Portable whiteboard system with vision input

We present a novel whiteboard system that uses one or more active input devices. The system is especially suitable for situations in which several users provide input on a large writing surface which also serves as a projection surface. That surface can have general orientation. We have implemented a system that uses an inexpensive, infrared-emitting stylus and an off-the-shelf videoconferencing camera fitted with an IR transmitting/visible blocking filter to capture handwritten strokes. The system uses a calibration method that uses projective mapping thus allowing off-axis camera placement. We also propose a self-calibrating system in which the capture device shares its optical system with the projector. In a system with multiple local users the question of who wrote what becomes relevant. Therefore, we address the question of attaching identity to stroke information.