Laserdrukker: Verskil tussen weergawes

'n '''Laserdrukker''' is 'n algemene tipe [[rekenaardrukker]] wat vinnig hoë-kwaliteit teks- en grafiese drukwerk op gewone papier kan lewer. Laserdrukkers gebruik net soos [[fotostaatmasjien]]e 'n [[xerografies]]e drukproses maar verskil van analoë fotostaatmasjiene deurdat die beeld geskep word deur 'n [[laser|laserstraal]] oor die drukker se fotoreseptor te skandeer.

 

The first commercial implementation of a laser printer was the [[IBM]] [[IBM model 3800 laser printer|model 3800]] in [[1976]], used for high-volume printing of documents such as invoices and mailing labels. It is often cited as "taking up a whole room," implying that it was a primitive version of the later familiar device used with a [[personal computer]]. While large, it was designed for an entirely different purpose. Many 3800s are still in use.

 

 

The first laser printer designed for use with an individual computer was released with the [[Xerox Star]] 8010 in [[1981]]. Although it was innovative, the Star was an expensive ($17,000) system that was only purchased by a small number of laboratories and institutions. After [[personal computer]]s became more widespread, the first laser printer intended for a mass market was the [[Hewlett-Packard|HP]] [[LaserJet]] 8ppm, released in [[1984]], using a [[Canon (company)|Canon]] engine controlled by HP software. The HP LaserJet printer was quickly followed by other laser printers from [[Brother Industries]], [[IBM]], and others.

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| Each horizontal strip of dots across the page is known as a [[raster scan|raster]] line or [[scan line]]. Creating the image to be printed is done by a [[Raster Image Processor]] (RIP), typically built into the laser printer. The source material may be encoded in any number of special page description languages such as Adobe PostScript (PS) or HP [[Printer Command Language]] (PCL), as well as unformatted text-only data. The RIP uses the page description language to generate a bitmap of the final page in the raster memory. Once the entire page has been rendered in raster memory, the printer is ready to begin the process of sending the rasterized stream of dots to the paper in a continuous stream.

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| A [[Corona discharge|corona wire]] (in older printers) or a primary charge roller projects an [[electrostatic]] charge onto the photoreceptor (otherwise named the photoconductor unit), a revolving photosensitive drum or belt, which is capable of holding an electrostatic charge on its surface while it is in the dark.

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| The laser is aimed at a rotating polygonal mirror, which directs the laser beam through a system of lenses and mirrors onto the photoreceptor. The beam sweeps across the photoreceptor at an angle to make the sweep straight across the page; the cylinder continues to rotate during the sweep and the angle of sweep compensates for this motion. The stream of rasterized data held in memory turns the laser on and off to form the dots on the cylinder. Some printers switch an array of [[laser diodes]] spanning the width of the page, and they signal to both the photoreceptor and their Quartz-clocked host in time to marks on the underpassing cylinder. Lasers are used because they generate a narrow beam for great distances. The laser beam neutralizes (or reverses) the charge on the white parts, leaving a mirror image of [[static electricity]] on the photoreceptor surface to lift powdered ink.

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Some printers use a very thin flexible metal, so that the hollow roller has a low mass and can be quickly warmed to the correct temperature. This both speeds printing from a cold idle state and permits the fuser to turn off more frequently to conserve power.

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== Steganographic anti-counterfeiting ("secret") marks ==

{{mainarticle|Printer steganography}}

Many modern color laser printers mark printouts by a nearly invisible dot [[raster]], for the purpose of identification.