Basic principles of bar code reading

Bar code technology first appeared in the 1940s. At that time, two American engineers studied the use of bar codes to express information, and obtained the world's first bar code patent in 1949. This earliest bar code is composed of black and white concentric circles, which is vividly called bull's-eye bar code. This bar code is consistent with the one-dimensional bar code that we widely use now in principle. Both of them use dark bars and bright spaces to represent "1" and "0" of binary numbers. However, at that time, the level of American printing industry and the development of commodity economy could not use barcode technology.