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L’imagerie polarimétrique active permet de révéler des contrastes invisibles à l’oeil humain et aux caméras classiques. Elle peut étendre les capacités de décamouflage des systèmes d’imagerie active et améliorer la détection d’objets dangereux sur des pistes. Elle possède également de nombreuses applications duales dans des domaines tels que l’imagerie biomédicale ou la vision industrielle.

We address the detection of manufactured objects in different types of environments with active polarimetric imaging. Using an original, fully adaptive imager, we compare several imaging modes having different numbers of polarimetric degrees of freedom. We demonstrate the efficiency of active polarimetric imaging for decamouflage and hazardous object detection, and underline the characteristics that a polarimetric imager aimed at this type of application should possess. We show that in most encountered scenarios the Mueller matrices are nearly diagonal, and sufficient detection performance can be obtained with simple polarimetric imaging systems having reduced degrees of freedom. Moreover, intensity normalization of images is of paramount importance to better reveal polarimetric contrast.

We 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.

This paper addresses the problem of evaluating the acoustic pressure field generated in the oceanic waveguide by a uniformly moving airborne source. The air, water, and seabed media are stationary and stratified. The pressure in the far field is obtained in terms of the normal modes usually utilized in underwater and aerial transmission loss calculation. The expression obtained is shown to be in accordance with specialized results found by other authors and is physically interpreted. The influence of the source movement on propagation loss is considered.