Optimization of resolution and color reproduction by controlling luminance and contrast levels of a liquid-crystal display monitor

LiNbO3 surfaces from a microscopic perspective

A large number of oxides has been investigated in the last twenty years as possible new materials for various applications ranging from opto-electronics to heterogeneous catalysis. In this context, ferroelectric oxides are particularly promising. The electric polarization plays a crucial role at many oxide surfaces, and it largely determines their physical and chemical properties. Ferroelectrics offer in addition the possibility to control/switch the electric polarization and hence the surface chemistry, allowing for the realization of domain-engineered nanoscale devices such as molecular detectors or highly efficient catalysts. Lithium niobate (LiNbO₃) is a ferroelectric with a high spontaneous polarization, whose surfaces have a huge and largely unexplored potential. Owing to recent advances in experimental techniques and sample preparation, peculiar and exclusive properties of LiNbO₃ surfaces could be demonstrated. For example, water films freeze at different temperatures on differently polarized surfaces, and the chemical etching properties of surfaces with opposite polarization are strongly different. More important, the ferroelectric domain orientation affects temperature dependent surface stabilization mechanisms and molecular adsorption phenomena. Various ab initio theoretical investigations have been performed in order to understand the outcome of these experiments and the origin of the exotic behavior of the lithium niobate surfaces. Thanks to these studies, many aspects of their surface physics and chemistry could be clarified. Yet other puzzling features are still not understood. This review gives a résumé on the present knowledge of lithium niobate surfaces, with a particular view on their microscopic properties, explored in recent years by means of ab initio calculations. Relevant aspects and properties of the surfaces that need further investigation are briefly discussed. The review is concluded with an outlook of challenges and potential payoff for LiNbO₃ based applications.

Polarimetric characterization of liquid-crystal-on-silicon panels

Mueller matrix imaging polarimetry of liquid-crystal-on-silicon (LCoS) panels provides detailed information useful for the diagnosis of LCoS problems and to understand the interaction of LCoS panels with other projector components. Data reduction methods are presented for the analysis of LCoS Mueller matrix images yielding contrast ratio, efficiency, spatial uniformity, and the calculation of optimum trim retarders. The effects of nonideal retardance, retardance orientation, and depolarization on LCoS system performance are described. The white-state and dark-state Mueller matrix images of an example LCoS panel are analyzed in terms of LCoS performance metrics typical for red-green-blue wavelengths of 470, 550, and 640 nm. Variations of retardance, retardance orientation, and depolarization are shown to have different effects on contrast ratio, efficiency, and brightness. Thus Mueller matrix images can diagnose LCoS problems in a way different from radiometric testing. The calculation of optimum trim retarders in the presence of spatial variations is discussed. The relationship of the LCoS retardance in single-pass (from front to back) to the double-pass retardance (from entrance to exit) is established and used to clarify coordinate system issues related to Mueller matrices for reflection devices.