Allied Guppy, Техническое руководство, Страница: 136 / 238

Controlling image capture
GUPPY Technical Manual V4.0.1
136
• 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 CCD
models when either a hardware or software 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 Micron CMOS sensor of the GUPPY F-036 uses a pipelined global shut-
ter , thus imitating the separate light sensitive and storage area of a CCD.
For the CCDs the uncertainty time delay before the start of exposure depends
on the state of the sensor. A distinction is made as follows:
FVal is active
Æ
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
max. uncertainty which is equivalent to the line time. The row time depends
on the sensor used and therefore can vary from model to model.
FVal is inactive
Æ
the sensor is ready, the camera is idle
Figure 64: Broadcast one-shot