Abstract
In this paper, an experimental method for measuring the 2-D cell parameter
distribution of a twisted nematic liquid crystal is presented. Based on
phase-sensitive imaging polarimeter with a common-path heterodyne
configuration, this study adopts an integrating-bucket method to extract 2-D
phase distribution on the detected heterodyne signal for the inverse
calculation of the azimuth angle (entrance director angle), twist angle, and
cell gap. The advantage of the heterodyne scheme introduces high sensitivity
on phase detections, and the multiple parameters could be easily extracted
through the genetic algorithm. The measurement range of the azimuth angle is
from 0$^{\circ}$ to 180$^{\circ}$ without ambiguity. By using standard 8-bit gray-level
charge-coupled device, the experimental results show that the 2-D standard
deviation of 0.4$^{\circ}$, 0.7$^{\circ}$, and 0.032 $\mu{\hbox {m}}$ in the measurement of azimuth angle, twist angle, and cell
thickness have been obtained.
© 2009 IEEE
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