Image reading device, multi-feed detecting method, and multi-feed detecting program

A multi-feed detecting method in an image reading device using an emission speaker unit configured to emit an ultrasonic wave in accordance with a driving voltage and a reception microphone unit configured to receive the ultrasonic wave, the emission speaker unit and the reception microphone unit being disposed so that a transport path for a medium transported by a transport roller unit is interposed therebetween, and the method including detecting presence or absence of multi-feed of the medium on a basis of a signal received by the reception microphone unit, wherein

• the image reading device including the transport path is configured to switch a posture into any of a first posture or a second posture, the first posture being a posture in which the transport path is sloped relative to a mounting surface where the device is mounted, the second posture being a posture in which an angle of the transport path relative to the mounting surface is smaller than that in the first posture, and
• the method includes a setting step in which a first driving voltage is set as the driving voltage when the posture is the first posture, and a second driving voltage lower than the first driving voltage is set as the driving voltage when the posture is the second posture, wherein
• when power supply to the image reading device is turned on, a control unit of the image reading device executes a determination processing for determining whether a signal received by the reception microphone unit in a state where no medium exists in the transport path exceeds a threshold value for calibration,
• the control unit sets a third driving voltage greater than the first driving voltage as the driving voltage when determining, in the determination processing, that the signal does not exceed the threshold value for calibration, and
• the control unit sets the driving voltage corresponding to the posture when determining, in the determination processing, that the signal exceeds the threshold value for calibration.

A non-transitory computer-readable storage medium storing a multi-feed detecting program that causes a device to execute processing, the device including a transport roller unit configured to transport a medium, an emission speaker unit configured to emit an ultrasonic wave in accordance with a driving voltage, and a reception microphone unit configured to receive the ultrasonic wave, the emission speaker unit and the reception microphone unit being disposed so that a transport path for the medium transported by the transport roller unit is interposed therebetween, the processing including detecting presence or absence of multi-feed of the medium on a basis of a signal received by the reception microphone unit, wherein

• the device is configured to switch a posture into any of a first posture or a second posture, the first posture being a posture in which the transport path is sloped relative to a mounting surface where the device is mounted, the second posture being a posture in which an angle of the transport path relative to the mounting surface is smaller than that in the first posture,
• the program causes the device to execute a setting function of setting a first driving voltage as the driving voltage when the posture is the first posture, and setting a second driving voltage lower than the first driving voltage as the driving voltage when the posture is the second posture,
• when power supply to the device is turned on, a control unit of the device executes a determination processing for determining whether a signal received by the reception microphone unit in a state where no medium exists in the transport path exceeds a threshold value for calibration,
• the control unit sets a third driving voltage greater than the first driving voltage as the driving voltage when determining, in the determination processing, that the signal does not exceed the threshold value for calibration, and
• the control unit sets the driving voltage corresponding to the posture when determining, in the determination processing, that the signal exceeds the threshold value for calibration.