Exposure Stage - Brother MFC8440D Service Manual

7/13/2019
2.7.2

Exposure stage

After the drum is positively charged, it is exposed to the light emitted from the laser unit.
Laser detector
Laser diode
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)
+870
+400
+150
Drum
sleeve
0
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Brother 8840D Service Manual
Drum
Paper
Laser beam
f lens
θ
Polygon mirror
Motor
Lens
Fig. 3-36
1 Cycle of drum
1 2 3
(a)
(b)
Time
Fig. 3-37
3-23
MFC-8440/8840D/8840DN, DCP-8040/8045D/8045DN
Primary charging
1
Laser beam exposure and developing
2
(a) Unexposed area
(Non image area)
(b) Exposed area
(Image area)
Transfer the image to paper
3
SERVICE MANUAL
Laser beam
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