Rendition of an imaging bolometer from Los Alamos National Laboratory

A bolometer is a device for measuring incident electromagnetic radiation. It was invented in 1878 by the American astronomer Samuel Pierpont Langley. Image File history File links BOLO3D.gif Summary Cartoon of an imaging Bolometer from Los Alamos National Laboratory Licensing File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links BOLO3D.gif Summary Cartoon of an imaging Bolometer from Los Alamos National Laboratory Licensing File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Los Alamos National Laboratory, aerial view from 1995. ... Electromagnetic radiation can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... Samuel Pierpont Langley. ...

It consists of an "absorber" connected to a heat sink (area of constant temperature) through an insulating link. The result is that any radiation absorbed by the absorber raises its temperature above that of the heat sink—the higher the power absorbed, the higher the temperature will be.

A thermometer of some kind, attached to the absorber, is used to measure the temperature, from which the absorbed power can be calculated. In some designs the thermometer is also the absorber; in others the absorber and thermometer are separate; this is known as "composite design". A common mercury thermometer A thermometer is a device which measures temperature or temperature gradient, using a variety of different principles. ...

While bolometers can be used to measure radiation of any frequency, for most wavelength ranges there are other methods of detection that are more sensitive. However, for sub-millimetre wavelengths (from around 200 µm to 1 mm wavelength), the bolometer is the most sensitive type of detector for any measurement over more than a very narrow wavelength range. The wavelength is the distance between repeating units of a wave pattern. ... Submillimetre Astronomy is the branch of observational astronomy that is conducted at submillimetre wavelengths. ...

Bolometers are therefore used for astronomy at these wavelengths. However, to achieve the best sensitivity, they must be cooled down to a fraction of a degree above absolute zero (typically from 50 millikelvins to 300 mK); this makes their operation technically somewhat challenging. A giant Hubble mosaic of the Crab Nebula, a supernova remnant Astronomy is the science of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earths atmosphere (such as auroras and cosmic background radiation). ... Absolute zero is the lowest possible temperature where nothing could be colder, and no heat energy remains in a substance. ... The Kelvin scale is a thermodynamic (absolute) temperature scale where absolute zero—the lowest possible temperature where nothing could be colder and no heat energy remains in a substance—is defined as zero kelvin (0 K). ...

The term bolometer is also used in high-energy physics (particle physics) to designate an unconventional particle detector. They use the same principle described above. The bolometers are sensitive not only to light but to every form of energy. The Compact Muon Solenoid (CMS) is an example of a large particle detector. ...

More conventional particle detectors are often sensitive to ionization effect of ionizating particles. Bolometers are almost directly sensitive to the energy left inside the absorber. For this reason they can be used not only for ionizating particles and photons, but also for non-ionizing particles, for any sort of radiation and even to search for unknown forms of mass or energy (like dark matter). They are very slow and have a high dead time. They completely lack of any sort of discrimination. On the other hand, compared to more conventional particle detectors, they are extremely efficient in energy resolution and in sensitivity. They can be used to test very high radio-purity. They are also known as thermal detectors. “Multivalent” redirects here. ... The word light is defined here as electromagnetic radiation of any wavelength; thus, X-rays, gamma rays, ultraviolet light, microwaves, radio waves, and visible light are all forms of light. ... Radiation in physics is the process of emitting energy in the form of waves or particles. ... In astrophysics and cosmology, dark matter is matter, not directly observed and of unknown composition, that does not emit or reflect enough electromagnetic radiation to be detected directly, but whose presence can be inferred from gravitational effects on visible matter. ... In particle and nuclear detectors the dead time is the time after each event detected by the detector in which the detector is not able to reveal another event if it happens. ...

The operating principle is similar to that of a calorimeter in thermodynamics. However, the approximations, ultra low temperature, and the different purpose of the device make the operational use rather different. In the jargon of high energy physics, these devices are not called calorimeters since this term is already used for a different type of detector (see Calorimeter (particle physics)). A calorimeter is a device used for calorimetry, the science of measuring the heat of chemical reactions or physical changes as well as heat capacity. ... Thermodynamics (from the Greek thermos meaning heat and dynamics meaning power) is a branch of physics that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analyzing the collective motion of their particles using statistics. ... Cryogenics is a branch of physics (or engineering) that studies the production of very low temperatures (below –150 °C, –238 °F or 123 K) and the behavior of materials at those temperatures. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... In particle physics, a calorimeter is an experimental apparatus that measures the energy of particles. ...

Their use as particle detectors is still at the developmental stage. Their use as particle detectors was proposed from the beginning of the 20th century, but the first regular, though pioneering, use was only in the 1980s because of the difficulty associated with having a system at cryogenic temperature. (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999... The 1980s refers to the years of 1980 to 1989. ... Cryogenics is the study of very low temperatures or the production of the same, and is often confused with cryobiology, the study of the effect of low temperatures on organisms, or the study of cryopreservation. ...

Langley's bolometer

The first bolometer used for infrared observatons by Langley had a very basic design: It consisted of two platinum strips, covered with lampblack, one strip was shielded from the radiation and one exposed to it. The strips formed two branches of a wheatstone bridge which was fitted with a sensitive galvanometer and connected to a battery. General Name, Symbol, Number platinum, Pt, 78 Chemical series transition metals Group, Period, Block 10, 6, d Appearance grayish white Atomic mass 195. ... Soot, also called lampblack or carbon black, is a dark powdery deposit of unburned fuel residues, usually composed mainly of amorphous carbon, that accumulates in chimneys, automobile mufflers and other surfaces exposed to smoke—especially from the combustion of carbon-rich organic fuels in the lack of sufficient oxygen. ... A Wheatstone bridge is a measuring instrument invented by Samuel Hunter Christie in 1833 and improved and popularized by Sir Charles Wheatstone in 1843. ... It has been suggested that Tangent galvanometer be merged into this article or section. ...

Electromagnetic radiation falling on the exposed strip would heat it, and change its resistance, the circuit thus effectively operating as a resistance temperature detector. A resistance temperature detector measures the relationship between electrical resistance and temperature. ...

This instrument enabled him to feel his way thermally over the whole spectrum, noting all the chief Fraunhofer lines and bands, which were shown by sharp serrations, or more prolonged depressions of the curve which gave the emissions, and discovered the lines and bands of the invisible infra-red portion. Solar Fraunhofer lines In physics and optics, the Fraunhofer lines are a set of spectral lines named for the German physicist Joseph von Fraunhofer (1787--1826). ...

Microbolometers

Main article: Microbolometer

A microbolometer is a specific type of bolometer used as a detector in a thermal camera. It is a grid of vanadium oxide or amorphous silicon heat sensors atop a corresponding grid of silicon. Infrared radiation from a specific range of wavelengths strikes the vanadium oxide and changes its electrical resistance. This resistance change is measured and processed into temperatures which can be represented graphically. The microbolometer grid is commonly found in two sizes, a 320×240 array or less expensive 160×120 array. Both arrays provide the same resolution with the larger array providing a wider field of view. Larger, 640×480 arrays were announced in 2005. A Microbolometer is a specific type of bolometer used as a detector in a thermal camera. ... A Microbolometer is a specific type of bolometer used as a detector in a thermal camera. ... Image of a small dog taken in mid-infrared (thermal) light (false color) 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 radiation, similar to a common camera that forms an image using visible... Vanadium(V) oxide (V2O5), commonly known as vanadium pentoxide, is the most important compound of vanadium. ... Amorphous silicon (a-Si) is the non-crystalline allotropic form of silicon. ... General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance as coarse powder, dark gray with bluish tinge Atomic mass 28. ... Image of two girls in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ... Radiation in physics is the process of emitting energy in the form of waves or particles. ... The wavelength is the distance between repeating units of a wave pattern. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... The field of view is the part of the observable world that is seen at any given moment. ...

References

• Knoll, Glenn F. (2000). Radiation Detection and Measurement, 3rd edition, New York: Wiley. ISBN 0-471-07338-5. 
• McCammon, D.; et al. (March 1993). "Thermal calorimeters for high resolution X-ray spectroscopy". Nuclear Instruments & Methods in Physics Research, Section A (Accelerators, Spectrometers, Detectors and Associated) A326 (1-2): 157-165. 
• This article incorporates text from the Encyclopædia Britannica Eleventh Edition article "Sun", a publication now in the public domain.

Encyclopædia Britannica, the 11th edition The Encyclopædia Britannica Eleventh Edition (1910–1911) is perhaps the most famous edition of the Encyclopædia Britannica. ... The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ...

External links

• NASA on the history of the Bolometer
• Langley's own words on the bolometer and its use