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II-31
2.5.2 Exposure Stage
After the drum is positively charged, it is exposed to the light emitted from the laser unit.
Fig. 2-38
The area exposed to the laser beam is the image to be printed. The surface potential of
the exposed area is reduced, forming the electrostatic image to be printed.
1 Cycle of drum
Surface Potential (V)
+1150
+700
+400
+300
123
4
(a)
(b)
Time
1
2
3
4
Primary charging
Laser beam exposure and developing
(a) Unexposed area
( Non image area )
(b) Exposed area
( Image area )
Transfer the image to paper
Erase the residual potential
Drum
Sleeve
Fig. 2-39
Drum
Paper
Laser beam
f lens
Polygon mirror
Motor
Lens
Laser diode
Laser detector
Laser Beam