Ricoh G148, Service Manual

Page: 444 / 537

Laser Exposure
Overview
There are four laser diodes. Four parallel beams write four lines at once, 24 lines with one complete rotation
of the polygon mirror, with the polygon motor rotating at 42,756 rpm.
This adoption of multi-beam operation achieves:
• Longer life of the polygon motor (four-beam writing requires fewer motor rotations)
• Quieter operation because fewer polygon motor revolutions are required.
Up to 5 image density levels (0 ~ 4) are used for each pixel. To achieve this, this machine controls the
duration of the laser exposure using PWM (Pulse Width Modulation).
(
 Digital Processes> Printing> Laser Printing> Image Processing)
The strength of each beam is 10 mW/channel at a wavelength of 788 nm.
Specifications
LD Unit
Semi-conductor laser encased in an aluminum die-cast bracket.
Wavelength: 788 nm
Output: 13.3 mW/channel
4-beam exposure
APC (Auto Power Control) provided
Gradation control with PWM
Line Writing
Light weight, aluminum die-cast housing
Main line writing by polygon mirror
F
θ
lens controls the beam position and focus in the main scan direction.
Beam focus correction by WTL.
Polygon Motor 42,756 rpm
A new ceramic shaft increases the durability of the polygon motor. This machine uses APC (Auto Power
Control), so no adjustments are required when the LD unit is replaced.
Laser Exposure
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