HIGHLY ACCURATE NONCONTACT CHARACTERIZATION OF ENGINEERING SURFACES USING CONFOCAL MICROSCOPY

Optical non-contact techniques are very interesting for 3D characteriz ation of sensitive and complex engineering surfaces. Unfortunately, th e application of optical techniques was for many years restricted to s elected types of surfaces which have only moderate variations of heigh t and surface slope relative to their lateral resolution and measureme nt field. Owing to the fact that artefacts and form deviations occur w ith high spatial frequencies in optically measured topographs, there w ere some difficulties in interpreting the results and comparing them w ith the tactile standard techniques for surface characterization. Furt hermore, artefacts in optically measured profiles have often been misi nterpreted in terms of the resolution of optical techniques being high er than that of the tactile techniques. This paper presents two optica l methods of confocal microscopy for highly accurate characterization of surfaces. The first method works on measurement fields of less than 1 mm(2) and is in practice absolutely comparable to the mechanical st ylus instrument, even on rough surfaces. For this method results compa re very well not only in surface statistics but also in topographic ra w data, as will be demonstrated for the PTB roughness standards. The s econd method works on measurement fields up to square centimetres.