JP2009124202A - Image reading apparatus and image forming apparatus with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent vertical streaks on a sheet in forming an image corresponding to a subsequent original on a sheet when a contamination deposition is generated on a contact glass during reading a plurality of continuous images. <P>SOLUTION: In both a front end detecting portion G1 and a rear end detecting portion G2 of an original G to be scanned, if portions in which the light receiving quantity of a CCD 14 is less than a threshold Hb are generated ("YES" in S3, S7), and the positions thereof match ("YES" in S10), it is considered that the contamination deposition t is generated on the contact glass 18a, and the emission quantity of corresponding LED devices L16, L17 is increased to allow the light receiving quantity to show a failure in the threshold Hb. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that reads an image based on reflected light when a document is irradiated in a line shape by a light source element that is a point light source, and an image forming apparatus including the image reading apparatus.

  An image reading apparatus used in an image forming apparatus such as a copying machine, a printer, or a facsimile irradiates an image surface of a document with a light source, and guides the reflected light to a solid-state imaging device such as a CCD through an imaging lens. read. Conventionally, rod-shaped light sources such as xenon lamps and cold cathode lamps have been used as light sources. Recently, however, light source elements such as LEDs (LED elements), which are point light sources with lower cost and longer life than these, are used. There has also been proposed a method in which a plurality of lines are aligned in the main scanning direction.

  By the way, when a foreign substance such as dirt or dust adheres to the reading optical system, the light emitted from a plurality of LED elements and reaching the CCD is insufficient in the amount of light received by the CCD at the location corresponding to the foreign substance. Become. In such a case, when the original is passed through the reading position set on the contact glass, that is, when the original is scanned, the output image output on the sheet based on the read image has a sheet passing width direction (main In the scanning direction), a single vertical streak occurs from the leading edge to the trailing edge of the sheet along the document conveyance direction (sub-scanning direction) at a position corresponding to the foreign matter, thereby degrading the quality of the output image. .

Therefore, in Patent Document 1, the light emission amount of the LED element is adjusted at the time of shading correction to suppress a decrease in the light reception amount of the CCD due to a foreign substance and to remove vertical stripes. That is, at the time of shading correction, the LED element is irradiated so that the white reference plate is irradiated by a plurality of LED elements, and the amount of light (received light amount) that is reflected by the white reference plate and reaches the CCD becomes uniform in the longitudinal direction of the CCD. Is adjusted individually or for each of a plurality of LED elements. At this time, the CCD pixel corresponding to the position of the foreign object is specified, and the light emission amount of the LED element corresponding to the pixel is adjusted to suppress the decrease in the light reception amount based on the foreign object, thereby preventing the occurrence of vertical stripes. is doing.
JP 2001-148765 A

  However, in the above-described prior art, the presence or absence of foreign matter attached to the optical system is detected at the time of shading correction. However, since shading correction is not performed for each document, the document is being read and scanned. The foreign matter adhering to the contact glass is not detected until the next shading correction. For this reason, when the adhesion of foreign matter is detected during the next shading correction, vertical streaks are detected from the output image corresponding to which original among the plurality of originals read from the previous shading correction to the next shading correction. It is difficult to know what happens. For this reason, when the adhesion of foreign matter is detected, the reading operation is interrupted, and it is necessary to read several previous documents again, which is complicated. Further, when an image is output based on an image read before the reading operation is interrupted, a plurality of output images with vertical stripes are likely to be formed.

  Therefore, according to the present invention, even when a foreign object adheres to the contact member in the middle of the flow reading of the original, it is not necessary to interrupt the flow reading of the original and output of the image based thereon, and even if it is not interrupted. An object of the present invention is to provide an image reading apparatus in which only one image is likely to contain vertical stripes, and an image forming apparatus having the image reading apparatus.

  The invention according to claim 1 irradiates light from the light source and reflects the light when the image surface of the document passes in the sub-scanning direction on the reading line set in the main scanning direction on the light-transmitting contact member. The present invention relates to an image reading apparatus that receives light with a solid-state imaging device through an imaging lens and reads an image. The image reading apparatus according to the present invention comprises a plurality of light source elements that are arranged in a line in the main scanning direction to constitute the light source and whose light emission amount can be individually controlled, and a light reception amount received by the fixed imaging element. A received light amount detecting means for detecting that the received light amount in the main scanning direction at a predetermined width inside from the front end of the document and a predetermined width inside from the rear end of the document is less than a predetermined threshold; Position detecting means for specifying the position in the main scanning direction of the portion where the received light amount detected by the received light amount detecting means is less than a predetermined threshold, and the light amount detecting means are provided on the leading edge side and the trailing edge side of the document. In both cases, the amount of received light less than a predetermined threshold value is detected, and the position in the main scanning direction specified by the position detecting means is substantially the same on both the leading edge side and the trailing edge side of the document. In the case, the contact member A determination unit that determines that a foreign matter adhesion part is generated due to a foreign matter attached, and when the judgment unit determines the occurrence of the foreign matter adhesion part, the light emission amount of the light source element corresponding to the foreign matter adhesion part is increased. And a control means for making it possible.

  According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, when the foreign matter adhering portion corresponds to one light source element, the control means emits light of one light source element. And the amount of emitted light of the two light source elements is increased when the foreign substance adhering portion corresponds to between two light source elements adjacent to each other in the main scanning direction.

  According to a third aspect of the present invention, in the image reading apparatus according to the first or second aspect, the control means increases the light emission amount of the light source element as the amount of decrease in the amount of received light based on the foreign matter adhesion portion increases. It is characterized by that.

  According to a fourth aspect of the present invention, in the image reading apparatus according to the third aspect, the control means emits light of the light source element located on both outer sides in the main scanning direction of the light source element with increased light emission. Is increased with a light emission amount smaller than the increased light emission amount.

  According to a fourth aspect of the present invention, in the image reading apparatus according to the third aspect, the control means emits light of the light source element located on both outer sides in the main scanning direction of the light source element with increased light emission. It is characterized by increasing.

  According to a fifth aspect of the present invention, an image reading unit that reads an image of a document, an image forming unit that forms an image on a sheet based on image information of the document read by the image reading unit, and the image forming unit The present invention relates to an image forming apparatus including a sheet feeding unit that supplies sheets. The image forming apparatus according to the present invention is characterized in that the image reading device according to any one of claims 1 to 4 is disposed in the image reading unit.

  According to the invention of claim 1, the leading edge and the trailing edge of the document passing on the reading line are read, and based on the amount of received light at that time, it is determined whether or not a foreign matter adhesion portion has occurred on the contact member, When it is determined that a foreign matter adhesion portion has occurred, the light amount of the light source element corresponding to the foreign matter adhesion portion is increased to suppress a decrease in the amount of light received due to the foreign matter adhesion portion. This eliminates or reduces the influence of the foreign matter generating part that causes the vertical streak of the output image when reading the next original (subsequent original) of the original used to detect the foreign matter adhesion part. Can do. In addition, when detecting the foreign matter adhesion portion, it is assumed that a portion with a small amount of received light is detected at both the leading edge and the trailing edge of the document and the foreign matter adhesion portion has occurred when the position in the main scanning direction is the same. False detection can be prevented. That is, in the case where the foreign matter adhesion portion is detected only at one end portion of the document, for example, such a case can be excluded because it cannot be distinguished from dirt on the end portion of the document.

  According to the invention of claim 2, when the position of the foreign substance adhering portion corresponds to one light source element, or corresponds to between the two adjacent light source elements. By increasing the amount of light of the two light source elements, it is possible to prevent a decrease in the amount of received light due to the foreign matter adhering portion.

  According to the third aspect of the present invention, in order to prevent a decrease in the amount of received light based on the foreign substance adhering portion, when the amount of light emitted from the corresponding light source element is increased, the received light amount of the portion corresponding to the portion adjacent to the foreign substance adhering portion May be excessive, and the amount of received light is not substantially uniform along the main scanning direction. Therefore, the uniformity of the amount of light received in the main scanning direction is maintained by changing the increase in the amount of light emitted from the light source element corresponding to the foreign matter attached portion according to the amount of decrease in the amount of received light caused by the foreign matter attached portion. ing.

  According to the invention of claim 4, not only the light source element corresponding to the foreign substance adhering portion but also the light emission amount of the light source element adjacent to both sides of the light source element is increased so that only the received light amount of the portion corresponding to the foreign substance adhering portion Can be prevented from increasing extremely.

  According to the invention of claim 5, the effects of the above-described claims 1 to 4 in the image reading apparatus can be exhibited as the image forming apparatus.

  Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings. In addition, in each drawing, the member etc. which attached | subjected the same code | symbol are the same structures, The duplication description about these shall be abbreviate | omitted suitably. Moreover, in each drawing, members and the like that are not necessary for the description are omitted as appropriate.

<Embodiment 1>
The image reading apparatus 10 according to the present invention will be described with reference to FIGS. Among these, FIG. 1 is a view of a longitudinal section of the image reading apparatus 10 as viewed from the front side (front side). FIG. 2 explains the positional relationship between the document placement contact glass 18, the placement position of the document G (A3 size in the figure), and the LED elements (light source elements) L1 to L35 constituting the light source 12. It is a top view. FIG. 3 is a perspective view illustrating how the LED elements L1 to L35 are arranged in a staggered manner. FIG. 4 shows the positional relationship of the LED elements L1 to L35, the contact glass 18a, the CCD 14, the original G to be scanned and the foreign matter adhesion portion t in the main scanning direction (direction along the reading line Ln) as viewed from above. It is a figure shown typically. FIG. 5 is a diagram for explaining a state in which the amount of light received by the CCD 14 has decreased below a threshold value due to the foreign matter adhesion portion t. FIG. 6 is a diagram for explaining a state where a portion where the amount of received light is reduced is equal to or greater than a threshold by increasing the amount of light emitted from the LED elements L16 and L17. FIG. 7 is a flowchart for explaining the flow of operations for eliminating vertical stripes. In the following description, the LED elements L1 to L35 as the light source elements are referred to as LED elements L when it is not necessary to distinguish them, when any one is described, or when collectively referred to, and the like. The directions such as front and rear, left and right, up and down indicated by arrows in FIGS.

  As shown in FIG. 1, the image reading device 10 includes an illumination device 11, an imaging lens 13, and a CCD (solid-state imaging device) 14, and the illumination device 11 further includes a light source 12 and a drive device 15. I have. The light source 12, the driving device 15, the imaging lens 13, and the CCD 14 are all disposed in a storage chamber S inside a rectangular parallelepiped housing (frame) 16. The casing 16 has an opening 17 on the upper surface thereof, and a transparent original placement contact glass 18 used when the original G is fixedly read is disposed in the opening 17. On the other hand, when the original G is read and read using the automatic original feeder 60 described later, the front-rear direction (main scanning direction, reading line direction and the like) arranged on the left side of the contact glass 18 is used. In the same manner, a long plate-like transparent sheet-through contact glass (contact member) 18a is used.

  As shown in FIG. 2, the contact glass 18 is formed in a rectangular shape that is larger than the maximum-size document G (A3 size in the present embodiment). A left indicator plate 20 is disposed at the left end of the contact glass 18 in the front-rear direction, and a rear indicator plate 21 and a front indicator plate 22 are disposed at the rear end and the front end in the left-right direction, respectively. Among these, the position where the left indicating plate 20 and the rear indicating plate 21 intersect becomes a reading reference position P01 when the document G is fixedly read. The original G placed on the contact glass 18 at the time of fixed reading is positioned with one corner aligned with the reference position P01, the left end aligned with the left indicating plate 20, and the trailing end aligned with the rear indicating plate 21. This is the reading position during fixed reading. In FIG. 2, an A3 size document G arranged at the reading position is displayed. It should be noted that a notation indicating the size of each document G is given to positions on the left instruction plate 20 and the rear instruction plate 21 corresponding to the front end and right end of each size document G. A light source 12 is disposed below the left end side of the contact glass 18. As will be described later, the light source 12 includes LED elements L1 to L35, which are point light sources, arranged in the front-rear direction so as to be long in the front-rear direction as a whole.

  As shown in FIG. 1, an illumination optical movement frame unit 23 is disposed below the left end side of the contact glass 18. The illumination optical moving frame unit 23 has a moving frame 24 that is long in the front-rear direction. A light source main substrate (substrate) 25 to which the light source 12 is attached, a light guide lens 19, a reflection plate 26, and a first mirror 27 are mounted on the moving frame 24. Among these, as shown in FIG. 2, the light source main substrate 25 is formed long in the front-rear direction, and the light source 12 is attached to the upper surface thereof. In the present embodiment, the light source 12 is configured by arranging a plurality (35 in FIG. 2) of LED elements L1 to L35, which are point light sources, in a line shape in the front-rear direction. Here, the line shape is not limited to a case where they are aligned on a single straight line, but includes, for example, a case where they are aligned in a staggered manner and are substantially linear as shown in FIG. To do. These LED elements L1 to L35 are aligned at a predetermined pitch P that can irradiate the image surface of the original G evenly along the front-rear direction. In FIG. 2, the long side (= 297 mm) of the A4 size document G having the maximum sheet passing width from the center of the last LED element L1 to the center of the frontmost LED element L35, or A3 size. The short side (= 297 mm) of the original G is set. The LED elements L1 to L35 will be further described later with reference to FIG.

  As shown in FIG. 1, the light source 12 constituted by the plurality of LED elements L1 to L35 irradiates the reading line Ln set on the upper surface of the contact glass 18a from the lower right side. These LED elements L1 to L35 are individually controlled to be turned on (on) and turned off (off) by the control means 70 shown in FIG. Further, the amount of light is also individually controlled by adjusting the current value or voltage value by the control means 70. The light guide lens 19 is held by the moving frame 24 so as to be positioned between the light source 12 and the reading line Ln, and guides light emitted from the light source 12 to the reading line Ln.

  As shown in FIG. 1, the reflection plate 26 is disposed on the opposite side of the light source 12 with respect to the perpendicular line drawn from the reading line Ln. As described above, since the light source 12 irradiates the original G on the contact glass 18 obliquely from the lower right side, a shadow is formed on the left end of the original G, and this shadow is read as a linear image in the front-rear direction. It tends to be. The reflection plate 26 reflects the light from the light source 12 and guides it to the reading line Ln to remove this shadow. In the present embodiment, the reflecting plate 26 is a member that reflects light from the light source 12 and indirectly irradiates the image surface of the original G, thereby reducing object surface illuminance unevenness and image surface illuminance unevenness due to direct irradiation. It is also used as.

  A first mirror 27 is disposed in a portion of the illumination optical movement frame unit 23 that is located immediately below the reading line Ln. The first mirror 27 is attached in a state in which 45 degrees on the upper left is turned. As described above, the illumination optical moving frame unit 23 is laid in the left-right direction with the light source 12, the light source main board 25, the light guide lens 19, the reflecting plate 26, and the first mirror 27 mounted on the moving frame 24. The optical rail (guide member) 29 can be moved in the left-right direction. That is, it is possible to move in the left-right direction orthogonal to the linear (linear) light source 12 in the front-rear direction. The illumination optical movement frame unit 23 emits light from the light source 12 toward the reading line Ln while moving rightward, and guides reflected light from the image surface of the original G to a second mirror 28 described below. Is.

  As shown in FIG. 1, below the left end side of the contact glass 18, a reflection optical moving frame unit 30 is disposed on the left side of the above-described illumination optical moving frame unit 23. The reflecting optical moving frame unit 30 has a moving frame 31 that is long in the front-rear direction. A second mirror 28 is mounted on the moving frame 31 in a state where the lower right angle is 45 degrees, and a third mirror 32 is mounted in an attitude where the upper right angle is 45 degrees. Further, the moving frame 31 rotatably supports the movable pulley 33 at its front end and rear end. As described above, the reflecting optical moving frame unit 30 can move in the left-right direction along the optical rail 29 laid in the left-right direction with the second mirror 28, the third mirror 32, and the movable pulley 33 mounted thereon. It is like that. The optical movement frame unit 30 for reflection reflects light from the first mirror 27 of the optical movement frame unit 23 for illumination described above by the second mirror 28 and the third mirror 32 while moving to the right. It leads to the imaging lens 13.

  As shown in FIG. 1, fixed left pulleys 34, 34 are provided at the front end and the rear end in the vicinity of the left end of the housing 16, and fixed right pulleys 35, 35 are provided at the front end and the rear end in the vicinity of the right end of the housing 16. Are rotatably arranged. Further, below the fixed right pulleys 35, 35, a motor 36 capable of rotating in the forward and reverse directions is disposed. Further, a drive pulley 38 that is integral with the drive shaft 37 is disposed on the left side of the motor 36, and a drive belt 41 is stretched between the output shaft 40 of the motor 36 and the drive pulley 38. Yes. Wire drums 42 and 42 are fixed to the front end and the rear end of the drive shaft 37, and optical wires 43 and 43 are wound around the wire drums 42 and 42, respectively.

  One end portions 44 of the optical wires 43 are fixed to the inner surface of the left side wall 45 of the housing 16. The optical wires 43, 43 extend rightward from here, hang around the right half of the movable pulleys 33, 33 of the reflecting optical moving frame unit 30, are folded back leftward, and left of the fixed left pulleys 34, 34. After being stretched over the half, it is folded rightward and extends toward the fixed right pulleys 35 and 35. Further, after being wound around the wire drums 42, 42 by one turn, after being wound around the right half of the fixed right pulleys 35, 35 and extending leftward, after being fixed to the illumination optical moving frame unit 23 on the way Further, it extends further to the left, hangs around the left half of the movable pulleys 33, 33, is folded back to the right, and is locked to a hook 47 protruding on the lens mount 46.

  When the motor 36 rotates counterclockwise in FIG. 1 based on the routing of the optical wires 43, 43, the wire drums 42, 42 are similarly turned through the drive belt 41, the drive pulley 38, and the drive shaft 37. Rotate clockwise. Along with this, the illumination optical movement frame unit 23 and the reflection optical movement frame unit 30 move to the right by being pulled by the optical wires 43 and 43. At this time, since the movable pulleys 33 and 33 of the reflecting optical moving frame unit 30 act as a so-called moving pulley, the moving distance becomes half of the moving distance of the illumination optical moving frame unit 23. As a result, the optical path length from the reading line Ln to the CCD 14 is kept constant regardless of the movement of the illumination optical moving frame unit 23 and the reflecting optical moving frame unit 30, and passes through the imaging lens 13 described below. The formed light forms an image on the CCD 14. In the present embodiment, the entire configuration for moving the light source 12 as described above corresponds to the driving device (moving device 15).

  As shown in FIG. 1, the imaging lens 13 is fixed on a lens mounting plate 48 fixed to a lens mounting base 46. The light emitted from the light source 12 is reflected by the image surface of the original G and follows an optical path K shown in FIG. That is, the reflected light from the image plane is reflected by the first mirror 27, the second mirror 28, and the third mirror 32, passes through the imaging lens 13, and forms an image on the CCD 14 described next. A bent CCD adjusting plate 49 is fixed to the rear end side of the lens mounting plate 48. The horizontal portion 49 of the CCD adjusting plate 49 has optical axis adjusting pins described later on the front end side and the rear end side. A female screw (not shown) to which 53 and 53 are screwed is engraved.

  The CCD 14 is attached to the surface (left surface in FIG. 1) of the CCD substrate 50 in an upright posture, and is covered with a box-shaped CCD cover 52 together with the CCD substrate 50 while being held by the CCD attachment plate 51. . The upper end of the CCD mounting plate 51 is a horizontal portion 51a bent to the left, and the horizontal portion 51a has a through-hole through which the optical axis adjusting pins 53 and 53 penetrate on the front end side and the rear end side. (Not shown) is drilled. The optical axis adjustment pins 53 and 53 penetrate through the through hole on the horizontal portion 51 on the CCD mounting plate 51 side from above, and are screwed into the female screw of the horizontal portion 49a on the CCD adjustment plate 49 side. Further, compression springs 54 and 54 that are penetrated by optical axis adjusting pins 53 and 53 are interposed between the horizontal portions 49a and 51a. The CCD mounting plate 51 is urged upward by the compression springs 54 and 54 with respect to the CCD adjustment plate 49 and is brought into contact with the large-diameter heads of the optical axis adjustment pins 53 and 53 from below. ing. The optical axis adjustment pins 53 and 53 can adjust the inclination of the CCD 14 in the front-rear direction by adjusting the screwing amount of the CCD adjustment plate 49 with respect to the horizontal portion 49a. The CCD 14 is connected to the control means 70 described above.

  As shown in FIG. 1, in the present embodiment, the image reading apparatus 10 includes an automatic document feeder 60 that can be opened and closed above the contact glass 18. By scanning the original G, the original G is scanned. The automatic document feeder 60 as a whole is supported such that the rear end side thereof is swingably supported by a portion of the housing 16 located behind the contact glass 18, and the front end side can be opened and closed substantially vertically. The automatic document feeder 60 includes a paper feed tray 61, a transport roller 62, a paper discharge guide 63, a paper discharge tray 64, and the like that are arranged in order from the upstream side in the transport direction of the document G. Among these, the paper discharge guide 63 is formed as an upwardly inclined surface on the upper surface on the left end side of the left indicating plate 20 described above.

  As shown in FIG. 1, the paper feed tray 61 regulates the positions of the rear end and front end of the placed document G (the right end and the left end when viewed toward the downstream side in the transport direction of the document G). Side regulating plates 65 and 66 are arranged to be movable in the front-rear direction. An interlocking mechanism (not shown) such as a rack and pinion is interposed between the side regulating plates 65 and 66, and is directed toward the center of the paper feed tray 61 in the paper passing width direction (front-rear direction). When the side regulating plate 65 (or 66) is moved, the other side regulating plate 66 (or 65) is similarly moved toward the center, and conversely, one side regulating plate 65 (or 66) is moved. Is moved in a direction away from the center, the other side regulating plate 66 (or 65) is similarly moved in a direction away from the center. That is, after placing the document G on the sheet feed tray 61, the side regulating plates 65 and 66 are pressed against the rear end and the front end of the document G, respectively, so that various documents G having different sheet passing widths are fed to the sheet feed tray 61. Can be arranged in the center in the paper passing width direction. That is, when the automatic document feeder 60 is used to flow and read the original G, the original G is read with a central reference.

  The paper feed tray 61 is provided with a size detection sensor (not shown) for detecting the paper passing width of the placed document G. As described above, the document G placed on the paper feed tray 61 is positioned at the center in the front-rear direction of the paper feed tray 61 by the side regulating plates 65 and 66 being brought into contact with the rear end and the front end, respectively. The The size detection sensor can detect the sheet passing width of the original G by detecting the positions of the side regulating plates 65 and 66 at this time.

  When reading the image of the document G, the image reading apparatus 10 having the above-described configuration performs both fixed reading for fixing the document G and moving the light source 12 and flow reading for fixing the light source 12 and moving the document G. It can be carried out. In either case, only the LED elements L necessary for the irradiation of the document G are turned on, and the LED elements L that do not contribute to the irradiation are turned off.

  In the former fixed reading, the automatic document feeder 60 is opened and the document G is set on the contact glass 18. At this time, the document G is set at the reading position based on the trailing edge. When the automatic document feeder 60 is closed from the top of the document G, all the LED elements L1 to L35 of the light source 12 are once turned on, and the reflected light from the document G is incident on the CCD. Based on the difference in the amount of incident light along the sheet passing width direction at this time, the size of the document G (sheet passing width) is detected. Based on the detection result, the control means 70 determines the LED element L to be lit when reading the image.

  Subsequently, the operator operates an operation panel (not shown) attached to the housing 16 and presses a reading start button (not shown). As a result, the illumination optical movement frame unit 23 is arranged at the reading start position on the left side of the left end of the original G, and moves to the right from here. Accordingly, the light source 12 mounted on the illumination optical movement frame unit 23 irradiates the image surface of the original G along the reading line Ln (main scanning), and moves to the right to perform sub-scanning. The image surface of G is irradiated with light over the entire area. The reflected light from the image plane is further reflected by the first mirror 27, the second mirror 28 and the third mirror 32, forms an image through the imaging lens 13, and is guided to the CCD 14. Thereby, the image surface of the original G is read over the entire area.

  On the other hand, in the latter flow scanning, the original G is placed on the paper feed tray 61 with the image surface thereof facing upward with the automatic document feeder 60 closed. By bringing the side regulating plates 65 and 66 into contact with the front ends, the document G is set in the center of the paper feed tray 61. Thereby, the sheet passing width of the original G is detected. When the reading start button on the operation panel is pressed, the illumination optical movement frame unit 23 moves to a reading position below the reading line Ln of the image reading portion R of the contact glass 18a on the left side of the left indicating plate 20. The original G on the paper feed tray 61 is conveyed to the image reading unit R by a conveyance roller 62 and the like. At this time, the irradiation light emitted from the light source 12 is reflected by the image surface of the original G passing through the reading line Ln, and the first mirror 27, the second mirror 28, and the third mirror are the same as in the case of the fixed reading described above. The light is reflected by 32, forms an image through the imaging lens 13, and is guided to the CCD 14. Thereby, the image surface of the original G is read over the entire area.

  The LED elements L1 to L35 will be described with reference to FIG. The LED elements L1 to L35 are arranged on the upper surface 25a of the light source main board 25 in a state where the LED elements L1 to L35 are linearly aligned in units of 5 or 6 and attached to the attachment plate 24b. The LED elements L1 to L35 as a whole are arranged in a staggered manner over two rows. That is, odd-numbered LED elements L1, L3... L (2n-1) (where 1 ≦ n ≦ 18) are arranged in a line at equal intervals with a predetermined pitch 2P, while the even-numbered LED elements L2, L4... L {2 (n−1)} are also arranged in a line at equal intervals at the same predetermined pitch 2P as the odd number described above. The odd-numbered LED elements L and the even-numbered LED elements L are arranged at a predetermined distance with respect to the position in the sub-scanning direction (left-right direction), and the position in the main scanning direction (front-back direction). Are arranged so that the even-numbered LED elements L are positioned between two adjacent odd-numbered LED elements L. Thus, the LED elements L1 to L35 are arranged at a predetermined pitch P in the main scanning direction. These LED elements L1 to L35 can be individually turned on and off, and the amount of emitted light can be controlled by the control means 70 shown in FIG.

  By the way, when the original G is scanned, the image surface of the original G is rubbed against the upper surface of the contact glass 18a. At this time, foreign matters such as dirt and dust attached to the original G are contact glass. 18a may adhere. When the foreign matter adheres to the contact glass 18a and the foreign matter attachment portion t is generated, part of the light emitted from the LED elements L1 to L35 is blocked by the foreign matter attachment portion t, and the CCD 14 is placed on the foreign matter attachment portion t. The amount of light received in the corresponding part is insufficient. As a result, when an image is formed by an image forming apparatus 1 to be described later based on this image reading, vertical streaks occur in the output image along the conveyance direction of the original G.

  Therefore, in the present invention, the amount of light received at the front end side and the rear end side of the original G is detected while the original G is being scanned, and the foreign matter attachment portion t is detected, and the LED element corresponding to the foreign matter attachment portion t is detected. The amount of light emission is increased to prevent a decrease in the amount of light received by the CCD 14, thereby preventing the occurrence of vertical stripes. Details will be described below.

  FIG. 4 is a diagram schematically showing the positional relationship in the front-rear direction when the LED elements L1 to L35, the contact glass 18a, the imaging lens 13, the CCD 14, and the document G are viewed from above. In the following description, while a plurality (n) of originals G are continuously being scanned and read, foreign matter such as dirt or dust is caused on the contact glass 18a by one preceding original G. It is assumed that a foreign matter adhesion portion t is generated in the contact glass 18a after being conveyed. Moreover, the generation | occurrence | production position of the foreign material adhesion part t shall be between LED element L16, L17 among LED elements L1-L35 arrange | positioned at a predetermined pitch from the rear end side to the front end side.

  When the subsequent original G is conveyed in the direction of arrow a (the direction from left to right) and passes through the reading line Ln, the image surface passes over the foreign matter adhesion portion t. In this state, Light emitted from the LED elements L1 to L35 is applied to the image surface. For this reason, a light amount deficient portion b is generated in a line shape from the front end Ga to the rear end Gb at the same position as the foreign matter adhering portion t along the main scanning direction in the original G, and corresponds to the light amount deficient portion b. As a result, a portion where the amount of received light is insufficient is generated in the CCD 14. Based on the reading result of the CCD 14, when an image is formed on the sheet P by the image forming apparatus 1 to be described later, vertical streaks occur at positions on the sheet P corresponding to the light quantity deficient portion b of the document G. .

  Therefore, in the present embodiment, the occurrence of vertical stripes is prevented according to the flow of the flowchart of FIG.

  When continuous flow reading of a plurality (n) of originals G is started and the LED element L and the leading edge Ga (see FIG. 4) of the first original G reach the reading line Ln (“YES” in S1), Reading of the image surface of the original G is started (S2). In many cases, the document G generally has no image (read image) to be read formed in the vicinity of the leading edge Ga and the vicinity of the trailing edge Gb. Therefore, in the present embodiment, a band-shaped portion formed between a position that is inward from the front end Ga by a predetermined width (for example, 1 mm) and the front end Ga is determined from the front end side detection unit G1 and the rear end Gb. A belt-like portion formed between a position that is inward by a width (for example, 1.5 mm) and the rear end Gb is defined as a rear end detection unit G2, and the front end detection unit G1 and the rear end detection unit G2 are The contact glass 18a is used to detect whether or not there is a foreign matter adhesion portion t. As described above, the width of the front end side detection unit G1 is 1 mm, whereas the width of the rear end side detection unit G2 is as large as 1.5 mm. This is because when detecting the position of the part G2, all of them are detected with the front end Ga as a reference, and a measurement error tends to occur on the rear end side.

FIG. 5 shows the distribution of the amount of received light in the main scanning direction of the CCD 14 (the arrangement direction of the LED elements L1 to L35) when the foreign matter adhesion portion t is generated. The average value of the amount of received light in the main scanning direction is Ha, and the threshold value of the amount of received light is Hb.
The threshold value Hb is a limit value at which vertical stripes are generated on the sheet P when an image is formed by the image forming apparatus 1 described later based on the reading result when the amount of light received by the CCD 14 is less than the threshold value Hb. Is set. In other words, when the amount of received light is equal to or greater than the threshold value Hb, the threshold value Hb is set as a level that is practically acceptable even if vertical stripes occur. When foreign matter adheres to the contact glass 18a and the foreign matter attachment portion t occurs, the received light amount of the portion corresponding to the foreign matter attachment portion t in the light reception amount of the CCD 14 in the main scanning direction decreases to Ht. Become.

  After reading of the leading edge side detection unit G1 on the leading edge Ga side of the document G (S2), the received light amount detecting means 71 detects whether or not there is a portion where the received light amount is less than the threshold value Hb (S3). The control unit 70 includes a received light amount detection unit 71, a position detection unit 72, and a determination unit 73, which will be described later. If there is a portion less than the threshold value Hb (“YES” in S3), the position of the portion in the main scanning direction is specified by the position detection means 72 and stored (S4). In this example, as shown in FIGS. 4 and 5, the position of the LED element L corresponding to the position where the amount of light received by the CCD 14 is less than the threshold value Hb is specified. In the example shown in FIGS. 4 and 5, the foreign matter adhering portion t is generated between two adjacent LED elements L16 and L17. In this case, the corresponding LED elements L are two adjacent LED elements L16. That is, the LED elements L16 and L17. In the present embodiment, as will be described later, when it is detected that the foreign matter adhering portion t is generated, the light emission amount of the LED element L is changed as a countermeasure. Therefore, it is sufficient to specify two adjacent LED elements L with respect to the position of the foreign matter adhesion portion t. In addition, when the position where the light reception amount is the threshold value Hb corresponds to one LED element L, this LED element L is the LED element L corresponding to the foreign matter generation part t.

The detection of whether or not the threshold value Hb is less than the threshold value Hb is continued until the front end side detection unit G1 finishes passing the reading line Ln (“NO” in S5), and after the passage (“YES” in S5), the document G Images are read. When the rear end side detection unit G2 reaches the reading line Ln (“YES” in S6), as in the case of the front end side detection unit G1, is there a portion where the received light amount Ht is less than the threshold value Hb by the received light amount detection unit? Whether or not is detected (S7). If there is a portion less than the threshold value Hb (“YES” in S7), the position in the main scanning direction is detected and stored by the position detection means 72 (S8). Also in this case, the LED element L corresponding to the position where the received light amount Ht in the CCD 14 is less than the threshold value Hb is detected. The detection of whether or not it is less than the threshold value Hb is continued until the rear end side detection unit G2 finishes passing the reading line Ln (“NO” in S9).

  When the rear end side detection unit G2 finishes passing through the reading line Ln (“NO” in S9), the position detected by the determination unit 73 by the position detection unit 72 below the threshold value Hb is substantially the same in S4 and S8. It is determined whether or not they are the same (S10). Here, being substantially the same means being between the two adjacent LED elements L16 and L17. When the position is the same (“YES” in S10), the determination unit 73 determines that the foreign matter adhesion portion t has occurred. And the control means 70 increases the light-emission quantity of LED element L16, L17 based on this determination result (S11). Note that the amount of light emission to be increased is determined in advance through experiments or the like. As shown in FIG. 6, by increasing the light emission amounts of the LED elements L16 and L17, the received light amount Ht of the CCD 14 corresponding to the foreign matter adhesion portion t becomes equal to or greater than the threshold value Hb. Thereby, generation | occurrence | production of a vertical stripe can be prevented or a vertical stripe can be made not conspicuous. In S10, when the determination unit 73 determines that the foreign matter adhesion portion t has occurred, the control unit 70 displays that fact on a display unit (not shown) of the operation panel. As a result, the user can clean the contact glass 18a, remove foreign matter, and eliminate the foreign matter generating portion t after the series of reading of the original G is completed.

On the other hand, if it is not “when the positions match” in S10 (“NO” in S10), the determination unit 73 determines that the foreign matter adhesion portion t has not occurred, and the LED elements L1 to L35 The amount of light emission is not changed (S12). Here, when it is not “when the positions match”, the following cases are included. The following cases are included when there is no other case.
(1) A case where a value less than the threshold Hb is not detected in any of the front end side detection unit G1 and the rear end side detection unit G2.
(2) A case where a value less than the threshold value Hb is detected only in one of the front end side detection unit G1 and the rear end side detection unit G2.
(3) When both of the front end side detection unit G1 and the rear end side detection unit G2 detect less than the threshold Hb, but these positions do not match.

  Of these, the value less than the threshold value Hb detected in (2) and (3) is not detected because the foreign matter adhesion portion t is generated on the contact glass 18a, but is detected, for example, due to dirt on the original G itself. It is considered.

  When the above (1), (2), and (3) are satisfied, that is, when “NO” in S10, the light emission amount of the LED element L is not changed and the normal light emission amount is maintained (S12). .

  The above operation is repeated for each of the originals G when continuously scanning a plurality of originals G ("NO" in S13), and ends when the reading of n originals G is completed. To do.

  According to the present embodiment, at the time of continuous reading of a plurality of documents G, each time each document G is read, it is detected whether or not there is a foreign matter adhesion portion t on the contact glass 18a. When detected, the amount of light of the LED element L corresponding to the position is increased. Therefore, when an image is formed based on the read result, an image is formed based on the original G from which the foreign matter adhesion portion t is detected. Although vertical stripes occur in the sheet P, vertical stripes do not occur in the sheet P that follows the sheet P.

  In addition, when the foreign substance adhesion part t corresponds to one LED element L instead of corresponding between two adjacent LED elements L, only the light emission amount of the one LED element L is increased. Thus, the occurrence of vertical stripes may be prevented.

  Further, as shown in FIG. 6, in the above description, when the foreign matter adhering portion t corresponds to between the LED elements L16 and 17, the light emission amount of the LED elements 16 and L17 located on both sides of the foreign matter generating portion t is increased. Thus, a reduction in the amount of light received by the CCD 14 corresponding to that portion is prevented. In this case, the amount of received light in the portions corresponding to the LED elements L16 and L17, excluding the foreign matter adhering portion t, is too large with respect to the average received light amount Ha, and there is a possibility that unevenness in the received light amount occurs. In such a case, for example, the LED elements L15 and L18 positioned on the outer sides of the LED elements L16 and L17 are also turned on to smooth the change in the amount of received light, thereby reducing unevenness. However, the increase in the light emission amount of the LED elements L15 and L18 in this case is set to be smaller than the increase in the light emission amount of the LED elements L16 and L17.

<Embodiment 2>
With reference to FIG. 8, an example of an image forming apparatus 1 (an image forming apparatus according to the present invention) including the image reading apparatus 10 according to the present invention will be described. FIG. 1 is a schematic view of the image forming apparatus 1 as viewed from the front side. An image forming apparatus 1 shown in FIG. 1 is an image forming apparatus such as an electrophotographic printer or a copying machine.

  As shown in FIG. 1, the image forming apparatus 1 includes a sheet feeding unit 2, an image forming unit 3, a fixing unit 4, and a sheet discharge unit 5. Among these, the sheet feeding unit 2 includes a sheet feeding cassette 2a, a sheet feeding roller 2b, a feeding roller 2c, a retard roller 2d, a conveying roller 2e, a registration roller 2f, and the like. The plurality of sheets P stored in a stacked state in the sheet feeding cassette 2a are fed by the feeding roller 2b and are prevented from being double fed by the feeding roller 2c and the retard roller 2d. Only one sheet is fed downstream. Further, the feeding roller pair 2e is brought into contact with the stopped registration roller pair 2f to correct skewing. Thereafter, the sheet P is supplied to the image forming unit 3 so as to be synchronized with the toner image formed on the photosensitive drum 3 a of the image forming unit 3.

  In the image forming unit 3, a photosensitive drum 3a, a charging roller 3b, an exposure device 3c, a developing device 3d, a tension roller 3e, a cleaning device 3f, and the like are disposed. The photosensitive drum 3a is rotationally driven in the direction of the arrow (clockwise) and is uniformly charged to a predetermined polarity and potential by the charging roller 3b. The charged photosensitive drum 3a is subjected to exposure by the exposure device 3c to remove the charge at the exposed portion and form an electrostatic latent image. This exposure is performed based on the image information of the original read and read by the image reading apparatus 10 described above.

  The electrostatic latent image formed on the photosensitive drum 3a is developed as a toner image with toner attached thereto by the developing device 3d.

  This toner image is transferred to the sheet P supplied from the sheet feeding unit 2 at a transfer nip formed between the photosensitive drum 3a and the transfer roller 3e.

  After the toner image is transferred, the toner (transfer residual toner) remaining on the surface of the photosensitive drum 3a is removed by the cleaning device 3f and used for the next image formation.

  On the other hand, the sheet P after the toner image is transferred is heated and pressed in the fixing unit 4 when passing through the fixing nip formed between the fixing roller 4a and the pressure roller 4b. Is established. The sheet P after the toner image is fixed is discharged onto the paper discharge tray 5b by the paper discharge roller pair 5a.

  In the image forming apparatus 1 described above, the effects of the image reading apparatus 10 described above can be achieved as the image forming apparatus 1.

  In the above description, the case where the image forming apparatus 1 is an electrophotographic image forming apparatus has been described as an example. However, the present invention is not limited to this, and an electrostatic recording method, an ink jet method, a wire dot method. The present invention can be similarly applied to an image forming apparatus such as a thermal transfer system, and substantially the same effect can be obtained.

  In the above-described embodiment, when the amount of light received by the CCD 14 is less than the threshold value Hb due to the foreign matter adhering portion t, the light emission amount of the LED elements L16 and L17 is increased to prevent the occurrence of vertical stripes.

  By the way, when the amount of light emission to be increased is more than necessary, the amount of received light in the vicinity of the portion corresponding to the LED elements L16 and L17 in the CCD 14 becomes excessively large, which may cause unevenness in the amount of received light. In such a case, it is preferable to set the light emission amount to be increased according to the light reception amount Ht of the portion corresponding to the foreign substance adhesion portion t. The smaller the amount of received light Ht, that is, the greater the amount of received light that is insufficient, the greater the amount of emitted light that is correspondingly increased. If the amount of received light is insufficient, the amount of light emission to be increased is reduced accordingly. Thereby, it is possible to prevent the amount of light emission to be increased from being increased more than necessary, and to suppress unevenness in the amount of received light.

  In the above description, the case where the present invention is used for an image reading apparatus has been described as an example. However, the present invention is a general case where a rod-shaped light source is configured by, for example, arranging a plurality of point light sources in a line shape. Can also be widely applied.

It is the figure which looked at the longitudinal section of the image reading device from the front side (front side). It is a top view explaining the positional relationship between a contact glass for placing a document, a placement position of a document (A3 size in the figure), and an LED element (light source element) constituting a light source. It is a perspective view explaining a plurality of LED elements arranged like a staggered pattern. It is a figure which shows typically the positional relationship of the main scanning direction, such as a LED element, contact glass, CCD, the original document flowed through, a foreign material adhesion part, seen from upper direction. It is a figure explaining the state by which the light-receiving amount of CCD fell below the threshold value by the foreign material adhesion part. It is a figure explaining the state which made the part to which the light-receiving amount fell more than a threshold value by increasing the light-emission amount of an LED element. It is a flowchart explaining the flow of the operation | movement for erasing a vertical stripe. FIG. 2 is a schematic view of the image forming apparatus viewed from the front side.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Sheet feeding part, 3 ... Image forming part, 4 ... Fixing part, 5 ... Sheet discharge part, 10 ... Image reading device, 12 ... Light source, 13 ... Imaging lens, 14... CCD (solid-state imaging device), 18 a... Contact glass (contact member) for sheet through, 70... Control means, 71. ... Judging means, G... Original, G1... Front end side detection unit, G2... Rear end side detection unit, Ga. , Hb... Threshold value of received light amount, Ht... Received light amount corresponding to the foreign matter adhesion portion, L, L1 to L35... LED element (light source element), Ln.

Claims (5)

When the image surface of the document passes in the sub-scanning direction on the reading line set in the main scanning direction on the light transmissive contact member, light is emitted from the light source, and the reflected light is solid-stated through the imaging lens. In an image reading apparatus that receives an image by an element and reads an image,
A plurality of light source elements that are arranged in a line in the main scanning direction to constitute the light source, and capable of individually controlling the light emission amount,
Of the amount of light received by the fixed imaging device, the amount of light received in the main scanning direction at a predetermined width inside from the front end of the document and a predetermined width inside from the rear end of the document is less than a predetermined threshold. A received light amount detection means for detecting;
Position detecting means for specifying the position in the main scanning direction of the portion where the received light amount detected by the received light amount detecting means is less than a predetermined threshold;
The light amount detection means detects the amount of received light that is less than a predetermined threshold on both the leading edge side and the trailing edge side of the document, and the position in the main scanning direction specified by the position detection means is the document. A determination means for determining that a foreign matter adheres to the contact member and a foreign matter adhesion portion is generated when both the front end side and the rear end side are substantially the same;
Control means for increasing the light emission amount of the light source element corresponding to the foreign matter adhesion portion when the judgment means determines the occurrence of the foreign matter adhesion portion;
An image reading apparatus. When the foreign matter adhering portion corresponds to one light source element, the control unit increases the light emission amount of the one light source element, and the foreign matter adhering portions are adjacent to each other in the main scanning direction. In the case of corresponding between two light source elements, the light emission amount of these two light source elements is increased.
The image reading apparatus according to claim 1. The control means increases the light emission amount of the light source element as the amount of decrease in the amount of received light based on the foreign substance adhesion portion increases.
The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus. The control means increases the light emission amount of the light source element located on both outer sides in the main scanning direction of the light source element having increased light emission amount with a light emission amount smaller than the increased light emission amount,
The image reading apparatus according to claim 3. An image reading unit that reads an image of an original, an image forming unit that forms an image on a sheet based on image information of the original read by the image reading unit, and a sheet feeding unit that supplies the sheet to the image forming unit In an image forming apparatus comprising:
The image reading device according to claim 1 is disposed in the image reading unit.
An image forming apparatus.

Images