Tremblay Gregoire, Roy Gilles, Bernier Robert, Cao Xiaoying
Appl Opt. 2019 Sep 1;58(25):6949-6957. doi: 10.1364/AO.58.006949.
Information about the size distribution of liquid droplets in a fog can be retrieved by measuring the backscattering lidar depolarization parameter D in circular polarization. Using a polarimetric off-axis lidar, measurements at different backscattering angles are performed on fogs made of water droplets and of mineral oil. Estimation of the effective droplet size is obtained using constrained linear inversion. Mie theory is used to calculate the variation in depolarization parameters for different effective droplet sizes. The calculation is performed for various scattering angles. These calculations provide a kernel for the constrained linear inversion scheme. It is shown that the refractive index has an effect on the retrieved droplet sizes as well as the choice of scattering angles. These measurements confirm that the circular depolarization parameter measured near the backscattering angle can be modeled as a function of the forward-scattering diffraction peak. The results of the constrained linear inversion of measurements are consistent with in situ measurement of the droplet size distribution.
通过测量圆偏振下的后向散射激光雷达退偏参数D，可以获取雾中液滴的尺寸分布信息。使用偏振离轴激光雷达，在由水滴和矿物油制成的雾上进行不同后向散射角度的测量。使用约束线性反演来估计有效液滴尺寸。米氏理论用于计算不同有效液滴尺寸下退偏参数的变化。针对各种散射角度进行计算。这些计算为约束线性反演方案提供了一个内核。结果表明，折射率对反演得到的液滴尺寸以及散射角度的选择都有影响。这些测量证实，在后向散射角附近测量的圆退偏参数可以建模为前向散射衍射峰的函数。测量的约束线性反演结果与液滴尺寸分布的原位测量结果一致。
