Metrological apparatus and a method of determining a surface characteristic or characteristics

摘要

A metrological apparatus comprises an optical measurement system (1) such as a coherence scanning interferometer to obtain measurement data representative of a surface of a workpiece and a rotation device (15) to effect relative rotation between the optical measurement system and the workpiece about a measurement axis to enable a plurality of measurement data sets to be obtained with each measurement data set being obtained by the optical measurement system at a respective one of a number of different relative rotational orientations of the optical measurement system and the workpiece. A data corrector (323) is provided to obtain correction data to enable correction of a measurement data set. The correction data may be an average of the plurality of measurement data sets. The measurement data sets may comprise roundness / surface height measurement data. A corresponding method of determining a surface characteristic of a surface of a workpiece is also claimed. Further claimed is a method comprising: using an optical measurement system of a first metrological apparatus to carry out a plurality of measurement operations on a surface of a first workpiece and effecting relative rotation between the optical measurement system and the first workpiece about a measurement axis between measurement operations to obtain a plurality of measurement data sets with each measurement data set being obtained at a respective one of a number of different relative rotational orientations of the optical measurement system and the first workpiece; using the plurality of measurement data sets to obtain first correction data for the first metrological apparatus; using the first metrological apparatus to carry out a measurement of a calibration sample, and correcting that measurement using the first correction data to provide calibration data for the calibration sample using a second metrological apparatus to measure the calibration sample to obtain second measurement data; and determining second correction data for the second metrological apparatus based on the second measurement data and the calibration data to enable a surface characteristic of a second workpiece to be determined by the second metrological apparatus.