Welch Allyn Scanteam 6180, Technical Manual

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2–3
Operational Description
Large aperture systems typically cannot resolve high density bar code or
the small printing features (voids within bars or dark specs within the light
areas) that small aperture systems would. Thus, they are more compatible
with low density bar code and more tolerant of printing defects
characteristic of poorly printed labels.
Small aperture systems (high resolution) are better able to resolve which
makes them compatible with high density good quality symbol reading
requirements.
The SCANTEAM 6180 is available with circular apertures ranging from 6
to 10 mil.
Most scanning applications can be satisfied with a 6 mil (high resolution)
or a 10 mil (low resolution) aperture. When selecting an aperture, it is
recommended that the aperture dimension be no less than 0.7 times the “X”
(width of the narrowest bar code coding element) dimension to be read.
An aperture size that is slightly smaller than the narrowest bar code
element, 0.9 times “X,” provides optimum resolution of the bars and results
in the generation of a digital signal which accurately represents the bar
code. An 8 mil (0.2mm) aperture is often a good compromise when labels
produced by different printing and label generation methods must be read
with one scanner. In no case should the viewing aperture exceed 1.2 the
“X” dimension.
Figure 2.1 Aperture and Depth of Field
2.4.3 Depth of Field
Depth of field is the maximum perpendicular distance from the scanner tip
to the bar code symbol surface at which the scanner is capable of operating
effectively. In general, most of the SCANTEAM 6180 scanners have a
depth of field of 0.065 inches (1.65mm) with a symbol appropriate for the
scanner.