激光束高斯特性对LDA测量精度的影响

本文通过理论推导,数值计算详细论述了激光束高斯特性对LDA(Laser Doppler Anemometer)测量精度的影响。首先从高斯光束的波动方程出发,推导出双光束激光多普勒测速仪相干区域的光学结构及随被测体一起运动的微粒所散射的光波函数。本文定量地论述了高斯光束的各因素对测量精度的影响;给出了测量误差表达式,经过各种情况下的理论计算值的对比和分析,得出了两束腰分别在测量区两侧,等距离时,干涉条纹空间频率梯度引起测量误差最小的结论。

Effect of Gaussian Properties of Laser Beams on the Accuracy of LDA Measurement

This paper discusses in detail the Gaussian properties of laser beam effect upon LDA (Laser Doppler Anemometer) measurement accuracy through theoretically deducing and calculating. Firstly, the optical structure of the measurement region of the dual beam laser Doppler velocimeter is derived exactly based upon the wave function of Gaussian beam.The Gaussian properties of laser beams may cause the appearance of gradients in the interference pattern in the measuring volume and a broadening of Doppler spectrum. This paper expounds how the factors of Gaussian beam effects the Doppler spectrum measuring error in the measuring volume quantitatively.The expression of this error is given.Comparing and analysing of the theoretical calculating value in any cases, it is concluded that this error is the least when the one beam waist is in front of the volume, the other behind it, and the two distances are equal.