Many consumers are interested in three-dimensional (3-D) technologies that make display images as real as possible. In response, a number of fairly mature 3-D technologies have already been introduced in various studies. Among them, we reviewed the integral imaging system and the multiview system, which can realize 3-D, from the past to the present. Those systems, however, suffer from problems such as depth range, two-dimensional (2-D) and 3-D conversions, and 3-D resolution. Therefore, a liquid lens is proposed as a technique to resolve the drawbacks. Using a liquid lens with variable focal length, the depth range was enhanced using a time-division multiplexing technique in an integral imaging system, and the function of 2-D and 3-D switching was enabled in a multiview system. Furthermore, methods were introduced to solve the problems of 3-D resolution reduction in multiview systems and vergence–accommodation conflicts in VR systems.
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).
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.
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.
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.