Calculation and analysis of knife-edge and slit scanning in OTF measuring equipment

GC-211 optical transfer function (OTF) analysis instrument made by the Dept. of optoelectronic Eng., Beijing Inst. of Technol., is a large precise instrument for measuring the OTF of complex system like periscope. It can utilize two measuring methods including knife-edge scanning and slit scanning. But in the process of application, the results of knife-edge scanning are always lower than the theoretical results. Through analysis and numerical calculation, it was found that the anti-jamming ability of knife-edge scanning is inferior to that of slit scanning under the same condition. The reason that the measuring data are often smaller than the actual ones with knife-edge scanning is clarified.