大视场远距离视觉测量系统的分步标定

Two-step calibration for vision measurement system with large field of view and high depth

为了克服工程大视场标定精度不高、标靶加工难度大以及现场操作繁琐的问题,本文基于工业近景摄影测量基本原理提出一种大视场多相机内、外参数的分步标定方法。首先,根据相机透视投影模型,在近距离采用小幅面标靶和角锥体法完成相机前截面内参数的解算;然后,在远距离被测空间内布置若干编码标志点,利用多片后方交会原理计算得到相机外参数;最后,对相机内、外参数进行整体光束平差优化,实现精确标定。为验证该方法的可行性和精度,进行了大视场视觉测量实验,测量结果表明本文标定方法的重投影误差小于0.08像素;外场试验实测10 m直升机旋翼总距角的相对误差小于0.1°。该方法可实现相机内参数标定实验室进行、外参数标定外场完成的操作分离。

To address the problems of low calibration accuracy,difficulties in large target fabrication,and complicated operation in engineering fields,a two-step camera calibration method for vision measurement system with a large field of view is herein proposed and implemented based on industrial close range photo⁃grammetry.The mathematical model of the perspective model of camera imaging is investigated.First,in the close range,the calibration of the internal parameters at the front section is realized using a small-scale cross target and the pyramid method.Second,in the far range,several coding mark points are arranged in the measured space,and the external parameters are calculated based on the principle of single image inter⁃section.Finally,all the internal and external parameters are optimized using bundle adjustment.To verify the feasibility and accuracy of the proposed method,a vision experiment with a large field of view is carried out.Experimental results show that the re-projection error is less than 0.08 pixels,the maximum absolute error of the three-dimensional measurement is 0.43 mm,and the pitch angle error of the rotor with a diam⁃eter of 10 m is less than 0.1°.It is therefore proved that the method can be used to achieve internal as well as external parameter calibration in the external field separately.