Cold reflection suppression in infrared imaging system

Cold reflection is the image of the detector detected by the reflection of the optical surface in the infrared imaging system. The control of cold reflection is an important task of the infrared imaging system. In this paper, a cooled infrared imaging system with Cassegrain reflection structure is designed, the cold reflection phenomenon of the system is analyzed, and the surface with serious cold reflection phenomenon is obtained. Then, the cold emission of these severe surfaces is reduced by Zemax software, and the system transfer function (MTF) is optimized while the cold reflection is controlled. Through Narcissus macro command (cold reflection analysis macro command), Tracepro modeling software and the actual imaging image, the optimized mid-wave infrared imaging system was compared with the system before the cold reflection suppression. The results show that the equivalent temperature difference (NITD) induced by the cold reflection from the image plane of the detector decreases from 1.0484 K to 0.1576 K, and the energy and size of the cold reflection spot have no obvious change during the focusing process, the optimized optical structure effectively controls the cold reflection of the system.