Panasonic IMAGECHECKER PV230 Manual page 79

Detailed item
Modulation
Unused Error
Correction
Contrast
Fixed Pattern Damage
Decode
Description
To evaluate the variation in the contrast of data parts (contents to be
decoded) in a 2D code.
If the contrast of the data parts is not clear for some reason such as ink
bleed, it may be judged as a flaw that is too large to be corrected with the
correction function of 2D code, and it may not be read. This item is to
control the contrast of data parts to prevent a reading failure from being
caused by bad printing conditions. The formula to calculate modulation is
as follows.
Modulation Mod = 2*(ABS(R-GT)) /SC
R: Grayscale value that is the closest to GT in data parts.
GT: Global threshold: (Max. luminance + Min. luminance)/2
SC: Contrast of fixed patterns (L-shaped alignment pattern,
Alignment pattern with a clock which bright cells and dark cells
are alternately arrayed or position detection pattern (3 points))
[Values in quality inspection]
Modulation 4 : Mod ≧ 0.50
Modulation 3 : Mod ≧ 0.40
Modulation 2 : Mod ≧ 0.30
Modulation 1 : Mod ≧ 0.20
Modulation : Mod ＜ 0.20
The left Data Matrix is composed of four Data Matrixes
to be one 2D code. The modulation evaluates these
four matrixes individually, and outputs the one with the
lowest contrast. (The upper right part in the left figure)
To evaluate the ratio of unused error corrections.
To evaluate the difference between the maximum and minimum luminance
in fixed patterns. If the contrast of fixed patterns is not clear, an
segmentation (position detection) error in 2D code occurs. This item is to
control the contrast of fixed patterns to prevent a segmentation error.
Fixed pattern
Data Matrix: L-shaped alignment pattern, Alignment pattern with a
clock which bright cells and dark cells are alternately arrayed
QR Code: Position detection pattern (3 points)
When Max. luminance is Rmax and Min. luminance is Rmin, it calculates
the rate of the difference between the luminance (Rmax-Rmin) regarding
the variation of 255 as 100% (1), and rates it on a scale of 0 to 4.
Rate of difference in luminance (SC) = (Rmax-Rmin)/255
Contrast 4 : SC ≧ 0.70
Contrast 3 : SC ≧ 0.55
Contrast 2 : SC ≧ 0.40
Contrast 1 : SC ≧ 0.20
Contrast 0 : SC ＜ 0.20
To evaluate the degree of damage of a fixed pattern, finder pattern, clock
pattern or quiet zone.
To evaluate whether decoding succeeded or failed.
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