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SYMBOL VERIFICATION OVERVIEW
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2.2 ISO/IEC 15415 2D STANDARD
The ISO-IEC 15415 Standard specifies the methodologies for the measurement of specific
attributes of two-dimensional bar code symbols, and methods for evaluating and grading
these measurements and deriving an overall assessment of symbol quality.
Two-dimensional symbol quality assessment shall be based on measurement and grading of
parameters of the reference Grey-scale image, the binarized image derived from it, and the
application of the reference decode algorithm to these.
Symbol Quality Grading of these parameters shall be used to provide a relative measure of
symbol quality under the measurement conditions used.
Each parameter shall be measured and a grade on a descending scale of integers from 4 to
0 shall be allocated to it. The grade 4 represents the highest quality, while the grade 0
represents failure.
Scan Grade:
The scan grade is the lowest grade achieved for the following seven parameters:
- Decode
- Symbol Contrast (SC)
- Modulation (MOD)
- Fixed Pattern Damage
- Axial Non-Uniformity (ANU)
- Grid Non-Uniformity (GNU)
- Unused Error Correction (UEC)
Overall Symbol Grade:
The (Overall) Symbol Grade is only meaningful if it is expressed in conjunction with the
measurement wavelength and aperture used. It should be shown in the format:
Grade / Aperture / Wavelength [ / Angle ]
Where:
“Grade” is the overall symbol grade (i.e. the the arithmetic mean of the individual Scan
Grades for a number of tested images of the symbol, normally one).
“Aperture” is the aperture reference number (from Standard’s table) or the diameter in
thousandths of an inch (to the nearest thousandth) of the synthetised aperture.
“Wavelength” is the peak light wavelength in nanometres.
“Angle” is the angle of incidence of the illumination relative to the plane of the symbol) of
the illumination (if 45° it is omitted).
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