Bar code technology is generated and developed in the computer application and practice of the widely used in the commercial, postal, books management, warehousing, industrial process control, a kind of automatic identification technology in the field of transportation, with input speed, high accuracy, low cost, high reliability advantages, in today's automatic identification technology plays an important role.

The concept of the barcode

Bar code is composed of a set of regularly arranged bar, empty, and the corresponding characters of tag, \"article\" means to light reflectance lower part, \"empty\" refers to the part of high light reflectivity, the article and empty data expression of certain information, and be able to use a specific device to read, convert compatible binary and decimal information with the computer. Usually for each item, its code is unique, for ordinary one-dimensional bar code, but also through database established codes and the corresponding relation of commodity information, when the bar code data to the computer, the computer application to manipulate and handle the data. Therefore, ordinary one dimensional bar code in the process of using only as identification information, its meaning is through to extract the corresponding information in the database of the computer system.

The barcode code system

Code system which refers to the barcode and empty arrangement rule, the commonly used system of one dimension code in the code include EAN code, code 39, cross 25 yards, UPC codes, 128 yards, 93 yards, and Codabar (Kurdish bar code), etc.

Different code system have their respective areas of application:

EAN code: is the international symbol system, is a kind of fixed length, bar code, the implication of the conveyed the message to all Numbers, mainly used in the labeling

: 39 yards and 128 yards to the current domestic enterprise internal custom code system, can according to need to determine the length of the bar code and information that it encoded information can be Numbers, can contain letters, mainly used in industrial production line, books management, etc

93 yards, is a kind of similar to a 39 bar code, its density is higher, can replace a 39

25 yards: as long as applied to packaging, transport and international air system ticket order no., etc

Codabar code: used in blood Banks, libraries, such as package tracking management

The composition of bar code symbol

The composition of a complete bar code sequence in the order: quiet zone (former), starting, data character, (middle separator, it is mainly used for EAN code), (calibration), terminators, quiet zone (after), as shown in figure:

Quiet area, refers to the barcode on the lateral and empty reflectivity of the same limited area, it can make the reader into a state of ready to read, when two bar code are separated by distance is close, quiet zone helps to distinguish between them and the width of the static usually should not be less than 6 mm width 10 times (or module).

Start/stop, at the beginning and end of a bar code article number and empty, marks the beginning of the barcode and end, at the same time provides the code system identification information and reading direction.

Data, article, in the middle of a bar code, the structure of the air, it contains specific information expressed by the bar code.

Constitute the basic unit of the barcode is module, the module is refers to the barcode in the narrow or empty, the width of the module is usually in mm or mil (one over one thousand of an inch). A bar or empty constitute a bar code is called a unit, a unit contains the number of modules is determined by the encoding, some code in the system, such as the EAN code, all unit consists of one or more modules. And some code system, such as code 39, all unit only two kinds of width, the wide and narrow units, the narrow unit is a module.

Several parameters of the barcode

The Density of Density (Density) : barcode refers to the unit length of bar code number of characters. For a kind of code system, the density is mainly determined by the size of the module, the module size is smaller, the greater the density, so the density value is usually expressed as a module size value to (e.g., 5 mil). The barcode below 7.5 mil usually referred to as high density barcode, above 15 mil barcode known as low density, the higher the density of the bar code, for barcode reading equipment, such as resolution) have the higher performance. High density barcode is usually used to identify small objects, such as precise electronic components, it is applied in long distance low density barcode reading occasions, such as the warehouse management.

Width than: for there are only two width unit code system, the ratio of wide and narrow units called width ratio, usually about 2-3 (commonly used a 2:1 and 3:1). Size is larger, the devices easier to distinguish between wide and narrow units, so easy to read.

Contrast (PCS) : bar code symbol of optical indicator, the greater the PSC value, the greater the optical properties of the barcode.

PCS = (RL - RD)/RL x 100%

Article (RL: reflectance RD: empty reflectivity)