视场在180°左右的鱼眼影像的变形主要包括由镜头球形结构引起的变形和光学畸变, 针对这两种畸变提出一种基于三维控制场的分步检校方法, 该方法基于直接线性变换(DLT)建立像方空间与物方空间的对应关系模型, 结合球面透视模型迭代解算与鱼眼结构有关的变换半径, 在第一步检校结果的基础上建立影像的畸变模型, 并将该模型引入到DLT中对光学畸变参数进行检校, 利用第二步检校的结果对影像进行再纠正, 解决了鱼眼影像严重的畸变问题, 并通过实验验证了该方法的有效性及精度。

The main distortions of fisheye images of a field view 180° are the distortion due to the spherical structure and optical distortion. A step-wise calibration method based on the three-dimensional control field is proposed, in which the relationship between 3D space and imagery space is constructed with direct linear transformation (DLT), and the transformation radius associated with fisheye structure is calibrated with the iteration method combining the spherical perspective model. The distortion model is constructed based on the correction result of the first calibration, and introduced into DLT to calibrate the distortion parameters. The images are corrected again with the result of second calibration, which solves the serious distortion of fisheye images. The experiments verify the effectiveness and accuracy of the proposed method.