2. Primary charging In preparation for the latent image formation, the imaging drum surface is charged so that it has a uniform negative potential. AC and DC bias are applied to the primary charging roller to create uniform negative potential charge on the drum surface. Figure 27. Primary charging of imaging drum 3. Laser beam exposure When the laser beam scans the imaging drum surface, the charge on the exposed area is decreased. This area then forms the electrostatic latent image. 144 Chapter 5 - Theory of operation EN