使用共軛焦偏振螢光顯微鏡重建液晶透鏡 3D 內部結構

Abstract

在傳統變焦鏡頭中，需要較大空間來配置各個透鏡之間的相對位置。液晶透鏡具有較薄、較輕、可變換焦距等優勢，因此非常適合於手機相機等應用。傳統上，我們藉由量測線性偏振光，經過液晶透鏡後的相位變化條紋(fringing atterns) 得以觀察液晶透鏡的各項光學特性。然而相位變化條紋乃是偏振光穿過液晶層的 積分結果，無法顯示液晶層內部的資訊細節，如：液晶分子等效折射率、液晶分 子排列狀況等。在本篇論文中，我們提出利用共軛焦偏振螢光顯微鏡 (Fluorescence Confocal Polarizing Microscopy)重建液晶透鏡內部液晶分子 3D結構。首先，將螢光分子摻雜於液晶中，藉由量測螢光強度推算液晶分子的轉動角度。更進一步，我們可以繪製出液晶透鏡內部的折射率變化狀況，並重建液晶透鏡的3D結構模型，藉此詳細分析光線在液晶層內部的光追跡過程，以及液晶透鏡的光場調變能力。在本篇論文中，我們分析液晶透鏡的折射率分佈，並且推算光波前經過液晶透鏡後的相位延遲變化，藉此推算液晶透鏡的一階光學性質。除此之外，利用共軛焦偏振螢光顯微鏡，我們可以藉由光波前的相位延遲變化，分析傳統相位變化條紋所不能分辨的正、負液晶透鏡特性。

Liquid Crystal lenses (LC lenses) are prospective devises in the mobile application, because they are slight and tunable-focus. Conventionally, the fringing patterns are utilized to analyze the optical properties of LC lenses by plotting the bright-dark stripes. However, the fringing pattern must lose some detail information in the LC cells, such as the refractive index distribution and the LC directors. The Fluorescence Confocal Polarizing Microscopy (FCPM) method for was proposed to image and analyze 3-Dimentional (3-D) directors of LC molecules. By detecting the excited fluorescence of the anisotropic dyes which is doping in the LC cell and can be along the director of LC molecules, the spatial refractive index of deformed LC layer can be calculated. In this thesis, we investigated the spatial variation of LC molecules in the LC lenses. The results of spatial phase retardation were compared by using FCPM method and conventional fringing pattern. The difference of LC lens driven in convex and concave modes was also illustrated by the FCPM method.