Proceedings Article | 31 March 2008
Proc. SPIE. 6972, Polarization: Measurement, Analysis, and Remote Sensing VIII
KEYWORDS: Polarization, Cameras, Polarizers, Polarimetry, Optical filters, Liquid crystals, Target detection, Image enhancement, Image filtering, Imaging systems
Many natural materials produce polarization signatures, but man-made objects, typically having more planar or smoother
surfaces, tend to produce relatively strong polarization signatures. These signatures, when used in combination with
other means, can significantly aid in the detection of man-made objects. To explore the utility of polarization signatures
for target detection applications we have developed a new type of polarimetric imaging sensor based on tunable liquid
crystal components. Current state-of-the-art polarimetric sensors employ numerous types of imaging polarimeters, the
most common of which are aperture division, micropolarizer, and rotating polarizer/analyzer. Our design uses an
electronically tunable device that rotates the polarization of incoming light followed by a single fixed oriented linear
polarizer. Its unique features include: 1) sub-millisecond response time switching speed, 2) ~75% transmission
throughput, 3) no loss of sensor resolution, 4) zero mechanical moving parts, 5) broadband (~75% of center wavelength),
6) ~100:1 contrast ratio, 7) wide acceptance angle (±10°), and 8) compact and monolithic architecture (~10 inch3). This
paper summarizes our tunable liquid crystal polarimetric imaging sensor architecture, benefits of our design, analysis of
laboratory and field data, and the applicability of polarization signatures in target detection applications.
