Canon 1000 Service Manual page 88

3. OPERATION AND TIMING
1. A bar code label is attached to the machine's standard white plate. At the factory, light of
a specific intensity is directed to each standard white plate, and the reflected light (values
REF.
of B, G, and R) is measured; the measurements are then converted to bar code nota
tions.
During copying, the machine reads the bar code to identify the degree of "white" of the
standard white plate before executing shading. The presence of the bar code has elimi
nated the calibration plate used in the past models.
2. The color balance of light areas may be adjusted using 'OFST' under 'COL-ADJ'.
3. If the density or the color balance cannot be corrected with a base film for copying of
negative film, make adjustments using 'NEGA' under 'PRJ-ADJ'.
4. The presence of scratches or dirt on the standard white plate will increase the effects of
shading correction over the affected areas, causing vertical white lines on the copies.
If such a problem cannot be corrected after cleaning the standard white plate, you may
change the position of shading correction using 'ADJ-S' under 'ADJ-XY' in service mode.
b. 3-Line CCD Position Matching
The machine's CCD consists of three independent CCDs covered with either a R, G, or B filter. For this
reason, the line image generated by each CCD at a given point in time has a discrepancy of about 0.5 mm (8
lines) in sub scanning direction in relation to the copyboard glass.
To correct such discrepancies, the R and G image signals are temporarily stored in line memory first and
transmitted after they are synchronized with the B image signals.
0.5 mm (8 lines)
Original
BGR
Figure 3-310
The delay in B image signals is maximum at 400% enlargement; in other words, the R image
signals are delayed for 64 lines, and the G image signals are delayed for 32 lines.
REF.
For instance, at 320% enlargement, the R image signals must be delayed by 51.2 lines; in
such a case, the following correction is made using data representing adjacent pixels:
51.2nd line pixel data
3-44
COPYRIGHT © 2001 CANON INC.
Scanning direction
R
G
B
CCD
= 0.8 × (51st line image data)
CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
R
Line memory
G
Line memory
B
Control circuit
Figure 3-311
+ 0.2 × (52nd line pixel data)