激光跟踪视觉导引测量中靶标球球心定位方法

Method for finding the 3D center positions of the target reflectors in laser tracking measurement system based on vision guiding

为解决现有激光跟踪测量系统中存在的搜索区域大、定位速度慢等问题,提出了一种基于单目视觉测量系统求解激光跟踪仪靶标球球心三维坐标,以此作为导引信息,引导单台激光跟踪仪实现多基准点自动测量的方法。对视觉测量所采用的椭圆识别和基于单目摄像机的球心定位算法进行了研究。首先,根据靶标球成像的特点,介绍了基于Gestalt的椭圆识别算法,实现了靶标球图像特征的自动提取与识别。然后,介绍了基于单目摄像机的球心定位算法,即根据图像椭圆方程、相机焦距和球半径求解球心三维坐标,并进行了仿真验证。最后,进行了实际的靶标球图像自动识别与球心定位实验。结果表明,采用文中方法测量两靶标球间已知距离约为550 mm时的RMS误差为1.728 2 mm。激光跟踪仪激光束搜索范围得到大幅减小,基本满足自动测量的快速性和高效性等要求。

In order to solve the problems of large searching region,low positioning speed existing in the laser tracking measurement system at present,a new method for finding the 3D positions of the target reflectors by using monocular model based on vision was proposed.The 3D coordinates of the centers of the reflectors were used to guide mono-laser tracker to fulfill the automatic measurement of multiple benchmarks.Its applied algorithms such as ellipse recognition in vision measurement and spatial spherical center positioning based on mono-camera were investigated.Firstly,based on imaging features of the target reflector such as area,ratio,compactness,the recognition algorithms for image ellipses based on Gestalt theory were presented.The automatic extractions and recognitions of the target reflectors were fulfilled.Then,spatial spherical center positioning algorithm was proposed to calculate the 3D coordinates of the center of the reflectors,based on the equation of image ellipse,camera focal length and spherical radius.Simulation was accomplished as well.Finally,experiments on image ellipse recognition and target reflector center positioning were carried out.Experimental results show that the RMS errors for distances which are about 550 mm between two reflectors fixed on scale bar measured by the method proposed is 1.728 2 mm.The searching range of laser beam is reduced substantially,it can satisfy the requirements of high speed and high efficiency in automatic measurements.