Shading Correction; A. Shading Correction - Canon CLC 1120 Service Manual

CHAPTER 4 IMAGE PROCESSING SYSTEM
B. Shading Correction
The output of the CCD will not necessarily be uniform even if the light it receives is from an
original of even density. To make up for any discrepancy, shading correction is performed and the
data (collected while scanning an original) is corrected to generate data representing uniform light
distribution.
Measurements for correction are taken when the power switch is turned on and at the end of
copying operation, thus preparing for the next copying job.
Volume 4>Chapter 4>IV-B "Shading Correction"

a. Shading Correction

1. The CCD reads the bar code found under the standard white plate, and determines a
correction target value (Reference 1).
2. The CCD measures the light reflected by the standard white plate, and generates its output.
3. The shading correction circuit compares the measurements taken in 2 against the target
value determined in 1, and saves the difference as the shading correction value.
Reference:
1. A bar code label is attached to the copier's standard white plate. At the factory, light of a
specific intensity is directed to the standard white plate and measured (B, G, and R
values); the result is converted, and printed in the form of a bar code for shipment.
2. The color balance of light areas may be adjusted in service mode
(ADJUST>COLOR>ADJ).
3. If the density or color balance of copies of a negative film cannot be corrected using a base
film, use service mode (PRJ>ADJUST>NEGA).
4. Scratches or dirt on the standard white plate will be subject to stronger shading correction,
causing vertical white lines on copies. If such is the case, clean the standard white plate; if
the problem is not corrected, try changing the position of shading correction using service
mode (ADJUST>ADJ-XY>ADJ-S).
4-6
COPYRIGHT © 1999 CANON INC.
Standard
Bar code
white plate
Glass
Figure 4-402
Copyboard glass
Scanning lamp
Lens
CANON CLC1120/1130/1150 REV.0 MAR. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CCD