Bar code technology was first produced in the trembling twenties, and it was born in the laboratory of Westinghouse. A man named John

Kermode, an eccentric inventor, wants to realize automatic sorting of postal documents in a whimsical way. At that time, every application of electronic technology

Every idea is very novel.

His idea is to put a barcode on the envelope, and the information in the barcode is the address of the recipient, just like today's postal code. for this reason

Kermode invented the earliest bar code recognition, and the design scheme is very simple (note: this method is called module comparison method), which is a "bar"

Represents the number "1", two bars represent the number "2", and so on. Then, he invented the bar code recognition composed of basic components.

Reading equipment: scanner (capable of emitting light and receiving reflected light); A method for measuring the band and space of reflected signal, namely edge positioning coil;

And a method of using the measurement result, namely a decoder.

Kermode's scanner uses a newly invented photocell to collect reflected light. "Empty" reflects a strong signal, "bar"

The reflected signal is a weak signal. Unlike the high-speed application of electronic components today, Kermode uses magnetic coils to measure the sum of "bars".

"Empty" is like a child connecting a wire to a battery and winding it around a nail to hold paper. Kermode is received by a coil with an iron core.

Close the switch when receiving the "empty" signal, and release the switch when receiving the "bar" signal to connect the circuit. Therefore, the most

Early bar code readers were very noisy. The switch is controlled by a series of relays, and the "on" and "off" are determined by the number of "strips" printed on the envelope.

Decide. In this way, the bar code symbol directly sorts the letters.

Shortly thereafter, Douglas Young, Kermode's collaborator, made some improvements on the basis of Kermode code.

Kermode code contains so little information that it is difficult to compile more than ten different codes. And the young code is used less.

However, the space size between bars varies, just as UPC bar code symbols today use four different space sizes. New bar code symbol

One hundred different regions can be encoded in the same space, while Kermode code can only encode ten different regions.

It was not until 1949 that the omni-directional bar code symbols invented by Noam Woodland and Bernard Silver first appeared.

No, there is no record of barcode technology in the patent literature before this, and there is no precedent for putting it into practical application. standard

The idea of Woodland and Bemard Silver is to use Kermode and YOung's vertical "strips" and "spaces" and bend them into a ring.

Much like an archery target. In this way, the scanner can decode the bar code symbol by scanning the center of the graph, regardless of the direction of the bar code symbol.

Toward.

In the process of continuous improvement by using this patented technology, science fiction writer Isaac Azimov wrote in his Naked.

The book "Exposed Sun" tells an example of automatic identification by using a new information coding method. At that time, people thought that the bar code symbols in this book

This number looks like a chessboard in Fang Gezi, but today's bar code professionals will immediately realize that it is a two-dimensional matrix bar code symbol.

Number. Although this bar code symbol has no direction, no positioning and no timing, it is obvious that it represents a digital code with high information density.

It was not until 1970 that Iterface Mechanisms developed a "two-dimensional code" and obtained a two-dimensional moment with a price suitable for sale.

Array bar code printing and reading equipment. At that time, two-dimensional matrix bar code was used to realize the automation of newspaper typesetting process. Two-dimensional matrix bar code printed on paper tape

In fact, it was scanned and read by today's one-dimensional CCD scanner. The light emitted by CCD shines on the paper tape, and each photocell is aimed at different areas of the paper tape. each

Photovoltaic cells output different patterns according to whether the bar code is printed on paper tape or not, and combine them to generate high-density information patterns. In this way, it can be used in the phase.

Print a single character in the same size space as a single bar in the early Kermode code. Also includes timing information,

So the whole process is reasonable. When the first system entered the market, the price of the whole set of equipment including printing and reading equipment was about $5,000.

Yuan.

Shortly thereafter, with the continuous development of LED (light emitting diode), microprocessor and laser diode, new symbols (

Symbolism) and the big explosion of its application, people call it "bar code industry". Today, it is rare to find a fast and accurate bar without direct contact.

Code technology companies or individuals. Because of the rapid technological progress and development in this field, there are more and more application fields every day.

Developed, it won't be long before bar codes will be as popular as light bulbs and transistor radios, making everyone's life more.

Increase ease and convenience.

Bar code recognition principle

To convert the bar code compiled according to certain rules into meaningful information, it needs to go through two processes: scanning and decoding. target

The color of is determined by the type of light it reflects. White objects can reflect various wavelengths of visible light, while black objects can absorb various wavelengths of visible light.

See the light, so when the light from the light source in barcode scanner is reflected on the bar code, the reflected light illuminates the photoelectric conversion inside barcode scanner.

On this device, the photoelectric converter converts reflected light signals with different intensities into corresponding electrical signals. According to different principles, scanners can be divided into

There are three kinds: light pen, CCD and laser. The electric signal is output to the amplification circuit of barcode scanner, and then sent to the shaping circuit to simulate the signal.

The signal is converted 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 measures

The number of bars and spaces can be determined by the number of pulse digital electrical signals 0, 1, and the width of bars and spaces can be determined by measuring the duration of signals 0, 1.

Degree. The data obtained at this time is still quite confusing. If you want to know the information contained in the bar code, you need to follow the corresponding coding rules (for example

E.g., EAN-8 code), and the bar code symbols are replaced by corresponding numerical and character information. Finally, the data is processed and managed by the computer system.

Identify the details of the product.

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 relatively simple optical scanning.

Instrument, 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 form an identification system to realize automatic identification, and can also be combined with

Connect other control devices to realize the automatic management of the whole system.

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 converts the brightness of the reflected light into a digital signal. No matter what rules are adopted to print bar codes, they are all composed of dead zones, initial characters, data

Characters and terminating 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 that static code analysis has ended, and it is also a check table.

The role of 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. bar code

There are three kinds of scanners: light pen, CCD and laser.

▲ 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

So as to 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.

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".

Enter ".

B high reliability: the error rate of keyboard input data is 300%, and the error rate of optical character recognition technology is110000.

The error rate of barcode technology is less than one in a million.

C. A large amount of information is collected: the traditional one-dimensional bar code can collect dozens of characters at a time, and the two-dimensional bar code is more portable.

Has thousands of characters of information, and has a certain ability of automatic error correction.

D. Flexible and practical: Bar code identification can be used as a means of identification alone or in combination with related identification equipment.

The system realizes automatic identification, and can also be connected with other control devices 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.

Training, and equipment is relatively cheap.