Barcodes fail due to two main reasons:
- Poor Image Quality: Scanners decode images. Inaccurate printing, lamination, shrink wrap and substrate characteristics can impact scanning
Lamination - Incorrect Data Structure: Barcode data must be prefixed and parsed in compliance with the applicable standard.
ISO standards grade various print quality parameters:
- Contrast: Reflectance difference of bars (or squares) and spaces.
- Modulation: Uniformity of light and dark reflective values.
- Defects: Voids in bars, spots in spaces.
- Decodability: Accuracy of bar (or dot) and space width and location.
- Grid and axial accuracy of dot placement in 2D symbols.
Other factors that degrade barcode performance:
- Gain: Pigment spread causing reflectance variation. The ISO standard will soon include gain as a parameter.
- X Dimension: All barcodes have a minimum size. Smaller barcodes may be difficult or impossible to scan.
- Design Errors: Quiet zones encroached by graphics or text, or inaccurate barcode placement in a white zone.
- Data Entry Errors: Human-readable features like parentheses should not be encoded in the barcode.
- Abrasion and Wear: Storage and handling can degrade barcode images.
Quiet Zone Violation - Temperature Extremes: High heat can fade or obliterate images on heat-sensitive labels.
- Color: Scanning is defeated with certain colors.
- Non-flat Surfaces: Scanners must capture a full image of the barcode.
- Metal Substrates: Silvered, glossy, or brushed-metal substrates can cause scanning difficulties.
Key Takeaways:
- Track gain visually to identify potential issues.
- Test barcodes in their final form (e.g., after lamination or application on a cylinder).
- Use an ISO-compliant verifier for testing, not just a smartphone scanner.
Testing is faster and cheaper than recovering from a barcode disaster.
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