Visual quality of high‐contrast projection screens. Part I: Visibility of screen‐based artifacts and noise

Abstract— The investigation of visual‐quality issues for high‐contrast projection screens such as those used for avionics projection displays and other applications requiring a high level of ambient light rejection will be described. Visibility of artifacts and noise generated by the optical and structural properties of a variety of high‐contrast projection screens was characterized by both empirical, subjective image quality evaluations and a suite of objective screen‐quality metrics. At least two of these metrics were found to provide very good correlation with the subjective assessment. These metrics are applicable to any display system where spatial‐noise artifacts are an issue, such as with direct‐view AMLCDs with anti‐glare treatments.     

The Visual Computing of Projector‐Camera Systems

This article focuses on real‐time image correction techniques that enable projector‐camera systems to display images onto screens that are not optimized for projections, such as geometrically complex, coloured and textured surfaces. It reviews hardware‐accelerated methods like pixel‐precise geometric warping, radiometric compensation, multi‐focal projection and the correction of general light modulation effects. Online and offline calibration as well as invisible coding methods are explained. Novel attempts in super‐resolution, high‐dynamic range and high‐speed projection are discussed. These techniques open a variety of new applications for projection displays. Some of them will also be presented in this report.     

A high‐contrast front‐projection display system optimizing the projected light‐angle range

Abstract— The problem with front‐projection displays is that the screen contrast ratio decreases under bright‐ambient conditions. To overcome this problem, the design of a special screen, composed of the diffuser whose diffusing property shows top‐hat characteristics and a sawtooth reflector, is proposed. The screen diffuses the incident image light arriving at a projection‐angle range that is a lower‐angle range than the viewing‐angle range, and reflects the ambient light out of the viewing‐angle range. In this paper, the projection‐angle range and the viewing‐angle range was optimized to improve the contrast ratio of a front‐projection display. As a result, a special screen with the above‐mentioned diffusing property was realized, and a high‐quality front‐projection display with a high contrast ratio, even in a bright room, was achieved.     

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.     

Multi‐planar plenoptic displays

Multi‐planar plenoptic displays consist of multiple spatially varying light‐emitting and light‐modulating planes. In this work, we introduce a framework to display light field data on this new type of display device. First, we present a mathematical notation that describes each of the layers in terms of the corresponding light transport operators. Next, we explain an algorithm that renders a light field with depth into a given multi‐planar plenoptic display and analyze the approximation error. We show two different physical prototypes that we have designed and built: The first design uses a dynamic parallax barrier and a number of bi‐state (translucent/opaque) screens. The second design uses a beam splitter to co‐locate two pairs of parallax barriers and static image projection screens. We evaluate both designs on a number of different 3D scenes. Finally, we present simulated and real results for different display configurations.     

Front‐projection optical‐system design for reflective LCoS technology

Abstract— Optical designs for three‐panel LCoS projection systems are reviewed. The impact of polarization aberrations in prism‐based systems is discussed and a simple model to analyze the sensitivity of contrast to thermal gradients in prisms is presented. To eliminate stress birefringence in LCoS projection systems, we have developed a projection optical system that does not require the use of polarizing prisms. An improved off‐axis design has been designed that simplifies manufacture and reduces cost. The performance of systems based on this architecture will be discussed.     

Design of carbon nanotubes for large‐area electron field‐emission cathodes

Abstract— Electron field‐emission displays offer a viable option for the next generation of flat‐panel screens. Boasting high‐quality images in terms of good color saturation, fast refresh rate, and high brightness, these displays have the potential to offer above and beyond what the current market leaders, LCD and plasma. However, for the realization of such a new display disrupting the incumbent LCD and plasma displays, not only does the image quality need to be better, but fabrication costs and suitable manufacturing processes need to be in place at reduced cost. Many viable cathode materials have been proposed in recent years, one of which being the use of carbon nanotubes (CNTs) in various forms (aligned growth, screen printing, and polymer matrix). In this review, a series of recent experiments investigating the field‐emission characteristics of carbon‐nanotube systems for possible use in the display industry is presented.     

High‐contrast front‐projection system for large‐screen displays suppressing reflection and diffusion of ambient light

Abstract— A new front‐projection system for large screens by diffusing only projected light to wards the viewing‐angle range and reflecting ambient light towards the other angle ranges is proposed. With this system, a high‐quality and large‐sized front‐projection display with a high contrast ratio even in a bright room has been realized.     

基于单投影仪与柱面反射镜的沉浸感显示系统

在分析传统沉浸感显示系统优缺点的基础上,设计并实现了一种新型的沉浸感显示系统。该系统使用柱面反射镜对单投影仪投射光线进行反射,并在弧形背投幕上成像,能够获得无缝画面,实现了广角度虚拟场景的连贯显示。通过合理设计柱面反射镜形状,实现了投影画面在水平方向上的均匀放大。通过对图像进行预变形可以基本消除因投影幕曲率而产生的投影画面形变,同时采用背投技术使参与者在虚拟场景中活动更加自如。该系统克服了传统的多投影仪或多显示器沉浸感显示系统中存在的图像拼接问题,且易于构建,经实验验证能够获得良好的沉浸感显示效果。     

Image correction based on homography in stereoscopic projection display

Abstract— Stereoscopic and autostereoscopic projection‐display systems use projector arrays to present stereoscopic images, and each projector casts one parallax image of a stereoscopic scene. Because of the position shift of the projectors, the parallax images have geometric deformation, which influences the quality of the displayed stereoscopic images. In order to solve this problem, a method based on homography is proposed. The parallax images are pre‐transformed before they are projected, and then the stereoscopic images without geometric distortion can be obtained. An autostereoscopic projection‐display system is developed to present the images with and without calibration. Experimental results show that this method works effectively.     

一种改进的LED显示屏通信软件设计与实现

用Visual C 编程读取屏幕像素值生成点阵文件的方法,实现了单基色LED显示屏以多种字体显示汉字、ASCII字符及简单图形.弥补了当前常用的计算机与LED显示屏通信软件的缺陷,丰富了单基色LED显示屏显示的方式.     

Seamless ultrathin rear projection display

A new architecture for a thin (2‐cm depth) rear projection display is described. In order to achieve this small depth, a very high density of rear projectors is used. Three prototype displays using rear projectors on both 5‐ and 2‐cm pitch arrays are described. The displays can achieve an effective screen pixel pitch of as small as 0.5 mm, which makes this technology competitive in terms of resolution with fine pitch LED displays; however, orders of magnitude fewer LEDs are required: Each rear projector requires only one white LED and a color liquid crystal light modulator. In the three prototypes, the projector light modulators utilize 101‐cm (40 in.), 80‐cm (31.5 in.), and 60‐cm (24 in.) diagonal liquid crystal display glass. To minimize cost, no lenses are utilized for the rear projectors. An RGB LED array may augment the projector array, which provides a low resolution component of the image onto which the high resolution component is superimposed by the projector array. Edge gaps between active areas on adjacent LCD glass units are completely eliminated by the rear projection approach enabling low profile wall‐size seamless displays. Display contrast depends on rear projection screen design.     

一种投影仪相机系统几何配准的鲁棒算法

目前投影屏的反射及几何特性决定了投影仪投影图像的显示效果。为解除投影仪对标准屏幕的依赖性,借助数码相机可构成反馈系统对显示表面的缺陷进行辐射度补偿和图像校正,而其前提即是建立投影图像面与相机图像面像素之间的配准关系。为实现这一目的提出了一种能实现投影仪相机系统几何配准方法的鲁棒算法。通过设计黑白二色编码图像、显示采集编码图像的方式并对捕获图像进行二值化以及形态学处理以定位和识别采样色块,建立几何配准函数关系。该算法在平面、曲面以及无图案与有图案等各种显示表面的投影场景中得以验证,其平均配准误差稳定在0.2～1.0个像素单位,且不依赖于色块的数量而变化,并能在10s内完成整个配准关系的建立。实验表明该方法能在适用范围以及精度和效率等方面满足相机反馈式投影仪像面配准的应用需求。     

Electro‐optical transfer function preferences for LCD TVs: The effect of display brightness and surround illumination on preferred gamma

Abstract— Recent commercial liquid‐crystal‐display (LCD) televisions are larger and brighter than traditional televisions, thus impacting the viewing conditions in which they are viewed. These changes in viewing conditions may require different electro‐optical transfer functions (EOTFs) for LCD TVs than those for conventional TVs. Here, the way various EOTFs affect the preferred image quality of test images with changes in brightness and surround illumination conditions are examined. The first method used a gain, offset, and gamma (GOG) function with a range of gamma values, and the second method altered the intrinsic EOTFs. Image preference for the simulated EOTFs was determined using a paired‐comparison experiment for ten images. The first experiment took place in a darkened room at two display luminance levels. The results indicated that a gamma of 1.6 was most preferred overall although more so at a lower screen luminance level. In a second experiment, the procedure was repeated with a dim surround of 10% of the display's white point. With this surround, preference for a gamma value of around 1.6 at both screen luminance levels was more enhanced. These results indicated that image preference for different EOTFs is dependent on display luminance and that this dependence is maintained with a dim surround.     

Novel screen technology for high‐contrast front‐projection display by controlling ambient‐light reflection

Abstract— One problem with front‐projection displays is that the screen contrast ratio decreases in bright ambient light. In this paper, we propose a new front‐projection display system that incorporates the control of reflection of ambient light in the screen design, providing a high contrast ratio even in a brightly lit room.     

Improved trust‐region gradient‐search algorithm for accelerated optimization of wideband antenna input characteristics

Full‐wave electromagnetic (EM) simulation models are ubiquitous in carrying out design closure of antenna structures. Yet, EM‐based design is expensive due to a large number of analyses necessary to yield an optimized design. Computational savings can be achieved using, for example, adjoint sensitivities, surrogate‐assisted procedures, design space dimensionality reduction, or similar sophisticated means. In this article, a simple modification of a rudimentary trust‐region‐embedded gradient search with numerical derivatives is proposed for reduced‐cost optimization of input characteristics of wideband antennas. The approach exploits information and history of relative changes of the design (as compared with the trust region size) during algorithm iterations to control the updates of components of the antenna response Jacobian, specifically, to execute them only if necessary. It is demonstrated that the proposed framework may lead to over 50% savings over the reference algorithm with only minor degradation of the design quality, specifically, up to 0.3 dB (or <3%). Numerical results are supported by experimental validation of the optimized antenna designs. The presented algorithm can be utilized as a stand‐alone optimization routine or as a building block of surrogate‐assisted procedures.     

Active‐matrix technology for high‐efficiency OLED displays

Organic light‐emitting device (OLED) technology has recently been shown to demonstrate excellent performance and cost characteristics for use in numerous flat‐panel‐display (FPD) applications. Universal Display Corp. (UDC), together with its academic partners at Princeton University and the University of Southern California, are developing high‐efficiency electrophosphorescent OLEDs, based on triplet emission. These material systems show good lifetimes, and are well suited for the commercialization of low‐power‐consumption full‐color active‐matrix OLED displays. Their very high conversion efficiencies may even allow them to be driven by amorphous‐silicon backplanes, and in this paper we consider design guidelines for an amorphous‐silicon pixel to minimize display non‐uniformities due to threshold voltage variations.     

Invited Paper: Depth reproducibility of multiview depth‐fused 3‐D display

Abstract— A multi‐view depth‐fused 3‐D (DFD) display that provides smooth motion parallax for wide viewing angles is proposed. A conventional DFD display consists of a stack of two transparent emitting screens. It can produce motion parallax for small changes in observation angle, but its viewing zone is rather narrow due to the split images it provides in inclined views. On the other hand, even though multi‐view 3‐D displays have a wide viewing angle, motion parallax in them is discrete, depending on the number of views they show. By applying a stacked structure to multi‐view 3‐D displays, a wide‐viewing‐angle 3‐D display with smooth motion parallax was fabricated. Experimental results confirmed the viewing‐zone connection of DFD displays while the calculated results show the feasibility of stacked multi‐view displays.     

Analysis and reduction of dark zone in ultra‐thin wedge‐plate displays

Abstract— A wedge plate can be used as the screen of a display, and the thickness of the display can be incredibly thin. In this paper, a basic formula for ray tracing in such a wedge plate is deduced. The fundamental limitation on the display quality of a wedge plate is explored, and the formation of a dark zone on the display screen is analyzed and verified numerically. Experimental exploration and confirmation of one 14‐in. acrylic wedge plate with a white‐light‐emitting diode is also provided. Two approaches to eliminate the dark zone are proposed, and the corresponding numerical demonstration of a 52‐in. wedge‐plate display is also shown.