The measurement of the temperature of objects by remote means is important in science, industry, and other areas. A technique often employed is ratio radiometry, in which the temperature of the object is related to the ratio of the radiometric signals derived from each of two measurement spectral bands. A lingering question as to whether this technique is valid for determining temperature is answered. Although the technique is generally valid, certain spectral-band pairs can produce ambiguous results, namely, the same ratio can be obtained by looking at two objects, each at a particular, yet different temperature. Ambiguities occur only for spectral-band arrangements in which one spectral band is completely contained within the other. Examples are presented to illustrate this finding.
Joseph D. Fehribach,
R. Barry Johnson,
"Temperature Measurement Validity For Dual Spectral-Band Radiometric Techniques," Optical Engineering 28(12), 281255 (1 December 1989). http://dx.doi.org/10.1117/12.7977140