JP2006148281A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus provided with a close contact image sensor that prevents its shading member from splotching with dirt of an original document without the need for provision of a mechanism for moving the shading member. <P>SOLUTION: An interval A between an image reading position 24 and the shading member 45 is selected widely more than an interval B between the close contact image sensor and a guide member for guiding the document C to the image reading position 24 of the close contact image sensor 40. Thus, the document C is carried without being in contact with the shading member 45. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image reading apparatus including a shading member that serves as a reference for shading correction.

  In an image reading apparatus used to capture image data into a copying machine, facsimile, or computer, a device that uses a reduction optical system composed of a plurality of mirrors, a lens, and an image sensor as a means for reading an image does not require a mirror. Some use a contact image sensor.

  When the reduction optical system is used, a large space is required because the optical path becomes long. However, since the contact image sensor reads an image in contact with the original, an optical path is not necessary and the optical path can be arranged in a narrow space. For this reason, a contact type image sensor is used in a small-sized image reading apparatus, and a reduction optical system and a contact type image sensor are often used together in an image reading apparatus capable of reading images on both sides of a document. .

  The contact image sensor includes a large number of light receiving elements, and the state of sensitivity, output, and the like of each light receiving element changes separately due to changes over time, ambient temperature changes, and the like. When the state of the light receiving element changes, even the same color is converted into an electrical signal as a different color. Therefore, the accuracy of the image read by the contact type image sensor in which the state of each individual light receiving element varies varies, such as color unevenness. It is falling. Therefore, in order to correct the variation in the state of the individual light receiving elements, the white reference data is read from the white shading member, and shading correction based on that is performed.

If the shading member is disposed at the reading position of the contact image sensor, dirt may adhere to the shading member from the document, and reference data cannot be obtained accurately, and shading correction may not be possible. For this reason, for example, in Patent Document 1, the contact image sensor is movable with respect to the document conveying roller and the shading member (white member). In Patent Document 2, the contact image sensor is contacted with the movable shading member. By moving the reading roller away from the contact image sensor, the shading member is moved to the reading position of the contact image sensor only during shading correction (pre-scan), and in other cases the contact image sensor There has been proposed an image reading apparatus that retracts to a position where a document to be read is not touched.
JP-A-7-177320 (pages 5-6, FIGS. 2, 3) JP-A-10-136167 (page 3, FIG. 3)

  However, in the image reading apparatus proposed in Patent Document 1, since it is necessary to provide a mechanism for moving the contact image sensor, noise is generated when the mechanism is operated, and the apparatus is complicated. Manufacturing costs increase due to the increase in parts.

  In the image reading apparatus proposed in Patent Document 2, it is necessary to provide a mechanism for moving the shading member to the reading position of the contact image sensor by separating the reading roller from the contact image sensor. Similar to the image reading apparatus, there are problems of noise and manufacturing cost.

  Therefore, an object of the present invention is to provide an image reading apparatus that can perform highly accurate shading correction without generating noise, and has a simple configuration and low manufacturing cost.

  (1) In order to achieve the above object, the present invention provides a contact image sensor that reads an image of a document, a guide member that guides the document to a reading position of the contact image sensor, and reading by the contact image sensor. In the image reading apparatus including a shading member used for shading correction at a position opposite to the position, a distance from the shading member to the reading position of the contact image sensor is determined from the rear end of the guide member in the document conveyance direction to the contact It is characterized by being longer than the distance to the mold image sensor.

  According to this configuration, the document is guided to the reading position of the contact image sensor by the guide member, and is conveyed without touching the shading member.

  (2) Further, in the image reading apparatus having the above-described configuration, the present invention is characterized in that the shading member is a roller supported rotatably.

  According to this configuration, shading correction is performed based on the white reference data obtained by reading the rotating roller (shading member) for a certain period of time.

  (3) According to the present invention, in the image reading apparatus having the above configuration, a roller cleaning member is attached to the roller.

  According to this configuration, a roller cleaning member such as a brush or a rubber blade is brought into contact with the rotating roller (shading member) to remove dust and dirt adhering to the roller.

  (4) Further, in the image reading apparatus having the above-described configuration, the entire guide member or a part of the rear end portion in the document transport direction of the guide member is made of an elastic body, and the rear end in the document transport direction of the guide member is the contact type It is in contact with the image sensor.

  According to this configuration, the rear end portion of the guide member in the document conveying direction is arranged to contact the contact image sensor, and the document guided to the guide member is connected to the rear end portion of the guide member made of an elastic body and the contact image sensor. And is conveyed while closely contacting the reading position of the contact image sensor.

  (1) According to the present invention, since the document is guided to the reading position of the contact image sensor by the guide member and conveyed without touching the shading member, a mechanism for moving the shading member relative to the contact image sensor is provided. Thus, an image reading apparatus can be obtained in which dirt on the document does not directly adhere to the shading member. Therefore, highly accurate shading correction can be performed based on the white reference data obtained from this shading member, and since it is not necessary to move the shading member relative to the contact image sensor, no noise is generated. In addition, an image reading apparatus that is simple in configuration and has few parts and is inexpensive to manufacture can be obtained. In addition, since the positions of the shading member and the contact image sensor are not changed, the white reference data used for the shading correction can always be read under the same conditions, so that the accuracy of the shading correction can be maintained.

  (2) Further, according to the present invention, even when the shading member becomes dirty due to dust adhering in the image reading apparatus or the like, the shading member is used as a roller, and the rotating shading member is read for a certain period of time. By obtaining the white reference data, it is possible to disperse the influence of the stain on the obtained white reference data, and by using the white reference data, the accuracy is greatly reduced as compared with the case where the shading member is not dirty. Without any shading correction.

  (3) According to the present invention, even when a shading member made of a roller is soiled, dirt such as dust is removed by bringing a roller cleaning member such as a rubber blade or a brush into contact with the rotating shading member. Even if dirt remains, by obtaining the white reference data from the rotating shading member, it is possible to perform shading correction without significantly reducing accuracy compared to the case where the shading member is not dirty.

  (4) Further, according to the present invention, since the entire guide member or a part of the rear end portion in the document conveying direction may be an elastic body and the rear end may be brought into contact with the contact image sensor, the guide member is made of a hard material. The guide member is not required to have a high dimensional accuracy and assembly accuracy for providing a gap that allows a document to pass between the contact image sensor as in the case of the case, and the dimensional accuracy and the assembly accuracy are provided with a margin. Therefore, an image reading apparatus can be obtained at a low cost.

  A first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic configuration diagram of a copying machine 10 provided with a document conveying device 20 according to an embodiment of an image reading apparatus of the present invention, and FIG. 2 is a partially enlarged view of the vicinity of a contact image sensor 40.

  First, the configuration and operation of each part of the copying machine 10 will be described. The copying machine 10 includes a main body 11 and a document conveying device 20 according to the embodiment of the image reading apparatus of the present invention placed above the main body 11. A control device 13 for controlling the entire operation of the copying machine 10 such as an image forming operation, an image reading operation, and a document conveying operation is provided on the upper portion of the main body 11.

  The document feeder 20 is attached to the main body 11 so that it can be opened and closed with the back side of the paper as a fulcrum. The document conveying device 20 also serves as the second image reading device 20. The document conveying device 20 includes a document feeding tray 21, a document conveying unit 22, a document discharge tray 25, a document cover 26, and a contact image sensor 40. Prepare. The document discharge tray 25 is integrally formed as a part of the upper surface of the document cover 26. The document feed tray 21 forms the upstream end of the document transport path d, and the document discharge tray 25 forms the downstream end of the document transport path d. In the document conveyance path d in the document conveyance unit 22, a pickup roller 22a, a registration roller pair 22b, a conveyance roller pair 22c, a guide member 22d, and a discharge roller pair 22e are provided in this order from the upstream side in the document conveyance direction. A contact image sensor 40 is disposed at a position facing the guide member 22d with the document conveyance path d interposed therebetween. Further, the first image reading position 23 is set to a position facing the conveying roller pair 22c on the upper surface of the transparent glass platen 12 on the upper surface of the main body 11, and the second image reading position 24 is a contact image sensor. It is set on the surface facing the 40 document transport path d.

  In the case of a so-called sheet-through method, when a copy start button (not shown) is pressed, the document C with images on both sides set on the document feed tray 21 is transported along the document transport path d by the rollers, and halfway. An image on one surface is read by the first image reading device 30 at the first image reading position 23, and the other image is read by the contact image sensor 40 of the second image reading device 20 at the second image reading position 24. The image of the surface is read. In the case of the document fixing method, the document (not shown) placed on the stationary document reading position 28 set on the upper surface of the platen 12 and pressed by the document cover 26 has an image on the surface in contact with the platen 12. 1 is read by one image reading device 30.

  The first image reading device 30 is disposed on the upper portion of the main body 10, and includes an exposure lamp 31 and a reflecting plate 32, a first mirror 33, a second mirror 34, a third mirror 35, a condenser lens 36, An image sensor (for example, a line type CCD) 37 is provided. The exposure lamp 31 and the first mirror 33 are mounted on a carriage 38 and are provided so as to be horizontally movable in FIG.

  When reading the image of the document C conveyed by the sheet-through method, the carriage 38 moves directly below the first image reading position 23 to expose the document C to which the irradiation light from the exposure lamp 31 is conveyed. . The irradiated light is reduced and imaged on the CCD 37 through the first mirror 33, the second mirror 34, the third mirror 35, and the condenser lens 36, and is read out as an electric signal through a photoelectric conversion process. On the other hand, when reading the image of the document by the document fixing method, the exposure lamp 31 and the first mirror 33 on the carriage 38 that moves to the right in FIG. By reading and scanning the document, the irradiation light is reduced and imaged on the CCD 37, read through the photoelectric conversion process to become an electrical signal, and this electrical signal is sent to the control device 13.

  Also at the second image reading position 24, only in the case of the sheet-through method, the original image is read by the contact type image sensor 40 provided in the second image reading apparatus 20 so as to become an electric signal. It is sent to the control device 13.

  Below the main body 11, a paper feeding device 50, an image forming unit 60, and a fixing device 70 are provided. First, the sheet feeder 50 will be described. A paper feed cassette 51 for storing paper P is disposed at the lowermost part of the main body 11, and the paper P is sent from here to the transport path e by a pickup roller 52, and is transported by a transport roller pair 53 and a registration roller pair 54. It is conveyed to the image forming unit 60.

  Next, the image forming unit 60 will be described. The image forming unit 60 includes a photosensitive drum 61 and a charger 62, an optical scanning unit 63, a developing device 64, a transfer roller 65, and a cleaning device 66 disposed around the photosensitive drum 61. The photosensitive drum 61 rotates clockwise, and first, the surface thereof is uniformly charged by the charger 62. Next, laser light is applied from the optical scanning unit 63 to the surface of the photosensitive drum 61 based on the electrical signal of the image read by the first image reading device 30 or the second image reading device 20 and sent to the control device 13. , The charge corresponding to the portion of the image formed on the paper P or the portion other than the image is erased, and an electrostatic latent image is formed. Then, toner is supplied to the electrostatic latent image by the developing device 64, and the electrostatic latent image is visualized as a toner image.

  When the photosensitive drum 61 further rotates and the toner image comes to a position facing the transfer roller 65, the sheet P is conveyed between the photosensitive drum 61 and the transfer roller 65 by the registration roller pair 54 accordingly. It will be. At this time, the toner image on the surface of the photosensitive drum 61 is transferred onto the paper P by applying a voltage having a polarity opposite to the charging polarity of the toner to the transfer roller 65. The toner remaining on the surface of the photosensitive drum 61 without being transferred to the paper P is removed by the cleaning device 66.

  On the other hand, the paper P onto which the toner image has been transferred is conveyed to a fixing device 70 comprising a heating roller 71 and a pressure roller 72, where the toner image is heated and pressurized and fixed on the paper P. Thereafter, the paper P is transported through the transport path e and is discharged to the paper discharge tray 82 by the discharge roller pair 81.

  Next, shading correction will be described. The contact image sensor 40 provided in the second image reading device 20 includes a light emitting body 40a such as an LED and a large number of light receiving elements 40b arranged in the front-rear direction of the paper surface as shown in FIG. The irradiation light of the body 40a irradiates and reflects the original C conveyed. The irradiation light transmitted through the second image reading position 24 is read by the light receiving element 40b so as to become an electric signal through a photoelectric conversion process. The individual light receiving elements 40b vary in the state of sensitivity, output, and the like due to changes with time and ambient temperature. The accuracy of the image read by the contact image sensor 40 in which the state of each of the light receiving elements 40b varies is reduced. Therefore, in order to correct the variation in the state of the individual light receiving elements 40b, the white shading member 45 is irradiated with the light emitting body 40a, and the irradiation light transmitted through the second image reading position 24 is read as white reference data. Based on the read result, the control device 13 performs shading correction. The shading correction is performed immediately after turning on the power of the copying machine 10 or when the accumulated usage time reaches a predetermined time after reading a predetermined number of images.

  In the present embodiment, as shown in FIG. 2, the shading member 45 is made of a plate-like member, and is provided at a position facing the second image reading position 24 with the sheet conveyance path d interposed therebetween. Further, the surface facing the second image reading position 24 is white suitable for shading correction. The guide member 22d has a gap that allows the original C to pass through the contact image sensor 40 so as to guide the conveyed original C so as to contact the second image reading position 24, and the first guide member 22d. The second image reading position 24 and the shading member 45 are arranged so as not to be positioned. Here, the interval A between the shading member 45 and the second image reading position 24 is set larger than the interval B between the rear end of the guide member 22d in the document conveying direction and the contact image sensor 40. Here, since the contact type image sensor 40 has a shallow depth of field, the shading member 45 may not be focused depending on the width of the interval A, but if the white reference data is obtained from the shading member 45, There is no problem because it is good.

  With this configuration, since the conveyed document C does not touch the shading member 45, dust and dirt attached to the document C do not directly adhere to the shading member 45 from the document C, and the second shading member 45 is not touched. The surface facing the image reading position 24 can maintain a clean white state. Therefore, since the second image reading apparatus 20 can obtain accurate white reference data, it can perform highly accurate shading correction. Further, since it is not necessary to move the contact image sensor 40 and the shading member 45 unlike the image reading devices proposed in Patent Document 1 and Patent Document 2, the configuration is simple and the number of parts can be reduced. It can be manufactured at low cost both in terms of cost and material cost. Further, since neither the second image reading position 24 nor the shading member 45 is moved, the interval A is constant, and the white reference data can always be read by the contact image sensor 24 under the same conditions.

  A second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a partially enlarged view of the vicinity of the contact image sensor 40 according to the second embodiment.

  In the second embodiment, as shown in FIG. 3, the shading member 45 is a roller, and the second image reading is performed in the axial direction at a position facing the second image reading position 24 across the paper conveyance path d. It is provided so as to be parallel to the position 24 and rotatable about the axis. Therefore, the distance A from the surface of the shading member 45 to the second image reading position 24 is constant even when the shading member 45 rotates. The surface of the shading member 45 is white suitable for shading correction.

  With this configuration, even when the shading member 45 is contaminated due to some cause such as dust adhering to the inside of the document conveying unit 22, the rotating shading member 45 is read for a certain period of time to obtain white reference data. By accumulating in the control device 13 and calculating the time average of the white reference data for each light receiving element 40b, the influence of the stain on the obtained white reference data can be averaged and dispersed. By using the data, it is possible to perform shading correction without significantly reducing accuracy compared to the case where the shading member 45 is not dirty.

  In the second embodiment, a roller cleaning member 46 such as a brush or a rubber blade may be provided so as to contact the shading member 45. Thereby, dust is removed from the rotating shading member 45. Further, even when dirt that cannot be removed by the roller cleaning member 46, such as dirt that is rubbed with toner, is obtained by obtaining the white reference data from the rotating shading member 45, the contamination of the obtained white reference data can be reduced. The influence can be dispersed.

  A third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a partially enlarged view of the vicinity of the contact image sensor 40 according to the third embodiment.

  In the third embodiment, as shown in FIG. 4, an elastic member 22 f made of an elastic body is attached to the rear end of the guide member 22 d in the document conveyance direction, and the elastic member 22 f is brought into contact with the contact image sensor 40. Further, the elastic member 22f is disposed so as not to be positioned between the second image reading position 24 and the shading member 45. The document guided to the guide member 22 d passes between the elastic body 22 f and the contact image sensor 40 and is conveyed while being in close contact with the second image reading position 24.

  When the guide member 22d is made of a hard material, a high dimensional accuracy and assembly accuracy are provided in the guide member 22d in order to provide a gap that allows a document to pass between the guide member 22d and the contact image sensor 40. Was necessary. However, with this configuration, the elastic body 22f may be disposed so as to be in contact with the contact image sensor 40. Therefore, a margin can be given to the dimensional accuracy and assembly accuracy of the guide member 22d and the elastic member 22f. The second image reading device 20 can be produced at low cost. Furthermore, since the document is conveyed while being in close contact with the second image reading device 24, the focused image sensor 40 having a shallow depth of field can stably read the focused image.

  In the third embodiment, the guide member 22d and the elastic member 22f may be integrated so that the entire guide member 22d is an elastic body, and the rear end portion in the document transport direction of the guide member 22d is brought into contact with the contact image sensor 40. Similar effects can be obtained.

  The image reading apparatus according to the present invention can be generally used for an image reading apparatus such as a scanner apparatus that captures image data into a computer, or an apparatus having an image reading unit such as a copying machine or a facsimile.

1 is a schematic configuration diagram of a copying machine including a document conveying device according to a first embodiment of an image reading apparatus of the present invention. Partial enlarged view around the contact image sensor according to the first embodiment Partial enlarged view of the vicinity of the contact image sensor according to the second embodiment Partial enlarged view of the vicinity of the contact image sensor according to the third embodiment

Explanation of symbols

22d Guide member 22f Elastic member 40 Contact type image sensor 45 Shading member 46 Roller cleaning member C Document

Claims (4)

A contact image sensor that reads an image of a document, a guide member that guides the document to a reading position of the contact image sensor, and a shading member that is used for shading correction at a position facing the reading position of the contact image sensor. In the image reading apparatus provided,
An image reading apparatus, wherein a distance from the shading member to a reading position of the contact image sensor is longer than a distance from a rear end of the guide member in the document conveyance direction to the contact image sensor.   The image reading apparatus according to claim 1, wherein the shading member is a roller that is rotatably supported.   The image reading apparatus according to claim 2, wherein a roller cleaning member is attached to the roller.   2. The guide member according to claim 1, wherein all of the guide member or a part of a rear end portion in the document conveying direction is made of an elastic body, and a rear end of the guide member in the document conveying direction is in contact with the contact image sensor. 4. The image reading apparatus according to any one of 3 above.

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