JP5772467B2 - Image reading apparatus, image forming apparatus, image reading apparatus control method, and image reading apparatus control program - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, an image forming apparatus, an image reading apparatus control method, and an image reading apparatus control program, and more particularly to an image reading apparatus, an image forming apparatus, and an image reading apparatus provided with a reference surface as a reference for image correction. And a control program for the image reading apparatus.

  There is an image reading apparatus that reads the surface of a document with a CIS (Contact Image Sensor) while conveying the document. In this type of image reading apparatus, the document is read (scanned) by the CIS by conveying the document to the CIS fixed to the image reading apparatus. The image reading apparatus is used in, for example, an image forming apparatus (MFP (Multi Function Peripheral), facsimile apparatus, copier, multifunction machine, etc.).

  In order to correct a CIS read image, a shading plate (opposing plate) is provided to face the CIS.

  Patent Document 1 below discloses an image reading apparatus in which a polygonal column having a reference surface serving as a reference for shading correction and a sheet passing surface is provided facing a CIS. This image reading apparatus is configured such that a reference plane and a sheet passing plane are switched by rotating a polygonal column with a motor. That is, in this image reading apparatus, a polygonal columnar shape is used as the shading plate.

  Patent Document 2 below discloses an image reading apparatus that obtains a CIS light quantity distribution correction coefficient based on reading data of a reference sheet and reading data of a shading reference plate that is separated from the reference sheet. Yes. The reference sheet is set at the same position as the original reading position by the user. The light quantity distribution correction coefficient is obtained by calculating a ratio of correction data based on both read data and creating correction coefficient data.

JP 2008-219101 A JP 2009-147546 A

  The image reading apparatus described in Patent Document 1 can switch between a reference surface and a sheet passing surface by appropriately rotating a polygonal column, so that when reading a plurality of documents continuously, between images (between documents). Correction data for shading correction can be obtained. However, like the sheet passing surface, the reference surface of the polygonal column is separated from the CIS reading surface by at least a distance corresponding to the thickness of the document. That is, there is a gap between the reference surface and the reading surface.

  FIG. 9 is a diagram for explaining the structure of a reading portion of a conventional image reading apparatus.

  As shown in FIG. 9, a polygonal column (here, for example, a hexagonal column) 831 is provided so as to face the CIS 801. On the side surface of the polygonal column 831, for example, a reference surface (white surface), a paper passing surface (not shown), and the like are provided. Acquisition of correction data (shading data) for CIS 801 shading correction is performed in a state where the reference plane of the polygonal column 831 faces the CIS 801. A document (paper) 880 read by the CIS 801 is conveyed in a state where the sheet passing surface of the polygonal column 831 faces the CIS 801, and is read by the CIS 801. The document 880 is conveyed so as to pass between the CIS 801 and the polygonal column 831. An arrow F indicates the conveyance direction of the document 880.

  When the document 880 is read, the upper surface of the document 880 becomes a reading surface (reading position). On the other hand, when the correction data is acquired, the reference surface facing the CIS 801 in the polygonal column 831 becomes the reading surface. As shown in FIG. 9, the distance b from the CIS 801 to the reference surface is longer than the distance a from the CIS 801 to the upper surface of the document 880. With respect to the distance a from the CIS 801 to the reading surface, the distance b from the CIS 801 to the reading surface of the polygonal column 831 when obtaining the correction data is increased by at least the thickness of the document 880. In other words, there is at least a gap (indicated by arrow G in FIG. 9) corresponding to the thickness of the document 880 between the reference surface document 880 and the reading surface.

  As described above, when there is a gap between the reference surface and the original reading surface, the light distribution profiles of the reading surface and the reference surface are different. For this reason, there is a limit in properly performing shading correction on the reading surface using the correction data obtained on the reference surface. In other words, in order to appropriately perform shading correction and appropriately read an image, it is necessary to consider the influence due to the existence of a gap between the reference surface and the original reading surface.

  In particular, when an LED light source having a high distance dependency is used as the light source, a change in the light distribution profile with respect to a change in the distance from the light source becomes large. Therefore, it has been important in the past to perform shading correction according to the distance as described above.

  In order to correct the influence of the gap between the reading surface and the reference surface, for example, there is a method in which the light amount distribution correction coefficient is obtained as described in Patent Document 2 above. However, the method described in Patent Document 2 has a problem in that it is necessary to set the sheet at the same position as the document conveyance position every time the light amount distribution correction coefficient is calculated, and the operation is very troublesome. The calculation of the light quantity distribution correction coefficient is performed at a timing (for example, a service mode) different from that at the time of image reading. Therefore, for example, when reading a plurality of documents continuously, it is not practical to perform shading correction after calculating a light amount distribution correction coefficient between images, and the productivity of the image reading apparatus cannot be increased. There is a problem.

  The present invention has been made in order to solve such a problem, and can perform image reading appropriately with high-precision shading correction, and has high productivity. It is an object of the present invention to provide an image reading apparatus control method and an image reading apparatus control program.

  In order to achieve the above object, according to one aspect of the present invention, an image reading apparatus is provided opposite to a reading unit that reads a document and a reference surface that serves as a reference for image correction of the reading unit. A columnar body on the surface, a conveying unit that conveys the document between the reading unit and the columnar body, a rotating unit that rotates the columnar body around a rotation axis that intersects the document conveying direction, and a reading unit that reads an image on the reference surface. The columnar body is configured such that the distance from the reading unit to the reference plane changes with the rotation of the columnar body. Based on the result of reading the image of the reference surface by the reading means in each of a plurality of states with different distances to the reference surface, correction data corresponding to the paper passing position of the conveyed document is obtained by calculation. Have obtained means, using the correction data acquired by the acquisition unit, performs predetermined image correction.

  Preferably, the contour in the cross section perpendicular to the rotation axis of the columnar body includes an elliptical arc portion.

  Preferably, the rotating unit rotates the columnar body with a motor, and the correcting unit specifies the distance from the reading unit to the reference plane based on information on the operation of the motor.

  Preferably, a cleaning member is attached to the columnar body, and the cleaning operation of the reading unit by the cleaning member is performed as the columnar body rotates.

  Preferably, the acquisition of correction data by the acquisition unit, the document conveyance operation by the conveyance unit, and the cleaning operation by the cleaning member are performed as a series of operations while the rotation unit rotates the columnar body as necessary.

  Preferably, the image reading apparatus further includes a second reading unit that reads a document surface different from the document surface read by the reading unit, and reads images on both sides of the document by one document transport operation by the transport unit.

  According to another aspect of the present invention, an image forming apparatus includes any of the image reading apparatuses described above.

  According to still another aspect of the present invention, a reading unit that reads a document, a columnar body that is provided opposite to the reading unit and that has at least a reference surface serving as a reference for image correction of the reading unit on the side peripheral surface, and a document A conveyance unit that conveys between the reading unit and the columnar body, a rotation unit that rotates the columnar body on a rotation axis that intersects the document conveyance direction, and a correction that reads a reference plane image by the reading unit and performs predetermined image correction. And the columnar body is configured such that the distance from the reading unit to the reference surface changes with the rotation of the columnar body. An acquisition step of acquiring correction data corresponding to a sheet passing position of a document to be conveyed by calculation based on a result of reading an image of a reference surface by a reading unit in each of a plurality of different states; Using the correction data obtained by the step, and a correcting step of performing a predetermined image correction.

  According to still another aspect of the present invention, a reading unit that reads a document, a columnar body that is provided opposite to the reading unit and that has at least a reference surface serving as a reference for image correction of the reading unit on the side peripheral surface, and a document A conveyance unit that conveys between the reading unit and the columnar body, a rotation unit that rotates the columnar body on a rotation axis that intersects the document conveyance direction, and a correction that reads a reference plane image by the reading unit and performs predetermined image correction. And a control program for an image reading apparatus configured such that the distance from the reading means to the reference surface changes with the rotation of the columnar body. An obtaining step for obtaining, by calculation, correction data corresponding to a paper passing position of a conveyed document based on a result of reading an image of a reference surface by a reading unit in each of a plurality of different states; Using the correction data acquired by the acquisition step, to execute a correction step of performing a predetermined image correction to the computer.

  According to these inventions, the correction data corresponding to the sheet passing position of the conveyed document is calculated based on the reading result of the image on the reference surface in each of the plurality of states whose distances from the reading unit are different from each other. A predetermined image correction is performed using the data. Therefore, there are provided an image reading apparatus, an image forming apparatus, an image reading apparatus control method, and an image reading apparatus control program capable of appropriately reading an image by performing more accurate shading correction and having high productivity. be able to.

1 is a diagram illustrating an image forming apparatus including an image reading apparatus according to one embodiment of the present invention. It is a figure which shows the control object connected to the ADF control part in ADF. It is a figure which shows the structure of the control mechanism of an ADF control part. It is a figure which shows the internal structure of a scanner. It is a figure explaining the positional relationship of CIS and a roller. It is a flowchart explaining the operation | movement at the time of the reading operation | movement of a scanner. It is a figure explaining the light quantity data when a reference plane is read by CIS. It is a figure explaining the relationship between the distance from CIS to a reference plane, and light quantity. It is a figure explaining the structure of the reading part of the conventional image reading apparatus.

  Hereinafter, an image reading apparatus according to one embodiment of the present invention will be described.

  The image reading apparatus is provided in, for example, an image forming apparatus. The image forming apparatus is, for example, an MFP (Multi Function Peripheral) having a scanner function, a copying function, a printer function, a facsimile function, a data communication function, and a server function. The scanner function is a function of reading an image of a set original by an image reading device and storing it in a HDD (Hard Disk Drive) or the like. The copying function is a function of printing (printing) it on paper or the like. The function as a printer is a function for printing on a sheet based on an instruction received from an external terminal such as a PC. The facsimile function is a function for receiving facsimile data from an external facsimile machine or the like and storing it in an HDD or the like. The data communication function is a function for transmitting / receiving data to / from a connected external device. The server function is a function that allows a plurality of users to share data stored in the HDD or the like.

  The image reading apparatus can simultaneously read both sides of a document. The image reading apparatus has a reading unit that reads the back side of a document using a CIS (Contact Image Sensor). Before the CIS reads an image, correction data for shading correction is acquired. A facing surface is provided at a position facing the CIS. The correction data is acquired using the facing surface.

  The facing surface can be switched by rotating it with a motor or the like. Specifically, the opposing surface is provided on a side peripheral surface of a roller that is a columnar body that is rotatable around a rotation axis that is separated from the CIS by a predetermined distance. In the present embodiment, a roller having a shape that includes an elliptical arc portion in a contour in a cross section perpendicular to the rotation axis is used. The opposing surface includes a white shading surface (white reference surface). In addition, the facing surface may include a black shading surface (black reference surface), a paper passing surface used when a document is passed through, and the like.

  The roller is provided with a cleaning brush. The image forming apparatus performs a series of operations of passing a document, acquiring correction data for shading correction, and cleaning with a cleaning brush while rotating a roller.

  The roller is rotated by a motor. In the present embodiment, the distance from the CIS to the facing surface changes as the roller rotates. The distance from the CIS to the opposite surface of the roller is specified from the amount of rotation of the motor.

  As the correction data, data at a position (paper passing position) corresponding to the reading surface of the document is obtained by calculation. That is, the facing surface is read while rotating the roller. Thereby, the reading result of the light quantity data according to the distance fluctuation from the CIS to the facing surface is obtained. Correction data for the reading surface (paper passing position) is calculated and acquired using a plurality of series of light amount data obtained for reference surfaces having different distances.

  The shading correction at the time of document reading is performed based on the acquired reading surface correction data. Therefore, even if there is a gap corresponding to the thickness of the document between the reading surface and the reference surface, it is possible to perform appropriate shading correction regardless of the gap. In particular, even when the light distribution profile changes greatly, such as when an LED light source having a high distance dependency is used as the light source, highly accurate shading correction can be performed regardless of this.

  [Embodiment]

  FIG. 1 is a diagram illustrating an image forming apparatus including an image reading apparatus according to one embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus 100 includes a scanner (an example of an image reading apparatus) 200, a printer 400, a control device 500, and an operation unit 600.

  The scanner 200 is provided with a CCD (an example of a second reading unit) 201 for surface reading and a scanner control unit 203. The scanner 200 includes an ADF (automatic document feeder; an example of a transport unit) 300. The ADF 300 is provided with a CIS (an example of a reading unit) 301 for reading the back surface and an ADF control unit 303. The scanner 200 can read both sides of a document with the CCD 201 and the CIS 301 when the document is transported once by the ADF 300.

  For example, the printer 400 prints an image on a sheet by electrophotography. The printer 400 is provided with a laser diode (LD) 401 and a printer control unit 403.

  The control device 500 includes a reading processing unit 501 that processes signals from the CCD 201 and the CIS 301, a compression IC 503 that compresses image data, an image memory (DRAM) 505, a DRAM control IC 507 that controls the image memory, A decompression IC 513 that decompresses image data, a write processing unit 515 that outputs an image with a printer, a non-volatile memory 511 that stores programs and constants, and an image control unit 509 that controls image processing are provided.

  The nonvolatile memory 511 stores, for example, a control program 511 a that is executed by the image control unit 509 or the like and performs various controls of the image forming apparatus 100.

  The image memory 505 includes a compression memory 505a and a page memory 505b.

  The operation unit 600 is provided with an LCD (Liquid Crystal Display) 601 for displaying various types of information to the operator, and an operation control unit 603 including a touch panel and keys.

  The image control unit 509 has a function of reading a reference surface image by the CCD 201 or the CIS 301 and performing predetermined image correction (shading correction or the like). These functions are performed by the image control unit 509 executing the control program 511a to control each unit of the image forming apparatus 100.

  FIG. 2 is a diagram illustrating a control target connected to the ADF control unit 303 in the ADF 300.

  The ADF control unit 303 to which the CPU is attached and the ADF drive board 305 are connected so that, for example, parallel transfer is possible. The ADF drive board 305 is connected to various motors 309, various sensors 311, and other loads 307. The ADF drive board 305 performs output to the motor 309, the load 307, etc., sensor input, and exchanges information with the ADF control unit 303.

  The various motors 309 include a document tray lift up / down motor 309b, a roller driving motor 309c for a CIS counter plate (roller), a paper feed and conveyance motor 310 for feeding a document, and the like. The various sensors 311 include a paper feed / conveyance sensor 311a and a cover open / close detection sensor 311b. Other loads 307 include a paper feed clutch 307a and a CIS lamp 307b of the CIS 301.

  The ADF drive board 305 has drive circuits such as a paper feed / conveyance motor 310 and a roller drive motor 309c. The ADF drive board 305 operates these motors in accordance with a drive signal from the ADF control unit 303.

  The paper feed conveyance sensor 311a is provided in the paper passing path. The sheet feed sensor 311a can detect passage of a document through a predetermined location. Based on the detection result of the paper feed conveyance sensor 311a, document conveyance control including paper feeding timing control is performed.

  When a paper jam occurs during document passing, the ADF 300 urgently stops its operation. The sheet passing path of the ADF 300 is opened and closed by a cover. As a result, even if a paper jam occurs, the original can be easily removed from the paper path. This cover open / close detection is detected by the cover open / close detection sensor 311b. When it is detected by the cover open / close detection sensor 311b that all the covers are closed and there is no paper on the document passing path, the ADF 300 becomes operable.

  FIG. 3 is a diagram illustrating a configuration of a control mechanism of the ADF control unit 303.

  The CPU 303a is used for mechanical control, for example. The CPU 303a includes a ROM, a RAM, and the like. The CPU 303a is connected to the SRAM 303b, the ASIC 303c, and the like via a bus. With the ASIC 303c, input / output can be expanded and additional motors can be controlled. The SRAM 303b stores, for example, various adjustment values used for control.

  FIG. 4 is a diagram illustrating an internal configuration of the scanner 200.

  As shown in FIG. 4, the scanner 200 roughly includes a scanner body having a document table 220 and an ADF 300 disposed above the scanner body. The scanner 200 can read a document placed on the document table 220 and can also read a document using the ADF 300.

  Inside the scanner main body, a light source 210, mirrors 205a, 205b, and 205c and a CCD 201 are arranged. The light emitted from the light source 210 and reflected by the surface of the document (the lower surface in FIG. 4) is reflected by the mirrors 205 a to 205 c and enters the CCD 201. The reflected light is read by the CCD 201 while the document is conveyed, so that the image on the surface of the document is read.

  The ADF 300 includes a document placement table 321 and a paper discharge tray 323. On the document placement table 321, a document that is transported into the ADF 300 and read is placed. The read original is discharged from the inside of the ADF 300 to the paper discharge tray 323.

  Inside the ADF 300, a paper path that connects the document placement table 321 to the paper discharge tray 323 is provided. A plurality of conveying rollers 341 to 348 (hereinafter, these may be referred to as conveying rollers 340 without being distinguished), rollers 230 and 330, CIS 301, and the like are provided along the sheet passing path.

  The roller 230 is disposed at a position facing the light source 210. The roller 230 is arranged so that the shading correction of the CCD 201 can be performed. Note that the roller 230 may not be provided.

  The CIS 301 is disposed on the downstream side in the document transport direction from the reading position on the surface of the document (position where the roller 230 is disposed) so as to face the back surface of the document. The roller 330 is disposed so as to face the CIS 301 across the sheet passing path.

  The transport roller 340 is driven by a paper feed motor 310 (paper feed motor 310a, registration motor 310b, reading motor 310c, and paper discharge motor 310d). That is, the paper feed motor 310 a feeds the originals on the document placement table 321 one by one by the pick roller 341 and the paper feed roller 342 by driving the paper feed clutch 315. The paper feed motor 310a drives the transport roller 343. The registration motor 310b drives the registration roller 344. The reading motor 310c drives the conveying rollers 345 to 347, the rollers 230 and 330, and the like. The paper discharge motor 310d drives the paper discharge roller 348.

  A paper feed conveyance sensor 311 a is disposed in the paper passage path between the conveyance roller 343 and the registration roller 344. Based on the detection result of the paper feed conveyance sensor 311a, the original is conveyed at an appropriate timing.

  The scanner 200 uses the ADF 300 to draw the document placed on the document placing table 321 in the direction of the arrow “A” in FIG. 4. When light is emitted from the light source 210 to the document conveyed to the position where the roller 230 is provided, the CCD 201 reads the image on the surface of the document via the mirrors 205a to 205c. Further, the ADF 300 conveys the document between the CIS 301 and the roller 230 and reads an image on the back side of the document with the CIS 301. Reading of an image of a document by the CCD 201 and the CIS 301 is performed while the document is being conveyed. The document that has been read is discharged onto a paper discharge tray 323 by a paper discharge roller 348.

  FIG. 5 is a diagram for explaining the positional relationship between the CIS 301 and the roller 330.

  As shown in FIG. 5, in the present embodiment, the roller 330 is disposed so as to be rotatable about a rotation shaft 335. The roller 330 is driven and rotated by, for example, a roller drive motor 309c. The rotation shaft 335 is arranged such that the direction substantially perpendicular to the document transport direction (direction perpendicular to the paper surface) is the longitudinal direction. That is, the roller 330 rotates around the rotation shaft 335 that intersects the document conveyance direction. The rotation shaft 335 is positioned so as to be parallel to the glass surface 301 a so as to be separated from the glass surface 301 a facing the roller 330 in the CIS 301 by a predetermined distance.

  The roller 330 includes a roller body 331 and a cleaning brush (an example of a cleaning member) 333 that protrudes from the roller body 331.

  The roller body 331 is a columnar body. The side peripheral surface of the roller main body 331 is configured to be a reference surface when the shading correction of the CIS 301 is performed. In other words, the roller main body 331 has a reference surface on the side peripheral surface that serves as a reference for image correction of the CIS 301.

  The roller main body 331 is formed so as to include an elliptical arc portion in a contour in a cross section orthogonal to the rotation shaft 335 (hereinafter, simply referred to as a roller cross section). The contour of the roller cross section is composed of an elliptical arc and a line segment perpendicular to the major axis of the ellipse to which the elliptical arc belongs. That is, the roller main body 331 has a shape surrounded by a flat surface 331b parallel to the rotation shaft 335 and an elliptic cylinder surface 331a. In the roller body 331, a part of the elliptic cylinder surface 331a is, for example, a white reference surface. A black reference surface may be provided on another part of the elliptical cylinder surface 331a.

  The rotation shaft 335 is located at the position of the center of the ellipse to which the elliptical arc of the roller body 331 belongs in the roller cross section, that is, the position where the major axis and the minor axis of the elliptical cylinder surface 331a intersect. The distance from the rotating shaft 335 to the elliptical cylindrical surface 331a of the roller body 331 differs around the rotating shaft 335. That is, the distance is the shortest at the position where the minor axis is present in the roller cross section and the longest at the position where the major axis is present.

  For example, the cleaning brush 333 is formed so as to protrude in a direction substantially perpendicular to the flat surface 331b. The cleaning brush 333 has a brush portion 333a at the tip. The cleaning brush 333 is provided along the longitudinal direction of the roller 330. The distance from the rotating shaft 335 to the tip of the brush portion 333a is slightly longer than the distance from the rotating shaft 335 to the glass surface 301a of the CIS 301.

  When the roller 330 is driven by the roller drive motor 309c, it rotates in the direction of arrow R in the figure.

  When the roller 330 rotates, the distance from the CIS 301 to the side peripheral surface of the roller body 331, that is, the reference surface (in this embodiment, the distance from the glass surface 301a to the elliptical cylindrical surface 331a) changes accordingly. The roller 330 rotates during a document reading operation, and is used for image correction of the document to be read such as a shading correction operation of the CIS 301.

  Further, when the roller 330 rotates and reaches the position where the cleaning brush 333 faces the CIS 301, the brush portion 333a contacts the glass surface 301a. The roller 330 is further rotated while the brush portion 333a is in contact with the glass surface 301a, whereby the glass surface 301a is cleaned by the brush portion 333a. As a result, dust and dirt adhering to the glass surface 301a are removed, and reading trouble due to dust and dirt is prevented.

  [Description of operation when reading document by CIS301]

  Here, when a document is read by the CIS 301, acquisition of correction data used for image correction of the document to be read, a document transport operation by the ADF 300, and a cleaning operation by the cleaning brush 333 are performed as a series of operations. These operations are performed while the roller drive motor 309c rotates the roller 330 in a timely manner as necessary.

  The document image correction includes shading correction. The correction data for shading correction is obtained based on the result of reading the reference surface image of the roller 330 by the CIS 301. The acquisition of the correction data is performed based on, for example, mainly control of the image control unit 509, but is not limited thereto, and may be performed based on control by other parts.

  The reference plane reading performed to obtain the correction data is performed, for example, three times while rotating the roller 330, that is, while changing the distance from the glass surface 301a of the CIS 301 to the elliptical cylinder surface 331a. In other words, the image of the reference plane is read by the CIS 301 in each of three states where the distances from the CIS 301 to the reference plane are different from each other.

  In the present embodiment, the image of the reference plane is read when the roller 330 is in the following three postures (rotation angles around the rotation axis 335). That is, in FIG. 5, the posture indicated by a broken line (rotation angle 0 degree; hereinafter referred to as A posture), and the posture indicated by a dotted line (rotation angle approximately 60 degrees; hereinafter referred to as B posture). 3) postures indicated by a solid line (rotation angle 90 degrees; hereinafter referred to as C posture). In FIG. 5, the cleaning brush 333 is not shown for the A posture and the B posture.

  When the roller 330 is in the A posture, the distance from the glass surface 301a to the reference surface on the elliptical cylinder surface 331a (hereinafter sometimes simply referred to as a distance) is, for example, 1.2 millimeters. When the roller 330 is in the B posture, the distance is, for example, 0.9 millimeter. When the roller 330 is in the C posture, the distance is, for example, 0.6 millimeters. In the present embodiment, the distance from the glass surface 301a to the document reading surface is assumed to be 0.3 mm. Although the distance to the reading surface varies depending on the thickness of the original, the above value is assumed assuming an average original.

  The image control unit 509 calculates correction data corresponding to the sheet passing position of the conveyed document based on the result of reading the image of the reference surface performed three times, for example. The image control unit 509 performs shading correction corresponding to the paper passing position, that is, shading correction for the position of the reading surface, using the calculated correction data.

  Here, the image control unit 509 acquires information regarding the operation of the roller drive motor 309c, and specifies that the roller 330 is in the A to C posture based on the information. Accordingly, the image control unit 509 can specify the distance from the glass surface 301a of the CIS 301 to the elliptical cylinder surface 331a, and calculates the correction data for the specified distance. For example, when the rotation amount of the roller drive motor 309c is 0 degrees, 60 degrees, and 90 degrees from the reference position, the posture of the roller 330 can be specified as the A posture, the B posture, and the C posture, respectively. Note that the rotation amount of the roller drive motor 309c and the distance data corresponding thereto may be recorded in advance, and the corresponding distance may be specified by acquiring the rotation amount.

  When the document is passed, the roller 330 is symmetric with respect to the rotation shaft 335 with respect to the above-described A-position roller 330 (paper passing position; the rotation angle is 180 degrees). That is, when the document is passed, the roller 330 is in such a posture that the major axis of the ellipse to which the elliptical arc of the roller body 331 belongs in the roller cross section substantially coincides with the document passing direction. As a result, the distance between the elliptical cylinder surface 331a and the glass surface 301a of the CIS 301 is the largest, and the roller 330 is difficult to touch the document, so that the document can be smoothly conveyed. It should be noted that the roller 330 may be in the A posture when the document is passed.

  FIG. 6 is a flowchart for explaining the operation during the reading operation of the scanner 200.

  In step S101, the image control unit 509 determines whether to start the reading operation. That is, the image control unit 509 determines whether to start shading correction. The image control unit 509 determines that the reading operation is started, for example, when a start button for starting reading is operated in a state where a document is placed on the document placing table 321. When it is determined to start the reading operation, the process proceeds to step S102. Note that. At this time, the roller is in the A posture.

  In step S102, the image control unit 509 rotates the roller 330 as necessary to bring the roller 330 into the A posture. When the roller 330 is in the A posture, the operation of this step may not be substantially performed.

  In step S <b> 103, the image control unit 509 reads the reference surface of the roller 330 by the CIS 301 in a state where the roller 330 is in the A posture. Thereby, data acquisition about the state where distance is distance A (1.2 millimeters) is performed.

  In step S <b> 104, the image control unit 509 rotates the roller 330 to take the B posture, and reads the reference surface of the roller 330 using the CIS 301. Thereby, the data acquisition about the state whose distance is the distance B (0.9 millimeter) is performed.

  In step S <b> 105, the image control unit 509 rotates the roller 330 to take the C posture, and reads the reference surface of the roller 330 by the CIS 301. Thereby, data acquisition about the state where distance is distance C (0.6 millimeters) is performed.

  In step S106, the image control unit 509 calculates correction data at the reading position based on the data acquired for each of the distance A, the distance B, and the distance C. That is, the image control unit 509 calculates correction data on the reading surface. Details of such arithmetic processing will be described later. Thereby, correction data on the reading surface is obtained.

  In step S107, the image control unit 509 rotates the roller 330 from the position of the C posture so that the roller 330 takes the paper passing posture.

  In step S <b> 108, the image control unit 509 passes the document and reads it with the CIS 301. At this time, the image control unit 509 performs shading correction on the read image using the correction data obtained by the calculation.

  In step S109, the image control unit 509 rotates the roller 330. Thereby, the cleaning brush 333 comes to be located in the glass surface 301a side.

  In step S <b> 110, the image control unit 509 continues to rotate the roller 330 and cleans the glass surface 301 a with the cleaning brush 333.

  In step S111, the image control unit 509 determines whether the last page has been read, that is, whether there are no more pages to be read.

  If the last page has not been read in step S111, the image control unit 509 determines in step S113 whether it is necessary to re-acquire correction data for shading correction. If necessary, after the processing from step S103 to step S106 is performed again, the next page is read and cleaned (step S107 to step S110). On the other hand, if not necessary, the next page is read as it is, and shading correction is performed using correction data that has already been calculated. Whether or not the correction data needs to be acquired may be determined according to, for example, the lighting time of the CIS light source, the number of documents read after calculating the previous correction data, and the like. In addition, the above-described determination may be performed in accordance with input from various sensors (such as a temperature sensor and an illuminance sensor).

  When reading of the last page is completed in step S111, a series of processing ends.

  FIG. 7 is a diagram for explaining light amount data when the reference plane is read by the CIS 301. FIG. 8 is a diagram illustrating the relationship between the distance from the CIS 301 to the reference plane and the amount of light.

  The correction data calculation method at the reading position will be described with reference to FIGS.

  In FIG. 7, the horizontal axis represents a value corresponding to the pixel position of the CIS 301 in the main scanning direction (the direction orthogonal to the paper passing direction of the document) (for example, up to the pixel counted from one end in the main scanning direction). Number of pixels). The vertical axis indicates the amount of light obtained by the CIS 301 when reading the reference surface. In FIG. 7, light quantity data (raw data) obtained by reading the reference surface when the distance from the glass surface 301a of the CIS 301 to the reference surface is 1.2 millimeters, 0.6 millimeters, and 0.3 millimeters, respectively. Is indicated by a solid line.

  In FIG. 8, the horizontal axis indicates the distance from the glass surface 301a of the CIS 301 to the reference surface, and the vertical axis indicates the amount of light obtained by the CIS 301 when reading the reference surface. FIG. 8 shows the relationship between the distance and the amount of light for two pixels of CIS 301 (a pixel at pixel position A and a pixel at pixel position B). Here, the two pixels in which the relationship between the distance and the light quantity is shown correspond to the pixel at the pixel position A and the pixel at the pixel position B shown in FIG.

  As shown in FIG. 7, the light amount is large at the central portion in the main scanning direction, and the light amount is relatively small at both ends in the main scanning direction. As described above, since the light distribution profile is not uniform, it is necessary to perform shading correction on the image read by the CIS 301. In the present embodiment, for example, an LED (light emitting diode) is used as the light source of the CIS 301. Since such an LED light source has high distance dependency, the non-uniformity of the light distribution profile changes according to the change in distance. That is, for example, in the light amount data when the distance is 0.6 millimeters and the light amount data when the distance is 1.2 millimeters, the latter has both end portions with respect to the light amount in the central portion in the main scanning direction. The degree to which the amount of light decreases is increased.

  Here, with respect to the reading surface of the document, the distance is 0.3 mm, but it is not possible to prepare a reference surface at a position where the distance is 0.3 mm. That is, correction data for shading correction on the reading surface cannot be obtained by directly reading with the CIS 301. Therefore, in the present embodiment, when the distance obtained by rotating the roller 330 as described above is 1.2 millimeters, 0.9 millimeters, and 0.6 millimeters, the reference plane is read by the CIS 301. Correction data on the reading surface is obtained by performing calculations based on the obtained three series of light amount data (raw data) of distances A to C.

  As shown in FIG. 8, for example, when three series of light quantity data 901a, 901b, and 901c are obtained for the pixel position A, the light quantity data 901a, 901b, and 901c are approximated by the least square method or the like. The next function is obtained. When the function to be approximated is obtained, the light amount data 905 in the case where the distance is 0.3 millimeter is obtained by extrapolation. Similarly, for the pixel position B, for example, a quadratic function is obtained for the three series of light quantity data 911a, 911b, and 911c, and the light quantity data 915 of the light quantity when the distance is 0.3 millimeter is obtained by extrapolation. .

  In this way, the light amount data on the reading surface having a distance of 0.3 mm is obtained by extrapolation using the three series of light amount data of distances A to C. The light amount data on the reading surface is calculated in each pixel. Thereby, as indicated by a broken line in FIG. 7, light amount data on the reading surface is obtained, and correction data corresponding to the light amount data is obtained by calculation. In the shading correction, an image is read with the gains at both ends in the main scanning direction where the light amount falls relatively larger than that in the central part in the main scanning direction. Since the shading correction is performed using the correction data on the reading surface acquired as described above, the image is appropriately corrected.

  In FIG. 7, the two-dot chain line shows the virtual light amount data when the distance is 0 millimeter and the virtual light amount data when the distance is 0.3 millimeter, that is, the reading surface. . The light amount data on the reading surface obtained by extrapolation as described above is in good agreement with the virtual light amount data indicated by the two-dot chain line. That is, by performing the calculation as described above, it is possible to obtain the light amount data at the position of the reading surface that cannot be directly measured with high accuracy.

  As described above, in the present embodiment, light amount data on the reading surface is calculated by extrapolation using three series of light amount data having different distances from the CIS 301 to the reference surface, and on the obtained reading surface. Correction data on the reading surface is obtained by calculation using the light amount data. As a result, it is possible to obtain correction data with high accuracy and appropriately perform shading correction without positioning the reference surface on the reading surface. Even when an LED light source having a high distance dependency is used as the light source of the CIS 301, correction data on the reading surface can be obtained, so that an image can be read appropriately.

  Correction data on the reading surface can be obtained without positioning the reference surface on the reading surface. It is not necessary for the user to bother to set the reference surface at the position of the reading surface, and the correction data can be obtained appropriately by rotating the roller 330 by the roller drive motor 309c. Therefore, for example, the correction data can be acquired again between the originals (between images) easily and quickly, and the productivity of the image forming apparatus 100 can be improved.

  Since the cleaning brush 333 is provided on the roller 330, the CIS 301 is cleaned as the roller 330 rotates. Accordingly, the original can be read in a good state at all times.

  The distance from the CIS 301 to the reference plane is specified based on the rotation amount of the roller drive motor 309c. Therefore, there is no need to separately provide a sensor for measuring the distance to the reference surface, an encoder for grasping the position of the roller, and the like, and the manufacturing cost of the image forming apparatus 100 can be reduced.

  [Others]

  Depending on the thickness of the original specified in advance, the distance from the assumed reading surface to the CIS may be changed to obtain correction data at that distance. A document thickness sensor may be provided in the ADF, and the assumed distance from the CIS of the reading surface may be changed according to the detection result of the document thickness by the thickness sensor.

  The light amount data may be read more than three series. Two series of light quantity data may be read. The light amount data on the reading surface may be calculated by linearly approximating the light amount data obtained by reading, or may be calculated by approximating with a function of third order or higher.

  The roller may not have an elliptical cylindrical surface. For example, the roller may have a curved reference surface of another type on the outer peripheral surface, and may be configured to change the distance from the CIS to the reference surface by rotating around the rotation axis. The roller may have a plurality of planar reference surfaces with different distances from the rotation axis. By obtaining light amount data for each reference surface having a different distance from the CIS, correction data on the reading surface can be calculated as in the above-described embodiment.

  Further, for example, the roller may be a polygonal column type or a cylindrical type. In such a case, the roller may be provided, for example, so that the rotation shaft is eccentric from the center axis thereof, and the distance from the CIS to the reference plane may be changed as the roller rotates. .

  The image forming apparatus provided with the image reading apparatus may be any one of a monochrome / color copying machine, a printer, a facsimile machine, and a complex machine (MFP) thereof. The present invention is also applicable to an image reading apparatus that does not have an image forming function.

  The image reading apparatus may include two CISs instead of the CCD. In this case, a roller as in the above embodiment may be provided for one of the CISs, or a roller as in the above embodiment may be provided in each of the two CISs. The roller provided for the CCD may have the configuration as in the above-described embodiment, or may have another configuration.

  The image reading apparatus may have only one combination of CIS and a roller as in the above-described embodiment as a reading unit for reading a document. In this case, one side of the document can be read by one document transport operation by the ADF. In addition, a document reversing mechanism is provided in the ADF sheet passing path so that one document passes through the reading unit twice instead of the front and back sides, so that both sides of the document can be easily used with one CIS. It may be configured to be readable.

  The features of the image reading apparatus may be combined as appropriate. Based on the data read while rotating the roller and changing the distance between the CIS and the reference surface of the roller, the correction data corresponding to the paper passing position of the document is calculated. Shading correction can be performed.

  The processing in the above embodiment may be performed by software or by using a hardware circuit.

  A program for executing the processing in the above-described embodiment can be provided, or the program can be recorded on a recording medium such as a CD-ROM, a flexible disk, a hard disk, a ROM, a RAM, or a memory card and provided to the user. It may be. The program may be downloaded to the apparatus via a communication line such as the Internet. The processing described in the text in the above flowchart is executed by the CPU according to the program.

  The above embodiment should 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.

100 image forming apparatus 200 scanner (an example of an image reading apparatus)
201 CCD (an example of second reading means)
300 ADF (an example of conveying means)
301 CIS (an example of reading means)
301a Glass surface 309c Roller drive motor 330 Roller (an example of a columnar body)
331 Roller body 331a Elliptical cylindrical surface 335 Rotating shaft 333 Cleaning brush (an example of cleaning member)
333a Brush unit 500 Control device 509 Image control unit 511a Control program

Claims (9)

Reading means for reading a document;
A columnar body provided opposite to the reading unit and having at least a reference surface as a reference for image correction of the reading unit on a side peripheral surface;
Conveying means for conveying a document between the reading means and the columnar body;
Rotating means for rotating the columnar body around a rotation axis that intersects the document conveying direction;
A correction unit that reads the image of the reference plane by the reading unit and performs predetermined image correction;
The columnar body is configured such that a distance from the reading unit to the reference surface changes with rotation of the columnar body,
The correction means includes
Based on the reading results of the image on the reference surface by the reading means in each of a plurality of states in which the distance from the reading means to the reference surface is different from each other, correction data corresponding to the paper passing position of the conveyed document is calculated. Having an acquisition means to acquire by
An image reading apparatus that performs the predetermined image correction using the correction data acquired by the acquisition unit.   The image reading apparatus according to claim 1, wherein a contour in a cross section perpendicular to the rotation axis of the columnar body includes an elliptical arc portion. The rotating means rotates the columnar body by a motor,
The image reading apparatus according to claim 1, wherein the correction unit specifies a distance from the reading unit to the reference plane based on information on the operation of the motor.   The image reading apparatus according to claim 1, wherein a cleaning member is attached to the columnar body, and a cleaning operation of the reading unit by the cleaning member is performed with the rotation of the columnar body. .   The acquisition of the correction data by the acquisition unit, the document conveyance operation by the conveyance unit, and the cleaning operation by the cleaning member are performed as a series of operations while the rotation unit rotates the columnar body as necessary. The image reading apparatus according to claim 4. A second reading means for reading an original surface different from the original surface read by the reading means;
The image reading apparatus according to claim 1, wherein images on both sides of the document are read by one document transport operation by the transport unit.   An image forming apparatus comprising the image reading apparatus according to claim 1. Reading means for reading a document;
A columnar body provided opposite to the reading unit and having at least a reference surface as a reference for image correction of the reading unit on a side peripheral surface;
Conveying means for conveying a document between the reading means and the columnar body;
Rotating means for rotating the columnar body around a rotation axis that intersects the document conveying direction;
A correction unit that reads the image of the reference plane by the reading unit and performs predetermined image correction;
The columnar body is a method of controlling an image reading apparatus configured such that a distance from the reading unit to the reference surface changes with rotation of the columnar body,
Based on the reading results of the image on the reference surface by the reading means in each of a plurality of states in which the distance from the reading means to the reference surface is different from each other, correction data corresponding to the paper passing position of the conveyed document is calculated. An acquisition step acquired by
And a correction step for performing the predetermined image correction using the correction data acquired in the acquisition step. Reading means for reading a document;
A columnar body provided opposite to the reading unit and having at least a reference surface as a reference for image correction of the reading unit on a side peripheral surface;
Conveying means for conveying a document between the reading means and the columnar body;
Rotating means for rotating the columnar body around a rotation axis that intersects the document conveying direction;
A correction unit that reads the image of the reference plane by the reading unit and performs predetermined image correction;
The columnar body is a control program for an image reading apparatus configured such that the distance from the reading unit to the reference surface changes as the columnar body rotates.
Based on the reading results of the image on the reference surface by the reading means in each of a plurality of states in which the distance from the reading means to the reference surface is different from each other, correction data corresponding to the paper passing position of the conveyed document is calculated. An acquisition step acquired by
A control program for an image reading apparatus that causes a computer to execute a correction step for performing the predetermined image correction using the correction data acquired in the acquisition step.

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