Optical profilometry and its application to mechanically inaccesible surfaces Part II: Application to elastomer/glass contacts

In part I, the principles of focus error detection were given and its application to roughness measurements through a glass plate on the surface were discussed. In this part, examples of such measurements are presented. These examples are related to the lubrication problem of rough elastomeric surfaces, as studied in seal research programs. Measurements are shown for the statically loaded contact between a smooth glass plate and a rough elastomer, both with and without a liquid in the contact area. The profile measurement for the dry contact is unreliable, but the real area of contact can be derived. Considering the dynamic situation of a sliding, lubricated contact, preliminary, qualitative measurements show that film thickness variations are detected. Finally, the focus error detection method is compared with other methods, which can in principle be used for these measurements and proves to be a good alternative.