Tue Jun 14 14:50:50 CST 2022
Several principles of common barcode scanners
Usually, when we buy things in the supermarket and pay the bill, the price scanned by the salesperson is the wifi barcode scanner. The scanner uses its own light source to irradiate the barcode, and then uses the photoelectric converter to receive the reflected light, and converts the light and shade of the reflected light into digital signals. No matter what kind of rule is adopted, the barcode is composed of dead zone, start character, data character and end character. Some barcodes have check characters between data characters and termination characters.
Static area: static area is also called blank area, which is divided into left blank area and right blank area. The left blank area is to make the scanning equipment ready for scanning, and the right blank area is to ensure that the scanning equipment correctly identifies the barcode end mark.
In order to prevent the left and right blank areas (quiet areas) from being occupied unintentionally during printing and typesetting, a symbol can be printed in the blank area (when there is no number on the left, <; If there is no number on the right side, add >; This symbol is called dead zone mark. The main function is to prevent the width of dead zone from being insufficient. As long as the dead zone width can be guaranteed, whether there is this symbol or not will not affect the barcode recognition.
Start character: the first character with a special structure. When the scanner reads this character, it will start to read the code formally.
Data character: the main content of barcode.
Verification character: check whether the data read is correct. Different coding rules may have different verification rules.
The termination character: the last character, also with a special structure, is used to inform the code that the scanning is completed, and at the same time, it only plays the role of verification calculation.
In order to facilitate two-way scanning, the start stop character has an asymmetric structure. Therefore, the scanner can automatically rearrange the barcode information when scanning. There are four kinds of barcode scanners: light pen, CCD, laser and image
Light pen: the most original scanning method, which requires manual movement of the light pen and contact with the barcode.
CCD: scanner with CCD as photoelectric converter and led as light source. In a certain range, automatic scanning can be realized. And can read all kinds of materials, uneven surface barcode, the cost is relatively low. But compared with laser scanning, the scanning distance is shorter.
Laser: scanner with laser as light source. It can also be divided into linear, full angle and so on.
Image: take photos with light source and decode with its own hard decoding board. Generally, image scanning can scan one-dimensional and two-dimensional barcodes at the same time.
Line type: mostly used for handheld scanners, with long range and high accuracy.
Full angle: mostly industrial fixed scanning, high degree of automation, in all directions can automatically read the barcode and output level signal, combined with the use of sensor.