一种基于球面透视投影约束的鱼眼镜头校正方法

鱼眼镜头摄像机具有较大视场，但是，使用鱼眼摄像机拍摄的图像会有非常严重的变形．该文研究基于球面透视投影约束的鱼眼镜头校正方法．球面透视投影约束是指空间直线的球面透视投影为球面上的大圆．作者首先使用含有变形校正参数的鱼眼变形校正模型，将空间直线的鱼眼投影曲线上的点映射为球面点，然后通过球面点到大圆的球面距离最小来拟合大圆，恢复了变形校正参数，从而实现了鱼眼图像的校正．模拟实验和真实图像实验表明，该方法能得到比较满意的校正结果．

Fisheye Lense Distortion Correction Using Spherical Perspective Projection Constraint

Fisheye lenses are often used to enlarge the field of view of a camera. But the images taken with the fisheye camera often have severe distortions. This paper proposes a new fisheye lenses distortion correction method using spherical perspective projection (SPP) constraint. Space line are generally projected into curves on a fisheye image. The SPP constraint means that a space line must be projected into a great circle on a unit sphere under the SPP model. The reason of using the SPP model is to handle the situation of larger-than-180-degree view-angles, and our case happens to be true. Our proposed distortion correction process consists of the following two main steps: Firstly, polynomial models for radial and tangential distortions with free parameters are selected; Secondly, these parameters are estimated based on the fact that the projected image curves of space lines should be mapped to great circles on a unit spherical surface, i.e., the SPP constraint. By minimizing the sum of errors, more specifically, the squares of spherical distances from mapped points to their corresponding best-fit great circles, the parameters are obtained. Our minimization process also consists of two steps, at first, an initial estimation is obtained by the linearization of the two distortion models, then Levenberg-Marquardt algorithm is employed for the final non-linear optimization. Finally, experimental results with synthetic data under different noise levels as well as with real fisheye images are reported, and the results appear satisfactory.