Brother HL-6050 Service Manual page 98

CHAPTER 3 THEORY OF OPERATION
2. The two laser beams reflected by the polygon mirror are refracted by the theta lens and
radiated from the right through to the left end of the reflection mirror as the polygon mirror
rotates. At this time, blur of the vertical direction of the laser beam by inclination of a
polygon mirror is corrected by passing a CYL lens.
3. The two laser beams reflected by the reflection mirror go straight toward the
photosensitive drum below it, then expose the photosensitive drum in two lines.
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
1 Cycle of drum
1 2 3
(a)
(b)
Time
Primary charging
1
2 Laser beam exposure and developing
(a) Unexposed area
(Non image area)
(b) Exposed area
(Image area)
Transfer the image to paper
3
Fig. 3-37
3-30