Using A Hardware Frame Start Trigger; Introduction - Basler ace acA640-90gm User Manual

Image Acquisition Control
7.4.3

Using a Hardware Frame Start Trigger

7.4.3.1

Introduction

If the Trigger Mode parameter for the frame start trigger is set to on and the Trigger Source
parameter is set to line 1, an externally generated electrical signal injected into physical input line 1
on the camera will act as the frame start trigger signal for the camera. This type of trigger signal is
generally referred to as a hardware trigger signal or as an external frame start trigger signal
(ExFSTrig).
A rising edge or a falling edge of the ExFSTrig 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 frame 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 frame start trigger" acquisition status because at that point, it cannot react to a new frame start
trigger signal. As soon as the camera is capable of reacting to a new frame start trigger signal, it
will automatically return to the "waiting for frame start trigger" acquisition status.
When the camera is operating under control of an ExFSTrig signal, the period of the ExFSTrig
signal will determine the rate at which the camera is acquiring frames:
1
------------------------------------------------------------------------ -
ExFSTrig period in seconds
For example, if you are operating a camera with an ExFSTrig signal period of 20 ms (0.020 s):
1
-------------- - = 50 fps
0.020
So in this case, the frame rate is 50 fps.
If you are triggering frame acquisition with an ExFSTrig signal and you attempt to
acquire frames at too high a rate, some of the frame trigger signals that you apply
will be received by the camera when it is not in a "waiting for frame start trigger"
acquisition status. The camera will ignore any frame start trigger signals that it
receives when it is not "waiting for frame 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.
For more information about setting the camera for hardware frame start triggering and selecting the
input line to receive the ExFSTrig signal, see Section 7.4.3.4 on
For more information about the electrical requirements for line 1, see Section 5.7 on
For more information about determining the maximum allowed frame rate, see Section 7.12 on
page 126.
82
= Frame Rate
page 85.
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