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首页> 外文期刊>Applied optics >Measurement uncertainty and temporal resolution of Doppler global velocimetry using laser frequency modulation
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Measurement uncertainty and temporal resolution of Doppler global velocimetry using laser frequency modulation

机译：使用激光频率调制的多普勒测速仪的测量不确定度和时间分辨率

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摘要

A Doppler global velocimetry (DGV) measurement technique with a sinusoidal laser frequency modulation is presented for measuring velocity fields in fluid flows. A cesium absorption cell is used for the conversion of the Doppler shift frequency into a change in light intensity, which can be measured by a fiber coupled avalanche photo diode array. Because of a harmonic analysis of the detector element signals, no errors due to detector offset drifts occur and no reference detector array is necessary for measuring the scattered light power. Hence, large errors such as image misalignment errors and beam split errors are eliminated. Furthermore, the measurement system is also capable of achieving high measurement rates up to the modulation frequency (100 kHz) and thus opens new perspectives to multiple point investigations of instationary flows, e.g., for turbulence analysis. A fundamental measurement uncertainty analysis based on the theory of Cramer and Rao is given and validated by experimental results. The current relation between time resolution and measurement uncertainty, as well as further optimization strategies, are discussed.
机译：提出了一种具有正弦波激光频率调制的多普勒全局测速（DGV）测量技术，用于测量流体流动中的速度场。铯吸收池用于将多普勒频移频率转换为光强度变化，可以通过光纤耦合雪崩光电二极管阵列进行测量。由于对检测器元件信号进行了谐波分析，因此不会发生由于检测器偏移漂移引起的误差，并且不需要参考检测器阵列来测量散射光功率。因此，消除了诸如图像未对准误差和分束误差之类的大误差。此外，该测量系统还能够实现高达调制频率（100 kHz）的高测量速率，从而为平稳流的多点研究（例如用于湍流分析）开辟了新的视角。给出了基于Cramer和Rao理论的基本测量不确定度分析，并通过实验结果进行了验证。讨论了时间分辨率与测量不确定度之间的当前关系，以及进一步的优化策略。

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