Imagerie acousto-optique de milieux diffusants épais par détection photoréfractive

Abstract : Using conventionnal optical imaging techniques does not allow to image a thick scattering medium because of the weakness of the ballistic transmitted photons. Acousto-optical imaging of the scattered light enables to get images of the local optical absorption with a millimetric transversal resolution. It is based on a focused acoustical beam, which generates a modulation of the phase of the scattered field thanks to the acousto-optical interaction. Coherent detections of the acousto-optical signal are often limited by the weakness of their optical etendue or of their bandwidth. Our setup is based on a heterodyne photorefractive detection through a dynamical holography at 1064nm built within a bulk GaAs photorefractive crystal. This technique allows to get both a good optical etendue and a bandwith compatible with the decorrelation of the biological media. Besides so as to get a millimetric resolution along the ultrasonic propagation axis, we have developped a technique of random phase modulation of both the acoustical and optical beams which creates a zone of controlled temporal coherence within the scattering medium. The implementation of these techniques enabled to image tissues-like phantoms of 3cm depth with millimetric resolutions.
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Max Lesaffre. Imagerie acousto-optique de milieux diffusants épais par détection photoréfractive. Optique [physics.optics]. Université Pierre et Marie Curie - Paris VI, 2009. Français. ⟨pastel-00556664⟩

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