Polarization imaging: principles and integrated polarimeters

Abstract

Polarization is a general descriptor of light and contains information about reflecting objects that traditional intensity-based sensors ignore. Difficult computer vision tasks such as image segmentation and object orientation are made tractable with polarization vision techniques. Specularities, occluding contours, and material properties can be readily extracted if the Stokes polarization parameters are available. Astrophysicists employ polarization information to measure the spatial distribution of magnetic fields on the surface of the sun. In the medical field, analysis of the polarization allows the diagnose of disease in the eyes. The retinae of most insect and certain vertebrate species are sensitive to polarization in their environment, but humans are blind to this property of light. Biologists use polarimeters to investigate behaviors of animals-vis-à-vis polarization-in their natural habitats. In this paper, we first present the basics of polarization sensing and then discuss integrated polarization imaging sensors developed in our laboratory.

Application of Surface Plasmon Polaritons in CMOS Digital Imaging

“…However, polarization offers a number of advantages for imaging [22][23][24]. Polarization filtering has long been used in photography through haze.…”

Fabrication of a dual-tier thin film micropolarization array

“…This sensory system integrates an array of imaging elements, a micro-polarization array and analog processing circuitry for polarimetric computation at the focal plane in order to achieve a compact, low power polarization sensitive system. Biologically inspired, polarization difference (contrast) imaging (PDI) sensors have been one of the dominant research topics in developing polarization sensitive systems [4][5][6]. Several imaging systems have been made where polarization-contrast information has been computed at the focal plane [4,5] or with bulky, power hungry set-ups composed of CMOS/CCD imaging sensors, electro/mechanically controlled polarization filters and DSPs/CPUs [6,7].…”

“…Biologically inspired, polarization difference (contrast) imaging (PDI) sensors have been one of the dominant research topics in developing polarization sensitive systems [4][5][6]. Several imaging systems have been made where polarization-contrast information has been computed at the focal plane [4,5] or with bulky, power hungry set-ups composed of CMOS/CCD imaging sensors, electro/mechanically controlled polarization filters and DSPs/CPUs [6,7]. These systems sample the environment via two orthogonal polarization filters and compute contrast information at the focal plane with translinear circuits or in the digital domain with a DSP/CPU.…”

“…The measured extinction ratios on the micro polarization filters are ~1000 in the blue and green visible spectrum and ~100 in the red spectrum. Various gas combinations for RIE have been explored in order to determine the right concentration mix of CF 4 and O 2 that gives optimum etching rate, in terms of speed and underetching. Theoretical explanation for the optimum etching rate has also been presented.…”

Image Sensor With Focal Plane Extraction of Polarimetric Information

“…This information is extracted by either temporally sampling two images filtered with two orthogonal polarized filters [4][5] [7] or integrating two orthogonal polarized filters over two neighboring photo elements [6]. The contrast extraction information is computed either on a DSP/CPU or at the focal plane with translinear circuits.…”