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-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.

In order to meet the high quality, high efficiency and low-cost manufacturing needs of large aperture optical components, robots have been introduced into the optical manufacturing field in large quantities. However, due to the low certainty of the TIFs in the combined optical manufacturing technology, such as bonnet polishing, computer controlled optical surfacing, etc., robot-based optical manufacturing technology is often applied to the middle and low manufacturing accuracy stage.

In order to improve the application of the robot in the field of high-precision optical manufacturing, the research team innovatively proposed the combination of the robot and magnetorheological polishing technology. However, the position error of robot is relatively low, and the TIFs is unstable during the polishing process, which cannot meet the high-precision polishing requirements of magnetorheological polishing technology. How to improve the certainty of the TIFs in the manufacturing process is the key to the application of robot-magnetorheological finishing (MRF) high-precision manufacturing.

The research team proposed the inverse distance interpolation method to accurately predict the TIFs at differing polishing gaps and 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 verify that the proposed method can utilize a low trajectory precision robot-MRF to achieve high-precision polishing of the target.

The method promoted the application of robots in the field of high-precision optical manufacturing.