平面长波红外相机阵列定位误差分析与计算

长波红外相机阵列对近空无人机等小目标有很好的全天候预警能力。针对红外传感器像元间距过大而导致阵列对空间目标定位精度低的缺点,本文引入像元亮度值信息,通过计算阵列目标图像的光斑质心,从而改进了阵列空间目标定位算法。在此基础上,建立了传感器采样量化带来的误差模型,并对定位误差进行计算和分析。结果表明,本文算法定位误差小,能够实现目标定位效果。     

Self-similarity based structural regularity for just noticeable difference estimation

In this paper, we introduce a novel just noticeable difference (JND) threshold estimation model based on a spatial masking function taking both luminance difference and structural regularity into account. Existing spatial masking functions underestimate the JND threshold for irregular textural regions, because they mainly consider the amplitude of luminance change for simplicity. As regular areas show weak masking effect due to their self-similar structures while irregular regions present strong masking effect, the spatial structure directly determines spatial masking. To effectively measure structural regularity in images under different contents, we propose an adaptive non-local self-similarity analysis based procedure. Then we weight luminance differences with similarity coefficients and deduce a new spatial masking function. Finally, an accurate JND estimation model is introduced. Experimental results demonstrate that the proposed JND model has a better visual effect than other models: it injects much noise into the insensitive regions, whereas little into the sensitive regions.     

如何理解目标高分辨率雷达图像及其像素值

经过图像定标后的雷达图像及其像素值具有雷达散射截面（radar cross section，RCS）的量纲，但是对于该像素值是否能代表目标实际RCS电平一直存在不同的理解.本文通过引入与传统RCS定义相一致的目标散射函数和散射分布函数基本概念，结合经典目标的散射机理和雷达像分析，讨论复杂目标高分辨率雷达图像理解和对像素值的解释.研究表明:雷达图像的像素值不应直接解释为目标的RCS电平，但在空间频率域和图像域，两者数据之间满足帕萨瓦定理；在小孔径角成像条件下，空间频率域的RCS均值等于强度图像的全部像素值之和.     

Grey scale, the “crispening effect”, and perceptual linearization

One way of optimizing a display is to maximize the number of distinguishable grey levels, which in turn is equivalent to perceptually linearizing the display. Perceptual linearization implies that equal steps in grey value evoke equal steps in brightness sensation. The key to perceptual linearization is hence to understand the relationship between screen luminance (differences) and perceived brightness (differences). We start with an overview of psychophysical laws on the brightness-luminance relationship. We present alternative models from the literature for describing this relationship. Existing models are compared with our human-performance data that were discussed in an earlier paper. We show that Whittle’s model provides a good fit to our experimental data, provided that some of the model parameters are allowed to depend on the surround luminance. An alternative model by Kingdom and Moulden, however, needs to be modified in order to accomplish agreement with experimental data.     

Subjective Evaluation of Apparent Reduction of Chromatic Blur Depending on Luminance Signals

Chromatic blur seen along the contours of a figure on a color TV display is not so annoying if the contour luminance signal is sharp. This is due to the human visual property that chromatic blur is masked by the luminance by spatial luminance changes. This paper describes the subjective evaluation of the visual masking effect of chromatic blur depending on luminance signals. From the experiments, the chromatic blur becomes less perceptible with the increase in level of superposed luminance signals and the blur is more annoying in red than in blue or yellow. Highly saturated red figures cause poor picture quality.     

Luminance uniformity compensation for OLED panels based on FPGA

Aiming at the problem of luminance uniformity for organic lighting-emitting diode （OLED） panels, a new brightness calculating method based on bilinear interpolation is proposed. The irradiance time of each pixel reaching the same lumi- nance is figured out by Matlab. Adopting the 64×32-pixel, single color and passive matrix OLED panel as adjusting luminance uniformity panel, a new circuit compensating scheme based on FPGA is designed. VH L is used to make each pixel＇s irradiance time in one flame period written in program. The irradiance brightness is controlled by changing its irradiance time, and finally, luminance compensation of the panel is realized. The simulation result indicates that the design is reasonable.     

Design Methodology for High Brightness Projectors

The low luminance levels of light-emitting diodes (LEDs) compared to arc lamps make it difficult to design high-brightness LED-based projectors. Besides, the specificities of LEDs do not always allow using the same design schemes as with arc lamp-based projection displays. This paper performs a taxonomy of the techniques that can be used to increase the brightness of LED-based projection displays. We show that, in etendue-limited systems, the perceived brightness depends on the system etendue limit, the efficiency of the light engine, and the source luminance. The ability to improve each of these parameters depends on the design constraints. The system etendue limit can be increased at the expense of bulkier, more complex, and more expensive designs. The light engine efficiency can be increased by using free-form shape components adapted to the shapes and the emission patterns of the considered LEDs. The apparent source luminance can be increased at the expense of the flux by either recycling light or restricting the light collection to a smaller etendue with higher average luminance. Luminance can also be increased by using multiple color primaries (spatial multiplexing) or pulsed LEDs (temporal multiplexing). Finally, we review how light recycling can be implemented to convert polarization without increasing etendue.     

等离子体显示器亮度和光效改进方法

本文阐述了提高等离子体显示器（ＰＤＰ）发光亮度和效率的重要性，并就影响大屏幕等离子体显示器发光亮度和效率的因素进行了分析，对显示器亮度和光效的改进方法进行了分类，并对发光亮度和效率改进方面的现状、进展及存在的问题进行了概括和总结。     

论业务量相关性对排队性能的影响

探讨业务量的相关性对排队系统性能究竟会带来什么样的影响,对于高速网络中流量控制机制和资源分配算法具有非常重要的意义。该文采用了一种独特的方法,来分析业务量的相关性在一定的网络环境下对于排队系统性能的影响。仿真的结果显示:一定时间尺度范围内的长期相关性导致排队性能的恶化,而且这种影响对于增加缓冲区的大小并不十分敏感。而且,业务量序列的边际分布和Hurst参数仍不足以充分决定排队性能的好坏。     

基于实测校正因子的实时伽马校正算法

针对等离子显示器(Plasma Display Panel,PDP)反伽马校正过程中因荧光粉亮度饱和以及APL临界切换引起的灰度级失真和闪烁现象,提出了一种基于PDP发光特性的实时反伽马校正算法。该算法采用实测关键灰度级亮度和基于图像APL的校正因子补偿算法,通过实测亮度和灰度级之间的对应关系实现了灰度级的线性输出,引入校正因子消除了不同图像切换过程时的闪烁。50 in(1 in=2.54 cm)PDP实验结果表明,该算法能够减少大面积暗场区域存在的闪烁现象,消除显示图像输出灰度的失真和反转,增强显示画面的细节,提高显示画质。此外,算法采用分段式多项式拟合进行实时反伽马计算,使算法具有处理速度快,对电路依赖性小等优点。     

彩色显示器亮度和对比度的最优化设置

实验研究了彩色显示器亮度和对比度设置对显示器颜色特性的影响.将Neso彩色显示器的亮度和对比度分别设置为最大值的20、50、80和100 %共16种组合,详细地测试和比较了每种设置下显示器的黑点亮度、白点亮度、阶调再现曲线(TRC)、通道可加性、色域和色品恒定性等颜色特性,实验结果表明,亮度设置对黑点亮度影响明显,对比度设置主要影响的白点亮度,黑点对通道可加性、色域和色品恒定性影响很大.通过亮度、对比度设置使黑点亮度尽可能小,白场亮度达到使用要求,同时TRC不出现"横剪切"和"纵剪切"现象,则显示器达到了最优化设置.     

实时测量液晶显示器辉度及响应时间的研究

提出将不同的仪器组合达到实时量测液晶显示器辉度及响应时间特性,即利用搭配视效响应滤光片的光探测器检测液晶显示器响应时间,光辉度计量测液晶显示器辉度及色度,此搭配滤光片的探测器有直径10mm的大感光面积。设计了一种由光纤及准直透镜至光探测器的光学系统,此系统具有较小收光探头体积、调整光点大小及容易对位的优势。采用不同光纤及准直透镜设计收光光点大小,对于检测辉度较小液晶显示器,可选用较大的准直透镜。对于较高空间分辨率或较小待测物,可利用搭配不同光纤及准直透镜达到小的收光光点。根据不同规格要求可设计光纤及光纤两边的准直透镜。分析了检测液晶显示器不同视角及对于此系统的校正方法。该系统将可实现液晶显示器实时多点检测,达到快速、高分辨率的优势。     

A new automatic exposure algorithm for video cameras using luminance histogram

Automatic exposure (AE) is one of the indispensable functions of modern video cameras. According to the attention mechanism of human visual systems, peak regions in luminance histogram correspond to the region of no interest in an image. Based on this assumption, a new AE algorithm using the luminance histogram of an image is proposed in this paper. The algorithm finds the first two largest peak regions in the histogram and calculates the mean weighted luminance (MWL) of the entire image by weighting the luminance of pixels inside the two peak regions. The MWL is then used to control the exposure of video cameras. The weight of pixel luminance is decided by a set of quadratic curves, and the parameters of the quadratic curves are affected by the brightness of the image background. Fuzzy logic is also applied to optimize the practical AE systems. Results show that the proposed algorithm gives efficient exposure control over various scene tests.     

Static Replication Strategies for Content Availability in Vehicular Ad-hoc Networks

This study investigates replication strategies for reducing latency to desired content in a vehicular peer-to-peer network. We provide a general constrained optimization formulation for efficient replication and study it via analysis and simulations employing a discrete random walk mobility model for the vehicles. Our solution space comprises of a family of popularity based replication schemes each characterized by an exponent n. We find that the optimal replication exponent depends significantly on factors such as the total system storage, data item size, and vehicle trip duration. With small data items and long client trip durations, n ∼ 0.5 i.e., a square-root replication scheme provides the lowest aggregate latency across all data item requests. However, for short trip durations, n moves toward 1, making a linear replication scheme more favorable. For larger data items and long client trip durations, we find that the optimal replication exponent is below 0.5. Finally, for these larger data items, if the client trip duration is short, the optimal replication exponent is found to be a function of the total storage in the system. Subsequently, the above observations are validated with two real data sets: one based on a city map with freeway traffic information and the other employing encounter traces from a bus network.     

Learning background restoration and local sparse dictionary for infrared small target detection

This paper proposes a method for learning background restoration for infrared small target detection, employing a local sparse dictionary alongside an equalized structural texture representation. The method is specifically designed for the detection of small infrared targets, accommodating various levels of brightness, spatial size, and intensity. Our proposed model intelligently combines global low-rankness and local sparsity to estimate the rank of the background tensor, leveraging spatial and structural information to overcome the limitations posed by insufficient detailed texture knowledge. Subsequently, a structural texture representation, combining local gradient maps and local intensity maps, is applied to emphasize small objects. By comparing our method with nine advanced and representative approaches and quantifying the comparison using various metrics, the experimental results indicate that our proposed method has achieved favorable outcomes in both quantitative assessments and visual results.     

液晶屏低灰阶下显示不均的改善和研究

针对目前液晶显示屏在低灰阶下显示不均匀的问题,对基于图像处理的亮度矫正方法在液晶显示屏中的改善进行了实验。基于高精度超暗亮度CCD采集器,采集液晶显示屏在低灰阶下单个像素的亮度信息及Gamma曲线数据,并逐个像素进行矫正。重点介绍了该采集系统与其他采集设备的优势及亮度和云纹矫正算法,试验结果表明:该采集系统可以一次完成所有像素的亮度信息的采集,并能有效分辨各像素点的亮度,理论上均匀度可以提高到100%,在正常显示状态下,可以独立实时地对每一帧画面进行矫正,确保显示信息的真实性。     

Two-dimensional analysis of emitter-size effect on current gain for GaAlAs/GaAs HBT's

The current-gain dependence on emitter size (emitter-size effect) is theoretically investigated for GaAlAs/GaAs heterojunction bipolar transistors with an ion-implanted extrinsic base region, using a two-dimensional numerical model. It is clarified that the current gain degrades with a decrease in emitter size, depending on the carrier lifetimes in the extrinsic base region. From the calculated results, it is shown that the emitter-size effect is suppressed for a very-thin-base or a graded-base structure. On the other hand, the effect is enhanced for a double-heterostructure. These results are explained by taking account of the electron-density profile in the extrinsic base region. The mechanism of a lateral diffusion of electrons into the extrinsic base region is also discussed.     

LED视角亮度关系及其对显示屏亮度均匀性的影响分析

LED显示屏的均匀性有诸多因素决定,其中亮度均匀性是影响视觉效果的最主要因素。在分析亮度均匀性的过程中发现,LED管发光特性所决定的其在沿光轴方向上光强最强,沿发光面向四周光强逐渐减弱,因此,以LED管为基本像素构成的LED显示屏在法线方向上的亮度也最高,当偏离法线方向时亮度会不同程度的降低,这样由于LED管的性能参数及制造工艺等的影响使LED显示屏出现麻点、马赛克等亮度不均匀现象。本文以LED单管和单元箱体为研究对象,通过实验得出了LED视角与亮度的变化关系,深入分析了影响LED显示屏亮度均匀性的原因,并对亮度数据的采集方法以及生产过程中须注意的问题提出了相关建议。     

Zonal brightness coherency for video tone mapping

Tone Mapping Operators (TMOs) compress High Dynamic Range (HDR) contents to address Low Dynamic Range (LDR) displays. While many solutions have been designed over the last decade, only few of them can cope with video sequences. Indeed, these TMOs tone map each frame of a video sequence separately, which results in temporal incoherency. Two main types of temporal incoherency are usually considered: flickering artifacts and temporal brightness incoherency. While the reduction of flickering artifacts has been well studied, less work has been performed on brightness incoherency. In this paper, we propose a method that aims at preserving spatio-temporal brightness coherency when tone mapping video sequences. Our technique computes HDR video zones which are constant throughout a sequence, based on the luminance of each pixel. Our method aims at preserving the brightness coherency between the brightest zone of the video and each other zone. This technique adapts to any TMO and results show that it preserves well spatio-temporal brightness coherency. We validate our method using a subjective evaluation. In addition, unlike local TMOs, our method, when applied to still images, is capable of ensuring spatial brightness coherency. Finally, it also preserves video fade effects commonly used in post-production.     

Investigation of large-area OLED devices with various grid geometries

Luminance homogeneity is an important aspect for large-area (>1 cm²) organic light emitting diodes (OLED). Especially, high sheet resistances of transparent contacts lead to a significant brightness inhomogeneity caused by a drop of local potential difference. Therefore the implementation of thin low-resistance metallic grids onto transparent contacts is a crucial development aspect for large-area OLED design. We develop a finite-element electro-optical simulation for OLED using grid structures to optimize geometry, thickness and width of grid elements. We find an exponential relationship between luminance homogeneity and grid material volume, which leads to limitations of minimal grid line width and maximal emissive area for efficient development of large-area OLED.