Figure 18.
Acquisition Timing Diagram
Trigger
Lighting Strobe
Exposure
Image Readout
3
2
1
1. User-configurable Trigger Delay
2. User-configurable Exposure Delay
3. Beginning of Image Readout
The trigger shown in the figure represents an external trigger, configured to use the rising edge
as the active edge. The time between the active edge of the trigger and the assertion of the
lighting strobe is a user-configurable trigger delay. The trigger delay can be specified as a
duration of time or as a number of edges on an input line.
The amount of time required from the assertion of a trigger to the start of the light strobe and
image exposure varies by application. For example, if a sensor that detects the presence of a
part is positioned before the ISC-178x on a conveyor belt, a trigger delay is required to ensure
that the image is not exposed until the part to be inspected passes in front of the ISC-178x. In
this case, specifying the trigger delay in terms of edge counts allows the ISC-178x to expose
the image when the part is in position regardless of changes in conveyor belt speed.
When using an Input line as the trigger source, you must specify the desired activation for
your trigger. The activation can be edge-based - rising, falling, or any - or level-based - high or
low. When using a level-based activation mode, the ISC-178x only acquires images while the
Input line is in the active state. The frame rate in this case is determined by the Acquisition
Frame Rate attribute. This is a special case where external and internal timing are blended.
When using a level-based activation mode, the trigger delay is ignored.
When using an internally timed acquisition, the activation mode and trigger delay do not
apply. When using a software trigger, the activation mode will also be ignored, but the trigger
delay is always applied.
Determining the Maximum Frame Rate
You can determine the maximum frame rate for your configuration in software by reading the
Max Frame Rate indicator in Vision Builder AI, reading the AcquisitionFrameRateLimit
attribute in LabVIEW, or reading the Max Frame Rate indicator in MAX.
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ISC-178x User Manual
Summary of Contents for ISC-1783
Page 1: ...ISC 1783...
