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Open Access

Adaptive DFT-Based Interferometer Fringe Tracking

  • Edward Wilson1Email author,
  • Ettore Pedretti2, 3,
  • Jesse Bregman4,
  • Robert W. Mah4 and
  • Wesley A. Traub2
EURASIP Journal on Advances in Signal Processing20052005:531501

Received: 1 June 2004

Published: 14 September 2005


An automatic interferometer fringe tracking system has been developed, implemented, and tested at the Infrared Optical Telescope Array (IOTA) Observatory at Mount Hopkins, Arizona. The system can minimize the optical path differences (OPDs) for all three baselines of the Michelson stellar interferometer at IOTA. Based on sliding window discrete Fourier-transform (DFT) calculations that were optimized for computational efficiency and robustness to atmospheric disturbances, the algorithm has also been tested extensively on offline data. Implemented in ANSI C on the 266 MHz PowerPC processor running the VxWorks real-time operating system, the algorithm runs in approximately milliseconds per scan (including all three interferograms), using the science camera and piezo scanners to measure and correct the OPDs. The adaptive DFT-based tracking algorithm should be applicable to other systems where there is a need to detect or track a signal with an approximately constant-frequency carrier pulse. One example of such an application might be to the field of thin-film measurement by ellipsometry, using a broadband light source and a Fourier-transform spectrometer to detect the resulting fringe patterns.

Keywords and phrases

fringe trackingDFTinterferometryIOTAreal time

Authors’ Affiliations

Intellization, Redwood Shores, USA
Harvard-Smithsonian Center for Astrophysics, Cambridge, USA
Astronomy Department, University of Michigan, Ann Arbor, USA
NASA Ames Research Center, Moffett Field, USA


© Wilson et al. 2005