Canon 1000S, Service Manual

Page: 97 / 840

COPYRIGHT © 2001 CANON INC. CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
3-53
3. OPERATION AND TIMING
l. Reproduction Ratio Processing
a) Reproduction Ratio Processing
1 Horizontal Reproduction Ratio (main scanning direction)
When writing image data into memory or reading image data from memory, data units are skipped
when writing (reduction) or are read a number of times when reading (enlargement).
2 Vertical Reproduction Ratio (sub scanning direction)
The scanner is moved at different speeds to change the width of the line, scanning each pixel on the
original.
See Table 3-302 for how the ratios are varied.
Table 3-302
b) Enlargement Correction Processing
The image data is corrected so that the difference in density between pixels will not vary excessively
when producing enlarged copies.
Figure 3-331 shows image data of an original, image data at time of enlargement, and image data after
enlargement correction.
Figure 3-331
Original
(image data)
(writing)
Line memory
(reading)
Copying
Reproduction
ratio in main
scanning
direction
Reproduction
ratio in sub
scanning
direction
Direct
All data is written in
memory as it is and read
as it is.
Reduction
To reduce to 1/2, every
other data unit is written in
memory.
The scanner is moved
faster to increase the
width of the line scanning
each pixel on the original.
Enlargement
To enlarge by 200%, all
data is written in memory
as it is but read twice.
The scanner is moved at
a lower speed to
decrease the width of
scanning over each pixel
on the original.
W
W
2W
W
W
2
W
1 pixel
a. Original
1 pixel
b. Enlargement at 300%
1 pixel
c. After correction
Image density Image density Image density