介電液體變焦透鏡

Electrically Tunable Dielectric Liquid Lens

鄭至成(Chih-Cheng Cheng)

指導教授 ： 葉哲良

國立清華大學/工學院/微機電工程研究所/博士(2006年)

https://doi.org/10.6843/NTHU.2006.00602

摘要

不同於使用電潤濕效應之透鏡，本研究提出利用介電力驅動之液體透鏡，並利用實驗分析該透鏡之光學表現。此透鏡係由高介電係數和低介電係數之二種不互溶液體組成，並以等密度形式封裝於腔體內。當電場通過二液體之介面，藉由介電係數差異產生介電力，利用該介電力調變液珠之外形而達到焦距調變之目的。
在此液體透鏡中，液珠之形狀主要受到表面張力、附著力、重力和介電力所調制。本研究藉由自行發展的理論模型預估液珠外形之變化並藉以計算焦距變化和球面像差。另外，利用等效電路模型可以了解液體透鏡對交流電場的頻率響應。由於液珠在操控過程中易產生透鏡之光軸偏移，本論文亦對此現象提出三種定心機制以為因應。
最後，本論文實作一4mm厚度之液體透鏡藉以驗證其理論上和實驗上之光學表現。當液體透鏡操作時，實驗發現液珠接觸角具有遲滯和延遲的效應，而透鏡之光學解析度，由於不同折射率材質之介面反射導致解析度下降。該透鏡之操作電壓在200V以內時，具有三倍變焦之能力，而光軸偏移角約1.3度。

關鍵字

介電液體 ； 變焦透鏡 ； 介電力 ； 液體透鏡 ； 液晶

並列摘要

Unlike electrowetting lens, a tunable liquid lens driven by dielectric force was demonstrated and it was analyzed its optical performance experimentally. The lens consisted of two liquids, a high dielectric liquid and a low dielectric liquid, sealed in one chamber with an iso-density. The dielectric force was induced by the difference of dielectric constants and it acted on the interface of two liquids to deform a droplet’s profile. Such a deformation causes a lensing effect by the difference of refractive index of the two immiscible liquids.
In the liquid lens, the deformation of a droplet was actuated by forces such as surface tension, adhesion, gravitation and dielectric force. Theoretical models were developed to calculate the deformation of a liquid droplet’s profile and to evaluate the spherical aberration of the lens. In addition, a circuit model was used to understand the frequency response while the lens is actuated. Three centering mechanisms were proposed to reduce angular misalignment of the optical axis of the liquid lens.
Finally, a convex liquid lens with a thickness of 4mm was demonstrated. This lens was analyzed its optical performance experimentally and theoretically. Contact angle hysteresis and contact angle retardation appeared while the droplet was actuated in the lens. The interfacial reflection in the lens module reduced the optical resolution that was estimated by software ASAP. Microbubbles and ITO erosion that were induced by high electric conductivity were observed. This lens had a triple change of focal length in the range of applied voltage of 0-200V. The maximum of the angular misalignment was measured to be about 1.3°.

並列關鍵字

dielectric liquid ； tunable lens ； dielectric force ； liquid lens ； liquid crystal

參考文獻

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