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FO-2970MU
f. Laser scanning unit
This unit controls the laser beam power and laser beam scanning.
The control is performed with the signals inputted outputted to or from
the CPU and ASIC.
+5VL
Q601
A1015
R603
30K
D601
PD481PI
+5VL
R606
10K
5
INH
R609
10K
1) Signal functions
PMCLK
Clock signal for driving the scanning (polygon) motor. (1.18KHz/770Hz)
PMD
Scanning motor ON/OFF signal.
APCSTT
Used to start the laser beam generation circuit.
SYNC
This signal is outputted when the laser beam scanned by the laser
beam sensor signal is sensed by sensor (Photo diode D601).
Used for the left margin control.
VIDEO
This signal is used to control the laser diode emitting.
Not only when the laser beam is emitted to perform the LEND proc-
ess, but also when the laser beam is emitted as image data, ASIC
controls and the signal is outputted from video terminal.
BD CIRCUIT
R604
820
CN604
Q602
1
C1815
+5VL
R605
2
SYNC-
240
3
GND
BD
APC CIRCUIT
IC601
IR3C07
C607
2200p
1
+5VL
OUT
2
Cp
3
IM
+
IC603
C606
2
220uF/10V
O/I
BU4S66
IC602
CN603
7805
+5VL
1
3
OUT
+5VL
2
+
C602
SYNC-
0.1uF
3
GND
C601
47uF/10V
BD
+5VL
+5VL
C608
4700p
VR601
15K
R607
R608
1K
30
1
I/O
C605
0.1uF
PD
LD
D602
LNC702
Fig. 9
2) Laser beam power control
The laser beam power is controlled in the laser emitting unit PWB.
This circuit functions to keep the laser beam output power at a constant
level.
The laser beam output is monitored with photo diode D602 for monitor.
When the laser beam output rises above the specified value, the imped-
ance of photo diode D602 is decreased to decrease the monitor input
(3PIN) voltage of the laser diode control IC (IC601).
Then the laser diode (LTO28GS) drive voltage is decreased to decrease
the laser beam output to the specified level.
When the laser beam output is decreased below the specified level, the
contrary operation are performed.
5 – 12
+24V
R601
CN601
130ohm/2W
1
1
IN
2
C603
0.1uF
3
4
5
6
7
8
R613
180
9
PD601
GP1S53
+24V
1
2
3
4
R610
9.1
5
R611
Q603
750
A1206
R612
510
+24V
GND
VIDEO
SAMP
SYNC-
APCSTT
PMCLK
PMD-
PE
LSU
CN602
GND
PMD-
+24V
PMCLK
GND
PM
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