Multi-ring color fiducial systems for scalable fiducial tracking augmented reality

Registration is one of the major issues in augmented reality (AR). It requires high accuracy or an error-correction mechanism in tracking. Fiducial tracking has been gaining interest as a solution of the registration problem. A single-size fiducial might help fast fiducial detection, but the system will have a narrow tracking range, since all fiducials have the same detection range. Different size fiducials have different detection ranges, and by combining a series of different detection ranges from multi-size fiducials, the whole tracking range can be extended seamlessly. Multi-ring color fiducials have different number of rings at different fiducial levels. We extend the concentric circular fiducials to multi-ring, multi-size fiducial systems. These provide scalability to fiducial tracking AR. Because the fiducial systems are incremental, they allow the tracking range to be easily extended. The fiducial systems also introduce a large number of unique fiducials, and that makes fiducial identification easier. These fiducial systems help in building large-scale applications by providing a convenient way to unify multiple local coordinate systems. It makes it easy to determine fiducial positions in a large-scale application with a small-range digitizer. We analyze the optimality of ring widths and develop formulas to get an optimal set of fiducials easily for any size of working area by plugging in some system-specific parameters. We provide a simple and low-cost way to achieve wide-area tracking.