Surface and thin film characterization using angle resolved light scattering: from roughness and defect analysis to in-situ coating inspection

Light scattering due to interface and coating imperfections is a significant concern for optical components, while on the other hand, scattered light contains valuable information about its source. This turns scattering based techniques into excellent tools for the characterization of surfaces and thin film coatings. At Fraunhofer IOF, angle resolved light scattering techniques are developed and used for the characterization of optical surfaces, coatings, and components for a broad range of applications. Examples will be shown, such as the analysis of ultra-low optical losses of an ultra-high reflecting mirror. Beyond that, the non-contact, fast, and robust measurement approach makes the technique even suitable for integration into fabrication processes or test environments. We show approaches for integration of a light scattering sensor into a roll-to-roll process for fabrication of colorshift foil by evaporation, as well as the sensor integration into even a magnetron sputtering coating system.