International comparison of flatness deviation in areal surface topography measurements

Abstract

An international comparison of surface topography flatness deviation was carried out. The comparison involved twelve optical surface topography instruments (focus variation instruments, confocal microscopes and coherence scanning interferometers) from six European research laboratories. The results demonstrated the following: (i) The flatness varies orders of magnitude between instruments, dependent on the measurement principle. (ii) The ISO proposed procedure gives meaningful results, especially for instruments based on the confocal principle. (iii) The selection of the measurement artefact is especially important for focus variation measurements, where the flatness deviation is influenced by the surface texture of the used artefact. (iv) A tilt in the used optical flat can significantly influence the measured flatness deviation.