Adaptive processing strategy of pulse ion beam for sub-nanometer precision optical components

Abstract

Ion-beam figuring (IBF) imposes strict requirements for machine tool accuracy when achieving nano-precision material removal. This study proposes a novel method for pulsed ion beam (PIB) processing. The continuous IBF ion beam is discretized and the fixed-point quantitative removal of the ion beam was accurately achieved by controlling the frequency and duty cycle of the pulsed beam flow. The impact of the dynamic performance of the machine tool on machining as well as the additional removal layer caused by continuous beam flow was examined. First, the principle of the PIB realization was explained, and its good processing performance and excellent material-removal resolution were verified. Second, the advantageous range of PIB machining was simulated and analyzed, leading to the development of a processing strategy based on the error distribution gradient. Furthermore, the ant colony algorithm was used for processing trajectory optimization, reducing 57.7 % of the invalid paths. Finally, using PIB and the novel processing strategy, an optical surface with an RMS of 0.552 nm was achieved within an effective aperture of 90 mm, thereby confirming the feasibility of the novel processing system and strategy.This study expands the application scenarios of ion beams as an ultraprecision machining method that can be positioned as a preferred approach in areas where large-area trace-material removal is required.