Image analysis – Histogram processing – For setting a threshold
Reexamination Certificate
2001-01-16
2004-09-14
Johns, Andrew W. (Department: 2621)
Image analysis
Histogram processing
For setting a threshold
C382S232000, C382S218000
Reexamination Certificate
active
06792142
ABSTRACT:
BACKGROUND
Many different image sensing systems are known in the art.
Viewing of images is limited by the resolution of the viewing screen that is being used. Sometimes, however, the resolution of a view screen is not sufficient to see a specified image, especially one with motion.
For example, a high dynamic range scene may have a dynamic range of 18 bits or even more. This would require a display device that could display 2
18
resolvable levels of brightness. Many display devices today, however, show only 2
8
=256 levels of brightness.
It is desirable to display an image on such a display while preserving much of its detailed information. Dynamic range compression can be used for this purpose.
It is known to compress dynamic range using logarithmic compression, homomorphic filtering, “cut and paste” methods, and histogram equalization and adjustment. Logarithmic compression carries out a transformation of
s
=
255
×
log
(
1
+
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g
&RightBracketingBar;
)
-
log
(
1
+
&LeftBracketingBar;
G
min
&RightBracketingBar;
)
log
(
1
+
&LeftBracketingBar;
G
max
&RightBracketingBar;
)
-
log
(
1
+
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G
min
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(
5.1
)
Homomorphic filtering is a frequency domain procedure which associates low frequencies of a Fourier transform of the log of the image with illumination high frequencies. These are associated with reflectance using a filter which associates low-frequency with illumination and high frequency with reflectance.
The cut and paste methods cuts data blocks from different intensity images and pastes them into one background image at corresponding locations. This may produce a gray level which is not a monotonic response to light level, which may produce distortion in the final displayed image.
REFERENCES:
patent: 5710828 (1998-01-01), Hashimoto
patent: 5729632 (1998-03-01), Tai
patent: 5761344 (1998-06-01), Al-Hussein
patent: 5809177 (1998-09-01), Metcalfe et al.
patent: 5815606 (1998-09-01), Baker et al.
patent: 5995671 (1999-11-01), Nagarajan et al.
patent: 6141450 (2000-10-01), Chen et al.
patent: 6307962 (2001-10-01), Parker et al.
patent: 6347156 (2002-02-01), Kamada et al.
Alavi Amir
Dickstein Shapiro Morin & Oskinsky LLP
Johns Andrew W.
Micro)n Technology, Inc.
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