Athermal design for mid-wave infrared lens with long EFFL

Abstract

When the environment temperature has changed, then each parameter in infrared lens has also changed, thus the image quality became bad, so athermal technology is one of key technology in designing infrared lens. The temperature influence of each parameter in infrared lens is analyzed in the paper. In the paper, an athermal mid-wave infrared optical system with long focal length by Code-v optical design software was presented. The parameters of the athermal infrared system are 4.0 f/number, 704mm effective focal length (EFL) , 1° field of view and 3.7-4.8 μm spectrum region 100% cold shield efficiency. When the spatial frequency is 16lp/mm, the Modulation Transfer Function (MTF) of all the field of view was above 0.5 from the working temperature range -40℃ to 60℃. From the image quality and thermal analysis result, we knew that the lens had good athermal performance.