可變焦距的液態透鏡(liquid lens)其變焦原理不同於傳統機械式的變倍透鏡(zoom lens)，液態透鏡是將二種互斥的液體作組合並進行封裝，因此液-液界面在介電力場的作用而使曲率發生改變。介電力場是利用不同介電係數的兩種液體受到外加電場所誘發的作用力。且因液體折射率的不同而使液-液界面有變焦距透鏡的功能。
由於液態透鏡是使用液體做為介質，為了要使這兩種液體能順利地進行封裝並運作，所選用的液體必須滿足多項物性及光學特性上的要求，如比重、折射率、黏度、介電係數、界面張力、沸點、冰點及穿透率等。另外液態透鏡有其市場應用的價值，特別是在消費性電子產品的相關應用，因此對液態透鏡而言，熱測試的要求是非常重要的，特別長時間貯藏溫度(storing temperature test, S.T.T)以及熱循環(thermal cycling test, T.C.T)這兩項標準測試。在熱測試之後，發現液體組合會產生霧化不透光的狀態，此為乳化(emulsion)現象，為一般常見油水相間的分散行為，而且這個狀態會使其所需的光學特性失效，因此了解乳化的形成原因並加以解決是本研究主要的重點。
本研究所選用的液體來源是由各大化學公司提供，在不透過化學合成的方法，本研究選用數種可用的液體組合，並在可滿足物性規格的條件下通過熱測試的要求。其中一種為油相液體，使用矽油並添加部份的有機化合物；另一種為水相液體，是由特定比例的混合醇水溶液所組成，其具有抗凍的能力。為了使液體組合同時滿足物性及熱測試的規格要求實屬困難，因此本研究試圖找出最佳配方，也就是在最接近物性規格的條件下，使乳化的現象在最短時間內回復。

A tunable-focus liquid lens, composed of liquids is a kind of optical devices. The lens consists of two immiscible liquids and the liquid-liquid interface is formed. Unlike the working principle of mechanical zoom lens, the focal length of liquid lens can be tuned by dielectric force. Dielectric force is induced by the difference of dielectric constants between the two immiscible liquids. That the interface deforms and causes a lensing effect is breakthrough of the optical lens.
Liquid lens must satisfy many requirement of physical and optical properties for the two immiscible liquids, for example, density, refractive index, viscosity, dielectric constant, surface tension, transparency, boiling and freezing point. Besides, liquid lens had its market, especially consumer electronic products. Therefore, passing thermal test including storing temperature test (S.T.T)and thermal cycling test(T.C.T) is a necessary condition for liquid lens. After thermal test, the liquid combination becomes opaque and has a low light transparency. This phenomenon is called emulsion, a dispersed system between the oil and water phase and makes the lensing effect fail. Therefore, understanding the mechanism of emulsion and trying to solve it are my research key point.

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