An Imaging Polarimeter for the Study of Biological Principles of Polarized-Light Vision

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9317927 Cronin Light in nature frequently becomes linearly polarized due to its interactions with scattering particles in the atmosphere and under water, and to its reflection from biological and nonliving dielectric surfaces. Under some circumstances, these events can produce light that is almost completely polarized, and partially linearly polarized light is widely present in nature. Because the interactions of light that produce partial linear polarization are complex, the actual pattern of polarization in any visual field is similarly complicated. Animals have exploited the polarization of natural light for a variety of functions, including navigation, orientation, location of water surfaces, and enhancement of visual contrast. In fact, it now seems that the great majority of animal species have visual specializations for the detection and analysis of partially linearly polarized light, and it is probable that for many of these species polarization vision plays a similarly significant role as color vision plays for species like ourselves. However, the study of polarization vision has been limited by our inability to visualize or analyze natural fields of polarization. In this proposal, we describe a design for a new, imaging polarimeter that will be capable of providing complete descriptions of the distribution of polarized light (e-vector orientation, percent polarization, and intensity) at single-pixel resolution throughout an extended visual field. The instrument will be completely portable, and usable both in terrestrial and aquatic environments. It will obtain polarization images rapidly and will present the data on line, using false-color displays to convey the polarization information in a form intuitively interpretable by a human observer. All data will be stored in numerical form for appropriate mathematical analysis, making possible transformations into the visual systems of animals. We believe that such an instrument will open new windows into the sensory worlds of other species, and will have broad application for studies of biology, perception, and machine vision.