Laser Exposure; Overview - Ricoh A66 Service Manual

5. LASER EXPOSURE

5.1 OVERVIEW

[C]
[F]
[D]
A: Laser Diode Unit
B: F-theta Lenses
C: Barrel Toroidal Lens (BTL)
D: Drum Mirror
I: OPC Drum
This machine uses a laser diode to produce electrostatic images on an OPC
drum [I]. The laser diode unit converts image data from the printer main
board into laser pulses, and the optical components direct these pulses to
the drum.
There are 16 gradations for each pixel using the laser pulses, controlled
through power modulation and pulse width modulation. However, to produce
a high quality copy image, dithering during image processing results in a
possible 256 gradations for each color for each 4 x 4 pixel unit.
Exposure of the drum by the laser beam creates the latent image. The laser
beam makes the main scan while drum rotation controls the sub scan.
The intensity of the beam is about 1.1 mW on the drum surface at a
wavelength of 780 nm.
SM
[B]
[I]
E: Laser Synchronization Detector Board-1
F: Laser Synchronization Detector Board-2
G: Polygon Mirror Motor
H: Cylindrical Lens
J: Shield Glass
2-65
LASER EXPOSURE
[G]
[E]
[A]
[J]
A166/A187/A189
[H]