c 4 and c 5 are assumed to be 0 and the tap coefficient c 3 is assumed to be 1 and if the amplitude of x 3 is not less than the predetermined threshold value the tap coefficients that are shown in fig6 may be used moreover if an edge for which the frequency of the module is more than the predetermined threshold value is detected the amplitude of the edge that is included in this module can be emphasized in this case in the transversal filter in fig5 when the module frequency is less than the threshold value 1 or when the amplitude of x 3 is less than the predetermined threshold value 2 the tap coefficients c 1 c 2 c 4 and c 5 are assumed to be 0 and the tap coefficient c 3 is assumed to be 1 when the frequency of the module is not less than the threshold value 1 and the amplitude of x 3 is not less than the threshold value the tap coefficients that are shown in fig6 may be used by changing the tap coefficients dynamically in accordance with the thick black bar and the thick white bar the emphasizing characteristics that emphasize the amplitude of the edge included in the module can be changed moreover in this embodiment a case of using an optical system that irradiates a bar code by a light beam to acquire reflected light is described however the present invention is not restricted to this case only and can also.