A technique to align automatically the beams of displacement-measuring interferometric gauges is described. The pointing of the launched beam is modulated in a circular pattern, and the resulting displacement signal is demodulated synchronously to determine the alignment error. This error signal is used in a control system that maintains the alignment for maximum path between a pair of fiducial hollow-cube corner retroreflectors, which minimizes sensitivity to alignment drift. The technique is tested on a developmental gauge of the type intended for the Space Interferometry Mission. The displacement signal for the gauge is generated in digital form; and the lock-in amplifier functions of modulation, demodulation, and filtering are all implemented digitally.
© 2002 Optical Society of America
[Optical Society of America ]
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.3940) Instrumentation, measurement, and metrology : Metrology
(220.1140) Optical design and fabrication : Alignment
Jennifer E. Logan, Peter G. Halverson, Martin W. Regehr, and Robert E. Spero, "Automatic Alignment of a Displacement-Measuring Heterodyne Interferometer," Appl. Opt. 41, 4314-4317 (2002)