Image Acquisition Control AW00123409000
112 Basler ace USB 3.0
Applying Trigger Signals
The paragraphs above mention "applying a trigger signal". There are two ways to apply a frame
burst start or a frame start trigger signal to the camera: via software or via hardware.
To apply trigger signals via software, you must first select the acquisition start or the frame start
trigger and then indicate that software will be used as the source for the selected trigger signal. At
that point, each time a Trigger Software command is executed, the selected trigger signal will be
applied to the camera.
To apply trigger signals via hardware, you must first select the frame burst start or the frame start
trigger and indicate that input line 1 or Line 3 or 4 if configured for input will be used as the source
for the selected trigger signal. At that point, each time a proper electrical signal is applied to the
selected input line, an occurrence of the selected trigger signal will be recognized by the camera.
The Trigger Selector
The concept of the "trigger selector" is very important to understand when working with the
acquisition start and frame start triggers. Many of the parameter settings and the commands that
apply to the triggers have names that are not specific to a particular type of trigger, for example, the
frame burst start trigger has a mode setting and the frame start trigger has a mode setting. But in
Basler pylon there is a single parameter, the Trigger Mode parameter, that is used to set the mode
for both of these triggers. Also, the Trigger Software command mentioned earlier can be executed
for either the frame burst start trigger or the frame start trigger. So if you want to set the Trigger
Mode or execute a Trigger Software command for the frame burst start trigger rather than the frame
start trigger, how do you do it? The answer is, by using the Trigger Selector parameter. Whenever
you want to work with a specific type of trigger, your first step is to set the Trigger Selector parameter
to the trigger you want to work with (either the frame burst start trigger or the frame start trigger). At
that point, the changes you make to the Trigger Mode, Trigger Source, etc., will be applied to the
selected trigger only.
Exposure Time Control
As mentioned earlier, when a frame start trigger signal is applied to the camera, the camera will
begin to acquire a frame. A critical aspect of frame acquisition is how long the pixels in the camera’s
sensor will be exposed to light during the frame acquisition.
A parameter called ExposureTime will determine the exposure time for each frame in the following
cases:
When the camera is set for software frame start triggering
When the camera is set for hardware frame start triggering and for the "timed" exposure mode
When the camera is triggered internally ("free run") which is enabled when the camera’s
Trigger Mode is set to "Off".
For hardware frame start triggering there is - for most camera models - the exposure mode.
available with two settings, "timed" and "trigger width".
With the "timed" exposure mode, the ExposureTime parameter will determine the exposure
time for each frame.
With the "trigger width" exposure mode, the way that you manipulate the rise and fall of the
hardware signal will determine the exposure time. The "trigger width" exposure mode is
especially useful, if you want to change the exposure time from frame to frame.
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