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Patent Number: 6,064,749
Date of Patent: 16 May 2000
Inventors: Gentaro Hirota (Carrboro, N.C.); Andrei State (Chapel Hill, N.C.)
Assignee: None
Appl. No.: 1996000691684
Filed: 2 August 1996
Int. Cl.: G06K 009/00
U.S. Cl.: 382/103; 345/7; 359/630
35 Claims

Abstract
Systems, methods and computer program products which have the registration accuracy of vision-based tracking systems and the robustness of magnetic tracking systems. Video tracking of landmarks is utilized as the primary method for determining camera position and orientation but is enhanced by magnetic or other forms of physical tracking camera movement and orientation. A physical tracker narrows the landmark search area on images, speeding up the landmark search process. Information from the physical tracker may also be used to select one of several solutions of a non-linear equation resulting from the vision-based tracker. The physical tracker may also act as a primary tracker if the image analyzer cannot locate enough landmarks to provide proper registration, thus, avoiding complete loss of registration. Furthermore, if 1 or 2 landmarks (not enough for a unique solution) are detected, several may be utilized heuristic methods are used to minimize registration loss. Catastrophic failure may be avoided by monitoring the difference between results from the physical tracker and the vision-based tracker and discarding corrections that exceed a certain magnitude. The hybrid tracking system is equally applicable to see-through and video augmented reality systems.