Spectral Directional Emittance Measurements In The Wavelength Range From 1 µm To 15 µm

It is the spectral emittance which governs the thermooptical behaviour of surfaces and coatings. It is also the spectral emittance which causes the most serious measuring problems in characterizing coatings. In principle there are two methods: the measurement of the emitted thermal radiation of heated samples and the measurement of the reflectance of opaque samples ( E( X) = 1 - 9(X)). The determination of the reflectance requires the measurement of the radiation reflected into the whole hemisphere, since most of the investigated surfaces are reflecting diffusely. In the spectral range from 1 pm to about 15 μm this can be done with the aid of integrating spheres.