Barcode recognition principle brief introduction

Because different colors of the object, its reflected visible light wavelength is different, white object can reflect a variety of wavelengths of visible light, black object absorbs a variety of wavelengths of visible light, so when the bar code scanner light source issued by the diaphragm and convex lens 1, irradiated to the black and white bar code, the reflected light is focused by convex lens 2, irradiated to the photoelectric converter, So the photoelectric converter receives the reflected light signal which is different from the corresponding strength of the white bar and the black bar, and converts it into the corresponding electrical signal and outputs it to the amplifier shaping circuit.

What is the principle of barcode recognition

The duration of the electrical signal varies with the width of the white bar and the black bar. However, the electrical signal output by the photoelectric converter and the bar code and space corresponding to the bar code is generally only about 10mV, can not be used directly, so the electrical signal output by the photoelectric converter must be sent to the amplifier for amplification.

The amplified electrical signal is still an analog electrical signal. In order to avoid the defects and stains in the bar code leading to the wrong signal, a shaper circuit needs to be added after the amplified circuit to convert the analog signal into a digital electrical signal, so that the computer system can accurately interpret it.

The pulse digital signal of shaping circuit is translated into digital and character information by decoder. It identifies the code system and scanning direction of bar code symbols by identifying the beginning and end characters. By measuring the number of pulse digital signal 0, 1 to distinguish the number of bars and Spaces. The width of the bar and space is determined by measuring the duration of 0 and 1 signals.

In this way, the number of bar code symbols and the corresponding width and the code system, according to the code system of the corresponding coding rules, the bar symbol can be changed into the corresponding number, character information, through the interface circuit to the computer system for data processing and management, it completes the whole process of bar code reading.