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.
The values of
Correction_HotPixelThreshold
and
Correc-
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.
h
o t
p i x e l
p
n
p
n - 1
p
n + 1
p
n
=
p
n - 1
+ p
n + 1
2
Figure 12.4: Defect pixel interpolation with pixels on the same row
72 of 143
MAN093 08/2021 V1.1
Summary of Contents for MV4 Series
Page 8: ...CONTENTS 8 of 143 MAN093 08 2021 V1 1 ...
Page 12: ...1 Preface 12 of 143 MAN093 08 2021 V1 1 ...
Page 40: ...4 Image Acquisition 40 of 143 MAN093 08 2021 V1 1 ...
Page 42: ...5 Exposure Control 42 of 143 MAN093 08 2021 V1 1 ...
Page 52: ...6 Counter Timer 52 of 143 MAN093 08 2021 V1 1 ...
Page 64: ...10 Image Format Control 64 of 143 MAN093 08 2021 V1 1 ...
Page 66: ...11 Frame Rate 66 of 143 MAN093 08 2021 V1 1 ...
Page 82: ...12 Pixel Data Processing 82 of 143 MAN093 08 2021 V1 1 ...
Page 92: ...12 Pixel Data Processing 92 of 143 MAN093 08 2021 V1 1 ...
Page 96: ...13 Precautions 96 of 143 MAN093 08 2021 V1 1 ...
Page 120: ...16 Troubleshooting 120 of 143 MAN093 08 2021 V1 1 ...
Page 126: ...19 Support and Repair 126 of 143 MAN093 08 2021 V1 1 ...
Page 128: ...20 References 128 of 143 MAN093 08 2021 V1 1 ...