JPH0516221B

PURPOSE:To relax the limitation of an original format by using an image sensor and an A/D converter of a picture input device, and performing double feed detection. CONSTITUTION:Original information read by the image sensor 2 is A/D-converted by the A/D converter 3, inputted to a gate 4, which opens a gate at the scanning of white level detecting region according to the original format of a storage circuit 9 by the indication from a central processing unit 8, and a signal is transmitted to a comparator 6. On the other hand, a gradation value of paper thickness of an input original is generated from a reference value generating circuit 5. The comparator 6 compares a signal from the gate 4 with a signal from the reference vlaue generating circuit 5, and when an input from the gate is higher than a predetermined value or over, a double feed detecting signal is transmitted.