航空光学成像与测量技术新进展

航空光学成像与测量技术具有高时效、低成本、高分辨、易判读等突出优势。作为一种不可或缺的光学遥感手段得到了广泛地应用。由于受到航空飞行的影响,光学载荷需要在有限的体积、重量和功耗约束下解决气动力(矩)干扰、振动、温度和气压的急剧变化等问题,从而获得更加清晰的光学影像和更精确的测量结果。面对本领域对航空光学成像与测量的新技术、新方法、新理论的需求,组织了航空光学成像与测量专题,在精密光学、精密机械、精确控制以及图像处理等方面介绍了一批优秀的研究成果。从理论引领和工程参考价值的角度,推动相关研究的进一步发展。     

三维激光扫描技术在海洋领域中的应用现状与前景展望

三维激光扫描技术作为获取空间信息的一门新兴测绘技术,通过非接触式主动测量,可大面积、自动连续的采集三维数据,快速构建目标的三维可视化模型,进行空间仿真和虚拟现实,具有高精度、高速度、实时性和主动性强、全数字化以及对任何物体都能扫描的特点。在简要介绍三维激光扫描技术及其发展的基础上,阐述了其在海洋领域中的成功应用,并对其未来发展趋势进行了分析和探讨。     

反求工程的一大利器——三维扫描仪

3D扫描仪的工作原理 三维激光扫描技术是国际上近期发展的一项高新技术.随着三维激光扫描仪在工程领域的广泛应用,这种技术已经引起了广大科研人员的关注.通过激光测距原理(包括脉冲激光和相位激光),瞬时测得空间三维坐标值的测量仪器,利用三维激光扫描技术获取的空间点云数据,可快速建立结构复杂、不规则的场景的三维可视化模型,既省时又省力,这种能力是现行的三维建模软件所不可比拟的.     

共聚焦激光扫描荧光显微镜扫描系统研制

为适应三维光学微细加工及三维光学信息存储研究的需要,研制了共聚焦激光扫描荧光显微镜的工作台式扫描系统,扫描范围138μm×138μm.工作台采用压电陶瓷驱动器( PZT actuator)驱动的方式来获得高分辨率的位移,采用带柔性铰链的杠杆放大装置来获得较大的位移范围.描述了工作台的工作原理,并对其静态和动态性能进行了测试,实验表明这一扫描系统能很好的应用于共聚焦激光扫描荧光显微镜系统.     

非球型回转体的内轮廓光电图象测量系统

介绍了一种基于人工视觉的三维内曲面轮廓的光电图象测量系统.该系统由光学测量、激光扫描、计算机图象处理、计算机控制各子系统所组成,用它来对现代工业工程中的非球型回转体曲型零件的内轮廓进行非接触测量,得到所需零件的边缘轮廓和三维内曲面的图象信息.并论述了系统的测量原理、组成和特点.     

三维激光扫描技术在轮毂逆向设计中的应用实践

以某矿山重载轮毂的逆向设计为例,首先介绍了三维扫描技术的测量原理及扫描过程;使用三维扫描技术对该轮毂进行扫描以获取三维点云数据,并利用逆向三维建模软件完成了该轮毂的逆向设计。结果表明:三维激光扫描系统具有与接触式三坐标测量仪相当的测量精度,使用三维激光扫描系统获得的数据,可直接作为轮毂逆向设计时的直接依据。     

三维激光扫描系统测量方法与前景展望

首先介绍了三维激光扫描技术的基本概念及其主要应用。在此基础上详细论述了三维激光扫描系统测距、测角、扫描及标定的原理和若干方法,进而介绍了三维激光扫描技术的发展现状,并通过对基于不同测距原理的三维激光扫描仪的参数进行对比,得出其适用范围。最后分析了三维激光扫描技术未来的发展趋势。     

基于MEMS技术的三维测量系统研究

通过结合光学MEMS(Micro Electro-Mechanical System)技术对三维测量系统进行了深入研究,分析了基于MEMS的三维测量系统测量原理,完成了三维测量系统核心器件选择及测量系统的搭建,对三维测量系统的三维结构进行了设计,并对安装壳体三维结构图、器件安装板安装示意图以及测量系统整体装配效果图进行了绘制。     

光学位感条纹动态测量理论及实验研究

正论文针对现有单目视觉测量技术不易实现结构三维振动同步测量及转动测量的问题,结合光学相干层析成像技术中通过干涉条纹获取结构三维信息的原理,提出一系列新型光学位感条纹(即对位移变化敏感的条纹)作为振动位移或旋转角位移传感器,以单台高速相机作为探测器,实现结构三维振动位移、转轴三维振动位移、旋转角位移及转速等多维度、多参数的非接触式同步动态测量,形成了光学位感条纹动态测量新方法、理论及系统。主要研究内容及创新点如下。     

光学非接触三维形貌测量技术新进展

三维物体表面轮廓测量是获取物体形态特征的一种重要手段,在机器视觉、自动加工、工业检测、产品质量控制领域具有重要意义和广阔的应用前景.光学非接触测量由于其高分辨率、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. 介绍了光学非接触测量方法中的光切法、基于调制度测量的原理及优缺点,重点介绍了光栅投射法的测量原理,并分析了其研究热点与发展方向.     

组合CCD图像和稀疏激光测距 数据的建筑物三维信息提取

对组合高分辨率航空CCD图像和机载稀疏激光扫描测距数据自动提取城市建筑物的三维信息进行了研究。航空CCD图像能清晰地给出建筑物的几何形状和分布,因此采用了自适应的Canny边缘检测算法来提取CCD图像上的全部边缘信息,然后根据双向投影直方图和线段匹配方法来自动而准确地提取建筑物的平面轮廓信息,最后根据CCD提取的轮廓信息从机载激光扫描测距数据中提取建筑物的高度信息,从而实现了每栋建筑物的三维信息提取。通过实际数据的处理和提取,说明了组合CCD图像和机载激光扫描测距数据可以自动重建建筑物的三维信息。     

A multi-view time-domain non-contact diffuse optical tomography scanner with dual wavelength detection for intrinsic and fluorescence small animal imaging

We present a non-contact diffuse optical tomography (DOT) scanner with multi-view detection (over 360°) for localizing fluorescent markers in scattering and absorbing media, in particular small animals. It relies on time-domain detection after short pulse laser excitation. Ultrafast time-correlated single photon counting and photomultiplier tubes are used for time-domain measurements. For light collection, seven free-space optics non-contact dual wavelength detection channels comprising 14 detectors overall are placed around the subject, allowing the measurement of time point-spread functions at both excitation and fluorescence wavelengths. The scanner is endowed with a stereo camera pair for measuring the outer shape of the subject in 3D. Surface and DOT measurements are acquired simultaneously with the same laser beam. The hardware and software architecture of the scanner are discussed. Phantoms are used to validate the instrument. Results on the localization of fluorescent point-like inclusions immersed in a scattering and absorbing object are presented. The localization algorithm relies on distance ranging based on the measurement of early photons arrival times at different positions around the subject. This requires exquisite timing accuracy from the scanner. Further exploiting this capability, we show results on the effect of a scattering hetereogenity on the arrival time of early photons. These results demonstrate that our scanner provides all that is necessary for reconstructing images of small animals using full tomographic reconstruction algorithms, which will be the next step. Through its free-space optics design and the short pulse laser used, our scanner shows unprecedented timing resolution compared to other multi-view time-domain scanners.     

Study and development of a low cost “OptInertial” 3D scanner

The 3D scanner domain normally relies on the presence of many tools and technologies. They are mainly divided between contact and non-contact ones, but at present a new trend is coming up, starting from the articulated arms family, where the traditional mechanical joints, allowing flexible measures on complex objects, have been replaced by handy scanner with laser trackers, or with markers. These new systems have the advantage to get the entire object shape without changing the object position itself, but moving the scanning device without the involvement of long software alignments and post treatment operations. Anyway, the use of laser trackers obliges the operator to maintain the scanner head always visible, while the marker usage is quite critical because the measure precision depends strongly on the marker position. Starting from these considerations, the research project presented in this paper has been focused on the design and development of a flexible 3D scanner, without trackers and markers, that merge low-cost optical technologies together with low-cost inertial sensors. Thanks to this synergy, the developed 3D scanner is able to measure the three-dimensional shape of the object recording its movement and transferring it to a control unit for obtaining a point cloud. The paper presents the main concepts of the 3D scanner design and is concluded by an experimental phase made with the use of a benchmark.     

大型散货堆体积的快速测量

针对现有散货测量系统对堆场环境适应性差、盘点时间长、效率低、操作复杂等不足,提出了一种散货堆体积快速测量方法。同时,利用二维激光扫描仪、差分GPS和姿态测量系统设计了一种体积测量系统。该系统用激光扫描仪动态测量堆体表面的几何信息,用姿态测量系统实时测量扫描仪的空间姿态数据,用GPS测出扫描仪在测量过程中的三维位置;最后通过数据融合计算形成堆体的三维点云,利用点云获得散货堆体积。文中基于单条堆体轮廓点云特征,提出快速堆体下边缘查找算法来去除扫描过程中地面点云的误差影响;采用投影剖分法完成完整堆体点云计算体积。实验显示,利用本文设计的测试系统可在30s内完成体积为69m3的标准堆体测量,平均相对误差为0.42%,重复测量误差为0.41%。在实际散货堆实验中,可在10min内完成大小约为31 500m3的散货堆测量,4个不同料堆体积测量的平均重复测量误差为0.74%。结果表明,本方法可在保证测量精度的同时,简单、高效地测量散货堆体积。     

<Emphasis Type="Italic">A Binary Morphology-Based Filtering Algorithm for Reverse Engineering</Emphasis>

A laser scanner is a common surface measurement tool in reverse engineering (RE). The point cloud obtained from a laser scanner usually has some noisy points. An algorithm based on a binary morphology technique is presented to identify the noisy points. After removing the noisy points, the filtered point cloud can be used to reconstruct the surface of a 3D object. The filtering algorithm described can remove both the points at a "far" distance from the scanned object and the "prods" on the surface of the object. ID="A1"Correspondance and offprint requests to: Dr C. L. Wang, Department of Mechanical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong. E-mail: wangcl@ust.hk     

基于激光扫描和SFM的非同步点云三维重构方法

室外场景具有测量数据量大、扫描数据易重叠及建筑物表面信息复杂等特点,单靠激光扫描方法能够获得场景精确的深度信息,但缺乏颜色和纹理信息,利用从运动中恢复结构(SFM)方法可获得丰富的彩色信息,但重构精度不高,若将两种设备固定进行在线实时同步测量,易受到测量环境和系统制约不易实现。针对此问题,提出了一种基于激光扫描和SFM结合的非同步点云数据融合的三维重构方法。首先,提出利用手动选择控制点进行7自由度初始配准,再利用迭代最近点(ICP)算法对初始配准结果进行精确配准,最后利用最近点搜索算法将分布在经基于面片的多视图立体视觉(PMVS)算法优化后的SFM数据中的颜色信息与激光扫描的点云坐标进行融合。实验结果和数据分析显示,本文的方法能有效地将激光扫描与SFM点云数据进行融合,实现了室外大场景的三维彩色重构。     

采用可编程逻辑控制器的大型物体三维扫描重建

本文提出了一种新颖且实用的三维重建系统,以获取大型物体的三维数据。文中对该系统的组成以及所采用的方法和原理进行了研究。该系统由一个基于红外的三维扫描仪、两个导轨和一个基于PLC(可编程逻辑控制器)模块的高精度运动控制系统组成。运动控制系统控制安装在导轨上的三维扫描仪做匀速运动;三维扫描仪向物体投射红外线,并重建物体上所投射的红外线段;接着,系统根据三维扫描仪的运动速度,拼接局部重建数据,最终获得大型物体完整的三维重建数据。实验结果表明:与基于激光测距拼接的方法相比,该方法的测量速度约提高了7倍,测量精度约提高了2.5倍。基本满足工业生产中大型物体自动三维重建的稳定可靠、精度高、速度快等要求。     

牙颌模型的三维激光测量及模型重建

牙颌模型的数据测量是进行口腔修复CAD/CAM的基础。本文采用自制三维激光测量仪对牙颌表面数据进行三维测量,获得了单颗后磨牙缺失的牙颌模型多片三维点云数据。将各片数据在反求软件Surfacer平台上通过三点定位法进行数据拼合,准确地表示出缺失牙上下颌的咬合关系,重建牙颌的实体模型。     

New data‐driven method from 3D confocal microscopy for calculating phytoplankton cell biovolume

Confocal laser scanner microscopy coupled with an image analysis system was used to directly determine the shape and calculate the biovolume of phytoplankton organisms by constructing 3D models of cells. The study was performed on Biceratium furca (Ehrenberg) Vanhoeffen, which is one of the most complex‐shaped phytoplankton. Traditionally, biovolume is obtained from a standardized set of geometric models based on linear dimensions measured by light microscopy. However, especially in the case of complex‐shaped cells, biovolume is affected by very large errors associated with the numerous manual measurements that this entails. We evaluate the accuracy of these traditional methods by comparing the results obtained using geometric models with direct biovolume measurement by image analysis. Our results show cell biovolume measurement based on decomposition into simple geometrical shapes can be highly inaccurate. Although we assume that the most accurate cell shape is obtained by 3D direct biovolume measurement, which is based on voxel counting, the intrinsic uncertainty of this method is explored and assessed. Finally, we implement a data‐driven formula‐based approach to the calculation of biovolume of this complex‐shaped organism. On one hand, the model is obtained from 3D direct calculation. On the other hand, it is based on just two linear dimensions which can easily be measured by hand. This approach has already been used for investigating the complexities of morphology and for determining the 3D structure of cells. It could also represent a novel way to generalize scaling laws for biovolume calculation.     

A visual seam tracking system for robotic arc welding

A novel circular laser three-dimensional (3D) scanner is developed instead of a one-dimensional laser spot scanner (1D) and two-dimensional (2D) striped laser light. Using the proposed circular laser scanner, a seam tracking system is constructed, and architecture based on the Visual C++ and RAPID languages which determines the cooperation among image processing modules is carried out. Finally, real seam tracking experiments are investigated and the error analysis is carried out. The results show that: (1) the proposed system can realize seam tracking; (2) the precision of this system is affected by the light scanning system, calibration results, image processing, and the welding seam 3D algorithm—the tracking accuracy is satisfied for robotic arc welding; (3) this system can be used in a welding robot system as a weld seam finder, flatness detector, and weld seam tracker.