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COPYRIGHT
©
2000 CANON INC. CANON imageRUNNER 600 REV.1 JAN. 2000 PRINTED IN U.S.A.
4-9
CHAPTER 4 IMAGE PROCESSING SYSTEM
C. Shading Correction
Part 2>Chapter 3>2
Figure 4-302 Shading Correction Block Diagram
CCD
Analog signal processing block
1. Gain correction
2. Offset correction
Shading correction
A/D conversionA/D conversion
Digital image
signal
AD-DT
CCD PCB
Image processing PCB
8
8
Odd-numbered
pixels
RAM
Shading Correction
1. Offset Correction
Turns the minimum outputs of the CCD while the
fluorescent lamp is off to '0'.
2. Scanning Lamp Intensity Adjustment
Turns on the fluorescence lamp, and adjusts its
activation voltage so that the maximum output of the
CCD in response to standard white paper will be
'255'.
3. Offset Correction Value
Stores the difference between '0' and the output of
each CCD cell while the fluorescent lamp is off.
4. Target Level Correction Value
Stores the difference between light reflected by
standard white plate and standard white paper.
Data for gain/offset adjustment
Analog image signal
Even-numbered pixels
Determining the Shading Correction Value (for each
copy)
1. Offset Correction
Stores the difference between '0' and the output of
each CCD cell while the fluorescent lamp is off, and
the value will be used as the correction value (for
correction of variation among the cells).
2. Gain Correction
Turns on the fluorescent lamp, and compares the
CCD outputsgenerated by the light reflected by the
standard white plate and the light reflected by
standard white paper for storage in memory; the
difference will be used as the correction value (to
correct thedeterioration of the fluorescent lamp).
Related Service Mode
If a faulty image is noted after executing
COPIER>FUNCTION>CCD>CCD-ADJ, enter the
value recorded on the service label.
COPIER>FUNCTION>CCD>CCD-ADJ
(shading auto adjustment)
For details of execution, see VIII. "Service Mode" in
Chapter 13.
COPIER>ADJUST>CCD>GAIN-E/O
(CCD output gain adjustment input)
COPIER>ADJUST>CCD>OFST-E/O
(CCD output offset adjustment value input)
COPIER>ADJUST>CCD>SH-TRGT
(white level target value input for shading
correction)