In the 1970s, IBM Corporation sought to avoid Xerox's patents for selenium drums by developing organic photoconductors as an alternative to the selenium drum. Amorphous selenium will hold an electrostatic charge in darkness and will conduct away such a charge under light. The drums in the copiers originally developed by Xerox Corporation were manufactured with a surface coating of amorphous selenium (more recently ceramic or organic photoconductor or OPC), applied by vacuum deposition. The end-to-end dimension is the width of print to be produced plus a generous tolerance. One revolution passes the drum surface through the steps described below. The drum rotates at the speed of paper output. A metal cylinder called the drum is mounted to rotate about a horizontal axis. The same process is used in microform printers and computer output laser or LED printers. In 1960, the automatic photocopier was created and many millions have been built since. 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.īy using a cylinder to carry the photosensor, automatic processing was enabled. 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. Xerography is now used in most photocopying machines and in laser and LED printers. This resulted in the first commercial automatic copier, the Xerox 914, being released by Haloid/Xerox in 1960. 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. Wilson, saw the promise of Carlson's invention, and saw to it that Haloid diligently worked to produce a working commercial product. Before that year, Carlson had proposed his idea to more than a dozen companies, but none was interested. In 1946, Carlson signed an agreement with Haloid Photographic Company to develop it as a commercial product. Carlson's original process was cumbersome, requiring several manual processing steps with flat plates. Patent 2,297,691 on October 6, 1942.Ĭarlson's innovation combined electrostatic printing with photography, unlike the dry electrostatic printing process invented by Georg Christoph Lichtenberg in 1778. Xerography was invented by American physicist Chester Carlson, based significantly on contributions by Hungarian physicist Pál Selényi. Originally called electrophotography, it was renamed xerography-from the Greek: 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 is a dry photocopying technique.
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