Completed - August 2012
The recent introduction of multi-touch sensitive displays has brought with it the challenge of recognizing tangibles on these kinds of screens.
There are several wide spread and/or sophisticated solutions to fulfill this need but they seem to have some flaws. Printed patterns, for example, can be recognized quite well by displays with integrated optical sensors, but those systems are either time-consuming to calibrate or don’t work properly in case of extensive use of illumination.
One popular system is an overlay frame that can be placed on a normal display with the corresponding size. The frame creates a grid with infra-red light emitting diodes. The disruption of this grid can be detected and messages with the positions are sent via USB to a connected computer.
This system is quite robust in matters of ambient light insensitivity and also fast to calibrate. Unfortunately it is not created with the recognition of tangibles in mind and printed patterns can not be resolved. The VEGA software is an attempt the create fiducials that are recognized by an infra-red multi-touch frame as fingers. Those false fingers are checked by a software for known patterns. Once a known pattern (= fiducial) has been recognized its position and orientation are send with the finger positions towards the interactive software.
For more info check out the github project page