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DP-C405/C305/C265
FEB 2008Ver. 1.1
6.4.2. Laser Exposure and Scanning
1. Laser Exposure
As the OPC drum rotates, the uniformly charged OPC drum is exposed by the modulated laser beam.
The vertically-moving OPC drum passes in front of horizontally scanning laser beam, and the negative
charge on the OPC drum surface are neutralized by the laser beam. This forms a latent image.
Laser output power is either approximately 0.075 mW (1200 dpi), 0.13 mW (600 dpi, Color) or 0.21
mW (600 dpi, Mono) on the OPC drum surface, depending on whether the printer is printing resolution
in 1200 dpi mode, or 600 dpi mode. The laser exposure, the negative potential on the OPC drum varies
from approximately -430 volts (unexposed) to -60 volts (fully exposed).
2.
Laser Scanning
A laser diode generates the laser beam, and lenses and mirror in the laser scanner direct the beam to
the OPC drum. The beam is parallel to the collimator lens, and is directed at the rotating polygonal
mirror, attached with the polygon motor. The beam is parallel to the collimator lens, and is directed at
the rotating polygon mirror. The polygon mirror rotates at approximately 24,800 to 40,000 constant
revolutions per minute.
This transforms the beam into a horizontally scanning beam, which is directed through the primary and
the secondary lens, altering the beam’s angular rotation motion into a constant horizontal motion. The
cylindrical mirrors corrects the beam for any vertical mis-registration. Next, the beam reflects off of a
mirror, and passes through a window where it scans across the rotating OPC drum. At the beginning of
each horizontal sweep, the horizontal sync mirrors deflect the laser beam to the horizontal sync sensor.
This informs the engine control board that the laser beam is beginning its horizontal sweep, and that it
can begin to modulate the signal with the data to be printed on that line of the image.
Intermediate
Transfer Belt
Polygon
Motor
First Bias Transfer Roller (FTR)
Toner
Cartridge
Y
Toner
Cartridge
M
Toner
Cartridge
C
Toner
Cartridge
BK
Laser Scanning Unit (LSU)
Mirror
Laser Beam
OPC
Drum
Y
OPC
Drum
M
OPC
Drum
C
OPC
Drum
BK
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