The optical design of highly efficient cold shield in IR detector based on ASAP

In order to obtain higher stray radiation suppression of a cold shield and enhance the cold shield efficiency of cooled infrared system, different configurations of the vanes inside cold shield are proposed. The effects of these configurations of vanes on stray radiation suppression are simulated and analysed by Advanced Systems Analysis Program (ASAP software), which not only trace ray by Monte Carlo method but also simulate the scattering of each surface. According to the analysis of results, vane plays an important role in the improvement of cold shield efficiency and the suppression of stray radiation. The cold shield with 6 vanes characterized by rounded-square hole, whose configuration is calculated based on the principle of laying out a set of vanes, suppresses 99.5% more stray radiation comparing to the original one without any vanes. However, considering that the cold shield with 6 vanes is complicated and difficult to fabricate, the cold shield with 3 vanes owing rounded-square hole is selected, since its stray radiation suppression level is acceptable.