Athermal MWIR objectives

Utilizing an athermal chart (the Xf(nu) -(nu) diagram), several different material combinations are identified which are suitable to form MWIR objectives that are athermal over a temperature range of -20 degree(s)C to +60 degree(s)C. Five of these combinations utilize a diffractive surface which effectively acts as a third material. Thin lens solutions are calculated, and the performance of optimized thick lenses is summarized.