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Flare 12M CXP User's Manual
There is a Frame Overhead Time (FOT) period after the sensor is triggered to stop integration
before the readout starts. When the sensor enters this FOT period there is a portion of time
where the photodiodes are still being exposed to light before the charge is transferred to the
storage elements. This Exposure Overhead Time (EOT), shown in Figure 10, is a known
constant value and only depends on the CoaXPress output format. For programmable
exposure modes this time is included in the exposure time value.
The minimum pulse width is 1 µs.
Exposure of the next frame cannot start until the readout of the current frame begins. Also
exposure of the next frame cannot end during the readout of the current frame. To ensure
this condition is met the camera does not look for the end of exposure transition until the
readout of the current frame has completed.
3.3.4 Edge-triggered double exposure
In edge-triggered double exposure mode two frames are captured in rapid succession when a
single trigger edge is seen. This type of exposure mode is typically used in Particle Image
Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) applications.
The first frame's exposure starts when the active trigger edge is detected and the exposure
time is set in the
Exposure 1
register. The first frame corresponds to the 'short' exposure
frame. After the Frame Overhead Time period of the first frame, exposure of the second
frame automatically starts and the duration is equal to the frame readout time. The second
frame corresponds to the 'long' exposure frame. Starting the second frame exposure
automatically ensures the smallest time between the frame exposures. The timing of this
mode is shown in Figure 11.
IO Industries Inc.
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Revision 2.0
Figure 10. Edge-triggered level-controlled exposure timing
Readout Time, Frame N-1
Input Trigger
(active high)
FOT
Readout Time, Frame N
Frame Period
FOT
Exposure Time, Frame N
Exposure Time, Frame N+1
EOT
EOT