Vignetting Correction for Pan-tilt Surveillance Cameras

It is a well know result that the geometry of pan and tilt (perspective) cameras auto-calibrate using just the image information. However, applications based on panoramic background representations must also compensate for radiometric effects due to camera motion. In this paper we propose a methodology for calibrating the radiometric effects inherent in the operation of pan-tilt cameras, with applications to visual surveillance in a cube (mosaicked) visual field representation. The radiometric calibration is based on the estimation of vignetting image distortion using the pan and tilt degrees of freedom instead of color calibrating patterns. Experiments with real images show that radiometric calibration reduce the variance in the background representation allowing for more effective event detection in background-subtraction-based algorithms.