Brother MFC-9420CN Service Manual page 44

2 Exposing
The exposing process means that the OPC belt surface is exposed to the laser beam to form an
electrostatic latent image.
(1) Structure of Laser ASSY PU
1) Laser ASSY PU is located as shown in Fig.3-9.
2) Luminous source of the laser beam is a semiconductor laser.
3) Scanning is made to laser light on OPC belt as converting the laser beam to the beam
light through lens and reflective mirror to form an electrostatic latent image.
(2) Process of Exposing (Refer to Fig.3-14.)
1) The OPC belt surface has been charged to the potential -Vo(V) in the charging
process.
2) Laser beam is scanned as rectangular to the forwarding direction of OPC belt.
3) High speed switching of laser is made according to the transmitted image data.
4) Charge of the areas radiated by the laser beam is discharged, where the potential is -
VR(V).
5) An invisible electrostatic latent image is formed on the OPC belt as shown in Fig.3-
14.
OPC Charger Roller PU
-V
O
Charging
Exposing
Fig. 3-14
3 - 1 2
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