JP2012054834A - Image reader and image formation apparatus with the same - Google Patents

Abstract

An image reading apparatus capable of determining whether a foreign material adheres to a facing member such as a transparent guide plate or a white reference member.
Each LED 82 of the illumination unit is selectively turned on or off to change the shadow of the foreign matter on the white reference member 66a, and each time reading is performed by the CCD, and each reading that has been read a plurality of times is performed. The images are compared to determine whether the foreign matter is attached to the transparent guide plate 65 or the white reference plate 66a from the change in the shadow position of the foreign matter, the gradation change in the read image, or the positional relationship between the foreign matter image and the shadow. is doing.
[Selection] Figure 12

Description

  The present invention relates to an image reading apparatus that reads a document through a transparent guide plate, and an image forming apparatus including the image reading apparatus.

  This type of image reading apparatus reads an image of a document and is also called a scanner, and is used alone or mounted on a copying machine or the like. When used alone, an image of the read original is output to an external printer or the like, and when used in a copying machine, the read original image is copied by the copying machine.

  In such an image reading apparatus, a transport path for transporting a document, a transparent guide plate and a counter member made of a glass plate or the like disposed across the transport path, an illuminating unit and a reading unit disposed below the transparent guide plate. An illumination unit that illuminates the document on the transparent guide plate while the document is being conveyed between the transparent guide plate and the opposing member, and the reading unit reads the document on the transparent guide plate. The illuminating unit has, for example, a plurality of light emitting elements arranged in a row, each light emitting element array is arranged along the scanning direction (main scanning direction) by the reading unit, and the light of each light emitting element is transparent guide plate The document is irradiated via The reading unit has an image sensor such as a CCD arranged along the main scanning direction, and light reflected by the original is incident on the image sensor through the transparent guide plate, and the original is read by the image sensor. .

  The facing member is, for example, a white reference member for shading correction. In this case, the illumination unit illuminates the white reference member via the transparent guide plate, the reading unit reads the white reference member via the transparent guide plate, and generates shading correction data from the output of the reading unit.

  Incidentally, foreign matters such as paper dust may adhere to the surface of the transparent guide plate and the surface of the white reference member. For example, if a foreign object adheres to the transparent guide plate, the document is read through the transparent guide plate. Therefore, the foreign material on the transparent guide plate is read together with the document, and the foreign object is lined in the sub-scanning direction on the read image of the document. Appear in the image, and the image quality deteriorates. In addition, when a foreign matter adheres to the white reference member, the foreign matter is read together with the white reference member, and an error occurs in the shading correction data, which also deteriorates the image quality. However, when reading the original, the white reference member is obscured by the original, so that the foreign matter on the white reference member is not read together with the original.

  Conventionally, in order to cope with contamination of the white reference member due to foreign matters such as paper dust, the white reference member is read by the reading unit at the time of factory shipment of the image reading apparatus in which the white reference member is not contaminated, and shading correction data. Is generated and stored in the memory, and the shading correction data is read from the memory and used in a timely manner during the operation of the image reading apparatus.

  In Patent Document 1, a guide surface of a document and a white reference surface for shading correction are provided separately on the peripheral surface of the roller, and when reading a document, the guide surface of the roller faces the image sensor, and the document is guided by the guide surface. While guiding, the document is read by the image sensor, and when generating shading correction data, the white reference surface of the roller is directed to the image sensor and the white reference surface is read by the image sensor. As a result, the white reference surface becomes difficult to get dirty.

  Furthermore, in Patent Document 2, reading is performed by a scanner in the absence of a document, and the image data is analyzed using an algorithm to determine which component such as a document feed roller, document exposure glass, or mirror is dirty. The determination result is displayed.

JP 2001-313794 A JP 2001-186512 A

  However, when reading the white reference member and generating shading correction data and storing it in the memory at the time of factory shipment of an image reading apparatus in which the white reference member is not contaminated, the light source is deteriorated or the optical system is deteriorated over time. Even if the change occurs, the initial shading correction data is continuously used, so that an error occurs in the shading correction and the image quality deteriorates.

  Further, only when generating shading correction data as in Patent Document 1, even if the white reference surface of the roller is pointed at the image sensor and the white reference surface is read by the image sensor, the white reference surface of the roller becomes dirty. Sometimes, it was not a permanent countermeasure.

  Furthermore, in Patent Document 2, an algorithm is used to determine a dirty part, but it has not been possible to determine which of the transparent guide plate and the white reference member described above is dirty. This is because the transparent guide plate and the white reference member are opposed to each other across the document transport path, and are located close to each other, so that foreign matters such as paper dust adhered to the transparent guide plate and the white reference member are detected. This is because it is difficult to determine whether the foreign matter is attached to the transparent guide plate or the white reference member even if it is possible. And if it cannot identify the adhesion part of a foreign material, exact countermeasure will become difficult. For example, it is necessary to visually check whether a foreign material is attached to the transparent guide plate or the white reference member, and to perform a complicated operation such as cleaning them.

  If it is possible to automatically determine which of the transparent guide plate and the white reference member is attached with the foreign matter, the method for dealing with the foreign matter can be simplified. For example, when foreign matter has adhered to the transparent guide plate, the foreign matter must be removed, and the transparent guide plate may be cleaned immediately. In addition, when a foreign matter adheres to the white reference member, it is only necessary to correct the data portion of the shading correction data corresponding to the location where the foreign matter is attached, without performing the cleaning operation of the white reference member.

  Thus, conventionally, the prevention and detection of contamination of the transparent guide plate and the white reference member are insufficient, and improvement has been desired.

  Even when the facing member is not a white reference member, it is desirable to be able to automatically determine which of the transparent guide plate and the facing member has foreign matter attached thereto.

  In view of the above, the present invention has been made in view of the above-described conventional problems, and an image reading apparatus capable of determining which foreign substance is attached to a facing member such as a transparent guide plate and a white reference member, and An object of the present invention is to provide an image forming apparatus including the same.

  In order to solve the above-described problems, an image reading apparatus according to the present invention includes a conveyance path for conveying a document, a transparent guide plate and a counter member arranged across the conveyance path, and the conveyance through the transparent guide plate. An illumination unit that illuminates the document on the path, and a reading unit that reads the document on the conveyance path via the transparent guide plate, and the illumination unit is for illuminating the document arranged in a reading scanning direction by the reading unit In the image reading apparatus having a plurality of light emitting elements, a light emission control unit for selectively turning on or off each light emitting element of the illumination unit, and each time each light emitting element is selectively turned on or off, The output of the reading unit that has read the counter member through the transparent guide plate is input, and a foreign object is placed on either the transparent guide plate or the counter member based on the output of the reading unit. And a determination section for determining attached.

  In such an image reading apparatus of the present invention, when a foreign material such as paper dust adheres to the transparent guide plate, when the light of each light emitting element is irradiated to the opposing member through the transparent guide plate, Since the opposing member is separated, the shadow of the foreign material on the transparent guide plate may be reflected on the opposing member. Moreover, when the foreign material has adhered to the opposing member, the shadow of a foreign material is hardly reflected on the opposing member. For this reason, it is possible to determine which of the transparent guide plate and the opposing member is attached with the foreign substance based on a change in the shadow of the foreign object reflected on the opposing member. Therefore, by selectively turning on or off each light emitting element, the shadow of the foreign material reflected on the opposing member is changed, and if the change of the shadow of the foreign material reflected on the opposing member is captured by the reading unit multiple times, the reading is performed. Based on the output of each part, it can be determined which of the transparent guide plate and the opposing member has foreign matter attached thereto.

  In the image reading apparatus of the present invention, the light emission control unit turns on each light emitting element by the first selective lighting or extinguishing control, and at least one selective lighting after the second time. Alternatively, each light-emitting element is divided into a plurality of blocks by turn-off control, one light-emitting element of each adjacent block is turned on and the other light-emitting element is turned off, and the determination unit selects the first selective element. Based on the output of the reading unit at the time of turning on or off, the position of the foreign material adhering to the transparent guide plate or the facing member is detected, and two of the first time and the second time and later are detected. Based on the respective outputs of the reading unit at the time of selective lighting or extinguishing control of the first time, it is determined which of the transparent guide plate and the opposing member has foreign matter attached, and the second and subsequent selections In the light on / off control, each light emitting element is divided into a plurality of blocks on the boundary of the position of the foreign matter detected by the determination unit at the time of the first selective light on / off control. .

  In this way, the position of the foreign object is detected at the time of the first selective lighting or extinguishing control, and each of the areas separated from the position of the foreign object at the time of the second or subsequent selective lighting or extinguishing control. When one of the light emitting elements in the block is turned on or off, the shadow of the foreign material reflected on the opposing member can be clearly changed, and it is easy to determine whether the foreign material is attached to the transparent guide plate or the opposing member. become.

  Furthermore, in the image reading apparatus of the present invention, each light emitting element of the illumination unit is divided into a plurality of blocks, and the light emission control unit selectively controls turning on or off each light emitting element in units of blocks, The determination unit inputs the output of the reading unit each time the light emitting elements are selectively controlled to be turned on or off in units of blocks, and based on the respective outputs of the reading unit, the transparent guide plate and the It is determined which of the opposing members a foreign object is attached.

  When each light emitting element is selectively turned on or off in units of blocks as described above, the shadow of the foreign matter reflected on the opposing member can be clearly changed, and the foreign matter adheres to either the transparent guide plate or the opposing member. It becomes easy to judge.

  In the image reading apparatus of the present invention, the light emission control unit selectively controls the light emitting elements to be sequentially turned on or off sequentially, and the determination unit selectively turns on or sequentially turns on the light emitting elements. Each time the turn-off control is performed, the output of the reading unit is input, and based on the output of the reading unit, it is determined which of the transparent guide plate and the opposing member has foreign matter attached.

  When each light emitting element is selectively turned on or off sequentially in this manner, the shadow of the foreign matter reflected on the opposing member can be clearly changed, and whether the foreign matter is attached to the transparent guide plate or the opposing member. Judgment becomes easy.

  Furthermore, in the image reading apparatus of the present invention, the determination unit compares each read image indicated by each output of the reading unit, and based on the change in the position of the shadow of the foreign matter in each read image, It is determined which of the guide plate and the counter member has foreign matter attached thereto.

  Here, the light incident direction with respect to the foreign matter on the transparent guide plate or the opposing member is changed by selectively turning on or off the light emitting elements. If foreign matter adheres to the transparent guide plate and the incident direction of light on the foreign matter changes, the transparent guide plate and the opposing member are separated from each other. The position of changes. In addition, when a foreign object adheres to the opposing member, even if the incident direction of light on the foreign object changes, the position of the shadow of the foreign object reflected on the opposing member only slightly changes. For this reason, it can be determined whether the foreign matter adheres to the transparent guide plate or the opposing member based on the change in the position of the shadow of the foreign matter in each read image.

  In the image reading apparatus of the present invention, the determination unit determines that foreign matter is attached to the transparent guide plate when the amount of change in the shadow position of the foreign matter in each read image exceeds a predetermined distance. ing.

  In this way, when the amount of change in the shadow position of the foreign object exceeds a predetermined distance, it may be determined that the foreign object is attached to the transparent guide plate.

  Furthermore, in the image reading apparatus of the present invention, the determination unit compares the read images indicated by the respective outputs of the reading unit, and the transparent guide is based on a partial tone change of the read images. It is determined whether the foreign matter is attached to either the plate or the facing member.

  Here, when foreign matter is adhered to the transparent guide plate, if the incident direction of light on the foreign matter is changed by selectively turning on or off each light emitting element, the shadow of the foreign matter on the transparent guide plate reflected on the opposing member The position changes, and the gradation of a part of each read image changes. In addition, when a foreign object is attached to the opposing member, the position of the shadow of the foreign object reflected on the opposing member is almost changed even if the incident direction of light on the foreign object is changed by selectively turning on or off each light emitting element. Without partial gradation change of each read image. For this reason, it is possible to determine which of the transparent guide plate and the opposing member is attached with foreign matter based on the gradation change of a part of each read image.

  In the image reading apparatus of the present invention, the determination unit determines that a foreign matter is attached to the transparent guide plate when the amount of change in partial gradation of each read image exceeds a predetermined gradation level. ing.

  In this way, when the amount of change in partial gradation of each read image exceeds a predetermined gradation level, it may be determined that foreign matter is attached to the transparent guide plate.

  Furthermore, in the image reading apparatus of the present invention, the determination unit compares each read image indicated by each output of the reading unit, and the presence of the shadow of the foreign matter separated from the foreign matter image in each read image. It is determined that foreign matter has adhered to the transparent guide plate.

  Here, when foreign matter is adhered to the transparent guide plate, if the incident direction of light on the foreign matter is changed by selectively turning on or off each light emitting element, the shadow of the foreign matter on the transparent guide plate reflected on the opposing member The position changes. In addition, when a foreign object is attached to the opposing member, the position of the shadow of the foreign object reflected on the opposing member is almost changed even if the incident direction of light on the foreign object is changed by selectively turning on or off each light emitting element. do not do. Of course, the position of the foreign matter on the transparent guide plate and the position of the foreign matter on the opposing member do not change. For this reason, by comparing the read images, it is possible to distinguish between the shadow of the foreign matter reflected on the opposing member and the image of the foreign matter on the transparent guide plate or the opposing member. It can be determined that foreign matter is attached to the transparent guide plate.

  In the image reading apparatus of the present invention, the surface of the facing member facing the transparent guide plate is white.

  Since the original is illuminated through the transparent guide plate, if the original is a thin sheet, the illumination light passes through the original and reaches the opposing member. If the surface of the facing member facing the transparent guide plate is white, the document is illuminated by the light reflected by the surface of the facing member, and the document read by the reading unit becomes bright. Conversely, if the surface of the facing member facing the transparent guide plate is black, the document read by the reading unit becomes dark. For this reason, it is preferable that the surface of the opposing member facing the transparent guide plate side is white. Further, when the surface of the facing member facing the transparent guide plate is white, the shadow of the foreign material on the transparent guide plate is clearly reflected on the facing member, and the detection of the shadow of the foreign material becomes easy.

  Furthermore, in the image reading apparatus of the present invention, the facing member is a white reference member for shading correction.

  Such a white reference member also has the same effect as when the surface of the opposing member facing the transparent guide plate is white.

  The image reading apparatus of the present invention further includes a calculation unit that generates shading correction data corresponding to the output of the reading unit that has read the white reference member, and the calculation unit is configured to perform the white reference by the determination unit. If it is determined that a foreign substance is attached to the member, the data portion of the shading correction data corresponding to the foreign substance attached portion is corrected.

  Alternatively, the image reading apparatus of the present invention includes a calculation unit that generates shading correction data corresponding to the output of the reading unit that has read the white reference member, and the calculation unit is configured to generate the white reference by the determination unit. When it is determined that a foreign substance is attached to the member, the generated shading correction data is replaced with the initial value of the shading correction data stored in advance in the memory.

  This eliminates the need for cleaning the white reference member.

  On the other hand, an image forming apparatus of the present invention includes the image reading apparatus of the present invention.

  Such an image forming apparatus of the present invention also has the same effects as the image reading apparatus of the present invention.

  The image forming apparatus according to the present invention further includes a display unit for displaying information related to the image reading apparatus.

  Furthermore, in the image forming apparatus of the present invention, the display unit displays a determination result by the determination unit of the image reading device.

  Thereby, it can be notified to a user whether the foreign material has adhered to either a transparent guide plate or an opposing member.

  In the image forming apparatus of the present invention, the display unit prompts cleaning of the transparent guide plate when the determination unit of the image reading apparatus determines that foreign matter is attached to the transparent guide plate. Is displayed.

  As a result, the user can be informed that the transparent guide plate needs to be cleaned.

  In the image reading apparatus of the present invention, the display unit does not need to be cleaned when the determination unit of the image reading apparatus determines that a foreign substance is attached to the counter member. Is displayed.

  Thereby, it can notify a user that cleaning of an opposing member is not required.

  According to such an image reading apparatus of the present invention, when a foreign material such as paper dust adheres to the transparent guide plate, the transparent guide is irradiated with the light of each light emitting element via the transparent guide plate. Since the plate and the facing member are separated from each other, the shadow of the foreign material on the transparent guide plate may be reflected on the facing member. Moreover, when the foreign material has adhered to the opposing member, the shadow of a foreign material is hardly reflected on the opposing member. For this reason, it is possible to determine which of the transparent guide plate and the opposing member is attached with the foreign substance based on a change in the shadow of the foreign object reflected on the opposing member. Therefore, by selectively turning on or off each light emitting element, the shadow of the foreign material reflected on the opposing member is changed, and if the change of the shadow of the foreign material reflected on the opposing member is captured by the reading unit multiple times, the reading is performed. Based on the output of each part, it can be determined which of the transparent guide plate and the opposing member has foreign matter attached thereto.

1 is a cross-sectional view illustrating an image forming apparatus to which a first embodiment of an image reading apparatus of the present invention is applied. It is sectional drawing which shows the image reading apparatus of FIG. It is a perspective view which shows the 1st scanning unit in an image reading apparatus. FIG. 4 is a cross-sectional view showing the first scanning unit of FIG. 3 as viewed from the side. It is a top view which shows the LED array of 2 rows in the 1st scanning unit of FIG. It is sectional drawing which shows the 1st scanning unit of FIG. 3 seeing from the front. (A) is sectional drawing which shows the illumination state by the LED array on two board | substrates, (b) is sectional drawing which shows the illumination state by the LED array on one board | substrate. It is a block diagram which shows the structure of the signal processing system in an image reading apparatus. It is sectional drawing which shows the path | route of the light when all the LED of the LED array of 1 row in a 1st scanning unit is lighted and the white reference board is illuminated. (A) is sectional drawing which shows the transparent guide plate to which the foreign material adhered, (b) is sectional drawing which shows the white reference board to which the foreign material adhered, (c) is in the state of (a), (b). It is a graph which shows the fluctuation | variation of the output level of CCD. It is a figure which shows the example which divided each LED of the LED array of 1 row into two blocks. (A) is sectional drawing which shows the state in which the light of LED of one block injected with respect to the foreign material of a transparent guide plate, (b) is the light of LED of the other block with respect to the foreign material of a transparent guide plate. It is sectional drawing which shows the state which injected, (c) is sectional drawing which shows the state in which the light of LED of one block injected with respect to the foreign material of a white reference board, (d) is the foreign material of a white reference board. On the other hand, it is sectional drawing which shows the state into which the light of LED of the other block entered. (A)-(d) is a figure which shows the reading image by CCD in each state of Fig.12 (a)-(d). (A)-(d) is a graph which shows the gradation change of the main scanning direction of the image read by CCD in each state of Fig.12 (a)-(d). It is the figure used in order to demonstrate the separation distance between the image of a foreign material, and the image of a shadow. 3 is a plan view showing an operation panel of the image forming apparatus. FIG. It is a graph which shows the characteristic line of the data for shading correction | amendment. (A), (b), and (c) when each LED of one row of LED array is divided into a plurality of blocks, each block is sequentially selected, and only the LEDs of the selected block are lit. It is a figure which shows the change of the shadow of the foreign material. It is sectional drawing which shows the modification of an image reading apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a sectional view showing an image forming apparatus to which the first embodiment of the image reading apparatus of the present invention is applied. The image forming apparatus 1 is a so-called multi-function machine having a scanner function, a copying function, a printer function, a facsimile function, and the like, and transmits an image of a document read by the image reading apparatus 2 to the outside (corresponding to a scanner function). The image of the read original or the image received from the outside is recorded and formed on a recording sheet in color or single color (corresponding to a copying function, a printer function, and a facsimile function).

  The image forming apparatus 1 includes an optical scanning device 11, a developing device 12, a photosensitive drum 13, a drum cleaning device 14, a charger 15, an intermediate transfer belt device 16, a fixing device 17, and a paper for printing an image on a recording paper. A transport path S, a paper feed tray 18, a paper discharge tray 19, and the like are provided.

  The image data handled in the image forming apparatus 1 uses data corresponding to a color image using each color of black (K), cyan (C), magenta (M), yellow (Y), or a single color (for example, black). This is in accordance with the monochrome image. For this reason, four each of the developing device 12, the photosensitive drum 13, the drum cleaning device 14, and the charger 15 are provided so as to form four types of toner images corresponding to the respective colors, and black, cyan, Four image stations Pa, Pb, Pc, and Pd are configured in association with magenta and yellow.

  Each photosensitive drum 13 has a photosensitive layer on the surface thereof. Each charger 15 is a charging means for uniformly charging the surface of each photosensitive drum 13 to a predetermined potential. In addition to a contact-type roller-type or brush-type charger, a charger-type charger. Is used.

  The optical scanning device 11 is a laser scanning unit (LSU) provided with a laser diode and a reflection mirror, and exposes the surface of each charged photosensitive drum 13 according to image data and corresponds to the image data on those surfaces. An electrostatic latent image is formed.

  Each developing device 12 develops the electrostatic latent image formed on the surface of each photosensitive drum 13 with toner of each color, and forms a toner image on the surface of these photosensitive drums 13. Each drum cleaning device 14 removes and collects toner remaining on the surface of each photosensitive drum 13 after development and image transfer.

  The intermediate transfer belt device 16 is disposed above each photosensitive drum 13 and includes an intermediate transfer belt 21, an intermediate transfer belt driving roller 22, a driven roller 23, four intermediate transfer rollers 24, and a belt cleaning device 25. ing.

  The intermediate transfer belt 21 is formed by forming a film having a thickness of about 100 μm to 150 μm into an endless belt shape. The intermediate transfer belt drive roller 22, the driven roller 23, each intermediate transfer roller 24, and the like stretch and support the intermediate transfer belt 21, and rotate the intermediate transfer belt 21 in the direction of arrow C.

  Each intermediate transfer roller 24 is rotatably supported in the vicinity of the intermediate transfer belt 21 and is pressed against the respective photosensitive drums 13 via the intermediate transfer belt 21.

  The toner images on the surfaces of the photosensitive drums 13 are sequentially transferred to the intermediate transfer belt 21 so as to form color toner images (each color toner image) on the intermediate transfer belt 21. Transfer of the toner image from each photosensitive drum 13 to the intermediate transfer belt 21 is performed by each intermediate transfer roller 24 that is in pressure contact with the back surface of the intermediate transfer belt 21. Each intermediate transfer roller 24 is a roller whose base is a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm and whose surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). Each intermediate transfer roller 24 is applied with a high-voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) in order to transfer the toner image. A high voltage is uniformly applied to the recording paper by the material.

  In this way, the toner images on the surfaces of the photosensitive drums 13 are stacked on the intermediate transfer belt 21 to become a color toner image indicated by the image data. This color toner image is conveyed together with the intermediate transfer belt 21 and transferred onto a recording sheet in a nip region between the intermediate transfer belt 21 and the transfer roller 26a of the secondary transfer device 26.

  The transfer roller 26a of the secondary transfer device 26 has a voltage (a high voltage having a polarity (+) opposite to the toner charging polarity (-)) for transferring the toner image of each color on the intermediate transfer belt 21 onto a recording sheet. Is applied. Further, in order to constantly obtain a nip region between the intermediate transfer belt 21 and the transfer roller 26a of the secondary transfer device 26, either the transfer roller 26a or the intermediate transfer belt drive roller 22 is made of a hard material (metal or the like). The other is made of a soft material such as an elastic roller (such as an elastic rubber roller or a foaming resin roller).

  In addition, the toner image on the intermediate transfer belt 21 may not be completely transferred onto the recording paper by the secondary transfer device 26, and the toner may remain on the intermediate transfer belt 21. Causes color mixing. For this reason, the residual toner is removed and collected by the belt cleaning device 25. The belt cleaning device 25 is provided with, for example, a cleaning blade that contacts the intermediate transfer belt 21 and removes residual toner as a cleaning member, and the back side of the intermediate transfer belt 21 is driven by a driven roller 23 at a portion where the cleaning blade comes into contact. Is supported.

  The recording sheet is conveyed to the fixing device 17 after the color toner image is transferred in the nip region between the intermediate transfer belt 21 and the transfer roller 26 a of the secondary transfer device 26. The fixing device 17 includes a heating roller 31, a pressure roller 32, and the like, and sandwiches and conveys a recording sheet between the heating roller 31 and the pressure roller 32.

  The heating roller 31 is controlled so as to have a predetermined fixing temperature based on a detection output of a temperature detector (not shown), and the color transferred to the recording paper by thermocompression bonding the recording paper together with the pressure roller 32. The toner image is melted, mixed, and pressed, and thermally fixed to the recording paper.

  On the other hand, the paper feed tray 18 is a tray for storing recording paper, and is provided below the image forming apparatus 1 to supply the recording paper in the tray.

  The image forming apparatus 1 has an S-shaped sheet conveyance path S for sending the recording sheet supplied from the sheet feeding tray 18 to the sheet discharge tray 19 via the secondary transfer device 26 and the fixing device 17. Is provided. A sheet registration roller 34, a fixing device 17, a transport roller 35, a paper discharge roller 36, and the like are arranged along the paper transport path S.

  A paper pick-up roller 33 is provided at the end of the paper feed tray 18, and the recording paper is pulled out from the paper feed tray 18 one by one by the paper pick-up roller 33 and transported to the paper transport path S.

  The conveyance roller 35 is a small roller for promoting and assisting conveyance of the recording paper, and a plurality of sets are provided.

  The paper registration roller 34 temporarily stops the recording paper that has been conveyed, aligns the leading edge of the recording paper, and is placed on the intermediate transfer belt 21 in the nip region between the intermediate transfer belt 21 and the transfer roller 26a of the secondary transfer device 26. In order to transfer the color toner image onto the recording sheet, the recording sheet is conveyed in a timely manner in accordance with the rotation of each photosensitive drum 13 and the intermediate transfer belt 21.

  Further, the recording paper is fixed with a color toner image by the fixing device 17, passes through the fixing device 17, and is then discharged face down on the paper discharge tray 19 by the paper discharge roller 36.

  In addition, when printing not only on the front side of the recording paper but also on the back side, the recording paper is stopped by rotating the paper discharge roller 36 while the recording paper is being conveyed by the paper discharge roller 36 in the paper conveyance path S, and recording is performed. The paper is passed through the reverse path Sr, the front and back sides of the recording paper are reversed, the recording paper is guided to the paper registration roller 34, and the image is recorded and fixed on the back surface of the recording paper in the same manner as the front surface of the recording paper. The paper is discharged to the paper discharge tray 19.

  Next, the image reading device 2 of the present embodiment mounted on the upper part of the main body of the image forming apparatus 1 of FIG. 1 will be described with reference to FIG. FIG. 2 is an enlarged cross-sectional view of the image reading device 2.

  The image reading apparatus 2 according to this embodiment includes a lower first reading unit 41 and an upper document conveying unit 42.

  The upper document transport section 42 is pivotally supported on the back side of the lower first reading section 41 by a hinge (not shown) and opened and closed by moving the front portion up and down. When the document transport unit 42 is opened, the platen glass 44 of the lower first reading unit 41 is opened, and the document is placed on the platen glass 44.

  The first reading unit 41 includes a platen glass 44, a first scanning unit 45, a second scanning unit 46, an imaging lens 47, a CCD (Charge Coupled Device) 48, and the like. The first scanning unit 45 includes an illumination unit 51 and a first reflecting mirror 52, and illuminates a document on the platen glass 44 while moving at a constant speed V by a distance corresponding to the document size in the sub-scanning direction. Exposure is performed by the LED array 81 of the unit 51, and the reflected light is reflected by the first reflecting mirror 52 and guided to the second scanning unit 46, thereby scanning the image on the document surface in the sub-scanning direction. The second scanning unit 46 includes second and third reflecting mirrors 53 and 54, and follows the first scanning unit 45 while moving at a speed V / 2, while reflecting the reflected light of the document to the second and third. The light is reflected by the reflection mirrors 53 and 54 and guided to the imaging lens 47. The imaging lens 47 condenses the reflected light of the document on the CCD 48 and forms an image on the surface of the document on the CCD 48. The CCD 48 repeatedly scans the document image in the main scanning direction, and outputs an analog image signal of one main scanning line each time.

  Further, the lower first reading unit 41 can read not only a stationary document but also an image on the surface of the document being conveyed by the document conveying unit 42. In this case, as shown in FIG. 2, the first scanning unit 45 is moved to the reading position below the transparent guide plate 65, and the second scanning unit 46 is positioned in accordance with the position of the first scanning unit 45. Then, the document conveyance unit 42 starts conveying the document.

  In the document transport unit 42, the pickup roller 55 is pressed against the document on the document tray 56 and rotated to pull out the document, transport the document through the document transport path 57, and transport the document to the transparent guide plate 65 of the first reading unit 41. The original is passed between the reading guide plates 66, and further, the original is passed through the second reading unit 43 and conveyed from the paper discharge roller 58 to the paper discharge tray 49. Along the document conveyance path 57, a registration roller 62 that conveys the document after aligning its leading edge and a conveyance roller 63 that conveys the document are arranged.

  When the document is transported, the surface of the document is illuminated through the transparent guide plate 65 by the LED array 81 of the illumination unit 51 of the first scanning unit 45, and the reflected light from the surface of the document is first and second scanning units 45, 46. Are reflected to the imaging lens 47 by the reflecting mirrors, and the reflected light from the document surface is condensed on the CCD 48 by the imaging lens 47, and an image of the document surface is formed on the CCD 48, whereby the image of the document surface is formed. Read.

  Further, at the same time as reading the image on the front side of the document being conveyed by the document conveying unit 42, the image on the back side of the document can be read by the second reading unit 43 built in the document conveying unit 42. The second reading unit 43 is disposed above the platen glass 44, and includes a contact image sensor (hereinafter referred to as CIS) 73 and a reading guide plate arranged with a conveyance path through which the document passes. 74 and a transparent guide plate 75. The CIS 73 includes an LED array 83 that illuminates the back side of the document through the transparent guide plate 75, a SELFOC (registered trademark) lens array 72 that collects reflected light of the document through the transparent guide plate 75 for each pixel, and SELFOC. An image sensor 73S that photoelectrically converts the reflected light of the document received through the lens array 72 and outputs an analog image signal is provided. The document that has passed over the transparent guide plate 65 of the first reading unit 41 passes between the reading guide plate 74 and the transparent guide plate 75 of the second reading unit 43 and is discharged to the discharge tray 49. When passing, the back surface of the document is illuminated by the LED array 83 via the transparent guide plate 75, and the reflected light from the back surface of the document enters the image sensor 73S via the transparent guide plate 75 and the Selfoc lens array 72, and the image sensor 73S. Thus, the image on the back side of the document is read.

  The original image read by the CCD 48 and the CIS 73 is output as an analog image signal from the CCD 48 and the CIS 73, and the analog image signal is A / D converted into a digital image signal. The digital signal is subjected to various image processing and then transmitted to the optical scanning device 11 of the image forming apparatus 1, where the image is recorded on a recording sheet, and the recording sheet is used as a copy original. Is output.

  By the way, in the image reading apparatus 2, since the document passes through the transport path on the transparent guide plate 65 of the first reading unit 41, foreign matters such as paper dust are on the upper surface of the transparent guide plate 65 and the lower surface of the reading guide plate 66. May adhere. When the foreign matter on the upper surface of the transparent guide plate 65 is left unattended, the foreign matter on the surface of the transparent guide plate 65 is repeatedly read together with the image of the original by the CCD 48, and streaks extending in the sub-scanning direction are generated on the read image. This streak appears on the copied manuscript. Further, a white reference plate (white reference member) 66a for shading correction is provided on the lower surface of the reading guide plate 66, and when a foreign matter adheres to the white reference plate 66a, the foreign matter becomes a white reference plate of the reading guide plate 66. An error occurs in the shading correction data that is read together with the plate 66a, and the image quality deteriorates. However, when the original is read, the white reference plate 66a is covered with the original, so that the foreign matter on the white reference plate 66a is not read together with the original.

  Therefore, as shown in FIG. 2, the first scanning unit 45 is moved to the reading position below the transparent guide plate 65, the second scanning unit 46 is moved and positioned, and the original is read with the transparent guide plate 65 and the reading guide. Reading is performed by the CCD 48 without passing between the plates 66, and foreign matter attached to the transparent guide plate 65 and the white reference plate 66 a of the reading guide plate 66 is detected based on the output of the CCD 48.

  Here, the transparent guide plate 65 and the white reference plate 66a of the reading guide plate 66 are opposed to each other with the conveyance path interposed therebetween, and are disposed close to each other. Therefore, even if the CCD 48 reads the transparent guide plate 65 and the white reference plate 66a and can detect foreign matter from the read image, the foreign matter is attached to the transparent guide plate 65 or the white reference plate 66a. Is difficult to determine. And if an adhesion part of a foreign material cannot be specified, an exact measure cannot be performed quickly.

  Therefore, in this embodiment, each LED of the LED array 81 of the first scanning unit 45 is selectively turned on or off to cause a shadow of foreign matter on the white reference plate 66a, and a read image read by the CCD 48. Based on the shadow of the foreign matter, whether the foreign matter is attached to the transparent guide plate 65 or the white reference plate 66a is determined. More specifically, each LED is selectively turned on or off to change the shadow of the foreign matter on the white reference member 66a, and each time reading is performed by the CCD 48, and the respective read images read a plurality of times are compared. Then, it is determined whether the foreign matter is attached to the transparent guide plate 65 or the white reference plate 66a from the change in the shadow position of the foreign matter, the gradation change of the read image, or the positional relationship between the foreign matter and the shadow.

  Although foreign matter adheres to the surface of the platen glass 44 as well, the original is placed on the platen glass 44 and the first and second scanning units 45 and 46 are moved in the sub-scanning direction. The foreign matter only appears spot-like on the obtained image, and the influence of the foreign matter is small. Further, the foreign matter can be removed simply by wiping the surface of the platen glass 44. For this reason, the foreign material on the surface of the platen glass 44 is not detected.

  Next, a configuration for selectively turning on / off each LED of the LED array 81 and detecting foreign matter based on a read image read by the CCD 48 will be described.

  First, the configuration of the first scanning unit 45 will be described. FIG. 3 is a perspective view showing the first scanning unit 45. FIG. 4 is a cross-sectional view showing the first scanning unit 45.

  As apparent from FIGS. 3 and 4, the first scanning unit 45 includes a moving scanning frame 77 and an illumination unit 51 mounted on the moving scanning frame 77.

  The moving scanning frame 77 is moved and scanned in the sub-scanning direction, and both ends 77a thereof are slidably supported and moved in the sub-scanning direction. The moving scanning frame 77 is provided with a first reflecting mirror 52. The first reflecting mirror 52 extends along the main scanning direction and with respect to the scanning surface (the surfaces of the transparent guide plate 65 and the platen glass 44). Are inclined at 45 °.

  A front end 77b of the moving scanning frame 77 is bent upward, and an opening slit 77c is formed in the front end 77b. A driver circuit 78 is mounted at the rear of the moving scanning frame 77.

  The illuminating unit 51 illuminates a document, has a slit St, and elongated substrates 76 that are parallel to each other are fixed to both sides of the slit St in the longitudinal direction.

  As shown in FIG. 5, each substrate 76 is mounted with an LED array 81 composed of a plurality of LEDs 82. Each LED 82 is connected to the wiring pattern of each substrate 76, and the wiring pattern of each substrate 76 is connected to the driver circuit 78 of the moving scanning frame 77 through a harness (not shown). The driver circuit 78 supplies power to each LED 82 through the harness and the wiring pattern of each board 76, and controls each LED 82 to be turned on and off.

  As is clear from FIG. 6, the substrate 76 and the LED array 81 on the substrate 76 are provided along the main scanning direction, and light from the LED array 81 is irradiated to the document MS through the transparent guide plate 65. .

  Further, since the surface of each substrate 76 is white, not only the light of each LED 82 on each substrate 76 is directly irradiated to the original document but also the surface of each substrate 76 as shown in FIG. The reflected light is also applied to the original, and the amount of light applied to the original increases. Further, as shown in FIG. 7B, it is possible to illuminate the document only by each LED 82 on one substrate 76.

  As shown in FIGS. 3 and 4, the first reflecting mirror 52 is positioned immediately below the slit St of the illumination unit 51. When each LED 82 of each substrate 76 emits light, the light of each LED 82 is emitted upward and is sent to the platen. The original MS is irradiated through the glass 44 or the transparent guide plate 65, and the reflected light from the original MS enters the slit St through the platen glass 44 or the transparent guide plate 65, and this reflected light enters the first reflecting mirror 52 through the slit St. The reflected light is emitted to the second reflecting mirror 53 of the second scanning unit 46 through the opening slit 77 c of the front end 77 b of the moving scanning frame 77.

  FIG. 8 is a block diagram showing a configuration of a signal processing system in the image reading apparatus 2. As shown in FIG. 8, the image reading apparatus 2 includes a first image processing unit 111, a second image processing unit 211, and a transport driving unit 215. The first image processing unit 111 converts an analog image signal from the CCD 48 of the first reading unit 41 (shown in FIG. 2) into a digital image signal, and performs various image processing on the digital image signal. The first and second scanning units 45 and 46 of the first reading unit 41 are driven and controlled, and the document conveyance unit 42 controls the conveyance of the document. Further, the second image processing unit 211 converts an analog image signal from the CIS 73 of the second reading unit 43 (shown in FIG. 2) of the document conveying unit 42 into a digital image signal, and performs various processing on the digital image signal. Image processing is performed, and document conveyance control by the document conveyance unit 42 is performed. A digital image signal is transmitted and received from at least one of the first and second image processing units 111 and 211 to the optical scanning device 11 of the image forming apparatus 1, and an image is recorded on a recording sheet in the image forming apparatus 1.

  The first image processing unit 111 receives the first sensor unit 113 including the LED array 81 and the CCD 48 of the first scanning unit 45 and the digital image signal from the first sensor unit 113, and outputs the digital image signal. A first calculation unit 114 that performs various image processing and a scanning drive unit 115 that drives the first and second scanning units 45 and 46 of the first reading unit 41 are provided.

  The first sensor unit 113 includes a driver circuit 78 for selectively turning on and off each LED 82 of the LED array 81, two analog front end circuits for A / D converting analog image signals from the CCD 48 and the CCD 48 into digital image signals. (Hereinafter referred to as AFE) 116 and an LSI 117 including a register that relays and transfers a digital image signal from each AFE 116.

  The first calculation unit 114 is used by the CPU 121, a central processing unit (hereinafter referred to as a CPU) 121 that controls the first image processing unit 111 in an integrated manner, a program memory 122 that stores a program executed by the CPU 121, and the CPU 121. A work memory 123, a flash memory 124 for storing shading correction data, a receiver 125 for inputting a digital image signal from the LSI 117 of the first sensor unit 113, and a digital image signal for receiving a digital image signal from the receiver 125. An SCAN ASIC (Application Specific Integrated Circuit) 126 that performs various image processing on the signal, an SDRAM (Synchronous DRAM) 127 used by the SCAN ASIC 126, and a receiver 128 that inputs a digital image signal from the second image processing unit 211. And SCAN Either the digital image signal from the ASIC 126 or the digital image signal from the second image processing unit 211 is input via the bus switch 129, and the input digital image signal is transmitted to the optical scanning device 11 of the image forming apparatus 1. A transmission unit 130 and an IOASIC 131 that controls input / output with respect to each sensor 141 and the like of the scan driving unit 115 are provided.

  The scanning drive unit 115 includes a plurality of sensors 141 that detect the positions of the first and second scanning units 45 and 46, and a driving motor 142 for moving the first and second scanning units 45 and 46. Yes. The CPU 121 of the first calculation unit 114 controls driving of the driving motor 142 while confirming the positions of the first and second scanning units 45 and 46 detected by the sensors 141, and the first and second scanning units 45. , 46 is controlled.

  The second image processing unit 211 inputs the digital image signal from the second sensor unit 213 constructed on the substrate on which the CIS 73 of the second reading unit 43 is mounted, and the second sensor unit 213 to the digital image signal. And a second arithmetic unit 214 that performs various image processing.

  The second sensor unit 213 converts the analog image signal from the LED array 83 of the CIS 73, the driver circuit 85 that selectively turns on and off each LED of the LED array 83, the image sensor 73S, and the image sensor 73S into a digital image signal A. Two analog front-end circuits (hereinafter referred to as AFE) 216 for / D conversion and an LSI 217 including a register for relaying and transferring a digital image signal from each AFE 216 are provided.

  The second calculation unit 214 is used by a central processing unit (hereinafter referred to as a CPU) 221 that controls the second image processing unit 211 in an integrated manner, a program memory 222 that stores a program executed by the CPU 221, and the CPU 221. A work memory 223, a flash memory 224 for storing shading correction data, a receiver 225 for inputting a digital image signal from the LSI 217 of the second sensor unit 213, and a digital image signal from the receiver 225 for inputting a digital image A SCANAASIC 226 that performs various image processing on the signal and an SDRAM 227 used by the SCAN ASIC 226 are provided.

  The transport driving unit 215 includes a plurality of sensors 231 that detect the presence or absence of a document set on the document tray 56 and the platen glass 44 and a document transport position in the document transport path 57 of the document transport unit 42. A motor 232 that rotationally drives a pickup roller, a registration roller, a conveyance roller, and the like, a clutch 233 that contacts and separates a drive transmission path between the roller and the motor shaft, and a drive control unit 234 that controls driving of the motor 232 and the clutch 233 are provided. ing. The CPU 121 of the first calculation unit 114 or the CPU 221 of the second calculation unit 214 drives and controls the motor 232 and the clutch 233 through the drive control unit 234 based on the detection output of each sensor 231, and conveys the document on the document conveyance path 57. Control.

  In the image reading apparatus 2 having such a configuration, as described above, the first scanning unit 45 is moved to the reading position below the transparent guide plate 65, the second scanning unit 46 is positioned, and the original is scanned. Each LED 82 of the LED array 81 of the first scanning unit 45 is selectively turned on or off so as not to pass between the transparent guide plate 65 and the reading guide plate 66 of the first reading unit 41, so that the transparent guide plate 65 or A shadow of the foreign matter adhering to the white reference plate 66a is generated, and it is determined whether the foreign matter is attached to the transparent guide plate 65 or the white reference plate 66a based on the shadow of the foreign matter in the read image read by the CCD 48. To do.

  Specifically, the CPU 121 of the first calculation unit 114 controls the driving of the driving motor 142 while confirming the positions of the first and second scanning units 45 and 46 detected by the sensors 141 and performs the first scanning. The unit 45 is moved to the reading position below the transparent guide plate 65, and the second scanning unit 46 is moved and positioned.

  Then, the CPU 121 selects the LED array 81 on one substrate 76 in the illumination unit 51 via the driver circuit 78, that is, selects the LED array 81 in one row, and selects all the LEDs 82 of this LED array 81. Light up. Further, the CPU 121 causes the CCD 48 of the first sensor unit 113 to read once in the main scanning direction while the LED array 81 in one row is lit. The output of the CCD 48 is converted into a digital signal by each AFE 116, and this digital signal is input to the CPU 121 via the LSI 117, the receiver 125, and the SCAN ASIC 126. The CPU 121 detects the position of the foreign matter based on a digital signal indicating the output of the CCD 48.

  Here, when each LED 82 of the LED array 81 in one row is turned on as shown in FIG. 9 in a state where the document does not pass between the transparent guide plate 65 and the reading guide plate 66 of the first reading unit 41, The light of each LED 82 enters the white reference plate 66a through the transparent guide plate 65, the incident light is reflected by the white reference plate 66a, and the reflected light is reflected by the first reflection mirror 52 of the first scanning unit 45. Then, this reflected light is reflected by each reflecting mirror of the second scanning unit 46 and enters the CCD 48 through the imaging lens 47, and the CCD 48 reads in the main scanning direction.

  The width of the main scanning line read by the CCD 48 is enlarged by the imaging lens 47 so as to be substantially the same as the width of the LED array 81 in the main scanning direction. The CCD 48 sequentially reads gradations of a plurality of pixels along the main scanning line, and sequentially outputs respective outputs indicating the gradations of the respective pixels.

  Accordingly, the CCD 48 receives the light transmitted through the transparent guide plate 65 and reflected by the white reference plate 66a, and reads the transparent guide plate 65 and the white reference plate 66a along the main scanning direction.

  At this time, for example, the foreign matter 241 adheres to the transparent guide plate 65 as shown in FIG. 10A, or the foreign matter 241 adheres to the white reference plate 66a as shown in FIG. If the foreign matter 241 exists on the main scanning line read by the CCD 48, the output level of the CCD 48 fluctuates (increases or decreases) when the foreign matter 241 is read as shown in FIG. Alternatively, the output level of the CCD 48 indicating the gradation of the pixels on the main scanning line corresponding to the foreign matter 241 varies.

  Therefore, as shown in FIG. 10C, when the output level (gradation) of the CCD 48 fluctuates by a certain value or more, it can be determined that the foreign substance 241 is present at the pixel position where the output level (gradation) fluctuated. The position of the pixel can be detected as the position of the foreign matter 241.

  Based on the digital signal indicating the output of the CCD 48, the CPU 121 compares the gradation of the pixel of interest with the gradation of other pixels in the vicinity of the pixel of interest for each pixel on the main scanning line. It is determined whether or not the level has fluctuated more than the level, and if there is a corresponding pixel, it is determined that the foreign matter 241 is present at the corresponding pixel position on the main scanning line, and the position of the corresponding pixel on the main scanning line is The position of the foreign object 241 is detected. Then, when the CPU 121 detects the position of the foreign object 241 on the main scanning line, for example, as shown in FIG. Divide into Ba and Bb. The relationship between the position of each pixel on the main scanning line and the position of each LED 82 of the LED array 81 in one column is stored in advance in the memory, and the CPU 121 refers to the positional relationship in the memory and stores one column. Each LED 82 of the LED array 81 is divided into two blocks Ba and Bb. At this time, if at least one LED 82 overlaps the position of the foreign matter 241, each LED 82 on one side of the LED 82 at this position is defined as one block Ba except for the LED 82 at this position. Each other LED 82 on one side is referred to as the other block Bb. If the position of the foreign matter 241 is between the two LEDs 82, each LED 82 on one side of this position is set as one block Ba, and each other LED 82 on the other side of this position is set as the other block Bb. And

  After that, the CPU 121 selects all the LEDs 82 included in one block Ba in the LED array 81 in one row via the driver circuit 78, turns on all the LEDs 82 in the block Ba, and all the LEDs 82 in the block Bb. Turn off the light. Then, the CPU 121 causes the CCD 48 of the first sensor unit 113 to read once in the main scanning direction while the LED 82 of the block Ba is lit, and outputs the CCD 48 via each AFE 116, LSI 117, receiver 125, and SCAN ASIC 126. The shadow of the foreign object is detected based on the output of the CCD 48.

  Subsequently, the CPU 121 selects all of the LEDs 82 included in the other block Bb in the LED array 81 in one column via the driver circuit 78, turns on all the LEDs 82 of the block Bb, and sets the LEDs 82 of the block Ba. All are turned off, and while the LED 82 of the block Bb is lit, the CCD 48 of the first sensor unit 113 performs one reading in the main scanning direction, the output of the CCD 48 is input, and the shadow of the foreign matter is cast based on the output of the CCD 48. To detect.

  Then, the CPU 121 is transparent based on the shadow of the foreign matter detected based on the output of the CCD 48 while the LED 82 of the block Ba is turned on and the shadow of the foreign matter detected based on the output of the CCD 48 while the LED 82 of the block Bb is turned on. It is determined which of the guide plate 65 and the white reference plate 66a has foreign matter attached.

  Here, as shown in FIG. 12A, when the foreign matter 241 is attached to the transparent guide plate 65, when only the LED 82 of the block Ba is turned on, the light of the LED 82 of the block Ba is transmitted to the transparent guide plate 65. Since the light is incident obliquely on the white reference plate 66a through the foreign matter 241, a shadow 242a of the foreign matter 241 is reflected on the white reference plate 66a. Also, as shown in FIG. 12B, when only the LED 82 of the block Bb is turned on, the light of the LED 82 of the block Bb is obliquely incident on the white reference plate 66a through the foreign matter 241 of the transparent guide plate 65. Thus, a shadow 242b of the foreign matter 241 is reflected on the white reference plate 66a. When the LED 82 of the block Ba is turned on and when the LED 82 of the block Bb is turned on, the incident direction of the light of the LED 82 with respect to the foreign matter 241 of the transparent guide plate 65 is reversed, so that it appears on the white reference plate 66a. The respective shadows 242a and 242b are separated with the foreign matter 241 therebetween. Further, since the blocks Ba and Bb are set substantially symmetrically with respect to the foreign matter 241 of the transparent guide plate 65, the light incident path of the LED 82 of the block Ba and the light of the LED 82 of the block Bb with respect to the foreign matter 241 of the transparent guide plate 65. Are substantially symmetrical with each other, and the separation distances of the shadows 242a and 242b with respect to the foreign matter 241 are substantially equal.

  On the other hand, as shown in FIGS. 12C and 12D, when the foreign matter 241 is attached to the white reference plate 66a, only the LED 82 of the block Ba is lit or only the LED 82 of the block Bb is lit. Even if the light from the LED 82 is incident on the white reference plate 66a obliquely, only a small shadow 243 that overlaps the foreign matter 241 appears on the white reference plate 66a.

  FIG. 13A shows that the light of the LED 82 of the block Ba is incident on the main scanning line by the CCD 48 when the light of the LED 82 of the block Ba enters the white reference plate 66a obliquely through the foreign matter 241 of the transparent guide plate 65 as shown in FIG. The read image read along is shown. FIG. 13B shows the main scanning by the CCD 48 when the light from the LED 82 of the block Bb is incident on the white reference plate 66a through the foreign matter 241 of the transparent guide plate 65 obliquely as shown in FIG. The read image read along the line is shown. In the read image of FIG. 13A, an image 244 of the foreign matter 241 and an image 245a of the shadow 242a on the white reference plate 66a that is spaced to the left from the image 244 of the foreign matter 241 are shown. In the read image of FIG. 13B, an image 244 of the foreign matter 241 and an image 245b of the shadow 242b on the white reference plate 66a spaced to the right side from the image 244 of the foreign matter 241 are shown. The separation distances of the images 245a and 245b of the shadows 242a and 242b with respect to the image 244 of the foreign matter 241 are substantially equal.

  FIG. 13C shows an image read by the CCD 48 when the light from the LED 82 of the block Ba is obliquely incident on the foreign matter 241 of the white reference plate 66a as shown in FIG. 12C. FIG. 13D shows an image read by the CCD 48 when the light from the LED 82 of the block Bb is obliquely incident on the foreign matter 241 of the white reference plate 66a as shown in FIG. 12D. 13C and 13D, only small images 246 of the shadows 243 that overlap the image 244 of the foreign matter 241 are shown.

  Therefore, the image read by the CCD 48 when only the LED 82 of the block Ba is turned on and the image read by the CCD 48 when only the LED 82 of the block Bb are turned on are compared, and the image 244 (position) of the foreign matter 241 is obtained. If the images 245a and 245b of the shadows 242a and 242b that are spaced apart at substantially the same distance are shown on both sides, it can be determined that the foreign matter 241 is attached to the transparent guide plate 65. Further, comparing these read images, if the images 245a and 245b of the shadows 242a and 242b that are separated from the image 244 (position) of the foreign material 241 by approximately the same distance on both sides are not reflected, the white reference plate 66a It can be determined that the foreign matter 241 is attached to the surface. That is, based on the images 245a and 245b of the shadows 242a and 242b, it can be determined which of the transparent guide plate 65 and the white reference plate 66a has the foreign matter 241 attached.

  Specifically, the CPU 121 recognizes the images 245a and 245b of the shadows 242a and 242b based on the gradation change in the main scanning direction of the image read by the CCD 48, and images 245a of the shadows 242a and 242b with respect to the position of the foreign matter 241. The positional relationship of 245b is obtained.

  14A corresponds to FIG. 12A and FIG. 13A, and the light of the LED 82 of the block Ba is incident on the white reference plate 66a obliquely through the foreign matter 241 of the transparent guide plate 65. FIG. The gradation change (change in the output level of the CCD 48) in the main scanning direction of the image read by the CCD 48 is shown. 14B corresponds to FIGS. 12B and 13B, and the gradation change in the main scanning direction of the image read by the CCD 48 when the light from the LED 82 of the block Bb is obliquely incident (CCD 48). Output level change). 14A and 14B, the gradation in the main scanning direction of the read image greatly decreases by substantially the same level at the same pixel position (main scanning timing of the same pixel) where the image 244 of the foreign matter 241 is reflected. The positions of the foreign matter 241 are slightly lowered at the positions (positions of the images 245a and 245b of the respective shadows 242a and 242b) which are separated from each other by a substantially same distance (the same number of pixels) on both sides.

  FIG. 14C corresponds to FIG. 12C and FIG. 13C, and the main image of the image read by the CCD 48 when the light from the LED 82 of the block Ba obliquely enters the foreign matter 241 of the white reference plate 66a. A gradation change in the scanning direction (change in output level of the CCD 48) is shown. 14D corresponds to FIGS. 12D and 13D, and the gradation change in the main scanning direction of the image read by the CCD 48 when the light from the LED 82 of the block Bb is obliquely incident (CCD 48). Output level change). 14C and 14D, the gradation in the main scanning direction of the read image greatly decreases at the same pixel position (main scanning timing of the same pixel) where the image 244 of the foreign matter 241 is reflected, and the shadow 243 Although the position of each pixel in which the image 246 is reflected is slightly reduced, it is difficult to distinguish between the gradation change of the image 244 and the gradation change of the image 246 because the image 244 and the image 246 are adjacent to each other.

  Here, as shown in FIGS. 10A to 10C, when all the LEDs 82 of the LED array 81 in one row are turned on, the position of the foreign matter 241 is detected based on the fluctuation of the output level of the CCD 48. is doing. For this reason, the CPU 121 changes the gradation in the main scanning direction of the read image by the CCD 48 when only the LED 82 of the block Ba is turned on, and the main scanning direction of the read image by the CCD 48 when only the LED 82 of the block Bb is turned on. Referring to the gradation change, it is determined whether or not the gradation is lowered by a predetermined gradation level or more at each position separated from the position of the foreign object 241 by approximately the same distance (the same number of pixels) at a predetermined distance or more on both sides. can do. If the gradation is lowered by a predetermined gradation level or more at each position, it can be considered that the shadows 242a and 242b of the foreign object 241 are reflected. The predetermined distance is a preset distance r as shown in FIG. 15, for example, the separation distance u between the transparent guide plate 65 and the white reference plate 66a, the separation distance v between the transparent guide plate 65 and the LED array 81, and It is set according to the distance w from the position of the foreign matter 241 in the main scanning direction to the lighting center position of the block. The substantially the same distance means that, for example, the difference between the distances (number of pixels) separated from both sides from the position of the foreign matter 241 is within a preset distance (number of pixels). The predetermined tone level is a preset tone change amount.

  Further, the CPU 121 is different from the position of the foreign object 241 to the both sides, for example, if the gradation is not lowered at each position separated from the position of the foreign object 241 by approximately the same distance (the same number of pixels) at a predetermined distance or more on both sides. If the gradation is reduced at each position separated by a distance, or if the gradation is reduced only on one side of the position of the foreign matter 241, it is considered that the shadows 242a and 242b of the foreign matter 241 are not reflected. Can do.

  If the CPU 121 determines that the shadows 242a and 242b are shown on both sides of the position of the foreign matter 241, the CPU 121 determines that the foreign matter 241 is attached to the transparent guide plate 65, and the shadows 242a and 242b are shown. If it is determined that the foreign object 241 is not attached, it is determined that the foreign matter 241 is attached to the white reference plate 66a.

  When the determination by the CPU 121 is thus made, the determination result is displayed on the display screen of the operation panel of the image forming apparatus 1. For example, as shown in FIG. 16, the operation panel 151 of the image forming apparatus 1 includes a plurality of operation keys 152, a display screen 153 of a liquid crystal display device, a transparent touch panel overlaid on the display screen 153, and the like. The liquid crystal display device is controlled by a control unit (not shown) of the forming apparatus 1, and operation guidance and the like of the image forming apparatus 1 are displayed on the display screen 153. The determination result by the CPU 121 of the image reading apparatus 2, that is, which of the transparent guide plate 65 and the white reference plate 66a is attached to the foreign matter 241 is displayed on the display screen 153 through the control unit of the image forming apparatus 1. At this time, if the foreign matter 241 adheres to the transparent guide plate 65 as well as the determination result, a message prompting the cleaning of the transparent guide plate 65 and the position of the foreign matter 241 on the transparent guide plate 65 are displayed on the display screen 153. May be. Alternatively, if the foreign matter 241 is attached to the white reference plate 66a, a message that does not require cleaning of the white reference plate 66a may be displayed on the display screen 153. As a result, when the foreign matter 241 adheres to the white reference plate 66a, it is not necessary to wastefully perform the cleaning work. These messages are stored in advance in the memory of the image forming apparatus 1 in association with the respective determination results, and the messages corresponding to the determination results by the CPU 121 of the image reading apparatus 2 are read and displayed on the display screen.

  When the foreign matter 241 adheres to the white reference plate 66a, if the white reference plate 66a is read by the CCD 48 and the shading correction data is generated, an error occurs in the shading correction data, but the white reference plate 66a is not cleaned. The error can be dealt with by correcting the shading correction data.

  Here, the shading correction data means that the first scanning unit 45 is moved to the reading position below the transparent guide plate 65 and the second scanning unit 46 is moved and positioned as shown in FIG. The LED array 81 in two rows of the illuminating unit 51 is turned on without passing between the transparent guide plate 65 and the reading guide plate 66, the white reference plate 66 a is illuminated by each LED array 81, and the white reference plate 66 a by the CCD 48. Is read in the main scanning direction (along the main scanning line), and the output of the CCD 48 at this time is converted into a digital signal by each AFE 116. This shading correction data is stored in the flash memory 124 and used. It is done.

  FIG. 17 is a graph showing a characteristic line W of shading correction data. In the graph of FIG. 17, the horizontal axis indicates the position of each pixel on the main scanning line, and the vertical axis indicates the shading correction level (tone). Further, “255” gradation corresponds to pure white, and “0” gradation corresponds to pure black. The characteristic line W draws a generally gradual mountain shape, and represents a gradation characteristic in which the characteristic line W becomes lower at both sides of the main scanning line and becomes higher at the center of the main scanning line.

  However, if the foreign matter 241 is attached to the white reference plate 66a, the gradation of the pixels on the main scanning line is suddenly changed by the foreign matter 241, and the shading correction level is also suddenly changed. For example, the characteristic line W falls into a valley shape or protrudes into a mountain shape. Therefore, pay attention to each pixel sequentially, and for each pixel of interest, find the difference between the pixel of interest and the shading correction level corresponding to the other pixels adjacent to the pixel of interest, and the absolute value of this difference must exceed a certain level. For example, it is considered that the shading correction level has changed abruptly, and the shading correction levels of the pixels immediately before the sudden change, that is, the shading correction levels of the pixels 251 at both edges of the valley shape immediately before the drop, or the peaks immediately before the protrusion. The shading correction levels of the pixels 252 at both edges of the mold are connected with a straight line, and correction is performed so as to smooth the characteristic line W. As a result, errors in the shading correction data can be suppressed, and the white reference plate 66a need not be cleaned.

  In the first embodiment, when a plurality of foreign substances 241 are attached to the transparent guide plate 65 and the white reference plate 66a, the positions of all the foreign substances 241 are detected, and the positions of the foreign substances 241 are determined for each foreign substance 241. Each LED 82 of the LED array 81 in one row is divided into two blocks Ba and Bb at the boundary, and the LEDs 82 of the blocks Ba and Bb are alternately turned on to obtain the shadows 242a and 242b of the foreign matter 241 to obtain a transparent guide. It is determined whether the foreign matter 241 is attached to the plate 65 or the white reference plate 66a.

  In addition, when the gradation varies more than a predetermined gradation level at each position separated from the position of the foreign object 241 by approximately the same distance (the same number of pixels) at a predetermined distance or more on both sides, each shadow 242a of the foreign object 241 is changed. 242b is considered to be reflected, but the gradation is simply reduced at each position separated from the position of the foreign object 241 by approximately the same distance (the same number of pixels) on both sides, or both sides of the position of the foreign object 241. In this case, it may be considered that the shadows 242a and 242b of the foreign matter 241 are reflected only by the gradation being lowered.

  Further, the position of the foreign matter 241 is detected based on the output level fluctuation of the CCD 48 when the foreign matter 241 is read as shown in FIG. 10C, and the CCD 48 when one LED 82 of each of the blocks Ba and Bb is turned on. It may be determined that the foreign material 241 is attached to the transparent guide plate 65 only by detecting any one of the images of the shadows 242a and 242b spaced from the position of the foreign material 241 based on the output level fluctuation.

  Although the determination accuracy varies depending on which method is used, the amount of calculation can be reduced by using a simple method.

  Next, a second embodiment of the image reading apparatus of the present invention will be described. The image reading apparatus 2 of the second embodiment is applied to the image forming apparatus 1 of FIG. 1 and has the same configuration as that shown in FIGS. 2 to 8, but each LED 82 of the LED array 81. The lighting method is different.

  In the second embodiment, each LED 82 of the LED array 81 in one row is divided into a plurality of blocks in advance, and each block is sequentially selected, and only the LED 82 of the selected block is turned on. Then, reading in the main scanning direction by the CCD 48 is performed.

  Specifically, the CPU 121 selects one row of LED arrays 81 via the driver circuit 78, sequentially selects each LED 82 of the LED array 81 in units of blocks, and turns on only the LEDs 82 of the selected block. . The CPU 121 causes the CCD 48 to read in the main scanning direction once every time the LED 82 of the block is turned on, and inputs the output of the CCD 48 via each AFE 116, LSI 117, receiver 125, and SCAN ASIC 126. Based on the respective outputs of the CCD 48 corresponding to the number of readings, it is determined which of the transparent guide plate 65 and the white reference plate 66a has foreign matter attached.

  For example, as shown in FIGS. 18A, 18B, and 18C, each LED 82 of the LED array 81 in one row is divided into blocks B1, B2, B3,..., And the blocks B1,. Only the LED 82 of the selected block is lit up.

  Regarding the foreign matter 241 attached to the transparent guide plate 65, when the LED 82 of the block that overlaps the position of the foreign matter 241 and the LED 82 of the block adjacent to both sides of the position of the foreign matter 241, the shadow 247 that is separated from the position of the foreign matter 241 appears. There is a possibility of being reflected on the white reference plate 66a. Since the incident direction of the light of the LED 82 with respect to the foreign matter 241 of the transparent guide plate 65 changes depending on which block of the LED 82 is lit, the shadow 247 reflected on the white reference plate 66a moves.

  For the foreign matter 241 attached to the white reference plate 66a, even if the LED 82 of any block is turned on, only a small shadow that overlaps the foreign matter 241 appears on the white reference plate 66a, and this shadow hardly moves.

  For this reason, each time the blocks B1,... Are sequentially selected and the LED 82 of the selected block is turned on, reading by the CCD 48 is performed, and each read image obtained by multiple readings is compared to find the position. An image of the foreign object 241 that does not change is specified, the position of the foreign object 241 is obtained, it is determined whether or not the image of the shadow 247 moving on both sides of the position of the foreign object 241 is reflected, and if the image of the shadow 247 is reflected, It can be determined that the foreign matter 241 is attached to the transparent guide plate 65. Further, if there are no images of the shadow 247 moving on both sides of the position of the foreign matter 241, it can be determined that the foreign matter 241 is attached to the white reference plate 66a. That is, based on the image of the foreign matter 241 and the image of the shadow 247, it can be determined whether the foreign matter 241 is attached to the transparent guide plate 65 or the white reference plate 66a.

  Specifically, the CPU 121 compares the gradation change in the main scanning direction of each read image obtained by reading by the CCD 48 a plurality of times, and compares the position of the same pixel (main scan timing of the same pixel) in at least two read images. ), If the gradation is lowered or increased, it is considered that the image of the foreign matter 241 is reflected on the pixel, and the position of the foreign matter 241 is obtained. Further, the CPU 121 considers that an image of the shadow 247 is captured if the gradation is lowered at each position separated from the position of the foreign object 241 at a distance from both sides in at least two read images. Furthermore, if the gradation does not decrease at each position that is spaced from the position of the foreign object 241 at both sides, or if the gradation decreases only on one side of the position of the foreign object 241, the CPU 121 It is assumed that the image of is not reflected.

  Then, if the CPU 121 considers that the shadow 247 images appear on both sides of the position of the foreign matter 241, it determines that the foreign matter 241 is attached to the transparent guide plate 65, and no image of the shadow 247 appears. In this case, it is determined that the foreign matter 241 is attached to the white reference plate 66a.

  In the second embodiment, it may be considered that the image of the shadow 247 is reflected only by the gradation being lowered at both sides of the position of the foreign matter 241.

  Moreover, it is preferable to distribute the same number of LEDs 82 to each block. Furthermore, the number of LEDs 82 included in the block is arbitrary, and the minimum number is 1. When the minimum number is 1, each LED 82 of the LED array 81 in one row is selected and turned on one by one, and each time the LED 82 is turned on, the CCD 48 performs one reading in the main scanning direction, and a plurality of times. Each read image obtained by reading (corresponding to the number of each LED 82) is compared, the image of the foreign object 241 whose position does not change is specified, the position of the foreign object 241 is obtained, and moved on both sides of the position of the foreign object 241. It is determined whether an image of the shadow 247 to be reflected is shown. As each block is subdivided, that is, as the number of LEDs 82 included in the block decreases, the accuracy of determination of the shadow 247 increases, but the number of readings by the CCD 48 increases and the amount of calculation by the CPU 121 also increases.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. It is understood.

  For example, a white reference plate 67 for shading correction may be provided on the upper surface of the end of the platen glass 44 as shown in FIG. In this case, the first scanning unit 45 is moved below the white reference plate 67, the second scanning unit 46 is moved and positioned, and the white reference plate 67 is read by the CCD 48 in a state where no original is passed. The shading correction data is acquired. Further, a simple white plate (or a plate having a color close to white) 68 is provided on the lower surface of the reading guide plate 66 in place of the white reference plate 66a for shading correction. Since the original is illuminated through the transparent guide plate 65, if the original is a thin sheet, the illumination light passes through the original and reaches the white plate 68. Therefore, the original is also illuminated by the light reflected by the white plate 68, and the read original is brightened. If the white plate 68 is replaced with a black plate (or a dark plate), the read original becomes dark. Therefore, it is preferable to provide the white plate 68 at a position opposite to the transparent guide plate 65. Even in such a configuration, according to the present invention, it is possible to determine which of the transparent guide plate 65 and the white plate 68 has foreign matter attached thereto.

  The second reading unit 43 also has a white upper surface of the reading guide plate 74 or is formed of a transparent glass plate for obtaining shading correction data, illuminating a document, and the like. When the lower surface of the reading guide plate 74 is white, it is possible to determine which foreign substance is attached to the transparent guide plate 75 or the reading guide plate 74 as in the first reading unit 41. In the second reading unit 43, each LED of the LED array 81 that illuminates the back side of the document is selectively turned on or off to cause a foreign object shadow, and an output change of the image sensor 73S corresponding to the foreign object shadow is generated. Detect and determine the shadow of the foreign object.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image reading apparatus 11 Optical scanning apparatus 12 Developing apparatus 13 Photosensitive drum 14 Drum cleaning apparatus 15 Charger 16 Intermediate transfer belt apparatus 17 Fixing apparatus 18 Paper feed tray 19 Paper discharge tray 41 First reading section 42 Document conveyance Unit 44 platen glass 45 first scanning unit 46 second scanning unit 47 imaging lens 48 CCD (Charge Coupled Device)
51 Illuminating section 52 First reflecting mirror 53 Second reflecting mirror 54 Third reflecting mirror 65 Transparent guide plate 66 Reading guide plate 66a White reference plate 76 Substrate 77 Moving scanning frame 78 Driver circuit 81, 83 LED array 82 LED
111 First image processing unit 113 First sensor unit 114 First calculation unit 115 Scanning drive unit 211 Second image processing unit 213 Second sensor unit 214 Second calculation unit 215 Transport driving unit

Claims (18)

A transport path for transporting a document, a transparent guide plate and a counter member disposed across the transport path, an illumination unit for illuminating the document on the transport path via the transparent guide plate, and the transparent guide plate An image reading apparatus including a plurality of light emitting elements for illuminating a document arranged in a reading scanning direction by the reading unit.
A light emission control unit for selectively turning on or off each light emitting element of the illumination unit;
Each time each of the light emitting elements is selectively turned on or off, the output of the reading unit that reads the counter member through the transparent guide plate is input, and the output of the reading unit is based on the output of the reading unit. An image reading apparatus comprising: a transparent guide plate and a determination unit that determines which of the opposing members has foreign matter attached thereto. The image reading apparatus according to claim 1,
The light emission control unit turns on each light emitting element by a first selective lighting or extinguishing control, and sets each light emitting element to a plurality of light emitting elements by at least one selective lighting or extinction control after the second time. Dividing into blocks, turn on one light emitting element of each adjacent block and turn off the other light emitting element,
The determination unit detects a position of a foreign matter attached to the transparent guide plate or the facing member based on an output of the reading unit at the time of the first selective lighting or extinguishing control. Foreign matter adheres to either the transparent guide plate or the opposing member based on the respective outputs of the reading unit at the time of selective lighting or extinguishing control of the first time and the second and subsequent times. Whether or not
In the second and subsequent selective lighting or extinguishing control, the light emitting elements are controlled at the position of the foreign matter detected by the determination unit during the first selective lighting or extinguishing control. An image reading apparatus that is divided into a plurality of blocks. The image reading apparatus according to claim 1,
Each light emitting element of the illumination unit is divided into a plurality of blocks,
The light emission control unit selectively turns on or off each light emitting element in units of blocks,
The determination unit inputs the output of the reading unit each time the light emitting elements are selectively controlled to be turned on or off in units of blocks, and based on the respective outputs of the reading unit, the transparent guide plate and the An image reading apparatus for determining which of the opposing members a foreign substance is attached to. The image reading apparatus according to claim 1,
The light emission control unit selectively turns on or off sequentially each light emitting element,
The determination unit inputs an output of the reading unit every time the light emitting elements are selectively sequentially turned on or off, and the transparent guide plate and the counter are opposed to each other based on the respective outputs of the reading unit. An image reading apparatus for determining which of the members a foreign substance is attached to. The image reading apparatus according to any one of claims 1 to 4,
The determination unit compares each read image indicated by each output of the reading unit, and based on the change in the position of the shadow of the foreign matter in each read image, the foreign matter is present on either the transparent guide plate or the facing member. An image reading apparatus for determining whether or not the image is attached. The image reading device according to claim 5,
The determination unit determines that foreign matter is attached to the transparent guide plate when a change amount of the shadow position of the foreign matter in each read image exceeds a predetermined distance. The image reading apparatus according to any one of claims 1 to 4,
The determination unit compares each read image indicated by each output of the reading unit, and foreign matter adheres to either the transparent guide plate or the facing member based on a partial gradation change of each read image. An image reading apparatus characterized by determining whether or not The image reading apparatus according to claim 7, comprising:
The determination unit determines that foreign matter is attached to the transparent guide plate when the amount of change in partial gradation of each read image exceeds a predetermined gradation level. The image reading apparatus according to any one of claims 1 to 4,
The determination unit compares each read image indicated by each output of the reading unit, and when there is a shadow of a foreign object separated from the image of the foreign object in each read image, a foreign object is present on the transparent guide plate. An image reading apparatus characterized in that it is determined to be attached. The image reading apparatus according to any one of claims 1 to 9,
The image reading apparatus according to claim 1, wherein a surface of the facing member facing the transparent guide plate is white. The image reading apparatus according to any one of claims 1 to 9,
The image reading apparatus according to claim 1, wherein the facing member is a white reference member for shading correction. The image reading device according to claim 11, comprising:
A calculation unit that generates shading correction data corresponding to the output of the reading unit that has read the white reference member;
When the determination unit determines that a foreign matter is attached to the white reference member, the calculation unit corrects a data portion of the shading correction data corresponding to the attached portion of the foreign matter. Image reader. The image reading device according to claim 11, comprising:
A calculation unit that generates shading correction data corresponding to the output of the reading unit that has read the white reference member;
When the determination unit determines that foreign matter is attached to the white reference member, the calculation unit converts the generated shading correction data into initial shading correction data stored in advance in a memory. An image reading apparatus characterized by being replaced.   An image forming apparatus comprising the image reading device according to claim 1. 15. The image forming apparatus according to claim 14, wherein
An image forming apparatus comprising a display unit for displaying information relating to the image reading apparatus. The image forming apparatus according to claim 15, wherein
The image forming apparatus, wherein the display unit displays a determination result by the determination unit of the image reading device. The image forming apparatus according to claim 15, wherein
The display unit displays an image prompting cleaning of the transparent guide plate when the determination unit of the image reading apparatus determines that a foreign matter is attached to the transparent guide plate. apparatus. The image forming apparatus according to claim 15, wherein
The display unit displays that the counter member does not need to be cleaned when the determination unit of the image reading apparatus determines that a foreign substance is attached to the counter member. .