JP2011124875A - Image reading apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus that improves the reading productivity and the shading accuracy of the image reading apparatus. <P>SOLUTION: The image reading apparatus 300, wherein the image of an original 1 that is being carried is read by an image reading means 20 arranged in a reading section 40 in which an exposure transmission means 21 is located, includes: a first density reference means 32 that is arranged opposite to the image reading means 20 in the reading section 40 and obtains first density information by reflecting light given from the side of the image reading means; and a second density reference means 44 to obtain second density information different from that of the first density reference means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image reading apparatus and an image forming apparatus.

Among image reading apparatuses of image reading apparatuses used in image forming apparatuses such as scanners, facsimiles, copiers, and composite machines of these, there is a sheet-through type that reads a document while conveying the document. CCD and CIS (Contact Image Sensor) are used. When a document is read by the image reading unit, generally, a white reference member disposed in the vicinity of the document reading unit is appropriately read before the start of a document reading job or between successive readings of the document, and this is used as a reference. A series of original reading is performed while appropriately correcting the read image of the original in white. A series of operations and processing for correction by the white reference member is referred to as “shading”. In such shading, the white reference member is arranged in the vicinity different from the original reading position, and the original reading means moves to the position for reading the white reference member and performs the shading while the original reading means reads the original.
The white reference member is movable to the reading position and the retracted position, and the reading means performs shading without moving the document reading position.
A configuration in which a background guide member including a document reading position also serves as a white reference member is already known.

  Patent Document 1 discloses a configuration that improves the usability by enabling reliable and automatic removal of foreign matters attached to a white reference member for the purpose of performing accurate shading correction.

  In Patent Document 2, for the purpose of performing good image reading and accurate shading correction, the reading unit is covered with a shutter except during reading so that no foreign matter adheres to the image reading unit, and the white color disposed on the shutter. A configuration is disclosed in which the reference member is moved so as to coincide with the reading surface, and the foreign matter adhering to the white reference member can be reliably and automatically removed.

  In Patent Document 3, Patent Document 4, Patent Document 5, and Patent Document 6, for the purpose of performing accurate shading correction, a roller-shaped white reference member disposed opposite to an image reading unit is rotated to form an image surface of a document. The distance to the image reading means is kept constant, and the surface also serves as a white reference for white shading correction and at the same time as a document conveyance guide member, and a surface provided inside the maximum outer peripheral surface locus is used as a reference white reading surface. The configuration is described. That is, there is described a configuration in which stable white shading correction can be performed by creating white density data as a reference white reading surface that is less likely to become dirty due to changes over time, etc., with a surface that is one paragraph from the outer periphery.

  In the above (1), since the image reading unit itself moves while the document reading unit reads the document, a waiting time is required until the moving time itself and the vibration generated during the movement are attenuated. Therefore, it takes time to obtain density information for this purpose, and it is difficult to improve reading productivity.

  On the other hand, in order to perform accurate shading correction, it is desirable that the document reading surface and the white reference member have the same focal length from the image reading unit, and the white reference member maintains a predetermined white color and is bent. It is necessary to have a uniform and stable shape at the facing portion of the image reading means without being deformed. However, in the above (2), it is generally difficult to move the white reference member at a high speed in the same manner as the image reading means is moved. Therefore, it is difficult to greatly improve the reading productivity during shading. Inevitably, a new space is required for the white reference member to move between the retracted position and the reading position. If the white reference member is made lighter and thinner in order to move at high speed as much as possible or make the space as small as possible, the rigidity decreases and it becomes difficult to maintain a uniform shape as the white reference member, and accurate shading is achieved. become unable. The shading operation for monochrome images can be suppressed to some extent by performing the shading operation intermittently. However, for full-color images, it is necessary to perform the shading operation one by one because of the characteristics of the image reading device. This is the current situation.

  In (3) above, since the conveyed document comes into contact with the white reference member that also serves as the background guide member, dirt may adhere to the white reference member, and accurate shading correction may not be possible. Although it is conceivable to add a means for cleaning the shading member against the adhesion of dirt, an installation space is required to add the cleaning means. In particular, in an image reading apparatus provided with a sheet-through type automatic document feeder, there is a large space limitation in the reading portion, and it is usually difficult to add a cleaning means, and the cost also increases. In this type of image reading apparatus, since the first density reference surface is necessarily located in a direction away from the original reading surface by the conveyance path gap, there is a problem that the focal length is not the same.

  In Patent Document 1, a white reference member is provided at a position opposite to the image reading unit, but there is no concept of improving productivity or saving space, and a concept of referring to another shading material is also described. Not. Furthermore, the problem of insufficient uniformity of the white reference member due to insufficient rigidity of the thin plate-like white reference member and its influence on shading correction cannot be solved.

  In Patent Document 2, a white reference member that can be rotated and vertically moved is provided at a position opposite to the image reading unit, but there is no concept of improving productivity or saving space. Since the operation during shading is a combination of rotation and vertical movement, speeding up is difficult. Further, the problem of insufficient uniformity of the white reference member due to insufficient rigidity of the thin plate-like white reference member and its influence on shading correction cannot be solved.

  In Patent Documents 3 to 6, the white reference member is a roller-shaped rotating body and includes a conveyance guide portion and a shading portion. However, there is no concept of improving productivity or saving space, and a roller-shaped white reference member is also included. Since the concept of the conveyance guide portion and the shading portion in the surface shape of the member is opposite to the present invention, there is a problem in that accurate shading that matches the shading portion and the reading surface cannot be performed.

  An object of the present invention is to provide an image reading apparatus and an image forming apparatus capable of improving the reading productivity and shading accuracy of the image reading apparatus.

  In order to achieve the above object, in an image reading apparatus that reads an image of a document being conveyed by an image reading unit disposed in a reading unit in which an exposure transmission unit is located, the image reading unit is disposed opposite to the image reading unit in the reading unit. First density reference means for obtaining first density information by reflecting light irradiated from the means side, and second density reference for obtaining second density information different from the first density reference means Means.

  The image reading apparatus according to the present invention is characterized in that the second density reference means is arranged at a position where it is not stained by the conveyed document.

  In the image reading apparatus according to the present invention, the first density reference means is constituted by a plate-like member extending in the sub-scanning direction of the image reading means.

  In the image reading apparatus according to the present invention, the first density reference means includes a conveyance guide unit that guides conveyance of the document conveyed to the reading unit.

  In the image reading apparatus according to the present invention, the image reading means includes at least a first position for obtaining first density information facing the first density reference surface of the first density reference means, and a second density reference. When the image reading means occupies the second position, the second density reference means is movable to the second position where the second density reference surface is obtained opposite to the second density reference surface of the means. The density reference surface of the second density reference means is disposed in close contact with the reading reference surface that is located between the image reading means and the reading original surface that the conveyed original does not reach.

  In the image reading apparatus according to the present invention, the image reading means includes at least a first position for obtaining first density information facing the first density reference surface of the first density reference means, and second density reference means. When the image reading means is moved to the first position and the second position, the image can be moved to the second position where the second density reference plane is opposed to the second position where the second density information is obtained. It has a moving guide member for guiding the image reading unit so that the distance between the reading unit and the second density reference surface and the distance between the image reading unit and the first density reference surface are constant.

  In the image reading apparatus according to the present invention, the image reading means includes at least a first position for obtaining first density information facing the first density reference surface of the first density reference means, and second density reference means. The first density reference surface of the first density reference means and the exposure transmission means are capable of conveying the document. The image reading means is arranged so that the position of the first density reference means is the same as the reading surface of the exposure transmission means when the first density information is acquired by the image reading means. It is characterized by moving to a position.

  In the image reading apparatus according to the present invention, the first density information obtained from the first density reference means and the comparison means for comparing the second density information obtained from the second density reference means, and the comparison means. Control means for correcting the density information in the first density reference means in accordance with the density difference between the first density information and the second density information when the second density reference means is used as a reference. It is said.

  In the image reading apparatus according to the present invention, the control means obtains a preset value of a comparison result between the first density information and the second density information obtained from the first density reference means and the second density reference means. If it exceeds, the image reading operation by the image reading means is controlled to be stopped.

  In the image reading apparatus according to the present invention, the control means obtains a preset value of a comparison result between the first density information and the second density information obtained from the first density reference means and the second density reference means. When it exceeds, control is performed so as to perform guidance display for prompting cleaning to the first concentration reference means.

  In the image reading apparatus according to the present invention, the control means obtains a preset value of a comparison result between the first density information and the second density information obtained from the first density reference means and the second density reference means. If it exceeds, the image reading operation by the image reading unit is controlled according to the density information of the second density reference unit.

  In the image reading apparatus according to the present invention, the control means prioritizes the first density information obtained from the first density reference means over the second density information obtained from the second density reference means. The first density information in the density reference means is used as a feature.

  In the image reading apparatus according to the present invention, the first density reference surface of the first density reference means is movable at the first position, and the control means compares the first density information with the second density information. When the result exceeds a preset value, the density reference surface of the first density reference means within which the density difference with the second density reference means is within the set value is a position facing the image reading means. The operation of the first density reference means is controlled so as to occupy.

  In the image reading apparatus according to the present invention, the first density reference means is characterized in that the density reference surface is formed in an arc shape and is constituted by a shaft member that is rotationally driven by the drive means.

  In the image reading apparatus according to the present invention, the first density reference means is characterized in that the density reference surface is formed in a polygonal shape and is constituted by a shaft member that is rotationally driven by the drive means.

  In the image reading apparatus according to the present invention, the control means calculates the density difference between the first density information and the second density information from the comparison result obtained by the comparison means, and the first original reads the image reading. The first density information obtained from the first density reference means is corrected by the density difference when the document is read by the image reading means.

  In the image reading apparatus according to the present invention, the control means calculates the density difference between the first density information and the second density information from the comparison result obtained by the comparison means immediately after the image reading of the final document is completed. When the reading operation is performed in the next image reading operation by the image reading unit, the first density information obtained from the first density reference unit is corrected by the density difference.

  The image reading apparatus according to the present invention includes a temperature detection unit that detects a temperature in the vicinity of the image reading unit, and a storage unit that stores density characteristic information corresponding to the temperature, and the control unit is detected by the temperature detection unit. On the basis of the temperature information, density characteristic information stored in the storage unit is selected, and the first density information obtained from the first density reference means is corrected by the selected density characteristic information.

  The image reading apparatus according to the present invention includes a temperature detection unit that detects a temperature in the vicinity of the image reading unit, and a storage unit that stores density characteristic information corresponding to the temperature of the second density reference unit. Based on the temperature information detected by the temperature detection means, the density characteristic information stored in the storage unit is selected, and the first density information obtained from the first density reference means is corrected with the selected density characteristic information. Thus, the shading correction is performed.

  An image forming apparatus according to the present invention includes any one of the image reading apparatuses described above.

  The image reading apparatus according to the present invention includes a cleaning unit that cleans the first density reference unit, and the control unit sets a preset value of a comparison result between the first density information and the second density information. If exceeded, the cleaning means may be controlled to operate.

  In the image reading apparatus according to the present invention, the distance between the density reference surface of the second density reference means and the image reading means is set to be the same as the distance between the density reference surface of the first density reference means and the image reading means. May be.

  In the image reading apparatus according to the present invention, the distance between the density reference surface of the first density reference means and the image reading means is the same as the distance between the density reference surface of the second density reference means and the image reading means. As described above, the first density reference means may be configured to be movable.

  According to the present invention, since the first density reference means is provided at the reading position facing portion of the image reading means, it is not necessary to move the image reading means during the reading operation for shading, so the paper interval is shortened. Therefore, it is possible to improve the reading productivity by realizing a high-speed reading operation. In addition, since the first density reference means includes the second density reference means for acquiring individual density information, the first density reference means compares the density information obtained from both in advance, so that the first density reference means is located at the reading position facing portion. The degree of contamination of one density reference means can be checked, and even if the first density reference means is dirty, correct density information can be calculated based on the density information obtained by the second density reference means. Thus, the shading accuracy can be improved.

  By arranging the first density reference means and the position of the density reference surface of the second density reference means in the same manner with respect to the image reading means, both shading conditions are equal, leading to further improvement in shading accuracy.

  When the stain on the first density reference means is too large to be corrected, the shading correction data is calculated by switching from the first density reference means to the density information obtained by the second density reference means. Even if the density reference means becomes extremely dirty, the system can perform a reading operation, and the downtime of the machine can be reduced while improving the shading accuracy.

1 is a schematic diagram illustrating one configuration of an image forming apparatus according to the present invention. FIG. 3 is an enlarged view illustrating a configuration example of an image forming unit of the image forming apparatus. FIG. 3 is an enlarged view illustrating a configuration example of an image reading apparatus. 2 is a block diagram illustrating one configuration of a control system of the image forming apparatus and the image reading apparatus. FIG. 2 is a block diagram illustrating a configuration of an image reading apparatus and a configuration of a control system. It is an enlarged view showing a configuration near a reading unit of a conventional image reading apparatus. It is an enlarged view showing a configuration near a reading unit of the image reading apparatus of the present invention. It is a flowchart which shows one control form of the shading correction by a control means. 6 is a flowchart illustrating a relationship between shading correction by a control unit and the number of documents. It is a flowchart which shows the control form of the reading operation according to the density difference of the image data by a control means. It is a flowchart which shows the control form of the reading operation | movement according to the density difference of the image data by a control means, and a re-reading operation | movement. It is a flowchart which shows the control form of the reading operation | movement according to the density difference of the image data by a control means, cleaning operation | movement, and rereading operation | movement. It is a flowchart which shows the control form which uses the reading operation | movement according to the density difference of the image data by a control means, and 2nd image data as 1st image data. It is an enlarged view showing a configuration of a reading unit in which the first density reference means is configured by a plate-like member and is movable in the sub-scanning direction. FIG. 4 is an enlarged view showing a configuration of a reading unit in which the first density reference means is configured by a belt member and is movable in the sub-scanning direction. It is a flowchart which shows one form of movement control of the 1st density | concentration reference | standard means which can move to a subscanning direction. It is an enlarged view showing a configuration of a reading unit provided with a rotatable first density reference means. It is an enlarged view showing a configuration of a reading unit provided with a first density reference means of a rotatable polyhedron. It is an enlarged view showing a configuration of a reading unit including a rotatable arc-shaped first density reference means. It is an enlarged view showing a configuration of a reading unit in which the heights of the first and second density reference surfaces are the same. It is an enlarged view which shows the structure of the reading part provided with the 3rd density | concentration reference plane. FIG. 4 is an enlarged view showing a configuration of a reading unit including first image reference means that can be rotated in a state where a density reference surface is in contact with the image reading surface. FIG. 4 is an enlarged view showing a configuration of a reading unit having a configuration for transporting a document closer to a first density reference surface. FIG. 6 is an enlarged view showing another configuration of a reading unit having a configuration for transporting a document closer to a first density reference surface. It is an enlarged view which shows another structure of the reading part provided with the conveyance guide member of the image reading means. FIG. 4 is an enlarged view showing a configuration of a reading unit including first image reference means that can be displaced with respect to an image reading surface. It is a flowchart which shows another control form of the shading correction by a control means. It is a flowchart which shows another control form of the shading correction by a control means. It is an enlarged view which shows another structure of the reading part provided with the temperature detection means. It is a flowchart which shows the control form of the shading correction | amendment based on the temperature information by a control means. It is an enlarged view showing a configuration of a reading unit having an image reading surface inclined. It is an enlarged view showing a configuration of a reading unit including an inclined image reading surface and a conveyance guide member for image reading means.

  Embodiments according to the present invention will be described below with reference to the drawings. An image forming apparatus 100 illustrated in FIG. 1 includes an image forming unit 200 that forms a color image and an image reading apparatus 300 that reads an image of a document.

  As shown in FIG. 2, the image forming unit 200 includes a paper feeding unit 210, a plurality of image forming units 220a, 220b, 220c, and 220d, an intermediate transfer belt 230 that serves as an intermediate transfer member, and a fixing unit 260. Yes. The sheet feeding unit 210 has a plurality of sheets 211 stacked on a tray (not shown), separated and fed into one sheet by a sheet feeding roller 212, and conveyed along a conveyance path 213 indicated by a dotted line. This tray has a function of adjusting the height of the sheet 211 with respect to the sheet feeding roller 212, similarly to the document tray 102 described above.

  The image forming units 220a to 220d form toner images on drum-shaped photoconductors 220Y, 220M, 220C, and 220K as image carriers by a generally known dry electrophotographic method, and are disposed below the image forming units. The intermediate transfer belt 230 is used as an intermediate transfer member. In this embodiment, the image forming units 220 a to 220 d form toner images of four colors of yellow, magenta, cyan, and black for each unit, and superimpose them on the intermediate transfer belt 230 to form a full color image. Of course, a single color image can be formed by any one image forming unit.

  The intermediate transfer belt 230 is wound around a plurality of rollers. When any of the rollers is driven to rotate, the intermediate transfer belt 230 rotates in the direction of the arrow in the drawing, and the color image formed on the belt is transferred to the transport path 213. To the secondary transfer roller 240 arranged facing the front.

  A secondary transfer backup roller 241 is disposed opposite to the secondary transfer roller 240 with the conveyance path 213 interposed therebetween. The secondary transfer backup roller 241, together with the secondary transfer roller 240, presses the sheet 211 a separated and fed by the sheet feeding roller 212 and the intermediate transfer belt 230. At this time, by applying a high potential difference (secondary transfer bias) between the secondary transfer roller 240 and the secondary transfer backup roller 241 by a high-voltage power source (not shown), the toner image formed on the intermediate transfer belt 230 becomes a sheet. Transferred onto 211a. The toner remaining on the intermediate transfer belt 230 after the transfer is removed by a cleaning unit 250 disposed around the belt.

  The fixing unit 260 heats and presses the sheet 211 to which the toner image is transferred, and fixes the toner image to the sheet. The sheet 211 that has passed through the fixing unit 260 and has undergone image formation is discharged from the image forming unit 200 to a discharge tray 270 serving as a sheet discharge unit. The image forming unit 200 includes a main body operation unit 108 and a main body control unit 60. When a print command is input from the main body operation unit 108, the image forming apparatus 1 executes a series of operations from image reading to image formation under the control of the main body control unit 60.

  As shown in FIG. 3, the image reading apparatus 300 reads an image of a document being conveyed by an image reading unit 20 disposed in a reading unit 40 where a reading glass 21 serving as an exposure transmission unit is located. In the case of the sheet-through type, a document image is read while moving the document 1 at a predetermined speed at the reading position 40. The basic configuration, operation, and operation of the image reading apparatus 300 will be described with reference to FIG. 3, and the control system will be described with reference to FIGS.

  As shown in FIG. 3, the image reading apparatus 300 includes a document setting unit A that sets a document 1, a separation feeding unit B that separates and feeds the document 1 from a bundle of the set documents 1, The registration unit C, which has a function of primary abutting alignment of the fed document 1 and a function of pulling out and transporting the document 1 after alignment, and the document 1 to be conveyed are turned, and an image reading means 20 is arranged on the document surface. The turn part D that conveys toward the image reading side, the first reading conveying part E that reads the surface image of the document 1 from below the reading glass 21 that serves as an exposure transmission means, and the back image of the document 1 after reading. A second reading / conveying unit F having an image reading unit 25 for reading, a paper discharge unit G for discharging the original 1 on which front and back image reading has been completed, and a stack unit H for stacking and holding the originals 1 after reading, In the order listed. The separation feeding unit B to the paper discharge unit G are arranged along the conveyance path R of the document 1.

  As shown in FIG. 4, the image reading apparatus 300 includes a pickup lifting / lowering motor 101, a paper feeding motor 102, a reading motor 103, a paper discharge motor 104, a bottom plate raising motor 105, a pull-out serving as a driving unit that drives the conveying operation of each unit. A motor 113, a reading entrance motor 114, a pickup transport motor 115, a document set sensor 5, a bottom plate home position sensor 6, a table raising sensor 8, a butting sensor 11, and a document width sensor 13 serving as a plurality of detection means for detecting various types of information. , Reading inlet sensor 15, registration sensor 17, paper discharge sensor 24, document length detection sensors 30, 31, separation sensors S1 to S3, controller unit 50 serving as a control means for controlling a series of image reading operations, and image reading Means 20 and 25 are provided. Each motor, each sensor, and image reading means 20 and 25 are connected to the controller unit 50 via a communication line. The controller 50 is configured by a known computer, and is connected to the main body control unit 60 via an interface (I / F) 107, and can transmit and receive various types of information to and from the main body control unit 60. The controller 50 has a function of receiving detection information from each sensor and a reading signal from the image reading means 20 and 50 and controlling the operation of each motor.

  As shown in FIG. 3, a document table 2 and a movable document table 3 are arranged in the document setting section A. On the document table 2 including the movable document table 3, one document 1 to be read or a plurality of documents 1 are bundled and the document 1 is set with the document surface facing upward. The document table 2 is positioned in a direction perpendicular to the conveyance direction of the document 1 by a side guide (not shown). The setting of the document 1 is detected by a set filler 4 and a set sensor 5 disposed in the document setting unit. The document set information is transmitted to the main body control unit 60 by the I / F 107 in FIG.

  In the image reading apparatus 300, an outline of the length in the transport direction of the document 1 is detected by the document length detection sensor 30 or 31 provided on the document table surface of the document table 2. The document length detection sensors 30 and 31 are composed of a reflection type sensor or an actuator type sensor that can detect even one document. The length of the document 1 in the conveyance direction can be detected by providing document length detection sensors 30 and 31 on the document table surface so that it can be determined whether the document is at least vertical or horizontal.

  The movable document table 3 is configured to be movable in the directions indicated by symbols a and b in FIG. 3 by the bottom plate raising motor 105. When the set filler 4 and the set sensor 5 detect that the document 1 is set, the bottom plate rises. The motor 105 is rotated forward to raise the movable document table 3 so that the uppermost surface of the document 1 comes into contact with the pickup roller 7 disposed to face the movable document table 3.

  When the pickup raising motor 101 is actuated, the pickup roller 7 is operated in a direction indicated by reference numerals c and d in FIG. 3 by a cam mechanism (not shown), and the movable table 3 is raised and pushed by the upper surface of the document on the movable table 3. The upper limit can be detected by the table ascending sensor 8 rising in the c direction. In the image reading apparatus 300, when a print key (not shown) of the main body operation unit 108 is operated, a document feed signal is transmitted from the main body control unit 60 to the controller unit 50 via the I / F 107, whereby the pickup roller 7. However, the roller is rotationally driven by the forward rotation of the paper feed motor 102 to pick up several (ideally one) originals 1 on the original table 2. The rotation direction is a direction in which the uppermost document 1 is conveyed to the sheet feeding port.

  The sheet feeding belt 9 disposed in the separation feeding unit B is driven in the sheet feeding direction by the normal rotation of the sheet feeding motor 102. A reverse roller 10 that is disposed opposite to and in contact with the paper feeding belt 9 is driven to rotate in the direction opposite to that of paper feeding by the forward rotation of the paper feeding motor 102, and the uppermost original 1 and the original 1 below it are driven. In this configuration, only the uppermost document 1 can be fed. More specifically, the reverse roller 10 is in contact with the paper feeding belt 9 at a predetermined pressure, and is rotated by the paper feeding belt 9 when in contact with the paper feeding belt 9 directly or through a document. When the original 1 enters between the paper feeding belt 9 and the reverse roller 10 in the unlikely event that the original 1 enters between the paper feeding belt 9 and the reverse roller 10, the rotational force is set to be lower than the torque of a torque limiter (not shown). ing. For this reason, the reverse roller 10 rotates in the clockwise direction, which is the original driving direction, and pushes back the excess original 1, thereby preventing double feeding.

  The document 1 separated into one sheet by the action of the sheet feeding belt 9 and the reverse roller 10 is sent into the conveyance path R by the sheet feeding belt 9 and is applied by the abutting sensor 11 disposed downstream in the document conveying direction. The leading edge is detected and conveyed to the resist section C. A pull-out roller pair 12 is arranged in the registration portion C, and the conveyed document 1 abuts against the roller pair 12. The document 1 is sent by a predetermined distance from the detection of the abutting sensor 11, and as a result, the paper feed motor 102 is stopped in a state where the original 1 is pressed against the pull-out roller pair 12 with a predetermined amount of bending. As a result, the driving of the paper feed belt 9 is stopped. At this time, the pickup lifting and lowering motor 101 is rotated to retract the pickup roller 7 from the upper surface of the document, and the document 1 is fed only by the conveying force of the paper feed belt 9, so that the leading edge of the document enters the nip of the pull-out roller pair 12. Then, tip alignment (skew correction) is performed.

  The pull-out roller pair 12 has the skew correction function and is a roller for conveying the skew-corrected document 1 to the intermediate roller pair 14 disposed in the turn portion D. Driven. At this time (when the paper feed motor 102 reverses), the pull-out roller pair 12 and the intermediate roller pair 14 arranged further downstream in the document transport direction are driven, but the pickup roller 7 and the paper feed belt 9 are driven. It has not been.

  A plurality of document width sensors 13 arranged between the pull-out roller pair 12 and the intermediate roller pair 14 are arranged in parallel in the apparatus depth direction (document width direction), and the document 1 conveyed by the pull-out roller pair 12 is conveyed. Detect the size in the width direction perpendicular to the direction. The length of the document 1 in the transport direction is detected from the motor pulse by reading the leading and trailing ends of the document 1 with the abutment sensor 11. When the document 1 is conveyed from the registration unit C to the turn unit D by driving the pull-out roller pair 12 and the intermediate roller pair 14, the conveyance speed at the registration unit C is higher than the conveyance speed at the first reading conveyance unit E. The processing time for feeding the document 1 to the first reading conveyance unit E at a high speed is shortened.

  When the leading edge of the document 1 is detected by the reading entrance sensor 15 disposed downstream of the intermediate roller pair 14 in the conveyance direction, the document is placed in the nip of the reading entrance roller pair 16 disposed further downstream of the reading entrance sensor 15. Before the leading edge enters, the document feeding speed starts to be the same as the reading conveyance speed, and at the same time, the reading motor 103 is driven to rotate forward to read the reading inlets arranged before and after the first reading conveyance unit E. The roller pair 16, the reading exit roller pair 23, and the CIS exit roller pair 27 disposed downstream of the second reading transport unit F are driven.

  When the leading edge of the document 1 is detected by the registration sensor 17 positioned downstream of the reading entrance roller pair 16, the document is decelerated over a predetermined conveyance distance, and is temporarily stopped before the reading position P <b> 1 where the image reading means 20 is disposed. At the same time, a registration stop signal is transmitted to the main body control unit 60 via the I / F 107. Subsequently, when a reading start signal is received from the main body control unit 60, the document 1 that has been stopped is conveyed at an increased speed so as to rise to a predetermined conveying speed until the leading edge of the document reaches the reading position.

  In the image reading apparatus 300, at the timing when the leading edge of the document detected by the pulse count of the reading motor 103 reaches the reading position P1, the main body control unit 60 moves in the sub scanning direction indicated by the arrow C on the first surface of the document 1. A gate signal indicating the effective image area is transmitted through the image reading means 20 until the trailing edge of the original comes off.

  In the image reading apparatus 300, in the case of single-sided document reading, the document 1 that has passed through the first reading conveyance unit E is conveyed to the paper discharge unit G through the first reading conveyance unit F in which the image reading unit 25 is disposed. At this time, when the front end of the document 1 is detected by the paper discharge sensor 24 arranged in front of the image reading means 25, the paper discharge motor 104 is rotated forward to drive the pair of paper discharge rollers disposed in the paper discharge section G. 28 is rotated. In addition, the discharge motor pulse count from the detection of the leading edge of the document 1 by the discharge sensor 24 reduces the drive speed of the discharge motor 104 immediately before the discharge roller pair 28 exits the nip, and puts it on the discharge tray 29. Control is performed so that the discharged document 1 does not jump out.

  In the case of double-sided original reading in the image reading apparatus 300, the image reading means is detected at the timing when the leading edge of the original reaches the image reading means 25 by the pulse count of the reading motor 103 after the paper discharge sensor 24 detects the leading edge of the original. A gate signal indicating an effective image area in the sub-scanning direction C is transmitted from the controller unit 50 to the image reading unit 25 until the trailing edge of the original is removed. The second reading roller 26 disposed opposite to the image reading unit 25 suppresses the floating of the document 1 in the second reading and conveying unit F, and at the same time serves as a reference white portion for acquiring density data in the second reading and conveying unit F. It also serves.

  FIG. 5 shows the configuration of the image reading means 20. The image reading means 20 includes a light source unit 310, a sensor chip 311 arranged in the document width direction, a diode 312 corresponding to the sensor chip 311, an A / D converter 313, an image processing unit 314, a frame memory 315, and an output control circuit 316. This is a well-known configuration. The controller 50 appropriately transmits a lighting signal and a timing signal to the image reading unit 20 to execute image capturing.

  FIG. 6 is a detailed view of a conventional first reading conveyance unit E. In this configuration, the reading glass 21 is disposed on the image reading unit 20, and at the same time as covering the image reading unit 20, the upper surface of the glass is configured as a reading surface. The document 1 is transported on the reading glass 21 and is scooped up by the scooping member 22 disposed downstream in the transporting direction to change the direction, and is delivered to the reading downstream guide member 42A and the guide member 42B facing the reading downstream guide member 42A. To be transported. On the pressure plate reading glass 43 on the back side of the scooping member 22, a density reference member 44 serving as a density reference means is disposed so that a shading surface 44a serving as a density reference surface is in close contact with the glass surface. The upper surfaces of the reading glass 21 and the pressure plate reading glass 43 are set to the same height. For this reason, the density reference member 44 is arranged at the same height with respect to the document 1 conveyed on the reading glass 21 and the document 1 placed on the pressure plate reading glass 43. The image reading unit 20 reads the original 1 conveyed at the reading position, and moves to the shading position where the density reference member 44 is disposed before the start of the reading job or between the original 1 and the original 1 being continuously read. Then, density data for shading by reading the white color of the shading surface 44a is acquired, and shading processing is performed based on the density data.

  With such a configuration and operation, the conventional image reading apparatus can read the shading surface 44a of the density reference member 44 which is the same height as the reading surface and is almost sealed and hardly adheres to dirt. However, since it takes time to move the image reading unit 20, it is difficult to increase the speed.

  Therefore, in the image reading apparatus 300 according to the present embodiment, as shown in FIG. 7, the light emitted from the light source unit 310 (see FIG. 4) disposed opposite to the image reading unit 20 at the reading position and provided in the image reading unit. The first density reference means that can obtain the first density data that becomes the first density information by being reflected, and the second density data that becomes the second density information different from the first density reference means. Second density reference means. In this embodiment, the first reference member is constituted by a reading guide plate 32, and the second density reference means is constituted by a reference member 44 disposed at a position different from the reading guide plate 32.

  The reading guide plate 32 has a surface facing the reading glass 21 as a shading surface 32a serving as a density reference surface. An interval is formed between the reading glass 21 and the shading surface 32a so that the document 1 can pass therethrough. For this reason, in the 1st reading conveyance part E, the conveyance path | route R will be formed between the reading glass 21 and the shading surface 32a, and the reading guide plate 32 is provided with a conveyance guide function. The shading surface 32a has a specific color, here, white which is the same color as the shading surface 44a of the density reference member 44.

  The roller member 19 shown in FIG. 3 may be attached to the reading guide plate 32. However, since the reading guide plate 32 is used not only as a document conveying guide but also as a shading member, the density reference surface 32a facing the image reading means 20 is used. It is desirable to adopt a form having a white plane or a shape and color close to it. The density reference member 44 is disposed at a position not affected by dirt such as paper dust. Specifically, the shading surface 44 a is disposed so as to be in close contact with the pressure plate reading glass 43. In this embodiment, reference numeral 1 denotes a position where the image reading unit of the image reading unit 20 and the density reference surface 32a face each other, and reference numeral P2 denotes shading where the image reading unit of the image reading unit 20 faces the shading surface 44a. Indicates the position. In this embodiment, the image reading means 20 is movable between a reading position P1 and a shading position P2, and a reading inlet motor 114 shown in FIG. 4 is used as the driving means.

  The operation and shading processing of the image reading apparatus 300 having such a configuration will be sequentially described with reference to flowcharts shown in FIG. In the flowcharts, the same processing contents are denoted by the same reference numerals, and overlapping descriptions are simplified or omitted.

  In the image reading apparatus 300, the controller 50 operates the reading entrance motor 114 and the image reading means 20 when the print signal is input and the reading job is not a reading job for reading the image of the document 1. As a result, the image reading means 20 moves between the reading position P1 of the reading guide plate 32 and the shading position P2 of the density reference member 44, and the shading surfaces 32a and 44a are moved as shown in steps ST1 and ST2 of FIG. Step ST3 for acquiring density data by reading. At this time, since the reference member 44 is disposed at a position not affected by dirt such as paper dust, the shading surface 44a does not become dirty. Therefore, even if the two shading surfaces 32a and 44a are originally the same white color (reflectance), the density data obtained from the reading guide plate 32 and the reference member 44 can be obtained when the reading guide plate 32 is soiled with paper dust or the like. Makes a difference. At this time, from the density data A01 acquired from the reflected light from the shading surface 32a of the reading guide plate 32 and the density data A0 acquired from the reflected light from the shading surface 44a of the reference member 44, the degree of contamination of the reading guide plate 32 is The density difference ΔA = A01−A0. Therefore, the controller 50 calculates (calculates) the density difference ΔA = A01−A0 in step ST4, and stores the density difference ΔA in the storage unit 51 (not shown) in step ST5.

  When a print signal is input to the main body control unit 60, the image reading apparatus 300 inputs the signal to the controller 50 via the I / F 107, and starts a document reading job. During the reading job, the image reading means 20 is always fixed at the reading position P1 and acquires the density data A01 of the reading guide plate 32. If the density data is acquired every time the document 1 is conveyed one by one, the density data An of the nth document is acquired by the following method.

  This method will be described with reference to the flowchart shown in FIG. In step ST11, the controller 50 reads the density A1n of the reading guide plate 32, and subtracts the density difference ΔA from the reference member 44 (An = A1n−ΔA) as true shading data, that is, image data in step ST12. Calculate with Therefore, even if the reading guide plate 32 is dirty, it is possible to perform shading while the image reading unit 20 is fixed during the reading job. Since the image reading unit 20 does not move during the reading job, the time required for the image reading unit 20 to move does not take time. As a result, productivity of image reading can be improved. Even when the reading guide plate 32 is dirty, the accuracy of density data used for shading is improved, so that accurate shading correction can be performed.

  When obtaining the density difference ΔA between the density data of the reading guide plate 32 and the density data of the reference member 44, it may be assumed that the density difference ΔA exceeds a certain value and correction cannot be performed. In such a case, the treatment shown in the flowchart of FIG. 10 may be executed. In FIG. 10, the controller 50 performs a determination process of the density difference ΔA in step ST21. If the density difference ΔA is equal to or larger than a predetermined value T preset in the storage unit 501, the reading operation is stopped in step ST22. If the density difference ΔA is less than the predetermined value T, the reading operation is continued in step ST23. The predetermined value T here corresponds to a density difference that cannot be recovered by correction.

  When the controller 50 performs such control processing, the reading guide plate 32 is extremely dirty, and when accurate shading cannot be performed even when correction is performed by the density difference ΔA from the density data obtained from the reference member 44, Since the reading operation of the density data from the density reference surface 32a is not performed, it is possible to prevent the reading operation with a lowered image quality from being performed. Further, when the reading operation is stopped in step ST22, for example, a warning content indicating that the reading guide plate 32 is dirty is displayed using a well-known display means such as an LCD provided in the operation unit 108 to notify the operator. Also good. Or it is good also as a form notified with an audio | voice.

  When the reading operation is stopped, for example, as shown in step ST22A of FIG. 11, a warning content that prompts cleaning of the reading guide plate 32 is displayed or expressed by voice, or that the reading guide plate 32 is soiled. Or it is good also as a structure which notifies an operator with an audio | voice.

  The controller 50 determines whether the density difference ΔA between the density data obtained from the reading guide board 32 and the density data obtained from the reference member 44 is within a predetermined value T as shown in step ST24 after the reading guide board 32 is cleaned. If it is determined whether or not it is within the predetermined value T, that is, if the concentration difference ΔA returns to an appropriate value, it is more preferable to proceed to step ST25 to cancel the display for prompting cleaning and to resume the reading operation.

  If the image reading apparatus 300 includes a cleaning unit that cleans the reading guide plate 32, as shown in FIG. 12, if the density difference ΔA is greater than or equal to a predetermined value T in step ST21, step ST22B is performed. In step ST26, the reading operation is stopped by the cleaning means of the reading guide plate 32. In step ST24, the concentration difference ΔA is a predetermined value. Continues within T, that is, until it returns to an appropriate value. When the density difference ΔA returns to within the predetermined value T, the reading operation may be resumed in step ST25. In other words, in this control mode, the reading guide plate 32 is automatically cleaned by the cleaning means when the density difference ΔA is equal to or greater than the predetermined value T, and is interrupted when the reading guide plate 32 is cleaned to a level that does not cause a problem in image quality. By automatically canceling the read operation and restarting the read operation by the image reading means 20, the down time of image reading can be reduced, and the productivity can be further increased.

  As another form of control by the controller 50, as shown in FIG. 13, when shading by the reading guide plate 32 cannot be correctly performed in step ST21 when the density difference ΔA is equal to or larger than a predetermined value T, the reading guide is read in step ST27. After the display prompting the cleaning of the plate 32, the process proceeds to step ST28, the image reading means 20 is moved to the shading position P2 of the density reference member 44, and density data is acquired from the shading surface 44a of the density reference member 44 and read guide. The reading operation may be continued by replacing the density data of the plate 32. The density reference member 44 is density data obtained from the reflected light from the shading surface 44a to which dirt is not attached. However, since the image reading unit 20 moves from the reading position with respect to the reading guide plate 32 (first position P1) to the reading position with respect to the density reference member 44 (shading position P2), the productivity decreases, but the document 1 Since the reading operation itself is continued without stopping, downtime as an image forming apparatus can be suppressed.

  Since the present invention has a problem of contamination of the shading surface 32A of the reading guide plate 32, the cleaning process by the cleaning means may be performed as described above. As an example of the cleaning means, for example, the configuration of the motor 25 that moves the cleaning bracket 20, the cleaning pad 21, and the cleaning bracket 20 in the main investigation direction described in Japanese Patent Laid-Open No. 2000-188664 already proposed by the present applicant. The configuration of the cleaning roller 11 described in JP-A-2002-25854 and the configuration of the cleaning sheet 101 and the cleaning sheet conveying unit 103 described in JP-A-2004-250141 can be used.

  Depending on the form of the cleaning means, it may not be mounted on the image reading apparatus 300, and even if it can be mounted, the size may be increased in order to secure a mounting space. Therefore, a plurality of portions serving as the density reference surface of the reading guide plate 32, that is, a shading surface may be provided or moved. For example, in the form shown in FIG. 14, the reading guide plate 32 is provided so as to be movable in the sub-scanning direction C with respect to the reading position P1. Examples of the moving mechanism include a driving motor 150 serving as a driving source, and a moving unit 160 such as a slider that movably supports the reading guide plate 32 in the sub-scanning direction C by the driving motor 150.

  In such a configuration, when the density difference ΔA is equal to or greater than the predetermined value T, the position of the shading surface 32a that directly faces the image reading unit 20 is translated in the sub-scanning direction C by operating the drive motor 150. Therefore, even if the shading surface 32a is not cleaned by the cleaning unit, if a part of the shading surface 32a is contaminated, the portion of the shading surface 32a that is less or unstained can be directly opposed to the image reading unit 20. . Therefore, highly accurate density data can always be obtained from the shading surface 32a of the reading guide plate 32.

  The movement form of the reading guide plate 32 is not limited to the parallel movement as shown in FIG. 14, but is wound around a plurality of rollers 129, 130 and 131 as shown in FIG. The first density reference means may be constituted by the endless belt 132 which is movable to C. In this case, the outer peripheral surface of the belt becomes the shading surface 132a.

  When the reading guide plate 32 as shown in FIG. 14 is configured to move in parallel in the sub-scanning direction C, the control operation as shown in FIG. If the density difference ΔA between the density data obtained from the reading guide plate 32 and the density reference member 44 is greater than or equal to the predetermined value T in step ST31 of FIG. 16, the process proceeds to step ST32 where the density difference ΔA is determined. If it is not greater than the predetermined value T, the process proceeds to step ST33 and the reading operation is continued.

  In step ST32, it is determined whether or not the reading guide plate 32 can be moved. If the reading guide plate 32 can be moved, the process proceeds to step ST34 where the reading guide plate 32 is operated, for example, the drive motor 150 is operated, and the initial line indicated by the solid line in FIG. Move in the sub-scanning direction C from the position to the correction position indicated by the alternate long and short dash line. As a form of movement, there are a case of moving in a stepwise manner from the initial position to the correction position and a case of movement from the initial position to the correction position. In this embodiment, it is configured to be movable in stages. In any case, since the position of the shading surface 32a for obtaining density data from the reading guide plate 32 is changed by the movement of the reading guide plate 32, the density difference ΔA of the shading surface changed in step ST35 is predetermined. It is determined whether or not the value is within T. If the density difference ΔA is not within the predetermined value T, it is assumed that accurate density data cannot be obtained on the moved shading surface 32a, and the reading guide plate 32 is moved again. If the density difference ΔA is within the predetermined value T in step ST35, it is assumed that accurate density data can be obtained at the position of the moved shading surface 32a. For example, the display prompting cleaning is canceled in step ST36 and the reading operation is performed. Resume.

  In the case where the first density reference means is the endless belt 132 shown in FIG. This fixed time is a time during which the shading surface 132a (belt outer peripheral surface) of the endless belt 132 that has been at the reading position P1 shifts and a new portion of the shading surface 132a moves to the reading position P1. In this case, if the drive motor 151 is composed of a stepping motor, the movement distance is determined from the number of steps. If the drive motor 151 is not a stepping motor, it is realized by measuring with a timer (not shown) and controlling the drive motor 151 according to the time. can do.

  Since the movement of the first shading surfaces 32a and 132a in the sub-scanning direction C is not limited to one place, the movement of the first shading surfaces 32a and 132a in several stages is searched for a point where the density difference ΔA is within the predetermined value T. Is also possible. If it is determined in step ST32 that the density difference ΔA does not fall within the predetermined value T even if the first shading unit (reading guide plate 32, endless belt 132) is moved, and the shading operation is not performed normally. Alternatively, the first shading member (reading guide plate 32, endless belt 132) cannot be moved, and the reading operation can be stopped there. Alternatively, the process proceeds from step ST32 to step ST37, the reading operation is continued, and the density data obtained from the density reference member 44 is acquired by moving the image reading means 20 to the density reference member 44 (shading position P2) in step ST38. Then, the downtime of the image forming apparatus 1 can be reduced by replacing the density data of the reading guide plate 32 and using it to continue the reading operation.

  The movement form of the first density reference means when there are a plurality of detection positions on the density reference surface is limited to that in which the shading surfaces 32a and 132a are translated in the sub-scanning direction C as shown in FIGS. For example, as shown in FIGS. 17 to 19, a form of rotational movement is also included.

  In the configuration shown in FIG. 17, the first shading member is configured by a shaft member 133 that is a rotating polyhedron having a square cross section, and in the configuration illustrated in FIG. 18, the first shading member is an axis that is a rotating polyhedron having a regular octagonal cross section. A member 134 is used.

  In such a configuration, the shading surfaces serving as the density reference surfaces are the outer surfaces 133a and 134a, respectively. One surface of each of the outer surfaces 133a and 134a is configured to be a flat surface and to be parallel to the reading glass 21 in order to obtain accurate reflected light. For this reason, when the density difference ΔA is equal to or greater than the predetermined value T, the shaft members are rotated by a certain angle by operating the drive motors 152 and 153 serving as drive sources until the outer surfaces 133a and 134a are parallel to the reading glass 21. As a result, the unclean outer surfaces 133a and 134a face the image reading means 20, respectively, so that the density data obtained from the outer surfaces 133a and 134a is stabilized, and the light of the light source unit 310 composed of the exposure lamp is ideally set. There is an advantage to reflect.

  As shown in FIG. 19, when the first concentration reference means is constituted by a shaft member 135 having a circular cross section and an outer peripheral surface having an arc shape, the outer peripheral surface serving as the concentration reference surface becomes a shading surface 135a. For this reason, by rotating the shaft member 135 with the drive motor 154 and moving the shading surface 135a steplessly, it becomes possible to secure a shading region (density reference surface) for one round. Therefore, since the first shading member can be used for a long period of time, the time for stopping the apparatus for parts replacement and cleaning is shortened, and the downtime of the image reading apparatus 300 can be reduced to improve productivity. it can.

Next, the conveyance gap at the reading position P1 and the shading position P2 will be described.
Although the conveyance gap at the reading position P1 is generally minute, as shown in FIG. 20, the distance (height) h from the reading reference surface 43a of the pressure plate reading glass 43 to the shading surface 44a of the density reference member 44 is read. By adjusting the distance (height) h1 from the reading reference surface 21a of the glass 21 to the shading surface 32a of the reading guide plate 32 serving as the first density reference means, the distance between the two shading surfaces and the image reading means 20 is achieved. The influence of the illuminance difference resulting from the difference between H and H1 can be extremely reduced.

  Further, as shown in FIG. 21, a shading member 144 serving as a density reference means dedicated to a book original separate from the density reference member 44 is provided on the scooping member 22 separately from the reference member 44, and the density reference surface of the shading member 144 is provided. The shading surface 144 a to be the same height as the shading surface 44 a of the reference member 44 is arranged near the pressure plate reading glass 43.

  In the case of this configuration, the moving distance of the image reading means 20 is extended to a position facing the shading surface 144a, and is stopped at the reading position P1, the shading position P2, and the shading position P3 facing the shading surface 144a. As a result, the shading conditions for the book document and the ADF document can be made the same.

  When the first density reference means is a shaft member 135 having a circular cross section, it is arranged so that the outer peripheral surface, that is, the shading surface 135a is in close contact with the image reading surface 21a of the reading glass 21, as shown in FIG. Thus, the height of the density reference member 44 relative to the shading surface 44a can be matched with the reading reference surface 43a. At this time, when an appropriate load is applied to the image reading surface 21a of the reading glass 21, the shaft member 135 is pressed against the image reading surface 21a even if the document 1 is waisted or lifted. The height of the shading surface 44a of the density reference member 44 can be easily adjusted.

  When the heights of the shading surfaces of the first density reference means and the second density reference means are matched, it is possible to convey the original 1 to be read along the first density reference means as much as possible. The top is also desirable.

  For example, in the configuration shown in FIG. 23, a guide plate 163 is placed on the image reading surface 21a of the reading glass 21 upstream of the reading position P1 in the document conveying direction. By providing the guide plate 160, the document 1 is lifted from the image reading surface 21a by the thickness of the guide plate 163, and is conveyed to the side closer to the reading guide plate 32 side. Also, as shown in FIG. 24, the document 1 is once guided to a position lower than the reading glass 21, and the conveying path R is laid out from the lower position toward the reading glass 21, whereby the document 1 is You may comprise so that the reading guide plate 32 vicinity may be conveyed. In this case, for example, the conveyance path R positioned upstream in the conveyance direction from the reading position P1 is formed lower than the image reading surface 21a of the reading glass 21, and is inclined upward from the lower portion toward the reading surface 21a. This can be achieved by forming the transport path R.

  Next, a method for changing the height on the image reading means 20 side will be described with reference to FIG. In the sheet-through method, a gap h <b> 2 is formed between the shading surface 32 a of the reading guide plate 32 and the image reading surface 21 a of the reading glass 21 in order to pass the document 1 because of the conveyance of the document 1. On the other hand, since the original 1 is placed on the pressure plate reading glass 43 on the density reference member 44 side, the shading surface 44a of the density reference member 44 is disposed on the same plane as the reading glass 21. There is no need to provide a gap between them. For this reason, when the image reading means 20 is translated between the reading glass 21 and the pressure plate reading glass 43, the distance h2 between the image reading means 20 and the shading surface 32a and the distance between the image reading means 20 and the shading surface 44a. Will be different.

  Therefore, a guide rail 145 as a movement guide member for guiding the image reading means 20 when moving in the sub-scanning direction C is continuously arranged below the reading glass 21 and the pressure plate reading glass 43. In the guide rail 145, a step h3 is formed between the reading glass 21 side and the pressure plate reading glass 43 side. Specifically, the step h3 is formed by making the guide rail 145 located below the pressure plate reading glass 43 lower than the guide rail 145 located below the reading glass 21 by a distance h2. That is, the interval h2 = the step h3.

  Thus, when the image reading means 20 is moved, the guide rail 145 that guides the image reading means 20 so as to be movable in the sub-scanning direction C absorbs the height difference between the reading glass 21 side and the pressure plate reading glass 43 side. When the step h3 corresponding to the distance h2 is formed as described above, the distance H2 between the shading surface 32a of the reading guide plate 32 and the image reading unit 20 and the distance H3 between the shading surface 44a of the density reference member 44 and the image reading unit 20 are set. Since they can be the same, the positional relationship between the two density reference means can be made the same without complicating the mechanism on the image reading apparatus 300 side, and variations in density data due to illuminance changes can be eliminated. More accurate image data can be obtained.

  In the above embodiment, the first density reference means is moved in the sub-scanning direction C. However, as shown in FIG. 26, for example, when the first density reference means is constituted by the shaft member 135 having a circular cross section, the shaft member 135 is provided so as to be movable by a moving means 161 in a direction approaching and separating from the image reading surface 21a of the reading glass 21, and this moving means 161 is operated by a drive motor 155 serving as a drive source. The distance may be displaceable. In this case, the positional relationship between the shaft member 135 and the density reference member 44 can be matched by lowering the shaft member 135 so that the shading 135a of the shaft member 135 contacts the image reading surface 21a only during shading. it can.

  The flowchart shown in FIG. 27 performs a shading correction process at the start of a reading job. In the figure, when the set filler 4 and the set sensor 5 detect that the document 1 is set on the image reading apparatus 300 by the user, it is determined that the job is started and the control by the controller 50 is started. When the control is started, first at step ST41, the image reading unit 20 acquires the density data A0 from the reading guide plate 32 at the reading position P1, and the shading position where the density reference member 44 is arranged. Moving to P2, density data A01 is acquired from the density reference member 44.

  Since the density reference member 44 is in a position that is not affected by dirt such as paper dust and toner, dirt does not occur. Therefore, even when the reading guide plate 32 is originally stained with paper dust or toner even if it is the same color, the density data A0 from the reading guide plate 32 and the density data A01 from the density reference member 44 are changed. A density difference ΔA occurs. Therefore, in step ST42, the density difference ΔA = A0−A01 is calculated from the acquired density data A0 and A01, and the density difference Δ is stored in the storage unit 51 of the controller 50. Here, n used in FIG. 27 is a value indicating the number of sheets of the document 1 conveyed, and n = 1 in the initial state.

  In step ST43, when the first document 1 is conveyed, the density data A1n of the reading guide plate 32 is acquired in a state where the image reading means 20 is always fixed at the reading position P1.

  In step ST44, using the acquired density data A1n and density difference ΔA, the data A1 used for shading correction is adjusted as An = A1n−ΔA, shading correction is performed in step ST45, and the first original is read in step ST46. Is done.

  In step ST47, it is determined whether or not the next original remains after the first original is read based on the output from the set sensor 5. If the next original remains, the process proceeds to step ST48 and n. Is counted up to n = 2, and the process returns to step ST43 to perform shading correction on the second and subsequent originals 1. If there is no next original remaining in step ST47, the reading of the final original ends, and the job ends.

  In this control mode, even if the reading guide plate 32 is dirty, accurate shading correction can be performed with the image reading unit 20 fixed. Further, when the shading correction is performed on the second and subsequent originals 1 in the same job, the image reading unit 20 does not move. Therefore, the time required for the image reading unit 20 to move can be saved and the paper can be saved. This makes it possible to shorten the interval and improve productivity as a whole.

  Further, since the difference data of the density data is calculated between the start of the job and the document reading, it is considered that the state of the reading guide plate 32 is not changed due to dirt or the like in a short time, and accurate adjustment of the shading correction data is performed. Is possible.

  With reference to the flowchart of FIG. 28, another embodiment of the timing and method of shading correction will be described. In this form, when the reading of the final document of the job is completed, the shading correction process is performed.

  When the reading of the final document of the job is completed, the controller 50 acquires density data A0 from the reading guide plate 32 at the reading position P1 by the image reading means 20 at the timing in step ST51, and then uses the image reading means 20 as the density reference member. 44 moves to the shading position P2 to obtain density data A01.

  Since the density reference member 44 is in a position not affected by dirt such as paper dust or toner, dirt does not occur. Therefore, even if the original color is the same, if the reading guide plate 32 is soiled with paper dust or toner, a difference occurs in the density of the density data acquired from the reading guide plate 32 and the density reference member 44. Therefore, in step ST52, the density difference ΔA = A0−A01 is calculated from the acquired density data A0 and A01, the data of the density difference ΔA is stored in the storage unit 51, and the job is ended in step ST53. .

  Thereafter, when the user sets a new document 1 on the image reading apparatus 300, the next job is started in step ST54. Here, in FIG. 28, n is a value indicating how many sheets of the conveyed document are, and n = 1 in the initial state. In step ST55, when the first document 1 is conveyed, the image reading unit 20 acquires density data A1n of the reading guide plate 32 while being fixed at the reading position P1.

  In step ST56, using the acquired density data A1n and density difference ΔA data, the data An used in the shading correction is adjusted as An = A1n−ΔA, the shading correction is performed in step ST57, and the first sheet in step ST58. Document reading is performed.

  In step ST59, when reading of the first document is completed, it is determined whether or not the next document remains based on the output from the set sensor 5. If the next document remains, n is incremented in step ST60. Then, n = 2, and the process returns to step ST55 to perform shading correction on the second and subsequent originals 1. If no next original remains in step ST59, reading of the final original is completed, and the process returns to step ST51.

  In this control mode, even when the reading guide plate 32 is dirty, accurate shading correction can be performed while the image reading unit 20 is held at the reading position P1. When the shading correction is performed on the second and subsequent originals 1 in the same job, the image reading unit 20 does not move. Therefore, the time required for the image reading unit 20 to move can be saved, and the paper interval can be shortened. It becomes possible to improve productivity as a whole. In addition, immediately after the reading of the final document in which the light source unit 310 such as a xenon lamp used in the image reading unit 20 is warmed, the density data ΔA is acquired to start the image reading apparatus 300 in order to acquire the density difference ΔA. Compared to the case where it is acquired immediately thereafter, density data at the time of actual document reading can be acquired, and more accurate shading correction can be performed.

FIG. 29 shows a form in which a temperature detecting means 70 such as a thermistor for detecting the temperature of the image reading means 20 is arranged in the vicinity of the image reading means 20 in the image reading apparatus 300. The temperature detection unit 70 is provided so as to be movable integrally with the image reading unit 20 and is connected to the controller 50, acquires temperature information t <b> 1 of the image reading unit 20, and transmits the temperature information t <b> 1 to the controller 50. Data on temperature and concentration characteristics is stored in advance in the storage unit of the main body control unit 60 that can communicate with the controller 50.
FIG. 30 is a flowchart showing a method of calculating density difference ΔA data used for shading correction adjustment in the configuration shown in FIG.

  In FIG. 30, in step ST61, the image reading unit 20 acquires the density data A0 of the reading guide plate 32 at the reading position P1, and the temperature detecting unit 70 acquires the temperature information t1 of the image reading unit 20 at that time.

  In step ST62, the image reading means 20 moves to the shading position P2 of the density reference member 44 to acquire density data A01, and the temperature detection means 70 acquires temperature information t2 of the image reading means 20 at that time.

  In step ST63, the density correction value Δa due to the temperature difference is set to Δa = a from the temperature information t1 and t2 acquired in step ST61 and step ST62 and the temperature and density characteristic data stored in the storage unit of the main body control unit 60. Calculate as (t2) -a (t1).

  In step ST64, the temperature-corrected density data A01 ′ is calculated as A01 ′ = A01−Δa from the density data A01 of the density reference member 44 and the density correction value Δa. In step ST65, the density difference ΔA is calculated as ΔA = A0−A01 ′ from the density data A0 acquired in step ST61 and the density data A01 ′ calculated in step ST64, and the density difference ΔA data is stored in the storage unit of the controller 50. Save to 51.

  In this control mode, when the density difference ΔA data of the density data is calculated, a value that varies depending on the temperature of the light source unit 310 is taken into account. It is possible to accurately calculate data for shading correction regardless of characteristics.

  In each of the above embodiments, the density reference member 44 is used as the second density reference means, and the reflection data from the shading surface 44a of the density reference member 44 is acquired as the density data A01. The means is not limited to the density reference member 44 as a member, but a database of density data A01 obtained by a test in advance is stored in the controller 50 or the main body control unit 60, and this database is stored in the second density reference means. It is good. In this case, since it is not necessary to move the image reading means 20 to the density reference member 44 in order to acquire the density data A01 as described above, the reading productivity can be further improved. Further, if not only the density data A01 database is used but also the density data A01 is changed according to changes in temperature information, the light output from the light source unit 310 may change depending on the temperature. The accuracy can be improved while improving the productivity of reading.

  In FIG. 31, the reading glass 21 and the shading surface 32a facing the reading glass 21 are disposed so as to be inclined downward in the document conveying direction, so that the image reading means 20 can be moved horizontally in the sub-scanning direction C. Then, the image reading means 20 performs the reading operation at the reading position P1 where the reading surface 21a of the reading glass 21 inclined at the standby position located on the left side in the drawing and the reading reference surface 43a of the pressure plate reading glass 43 are at the same height. Do. In such a configuration, when the first density information is acquired by the image reading means 20, that is, when the density is adjusted, the reading can be performed at the reading position P1, but the reading reference surface 43a of the pressure plate reading glass 43 By acquiring the density data by moving the image reading unit 20 by a small amount to the reading position P3 having the same height as the shading surface 32a, it is possible to perform density adjustment with higher accuracy.

  FIG. 32 is based on the configuration of FIG. 31, and guide rails 145 as movement guide members for guiding the image reading means 20 when moving in the sub-scanning direction C are provided below the reading glass 21 and the pressure plate reading glass 43. They are arranged continuously. The guide rail 145 includes an inclined portion 145 a parallel to the reading glass 21 and a horizontal portion 145 b parallel to the pressure plate reading glass 43.

  When the object to be read is a book document, it moves in the sub-scanning direction C along the horizontal portion 145b in parallel with the pressure plate reading glass 43, and when the object to be read is the document 1 conveyed to the conveyance path R, It can move to move in parallel with the reading glass 21 along the inclined portion 145a.

  During normal document reading, a reading operation is performed at a reading position P1 where the reading surface 21a of the reading glass 21 inclined at the standby position located on the left side in the drawing and the reading reference surface 43a of the pressure plate reading glass 43 are at the same height. I do. In such a configuration, when the first density information is acquired by the image reading means 20, that is, when the density is adjusted, the reading can be performed at the reading position P1, but the reading reference surface 43a of the pressure plate reading glass 43 By acquiring the density data by moving the image reading unit 20 by a small amount to the reading position P3 having the same height as the shading surface 32a, it is possible to perform density adjustment with higher accuracy. As described above, when the image reading unit 20 is moved to the reading position P1 to the reading position P3, the image reading unit 20 can be moved in parallel with the inclined reading surface 21a, so that the image reading unit 20 at the reading position P1 and the reading position P3 Since the distance from the shading surface 32a is the same, the reading operation can be performed without changing the optical characteristics at the time of image reading and density data acquisition, and shading correction with higher accuracy can be performed.

DESCRIPTION OF SYMBOLS 1 Document 20 Image reading means 21 Exposure transmission means 21a Reading surface of exposure transmission means 32 First density reference means 32a First density reference surface 40 Reading section 43a Reading reference surface 44 Second density reference means 44a Second density Reference surface 50 Control means 51 Storage section 52 Comparison means 70 Temperature detection means 100 Image forming apparatus 135 Arc-shaped shaft member 133,134 Polygonal shaft member 145 Movement guide member 150-152 Driving means 300 Image reading device ΔA Density difference Δa Density correction value A0 First density information A1 Second density information C Sub-scanning direction H Distance between image reading means and first density reference plane H1 Distance between image reading means and second density reference plane P1 First Position P2 second position T set value t1 temperature information

JP 2006-261844 A JP 2005-328156 A JP 2003-125177 A JP 2003-101734 A JP 2003-092669 A Japanese Patent Laid-Open No. 2003-060907

Claims (20)

In an image reading apparatus that reads an image of a document being conveyed by an image reading unit disposed in a reading unit where an exposure transmission unit is located,
A first density reference means disposed in opposition to the image reading means in the reading section, wherein first density information is obtained by reflecting light irradiated from the image reading means side; and a first density reference An image reading apparatus comprising: second density reference means for obtaining second density information different from the means.   2. The image reading apparatus according to claim 1, wherein the second density reference means is disposed at a position where the second original is not stained by the conveyed document.   The image reading apparatus according to claim 1 or 2, wherein the first density reference means is constituted by a plate-like member extending in the sub-scanning direction of the image reading means.   The image reading apparatus according to claim 1, wherein the first density reference unit includes a conveyance guide unit that guides conveyance of the document conveyed to the reading unit. The image reading means includes a first position for obtaining first density information facing at least the first density reference plane of the first density reference means, and a second density reference plane of the second density reference means. To the second position to obtain the second density information opposite to
When the image reading means occupies the second position, the density of the second density reference means is located between the second density reference means and the image reading means, and the reading reference surface on which the conveyed document does not reach. The image reading apparatus according to claim 1, wherein the reference planes are arranged in close contact with each other. The image reading means includes a first position for obtaining first density information facing at least the first density reference plane of the first density reference means, and a second density reference plane of the second density reference means. To the second position to obtain the second density information opposite to
When the image reading means moves to the first position and the second position, the distance between the image reading means and the second density reference surface, and the distance between the image reading means and the first density reference surface. The image reading apparatus according to claim 1, further comprising a movement guide member that guides the image reading unit so that the distance is constant. The image reading means includes a first position for obtaining first density information facing at least the first density reference plane of the first density reference means, and a second density reference plane of the second density reference means. To the second position to obtain the second density information opposite to
The first density reference surface of the first density reference means and the exposure transmission means are arranged to be inclined downward in the document conveying direction,
The image reading unit moves to a position where the position of the first density reference unit is in the same positional relationship as the reading surface of the exposure transmission unit when the first density information is acquired by the image reading unit. The image reading apparatus according to claim 1. Comparing means for comparing the first density information obtained from the first density reference means and the second density information obtained from the second density reference means;
The density information in the first density reference means is corrected according to the density difference between the first density information and the second density information based on the second density reference means obtained by the comparison means. The image reading apparatus according to claim 1, further comprising a control unit.   When the comparison result between the first density information and the second density information obtained from the first density reference means and the second density reference means exceeds a preset value, the control means The image reading apparatus according to claim 8, wherein the image reading operation is controlled to be stopped.   If the comparison result of the first density information and the second density information obtained from the first density reference means and the second density reference means exceeds a preset value, the control means 10. The image reading apparatus according to claim 8, wherein control is performed so as to perform a guidance display for prompting cleaning to the reference means.   When the comparison result between the first density information and the second density information obtained from the first density reference means and the second density reference means exceeds a preset value, the control means 11. The image reading apparatus according to claim 8, wherein control is performed so that the image reading operation by the image reading means is continued according to density information of a reference means.   The control means prioritizes the first density information obtained from the first density reference means over the second density information obtained from the second density reference means, and controls the first density information in the first density reference means. 9. The image reading apparatus according to claim 8, wherein density information is used. The first density reference surface of the first density reference means is movable at the first position;
When the comparison result between the first density information and the second density information exceeds a preset value, the control means causes the density difference with the second density reference means to be within the set value. The operation of the first density reference means is controlled so that a density reference surface of the density reference means occupies a position facing the image reading means. The image reading apparatus described.   14. The image reading apparatus according to claim 13, wherein the first density reference means comprises a shaft member whose density reference surface is formed in an arc shape and is rotationally driven by the drive means.   14. The image reading apparatus according to claim 13, wherein the first density reference means has a density reference surface formed in a polygonal shape and is constituted by a shaft member that is rotationally driven by the drive means.   The control means calculates the density difference between the first density information and the second density information from the comparison result obtained by the comparing means until the first original is conveyed to the image reading means. 15. The method according to claim 8, wherein the first density information obtained from the first density reference means is corrected by the density difference when a document reading operation is performed by the image reading means. The image reading apparatus described in one.   The control means calculates the density difference between the first density information and the second density information from the comparison result obtained by the comparison means immediately after the image reading of the final document is completed, The first density information obtained from the first density reference means is corrected by the density difference when the reading operation is performed in the image reading operation. The image reading apparatus described. A temperature detecting means for detecting the temperature in the vicinity of the image reading means, and a storage unit in which density characteristic information corresponding to the temperature is stored;
The control means selects density characteristic information stored in the storage unit based on temperature information detected by the temperature detection means, and a first density reference means obtained from the first density reference means by the selected density characteristic information. The image reading apparatus according to claim 8, wherein one density information is corrected. Temperature detecting means for detecting the temperature in the vicinity of the image reading means;
A storage unit storing density characteristic information according to the temperature of the second density reference unit;
The control means selects density characteristic information stored in the storage unit based on the temperature information detected by the temperature detection means, and a first density reference means obtained from the first density reference means with the selected density characteristic information. 5. The image reading apparatus according to claim 1, wherein shading correction is performed by correcting one density information.   An image forming apparatus comprising the image reading apparatus according to claim 1.

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