Barcode scanners for inventory management are typically mobile versions of the familiar red-beam lasers in grocery
checkout lanes. But in practice, a huge variety of barcode inventory scanners -- fixed and mobile -- are used in today's warehouses. The choice depends on the nature of the goods and packages you're trying to track, the barcodes that identify them, and the layout and workflow of the warehouse.
There are two main kinds of barcode inventory scanners: lasers, and imagers, according to Bert Moore, director of communications and media relations for AIM, an association of automatic identification and mobility vendors. Laser scanners use an invisible laser beam to pass over a barcode and convert the waveform data of the reflected light from analog to digital for decoding into software. (Visible light is only added to help the user aim the laser.) Imagers are cameras that use the same technology in digital cameras and smart phones to take a picture of the barcode while a light shines on it.
Moving beam (linear) laser scanners, which must be oriented in the right direction to sweep a straight line across the barcode's light/dark pattern, are the most common kind in warehouses, Moore said. In contrast, omnidirectional lasers spread out the light in a rastered, cross-hatched, or starburst pattern to improve readability of a wider variety of barcodes.
Moore says the barcode inventory scanners in warehouses are primarily handheld units attached to mobile computers or data-collection terminals. Ring-style devices are sometimes used where workers need their hands free to handle items. "For supervisors, there's a growing trend towards using cameras in smart phones and similar devices for some routine activities," Moore said.
Not all warehouse scanners are mobile. Major shipping carriers, for example, use fixed scanners above conveyor belts.
Barcode inventory scanner symbolology
Barcode designs conform to languages called "symbologies" that affect your choice of scanner technologies. Linear (1D) symbologies include the familiar Universal Product Code (UPC) pattern of straight black lines alongside a 12- or 13-digit number. 2D symbologies use two dimensions to encode more information than 1D, which allows more data-rich barcodes or -- importantly -- ones that can hold the same amount in a much smaller space.
"2D symbologies fall into two categories: stacked barcodes and matrix codes," Moore said. "Stacked barcodes can be read with either a laser scanner or 2D imager. Matrix codes can only be read with imagers." In addition, matrix symbologies have algorithms that can tolerate damage, such as partial erasure.
One popular stacked code, PDF417, which looks a bit like a scrambled UPC code, was mandated by the U.S. Department of Defense for shipping labels and has been appearing in other applications, according to Moore. The United Parcel Service uses a matrix format called MaxiCode for parcel handling, and a composite type, GS1 DataBar (formerly called Reduced Space Symbology, or RSS), a denser variation on UPC, is catching on in small items such as pharmaceuticals and consumer products.
Moore says only 2D imagers can read both kinds; they used to be more expensive but have recently reach parity with lasers. But there are nuances. "PDF417 stacked barcode is best read with either a rastering laser or 2D imager, but can be read with a linear laser scanner," said Moore. "GS1 DataBar symbols can probably be effectively read with a linear laser." This crossover ability of linear scanners is attributable to the fact that linear symbologies are essentially groups of linear codes stacked on top of each other, which makes them decipherable by a laser making multiple sweeps.
"There is a continuing trend towards smaller, lighter, faster, cheaper," Moore said. "Scanning and printing hardware is increasingly focused on the mobile workforce, and that includes warehouse workers. At the same time, improving the ruggedness, reliability and capabilities of scanning and printing hardware is an ongoing task for manufacturers.
Moore's other advice about selecting barcode scanners for inventory management:
- Be aware of the ways lighting can affect readability and thus, which scanning technology works best. Low-light warehouses might benefit from imaging scanners' ability to flood the barcode with light, for example.
- Have employees try out scanners and mobile computers for ergonomics, ease-of-use, and suitability to the work environment.
- Evaluate how equipment integrates with the workflow. Does having to pick up a scanner slow down the workflow, while an overhead scanner speeds it up?
- Don't treat barcode equipment as a commodity and assume devices are interchangeable.
- Plan for success: choose technologies that are more likely to expand with your business.
About the author: Freelancer David Essex has covered information technology for BYTE, Computerworld, PC World, and numerous other publications and web sites.