SURFACE MEASUREMENT APPARATUS AND METHOD

摘要

A stylus is deflected as a tip of the stylus follows surface variations along a measurement path on a surface of a workpiece. A transducer provides measurement data in a measurement coordinate system. A data processor is configured to: determine a relationship between the data in the measurement coordinate system and nominal surface data representing the expected surface characteristic of the workpiece in a workpiece coordinate system; simulate a measurement data set for the nominal surface using the nominal surface data and the determined relationship; if a simulated range of the simulated data set does not meet a given criterion, adjust a selected measurement data value for a selected point and repeat the simulation to determine an adjusted data value for which the simulated range meets the criterion; and determine start conditions required for a measurement procedure to provide the adjusted data value for the selected measurement point.

主权项

1. A metrological apparatus for measuring a surface characteristic of a workpiece, the apparatus comprising:
a mover to carry out a measurement procedure by effecting relative movement in a measurement direction between a workpiece and a stylus such that the stylus is deflected as a stylus tip of the stylus follows surface variations along a measurement path on a surface of the workpiece; a transducer to provide a measurement data set in a measurement coordinate system representing the deflection of the stylus at measurement points along the measurement path, the transducer having a measurement range; and a data processor configured to: receive nominal surface data representing the expected surface characteristic of the workpiece in a workpiece coordinate system; determine a relationship between the measurement data in the measurement coordinate system and the nominal surface data in the workpiece coordinate system; simulate a measurement data set for the nominal surface using the nominal surface data and the determined relationship, the simulation providing a simulated measurement data set having a simulated range of simulated measurement values; determine whether the simulated range meets a given criterion; if the simulated range does not meet the given criterion, adjust a selected measurement data value for a selected measurement point and repeat the simulation to determine an adjusted measurement data value for which the simulated range meets the given criterion; and determine measurement start conditions required for a measurement procedure to provide the adjusted measurement data value for the selected measurement point.