Light propagation and color variations in liquid-crystal displays

General theories for light propagation are applied to specific liquid crystal displays. For the case of a homogeneous molecular distribution as well as that of a uniform twist we elaborate the classical Poincaré sphere method and a modified Jones calculus. The evolution of the polarization ellipse in the different configurations is studied and is depicted in an original way, which gives a better understanding of the color effects in liquid-crystal displays. Practical quantitative calorimetric conclusions are drawn in order to facilitate the experimental study of thickness variations in liquid crystal displays.