Cognex DataMan Communications And Programming Manual page 43

Property
gridNonUniformity
extremeReflectance
Type 1D Standards
Metric
Metric
43
DataMan Application Development
2D Standards
ISO/IEC 15415
(DataMatrix, QR,
DotCode), AIM/DPM
ISO/IEC TR-29158
(DataMatrix, QR)
ISO/IEC 15415
(DataMatrix, QR)
Description
The grid non-
uniformity. Grid non-
uniformity measures
the difference
between the optimal
placement of cells
based on the overall
grid and their actual
placements. This is
similar to the axial
non-uniformity
measurement, but
instead of measuring
a stretching or
compressing of the
whole grid, this
measures how much
the individual cells
deviate from their
expected positions.
Poor grid non-
uniformity usually
indicates a printing
process which is not
consistent in its
placement of the cells.
The extreme
reflectance. This
metric measures the
brightness of the
background on which
the code is printed. A
too high value might
indicate lighting or
imaging trouble that
could lead to a code
being washed out and
difficult to read. A low
value may indicate
that not enough light
is being applied to the
code, and that
contrast may be poor,
leading to difficulty in
reading. A poor
extreme reflectance
grade may also
indicate trouble
relating to the
positioning of lights
such as hotspots.