Calibration Procedure and Industrial Applications of Coherence Scanning Interferometer

Licentiatavhandling, 2016

Countless industrial applications over the past decades have indicated the increased need to relate surface texture to surface function. Measurement and characterization of the areal nature of the surface allows the manufacturer to alter how the surface interacts with surroundings. Surface metrology covers the questions related to surface measurements, its analysis, representation, and interpretation. Despite the long experience of surface measurements there are still a lot of open questions. One of question was listed in this thesis is: “Is there a universal analysis technique available for understanding and interpreting the properties of surface topography?” The simple answer is: There is no universal analysis technique. However, for a better understanding and interpretation of the properties of a surface, a combination of different techniques can be necessary. The use of Power Spectral Density (PSD) analysis in this thesis showed to be a powerful analysis tool for identification of the differences and equalities between different instruments measuring similar topographies. This enables a selection of the proper instruments for measuring topographies with specific spatial frequencies or combination of frequencies.   Another focus area of this thesis was calibration of optical surface measuring instruments in particular Coherence Scanning Interferometer (CSI). The complexity of design of optical surface measuring instruments makes them difficult to calibrate. Since calibration procedure is an important part of quality control in the production, it is one of reason that those instruments are not used in production. The calibration procedure for the examining of some of the main metrological characteristics of Coherence Scanning Interferometry as an example of optical surface measuring instruments is discussed in this thesis. The concept of traceability is one of the fundamentals in metrology and assures the accuracy of measurements. The traceability and uncertainty are inseparable as it is impossible to compare measurements and hence calibrate instruments without statement of uncertainty. From the calibration procedure it was found that the dominant component for uncertainty estimation in the z-scale for CSI is the noise contribution and the dominant component for the x- and y- scale is the lateral resolution. Future works based on the thesis results include to summarize good practice guide for users of CSI and a continued analytical and empirical study of the influence of spatial content of surfaces for different applications.