Patent US 4,147,295

A bar code recognition system in which a threshold value for discriminating each bar of bar codes is automatically corrected. Bar codes representing information are constituted by a combination of wide and narrow bars to be scanned and converted into a rectangular signal having a time width proportional to the width of each bar. In proportion to the total time widths of the rectangular signal generated in each scanning cycle, the threshold value with reference to which each bar width is discriminated is determined to enhance the recognition operation of the system.