Barcode scanning

4. Barcode scanning

Barcode scanning requires a scanner. The scanner uses its own light source to illuminate the barcode, and then uses the photoelectric converter to receive the reflected light, and converts the brightness of the reflected light into a digital signal. No matter what kind of rules are used to print bar codes, they are composed of dead zone, start character, data character and end character. Some barcodes have check characters between the data characters and the termination characters.

â–² Quiet zone: As the name suggests, an area that does not carry any information serves as a reminder.

â–² Starting character: The first character has a special structure. When the scanner reads the character, it starts to read the code formally.

â–² Data characters: the main content of the barcode.

â–² Check character: check whether the read data is correct. Different coding rules may have different verification rules.

â–² Termination character: The last character also has a special structure, which is used to notify the code that scanning is completed, and at the same time, it also plays the role of just performing verification calculation.

To facilitate two-way scanning, the start and stop characters have an asymmetric structure. Therefore, the scanner can automatically rearrange the barcode information when scanning. There are three types of barcode scanners: light pen, CCD and laser

â–² Light pen: The most primitive scanning method, you need to manually move the light pen, and also need to contact with the barcode.

â–² CCD: Use CCD as the photoelectric converter and LED as the light source scanner. Within a certain range, automatic scanning can be achieved. In addition, it can read various materials and barcodes on uneven surfaces, and the cost is relatively low. However, compared with the laser type, the scanning distance is shorter.

â–² Laser: A scanner that uses laser as a light source. It can be divided into linear type, full angle and so on.

Linear type: mostly used for handheld scanners, with long range and high accuracy.

Full angle: mostly horizontal, with high degree of automation, and can automatically read barcodes in various directions

Five, the advantages of bar code technology

Barcode is by far the most economical and practical automatic identification technology. Barcode technology has the following advantages

A. Fast input speed: Compared with keyboard input, barcode input speed is 5 times faster than keyboard input, and it can realize "instant data input".

B. High reliability: The error rate of keyboard input data is one third, the error rate using optical character recognition technology is one in 10,000, and the error rate using barcode technology is less than one in one million.

C. Large amount of collected information: The traditional one-dimensional barcode can collect information of tens of characters at a time, and the two-dimensional barcode can carry information of thousands of characters, and has certain automatic error correction capabilities.

D. Flexible and practical: Bar code identification can be used alone as a means of identification, or it can form a system with related identification devices to realize automatic identification, and can also be connected with other control devices to achieve automatic management.

In addition, bar code labels are easy to make, there are no special requirements for equipment and materials, identification equipment is easy to operate, no special training is required, and the equipment is relatively cheap.

6. Barcode encoding rules

Uniqueness: products of the same specification and the same type correspond to the same product code, and different specifications of the same product should correspond to different product codes. According to the different properties of the product, such as: weight, packaging, specifications, smell, color, shape, etc., give different commodity codes.

Permanent: Once the product code is assigned, it will not be changed and it will be life-long. When such products are no longer produced, their corresponding product codes can only be put on hold, and they cannot be reused and then distributed to other commodities.

Meaningless: In order to ensure that the code has enough capacity to meet the needs of frequent product replacement, it is best to use a meaningless sequence code.

Barcode verification code formula:

1. First, serialize the barcodes from right to left in sequence as "... 4, 3, 2, 1." Starting from serial number two, add and sum all the numbers on the even-numbered digits, multiply 3 Then, starting from the serial number three, sum all the numbers on the odd serial numbers, add the product of the sum of the numbers on the even serial numbers and multiply by 3, and then get the sum. Then subtract the sum by the smallest multiple of 10 greater than this sum to get the check code.

for example:

The barcode is X (X is the check code).

1. 1 + 6 + 2 + 7 + 1 + 7 = 24

2. 24 × 3 = 72

3. 0 + 1 + 1 + 6 + 7 + 9 = 24

4. 72 + 24 = 96

5, 100-96 = 4

So the final check code X = 4. The barcode is 9771671216014.