PURPOSE: To simplify constitution and to attain low cost by dividing a light source into blocks having the same number as the number of photosensing element blocks, and driving synchronizingly both the blocks.

CONSTITUTION: The light source for optical information 8 is divided into the blocks P1∼P3 having the same number as the a1∼a3 blocks of the light sensor and they are drives sequentially synchronizingly by using a synchronizing circuit. Thus, since a reverse flow blocking diode is eliminated, the constitution of the light sensor board is simplified.