Quality assessment and process control are important tools in the production of high-quality products. In coating processes, for example, it is necessary to determine essential properties of the applied layers. This includes the layer thickness and the refractive index.
At the electronica and COMPAMED trade fairs, the CiS Research Institute will present the status of a current sensor development for determining the thickness and refractive indices of thin surface layers, the latter being closely dependent on the chemical and/or stoichiometric composition of the coating materials used.
The compact sensor measures the polarisation-dependent reflection of two different lasers at inclined angles of incidence. The sensor operates without moving components, is characterised by low maintenance requirements and is suitable for applications in harsh environments. Up to four sample properties (layer thickness, refractive index) can be determined by fitting the experimental data with a transfer matrix model using Levenberg-Marquard routines.
Target applications of the development are the monitoring/control of thin-film coatings or of growth processes, e.g. in glass finishing or in semiconductor processing.