TARGET DETECTION IN OPTICALLY SCATTERING MEDIA BY POLARIZATION-DIFFERENCE IMAGING

Polarization-difference imaging (PDI) was recently presented by us as a method of imaging through scattering media [Opt. Lett. 20, 608 (1995 )]. Here, PDI is compared with conventional, polarization-blind imagin g systems under a variety of conditions not previously studied. Throug h visual and numerical comparison of polarization-difference and polar ization-sum images of metallic targets suspended in scattering media, target features initially visible in both types of images are shown to disappear in polarization-sum images as the scatterer concentration i s increased, whereas these features remain visible in polarization-dif ference images. Target features producing an observed degree of linear polarization of less than 1% are visible in polarization-difference i mages. The ability of PDI to suppress partially polarized background v ariations selectively is demonstrated, and discrimination of target fe atures on the basis of polarization information is discussed. Our resu lts show that, when compared with conventional imaging, PDI yields a f actor of 2-3 increase in the distance at which certain target features can be detected. (C) 1996 Optical Society of America