Abstract
The precision of optical imaging to study free surface dynamics is analyzed. The damping of a liquid bridge free surface oscillation is used to validate this method. Images are acquired with a digital camera at relatively high frame rates and processed by several techniques. Oscillations with amplitudes of about 20 times smaller than the pixel size are measured, which allows one to reach the nanometer scale in the analysis. The experimental results presented in this paper constitute the first quantitative validation of optical imaging to study free surface dynamics at the nanometer scale. As a secondary goal, we propose an image processing technique based on the local thresholding criterion to determine the free surface position with sub-pixel resolution. This yields more precision (less noise) than the standard technique when considering very small oscillations. Further improvement of the results is obtained by a simple smoothing technique.
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Acknowledgments
This research was supported by the Ministerio de Educación y Ciencia (Spain) through Grant No. DPI2007-63559. Partial support from the Junta de Extremadura through Grant No. GRU07003 is also acknowledged.
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Vega, E.J., Montanero, J.M. & Fernández, J. On the precision of optical imaging to study free surface dynamics at high frame rates. Exp Fluids 47, 251–261 (2009). https://doi.org/10.1007/s00348-009-0657-y
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DOI: https://doi.org/10.1007/s00348-009-0657-y