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首页> 外文期刊>Measurement Science & Technology >Improvement in two-frame correlations by confocal microscopy for temporally resolved micro particle imaging velocimetry
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Improvement in two-frame correlations by confocal microscopy for temporally resolved micro particle imaging velocimetry

机译：共聚焦显微镜用于时间分辨微粒成像测速的两帧相关性改进

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摘要

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.
机译：提出了对两帧微颗粒图像测速技术（μPIV）相关性的研究，该技术利用了高速旋转盘共聚焦微颗粒图像测速技术（SDμPIV）。该系统使用Nipkow圆盘共聚焦落射荧光显微镜和高速相机使用两帧互相关来捕获不稳定的微尺度流。在μPIV中，集成平均通常用于减少由于散焦粒子产生的噪声而导致的误差。但是，不稳定的非周期性流需要两帧相关，而使用μPIV很难以可接受的精度实现。共聚焦显微镜使用针孔空间滤波来去除大部分来自焦平面外部的光，减少来自散焦粒子的光并提高两帧互相关（μ）PIV的准确性。共焦系统提供的两帧PIV相关性的改进是使用相关峰信噪比和稳定Poiseuille流中的通用离群值检测（取决于粒子体积分数和进入通道的焦深）来评估的。我们发现，在存在大量散焦粒子的情况下，共聚焦系统会提高所有情况下的平均相关信噪比，并减少错误矢量的比例。通过测量由电动不稳定性产生的示例性非恒定流，证明了时间分辨的高速PIV。

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