User`s manual

AW00098504000 Image Acquisition Control
Basler ace Camera Link 125
Use Case 3 - Acquisition Start Trigger On - Frame Start Trigger Off
Use case three is illustrated on page 126.
In this use case, 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
line 1 and the activation to rising edge, so an externally generated electrical signal applied to line 1
will serve as the acquisition start trigger signal. The Acquisition Frame Count parameter has been
set to 3.
(Note that the GPIO line is designated as line 1 and in this case it has been set to act as in input
line.)
When a rising edge of the electrical signal is applied to 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 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 when the camera is parameterized via Basler
pylon or by the Acquisition Frame Period Raw register the camera is parameterized via direct
register access. If the Acquisition Frame Rate Abs parameter or the Acquisition Frame Period Raw
register (respectively) 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 line 1 on the camera. When the electrical signal is received on 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 both area.)
For more information about the Acquisition Frame Rate Abs parameter and the Acquisition Frame
Period Raw register, see Section 7.3.1.1 on page 78 and Section 7.3.1.3 on page 81.