A number of studies suggest that the Short Wave InfraRed (SWIR) band (0.9-1.7μm), offers a significant advantage over the visible for long-range daytime scenarios. This advantage of SWIR is due in particular to its excellent optical penetration in the presence of aerosols thanks to reduced light-scattering effects, allowing good scene contrast to be maintained over very long distances. This study reports the results of a field evaluation campaign, involving Lynred’s SNAKE TECLESS (TL) sensor (640x512@15μm, InGaAs) along size narrow field optics. This year-long campaign features a variety of atmospheric conditions, weathers and aerosol types. Those targets are at distances ranging between 10km and 84km. Finally, we compare the image obtained with SWIR sensors having a pixel pitch of 15μm and 10μm, with the same objective lenses, in order to conclude on the interest of reducing the pixel pitch for a gain in range.
We report on the development and field trials of an active polarimetric imager in the SWIR domain. Polarization states are controlled for both emission and analysis. Based on past experience, we focus on Orthogonal State Contrast (OSC) imaging for which two images with orthogonal polarizations are needed. An important feature of the imager is the use of two InGaAs imaging detectors mounted orthogonally on a polarization beam splitter. This allows the synchronous imaging with the two orthogonal polarizations and the real time acquisition of OSC images at video frame rate without temporal artefacts. The demonstrator has been operated during field trials with static and moving scenes. These trials were mainly aimed at the detection of man-made objects (weapons, vehicles …) in complex scenes at up to a few hundreds of meters. Along with the presentation of some example of results, we discuss different representation modes of the polarimetric information.
We describe an active polarimetric imager with laser illumination at 1.5 µm that can generate any illumination and analysis polarization state on the Poincar sphere. Thanks to its full polarization agility and to image analysis of the scene with an ultrafast active-contour based segmentation algorithm, it can perform adaptive polarimetric contrast optimization. We demonstrate the capacity of this imager to detect manufactured objects in different types of environments for such applications as decamouflage and hazardous object detection. We compare two imaging modes having different number of polarimetric degrees of freedom and underline the characteristics that a polarimetric imager aimed at this type of applications should possess.
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