| Liquid crystals are very special kind of material that exhibit fluidity properties and yet have a certain degree of order. They are important electro-optical materials due to their large birefringence and relatively ease to change it. Nowadays, they are used extensively in various kinds of information displays. Ranging from the simplest static drive digital timers to highly sophisticated active matrix TFT (thin film transistor) liquid crystal flat panel monitors, or the newly invented LCoS (liquid crystal on silicon) micro-displays. All these displays utilize the light polarization modulation properties of liquid crystals. That is why polarizer is an essential component of these devices. No doubt, this polarization modulation property is the most important optical property of a liquid crystal display. The objective of this thesis work was to explore the polarization transformation properties of a liquid crystal layer and their possible applications. The first part of the thesis contains the core theory of polarization transformation in a twisted nematic layer. All necessary relations for different kinds of polarization transformations are derived. Both Jones and Mueller matrix approaches are used. A j-circle method for polarized light treatment is also developed. The second part of the thesis is dedicated to various applications including the LC display modes design, measurement systems, and LC polarization control devices. For the LC display modes design, a polarization-mode-switching scheme is proposed. This scheme not only explains all General Twisted Nematic display modes already exist, but also predicts the existence of some other new display modes. Examples are the single polarizer reflective LCDs and the bistable twisted nematic LCDs. The measurement systems discussed are divided into spectroscopic and monochromatic methods. Unique Stokes parameter methods are invented. At last discussions on LC polarization control devices especially arbitrary polarization state rotator, polarization controller and polarimeter are given. |
