显微散焦粒子识别与追踪测速

Identification and tracking about three-dimensional microscopic defocusing particle

摘要:

根据三孔挡板散焦成像的原理,使用高速散焦显微粒子测速装置开展三维显微粒子追踪测速研究。在粒子散焦像识别的过程中利用了其对应三角模型相似的特点,通过散焦像斑灰度呈二维高斯分布特征计算其质心。在粒子三维位置测量算法分析的过程中选择了多达29颗的样品粒子,对29组不同深度的数据采用线性拟合的方式进行粒子深度方向的标定,并用二元多项式对870组数据拟合获得了关于粒子平面位置漂移的补偿函数。针对长直微通道内雷诺数Re分别为0.05和0.1的流场进行了验证性测量,采用20′0.4显微物镜,使用高速CMOS相机对直径为2mm的粒子进行追踪。结果显示,计算出的示踪粒子速度分布与数值仿真曲线吻合良好。

Abstract:

According to the principle of a three-pinhole mask’s defocused imaging, a set of high-speed defocusing micro-PTV devices was employed for further research on the three-dimensional micro particle tracking velocimetry. The similar characteristics among particles’ corresponding triangle models was used in the process of their defocusing images recognition, and the centroid of particle defocusing image spot was calculated by its gray in two-dimensional Gaussian distribution. As many as 29 sample particles were selected in the process of measurement algorithm analysis about particle’s three-dimensional position, and 29 different depth data were utilized for calibrating in the particles’ depth direction with the method of linear fitting, and the drift compensation functions about the in-plane position of particle was acquired by quadratic polynomial fitting with 870 groups of data. A microscope objective lens of 20′0.4 and high speed CMOS camera were adopted to trace the particles of 2mm diameter in the verification measurement of a long straight micro-channel flow field whose Reynolds number were 0.05 and 0.1 respectively. The results showed that the particle velocity distribution calculated was in good agreement with the numerical simulation curve.