In the last years, there has been a huge improvement in Electro-Optical (EO) systems effectiveness, due to the availability of large staring arrays detectors with higher performance, as well as strong processing capability. So both in homeland surveillance and for military situational awareness, the use of EO systems, operating from Visible to Infrared, has dramatically grown.
Operations in Degraded Visual Environment (DVE) are frequent during military actions, due to many factors: either natural (poor light, fog, glare etc.) or intentionally produced (smoke, dust etc.). In these conditions the performance of EO sensors is degraded and therefore their effectiveness for Detection, Recognition and Identification (DRI) and Navigation capability. In general, the situational awareness is strongly affected as well as the safety of personnel. Proper techniques are needed to restore (at least partially) the imaging capabilities of EO sensors in DVEs. The project SPIDVE (Study on EO Sensors Performance Improvement in Degraded Visual Environment), promoted by the European Defense Agency (EDA), is focused on the analysis of the impact on EO sensors performance by the adverse visual conditions. It starts from the analysis of the status of the art in terms of technology, processing, measurements and modeling methodologies, based on the existing scientific literature, to carry out an assessment of the most promising technologies for image enhancement and restoration in different DVEs.
Particular care is devoted to the discussion with the final users (the military personnel) to identify the cases of higher interest for their operations. On this basis the possible candidate methodologies shall be analyzed more deeply, evaluating their performance with the aim of selecting the most promising one.
At the end, a possible roadmap for new initiatives to exploit and develop the findings shall be defined.
This paper deals with the design of two second generation thermal imagers that Alenia Difesa OFFICINE GALILEO has successfully developed for the Navigation FLIR of the NH90 Tactical Transportation Helicopter (NH90 TTH) and for the Electro-Optical Surveillance and Tracking System for the Italian 'Guardia di Finanza' ATR42 Maritime Patrol Aircraft (ATR42 MPA). Small size, lightweight and low power consumption have been the main design goals of the two programs. In particular the NH90 TTH Thermal Imager is a compact camera operating in the 8 divided by 12 micrometers bandwidth with a single wide field of view. The thermal imager developed for the ATR42 MPA features a three remotely switchable fields of view objective equipped with diffractive optics. Performance goals, innovative design aspects and test results of these two thermal imagers are reported.
The loss of the energy falling on a IR CCD array due to the effect of finite image size of point targets and of its motion on the focal plane was computed through a Monte Carlo simulation. The aberration-free point spread function (PSF) of the system was supposed to move in the focal plane with spatial steps having an amplitude of the order of the linear scan velocity times the IR CCD integration time. The starting position of the motion was varied randomly near to a reference detector element and each position was assumed to have the same probability of occurrence. By considering the energy integrated by the single detectors it is possible to compute the effective signal-to-noise ratio and the overall detection probability of the system. A new figure of merit, called the spreading factor (SF), can be defined by considering the maximum ratio of the energy integrated by the single detectors to the total energy subtended by the PSF and by taking the average of these maxima over all the random displacements. With the parameters considered in this simulation, the SF turns out to be in the range between 0.2 and 0.5, with a considerable reduction of the corresponding detection range.