Liquid Lens Array Research Articles

Novel laser micro-texturing on silicon with liquid lenses by breath figure method

Surface texturing is a way of managing the surface properties of a material. This paper adopts a novel approach to laser texturing by using it in conjunction with liquid glycerin lenses and a polymer template. Such a process can effectively be used to produce micro- or even nano-scale textures on complex three-dimensional surfaces. A polymer film with an array of glycerin–water-mixed droplets proved economical and easy to produce. The resulting liquid lenses were penetrated by a nanosecond pulsed Nd:YAG laser. As the laser beam passed through the liquid lens array, it was refocused and converted to multiple beams that all engineered the substrate surface. The surface was thus successfully textured. The adaptation laser texturing technology shows potential for the application of textures to complex three-dimensional objects. In this study, a large area of microscale surface texturing on a silicon substrate was demonstrated; the texturing size lay between 1 and 3 μm, and the depth of the texturing was around 20 nm.

Depth plane adaptive integral imaging system using a vari-focal liquid lens array for realizing augmented reality.

Augmented reality (AR) is an interactive experience of a real-world environment where the objects that reside in the real world are enhanced by computer-generated perceptual information. Despite its attractive features, AR has not become popular because of the visual fatigue that many people face when they experience it. Many methods have been introduced to solve this visual fatigue problem and one of these methods is an integral imaging system that provides images almost continuous viewpoints and full parallax. However, the integral imaging system, which uses a lens array with a fixed focal length, has limited depth of focus (DOF) range. As a result, images that are outside of the DOF range become distorted. In this paper, a vari-focal liquid lens array was fabricated and the optical characteristics of the lens array were evaluated. Using the vari-focal liquid lens array, the DOF range was extended and high-resolution images are realized without restriction of depth range in an AR system.

Fabrication of an electrowetting liquid microlens array for a focus tunable integral imaging system

The main advantage of an integral imaging system is that it does not cause a vergence-accommodation conflict to the viewer, as happens in other types of three-dimensional (3D) display systems. However, it still has the disadvantage of having a limited depth range. In this Letter, the fabrication of the electrowetting liquid lens array with an adjustable focal length is presented. With the liquid microlens array, we propose a focus tunable integral imaging system having an enhanced expressible depth range. The fabricated lens array has 1 mm lens pitch, 100 µm sidewall, 20 × 14 m m total size, − 542 to − 89 D focus variability, and 11.6 ms response time. The fabrication process, a measurement of optical characteristics, and a demonstration of the focus tunable integral imaging system are presented in this Letter.

用于波前补偿的三液体透镜阵列的设计分析

用于波前补偿的三液体透镜阵列的设计分析

Method to reduce the aberration of a polygonal aperture focus-tunable lens array for high fill factor.

Focus-tunable liquid lens arrays have been used to improve depth in glass-free three-dimensional devices where high fill factor is required. For high fill factors, polygonal apertures should be used, but due to the difficulty of controlling aberrations during focus tuning, polygonal aperture focus-tunable lenses have rarely been studied. This Letter proposes a new structure with walls at the lens boundaries using a square parabolic lens model to control the quadrafoil aberration induced by the square aperture. ANSYS simulation confirmed that the lens surface was closest to the parabolic lens model when the wall thickness was 1.4mm. A fabricated lens array demonstrated the quadrafoil inhibitory effect and confirmed the utility of the new structure.

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.

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.

80-1: An Integral Imaging Display Based on a Micro Liquid Lens Array

An integral imaging (II) 3D display based on a micro liquid lens array (MLLA) is presented. The II 3D display is composed of a MLLA proposed by us and 2D display panel. An II display prototype based on the MLLA is developed and realizes II 3D display and 2D display

Liquid crystal-based lenticular lens array with laterally shifting capability of the focusing effect for autostereoscopic displays

We demonstrate a liquid crystal (LC)-based lenticular lens array with the laterally shifting capability of the focusing effect in a complementary geometry with an offset between the center of the convex lens in the bottom substrate and that of the concave lens in the top substrate. Depending on the index matching between each of two different polymer lenses and the LC, either the focusing effect from the convex lens–LC interface or that from the LC–concave lens interface is achieved. The lateral shift of the focusing effect of our complementary lens array is dictated by the amount of the offset between the convex lens and the concave lens whereas the focal length depends on the amount of the index mismatching. For the input beam polarized linearly along the direction of the lenticular lens, according to an applied voltage, the ordinary and extraordinary indices of the LC coincide with the index of the convex lens and that of the concave lens made of two different polymers, respectively. Our lenticular lens array shows distinct three-dimensional viewing characteristics with laterally shifting zones.

Optical characteristics of frequency-driven 128 × 128 elements nematic liquid crystal cylindrical lens array based on equivalent circuit theory

In this paper, we propose a novel approach for realising a nematic liquid crystal 128 × 128 elements cylindrical lens array. This liquid crystal-cylindrical lens array is realised with an element clear aperture of 200 μm × 60 μm. In addition, its electro-optical feature is tuneable via the change of external electric field frequency. Based on the equivalent circuit theory proposed, the electro-optical features of the proposed liquid crystal-cylindrical lens array are analysed from the electric perspective. Experiments have been conducted to confirm the validity of the proposed algorithm. According to the experimental result, the liquid crystal device is able to focus collimated light in the range of 20–600 μm when the frequency of the applied voltage ranges from 100 Hz to 100 KHz. Thus, the effect of frequency-driving focusing is similar to that of applied voltage-driving focusing, which suggests a new way for liquid crystal device driving. Besides, power consumption of liquid crystal devices can also be reduced with the proposed method.

Depth plane adaptive integral imaging using a varifocal liquid lens array.

This paper proposes an enhanced integral imaging system with an electrically controllable image plane to address the issue of the limited depth problem in integral imaging. For implementation of the variable image plane, a varifocal liquid lens array and driving device are adopted instead of an ordinary solid lens array. The position of the central depth plane is varied by adjusting the focal length of the lens array. The proposed system enables matching between the object position and depth plane electrically, and thus an object moving from 5.15 to 11.72 cm is clearly displayed with this method.

Using an “underwater superoleophobic pattern” to make a liquid lens array

A new strategy to realize a real liquid lens array without evaporation problems based on a femtosecond laser-induced underwater superoleophobic–oleophobic heterogeneous pattern.

Liquid crystal-based square lens array with tunable focal length

We demonstrate a liquid crystal (LC)-based square lens array with two focusing modes according to the polarization state of the input light. The homogeneously aligned LC layer is placed on an array of static square lenses fabricated using a photo-curable polymer whose refractive index is matched with the refractive index of the LC. For the input beam polarized parallel to the easy axis of the LC, the focal length is varied with the applied voltage from a few meters to 21 mm which corresponds to the focal length of the static lens. For the perpendicularly polarized input beam, the focal length is independent of the applied voltage and remains constant. The two focusing effects with high optical performance over fully activated areas are useful for polarization-dependent imaging systems and three-dimensional displays in projection and integral imaging.

Electrowetting lenses for compensating phase and curvature distortion in arrayed laser systems

We have demonstrated a one-dimensional array of individually addressable electrowetting tunable liquid lenses that compensate for more than one wave of phase distortion across a wavefront. We report a scheme for piston control using tunable liquid lens arrays in volume-bound cavities that alter the optical path length without affecting the wavefront curvature. Liquid lens arrays with separately tunable focus or phase control hold promise for laser communication systems and adaptive optics.

Simulation of electrowetting lens and prism arrays for wavefront compensation

A novel application of electrowetting devices has been simulated: wavefront correction using an array of electrowetting lenses and prisms. Five waves of distortion can be corrected with Strehl ratios of 0.9 or higher, utilizing piston, tip-tilt, and curvature corrections from arrays of 19 elements and fill factors as low as 40%. Effective control of piston can be achieved by placing the liquid lens array at the focus of two microlens arrays. Seven waves of piston delay can be generated with variation in focal length between 1.5 and 500 mm.

Optical and Synthetic Focusing Using Liquid Lens Array

Optical and Synthetic Focusing Using Liquid Lens Array

Three-Dimensional Image Information Media: Optical and Synthetic Focusing Using Liquid Lens Array

Synthetic focusing methods, which superimpose pre-acquired multi-view images onto post-defined surfaces, are intended to simulate a camera with a large aperture and variable focus. We developed a synthetic focusing system with increased flexibility. The flexibility comes from independent control of the optical focuses of the input multi-view image. We arranged liquid lenses in a compact 8×8 array, in which focal lengths can be changed independently using electric signals, and placed a video camera behind the lens array to capture multi-view images. We found that if the optical and synthetic focuses coincide with each other, we can obtain images with more natural blurring effects. Furthermore, we can also set the optical focuses to multiple levels to increase the target depths of the synthetic focusing.

Fabrication and Demonstration of Electrowetting Liquid Lens Arrays

Reported is the fabrication and demonstration of an array of >12 000 switchable liquid microlenses, each ~300 mum in diameter and switchable through plano-concave to plano-convex. Electrowetting is used to modulate the contact angle of an aqueous/oil liquid system over a range of 100deg, resulting in a switchable dioptric range of -360 m-1 to 230 m-1. Compared to previous reports of single 2-6 mm electrowetting lenses, the fabrication process reported herein reduces the individual lenslet size by ~10times. To dose liquids into large arrays of these small liquid lenslets, a scalable self-assembled dosing process was developed. The completed liquid lens array has a fill factor of 50% which can be extended to >80%.

Novel components for tunable micro-optics

We will present some technologies and devices employed for the fabrication of tunable micro-optics. Tunable liquid lenses and lens arrays as well as polymer membrane-based microlenses and scanning mirrors are of both academic and industrial interest in this area.