LASER EXPOSURE
G065 6-12 SM
6.4.3 DUAL BEAM WRITING
This LD unit employs two laser
diodes [A] (LD) and [B] (L2). Each
face of the polygon mirror writes two
main scan lines, and twelve main
scans are produced when the
polygon mirror rotates once. This
reduces polygon motor rotation
speed, reduces noise generated by
the polygon motor, and reduces the
frequency of the image data clock.
The two laser beams follow the path:
collimating lenses [C] → prism [D] →
polygon mirror [E]
The two laser beams arrive on the drum surface about 2 mm apart in the main
scan direction and about 0.06 mm apart (at 400 dpi) in the sub scan direction. The
two-mm difference in the main scan direction allows the machine to detect the laser
synchronization signal for each beam.
G065D203.WMF
G065D204.WMF
[D]
P1: 400 dpi
P2: 600 dpi
2 mm
P1
P2
[C]
[B]
[A]
[E]
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