Image-formation process
Laser printing requires the interaction of several different technologies, including electronics, optics, and
electrographics, to produce a printed page. Each process functions independently and must be
coordinated with the other processes. Image formation consists of the following four processes:
1. Latent-image formation
2. Developing
3. Image transfer
4. Fusing
Drum cleaning block
Transfer block
Electrostatic latent-image-formation block
Develoment block
2. Laser beam exposure
Fusing block
6. Fusing
Delivery
5. Separation 4. Transfer
7. Drum cleaning
3. Development
1. Primary charging
Paper path
Direction of the drum rotation
Pick-up
Figure 4-9 Image-formation process
Latent-image formation block
During the two steps that comprise this block, a negative charge is applied to the photosensitive drum
to form a latent image, which is invisible.
Step 1: primary charging
A high-voltage DC bias is applied to the primary charging roller, which is made of conductive rubber and
is in contact with the drum surface. As the roller moves across the drum, it applies the negative charge.
0
Time (t)
Surface potential (V)
Laser
beam
exposure
(step 2)
Transfer
(step 4)
Primary
charging
(step 1)
Primary
charging
(step 1)
Exposed area
Unexposed area
Figure 4-10 Primary charging
60 Chapter 4 Theory of operation ENWW
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