ISO/IEC 15415 Grading Parameters

The 2D barcode grading process begins with a pass/fail test.

  • If the software can decode the code, the code passes the first test.
  • If the software cannot decode the code, the software automatically assigns an “F” grade to the code.

The lowest individual grade becomes the overall grade for the code.

The software decodes a code, then grades it for symbol contrast, modulation, reflectance margin, fixed pattern damage, axial non-uniformity, grid non-uniformity, and unused error correction.

Quality parameters for 2D codes Description Possible solutions

Unused Error Correction

(UEC)

 This is the percentage of error correction capability that is available for further incorrect modules.
  • Modify artwork by changing the module colors that are failing to the opposite color
  • Check for physical damage to the code
  • Look for bar width growth or print growth

Symbol contrast

(SC)

 The difference in reflectivity between the brightest module and the darkest module.
  • Change the paper type
  • Change ink color or amount
  • Add a light-colored background behind the code
  • Change the lighting angle

Modulation and Reflectance Margin

(MOD) and (RM)

This is a grade based on the amount of variability in reflectivity of the modules. A multi -step process is used to get the modulation grade.

MOD and RM are often the same, differing only when some modules are determined to be the wrong color and error correction is used.
  • Reduce BWG by adjusting the amount of ink used.
  • Change the speed or temperature of the marking process
  • Adjust the scale of the artwork.
  • Look for defects in the print
  • Is there show through with the paper choice?

Decode

(DEC)

Report whether the 2D Symbol was decoded in accordance with the reference decode algorithm with the specified aperture.

Note:

Note that when Auto Aperture or Auto 80% is selected for Aperture, it is possible for decoded results to be reported but for a failure to occur when decoding using the selected aperture.

In this case, the DECODE grade will be F and a message will be reported in the grade section of the report.
  • Are you using the correct aperture?
  • Are you using the right ISO Standard?
  • Are you using the right lighting angle?
  • Is the symbology enabled?
  • Is the symbol “mirrored”?
  • Is the camera in focus?
  • Is the code in the center of the FOV?
  • Do the cell sizes look proportionate to one another?
  • Are the edges of the cells crisp?
  • Are all the components of the finder pattern present?
  • Is the inkjet nozzle blocked?
  • Is the thermal element faulty?

Fixed pattern damage

(FPD)

Overall grade for all the fixed pattern components.

This grade is equal to the lowest grade of the finder pattern components.
  • Issues with printer nozzle, needle, laser, or thermal element
  • Physical damage to the code
  • Are there gaps in the L, or dirt in the quiet zone?

Axial Non-Uniformity

(ANU)

Tests for uneven scaling of the symbol, which would make readability more difficult at some non- normal viewing angles.

In other words, a measure of the overall aspect ratio of the symbol.

Can be caused by:

  • Improper printing
  • Marking speed or speed mismatch
  • Printing software errors

Grid Non-Uniformity

(GNU)

Measures and grades the largest vector deviation for the grid intersections from their ideal calculated position.

In other words when module grid alignment is not centered based on the calculated grid.

Can be caused by:

  • Inconsistent print or marking speeds, vibration, or slippage interference
  • Odd shaped parts and incorrect print distance, angle, or speed
  • Poorly managed artwork or pixel round off