Non-Metric Calibration of Wide Angle Lenses

Images taken with wide-angle cameras tend to have severe distortions which pull points towards the optical center. This paper proposes a new method for recovering the distortion parameters without using any calibration objects. The distortions cause straight lines in the scene to appear as curves in the image. Our algorithm seeks to find the distortion parameters that would map the image curves to straight lines. The user selects a small set of points along the image curves. Recovery of the parameters is formulated as the minimization of an objective function which is designed to explicitly account for noise in the selected image points. Experimental results are provided for synthetic data with different noise levels as well as for real images. The computed distortion parameters are used to undistort a video stream in real time, using a look-up table.