Aspheric mirror fabrication by flycutting with cutting depth control synchronized to tool rotational angle.

A numerically controlled, precision diamond flycutting mechanism has been developed, where tool cutting depth is dynamically controlled in synchronizing to tool rotational angle. This technique permits fabrication of aspheric mirrors used in soft X-ray application equipments, with a contour accuracy of 0.1 μm peak to valley. A piezoelectric stack actuator is used for tool cutting depth control. To correct hystcresis and drift with a piezo-acytuator, a referential piezo-actuator with the same characterisitics as that of the tool is driven in a closed roop control. The signal supplied to the referential piezo-actuator simultaniously drives the tool actuator. Aspherical mirror and a toroidal mirror are cut to evaluate developed flycutting technology.