1 September 2004 Two-dimensional velocimetry measurements with self-mixing technique in diode pumped Er glass laser
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The optical feedback into a class B laser can be used as optical velocimeter. This self-mixing technique is simple, self-aligned and very sensitive on low cooperative target. However, the resulting frequency beating only allows deducing the longitudinal speed component along the laser beam. In some cases, such geometry becomes unpractical compared to classical laser Doppler velocimetry (LDV). By using two beams geometry, we have demonstrated the possibility to simultaneously measure both transverse and longitudinal components of the speed vector. This new self-mixing scheme is demonstrated using a single-frequency diode pumped Yb3+:Er3+ phosphate glass laser selected for its inherent very high sensitivity to optical feedback. The principle is validated on a rotating disc with diffusing surface and the tangential linear speed of the disc is precisely measured from 1m/s up to 10m/s without knowing the exact orientation of the disc. Moreover, the technique is spatially selective thanks to the peculiar dynamical response of the laser showing three characteristic beating frequencies in the power spectra when the target is precisely located at the focus point. The dynamic and resolution of the optical sensor are discussed depending on the characteristics of the laser and the geometry of the optical design.
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Luc Kervevan, Herve Gilles, Sylvain Girard, Mathieu Laroche, "Two-dimensional velocimetry measurements with self-mixing technique in diode pumped Er glass laser", Proc. SPIE 5459, Optical Sensing, (1 September 2004); doi: 10.1117/12.545447; https://doi.org/10.1117/12.545447


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