基于VC＋＋的LED光电参数测试系统设计

本文针对发光二极管（LED）生产的实际需求,给出了新型LED光电参数测试系统的软硬件设计方案。利用功能强大的AVR单片机,结合高精度数控恒流源技术、光电转换处理技术、USB通信技术以及VC＋＋技术,实现了LED光电参数的在线测试,并提供了与分选设备通信的接口,适用于工业生产流水线上。实践证明,本测试系统实现了快速、准确、可靠的测试,以及测试自动化,提高了工作效率。     

基于脉冲式U-I 特性的高功率型LED 热学特性测试

热学特性是影响功率型LED光学和电学特性的主要因素之一,设计了一套基于脉冲式U-I特性的功率型LED热学特性测试系统,可以测试在不同结温下LED工作电流与正向电压的关系,从而获得LED的热学特性参数。该系统通过产生窄脉冲电流来驱动LED,对其峰值时的电压电流进行采样,同时控制和采集LED的热沉温度,从而获得不同温度下LED的U-I特性曲线。与其他U-I测试系统相比,文中采用了窄脉冲(1 s)工作电流,LED器件PN结区处于发热与散热的交替过程,不会造成大的热积累,大大提高了测量精度。实验中,对某功率型LED进行了测试,获得了该器件的电压、电流和结温特性曲线,并利用B样条建立该器件的U-I-T模型,进而实现了对其结温的实时在线检测。     

基于虚拟仪器技术的LED/LD P-I特性测试系统

介绍了一种基于虚拟仪器技术的LED/LDP I特性测试系统。系统采用虚拟仪器开发软件LabVIEW,提高了数据采集、处理能力及系统的拓展升级能力,达到了简化系统结构、降低系统成本的目的。实际测试证明本系统使用方便、效率高、结果可靠。     

采用光激励和光检测的LED电特性测试方法

针对目前用于测试LED光电特性多采用接触式的电注入检测方法存在系统复杂、成本高、检测效率低且易造成芯片损伤等不足,提出一种采用光激励和光检测的非接触式检测方法。通过获取光激励LED p-n结产生的光致发光（PL）光谱,在建立了LED PL、电致发光（EL）效应间的确切联系以及LED发光光谱特性与其电特性间的对应关系的基...     

非接触式LED结温测试

研究和分析了用LED的发光强度来表征LED的相对辐射强度和结温之间存在的线性关系,据此设计并实现了类似于正向电压法,基于相对辐射强度的非接触式测试系统,使用NI USB6210数据采集卡在虚拟仪器平台上完成了图像采集、图像处理、线性拟合、界面设计的任务,得到相对辐射强度值与结温之间的关系,根据线性拟合关系式可得到被测器件的结温。本系统具有界面简洁、算法可靠和结果稳定的优点,使用该系统分别对单颗LED和LED阵列的实验数据进行拟合发现结温和相对辐射强度之间具有较好的线性关系,从而验证了非接触LED结温测试系统的可靠性。     

可见光通信中的LED频率特性测试方法研究

针对可见光通信系统中LED的频率特性问题,提出了采用频谱分析仪的测试方案,设计、制作了以PinPD作为光电探测器的LED频率特性测试电路及收发系统。对流明、科瑞、欧司朗、三星等多种商用白光LED以及日本滨松的光通信用红光LED进行了测试,得出了具有较大参考价值的结论。     

多功能LED参数测试系统的研制

针对半导体发光二极管(LED)参数检测仪器智能化程度不高、功能单一、效率低等缺陷,利用功能强大的C8051F020单片机,结合高精度数控恒流/恒压电源技术,光电转换处理技术和虚拟仪器技术,实现了LED的电参数、色参数和空间参数等功能的实时测量.参数测试实验表明,该LED参数测试分析系统操作简单,测试效率高.     

彩色摄像机颜色分辨力测量

为实现对彩色摄像机颜色分辨力测试,设计了通过双离散颜色源、反射式准直光学系统和四杆靶靶标模块组成的测试装置。双离散颜色源分别产生经过标定的前景和背景颜色光束,经过准直光学系统,最终合成四杆靶测试靶标图像。该系统在测量过程分别获取各频率下从靶标图像中提取的目标靶标并对其进行色差计算,通过图像算法对测试靶标进行判断和识别,获得彩色摄像机的最小可分辨色差(minimum resolvable E difference,MRED)和最小可探测色差(minimum detectable E difference,MDED),实现对彩色摄像机颜色分辨力的客观检测。     

LED波长一致性和温度均匀性对背光源色差的影响

直下式动态三基色LED背光源具有色域广、寿命长、节能环保、对比度高等优势,但许多因素限制了其颜色的表现力。研究了LED波长一致性、背光温度均匀度两个因素对色差的影响,指出为使色差小于人眼所能分辨范围(CIE1976色坐标体系Δu′v′小于0.005),LED的主波长波动范围应低于5nm,背光源不同位置的最大温差应低于8℃。     

无线智能控制LED路灯系统的设计

随着社会生活和工业生产对环境保护、节约能源等的需求越来越多,LED路灯得到了越来越广泛的应用。本系统以MSP430F5438A单片机为调节核心,以LY-BL001无线蓝牙传输模块作为通信核心,由Buck变换器及其驱动电路、电压电流检测和报警等模块组成,建立了无线智能控制LED路灯系统。系统实现了光强检测、报警、过欠压闭锁等功能;无线智能控制LED路灯系统能够与Android手机进行信息交互,实现远程无线操作。     

荧光粉混色检测算法研究

在彩色显象管生产过程中,荧光粉混色是影响正品率的主要原因之一。本文对产生混色的原因进行了分析,归纳出绿粉残留、偏移、覆盖和颗粒四种混色类型,并在计算机上进行模拟。同时提出了一种基于方向数组搜索的混色检测算法。最后在DPS-8/15中型计算机系统上进行仿真实验,其结果表明,该算法具有检测正确率高,抗噪声能力强,运算速度快等特点。     

CSV: Image quality assessment based on color,structure, and visual system

This paper presents a full-reference image quality estimator based on color, structure, and visual system characteristics denoted as CSV. In contrast to the majority of existing methods, we quantify perceptual color degradations rather than absolute pixel-wise changes. We use the CIEDE2000, color difference formulation to quantify low-level color degradations and the Earth Mover's Distance between color name probability vectors to measure significant color degradations. In addition to the perceptual color difference, CSV also contains structural and perceptual differences. Structural feature maps are obtained by mean subtraction and divisive normalization, and perceptual feature maps are obtained from contrast sensitivity formulations of retinal ganglion cells. The proposed quality estimator CSV is tested on the LIVE, the Multiply Distorted LIVE, and the TID 2013 databases, and it is always among the top two performing quality estimators in terms of at least ranking, monotonic behavior or linearity.     

一种改进的火灾颜色模型检测算法

从火焰的颜色特征出发,综合考虑已有颜色模型的优缺点,提出一种改进的基于颜色模型的火灾检测方法.首先结合HSI颜色模型和YCbCr颜色模型对火灾图像进行预处理提取出可能火焰区域,然后在HSI空间上采用颜色空间距离法去除噪声.实验结果表明,该方法提高了火灾图像识别的准确度,并能在一定程度上消除干扰,具有较好的适用性.     

Color impulsive noise removal based on quaternion representation and directional vector order-statistics

A new method for detecting and suppressing impulsive noise in color images is presented in this paper. The proposed method is a type of switching vector filters, where the impulse detection is based on the order-statistic information about the color samples in the horizontal, vertical, and diagonal directions. The new solution first uses quaternion-based representation of color differences and median deviation-based techniques to search for the edge direction with the maximum number of similar pixels, and then utilizes the samples aligning with this edge direction to judge whether the current pixel is noisy or not and control the switching between identity (no filtering) and vector median filtering actions. Extensive experimental comparisons exhibit the validity of the proposed approach by showing significant performance improvements over other well-known color image filtering techniques.     

用计算机VGA显示器复现指定颜色的研究

如能用计算机控制在普通ＶＧＡ显示器上准确地显示出指定的颜色，那么计算机显示系统就将成为色度学、彩色视觉、印刷、印染等领域方便的、价格低廉的研究手段，为此要对计算机显示系统的颜色空间进行标定，这时遇到的主要困难是显示器显示特性的非线性，以及Ｒ、Ｇ、Ｂ三个通道之间的交联作用，我们通过对几种不同瑾显示的研究，对Ｒ、Ｇ、Ｂ三角交联规律作了探索并提出了存在三色交联时的显示特性表示公式和参数标定方法，从而实现     

Collaborative color calibration for multi-camera systems

This paper proposes a collaborative color calibration method for multi-camera systems. The multi-camera color calibration problem is formulated as an overdetermined linear system, in which a dynamic range shaping is incorporated to ensure the high contrasts for captured images. The cameras are calibrated with the parameters obtained by solving the linear system. For non-planar multi-camera systems, we design a novel omnidirectional color checker and present a method for establishing global correspondences to facilitate automatic color calibration without manual adjustment. According to experimental results on both synthetic and real-system datasets, the proposed method shows high performance in achieving inter-camera color consistency and high dynamic range. Thanks to the generality of the linear system formulation and the flexibility of the designed color checker, the proposed method is applicable to various multi-camera systems.     

引起阻焊膜色差的关键因素分析

在PCB阻焊外观品质控制中,阻焊的颜色是比较重要的一项控制点,对于使用同一型号阻焊油墨的一款生产板,板面阻焊出现明显的色差,客户一般不接受,目前业内对于引起阻焊色差的深层原因罕见报道。本文主要针对阻焊色差问题,研究了阻焊厚度、预烘时间、曝光能量、热固化温度时间等对阻焊颜色的影响,尝试从光学角度和阻焊的微观结构来解释引起阻焊色差的根本原因,同时研究了阻焊膜的色差所带来的可靠性问题,从结合力和其耐化学性方面做深入探讨。     

HDTV色度空间变换电路的设计与实现

介绍了色度空间变换电路的两种基本实现方法,即模拟方法与数字方法,说明了如何用可编程逻辑器件实现ＨＤＴＶ数字式色度空间变换电路及相应的色差信号滤波,抽取电路,并给出了电路设计的仿真结果。     

SIFT-flow-based color correction for multi-view video

During the multi-view video acquisition, color variation across the views tends to be incurred due to different camera positions, orientations, and local lighting conditions. Such color variation will inevitably deteriorate the performance of the follow-up multi-view video processing, such as multi-view video coding (MVC). To address this problem, an effective color correction algorithm, called the SIFT flow-based color correction (SFCC), is proposed in this paper. First, the SIFT-flow technique is used to establish point-to-point correspondences across all the views of the multi-view video. The average color is then computed based on those identified common corresponding points and used as the reference color. By minimizing the energy of the difference yielded between the color of those identified common corresponding points in each view with respect to the reference color, the color correction matrix for each view can be obtained and used to correct its color. Experimental results have shown that the proposed SFCC algorithm is able to effectively eliminate the color variation inherited in multi-view video. By further exploiting the developed SFCC algorithm as a pre-processing for the MVC, extensive simulation results have shown that the coding efficiency of the color-corrected multi-view video can be greatly improved (on average, 0.85 dB, 1.27 dB and 1.63 dB gain for Y, U, and V components, respectively), compared with that of the original multi-view video without color correction.     

基于德劳内三角剖分的彩色图像加权直方图表示及检索技术

经典的颜色直方图方法存在诸多缺陷，例如它不能表示图像中颜色的空间分布信息。为了进一步的提高图像检索能力，在分析图像特征的基础上，文章给出了一种基于角度图的直方图加权的图像表示方法。这种方法不仅保持了图像直方图简单方便的特点，同时又有效地将颜色的空间分布信息集成到直方图中。实验结果表明，对比经典直方图表示这种彩色图像的表示方法能获得更好的检索效果。