Physics and Reverse-Engineering of Polarization Vision in Nature, Biologically-Inspired Polarization Imaging and Sensing
Polarization Imager Sensor Fabrication and Integration
Polarization vision contains important information about the imaged environment, such as surface shapes, curvature and material properties, which are ignored with traditional imaging systems. Several species of invertebrate, such as cuttlefish, honeybees, desert ants, and others, rely on contrast enhancement using polarized vision, which is a vital survival mechanism in optically scattering media. The human eye perceives visual information in terms of color and intensity but it is blind to polarization. We are developing an imaging system capable of extracting polarization information from the imaged environment in real time and presenting the polarization information in parallel with the intensity information. This sensory system integrates: 1) micro-polarization array 2) novel current mode imaging sensor and 3) low power analog electronics for polarization processing at the focal plane.
A block diagram overview of the polarization image sensor is presented in the figure below. The micropolarizer array contains pixel filter pattern matched to the pixel pitch of the image sensor. The image sensor architecture allows for simulations access of a neighborhood of 2 by 2 pixels. In the pixels neighborhood of interest, one pixel records the 0 degree projected polarized image (I(0°,0)), another records the 45 degree projected polarized image (I(45°,0)) and two pixels record the unfiltered intensity image (It). The polarimetric parameters i.e. the first three Stokes parameters are estimated by reading out all four pixels in parallel and scaling them individually at the periphery, i.e. away form the imaging array, with programmable analog scaling circuitry. We are developing this bio-inspired imaging sensors for a variety of applications.
For details regarding this image, please see, V. Gruev, K. Wu, J. Van der Spiegel and N. Engheta, "Real Time Extraction of Polarimetric Information at the Focal Plane," Proc. SPIE, Orlando, Florida, March 2006.