基于圆形靶标的数码相机外部参数标定算法

数码相机的外部参数标定是应用计算机视觉进行现场测量和图像处理的关键技术。提出一种基于圆形靶标的数码相机外部参数标定算法,首先提出一种用于估计靶标上圆的圆心在该相机像平面的像坐标的迭代学习算法,在此基础上,利用已知的数码相机内部参数和成像几何模型计算出数码相机的外部参数。实验结果表明算法具有较高的精度和良好的稳定性。     

一种使用校正模板的非线性摄像机标定方法

基于图像点满足的特定直线方程以及相邻图像点之间距离相等的性质,对标定模板图像进行校正,并通过改进的张正友标定法,提出了一种新的使用校正模板的非线性摄像机标定方法。与现存的方法进行比较发现,该方法能够实现较高精度的摄像机标定,鲁棒性比较强,且能够大大地降低算法的复杂度。     

一种基于MATLAB的摄象机标定方法的实现

使用MATLAB实现了一种简便的摄象机参数的标定方法。先由四个标定点的坐标计算出透视投影矩阵，从而计算出标定模板上其它节点的图象坐标，之后进行内部参数和外部参数的计算。此方法具有易于实施、速度较快、精度较高等特点，是一种简便实用的方法。     

利用CCD摄像机求解飞行器运动参数

针对飞行器的视觉导航应用,提出了利用CCD摄像机来估算飞行器运动参数的实时方案。在利用CCD摄像机所拍摄的序列图像中,首先,自动提取出第1帧图像中比较明显的特征点,并在后续的图像中对所提取的特征点进行追踪。然后,利用多视图几何技术来标定摄像机的外参数。所标定的摄像机的外参数经过转换就可以获得飞行器的运动参数。通过对实际拍摄的图像进行计算,反投影误差的最大值为0.03911,而处理26帧图像需要的时间为0.9194s,说明本方案在计算精度和实时性上是可行的。     

A camera calibration technique using three sets of parallel lines

This paper presents a new method for three-dimensional camera calibration in which the rotation parameters are decoupled from the translation parameters. First, the rotation parameters are obtained by projecting three sets of parallel lines independently of the translation parameters and the imaging distance from the lens to the image plane. The virtual line passing through the image center, which is calculated by perspective projection of a set of parallel lines, depends only on the rotation parameters. Next, the translation parameters and the imaging distance are analytically obtained. Experimental results are used to show how the camera model can be accurately reconstructed in an easily prepared environment.     

一种基于TOF相机与CCD相机的联合标定算法研究

针对基于Time-of-Flight(TOF)相机的彩色目标三维重建需标定CCD相机与TOF相机联合系统的几何参数,在研究现有的基于彩色图像和TOF深度图像标定算法的基础上,提出了一种基于平面棋盘模板的标定方法。拍摄了固定在平面标定模板上的彩色棋盘图案在不同角度下的彩色图像和振幅图像,改进了Harris角点提取,根据棋盘格上角点与虚拟像点的共轭关系,建立了相机标定系统模型,利用Levenberg-Marquardt算法求解,进行了标定实验。获取了TOF与CCD相机内参数,并利用像平面之间的位姿关系估计两相机坐标系的相对姿态,最后进行联合优化,获取了相机之间的旋转矩阵与平移向量。实验结果表明,提出的算法优化了求解过程,提高了标定效率,能够获得较高的精度。     

一种基于非量测畸变校正的摄像机标定方法

设计一种基于非量测畸变校正的摄像机标定方法.该方法利用单参数除式模型校正镜头畸变,根据直线透视投影保留同素性,通过拉凡格氏法（LM）优化标定出畸变模型系数和摄像机主点坐标,然后校正成像点,使其满足针孔模型映射关系.根据内参数的两个基本方程,线性求解剩余参数.实验表明,该方法在非量测标定过程具有较好的鲁棒性,且对比张正友标定方法,可在单幅标靶图像下进行标定,避免了模型内外参数耦合在一起,提高了标定效率.     

一种立体视觉的摄像机标定参数遗传优化方法

首先利用线性模型构建线性方程,通过最小二乘法估算出摄像机的内、外参数,然后考虑到摄像机的畸变影响加入非线性畸变方程。利用遗传算法具有良好全局优化的特点,对摄像机参数进行优化,提高了摄像机标定的精度和可靠性。实验结果表明,该方法达到预期目的且具有很好的实用性。     

采用棋盘格靶标的全自动相机标定方法

为了去除相机标定过程中的人为干预,提出了一种采用改进的棋盘格靶标的全自动相机标定方法。识别出每幅标定图像中的四个标志圆,利用四个标志圆圆心的图像坐标和物理坐标计算二维射影变换矩阵。依据该射影变换矩阵计算出棋盘格角点的初始图像位置,接着提取亚像素精度的角点位置。迭代求解需要标定的相机参数。由实验可知,该全自动相机标定方法的棋盘格角点识别能力和相机标定精度,与Bouguet的相机标定工具箱相当,且可以显著地减少标定时间和工作量。利用20幅分辨率为640×480的靶标图像标定相机仅需16 s。     

基于角度不变的线阵推扫式CCD相机几何畸变在轨检校方法

对航天遥感相机进行在轨检校,是提高卫星产品质量,扩大产品应用效果的重要技术内容.文中研究了一种基于角度不变的线阵推扫式CCD相机几何畸变在轨检校方法.该方法利用相机外方元素对于相机视向量夹角角度影响比较小的原理,根据地面控制点和一级产品图像,求解相机视向量夹角,从中提取相机光学部件的畸变模型参数,从而实现相机内外方元素解耦.相机畸变模型采用一维3阶多项式,对焦距和主点等引起的低阶误差能够很好地吸收.该方法用在HJ-1A/B卫星的宽幅盖CCD相机几何畸变校正上,检校误差残留在2—6个像元,和参考数据精度相似,表明取得了很好的校正效果.     

捷联惯导系统误差系数动态标定方法探究

随着工作时间的推移,捷联惯性导航系统中的惯性器件测量精度会因为误差参数发生变化而降低,误差逐渐被积累,进而降低系统导航精度。针对此问题,提出了一种基于GPS速度、位置信息的捷联惯导系统惯性测量装置输出误差系数动态标定的方法。首先采用Sage-Husa自适应滤波实现组合导航状态最优估计,然后引入迭代最小二乘法,利用导航误差对系统惯性器件的误差系数进行标定。经计算机仿真验证,该方法可以实现在运动中对系统误差系数进行标定,进而提高捷联式惯性导航系统的导航精度。     

用于视频中车速自动检测的摄像机自动标定方法

针对目前基于视频的车辆测速方法均需通过手工标定而造成的低效和可操作性差的问题,提出了一种对典型配置的道路监控摄像机的焦距、俯仰角、离地距离等重要参数进行自动标定的方法。首选利用自然场景中两组正交平行线在视频图像中形成的消失点之间的内在关系对摄像机的焦距和俯仰角实施精确标定;在此基础上利用视频中目标车辆群体的平均宽度对摄像机与地面之间距离进行自动标定。实验表明,该算法具有参数测量精度高和可靠性好等优点,可作为现有道路视频监控设备实施车辆速度、类别、流量等数据的自动采集、分析和监控,以及电子违章抓拍设备的有效自动标定手段。     

A robust method to recognize critical configuration for camera calibration

When space points and camera optical center lie on a twisted cubic, no matter how many pairs there are used from the space points to their image points, camera parameters cannot be determined uniquely. This configuration is critical for camera calibration. We set up invariant relationship between six space points and their image points for the critical configuration. Then based on the relationship, an algorithm to recognize the critical configuration of at least six pairs of space and image points is proposed by using a constructed criterion function, where no any explicit computation on camera projective matrix or optical center is needed. Experiments show the efficiency of the proposed method.     

一种快速的人工场景图像消失点检测方法

人工场景中包含了大量的空间平行线以及垂直边,这些空间平行线映射到图像中相交产生的交点即消失点。消失点检测对摄像机标定、三维场景重建等都有着重要的意义。传统的消失点检测算法往往基于二维霍夫参数空间,复杂度高、效率低。因此,提出一种新的方法,先检测图像中较长的边界线,并将检测到的线段进行筛选、分组;然后利用消失点与焦距之间的制约关系,确定三向消失点的位置以及焦距的大小。该方法将传统的二维霍夫参数空间转换为二级一维霍夫参数空间。实验表明,这种方法运算复杂度低、运行时间短。在室外场景图像中,鲁棒性好,且保持较高的准确率。     

基于光束法平差的双线阵系统标定技术

针对线阵相机特殊使用场景中所需要的高精度图像,对线阵相机进行高精度标定。提出一种基于光束法平差的双线阵相机标定方法。通过背景差分法获取线阵相机的特征点的像素坐标。再利用已有的直接线性变换方法和非线性优化方法求出相机的内参,外参,畸变参数后,将得到的初始参数与世界坐标作为待优化集合,利用LM法和光束法平差对该集合进行更进一步的优化,使得双线阵系统的重投影误差降到最低。实验表明,该方法与传统的线阵相机标定方法相比重投影误差降低了75.01%。     

A low-cost calibration method for automated optical mensuration using a video camera

Automated optical mensuration gauges the acquired image of the inspected unit while assessing its actual size and shape. The mensuration requires the following preparations: (1) alignment of the video camera perpendicularly to the inspection table, and (2) calibration of the scale ratios of image acquisition, notably, the stretching ratio caused by signal conversion and the magnification ratio of optical coupling. This paper presents the unique two-stage calibration method. The first stage applies the parallelogram conservation property, a property very sensitive to misorientation, to test against the potential misalignment. Once detected, we adjust the misalignment towards orthogonal alignment using image patterns of the calibration template. Then, the second stage determines the scale ratios. The proposed calibration method is suitable for on-site applications, and its implementation cost is low. Sensitivity analysis and experimental results are reported.     

A new continuous-curvature line/path-tracking method for car-like vehicles

In this paper, we first investigate the problem of finding an algorithm for the movement of a car-like vehicle to track a given directed straight line. Car-like vehicles' motions possess 2 d.o.f., speed v and path curvature κ. We compute the 'derivative of path curvature', λ = dκ/ds, rather than the path curvature κ itself, to enforce continuous-curvature vehicle motions. Specifically, we compute λ as a linear function of the current path curvature, orientation and positional difference of the vehicle against the given line. We call this function λ the steering function. The uniform asymptotic stability of the feedback rule is proved through linearization and a Lyapunov function. Next, this basic line-tracking result is applied to the problem of path tracking where a path consists of directed straight lines. The main advantages and features of the results are summarized as follows. (i) Since the derivative dκ/ds of path curvature is obtained, the path curvature is always continuous while a vehicle converges to the line. (ii) By assuming the critical damping condition, the steering function contains one parameter σ that controls the smoothness (or equivalently, sharpness) of vehicle motions. (iii) This theory can be applied to a vehicle with any wheel architecture, i.e. this theory is vehicle independent. (iv) The theory can easily be extended to the more general problem of tracking a path consisting of any number of directed lines with a new principle of neutral switching. (v) The simplicity and machine independence of this theory makes implementation of this theory on vehicles easy. We present numerous simulation results of line/path-tracking motions. These results verify the effectiveness of this continuous-curvature motion control method. Some successful results obtained on the autonomous robot Yamabico at the Naval Postgraduate School are also included.     

A method of vertical and horizontal force estimation by using air-filled material and camera for soft physical human-robot interaction: fundamental experiments

A method of vertical and horizontal force estimation for soft physical human–robot interaction by using an air-filled material and a camera was proposed in this study. First, we considered hypotheses for vertical and horizontal force applied to the air-filled material. Second, the prototype of air-filled material and vision-based force-sensing device (AVFSD) was constructed. Based on the result of preliminary experiments, the relationships between force, pneumatic pressure, and contact surface displacement were formulated. The vertical and horizontal force could be estimated using the AVFSD with percentage errors of 3.6 and 5.8%, respectively, and the hypotheses were verified through the experiments.