A high-sensitivity heterodyne interferometer for industrial metrology
Author(s): Thilo Schuldt 12, Martin Gohlke 23, Dennis Weise 3, Achim Peters 2, Ulrich Johann 3, Claus Braxmaier 13
Affiliation(s): 1 University of Applied Sciences Konstanz (HTWG), Brauneggerstr. 55, 78462 Konstanz; 2 Humboldt-University Berlin, Hausvogteiplatz 5-7, 10117 Berlin; 3 EADS Astrium GmbH, Claude-Dornier-Straße, 88039 Friedrichshafen
Topic: 2. Development of Optical Measurement Systems
High precision position metrology is needed in many industrial applications as e.g. nano-positioning control, surface property measurements and 3D profilometry. It is also a key technology for several future space missions as e.g. Darwin and LISA (Laser Interferometer Space Antenna) where in case of LISA the relative position and tilt of a free flying proof mass with respect to the satellite housing must be measured with pm/sqrt(Hz)-sensitivity for the translation measurement and nrad/sqrt(Hz)-sensitivity for the tilt measurement. The University of Applied Sciences Konstanz (HTWG) – together with EADS-Astrium Friedrichshafen and the Humboldt-University Berlin – develops a compact highly symmetric heterodyne interferometer utilizing differential wavefront sensing for the tilt measurement. With this setup noise levels below 5 pm/sqrt(Hz) in translation measurement and below 10 nrad/sqrt(Hz) in tilt measurement, both for frequencies above 10 mHz, were demonstrated. In a next step, the existing interferometer will be adapted for use in industrial applications. Therefore, we develop a high-precision low-noise actuator based on micro-system technology which will enable a scan of the measurement beam of the interferometer and hence surface property measurements. Also, we develop a new compact and ruggedized interferometer setup utilizing ultra-low expansion glass as e.g. Zerodur, where the optical components are connected to the baseplate via hydroxide-catalysis bonding technology.