Low cost varying synthetic wavelength technique for absolute distance measurement

S. Le Floch; Y. Salvadé

doi:10.1117/12.854889

13 May 2010 Low cost varying synthetic wavelength technique for absolute distance measurement

S. Le Floch, Y. Salvadé

Proceedings Volume 7726, Optical Sensing and Detection; 77260T (2010) https://doi.org/10.1117/12.854889
Event: SPIE Photonics Europe, 2010, Brussels, Belgium

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.

Citation Download Citation

S. Le Floch and Y. Salvadé "Low cost varying synthetic wavelength technique for absolute distance measurement", Proc. SPIE 7726, Optical Sensing and Detection, 77260T (13 May 2010); https://doi.org/10.1117/12.854889

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