可調變微機電光學回射器陣列之分析與製作

Abstract

近年來因為科技快速的發展，許多日常生活用品如身份識別證、貨幣…等，已逐漸改由電子產品的形式呈獻。像是現在人手一張的優遊卡、信用卡、提款卡或是住家大樓、公司行號的身份識別證。本篇論文利用光的準直、不易發散特性，來改善當前RFID (Radio frequency Identification)電磁波向四面八方傳播，資料易被竊取的缺點。而Corner cube retro-reflector以及貓眼回射器(Cat’s eyes retro-reflector)元件，則於光學辨識系統中扮演重要角色。進入回射器的光線，將依循原路徑回射至訊號發送源。藉此系統可辨別辨識物資料之真偽或電子貨幣交易。 我們以Fred光學追跡軟體模擬回射器陣列的表現，找出理想的元件深、寬以及週期比。並模擬於實際製程所可容許的誤差範圍，以及可採用的調變機制。藉此找出合適的製程方法與調變模式。 最後，我們採用光阻熱流法(photoresist thermal reflow)製作微透鏡及微反射面鏡，經過組裝後得到貓眼回射器陣列。並於其中加入調光薄膜(smart film)，藉由電壓控制調光薄膜的光穿透率，來達到動態圖形傳遞的功能。動態圖形之傳遞，除了與RFID同樣可於時間軸上做資訊加密之外，還多了空間上資訊加密之特性。因此此光學辨識系統(Optical identification system)，可大大提升資訊傳遞的安全性及隱密性。

Because of the fast paced development of technology, many daily necessities such as currency and ID card have transformed into electrical products gradually. Examples of applications include product identification, in a supply chain, easycard, and making transactions with VISA payWave, etc. In this thesis, we utilize light, which is collimated and directional, to improve the RFID (radio frequency identification), whose radio frequency signal propagate isotropically, lest the information to be intercepted and eavesdropped. In this way, the corner cube retro-reflector and cat’s eyes retro-reflector play an important role in the optical identification system. The optical signal into the retro-reflector will be reflected along its incoming path to the original emitter. By this system, we can distinguish the items or to do the electronic transactions. The ray tracing software Fred was used to simulate the performance of the retro-reflector arrays and to find the optimized height, width and period. Also, we find out the tolerance of verticality of the vertical sidewall in fabrication process and the proper modulation mechanisms. Finally, we use photoresist thermal reflow method to fabricate the micro lens array and micro reflecting mirror. After the assembly with smart film, the switchable cat’s eye array is attained. By controlling the applied voltage, the transparency of smart film is changed. Hence, we can transmit the dynamic image and increase the security of the system.