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Laser Scanners

Laser Scanners

Laser scanning is in widespread use among a variety of applications and integrated in hand held laser guns, projection or fixed scanners used in conveyor systems, and in-counter scanners as seen in many supermarkets. Laser scanners project a beam of energy off an oscillating mirror or rotating prism and generate what appears to be a red scan line. An omnidirectional projection scanner creates a pattern or raster of red scan lines. In reality, the scan line(s) is a laser spot rapidly moving across at 30 or 40 times per second. Laser scanning is "automatic" in a sense that it generates multiple scans activated either by sensing an object that is placed in front of the scanner (known as autosense) or by simply pulling a trigger. In comparison, a wand must be moved manually across a bar code by hand and thus is a manual scanning device.

One of the newest technologies regarding laser scanning is "Fuzzy Logic." Fuzzy logic technology applies artificial intelligence to reading poorly printed bar codes and is ideal for low-contrast, high density bar codes. Fuzzy logic offers the highest level of performance and best first-time read rate across a range of bar code qualities including harsh environments and rugged operating conditions.

Projection scanners are commonly used in material movement configurations. Both tabletop and fixed mount projection scanners are popular units at many checkout counters and conveyors systems respectively. Grocery store clerks move items across tabletop scanners almost as fast as it takes to remove the items from a cart alone. Likewise conveyor systems scan at a much higher rates than anyone is able to without making mistakes.

Laser technology is very popular in the United States primarily due to patent grants. Only a hand full of companies hold the central patents in this technology preventing further domestic and foreign competition. CCD technology is more popular among other countries because of this legal issue.

Every laser scanner has a depth of field. The depth of field is the range between the minimum and maximum distance in which a laser scanner can successfully read a particular bar code, and it is directly related to the density of the bar code. For example, the higher the density of the bar code, the closer the laser has to be to read a symbol. Likewise, the lower the density of the bar code, the farther away the laser has to be to read a symbol. There will be some overlap between the range of various bar codes, but as a general rule, the user must keep this is mind when scanning. In regards to bar coding, some common problems may exist with the set up. The table on the next page outlines some of these problems and the appropriate step(s) to take.