Exposure Stage - Brother HL-720 - B/W Laser Printer Service Manual

2.5.2

Exposure stage

After the drum is positively charged, it is exposed to the light emitted from the laser
unit.
Laser detector
Laser diode
The exposed area is the part to be printed. The surface potential of the exposed
area is recreated forming an electrostatic image to be printed.
1
+1000
+700
+400
Drum +300
Sleeve
Drum
Paper
Laser beam
f lens
Polygon mirror
Motor
Lens
Fig. 2.32
1 Cycle of drum
2 3 4
(a)
(b)
Time
Fig. 2.33
II-29
Laser Beam
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
Erase the residual potential
4