Scanners

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A scanner is an input device that captures analog images in the form of text, photographs, or drawings and converts them to digital information (0s and 1s) that can be recognized by a computer system and supporting scanner software. A scanner uses a sensor to capture the reflection of light from a desired object to create a digitized image. Scanner software or supporting applications can be used to modify the digital image to suit the needs of the user. Finally, the image can be duplicated, printed, saved as a file, or sent as an e-mail attachment.

Optical scanners and digital cameras use Charge-Coupled Devices (CCDs) to sense variations in light reflected off an image. These tiny CCDs are lined up in rows or arrays.

A CCD represents a pixel. A pixel (picture element) is an area in a graphic image. Computer monitors, for example, are split into sections that are represented by millions of pixels. The more pixels there are to an area, the sharper the graphic image or monitor resolution. Scanner resolution is measured in optical dots per inch (dpi). In simple terms, a CCD in a scanner represents one dot on a graphic image. The more CCDs there are per area in a scanner, the sharper the final image will be.

Scanners are available in various forms and offer different delivery methods:

  • Flatbed scanner. The most common type of scanner, larger flatbed scanners that bind documents together are often seen in business environments. With a flatbed scanner, a document or image is placed on a flat glass surface. A light source and an array of sensors (CCDs) pass below the document.

  • Single sheet-fed scanner. Smaller, single-feed flatbed scanners can be purchased at reasonable prices for home use. This type of scanner uses a set of rollers to feed the image to be scanned past the light source and sensors. This is not a useful scanner for large amounts of information to be scanned.

  • Handheld scanner. A handheld scanner is a flexible device that allows you to scan stationary objects or images. It is also a useful tool for gathering inventory information; for example, a bar code scanner can be used to gather stock information at a grocery store or warehouse.

There are several ways to interface a scanner to your computer system, including parallel, SCSI, and USB connections. These types of connectors are discussed in detail in Chapter 8.



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A+ Complete Study Guide, Third Edition (220-301 and 220-302)
The A+ Exams Guide: (Exam 220-301), (Exam 220-302) (TestTakers Guides)
ISBN: 1584503076
EAN: 2147483647
Year: 2003
Pages: 237

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