NLS-Glossary

A fixed scanner (used at supermarket checkouts) which can read bar code symbols at any angle in a plane parallel to or near parallel to the scanner window. Flat bed scanners are typically capable of reading bar code symbols from many different orientations. The term “Omni-Directional” scanning is referred to with this type of scanner.

The focal length is the distance from the Image side principal plane to the image of objects at infinity. For single lenses in air that is equal to the distance from the first focal point to the first principal point.
The larger the focal length, the smaller the aperture angle of the lens and the smaller the object section that is displayed full-frame on the sensor. The smaller the focal length, the larger the aperture angle of the lens and the larger the object section which is displayed full-frame on the sensor.

A full permutation symmetry exists when all of the frequencies contained in a susceptibility are far away from any resonance frequencies of a material so that the material causes no loss or gain to the optical field at those frequencies.

Function (FNC) codes define instructions for a bar code reader decoding Code 128 bar codes. FNC 1, for example, is a required component of the UCC-128 specification. FNC 2 tells the reader to store the data read and transmit it with the next symbol. FNC 3 is reserved for code reader intializing and other reader functions. FNC 4 is reserved for future use.

The distance between the imaginary grid lines that form the spacing baseline of a PosiCode symbol. The bars are centered on these grid lines, and the data is encoded by using the width of the spaces between bars.

Its working substance is gas. Now there are various kinds of gas atoms, ions, metal vapor, gas molecular lasers. Commonly used are carbon dioxide laser, helium neon laser and carbon monoxide laser, whose shape is like a common discharge tube, characterized by stable output, good monochromaticity, long life, but small power, low conversion efficiency.