Bio-Inspired Sensing and Display of Polarization Imagery

Abstract

Polarization is an important feature of electromagnetic waves, and it can be affected by surface shapes, materials, local curvature and features, and relative location of sources and objects, and thus it can provide useful information about the observed scene and objects. Of the several characteristics of visible light, only two -intensity and wavelength -are encoded by the human eye and subsequently mapped by the visual system into perceptual qualities. Intensity is mapped to brightness and wavelength information is mapped to perceived color. In contrast, without appropriate instruments human eyes cannot effectively utilize light's polarization. However, it is well known that eyes of certain animal species are sensitive to the polarization of light. Polarization sensing has mostly been shown to provide information for navigation, as originally discovered by the Nobel laureate Karl von Frisch in his work with honeybees. In addition, it has been hypothesized that some species may have evolved polarization sensitivity as a mechanism of enhancing the contrast of targets in media that scatter light (e.g., under water). Indeed, in our earlier work, we have shown that an optical imaging system utilizing such contrast enhancement through polarization differencing can increase the distance over which targets can be detected, and their critical features discriminated. Thus, "polarization imagery" is a naturally occurring and demonstrably successful strategy for enhancing vision.Since the human eye is effectively polarization-blind, in mapping polarization information into visual displays, the output should be exhibited in a way compatible with the biology of the human visual system. In our group's earlier work, we have shown one such bio-inspired mapping, in which polarization information was pseudo color-coded, based on the opponent-colors model of human vision. The results established several promising imaging strategies for making available in a natural way the contrast enhancement of polarization imagery of objects in scattering media.During our research efforts in the period of March 1, 2002 till December 31, 2004, we have explored and investigated various bio-inspired display methodologies for mapping polarization information into visual information that can be readily perceived by the human visual system, and we have studied those mappings most suitable for specific applications for object detection, scene classifications, and visibility enhancement. We have introduced and developed various imaging algorithms, sensing schemes and visualization and display methodologies inspired -and informeciby biological consideration. Ourresearch efforts have demonstrated that these bio-inspired polarization sensing and imaging techniques enable us to achieve better target detection, enhanced visibility in otherwise low-contrast conditions, longer detection range in optically scattering media, man-made polarizationsensing adaptation based on changing environments, surface deformation/variation detection (e.g., detection ...