Patent ID: 7669508

Claim:
An apparatus for machining a cylindrical work piece, comprising: a substantially cylindrical work piece mounted for rotational movement and having a surface to be machined; a drive unit connected to the work piece for rotating the work piece; a tool post mounted on a track for movement substantially parallel to the surface of the work piece to be machined; a shank secured on the tool post and having a surface for mounting a tool tip; a tool tip, having a plurality of diffractive features, mounted on the surface of the shank; and a controller, connected to the drive unit and the tool post, for controlling the movement of the tool tip relative to the work piece via the drive unit and for controlling the movement of the tool post parallel to the surface of the work piece to be machined, wherein during the machining the plurality of diffractive features on the tool tip are in contact with the surface of the work piece to machined, wherein a size and shape of the plurality of diffractive features, and a spacing between the plurality of diffractive features, are designed for an amount or degree of diffraction of light desired for an optical film made from the machined work piece, wherein the diffractive feature in the tool tip comprises a groove.