Infrared thermography

Description

A technique that measures temperature variations of an object or area. Infrared thermography is used to evaluate cool and warm air pockets in a room as well as to pinpoint heat loss locations. As a non destructive testing method, it can be also used to detect voids or delaminations in solid structures. To detect voids, the back surface of an object (wood, ceramic, metal, plaster, etc.) is cooled or heated while the front surface is monitored by infrared thermography. Because air has low thermal conductivity, air pockets will transmit heat differently than surrounding materials that are contiguous. This results in cool or warm areas on the surface that correspond to the voids. Photographic film or, more typically, an infrared camera is used to detect the temperature variations. Such cameras are very sensitive and can detect variations of 0.2 °C. The resultant image is called a thermogram. False colors are often used to enhance the temperature variations. Most thermal imaging cameras use specialized focal plane arrays that respond to infrared radiation. The most common types are InSb, InGaAs, HgCdTe... The newest technologies are using low-cost and uncooled microbolometers sensors. Their resolution is considerably lower than of optical cameras, mostly 160x120 up to 640x512 for the most expensive models. Thermographic cameras are much more expensive than their visible-spectrum counterparts.

Synonyms and Related Terms

thermographie infrarouge (Fr.); Infrarot Thermographie (Deut.)

Resources and Citations

• B.F.Miller, "The Feasibility of Using Thermography to Detect Subsurface Voids in Painted Wooden Panels" JAIC 16(2):27-35, 1977.

• J.C. Candoré, J.L Bodnar, V. Detalle, Ph. Grossel: Non destructive testing in situ, of works of art by stimulated infra-red thermography, Journal of physics conferences series, 214, (2010) 012068