Active spectral imaging

Abstract

With the ability to image a scene in tens to hundreds of spectral bands, multispectral and hyperspectral imaging sensors have become powerful tools for remote sensing. However, spectral imaging systems that operate at visible through nearinfrared wavelengths typically rely on solar illumination. This reliance gives rise to a number of limitations, particularly with regard to military applications. Actively illuminating the scene of interest offers a way to address these limitations while providing additional advantages. We have been exploring the benefits of using active illumination with spectral imaging systems for a variety of applications. Our laboratory setup includes multispectral and hyperspectral sensors that are used in conjunction with several laser illumination sources, including a broadband white-light laser. We have applied active spectral imaging to the detection of various types of military targets, such as inert land mines and camouflage paints and fabrics, using a combination of spectral reflectance, fluorescence, and polarization measurements. The sensor systems have been operated under a variety of conditions, both in the laboratory and outdoors, during the day and at night. Laboratory and outdoor tests have shown that using an active illumination source can improve target-detection performance while reducing false-alarm rates for both multispectral and hyperspectral imagers