Comparison Of Light Scattering From Rough Surfaces With Optical And Mechanical Profilometry

Abstract

Comparison of light scattering from rough surfaces with optical and mechanical profilometryR. Brodmann, M. AllgauerOptische Werke G. Rodenstock, Munich, W.- GermanyABSTRACTLight scattering and non -contact sensing of rough surfaces with a laser focus are twooptical methods which recently have also become available as commercial instruments. Opticalmeasurements are compared with mechanical stylus measurements and the results are discussedunder consideration of the physics of the different measuring principles.INTRODUCTIONIn the last few years significant advances have been made in the field of optical rough-ness measurement. Light scattering technique1f2 or interferometric methods3f4, for example,are being used increasingly for the evaluation of ultra -precision surfaces for optical appli-cations. However, positive signs can also be found in the fine machining sector where mechani-cal measuring methods had previously enjoyed clear predominance. Light scattering sensorshave already been in use successfully e.g. in the production of ball- bearings and in thegrinding of large steel rools5f6. In addition to these integral light scattering methods opti-cal profilometers have also been introduced to the market very recently7f8'9. Within two yearsthese instruments have opened up new and very interesting applications especially in the fieldof roughness measurement on soft materials.Due to the importance of the light scattering method for use in series production, thefirst part of this paper deals with the properties of the light scattering method and withcomparison measurements with mechanical stylus instruments. The second part of the paperdeals mainly with the common features and the differences of mechanical and optical profilo-