JP2018067890A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader configured to prevent degradation of quality of a read image.SOLUTION: A multifunction peripheral (MFP) as an image reader includes: read means which reads a document image and a background image thereof in a predetermined read position RP along a conveyance path TP; a background member 50 arranged in the read position RP; and a moving means. The background member 50 includes a high-density part 61, a low-density part 62, a high-density part 63, and a cleaning unit 52. The moving means positions the high-density part 61, low-density part 62, and high-density part 63 sequentially in the read position RP at a timing when the document passes through the read position RP. The moving means positions the cleaning unit 52 in the read position RP to be brought into contact with a contact glass 32, at a timing when the document does not pass through the read position RP.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image reading apparatus. More specifically, the present invention relates to an image reading apparatus including a background member that provides a background image of an original image when the reading unit reads the original image.

  The image reading device irradiates light on a document and receives light reflected by an image of the document to read the image. Some image reading apparatuses are equipped with an automatic document feeder such as an ADF (Auto Document Feeder). According to an image reading apparatus equipped with an ADF, if an original is first set on the ADF, an image of the original can be automatically read by the image reading apparatus while flowing a plurality of originals one by one.

  In recent years, by improving the awareness of the global environment (eco), cost savings, or the spread of PCs (Personal Computers) and tablets, etc., it has been attempted to improve operational efficiency by changing the materials to be stored from printed matter to scan data. Companies are increasing. In this case, the scan data is created by reading an image of a printed matter with an image reading device.

  A difference in quality tends to occur between when data is stored as printed matter and when it is stored as scan data. In other words, when storing data as printed matter, the image is printed on different paper for each page, so there is an inclination of the image on a specific page, a difference in magnification in the main scanning direction or sub-scanning direction between pages, and the like. Even if they occur, they are often not visible and are often tolerated. On the other hand, when storing data as scan data, each page of the scan data is displayed in order on the monitor by a scroll operation. For this reason, if an inclination of an image on a specific page or a difference in magnification in the main scanning direction or the sub-scanning direction between pages occurs, they are easily noticeable and are not allowed.

  There are an increasing number of companies that store forms as electronic data, and there are also industries that handle non-standard paper, so the opportunities for handling scan data in companies are increasing. In addition, companies that increase operational efficiency by cutting out images from scan data and performing OCR (Optical Character Recognition) processing are increasing.

  Therefore, a technique for correcting an image of a document read by an image reading apparatus has been proposed. For example, Patent Documents 1 and 2 listed below propose techniques for easily detecting the apex of an original image when correcting the original image.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique of using a background plate in which a portion straddling a paper edge is black and a central portion is white when a paper on which a calibration patch is formed is read. By scanning using this background plate, the edge of the paper can be detected on the scanned image from the density difference that occurs at the boundary between the edge of the paper and the black portion of the background plate. It can be read with the part as the background.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses a document both-end detection device including an image reading device and a black and white reference plate that is color-coded in white and black and can switch between a white portion and a black portion at a focal position of the image sensor. ing. The apparatus for detecting both ends of a document includes means for scanning the leading edge of the document with a black portion and a white portion of a black and white reference plate, and means for detecting change points of the first and second scan signals at the leading edge of the document with the black portion. The left edge of the document is determined by comparing the change point of the third and fourth scan signals in the white portion with the change point of the first scan signal and the change point of the third scan signal. And means for comparing the change point of the second scan signal and the change point of the fourth scan signal to determine the right end of the document.

JP 2014-116676 A JP 2003-219117 A

  However, in the techniques of Patent Documents 1 and 2, there is no method for automatically removing foreign matter when foreign matter adheres to the original glass. If foreign matter adheres to the original glass, streak-like noise (image streak noise) may occur in an image of a portion that has passed through the portion where the foreign matter exists, leading to a reduction in the quality of the read image.

  In addition, in the technique of Patent Document 1, when reading an irregular-size document, it is necessary to rotate the counter plate in which the entire area in the main scanning direction is black in the direction opposite to the sheet feeding direction. As a result, the opposed plate comes into contact with the conveyed document, increasing the conveyance resistance, leading to a decrease in the quality of the read image.

  Furthermore, in the technique of Patent Document 2, when a thin paper original is read with a white background color, it is difficult to detect the vertex, and the vertex detection accuracy is lowered. Further, when a thin paper document is read with the background color being black, image fogging, which is a phenomenon in which the background color can be seen through the white portion of the image of the document, occurs over the entire page. As a result, magnification correction, trapezoidal correction, and the like cannot be performed accurately, leading to a decrease in the quality of the read image.

  SUMMARY An advantage of some aspects of the invention is that it provides an image reading apparatus capable of suppressing deterioration in quality of a read image.

  An image reading apparatus according to an aspect of the present invention includes a conveying unit that conveys a document, and a document image and a background of the document image via a reading surface at a predetermined reading position along a document conveying path by the conveying unit. A reading means for reading an image, and a background member provided at a reading position, the background member forming a background image, the background member having a first portion having a first density, and a second density A second portion having a third density, a third portion having a third density, and a cleaning unit, each of the first and third densities being higher than the second density, and conveying the document at the reading position. The moving device further includes moving means for sequentially positioning each of the first portion, the second portion, the third portion, and the cleaning portion at the reading position by moving the background member along the direction. At the timing when passes through the reading position. The first portion, the second portion, and the third portion are sequentially positioned at the reading position, and the moving unit positions the cleaning unit at the reading position at a timing when the document does not pass the reading position, thereby reading the reading surface. Contact.

  Preferably, in the image reading apparatus, the moving unit rotates each of the first part, the second part, the third part, and the cleaning unit by rotating the background member in one direction around the rotation axis. The reading position is sequentially positioned, and one direction at the reading position coincides with the document conveyance direction at the reading position.

  Preferably, in the image reading apparatus, the rotation speed of the background member is the same as the speed at which the document is conveyed by the conveying means.

  Preferably, in the image reading apparatus, the background member further includes a background portion having a semicircular shape when viewed in a cross section taken along a plane whose normal is the extending direction of the rotation shaft, and the first portion The second portion and the third portion are provided on the curved surface of the background portion, and the cleaning portion extends outward from a portion other than the curved surface of the background portion.

  Preferably, in the image reading apparatus, each of the first portion, the second portion, and the third portion rotates when viewed in a cross section cut by a plane whose normal is the extending direction of the rotation axis. The central angle around the axis is 60 degrees.

  Preferably, the image reading apparatus further includes a detecting unit that detects the document upstream of the reading position along the document transport path, and the moving unit includes the first moving unit before detecting the front end of the document. Is positioned at the reading position, and when the first time has elapsed since the detection means detects the front edge of the document, the moving means positions the second portion at the reading position and the detection means When the second time elapses after the end is detected, the moving unit positions the third portion at the reading position, and the detection unit detects the trailing end of the document, and the moving unit is longer than the second time. When the time 3 has elapsed, the moving means positions the cleaning unit at the reading position.

  Preferably, in the image reading apparatus, each of the first portion, the second portion, and the third portion has a uniform density along the main scanning direction.

  Preferably, in the image reading apparatus, an extraction unit that extracts an image of a document from an image read by the reading unit, and an area in which the first part or the third part of the document image is a background image Correction means for correcting based on an area in which the second portion of the image is a background image.

  ADVANTAGE OF THE INVENTION According to this invention, the image reading apparatus which can suppress the fall of the quality of a read image can be provided.

1 is a diagram schematically showing an appearance of MFP 100 according to an embodiment of the present invention. 2 is a block diagram showing a functional configuration of MFP 100 in an embodiment of the present invention. FIG. It is sectional drawing which shows schematic structure of the scanner part 30 in one embodiment of this invention. It is sectional drawing which shows the structure of the opposing member 50 in one embodiment of this invention. It is a top view which shows the structure of the opposing member 50 in one embodiment of this invention. FIG. 6 is a first diagram schematically showing an operation when MFP 100 reads an image on paper M in an embodiment of the present invention. FIG. 10 is a second diagram schematically showing an operation when MFP 100 reads an image on paper M in an embodiment of the present invention. FIG. 10 is a third diagram schematically showing an operation when MFP 100 reads an image on paper M in an embodiment of the present invention. FIG. 10 is a fourth diagram schematically showing an operation when MFP 100 reads an image on paper M in one embodiment of the present invention. FIG. 10 is a fifth diagram schematically illustrating an operation when MFP 100 reads an image on sheet M in the embodiment of the present invention. FIG. 16 is a sixth diagram schematically illustrating an operation performed when MFP 100 reads an image on sheet M according to the embodiment of the present invention. FIG. 17 is a seventh diagram schematically illustrating an operation performed when MFP 100 reads an image on sheet M according to an embodiment of the present invention. FIG. 20 is an eighth diagram schematically illustrating an operation when MFP 100 reads an image on sheet M in the embodiment of the present invention. FIG. 10 is a diagram schematically showing a change in the position of the sheet M along the transport path TP with time in the embodiment of the present invention. In one embodiment of the present invention, it is a diagram schematically showing an image IM1 read by a reading unit 30B. It is a figure which shows typically image IM2 which the image process part 109 extracted in one embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In the following embodiment, a case where the image reading apparatus is an MFP will be described. The image reading apparatus may be a scanner, a copier, or the like in addition to the MFP.

  First, the configuration of MFP 100 in the present embodiment will be described.

  FIG. 1 is a diagram schematically showing the appearance of MFP 100 according to an embodiment of the present invention.

  Referring to FIG. 1, MFP 100 (an example of an image reading apparatus) in the present embodiment mainly includes MFP main body 10, operation panel 20, and scanner unit 30. The operation panel 20 is provided on the front surface of the MFP main body 10. The operation panel 20 performs various displays for the user and accepts various operations from the user. The scanner unit 30 is provided on the upper part of the MFP main body 10.

  FIG. 2 is a block diagram showing a functional configuration of MFP 100 according to the embodiment of the present invention.

  Referring to FIG. 2, MFP 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, an image reading unit 104, a network interface 105, and an operation panel. A control unit 106, an auxiliary storage device 107, an image forming unit 108, and an image processing unit 109 are included. The CPU 101, the ROM 102, the RAM 103, the image reading unit 104, the network interface 105, the operation panel control unit 106, the auxiliary storage device 107, the image forming unit 108, and the image processing unit 109 are mutually connected by a bus or the like. Yes.

  CPU 101 operates in accordance with the control program and controls MFP 100 as a whole.

  The ROM 102 stores a control program.

  A RAM 103 is a working memory for the CPU 101 and temporarily stores various data.

  The image reading unit 104 reads an image of a document by controlling the scanner unit 30. The image reading unit 104 includes a driving unit 104a (an example of a moving unit). The drive unit 104a rotationally drives a counter member 50 described later. The image reading unit 104 further includes a counter (not shown) that measures time.

  Network interface 105 transmits and receives information to and from external devices connected to MFP 100 through a network (not shown).

  The operation panel control unit 106 displays various information on the operation panel 20 and accepts various operations through the operation panel 20.

  The auxiliary storage device 107 is, for example, an HDD (Hard Disk Drive), and stores various data such as image data read by the image reading unit 104.

  The image forming unit 108 performs printing on a sheet inside the MFP main body 10. The image forming unit 108 is roughly composed of a toner image forming unit, a fixing device, a paper transport unit, and the like. The image forming unit 108 forms an image on a sheet by, for example, electrophotography. The toner image forming unit combines four color images by a so-called tandem method, and forms a color image on a sheet. The toner image forming unit includes a photoconductor provided for each color of C (cyan), M (magenta), Y (yellow), and K (black), and an intermediate in which a toner image is transferred (primary transfer) from the photoconductor. The image forming apparatus includes a transfer belt and a transfer unit that transfers an image from the intermediate transfer belt to a sheet (secondary transfer). The fixing device has a heating roller and a pressure roller. The fixing device conveys the sheet on which the toner image is formed between the heating roller and the pressure roller while heating and pressurizing the sheet. As a result, the fixing device melts the toner adhering to the paper and fixes it on the paper to form an image on the paper. The paper transport unit includes a paper feed roller, a transport roller, and a motor that drives them. The paper transport unit feeds paper from the paper feed cassette and transports it inside the MFP main body 10. The paper transport unit discharges the paper printed inside the MFP main body 10 to the outside of the MFP main body 10.

  The image processing unit 109 corrects the image read by the scanner unit 30.

  FIG. 3 is a cross-sectional view showing a configuration of the scanner unit 30 according to the embodiment of the present invention. In this specification, the main scanning direction of the reading unit 30B is the x axis, the sub scanning direction of the reading unit 30B is the y axis, and the direction perpendicular to each of the main scanning direction and the sub scanning direction of the reading unit 30B is z. It is defined as an axis.

  Referring to FIG. 3, the scanner unit 30 includes a paper transport unit 30 </ b> A (an example of a transport unit) that is an ADF (Auto Document Feeder), a reading unit 30 </ b> B (an example of a read unit), and a counter member 50 (a background member). An example) and a sensor 60 (an example of a detection means). When an instruction to read an image is received from the user through the operation panel 20 with the paper M placed on the document placement table 35a, the paper transport unit 30A transfers the paper M placed on the document placement table 35a to the transport path. The paper is conveyed along the TP to a reading position (reading line of vision) RP, and then discharged to the paper discharge tray 35b. An arrow S indicates the conveyance direction of the paper M. The transport path TP is a path from the document placement table 35a to the paper discharge tray 35b inside the housing of the paper transport unit 30A. The reading unit 30B reads the image of the paper M and the background image of the image of the paper M through the contact glass (original glass) 32 (an example of a reading surface) at a predetermined reading position RP along the transport path TP.

  The paper transport unit 30A includes a document table 35a, a paper discharge tray 35b, a pickup roller 36, a paper feed roller 37a, transport rollers 37b and 37c, an upstream transport roller 37d, a downstream transport roller 37e, A conveyance roller 37f and a paper discharge roller 37g are included. Each of the pickup roller 36, the paper feed roller 37a, the transport rollers 37b and 37c, the upstream transport roller 37d, the downstream transport roller 37e, the transport roller 37f, and the paper discharge roller 37g extends from the upstream side to the downstream side of the transport path TP. In this order, the sheets M are transported along the transport path TP.

  The pickup roller 36 and the paper feed roller 37a feed the paper M on the document placing table 35a one by one. The transport rollers 37b and 37c and the upstream transport roller 37d immediately before the reading position RP transport the paper M to the reading position RP. The downstream side conveyance roller 37e and the conveyance roller 37f immediately after the reading position RP convey the paper M that has been read. The paper discharge roller 37g provided on the most downstream side of the transport path TP discharges the paper M onto the paper discharge tray 35b.

  The reading unit 30B includes a contact glass 32, a light source 33a, an image sensor 33b, mirrors 34a, 34b, and 34c, and a lens 34d. The light source 33a emits light. The light emitted along the reading position RP is reflected by the front surface (the lower surface in FIG. 2) of the paper M passing through the reading position RP and the facing member 50. The reflected light is further reflected by the mirrors 34a, 34b, and 34c, converged by the lens 34d, and enters the image sensor 33b. The image sensor 33b reads an image of the surface of the paper M and a background image formed by the facing member 50 as image data. The image sensor 33b is composed of, for example, a CCD (Charge-Coupled Device).

  The facing member 50 constitutes a background image of the image of the paper M read by the reading unit 30B. The facing member 50 is provided at the reading position RP and faces the contact glass 32 and the light source 33a with the transport path TP interposed therebetween.

  The sensor 60 detects the presence or absence of the sheet M on the upstream side of the reading position RP along the transport path TP.

  FIG. 4 is a cross-sectional view showing the configuration of the facing member 50 in one embodiment of the present invention. In FIG. 4, the structure of the opposing member 50 at the time of seeing in the cross section cut by the plane which makes the extending direction of rotating shaft AX of the opposing member 50 a normal is shown. In FIG. 4, the contact glass 32 is shown together with the facing member 50 for convenience of explanation.

  Referring to FIG. 4, counter member 50 rotates only in one rotation direction indicated by arrow K around rotation axis AX as controlled by drive unit 104 a (FIG. 2) (that is, counter member 50 has an arrow mark). Does not rotate in the opposite direction to K). The rotation direction indicated by the arrow K at the reading position RP matches the conveyance direction indicated by the arrow S at the reading position RP. The rotation speed of the facing member 50 is the same as the speed at which the paper transport unit 30A transports the document.

  The facing member 50 includes a background portion 51 and a cleaning portion 52. The background portion 51 has a semi-cylindrical shape which is a shape obtained when the cylinder is cut in half on a plane including the central axis. The background portion 51 has a semicircular shape when viewed in the cross section of FIG. The facing member 50 further includes a high concentration portion 61 (an example of a first portion), a low concentration portion 62 (an example of a second portion), and a high concentration portion 63 (an example of a third portion). Yes. The high density part 61, the low density part 62, and the high density part 63 constitute a background image of the image of the paper M read by the reading part 30B. Each of the high density portions 61 and 63 has a higher density than the low density portion 62. Each of the high density portion 61, the low density portion 62, and the high density portion 63 has a uniform density along the x-axis direction (main scanning direction). Typically, the high density portions 61 and 63 are black, and the low density portion 62 is white.

  Each of the high concentration portion 61, the low concentration portion 62, and the high concentration portion 63 is provided in this order in the direction opposite to the arrow K on the curved surface (the arc-shaped portion in FIG. 4) of the background portion 51. Each of the high concentration portion 61, the low concentration portion 62, and the high concentration portion 63 has such a length that the central angles around the rotation axis AX are angles α1, α2, and α3. Each of the angles α1, α2, and α3 is preferably 60 degrees.

  The high density part 61, the low density part 62, and the high density part 63 may be produced by a method of applying a necessary color to the background part 51 made of resin, or a sheet material on which a necessary color is printed. Alternatively, it may be attached to the background 51 using a double-sided tape or the like.

  The cleaning unit 52 is a part that removes foreign matters (paper dust and dust) from the contact surface of the contact glass 32 with the paper M and cleans the contact glass 32. The cleaning part 52 extends outward from a part other than the curved surface in the background part 51 (a part on the opposite side of the low concentration part 62 across the rotation axis AX). The cleaning unit 52 is made of a flexible material such as resin.

  FIG. 5 is a plan view showing the configuration of the facing member 50 according to the embodiment of the present invention. In FIG. 5, the structure of the opposing member 50 at the time of seeing from the opposite side to the side in which the contact glass 32 exists is shown.

  Referring to FIGS. 4 and 5, counter member 50 extends along the x-axis direction (main scanning direction). The width (length in the x-axis direction) W1 of the facing member 50 is larger than the width of the paper M (maximum value of the width of the document that can be read by the reading unit 30B) W2. Thereby, the opposing member 50 forms a background image of the image of the paper M read by the reading unit 30B.

  Next, an operation when MFP 100 reads an image on sheet M in the present embodiment will be described.

  The drive unit 104a moves (rotates) the opposing member 50 along the conveyance direction indicated by the arrow S at the reading position RP, thereby causing the high concentration unit 61, the low concentration unit 62, the high concentration unit 63, and the cleaning unit 52 to move. Each is sequentially positioned at the reading position RP. The drive unit 104a sequentially positions the high density portion 61, the low density portion 62, and the high density portion 63 at the reading position RP at the timing when the paper M passes the reading position RP, and the paper M passes the reading position RP. The cleaning unit 52 is brought into contact with the contact glass 32 by positioning the cleaning unit 52 at the reading position RP at a timing that is not.

  6 to 13 are diagrams schematically showing an operation when the MFP 100 reads an image on the sheet M in the embodiment of the present invention. FIG. 14 is a diagram schematically showing a change in the position of the sheet M along the transport path TP with time in one embodiment of the present invention.

  Referring to FIG. 6, at time T = t0 before the sensor 60 detects the front edge of the paper M, the drive unit 104a positions the central position in the circumferential direction of the high density unit 61 at the reading position RP. This state is the initial state of the opposing member 50, and the center position in the circumferential direction of the high concentration portion 61 is the initial position of the opposing member 50. Thus, the background image near the leading edge of the paper M is constituted by the high density portion 61.

  7 and 14, at time T = t1 after time T = t0, when the front end of the paper M reaches the detection position SP of the sensor 60 and the sensor 60 detects the front edge of the paper M ( When the sensor 60 is turned on), the driving unit 104a starts measuring time (counting) with a counter.

  Referring to FIGS. 8 and 14, at time T = t2 after time T = t1, the front end of the sheet M advances by a distance LH (mm) and reaches the reading position RP, and the reading unit 30B moves to the sheet. Start reading M images. The distance LH (mm) is a distance from the detection position SP of the sensor 60 to the reading position RP.

  Even when the reading unit 30B starts reading, the driving unit 104a keeps the center position in the circumferential direction of the high concentration unit 61 at the reading position RP, and the counter continues to measure time.

  With reference to FIGS. 9 and 14, at time T = t3 after time T = t2 and when time TM1 (an example of the first time) has elapsed from time T = t1, End time measurement. The drive unit 104a rotates the counter member 50 in the direction indicated by the arrow K, and positions the center position in the circumferential direction of the low concentration unit 62 at the reading position RP. As a result, the background image at the center of the sheet M is constituted by the low density portion 62.

  The central position in the circumferential direction of the low concentration portion 62 is the first displacement position of the facing member 50. The rotation angle of the facing member 50 for moving from the initial position to the first displacement position is 60 degrees.

  The time TM1 is the time from when the sensor 60 detects the front edge of the paper M until the position upstream in the transport direction from the front edge of the paper M by the distance X (mm) passes the reading position RP. Is calculated using the following equation (1), where the reading speed is the reading speed V (mm / s).

  Time TM1 (s) = {distance LH (mm) + distance X (mm)} / reading speed V (mm / s) (1)

  Referring to FIGS. 10 and 14, at time T = t4 after time T = t3, the trailing edge of paper M reaches detection position SP of sensor 60, and sensor 60 detects the trailing edge of paper M. Then (when the sensor 60 is turned off), the drive unit 104a starts measuring time with a counter.

  Referring to FIGS. 11 and 14, at time T = t5 when time TM2 (an example of the second time) has elapsed from time T = t4, drive unit 104a rotates counter member 50 in the direction indicated by arrow K. Thus, the central position in the circumferential direction of the high density portion 63 is positioned at the reading position RP. As a result, the background image in the vicinity of the rear end of the sheet M is constituted by the high density portion 63. Even when the time TM2 has elapsed, the counter continues to measure time.

  The central position in the circumferential direction of the high concentration portion 63 is the second displacement position of the facing member 50. The rotation angle of the facing member 50 for moving from the first displacement position to the second displacement position is 60 degrees.

  The time TM2 is the time from when the sensor 60 detects the trailing edge of the paper M until the position downstream in the transport direction from the trailing edge of the paper M by the distance Y (mm) passes the reading position RP. When the reading speed of the unit 30B is set to the reading speed V (mm / s), the calculation is performed using the following equation (2). Typically, Y (mm) = X (mm).

  Time TM2 (s) = {distance LH (mm) -distance Y (mm)} / reading speed V (mm / s) (2)

  Referring to FIGS. 12 and 14, at time T = t6 after time T = t5 and when time TM3 (an example of the third time, TM2 <TM3) has elapsed from time T = t4. The sensor 60 ends the time measurement. The drive unit 104a rotates the counter member 50 by 240 degrees in the direction indicated by the arrow K, and positions the central position (initial position) in the circumferential direction of the high concentration unit 61 at the reading position RP.

  With reference to FIG. 13 and FIG. 14, at time T = t7 when the facing member 50 is rotating, the cleaning unit 52 passes the reading position RP (the cleaning unit 52 is positioned at the reading position RP). The contact surface of the contact glass 32 contacts the sheet M. As a result, the contact surface of the contact glass 32 with the paper M is cleaned by the cleaning unit 52, and image streak noise caused by foreign matter can be suppressed.

  The time TM3 is the time from when the sensor 60 detects the trailing edge of the paper M until the trailing edge of the paper M passes the reading position RP, and the reading speed of the reading unit 30B is determined as the reading speed V (mm / s). ) Is calculated using the following equation (3).

  Time TM3 (s) = distance LH (mm / reading speed V (mm / s) (3)

  The image processing unit 109 (FIG. 2) performs the following processing on the image read by the reading unit 30B.

  FIG. 15 is a diagram schematically showing an image IM1 read by the reading unit 30B in the embodiment of the present invention.

  Referring to FIG. 15, an image IM1 read by reading unit 30B includes an image IM2 of paper M and a background image IM3. The image processing unit 109 extracts the image IM2 of the paper M from the image IM1.

  The background image IM3 of the region RG1 on the front end side in the image IM1 is configured by the high density portion 61. Since the paper M has a low density (typically white), the contrast (brightness difference) between the background image IM3 and the image IM2 near the front edge is strong, and the vertices C1 and C2 on the front edge side of the paper M are in the image IM1. It appears clearly.

  Similarly, the background image IM3 of the rear end side region RG3 in the image IM1 is configured by the high density portion 63. Since the paper M has a low density, the contrast between the background image IM3 and the image IM2 in the vicinity of the rear end is strong, and the vertices C3 and C4 on the rear end side of the paper M clearly appear in the image IM1.

  As a result, the image processing unit 109 can extract the image IM2 of the sheet M with an accurate boundary line based on the vertices C1, C2, C3, and C4. The image processing unit 109 can perform image tilt correction, magnification correction, trapezoid correction, and the like based on the vertices C1, C2, C3, and C4.

  The background image IM3 of the central region RG2 in the image IM1 is configured by the low density portion 62. Since the paper M has a low density, the contrast between the background image IM3 and the central image IM2 is weak, and the occurrence of image fogging in the central image IM2 can be suppressed when the paper M is a thin paper. . In particular, the central image IM2 is likely to contain important information such as characters and images, as compared to the image IM2 near the front end and near the rear end. Is possible. Further, when the image processing unit 109 performs OCR processing on the document image IM2, the density difference between the character and the background is clear, so that the character discrimination accuracy can be improved.

  The image processing unit 109 performs the following correction on the image IM2 (or the image IM1) as necessary.

  FIG. 16 is a diagram schematically showing an image IM2 extracted by the image processing unit 109 according to the embodiment of the present invention.

  Referring to FIG. 16, region RG1 in image IM2 is a region where high density portion 61 is a background image, and region RG3 in image IM2 is a region where high density portion 63 is a background image. For this reason, when the paper M is a thin paper, the image fogging ER is highly likely to occur in the regions RG1 and RG3 in the image IM2. On the other hand, a region RG2 in the image IM2 is a region in which the low density portion 62 is a background image. For this reason, even if the paper M is a thin paper, there is a low possibility that an image fogging ER will occur in the region RG2 in the image IM2.

  Therefore, the image processing unit 109 corrects the regions RG1 and RG3 in the image IM2 based on the region RG2 in the image IM2. Thereby, the image fogging of the regions RG1 and RG3 in the image IM2 can be relaxed, and the quality of the image IM2 can be further improved.

  [Effect of the embodiment]

  According to the present embodiment, since the cleaning unit 52 removes the foreign matter adhering to the contact glass 32, the generation of image streak noise can be suppressed and the deterioration of the quality of the read image can be suppressed.

  Further, since the opposing member 50 rotates along the conveyance direction of the paper M, a situation in which the conveyance resistance of the paper M increases due to the rotation of the opposing member 50 can be avoided, and deterioration of the quality of the read image is suppressed. Can do.

  Further, since the contrast between the background image IM3 and the image IM2 near the front edge and the rear edge of the paper M is strong, the detection accuracy of the vertices C1, C2, C3, and C4 of the paper M can be improved. Further, since the background image IM3 at the center of the image IM2 is the low density portion 62, the occurrence of image fog can be suppressed to a minimum when the paper M is a thin paper. As a result, image processing such as image extraction, magnification correction, or trapezoid correction can be performed accurately, and deterioration of the quality of the read image can be suppressed.

  Furthermore, since the cleaning unit 52 cleans the contact glass 32 at a timing when the paper M does not pass through the reading position RP, it is possible to suppress a decrease in productivity due to time for cleaning.

  [Others]

  The opposing member only needs to have an arbitrary shape. In addition to the shape of the above-described embodiment, the surface of the belt that rotates each of the first portion, the second portion, the third portion, and the cleaning portion. It may have a shape or the like.

  The processing in the above-described embodiment may be performed by software or by using a hardware circuit. It is also possible to provide a program for executing the processing in the above-described embodiment, and record the program on a recording medium such as a CD-ROM, a flexible disk, a hard disk, a ROM, a RAM, or a memory card and provide it to the user. You may decide to do it. The program is executed by a computer such as a CPU. The program may be downloaded to the apparatus via a communication line such as the Internet.

  The above-described embodiment is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 10 MFP (Multifunction Peripheral) main body 20 Operation panel 30 Scanner part 30A Paper conveyance part (an example of a conveyance means)
30B Reading unit (an example of reading means)
32 Contact glass 33a Light source 33b Image sensor 34a, 34b, 34c Mirror 34d Lens 35a Document placement table 35b Paper discharge tray 36 Pickup roller 37a Paper feed roller 37b, 37c, 37f Transport roller 37d Upstream transport roller 37e Downstream transport roller 37g Exhaust Paper roller 50 Opposing member 51 Background portion 52 Cleaning portion 60 Sensor (an example of detection means)
61, 63 High density part 62 Low density part 100 MFP (an example of an image reading apparatus)
101 CPU (Central Processing Unit)
102 ROM (Read Only Memory)
103 RAM (Random Access Memory)
104 image reading unit 104a driving unit (an example of moving means)
105 Network Interface 106 Operation Panel Control Unit 107 Auxiliary Storage Device 108 Image Forming Unit 109 Image Processing Unit AX Rotation Axis C1, C2, C3, C4 Vertex ER Image Fog IM1 Scanned Image IM2 Paper M Image IM3 Background Image LH Detection Position SP Distance from the reading position RP M Paper RG1 Front end side area in the image IM1 RG2 Center area in the image IM1 RG3 Rear end side area in the image IM1 RP Reading position SP Detection position TP Conveyance path

Claims (8)

Conveying means for conveying an original;
A reading unit that reads an image of the original and a background image of the image of the original through a reading surface at a predetermined reading position along the conveyance path of the original by the conveying unit;
A background member provided at the reading position, the background member constituting the background image,
The background member includes a first portion having a first concentration, a second portion having a second concentration, a third portion having a third concentration, and a cleaning unit. And each of the third concentrations is higher than the second concentration;
By moving the background member along the document conveyance direction at the reading position, each of the first portion, the second portion, the third portion, and the cleaning portion is sequentially read. Further comprising a moving means for positioning at a position;
The moving means positions the first portion, the second portion, and the third portion in order at the reading position at a timing when the document passes through the reading position,
The moving unit is an image reading apparatus that contacts the reading surface by positioning the cleaning unit at the reading position at a timing when the document does not pass through the reading position.   The moving means rotates the background member in one direction around the rotation axis, so that each of the first portion, the second portion, the third portion, and the cleaning portion is sequentially turned. The image reading apparatus according to claim 1, wherein the image reading apparatus is positioned at the reading position, and the one direction at the reading position coincides with a conveyance direction of the document at the reading position.   The image reading apparatus according to claim 2, wherein a rotation speed of the background member is the same as a speed at which the document is conveyed by the conveying unit. The background member further includes a background portion having a semicircular shape when viewed in a cross section cut by a plane whose normal is the extending direction of the rotating shaft,
The first portion, the second portion, and the third portion are provided on a curved surface of the background portion, and the cleaning portion extends outward from a place other than the curved surface of the background portion. Item 4. The image reading apparatus according to Item 2 or 3.   Each of the first portion, the second portion, and the third portion is centered on the rotation axis when viewed in a cross section cut along a plane whose normal is the extending direction of the rotation shaft. The image reading apparatus according to claim 4, wherein the image reading apparatus has a length with a central angle of 60 degrees. A detection unit for detecting the document on the upstream side of the document along the conveyance path of the document;
Before detecting the front edge of the document by the detecting means, the moving means positions the first portion at the reading position,
When the first time has elapsed since the detection unit detects the front edge of the document, the moving unit positions the second part at the reading position;
When a second time has elapsed since the detection unit detects the trailing edge of the document, the moving unit positions the third portion at the reading position;
The moving means positions the cleaning unit at the reading position when a third time longer than the second time has elapsed since the detection means detects the trailing edge of the document. The image reading device according to any one of?   The image reading apparatus according to claim 1, wherein each of the first portion, the second portion, and the third portion has a uniform density along a main scanning direction. Extracting means for extracting an image of the document from an image read by the reading means;
An area where the first part or the third part of the original image is the background image is corrected based on an area where the second part of the original image is the background image. The image reading apparatus according to claim 1, further comprising a correction unit.

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