DLS: dynamic backlight luminance scaling of liquid crystal display

Backlight systems dominate the power requirements of battery-operated hand-held devices with color thin-film transistor (TFT), liquid crystal displays (LCDs). We introduce dynamic luminance scaling of the backlight with appropriate image compensation. Dynamic backlight luminance scaling (DLS) keeps the perceived intensity or contrast of the image as close as possible to the original while achieving significant power reduction. DLS compromises quality of image between power consumption, which fulfills a large variety of user preferences in power-aware multimedia applications. DLS saves 20% to 80% of power consumption of the backlight systems while keeping a reasonable amount of image quality degradation.     

用LCD显示器测量人眼亮度对比度敏感视觉特性

根据LCD显示器亮度的均匀性和显示光栅对比度的稳定性实验分析,提出了一种采用LCD显示器显示光栅测量人眼对比度敏感视觉特性的实验方法,并测量了48位青年对象对3种平均亮度光栅的对比度视觉特性,且与目前有代表性的测量方法和结果进行了对比分析。结果表明该测量方法是一种有效、实用和简便易行的人眼对比度敏感视觉特性测量方法。     

自动立体显示屏高亮度背光模块设计

使用自动立体显示器,用户不需要立体眼镜,裸眼就能看到立体图像.目前主流的液晶自动立体显示器的亮度不够,影响到使用.为了提高亮度,研究新的背光模块设计方法.采用高亮度发光二极管,用菲涅耳透镜和柱透镜使光线集中在用户眼睛上,大幅度提高图像亮度,由于左右眼看到的图像不一致,产生立体感.结合具体的显示器研制背光模块,选择二极管,设计光路和透镜,对光路仿真,探索出设计方法.该方法对自动立体显示器的设计有指导意义.     

液晶显示器NVIS高亮LED背光源研究

提出了一种满足液晶显示器NVIS的高亮LED背光设计方法。介绍了白灯LED+OGB LED背光阵列优化设计,降低混光距离比、提高均匀度的方法,并通过试差法,对配色后测量结果进行分析,求出最佳配色方案;模拟与实验结果表明,该设计方法完全能够满足夜航要求。     

侧入式局域动态调光背光聚光特性研究

针对HDR技术在侧入式局域动态调光中的特殊要求,采用结构导光板搭配LED灯条进行聚光,以此提高背光对比度,实现液晶显示器的分区动态调光控制。首先,基于现有导光板出光面亮度分布,确定了导光板出光面微结构为锯齿形,然后利用光线追迹法对结构导光板进行仿真,分析了不同结构的导光板出光面微结构棱高、棱宽比和曲率对聚光性能的影响,结果表明,聚光性与导光板出光面结构直接相关,光学胶折射率为1.49,棱高为20μm,棱宽比为0.47时,聚光性能最佳;根据仿真结果开发了实际背光产品,并对此产品进行了测试,测试结果表明,与传统的导光板相比,使用结构导光板后,背光聚光效果显著,对比度由6.01提升到127.15,满足动态调光聚光性要求。     

结合视觉特性的红外图像增强方法

为了增强红外图像的细节信息,改善图像视觉效果,将视觉特性与红外图像特征结合,提出了一种结合视觉特性的图像增强方法。首先,对图像运用Weber定律进行亮度处理,并在对数域角度,利用背景强度与光强梯度呈局部线性关系的特性,模拟视觉系统来分割图像。然后,分别对分割图像进行增强处理,过暗、过亮区域采用改进的自适应直方图均衡算法、Weber区域采用多尺度Retinex算法。最后,三区域构建图像,输出细节突出、亮度适中的红外图像。实验结果表明:本文算法增强了图像细节、缩短了运行时间、有效地消除“光晕”现象,改善了图像的视觉效果,具有较好的应用前景。     

A luminance signal bandwidth expansion method for NTSC system

Bandwidth expansion of the luminance signal is discussed as a method of picture quality improvement in the NTSC television system. By modulating the high-frequency component over a 4.2-MHz luminance signal using a new subcarrier whose phase is field-alternated and multiplexing the aliasing component resulting from that to a low-frequency component, the transmissible bandwidth of the luminance signal can be expanded, with compatibility to NTSC receivers. A method based on this principle is proposed. Expanding the bandwidth as described, the transmissible two-dimensional spatial frequency area is matched with the visual characteristics and an improved image sharpness is achieved. Experiments confirmed that the bandwidth can be expanded while maintaining compatibility with NTSC receivers. In addition, subjective evaluation tests indicated that there is not much deterioration of image sharpness through the method's deletion of the oblique high spatial frequency component, and that sharpness is improved in pictures including detailed images through the proposed method. A novel phase regeneration circuit is also proposed     

大屏幕LCD背光照明的控制方案

近来,CTV产品中的LCD屏幕尺寸越来越大,已经超过40英寸。由于屏幕尺寸的增大,CCFL的数目及其驱动电路也有所增加。目前有很多种方法将CCFL置于大型LCD屏幕的背面,以便为整个屏幕提供背光照明。     

CRT与LCD技术的视觉刺激显示性能评价

为了定量评价两种技术在视觉研究实验中的适用性,本文根据文献分析和视觉研究需求设计了显示器性能测试系统与测试流程,对一台阴极射线管(CRT)显示器和两台通用液晶显示器作为视觉刺激显示设备的关键性能进行测试。结合心理物理学理论,特别是韦伯定律,详细地分析和比较了各项测试结果。实验结果显示所有的显示器有不同的Gamma特性,需要进行相应的Gamma校正之后才能线性呈现图像的灰度级;CRT显示器在响应时间上具有绝对优势,但屏幕空间均匀性和独立性较差;相比于CRT显示器,LCD显示器具有较高的亮度和较好的空间均匀性和独立性,但是响应时间偏慢,而且相邻两帧图像之间独立性较差。这些测试结果表明,CRT显示器仍然是高动态特性视觉刺激显示的首选,而LCD显示器可以用于呈现对空间亮度一致性和空间的独立性要求高,但对响应速度要求不高的视觉刺激。     

Supply and threshold voltage scaling for low power CMOS

This paper investigates the effect of lowering the supply and threshold voltages on the energy efficiency of CMOS circuits. Using a first-order model of the energy and delay of a CMOS circuit, we show that lowering the supply and threshold voltage is generally advantageous, especially when the transistors are velocity saturated and the nodes have a high activity factor, In fact, for modern submicron technologies, this simple analysis suggests optimal energy efficiency at supply voltages under 0.5 V. Other process and circuit parameters have almost no effect on this optimal operating point. If there is some uncertainty in the value of the threshold or supply voltage, however, the power advantage of this very low voltage operation diminishes. Therefore, unless active feedback is used to control the uncertainty, in the future the supply and threshold voltage will not decrease drastically, but rather will continue to scale down to maintain constant electric fields     

Patchwise scaling method for content-aware image resizing

Image resizing becomes more and more important in content-aware image displaying. This paper proposes a patchwise scaling method to resize an image to emphasize the important areas and preserve the globally visual effect (smoothness, coherence and integrity). This method for resizing image is based on optimizing the image distance presented in this paper. The image distance is defined based on so-called local bidirectional similarity measurement and smoothness measurement to quantify the quality of resizing outputs. The original image is divided into small important patches and unimportant patches based on an important map. The important map is generated automatically using a novel combination of image edge and saliency measurement. A scaling factor is computed for each small patch. The resized image is produced by iteratively optimizing, which is based on our image distance, the scaling factor for each small patch. Experiments of different type images demonstrate that our method can be effectively used in image processing applications to locally shrink and enlarge important areas while preserving image quality.     

An analog compensation method for asymmetric IMD characteristics of power amplifier

The modulation frequency affects the asymmetric intermodulation distortion (IMD) products of a RF power amplifier. This effect reduces IMD cancellation performance of power amplifiers in connection with predistortion linearization. A phase extraction method to determine phase difference between upper and lower third-order IMD products and a phase compensation circuit using an envelope injection technique is proposed. The experimental results demonstrate a significant improvement in the third-order IMD cancellation performance.     

Human visual system based data embedding method using quadtree partitioning

In this paper, we proposed a data embedding method based on human visual system (HVS) and quadtree partitioning. For most HVS-based methods, the amount of embedded data is based on the measurement of differences of pixel pairs or the standard deviation of image blocks. However, these methods often result in larger image distortion and are vulnerable to statistical attacks. The proposed method employs a specially designed function to measure the complexity of image blocks, and uses quadtree partitioning to partition images into blocks with different sizes. Larger blocks are associated with smooth regions in images whereas smaller blocks are associated with complex regions. Therefore, we embed less data into larger blocks to preserve the image quality and embed more data into smaller blocks to increase the payload. Data embedment is done by using the diamond encoding technique. Experimental results revealed that the proposed method provides better image quality and offers higher payload compared to other HVS-based methods.     

A depth perception and visual comfort guided computational model for stereoscopic 3D visual saliency

With the emerging development of three-dimensional (3D) related technologies, 3D visual saliency modeling is becoming particularly important and challenging. This paper presents a new depth perception and visual comfort guided saliency computational model for stereoscopic 3D images. The prominent advantage of the proposed model is that we incorporate the influence of depth perception and visual comfort on 3D visual saliency computation. The proposed saliency model is composed of three components: 2D image saliency, depth saliency and visual comfort based saliency. In the model, color saliency, texture saliency and spatial compactness are computed respectively and fused to derive 2D image saliency. Global disparity contrast is considered to compute depth saliency. Particularly, we train a visual comfort prediction function to distinguish stereoscopic image pair as high comfortable stereo viewing (HCSV) or low comfortable stereo viewing (LCSV), and devise different computational rules to generate a visual comfort based saliency map. The final 3D saliency map is obtained by using a linear combination and enhanced by a “saliency-center bias” model. Experimental results show that the proposed 3D saliency model outperforms the state-of-the-art models on predicting human eye fixations and visual comfort assessment.     

用显示器测量人眼视觉的亮度最小可觉差

最小可觉差是人眼视觉重要特性之一,随着计算机显示器的普及,显示器环境下的亮度最小可觉差对图像细节有重要的应用价值。利用10bit图像显示卡和液晶显示器方便、精确控制亮度刺激,在显示器显示亮度范围内产生27个不同亮度背景,采样心理物理学亮度视觉匹配实验测得亮度最小可觉差。实验结果表明,在背景亮度为11.89~142.3cd/m~2中等亮度下人眼最小可觉差与背景亮度的比值约为0.017,并遵守韦伯定律;在背景亮度为0.38~9.36cd/m~2的弱亮度情况下,人眼最小可觉差与背景亮度的比值随亮度的增加呈单调递减趋势。在显示器上测量的中等亮度下人眼亮度最小可觉差与Koenig and Brodhun采用传统光学方法得到的实验结果基本一致。     

A morphology screen coding anti-counterfeiting method based on visual characteristics

A paper information anti-fake and tamper-proofing method based on human visual characteristics and morphol-ogy screen coding technology is proposed. Through controlling the distribution of mathematical morphology of screen dot-matrix,warning mark and information are hidden in the background texture. Because of the differ-ences between human vision and the duplicate characteristics of copy machine,warning mark which can not be discriminated by human eyes will emerge after copy. Tampered or fake certificates can be verified by compar-ing embedded information which is extracted from scanned image of certificate with plain text printed on the certificate. This method is applied in many bills and certificates. Experimental results show that the identifica-tion accuracy is above 98%     

A morphology screen coding anti-counterfeiting method based on visual characteristics

A paper information anti-fake and tamper-proofing method based on human visual characteristics and morphology screen coding technology is proposed. Through controlling the distribution of mathematical morphology of screen dot-matrix, warning mark and information are hidden in the background texture. Because of the differences between human vision and the duplicate characteristics of copy machine, warning mark which can not be discriminated by human eyes will emerge after copy. Tampered or fake certificates can be verified by comparing embedded information which is extracted from scanned image of certificate with plain text printed on the certificate： This method is applied in many bills and certificates. Experimental results show that the identifica- tion accuracy is above 98%.     

基于CCD图像的LED显示屏亮度均匀性评估方法

将CCD摄像机用于LED显示屏亮度特征数据的采集,深入分析了LED显示屏CCD感光图像的特点,在此基础上,完成了感光单元的识别以及亮度特征数据的提取,提出了一种通过计算亮度特征图像各部分之间的相似程度评估显示屏亮度均匀性的方法。针对亮度特征图像,采用在水平和垂直方向上各等分为2块以及直接将其等分为4块2种分块方法,分别计算各图像分块之间奇异值向量的夹角以度量其相似程度,最后将各分块相似度的平均值作为该显示屏样块亮度均匀性的度量。实验结果表明,2种分块方法对同一组显示屏样块的亮度均匀性评估结果是一致的,均与人的主观感觉相符。