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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.

Hinweis

Note on the schematics

The following illustrations show a schematic view of the image capture sequence. The sensor exposure and readout times and the transmission times depend on the camera model and the current parameter settings. The pre-processing time depends on the API functions you are using (e.g. color conversion, edge enhancement).

For details on flash timing, see the Digital Input/Output (Trigger/Flash) chapter.

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

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).

Achtung

When you use triggered image capture, the camera is only ready to process the next trigger signal after completion of the data transfer to the PC. Trigger events that occur during image exposure or data transfer are ignored. An internal counter records the number of ignored trigger events and can be read out from the PC.

Where supported, an overlap trigger mode allows overlapping the trigger for a new image capture with the readout of the previous image (currently only supported by the sensors of the UI-214x / UI-614x models).

Figure 14: Hardware trigger mode with continuous image capture

Figure 14: Hardware trigger mode with continuous image capture

*) Optional flash function. See also Digital Input/Output (Trigger/Flash)

Frame rate in trigger mode

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

Figure 15: Freerun synchronization with hardware trigger

*) Optional flash function. See also Digital Input/Output (Trigger/Flash)

See also:

Basics: Freerun Mode
uEye Demo: Trigger

 

Programming:


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