96 Appendix B: Camera interface reference
Trigger mode
The trigger mode is used to capture a single image or a sequence of images at a
certain moment in time.
In trigger mode, as in continuous mode, the camera continuously outputs images
at a fixed frame rate. However, to grab a frame, the frame grabber must receive an
external trigger signal.
Y Note that the frame grabber will ignore an external trigger pulse that arrives before
the completion of the current frame period has finished grabbing the frame.
R Therefore, to ensure that all required frames are captured, the shortest time
between external trigger pulses must be greater than the sum of the exposure time
A 5 and the frame transfer time.
IN 0 In addition to the external trigger signal, the video output and synchronization
signals are provided to the frame grabber.
0 The following illustrates the timings for trigger mode:
LIM Y 2 camera
video signal1
syncs*2
pixel clock*3
frame grabber
E Aexternal trigger
The trigger can arrive at any point during a frame,
yet the acquired frame will be the next frame.
PR19 Macquiredframe
non-interlaced video signal
* optional signal
1. analog or digital
2. bi-directional
3. internal or external
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