Can We Consider Central Catadioptric Cameras and Fisheye Cameras within a Unified Imaging Model

Abstract

There are two kinds of omnidirectional cameras often used in computer vision: central catadioptric cameras and fisheye cameras. Previous literatures use different imaging models to describe them separately. A unified imaging model is however presented in this paper. The unified model in this paper can be considered as an extension of the unified imaging model for central catadioptric cameras proposed by Geyer and Daniilidis. We show that our unified model can cover some existing models for fisheye cameras and fit well for many actual fisheye cameras used in previous literatures. Under our unified model, central catadioptric cameras and fisheye cameras can be classified by the model’s characteristic parameter, and a fisheye image can be transformed into a central catadioptric one, vice versa. An important merit of our new unified model is that existing calibration methods for central catadioptric cameras can be directly applied to fisheye cameras. Furthermore, the metric calibration from single fisheye image only using projections of lines becomes possible via our unified model but the existing methods for fisheye cameras in the literatures till now are all non-metric under the same conditions. Experimental results of calibration from some central catadioptric and fisheye images confirm the validity and usefulness of our new unified model.