People usually take the machining of elements with super- smooth surfaces just as a polishing process. But occasionally super-smooth polishing cannot be accomplished even conducted under a succeeded polishing procedure, resulting in the failure of obtaining super-smooth surfaces repeatedly. A concept of super-smooth surfaces machining 'process technology' is proposed which takes super-smooth surfaces machining as a system in general, not merely a polishing process. We take the machining of super-smooth surfaces as a chain consisted of some key nodes. The failure at any node will result in the failure of the final surfaces. The nodes in the process technology system refer to a series of key sub- items, such as sample material selection, pre-machining, and super-smooth surface evaluation, et al. With the aid of polishing experiments, the effects of some key sub-items are discussed.
Ultrasmooth optical surfaces are of important application due to low-loss and low-scatter properties. Especially, in soft X- ray region, the surface roughness of substrates of multilayered mirrors is demanded to be below 1 nm rms. Furthermore, the excellent reflectors usually take advantage of the surface roughness less than 0.1 nm rms. Polishing by a tin plate is one of the remarkable methods for fabricating mirror surfaces. We studied the tin polisher for polishing ultrasmooth surfaces. The characteristic of tin as a polisher material is presented. Non-contact, direct-contact and selfweight polishing states are studied. Polishing experiments on many materials are carried out with perfect surface quality. Surface roughness around 0.5 nm rms is obtained on BK7 glass, Zerodur, and sapphire plates. This paper submits a profile of the work on superpolishing with a tin polisher.