Art ARTTRACK Installation Manual page 79

5.7 Markers and targets (rigid bodies)
Synchronization of active markers The easiest way to create an active marker is to
have it emit IR light continuously. However, this would be inefficient in respect to energy
dissipation and would yield low signal-to-noise ratios. ART tracking cameras have very
short exposure times, i.e. narrow time slots of sensitivity. Most of the light emitted by
the markers would hit the cameras sensors at times when it is inactive rendering the light
useless for tracking. As a consequence, the range between cameras and marker would
become significantly shorter. Additionally the active markers can be configured to emit
high power intensities by flashing just like the camera flash. This also helps with en-
ergy dissipation due to an upper limit allowed for each single LED. Therefore, most active
ART
markers supplied by are synchronized with the cameras to emit radiation only during
exposure times. This allows both more robust and longer ranging targets.
Synchronization can be done either by a wired connection between the tracking system
and the pc-board controlling the active markers but also in a wireless way. For wireless
synchronization a coded (i.e. modulated) IR flash is being sent out by a tracking camera.
The active marker's PC board recognizes the coded flash and activates the LEDs.
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