Analysis of longitudinal viewing freedom of reduced‐view super multi‐view display and increased longitudinal viewing freedom using eye‐tracking technique

Abstract— The viewing freedom of the reduced‐view super multi‐view (SMV) display was analyzed. It was found that there are separate multiple viewing ranges in the depth direction; thus, a technique that selects an appropriate viewing range to increase the longitudinal viewing freedom has been developed. Pixels of a flat‐panel display viewed by the viewer's eyes through a lenticular lens were determined from three‐dimensional (3‐D) positions of the viewer's eyes, which were obtained using an eye‐tracking system that employed a stereo camera. Parallax images corresponding to the 3‐D positions of the viewer's eyes were generated, which were displayed by the determined pixels. The experimental results show that the proposed technique successfully increased the longitudinal viewing freedom. It is also shown that a video camera was able to focus on the produced SMV images.     

Double‐viewing‐zone integral imaging 3D display without crosstalk based on a tilted barrier array

We propose an integral imaging (II) three‐dimensional (3D) display using a tilted barrier array and a stagger microlens array. The tilted barrier array consists of two orthogonally polarized sheets. In the stagger microlens array, the center of the microlens has p/2 shift with the elemental image along the horizontal direction, where p is the pitch of the microlens. The proposed II 3D display produces two different viewing zones and each of them is almost equal to that of the conventional II 3D display, and it has no crosstalk. We verify the feasibility of the proposed II 3D display in the simulation results.     

3‐D mobile display based on dual‐directional light guides with a fast‐switching liquid‐crystal panel

Abstract— An autostereoscopic display based on dual‐directional light guides with a fast‐switching liquid‐crystal panel was designed and fabricated to provide better 3‐D perception with image qualities comparable to that of 2‐D displays. With two identical micro‐grooved light guides, each with a light‐controlled ability in one direction, two restricted viewing cones are formed to project pairs of parallax images to the viewer's respective eyes sequentially. Crosstalk of less than 10% located within ±8°–±30° and an LC response time of 7.1 msec for a 1.8‐in. LCD panel can yield acceptable 3‐D perceptions at viewing distance of 5.6–23 cm. Moreover, 2‐D/3‐D compatibility is provided in this module.     

LC GRIN lens mode with wide viewing angle for rotatable 2D/3D tablet

To widen the vertical and horizontal angular ranges where the lens performs well, the off‐axis performance of a liquid crystal gradient index (LC GRIN) lens is analyzed by the combined simulation system of an LC director simulator and a ray‐tracing simulator. We found that the angular difference between an LC alignment direction and an electrode array direction of the LC GRIN lens is one of significant parameters, and detailed conditions of structure are established. The measurement result shows that the developed structure reduces the degradation ratio in a luminance profile from 61% to 3.2%. We have applied a user tracking system for the rotatable 3D display, equipped with a detection of a panel orientation and a face position. As a result, we have developed a rotatable 2D/3D tablet whose 3D viewing azimuth angle is over 30° in both landscape and portrait orientations.     

A novel quarter‐wave retardation film for improving viewing angle properties in time‐sequential stereoscopic 3D‐LCDs

We have successfully developed a quarter‐wave retardation film (QWF) for wide viewing angle 3D liquid crystal displays (3D‐LCDs) that provides high luminance, low crosstalk, low color change, and low head‐tilt‐angle dependency. It was found that the out‐of‐plane retardation (Rth) of the QWF in the LCD needs to be close to 0 nm in order to improve the 3D display properties at an off‐axis position and that the in‐plane retardation (Re) needs to be adjusted from 120 to 130 nm to achieve low color change with head tilting. We adopted a coating process for making our QWF because of its potential for retardation control. 3D‐LCDs with this QWF whose Rth was nearly zero had high performance and allowed off‐axis other than on‐axis.     

Objective evaluation of qualified viewing spaces for near‐to‐eye and autostereoscopic two‐view displays

Abstract— Virtual‐image (near‐to‐eye) and two‐view autostereoscopic (3‐D) displays share similar optical properties in the comfortable user position for viewing. In this paper, the definitions and criteria of qualified viewing space (QVS) and qualified stereoscopic viewing space (QSVS) are discussed. Due to the complex nature of these viewing spaces, the related presumptions and the required optical characteristics and their measurements are specified. The effects of different display and observer parameters, such as interpupillary distance, to the resulting viewing spaces are discussed. Finally, real measurement data of two autostereoscopic display devices are presented.     

A high‐aperture‐ratio and low‐crosstalk pixel structure design for in‐plane‐switching‐mode TFT‐LCDs

Abstract— The TFT‐LCD market is growing rapidly, and the replacement of CRT TV by LCD TV requires the implementation of LC modes with wide viewing angles and high brightness. The IPS mode is an excellent technology to realize wide viewing angles, but it has a low aperture ratio that has now been improved by Advanced Super‐IPS (AS‐IPS). In this paper, we propose a novel pixel structure design that not only increases the aperture ratio but also reduces the crosstalk. We have improved the current AS‐IPS aperture ratio by 1.25 times and effectively reduced the capacitive coupling ratio from 1.2% to 0.05%.     

Robust control of 3-DOF parallel robot driven by PMAs based on nominal stiffness model

This paper deals with an efficient implementation of robust controller on 3-DOF parallel robot driven by pneumatic muscle actuators (PMAs). PMA is a new flexible pneumatic actuator with relatively complex mathematical model. For the purpose of controlling robot, a new method to establish mathematical model of PMA is proposed. Based on analysis of stiffness characteristics of PMA, the concept of nominal stiffness coefficient is put forward and applied to establishment of mathematical model of PMA. According to 3-DOF robotic decoupling property, two rotational freedom of X, Y-axis are controlled by robust controller. Based on the dynamics, trajectory tracking control in simulation performs well under the circumstances of different interference via robust controller. Experimental results show that robust controller has satisfactory tracking performance and the characteristic of high real time. Its maximum tracking errors around X–Y axis are not more than 0.4°. Due to its less interference in motion around Z-axis, controlling Z-axis also has good tracking performance via computed torque method.     

Influence of 3‐D cross‐talk on qualified viewing spaces in two‐ and multi‐view autostereoscopic displays

Abstract— To estimate the qualified viewing spaces for two‐ and multi‐view autostereoscopic displays, the relationship between image quality (image comfort, annoying ghost image, depth perception) and various pairings between 3‐D cross‐talk in the left and right views are studied subjectively using a two‐view autostereoscopic display and test charts for the left and right views with ghost images due to artificial 3‐D cross‐talk. The artificial 3‐D cross‐talk was tuned to simulate the view in the intermediate zone of the viewing spaces. It was shown that the stereoscopic images on a two‐view autostereoscopic display cause discomfort when they are observed by the eye in the intermediate zone between the viewing spaces. This is because the ghost image due to large 3‐D cross‐talk in the intermediate zone elicits different depth perception from the depth induced by the original images for the left and right views, so the observer's depth perception is confused. Image comfort is also shown to be better for multi‐views, especially the width of the viewing space, which is narrower than the interpupillary distance, where the parallax of the cross‐talking image is small.     

Effect of number of views to the viewing experience with autostereoscopic 3‐D displays

Abstract— The observers' 3‐D viewing experience when the way the content is created and shown on an autostereoscopic 3‐D display alternate is evaluated. The observer's depth impression, and the perceived contour accuracy and image naturalness or peskiness of the content shown on a 3‐D display, has been investigated. In addition, the consequences of the way the content is created to the results from the optical characterization for the same display have been studied. The alternation of the content was realized in two different ways. Firstly, the number of views for creating the image was varied. Two, five, and 14 views were used; the main focus being on testing the same display and treating it as an ordinary two‐view and a 14‐view display with inter‐sub‐view crosstalk. Also, the intermediate condition where five views with non‐uniform view‐specific crosstalk were used has been investigated. Secondly, the way the content is created was varied by using images with computer‐generated content and photos. The effect of these parameters on viewing experience as such and especially the effect of 3‐D crosstalk on the viewing experience were studied.     

Multi‐view 3‐D display employing a flat‐panel display with slanted pixel arrangement

Abstract— A flat‐panel display with a slanted subpixel arrangement has been developed for a multi‐view three‐dimensional (3‐D) display. A set of 3M × N subpixels (M × N subpixels for each R, G, and B color) corresponds to one of the cylindrical lenses, which constitutes a lenticular lens, to construct each 3‐D pixel of a multi‐view display that offers M × N views. Subpixels of the same color in each 3‐D pixel have different horizontal positions, and the R, G, and B subpixels are repeated in the horizontal direction. In addition, the ray‐emitting areas of the subpixels within a 3‐D pixel are continuous in the horizontal direction for each color. One of the vertical edges of each subpixel has the same horizontal position as the opposite vertical edge of another subpixel of the same color. Cross‐talk among viewing zones is theoretically zero. This structure is suitable for providing a large number of views. A liquid‐crystal panel having this slanted subpixel arrangement was fabricated to construct a mobile 3‐D display with 16 views and a 3‐D resolution of 256 × 192. A 3‐D pixel is comprised of 12 × 4 subpixels (M = 4 and N = 4). The screen size was 2.57 in.     

The effect of stereoscopic viewing in a word‐search task with a layered background

Abstract— The benefits of stereoscopic viewing were explored in searching in words superimposed over a background. In the first experiment, eight participants searched for text in a normal 2‐D display, a 3‐D display using a parallax barrier, and a darkened 2‐D display of equivalent brightness to the 3‐D display. Word‐search performance was significantly faster for the bright 2‐D display vs. the 3‐D display, but when brightness was controlled, performance on the 3‐D display was better relative to the 2‐D (dim) display. In a second experiment, the effect of floating text vs. sinking background disparity was assessed across four background conditions. Twenty participants saw only the floating‐text (FT) condition and 20 participants saw only the sinking‐background (SB) condition. Performance of the SB group was significantly better than that of FT group, and the advantage of SB disparity was greater with the more‐complex backgrounds. Thus, when a parallax‐barrier 3‐D display is used to view text or other figural information overlaid on a background, it is proposed that the layer of primary interest (foreground) should be displayed with zero disparity (on the physical display surface) with the secondary layer (background) appearing to be sunk beneath that surface.     

An integral‐imaging three‐dimensional display with wide viewing angle

Abstract— The viewing angle and flipping areas of a conventional integral‐imaging three‐dimensional (3‐D) display were analyzed. The pitches of the elemental image and micro‐lens are identical. The more micro‐lenses used, the smaller the viewing angle becomes and the wider the flipping areas become. In this paper, an improved integral‐imaging 3‐D display is presented. The pitch of the elemental image is larger than that of the micro‐lens. The single‐viewing angles of all micro‐lenses converge and there are no flipping areas at the optimal viewing distance. Computational reconstructions of improved and conventional integral imaging were carried out, and experimental results demonstrate that improved integral‐imaging 3‐D displays have a wider viewing angle than the conventional ones and do not have flipping areas at the optimal viewing distance.     

High‐visibility 2‐D/3‐D LCD with HDDP arrangement and its optical characterization methods

Abstract— A 3.1‐in.‐diagonal 2‐D/3‐D LCD with a novel pixel arrangement, called horizontally double‐density pixels (HDDP), for high‐quality 3‐D images has been developed. 3‐D visibility has been improved by broadening the qualified stereoscopic viewing space (QSVS) where high‐quality 3‐D images can be seen. In order to evaluate the QSVS, optical characterization methods, based on the ergonomics for stereoscopy, such as 3‐D crosstalk, interocular luminance difference and 3‐D moiré have been proposed. The implementation results show that these methods can correctly evaluate high‐visibility autostereoscopic displays.     

New Finite Algorithm for Solving the Generalized Nonhomogeneous Yakubovich‐Transpose Matrix Equation

In this paper, the development of the conjugate direction (CD) method is constructed to solve the generalized nonhomogeneous Yakubovich‐transpose matrix equation AXB + CX^TD + EYF = R. We prove that the constructed method can obtain the (least Frobenius norm) solution pair (X,Y) of the generalized nonhomogeneous Yakubovich‐transpose matrix equation for any (special) initial matrix pair within a finite number of iterations in the absence of round‐off errors. Finally, two numerical examples show that the constructed method is more efficient than other similar iterative methods in practical computation.     

Liquid‐crystal chiral‐nematic systems with photoinduced helix inversion

Abstract— The induced helical pitch in liquid‐crystalline systems based on 4‐pentyl‐4′‐cyanobiphenyl (5CB) and containing chiral 6‐arylidene derivatives of 3(R)‐methylcyclohexanone has been found to change its sign and to decrease in the absolute value when exposed to the UV irradiation. After the photostationary state is reached, the pitch remains invariable regardless of any consequent light radiation. This state is characterized by a large helical twist which exceeds an initial one in more than three times, thereby making it possible to obtain compositions with the selective reflection of light in the visible spectral region. This phenomenon could be utilized in colour filters for display devices. The effect observed is caused by the effective reversible photochemical E‐Z‐isomerization of the chiral dopant. This was proved by photochemical preparative synthesis of one of the respective Z‐isomers and independent studies of its behaviour in 5CB.     

An integral‐imaging‐based head‐mounted light field display using a tunable lens and aperture array

A head‐mounted light field display based on integral imaging is considered as one of the promising methods that can render correct or nearly correct focus cues and address the well‐known vergence‐accommodation conflict problem in head‐mounted displays. Despite its great potential, it still suffers some of the same limitations of conventional integral imaging‐based displays such as low spatial resolution and crosstalk. In this paper, we present a prototype design using tunable lens and aperture array to render 3D scenes over a large depth range while maintaining high image quality and minimizing crosstalk. Experimental results verify and show that the proposed design could significantly improve the viewing experience.     

The construction and performance of a multiviewer 3‐D television display

Abstract— The De Montfort University (DMU) autostereoscopic 3‐D display, intended for television applications, is described. It provides freedom of viewer movement over a typical “living room” sized area, with no restrictions on viewer's head positions. The display is capable of supplying 3‐D images to multiple viewers who do not need to wear special glasses. It operates by producing regions (exit pupils) in the viewing field where either a left or a right image is perceived. The positions of the exit pupils are steered to the viewers' eyes by the use of head tracking. Design issues that became apparent during the construction of a first prototype, and the findings from tests on it, are described. In addition, the current status of a more advanced prototype is reported.     

眼球光心标定与距离修正的3维注视点估计

目的 在基于双目视线相交方法进行3维注视点估计的过程中,眼球光心3维坐标手工测量存在较大误差,且3维注视点估计结果在深度距离方向偏差较大。为此,提出了眼球光心标定与距离修正的方案对3维注视点估计模型进行改进。方法 首先,通过图像处理算法获取左右眼的PCCR（pupil center cornea reflection）矢量信息,并使用二阶多项式映射函数得到左、右眼的2维平面注视点;其次,通过眼球光心标定方法获取眼球光心的3维坐标,避免手工测量方法引入的误差;然后,结合平面注视点得到左、右眼的视线方向,计算视线交点得到初步的3维注视点;最后,针对结果在深度距离方向抖动较大的问题,使用深度方向数据滤波与Z平面截取修正法对3维注视点结果进行修正处理。结果 选择两个不同大小的空间测试,实验结果表明该方法在3050 cm的工作距离内,角度偏差0.7°,距离偏差17.8 mm,在50130 cm的工作距离内,角度偏差1.0°,距离偏差117.4 mm。与其他的3维注视点估计方法相比较,在同样的测试空间条件下,角度偏差和距离偏差均显著减小。结论 提出的眼球光心标定方法可以方便准确地获取眼球光心的3维坐标,避免手工测量方法带来的误差,对角度偏差的减小效果显著。提出的深度方向数据滤波与Z平面截取修正法可以有效抑制数据结果的抖动,对距离偏差的减小效果显著。     

Optical design and roll‐to‐roll fabrication process of microstructure film for wide viewing LCDs

We have developed a new microstructure film for wide viewing liquid crystal displays (LCDs). By attaching it to the surface of a conventional LCD, the viewing angle characteristics of LCD has drastically improved without causing a blur of the frontal image and a decrease in the contrast ratio under bright ambient light conditions. This film can be applied to various LC modes including twisted nematic and multidomain vertical alignment by changing its internal micrometer‐size 3D structure. Further, this film can be mass‐produced efficiently by self alignment roll‐to‐roll process.