如何验证相机校准是否正确?(或如何估计重投影的误差) [英] How to verify that the camera calibration is correct? (or how to estimate the error of reprojection)

问题描述

校准的质量是通过重投影误差来衡量的(有替代方法吗?)，这需要一些 3d 点的知识世界坐标.

The quality of calibration is measured by the reprojection error (is there an alternative?), which requires a knowledge world coordinates of some 3d point(s).

有没有一种简单的方法来产生这样的已知点?有没有办法通过其他方式验证校准(例如，张的校准方法只要求校准对象是平面的，不需要知道系统的几何形状)

Is there a simple way to produce such known points? Is there a way to verify the calibration in some other way (for example, Zhang's calibration method only requires that the calibration object be planar and the geometry of the system need not to be known)

推荐答案

您可以独立于位姿验证估计的非线性镜头畸变参数的准确性.捕获跨越视场的直边(例如铅垂线或平面上的激光条纹)的图像(跨越 FOV 的一种简单方法是旋转相机保持铅垂线固定，然后添加所有图像).在所述线图像上选取点，不扭曲它们的坐标，拟合数学线，计算误差.

You can verify the accuracy of the estimated nonlinear lens distortion parameters independently of pose. Capture images of straight edges (e.g. a plumb line, or a laser stripe on a flat surface) spanning the field of view (an easy way to span the FOV is to rotate the camera keeping the plumb line fixed, then add all the images). Pick points on said line images, undistort their coordinates, fit mathematical lines, compute error.

对于线性部分，您还可以以已知的相对姿势捕获多个平面装备的图像，或者使用可重复/精确的装备(例如转盘)移动一个平面目标，或者从每个平面以已知角度安装多个平面目标其他(例如，彼此成 90 度的三个平面).

For the linear part, you can also capture images of multiple planar rigs at a known relative pose, either moving one planar target with a repeatable/accurate rig (e.g. a turntable), or mounting multiple planar targets at known angles from each other (e.g. three planes at 90 deg from each other).

与往常一样，需要在准确性要求和预算之间进行折衷.有足够的钱和附近的友好机加工店，您可以让您的幻想在钻机几何上狂奔.我曾经有一个葡萄柚大小的十二面体，用白色塑料加工成 1/20 毫米规格.用它来校准机械臂末端执行器上相机的姿势，将其在围绕固定点的球体上移动.十二面体在遮挡角度方面具有非常好的特性.不用说，这都是专利.

As always, a compromise is in order between accuracy requirements and budget. With enough money and a friendly machine shop nearby you can let your fantasy run wild with rig geometry. I had once a dodecahedron about the size of a grapefruit, machined out of white plastic to 1/20 mm spec. Used it to calibrate the pose of a camera on the end effector of a robotic arm, moving it on a sphere around a fixed point. The dodecahedron has really nice properties in regard to occlusion angles. Needless to say, it's all patented.

这篇关于如何验证相机校准是否正确?(或如何估计重投影的误差)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！