A transmitter transmits ultrasonic wave of a predetermined volume. A reflected ultrasonic wave receiver receives reflected ultrasonic wave, transmitted from the transmitter and reflected by a sheet. A permeated ultrasonic wave receiver receives permeated ultrasonic wave, transmitted by the transmitter and permeated through the sheet. A volume detector detects reflected volume of the reflected ultrasonic wave, and permeated volume of the permeated ultrasonic wave. The decider identifies a thickness of the sheet being transported by a transport device, and decides whether multifeed of the sheets is occurring, on a basis of a comparison result between the detected reflected volume and a reference reflected volume, and a comparison result between the detected permeated volume and a reference permeated volume.

An image forming apparatus includes a print engine to form an image on recording medium, a sensor including first and second electrodes disposed to oppose each other based on a recording medium transport path, along which the recording medium is transported, and to detect a capacitance between the first and second electrodes, and a processor to determine a state of the recording medium fed along the recording medium transport path by using the capacitance detected by the sensor and to control the print engine based on the state of the recording medium.

A feed detection unit which detects a document which is fed is provided at a position between a pinching position at which a feed roller and a frictional force application portion pinch the document and an intersecting position at which a tangential line of the feed roller which is closer to a downstream side in a transport direction than the pinching position is perpendicular to a transport path in the transport direction, which is a different position from the feed roller in a width direction which intersects the transport direction.

A theoretical threshold corresponding to a transport path is set, and a control unit acquires a calculation value calculated based on a detection result of double feeding detection unit and a transport length of a document, determines occurrence of double feeding when the calculation value is greater than the theoretical threshold (step S120), and determines non-occurrence of double feeding when the calculation value is smaller than the theoretical threshold. In addition, if a non-detection period for double feeding occurs (step S110), the control unit sets a cumulative value in step S115. As a result, detection of double feeding is ended in a short period while a document is being transported, and in a case that double feeding is no longer detected, determination of double feeding will not be made.

A sheet feeder includes a controller configured to control an emitter to emit an ultrasonic wave toward a target sheet being fed along a sheet guide, control a measurer to measure a first reception intensity of a first component of the ultrasonic wave received by a receiver during a first period of time, control the measurer to measure a second reception intensity of a second component of the ultrasonic wave received by the receiver during a second period of time, and determine a feeding state of the target sheet in a detectable area between the emitter and the receiver within the sheet guide, based on the first reception intensity and the second reception intensity.

A feeding apparatus includes a feeding member, first and second conveying members, a separation member, and drive and control units. The feeding member feeds a recording material placed on a tray. The separation member and the first conveying member form a nip portion and separates recording materials at the nip portion. The second conveying member conveys a conveyed recording material. The drive unit drives at least the feeding member. The control unit controls to feed first and second recording materials such that a second recording material front edge passes the nip portion before a first recording material rear edge passes the nip portion, and controls to stop the second recording material after the second recording material front edge has passed the nip portion such that the first recording material rear edge reaches the second conveying member before the second recording material front edge reaches the second conveying member.

A sheet conveyance apparatus including a transmission unit that transmits an ultrasonic wave toward a sheet and a reception unit that receives the ultrasonic wave includes a change unit that changes a distance of a conveyance path of the sheet according to sheet information about the sheet to be conveyed.

Provided is a paper transporting device and the like capable of suppressing errors in determining jam occurrences. A paper transporting device has: a transport mechanism; an audio signal output unit that outputs an audio signal according to the sound generated during paper transport; an audio jam determination unit that determines, on the basis of the audio signal, whether a jam has occurred; and a control unit that stops paper transport when the audio jam determination unit determines that a jam has occurred. The control unit controls, in the case of card stock or paperboard being transported by the transport mechanism, so that the audio jam determination unit determines whether a jam has occurred at predetermined times using a determination method that is different than the method at other times or so that the audio jam determination unit does not determine whether a jam has occurred.

A sheet conveying device includes: a sending unit configured to send an ultrasonic wave; a receiving unit positioned to face the sending unit across a conveyance path, along which a sheet is conveyed, and configured to receive a first ultrasonic wave, the first ultrasonic wave being an ultrasonic wave sent from the sending unit and passed through the sheet, and output a first voltage corresponding to the first ultrasonic wave; an adjusting unit configured to adjust the first voltage into an adjusted first voltage according to a setting; an amplification unit configured to amplify the adjusted first voltage by a preset amplification factor for multi-feed determination into an amplified first voltage; and a determining unit configured to determine whether or not multi-feed of the sheet has occurred based on the amplified first voltage.

A method for detecting overlapped bank notes is provided. The method includes: step 10, collecting original image data of bank notes; step 20, performing security thread positioning detection on the original image data of the bank notes, to obtain security thread detection data; step 40, determining whether the security thread detection data meets a preset security thread reference condition, going to step 60 if the security thread detection data meets the preset security thread reference condition, and going to step 70 if the security thread detection data does not meet the preset security thread reference condition; step 60, obtaining a determination result that the bank notes are not overlapped, and ending the method; and step 70, obtaining a determining result that the bank notes are overlapped, and ending the method.