基于直线间结构信息的立体视觉图像动态匹配方法

针对立体视觉匹配问题，介绍一种改进的动态规划图像匹配方法，它将边缘直线相似测度分为局部相似测度和全局相似测度，在后者中加入图像边缘直线之问的结构关系信息，并在动态搜索最优匹配路径的过程中利用结构关系约束删除不合理的匹配路径。仿真实验结果证明，采用该方法解决立体视觉中边缘线段的匹配问题，不仅提高了匹配的准确率，而且大大减少了匹配时间。     

Terrain mapping under extreme light conditions with direct stereo matching method through aggregating matching costs by weight

One of the biggest problems in applying stereo vision techniques in field robotics is how to acquire 3D terrain maps under extreme light conditions. Through multiple exposures, the dynamic range of images can be increased. In this paper, instead of using existing lighting enhancement methods such as exposure fusion to increase the texture of 2D image, we propose that the matching costs of the images grabbed with multiple exposures are directly summed by weight. Compared with the previous methods such as exposure fusion, with the proposed method, it is not necessary to fuse the 2D images captured with multiple exposures, and for each pixel of the matching image, the local information in its local window can be better retained. Since it is possible that the camera is moved between exposures when the images are grabbed, the images captured with multiple exposures are aligned to the image acquired with auto exposure. In order to evaluate the performance of the proposed method, two different stereo matching algorithms were used: a local window-based method and semi-global method. Through experiments in laboratory and outdoors with a stereo vision camera fixed on a tripod and held in the hand, it was verified that the proposed method consistently allowed more valid points to be obtained and the 3D model of terrain can be built more accurately. Especially when the local window-based method was used, the proposed method performed much better.     

一种利用动态规划和左右一致性的立体匹配算法

立体匹配是计算机视觉领域研究的一个重要课题,为了得到准确、稠密的视差图,提出了一种利用动态规划和左右一致性的立体匹配算法。该算法首先分别以左、右图像为基元图像,计算各自的视差空间图像,在视差空间图像上利用动态规划,计算得到左视差图和右视差图;然后通过使用左右视差图之间的一致性关系,消除误匹配点,得到较为准确的部分视差图;最后利用视差图的顺序约束关系,给出未匹配视差点的搜索空间计算方法,并利用一种简单有效的方法来计算这些点的视差值。在一些标准立体图像对上所做的实验结果表明,该算法效果良好。     

双目视觉小波域SIFT匹配与极线约束算法研究

研究双目立体视觉技术,特征的提取和匹配是双目视觉的最基本的问题。目前,SIFT已经被证明鲁棒性最好的局部不变特征描述符。但是SIFT算法产生的误匹配较多,精度偏低,为了解决这一问题,同时降低算法特征提取与匹配的复杂度,达到双目立体视觉实时性的要求,文中提出了一种结合小波变换和SIFT特征点的双目立体视觉匹配方法。首先,对双目视觉系统采集的左、右图像进行小波分解,把分解得到的低频图像作为输入,用SIFT算法进行特征点的初始匹配,再利用极线约束的理论求得精确匹配。实验结果表明,该方法具有较强的适应性,能够在减少误匹配的同时,大大加快运算速度。     

一种沿区域边界的动态规划立体匹配算法

提出一种基于图像区域分割的立体匹配算法.与通常的沿扫描行进行动态规划的立体匹配算法不同,该算法以图像"区域"为基元计算视差.首先使用相关法得到初始视差,然后利用一种区域边界上的多种子动态规划算法对视差进行精细计算,最终通过插值得到整个图像的稠密视差.实验结果表明,此算法速度较快、可靠性较高.     

基于双序列比对算法的立体图像匹配方法*

在分析现有立体匹配方法的基础上,提出一种基于双序列比对算法的立体图像匹配方法。将立体图像对中同名极线上的像素灰度值看做是一对字符序列,使用基于动态规划思想的双序列比对算法对这些对字符序列进行匹配,以获取立体图像视差。为验证该方法的可行性和适用性,采用人脸立体图像对进行实验。实验结果表明,使用该方法进行立体图像匹配能获得光滑的、稠密的视差图。基于动态规划思想的双序列比对算法能够有效地解决立体图像匹配问题,从而为图像的立体匹配提供了一个实用有效的方法。     

改进型SIFT立体匹配算法研究

针对机器人视觉系统立体匹配中存在的匹配重复或错误等问题,提出了一种基于尺度不变特征变换（Scale Invariant Feature Transform,SIFT算法）和余弦相似度匹配规则的立体匹配方法。该方法以左、右两幅图像中特征向量较多的图像作为基准匹配图像,另一幅图像作为待匹配图像;再由二者的特征向量之间的余弦相似度所建立的匹配规则进行立体匹配。实验结果表明,改进型立体匹配方法有效地降低了匹配错误或重复比,具有较强的鲁棒性,匹配效果较佳,更加有利于机器人视觉系统的三维重建与定位。     

基于线性滤波的树结构动态规划立体匹配算法

传统的动态规划立体匹配算法能有效保证匹配精度的同时提高运行速度, 但得到的视差深度图会出现明显的条纹现象,同时在图像弱纹理区域以及边缘存在较高的误匹配. 针对该问题,提出了一种新的基于线性滤波的树形结构动态规划立体匹配算法. 算法首先运用改进的结合颜色和梯度信息参数可调的自适应测度函数构建左右图像的匹配代价, 然后以左图像为引导图对构建的匹配代价进行滤波; 再运用行列双向树形结构的动态规划算法进行视差全局优化, 最后进行视差求精得到最终的视差图.理论分析和实验结果都表明, 本文的算法能有效地改善动态规划算法的条纹现象以及弱纹理区域和边缘存在的误匹配.     

金字塔双层动态规划立体匹配算法

针对控制点修正的动态规划立体匹配算法存在控制点求取时阀长、实时性差的问题．提出一种金字塔双层动态规划立体匹配算法．采用金字塔算法求取低、商分辨率图像，然后分别在低、商分辨宰图像上求取候选控制点集和最终控制点集，并用最终控制点集修正商分辨率图像上的动态规划立体匹配．由干候选控制点集的求取在低分辨率图像上进行，算法用时大为减少．实验证明，此算法匹配率商、速度快．     

一种室外非理想光照条件下的立体匹配算法

针对室外非理想光照条件和图像低纹理、低对比度造成立体匹配效果较差的问题,提出一种HSL(色相-饱和度-亮度)颜色空间下基于边缘图分割的立体匹配算法.区别于传统的RGB颜色空间下基于像素强度的度量方式,该算法采用一种HSL颜色空间下的像素非相似性度量公式来获得匹配代价,然后基于左右输入图像的边缘检测结果进行图像区域分割和立体匹配.在实验中采用一系列不同光照条件的图片集和具有明显低纹理区域的图片集,对本文算法与现有算法进行对比验证.实验结果证明,该算法能够得到比较理想的视差图,对非理想的光照条件和低纹理图像具有很好的鲁棒性,并且基本达到实时性要求.     

双目视觉下基于区域生长的三维人脸重建算法

为解决传统立体匹配算法匹配低纹理人脸图像时极易产生误匹配的问题,提出一种基于区域生长的人脸立体匹配算法。该算法利用级联回归树算法提取的人脸特征点将人脸划分为不同区域以分别限制各区域的视差搜索范围,从而避免在全局范围上查找匹配点;同时利用人脸的局部形状特性,采用局部曲面拟合的方式筛除误匹配种子点并生成大量可靠种子点用于区域生长;最后,分别在实验室环境采集的人脸图像和FRGC v2.0人脸数据库上进行定性和定量实验。实验结果表明,与传统算法相比,所提算法能够重建出更加准确的三维人脸模型。经点云配准后与人脸点云真实值的均方根误差在2 mm以内,且不同光照、姿态、表情下人脸图像的重建表明所改进的立体匹配算法具有较好的鲁棒性。     

Stereo by intra- and inter-scanline search using dynamic programming

This paper presents a stereo matching algorithm using the dynamic programming technique. The stereo matching problem, that is, obtaining a correspondence between right and left images, can be cast as a search problem. When a pair of stereo images is rectified, pairs of corresponding points can be searched for within the same scanlines. We call this search intra-scanline search. This intra-scanline search can be treated as the problem of finding a matching path on a two-dimensional (2D) search plane whose axes are the right and left scanlines. Vertically connected edges in the images provide consistency constraints across the 2D search planes. Inter-scanline search in a three-dimensional (3D) search space, which is a stack of the 2D search planes, is needed to utilize this constraint. Our stereo matching algorithm uses edge-delimited intervals as elements to be matched, and employs the above mentioned two searches: one is inter-scanline search for possible correspondences of connected edges in right and left images and the other is intra-scanline search for correspondences of edge-delimited intervals on each scanline pair. Dynamic programming is used for both searches which proceed simultaneously: the former supplies the consistency constraint to the latter while the latter supplies the matching score to the former. An interval-based similarity metric is used to compute the score. The algorithm has been tested with different types of images including urban aerial images, synthesized images, and block scenes, and its computational requirement has been discussed.     

基于控制点的分层双向动态规划立体匹配算法

提出一种基于控制点的分层双向动态规划立体匹配算法．首先，利用改进Volumetric迭代算法获取具有高可靠度的控制点，将其作为具有正确视差的匹配点．其次，在高可靠度控制点的指导下，利用分层双向动态规划算法在DSI（disparity-space image）视差空间图中进行初匹配，进而在Delta DSI（delta disparity-space image）视差变化空间图中进行精匹配，从而获取高密度视差图．实验结果表明，该算法不仅可以改善传统直接动态规划立体匹配算法产生的带状条纹瑕疵，而且计算速度较快，匹配结果也优于传统动态规划的匹配结果．     

一种改进的区域双目立体匹配方法

双目立体匹配是机器视觉中的热点、难点问题。分析了区域立体匹配方法的优缺点,提出了改进的区域立体匹配方法。首先,采集双目视觉图像对对图像对进行校正、去噪等处理,利用颜色特征进行图像分割,再用一种快速有效的块立体匹配算法对图像进行立体匹配。然后,在匹配过程中使用绝对误差累积(SAD)的小窗口来寻找左右两幅图像之间的匹配点。最后,通过滤波得到最终的视差图。实验表明:该方法能够有效地解决重复区域、低纹理区域、纹理相似区域、遮挡区域等带来的误匹配问题,能得到准确清晰的稠密视差图。     

Implementation of a 3D Vision System on DSPs TMS320C31

In this paper, the implementation of a new stereo vision process on a specialized architecture which comprises of three DSPs TMS320C31 is described. The first step of our stereo vision system is a self-adaptive image segmentation algorithm based on a new concept that we call declivity. The second step is a new and fast stereo matching algorithm based on dynamic programming and using self-adaptive decision parameters. The goal of our work is to develop a stereo vision system that achieves an acceptable level of performance using a modest amount of hardware. This implementation is organized as follows: declivity extraction from the two stereo images is performed in parallel on two DSPs, one for the right image and the other for the left one. Then, the last DSP computes the declivity matching based on our dynamic programming method as well as the 3D maps calculation. Finally, experimental results obtained using real pairs of stereo images on a VME 150/40 Imaging Technology Vision System are presented. They show the feasibility and the effectiveness of our system. These results can surely be improved by using a new generation of DSP in order to consider real-time applications.     

Convolutional Sparse Coding for High Dynamic Range Imaging

Current HDR acquisition techniques are based on either (i) fusing multibracketed, low dynamic range (LDR) images, (ii) modifying existing hardware and capturing different exposures simultaneously with multiple sensors, or (iii) reconstructing a single image with spatially‐varying pixel exposures. In this paper, we propose a novel algorithm to recover high‐quality HDRI images from a single, coded exposure. The proposed reconstruction method builds on recently‐introduced ideas of convolutional sparse coding (CSC); this paper demonstrates how to make CSC practical for HDR imaging. We demonstrate that the proposed algorithm achieves higher‐quality reconstructions than alternative methods, we evaluate optical coding schemes, analyze algorithmic parameters, and build a prototype coded HDR camera that demonstrates the utility of convolutional sparse HDRI coding with a custom hardware platform.     

Exposure Fusion for Time‐Of‐Flight Imaging

This work deals with the problem of automatically choosing the correct exposure (or integration) time for time‐of‐flight depth image capturing. We apply methods known from high dynamic range imaging to combine depth images taken with differing integration times in order to produce high quality depth maps. We evaluate the quality of these depth maps by comparing the performance in reconstruction of planar textured patches and in the 3D reconstruction of an indoor scene. Our solution is fast enough to capture the images at interactive frame rates and also flexible to deal with any amount of exposures.     

基于极线几何的改进多约束图像立体匹配

针对计算机视觉和模式识别领域基本而重要的问题--立体匹配,提出了一种基于极线几何、结合特征匹配与区域匹配、视差梯度约束等多约束立体匹配算法,实现图像快速准确匹配.该算法将现有的基于特征和基于窗口匹配两种方法相结合,并加入视差梯度等约束条件,有效弥补了单一匹配算法的不足,同时增强了算法适应性.实验表明,该算法具有更高的求解质量和求解效率,可以满足双目立体视觉系统的需要.     

自适应窗口的时间规整立体匹配算法

针对立体视觉中图像对应点的误匹配问题,以时间规整算法(DTW)为基础,提出了自适应窗口的立体匹配算法．根据外极线的约束,在自适应窗口内采用灰度相关技术得到长度不相等的两个灰度段作为相容的匹配序列;利用动态规划法及连续性约束寻找一条最佳的匹配路径．根据回溯得到的匹配路径及其坐标值得到高密度视差图．实验结果表明,该算法具有较高的运行效率和良好的匹配效果．     

基于径向基神经网络的立体匹配算法*

针对双目视觉中的图像立体匹配问题,提出了一种基于径向基神经网络的立体匹配算法。该算法提取图像的尺度不变特征变换（SIFT）特征建立特征匹配矩阵,对特征匹配向量进行约简,最后将约简的特征匹配向量输入径向基神经网络进行识别输出。仿真和实际图像实验表明,该算法的匹配正确率比标准的SIFT有所到提高。