Editing Image scanner (section)

==== Fax and wirephoto ====
{{See also|Fax#History|Wirephoto#History}}
Image scanners are considered the successors of early [[fax|facsimile]] (fax) and [[wirephoto]] machines. Unlike scanners, these devices were used to transmit images over long distances rather than for processing and storing images locally.<ref name=fundamentals>{{cite book | last=Trussell | first=H. J. | author2=M. J. Vrhel | date=2008 | url=https://books.google.com/books?id=uWrVD50DU-YC | title=Fundamentals of Digital Imaging | publisher=Cambridge University Press | isbn=9780521868532 | via=Google Books}}</ref>{{rp|2}}<ref name=principles />{{rp|305}} The earliest attempt at a fax machine was patented in 1843 by the Scottish clockmaker [[Alexander Bain (inventor)|Alexander Bain]] but never put into production. In his design, a metal [[stylus]] linked to a pendulum scans across a [[copper]] plate with a raised image. When the stylus makes contact with a raised part of the plate, it sends a pulse across a pair of wires to a receiver containing an [[electrode]] linked to another pendulum. A piece of paper impregnated with an electrochemically sensitive solution resides underneath the electrode and changes color whenever a pulse reaches the electrode. A gear advances the copper plate and paper in tandem with each swing of the pendulum; over time, the result is a perfect reproduction of the copper plate. In Bain's system, it is critical that the pendulums of the transceiver and receiver are in perfect step, or else the reproduced image will be distorted.<ref name=cisco>{{cite book | last=Hanes | first=David | author2=Gonzalo Salgueiro | date=2008 | url=https://books.google.com/books?id=mmocBBbJaa0C | title=Fax, Modem, and Text for IP Telephony | publisher=Cisco Press | pages=54–56 | isbn=9781587052699 | via=Google Books}}</ref><ref name=gtm>{{cite book | last=Solymar | first=Laszlo | date=2021 | url=https://books.google.com/books?id=pekrEAAAQBAJ | title=Getting the Message: A History of Communications | publisher=Oxford University Press | pages=246–248 | isbn=9780198863007 | via=Google Books}}</ref>

In 1847, the English physicist [[Frederick Bakewell]] developed the first working fax machine. Bakewell's machine was similar to Bain's but used a revolving drum coated in tinfoil, with non-conductive ink painted on the foil and a stylus that scans across the drum and sends a pulse down a pair of wires when it contacts a conductive point on the foil. The receiver contains an electrode that touches a sheet of chemically treated paper, which changes color when the electrode receives a pulse; the result is a reverse contrast (white-on-blue) reproduction of the original image. Bakewell's fax machine was marginally more successful than Bain's but suffered from the same synchronization issues. In 1862, [[Giovanni Caselli]] solved this with the [[pantelegraph]], the first fax machine put into regular service. Largely based on Bain's design, it ensured complete synchronization by flanking the pendulums of both the transceiver and receiver between two magnetic regulators, which become magnetized with each swing of the pendulum and become demagnetized when the pendulum reaches the maxima and minima of each oscillation.<ref name=worldwide />

In 1893, the American engineer [[Elisha Gray]] introduced the [[telautograph]], the first widely commercially successful fax machine that used linkage bars translating [[Cartesian coordinate system|''x''- and ''y''-axis]] motion at the receiver to scan a pen across the paper and strike it only when actuated by the stylus moving across the transceiver drum. Because it could use commodity stationery paper, it became popular in business and hospitals.<ref name=worldwide>{{cite book | last=Huurdeman | first=Anton A. | date=2003 | url=https://books.google.com/books?id=SnjGRDVIUL4C | title=The Worldwide History of Telecommunications | publisher=Wiley | pages=147–151 | isbn=9780471205050 | via=Google Books}}</ref> In 1902, the German engineer [[Arthur Korn]] introduced the phototelautograph, a fax machine that used a light-sensitive [[selenium cell]] to scan a paper to be copied, instead of relying on a metallic drum and stylus. It was even more commercially successful than Gray's machine and became the basis for wirephoto (also known as telephotography) machines used by newspapers around the world from the early 1900s onward.<ref name=gtm />