Experimental SWIR gated viewing in accumulation mode

Abstract

Abstract The recent availability of imaging sensors able to work in accumulation mode in the SWIR spectral range allows the realization of new efficient range-gated viewing systems. Such systems relax the illumination constraint so that the energy required to build an image can be distributed over several laser pulses. Semiconductor or fiber lasers can be used instead of high peak power solid state lasers. Such a system was realized in our laboratory, tested, and compared to a more classical flash system under outdoor conditions. In a first step, images of the same scenes recorded in the same weather conditions were compared to those recorded with a classical system working in flash mode. The MTF analysis shows an improvement of up to 40% with the system working in accumulation mode. In order to remove the influence of two different laser sources as well as of two different cameras, a second experiment was conducted. For this purpose, a shorter range and only one system were employed. Both operating modes, the flash and the accumulation mode, were examined. The second experiment confirms that accumulation mode can decrease significantly the value of the scintillation index resulting in a higher resistance to optical perturbations. These results increase the relevance of the accumulation mode for active imaging applications in the SWIR spectral region.