大型复杂曲面产品近景工业摄影测量系统开发

针对大型工件的复杂曲面难以精确测量,国外的商用摄影测量软件占据垄断地位.在国内率先开发了近景工业摄影测量系统XJTUDP,介绍了系统的组成、开发内容,研究了基于亚像素边缘拟合的高精度标志点中心检测方法、编码点设计及编码点自动检测方法.重点研究了基于摄影测量的相机标定和三维重建技术,包括共线方程、基于共面方程的像片定向、直接线性变换解法、外极线几何约束和光束平差解法.参照VDI/VDE2634测试方案,以自行设计的立方体框架为对象,对XJTUDP系统和TRITOP系统进行了测试,得出两者精度均小于0.1mm/m的结论,证明开发的系统完全可以应用在工业测量领域.     

白车身视觉检测系统中多类型传感器全局校准技术

针对白车身视觉检测系统中传感器数量多、种类各异、分布空间大、位置关系复杂等问题,提出了一种适用于工业现场的多视觉传感器全局校准技术。基于坐标系间接统一法,设计多个精密立体靶标作为坐标系转换中介,利用激光跟踪仪获取现场校准数据,在单位四元数数学模型的基础上,求解两坐标系间最优转换矩阵,将固定式传感器和柔性传感器的测量坐标系统一到全局坐标系。该方法已在某企业在线测量项目中成功应用,现场只需完成传感器坐标系与全局坐标系转换关系标定,降低了复杂现场环境对多传感器全局校准的限制,简化了校准过程,提高了环境适应性,校准后检测系统各向测量精度均优于±0.2 mm,满足白车身在线测量精度要求。     

基于结构光技术的高温锻件三维尺寸实时在位测量系统

针对我国高温锻件检测系统缺乏和测量方案不完善的问题,开发出基于结构光技术的锻件三维尺寸在位测量系统。该文设计结构光投影仪的光栅参数优化设计算法以及功率可调节光源系统,并配合三相机摄影设备搭建针对高温锻件三维尺寸实时在位测量系统。同时建立完整的在位检测方法流程,阐述参数标定、特征提取、对比度实时调节以及特征匹配的技术细节。实验结果证明,锻件三维尺寸摄影测量系统可适用于锻件热态测量且尺寸测量精度优于2mm,能够满足对高温锻件高精度尺寸测量的应用需。     

面激光测量传感器快速标定方法

本文提出了一种基于平面靶标的结构光系统参数快速标定方法。该方法基于摄影测量技术,使用编码点制作的平面靶标,由相机获取靶标平面光条图像,根据编码点的图像坐标以及靶标坐标,经过仿射变换和后方交会等处理,可以快速方便的得到光平面标定点的相机坐标,将标定点进行拟合即可完成标定。实验表明,该方法的光平面拟合中误差优于0.07 mm,系统测量精度的平均相对误差优于0.33%,具有较高的标定精度。同时该方法可以实现点、线、面等模式的结构光参数标定,通用性较强,标定效率较高,方法灵活,适合现场标定。     

双目动态摄影测量技术研究与实现

针对振动条件下雷达天线型面变形测量问题,设计了基于双目视觉动态摄影测量系统.介绍了系统的组成和工作流程,并对其中的相机同步技术、相机控制场标定技术、圆形标志点中心定位技术、像点自动匹配技术进行了研究.系统通过图像采集卡实现了一种廉价的ns级双相机同步方式.用10参数模型对相机进行了标定.采用了一种高反射率的圆形人工标志,通过Canny灰度质心的方法实现了圆形标志点中心的定位.系统用两种方法实现了像点的自动匹配:第一种是基于待测物体近似坐标的驱动点匹配方法.第二种则是运用核线约束、像点残差约束和相对关系约束,完成像点自动匹配.进行了振动测量试验,试验结果表明在物距为1.5 m和物体振动频率小于50 Hz条件下,系统点位测量精度小于0.3 mm,平面度测量精度小于0.1 mm.     

光栅投影式三维摄影测量仪的几何标定方法

光栅投影式三维摄影测量仪利用了时域结构光投影技术和立体视觉测量原理获得三维点坐标。针对传统标定方法易受镜头畸变影响和标定约束方程少导致精度下降的问题,采用了非线性的摄像机和投影机模型,并提出了二维的投影机模型;使用多平面法标定了系统测量所需的摄像机和投影机几何参数;为进一步提高参数精度,采用Levenberg-Marquardt算法优化了摄像机和投影机模型。实验结果表明,该方法操作简单,无需精确的位置和姿态调整,标定的绝对精度为0.2pixel,相对精度为1/5000。     

基于面阵CCD的大视场在线检测系统研究

设计了一套非接触在线检测系统,该系统基于近景摄影测量原理,与传统测量方法相比,它可以对大视场内多目标同时进行检测.对CCD像机进行精密标定,利用光线束平差原理求解空间坐标,采用亚像素技术处理图像以及同名像点匹配等技术的运用,大大提高了检测精度.系统单幅拍摄线视场为141 mm,最终可以检测500mm× 500mm范围内的目标,空间坐标检测精度优于0.03mm.该系统可应用于工业现场检测等众多相关领域.     

面向机器人标定的单激光跟踪仪顺序多站式测量系统建模与分析

为实现大型串联工业机器人的高精度标定,搭建了一种单激光跟踪仪的顺序多站式测量系统。该系统仅需单台激光跟踪仪,先后在不同的基站位置对工业机器人的末端位置进行独立测量,并基于多边测量方法计算机器人的末端位置。计算过程中仅需激光跟踪仪的距离信息,有效地优化了末端位置的测量不确定度。首先,建立了该测量系统的仿真模型,深入地分析了测量点的数量与分布形状、测量距离以及工业机器人定位精度等因素对系统测量精度的影响;然后,依据分析结果确定单激光跟踪仪顺序多站式测量系统的搭建方案。实验结果表明:该系统在2.5m距离上的测量误差仅为0.023mm,优于激光跟踪仪的测量精度,满足大型串联工业机器人参数标定的测量精度要求。     

多目视觉测量系统的光束法平差改进

为了消除三维扫描测量机器人系统中工业机器人定位误差对测量结果的不利影响,搭建了多目视觉测量系统对三维扫描测头进行空间同步定位。由于系统中相机与标志点之间的距离变化较大,标志点重投影误差难以评价空间定位误差,另外受相机标定精度影响,光束法平差对三维坐标修正不明显。为解决上述问题,本文改进了光束法平差,在传统光束法平差的误差方程中引入摄影比例尺,再将整体参数的优化分为两步,先修正相机内、外参数,再修正被测点三维坐标,以提升系统的三维重建精度。实验结果表明,在对一维基准尺长度的测量实验中,测量结果与参考值之间的偏差小于0.300 mm,标准差不大于0.110 mm,满足三维扫描测量机器人系统的应用需求。     

三线阵CCD相机亚像元精度几何标定方法研究

为了解决三线阵CCD立体测绘相机内方位元素的几何标定问题,提出了一种实现相机亚像元精度内方位元素和交会角标定的方法。该方法利用光学高精度角度发生器和CCD细分测量相结合的检测方法,由最小二乘回归分析,实现相机内方位元素的标定,并通过扫描星点图像标定交会角。校飞实验的数据处理结果验证了该方法的有效性。     

俯仰轴轴线位置的视觉标定方法研究

针对气膜孔五轴视觉测量系统中的俯仰轴轴线标定问题,提出了一种应用工业级摄像机和定制的标定靶标来确定俯仰轴轴线的空间位置的新方法.以具有锋利和完整直边特征的长方体金属块作为标定靶标,通过系统中俯仰轴的运动使靶标处于不同的位置和姿态,并由三维运动平台带动摄像机运动,使其对焦于处于不同状态的靶标表面,并采集包含目标棱边的前表...     

一种立体视觉测量高精度标定新方法

提出一种实现通用摄像机标定和现场高精度立体视觉传感器标定的新方法。该方法无需预先给定初始参数,而是根据投影矩阵计算摄像机参数的初始值,结合镜头畸变的标定数学模型,实现通用摄像机标定;在立体视觉传感器三维测量模型基础上,引入目标距离约束建立结构参数标定优化目标函数,从而得到使空间距离偏差最小的最优结构参数,实现传感器现场高精度标定。实验结果表明,上述方法标定精度较高,已标定传感器空间距离测量相对误差小于0.45%。     

Research on the application of single camera stereo vision sensor in three-dimensional point measurement

A single camera stereo vision sensor model based on planar mirror imaging is proposed for measuring a three-dimensional point. The model consists of a CCD camera and a planar mirror. Using planar mirror reflections of a scene, a picture with parallax is obtained by shooting the target object and its virtual image. This is equivalent to shooting the target object from different angles with the camera and the virtual camera in the planar mirror, so it has the function of binocular stereo vision. In addition, the measurement theory of the three-dimensional point is discussed. The mathematical model of a single camera stereo vision sensor is established, the intrinsic and extrinsic parameters are calibrated, and the corresponding experiment has been done. The experimental results show that the measuring method is convenient and effective; it also has the advantages of simple structure, convenient adjustment, and is especially suitable for short-distance measurement with high precision.     

Close-range photogrammetry applied to the documentation of cultural heritage using telescopic and wide-angle lenses

Close-range photogrammetry is widely used for numerically and graphically representing historical buildings for documentation. Such data can be later used as the base for conservation and restoration processes. The highest precision in point determination in photogrammetry can be achieved using a metric camera, although it is expensive. Recently, many studies have used SLR non-metric cameras, which have the advantage of a self-calibration method and furthermore, are cheaper than the metric camera. In most cases, for close-range photogrammetry applications that use an SLR digital camera, the object is close to the camera (less than 50 m), requiring a wide-angle setting. In our study, the precision achieved is based on a compact camera (Lumix TZ-10) used in building restitution. We experimented with the two extremes in close-range photogrammetry: close object, less than 15 m between the camera lens and to building façade; and distant object, up to 200 m between camera lens and building. In both cases, the precision achieved was suitable for the restitution of the historical buildings: under 1 cm for near objects using a 25-mm wide-angle lens and 3 cm for the distant object using a 280-mm telescopic lens. We achieved remarkable precision in the case of the tele lens, where it is unusual to use the focal length for building restitution in close-range photogrammetry. Nevertheless, a tele lens becomes necessary when it is not possible to place the camera near the object, as in the case of the northern façade of the Alhambra in Granada, Spain.     

Novel method of calibration with restrictive constraints for stereo-vision system

Regarding the calibration of a stereo vision measurement system, this paper puts forward a new bundle adjustment algorithm based on the stereo vision camera calibration method. Multiple-view geometric constraints and a bundle adjustment algorithm are used to optimize the inner and outer parameters of the camera accurately. A fixed relative constraint relationship between cameras is introduced. We have improved the normal equation construction process of the traditional bundle adjustment method, so that each iteration process occurs just outside the parameters of two images that are taken by a camera that has been optimized to better integrate two cameras bound together as one camera. The relationship between the fixed relative constraints can effectively increase the number of superfluous observations of the adjustment system and optimize higher accuracy while reducing the dimension of the normal matrix; it means that each iteration will reduce the time required. Simulation and actual experimental results show the superior performance of the proposed approach in terms of robustness and accuracy, and our approach also can be extended to stereo-vision system with more than two cameras.     

基于摄影测量的基准尺长度测量系统的调节与误差分析

基准尺作为摄影测量长度基准,其精度直接影响测量结果的准确性,为了保证基准尺长度的测量精度,设计了由气体静压导轨、激光干涉仪、CCD成像系统组成的测量系统。分析了影响测量精度的因素,并对组成基准尺的标志圆成像位置、CCD相机光轴、激光干涉仪、基准尺和CCD成像系统绕自身光轴旋转的调节误差进行了计算分析,用于指导CCD成像系统、激光干涉仪和基准尺的调节。最后应用该系统对基准尺进行多次测量,结果表明基准尺长度测量的标准差可达到1 μm,满足工业摄影测量的要求。     

Optical dilatometry for the control of microstructure development during sintering

An optical method for the in situ measurement of sintering shrinkage has been developed. It relies on a simple and robust CCD camera technique and is applicable up to high temperatures (2000 °C) and heating rates (10 K/min) in industrial furnace atmospheres. A resolution of less than 1 μm for a sample diameter of 10 mm has been achieved using a special geometrical arrangement and a smart image analysis algorithm. Systematic errors are small (<0.1%) and can be corrected by an additional measurement. A high reproducibility of shrinkage measurement has been observed in various sintering experiments. The optical dilatometer is very flexible: it has been used also for an accurate temperature calibration and for wetting experiments and it can be adjusted to different furnace types. Received: 17 May 2000 / Reviewed and accepted: 26 June 2000     

水下摄影测量共线理论与相机标定方法

基于摄影光学理论,分析了相机在空气中和水下成像基点位置关系,提出水下摄影三点共线理论,并推导出相机在水下主距变化模型;分析了相机水下摄影视场和畸变大小的变化,设计了水下摄影测量相机标定方法;最后通过水下摄影试验标定,验证了水下摄影三点共线理论的正确性和水下相机标定方法的实用性。     

Stereo calibration of binocular ultra-wide angle long-wave infrared camera based on an equivalent small field of view camera

ABSTRACT

In this paper, a stereo calibration method for binocular ultra-wide angle long-wave infrared camera is proposed on the basis of an equivalent small field of view camera. Extrinsic parameters are calibrated through the corrected images from the left and right cameras. They can be viewed as images taken by a small field of view camera. The calibration procedure consists of three steps: monocular calibration, distortion correction and extrinsic parameters calibration. In order to evaluate the accuracy of the method, stereo vision of the camera is modelled and a 3D reconstruction approach is presented. A series of experiments, including intrinsic parameters, extrinsic parameters and 3D reconstruction, are conducted to validate the proposed method. The results show that the baseline length error decreases to 0.67%, and the relative error for the 3D reconstruction of corners is smaller than 8.11%. In contrast to the common stereo calibration method, it improves calibration accuracy.     

光学三维测量中结构光栅投影系统的开发

为解决结构光三维测量系统中的光栅投影质量问题,提出并实现了以物理光栅为核心的结构光栅投影系统。该系统以现代光栅制造技术制造的精密光栅元件为核心,基于幻灯投影原理实现高质量的光栅条纹投影,利用步进电机带动高精密滚轴丝杆进行平移实现投影光栅的切换。实验结果表明,基于该系统实现的光学三维测量系统的可以达到1：100以上的对比度,具有较大的光强和良好的景深,同时能获得连续的强度分布及较好的正弦性,测量误差小于0．04mm,测量精度约为0．03mm,满足工业应用的要求。