Comparison of passive athermalization results of LWIR optical designs utilizing different infrared optical materials

In this paper, different optical designs, which are composed of different LWIR optical materials, are utilized for passive athermalization and their performance in athermalization are analyzed. The optical designs are carried out by preserving the athermal property as well as keeping the image quality at higher levels within the working temperature between –40 °C and +60 °C. Our designs consist of two different infrared optical elements to maintain the focus positions as stable as possible within the working temperature. The passive athermalization process begins with the calculation of athermalization conditions of candidate material properties. By taking into account these conditions, athermal material pairs are chosen. The optical design begins with an optimization process using paraxial optics. In order to reduce aberrations such as coma, astigmatism, spherical and chromatic, aspherical surfaces are utilized during the optimization process. At the end of the design phase, the performance of different configurations of athermal optical material pairs, which are enclosed by aluminum alloy housing material, are presented.