Brother International HL-1070 Service Manual - Page 38

Exposure Stage, Fig. 2.28, reduced forming the electrostatic image to be printed.

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2.5.2 Exposure Stage After the drum is positively charged, it is exposed to the light emitted from the laser unit. Drum Laser Beam Laser detector Laser diode Lens Paper Laser beam f  lens Polygon mirror Motor Fig. 2.28 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. Surface Potential (V) +1000 +700 1 Cycle of drum 1 2 34 (a) +400 Drum +300 Sleeve (b) Time Fig. 2.29 1 Primary charging 2 Laser beam exposure and developing (a) Unexposed area ( Non image area ) (b) Exposed area ( Image area ) 3 Transfer the image to paper 4 Erase the residual potential II-22

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II-22
2.5.2
Exposure Stage
After the drum is positively charged, it is exposed to the light emitted from the laser unit.
Fig. 2.28
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)
+1000
+700
+400
+300
1
2
3
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. 2.29
Drum
Paper
Laser beam
f lens
Polygon mirror
Motor
Lens
Laser diode
Laser detector
Laser Beam