Laser printer

Laser printer
Name	Laser printer
Caption	A typical modern laser printer
Inventor	Gary Starkweather
Invented	1969
Company	Xerox
Related	Xerox 9700

Laser printer. A laser printer is a non-impact, digital printing device that produces high-quality text and graphics by directing a laser beam across a photosensitive drum to create an electrostatic image. This latent image attracts toner, a fine powder, which is then transferred and fused onto paper using heat and pressure. The technology, a key application of xerography, revolutionized office printing due to its speed, precision, and low cost per page compared to earlier methods.

History

The foundational concept was developed at Xerox's Palo Alto Research Center (PARC) in 1969 by researcher Gary Starkweather, who modified a Xerox 7000 copier by adding a laser scanning system. The first commercial implementation was the Xerox 9700 Electronic Printing System, introduced in 1977 for computer print centers. The first desktop model for office use was the Xerox Star workstation system in 1981, but widespread adoption began with Hewlett-Packard's launch of the affordable HP LaserJet in 1984, which used an engine from Canon. This sparked intense competition with other manufacturers like Brother Industries, Lexmark, and Kyocera, solidifying the laser printer's dominance in business environments throughout the 1990s.

Operation

The process, based on the principles of xerography, begins with a corona wire or primary charge roller applying a uniform negative electrostatic charge to the surface of the rotating photosensitive drum. A laser beam, precisely modulated by the printer's raster image processor, scans across the drum, discharging points to form a latent electrostatic image. Negatively charged toner particles are then attracted to these discharged areas. A sheet of paper, given a positive charge by a transfer corona or roller, moves past the drum, pulling the toner onto its surface. The paper then passes through the fuser, a pair of heated rollers that melt and permanently bond the toner to the paper fiber.

Components

Key subsystems include the toner cartridge, which often integrates the photosensitive drum, developer unit, and waste toner reservoir. The laser scanning unit uses a laser diode, a rotating polygon mirror, and focusing lenses to direct the beam. The fuser assembly contains a halogen lamp or other heating element within a Teflon-coated roller. The formatter board or controller interprets data from the host computer, typically via USB or a network connection like Ethernet, and uses a page description language such as HP-PCL or PostScript to rasterize the image. The paper pickup roller and paper path guides, along with a duplexing unit for double-sided printing, manage media handling.

Types

Common classifications include personal or SOHO printers, like the HP LaserJet Pro series, and workgroup or departmental printers designed for higher volumes, such as those from Ricoh or Toshiba. Multifunction printers (MFPs), also known as all-in-ones, integrate scanning, copying, and sometimes fax machine capabilities, exemplified by models from Canon and Sharp Corporation. Color laser printers, utilizing separate CMYK toner cartridges, are offered by companies like OKI Electric Industry and Xerox. High-speed production printers, such as the Xerox iGen and Kodak Nexpress, are used in commercial print on demand and transactional printing environments.

Applications

The primary domain remains the office environment for producing documents, reports, and correspondence. They are essential in legal and financial services firms for generating crisp, archival-quality contracts and statements. In education, they are used for administrative materials and high-volume handouts. Government agencies rely on them for forms and official publications. The technology is also critical in direct mail production, book publishing for proofs and short runs, and label printing for shipping and product identification, often integrated into larger automated systems.

Comparison with other printing technologies

Compared to inkjet printers, laser printers generally offer faster print speeds, lower cost per page for text, and water-resistant output, but often have higher initial costs and larger footprints. While dot matrix printers are durable and can produce carbon copy forms, laser printing provides vastly superior print quality and quiet operation. For the highest quality photographic reproduction, dye-sublimation printers and professional inkjet systems like those from Epson or Canon imagePROGRAF surpass color lasers. However, for high-volume monochrome text, laser printers are typically more economical than solid ink printers, a technology championed by Tektronix and later Xerox.

Category:Printing Category:Computer peripherals Category:American inventions