Optical tracking: A.R.T. Setup
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A.R.T. tracking cameras are equipped with CCD image sensors, working in the near infrared light spectrum. An infrared light flash (not visible for the human eye) illuminates the measurement volume periodically.
The figure shows the principles of the system setup. At least two, maximum 16 tracking cameras are connected with the central PC (with the A.R.T. Software DTrack) by an ethernet switch and twisted pair cables. Usually the DTrack PC is equipped with two 100 Base-TX fast ethernet boards: one for the connection to the cameras and one for data output.
The DTrack PC contains a PCI slot card (Sync-Card) for synchronization of the IR cameras. The Sync-Card allows input of an external synchronization signal (rectangular or video sync signal), or is able to generate an internal sync signal. All sync signals are transferred via BNC connections to the cameras. Usually the cameras are connected with the sync output no. 1 of the Synccard like a chain that is finished by a 75 Ω terminator resistor. If the cameras have to be grouped into different flash groups, in order to avoid blinding, two or more BNC chains are used at the sync outputs no. 1, 2 or 3 of the Synccard.
Step by step: How does ARTtrack and DTrack work?
Step 1:
Measurement volume is illuminated by an IR flash and camera images are taken.
Step 2:
The calculation units within the cameras recognize the markers and calculate the marker positions in image coordinates (2D) with high accuracy.
Step 3:
The 2D marker coordinates of the single tracking cameras are handed over to the central PC via Ethernet.
Step 4:
3dof marker positions and/or 6dof target positions are calculated by A.R.T. Software DTrack.
Step 5:
DTrack transfers 3dof and 6dof data via ethernet to application software. For a list of graphics software applications that are already running with A.R.T. tracking systems and Software DTrack please see here.
