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为了测量透明物体横向运动时的位移速度,提出了一套基于激光外差干涉技术的折射式激光多普勒测速系统,并对该系统所采用的多普勒效应测速方法进行了研究。首先,通过外差干涉系统使测量光与参考光发生干涉,利用信号探测系统探测它们合光束光强变化波形。然后,使用信号分析软件分析此波形,得到合光束的拍频,即测量光与参考光的频率之差。最终,利用此拍频值进行理论计算,求出垂直于探测光方向匀速运动时三棱镜样品的位移速度,并分析了整个系统的测量误差。实验结果表明,对20μm/s、80μm/s、140μm/s、200μm/s等给定的位移速度,该系统的速度测量误差不超过1.5%。测量结果具有良好的可重复性,证实了该系统的有效性与可靠性。实验系统原理简单,输出信号信噪比较高,测量精度高,具有广泛的适用性。
In order to measure the displacement velocity of transparent objects during lateral movement, a laser Doppler velocimetry system based on laser heterodyne interferometry is proposed, and the Doppler velocimetry method adopted in this system is studied. First of all, the measurement light and the reference light interfere with each other by the heterodyne interference system, and the signal detection system is used to detect the waveforms of their combined light intensity changes. The waveform is then analyzed using signal analysis software to obtain the beat frequency of the combined beam, which is the difference between the measured and reference beam frequencies. Finally, the theoretical value of the beat frequency is used to calculate the displacement velocity of the prism sample at a constant velocity perpendicular to the direction of the probe light, and the measurement error of the whole system is analyzed. The experimental results show that the speed measurement error of the system does not exceed 1.5% for a given displacement speed of 20μm / s, 80μm / s, 140μm / s and 200μm / s. The measurement results have good repeatability, confirming the validity and reliability of the system. The experimental system has the advantages of simple principle, high signal-to-noise ratio of output signal, high measuring accuracy and wide applicability.