Shading Adjustment; Shading Correction - Canon Image Reader-A1 iR5000i Service Manual

3.2.2 Shading Adjustment

In this adjustment, the density of white paper and that of the standard white plate are mea-
sured, and the results are stored in memory.
The data is computed for use as the target level during shading correction. The adjustment
is designed for service mode and is used upon installation of the machine, after replacement
of the scanning lamp, or when correcting changes in the intensity of the scanning lamp oc-
curring over time.

3.2.3 Shading Correction

This correction is executed each time an original is scanned. The density of the standard
white plate is measured and the result is compared against the target value stored in the
shading correction circuit. The difference is used as the shading correction value, which will
be used to correct the variation in CCD pixels, thereby ensuring a specific level of image
density.
CCD output
Target value
Results of
measurement
COPYRIGHT © 2001 CANON INC.
Standard white plate
F03-302-01
2000 2000 2000 2000 CANON iR5000i/iR6000i REV.0 JUNE 2001
CHAPTER 3 IMAGE PROCESSING SYSTEM
Characteristics
after correction
Characteristics
before correction
White
Original density
3-5 R