HP LaserJet Pro M402d - Page 40

Step 2: Laser-beam exposure
The laser beam scans the photosensitive drum to neutralize the negative charge on portions of the drum
surface. An electrostatic latent image forms where the negative charge was neutralized.
Figure 1-14 Laser-beam exposure
Photosensitive drum
Laser beam
Step 3: Development
Toner acquires a negative charge as a result of the friction from the developing roller rotating against the
developing blade. When the negatively charged toner comes in contact with the drum, it adheres to the
electrostatic latent image. When the toner is on the drum, the image becomes visible. The developing bias is
applied to the developing roller.
Figure 1-15 Development
Developer roller
Developing bias
Photosensitive drum
Developer blade
22 Chapter 1 Theory of operation ENWW