To convert the bar code compiled according to certain rules into meaningful information, it needs to go through two processes: scanning and decoding. The color of an object is determined by the type of light it reflects. White objects can reflect various wavelengths of visible light, while black objects absorb various wavelengths of visible light. Therefore, when the light emitted by the light source of the barcode scanner is reflected on the barcode, the reflected light shines on the photoelectric converter inside the barcode scanner, and the photoelectric converter converts it into corresponding electrical signals according to the reflected light signals with different intensities. According to different principles, scanners can be divided into three types: light pen, CCD and laser. The electrical signal is output to the amplification circuit of the barcode scanner to enhance the signal, and then sent to the shaping circuit to convert the analog signal into a digital signal. The widths of white bars and black bars are different, and the duration of corresponding electrical signals is also different. Then, the decoder determines the number of bars and spaces by measuring the number of pulse digital electrical signals 0 and 1. By measuring the duration of 0, 1 signal, the width of bars and spaces can be judged. The data obtained at this time is still quite confusing. In order to know the information contained in bar code, it is necessary to convert bar code symbols into corresponding digital and character information according to the corresponding coding rules (such as EAN-8 code). Finally, the detailed information of the article is identified by the computer system, and the data is processed and managed.
[Edit this paragraph] III. Advantages of barcode
1. Strong reliability. The reading accuracy of bar code far exceeds manual recording, and an error will appear every 15000 characters on average.
2. High efficiency. The reading speed of bar code is very fast, which is equivalent to 40 characters per second.
3. Low cost. Compared with other automatic identification technologies, barcode technology only needs a small sticker and a relatively simple optical scanner, and the cost is quite low.
4. Easy to make. Bar code writing is very simple, just need to print, so it is called "printable computer language".
5. Simple operation. Bar code recognition equipment is simple in structure and convenient to use.
6. Flexible and practical. Bar code symbols can be input by manual keyboard, can also be combined with related equipment to realize automatic identification, and can also be linked with other control equipment to realize automatic management of the whole system.
[Edit this paragraph] 4. Bar code scanning
The scanning of bar code needs a scanner. The scanner uses its own light source to illuminate the bar code, and then uses a photoelectric converter to receive the reflected light and convert the brightness of the reflected light into a digital signal. No matter what rules are adopted to print bar codes, they are composed of dead zones, start characters, data characters and end characters. Some barcodes also have a check character between the data character and the termination character.
▲ Quiet zone: As the name implies, an area that does not carry any information plays a prompting role.
▲ Start character: the first character with special structure. When the scanner reads this character, it begins to read the code formally.
▲ Data characters: the main content of bar code.
▲ Check the characters: check whether the read data is correct. Different coding rules may have different checking rules.
▲ Termination character: the last character, which is also a special structure, is used to inform the end of static code analysis, and also plays a role in checking calculation.
In order to facilitate bidirectional scanning, the start and stop characters have asymmetric structures. Therefore, the scanner can automatically rearrange the barcode information when scanning. There are three kinds of light pen, CCD and laser in barcode scanner.
▲ light pen: the most primitive scanning method requires manual movement of the light pen and contact with the bar code.
▲CCD: scanner with CCD as photoelectric converter and LED as light source. In a certain range, automatic scanning can be realized. And can read bar codes on various materials and uneven surfaces, and the cost is relatively low. But the scanning distance is shorter than that of the laser type.
▲ Laser: a scanner with laser as the light source. It can also be divided into linear, full angle and so on.
Linetype: mostly used for hand-held scanners, with long action distance and high precision.
All angles: mostly horizontal, with high degree of automation, which can automatically read bar codes in all directions.
[Edit this paragraph] V. Advantages of barcode technology
Bar code is by far the most economical and practical automatic identification technology. Bar code technology has the following advantages.
A. Fast input speed: Compared with keyboard input, bar code input speed is five times that of keyboard input, which can realize "instant data input".
B High reliability: the error rate of keyboard input data is 300%, the error rate of optical character recognition technology is110000, and the error rate of barcode technology is less than110000.
C. The amount of information collected is large: the traditional one-dimensional bar code can collect dozens of characters at a time, and the two-dimensional bar code can carry thousands of characters, and it has certain automatic error correction ability.
D. Flexible and practical: Bar code identification can be used as a means of identification alone, can also be combined with related identification equipment to realize automatic identification, and can also be connected with other control equipment to realize automatic management.
In addition, the bar code label is simple to make, has no special requirements for equipment and materials, and the identification equipment is simple to operate without special training, and the equipment is relatively cheap.