User manual

Phantom Help File364
© 2010 Vision Research - An AMETEK Company
9.3 Image-Based Auto-Trigger
The Image-Based Auto-Trigger feature allows selected Phantom camera models, (Miro eX 2
(optional), Miro eX 4, and soon the “newer” v-Series cameras, to trigger themselves when the image
changes in a selectable region of the frame. For the v-Series implementation, there will also be a
mode which allows this feature to generate a hardware trigger signal for multi-camera installations.
A few user definable parameters allow the auto-trigger behavior to be adjusted to operating
conditions, filtering out unintended triggers due to vibration, changes in illumination, slow-moving
shadows, etc.
The Auto-Trigger operation begins by the user selecting a rectangular area within the image, similar
to the region used for auto-exposure, the Auto-Trigger region.
As each frame is captured, the image in the Auto-Trigger region is compared to an earlier copy of the
same region that has been stored in a dedicated memory. After the comparison is made, the image in
memory is updated to the current image, to be used in the future.
The result of the comparison determines if a trigger is generated. A pixel being compared is
considered “active" if its level has changed, (brightened or darkened), by more than a preset
threshold. The number of active pixels for a given frame is counted, and if it exceeds a set number, a
trigger is generated. The required number of active pixels is specified as a percentage of the area of
the Auto-Trigger region.
When an Auto-Trigger condition is detected, the Auto-Trigger signal of the camera is pulled low. The
Auto-Trigger signal is available on Pin-N of the Capture connector.
IMAGE-BASED AUTO-TRIGGER OPERATING MODES
Several operating modes are possible for the Image-Based Auto-Trigger system:
MODE
FUNCTIONAL DESCRIPTION
Mode 0
Image-Based Auto-Trigger is disabled.
Mode 1
Camera will drive both the auto-trigger and trigger itself when an auto-trigger is
detected. If the auto-trigger signal is pulled low by an external device, the camera will
be triggered.
Mode 2
The image changes are analyzed, and when an auto-trigger condition has been
detected, the auto-trigger signal will be pulled low, as in Mode 1. However, the
camera will not trigger itself. An external device pulling the auto-trigger signal low will
not trigger the camera either.
Mode 2 is useful when external control of the auto-trigger is desired, for instance, it is
required that the auto-trigger feature is disabled for some known transient event. The
auto-trigger signal from the camera will be routed through some external device and
back into the trigger input of the camera.