Varying The Reproduction Ratio - Canon PC920 Service Manual

CHAPTER 3 EXPOSURE SYSTEM
B.

Varying the Reproduction Ratio

The reproduction ratio in the drum axial direction (main scanning direction) is varied by the
lens drive system, and that in the drum peripheral direction (sub scanning direction) is changed by
the scanner drive system.
In the lens drive system, the positions of the fixed focal point lens and the No. 4/5 mirror are
changed to vary the reproduction ratio.
In the scanner system, the relative speed of the No. 1 mirror mount is made higher (for reduc-
tion) or lower (for enlargement) than the drum peripheral speed.
3-2
Direct
F
Optical length
Reduction
Optical length
Enlargement
F
Optical length
Optical length: L1 < L2, L1 < L3
Figure 3-102
COPYRIGHT © 1999 CANON INC.
F'
L1
F'
F
L2
F'
L3
CANON PC800s/900s REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)