ALLIED Vision Technologies Bonito CL-400 200 fps User Manual
Page 53
Parameters and commands
Bonito Technical Manual V2.3.0
53
•
Sets Exposure feature mode to Standard (weight =
0)
For technical reasons, exposure control is not available in PIV mode, the expo-
sure is permanently active (the reset gate in every pixel is always closed). This
has two practical implications:
•
A synchronized pulsed light source is necessary in order to generate rele-
vant images that can be evaluated. To generate contrast-rich images,
ambient light has to be minimized.
•
To change the exposure time, change the frame rate. Exposure time of
each image is directly determined by the frame rate. End of exposure is
defined by the end of the internal charge transfer.
There are two ways to control the frame rate:
•
use parameter
F to control the frame duration
•
use an external trigger signal and apply parameter
T to select the trigger
source
However, the camera outputs two images per trigger event, therefore the high-
est trigger rate is limited to approx. half the usual (non PIV mode) rate.
Start of the PIV
sequence
Since the exposure is always active, the sensor‘s photo-sensitive pixels are
always integrating charge. No shutter control is available; exposure time is only
determined by the frame rate.
The PIV sequence is triggered by the usual trigger input and timing settings of
the camera. Each rising edge of the selected input signal starts the PIV
sequence.
The trigger high duration t
TH
should be shorter than the duration of N+1 lines,
but at least 500 ns.
If not in Continuous mode, the time between two rising trigger edges must
exceed 2 * ((N+1)+1)+1 line durations t
L
Table 17: PIV mode timing param-
eters not depending on the setting of other parameters.
If in Continuous mode, the camera is free-running and needs the time of 2 *
((N+1)+1) line durations t
L
per PIV pair.
For that reason, the trigger signals‘ rising edge can be placed at least one line
duration after the second readout of the previous PIV sequence is complete.
Note
You cannot use the Exposure feature mode if the PIV mode is
active.
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For practical applications of particle image velocimetry, refer
to the AVT application notes online: