II - 19
2.5.2
Exposure stage
After the drum is positively charged, it is exposed to the light emitted from the laser
unit.
Fig. 2.25
The exposed area is the part to be printed. The surface potential of the exposed area
is decreated forming an electrostatic image to be printed.
Drum
Paper
Laser detector
Laser diode
Motor
Laser beam
f lens
Polygon mirror
Lens
+
+
+
+
+
+
-
-
-
-
-
-
Laser Beam
1 Cycle of drum
Surface Potential (V)
+700
+500
+100
1
2
3
4
(a)
(b)
Time
1
2
3
4
Primary charging
Laserbeam exposure and developing
(a) Unexposed area
( Non image area )
(b) Exposed area
( Image area )
Transfer the image to paper
Erase the residual potential
Fig. 2.26
