Durst F, Zaré M
Appl Opt. 1974 Nov 1;13(11):2562-79. doi: 10.1364/AO.13.002562.
Laser Doppler anemometry permits, in principle, the measurement of both magnitude and direction of components of a particle's velocity vector. Most exiting anemometers, however, permit measurements only with a directional ambiguity of 180 degrees , resulting in errors in certain flow fields. Available methods of eliminating the directional ambiguity of Laser Doppler anemometers are reviewed, covering frequency shifting of the incident and scattered light beams, the use of beams with different polarization properties, and employment of multicolor laser beams. The advantages and disadvantages of existing methods are summarized, and suggestions for alterations are made. Different techniques used to remove the pedestal of laser Doppler anemometer signals are also reviewed. Optical techniques should be employed in any advanced optical anemometer system to avoid dynamic range limitations by electronic bandpass filters. Suggestions are made for advanced optical anemometers employing multielement avalanche photodiodes that can be used for simultaneous measurements of two velocity components. These anemometers incorporate devices to sense the direction of the velocity components and to eliminate optically the pedestal of laser Doppler signals.
原则上，激光多普勒风速仪能够测量粒子速度矢量分量的大小和方向。然而，大多数现有的风速仪仅能在180度的方向模糊度下进行测量，这在某些流场中会导致误差。本文综述了消除激光多普勒风速仪方向模糊度的现有方法，包括入射光束和散射光束的频移、使用具有不同偏振特性的光束以及采用多色激光束。总结了现有方法的优缺点，并提出了改进建议。还综述了用于去除激光多普勒风速仪信号基线的不同技术。在任何先进的光学风速仪系统中都应采用光学技术，以避免电子带通滤波器对动态范围的限制。对于采用多元素雪崩光电二极管的先进光学风速仪提出了建议，这种风速仪可用于同时测量两个速度分量。这些风速仪集成了用于感测速度分量方向并从光学上消除激光多普勒信号基线的装置。
