Many applications in materials research and production require accurate, non-contact surface temperature measurements on various materials under a variety of conditions. All such surfaces emit radiation, which may be used as a measure of their surface temperature, providing the surface's emissivity is known. Unfortunately, emissivity values are usually uncertain, which leads to errors in conventional pyrometry. This proposal concerns a new active pyrometer method, wherein the ratio of target reflectances at two separate wavelengths is measured together with the target radiances at these same wavelengths. From these values the surface emissivity may be determined and the target temperature accurately measured for materials having arbitrary surface textures. Quantum Logic Corporation has developed and markets a line of single- wavelength laser-based active pyrometers, but they are effective only for targets known in advance to have diffusely scattering or perfectly specular surfaces. Also, the semiconductor lasers required for these instruments are available only at wavelengths suitable for very high temperature measurements. We plan to develop a two-wavelength active pyrometer as described above employing non-coherent radiation sources which will be suitable for a very wide range of temperatures and for targets having arbitrary surface textures, thereby greatly extending the applications of active pyrometer technology.
