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Omnidirectional Scanning
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Why select a laser bar code scanner with an omnidirectional scan pattern? The reason is really quite visible. Omnidirectional scanning, as defined by Roger C. Palmer, The Bar Code Book, is when a "series of straight or curved scanning lines of varying directions in the form of a starburst, a lissajous pattern, or other multiangle arrangement are projected at the symbol and one or more of them will be able to cross all of the symbol's bars and spaces, no matter what the orientation."
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With an omnidirectional pattern, you don't have to pay much attention to the orientation of the bar code within the scan field. In single line scanning, only one laser line is available to read the bar code, consequently the line or the bar code must be turned so all the bars and spaces are crossed by the beam. Metrologic's omni scanners provide you 20 to 25 interlocking lines within the scan field. This can be of great value when you need to present many different bar coded products to the scanner, and the bar codes are of no specific position or direction. Omnidirectional scanners are also better at reading poorly printed, wrinkled, or even torn bar codes.
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Perhaps a better understanding of the way an omnidirectional laser bar code scanner emits its scan lines would be helpful.
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A visible laser diode (VLD) is placed within the scanner as the light source. A rotating polygon consisting of faceted mirrors is centrally positioned to reflect the laser beam. The mirrors are mounted on the polygon at different angles, allowing the laser light to be reflected at various elevations. As the polygon spins, the laser beam coming off the mirrors is swept through an arc. The number of lines created is determined by the number of facets on the polygon, at Metrologic we typically use four facets. The swept beam is then redirected by an arrangement of fixed mirrors, creating fields. By multiplying the facets by the number of fields we come up with the number of scan lines. Thus, 4 x 5 = 20. The angle of the different fields is manipulated to work together throughout the depth-of-field to create the scan pattern. The yield, a dense pattern of interlocking scan lines, assures the bar code is read regardless of orientation.
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The scanners that are commonly built into counter tops in supermarkets, like the Metrologic MS7600 Horizon or the Stratos Series, fall within this category. In-counter scanners are the preferred scanner when high volume, and fast throughput is essential. However, these scanners are not just for retail anymore. Commercial applications are continually popping up. In-counter scanners are being used for secured automated entry, time/attendance, and document processing (see library application on page 2).
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Fixed projection scanners, like our MS7820 Solaris, also emit an omnidirectional scan pattern. While not installed within the counter top, the MS7820 Solaris small footprint fits most anywhere. For industrial applications, the Tech 7 and Tech 10 units are the scanner of choice. These rugged projection scanners are equally fast, aggressive, and reliable.
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The Right Scanner for the Right Application
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A guideline for qualifying an omnidirectional scanner. Does your application involve any of the following?
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· High Volume
· Fast Throughput
· Minimal Orientation of Bar Code to Scanner
· Poor Quality Bar Codes
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