1 Definition and relationship to the electromagnetic spectrum 2 Natural infrared 3 Regions within the infrared
3.1 Commonly used sub-division scheme
3.2 CIE division scheme
3.3 ISO 20473 scheme
3.4 Astronomy division scheme
Sensor response division scheme 3.6 Telecommunication
Telecommunication bands in the infrared
4 Heat 5 Applications
5.1 Night vision
5.3 Hyperspectral imaging
5.4 Other imaging
5.10 Thin film metrology
Infrared cleaning 5.15 Art conservation and analysis 5.16 Biological systems 5.17 Photobiomodulation 5.18 Health hazard
6 History of infrared science 7 See also 8 References 9 External links
Definition and relationship to the electromagnetic spectrum
Infrared radiation extends from the nominal red edge of the visible spectrum at 700 nanometers (nm) to 1 mm. This range of wavelengths corresponds to a frequency range of approximately 430 THz down to 300 GHz. Below infrared is the microwave portion of the electromagnetic spectrum.
Infrared in relation to electromagnetic spectrum
Gamma ray less than 0.01 nm more than 30 EHz 124 keV – 300+ GeV
X-ray 0.01 nm – 10 nm 30 EHz – 30 PHz 124 eV – 124 keV
Ultraviolet 10 nm – 400 nm 30 PHz – 790 THz 3.3 eV – 124 eV
Visible 400 nm–700 nm 790 THz – 430 THz 1.7 eV – 3.3 eV
Infrared 700 nm – 1 mm 430 THz – 300 GHz 1.24 meV – 1.7 eV
Microwave 1 mm – 1 meter 300 GHz – 300 MHz 1.24 µeV – 1.24 meV
Radio 1 meter – 100,000 km 300 MHz – 3 Hz 12.4 feV – 1.24 µeV
Natural infrared Sunlight, at an effective temperature of 5,780 kelvins, is composed of near thermal-spectrum radiation that is slightly more than half infrared. At zenith, sunlight provides an irradiance of just over 1 kilowatt 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. Nearly all the infrared radiation in sunlight is near infrared, shorter than 4 micrometers. On the surface of Earth, at far lower temperatures than the surface of the Sun, almost all thermal radiation consists of infrared in mid-infrared region, much longer than in sunlight. 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. Regions within the infrared 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. Therefore, the infrared band is often subdivided into smaller sections. Commonly used sub-division scheme A commonly used sub-division scheme is:
Division Name Abbreviation Wavelength Frequency Photon Energy Temperature† Characteristics
NIR, IR-A DIN
Defined by the water absorption,[clarification needed] and commonly
used in fiber optic telecommunication because of low attenuation
losses in the SiO2 glass (silica) medium. Image intensifiers are
sensitive to this area of the spectrum; examples include night vision
devices such as night vision goggles.
Near-infrared spectroscopy is another common application.
Short-wavelength infrared SWIR, IR-B DIN 1.4–3 µm 100–214 THz 413–886 meV 2,070–966 K (1,797–693 °C) Water absorption increases significantly at 1450 nm. The 1530 to 1560 nm range is the dominant spectral region for long-distance telecommunications.
Mid-wavelength infrared MWIR, IR-C DIN; MidIR. Also called intermediate infrared (IIR) 3–8 µm 37–100 THz 155–413 meV 966–362 K (693–89 °C) 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 also known as thermal infrared.
Long-wavelength infrared LWIR, IR-C DIN 8–15 µm 20–37 THz 83–155 meV 362–193 K (89 – −80 °C) 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".
Far infrared FIR 15–1000 µm 0.3–20 THz 1.2–83 meV 193–3 K (−80.15 – −270.15 °C) (see also far-infrared laser and far infrared)
† Temperatures of black bodies for which spectral peaks fall at the given wavelengths, according to Wien's displacement law
A comparison of a thermal image (top) and an ordinary photograph (bottom) shows that a trash bag is transparent but glass (the man's spectacles) is opaque in long-wavelength infrared.
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.
CIE division scheme
International Commission on Illumination
International Commission on Illumination (CIE) recommended the division of infrared radiation into the following three bands:
Abbreviation Wavelength Frequency
IR-A 700 nm – 1400 nm (0.7 µm – 1.4 µm) 215 THz – 430 THz
IR-B 1400 nm – 3000 nm (1.4 µm – 3 µm) 100 THz – 215 THz
IR-C 3000 nm – 1 mm (3 µm – 1000 µm) 300 GHz – 100 THz
ISO 20473 scheme ISO 20473 specifies the following scheme:
Designation Abbreviation Wavelength
Near-Infrared NIR 0.78–3 µm
Mid-Infrared MIR 3–50 µm
Far-Infrared FIR 50–1000 µm
Astronomy division scheme Astronomers typically divide the infrared spectrum as follows:
Designation Abbreviation Wavelength
Near-Infrared NIR (0.7–1) to 5 µm
Mid-Infrared MIR 5 to (25–40) µm
Far-Infrared FIR (25–40) to (200–350) µm.
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.
The most common photometric system used in astronomy allocates capital
letters to different spectral regions according to filters used; I, J,
H, and K cover the near-infrared wavelengths; L, M, N, and Q refer to
the mid-infrared region. These letters are commonly understood in
reference to atmospheric windows and appear, for instance, in the
titles of many papers.
Sensor response division scheme
Plot of atmospheric transmittance in part of the infrared region.
A third scheme divides up the band based on the response of various detectors:
Near-infrared: from 0.7 to 1.0 µm (from the approximate end of
the response of the human eye to that of silicon).
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.
Mid-wave infrared: 3 to 5 µm (defined by the atmospheric window
and covered by
Indium antimonide [InSb] and HgCdTe
HgCdTe and partially by lead selenide [PbSe]). Long-wave infrared: 8 to 12, or 7 to 14 µm (this is the atmospheric window covered by HgCdTe
HgCdTe and microbolometers). Very-long wave infrared (VLWIR) (12 to about 30 µm, covered by doped silicon).
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 InGaAs's sensitivity starts
around 950 nm and ends between 1,700 and 2,600 nm, depending
on the specific configuration). No international standards for these
specifications are currently available.
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 lasers, 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. Intense light sources providing wavelengths as long as 1050 nm can be seen as a dull red glow, 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 Wood effect
Wood effect that consists of IR-glowing foliage. Telecommunication
Telecommunication bands in the infrared 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:
O band Original 1260–1360 nm
E band Extended 1360–1460 nm
S band Short wavelength 1460–1530 nm
C band Conventional 1530–1565 nm
L band Long wavelength 1565–1625 nm
U band Ultralong wavelength 1625–1675 nm
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. Heat Main article: Thermal radiation
Materials with higher emissivity appear to be hotter. In this thermal image, the ceramic cylinder appears to be hotter than its cubic container (made of silicon carbide), while in fact they have the same temperature.
Infrared radiation is popularly known as "heat radiation", but light and electromagnetic waves of any frequency will heat surfaces that absorb them. Infrared
Infrared light from the Sun
Sun accounts for 49% of the heating of Earth, with the rest being caused by visible light that is absorbed then re-radiated at longer wavelengths. Visible light
Visible light or ultraviolet-emitting lasers can char paper and incandescently hot objects emit visible radiation. Objects at room temperature will emit 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). Heat
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
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
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
X-ray regions (e.g. 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. 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 if they have differing emissivity. For example, for any pre-set emissivity value, objects with higher emissivity will appear hotter, and those with a lower emissivity will appear cooler. For that reason, incorrect selection of emissivity will give inaccurate results when using infrared cameras and pyrometers. Applications
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Night vision Main article: Night vision
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. Night vision
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. Infrared
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. 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. Thermography
Thermography helped to determine the temperature profile of the Space Shuttle thermal protection system during re-entry.
Main article: Thermography
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
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. Thermographic cameras
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). Hyperspectral imaging Main article: Hyperspectral imaging
Hyperspectral thermal infrared 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 spectra of the different objects such as the watch clasp have clearly distinctive characteristics. The contrast level indicates the temperature of the object.
A hyperspectral image is a "picture" containing continuous spectrum
through a wide spectral range at each pixel.
Hyperspectral imaging is gaining importance in the field of applied spectroscopy particularly with NIR, SWIR, MWIR, and LWIR spectral regions. Typical applications include biological, mineralogical, defence, and industrial measurements. Thermal infrared hyperspectral imaging can be similarly performed using 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
UAV applications. Other imaging In infrared photography, infrared filters are used to capture the near-infrared spectrum. Digital cameras often use infrared 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 'T-ray' imaging, which is imaging using far-infrared or terahertz radiation. Lack of bright sources can make 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.
Reflected light photograph in various infrared spectra to illustrate the appearance as the wavelength of light changes.
Infrared homing Infrared
Infrared tracking, also known as infrared homing, refers to a passive missile guidance system, which uses the emission from a target of electromagnetic radiation in the infrared part of the 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. Heating Main article: Infrared
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Infrared radiation can be used as a deliberate heating source. For example, it is used in infrared saunas to heat the occupants. It may also be used in other heating applications, such as to remove ice from the wings of aircraft (de-icing). Infrared
Infrared can be used in cooking and heating food as it predominantly heats the opaque, absorbent objects, rather than the air around them. Infrared heating
Infrared heating is also becoming more popular in industrial manufacturing processes, e.g. curing of coatings, forming of plastics, annealing, plastic welding, and print drying. In these applications, infrared heaters replace convection ovens and contact heating. Efficiency is achieved by matching the wavelength of the infrared heater to the absorption characteristics of the material. Cooling Main article: Radiative cooling A variety of technologies or proposed technologies take advantage of infrared emissions to cool buildings or other systems. The LWIR (8–15 µm) region is especially useful since some radiation at these wavelengths can escape into space through the atmosphere. Communications IR data transmission is also employed in short-range communication among computer peripherals and personal digital assistants. These devices usually conform to standards published by IrDA, the Infrared Data Association. Remote controls and IrDA devices use infrared light-emitting diodes (LEDs) to emit infrared radiation that is focused by a plastic lens into a narrow beam. The beam is modulated, i.e. switched on and off, to prevent interference from other sources of infrared (like sunlight or artificial lighting). 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
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
Infrared is the most common way for remote controls to command appliances. Infrared
Infrared remote control protocols like RC-5, SIRC, are used to communicate with infrared. Free space optical communication
Free space optical communication using infrared lasers 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, except for the radiation damage. "Since the eye cannot detect IR, blinking or closing the eyes to help prevent or reduce damage may not happen." Infrared
Infrared lasers are used to provide the light for optical fiber communications systems. Infrared
Infrared light with a wavelength around 1,330 nm (least dispersion) or 1,550 nm (best transmission) are the best choices for standard silica fibers. 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. Transmitting IR data from one device to another is sometimes referred to as beaming. Spectroscopy Infrared
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., CH2) 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 compounds using light radiation from 4000–400 cm−1, 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−1). Thin film metrology In the semiconductor industry, infrared light can be used to characterize materials such as thin films and periodic trench structures. By measuring the reflectance of light from the surface of a semiconductor wafer, the index of refraction (n) and the extinction Coefficient (k) can be determined via the Forouhi-Bloomer dispersion equations. The reflectance from the infrared light can also be used to determine the critical dimension, depth, and sidewall angle of high aspect ratio trench structures. Meteorology
IR Satellite picture taken 1315 Z on 15th October 2006. A frontal
system can be seen in the
Gulf of Mexico
Gulf of Mexico with embedded Cumulonimbus cloud. Shallower Cumulus and Stratocumulus
Stratocumulus can be seen off the Eastern Seaboard.
Weather satellites 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).
High, cold ice clouds such as Cirrus or
Cumulonimbus show up bright white, lower warmer clouds such as Stratus or Stratocumulus
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. 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
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. 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.
Climatology 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.
Schematic of the greenhouse effect
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.
Infrared astronomy and far-infrared astronomy
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.
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
atmospheric windows. 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.
The infrared portion of the spectrum has several useful benefits for
astronomers. Cold, dark molecular clouds 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 protostars 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 planets can be more readily detected. (In the visible light spectrum, the glare from the star will drown out the reflected light from a planet.) Infrared
Infrared light is also useful for observing the cores of 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. Infrared
Infrared cleaning Infrared cleaning is a technique used by some motion picture film scanners, film scanners and flatbed scanners to reduce or remove the effect of dust and scratches upon the finished scan. It works by collecting an additional infrared channel from the scan at the same position and resolution as the three visible color channels (red, green, and blue). The infrared channel, in combination with the other channels, is used to detect the location of scratches and dust. Once located, those defects can be corrected by scaling or replaced by inpainting. Art conservation and analysis
The Arnolfini Portrait
The Arnolfini Portrait by Jan van Eyck, National Gallery, London
Infrared reflectography (fr; it; es), as called by art conservators, can be applied to paintings to reveal underlying layers in a completely non-destructive manner, in particular the underdrawing or outline drawn by the artist as a guide. This often reveals the artist's use of 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 conservators are looking to see whether the visible layers of paint differ from the underdrawing or layers in between – such alterations are called 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. Among many other changes in the Arnolfini Portrait
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 infrared reflectograms. Recent progress in the design of infrared sensitive cameras made it possible to discover and depict not only underpaintings and pentimenti but entire paintings which were later overpainted by the artist. Notable examples are Picasso's "Woman ironing" and " Blue
Blue room", where in both cases, a portrait of a man has been made visible under the painting as it is known today. Similar uses of infrared are made by conservators and scientists 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 Dunhuang Caves. Carbon black used in ink can show up extremely well. Biological systems Main article: Infrared
Infrared sensing in snakes
Thermographic image of a snake eating a mouse
The 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. Other organisms that have thermoreceptive organs are pythons (family Pythonidae), some boas (family Boidae), the Common Vampire Bat (Desmodus rotundus), a variety of jewel beetles (Melanophila acuminata), darkly pigmented butterflies (Pachliopta aristolochiae and Troides rhadamantus plateni), and possibly blood-sucking bugs (Triatoma infestans). Although near-infrared vision (780–1000 nm) has long been deemed impossible due to noise in visual pigments, sensation of near-infrared light was reported in the common carp and in three cichlid species. Fish use NIR to capture prey and for phototactic swimming orientation. NIR sensation in fish may be relevant under poor lighting conditions during twilight and in turbid surface waters. Photobiomodulation 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. Research projects include work on central nervous system healing effects via cytochrome c oxidase upregulation and other possible mechanisms. Health hazard Strong infrared radiation in certain industry high-heat settings may be hazardous 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. History of infrared science
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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 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. Other important dates include:
Infrared radiation was discovered in 1800 by William Herschel.
Émilie du Châtelet
Émilie du Châtelet predicted what is today known as infrared radiation in Dissertation sur la nature et la propagation du feu. 1835: Macedonio Melloni
Macedonio Melloni made the first thermopile IR detector. 1840: John Herschel
John Herschel produces the first thermal image thermogram. 1860: Gustav Kirchhoff
Gustav Kirchhoff formulated the blackbody theorem
E = J ( T , n )
Willoughby Smith discovered the photoconductivity of selenium. 1878: Samuel Pierpont Langley
Samuel Pierpont Langley invents the first bolometer, a device which is able to measure small temperature fluctuations, and thus the power of far infrared sources. 1879: Stefan-Boltzmann law
Stefan-Boltzmann law formulated empirically that the power radiated by a blackbody is proportional to T4. 1880s & 1890s: Lord Rayleigh and Wilhelm Wien
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
Infrared Catastrophe". 1901: Max Planck
Max Planck published the blackbody equation and theorem. He solved the problem by quantizing the allowable energy transitions. 1905: Albert Einstein
Albert Einstein developed the theory of the photoelectric effect. 1917: Theodore Case
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). 1935: Lead salts – early missile guidance in World War II. 1938: Teau Ta – predicted that the pyroelectric effect could be used to detect infrared radiation. 1945: The Zielgerät 1229
Zielgerät 1229 "Vampir" infrared weapon system was introduced as the first portable infrared device for military applications. 1952: H. Welker grew synthetic InSb
InSb crystals. 1950s: Paul Kruse (at Honeywell) and Texas Instruments recorded infrared images. 1950s and 1960s: Nomenclature and radiometric units defined by Fred Nicodemenus, G.J. Zissis and R. Clark; Robert Clark Jones defined D*. 1958: W.D. Lawson ( Royal Radar Establishment in Malvern) discovered IR detection properties of HgCdTe. 1958: Falcon and Sidewinder missiles were developed using infrared technology. 1961: J. Cooper demonstrated pyroelectric detection. 1964: W.G. Evans discovered infrared thermoreceptors in a pyrophile beetle. 1965: First IR Handbook; first commercial imagers (Barnes, Agema now part of FLIR Systems
FLIR Systems Inc. ; Richard Hudson's landmark text; F4 TRAM FLIR by Hughes; phenomenology pioneered by 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. 1970: Willard Boyle
Willard Boyle and George E. Smith
George E. Smith proposed CCD at Bell Labs
Bell Labs for picture phone. 1972: Common module program started by NVESD. 1978: Infrared
Infrared imaging astronomy came of age, observatories planned, IRTF on Mauna Kea opened; 32 by 32 and 64 by 64 arrays produced using InSb, HgCdTe
HgCdTe and other materials. 2013: On February 14 researchers developed a neural implant that gives rats 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.
Infrared non-destructive testing of materials Infrared
Infrared solar cells Infrared
Infrared thermometer Infrared
Infrared window List of infrared articles People counter
^ Sliney, David H.; Wangemann, Robert T.; Franks, James K.; Wolbarsht,
Myron L. (1976). "Visual sensitivity of the eye to infrared laser
radiation". Journal of the Optical Society of America. 66 (4):
339–341. doi:10.1364/JOSA.66.000339. (Subscription required (help)).
The foveal sensitivity to several near-infrared laser wavelengths was
measured. It was found that the eye could respond to radiation at
wavelengths at least as far as 1064 nm. A continuous 1064 nm laser
source appeared red, but a 1060 nm pulsed laser source appeared green,
which suggests the presence of second harmonic generation in the
^ Lynch, David K.; Livingston, William Charles (2001). Color and Light
in Nature (2nd ed.). Cambridge, UK: Cambridge University Press.
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Limits of the eye's overall range of sensitivity extends from about
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Find more aboutInfraredat's sister projects
Definitions from Wiktionary Media from Wikimedia Commons News from Wikinews Texts from Wikisource Textbooks from Wikibooks Learning resources from Wikiversity
Infrared: A Historical Perspective (Omega Engineering)
Infrared Data Association, a standards organization for infrared data interconnection SIRC Protocol How to build an USB infrared receiver to control PC's remotely Infrared
Infrared Waves: detailed explanation of infrared light. (NASA) Herschel's original paper from 1800 announcing the discovery of infrared light The thermographic's library, collection of thermogram Infrared reflectography
Infrared reflectography in analysis of paintings at ColourLex Molly Faries, Techniques and Applications – Analytical Capabilities of Infrared
Infrared Reflectography: An Art Historian s Perspective, in Scientific Examination of Art: Modern Techniques in Conservation and Analysis, Sackler NAS Colloquium, 2005
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Gamma rays X-rays Ultraviolet Visible Infrared Terahertz radiation Microwave Radio
← higher frequencies longer wavelengths →
Violet Blue Green Yellow Orange Red
W band V band Q band Ka band K band Ku band X band S band C band L band
EHF SHF UHF VHF HF MF LF VLF ULF SLF ELF
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v t e
Acoustic, sound, vibration
Geophone Hydrophone Microphone Seismometer
Air–fuel ratio meter
Blind spot monitor
Crankshaft position sensor
Engine coolant temperature sensor
Hall effect sensor
Mass flow sensor
Radar gun Speed sensor Speedometer Throttle position sensor Tire-pressure monitoring system Torque sensor Transmission fluid temperature sensor Turbine speed sensor Variable reluctance sensor Vehicle speed sensor Water sensor Wheel speed sensor
Carbon dioxide sensor
Carbon monoxide detector
Catalytic bead sensor
Chemical field-effect transistor
Electrochemical gas sensor
Fluorescent chloride sensors
Hydrocarbon dew point analyzer
Hydrogen sulfide sensor
Infrared point sensor Ion selective electrode Microwave
Microwave chemistry sensor Nitrogen oxide sensor Nondispersive infrared sensor Olfactometer Optode Oxygen sensor Pellistor pH glass electrode Potentiometric sensor Redox electrode Smoke detector Zinc oxide nanorod sensor
Electric, magnetic, radio
Current sensor Electroscope Galvanometer Hall effect sensor Hall probe Magnetic anomaly detector Magnetometer MEMS magnetic field sensor Metal detector Planar Hall sensor Radio direction finder Test light
Environment, weather, moisture
Electrochemical gas sensor
Frequency domain sensor Gas detector Hook gauge evaporimeter Humistor Hygrometer Leaf sensor Psychrometer Pyranometer Pyrgeometer Rain gauge Rain sensor SNOTEL Snow gauge Soil moisture sensor Stream gauge Tide gauge Weather radar
Flow, fluid velocity
Air flow meter Anemometer Flow sensor Gas meter Mass flow sensor Water metering
Ionising radiation, subatomic particles
Bubble chamber Cloud chamber Geiger–Müller tube Geiger counter Ionization chamber Neutron detection Particle detector Proportional counter Scintillation counter Semiconductor detector Scintillator Thermoluminescent dosimeter Wire chamber
Airspeed indicator Machmeter Altimeter Attitude indicator Depth gauge Fluxgate compass Gyroscope Inertial navigation system Inertial reference unit Magnetic compass MHD sensor Ring laser gyroscope Turn coordinator Variometer Vibrating structure gyroscope Yaw-rate sensor
Position, angle, displacement
Angular rate sensor
Capacitive displacement sensor
Integrated circuit piezoelectric sensor
Laser rangefinder Laser
Laser surface velocimeter Lidar Linear encoder Linear variable differential transformer Liquid capacitive inclinometers Odometer Photoelectric sensor Piezoelectric accelerometer Position sensor Rotary encoder Rotary variable differential transformer Selsyn Sudden Motion Sensor Tachometer Tilt sensor Ultrasonic thickness gauge Variable reluctance sensor Velocity receiver
Optical, light, imaging
Active pixel sensor
Contact image sensor
Kinetic inductance detector
LED as light sensor Light-addressable potentiometric sensor Nichols radiometer Optical fiber Photodetector Photodiode Photoelectric sensor Photoionization detector Photomultiplier Photoresistor Photoswitch Phototransistor Phototube Position sensitive device Scintillometer Shack–Hartmann wavefront sensor Single-photon avalanche diode Superconducting nanowire single-photon detector Transition edge sensor Tristimulus colorimeter Visible-light photon counter Wavefront sensor
Barograph Barometer Boost gauge Bourdon gauge Hot-filament ionization gauge Ionization gauge McLeod gauge Oscillating U-tube Permanent Downhole Gauge Piezometer Pirani gauge Pressure gauge Pressure sensor Tactile sensor Time pressure gauge
Force, density, level
Bhangmeter Force gauge Hydrometer Level sensor Load cell Magnetic level gauge Nuclear density gauge Piezoelectric sensor Strain gauge Torque sensor Viscometer
Thermal, heat, temperature
Exhaust gas temperature gauge
Heat flux sensor Infrared
Infrared thermometer Microbolometer Microwave
Microwave radiometer Net radiometer Quartz thermometer Resistance thermometer Silicon
Silicon bandgap temperature sensor Special
Special sensor microwave/imager Thermistor Thermocouple Thermometer
Alarm sensor Doppler radar Motion detector Occupancy sensor Passive infrared sensor Proximity sensor Reed switch Stud finder Touch switch Triangulation sensor Wired glove
Active pixel sensor
Carbon paste electrode
Image sensor format Inductive sensor Intelligent sensor Lab-on-a-chip Leaf sensor Machine vision Microelectromechanical systems Photoelasticity Quantum sensor Radar
Ground-penetrating radar Synthetic aperture radar
Radar tracker Sensor
Sensor array Sensor
Sensor fusion Sensor
Sensor grid Sensor
Sensor node Soft sensor Sonar Staring array Transducer Ultrasonic sensor Video sensor technology Visual sensor network Wheatstone bridge Wireless sensor network
List of sensors
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