PURPOSE:To provide a big bang code high in recording density and capable of being accurately read in a spot-like state. CONSTITUTION:A big bang code 31 recording optically readable bit information in intersections between circumferential lines forming polar coordinates and radial lines is read out by a big bang code reader 51 having a light emitting element 53 for projecting light rays forwards in a state opposed to almost the center of the circumferential lines and plural light receiving elements 54 for receiving bit information existing in an optical path by the existence of reflected light so as to distinguish it from others. Consequently the big bang code 31 improving the recording density of bit information per unit area can be accurately read in the spot-like state.
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