An alternative method for simultaneously measuring cell parameters of a twisted-nematic liquid crystal cell

Abstract

A phase-sensitive method is developed to simultaneously measure the cell parameters of a TNLC (twisted-nematic liquid crystal) cell based on Jones calculus and the heterodyne interferometric ellisometry. These cell parameters include the twist angle, the cell gap, and the angle of the entrance LC director. When a circularly polarized heterodyne light beam normally passes through a TNLC cell, the phase difference between the p- and s- polarization of the interference signal can be measured accurately with an analyzer and the heterodyne interferometric ellisometry. The phase difference depends on the azimuth angle of the analyzer and the parameters. By substituting the measured values of the phase differences at three different azimuth angles of the analyzer into the special equations derived with Jones calculus. Hence these three para meters can be esitimated by using a personal computer with numerical analysis technique. Because of its common path optical configuration and its heterodyne interferometric ellisometry, this method has many merits such as high stability against the surrounding vibration, high resolution, and easy operation.