Acquisition Synchronization
This board is capable to acquire synchronously images from two or more line-scan cameras.
Synchronized acquisition
As shown on the picture, the synchronization is achieved through a "SyncBus" that interconnects all the acquisition channels. The bus is driven by one of the participating acquisition channels; this channel is named the "master channel", the other being designated as the "slave" channel(s).
The SyncBus conveys two synchronization signals:
- a line trigger signal, that typically originates from the motion encoder
- a start (and optionally end) of acquisition signal, that originates from the acquisition controller of the master channel
The synchronization signals are propagated to all the camera and acquisition controllers of all the participating channels, including the master one.
In the general case of a SyncBus linking channels located on different boards of the same system, it is mandatory to implement an electrical wiring that interconnects the IOUT3/IOUT4 output ports of the master channel to the IIN3/IIN4 input ports of all the participating channels.
In the specific case of a SyncBus linking only the 2 channels of Grablink DualBase, the SyncBus doesn't require the use of the I/O ports; instead, it is routed locally inside the FPGA.
Requirements
For adequate synchronization, the line rate of the cameras must be controlled by the frame grabber. Synchronization acquisition is allowed exclusively for the following operation modes: LxxxxRC, LxxxxRG, LxxxxRG2, and LxxxxRP.
The exposure settings of all cameras must be identical:
- For cameras having the exposure time controlled by the frame grabber, the value of Expose_us and ExposeTrim must be identical on all channels.
- When the exposure time is controlled by the camera, all cameras must be configured identically, and the value of TrueExp_us must be identical on all channels.
The line capture controller must be configured to take all lines (LineCaptureMode=ALL); the pick-A-line mode (LineCaptureMode=PICK) is not allowed.
Control Parameters
The feature is configured by means of the SynchronizedAcquisition parameter.
By default, the parameter is set to OFF, disabling the synchronized acquisition feature. If synchronized acquisition is not intended to be used, this parameter can be left to its default value.
To configure the synchronized acquisition and the participating channels, proceed as follows:
On the master channel:
- Select a line-scan acquisition mode by setting the value WEB, PAGE, LONGPAGE to AcquisitionMode.
- Set the value MASTER (or LOCAL_MASTER if local wiring can be used) to SynchronizedAcquisition.
- Configure remaining acquisition control parameters as for a stand-alone channel.
- Configure the trigger control, and the encoder control parameters as for a stand-alone channel.
- Configure the exposure control parameters.
On the slave channel(s):
- Assign to AcquisitionMode the same value as on the master channel.
- Set the value SLAVE (or LOCAL_SLAVE if local wiring can be used) to SynchronizedAcquisition.
- Configure the remaining acquisition control parameters as follows:
- TrigMode and NextTrigMode are automatically set by MultiCam to the appropriate values, they may not be modified.
- EndTrigMode must be set to SLAVE if it is configured to HARD on the master channel. Otherwise, it remains at its default value AUTO.
- BreakEffect, PageLength_Ln, SeqLength_Pg and SeqLength_Ln, when applicable, must be configured to the same values as on the master channel.
- All the trigger control parameters are irrelevant and don't need to be configured.
- The LineRateMode parameter is automatically set to SLAVE; the other parameters of the encoder control category are irrelevant.
- Apply to exposure control parameters the same settings as the master channel.