Design of the infrared dual-band athermalized optical system based on HDE

A dual-band infrared optical system adopting an uncooled LW infrared detector and a cooled MW infrared detector is designed and manufactured, based on the athermal ability and special diffractive properties of harmonic diffractive elements. The design shows in the MW IR band the F/# is 2 and the focal length is 72 mm, for the temperature range -40 °C ~ 70°C the MTF value is over 0.4 at 20 lp/mm; while in the LW IR band the F/# is 1 and the focal length is 114 mm, for the temperature range -40° ~ 70° the MTF value is over 0.5 at 10 lp/mm. Finite element method is applied to the opto-mechanic structure of the system for thermal analysis, which confirms the imaging ability of the system in a wide temperature range.