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Etude d’algorithmes de reconstruction ultrasonore dans le domaine de Fourier pour l’imagerie rapide 2D et 3D en contrôle non- destructif

Abstract : This research work deals with ultrasound imaging with transducer arrays for Non Destructive Testing (NDT), and aims at speeding up the formation of 2D and 3D images. The methods studied in this manuscript are inspired from reconstruction algorithms in the Fourier frequency-wavenumber (f-k) domain introduced in seismic imaging in the 70’s. The literature shows that f-k methods offer a numerical advantage over the more conventional time-domain focusing algorithms. On the other hand, the rise of transducer arrays has allowed for the exploration of new emission modes, such as plane wave emissions in ultra-fast medical imaging. In this thesis, we propose to combine fast f-k algorithms with plane wave emissions to form 2D and 3D images as fast as possible. These algorithms are adapted to deal with realistic NDT inspection configurations. Analyses of algorithmic complexities, computation times, and image qualities are carried out in 2D, and a comparison with the time-domain Plane Wave Imaging (PWI) shows a clear advantage for f-k methods. This is confirmed in 3D, where we show that Fourier domain algorithms improve image quality while reducing computation times by a factor up to 300 compared to PWI. Finally, the f-k methods are generalized to multi-modal imaging to characterize cracks. The theory, which accounts for mode conversions and reflections at the specimen interfaces, is first presented, and we then demonstrate that it is possible to improve the reconstruction quality thanks to spectral windowing in the image frequency-domain. This spectral filter cancels undesired artifacts caused by interface echoes, and improves the image contrast.
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Submitted on : Tuesday, October 13, 2020 - 3:43:23 PM
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Lucas Merabet. Etude d’algorithmes de reconstruction ultrasonore dans le domaine de Fourier pour l’imagerie rapide 2D et 3D en contrôle non- destructif. Physique [physics]. Université Paris sciences et lettres, 2019. Français. ⟨NNT : 2019PSLET060⟩. ⟨tel-02965874⟩

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