AW00011916000 Image Acquisition Control
Basler scout GigE 135
9.6.3 Using a Hardware Acquisition Start Trigger
(Legacy Mode)
9.6.3.1 Introduction
If the Trigger Mode parameter for the acquisition start trigger is set to on and the Trigger Source
parameter is set to e.g. input line 1, an externally generated electrical signal applied to input line 1
on the camera will act as the acquisition start trigger signal for the camera. This type of trigger signal
is generally referred to as a hardware trigger signal or as an external acquisition start trigger signal
(ExASTrig).
A rising edge or a falling edge of the ExASTrig signal can be used to trigger frame acquisition. The
Trigger Activation parameter is used to select rising edge or falling edge triggering.
Assuming that the camera is in a "waiting for acquisition start trigger" acquisition status, frame
acquisition will start whenever the appropriate edge transition is received by the camera.
When the camera receives a hardware trigger signal and begins exposure, it will exit the "waiting
for acquisition start trigger" acquisition status because at that point, it cannot react to a new
acquisition start trigger signal. As soon as the camera is capable of reacting to a new acquisition
start trigger signal, it will automatically return to the "waiting for acquisition start trigger" acquisition
status.
When the camera is operating under control of an ExASTrig signal, the period of the ExASTrig
signal will determine the rate at which the camera is acquiring frames:
For example, if you are operating a camera with an ExASTrig signal period of 20 ms (0.020 s):
So in this case, the frame rate is 50 fps.
For more information about setting the camera for hardware acquisition start triggering and
selecting the input line to receive the ExASTrig signal, see Section 9.6.3.4 on page 139.
If you are triggering frame acquisition with an ExASTrig signal and you attempt to
acquire frames at too high a rate, some of the acquisition trigger signals that you
apply will be received by the camera when it is not in a "waiting for acquisition start
trigger" acquisition status. The camera will ignore any acquisition start trigger
signals that it receives when it is not "waiting for acquisition start trigger". (This
situation is commonly referred to as "over triggering" the camera.
To avoid over triggering, you should not attempt to acquire frames at a rate that
exceeds the maximum allowed with the current camera settings.
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