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 4.27: Hot pixel interpolation
4.4.3
Gain Correction
The gain correction is based on a gray reference image, which is taken at uniform illumination
to give an image with a mid gray level.
Gain correction is not a trivial feature. The quality of the gray reference image
is crucial for proper gain correction.
Gain correction algorithm
After configuring the camera with a black and gray reference image, the camera is ready to
apply the gain correction:
1.
Determine the average value of the gray reference image.
2.
Subtract the offset correction matrix from the gray reference image.
3.
Divide the average value by the offset corrected gray reference image.
4.
Pixels that have a gray level bigger than a certain threshold are marked as hot pixels.
5.
Store the result in the camera as the gain correction matrix.
6.
During image acquisition, multiply the gain correction matrix from the offset-corrected
acquired image and interpolate the hot pixels (see Section 4.4.2).
:
7
1 0
9
7
9
7
8
7
9
4
3
2
3
4
1
1
9
6
8
4
6
1 0
1
3
4
g r a y r e f e r e n c e
p i c t u r e
a v e r a g e
o f g r a y
r e f e r e n c e
p i c t u r e
)
1
1 . 2
1
0 . 9 1
1 . 2
- 2
0 . 9 1
1
- 1
1
0 . 8
1
1
0
1 . 3
0 . 8
1
0
1
1
- 2 - 2 - 2
=
1
1
1
2
- 1
2
- 2
- 1 0
1
- 1
1
- 1
0
2
0
- 1
0
- 2
0
1
1
- 2 - 2 - 2
-
)
o f f s e t c o r r e c t i o n
m a t r i x
g a i n c o r r e c t i o n
m a t r i x
Figure 4.28: Gain Correction
Gain correction always needs an offset correction matrix, so the offset correction
has to be performed before the gain correction.
4.4 Image Correction
35
Summary of Contents for CameraLink MV-D1024E-160
Page 1: ...User Manual MV D1024E CameraLink Series CMOS Area Scan Cameras MAN028 03 2008 V1 3...
Page 2: ......
Page 4: ...2...
Page 8: ...CONTENTS 6...
Page 14: ...2 How to get started CameraLink 12...
Page 20: ...3 Product Specification 18...
Page 46: ...4 Functionality 44...
Page 94: ...9 Warranty 92...
Page 96: ...10 References 94...
Page 100: ...11 Pinouts 98...
