Laser printer
Laser printers are now the dominant printer technology; they can print both text and images. The technology was created at Xerox PARC, drawing in part by earlier Xerox photocopying technology.
In those earlier machines, a 'drum' made out of a special material is given an electrostatic charge across its surface. The image to be copied is shone onto the drum, knocking the electrons off where the light shines; very fine solid ink particles ('toner') will then adhere to the places on the drum which have retained their charge. A heated roller then melts the ink particles onto the paper.
This process was adapted to printing by replacing the bright illumination of the original image, as a source of light onto the drum, with a laser beam (chosen as a source since they can produce very precise and intense light beams, which can be turned off and on very quickly). The laser beam is scanned across the drum in a raster process.
History
The basic idea was conceived by Gary Starkweather in 1967, while he was at Xerox's research laboratory in Webster, New York. He made a crude prototype there in 1968 and 1969, but there was little interest in his ideas at the Webster laboratory, so in 1971 he transferred to Xerox PARC, where his work was enthusiastically supported.
An early prototype unit was the 'SLOT' ("Scanning Laser Output Terminal"), from 1971. The first functional printing protype was called EARS ("Ethernet-Alto-Research character generator-Scanning laser output terminal"), and it was much used after its introduction in 1973.
Next, in 1976, a small group of PARC researchers under John Ellenby began buying used Xerox 7000 copiers, stripping out the existing document photo-copying optics, and replacing those with laser output heads. The resulting printers, Dovers, were used in Xerox, and more importantly, made part of the package of PARC equipment distributed to several prominent universities as part of a grant.
Soon thereafter, Xerox and several other companies, began selling laser printers as products; Xerox’s first commercial unit was the 9700, which came out in 1977.
