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Trigger Mode |
uEye Camera Manual Version 3.80
Trigger Mode
In trigger mode, the sensor is on standby and starts exposing on receipt of a trigger signal. A trigger event can be initiated by a software command (software trigger) or by an electrical signal via the camera’s digital input (hardware trigger).
This chapter describes the different trigger modes you can use with the uEye cameras. To choose a mode, go to the camera properties of the uEye Demo application or use the API command.
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Software trigger mode
When this mode is enabled, calling the Snap function triggers the capture of an image, which is then transferred to the PC. If you call the Live function in this mode, the image capture is triggered continuously and images are transferred continuously.
Figure 13: Software trigger mode with continuous image capture
*) Optional flash function. See also Digital Input/Output (Trigger/Flash)
Hardware trigger mode
When this mode is enabled, calling the is_FreezeVideo() (Snap) function makes the camera ready for triggering just once. When the camera receives an electrical trigger signal, one image is captured and transferred.
If you call the is_CaptureVideo() (Live) function, the camera is made ready for triggering continuously. An image is captured and transferred each time an electrical trigger signal is received; the camera is then ready for triggering again (recommended procedure).
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Figure 14: Hardware trigger mode with continuous image capture
*) Optional flash function. See also Digital Input/Output (Trigger/Flash)
With many sensors, the maximum frame rate is lower in trigger mode than in freerun mode because these sensors expose and transfer sequentially. Which frame rate is possible in trigger mode therefore depends on the exposure time. The time required for capturing a frame in trigger mode can be approximated with the following formula:
tcapture = Current exposure time + ( 1/max. frame rate )
Example: At the maximum exposure time, the frame rate is about half as high as in freerun mode; at the minimum exposure time, the frame rate is about the same.
Frame rate in overlap trigger mode
Some sensors support an overlap trigger mode (currently only sensors of the UI-214x / UI-614x models). This feature allows overlapping the trigger for a new image capture with the readout of the previous image. These sensors provide almost the same frame rate in trigger mode as in freerun mode.
With these sensors, the possible frame rate in trigger mode is independent of the exposure time. As in freerun mode, the maximum frame rate is set with the is_SetFrameRate() function. To achieve long exposure times in trigger mode, set a low frame rate.
Freerun synchronization
In this mode, cameras running in freerun mode (live mode, see above) can be synchronized with an external trigger signal. The cameras still remain in freerun mode. The trigger signal stops and restarts the current image capture process. You can use this mode to synchronize multiple cameras that you are operating in the fast live mode. Not all camera models support this mode.
Figure 15: Freerun synchronization with hardware trigger
*) Optional flash function. See also Digital Input/Output (Trigger/Flash)
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Programming: |