A silicon retina for polarization contrast vision

Polarization vision is prevalent among insects, and offers visual capabilities that contribute to object discrimination and homing tasks. We present a CMOS imager that is capable of extracting polarization contrast in a scene. A similar visual modality has been seen in Octopus. The polarimetric vector is a more general descriptor of light than intensity information alone, and it contains physical information about the imaged objects in a scene that traditional intensity based sensors ignore. Polarimeters-devices that measure polarization-are used to extract physical features from an image such as specularities, occluding contours, and material properties. Polarization information is used to perform difficult tasks such as image segmentation and surface reconstruction, object orientation, material classification, atmospheric and solar analysis. The polarization contrast retina is a CMOS sensor/imager that uses a birefringent crystal micropolarizer mounted on the focal plane to sense two orthogonal directions of linear polarization. The CMOS imager uses analog translinear circuitry to compute, in real-time on the focal-plane, polarization contrast: a measure of the orientation and degree of linear polarization in an imaged scene