CN1254956C - Calibrating method of pick-up device under condition of traffic monitering - Google Patents

Calibrating method of pick-up device under condition of traffic monitering Download PDF

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CN1254956C
CN1254956C CN 200410017703 CN200410017703A CN1254956C CN 1254956 C CN1254956 C CN 1254956C CN 200410017703 CN200410017703 CN 200410017703 CN 200410017703 A CN200410017703 A CN 200410017703A CN 1254956 C CN1254956 C CN 1254956C
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camera
line
coordinates
calibration
intersection
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CN1564581A (en
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陈兆学
施鹏飞
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上海交通大学
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Abstract

一种交通监视环境下的摄像机标定方法,从交通场景中选择出一组彼此间隔已知的三条平行边和一条斜率已知的与平行线相交的直线作为所需要的标定目标,找到它们在图像中所对应的各投影直线并求出各投影直线的所有交点坐标,根据这些数据求得摄像机的焦距、方向和位置参数。 A camera calibration method in environmental monitoring traffic, the traffic scene selected from a set of calibration target is known spaced from one another and a three parallel sides parallel to the slope of the line known as the line intersecting required, they find in the image corresponding to each projection as the linear straight and finding all the intersections of each projection coordinates calculated focal length, camera orientation and position parameters based on these data. 本发明可以利用城市交通场景内类似斑马线以及包含道路两侧边缘在内的车道线等易于提取的典型特征,根据路面上诸多特殊直线的分布信息,进行摄像机相关参数的确定,方法实现简单,针对性和通用性好,且具有线性计算复杂度,可应用于传统标定方法不可能应用的诸多交通监控场合下完成摄像机标定。 The present invention may be utilized in urban traffic scene of similar characteristic and typical lane crossing lines containing both side edges of the road, including easily extracted, according to the linear array of special distribution information on the road, the determination of the camera parameters, the method is simple, for and common good, and linear computational complexity can be used to complete the conventional calibration method of camera calibration impossible to apply many traffic surveillance applications.

Description

交通监视环境下的摄像机标定方法 Camera calibration method in the traffic monitoring environment

技术领域 FIELD

本发明涉及一种交通监视环境下的摄像机标定方法,主要用于交通监视环境下摄像机方位参数和焦距的求取,为基于视频的各种交通信息的实时准确检测提供基本保证。 The present invention relates to a camera calibration method at a traffic monitoring environment, the main parameters for obtaining the camera position and focal length of the lower traffic monitoring environment, provide the basic guarantee for the accurate detection of a variety of real-time video-based traffic information. 属于智能交通技术领域。 Belonging to the field of intelligent transportation technology.

背景技术 Background technique

通过交通智能监控系统实现交通信息的自动采集和处理是各国乃至全球智能交通系统(ITS,Intelligent Transportation System)中最基本要素之一,随着传感器技术、通信与网络技术以及模式识别、图像处理与计算机视觉等高新技术的发展,智能交通信息监测技术也得到长足的进展。 Automatic collection and processing of traffic information through the intelligent traffic monitoring system is one of the elements of national and global Intelligent Transportation Systems (ITS, Intelligent Transportation System) in the most basic, along with sensor technology, communications and network technology as well as pattern recognition, image processing and development of computer vision and other high-tech, intelligent traffic information monitoring technology has also been considerable progress. 一般说来,交通状态和交通流量数据可通过各种类型的传感器获得,如埋藏于路面下的电感传感器和设置于路面上的雷达、红外线、超声波、微波传感器等等。 In general, the state of traffic and traffic data can be obtained by various types of sensors, such as buried under a road surface and an inductive sensor disposed on the road surface radar, infrared, ultrasonic, microwave sensors. 但是由于这些“点”传感器所获取的信号不直观,检测精度不高而且监测范围和检测参数都非常有限,不能提供全面而直接的交通信息。 However, since the signals of these "point" sensors acquired not intuitive, the detection accuracy is not high and the monitoring range and detection parameters are very limited and can not provide a full and direct the traffic information. 近年来,以摄像机等视觉传感器和计算机视觉理论为基础的车辆识别与交通运行状态检测技术已经逐渐成熟,开始应用于交通信息的自动采集与处理过程中,在不需要人的干预、或者只需要很少干预的情况下,通过对摄像机拍录的视频序列分析实现动静态车辆的检测、分割、识别和跟踪,判断车辆的行为,提取交通状态信息并予以适当控制和诱导,实现对交通系统的有效管理。 In recent years, the visual sensor like a camera and computer vision theory based on vehicle identification and vehicle running state detection technology has matured, began to be used during the automatic acquisition and processing of traffic information, without the need for human intervention, or only with little intervention by the video camera recording the sequence of static and dynamic analysis to achieve vehicle detection, segmentation, identification and tracking to determine the behavior of the vehicle, traffic status information is extracted and properly controlled and induction, to achieve the transport system effective management. 摄像机标定是一个必要和基本的处理步骤,它可以确定两维图像坐标和三维世界坐标之间的映射关系,是车速、车型、事故勘察等与空间尺寸相关的交通信息有效提取的前提和基本保证。 Camera calibration is a necessary and basic processing steps, it can determine the mapping between the two-dimensional image coordinates and three-dimensional world coordinates, and the basic premise is to ensure that traffic information related to the spatial dimensions of speed, car, accident investigation and other effective extraction .

在计算机视觉、工业测量、智能机器人导航以及质量控制等领域,针对各种具体应用场合,人们常用的摄像机标定方法有以下几种:(1)利用三维结构的标定块与图像点的对应点进行标定的方法;(2)利用消失点标定的方法,这种方法利用平行线在图像中形成的消失点和消失线的性质来求解摄像机参数;(3)利用平面对应矩阵标定的方法;(4)基于对应点的自标定方法,该方法利用摄像机在两组平移或旋转中拍摄的序列图像之间的对应关系求取摄像机的内参数等等。 In computer vision, industrial measurement, quality control of the intelligent robot navigation, and other fields for a variety of specific applications, the camera calibration method often used are the following: (1) using the corresponding point calibration block and three-dimensional structure of the image point calibration method; (2) using the method of calibration points disappear, this method using a vanishing point and the vanishing line nature parallel lines in the images are formed to solve the camera parameters; (3) a method using a calibration matrix corresponding plane; (4 ) from the corresponding point calibration method based on the method of obtaining the camera parameters and the like with the corresponding relationship between the sequence of images captured by the camera in the two rotation or translation. 这些方法由于没有考虑交通场景的特殊性和交通景物的具体特点,当用在视频交通监控场合时存在一定的缺点,缺乏具体的针对性和通用性。 These methods are not considered due to the specific characteristics of the special nature of the traffic scene and traffic scene, there are some disadvantages when used in video traffic surveillance applications, the lack of specific relevance and versatility. 对于交通场景中的摄像机标定过程而言,标定目标的方便快捷地提取和辨识是一个必不可少的步骤和要求。 For the camera calibration process traffic scene, convenient calibration target quickly and easily extract and identification is an essential step and requirements. 基于路面上相邻车道线段的几何特性,Nelson,Grantham,和George等人曾引入了一种新型的交通视频监控系统摄像机标定方法(“Anovel camera calibration technique for visual traffic surveillance,”Proc.7thWorld Congress on Intelligence Transportation Systems,paperno.3024,2000)。 Based on the road adjacent lane segment of geometric characteristics, Nelson, Grantham, such as George and who had introduced a new type of traffic video surveillance system camera calibration method ( "Anovel camera calibration technique for visual traffic surveillance," Proc.7thWorld Congress on Intelligence Transportation Systems, paperno.3024,2000). 由于在很多情况下,相邻两车道线段平行且各端点顺时针递次相连所成四边形往往为矩形,该方法充分利用此类矩形目标四个顶点的空间位置关系以及它们在图像平面中的投影所成对应点的图像坐标,在车道间距已知的前提下,可以直接导出求取摄像机焦距和方位参数的解析表达式。 Since in many cases, two adjacent lane and parallel line segments connected to each of the endpoints clockwise delivery times tend to be formed by a rectangular quadrilateral, which takes full advantage of such a four rectangular target spatial relationships, and their vertex in the image plane of the projection the image coordinates of the corresponding point into, known under the premise lane spacing, the analytical expression derived directly strike the camera focal length and orientation parameters. 它实现简单,具有线性时间计算复杂度,能够简单、快速地完成摄像机标定并且具有相当的针对性,不失为一种高效的标定方法。 It is simple, linear computational complexity time can be easily and quickly completed and the camera calibration considerable targeted, after all, a highly efficient calibration method. 然而,在很多交通场合,矩形标定目标并不是很容易被发现的,比如在城市交通路口的视频监控场景下就很难直接找到类似的目标,这是一个不容忽视的局限性,因此该方法在交通监视环境下必然缺乏通用性。 However, in many traffic situations, rectangular calibration target is not very easy to be found, for example, it is difficult to directly find similar objectives in urban traffic intersection scene video surveillance, which is a limitation can not be ignored, so the method in the inevitable lack of versatility under traffic monitoring environment.

发明内容 SUMMARY

本发明的目的在于针对现有摄像机标定技术的不足,提供一种新的交通监视环境下的摄像机标定方法,实现容易,能充分保证交通监视环境下的针对性或通用性,满足智能交通信息视频监测系统交通参数准确提取的实际需要。 The purpose of the invention is insufficient calibration technology for existing cameras, camera calibration method provided under a new traffic monitoring environment, easy to implement, can fully guarantee universal or targeted at the traffic monitoring environment to meet intelligent video traffic information accurate traffic monitoring system parameters extracted from actual needs.

为实现这样的目的,本发明利用了城市交通场景内易于提取的一些典型特征,根据路面上诸多特殊直线的分布信息,进行摄像机相关参数的确定。 To achieve this object, the present invention takes advantage of some of the typical characteristics of urban traffic scene easily extracted, according to the linear array of special distribution information on the road, the determination of the camera parameters. 本发明作为一种通用的交通场景摄像机标定新方法,无需一个规则的标定矩形,仅需要路面上一组彼此间隔已知的三条平行边和一条斜率已知的与平行线相交的直线以及它们在图像平面上的投影来求取摄像机焦距长度和方位参数。 Calibration of the present invention as a general rectangular traffic scene new camera calibration method, without a rule, need the road from each other a known set of three parallel spaced edges and a line parallel to the slope of the known straight line intersecting and only their projected on the image plane is obtained by the camera focal length and orientation parameters. 该组平行边彼此之间的距离需要预先确定,所选用相交直线及其斜率也需要被事先选择并计算出来。 The distance between the parallel sides set another predetermined required, and the slope of the line of intersection of the chosen also need to be pre-selected and calculated. 在实际应用场合中,类似斑马线以及包含道路两侧边缘在内的车道线可能是所需要平行边集合的良好选择,也是城市交通场景中非常有代表性的典型特征。 In practical applications, similar to the zebra crossing and a lane line includes both sides of the road, including the edge may be a collection of parallel sides needed a good choice, but also in urban traffic scene very representative of the typical characteristics. 斜率已知且与三平行边相交的直线在交通场景中同样很容易被找到或者被预置,这充分保证了交通监视环境下本发明所提出摄像机标定方法的针对性和通用性。 It is known and the slope of the three-line intersecting the parallel sides in the same traffic scene can be easily found or is preset, that the present invention fully guarantee the traffic monitoring environment pertinence and a camera calibration method proposed. 要完成摄像机标定,本发明首先从交通场景中选择出所需要的标定目标,测量路面上三平行线彼此间距并计算出与它们相交直线的空间斜率,同时找到它们在图像中所对应的各投影直线并求出各投影直线的所有交点坐标,将这些数据作为原始输入,最终可求得摄像机的焦距、方向和位置参数。 To complete calibration, the present invention first selects the calibration target required from traffic scene, measured on the road surface three parallel lines distance from each other and calculate the spatial slope they intersect a straight line, while finding each projection linearly they correspond in the image each projection line is determined and all intersection coordinates, the original data as input, the focal length can be obtained finally, the position and orientation parameters of the camera.

本发明方法的具体步骤如下:(1)标定目标的选取和相关坐标系的建立:在交通场景中选择路面上一组彼此间隔已知的三条平行线、一条斜率已知并与三条平行线相交的直线作为标定目标,并确定标定目标在图像中的各投影对应直线和对应交点。 Specific steps of the method of the present invention are as follows: Picking and associated coordinates system (1) Calibration target: selecting a set of known spaced from one another on three parallel lines in the road traffic scene, a known slope and intersects three parallel lines a linear calibration target, and determining the calibration target corresponding to each of the projected image corresponding to the intersection of the straight line and. 建立世界坐标系,设定世界坐标系原点位于中间一条平行线与相交直线的交点,Y轴正向沿中间平行线指向前方,正Z轴垂直于地面方向向上,X轴正向水平指向右方。 Establishment of the world coordinate system, the origin of the world coordinate system is set in the middle of a line parallel to the intersection of intersecting lines, Y-axis positive direction intermediate parallel lines pointing to the front, the positive Z-axis direction perpendicular to the surface direction, X-axis positive horizontally directed rightward . 建立以摄像机为中心的坐标系,该坐标系以透镜中心为原点,摄像机的光轴作为V轴,并使UW坐标轴的平面平行于图像平面,且与透镜中心间距为摄像机焦距。 Establish a camera-centric coordinate system, the coordinate system origin to the center of the lens, the optical axis of the camera as the V axis, and a plane parallel to the axis UW image plane, and a pitch of the focal length of the camera lens center.

(2)标定输入数据初始化:相对于以摄像机为中心的坐标系,用最小二乘法计算出标定目标在图像中各投影对应直线的所有交点的坐标,同时求出它们在图像平面上的斜率。 (2) the calibration data input to initialize: centered with respect to the camera coordinate system is calculated by least squares calibration target in the image corresponding to each projection coordinates of all intersections of a straight line, while the slope which is obtained in the image plane.

(3)关于地面所对应消失线和相交直线所对应消失点的计算:根据三平行线中相邻两直线间距、相交直线与三平行线空间交点坐标、以及相对于以摄像机为中心的坐标系得到的三平行线和相交直线在图像平面上相应投影直线的各交点坐标参数,得到地面所对应消失线斜率和一般式方程,求出相交直线在图像平面上的投影直线与消失线的交点坐标,即求得相交直线在图像平面上所对应的消失点坐标。 (3) calculates the vanishing point and the vanishing line corresponding to the intersection of the straight line on the ground corresponding to: The linear spacing of two adjacent three parallel lines, parallel lines, intersecting lines and three intersections coordinate space, and centered with respect to the camera coordinate system each intersection coordinates obtained in three parallel lines and intersecting lines on an image plane corresponding to the projected straight line, the slope and the vanishing line to give a general formula corresponding to the ground equations, the intersection coordinates obtained straight line of intersection of the projection of the vanishing line in the image plane , i.e., to obtain a straight line intersecting the vanishing point on the image plane coordinates corresponding.

(4)摄像机参数标定:由三平行线中相邻两直线间距、相交直线与三平行线空间交点坐标、三平行线和相交直线在图像中投影直线的各交点坐标、消失线斜率以及相交直线的投影直线与消失线的交点坐标求得摄像机的旋转角、偏角、俯仰角以及摄像机焦距,最后根据本发明所定义两坐标系的相关变换关系得到摄像机镜头中心的三维位置坐标,完成摄像机标定。 (4) Calibration camera parameters: three linear spacing of two adjacent parallel lines, parallel lines, intersecting lines and three space coordinate intersections, three parallel lines and the straight line intersect each intersection coordinates in the image projected straight line intersecting the straight line and the slope of the vanishing line the intersection coordinates of the projection straight line is obtained with the disappearance of the rotation angle, angle, pitch angle and the camera focal length of the camera, the 3D position coordinates last transformation between two coordinate systems related to the center of the camera lens obtained according to the present invention is defined, complete camera calibration .

本发明的方法实现简单,针对性和通用性好,且具有线性计算复杂度,可应用于传统标定方法不可能应用的诸多交通监控场合下完成摄像机标定。 The method of the present invention is simple, specific and general good linear computational complexity and can be used to complete the calibration camera calibration method can not use traditional traffic monitoring many occasions.

附图说明 BRIEF DESCRIPTION

图l为本发明中世界坐标系和标定目标的关系示意图。 Invention showing the relationship between a world coordinate system and the calibration target present in Figure l.

图2为本发明中标定目标投影图像与地面消失线的示意图。 A schematic view of the target image projected to the ground vanishing line in FIG. 2 of the present invention the calibration.

图3为本发明的摄像机坐标系。 FIG 3 the camera coordinate system of the present invention.

图4为本发明实施例所采用的交通场景原始图像。 Traffic scene of the original image in FIG. 4 embodiment employed in an embodiment of the present invention.

图5为本发明实施例从原始图像中选择的标定目标示意图。 FIG 5 a schematic diagram of the calibration target from an original image selected embodiments of the present invention.

具体实施方式 Detailed ways

为了更好地理解本发明的技术方案,以下结合附图和实施例作进一步详细描述。 To better understand the technical solutions of the present invention, the following embodiments in conjunction with the accompanying drawings and described in further detail.

1)标定目标的选取和相关坐标系的建立:在交通场景中选择标定目标即一组彼此间距己知的三条平行线以及一条与该组平行线相交的已知斜率的直线。 1) Selection and establishment of the coordinate system associated calibration target: selecting a set of calibration target i.e. three parallel straight lines known distance from each other and the known slope of an intersecting sets of parallel lines in the traffic scene. 它们在实际路面上分别被表示为a,b,c,d,直线a,b,c表示三条平行线,直线d与它们相交,三条平行线与直线d的交点分别被表示为A,O,B,如图1所示。 They are represented on the actual road surface of a, b, c, d, a straight line a, b, c represents three parallel lines, straight lines d and which intersect, three parallel lines and intersection of the line d are denoted as A, O, B, as shown in FIG. 这里,直线d的斜率已经预先测出,表示为m,直线a,b,c中两相邻平行线的间距顺次表示为d1,d2。 Here, the slope of the straight line d has been previously measured, is represented as pitch m, a straight line a, b, c of the two sequentially adjacent parallel lines is expressed as d1, d2. 本发明将标定目标在图像中所对应的投影直线分别表示为a',b',c',d',并将直线d'与直线a',b',c'的交点相应表示为A',O',B',如图2所示。 The present invention is the calibration target in the image projected straight lines corresponding respectively to a ', b', c ', d', and straight line d 'and the straight line a', b ', c' of intersection of the respective represented as A ' , O ', B', as shown in FIG. 需要说明的是,图2中直线 It should be noted that the straight line 2 in FIG. 表示图像中路面平面所对应的消失线。 It represents the road surface in the image plane corresponding to the vanishing line. 其中,点VD表示平行线组投影a',b',c'所对应的消失点,而VO表示直线d'所对应消失点。 Wherein VD represents the point set of projection parallel lines a ', b', c 'corresponding to the vanishing point, a straight line representing the VO d' corresponding to the vanishing point.

为了标定摄像机的方向和焦距参数,需要定义两个右手坐标系:世界坐标系和以摄像机为中心的坐标系。 In order to calibrate the direction and focus parameters of the camera, we need to define two right-handed coordinate system: the world coordinate system and camera-centric coordinate system. 假定世界坐标系的原点位于直线b和d的交点O,Y轴正向沿直线b指向前方,正Z轴垂直于地面方向向上,而X轴正向则水平指向右方,则交点A,O,B坐标可以被表示为(xA=-d1,yA,zA=0),(xo=0,yo=0,zo=0),(xB=+d2,yB,zB=0),计算路面直线d斜率m=(yB-yA)/(d2+d1)。 Assumed origin of the world coordinate system is at the intersection of the straight line b, and d O, Y-axis positive directed forward in a straight line b, the positive Z-axis direction perpendicular to the direction of the ground, while the positive X axis is directed horizontally to the right, then the intersection point A, O , B coordinates can be expressed as (xA = -d1, yA, zA = 0), (xo = 0, yo = 0, zo = 0), (xB = + d2, yB, zB = 0), the road surface is calculated linear d slope m = (yB-yA) / (d2 + d1).

摄像机坐标系以透镜中心为原点如图3所示。 Center of the lens to the camera coordinate system origin shown in Fig. V轴是摄像机的光轴,位于V=f处的UW平面平行于图像平面,其中-f表示摄像机焦距。 V axis is the optical axis of the camera, located at f V = UW plane parallel to the image plane, wherein -f represents a focal length of the camera. 假设图像平面上的任一点的坐标相对于摄像机坐标系而言,用(u,w)表示。 Suppose the coordinates of any point on the image plane with respect to the camera coordinate system, it is represented by (u, w).

2)标定输入数据初始化:用最小二乘法计算图像中投影直线a′,b′,c′的公共交点VD的坐标为(uD,wD),同时得到它们与直线d′交点A′,O′,B′坐标分别为(uA′,wA′),(uo′,wo′),(uB′,wB′),假设直线a′,b′,c′,d′斜率分别为k-1、k0和k1和k2,则有k-1=wA′-wDuA′-uD,k0=wo′-wDuo′-uD,k1=wB′-wDuB′-uD,k2=wB′-wA′uB′-uA′;]]>3)关于消失线和相交直线消失点的计算:计算中间变量X45,X56,X46,X456D值分别为X45=(2k-1k1-k0k1-k0k-1)(d1/d2)+(k1k-1-k0k-1)(d1/d2)2+(k1k-1-k0k1)(k0-k1)(d1/d2)2+(2k0-k-1-k1)(d1/d2)+(k0-k-1),]]>X56=(k0-k1)(d1/d2)+(k0-k-1)(k1-k0)(k-1uD-wD)(d1/d2)+(k-1-k0)(k1uD-wD),]]>X46=X45·X56X456D=uD·X56-wD·X46则路面直线在图像中投影所对应的消失线方程为k·u-w+(wD-k·uD)=0,其中k=-X45,为消失线斜率。 2) Calibration data initialization input: linear projection image is calculated by a least square method ', b', c 'coordinates VD is common intersection point (uD, wD), and simultaneously give them a straight line d' intersection points A ', O' , B 'coordinates are (uA', wA '), (uo', wo '), (uB', wB '), assuming a straight line a', b ', c', d 'slopes are k-1, k0 and k1 and k2, there are k1 = wA & prime; -wDuA & prime; -uD, k0 = wo & prime; -wDuo & prime; -uD, k1 = wB & prime; -wDuB & prime; -uD, k2 = wB & prime; -wA & prime; uB & prime; - uA & prime ;;]]> 3) lines and the line of intersection of the vanishing point computing disappearance: calculating intermediate variables X45, X56, X46, X456D values ​​of X45 = (2k-1k1-k0k1-k0k1) (d1 / d2) + (k1k-1-k0k1) (d1 / d2) 2+ (k1k-1-k0k1) (k0k1) (d1 / d2) 2+ (2k0-k1-k1) (d1 / d2) + (k0-k1),]]> X56 = (k0-k1) (d1 / d2) + (k0-k1) (k1-k0) (k-1uD-wD) (d1 / d2) + (k-1-k0) (k1uD-wD),]]> vanishing line equations X46 = X45 · X56X456D = uD · X56-wD · X46 is pavement straight line in the projected image corresponding to k · u-w + (wD -k · uD) = 0, where k = -X45, the slope of the line disappears.

直线d′通过O′(uo′,wo′)点,且已求得斜率为k2,其方程可表示为k2·u-w+(wo′-k2·uo′)=0则通过消失线和直线d′方程能够计算出消失线的交点坐标(u,w);4)摄像机参数标定: Straight d 'through O' (uo ', wo') point, and has been determined as the slope k2, which can be expressed as the equation k2 · u-w + (wo'-k2 · uo ') = 0 and the straight line through the vanishing line d 'equation can be calculated intersection coordinates (u, w) of the vanishing line; 4) calibration camera parameters:

假定摄像机镜头中心位于空间点(xc,yc,zc),并且摄像机的偏角(Pan),俯仰角(Tilt)和旋转角(Swing)分别被表示为θ,,Ψ,则计算旋转角(Swing)Ψ。 Assumed that the rotation angle of the camera lens is located in the center of the space point (xc, yc, zc), and the camera angle (Pan), pitch angle (Tilt), and the rotation angle (the Swing) are denoted as θ, , Ψ, is calculated ( Swing) Ψ. 公式为Ψ=arctg(X45)计算摄像机的偏角(Pan)θ为{θ|θ=k1π+arcsin[(2X+m)/1+m2]/2-[k2π+arctg(m)]/2or]]>θ=(2k1+1)π/2-arcsin[(2X+m)/1+m2]/2-[k2π+arctg(m)]/2,]]>k1,k2=…-1,0,1,2…,-π/2≤θ≤π/2}其中X=X456D/[(1+X452)·X56·(u-uD)],]]>计算俯仰角(Tilt)φ为:φ=arcsin(tgθ/X456D)计算摄像机焦距为:f=-wD·cosψ+uD·sinψtgφ]]>考虑世界坐标系中地面上的一点P(x,y,z),假定它在图像平面上的投影点是P'=(u,w),并定义A=cosθcosψ+sinθsinφsinΨ,B=sinθcosΨ-cosθsinφsinψ,C=cosφsinΨ,D=-sinθcosφ,E=cosθcosφ,F=sinφ,G=sinθsinφcosΨ-cosθsinΨ,H=-cosθsinφcosψ-sinθsinΨ,I=cosφcosΨ,则摄像机透镜中心的实际坐标可由如下方程式给出(LLWang,and WHTsai,“Camera Calibration by Vanishing Lines for 3-D Computer Vision,”IEEE Transactions on Pattern Analysis and Machine Intelligence Formula Ψ = arctg (X45) calculated camera angle (Pan) θ is {theta &; | & theta; = k1 & pi; + arcsin [(2X + m) / 1 + m2] / 2- [k2 & pi; + arctg (m )] / 2or]]> & theta; = (2k1 + 1) & pi; / 2-arcsin [(2X + m) / 1 + m2] / 2- [k2 & pi; + arctg (m)] / 2,]]> k1, k2 = ... -1,0,1,2 ..., -π / 2≤θ≤π / 2} where X = X456D / [(1 + X452) & CenterDot; X56 & CenterDot; (u-uD)],]] > calculated pitch angle (Tilt) φ is: φ = arcsin (tgθ / X456D) calculated camera focal length: f = -wD & CenterDot; cos & psi; + uD & CenterDot; sin & psi; tg & phi;]]> consider the world coordinate system a point P on the ground (x, y, z), it is assumed that the projected point on the image plane is P '= (u, w), is defined and a = cosθcosψ + sinθsinφsinΨ, B = sinθcosΨ-cosθsinφsinψ, C = cosφsinΨ, D = -sinθcosφ, E = cosθcosφ, F = sinφ, G = sinθsinφcosΨ-cosθsinΨ, H = -cosθsinφcosψ-sinθsinΨ, I = cosφcosΨ, the actual coordinates of the center of the camera lens is given by the following equation (LLWang, and WHTsai, "camera Calibration by Vanishing Lines for 3-D Computer Vision, "IEEE Transactions on Pattern Analysis and Machine Intelligence ,vol.13,no.4,pp.370-376,April 1991.):xc=x+h(uA+fD+wG)/(uC+fF+wI),yc=y+h(uB+fE+wH)/(uC+fF+wI),zc=z+h---(1)]]>其中,h为摄像机的安装高度。 , Vol.13, no.4, pp.370-376, April 1991):. Xc = x + h (uA + fD + wG) / (uC + fF + wI), yc = y + h (uB + fE + wH) / (uC + fF + wI), zc = z + h --- (1)]]> where, h is the height of the camera mounting.

根据式(1)中关于xc的表达式,计算摄像机安装高度为h=(d1+d2)/(ab),其中 The formula (1) in the expression for the xc is calculated as the camera installation height h = (d1 + d2) / (ab), wherein

a=(uA′A+fD+wA′G)/(uA′C+fF+wA′I),b=(uB′A+fD十wB′G)/(uB′C+fF+wB′I)由于O点坐标为(xo=0,yo=0,zo=0),根据式(1)计算摄像机镜头中心三维位置坐标为:xc=h(uo′A+fD+wo′G)/(uo′C+fF+wo′I),yc=h(uo′B+fE+wo′H)/(uo′C+fF+wo′I),zc=h]]>根据A到I定义计算A,B,C,D,E,F,G,H,I的值并取验证式|uD-B·fE|+|wD-H·fE|<T]]>(T为一接近零的阈值)以检验所得多组θ,φ,Ψ,f的值,最终选择出摄像机方位参数准确解组。 a = (uA'A + fD + wA'G) / (uA'C + fF + wA'I), b = (uB'A + fD ten wB'G) / (uB'C + fF + wB'I ) Since the O point coordinates (xo = 0, yo = 0, zo = 0), calculates the camera lens center 3D position coordinates according to the formula (1): xc = h (uo & prime; A + fD + wo & prime; G) / ( uo & prime; C + fF + wo & prime; I), yc = h (uo & prime; B + fE + wo & prime; H) / (uo & prime; C + fF + wo & prime; I), zc = h]]> the A to I defined calculation a, B, C, D, E, F, G, H, I value and taken to verify the formula | uD-B & CenterDot; fE | + | wD-H & CenterDot; fE | & lt; T]]> (T is a near-zero threshold value) to test the resulting plurality of sets of θ, φ, Ψ, the values ​​of f, finally selected camera position accuracy parameter unmarshalling.

为了验证本发明所提出方法的有效性,本发明的一个实施例采用了以图4所示的实际交通场景图像,并在此实际交通场景图像中选择了标定目标,如图5所示。 In order to verify the validity of the proposed method of the present invention, a present embodiment of the invention uses the actual traffic scene image shown in FIG. 4, and select the actual calibration target In this traffic scene image, as shown in FIG. 选择图像中共点于VD的三条相邻车道线作为标定所需要的一组平行线,分别标识为a′,b′,c′,以停车线作为相交直线d′,它们在世界坐标系中的实际对应直线分别表示为a,b,c,d,其中直线d斜率m=0,直线a和b以及直线b与c之间的距离也事先已知。 Selecting an image point in the three adjacent lane line VD of the CPC as a set of parallel lines required for calibration, respectively denoted as a ', b', c ', to the stop line as the line of intersection of d', which in the world coordinate system actually corresponds to the straight line are denoted as a, b, c, d, where the slope of the straight line d m = 0, the straight line distance between the straight lines a and b and c and b are also known in advance.

实验结果表明,标定参数的求取与四条直线选择的精度有密切关系,但是经过仔细选择,可以得到平均浮动误差约为5%的稳定结果,如表1所列为焦距f和摄像机安装高度h的标定值和实际值的比较(摄像机方向数据因无法测量,难以给出实际值予以比较,故从略),这说明本方法完全能够满足交通监控系统的精度要求,该实验在一定程度上证明了本发明所提出方法的有效性。 Experimental results show that the calibration parameters and obtaining four straight lines is closely related to the selected accuracy, but carefully selected, the results can be obtained stably floating average error is about 5%, as listed in Table 1 is mounted and the height h of the camera focal length f comparing the calibration value and the actual value (due to the camera orientation data can not be measured, it is difficult to be given actual value comparison, it is omitted), which shows the present process can fully meet the accuracy requirements of the traffic monitoring system, which proved to some extent the effectiveness of the method proposed by the present invention.

表1摄像机焦距和安装高度的实验标定结果 Table 1 camera focal length and mounting height of the experimental calibration results

Claims (1)

1.一种交通监视环境下的摄像机标定方法,其特征在于包括如下步骤:1)标定目标的选取和相关坐标系的建立:在交通场景中选择路面上一组彼此间隔已知的三条平行线、一条斜率已知并与三条平行线相交的直线作为标定目标,并确定标定目标在图像中的各投影对应直线和对应交点,建立世界坐标系,设定世界坐标系原点位于中间一条平行线与相交直线的交点,Y轴正向沿中间平行线指向前方,正Z轴垂直于地面方向向上,X轴正向水平指向右方,建立以摄像机为中心的坐标系,该坐标系以透镜中心为原点,摄像机的光轴作为V轴,并使UW坐标轴的平面平行于图像平面,且与透镜中心间距为摄像机焦距;2)标定输入数据初始化:相对于以摄像机为中心的坐标系,用最小二乘法计算出标定目标在图像中各投影对应直线的所有交点的坐标,同时求出它们在图像 A traffic monitoring camera under environmental calibration method, comprising the steps of: 1) selecting and establishing a coordinate system associated calibration target: selecting a set of the road from each other spaced a known three parallel lines in traffic scenes , a known slope with three parallel straight lines intersecting the parallel lines as an intermediate calibration target, and determining the calibration target corresponding to each projection and corresponding to the intersection of the straight line in the image, the establishment of the world coordinate system, the origin of the world coordinate system is set and positioned the intersection of crossing straight lines, Y-axis positive direction pointing to the front intermediate parallel lines, perpendicular to the ground the positive Z-axis upward direction, X-axis forward horizontally to the right and the center of the camera to establish a coordinate system, the coordinate system for the lens center origin, the optical axis of the camera as the V axis, and a plane parallel to the axis UW image plane and the focal distance of the camera lens center; 2) calibration initialization input data: the camera with respect to the center of the coordinate system, with a minimum squares calculate the coordinates of all intersections of the calibration target in the image corresponding to each projection of the straight line, while the image thereof is obtained 面上的斜率;3)关于地面所对应消失线和相交直线所对应消失点的计算:根据三平行线中相邻两直线间距、相交直线与三平行线空间交点坐标、以及相对于以摄像机为中心的坐标系得到的三平行线和相交直线在图像平面上相应投影直线的各交点坐标参数,得到地面所对应消失线斜率和一般式方程,求出相交直线在图像平面上的投影直线与消失线的交点坐标,即求得相交直线在图像平面上所对应的消失点坐标;4)摄像机参数标定:由三平行线中相邻两直线间距、相交直线与三平行线空间交点坐标、三平行线和相交直线在图像中投影直线的各交点坐标、消失线斜率以及相交直线的投影直线与消失线的交点坐标求得摄像机的旋转角、偏角、俯仰角以及摄像机焦距,最后根据两坐标系的变换关系得到摄像机镜头中心的三维位置坐标,完成摄像机标定。 The slope face; 3) calculates the vanishing line and the line of intersection of the ground corresponding to the vanishing point corresponding to: The linear spacing of two adjacent three parallel lines, parallel lines, intersecting lines and three spatial intersection coordinates, as well as with respect to the camera three parallel lines obtained center coordinates and the straight line intersect each intersection point on an image plane coordinates corresponding to the projected straight line, the slope of the vanishing line and ground to obtain a general formula corresponding equations, obtains a straight line intersecting the straight line projected on the image plane and disappear line intersection coordinates, i.e., coordinates of the vanishing point intersects a straight line is obtained on an image plane corresponding; 4) calibration of camera parameters: three linear spacing of two adjacent parallel lines, parallel lines, intersecting lines and three space coordinate intersections, three parallel each intersection of crossing straight lines and the coordinates in the image projection line, the slope and intersection coordinates vanishing line intersecting the straight line and the projection of the vanishing line calculated rotation angle, angle, pitch angle and the camera focal length of the camera, according to the two last coordinates transform relations between the three-dimensional position coordinates of the center of the camera lens, camera calibration is completed.
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