Introduction to Adaptive Lenses

Chapter 6

Liquid Crystal Lens

6.1 Introduction

Unlike ordinary fluids whose optical and electrical properties are isotropic in nature, liquid crystal (LC) is a fascinating anisotropic material possessing optical and dielectric anisotropies. Presently, LC has been widely used in various electro-optical devices, including displays (1–4), adaptive focus (5, 6), beam steering (7, 8), spatial light modulators (9, 10), variable optical attenuators (11, 12), axial or radial polarization rotation (13–15), and other photonic devices (16–19). New applications of LC materials are still being discovered which continue to provide effective solutions to many different problems. Most of the LC amplitude or phase modulations are based on the field-induced director reorientation, which in turn causes refractive index change. The control of light using LC is regarded as a fairly mature technology. It has made a tremendous impact on many branches of science and engineering, as well as on our daily lives.

The effective LC birefringence can be controlled by an external voltage. Thus, the electro-optic effects based on the LC molecular reorientation can be obtained easily. Depending on the molecular alignment, several useful LC devices have been developed, such as twisted-nematic liquid crystal (TNLC), homogeneous LC, homeotropic LC (also known as vertical alignment), polymer-dispersed liquid crystal (PDLC), and polymer-stabilized liquid crystal (PSLC), just to name a few. Among them, TN, in-plane switching ...