利用複合式液晶透鏡之電控式光學變焦系統

Abstract

本文提出一種利用液晶透鏡之電控光學變焦系統(zoom system)，其原理是利用一種複合式液晶透鏡可電控調整焦距，讓光學系統實現電控對焦與影像放大縮小的目的。液晶透鏡是利用液晶分子雙折射性的性質，利用電場的不均勻分佈，控制空間中的折射率變化，得到聚焦的效果。光學系統利用此元件作設計，可達成非機械式的電控變焦。本論文中，由探討系統成像條件與放大率計算出發，分析探討液晶透鏡聚焦能力對於系統縮放比的影響，並藉由分析結果設計出包含兩個子透鏡之新型複合式液晶透鏡結構：具有固定焦距之高分子聚合物薄膜及可電控調焦的液晶層子透鏡，此設計可使負透鏡曲光度位移使光學變焦系統擁有大倍率縮放比。利用液晶透鏡之電控光學變焦系統，此系統具高縮放比(zoom ratio) 約7.9:1及小的系統長度(< 10cm)，此外在對焦距離無限遠至十公分時，此電控光學變焦系統可連續地電控系統放大率及縮小率。我們也將此電控光學變焦系統應用於微型投影機及網路攝影機之成像。

An electrically-tunable optical zoom system using composite liquid crystal (LC) lenses is demonstrated. The main mechanism of electrically tunable focal length of composite LC lenses results from the gradient distribution of refractive indices owning to the orientations of LC directors. In this thesis, we start from analyzing the imaging conditions and the magnification of the optical zoom system. Based on the developed relation between the focusing properties of LC lenses and zoom ratio of the optical zoom system, we developed a composite LC lens consisting of a sub-LC lens and a built-in planar polymeric lens in order to shift negative lens power when the composite LC lens is operated as a negative lens. The electrically-tunable optical zoom system using composite LC lenses has high zoom ratio (~7.9:1), short system length (<10cm) and the object can be zoomed in or zoomed out continuously at the objective distance of infinity to 10 cm. The applications of the optical zoom system using composite LC lenses are also demonstrated in this thesis, such as pico-projectors and webcams.