Phase-shift imaging polarimetry for measuring the physical parameters of a twisted nematic liquid crystal device without periodic ambiguity

The polarization conversion of a twisted nematic liquid crystal device can be completely characterized by the physical parameters, including the cell parameters and equivalent birefringent parameters. Periodic ambiguity is unavoidable in the measurement; therefore, the exact values of these parameters cannot be uniquely determined. To solve this problem, phase-shift imaging polarimetry is developed to measure the spatial distribution of the physical parameters of a twisted nematic liquid crystal device without periodic ambiguity. The proposed method experimentally showed that as few as eight intensity images are adequate to uniquely determine all of the physical parameters based on an analytical approach.