Canon FAX L1000 Service Manual page 195

b) Electrostatic latent image formation block
This block follows two steps to produce an electrostatic latent image on the photosensitive
drum.
When "Laser beam exposure" of this block is completed, negative charge remains in the
unexposed "dark" areas; however, those in the exposed "light" areas are eliminated.
This image of negative charges on the drum is invisible to the human eye, so it is called an
"electrostatic latent image."
Surface potential (V)
b-1) Primary charging
AC bias
DC bias
In preparation for the latent image formation, a uniform negative potential is applied to the
photosensitive drum surface. For primary charging, the printer uses the charging method,
which directly charges the drum.
The primary charging roller is made of conductive rubber. In addition to DC bias, AC bias
is also applied to the primary charging roller to keep the potential on the drum surface
uniform. The DC bias changes with the developing DC bias.
FAX-L1000 Chapter 3: Technical Reference
0
-100
-500
Primary
charging
Laser beam exposure
Figure 3-19 Surface Potential
Primary charging roller
Photosensitive drum
Figure 3-20 Primary Charging
3-51
Time t
Exposed area
Unexposed
area
Primary
charging
Transfer