Controlling The Laser Diode Emission - Canon CP660 Service Manual

CHAPTER 3 LASER EXPOSURE SYSTEM
E.

Controlling the Laser Diode Emission

The laser drive circuit turns on and off the laser diode according to laser drive signals
from the PWM IC when the image enable signal (LENB*) from the DC controller PCB is
'0' and the APC sampling timing signal (SAMPLE*) is '1'.
The GA (IC204) puts video signals (DVDO0 through 7*) through masking processing
for left/right and top/down directions for transmission to the PWM IC.
The paper size is communicated to the D-CPU (IC201) by means of a paper size
command coming from the cassette size detecting switch in the case of cassette pickup
or from the printer board*
HORZEN
Note:
1. The laser beam is capable of writing within the shaded area.
2. T1 throng T3 differ according to paper size.
3. If the paper size command from the printer board does not indicate a paper size
when the multifeeder is used, the printer unit assumes T3 is 12x18.5 (maximum
paper size) in the absence of data.
The multifeeder tray is equipped with a paper width sensor (PS1701) for detection
of the width of paper.
The CPU identifies the size of paper in relation to the length of print paper detect-
ed by PS1 when the trailing edge of the paper moves past the registration paper
sensor (PS1).
1
* Reader controller PCB (when making prints with the reader unit installed).
3-8
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1
in the case of multifeeder pickup.
LSYNC*
Left/right
masking signal
T1
5 mm
Figure 3-202
T2
5 mm
CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)