Research on removal function and ion beam figuring process for ultra-precision manufacturing optical components

Surface of fused silica optical components were polished by Ion Beam Figuring (IBF) ultra-precision process. Based on the analysis of the relationship between the ion beam current density distribution parameters obtained by faraday scan and the removal function, the removal function model for IBF was established. The IBF experiment for fused silica optical materials were carried out. The experimental results show that the IBF method based on faraday scan can achieve the same figure correcting ability as the traditional IBF method based on line scan experiment. But the offline calculation time of the removal function can be reduced from 2 hours to 5minutes, which improves the efficiency of IBF greatly. After several cycles the initial surface figure error of the optical element before processing, with a PV value from more than 500 nm to less than 15nm and an RMS value from more than 120nm to less than 1.5 nm. Ultra-precision surface of fused silica optical components with nanometer scale were obtained by IBF.