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Polarization Imaging Apparatus with Auto-Calibration

United States Patent Application

View the Complete Application at the US Patent & Trademark Office
A polarization imaging apparatus measures the Stokes image of a sample. The apparatus consists of an optical lens set, a first variable phase retarder (VPR) with its optical axis aligned, a second variable phase retarder with its optical axis aligned, a linear polarizer, a imaging sensor for sensing the intensity images of the sample, a controller and a computer. Two variable phase retarders were controlled independently by a computer through a controller unit which generates a sequential of voltages to control the phase retardations of the first and second variable phase retarders. A auto-calibration procedure was incorporated into the polarization imaging apparatus to correct the misalignment of first and second VPRs, as well as the half-wave voltage of the VPRs. A set of four intensity images, I.sub.0, I.sub.1, I.sub.2 and I.sub.3 of the sample were captured by imaging sensor when the phase retardations of VPRs were set at (0,0), (.pi.,0), (.pi.,.pi.) and (.pi./2,.pi.), respectively. Then four Stokes components of a Stokes image, S.sub.0, S.sub.1, S.sub.2 and S.sub.3 were calculated using the four intensity images.
Zou, Yingyin Kevin (Lexington, MA), Zhao, Hongzhi (Maiden, MA), Chen, Qiushui (Andover, MA)
12/ 763,173
April 19, 2010
STATEMENT OF GOVERNMENTAL INTEREST [0002] This invention was made partially with Government supports under grant No. NNJO5JC13C awarded by NASA and No. DE-FG02-08ER85109 awarded by Department of Energy. The government has certain rights in this invention.