Teledyne PIXIS-XF, Системное руководство

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60 PIXIS-XF System Manual Issue 5
6.1.2 External Sync {Readout Per Trigger}
In this mode all exposures are synchronized to an external source. As illustrated in
Figure 6-3 , this mode can be used in combination with Normal or PreOpen {Open
Before Trigger} shutter operation.
Figure 6-3: High-Level Block Diagram: External Sync, Shutter Preopen vs. Normal
In Normal Shutter {Normal} mode, the camera waits for an External Sync pulse and then
opens the shutter for the programmed exposure period. As soon as the exposure is
complete, the shutter closes and the CCD array is read out. The shutter requires up to
8 ms or more to open completely, depending on the shutter model.
External synchronization depends on an edge trigger (negative- or positive-going)
which must be supplied to the EXT SYNC connector on the back of the camera. The
type of edge must be identified in the application software to ensure that the shutter
opening is initiated by the correct edge (in WinX/32, this is done on the Experiment
Setup
►
Timing tab, in LightField on the Trigger/Shutter expander). Since the shutter
requires up to 8 ms to fully open, the External Sync pulse provided by the experiment
must precede the actual signal by at least that much time. If not, the shutter will not be
open for the duration of the entire signal, or the signal may be missed completely.
Also, since the amount of time from initialization of the experiment to the first External
Sync pulse is not fixed, an accurate background subtraction may not be possible for the
first readout. In multiple-shot experiments this is easily overcome by simply discarding
the first frame.
In PreOpen Shutter {Open Before Trigger} mode shutter operation is only partially
synchronized to the experiment. As soon as the camera is ready to collect data, the
shutter opens. Upon arrival of the first External Sync pulse at the EXT SYNC connector,
the shutter remains open for the specified exposure period, closes, and the CCD is read
out. As soon as readout is complete, the shutter reopens and waits for the next frame.
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