Method and apparatus for optical polishing

A lapping tool for localised optical polishing of a workpiece, the tool having a flexible working surface and being characterised by means for selectively varying the pressure applied, in use, on the workpiece by different regions of the tool working surface whereby to vary the effective area of contact with the workpiece. A method of optical polishing and optical workpiece using a lapping tool whose maximum working surface area is substantially smaller than the workpiece, comprising determining the path to be travelled by the tool across the workpiece, and determining the pressure and effective area of contact of the tool on the workpiece, in order to achieve the next stage of polishing, and then driving the tool over that path while dynamically varying the said applied pressure and effective contact area. Apparatus for guiding a body, such as an optical polishing tool, over a generally flat structure, such as an optical workpiece, comprising a three dimensional drive mechanism for the controlled movement of the body across the surface of the structure, and a pivoted linkage (14,15) linking the drive mechanism to the body such as to constrain the body to pivotal motion about a virtual pivot point (P) which is fixed relative to the drive mechanism (11) and is located at the interface between the body and the workpiece.