BARCODE QUALITY
About barcode verification and standards.
The Importance of Verification
The ease with which a bar code can be read depends upon how well the code has been printed, and on certain parameters of the scanner. Specifications lay down the ideal dimensions and methods of production of codes, but it is not always possible to adhere to the ideal conditions. Therefore, in practice, bar codes can be produced that are not perfect and which may or may not scan successfully. In addition there are other problems that can occur in the printing or production process which may contribute to the difficulty of scanning.
So how can the chances of a code scanning be assessed?
Traditionally there have been a few ways of trying to ensure that a code will scan. The retail code system, which is organised world wide by the EAN organisation, has relied on accurate film masters to be used in the creation of printing plates to attain the quality required. However, not all codes are printed on large presses, and these other printing processes have various limitations and potential error conditions.
Verification equipment has been around for some years to assess the dimensional accuracy of printed codes. Although these devices have proved extremely useful, their results may not fully explain why a code will or will not read.
New Verification Standards
In order to create a universal international standard for verification equipment that assesses the printed bar code from the point of view of scanning and decoding rather than the dimensional accuracy of the ink on the paper, the American National Standards Institute (ANSI) has developed a new method of analysing the printed code.
This method, which has already been adopted in the European Community (CEN) and is now a world standard (ISO), is far more detailed than the previous methods of verification, but it does reveal more possible problems with a printed bar code.
In particular it highlights problems that are associated with printers used for generating bar-coded labels, where printer machinery faults may cause unwanted gaps, holes or specks of ink in places where smooth coverage of ink or absence of ink should exist. It also highlights the problems that can occur when mixtures of colours are used, such as on magazine covers.
Verifiers use the ANSI/CEN/ISO grading system which takes into account seven main parameters:
· Minimum Reflectance
· Symbol Contrast
· Minimum Edge Contrast
· Modulation
· Defects
· Decodability
· Decode
For each scan the lowest single grade of these seven (being the weakest link in the chain) becomes the overall grade. After the recommended ten scans have been taken, the results are averaged, and each parameter, including the overall grade, is graded A-F (ANSI) or 4-0 (CEN/ISO).
The required pass grade for most major retailers is a grade 2 (C) or above for all bar codes, with the exception of those printed directly onto corrugated fibreboard, for which a Grade 1 (D) is normally acceptable.
However, you should check with your customers for their specific grade requirements.
SCANOLOGY B.V.
"EASY AND EFFECTIVE IDENTIFICATION SOLUTIONS"
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