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AIS Barcode Verification Advice

Barcode Validation v's Barcode Print Verification

The ISO (International Organization for Standardization) and IEC (International Electro-technical Commission) groups formed a specialized system for worldwide standardization to ensure that barcode symbols would be produced in such a way as to be reliably decoded at its point of use.

In August of 2000, the ISO/IEC released document ISO/IEC 15416 that combined the technical content of the pre-existing separate American (ANSI X3.182) and European (EN1635) specifications into one technically equivalent document for worldwide use.

There has been much confusion in the world of barcoding regarding the difference between VALIDATION and VERIFICATION. This article attempts to explain the difference in clear and concise terms.

Validation
Validation is all about “Syntax.” Validation of a barcode is the process of checking that the proper character sequence and data has been encoded in the printed barcode symbol. Examples of expected results of validation could be sequentially matching the encoded characters to a database, checking presence of a check-digit according to a special algorithm, etc. Validation is specific to the scanner performing the validation. There is no correlation to “if” or “how well” another scanner will decode the same symbol.
The process of validation is not documented in any industry standard.

Barcodes are validated according to rules established by the party performing the validation. Scanner manufacturers are free to use any technique to enable a scanner to decode a symbol. The results, therefore, are subjective in nature.

Verification
Barcode verification is an ISO STANDARDS based process wherein all barcodes are subject to Symbology Specifications. Symbology Specifications state EXACTLY how a given barcode, in a given symbology, must be constructed. Within every symbology specification is a section called the “Reference decode algorithm.” A verifier is also governed by ISO STANDARDS. A verifier must decode the symbol by strictly applying the reference decode algorithm and must be manufactured to ISO/IEC 15426-1 (in the case of linear symbols) and ISO/IEC 15426-2 (in the case of two-dimensional symbols) conformance specifications. Once the verifier decodes a symbol, various measurements are performed and the results GRADED. The methodology for performing such measurements and determining a GRADE is documented in the following two ISO standards:

ISO/IEC 15415 – Barcode print quality test specification – Two-dimensional symbols

ISO/IEC 15416 – Barcode print quality test specification – Linear symbols

These graded measurements are designed to ensure a barcode is of such good print quality that it is able to be read not only by the verifier but also by all scanners in the supply chain. In other words, verification is the process of GRADING a barcode symbol (according to ISO STANDARDS) in an effort to predict the symbols first pass scan success probability for every scanner in the supply chain.

The verifier is the “Great Arbitrator” between the printer of the barcode symbol and the scanner of the barcode symbol. When a scanner fails to read a barcode symbol, is it the fault of the scanner or the printer? That is where the verifier comes into play. The verifier grades the barcode symbol on a scale of A (4.0) to F (0.0). If the barcode symbol receives a grade of F, the scanner has no obligation to decode the symbol. That is not to say that it won’t decode the symbol, just that it is not required by ISO standards to decode it. If the verifier grades the barcode symbol A through D, the scanner MUST, by ISO standards decode the symbol.

Things to ask when buying a barcode verifier

A barcode verifier is a fairly technical and expensive device but the reason you need one is straightforward: you need to manage your barcode-related risk; you’ve got customer relationships, your reputation and future business on the line.

How do you make sure the verifier you’re thinking about buying is the right tool for your needs and your situation?

Here are some things to ask before you authorise that Purchase Order.

1. What barcode types or symbologies does the verifier test?

2. Is the barcode verifier itself complaint? This is not the same thing as the verification report. Most barcode verifiers use the ISO specification as the format of their test reports, but not all verifiers are themselves compliant to the ISO specification that describes how the machine itself performs. If the verifier is not ISO compliant, the report is meaningless.

3. Beware of a barcode verifier that is partial ANSI or ISO compliant

4. How long is the warranty and what does it include? Beware of manufacturers who don’t clearly state their equipment warranty on the data sheets.

5. Does the barcode verifier require periodic re-calibration? Is the re-calibration card included in the quoted price for the verifier or is it an extra-cost option?

6. Beware of a barcode verifier that claims to never need re-calibration

How would you trust it over the long haul.

7. How does the barcode verifier report and grade the tested symbols? The globally-preferred method is ISO numerical grading, but many Americans prefer ANSI letter grades.

8. What is the verifier form factor? If the device is portable, how do you get the test data into your PC (or Mac) for viewing, archiving, printing or emailing?

Aspects to consider in machine vision illumination

Cameras do not see objects. They merely see light which is reflected from objects. The intrinsic qualities of materials control how it reacts to different lighting. Therefore to get a lighting solution that would work reliably for the intrinsic properties of the material being inspected is the key. While this would be the primary consideration when considering a lighting solution, there are other factors which need to be investigated such as:

  • What speed will the application run.
  • What is the size of the physical area that needs to be illuminated.
  • What does the service life of the lighting need to be.
  • What are the mechanical constraints.
  • What are the environmental constraints.

It’s critical that you choose the correct illumination for all 2D Vision applications. The rule of thumb is that if you can distinguish the features you want to extract from an image with the naked eye, then your software will be able to do it. You don’t really need a full machine vision system to determine your chances of success. Just look at the captured image with the correct illumination and if you can easily pick out the features that you need to detect without angling it or magnifying it, then the chances are good.

Machine Vision optics generally refers to the lenses that are used. Again here with machine vision, there are quite a variety of factors to consider such as:

  • Magnification
  • Resolution
  • Field of View Distance to object
  • Depth of Field Amount of light available
  • Camera sensor size

For more information on vision system applications and solutions please call us on 01 6205742.