Multi-Wavelength Pyrometry

The main problem in the application of radiation pyrometry to the measurement of true surface temperatures is the large error arising from the unknown or varying emissivity of the surface. The nature of the additional information required for the class of techniques which utilize only the thermal radiation emitted from the surface is discussed. The suggestions that multi-wavelength pyrometry, requiring measurements at many different wavelengths, may be employed to solve the problem without additional information are analyzed, and shown to possess distinct disadvantages.