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

Justin Jacquot Kielar (1) , Pascal Lemaitre (2) , Carole Gobin (1) , Wu Yingchun (1) , Emmanuel Porcheron (2) , Sébastien Coëtmellec (1) , Gérard Gréhan (1) , Marc Brunel (1)

1 CORIA - Complexe de recherche interprofessionnel en aérothermochimie
2 IRSN - Institut de Radioprotection et de Sûreté Nucléaire

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).

Mots clés: Interferometric out-of-focus imaging; Ice crystals; Interferometric particle imaging; Speckle

Domaines: Optique / photonique

Justin Jacquot Kielar, Pascal Lemaitre, Carole Gobin, Wu Yingchun, Emmanuel Porcheron, et al.. Simultaneous interferometric in-focus and out-of-focus imaging of ice crystals. Optics Communications, 2016, 372, pp.185-195. ⟨10.1016/j.optcom.2016.04.004⟩. ⟨hal-02110862⟩