CHAPTER 3 THEORY OF OPERATION
3-28
2.6.2 Exposure stage
After the drum is positively charged, it is exposed to the light emitted from the laser unit.
Fig. 3-31
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)
+870
+400
+150
123
(a)
(b)
Time
1
2
3
Primary charging
Laser beam exposure and developing
(a) Unexposed area
( Non image area )
(b) Exposed area
( Image area )
Transfer the image to paper
Drum
Sleeve
0
Fig. 3-32
Drum
Lens
Laser beam
Polygon mirror
Paper
Laser detector
Laser diode
Motor
Laser beam
f θ lens
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