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depth of field: The range of distances over which a scanner can reliably read a
symbol of given characteristics. Equal to the range of the scanner minus its
optical throw.
discrete bar code symbol: A symbology in which the spaces between symbol
characters (intercharacter gaps) do not contain information as each character
begins and ends with a bar. Compare to “continuous code.”
EAN: Abbreviation for EAN International. Also used to refer to the bar code
symbology used for marking of consumer products in accordance with this body's
specifications.
EAN/UPC: A fixed-length, numeric 13-digit bar code symbol consisting of 30
dark elements and 29 intervening light elements. Each character is represented
by 2 bars and 2 spaces over 7 modules. A bar may be comprised of 1, 2, 3, or 4
modules. Each EAN/UPC symbol consists of a leading quiet zone, a start
pattern, seven left-hand data characters, a center bar pattern, 5 right-hand data
characters, a Modulo 10 check character, a stop pattern, and a trailing quiet
zone. U.P.C. is often considered a 12-digit code. The 13th digit of EAN/UPC
symbol is a derived character in the left most position. In the case of UPC this
derived left-most character is a 0. See appropriate ISO/IEC JTC 1/SC 31
reference, when available.
edge contrast (EC): The difference between bar reflectance (R
b
) and space
reflectance (R
s
) of two adjacent elements.
effective aperture: The apparent field of view of a scanner or similar device
determined by the smaller of the spot size and the physical aperture of the
scanner for reception of reflected light.
element: A single bar or space in bar code or multi-row symbologies or a single
cell in matrix symbologies.
element edge: The location where the scan reflectance profile intersects the
midpoint between the space reflectance (R
s
) and bar reflectance (R
b
) of
adjoining elements. Visual measuring techniques will generally locate the
element edge closer to the center of the bar.
element reflectance non-uniformity (ERN): The reflectance difference
between the highest peak and the lowest valley in a profile of an individual
element or quiet zone.
element width: The thickness of an element measured from the leading edge of
an element to the trailing edge of the same element. See "X dimension.”
extended ASCII: An extended code set encoded in 8 bits giving values from 0
to 255 in accordance with ISO standard 8859.
eye-readable character: See “human-readable character.”
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