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%.     

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 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     

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 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。     

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     

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.     

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.     

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.     

基于计算机视觉的织物疵点自动检测

介绍了基于计算机视觉的织物疵点自动检测的工作原理;分析了织物疵点自动检测的功能结构和自动检测硬件组成框图;阐述了织物疵点图像的半阈值化处理、边缘检测和疵点特征求取方法;给出了织物疵点自动检测的程序框图、织物疵点的坯布图像及其疵点统计结果。     

一类特殊导线的自动切线控制系统研制

为了满足航空、航天等领域对带尼龙保护层导线切割的特殊要求,研制了一种专用自动切线控制系统。该系统以ARM7系列微处理器LPC2131为控制核心,采用滚轮连续运转带动导线进给,鼓风机通过加热枪管吹出高温热风烫化导线保护层,切刀高速运动切割导线的方式实现系统送线、烫线、切线一体化操作,使系统全程自动化。     

基于立体视觉的接触式三维测量系统

传统的三维接触式测量方法存在着速度慢、测量范围受限等缺点,而纯粹的非接触式测量方法则存在着特征边缘无法获取的问题。结合两种测量方法,设计了一种新的三维测量系统,该系统采用立体视觉技术对接触式测头的空间位置和姿态进行定位,进而间接计算接触式探针针尖位置来完成空间点的三维坐标测量。实验结果表明:系统测量精度优于0.2 mm,能够应用于工业现场进行复杂工件的典型几何特征检测和模型重构。