Design, Fabrication, and Characterization of Solid Tunable Micro Apertures

本研究提出一個創新的方法，且經實驗後成功製出固體微型可調變光圈元件，而光圈的透光孔徑可藉由施加不同電壓產生連續調變的效果。 在元件的設計中，分為半球型微透鏡結構與高分子分散型液晶薄膜（Polymer-dispersed liquid crystal, PDLC）兩個主要部分。其中，本研究對於微透鏡結構，提出兩種不同的製作方法，分別為黃光顯影製程中的熱整流法（Thermal reflow process），以及使用微量型注射器（Nanoliter injector）進行微結構的滴定。而元件的調變機制，是透過兩平行基板間因微透鏡結構產生的高度差，在施加相同電壓下會產生不同強度分布的電場值，利用該電場值差異來驅使高分子分散型液晶產生透光率的改變。而由於光圈元件中央的薄膜較薄，因此光圈的開孔變化會由中心向外漸行透光，以達到改變電壓下的連續調變效果。 在光圈孔徑的量測上，本研究使用顯微鏡搭配CCD進行開孔影像的對焦和捕捉，再透過優化後的演算法求得光圈束寬與電壓的對應關係。最後，藉由改變結構高度及液晶薄膜厚度等製程參數，進一步探討元件優化前後的差異。The thesis proposes an innovative way to fabricate solid tunable micro apertures. The aperture size can be changed continuously by applied different voltages. By appropriately combining two liquid materials, E7 and NOA-65, we make PDLC (Polymer-dispersed liquid crystal) which plays an important role in the transmittance of light in the device. In addition, we try to make a micro lens structure by two different methods, which are photolithography with Thermal reflow process , and the way to produce NOA-65 micro droplets by a nanoliter injector. With the change of the gap formed by the micro lens structure between two substrates, the various electric field will be yielded inside the device as applied constant voltage. At the same time, liquid crystals in the PDLC film direct in distinct angles due to the different electric field. And this status can make a difference of light transmittance on the surface of device. By the symmetric structure of micro lens, we can successfully fabricate an aperture with a circle shape and the aperture size can be enlarged or narrowed with various intensity of applied voltage. Finally, we use microscope with CCD to capture images of aperture and find out a valid way to measure the true aperture size on the device by switching focal planes. With the optimized program to deal with images taken by camera, we have a reliable way to find the relationship between the tendency of the various apertures and the increasing applied voltage. Besides, the different parameters in the fabrication of the device are completed. And we will make a comparison on different kinds of devices in the section of discussion