By K.-P. Möllmann, F. Pinno, M. Vollmer, Brandenburg University of Applied Sciences, Germany
Two-color or ratio pyrometry is a well-established method to overcome the fundamental difficulties in determining and eliminating the effect of emissivity in the temperature measurement. As an approach for an "emissivity-free" radiation thermometry, the radiance within two narrow spectral bands is measured and the object temperature is determined from the signal ratio while at the same time eliminating the influence of the emissivity under certain conditions. The improved sensitivity of IR camera detectors allows the application of this method to infrared thermal imaging. Based on a discussion of the theoretical basics of this measurement principle, the paper will give a detailed analysis of the most important parameters influencing the accuracy of the temperature measurement using ratio thermal imaging:
Following this analysis, we discuss the necessary measurement conditions as well as the potentials and the limits of ratio thermal imaging. Experimental investigations were carried out using a FLIR SC6000 research camera with narrow band pass filters.