Siemens SIMATIC MV420, Руководство по эксплуатации

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Image processing
4.2 Code verification
SIMATIC MV420 / SIMATIC MV440
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Operating Instructions, 04/2013, A5E02371045-06
4.2.5 Barcode verification
The principles underlying barcode verification are similar to those of data matrix verification.
These principles are, however, diversified to make full use of the characteristics of one-
dimensional barcodes.
ISO/IEC 15416
The code is scanned in several parallel scan lines to obtain a reliable measured value for the
marking quality of a barcode.
Each scan line has its own set of quality grades and the lowest of these decides the overall
quality grade of the reflectance profile of the scan line. The average value of the quality
values of the reflectance profile is the overall quality grade of the code.
The reader uses ten scan lines that result in individual results for each of the following quality
parameters.
Quality parameters
● Scan grade:
Lowest grade of all characteristics of the reflectance profile for a scan line.
● Edge determination:
Clarity of the identification of element edges in the scan reflectance profile.
● Reference decode:
A symbology reference algorithm is used to decode based on the edge detection.
● Maximum reflectance:
Percentage of the reflectance of the lightest gap.
● Minimum edge contrast:
Lowest value of the edge contrast. The edge contrast is the difference between the bar
reflectance and the gap reflectance of two adjacent elements.
● Minimum reflectance:
Percentage of the reflectance of the darkest bar.
● Symbol contrast:
Difference between the maximum and minimum reflectance.
● Decodability:
The proportion of the available surrounding space (between the ideal dimension of an
element or a combination of elements and the relevant reference threshold value) that is
not used by the element or the combination of elements. The ratio is calculated for the
element or the combination of elements that deviates most from the ideal dimension.