Scanner is a machine that translates printed pages, photographs, and other materials into digital code for use by computers. The machine scans the material one tiny area at a time. An electronic device called a charge-coupled device measures the amount of light reflected from each area. The scanner then translates the measurement into digital code. Most scanners can digitally reproduce both black-and-white and color materials. A flat bed scanner scans material through a plate of glass on which the material lies flat. A drum scanner scans material that has been mounted on a rotating cylinder.
A scanner usually separates color images into the four colors used to produce a full-color effect in printing. These colors are yellow, magenta (purplish red), cyan (blue), and black. The scanner is programmed to produce the yellow, magenta, and cyan components. The computer creates the black component using the color information.
One common use of scanners is to convert text that was not produced on computers into a form that computers can process and store. If scanned text is to be edited, special computer software is used to convert individual letters, numbers, and other symbols. This software uses a technique known as optical character recognition.
Printing companies use scanners in the production of printing plates and cylinders. The digital files produced by a scanner can be output to digital printers, or to platemaking machines called imagesetters or platesetters.
