Chapter 6
Image Acquisition
NI 177x Smart Camera User Manual
6-4
ni.com
The trigger shown in Figure 6-1 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 configured in either milliseconds or
edge counts.
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 NI 177x
Smart Camera 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
NI 177x Smart Camera. In this case, specifying the trigger delay in terms
of edge counts allows the NI 177x Smart Camera to expose the image when
the part is in position regardless of changes in conveyor belt speed. For
other applications, a delay specified in milliseconds is sufficient.
If you are strobing a light, there is a delay of 500
µ
s while the lighting
controller turns on the light.
After the lighting turn-on time, the exposure begins. The width of the
exposure pulse determines how long the sensor is exposed. The exposure
time can be adjusted by setting the
Exposure Time
control in Vision
Builder AI, setting the
ExposureTime
attribute in LabVIEW, or by setting
the
Exposure Time
control in MAX. The lighting strobe deasserts at the
end of the exposure pulse. The end of an exposure starts the image readout
from the sensor.
The maximum trigger rate is determined by the maximum frame rate
for your configuration. Refer to the
section for
information about the factors that affect the maximum frame rate.
Summary of Contents for NI ISC-1772C
Page 1: ...ISC 1772C...
