Automatic color correction for multi-projector display systems

A hierarchical color correction framework is presented to automatically calibrate multiple projectors. The proposed framework consists of two sub-methods: a simple color correction method and an advanced color correction method. An automatic selection scheme is designed to choose between the two sub-methods according to specific conditions. The simple color correction method uses a parameter model to map projected images into the Common Achievable Response (CAR) space for color consistent outputs. The advanced color correction method takes the projector properties, the display surface optical properties, and the relative distances between the screen and the projectors into consideration. A pre-processing step is designed to eliminate isolated abnormal sampling points, resulting in better quality outputs. In the experiment part, the effectiveness of the proposed framework is verified with both front projection systems and rear projection systems. The experimental results show that the proposed framework achieves better calibration results comparing with traditional methods.     

多投影仪组合显示的自反馈亮度校正

针对目前的亮度校正方法存在的问题,提出了闭环的自反馈亮度校正方法。该方法首先计算一个初始模板;然后在反馈过程中,使用模板对白色图像进行亮度衰减,根据相机获取的投影图像,以及屏幕与投影仪坐标的对应关系,用一定的模板修正规则来修正每个投影仪对应的亮度校正模板;重复反馈过程,直到达到亮度一致的约束条件。该方法避免了亮度响应曲线的复杂又耗时的测量工作,通过迭代反馈来不断修正亮度校正模板,最终使得亮度校正后的图像投影后逼近亮度一致。自反馈亮度校正方法中计算的初始亮度校正模板过渡更均匀,消除了模板中的三角带问题;采用的模板更新方法能够使迭代反馈过程更快地收敛。实验证明,该方法能够有效地解决自由立体投影显示系统中的亮度校正问题。     

A high-luminance and high-resolution CRT for projection HDTV display

Abstract— We have developed a 3-in. YAG (yttrium aluminum garnet) projection CRT for an HDTV display. The densely packed phosphor screen with a multi-layer interference filter is prepared by depositing phosphor on a YAG faceplate using a centrifugal sedimentation method. The tube's envelope is made from a glass whose expansion coefficient is well-matched with that of YAG. The focusing characteristics of an optimally designed pre-focusing electron gun and focusing magnet are improved for a HDTV display application. As a result, the green, red, and blue tubes reached luminances of 1.4 × 10⁵, 6.2 × 10⁴, and 8 × 10³ cd/m² at a cathode current of 1.0 mA and an anode voltage of 29 kV, respectively, with a half-intensity linewidth of 85 μm. An experimental 48-in. rear-projection TV set using the YAG projection tubes achieves more than 1000-TV-lines horizontal resolution and 300-cd/m² mean white luminance.     

改进的多投影仪显示墙几何校正技术

针对传统几何校正的不足,提出一种改进的几何校正的方法,只需少许人工干预就能很高精度的完成几何校正.介绍一种相机自动定位和拍照的方法,避免人工调整相机位置的繁琐工作,实现相机控制的自动化;提出一种基于递归的去除图片公共噪声区域算法,更精确地识别出特征点;通过临近的特征点,使用平行四边形插值算法与最小二乘法曲线拟合算法对被遮挡住的特征点坐标进行估计.实验结果表明,相机控制方法提高了几何校正的自动化程度,去噪算法提高了识别特征点的精度,平行四边形插值算法可以很好地对被遮挡的特征点坐标进行估计.     

针对多投影仪显示墙画面校正的图像对准技术

针对多投影仪显示墙画面校正问题中相机与投影仪间图像对准问题,提出一种基于自适应细分网格的稀疏对应点加密方法,可以得到任意光滑屏幕上投影图像与相机图像间的像素级对应关系。该方法利用改进的自适应4点插值细分曲线思想构造细分网格方法,可以将投影仪图像与相机图像间稀疏对应点网格加密到任意精度,从而建立从相机到投影仪图像间的像素级一一映射关系,为多投影仪显示墙系统的几何和色彩校正提供精确的图像对准基础。与现有算法的对比分析和虚拟机场塔台仿真系统中的实际应用表明,该方法具有较高的图像对准精度,并且无显式的需求投影仪、投影屏幕和相机的内部参数。     

A flexible OLED display with an OTFT backplane made by scalable manufacturing process

Abstract— A full‐color top‐emission AMOLED display driven by an organic TFT backplane manufactured using a scalable, lift‐off‐free, and shadow‐mask‐free process has been developed. It was shown that cost‐efficient copper can be used for S/D electrodes. The display has shown no significant degradation over a storage life of more than 10 months and operation over 25 hours during which the display is bent over 10,000 times.     

A display package for CAD of control systems

A multi-access computer system has been installed at the Control Systems Centre of the University of Manchester Institute of Science and Technology. The application of this computer to research into the computer aided design of industrial control systems involved the connection of two keyboard display terminals to the system. The ARDS storage tube displays chosen had the advantages of being teletypewriter compatible and not requiring the connection of a satellite computer A graphics package for the entry and structuring of data derived from the stability analysis of control systems was required as soon as possible after the installation was commissioned. The initial package enabled data to be entered by program and then selected and plotted by keyboard requests. Translation, scaling, alteration of the method of plotting (with points or vectors) and the selection of different items for the display were all carried out by keyboard interaction For long term CAD work a more extensive graphics package was required, the specification was determined following feedback from users of the initial package. It provided additional facilities for graphic interaction, alphanumeric annotation of the displays, specialized drawing and data entry functions and the storing of any pictures built up by the user, as well as a more linked data structure. The structure and facilities of this package are described.     

Image modification for immersive projection display based on pseudo‐projection models

This paper describes a practical method that enables actual images to be converted so that they can be projected onto an immersive projection display (IPD) screen. IPD screens are particularly unique in that their angle of view is extremely wide; therefore, the images projected onto them need to be taken on a special format. In practice, however, it is generally very difficult to shoot images that completely satisfy the specifications of the targeting IPD environment due to cost, technical problems or other reasons. To overcome these problems, we developed a method to modify the images by abandoning geometrical consistency. We were able to utilize this method by assuming that the given image was shot according to a special projection model. Because this model differed from the actual projection model with which the image was taken, we termed it the pseudo‐projection model. Since our method uses simple geometry, and can easily be expressed by a parametric function, the degree of modification or the time sequence for modification can readily be adjusted according to the features of each type of content. Copyright © 2003 John Wiley & Sons, Ltd.     

Advances towards high‐resolution pack‐and‐go displays: A survey

Abstract— Tiled displays provide high resolution and large scale simultaneously. Projectors can project on any available surface. Thus, it is possible to create a large high‐resolution display by simply tiling multiple projectors on any available regular surface. The tremendous advancement in projection technology has made projectors portable and affordable. One can envision displays made of multiple such projectors that can be packed in one's car trunk, carried from one location to another, deployed at each location easily to create a seamless high‐resolution display, and, finally, dismantled in minutes to be taken to the next location — essentially a pack‐and‐go display. Several challenges must be overcome in order to realize such pack‐and‐go displays. These include allowing for imperfect uncalibrated devices, uneven non‐diffused display surfaces, and a layman user via complete automation in deployment that requires no user invention. We described the advances we have made in addressing these challenges for the most common case of planar display surfaces. First, we present a technique to allow imperfect projectors. Next, we present a technique to allow a photometrically uncalibrated camera. Finally, we present a novel distributed architecture that renders critical display capabilities such as self‐calibration, scalability, and reconfigurability without any user intervention. These advances are important milestones towards the development of easy‐to‐use multi‐projector displays that can be deployed anywhere and by anyone.     

Evaluation of true 3 D display systems for visualizing medical volume data

The last few years have witnessed extraordinary advances in medical imaging. The new digital methods, such as CT or MRI, share the common characteristic of providing three-dimensional volume data. The urgent need for efficient techniques for visualizing volume data has recently been recognized not only in diagnostic medicine, but also in computer-assisted surgery and radiation-therapy planning. In recent years, new display technologies have emerged, in which depth perception has been improved significantly, because it relies in principle on physiological depth cues. This paper presents the state-of-theart is true 3D displays (with a special emphasis placed on equipment that has reached relative maturity) and a discussion of their most important advantages and disadvantages with respect to visualizing medical data.     

Analyzing the performance of a cluster-based architecture for immersive visualization systems

Cluster computing has become an essential issue for designing immersive visualization systems. This paradigm employs scalable clusters of commodity computers with much lower costs than would be possible with the high-end, shared memory computers that have been traditionally used for virtual reality purposes. This change in the design of virtual reality systems has caused some development environments oriented toward shared memory computing to require modifications to their internal architectures in order to support cluster computing. This is the case of VR Juggler, which is considered one of the most important virtual reality application development frameworks based on open source code.     

Thin‐film micromirror array (TMA) for large information‐display systems

Abstract— The thin‐film micromirror array (TMA) is a new reflective‐type spatial light modulator fabricated with microelectromechanical systems (MEMS) technology. Micromachined thin‐film piezoelectric actuators are used to control the tilt angle of each micromirror, which defines the gray scale of the matching screen pixel. A working projector prototype of 5400 true ANSI lumens was presented at Asian Display '98 with three VGA‐format TMAchips and a 1‐kW xenon lamp. The prototype showed a light‐transmitting efficiency of 22%. An XGA‐format TMA was developed for commercial purposes. The size of each micromirror of the XGA‐format TMA is reduced to half the size of the micromirror of a VGA‐format TMA. Efforts have been made to maintain the light‐transmitting efficiency of the XGA TMA projector over 21%, as well as to improve the uniformity.     

复杂表面投影几何校正技术研究

当投影仪将图像投影到复杂表面时,为使观察者观看到不失真图像,提出了基于角点检测的几何校正方法。该方法利用对复杂表面投影白色区域图像的阈值分割来提取校正区域;进行横纵特征条纹的提取和处理,获取投影系统中特征点的坐标;通过对观察者所需的理想图像进行变换获得投影仪所需预变形图像。编写了基于OpenCV的校正软件。实验表明,该方法可以有效消除复杂表面引起的几何畸变,得到良好的观看效果。     

一种投影显示图像颜色失真校正方法

颜色校正是提高投影显示图像视觉效果及内容感知理解程度的重要环节,针对此,提出了一种基于颜色空间变换和亮度响应函数(ITF)的颜色校正方法。设计一幅16×16的灰度渐变棋盘格作为标定图像,进行采样;利用测光表测量环境光,以调整相机拍摄参数;根据投影仪-相机系统映射关系矩阵,求解匹配采样点对;建立亮度响应曲线的经验参数模型,利用最小二乘法估计曲线参数;依据亮度响应曲线的反函数建立颜色查找表,从而实现投影显示图像的颜色失真校正。在LCD投影仪上进行了该算法的可行性和效果测试,实验结果表明:该算法校正后的投影画面质量较好,且实现简单。     

A directional and scalable streaming deblocking filter hardware architecture for HEVC decoder

In this work, a directional streaming hardware architecture for Deblocking Filter (DBF) of High-Efficiency Video Coding (HEVC) decoder is presented. The architecture uses adaptive parallel and pipeline processing strategies for low power and high-performance applications including broadcasting and Virtual reality etc. In order to remove the dependency from neighboring blocks, a restructured block size have been used. Since, the developed architecture is scalable, 68 × 68 Coding Unit (CU) block processing supports splitting into 36 × 36, 20 × 20 and 12 × 12. The proposed architecture uses 3-stage pipeline to complete the 68 × 68 CU block processing of DBF. The stage-1 micro-pipeline stages of 8, 4, 2 and 1 varied in accordance with CU sizes 68 × 68, 36 × 36, 20 × 20 and 12 × 12 respectively. In stage-2 of main pipeline, the blocks are further processed into single cycle parallel edge-filter. Each 8 × 8 block is processed for DBF Horizontal Filtering (HF) and Vertical Filtering (VF) simultaneously. During the stage-3 process of write-back operations, 4 × 8 blocks are stored into the memory to reconstruct the frame. The design has been implemented in both Field Programmable Gate array (FPGA) Virtex-6 and Application Specific Integrated Circuit (ASIC) using 180 nm technology. The results show that 68 × 68, 36 × 36 and 20 × 20 CU blocks have higher processing speed with reduced resources of 254K, 31K and 14.7K as compared with the previous works. The proposed architecture supports low power and high processing speed applications because of variable throughput.     

A preliminary investigation of the time tunnels display design technique

Two forms of decision support were evaluated using a simulated process control task environment. The time tunnel display design concept provides temporal (historical) information about the value of variables and relationships over time using perspective geometry and the depth plane. The compensated level variable is a quickened display that provides estimates of system state that is not confounded by counter-intuitive and time-delayed thermodynamic effects. These two forms of decision support were applied factorially (present, absent) to produce four experimental conditions. The results for system control and fault detection tasks indicate that display quickening improved performance significantly while the time tunnel displays did not. The results for data extraction tasks (reporting the values of system variables) were dependent upon the quality of the mapping between properties in the domain and visual features in the display. Methodological factors that may have influenced the results are considered and subsequent evaluations of the time tunnels design technique, using alternative methodologies, are discussed. It is concluded that the time tunnels display design concept has potential as a form of decision support and is worthy of additional research efforts.     

A scalable architecture for concurrent online auctions

Online auction systems are characterised by a number of functional and performance management requirements, caused by the potentially very large numbers of distributed concurrent bidders, as well as by the auction rules. Such systems are typically implemented as three tier, thread‐based architectures, whose performance does not scale up well with an increase in the number of concurrent bidders. Nor such systems can take advantage of new Cloud based environments. In this paper, we propose an architectural framework for online auctions developed on top of a soft real‐time platform (Open Telecom Platform) using a concurrent language (Erlang) and an embedded Web server (Yaws). The proposed framework can scale up to hundreds of thousands of concurrent users while its performance can benefit from multicore and symmetric multiprocessing computer architectures. We demonstrate the capabilities of the framework by developing prototypes for two auction types known as ‘unique bid’ and ‘penny’, analyse their performance characteristics and compare them with that of existing auction systems. Copyright © 2013 John Wiley & Sons, Ltd.     

Evaluation of high‐resolution and mobile display systems for digital radiology in dark and bright environments using human and computational observers

Abstract— As digital display systems replace film traditionally used for reading radiographic images, resource‐intensive acceptance testing must be performed to ensure that quality meets and maintains desired specifications. If machine observers can replace human readers, whose performances are highly variable, the results will be more consistent and less costly. To be effective, however, the automated observers must track human performance. An approach for a model observer, validated with human readers, for the evaluation of the visibility of low‐contrast small targets in high‐resolution and mobile displays under different ambient illumination, will be described. The displays were tested using CDMAM‐like digital phantoms containing disks of varying diameters and contrasts on a flat background. For this task, we find the best indicator of display performance to be the display's ability to represent small luminance contrast, not resolution or pixel size. The results confirm that high‐resolution systems perform better under low illumination while illuminance has a minor impact on the mobile‐display performance. Finally, the results show that the machine observer tracks the performance of human readers. Machine observers with proper validation can replace humans in the acceptance testing procedures, saving the testers both time and money.     

A Unified Subdivision Scheme for Polygonal Modeling

Subdivision rules have traditionally been designed to generate smooth surfaces from polygonal meshes. In this paper we propose to employ subdivision rules as a polygonal modeling tool, specifically to add additional level of detail to meshes. However, existing subdivision schemes have several undesirable properties making them ill suited for polygonal modeling. In this paper we propose a general set of subdivision rules which provides users with more control over the subdivision process. Most existing subdivision schemes are special cases. In particular, we provide subdivision rules which blend approximating spline based schemes with interpolatory ones. Also, we generalize subdivision to allow any number of refinements to be performed in a single step.     

Spatial Patches - A Primitive for 3D Model Representation

The commonly used solution for real-life 3D model representation is polygonal spatially consistent geometry, with texture, and, optionally, bump or displacement maps attached. Although the idea of displacement mapping is well known, there are just a few approaches to its efficient implementation. In this paper we develop a technique that allows for efficient representation and rendering of 3D models by getting a new angle on the displacement mapping concept. We introduce a new primitive that is defined as the range image of a small part of the model's surface; therefore, it is called a spatial patch. The whole model is just a collection of patches with no connectivity information between them. Such a representation can be directly acquired by 3D scanning machinery, and stored in a compact uniform form. It also allows for efficient visualization, which is the major focus of this paper. Thus, we present the logical structure of a rendering unit based on conventional z-buffering, and discuss the involved algorithms in detail. These algorithms benefit from modern features of computing units for which we believe the proposed technique can be used in a wide range of applications dealing with real-life 3D data.