Selecting a verifier
Code type, code size, and substrate influence a user’s specific verification needs
While many parameters, such as bar width growth, axial non uniformity, and quiet zone are used to specify symbols’ dimensional accuracy, other qualities—such as contrast and reflectance—affect the optics of barcode readers and how they “see” a code. Barcode verifiers test both image-related and data-related quality parameters to assess a code’s readability. Users must select a barcode verifier model with the precise field-of-view, lighting, and optics to suit their code size, substrate, and shape.
Four simple questions can help define what to look for when purchasing a verifier:
What is the code size range?
Consider the size of the narrowest bar or smallest module printed (normally expressed in mils, or .001 of an inch). To determine required camera resolution, look for a verifier with a minimum x-dimension that is smaller or equal to the smallest bar width or module. The total width of the largest barcode printed will determine the required field of view. A verifier’s field of view needs to be large enough to show the entire code including its quiet zone (space surrounding the outside of the code).
What are the codes printed on?
Codes appear differently to a barcode reader’s camera depending on the material they are printed on. To achieve proper illumination for some surfaces, specific lighting angles are required. Most verification standards for 1-D and 2-D codes specify 45° lighting for codes printed on labels. This ensures that some light reflects off of the label and goes back to the camera. For direct part marks (DPM) on a shiny, textured, or curved surfaces, a verifier with 30° and 90° or dome lighting option is necessary.
Are there oddly shaped parts?
Verifiers with adjustable height stands make it much easier to position codes on small, oddly shaped parts underneath the camera. When dealing with symbols on recessed areas of a part, a verifier’s software should be able to select specific regions and tell the camera exactly where to analyze a code.
What are the software features?
A barcode verifier’s software should be able to grade and diagnose issues within the barcode printing process. The right barcode verifier will generate reports that grade against relevant ISO and application standards.