Profilometer

A profilometer is a measuring instrument used to measure a surface's profile, in order to quantify its roughness. Critical dimensions as step, curvature, flatness are computed from the surface topography. While the historical notion of a profilometer was a device similar to a phonograph that measures a surface as the surface is moved relative to the contact profilometer's stylus, this notion is changing with the emergence of numerous non-contact profilometry techniques. Non-scanning technologies are able to measure the surface topography within a single camera acquisition, XYZ scanning is no longer needed. As a consequence, dynamic changes of topography are measured in real-time. Contemporary profilometers are not only measuring static topography, but now also dynamic topography – such systems are described as time-resolved profilometers. Optical methods include interferometry based methods such as digital holographic microscopy, vertical scanning interferometry/white light interferometry, phase shifting interferometry, and differential interference contrast microscopy (Nomarski microscopy); focus detection methods such as intensity detection, focus variation, differential detection, critical angle method, astigmatic method, foucault method, and confocal microscopy; pattern projection methods such as Fringe projection, Fourier profilometry, Moire, and pattern reflection methods. Contact and pseudo-contact methods include stylus profilometer (mechanical profilometer) atomic force microscopy, and scanning tunneling microscopy A diamond stylus is moved vertically in contact with a sample and then moved laterally across the sample for a specified distance and specified contact force. A profilometer can measure small surface variations in vertical stylus displacement as a function of position. A typical profilometer can measure small vertical features ranging in height from 10 nanometres to 1 millimetre. The height position of the diamond stylus generates an analog signal which is converted into a digital signal, stored, analyzed, and displayed.