Canon MF4500 Series Service Manual

22 2-162-16Technical Overview > Image Formation System > Overview/Configuration > Static Latent Image Formation BlockTechnical Overview > Image Formation System > Overview/Configuration > Static Latent Image Formation Block■ Static Latent Image Formation BlockThis block is comprised of two steps and forms static latent images on the photosensitivedrum.When the final step of this block completes, negative charge remains at dark areas on thedrum surface where laser beam has not been exposed, and negative charge is eliminatedfrom bright areas on the drum surface with laser beam exposed. The images on the drumwith negative charge are called static latent images because human eyes cannot detect them.0 Time (t)Surfacepotential(V)Laserbeamexposure(step 2)Transfer(step 4)Primarycharging(step 1)Primarycharging(step 1)Exposed areaUnexposed areaStep 1: Primary chargingFor preparation of latent image formation, the surface of photosensitive drum is chargedwith even negative potential. In this primary charging, the charge is applied from the primarycharging roller directly to the photosensitive drum.DC bias is applied to the primary charging roller to maintain an even potential on the surfaceof the photosensitive drum.Primary charging rollerPhotosensitive drumDC biasF-2-19F-2-20Step 2: Laser beam exposureIn 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 areaslose their charges, eliminating negative potential on the surface of the photosensitive drum;on those portions, static latent images are formed.Laser beamExposedareaUnexposedareaF-2-21