Emissivity Measurements: Infrared Imaging Radiometric Cameras

Authored by: Robert P. Madding

Encyclopedia of Optical and Photonic Engineering

Print publication date:  September  2015
Online publication date:  September  2015

Print ISBN: 9781439850978
eBook ISBN: 9781351247184
Adobe ISBN:

10.1081/E-EOE2-120009789

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Abstract

Emissivity is the efficiency of an object as a radiator of electromagnetic energy. It is dependent on material surface properties, shape, viewing angle, wavelength, and, to some degree, temperature. As such, measuring target emissivities with the same infrared camera as will be used for routine work gives the thermographer a much better estimate than could be obtained through published tables or other sources. In this entry, an example is given using a simplified result that assumes that atmospheric effects are negligible. The example illustrates that temperature measurement for emissivities below about 0.5 have a rapidly increasing uncertainty largely due to the emissivity value in the denominator.

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