Fixed/Variable Length
Some symbologies can encode only certain length of data. For example,
UPC only accepts 11 digits and Code39 encodes any length of data.
X Dimension
X dimension describes the nominal width of the narrowest elements (both
bars and spaces). For 2D matrix symbologies, X refers to the nominal
dimension of the smallest data cell.
The X dimension largely decides the barcode density ( how many
characters can be encoded in one inch). The resolution of a barcode readers
is also measured by the X-dimension that the reader can recognize. A high
resolution barcode scanner can recognize a barcode with X dimension at 5
mils.
The barcode symbols in an open system usually have a X dimension equal
to 10 mils.
Wide-to-Narrow Ratio (N)
Most linear symbologies employs two widths, one for the wide element and
one for narrow element. The ratio between the wide element and the narrow
element is called N. N typically have a value ranging from 2.0 to 3.0. The
large the N is, the allowable printing tolerance increases. N also slightly
impact the density of a symbol.
Self-Checking
If a single printing defect will not cause a character to be recognized
as another one, the symbology is regarded as self-checking. A
non-self-checking symbology usually has a check character to make sure that
the error is detected.
Start/Stop Character
Start/Stop character is placed to indicate where the barcode symbol
starts and ends. It also indicates the scanning direction in some
symbologies
Quiet Zone
Quiet zone refers to the spaces around the barcode that must
contains no dark marks. Most of symbology requires quiet zone preceding and
following barcode. |
