Exposure - Printronix L5535 Maintenance Manual

Chapter 8
Photoconductive Section

Exposure

When the photoreceptor drum (which has been positively and uniformly
charged in the main charging step) is exposed to light, the exposed areas of
the photosensitive drum surface film go into conduction. Thus the charge in
the exposed area is neutralized while the unexposed portions of the drum
maintain approximately +580 volts. The electrical pattern formed by this
process is called the "latent image."
The printer draws on this principle. A bit-mapped image of the page, received
from the host computer, is contained in random access memory (RAM), on
the processor board. The image data illuminates the LED array, and the drum
rotates to form an electrostatic latent (invisible) print image on the positively-
charged surface.
The LED array consists of LED elements which are arranged in the direction
of printing width and related to printing pixels on a one-to-one basis. It
converts one raster (horizontal scanning line) of image data into a row of
illumination dots.
LED array
LED Array
II–116
Dark Area Exposed Area
+ + +
Neutralized Charge
Insulated Becomes Conductive
- - -
Photoreceptor Drum
Photoreceptor Drum
Light
Se/Te Alloy
Photosensitive Film
Aluminum Sleeve
Electrostatic Latent Image