Canon LBP3300 Series, Service Manual

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Chapter 2
2-2
2.3 LASER EXPOSURE SYSTEM
2.3.1 Overview/Configuration
2.3.1.1 Outline
0011-2430
The laser/scanner system consists of the laser driver and the scanner motor etc. It is controlled by the signals sent from the engine controller and the video controller.
The laser driver allows the laser diode to emit light according to the LASER CONTROL signals (CNT0, CNT1, CNT2) from the engine controller or the VIDEO
signals (/VDO1, /VDO2, VDO1,
VDO2) from the video controller.
F-2-2
The laser/scanner unit of this printer utilizes a "twin beam method" (see Note). It scans two lines simultaneously with 2 laser diodes in order to realize a high-speed
laser scanning.
The operational sequence of the laser/scanner unit is described below.
1) When the video controller sends a print command, the engine controller rotates the scanner motor in order to rotate the four-sided mirror.
2) When the scanner motor starts to rotate, the engine controller forces the laser to emit light with the LASER CONTROL signal and then it starts to control the
scanner motor rotation.
3) The engine controller controls the scanner motor to rotate at a constant speed with the SCANNER MOTOR SPEED CONTROL signal.
4) The video controller sends the VIDEO signals to the laser driver PCB after the scanner motor rotation reaches its targeted speed.
5) The laser driver allows two laser diodes to emit light according to these signals.
6) The two laser beams pass through the collimator lens and the cylindrical lens to strike the four-sided mirror, which is rotating at a constant speed.
7) The laser beam reflected by the four-sided mirror focuses on the photosensitive drum passing through the focus lens and the reflective mirror at the front of the
four-sided mirror.
8) When the four-sided mirror starts to rotate at prescribed speed, the laser beam on the photosensitive drum starts to scan the surface of the drum at its prescribed
speed.
9) When the photosensitive drum rotates and the laser beam scans on the drum at each prescribed speed, the latent image is formed on the photosensitive drum.
Twin beam method
The laser unit unifies with two laser diodes (LD1, LD2). In one scanning operation, the two diodes (LD1, LD2) emit light to write two lines simultaneously.
This enables a twofold printing with same printing speed.
Photsensitive drum
BD sensor
Mirror
Four-sided mirror
Laser driver PCB
Cylindrical lens
Focusing lens
Scanner motor
Video controller PCB
Engine controller PCB
/BDO /BDI CNT0 CNT1
VDO1
/VDO1
VDO2
/VDO2
CNT2
/ACC /DEC