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Concept
Xerography
Summary
Xerography is a dry photocopying technique. Originally called electrophotography, it was renamed xerography—from the n roots ξηρός xeros, meaning "dry" and -γραφία -graphia, meaning "writing"—to emphasize that unlike reproduction techniques then in use such as cyanotype, the process of xerography used no liquid chemicals.
Xerography was invented by American physicist Chester Carlson, based significantly on contributions by Hungarian physicist Pál Selényi. Carlson applied for and was awarded on October 6, 1942.
Carlson's innovation combined electrostatic printing with photography, unlike the dry electrostatic printing process invented by Georg Christoph Lichtenberg in 1778. Carlson's original process was cumbersome, requiring several manual processing steps with flat plates.
In 1946, Carlson signed an agreement with Haloid Photographic Company to develop it as a commercial product. Before that year, Carlson had proposed his idea to more than a dozen companies, but none was interested. Haloid's president, Joseph C. Wilson, saw the promise of Carlson's invention, and saw to it that Haloid diligently worked to produce a working commercial product.
It was almost 18 years before a fully automated process was developed, the key breakthrough being the use of a cylindrical drum coated with selenium instead of a flat plate. This resulted in the first commercial automatic copier, the Xerox 914, being released by Haloid/Xerox in 1960.
Xerography is now used in most photocopying machines and in laser and LED printers.
The first commercial use was hand processing of a flat photosensor (an electrostatic component that detects the presence of visible light) with a copy camera and a separate processing unit to produce offset lithographic plates. Today this technology is used in photocopy machines, laser printers, and digital presses which are slowly replacing many traditional offset presses in the printing industry for shorter runs.
By using a cylinder to carry the photosensor, automatic processing was enabled.
Official source
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