REA
VERIFIER
© REA Elektronik GmbH, 64367 Mühltal, Germany --- REA MLV-2D Manual Version 3 – 21/12/2015
Page 57 of 98
9.5
Print gain / growth
Print gain is shown graphically for the x- and y-axis.
The value -118 is the lower limit value, 70 is the upper limit value and -24 is the
arithmetical mean for print gain. In the ideal case, all values would be zero
(unattainable in practice). All values are reported in microns (µm)
There are no defined tolerances for module widths for the Data Matrix code and other
similar matrix symbologies. The limits of the permissible have been reached if the
module is identified as black rather than white or vice versa, or if modulation is
classified as too low.
9.6
Histogram
There are two histograms. One is valid for the image once it has been filtered through
the synthetic aperture (standard criterion). The other histogram relates to the original
image captured.
Figure: Original histogram
Figure: Reflectance histogram
In both histograms, the y-axis plots the number of pixels while the x-axis plots the
reflectance in per cent. The higher the curve in relation to the y-axis, the more pixels
have the corresponding reflectance. Ideally, the curve should have the contours of a
bathtub slit down the middle.
In the grayscale histogram, Rmin and Rmax produce the symbol contrast as SC = Rmax-Rmin.
ROB and ROW represent the highest and lowest reflectance in the unfiltered original image (OB
= Original Black, OW = Original White). The Global Threshold (GT Decod.) is the point at which
the system evaluates which grey pixels are to be regarded as light and which as dark.
