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Figure 9: NUC Tab.
7.7.5 Auto Exposure Control (ALC)
The "Auto" tab gives control over the ALC. Adjusting the parameters shown in Figure 11 will fine
tune the ALC to the users liking, which will depend on factors just as signal strength, the users
application etc. A description of what these control parameters do is stated below:
ALC from Peak & ALC from Mean:
Peak video is determined from a rolling average of 4 pixels. Current pixel + 3 previous pixels are used
to derive the peak value. This peak value is monitored for the ROI (Region of Interest) and latched at
the end of frame.
An average video level is calculated for the active ROI. This value will be calculated in real time, i.e.
as pixel data in the ROI is captured from the sensor it is fed directly to an Accumulator. At the end of
frame, the Accumulator is divided to give a true average.
The user can adjust the percentage they want to take from the peak & average to drive the ALC.
Taking a greater percentage from the peak value will result in smaller exposure times being set.
Taking a greater percentage of the average to drive the ALC will result in larger exposure times being
set.
ALC Level & AGC+ALC Speed: Adjusts the "level" of the ALC. Making the level and speed set points
higher will drive the ALC to set larger exposure times.
By default, the state of the
NUC that should be used is
the full 3-point NUC
(Offset+Gain+Dark
corrections). User has the
option to view each state
of the NUC or the raw data
from the sensor with no
corrections applied
(Normal).
Ramp test pattern can also
be enabled.
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