Active polarimetric imaging with adaptive contrast optimization (Orale)

International audienceWe propose a method for semi-automatic target detection and contrast optimization making joint use of an adaptive polarimetric imager and a statistical image segmentation algorithm. It can be used to detect targets that differ from the background by their polarimetric properties. This method illustrates the benefits of integrating digital processing algorithms in the image acquisition process, rather than using them only for post-processing

Excited state absorption : a key phenomenon for the improvement of biphotonic based optical limiting at telecommunication wavelengths

International audienceSpectroscopic properties, two-photon absorption (TPA) and excited state absorption (ESA), of two organic cyanine dyes and of a ruthenium based organometallic cyanine are compared in order to rationalize their similar ns-optical power limiting (OPL) efficiency in the telecommunication wavelength range. The TPA contribution to the ns-OPL behavior is higher for both organic cyanines, while the main process is a TPA-induced ESA in the case of the organometallic system, in which the ruthenium induces a broadening of the NIR-ESA band and resulting in a strong spectral overlap between TPA and ESA spectra

Performance and limitations of dual-comb based ranging systems

International audienceDual-comb LiDARs have the potential to perform high-resolution ranging at high speed. Here, through an implementation involving electro-optic modulators and heterodyne detection, we quantify the ranging systems trade-off between precision and non-ambiguity range (NAR) using a unique performance factor. We highlight the influence of the comb amplitude envelope on the precision with a distance measurement limited by the repetition rate of the optical comb. The influence of the combs repetition rate on the NAR and on the precision is illustrated through a setup allowing distance measurement with a tunable NAR. Finally, we demonstrate the impossibility to resolve different targets, quantify the impact on the measured distance and develop on the conditions in which non-linear effects of the interference make the measurement impossible

Dendron-decorated cyanine dyes for optical limiting applications in the range of telecommunication wavelengths

International audienceCyanine dyes decorated with 2,2-bis(methylol)propionic acid (bis-MPA) based dendrons up to third generation were synthesized. Dendrons were attached to the chromophore using a “click chemistry” reaction. Photophysical characterizations of these dyes show intense absorption and emission in the near-infrared (NIR), while nonlinear transmission experiments of the dendron-decorated chromophores indicate that properties in the IR of the parent dyes are conserved. This synthetic approach is a crucial preliminary step towards the preparation of solid functional materials for optical limiting (OL) applications in the IR

Imagerie polarimétrique active adaptative dans l’infrarouge (Orale)

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Comparison of different active polarimetric imaging modes for target detection in outdoor environment

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Near IR two photon absorption of cyanines dyes: application to optical power limiting at telecommunication wavelengths

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AUTOPOL - Imagerie polarimétrique active dans l’infrarouge (poster)

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Active polarimetric imager with near infrared laser illumination for adaptive contrast optimization

International audienceWe designed and built an active polarimetric imager with laser illumination at 1.5 μm wavelength for adaptive polarimetric contrast optimization. It can generate and analyze any polarization state on the Poincaré sphere in order to best adapt to the polarimetric properties of the scene. Polarimetric contrast optimization is performed by analyzing the scene with an ultrafast active-contour-based segmentation algorithm. This device is, to the best of our knowledge, the first fully adaptive imager controlled by image processing algorithms for polarimetric contrast enhancement. Its capabilities are illustrated in some examples of real-world decamouflage applications