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Proceedings Paper

Low cost varying synthetic wavelength technique for absolute distance measurement
Author(s): S. Le Floch; Y. Salvadé
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Paper Abstract

A new low-cost superheterodyne configuration, without acousto-optic modulator, is applied to the two-wavelength interferometry for absolute distance measurement. The principle relies on a synchronized frequency sweep of two optical signals, but with different frequency excursions. The frequency difference between the two optical waves is highly accurate. This is realized by injecting a frequency modulated laser signal in an intensity modulator that is biased at halfwave voltage and driven by a digitally swept radio-frequency signal between 13 and 15 GHz. This latter is a continuous up and down ramp. The two synchronized optical signals emerging from the modulator produce in a Michelson interferometer a distance dependent superheterodyne signal, with a variable synthetic wavelength of about 10 mm. The superheterodyne frequency depends linearly on distance and on the radio-frequency excursion. The integration time for a distance measurement point corresponds to the duration of single sweep (i.e. one millisecond in our case). Absolute distance measurements from 1 to 15 meters yield an accuracy of ±50 μm, showing the validity of the technique.

Paper Details

Date Published: 13 May 2010
PDF: 7 pages
Proc. SPIE 7726, Optical Sensing and Detection, 77260T (13 May 2010); doi: 10.1117/12.854889
Show Author Affiliations
S. Le Floch, HE-ARC Engineering (Switzerland)
Y. Salvadé, HE-ARC Engineering (Switzerland)

Published in SPIE Proceedings Vol. 7726:
Optical Sensing and Detection
Francis Berghmans; Anna Grazia Mignani; Chris A. van Hoof, Editor(s)

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