電壓漸變式液晶透鏡於手持行動裝置之成像系統與應用

Abstract

在最近幾年的手機市場，照相變成一種基本功能，幾乎每支手機都是照相手機，而且畫質已經漸漸追上一般數位相機。在一般相機中，光學變焦是非常炙手可熱的一項功能。在傳統光學中，光學變焦依靠鏡組間的機械移動來改變其等效焦長。由於空間上的限制，目前沒有光學變焦的手機鏡頭，所有手機鏡頭的變焦都只是數位變焦。 液晶透鏡是一種可自我調變焦距的透鏡，因為其焦距可調，因此可用於小體積的光學變焦。本研究提出一種電壓漸變式液晶透鏡，這種透鏡解決了傳統液晶的兩大缺點—數十秒的聚焦時間與數十伏特(甚至近百伏特)的驅動電壓。電壓漸變式液晶透鏡是一種內置電極液晶透鏡，其控制電極直接接觸液晶層。其關鍵技術為，在控制透明電極之上鍍一層高電阻材料，這層材料可以有效地把能量留在液晶層，讓能量不會浪費在其他地方。因為高電阻層的幫忙，電壓漸變式液晶透鏡的驅動電壓只需要不到4伏特，而搭配本實驗室之前提出之過驅動方法，可以有效地將聚焦時間縮短到0.8秒。 將電壓漸變式液晶透鏡搭配傳統的塑膠鏡頭組成一簡易式光學成像系統，此成像系統印證了電壓漸變式液晶透鏡的實用性。相信假以時日，電壓漸變式液晶透鏡可以成功應用在光學變焦系統之中。

In mobile devices, camera has become a basic function today, almost every mobiles has a camera. In photography, optical zoom was eager for consumers nowadays. Optical zoom utilized mechanical movement of lens elements to change the focal length. Since the limit of space, there are no optical zoomable cameras in mobile devices. Liquid Crystal lens is type of electrically-tunable focus lens. However, high operating voltage and slow focusing time are two of the major issues in the liquid crystal lens applications. Spherical Gradient Driven Liquid Crystal Lens (sGD-LC lens) was proposed to solve these two issues. A high-resistance layer was spin-coated above the patterned electrodes, which create a gradient distribution of electric field and preserved majority energy was applied. For a specification with 60□m LC cell-gap and 2mm lens aperture, the operating voltage was reduced down to less than 4 volts for 5cm focal length, and the focusing time was dramatically improved to 0.8 seconds. Combining with sGD-LC lens, an auto-focusing system for mobile lens application was realized in this thesis. These features made mobile devices employing LC lens feasible and practical, while LC optical zoom system is also realizable by appropriate optical design.