Ricoh A230, Service Manual, Page: 85 / 1134

LASER EXPOSURE
2-22
A230/A231/A232 SM
2.3 LASER EXPOSURE
2.3.1 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 copy image, these 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 0.336 mW (A230 and A231), 0.430 mW
(A232) on the drum surface at a wavelength of 780 nm.
The polygon motor speed is as follows.
Motor Speed (rpm)
1 line cycle (
µ
s)
Resolution Modes
A230/
A231
A232 A230/
A231
A232
400 dpi Copy, Fax Approx. 14170 Approx. 18110 353 276
600 dpi Printer Approx. 21260 Approx. 27170 235 184
391.2 dpi Fax (image
rotation) Approx. 14400 Approx. 18400 694 543
406.4 dpi Fax (mm
printing) Approx. 13860 Approx. 17710 361 282
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) varies also, so there is no simple relationship between resolution and
mirror speed.