JP4407547B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus that reads an image on a sheet while conveying the sheet on which an image is recorded.

  There has been proposed an image reading apparatus that reads an image of a sheet on which the sheet on which the image is recorded is conveyed. In this type of image reading apparatus, a contact glass as a paper placement member is provided on a paper conveyance path, and the paper conveyed by the conveyance means is placed (supported) and light can be transmitted. An imaging element (photoelectric conversion element) such as a CCD (Charge Coupled Device) is provided on the contact glass side with respect to the conveyance path, and the reflected light of the light irradiated on the paper by the light source is passed through the contact glass. Detected and converted to an electrical signal. For example, an image processing unit provided in the image reading apparatus is connected to the image sensor, and captured image data of a sheet is generated based on an electrical signal from the image sensor. The light emitted from the light source is irradiated onto the paper on the contact glass, the reflected light is transmitted through the contact glass, and the photoelectric conversion element detects the reflected light and converts it into an electrical signal. Based on this electrical signal, for example, The image processing unit performs image processing to generate captured image data and obtain a captured image of the image on the paper.

  Here, if the configuration is such that the image of the paper is simply read by the imaging device, reading unevenness due to unevenness in the light amount of the light source and sensitivity of the imaging device will occur. Therefore, a white reference plate or the like is used to correct this reading unevenness. Color reference plates are provided. The color reference plate is disposed on the paper placement side of the contact glass (more specifically, on the paper conveyance path and on the optical axis of the image sensor), and the color of the color reference plate is read by the image sensor. The color reading on the color reference plate is performed prior to the image reading on the paper, and the image processing unit preliminarily creates captured image data of the color reference plate. Based on the captured image data of the color reference plate, the image processing unit detects the reading unevenness and creates a correction parameter corresponding to the reading unevenness. This correction parameter is used for correcting captured image data obtained by subsequent image reading of a sheet. The image processing unit corrects the captured image data of the paper image according to the correction parameter, thereby generating captured image data that can suppress the reading unevenness (hereinafter, shading correction). Accordingly, it is possible to obtain a captured image in which the reading unevenness is suppressed.

  As such a color reference plate for shading correction, there is one in which an endless belt is applied, which is disclosed in Patent Document 1 below.

  In the invention disclosed in Patent Document 1, the endless belt is disposed on the paper placement side of the contact glass. This endless belt also serves as the above-mentioned transport means, and transports the paper and presses the paper against the contact glass. A white film is applied to the endless belt, and it is used as the color reference plate for shading correction.

  However, in the invention disclosed in Patent Document 1, since the white film comes into direct contact with the paper when the paper is conveyed, there is a possibility that the white film may become dirty during long-term use.

  In view of this, an invention for removing dirt adhering to a color reference plate for shading correction has been proposed, and is disclosed in Patent Document 2 below.

  In the invention disclosed in Patent Document 2, the white reference plate as the color reference plate can be moved in and out of the conveyance path of the paper, and the white reference plate appears on the conveyance path when preparing the shading correction to create the correction parameters for the shading correction. On the other hand, the white reference plate is retracted from the conveyance path when reading the image of the paper. A cleaning unit is provided on the movement path of the white reference plate, and the cleaning unit adheres to the white reference plate by moving the white reference plate to rub against the white reference plate. It is designed to remove dirty dirt.

However, in the invention disclosed in Patent Document 2, reflected light from the white reference plate is detected by the image sensor through the contact glass when preparing for shading correction, so that the contact glass is contaminated with dust, paper dust, and the like. If the white reference plate is attached, the captured image of the white reference plate is affected by the contamination of the contact glass even if the white reference plate is not dirty.
JP-A-5-300306 JP-A-6-62245

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an image reading apparatus that can read the color of a color reference plate for shading correction without being affected by dirt on a paper placement member.

  An image reading apparatus according to a first aspect of the present invention includes a sheet placement member provided on one side of a predetermined conveyance path of a sheet on which an image is recorded, and the sheet placement member with respect to the conveyance path. Is provided on the opposite side, and an image sensor that reads an image of the paper that is transported along the paper placement member on the transport path, and a shading correction that is provided on the image sensor side with respect to the transport path. And a shading correction color reference plate for directly reading its own color by the image pickup device at the time of preparation.

  In the image reading apparatus according to the first aspect of the present invention, since the paper placing member and the imaging element are provided across the predetermined conveyance path of the sheet on which the image is recorded, the imaging element is arranged on the conveyance path. It is possible to directly read an image of a sheet conveyed along the sheet placing member.

  Here, in the present image reading apparatus, a color reference plate for shading correction is provided on the image sensor side with respect to the conveyance path, and the color reference plate is used at the time of shading correction preparation (here, at the time of shading correction preparation) In order to create a correction parameter for shading correction, when the image sensor reads the color of the color reference plate in advance, its own color is directly read by the image sensor. Therefore, even if the paper placement member is soiled with dust or paper dust, the image sensor can read the color of the color reference plate without being affected by the stain of the paper placement member.

The image reading apparatus according to the first aspect of the present invention is provided with the color reference plate and has an elastic force. When the shading correction preparation is performed, the image reading device is moved toward the image sensor. The color reference plate is moved to an image reading position where the image can be read, and when the image sensor reads the image on the paper, the color reference plate is moved away from the image reading position by moving itself. And a sheet pressing member that presses the sheet conveyed to the image reading position against the sheet placing member.

In the image reading apparatus according to the first aspect of the invention, the color reference plate is provided on the paper pressing member, and when the shading correction is prepared, the paper pressing member is moved so that the color reference plate is Are moved to an image reading position where the image on the paper can be read .

  On the other hand, when the image sensor reads the image of the paper conveyed to the image reading position, the color pressing plate is moved to the retracted position away from the image reading position by moving the paper pressing member, and the image reading position. The sheet conveyed to the sheet is pressed against the sheet placing member by the sheet pressing member and by the elastic force of the sheet pressing member. For this reason, the paper is transported along the paper placement member without being lifted or deformed from the paper placement member. As a result, the image pickup device can pick up an image of the paper with an appropriate focal length, so that the image quality of the picked-up image can be prevented from deteriorating.

Also as this, the image reading apparatus according to claim 1, wherein the movement, since it is configured to move between an image reading position and the retracted position the color reference plate by the paper pressing member is moved, the color reference plate A dedicated movable member or movable means is not required.

Further, in the image reading apparatus according to the first aspect of the present invention, the paper pressing member may be configured so that when the image sensor does not read either the image of the paper or the color of the color reference plate, It moves to the non-contact position which does not contact, It is characterized by the above-mentioned.

In the image reading apparatus according to the first aspect, when the image sensor does not read either the image of the paper or the color of the color reference plate, the paper pressing member moves to a non-contact retreat position that does not contact the paper being conveyed. Thus, the paper pressing member does not apply unnecessary force to the paper being conveyed. Therefore, the image reading apparatus according to the first aspect of the present invention can reduce the occurrence rate of paper conveyance jam or the like when neither the paper image nor the color of the color reference plate is read.

An image reading apparatus according to a second aspect of the invention is characterized in that a cleaning member for cleaning the surface of the color reference plate is provided in the middle of the movement path of the color reference plate.

In the image reading apparatus according to the second aspect of the present invention, since the cleaning member for cleaning the surface of the color reference plate is provided in the middle of the movement path of the color reference plate, the color reference is accompanied with the movement of the paper pressing member. The surface of the plate is cleaned by the cleaning member. As a result, even if dirt such as dust or paper dust adheres to the color reference plate, this dirt can be removed.

In the image reading apparatus according to claim 3 , black coating or flocking is applied to at least a part of the image sensor side surface with respect to the movement path of the paper pressing member among the paper pressing members. It is characterized by that.

In the image reading apparatus according to the third aspect of the present invention, at least a part of the image sensor side surface of the sheet pressing member is subjected to black coating or flocking with respect to the movement path of the sheet pressing member. The irregular reflection of light can be suppressed at a portion of the image sensor side surface where black coating or flocking is possible.

An image reading apparatus according to a fourth aspect of the invention is characterized in that the color reference plate is at least one of a white reference plate and a black reference plate.

In the image reading apparatus according to the invention described in claim 4 , since the color reference plate is at least one of white and black, the color reference plate of the image reading apparatus described in claim 4 is a color reference for shading correction. Ideal for use as a board.

An image reading apparatus according to a fifth aspect of the present invention is characterized in that, in the pressing member, a resolution evaluation pattern for examining the reading resolution of the image pickup device is arranged together with the color reference plate.

In the image reading apparatus according to the fifth aspect of the present invention, since the resolution evaluation pattern for examining the reading resolution of the image pickup element in the paper pressing member is juxtaposed with the color reference plate, for example, the image pickup element is colored when preparing for shading correction. The resolution evaluation pattern is read together with the reference plate, and the reading resolution of the image sensor is examined based on the captured image of the resolution evaluation pattern. As a result, the image reading apparatus according to the fifth aspect can detect such a problem that dirt such as dust or paper dust adheres to the light receiving surface of the image sensor.

  As described above, the image reading apparatus according to the present invention has an excellent effect of being able to read the color of the color reference plate for shading correction without being affected by the stain on the paper placement member.

  FIG. 1 schematically shows an image reading apparatus 10 according to an embodiment of the present invention. The image reading device 10 reads an image on the paper 30 while conveying the paper 30 on which an image is recorded (see FIG. 2). Hereinafter, for convenience of explanation, in FIG. 1, the left side is the upstream side in the transport direction, and the right side is the downstream side in the transport direction.

  The image reading apparatus 10 includes a housing 18 having a substantially rectangular box shape. The housing 18 has a pair of side walls 32 and 34 that face each other.

  A bottom wall 36 is integrally formed at the lower ends of the pair of side walls 32, 34. The bottom wall 36 is formed in a shape protruding somewhat downward. A central portion in the left-right direction of the bottom wall 36 is opened, and this opened portion is an image reading window 20.

  The lamp 12 is accommodated in the housing 18 as described above. The lamp 12 is disposed on the upper left side of the image reading window 20. The lamp 12 has a reflection plate 13 formed so as to wrap around the outer periphery from the lower left to the right substantially clockwise, and the lamp 12 extends in the lower right direction including the image reading window 20 side. Emits light. The lamp 12 is, for example, an Xe (xenon) lamp or a halogen lamp.

  A flat reflector 14 is housed inside the housing 18. The reflection plate 14 is disposed on the upper right side of the image reading window 20. The reflecting plate 14 corresponds to the lamp 12 and is disposed with the reflecting surface facing downward to the left. The reflecting plate 14 reflects the light emitted from the lamp 12 in the lower left direction including the image reading window 20 side. The reflecting plate 14 is, for example, an aluminum plate whose surface is polished.

  A photoelectric conversion element 16 as an imaging element is accommodated in the housing 18. The photoelectric conversion element 16 corresponds to the center position of the image reading window 20 and is disposed above the lamp 12 and the reflection plate 14. The photoelectric conversion element 16 is opposed to a back plate 28 as a sheet placing member described later, and its optical axis is directed downward. The photoelectric conversion element 16 reads an image of the sheet 30 conveyed along the back plate 28 by at least one of a roller pair 60 and a tension roller pair 61 which will be described later. Such a photoelectric conversion element 16 is, for example, a CCD (Charge Coupled Device) or a CMOS type line sensor, and detects light from below and converts it into an electric signal. The photoelectric conversion element 16 constitutes a photoelectric conversion means together with a contact reading type optical system (not shown) using a SELFOC lens or a reduction optical system (not shown) combining a plurality of lenses and mirrors.

  An image processing unit (not shown) is connected to the photoelectric conversion element 16, and the image processing unit generates captured image data of an image on the paper 30 based on an electrical signal from the photoelectric conversion element 16, and is used for shading correction. Correction parameters are created, or shading correction is performed on the captured image data of the image of the paper 30 in accordance with the correction parameters.

  In addition, the paper pressing member 26 is provided in the housing 18 at a portion of the outside (bottom surface) of the bottom wall 36 on the left side (upstream side in the transport direction) of the image reading window 20. That is, the sheet pressing member 26 is generally on the photoelectric conversion element 16 side with respect to the conveyance path of the sheet 30 (see, for example, the two-dot chain line in FIG. 1) and to the left of the optical axis position of the photoelectric conversion element 16 ( Located upstream in the transport direction). The paper pressing member 26 is a smooth member having an elastic force and having a relatively low surface frictional force. For example, a polyester film having a thickness of about 0.1 mm is suitable.

  The paper pressing member 26 is connected to a movable member such as a swing type solenoid or a linear type solenoid, or a movable means such as a combination of a motor and a rotary encoder, and is movable connected to the paper pressing member 26. The sheet pressing member 26 is rotated or linearly moved substantially along the bottom wall 36 by driving and controlling the member or the movable means by a control unit (not shown). Hereinafter, in this embodiment, it is assumed that a swing type or linear type solenoid is connected to the paper pressing member 26.

  By moving the sheet pressing member 26 as described above, the leading end of the sheet pressing member 26 moves to the image reading position on the optical axis of the photoelectric conversion element 16 on the conveyance path of the sheet 30 (see FIG. 1). It is possible. The leading end of the paper pressing member 26 can be moved from the image reading position to a retracted position (see FIG. 2) on the conveyance path of the paper 30 and escaped from the image reading position. In a state where the leading end is located at the retracted position, the sheet pressing member 26 presses the sheet 30 conveyed to the image reading position with its own elastic force against the back plate 28. Further, the leading end of the paper pressing member 26 can be moved from the retracted position to the storage position (see FIG. 3) near the edge of the image reading window 20, and the front end of the paper pressing member 26 is moved to the storage position. In the positioned state, the sheet pressing member 26 does not contact the sheet 30 (hereinafter, the position of the sheet pressing member 26 in this state is referred to as a non-contact retracted position).

  A white reference plate 27 as a color reference plate for shading correction is provided at the front end portion of such a paper pressing member 26. The white reference plate 27 is closely fixed to the surface on the photoelectric conversion element 16 side at the front end portion of the paper pressing member 26, and the white reference plate 27 is located between the image reading position and the storage position together with the front end portion of the paper pressing member 26. It can be moved via the retreat position. The white reference plate 27 has its own color white and is used as a reference color for shading correction, and its own color is imaged by the photoelectric conversion element 16 at the image reading position. The white reference plate 27 is, for example, a member such as a white plastic or a white painted metal plate.

  Further, a back plate 28 is disposed on the opposite side of the conveyance path of the paper 30 from the photoelectric conversion element 16. The back plate 28 has a plate shape except for both end portions in the left-right direction (conveyance direction), and the paper 30 is placed on the upper surface thereof. The upper surface (sheet placement surface) of the back plate 28 is opposed to the light receiving surface of the photoelectric conversion element 16, so that it is emitted from the lamp 12 and directly or indirectly (via the reflector 14). The light irradiated on the paper 30 on the face plate 28 is reflected toward the photoelectric conversion element 16 side.

  In the image reading apparatus 10 described above, the above-described lamp 12, photoelectric conversion element 16, and solenoid (not shown) of the paper pressing member 26 are connected to a control unit (not shown). The operation of each of the conversion element 16 and the solenoid of the paper pressing member 26 is controlled.

  Here, when the photoelectric conversion element 16 does not read either the image of the paper 30 or the color of the white reference plate 27, the white reference plate 27 is moved by moving the paper pressing member 26 according to an instruction from the control unit. 3 is located at the storage position. In addition, when the photoelectric conversion element 16 reads an image on the paper 30, the white reference plate 27 is positioned at the retracted position as shown in FIG. 2 by moving the paper pressing member 26 according to an instruction from the control unit. It has become. Further, when the photoelectric conversion element 16 reads the white reference plate 27 (hereinafter also simply referred to as preparation for shading correction), the white reference plate 27 is moved by the paper pressing member 26 in accordance with an instruction from the control unit. As shown in FIG. 1, it is positioned at the image reading position.

  In such an image reading apparatus 10, the creation of correction parameters for shading correction is executed prior to the image reading of the paper 30. When the correction parameter is created, the color of the white reference plate 27 is read, and the imaged image data of the white reference plate 27 is created in advance by the image processing unit. Based on the imaged image data of the white reference plate 27, the image processing unit detects reading unevenness due to unevenness in the light amount of the lamp 12 and sensitivity unevenness of the photoelectric conversion element 16, and the correction parameter corresponding to the reading unevenness is set. Created. This correction parameter is used for correcting captured image data obtained by subsequent image reading of the sheet 30. That is, the image processing unit corrects the captured image data of the image on the paper 30 according to the correction parameter, thereby generating captured image data that can suppress the reading unevenness. Accordingly, it is possible to obtain a captured image in which the reading unevenness is suppressed.

  The image reading apparatus 10 as described above is incorporated in, for example, the image forming apparatus 38 shown in FIG. 4 and is used as a quality inspection apparatus (image quality inspection apparatus) for images formed by the image forming unit 39 of the image forming apparatus 38. used. In the image forming apparatus 38, the image quality inspection by the image reading apparatus 10 is performed periodically, for example, once a day or at a timing designated by the user. The image reading apparatus 10 performs an image quality inspection by reading a test chart (image on the paper 30) for image quality inspection formed (printed) on the paper 30A. The image reading frequency of the image reading apparatus 10 used for such an application is relatively low.

  The image forming apparatus 38 described below is an apparatus for producing the above-described sheet 30 by forming a color image on the sheet 30A. The paper 30A is stored in a paper feed tray 58 of the image forming apparatus 38, and is fed out one by one by a pickup roller 59 provided on the paper 30A feeding side of the paper feed tray 58. The fed paper 30A is conveyed at a substantially constant speed along a conveyance path formed in the machine body by a predetermined number of roller pairs 60. Toner image formation for forming toner images of C (cyan), M (magenta), Y (yellow), and K (black) colors on the upper side of the conveyance path of the sheet 30A with an intermediate transfer belt 41 described later. The portions 40A, 40B, 40C, and 40D are arranged at substantially equal intervals along the circulation path (described later) of the intermediate transfer belt 41.

  The toner image forming units 40A, 40B, 40C, and 40D have the same configuration except for the color of the toner image to be formed, and the photosensitive drum 42 is arranged so that the axis is orthogonal to the circulation direction of the intermediate transfer belt 41. It has. Around the photosensitive drum 42, a charger 44 for charging the photosensitive drum 42, and light (laser light in the present embodiment) is irradiated on the charged photosensitive drum 42 to electrostatic latent image A predetermined color toner is supplied to the electrostatic latent image forming portion on the photosensitive drum 42 and the electrostatic latent image is developed to form a predetermined color toner image on the photosensitive drum 42. A developing device 48 to be formed, a transfer device 50 disposed opposite to the photosensitive drum 42, a static eliminator (not shown) that neutralizes the photosensitive drum 42, a cleaner blade (not shown) for removing residual toner on the photosensitive drum 42, and Each of the cleaner brushes is arranged and configured.

  The toner image forming units 40A, 40B, 40C, and 40D form toner images of different colors on the peripheral surface of the photosensitive drum 42 by the charger 44, the light exposure device 46, and the developing unit 48, and then the toner images. Is transferred (primary transfer) onto an intermediate transfer belt 41 described later by the transfer unit 50. A series of processes of charging, exposure (electrostatic latent image formation), development (toner image formation), and transfer in each of the toner image forming units 40A, 40B, 40C, and 40D is performed in each of the toner image forming units 40A, 40B, 40C, and 40D. The execution timing is controlled so that the toner images formed in the above overlap on the intermediate transfer belt 41. As a result, a full-color toner image (for example, a toner image corresponding to the test chart) is formed on the intermediate transfer belt 41.

  The intermediate transfer belt 41 is provided below the toner image forming portions 40A, 40B, 40C, and 40D. The intermediate transfer belt 41 is an endless belt and circulates counterclockwise in FIG. The intermediate transfer belt 41 circulates while being held between the photosensitive drums 42 of the toner image forming units 40A, 40B, 40C, and 40D and the transfer units 50. On the intermediate transfer belt 41, the toner image forming unit is circulated. The toner images formed by 40A, 40B, 40C, and 40D are transferred and superimposed.

  The lower end portion of the circulation path of the intermediate transfer belt 41 intersects with the conveyance path (forward conveyance path) of the paper 30 </ b> A fed out from the paper feed tray 58 described above. A secondary transfer roller pair 62 is provided to sandwich the intermediate transfer belt 41 at a position where the circulation path of the intermediate transfer belt 41 and the conveyance path of the sheet 30A intersect, and the secondary transfer roller pair 62 is fed into itself. By pressing the intermediate transfer belt 41 against the sheet 30A, the color image on the intermediate transfer belt 41 is collectively transferred (secondary transfer) to the sheet 30A.

  A fixing unit 52 is disposed downstream of the secondary transfer roller pair 62 in the transport direction. The fixing unit 52 is provided with a heating roller 54 and a pressure endless belt 56 facing each other, and the toner image is sandwiched between the heating roller 54 and the pressure endless belt 56 by sandwiching the paper 30A onto which the toner image has been transferred. A fixing device of a heat fixing type that fixes the toner image on the paper 30A by heating the forming surface and pressurizing the paper 30A. The sheet 30A on which the toner image is fixed in this manner is the sheet 30 described above.

  The above-described image reading device 10 is disposed downstream of the fixing unit 52 in the transport direction. The image reading device 10 reads the image (the test chart) on the paper 30 in the body of the image forming device 38. In the image forming apparatus 38, the controller 64 determines the print quality of the paper 30 based on the captured image data of the test chart output from the image reading apparatus 10, and the image formation of the image forming apparatus 38 is performed according to the determination result. An instruction (image quality adjustment instruction) for appropriately performing processing is given to each of the toner image forming units 40A, 40B, 40C, and 40D.

  A tension roller pair 61 is provided on the downstream side in the transport direction of the image reading device 10, and the paper 30 feeding speed is somewhat higher than that of the roller pair 60. Thus, the tension roller pair 61 cooperates with the roller pair 60 immediately upstream in the transport direction to pull the paper 30 along the transport direction to remove the slack in the transport direction of the paper 30 and to remove the paper 30 from the back. It is conveyed along the face plate 28.

  A discharge tray 64 is provided on the downstream side of the tension roller pair 61 in the conveying direction, and the discharge tray 64 receives the paper 30 taken out from the body of the image forming apparatus 38.

  In the image forming apparatus 38 as described above, the toner image forming units 40A, 40B, 40C, and 40D, the intermediate transfer belt 41, the secondary transfer roller pair 62, and the fixing unit 52 form an image on the paper 30A. An image forming unit 39 for manufacturing 30 is configured.

  Next, the operation of the embodiment of the present invention will be described.

  The light exposure device 46 operates, and laser light is emitted from the light exposure device 46 in accordance with the image data for creating the test chart. The laser beam forms an image on the photosensitive drum 42 charged by the charger 44. That is, the laser beam emitted from the light exposure device 46 is scanned on the photosensitive drum 42, whereby an electrostatic latent image is formed on the photosensitive drum 42.

  Next, the developing device 48 supplies toner of a predetermined color to the electrostatic latent image forming portion on the photosensitive drum 42 and develops the electrostatic latent image, whereby a toner image of the predetermined color is formed on the photosensitive drum 42. Is formed.

  This toner image is transferred (primary transfer) onto the intermediate transfer belt 41 by the transfer device 50. In this case, as the intermediate transfer belt 41 moves along the circulation path, the toner images of the respective colors are sequentially superimposed on the intermediate transfer belt 41 to form a full-color toner image (a toner image corresponding to the above test chart). The

  Next, the toner image formed on the intermediate transfer belt 41 is taken out from the paper feed tray 58 and conveyed by the roller pair 60 at the pressure contact position of the secondary transfer roller pair 62 (position where the secondary transfer roller pair 62 is in pressure contact). Transfer (secondary transfer) to the sheet 30A. The sheet 30A on which the toner image is transferred from the intermediate transfer belt 41 is conveyed to the fixing unit 52 by the roller pair 60, and is transferred from the intermediate transfer belt 41 to the sheet 30A by the heating roller 54 and the pressure endless belt 56. The toner image is heat-fixed.

  The paper 30A that has been subjected to the above processing is used as the paper 30 on which an image (the above-described test chart) is formed, and is conveyed onto the back plate 28 of the image reading apparatus 10 by the roller pair 60. Here, the sheet 30 conveyed onto the back plate 28 is in a state where the image surface (the surface on which the test chart is formed) is directed upward (on the photoelectric conversion element 16 side).

  In the image reading apparatus 10, the back plate 28 and the photoelectric conversion element 16 are provided to face each other across the conveyance path of the paper 30, so that the photoelectric conversion element 16 is conveyed along the back plate 28 on this conveyance path. The test chart of the paper 30 being read can be directly read.

  Here, when the photoelectric conversion element 16 reads the test chart of the sheet 30 conveyed to the image reading position (the position on the conveyance path of the sheet 30 and on the optical axis of the photoelectric conversion element 16), a control unit (not shown) When the paper pressing member 26 is moved by the solenoid according to the instruction, the white reference plate 27 is moved away from the image reading position (on the conveyance path of the paper 30 and upstream of the image reading position in the conveyance direction). The sheet 30 moved to the position) and conveyed to the image reading position is pressed against the back plate 28 by the sheet pressing member 26 and by the elastic force of the sheet pressing member 26 (see FIG. 2). For this reason, the paper 30 does not float from the back plate 28 or deforms (for example, the paper 30 bends, etc.) along the back plate 28 (while being in close contact with the back plate 28). Be transported. Thereby, since the photoelectric conversion element 16 can image the test chart of the paper 30 at an appropriate focal length, it is possible to prevent the image quality of the captured image of the test chart from being deteriorated.

  By the way, as a pre-process for imaging such a test chart, the image reading device 10 of the image forming device 38 creates a correction parameter for shading correction. When creating this correction parameter (when preparing for shading correction), the paper pressing member 26 is moved by the solenoid described above in accordance with an instruction from a control unit (not shown), so that the white reference plate 27 is moved to the image reading position. (See FIG. 1). In the image reading apparatus 10, since the white reference plate 27 for shading correction is provided on the photoelectric conversion element 16 side with respect to the conveyance path of the paper 30, the white reference plate 27 has its own color (white) converted to photoelectric. Read directly by element 16. Therefore, even if the back plate 28 is soiled with dust or paper dust, the photoelectric conversion element 16 can read the color of the white reference plate 27 without being affected by the stain on the back plate 28. The white reference plate 27 is preferably performed during movement of the sheet pressing member 26 so that the image of the sheet 30 can be read in a plurality of lines in order to suppress the influence of in-plane non-uniformity and the like.

  On the other hand, when the photoelectric conversion element 16 of the image reading apparatus 10 does not read either the image of the paper 30 or the color of the white reference plate 27, the paper pressing member 26 is moved by the solenoid according to an instruction from a control unit (not shown). By doing so (for example, when the paper pressing member 26 is pulled up so as not to press the paper 30 against the back plate 28), the paper pressing member 26 is moved to a non-contact retreat position where it does not contact the paper 30 being conveyed ( In this case, the white reference plate 27 is moved to the storage position (see FIG. 3), whereby the paper pressing member 26 does not apply unnecessary force to the paper 30 being conveyed. Therefore, the image reading apparatus 10 can reduce the occurrence rate of a paper jam or the like of the paper 30 when neither the image of the paper 30 nor the color of the white reference plate 27 is read.

  As described above, in the image reading apparatus 10, the paper pressing member 26 is moved to move the white reference plate 27 between the image reading position and the retracted position (more specifically, the image reading via the retracted position). Therefore, a dedicated movable member or movable means for moving the white reference plate 27 is not necessary.

  Further, the white reference plate 27 is attached to the paper pressing member 26 so as to face the side opposite to the transport path of the paper 30 with respect to the movement path (the photoelectric conversion element 16 side with respect to the transport path of the paper 30). Resistant to dirt such as dust, paper powder, or printing toner or ink (when the image forming apparatus is an inkjet apparatus).

  In the image reading apparatus 10, the white reference plate 27 is applied as the color reference plate, but the present invention is not limited to this. When black is required as the reference color for shading correction, for example, the present invention applies a black black reference plate as the color reference plate in place of the white reference plate 27, or the white reference plate 27 and the black reference plate. Both of the reference plate and the reference plate may be applied (for example, a black reference plate may be juxtaposed with the white reference plate 27). Alternatively, the white reference plate 27 may be read when the lamp 12 is turned off. As described above, when the black reference plate or both the white reference plate 27 and the black reference plate are applied as the color reference plate, the color reference plate for shading correction is used in the same manner as the white reference plate 27 of the present embodiment described above. Ideal for use as.

Further, the image reading apparatus 10 performs black coating (for example, matte black coating) or flocking processing (for example, matte black coating) on at least a part of the surface of the photoelectric conversion element 16 with respect to the movement path of the sheet pressing member 26 of the sheet pressing member 26. , Flocking paper, etc.). In this case, irregular reflection of light can be suppressed at a portion of the surface on the photoelectric conversion element 16 side where black coating or flocking is possible.
(Modification)
Hereinafter, a modified example of the image reading apparatus 10 according to the present embodiment will be described.

  In this modification, a brush 68 as a cleaning member is attached to the outside of the bottom wall 36 of the housing 18 and protrudes on the movement path of the paper pressing member 26.

  As shown in FIGS. 5 and 6, a guide member 66 having a plate-like portion is provided below the bottom wall 36 in the transport direction upstream of the image reading window 20 in the housing 18. The guide member 66 has a width that is orthogonal to both the conveyance direction of the paper 30 (left and right direction in FIGS. 5 and 6) and the optical axis direction of the photoelectric conversion element 16 (up and down direction in FIGS. 5 and 6). In the direction, both end portions (not shown) are integrated with both end portions in the width direction of the housing 18.

  A gap is provided between the main part of the guide member 66 and the bottom wall 36 of the housing 18, and the paper pressing member 26 described above is inserted into the gap. The guide member 66 inserts the paper pressing member 26 into the gap. As shown in FIG.

  A brush 68 is provided in the middle of the movement path of the white reference plate 27 (here, the movement path between the retracted position and the storage position). The brush 68 is attached to the outer side (lower surface side) of the bottom wall 36 in the gap, and protrudes on the moving path of the white reference plate 27. The brush 68 cleans the surface of the white reference plate 27 by moving the white reference plate 27 at the position where the brush 68 is disposed and rubbing the surface of the white reference plate 27 against the brush 68.

  That is, when the white reference plate 27 moves the arrangement position of the brush 66 as the paper pressing member 26 moves, the surface of the white reference plate 27 is rubbed against the brush 68. As a result, the surface of the white reference plate 27 is cleaned. Thereby, even if dirt such as dust or paper dust adheres to the white reference plate 27, this dirt can be removed. In this way, the measure against contamination of the white reference plate 27 can be further enhanced.

  In the modification of the present invention, the brush 68 is applied as the cleaning member, but the modification of the present invention is not limited to this. In the modified example of the present invention, a cleaning blade may be applied as the cleaning member instead of the brush. In this case, the same effect as that of the modified example is achieved.

  The image reading apparatus 10 according to the embodiment of the present invention and the modifications thereof have been described above, but the present invention is not limited to this. For example, in the present invention, a resolution evaluation pattern such as a resolution evaluation chart for evaluating the resolution of the photoelectric conversion element 16 is placed at the front end portion of the paper pressing member 26 together with a color reference plate (for example, the above-described white reference plate 27). May be. In this case, for example, when preparing for shading correction, the paper pressing member 26 is slightly moved in accordance with an instruction from a control unit (not shown) to move the resolving power evaluation pattern at the image reading position, and the photoelectric conversion element 16 and the color reference plate together with the resolving power The evaluation pattern is read, and the reading resolution of the photoelectric conversion element 16 is examined based on the captured image of the resolution evaluation pattern. As a result, the image reading apparatus 10 can detect such a problem that dirt such as dust or paper dust adheres to the light receiving surface of the photoelectric conversion element 16.

1 is a diagram schematically illustrating an image reading apparatus according to an embodiment of the present invention, and is a diagram illustrating a state in which a white reference plate is positioned at an image reading position. It is a figure corresponding to FIG. 1 which shows the state in which a white reference board is located in a retracted position. FIG. 2 is a view corresponding to FIG. 1 illustrating a state where a sheet pressing member is located at a non-contact retreat position. 1 is a diagram showing an outline of an image forming apparatus incorporating an image reading device. It is a figure which shows the outline of the modification of an image reading apparatus. It is a principal part enlarged view of FIG.

Explanation of symbols

10 Image Reading Device 16 Photoelectric Conversion Element (Imaging Element)
26 Paper pressing member 27 White reference plate (color reference plate)
28 Back plate (paper placement member)
30 Paper 68 Brush (cleaning member)

Claims (5)

A paper placement member provided on one side of a predetermined conveyance path of paper on which an image is recorded;
An image sensor that is provided on the opposite side of the transport path with respect to the paper placement member and reads an image of the paper that is transported along the paper placement member on the transport path;
A color reference plate for shading correction, which is provided on the image sensor side with respect to the conveyance path, and which directly reads its own color by the image sensor when preparing for shading correction;
With
The color reference plate is provided and has elasticity, and when the shading correction is prepared, the color reference plate is moved to an image reading position where the image pickup device can read the image on the paper by moving itself. When the image sensor reads the image on the paper, the image sensor moves to move the color reference plate to a retracted position that escapes from the image reading position, and moves the paper conveyed to the image reading position. A paper pressing member that presses against the paper mounting member;
The paper pressing member is moved to a non-contact position where it does not come into contact with the paper being transported when the image sensor reads neither the image of the paper nor the color of the color reference plate .
An image reading apparatus.   In the middle of the movement path of the color reference plate, a cleaning member for cleaning the surface of the color reference plate is provided.
  The image reading apparatus according to claim 1.   At least a part of the image sensor side surface with respect to the movement path of the paper pressing member among the paper pressing members is subjected to black coating or flocking processing,
  The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus.   The color reference plate is at least one of a white reference plate and a black reference plate.
  The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus.   In the pressing member, a resolution evaluation pattern for examining the reading resolution of the image sensor is juxtaposed with the color reference plate.
  The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus.

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