| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect a prepaid card medium which is altered or forged by copying stored information. SOLUTION: A magnetic head 143 reads magnetically stored information such as money amount information and reference gradation distribution information out of a prepaid card under the control of a data read write part 142. An abnormality detection part 144 compares and matches actual gradation distribution information, which is detected by an optical sensor 145 from a specific bar code print position and quantized by a quantizing process part 146, against reference gradation distribution information read out through the data read write part 142 and decides that an illegal prepaid card has been inserted when the both do not match each other, thereby detecting the abnormality. The optical sensor 145 is controlled by an abnormality detection part 144 to detect the reference gradation information from the specific bar code print position corresponding to the reference gradation distribution information and supply it to the quantizing process part 146. |
