Analysis to Stray Radiation of Infrared Detecting System

In order to improve the detecting ability of dark target by infrared detecting system, stray radiation of the system should be studied before and suppression methods should be adopted. In the infrared detecting system, thermal emission of a room-temperature instrument may be several orders of magnitude larger than the flux of sources of target to be observed. When baffles and vanes are designed to suppress the stray radiation coming from sources outside of the field of view of the detecting system, their thermal radiation should be discussed together. In this article, the stray radiation of thermal emission of infrared detecting system is studied. How to design baffles, vanes and stops is introduced. Their structure models are established in TracePro. Their thermal emissions are simulated and analyzed by ray tracing program. The number of photons on a pixel which emitted from suppression structure which varies from 260K to 310K is given by simulation. From the simulation result, we can find that the stray radiation of thermal emission from inner baffle of primary mirror is the predominant source; The stray radiation of thermal emission of system with vanes on main tube is slightly bigger than that of the system with no vanes; the field stop placed at the first image plane can effectively decrease the number of photons of stray radiation.