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.
Lenticular type multi-view display is one of the most popular ways for implementing three dimensional display. This method has a simple structure and exhibits a high luminance. However, fabricating the lenticular lens is difficult because it requires optically complex calculations. 2D-3D conversion is also impossible due to the fixed shape of the lenticular lens. Electrowetting based liquid lenticular lens has a simple fabrication process compared to the solid lenticular lens and the focal length of the liquid lenticular lens can be changed by applying the voltage. 3D and 2D images can be observed with a convex and a flat lens state respectively. Despite these advantages, the electrowetting based liquid lenticular lens demands high driving voltage and low breakdown voltage with a single dielectric layer structure. A certain degree of thickness of the dielectric layer is essential for a uniform operation and a low degradation over time. This paper presents multilayer dielectric structure which results in low driving voltage and the enhanced dielectric breakdown. Aluminum oxide (Al2O3), silicon oxide (SiO2) and parylene C were selected as the multilayer insulators. The total thickness of the dielectric layer of all samples was the same. This method using the multilayer dielectric structure can achieve the lower operating voltage than when using the single dielectric layer. We compared the liquid lenticular lens with three kinds of the multilayer dielectric structure to one with the parylene C single dielectric layer in regard to operational characteristics such as the driving voltage and the dielectric breakdown.
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.
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.
Lenticular multi-view system has great potential of three dimensional image realization. This paper introduces a fabrication of liquid lenticular lens array and an idea of increasing view points with a same resolution. Tunable liquid lens array can produce three dimensional images by using electro-wetting principle that changes surface tensions by applying voltage. The liquid lenticular device consists of a chamber, two different liquids and a sealing plate. To fabricate the chamber, an <100> silicon wafer is wet-etched by KOH solution and a trapezoid shaped chamber can be made after a certain time. The chamber having slanted walls is advantageous for electro-wetting achieving high diopter. Electroplating is done to make a nikel mold and poly methyl methacrylate (PMMA) chamber is fabricated through an embossing process. Indium tin oxide (ITO) is sputtered and parylene C and Teflon AF1600 is deposited for dielectric and hydrophobic layer respectively. Two immiscible liquids are injected and a glass plate as a sealing plate is covered with polycarbonates (PC) gaskets and sealed by UV adhesive. Two immiscible liquids are D.I water and a mixture of 1-chloronaphthalene and dodecane. The completed lenticular lens shows 2D and 3D images by applying certain voltages. Dioptric power and operation speed of the lenticular lens array are measured. A novel idea that an increment of viewpoints by electrode separation process is also proposed. The left and right electrodes of lenticular lens can be induced by different voltages and resulted in tilted optical axis. By switching the optical axis quickly, two times of view-points can be achieved with a same pixel resolution.
Tunable liquid lens arrays can produce three dimensional images by using electrowetting principle that alters surface tensions by applying voltage. This method has advantages of fast response time and low power consumption. However, it is challenging to fabricate a high fill factor liquid lens array and operate three dimensional images which demand high diopter. This study describes a hybrid structure lens array which has not only a liquid lens array but a solid lens array. A concave-shape lens array is unavoidable when using only the liquid lens array and some voltages are needed to make the lens flat. By placing the solid lens array on the liquid lens array, initial diopter can be positive. To fabricate the hybrid structure lens array, a conventional lithographic process in semiconductor manufacturing is needed. A negative photoresist SU-8 was used as chamber master molds. PDMS and UV adhesive replica molding are done sequentially. Two immiscible liquids, DI water and dodecane, are injected in the fabricated chamber, followed by sealing. The fabricated structure has a 20 by 20 pattern of cylindrical shaped circle array and the aperture size of each lens is 1mm. The thickness of the overall hybrid structure is about 2.8mm. Hybrid structure lens array has many advantages. Solid lens array has almost 100% fill factor and allow high efficiency. Diopter can be increased by more than 200 and negative diopter can be shifted to the positive region. This experiment showed several properties of the hybrid structure and demonstrated its superiority.
Liquid-filled square lens array has been developed for an alternative to solid lens array because of its advantage in variable focus length. In addition, the square lens array has advantage with high fill factor compared to liquid circular lens array which is another alternative. However, one of the main limitations of conventional square lens array is the distortion. In this paper, distortion-free liquid square lens array is proposed. The partition walls of the proposed square lens array is fabricated into hemispherical shape to reduce the distortion, and then additional vertical walls are set up on the hemispherical structures to unify the height of partition walls and divide chamber sections. UV lithography techniques are used to fabricate this structure, and diffuser which has an angle of 80 degrees is used in the process. Photoresist is exposed to scattered ultraviolet rays which pass through the diffuser, and hemispherical lens-shaped structures of photoresist remains after development process. Supplementary vertical partition walls are obtained by additional photoresist patterning process on the structure. In this structure, the interface between oil and water comes into contact with the surface of the hemispherical walls, and the refractive index of oil and the walls are equally matched to maximize the part which acts as lens in the chamber. The proposed liquid square lens array can provide us with aberration-free 3D images with high fill factor.
This paper aims to describe a slanted liquid microlens array using diffusers. Ordinary liquid microlens has vertical side walls. The shape of it, however, has several weaknesses such as a low value of diopter and a difficulty in evaporating electrode. The diffuser causes UV light to spread slantly not straightly. This research shows a result of a slanted liquid micro lens having side walls with an angle of 74 degrees and verifies a high value of diopter and a well-filmed electrode. In order to achieve a high percentage of fill factor, it also presents matching values for refractive indices of the two media, oil and chamber.