1. Laboratory for Optical Systems, Department for Microsystems Engineering–IMTEK, University of Freiburg, Georges-Köhler-Allee 102, 79110 Freiburg, Germany
2. Institute of Automation and Electrometry, Russian Academy of Sciences, Koptyug Avenue 1, 630090 Novosibirsk, Russia
3. Fraunhofer Institute for Physical Measurement Techniques IPM, Georges-Köhler-Allee 301, 79110 Freiburg, Germany