Bubbles, drops, and solid particles recognition from real or virtual photonic jets reconstructed by digital in-line holography

Abstract

The image of the photonic jet (also called caustic) formed by a large, transparent, and spherical particle, reconstructed by digital in-line holography, is shown to be similar to the Airy pattern observed at the focus of a diffraction-limited lens. The analysis of this image, real or virtual depending on whether the particle relative refractive index is above or below one, allows characterizing the particle composition via its refractive index. Experiments clearly demonstrate the value of this method for the simultaneous 3D characterization and differentiation of the dynamics, size, and composition of gas, liquid, and solid particles in multiphase flows.

A hybrid image processing method for measuring 3D bubble distribution using digital inline holography

“…Recently, digital inline holography (DIH) was introduced as a low cost and compact solution for measuring bubble size distribution in 3D (Tian et al 2011, Tapapatra et al 2012, Liu et al 2013, Sentis et al 2018. DIH employs a single beam light source to illuminate the objects and uses a digital sensor to record the holograms generated from the interference between the scattered light from the objects and un-scattered portions of the beam.…”

“…The hologram processing program was assessed through measuring a well-mixed bubbly flow with mostly spherical bubbles in a static water tank. Similar approach was also implemented by Sentis et al (2018) for measuring a mixture of diluted bubbles and oil droplets rising in a quiescent water tank, capable of distinguishing the signature of bubbles and oil droplets based on their minimum intensity metric. In addition, multiple investigations have attempted to incorporate additional segmentation criterions such as shapes or intensity gradients to improve the accuracy of segmentation and localization of the bubbles from holograms (e.g.…”

“…Over 8000 holograms are captured through the span of the experiments corresponding to a time scale of 2.71 s. The bubble sizes are in a range of 2 to 180 pixels, which correspond to a bubble diameter of 0.1 mm to 9 mm. of challenges in the processing of holograms from real water tunnel experiments, which has not been adequately addressed by the previous techniques yet (Tian et al 2011, Tapapatra et al 2012, Liu et al 2013, Sentis et al 2018). These challenges include strong background noise, high dynamic range of the bubble size and shape, and bubble clustering as shown in the supplemental video S1.…”

Contribution of Debye series to particle characterization with holography and the photonic jet method

“…We have recently proposed a new and numerical-effective method to measure with Digital-in-Line Holography (DIH)[1] the refractive index (real, m) of transparent and spherical particles [2][3][4]. This "photonic jet method" (PJM) is based on the analysis of the "photonic jet" (also named "forward caustic" [3,5]) produced by the aforementioned particles.…”

“…In the frame of the scalar diffraction theory, and more particularly the Fresnel's Approximation, we have recently demonstrated that the PJ reconstructed by DIH is formally similar to the Airy pattern of a thin lens [4,6], and that the reconstructed near field exhibits some real (m>1) or virtual features (m<1). To further extend the capability and accuracy of the DIH-PJM, it is a priori necessary to not only account for Geometrical and Physical Optics (GPOA) effects but also semi-classical effects (e.g.…”