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What's a Bar Code?
Charged Coupled Devices
Charged coupled devices (CCDs) are extremely durable scanners for near contact and contact applications. Less expensive than their laser counterparts, CCDs having no moving parts to wear out or break.
How CCDs Work CCD scanners use one or more LEDs to flood the bar code area with light, and an image of the code is transferred to an array of photodetectors. The characteristics of the bar code are determined by electronically sampling each individual photodetector which interprets each bar and space by the number of adjacent detectors sensing black or white. In other words, instead of reading each bar and space in succession, the CCD "takes a picture" of a very thin portion of the complete bar code which it then converts into a signal that may be decoded. Charged Coupled Devices (CCDs) do not require the user to move the scanner across the bar code, however, many CCD's must come in contact, or within one inch of the symbol. CCDs use an LED light source and are limited to a specific field width making some code unreadable. Next generation long range CCD's have been introduced which can read at a distance of six inches, approaching laser performance.
CCDs are a viable
alternative, if not primary choice, to lasers. CCDs are less
expensive, lower in repair costs, more durable, consume less
power and perform to meet the needs of small- to medium- sized
retailers. CCDs offer numerous
advantages over competing technologies. Though less expensive
than lasers CCDs also read various code densities, are easy to
use, and require very little training. They are lighter and more
rugged than lasers and, unlike wands, may be used for non-contact
applications. New models offer depth of field that is well suited
for most retail, banking and manufacturing applications.
CCDs can read curved surfaces as well if not better than lasers because laser readings are distorted on curved surfaces. Like anything else, CCDs have their disadvantages. They have less depth of field, limited windows and often must have direct contact with the bar code symbol. While CCDs are an excellent choice for the applications listed above, they are not appropriate for long range scanning applications such as warehousing. CCDs are also not the best technology choice for applications in which a wide variety of label lengths and formats are used. Long messages or very low density codes can easily result in bar codes that exceed the width of the scan head, rendering them unreadable.
