Junsik Lee

Electrowetting Lenticular Lens for a Multi-View Autostereoscopic 3D Display

The multi-view autostereoscopic display has become a major form of technology for implementing 3D displaying because of its simple structure and good image characteristics compared with other methods. In particular, the lenticular type multi-view display has a higher luminance than the parallax barrier type display, which is a significant advantage. However, the lenticular lens is difficult to fabricate and uncontrollable in 2D-3D conversion. Here, we describe the fabrication of an electrowetting-based lenticular lens and a multi-view display system that utilizes that lens. With a lenticular shaped lens chamber and electrowetting liquids, the focal length of the lenticular lens can be controlled by applying voltage. By putting this device on a display panel, a 3D image can be observed with a convex lens state, and a 2D image is observed with a flat state. In this letter, an electrowetting lenticular lens is fabricated and a 2D and 3D mode switch multi-view display is demonstrated.

Improving the performance of an electrowetting lenticular lens array by using a thin polycarbonate chamber

In this paper, we used a thin polycarbonate (PC) chamber to improve the performance of an electrowetting lenticular lens array. The polycarbonate chamber changed the radius of curvature (ROC) of the oil acting as a lens, which increased the dioptric power of the liquid lens to 1666.7D. The increase in dioptric power required a reduction in the distance between the optical center of the lens and the display pixels under the chamber, which was accomplished by reducing the thickness of the chamber. The optimal thickness of the chamber was determined to be 0.5mm. Using this thin PC chamber, transmittance and viewing angle were measured and compared with an electrowetting lenticular lens with a conventional 1mm poly methyl methacrylate (PMMA) chamber was done. Crosstalk which degrades clear 3D images, is an inevitable factor in lenticular lens type multi-view systems. With the 0.5mm PC chamber, the viewing zone was expanded and the ratio of the crosstalk area was reduced, which resulted in a clear 3D image. The new method of depositing the electrode layer also ensured the uniform operation of the liquid lens array.

A fabrication method of opened structures for uniform liquid dosing in liquid lenticular systems

This study introduces a 3D lenticular system and its fabrication method operating with liquids. The lenses of the lenticular system consists of two immiscible liquids requiring a good uniformity of their amount. The amount is controlled by an opened structures fabricated by silicon KOH etching process. For the fabrication, a low pressure silicon nitride (LSN) is deposited on a bare <1 0 0> silicon wafer followed by a photolithography and a reactive ion etching (RIE) remaining a 200nm LSN layer. A KOH etching process is done for 2 hours with a KOH solution of 40wt% in deionized water. To fabricate the opened structure, a time controlling is required not to be fully etched. The finalized silicon wafer is sputtered by a copper layer as a seed layer for an electroplating. By the electroplating with nickel, a master mold is made. To get the high transparency, poly methyl methacrylate (PMMA) is chosen for the substrate and a hot embossing process is done by fabricated nickel mold with PMMA. The PMMA is coated by gold as an electrode and parylene C and Teflon multi-layer as dielectric layers. For two immiscible liquids, deionized water and a mixture of dodecane and 1-Chloronaphthalene are used. The dosing process is done in underwater environment and the mixed oil is dosed uniformly as the oil has tendency to spread onto the substrate. After sealing the active liquid lenticular devices is fabricated and good uniformity is achieved.

Optimization of a Liquid Lenticular System for 2D and 3D Conversion

This letter deals with a 2D and 3D convertible device implemented using a liquid lens. The electro-wetting on dielectric (EWOD) phenomenon was used to operate the liquid lens. The research aimed to display 3D images clearly by achieving the highest dioptric power. The 2D state and the 3D state were switched by a meniscus of two immiscible liquids, and concave to convex lens states were formed by the meniscus. In a previous iteration, during EWOD operation, the oil phase moved in unexpected directions. This movement degraded the total quality of the lenticular system when displaying the 3D state. Here, a method is suggested to avoid the phenomenon by controlling the area of the electrode. Since the dioptric power of the lens is determined by the contact angle of the oil and the water, the electrode location, which determines the volume of the oil phase, was investigated to obtain the maximum dioptric power range. The two liquids were dosed into transparent chambers where the dielectric layer and the electrode were deposited. Finally, the highest diopter was achieved, which showed improved 3D image quality.

Analysis and Reduction of Crosstalk in the Liquid Lenticular Lens Array

In this paper, we analyze the crosstalk of the liquid lenticular lens array and reduce the crosstalk by blocking light leakages from the top and wall parts of the chamber. A variety of factors affecting the crosstalk of the liquid lenticular lens array are proposed. The ratio of the unnecessary light from the top and wall parts of the chamber are theoretically calculated and compared with the measured values. By using laminating foil and increasing the thickness of the electrode layer compared to the conventional sample, the light leakages from the top and wall parts of the chamber are blocked, and thus, the crosstalk is reduced to 21.23%, which is similar to that of the solid lenticular lens array. Image tests were conducted to demonstrate that crosstalk is reduced using a new sample.

Enhanced 3D performance by biconvex electrowetting lenticular lens structure

In this paper, the drawbacks of the conventional electrowetting lenticular lens such as unstable operation, low dioptric power, high operating voltage, and low fill factor were resolved through a biconvex structure. In our previous study, there was only one interface between DI water and oil. However, an interface between ETPTA and oil was added to form a biconvex structure. The biconvex structure was fabricated by exploiting the phenomenon that the liquid ETPTA changes into a solid upon exposure to UV light. The amount of ETPTA was adjusted to control the curvature of the interface between the ETPTA and oil. Also, the volume of oil was controlled to realize zero dioptric power at 0V. The biconvex electrowetting lenticular lens has powerful optical properties, showing the highest dioptric power of 2000D with a 414.7um aperture diameter, and operating with a voltage 0-17V. The dioptric power was 0D at 0V, which means the shape of the lens is flat, and 2000D at 17V, which means the shape of the lens is sufficiently convex to view a 3D image. The viewing angle was measured as 46 degrees and the response time was measured as 0.83ms. Also, crosstalk of 16.18 % was measured. A 24- view image was tested by combining the fabricated 5-inch lenticular lens with a display (G Pro 2).

Novel biconvex structure electrowetting liquid lenticular lens for 2D/3D convertible display

Recently, a planoconvex structure electrowetting lenticular lens capable of 2D/3D conversion through a varifocal property by an electrowetting phenomenon has been developed. However, even though it has a similar planoconvex structure to that of a commercial solid lenticular lens, comparable 3D performance could not be realized because the refractive index difference between nonconductive liquid and conductive liquid was not large. Therefore, the goal of the present study is to obtain better 3D performance compared to the conventional planoconvex structure by introducing a novel biconvex structure using ETPTA. The newly developed biconvex structure electrowetting lenticular lens showed greatly improved characteristics compared to the planoconvex structure: dioptric power (171.69Du2009→u20091,982.56D), viewing angle (26degreesu2009→u200946degrees), and crosstalk ratio (27.27%u2009→u200916.18%). Thanks to these improvements, a fine 3D image and a natural motion parallax could be observed with the biconvex structure electrowetting lenticular lens. In addition, the novel biconvex structure electrowetting lenticular lens was designed to achieve a plane lens state with a no voltage applied condition, and as such it could show a clean 2D image at 0 V. In conclusion, a novel biconvex structure electrowetting lenticular lens showed 2D/3D switchable operation as well as excellent 3D performance compared to a solid lenticular lens.

Electro-wetting lenticular lens with improved diopter for 2D and 3D conversion using lens-shaped ETPTA chamber

In this paper, we introduce a method for improving the lens diopter of 2D/3D convertible devices using electro-wetting. For stable operation, an electro-wetting device requires high dioptric performance and this was achieved using bi-convex liquid-liquid-solid phases. 1-Chloronaphthalene with a refractive index of 1.633 was used as an oil phase to achieve high diopters. ETPTA (trimethylolpropane ethoxylate triacrylate), a UV-sensitive material with low chemical reactivity to the 1-Chloronaphthalene, was used as a chamber material. This resulted in a diopter of 3030D for high quality multi-view images without unstable oil movement or trembling. The ETPTA was molded on a 0.3mm thick glass substrate that was coated with UV adhesive (NOA 81). The maximum diopter capable of stable operation was 3425D. 2D and 3D conversion and parallax motion were demonstrated.

A new method of fabricating the liquid lenticular lens array with Pyrex glass chamber

Liquid lenticular lens array can solve the disadvantages of currently available lenticular type three-dimensional (3D) display with solid lenses in that it enables 2D-3D conversion and has no complex calculations to fabricate. Liquid lenticular lens array needs a chamber which contains liquids and this chamber is usually made of a polymer-based plastic such as poly methyl methacrylate (PMMA) and poly carbonate (PC). However, oil acting as a lens permeates into these plastics because they are porous. For this reason, although the liquid lenticular lens array has many advantages, it is not easy to apply to 3D display system because of its short life time. In this paper, the liquid lenticular lens array with a new chamber using Pyrex glass is presented. A multilayer of metal, Cr/Au/Cr/Au, in combination with AZ2070 photoresist was used for wet etching of glass which was conducted in concentrated hydrofluoric acid (HF). The metal multilayer was deposited by using the thermal evaporator and serves as a mask for glass etching and another Cr/Au/Cr/Au multilayer was deposited on the opposite part of the glass. The Pyrex glass was etched at a rate of 7.5μm/s in 49% HF solution. With the completed Pyrex chamber, the liquid lenticular lens array was fabricated and operation tests were done. We also compared the new liquid lenticular lens array with the Pyrex glass chamber to one with the polymer-based plastic chamber in regard to reliability.

Fabrication of electro-wetting liquid lenticular lens by using diffuser

Liquid lenticular multi-view system has great potential of three dimensional image realization. This paper aims to introduce a novel fabrication method of electro-wetting liquid lenticular lens using diffuser. The liquid lenticular device consists of a Ultraviolet (UV) adhesive chamber, two immiscible liquids and a sealing plate. The diffuser makes UV light spread slantly not directly to negative photoresist on a glass substrate. In this process, Su-8, the suitable material to fabricate a structure in high stature, is selected for negative photoresist. After forming a Su-8 chamber, the UV adhesive chamber is made through a PDMS sub-chamber that is made from the Su-8 chamber. As such, this research shows a result of a liquid lenticular lens having slanted side walls with an angle of 75 degrees. The UV adhesive chamber having slanted side walls is more advantageous for electro-wetting effect achieving high diopter than the chamber having vertical side walls. After that, gold is evaporated for electrode, and Parylene C and Teflon AF1600 is deposited for dielectric and hydrophobic layer respectively. For two immiscible liquids, DI water and a blend of 1-Chloronaphthalene and Dodecane with specific portions are used. Two immiscible liquids are injected in underwater environment and a glass that is coated with ITO on one side is sealed by UV adhesive. The completed tunable lenticular lens can switch two and three dimensional images by using electro-wetting principle that changes surface tensions by applying voltage. Also, dioptric power and response time of the liquid lenticular lens array are measured.