New optical measuring system for solder joint inspection

Due to specularity and complex 3D geometry, the visual inspection of solder joints has been regarded as one of the most difficult tasks and thus has not guaranteed accurate inspection results. This paper deals with an optical sensing system designed to inspect solder joints automatically. Taking into account a specular characteristic, a new optical solder joint inspection system is proposed to obtain the external profile of solder joints accurately. A laser scanning unit scans the area of solder joint and observes the angle of the reflected beam. To realize this measuring principle, the system is so composed that a galvanometer steers the direction of laser beam to a point to be measured, a mirror unit (a parabolic and a conic mirror) gathers the specular components of the reflected beam toward its center and a beam-receiving unit positioned along the mirror unit's center line detects the reflected beam. To classify the defects of solder joint, a statistical pattern recognition method is utilized. To verify the validity of the developed system, a series of experiments was performed for SOPs and QFPs in insufficient, normal and excess soldering condition. Based upon observation of the experimental results, the proposed system is found to show good performance for inspection of solder joint defects.     

Development of an ultrasonic inspection robot using an electromagnetic acoustic transducer for a Lamb wave and an SH-plate wave

For inspection of a storage tank and pipeline in service, the application of an automatic inspection system (nondestructive inspection robot) is desirable, because manual inspection is difficult to perfectly and exactly perform due to the enormous amount of inspection needed. However, an ultrasonic nondestructive inspection robot with a piezoelectric oscillator needs to touch only the material surface to be directly inspected using a coupling medium. That is, the material surface and the sensor must always be held by constant pressure in the vertical direction on the material side. Actually, it is difficult to overcome these problems; thus an ultrasonic inspection robot could not be widely applied. We then tried to develop an ultrasonic inspection robot with an electromagnetic acoustic transducer (EMAT) which did not require a coupling medium to inspect the circumferential pipe parts. We developed a special EMAT that could transmit and receive alternately a Lamb wave with high sensitivity and a SH-plate wave without influence by the welded part. The method by which the inspection robot turned around the direction of the steel pipe surroundings was executed by observing the tape pasted in the direction of the steel pipe surroundings with an installed CCD camera. In this report, the basic mechanism of this inspection robot and an examination of results are described.     

Scanning moiré and spatial-offset phase-stepping for surface inspection of structures

In order to develop a high-speed and accurate surface inspection system of structures such as tunnels, a new surface profile measurement method using linear array sensors is studied. The sinusoidal grating is projected on a structure surface. Then, the deformed grating is scanned by linear array sensors that move together with the grating projector. The phase of the grating is analyzed by a spatial offset phase-stepping method to perform accurate measurement. The surface profile measurements of the wall with bricks and the concrete surface of a structure are demonstrated using the proposed method. The change of geometry or fabric of structures and the defects on structure surfaces can be detected by the proposed method. It is expected that the surface profile inspection system of tunnels measuring from a running train can be constructed based on the proposed method.     

圆结构光视觉三维点管道缺陷检测及重构

管道内表面的缺陷检测对于保证介质运输安全,避免泄漏和爆炸事故非常重要。在分析三维点分布几何特征的基础上,对基于视觉检测获得的管道内表面三维点,通过判断同一圆周上相邻点法线夹角变化检测管道内表面的凹凸缺陷,采用空间点相邻三角平面法线加权平均获取空间点的法线。依据三维点呈圆周分布的特点,采用相邻圆周上点顺次连接进行快速三角剖分。基于上述方法对实际测量的管道内表面三维点和仿真三维点分别进行了凹凸缺陷检测和三维重构。该方法能实现径向变化小于0.1 mm的管道凹凸缺陷的检测和识别,三维测量精度为0.081 mm。     

非接触光电窥测仪瞄准及定位方法研究

在非接触光电窥测仪的设计中需要解决两个基本问题：一是如何通过特殊的光学手段把在内孔狭小空间中的被测信息提取出来;二是如何进行测头定位来解决测量基准问题。本文报导了我们设计的非接触光电窥测装置的工作原理。通过方案比较,提出了以图像位置偏移作为瞄准判据及５ 步定位方法,分析了它们的精度及灵敏度     

无限液体介质内管道轴对称纵向导波激发与传播特性研究

利用声-结构耦合有限元法,分别对轴对称分布径的向及轴向外力作用在无限液体介质内未充液及充液管道内壁所激发导波进行了模拟,并进一步利用短时傅里叶变换技术对瞬态波形作时频分析,在此基础上,结合色散及衰减曲线,探讨了外力分布特征对导波激发的影响。研究表明,无限液体介质内未充液管中L(0,2)模式及充液管中L(0,3)~L(0,4)模式皆具有高群速度、弱色散且弱衰减频带,适宜用于缺陷探测,而通过控制轴对称分布外力的频率,并令其沿轴向作用于管内壁或外壁,可实现上述导波模式的高效激发。      

基于梯度折射率透镜的管道内窥镜设计

 针对管道测试的需求,将梯度折射率透镜的光学性能与显微镜相结合,设计了具有大景深的管道内窥镜光学系统.在保证所需放大倍率的同时,利用梯度折射率透镜介质折射率渐变的特点,使该系统的景深增大为原来的200倍.该系统像面近似球面的特点使其更适合圆形管道内壁的检测,当它与CCD等器件相结合,不仅实现管道内窥镜的数字化测试,而且能通过监视器在更大景深范围内、方便的监测管道内壁的裂痕、磨损等清晰的图像.     

基于亚像素定位和虚拟圆扫描的齿轮在线检测研究

采用图像识别技术对微小塑料齿轮进行质量检测,针对缺齿、齿歪、披峰等齿形误差的随机性,运用三点定圆心法实现塑料齿轮内圆的粗定位,试验数据说明其运行时间比传统Hough变换大大缩短,并为亚像素定位提供了原始数据;提出的降维灰度矩法与最小二乘圆法结合,实现内圆圆心的亚像素定位,同时运用3σ原则迭代法提高了亚像素定位精度;用"虚拟圆扫描法"实现大小轮齿的齿形检测。结果表明该方法可以满足齿轮的自动检测。     

Optical detection of mechanically damaged areas on manufactured metal parts by spatial frequency filtering

An inspection of mechanically damaged areas on manufactured metal parts is necessary to produce high-quality products. A scanning probe on a sample is necessary for a conventional surface inspection system, which is time-consuming. We propose a novel high-speed detection method for defects on metal surfaces with rolling indentations. To obtain a large field of view in a measurement, we used a laser sheet that was expanded with a laser line generator and also used an expanded collimated beam, rather than a small laser spot as used in conventional techniques. Furthermore, we used an obliquely incident laser beam to suppress the effect of the rolling indentations surrounding defects, and also applied spatial frequency filtering to extract only defects. The spatial frequency filtering under oblique incidence is theoretically explained and defect extraction was investigated in experiments.     

基于BP神经网络的焊点自动光学检测

提出了一种新的表面组装焊点的自动光学检测分类方法。采用单层环形光源获取焊点图像,并根据归一化分割曲线方程将焊点图像分成四部分,分别提取其特征。使用BP神经网络将焊点按照锡量多少分成三类:少锡,容许和多锡。实验结果证明该方法分类正确率达到了99.2%,具有较高的实用价值。     

面向单向器星轮自动化装配的视觉检测定位

针对传统单向器星轮人工装配效率低下问题,分析了单向器星轮装配过程,构建了基于计算机视觉技术的工业机器人自动化装配方案。首先利用CCD摄像机捕捉星轮表面形貌图像,然后利用Open CV视觉库进行了摄像机标定,再结合图像噪声去除,Hough圆检测,轮廓提取等技术,实现了星轮位姿的非接触式视觉检测。最后以单向器为例验证了该检测方法的有效性,机器人通过视觉获取的星轮位姿信息完成自动化装配。     

Application of the laser generated focused-Lamb wave for non-contact imaging of defects in plate

The laser generation method of focused-Lamb wave is expected to have high defect-detection ability with advantages of non-contact testing. In this method, the laser beam is illuminated on the surface of the object through an arrayed-arc slit, and then the energy of the generated Lamb wave is concentrated on the focus point of arc. This focusing effect enables the concentration of higher wave intensity on the focus with better S/N ratio of signal, and has better spatial resolution compared to the conventional line arrayed method. This paper describes a 2-D imaging system using this laser generated, focused-Lamb wave combined with its detection by the air-coupled transducer. This technique is fully non-contact so it can be easily applied for the automatic inspection. The effectiveness of the proposed method was verified by experiments on a 1-mm thick aluminum plate with artificial drill-hole defect with diameters of 1mm. The 2-D image of was constructed by scanning and the result showed that the location and size of defects were clearly detected.     

紫外臭氧廓线探测仪快视系统的设计与实现

为了实现紫外臭氧廓线探测仪图像数据的实时处理,并为其装调和自动定标提供必要的功能支持,实现了臭氧廓线探测仪快视系统。该系统分析了臭氧廓线探测仪图像数据下传原理和自动定标的工作流程,设计了相互协调的三线程的工作方式,保证系统流畅运行;采用命名管道通讯机制实现自动定标功能。实验结果表明：该系统实时完成2个波段的数据解析、图像显示和辅助线绘制等功能,实验过程中系统运行流畅,无丢包现象,叠加线可提供像素级的对准精度;以50ms的积分时间进行自动定标,定标速度可达每分钟39个波段,三倍于两个熟练配合测试人员的定标效率。     

Inspection of a micro-cantilever’s opened and concealed profile using integrated vertical scanning interferometry

In this paper, we describe a method based on the proposed vertical scanning interferometry (VSI) for the measurement of both surface profile of the micro-cantilever and corresponding etching sacrificial layer beneath the cantilever by only one scanning. A white light source illuminates a micro-cantilever at a certain incident angle through a Mirau interference objective. With this arrangement the top surface of the cantilever and a normally obstructed surface profile beneath the cantilever can be assessed in the same system. A digital filtering technique based on Fourier transform and a Gaussian fit are implemented to simultaneously retrieve an envelope of two series of interferograms at the top surface of a cantilever and as well as area of interest underneath the cantilever. The retrieved envelope peaks, which represent the height information of points on the test surface, are plotted to show whole field surface contour and demonstrate its effectiveness as a means for micro-electro-mechanical systems (MEMS) dual/multi-layer inspection. Results obtained agree well with those of a commercial instrument and show that the proposed method is simple and accurate.     

Study on energy attenuation of ultrasonic guided waves going through girth welds

Ultrasonic guided wave is introduced as a new non-destructive long range pipe inspection method. It can be used to inspect pipe which is inaccessible to other conventional NDT methods, and rapid, long distance inspection can be achieved. An investigation of the guided ultrasonic waves traveling along pipe with special geometry characteristics, such as elbow, several girth welds, and some artificial defects is described. In this paper, factors that may cause attenuation of ultrasonic guided waves are discussed and energy attenuation of longitudinal and torsional guided waves is studied on an experimental pipe having seven girth welds. Good agreement has been obtained between the experiments and the predictions. In the end, the detection sensitivity and locating precision of two guided waves, namely longitudinal and torsional, were compared on defects, such as notch, burr and branch.     

Theoretical and experimental guideline of optimum design of defect-inspection apparatus for transparent material using phase-shift illumination approach

Optical Review - Machine vision system has great significance for the automatic inspection to enhance unclear defects. For the purpose of the improvement of the recognition accuracy in the...     

细管道内表面光电检测方法研究

管道是气体和液体传输的重要手段,管道内表面的检测对于工业和国防中管道泄漏事故的预防,减少环境污染和经济损失非常重要。随着电子和半导体技术的发展,光电器件逐步趋于小型化。介绍了基于激光阵列、PSD光电检测、光环截面以及结构光检测等光电检测方法的测量原理和系统构成,并在此基础上对不同光电检测方法的优缺点进行了分析和比较。分析结果表明：光电检测技术适用于管道内表面检测;并朝着快速识别缺陷、管道内表面瑕疵的精确三维测量以及三维图像直观显示管壁缺陷的方向发展。     

A Novel Laser-Based System for Measuring Internal Thread Parameters

Based on the theory of laser measurements, we propose a novel laser-based automatic inspection system for measuring the internal thread parameters, which integrates the laser-based measuring unit to detect the longitudinal section of the thread profile and the dual-axis moving stage for the movement of an undetected object. We design a special laser probe based on the bidirectional inclination scanning method for obtaining the thread-profile data. This method and structural design enables the laser probe to overcome the shortcomings of traditional methods for measuring large inclined surfaces and eliminate the impact of the lead angle. We compare our results of internal thread-parameter measurements with the coordinate measuring machine (CMM) system and investigate the repeatability with one internal screw ring gage by the system proposed. The experimental results show that the measurement accuracy of the thread angle is 2′ and the other parameters are less than 4 μm.     

Highly effective three-dimensional large-scale microfabrication using a continuous scanning method

Effective scanning is an important issue in two-photon induced stereolithography (TPS) for the reduction of the processing time required to fabricate three-dimensional (3D) nano/microstructures. In large-scale TPS based on a stage-scanning system, the large processing time due to the intrinsic slow response in the stage scanning system is a major obstacle to its use as a practical nanofabrication process. To overcome this drawback, we propose a continuous scanning method (CSM) for a stage-scanning system. In CSM, a pattern is generated with continuous movement of the stage during laser beam exposure. A stable fabrication window (SFW), which enables uniform motion of the stage without errors considering the stage characteristics, was obtained from fundamental experiments. Within the condition of a SFW, 2D and 3D microstructures having nanoscale details were fabricated with a whole scale range of several hundred micrometers using CSM.     

Automatic defect recognition of TFT array process using gray level co-occurrence matrix

This study proposed an automatic optical inspection (AOI) system for detection of thin-film transistor (TFT) array defects. gray level co-occurrence matrix (GLCM) and MATLAB regionprops function were used to calculate 53 TFT array defect features, which were inputted into the neural network to train the defect classifier. The images to be inspected were compared with a standard image first, in order to judge whether the TFT array samples have defects. For defective images of a TFT array, the proposed defect classifier can successfully recognize five kinds of defects in the process. According to the experimental results, the defect recognition rate of proposed system is verified to be 83.3%, which can replace manual inspection and reduce the risks of false inspections due to long duration manual work. Moreover, the proposed AOI system can improve testing efficiency and reduce manufacturing costs.