ISO IEC 15416 pdf download – Information technology — Automatic identification and data capture techniques — Bar code print quality test specification — Linear symbols

ISO IEC 15416 pdf download – Information technology — Automatic identification and data capture techniques — Bar code print quality test specification — Linear symbols
4 Symbols and abbreviated terms
4.1 Abbreviations
EC: Edge contrast
EC min : Minimum value of EC
ERN: Element reflectance non-uniformity
ERN max : Maximum value of ERN
GT: Global threshold
MOD: Modulation
PCS: Print contrast signal
RT: Reference threshold
SC: Symbol contrast
SRD: Static reflectance difference
4.2 Symbols
A: Average achieved width of element or element combinations of a particular type
e: Width of widest narrow element
E: Width of narrowest wide element
e i : i th edge to similar edge measurement, counting from leading edge of symbol character
K: Smallest absolute difference between a measurement and a reference threshold
k: number of element pairs in a symbol character in a (n, k) symbology
M: Width of element showing greatest deviation from A
m: Number of modules in a symbol character
N: Average achieved wide to narrow ratio
n: number of modules in a symbol character in a (n, k) symbology
R b : Bar reflectance
R D : Dark reflectance
R L : Light reflectance
R s : Space reflectance
R max : Maximum reflectance
R min : Minimum reflectance
RT j : Reference threshold between measurements j and (j+1 ) modules wide
S: Total width of a character
V: Decodability value
V C : Decodability value for a symbol character
X: Nominal narrow element dimension
Z: Average achieved narrow element dimension
5 Measurement methodology
5.1 General requirements
The measurement methodology defined in this standard is designed to maximize the consistency of both reflectivity and bar and space width measurements of bar code symbols on various substrates.
This methodology is also intended to correlate with conditions encountered in bar code scanning hardware. Measurements shall be made with a single light wavelength and a measurement aperture of a diameter defined by the application specification or determined in accordance with 5.2.1 and 5.2.2.
Whenever possible, measurements shall be made on the bar code symbol in its final configuration, i.e. the configuration in which it is intended to be scanned. If this is impossible, refer to annex D for the method to be used for measuring reflectance for non-opaque substrates.
The sampling method should be based on a statistically valid sample size within the lot or batch being tested. A minimum grade for acceptability shall be established prior to quality control inspection. In the absence of a Copyright International Organization for Standardizationsampling plan defined in formal quality assurance procedures or by bilateral agreement, a suitable plan may be based on the recommendations in ISO 2859 or ISO 3951 .
5.2 Reference reflectivity measurements Equipment for assessing the quality of bar code symbols in accordance with this standard shall comprise a means of measuring and analysing the variations in the diffuse reflectivity of a bar code symbol on its substrate along a number of scan paths which shall traverse the full width of the symbol including both quiet zones. The basis of this methodology is the measurement of diffuse reflectance from the symbol. All measurements on a bar code symbol shall be made within the inspection band defined in accordance with 5.2.4. The measured reflectance values shall be expressed in percentage terms either with reference to the reflectance of a barium sulphate or magnesium oxide reference sample complying with the requirements of ISO 7724, which shall be taken as 1 00 %, or by means of calibration and reference to recognised national standards laboratories for samples illuminated at 45° with the diffusely reflected light being collected perpendicular to the surface.
5.2.1 Measurement wavelength(s) The peak light wavelength used for measurements should be specified in the application specification to suit the intended scanning environment. When the wavelength is not specified in the application specification, measurements should be made using the wavelength of light that approximates most closely to the wavelength expected to be used in the scanning process. Refer to annex F for guidance on the selection of the wavelength of light.
5.2.2 Measuring aperture The nominal diameter of the measuring aperture should be specified by the user application specification, to suit the intended scanning environment. When the measuring aperture diameter is not specified in the application specification, Table 1 should be used as a guide. In an application where a range of X dimensions will be encountered, all measurements shall be made with the aperture appropriate to the smallest X dimension to be encountered. In the absence of a defined X dimension, the Z dimension shall be substituted. The effective measuring aperture diameter may vary slightly from its nominal dimension due to manufacturing tolerances and optical effects. Note that the measured width of some of the narrow elements may be smaller than the measuring aperture diameter.