The percentage of the light background accounted for by the difference between the bars and spaces. PCS was defined
as a measure of contrast the human eye perceives long before and outside the context of measuring barcode contrast.
The measurement is made relative to the brightness of the background. The fact that it is relative to the background
means that the darker (worse) the background color is, the higher (supposedly better) the value of PCS. Scanners are
sensitive to the absolute difference between the reflectance of bars and spaces. Scanners are especially sensitive to
variations in contrast within the same scan.
MRD
Minimum Reflectance Difference (MRD) quantifies the minimum difference anywhere across the barcode. MRD
considers the brightest (worst) bar and the darkest (worst) space anywhere in the barcode. These worst-case bar and
space are not necessary adjacent to one another.
ISO/IEC 15416 (ANSI x3.182) Grading Parameters
The ANSI parameters section lists each of the nine ANSI parameters and gives a summary of the measurements based
on all scans taken. For a review of the ANSI process given on each of your codes, check the ANSI Matrix for each code
described below.
Note
: Some of these parameters are average values over all of the scans, and the averages can skew or alter the
apparent results.
The descriptions of each parameter explain what is measured in the case where a barcode is read and not read. When a
code is not read, the scan is analyzed for apparent quiet zones and the bars and spaces in between are used for the
ANSI analysis.
1.
EDGE: Edge Determination
Checks if the edge between bar and space can be detected and no false bars or spaces appear due to “splitting”
of bars or ink splattered into spaces. If at least one scan results in a decoded barcode, the EDGE value is the
number of bars and spaces, not including quiet zones, in the code. If no scans result in a decoded barcode, the
EDGE value shown is the number of bars and spaces found between quiet zones or apparent quiet zones on the
scan on which the most bars and spaces were found. The Scan Reflectance Profile graph can also help in
analyzing a code that cannot be decoded.
2.
Rl/RD: Minimum Reflectance
Checks if the darkness of the bars is sufficient. The amount of light reflected by the bars (bar reflectance) must be
less than half the light reflected by the spaces (space reflectance). The values shown are the light reflectance and
the dark element reflectance separated by a slash. The light reflectance is the maximum reflectivity found in the
scan (lightest or best space), and the dark reflectivity is the minimum reflectivity found in the scan (darkest or best
bar). The requirement is for the minimum reflectivity to be no more than half the maximum reflectivity. If this
requirement is met, the grade is A, otherwise it is F.
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Grading Standards and their Parameters