JP2009152656A - Automatic document feeder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic document feeder which can perform reading well regardless of the reading system without being affected by foreign material. <P>SOLUTION: The automatic document feeder includes a first platen 61 fixed to a second reading section 25 and covers the side of the second reading section 25 facing the conveyance route, a second platen 62 arranged at a position of the first platen 61 facing a document, and a means for moving the second platen 62 while keeping a distance between the second platen 62 and the second reading section 25. The automatic document feeder is constituted such that the second reading section 25 is arranged on the upper surface in the conveyance route, and the moving means moves the second platen 62 in the sub-scanning direction of the second reading section 25 while keeping the distance between the second platen 62 and the second reading section 25. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an automatic document feeder, and more particularly to an automatic document feeder that performs reading while moving a document.

  Conventionally, this type of automatic document feeder includes a first reading area where the platen glass and the document are in contact immediately below the platen roller, and a second reading area where the platen glass and the document are not in contact under the white guide. Two reading areas are provided, and normally the first reading area where the original is in contact with the platen glass is set as the reading position, so that floating dust generated in the original conveyance is scattered and stays on the platen glass. When the ink or adhering dust adhering to the original is rubbed against the platen glass and adheres to the first reading area, the reading area is changed to the second reading area. In order to prevent the adhering dust from being read as a streak image (see, for example, Patent Document 1).

In addition, this type of automatic document feeder detects stains that cause black streak noise on image data due to ink stains or scuffing on the platen. If the platen remains smudged or scratched on the platen surface by changing the sheet-through reading position on the platen by sliding the platen, There is known one that performs image reading without noise (for example, see Patent Document 2).
Japanese Patent No. 3814584 JP 2003-60853 A

  However, in the technique described in Patent Document 1, the reading area is used only when reading is performed by a method of transmitting light from the reading area to an image pickup device such as a CCD by a mirror or a lens, that is, a so-called reduction optical system reading method. However, when reading is performed by a reading method using a so-called equal-magnification image sensor such as CIS (Contact Image Sensor), the positional relationship between the reading area on the platen glass and the image sensor Is fixed, and there is a problem that the reading area cannot be switched.

  Further, the device described in Patent Document 2 has a problem that foreign matters such as dust are mixed in the reading means when the platen is moved.

  The present invention has been made to solve the above-described conventional problems, and provides an automatic document feeder that can perform good reading without being affected by foreign matter regardless of the reading method. Objective.

  The automatic document conveying apparatus according to the present invention is an automatic document conveying apparatus comprising: a conveying unit that conveys a document in a conveying path; and a reading unit that reads a document conveyed by the conveying unit at a reading position. A transparent first protective member that is fixed to the reading unit and covers a side of the reading unit that faces the conveyance path, and a document that is conveyed to the reading position of the reading unit by the conveying unit and the first protective member. A transparent second protective member disposed therebetween, and a moving means for moving the second protective member relative to the reading means while maintaining a distance between the second protective member and the reading means. , Provided.

  According to this configuration, even if dirt is attached to the second protective member, the second protective member is moved with respect to the reading means, so that the second protective member is read through a place where the dirt is not attached. Since the original can be read at the reading position of the means, even if the reading means is composed of a 1x close contact image sensor with a shallow depth of focus, high quality image data with excellent focus is obtained without being affected by dust. In addition, since the first protection member remains covered with the reading means, it is possible to prevent foreign matter from entering the reading member. Therefore, reading can be performed satisfactorily without being affected by foreign matter regardless of the reading method.

  In the automatic document feeder according to the present invention, the reading unit is disposed on an upper surface in the conveyance path, and the moving unit maintains a distance between the second protection member and the reading unit. The second protection member is moved in the sub-scanning direction of the reading means.

  With this configuration, by moving the second protection member in the sub-scanning direction, the moving distance of the second protection member can be shortened as compared with the case where the second protection member is moved in the main scanning direction. .

  In the automatic document feeder according to the present invention, the reading unit includes a guide groove that is in sliding contact with the second protection member, and the second protection member moves along the guide groove. Features.

  With this configuration, the distance between the second protective member and the reading unit can be stabilized by moving the second protective member along the guide groove of the reading unit. In particular, even when the reading unit is constituted by an equal magnification contact image sensor having a shallow depth of focus, it is possible to acquire high-quality image data with excellent focus without being affected by dust.

  The automatic document feeder according to the present invention is disposed at a position facing the reading unit on the lower surface of the transport path, and the reading unit uses the white reference member used for acquiring white reference data, the reading unit, And a supporting member that supports the second protective member and the white reference member so as to maintain the positional relationship between the reading means, the second protective member, and the white reference member. .

  With this configuration, since the positional relationship among the reading unit, the second protection member, and the white reference member is maintained by the support member, the positioning accuracy of the reading unit, the second protection member, and the white reference member can be improved. Even when the conveyance path is inclined, the positions of the second protective member and the white reference member relative to the reading unit do not change.

  In the automatic document feeder according to the present invention, the second protection member is formed of a transparent sheet, and a winding unit that winds up the second protection member, and a sending-out unit that sends out the second protection member; And a driving means for driving the winding means and the feeding means, and the second protective member, the winding means and the feeding means are integrally attached to and detached from the reading means. It is characterized by that.

  With this configuration, when dirt is attached to the second protective member, the original can be moved through the non-stained portion of the second protective member only by moving the second protective member by the winding means and the feeding means. Can be read. In addition, since the second protective member, the winding means and the feeding means can be integrally attached to and detached from the reading means as one unit, it can be easily replaced even when the entire area of the second protective member is dirty. can do.

  The automatic document feeder according to the present invention further comprises a movement control means for moving the second protective member by the moving means when the original does not pass the reading position of the reading means. Features.

  With this configuration, since the second protective member is moved during reading of each document when a plurality of documents are read, the next document is transported and read after the document is transported and read. Can be used effectively.

  In the automatic document feeder according to the present invention, when the document does not pass the reading position of the reading unit, the moving unit moves the second protective member and the reading unit moves the white reference. A reading control means for reading the member is provided.

  With this configuration, it is possible to avoid the influence of dirt attached to the second protective member when the reading unit reads the white reference member and acquires the white reference data.

  Also, the automatic document feeder according to the present invention calculates a peak for each pixel averaged by a preset number of lines in the sub-scanning direction from read data obtained by the reading unit reading the white reference member. Shading data generation means for generating shading data is provided.

  With this configuration, it is possible to reduce the influence of the second protective member on the shading data.

  In the automatic document feeder according to the present invention, the reading unit reads the white reference member and then reads the document, and performs a shading process using the shading data generated by the shading data generation unit. It is characterized in that it comprises a dirt detecting means for detecting the position of dirt attached to the second protective member by detecting a level difference equal to or greater than a set value.

  With this configuration, the second protection member can be moved by the moving means so that the reading means reads the document through the position where the dirt of the second protection member is not attached. The document can be read by the reading means while avoiding the dirt adhesion position.

  Further, in the automatic document feeder according to the present invention, when the dirt detecting unit detects that dirt is attached to the second protection member, the dirt attached to the second protection member is detected as the dirt detection unit. It is characterized by comprising repetitive movement control means for moving the second protective member by the moving means until it is no longer detected by the means.

  With this configuration, since the original can be read through a portion where the dirt on the second protective member is not always attached, the influence of the dirt on the second protective member affects the image data obtained by reading the original. It is possible to prevent this from happening.

  In the automatic document feeder according to the present invention, the dirt position storage means for storing the position of dirt attached to the second protective member detected by the dirt detection means, and the dirt position storage means are stored. And a dirt position avoidance movement control means for moving the second protective member by the repetitive movement control means excluding the position of dirt.

  With this configuration, the second protection member is not moved to the dirt adhesion position stored in the dirt position storage means by the repetitive movement control means. Therefore, the reading means can efficiently avoid the dirt adhesion position of the second protection member. Thus, the original can be read.

  Further, the automatic document feeder according to the present invention is characterized in that it comprises an erasing means for erasing the information on the position of the dirt stored in the dirt position storage means.

  With this configuration, when the second protection member is cleaned or replaced, the position information for moving the second protection member is deleted by deleting the information on the position of the dirt. It is possible to return to the state.

  Further, the automatic document feeder according to the present invention is characterized in that the reading means is composed of an equal magnification contact image sensor.

  With this configuration, even when the reading unit is configured with an equal magnification contact image sensor with a shallow depth of focus, it is possible to acquire high-quality image data with excellent focus without being affected by dust.

  According to the present invention, it is possible to provide an automatic document feeder that can perform good reading without being affected by foreign matter regardless of the reading method.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a sectional view showing a configuration of an automatic document feeder according to a first embodiment of the present invention.

  First, the configuration will be described.

  As shown in FIG. 1, the automatic document feeder 40 is placed on a document table 2 on which a document bundle 1 composed of a plurality of documents is placed with a document surface facing upward in a housing 40 a. A pickup roller 7 that conveys the uppermost original from the original bundle 1, a paper feed belt 9 that separates the original conveyed by the pickup roller 7, and a reverse roller 10, and a single original that is separated. The pull-out roller 12, the intermediate roller 14, and the reading entrance roller 16 that convey the image to the vicinity of the slit glass 21 of the image forming apparatus main body 400, and the original that has been conveyed to the vicinity of the slit glass 21 are placed on the slit glass 21 of the first reading unit 20. A reading roller 19 that conveys the document while being in contact with it, a reading exit roller 23 that further conveys the document that has been read by the first reading unit 20, and a reading Includes a discharge roller 28 for discharging the conveyed document, a paper discharge tray 29 ejected document is placed by the exit roller 23. A second reading unit 25 is disposed on the upper surface in the transport path downstream in the transport direction from the first reading unit 20. The 1st reading part 20 and the 2nd reading part 25 are comprised from the equal magnification contact image sensor called CIS (Contact Image Sensor).

  Further, an image forming apparatus main body 400 is disposed below the automatic document feeder 40, and the automatic document feeder 40 is attached to the image forming apparatus main body 400 through an opening / closing mechanism (not shown) so as to be freely opened and closed. Yes. The image forming apparatus main body 400 includes a scanner unit (not shown) that reads a document conveyed by the automatic document conveying device 40, a printer unit that prints on transfer paper, a paper feeding unit, and a control unit (not shown) that controls the operation of each unit. Yes. The automatic document feeder 40 and the image forming apparatus main body 400 constitute an image forming apparatus 450.

  The document placed on the document table 2 passes through each part of the transport path before being discharged to the discharge tray 29. The conveyance path is fed with a document setting unit A on which the document bundle 1 is placed, and a separation feeding unit B that separates and feeds the uppermost one document from the placed document bundle 1. A registration unit C that aligns the original by contacting the original and pulls out the aligned original and conveys it, and a turn part D that turns the conveyed original and conveys the first surface of the original downward. The first reading conveyance unit E that reads the first surface of the document from below the slit glass 21, the second reading conveyance unit F that reads the second surface of the document, and the document that has been read on both sides are discharged to the outside. The paper discharge unit G is configured to include a stack unit H on which the discharged document is placed. The first surface of the document is a surface that faces upward on the document table 2 and is read by the first reading and conveying unit E, and the second surface of the document faces downward on the document table 2 and is the second surface. A surface on which reading is performed in the reading conveyance unit F.

  FIG. 2 is a block diagram showing the configuration of the control unit of the automatic document feeder according to the first embodiment of the present invention.

  As shown in FIG. 2, the automatic document feeder 40 includes a controller 100 that controls the entire automatic document feeder 40. The automatic document feeder 40 also includes a registration sensor 17, a document set sensor 5, a paper discharge sensor 24, a butting sensor 11, a document width sensor 13, a reading entrance sensor 15, and a table as sensors for inputting signals to the controller 100. The lift sensor 8, the home position sensor 6, the first end detection sensor 250, and the second end detection sensor 251 are provided. Further, the automatic document feeder 40 is a second reading unit 25, a pickup motor 101, a paper feed motor 102, a reading motor 103, a paper discharge motor 104, a bottom plate ascending as an actuator or the like for driving and controlling by outputting a signal from the controller 100. A motor 105 and a second platen moving motor 63 are provided.

  The image forming apparatus main body 400 includes a main body control unit 111 that controls the image forming apparatus main body 400 and an operation unit 108 that performs various input operations and instruction operations. The main body control unit 111 is provided with a storage area for storing various setting information. Further, the main body control unit 111 is configured to perform processing related to dirt detection described later. The controller 100 and the main body control unit 111 are connected via an I / F (Interface) 107, and data such as a control signal is exchanged between them.

  FIG. 3 is a block diagram showing the configuration of the second reading unit of the automatic document feeder according to the first embodiment of the present invention.

  As shown in FIG. 3, the second reading unit 25 is composed of a 1 × contact image sensor called a CIS (Contact Image Sensor), and illuminates the document based on a lighting signal from the controller 100. 200, a plurality of sensor chips 201 each including a photoelectric conversion element and a condensing lens and receiving reflected light from a document; and a plurality of amplifier circuits 202 that amplify signals output from the sensor chips 201; From the A / D converter 203 that converts the converted signal from an analog signal to a digital signal, the image processing unit 204 that performs image processing on the digitally converted signal, the frame memory 205 that stores the image processed signal, and the controller 100 Output control for controlling the output of the signal stored in the frame memory 205 based on the timing signal. A control circuit 206 and an I / F circuit 207 that outputs a signal from the output control circuit 206 to the main body control unit 111 are provided. The second reading unit 25 is supplied with power from the controller 100.

  In the second reading unit 25, when a lighting ON signal is sent from the controller 100 to the light source unit 200 before a document (not shown) enters the reading position, the light source unit 200 is turned on and this light has entered. The second surface of the document is irradiated. The reflected light reflected from the second surface of the document is condensed on the photoelectric conversion element by the condensing lens and read as image information in the plurality of sensor chips 201. Image information read by the sensor chip 201 is amplified by the amplifier circuit 202 and then converted into digital image information by the A / D converter 203. The digital image information is input to the image processing unit 204, subjected to shading correction and the like, and then temporarily stored in the frame memory 205. Thereafter, the digital image information is converted into a data format that can be received by the main body control unit 111 by the output control circuit 206, and then output to the main body control unit 111 via the I / F 107.

  It should be noted that the controller 100 outputs a timing signal and a light source lighting signal for notifying the timing at which the leading edge of the document reaches the reading position of the second reading unit 25 to the second reading unit 25 and is supplied with power. It has become.

  Here, the configuration of the automatic document feeder 40 will be described according to the order in which the documents placed on the document table 2 are discharged to the discharge tray 29.

  First, a document bundle 1 composed of a plurality of documents is placed on a document table 2 including a movable document table 3 with the first surface facing upward. Next, the position in the width direction of the document bundle 1, that is, the position in the direction orthogonal to the conveyance direction is positioned by a side guide (not shown). The placement of the document on the document table 2 is detected by the set filler 4 and the document set sensor 5, and a detection signal is output to the main body control unit 111 of the image forming apparatus main body 400 via the I / F 107. An outline of the length of the document in the conveyance direction is detected by document length detection sensors 30 and 31 provided on the surface of the document table 2. As the document length detection sensors 30 and 31, a reflection type sensor that detects without contacting the document by optical means or a contact type actuator type sensor that can detect even when there is only one document can be used. The document length detection sensors 30 and 31 are arranged so that it can be determined whether the document is placed vertically or horizontally.

  The movable document table 3 is configured to move up and down in the directions of arrows a and b in FIG. When it is detected by the set filler 4 and the document set sensor 5 that the document is placed on the document table 2, the controller 100 rotates the bottom plate raising motor 105 in the normal direction so that the uppermost document in the document bundle 1. The movable document table 3 is lifted so that is in contact with the pickup roller 7.

  The pickup roller 7 is operated in the directions of arrows c and d in FIG. 1 by a pickup motor 101 via a cam mechanism, and is pushed by the document on the raised movable document table 3 and lifted in the direction of arrow c. 8, the upper limit of movement is detected. The table raising sensor 8 is a sensor for detecting that the movable original table 3 is raised and the uppermost original of the original bundle 1 is maintained at an appropriate height.

  When the operation unit 108 is operated to specify either the double-side mode or the single-side mode, the print key is pressed, and a document feed signal is output from the main body control unit 111 to the controller 100 via the I / F 107. The controller 100 rotates the pickup roller 7 by rotating the paper feed motor 102 forward. The pickup roller 7 that has started rotating picks up the uppermost document on the document table 2 or several documents including the uppermost document.

  Note that the setting of the duplex mode or the simplex mode in the operation unit 108 may be the same for all documents placed on the document table 2 or may be different for each document. For example, the double-side mode can be designated for the first and tenth originals, and the single-side mode can be designated for the other originals among all ten originals.

  Next, when the paper feeding motor 9 is rotated forward by driving the paper feeding belt 9 and the reverse roller 10 clockwise, the paper feeding belt 9 guides the original in the paper feeding direction, and the reverse roller 10 sets the original in the paper feeding direction. Since the document is pushed out in the opposite direction, the uppermost document in the document stack 1 and the original document below the separated document are separated, and only the uppermost document is fed.

  Specifically, the reverse roller 10 is in contact with the paper feed belt 9 at a predetermined pressure, and in the state of being in direct contact with the paper feed belt 9 or in the state of being in contact with one original, the paper feed belt 9. 9 is rotated counterclockwise different from the original driving direction by the action of a torque limiter (not shown). Further, when two or more documents enter between the paper feed belt 9 and the reverse roller 10, the reverse roller 10 does not rotate with the paper feed belt 9, but rotates in the clockwise direction, which is the original driving direction. It works to push back excess documents and prevent double feeding.

  The document separated into one sheet by the action of the sheet feeding belt 9 and the reverse roller 10 is sent by the sheet feeding belt 9, then the leading edge is detected by the abutting sensor 11, and is further conveyed and stopped. Abuts on the roller 12. Next, when the original fed by a predetermined distance from the position detected by the abutting sensor 11 is pressed against the pull-out roller 12 with a predetermined amount of deflection, the paper feed motor 102 is stopped and the paper feed belt 9 is stopped. Drive stops. At this time, the pickup motor 101 is rotated to retract the pickup roller 7 from the upper surface of the document, and the document is fed only by the conveying force of the paper feed belt 9, whereby the leading edge of the document is sandwiched between the pull-out rollers 12 and Matching, so-called skew correction is performed.

  The pull-out roller 12 has a skew correction function, and is used for conveying the skew-corrected document after separation to the intermediate roller 14, and is driven by the reverse rotation of the paper feed motor 102. When the paper feed motor 102 rotates in the reverse direction, the pull-out roller 12 and the intermediate roller 14 are driven, but the pickup roller 7 and the paper feed belt 9 are not driven.

  The document width sensor 13 includes a plurality of photoelectric conversion elements, such as a CIS (Contact Image Sensor), which are arranged in a direction perpendicular to the document conveyance direction, such as an equal-magnification contact image sensor. The light reception level of the direct light emitted from the irradiation light source (not shown) arranged in the unit is output. The controller 100 detects a level difference between a portion shielded by the document and a portion not shielded by the light reception level of the document width sensor 13 when the document passes the position of the document width sensor 13, and the pull-out roller 12 The size of the conveyed document in the width direction is determined and notified to the main body control unit 111. The length of the document in the conveyance direction is detected from the motor pulse by reading the leading edge and the trailing edge of the document with the butting sensor 11. When the document is transported from the resist section C to the turn section D by driving the pull-out roller 12 and the intermediate roller 14, the transport speed at the resist section C is set higher than the transport speed at the first reading transport section E. Thus, the processing time for sending the document to the first reading conveyance unit E is shortened.

  When the leading edge of the document is detected by the reading entrance sensor 15, the document conveying speed is reduced to make the document conveying speed equal to the reading conveying speed before the leading edge of the document enters the reading inlet roller 16, and the reading motor 103 is driven forward to drive the reading inlet roller 16, the reading outlet roller 23, and the CIS outlet roller 27. When the leading edge of the document is detected by the registration sensor 17, the document conveyance speed is reduced over a predetermined conveyance distance, the document is temporarily stopped (resist stop) in front of the first reading unit 20, and the I / F 107 is also used. A registration stop signal is output to the main body control unit 111 via When a reading start signal is received from the main body control unit 111, the document whose registration has been stopped is accelerated and conveyed so as to rise to a predetermined conveyance speed before the leading end reaches the first reading unit 20. At the timing when the leading edge of the document detected by the pulse count of the reading motor 103 reaches the first reading unit 20, a gate signal indicating an effective image area in the sub-scanning direction on the front surface is output to the main body control unit 111. Note that the gate signal is continuously output until the trailing edge of the document passes through the first reading conveyance unit E.

  When the operation mode is the single-sided mode, the document that has passed through the first reading and conveying unit E is conveyed to the paper discharge unit G through the second reading unit 25. At this time, when the leading edge of the document is detected by the paper discharge sensor 24, the paper discharge roller 104 is rotated counterclockwise by the normal rotation drive of the paper discharge motor 104. Further, the drive speed of the discharge motor 104 is reduced immediately before the trailing edge of the document comes out of the nip area of the discharge roller 28 by the pulse count of the discharge motor 104 after the discharge sensor 24 detects the leading edge of the document. By doing so, the document discharged onto the discharge tray 29 is prevented from jumping out.

  When the operation mode is the duplex mode, the second timing is reached when the leading edge of the document reaches the second reading unit 25 based on the pulse count of the reading motor 103 after the leading edge of the document is detected by the paper discharge sensor 24. A gate signal indicating an effective image area in the sub-scanning direction is output from the controller 100 to the reading unit 25. The gate signal is continuously output from the second reading unit 25 until the trailing edge of the original comes out. The white reference member 66 is a white flat plate-like member, and suppresses the floating of the original in the second reading unit 25 and at the same time serves as a reference white part for acquiring white reference data and shading data in the second reading unit 25. It also serves. Note that the white reference member 66 may be configured by a white roller.

  FIGS. 4A and 4B are a side view and a front view, respectively, showing the configuration of the first reading unit of the automatic document feeder according to the first embodiment of the present invention. FIGS. 5A to 5C are side views showing the configuration of the first reading unit of the automatic document feeder according to the first embodiment of the present invention.

  As shown in FIGS. 4 (a) and 4 (b), the first reading unit 20 reads the first surface of the document, and is composed of an equal-magnification close-contact image sensor. have. On the side of the first platen 51 facing the document, a second platen 52 is disposed and held by connection guides 54 a and 54 b provided at both ends of the first reading unit 20. Guide grooves 55 a and 55 b are provided at both ends of the first reading unit 20 in parallel with the surface of the first platen 51. The connection guides 54a and 54b are respectively provided with guide rollers 54c and 54d that are in sliding contact with the guide grooves 55a and 55b. The connection guides 54 a and 54 b are fixed to both side surfaces of the second platen 52.

  A second platen movement motor 53 is attached to the connection guide 54a, and an output shaft of the second platen movement motor 53 is connected to a guide roller 54c.

  The first platen 51 is made of transparent glass or resin molded into a rectangular flat plate shape, and serves as an exterior cover for preventing foreign matters such as dust from entering the first reading unit 20. The side on which the original is conveyed is covered. The first platen 51 is fixed to the first reading unit 20 by a method such as adhesion.

  The second platen 52 is formed by molding transparent glass or resin or the like into a rectangular flat plate shape, and is disposed between the first platen 51 and the transport path, and is connected to the first platen 51 by connection guides 54a and 54b. The surface of the first platen 51 is held in a state where a minute gap is formed with the surface of the first platen 51.

  A guide member 32 (see FIG. 1) is disposed on the side of the second platen 52 facing the conveyance path, with a slight gap from the second platen 52, and the document read by the first reading unit 20. Is conveyed while contacting the second platen 52 and the guide member 32. The first reading unit 20 reads a document at a reading position at a central portion in the document transport direction of the first reading unit 20. This reading position extends in the main scanning direction (the front and back directions in FIG. 4A). The guide member 32 is a white flat plate-like member that suppresses the floating of the original in the first reading unit 20 and also serves as a reference white part for acquiring white reference data and shading data in the first reading unit 20. Is. In addition, you may comprise the guide member 32 with a white roller.

  As shown in FIGS. 5A to 5C, when the guide roller 54c is rotated by the driving of the second platen moving motor 53, the second platen 52 is connected along the guide grooves 55a and 55b. , 54b together with the surface of the first platen 51 and moves in the sub-scanning direction. Therefore, when the second platen 52 moves, the distance between the second platen 52 and the first reading unit 20 is kept constant before and after the movement. The sub-scanning direction is the left-right direction in FIG.

  In the first reading unit 20, when the first platen 51 and the second platen 52 have the same shape and material, the same member can be used as the first platen 51 and the second platen 52. The manufacturing cost of the first platen 51 and the second platen 52 can be reduced as compared with the case where the shapes and materials of the 51 and the second platen 52 are different.

  FIG. 6 is a perspective view showing the configuration of the second reading unit of the automatic document feeder according to the first embodiment of the present invention. FIG. 7 is a perspective view showing the configuration of the second reading unit of the automatic document feeder according to the first embodiment of the present invention.

  As shown in FIG. 6, the second reading unit 25 reads the second surface of the document, and is composed of an equal magnification contact image sensor, and has a first platen 61 on the surface thereof. The second reading unit 25 has a movable second platen 62. Guide grooves 65 a and 65 b are provided at both ends of the second reading unit 25. At both ends of the second reading section 25, connection guides 64a and 64b are provided which slide in contact with the guide grooves 65a and 65b and slide along the guide grooves 65a and 65b. The connection guides 64 a and 64 b are fixed to both side surfaces of the second platen 62.

  The first platen 61 is configured by molding transparent glass or resin into a rectangular flat plate shape, and serves as an exterior cover for preventing foreign matters such as dust from entering the second reading unit 25. The side on which the original is conveyed is covered. The first platen 61 is fixed to the second reading unit 25 by a method such as adhesion.

  The second platen 62 is configured by molding transparent glass or resin or the like into a rectangular flat plate shape, and is disposed between the first platen 61 and the conveyance path, and is connected to the first platen 61 by connection guides 64a and 64b. The surface of the first platen 61 is held in a state where a minute gap is formed with the surface of the first platen 61.

  A white white reference member 66 is disposed below the second platen 62 so that the document passes between the second platen 62 and the white reference member 66. The white reference member is for obtaining shading data in the second reading unit 25 while suppressing the floating of the original in the second reading unit 25. Note that the white reference member 66 may be configured by a white roller. The second reading unit 25, the first platen 61, the second platen 62, and the white reference member 66 are supported by a housing 40a (see FIG. 1), and the second reading unit 25, the first platen 61, and the second platen 62 are supported. And the mutual positional relationship of the white reference member 66 is maintained by the housing 40a.

  A second platen moving motor 63 is provided at one end of the second reading unit 25, and the rotating part 63a fixed to the output shaft of the second platen moving motor 63 comes into contact with the connecting guide 64a, thereby The guides 64a and 64b and the second platen 62 are moved. The second reading unit 25 reads a document at a reading position at the center of the second reading unit 25 in the document transport direction. This reading position extends in the main scanning direction (front side and back side directions shown in FIG. 6). The size relationship between the guide member distance L, which is the distance between the two connecting guides 64a, 64b, and the maximum document width allowable distance A, which is the distance in the width direction of the maximum size document, satisfies L> A. By setting the inter-member distance L to be larger than the maximum document width allowable distance A, the second platen 62 can be moved without hindering the document conveyance even if the document is the maximum size.

  As shown in FIG. 7, the second platen 62 of the second reading unit 25 is driven by the second platen movement motor 63 along the guide grooves 65a and 65b along with the connection guides 64a and 64b. And move in the sub-scanning direction. Therefore, when the second platen 62 moves, the distance between the second platen 62 and the second reading unit 25 is kept constant before and after the movement. The sub-scanning direction is the left-right direction in FIG. 7 and is equal to the document conveyance direction.

  In the second reading unit 25, when the first platen 61 and the second platen 62 have the same shape and material, the same member can be used as the first platen 61 and the second platen 62. The manufacturing cost of the first platen 61 and the second platen 62 can be reduced as compared with the case where the shapes and materials of the 61 and the second platen 62 are different.

  FIG. 8 is a cross-sectional view showing the configuration of the white shading correction circuit of the automatic document feeder according to the first embodiment of the present invention. FIG. 9 is a conceptual diagram illustrating average value calculation processing in the white shading correction circuit of the automatic document feeder according to the first embodiment of the present invention.

  As shown in FIG. 8, the white shading correction circuit 41 includes a white shading data creation circuit 42 that creates white shading data and a white shading computation circuit 43 that performs white shading computation.

  The white shading data creation circuit 42 includes an average value circuit 44, peak hold circuits 45 and 46, and a register 47, and creates white shading data.

  In the white shading data generation circuit 42, when the gate signal “SHGATE” is output from the controller 100, image data obtained by the second reading unit 25 reading a certain range of the white reference member 66 is input to the average value circuit 44. Then, in the average value circuit 44, as shown in FIG. 9, the image data is divided into m blocks for each L line, and a simple average value of the L lines in each block is obtained. That is, the average value circuit 44 obtains a simple average value of the values of each pixel in each line in each block. The number L of lines is preset in the storage area of the main body control unit 111. The simple average value obtained by the average value circuit 44 is stored in the register 47. The simple average value obtained by the average value circuit 44 is input to the peak hold circuit 45, and the peak hold circuit 45 calculates the peak value of the simple average value of each pixel for each block. That is, the peak hold circuit 45 calculates the peak value in the main scanning direction of the simple average value of each pixel. The peak hold circuit 46 calculates the peak value among the peak values obtained by the peak hold circuit 45 for each block. The white shading data creation circuit 42 outputs the simple average value obtained by the average value circuit 44 for the block having the peak value from the register 47 to the white shading calculation circuit 43 as white shading data.

  In this way, the main body control unit 111 calculates the peak for each pixel averaged with the preset number of lines L in the sub-scanning direction from the read data obtained by the second reading unit 25 reading the white reference member 66. To generate shading data.

  Here, the processing performed in the white shading data creation circuit 42 will be described in more detail.

In the average value circuit 44, a simple average calculation is performed in each of the blocks 1 to L using a mathematical formula of Dm (n) = INT [ΣD (n) / L]. Here, Dm (n) is operation data of the nth pixel of the m-th block, and INT [] means that the numbers in [] are rounded off. L is the number of lines in one block, and ΣD (n) is an added value from 1 to L lines of D (n).
A line in the m block is in a range from m × L to (m + 1) × L−1, and D (n) is read data of the nth pixel.

Further, in the peak hold circuit 45, peak value detection in each block is performed using an equation of Dmmax = Dm (n). Here, Dmmax means the peak value of the m-th block.
Further, in the peak hold circuit 46, when Dpmax is set to the peak value in the m block, in the case of Dpmax <Dmmax, within the effective image area in the sub-scanning direction indicated by the gate signal “SHGATE” according to the equation Dpmax = Dmmax. In the case of Dpmax ≧ Dmmax, the peak value in the sub-scanning direction effective image area indicated by the gate signal “SHGATE” is detected according to the equation Dpmax = Dpmax. The first block is Dpmax = Dmmax, and the shading data is the mth block data with Dmmax.

  Further, in the white shading calculation circuit 43, when the shading data is Dp (n), the shading correction calculation is performed using an equation of Dsh = {D (n) / Dp (n)} × 255.

  FIGS. 10A and 10B are diagrams for explaining dust detection processing of the automatic document feeder according to the first embodiment of the present invention. FIGS. 11A and 11B are diagrams for explaining dust detection processing of the automatic document feeder according to the first embodiment of the present invention.

  As shown in FIG. 10A, when dust is attached to the second platen 62 of the second reading unit 25, the shading data (solid line) generated by reading the white reference member 66 and the original The image data (broken line) at the time of reading has a reduced output level at the dust adhesion position A.

  As shown in FIG. 10B, after the shading process is performed on the data in FIG. 10A, the level difference that can detect the dust adhesion position A is detected in the image data read by the second reading unit 25. Does not appear.

  As shown in FIG. 11A, when no dust is attached to the second platen 62 of the second reading unit 25, shading processing is performed using shading data (solid line) generated from the white reference member 66. Since the level reduction due to dust adhering to the second platen 62 also appears as a level difference in the image data (dashed line) when the original is read, as shown in FIG. 11B, dust detection inside the main body control unit 111 is detected. By detecting this level difference in the block, it is possible to detect that dust has adhered to the second platen 62. Note that the level difference for determining the dust is preset in the storage area of the main body control unit 111.

  As described above, the main body control unit 111 reads the original after reading the white reference member 66 by the second reading unit 25 and performs a shading process using the generated shading data. By detecting the difference, the position of the dirt adhering to the second platen 62 is detected.

  Next, the operation will be described.

  When the operation mode is the duplex mode, the second reading is performed at the timing when the leading edge of the document reaches the second reading unit 25 based on the pulse count of the reading motor 103 after the leading edge of the document is detected by the paper discharge sensor 24. A gate signal indicating an effective image area in the sub-scanning direction is output from the controller 100 to the unit 25, and this gate signal is continuously output from the second reading unit 25 until the trailing edge of the original comes out. The second reading unit 25 reads the second surface of the document based on the gate signal transmitted from the controller 100. In the second reading unit 25, a period from when one of the plurality of originals is read until the next original is read (between sheets), that is, the original passes through the reading position of the second reading unit 25. When there is not, the following platen contamination countermeasure process is executed. Since the operation of the controller 100 is centrally controlled by the main body control unit 111, the following description will be made assuming that the main body control unit 111 is the main body of control.

  FIG. 12 is a flowchart showing platen contamination countermeasure processing of the automatic document feeder according to the first embodiment of the present invention.

  As shown in FIG. 12, first, the main body control unit 111 determines whether or not the light source unit 200 has been turned on in order to acquire image data (step S1), and when the light source unit 200 has been turned on. When the process proceeds to step S4 and the light source unit 200 is not already lit, the light source unit 200 is turned on. (S2).

  Next, the main body control unit 111 determines whether a time necessary for the output of the light source unit 200 to stabilize has elapsed (step S3), and when the necessary time has elapsed, the total of the second platen 62 is summed up. A counter for recording the number of times of movement, that is, the number of times of movement of the second platen 62 is set to 0 (step S4), and when the necessary time has not elapsed, the determination is “Yes”. Step S3 is repeated until. The total number of movements of the second platen 62 is stored in a predetermined storage area of the main body control unit 111.

  After step S3, the main body control unit 111 causes the second reading unit 25 to read the white reference member 66 to acquire white reference data (S5), and the white shading correction circuit 41 based on the white reference data. The dirt data is calculated (step S6).

  Next, the main body control unit 111 determines whether or not the calculated dirt data exceeds a preset allowable amount (step S7), and if it exceeds the allowable amount, the dirt on the second platen 62 is determined. The position is stored (step S8), and the second platen 62 is moved by driving the second platen movement motor 63 (step S9). The allowable amount used for the determination in step S7 is set in advance in the storage area of the main body control unit 111. The dirt position stored in step S8 is information indicating which position in the movement direction of the second platen 62 is dirt. For example, the distance from the initial position of the second platen 62 is the first distance. It is obtained by calculating based on the number of motor pulses of the two-platen moving motor 63. On the other hand, if it is less than the allowable amount in step S7, the original is read by the second reading unit 25 (step S19), the light source unit 200 is turned off (step S20), and there is a next original to be read. (Step S21), if there is a next document, the process returns to step S1, and if there is no next document, the platen stain handling process is terminated.

  Next, the main body control unit 111 determines whether or not the stop position after moving the second platen 62 is the dirt position stored in step S8 (step S10), and when the stop position is the dirt position. Returns to step S9 and moves the second platen 62 again. As described above, the position of the dirt adhered to the second platen 62 is stored, and the second platen 62 is moved excluding the stored dirt position, so that the dirt is detected at the position that is known to be the dirt position. This eliminates the waste of reconfirming the presence or absence. On the other hand, if the stop position is not the dirt position, the total number of movements of the second platen 62 is updated to reacquire white reference data (step S11).

  Next, the main body control unit 111 determines whether or not the stored total number of movements of the second platen 62 is equal to or less than a preset maximum number of movements (step S12). In step S5, when the number of times of movement is equal to or greater than the maximum number of movements, it is determined that it is difficult to move to a portion where dirt is not attached, and the second platen 62 needs to be cleaned or replaced. After notifying the user via the I / F 107 (step S13), the conveyance of the document is stopped (step S14), and the reading request cannot be accepted (step S15). The maximum number of movements used for the determination in step S12 is preset in the storage area of the main body control unit 111. The inability to accept a read request in step S15 is a state in which an instruction for a read operation from the operation unit 108 is not accepted. Thus, until the maximum number of movements is reached in step S12, steps S5 to S12 are repeated, and the second platen movement is performed until the determination in step S7 becomes “No”, that is, until no stain exceeding the allowable amount is detected. The second platen 62 is moved by the motor 63.

  Next, the main body control unit 111 determines whether or not the second platen 62 has been cleaned or replaced and a cleaning completion notification has been received (step S16). If the cleaning completion notification has been received, the stored dirt position is determined. Erasing is performed (step S17), and the acceptance of the read request is canceled (step S18). Specifically, in step S17, when the operation unit 108 is input as a cleaning completion notification that the second platen 52 has been cleaned or replaced, information on the dirt position stored in the main body control unit 111 is displayed. It is supposed to be erased.

  Next, the main body control unit 111 turns off the light source unit 200 (step S20), determines whether there is a next document to be read (step S21), and if there is a next document, proceeds to step S1. Returning, if there is no next original, the platen contamination countermeasure process is terminated.

  FIG. 13 is a flowchart showing platen movement processing of the automatic document feeder according to the first embodiment of the present invention. This platen movement process shows the details of the process in step S9 of the platen contamination countermeasure process of FIG.

  As shown in FIG. 13, first, the main body control unit 111 starts driving the second platen movement motor 63 according to the current value of the rotation direction flag (forward rotation or reverse rotation) (step S31).

  Next, the main body control unit 111 determines whether or not the number of motor pulses of the driven second platen moving motor 63 is equal to or greater than a preset dirt detection image acquisition interval (Ld) (step S32). If the image acquisition interval (Ld) is exceeded, the second platen movement motor 63 is stopped (step S35), and the platen movement process is terminated. The dirt detection image acquisition interval (Ld) used in the determination in step S32 is a distance (for example, several tens of reading lines) to move the second platen 62 in one process of step S32. , Stored in advance in the storage area of the main body control unit 111.

  On the other hand, if it is less than the stain detection image acquisition interval (Ld) in step S32, that is, the number of motor pulses of the driven second platen movement motor 63 is less than the preset stain detection image acquisition interval (Ld). When the second platen moving motor 63 cannot rotate, the main body control unit 111 determines whether the first end detection sensor 250 or the second end detection sensor 251 has detected the end of the second platen 62. (Step S33) When the end of the second platen 62 is detected, the rotation direction flag is reversed to change the rotation direction of the second platen movement motor 63 to the reverse direction (Step S34), and the process proceeds to Step S35. . On the other hand, if the end of the second platen 62 is not detected in step S33, the process returns to step S32.

  As described above, in the platen contamination countermeasure process and the platen movement process, the main body control unit 111 causes the second platen movement motor 63 to move the second platen 62 when the document does not pass the reading position of the second reading unit 25. It is designed to move. Further, when the document does not pass the reading position of the second reading unit 25, the second platen 62 is moved by the second platen moving motor 63 and the white reference member 66 is read by the second reading unit 25. It has become. Further, when it is detected that dirt is attached to the second platen 62, the second platen 62 is moved by the second platen movement motor 63 to a position where the dirt is not detected. Further, the position of dirt attached to the second platen 62 is stored, and the second platen 62 is moved excluding the stored position of dirt. Further, when it is input that the second platen 52 has been cleaned or replaced, the information on the position of the dirt stored in the main body control unit 111 is erased.

  12 and 13, the case where the second platen moving motor 63 is driven to move the second platen 62 of the second reading unit 25 has been described. However, the second platen moving motor 53 is driven to drive the second platen moving motor 53. The movement of the second platen 52 of the one reading unit 20 is also performed in the same manner as the above processing.

  As described above, the automatic document feeder according to the present embodiment includes the first platen 61 that is fixed to the second reading unit 25 and covers the side facing the conveyance path of the second reading unit 25, and the second reading unit. 25, the second platen 62 disposed between the original fed to the reading position and the first platen 61, and the second platen 62 while maintaining the distance between the second platen 62 and the second reading unit 25. The second platen moving motor 63 that moves relative to the second reading unit 25 is provided, so that even if the second platen 62 is contaminated, the second platen 62 is moved relative to the second reading unit 25. As a result, since the original can be read at the reading position of the second reading unit 25 through the portion where the dirt on the second platen 62 is not adhered, the second reading unit 25 has the same focal depth image sensor with a shallow focal depth. From Even in this case, it is possible to obtain high-quality image data with excellent focus without being affected by dust, and the first platen 61 remains covered with the second reading unit 25. It is possible to prevent foreign matter from entering the reading unit 25. Therefore, reading can be performed satisfactorily without being affected by foreign matter regardless of the reading method.

  In the automatic document feeder according to the present embodiment, the second reading unit 25 is disposed on the upper surface in the conveyance path, and the second platen moving motor 63 is disposed between the second platen 62 and the second reading unit 25. Since the second platen 62 is moved in the sub-scanning direction of the second reading unit 25 while maintaining the distance, the second platen 62 is moved in the main scanning direction by moving the second platen 62 in the sub-scanning direction. Compared with the case, the moving distance of the second platen 62 can be shortened.

  In the automatic document feeder according to the present embodiment, the second reading unit 25 has guide grooves 65a and 65b that are in sliding contact with the second platen 62, and the second platen 62 extends along the guide grooves 65a and 65b. Therefore, the distance between the second platen 62 and the second reading unit 25 can be stabilized by moving the second platen 62 along the guide grooves 65a and 65b of the second reading unit 25. In particular, even when the second reading unit 25 is configured with an equal magnification contact image sensor with a shallow depth of focus, it is possible to acquire high-quality image data with excellent focus without being affected by dust.

  The automatic document feeder according to the present embodiment is disposed at a position facing the second reading unit 25 on the lower surface of the conveyance path, and the second reading unit 25 uses a white reference member 66 used for acquiring white reference data. Since the second reading unit 25, the second platen 62, and the white reference member 66 are provided with the housing 40a that supports the second reading unit 25, the second platen 62, and the white reference member 66 so as to maintain the mutual positional relationship. Since the positional relationship among the second reading unit 25, the second platen 62, and the white reference member 66 is maintained by the housing 40a, the positioning accuracy of the second reading unit 25, the second platen 62, and the white reference member 66 is improved. Even when the conveyance path is inclined, the positions of the second platen 62 and the white reference member 66 relative to the second reading unit 25 are not changed.

  Further, in the automatic document feeder according to the present embodiment, the main body control unit 111 causes the second platen movement motor 63 to cause the second platen 62 when the document does not pass the reading position of the second reading unit 25. Since the second platen 62 is moved during reading of each original when a plurality of originals are read, the next original is transferred after the original is conveyed and read. Time until conveyance and reading can be used effectively.

  Further, in the automatic document feeder according to the present embodiment, the main body control unit 111 causes the second platen movement motor 63 to cause the second platen 62 when the document does not pass the reading position of the second reading unit 25. The white reference member 66 is read by the second reading unit 25, so that the second platen 62 is read when the second reading unit 25 reads the white reference member 66 and acquires white reference data. It is possible to avoid the influence of dirt adhering to the surface.

  In the automatic document feeder according to the present embodiment, the white shading correction circuit 41 controlled by the main body control unit 111 preliminarily reads from the read data obtained by the second reading unit 25 reading the white reference member 66. Since the shading data is generated by calculating the peak for each pixel averaged with the set number of lines in the sub-scanning direction, the influence of the dirt on the second platen 62 on the shading data can be reduced. .

  In the automatic document feeder according to the present embodiment, the main body control unit 111 reads the white reference member 66 by the second reading unit 25 and then reads the document, and performs a shading process using the generated shading data. By detecting a level difference equal to or greater than a preset value from the result of the detection, the position of the dirt adhered to the second platen 62 is detected, so the position where the dirt of the second platen 62 is not adhered. Since the second platen 62 can be moved by the second platen movement motor 63 so that the second reading unit 25 reads the original via the second reading unit 25, the second reading unit 25 avoids the dirt adhesion position of the second platen 62. Thus, the original can be read.

  Further, in the automatic document feeder according to the present embodiment, when the main body control unit 111 detects that dirt is attached to the second platen 62, the dirt attached to the second platen 62 is not detected. Since the second platen 62 is moved by the second platen moving motor 63, the original can always be read through a portion where the dirt on the second platen 62 is not attached. It is possible to prevent the influence of dirt on the two platen 62 from affecting image data obtained by reading a document.

  Further, in the automatic document feeder according to the present embodiment, the main body control unit 111 stores the position of dirt attached to the second platen 62 and excludes the stored position of dirt to remove the second platen 62. Since the second platen 62 is not moved to the stored dirt adhering position, the second reading unit 25 can efficiently read the original by avoiding the dirt adhering position of the second platen 62. It can be carried out.

  Also, in the automatic document feeder according to the present embodiment, when it is input from the operation unit 108 that the second platen 52 has been cleaned or replaced, information on the position of the dirt stored in the main body control unit 111. Therefore, when the second platen 62 is cleaned or replaced, the position information for moving the second platen 62 is made dirty in the second platen 62 by erasing the information on the position of the dirt. It is possible to return to the state when there is no.

  Further, in the automatic document feeder according to the present embodiment, since the second reading unit 25 is configured by a 1 × contact image sensor, the second reading unit 25 is configured by a 1 × contact image sensor having a shallow focal depth. Even so, it is possible to obtain high-quality image data with excellent focus without being affected by dust.

(Second Embodiment)
FIG. 14 is a side view showing the configuration of the second platen of the automatic document feeder according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and description is abbreviate | omitted.

  As shown in FIG. 14, in the present embodiment, in the second reading unit 25, a second platen 306 made of a transparent sheet-like member is provided on the side of the first platen 61 that faces the document conveyance path. Is provided. Both ends of the second platen 306 are attached to the feed roller 301 and the take-up roller 302, respectively. The take-up roller 302 is driven by a moving motor 305. A drive transmission belt (not shown) is stretched between the feed roller 301 and the take-up roller 302, and the feed roller 301 is also rotated when the take-up roller 302 is rotated. The second platen 306 is supported by two support rollers 304.

  A first end detection sensor 250 is provided in the vicinity of the feed roller 301, and the first end detection sensor 250 detects the end of the second platen 306 attached to the feed roller 301. Yes. Further, a second end detection sensor 251 is provided in the vicinity of the take-up roller 302, and the end of the second platen 306 attached to the take-up roller 302 is detected by the second end detection sensor 251. It is like that. These second platen 306, delivery roller 301, take-up roller 302, support roller 304, and moving motor 305 are provided in case 300. The case 300 can be attached to and detached from the second reading unit 25 integrally. For this reason, when the entire area of the second platen 306 is dirty, the second platen 306 can be easily replaced with the case 300.

  The controller 100 detects when the end of the second platen 306 attached to the feed roller 301 is detected by the first end detection sensor 250 and when the end of the second platen 306 attached to the take-up roller 302 is the second end. When detected by the end detection sensor 251, the rotation direction of the moving motor 305 is switched. That is, when the second platen 306 is fed from the feed roller 301 and taken up by the take-up roller 302, and the first end detection sensor 250 detects the end of the second platen 306, the controller 100 rotates the moving motor 305. The direction is switched to the opposite direction, and the second platen 306 is fed from the take-up roller 302 and taken up by the feed roller 301.

  The operation in the present embodiment is performed in the same manner as in the first embodiment. That is, in the first embodiment, the second platen moving motor 63 is driven to move the second platen 62 of the second reading unit 25, or the second platen moving motor 53 is driven to drive the first reading unit. In the second embodiment, the same processing as that shown in the flowcharts of FIGS. 12 and 13 is performed, and the moving motor 305 is driven. The second platen 306 is moved.

  In the present embodiment, the moving direction of the second platen 306 is the sub-scanning direction, that is, the document conveying direction, but the moving direction of the second platen 306 is the main scanning direction, that is, the document width direction. A delivery roller 301 and a take-up roller 302 may be arranged.

  As described above, in the automatic document feeder according to the present embodiment, the second platen 306 is made of a transparent sheet, the take-up roller 302 that winds up the second platen 306, and the feed-out roller 301 that sends out the second platen 306. And a moving motor 305 for driving the take-up roller 302 and the feed roller 301, and the case 300 for housing the second platen 306, the take-up roller 302 and the feed roller 301 is integrated with the second reading unit 25. When the second platen 306 is contaminated, the second platen 306 is moved only by the take-up roller 302 and the feed roller 301 and the second platen 306 is moved through the non-dirty portion. Can read the original. Further, since the second platen 306, the take-up roller 302, and the delivery roller 301 can be integrally attached to and detached from the second reading unit 25 as one unit, it is easy even when the entire area of the second platen 306 is dirty. Can be exchanged.

  As described above, the automatic document feeder according to the present invention has the effect of being able to read well without being affected by foreign matter regardless of the reading method, and performs reading while moving the document. This is useful as an automatic document feeder.

1 is a cross-sectional view showing a configuration of an automatic document feeder according to a first embodiment of the present invention. FIG. 3 is a block diagram illustrating a configuration of a control unit of the automatic document feeder according to the first embodiment of the present invention. FIG. 3 is a block diagram illustrating a configuration of a second reading unit of the automatic document feeder according to the first embodiment of the present invention. FIG. 2A is a side view showing a configuration of a first reading unit of the automatic document feeder according to the first embodiment of the present invention. FIG. 2B is a front view showing the configuration of the first reading unit of the automatic document feeder according to the first embodiment of the present invention. (A)-(c) is a side view which shows the structure of the 1st reading part of the automatic document feeder based on the 1st Embodiment of this invention. FIG. 3 is a perspective view illustrating a configuration of a second reading unit of the automatic document feeder according to the first embodiment of the present invention. FIG. 3 is a perspective view illustrating a configuration of a second reading unit of the automatic document feeder according to the first embodiment of the present invention. 1 is a cross-sectional view showing a configuration of a white shading correction circuit of an automatic document feeder according to a first embodiment of the present invention. 3 is a conceptual diagram illustrating an average value calculation process in a white shading correction circuit of the automatic document feeder according to the first embodiment of the present invention. FIG. (A), (b) is a figure explaining the dust detection process of the automatic document feeder which concerns on the 1st Embodiment of this invention. (A), (b) is a figure explaining the dust detection process of the automatic document feeder which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the platen dirt countermeasure processing of the automatic document feeder according to the first embodiment of the present invention. It is a flowchart which shows the platen movement process of the automatic document feeder based on the 1st Embodiment of this invention. FIG. 6 is a side view showing a configuration of a second platen of an automatic document feeder according to a second embodiment of the present invention.

Explanation of symbols

20 1st reading part (reading means)
23 Reading exit roller (conveying means)
25 Second reading section (reading means)
27 CIS exit roller (conveyance means)
32 Guide member (white reference member)
40 Automatic document feeder 40a Housing (supporting member)
41 White shading correction circuit (shading data generation means)
51 First platen (first protective member)
52 Second platen (second protective member)
53 Second platen moving motor (moving means)
55a, 55b Guide groove 61 First platen (first protection member)
62 Second platen (second protective member)
63 Second platen moving motor (moving means)
65a, 65b Guide groove 66 White reference member 111 Main body control unit (movement control means, reading control means, dirt detection means, repeated movement control means, dirt position storage means, dirt position avoidance movement control means, erasure means)
301 Feeding roller (feeding means)
302 Winding roller (winding means)
305 Moving motor (driving means)
306 Second platen (second protection means)

Claims (13)

Conveying means for conveying the document in the conveying path;
In an automatic document feeder provided with reading means for reading a document conveyed by the conveying means at a reading position,
A transparent first protective member fixed to the reading means and covering a side of the reading means facing the conveyance path;
A transparent second protective member disposed between the original conveyed by the conveying unit to the reading position of the reading unit and the first protective member;
An automatic document feeder comprising: moving means for moving the second protective member relative to the reading means while maintaining a distance between the second protective member and the reading means. The reading means is disposed on an upper surface in the transport path;
The said moving means moves the said 2nd protection member in the subscanning direction of the said reading means, maintaining the distance between the said 2nd protection member and the said reading means. Automatic document feeder. The reading means has a guide groove in sliding contact with the second protective member;
The automatic document feeder according to claim 1, wherein the second protection member moves along the guide groove. A white reference member disposed at a position facing the reading unit on the lower surface of the conveyance path, and used by the reading unit to acquire white reference data;
A support member that supports the reading means, the second protection member, and the white reference member so as to maintain a mutual positional relationship between the reading means, the second protection member, and the white reference member. The automatic document feeder according to any one of claims 1 to 3, wherein The second protection member is made of a transparent sheet;
Winding means for winding the second protective member;
Delivery means for delivering the second protection member;
Drive means for driving the winding means and the delivery means,
The automatic according to any one of claims 1 to 4, wherein the second protection member, the winding means and the delivery means are integrally attached to and detached from the reading means. Document transport device.   6. The moving control means for moving the second protection member by the moving means when the document does not pass through the reading position of the reading means. An automatic document feeder according to claim 1.   Read control means for moving the second protective member by the moving means and reading the white reference member by the reading means when the document does not pass the reading position of the reading means. The automatic document feeder according to any one of claims 1 to 6.   Shading data generating means for generating shading data by calculating a peak for each pixel averaged with a preset number of lines in the sub-scanning direction from reading data obtained by reading the white reference member by the reading means. The automatic document feeder according to claim 7.   By reading the white reference member after reading the white reference member, reading the original, and performing a shading process using the shading data generated by the shading data generating means, and detecting a level difference greater than a preset value. 9. The automatic document feeder according to claim 8, further comprising a dirt detecting means for detecting a position of dirt attached to the second protective member.   When the dirt detecting means detects that the dirt is attached to the second protective member, the moving means until the dirt attached to the second protective member is not detected by the dirt detecting means. The automatic document feeder according to claim 9, further comprising a repetitive movement control unit that moves the second protective member. Dirt position storage means for storing the position of dirt attached to the second protective member detected by the dirt detection means;
The dirt position avoidance movement control means for removing the dirt position stored in the dirt position storage means and moving the second protection member by the repetitive movement control means. The automatic document feeder described in 1.   12. The automatic document feeder according to claim 11, further comprising an erasing unit for erasing information on a dirt position stored in the dirt position storage unit.   The automatic document feeder according to any one of claims 1 to 12, wherein the reading means is constituted by a unit-size contact image sensor.

Images