Canon imageRUNNER ADVANCE C3330 Series Service Manual page 72

2. The APC mode is set for the Y/M and C/Bk Laser Driver PCB ICs, and the laser diode of each color is forcibly emitted. The
photo diode (PD) monitors the laser diode (LD), and each Laser Driver IC adjusts the output of laser diode until the laser
light intensity reaches a specified level.
■ BD correction control
Purpose
Corrects the displacement of each color's laser write start position due to the varied angle of the Polygon Mirror surface.
Execution timing
At power-on, and at each print
Control description
1. The Main Controller PCB measures the BD interval after the completion of constant speed rotation control of the Scanner
Motor.
2. The Main Controller PCB calculates the correction value from the displacement of the BD interval.
3. The write start position is corrected by correcting the write start timing based on the above correction value.
Scanner motor control finish
BD interval measurement
correction value calculation
Related Error Code
• E100-0001: BD error
Laser Scanner Unit
Y/M Laser Driver
PCB(UN08)
APC Signal
ASIC
C/Bk Laser Driver
PCB(UN09)
START
(Constant-speed
rotation detection)
Write start position
Write start position
correction value
END
LD
LD
PD
LD
LD
PD
LD
LD
PD
LD
LD
PD
BD interval
Specified
value
BD1
Gap
Before
correction
BD1
Gap
After
correction
BD1
60
2. Technology
Y Laser
M Laser
C Laser
Bk Laser
BD2
Gap
BD2
Gap
BD2