LIGHT IM­PRES­SION

HOW A BEAM OF LIGHT CRE­ATES CRISP TEXT AND IMAGES IN A LASER PRINTER

Gadgets and Gizmos (India) - - KNOW TECH - TEXT AND GRAPH­ICS BY SAN­TOSH KUSH­WAHA

A laser printer is a com­puter printer that quickly pro­duces good qual­ity text and graph­ics on blank pa­per. As with dig­i­tal pho­to­copiers and mul­ti­func­tion print­ers (MFPS), laser print­ers em­ploy a xero­graphic print­ing process, but dif­fer from ana­log pho­to­copiers in that the im­age is pro­duced by the di­rect scan­ning of a laser beam across the printer’s pho­tore­cep­tor.

LASER PRINT­ERS VS INKJET PRINTER

Laser printer ad­van­tages: Speed: A laser printer can turn out pages faster than an inkjet printer. Low cost: Over time, toner costs for a laser printer will to­tal far less per page than re­fill­ing/re­plac­ing inkjet printer car­tridges. Quiet op­er­a­tion: A laser printer is gen­er­ally qui­eter than low-cost inkjet print­ers. Best-qual­ity text: No inkjet printer—no mat­ter how much you pay for it—will ever turn out black text and line graph­ics as crisp as a laser printer. Inkjet printer ad­van­tages: Ver­sa­til­ity: A colour inkjet can print on many types of me­dia, in­clud­ing craft pa­per, T-shirt trans­fers and even printable CD/DVD discs. Smaller size: This saves you space on your desk­top. Larger pa­per sizes: If you spend more, you can add a large-for­mat inkjet printer to your sys­tem that can print 11-x-17-inch or larger items.

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printer PC sends for com­mand a print job. to Con­troller cir­cuitry (in­side printer) queue up and trans­late print­ing data; a raster im­age pro­ces­sor (RIP) con­verts images and text into a vir­tual ma­trix of tiny dots.

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Con­troller cir­cuitry ap­plies a pos­i­tive elec­tri­cal charge to the drum unit. Af­ter­wards, the laser sys­tem ‘writes’ the page im­age onto the drum with a neg­a­tive charge, cre­at­ing an elec­tric “vir­tual neg­a­tive” of the im­age

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The drum unit ro­tates, and as the im­age is writ­ten on it, it picks up the toner, the laser printer equiv­a­lent of ink. The toner is pos­i­tively charged, and so it sticks to the im­age that the laser drew. The pa­per presses against the drum, and re­ceives the toner im­age.

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When the pa­per first picks up the toner, the im­age is not set. The toner is a dry, dusty ma­te­rial, and the elec­tric charge can­not hold it strongly to the pa­per. In or­der to make the im­age per­ma­nent, the pa­per runs through the fuser, which heats it, and melts the toner onto the page. The pa­per ex­its the printer, and you have your print out.

Pa­per

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The fuser

The fuser

Pho­to­con­duct­ing drum

De­vel­oper roller

A laser beam

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Charg­ing roller

A clean­ing blade

Pa­per tray

A laser beam

Charg­ing wire

Pho­to­con­duct­ing drum

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Toner hop­per

De­vel­oper roller

Roller assem­bly

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Con­troller cir­cuitry

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