Real-Time Spherical Mosaicing Using Whole Image Alignment

When a purely rotating camera observes a general scene, overlapping views are related by a parallax-free warp which can be estimated by direct image alignment methods that iterate to optimise photoconsistency. However, building globally consistent mosaics from video has usually been tackled as an off-line task, while sequential methods suitable for real-time implementation have often suffered from long-term drift. In this paper we present a high performance real-time video mosaicing algorithm based on parallel image alignment via ESM (Efficient Second-order Minimisation) and global optimisation of a map of keyframes over the whole viewsphere. We present real-time results for drift-free camera rotation tracking and globally consistent spherical mosaicing from a variety of cameras in real scenes, demonstrating high global accuracy and the ability to track very rapid rotation while maintaining solid 30Hz operation. We also show that automatic camera calibration refinement can be straightforwardly built into our framework.