User Manual

Controlling image capture
Guppy PRO Technical Manual V4.0.0
160
The following screenshot shows an example of broadcast commands sent with
the Firedemo example of FirePackage:
• Line 1 shows the broadcast command, which stops all cameras con-
nected to the same IEEE 1394 bus. It is generated by holding the Shift
key down while clicking on Write.
•Line 2 generates a broadcast one_shot in the same way, which forces
all connected cameras to simultaneously grab one image.
Jitter at start of exposure
The following chapter discusses the latency time which exists for all Guppy
PRO CCD models when a hardware trigger is generated, until the actual image
exposure starts.
Owing to the well-known fact that an Interline Transfer CCD sensor has both
a light sensitive area and a separate storage area, it is common to interleave
image exposure of a new frame and output that of the previous one. It makes
continuous image flow possible, even with an external trigger.
The uncertain time delay before the start of exposure depends on the state
of the sensor. A distinction is made as follows:
FVal is active  the sensor is reading out, the camera is busy
In this case the camera must not change horizontal timing so that the trigger
event is synchronized with the current horizontal clock. This introduces a
maximum uncertainty which is equivalent to the line time. The line time
depends on the sensor used and therefore can vary from model to model.
FVal is inactive  the sensor is ready, the camera is idle
Figure 75: Broadcast one-shot