Simple parameter determination for twisted nematic liquid-crystal display

A simple and accurate measurement method for determining the cell parameters of a twisted nematic liquid-crystal display (TN-LCD) is proposed. Based on the measurement of the maximum reflectance and the maximum transmittance of a TN-LCD by rotating the polarizer at a particular angle, between the front director of the liquid crystals and the transmission axis of the polarizer, the cell gap and the twist angle can be determined according to the Jones matrix theory, and the twist sense can also be determined easily by applying an external small voltage to slightly change the effective refractive index of the liquid crystal.