JP6299662B2 - Image reading apparatus and image forming apparatus having the same - Google Patents

Description

  The present invention relates to an image reading apparatus used for a digital copying machine, an image scanner, and the like for scanning and reading a document, and an image forming apparatus including the image reading apparatus.

  2. Description of the Related Art Conventionally, in an image reading apparatus mounted on a multifunction machine or the like using an electrophotographic process, in order to read a sheet-like document, it is sequentially fed to a document placing table (contact glass) and discharged from the document placing table after the reading is completed. Some of them are equipped with such an automatic document feeder. In such an image reading apparatus, a sheet-through method in which a document is automatically conveyed and read by a document conveying device in a state where a reading module is fixed, and a document pressing unit is opened and closed each time a document on a document placing table is opened. Two types of reading methods are possible: a document fixing method in which one document is replaced and the reading module is scanned and moved to read the document.

  In recent years, in the above-described sheet through method, a double-sided simultaneous reading method in which a front side and a back side of a double-sided document are simultaneously read using different reading modules in a single document transport operation by a document transport device has become mainstream.

  Also, by reading the white reference plate with the reading module before reading the document, it is necessary to correct variations in illumination in the main scanning direction by the light source mounted on the reading module, lens vignetting, and pixel-to-pixel variation of the CCD sensor. Shading correction is performed. At this time, if the reading (sampling) of the white reference plate is only one line in the main scanning direction, when a black spot or dust adheres to the reading line of the white reference plate, that portion becomes a streak. Therefore, in order to reduce the influence of black spots and dust, sampling is generally performed on a plurality of lines in the main scanning direction, and the acquired white reference data is averaged and used.

  Here, the reading module for the front surface can be moved below the surface of the contact glass by a driving source such as a motor in order to cope with the document fixing method. Therefore, when shading correction is performed, a plurality of lines in the main scanning direction can be sampled while moving under the white reference plate in the sub scanning direction. On the other hand, the reading module for the back surface is fixed in the document conveying device, and the reading module itself cannot be moved.

  Therefore, a white reference plate, white reference roller, etc. are placed at a position facing the reading module for the back side, and they are moved or rotated during shading correction to eliminate the influence of black spots and dust. Yes. For example, in Patent Document 1, a white reference plate (back surface white reference plate) used for shading correction of the back surface reading module is arranged in the front surface reading module, and the back surface reading is performed in accordance with the movement of the front surface module. A configuration for performing shading correction of a module is disclosed.

JP 2004-166145 A

  When the white reference plate for the back surface is arranged on the reading module for the front surface as in Patent Document 1, the white reference plate for the back surface arranged at a distance from the contact glass surface is read through the glass in consideration of the warpage of the contact glass. There is a need. However, since the reading module for the front surface has a home position directly below the white reference plate (front white reference plate) used for shading correction of the reading module for the front surface, the white reference plate for the back surface is opposed to the reading module for the back surface. It cannot be placed at the position to be.

  Further, the reading light source irradiates obliquely with respect to the reading optical axis, and the distribution of illumination light in the height direction is not uniform, and does not necessarily change at the same rate depending on each position in the main scanning direction. For this reason, as the back reference white reference plate is separated from the back reading module, accurate shading correction becomes difficult. Although a method of moving the front-side reading module so that the back-side white reference plate faces the back-side reading module and then moving it to the home position again can be considered, the time required for shading correction becomes longer.

  SUMMARY An advantage of some aspects of the invention is that it provides an image reading apparatus that can accurately perform shading correction of a reading module for a back surface with a simple configuration, and an image forming apparatus including the image reading apparatus.

  In order to achieve the above object, a first configuration of the present invention includes a contact glass, a document conveying device, a first reading module, a second reading module, a first white reference plate, and a second white reference plate. And an image reading apparatus. The contact glass is fixed to the upper surface of the scanner frame, and is divided into a manually placed original glass and an automatic reading glass. The document conveying device can be opened and closed upward with respect to the contact glass, and conveys the document to the upper surface of the automatic reading glass. The first reading module is disposed below the contact glass so as to be reciprocally movable in the sub-scanning direction, and can scan and read an image on the surface side of the document placed on the manually placed document glass in the sub-scanning direction. The image on the front side of the document conveyed to the upper surface of the automatic reading glass can be read in a state where the image is stopped at the reading position facing the automatic reading glass. The second reading module is arranged in the document conveying device and can read an image on the back side of the document conveyed to the upper surface of the automatic reading glass. The first white reference plate is disposed to face the first reading module, and is used for acquiring white reference data by the first reading module. The second white reference plate is disposed to face the second reading module, and is used for acquiring white reference data by the second reading module. The first reading module acquires the white reference data of the first white reference plate while moving in the sub-scanning direction along the contact glass, and executes shading correction. The second reading module acquires the white reference data of the second white reference plate that moves in a direction parallel to the surface facing the second reading module as the first reading module moves, and executes shading correction.

  According to the first configuration of the present invention, when performing the shading correction while moving the first reading module, the shading of the second reading module is performed while moving the second white reference plate using the moving force of the first reading module. Corrections can be made at the same time. Therefore, in both the first reading module and the second reading module, it is possible to perform highly accurate shading correction while removing the influence of black spots and dust. Further, it is not necessary to separately provide a drive source for moving the second white reference plate, and the configuration is simplified and the cost can be reduced.

Side surface sectional view showing an entire configuration of an image forming apparatus 100 including the image reading unit 6 of the present invention. 1 is a side sectional view showing an internal structure of an image reading unit 6 according to a first embodiment of the present invention and a document conveying device 27 that automatically conveys a document to the image reading unit 6. FIG. 2 is an enlarged view around the back side reading module 51 and the back side white reference plate 57 of FIG. FIG. 2 is an enlarged view around the surface reading module 50 and the surface white reference plate 55 in FIG. The figure which shows the state which the reading module 50 for front surfaces, and the white reference board 57 for back surfaces contacted The figure which shows a mode that the white reference board 57 for back surfaces moves from the state of FIG. 5 with the movement of the reading module 50 for front surfaces. The top view which looked at the periphery of the white reference board 57 for back surfaces of the image reading part 6 which concerns on 2nd Embodiment of this invention from upper direction. 7 is a diagram showing a state in which the back surface white reference plate 57 moves with the movement of the front surface reading module 50 from the state of FIG. Side sectional view showing an internal structure of an image reading unit 6 according to a third embodiment of the present invention and an original conveying device 27 that automatically conveys an original to the image reading unit 6 FIG. 9 is a diagram illustrating a state in which the back surface white reference plate 57 moves from the state of FIG. 9 as the front surface reading module 50 moves.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus 100 including an image reading unit 6 according to an embodiment of the present invention. In FIG. 1, in an image forming apparatus 100 (here, a digital multifunction peripheral is shown as an example), when performing a copy operation, image data of a document is read and converted into an image signal by an image reading unit 6 described later. On the other hand, in the image forming unit 3 in the multifunction machine main body 2, the photosensitive drum 5 that rotates in the clockwise direction in the drawing is uniformly charged by the charging unit 4. An electrostatic latent image based on the document image data read by the image reading unit 6 is formed on the photosensitive drum 5 by a laser beam from the exposure unit (laser scanning unit or the like) 7. A developer (hereinafter referred to as toner) is attached to the formed electrostatic latent image by the developing unit 8 to form a toner image. The toner is supplied to the developing unit 8 from the toner container 9.

  The sheet is conveyed from the sheet feeding mechanism 10 to the image forming unit 3 via the sheet conveying path 11 and the registration roller pair 12 toward the photosensitive drum 5 on which the toner image is formed as described above. The conveyed paper passes through the nip portion between the photosensitive drum 5 and the transfer roller 13 (image transfer portion), whereby the toner image on the surface of the photosensitive drum 5 is transferred. The sheet onto which the toner image has been transferred is separated from the photosensitive drum 5 and conveyed to a fixing unit 14 having a fixing roller pair 14a to fix the toner image. The paper that has passed through the fixing unit 14 is conveyed to a paper conveyance path 15 that branches in a plurality of directions. The paper is distributed in the transport direction by the path switching mechanisms 21 and 22 having a plurality of path switching guides provided at the branching points of the paper transport path 15 and is sent to the reverse transport path 16 as it is (or after both sides are copied). ), And is discharged to a paper discharge section including a first discharge tray 17a and a second discharge tray 17b.

  Further, although not shown, a static elimination device that removes residual charges on the surface of the photosensitive drum 5 is provided on the downstream side of the cleaning device 18 with respect to the rotation direction of the photosensitive drum 5. Further, the paper feed mechanism 10 is detachably attached to the multifunction machine main body 2 and includes a plurality of paper feed cassettes 10a and 10b for storing paper and a stack bypass (manual feed tray) 10c provided above the paper feed cassettes 10a and 10b. These are connected to the image forming unit 3 including the photosensitive drum 5 and the developing unit 8 by the paper transport path 11.

  An image reading unit 6 is arranged on the upper part of the multifunction machine main body 2, and a document placed on the contact glass 25 (see FIG. 3) of the image reading unit 6 is pressed on the upper surface of the multifunction machine main body 2. A holding platen (original presser) 24 is provided so as to be openable and closable, and an original conveying device 27 is provided on the platen 24.

  Specifically, the sheet conveyance path 15 is first branched into left and right forks on the downstream side of the fixing roller pair 14a, and one path (the path branched in the right direction in FIG. 1) communicates with the first discharge tray 17a. It is configured as follows. The other path (the path that branches in the left direction in FIG. 1) branches into two branches via the conveying roller pair 19, and the other path (the path that branches in the left direction in FIG. 1) is the second discharge tray 17b. It is comprised so that it may communicate with. On the other hand, the other path (the path branched downward in FIG. 1) is configured to communicate with the reverse conveyance path 16.

  FIG. 2 is a side sectional view showing the internal structure of the image reading unit 6 and the document conveying device 27 that automatically conveys the document to the image reading unit 6 according to the first embodiment of the present invention. A contact glass 25 made up of an automatic reading glass 25a and a manually placed original glass 25b is disposed on the upper surface of the image reading unit 6. A front side reading module 50 is arranged inside the image reading unit 6. The front-side reading module 50 reads a document image placed on the manually placed document glass 25b while moving in the sub-scanning direction (left-right direction in FIG. 2). Further, the front surface reading module 50 reads an image on the front surface side of the document conveyed by the document conveying device 27 in a state of being stopped just below the automatic reading glass 25a.

  Between the automatic reading glass 25a and the manually placed document glass 25b, a conveyance guide 54 for scooping up the leading edge of the document conveyed by the document conveying device 27 is disposed. A front surface white reference plate 55 for correcting shading of the front surface reading module 50 is disposed below the conveyance guide 54. Further, on the upstream side (left side) of the automatic reading glass 25a with respect to the document conveying direction on the contact glass 25 (from left to right in FIG. 2), the back side white reference for shading correction of the back side reading module 51 is provided. A plate 57 is arranged.

  A document transport path d from the document feed tray 29 to the document discharge tray 32 is formed in the cover member 31 of the document transport device 27, and along the document transport path d, a pickup roller 33, a paper feed belt 34, and A document conveying member including a separation roller 35, a registration roller pair 36, a conveyance roller pair 37 and 38, a discharge roller pair 43, and the like, and a back surface reading module 51 for reading an image on the back surface side of the document are provided.

  The sheet feeding belt 34 is wound around a driving roller 44a and a driven roller 44b, and a separation roller 35 is in contact with the roller at a predetermined pressure from below. The separation roller 35 has a built-in torque limiter, and is driven to rotate with the paper feed belt 34 only when the rotational load exceeds a predetermined torque.

  The document conveyance path d is curved so as to be reversed between the registration roller pair 36 and the automatic reading glass 25a. A plurality of paper detection sensors (not shown) including a paper feed sensor and a discharge sensor for detecting the presence / absence or passage of the original are provided at appropriate positions on the original transport path d.

  Next, a sheet-through type document conveying operation using the document conveying device 27 will be described. In the sheet-through method, a plurality of documents are set on the document feed tray 29 with the image surface facing upward. Thereafter, when the copy start button on the operation panel 55 (see FIG. 1) of the image forming apparatus 100 is turned on, a lift plate (not shown) raised by an elevating mechanism (not shown) is picked up by the pickup roller 33 via the document. Push up. As a result, the weight of a frame (not shown) including the pickup roller 33 is applied to the lift plate, so that the upper surface of the document is pressed against the pickup roller 33 with a predetermined pressure (feed pressure).

  Here, the pickup roller 33, the driving roller 44a, the driven roller 44b, and the paper feed belt 34 are arranged in a frame body (not shown). The pickup roller 33 is connected to a driving roller 44a by a gear (not shown). When the driving roller 44a is rotated by a roller driving motor (not shown), the pickup roller 33 is stretched by the driving roller 44a and the driven roller 44b. The paper belt 34 is driven to rotate, and the pickup roller 33 is also driven to rotate.

  The document set on the document feed tray 29 is usually fed by the pickup roller 33 to the nip portion between the feed belt 34 and the separation roller 35 as a plurality of upper sheets. Then, only the uppermost one of the plurality of documents is separated by the separation roller 35 and conveyed toward the registration roller pair 36. At that time, after the leading edge of the document is detected by the sheet feeding sensor, the document is conveyed by a predetermined distance, and then the rotation driving of the pickup roller 33 and the sheet feeding belt 34 is stopped by stopping the operation of the roller driving motor. The paper ends. The document that has been primarily fed is stopped in a state where the leading end of the document is bent at the nip portion of the registration roller pair 36.

  Secondary feeding is started after a predetermined time has elapsed since the completion of primary feeding. That is, the registration roller pair 36 is rotationally driven by the operation of a secondary paper feed drive motor (not shown). The document is conveyed by the registration roller pair 36 and the conveyance roller pair 37 toward the automatic reading glass 25a. The document conveyed to the automatic reading glass 25a is pressed against the automatic reading glass 25a from above by coming into contact with the document pressing member 53 disposed opposite to the automatic reading glass 25a. An image on the front side (automatic reading glass 25a side) of the original is read by the front side reading module 50 through the automatic reading glass 25a.

  Thereafter, the document that has passed through the automatic reading glass 25 a is transported toward the transport roller pair 38 and the discharge roller pair 43 through the transport guide 54, and finally discharged onto the document discharge tray 32 by the discharge roller pair 43. Is done. At that time, the completion of image reading of one document is detected by detecting the passage of the trailing edge of the document by the discharge sensor. Here, the discharge sensor has a count function for counting the number of documents every time the document conveyance is completed. If the paper feed sensor detects a subsequent document, the conveyance of the second and subsequent documents is the same as described above. To continue.

  When reading a double-sided document, an image on the back side of the document is read by the back-side reading module 51 provided on the upstream side of the document pressing member 53 and then an image on the surface of the document is read by the front-side reading module 50.

  FIG. 3 is an enlarged view around the back side reading module 51 and the back side white reference plate 57 of FIG. As shown in FIG. 3, the back surface reading module 51 is a CCD sensor type reading module, and includes a light source 70, a condensing lens 71 composed of a plurality of lenses, and a CCD sensor 73 as reading means. The light emitted from the light source 70 is reflected by a document (not shown), and then condensed by a condenser lens 71 and guided to a CCD sensor 73. The CCD sensor 73 is supported on the CCD substrate 75.

  Although not described here, the front surface reading module 50 (see FIG. 4) is also a CCD sensor type reading module, and similarly to the back surface reading module 51, a light source 70, a condensing lens 71, a CCD sensor 73, A CCD substrate 75 is provided. The front reading module 50 has a home position directly below the front white reference plate 55 (see FIG. 4).

  The back-side white reference plate 57 has a convex shape in side view having an engaging portion 57 a on the upper surface, and the engaging portion 57 a is fitted in a guide groove 6 b formed in the scanner frame 6 a of the image reading portion 6. An inclined surface 57b is formed on the left side surface of the engaging portion 57a, so that the document conveyed by the document conveying device 27 can be conveyed without being caught. Further, the right side surface portion of the engaging portion 57a is flush with the upper surface of the scanner frame 6a or slightly above the upper surface of the scanner frame 6a. Thereby, it is possible to prevent the document that has passed through the back-side white reference plate 57 from being caught by the step of the scanner frame 6a.

  Further, the width of the guide groove 6b in the document transport direction (from left to right in FIG. 3) is formed larger than that of the engaging portion 57a, and the white reference plate 57 for the back surface of the scanner frame 6a is within the range of the guide groove 6b. It is slidable in the document transport direction along the lower surface. In addition, one end of a coil spring 80 is fixed to the downstream end of the white reference plate 57 for the back surface with respect to the document conveying direction, and the other end of the coil spring 80 is fixed in the image reading unit 6. The coil spring 80 biases the back-side white reference plate 57 toward the downstream side in the document conveyance direction (right direction in FIG. 3).

  In the above configuration, when an original image is read by the original fixing method, first, an original (not shown) is placed on the manually placed original glass 25b with its surface facing downward. Then, the front-side reading module 50 is moved from the scanner home side (left side in FIG. 2) to the scanner return side (right side in FIG. 2) at a predetermined speed while irradiating the image surface of the document with light from the light source 70. As a result, the light reflected by the image plane is imaged on the CCD sensor 73 as image light. The imaged image light is separated into pixels by the CCD sensor 73, converted into an electrical signal corresponding to the density of each pixel, and an image is read.

  On the other hand, when reading a document image by the sheet-through method, the front surface reading module 50 is moved directly below the automatic reading glass 25a. Then, the image light reflected on the image surface is projected onto the CCD sensor 73 while irradiating the surface of the document sequentially conveyed while being lightly pressed toward the automatic reading glass 25 a by the document conveying device 27 with light from the light source 70. The image is read on the image.

  Next, shading correction of the front side reading module 50 and the back side reading module 51 when the double-sided image is read by the image reading unit 6 of the present embodiment will be described. FIG. 4 is an enlarged view of the periphery of the surface reading module 50 and the surface white reference plate 55 in FIG.

  As shown in FIG. 4, first, the front-side white reference plate 55 disposed below the transport guide 54 while moving the front-side reading module 50 from the home position to the upstream side in the document transport direction (the arrow direction in FIG. 4). Read the white reference data. Specifically, the white reference data is sampled in a plurality of lines in the main scanning direction (direction perpendicular to the paper surface of FIG. 4) of the front white reference plate 55, and the obtained white reference data is averaged to perform shading correction. .

  As shown in FIG. 5, the front surface reading module 50 is in contact with the back surface white reference plate 57 at a predetermined position in the middle of movement. Then, the white reference plate 57 for the back surface is moved along the document conveying direction together with the front surface reading module 50 while extending the coil spring 80 from a position before contacting the front surface reading module 50 (the position in FIG. 3, hereinafter referred to as a first position). It moves a predetermined distance upstream (in the direction of the arrow in FIG. 5). As a result, as shown in FIG. 6, the back surface white reference plate 57 is disposed at a position in contact with the upstream end portion of the guide groove 6 b (the position in FIG. 6, hereinafter referred to as the second position).

  The back side reading module 51 reads the white reference data of the moving back side white reference plate 57. Specifically, the white reference data is sampled in a plurality of lines in the main scanning direction (direction perpendicular to the paper surface of FIG. 6) of the back side white reference plate 57, and the obtained white reference data is averaged to perform shading correction. .

  Thereafter, the front-side reading module 50 is moved by a predetermined amount in the opposite direction (right direction in FIG. 6), stopped at the reading position immediately below the automatic reading glass 25a, and double-sided reading is started. The back side white reference plate 57 returns to the first position shown in FIG. 3 again by the biasing force of the coil spring 80.

  As described above, in the image reading unit 6 of the present embodiment, when the shading correction is performed while moving the front surface reading module 50, the back surface white reference plate 57 is moved to the first position using the moving force of the front surface reading module 50. The shading correction of the reading module 51 for the back surface is simultaneously performed while moving from the first position to the second position. Therefore, in both the front surface reading module 50 and the back surface reading module 51, highly accurate shading correction can be performed while removing the influence of black spots and dust. Further, it is not necessary to separately provide a drive source or a drive mechanism for moving the white reference plate 57 for the back surface, and the configuration is simplified and the cost can be reduced. Further, the back white reference plate 57 can be disposed immediately below the back reading module 51 in the vicinity of the document reading position, and shading correction with higher accuracy can be achieved.

  Further, since the back side white reference plate 57 is moved in the sub-scanning direction orthogonal to the main scanning direction, black spots and dust on the back side white reference plate 57 existing on the reading line of the back side reading module 51 are read for the back side. It moves in a direction away from the reading line of the module 51. Therefore, the influence of black spots and dust can be effectively eliminated.

  When the back surface white reference plate 57 is moved to the second position, a gap G is generated between the right end portion of the back surface white reference plate 57 and the scanner frame 6a as shown in FIG. However, in this embodiment, when the front side reading module 50 is moved to the image reading position, the white reference plate 57 for the back side is returned to the first position by the coil spring 80, so that there is no possibility that the document will be caught at the time of reading the image.

  7 and 8 are plan views of the periphery of the white reference plate 57 for the back surface of the image reading unit 6 according to the second embodiment of the present invention as viewed from above. In the present embodiment, the back-side white reference plate 57 is configured to move in the front-rear direction of the image reading unit 6 (vertical direction in FIG. 7) along the guide groove 6b of the scanner frame 6a. The internal structures of the image reading unit 6 and the document conveying device 27 are the same as those in the first embodiment shown in FIG.

  As shown in FIG. 7, the guide groove 6 b is formed longer than the dimension in the longitudinal direction of the back surface white reference plate 57. One end of a coil spring 80 is fixed to the back end (upper side in FIG. 7) of the white reference plate 57 for the back surface, and the other end of the coil spring 80 is fixed in the image reading unit 6. An inclined portion 81 is formed on the side edge of the back surface white reference plate 57 facing the front surface reading module 50, and a convex portion 83 is formed on the front surface reading module 50 at a position facing the inclined portion 81. ing.

  Next, shading correction of the front side reading module 50 and the back side reading module 51 when the double-sided image is read by the image reading unit 6 of the present embodiment will be described. First, while moving the front-side reading module 50 from the home position to the upstream side in the document conveyance direction (in the direction of the arrow in FIG. 7), the white color of the front-side white reference plate 55 (see FIG. 2) disposed below the conveyance guide 54. Read the reference data. The surface reading module 50 averages the acquired white reference data and performs shading correction.

  The convex portion 83 contacts the inclined portion 81 of the white reference plate 57 for the back surface at a predetermined position in the middle of the movement of the front surface reading module 50 from the state of FIG. And since the component force of the force which the convex part 83 presses the inclination part 81 acts on the inclination part 81 in the orthogonal | vertical direction, the edge part of the front side (lower side of FIG. 7) of the white reference board 57 for back surfaces guides. The coil spring 80 is compressed from the position (first position) in contact with the edge of the groove 6b while moving in the depth direction (arrow direction in FIG. 8) by a predetermined distance. As a result, as shown in FIG. 8, the front end of the back surface white reference plate 57 is disposed at a position (second position) that is separated from the end edge of the guide groove 6b. The back surface reading module 51 (see FIG. 2) reads the white reference data of the moving white back reference plate 57, averages the acquired white reference data, and performs shading correction.

  Thereafter, the front-side reading module 50 is moved by a predetermined amount in the opposite direction (right direction in FIG. 8), stopped at the reading position immediately below the automatic reading glass 25a (see FIG. 2), and double-sided reading is started. Note that the back-side white reference plate 57 returns to the first position shown in FIG. 7 again by the biasing force of the coil spring 80.

  In the image reading unit 6 of this embodiment, the back surface white reference plate 57 is moved from the first position to the second position by using the moving force of the front surface reading module 50 as in the first embodiment. The reading module 51 is configured to perform shading correction simultaneously. Therefore, in both the front surface reading module 50 and the back surface reading module 51, highly accurate shading correction can be performed while removing the influence of black spots and dust.

  In the present embodiment, the back surface white reference plate 57 moves in the main scanning direction (vertical direction in FIG. 7). Therefore, when there are black spots or dust on the back surface white reference plate 57, the back surface reading module 51. Will move on the reading line. Therefore, the effect of eliminating the influence of black spots and dust is slightly inferior to that of the first embodiment. However, since the back surface reading module 51 samples the white reference data in a plurality of lines in the main scanning direction and averages the acquired white reference data to perform shading correction, the back surface white reference plate 57 is not moved. The effect of sunspots and dust can be reduced.

  9 and 10 are side cross-sectional views showing the internal structure of the image reading unit 6 and the document conveying device 27 that automatically conveys the document to the image reading unit 6 according to the third embodiment of the present invention. In the present embodiment, the back surface reading module 51 is arranged in a vertical portion of the document transport path d, and the back surface white reference plate 57 transports the document so as to face the back surface reading module 51 across the document transport path d. Arranged inside the device 27.

  A first link member 85 that is movable in the sub-scanning direction (left-right direction in FIG. 9) is disposed inside the image reading unit 6 adjacent to the front-side reading module 50. One end of a coil spring 80 is fixed to the downstream end portion of the first link member 85 with respect to the document conveying direction, and the other end of the coil spring 80 is fixed in the image reading unit 6. The coil spring 80 biases the first link member 85 to the downstream side in the document transport direction (the right direction in FIG. 9).

  A second link member 87 is fixed to the lower end portion of the back white reference plate 57. The lower end portion of the second link member 87 protrudes from the lower surface of the document conveying device 27 and is opened from the opening hole on the upper surface of the image reading portion 6 with the document conveying device 27 closed with respect to the image reading portion 6 as shown in FIG. Inserted into.

  Next, shading correction of the front side reading module 50 and the back side reading module 51 when the double-sided image is read by the image reading unit 6 of the present embodiment will be described. First, the white reference data of the front white reference plate 55 disposed under the conveyance guide 54 is read while the front reading module 50 is moved from the home position to the upstream side in the document conveyance direction (the direction of arrow A in FIG. 10). . The surface reading module 50 averages the acquired white reference data and performs shading correction.

  As shown in FIG. 10, the front surface reading module 50 contacts the first link member 85 at a predetermined position in the middle of movement. The first link member 85 moves to the upstream side in the document transport direction (in the direction of arrow A in FIG. 10) together with the front surface reading module 50 while extending the coil spring 80. As a result, the tip end portion of the first link member 85 comes into contact with the second link member 87, and the second link member 87 is pushed up in the arrow B direction along the inclination of the first link member 85. The back-side white reference plate 57 moves together with the second link member 87 by a predetermined distance from the position shown in FIG. 9 (first position) and is arranged at the position shown in FIG. 10 (second position). The back surface reading module 51 reads the white reference data of the moving white back reference plate 57, averages the acquired white reference data, and performs shading correction.

  In the image reading unit 6 of the present embodiment, the back surface white reference plate 57 is moved from the first position to the second position by using the moving force of the front surface reading module 50 as in the first and second embodiments. Thus, the shading correction of the back surface reading module 51 is performed simultaneously. Therefore, in both the front surface reading module 50 and the back surface reading module 51, highly accurate shading correction can be performed while removing the influence of black spots and dust.

  Similarly to the first embodiment, the back side white reference plate 57 is moved in the sub-scanning direction (original transport direction) orthogonal to the main scanning direction (direction perpendicular to the paper surface of FIG. 9). Black spots and dust existing on the plate 57 move in a direction away from the reading line of the reading module 51 for the back surface. Therefore, the influence of black spots and dust can be effectively eliminated.

  Further, since the front surface reading module 50 and the back surface white reference plate 57 are interlocked using the first link member 85 and the second link member 87, the front surface reading module 50 is arranged in the image reading unit 6. Even when the back surface white reference plate 57 is disposed in the document conveying device 27, the back surface white reference plate 57 is moved from the first position to the second position by using the moving force of the front surface reading module 50. Can be made.

  In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in each of the above-described embodiments, the CCD sensor method using the CCD sensor 73 as shown in FIG. 4 is described as an example of the reading method of the surface reading module 50, but the present invention is a CMOS (Complementary MOS). The present invention can also be applied to the CIS sensor type surface reading module 50 using a photoelectric conversion element called a sensor.

  In each of the above embodiments, the image reading unit 6 mounted on the image forming apparatus 100 has been described as an example of the image reading apparatus according to the present invention. However, the image reading apparatus 6 is an image scanner used separately from the image forming apparatus 100. Can be applied in exactly the same way.

  The present invention is applicable to an image reading apparatus including a front surface reading module provided in an image reading apparatus main body and a back surface reading module provided in a document conveying device. By using the present invention, it is possible to provide an image reading apparatus capable of accurately performing shading correction of the back surface reading module with a simple configuration.

6 Image reading unit (image reading device)
6a Scanner frame 6b Guide groove 25 Contact glass 25a Glass for automatic reading 25b Glass for manually placed document 27 Document conveying device 50 Surface reading module (first reading module)
51 Back side reading module (second reading module)
54 Transport guide 55 Front white reference plate (first white reference plate)
57 White reference plate for back side (second white reference plate)
57a Engaging portion 57b Inclined surface 70 Light source 71 Mirror 73 Condensing lens 75 CCD sensor 80 Coil spring (biasing member)
81 Inclined portion 83 Convex portion 85 First link member 87 Second link member 100 Image forming apparatus

Claims (5)

Contact glass fixed on the upper surface of the scanner frame and partitioned into glass for manual placement and automatic reading glass;
A document conveying device that can be opened and closed upward with respect to the contact glass, and conveys a document to the upper surface of the automatic reading glass;
It is arranged below the contact glass so as to be able to reciprocate in the sub-scanning direction, and can read an image on the surface side of the document placed on the manually placed document glass while moving in the sub-scanning direction A first reading module capable of reading an image on the front side of the document conveyed to the upper surface of the automatic reading glass in a state of being stopped at a reading position facing the automatic reading glass;
A second reading module that is arranged in the document conveying device and capable of reading an image on the back side of the document conveyed to the upper surface of the automatic reading glass;
A first white reference plate disposed opposite to the first reading module for obtaining white reference data by the first reading module;
A second white reference plate disposed opposite to the second reading module for obtaining white reference data by the second reading module;
In an image reading apparatus comprising:
The second white reference plate is movably disposed on the upper surface of the scanner frame,
The first reading module acquires white reference data of the first white reference plate while performing a shading correction while moving along the contact glass in a direction approaching the second white reference plate in the sub-scanning direction. ,
The second reading module moves in a direction parallel to the surface facing the second reading module along the upper surface of the scanner frame by contacting the first reading module. An image reading apparatus which acquires data and executes shading correction. The second white reference plate moves in contact with the first reading module and the first position before moving in contact with the first reading module, and shading correction of the second reading module is executed. Reciprocating between the second position after
The image reading apparatus according to claim 1, further comprising an urging member that urges the second white reference plate in the first position direction . The second white reference plate is disposed so as to be capable of reciprocating between the first position on the downstream side and the second position on the upstream side in the document conveyance direction along a guide groove formed in the scanner frame. Has been
The first reading module is separated from the second white reference plate by moving to the reading position after the shading correction of the second reading module is performed, and the second white reference plate is attached to the biasing member. 3. The image reading apparatus according to claim 2, wherein the image reading apparatus is moved from the second position to the first position by an urging force to come into contact with the downstream edge of the guide groove . The second white reference plate is arranged so as to be flush with the upper surface of the contact glass or protrude from the upper surface of the contact glass, and the upstream side surface with respect to the document conveying direction has an upward slope in the document conveying direction. the image reading apparatus according to any one of claims 1 to 3, characterized in that the inclined surface is formed. An image forming apparatus on which the image reading apparatus according to claim 1 is mounted .

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