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12 Pixel Data Processing
•
Using the black reference image: every pixel with an intensity value above 50 DN @ 8 bit
(800 DN @ 12 bit) is marked as a defect pixel.
•
Note that reference images are acquired at PreGain=1.0 and the thresholds described
above relate to the grey levels in those images.
•
The reference images stored in the camera can be displayed by setting Correction_Mode to
BlackRefOut or GreyRefOut.
The AutoThreshold feature determines how the cold-pixel-threshold and hot-pixel-threshold
are set:
•
If AutoThreshold is set then the thresholds are set internally in the Calculate step using a
histogram of the grey reference image.
•
If AutoThreshold is not set then the thresholds must be set by the user. The default values
will most likely not be a good choice. A histogram of the grey reference image is required
to set the threshold manually.
The grey levels used in the determination of defect pixels refer to the grey levels
of the reference images which are acquired with PreGain=1.0.
It is possible to see which defect pixel thresholds were used in the Calcu-
late step when AutoThreshold was enabled by disabling AutoThreshold after
the Calculate step.
tion_ColdPixelThreshold were chosen by the AutoThreshold algorithm.
Defect pixel correction
If the hot pixel correction is switched on, the camera replaces the value of a defect pixel by an
average of its neighbour pixels.
Defect pixel interpolation based on the mean of the pixels on the left and right side of the
defect pixel (see Fig. 12.4).
Most defect pixels will only be corrected if a grey reference image has been set
prior to the Calculate step.
Figure 12.4: Defect pixel interpolation with pixels on the same row
72 of 143
The values of Correction_HotPixelThreshold and Correc-
D o t
p i x e l
p
p
p
n - 1
n
n + 1
p
+ p
n - 1
n + 1
p
=
n
2
MAN093 08/2021 V1.1
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Table of Contents
Troubleshooting
