[International Organization for Standardization|ISO]] 20473 specifies the following scheme:<ref>ISO 20473:2007</ref>
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| {| class="wikitable"
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| ! style="width:100pt; text-align:left;"| Designation
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| ! style="width:100pt; text-align:center;"| Abbreviation
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| ! style="width:150pt; text-align:center;"| Wavelength
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| |-
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| |align="left"| Near-Infrared
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| | style="text-align:center;"| NIR
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| | style="text-align:center;"| 0.78–3 µm
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| |-
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| |align="left"| Mid-Infrared
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| | style="text-align:center;"| MIR
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| | style="text-align:center;"| 3–50 µm
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| |-
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| |align="left"| Far-Infrared
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| | style="text-align:center;"| FIR
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| | style="text-align:center;"| 50–1000 µm
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| |}
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| ===Astronomy division scheme===
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| Astronomers typically divide the infrared spectrum as follows:<ref>{{cite web |url=http://www.ipac.caltech.edu/Outreach/Edu/Regions/irregions.html |title=Near, Mid and Far-Infrared |publisher=NASA IPAC |accessdate=2007-04-04}}</ref>
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| {| class="wikitable"
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| |-
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| ! style="width:100pt; text-align:left;"| Designation
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| ! style="width:100pt; text-align:center;"| Abbreviation
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| ! style="width:150pt; text-align:center;"| Wavelength
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| |-
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| |align="left"| Near-Infrared
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| | style="text-align:center;"| NIR
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| | style="text-align:center;"| (0.7–1) to 5 µm
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| |-
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| |align="left"| Mid-Infrared
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| | style="text-align:center;"| MIR
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| | style="text-align:center;"| 5 to (25–40) µm
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| |-
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| |align="left"| Far-Infrared
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| | style="text-align:center;"| FIR
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| | style="text-align:center;"| (25–40) to (200–350) µm.
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| |}
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| These divisions are not precise and can vary depending on the publication. The three regions are used for observation of different temperature ranges, and hence different environments in space.
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| ===Sensor response division scheme===
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| [[File:Atmosfaerisk spredning.gif|thumb|Plot of atmospheric transmittance in part of the infrared region.]]
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| A third scheme divides up the band based on the response of various detectors:<ref name="Miller">Miller, ''Principles of Infrared Technology'' (Van Nostrand Reinhold, 1992), and Miller and Friedman, ''Photonic Rules of Thumb'', 2004. ISBN 9780442012106{{Page needed|date=September 2010}}</ref>
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| *Near-infrared: from 0.7 to 1.0 µm (from the approximate end of the response of the [[human eye]] to that of silicon).
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| *Short-wave infrared: 1.0 to 3 µm (from the cut-off of silicon to that of the MWIR atmospheric window). InGaAs covers to about 1.8 µm; the less sensitive lead salts cover this region.
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| *Mid-wave infrared: 3 to 5 µm (defined by the atmospheric window and covered by [[Indium antimonide]] [InSb] and [[HgCdTe]] and partially by [[lead selenide]] [PbSe]).
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| *Long-wave infrared: 8 to 12, or 7 to 14 µm (this is the atmospheric window covered by HgCdTe and [[microbolometer]]s).
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| *Very-long wave infrared (VLWIR) (12 to about 30 µm, covered by doped silicon).
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| Near-infrared is the region closest in wavelength to the radiation detectable by the [[human eye]], mid- and [[far-infrared]] are progressively further from the [[visible spectrum]]. Other definitions follow different physical mechanisms (emission peaks, vs. bands, water absorption) and the newest follow technical reasons (The common [[silicon]] detectors are sensitive to about 1,050 nm, while [[indium gallium arsenide|InGaAs]]' sensitivity starts around 950 nm and ends between 1,700 and 2,600 nm, depending on the specific configuration). Unfortunately, international standards for these specifications are not currently available.
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| The onset of infrared is defined (according to different standards) at various values typically between 700 nm and 800 nm, but the boundary between visible and infrared light is not precisely defined. The human eye is markedly less sensitive to light above 700 nm wavelength, so longer wavelengths make insignificant contributions to scenes illuminated by common light sources. However, particularly intense near-IR light (e.g., from IR [[laser]]s, IR LED sources, or from bright daylight with the visible light removed by colored gels) can be detected up to approximately 780 nm, and will be perceived as red light. Sources providing wavelengths as long as 1050 nm can be seen as a dull red glow in intense sources, causing some difficulty in near-IR illumination of scenes in the dark (usually this practical problem is solved by indirect illumination). Leaves are particularly bright in the near IR, and if all visible light leaks from around an IR-filter are blocked, and the eye is given a moment to adjust to the extremely dim image coming through a visually opaque IR-passing photographic filter, it is possible to see the ''[[Robert W. Wood|Wood]] effect'' that consists of IR-glowing foliage.<ref>{{Cite journal|title=The Sensitivity of the Human Eye to Infra-Red Radiation |journal=J. Opt. Soc. Am. |volume=37 |issue=7 |pages=546–553 |year=1947 |doi=10.1364/JOSA.37.000546|last1=Griffin|first1=Donald R.|last2=Hubbard|first2=Ruth|last3=Wald|first3=George}}</ref>
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| ===Telecommunication bands in the infrared===
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| In [[optical communications]], the part of the infrared spectrum that is used is divided into seven bands based on availability of light sources transmitting/absorbing materials (fibers) and detectors:<ref>{{cite web|last=Ramaswami |first=Rajiv |date=May 2002 |url=http://ieeexplore.ieee.org/iel5/35/21724/01006983.pdf |format=PDF |title=Optical Fiber Communication: From Transmission to Networking |publisher=IEEE |accessdate=2006-10-18}}</ref>
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| {| class="wikitable"
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| |-
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| !Band
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| !Descriptor
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| !Wavelength range
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| |-
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| |O band
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| |Original
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| |1260–1360 nm
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| |-
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| |E band
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| |Extended
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| |1360–1460 nm
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| |-
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| |S band
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| |Short wavelength
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| |1460–1530 nm
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| |-
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| |C band
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| |Conventional
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| |1530–1565 nm
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| |-
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| |L band
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| |Long wavelength
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| |1565–1625 nm
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| |-
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| |U band
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| |Ultralong wavelength
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| |1625–1675 nm
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| |}
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| The C-band is the dominant band for long-distance [[telecommunication]] networks. The S and L bands are based on less well established technology, and are not as widely deployed.
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| ==Heat==
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| {{Main|Thermal radiation}}
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| Infrared radiation is popularly known as "heat radiation", but light and electromagnetic waves of any frequency will heat surfaces that absorb them. Infrared light from the Sun accounts for 49%<ref>{{cite web|title=Introduction to Solar Energy |work=Passive Solar Heating & Cooling Manual |publisher=Rodale Press, Inc. |year=1980 |url=http://www.azsolarcenter.com/design/documents/passive.DOC |format=[[DOC (computing)|DOC]] |accessdate=2007-08-12}}</ref> of the heating of Earth, with the rest being caused by visible light that is absorbed then re-radiated at longer wavelengths. Visible light or [[ultraviolet]]-emitting [[laser]]s can char paper and incandescently hot objects emit visible radiation. Objects at room [[temperature]] will [[spontaneous emission|emit]] [[Thermal radiation|radiation]] concentrated mostly in the 8 to 25 µm band, but this is not distinct from the emission of visible light by incandescent objects and ultraviolet by even hotter objects (see [[black body]] and [[Wien's displacement law]]).<ref>{{cite web|last=McCreary |first=Jeremy |date=October 30, 2004 |url=http://dpfwiw.com/ir.htm |title=Infrared (IR) basics for digital photographers-capturing the unseen (Sidebar: Black Body Radiation) |publisher=Digital Photography For What It's Worth |accessdate=2006-11-07}}</ref>
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| [[Heat]] is energy in transit that flows due to temperature difference. Unlike heat transmitted by [[thermal conduction]] or [[thermal convection]], thermal radiation can propagate through a [[vacuum]]. Thermal radiation is characterized by a particular spectrum of many wavelengths that is associated with emission from an object, due to the vibration of its molecules at a given temperature. Thermal radiation can be emitted from objects at any wavelength, and at very high temperatures such radiations are associated with spectra far above the infrared, extending into visible, ultraviolet, and even X-ray regions (i.e., the [[solar corona]]). Thus, the popular association of infrared radiation with thermal radiation, is only a coincidence based on typical (comparatively low) temperatures often found near the surface of planet Earth.
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| The concept of [[emissivity]] is important in understanding the infrared emissions of objects. This is a property of a surface that describes how its thermal emissions deviate from the ideal of a [[black body]]. To further explain, two objects at the same physical temperature will not show the same infrared image{{clarify|reason=what property of the emission will differ between the two? Wavelength or intensity?|date=November 2013}} if they have differing emissivities.{{citation needed|date=November 2013}}
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| ==Applications==
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| {{Refimprove section|date=August 2007}}
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| ===Night vision===
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| {{Main|Night vision}}
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| [[File:Active-Infrared-Night-Vision.jpg|thumb|Active-infrared night vision : the camera illuminates the scene at infrared wavelengths invisible to the [[human eye]]. Despite a dark back-lit scene, active-infrared night vision delivers identifying details, as seen on the display monitor.]] Infrared is used in night vision equipment when there is insufficient [[visible light]] to see.<ref name="how nightvision works">{{cite web|title=How Night Vision Works |publisher=American Technologies Network Corporation |url=http://www.atncorp.com/HowNightVisionWorks |accessdate=2007-08-12}}</ref> [[Night vision devices]] operate through a process involving the conversion of ambient light photons into electrons that are then amplified by a chemical and electrical process and then converted back into visible light.<ref name="how nightvision works"/> Infrared light sources can be used to augment the available ambient light for conversion by night vision devices, increasing in-the-dark visibility without actually using a visible light source.<ref name="how nightvision works"/>
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| The use of infrared light and night vision devices should not be confused with [[thermal imaging]], which creates images based on differences in surface temperature by detecting infrared radiation ([[heat]]) that emanates from objects and their surrounding environment.<ref>{{cite web|last=Bryant |first=Lynn |title=How does thermal imaging work? A closer look at what is behind this remarkable technology |date=2007-06-11 |url=http://www.video-surveillance-guide.com/how-does-thermal-imaging-work.htm |accessdate=2007-08-12}}</ref>
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| ===Thermography===
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| [[File:STS-3 infrared on reentry.jpg|thumb|left|150px|Thermography helped to determine the temperature profile of the [[Space Shuttle thermal protection system]] during re-entry.]]{{Main|Thermography}}
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| Infrared radiation can be used to remotely determine the temperature of objects (if the emissivity is known). This is termed thermography, or in the case of very hot objects in the NIR or visible it is termed [[pyrometry]]. Thermography (thermal imaging) is mainly used in military and industrial applications but the technology is reaching the public market in the form of infrared cameras on cars due to the massively reduced production costs.
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| [[Thermographic cameras]] detect radiation in the infrared range of the electromagnetic spectrum (roughly 900–14,000 nanometers 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]] radiation law, thermography makes it possible to "see" one's environment with or without 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).
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| ===Hyperspectral imaging===
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| {{Main|Hyperspectral imaging}}
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| [[File:Specim aisaowl outdoor.png|thumb|left| Hyperspectral thermal infrared [[Emission spectrum|emission]] measurement, an outdoor scan in winter conditions, ambient temperature −15 °C, image produced with a [[Specim]] LWIR hyperspectral imager. Relative radiance spectra from various targets in the image are shown with arrows. The [[Infrared spectroscopy|infrared spectra]] of the different objects such as the watch clasp have clearly distinctive characteristics. The contrast level indicates the temperature of the object.<ref name=Holma>Holma, H., (May 2011), [http://www.photonik.de/index.php?id=11&np=5&artid=848&L=1 Thermische Hyperspektralbildgebung im langwelligen Infrarot], Photonik</ref>]] [[File:P1020168.JPG|thumb|Infrared light from the [[LED]] of an [[Xbox 360]] [[remote control]] as seen by a digital camera.]]
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| A hyperspectral image, a basis for chemical imaging, is a "picture" containing continuous [[Infrared spectroscopy|spectrum]] through a wide spectral range. Hyperspectral imaging is gaining importance in the applied spectroscopy particularly in the fields of NIR, SWIR, MWIR, and LWIR spectral regions. Typical applications include biological, mineralogical, defence, and industrial measurements.
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| Thermal Infrared Hyperspectral Camera can be applied similarly to a [[Thermographic camera]], with the fundamental difference that each pixel contains a full LWIR spectrum. Consequently, chemical identification of the object can be performed without a need for an external light source such as the Sun or the Moon. Such cameras are typically applied for geological measurements, outdoor surveillance and [[UAV]] applications.<ref name="Frost&Sullivan Specim Owl">Frost&Sullivan, Technical Insights, Aerospace&Defence (Feb 2011): [http://www.frost.com/prod/servlet/segment-toc.pag?segid=D870-00-48-00-00&ctxixpLink=FcmCtx3&ctxixpLabel=FcmCtx4 World First Thermal Hyperspectral Camera for Unmanned Aerial Vehicles]</ref>
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| ===Other imaging===
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| In [[infrared photography]], [[infrared filter]]s are used to capture the near-infrared spectrum. [[Digital camera]]s often use infrared [[Filter (optics)|blockers]]. Cheaper digital cameras and [[camera phones]] have less effective filters and can "see" intense near-infrared, appearing as a bright purple-white color. This is especially pronounced when taking pictures of subjects near IR-bright areas (such as near a lamp), where the resulting infrared interference can wash out the image. There is also a technique called '[[Terahertz radiation|T-ray]]' imaging, which is imaging using [[far-infrared]] or [[terahertz radiation]]. Lack of bright sources makes terahertz photography more challenging than most other infrared imaging techniques. Recently T-ray imaging has been of considerable interest due to a number of new developments such as [[terahertz time-domain spectroscopy]].
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| ===Tracking===
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| {{Main|Infrared homing}}
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| Infrared tracking, also known as infrared homing, refers to a [[Missile guidance#Passive homing|passive missile guidance system]], which uses the [[light emission|emission]] from a target of [[electromagnetic radiation]] in the infrared part of the [[Electromagnetic spectrum|spectrum]] to track it. Missiles that use infrared seeking are often referred to as "heat-seekers", since infrared (IR) is just below the visible spectrum of light in frequency and is radiated strongly by hot bodies. Many objects such as people, vehicle engines, and aircraft generate and retain heat, and as such, are especially visible in the infrared wavelengths of light compared to objects in the background.<ref>{{cite journal|author=Mahulikar, S.P., Sonawane, H.R., & Rao, G.A.|year=2007|title=Infrared signature studies of aerospace vehicles|journal=Progress in Aerospace Sciences|volume=43|issue=7–8|pages= 218–245|url=http://dspace.library.iitb.ac.in/xmlui/bitstream/handle/10054/613/5740.pdf|doi=10.1016/j.paerosci.2007.06.002|bibcode = 2007PrAeS..43..218M }}</ref>
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| ===Heating===
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| {{Main|Infrared heating}}
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| {{Unreferenced section|date=November 2013}}
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| Infrared radiation can be used as a deliberate heating source. According to this Mayo Clinic article{{Citation needed|date=November 2013}} states that, "Several studies have looked at using infrared saunas in the treatment of chronic health problems, such as high blood pressure, congestive heart failure and rheumatoid arthritis, and found some evidence of benefit." For example it is used in infrared saunas to heat the occupants, and also to remove ice from the wings of aircraft (de-icing). Far infrared is also gaining popularity as a safe heat therapy method of natural healthcare and physiotherapy. Infrared can be used in cooking and heating food as it predominantly heats the opaque, absorbent objects, rather than the air around them.
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| Infrared heating is also becoming more popular in industrial manufacturing processes, e.g. curing of coatings, forming of plastics, annealing, plastic welding, print drying. In these applications, infrared heaters replace convection ovens and contact heating.
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| Infrared heaters produce heat that is a product of invisible light and they consist of three parts: infrared light bulbs, a heat exchanger and a fan that blows air onto the exchanger to disperse the heat.
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| Efficiency is achieved by matching the wavelength of the infrared heater to the absorption characteristics of the material.
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| ===Communications===
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| IR data transmission is also employed in short-range communication among computer peripherals and [[personal digital assistant]]s. These devices usually conform to standards published by [[Infrared Data Association|IrDA]], the Infrared Data Association. Remote controls and IrDA devices use infrared [[light-emitting diode]]s (LEDs) to emit infrared radiation that is focused by a plastic [[Lens (optics)|lens]] into a narrow beam. The beam is [[modulation|modulated]], i.e. switched on and off, to encode the [[data]]. The receiver uses a [[silicon]] [[photodiode]] to convert the infrared radiation to an [[electric current]]. It responds only to the rapidly pulsing signal created by the transmitter, and filters out slowly changing infrared radiation from ambient light. Infrared communications are useful for indoor use in areas of high population density. IR does not penetrate walls and so does not interfere with other devices in adjoining rooms. Infrared is the most common way for [[remote control]]s to command appliances.
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| Infrared remote control protocols like [[RC-5]], [[Sony Infrared Remote Control|SIRC]], are used to communicate with infrared.
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| [[Free space optical communication]] using infrared [[laser]]s can be a relatively inexpensive way to install a communications link in an urban area operating at up to 4 gigabit/s, compared to the cost of burying fiber optic cable.
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| Infrared lasers are used to provide the light for [[optical fiber]] communications systems. Infrared light with a wavelength around 1,330 nm (least [[Dispersion (optics)|dispersion]]) or 1,550 nm (best transmission) are the best choices for standard [[silica]] fibers.
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| IR data transmission of encoded audio versions of printed signs is being researched as an aid for visually impaired people through the [[RIAS (Remote Infrared Audible Signage)]] project.
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| ===Spectroscopy===
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| [[Infrared spectroscopy|Infrared vibrational spectroscopy]] (see also [[near-infrared spectroscopy]]) is a technique that can be used to identify molecules by analysis of their constituent bonds. Each chemical bond in a molecule vibrates at a frequency characteristic of that bond. A group of atoms in a molecule (e.g., CH<sub>2</sub>) may have multiple modes of oscillation caused by the stretching and bending motions of the group as a whole. If an oscillation leads to a change in [[dipole]] in the molecule then it will absorb a [[photon]] that has the same frequency. The vibrational frequencies of most molecules correspond to the frequencies of infrared light. Typically, the technique is used to study [[organic compound]]s using light radiation from 4000–400 cm<sup>−1</sup>, the mid-infrared. A spectrum of all the frequencies of absorption in a sample is recorded. This can be used to gain information about the sample composition in terms of chemical groups present and also its purity (for example, a wet sample will show a broad O-H absorption around 3200 cm<sup>−1</sup>).
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| ===Meteorology===
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| [[File:US IR satpic.JPG|thumb|left| IR Satellite picture taken 1315 Z on 15th October 2006. A [[weather front|frontal]] system can be seen in the [[Gulf of Mexico]] with embedded Cumulonimbus cloud. Shallower Cumulus and Stratocumulus can be seen off the [[Eastern Seaboard]].]]
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| [[Weather satellite]]s equipped with scanning radiometers produce thermal or infrared images, which can then enable a trained analyst to determine cloud heights and types, to calculate land and surface water temperatures, and to locate ocean surface features. The scanning is typically in the range 10.3–12.5 µm (IR4 and IR5 channels).
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| High, cold ice clouds such as [[Cirrus cloud|Cirrus]] or [[Cumulonimbus]] show up bright white, lower warmer clouds such as [[Stratus cloud|Stratus]] or [[Stratocumulus]] show up as grey with intermediate clouds shaded accordingly. Hot land surfaces will show up as dark-grey or black. One disadvantage of infrared imagery is that low cloud such as stratus or [[fog]] can be a similar temperature to the surrounding land or sea surface and does not show up. However, using the difference in brightness of the IR4 channel (10.3–11.5 µm) and the near-infrared channel (1.58–1.64 µm), low cloud can be distinguished, producing a ''fog'' satellite picture. The main advantage of infrared is that images can be produced at night, allowing a continuous sequence of weather to be studied.
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| These infrared pictures can depict ocean eddies or vortices and map currents such as the Gulf Stream, which are valuable to the shipping industry. Fishermen and farmers are interested in knowing land and water temperatures to protect their crops against frost or increase their catch from the sea. Even [[El Niño]] phenomena can be spotted. Using color-digitized techniques, the gray-shaded thermal images can be converted to color for easier identification of desired information.
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| The main water vapour channel at 6.40 to 7.08 µm can be imaged by some weather satellites and shows the amount of moisture in the atmosphere.
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| {{clear}}
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| ===Climatology===
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| In the field of climatology, atmospheric infrared radiation is monitored to detect trends in the energy exchange between the earth and the atmosphere. These trends provide information on long-term changes in Earth's climate. It is one of the primary parameters studied in research into [[global warming]], together with [[solar radiation]].
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| A [[pyrgeometer]] is utilized in this field of research to perform continuous outdoor measurements. This is a broadband infrared radiometer with sensitivity for infrared radiation between approximately 4.5 µm and 50 µm.
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| ===Astronomy===
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| {{Main|Infrared astronomy|far-infrared astronomy}}
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| [[File:ESO - Beta Pictoris planet finally imaged (by).jpg|thumb|[[Beta Pictoris]], the light-blue dot off-center, as seen in infrared. It combines two images, the inner disc is at 3.6 µm.]]
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| [[File:Spitzer- Telescopio.jpg|thumb|left|The [[Spitzer Space Telescope]] is a dedicated infrared space observatory currently in orbit around the Sun. ''[[NASA]] image.'']]
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| Astronomers observe objects in the infrared portion of the electromagnetic spectrum using optical components, including mirrors, lenses and solid state digital detectors. For this reason it is classified as part of [[optical astronomy]]. To form an image, the components of an infrared telescope need to be carefully shielded from heat sources, and the detectors are chilled using liquid [[helium]].
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| The sensitivity of Earth-based infrared telescopes is significantly limited by water vapor in the atmosphere, which absorbs a portion of the infrared radiation arriving from space outside of selected [[Infrared window|atmospheric window]]s. This limitation can be partially alleviated by placing the telescope observatory at a high altitude, or by carrying the telescope aloft with a balloon or an aircraft. Space telescopes do not suffer from this handicap, and so outer space is considered the ideal location for infrared astronomy.
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| The infrared portion of the spectrum has several useful benefits for astronomers. Cold, dark [[molecular cloud]]s of gas and dust in our galaxy will glow with radiated heat as they are irradiated by imbedded stars. Infrared can also be used to detect [[protostar]]s before they begin to emit visible light. Stars emit a smaller portion of their energy in the infrared spectrum, so nearby cool objects such as [[planet]]s can be more readily detected. (In the visible light spectrum, the glare from the star will drown out the reflected light from a planet.)
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| Infrared light is also useful for observing the cores of [[active galaxy|active galaxies]], which are often cloaked in gas and dust. Distant galaxies with a high [[redshift]] will have the peak portion of their spectrum shifted toward longer wavelengths, so they are more readily observed in the infrared.<ref name="ir_astronomy" />
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| ===Art history===
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| [[File:Van Eyck - Arnolfini Portrait.jpg|thumb|left|180px|''[[The Arnolfini Portrait]]'' by [[Jan van Eyck]], [[National Gallery, London]]]]
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| [[File:Infrared reflectography-en.svg|right|200px]]
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| {{Ill2|Infrared reflectography|fr|réflectographie infrarouge|it|Riflettografia|es|Reflectografía infrarroja}}, as called by art historians,<ref>{{cite web|url=http://www.sensorsinc.com/artanalysis.html |title=IR Reflectography for Non-destructive Analysis of Underdrawings in Art Objects |publisher=Sensors Unlimited, Inc. |accessdate=2009-02-20}}</ref> are taken of paintings to reveal underlying layers, in particular the [[underdrawing]] or outline drawn by the artist as a guide. This often uses [[carbon black]], which shows up well in reflectograms, as long as it has not also been used in the ground underlying the whole painting. Art historians are looking to see whether the visible layers of paint differ from the under-drawing or layers in between – such alterations are called [[pentimento|pentimenti]] when made by the original artist. This is very useful information in deciding whether a painting is the [[prime version]] by the original artist or a copy, and whether it has been altered by over-enthusiastic restoration work. In general, the more pentimenti the more likely a painting is to be the prime version. It also gives useful insights into working practices.<ref>{{cite web|url=http://www.clevelandart.org/exhibcef/ConsExhib/html/grien.html |title=The Mass of Saint Gregory: Examining a Painting Using Infrared Reflectography |publisher=The Cleveland Museum of Art |accessdate=2009-02-20}}</ref>
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| Among many other changes in the [[Arnolfini Portrait]] of 1434 (left), the man's face was originally higher by about the height of his eye; the woman's was higher, and her eyes looked more to the front. Each of his feet was underdrawn in one position, painted in another, and then overpainted in a third. These alterations are seen in infra-red reflectograms.<ref>National Gallery Catalogues: The Fifteenth Century Netherlandish Paintings by Lorne Campbell, 1998, ISBN 185709171{{Page needed|date=September 2010}}</ref>
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| Similar uses of infrared are made by historians on various types of objects, especially very old written documents such as the [[Dead Sea Scrolls]], the Roman works in the [[Villa of the Papyri]], and the Silk Road texts found in the [[Mogao Caves|Dunhuang Caves]].<ref>{{cite web|url=http://idp.bl.uk/pages/technical_resources.a4d |title=International Dunhuang Project An Introduction to digital infrared photography and its application within IDP -paper pdf 6.4 MB |publisher=Idp.bl.uk |accessdate=2011-11-08}}</ref> Carbon black used in ink can show up extremely well.
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| ===Biological systems===
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| {{main|Infrared sensing in snakes}}
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| [[File:wiki snake eats mouse.jpg|thumb|Thermographic image of a snake eating a mouse]]
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| [[File:wiki bat.jpg|thumb|Thermographic image of a [[fruit bat]].]]
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| The [[Crotalinae|pit viper]] has a pair of infrared sensory pits on its head. There is uncertainty regarding the exact thermal sensitivity of this biological infrared detection system.<ref>{{Cite journal|title=Thermal Modeling of Snake Infrared Reception: Evidence for Limited Detection Range |journal=Journal of Theoretical Biology |volume=209 |issue=2 |pages=201–211 |year=2001 |doi=10.1006/jtbi.2000.2256 |pmid=11401462|last1=Jones|first1=B.S.|last2=Lynn|first2=W.F.|last3=Stone|first3=M.O.}}</ref><ref>{{Cite journal|title=Biological Thermal Detection: Micromechanical and Microthermal Properties of Biological Infrared Receptors |journal=Biomacromolecules |volume=3 |issue=1 |pages=106–115 |year=2002 |doi=10.1021/bm015591f |pmid=11866562|last1=Gorbunov|first1=V.|last2=Fuchigami|first2=N.|last3=Stone|first3=M.|last4=Grace|first4=M.|last5=Tsukruk|first5=V. V.}}</ref>
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| Other organisms that have thermoreceptive organs are pythons (family [[Pythonidae]]), some boas (family [[Boidae]]), the [[Common Vampire Bat]] (''Desmodus rotundus''), a variety of [[jewel beetle]]s (''[[Melanophila acuminata]]''),<ref name=Evans>{{Cite journal|last=Evans |first=W.G. |title=Infrared receptors in ''Melanophila acuminata'' De Geer |journal=Nature |volume=202 |page=211 |year=1966 |doi=10.1038/202211a0|bibcode = 1964Natur.202..211E |issue=4928}}</ref> darkly pigmented butterflies (''[[Pachliopta aristolochiae]]'' and ''[[Troides rhadamantus plateni]]''), and possibly blood-sucking bugs (''[[Triatoma infestans]]'').<ref>{{Cite journal |title=Biological infrared imaging and sensing |journal=Micrometre |year=2002 |volume=33 |issue=2 |pages=211–225 |doi=10.1016/S0968-4328(01)00010-5 |pmid=11567889 |last1=Campbell |first1=Angela L. |last2=Naik |first2=Rajesh R. |last3=Sowards |first3=Laura |last4=Stone |first4=Morley O.}}</ref>
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| Although near-infrared vision (780–1000 nm) has long been deemed impossible due to noise in visual pigments,<ref name="Meuthen et al.">{{Cite journal|title=Visual prey detection by near-infrared cues in a fish|journal=Naturwissenschaften |year=2012 |doi=10.1007/s00114-012-0980-7|last1=Meuthen|first1=Denis|last2=Rick|first2=Ingolf P.|last3=Thünken|first3=Timo|last4=Baldauf|first4=Sebastian A.|volume=99|issue=12|pages=1063–6|pmid=23086394|bibcode = 2012NW.....99.1063M }}</ref> sensation of near-infrared light was reported in the common carp and in three cichlid species.<ref name="Meuthen et al." /><ref>{{Cite journal|title= Postural control in tilapia under microgravity and the near infrared irradiated conditions |author= Endo, M.; Kobayashi R.; Ariga, K.; Yoshizaki, G. and Takeuchi, T. |journal= Nippon Suisan Gakkaish |volume=68 |pages=887–892| year=2002|doi= 10.2331/suisan.68.887|issue= 6 }}</ref><ref>{{Cite journal|title= Sensitivity of tilapia to infrared light measured using a rotating striped drum differs between two strains |author= Kobayashi R.; Endo, M.; Yoshizaki, G. and Takeuchi, T.|journal= Nippon Suisan Gakkaish |volume=68 |pages=646–651| year=2002|doi= 10.2331/suisan.68.646|issue= 5 }}</ref><ref>{{Cite journal|title= The eyes of the common carp and Nile tilapia are sensitive to near-infrared |doi=10.1111/j.1444-2906.2005.00971.x |journal= Fisheries Science |volume=71 |pages=350–355| year=2005|last1= Matsumoto|first1= Taro|last2= Kawamura|first2= Gunzo|issue= 2 }}</ref><ref name="Shcherbakov et al.">{{Cite journal|title= Near-infrared orientation of Mozambique tilapia ''Oreochromis mossambicus'' |journal= Zoology |volume=115 |pages=233–238| year=2012 | doi=10.1016/j.zool.2012.01.005|last1= Shcherbakov|first1= Denis|last2= Knörzer|first2= Alexandra|last3= Hilbig|first3= Reinhard|last4= Haas|first4= Ulrich|last5= Blum|first5= Martin|issue= 4|pmid= 22770589}}</ref> Fish use NIR to capture prey<ref name="Meuthen et al." /> and for phototactic swimming orientation.<ref name="Shcherbakov et al." /> NIR sensation in fish may be relevant under poor lighting conditions during twilight<ref name="Meuthen et al." /> and in turbid surface waters.<ref name="Shcherbakov et al." />
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| ===Photobiomodulation===
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| Near-infrared light, or [[photobiomodulation]], is used for treatment of chemotherapy-induced oral ulceration as well as wound healing. There is some work relating to anti-herpes virus treatment.<ref>{{cite journal | last1 = Hargate | first1 = G | title = A randomised double-blind study comparing the effect of 1072-nm light against placebo for the treatment of herpes labialis | journal = Clinical and experimental dermatology | volume = 31 | issue = 5 | pages = 638–41 | year = 2006 | pmid = 16780494 | doi = 10.1111/j.1365-2230.2006.02191.x }}</ref> Research projects include work on central nervous system healing effects via cytochrome c oxidase upregulation and other possible mechanisms.<ref>{{cite journal | author=Desmet KD, Paz DA, Corry JJ, Eells JT, Wong-Riley MT, Henry MM, Buchmann EV, Connelly MP, Dovi JV, Liang HL, Henshel DS, Yeager RL, Millsap DS, Lim J, Gould LJ, Das R, Jett M, Hodgson BD, Margolis D, Whelan HT | title = Clinical and experimental applications of NIR-LED photobiomodulation | journal = Photomedicine and laser surgery | volume = 24 | issue = 2 | pages = 121–8 | year = 2006 | pmid = 16706690 | doi = 10.1089/pho.2006.24.121 }}</ref>
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| ===Health hazard===
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| Strong infrared radiation in certain industry high-heat settings may be hazard to the eyes, resulting in damage or blindness to the user. Since the radiation is invisible, special IR-proof goggles must be worn in such places.<ref>{{cite book|author=Rosso, Monona l|title=The Artist's Complete Health and Safety Guide|url=http://books.google.com/books?id=E7-9unTgJrwC&pg=PA33|year=2001|publisher=Allworth Press|isbn=978-1-58115-204-3|pages=33–}}</ref>
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| ==Earth as an infrared emitter==
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| [[File:Greenhouse Effect.svg|thumb|right|340px|Schematic of the [[greenhouse effect]]]]
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| [[Earth]]'s surface and the clouds [[absorption (electromagnetic radiation)|absorb]] visible and invisible radiation from the [[sun]] and re-emit much of the energy as infrared back to [[Earth's atmosphere|atmosphere]]. Certain substances in the atmosphere, chiefly cloud droplets and [[water]] vapor, but also [[carbon dioxide]], [[methane]], [[nitrous oxide]], [[sulfur hexafluoride]], and [[chlorofluorocarbons]],<ref>{{cite web|title=Global Sources of Greenhouse Gases |work=Emissions of Greenhouse Gases in the United States 2000 |publisher=Energy Information Administration |date=2002-05-02 |url=http://www.eia.doe.gov/oiaf/1605/gg01rpt/emission.html |accessdate=2007-08-13}}</ref> absorb this infrared, and re-radiate it in all directions including back to Earth. Thus, the [[greenhouse effect]] keeps the atmosphere and surface much warmer than if the infrared absorbers were absent from the atmosphere.<ref>{{cite web|title=Clouds & Radiation |url=http://earthobservatory.nasa.gov/Library/Clouds/ |accessdate=2007-08-12}}</ref>
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| ==History of infrared science==
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| {{Refimprove|date=July 2006}}
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| The discovery of infrared radiation is ascribed to [[William Herschel]], the [[astronomer]], in the early 19th century. Herschel published his results in 1800 before the [[Royal Society of London]]. Herschel used a [[Triangular prism (optics)|prism]] to [[refract]] light from the [[sun]] and detected the infrared, beyond the [[red]] part of the spectrum, through an increase in the temperature recorded on a [[thermometer]]. He was surprised at the result and called them "Calorific Rays". The term 'Infrared' did not appear until late in the 19th century.<ref>{{cite journal|last=Herschel|first=William|title=Experiments on the Refrangibility of the Invisible Rays of the Sun|journal=Philosophical Transactions of the Royal Society of London|year=1800|volume=90|pages=284–292|jstor=107057|doi=10.1098/rstl.1800.0015}}</ref><ref>{{cite web|url=http://coolcosmos.ipac.caltech.edu/cosmic_classroom/classroom_activities/herschel_bio.html |title=Herschel Discovers Infrared Light |publisher=Coolcosmos.ipac.caltech.edu |accessdate=2011-11-08}}</ref>
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| Other important dates include:<ref name="Miller"/>
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| [[File:William Herschel01.jpg|thumb|upright|Infrared radiation was discovered in 1800 by William Herschel.]]
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| *1737: [[Émilie du Châtelet]] predicted what is today known as infrared radiation in ''Dissertation sur la nature et la propagation du feu''.
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| *1835: [[Macedonio Melloni]] made the first [[thermopile]] IR detector.
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| *1860: [[Gustav Kirchhoff]] formulated the [[Kirchhoff's law of thermal radiation|blackbody theorem]] <math>E=J(T,n)</math>.
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| *1873: [[Willoughby Smith]] discovered the photoconductivity of [[selenium]].
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| *1879: [[Stefan-Boltzmann law]] formulated empirically that the power radiated by a blackbody is proportional to T<sup>4</sup>.
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| *1880s & 1890s: [[John Strutt, 3rd Baron Rayleigh|Lord Rayleigh]] and [[Wilhelm Wien]] solved part of the blackbody equation, but both solutions diverged in parts of the electromagnetic spectrum. This problem was called the "[[Ultraviolet catastrophe]] and Infrared Catastrophe".
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| *1901: [[Max Planck]] published the [[Planck's law|blackbody equation]] and theorem. He solved the problem by quantizing the allowable energy transitions.
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| *1905: [[Albert Einstein]] developed the theory of the [[photoelectric effect]].
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| *1917: [[Theodore Case]] developed the [[thallous sulfide]] detector; British scientist built the first [[infra-red search and track]] (IRST) device able to detect aircraft at a range of one mile (1.6 km).
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| *1935: Lead salts – early missile guidance in [[World War II]].
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| *1938: [[Teau Ta]] – predicted that the pyroelectric effect could be used to detect infrared radiation.
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| *1945: The [[Zielgerät 1229]] "Vampir" infrared weapon system was introduced as the first portable infrared device for military applications.
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| *1952: [[H. Welker]] grew synthetic InSb crystals.
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| *1950s: [[Paul Kruse (engineer)|Paul Kruse]] (at Honeywell) and Texas Instruments recorded infrared images.
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| *1950s and 1960s: Nomenclature and radiometric units defined by [[Fred Nicodemenus]], [[G.J. Zissis]] and [[R. Clark]]; [[Robert Clark Jones]] defined ''D''*.
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| *1958: [[W.D. Lawson]] ([[Royal Radar Establishment]] in Malvern) discovered IR detection properties of HgCdTe.
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| *1958: [[Falcon (rocket family)|Falcon]] and [[AIM-9 Sidewinder|Sidewinder]] missiles were developed using infrared technology.
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| *1961: [[J. Cooper]] demonstrated pyroelectric detection.
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| *1964: W.G. Evans discovered infrared thermoreceptors in a pyrophile beetle.<ref name=Evans/>
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| *1965: First IR Handbook; first commercial imagers ([[Barnes, Agema]] {now part of [[FLIR Systems]] Inc.}; [[Richard Hudson (physicist)|Richard Hudson]]'s landmark text; F4 TRAM FLIR by [[Hughes Aircraft Company|Hughes]]; phenomenology pioneered by [[Fred Simmons (scientist)|Fred Simmons]] and [[A.T. Stair]]; U.S. Army's night vision lab formed (now [[Night Vision and Electronic Sensors Directorate]] (NVESD), and [[Rachets]] develops detection, recognition and identification modeling there.
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| *1970: [[Willard Boyle]] and [[George E. Smith]] proposed CCD at [[Bell Labs]] for [[picture phone]].
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| *1972: [[Common module program]] started by NVESD.
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| *1978: Infrared imaging astronomy came of age, observatories planned, [[NASA Infrared Telescope Facility|IRTF]] on Mauna Kea opened; 32 by 32 and 64 by 64 arrays produced using [[InSb]], [[HgCdTe]] and other materials.
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| *2013: On February 14th researchers developed a [[neural implant]] that gives [[rat]]s the ability to sense [[infrared]] light which for the first time provides [[living creatures]] with new abilities, instead of simply replacing or augmenting existing abilities.<ref>{{cite web|url=http://www.wired.co.uk/news/archive/2013-02/14/implant-gives-rats-sixth-sense-for-infrared-light|title=Implant gives rats sixth sense for infrared light|work=Wired UK|date=14 February 2013|accessdate=14 February 2013}}</ref>
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| ==See also==
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| {{Columns-list|2|
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| *[[Black-body radiation]]
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| *[[Solar cell#Infrared solar cells|Infrared solar cells]]
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| *[[Infrared thermometer]]
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| *[[Infrared window]]
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| *[[List of infrared articles]]
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| *[[People counter]]
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| }}
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| ==References==
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| {{Reflist|30em}}
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| ==External links==
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| {{Sister project links|wikt=infrared|commons=Category:Infrared|q=no}}
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| * [http://www.omega.com/literature/transactions/volume1/historical1.html Infrared: A Historical Perspective] (Omega Engineering)
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| * [http://www.irda.org/ Infrared Data Association], a standards organization for infrared data interconnection
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| * [http://yengal-marumugam.blogspot.com/2011/06/sirc-part-i-basics.html SIRC Protocol ]
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| * [http://www.ocinside.de/html/modding/usb_ir_receiver/usb_ir_receiver.html How to build an USB infrared receiver to control PCs remotely]
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| * [http://imagers.gsfc.nasa.gov/ems/infrared.html Infrared Waves]: detailed explanation of infrared light. (NASA)
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| * [http://ia700600.us.archive.org/23/items/philtrans08733349/08733349.pdf Herschel's original paper from 1800 announcing the discovery of infrared light]
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| * [http://www.thethermograpiclibrary.org/index.php/Cat%C3%A9gorie:Library The thermographic's library], collection of thermogram
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| {{EMSpectrum}}
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| {{DEFAULTSORT:Infrared}}
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| [[Category:Electromagnetic spectrum]]
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| [[Category:Infrared]]
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