Patent ID: 6344656
Filing Date: 2002-02-05
Classification: G01B

Abstract:
A metrological apparatus for measuring a surface characteristic of a surface of a workpiece, the metrological apparatus comprising:a housing; a probe carriage for carrying an elongate sensing probe having a longitudinal axis so as to allow the elongate sensing probe to move relative to the probe carriage in a measurement direction parallel to the longitudinal axis thereby enabling the elongate sensing probe to follow the surface being measured, wherein the probe carriage is mounted on the housing so as to allow relative movement between the probe carriage and the housing in the measurement direction; first moving means for causing relative movement between the elongate sensing probe and the workpiece to allow the elongate sensing probe to traverse the surface of the workpiece; a first sensor for providing a measurement of a displacement of the elongate sensing probe relative to the housing as the elongate sensing probe follows the surface during operation of the first moving means; an optical sensor for providing a signal indicative of a displacement of the elongate sensing probe relative to the probe carriage; second moving means for causing relative movement between the probe carriage and the housing in the measurement direction; and a control unit for controlling the second moving means to move the probe carriage relative to the housing in response to the signal provided by the optical sensor to maintain the elongate sensing probe in an operational range.