JP2017169039A - Image reading apparatus, control method, and control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reading device, a control method, and a control program that appropriately detect inclination of an imaging unit while suppressing increasing of cost and device size.SOLUTION: An image reading device 100 comprises imaging units 133a, 133b that image a manuscript conveyed, opposite members 134b, 134a being placed in an opposite position to the imaging units, in one of which opposite members a mark is shown only at one end in a direction orthogonal to a conveying direction of the manuscript in an imaging range of the imaging unit, a storage unit 301 that stores a reference position at which the mark is shown in a reference image where the manuscript is imaged by the imaging unit in a state in which the manuscript is not conveyed, a detection unit 161 that detects inclination amount of the imaging unit by comparing a comparison position at which the mark is shown in a comparison image imaged by the imaging unit and the reference position in a state in which the manuscript is carried, and a correction unit 164 that corrects the comparison image according to the inclination amount.SELECTED DRAWING: Figure 6

Description

  The present disclosure relates to an image reading apparatus, a control method, and a control program, and more particularly, to an image reading apparatus, a control method, and a control program that detect an inclination of an imaging unit.

  In an image reading apparatus such as a scanner that captures both sides of a document, in order to shorten the transport path of the apparatus and reduce the size of the apparatus, an image capturing unit that captures the front surface and an image capturing unit that captures the back surface sandwich the document transport path. In many cases, they are provided facing each other. In such an image reading apparatus, when images of various thickness documents such as copy paper, cardboard, plastic cards, etc. are imaged, focus deviation, brightness unevenness, etc. do not occur. One imaging unit is movably provided in accordance with the thickness. However, if the image pickup surface of the image pickup unit is inclined with respect to the document conveyance surface, an image cannot be appropriately picked up. Therefore, the image reading apparatus is required to appropriately detect the inclination of the image pickup unit.

  A document reading apparatus is disclosed in which a resolution pattern is formed on both left and right sides of a document back plate, and the resolution pattern is read by a CCD sensor to set the distance between the contact glass and the document back plate (see Patent Document 1). .

  In addition, a reference standard part is formed on both outer sides of the transport area of the original of the light transmitting body that makes the light emitted from the transmissive light source part incident on the CIS side, and according to the MTF value of the pixel corresponding to the reference standard part An image reading apparatus that outputs a correction signal is disclosed (see Patent Document 2).

JP 2006-237661 A JP 2008-311953 A

  An image reading apparatus is required to appropriately detect the inclination of the imaging unit while suppressing an increase in cost and apparatus size.

  An object of the image reading apparatus, the control method, and the control program is to appropriately detect the tilt of the imaging unit while suppressing an increase in cost and apparatus size.

  An image reading apparatus according to one aspect of the present embodiment is provided in an image capturing unit that captures an image of a conveyed document and a position facing the image capturing unit, and in a direction orthogonal to the document transport direction within an image capturing range of the image capturing unit. An opposing member having a mark only on one end, a storage unit for storing a reference position where the mark appears in a reference image captured by the imaging unit when the document is not conveyed, and an imaging unit with the document conveyed A detection unit that detects the amount of inclination of the imaging unit by comparing the comparison position where the mark is captured in the comparison image captured by the reference and the reference position, and a correction unit that corrects the comparison image according to the amount of inclination. Have.

  In addition, a control method according to one aspect of the present embodiment controls an image reading apparatus that includes an imaging unit that captures an image of a conveyed document, a facing member provided at a position facing the imaging unit, and a storage unit. In the method, the opposing member has a mark only at one end in a direction orthogonal to the document conveyance direction within the imaging range of the imaging unit, and the storage unit allows the imaging unit to be in a state where the document is not conveyed. The reference position where the mark appears in the captured reference image is stored, and the comparison position where the mark appears in the comparison image captured by the imaging unit in a state where the document is conveyed is compared with the reference position, thereby obtaining the imaging unit. And the correction of the comparison image in accordance with the amount of inclination.

  In addition, a control program according to one aspect of the present embodiment controls an image reading apparatus that includes an imaging unit that captures an image of a conveyed document, a facing member provided at a position facing the imaging unit, and a storage unit. In the program, a mark is shown only on one end of the opposing member in a direction orthogonal to the document conveyance direction within the imaging range of the imaging unit, and the storage unit allows the imaging unit to detect the document without being conveyed. The reference position where the mark appears in the captured reference image is stored, and the comparison position where the mark appears in the comparison image captured by the imaging unit in a state where the document is conveyed is compared with the reference position, thereby obtaining the imaging unit. The image reading apparatus is caused to detect the inclination amount of the image and correct the comparison image according to the inclination amount.

  According to the present embodiment, the image reading apparatus, the control method, and the control program can appropriately detect the inclination of the imaging unit while suppressing an increase in cost and apparatus size.

1 is a configuration diagram of an example of an image processing system according to an embodiment. 2 is a perspective view of the image reading apparatus 100 in a state where a document table 103 is set. FIG. 3 is a diagram for explaining a conveyance path inside the image reading apparatus 100. FIG. It is a figure for demonstrating the 1st imaging unit 130a etc. FIG. It is a figure for demonstrating operation | movement of the 2nd imaging unit 130b. FIG. 2 is a view of the image reading apparatus 100 as viewed from above. It is a schematic diagram which shows the other example of the mark 136a. It is a schematic diagram which shows the other example of the mark 136a. 2 is a diagram for describing an example of a hardware configuration of an image reading apparatus 100. FIG. 2 is a diagram showing a schematic configuration of a storage device 301 and a CPU 300. FIG. It is a flowchart which shows the example of operation | movement of the initialization process. It is a figure for demonstrating the relationship between deviation | shift amount and inclination amount. It is a figure for demonstrating the relationship between deviation | shift amount and inclination amount. It is a figure for demonstrating the relationship between deviation | shift amount and inclination amount. It is a graph which shows an example of the relationship between the position of the 1st reference member 134a, and illumination intensity. It is a graph which shows an example of the relationship between the horizontal position of each pixel, and a correction coefficient. 5 is a flowchart illustrating an example of an operation of document reading processing. It is a flowchart which shows the example of operation | movement of a correction process. It is a schematic diagram which shows an example of a 2nd comparison image. It is a figure for demonstrating the inclination of the 2nd imaging device 133b. It is a graph which shows an example of the relationship between the position of a document etc. and illuminance. It is a graph which shows an example of the relationship between the horizontal position of each pixel, and a correction coefficient. It is a schematic diagram for demonstrating the deviation | shift amount when an imaging device inclines. FIG. 10 is a schematic diagram for explaining another imaging device 133. FIG. 12 is a schematic diagram for explaining another imaging device 133. It is a block diagram showing a schematic configuration of another image processing LSI 402.

  Hereinafter, an image reading apparatus, a control method, and a control program according to an aspect of the present disclosure will be described with reference to the drawings. However, it should be noted that the technical scope of the present disclosure is not limited to the embodiments, and extends to the invention described in the claims and equivalents thereof.

  FIG. 1 is a configuration diagram of an example of an image processing system according to the embodiment.

  The image reading apparatus of this embodiment is configured as an image reading apparatus 100 such as an image scanner. The image processing system 1 includes an image reading device 100 and an information processing device 10. In FIG. 1, the image reading apparatus 100 is depicted in a perspective view.

  The image reading apparatus 100 includes a lower casing 101, an upper casing 102, a document table 103, a front cover 105a, an open / close detection unit 107, and the like, and is connected to the information processing apparatus 10. The information processing apparatus 10 may be a personal computer, a portable information terminal, or the like, for example.

  FIG. 2 is a perspective view of the image reading apparatus 100 in a state where the document table 103 is set.

  The image reading apparatus 100 includes a top cover 105b, an auxiliary cover 105c, and operation buttons 106. As shown in FIG. 1, the document table 103 is engaged with the lower casing 101 by a hinge so as to be rotatable in a direction indicated by an arrow A1. In the state shown in FIG. 1, the document table 103 is arranged at a position covering the upper casing 102, the upper cover 105b, and the auxiliary cover 105c, and functions as an exterior cover.

  On the other hand, in the state shown in FIG. The document table 103 is provided with side guides 104a and 104b that are movable in the left-right direction with respect to the document conveyance direction. By positioning the side guides 104a and 104b according to the width of the document, the width direction of the document can be regulated.

  The front cover 105a is engaged with the lower casing 101 by a hinge so as to be rotatable in the direction indicated by the arrow A2. The upper surface cover 105b is connected to the front cover 105a on one end side and is connected to the auxiliary cover 105c on the other end side. The auxiliary cover 105c is extended from the upper surface cover 105b to hold the document when necessary.

  The operation button 106 is disposed on the surface of the upper casing 102 and, when pressed, generates and outputs an operation detection signal. The open / close detection unit 107 includes a contact detection sensor disposed at a position facing the document table 103 in a closed state, and detects the open / closed state of the document table 103. The open / close detection unit 107 generates and outputs an open / close detection signal whose signal value changes depending on whether the document table 103 is open or closed.

  FIG. 3 is a diagram for explaining a conveyance path inside the image reading apparatus 100. The image reading apparatus 100 includes a first sensor 110, a pick arm 111, a flap 112, a paper feed roller 113, a retard roller 114, an ultrasonic transmitter 115a, an ultrasonic receiver 115b, a first transport roller 116, and a first driven roller 117. Is provided. The image reading apparatus 100 also includes a second sensor 118, an imaging unit guide 120, a first imaging unit 130a, a second imaging unit 130b, a second transport roller 140, a second driven roller 141, and the like.

  The lower surface of the upper housing 102 forms the upper guide 108a of the document conveyance path, and the upper surface of the lower housing 101 forms the lower guide 108b of the document conveyance path. 2 and 3, an arrow A3 indicates the conveyance direction of the document. Hereinafter, upstream means upstream in the document transport direction A3, and downstream means downstream in the document transport direction A3.

  The first sensor 110 is a contact detection sensor and is arranged on the upstream side of the pick arm 111 and detects whether or not a document is placed on the document table 103. The first sensor 110 generates and outputs a first document detection signal whose signal value changes depending on whether the document is placed on the document table 103 or not.

  The paper feed roller 113 is rotatably supported by the main body of the image reading apparatus 100. A contact member 142 that contacts the document placed on the document table 103 is provided on the outer peripheral surface of the sheet feed roller 113. The contact member 142 is a member having a large frictional force with a document such as rubber.

  The retard roller 114 is disposed to face the paper feed roller 113 and regulates the conveyance of the document that is not in contact with the paper feed roller 113 in the conveyance direction A3. The retard roller 114 is rotatably supported by the main body of the image reading apparatus 100. A contact member 143 that contacts the document placed on the document table 103 is provided on the outer peripheral surface of the retard roller 114. The contact member 143 is a member having a large frictional force with a document such as rubber.

  The ultrasonic transmitter 115a and the ultrasonic receiver 115b are arranged in the vicinity of the document conveyance path so as to face each other with the conveyance path interposed therebetween. The ultrasonic transmitter 115a transmits ultrasonic waves. On the other hand, the ultrasonic receiver 115b detects the ultrasonic wave transmitted by the ultrasonic transmitter 115a and passed through the document, and generates and outputs an ultrasonic signal that is an electrical signal corresponding to the detected ultrasonic wave. Hereinafter, the ultrasonic transmitter 115a and the ultrasonic receiver 115b may be collectively referred to as an ultrasonic sensor 115.

  The first conveying roller 116 and the first driven roller 117 are rotatably supported by the main body of the image reading apparatus 100, respectively. The first conveyance roller 116 and the first driven roller 117 are disposed on the upstream side of the first imaging unit 130 a and the second imaging unit 130 b, and the first driven roller 117 faces the first conveyance roller 116 and the first conveyance roller 116. Is disposed above. The first conveying roller 116 is fixed, and the first driven roller 117 is arranged to be movable upward (in the direction of arrow A4) with respect to the first conveying roller 116.

  The second transport roller 140 and the second driven roller 141 are each rotatably supported by the main body of the image reading apparatus 100. The second conveyance roller 140 and the second driven roller 141 are disposed on the downstream side of the imaging unit 130, and the second driven roller 141 is disposed above the second conveyance roller 140 so as to face the second conveyance roller 140. The second transport roller 140 is fixed, and the second driven roller 141 is arranged to be movable upward (in the direction of arrow A5) with respect to the second transport roller 140.

  FIG. 4 is a diagram for explaining the first imaging unit 130a, the second imaging unit 130b, and the imaging unit guide 120. The first imaging unit 130a images the front side of the conveyed document, and the second imaging unit 130b images the back side of the conveyed document. The second imaging unit 130b is disposed above the first imaging unit 130a so as to face the first imaging unit 130a. The second imaging unit 130b includes an imaging unit guide 120 for guiding a document between the first imaging unit 130a and the second imaging unit 130b. Hereinafter, the first imaging unit 130a and the second imaging unit 130b may be collectively referred to as the imaging unit 130.

  While the first imaging unit 130a is fixed to the lower casing 101, the second imaging unit 130b is supported by the upper casing 102 so as to be movable in a direction perpendicular to the document conveyance path. The second imaging unit 130b includes an urging spring 131 on the upper side, and is urged by the urging spring 131 in a direction toward the first imaging unit 130a. When the document is not present on the conveyance path, the urging spring 131 is urged. Return to the initial position by the urging force. That is, the second imaging unit 130b is provided to be movable between an initial position facing the first imaging unit 130a and a position facing the first imaging unit 130a and away from the first imaging unit 130a from the initial position. It has been.

  When the second imaging unit 130b is in the initial position, the width of the gap between the opposing first imaging unit 130a and the second imaging unit 130b is larger than the thickness of copy paper or printing paper. For this reason, even if these originals are conveyed, the second imaging unit 130b does not move from the initial position.

  The first imaging unit 130a includes a first light source 132a, a first imaging device 133a, a first reference member 134a, a first glass surface 135a, and the like. The second imaging unit 130b includes a second light source 132b, a second imaging device 133b, a second reference member 134b, a second glass surface 135b, and the like. Hereinafter, the first imaging device 133a and the second imaging device 133b may be collectively referred to as the imaging device 133. The first reference member 134a and the second reference member 134b may be collectively referred to as a reference member 134.

  The first light source 132a includes RGB light emitting diodes (RGB) and a light guide member, and irradiates illumination light on the surface of the document. When there is no document at the irradiated location, the illumination light is irradiated to the second reference member 134b of the second imaging unit 130b. Similarly, the second light source 132b includes LEDs of RGB colors and a light guide member, and irradiates illumination light on the back surface of the document. When there is no document at the irradiated location, the illumination light is irradiated to the first reference member 134a of the first imaging unit 130a.

  The first imaging device 133a and the second imaging device 133b are examples of an imaging unit. The first imaging device 133a has an equal magnification optical system type CIS (Contact Image Sensor) provided with imaging elements by CCDs (Charge Coupled Devices) arranged linearly in the main scanning direction. The first imaging device 133a reads the surface of the conveyed document to capture an image, and generates and outputs an image signal. Similarly, the second imaging device 133b has a CIS of the same-magnification optical system type that includes an imaging device by CCD arranged linearly in the main scanning direction. The second imaging device 133b reads the back side of the document to capture an image, and generates and outputs an image signal. Further, CMOS (Complementary Metal Oxide Semiconductor) may be used instead of CCD. Further, a reduction optical system type image sensor may be used instead of the CIS.

  The first reference member 134a is an example of a counter member. The first reference member 134a is a white reference plate and is disposed at a position facing the second imaging device 133b. The second imaging device 133b generates an image signal obtained by imaging the first reference member 134a when the document is not conveyed to the imaging unit 130. Similarly, the second reference member 134b is disposed at a position facing the first imaging device 133a. The first imaging device 133a generates an image signal obtained by imaging the second reference member 134b when the document is not conveyed to the imaging unit 130. The image reading apparatus 100 can correct an image such as shading based on an image signal obtained by imaging the first reference member 134a and the second reference member 134b.

  The first glass surface 135a and the second glass surface 135b form a document transport path, and the document is transported to a space sandwiched between the first glass surface 135a and the second glass surface 135b. The second glass surface 135b serves as a document transport surface.

  The imaging unit guide 120 is provided with a guide member 121 that guides a document between the first imaging unit 130a and the second imaging unit 130b. A second sensor 118 is disposed above the guide member 121, and a lever portion 118 b of the second sensor 118 passes through a through-hole 122 provided in the guide member 121 and contacts a document on the conveyance path.

  FIG. 5 is a diagram for explaining the operation of the second imaging unit 130b during document conveyance. In the example illustrated in FIG. 5, a case is assumed in which a thick medium such as a thick paper, a bank card, or a credit card, which is thicker than the copy paper and the printing paper, is conveyed as the original 150.

  When the thick medium original 150 is conveyed to the position of the imaging unit guide 120, the original 150 having a certain degree of strength comes into contact with the guide member 121. As a result, the imaging unit guide 120 and the second imaging unit 130b move in the direction of the arrow A10 that is away from the conveyance path. On the other hand, even if a thin medium original 150 such as copy paper or printing paper is conveyed to the position of the image pickup unit guide 120, the second image pickup unit 130b does not move from the initial position.

  Thereafter, the document 150 that has contacted the guide member 121 contacts the lever portion 118 b of the second sensor 118 that passes through the through-hole 122 of the guide member 121. As a result, the second sensor 118 detects that the document 150 exists at the position of the lever portion 118b. The second sensor 118 has a first value when the lever portion 118b is not in contact with the document 150, and detects a second document having a second value when the lever portion 118b is in contact with the document 150. Generate and output a signal.

  The second imaging unit 130b (second imaging device 133b) may be inclined with respect to the first imaging unit 130a (first reference member 134a) by repeatedly moving. In particular, the second imaging unit 130b may be inclined with respect to the document conveyance surface in a plane P1 (see FIG. 2) orthogonal to the document conveyance direction A3. That is, the second imaging unit 130b can be tilted so that the distance between each end of the second imaging unit 130b and the first reference member 134a in a direction (main scanning direction) orthogonal to the document conveyance direction A3 is shifted. There is sex.

  FIG. 6 is a view of the image reading apparatus 100 as viewed from above with the upper housing 102 removed.

  As shown in FIG. 6, the mark 136a is shown on the first reference member 134a only at one end in the direction A4 orthogonal to the document transport direction A3 within the imaging range of the second imaging device 133b. A region R1 between the side guides 104a and 104b arranged farthest apart in a direction A4 orthogonal to the document transport direction A3 is a document region where the document to be transported is captured. The mark 136a is silk-printed in a region R2 outside the document region R1. A region R3 on the opposite side of the mark region R2 where the mark 136a is captured across the document region R1 is a reference member region where a white reference plate is captured even during document transportation, and is used for performing shading correction. That is, all of the document area R1, the mark area R2, and the reference member area R3 are imaging areas that are imaged by the second imaging device 133b.

  The mark 136a includes a plurality of straight lines extending in the document transport direction A3 and having different thicknesses. For example, the width of one straight line is determined to be the minimum value of a size that can be read in a state where the resolution for reading a document is set to 300 dpi (dots per inch). The width of the other straight line is set to the minimum value of the size that can be read in the state where the resolution for document reading is set to 600 dpi. Note that the mark 136a may include only one straight line, or may include three or more straight lines.

  Since the mark 136a includes a straight line extending in the document conveyance direction A3, even if the second imaging device 133b is inclined in a plane orthogonal to the document conveyance surface and parallel to the document conveyance direction, the second imaging device 133b can reliably image the mark 136a. In addition, since the mark 136a includes a plurality of straight lines having different thicknesses, the second imaging device 133b can capture the mark 136a more reliably even when the resolution for reading the document is changed.

  Further, although not shown, the mark 136a is formed only on one end of the second reference member 134b in the direction A4 perpendicular to the document transport direction A3 within the imaging range of the first imaging device 133a, similarly to the first reference member 134a. Similar marks are shown.

  7A and 7B are schematic views showing other examples of the mark 136a.

  As shown in FIG. 7A, the mark 136a may include a plurality of circles each having a different size. In addition, the mark 136a may include only one circle, or may include three or more circles. Furthermore, the mark 136a may include any shape such as a wavy line, an ellipse, or a triangle instead of a circle.

  As shown in FIG. 7B, the mark 136a may have gradation. Thereby, the image reading apparatus 100 can detect the position of the mark 136a with high accuracy by detecting the center of the gradation.

  FIG. 8 is a diagram for explaining an example of a hardware configuration of the image reading apparatus 100. In addition to the configuration described above, the image reading apparatus 100 includes a CPU (Central Processing Unit) 300, a storage device 301, an image processing LSI (Large Scale Integration) 302, a buffer memory 303, and a communication interface circuit 304. In the accompanying drawings and the following description, the interface may be referred to as “IF”.

  The image reading apparatus 100 includes a light source driving circuit 310, an imaging device driving circuit 311, an ultrasonic sensor driving circuit 312, an ultrasonic sensor output reading circuit 313, a motor 314, a motor driving circuit 315, and an input IF circuit 316. The first imaging unit 130a and the second imaging unit 130b include a first AFE (Analog Front-End Processor) 320a and a second AFE 320b, respectively.

  The CPU 300 controls the operation of the image reading apparatus 100 according to the computer program stored in the storage device 301. Note that the CPU 300 may perform part or all of image processing of an image read by the image reading apparatus 100. Instead of the CPU 300, a digital signal processor (DSP), a large scale integration (LSI), or the like may be used. Further, in place of the CPU 300, an application specific integrated circuit (ASIC), a field-programming gate array (FPGA), or the like may be used.

  The storage device 301 includes a memory device such as a RAM (Random Access Memory) and a ROM (Read Only Memory), a fixed disk device such as a hard disk, or a portable storage device such as a flexible disk and an optical disk. Further, the storage device 301 stores computer programs, databases, tables, and the like that are used for various processes of the image reading apparatus 100. The computer program may be installed in the storage device 301 from a computer-readable portable recording medium using a known setup program or the like. Examples of the portable recording medium include a CD-ROM (compact disk read only memory) and a DVD-ROM (digital versatile disk read only memory).

  In addition, the storage device 301 stores a reference image captured by the second imaging device 133b in a state where no document is conveyed, and a reference position where a mark appears in the reference image. The reference image is an image of one line extending in a direction (horizontal direction) orthogonal to the document transport direction. The reference position is a horizontal position (coordinates) in the reference image, and is, for example, the coordinate of the horizontal center position or end position of each straight line included in the mark.

  The first AFE 320a and the second AFE 320b generate digital image data by analog-to-digital conversion of analog image signals output from the first imaging device 133a of the first imaging unit 130a and the second imaging device 133b of the second imaging unit 130b. To do. The first AFE 320a and the second AFE 320b output the image data to the image processing LSI 302.

  The image processing LSI 302 performs predetermined image processing on the image data received from the imaging unit 130. The image processing LSI 302 stores the image data subjected to the image processing in the buffer memory 303. In place of the image processing LSI 302, a DSP, ASIC, FPGA, or the like may be used.

  The communication IF circuit 304 is a wired and / or wireless communication interface between the image reading apparatus 100 and the information processing apparatus 10. The CPU 300 reads the image data from the buffer memory 303 and transmits it to the information processing apparatus 10 via the communication IF circuit 304.

  The light source driving circuit 310 drives the first light source 132a of the first imaging unit 130a and the second light source 132b of the second imaging unit 130b according to control by the CPU 300. The imaging device drive circuit 311 drives the first imaging device 133a of the first imaging unit 130a and the second imaging device 133b of the second imaging unit 130b according to control by the CPU 300.

  The ultrasonic sensor drive circuit 312 drives the ultrasonic transmitter 115a to transmit ultrasonic waves. The ultrasonic sensor output reading circuit 313 reads the output signal of the ultrasonic receiver 115b and transmits it to the CPU 300 via the bus.

  The motor 314 applies a rotational driving force to the paper feed roller 113, the retard roller 114, the first transport roller 116, and the second transport roller 140. A plurality of motors 314 may be provided. The motor drive circuit 315 generates a drive current to be given to the motor 314 according to control by the CPU 300.

  The input IF circuit 316 receives the operation detection signal output from the operation button 106, the first document detection signal output from the first sensor 110, and the second document detection signal output from the second sensor 118, and passes through the bus. To the CPU 300.

  Note that the hardware configuration shown in FIG. 8 is merely an example for explaining the embodiment. The image reading apparatus 100 may adopt any other hardware configuration as long as the operation described below is executed.

  FIG. 9 is a diagram illustrating a schematic configuration of the storage device 301 and the CPU 300.

  As illustrated in FIG. 9, the storage device 301 stores programs such as a detection program 151, a determination program 152, a notification program 153, a correction program 154, and an image generation program 155. Each of these programs is a functional module implemented by software operating on the processor. The CPU 300 functions as the detection unit 161, the determination unit 162, the notification unit 163, the correction unit 164, and the image generation unit 165 by reading each program stored in the storage device 301 and operating according to each read program.

  FIG. 10 is a flowchart illustrating an example of the operation of the initialization process of the image reading apparatus 100.

  Hereinafter, an example of the operation of the initialization process of the image reading apparatus 100 will be described with reference to the flowchart shown in FIG. The operation flow described below is mainly executed by the CPU 300 in cooperation with each element of the image reading apparatus 100 based on a program stored in the storage device 301 in advance. The operation flow shown in FIG. 10 is executed when the apparatus is activated, when the opened front cover 105a is closed, when communication connection with the information processing apparatus 10 is started, and the like. Note that the operation flow shown in FIG. 10 may be executed at an arbitrary timing when the document reading process is not executed, periodically or in accordance with an instruction from the user.

  First, the detection unit 161 drives the imaging device driving circuit 311 to cause the second imaging device 133b to capture first comparative images obtained by capturing the first reference members 134a. And the detection part 161 acquires a 1st comparison image from the 2nd imaging device 133b via 2nd AFE320b (step S101). The first comparison image is an image captured by the second imaging device 133b in a state where the document is not conveyed.

  Next, the detection unit 161 detects a first comparison position where a mark is reflected in the first comparison image, and calculates an initial deviation amount between the first comparison position and the reference position in a direction orthogonal to the document conveyance direction ( Step S102). The first comparison image is an image of one line extending in the direction (horizontal direction) orthogonal to the document conveyance direction, like the reference image. The first comparison position is a horizontal position (coordinate) in the first comparison image corresponding to the reference position in the reference image. For example, the horizontal center position or end position of each straight line included in the mark Coordinates etc.

  The detection unit 161 scans the first comparison image, detects a mark from the first comparison image, and specifies the first comparison position. Then, the detection unit 161 calculates a difference between the first comparison position and the reference position as an initial deviation amount. When a plurality of positions are included in each of the reference position and the first comparison position, the detection unit 161 calculates an average value of differences between the reference position and the first comparison position corresponding to each other as an initial deviation amount.

  Next, the detection unit 161 detects the initial inclination amount of the second imaging device 133b in a plane orthogonal to the document conveyance direction based on the calculated initial deviation amount (step S103). The image reading apparatus 100 calculates the relationship between the shift amount and the tilt amount by, for example, a prior experiment, and stores a table representing the calculated relationship in the storage device 301. The detection unit 161 detects an initial inclination amount using a table stored in the storage device 301.

  11A, 11B, and 11C are diagrams for explaining the relationship between the shift amount and the tilt amount.

  11A and 11B show the relationship between the first imaging unit 130a and the second imaging unit 130b when the first imaging unit 130a and the second imaging unit 130b are viewed from the downstream side to the upstream side in the document transport direction A3. Represent. 11A and 11B show the relationship between the first imaging unit 130a and the second imaging unit 130b in the plane P1 orthogonal to the document transport direction A3. FIG. 11A shows a state in which the second imaging unit 130b (second imaging device 133b) is not inclined with respect to the first imaging unit 130a (first reference member 134a). On the other hand, FIG. 11B shows a state in which the second imaging unit 130b (second imaging device 133b) is inclined with respect to the first imaging unit 130a (first reference member 134a).

  As shown in FIG. 11A, when the second imaging device 133b is not inclined with respect to the first reference member 134a, both ends E1 and E2 of the mark 136a shown on the first reference member 134a are opposed to the second imaging device. Images are taken at positions E1 ′ and E2 ′ of 133b. However, as shown in FIG. 11B, when the second imaging device 133b is inclined with respect to the first reference member 134a, both ends E1 and E2 of the mark 136a are positioned at the positions E1 ′ and E2 of the opposing second imaging device 133b. Images are taken at positions E1 ″ and E2 ″ deviated from “.

  FIG. 11C shows the gradation value of an image obtained by imaging the mark 136a by the second imaging device 133b. In FIG. 11C, the horizontal axis indicates the horizontal position (coordinates in the horizontal direction) in the image, and the vertical axis indicates the gradation value. A graph 1101 in FIG. 11C shows a gradation value of an image obtained by imaging the mark 136a in the state shown in FIG. 11A, and a graph 1102 shows a gradation value of an image obtained by imaging the mark 136a in the state shown in FIG. 11B. As shown in FIG. 11C, the position of each pixel corresponding to the mark 136a is an image captured in a state where the second imaging device 133b is not tilted and an image captured in a state where the second imaging device 133b is tilted. Deviation from each other.

  Further, the larger the inclination amount of the second imaging device 133b with respect to the first reference member 134a, the larger the deviation amount between the positions E1 ′ and E2 ′ and the positions E1 ″ and E2 ″. Therefore, the detection unit 161 detects the tilt amount of the imaging device in the plane P1 orthogonal to the document conveyance direction A3 based on the amount of deviation between the comparison position and the reference position in the direction A4 orthogonal to the document conveyance direction A3. be able to.

  As described above, the detection unit 161 detects the amount of inclination of the second imaging device 133b by comparing the comparison position with the reference position.

  Next, the determination unit 162 determines whether the second imaging device 133b is tilted based on the detected initial tilt amount (step S104). The determination unit 162 determines whether or not the initial inclination amount is equal to or greater than the first threshold value. The first threshold value is set to an amount of tilt detected when the second imaging device 133b is tilted by the maximum amount guaranteed by the image reading device 100. The determination unit 162 determines that the second imaging device 133b is tilted when the initial tilt amount is greater than or equal to the first threshold, and the second imaging device 133b is tilted when the initial tilt amount is less than the first threshold. Judge that there is no.

  When it is determined that the second imaging device 133b is tilted, the notification unit 163 transmits information indicating that the second imaging device 133b is tilted to the information processing device 10 via the communication IF circuit 304, and notifies the user. Notification is made (step S105), and the series of steps is terminated. Thus, the user can know that the second imaging device 133b is tilted in a state where the document is not conveyed, and can take appropriate measures such as repair before the document is conveyed.

  On the other hand, when it is determined that the second imaging device 133b is not tilted, the correction unit 164 creates a reference correction table (step S106) and ends a series of steps. The reference correction table is used for correcting an image obtained by capturing an original.

  FIG. 12A is a graph illustrating an example of the relationship between the position of the first reference member 134a and the illuminance in a direction orthogonal to the document conveyance direction.

  The horizontal axis of FIG. 12A indicates the position of the first reference member 134a in the direction orthogonal to the document transport direction, and the vertical axis indicates the illuminance of the first reference member 134a. A graph 1201 shows the illuminance of the first reference member 134a when the second imaging device 133b is not tilted. A graph 1202 shows the illuminance of the first reference member 134a when the second imaging device 133b is slightly inclined. A graph 1203 shows the illuminance of the first reference member 134a when the second imaging device 133b is greatly inclined.

  As shown in FIG. 11A, when the second imaging device 133b is not tilted, the distance between the second light source 132b and the first reference member 134a is constant along the direction orthogonal to the document conveyance direction. Therefore, as shown in the graph 1201, the illuminance of the first reference member 134a illuminated by the light emitted from the second light source 132b does not change according to the position in the direction orthogonal to the document conveyance direction.

  On the other hand, as shown in FIG. 11B, when the second imaging device 133b is inclined, the distance between the second light source 132b and the first reference member 134a changes along the direction orthogonal to the document conveyance direction. Go. Therefore, as shown in the graph 1202, the illuminance of the first reference member 134a illuminated by the light emitted from the second light source 132b changes according to the position in the direction orthogonal to the document conveyance direction. That is, as the distance between the second light source 132b and the first reference member 134a increases, the illuminance of the first reference member 134a decreases.

  Further, when the second imaging device 133b is greatly inclined, the second light source 132b and the first reference are aligned along the direction orthogonal to the document conveyance direction, as compared with the case where the second imaging device 133b is slightly inclined. The degree to which the distance between the members 134a changes increases. Therefore, as shown in the graph 1203, when the second imaging device 133 b is greatly inclined, the first imaging device 133 b is first according to the position in the direction orthogonal to the document conveyance direction than when the second imaging device 133 b is slightly inclined. The degree to which the illuminance of the reference member 134a changes increases. That is, as the tilt amount of the second imaging device 133b increases, the degree to which the illuminance of the first reference member 134a decreases according to the position in the direction orthogonal to the document conveyance direction increases.

  FIG. 12B is a graph illustrating an example of the relationship between the horizontal position of each pixel in the image captured by the second imaging device 133b and the correction coefficient to be applied to each pixel. The correction coefficient shown in FIG. 12B is a coefficient used to correct each pixel by dividing from the gradation value of each pixel.

  The horizontal axis of FIG. 12B indicates the horizontal position of each pixel in the image, and the vertical axis indicates the value of the correction coefficient to be applied to each pixel. A graph 1211 shows a correction coefficient for correcting an image obtained by capturing the first reference member 134a having the illuminance in the graph 1201 of FIG. 12A. A graph 1212 shows a correction coefficient for correcting an image obtained by capturing the first reference member 134a having the illuminance shown in the graph 1202 of FIG. 12A. A graph 1213 shows a correction coefficient for correcting an image obtained by capturing the first reference member 134a having the illuminance shown in the graph 1203 of FIG. 12A.

  As shown in the graph 1211, when the second imaging device 133 b is not tilted, the illuminance of the first reference member 134 a does not change according to the position in the direction orthogonal to the document conveyance direction, so that each pixel in the image is corrected. There is no need to be done. For this reason, the value of the correction coefficient is a constant value (1).

  As shown in the graph 1212, when the second imaging device 133 b is tilted, the illuminance of the first reference member 134 a changes according to the position in the direction orthogonal to the document conveyance direction. It is necessary to correct so that the gradation value becomes a constant value. Therefore, the value of the correction coefficient is determined so as to change in the same manner as the degree of change in illuminance of the first reference member 134a according to the horizontal position.

  As shown in the graph 1213, even when the second imaging device 133b is greatly inclined, the value of the correction coefficient is determined so as to change in the same manner as the illuminance change degree of the first reference member 134a according to the horizontal position. It is done. That is, each value of the correction coefficient when the second imaging device 133b is greatly inclined is smaller than each value of the correction coefficient when the second imaging device 133b is slightly inclined.

  First, the correction unit 164 specifies the distance between the second light source 132b and the first reference member 134a at each position along the direction orthogonal to the document conveyance direction according to the amount of inclination of the second imaging device 133b. . Next, the correction unit 164 determines a correction coefficient for each pixel in the image according to the distance between the second light source 132b and the first reference member 134a at a position corresponding to the horizontal position of each pixel. Then, the correction unit 164 creates a reference correction table in which the horizontal position of each pixel is associated with the correction coefficient.

  Note that the correction coefficient may be a coefficient used to correct each pixel by multiplying the gradation value of each pixel. In that case, the correction coefficient increases as the distance between the second light source 132b and the first reference member 134a increases. Further, the correction coefficient may be determined in advance by a prior experiment, for example.

  FIG. 13 is a flowchart illustrating an example of an operation of document reading processing of the image reading apparatus 100.

  Hereinafter, an example of the operation of the original reading process of the image reading apparatus 100 will be described with reference to the flowchart shown in FIG. The operation flow described below is mainly executed by the CPU 300 in cooperation with each element of the image reading apparatus 100 based on a program stored in the storage device 301 in advance.

  First, the CPU 300 stands by until the user presses the operation button 106 for instructing reading of a document and receives an operation detection signal for instructing reading of the document from the operation button 106 (step S201).

  Next, CPU 300 determines whether or not a document is placed on document table 103 based on the first document detection signal received from first sensor 110 (step S202).

  If no document is placed on the document table 103, the CPU 300 returns the process to step S201 and waits until a new operation detection signal is received from the operation button 106.

  Next, the detection unit 161 drives the motor 314 via the motor drive circuit 315 to rotate the paper feed roller 113, the retard roller 114, the first conveyance roller 116, and the second conveyance roller 140 to convey the document. (Step S203).

  Next, the detection unit 161 causes the first imaging device 133a and the second imaging device 133b to capture document images obtained by capturing images of each side of the conveyed document. The detection unit 161 acquires a document image from the first imaging device 133a and the second imaging device 133b via the first AFE 320a and the second AFE 320b, and uses the document image captured by the second imaging device 133b as a second comparison image. Obtain (step S204). The second comparison image is an image captured by the second imaging device 133b in a state where the document is conveyed.

  Next, the detection unit 161 calculates a second comparison position where the mark is reflected in the second comparison image, and calculates a deviation amount between the second comparison position and the reference position in a direction orthogonal to the document transport direction (step). S205). The detection unit 161 detects the second comparison position for each horizontal line extending in the horizontal direction in the second comparison image, and calculates a deviation amount between the second comparison position and the reference position. Similar to the first comparison position, the second comparison position is a horizontal position (coordinates) in the second comparison image corresponding to the reference position in the reference image. These are the coordinates of the center position or end position in the direction orthogonal to the transport direction.

  The detection unit 161 scans each horizontal line of the second comparison image, detects a mark from each horizontal line, and specifies the second comparison position. Then, the detection unit 161 calculates a difference between the second comparison position and the reference position as a deviation amount. When a plurality of positions are included in each of the reference position and the second comparison position, the detection unit 161 calculates the average value of the differences between the reference position and the second comparison position corresponding to each other as a deviation amount.

  Next, the detection unit 161 detects the inclination amount of the second imaging device 133b in a plane orthogonal to the document conveyance direction based on the calculated deviation amount (step S206). As described above, the image reading apparatus 100 calculates the relationship between the shift amount and the tilt amount by, for example, a prior experiment, and stores a table representing the calculated relationship in the storage device 301. The detection unit 161 detects the amount of tilt using a table stored in the storage device 301. As described above, the detection unit 161 detects the amount of inclination of the second imaging device 133b by comparing the comparison position with the reference position.

  Next, the determination unit 162 determines whether the second imaging device 133b is tilted based on the detected tilt amount (step S207). The determination unit 162 determines whether or not the maximum amount of inclination detected by the detection unit 161 is equal to or greater than a first threshold value. The determination unit 162 determines that the second imaging device 133b is tilted when the maximum tilt amount is equal to or greater than the first threshold value, and when the maximum tilt amount is less than the first threshold value, the second imaging device 133b is Judge that it is not tilted.

  When it is determined that the second imaging device 133b is tilted, the notification unit 163 transmits information indicating that the second imaging device 133b is tilted to the information processing device 10 via the communication IF circuit 304, and notifies the user. Notification is made (step S208), and the series of steps is terminated. Thereby, the user can know that the second imaging device 133b is tilted, and prevents an inappropriate image captured by the tilted second imaging device 133b from being used by mistake. Can do.

  On the other hand, when it determines with the 2nd imaging device 133b not inclining, the correction | amendment part 164 performs a correction process (step S209). The correction unit 164 corrects the second comparison image according to the amount of inclination detected by the detection unit 161 in the correction process. Details of the correction processing will be described later.

  Next, the image generation unit 165 transmits a document image including the corrected second comparison image to the information processing apparatus 10 via the communication IF circuit 304 (step S210).

  Next, the CPU 300 determines whether or not a document remains on the document table 103 based on the first document detection signal received from the first sensor 110 (step S211).

  When the document remains on the document table 103, the CPU 300 returns the process to step S203 and repeats the processes of steps S203 to S211. On the other hand, if no document remains on the document table 103, the CPU 300 ends the series of processes.

  FIG. 14 is a flowchart illustrating an example of the operation of the correction process.

  The operation flow shown in FIG. 14 is executed in step S209 of the flowchart shown in FIG.

  First, the correction unit 164 reads a specific horizontal line in the second comparison image (step S301). Note that the processing in steps S302 to S305 is sequentially executed for each horizontal line in the second comparison image. For example, the correction unit 164 reads the horizontal line of the next address in order from the horizontal line of the first address in the vertical direction, and then reads up to the horizontal line of the final address.

  Next, the correction unit 164 determines whether or not the amount of inclination detected by the detection unit 161 in the read horizontal line is equal to or greater than the second threshold (step S302). The second threshold value is, for example, between the first imaging unit 130a and the second imaging unit 130b at the initial position at one end in the direction orthogonal to the document conveyance direction between the first imaging unit 130a and the second imaging unit 130b. The amount of inclination is determined when a document thicker than the width of the gap exists. The second threshold is a value smaller than the first threshold, and is set to a value that is ½ of the first threshold, for example.

  The correction unit 164 generates a document correction table when the tilt amount is equal to or greater than the second threshold (step S303). Similar to the reference correction table, the document correction table is used to correct the second comparison image document image.

  FIG. 15 is a schematic diagram illustrating an example of the second comparison image.

  A second comparative image 1500 illustrated in FIG. 15 is an image obtained by capturing the document 1511. The area 1501 of the second comparison image 1500 corresponds to the document area R1, the area 1502 corresponds to the mark area R2, and the area 1503 corresponds to the reference member area R3. A document 1511 is a sheet 1513 in which a thick medium 1512 such as a photograph or a plastic card is attached to one side in the horizontal direction (the right side in FIG. 15). The thickness of the sheet 1513 is smaller than the width of the gap between the first imaging unit 130a and the second imaging unit 130b when the second imaging unit 130b is in the initial position. On the other hand, the thickness of the medium 1512 is larger than the width of the gap between the first imaging unit 130a and the second imaging unit 130b when the second imaging unit 130b is in the initial position.

  When such a document 1511 is conveyed, even if the leading edge 1521 of the paper 1513 is conveyed between the first imaging unit 130a and the second imaging unit 130b, the second imaging unit 130b does not move from the initial position. On the other hand, when the tip 1522 of the medium 1512 contacts the imaging unit guide 120, the second imaging unit 130b moves in a direction away from the first imaging unit 130a together with the imaging unit guide 120. Since the medium 1512 exists on one side in the direction orthogonal to the document conveyance direction, the second imaging unit 130b is inclined with respect to the first imaging unit 130a. When the rear end 1523 of the medium 1512 moves away from the second imaging unit 130b, the second imaging unit 130b returns to the initial position.

  Therefore, the second comparison positions 1531 and 1532 of the mark 136a shown in the mark area R2 are shifted from the reference position only in the area R4 corresponding to the period in which the second imaging unit 130b is moving from the initial position, and in the other areas It almost coincides with the position.

  That is, when the amount of deviation between the second comparison position and the reference position is sufficiently small, and the amount of inclination of the second imaging device 133b is less than the second threshold, it is estimated that the second imaging unit 130b is at the initial position. For this reason, the second comparison image is appropriately corrected using a reference correction table created based on the first comparison image captured in a state where the document is not conveyed. On the other hand, when the amount of deviation between the second comparison position and the reference position is large and the amount of inclination of the second imaging device 133b is greater than or equal to the second threshold, it is estimated that the second imaging unit 130b is not at the initial position. For this reason, the second comparison image is not correctly corrected even if the reference correction table is used.

  FIG. 16A is a diagram for explaining the inclination of the second imaging device 133b when a document is conveyed.

  FIG. 16A is a schematic diagram of the first imaging unit 130a and the second imaging unit 130b in a state where the document 1511 illustrated in FIG. 15 is transported as viewed from the downstream side to the upstream side in the document transport direction A3.

  As shown in FIG. 16A, when the second imaging device 133b is inclined by the medium 1512, the distance L3 from the left end E3 in the horizontal direction of the document 1511 to the second imaging unit 130b and the distance from the right end E4 to the second imaging unit 130b. The distance L4 is greatly different. Further, since the first glass surface 135a exists between the first reference member 134a and the second imaging unit 130b, the distance L5 from the surface E5 of the first reference member 134a to the second imaging unit 130b is the distance L3 and It is much different than L4.

  FIG. 16B is a graph illustrating an example of the relationship between the illuminance and the position of the original and the first reference member 134a in a direction orthogonal to the conveyance direction of the original. The document shown in FIG. 16B is white, and when this document and the first reference member 134a are irradiated with the same amount of light under the same conditions, the illuminance of this document and the first reference member 134a is the same. To do.

  In FIG. 16B, the horizontal axis indicates the positions of the original and the first reference member 134a in the direction orthogonal to the original conveyance direction, and the vertical axis indicates the illuminance of the original and the first reference member 134a. A graph 1601 indicates the illuminance of the document when the second imaging device 133b is not tilted, and a graph 1602 indicates the illuminance of the document when the second imaging device 133b is tilted. A graph 1603 shows the illuminance of the first reference member 134a when the second imaging device 133b is not tilted, and a graph 1604 shows the illuminance of the first reference member 134a when the second imaging device 133b is tilted.

  As shown in FIG. 16A, when the second imaging device 133b is tilted, the distance between the second light source 132b and the document 1511 changes along the direction orthogonal to the document transport direction. Therefore, as shown in the graph 1602, the illuminance of the document 1511 illuminated by the light emitted from the second light source 132b changes according to the position in the direction orthogonal to the document transport direction. That is, as the distance between the second light source 132b and the document 1511 increases, the illuminance of the document 1511 decreases.

  Similarly, the distance between the second light source 132b and the first reference member 134a also changes along the direction orthogonal to the document conveyance direction, but the distance between the second light source 132b and the first reference member 134a is changed. The distance between the second light source 132b and the original 1511 is larger. Therefore, as shown in the graph 1604, the illuminance of the first reference member 134a illuminated by the light emitted from the second light source 132b changes (becomes low) according to the position in the direction orthogonal to the document conveyance direction, On average, it is lower than the illuminance of the original 1511.

  Further, when the second imaging unit 130b is inclined by the medium 1512, the second light source 132b and the first reference member 134a are arranged along the direction orthogonal to the document conveyance direction, compared to the case where the document is not conveyed. The degree of change in the distance increases. Therefore, compared to the illuminances 1202 and 1203 of the first reference member 134a when the document is not transported as shown in FIG. The degree of change (decrease) increases.

  FIG. 16C is a graph showing an example of the relationship between the horizontal position of each pixel in the second comparison image and the correction coefficient to be applied to each pixel. The correction coefficient shown in FIG. 16C is a coefficient used to correct each pixel by dividing from the gradation value of each pixel.

  The horizontal axis of FIG. 16C indicates the horizontal position of each pixel in the second comparison image, and the vertical axis indicates the value of the correction coefficient to be applied to each pixel. A solid line graph 1611 indicates a correction coefficient for correcting the original with the illuminance of the graph 1602 in FIG. 16B and the second comparative image obtained by imaging the first reference member 134 a with the illuminance of the graph 1604.

  As shown in the graph 1611, since the illuminance of the original and the first reference member 134a changes according to the position in the direction orthogonal to the original conveyance direction, each pixel in the second reference image has a constant gradation value. It needs to be corrected to be a value. Therefore, the value of the correction coefficient is determined so as to change in the document region R1 in the same manner as the change in the illuminance of the document according to the horizontal position. In the reference member region R3, the first reference member 134a is determined according to the horizontal position. It is determined to change in the same manner as the degree of change in illuminance. Each value of the correction coefficient is smaller than each value of the correction coefficient calculated based on the illuminance of the first reference member 134a when the document illustrated in FIG. 12B is not conveyed. Since mark 136a is shown in mark area R2, mark area R2 is deleted from the original image without correction.

  The correction unit 164 first determines the distance between the second light source 132b and the first glass surface 135a at each position along the direction orthogonal to the document conveyance direction, and the second light source according to the tilt amount of the imaging device. The distance between 132b and the first reference member 134a is specified. Next, for each pixel in the document region R1 of the second comparison image, the correction unit 164 depends on the distance between the second light source 132b and the first glass surface 135a at a position corresponding to the horizontal position of each pixel. Determine the correction factor. Further, the correction unit 164, for each pixel in the reference member region R3 of the second comparison image, according to the distance between the second light source 132b and the first reference member 134a at a position corresponding to the horizontal position of each pixel. Determine the correction factor. Then, the correction unit 164 creates a document correction table in which the horizontal position of each pixel is associated with the correction coefficient.

  Similar to the reference correction table, in the original correction table, the correction coefficient may be a coefficient used to correct each pixel by multiplying the gradation value of each pixel. In this case, the correction coefficient increases as the distance between the second light source 132b and the first glass surface 135a or the first reference member 134a at a position corresponding to the horizontal position of each pixel increases. Further, the correction coefficient may be determined by a prior experiment, for example.

  Note that the correction unit 164 may omit the process of step S302 when the document correction table for the target tilt amount has already been created. Further, the image reading apparatus 100 may create all document correction tables corresponding to the respective tilt amounts in advance and store them in the storage device 301. Also in this case, the process of step S302 is omitted, and the image reading apparatus 100 can reduce the processing load in the correction process.

  Next, the correcting unit 164 corrects the second comparison image based on the created document correction table (step S304). The correction unit 164 corrects the pixel value of the second comparison image by applying each correction coefficient stored in the document correction table to each pixel in the second comparison image.

  As described above, the document correction table is created so that the correction amount varies depending on the position of each pixel in the second comparison image in the direction orthogonal to the document transport direction. Therefore, the correction unit 164 corrects the second comparison image so that the correction amount varies according to the position of each pixel in the second comparison image in the direction orthogonal to the document conveyance direction. The document correction table is created so that the correction amount is continuous in each of the document region R1 and the reference member region R3, and the correction amount is discontinuous at the boundary position between the document region R1 and the reference member region R3. . Therefore, the correction unit 164 performs the second correction so that the correction amount is continuous in each of the document region R1 and the reference member region R3, and the correction amount is discontinuous at the boundary position between the document region R1 and the reference member region R3. Correct the comparative image.

  On the other hand, when the inclination amount is less than the second threshold, the correction unit 164 corrects the second comparative image based on the reference correction table (step S305). The correction unit 164 corrects the pixel value of the second comparison image by applying each correction coefficient stored in the reference correction table to each pixel in the second comparison image. Since the correction unit 164 does not create a document correction table corresponding to a horizontal line whose tilt amount is less than the second threshold value, the processing load in the correction process can be reduced.

  Next, the correcting unit 164 determines whether or not the processing in steps S301 to S305 has been completed for all horizontal lines in the second comparison image (step S306).

  If there is a horizontal line that has not been processed, the correction unit 164 returns the process to step S301 and repeats the processes of steps S301 to S305.

  On the other hand, when the processing is completed for all the horizontal lines, the correction unit 164 determines the amount of inclination detected for the last line in the second comparison image and the amount of inclination (initial inclination amount) when the reference correction table is created. It is determined whether or not the difference is equal to or greater than a third threshold value (step S307).

  When the difference between the inclination amount detected for the last line in the second comparison image and the inclination amount when the reference correction table is created is less than the third threshold value, the correction unit 164 ends a series of steps.

  On the other hand, when the difference between the amount of inclination detected for the last line in the second comparison image and the amount of inclination when the reference correction table is created is equal to or greater than the third threshold, the correction unit 164 updates the reference correction table. (Step S308), and a series of steps is completed. The correction unit 164 recalculates the correction coefficient using the inclination amount detected for the final line in the second comparison image, and updates the reference correction table using the recalculated correction coefficient.

  When the final line in the second comparison image is captured, the document has already passed between the first imaging unit 130a and the second imaging unit 130b, and between the first imaging unit 130a and the second imaging unit 130b. Is not considered to exist. Therefore, when the amount of inclination detected for the last line in the second comparison image is significantly different from the amount of inclination when the reference correction table is created, the amount that the second imaging unit 130b is constantly inclined is There is a high possibility that it fluctuates more than when the reference correction table is calculated. Therefore, the correction unit 164 can correct the second comparison image more appropriately in the subsequent correction processing by updating the reference correction table.

  Note that, instead of creating the reference correction table and the document correction table, the correction unit 164 calculates an expression indicating the relationship between the horizontal position in the second comparison image and the correction coefficient at each horizontal position. The second comparison image may be corrected based on the second comparison image.

  Similarly to the first reference member 134a, the second reference member 134b has a mark similar to the mark 136a only at one end in the direction A4 orthogonal to the document transport direction A3 within the imaging range of the first imaging device 133a. May be. In that case, the detection unit 161 also uses the reference image, the first comparison image, and the second comparison image obtained by imaging the mark indicated on the second reference member 134b by the first imaging device 133a, and the second imaging device 133b. Can be detected. In addition, the detection unit 161 has each image obtained by the second imaging device 133b picking up the mark 136a shown on the first reference member 134a and the first imaging device 133a picked up the mark shown on the second reference member 134b. The inclination amount of the imaging device 133 may be detected using both of the images. Thereby, the image reading apparatus 100 can detect the inclination amount of the imaging apparatus 133 with higher accuracy.

  Further, the image reading apparatus 100 may be configured such that the first imaging unit 130a provided below the conveyance path does not move instead of the second imaging unit 130b provided above the conveyance path. Good. When the first imaging unit 130a moves, the first imaging unit 130a may be inclined with respect to the second imaging unit 130b. In this case, the detection unit 161 compares the comparison position with each reference position using an image obtained by imaging the mark by the first imaging device 133a and / or the second imaging device 133b, whereby the first imaging unit 130a ( Each inclination amount of the first imaging device 133a) is detected. The determination unit 162 determines whether the first imaging unit 130a (first imaging device 133a) is tilted with respect to the second imaging unit 130b (second reference member 134b) based on the detected tilt amount. . The correction unit 164 corrects the second reference image captured by the first imaging device 133a based on the detected tilt amount.

  As described above in detail, by operating according to the flowcharts shown in FIGS. 10, 13, and 14, the image reading apparatus 100 determines the inclination amount of the imaging device 133 based on the mark shown only at one end of the reference member 134. To detect. Therefore, the image reading apparatus 100 can reduce the size of the reference member 134 and reduce the overall width of the image reading apparatus 100 as compared with the case where marks are shown at both ends of the reference member 134. As a result, the image reading apparatus 100 can appropriately detect the inclination of the imaging device 133 while suppressing an increase in cost and device size.

  FIG. 17 is a schematic diagram for explaining a shift amount when the second imaging device 133b is tilted.

As shown in FIG. 17, when the second imaging device 133b is inclined with respect to the first reference member 134a by an angle θ, the deviation amount D between the reference position and the second comparison position in the image captured by the first imaging device 133a is Is calculated by the following equation.
D = L × sin θ
Here, L is the distance between the second imaging device 133b and the first reference member 134a.

  Therefore, by increasing the distance L between the first imaging device 133a and the second imaging device 133b, the range of the deviation amount D between the reference position and the second comparison position is increased, and the inclination amount of the second imaging device 133b is increased. It becomes possible to detect with high accuracy. That is, by increasing the distance until the light reflected by the mark 136a reaches the second imaging device 133b, the tilt amount of the second imaging device 133b can be accurately detected.

  FIG. 18A is a schematic diagram for explaining an imaging device 133 according to another embodiment.

  In the example illustrated in FIG. 18A, the second imaging unit 130b is provided with a mirror 137b that reflects the light reflected by the mark 136a toward the first imaging unit 130a. Further, the first imaging unit 130a is provided with a mirror 137a that reflects the light reflected by the mirror 137b toward the second imaging device 133b. The second imaging device 133b captures the reference image and each comparative image by capturing the mark 136a via the mirror 137b and the mirror 137a. This makes it possible to increase the distance until the light reflected by the mark 136a reaches the second imaging device 133b, and to detect the tilt amount of the second imaging device 133b with higher accuracy.

  FIG. 18B is a schematic diagram for explaining an imaging device 133 according to still another embodiment.

  In the example illustrated in FIG. 18B, the first imaging unit 130a is provided with a mirror 138a that reflects the light reflected by the mark 136a toward the second imaging device 133b. The second imaging device 133b captures the reference image and each comparative image by capturing the mark 136a through the mirror 138a. Also in this case, the distance until the light reflected by the mark 136a reaches the second imaging device 133b can be increased, and the tilt amount of the second imaging device 133b can be detected with higher accuracy.

  As described in detail above, by providing a mirror in the first imaging unit 130a or the second imaging unit 130b, the tilt amount of the second imaging device 133b can be detected with higher accuracy.

  FIG. 19 is a block diagram showing a schematic configuration of an image processing LSI 402 in an image reading apparatus according to another embodiment.

  The image processing LSI 402 is used in place of the image processing LSI 302 of the image reading apparatus 100, and executes initialization processing, document reading processing, and correction processing instead of the CPU 300. The image processing LSI 402 includes a detection circuit 171, a determination circuit 172, a notification circuit 173, a correction circuit 174, an image generation circuit 175, and the like.

  The detection circuit 171 is an example of a detection unit and has the same function as the detection unit 161. The detection circuit 171 acquires the reference position from the storage device 301, acquires the first comparison image and the second comparison image from the imaging device 133, the shift amount between the first comparison position and the reference position, and the second comparison position and the reference position. Based on the positional deviation amount, the inclination amount of the imaging device 133 is detected.

  The determination circuit 172 is an example of a determination unit and has the same function as the determination unit 162. The determination circuit 172 acquires the tilt amount from the detection circuit 171 and determines whether the second imaging device 133b is tilted based on the tilt amount.

  The notification circuit 173 is an example of a notification unit and has the same function as the notification unit 163. The notification circuit 173 obtains a determination result as to whether or not the second imaging device 133b is tilted from the determination circuit 172. When the second imaging device 133b is tilted, the communication IF circuit 304 indicates that the imaging device is tilted. Is transmitted to the information processing apparatus 10.

  The correction circuit 174 is an example of a correction unit and has the same function as the correction unit 164. The correction circuit 174 acquires the amount of inclination from the detection circuit 171, acquires the second comparison image from the imaging device 133, corrects the second comparison image according to the amount of inclination, and displays the corrected second comparison image as an image. Transmit to the generation circuit 175.

  The image generation circuit 175 is an example of an image generation unit and has the same function as the image generation unit 165. The image generation circuit 175 acquires the corrected second comparison image from the correction circuit 174, and transmits the document image including the corrected second comparison image to the information processing apparatus 10 via the communication IF circuit 304.

  As described above in detail, even when the image processing LSI 402 is used, the image reading apparatus can appropriately detect the inclination of the imaging device 133 while suppressing an increase in cost and device size. .

DESCRIPTION OF SYMBOLS 100 Image reader 133a 1st imaging device 133b 2nd imaging device 134a 1st reference member 134b 2nd reference member 136a Mark 137a, 137b, 138a Mirror 161 Detection part 162 Determination part 163 Notification part 164 Correction part 301 Storage device

Claims (11)

An imaging unit for imaging the conveyed document;
An opposing member provided at a position facing the imaging unit and having a mark shown only at one end in a direction orthogonal to the document conveyance direction within the imaging range of the imaging unit;
A storage unit for storing a reference position at which the mark appears in a reference image captured by the imaging unit in a state where the document is not conveyed;
A detection unit that detects a tilt amount of the imaging unit by comparing the reference position with the comparison position in which the mark is reflected in the comparison image captured by the imaging unit in a state where the document is conveyed;
A correction unit that corrects the comparison image according to the amount of inclination;
An image reading apparatus comprising:   The detection unit detects an amount of inclination of the imaging unit in a plane orthogonal to the document conveyance direction based on a deviation amount between the comparison position and the reference position in a direction orthogonal to the document conveyance direction. The image reading apparatus according to 1.   3. The image according to claim 1, wherein the correction unit corrects the comparison image so that a correction amount varies according to a position of each pixel in the comparison image in a direction orthogonal to a document conveyance direction. Reader.   The correction unit is configured such that the correction amount is continuous in a document area where a document is shown in the comparison image and in a counter member area where the counter member is shown, and a boundary position between the document area and the counter member area The image reading apparatus according to claim 3, wherein the comparison image is corrected so that the correction amount becomes discontinuous. A determination unit that determines whether the imaging unit is tilted based on an inclination amount of the imaging unit;
The image reading apparatus according to claim 1, further comprising: a notification unit that notifies a user when it is determined that the imaging unit is tilted.   The image reading apparatus according to claim 1, wherein the mark includes a straight line extending in a document transport direction.   The image reading apparatus according to claim 6, wherein the mark includes a plurality of the straight lines having different thicknesses.   The image reading apparatus according to claim 1, wherein the mark has gradation. A mirror that reflects the light reflected by the mark;
The image reading apparatus according to claim 1, wherein the imaging unit captures the reference image and the comparative image by capturing the mark through the mirror. A method for controlling an image reading apparatus, comprising: an imaging unit that captures an image of a conveyed document; a facing member provided at a position facing the imaging unit; and a storage unit.
The opposing member has a mark only at one end in a direction orthogonal to the document conveyance direction within the imaging range of the imaging unit,
The storage unit stores a reference position at which the mark appears in a reference image captured by the imaging unit in a state where no document is conveyed.
By comparing the reference position and the comparison position where the mark is reflected in the comparison image captured by the imaging unit in a state where the document is conveyed, the inclination amount of the imaging unit is detected,
Correcting the comparative image according to the amount of inclination;
A control method comprising: A control program for an image reading apparatus, comprising: an imaging unit that captures an image of a conveyed document; a facing member provided at a position facing the imaging unit; and a storage unit.
The opposing member has a mark only at one end in a direction orthogonal to the document conveyance direction within the imaging range of the imaging unit,
The storage unit stores a reference position at which the mark appears in a reference image captured by the imaging unit in a state where no document is conveyed.
By comparing the reference position and the comparison position where the mark is reflected in the comparison image captured by the imaging unit in a state where the document is conveyed, the inclination amount of the imaging unit is detected,
Correcting the comparative image according to the amount of inclination;
A control program for causing the image reading apparatus to execute the above-described operation.