Exposure Stage - Brother HL-1850 Service Manual

CHAPTER 3 THEORY OF OPERATION
2.6.2

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.
+870
+400
+150
Drum
Sleeve 0
Drum
Paper
Laser beam
f θ lens
Lens
1 Cycle of drum
1 2 3
(a)
(b)
Time
Polygon mirror
Motor
Fig. 3-31
Primary charging
1
2 Laser beam exposure and developing
(a) Unexposed area
( Non image area )
(b) Exposed area
( Image area )
3
Transfer the image to paper
Fig. 3-32
3-28
Laser beam