Active multispectral near-IR detection of small surface targets

The detection and identification of small surface targets with Electro-Optical sensors is seriously hampered by ground clutter, leading to false alarms and reduced detection probabilities. Active ground illumination can improve the detection performance of EO sensors compared to passive skylight illumination because of the knowledge of the illumination level and of its temporal stability. Sun and sky cannot provide this due to the weather variability. In addition multispectral sensors with carefully chosen spectral bands ranging from the visual into the near IR from 400-2500 nm wavelength can take benefit of a variety of cheap active light sources, ranging from lasers to Xenon or halogen lamps. Results are presented, obtained with a two-color laser scanner with one wavelength in the chlorophyll absorption dip. Another active scanner is described operating at 4 wavebands between 1400 and 2300 nm, using tungsten halogen lamps. Finally a simple TV camera was used with either a set of narrow band spectral filters or polarization filters in front of the lamps. The targets consisted of an array of mixed objects, most of them real mines. The results show great promise in enhancing the detection and identification probabilities of EO sensors against small surface targets