介電彈性致動器應用於可變焦透鏡系統之研究

Abstract

隨著科技的蓬勃發展，各式元件都朝著低耗能及輕薄短小的趨勢發展。現今 市面上所販售的變焦機制，係利用多個透鏡所組成的透鏡組，並藉由線性馬達及 齒輪組來改變各個透鏡之間的間距，以達到變焦的效果。但是此機制所需求的裝 置空間較大，為了縮減佔有的空間，近年來，便有人發展出了可變焦的透鏡。本 論文運用了介電致動高分子材料來製作可變焦的透鏡，由於介電致動高分子材料 具有良好的力學性質、方便製作、低成本並且不受溫濕度變化的特性。介電致動 器係由兩片平整的電極和一層介電高分子材料所組成，結構就像三明治一樣。它 的驅動特性，會受驅動電壓大小及其幾何尺寸上的限制影響；隨著施加的電壓上 升，因其所受的靜電力增加而使得上下兩電極逐漸靠攏並擠壓中間的介電高分子 材料。然而，在邊界受限制的情況下，被擠壓的介電高分子材料會產生翹曲的情 形，本論文運用此結果作為可變焦透鏡的工作原理。在製程方面，本論文用懸浮 的方式來製作超薄且均勻的聚二甲基矽氧烷(PDMS)薄膜並以食鹽水溶液來作為透 明電極使用。本論文中使用了兩種常見的焦距量測方式來測量可變焦的焦距，實 驗結果顯示本論文中所製作的可變焦透鏡可達到3 mm 的變焦範圍在電壓從0 施加 到900 V 的範圍內。從電流的量測結果可以看出，此介電致動器的能量消耗主要 是用於每一次的變焦，並且只需要持續提供很微量的能量來維持變形量。在600 V 的情況下，電流很穩定，但是在600 V 以上的電流圖就有不規則的突波產生，經 觀察並推測，在大變形量下，金電極表面會有些微的裂紋產生。本論文最後將此 可變焦透鏡安裝於市售筆記型電腦的視訊鏡頭，並得到良好的影像輸出。

With the rapid development of science and technology, all kinds of devices are in the trend of becoming thinner, lighter, smaller, and having lower power consumption. Current mechanism of commercial tunable lenses utilizes multiple lenses of different focal lengths to form a sophisticated optical system. With the linear motor and gears, the focal length can be tuned by changing the spacing between lenses. However, this mechanism needs a larger System volume. In recent years, many efforts have been taken to develop tunable lens to reduce the system volume. In this thesis, we present a tunable lens which is driven by dielectric elastomer actuator (DEA). DEA has good mechanical properties, low cost, low power consumption, and is less affected by temperature and humidity. DEA is formed by a layer of dielectric elastomer sandwiched by two complaint electrodes. The operating characteristics of DEA are dominated by the applied voltage and the geometric configuration. With increasing applied voltage, which increases electrostatic force, the complaint electrodes of the actuator gradually become closer to each other and the dielectric elastomer is squeezed. Under boundary restrictions, extruded dielectric elastomer will be buckled. This thesis uses this result on tunable lens system. In the process, the release method is used to fabricate thin and uniform polydimethylsiloxane (PDMS) membrane and NaCl solution is used as a transparent electrode. In the experiments, we used two common methods to measure the focal length of our tunable lens system. The experimental results show that the focal length can be tuned by 3 mm by applying voltage from 0 V to 900 V. From the current measurement results, the energy is mainly consumed at the moment of DEA deformation. It only needs little energy to maintain the deformation. When the applied voltage is below 600 V, the current is stable. However, the current has irregular impulses when the applied voltage is over 600 V. By observation and speculation, the gold electrode surface has some defects in large deformation. Finally, we setup our tunable lens on the webcam of a commercial notebook computer to function and capture clear images.