Triggering
121
Alvium USB Cameras User Guide V3.1.3
Trigger signal flow
Figure 57
shows an ideal diagram for the trigger signal flow. The external signal can be a physical source,
such as light barrier as hardware trigger or a software trigger. This external signal starts the exposure of a
frame. The end of exposure starts the readout. High levels show the active state of a signal.
Trigger latency
In theory, a trigger creates a camera response at speed of light, depending on the
cable length. In practice, the computer may add a delay that is mostly
unpredictable, especially on Windows systems. In addition, camera electronics and
sensors have a delay.
Electronic rolling shutter (ERS) cameras in this document also have exposure delay,
depending on camera settings, see
Triggering with rolling shutter cameras
122. Electronic rolling shutter is commonly called rolling shutter.
Features availability
States shown in the following graphic apply to Alvium USB cameras. Not all of the
corresponding features may be supported. See the Alvium Cameras Features
Reference at
www.alliedvision.com/en/support/technical-documentation/
for details.
Figure 57: Schematic trigger signal flow
Term
Description
External signal
Electrical trigger signal starting the signal flow
ExposureActive
Exposing a frame
ReadoutActive
Reading out a frame
FrameTriggerWait
Waiting for a trigger
AcquisitionActive
Enables frame acquisition: Expose, read out data, or wait for triggers.
Table 54: Trigger signal flow terms
External signal
džƉŽƐƵƌĞĐƟǀĞ
ZĞĂĚŽƵƚĐƟǀĞ
FrameTriggerWait
ĐƋƵŝƐŝƟŽŶĐƟǀĞ
Frame 1
1
2
Frame 2
Frame 2
Frame 1
