Abstract
A method is proposed for determining the cell gap, twist
angle and pretilt angle of twisted nematic liquid crystal (TNLC) cells. In
the proposed approach, the effective optical parameters of the TNLC cells
are measured using a Stokes polarimetry method and the physical optical parameters
are then extracted from these effective parameters using a simple analytical
technique. The experimental results for the TNLC cell show that the extracted
values of the twist angle, pretilt angle and cell gap are
$\Phi=89.864^{\circ}\pm 0.028^{\circ}$
,
$\xi=1.806^{\circ}\pm 0.050^{\circ}$
and
${\rm d}=10.696\
\mu{{m}}\pm 0.025\ \mu{{m}}$
, respectively. The
experimental results for the twist angle and cell gap deviate from the known
values by just
$\Delta\Phi=0.136^{\circ}$
and
$\Delta{\rm
d}=0.196\ \mu{{m}}$
, respectively. Moreover, the pretilt
angle is found to lie in the reliable range. In contrast to existing methods,
the technique proposed in this study requires the use of only a single illuminating
wavelength. As a result, it provides a cheaper and more straightforward approach
for extracting the three physical parameters of TNLC cells than existing optical-parameter
measurement schemes.
© 2014 IEEE
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