Topography is the measurement of form and roughness of surfaces, tribologically this is also referred to a profilometry. The measurements of this can be done with a contacting instrument through a stylus or tip that glides over the surface, the Atomic Force Microscopy (AFM page) and contact profilometers (Contact page) are examples equipment available within nCATS. Optically systems are also employed to measure surfaces and these can perform the measurement in a number of manners from interferometry and chromatic aberration, to lasers that raster over the surface. Techniques such as focus variation (Alicona page) using a special microscope and the use of special software and scanning electron microscopy (FEG page), in the latter two or three images are taken at specific orientations and the software determines the height.
Topography/profilometry measurements can be used to examine form to determine shape and any distortion from the designed specifications, as well as any wear either as removal or displacement or even transfer. Roughness measurements are typically performed before surfaces are tested or put in-services to ensure they are as intended, but surface roughening during wear can also be evaluated by measuring afterwards as well.