基于点阵编码的三维主动视觉标定

提出一种基于位错点阵编码三维成像系统的标定方法.首先在物空间建立三维数据基准,然后通过基准传递的概念标定摄像子系统,再通过建立摄像子系统坐标系与投影子系统坐标系之间的约束关系,将标定后的摄像子系统的准确度传递到投影子系统坐标系.摄像子系统坐标系与投影子系统都具有标定的准确度之后,可以根据位错点阵编码三维成像技术的解码算法获得深度图像空间坐标的计算值,然后将其与物体空间的三维标定数据基准进行比较,建立目标函数为误差平方和最小的非线性优化方程.通过迭代求解这个优化方程,最终获得三维系统的结构参量.实验结果表明,经过三维标定的位错点阵编码三维成像系统,对300×300×80 mm3的测量体积内,可以获得X方向的标准差为0.29mm和Y方向的标准差为0.24mm,Z方向的标准差为0.29mm的测量准确度.     

基于机器视觉的高速带钢孔洞检测系统

针对宝钢冷轧1420酸轧联合机组带钢孔洞缺陷在线检测需求，结合机组现场条件，自主开发了恶劣危险环境下的高速带钢孔洞检测系统。该系统以机器视觉技术为基础，配置高性能透射式照明光源和高速线扫描CCD图像传感器，能够获得高质量的带钢图像；系统检测软件采用快速高效的目标识别和边缘检测算法，可在30ms内完成1幅图像的处理计算，实时判定孔洞的存在与否，并将检测结果发送至服务器。系统采用C/S模式作为网络架构，实现检测数据在客户端和服务器之间的可靠传递。系统两年多的上线运行证明：该系统在冷轧机出口十分恶劣的环境条件下，可长期连续工作，准确高效地检出带钢孔洞缺陷，具有卓越的检测性能和良好的稳定性。     

基于光学原理的三维形貌测量技术研究

为了加快产品开发和保证产品制造质量需要对物体的三维形貌进行精确的测量。光学形貌测量技术由于其高分辨率、无破坏、数据获取速度快等优点而被认为是最有前途的三维形貌测量方法。介绍了各种基于光学原理的三维形貌测量技术,并作了比较深入的分析和对比,为正确和广泛应用三维形貌测量技术提供了参考。给出了在该领域的发展方向和研究热点。     

3-D computer vision in experimental mechanics

Optical methods that give displacement or strain fields are now widely used in experimental mechanics. Some of the methods can only measure in-plane displacements/strains on planar specimens and some of them can give both in-plane and out-of-plane displacement/strain fields on any kind of specimen (planar or not). In the present paper, the stereovision technique that uses two cameras to measure 3-D displacement/strain fields on any 3-D object is presented. Additionally, a quite inclusive list of references on applications of stereovision (and 3-D DIC) to experimental mechanics is given at the end of the paper.     

3-D vision and range finding techniques

The introduction of third generation robots in automated systems is impeded by the absence of 3-D sensors collecting panoramic range data at medium distance (0–10 meters) in a large volume (up to 100 m³). The work described in the present paper offers a certain number of solutions to this general problem. Our system is built around a 2-D passive machine vision connected to various cameras (VIDICON and CCD). The host computer (HP 1000) pilots numerous sorts of range finders (acoustic and optical).

The concept of multisensory range finders is introduced to allow the best use of each type (active methods). This 3-D vision has been tested in two fields of application:

• -in robotics for the absolute of a mobile robot;

• -in audiovisual for fixing objects or actors in a 3-D synthetic scene.

In some cases the absolute location problem is solved with an opto-electronic remote tracking measurement system. It is the last part of our 3-D machine vision.     

Active vibration control for structural-acoustic coupling system of a 3-D vehicle cabin model

This paper presents an active vibration control system for use with structural-acoustic coupling system using piezoelectric actuators and piezoelectric sensors. For modelling a complicated 3-D vehicle cabin model, the structural-acoustic coupling system is analyzed by combining the structural data from modal testing with the acoustic data from the finite element method. Through the structural-acoustic analysis program, the control plate and the control modes are selected, which are most effective for attenuating its noise. A robust LQG controller with two sensor signal filters is designed to remove the experimental problems such as the spillover effect due to uncontrolled modes. The robust LQG controller for the structural-acoustic coupling system can reduce the interior noise of the cavity as well as the structural vibration of the cabin.     

Shifted-phase calibration for a 3-D shape measurement system based on orthogonal composite grating projection

This paper proposes a novel method for reducing measurement error caused by spectrum overlapping in orthogonal-composite-grating-based 3-D measurement method. For 3-D measurement systems based on orthogonal composite grating projection, spectrum overlapping causes phase of each deformed phase-shifting fringe changed differently, which violates the principle that the shifted phases between adjacent deformed fringes must be equivalent to 2π/3, and therefore results in phase measurement error. The proposed shifted-phase calibration method is based on that phase variation of each deformed fringe is independent of height and reflectivity of the measured object. Three composite gratings are projected on the reference plane, and each carrier channel includes three phase-shifting gratings needed in phase measuring profilometry (PMP). Because the adjacent phase-shifting fringes demodulated from the same carrier channel have the phase difference of 2π/3, we can respectively calculate the reference plane's phases of three carrier channels by the phase algorithm of PMP method, and the shifted phases between them are obtained. When an object is measured, the shifted phases between deformed phase-shifting fringes can be calibrated. A new 3-D measurement mathematical model is set to reconstruct object. Our experiments prove that the proposed method can effectively restrain the effect of spectrum overlapping and improve measurement accuracy almost one times.     

Real-time 3D shape inspection system of automotive parts based on structured light pattern

The non-contact 3D area sensor technology has achieved many successes in a variety of offline measurements. However, it has not been implemented for online measurement in the automotive production lines. The biggest challenge is the capability of simultaneously satisfying the efficiency, reliability, and accuracy requirements. For this purpose, a real-time 3D area sensor based on structured light pattern is proposed. To satisfy the requirement of online measurement, a one-shot pattern using monochromatic light is proposed. Compared with the previous patterns, this pattern is more robust because it can avoid the influence of the ambient light and the inspected part reflective property. Moreover, the requirement of the accuracy performance is achieved by the pattern primitive which is similar to the corner of the checkerboard since it can provide high accuracy performance even when the occlusion occurs; also, the pixel-to-pixel calibration strategy is utilized to increase the accuracy of the inspection system. Such a real-time shape measurement system has been successfully developed in our laboratory. Last, the evaluation experiments are conducted. The experiment results demonstrate the robustness and accuracy of the approach on automotive parts with different surface properties.     

三维形貌检测中自动参考栅技术的改进

通过对形貌检测中理论参考面相位分布规律的分析 ,对三维形貌轮廓术中参考面相位自动生成技术进行了研究。利用采集的待测物体栅线图样中未变形区域对应相位信息 ,通过最小二乘迭代法数据拟合 ,获得理想参考面相位分布参数 ,也就是获得理想参考面上的相位分布。由于不需另外采集实物参考面变形光栅图像 ,不仅减少了实物参考面的采集步骤 ,而且不需要对实物参考面相位进行求解 ,这样就可以真正实现只采集一幅图像解调形貌 ,从而提高测试速度 ,同时还可避免由于采用实物参考面而存在的误差 ,使得求解兼有理想参考面方法与实物参考面方法的优点。利用改进的方法对塑胶小熊猫面具进行了实际测量 ,给出了测试结果     

基于图像处理的钢坯侧面形状检测系统

基于机器视觉的钢坯侧面形状检测系统是由面阵CCD、激光发射器、激光接收器以及工控计算机等组成。通过面阵CCD拍摄到钢坯侧面图像,经过工业控制计算机进行数字图像处理分析和计算,提取钢坯侧面边缘高度和厚度,进而通过专用软件分析出钢坯头部和尾部的形状信息,从而有效地对入口钢坯翘头扣尾的异常状态发出报警信号。将异常信号传送给外围控制系统,以实现对钢坯的控制。     

Moiré technique in 3-D machine vision

Moiré technique using projected fringes is a promising method in 3-D machine vision for the mapping of surface profiles of objects compared to ideal masters. This paper describes a CAD-integrated system using a CCD camera and a digital image processor. Applications to industrial inspection of CAD-generated master objects are presented.     

基于SfS的3D视觉测量研究

提出了一种将Shape from Silhouette(SfS)技术应用在三坐标机上的新方法,即用摄像机获取图像,用三坐标机作移动平台,构建视觉测量系统,应用SfS技术对物体进行三维测量。该视觉测量系统扩展了坐标机功能,扩大了其应用范围。实验结果表明,该视觉测量系统具有SfS技术和坐标机两者的优点,重构物体三维模型的过程简单快捷,精度高于0.4mm,其结果可作为坐标机智能测量的基础,是一种非常实用的方法。     

Dynamic 3-D shape measurement method based on FTP

In this paper, we propose a method for dynamic three-dimensional (3-D) shape measurement based on Fourier transform profilometry. A sequence of dynamic deformed fringe images can be grabbed by a CCD camera and saved on a disk rapidly. By a Fourier transform, filtering and inverse Fourier transform, a sequence of phase-maps can be obtained. By unwrapping these phase maps in 3-D phase space, we can obtain the shape of the dynamic object at different times. In this paper we also propose the algorithm of a phase difference between two deformed fringes, and the 3-D phase unwrapping method based on the phase difference algorithm. The computer simulation and experiment results show that this method can efficiently deal with the dynamic 3-D shape measurement.     

3-D shape measurement based on complementary Gray-code light

A combination of phase-shift with Gray-code light projection into a three-dimensional (3-D) measurement system has been exploited to digitalize 3-D shape information of a tested object, even with a discontinuous surface. Unfortunately, the phase unwrapping will fall into an error, when an improper value of Gray coding is caused by mistake at the partial boundary of two adjacent binary words. To this end, a new complementary Gray-code method is proposed in this paper as well as the corresponding phase-unwrapping method. This problem of phase unwrapping could be cleverly solved by projecting an additional Gray-code pattern to extend this code and using the different and complementary boundary locations of the traditional and additional codes. The results of computer simulation and experiment confirm that this proposed method based on complementary Gray-code can reliably reconstruct the nature phase distribution of the tested object with only one extra fringe pattern.     

Active infrared thermographic inspection technique for elevated concrete structures using remote heating system

Conventionally, the inspection of elevated concrete structures requires the use of scaffolding or an aerial truck. In this study, elevated railway structures constructed of reinforced concrete were inspected using active infrared thermography. The inspection area corresponded to half of the middle slab covering an area of 16.8 m²; one inspection was carried out that took about 15 min. A remote heating system consisting of a 6-kW air-cooled xenon arc lamp and a scanner system was developed to detect hidden defects in elevated concrete structures without the need for an aerial truck or scaffolding. The generation of a thermal image and irradiation are carried out simultaneously by the beam scanning. High-contrast infrared thermal images can be obtained by the simple image processing procedure that is proposed.     

A novel calibration approach to structured light 3D vision inspection

Structured light 3D vision inspection is a commonly used method for various 3D surface profiling techniques. In this paper, a novel approach is proposed to generate the sufficient calibration points with high accuracy for structured light 3D vision. This approach is based on a flexible calibration target, composed of a photo-electrical aiming device and a 3D translation platform. An improved algorithm of back propagation (BP) neural network is also presented, and is successfully applied to the calibration of structured light 3D vision inspection. Finally, using the calibration points and the improved algorithm of BP neural network, the best network structure is established. The training accuracy for the best BP network structure is 0.083 mm, and its testing accuracy is 0.128 mm.     

An artificial immune approach for optical image based vision inspection

This paper presents a novel approach of visual inspection for texture surface defects. The approach uses artificial immune theory in learning the detection of texture defects. In this paper, texture defects are regards as non-self, and normal textures are regarded as self. Defect filters and segmentation thresholds used for defect detection are regarded as antibodies. The clonal selection algorithm stemmed from the natural immune system is employed to learn antibodies. Experimental results on textile image inspection are presented to illustrate the merit and feasibility of the proposed method.     

基于数字彩色结构光投影的唇动三维测量

提出了基于数字彩色结构光投影的动态三维测量轮廓术,用于人在讲话过程中嘴唇的三维测量。介绍了彩色编码轮廓术的基本原理,再通过分色和条纹细化处理,实现了对动态不连续嘴唇的测量。实验验证了测量方案的有效性。     

An automatic optical inspection system for the detection of three parallel lines in solar panel end face

This study inspected and tracked the location state of a test object in the telemetry monitoring of a wafer or solar panel, and the relevant optoelectronic devices. A CCD camera, triggered by the proposed system, captures the test target image in real time, which is transferred to the system for low-pass filtering, image binarization, spatial masking, boundary tracing, and other means of image processing. The new edge point detection algorithm is then applied to identify the edge points of three parallel lines. Three different group edge points are determined using the edge point detection algorithm, and the three groups are computed using a single linear regression equation. Multiple-linear regression is conducted to obtain the sections of straight lines of the groups that can best satisfy the expected requirements. Finally, whether the detection results are consistent with the expected requirements is determined to inspect whether the test object is consistent with the process specifications in order to reduce undesirable losses, as caused by inappropriate placement angle in subsequent manufacturing, thus, enhancing subsequent manufacturing to achieve high yield.     

无需系统标定的三维视觉重建北大核心CSCD

为了解决传统三维重建需要依赖系统标定信息的问题,提出了一种基于相位图的不需要系统标定信息的三维视觉重建算法。首先使用结构光测量技术获得被测物体表面的相位图,再利用相位图的横向和纵向空间扭曲特性计算物体表面相对深度信息,最后实现被测物体的三维视觉重建。这种方法可以用在无法进行标定或无法获取标定信息的场合。实验结果表明,当被测物体表面结构简单时,这种方法的三维视觉重建效果较好。并通过对比传统三维重建结果验证了该方法的有效性。