Each barcode scanner has certain requirements for ambient light sources

A bar code symbol is an information symbol composed of "bar" and "empty" with different reflectances according to certain coding rules. Because the "bar" and "space" in the bar code symbol have different reflectivity to light, the bar code scanner receives reflected light signals of different strengths and weakly, and accordingly generates electric pulses with different potentials. The width of the "bar" and "empty" in the bar code symbol determines the length of the electrical pulse signal with different potential levels. The optical signal received by the scanner needs to be photoelectrically converted into an electrical signal and amplified by an amplifying circuit. Because the scanning spot has a certain size, edge ambiguity during barcode printing, and some other reasons, the electrical signal of the barcode amplified by the circuit is a smooth undulating signal, which is called an "analog electrical signal". The "analog electrical signal" needs to be shaped into the usual "digital signal". According to the coding rules corresponding to the coding system, the decoder can read and translate "digital signals" into digital and character information.

Bar code scanners are generally composed of light sources, optical lenses, scanning modules, analog-to-digital conversion circuits, and plastic or metal housings. Each barcode scanner has certain requirements on the ambient light source. If the ambient light source exceeds the maximum fault tolerance requirements, the barcode scanner will not be able to read normally. When a barcode is printed on a metal or silver-plated surface, the light beam will be reflected by a high-brightness surface. If the light reflected by the metal enters the light-receiving element of the barcode scanner, it will affect the reading stability of the scanner. Metal surfaces are covered or painted with black paint.