JP7565712B2 - MEDIUM CONVEYING DEVICE, CONTROL METHOD, AND CONTROL PROGRAM - Google Patents

Description

The present invention relates to a media transport device, a control method, and a control program, and in particular to a media transport device that transports and images a medium, a control method, and a control program.

In media transport devices such as scanners that transport and image media, skew (oblique movement) can occur, causing the media to be transported at an angle, resulting in the media not being imaged in its entirety or colliding with the side wall of the transport path and being damaged. In media transport devices, it is desirable to control the transport of the media so that the media is properly imaged and damage to the media does not occur.

An image reading device is disclosed that has multiple document detection units that detect the passage of a document at a predetermined location in the document width direction (see Patent Document 1). This image reading device determines whether or not the skew of the document can be corrected based on the detection results of the multiple document detection units, and if it is determined that the skew of the document can be corrected, corrects the skew of the document by making the conveying speeds of multiple conveying roller pairs different from each other.

JP 2017-197318 A

In a media transport device, it is desirable to more appropriately control the transport of the media when the media is transported at an angle.

The object of the present invention is to provide a media transport device, a control method, and a control program that can more appropriately control the transport of media when the media is transported at an angle.

A media transport device according to one aspect of the present invention includes a plurality of feed rollers arranged at intervals in a direction perpendicular to the media transport direction and each of which rotates independently to feed a medium, an imaging unit which images the medium being fed to generate an input image, a detection unit which detects the amount of inclination of the medium being fed, a feed correction unit which corrects the inclination of the medium by varying the peripheral speeds of the plurality of feed rollers, an image correction unit which corrects the inclination of the medium by image processing of the input image or an image based on the input image, and a selection unit which selects whether to perform correction by the feed correction unit or correction by the image correction unit based on the amount of inclination detected by the detection unit.

A control method according to one aspect of the present invention is a control method for a media transport device having a plurality of feed rollers arranged at intervals in a direction perpendicular to the media transport direction and each of which rotates independently to feed the media, and an imaging unit which captures an image of the fed media to generate an input image, the control method detects the amount of tilt of the fed media, and selects, based on the detected amount of tilt, whether to correct the media tilt by varying the circumferential speeds of the plurality of feed rollers, or to correct the media tilt by image processing of the input image or an image based on the input image.

A control program according to one aspect of the present invention is a control program for a media transport device having a plurality of feed rollers arranged at intervals in a direction perpendicular to the media transport direction and each of which rotates independently to feed the media, and an imaging unit which images the fed media to generate an input image, and causes the media transport device to detect the amount of tilt of the fed media, and select, based on the detected amount of tilt, whether to correct the media tilt by varying the circumferential speeds of the plurality of feed rollers, or to correct the media tilt by image processing of the input image or an image based on the input image.

According to the present invention, the medium transport device, control method, and control program are capable of more appropriately controlling the transport of the medium when the medium is transported at an angle.

1 is a perspective view showing a medium conveying device 100 according to an embodiment. 2 is a diagram for explaining a transport path inside the medium transport device 100. FIG. FIG. 2 is a schematic diagram for explaining the arrangement positions of an optical sensor 114 and the like. 1 is a block diagram showing a schematic configuration of a medium conveying device 100. FIG. FIG. 1 is a diagram showing a schematic configuration of a storage device 160 and a processing circuit 170. 10 is a flowchart illustrating an example of the operation of a medium reading process. 10 is a flowchart illustrating an example of the operation of a medium reading process. 1A and 1B are schematic diagrams for explaining the size and tilt amount of a medium. 1A and 1B are schematic diagrams for explaining the size and tilt amount of a medium. FIG. 13 is a diagram showing a schematic configuration of another processing circuit 270.

Below, a medium conveying device according to one aspect of the present invention will be described with reference to the drawings. However, please note that the technical scope of the present invention is not limited to these embodiments, but extends to the inventions described in the claims and their equivalents.

FIG. 1 is a perspective view showing a medium conveying device 100 configured as an image scanner. The medium conveying device 100 conveys a medium, which is an original document, and captures an image. The medium is paper, cardboard, a card, a booklet, a passport, or the like. The medium conveying device 100 may be a facsimile, a copier, a multifunction printer (MFP, Multifunction Peripheral), or the like.

The medium transport device 100 includes a lower housing 101, an upper housing 102, a loading platform 103, an ejection platform 104, an operation device 105, and a display device 106.

The upper housing 102 is positioned to cover the top surface of the media transport device 100, and engages with the lower housing 101 by a hinge so that it can be opened and closed when media becomes jammed or when cleaning the inside of the media transport device 100, etc.

The loading platform 103 engages with the lower housing 101 so that the transported media can be loaded onto it. The ejection platform 104 engages with the lower housing 101 so that the ejected media can be held.

The operation device 105 has an input device such as a button and an interface circuit that acquires signals from the input device, accepts input operations by a user, and outputs an operation signal corresponding to the user's input operation. The display device 106 has a display including a liquid crystal, an organic EL (Electro-Luminescence), or the like, and an interface circuit that outputs image data to the display, and displays the image data on the display.

Figure 2 is a diagram illustrating the transport path inside the media transport device 100.

The transport path inside the media transport device 100 includes a first sensor 111, multiple feed rollers 112a, b, multiple brake rollers 113a, b, an optical sensor 114, multiple second sensors 115a-d, multiple first transport rollers 116a, b, multiple second transport rollers 117a, b, a first imaging device 118a, a second imaging device 118b, multiple third transport rollers 119a, b, and multiple fourth transport rollers 120a, b, etc.

In the following, the feed rollers 112a, b may be collectively referred to as feed rollers 112. The brake rollers 113a, b may be collectively referred to as brake rollers 113. The second sensors 115a-d may be collectively referred to as second sensor 115. The first conveyor rollers 116a, b may be collectively referred to as first conveyor rollers 116. The second conveyor rollers 117a, b may be collectively referred to as second conveyor rollers 117. The first imaging device 118a and the second imaging device 118b may be collectively referred to as imaging device 118. The third conveyor rollers 119a, b may be collectively referred to as third conveyor rollers 119. The fourth conveyor rollers 120a, b may be collectively referred to as fourth conveyor rollers 120. The number of rollers is not limited to two, and each roller may have one or three or more rollers.

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. 2, arrow A1 indicates the medium transport direction. In the following, 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.

The first sensor 111 is disposed upstream of the feed roller 112 and the brake roller 113. The first sensor 111 has a contact detection sensor and detects whether or not a medium is placed on the placement table 103. The first 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.

The feed roller 112 is provided in the lower housing 101 and feeds the media placed on the mounting table 103 from the bottom up. The brake roller 113 is provided in the upper housing 102 and is positioned opposite the feed roller 112.

The first transport roller 116 and the second transport roller 117 are examples of transport rollers, and are arranged facing each other downstream of the feed roller 112 in the media transport direction A1. The first transport roller 116 and the second transport roller 117 transport the medium fed by the feed roller 112 and the brake roller 113 to the imaging device 118.

The first imaging device 118a has a line sensor using a CIS (Contact Image Sensor) of a 1:1 optical system type having imaging elements using CMOS (Complementary Metal Oxide Semiconductor) arranged in a line in the main scanning direction. The first imaging device 118a also has a lens that forms an image on the imaging element, and an A/D converter that amplifies the electrical signal output from the imaging element and performs analog/digital (A/D) conversion. The first imaging device 118a images the surface of the medium being fed, generates an input image, and outputs it according to control from a processing circuit described below.

Similarly, the second imaging device 118b has a line sensor using a CIS of a life-size optical system type having CMOS imaging elements arranged in a line in the main scanning direction. The second imaging device 118b also has a lens that forms an image on the imaging element, and an A/D converter that amplifies the electrical signal output from the imaging element and performs analog-to-digital (A/D) conversion. The second imaging device 118b images the back side of the medium being fed, generates an input image, and outputs it according to control from a processing circuit described below.

The first imaging device 118a and the second imaging device 118b are examples of an imaging section. Note that the medium conveying device 100 may have only one of the first imaging device 118a and the second imaging device 118b arranged, and may read only one side of the medium. Also, instead of a line sensor based on a CIS of an equal magnification optical system type having a CMOS imaging element, a line sensor based on a CIS of an equal magnification optical system type having a CCD (Charge Coupled Device) imaging element may be used. Also, a line sensor based on a reduced optical system type having a CMOS or CCD imaging element may be used.

The media placed on the mounting table 103 is transported between the lower guide 107a and the upper guide 107b in the media transport direction A1 by the rotation of the feed roller 112 in the direction of the arrow A2 in FIG. 2, i.e., the media feed direction. When transporting the media, the brake roller 113 rotates in the direction of the arrow A3, i.e., the opposite direction to the media feed direction. When multiple media are placed on the mounting table 103, the feed roller 112 and the brake roller 113 function to separate only the media placed on the mounting table 103 that is in contact with the feed roller 112. This operates to restrict the transport of media other than the separated media (preventing double feeding).

The medium is fed between the first transport roller 116 and the second transport 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 transport roller 116 and the second transport roller 117 rotate in the directions of the arrows A4 and A5, respectively. The medium read by the imaging device 118 is discharged onto the discharge tray 104 as the third transport roller 119 and the fourth transport roller 120 rotate in the directions of the arrows A6 and A7, respectively.

Figure 3 is a schematic diagram for explaining the positions of the feed roller 112, the optical sensor 114, and the second sensor 115. Figure 3 is a schematic diagram of the lower housing 101 viewed from above with the upper housing 102 removed.

As shown in FIG. 3, the feed rollers 112a, b are arranged at intervals in the width direction A8 perpendicular to the medium transport direction. Each feed roller 112a, b is arranged to rotate independently by a separate motor to feed the medium. Note that each feed roller 112a, b may be arranged to rotate by a common motor.

The optical sensor 114 is disposed downstream of the feed roller 112 and upstream of the first conveying roller 116 and the second conveying roller 117 in the media conveying direction A1, that is, between the feed roller 112 and the imaging device 118. The optical sensor 114 is also disposed approximately in the center in the width direction A8 perpendicular to the media conveying direction. The optical sensor 114 has a light emitter and a light receiver provided on the same side of the media conveying path, and detects the movement of the medium in the media conveying direction A1 and the width direction A8 perpendicular to the media conveying direction. The light emitter is an LED (light emitting diode) or the like, and emits light toward the conveying path. The light receiver captures an image according to the light received at regular intervals, and detects a common part between the latest image and the previous image. The light receiver calculates the movement direction and movement speed of the conveyed medium based on the change in position of the detected common part in the image, and generates and outputs a movement signal indicating the calculated movement direction and movement speed. The certain period of time is, for example, a period equivalent to 100 operating pulses of the motor described below.

For example, the movement direction indicates a movement component in which the positive direction is from the upstream side to the downstream side in the medium transport direction A1, and a movement component in which the positive direction is from the feed roller 112b side to the feed roller 112a side in the width direction A8. The light receiver has a resolution of, for example, 400 dpi (dots per inch) and is configured to be able to detect a movement of up to 304.8 mm per second. A known optical sensor can be used as the optical sensor 114.

The media conveying device 100 uses the optical sensor 114 to detect the two-dimensional movement of the media on the conveying path, allowing it to detect the amount of media tilt with high precision without damaging the media being fed.

The optical sensor 114 may have a plurality of optical encoders arranged at intervals in the width direction A8 to detect the movement of the medium in the medium transport direction A1 and the width direction A8. Each encoder has a disk formed with a number of slits (light transmission holes) and arranged to rotate according to the medium being fed, and a light emitter and a light receiver arranged to face each other across the disk. The light receiver calculates the movement speed of the transported medium based on the number of changes during a certain period between 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 the light receiver is blocked by the disk. The optical sensor 114 calculates the movement direction of the medium based on the distance between each disk and the difference or ratio of the movement speeds calculated by each light receiver, and generates and outputs a movement signal indicating the calculated movement direction and movement speed.

The second sensor 115 is disposed downstream of the feed roller 112 and upstream of the first transport roller 116 and the second transport roller 117 in the media transport direction A1, i.e., between the feed roller 112 and the imaging device 118. The second sensor 115 may be disposed in the same position as the optical sensor 114 in the media transport direction A1. In addition, each of the second sensors 115a-d is disposed in a line with a space between them, outside the optical sensor 114 (toward the side wall W of the media transport path) in the width direction A8 perpendicular to the media transport direction. The second sensor 115 has a light emitter and a light receiver provided on one side of the media transport path, and a reflective member such as a mirror provided in a position facing the light emitter and the light receiver across the media transport path. The light emitter irradiates light toward the media transport path. On the other hand, the light receiver receives the light that is irradiated by the light emitter and reflected by the reflecting member, and generates and outputs a second medium signal, which is an electrical signal corresponding to the intensity of the received light.

When a medium is present at the position of the second sensor 115, the light emitted by the light emitter is blocked by the medium. Therefore, the signal value of the second medium signal changes depending on whether a medium is present at the position of the second sensor 115 or not. In this way, the second sensor 115 detects whether a medium is present at that position and detects the fed medium. The light emitter and light receiver of the second sensor 115 are provided in positions facing each other across the transport path, and the reflective member may be omitted.

The second sensors 115a-d are an example of a media sensor, and are used to detect the size of the media based on whether the media passes the position of each second sensor 115. For example, if the maximum media size supported by the media conveying device 100 is A4, the size of the imaging device 118 in the width direction A8 (main scanning direction) is set to the size obtained by adding a margin to the A4 horizontal size (size in the short direction). In this case, the second sensors 115a and 115d arranged on the outside are set to be the same distance away from the center position of the media conveying path in the width direction A8, and the distance between the sensors is set to be the A4 horizontal size minus the margin, so that it is possible to determine whether the media is A4 size or larger. The second sensors 115b and 115c arranged on the inside are set to be the same distance away from the center position of the media conveying path in the width direction A8, and the distance between the sensors is set to be the A5 horizontal size minus the margin, so that it is possible to determine whether the media is A5 size or larger.

By using multiple second sensors 115, the media conveying device 100 can easily detect the size of the media being fed, thereby reducing device costs.

Note that either the combination of second sensors 115a and 115d or the combination of second sensors 115b and 115c may be omitted. Also, five or more sensors may be used as second sensors 115.

Figure 4 is a block diagram showing the general configuration of the medium conveying device 100.

In addition to the above-mentioned configuration, the medium conveying device 100 further includes a motor 151, an interface device 152, a memory device 160, and a processing circuit 170.

The motor 151 has 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 170 to feed and transport the medium. In particular, the motor 151 has separate motors that rotate the feed rollers 112a and 112b independently. Note that the motor 151 may rotate the feed rollers 112a and 112b using a common motor. In this case, a driving force transmission mechanism (not shown), such as a gear between the motor 151 and the feed rollers 112a and 112b, is provided so that the rotation speed of each of the feed rollers 112a and 112b can be changed independently in response to a control signal from the processing circuit 170.

The interface device 152 has an interface circuit conforming to a serial bus such as USB, and is electrically connected to an information processing device (not shown, for example, a personal computer, a portable information terminal, etc.) to transmit and receive input images and various information. Also, instead of the interface device 152, 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). The communication unit may have a wired communication interface device for transmitting and receiving signals through a wired communication line according to a communication protocol such as a wired LAN.

The storage device 160 includes a memory device such as a RAM (Random Access Memory) or a ROM (Read Only Memory), 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 160 also stores computer programs, databases, tables, and the like used for various processes of the medium conveying device 100. Computer programs may be installed into the storage device 160 from a computer-readable portable recording medium using a known setup program or the like. Portable recording media include, for example, a CD-ROM (compact disc read only memory) or a DVD-ROM (digital versatile disc read only memory).

The processing circuit 170 operates based on a program previously stored in the storage device 160. The processing circuit is, for example, a CPU (Central Processing Unit). The processing circuit 170 may be 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.

The processing circuit 170 is connected to the operation device 105, the display device 106, the first sensor 111, the optical sensor 114, the second sensor 115, the imaging device 118, the motor 151, the interface device 152, the storage device 160, and the like, and controls each of these components. The processing circuit 170 performs drive control of the motor 151, image capture control of the imaging device 118, and the like, generates an input image, and transmits it to the information processing device via the interface device 152. The processing circuit 170 also detects the amount of tilt of the medium being fed based on the movement signal generated by the optical sensor 114, selects a method of correcting the tilt of the medium based on the detected amount of tilt, and corrects the tilt of the medium using the selected method.

Figure 5 shows the schematic configuration of the memory device 160 and the processing circuit 170.

As shown in FIG. 5, the storage device 160 stores a control program 161, a detection program 162, a selection program 163, a feed correction program 164, an image acquisition program 165, and an image correction program 166. Each of these programs is a functional module implemented by software running on a processor. The processing circuit 170 reads each program stored in the storage device 160 and operates according to the read program. As a result, the processing circuit 170 functions as a control unit 171, a detection unit 172, a selection unit 173, a feed correction unit 174, an image acquisition unit 175, and an image correction unit 176.

Figure 6 is a flowchart showing an example of the operation of the media reading process of the media conveying device 100.

Below, an example of the operation of the media reading process of the media conveying device 100 will be described with reference to the flowcharts shown in Figures 6 and 7. Note that the flow of the operation described below is executed mainly by the processing circuit 170 in cooperation with each element of the media conveying device 100 based on a program previously stored in the storage device 160. The flow of the operation shown in Figures 6 and 7 is executed periodically.

First, the control unit 171 waits until the user inputs an instruction to read a medium using the operation device 105 and receives an operation signal from the operation device 105 instructing the user to read a medium (step S101).

Next, the control unit 171 acquires a first medium signal from the first sensor 111, and determines whether or not a medium is placed on the placement table 103 based on the acquired first medium signal (step S102).

If no medium is placed on the placement table 103, the control unit 171 returns to step S101 and waits until a new operation signal is received from the operation device 105.

On the other hand, if a medium is placed on the placement table 103, the control unit 171 drives the motor 151 to rotate the feed roller 112, the brake roller 113, and the first to fourth transport rollers 116, 117, 119, and 120 to feed and transport the medium (step S103). At this time, the control unit 171 rotates the feed roller 112 so that the peripheral speeds of the multiple feed rollers 112a, b are the same reference speed.

Next, the control unit 171 determines whether the leading edge of the medium has passed the measurement position (step S104). The control unit 171 periodically acquires a movement signal from the optical sensor 114, and determines whether the leading edge of the medium has passed the position of the optical sensor 114 based on the acquired movement signal. The control unit 171 determines that the leading edge of the medium has passed the position of the optical sensor 114 when the movement speed indicated in the movement signal changes from 0 to a non-zero value. The control unit 171 determines that the leading edge of the medium has passed the measurement position when a predetermined time has elapsed since the leading edge of the medium passed the position of the optical sensor 114. The control unit 171 waits until the leading edge of the medium has passed the measurement position.

When the leading edge of the medium passes the measurement position, the detection unit 172 detects the size of the medium being fed (step S105). The detection unit 172 detects the size of the medium being fed based on the detection results of the multiple second sensors 115. The detection unit 172 acquires second medium signals from the multiple second sensors 115, and determines whether or not a medium is present at the position of each second sensor 115 based on the acquired second medium signals.

Figures 8 and 9 are schematic diagrams for explaining the size and tilt of the medium. Similar to Figure 3, Figures 8 and 9 are schematic diagrams of the lower housing 101 viewed from above with the upper housing 102 removed. Figure 8 shows the state when a large medium M1 is transported, and Figure 9 shows the state when a small medium M2 is transported.

As shown in Fig. 8, when the medium is present at the positions of all the second sensors 115, the detection unit 172 detects that the size of the medium in the width direction A8 (medium width) is equal to or greater than the second width value W _S2 as the size of the medium to be fed. The second width value W _S2 is the distance in the width direction A8 between the second sensors 115a and d that are located on the outer side among the four second sensors 115. As shown in Fig. 9, when the medium is not present at the positions of the second sensors 115a and d but is present at the positions of both the second sensors 115b and c, the detection unit 172 detects that the medium width is equal to or greater than the first width value W _S1 and less than the second width value W _S2 as the size of the medium to be fed. The first width value W _S1 is the distance in the width direction A8 between the second sensors 115b and c that are located on the inner side among the four second sensors 115. In other cases, particularly when the medium is not present at the position of the second sensor 115b or 115c, the detection unit 172 detects that the medium width is less than the first width value W _S1 as the size of the medium being fed.

Next, the detection unit 172 detects the amount of tilt of the medium being fed (step S106). The detection unit 172 detects the amount of tilt of the medium being fed based on the detection result by the optical sensor 114. The detection unit 172 acquires a movement signal from the optical sensor 114, and detects the amount of tilt of the medium based on the movement direction of the medium indicated in the acquired movement signal. As shown in Figures 8 and 9, the detection unit 172 calculates the arctangent of the divided value obtained by dividing the movement component in the width direction A8 of the medium by the movement component in the medium transport direction A1 as the tilt θ of the medium's travel direction relative to the medium transport direction A1, and detects the magnitude of the tilt θ as the amount of tilt.

Next, the selection unit 173 determines whether the medium width detected by the detection unit 172 is equal to or greater than the second width value W _S2 (Step S107).

If the medium width is equal to or greater than the second width value W _S2 , the selection unit 173 determines whether the amount of tilt detected by the detection unit 172 is equal to or greater than a reference threshold (step S108). The reference threshold is set to an amount of medium tilt (e.g., 0.1°) at which it can be assumed that no medium skew has occurred.

If the amount of tilt is less than the reference threshold, the selection unit 173 selects not to perform a correction process to correct the tilt of the medium (step S109) and transitions to step S115.

On the other hand, if the amount of tilt is equal to or greater than the reference threshold, the selection unit 173 selects to execute a feed correction process that corrects the tilt of the medium by varying the circumferential speeds of the multiple feed rollers 112 (step S110).

Next, the feed correction unit 174 executes a feed correction process (step S111) and proceeds to step S115. In the feed correction process, the feed correction unit 174 corrects the inclination (skew) of the medium being fed by varying the circumferential speeds of the multiple feed rollers 112a, b.

The feed correction unit 174 sets each circumferential speed so that the circumferential speed of the feed roller 112 located on the side where the medium is moving is greater than the circumferential speed of the feed roller 112 located on the other side. That is, in the example shown in FIG. 8, each circumferential speed is set so that the circumferential speed of the feed roller 112a is greater than the circumferential speed of the feed roller 112b. For example, the feed correction unit 174 sets the circumferential speed of the feed roller 112 located on the side where the medium is moving to a speed greater (faster) than the reference speed, and sets the circumferential speed of the feed roller 112 located on the other side to the reference speed. Note that the feed correction unit 174 may set the circumferential speed of the feed roller 112 located on the side where the medium is moving to the reference speed, and set the circumferential speed of the feed roller 112 located on the other side to a speed less (slower) than the reference speed. The feed correction unit 174 may also set the circumferential speed of the feed roller 112 located on the side toward which the medium is moving to a speed greater (faster) than the reference speed, and set the circumferential speed of the feed roller 112 located on the other side to a speed less (slower) than the reference speed.

As a result, the medium rotates around a predetermined position between the feed roller 112, located on the side the medium is not facing, and the end of the side the medium is not facing, eliminating skew in the medium.

The feed correction unit 174 also returns the circumferential speed of each feed roller 112 to the reference speed before the leading edge of the medium being fed reaches the positions of the first conveyor roller 116 and the second conveyor roller 117. That is, the feed correction unit 174 controls the feeding of the medium so as to correct the inclination of the medium before the leading edge of the medium being fed reaches the positions of the first conveyor roller 116 and the second conveyor roller 117. After the leading edge of the medium being fed reaches the positions of the first conveyor roller 116 and the second conveyor roller 117, the medium is conveyed by the first conveyor roller 116 and the second conveyor roller 117. At that time, if the inclination of the medium is corrected by the feed roller 112, each roller may apply a load to the medium in a different direction, which may damage the medium. The feed correction unit 174 corrects the inclination of the medium before the leading edge of the medium being fed reaches the positions of the first conveyor roller 116 and the second conveyor roller 117, thereby suppressing damage to the medium.

The medium conveying device 100 may previously set in the storage device 160 a relationship between the medium movement direction, the circumferential speed of each feed roller 112 for correcting the movement direction to the medium conveying direction A1, and the correction time for rotating each feed roller 112 at that circumferential speed. In this case, the feed correction unit 174 rotates each feed roller 112 at a circumferential speed associated with the medium movement direction indicated by the movement signal acquired from the optical sensor 114, for a correction time associated with that movement direction.

On the other hand, if the medium width is less than the second width value _W in step S107, the selection unit 173 calculates a fluctuation threshold (step S112). The fluctuation threshold is set according to the size of the medium being fed and the arrangement positions of the second sensor 115, the side wall W of the transport path, and the imaging device 118 on the medium transport path.

ここで、Ｗ_cは撮像装置１１８の幅方向Ａ８の撮像範囲であり、Ｗ_Wは両端に配置された搬送路の側壁Ｗの間の距離であり、Ｗ_S2は外側に配置された第２センサ１１５ａ、ｄの間の幅方向Ａ８の距離である。また、Ｄ_cは第２センサ１１５から撮像装置１１８の撮像位置までの媒体搬送方向Ａ１の距離であり、Ｄ_Wは第２センサ１１５から搬送路の側壁Ｗの下流側の端部までの媒体搬送方向Ａ１の距離である（図８を参照）。これらのパラメータは、予め記憶装置１６０に記憶される。なお、式（１）で算出される第１変動閾値θ_C及び式（２）で算出される第２変動閾値θ_Wが、予め記憶装置１６０に記憶されていてもよい。 When the medium width is equal to or greater than the first width value W _S1 , the selection unit 173 calculates the first variable threshold θ _C according to the following formula (1), and calculates the second variable threshold θ _W according to the following formula (2).

Here, _Wc is the imaging range of the imaging device 118 in the width direction A8, _Ww is the distance between the side walls W of the transport path arranged at both ends, and _Ws2 is the distance in the width direction A8 between the second sensors 115a and d arranged on the outside. Also, _Dc is the distance in the medium transport direction A1 from the second sensor 115 to the imaging position of the imaging device 118, and _Dw is the distance in the medium transport direction A1 from the second sensor 115 to the downstream end of the side wall W of the transport path (see FIG. 8). These parameters are stored in the storage device 160 in advance. The first fluctuation threshold _θc calculated by the formula (1) and the second fluctuation threshold _θw calculated by the formula (2) may be stored in the storage device 160 in advance.

The first fluctuation threshold θ _C is an angle formed by a straight line extending in the medium transport direction A1 and a straight line extending from the arrangement position of the second sensors 115 a, d arranged on the outside to the end of the imaging range of the imaging device 118. In other words, if the medium M1 whose end has passed outside the second sensors 115 a, d proceeds at an angle of the first fluctuation threshold θ _C , there is a possibility that a part of the medium M1 will not be imaged by the imaging device 118. On the other hand, the second fluctuation threshold θ _W is an angle formed by a straight line extending in the medium transport direction A1 and a straight line extending from the arrangement position of the second sensors 115 a, d arranged on the outside to the end downstream of the side wall W of the transport path. In other words, if the medium M1 whose end has passed outside the second sensors 115 a, d proceeds at an angle of the second fluctuation threshold θ _W , there is a possibility that the medium M1 will collide with the side wall W of the transport path.

ここで、Ｗ_S1は内側に配置された第２センサ１１５ｂ、ｃの間の幅方向Ａ８の距離である（図９を参照）。このパラメータは、予め記憶装置１６０に記憶される。なお、式（３）で算出される第１変動閾値θ_C及び式（４）で算出される第２変動閾値θ_Wが、予め記憶装置１６０に記憶されていてもよい。 On the other hand, when the medium width is less than the first width value W _S1 , the selection unit 173 calculates the first variable threshold θ _C according to the following formula (3), and calculates the second variable threshold θ _W according to the following formula (3).

Here, W _S1 is the distance in the width direction A8 between the second sensors 115b and 115c arranged on the inner side (see FIG. 9 ). This parameter is stored in advance in the storage device 160. Note that the first variation threshold value θ _C calculated by the formula (3) and the second variation threshold value θ _W calculated by the formula (4) may be stored in advance in the storage device 160.

The first fluctuation threshold θ _C is an angle formed by a straight line extending in the medium transport direction A1 and a straight line extending from the arrangement position of the second sensors 115 b, c arranged on the inside to the end of the imaging range of the imaging device 118. In other words, if the medium M2 whose end has passed outside the second sensors 115 b, c proceeds at an angle of the first fluctuation threshold θ _C , a part of the medium M2 may not be imaged by the imaging device 118. On the other hand, the second fluctuation threshold θ _W is an angle formed by a straight line extending in the medium transport direction A1 and a straight line extending from the arrangement position of the second sensors 115 b, c arranged on the inside to the end downstream of the side wall W of the transport path. In other words, if the medium M2 whose end has passed outside the second sensors 115 b, c proceeds at an angle of the second fluctuation threshold θ _W , the medium M2 may collide with the side wall W of the transport path.

The selection unit 173 sets the smaller of the calculated first fluctuation threshold value θ _C and second fluctuation threshold value θ _W as the fluctuation threshold value. That is, the fluctuation threshold value is set to the threshold value of the angle at which at least one of an image loss of a part of the medium in the input image and a collision of the medium occurs.

Next, the selection unit 173 determines whether the amount of tilt detected by the detection unit 172 is equal to or greater than the set fluctuation threshold (step S113). If the amount of tilt is equal to or greater than the fluctuation threshold, the selection unit 173 determines that the imaging device 118 is unable to capture an image of the entire medium being fed, or that the medium being fed is in contact with the side wall W of the transport path, and transitions to step S110. That is, in this case, the selection unit 173 selects to execute a feed correction process (step S110), and the feed correction unit 174 executes the feed correction process (step S111).

On the other hand, if the amount of tilt is less than the variation threshold, the selection unit 173 determines that the imaging device 118 can capture the entire medium being fed and that the medium being fed does not come into contact with the side wall W of the transport path. The selection unit 173 selects to execute an image correction process that corrects the tilt of the medium by image processing of the input image or an image based on the input image (step S114), and transitions to step S115. The image correction process is executed by the image correction unit 176 after the input image is generated by the image acquisition unit 175.

In this way, the selection unit 173 selects whether to perform correction by the feeding correction unit 174 or correction by the image correction unit 176 based on the amount of tilt and size of the medium being fed detected by the detection unit 172. That is, the selection unit 173 selects whether to perform correction of the medium tilt by making the circumferential speeds of the multiple feeding rollers 112 different from each other, or correction of the medium tilt by image processing of the input image or an image based on the input image, based on the amount of tilt and size of the medium.

In particular, the selection unit 173 determines whether the imaging device 118 is capable of capturing an image of the entire medium being fed, and whether the medium being fed comes into contact with the side wall W of the transport path, based on the amount of tilt and size of the medium.

When the selection unit 173 determines that the imaging device 118 can capture an image of the entire medium being fed and that the medium being fed will not come into contact with the side wall W of the transport path, the selection unit 173 selects to perform correction by the image correction unit 176. The medium transport device 100 can correct the tilt on the image and does not change the physical feed control of the medium if the medium does not collide with the side wall W of the transport path, so that it is possible to reduce the risk of putting stress on the medium and causing damage when a weak medium such as thin paper is transported. Also, in this case, since the medium transport device 100 does not change the physical feed control of the medium, it is possible to reduce the medium transport time.

On the other hand, if the selection unit 173 determines that the imaging device 118 cannot capture the entire medium being fed, or if it determines that the medium being fed will come into contact with the side wall W of the transport path, it selects to perform correction by the feed correction unit 174. If correction cannot be made by image processing, or if the medium collides with the side wall W of the transport path, the medium transport device 100 physically corrects the inclination of the medium and changes the direction of travel of the medium, making it possible to capture the entire medium while suppressing damage to the medium.

The selection unit 173 also determines whether the imaging device 118 can capture an image of the entire medium being fed and whether the fed medium contacts the side wall W of the transport path based on the arrangement positions of the second sensor 115 and the side wall W of the transport path, and the imaging range of the imaging device 118. Therefore, for each of the various types of media transport devices, the selection unit 173 can appropriately determine whether the imaging device 118 can capture an image of the entire medium being fed and whether the fed medium contacts the side wall W of the transport path.

Next, the image acquisition unit 175 determines whether the entire medium has been imaged by the imaging device 118 (step S115). The image acquisition unit 175 periodically acquires a second medium signal from the second sensor 115, and determines whether a medium is present at the position of the second sensor 115 based on the acquired second medium signal. The image acquisition unit 175 determines that the rear end of the medium has passed the position of the second sensor 115 when the signal value of the second medium signal changes from a value indicating the presence of a medium to a value indicating the absence of a medium. The image acquisition unit 175 determines that the entire medium has been imaged when a predetermined time has elapsed since it was determined that the rear end of the medium has passed the position of the second sensor 115. The image acquisition unit 175 waits until the entire medium has been imaged.

On the other hand, when the entire medium has been imaged, the image acquisition unit 175 acquires an input image from the imaging device 118 and stores it in the storage device 160 (step S116). Note that the image acquisition unit 175 may acquire a partial image from the imaging device 118 and store it in the storage device 160 each time the imaging device 118 generates a partial image of one or more predetermined lines, and may integrate all the partial images to generate an input image when the entire medium has been imaged.

Next, the image correction unit 176 determines whether or not the selection unit 173 has selected to execute the image correction process in the process of step S114 (step S117). If the selection unit 173 has not selected to execute the image correction process, the image correction unit 176 transitions to the process of step S119.

On the other hand, if the selection unit 173 has selected to execute the image correction process, the image correction unit 176 executes the image correction process (step S118). In the image correction process, the image correction unit 176 corrects the inclination of the medium by performing image processing on the input image or an image based on the input image.

The image correction unit 176 calculates the absolute value of the difference in gradation values between the pixels adjacent to each pixel in the input image for each of the horizontal and vertical directions (hereinafter referred to as the adjacent difference value), and extracts the pixel as an edge pixel if the adjacent difference value exceeds the gradation threshold. The gradation value is a luminance value or a color value (R value, G value, or B value). The gradation threshold can be set to a gradation value difference (e.g., 20) that allows a person to visually distinguish the difference in luminance on the image. The image correction unit 176 may calculate the absolute value of the difference in gradation values between two pixels that are a predetermined distance away from each pixel in the input image as the adjacent difference value. The image correction unit 176 may also extract edge pixels by comparing the gradation value of each pixel in the input image with a threshold. For example, if the gradation value of a specific pixel is less than the threshold 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, the image correction unit 176 regards the specific pixel as an edge pixel. The image correction unit 176 generates an edge image consisting of edge pixels in both the horizontal and vertical directions.

Next, the image correction unit 176 extracts multiple straight lines from each edge image generated for each of the horizontal and vertical directions. The image correction unit 176 detects the straight lines using a Hough transform. The image correction unit 176 may also detect the straight lines using the least squares method. The image correction unit 176 may also group adjacent edge pixels in each edge image by labeling, and detect an approximate straight line connecting two edge pixels located at both ends of each group in the horizontal or vertical direction as a straight line.

Next, the image correction unit 176 detects a rectangle from the detected straight lines. The image correction unit 176 extracts a plurality of rectangle candidates consisting of four straight lines, two of which are approximately perpendicular to each other, from the detected straight lines. The image correction unit 176 first selects one horizontal straight line (hereinafter referred to as the first horizontal line), and extracts a horizontal straight line (hereinafter referred to as the second horizontal line) that is approximately parallel to the selected straight line (for example, within ±3°) and is a first distance or more away from the selected straight line. Next, the image correction unit 176 extracts a vertical straight line (hereinafter referred to as the first vertical line) that is approximately perpendicular to the first horizontal line (for example, within ±3° of 90°). Next, the image correction unit 176 extracts a vertical straight line (hereinafter referred to as the second vertical line) that is approximately perpendicular to the first horizontal line and is a second distance or more away from the first vertical line. The first distance and the second distance are determined in advance according to the size of the medium to be read by the medium conveying device 100, and may be the same value.

The image correction unit 176 extracts all combinations of the first horizontal line, second horizontal line, first vertical line, and second vertical line that satisfy the above conditions for all extracted straight lines, and detects the rectangular candidate with the largest area among the rectangular candidates formed from each extracted combination as the medium area. The image correction unit 176 generates a cut-out image by cutting out the medium area from the input image. That is, the cut-out image is an image in which, among the pixels in the input image, pixels in which the medium is not captured are replaced with invalid pixels (e.g., pixels that show white). The cut-out image is an example of an image based on the input image.

The image correction unit 176 calculates the average value of the angles between a straight line extending in the vertical direction and each of the first vertical line, the second vertical line, the straight line perpendicular to the first horizontal line, and the straight line perpendicular to the second horizontal line that constitute the medium area as the inclination of the medium area. The image correction unit 176 uses a known image processing technique to correct the cut-out image so as to rotate (convert the coordinates of each pixel) the calculated inclination in the direction opposite to the direction in which the medium area is tilted. Note that the image correction unit 176 may correct the input image, instead of the cut-out image, so as to rotate the input image in the direction opposite to the direction in which the medium area is tilted in the calculated inclination. The image correction unit 176 may also generate a cut-out image from the input image by directly arranging each pixel included in the medium area in the input image at the corresponding coordinate position of the rotated medium area in the cut-out image.

Next, the image acquisition unit 175 transmits the input image or the cut-out image to the information processing device via the interface device 152 (step S119). If the input image or the cut-out image has been corrected in step S118, the image acquisition unit 175 transmits the corrected input image or the cut-out image to the information processing device. The information processing device displays the received input image or the cut-out image in accordance with a request from the user.

Next, the control unit 171 determines whether or not a medium remains on the placement table 103 based on the medium detection signal obtained from the first sensor 111 (step S120). If a medium remains on the placement table 103, the control unit 171 returns the process to step S104 and repeats the processes of steps S104 to S120.

On the other hand, if there is no media remaining on the mounting table 103, the control unit 171 stops the motor 151 (step S121) and ends the series of steps.

The selection unit 173 may select whether to perform correction by the feed correction unit 174 or correction by the image correction unit 176 based only on the amount of tilt of the medium without using the size of the medium. In this case, the processes of steps S105 and S107 are omitted, and the selection unit 173 performs the processes of steps S112 to S113 regardless of the size of the medium. In addition, in step S112, the selection unit 173 calculates the first variation threshold θ _C according to formula (1) regardless of the medium width, and calculates the second variation threshold θ _W according to formula (2). The selection unit 173 may calculate the first variation threshold θ _C according to formula (3) and calculate the second variation threshold θ _W according to formula (4) regardless of the medium width.

Even if the selection unit 173 does not use the size of the medium, it can properly image the medium and control the feeding of the medium so as not to cause damage to the medium. However, by using the size of the medium, the selection unit 173 can more properly image the medium and more properly control the feeding of the medium.

Also, in step S112, the selection unit 173 may calculate the first variation threshold θ _C as the variation threshold without calculating the second variation threshold θ _W. In this case, in step S113, the selection unit 173 determines whether or not the imaging device 118 can capture the entire fed medium based on the tilt amount detected by the detection unit 172. If it is determined that the imaging device 118 can capture the entire fed medium, the selection unit 173 selects to execute correction by the image correction unit 176 in step S114. On the other hand, if it is determined that the imaging device 118 cannot capture the entire fed medium, the selection unit 173 selects to execute correction by the feed correction unit 174 in step S110. This allows the selection unit 173 to properly capture the medium.

Also, in step S112, the selection unit 173 may calculate the second variation threshold θ _W as the variation threshold without calculating the first variation threshold θ _C. In this case, in step S113, the selection unit 173 determines whether or not the fed medium contacts the side wall W of the transport path based on the amount of tilt detected by the detection unit 172. If it is determined that the fed medium does not contact the side wall W of the transport path, the selection unit 173 selects to execute correction by the image correction unit 176 in step S114. On the other hand, if it is determined that the fed medium contacts the side wall W of the transport path, the selection unit 173 selects to execute correction by the feed correction unit 174 in step S110. This allows the selection unit 173 to control the feeding of the medium so that damage to the medium does not occur.

Also, an optical sensor similar to optical sensor 114 may be used as second sensor 115. In this case, in step S105, detection unit 172 acquires movement signals from multiple second sensors 115 and determines whether or not a medium is present at the position of each second sensor 115 based on the acquired movement signals. If the movement speed indicated in the movement signal is a non-zero value, detection unit 172 determines that a medium is present at the position of second sensor 115, and if the medium is being transported (motor is being driven) and the movement speed is 0, it determines that a medium is not present at the position of second sensor 115.

As described above in detail, the medium conveying device 100 selects whether to perform physical correction of the medium tilt using the feed roller 112 or correction of the medium tilt using image processing based on the amount of tilt of the medium being fed. By using the amount of tilt of the medium being fed, the medium conveying device 100 can appropriately determine whether the tilt of the medium should be corrected physically or by image processing. Therefore, the medium conveying device 100 is able to more appropriately control the conveyance of the medium when the medium is conveyed tilted.

In particular, the medium conveying device 100 corrects the inclination of the medium through image processing when there is no need to change the physical feeding control of the medium, and physically corrects the inclination of the medium only when there is a need to change the physical feeding control of the medium. Therefore, the medium conveying device 100 can reduce the risk of damaging the medium by putting stress on it when a weak medium such as thin paper is being conveyed.

Figure 10 is a diagram showing a schematic configuration of a processing circuit 270 in a medium conveying device according to another embodiment. The processing circuit 270 is used in place of the processing circuit 170 of the medium conveying device 100, and executes media reading processing and the like in place of the processing circuit 170. The processing circuit 270 has a control circuit 271, a detection circuit 272, a selection circuit 273, a feed correction circuit 274, an image acquisition circuit 275, an image correction circuit 276, and the like. Each of these components may be composed of an independent integrated circuit, microprocessor, firmware, and the like.

The control circuit 271 is an example of a control unit, and has the same functions as the control unit 171. The control circuit 271 receives an operation signal from the operation device 105 and a first medium signal from the first sensor 111, and drives the motor 151 in response to each received signal to control the feeding and transport of the medium.

The detection circuit 272 is an example of a detection unit, and has the same function as the detection unit 172. The detection circuit 272 receives a movement signal from the optical sensor 114 and a second medium signal from the second sensor 115, detects the amount of tilt and size of the medium based on the received signals, and stores the detection results in the storage device 160.

The selection circuit 273 is an example of a selection unit, and has the same function as the selection unit 173. The selection circuit 273 reads the detection results of the amount of tilt and size of the medium from the storage device 160, selects whether to perform correction by the feed correction circuit 274 or correction by the image correction circuit 276 based on the detection results that have been read, and stores the selection result in the storage device 160.

The feed correction circuit 274 is an example of a feed correction unit, and has the same function as the feed correction unit 174. The feed correction circuit 274 reads the selection result from the storage device 160, and when correction by the feed correction circuit 274 is selected, corrects the inclination of the medium by controlling the motor 151 so that the peripheral speeds of the multiple feed rollers 112 are different from each other.

The image acquisition circuit 275 is an example of an image acquisition unit, and has the same functions as the image acquisition unit 175. The image acquisition circuit 275 receives an input image from the imaging device 118 and stores it in the storage device 160. The image acquisition circuit 275 also reads out the input image or the cut-out image from the storage device 160 and transmits it to the information processing device via the interface device 152.

The image correction circuit 276 is an example of a correction unit, and has the same function as the image correction unit 176. The image correction circuit 276 reads the selection result from the storage device 160, and if correction by the image correction circuit 276 is selected, it reads the input image from the storage device 160. The image correction circuit 276 corrects the tilt of the medium by image processing of the input image or the cut-out image, and stores the corrected image in the storage device 160.

As described above in detail, the media conveying device is now able to more appropriately control the conveyance of the media when the media is conveyed at an angle, even when using the processing circuit 270.

REFERENCE SIGNS LIST 100 Medium conveying device 112 Feeding roller 114 Optical sensor 115 Second sensor 116 First conveying roller 117 Second conveying roller 118 Imaging device 172 Detection section 173 Selection section 174 Feeding correction section 176 Image correction section

Claims (8)

A plurality of feed rollers arranged at intervals in a direction perpendicular to the medium transport direction and each of which rotates independently to feed the medium;
an imaging unit that captures an image of the medium being fed and generates an input image;
a detection unit that detects the amount of inclination and the width size of the medium being fed;
a feeding correction unit that corrects a skew of the medium by making the peripheral speeds of the plurality of feeding rollers different from one another;
an image correction unit that corrects a tilt of a medium by image processing on the input image or an image based on the input image;
a selection unit that selects whether the correction by the feed correction unit or the correction by the image correction unit is to be performed by comparing the amount of tilt detected by the detection unit with a threshold value,
The selection unit changes the threshold value in accordance with the width direction size detected by the detection unit.
A medium transport device comprising: The selection unit is
determining whether or not the imaging unit is capable of imaging the entire medium being fed by comparing the amount of tilt detected by the detection unit with the threshold value;
When it is determined that the imaging unit can image the entire medium being fed, a selection is made to execute correction by the image correction unit;
The medium conveying device according to claim 1 , wherein, when it is determined that the imaging section cannot capture an image of the entire medium being fed, a selection is made to execute correction by the feeding correction section. The selection unit is
determining whether the medium being fed comes into contact with a side wall of the transport path by comparing the amount of tilt detected by the detection unit with the threshold value;
When it is determined that the medium being fed does not contact a side wall of the transport path, a correction is selected to be performed by the image correction unit;
The medium transport device according to claim 1 , further comprising a step of selecting execution of correction by the transport correction unit when it is determined that the medium being transported will come into contact with a side wall of the transport path. an optical sensor disposed between the feed roller and the imaging unit in a medium transport direction and configured to detect movement of the medium in the medium transport direction and in a direction perpendicular to the medium transport direction;
4. The medium transport device according to claim 1, wherein the detection unit detects an amount of tilt of the medium being fed based on a detection result by the optical sensor. a conveying roller disposed downstream of the feeding roller in a medium conveying direction and configured to convey the medium fed by the feeding roller to the imaging unit;
5. The medium transport device according to claim 1, wherein the transport correction unit corrects a skew of the medium before a leading edge of the medium being transported reaches a position of the transport roller. a plurality of media sensors arranged at intervals in a direction perpendicular to the media transport direction;
6. The medium transport device according to claim 1, wherein the detection unit detects a width direction size of the medium being fed based on detection results from the plurality of medium sensors. A method for controlling a medium transport device having a plurality of feed rollers arranged at intervals in a direction perpendicular to a medium transport direction and each of which rotates independently to transport a medium, and an imaging unit which captures an image of the medium being transported to generate an input image, comprising the steps of:
Detecting the amount of inclination and the width size of the medium being fed,
and selecting whether to perform correction of the skew of the medium by making the peripheral speeds of the plurality of feed rollers different from each other or correction of the skew of the medium by image processing of the input image or an image based on the input image by comparing the detected amount of skew with a threshold value;
In the selection, the threshold value is changed according to the detected width direction size.
A control method comprising: A control program for a medium transport device having a plurality of feed rollers arranged at intervals in a direction perpendicular to a medium transport direction and each of which rotates independently to transport a medium, and an imaging unit which captures an image of the medium being transported to generate an input image, the control program comprising:
Detecting the amount of inclination and the width size of the medium being fed,
causing the medium transport device to select whether to perform a correction of the medium tilt by making the peripheral speeds of the plurality of feed rollers different from each other or a correction of the medium tilt by image processing of the input image or an image based on the input image by comparing the detected amount of tilt with a threshold value;
In the selection, the threshold value is changed according to the detected width direction size.
A control program comprising:

Images