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

摘要

A metrological apparatus has a surface data determiner to determine from measurement data a measured surface roughness data set (150) representing measured surface roughness and including any vibration induced measurement error and a harmonic model provider (120) providing a harmonic model representing vibration-induced surface characteristics of the surface as a set of harmonic components selected based on a surface form of the surface of the workpiece. A surface roughness determiner (140) uses the harmonic model and the measured surface roughness data to obtain a modified surface roughness data set in which vibration induced measurement error is suppressed.