12.2 Image Correction
The reference images are not stored permanently in flash memory with
Correc-
tion_SaveToFlash
, only the calibration values are stored permanently.
PreGain is internally set to 1.0 while setting correction reference images.
12.2.2
Offset Correction
The offset correction is based on a black reference image, which is taken at no illumination
(e.g. lens aperture completely closed). The black reference image contains the fixed-pattern
noise of the sensor, which can be subtracted from the live images in order to minimise the
static noise.
Offset correction algorithm
After configuring the camera with a black reference image, the camera is ready to apply the
offset correction:
1.
Determine the average value of the black reference image.
2.
Subtract the black reference image from the average value.
3.
Store the result in the camera as the offset correction matrix.
4.
During image acquisition, subtract the correction matrix from the acquired image and
interpolate the defect pixels (see Section 12.2.4).
4
4
4
3
1
2
1
3
1
4
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2
3
4
1
1
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1
4
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3
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b
l a c k r e f e r e n c e
i m a g e
1
1
1
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- 1
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- 1
0
1
- 1
1
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0
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a v e r a g e
o f b l a c k
r e f e r e n c e
p i c t u r e
=
-
o f f s e t c o r r e c t i o n
m a t r i x
Figure 12.2: Schematic presentation of the offset correction algorithm
How to Obtain a Black Reference Image
In order to improve the image quality, the black reference image must meet certain
requirements.
The detailed procedure to set the black reference image is described in Section
C.6.
MAN093 08/2021 V1.1
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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 ...