Simulation method and its test verification of cryogenic infrared lens design

At low temperature, the lens structure will produce thermal deformation, which will affect the modulation transfer function (MTF) and defocus of the lens, thus affecting the quality of optical imaging. Based on an infrared remote sensor, a set of transmission cryogenic lens with thermal unloading function was designed for the 210 K low-temperature working environment. The finite element model was established, and the thermal deformation data was obtained by loading the simulation of the in-orbit working environment temperature field. Finally, the variation of lens MTF and defocusing amount were calculated, and the structure of cryogenic lens was optimized through this simulation analysis method. After the installation and adjustment of the cryogenic lens, the cryogenic lens and other test equipment were placed in a vacuum tank, and MTF and the best focal plane position of the lens were tested and calibrated under ambient temperature and low temperature conditions. The test results show that the errors are within the acceptable range, the MTF variation is only 0.2%, indicating that the cryogenic lens multi-field coupling simulation method is reliable and can guide the design of cryogenic lens for infrared remote sensor.