A new switched-capacitor frequency modulated driver for light emitting diodes

A new type of drivers for light emitting diodes (LEDs) is introduced based on the switched-capacitor frequency modulation. In contrast to conventional constant dc current drivers, the current pulse is provided by this new switched-capacitor LED driver. In the present driver, the charging capacitor is charged and discharged through a LED and the current flow direction is controlled by a metal oxide semiconductor switch. The input current (and thus the LED brightness) is proportional to the switch clock frequency at relatively low frequencies and becomes saturated at relatively high frequencies. This new driver circuit is simple and robust and maintains high efficiency for a wide range of input powers. In addition, the dimming control is easily realized by modulating clock frequency. Finally, this LED driver consumes no dc current and thus provides inherent protection to LED in standby mode.     

将数学形态学应用于检测芯片机器视觉的研究

研制检测集成电路芯片的机器视觉系统,采用数学形态学方法对芯片图像进行滤波平滑处理,用于改善芯片图像的质量。结果表明:将数学形态学应用于检测芯片的机器视觉系统,提高了系统的检测速度和检测的准确性,满足了检测流水线对机器视觉系统检测实时性的要求。     

Efficient sampling for computer vision straightness inspection

Computer vision systems are the most versatile non-contact inspection systems. However, 100% scanning for the inspection of straightness of discrete industrial workpieces is time-consuming. As a result, a critical problem is the determination of the sample size for straightness inspection using computer vision inspection systems.This paper develops the methods to determine the acceptable sample size for estimating the mean line in the straightness inspection. The widest-prediction interval at different degrees of confidence to determine the sample size for estimating the mean line has been studied. The partial sequential test for testing the slope and intercept of the estimated mean line to determine the quality of straightness have also been discussed in this paper.     

计算机视觉二维刀具预调仪的研究

研究了计算机视觉二维刀形检测系统。由面阵CCD摄像机摄取刀形图像,通过硬件解调电路提取刀形轮廓数据并送入计算机。数据处理程序给出刀形曲线的参数值,并存入数据库及绘制出刀形曲线。根据系统的特性给出了定标方法。由于测试结果是以参数值的形式给出,便于程控加工时调用。系统具有高精度、高速度、自动化测试的特点,测量精度优于3μm。     

Dynamic junction temperature measurement for high power light emitting diodes

Junction temperature of high power light emitting diodes (LEDs), which is crucial for the thermal management of solid-state lighting, needs to be measured accurately. In this paper, a dynamic junction temperature measurement system for LEDs was proposed and the calibration including instrument calibration and factor K calibration were presented. The influence of the fast switch time in dynamic junction temperature test was analyzed and measurement errors caused by sampling delay were quantified. To prove the accuracy of the present system, comparison experiment was conducted. It shows a good agreement between the experimental data and reference value. Experiments also show that the measurement accuracy of the instrument can be up to 0.1?°C, and the standard error of temperature measurement can be controlled within 1%.     

Versatile multispectral microscope based on light emitting diodes

We describe the development of a novel multispectral microscope, based on light-emitting diodes, capable of acquiring megapixel images in thirteen spectral bands from the ultraviolet to the near infrared. The system captures images and spectra in transmittance, reflectance, and scattering modes. We present as examples of applications ground truth measurements for remote sensing and parasitology diagnostics. The system is a general purpose scientific instrument that could be used to develop dedicated simplified instruments with optimal bands and mode selection.     

Calibration of a wide-field frequency-domain fluorescence lifetime microscopy system using light emitting diodes as light sources

High brightness light emitting diodes are an inexpensive and versatile light source for wide‐field frequency‐domain fluorescence lifetime imaging microscopy. In this paper a full calibration of an LED based fluorescence lifetime imaging microscopy system is presented for the first time. A radio‐frequency generator was used for simultaneous modulation of light emitting diode (LED) intensity and the gain of an intensified charge coupled device (CCD) camera. A homodyne detection scheme was employed to measure the demodulation and phase shift of the emitted fluorescence, from which phase and modulation lifetimes were determined at each image pixel. The system was characterized both in terms of its sensitivity to measure short lifetimes (500 ps to 4 ns), and its capability to distinguish image features with small lifetime differences. Calibration measurements were performed in quenched solutions containing Rhodamine 6G dye and the results compared to several independent measurements performed with other measurement methodologies, including time correlated single photon counting, time gated detection, and acousto optical modulator (AOM) based modulation of excitation sources. Results are presented from measurements and simulations. The effects of limited signal‐to‐noise ratios, baseline drifts and calibration errors are discussed in detail. The implications of limited modulation bandwidth of high brightness, large area LED devices (～40 MHz for devices used here) are presented. The results show that phase lifetime measurements are robust down to sub ns levels, whereas modulation lifetimes are prone to errors even at large signal‐to‐noise ratios. Strategies for optimizing measurement fidelity are discussed. Application of the fluorescence lifetime imaging microscopy system is illustrated with examples from studies of molecular mixing in microfluidic devices and targeted drug delivery research.     

基于计算机视觉的圆轴直径精密检测

应用计算机视觉技术精密检测圆轴直径 ,在对圆轴图像边缘进行空间矩亚像素定位的基础上 ,直接利用截面边缘亚像素位置信息 ,精确计算分辨率截面的直径 ,并给出整个圆轴直径的估计。实践表明 ,本算法可达到 0 0 0 11mm的精度     

基于计算机视觉的晶振帽缺陷自动检测系统

针对工业现场中晶振帽的主要缺陷,通过计算机视觉系统来实现缺陷的自动检测.结合晶振帽的缺陷特点,论述了晶振帽缺陷检测系统的构成、图像处理及检测流程,提出一种基于计算机视觉的晶振帽缺陷检测方法.设计了缺陷检测系统的具体软件结构,并用模块化方法实现软件功能.该软件主要包括主程序模块、图像采集模块、图像处理模块和通信模块.实验证明,该检测系统能够准确地实现晶振帽缺陷的检测,满足自动化生产的需要,可在实际生产中代替人工检测.     

生产线零件编号检测系统的计算机视觉研究

计算机视觉检测(Autom ated V isual Inspection,AVI)技术是计算机检测的新发展,它使检测更具智能化和柔性化。提出一种新的TTFM算法,成功实现生产线零件编号的快速、精确的检测。     

Bootstrap approach for estimating process quality yield with application to light emitting diodes

Process capability indices have been widely used by quality professionals for measuring process performance. Although process yield is the most common criterion used in the manufacturing industry for measuring process performance, a more advanced measurement formula Y_q, called quality yield index, has been proposed as an alternative measure of process performance. Quality yield can be viewed as the classical process yield minus the truncated expected relative process loss, within the specifications, which focuses on customer satisfaction. By taking customer loss into consideration, the advantage of using the quality-yield measure as process performance is that the formula can be applied to processes with arbitrary distributions. Unfortunately, statistical properties of the estimated Y_q are mathematically intractable. Therefore, capability testing cannot be performed. In this paper, a nonparametric but computer intensive method called bootstrap is used to obtain a lower confidence bound on quality yield for capability testing purposes. Simulation studies are conducted to examine the sampling distribution of the estimated Y_q. An application using the index Y_q for the light emitting diode manufacturing process is presented for illustration purposes.     

基于双目视觉的水下定位系统

通过改进传统水上双目立体视觉定位方法使其适于水下机器人(ROV)的机械手等的定位.为适应复杂水下透视环境,针对水下的液体环境设计摄像机密封结构,引入了高次畸变参数对摄像机进行标定,以得到相机水下内外参数,然后针对传统较为复杂的双目摄像机视线(射线)相交求取目标点的方法,提出了一种基于前向平行校正的简单定位算法,并进行试...     

A real-time vision system for defect inspection in cast extrusion manufacturing process

The cast extrusion manufacturing process is the initial step which enables the creation of the raw materials, such as clear polypropylene film, needed for the flexible packaging printing process. The current methodology of controlling extrusion-related defect occurrences is attempted by a combination of statistical sampling and human inspection. However, due to the fact that the defects are small in size and hard to visualise in a clear thin film 2 m in width moving at a speed of 50 m/min. This results in poor product quality and high return ratio from customers. To the best of our knowledge, there is no system available that can accurately detect such defects. This research investigates possible defect detection methodologies and has subsequently proposed a system that is capable of real-time monitoring of defects on the cast extrusion manufacturing process. The proposed system utilises the refraction of a collimated light source, which is referred to as Mie light scattering. A vision analysis system is subsequently used to perform a blob analysis to detect the contrasting dark regions of the defects. Two test rigs were constructed to test the feasibility of the system. The first test rig was created to test the theoretical Mie scattering principles and the performance of the image analysis software in practice. The second test rig was created to test the practicability of integrating the Mie scattering theory on the physical cast extrusion line. The results obtained from the tests indicated a success rate of 90% in identifying gels and a 100% success rate in correctly identifying all the die lines presented in the tested samples. It is also deduced that the software has a capability to detect gel granules with a diameter greater than 480 μm and die lines with a thickness greater than 320 μm amid complete repeatability, ensuring that the proposed system fully conforms to the standard industrial requirements.     

基于机器视觉的汽车刹车片自动检测系统

为了提高汽车刹车片的检测效率和准确性,设计了基于机器视觉的汽车刹车片自动化检测系统。针对自动化检测需求搭建了基于可编程逻辑控制器(PLC)的自动化测试平台,开发了相应的视觉系统。结合VisionPro和C#语言开发了检测软件,完成了图像获取、图像校准、图像定位、尺寸测量、缺陷标示、字符识别等任务。实验结果表明,系统可快速、准确地识别出工件的尺寸、表面缺陷和字符。     

基于机器视觉的活塞环闭口间隙自动检测

利用位置补偿功能对标准环规进行自动定位,通过线阵CCD实现对活塞环图像的高分辨率图像采集,应用小波变换准确提取活塞环的图像边缘,自动计算活塞环的闭口间隙,从而为自动判定闭口间隙尺寸是否合格提供可靠的测量依据,实现对活塞环闭口间隙的自动检测。     

双目立体视觉检测系统正向最优化设计方法研究

立体视觉技术在工业检测中的应用越来越广泛,如何提高检测精度、降低系统构建难度至关重要。本文提出了一种视觉检测系统正向设计最优化方法,以系统的检测精度为目标函数,以可选器件、工作环境、被检工件为约束条件,以光学参数和系统参数为决策变量,将系统设计问题转化为多目标不等式约束的非线性最优化模型,通过Kuhn-Tucker约束条件极值点的求解,获得最优的系统设计参数。本方法为立体视觉检测系统的设计提供了理论参考,可避免传统逆向设计方法中依赖主观经验而无法确认结果的最优性,以及大量反复试验而造成设计成本浪费等问题,实验验证了方法的可行性。     

汽车平面显示器计算机视觉检测系统

现代汽车上广泛采用了平面显示器显示一些驾驶信息,对其逻辑显示状态必须进行视觉检测.本研究采取了基于VB和VC图像处理的方法设计测试系统.该系统利用CAN总线通讯模块实现平面显示器的控制,利用摄像头采集图像,并把采集到的图像和标准图片比对.从结果来看,产品的测试正确性在99.8%以上,实践证明此方法实现了对平面显示器的快速自动化检测,是一种行之有效的方法.     

Ball stud inspection system using machine vision

In this paper, a vision-based inspection system that measures the dimensions of a ball stud is designed and implemented. The system acquires silhouetted images by backlighting and extracts the outlines of the nearly dichotomized images in subpixel accuracy. The sets of boundary data are modeled with reasonable geometric primitives and the parameters of the models are estimated in a manner that minimizes error. Jig-fixtures and servo systems for the inspection are also contrived. The system rotates an inspected object to recognize the objects in space not on a plane. The system moves the object vertically so that it may take several pictures of different parts of the object, resulting in improvement of measuring resolution. The performance of the system is evaluated by measurement of the dimensions of a standard ball, a standard cylinder, and a ball stud.     

Glue dispenser route inspection by using computer vision and neural network

Design of a glue dispenser route inspection system based upon the track of adhesive glue is the focus of this article. The defects of the glue track such as deformation, offset, scrape, and broken glue may affect the quality of production and efficiency. An automatic dispenser route inspection system in combination with the techniques of back-propagation neural (BPN) network with computer vision is developed. Before dispensing, the positioning process of the dispenser system is significant. A simple positioning method is developed to ensure the glued object mounted on a platform is in an acceptable position for glue shooting so that any likely failure due to inaccurate positioning is avoided. Thus, the positioning problem will therefore not influence the cause-and-effect failure investigation of other factors. The images of the track are acquired and then preprocessed to extract the features (coordinates of edge) for inspections. By checking the number of the searched pixels of the boundary of the glue track compared to the edge number of a uniform one, serious failure can be identified. For further diagnosis, six parameters including the average width and its standard deviation (SD) of the track, average offset and its SD, and the average deviation between the neighboring points on the left and right sides are designed as the input units in the input layer of a three-layer neural network and trained with experimental patterns. Using this BPN network system, the recognition rate is able to achieve 96.45% for additional arbitrarily chosen samples.     

基于机器视觉的封印产品防伪条码在线检测系统

本文介绍了应用机器视觉技术开发的封印产品防伪条码在线检测系统,采用虚拟仪器开发平台LabVIEW完成系统的软件开发,实现了封印产品条码的在线自动化检测及顺序检验.针对检测环境中光照不均对识别率的影响,本文提出了一种基于ROI分割的相机增益智能调节方法,有效提高了在单次检测中不同位置的封印产品条码的识别率.实践证明该系统在识别率、效率和稳定性上均满足大批量生产的要求.