Size-of-source (SSE) effect of broadband and interference filters for Double Wavelength Thermometers

In this work we present a comparative study of an impact of several optical windows (the SCHOTT glass filters (KG1 to KG5) with a broadband transmittance in the visible spectral range) and an interference filter (with a peak transmittance at 650 nm) on the size-of-source effect (SSE) of a radiation thermometer. The investigations were performed in the scope of the development of a Double Wavelength Radiation (DWT) thermometer at UME. There are two radiometric channels in the DWT, where one of the channels will comprise of a broadband transmittance filter, while the other - an interference filter. In order to exclude the optical path effects on the SSE measurements the investigations were performed on a single channel radiation thermometer. The SSE measurements were performed by means of the indirect method. The SSE measurement results are illustrated and discussed. (paper)