Rockwell Automation 2755 High Performance VLD Scanner - Manual (Page 51)

Glossary G–3
Depth of Field
The distance between the maximum and minimum reading distances
where a symbol can be read.
Diffuse Reflection
Reflection of light in all directions. Diffuse reflection occurs from
non-glossy surfaces. See specular reflection.
Dirt
In paper, refers to the presence of relatively non-reflective foreign
particles embedded in the sheet. The size and lack of reflectance of
the particles may cause the optical scanner to mistake the dirt for
inked areas (i.e. paper noise).
Discrete Code
A bar code or symbol that contains spaces between the encoded
characters, i.e. intercharacter gap. Code 39 is an example of a
discrete bar code symbol. See continuous code.
Diverging Beam
A beam of light that is optically controlled so the light extends in
different directions from the source.
Element
Any bar or space in a bar code symbol.
Encoded Area
The total linear dimension consisting of all the characters of a code
pattern, including start/stop characters and data.
Extraneous Ink
Ink in a scan area not intended to be there.
Guard Bars
Bars at the ends and center of a UPC and EAN symbol. They ensure
a complete scan of the bar code.
Height of Scan
The maximum vertical scanning dimension of a moving beam
scanner at a specific distance from the face of the scanner.
Intercharacter Gap
The space between two adjacent bar code characters. For example,
the white space between two characters in AIM USS-39.
LED
Light emitting diode.