BS ISO IEC 15415:2011 pdf – lnformation technology —Automatic identification and data capture techniques—Bar code symbol print quality test specification — Two-dimensional symbols
BS ISO IEC 15415:2011 pdf – lnformation technology —Automatic identification and data capture techniques—Bar code symbol print quality test specification — Two-dimensional symbols.
A. 1 Application
Because of differences in symbology structures and reference decode algorithms, the specific grading rules to apply to each symbology (especially with respect to fixed pattern damage) must be defined and specified fo each particular symbology, either in this International Standard or within the Symbology Specification for that particular symbology.
This annex defines values corresponding to grade thresholds for Fixed Pattern Damage for Maxicode (ISO/IEC 16023). The first edition publication of this international standard also defined the fixed pattern damage grading parameters for Data Matnx and OR Code but these definitions are now induded ii the symbology specifications,
Where a symbology specification specifies the basis for grading these parameters, and makes express reference to this International Standard, the basis or values in the symbology specification shall ovemde those indicated in this Annex.
Some symbologies may requie additional parameters. These shall be added to the quality assessment of this standard in accordance with 7.8,9.
A.2 Data Matrix Fixed Pattern Damage
Data Matnx Fixed Pattern Damage (FPD) shall be assessed in accordance with ISO1IEC 16022.
NOTE The onginal version of the Intemaional Standard contained details of fixed paflem grading for Data Matrix. Such details e now found in ISOIIEC 16022.
A.3 Maxicode Fixed Pattern Damage
A.3.1 Features to be assessed
The Fixed Patterns of a Maxicode symbol are (a) a 3-ring circular bullseye near the centre of the symbol and (b) six 3-module orientation patterns surrounding it. These are shown in Figure kl.
The key characteristics of these are as follows
A heurn-neon laser is a gas-flied laser tube which emits highly monochromatic coherent light at a peak wavelength of 632,8 nm (usually rounded to 633 nm), in the vi&ble red area of the spectrum.
A light-emitting diode is a low-power solid-state component most frequently found as the light source in a light pen (wand) or CCD scanner. Operating wavelengths in the visible spectrum may be from 620 to 680 nm:
most commonly either 633(640 or about 660 nm. In the infra-red spectrum, 880 to 940 nm Is the most common range of wavelengths.
A laser diode is also a low power solid-stale component emitting highly monochromatic coherent bght. Typical wavelengths in the visible spectrum used by these, at the date of publication of this standard, are 660 and 670 nm, In the infra4ed spectrum 780 nm is common. They are frequently found In hand-held (laser) scanning equipment and a number of fixed scanners.
Broadband light sources are mainly found in systems using two-dimensional imaging and image processing technology rather than scanning techniques.
Incandescent lamps have a power distribution covering much of the visible spectrum and well into the near infra-red spectrum: their oplical charactenstics are more easily defined in colour temperature terms rather than in those of peak wavelength, because of the wide bandwxlth and relative absence of clearly-defined peaks In the power distnbution. These broadband power distribution characteristics mean that the symbol contrast values obtained from symbols may vary with different colour temperatures to a significantly lesser extent than values obtained with light sources whose power distributions peak sharply with narrow bandwidth.
Halogen lamps (also known, more correctly, as tungsten halogen lamps) are a development of incandescent Lamps with a higher colour temperature and a smooth power distribution curve across the spectrum, extending well into the near infra-red.
Fluorescent light sources also produce nomanally white light and have broadband power distribution characteristics, which, in comparison with those of an incandescent source, tend more towards the bluer region of the visible spectrum, often with a significant ultra-violet component, and a number of peaks ii their spectral power distribution. Typical colour temperatures for such lighting are in the region of 3200” to 5500”K. The physical structure of a fluorescent lamp is that of a tube which can be formed into various shapes, and an annular shape concentric with the optical axis of a reading device provides veiy satisfactory uniform diffuse illumination.
Light emitting diodes with nominally “while light” characteristics emit “cool” white light and may have a nominal colour temperature in the region of 7000” K. Their actu spectral distnbution may show a number of peaks e.g. in the blue and yellow cm orange regions.
Gas discharge lamps tend to have spectral distributions with multiple sharp peaks at wavelengths depending on the precise mixture of gases used. For example, sodium vapour emits light with a well-defined peak at around 580 nm (yellow-orange) and mercury vapour emits a green-blue light at around 520 nm.
The use of fIlters to modify the spectral distribution of the illumination system is common. For example, when used in conjunction with a Wratten 26 filter, the light characteristics of a 2856”K tamp approximate to those of a 620-633 nm source. The use of infra-red andlor ultra-violet absorbing filters is also common in scanning systems. It is possible to alter the apparent colour temperature of a source by the use of filters.