Controlling The Laser Activation Timing - Canon i-SENSYS MF229dw Service Manual

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Technical Overview > Laser Exposure System > Controlling the Laser Activation Timing > Horizontal Sync Control

Controlling the Laser Activation Timing

■ Laser ON/OFF Control
In this control, the laser driver turns on/off the 2 laser diodes (LD1, LD2) according to the
laser control signal sent from the engine controller.
The following is the circuit diagram of the laser control.
Engine
controller PCB
IC101
+5V
CPU
J102 J11
-13 -1
-2 VDO1 -12
-4 /VDO1 -10
-8 VDO2 -6
-10 /VDO2 -4
IC102
-11 PDOUT -3
ASIC
C16
-5 CNT0 -9
-6 CNT1 -8
-7 -7
CNT2
-3/9/12
-2/5/11
J116-2 /BDI J31-2
2 Technical Overview > Laser Exposure System > Controlling the Laser Activation Timing > Horizontal Sync Control
Laser driver PCB
LD1 PD LD2
VCC
LD1
LD2
switching
switching
circuit
circuit
Comparator
Comparator
Standard voltage
Sample
Sample
hold circuit
hold circuit
Logic circuit
GND
Laser driver IC
BD PCB
The engine controller sends the laser control signals (CNT0, CNT1, CNT2) for changing
the operation mode of the laser to the logic circuit in the laser driver IC, as well as the video
signals (VDO1, /VDO1, VDO2, /VDO2) for image formation.
The laser driver IC executes laser control according to the combination of the CNT0, CNT1,
CNT2 signals.
The following is the combination of the laser control signal (CNT0, CNT1, CNT2).
Operation mode CNT0
Standby L
Print H
LD1 forced ON L
LD2 forced ON H
LD forced OFF H
■ Horizontal Sync Control
This is the control to adjust the writing position in the image horizontal direction.
The following is the details of control procedure.
1) The engine controller controls the laser control signal during unblanking (*) to emit the laser
diode (LD) forcibly.
2) The BD PCB exists on the scanning route of the laser beam, which is sent to the BD PCB.
3) The BD PCB detects this laser beam, creates BD input signal (/BDI) and sends it to the
engine controller.
4) The engine controller creates horizontal sync signals (/BD) based on /BDI signal and sends
the /BD signal to the main controller.
5) When /BD signal is input, the main controller outputs the video signal (VD0, /VD0) to the
C18
engine controller to adjust the writing position in image horizontal direction.
*: Unblanking period
The period during which the laser diode is emitted in non-image area.
F-2-14
CNT1 CNT2 Details
L L Laser control OFF
H H Can emit the laser according to the video signal
H L LD1 forcibly turned ON
L L LD2 forcibly turned ON
H L LD1, LD2 forcibly turned OFF
2-12
T-2-3
2-12