The principle of bar code recognition is that the visible light reflected by objects of different colors has different wavelengths, so when the light emitted by the light source of barcode scanner passes through the diaphragm and convex lens, it shines on the photoelectric converter, so the photoelectric converter receives the 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, which converts analog signals into digital electrical signals, and then translates them into digital character information through the decoding interface circuit.

The widths of white bars and black bars are different, so the duration of corresponding electrical signals is also different. However, the electrical signal corresponding to the bar code and space output by photoelectric converter is generally only about 10mV, so it cannot be used directly. Therefore, the electrical signal output by the photoelectric converter should be sent to the amplifier for amplification first.

The amplified electrical signal is still analog. In order to avoid false signals caused by defects and stains in bar codes, it is necessary to add a shaping circuit after the amplification circuit to convert analog signals into digital electrical signals so that the computer system can accurately interpret them.

Extended data

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, which 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.