| In addition to the display application, Liquid Crystals (LC) can be very useful in other applications such as beam steering, tunable lenses, etc.;Electro-optical LC tunable lenses have been considered as an alternative to conventional glass lenses because of their ability to change their focal length with the application of a control voltage, as well as small size and weight and low power consumption, fast speed, etc. They have a great potential in many applications such as: imaging systems of compact cameras, eye correction, and 3D display systems. So far, while many LC lens designs have been published, high quality performance has been only mentioned in very few papers; also, the level of details in those work is less than what is required to have an accurate evaluation of the performance as well as how it could be improved.;Therefore, the main goal of the work in this dissertation is designing high quality or near diffraction limited LC tunable lenses. We will not only introduce our design concepts and considerations, but also demonstrate fine details about the fabrication and evaluations. More importantly, we will use both simulation and experimental approaches for fully understanding the fundamental limiting factors affecting LC lenses. Consequently, we will introduce how they could be optimized and demonstrate the improved performance. In addition, there will be work addressing the concerns about speed, optical power, and off-axis performance.;The outline of the dissertation is given as follows, and each chapter has its own focus: In chapter 2, we will review the background of tunable LC lenses, introduce our design, and evaluate its performance in details; in chapter 3, we will investigate the physical limitations and fundamental factors affecting LC lens performance with both simulation and experimental results; in chapter 4, we will introduce the optimized design and demonstrate the improved performance; in chapter 5, we will introduce a multi-cell approach to improve its off-axis imaging performance and achieve a higher optical power, while keeping the fast switching speed; in chapter 6, we will discuss the phase reset methods to achieve higher optical power and fast response; finally in the last chapter, we will make the conclusion and summary. Also, there are four appendices in which we show the detailed LC lens fabrication process, complete optical characterization methods, simulation methods used in this dissertation work and the core Matlab codes, respectively. |
