CHAPTER 3 IMAGE READING/PROCESSING SYSTEM
COPYRIGHT
©
2002 CANON INC. 2000 CANON iR1600/iR2000 REV.1 JAN. 2002
3-12
4.4.1 Black Shading Correction
The input signal of the CS while the LEDs are kept OFF is read, and is subjected to A/D
conversion (black correction), storing the result (digital signal) in memory.
When an image is read, the black correction value is subtracted from the value of the
image signal read by each pixel of the CS by way of full pixel black shading correction.
4.4.2 White Shading Correction
The light of the LEDs is directed against the standard white plate, and the CS input signal
is read. The result is subjected to A/D conversion (white correction), storing the result (digi-
tal signal) in memory.
The image data to which black shading correction was executed is then subjected to com-
putation using the white correction value, thus executing full pixel white shading correction.
As a result, the variation in LED intensify and in the intensity of the rod lens array are cor-
rected, evening out the image density level.
Shading correction is executed as follows:
· When the Start key is pressed.
The image data after shading correction is converted from 10-bit into 8-bit data.
4.5 Re-Ordering
The input signals from the CS consist of image data read simultaneously by each of the 4
systems of CCD device units; thus, they are not in the same sequence as the signals that rep-
resent the original image, re-ordering.
F03-405-01
a
2
a
1
,
.....
b
2
b
1
,
.....
c
2
c
1
,
.....
d
2
d
1
,
.....
a
1
..........
b
1
c
1
d
1
a
2
b
2
c
2
a
1
....... ...........
a
2
a
3
b
1
b
2
OS1 OS2 OS3 OS4
CS unit
Read image
data
Data items of
correct order
(original image data)
Re-ordering
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