Wavelength-agile, compact, polarization imaging

Optical target acquisition and identification meets with some severe problems under difficult lighting conditions. For example, the target object may be obscured by smoke or fog. In addition, the ability to distinguish the appropriate target may dependupon its material composition. Spectral-polarization imaging provides means of removing the effects of obscuring aerosols and means of distinguishing the material composition of the target object. This ability will be in high demand in the militarysector. Its utility in aiding the scope of machine vision for industrial applications should lead to an even greater demand in the private sector.Conventional methods for detecting and identifying objects revolve around the sensing of reflected and emitted light intensity. Conventional imaging records intensity, which is the square of the electric field associated with the electromagnetic radiationfield. This works well when an object to be detected has high contrast relative to its background or foreground. However, when the object exhibits low contrast against the background or foreground, identification is often blurred by the 'noise' light,which is produced by surrounding non-vital objects. The spectral and polarization signatures of the target can enhance the contrast of the target with respect to the background.Wavelength agile polarization imaging technology is expected to play a dominant role in the market place in the very near future, not only for the military market but also more significantly for the consumer market. For example, it will impactsignificantly on machine vision (process and quality control), agriculture (e.g., vegetation mapping), medicine (e.g., skin cancer detection), geology (e.g., mineral surveys), robotics and astronomy. It will also enhance the detection of targets indifficult lighting conditions (e.g. low light, smoke) by aerial and ground based surveillance systems and provide material identification for the targets by their characteristic spectral-polarization signatures.Many of the previous approaches have not succeeded in producing commercial systems, in part because of immature technology, which has led others to use moving mechanical parts, leading to systems which are bulky, expensive and plagued with reliabilityissues. Our approach to spectral-polarization imaging uses non-moving parts in a compact geometry, which is expected to produce a reliable system needed for critical missions in the military.