1, scanning grab principle. Due to the different wavelengths of visible light reflected by objects of different colors, white objects can reflect visible light of various wavelengths, while black objects absorb visible light of various wavelengths. When the light emitted by the light source of barcode scanner passes through the diaphragm and convex lens 1 to irradiate the black-and-white bar code, the reflected light is focused by convex lens 2 and irradiated on the photoelectric converter. Therefore, the photoelectric converter receives reflected light signals with different intensities corresponding to white bars and black bars, and converts them into corresponding electrical signals to be output to the amplification and shaping circuit. The widths of white bars and black bars are different, and the duration of corresponding electrical signals is also different. The pulse digital signal of the shaping circuit is converted into digital and character information by the decoder. The coding system and scanning direction of bar code symbols can be determined by identifying the start and end characters, and the number of bars and spaces can be determined by measuring the number of pulse digital electrical signals 0, 1. The widths of bars and spaces can be determined by measuring the duration of 0 and 1 signals. In this way, the number of bars and spaces of bar code symbols, the corresponding widths and the coding system used are obtained. According to the coding rules corresponding to the coding system, bar code symbols can be converted into corresponding digital and text information, and sent to the computer system for data processing and management through the interface circuit, thus completing the whole process of bar code recognition and reading.
2. The scanning and grabbing operation is very simple. For the bar code on the goods, the scanner will give a scanning prompt tone, and the price of the goods will appear on the computer of the cash register.