Organic abrasive machining system for optical fabrication with 0.1-mm spatial resolution

High-precision optics for short-wavelength regions, such as x rays and extreme ultraviolet light, generally require nanometer-level figure accuracy on their surfaces. Such optics are finished via a numerically controlled figure correction process in which the dwelling time of the machining tool on the workpiece is controlled. Due to the limitation of the machined spot size, it is difficult to remove mid-spatial-frequency (1 to 10 mm^-1) errors on an optical surface. To realize a high-spatial-resolution figure correction process for high-precision optics, we have been developing the organic abrasive machining (OAM) technique, which can generate a 100 µm machined spot using a small elastic rotation tool in a slurry that includes acrylic particles. In this study, an OAM apparatus that can measure the machining load was constructed. The effects of the machining and slurry conditions were investigated and high-spatial-resolution machining on a flat glass substrate was demonstrated. The root-mean-square roughness of the surface after OAM processing was below 0.2 nm. Patterns with a minimum line and space size of 100 µm were successfully fabricated.