DLP和LCD投影机对比分析

投影机是一种重要的计算机图形图像显示设备.本文从介绍投影机的分类入手,分别详细介绍分析了LCD和DLP两种主流投影机的工作原理,并且就这两种投影机的技术特点进行了性能对比分析.可以看出,数字化的DLP投影技术在许多方面是具有很大优势的.     

亲“日”还是亲“美”——比较LCD投影技术与DLP投影技术

根据核心成像原理,投影机一般分为三种:CRT投影机、LCD投影机和DLP投影机。CRT投影机因为亮度较低、操作复杂、体积较大、已逐渐被LCD投影机和DLP投影机所代替。需要指出的是,LCD投影技术代表了日本的技术流派,而DLP投影技术则是美国TI公司掌握核心技术。目前,Acer、Infocus、EPSON等公司主要是发展DLP投影机,而Microtek公司则主要发展LCD投影机。那么LCD与DLP在投影技术上有什么区别呢?     

无线高亮度——BenQ PB8265投影机

投影机PC World 中国实验室单片DLP 投影机的色彩表现能力一直为人们所诟病,这也是包括TI 在内的所有与DLP 投影机相关的厂商一直在努力改善的一个方面, 其中BenQ 的黄金色轮技术就是一种理想的解决方案。黄金色轮技术是BenQ 在其2004年的部分投影机产品中使用的一种新型色轮技术,旨在改善DLP 投影机的色彩表现能力。它采用了5段色轮,在传     

现代投影机技术发展探讨

该文介绍现代投影机的三种显示技术实现,即CRT投影技术、LCD投影技和DLP投影技术。对投影机的主要技术指标如面板技术、使用光源、应用领域等方面进行了介绍。     

选购投影机标准更新

投影机在现代商务生活中扮演着越来越重要的角色,无论是内部会议、日常培训、以及提案演示,都缺少不了投影机。由于投影机技术发展日新月异,选购投影机的标准也在不断发生变化。投影系统与技术要求高标准就投影机核心技术来看,市场有两大主流阵营:DLP数码投影机与LCD技术投影机。05年以来,两者所占比例已渐由过去LCD占绝对优势,转变为势均力敌的局面(DLP:LCD=49:51)。Intertek曾针对DLP芯片和LCD技术的前投影机进行长期性研究。该项目意在追踪这两种显示技术所产生的影像质量,以及随着时间推移所产生的变化。05年12月,Intertek公…     

DLP诠释投影机未来

DLP投影机技术进步的速度毋庸置疑,作为DLP核心技术的独家提供商,德州仪器在投影机整体技术发展方面具有足够的前瞻性,帮助整个产业确立发展方向。7月10日,德州仪器DLP在上海举办了“德州仪器DLP 2008中国创新高峰论坛”,其间展示了多项创新产品,并诠释了投影机发展的多个方向。     

DLP出货量要占30%

“明年DLP投影机的出货量要占到神州数码投影机出货总量的30%。”神州数码有限公司投影机部常务副总经理王哲在“奥图码-神州数码投影机业务合作签约暨新品发布会”上表示,“虽然我们在自有品牌和代理品牌中有DLP投影机,但是这些产品大多为2万元人民币以上的高端产品,要想卖出量来还有一定的困难,所以需要中低端普及型的DLP产品来丰富产品线。经过市场调查,我们选择代理了只做DLP投影机的美国奥图码(Optoma)公司。”在中国市场,投影机以LCD(液晶透射式投影)和DLP(数字光输反射式投影)两种显示方式为主。在国内投影机产业每年近50%增…     

投影机种类知多少

当前市场上的投影机产品主要包括LCD和DLP两大阵营。 LCD产品推出时间较早,在价格、视频稳定性和色彩还原度等方面拥有一定的优势。因此,固守LCD阵地不乏爱普生、索尼等这样在打印成像领域成名已久的知名厂商。 DLP技术的投影机可以实现尺寸更小重量更轻,符合未来投影机便携、无线的发展趋势。所以DLP技术代表着未来投影机的发展方向。DLP一方面是数字优势,它通过采用数字技术,使对比度、灰度等级(256-1024级)、色彩(2563～10243种)、画面质量等方面都非常     

DLP会坐直升机吗？：DLP投影机后势强劲 强拓市需破两大门槛

8月上旬,德州仪器公司(T1)以及全力支持DLP(Digital LightProcessor,数字光传输处理器)技术的部分投影机厂商在全球市场上发动了新一轮攻势。整个攻势给人的感觉是,DLP投影机的市场似乎要坐着直升飞机快速上升了。实际上DLP投影机的市场份额也确实在快速提升,根据一些市场调查公司的数据,2002年DLP投影机市场占有率为21％,预计2003年会达到26％,而在5磅(约2.3     

Envision回到中国

随着教育信息化的逐步深入,今年教育行业用户在投影机采购方面也掀起了一股热潮。据业内人士统计,仅今年暑假一次性采购100台以上的标案就达18个之多。而以往投影机采购中LCD投影机一枝独秀的情况,也正随着DLP投影技术的飞速发展和DLP投影机的日益崛起有所改观。 事实上,由于采用的核心技术不同,LCD投影机与DLP投影机应该说互有短长,而两者展开的所谓市场主流之争也由来已久。不过DLP投影机在教育市场优势日益明显却是不争的事实。那么,究竟是什么原因改变了DLP与LCD投影机的力量对比,进而使DLP投影机赢得了教育行业的青睐呢?为此,记者采访了明基电通公司数位媒体事业群总经理陈其宏。陈先生在显示设备领域工作了近20年,对     

Exploiting DLP Illumination Dithering for Reconstruction and Photography of High-Speed Scenes

In this work, we recover fast moving scenes by exploiting the high-speed illumination “dithering” of cheap and easily available digital light processing (DLP) projectors. We first show how to reverse-engineer the temporal dithering for off-the-shelf projectors, using a high-speed camera. DLP dithering can produce temporal patterns commonly used in active vision techniques. Since the dithering occurs at a very high frame-rate, such illumination-based methods can be “speed up” for fast scenes. We demonstrate this with three applications, each of which only requires a single slide to be displayed by the DLP projector. The quality of the result is determined by the camera frame-rate available to the user. Pairing a high-speed camera and a DLP projector, we demonstrate structured light reconstruction at 100 Hz. With the same camera and three or more DLP projectors, we show photometric stereo and demultiplexing applications at 300 Hz. Finally, with a real-time (60 Hz) or still camera, we show that DLP illumination acts as a very fast flash, allowing strobe photography of high-speed scenes. We discuss, in depth, some characteristics of the temporal dithering with a case study of a particular projector. Finally, we describe limitations, trade-offs and other issues relating to this work.     

Advances in contrast enhancement for DLP projection displays

Abstract— Increased contrast ratios are essential to the continued success of DLP? products in the marketplace, from rear‐projection televisions and home‐theatre systems to large venue displays and DLP Cinema?. The contrast of DLP projection systems has increased steadily over the past 5 years due to improvements in illumination and projection optics, as well as changes to the DMD itself. The authors will present an overview of the contrast performance of DLP projectors over time as well as describe illumination and projection techniques that optimize the performance of the DMD.     

Fast Spectral Reflectance Recovery Using DLP Projector

Spectral reflectance is an intrinsic characteristic of objects that is independent of illumination and the used imaging sensors. This direct representation of objects is useful for various computer vision tasks, such as color constancy and material discrimination. In this work, we present a novel system for spectral reflectance recovery with high temporal resolution by exploiting the unique color-forming mechanism of digital light processing (DLP) projectors. DLP projectors use color wheels, which are composed of a number of color segments and rotate quickly to produce the desired colors. Making effective use of this mechanism, we show that a DLP projector can be used as a light source with spectrally distinct illuminations when the appearance of a scene under the projector’s irradiation is captured with a high-speed camera. Based on the measurements, the spectral reflectance of scene points can be recovered using a linear approximation of the surface reflectance. Our imaging system is built from off-the-shelf devices, and is capable of taking multi-spectral measurements as fast as 100 Hz. We carefully evaluated the accuracy of our system and demonstrated its effectiveness by spectral relighting of static as well as dynamic scenes containing different objects.     

Colorimetric characterization of LCD and DLP projection displays

Abstract— Successful color‐management of projection systems depends on knowledge of their characteristics. In this study, two typical portable projectors were characterized. The projectors are based on different technologies, liquid‐crystal display (LCD) and digital light‐processing (DLP). Measurements were made with a spectroradiometer. The properties measured were spectral characteristics and the intensity of the primary and white colors, basic colorimetric characteristics, inter‐channel dependency, tone characteristics, color‐tracking characteristics, spatial non‐uniformity, dependency on background, and temporal stability. Based on the characterization results, the possibility of color‐management of the tested projectors is discussed.     

DLP Cinema™ projection: A hybrid frame‐rate technique for flicker‐free performance

Abstract— Film is recorded at 24 Hz, which is sufficient to achieve the effect of motion but is well within the flicker sensitivity of the human‐visual system (HVS) and thus would result in severe flicker. To avoid this, film projectors project at twice this rate, using a 48‐Hz screen refresh rate. While this greatly mitigates flicker, projected film images still exhibit considerable flicker in bright scenes. DLP Cinema? projection technology allows us to display images at any frame rate, and in practice we have been able to match the 48‐Hz refresh rate of film projectors. This paper describes a technique by which we take advantage of the fact that the HVS temporal sensitivity curve shows more sensitivity with bright content but much less sensitivity as content dims. This is done using the control versatility of the Digital Micromirror Device? (DMD?), which allows independent control of every bit. The result is an overall image signal that is beyond the HVS temporal sensitivity curve, resulting in the complete removal of any visible flicker. This technique gives DLP Cinema? projection its characteristic “solid” and “stable” appearance that standard film projection does not provide.     

Surround structured lighting: 3-D scanning with orthographic illumination

This paper presents a new system for rapidly acquiring complete 3-D surface models using a single orthographic structured light projector, a pair of planar mirrors, and one or more synchronized cameras. Using the mirrors, we project structured light patterns that illuminate the object from all sides (not just the side of the projector) and are able to observe the object from several vantage points simultaneously. This system requires that projected planes of light to be parallel, so we construct an orthographic projector using a Fresnel lens and a commercial DLP projector. A single Gray code sequence is used to encode a set of vertically-spaced light planes within the scanning volume, and five views of the illuminated object are obtained from a single image of the planar mirrors located behind it. From each real and virtual camera we recover a dense 3-D point cloud spanning the entire object surface using traditional structured light algorithms. A key benefit of this design is to ensure that each point on the object surface can be assigned an unambiguous Gray code sequence, despite the possibility of being illuminated from multiple directions. In addition to presenting a prototype implementation, we also develop a complete set of mechanical alignment and calibration procedures for utilizing orthographic projectors in computer vision applications. As we demonstrate, the proposed system overcomes a major hurdle to achieving full 360° reconstructions using a single structured light sequence by eliminating the need for merging multiple scans or multiplexing several projectors.     

The Least Fixpoint Transformation for Disjunctive Logic Programs

The paradigm of disjunctive logic programming(DLP)enhances greatly the expressive power of normal logic programming(NLP)and many(declarative)semantics have been defined for DLP to cope with various problems of knowledge representation in artificial intelligence.However,the expressive ability of the semantics and the soundness of program transformations for DLP have been rarely explored.This paper defines an immediate consequence operatro T^GP for each disjunctive program and shows that T^GP has the least and computable fixpoint Lft(P),Lft is,in fact,a program transformation for DLP,which transforms all disjunctive programs into negative programs.It is shown that Lft preserves many key semantics,including the disjunctive stable models,well-founded model,disjunctive argunent semantics DAS,three-valued models,ect.Thic means that every disjunctive program P has a unique canonical form Lft(P)with respect to these semantics.As a result,the work in this paper provides a unifying framework for studying the expressive ability of various semantics for DLP On the other hand,the computing of the above semantics for negative programs is ust a trivial task,therefore,Lft(P)is also an optimization method for DLP.Another application of Lft is to derive some interesting semantic results for DLP.     

Registration techniques for using imperfect and partially calibrated devices in planar multi-projector displays

Multi-projector displays today are automatically registered, both geometrically and photometrically, using cameras. Existing registration techniques assume pre-calibrated projectors and cameras that are devoid of imperfections such as lens distortion. In practice, however, these devices are usually imperfect and uncalibrated. Registration of each of these devices is often more challenging than the multi-projector display registration itself. To make tiled projection-based displays accessible to a layman user we should allow the use of uncalibrated inexpensive devices that are prone to imperfections. In this paper, we make two important advances in this direction. First, we present a new geometric registration technique that can achieve geometric alignment {\em in the presence of severe projector lens distortion} using a relatively inexpensive low-resolution camera. This is achieved via a closed-form model that relates the projectors to cameras, in planar multi-projector displays, using rational Bezier patches. This enables us to geometrically calibrate a 3000 x 2500 resolution planar multi-projector display made of 3 x 3 array of nine severely distorted projectors using a low resolution (640 x 480) VGA camera. Second, we present a photometric self-calibration technique for a projector-camera pair. This allows us to photometrically calibrate the same display made of nine projectors using a photometrically uncalibrated camera. To the best of our knowledge, this is the first work that allows geometrically imperfect projectors and photometrically uncalibrated cameras in calibrating multi-projector displays.     

双析取逻辑程序设计基础（Ⅰ）

析取逻辑程序设计是传统逻辑程序设计最重要的扩充之一，本文通过一些实例说明，现存语义无法充分 表示信息的不完全性。为此，本文提出了双析取逻辑程序设计的概念，我们不仅从句法上将正规则析取逻辑程序推广为双析取逻辑程序。而且建立了一种高度直观，灵活的辩论语义框架ＢＤＡＳ。     

对一个基于离散对数代理盲签名方案的分析与改进

通过对何俊杰等人提出的一个基于离散对数代理盲签名方案进行分析, 从中发现该方案会引起原始签名人的公钥替换攻击。为了解决该方案的安全缺陷, 提出了一种新的改进方案。分析表明, 改进后的新方案可以抵抗原始签名人的公钥替换攻击, 并且在基于离散对数问题下保证了代理盲签名的所有安全性要求, 而且提高了效率。