We demonstrate the use of a novel technique for the detection of heterodyne laser-induced thermal acoustic signals that allows the construction of a highly stable seedless laser velocimeter. A common-path configuration is combined with quadrature detection to provide flow direction, to greatly improve robustness to misalignment and vibration, and to give reliable velocity measurement at low-flow velocities. Comparison with Pitot tube measurements in the free stream of a wind tunnel shows root-mean-square errors of 0.67 m/s over the 0–55-m/s velocity range.
© 2002 Optical Society of America
(120.7250) Instrumentation, measurement, and metrology : Velocimetry
(280.2490) Remote sensing and sensors : Flow diagnostics
(280.3340) Remote sensing and sensors : Laser Doppler velocimetry
(280.7250) Remote sensing and sensors : Velocimetry
(350.2770) Other areas of optics : Gratings
Roger C. Hart, G. C. Herring, and R. Jeffrey Balla, "Common-path heterodyne laser-induced thermal acoustics for seedless laser velocimetry," Opt. Lett. 27, 710-712 (2002)