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Accueil > Équipes > OPTique et IMAgeries > Instrumentation et Méthodes > Wave manipulation

Through optical patterning

publié le

A first approach consists in taking profit from patterns naturally formed after propagation through the medium of interest, such as speckle patterns. In the context of imaging through biological tissue, analogously to the imaging methods that benefit from the statistical properties of an optical speckle (mainly its autocorrelation given by the NA of the imaging system and the isoplanatism effect), we propose to apply fluorescence fluctuation techniques through a scattering layer. In contrast to the experiments we previously did on sparse layers of dielectric beads, we now want to address situations where there is no more ballistic light. In this case, we are left with a speckle pattern, where each grain contains a small number of molecules. By spatially averaging the temporal cross-correlation of successive images recorded at a very high frame rate, it should be possible to assess the concentration and mobility of molecules hidden behind an opaque medium. One key question will be to know whether this approach can be applied to real biological situations, where tissues rarely exhibit the ideal scattering properties. In addition, aberrations often superimpose on light scattering, a situation that should not be detrimental because the memory effect can be generalized to low order aberration modes. In the context of imaging through multimode fibers, we will exploit speckle patterns formed at the output of the fiber to implement imaging : current methods require a precalibration step where speckle patterns are measured by a camera prior to measuring the sample of interest. By coupling compressed-sensing and neural networks approaches, our objective will be to perform image reconstruction through multi-mode fibers without knowing explicitly the output speckle patterns. The filing of a patent based on preliminary results is currently under preparation.