Bar Codes
Perhaps the oldest of the AIDC technologies, bar codes can be looked upon as the best known and probably most
successful to date of the technologies. We are all familiar with the basic
bar code on our box of cereal, or the jar of honey that we buy in the
supermarket. This bar code is called UPC/EAN and is but one variation of over
250 bar codes that have been designed over time. Bar codes like this are referred to as linear bar codes as they are made up off a collection of bars and spaces
side by side. Fortunately many of these bar codes have never gained broad acceptance and we usually only consider 10-12 linear bar codes. The most common examples in use today are: UPC/EAN, Code 128, Code 39, Code 93, and Interleaved
2 of 5. Typical data content capacity varies from 8 to 30 characters with some bar codes restricted to numerals only, and others using full alpha-numeric information. Standards for these bar codes are published by AIM and are currently in progress at ISO.
Linear bar codes are used in
many applications where the use of a simple numeric or alpha-numeric code can provide the key to a database of "products". The most obvious
limitation is the amount of data that can be stored in a linear bar code, though other problems can exist with the substrate that the bar code is printed on providing insufficient contrast or poor ink receptivity which can cause the
quality of the bar code to be less than ideal.
2D Bar Codes
A new growth area in the world of bar code is the two-dimensional versions. Several variations of 2D are available and as these do not all comprise bars and spaces the more accurate name of 2D symbologies is used. 2D symbologies provide a means of storing large amounts of data in a very small space. Whether you consider stacked symbologies (linear bar codes stacked on top of each other), matrix symbologies (comprising a matrix of light and dark elements, circles, squares, or hexagons), or packet symbologies (a collection of linear symbols "randomly" arranged on a page). Examples of the three types include PDF417, Code 49 Code 16K (stacked),
Code One, MaxiCode, Data Matrix, Aztec Code, QR Code (matrix), and Super Code(packet). Standards for each of these symbologies are either available from AIM
or are in progress. Several of these standards have also been submitted to ISO
for standardization.
2D symbologies have a major
advantage over linear bar codes, they can store vast amounts of data. Individual symbols can store as much as 7000 numeric only or 4200 alpha-numeric characters. Many of the symbologies also have the ability to use a device called structured append that allows messages to be split over multiple
symbols, providing almost infinite storage space. The disadvantage of the 2D symbologies is that a special scanner is needed. Matrix symbologies need a vision based scanner to read the data, though some of the stacked symbologies
can be read with a rastering laser scanner. Expect to see many new scanners with variations in technology in the next year or so.
Contributed by Steve Halliday,
President, High Tech Aid
http://www.hightechaid.com
