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.
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机译：我们演示了一种用于检测外差激光诱导的热声信号的新技术，该技术允许构建高度稳定的无核激光测速仪。公共路径配置与正交检测相结合，可以提供流向，从而大大提高了对不准和振动的鲁棒性，并在低流速下提供了可靠的速度测量。在风洞的自由流中与皮托管进行的测量比较表明，在0-55-m / s的速度范围内，均方根误差为0.67 m / s。
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