采用复合式靶标的近景大视场相机标定方法

Camera calibration method for close range large field of view camera based on compound target

针对风洞内视觉测量视场较大,测量物体较近以及图像畸变过大等导致的标定精度低,标定物成本高等问题,提出了一种基于复合式靶标分区域分约束近景大视场相机标定方法。该方法利用一维标定架与二维标定平面构造的复合式靶标充满测量视场将测量视场划分区域,针对不同参照物信息采用分约束的方式完成整个视场的分区域准确标定,重建时针对感兴趣特征所处图像不同区域选取不同像机内外参数与畸变系数进行3D重建,完成基于复合式靶标的三维信息求取。最后,针对所提出的标定方法进行了标定精度对比以及验证实验。实验结果表明:内区域标定均方根误差为0.165,外区域标定均方根误差为0.276,标定精度高,满足了测量精度要求。

A compound target for camera calibration in wind tunnels is developed, solving problems of low precision and high costs caused by a large field of view, small object distance and severe distortions of optical images. Moreover, a camera calibration method for close range photogrammetry system based on different constraints in different regions was presented in this paper. The 1-D calibration frame and 2-D planar in the compound target were utilized to divide the field-of-view into two regions. Based on distinguished constraints offered by the two calibration references, camera intrinsic, extrinsic and distortion parameters for the two regions were calculated respectively. Then the 3-D coordinates of targets can be reestablished with high precision according to the image region where interesting features lie in. In the end, accuracy contrast test and verification test with respect to the proposed calibration method had been conducted. The results show that the root mean square calibration error of inner region is 0.165 and the root mean square calibration error of exterior region is 0.276, verifying that this method is simple,effective and of high accuracy, meeting the precision requirements.