A vision measurement model of laser displacement sensor and its calibration method

Laser displacement sensors (LDSs) use a triangulation measurement model in general. However, the non-linearity of the triangulation measurement model influences the measurement accuracy of the LDS, and the geometric parameters calibration process of the components of the LDS is tedious. In this paper, we present a vision measurement model of the LDS based on the perspective projection principle. Furthermore, a corresponding calibration method is proposed. A planar target with featured lines is moved by a 2D moving platform to some preset known positions. At each position, the world coordinates of calibration points are obtained by the cross ratio invariance principle and the linear array camera of the LDS is used for collecting target images. The simulations verify the effectiveness of the proposed model and the feasibility of the calibration method. The experimental results indicate that the calibration method achieves a calibration accuracy of 0.026 mm. Compared with the traditional measurement model, the vision measurement model of the LDS is more comprehensive and avoids a linear approximation procedure, and the corresponding calibration method is easily complemented.     

CCD摄像机用于测量中存在的问题及解决方法

本文从ＣＣＤ面阵探测器的光电响应不均匀性、非线性以及摄像机内部的制式转换电路、自动增益控制（ＡＧＣ）电路和γ校正电路等方面阐述了ＣＣＤ摄像机用于能量分布测量存在的问题，并给出了相应的解决方法。同时对去除噪声的多幅积分法作了介绍。     

空间CCD相机的定标方法研究

介绍了相机定标的测试方法。通过对空间CCD相机成像时的地物辐射能量进行分析,提出了以成像方式进行相机定标测试的方法,并对数据处理方式进行了分析。     

用于标定CCD相机的高精度数控LED点光源

介绍了一种以发光二极管（LED）点光源作为相机标定光源的方法。根据LED点光源的特性,用恒流源给LED点光源提供所需的电流,用光照度计测量LED光源的光强度。由ARM单片下位机控制恒流源;通过串行通讯与上位机交换数据;由计算机作为上位机来管理数控恒流源和光照度计;根据所测光度值来调节电流,直到光度达到预想值。实验分析显示：LED点光源作为标定光源可以达到CCD标定的要求,精度也较高,能够很好地自适应控制LED的光照强度,达到了预期的效果,且系统使用方便灵活,性能稳定可靠。     

用正交线阵CCD实现高精度小圆孔自动测量

提出了一种使用线阵CCD自动测量小圆孔参数的方法。该方法充分利用了线阵CCD分辨率高的特点 ,适当的光学设计使两个线阵CCD正交 ,通过测量小圆孔的夫琅和费衍射条纹 ,实现了小圆孔半径的一维参数高精度自动测量和圆度误差的二维参数定性自动测量。该方法具有一定的实用价值及应用前景。     

CCD摄像系统光学特性的一种标定方法

从定量化光学遥感测量的需求出发 ,给出了一种对 CCD摄像系统的像素间隔、光电响应的非线性和非均匀性等光学特性进行标定的方法 ,详细介绍了标定过程 ,并给出了部分测试结果。     

摄影测量中CCD相机精度对比方法研究

数字摄影测量在逆向工程和三维检测方面具有广泛应用。对摄影测量中CCD相机的测量精度进行探讨,提出一种基于数理统计的计算方法。通过相机拍摄多组照片,在XJTUDP软件下计算相同条件的编码点或非编码点之间的距离,得出其平均值,将测得的每组单个数值减去平均值,可获得每次测量的个体误差。求个体误差与平均值的比值的绝对值,可得出单组数组的测量精度。对测量精度求平均值,得出标准精度的概念。将标准精度作为衡量CCD相机测量精度的指标。结合试验数据,应用本方法对Cannon400D定焦相机和变焦相机进行较详细的分析,为定焦和变焦相机的选取提供依据。     

A camera calibration method for large field optical measurement

A camera calibration method is presented for large field optical measurement, where the camera is close to the ground and the control points can only be located close to the ground, too. In such conditions, the camera's optical center and the control points are approximately coplanar. Only a single image of these control points captured by the camera in measurement state is used in the method. Neither to distribute the control points in space rationally nor to calibrate the camera's intrinsic parameters in laboratory in advance is needed. By the presented method, the camera's principal point position, focal length, radial and transverse tangency lens distortion coefficients, and the camera's position and attitude parameters can be estimated precisely. Then the calibration results can be used for precise large field optical measurement in the conditions that the camera's longitudinal tangency lens distortion can be neglected or the objects’ movement field is close to the ground, which is usually factual in practical applications. The presented camera calibration method has been successfully used in applications, such as automatic landing of UAV (Unmanned Aerial Vehicle) based on optical measurement guidance, to calibrate the cameras precisely.     

A LabVIEW-based real-time measurement system for polarization detection and calibration

A rapid real-time polarization measurement system was designed and implemented in this paper. The system is centered round a computer running application developed for the purpose. The paper illustrates how to build such an excellent application with National Instruments’ graphical programming language LabVIEW, a synchronized high speed multi-channels data acquisition card and some photoelectric conversion module in detail. With simple and friendly user interface, the experimental result shows that the measurement system has high computational efficiency, high precision calibration matrix, which can be efficiently utilized in experiments relating to the measurement of polarization.     

高精度光电弹道测量系统

 利用光电跟踪系统实时测量导弹类飞行目标已成为靶场测试手段的发展趋势之一,光电跟踪系统需要具备高精度跟踪高速飞行目标、实时输出目标飞行轨迹数据以及目标飞行姿态等实时图像信息。提出一种新型车载光电弹道测量系统,应用高强度轴承改善角位置输出的稳定性;利用再生反馈控制技术抑制跟踪快速目标时产生的滞后误差,提高光电弹道系统的测量精度;将测量数据归一化为垂线测量坐标系中的测量值,以20 ms的刷新率对外输出;提出模拟航路检测方式,可在野外条件下完成对光电设备性能检测,实际稳态跟踪精度可达到0.21 mrad。     

Line-scan CCD camera calibration in 2D coordinate measurement

We present a line-scan camera calibration method in a plane not perpendicular to but parallel to the optical axis, without requiring the camera motion or a complex calibration pattern. A random 2D reference coordinate system in the calibration plane can be used, images of a rod perpendicular to the calibration plane at known coordinates are captured by the camera, the relation between the given coordinates and the rod image centroid position are analyzed based on a reduced pinhole model and image processing, and then the camera parameters and distortion factors are all estimated. These distortion factors build a sample relation only between the image position in theory and in practice, and they do not change with object position. Two wide-angle line-scan cameras that are used in a 2D-coordinate measurement system are calibrated by this method; the application results illustrate the effectiveness and convenience of this method.     

A novel TCF calibration method for robotic visual measurement system

An accurate TCF (tool control frame) model is essential for high-accuracy robot off-line programming. Meanwhile, TCF calibration is an important procedure for production recovery after robot collides in industrial field. This article proposes a novel TCF calibration method in robotic visual measurement system in which the robot TCF is defined based on the model of visual sensor and a standard sphere with known diameter is utilized as the calibration target. With the translational and rotational movements of the industrial robot, the visual senor measures the center of standard sphere from multiple different robot postures, TCF orientation and TCP position are determined in two steps. Robot off-line programming is performed based on the TCF calibration result, and robot collision is simulated on an ABB IRB2400 industrial robot. Experimental results have validated the effectiveness and efficiency of the standard sphere-based TCF calibration method, which could control the deviation of an identical featured point within 0.5 mm measured before and after collision recovery.     

Sphere-based calibration method for trinocular vision sensor

A new method to calibrate a trinocular vision sensor is proposed and two main tasks are finished in this paper, i.e. to determine the transformation matrix between each two cameras and the trifocal tensor of the trinocular vision sensor. A flexible sphere target with several spherical circles is designed. As the isotropy of a sphere, trifocal tensor of the three cameras can be determined exactly from the feature on the sphere target. Then the fundamental matrix between each two cameras can be obtained. Easily, compatible rotation matrix and translation matrix can be deduced base on the singular value decomposition of the fundamental matrix. In our proposed calibration method, image points are not requested one-to-one correspondence. When image points locates in the same feature are obtained, the transformation matrix between each two cameras with the trifocal tensor of trinocular vision sensor can be determined. Experiment results show that the proposed calibration method can obtain precise results, including measurement and matching results. The root mean square error of distance is 0.026 mm with regard to the view field of about 200×200 mm and the feature matching of three images is strict. As a sphere projection is not concerned with its orientation, the calibration method is robust and with an easy operation. Moreover, our calibration method also provides a new approach to obtain the trifocal tensor.     

基于计算机视觉的平视显示器视差测量方法的研究

针对平视显示器的视差测量要求,在分析各种传统检测方法的基础上,提出了一种利用CCD和数字图像处理技术相结合的基于计算机视觉的视差自动测量方法。详细论述了该方法的测量原理,推导并建立了视差角与离焦量的关系,对该测量装置的光学系统进行了合理设计,并对后期图像处理和分析进行了具体研究。该方法利用CCD取代人眼的主观判读,测量精度在30″以内,具有快速准确、定量直观等特点,大大提高了平视显示器的调校精度和效率。     

高精度单轴旋转姿态测量系统研究

 采用90型二频机抖激光陀螺和石英挠性加速度计,利用单轴旋转惯性组件的方法,研制了高精度姿态测量系统。介绍了系统的硬件结构组成和无减震结构设计方案,给出了初始对准和姿态测量系统的算法。系统的初始对准采取粗对准和精对准两种方式, 姿态测量系统的误差传播特性由系统的误差模型来描述。对该系统进行了静态导航实验和长时间单轴旋转导航实验。实验结果表明：系统水平姿态24h保持精度优于30″,24h航向保持精度优于30″。     

小视场长焦距镜头畸变高精度测量研究

利用由精密测角仪、显微摄像测量系统、微型双光栅平面干涉仪、平行光管以及星点组成畸变测量系统,对小视场长焦距的镜头进行畸变测量。在计算镜头畸变中,利用中心视场区域内畸变设计无穷小,采用三次多项式拟和的方法,计算镜头理论焦距;在边视场采用像高高次方和视场角正弦高次方加权平均的方法对测量偏差角进行修正,得到各视场的相对和绝对畸变。通过实际测量和计算验证,镜头全视场畸变测量精度可达到0.02%。     

多台线列CCD相机组合交汇目标脱靶量测量

提出一种新的测量方法 ,在两台线列CCD相机不能满足大尺寸光电靶面的测量需要时 ,由多台线列CCD相机组合交汇测量 ,并给出了两种不同的布站方式。在分析了测量精度的数学模型后 ,分别计算了两种布站方式的光电靶面上不同位置点的交汇测量精度。根据精度分析并结合测量条件 ,给出了适合实际测量条件的最优布站方式     

高精度CCD室内立靶测试系统设计

针对室内靶道,设计了一种基于双线阵CCD图像采集的立靶密集度测试系统,论述了系统的工作原理和组成。提出了一种新的数学模型,有效地抑制了传统测试方法中对两个相机相对位置的精度要求,配合阵列LED背射主动光源,通过一体化靶架设计,提高了测试精度,极大地减少了系统布靶时间。实弹射击试验验证了系统的工作性能。结果表明,所研制的测试系统布靶快捷,在1m×1m测试范围内,立靶坐标偏差均方根小于1mm,能够实现连发测试。     

Using distortion correction to improve the precision of camera calibration

Optical Review - In this paper, we proposed a method to improve the precision of camera calibration through distortion correction. Before calibrating parameters of the camera, we first corrected...     

基于单数码相机的三维视觉测量数据拼接方法

针对大型物体三维形貌视觉测量,提出了一种新的视觉测量三维数据拼接方法。以一台高分辨率数码相机作为全局测量设备,在测量过程中固定不动,并以数码相机坐标系作为全局坐标系。视觉传感器流动到不同位置对物体各子区域进行测量,获得局部坐标系下的三维数据。以一平面靶标为中介将视觉传感器在各位置的局部坐标系统一到全局坐标系下,从而将三维数据统一到全局坐标系下,完成三维拼接。该方法无需在被测物上贴标记,因此适用于任何材质的被测物,且消除了拼接累积误差。实验结果表明,该方法相对拼接误差为0.076%。以Venus石膏像为被测对象,视觉传感器对其三个局部区域进行测量,给出了局部测量结果及拼接结果。