II-4
2. LASER SYSTEM
Laser unit driver
Collimator lens
Cylindrical lens
Laser unit motor
Scanning mirror
Focusing lenses
Beam detect mirror
Reflective mirror
Photosensitive drum
Optical sensor
To external device
Main PCB
SBD DATA VOFF
Figure 2.4
In response to the print signal transmitted from the external device, the main PCB
generates the drive signals (DATA,VOFF) for the laser diode and sends the signals to the
laser unit.
The laser diode in the laser unit generates a laser beam modulated by DATA.
The modulated laser beam is aligned into a parallel beam by a collimator lens and a
cylindrical lens and then brought to the scanning mirror which is rotating at a constant
speed.
The laser beam reflected by the scanning mirror focuses on the photosensitive drum via
the focusing lenses arranged in front of the scanning mirror.
The path of the beam coming through the focusing lenses is reflected by the reflective
mirror.
As the scanning mirror rotates at a constant speed, the laser beam scans the
photosensitive drum at a constant speed.
As the photosensitive drum rotates at a constant speed and the laser beam scans the
drum, an images is formed on the drum.
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