Automatic radial distortion correction in zoom lens video camera

Abstract

We present a novel method for automatically correcting the radial lens distortion in a zoom lens video camera system. We first define the zoom lens distortion model using an inherent characteristic of the zoom lens. Next, we sample some video frames with different focal lengths and estimate their radial distortion parameters and focal lengths. We then optimize the zoom lens distortion model with preestimated parameter pairs using the least-squares method. For more robust optimization, we divide the sample images into two groups according to distortion types (i.e., barrel and pincushion) and then separately optimize the zoom lens distortion models with respect to divided groups. Our results show that the zoom lens distortion model can accurately represent the radial distortion of a zoom lens. © 2010 SPIE and IS&T.

Radial Distortion from Epipolar Constraint for Rectilinear Cameras

“…These two answers are then processed, and the one yielding more inliers is selected and ultimately tested against the convergence condition of Equation (11). Hence, only one model is required in contrast to using two models [6].…”

“…In other words, the sign of the radial distortion parameters may change with zoom. Computationally, this may be dealt with, e.g., by using two separate models [6].…”

A Flexible, Generic Photogrammetric Approach to Zoom Lens Calibration

“…Accordingly, a second order polynomial of focal length is used to model the principal distance variation. Radial distortion generally decreases non-linearly as the focal length increases, reaching a maximum at the shortest focal length [21,22]. Based on this characteristic, radial distortion parameters are represented as a function of the inverse of the focal length.…”

“…Intrinsic camera parameters in Brown's model consist of interior orientations and correction terms for radial and decentering lens distortions [4]. When it comes to the variation of intrinsic parameters with lens settings, a large number of studies can be referred to in the field of both close-range photogrammetry and computer vision [20][21][22]26,29,34,36]. In particular, the principal point has usually been considered as a fixed position during zooming and focusing operations [16,30,34] since some errors in principal point offsets can be compensated by correlated parameters, such as decentering distortion parameters and EO parameters [5,34,37].…”

“…Efforts have previously been made in the calibration of various digital-zoom lens devices, such as computer controllable lens systems [18,19], single-lens reflex cameras [16,20], still video cameras [21,22], pan-tilt-zoom (PTZ) systems [23,24], and industrial cameras [25]. As zoom lenses are predominantly used in computer vision, research into their calibration arose from the computer vision community [26].…”