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Abstract
During sub-aperture tool polishing of glass optics, mid-spatial surface ripples are generated because of material removal non-uniformities during tool linear translation (resulting in feed ripples) and tool pathway step overlaps (resulting in pitch ripples). A variety of tool influence function (TIF) spots, trenches, and patches were created to understand and minimize such ripples on fused silica workpieces after polishing with cerium oxide slurry using a rotating hemispherical pad-foam tool. The feed ripple amplitude can be decreased by reducing the non-uniformities in the pad texture and/or by minimizing a derived feed ripple metric (${r_{f}} = V_{\rm{max}}^{0.5}{V_{f}}/{R_t}$) via adjustments in processing parameters. Pitch ripples can be minimized by reducing relative step distance to spot radius ratio (${x_s}/{a_t}$) and by achieving a flat bottom trench shape cross section or by reducing the material removal per pass. Using the combined methods, an overall ripple error of ${\sim}{1.2}\;{\rm{nm}}$ rms has been achieved.
© 2022 Optica Publishing Group
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