| 摘要 |
In the decoding method, the photoelectric conversion is performed on the light reflected by a code image, a read signal indicating intensity of the reflected light is produced, and the produced read signal is differentiated to produce a derivative signal. On the assumption of this, the inflection points of intensity of the reflected light in the read signal are detected from the produced derivative signal and peak levels as shown in FIG. 9, each of which is an extreme value of the intensity of the reflected light, the peak level corresponding to a width length between the detected inflection points, are detected. A difference between the detected peak levels is then obtained and threshold values ThB2, ThS2 for decoding the read signal are set from the obtained difference between the peak levels. This enables the read signal of the code image to be decoded even when the code image is spotted with a stain or its printing quality is inferior or even when the read signal is read in its defocus state.
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