The laser interferometer space antenna (LISA) mission utilizes as current baseline a high sensitivity optical readout for measuring the relative position and tilt of a free flying proof mass with respect to the satellite housing. The required sensitivities are ~5pm/&sqrt; Hz for the translation measurement and ~20 nrad/&sqrt;Hz for the tilt measurement. For this purpose, EADS Astrium GmbH - in collaboration with the Humboldt-University Berlin and the University of Applied Sciences Konstanz - develops a fiber-coupled heterodyne interferometer including differential wavefront sensing for the tilt measurement. The interferometer is based on a highly symmetric design where both, measurement and reference beam have the same optical pathlength, frequency and polarization. We realized a mechanically highly stable and compact setup which is located in a temperature stabilized vacuum chamber and utilizes frequency stabilization of the laser and intensity stabilization of the heterodyne frequencies at the fibre outputs. Noise levels below 5 pm/&sqrt; Hz in translation movement and below 10 nrad/&sqrt;Hz in tilt movement (both for frequencies above 10^-2 Hz) were measured. While this setup is developed with respect to the requirements of the LISA space mission, it also has potential applications beyond: In industry, high precision position measurements - with ever increasing sensitivity - are needed e.g. for guaranteeing very small tolerances for automobile industry components. While current systems developed for this purpose use for instance whitelight-interferometry with resulting sensitivities in the nm-range, our interferometer opens the possibility to further improve the sensitivity. Here, we discuss possible implementations of our interferometer for industrial applications.

Date Published: 18 June 2007
PDF: 6 pages
Proc. SPIE 6616, Optical Measurement Systems for Industrial Inspection V, 661649 (18 June 2007); doi: 10.1117/12.726180

Published in SPIE Proceedings Vol. 6616:
Optical Measurement Systems for Industrial Inspection V
Wolfgang Osten; Christophe Gorecki; Erik L. Novak, Editor(s)