EQUIPMENT
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Thermal imaging
cameras vary according to the type of detectors used, the wavelength, the
cooling methods employed, the useful application, and the digital features
incorporated.
For a good discussion on the advancements in thermal imaging equipment, refer to the magazine, BioPhotonics International - Nov/Dec 1998 issue, pages 48-53. A Laurin Publication. Laurin Publishing Co. Inc., Berkshire Common, PO Box 4949, Pittsfield, MA 01202-4949. The March 1998 issue of Optoelectronics World has an interesting article for "Understanding and Using Focal-Plane arrays. It discusses detector materials, pros/cons of various FPAs, nonuniformity correction, ambient temperature compensation and chromatic aberration. These are all technical hurdles to overcome with this new class of detectors, and addressed with varying degrees of success, depending upon the manufacturer and the design considerations. This interesting discussion is handled knowledgeably by Andrew C. Teich, V.P. of thermography systems at Inframetrics Inc., 16 Esquire Road, N. Billerica, MA 01862. According to Mark G. Rockley, Ph.D., Chemistry Dept., Oklahoma State University, both MCT and Bolometer Focal Plane Arrays suffer from some characteristic performance flaws. Each element is independent of every other. Therefore, while the NEDT might be useful, the responsiviity of the individual detectors changes from one to the next. Over time this becomes a problem and the entire array needs to be recalibrated pixel by pixel with a new look up table, converting reading into temperature in a way that is the same for every pixel. The result is that FPAs are fine for real time imaging, but for serious consistent study, a unit in which the detector variability (and cross talk between pixels) is minimized would be the most desirable. Dr. Rockley's scientific
designs are the basis for the highly sensitive medical infrared system,
the Teletherm Mark/1026, shown here on a counter-balanced camera stand.
For information on this camera, click on the following URL: http://www.thermology.com/teletherm
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