Oki B6200 Maintenance Manual page 607

In the exposure step, the surface of the drum negatively charged by the previous charging step is
scanned by a thin laser beam. The light radiated from the laser diode of the ROS (Raster Output
Scanner) scans the drum from one end to the other. The light passes via a rotating polygon mirror (12
facets for 34PPM, and 6 facets for 24PPM) and also via a lens.
The radiation of the laser beam is adjusted according to a video signal from the PWBA ESS.
The laser beam shot at the drum excites electrons directed to the photoconductor. As a result, electron-
hole pairs are induced in the photoconductive layer. Since electrons are moved toward the body inside
the drum by the electric field, the electron-hole pairs move to the surface of the photoconductive layer.
Negative charges in this portion decrease, thus creating an invisible electrostatic latent image there.
Toner particles are adsorbed onto this electrostatic latent image in the next step. Thus, the image is
developed. The toner particles adsorbed to the drum are attracted to positive charges supplied by the
BTR, and are transferred to the paper. The drum is sent for peeling and cleaning steps.
• Electrostatic latent image formed on drum
Laser beam
Electrons
Photoconductor
Conductor
Electron-hole pairs
Laser beam
Electrostatic latent image
Peeling
6 - 3
Chapter 6 Principle of Operation
Decrease in
negative charges
JG6104AA