Offices' Machines and Tools

Scanning devices

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Scanning devices allow visual information to be transferred into a computer. This information

ranges from simple black-and-white product bar codes to full-color photographic images. In

all cases, light is reflected by or transmitted through the object being scanned to collect data

on the brightness of different areas. This data is converted into an electric signal that is then

digitally encoded.

One of the most widespread scanning devices today is the flatbed scanner which was once

an expensive professional machine but is now a low-cost, personal-computer accessory.

Scanners divide up images into thousands of pixels (picture elements) for display on a computer

screen or reproduction by a printer. Low-cost scanners use fluorescent light and a series of

mirrors to direct reflected light from a strip of the image onto a charge-coupled device (CCD).

Professional drum scanners in the printing industry use a laser beam to scan the surface of the

original, and measure the intensity of the reflected light.

Bar-code scanners, which are even more widespread, measure the intensity of light reflected

from white an black areas on a bar code. The simplest bar-code readers are pens or guns that

are laid directly over the top of the bar-code, but more advanced models use sophisticated optics

to trace a laser beam through a three-dimensional grid of space, so it will pick up light reflected

from a bar-code held at almost any angle.