橢圓偏光儀基本上是利用反射光相對於入射光偏極態的轉變，以反推介質的光學特性。為了測量變化中的材料，如電漿蝕刻薄膜、真空鍍膜過程的沉積速率和厚度、加溫中的晶體以及高分子的感光過程，對橢圓偏光儀測量速度的改進已成為近年來業界研究的主要目標。本實驗室從簡式到線上即時監控的橢圓偏光儀的研究已有十多年。從將補波片換成光彈調變器，我們將快速資料擷取卡裝置在系統中。最近所提出的記錄後分析法，已可在20us測量一組橢圓偏光參數。

Utilizing the polarization changes by refl ection, ellipsometry can extract the physical properties of a medium. For measuring the dynamic changes when a material is under heating, etching, deposition, exposure to light, etc. The measuring speed becomes one of the major targets for developing in ellipsometry. This laboratory started to measure a static thin fi lm by measuring three intensities at specifi c positions of analyzer through a simple PSA confi guration. Later, we employed the photo- elastic modulator to substitute the quarter wave plate in a PCSA confi guration for establishing the real time/in situ monitoring the etching process in a plasma etching chamber. In stead of using lock-in
amplifi er, we installed a DAQ system in our own laboratory. By post fl ight analysis technique, we are able to measure the ellipsometric parameters in 20us.