MEDIUM RECOGNIZING DEVICE

PURPOSE:To suppress the increase of an overall read data amount by providing an image sensor in which the arrangement density of a picture element detecting element is different, in the main scanning direction on a medium to be recognized. CONSTITUTION:In a part of an image sensor 10 corresponding to fine pattern regions 2A, 2B on a medium 2 which is to be read by a high resolution, the arrangement density of an element 1 of the image sensor 10 is high. That is to say, it is in a dense arrangement (b group and d group), and in other parts, the arrangement of the element 1 is coarse (a, c and e groups). Also, as for the read of the minute pattern areas 2A, 2B, the internal of a main scanning line is narrow, and in the sub-scanning direction, as well, a read density is increased (B zone and D zone). A read density in the sub-scanning direction to other part is coarse (A, C and E zones), and the read density in the sub- scanning direction can be varied by making the carrying speed of the medium constant and changing the output period of a start pulse S, or making the output period of the start pulse S constant and changing the carrying speed of the medium 2.