Simultaneous interferometric in-focus and out-of-focus imaging of ice crystals

Using a freezing column, dendrite-like ice crystals are generated and characterized simultaneously using in-focus imaging and interferometric out-of-focus imaging. This simultaneous analysis allows a validation of size measurements made from the analysis of the 2D-autocorrelation of speckle-like int...

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Veröffentlicht in:Optics communications 2016-08, Vol.372, p.185-195
Hauptverfasser: Kielar, Justin Jacquot, Lemaitre, Pascal, Gobin, Carole, Yingchun, Wu, Porcheron, Emmanuel, Coetmellec, Sébastien, Grehan, Gérard, Brunel, Marc
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Sprache:eng
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Zusammenfassung:Using a freezing column, dendrite-like ice crystals are generated and characterized simultaneously using in-focus imaging and interferometric out-of-focus imaging. This simultaneous analysis allows a validation of size measurements made from the analysis of the 2D-autocorrelation of speckle-like interferometric out-of-focus patterns of ice crystals. Measurements of the same particles by in-focus and out-of-focus techniques are in good agreement for 75% of the particles tested. Simulations of out-of-focus patterns are in very good agreement with experimental images. The analysis of the 2D-Fourier transform of the speckle-like patterns confirms that it is possible to evaluate the 2D-autocorrelation of the global shape of the particle (i.e. its 2D-projection on the plane of the CCD sensor). •Interferometric out-of-focus imaging is used to measure size and shape of ice crystals.•Results are validated by simultaneous in-focus imaging.•Rate of errors is evaluated.
ISSN:0030-4018
1873-0310
DOI:10.1016/j.optcom.2016.04.004