Exposure - Epson AcuLaser C8500 Service Manual

EPSON AcuLaser C8500

2.1.3.2 Exposure

This is the step where the negatively charged drum surface is scanned with
laser radiation, forming an invisible electrostatic latent image.
Laser radiation is emitted in accordance with print data (image data) from
the printer controller. Laser radiation is output when print data instructs the
printer to print a pixel; laser radiation is not output when instructed not to
print (laser beam is emitted for the part to be developed with toner, and not
emitted for the part not to be developed with toner).
Laser radiation is emitted from the laser diode inside the ROS ASSY. The
drum surface is scanned lengthwise from end to end using a rotating
polygon mirror, stationary mirror, and lens attached to the Scanner Assy of
the ROS ASSY.
The laser radiation exposed to the drum surface generates a (electron <= >
hole) inside the photoconductive layer. (Electrons are excited in the
photoconductive band, thus producing a hole in the valence band.)
Attracted to the electric field, the electrons migrate toward and flow into the
metal part inside.
Figure 2-4. Exposure-1
Operating Principles
The hole moves toward the outer surface of the photoconductive layer,
where it reunites with the negative charge (electron) of the outer surface,
thus reducing the negative charge. As a result, an invisible electrostatic
latent image (print image) is formed on the part where the potential of the
drum surface rises.
Figure 2-5. Exposure-2
Revision C
2-5