Static Latent Image Formation Block - Canon MF4500 Series Service Manual

2
Technical Overview > Image Formation System > Overview/Configuration > Static Latent Image Formation Block

■ Static Latent Image Formation Block

This block is comprised of two steps and forms static latent images on the photosensitive
drum.
When the final step of this block completes, negative charge remains at dark areas on the
drum surface where laser beam has not been exposed, and negative charge is eliminated
from bright areas on the drum surface with laser beam exposed. The images on the drum
with negative charge are called static latent images because human eyes cannot detect them.
0
Surface
potential
(V)
Primary
charging
(step 1)
Step 1: Primary charging
For preparation of latent image formation, the surface of photosensitive drum is charged
with even negative potential. In this primary charging, the charge is applied from the primary
charging roller directly to the photosensitive drum.
DC bias is applied to the primary charging roller to maintain an even potential on the surface
of the photosensitive drum.
Primary charging roller
Photosensitive drum
2 Technical Overview > Image Formation System > Overview/Configuration > Static Latent Image Formation Block
Time (t)
Exposed area
Unexposed area
Laser Transfer Primary
beam (step 4) charging
exposure (step 1)
(step 2)
F-2-19
DC bias
F-2-20
Step 2: Laser beam exposure
In this step, static latent images are formed on the photosensitive drum with laser beam.
When laser beams are scanned on the photosensitive drum negatively charged, bright areas
lose their charges, eliminating negative potential on the surface of the photosensitive drum;
on those portions, static latent images are formed.
Unexposed
area
Laser beam
Exposed
area
F-2-21
2-16
2-16