For opaque coatings the diffuse and regular components of transmittance, vanish and for a rough surface the regular reflectance, also vanishes and depends only on the diffuse reflectance. For military applications the emissivity may be as important as the temprature in creating the 'signature' of a target for passive IR systems, while for IR LIDAR the reflectance at the chosen laser wavelength is the key property. The measurement of diffuse reflectance or of emissivity requires complete hemispherical irradiation or collection of radiation, and no regularly available commercial spectrophotometer accessories can achieve this. A knowledge of the spectral emissivity over the thermal IR spectrum enables accurate total emissivities, to be computed at intervals of temperature T over a range of temperatures of interest: The NPL reflectometer/transmissometer has been used to investigate the complete set of radiometric properties of a variety of materials; the technique is described at this conference by Clarke and Larkin. We have made a series of measurements on possible materials for use in the construction of the Anglo-Dutch millimetre wave telescope to be built at an altitude of 4500 metres on the summit of Mauna Kea in Hawaii. The millimetre wave telescope will give between 10 and 100 times better resolution than conventional centimetre or decimetre wave telescope.
Radiometric properties of radome coatings and detector blacks
Radiometrisches Verhalten von Radom-Beschichtungsmaterial und Infrarotdetektor-Schwarzabdeckungen
1985
3 Seiten, 4 Bilder
Aufsatz (Konferenz)
Englisch