Laser Printer

A computer-driven, plain-paper output device used to generate proofs, masters, or general on demand outout. Most laser printers can output device attached to home and office computers, having replaced in most cases the old domatrix printer, especially as laser printers have com down in price and creased in quality.

A laser printer works generally on the same principle as a photocopier, imaging on paper by means of electrophotography. A laser printer contains an electricially charged, light –sensitive metal drum or cylinder. Controlled by information received from the printer driver installed in the computer, the laser exposes the charged drum in those region corresponding to image areas, forming an image out of many tiny, virtually microscopic dots (more correctly called spots, especially to distinguish them from halftone dots). The areas of drum exposed by the laser becom oppositely charged from the rest of the drum, and will accept oppositely charged particles of toner, a fine black or colored powder. The toner adheres to drum in thso region exposed by the laser, and is transferred to the substrate passing beneath it. Heat and pressure are then used to fuse or fix the toner to the subtrate, preventing it from being easily rubbed of.

One of the drawbacks of most laser printers (as of this writing) is that their maximum resolution is 600 dpi, which is a adequate for most text and line art output, but inadequate for halftone output, which usually need depending upon the screen count around 1200-1500 dpi. Color laser printers are also increasing in popularity and coming down in price .Laser printers are primarily used to generate galleys, proofs, and general output, while hight-end imagesetters are typically used to generate high-quality, camera –ready output or film.
As laser printer resolution has evolved from 300 to 600 and now to 1200 dpi we have seen plain-paper output used for camera-ready copy by small and quick printers with camera –platemaking systems. Many books are output at 600 pdi or better and photographed to imposed film or plate using step –and- repeat systems. Plain –paper laser printers are also used to output special offset plate material.