A non-impact high-resolution printer which uses a rotating disk to reflect laser beams to form an electrostatic image on a selenium imaging drum. The developer drum transfers toner from the toner bin to the charged areas of the imaging drum, which then transfers it onto the paper into which it is fused by heat. Toner is dry ink powder, generally a plastic heat-sensitive polymer.
The print speed may exceed 21,000 lines per minute, though printing speed is more often given in pages per minute. If a laser printer is rated at 12 pages per minute (PPM), this figure would be true only if the printer is printing the same data on each of the twelve pages, so that the bit map is identical. This speed however, is rarely reached if each page contains different codes, text, and graphics.
Colour laser printers can reach 2400 DPI easily (e.g. an HP LaserJet 8550). Some printers with large amounts of RAM can print at engine speed with different text pages and some of the larger lasers intended for graphics design work can print graphics at full engine speed.