Dual Beam Writing - Ricoh G035 Service Manual

2.2.4 DUAL BEAM WRITING

[B]
[A]
[D]
This LD unit has two laser diodes; LD1 [A] and LD2 [B] for writing the image. Each
face of the polygon mirror writes two main scan lines, and twelve main scans are
produced when the polygon mirror rotates once. The reasons for this mechanism
are as follows.
1) To reduce the polygon mirror motor rotation speed
2) To reduce the noise generated by the polygon mirror motor
3) To reduce the frequency of the image data clock
Two laser beams are transferred to the polygon mirror [C] through the collimating
lens [D] and prism [E]. The two laser beams arrive on the drum surface about 2
mm away from each other in the main scan direction and about 0.06 mm (at 400
dpi) in the sub-scan direction (see the next page).
The reason for the two-mm difference in the main scan direction is so that the
machine can detect a laser synchronization signal for each beam.
SM
[D]
[E]
G035D203.WMF
2-13
LASER EXPOSURE
[C]
G035