Athermalization of a fast infrared telescope objective

摘要

In high performance optical systems, a frequent requirement is 'athermalization' or the stabilization of optical performance with environmental temperature. This is particularly relevant in the case of refracting infrared systems for which the variations of refractive index as a function of temperature are relatively large. In this paper, as an example of an athermalization problem, the approach adopted for the stabilization of an infrared multi- magnification 'zoom' telescope objective is reviewed and the mechanism devised for introducing the necessary adjustments is described. Finally, the variation in performance of an actual athermalized system, following heat soak over a temperature range of 130 degrees Celsius, is discussed. The telescope, which was designed for use in the 8.0 micrometer to 13.0 micrometer waveband, provides a set of four fixed magnifications ranging from $MUL@3.5 to $MUL@20. It employs germanium and zinc selenide as refracting materials.