科研之友
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摘要
A unique algorithm named single pixel evaluation (SPE) has been developed to enhance the resolution of micro-PIV to its physical limit, one pixel. Based on some presumed conditions, an experimentally ultimate in-plane resolution of micro-PIV is estimated. An extremely high resolution of 64.5 nm can be achieved when a 60-nm particle is resolved. However, there exist discrepancies between the analytic predictions and the experimental measurements. Therefore, another task of this paper is to characterize the algorithm and provide practical criteria as applying SPE. Five general parameters were investigated with synthetic particle images governed by a parabolic flow profile. The parameters include particle image quality, particle image density, search radius, particle image displacement, and particle image diameter. The results indicate that all parameters have significant improvements on the random error, yet minor or no effects on the bias error. The tendencies of optimal values subject to different parameters are discussed in the context. Moreover, SPE was compared with fast Fourier transform-based cross-correlation under a desired signal-to-noise ratio. To complete the study, measurements in a straight microchannel were implemented to verify the predictions and the estimated resolution. The measured images following the suggested criteria showed qualitatively good agreements with the predictions. In practice, a spatial resolution of only 129 nm was achieved since the minimal particle diameter that can be visualized by our micro-PIV system was around 100 nm.
- 出版日期2012-7
