Image of two people in mid-infrared ("thermal") light (false-color)

Infrared (IR) radiation is electromagnetic radiation whose wavelength is longer than that of visible light, but shorter than that of terahertz radiation and microwaves. A false-color image is an image that depicts a subject in Colors that differ from those a faithful full-color photograph would show Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. Electromagnetic waves sent at terahertz frequencies, known as terahertz radiation, submillimeter radiation, terahertz waves, terahertz Microwaves are electromagnetic waves with Wavelengths ranging from 1 mm to 1 m or frequencies between 0 The name means "below red" (from the Latin infra, "below"), red being the color of visible light with the longest wavelength. Red is any of a number of similar Colors evoked by light consisting predominantly of the longest wavelengths of Light discernible by the human eye in the wavelength Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 Infrared radiation has wavelengths between about 750 nm and 1 mm, spanning three orders of magnitude. A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a The Millimetre ( American spelling: millimeter, symbol mm) is a unit of Length in the Metric system, equal to An order of magnitude is the class of scale or magnitude of any amount where each class contains values of a fixed ratio to the class preceding it Humans at normal body temperature can radiate at a wavelength of 10 microns. ^[1]

Infrared imaging is used extensively for both military and civilian purposes. Military applications include target acquisition, surveillance, night vision, homing and tracking. In the military target acquisition denotes any process that provides detailed information about enemy forces and locates them with sufficient accuracy to permit continued monitoring or Night vision is the ability to see in a dark environment Whether by biological or technological means night vision is made possible by a combination of two approaches sufficient Non-military uses include thermal efficiency analysis, remote temperature sensing, short-ranged wireless communication, spectroscopy, and weather forecasting. Wireless communication is the transfer of information over a distance without the use of electrical conductors or " Wires quot Spectroscopy was originally the study of the interaction between Radiation and Matter as a function of Wavelength (λ Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location Infrared astronomy uses sensor-equipped telescopes to penetrate dusty regions of space, such as molecular clouds; detect cool objects such as planets, and to view highly red-shifted objects from the early days of the universe. Infrared astronomy is the branch of Astronomy and Astrophysics which deals with objects visible in Infrared (IR radiation A telescope is an instrument designed for the observation of remote objects and the collection of Electromagnetic radiation. See also Solar nebula A molecular cloud, sometimes called a stellar nursery if Star formation is occurring within is a type of Interstellar A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is In Physics and Astronomy, redshift occurs when Electromagnetic radiation – usually Visible light – emitted or reflected by The Universe is defined as everything that Physically Exists: the entirety of Space and Time, all forms of Matter, Energy ^[2]

At the atomic level, infrared energy elicits vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states. History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny Vibration refers to mechanical Oscillations about an equilibrium point. In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by Infrared spectroscopy examines absorption and transmission of photons in the infrared energy range, based on their frequency and intensity. Infrared spectroscopy (IR spectroscopy is the subset of Spectroscopy that deals with the Infrared region of the Electromagnetic spectrum. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena ^[3]

Origins of the term

The name means below red (from the Latin infra, "below"), red being the color of the longest wavelengths of visible light. IR light has a longer wavelength than that of red light. A longer wavelength means it has a lower frequency than red, hence below. Frequency is a measure of the number of occurrences of a repeating event per unit Time.

Different regions in the infrared

Objects generally emit infrared radiation across a spectrum of wavelengths, but only a specific region of the spectrum is of interest because sensors are usually designed only to collect radiation within a specific bandwidth. As a result, the infrared band is often subdivided into smaller sections.

The International Commission on Illumination (CIE) recommended the division of optical radiation into the following three bands:^[4]

• IR-A: 700 nm–1400 nm
• IR-B: 1400 nm–3000 nm
• IR-C: 3000 nm–1 mm

A commonly used sub-division scheme is:

• Near-infrared (NIR, IR-A DIN): 0. Established in 1913 and based in Vienna, Austria, the International Commission on Illumination (usually known as the CIE for its French name Commission Deutsches Institut für Normung eV ( DIN; in English, the German Institute for Standardization) is the German national organization for 75-1. 4 µm in wavelength, defined by the water absorption, and commonly used in fiber optic telecommunication because of low attenuation losses in the SiO₂ glass (silica) medium. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre An optical fiber (or fibre) is a Glass or Plastic fiber that carries Light along its length The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide Image intensifiers are sensitive to this area of the spectrum. Examples include night vision devices such as night vision goggles.

• Short-wavelength infrared (SWIR, IR-B DIN): 1. 4-3 µm, 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

• Mid-wavelength infrared (MWIR, IR-C DIN) also called intermediate infrared (IIR): 3-8 µm. 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 IR signature of the target aircraft, typically the jet engine exhaust plume.

• Long-wavelength infrared (LWIR, IR-C DIN): 8–15 µm. This is the "thermal imaging" region, in which sensors can obtain a completely passive picture of the outside world based on thermal emissions only and requiring no external light or thermal source such as the sun, moon or infrared illuminator. Forward-looking infrared (FLIR) systems use this area of the spectrum. A forward looking infrared (FLIR is an imaging device that senses infrared radiation Sometimes also called the "far infrared. "

• Far infrared (FIR): 15-1,000 µm (see also far infrared laser)

NIR and SWIR is sometimes called reflected infrared while MWIR and LWIR is sometimes referred to as thermal infrared. Far infrared laser ( FIR laser, terahertz laser) is a Laser with output Wavelength in Far infrared part of the Electromagnetic 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.

Astronomers typically divide the infrared spectrum as follows:^[5]

• near: (0. 7-1) to 5 µm
• mid: 5 to (25-40) µm
• long: (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.

Plot of atmospheric transmittance in part of the infrared region.

A third scheme divides up the band based on the response of various detectors:^[6]

• Near infrared (NIR): from 0. 7 to 1. 0 micrometers (from the approximate end of the response of the human eye to that of silicon)
• Short-wave infrared (SWIR): 1. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre 0 to 3 micrometers (from the cut off of silicon to that of the MWIR atmospheric window. InGaAs covers to about 1. 8 micrometers; the less sensitive lead salts cover this region
• Mid-wave infrared (MWIR): 3 to 5 micrometers (defined by the atmospheric window and covered by Indium antimonide [InSb] and HgCdTe and partially by lead selenide [PbSe])
• Long-wave infrared (LWIR): 8 to 12, or 7 to 14 micrometers: the atmospheric window (Covered by HgCdTe and microbolometers)
• Very-long wave infrared (VLWIR): 12 to about 30 micrometers, covered by doped silicon

These divisions are justified by the different human response to this radiation: 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 regime. Indium antimonide ( is a Narrow gap Semiconductor material from the III - V group used in Infrared detectors including Thermal HgCdTe or mercury Cadmium Telluride (also cadmium mercury telluride, MCT or CMT) is an Alloy of Lead selenide () or lead(II selenide, a Selenide of Lead, is a Semiconductor material. A microbolometer is a specific type of Bolometer used as a detector in a Thermal camera. 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' sensitivity starts around 950 nm and ends between 1,700 and 2,600 nm, depending on the specific configuration). Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Indium gallium arsenide ( InGaAs) is a Semiconductor composed of Indium, Gallium and Arsenic. Unfortunately, international standards for these specifications are not currently available.

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 shorter frequencies make insignificant contributions to scenes illuminated by common light sources. Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain But particularly intense light (e. g. , from lasers, or from bright daylight with the visible light removed by colored gels[1]) can be detected up to approximately 780 nm, and will be perceived as red light. A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. The onset of infrared is defined (according to different standards) at various values typically between 700 nm and 800 nm.

Telecommunication bands in the infrared

In optical communications, the part of the infrared spectrum that is used is divided into several bands based on availability of light sources, transmitting/absorbing materials (fibers) and detectors:^[7]

The C-band is the dominant band for long-distance telecommunication networks. Optical communication is any form of Telecommunication that uses Light as the transmission medium The S and L bands are based on less well established technology, and are not as widely deployed.

Heat

Main article: Thermal radiation

Infrared radiation is popularly known as "heat" or sometimes "heat radiation", since many people attribute all radiant heating to infrared light and/or to all infrared radiation to being a result of heating. Thermal radiation is Electromagnetic radiation emitted from the surface of an object which is due to the object's Temperature. This is a widespread misconception, since light and electromagnetic waves of any frequency will heat surfaces that absorb them. Infrared light from the Sun only accounts for 49%^[8] of the heating of the Earth, with the rest being caused by visible light that is absorbed then re-radiated at longer wavelengths. Visible light or ultraviolet-emitting lasers can char paper and incandescently hot objects emit visible radiation. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. It is true that objects at room temperature will emit radiation mostly concentrated in the 8 to 12 micrometer 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). Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Spontaneous emission is the process by which a light source such as an Atom, Molecule, Nanocrystal or nucleus in an Excited state Thermal radiation is Electromagnetic radiation emitted from the surface of an object which is due to the object's Temperature. In Physics, a black body is an object that absorbs all light that falls on it ^[9]

Heat is energy in transient form that flows due to temperature difference. In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature Unlike heat transmitted by thermal conduction or thermal convection, radiation can propagate through a vacuum. Heat conduction or thermal conduction is the spontaneous transfer of thermal energy through matter from a region of higher Temperature to a region of lower Convective heat transfer is a mechanism of Heat transfer occurring because of bulk motion (observable movement of fluids This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner.

The concept of emissivity is important in understanding the infrared emissions of objects. The emissivity of a material (usually written \epsilon is the ratio of energy radiated by a particular material to energy radiated by a Black body at This is a property of a surface which describes how its thermal emissions deviate from the ideal of a black body. In Physics, a black body is an object that absorbs all light that falls on it To further explain, two objects at the same physical temperature will not 'appear' the same temperature in an infrared image if they have differing emissivities.

Applications

Infrared Filters

Main article: Night vision

Infrared (IR) filters can be made from many different materials. Night vision is the ability to see in a dark environment Whether by biological or technological means night vision is made possible by a combination of two approaches sufficient One type is made of polysulphone plastic that blocks over 99% of the visible light spectrum from “white” light sources such as incandescent filament bulbs. Polysulfone describes a family of Thermoplastic polymers These polymers are known for their toughness and stability at high temperatures Infrared filters allow a maximum of infrared output while maintaining extreme covertness. Currently in use around the world, infrared filters are used in Military, Law Enforcement, Industrial and Commercial applications. The unique makeup of the plastic allows for maximum durability and heat resistance. IR filters provide a more cost effective and time efficient solution over the standard bulb replacement alternative. All generations of night vision devices are greatly enhanced with the use of IR filters.

Night vision

Main article: Night vision

Active-infrared night vision. Night vision is the ability to see in a dark environment Whether by biological or technological means night vision is made possible by a combination of two approaches sufficient 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. ^[10] Night vision devices operate through a process involving the conversion of ambient light photons into electrons which are then amplified by a chemical and electrical process and then converted back into visible light. A night vision device (NVD is an Optical instrument that allows images to be produced in levels of light approaching total darkness ^[10] 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. ^[10]

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^[11]

Thermography

Main article: Thermography

A thermographic image of a dog

Infrared radiation can be used to remotely determine the temperature of objects (if the emissivity is known). wiki stranglesnakejpg|thumb|Thermographic image of a Snake held by a human]] Infrared Thermography, thermal imaging, or thermal video, is a type of In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature wiki stranglesnakejpg|thumb|Thermographic image of a Snake held by a human]] Infrared Thermography, thermal imaging, or thermal video, is a type of This is termed thermography, or in the case of very hot objects in the NIR or visible it is termed pyrometry. wiki stranglesnakejpg|thumb|Thermographic image of a Snake held by a human]] Infrared Thermography, thermal imaging, or thermal video, is a type of Pyrometry is the non-contact measurement of the Temperature of an object by measuring its self-emission and Emissivity. 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 detect radiation in the infrared range of the electromagnetic spectrum (roughly 900–14,000 nanometers or 0. A thermographic camera, sometimes called a FLIR (Forward Looking InfraRed or an infrared camera less specifically is a device that forms an image using Infrared 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. In Physics, a black body is an object that absorbs all light that falls on it The amount of radiation emitted by an object increases with temperature, therefore thermography allows one to see variations in temperature (hence the name).

Other imaging

Infrared light from the LED of a remote control as seen by a digital camera. A remote control is an electronic device used for the remote operation of a Machine.

In infrared photography, infrared filters are used to capture the near-infrared spectrum. An infrared filter is a filter to remove visible light and only pass Infrared light in different Wavelengths These are mainly used in Infrared photography Digital cameras often use infrared blockers. Many compact digital still cameras can record Sound and moving Video as well as still Photograph. Cheaper digital cameras and camera phones have less effective filters and can "see" intense near-infrared, appearing as a bright purple-white color. Many compact digital still cameras can record Sound and moving Video as well as still Photograph. A camera phone is a Mobile phone which is able to capture either still Photographs or Motion video. 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. Electromagnetic waves sent at terahertz frequencies, known as terahertz radiation, submillimeter radiation, terahertz waves, terahertz Electromagnetic waves sent at terahertz frequencies, known as terahertz radiation, submillimeter radiation, terahertz waves, terahertz Lack of bright sources makes terahertz photography technically 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. In Physics, terahertz time-domain spectroscopy (THz-TDS is a spectroscopic technique where a special generation and detection scheme is used to probe material

Tracking

Main article: Infrared homing

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. Infrared homing refers to a passive missile guidance system which uses the emission from a target of Electromagnetic radiation in the Infrared This is a list of sources of Light, including both natural and artificial sources and both processes and devices. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies Missiles which 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 infra-red wavelengths of light compared to objects in the background.

Heating

Main article: Infrared heating

Infrared radiation can be used as a deliberate heating source. An infrared heater is a body with a higher temperature which transfers energy to a body with a lower temperature through electromagnetic radiation For example it is used in infrared saunas to heat the occupants, and also to remove ice from the wings of aircraft (de-icing). An infrared sauna is a Sauna that heats its occupants with heaters that emit far Infrared radiant heat. FIR is also gaining popularity as a safe method of natural health care & physiotherapy. Far infrared thermomedic therapy garments use thermal thechnology to provide compressive support and healing warmth to assist symptom control for arthritis, injury & pain. 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 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. Efficiency is achieved by matching the wavelength of the infrared heater to the absorption characteristics of the material.

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. The Infrared Data Association ( IrDA) defines physical specifications Communications protocol standards for the short-range exchange of Data Remote controls and IrDA devices use infrared light-emitting diodes (LEDs) to emit infrared radiation which is focused by a plastic lens into a narrow beam. A lens is an optical device with perfect or approximate Axial symmetry which transmits and refracts Light, converging or diverging The beam is modulated, i. In Telecommunications, modulation is the process of varying a periodic Waveform, i e. switched on and off, to encode the data. Debt AIDS Trade in Africa (or DATA) is a Multinational non-government organization founded in January 2002 in London by U2 's The receiver uses a silicon photodiode to convert the infrared radiation to an electric current. Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 A photodiode is a type of Photodetector capable of converting Light into either current or Voltage, depending upon the mode of operation Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. 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 controls to command appliances. A remote control is an electronic device used for the remote operation of a Machine.

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. In Telecommunications Free Space Optics (FSO is an Optical communication technology that uses light propagating in free space to transmit data between two points A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission.

Infrared lasers are used to provide the light for optical fiber communications systems. An optical fiber (or fibre) is a Glass or Plastic fiber that carries Light along its length 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. In Optics, dispersion is the phenomenon in which the Phase velocity of a wave depends on its frequency The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide

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. Remote Infrared Audible Signage (RIAS was developed by Smith-Kettlewell Eye Research Institute so that print-handicapped people ( Blindness /low-vision/illiterate/foreign/

Spectroscopy

Infrared vibrational spectroscopy (see also near infrared spectroscopy) is a technique which can be used to identify molecules by analysis of their constituent bonds. Infrared spectroscopy (IR spectroscopy is the subset of Spectroscopy that deals with the Infrared region of the Electromagnetic spectrum. Near infrared spectroscopy (NIRS is a Spectroscopic method utilising the near Infrared region of the Electromagnetic spectrum (from about 800 nm to 2500 Each chemical bond in a molecule vibrates at a frequency which is 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 which has the same frequency. In physics there are two kinds of dipoles ( Hellènic: di(s- = two- and pòla = pivot hinge An electric dipole is a In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena 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. An organic compound is any member of a large class of Chemical compounds whose Molecules contain Carbon. 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 3200cm^-1).

Meteorology

IR Satellite picture taken 1315 Z on 15th October 2006. A frontal system can be seen in the Gulf of Mexico with embedded Cumulonimbus cloud. A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena. The Gulf of Mexico ( Spanish: Golfo de México) is the ninth largest Body of water in the world Shallower Cumulus and Stratocumulus can be seen off the Eastern Seaboard. The East Coast of the United States, also known as the "Eastern Seaboard" or "Atlantic Seaboard" refers to the easternmost coastal states in the central and northern

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. A weather satellite is a type of Satellite that is primarily used to monitor the Weather and Climate of the Earth. The scanning is typically in the range 10. 3-12. 5 µm (IR4 and IR5 channels).

High, cold ice cloud such as Cirrus or Cumulonimbus show up bright white, lower warmer cloud such as Stratus or Stratocumulus show up as grey with intermediate clouds shaded accordingly. Cumulonimbus (Cb is a type of Cloud that is tall dense and involved in Thunderstorms and other intense Weather. A stratocumulus Cloud belongs to a class characterized by large dark rounded masses usually in groups lines or waves the individual elements being larger than those in 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. Fog is a cloud that is in contact with the ground Stratus clouds are usually the only clouds that touch the ground 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 phenomena can be spotted. El Niño-Southern Oscillation ( ENSO; commonly referred to as simply El Niño) is a global coupled ocean-atmosphere phenomenon Using color-digitized techniques, the gray shaded thermal images can be converted to color for easier identification of desired information.

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 the earth's climate. It is one of the primary parameters studied in research into global warming together with solar radiation. Global warming is the increase in the average measured temperature of the

A pyrgeometer is utilized in this field of research to perform continuous outdoor measurements. A pyrgeometer is a device that measures the atmospheric Infra-red radiation Spectrum that extends approximately from 4 This is a broadband infrared radiometer with sensitivity for infrared radiation between approximately 4. 5 µm and 50 µm.

Astronomy

The Spitzer Space Telescope is a dedicated infrared space observatory currently in orbit around the Sun. The Spitzer Space Telescope (formerly the Space Infrared Telescope Facility, SIRTF) is an Infrared Space observatory. (Note the black side to the telescope, to maximize infrared radiation. ) NASA image. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program

Main articles: 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. Infrared astronomy is the branch of Astronomy and Astrophysics which deals with objects visible in Infrared (IR radiation Far infrared astronomy is the branch of Astronomy and Astrophysics which deals with objects visible in Far-infrared radiation (extending from 30 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. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical

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. The atmospheric window refers to those parts of the Electromagnetic spectrum that are with the Earth's atmosphere in its natural state not absorbed at 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. See also Solar nebula A molecular cloud, sometimes called a stellar nursery if Star formation is occurring within is a type of Interstellar Infrared can also be used to detect protostars before they begin to emit visible light. A protostar is a large object that forms by contraction out of the gas of a Giant molecular cloud in the Interstellar medium. Stars emit a smaller portion of their energy in the infrared spectrum, so nearby cool objects such as planets can be more readily detected. A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is (In the visible light spectrum, the glare from the star will drown out the reflected light from a planet. )

Infrared light is also useful for observing the cores of active galaxies which are often cloaked in gas and dust. An active galactic nucleus ( AGN) is a compact region at the centre of a Galaxy which has a much higher than normal luminosity over some or all of the Electromagnetic 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. In Physics and Astronomy, redshift occurs when Electromagnetic radiation – usually Visible light – emitted or reflected by ^[2]

Art history

The Arnolfini Portrait by Jan van Eyck, National Gallery, London

Infra-red (as art historians call them) reflectograms are taken of paintings to reveal underlying layers, in particular the underdrawing or outline drawn by the artist as a guide. The Arnolfini Portrait is a Painting in oils on Oak Panel executed by the Early Netherlandish painter Jan van Jan van Eyck or Johannes de Eyck (jɑn vɑn ɛik (before c 1395 &ndash before July 9, 1441) was an Early Netherlandish painter active Underdrawing is the Drawing done on a painting ground before paint is applied for example an Imprimatura or an Underpainting. This often uses carbon black which shows up well in reflectograms, so long as it has not also been used in the ground underlying the whole painting. Carbon black is a material produced by the incomplete Combustion of heavy Petroleum products such as FCC tar coal tar ethylene cracking tar and a small amount from Art historians are looking to see if the visible layers of paint differ from the under-drawing or layers in between - such alterations are called pentimenti when made by the original artist. A pentimento (plural pentimenti) is an alteration in a painting evidenced by traces of previous work showing that the artist has changed his mind as to the composition during 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. Generally the more pentimenti, the more likely a painting is to be the prime version. It also gives useful insights into working practices. [2]

Among many other changes in the Arnolfini Portrait of 1434 (right), his face was higher by about the height of his eye, hers was higher, and her eyes looked more to the front. The Arnolfini Portrait is a Painting in oils on Oak Panel executed by the Early Netherlandish painter Jan van 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. ^[12]

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 Dunhuang Caves. The Dead Sea Scrolls consist of roughly 1000 documents including texts from the Hebrew Bible, discovered between 1947 and 1979 in eleven Caves The Villa of the Papyri is a private house in the ancient Roman city of Herculaneum (current commune of Ercolano) The Mogao Caves, or Mogao Grottoes ( (also known as the Caves of the Thousand Buddhas and Dunhuang Caves) form a system of 492 temples 25km (15 ^[13] Carbon black used in ink can show up extremely well.

Biological systems

Thermographic image of a snake eating a mouse

Thermographic image of a fruit bat. For other uses of the term "Flying fox" see Flying fox (disambiguation Megabats is the term used informally to refer to bats

The pit viper is known to have two infrared sensory pits on its head. Common names: pit vipers pitvipers The Crotalinae, or crotalines are a subfamily of venomous vipers found There is controversy over the exact thermal sensitivity of this biological infrared detection system. ^[14][15]

Other organisms that actively employ thermo-receptors are rattlesnakes (Crotalinae subfamily) and boas (Boidae family), the Common Vampire Bat (Desmodus rotundus), a variety of jewel beetles (Melanophila acuminata),^[16] darkly pigmented butterflies (Pachliopta aristolochiae and Troides rhadamantus plateni), and possibly blood-sucking bugs (Triatoma infestans). Rattlesnakes are a group of venomous Snakes, genera Crotalus and Sistrurus. Boa Kwon (born November 5, 1986) have contributed to her commercial success in South Korea and Japan and her popularity throughout Asia The Common Vampire Bat ( Desmodus rotundus) is a species of Vampire bat. Buprestidae is a family of Beetles known as jewel beetles or metallic wood-boring beetles because of their glossy Iridescent The Common Rose ( Atrophaneura (Pachliopta aristolochiae) is a Swallowtail butterfly belonging to the Pachliopta subgenus the Roses of the genus Triatoma infestans is a blood-sucking bug (like all the members of its subfamily Triatominae) and the most important vector of Chagas disease ^[17]

Photobiomodulation

Near infrared light is currently used for treatment of chemotherapy induced oral ulceration as well as wound healing. There is some work relating to anti herpes virus treatment. ^[18] Research projects include work on central nervous system healing effects via cytochrome c oxidase upregulation and other possible mechanisms. ^[19]

The Earth as an infrared emitter

The Earth's surface and the clouds absorb visible and invisible radiation from the sun and re-emit much of the energy as infrared back to the atmosphere. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 In Physics, absorption of electromagnetic radiation is the process by which the Energy of a Photon is taken up by matter typically the electrons of an The Sun (Sol is the Star at the center of the Solar System. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five Certain substances in the atmosphere, chiefly cloud droplets and water vapor, but also carbon dioxide, methane, nitrous oxide, sulfur hexafluoride, and chlorofluorocarbons,^[20] absorb this infrared, and re-radiate it in all directions including back to Earth. Water is a common Chemical substance that is essential for the survival of all known forms of Life. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Nitrous oxide, commonly known as " laughing gas," is a Chemical compound with the Chemical formula N 2 O. Sulfur hexafluoride is an Inorganic compound with the formula. The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of Chemical compounds consisting of Alkanes such as Methane Thus the greenhouse effect keeps the atmosphere and surface much warmer than if the infrared absorbers were absent from the atmosphere. The Greenhouse effect refers to the change in the Thermal equilibrium temperature of a planet or moon by the presence of an Atmosphere containing gas that absorbs ^[21]

History of infrared science

The discovery of infrared radiation is ascribed to William Herschel, the astronomer, in the early 19th century. Sir Frederick William Herschel FRS KH ( 15 November 1738 – 25 August 1822) was a German -born British Historically Astronomy was more concerned with the classification and description of phenomena in the sky while Astrophysics attempted to explain these phenomena Herschel published his results in 1800 before the Royal Society of London. The Royal Society of London for the Improvement of Natural Knowledge, known simply as The Royal Society, is a Learned society for science that was founded in 1660 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. In Optics, a dispersive prism is a type of optical prism, normally having the shape of a geometrical triangular prism. Refraction is the change in direction of a Wave due to a change in its Speed. The Sun (Sol is the Star at the center of the Solar System. Red is any of a number of similar Colors evoked by light consisting predominantly of the longest wavelengths of Light discernible by the human eye in the wavelength The thermometer is a device that measures Temperature or Temperature gradient using a variety of different principles it comes from the Greek roots He was surprised at the result and called them "Calorific Rays". The term 'Infrared' did not appear until late in the 19th century. ^[22]

Other important dates include:^[6]

• 1835: Macedonio Melloni makes the first thermopile IR detector;
• 1860: Gustav Kirchhoff formulates the blackbody theorem E = J(T,n);
• 1873: Willoughby Smith discovers the photoconductivity of selenium;
• 1879: Stefan-Boltzmann law formulated empirically
• 1880s & 1890s: Lord Rayleigh and Wilhelm Wien both solve part of the blackbody equation, but both solutions are approximations that "blow up" out of their useful ranges. Macedonio Melloni ( April 11 1798 – August 11 1854) was an Italian Physicist, notable for demonstrating that Radiant A thermopile is an electronic device that converts Thermal energy into Electrical energy. Gustav Robert Kirchhoff ( March 12, 1824 &ndash October 17, 1887) was a German Physicist who contributed to the fundamental See also Kirchhoff's laws for other laws named after Kirchhoff. Willoughby Smith ( April 6, 1828, Great Yarmouth, Norfolk — July 17, 1891, Eastbourne, Sussex) was Selenium (səˈliniəm is a Chemical element with the Atomic number 34 represented by the chemical symbol Se, an atomic mass of 78 The Stefan–Boltzmann law, also known as Stefan's law, states that the total Energy radiated per unit surface Area of a Black body in unit John William Strutt 3rd Baron Rayleigh OM (12 November 1842 &ndash 30 June 1919 was an English Physicist who with William Ramsay, discovered Wilhelm Carl Werner Otto Fritz Franz Wien ( German:) ( 13 January 1864 &ndash 30 August 1928) was a German physicist This problem was called the "UV Catastrophe and Infrared Catastrophe".
• 1901: Max Planck published the blackbody equation and theorem. For a general introduction see Black body. In Physics, Planck's law describes the spectral radiance of Electromagnetic radiation He solved the problem by quantizing the allowable energy transitions.
• Early 1900s: Albert Einstein develops the theory of the photoelectric effect, determining the photon. Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical Introduction When a Metallic surface is exposed to Electromagnetic radiation above a certain threshold Frequency, the light is absorbed and Electrons In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena Also William Coblentz in spectroscopy and radiometry. William Weber Coblentz ( November 20, 1873 &ndash September 15, 1962) was an American Physicist notable for his contributions Spectroscopy was originally the study of the interaction between Radiation and Matter as a function of Wavelength (λ In Optics, radiometry is the field that studies the Measurement of Electromagnetic radiation, including Visible light.
• 1917: Theodore Case develops thallous sulfide detector; British develop the first infra-red search and track (IRST) in World War I and detect aircraft at a range of one mile;
• 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. Theodore Willard Case (1888 Auburn New York &ndash 1944 known for the invention of the Movietone Sound-on-film Sound film system was born Thallium(I sulfide, Tl2S is a chemical compound of Thallium and Sulfur. An infra-red search and track ( IRST) system (sometimes known as infra-red sighting and tracking) is a method for detecting and tracking objects which give off World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including
• 1952: H. Welker discovers InSb;
• 1950s: Paul Kruse (at Honeywell) and Texas Instruments form infrared images before 1955;
• 1950s and 1960s: Nomenclature and radiometric units defined by Fred Nicodemenus, G. J. Zissis and R. Clark, Jones defines D*;
• 1958: W. D. Lawson (Royal Radar Establishment in Malvern) discovers IR detection properties of HgCdTe;
• 1958: Falcon & Sidewinder missiles developed using infrared and the first textbook on infrared sensors appears by Paul Kruse, et al. The Royal Radar Establishment, or RRE, was a renaming of the Radar Research Establishment, which was formed in 1953 from the merger of the Telecommunications The AIM-9 Sidewinder is a heat-seeking, short-range Air-to-air missile carried by Fighter aircraft and recently certain gunship helicopters
• 1961: J. Cooper demonstrated pyroelectric detection;
• 1962: Kruse and ? Rodat advance HgCdTe; Signal Element and Linear Arrays available;
• 1965: First IR Handbook; first commercial imagers (Barnes, Agema {now part of FLIR Systems Inc. FLIR Systems ( is a US -based Infrared (thermal imaging systems for airborne applications manufacturer }; Richard Hudson's landmark text; F4 TRAM FLIR by Hughes; phenomenology pioneered by Fred Simmons and A. Hughes Aircraft Company was a major aerospace and defense company founded by Howard Hughes. The Foot Fist Way is a 2008 low-budget Comedy film directed by Jody Hill and starring Danny R 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 & George E. Smith propose CCD at Bell Labs for picture phone;
• 1972: Common module program started by NVESD;
• 1978: Pommernig & ? Francis fabricate IRCCDs; US Common Module leads to a proliferation of IR Sensors in the U. Willard S Boyle (born August 19 1924) is a Canadian physicist and co-inventor of the Charge-coupled device. George E Smith (born May 10, 1930) is an American scientist and co-inventor of the Charge-coupled device. Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) is the Research organization A videophone, also known by the trademarked name Picturephone, is a Telephone which is capable of both audio and Video Duplex transmission S. military; commercial IR companies formed (Inframetrics in Boston, MA and FLIR Systems Inc. FLIR Systems ( is a US -based Infrared (thermal imaging systems for airborne applications manufacturer in Portland OR); Infrared imaging astronomy comes of age, observatories planned, IRTF on Mauna Kea opened; 32 by 32 and 64 by 64 arrays are produced in InSb, HgCdTe and other materials. The NASA Infrared Telescope Facility (NASA IRTF is a 30 meter Telescope optimized for use in Infrared astronomy and located at the Mauna Kea Observatory Indium antimonide ( is a Narrow gap Semiconductor material from the III - V group used in Infrared detectors including Thermal HgCdTe or mercury Cadmium Telluride (also cadmium mercury telluride, MCT or CMT) is an Alloy of

See also

References

External links

Journals

• Infrared Physics and Technology (Elsevier) (last access June 2005).

Web sites

• Infrared Spectroscopy NASA Open Spectrum wiki site
• Infrared Waves Detailed explanation of infrared light.
• U.S. Navy - Electronic Warfare and Radar Systems Engineering Handbook Source of transmittance diagram and further information on electro-optics.
• Infrared a Historical Perspective