SVS-Vistek CoaXPress shr411 Manual page 35

5 Feature description
Light control with rolling shutter
As being said, not all sensor lines are sensitive to light at the same time. Make
sure your light is ON as long any pixel are going to e exposed. An exo183xGE
i.e. needs about 62ms of minimal scanning time. An exo183xCL i.e. needs
about 120ms of minimal scanning time. Minimum scan time in most cases is
about 1 frame length.
There are 2 general guidelines for flashing with rolling shutter:
Make sure your light is ON and stable the whole period of time while scan-
l
ning / exposing. Minimum flash time is scanning time plus exposure time. In
this case, while flashing you will get geometric distortions as mentioned
above. Exposure will be determined by camera exposure time and light
intensity.
If flash time is less than scanning time then exposure time has to be at least
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scanning time + flash time, with a delay of scanning time. In other words,
your exposure time will be scanning time plus flash time, while you use a
flash delay of scanning time. Thus flash release will start after the delay of
scanning time, as soon the sensor is fully open. You should keep the object
in total darkness while the first scanning time.
In this case, as all lines are sensitive to light at the same time after the first
scan time, flashing time can be as short as you like. You will not see the typ-
ical geometric rolling shutter distortions as shown above. Imaging will be
similar to global shutter. Exposure will be determined by flash time / intens-
ity.
Fig.: 5-14: Rolling shutter lines light sensitivity versus time
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