Double feeding detection device, control method, and control program

A control method of a multi-feed detection apparatus, the method comprising:

• feeding a medium placed on a medium tray by a feed roller;
• transmitting an ultrasonic wave by an ultrasonic transmitter;
• generating an ultrasonic signal corresponding to a ultrasonic wave received by a an ultrasonic receiver;
• determining that feeding of the medium is normal when a signal value of the ultrasonic signal is equal to or more than a first threshold value;
• determining that a multi-feed of the medium has occurred when the signal value of the ultrasonic signal is less than the first threshold value;
• and
• controlling the feed roller to return the fed medium to a direction of the medium tray when the signal value of the ultrasonic signal is less than a second threshold value smaller than the first threshold value, and not to return the fed medium to the direction of the medium tray when the signal value of the ultrasonic signal is less than the first threshold and equal to or more than the second threshold even when it is determined that the multi-feed of the medium has occurred.

A computer-readable, non-transitory medium storing a computer program, wherein the computer program causes a multi-feed detection apparatus including a medium tray, a feed roller to feed a medium placed on the medium tray, an ultrasonic sensor including an ultrasonic transmitter to transmit an ultrasonic wave and an ultrasonic receiver to generate an ultrasonic signal corresponding to a received ultrasonic wave, to execute a process, the process comprising:

• determining that feeding of the medium is normal when a signal value of the ultrasonic signal is equal to or more than a first threshold value;
• determining that a multi-feed of the medium has occurred when the signal value of the ultrasonic signal is less than the first threshold value;
• and
• controlling the feed roller to return the fed medium to a direction of the medium tray when the signal value of the ultrasonic signal is less than a second threshold value smaller than the first threshold value, and not to return the fed medium to the direction of the medium tray when the signal value of the ultrasonic signal is less than the first threshold and equal to or more than the second threshold even when it is determined that the multi-feed of the medium has occurred.