Due to manufacturing, assembly, workmanship etc, there are various distortion phenomenon of image. In order to improve the accuracy of the camera stitching, the imaging lens distortion must be considered when making the image stitching. The general distortion is divided into internal distortion and external distortion.
The internal distortion is due to the the structure of the photography itself, the external distortion is due to the geometric factors of projection method. Lens distortion is an internal distortion, the distortion generated by the lens can be divided into radial distortion and tangential distortion. Radial distortion is the aberration of geometric optics, mainly due to the different radial curvature of the lens, there are barrel distortion and pillow distortion these two types. Tangential distortion is generally considered to be caused by the not collinear optical center of lens set, including various generating errors and assembly errors. It is generally believed that, in the process of optical system imaging, radial distortion is the main factor leading to image distortion.