Nonparametric correction of distortion

Images taken with wide angle and inexpensive medium angle lenses show substantial distortion, which will cause many computer vision applications to malfunction. Parametric calibration algorithms cannot handle the wide range of possible distortion functions and they require a known image center, expensive equipment, and/or estimation of unneeded parameters. We present a new algorithm to remove distortion. It is similar to the plumb line method but it: (a) uses images of spheres rather than lines, (b) corrects to stereographic rather than perspective projection, (c) calibrates aspect ratio, and (d) uses a nonparametric distortion model.