Minimum-Error Splitting Algorithm for a Dual Layer LCD Display—Part I: Background and Theory

A Dual Layer high dynamic range liquid crystal display (LCD) can be built by stacking two panels one on top of the other. In this way, the dynamic range is theoretically squared and the bit depth is also increased. However, in order to minimize the parallax and reconstruction errors, dedicated splitting algorithms are needed to generate the two images which drive the panels. In this paper, we present an algorithm, based on variational techniques, which seeks the joint minimization of both errors. We propose a simplified visible difference metric that exploits some limitations of the human visual system and can be easily incorporated into an optimization algorithm. The image splitting task is formulated as a quadratic programming problem, which can be efficiently solved by means of appropriate numerical methods. Preliminary tests on medical images showed that the algorithm has good performances and appears robust with respect to the parameter adjustment.      

液晶材料与3D显示

介绍了3D显示的基本原理,重点介绍了目前3D显示的主流技术类型,包含了眼镜式3D技术以及裸眼式3D技术,其中眼镜式3D技术包含色差式3D技术、偏光式3D技术和主动快门式3D技术;裸眼式3D技术包含视差屏障式3D技术、柱状透镜式3D技术、指向光源式3D技术和多层显示式3D技术。阐述了各种3D显示技术的基本实现原理和应用领域、并对涉及液晶显示的几种3D技术的优缺点进行了对比。结合液晶材料的特点与3D液晶显示的实际要求,阐述了3D液晶面板对液晶材料快速响应方面的要求,以及液晶透镜对液晶材料光学各向异性参数的要求。     

自由立体显示拍摄系统中摄像机空间自由度的确定

自由立体显示器的立体显示效果与视差图的视差大小及性质密切相关,而视差的大小是受获取视差图时相机的摆放方式影响的。文章提出利用双目相机标定技术求解左右摄像机中心的空间位置关系以及两个摄像机光轴的空间夹角,并通过标定结果不断调节摄像机的位置,从而使两个摄像机光轴达到近似平行,此时获取的视差图就可以保证更好的立体显示效果。通过实验研究得到了两个相机空间夹角允许的变化范围。该研究结果可用于指导自由立体显示器拍摄系统的调节。     

基于光源偏振补偿的硅基液晶激光三维显示光学引擎

基于光源偏振补偿硅基液晶(LCOS)光学引擎的激光三维(3D)显示系统对传统的LCOS光学引擎引起的偏振光损失进行了补偿,使经由照明系统进入光学引擎的不同偏振方向的激光全部参与成像,既可以实现激光3D立体显示,还提高了二维(2D)显示时的光能利用率。进行2D显示时,入射激光的s偏振光和p偏振光分别对应于不同LCOS同时成像,成像后的图像在屏幕上相互叠加,投影后图像的亮度约为未进行偏振补偿时的2倍。当输入3D视频信号时,正交偏振的p偏振光和s偏振光分别对应于左右眼图像同时成像,观看者配戴由正交偏振片制成的眼镜,可实现双像分离,实现激光3D显示。     

Dynamic Backlight Gamma on High Dynamic Range LCD TVs

A high dynamic range liquid crystal display (HDR-LCD) can enhance the contrast ratio of images by utilizing locally controlled dynamic backlight. We studied the HDR-LCD as a dual-panel display: a backlight module and a liquid crystal (LC) cell. As the gamma of the LC signal, the backlight module was also endowed with a gamma function to control the contrast ratio of HDR images. The inverse of a mapping function (IMF) method proposed as a dynamic gamma mapping curve for the backlight module, has been demonstrated to further improve in HDR image quality. By implementing the IMF method on a HDR-LCD TV with 88 backlight zones, the image contrast ratio can reach while maintaining high brightness, clear image detail, and an average power reduction of 30%.     

基于双目视觉的六旋翼无人机立体匹配算法

针对六旋翼无人机双目视觉成像时,经双目融合后反馈的图像噪点过多,以及图像精度不够理想的问题,提出了一种在匹配过程中融入全局差错能量最小化的区域立体视觉匹配算法。由于视差的求解是立体匹配过程中最重要的环节,因此本文利用最小化差错能量矩阵求解最优视差的原理。通过提高立体视觉的视差精度,从而减少视觉融合过程中因数据问题产生的噪声干扰,最终提高了对场景信息三维重构的准确度。通过分别在室内外的仿真实验与真实环境重构实验,验证了本文提出的基于双目视觉的六旋翼无人机立体匹配算法的有效性与可靠性。     

3-D Mobile Display Based on MoirÉ-Free Dual Directional Backlight and Driving Scheme for Image Crosstalk Reduction

A novel micro-grooved structure of lightguides and a sequential driving scheme of light sources were demonstrated in achieving comparable image qualities of 3-D displays to that of 2-D displays. The modified distribution of micro-grooves not only locates viewing cones for respective eyes but also suppresses the moire pattern, which might occur when a periodic micro-grooved structure and a color filter are superimposed. The configuration of lightguides for a 1.8-in liquid crystal display (LCD) panel can yield acceptable 3-D perceptions at the viewing distance of 7-23 cm and the brightness uniformity of greater than 83%. In addition, the driving scheme of light sources in synchronization with parallax images can project images to the viewer's respective eyes sequentially. With the refreshing sub-frame rate of 190 Hz and double displaying parallax images, the image crosstalk of 3-D perceptions can be efficiently reduced for an LC response time of 7.0 ms.     

Reflective liquid crystal television display

A new reflective television display, operating off the air, is described. The display uses the dynamic scattering mode (DSM) in nematic liquid crystals and can be viewed in high-brightness ambients. The liquid crystal cell, 6 to 12 µm thick, was addressed in real time by means of an electron beam using a wire-mosaic faceplate on a demountable cathode ray tube. Two different liquid crystal materials--anasylidene paraamino phenyl acetate (APAPA) and an RCA proprietary room temperature liquid crystal--were tested with similar results except for the difference in operating temperature (82 to 110° C and room temperature, respectively). The resolution of the 3.1-cm-square display was somewhat less than that required for commercial television (∼150 lines), limited by the mosaic structure but not the liquid crystal. Adequate resolution should be achievable in slightly larger displays. The contrast was not optimized (7.5 to 1) but several techniques are available to improve this value to 15 or 20 to 1 as has been demonstrated in static displays. The subjective evaluation of this display points out the attractiveness of reflective television panels; under suitable external illumination the panel has a wide viewing angle (±45° approximately). The current and voltage requirements to achieve the DSM in liquid crystals are such as to raise hopes that an integrated addressing approach suitable for flat television panels can be found.     

基于空间光调制器的合成全息显示技术研究

提出了一种基于液晶空间光调制器和计算全患技术的合成全患显示新方法.由计算机设计三维物体模型并获取带有视差信息的系列二维体视数字图像,通过计算全患方法对每一幅二维图像计算得到相应的全息图,再现时将左右眼视图对应的全息图同时输出到两个空间光调制器进行实时光电再现,并使再现像的位置符合人眼双目观察需要,计算机控制不同视角全患图顺序输出,从而实现合成全患立体显示,同时可观察合成全息动感,而观察者位置不必移动,与传统的合成全息显示相比操作灵活,易于控制.在实验中用液晶背投影光学引擎系统设计了硬件实验系统,设计了相关的控制软件,并给出了实验结果.     

Reduction of power consumption in compact DFD display by using FS color technology

A method to drastically reduce the power consumption of the backlight in a compact depth-fused three-dimensional display, which consists of a stack of two liquid crystal (LC) panels, is proposed and experimentally validated. To remove the color filters in the LC panels, we introduced the field-sequential technique for color display. The transmittance of the display could be improved by more than one order. Therefore, the luminance of the backlight could be reduced to less than that of a two-dimensional LC display.     

基于柱面光栅的液晶三维自由立体显示

根据双目视差原理和柱面光栅的分光特性研制了液晶三维自由立体显示器.该立体显示器由二维平板液晶显示器和柱面光栅有机耦合而成.采用九个视差图实现了三维静态、动态和视频的显示效果.一个19英寸的立体显示器具有相对应的平面显示器相同的亮度、对比度和色彩,其分辨率在垂直和水平方向都有合理的下降.该立体显示器的观看距离是(1000±500)mm,视角为 90°,可供多人不戴立体眼镜就能自由观看立体图像.     

一种纹理与结构光叠加的立体视觉改进算法

为降低复杂纹理与结构光叠加对立体匹配算法视差结果的影响,提出一种针对纹理与空间编码结构光叠加情况下的立体视觉改进算法。通过4种空间编码结构光与三种立体匹配算法(BM、SGBM、NCC)对单一平面与电木压模工件进行视差重建,发现叠加会导致双目立体视觉无法计算出真实视差。本文通过对比引入结构光前后两次拍照视差,在纹理复杂区域内用加入结构光之前视差替换加入结构光后坏点视差,实现对纹理与结构光叠加处视差优选,从而提高视差重建完整性。实验对比发现,在四种不同性能结构光下改进前后的三维重建结果可以验证算法有效性,算法提升了平面区域深度检测精度的1%,优化了工件视差重建,达到了提高三维重建完整性的目的。     

彩色立体图像匹配算法研究

立体图像匹配对于自由立体重建、三维测量以及立体显示中图像压缩来说是非常重要的。针对区域灰度互相关图像匹配的计算量大、速度慢的情况,运用了一组快速灰度互相关计算公式,提出了用视差限制搜索空间。同时,针对彩色图像的特点,将彩色图像的色彩信息考虑进图像的匹配过程中,将彩色图像的R、G、B三单色图像分别进行灰度相关匹配,定义并采用了颜色分量权重系数来抑制误匹配点。实验表明,该方法有效地减少了计算量,加快了计算速度,提高了图像匹配精度,具有较好的实时性。该方法将应用于三维立体显示中基于视差图的视差进行图像压缩。     

Performance characteristics of nematic liquid crystal display devices

Display devices using nematic liquid crystal materials offer advantages over other display media in low-voltage low-power operation, cost of materials and fabrication methods, electrical compatibility with MOS drive circuits, and flexibility of character size and format. This paper describes liquid crystal display devices that utilize dynamic scattering to modify transmitted or reflected light. We have synthesized individual materials that have nematic temperature ranges as large as -15-115°C without super-cooling effects at low temperatures. When these materials are used in transmissive displays having liquid crystal layers 12 µm thick sandwiched between transparent electrodes, contrast ratios of 30:1 to 50:1 are realized at 10-40 V dc or ac with a current density of ∼1-10 µA/cm². Turn-on times are 10-50 ms and turn-off times are 30-100 ms, precise values being dependent on the specific material, temperature, and voltage used. The contrast ratio versus voltage exhibits a threshold so that it may be possible to matrix address liquid crystal display panels. Operating lifetime and display applications are also discussed.     

集成成像立体显示技术研究进展

集成成像立体显示是一种水平和垂直方向同时具有运动视差的真三维立体显示技术。本文概述了集成成像立体显示在显示三维图像时存在的景深范围小,视角范围窄,赝像等问题,介绍了提升景深范围、扩大视角、消除赝像的技术方法。介绍了利用子图像阵列进行计算机三维虚拟重建的最新研究进展。通过研究指出,具有二维和三维显示模式转换功能的集成成像立体显示技术是超薄型真三维立体显示器的重要发展方向。     

Liquid Crystal Motion Picture Projector

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Stereo imaging quality evaluation in a full-color three-dimensional display system

To evaluate the light field display system with a liquid crystal display (LCD) and a holographic functional screen (HFS), the voxel theory based on the ray tracing is used. By analyzing the voxels defined by the cases of corresponding pixels overlapping completely and partially in the image space, the resolution characteristics of the system are discussed. The theoretical model is verified in the reconstruction experiment of a resolution target and compared with the calculation result of the presented system. Finally, we give an optimization method for the display image quality.     

无狭缝计算全息图的白光再现

利用彩虹全息是实现白光全息的常用方法,由于记录过程中引入狭缝使得再现像的视场非常狭小,且只有水平视差。在计算全息中模拟无狭缝记录,通过博奇编码获得菲涅耳全息图,以视频信号输入液晶板(LCD)显示,在白色发光二极管(LED)照明下获得同时具有水平和垂直视差的彩色全息再现像,大小为15 mm×15 mm。调整物面采样间距和滤波小孔孔径以减小色模糊、提高再现光的空间相干性,获得的白光再现像与彩虹全息图的再现像相比,前者虽然牺牲了一定的像质,但垂直视场角远大于后者,且整个系统简单紧凑、操作方便,再现像视场范围大,利于观察和接收,另外宽光谱光源和空间光调制器的使用为实现实时三维彩色全息打下了基础。     

LCD显示器的白平衡调整

在液晶显示器生产过程中,白平衡的调整是一个关键部分,目前大都采用PC机调整。针对现有调整方法的不足,提出了一种白平衡调整方案。该方案包括了两个步骤,首先,利用LCD显示器自身的嵌入式平台实现输入信号和前端采样A/D的误差校正;然后,采用PC机与彩色分析仪Chroma7120,通过曲线拟合的方法补偿后端显示屏的色温差异,实现LCD白平衡的自动调整。实验结果表明该方案既方便又能满足白平衡的调整要求。     

立体图像生成的视差控制

获取合适的视差信息是立体图像得到舒适观看的重要条件。为达到上述目的,提出了一种立体图像视差检测和控制方案。首先分析2种人眼视觉生理学限制的数学模型,并结合人眼跟踪技术获取生理视差容限。然后使用OpenGL图像绘制引擎获取显示场景的极值深度信息,进而计算出画面视差范围。最终通过比对虚拟场景的视差与观察者的生理视差容限,确定场景视差正确性并加以修正。实验证明,方案可以实时地进行视差控制,为立体图像生成提供了可靠依据。