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对基于彩虹现象的光学颗粒测量进行研究,提出了一种新的参数反演模型和算法,可同时测量颗粒的粒径和折射率。新算法基于经验模态分解的去噪技术,并采用一种特征点提取技术和基于Debye理论的反演最优点搜索算法,能较精确的迅速找到反演最优点。数值模拟结果表明,当信噪比降至5 dB时,直径反演最大误差小于10%,折射率反演最大误差小于0.1%。对不同温度下自由下落的水滴进行实验研究,水滴由波长532 nm功率14mW的连续激光源照射,产生的彩虹光线经大口径透镜收集,被位于透镜焦平面的CCD相机接收。实验结果同样表明此测量方法具有较好的精度和可靠性。
A new parameter inversion model and algorithm is proposed to study the measurement of optical particles based on rainbow phenomenon. The particle size and refractive index can be measured simultaneously. The new algorithm is based on the de-noising technique of empirical mode decomposition and adopts a feature point extraction technique and the optimal point search algorithm based on Debye theory to find the optimal point of inversion quickly and accurately. The numerical simulation results show that the maximum error of diameter inversion is less than 10% and the maximum error of refractive index inversion is less than 0.1% when the SNR decreases to 5 dB. Experiments were carried out on water droplets falling freely at different temperatures. The water droplets were irradiated by a continuous laser source with a power of 14 mW at a wavelength of 532 nm. The resulting rainbow light was collected by a large-aperture lens and received by a CCD camera at the focal plane of the lens. The experimental results also show that this method has better accuracy and reliability.