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Active and passive EO sensing for the detection of humans and handheld objects

Some results from a low light trial in Porton Down UK are described. The purpose was to compare imaging performance for active and passive sensors in the visible, NIR, SWIR, MWIR and LWIR bands concerning detection and identification of humans carrying certain handheld objects and performing associated activities. This paper will concentrate on results from active and passive NIR and SWIR only. Both NIR and SWIR sensors provided passive imagery down to illumination levels between 1-10 lux corresponding to sunset-overcast to moonlight. The active mode gave usable imagery out to 2-3 km at much lower light levels. NIR and SWIR sensor images are compared concerning target to background contrast, cloth recognition and the detection of humans, activities and handheld objects. The target to background contrast was often somewhat better in the SWIR as compared with the NIR wavelength region. The contrast between different types of clothing was in general more discriminative in the NIR vs the SWIR. This was especially true for the active sensing modes. The recognition of large weapons could be done out to 600-1000 m range and handguns out to the 300-600 meter range. We found that activities could be detected and recognized out to 1400 m at least, but depends on the contrast between the person the background.