Medium conveyance device, control method and control program

Abstract

To provide a medium conveyance device, control method and control program which can more accurately determine whether or not a conveyance abnormality of a medium has occurred.SOLUTION: A medium conveyance device comprises: a conveyance unit which conveys a medium; an end detection unit which detects a position of an end of a medium conveyed by the conveyance unit; an overlap detection unit which detects an overlap of the media conveyed by the conveyance unit in a detection region; a determination unit which determines whether the overlap detection is effective or ineffective on the basis of a physical relation between a position where the end detection unit detects the end of the medium and the detection region; and a control unit which executes processing against abnormality caused by multi-feeding, on the basis of the detection result of the overlap detection unit when the determination unit determines that the overlap detection is effective.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a medium conveying device, a control method, and a control program, and more particularly to a medium conveying device, a control method, and a control program that determine whether or not a duplicate feed of media has occurred. [Background technology]

[0002] Generally, media transport devices such as scanners have the ability to detect whether a double feed has occurred, in which multiple media are transported at the same time, and to automatically stop transporting the media when a double feed has occurred.

[0003] For example, a multi-feed detection device has been disclosed that uses an ultrasonic sensor to determine whether or not a multi-feed of media has occurred based on the amount of ultrasonic waves transmitted through the medium (see Patent Document 1). This multi-feed detection device compares the signal value of the ultrasonic waves transmitted through the medium with a determination threshold value to determine whether or not a multi-feed of media has occurred. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-100459 A Summary of the Invention [Problem to be solved by the invention]

[0005] It is desirable for a medium conveying device to be able to determine with greater accuracy whether or not a double feed of media has occurred.

[0006] An object of the present invention is to provide a medium conveying device, a control method, and a control program that are capable of determining with greater accuracy whether or not a duplicated medium feed has occurred. [Means for solving the problem]

[0007] A medium transport device according to one aspect of the present invention has a transport unit that transports a medium, an end detection unit that detects the position of the end of the medium transported by the transport unit, an overlap detection unit that detects an overlap of the medium transported by the transport unit in a detection area, a determination unit that determines whether overlap detection is valid or invalid based on the positional relationship between the position where the end detection unit detects the end of the medium and the detection area, and a control unit that executes abnormal processing due to double feeding based on the detection result of the overlap detection unit if the determination unit determines that overlap detection is valid.

[0008] Furthermore, a control method according to one aspect of the present invention is a control method for a medium transporting device having a transporting section that transports a medium, an end detection section that detects the position of the end of the medium transported by the transporting section, and an overlap detection section that detects an overlap of the medium transported by the transporting section in a detection area, in which the overlap detection is determined to be valid or invalid based on the position where the end detection section detects the end of the medium and the positional relationship between the detection area and the overlap detection, and if it is determined that the overlap detection is valid, abnormality processing due to double feeding is performed based on the detection result of the overlap detection.

[0009] Furthermore, a control program according to one aspect of the present invention is a control program for a medium transporting device having a transporting section that transports a medium, an end detection section that detects the position of the end of the medium transported by the transporting section, and an overlap detection section that detects an overlap of the medium transported by the transporting section in a detection area, and causes the medium transporting device to determine whether overlap detection is valid or invalid based on the positional relationship between the position where the end detection section detects the end of the medium and the detection area, and if it is determined that overlap detection is valid, to perform abnormality processing due to double feeding based on the detection result of the overlap detection. Effect of the Invention

[0010] According to the present invention, the medium conveying device, the control method, and the control program are capable of determining with higher accuracy whether or not a duplicated medium feed has occurred. [Brief description of the drawings]

[0011] [Figure 1]FIG. 1 is a perspective view showing a medium conveying device 100 according to an embodiment. [Diagram 2] 2 is a diagram for explaining a transport path inside the medium transport device 100. FIG. [Diagram 3] FIG. 2 is a schematic diagram for explaining the arrangement of ultrasonic sensors 115 and the like. [Figure 4] 1 is a block diagram showing a schematic configuration of a medium conveying device 100. FIG. [Diagram 5] FIG. 2 is a diagram showing a schematic configuration of a storage device 140 and a processing circuit 150. [Figure 6] 10 is a flowchart illustrating an example of the operation of a medium reading process. [Figure 7] 13 is a flowchart showing an example of the operation of a validity determination process. [Figure 8] 1A shows an example of a medium image, and FIG. 1B is an example of a graph showing the luminance value of each pixel in a specific line image within the medium image. [Figure 9] (A) is a diagram showing an example of the positional relationship between the position of the edge of the medium and the inspection area, (B) is a diagram showing another example of the positional relationship between the position of the edge of the medium and the inspection area, and (C) is a diagram showing yet another example of the positional relationship between the position of the edge of the medium and the inspection area. [Figure 10] 4 is a schematic diagram for explaining the characteristics of the intensity of an ultrasonic signal output from an ultrasonic sensor; FIG. [Figure 11] 13 is a flowchart showing an example of the operation of a multifeed detection process of the medium conveying device 100. [Figure 12] 13A and 13B are diagrams illustrating another example of detecting the position of an edge of a medium. [Figure 13] 13 is a schematic diagram for explaining still another means for detecting the position of the edge of the medium. FIG. [Figure 14] FIG. 13 is a diagram showing a schematic configuration of another processing circuit 250. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a medium conveying device according to one aspect of the present invention will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to the embodiment, but extends to the inventions described in the claims and their equivalents.

[0013] FIG. 1 is a perspective view showing a medium conveying device 100 according to an embodiment configured as an image scanner. The medium conveying device 100 conveys a medium, which is an original, and captures an image. The medium is paper, a card, a booklet, or the like. The paper includes thin paper or thick paper, and the booklet includes a passport or a bankbook, and the medium conveying device 100 may be a facsimile, a copier, a multifunction printer (MFP, Multifunction Peripheral), or the like. Note that the medium being conveyed may not be an original but may be a print target, and the medium conveying device 100 may be a printer, or the like.

[0014] The medium conveying device 100 includes a lower housing 101, an upper housing 102, a placement table 103, a discharge table 104, an operation device 105, a display device 106, and the like.

[0015] The upper housing 102 is disposed in a position that covers the top surface of the medium conveying device 100, and engages with the lower housing 101 by a hinge so that it can be opened and closed when the medium is jammed or when the inside of the medium conveying device 100 is cleaned.

[0016] The top surface of the lower housing 101 forms a lower guide 107a of the medium transport path, and the bottom surface of the upper housing 102 forms an upper guide 107b of the medium transport path. In Fig. 1, an arrow A1 indicates the medium transport direction. Hereinafter, "upstream" refers to the upstream side of the medium transport direction A1, and "downstream" refers to the downstream side of the medium transport direction A1.

[0017] The placement table 103 engages with the lower housing 101 so that the medium to be transported can be placed thereon. The placement table 103 has a placement surface 103a on which the medium is placed. A first side guide 109a and a second side guide 109b are provided on the placement surface 103a. The first side guide 109a and the second side guide 109b regulate the position of the medium in the width direction A2. Hereinafter, the first and second side guides 109a, 109b may be collectively referred to as side guides 109. Each side guide 109a, 109b is provided so as to be movable in the width direction A2 perpendicular to the medium transport direction of the placement table 103. Each side guide 109a, 109b has a predetermined height in the height direction A3 and regulates the width direction of the medium placed on the placement table 103. Usually, the first side guide 109a is disposed at the leftmost position, and the second side guide 109b is moved according to the width of the medium.

[0018] The ejection platform 104 is engaged with the lower housing 101 so as to be able to hold the ejected medium.

[0019] The operation device 105 has an input device such as a button and an interface circuit for acquiring a signal from the input device, accepts an input operation by a user, and outputs an operation signal according to the input operation by the user. The display device 106 has a display including a liquid crystal, an organic EL (Electro-Luminescence), or the like, and an interface circuit for outputting image data to the display, and displays the image data on the display.

[0020] FIG. 2 is a diagram for explaining a transport path inside the medium transport device 100. As shown in FIG.

[0021] The transport path inside the medium transport device 100 includes a contact sensor 111, a feed roller 112, a brake roller 113, a medium sensor 114, an ultrasonic transmitter 115a, an ultrasonic receiver 115b, a first transport roller 116, a second transport roller 117, a first imaging device 118a, a second imaging device 118b, a third transport roller 119, and a fourth transport roller 120. The feed roller 112, the brake roller 113, the first transport roller 116, and the second transport roller 117 are an example of a transport unit that transports the medium. Note that the number of each roller is not limited to one, and each roller may be multiple. In the following, the first imaging device 118a and the second imaging device 118b may be collectively referred to as the imaging device 118.

[0022] The contact sensor 111 is disposed upstream of the feed roller 112 and the brake roller 113. The contact sensor 111 detects whether or not a medium is placed on the placement table 103 by contacting and detecting the medium. The contact sensor 111 generates and outputs a first medium signal whose signal value changes depending on whether or not a medium is placed on the placement table 103.

[0023] The feed roller 112 is provided in the lower housing 101, and feeds the media placed on the placement table 103 from the bottom up. The brake roller 113 is provided in the upper housing 102, and is disposed opposite the feed roller 112.

[0024] The medium sensor 114 is disposed downstream of the feed roller 112 and the brake roller 113 and upstream of the first conveyor roller 116 and the second conveyor roller 117. The medium sensor 114 detects whether or not a medium is present at that position. The medium sensor 114 includes a light emitter and a light receiver provided on one side of the medium conveyance path, and a reflecting member (not shown) such as a mirror provided at a position facing the light emitter and the light receiver across the conveyance path. The light emitter irradiates light toward the conveyance path. On the other hand, the light receiver receives the light irradiated by the light emitter and reflected by the reflecting member, and generates and outputs a second medium signal, which is an electrical signal according to the intensity of the received light. When a medium is present at the position of the medium sensor 114, the light irradiated by the light emitter is blocked by the medium, so the signal value of the second medium signal changes depending on whether a medium is present at the position of the medium sensor 114 or not. The light emitter and the light receiver are provided at positions facing each other across the conveyance path, and the reflecting member may be omitted.

[0025] The ultrasonic transmitter 115a and the ultrasonic receiver 115b are disposed downstream of the feed roller 112 and the brake roller 113 in the medium conveying direction A1 and upstream of the first conveying roller 116 and the second conveying roller 117 in the medium conveying direction A1. The ultrasonic transmitter 115a and the ultrasonic receiver 115b are disposed near the medium conveying path and facing each other across the conveying path. The ultrasonic transmitter 115a can output ultrasonic waves. On the other hand, the ultrasonic receiver 115b receives ultrasonic waves transmitted by the ultrasonic transmitter 115a and passing through the medium, and generates and outputs an ultrasonic signal, which is an electrical signal corresponding to the received ultrasonic waves. Hereinafter, the ultrasonic transmitter 115a and the ultrasonic receiver 115b may be collectively referred to as the ultrasonic sensor 115. The ultrasonic sensor 115 is an example of an overlap detection unit that detects an overlap of the media conveyed by the conveying unit in the detection area.

[0026] The first transport roller 116 and the second transport roller 117 are disposed downstream of the feed roller 112 and the brake roller 113 in the medium transport direction A1 and upstream of the imaging device 118 in the medium transport direction A1.

[0027] The first imaging device 118a is disposed downstream of the first conveying roller 116 and the second conveying roller 117 in the medium conveying direction A1. The first imaging device 118a has a line sensor using a CIS (Contact Image Sensor) of a life-size optical system type having imaging elements using CMOS (Complementary Metal Oxide Semiconductor) linearly arranged in the main scanning direction. Here, the main scanning direction is a direction perpendicular to the medium conveying direction. The line sensor is an example of an imaging sensor that captures an image of a medium. The first imaging device 118a also has a light source that irradiates light toward the medium being conveyed, a lens that forms an image on the imaging element, and an A / D converter that amplifies and analog-to-digital (A / D) converts the electrical signal output from the imaging element. The first imaging device 118a captures an image of an area facing the line sensor on the surface of the medium being conveyed at regular intervals, sequentially generates line images, and outputs the line images. That is, the number of pixels in the vertical direction (sub-scanning direction) of the line image is one, and the number of pixels in the horizontal direction (main scanning direction) is multiple. The first imaging device 118a is an example of an edge detection unit that detects the position of an edge of the medium transported by the transport unit. The line image is an example of an input image obtained by capturing an image of the medium.

[0028] Similarly, the second imaging device 118b is disposed downstream in the medium conveying direction A1 with respect to the first conveying roller 116 and the second conveying roller 117. The second imaging device 118b has a line sensor using a CIS of a life-size optical system type having imaging elements using CMOS arranged in a line in the main scanning direction. The line sensor is an example of an imaging sensor that images a medium. The second imaging device 118b also has a light source that irradiates light toward the medium being conveyed, a lens that forms an image on the imaging element, and an A / D converter that amplifies and analog-to-digital (A / D) converts the electrical signal output from the imaging element. The second imaging device 118b captures an area facing the line sensor on the back side of the medium being conveyed at regular intervals, sequentially generates line images, and outputs them. The second imaging device 118b is an example of an edge detection unit that detects the position of the edge of the medium being conveyed by the conveying unit.

[0029] The medium conveying device 100 may have only one of the first imaging device 118a and the second imaging device 118b arranged to read only one side of the medium. Also, instead of a CIS line sensor of an equal magnification optical system type having a CMOS imaging element, a CIS line sensor of an equal magnification optical system type having a CCD (Charge Coupled Device) imaging element may be used. Also, a reduction optical system type line sensor having a CMOS or CCD imaging element may be used.

[0030] The medium placed on the mounting table 103 is transported between the lower guide 107a and the upper guide 107b in the medium transport direction A1 by the rotation of the feed roller 112 in the direction of the arrow A4 in FIG. 2. The brake roller 113 rotates in the direction of the arrow A5 when transporting the medium. When multiple media are placed on the mounting table 103, the feed roller 112 and the brake roller 113 work to separate only the media placed on the mounting table 103 that are in contact with the feed roller 112. This operates to restrict the transport of media other than the separated media (preventing double feeding). The feed roller 112 and the brake roller 113 are an example of a feed section that separates and feeds the media placed on the mounting table 103.

[0031] The medium is fed between the first conveyor roller 116 and the second conveyor roller 117 while being guided by the lower guide 107a and the upper guide 107b. The medium is fed between the first imaging device 118a and the second imaging device 118b as the first conveyor roller 116 and the second conveyor roller 117 rotate in the directions of the arrows A6 and A7, respectively. The medium read by the imaging device 118 is discharged onto the discharge tray 104 as the third conveyor roller 119 and the fourth conveyor roller 120 rotate in the directions of the arrows A8 and A9, respectively.

[0032] Fig. 3 is a schematic diagram for explaining the arrangement of ultrasonic transmitter 115a etc. Fig. 3 is a schematic diagram of lower guide 107a of medium conveying device 100 as viewed from above.

[0033] As shown in FIG. 3, the two ultrasonic receivers 115b are disposed between the feed roller 112 and the third conveyor roller 119 in the medium conveying direction A1. The two ultrasonic receivers 115b are disposed side by side with a gap in the width direction A2. In the example shown in FIG. 3, the ultrasonic receiver 115b is disposed at both ends of the lower guide 107a in the width direction A2. The two ultrasonic transmitters 115a are disposed at a position of the upper guide 107b facing the ultrasonic receiver 115b. In the medium conveying device 100, the two ultrasonic transmitters 115a (ultrasonic sensors 115) are disposed spaced apart in the width direction A2 of the lower guide 107a, so that both ends of the medium in the width direction can be detected. The number of ultrasonic sensors 115 is not limited to two, and may be one or three or more.

[0034] The medium sensor 114 is disposed between the ultrasonic transmitter 115a and the feed roller 112 in the medium transport direction A1.

[0035] FIG. 4 is a block diagram showing a schematic configuration of the medium conveying device 100. As shown in FIG.

[0036] In addition to the components described above, the medium conveying device 100 further includes a motor 131, an interface device 132, a storage device 140, a processing circuit 150, and the like.

[0037] The motor 131 includes one or more motors, and rotates the feed roller 112, the brake roller 113, and the first to fourth transport rollers 116, 117, 119, and 120 in response to a control signal from the processing circuit 150 to transport the medium.

[0038] The interface device 132 has an interface circuit conforming to a serial bus such as USB, and is electrically connected to an information processing device (not shown) to transmit and receive medium images and various information. Also, instead of the interface device 132, a communication unit having an antenna for transmitting and receiving wireless signals and a wireless communication interface device for transmitting and receiving signals through a wireless communication line according to a predetermined communication protocol may be used. The predetermined communication protocol is, for example, a wireless LAN (Local Area Network).

[0039] The storage device 140 includes a memory device such as a random access memory (RAM) or a read only memory (ROM), a fixed disk device such as a hard disk, or a portable storage device such as a flexible disk or an optical disk. The storage device 140 also stores computer programs, databases, tables, and the like used for various processes of the medium conveying device 100. The computer programs may be installed in the storage device 140 from a computer-readable, non-transitory portable recording medium using a known setup program or the like. The portable recording medium is, for example, a compact disc read only memory (CD-ROM), a digital versatile disc read only memory (DVD-ROM), or the like.

[0040] The storage device 140 stores, as data, the position of the ultrasonic sensor 115 and the position of the imaging device 118 on the medium transport path.

[0041] The processing circuit 150 operates based on a program previously stored in the storage device 140. The processing circuit 150 is, for example, a CPU (Central Processing Unit). As the processing circuit 150, a DSP (digital signal processor), an LSI (large scale integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or the like may be used.

[0042] The processing circuit 150 is connected to the operation device 105, the display device 106, the contact sensor 111, the medium sensor 114, the ultrasonic sensor 115, the imaging device 118, the motor 131, the interface device 132, the storage device 140, and the like, and controls each of these components. The processing circuit 150 performs drive control of the motor 131, image capture control of the imaging device 118, and the like, generates a medium image, and transmits the medium image to the information processing device via the interface device 132. The processing circuit 150 also determines whether overlap detection is valid or invalid based on the line image from the imaging device 118, and the like. If it is determined that overlap detection is valid, the processing circuit 150 determines whether or not double feeding of media has occurred based on the ultrasonic signal from the ultrasonic sensor 115, and the like.

[0043] FIG. 5 is a diagram showing a schematic configuration of the storage device 140 and the processing circuit 150. As shown in FIG.

[0044] 5, the storage device 140 stores a control program 141, an image generation program 142, a determination program 143, etc. Each of these programs is a functional module implemented by software that runs on a processor. The processing circuitry 150 reads each program stored in the storage device 140 and operates according to the read program. In this way, the processing circuitry 150 functions as a control unit 151, an image generation unit 152, and a determination unit 153.

[0045] FIG. 6 is a flowchart showing an example of the operation of the medium reading process of the medium conveying device 100.

[0046] An example of the operation of the medium reading process of the medium conveying device 100 will be described below with reference to the flowchart shown in FIG. 6. The flow of the operation described below is executed mainly by the processing circuit 150 in cooperation with each element of the medium conveying device 100 based on a program previously stored in the storage device 140. The flow of the operation shown in FIG. 6 is executed periodically. The medium conveying device 100 has, as a feeding mode for feeding the medium, a separation mode in which multiple media are separated and fed, and a non-separation mode in which the media are fed without being separated. The flow of the operation shown in FIG. 6 is executed when the feeding mode is set to the separation mode.

[0047] First, the control unit 151 waits until a user inputs an instruction to read a medium using the operation device 105 and an operation signal instructing to read a medium is received from the operation device 105 (step S101).

[0048] Next, control unit 151 acquires a first medium signal from contact sensor 111, and determines whether or not a medium is placed on placement table 103 based on the acquired first medium signal (step S102).

[0049] If no medium is placed on the placement table 103, the control unit 151 returns the process to step S101 and waits until a new operation signal is received from the operation device 105.

[0050] On the other hand, when a medium is placed on the placement table 103, the control unit 151 drives the motor 131 to rotate the feed roller 112, the brake roller 113, and the first to fourth transport rollers 116, 117, 119, and 120 to transport the medium (step S103). In the separation mode, the control unit 151 drives the motor 131 to rotate the feed roller 112 and the first to fourth transport rollers 116, 117, 119, and 120 in the directions of the arrows A4, A6, A7, A8, and A9 (medium feed direction or medium transport direction), respectively. The control unit 151 also drives the motor 131 to rotate the brake roller 113 in the direction of the arrow A5 (opposite the medium feed direction).

[0051] Next, the determination unit 153 determines whether the overlap detection is determined to be valid or invalid in the validity determination process (step S104). In the validity determination process, the determination unit 153 determines whether the overlap detection is valid or invalid based on the positional relationship between the position where the image capture device 118 detects the edge of the medium and the detection area of ​​the medium through which the ultrasonic wave passes. Details of the validity determination process will be described later.

[0052] When it is determined that the overlap detection is valid (step S104-Yes), the determination unit 153 determines whether or not it is determined that a multifeed of media has occurred in the multifeed determination process (step S105). The details of the multifeed determination process will be described later.

[0053] If the determining unit 153 determines that a multi-feed of media has occurred, the control unit 151 determines that a multi-feed of media has occurred (step S106).

[0054] Next, when it is determined that a medium transport abnormality has occurred, the control unit 151 stops the motor 131 to stop the feeding and transport of the medium (step S107). When a double feed of media has occurred, the control unit 151 can prevent the media from being damaged by stopping the feeding and transport of the media. Furthermore, the control unit 151 displays the fact that a double feed has occurred on the display device 106, or transmits the fact to the information processing device via the interface device 132, and notifies the user of a warning.

[0055] Next, the control unit 151 drives the motor 131 to rotate the feed roller 112 and the first to fourth transport rollers 116, 117, 119, 120 in the directions opposite to the arrows A4, A6, A7, A8, A9 (medium feed direction or medium transport direction), respectively. The control unit 151 also drives the motor 131 to rotate the brake roller 113 in the direction of the arrow A5 (the direction opposite to the medium feed direction). As a result, the control unit 151 reverses the medium and returns it to the placement table 103 (step S108).

[0056] Next, the control unit 151 changes the feeding mode from the separation mode to the non-separation mode (step S109). In the non-separation mode, the control unit 151 rotates the feeding roller 112 and the first to fourth conveying rollers 116, 117, 119, and 120 in the directions of the arrows A4, A6, A7, A8, and A9 (medium feeding direction or medium conveying direction), respectively. In the non-separation mode, the control unit 151 cuts off the driving force from the motor 131 to the brake roller 113 to turn off the separation function of the medium to be fed. The control unit 151 may turn off the separation function of the medium to be fed by rotating the brake roller 113 in the medium feeding direction (opposite direction of the arrow A5) or by reducing the separation force of the brake roller 113. In step S109, instead of turning off the separation function, the control unit 151 may control the driving force to the brake roller 113 to reduce or increase the separation force.

[0057] Next, the control unit 151 drives the motor 131 again to rotate the feed roller 112 and the first to fourth transport rollers 116, 117, 119, 120 again in the medium feed direction or medium transport direction to re-feed and re-transport the medium (step S110). Next, the control unit 151 shifts the process to step S104. At this time, the brake roller 113 is driven by the feed roller 112 or rotated in the medium feed direction by the motor 131, and does not separate the medium.

[0058] In this way, when the control unit 151 stops feeding of the medium, it returns the medium to the placement table 103 once, and controls the feeding roller 112 and the brake roller 113 to re-feed the medium without separating it. This eliminates the need for the user to turn off the medium separation function and re-feed the medium, allowing the control unit 151 to improve user convenience. Note that the processing of steps S108 and S110 may be omitted, and the control unit 151 may execute only the change of the feeding mode while stopping the feeding and transport of the medium. In that case, the user does not need to change the feeding mode, allowing the control unit 151 to improve user convenience.

[0059] On the other hand, if the determination unit 153 determines that the overlap detection is invalid (step S104-No) or if the determination unit 153 determines that no overlap occurs (step S105-No), the control unit 151 determines whether or not the entire medium has passed the imaging position of the imaging device 118 (step S111). The control unit 151 determines whether or not the rear end of the medium has passed the position of the media sensor 114, for example, based on the second medium signal received from the media sensor 114. The control unit 151 periodically acquires the second medium signal from the media sensor 114, and determines that the rear end of the medium has passed the position of the media sensor 114 when the signal value of the second medium signal changes from a value indicating that the medium is present to a value indicating that the medium is not present. The control unit 151 determines that the rear end of the medium has passed the imaging position of the imaging device 118 and that the entire medium has been imaged when a predetermined time has elapsed since the rear end of the medium passed the position of the media sensor 114. Note that the control unit 151 may determine that the entire transported medium has been imaged when a predetermined time has elapsed since the start of feeding the medium. If the entire medium has not yet passed the imaging position, the control unit 151 returns the process to step S104.

[0060] On the other hand, if the entire medium has passed the imaging position, the control unit 151 determines that a double feed of media has not occurred (step S112).

[0061] Next, the image generation unit 152 acquires each line image generated during medium transport from the imaging device 118, synthesizes all the acquired line images to generate a medium image, and transmits it to the information processing device via the interface device 132 (step S113).

[0062] Next, control unit 151 determines whether or not a medium remains on mounting table 103 based on the first medium signal acquired from contact sensor 111 (step S114). If a medium remains on mounting table 103, control unit 151 returns the process to step S104, and repeats the processes of steps S104 to S114.

[0063] On the other hand, if there are no media remaining on mounting table 103, control unit 151 stops motor 131 to stop the transport of the media (step S115), and ends the series of steps.

[0064] It should be noted that the processes of steps S108 to S110 may be omitted, and when control unit 151 stops feeding and transporting the medium, the series of steps may be ended without feeding the medium again.

[0065] FIG. 7 is a flowchart showing an example of the operation of the validity determination process.

[0066] An example of the operation of the validity determination process of the medium conveying device 100 will be described below with reference to the flowchart shown in Fig. 7. The flow of the operation described below is executed mainly by the processing circuit 150 in cooperation with each element of the medium conveying device 100 based on a program previously stored in the storage device 140. The flow of the operation shown in Fig. 7 is executed periodically during medium conveyance.

[0067] First, the determination unit 153 determines whether or not a new line image has been acquired from the imaging device 118 (step S201). If a new line image has not been acquired, the process returns to step S201 (step S201-No).

[0068] When a new line image is acquired from the imaging device 118 (step S201-Yes), the control unit 151 identifies the position of the edge of the medium based on this line image (step S202).

[0069] The control unit 151 extracts edge pixels from a line image newly acquired by the imaging device 118. The control unit 151 calculates the absolute value of the difference in luminance values ​​between the pixels adjacent to each other in the horizontal direction of each pixel in the line image (hereinafter referred to as adjacent difference value), and extracts the pixel as an edge pixel if the adjacent difference value exceeds a threshold value Th1. This threshold value Th1 can be set to a difference in luminance values ​​(e.g., 20) that allows a person to visually distinguish the difference in luminance on the image. The control unit 151 detects the edge pixel located on the leftmost side in the line image as the left edge pixel, and detects the edge pixel located on the rightmost side as the right edge pixel.

[0070] The control unit 151 may calculate the average value of the luminance of a plurality of pixels including each pixel and adjacent to the side where the pixel is located for two adjacent pixels in the line image, and extract edge pixels based on the absolute value of the difference between the average values ​​of the two luminance values. The control unit 151 may also calculate the absolute value of the difference in the gradation values ​​of two pixels that are a predetermined distance away from each pixel in the line image as an adjacent difference value. The control unit 151 may also detect edge pixels by comparing the gradation value of each pixel in the input image with a threshold value. For example, when the gradation value of a specific pixel is less than the threshold value and the gradation value of a pixel adjacent to the specific pixel or a pixel that is a predetermined distance away from the specific pixel is equal to or greater than the threshold value, the control unit 151 detects the specific pixel as an edge pixel.

[0071] The control unit 151 refers to the position of the imaging device 118 stored in the memory device 140, and identifies the position on the medium transport path corresponding to the positions of the left-most edge pixel and the right-most edge pixel extracted in the line image as the position of the end of the medium being transported.

[0072] Fig. 8(A) shows an example of a medium image, and Fig. 8(B) is an example of a graph showing the luminance value of each pixel in a specific line image in the medium image.

[0073] The horizontal axis of Fig. 8(B) indicates the position of a pixel in the line image, and the vertical axis indicates the brightness value of each pixel. As shown in Fig. 8(A) and Fig. 8(B), the brightness value changes at the boundary between the medium and the background in the line image. In the example shown in Fig. 8(A) and Fig. 8(B), the pixels corresponding to the left edge position M1 and the right edge position M2 of the medium are extracted as the left edge pixel and the right edge pixel.

[0074] Next, the determination unit 153 determines whether or not the position of the edge of the transported medium is included in the detection area of ​​the ultrasonic sensor 115 (step S203). The detection area is the area on the medium that passes over the ultrasonic receiver 115b, or the ultrasonic receiver 115b and its periphery. The periphery of the ultrasonic receiver 115b is an area in which the signal value of the ultrasonic signal may vary due to the quenching phenomenon described below. The determination unit 153 refers to the arrangement positions of the ultrasonic sensors 115 stored in the storage device 140, and determines whether or not the position of the edge of the medium is included in either of the two detection areas for each of the two ultrasonic sensors 115.

[0075] If the position of the edge of the transported medium is included in the detection area of ​​the ultrasonic sensor 115 (step S203-Yes), the determination unit 153 determines that the detection of overlapping of the medium is invalid (step S205). On the other hand, if the position of the edge of the transported medium is not included in the detection area of ​​the ultrasonic sensor 115 (step S203-No), the determination unit 153 determines that the detection of overlapping of the medium is valid (step S204).

[0076] Fig. 9(A) is a diagram showing an example of the positional relationship between the position of the edge of the medium and the detection area, Fig. 9(B) is a diagram showing another example of the positional relationship between the position of the edge of the medium and the detection area, and Fig. 9(C) is a diagram showing yet another example of the positional relationship between the position of the edge of the medium and the detection area. Figs. 9(A) to 9(C) show detection area 310 on the medium that passes over one of two ultrasonic receivers 115b while the medium 300 is transported.

[0077] 9A, the position of the end of medium 300 in width direction A2 perpendicular to the medium transport direction is not included in detection area 310. In this case, determination unit 153 determines that the position of the edge of the transported medium is not included in the detection area.

[0078] 9(B), medium 300 is transported without tilting, and end 301 of medium 300 in width direction A2 perpendicular to the medium transport direction is included in detection area 310. In this case, determination unit 153 determines that the positions of the end of the medium are included in the detection area at all positions within the transported medium in medium transport direction A1, and does not determine whether or not double feeding of media has occurred over the entire area of ​​the medium.

[0079] 9(C), medium 300 is transported at an angle, and a portion 302 of the end of medium 300 in width direction A2 perpendicular to the medium transport direction and a portion 303 of the end of medium 300 in medium transport direction A1 are included in detection area 310. In this case, determination unit 153 determines that the position of the end of the medium is included in the detection area at a partial position within the transported medium in medium transport direction A1, and does not determine whether or not a duplicate feed of media has occurred at that partial position.

[0080] The following describes the technical significance of invalidating the determination of a double feed of media when the position of the edge of the transported medium is included in the detection area.

[0081] FIG. 10 is a schematic diagram for explaining the characteristics of an ultrasonic signal output from an ultrasonic sensor.

[0082] FIG. 10 is a graph showing the signal value of the ultrasonic signal when the medium 300 is transported as shown in FIG. 9(C). The horizontal axis of FIG. 10 shows the position of the transported medium, and the vertical axis shows the signal value of the ultrasonic signal (the intensity of the ultrasonic wave transmitted through the medium). The signal value of the ultrasonic signal shows a relatively high value when the medium does not overlap. On the other hand, the signal value of the ultrasonic signal shows a relatively low value when the medium overlaps. However, as shown in FIG. 10, when the positions of the ends 302 and 303 of the medium 300 are included in the detection area 310, the so-called quenching phenomenon may occur, in which the transmitted intensity of the ultrasonic wave becomes unstable. This quenching phenomenon causes the signal value of the ultrasonic signal to vary, and the signal value may show the same level as when the medium overlaps. The quenching phenomenon is caused by the ultrasonic wave hitting the end of the medium, diffracting and causing interference, which reduces the ultrasonic signal intensity. The quenching phenomenon is also caused by the vibration of the edge of the medium due to the ultrasonic waves hitting the medium, which reduces the intensity of the ultrasonic waves passing through the medium. In this way, when the positions of the edges 302 and 303 of the medium 300 are included in the detection area 310, it may be erroneously determined that a multi-feed has occurred even though a multi-feed has not occurred. When the position of the edge of the transported medium is included in the detection area, the determination unit 153 disables the multi-feed determination of the medium, thereby preventing erroneous determination that a multi-feed has occurred.

[0083] FIG. 11 is a flowchart showing an example of the operation of the multifeed determination process of the medium conveying device 100.

[0084] An example of the operation of the multifeed determination process of the medium conveying device 100 will be described below with reference to the flowchart shown in Fig. 11. The flow of the operation described below is executed mainly by the processing circuit 150 in cooperation with each element of the medium conveying device 100 based on a program previously stored in the storage device 140. The flow of the operation shown in Fig. 11 is executed periodically during medium conveyance.

[0085] First, the determination unit 153 acquires an ultrasonic signal from the ultrasonic sensor 115 (step S301). Next, the determination unit 153 determines whether or not the signal value of the acquired ultrasonic signal is less than a multi-feed threshold (step S302). The multi-feed threshold is set to a value between the signal value of the ultrasonic signal when one medium is being conveyed and the signal value of the ultrasonic signal when a multi-feed of media occurs.

[0086] If the signal value of the ultrasonic signal is equal to or greater than the multi-feed threshold, the determination unit 153 determines that a multi-feed of media has not occurred (step S303), and ends the series of steps. On the other hand, if the signal value of the ultrasonic signal is less than the multi-feed threshold, the determination unit 153 determines that a multi-feed of media has occurred (step S304), and ends the series of steps.

[0087] In this manner, the determination unit 153 determines whether or not a duplicated medium feed has occurred based on the ultrasonic signal.

[0088] As described above in detail, the medium conveying device 100 invalidates the determination of a double feed of the medium when the position of the edge of the conveyed medium is included in the area where the ultrasonic wave passes through the medium. This makes it possible for the medium conveying device 100 to prevent erroneous determination of a double feed, and to more accurately determine whether or not a double feed of the medium has occurred.

[0089] In the above-described embodiment, the abnormality process is performed after the detection of the position of the edge of the medium, but the abnormality process may be performed after the generation of the medium image in which the line image photographed by the imaging device 118 is combined. In this case, the processes of steps S104 to S110 are performed after the medium image is generated in step S113. When the medium image is generated, the determination unit 153 identifies the position of the edge of the medium for each horizontal line in the medium image, determines whether the position of the edge is included in the detection area, and determines whether the overlap detection is valid or invalid. In addition, the determination unit 153 periodically acquires an ultrasonic signal, and stores the signal value of the ultrasonic signal in the storage device 140 for each position in the medium transport direction A1 in the medium. When the medium image is generated, the determination unit 153 determines whether or not a double feed of the medium has occurred based on the signal value of the ultrasonic signal stored in the storage device 140 for each position in the medium transport direction A1 in the medium corresponding to the line in which the overlap detection is valid.

[0090] In the above-described embodiment, an ultrasonic sensor that outputs ultrasonic transmission information is used as the overlap detector, but a thickness sensor that detects thickness information of the medium may be used as the overlap detector. The thickness sensor is disposed at a position where each ultrasonic sensor 115 is disposed. The thickness sensor includes a light emitter and a light receiver disposed near the medium transport path and facing each other across the transport path. The light emitter irradiates light (infrared light or visible light) toward the light receiver. Meanwhile, the light receiver receives the light irradiated by the light emitter, and generates and outputs a thickness signal, which is an electrical signal according to the intensity of the received light. When a medium is present at the position of the thickness sensor, the light irradiated by the light emitter is attenuated by the medium, and the greater the thickness of the medium, the greater the amount of attenuation. For example, the thickness sensor generates a thickness signal such that the signal value becomes greater as the thickness of the medium increases.

[0091] In addition, a reflected light sensor, a pressure sensor, or a mechanical sensor may be used as the thickness sensor. The reflected light sensor includes a pair of a light emitter and a light receiver provided on one side of the medium transport path, and a pair of a light emitter and a light receiver provided on the other side. The reflected light sensor detects the distance between each pair and each side of the medium from the time from when one pair irradiates one side of the medium with light to when it receives the reflected light, and the time from when the other pair irradiates the other side of the medium with light to when it receives the reflected light. The reflected light sensor generates a thickness signal indicating a subtraction value obtained by subtracting each detected distance from the distance between the two pairs as thickness information. The pressure sensor detects pressure that changes according to the thickness of the medium, and generates a thickness signal indicating the detected pressure as thickness information. The mechanical sensor detects the amount of movement of a roller in contact with the medium, and generates a thickness signal indicating the detected amount of movement as thickness information.

[0092] When a thickness sensor is used as the overlap detection unit, an area facing each sensor on the transported medium is specified as the detection area of ​​the thickness sensor. In the multi-feed determination process, the determination unit 153 acquires a thickness signal from the thickness sensor instead of an ultrasonic signal, and determines whether a multi-feed of media has occurred based on whether the signal value of the acquired thickness signal is equal to or greater than the multi-feed threshold. As with the ultrasonic signal, in the thickness signal, if the end of the medium is crushed or bent in the surface direction at the end position, the signal value of the thickness signal may vary, and the signal value may show the same level as when an overlap of media has occurred. When the position of the end of the transported medium is included in the detection area of ​​the thickness sensor, the determination unit 153 disables the multi-feed determination of the medium, thereby preventing the occurrence of a false determination that a multi-feed has occurred.

[0093] In addition, in the above-described embodiment, the feed roller 112 was positioned below the brake roller 113 to feed the media placed on the mounting table 103 from the bottom up, but the feed roller may be positioned above the brake roller so as to feed the media placed on the mounting table from the top up.

[0094] In the above-described embodiment, an imaging device is used as the end detector, but the end detector is not limited to this.

[0095] FIG. 12 is a schematic diagram for explaining another means for detecting the position of the edge of the medium.

[0096] 12, the edge detection unit includes a distance measurement sensor 108 for detecting the position of second side guide 109b that regulates the position of the medium in the width direction, and control unit 151 specifies the position of the edge of the medium based on the detection result of distance measurement sensor 108. In the example shown in Fig. 12, it is described that the position of second side guide 109b is measured, but the position of first side guide 109a may also be measured in a similar manner using a distance measurement sensor.

[0097] The distance measuring sensor 108 is disposed in the medium conveying direction A1, i.e., in a predetermined position on the end side of the conveying path in the width direction A2 so as to overlap with the second side guide 109b, and measures the distance from the predetermined position to the second side guide 109b. The distance measuring sensor 108 measures the distance to an object located at the opposite position from the time difference between emitting infrared light and receiving the reflected infrared light. The distance measuring sensor 108 includes a light emitter 108a and a light receiver 108b. The light emitter 108a emits light (infrared light) toward the center side in the width direction A2, i.e., toward the second side guide 109b. On the other hand, the light receiver 108b receives the light irradiated by the light emitter 108a and reflected by the second side guide 109b, and generates and outputs a detection signal, which is an electrical signal corresponding to the time from when the light emitter 108a irradiates light to when the light receiver 108b receives the light. That is, the detection signal is a signal corresponding to the distance from a predetermined position where distance measuring sensor 108 is disposed to second side guide 109b. Control unit 151 obtains the distance between distance measuring sensor 108 and second side guide 109b based on the position where distance measuring sensor 108 is disposed and the detection signal. Then, control unit 151 identifies the position of the edge of the medium on the second side guide 109b side based on the position where distance measuring sensor 108 is disposed, the distance between distance measuring sensor 108 and second side guide 109b, and the thickness of second side guide 109b.

[0098] The distance measuring sensor 108 may include a transmitter that emits ultrasonic waves and a receiver that receives ultrasonic waves instead of the light emitter 108a and the light receiver 108b, and may measure the distance to the second side guide 109b from the time difference between when the ultrasonic waves are emitted and when the reflected ultrasonic waves are received. In this case, the distance measuring sensor 108 generates an electric signal as a detection signal according to the time between when the transmitter emits ultrasonic waves and when the receiver receives the ultrasonic waves. Alternatively, the distance measuring sensor 108 may include a transmitter that emits audible sounds and a receiver that receives audible sounds, and may measure the distance to the second side guide 109b from the time difference between when the audible sounds are emitted and when the reflected audible sounds are received. In this case, the distance measuring sensor 108 generates an electric signal as a detection signal according to the time between when the transmitter emits audible sounds and when the receiver receives the audible sounds.

[0099] Alternatively, a conductor such as a metal may be attached to the second side guide 109b, and an inductive proximity sensor including a coil and detecting magnetic loss due to eddy currents generated on the surface of the conductor may be used as the distance measuring sensor 108. In this case, the distance measuring sensor 108 generates an electric signal corresponding to the magnitude of impedance in the coil as the detection signal. Alternatively, a metal or dielectric may be attached to the second side guide 109b, and a capacitive proximity sensor detecting a change in capacitance between the second side guide 109b and the distance measuring sensor 108 may be used as the distance measuring sensor 108. In this case, the distance measuring sensor 108 generates an electric signal corresponding to the magnitude of capacitance between the second side guide 109b and the distance measuring sensor 108 as the detection signal.

[0100] Also, a magnet may be attached to the second side guide 109b, and a magnetic sensor that detects the magnitude of the earth field (magnetic field) between the second side guide 109b and the distance measuring sensor 108 may be used as the distance measuring sensor 108. In this case, the distance measuring sensor 108 generates an electric signal according to the magnitude of the magnetic field between the second side guide 109b and the distance measuring sensor 108 as a detection signal.

[0101] Alternatively, a sensor including an optical rotary encoder and detecting the amount of movement of second side guide 109b from its initial position (predetermined position) may be used as distance measuring sensor 108. The rotary encoder has a disk in which many slits are formed and which is arranged to rotate in accordance with the movement of second side guide 109b, and a light emitter and a light receiver which are arranged to face each other across the disk. In this case, distance measuring sensor 108 generates an electric signal as a detection signal according to the number of times that a state in which there is a slit between the light emitter and the light receiver and a state in which there is no slit and they are blocked by the disk.

[0102] Further, a sensor including an optical linear encoder and detecting the amount of movement of second side guide 109b from its initial position (predetermined position) may be used as distance measuring sensor 108. The optical linear encoder has a glass scale on which a lattice scale is formed, and a light emitter and a light receiver that face each other across the glass scale and move in accordance with the movement of second side guide 109b. In this case, distance measuring sensor 108 generates an electrical signal corresponding to the number of times the amount of light changes in the light receiver as a detection signal.

[0103] Further, a sensor including a magnetic linear encoder and detecting the amount of movement of the second side guide 109b from its initial position (predetermined position) may be used as the distance measuring sensor 108. The magnetic linear encoder has a magnetic scale on which a predetermined magnetic pattern is formed, and a magnetic detection head that faces the magnetic scale and moves in accordance with the movement of the second side guide 109b. In this case, the distance measuring sensor 108 generates an electric signal as a detection signal according to the number of magnetic changes detected by the magnetic detection head.

[0104] Further, a sensor including a sliding resistor and detecting the voltage generated by the sliding resistor may be used as the distance measuring sensor 108. The sliding resistor has a resistor extending in the width direction A2 and having a constant voltage applied from terminals at both ends, and a contact (slider) provided to move in accordance with the movement of the second side guide 109b while abutting against the resistor. In this case, the second side guide 109b generates an electric signal as a detection signal according to the magnitude of the voltage applied from one end of the resistor to the slider.

[0105] FIG. 13 is a schematic diagram for explaining still another means for detecting the position of the edge of the medium.

[0106] In the example shown in FIG. 13, the edge detection unit includes four medium sensors 114a to 114d, and the control unit 151 identifies the position of the edge of the medium based on the detection results of the four medium sensors 114a to 114d.

[0107] The pair of medium sensors 114a, 114b and the pair of medium sensors 114c, 114d are disposed in the width direction A2 so as to sandwich a separate ultrasonic receiver 115b therebetween.

[0108] When the position of the edge of the medium is located between a pair of media sensors, one media sensor 114 detects the medium, but the other media sensor does not detect the medium. When the position of the edge of the medium is located between a pair of media sensors, the determination unit 153 determines that the position of the edge of the transported medium is included in the detection area, and disables overlap detection.

[0109] Furthermore, medium conveying device 100 may detect the position of the edge of the medium by arranging multiple medium sensors 114 side by side in the width direction perpendicular to the medium conveying direction.

[0110] 14 is a diagram showing a schematic configuration of a processing circuit 250 in a medium conveying device according to another embodiment. The processing circuit 250 is used in place of the processing circuit 150 of the medium conveying device 100, and executes the medium reading process and the determination process in place of the processing circuit 150. The processing circuit 250 has a control circuit 251, an image generating circuit 252, a determination circuit 253, etc. Each of these components may be composed of an independent integrated circuit, microprocessor, firmware, etc.

[0111] The control circuit 251 is an example of a control unit, and has the same functions as the control unit 151. The control circuit 251 receives an operation signal from the operation device 105, a first medium signal from the contact sensor 111, and a second medium signal from the medium sensor 114, and reads out the determination result of the double feed of media from the storage device 140. The control circuit 251 outputs a control signal to the motor 131 so as to control the feeding and transport of the media according to each piece of information received or read out. The control circuit 251 also executes abnormality processing due to the double feed based on the determination result of the double feed of media.

[0112] The image generation circuit 252 is an example of an image generation unit, and has the same function as the image generation unit 152. The image generation circuit 252 receives a line image from the imaging device 118 and stores it in the storage device 140, and also generates a medium image and transmits it to the information processing device via the interface device 132.

[0113] The determination circuit 253 is an example of a determination unit, and has the same function as the determination unit 153. The determination circuit 253 reads out a line image from the storage device 140, receives an ultrasonic signal from the ultrasonic sensor 115, and determines whether or not a duplicated feed of media has occurred based on each piece of information received or read out, and stores the determination result in the storage device 140.

[0114] As described above in detail, even when the processing circuit 250 is used, the medium conveying device is able to more accurately determine whether or not a medium conveyance abnormality has occurred. [Explanation of symbols]

[0115] 100 medium conveying device, 103 placement table, 111 contact sensor, 112 feed roller, 113 brake roller, 114 medium sensor, 115 ultrasonic sensor, 116 first conveying roller, 117 second conveying roller, 118 imaging device, 151 control unit, 152 image generating unit, 153 determination unit

Claims

1. A transport unit that transports the medium; an edge detection unit that detects the position of an edge of the medium transported by the transport unit in a direction perpendicular to the medium transport direction; an overlap detection unit that detects an overlap of the medium transported by the transport unit in a detection area; a determination unit that determines whether overlap detection is valid or invalid based on whether the position at which the edge detection unit detects the edge of the medium is included in the detection area; a control unit that executes an abnormality process due to a double feed based on a detection result of the overlap detection unit when the overlap detection unit determines that the overlap detection is valid; A medium transport device comprising:

2. The overlap detection unit includes a receiving unit that detects a transmission intensity of an ultrasonic wave transmitted through a medium, The media transport device of claim 1 , wherein the detection area is an area on the media passing over the receiver.

3. the edge detection unit is an imaging unit that captures an image of a medium and generates an input image; The medium transport device according to claim 1 , wherein the control unit is configured to identify a position of an edge of the medium in a direction perpendicular to a medium transport direction based on the input image.

4. The medium conveying device according to claim 3 , wherein the control unit executes the abnormality processing after detecting the position of an edge of the medium or after generating a medium image by combining the input image captured by the imaging unit.

5. the edge detection unit includes a first detection sensor for detecting a medium; The medium transport device according to claim 1 , wherein the control unit is configured to identify a position of an edge of the medium in a direction perpendicular to a medium transport direction based on a detection result of the first detection sensor.

6. the edge detection unit includes a second detection sensor for detecting a position of a side guide that regulates a position of the medium in a width direction; The medium transport device according to claim 1 , wherein the control unit identifies a position of an edge of the medium in a direction perpendicular to a medium transport direction based on a detection result of the second detection sensor.

7. The medium transport device according to claim 5 , wherein the control unit executes the abnormality process while the medium is being transported by the transport unit.

8. 8. The medium transport device according to claim 1, wherein the determination unit invalidates the overlap detection when a position of an edge of the transported medium is included in the detection area.

9. A method for controlling a medium transport device having a transport unit that transports a medium, an edge detection unit that detects a position of an edge of the medium transported by the transport unit in a direction perpendicular to a medium transport direction, and an overlap detection unit that detects an overlap of the medium transported by the transport unit in a detection area, comprising: determining whether overlap detection is valid or invalid based on whether the position at which the edge detection unit detects the edge of the medium is included in the detection area; If it is determined that the overlap detection is effective, a process for preventing an abnormality caused by a double feed is executed based on the result of the overlap detection. A method for controlling a medium transport device comprising:

10. A control program for a medium conveying device having a conveying unit that conveys a medium, an end detection unit that detects a position of an end of the medium conveyed by the conveying unit in a direction perpendicular to a medium conveying direction, and an overlap detection unit that detects an overlap of the medium conveyed by the conveying unit in a detection area, determining whether overlap detection is valid or invalid based on whether the position at which the edge detection unit detects the edge of the medium is included in the detection area; If it is determined that the overlap detection is effective, a process for preventing an abnormality caused by a double feed is executed based on the result of the overlap detection. A control program for a medium transport device, the control program causing the medium transport device to execute the above steps.

Images