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Pseudo-random tool paths for CNC sub-aperture polishing and other applications

Mid spatial frequency features have long beset aspheric optics manufacture. Although an optical surface can have a very small form error, the presence of mid-spatial features will introduce both geometric effects and diffraction, thus degrading the system’s imaging performance (point-spread function and stray light). Polishing with CNC machines is universally-known to introduce mid-spatials through the very nature of small tools and repetitive (e.g. raster or spiral) tool paths. In this paper, a (now patented) new paradigm of tool-paths is reported, based on the theory of unicursal mazes. These paths cross nowhere, and can fill any arbitrary shape, even with perforations. It opens a new approach to tool-path design which, through the avoidance of repeating structures, mitigates mid-spatials. This type of approach has application in a wide range of challenging optics, from space optics, through photolithography, to high-power lasers and potential laser-fusion