Research on stable operation and dioptric power enhancement in an electrowetting lenticular lens

Abstract

Auto-stereoscopic 2D/3D switchable displays recently have been drawing attention as next-generation displays. While there are many ways to realize auto-stereoscopic 2D/3D switchable displays, the electro-wetting lenticular lens is superior due to the high optical efficiency and short response time. The electrowetting lenticular lens consists of two immiscible liquids. One is conducting fluid and the other is insulating fluid. These two types of different liquid form various interfaces. The various curvature of electrowetting lenticular lens is feasible with the applied voltage between electrode and conducting liquid. Therefore, through the elec-trowetting lenticular lens, a 2D/3D switchable display can be achieved. A two-dimensional image is observed in the construction of a flat lens and a three-dimensional image is obtained with a convex lens. This indicates the importance of maintaining the shape of the lens stably. The electrowetting lenticular lens was fabricated on the basis of MEMS technology. The chamber for the electrowetting was fabricated by hot embossing process with a 0.5T PC (Poly Carbonate). The vertical length is 24.9mm and the total number of the cells is 106. A lens pitch of 414.7um is selected, and the width of the peak is set to 60um. The slope of the side wall was formed with a 54.7 degree angle. The slanted chamber is superior to the vertical chamber in terms of the deposition of the electrode layer, the dioptric pow-er, and the structural stability. Electrodes were deposited by thermal evaporation. The 2um Parylene C was coated as insulating layer by creating a hydrophobic surface. An oil mixture of chloronaphthalene with do-decane was used as a non-conducting liquid and deionized water was used as an electrolyte. The oil mixture was spread out in the air. An ITO (Indium Tin Oxide) coated glass was covered in the water tank and sealed by tapes and UV adhesives (NOA-61). In this paper, it was proven that the width of electrode and the volume of oil are key factors for stable driving. With a wide width of electrode and a large amount of oil, the oil layer was broken easily and the len-ticular lens was damaged at relatively low voltage. Therefore, controlling the range of electrode and the amount of oil is crucial to obtain the required dioptric power with stability. The dioptric power was measured by varying the width of electrode and the volume of oil. The optical characteristics were finally analyzed in the electrowettting lenticular lens array with a proper width of electrode and a suitable amount of oil. This study sheds light on microfluidic phenomena in liquid lenticular lens array.