Polarization modulation polarimeter for measuring two-dimensional distribution of five cell parameters of a twisted nematic liquid crystal display

In this study, an intensity-sensitive polarization modulation polarimeter (IPMP) was proposed and set up in order to measure the cell parameters of a twisted-nematic liquid crystal display (TNLCD). Both Yeh and Gu's transfer matrix and Lien's transfer matrix of a TNLCD are used and they are able to characterize all five cell parameters of a TNLCD including the cell gap, pretilt angle, rubbing angle, twist angle and untwisted phase retardation simultaneously. The optical setup is based on a single CCD camera and the ratio of p- and s-linear polarization intensity signals whereas we rotate a calibrated quarter wave plate to produce the polarization modulation during measurement. Thus, all five cell parameters are determined numerically by use of the least square curve fitting algorithm between the measured data and theoretical prediction following Yeh & Gu's and Lien's models of a TNLCD at same time. Finally, the advantages of this proposed IPMP are discussed.