Multi-Mode Fresnel Lens Using Polymer-Stabilized Liquid Crystal

• Main Authors: Shao-Chi Li, 李劭祁
• Other Authors: His-Fu Shih
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/72157150594648693320

碩士 === 國立中興大學 === 機械工程學系所 === 98 === The lens is an indispensable component for a general optical system, but its large structure would have some restrictions on the development of reducing the device dimension. This study is based on two characteristics of liquid crystal (LC), which are the birefringence and the electro-optical activity of alignment by the electric field. We demonstrate the LC Fresnel lens with multi-modes by using the technologies of polymer stabilized liquid crystal (PSLC) and electrode pattern design. Moreover, owing to the dependence of glass thickness for the device size, the device of the whole module can be microminiaturized and the focal variation achieved. With the simulations by scalar diffraction theory, the diffraction efficiency of the device has been discussed. Then, we adopted the lens module of a cell phone with the fixed focal length as the simulation model and discussed the image changes from different diffraction modes with the aid of the optical design software. In fabrication, we demonstrated the monolithic liquid crystal Fresnel lens with triplex diffraction modes using the techniques of mixing LC and UV-curable monomer (RM257) as the device material and designing novel electrodes. The experiments show that the diffraction patterns projected on the screen can be switched under different diffraction modes. Besides, the input image will also produce different image formations corresponding to different diffraction modes. The focusing of the LC lens is tunable by adjusting the applied voltage. In this research, we successfully combine different types of Fresnel electrode pattern in a diffractive optical element and make the multi-mode LC lens possible.