REA MLV-2D, Руководство по эксплуатации

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REA VERIFIER
© REA Elektronik GmbH, 64367 Mühltal, Germany --- REA MLV-2D Manual Version 3 – 21/12/2015 Page 88 of 98
Other verification criteria
Measurement
parameter Unit Tolerance Reference
Symbol contrast % +/- 8%
(calculated from
Rmax and
Rmin) Measurement
values on the
stamped
reference
verification
report
Modulation Degree +/- 0
Module size µm +/- 5 µm
Print growth µm +/- 10 µm
12.2 Calibration for white and red light
Only one verification report with reference results is included with the calibration card.
These results are created using red light with a REA reference machine during
production.
If white light will be used for measurement and white light measurement should also
be calibrated, then the check process described in section 12.1 is executed. In this
case, the reference is also the verification report created by using red light. This
simplification is possible because, whichever lighting type is used, black and white
must return REA calibration card reflectance values that are within the permissible
device tolerances. The applicability of this method has been crosschecked with
reflectance standards (calibrated barium sulphate standards) exhibiting all reflectance
measured values from blue to red (light wavelengths of approx. 400 to 700 nm).
13 Synthetic aperture/measurement aperture
The term "aperture" is usually understood to refer to the aperture of a camera lens.
This is not the case in this context. The aperture of the lens in the REA MLV-2D is
given a factory-set preset that achieves the best compromise between the maximum
possible depth of field and the minimum possible degree of diffraction.
The synthetic aperture simulates the spot of light from a laser scanner. This is
achieved via the mathematical filtering of the recorded measurement image. The
measurement results may vary, depending on the aperture used in code verification.
The synthetic aperture is always automatically set to 80% of the module width of the
verified 2D matrix codes.
Alternatively, the synthetic aperture can also be set manually.
From the perspective of image processing, the synthetic aperture is an optical filter
that produces a degree of blurring. This is advisable for suppressing distortions in the
image at the small/tiny scale and thus not relevant for verification.
Symbols that exhibit many distortions can disrupt the automatic calculation of the
synthetic aperture. If this is the case, the measurement results may vary or invalid
measurements may be made. In such cases, manual determination of the synthetic
aperture is recommended (based on the assumption that the symbols always have the
same module size).