基于极线校正的相移结构光三维测量

被动式方法对表面无明显特征的物体难以获取稠密的三维重建点,无法进行精确而快速的测量.针对这一问题,采用双目立体视觉测量系统,结合主动式方法的相位移动结构光法对每个图像像素点进行处理,获取三维物体表面稠密的数据,实现真正的全场测量.双目系统经过极线校正,对应点的极线处在同一水平线上,匹配时不用逐点计算每个像素点的极线,大大减少匹配时间.实验结果表明此方法能快速获得复杂表面物体的稠密测量.     

光轴外扩式布置的双目相机图像立体校正

摘要： 针对宽视野光轴外扩式布置双目图像采集和显示系统的图像立体校正问题,利用三维重建误差,提出了一种基于双目图像视差特性的立体校正方法.在分析光轴外扩式布置双目相机图像视差特性的基础上,针对相机光心与显示投影中心间的位置误差和相机光轴与显示视轴间的角度误差,建立图像仿射变换、水平视差畸变和垂直视差的校正函数,利用一组空间采样点的三维重投影误差作为目标函数通过优化方法求解校正参数.仿真实验表明：在视轴外扩夹角为30°时,本方法可以有效地消除光心位置误差和光轴角度误差对图像视差造成的影响.真实图像校正实验表明：校正后的图像水平畸变小,在显示宽视野双目图像时,能保持正确的三维立体感.
关键词：中图分类号：文献标志码： A     

用多基线立体视觉系统恢复稠密深度图像

为有效地减少错误匹配,提高匹配精度并恢复稠密深度图像。利用多基线立体视觉恢复景物深度数据的冗余性,使用简单条纹模式投影光源标记景物,很好地解决了弱纹理区域或无纹理区域的对应性问题。通过对图像进行避部规范化处理,在外极线、唯一性和连续性约束条件下,使用应用域知识和统计模型,建立准确的匹配关系,实现三维景物高精度恢复。所恢复景物的高精度稠密深度图像,在１．５～３．５ｍ的距离范围内,深度值偏差小于２ｍｍ     

基于倾斜校正和视差估计的遥感影像稠密匹配方法

针对遥感影像稠密匹配效率较低、匹配精度和密度不够高的缺陷,提出了一种基于倾斜校正和视差估计的遥感影像稠密匹配方法。首先基于稀疏同名点、通过倾斜校正生成核线影像;利用稀疏同名点构造三角网,以三角形为插值单元,预测核线影像对中各像素的初始视差;在初始视差的邻域内沿核线一维搜索最佳匹配点,搜索时增量计算匹配窗口的灰度均值,且将搜索步长设为2,以提高搜索效率。实验结果表明,本文方法可以达到逐像素的匹配密度,且匹配的正确率和精度很高;基于稠密点重建的真实感三维场景证明了本文方法的有效性和实用性。     

基于双目视觉和旋转云台的远距离虹膜识别系统

 虹膜识别技术是一种新兴的生物特征识别技术,相对于指纹识别和人脸识别具有更高的准确率和稳定性,影响虹膜识别的瓶颈问题在于虹膜图像获取不太方便。当前该领域的热点就是研发一种可以在远距离、全自动地拍摄虹膜图像的设备,以解决虹膜识别的易用性问题。设计了一种基于双目视觉和旋转云台的远距离虹膜识别系统,该系统首先对摄像机进行标定,对双目摄像机中的人脸图像进行配准,从而估计人脸在空间中的大致位置;然后,系统利用旋转云台将虹膜摄像机自动对准人的眼睛并进行自动对焦,在捕获到清晰地虹膜图像后进行虹膜识别。实验证明,本文的立体视觉方法可以比较准确地定位物体空间位置,系统自动获取的虹膜图像质量好,识别率高。这种系统有望能够在未来的虹膜识别领域得以大规模应用。     

Motion direction, speed and orientation in binocular matching

The spatial differences between the images seen by the two eyes, called binocular disparities, can be used to recover the volumetric (three-dimensional) aspects of a scene. The computation of disparity depends upon the correct identification of corresponding features in the two images. Understanding what image features are used by the brain to solve this matching problem is one of the main issues in stereoscopic vision. Many cortical neurons in visual areas V1 (ref. 2), MT (refs 3, 4) and MST (refs 5, 6) that are tuned to binocular disparity are also tuned to orientation, motion direction and speed. Although psychophysical work has shown that motion direction can facilitate binocular matching, the psychophysical literature on the role of orientation is mixed, and it has been argued that speed differences are ineffective in aiding correspondence. Here we use a different psychophysical paradigm to show that the visual system uses similarities in orientation, motion direction and speed to achieve binocular correspondence. These results indicate that cells that multiplex orientation, motion direction, speed and binocular disparity may help to solve the binocular matching problem.     

Depth is encoded in the visual cortex by a specialized receptive field structure

Binocular neurons in the visual cortex are thought to perform the first stage of processing for the fine stereoscopic depth discrimination exhibited by animals with frontally located eyes. Because lateral separation of the eyes gives a slightly different view to each eye, there are small variations in position (disparities), mainly along the horizontal dimension, between corresponding features in the two retinal images. The visual system uses these disparities to gauge depth. We studied neurons in the cat's visual cortex to determine whether the visual system uses the anisotropy in the range of horizontal and vertical disparities. We report here that there is a corresponding anisotropy in the cortical representation of binocular information: receptive-field profiles for left and right eyes are matched for cells that are tuned to horizontal orientations of image contours. For neurons tuned to vertical orientations, left and right receptive fields are predominantly dissimilar. Therefore, a major modification is required of the conventional notion of disparity processing. The modified scheme allows a unified encoding of monocular form and binocular disparity information.     

塔里木盆地西北部地壳三维构造研究

利用Ｑ值成像和震源分布图像方法,得到了伽师地区中、上地壳的三维Ｑ值结构和发震时间的平面图像。结果表明：水平截面不同深度的Ｑ值图像都存在低Ｑ值带,主要展布方向为东西向、北北东向和北北西向,与研究区的柯坪断裂、羊达曼断裂和麦盖提断裂有一定的对应关系,推测低Ｑ值带可能是研究区的几条深部断裂;垂直剖面沿77°E的条带有大面积的低Ｑ值区,并且在这个带的两侧Ｑ值结构有明显差异。发震时间的平面图像显示出优势取向为北北西和北东,并且相交于余震分布的密集处,这些特征是该区域的活动构造背景。为区域地质构造研究和油气资源的探测提供了深部构造信息。     

Interocular rivalry revealed in the human cortical blind-spot representation

To understand conscious vision, scientists must elucidate how the brain selects specific visual signals for awareness. When different monocular patterns are presented to the two eyes, they rival for conscious expression such that only one monocular image is perceived at a time. Controversy surrounds whether this binocular rivalry reflects neural competition among pattern representations or monocular channels. Here we show that rivalry arises from interocular competition, using functional magnetic resonance imaging of activity in a monocular region of primary visual cortex corresponding to the blind spot. This cortical region greatly prefers stimulation of the ipsilateral eye to that of the blind-spot eye. Subjects reported their dominant percept while viewing rivalrous orthogonal gratings in the visual location corresponding to the blind spot and its surround. As predicted by interocular rivalry, the monocular blind-spot representation was activated when the ipsilateral grating became perceptually dominant and suppressed when the blind-spot grating became dominant. These responses were as large as those observed during actual alternations between the gratings, indicating that rivalry may be fully resolved in monocular visual cortex. Our findings provide the first physiological evidence, to our knowledge, that interocular competition mediates binocular rivalry, and indicate that V1 may be important in the selection and expression of conscious visual information.     

Probing the human stereoscopic system with reverse correlation.

Our two eyes obtain slightly different views of the world. The resulting differences in the two retinal images, called binocular disparities, provide us with a stereoscopic sense of depth. The primary visual cortex (V1) contains neurons that are selective for the disparity of individual elements in an image, but this information must be further analysed to complete the stereoscopic process. Here we apply the psychophysical technique of reverse correlation to investigate disparity processing in human vision. Observers viewed binocular random-dot patterns, with 'signal' dots in a specific depth plane plus 'noise' dots with randomly assigned disparities. By examining the correlation between the observers' ability to detect the plane and the particular sample of 'noise' disparities presented on each trial, we revealed detection 'filters', whose disparity selectivity was remarkably similar to that of individual neurons in monkey V1. Moreover, if the noise dots were of opposite contrast in the two eyes, the tuning inverted, just like the response patterns of V1 neurons. Reverse correlation appears to probe disparity processing at the earliest stages of binocular combination, prior to the generation of a full stereoscopic depth percept.     

人眼特征提取技术研究综述

基于语义的图像检索是目前人脸图像检索领域研究发展的新趋势,所谓语义化人脸图像检索,通常是指根据待检索人脸图像的特征,去语义数据库中搜索最为匹配的人脸图像的过程,眼睛是人脸部特征的重要组成部分,眼睛的检测对于人脸信息的处理具有重要的意义;当前学术领域关于眼部特征提取的研究有很多,目前还没有一种眼部特征提取技术是公认快速有效的,主要讨论了人眼特征提取技术的一些主要方法,对现有的人眼定位,人眼区域分割,人眼特征提取的方法进行分析和讨论;最后对基于眼部特征语义化图像检索的发展和应用做一个简单的展望。     

基于分割的立体匹配法提取光场视差图

为了解决从光场相机采集的图像中提取物体深度信息的问题,提出一种利用Lytro光场相机设备,基于图像分割的立体匹配方法估计光场图像深度。首先对Lytro相机采集的原始灰度图进行解码和颜色校正,提取相应的子光圈图像;在Matlab环境下,结合图像颜色分割、自适应立体匹配对子图像进行处理,通过平面拟合技术和BP优化得到相应的深度估计图。实验结果表明,该方法提取到深度图在视觉精度上有了明显的提高。     

Resistance to positional noise in human vision

Human eyes are in constant and rapid motion even when observers try to maintain steady fixation. Also, the visual system has a sluggish temporal response. In combination, these two factors would be expected to blur stimuli and reduce spatial sensitivity. But observers are able to detect a difference in separation of a few seconds of arc between two closely spaced parallel lines. Here we report that even very large amounts of positional jitter of the line pair has minimal impact on this ability. This result is in marked contrast to the deterioration observed when targets are swept linearly across the retina, but is consistent with a system that must ignore oculomotor jitter. To explain these results will require a re-evaluation of current models of position coding in human vision.     

机器视觉下排球手位置轮转的空间多变性优化

在计算机机器视觉下,采用传统方法研究排球手位置轮转的空间特征时,随着排球手位置轮换的不确定性增强,空间状态识别效果不好,对调整战术的指导性不强。提出一种基于机器视觉空间降维的排球手位置轮转空间多变性优化方法。通过构建机器视觉下排球手位置轮转的图像处理模型,完成排球手空间位置变化的像素点采样和特征分析。通过构建图像特征输出函数,实现空间像素点量化特征降维。通过求解排球手空间位置轮转视觉特征图像的运动参数方程式,完成位置轮转空间多变性的优化。实验结果表明,采用该算法能准确有效对机器视觉下排球手位置轮转的空间特征进行分析和识别,对于提高队员的协调和配合素质有重要的指导意义。     

基于监视器的双目立体视觉的立体效果

首先提出了一个基于监视器的双目立体视觉模型，然后重点分析了由视差引起的立体效果，以及直线段立体成像的立体效果．最后通过实验证实了论文的结论，并给出了一个虚拟植物可视化立体展现的实例．对于直线段立体成像的情形，定量分析和实验表明，当观察者保持双眼平行地远离或靠近屏幕时，看到的各点深度都相同的图像虽然会产生移动，但是不会感到有明显的形变．这为立体图像尺寸的测定提供了可行的方法．     

基于平行双目视觉的目标距离计算

为了快速的计算出相机与目标物之间的距离,需要找到两幅图像的对应点。采用SIFT算法提取图像特征向量后,在匹配时加入外极线的约束条件,可以有效地去除误匹配,提高测量精度。实验结果表明,距离测量的相对误差在2%以内。     

一种适用于PC机的视觉注意点定位算法

人眼观察屏幕时,其脸部姿态与屏幕视觉注意点具有内在对应关系。摒弃传感器、头盔等跟踪设备,提出并研究一种适用于日常PC机的视觉注意点位置获取方法。使用摄像头抓取人脸实时图像,经Haar级联分类器提取能够反映脸部姿态的特征:双眼、口、鼻等,通过BP神经网络训练出特征相对坐标与视觉注意点之间的对应关系。实验证明该方法在无需任何专门设备支持的条件下,即能够检测视觉注意点位置,检测精度达到0.1视距。为立体影像或虚拟场景的裸眼立体观察,提供了一种新的解决方式及方法。     

人眼动态视觉特性分析

人眼作为电视系统的接收终端,其视沉特性直接决定着对电视系统的特性要求;也是对电视图象信号进行频带压缩处理的基础,本文基于人眼的视觉特性,提出了人眼视觉响应模型,分析了人眼动态视觉特性,分析表明,由于视觉残留的影响,人眼对活动图象的空间分辨力将降低,而对时变图象则表现为对层次的分辨力下降,其结果都降低了对单幅图象的有效息信量,从而为对视频图象信号的频带压缩提供了可能。     

一种检测宽度的线特征提取方法

线特征提取是计算机视觉及图像处理中的低级处理过程,应用广泛。有关的研究大多数关注于线的位置而忽略了线宽。定义了高斯模板作为局部图像区域,考察区域内灰度值的相似性,通过灰度比较函数获得线响应进行线检测,模板半径与检测到的线宽有着密切的联系。实验结果表明该方法有效地提取了线位置及线宽。     

Postsaccadic visual references generate presaccadic compression of space

With every rapid gaze shift (saccade), our eyes experience a different view of the world. Stable perception of visual space requires that points in the new image are associated with corresponding points in the previous image. The brain may use an extraretinal eye position signal to compensate for gaze changes, or, alternatively, exploit the image contents to determine associated locations. Support for a uniform extraretinal signal comes from findings that the apparent position of objects briefly flashed around the time of a saccade is often shifted in the direction of the saccade. This view is challenged, however, by observations that the magnitude and direction of the displacement varies across the visual field. Led by the observation that non-uniform displacements typically occurred in studies conducted in slightly illuminated rooms, here we determine the dependence of perisaccadic mislocalization on the availability of visual spatial references at various times around a saccade. We find that presaccadic compression occurs only if visual references are available immediately after, rather than before or during, the saccade. Our findings indicate that the visual processes of transsaccadic spatial localization use mainly postsaccadic visual information.