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{{Short description|Device that optically scans images, printed text}} [[File:Epson V850 scanner open 20230920.jpg|thumb|A flatbed scanner ([[Epson]] Perfection V850 Pro) with its lid open. Documents or images are placed face-down on the glass bed (the platen).]] An '''image scanner''' (often abbreviated to just '''scanner''') is a device that optically scans images, printed text, [[handwriting]], or an object and converts it to a [[digital image]]. The most common type of scanner used in the home and the office is the '''flatbed scanner''', where the document is placed on a glass bed. A '''sheetfed scanner''', which moves the page across an image sensor using a series of rollers, may be used to scan one page of a document at a time or multiple pages, as in an [[automatic document feeder]]. A '''handheld scanner''' is a portable version of an image scanner that can be used on any flat surface. Scans are typically downloaded to the [[computer]] that the scanner is connected to, although some scanners are able to store scans on standalone [[Flash memory|flash media]] (e.g., [[memory card]]s and [[USB flash drive|USB drives]]). Modern scanners typically use a [[charge-coupled device]] (CCD) or a [[contact image sensor]] (CIS) as the image sensor, whereas [[drum scanner]]s, developed earlier and still used for the highest possible image quality, use a [[photomultiplier tube]] (PMT) as the image sensor. [[Document camera]]s, which use commodity or specialized high-resolution cameras, photograph documents all at once. == History{{anchor|History of scanners}} == === Precursors === ==== 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 /> ==== Analog scanners{{Anchor|Analog era}} ==== Before the advent of [[digital image processing]] in the middle of the 20th century, the term ''scanner'' originally referred to analog equipment used within [[Offset printing|offset printing press]]es. These analog scanners varied in design depending on their purpose: some scanned images stored as [[color transparency film]] onto [[color separation]] plates that could be used to print the original image en masse; while others were used to convert simple [[CMY color model|cyan, magenta, and yellow]] (CMY) plates into [[CMYK color model|cyan, magenta, yellow, and black]] (CMYK) in order to produce prints with darker, richer colors—a process known then in the trade as color correction (unrelated to the modern, [[Color correction|cinematographic sense]]). Converting from CMY to CMYK used to be a highly manual affair involving techniques such as [[Masking (art)|masking]]. Analog scanners automated this process to a large extent.<ref name=principles>{{cite book | last=Yule | first=J. A. C. | date=2000 | edition=Updated Reprint | orig-date=1967 | url=https://archive.org/details/principlesofcolo0000yule | title=Principles of Color Reproduction: Applied to Photomechanical Reproduction, Color Photography, and the Ink, Paper, and Other Related Industries | publisher=GATFPress | isbn=088362222X | via=the Internet Archive}}</ref>{{rp|305}} Alexander Murray and Richard Morse invented and patented the first analog color scanner at [[Eastman Kodak Company|Eastman Kodak]] in 1937. Their machine was of a [[drum scanner]] design that imaged a color transparency mounted in the drum, with a light source placed underneath the film, and three [[photocell]]s with [[RGB color model|red, green, and blue]] color filters reading each spot on the transparency to translate the image into three electronic signals. In Murray and Morse's initial design, the drum was connected to three [[lathe]]s that etched CMY [[Halftone|halftone dots]] onto three offset cylinders directly. The rights to the patent were sold to Printing Developments Incorporated (P.D.I.) in 1946, who improved on the design by using a [[photomultiplier tube]] to image the points on the negative, which produced an amplified signal that was then fed to a single-purpose computer that processed the RGB signals into color-corrected CMYK values. The processed signals are then sent to four lathes that [[Photo etching|etch]] CMYK halftone dots onto the offset cylinders.<ref name=hunt>{{cite book | last=Hunt | first=R. W. G. | date=2005 | url=https://books.google.com/books?id=Cd_FVeuO10gC | title=The Reproduction of Colour | publisher=Wiley | pages=519–523 | isbn=9780470024263 | via=Google Books}}</ref><ref name=molla>{{cite book | last=Molla | first=Rafiqul K. | date=1988 | url=https://archive.org/details/electroniccolors0000moll/page/34/ | title=Electronic Color Separation | publisher=R. K. Printing and Publishing | page=34 | isbn=0962045306 | via=the Internet Archive}}</ref> In 1948, Arthur Hardy of the Interchemical Corporation and F. L. Wurzburg of the [[Massachusetts Institute of Technology]] invented the first analog, color flatbed image scanner,<ref>{{cite book | last=Hand | first=Di | author2=Steve Middleditch | date=2014 | url=https://books.google.com/books?id=JXwABAAAQBAJ | title=Design for Media: A Handbook for Students and Professionals in Journalism, PR, and Advertising | publisher=Taylor & Francis | page=24 | isbn=9781317864011 | edition=ebook | via=Google Books}}</ref> intended for producing color-corrected [[Lithography|lithographic]] plates from a color negative. In this system, three color-separated plates (of CMY values) are prepared from a color negative via [[dot etching]] and placed in the scanner bed. Above each plate are rigidly fixed, equidistant [[light beam]] projectors that focus a beam of light onto one corner of the plate. The entire bed with all three plates moves horizontally, back and forth, to reach the opposite corners of the plate; with each horiztonal oscillation of the bed, the bed moves down one step to cover the entire vertical area of the plate. While this is happening, the beam of light focused on a given spot on the plate gets reflected and bounced off to a photocell adjacent to the projector. Each photocell connects to an [[Analog image processing|analog image processor]], which evaluates the [[reflectance]] of the combined CMY values using [[Neugebauer equations]] and outputs a signal to a light projector hovering over a fourth, unexposed lithographic plate. This plate receives a color-corrected, [[continuous tone|continuous-tone]] dot-etch of either the cyan, magenta, or yellow values. The fourth plate is replaced with another unexposed plate, and the process repeats until three color-corrected plates, of cyan, magenta and yellow, are produced. In the 1950s, the [[RCA|Radio Corporation of America]] (RCA) took Hardy and Wurzburg's patent and replaced the projector-and-photocell arrangement with a [[video camera tube]] focusing on one spot of the plate.<ref name=hunt /><ref name=molla /> === Use in digital imaging{{Anchor|Digital era}} === {{See also|Digital imaging#History}} [[File:NBSFirstScanImageRestored.jpg|thumb|The first image ever scanned to a computer, of [[Russell Kirsch|Russell A. Kirsch]]'s newborn son, Walden (1957)]] The first [[digital imaging]] system was the [[Bartlane system]] in 1920. Named after the pair who invented it, Harry G. Bartholomew and Maynard D. McFarlane, the Bartlane system used [[Zincography|zinc plates]] etched with an image from a [[film negative]] projected at five different exposure levels to correspond to five quantization levels. All five plates are affixed to a long, motor-driven rotating cylinder, with five equidistant contacts scanning over each plate at the same starting position. The Bartlane system was initially used exclusively by telegraph, with the five-bit [[Baudot code]] used to transmit the [[grayscale]] digital image. In 1921, the system was modified for offline use, with a five-bit [[punched tape|paper tape punch]] punching holes depending on whether its connections to the contacts are bridged or not. The result was a stored digital image with five gray levels. Reproduction of the image was achieved with a lamp passing over the punched holes, exposing five different intensities of light onto a film negative.<ref name=fundamentals /><ref>{{cite book | last=Dougherty | first=Edward R. | author-link=Edward R. Dougherty | date=1999 | url=https://books.google.com/books?id=G040Use2M8wC | title=Electronic Imaging Technology | publisher=SPIE Optical Engineering Press | pages=7–8 | isbn=9780819430373 | via=Google Books}}</ref> The first scanner to store its images digitally onto a computer was a drum scanner built in 1957 at the [[National Institute of Standards and Technology|National Bureau of Standards]] (NBS, later NIST) by a team led by [[Russell Kirsch|Russell A. Kirsch]]. It used a photomultiplier tube to detect light at a given point and produced an amplified signal that a computer could read and store into memory. The computer of choice at the time was the [[SEAC (computer)|SEAC]] [[Mainframe computer|mainframe]]; the maximum horizontal resolution that the SEAC was capable of processing was 176 pixels. The first image ever scanned on this machine was a photograph of Kirsch's three-month-old son, Walden.<ref name=fundamentals /><ref>{{cite book | last=Loubere | first=Philip | date=2021 | url=https://books.google.com/books?id=Oe8eEAAAQBAJ | title=A History of Communication Technology | publisher=Taylor & Francis | page=254 | isbn=9780429560712 | via=Google Books}}</ref> In 1969, [[Dacom]] introduced the 111 fax machine, which was the first digital fax machine to employ [[data compression]] using an on-board computer. It employed a flatbed design with a continuous feed capable of scanning up to [[letter paper]] in [[1-bit color|1-bit]] monochrome (black and white).<ref>{{cite journal | last=Rosenwald | first=Jeffrey | date=February 1988 | url=https://link.gale.com/apps/doc/A6501274/GPS?u=wikipedia | title=Getting the Fax Straight | journal=Administrative Management | publisher=Dalton Communications | volume=49 | issue=1 | pages=41 ''et seq'' | via=Gale}}</ref><ref>{{cite book | last=Costigan | first=Daniel M. | date=1971 | url=https://archive.org/details/faxprinciplespra0000cost/page/213/ | title=Fax: The Principles and Practice of Facsimile Communication | publisher=Chilton Book | page=213 | isbn=9780801956416 | via=the Internet Archive}}</ref> [[File:Autokon 1000DE.jpg|thumb|Autokon B&W flatbed standalone scanner.|alt=ECRM Autokon 1000DE, a standalone flatbed scanner for newspaper and commercial applications]] The first flatbed scanner used for digital image processing was the Autokon 8400, introduced by ECRM Inc., a subsidiary of [[AM International]], in 1975.<ref name=solving>{{cite journal | last=Bruno | first=Michael H. | date=May 1983 | url=https://books.google.com/books?id=hU4gAQAAMAAJ | title=Solving the Equipment/Technology Equation | journal=American Printer | publisher=Maclean Hunter Publishing | volume=191 | issue=2 | pages=31–35 | via=Google Books}}</ref><ref name=scaling>{{cite journal | last=Bruno | first=Michael H. | date=October 1985 | url=https://books.google.com/books?id=hU4gAQAAMAAJ | title=Scaling the Heights of High Technology | journal=American Printer | publisher=Maclean Hunter Publishing | volume=196 | issue=1 | pages=39–43 | via=Google Books}}</ref><ref name=advances>{{cite book | last=Banks | first=W. H. | date=1984 | url=https://archive.org/details/advancesinprinti0000inte_y6z3/page/63/ | title=Advances in Printing Science and Technology: Proceedings of the 17th International Conference of Printing Research Institutes, Saltsjöbaden, Sweden, June 1983 | publisher=Pentech | pages=63–64 | isbn=978-0-7273-0109-3 | via=the Internet Archive}}</ref> The Autokon 8400 used a [[Laser|laser beam]] to scan pages up to 11 by 14 inches at a maximum resolution of 1000 lines per inch. Although it was only capable of scanning in 1-bit monochrome, the on-board processor was capable of halftoning, [[unsharp mask]]ing, contrast adjustment, and [[Anamorphic stretch transform|anamorphic distortions]], among other features.<ref name=advances /><ref name=concise>{{cite book | last= Wallis | first=L. W. | date=1988 | url=https://archive.org/details/concisechronolog0000wall/page/53/ | title=A Concise Chronology of Typesetting Developments, 1886–1986 | publisher=Severnside Printers | isbn=0853315388 | via=Google Books}}</ref>{{rp|53}} The Autokon 8400 could either be connected to a [[film recorder]] to create a negative for producing plates or connected to a mainframe or minicomputer for further image processing and digital storage.<ref name=concise />{{rp|53}}<ref>{{cite journal | last=Staff writer | date=February 1981 | url=https://archive.org/details/sim_editor-publisher_1981-05-09_114_19/page/60/ | title=Exhibitor listing for Atlantic City ANPA/RI Conference: AM ECRM | journal=Editor and Publisher | publisher=Duncan McIntosh | volume=114 | issue=19 | page=60 | via=the Internet Archive}}</ref> The Autokon 8400 enjoyed widespread use in newspapers—ECRM shipped 1,000 units to newspaper publishers by 1985<ref name=scaling />—but its limited resolution and maximum scan size made it unsuitable for commercial printing. In 1982, ECRM introduced the Autokon 8500, capable of scanning up to 1200 lines per inch. Four of ECRM's competitors introduced commercial flatbed scanners that year, including [[Scitex]], [[Agfa-Gevaert]], and [[Linotype-Hell]], all of which were capable of scanning larger prints at higher resolutions.<ref name=solving /> ECRM introduced the Autokon 1000DE in 1985 to address the shortcomings of the Autokon 8400/8500. The 1000DE (digital enhancement) used a microprocessor to produce the sharpening effect as against the 8400 which used analogue electronics and an optical method to create sharpening. The Autokon 1000DE had a touchpad rather than analogue rotary controls. The Autokon 1000DE had applications in both commercial and newspaper environments where only a single halftone was required ie black and white. Whilst typically the Autokon 8400 was a standalone output device that scanned and then output to either photosensitive, roll format bromide paper or film, the Autokon 1000DE was often connected to Apple Macintoshes or PCs via a dedicated interface such as those from HighWater Designs. The last Autokon was a wider format, online only device which utilised both a red and green laser to improve the response to the scanning of colour photographs. In 1977, [[Ray Kurzweil|Raymond Kurzweil]], of his start-up company Kurzweil Computer Products, released the Kurzweil Reading Machine, which was the first flatbed scanner with a [[charge-coupled device]] (CCD) imaging element.<ref name=arnst>{{cite journal | last=Arnst | first=Catherine | date=February 9, 1976 | url=https://books.google.com/books?id=hFovUfeJp0wC&pg=PA6 | title=System 'Reads' Printed Pages to Blind | journal=Computerworld | publisher=CW Communications | volume=X | issue=6 | page=6 | via=Google Books}}</ref><ref>{{cite book | last=Peres | first=Michael R. | edition=4th | date=2012 | url=https://books.google.com/books?id=g4Wx9yKrDS0C | title=The Focal Encyclopedia of Photography | publisher=Taylor & Francis | page=16 | isbn=9781136106132 | via=Google Books}}</ref> The Kurzweil Reading Machine was invented to assist [[Blindness|blind people]] in reading books that had not been translated to [[braille]]. It comprised the image scanner and a [[Data General]] [[Data General Nova|Nova minicomputer]]—the latter performing the image processing, [[optical character recognition]] (OCR), and [[speech synthesis]].<ref name=arnst /> The first scanners for [[personal computer]]s appeared in the mid-1980s, starting with ThunderScan for the [[Mac (computer)|Macintosh]] in December 1984.<ref>{{cite journal | last=Bobker | first=Steven | date=March 1990 | url=https://link.gale.com/apps/doc/A8090704/GPS?u=wikipedia | title=Bobker's Dozen: Good Things and Small Packages | journal=MacUser | publisher=IDG Communications | volume=6 | issue=3 | pages=38 ''et seq'' | via=Gale}}</ref> Designed by [[Andy Hertzfeld]] and released by Thunderware Inc., the ThunderScan contains a specialized image sensor built into a plastic housing the same shape as the [[ink ribbon]] cartridge of [[Apple Inc.|Apple]]'s [[ImageWriter]] printer. The ThunderScan slots into the ImageWriter's ribbon carrier and connects to both the ImageWriter and the Macintosh simultaneously. The ImageWriter's carriage, controlled by the ThunderScan, moves left-to-right to scan one 200-[[Dots per inch|dpi]] (dots per inch) line at a time, with the carriage return serving to advance the scanner down the print to be scanned. The ThunderScan was the Macintosh's first scanner and sold well but operated very slowly and was only capable of scanning prints at 1-bit monochrome.<ref>{{cite book | last=Hertzfeld | first=Andy | author1-link=Andy Hertzfeld | author2=Steve Capps | date=2005 | url=https://books.google.com/books?id=VQQCtFT1CGIC | title=Revolution in The Valley: The Insanely Great Story of How the Mac Was Made | publisher=O'Reilly Media | page=242 | isbn=9780596007195 | via=Google Books}}</ref><ref name=mcneill>{{cite journal | last=McNeill | first=Dan | date=August 1985 | url=https://archive.org/details/popular-computing-1985-08/page/n69/ | title=Image Processing: The computer becomes a copier | journal=Personal Computing | publisher=McGraw-Hill | volume=4 | issue=10 | pages=64–66, 124–125 | via=the Internet Archive}}</ref> In 1999, [[Canon Inc.|Canon]] iterated on this idea with the IS-22, a cartridge that fit into their inkjet printers to convert them into sheetfed scanners.<ref>{{cite journal | url=https://books.google.com/books?id=Tyh48FdECXYC&pg=PA88 | journal=American Photo | date=December 1997 | via=Google Books | title=Output Puts Out | author=Staff writer | volume=VIII | number=6}}</ref> In early 1985, the first flatbed scanner for the [[IBM Personal Computer|IBM PC]], the [[Datacopy]] Model 700, was released. Based on a CCD imaging element, the Model 700 was capable of scanning letter-sized documents at a maximum resolution of 200 dpi at 1-bit monochrome. The Model 700 came with a special interface card for connecting to the PC, and an optional, aftermarket OCR software card and software package were sold for the Model 700.<ref name=mcneill /><ref name=concise />{{rp|69}}<ref>{{cite journal | last=Bermant | first=Charles | date=December 11, 1984 | url=https://archive.org/details/PC-Mag-1984-12-11/page/n57/ | title=Hardware At COMDEX: Peripherals Dominate | journal=PC Magazine | publisher=Ziff-Davis | volume=3 | issue=24 | pages=54–56 | via=Google Books}}</ref> In April 1985, LaserFAX Inc. introduced the first CCD-based color flatbed scanner, the SpectraSCAN 200, for the IBM PC. The SpectraSCAN 200 worked by placing color filters over the CCD and taking four passes (three for each primary color and one for black) per scan to build up a color reproduction. The SpectraSCAN 200 took between two and three minutes to produce a scan of a letter-sized print at 200-dpi; its grayscale counterpart, the DS-200, took only 30 seconds to make a scan at the same size and resolution.<ref>{{cite journal | last=Rosenthal | first=Steve | date=July 9, 1985 | url=https://books.google.com/books?id=SprPDrQRvM8C&pg=PA128 | title=Scanners at a Glance | journal=PC Magazine | publisher=Ziff-Davis | volume=4 | issue=14 | pages=128–133 | via=Google Books}}</ref><ref>{{cite journal | last=Doherty | first=Rick | date=April 8, 1985 | url=https://link.gale.com/apps/doc/A617831/GPS?u=wikipedia | title=LaserFAX Is 1st Graphics Scanner Computer System | journal= Electronic Engineering Times | publisher=UBM LLC | issue=324 | page=45 | via=Gale}}</ref> The first relatively affordable flatbed scanner for personal computers appeared in February 1987 with [[Hewlett-Packard]]'s [[HP ScanJet|ScanJet]], which was capable of scanning 4-bit (64-shade) grayscale images at a maximum resolution of 300 dpi.<ref>{{cite journal | last=Bridges | first=Linda | date=March 3, 1987 | url=https://link.gale.com/apps/doc/A4683850/GPS?u=wikipedia | title=New HP Laser Printer Compact, Less Expensive | journal=PC Week | publisher=Ziff-Davis | volume=4 | issue=9 | pages=1 ''et seq'' | via=Gale}}</ref><ref name=scanjetunlimited>{{cite book | last=Dickman | first=Chris | author2=Salvatore Parascandolo | author3=Steve Roth | date=1990 | url=https://archive.org/details/scanjetunlimited00dick | title=ScanJet Unlimited | publisher=Peachpit Press | pages=iii–iv | isbn=9780938151098 | via=the Internet Archive}}</ref> By the beginning of 1988, the ScanJet had accounted for 27 percent of all scanner sales in terms of dollar volume, per [[Gartner Dataquest]].<ref>{{cite journal | last=Bannister | first=Hank | date=January 12, 1988 | url=https://link.gale.com/apps/doc/A6172276/GPS?u=wikipedia | title=Mac market proving receptive to scanner use | journal=PC Week | publisher=Ziff-Davis | volume=5 | issue=2 | pages=94 ''et seq'' | via=Gale}}</ref> In February 1989, the company introduced the ScanJet Plus, which increased the bit depth to 8 bits (256 shades) while costing only US$200 more than the original ScanJet's $1990 ({{inflation|US|1990|1989|fmt=eq}}).<ref name=scanjetunlimited /> This led to a massive price drop in grayscale scanners with equivalent or lesser features in the market.<ref>{{cite journal | last=Cavuoto | first=James | date=September 1989 | url=https://link.gale.com/apps/doc/A7646738/GPS?u=wikipedia | title=Desktop Scanners: Users Benefit from Advances in Gray Scale, Color, and Resolution | journal=Computer Graphics World | publisher=PennWell Publishing | volume=12 | issue=9 | pages=43 ''et seq'' | via=Gale}}</ref> The number of third-party developers producing software and hardware supporting these scanners jumped dramatically in turn, effectively popularizing the scanner for the personal computer user.<ref name=scanjetunlimited /><ref>{{cite journal | date=August 1994 | url=https://books.google.com/books?id=U88jAQAAMAAJ&q=%22scanjet+was+the%22 | title=Peripheral Visions | journal=Computer Buyer's Guide and Handbook | publisher=Computer Information Publishing | volume=12 | issue=8 | pages=33–47 | via=Google Books}}</ref> By 1999, the cost of the average color-capable scanner had dropped to $300 ({{inflation|US|300|1999|fmt=eq}}). That year, ''[[Computer Shopper (US magazine)|Computer Shopper]]'' declared 1999 "the year that scanners finally became a mainstream commodity".<ref>{{cite journal | last=Labriola | first=Don | date=January 1999 | url=https://link.gale.com/apps/doc/A53342675/GPS?u=wikipedia | title=Scanner: HP ScanJet 5100C Series | journal=Computer Shopper | publisher=SX2 Media Labs | page=194 | via=Gale}}</ref> == Types == === Flatbed ===<!-- [[Flatbed scanner]] redirects here --> [[File:HP-Scanjet-IIC 05.jpg|thumb|A flatbed scanner ([[HP ScanJet|HP ScanJet IIC]]) with its lid closed]] A flatbed scanner is a type of scanner that provides a glass bed ([[platen]]) on which the object to be scanned lies motionless. The scanning element moves vertically from under the glass, scanning either the entirety of the platen or a predetermined portion. The driver software for most flatbed scanners allows users to prescan their documents—in essence, to take a quick, low-resolution pass at a document in order to judge what area of the document should be scanned (if not the entirety of it), before scanning it at a higher resolution. Some flatbed scanners incorporate sheet-feeding mechanisms called [[automatic document feeder]]s (ADFs) that use the same scanning element as the flatbed portion.<ref>{{cite web | date=n.d. | url=https://www.pcmag.com/encyclopedia/term/flatbed-scanner | title=Definition of flatbed scanner | work=PC Magazine | publisher=Ziff-Davis | archiveurl=https://web.archive.org/web/20231209215942/https://www.pcmag.com/encyclopedia/term/flatbed-scanner | archivedate=December 9, 2023}}</ref><ref>{{cite book | last=Gookin | first=Dan | author-link=Dan Gookin | date=2013 | url=https://books.google.com/books?id=-H_6Ml7nnQAC | title=PCs for Dummies | publisher=Wiley | page=304 | edition=12th, ebook | isbn=9781118232613 | via=Google Books}}</ref> This type of scanner is sometimes called a ''reflective scanner'', because it works by shining white light onto the object to be scanned and reading the intensity and color of light that is reflected from it, usually a line at a time. They are designed for scanning prints or other flat, opaque materials, but some have available transparency adapters, which—for a number of reasons—in most cases, are not very well suited to scanning film.<ref name="basics">{{cite web | url=http://www.dl-c.com/basics.pdf | title=Digital Image Basics | last=Sachs | first=J. | publisher=Digital Light & Color | date=February 1, 2001 | access-date=November 19, 2015 | url-status=dead | archive-url=https://web.archive.org/web/20151120202325/http://www.dl-c.com/basics.pdf | archive-date=November 20, 2015}}</ref> === Sheetfed{{anchor|Roller scanner}} === [[File:ScanSnap iX500 029 (8703118513).jpg|thumb|An [[automatic document feeder]] ([[Fujitsu]] ScanSnap iX500)]] A sheetfed scanner, also known as a document feeder,<ref>{{cite web | date=n.d. | url=https://www.pcmag.com/encyclopedia/term/sheet-feeder | title=Definition of sheet feeder | work=PC Magazine | publisher=Ziff-Davis | archiveurl=https://web.archive.org/web/20240418115952/https://www.pcmag.com/encyclopedia/term/sheet-feeder | archivedate=April 18, 2024}}</ref> is a type of scanner that uses motor-driven rollers to move one single sheet of paper at a time past a stationary scanning element (two scanning elements, in the case of scanners with duplex functionality).<ref name=sheetfeddef /><ref name=brotherds /> Unlike flatbed scanners, sheetfed scanners are not equipped to scan [[Bookbinding|bound]] material such as books or magazines, nor are they suitable for any material thicker than plain printer paper.<ref name=sheetfeddef>{{cite web | date=n.d. | url=https://www.pcmag.com/encyclopedia/term/sheet-fed-scanner | title=Definition of sheet-fed scanner | work=PC Magazine | publisher=Ziff-Davis | archiveurl=https://web.archive.org/web/20230925002449/https://www.pcmag.com/encyclopedia/term/sheet-fed-scanner | archivedate=September 25, 2023}}</ref><ref>{{cite book | last=Mueller | first=Scott | date=1999 | url=https://books.google.com/books?id=6M1XAAAAYAAJ | title=Upgrading and Repairing PCs | publisher=Que | page=1194 | isbn=9780789719034 | via=Google Books | edition=11th}}</ref> Some sheetfed scanners, called automatic document feeders (ADFs), are capable of scanning several sheets in one session,<ref>{{Cite web | url=https://www.yuenx.com/2021/review-epson-workforce-es-580w-wifi-color-duplex-desktop-scanner-with-adf/ | title=Review: Epson Workforce ES-580W WiFi Color Duplex Desktop Scanner with ADF | first=Michael | last=Yuen | work=Yuenx | date=April 12, 2021}}</ref><ref>{{Cite magazine | url=https://www.wired.com/2008/01/review-fujitsu/ | title=Review: Fujitsu ScanSnap S300 Scans And Delivers | first=Daniel | last=Dumas | magazine=Wired | publisher=Condé Nast | archiveurl=https://web.archive.org/web/20151120070057/https://www.wired.com/2008/01/review-fujitsu/ | archivedate=November 20, 2015 | date=January 24, 2008}}</ref> although others only accept one page at a time.<ref name=brotherds>{{cite web | url=https://www.pcmag.com/reviews/brother-dsmobile-ds-940dw | title=Brother DSmobile DS-940DW Review | work=PCMag | publisher=Ziff-Davis | last=Harrel | first=William | date=March 2, 2020 | archiveurl=https://web.archive.org/web/20200305052834/https://www.pcmag.com/reviews/brother-dsmobile-ds-940dw | archivedate=March 5, 2020}}</ref> Some sheetfed scanners are [[#Portable|portable]], powered by batteries, and have their own storage, eventually transferring stored scans to a computer.<ref name=brotherds /> === Handheld{{anchor|Hand}} === [[File:Logitech ScanMan Color-P4191193-white.jpg|thumb|A handheld scanner ([[Logitech]] ScanMan Color)]] A handheld scanner is a type of scanner that must be manually dragged or gilded by hand across the surface of the object to be scanned. Scanning documents in this manner requires a steady hand, as an uneven scanning rate produces distorted images.<ref>{{cite web | date=n.d. | url=https://www.pcmag.com/encyclopedia/term/handheld-scanner | title=Definition of handheld scanner | work=PC Magazine | publisher=Ziff-Davis | archiveurl=https://web.archive.org/web/20240303064613/https://www.pcmag.com/encyclopedia/term/handheld-scanner | archivedate=March 3, 2024}}</ref> Some handheld scanners have an indicator light on the scanner for this purpose, actuating if the user is moving the scanner too fast.<ref>{{cite book | last=Baeseler | first=Frank | author2=Bruce Bovill | date=1993 | url=https://books.google.com/books?id=8qHbAAAAMAAJ | title=Scanning and Image Processing for the PC | publisher=McGraw-Hill | page=47 | isbn=9780077078195 | via=Google Books}}</ref> They typically have at least one button that starts the scan when pressed; it is held by the user for the duration of the scan. Some other handheld scanners have switches to set the [[optical resolution]], as well as a roller, which generates a clock pulse for synchronization with the computer.<ref name=gruman>{{cite journal | last=Gruman | first=Galen | date=April 29, 1991 | url=https://books.google.com/books?id=y1AEAAAAMBAJ&pg=PT53 | title=Scanning on a Budget | journal=InfoWorld | publisher=IDG Publications | volume=13 | issue=17 | pages=51–62 | via=Google Books}}</ref><ref>{{cite book | last=Busch | first=David D. | author-link=David D. Busch | date=1991 | url=https://books.google.com/books?id=SyYzAAAAMAAJ | title=The Complete Scanner Toolkit for the IBM PC | publisher=Business One Irwin | page=97 | isbn=9781556234798 | via=Google Books}}</ref> Older hand scanners were [[monochrome]], and produced light from an array of green [[Light-emitting diode|LED]]s to illuminate the image; later ones scan in monochrome or color, as desired.<ref>{{cite journal | last=Pastrick | first=Greg | date=November 24, 1992 | url=https://books.google.com/books?id=RJBJPJvct40C&pg=PA40 | title=Logitech's New Hand Scanner Does 24-Bit Color | journal=PC Magazine | publisher=Ziff-Davis | volume=11 | issue=20 | page=40 | via=Google Books}}</ref> A hand scanner may also have a small window through which the document being scanned could be viewed. As hand scanners are much narrower than most normal document or book sizes, software (or the end user) needed to combine several narrow "strips" of scanned documents to produce the finished article.<ref name=gruman /><ref>{{cite journal | last=Falkner | first=Mike | date=November 29, 1988 | url=https://books.google.com/books?id=TJuFGeKsMJ0C&pg=PA295 | title=Hand Scanners Inch Forward | journal=PC Magazine | publisher=Ziff-Davis | volume=7 | issue=20 | pages=277–308 | via=Google Books}}</ref> Inexpensive, [[#Portable|portable]], battery-powered or USB-powered wand scanners and pen scanners, typically capable of scanning an area as wide as a normal letter and much longer, remain available {{As of|2024|lc=on}}.<ref name=best /><ref>{{Cite web | url=https://me.pcmag.com/en/accessories/2781/irispen-executive-7 | title=IRISPen Executive 7 | date=July 26, 2015 | work=PCMag Middle East | publisher=Ziff-Davis | last=Fernando | first=Chris | archiveurl=https://web.archive.org/web/20221003124123/https://me.pcmag.com/en/accessories/2781/irispen-executive-7 | archivedate=October 3, 2022}}</ref><ref>{{Cite web | last=Calderone | first=Nicholas | url=https://macsources.com/irispen-air-7-smart-wireless-pen-scanner-review/ | title=IRISPen Air 7 Smart Wireless Pen Scanner Review | date=April 25, 2018 | work=MacSources | archiveurl=https://web.archive.org/web/20190525214346/https://macsources.com/irispen-air-7-smart-wireless-pen-scanner-review/ | archivedate=May 25, 2019}}</ref> Some [[Computer mouse|computer mice]] can also scan documents.<ref>{{cite web | url=https://www.pcmag.com/reviews/iriscan-mouse-executive-2 | title=IRIScan Mouse Executive 2 Review | work=PCMag | publisher=Ziff-Davis | last=Harrel | first=William | date=February 7, 2020 | archiveurl=https://web.archive.org/web/20200215191555/https://www.pcmag.com/reviews/iriscan-mouse-executive-2 | archivedate=February 15, 2020}}</ref> === Drum === {{Main|Drum scanner}} [[File:1977 Januar Wuppertal 027.jpg|thumb|A [[drum scanner]] ([[Linotype-Hell|Hell]] Chromagraph DC 300) being operated]] A [[drum scanner]] is a type of scanner that uses a clear, motor-driven rotating cylinder (drum) onto which a print, a film negative, a transparency, or any other flat object is taped or otherwise secured. A beam of light either projects past, or reflects off, the material to be scanned onto a series of mirrors, which focus the beam onto the drum scanner's photomultiplier tube (PMT). After one revolution, the beam of light moves down a single step. When scanning transparent media, such as negatives, a light beam is directed from within the cylinder onto the media; when scanning opaque items, a light beam from above is reflected off the surface of the media. When only one PMT is present, three passes of the image are required for a full-color RGB scan. When three PMTs are present, only a single pass is required.<ref name=drumdef>{{cite web | date=n.d. | url=https://www.pcmag.com/encyclopedia/term/drum-scanner | title=Definition of drum scanner | work=PC Magazine | publisher=Ziff-Davis | archiveurl=https://web.archive.org/web/20230930230924/https://www.pcmag.com/encyclopedia/term/drum-scanner | archivedate=September 30, 2023}}</ref> The photomultiplier tubes of drum scanners offer superior dynamic range to that of CCD sensors. For this reason, drum scanners can extract more detail from very dark shadow areas of a transparency than flatbed scanners using CCD sensors. The smaller dynamic range of the CCD sensors (versus photomultiplier tubes) can lead to loss of shadow detail, especially when scanning very dense transparency film.<ref>{{cite web | url=http://www.dl-c.com/Temp/downloads/Whitepapers/Scan.pdf | title=Scanners and How to Use Them | last=Sachs | first=J. | publisher=Digital Light & Color | date=February 1, 2001 | access-date=November 8, 2015}}</ref> Drum scanners are also able to resolve true detail in excess of 10000 dpi, producing higher-resolution scans than any CCD scanner.<ref name=drumdef /> === Overhead{{anchor|Book scanners}}{{anchor|Document camera scanner}}{{anchor|Planetary scanner}} === {{See also|Book scanning|Document camera|Planetary scanner}} [[File:ET Series Book Scanner.png|thumb|An overhead [[book scanner]] (CZUR ET Series) with lasers for calibration]] An overhead scanner is a type of scanner that places the scanning element in a housing on top of a vertical post, hovering above the document or object to be scanned, which lies stationary on an open-air bed. [[Chinon Industries]] patented a specific type of overhead scanner, which uses a rotating mirror to reflect the contents of the bed onto a linear CCD, in 1987. Although very flexible—allowing users to scan not only two-dimensional prints and documents but any 3D object, of any size—the Chinon design required the user to provide uniform illumination of the object to be scanned and was more cumbersome to set up.<ref>{{cite journal | last=Staff writer | date=December 1, 1987 | url=https://link.gale.com/apps/doc/A6117970/GPS?u=wikipedia | title=Chinon's PC-, Mac-Compatible Overhead Scanner Doesn't Require Special Lighting | journal=PC Week | publisher=Ziff-Davis | volume=4 | issue=48 | page=35 | via=Gale}}</ref><ref>{{cite journal | last=Linzmayer | first=Owen W. | date=September 1990 | url=https://link.gale.com/apps/doc/A8679416/GPS?u=wikipedia | title=Desktop Scanners | journal=MacUser | publisher=IDG Communications | volume=6 | issue=9 | pages=136 | via=Gale}}</ref><ref>{{cite journal | last=Karney | first=James | date=April 14, 1992 | url=https://books.google.com/books?id=AoKUhNoOys4C&pg=PP273 | title=Marching to a Different Drummer: The Chinon DS-3000 Color Scanner | journal=PC Magazine | publisher=Ziff-Davis | volume=11 | issue=7 | page=251 | via=Google Books}}</ref> A more modern type of overhead scanner is a [[document camera]] (also known as a video scanner), which uses a [[digital camera]] to capture a document all at once. Most document cameras output live video of the document and are usually reserved for displaying documents to a live audience, but they may also be used as replacements for image scanners, capturing a single frame of the output as an image file. Document cameras may even use the same [[#Applications programming interface|API]]s as scanners when connected to computers.<ref>{{cite web | last=Juniper | first=Adam | date=April 11, 2024 | url=https://www.digitalcameraworld.com/buying-guides/best-document-camera | title=Best document camera in 2024: which visualizer is the right one for you? | work=Digital Camera World | publisher=Future Publishing}}</ref> A [[planetary scanner]] is a type of very-high-resolution document camera used for capturing certain fragile documents.<ref>{{cite book | last=Monson | first=Jane D. | date=2017 | url=https://books.google.com/books?id=MXs4DwAAQBAJ | title=Getting Started with Digital Collections: Scaling to Fit Your Organization | isbn=9780838915431 | publisher=American Library Association | via=Google Books}}</ref> A [[Book scanning|book scanner]] is another kind of document camera, pairing a digital camera with a scanning area defined by a mat to assist in scanning books. Some more advanced models of book scanners project a laser onto the page for calibration and software skew correction.<ref>{{cite web | url=https://www.pcmag.com/reviews/czur-shine-ultra-pro | title=CZUR Shine Ultra Pro Review | work=PCMag | publisher=Ziff-Davis | last=Harrel | first=William | date=May 3, 2022 | archiveurl=https://web.archive.org/web/20220504003440/https://www.pcmag.com/reviews/czur-shine-ultra-pro | archivedate=May 4, 2022}}</ref><ref>{{Cite web | url=https://www.zdnet.com/home-and-office/smart-office/fujitsu-scansnap-sv600-review/ | title=Do you dream of digitizing your entire book collection? This book scanner can help | website=ZDNET | publisher=Ziff-Davis | last=Gewirtz | first=David | date=October 3, 2022 | archiveurl=https://web.archive.org/web/20221003171500/https://www.zdnet.com/home-and-office/smart-office/fujitsu-scansnap-sv600-review/ | archivedate=October 3, 2022}}</ref> === Film === {{Main article|Film scanner}} [[File:Reflecta DigitDia 6000 Slide Scanner (1).jpg|thumb|A [[film scanner]] (Reflecta DigitDia 6000) designed for scanning [[Slide projector|slides]]]] A [[film scanner]], also known as a slide scanner or a transparency scanner, is a type of specialized flatbed scanner specifically for scanning film negatives and [[Slide projector|slides]]. A typical film scanner works by passing a narrowly focused beam of light through the film and reading the intensity and color of the light that emerges.<ref name="basics"/> The lowest-cost dedicated film scanners can be had for less than $50, and they might be sufficient for modest needs. From there they inch up in staggered levels of quality and advanced features upward of five figures.<ref>{{cite web | url=https://www.bhphotovideo.com/explora/photography/buying-guide/film-scanners | title=Film Scanners: A Buying Guide | last=Weitz | first=A. | publisher=B&H Photo Video | date=November 6, 2015 | access-date=November 19, 2015}}</ref> === Portable === [[File:Card Scanner.svg|thumb|An illustration of a portable business card scanner]] Image scanners are usually used in conjunction with a [[computer]] which controls the scanner and stores scans. Small portable scanners, either [[#Sheetfed|sheetfed]] or [[#Handheld|handheld]] and operated by batteries and with storage capability, are available for use away from a computer; stored scans can be transferred later.<ref name=best>{{cite web | last=Brant | first=Tom | author2=John Burek | date=July 1, 2024 | url=https://www.pcmag.com/picks/the-best-portable-scanners | title=The Best Portable Scanners for 2024 | work=PCMag | publisher=Ziff-Davis | archiveurl=https://web.archive.org/web/20240804180551/https://www.pcmag.com/picks/the-best-portable-scanners | archivedate=August 4, 2024}}</ref> Many can scan both small documents such as [[business card]]s and till [[receipt]]s, as well as letter-sized documents.<ref name=best /><ref>{{cite book | last=Baldridge | first=Aimee | date=2009 | url=https://books.google.com/books?id=Ewvuqm-1YboC | title=Organize Your Digital Life: How to Store Your Photographs, Music, Videos, and Personal Documents in a Digital World | publisher=National Geographic | page=163 | isbn=9781426203343 | via=Google Books}}</ref> === Software scanners{{anchor|Smartphone scanner app}} === The higher-resolution cameras fitted to some [[smartphone]]s can produce reasonable quality document scans by taking a photograph with the phone's camera and post-processing it with a scanning app, a range of which are available for most phone [[operating system]]s, to whiten the background of a page, correct perspective distortion so that the shape of a rectangular document is corrected, convert to black-and-white, etc. Many such apps can scan multiple-page documents with successive camera exposures and output them either as a single file or multiple-page files. Some smartphone scanning apps can save documents directly to online storage locations, such as [[Dropbox (service)|Dropbox]] and [[Evernote]], send via email, or fax documents via email-to-fax gateways.<ref name=mit /> Smartphone scanner apps can be broadly divided into three categories: # Document scanning apps primarily designed to handle documents and output PDF, and sometimes JPEG, files # Photo scanning apps that output JPEG files, and have editing functions useful for photo rather than document editing; # Barcode-like [[QR code]] scanning apps that then search the internet for information associated with the code.<ref name=mit>{{cite web | url=https://www.technologyreview.com/s/425907/scan-anything-and-let-your-phone-do-the-rest/ | title=Scan Anything and Let Your Phone Do the Rest | work=MIT Technology Review | publisher=Massachusetts Institute of Technology | last=Muller | first=Ian E.}}</ref> == Scanning elements == === Charge-coupled device (CCD) === {{Main article|Charge-coupled device}} Scanners equipped with [[charge-coupled device]] (CCD) scanning elements require a sophisticated series of mirrors and lenses to reproduce an image, but the result of this complexity is a much higher-quality scan. Because CCDs have a much greater depth of field, they are more forgiving when it comes to scanning documents that are difficult to get perfectly flat against the platen (such as bound books).<ref name=sense>{{cite journal | last=Staff writer | date=July 1999 | url=https://link.gale.com/apps/doc/A54840845/GPS?sid=wikipedia | title=Making Sense of the Sensors | journal=Computer Shopper | publisher= SX2 Media Labs | volume=19 | issue=7 | page=223 | via=Gale}}</ref> === Contact image sensor (CIS) === {{Main article|Contact image sensor}} [[File:Overwiew - Scanner unit CIS Canon MP500 5of5.jpg|thumb|Scanner unit with CIS. A: assembled, B: disassembled; 1: housing, 2: light conductor, 3: lenses, 4: chip with two RGB-LEDs, 5: CIS]] Scanners equipped with [[contact image sensor]] (CIS) scanning elements are designed to be in near-direct contact with the document to be scanned and thus do not require the complex optics of CCDs scanners. However, their depth of field is much worse, resulting in blurry scans if the scanned document is not perfectly flush against the platten. Because the sensors require far less power than CCD scanners, CIS scanners are able to be manufactured down to a low cost and are typically much lighter in weight and depth than CCD scanners.<ref name=sense /> === Photomultiplier tube (PMT) === {{Main article|Photomultiplier tube}} Scanners equipped with [[photomultiplier tube]]s (PMT) are nearly exclusively [[drum scanner]]s.<ref name=drumdef /> == Scan quality == Color scanners typically read RGB (red-green-blue) color data from the array. This data is then processed with some proprietary algorithm to correct for different exposure conditions, and sent to the computer via the device's [[input/output]] interface (usually USB, previous to which was [[SCSI]] or bidirectional [[parallel port]] in older units). [[Color depth]] varies depending on the scanning array characteristics, but is usually at least 24 bits. High-quality models have 36-48 bits of color depth. Another qualifying parameter for a scanner is its [[Image resolution|resolution]], measured in [[Pixel density|pixels per inch]] (ppi), sometimes more accurately referred to as [[samples per inch]] (spi). Instead of using the scanner's true optical resolution, the only meaningful parameter, manufacturers like to refer to the interpolated resolution, which is much higher thanks to software [[interpolation]]. {{As of|2009}}, a high-end flatbed scanner can scan up to 5400 ppi and drum scanners have an optical resolution of between 3000 and 24000 ppi. ''Effective resolution'' refers to the true resolution of a scanner, and is determined by using a resolution test chart. The effective resolution of most all consumer flatbed scanners is considerably lower than the manufactures' given optical resolution.<ref name="filmscanner.info">{{cite web | date=2007 | url=http://www.filmscanner.info/en/EpsonPerfectionV750Pro.html | title=Scanner test report: Epson Perfection V750 Pro | work=ScanDig | last=Wagner | first=Patrick | archiveurl=https://web.archive.org/web/20240407050047/https://www.filmscanner.info/en/EpsonPerfectionV750Pro.html | archivedate=April 7, 2024}}</ref> Manufacturers often claim interpolated resolutions as high as 19200 ppi; but such numbers carry little meaningful value because the number of possible [[digital zoom|interpolated pixels]] is unlimited, and doing so does not increase the level of captured detail. The size of the file created increases with the square of the resolution; doubling the resolution quadruples the [[file size]]. A resolution must be chosen that is within the capabilities of the equipment, preserves sufficient detail, and does not produce a file of excessive size. The file size can be reduced for a given resolution by using "lossy" compression methods such as JPEG, at some cost in quality. If the best possible quality is required lossless compression should be used; reduced-quality files of smaller size can be produced from such an image when required (e.g., image designed to be printed on a full page, and a much smaller file to be displayed as part of a fast-loading web page). Purity can be diminished by scanner noise, optical flare, poor analog to digital conversion, scratches, dust, [[Newton's rings]], out-of-focus sensors, improper scanner operation, and poor software. Drum scanners are said to produce the purest digital representations of the film, followed by high-end film scanners that use the larger Kodak Tri-Linear sensors. The third important parameter for a scanner is its [[dynamic range]] (also known as density range). A high-density range means that the scanner is able to record shadow details and brightness details in one scan. Density of film is measured on a base 10 log scale and varies between 0.0 (transparent) and 5.0, about 16 stops.<ref name="ReferenceA">{{cite web | url=http://www.filmscanner.info/en/Dichte.html | title=Density and density range of scanners | work=ScanDig | last=Wagner | first=Patrick | date=n.d. | archiveurl=https://web.archive.org/web/20240413044016/https://www.filmscanner.info/en/Dichte.html | archivedate=April 13, 2024}}</ref> Density range is the space taken up in the 0 to 5 scale, and Dmin and Dmax denote where the least dense and most dense measurements on a negative or positive film. The density range of negative film is up to 3.6d,<ref name="ReferenceA"/> while slide film dynamic range is 2.4d.<ref name="ReferenceA"/> Color negative density range after processing is 2.0d thanks to the compression of the 12 stops into a small density range. Dmax will be the densest on slide film for shadows, and densest on negative film for highlights. Some slide films can have a Dmax close to 4.0d with proper exposure, and so can black-and-white negative film. Consumer-level flatbed photo scanners have a dynamic range in the 2.0–3.0 range, which can be inadequate for scanning all types of [[photographic film]], as Dmax can be and often is between 3.0d and 4.0d with traditional black-and-white film. Color film compresses its 12 stops of a possible 16 stops (film latitude) into just 2.0d of space via the process of dye coupling and removal of all silver from the emulsion. Kodak Vision 3 has 18 stops. So, color-negative film scans the easiest of all film types on the widest range of scanners. Because traditional black-and-white film retains the image creating silver after processing, density range can be almost twice that of color film. This makes scanning traditional black-and-white film more difficult and requires a scanner with at least a 3.6d dynamic range, but also a Dmax between 4.0d to 5.0d. High-end (photo lab) flatbed scanners can reach a dynamic range of 3.7, and Dmax around 4.0d. Dedicated film scanners <ref>{{cite web | url=https://www.filmscanner.info/en/FilmscannerRangliste.html | title=Film scanner ranking and scanner comparison | last=Wagner | first=Patrick | date=n.d. | archiveurl=https://web.archive.org/web/20240525213133/https://www.filmscanner.info/en/FilmscannerRangliste.html | archivedate=May 25, 2024}}</ref> have a dynamic range between 3.0d–4.0d.<ref name="ReferenceA"/> Office document scanners can have a dynamic range of less than 2.0d.<ref name="ReferenceA"/> Drum scanners have a dynamic range of 3.6–4.5. For scanning film, {{visible anchor|infrared cleaning|text=[[infrared cleaning]]}} is a technique used to remove the effects of dust and scratches on images scanned from film; many modern scanners incorporate this feature. It works by scanning the film with infrared light; the dyes in typical color film emulsions are transparent to infrared light, but dust and scratches are not, and block infrared; scanner software can use the visible and infrared information to detect scratches and process the image to greatly reduce their visibility, considering their position, size, shape, and surroundings. Scanner manufacturers usually have their own names attached to this technique. For example, [[Seiko Epson|Epson]], [[Minolta]], [[Nikon]], [[Konica Minolta]], [[Microtek]], and others use [[Digital ICE]], while [[Canon Inc.|Canon]] uses its own system, [[Film Automatic Retouching and Enhancement|FARE]] (Film Automatic Retouching and Enhancement).<ref>{{cite web | url=http://www.canon.com/technology/canon_tech/explanation/fare.html | publisher=Canon Inc. | access-date=May 2, 2007 | title=Film Automatic Retouching and Enhancement | url-status=dead | archive-url=https://web.archive.org/web/20101023211251/http://www.canon.com/technology/canon_tech/explanation/fare.html | archive-date=October 23, 2010}}</ref> [[Plustek]] uses [[LaserSoft Imaging]] [[iSRD]]. Some independent software developers design infrared cleaning tools. By combining full-color imagery with 3D models, modern hand-held scanners are able to completely reproduce objects electronically. The addition of 3D color printers enables accurate miniaturization of these objects, with applications across many industries and professions. For scanner apps, the scan quality is highly dependent on the quality of the phone camera and on the framing chosen by the user of the app.<ref>{{Cite web | url=http://help.thegrizzlylabs.com/article/94-what-is-the-resolution-in-dpi-of-the-scans | title=What is the DPI of my scans? | work=The Grizzly Labs | access-date=December 8, 2017 | archiveurl=https://web.archive.org/web/20240530140134/http://help.thegrizzlylabs.com/article/94-what-is-the-resolution-in-dpi-of-the-scans | archivedate=May 30, 2024}}</ref> == Connectivity{{anchor|Computer connection}} == [[File:Photoshop goddess version 1.05 (3378276180).jpg|thumb|A [[photographic print]] being scanned into a computer at the photo desk of the ''[[The Detroit News|Detroit News]]'' in the early 1990s]] Scans must virtually always be transferred from the scanner to a computer or information storage system for further processing or storage. There are two basic issues: (1) how the scanner is physically connected to the computer and (2) how the application retrieves the information from the scanner. === Direct connection {{anchor|Direct physical connection to a computer}} === The file size of a scan can go up to about 100 MB for a 600 dpi, 23 × 28 cm (slightly larger than [[ISO 216|A4 paper]]) uncompressed [[24-bit color|24-bit]] image. Scanned files must be transferred and stored. Scanners can generate this volume of data in a matter of seconds, making a fast connection desirable. Scanners communicate to their host computer using one of the following physical interfaces, listing roughly from slow to fast: * [[Parallel port]] – Connecting through a parallel port is the slowest common transfer method. Early scanners had parallel port connections that could not transfer data faster than 70 [[kilobyte]]s/[[second]]. The primary advantage of the parallel port connection was economic and user skill level: it avoided adding an interface card to the computer. * [[GPIB]] – General Purpose Interface Bus. Certain drum scanners like the Howtek D4000 featured both a SCSI and GPIB interface. The latter conforms to the IEEE-488 standard, introduced in the mid-1970s. The GPIB interface has only been used by a few scanner manufacturers, mostly serving the DOS/Windows environment. For Apple Macintosh systems, National Instruments provided a [[NuBus]] GPIB interface card. * [[SCSI|Small Computer System Interface (SCSI)]] – SCSI is rarely used since the early 21st century, supported only by computers with a SCSI interface, either on a card or built-in. During the evolution of the SCSI standard, speeds increased. Widely available and easily set up USB and Firewire largely supplanted SCSI. * [[USB|Universal Serial Bus (USB)]] – USB scanners can transfer data quickly. The early USB 1.1 standard could transfer data at 1.5 megabytes per second (slower than SCSI), but the later USB 2.0/3.0 standards can transfer at more than 20/60 megabytes per second in practice. * [[IEEE 1394|FireWire]] – Also known as IEEE-1394, FireWire is an interface of comparable speed to USB 2.0. Possible FireWire speeds are 25, 50, and 100, 400, and 800 megabits per second, but devices may not support all speeds. * [[Proprietary hardware|Proprietary]] interfaces – Bespoke interfaces were used on some early scanners that used a proprietary interface card rather than a standard interface.<!--Mustek?--> === Indirect connection {{anchor|Indirect (network) connection to a computer}} === During the early 1990s professional flatbed scanners were available over a [[Local area network|local computer network]]. This proved useful to publishers, print shops, etc. This functionality largely fell out of use as the cost of flatbed scanners reduced enough to make sharing unnecessary. From 2000 all-in-one multi-purpose devices became available which were suitable for both small offices and consumers, with printing, scanning, copying, and fax capability in a single apparatus that can be made available to all members of a workgroup. Battery-powered portable scanners store scans on internal memory; they can later be transferred to a computer either by direct connection, typically USB, or in some cases a [[memory card]] may be removed from the scanner and plugged into the computer. === Applications programming interface {{anchor|Applications Programming Interface}} === A raster image editor must be able to communicate with a scanner. There are many different scanners, and many of those scanners use different protocols. In order to simplify applications programming, some [[application programming interface]]s (APIs) were developed. The API presents a uniform interface to the scanner. This means that the application does not need to know the specific details of the scanner in order to access it directly. For example, [[Adobe Photoshop]] supports the [[TWAIN]] standard; therefore in theory Photoshop can acquire an image from any scanner that has a TWAIN driver.<!--GIMP + SANE?--> In practice, there are often problems with an application communicating with a scanner. Either the application or the scanner manufacturer (or both) may have faults in their implementation of the API. Typically, the API is implemented as a [[Library (computing)|dynamically linked library]]. Each scanner manufacturer provides software that translates the API procedure calls into primitive commands that are issued to a hardware controller (such as the SCSI, USB, or FireWire controller). The manufacturer's part of the API is commonly called a [[device driver]], but that designation is not strictly accurate: the API does not run in kernel mode and does not directly access the device. Rather the scanner API library translates application requests into hardware requests. Common scanner software API include: * [[TWAIN]] – An API used by most scanners. Originally used for low-end and home-use equipment, it is now widely used for large-volume scanning. * [[Scanner Access Now Easy|SANE (Scanner Access Now Easy)]] – A [[Free software|free]]/[[Open-source model|open-source]] API for accessing scanners. Originally developed for [[Unix]] and [[Linux]] operating systems, it has been ported to [[OS/2]], [[macOS|Mac OS X]], and [[Microsoft Windows]]. Unlike TWAIN, SANE does not handle the user interface. This allows batch scans and transparent network access without any special support from the device driver. * [[Windows Image Acquisition|Windows Image Acquisition (WIA)]] – An API provided by Microsoft for use on [[Microsoft Windows]]. * [[Image and Scanner Interface Specification|Image and Scanner Interface Specification (ISIS)]] – Created by Pixel Translations, which still uses [[SCSI-2]] for performance reasons, ISIS is used by large, departmental-scale, machines. === Bundled applications === Although no software beyond a scanning utility is a feature of any scanner, many scanners come bundled with software. Typically, in addition to the scanning utility, some type of [[raster image editor]] (such as Photoshop or [[GIMP]]) and optical character recognition (OCR) software are supplied. OCR software converts graphical images of text into standard text that can be edited using common word-processing and text-editing software; accuracy is rarely perfect. == Output data == Some scanners, especially those designed for scanning printed documents, only work in black and white, but most modern scanners work in color. For the latter, the scanned result is a non-compressed RGB image, which can be transferred to a computer's memory. The color output of different scanners is not the same due to the spectral response of their sensing elements, the nature of their light source, and the correction applied by the scanning software. While most image sensors have a linear response, the output values are usually [[Gamma correction|gamma-compressed]]. Some scanners compress and clean up the image using embedded [[firmware]]. Once on the computer, the image can be processed with a [[raster graphics editor]] (such as Photoshop) and saved on a storage device (such as a [[Hard disk drive|hard disk]]). Scans may be stored uncompressed in [[image file format]]s such as [[BMP file format|BMP]]; stored [[Lossless compression|lossless]]ly compressed in file formats such as [[TIFF]] and [[PNG]]; stored [[Lossy compression|lossy-compressed]] in file formats such as JPEG; or stored as embedded images or converted to [[vector graphics]] within a [[PDF]]. Optical character recognition (OCR) software allows a scanned image of text to be converted into editable text with reasonable accuracy, so long as the text is cleanly printed and in a typeface and size that can be read by the software. OCR capability may be integrated into the scanning software, or the scanned image file can be processed with a separate OCR program. == Specific uses == === Document processing === {{Main article|Document processing}} [[Document processing]] requirements differ from those of image scanning. These requirements include scanning speed, automated paper feed, and the ability to automatically scan both the front and the back of a document. On the other hand, image scanning typically requires the ability to handle fragile and or three-dimensional objects as well as scan at a much higher resolution. Document scanners have document feeders, usually larger than those sometimes found on copiers or all-purpose scanners. Scans are made at high speed, from 20 up to 420 pages per minute, often in grayscale, although many scanners support color. Many scanners can scan both sides of double-sided originals (duplex operation). Sophisticated document scanners have firmware or software that cleans up scans of text as they are produced, eliminating accidental marks and sharpening type; this would be unacceptable for photographic work, where marks cannot reliably be distinguished from desired fine detail. Files created are compressed as they are made. The resolution used is usually from 150 to 300 dpi, although the hardware may be capable of 600 or higher resolution; this produces images of text good enough to read and for OCR, without the higher demands on storage space required by higher-resolution images. Document scans are often processed using OCR technology to create editable and searchable files. Most scanners use [[Image and Scanner Interface Specification|ISIS]] or TWAIN device drivers to scan documents into TIFF format so that the scanned pages can be fed into a [[document management system]] that will handle the archiving and retrieval of the scanned pages. Lossy JPEG compression, which is very efficient for pictures, is undesirable for text documents, as slanted straight edges take on a jagged appearance, and solid black (or other color) text on a light background compresses well with lossless compression formats. While paper feeding and scanning can be done automatically and quickly, preparation and indexing are necessary and require much work by humans. Preparation involves manually inspecting the papers to be scanned and making sure that they are in order, unfolded, without staples or anything else that might jam the scanner. Additionally, some industries such as legal and medical may require documents to have [[Bates numbering|Bates Numbering]] or some other mark giving a document identification number and date/time of the document scan. Indexing involves associating relevant keywords to files so that they can be retrieved by content. This process can sometimes be automated to some extent, but it often requires manual labour performed by [[data entry clerk|data-entry clerks]]. One common practice is the use of [[barcode]]-recognition technology: during preparation, barcode sheets with folder names or index information are inserted into the document files, folders, and document groups. Using automatic batch scanning, the documents are saved into appropriate folders, and an index is created for integration into document management systems. [[File:2020-03-27 16.38.23 Scan Room in South Korea.jpg|thumb|[[Ministry of Culture, Sports and Tourism (South Korea)|Ministry of Culture, Sports and Tourism]] of [[South Korea]] issued an interpretation in June 2011 that it is a violation of [[wikisource:ko:저작권법 (대한민국)|copyright]] to scan a book by a third party who is not a copyright holder or a book owner. Therefore, in South Korea, book owners visit a "scan room" to [[Book scanning|scan books]] by themselves.]] A specialized form of document scanning is book scanning. Technical difficulties arise from the books usually being bound and sometimes fragile and irreplaceable, but some manufacturers have developed specialized machinery to deal with this. Often special [[Robotics|robotic]] mechanisms are used to automate the page-turning and scanning process. === Other uses === Flatbed scanners have been used as [[Digital camera back|digital backs]] for [[Large format|large-format]] [[camera]]s to create high-resolution digital images of static subjects. A modified flatbed scanner has been used for documentation and quantification of [[Thin-layer chromatography|thin layer chromatograms]] detected by [[Quenching (fluorescence)|fluorescence quenching]] on [[silica gel]] layers containing an [[ultraviolet]] (UV) indicator.<ref>{{cite journal | last=Campbell | first=Alison | author2=Michael J. Chejlava | author3=Joseph Sherma | date=December 30, 2003 | url=https://link.springer.com/article/10.1556/JPC.16.2003.3.14 | title=Use of a Modified Flatbed Scanner for Documentation and Quantification of Thin Layer Chromatograms Detected by Fluorescence Quenching | doi=10.1556/JPC.16.2003.3.14 | journal=JPC – Journal of Planar Chromatography – Modern TLC | publisher=Springer Nature | volume=16 | issue=3 | pages=244–246| url-access=subscription }}</ref> The ChromImage is allegedly the first commercial flatbed scanner [[densitometer]]. It enables acquisition of TLC plate images and [[Quantification (science)|quantification]] of chromatograms by use of Galaxie-TLC software.<ref>{{cite web | url=http://ar2i.fr/en/instrumentation-chromatographie/nos-solutions/chromimage | title=ChromImage | publisher=AR2I | date=October 20, 2013 | access-date=November 3, 2015 | archive-date=March 4, 2016 | archive-url=https://web.archive.org/web/20160304093857/http://ar2i.fr/en/instrumentation-chromatographie/nos-solutions/chromimage | url-status=dead}}</ref> Other than being turned into densitometers, flatbed scanners were also turned into colorimeters using different methods.<ref>{{cite book | last=Farrell | first=Joyce | author2=Doron Sherman | author3=Brian Wandell | date=1994 | url=https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=305301574d3ab41678f4ac95cf15b9a636c2ac12 | chapter=How to Turn your Scanner into a Colorimeter | title=10th International Congress on Advances in Non-Impact Printing Technologies | publisher=Society for Imaging Science & Technology | pages=579–581}}</ref> [[Trichromatic Color Analyser]] is allegedly the first distributable system using a flatbed scanner as a tristimulus colorimetric device. Flatbed scanners may also be used to create artwork directly, in a practice known as [[scanography]]. In the biomedical research field, detection devices for [[DNA microarray]]s are also referred to as scanners. These scanners are high-resolution systems (up to 1 μm/pixel), similar to microscopes. Detection is performed using CCDs or photomultiplier tubes. In [[pathology]], scanners are used to capture glass slides with tissue from [[biopsy|biopsies]] and other kinds of sampling, allowing for various methods of [[digital pathology]] such as [[telepathology]] and the application of [[artificial intelligence]] for interpretation. == See also == * [[3D scanner]] * [[Barcode reader]] * [[Display resolution]] * [[Photocopier]] * [[Telecine]] == References == {{Reflist|30em}} == External links == {{Commons category|Imaging scanners}} {{Basic computer components}} {{Authority control}} [[Category:Image scanners| ]] [[Category:Information management]] [[Category:Office equipment]] [[Category:Records management]] [[Category:Records management technology]] [[Category:American inventions]] [[Category:English inventions]] [[Category:German inventions]] [[Category:Italian inventions]]
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