Surface profiles obtained by means of optical methods – are they true representations of the real surface? – W. Hillman

Abstract

The surface profile of the well known surface of a PTB roughness standard has been recorded by several methods and the results have been compared. The result of the contact stylus method, in particular that using a very small tip radius, is in good conformity with that deduced from SEM stereo images. The optical methods, i.e. laser focus system and interference microscope with image processing, result significant deviation. On the other hand, when the surface of a diamond turned copper mirror is measured, there is a difference of only a few nanometers between contact stylus methods and the interference microscope. Additional investigations will be necessary to find out potential fields of application of the optical methods and to determine the limits set to their application.