基于平行激光测距的图像自标定方法

doi:10.16183/j.cnki.jsjtu.2021.447

摘要/Abstract

摘要：

针对现有照相机图像标定方法存在的依赖外部图像特征、要求照相机特殊位姿、需要标定物、操作复杂等不足之处,提出了一种基于平行激光测距的实时自标定方法.该方法在图像拍摄过程中,利用高精度激光测距仪连续测量以获得被测物表面的实时位置信息.在此基础上,对物面方程进行求解,选取物面和像面上至少4组对应点的二维坐标,求解得到表示两个平面之间变换关系的单应性矩阵,从而简便快速地完成标定.采用自主研制的标定装置,开展了不同场景下的图像自标定精度测试.结果表明,图像中各线段长度的测量误差介于-0.49%~0.15%,平均误差仅为-0.14%,验证了所提平行激光测距自标定方法具有很高的准确性和稳定性.对标定误差来源进行进一步分析,得到了激光测距误差、激光倾角误差、偏置误差等因素的定量影响规律,并给出了相应的误差规避方法,为该自标定方法在图像测量领域中的应用提供参考.

关键词: 图像测量, 自标定方法, 激光测距, 物面方程, 单应性矩阵

Abstract:

Regarding the disadvantages of existing camera calibration methods, such as external information relative, special camera poses,the need for calibration targets, and complex operations, this paper proposes a real-time self-calibration method based on parallel laser ranging by employing high-precision laser rangefinders to synchronously measure the position of the measured object plane when taking pictures, so that the object plane equation can be solved. The 2D coordinates of at least four sets of corresponding points on object plane and image planes are selected to obtain the homography matrix, which represents the mapping relationship between object and image planes, so as to complete the calibration simply and quickly. A calibration device is developed to validate the accuracy of the proposed self-calibration method in different testing scenarios. The results show that the measurement error of line segments length in the image are between -0.49% and 0.15%, and the average errors are merely -0.14%, which indicates that the parallel laser ranging self-calibration method proposed in this paper is accurate and robust. The causes of measurement error are further investigated by analyzing the influences of laser ranging, laser inclination, and device offset. The error eliminating suggestions are provided to give references for the application of the proposed self-calibration method in the field of image measurement.

Key words: image measurement, self-calibration method, laser ranging, object plane equation, homography matrix

中图分类号:

TP391.4

程斌, 黄斌, 李得睿. 基于平行激光测距的图像自标定方法[J]. 上海交通大学学报, 2022, 56(7): 850-857.

CHENG Bin, HUANG Bin, LI Derui. An Image Self-Calibration Method Based on Parallel Laser Ranging[J]. Journal of Shanghai Jiao Tong University, 2022, 56(7): 850-857.

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场景	各点激光测距值/mm
场景	C_L	C_T	C_R
I	245	245	244
II	345	345	344
III	445	446	443
IV	545	545	543
V	645	646	644

线段	场景I		场景II		场景III		场景IV		场景V
线段	测量值/ mm	相对误差/%	测量值/ mm	相对误差/%	测量值/ mm	相对误差/%	测量值/ mm	相对误差/%	测量值/ mm	相对误差/%
l_A₃_A₇	95.857	-0.15	95.610	-0.41	96.088	0.09	96.057	0.06	95.678	-0.34
l_A₄_A₈	95.785	-0.22	95.582	-0.44	95.923	-0.08	96.148	0.15	95.834	-0.17
l_A₅_A₉	95.532	-0.49	95.577	-0.44	95.928	-0.08	96.084	0.09	95.779	-0.23
l_A₆_A₁₀	95.666	-0.35	95.661	-0.35	95.717	-0.29	96.127	0.13	95.984	-0.02
l_A₁_A₂	96.088	0.09	95.978	-0.02	96.027	0.03	95.975	-0.03	95.879	-0.13