Short focal length tunable liquid crystal lenticular lens array based on fringe field effect

A liquid crystal (LC) lenticular lens array based on fringe field effect is proposed. The gradient refractive index (GRIN) profile can be generated in the LC layer because of the fringe field between the strip‐shaped electrodes and the bottom electrode. The proposed LC lenticular lens array possesses ideal lens‐like phase profile and shortest focal length (1.199 mm) when the driving voltage is 5.4 V. The focal length can be tuned with millisecond response time by changing the driving voltage of the proposed LC lenticular lens array. The rise time τ_rise and decay time τ_decay of the proposed LC lenticular lens array are 162 and 94 ms, respectively.     

自由立体显示系统背光控制

介绍一种基于瞳孔跟踪的多用户自由立体显示器,利用菲涅尔透镜形成左右眼分立照明区域。本系统采用LCD作为基本显示屏幕,通过指向式LED照明背光设计,高精度瞳孔实时定位装置对人眼位置的探测,AVR单片机的系统控制,形成实时定向跟踪人眼的立体视窗。本装置可提供±25°水平视角范围内1至3人的实时无辅助立体显示。     

Distributed real-time rendering for ultrahigh-resolution multiscreen 3D display

Large-scale autostereoscopic three-dimensional (3D) displays can give audiences a truly immersive feeling with strong visual impact. However, the traditional autostereoscopic 3D display systems are limited by the display hardware, making it difficult to directly achieve large-scale 3D displays with high resolution. Multiscreen splicing with laser backlights can be used for large-scale and ultrahigh-resolution 3D display, but it normally results in subscreen image asynchronization, view zone error, or obvious edge overlapping. To solve the problems mentioned above, a distributed real-time rendering system for ultrahigh-resolution multiscreen 3D display is proposed. Fifteen 3D LCD display devices are driven through a host, cooperating with laser backlights, a lenticular lens array (LLA), and a directional diffuser to display high resolution, high frame rate, large size, and wide-viewing angle 3D images. The resolution of the whole display system can reach 23,040 × 21,600. The rendering system provides a large-scale and real-time 3D scene image with an ultrahigh-definition resolution at a speed of 40 frames per second and high quality.     

2‐D/3‐D switchable displays

Abstract— In this paper, the design of a lenticular‐based 2‐D/3‐D display for mobile applications is described. This display combines look‐around capability with good 3‐D resolution. In order to allow high‐resolution datagraphic applications, a concept based on actively switched lenses has been developed. A very noticeable problem for such displays is the occurrence of dark bands. Despite slanting the lenticular and defocusing the lens, banding becomes unacceptable when the display is viewed from an angle. As a solution, fractional viewing systems to reduce the banding intensity by almost two orders of magnitude is introduced. The resulting 3‐D display can be viewed from any horizontal direction without banding.     

Optical simulation for cross‐talk evaluation and improvement of autostereoscopic 3‐D displays with a projector array

Abstract— Multi‐view spatial‐multiplexed autostereoscopic 3‐D displays normally use a 2‐D image source and divide the pixels to generate perspective images. Due to the reduction in the resolution of each perspective image for a large view number, a super‐high‐resolution 2‐D image source is required to achieve 3‐D image quality close to the standard of natural vision. This paper proposes an approach by tiling multiple projection images with a low magnification ratio from a microdisplay to resolve the resolution issue. Placing a lenticular array in front of the tiled projection image can lead to an autostereoscopic display. Image distortion and cross‐talk issues resulting from the projection lens and pixel structure of the microdisplay have been addressed with proper selection of the active pixel and adequate pixel grouping and masking. Optical simulation has shown that a 37‐in. 12‐view autostereoscopic display with a full‐HD (1920 × 1080) resolution can be achieved with the proposed 3‐D architecture.     

Dual‐lenticular‐lens‐based 2‐D/3‐D convertible autostereoscopic display

Abstract— A 2‐D/3‐D convertible display using two lenticular lenses has been developed. It shows 2‐D pictures in full resolution and 3‐D autostereoscopic pictures in half resolution by moving one lens relative to the other. The lens assembly consists of thin metal frames, two lenticular lenses, and two shape‐memory‐alloy (SMA) wires used as actuators. While this assembly is applicable to flat‐panel displays of any kind, its simple structure and low power consumption make it best suited to mobile terminals, such as PDAs and mobile phones. Here, we describe its structure and present evaluation results.     

A thin multi-ring negative liquid crystal lens enabled by high-�� dielectric material

This study is dedicated to design an liquid crystal (LC) negative lens with unequal width electrodes, which is made for a camera lens and with the aim to replace conventional negative lenses. The structure of the LC negative lens is symmetric for producing a symmetrical electric field. The unequal widths are adopted and determined inversely proportional to the slopes of the desired applied voltages at varied radial positions. There are four ring electrodes in the lens and the associated with applied different voltages. In addition, the performance of the designed LC lens is verified by the software DIMOS.2D. The special structure and the material are used to realize the designed LC lens. Moreover, a new fabrication process in the wafer level to bury bus lines is developed in order to smooth the generated electric field distribution. In addition, a high-?? dielectric layer is coated between the electrodes and the LC layer for minimizing required applied voltage. Finally, differential effects of the LC lens structure with high-?? and without high-?? are discussed based on simulation results.     

Electric‐field‐driven LC lens for 3‐D/2‐D autostereoscopic display

Abstract— The use of an electric‐field‐driven liquid‐crystal (ELC) lens cell for switching between a 3‐D and 2‐D display is proposed. Due to the phase retardation of the non‐uniform LC directors, an ELC lens functions the same as a geometric lens. The parameters of an ELC for 3‐D applications are optimized through the simulation of the electrode configuration and voltage levels. A prototype was made where the ELC lens is placed in front of a liquid‐crystal display (LCD) 15 in. on the diagonal with a 99‐μm subpixel pitch. Under zero voltage, the ELC lens is a transparent medium and the users can see a clear 2‐D image. In 3‐D mode, the ELC lens array performs the same as a cylindrical lens array to the incident vertical polarization under suitable driving voltages. Placing a half‐wave plate between the LCD and ELC lens is proposed to change the polarization of the LCD to be parallel with the polarization lens direction of the ELC lens. The measurement of the horizontal luminance profile, performance of the ELC lens, and feasibility for 3‐D/2‐D switching was verified. The fabrication process for the ELC lens is compatible with the current LCD production process and enables the accurate control of the lens pitch of the ELC lens.     

Tabletop integral imaging 3D display system based on annular point light source

When the viewers sitting around the table observe 3D images, the viewing direction is generally oblique and the viewpoints should be distributed as annular. In this paper, a tabletop integral imaging (II) three-dimensional (3D) display system based on annular point light sources is demonstrated, which can present 3D images to multiple viewers in a standard annular viewing area with oblique viewing direction. The proposed system consists of annular point light sources, a Fresnel lens, a lens array, a two-dimensional (2D) display panel, and a diffuser screen. Each point light source illuminates the Fresnel lens to form parallel light and then illuminates the lens array and the display panel. A viewing sub-area is generated at the position of the diffuser screen, in which the 3D images can be viewed. Multiple viewing sub-areas are created in a way of time-division multiplexing to form a 360° annular viewing area. Compared with the previous tabletop 3D display, the viewing area can be concentrated at an oblique angle near the tabletop. The experimental results demonstrate the feasibility of the tabletop II 3D display system.     

Floating autostereoscopic display with in situ interaction

Floating three‐dimensional (3D) display implements direct interaction between human hands and virtual 3D images, which offers natural and effective augmented reality interaction. In this study, we propose a novel floating autostereoscopic display, combining head tracking lenticular display with an image projection system, to offer the observers with an accurate 3D image floating in midair without any optical elements between observers and the virtual 3D image. Combined with a gesture recognition device, the proposed system can achieve in situ augmented reality interaction with the floating 3D image. A distortion correction method is developed to achieve 3D display with accurate spatial information. Moreover, a coordinate calibration method is designed to improve the accuracy in the in situ interaction. Experiments were performed to prove the feasibility of the proposed system, and the good results show the potential of human‐computer interaction in medicine and life sciences.     

The design and optimization of lens array for LED backlight in LCD imaging engine of helmet‐mounted display

The light‐emitting diode has become the mainstream lightsource for backlight in the liquid crystal display imaging engine of helmet‐mounted display. The paper proposes a secondary‐optics‐based design to increase the luminance and obtain a uniform illumination. Based on a point lightsource, a single double‐freeform‐surface lens is firstly designed. Then an optimization is performed according to the theory of edge‐ray to improve the uniformity for planar source. As a result, the uniformity reaches 83.4% in a circular illumination with a diameter of 8 mm. Then the lens is cut and four rectangular lenses are combined to form a lens array. But the combination leads to a non‐uniformity. So a method of optimizing the light energy distribution on the target surface is proposed. Finally, the designed lens array is manufactured. The practical measurement results show that the luminance increases by 96.4% compared with the traditional backlight and that the non‐uniformity slightly decreases by 0.86%. The lens array designed in this paper presents high practicability for applications in helmet‐mounted display.     

Experiment and design of a high-resolution optical encoder

An optical mechanism proposed in this paper is composed of a movable part and a fixed part for the increment high-resolution optical displacement encoders. A parallel light source is set on the moving part and a double-concave lens, a specially designed optical grating and a phototransistor array receiver are set on the fixed part. The parallel light emitted from the movable part passes through the double-concave lens and the specially designed optical grating; it is then projected onto the phototransistor array receiver to indicate the displacement of the movable part. The relationship equation of the lens is developed to design an optical mechanism, which can enlarge the displacement so that it becomes observable. Based on the simulation results, three different radii in the curvature of the double-concave lens were proposed. The simulation results indicated that the optical mechanism with 50 times magnification could make the 10 nm movement intervals of a light source be about 500 nm movement intervals in the detecting surface. Furthermore, considering the limitation of the precision of existing tools, an experimental system with a 200 nm resolution was established to verify the possibility of the proposed structure. The experimental result indicates the possibility of using the proposed theorem to achieve the desired results.     

A new liquid crystal lens with axis-tunability via three sector electrodes

A novel liquid crystal (LC) lens with an on-line tunability on focus length and optical axis is proposed in this study. The designed lens has a LC layer sandwiched by two ITO glasses, one of which is patterned with three sector electrodes. With varied sets of pre-designed voltages applied to these three electrodes, the LC lens can not only render focusing effects but also tunability on the optical axis of the lens to an arbitrary axis. A vector-form equation is developed to predict the direction of axis tuning. Simulations are next conducted to predict dynamics of the LCs in the lens and also the focusing and axis-tuning properties of the lens. Important sizes and materials and fabrication process of the lens are determined and optimized based on simulation results. The designed LC lens is fabricated, and then experiments are conducted to demonstrate the performance of the designed LC lens on axis tuning. It shows that the focusing axis of the LC lens can be effectively changed by pre-calculated combinations of three voltages. It is also shown that the average movement of the focal point per applied voltage reaches 4.778?μm/V.     

A carbon‐nanotube field‐emission display with simple electron‐beam trajectory control

Abstract— A unique gated cathode structure for a carbon‐nanotube‐based field‐emission display has been designed and built. This structure optimizes the electron‐beam profiles to assure a good color gamut and high anode efficiency without requiring specific focusing electrodes or structure. A computer simulation, written to analyze and improve the device design, shows good correlation with the experimental data and helps predict design margins. A full‐color frit‐sealed display built with this approach demonstrates an excellent color gamut of the phosphor, and the model predicts avenues for further color‐gamut improvements.     

Prototyping and optical evaluation of 9‐in. OCB time‐division‐multiplexing 18‐view 3‐D display

Abstract— An integral imaging time‐division‐multiplexing 18‐view 3‐D display based on the one‐dimensional integral‐imaging (1‐D‐II) technique using a 9‐in. OCB‐LCD, lenticular sheet, and active shutter has been developed. By simulating a lens shape and a shutter structure and analyzing the light‐beam profile of the increasing‐parallax‐number region to find the best conditions, depth range, and viewing angle were an enhanced and a brighter and flicker‐less 3‐D image with smooth motion parallax was obtained.     

A high‐resolution autostereoscopic display system with a wide viewing angle using an LCOS projector array

Abstract— This study develops an autostereoscopic display based on a multiple miniature projector array to provide a scalable solution for a high‐resolution 3‐D display with large viewing freedom. To minimize distortion and dispersion, and to maximize the modulation transfer function (MTF) of the projection image to optimize 3‐D image quality, a dedicated projection lens and an accurate six‐axis adjusting platform for the miniature projector were designed and fabricated. Image‐blending technology based on a lookup table was adopted to combine images from 30 miniature projectors into a seamless single image. The result was a 35‐in. autostereoscopic display with 60 views ata 30° viewing angle, 90° FOV, and large range of viewing distance. The proposed system exhibits very smooth motion parallax when viewers move around in front of it.     

面向电阻抗成像检测的多电极阵列微流控芯片设计

设计了一种用于微尺度流动状态下电阻抗成像检测的多电极阵列微流控芯片,包括微流控芯片的结构设计、材料选择和加工工艺。设计的微流控芯片包含3个圆形电极横截面,每个横截面包含一组电极阵列。该阵列有3种数目的电极,分别为8电极,12电极和16电极。之后通过数值仿真方法实现了三种电极数目（8,12和16）微流控芯片的电阻抗成像,并与之前研究出来的菱形横截面8电极微流控芯片进行了对比,发现设计出来的16电极圆形微流控芯片具有较高的成像质量,验证了微流控芯片用于细胞电阻抗成像检测的可行性。     

基于声异常透射效应的高强度聚焦超声换能器

高强度聚焦超声（High intensity focused ultrasound,HIFU）作为一种新型无创的外科技术已在临床上应用于各种良恶性实体肿瘤治疗。为了实现安全高效的肿瘤治疗,HIFU换能器的聚焦效率仍然有待提高。本文综述了声异常透射效应的基本原理,以及近期利用声异常透射效应的HIFU聚焦超声换能器的研究。主要涉及两个方面的工作：（1）将声人工结构引入凹面型声透镜的设计,设计并制作了声超常透镜,对声透镜式聚焦换能器进行改进,达到了降低旁瓣的效果,从而提高了HIFU治疗的安全性;（2）基于球弧周期槽阵列设计并制作了超构聚焦换能器,以增强HIFU换能器聚焦效率。从理论及实验两方面研究了超构聚焦换能器与传统凹面换能器的声压分布和在组织中产生的温升。本文研究结果可进一步促进HIFU在临床治疗的广泛应用。     

2‐D/3‐D switchable autostereoscopic display with multi‐electrically driven liquid‐crystal (MeD‐LC) lenses

Abstract— A cylindrical multi‐electrically driven liquid‐crystal lens (MeD‐LC lens) is proposed to extend the range of focusing. The MeD‐LC lens could be applied to switching 2‐D and 3‐D images by supplying a specific operating voltage on each electrode. Therefore, the MeD‐LC lens has less cross‐talk than that of a conventional LC lens. Furthermore, the simplified structure of a MeD‐LC lens with a homogeneous LC layer is much easier for fabrication without a LC‐alignment issue.     

Dual-side see-through integral imaging 3D display system based on lens array holographic optical element

We propose a dual-side see-through integral imaging 3D display based on a lens array holographic optical element (LAHOE). The display system consists of two projectors and a LAHOE. The LAHOE is fabricated according to the theory of reflective volume holograms. An interference pattern is formed by a plane-wave beam and a spherical-wave array beam, and the interference pattern is recorded into a photopolymer material. Thus, the LAHOE is formed. When a reference beam is projected into the LAHOE, the wavefront of a convex micro-lens array is reconstructed. When a phase conjugation reference beam is projected into the LAHOE, the wavefront of a concave micro-lens array is reconstructed. So, the LAHOE possesses the optical properties of a convex micro-lens array and a concave micro-lens array. The proposed display is developed using integral imaging principle and it realizes dual-side see-through integral imaging 3D display.