Study on rapid convergence strategy of nano-precision optical surface by ion beam figuring.

Ion beam figuring (IBF) provides a deterministic figuring method for fabricating ultra-high precision optical components such as lithographic objective lenses. But in the previous IBF process, the convergence of surface accuracy is often uncertain. Therefore, the iterative processing methods are mostly adopted. In the iterative process, the convergence ratio (the ratio of root mean square before and after figuring) of single figuring is relatively low. With the improvement of machining accuracy, the convergence ratio continues to decrease. The study analyzes the factors that limit the convergence ratio of single processing and the influence form and degree of each element on the convergence ratio. Furthermore, we present an IBF strategy with a high convergence ratio based on an optimized removal function. Based on this strategy, we complete the figuring experiment. The convergence ratio is much higher than the previous level. Compared with the surface of iterative figuring, the surface is simple and more favorable to figuring to sub-nanometer precision. The experimental results show that we can optimize the removal function to achieve rapid optical surface fabrication with nanometer precision. • A rapid manufacturing method with a high convergence ratio for nanometer precision optical elements is explored. • A more comprehensive analysis of the factors affecting the single IBF processing convergence ratio. • The method is based on the dynamic adjustment of equipments' performance to pursue the best convergence effect. • Evaluation of equipment processing capability while improving processing efficiency. [ABSTRACT FROM AUTHOR]