PolNor

Active polarimetric imaging systems proved to be efficient in military (decamouflage, object detection) and civilian (biomedical imaging, 3D imaging) contexts since they make it possible to reveal contrasts that do not appear in classical images. During the ASTRID project “AUTOPOL” (2013-2015), an active polarimetric imaging system with total control over the illumination and analysis polarisation states has been designed and built. It is the first imaging system in the world having this capacity. The experiments performed with this imager have demonstrated the efficiency of active polarimetric imaging in such applications as decamouflage and object detection in complex environments. However, these results are limited by the fact that the instrument is difficult to move and has a relatively low image acquisition rates (that depends on the operating mode). There is thus a need to validate this imaging concept in conditions closer to the operational ones. Our objective in this project is to build an active polarimetric imaging demonstrator that is compact and movable in order to be tested and validated in the field. To reach this objective, all the elements of the imager will be improved compared to the AUTOPOL demonstrator, taking into account the conclusion of this project. The illumination module will be equipped with a more powerful laser source. A compact and innovative detection module will be designed and built. Since the AUTOPOL project has shown that it is necessary to normalize the polarimetric images in order to get rid of the spatial variations of intensity reflectivity, the module will consist of a polarized beam splitter and two InGaAs sensors, and will deliver an intensity image and a normalized polarization image at video rate. The polarization state generation modules for illumination and analysis will be simplified since the AUTOPOL project has shown that in many applications, an imager having less polarimetric degrees of freedom has sufficient efficiency. This will make these modules faster and more robust, while giving the user access to a whole range of polarimetric imaging modes adapted to each application. These different technological innovations should lead to patent applications. The demonstrator will have an operating range of about one kilometer. It will make it possible to validate active polarimetric imaging on realistic scenarios involving decamouflage in different conditions (scenes, observation distance) with observed objects representative of threats (weapons, vehicles), and hazardous object detection on roads, tracks or runways. Thanks to the simultaneous acquisition of two images with the two sensors of the detection module, it will also be able to address dynamic situations where the target is moving. Systematic validation and analysis of the obtained results will make it possible to determine the application domains of this system and will give access to parameters essential for its practical use, such as probability of detection or operational range. Furthermore, the collected information in terms of performance, range and technological design will make it possible to design a polarimetric imager with longer range or to fit an already existing very-long range active imager with polarimetric capability.