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AW00011916000 Image Acquisition Control
Basler scout GigE 149
Use Case 3 - Acquisition Start Trigger On - Frame Start Trigger Off
Use case three is illustrated on page 150 .
In this use case, the Acquisition Mode parameter is set to continuous. The Trigger Mode parameter
for the acquisition start trigger is set to on and the Trigger Mode parameter for the frame start trigger
is set to off.
Because the acquisition start trigger mode is set to on, the user must apply an acquisition start
trigger signal to the camera. In this case, we have set the acquisition start trigger signal source to
input line 1 and the activation to rising edge, so an externally generated electrical signal applied to
input line 1 will serve as the acquisition start trigger signal. The Acquisition Frame Count parameter
has been set to 3.
When a rising edge of the electrical signal is applied to input line 1, the camera will exit the "waiting
for acquisition start trigger" acquisition status and enter a "waiting for frame start trigger" acquisition
status. Once the camera has acquired 3 frames, it will re-enter the "waiting for acquisition start
trigger" acquisition status. Before any more frames can be acquired, a new rising edge must be
applied to input line 1 to make the camera exit the "waiting for acquisition start trigger" acquisition
status.
Because the frame start trigger is set to off, the user does not need to apply frame start trigger
signals to the camera. The camera will generate all required frame start trigger signals internally.
The rate at which the frame start trigger signals will be generated is normally determined by the
camera’s Acquisition Frame Rate Abs parameter. If the Acquisition Frame Rate Abs parameter is
disabled, the camera will acquire frames at the maximum allowed frame rate.
This type of camera setup is used frequently in intelligent traffic systems. With these systems, a
typical goal is to acquire several images of a car as it passes through a toll booth. A sensing device
is usually placed at the start of the toll booth area. When a car enters the area, the sensing device
applies an electrical signal to input line 1 on the camera. When the electrical signal is received on
input line 1, it serves as an acquisition start trigger signal and the camera exits from the "waiting for
acquisition start trigger" acquisition status and enters a "waiting for frame trigger" acquisition status.
In our example, the next 3 frame start trigger signals internally generated by the camera would
result in frame acquisitions. At that point, the number of frames acquired would be equal to the
setting for the Acquisition Frame Count parameter. The camera would return to the "waiting for
acquisition start trigger" acquisition status and would no longer react to frame start trigger signals.
It would remain in this condition until the next car enters the booth area and activates the sensing
device.
This sort of setup is very useful for traffic system applications because multiple frames can be
acquired with only a single acquisition start trigger signal pulse and because frames will not be
acquired when there are no cars passing through the booth (this avoids the need to store images
of an empty toll booth area.)
For more information about the Acquisition Frame Rate Abs parameter, see Section 9.5.1.1 on
page 119 and for information about setting the parameter, see Section 9.5.1.3 on page 121 .