Laser Exposure; Overview - Ricoh G035 Service Manual

LASER EXPOSURE

2.2 LASER EXPOSURE

2.2.1 OVERVIEW

This machine uses two laser diodes to produce electrostatic images on an OPC
drum. The laser diode unit converts image data from the BICU board into laser
pulses, and the optical components direct these pulses to the drum.
To produce a high quality print image, there are 256 gradations for the laser
pulses, controlled through power modulation (32 levels) and pulse width
modulation (8 levels).
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 combined strength of both beams is 0.430 mW on the drum surface at a
wavelength of 780 nm.
The polygon motor speed is as follows.
Resolution
400 dpi
600 dpi
In previous models, the mirror speed increased for higher resolutions. However, for
this machine, the line cycle (time taken to output one main scan line of data to the
laser diode) also varies, so a simple relationship does not exist between the
resolution and the mirror speed.
G035
Motor Speed (rpm)
Approx. 18110
Approx. 27170
2-10
1 line cycle (µs)
276
184
SM