Canon M3010 Series, Service Manual

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Technical Overview > Laser Exposure System > Controlling the Laser Activation Timing > Horizontal Sync Control
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 laser diode (LD) according to the laser control
signal sent from the engine controller.
The following is the circuit diagram of the laser control.
Engine
Controller
Main
Controller
Laser driver PCB
Laser driver IC
BD Sensor
LD PD
C1
CNT1
CNT0
VOD
/VOD
Sample hold
circuit
Drive
circuit
Comparator
Logic PCB
/BD
+3.3V
/BDI
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The engine controller sends the laser control signals (CNT0, CNT1) for changing the
operation mode of the laser to the logic circuit in the laser driver IC, as well as the video
signals (VDO, /VDO) for image formation.
The laser driver IC executes laser control according to the combination of the CNT0, CNT1
signals.
The following is the combination of the laser control signal (CNT0, CNT1).
Operation mode CNT0 CNT1 Remarks
Discharge L L The capacitor (C1) is discharged.
Data output H H At normal print
APC H L At using APC
Forced OFF L H At using image mask
■ 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 (VDO, /VDO) to the
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.
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