Practical self-calibration of pan-tilt cameras

The authors propose a practical self-calibration method of rotating and zooming cameras. The problem with previous methods occurs when the camera motion is almost fully zoomed with very little rotation, which is called the 'near-degenerate' configuration. In that case, the solutions become unstable and rotation angles cannot be calculated. When a pan-tilt camera (without z-axis rotation) is adopted and the intrinsic camera parameters are simplified. the near-degenerate configuration can be overcome and a closed-form solution obtained. Because pan-tilt cameras can be assumed for most stationary cameras (i.e. without translation) and the assumptions about the intrinsic camera parameters do not seem to effect the self-calibration, the method provides a simple, practical solution to the self-calibration problem, In addition, the authors introduce a nonlinear algorithm that adjusts not only the camera parameters but also the inter-image homography so that more accurate image registration is made possible. Simulations and experiments with real images are presented.