In a study published in Optics Express, a research group led by Prof. ZHANG Xuejun from the Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences (CAS) proposed a high-precision robot-magnetorheological finishing (MRF) polishing strategy based on variable tool influence functions (TIFs) and surface shape errors of polished optics to achieve high-precision polishing without compensating for trajectory errors.

To realize high quality, high efficiency and low-cost manufacturing of large aperture optical components, robots have been introduced into optical manufacturing in large quantities. However, due to the low certainty of the TIFs such as bonnet polishing and computer controlled optical surfacing, robot-based optical manufacturing technology is often applied to the middle and low manufacturing accuracy stage. How to improve the certainty of the TIFs in the manufacturing process is the key to the application of high-precision robot-MRF manufacturing.

The researchers proposed the inverse distance interpolation method to accurately predict the TIFs at differing polishing gaps. They introduced a novel high-precision polishing method for the robot-MRF based on variable TIFs and surface figures of polished optics. This method, devoid of reliance on trajectory error-measuring apparatus or robot operating error compensation, can accurately predict changes in TIFs during the process.

The experimental results indicated that the polishing accuracy of the plane mirror can be improved from 0.11 λ root mean square (RMS) to 0.013 λ RMS by utilizing variable TIFs, and there were no systematic surface shape errors attributable to operational errors.

These findings verified that the proposed method can utilize a low trajectory precision robot-MRF to achieve high-precision polishing of the target. The method will promote the application of robots in the field of high-precision optical manufacturing.