Laser printer
Writing: A laser beam is directed at a rotating polygonal mirror, which redirects the beam onto the photosensitive drum. The rasterized data in memory is now read, and used to control whether the laser is on or off, as the beam sweeps across the drum - where the laser beam strikes the drum the charge is reversed, creating a latent electrical image on the surface. Some laser printers use an array of tiny LEDs instead of a sweeping laser beam.