一种针对蜂窝芯外形曲面特征的测量方法

针对蜂窝芯外形曲面特征测量过程中出现的数据不完整、精度低等问题,提出一种基于三维光学扫描的测量方法。首先在蜂窝芯外形曲面紧密贴合覆盖层,以覆盖层外形特征代替蜂窝芯外形曲面特征,然后采用三维光学扫描技术采集覆盖层外形的点云数据。通过计算点云数据的法向矢量,并在矢量方向偏置覆盖层厚度,从而获得蜂窝芯曲面特征的轮廓数据,完成蜂窝芯外形曲面特征测量。通过对某型号蜂窝芯材料的测量,证明该方法的可行性和精确性,具有实际工程应用价值。     

基于Halcon的单目相机标定方法与测量实验

机器视觉已经在现代工业自动化生产中得到了广泛应用,尤其是在三维测量领域。物体三维空间与二维图像间的关系求解离不开相机标定,尤其是相机标定结果的优劣直接决定了机器视觉的测量精度。通过搭建单目相机视觉系统实验平台,先分析了相机标定的工作原理,再利用Halcon软件的标定助手功能对型号为GB050-2-7×7的圆点标定板进行相机标定,获得了相机的内参和外参。在进一步测量实验中验证了单个特征圆点测量偏差为0.03862 mm、多个特征圆点测量平均偏差为0.05655 mm,二者测量精度都高于0.1 mm,说明了利用机器视觉进行测量能够满足常用精度需求。     

关节式坐标测量机激光测量头参数标定

在三维视觉测量中,标定方法对测量结果的影响是决定性的.本文通过分析、比较各种视觉模型及标定方法,采用考虑镜头畸变因素的三维视觉模型以满足高精度测量系统的需求.由于关节式坐标测量机的激光测量头,使用单摄像机和线结构光来匹配被测物体表面的三维数据,本文设计了一种新型的阶梯形标定块,通过标定块图像和激光条纹图像完成了摄像机的内外参数标定和激光平面参数标定.实验证明,该标定操作过程简单,易于实现自动化,且具有较高的标定精度.     

仿生复眼系统标定及测量方法研究

为了实现对近景目标物的三维测量,研制了一种小型仿生复眼系统。介绍了该复眼系统的结构及其参数设计原则,并对该系统采用的标定、三维测量等算法进行研究。首先根据复眼成像特点搭建了标定和测量平台,并分别使用张正友的方法、直接线性变换法、Tsai式两步法三种摄像机标定方法对复眼的中心子眼进行标定,通过比较实验结果发现Tsai式标定方法精度更高,更适用于本复眼系统的标定。然后针对边缘子眼光轴与图像传感器不垂直问题,提出了一种新的图像畸变数学模型,有效的提高了边缘子眼的标定精度。最后建立了多子眼三维探测模型,并探索了多子眼成像对复眼相机测量精度的影响,认为三子眼可获得比双子眼更高的精度和稳定性。实验结果表明,在距离复眼相机150?260 mm范围内,该复眼探测系统的三维测量相对误差在2%左右,在满足仪器小型化的同时能基本实现近景三维测量。     

利用系统辨识的星敏感器模型修正与测角精度检测

2.中国科学院大学,北京100049)摘要:为了提高星敏感器的测角精度,提出了一种采用系统辨识法对星敏感器模型进行修正以及测角精度检测的方法。首先分析了星敏感器的理论测量模型以及像面坐标与星点目标的空间位置关系,然后给出了用模型修正来提高星敏感器测角精度的原理和数学模型。修正模型由系统辨识方法得到,同时为了提高辨识精度,文中采用将星敏感器像面划分为多个区域,每个区域单独建模辨识的方式。最后利用某星敏感器进行了实验,利用该方法进行模型修正后,星敏感器的测角精度为σx=1.68″、σy=1.91″,而修正前的测角精度为σx=17.43″、σy=23.46″。结果表明,采用该方法可以使星敏感器测角精度得到大幅提高,同时也完成了测角精度的检测。     

傅里叶变换轮廓术中三维坐标同时校准方法

在相位测量型光学三维面形测量中,最终都要将相位信息转换成被测物体的高度分布信息,这个过程往往是通过对已知世界空间坐标的特征点事先标定,获得测量系统的内外特征参数后,完成被测物体的三维坐标转换.因此,标定是三维面形测量的关键环节.本文基于双向二次相位-高度映射方法和摄像机针孔模型线性无畸变标定技术,充分利用傅里叶变换的频谱方向特性,提出了对含有特征点的二维标定物表面变形条纹的频谱进行方向滤波操作,同时获取测量系统XYZ三个方向上的标定数据,对测量系统进行立体校准的系统标定方法.结合旋转风扇叶片形变的测量系统,给出了该方法的标定结果:在XY面内(230mm×230mm)的标准偏差小于0.27mm;在Z方向上小于0.022mm,位移测量灵敏度优于0.05mm.该方法为测量系统的实用化奠定了基础.     

跟踪测距式三维坐标视觉测量系统

提出了一种跟踪测距式视觉坐标测量系统,主要由一架摄像机、一台激光测距仪、一台计算机和一支光笔组成。测量时,摄像机测量光笔上四个光反射点的方向,依据这些方向激光测距仪可跟踪捕捉到任一光反射点,并测量出某一光反射点到激光测距仪的距离,由测得的方向和距离系统可计算出光笔笔尖接触点的三维坐标。根据四点透视问题(P4P)原理建立了系统的数学模型,由于摄像机测得的距离参数的引入,使得该数学模型(P4P问题)可以线性求解,而且解具有唯一性,推导出了被测点三维坐标的求解公式。和单摄像机视觉坐标测量系统的比对实验结果表明,在Z,Y,X轴方向上的测量稳定性精度可分别提高0.366mm、0.031mm和0.011mm。     

基于激光跟踪仪折射补偿的三维模体定位精度原位检测方法

提出了基于激光跟踪仪折射补偿的三维模体定位精度原位检测方法,建立了ADM和IFM测距误差补偿与靶球空间位置坐标求解模型,进行了理论模型验证实验与三维模体定位精度检测对比实验,实现了激光跟踪仪在玻璃介质下的高精度测量。实验结果表明:X、Y、Z坐标补偿前后的平均偏差分别由3.410mm、0.407mm、1.732mm减小到0.022mm、0.015mm、0.035mm,相邻点距离的平均偏差由0.266mm减小到0.017mm,与空气中激光跟踪仪的测量精度相当。在此基础上,以无玻璃遮挡的悬挂式检测方法为基准,两种方法测得的定位误差基本吻合。最后,利用蒙特卡洛法分析得到相邻点距离测量误差的标准差为0.012mm,满足检测要求。     

USB2.0接口数据采集分析系统的设计及应用

针对三维动态目标跟踪测量的技术要求，设计了一个具有USB2．0接口的高速数据采集装置。该系统完成信号采集、传输和电机控制任务，作为下位机与PC机协作可以进行动态目标跟踪测量。     

基于视频测量的运行状态模态分析

视频测量技术通过摄像机记录被测结构的振动过程,采用图像处理方法实现对结构上测点的多目标跟踪,具备全场非接触、测试过程简便、测量精度高等突出优点。基于摄像机成像模型,采用光束法平差提取出结构测点三维方向位移振动信息,每个测点等效于一个三轴"微位移传感器",对多测点目标跟踪可视为多通道同步数据采集。对摄像机成像系统进行校准,依照结构形状特性分布测点,由结构静止时各测点的空间位置构建出测试结构的几何模型,进行视频采集和多目标跟踪获取各测点动态响应数据,采用运行状态模态分析方法,识别出被测结构的固有模态参数。基于视频测量实现了测试结构几何建模和信号采集,并与模态分析软件紧密结合,形成了完整的视频采集与分析系统,具备良好的空间域展现能力,特别适用于柔性低频结构的动态测试与分析。以轻质风扇叶片、若干树叶等结构为对象进行实验研究,验证了该技术和方法的有效性。     

三维点云模型高鲁棒性多重盲水印算法研究

目的为了满足多用户共享三维模型版权时的单用户版权独立认证等需求,结合CDMA技术,提出一种三维点云模型高鲁棒性多重盲水印算法。方法为不同用户分配不同的Walsh码,并利用Walsh码,对各自的二值水印图像进行编码,得到多路混合的水印;对三维点云模型进行仿射不变性处理,并将模型的顶点坐标转换为球面坐标,角度值按照升序排序,按顺序选择顶点到重心的距离组成的二维矩阵,作为水印的嵌入对象。对二维矩阵进行二级小波变换,将多路混合的水印嵌入到对角线方向高频部分,经过小波逆变换得到含多重水印的三维点云模型。结果该算法对噪音、仿射、重排序等攻击具有很强的鲁棒性。能够嵌入多重水印,且多重水印之间没有发生相互碰撞。结论文中算法能够满足多用户共享三维模型版权时单用户版权独立认证和版权保护的需求。     

用于机器人视觉的大景深便携式三维扫描系统

针对机器人视觉对便携式三维扫描系统的大景深要求,利用Scheimpflug条件对CCD平面进行偏转,成功地将扫描系统的景深从30mm提高到了100mm以上;并根据CCD偏转后的摄像机模型,在理论上完整地推导了便携式集成三维扫描系统的物像关系方程。针对景深扩大后带来的测量精度降低的问题,提出了一种对系统全景深范围进行分段校准的新方法,提高了测量精度与系统分辨率。三维重建时,根据被扫描物体所对应的图像点在像平面上的不同位置分别调用不同的标定参数将二维图像坐标转变为物体的空间坐标,测量精度可以达到0.06mm。     

基于3DS MAX的物流自动化分拣系统3D仿真

针对物流自动化分拣项目的系统设计,提出基于3DS MAX的3D动画仿真方法,以某烟草自动化分拣系统方案为例,阐述了利用3DS MAX作为系统3D仿真平台对系统设计进行3D仿真的过程。通过建立分拣系统数据模型与3D模型,利用3D动画技术、渲染技术进行系统3D仿真,为系统设计提供了可视化的展示与交流平台,并为项目可行性与可靠性提供可视化参考依据,此方法在企业同类项目中得到成功推广。     

Image-based rendering for photo-realistic visualization

Digital models of objects have long stood synonymous for 3D models with fixed textures. More recently, image-based rendering has made its way to offer an effective alternative. Rather than producing a 3D model, views are created by interpolating between images taken from many different viewpoints. The advantages are that the resulting visualizations look very realistic and that a wider range of objects can be dealt with. One can go a step further and follow a similar strategy for the illumination direction: for every reference viewpoint, now take multiple images, each with a different illumination. Again, images for novel illumination directions follow from interpolation. But there is an obvious catch in that many, many images are needed, unless at least a crude 3D shape model and preferably also a model for the surface reflectance are used to support the interpolation from more sparsely taken images. Even then, the number of images needed remains appreciable. Hence, we present a dome to efficiently capture such images.

Fortunately, it is possible to generate this crude 3D model, as well as the surface reflectance characteristics' directly from the images. We describe methods to achieve this. Also, in order to make real-time visualization possible, all critical steps of the visualization pipeline are programmed on off-the-shelf graphics hardware. The dome provides an easy to use and structured acquisition procedure. Yet, the applicability of the algorithms is not limited to structured input. The images could, for example be taken with a hand-held camera.     

Image-based rendering for photo-realistic visualization

Digital models of objects have long stood synonymous for 3D models with fixed textures. More recently, image-based rendering has made its way to offer an effective alternative. Rather than producing a 3D model, views are created by interpolating between images taken from many different viewpoints. The advantages are that the resulting visualizations look very realistic and that a wider range of objects can be dealt with. One can go a step further and follow a similar strategy for the illumination direction: for every reference viewpoint, now take multiple images, each with a different illumination. Again, images for novel illumination directions follow from interpolation. But there is an obvious catch in that many, many images are needed, unless at least a crude 3D shape model and preferably also a model for the surface reflectance are used to support the interpolation from more sparsely taken images. Even then, the number of images needed remains appreciable. Hence, we present a dome to efficiently capture such images.

Fortunately, it is possible to generate this crude 3D model, as well as the surface reflectance characteristics’ directly from the images. We describe methods to achieve this. Also, in order to make real-time visualization possible, all critical steps of the visualization pipeline are programmed on off-the-shelf graphics hardware. The dome provides an easy to use and structured acquisition procedure. Yet, the applicability of the algorithms is not limited to structured input. The images could, for example be taken with a hand-held camera.     

Efficient depth map compression for view rendering in 3D video

Abstract

A depth map represents three-dimensional (3D) scene information, which is used to synthesise virtual views in 3D video coding. Since the quality of synthesised virtual view highly depends on the quality of depth map, efficient depth coding is crucial for the 3D video system. However, depth map is not directly used for display but to generate virtual views. Compressing depth map using existing video coding techniques yields unacceptable distortions in rendered virtual view. Thus, the depth map needs to be compressed in a way that can minimise distortions in the rendered views. To solve this problem, we propose an efficient depth map compression method for view rendering based on view rendering distortion other than depth map distortion itself. Firstly, we derive relationship between distortion in coded depth map and the rendered view. Then, a region-based video characteristic distortion model is proposed to precisely estimate distortion in view synthesis. Finally, a multilateral filtering is applied as an in-loop filter to reduce rendering artefacts. Experimental results show that the proposed method achieves 2 dB coding gain in terms of PSNR and subjective quality improvement of synthesised views.     

基于混合坐标系的FDM型3D打印机研制

传统FDM（fused deposition molding，熔融沉积成型）型3D打印机在打印倒体件的过程中需设置辅助支撑结构，打印完成后去除支撑结构，这会导致成型件的精度降低。为解决传统FDM型3D打印机存在的问题，设计了一种基于混合坐标系的FDM型3D打印机。将基于笛卡尔坐标系的运动方式转换为基于拟球坐标系的运动方式，由X-Z平面内的旋转运动、X-Y平面内的旋转运动和Z轴方向的直线运动组合成拟球坐标系内的运动，达到无支撑3D打印的目的。介绍了基于混合坐标系的FDM型3D打印机控制系统的硬件和软件设计。用传统FDM型和基于混合坐标系的FDM型3D打印机进行打印实验并作对比，结果表明在同等级精度硬件配置的情况下，基于混合坐标系的FDM型3D打印机可以实现更高的打印精度。基于混合坐标系的FDM型3D打印机创新性强、造价低，拥有自主知识产权，具有广阔的市场前景。     

三维配光曲线的模型设计及其网络实时再现

以标准配光曲线数据文件为基础,经过信息文件解析、数据优化处理、关键点数据插值等过程,创建了三维配光曲线数学模型,并在此基础上运用计算机图形学理论,以Flash为开发平台,采用面向对象编程技术开发出了三维平台,绘制相应的三维配光曲线图。为了用户从各种角度观察三维配光曲线,还开发了方便的人机接口界面,用户可以使用鼠标拖动等方法对三维配光曲线进行实时浏览。     

A 3D modeling and free‐view generation system using environmental stereo cameras

We propose a 3D video system that uses environmental stereo cameras to display a target object from an arbitrary viewpoint. This system is composed of the following stages: image acquisition, foreground segmentation, depth field estimation, 3D modeling from depth and shape information, and arbitrary view rendering. To create 3D models from captured 2D image pairs, a real‐time segmentation algorithm, a fast depth reconstruction algorithm, and a simple and efficient shape reconstruction method were developed. For viewpoint generation, the 3D surface model is rotated toward the desired place and orientation, and the texture data extracted from the original camera is projected onto this surface. Finally, a real‐time system that demonstrates the use of the aforementioned algorithms was implemented. The generated 3D object can easily be manipulated, e.g., rotated or translated, to render images from different viewpoints. This provides stable scenes of a minimal area that made it possible to understand the target space, and also made it easier for viewers to understand in near real‐time. © 2008 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 17, 367–378, 2007     

三维机织结构的几何模型

根据三维机织结构中纱线系统的组成和相应纱线的几何形态,建立了具有普适意义的几何模型,获得了组成三维机织结构各纱线系统在一个结构单元内的纱线长度和取向角,进而计算出纤维体积分数。随后,选择了基于11种不同接结组织的三维机织复合材料试样,测试了试样的纤维体积分数,所得的测试结果与模型输出的预测值有很好的一致性。利用所建立的模型还定量讨论了接结组织对纤维体积分数和取向角的影响。结果表明:分层接结可以提供比正交接结高的纤维体积分数;而正交接结中接结经具有较大的取向,有利于增强三维机织复合材料在厚度方向上的力学性能。