Supposons qu'on image en transmission ou en rétrodiffusion un milieu éclairé en lumière cohérente. Supposons également que ce milieu est tel que la phase du champ rétrodiffusé apparaît en tout point comme aléatoire. On obtient alors un motif également aléatoire constitué de grains: du speckle. Si, de plus, le milieu varie au cours du temps, le sign...
We demonstrate the ability of high-speed acquisition (up to 30 kHz) of dynamic speckle to provide images of the human vascularization at various scales. A comparative study involving the speckle contrast, the first term of the intensity autocorrelation function, and the zero-crossings of the field intensity is proposed, together with a proper prepr...
Les travaux menés durant cette thèse s'inscrivent dans le cadre du développement d'instruments de métrologie pour la mécanique des fluides, notamment dans le domaine de la visualisation des écoulements.La BOS3D (pour Background Oriented Schlieren 3D) est une technique capable de fournir des champs 3D instantanés de densité ou de température. Dévelo...
In the last 30 years, the contrast-to-noise ratio (CNR) has been used to estimate the contrast and lesion detectability in ultrasound images. Recent studies have shown that the CNR cannot be used with modern beamformers, as dynamic range alterations can produce arbitrarily high CNR values with no real effect on the probability of lesion detection. ...
Ces travaux proposent une analyse de l’écho radar de mer grâce au traitement d’une base de données issue de campagnes de mesures en zone côtière. L'analyse de l'amplitude de l’onde rétrodiffusée montre qu’elle respecte un modèle à deux échelles, combinaison de deux composantes nommées texture et speckle. La texture restitue les variations de la pui...
International audience
This paper proposes a realistic wavelength decorrelation induced speckle noise simulator. The investigation of the dependence of the coherence factor versus the surface shape, the surface roughness and the wavelength change is carried out.
We characterize the spatial and temporal coherence properties of hard X-ray pulses from the Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL, Pohang, Korea). The measurement of the single-shot speckle contrast, together with the introduction of corrections considering experimental conditions, allows obtaining an intrinsic degree of...
Contrast Echocardiography (CE) ultrasound with microbubble contrast agents (UCA) has significantly advanced our capability for assessment of cardiac function, including myocardium perfusion quantification. However in standard CE techniques obtained with line by line scanning, the frame rate and image quality are limited. Recent research has shown s...
When an electromagnetic wave is scattered by a rough surface, a speckle field is formed, which characteristics are depending on the surface properties. Polarimetry of speckle fields leads to new variables for the characterization of material properties.However, polarimetric measurement is challenging in the case of low reflectance samples, or at th...
