The Influence of the Temperature Coefficient of Refractive Index on a Thermal Imager.

摘要

The temperature coefficient of refractive index for germanium was determined in the 8-12 micrometers and 3-5 micrometers wavebands. The Strehl intensity ratio and frequency response of an optical system are related to a lens temperature changes, and a simple factor for a comparison of different lens materials is included. The relative change in minimum resolvable temperature difference MRTD of a thermal imaging system is shown for a defocused optical system, where the defocus is related to a lens temperature change. It is shown that the criterion for a good optical performance may be applied to the relative change in MRTD for a thermal imager, and that the Marechal approximation to the Strehl ratio may be used to determine a tolerance upon a change in lens temperature. (Author)