LASER EXPOSURE 20 June 2005
6-50
6.6.3 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] Î prism [D] Î
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.
B195D918.WMF
B195D919.WMF
[A]
[B]
[E]
[C]
[D]
P1: 400 dpi
P2: 600 dpi
2 mm
P1
P2
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