EFFECTIVE IMPLEMENTATION OF FISHEYE LENS CALIBRATION BASED ON GEOMETRIC PROJECTION MODEL

摘要

Due to ultra wide-angle characteristics, fisheye lenses are widely used in artistic photography, surveillance application, forest science, self-driving obstacle avoidance, etc. Some applications that need to collect panoramic geo-information are especially suitable for using this kind of cameras. However, the imaging distortion of the fisheye image is significant, so the validity of fisheye lens calibration would largely depend on the correctness of geometric modelling between the image points and the object points. Since the fisheye lens has its own specific type of imaging formation, using collinearity equation attached by additional lens distortion parameters cannot set up a sufficient model. To achieve the relevant requirements of the metric measurement, this study adopts the rigorous object-image corresponding model to include geometric projection model for fisheye lens calibration. The discrepancy between the ideal image point and the actual image point is treated as the effect of lens distortion and modeled by additional parameters. This study verifies the validity of the employed fisheye lens calibration model by quantitatively assessing the calibration results. In addition, operational conditions and strategies that support effective and accurate fisheye lens calibration tasks are also analyzed and suggested.