Improvement in two-frame correlations by confocal microscopy for temporally resolved micro particle imaging velocimetry
Improvement in two-frame correlations by confocal microscopy for temporally resolved micro particle imaging velocimetry
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DOI：
10.1088/0957-0233/21/10/105409
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发表时间：
2010-10-01
影响因子：
2.4
通讯作者：
Posner, J. D.
中科院分区：
文献类型：
--
作者：
Klein, S. A.;Posner, J. D.
提出了利用高速旋转盘共焦微粒图像测速 (SD mu PIV) 系统对两帧微粒图像测速 (mu PIV) 相关性进行的研究。该系统使用 Nipkow 圆盘共焦落射荧光显微镜和高速相机，利用两帧互相关来捕获不稳定的微尺度流。在 mu PIV 中，集合平均通常用于减少由于失焦粒子的噪声而产生的误差。然而，不稳定的非周期流需要两帧相关，而使用 mu PIV 很难以可接受的精度实现这一点。共焦显微镜使用针孔空间过滤来去除大部分来自焦平面之外的光，减少来自失焦粒子的光，并提高两帧互相关 mu PIV 的精度。使用稳定泊肃叶流中的相关峰值信噪比和通用异常值检测作为粒子体积分数和进入通道的焦点深度的函数，评估共焦系统提供的两帧 PIV 相关性的改进。我们发现，共焦系统提高了所有情况下的平均相关信噪比，并在存在大量失焦粒子的情况下减少了错误矢量的比例。通过测量动电不稳定性产生的不稳定流示例，演示了时间分辨高速 PIV。
An investigation of two-frame micro particle image velocimetry (mu PIV) correlations is presented that utilizes a high-speed, spinning disk confocal micro particle image velocimetry (SD mu PIV) system. The system uses Nipkow disk confocal epifluorescence microscopy and a high-speed camera to capture unsteady microscale flows using two-frame cross correlations. In mu PIV, ensemble averaging is often used to reduce errors due to noise from out-of-focus particles. However, unsteady non-periodic flows require two-frame correlations which can be difficult to achieve with acceptable accuracy using mu PIV. The confocal microscope uses pinhole spatial filtering to remove much of the light originating from outside the focal plane, reducing light from out-of-focus particles and improving the accuracy of two-frame cross correlation mu PIV. Improvements to two-frame PIV correlations provided by the confocal system are evaluated using the correlation peak signal to noise ratio and universal outlier detection in steady Poiseuille flow as a function of particle volume fraction and focal depth into the channel. We find that the confocal system increases the mean correlation signal to noise ratio for all cases and reduces the fraction of erroneous vectors under conditions where there is a large number of out-of-focus particles. Time-resolved high-speed PIV is demonstrated through the measurement of an example unsteady flow created by an electrokinetic instability.