Bonito Technical Manual
V2.4.0
56
Parameters and commands
The internal readout of the first PIV frame, from the sensor‘s pixel memory to the
Camera Link output ports, starts immediately after the end of the charge trans-
fer, taking the time of (N+1) line durations.
At the same time, the sensor‘s photo detectors continue to integrate charge,
even during the readout process. The charge accumulated during this phase con-
tributes to the exposure of the second PIV frame.
The internal charge transfer of the second PIV frame automatically starts directly
after the internal readout of the first PIV frame is complete. It takes the time of
one line duration (t
L
), during which the sensor‘s photo detectors keep integrat-
ing charge for the second PIV frame.
When the charge transfer of the second PIV frame is complete, its internal read-
out starts automatically, which also takes the time of (N+1) line durations.
During this phase, the exposure of the next first PIV image has already started.
However, this image already belongs to the succeeding PIV image pair, which is
not yet triggered at this stage.
After readout of the second PIV frame from the pixel memory is completed, the
trigger may start the whole sequence anew.
Synchronization output
The synchronization output signal determines how the images are paired by
externally communicating the start and end of each PIV sequence‘s first charge
transfer. It allows to synchronize external devices, such as flashes, with the PIV
sequence.
The falling edge at the synchronization output signals that the charge transfer
of the first PIV frame has begun (See
Figure 28: PIV mode flow diagram
58). This requires the setting
J=1
, which may be used to trigger the first flash
pulse. The recommended guard interval t
G1
of the flash pulse should not be
undercut.
The rising edge at the synchronization output signals externally that the expo-
sure of the first PIV frame has ended. This requires setting
J=1
, and may be used
to trigger the second flash pulse. The recommended guard interval t
G2
will be
kept automatically.
To move the second flash pulse closer to the first end of charge transfer, use an
external timing device that is triggered by an external camera trigger or the pre-
vious falling edge of the synchronization output.
Depending on the synchronization output setting (parameter
J
), the corre-
sponding pin at the camera's control connector may directly output the first
charge transfer pulse for each PIV pair. By default, the falling edge of the syn-
chronization signal always coincides with the beginning of the charge transfer
of the first image, plus some delay (t
S1
).
When the first charge transfer ends, the synchronization signal rises back to
high level, again with a delay (t
S2
).
