Extracting the Physical Optical Parameters of TNLC Cell Using Effective Parameters and Stokes Polarimetry Method

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 ${\rm d}=10.696 \mu{\hbox{m}}\pm 0.025 \mu{\hbox{m}}$ , respectively. The experimental results for the twist angle and cell gap deviate from the known values by just $\Delta\Phi=0.136^{\circ}$ and $\Delta{\rm d}=0.196 \mu{\hbox{m}}$ , 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.