Electrostatic Laser Printers

How do they work?

Laser Printer Basics

Laser printers use lasers to produce high quality images on paper. To do this it receives an output from computers, and the high precision laser produces an image on the photoconducting drum.

Laser Printer in detail

Initially, the drum is given a total positive charge by the charge corona wire or a charged roller, a wire with an electrical current running through it. As the drum revolves, the printer shines a laser beam of light across the surface of the paper to discharge certain points. In this way, the laser draws the letters and images to be printed as a pattern of electrical charges. After the pattern is set, the printer coats the drum with positively charged toner. Since it has a positive charge, the toner clings to the negative discharged areas of the drum, but not to the positively charged areas. This is how the image is coloured black so we can see it. With the pattern on the drum a sheet of paper is rolled on a belt under the belt. The paper is given a negative charge by the corona wire. This change is the same as the drum and is stronger so it is able to pull the toner away from the drum. The paper picks up the exact image from the drum and is discharged by the detac corona wire to keep it from clinging.


How a laser printer works