TouchBridge was an active tangible marker system for optical based multi-touch surfaces. It built on a previously proposed method of marker tracking based upon the augmentation of physical objects with IR Light Emitting Diodes (LEDs). In this previous method, the LEDs transmitted a modulated signal that was tracked by a camera; this signal was able to transmit a unique ID for each object in addition to a small amount of state information. However, this system was physically limited in terms of bandwidth as a camera was used to receive the modulated signal.
Our prototype utilised modulated Infrared light to provide a bi-directional communication channel between objects and the surface. A separate transceiver replaced the camera, allowing for the reliable tracking of the position and orientation of 16 uniquely identiﬁed physical objects at an update rate equal to the camera frame rate. Our system could also transmit information about the state of each object at a higher data rate than previous systems. It therefore presented the potential for Tangible User Interfaces that responded to complex manipulations of controls embedded within physical objects.
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