Editing Contact image sensor

{{short description|Type of image sensor}}
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[[File:Flatbed scanner CIS sensor bar.jpg|thumb|CIS of a flatbed scanner]]
'''Contact image sensors''' ('''CIS''') are image sensors used in [[Image scanner|flatbed scanners]] almost in direct contact with the object to be scanned. [[Charge-coupled device]]s (CCDs), the other kind of sensor often used in scanners, use mirrors to bounce light to a stationary sensor. Scanners using CISs are much smaller than ones that use CCDs, use typically a tenth as much power, and are particularly suitable for low power and portable applications, often powered over [[USB]].<ref>{{cite web|url=http://www.canon-compo.co.jp/e/technology/cis.html|title=Canon CIS technology overview|last=|first=|date=|website=|url-status=dead|archive-url=https://web.archive.org/web/20180124022344/http://www.canon-compo.co.jp/e/technology/cis.html|archive-date=January 24, 2018|accessdate=Jan 25, 2012}}</ref>

[[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]]
A CIS typically consists of a linear array of detectors, covered by focusing lenses and flanked by red, green, and blue [[LED]]s for illumination.  The use of LEDs allows the CIS to be highly power efficient, allowing scanners to be powered through the minimal line voltage supplied via a [[USB]] connection.  CIS devices typically produce lower image quality compared to CCD devices; in particular, the [[depth of field]] is greatly limited, which poses a problem for material that is not perfectly flat. However, a CIS contact sensor is smaller and lighter than a CCD line sensor, and allows all the necessary optical elements to be included in a compact module, thus helping to simplify the inner structure of the scanner.  With a CIS contact sensor, the scanner can be portable, with a height of only around 30&nbsp;mm.
CIS is a key component widely used in scanners (especially portable scanners), electrographs, bar code readers and optical identification technology.

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[[Category:Optical devices]]


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