Research on the technology of realizing normal operation of medium-wave infrared camera in space by simulating a vacuum environment on the ground

To enable the operation of a mid-wave infrared (MWIR) camera under vacuum and low-temperature conditions for space-based Earth imaging optical systems, research was conducted on the optical system, mechanical structure, and vacuum and low-temperature testing methods employed in the MWIR optical system. A low-temperature MWIR camera was designed to operate under normal atmospheric pressure, vacuum, and low-temperature conditions. The camera comprises independent optical lenses, an MWIR dewar, an image processing unit, a vacuum refrigeration unit, and preset water cooling pipes. The MWIR lens consists of a front lens unit, a focusing lens unit with a two-stage reduction mechanism, and a rear lens. The assembly temperature of the MWIR camera is 293 K with an operational temperature of 100 K, and the temperature variation does not exceed 193 K. A structural thermal-optical performance analysis of the MWIR lens was conducted to evaluate the optical performance degradation caused by temperature changes. The measurement of the MWIR lens was described using an MWIR interferometer and a spherical standard MWIR mirror, providing on-axis and off-axis wave aberrations. One method was proposed to test the modulation transfer function of the MWIR camera under two different conditions. Experimental results confirmed that the overall design of the MWIR camera ensures normal operation in a vacuum low-temperature environment.