Interferometric out-of-focus imaging simulator for irregular rough particles

We present the development of an original simulator to predict interferometric out-of-focus patterns created by irregular rough particles. Despite important simplifications of the scattering properties, this simulator allows to predict quantitative properties of the speckle-like patterns: i.e. the dimension of the central peak of the 2D-autocorrelation of the pattern. This parameter can then be linked to the size and the shape of the particle projected on the CCD sensor, in cases where there is no exact theoretical formulation to calculate the scattered intensity. An experimental demonstration is performed with irregular NaCl salt crystals

Digital in-line holography assessment for general phase and opaque particle

We propose using the circle polynomials to describe a particle’s transmission function in a digital holography setup. This allows both opaque and phase particles to be determined. By means of this description, we demonstrate that it is possible to estimate the digital in-line hologram produced by a spherical particle. The experimental intensity distribution due to an opaque micro-inclusion is compared to the theoretical one obtained by our new model. Moreover, the simulated hologram and reconstructed image of the particle by an optimal fractional Fourier transformation under the opaque disk, quadratic phase, and quasi-spherical phase approximation are compared with the results obtained by simulating holograms by the Lorenz–Mie Theory (LMT). The Zernike coefficients corresponding to the considered particles are evaluated using the double exponential (DE) method which is optimal in various respects

General formulation of digital in-line holography from correlation with a chirplet function

International audienceDigital in-line holography is revisited to propose a mathematical model that describes the recording-reconstruction process as a linear shift-invariant system with a pseudo-point spread function even when the images are out of the optimal plane in the sense of signal processing. A particular case is treated to show that the optimal plane is the best focus plane in the sense of optics. Next, an exact solution of the holographic reconstruction by correlation is given. By means of the previous results, we study the behavior of the result of the correlation function between the diffraction pattern function produced by an opaque disk and a chirplet function and between the diffraction pattern produced by a phase disk and the same chirplet function

Digital in-line holography in a droplet with cavitation air bubbles

In this publication, the modelisation of an air bubble as inclusion in a droplet is treated from scalar theory point of view (Fresnel’s theory). The elaborated model is compared with Lorenz–Mie scattering theory and with an experimental results. Circle polynomials and scaled pupil function are the background of this work to take into account the critical angle effect that arises at a transition from a higher index to a lower index medium

Simultaneous 3D location and size measurement of spherical bubbles using cylindrical interferometric out-of-focus imaging

International audienceA cylindrical interferometric out-of-focus imaging set-up is presented for the characterization of spherical bubbles. The design of the set-up is realized using transfer matrix based models. The simultaneous three-dimensional (3D) location and size measurement of bubbles is demonstrated using fast Fourier transform algorithms. Experimental results are in very good agreement with theoretical predictions

Particle field digital holographic reconstruction in arbitrary tilted planes

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Interferometric out-of-focus imaging simulator for irregular rough particles

International audienceWe present the development of an original simulator to predict interferometric out-of-focus patterns created by irregular rough particles. Despite important simplifications of the scattering properties, this simulator allows to predict quantitative properties of the speckle-like patterns: i.e. the dimension of the central peak of the 2D-autocorrelation of the pattern. This parameter can then be linked to the size and the shape of the particle projected on the CCD sensor, in cases where there is no exact theoretical formulation to calculate the scattered intensity. An experimental demonstration is performed with irregular NaCl salt crystals

Interferometric out-of-focus imaging for the 3D tracking of spherical bubbles in a cylindrical channel

International audienceWe present an original interferometric out-of-focus imaging set-up to track the 3D position and the size of spherical bubbles in a cylindrical channel. Experimental results confirm theoretical predictions. Using a double acquisition, a 3 component velocimetry of bubbles can be performed simultaneously with size measurements

Digital in-line holography: influence of the shadow density on particle field

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Fractional-order Fourier analysis for ultrashort pulse characterization

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