A mechanism of automatic 3D object modeling

The symbolic representation of 3D objects is the fundamental knowledge for computer systems to understand the environment. This knowledge is usually assumed to exist in a computer but can also be acquired by accumulating spatial features extracted from sensory inputs at different viewing directions. This paper first investigates surface visibility and, then, after introducing mass vector chains (MVC), discusses the relationship between MVC and the spatial closure of object models. An automatic modeling mechanism is established with the observation that the boundary of an object is closed only if the MVC of its model is closed or, alternatively, the tail-to-head vector of an unclosed MVC estimates the visible direction of the missing surfaces. Experimental results and an algorithm are also given at the end     

结构光三维测量系统的建模与标定

改进了结构光三维测量系统的数学模型,将投影仪的内外部参数引入其中,并在该模型的基础上采用了一种投影仪标定的新方法.为了提高黑白摄像机在暗区的对比度用红/蓝棋盘代替了黑/白棋盘.将投影仪看作是摄像机的倒置,统一了标定摄像机和投影仪的方法.在3dMA×仿真环境下分别标定了摄像机和投影仪,标定实验的相对误差小于0.32%.利用已经标定的结构光三维测量系统进行重构仿真实验,测量误差小于0.136mm.     

A high-speed and continuous 3D measurement system

A new system for high-speed and continuous 3D measurement is presented. It is based on the slit-ray projection method. The key component is the image plane constructed by a position-sensitive device (PSD) array that is horizontally un segmented and linear, but vertically numbered. All PSD row elements are attached to their respective analog signal processors. The analog signals are multiplexed and digitized by multiplexers and A/D converters at appropriate sampling intervals and stored in memory. By virtue of this configuration of the image plane, basis data for 3D measurement are acquired during only one scan of the slit ray at high speed in the form of memory addresses and data. Moreover, if we use large capacity and/or dual port memories, we can continuously obtain 3D range data for as many scenes as needed. The trial system has been implemented with a newly designed 128-channel PSD array and has verified our method, enabling us to obtain successive 3D range data at video rates with an error within±0.3%.     

复杂矿床三维建模与地质自动绘图技术研究*

运用大型三维矿业软件Surpac创建了某矿深部矿床的地质数据库,构建了断层、地层和矿体的三维实体模型,并以此为基础对Surapc进行了二次开发,编制了适合多个中段的复杂地质自动绘图程序。实际应用表明,所建立的矿床三维模型可靠,利用开发的自动绘图程序生成的地质剖面图与传统绘图相比,在绘图质量、方便性等方面有突出优势,可应用于矿山资源评估、开采计划编制以及采矿设计等工作。     

A cost-effective and automatic surface defect inspection system for hot-rolled flat steel

Defective steel brings economic and commercial reputation losses to the hot-strip manufacturers, and one of the main difficulties in using machine-vision-based technique for steel surface inspection is time taken to process the massive images suffering from uneven illumination. This paper develops a modular and cost-effective AOI system for hot-rolled flat steel in real time. Firstly, a detailed system topology is constructed according to the design goals covering the vast majority of steel mills, lighting setup and typical defect patterns are presented as well. Secondly, the image enhancement method is designed to overcome the uneven-lighting, over- or under-exposure. Thirdly, the defect detection algorithm is developed based on variance, entropy and average gradient derived from non-overlapping 32×32 pixel blocks of steel surface images. Fourthly, the proposed algorithms are implemented on FPGA in parallel to improve the inspection speed. Finally, 18,071 contiguous images (4096×1024 pixel) acquired from 7 defective steel rolls have been inspected by the realized AOI system to evaluate the performance. The experimental results show that the proposed method is speedy and effective enough for real applications in the hot-rolled steel manufacturing, with 92.11% average accuracy while 5.54% false-negative rate.     

Automatic 3D model reconstruction of cutting tools from a single camera

Collision detection by machining simulation requires the 3D models of rotating cutters. However, the 3D models of a cutter and holder are not always available. In this paper, a new method is proposed to design an automatic vision-based 3D modeling system, which is able to quickly reconstruct the 3D model of a cutter and holder when they are installed onto the spindle. Only a single camera is mounted on the machine tool to capture the image of the rotating cutter and holder. By viewing the rotating cutter and holder as an object of surface of revolution, the contour of the imaged cutter and holder can be used to reconstruct the 3D model as a stack of circular cross-sections. Then the complete generating function of the cutter and holder can be recovered from the cross-sections. Finally, the 3D model of the cutter is built by rotating the generating function around the spindle axis. The effectiveness and accuracy of the proposed method are verified by experiments on-machine using 12 kinds of cutters and holders, which can satisfy the requirement of collision detection.     

A vision-based system for automatic growing ring detection and measurement

An automatic visual inspection system for wood growing ring identification and measurement is described. Given the irregular contrast distributions in wood samples, the identification of these elements is not straightforward. Furthermore, it is observed that many rings exhibit very narrow widths. To overcome these problems, several new methods are introduced, namely at the local image scale definition and at the image segmentation levels. First, local scales are automatically computed and applied for ring center identification. This information is then used to reconstruct the noisy image signal, which is segmented using a local minimum distance-minimum cross-entropy principle. The system uses a reduced and intuitive set of user defined parameters; for this reason, it is easy to tune.     

西林瓶缺陷自动视觉检测方法与系统研究

与传统的西林瓶缺陷人工检测方法相比,在线视觉自动检测具有巨大优越性。设计了一套西林瓶缺陷自动视觉在线检测系统,研究了系统的机械与电气结构,并设计了针对西林瓶的视觉成像与图像获取装置;根据西林瓶各部位的形状特殊性,针对性地提出了具体的检测方法。选取各类缺陷样品100瓶进行测试,结果表明该系统检测准确度较高,能满足实际生产的需求。     

Stereo vision system for precision dimensional inspection of 3D holes

This paper presents a machine vision system for the high-accuracy 3D measurement of holes on the surface of industrial components. This is a very important application for inline quality inspection in assembly plants. A CAD-based stereo vision approach is adopted. The introduction of several novel techniques enables the system to achieve high robustness in versatile industrial environments, rapid response, and accuracy below 0.1 mm. These are demonstrated by extensive experiments with synthetic and real data.Received: 10 May 2002, Accepted: 25 April 2003, Published online: 7 October 2003     

A multiview 3D modeling system based on stereo vision techniques

This paper introduces a stereo vision system to automatically generate 3D models of real objects. 3D model generation is based on the merging of multiview range images obtained from a digital stereo camera. Stereo images obtained from the camera are rectified, and a correlation-based stereo matching technique reconstructs range images from them. A turntable stage is also employed to obtain multiple range images of the objects. To register range images into a common coordinate system automatically, we introduce and calibrate a turntable coordinate system with respect to the camera coordinate system. After the registration of multiview range images, a 3D model is reconstructed using a volumetric integration technique. Error analysis on turntable calibration and 3D model reconstruction shows the accuracy of our 3D modeling system.Received: 2 August 2003, Accepted: 20 September 2004, Published online: 25 February 2005 Correspondence to: S.Y. Park     

A CAD-based 3D data acquisition strategy for inspection

The use of a laser range sensor in the 3D digitalization process allows significant improvement in acquisition speed and in 3D measurement point density. However, if we want to use these 3D data in applications that require data with a high degree of accuracy like inspection tasks, it is mandatory that the 3D points be acquired under the best conditions of accuracy. During 3D capture of a part, several sources of error can alter the measured values. Thus we must find and model the most important parameters affecting the accuracy of the range sensor. This error model, along with the CAD model of the part, is used to produce a sensing plan to completely and accurately acquire the geometry of the part. The sensing plan is comprised of the set of viewpoints that defines the exact position and orientation of the camera relative to the part. There is no limitation with regard to the shape of the part to be digitalized. An autosynchronized range sensor fixed on a coordinate measuring machine was used. For this sensor, the accuracy of the 3D measured points is a function of the distance and of the angle of incidence relative to the surface. The strategy proposed to find the acquisition plan guarantees that the viewpoints meet the best accuracy conditions in the scanning process, solving the occlusion problems. It was found that the 3D data acquired by using the proposed strategy are around 30% more accurate than the 3D data obtained in a standard acquisition.Received: 6 May 2001, Accepted: 8 November 2002, Published online: 13 November 2003 Correspondence to: Flavio Prieto     

一种新型人体三维建模系统的设计

设计了一款新型的人体三维建模识别系统。系统采用2片TI TMS320C64x+数字信号处理器组成算法核心单元,采用S3C6410嵌入式处理器实现时序及总线控制功能。该系统无需人体佩戴任何骨骼传感器网络,仅通过光学摄像头及图像处理算法即可完成人体三维运动建模,并可实现多人体运动目标的实时追踪功能。给出了该系统的实时多人三维运动建模结果,实测效果良好。     

基于CATIA的三维自动布线系统开发

提出了一种新颖的整机三维布线设计模型,以CATIA V5R20 SP7为平台,通过二次开发,调用预先设计好的接线表和器件表,实现了三维环境下在整机中的自动三维布线,解决了目前二维电子整机布线设计繁琐的问题,使得布线设计与工艺设计紧密结合,从而直观有效地验证布线过程的正确性,实验表明辅设效果较为理想。     

An automatic inspection system for printed wiring board masks

This paper describes an automatic inspection system for printed wiring board masks. This system utilizes a hierarchical defect detection algorithm developed for inspecting high precision mask patterns for both printed wiring boards and integrated circuits. This algorithm makes use of geometrical characteristics of mask patterns to discriminate defects. Sufficient defect detection capability, as well as high inspection throughput, has been accomplished by hardware-implementation of the algorithm and inspection result utilization through retouching machines.     

An automatic surface inspection system for flat rolled steel

The paper describes a feasibility study of on-line classification of visible defects in flat rolled steel, as the steel emerges from the rolling mill. A visual signal developed by a television camera is processed by a software simulation of the proposed hardware system which stores information from the scans and alerts a small computer when a possible flaw has been detected. A pattern recognition algorithm, executable by the computer, makes the final detection and classification decision before the next coil is rolled. A detailed simulation of the hardware using photographs of steel defects is presented.     

A tangible goal for 3D modeling

As we progress into applications that incorporate interactive life-like 3D computer graphics, the mouse falls short as a user interface device, and it becomes obvious that 3D computer graphics could achieve much more with a more intuitive user interface mechanism. Haptic interfaces, or force feedback devices, promise to increase the quality of human-computer interaction by accommodating our sense of touch. The article discusses the application of touch feedback systems to 3D modelling. To achieve a high interactivity level requires novel rendering techniques such as volume-based rendering algorithms     

Design and development of automatic visual inspection system for PCB manufacturing

Inspection of solder joints has been a critical process in the electronic manufacturing industry to reduce manufacturing cost, improve yield, and ensure product quality and reliability. This paper proposes two inspection modules for an automatic solder joint classification system. The “front-end” inspection system includes illumination normalisation, localisation and segmentation. The “back-end” inspection involves the classification of solder joints using the Log-Gabor filter and classifier fusion. Five different levels of solder quality with respect to the amount of solder paste have been defined. The Log-Gabor filter has been demonstrated to achieve high recognition rates and is resistant to misalignment. This proposed system does not need any special illumination system, and the images are acquired by an ordinary digital camera. This system could contribute to the development of automated non-contact, non-destructive and low cost solder joint quality inspection systems.