Abstract: The apparatus and method permit simultaneous and precise determination of the temperature and spectral emittance, over a wide spectral region, of a hot sample. Radiance, and hemispherical reflectance and transmittance measurements are employed, and FT-IR technology is advantageously applied. Reflectance and (where necessary) transmittance measurements are utilized to determine the fraction of incident radiation, of selected wavelength, that is absorbed by the sample, in turn establishing a spectral emittance value. Taken with the measured radiance at the same wavelength, the spectral emittance value will provide a quantity that can be matched with the spectral radiance of a theoretical black body, again at the selected wavelength, to thereby derive the temperature of the hot sample; this in turn enables determination of the spectral emittance of the sample over a desired spectral range.

Abstract: The spectrometer permits transmission and emission measurements to be made selectively and accurately without extinguishing the internal radiation source. It includes a device that blocks the divergent source-beam radiation that would otherwise corrupt the emission signal received by the detector.

Abstract: An optical technique for determining surface temperature utilizes the Christiansen effect that is exhibited by dielectric materials; i.e., strong absorption bands at certain wavenumber values, causing the radiance of the material to be that which would characterize a theoretical black body at that wavenumber value.