Laser Driver Circuit; Controlling The Laser System - Canon CLC 1120 Service Manual

CHAPTER 5 LASER EXPOSURE SYSTEM
III. LASER DRIVER CIRCUIT
A. Controlling the Laser System
The laser driver circuit converts video signals (VD0 to VD7) into laser intensity control signals
used to drive the semiconductor laser.
The laser driver circuit has the following functions:
1. Controlling laser emission.
2. Controlling the laser intensity (APC control).
3. Switching laser outputs.
Each of the signals has the following function:
1. PH/TX/h200 (switch signal to suit copying mode)
Serves to switch resolutions in main scanning direction (i.e., to suit text output or photo
output; in sub scanning direction, it is fixed to 400 dpi).
2. PVE (sync signal)
Serves as the sync signal when transmitting video signals.
3. 400* Signal
Serves to select 400 dpi when '1'.
Image
processor
PCB
VD0-VD7
VCLK
[1]
PH/TX/H200
[2]
PVE
BD
CPU PCB
CPU Bus
ITOP
5-4
COPYRIGHT © 1999 CANON INC.
Laser
controller
PCB
8
Control
panel
400*
L-ON
L-RDY
APCHOLD
Figure 5-301
CANON CLC1120/1130/1150 REV.0 MAR. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
Laser driver PCB
8
Laser
[3]
intensity
control
[5]
circuit
[6]
VR1
[4]
Laser
intensity
correction
circuit
Laser
driver
circuit
Laser
limiter
circuit
VR2
TH
H