Design of athermal and lightweight optical system based on long-wave infrared detector

Using chalcogenide glass and binary diffraction surface, an infrared athermalization system based on the uncooled long-wave infrared detector (1 024×768 pixel) was designed. The system was composed of 3 pieces of glass, and the system had a focal length of 75 mm, an F −number of 1, a total length of 97 mm, and a total weight of 203 g. The simulation analysis using ZEMAX shows that, within a temperature range of −40℃～50℃, the modulation transfer function（MTF）value at the Nyquist frequency (42 lp/mm) of the system is greater than 0.37, which is close to the diffraction limit; between −70℃ and 70℃, the MTF at the system Nyquist frequency (42 lp/mm) under temperature can also meet the requirements. The system has the characteristics of large relative aperture, excellent full-field image quality, lightweight structure, and good manufacturability.