Multi-step overlap path for suppressing mid-spatial frequency error in bonnet polishing

Bonnet polishing has been extensively applied in the fabrication of optical components due to its high material removal efficiency and superior surface-shaping capability. However, the conventional raster polishing path inevitably introduces mid-spatial frequency (MSF) error. To address this issue, the influence mechanism of the tool influence function (TIF) and the azimuthal angle of the feed direction on MSF error were investigated. Based on the principle of uniformly distributing MSF error, a multi-step overlap path strategy was proposed, and its feasibility was validated through numerical simulations. Subsequently, polishing experiments were conducted to further validate the effectiveness of the method. After figuring, the peak power spectral density (PSD) at the polishing interval of the traditional raster path was 1160.44 nm²·mm, whereas that of the proposed multi-step overlap path was reduced to 235.6 nm²·mm, demonstrating a remarkable suppression of MSF error. These findings suggest that optimizing the azimuthal feed angle and employing a multi-step overlap path provide an effective approach for reducing MSF error in optical component manufacturing.