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標題: | 可運用於光學辨識系統之磁驅動微型貓眼回射器陣列 Magnetically-driven micro cat’s eye retro-reflector array for optical identification |
作者: | Tzu-Yu Chen 陳姿羽 |
指導教授: | 蔡睿哲(Jui-che Tsai) |
關鍵字: | 貓眼回射器,磁驅動,微機電系統,光學標籤,磁性粒子, cat’s eye retro-reflectorm,agnetically-actuated,MEMS,magnetic beads,optical tags, |
出版年 : | 2015 |
學位: | 碩士 |
摘要: | 現今常見的辨識系統包含無線射頻辨識(RFID)系統和光學辨識系統,無線射頻辨識系統是以發散式的電磁波來傳遞訊號,不需要建立機械或光學接觸即可讀取資訊,卻容易受外界訊號干擾;光學條碼辨識系統是將入射條碼的光以散射光方式傳回,操作簡便,但訊號強度相對較弱,兩種辨識系統傳遞資訊均為全方向性(omnidirectional),資料易被從旁竊取,會有侵犯隱私的疑慮。 本論文提出光學貓眼回射器改善上述的問題,回射器可將反射光沿原入射路徑回傳,傳遞方向單一可以提高資料傳輸的隱密性。貓眼回射器由前聚焦微透鏡和後凹面反射鏡所構成,調整適當的前後模組間距,可以讓入射光線聚焦在後反射鏡上,使得反射光沿原入射方向行進。為了增加光學標籤的多樣性,調變貓眼回射器也是本文重要的一環,從文獻可知調變微透鏡的方法有許多種,例如透過腔內壓力的變化來改變透鏡的曲率,或是以液晶作為透鏡材料,施加電壓改變透鏡焦距等,大多著重於微透鏡曲率的調變,本文將結合磁性材料與經過微機電系統製程的後反射模組,利用磁鐵作為外加磁場,吸引磁性粒子進而帶動後反射鏡轉動,讓回射器能呈現ON或OFF的狀態。 本文利用磁驅動方式調變貓眼回射器,調變前回射效率可達到15 %,調變後,後反射鏡可達到最大轉動角度為25.8°,而回射效率僅剩1.72 %,藉由調控磁鐵的位置,此可獨立調變的光學元件能作為光學標籤的基礎,運用於光學辨識系統中。 Radio frequency identification(RFID) system is widely used and applied in our daily life. The RFID system is a wireless use of electromagnetic fields to transfer information. It can function without batteries and identify tags without attaching to objects. However, due to the radiating nature of electromagnetic waves, received signals are easily to be intercepted. Optical identification is another dominant ID technology. Examples of optical ID tags include 1-D and 2-D barcodes. They can easily be read by barcode readers. However, the barcode scatters, instead of reflecting, the scanning laser beam sent from the reader. Therefore, the information contained in barcodes is not secure. An optical retro-reflector directs the light back along its incoming path instead of scattering the light. With a properly designed acceptance angle, the security of optical ID tags can be enhanced. In this thesis, we present a MEMS tunable cat’s eye retro-reflector consisting of a front micro lens and a rotational back concave reflecting mirror. Magnetic beads are attached to the rotatable unit to enable magnetic actuation. The magnetically-actuated reflecting mirror achieves a large rotation angle. The rotational angle of the concave micro mirror of the cat’s eye retro-reflector can be change from 0° to 25.8°, with the retro-reflection efficiency varying from 15 % to 1.72 %. A dynamic image is also demonstrated by changing the position of magnets. This tunable device can be used as a optical tag in identification system. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/17741 |
全文授權: | 未授權 |
顯示於系所單位: | 光電工程學研究所 |
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ntu-104-1.pdf 目前未授權公開取用 | 6.54 MB | Adobe PDF |
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