Efficient multiple phase shift patterns for dense 3D acquisition in structured light scanning

Although phase shifts (PS) are frequently used to acquire colored surfaces of static objects, especially when acquisition time is not critical, the periodic nature of relative (wrapped) PS maps makes it necessary to deal with the issue of phase unwrapping. Consequently, multiple phase shifts (MPS) have been widely used as an alternative, but this usually involves a large number of different PS maps to unwrap an absolute (unique) phase. In this paper we propose a new MPS method to unwrap a phase and accurately perform the dense 3D acquisition of neutral and colored objects using only two PS maps. Accuracy is reported including a quantitative and qualitative evaluation of the results.     

基于二维平行轮廓线的三维表面重建

研究了基于二维平行轮廓线的前列腺三维表现重建问题。采用Roberts边缘检测算子检测前列腺的边缘，提取其轮廓线。分析了BPL1算法在处理相信轮廓线无匹配部分时存在的缺陷。文章采用BPL1算法和相信轮廓线同步前进法相结合的方案被了前列腺表现的三维重建，给出了实验结果。实验表明重建的三维表面清晰、准确。     

双摄象头三维视觉系统

本文介绍了一种较实用的双摄象头三维视觉系统.主要讨论了视场内具有六个自由度物体的定位问题.系统以Frei和Chen方法抽取边缘,并运用了非均匀量化和预加重技术.采用了改进的Moravec兴趣算子法,实现了特征点的自动抽取.基于边缘的序贯分层配准法大大缩短了配准时间.在用三维数据获取物体姿态时.根据刚体运动总结的规则解决了工作特征点和模型点匹配时的组合爆炸问题和多义性问题.     

3D geometry reconstruction from orthographic views: A method based on 3D image processing and data fitting

Industrial esthetic designers typically produce hand-drawn sketches in the form of orthographic projections. A subsequent translation from 2D-drawings to 3D-models is usually necessary. This involves a considerably time consuming process, so that some automation is advisable.     

A structured light vision system for out-of-plane vibration frequencies location of a moving web

In this paper, we address the problem of the detection of out-of-plane web vibrations by means of a single camera and a laser dots pattern device. We have been motivated by the important economical impact of web vibrations phenomena which occur in winding/unwinding systems. Among many sources of disturbances, out-of-plane vibrations of an elastic moving web are well-known to be one of the most limiting factors for the velocity in the web transport industry.The new technique we proposed for the contact-less estimation of out-of-plane web vibration properties and during the winding process is the main contribution of this work. As far as we know, this is the first time a technique is proposed to evaluate the vibrations of a moving web with a camera. Vibration frequencies are estimated from distance variations of a web cross-section with respect to the camera.Experiments have been performed on a winding plant for elastic fabric with a web width of 10 cm. Distances from the web surface to the camera have been estimated all along an image sequence and the most significant frequencies have been extracted from the variations of this signal (forced and free vibrations) and compared to those provided with strain gauges and also with a simple elastic string model, in motion.     

Building 3-D Visual Perception of a Mobile Robot Employing Extended Kalman Filter

The paper aims at designing a novel scheme for sensory data fusion by a mobile robot for reconstructing its 3-D world from their multiple gray images. Extended Kalman filter has been employed for determining the coordinates of the 3-D vertices and equation of the planes of the obstacles in the robot's workspace from their multiple images. The geometric relations among these 3-D planes are then determined by using a logic program for recognizing the obstacles. The time required for recognition of a typical planer obstacle such as a box on a Pentium-III client with 64 MB RAM and a Pioneer-2 type robot server including the time involvement for the motion of the robot around the obstacle is approximately 18 seconds.     

基于光线投射法的目标三维重构技术

针对距离选通激光成像系统获得的图像源,为了减小断层图像间的距离远大于断层图像内像素间的距离这一因素对三维可视化的影响,增强三维显示效果,提高运算速度,在研究了光线投射三维重构算法的基础上,提出了距离分辨率远小于成像分辨率的插空帧光线投射法和通过旋转体数据实现从不同的视线角度进行观察的三维重构方法.仿真结果表明:提出的方法可行、有效,提高了目标的探测和识别概率.     

心内膜几何模型的计算机三维重建技术

心内膜标测系统中,三维心内膜几何模型的构建是一个重大进步,在手术中导航导管起着关键的作用。本文介绍了一种利用凸包算法,从心腔内导管电极的位置信息中提取建模数据的方法。并用Matlab仿真,证明该法可以筛除心腔内的数据点,而提取心内膜表面上的点,构建心腔舒张期的三维心内膜模型。     

3-D shape reconstruction in an active stereo vision system using genetic algorithms

The recovery of 3-D shape information (depth) using stereo vision analysis is one of the major areas in computer vision and has given rise to a great deal of literature in the recent past. The widely known stereo vision methods are the passive stereo vision approaches that use two cameras. Obtaining 3-D information involves the identification of the corresponding 2-D points between left and right images. Most existing methods tackle this matching task from singular points, i.e. finding points in both image planes with more or less the same neighborhood characteristics. One key problem we have to solve is that we are on the first instance unable to know a priori whether a point in the first image has a correspondence or not due to surface occlusion or simply because it has been projected out of the scope of the second camera. This makes the matching process very difficult and imposes a need of an a posteriori stage to remove false matching.In this paper we are concerned with the active stereo vision systems which offer an alternative to the passive stereo vision systems. In our system, a light projector that illuminates objects to be analyzed by a pyramid-shaped laser beam replaces one of the two cameras. The projections of laser rays on the objects are detected as spots in the image. In this particular case, only one image needs to be treated, and the stereo matching problem boils down to associating the laser rays and their corresponding real spots in the 2-D image. We have expressed this problem as a minimization of a global function that we propose to perform using Genetic Algorithms (GAs). We have implemented two different algorithms: in the first, GAs are performed after a deterministic search. In the second, data is partitioned into clusters and GAs are independently applied in each cluster. In our second contribution in this paper, we have described an efficient system calibration method. Experimental results are presented to illustrate the feasibility of our approach. The proposed method yields high accuracy 3-D reconstruction even for complex objects. We conclude that GAs can effectively be applied to this matching problem.     

基于转台系列照片三维重建算法的研究

如何从真实世界中获取具有真实感的三维场景模型一直是计算机图形学中的一个难点,该文给出了一种从真实世界的照片中重建三维场景模型的算法,算法根据在空间稀疏分布的不同视点处的真实场景照片中物体的轮廓线和颜色的一致性信息来建立三维场景模型的;这种方法是通过对转台上的物体不同位置拍照,来获取系列图片而不是通过机器视觉的两幅图片进行重建;文中方法可用于真实世界复杂形体真实感三维模型的建立,经实验表明该方法是可行的.     

3-D object segmentation using ant colonies

3-D object segmentation is an important and challenging topic in computer vision that could be tackled with artificial life models.A Channeler Ant Model (CAM), based on the natural ant capabilities of dealing with 3-D environments through self-organization and emergent behaviours, is proposed.Ant colonies, defined in terms of moving, pheromone laying, reproduction, death and deviating behaviours rules, is able to segment artificially generated objects of different shape, intensity, background.The model depends on few parameters and provides an elegant solution for the segmentation of 3-D structures in noisy environments with unknown range of image intensities: even when there is a partial overlap between the intensity and noise range, it provides a complete segmentation with negligible contamination (i.e., fraction of segmented voxels that do not belong to the object). The CAM is already in use for the automated detection of nodules in lung Computed Tomographies.     

三维重构中的杂乱点云排序问题研究

针对三维重构中的杂乱点云数据预处理问题,给出了一种快速、有效的排序算法。算法通过先对点云进行平行切割,再对切割后的截线云进行插入排序。由于滤除了大量冗余的信息,从而大大提高了排序的速度。实践结果证明,这种算法高效、稳定、易于实现。     

基于VTK的二维轮廓线的三维可视化重建

可视化工具包(VisualizationToolkit)是一个开放源码、自由获取的软件系统。VTK封装了许多常用的可视化算法,为研究人员提供了极大的便利。本文讨论了二维轮廓线的表面重建算法并利用VTK库在VC 的编译环境下实现了一组轮廓线的三维表面重建。     

利用BP神经网络实现三维物体姿态的测定

本文利用BP(Back-Propagation)人工神经网络对三维物体的姿态测定进行了研究。姿态测定一直缺少通用而实际的方法,人工神经网络由于具有强大的自组织、自适应学习能力,迅速的并行信息处理能力,可望解决这个问题。但现有BP算法存在训练慢和易陷入局部最小两个问题.本文提出的级联形式网络结构,使BP网络的训练速度大为提高,陷入局部最小的可能性大为降低。利用这种级联结构对飞机模型姿态测定,取得了较好的实验结果。     

脊柱CT图象的三维重建

先将脊柱ＣＴ图象经灰度校正、图象增强、二值分割、边缘跟踪、取样，获得一系列边缘取样点的坐标，然后进行内插、曲线拟合、曲面拟合，最后通过绕ｘ，ｙ，ｚ轴等多种方式的旋转与消除，从而获得满意的ＣＴ图象重建物体三维形貌。这样可以达到良好的视觉效果，以从不同角度看到脊柱内部组织的生长情况，对医务工作者的诊断和手术具有指导意义。     

3-D reconstruction of homogeneous objects from two poisson-distributed projections

It is computationally very convenient to view the problem of reconstructing a homogeneous 3-D object from two orthogonal projections as a flow problem in a capacitated network. This network flow approach is extended here to incorporate the Poisson nature of the projection data, as is the case in X-ray imaging.     

基于未标定单平面造影图像的冠状动脉树三维重建

提出了一种基于两幅未标定单平面造影图像的冠状动脉树三维重建新方法.该方法在不对设备和图像进行标定的情况下,仍然能够对低阶的畸变进行校正,对C型臂运动模型进行估计,并且充分利用到了病床的运动信息;同时,该方法不仅能够用于投影焦距不变的系统,同样也能够应用于投影焦距发生较大改变的系统,具有较大的灵活性.实验结果统计表明:该文提出的冠状动脉三维重建方法具有较高的有效性和鲁棒性,能够获得小于0.26mm的重投影误差,大大提高了基于非标定造影图像冠状动脉三维重建的精度.     

基于二次样条曲线的不规则物体3D重建

在分析目前不规则物体3D重建算法存在的不足的基础上,采用二次样条曲线作为3D重建算法的基元,实验结果表明该文方法不仅在重建精度上比以往方法有许多提高,而且计算耗费和复杂度上也有较大改进。     

Recognition of 3-D objects by forward checking constrained search

An attempt to recognize 3-D objects from range images is described. Objects are represented by surface patches obtained by segmenting image at depth or orientation discontinuity. To find the best matching pairs between model surface patches (MSPs) and scene surface patches (SSPs), we use forward checking constrained tree search that is a sequential constrained tree search with a forward checking mechanism. It checks geometric constraints between current partial matching pairs and unexplored possible pairs and drastically reduces the number of candidate MSPs matchable to unexplored SSPs. Futhermore, it yields powerful search termination criteria. As an alternative to the sequential search method, we also applied the optimal search algorithm (A^*). To verify advantages of the forward checking, we evaluated the perfomance of the matching algorithms using real range images. The experimental results demonstrated significant gains in computation. Comparing with other methods, our approach is particularly advantageous for the difficult problems in that model objects are very much similar to each other. Our method detects part in difference in advance and so reduces time to discriminate the similar objects. It is confirmed by an evaluation.