Canon iR4570 Series Service Manual page 183

To vary the magnification in sub scanning direction, the machine operates as follows depending on the selected
method of reading the original and the selected rate of magnification:
1. In Book Mode
To suit the selected rate of magnification, the speed at which the original is read is varied and the data is processed
by the reader controller PCB/main controller PCB.
EX: for reduction to 25%, the original is read at 236 mm/sec and the data is varied for 50% reduction by the reader
controller PCB (skipping data for 1/2) and for 50% reduction by the main controller PCB (skipping data for 1/2).
EX: at 100%, the original is read at a speed of 236 mm/sec.
Varying the speed of reading the
original (mm/sec)
Processing the data (digital; %) by
the reader controller PCB
Processing the data (digital; %) by
the main controller PCB
2. In ADF Mode
To suit the selected rate of magnification, the speed at which the original is read is varied and the data is processed
by the reader controller PCB/main controller PCB.
EX: for reduction to 25%, the original is read at 236 mm/sec, and the data is processed for 50% reduction (skipping
for 1/2) by the reader controller PCB and for 50% (skipping for 1/2) by the main controller PCB.
EX: for enlargement to 400%, the original is read at a speed of 118 mm/sec, and the data is processed for 200%
enlargement (doubling) by the main control PCB.
Varying the speed at which the
original is read (mm/sec)
Processing the data (digital; %) by
the reader controller PCB
Processing the data (digital; %) by
the main controller PCB
Operation
Operation
236 to 168
T-5-5
Magnification
25% to
50% to 99%
49%
236 to 120 236 to 119
50 50
50 100
T-5-6
Magnification
25% to 43% to 85% to
42% 84% 170%
274 to 277 to
140
50 50
50 100
100% to 400%
236 to 59
100
100
171% to
400%
276 to 118
139
100 100
100 200
Chapter 5
5-15