Siemens SIMATIC MV500 Operating Instructions Manual page 57

Note
Orientation of the code to be verified
The verification according to ISO/IEC 29158 uses an algorithm for quality calculation to
connect the separate code cells typically generated in the image when using the DPM
method. This algorithm requires the code to be aligned parallel to the borders of the image. A
twisted code can affect the quality calculation and, in extreme cases, even result in
verification errors.
Quality parameters
• Axial non-uniformity:
Difference between the height and width relative to the rows and columns.
• Cell contrast:
Measure of the uniformity of the average reflectance of the light pixels and the dark
pixels. This corresponds to "symbol contrast" according to ISO/IEC 15415, however with
different details in the implementation.
• Cell modulation:
Measurement of the uniformity of the reflectance of the dark and light areas of the data
matrix. Similar to "Modulation" according to ISO/IEC 15415, however with different details
in the implementation and lower limits for the quality levels.
• L/F fixed pattern damage:
Measure of the errors in the borders of the data matrix and all errors in the quiet zone
around the code necessary for decoding.
• Grid non-uniformity:
This is the deviation of the measured grid relative to the ideal grid starting from the four
corners of a data matrix.
• Minimum reflectance:
The lowest reflectance of any area in the data matrix.
• Reference decode:
Based on a binary image of the code according to ISO/IEC 16022:2006, a code is decoded
using the decoder described in the data matrix standard. If the code can be successfully
decoded, the quality grade "4" is assigned; if not, the quality grade "0".
• Unused error correction:
Proportion of error correction information not used for correction of the read result.
• Print growth:
Positive or negative size ratio of the printed cells relative to the ideal grid. Calculated only
as a reference.
SIMATIC MV500
Operating Instructions, 03/2021, C79000-G8976-C494-05
Image processing
3.2 Code verification
57