Abstract
The development of infrared countermeasure technologies imposed higher requirements on detection performance. The beam-splitting dual-band infrared detector fulfills these requirements by integrating a beam splitter inside the dewar. As the beam splitter operates at cryogenic temperatures, it significantly reduces the background noise of the optical structure while offering high sensitivity and high integration. Encircled energy is a key performance indicator for this type of detector, but the surface figure of beam splitter's surface figure degrades at cryogenic temperatures, reducing it. This study addresses cryogenic surface figure control of the beam splitter, which is supported by a thin-walled cold shield via adhesive bonding under tight size and weight constraints. Through simulation and experiments, the bonding process and support structure were optimized. Using a novel copper-based composite material for the cold shield and a segmented bonding method, the beam splitter's surface figure PV change from 293 K to 120 K remained under 3 μm. The assembly survived 500 thermal shock cycles and passed mechanical tests. Imaging showed less than 5%deviation in encircled energy from the design value. The improved component meets structural, optical, and reliability requirements, demonstrating high engineering significance.