Conventional camera calibration that employs calibration targets is a commonly used method to acquire a camera's intrinsic and/or extrinsic parameters. The calibration targets are usually designed as periodic arra...Conventional camera calibration that employs calibration targets is a commonly used method to acquire a camera's intrinsic and/or extrinsic parameters. The calibration targets are usually designed as periodic arrays of simple high-contrast patterns that provide highly accurate world coordinate system points and the corresponding image pixel coordinate system points. The existing pixel coordinate extraction algorithms can reach a sub-pixel level; however, they treat each single pattern in one image as an independent individual, which makes it difficult to further improve extraction accuracy. In this paper, a novel method is proposed by utilizing the periodic arrangement characteristics of the calibration target pattern as a global constraint to improve the calibration accuracy. Based on a camera's pinhole model, the intersection point of two fitted curves is used as an optimized pixel point to replace the initial one. Following the pixel coordinate optimization procedures, experiments were performed using real data from a 3D laser line scanner and a dynamic precision calibration target. Our results show that the relative errors of camera homography matrix elements obtained by the proposed optimization method were reduced compared with the commonly used method. The average coordinate measurement accuracy can be improved by nearly 0.05 mm. It is shown that the proposed optimization method can enhance the camera calibration accuracy,especially when the extracted pixels are of poorer precision.展开更多
六极铁作为高能同步辐射光源(High Energy Photon Source,HEPS)储存环八铁单元的重要部件之一,其技术工艺较为复杂,对加工精度和中心引出精度要求都很高。本文对HEPS六极铁的机械中心引出标定方案进行了研究,利用极缝偏差角对常规标定...六极铁作为高能同步辐射光源(High Energy Photon Source,HEPS)储存环八铁单元的重要部件之一,其技术工艺较为复杂,对加工精度和中心引出精度要求都很高。本文对HEPS六极铁的机械中心引出标定方案进行了研究,利用极缝偏差角对常规标定坐标系进行旋转,使三个极缝面更接近理论位置,从而减小磁铁主场斜分量;对每块磁铁进行两次机械中心标定,极缝间距的实测值与设计值的标准偏差在0.015 mm,坐标系旋转前后的基准点偏差标准值为0.09 mm,旋转角最大可达0.6 mrad。这种考虑极缝偏差角的建系方法可以提高标定的精度,能为实际工作中同类型、准直精度有相同要求的设备标定提供参考,有利于加速器装置的顺利安装,对加速器准直测量具有十分重要的意义。展开更多
针对传统手眼标定中坐标转换过程繁杂、标定精确度受人为因素影响较大等问题,提出了一种基于相机畸变校正(DC)与回归随机森林(RRF)的改进手眼标定算法。首先,对实验所用的相机进行畸变校正;其次,使用Eye to Hand形式搭建实验台,采集图...针对传统手眼标定中坐标转换过程繁杂、标定精确度受人为因素影响较大等问题,提出了一种基于相机畸变校正(DC)与回归随机森林(RRF)的改进手眼标定算法。首先,对实验所用的相机进行畸变校正;其次,使用Eye to Hand形式搭建实验台,采集图像坐标及其对应的机械臂坐标,建立坐标数据集;最后,使用DC-RRF算法、线性回归算法以及传统手眼标定算法在坐标数据集上进行训练,将不同算法下的平均绝对误差、均方误差等评价指标进行对比。实验结果表明,DC-RRF算法在X/Y/Z三轴上的精准度均为最佳,平均误差可控制在1.77 mm,该算法的精准性在很大程度上保证了机器视觉与机械臂的有效结合并在分拣系统中得到精准应用。展开更多
基金supported by the National Natural Science Foundation of China(No.61535008)
文摘Conventional camera calibration that employs calibration targets is a commonly used method to acquire a camera's intrinsic and/or extrinsic parameters. The calibration targets are usually designed as periodic arrays of simple high-contrast patterns that provide highly accurate world coordinate system points and the corresponding image pixel coordinate system points. The existing pixel coordinate extraction algorithms can reach a sub-pixel level; however, they treat each single pattern in one image as an independent individual, which makes it difficult to further improve extraction accuracy. In this paper, a novel method is proposed by utilizing the periodic arrangement characteristics of the calibration target pattern as a global constraint to improve the calibration accuracy. Based on a camera's pinhole model, the intersection point of two fitted curves is used as an optimized pixel point to replace the initial one. Following the pixel coordinate optimization procedures, experiments were performed using real data from a 3D laser line scanner and a dynamic precision calibration target. Our results show that the relative errors of camera homography matrix elements obtained by the proposed optimization method were reduced compared with the commonly used method. The average coordinate measurement accuracy can be improved by nearly 0.05 mm. It is shown that the proposed optimization method can enhance the camera calibration accuracy,especially when the extracted pixels are of poorer precision.
文摘针对传统手眼标定中坐标转换过程繁杂、标定精确度受人为因素影响较大等问题,提出了一种基于相机畸变校正(DC)与回归随机森林(RRF)的改进手眼标定算法。首先,对实验所用的相机进行畸变校正;其次,使用Eye to Hand形式搭建实验台,采集图像坐标及其对应的机械臂坐标,建立坐标数据集;最后,使用DC-RRF算法、线性回归算法以及传统手眼标定算法在坐标数据集上进行训练,将不同算法下的平均绝对误差、均方误差等评价指标进行对比。实验结果表明,DC-RRF算法在X/Y/Z三轴上的精准度均为最佳,平均误差可控制在1.77 mm,该算法的精准性在很大程度上保证了机器视觉与机械臂的有效结合并在分拣系统中得到精准应用。
