What is the story on these new two dimensional barcodes?
Normal linear or one dimensional barcodes are limited in the amount of information that they can hold. Other technologies, such as magnetic stripe or RF tags can hold more information but are more expensive to implement. In an effort to develop barcode symbologies that would hold more information, stacked codes were first developed. These were nothing more that several linear barcodes printed one above the other to form a single symbol. These codes could be read by conventional reading equipment, like laser guns or CCDs. To increase the density of information even further, matrix codes were developed. Most of these codes consist of a pattern of round or square black marks arranged in a two dimensional array. There is usually some standard locator pattern, that is part of the image, to assure correct orientation when decoding the symbol. Since they are not really "barcodes" anymore, these codes can no longer be read by conventional scanners. They are normally read by scanners using two dimensional CCD devices (like camcorders and the new digital cameras use) that can capture an image of the entire symbol. They are referred to as "imagers", rather than scanners.