非球面創成研磨に関する研究(第2報)

非軸対称非球面形状の研磨加工

抄録

Computer controlled polishing using a small rotating polisher is one of the most suitable methods to generate a very precise aspherical surface. In this study, a new type of polishing head for asymmetric aspherical surface was developed, and the aspherical surface polishing of an off-axis ellipsoidal mirror for synchrotron radiation was examined. The characteristics of this polishing head are as follows : (1) A soft disk type polyurethane polisher was used as the polishing tool, and its rotating axis was controlled to be parallel to the tangent plane of the machining point on the workpiece surface. Therefore the profile of the polishing trace was more uniform and was suitable for precisely generating the required asymmetric aspherical surface. (2) The polishing load was applied in the normal direction at the machining point and was controlled to be constant. In tests, a large fused silica mirror was polished to an off-axis ellipsoidal shape. A form accuracy of ±0.6 μm and a surface roughness of less than 0.5 nm Rrms were obtained.