laser printer

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laser printer,

a computer printerprinter,
device that reproduces text, images, or other data from a computer, digital camera, smartphone, or the like on paper or another medium.

Impact printers, which mostly have been superseded by ink-jet and laser printers, use a mechanical hammering device to produce
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 that produces high-resolution output by means of a process that is similar to photocopyingphotocopying,
process whereby written or printed matter is directly copied by photographic techniques. Generally, photocopying is practical when just a few copies of an original are needed. When many copies are required, printing processes are more economical.
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. In place of reflected light from an image (as is used in xerographyxerography
, also called electrophotography, method of dry photocopying in which the image is transferred by using the attractive forces of electric charges. A beam of light, usually from a laser, is made to strike the original material, e.g., a white page with black lettering.
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), a laser printer uses data sent from a computer to turn a laser beam on and off rapidly as it scans a charged drum. The drum then attracts toner powder to the areas not exposed to the light. Finally, the toner is fused to paper over a belt by heated rollers. In a write-black printer the laser positively charges the printed areas to attract the toner, which gives better detail than a write-white printer. In a write-white printer, the beam negatively charges the areas not to be printed to repel the toner, which gives a denser image. Faster, quieter, and capable of producing more attractive results than standard printers, laser printers have become an important means of printing business documents since they became more generally available (1984) for personal computerspersonal computer
(PC), small but powerful computer primarily used in an office or home without the need to be connected to a larger computer. PCs evolved after the development of the microprocessor made possible the hobby-computer movement of the late 1970s, when some computers
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. See also desktop publishingdesktop publishing,
system for producing printed materials that consists of a personal computer or computer workstation, a high-resolution printer (usually a laser printer), and a computer program that allows the user to select from a variety of type fonts and sizes, column
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.

laser printer

[′lā·zər ‚print·ər]
(graphic arts)
An extremely fast printer that uses a laser to form areas of static electric charge which attract a metallic powder to the paper.

laser printer

a quiet high-quality computer printer that uses a laser beam shining on a photoconductive drum to produce characters, which are then transferred to paper

laser printer

(printer)
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.

Print resolution currently (2001) ranges between 300 and 2400 dots per inch (DPI). Laser printers using chemical photoreproduction techniques can produce resolutions of up to 2400 DPI.

Print speed is limited by whichever is slower - the printer hardware (the "engine speed"), or the software rendering process that converts the data to be printed into a bit map.

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.

In 2001, Xerox's Phaser 1235 and 2135 (with Okidata engines) could print up to 21 colour ppm at 1200x1200 DPI using a single-pass process.

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.

Although there are dozens of retail brands of laser printers, only a few original equipment manufacturers make print engines, e.g. Canon, Ricoh, Toshiba, and Xerox.

laser printer

A printer that uses a laser and the electrophotographic method to print a full page at a time. The laser "paints" a charged drum with light, to which toner is applied and then transferred onto paper (see electrophotographic for more details). Desktop laser printers use cut sheets like a copy machine. Large printers may use paper rolls that are cut after printing.

Resolution and Features
Laser printer resolution is typically from 300 to 1200 dpi, but specialty printers can reach imagesetter resolution of 2400 dpi. Options such as duplex printing (both sides) as well as collation, stapling and 3-hole punching may be available.

Small, Medium and Large
Low-end laser printers print in the 4 to 8 ppm range, while typical office workgroup units print 17 to 32 ppm. Midrange units print in the 40-60 ppm range, with a large jump to high-end printers that print from 150 to more than 1,000 ppm.

Color
Color lasers are slower than their monochrome counterparts, typically in the 4 to 10 ppm range. At the other end of the spectrum, high-end "digital printing presses" can print 70 or more duplexed color pages per minute, producing finished booklets and manuals. See color laser printer and digital printing.

Laser-Class
There are several technologies that fall into the laser category, but do not actually use a laser. LED printers use an array of LEDs to beam the image onto the drum, and electron beam imaging (ion deposition) creates the image with electricity rather than light. Solid ink printers propel a waxlike ink onto the drum.

History
In 1975, IBM introduced the first laser printer, the model 3800. Later, Siemens came out with the ND 2 and Xerox with the 9700. These self-contained printing presses were online to a mainframe or offline, accepting print image data on tape or disk.

In 1984, HP introduced the LaserJet, the first desktop laser printer, which rapidly became a huge success and a major part of the company's business. Desktop lasers made the clackety daisy wheel printers obsolete, but not dot matrix printers, which are still widely used for labels and multipart forms.


The Laser Mechanism
The laser printer uses electrostatic charges to (1) create an image on the drum, (2) adhere toner to the image, (3) transfer the toned image to the paper, and (4) fuse the toner to the paper. The laser creates the image by "painting" a negative of the page to be printed on the charged drum. Where light falls, the charge is dissipated, leaving a positive image to be printed.








The LaserJet
Noisier than today's models, but built like a tank, HP created a revolution in desktop printing with its 1984 introduction of the LaserJet. The LaserJet's reliability became legendary and caused HP to become the world leader in desktop laser printers. (Image courtesy of Hewlett-Packard Company.)








Midrange Laser Printer
This Dataproducts printer prints up to 60 ppm and uses a unique drum system. The unit does not have to be stopped except once each 100,000 pages to advance the drum sleeve. The drum lasts for a million pages, because it contains 10 sleeves in the cylinder. (Image courtesy of Hitachi Koki Imaging Solutions, Inc.)








Continuous Forms Laser Printing
This Printronix printer uses continuous forms. Continuous forms printers provide tighter registration over cut sheets and support non-standard paper sizes. In addition, a huge amount of paper can be printed without operator intervention. (Image courtesy of Printronix, Inc.)








The Versatile Network Printer
This Xerox printer offers paper handling options, including an envelope feeder (middle) and private collator (top) that keeps sensitive documents locked in bins that must be opened with a password. (Image courtesy of Xerox Corporation.)