Design of LWIR athermalization optical system with large relative aperture

Addressing the design requirements of infrared imaging systems for high luminous flux, compact structure, and temperature insensitivity in complex environments. In this paper, a large relative aperture athermalized infrared optical system with a wavelength range of 8~12μm, an F-number of 0.8, a clear aperture of 200mm, and a field of view of 10°×5° was designed by determining the passive athermalization mode and the structure form of the transmission optical system and introducing the aspheric surface type, and the image quality analysis was carried out at different temperatures. The design results demonstrate that within the temperature range of -40°C to 60°C, the MTF at 33.3 lp/mm exceeds 0.3 for all fields of view, and the RMS radius of the point spread function remains smaller than the Airy disk radius across the entire FOV. The achieved design boasts a compact structure, exceptional imaging quality, and effective athermalization, thereby fulfilling the design specifications. This work holds significant research value for advancing the development of wide-temperature-range, large relative aperture infrared optical imaging systems.