Polarization Studies in Passive ASW

As discussed in the solicitation for this SBIR, EPAS and other current passive ASW sensors have not yet incorporated the use of polarization analyzers to mitigate the effects of high background clutter their imaging systems. It is postulated that proper use of polarization analyzers can reduce the false alarm rate and improve the probability of detection near the solar glint pattern. It is also possible that the polarization signatures at look angle between 40 and 80 degrees will be useful in detecting other features associated with the presence of a submarine. This proposal leverages a current Advanced Coherent Technologies SBIR which is collecting Stokes Vector imager from the Coronado Bay Bridge. In that effort a four camera / four aperture imaging system is used to collect four polarization channels. The polarization imagery will be used to enhance both wake induced wave slope variations and to reduce near sun glint background clutter which contributes to passive ASW system false alarm rates. The program is utilizing the PAR Government System MANTIS-3T system. A small MANTIS-3T four channel system weighs less than five pound and downlink control and imagery easily using existing relatively low tech communication links. This type of sensor might thus be appropriate not necessarily as a stand alone system in an EPAS concept but as an EO validation sensor / false target reducer for a Digital MAD system. In that application the bulk of the payload is the Digital MAD. As a Digital MAD adjunct sensor the FOV of MANTIS would need to be on the order of 10-30 degrees full angle and operating with four spectral filters. In order to detect others feature associated with a target presence outside of the MAD swath the sensor would need a narrower field of view and a single blue-green band (or even a single red band) used with the Stokes Vector Polarization filters. If the MANTIS could be enhanced such that is could be switched in flight between the two modes without increasing size and weight the sensor would have utility both as a MAD target validator and as a complementary search sensor. BENEFITS: This development will demonstrate and advance the use of small low cost multichannel imaging systems. With channel available to either multiple spectral band, multiple polarization analyzers, or combinations the sensor will have applicablity in search and rescue, harbor security, and environmental monitoring as well as numerous military applications.