鱼眼相机等效焦距三点标定法

A three-point calibration method for fish-eye camera equivalent focal length

为简化鱼眼相机等效焦距的标定,提出一种"三点标定法"。基于鱼眼相机的等距投影模型、余弦定理和空间模型,导出了只含有等效焦距一个未知量的方程。在实际标定过程中,首先在地面上随机选取3个不重合的点,并测量出它们之间的距离;然后利用鱼眼相机采集到含有这3个点的图像,计算出等效焦距。实验结果表明,本文方法简化了相关相机标定的过程和实验复杂度;相比于传统的方法,本文方法得出的结果更接近于鱼眼镜头的真实参数。

To calibrate the equivalent focal length of a fish-eye camera is a complicated problem. This paper puts forward a three-point calibration method to solve the challenging situation. Based on the equidistant projection model and the spatial model of a fish-eye camera,considering the cosine theorem,this paper derives a theoretic equation, only containing one unknown quantity of equivalent focal length, which lays a solid foundation for measuring the equivalent focal length of a fish-eye camera by the three-point method. To verify the three-point calibration method experimentally, this paper conducts a simulation test in practice. Randomly select three coinciding points on the ground,measure the distance among them and then calculate the equivalent focal length by the fish-eye camera image which contains the three points. The three-point calibration method simplifies the procedure and reduces the complexity of meas- uring a fish-eye camera equivalent focal length. The results of the simulation show the accuracy and the feasibility of the three-point method. The equivalent focal length calibrated by using the three-point method is more close to the factory parameter of fish-eye lens than other traditional methods and toolbox.