To provide a double feed detection device that can accurately detect double feed regardless of the kind of recording material even using an optical double feed detector.
The double feed detection device 200 includes: a double feed detection means 23 provided with a transmission sensor 23A for transmitting an ultrasonic signal, and a receiving sensor 23B disposed opposite to the transmission sensor across a conveyance path along which a recording material S is conveyed and for receiving the ultrasonic signal transmitted from the transmission sensor; a double feed determination circuit 210 for detecting a conveyance state of the recording material according to a level of receiving the ultrasonic signal transmitted from the transmission sensor and received by the receiving sensor; a controller 201 for controlling the transmission of the ultrasonic signal from the transmission sensor by at least synchronizing with the conveyance of the recording material; and a sampling period changing means 202 for changing a sampling period of the ultrasonic signal transmitted from the transmission sensor according to the size of the continuously conveyed recording material and the timing when the recording material passes through between the transmission sensor and the receiving sensor.
Toru Kabayama
Shuichi Kudo