Thermography

Information about Thermography

This article is about the infrared imaging technique. For the printing technique called thermography, see thermographic printing

Image of a small dog taken in mid-infrared ("thermal") light (false color)

Thermographic image of two ostriches

Thermographic image of a snake held by a human

Thermographic image of a lion

Thermographic image of a traditional building in the background and a 'passive house' in the foreground

Thermography, thermal imaging, or thermal video, is a type of infrared imaging. Thermographic cameras detect radiation in the infrared range of the electromagnetic spectrum (roughly 900–14,000 nanometers or 0.9–14 Âµm) 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). When viewed by thermographic camera, warm objects stand out well against cooler backgrounds; humans and other warm-blooded animals become easily visible against the environment, day or night. As a result, thermography's extensive use can historically be ascribed to the military and security services.

Thermal imaging photography finds many other uses. For example, firefighters use it to see through smoke, find persons, and localize the base of a fire. With thermal imaging, power lines maintenance technicians locate overheating joints and parts, a telltale sign of their failure, to eliminate potential hazards. Where thermal insulation becomes faulty, building construction technicians can see heat leaks to improve the efficiencies of cooling or heating air-conditioning. Thermal imaging cameras are also installed in some luxury cars to aid the driver, the first being the 2000 Cadillac DeVille. Some physiological activities, particularly responses, in human beings and other warm-blooded animals can also be monitored with thermographic imaging. [1]

The appearance and operation of a modern thermographic camera is often similar to a camcorder. Enabling the user to see in the infrared spectrum is a function so useful that ability to record their output is often optional. A recording module is therefore not always built-in.

Instead of CCD sensors, most thermal imaging cameras use CMOS Focal Plane Array (FPA). The most common types are InSb, InGaAs, QWIP FPA. The newest technologies are using low cost and uncooled microbolometers FPA sensors. Their resolution is considerably lower than of optical cameras, mostly 160x120 or 320x240 pixels, up to 640x512 for the most expensive models. Thermographic cameras are much more expensive than their visible-spectrum counterparts, and higher-end models are often export-restricted. Older bolometers or more sensitive models as InSB require cryogenic cooling, usually by a miniature Stirling cycle refrigerator or liquid nitrogen.

Difference between IR film and thermography

IR film is sensitive to temperatures between 250 Â°C and 500 Â°C while thermography is sensitive to approximately -50 Â°C to over 2,000 Â°C. So for a IR film to show something it must be over 250 Â°C or be reflecting infrared radiation from something that is at least that hot. Night vision goggles normally just amplify the small amount of light that is available outside like starlight or moon light and can't see heat or work in complete darkness.

Advantages of Thermography

You get a visual picture so that you can compare temperatures over a large area
It is real time capable of catching moving targets
Able to find deteriorating components prior to failure
Measurement in areas inaccessible or hazardous for other methods

Limitations & disadvantages of thermography

Quality cameras are expensive and are easily damaged
Images can be hard to interpret accurately even with experience
Accurate temperature measurements are very hard to make because of emissivities
Most cameras have Â±2% or worse accuracy (not as accurate as contact)
Training and staying proficient in IR scanning is time consuming

Applications

Condition monitoring
Medical imaging
Research
Process control
Non destructive testing
Chemical imaging

Thermal infrared imagers convert the energy in the infrared wavelength into a visible light video display. All objects above 0 kelvins emit thermal infrared energy so thermal imagers can passively see all objects regardless of ambient light. However, most thermal imagers only see objects warmer than -50 Â°C.

The spectrum and amount of thermal radiation depend strongly on an object's surface temperature. This makes it possible for a thermal camera to display an object's temperature. However, other factors also influence the radiation, which limits the accuracy of this technique. For example, the radiation depends not only on the temperature of the object, but is also a function of the emissivity of the object. Also, radiation also originates from the surroundings and is reflected in the object, and the radiation from the object and the reflected radiation will also be influenced by the absorption of the atmosphere.

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Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. The name means "below red" (from the Latin infra, "below"), red being the color of visible light with the longest wavelength.
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Electromagnetic (EM) radiation is a self-propagating wave in space with electric and magnetic components. These components oscillate at right angles to each other and to the direction of propagation, and are in phase with each other.
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electromagnetic (EM) spectrum is the range of all possible electromagnetic radiation. The "electromagnetic spectrum" (usually just spectrum) of an object is the frequency range of electromagnetic radiation with wavelengths from thousands of kilometers down to fractions of
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1 nanometre =
SI units
010⁻⁹ m 010⁻³ μm
US customary / Imperial units
010⁻⁹ ft 010⁻⁹ in

A nanometre (American spelling: nanometer, symbol nm
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black body is an object that absorbs all electromagnetic radiation that falls onto it. No radiation passes through it and none is reflected. It is this lack of both transmission and reflection to which the name refers.
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For a general introduction, see black body.

In physics, Planck's law describes the spectral radiance of electromagnetic radiation at all wavelengths from a black body at temperature .
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visible spectrum (or sometimes optical spectrum) is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light.
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firefighter (also called a fireman or firewoman, although these terms have gone out of use in many countries) is trained and equipped to extinguish fires. Increasingly a firefighter is also a rescuer, trained and equipped to rescue people from car accidents, collapsed
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Smoke is the airborne solid and liquid particulates and gases emitted when a material undergoes pyrolysis or combustion, together with the quantity of air that is entrained or otherwise mixed into the mass.
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Electric power transmission, a process in the delivery of electricity to consumers, is the bulk transfer of electrical power. Typically, power transmission is between the power plant and a substation near a populated area.
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thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer.

Heat is transferred from one material to another by conduction, convection and/or radiation.
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construction is the building or assembly of any infrastructure on a site or sites. Although this may not be thought of as a single activity, in fact construction is a feat of multitasking.
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The term air conditioning most commonly refers to the cooling and dehumidification of indoor air for thermal comfort. In a broader sense, the term can refer to any form of cooling, heating, ventilation or disinfection that modifies the condition of air.
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DeVille (also De Ville and de Ville) name has been used on many of Cadillac's luxury car models. After the Fleetwood was dropped from the Cadillac lineup the DeVille became the largest Cadillac sedan.
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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 light.
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A camcorder is a portable electronic device for recording video images and audio onto an internal storage device. The camcorder contains both a video camera and (traditionally) a videocassette recorder in one unit, hence its portmanteau name.
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charge-coupled device (CCD) is an analog shift register, enabling analog signals (electric charges) to be transported through successive stages (capacitors) controlled by a clock signal.
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Complementary metal–oxide–semiconductor (CMOS) ("see-moss", IPA: /ˈsiːmɒs/), is a major class of integrated circuits.
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FPA may refer to:

Foreign Policy Association, a U.S. Educational Organization
Family Planning Association, a UK sexual health charity
Federal Power Act
Financial Planning Association
First-person adventure A video game genre.

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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.
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pixel (short for picture element, using the common abbreviation "pix" for "pictures") is a single point in a graphic image. Each such information element is not really a dot, nor a square, but an abstract sample.
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bolometer is a device for measuring the energy of incident electromagnetic radiation. It was invented in 1878 by the American astronomer Samuel Pierpont Langley.

It consists of an "absorber" connected to a heat sink (area of constant temperature) through an insulating link.
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In the family of heat engines, 'Stirling engine' defines a closed-cycle regenerative hot air engine, though the term is often used incorrectly to refer generically to a much wider range of hot air engine types.
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Liquid nitrogen (liquid density at the triple point is 0.807 g/mL) is the liquid produced industrially in large quantities by fractional distillation of liquid air and is often referred to by the abbreviation, LN₂. It is pure nitrogen, in a liquid state.
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Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). The degree Celsius (symbol: Â°C) can refer to a specific temperature on the Celsius scale
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Please help [ improve this article] by checking for inaccuracies. This article has been tagged since August 2007.
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Light is electromagnetic radiation of a wavelength that is visible to the eye (visible light). In a scientific context, the word "light" is sometimes used to refer to the entire electromagnetic spectrum.
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Starlight is a common word for the light emitted by stars, more specifically stars other than the Sun, light emitted by the Sun is called Sunlight.

Other uses of this term:

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