Electrically tunable focusing liquid crystal lenses and applications

• Main Authors: Lin, Hung-Chun, 林弘峻
• Other Authors: Lin, Yi-Hsin
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/60599425848446453289

博士 === 國立交通大學 === 光電工程學系 === 101 === Electrically tunable focusing liquid crystal lenses were first proposed in 1979. However, the slow response time, small tunable focal range and high driving voltage of the LC lens impede applications. In this dissertation, we started from a study of optics and physics of the LC lens and discussed the design guideline of the LC lens. In the conventional operation of a positive LC lens only in the imaging system, the large tunable focal range of the LC lens requires the large thickness of the LC layer (or cell gap), but in this way the response time is slow (~30 sec) and the light scattering is strong. To obtain fast response time(<1 sec) and large tunable range (350 cm to 10 cm), we demonstrated a image system using two mode switching which is based on the phase change between the positive and the negative LC lens. Moreover, in order to reduce the driving voltage of the conventional LC lens with hole-patterned electrode and obtain a LC lens with a short focal length which is required in most of image system and is also difficult to realize with a homogeneous cell gap, we designed a LC lens with low driving voltage and short focal length by adopting the built-in polymeric layer. By controlling the spatial distribution of the refractive indices and the spatial distribution of the dielectric constants of the built-in polymeric layer, the polymeric layer can not only be a built-in lens with fixed focal length but also adjust the voltage distribution across the LC layer and align LC directors. As a result, the focal length of the LC lens could be shifted to be short; meanwhile, the driving voltage can be reduced by the polymeric layer. Besides the image system, we also demonstrated the electrically tunable focusing pico projectors with the conventional LC lens and the LC lens adopting the polymeric layer. Ultimately, a holographic projector with optical zooming function by using a LC lens is also demonstrated. The LC lens can be used to solve the color breakup in holographic projectors. In this dissertation, we have overcame several main problems of the LC lens, such as response time, tunable range and the driving voltage, and we also demonstrated various applications based on the LC lenses. We believe this dissertation can open a new window in optical designs based on the classic geometrical optics and also inspire new applications in endoscopes, image stabilization systems, night vision systems, solar cells and eyeglasses.