Patent ID: 7371993

Claim:
A method of laser micro-machining a work piece with a laser, the method comprising by the steps of: locating the workpiece on a carrier forming a part of a transport system whereby the carrier can be displaced along a path parallel to an X-axis of the workpiece, a Y-axis lying transverse the path, and a Z-axis lying transverse the path; focusing an image generated by an output beam from the laser, at a working datum position defined relative to the path, the path is established by the transport system to traverse the first datum position; defining a plane by the X- and Y-axis lying substantially perpendicular to the output beam; displacing the workpiece along the path by way of the transport system so as to enable the work piece to be subject to micro-machining by way of the laser; maintaining a distance between the datum position and a current first surface position of the work piece in a vicinity of the of the datum position; and varying the working datum position to accord with local variations in thickness of the work piece so that the working datum position is maintained at a fixed distance relative to a surface of the work piece; and sensing undertaken by way of a distance sensing device comprising a body member riding on a fluid cushion on a first surface of the work piece, the fluid cushion being established by a flow of fluid fed from the body member so as to maintain the body member at a predetermined distance from first surface; so that in the event the body member is displaced from a current position of the body member due to a variation in thickness of the work piece, any change in position of the body member perpendicular to the first surface is used to modify position of the lens to cause a corresponding change in the current datum position to restore the working datum position to a fixed distance relative to the first surface of the work piece.