JP2010093440A - Image reader and image forming device including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader properly and promptly obtaining a shading correction level. <P>SOLUTION: A first reference white plate 77 is read by a CIS (Contact Image Sensor) 73, and a second reference white plate 78 in a non-passing region 81 adjacent to a document passing region 75 is read at the same time. A shading correction level is obtained from the output level of the CIS 73 corresponding to the second reference white plate 78, and the shading correction level is corrected based on the output level of the CIS 73 corresponding to the second reference white plate 78. The output level V2 of the CIS 73 corresponding to the second reference white plate 78 shows the white level of a document in the document passing region 75. When the output level V1 of the CIS 73 corresponding to the first reference white plate 77 is increased to almost equal to the output level V2, and is obtained as a shading correction level, an error caused by displacement between the first reference white plate 77 and the document passage region 75 is reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that reads a document and an image forming apparatus including the image reading apparatus.

  As is well known, in an image reading apparatus, a document in this passage area is read by a document reading means while the document is conveyed and passed through the document passage area. Alternatively, the original is placed on the platen glass, and the original is scanned and read by the optical scanning system and the original reading means below the platen glass. Examples of the document reading means include a contact image sensor and a CCD (Charge Coupled Device).

  Further, in order to correct the uneven illumination of the original and the sensitivity unevenness of the original reading means, the reference white plate is read by the original reading means before reading the original, and the shading correction is performed from the read output level of the original reading means corresponding to the reference white board. The level is obtained and set, and the reading output level of the document reading unit that reads the document is corrected based on the shading correction level to eliminate the influence of uneven illumination of the document and sensitivity unevenness of the document reading unit.

Further, in Patent Document 1, a glass plate is used as a document passage region, a first reference white plate is disposed in the document passage region, a document reading unit is provided below the glass plate, and the document reading region is passed through the glass plate by the document reading unit. If the shading correction level is obtained based only on the read output level of the original reading means corresponding to the first reference white plate, assuming that the original document and the first reference white plate are read, the glass plate Since an error occurs in the shading correction level when it becomes dirty, a second reference white plate is provided on the lower surface of the glass plate, and the second reference white plate is also read by the document reading means, and the document reading corresponding to the first and second reference white plates is performed. The shading correction level is obtained based on the respective read output levels of the means, and the error of the shading correction level is reduced.
JP-A-10-224571

  However, in Patent Document 1, since both the first and second reference white plates are arranged in the document passage area, it is necessary to perform reading scanning by the document reading means for each of the first and second reference white plates. For every pixel in the scanning direction, it is necessary to calculate the shading correction level one by one based on the respective read output levels of the document reading means corresponding to the first and second reference white plates, which takes time.

  Accordingly, the present invention has been made in view of the above-described conventional problems, and an object thereof is to provide an image reading apparatus capable of accurately and promptly obtaining a shading correction level and an image forming apparatus including the image reading apparatus. To do.

  In order to solve the above problems, an image reading apparatus of the present invention sequentially arranges a document reading means for reading a document, a document passage area through which a document read by the document reading means passes, a translucent plate, and a first reference white plate. The original reading unit reads the first reference white plate through the original passage area and the light transmitting plate, and sets the shading correction level from the read output level of the original reading unit corresponding to the first reference white plate. In the reading apparatus, a second reference white plate provided by a portion adjacent to the document passage area where the document does not pass and read by the document reading unit, and a reading output level of the document reading unit corresponding to the second reference white plate Correction means for correcting the shading correction level based on the above.

  The correction means obtains a difference between a reading output level of the original reading means corresponding to the second reference white plate and a reading output level of the original reading means corresponding to the first reference white plate, and uses the difference as a shading correction level. In addition, the shading correction level is corrected.

  For example, the correction means may include an average value of the read output level of the original reading means corresponding to the second reference white plate and a read output of the original reading means corresponding to a specified area of the first reference white plate near the second reference white board. A difference from the average value of the levels is obtained, and this difference is added to the shading correction level to correct the shading correction level.

  In another image reading apparatus according to the present invention, an original passage area through which an original passes, a translucent plate, a first reference white plate, and an original reading means for reading the original in the original passage area are sequentially arranged, and the original reading means In the image reading apparatus for reading the first reference white plate and setting the shading correction level from the read output level of the document reading means corresponding to the first reference white plate, the image reading device is provided at a location where the document adjacent to the document passage area does not pass. And a correction unit that corrects the shading correction level based on a reading output level of the document reading unit corresponding to the second reference white plate.

  The correction unit obtains a difference between an output level of the document reading unit corresponding to the second reference white plate and a reading output level of the document reading unit corresponding to a specified area of the first reference white plate, and calculates the difference as the shading. The shading correction level is corrected by subtracting from the correction level.

  For example, the correction means may include an average value of the read output level of the original reading means corresponding to the second reference white plate and a read output of the original reading means corresponding to a specified area of the first reference white plate near the second reference white board. A difference from the average value of the levels is obtained, and the difference is subtracted from the shading correction level to correct the shading correction level.

  Further, the second reference white plate is provided at one place where a document in the vicinity of one side of the document passage area does not pass.

  For example, the document reading unit is a contact image sensor.

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

  In the image reading apparatus of the present invention, the document reading means, the document passage area, the translucent plate, and the first reference white plate are sequentially arranged, and the first reference white plate is read by the document reading means through the document passage area and the translucent plate. The shading correction level is set from the reading output level of the document reading means corresponding to the first reference white plate. In this case, since the translucent plate is interposed between the original passage area and the first reference white plate, if the translucent plate becomes dirty due to the contact of the original, the reading output level of the original reading unit fluctuates and an error occurs in the shading correction level. Arise. Further, since the position of the first reference white plate and the position of the document passage area with respect to the document reading means are different, even if the white level of the first reference white plate and the white level of the document in the document passage area are the same, these white levels are reduced. The reading output levels of the corresponding document reading means are different, and this also causes an error in the shading correction level.

  Therefore, in the present invention, a second reference white plate is provided at a location where the document adjacent to the document passage area does not pass, and the shading correction level is corrected based on the read output level of the document reading means corresponding to the second reference white plate. ing. Since the second reference white plate is provided at a position where the original in the vicinity of the original passage area does not pass, the second reference white board is not affected by the dirt of the light transmitting plate and is at the same height as the original passage area. Accordingly, the reading output level of the document reading means corresponding to the second reference white plate does not include errors caused by the contamination of the light transmitting plate or the positional deviation between the document passage area and the second reference white plate. For this reason, by correcting the shading correction level based on the read output level corresponding to the second reference white plate, the shading caused by the contamination of the translucent plate and the positional deviation between the document passage area and the first reference white plate. Correction level errors can be reduced. In addition, the shading correction level of all the pixels can be corrected collectively, and the calculation process is simple.

  In addition, since the first reference white plate is provided so as to overlap the document passage region and the second reference white plate is provided adjacent to the document passage region, the first and second reference plates are scanned once by the document reading means. The white plate can be read together.

  Here, since the second reference white plate adjacent to the document passage area is closer to the document reading means than the first reference white plate, the reading output level of the document reading means corresponding to the second reference white plate is the first reference white plate. Higher than the reading output level of the document reading means corresponding to. Therefore, the correcting means obtains a difference between the reading output level of the document reading means corresponding to the second reference white plate and the reading output level of the document reading means corresponding to the first reference white plate, and adds this difference to the shading correction level. The shading correction level is corrected.

  Furthermore, the illumination levels of the first and second reference white plates are not necessarily uniform, and vary depending on the illumination position. Therefore, the specified area of the first reference white board in the vicinity of the second reference white board, that is, the specified area of the first reference white board in the vicinity of the second reference white board that is assumed to have an illumination level substantially equivalent to that of the second reference white board is specified. The difference between the average value of the read output level corresponding to the second reference white plate and the average value of the read output level corresponding to the specified area of the first reference white plate is obtained, and this difference is added to the shading correction level. Thereby, it is possible to reduce the influence of unevenness of the illumination level due to the illumination position, and to improve the correction accuracy of the shading correction level.

  In another image forming apparatus of the present invention, a document passage area, a translucent plate, a first reference white plate, and a document reading unit are sequentially arranged, and the first reference white plate is read by the document reading unit. The shading correction level is set from the reading output level of the document reading means corresponding to the above. In this case, although the first reference white plate is not soiled by the contact of the document, the position of the first reference white plate and the position of the document passage area with respect to the document reading means are different. Even if the white levels of the originals are the same, the read output levels of the original reading means corresponding to these white levels are different, and an error occurs in the shading correction level.

  In view of this, a second reference white plate is provided at a location where a document in the vicinity of the document passage area does not pass, and the shading correction level is corrected based on the read output level of the document reading means corresponding to the second reference white plate. The second reference white plate is provided at a position where the original in the vicinity of the original passage area does not pass and is provided at the same height as the original passage area. Therefore, the reading output level of the document reading unit corresponding to the second reference white plate does not include an error caused by the positional deviation between the document passage area and the second reference white plate. Therefore, by correcting the shading correction level based on the read output level corresponding to the second reference white plate, the error of the shading correction level caused by the positional deviation between the document passage area and the first reference white plate is reduced. Can do. In addition, the shading correction level of all the pixels can be corrected collectively, and the calculation process is simple.

  In addition, since the first reference white plate is provided in the document passage region and the second reference white plate is provided adjacent to the document passage region, both the first and second reference white plates are read by one scan of the document reading means. Can do.

  Here, since the second reference white plate adjacent to the document passage area is located farther from the document reading means than the first reference white plate, the read output level of the document reading means corresponding to the second reference white plate is the first reference white plate. It becomes lower than the reading output level of the document reading means corresponding to the white plate. Therefore, the correcting means obtains a difference between the reading output level of the document reading means corresponding to the second reference white plate and the reading output level of the document reading means corresponding to the first reference white plate, and subtracts this difference from the shading correction level. The shading correction level is corrected.

  Further, the illumination levels of the first and second reference white plates are not necessarily uniform and are uneven depending on the illumination position. Therefore, the average value of the read output level corresponding to the second reference white plate and the second reference white plate in the vicinity of the second reference white plate. The difference from the average value of the read output level corresponding to the prescribed area of one reference white board is obtained, and this difference is subtracted from the shading correction level. Thereby, it is possible to reduce the influence of unevenness of the illumination level due to the illumination position, and to improve the correction accuracy of the shading correction level.

  On the other hand, since the image forming apparatus according to the present invention includes the image reading apparatus according to the present invention, the same effects can be obtained.

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

  FIG. 1 is a cross-sectional view showing an image forming apparatus to which an embodiment of an image reading apparatus of the present invention is applied. The image forming apparatus 100 records and forms a document image read by the image reading apparatus 101 or an externally received image on a recording sheet in color or single color, and includes a laser exposure apparatus 1, a developing apparatus 2, and a photoreceptor. The drum 3, the charger 5, the cleaner device 4, the intermediate transfer belt device 8, the fixing device 12, the paper transport path S, the paper feed tray 10, the paper discharge tray 15, and the like.

  The image data handled in the image forming apparatus 100 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. Accordingly, four each of the developing device 2, the photosensitive drum 3, the charger 5, and the cleaner device 4 are provided so as to form four types of latent images corresponding to the respective colors, and black, cyan, magenta, and yellow are respectively provided. Four image stations Pa, Pb, Pc, and Pd are configured in association with each other.

  The photoconductor drum 3 is disposed at substantially the center of the image forming apparatus 100.

  The charger 5 is a charging means for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. In addition to a contact type roller type or brush type charger, a charger type charger is used. .

  The laser exposure apparatus 1 is a laser scanning unit (LSU) provided with a laser diode and a reflection mirror, which exposes the surface of a charged photosensitive drum 3 according to image data and statically responds to the surface according to the image data. An electrostatic latent image is formed.

  The developing device 2 develops the electrostatic latent image formed on the photosensitive drum 3 with (K, C, M, Y) toner to form a toner image on the surface of the photosensitive drum 3. The cleaner device 4 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer.

  The intermediate transfer belt device 8 disposed above the photosensitive drum 3 includes an intermediate transfer belt 7, an intermediate transfer belt drive roller 21, a driven roller 22, an intermediate transfer roller 6, and an intermediate transfer belt cleaning device 9. .

  The intermediate transfer belt drive roller 21, the intermediate transfer roller 6, the driven roller 22, etc. stretch and support the intermediate transfer belt 7, and move the intermediate transfer belt 7 in the direction of arrow C.

  The intermediate transfer roller 6 is rotatably supported in the vicinity of the intermediate transfer belt 7, is pressed against the photosensitive drum 3 via the intermediate transfer belt 7, and transfers the toner image on the surface of the photosensitive drum 3 to the intermediate transfer belt 7. The transfer bias is applied. The intermediate transfer roller 6 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). With this conductive elastic material, a high voltage can be uniformly applied to the recording paper.

  The intermediate transfer belt 7 is provided so as to be in contact with each photoconductive drum 3, and a color toner image (each color is transferred by sequentially superimposing and transferring the toner image on the surface of each photoconductive drum 3 onto the intermediate transfer belt 7. Toner image). This transfer belt is formed in an endless belt shape using a film having a thickness of about 100 μm to 150 μm.

  As described above, the toner images on the surfaces of the respective photosensitive drums 3 are stacked on the intermediate transfer belt 7 and become a color toner image indicated by the image data. The toner images of the respective colors stacked in this way are transported together with the intermediate transfer belt 7 and transferred onto the recording paper by the transfer roller 11a of the secondary transfer device 11 that is in contact with the intermediate transfer belt 7.

  The intermediate transfer belt 7 and the transfer roller 11a of the secondary transfer device 11 are pressed against each other to form a nip region. Further, the transfer roller 11a of the secondary transfer device 11 has a voltage for transferring the toner image of each color on the intermediate transfer belt 7 onto a recording sheet (high polarity (+) opposite to the toner charge polarity (-)). Voltage) is applied. Further, in order to constantly obtain the nip region, either the transfer roller 11a of the secondary transfer device 11 or the intermediate transfer belt drive roller 21 is made of a hard material (metal or the like), and the other is a soft material such as an elastic roller. (Elastic rubber roller, foaming resin roller, etc.).

  In addition, the toner image on the intermediate transfer belt 7 may not be completely transferred onto the recording paper by the secondary transfer device 11, and the toner may remain on the intermediate transfer belt 7. Causes color mixing. Therefore, the residual toner is removed and collected by the intermediate transfer belt cleaning device 9. The intermediate transfer belt cleaning device 9 is provided with, for example, a cleaning blade as a cleaning member that comes into contact with the intermediate transfer belt 7 to remove residual toner, and the intermediate transfer belt is driven by a driven roller 22 at a portion where the cleaning blade comes into contact. 7 The back side is supported.

  The paper feed tray 10 is a tray for storing recording paper, and is provided below the image forming apparatus 100 to supply the recording paper in the tray.

  The image forming apparatus 100 has an S-shaped sheet conveyance path S for sending the recording sheet supplied from the sheet feeding tray 10 to the sheet discharge tray 15 via the secondary transfer device 11 and the fixing device 12. Is provided. Along the paper conveyance path S, a paper pickup roller 16, a paper registration roller 14, a fixing device 12, and a conveyance roller for conveying the recording paper are arranged.

  The paper pick-up roller 16 is a calling roller that is provided at the end of the paper feed tray 10 and supplies recording paper from the paper feed tray 10 to the paper transport path S one by one. The conveyance rollers are small rollers for promoting and assisting conveyance of the recording paper, and a plurality of conveyance rollers are provided.

  The paper registration roller 14 temporarily stops the recording paper that has been conveyed, aligns the leading edge of the recording paper, and is on the intermediate transfer belt 7 in the nip region between the intermediate transfer belt 7 and the transfer roller 11 a of the secondary transfer device 11. The recording paper is conveyed in a timely manner in accordance with the rotation of the photosensitive drum 3 and the intermediate transfer belt 7 so that the color toner image is transferred onto the recording paper.

  For example, the paper registration roller 14 detects the color toner image on the intermediate transfer belt 7 in the nip area between the intermediate transfer belt 7 and the transfer roller 11a of the secondary transfer device 11 based on the detection output of a pre-registration detection switch (not shown). The recording paper is transported so that the leading edge is aligned with the leading edge of the image forming area of the recording paper.

  The fixing device 12 includes a heating roller 31, a pressure roller 32, and the like. The heating roller 31 and the pressure roller 32 sandwich and convey the recording paper that has passed through the nip region between the intermediate transfer belt 7 and the transfer roller 11a of the secondary transfer device 11.

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

  The recording paper after the fixing of the toner images of the respective colors is discharged face down onto the paper discharge tray 15 by the transport roller.

  Next, the image reading apparatus 101 of the present embodiment mounted on the image forming apparatus 100 of FIG. 1 will be described with reference to FIG. FIG. 2 is an enlarged cross-sectional view of the image reading apparatus 101.

  The image reading apparatus 101 according to this embodiment includes a lower first reading unit 41 and an upper document conveying unit 42.

  The upper document conveying section 42 is pivotally supported on one 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 conveying 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 exposure lamp (halogen lamp, xenon lamp, fluorescent lamp, etc.) 51 and a first reflecting mirror 52, and moves at a constant speed V by a distance corresponding to the document size in the sub-scanning direction. While the original on the platen glass 44 is exposed by the exposure lamp 51, the reflected light is reflected by the first reflecting mirror 52 and guided to the second scanning unit 46, whereby the image on the surface of the original is sub-scanned. To scan. 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.

  The first and second scanning units 45 and 46 are provided with respective pulleys (not shown), wires (not shown) are bridged between these pulleys, and the wires are driven by a stepping motor. The first and second scanning units 45 and 46 are moved synchronously.

  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 and second scanning units 45 and 46 are positioned, and in this state, the conveyance of the document by the document conveyance unit 42 is started.

  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 onto the glass plate 65 of the first reading unit 41. Further, the original is further 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 conveyed, the exposure lamp 51 of the first scanning unit 45 illuminates the document surface through the glass plate 65, and the reflected light from the document surface is reflected by the reflection mirrors of the first and second traveling units 45 and 46. Guided to the imaging lens 47, the reflected light from the document surface is condensed on the CCD 48 by the imaging lens 47, and an image on the document surface is formed on the CCD 48, thereby reading the image on the document surface.

  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 first glass plate 74 through which a document passes. The CIS 73 photoelectrically converts the LED array 71 that illuminates the back side of the original, the SELFOC (registered trademark) lens array 72 that collects the reflected light of the original for each pixel, and the reflected light of the original received through the SELFOC lens array 72. And a line sensor 73S for outputting an analog image signal. The document that has passed over the glass plate 65 of the first reading unit 41 passes through the first glass plate 74 of the second reading unit 43 and is discharged to the paper discharge tray 49. , The back surface of the document is illuminated by the LED array 71, the reflected light from the back surface of the document is input to the line sensor 73S via the SELFOC lens array 72, and the image on the back surface of the document is read by the line sensor 73S.

  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 sent to the laser exposure apparatus 1 of the image forming apparatus 100, where the image is recorded on a recording sheet.

  FIG. 3 is a block diagram showing the configuration of the signal processing system of the image reading apparatus 101 of this embodiment. As shown in FIG. 3, the image reading apparatus 101 includes a first image processing unit 111 and a second image processing unit 211. 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 one reading unit 41 are driven and controlled. 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. Either one of the first and second image processing units 111 and 211 transmits and receives a digital image signal to the laser exposure apparatus 1 of the image forming apparatus 100, and the image forming apparatus 100 records an image on a recording sheet.

  The first image processing unit 111 receives the first sensor unit 113 constructed on the substrate on which the CCD 48 of the first scanning unit 45 is mounted, and the digital image signal from the first sensor unit 113, and converts the digital image signal into the digital image signal. The image processing apparatus includes a first calculation unit 114 that performs various types of image processing, and a scanning driving unit 115 that drives the first and second scanning units 45 and 46 of the first reading unit 41.

  The first sensor unit 113 includes an exposure lamp 51 of the first scanning unit 45, a CCD 48, two analog front end circuits (hereinafter referred to as AFE) 116 for A / D converting analog image signals from the CCD 48 into digital image signals, And an LSI 117 including a register for relaying and transferring the 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. Work memory 123, flash memory 124 for storing shading correction level and the like, receiver 125 for inputting digital image signal from LSI 117 of first sensor unit 113, and digital image signal for receiving digital image signal from receiver 125 A SCAN ASIC (Application Specific Integrated Circuit) 126 that performs various image processing on the SCAN ASIC, 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, , SCAN Either the digital image signal from the SIC 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 laser exposure apparatus 1 of the image forming apparatus 100. 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 the driving of the driving motor 142 based on the detection output of each sensor 141 and controls the movement of the first and second scanning units 45 and 46.

  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. The image processing apparatus includes a second calculation unit 214 that performs various types of image processing, and a conveyance driving unit 215 that conveys the document in the document conveyance unit 42.

  The second sensor unit 213 includes an LED array 71 of the CIS 73, a line sensor 73S, two analog front end circuits (hereinafter referred to as AFE) 216 for A / D converting analog image signals from the line sensor 73S into digital image signals, And an LSI 217 including a register for relaying and transferring the digital image signal from each AFE 216.

  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. Work memory 223, flash memory 224 for storing shading correction level, receiver 225 for inputting digital image signal from LSI 217 of second sensor unit 213, input for digital image signal from receiver 225, digital image signal Are provided with a SCANAASIC (Application Specific Integrated Circuit) 226 that performs various image processing, and an SDRAM (Synchronous DRAM) 227 used by the SCAN ASIC 226.

  The conveyance driving unit 215 includes a plurality of sensors 231 that detect the conveyance position of the document in the document conveyance path 57 of the document conveyance unit 42, and a motor 232 that rotationally drives a pickup roller, a registration roller, a conveyance roller, and the like of the document conveyance path 57. A clutch 233 that contacts and separates the drive transmission path between the roller and the motor shaft, and a drive control unit 234 that controls the drive of the motor 232 and the clutch 233 are provided. The CPU 221 of the second calculation unit 214 controls the driving of the motor 232 and the clutch 233 through the drive control unit 234 based on the detection output of each sensor 231 and controls the conveyance of the document on the document conveyance path 57.

  In the first and second reading sections 41 and 43 of the image reading apparatus 101, there are uneven illumination of the original and uneven sensitivity of the CCD 48 and the line sensor 73S of the CIS 73. Therefore, the image read due to these unevenness. Quality may be degraded. Therefore, in order to correct such unevenness, the shading correction levels of the CCD 48 and CIS 73 are obtained and set prior to reading the document, and the output levels of the CCD 48 and CIS 73 that read the document based on these shading correction levels are set. Corrections are made to eliminate the influence of uneven illumination of the original and uneven sensitivity of the CCD 48 and CIS 73.

  However, since the first reference white plate used for obtaining the shading correction levels of the CCD 48 and the CIS 73 is not arranged in the document passage area so as to avoid contact with the document, the position of the first reference white plate relative to the CCD 48 and the CIS 73 and the document Even if the positions of the passage areas are different and the white level of the first reference white plate and the white level of the original in the original passage area are the same, the output levels of the CCDs 48 corresponding to these white levels are different, and the white levels thereof are also different. Each output level of the CIS 73 corresponding to the level is different. Therefore, if the shading correction level is obtained using only the first reference white plate, an error occurs in the shading correction level.

  Therefore, in the present embodiment, a second reference white plate is provided at a location where a document in the vicinity of the document passage area does not pass, and the shading correction levels of the CCD 48 and the CIS 73 are corrected using the second reference white plate. The error of the correction level is reduced.

  Next, a method for obtaining and correcting the shading correction level of the CIS 73 in the second reading unit 43 will be described. 4 and 5A are a cross-sectional view showing the vicinity of the first glass plate 74 in the second reading unit 43 of the document conveying unit 42 as viewed from the side, and a front view schematically showing the document in the document conveying direction. It is.

  As shown in FIGS. 4 and 5A, the second glass plate 76 and the CIS 73 are disposed above the first glass plate 74, and a space between the first glass plate 74 and the second glass plate 76 serves as a document passage area 75. Yes. A first reference white plate 77 is disposed on the lower surface of the first glass plate 74, and a second reference white plate 78 is disposed on the upper surface of the first glass plate 74.

  As shown in FIG. 5A, the document passage area 75 has a maximum document width (for example, A4 size width) that can be read by the image reading apparatus 101, and the maximum size document is the document passage area 75. Is passed to the right side of the room. On the left side of the document passage area 75, a void area 79 and a document non-passage area 81 through which a document does not pass are provided.

  The first reference white plate 77 is set to have the same length as the width of the document passage area 75 and is arranged so as to overlap with the document passage area 75.

  The second reference white plate 78 is set to have the same length as the width of the document non-passing area 81 and is arranged so as to overlap with the document non-passing area 81.

  The CIS 73 is set to have the same length as the entire width of the document passage area 75, the void area 79, and the document non-passage area 81, and is arranged so as to overlap with these areas 75, 79, and 81. Accordingly, the CIS 73 can read a document passing through the document passage area 75 and can simultaneously read the first and second reference white plates 77 and 78.

  Since the line sensor 73S of the CIS 73 has a plurality of photoelectric conversion elements arranged in the main scanning direction, when the original in the original passage area 75 is read, the output of the first to mth photoelectric conversion elements on the right side is the original. It can be extracted as a document image of the passage area 75. When the first and second reference white plates 77 and 78 are read at the same time, the outputs of the first to mth photoelectric conversion elements on the right side are extracted as indicating the first reference white plate 77, and the nth to pth. The output of each of the photoelectric conversion elements can be extracted as indicating the second reference white plate 78.

  In such a second reading unit 43, the shading correction level is obtained using the output level of the CIS 73 corresponding to the first reference white plate 77. However, as apparent from FIG. 5A, the upper side of the first glass plate 74 is the document passage area 75, and the first reference white plate 77 is disposed on the lower surface of the first glass plate 74. With respect to the array 71 (shown in FIG. 4), the position of the first reference white plate 77 is farther than the position of the document passage area 75, and the white level of the first reference white plate 77 and the white level of the document in the document passage area 75 are different. Even if they are the same, the output level of the CIS 73 corresponding to the white level of the first reference white plate 77 is lower than the output level of the CIS 73 corresponding to the white level of the document. For this reason, if the shading correction level is obtained using only the output level of the CIS 73 corresponding to the first reference white plate 77, an error occurs in the shading correction level.

  In addition, since the first glass plate 74 is interposed between the CIS 73 and the first reference white plate 77, the first glass plate 74 may become dirty due to contact with the document. In this case, the output level of the CIS 73 corresponding to the first reference white plate 77 is further lowered, and the error of the shading correction level is increased.

  Accordingly, the first reference white plate 77 is read by the CIS 73 and simultaneously the second reference white plate 78 of the document non-passing area 81 adjacent to the document passage area 75 is simultaneously read to output the output level of the CIS 73 corresponding to the second reference white board 78. The shading correction level is corrected based on the above.

  The second reference white plate 78 is provided in the document non-passing area 81 adjacent to the document passing area 75, provided at the same height as the document passing area 75, and provided on the upper surface of the first glass plate 74. . Therefore, the output level of the CIS 73 corresponding to the second reference white plate 78 is caused by a level decrease caused by a positional deviation between the second reference white plate 78 and the document passage area 75 and contamination of the first glass plate 74. The level is not reduced. Therefore, if the white level of the second reference white plate 78 and the white level of the document in the document passage area 75 are the same, the output level of the CIS 73 corresponding to the white level of the second reference white plate 78 becomes the white level of the document. It becomes equivalent to the output level of the corresponding CIS73.

  For example, as shown in FIG. 5B, when the output level of the first to m-th photoelectric conversion elements on the right side in the line sensor 73S of the CIS 73, that is, the output level of the CIS 73 corresponding to the first reference white plate 77 is V1, If the output level V1 is low and the output level of each of the n-th to p-th photoelectric conversion elements in the line sensor 73S of the CIS 73, that is, the output level of the CIS 73 corresponding to the second reference white plate 78 is V2, this output level V2 Becomes higher and V1 <V2. This is because the position of the first reference white plate 77 with respect to the CIS 73 is farther than the position of the second reference white plate 78 adjacent to the document passage area 75 and the first glass plate 74 is between the CIS 73 and the first reference white plate 77. This is because the first glass plate 74 is not interposed between the CIS 73 and the second reference white plate 78 in contrast to the interposition.

  Since the output level V2 of the CIS 73 corresponding to the second reference white plate 78 indicates the white level of the document in the document passage area 75, it corresponds to the first reference white plate 77 until it is substantially equal to the output level V2. If the output level V1 of the CIS 73 is increased and obtained as a shading correction level, an error caused by the positional deviation between the first reference white plate 77 and the document passage area 75 and the contamination of the first glass plate 74 are eliminated. It is possible to eliminate the influence of the cause error.

  Specifically, as shown in FIG. 5C, the output levels of the n-th to p-th photoelectric conversion elements in the line sensor 73S of the CIS 73 are averaged, and this average value corresponds to the second reference white plate 78. The average output level v2 of the CIS 73 is assumed. Further, the output levels of the same number of (m− (pn)) th to mth photoelectric conversion elements as the nth to pth photoelectric conversion elements in the line sensor 73S of the CIS 73 are averaged, and this average is obtained. The value is the average output level v1 of the CIS 73 corresponding to the first reference white plate 77. Then, the average output level v1 is subtracted from the average output level v2 to obtain the difference ΔA, and this difference ΔA is added to the output levels of the first to mth photoelectric conversion elements on the right side of the line sensor 73S one by one. Is obtained as the shading correction level of each of the first to m-th photoelectric conversion elements on the right side. As a result, a shading correction level that eliminates the error caused by the positional deviation between the first reference white plate 77 and the document passage area 75 and the error caused by the contamination of the first glass plate 74 is obtained.

  Here, as the average output level v1 of the CIS 73 corresponding to the first reference white plate 77, the average value of the output levels of the (m− (pn)) th to mth photoelectric conversion elements in the vicinity of the second reference white plate 78. Seeking. If this is specified in the vicinity of the second reference white plate 78, the illumination unevenness between the second reference white plate 78 and its vicinity is reduced, and the influence of this illumination unevenness is substantially eliminated to improve the accuracy of the shading correction level. It is because it can do.

  Such processing for obtaining and correcting the shading correction level of the CIS 73 is performed by the second image processing unit 211 in FIG. 3 when the image forming apparatus 100 is turned on. The second image processing unit 211 inputs the output level of each photoelectric conversion element in the line sensor 73S of the CIS 73 as a digital signal, and calculates the shading correction level by processing the output level of each photoelectric conversion element indicated by this digital signal. To correct. The processing by the second image processing unit 211 will be described with reference to the flowchart of FIG.

  First, when the image reading apparatus 101 is activated by turning on the power of the image forming apparatus 100 (step S301), the CPU 221 initializes the register of the LSI 217 and each AFE 216 through the SCAN ASIC 226 (step S302), and then A gain is set (step S303).

  Then, the CPU 221 turns off the LED array 71 through the SCAN ASIC 226, and performs reading by the CIS 73 in this state (step S304), and the output levels of the first to mth photoelectric conversion elements on the right side in the line sensor 73S of the CIS 73. Are stored in the flash memory 224 as the respective dark output correction levels, and the respective dark output correction levels already stored in the flash memory 224 are updated (step S305). .

  Subsequently, the CPU 221 turns on the LED array 71 through the SCAN ASIC 226 (step S306) and illuminates the first and second reference white plates 77 and 78. In this state, the CPU 221 performs reading by the CIS 73, and the CIS 73 line sensor. The output levels of the first to m-th photoelectric conversion elements on the right side in 73S, that is, the output level V1 of the CIS 73 corresponding to the first reference white plate 77, and the n-th to p-th photoelectric conversion elements of the line sensor 73S of the CIS 73 The output level, that is, the output level V2 of the CIS 73 corresponding to the second reference white board 78 is taken into the second arithmetic unit 214, and these output levels V1 and V2 are stored in the flash memory 224 (steps S307 to S312).

  In steps S307 to S312, the capture of the output level V1 of the CIS 73 corresponding to the first reference white plate 77 and the capture of the output level V2 of the CIS 73 corresponding to the second reference white plate 78 are shown separately. Takes in each of the output levels V1 and V2 almost simultaneously by reading the CIS 73 once.

  Thereafter, the CPU 221 refers to the output levels V1 and V2 in the flash memory 224, averages the output levels of the n-th to p-th photoelectric conversion elements in the line sensor 73S of the CIS 73, and performs the second reference white plate 78. The average output level v2 of the CIS 73 corresponding to the first reference white plate 77 is obtained by averaging the output levels of the (m- (pn))-th to m-th photoelectric conversion elements in the line sensor 73S of the CIS 73. The average output level v1 of the CIS 73 corresponding to is obtained, the average output level v1 is subtracted from the average output level v2, and the difference ΔA is obtained (step S313). Then, the CPU 221 adds this difference ΔA to the output levels of the first to m-th photoelectric conversion elements on the right side of the CIS 73 one by one, and adds the respective sums to the shading correction levels of the first to m-th photoelectric conversion elements on the right side. (Step S314), these are stored in the flash memory 224 as the respective shading correction levels, and the respective shading correction levels already stored in the flash memory 224 are updated (Step S315). Then, the CPU 221 turns off the LED array 71 (step S316), and ends the process for obtaining the shading correction level of the CIS 73.

  Thus, the dark output correction level and the shading correction level of the first to mth photoelectric conversion elements on the right side in the line sensor 73S stored in the flash memory 224 are transferred from the flash memory 224 to the SCAN ASIC 226 and stored therein. When the SCAN ASIC 226 reads a document by the second reading unit 43, the SCAN ASIC 226 extracts the outputs of the first to mth photoelectric conversion elements on the right side of the line sensor 73S as the document image of the document passage area 75, and extracts the document image. The dark output correction level of each photoelectric conversion element is subtracted one by one from the output of each photoelectric conversion element shown to eliminate the influence of dark output, and the output of each photoelectric conversion element showing a document image is normalized by the respective shading correction level. Turn into. As a result, it is possible to obtain a digital image signal that eliminates uneven illumination of the document and uneven sensitivity of the CIS 73. The digital image signal is transmitted from the SCAN ASIC 226 to the laser exposure apparatus 1 of the image forming apparatus 100 via the bus switch 129 and the transmission section 130 of the first image processing unit 111, and the image is formed on the recording paper in the image forming apparatus 100. To be recorded.

  Next, a method for obtaining and correcting the shading correction level of the CCD 48 in the first reading unit 41 will be described. FIG. 7 and FIG. 8A are a cross-sectional view showing the vicinity of the glass plate 65 in the first reading unit 41 when viewed from the side and a front view schematically showing the original reading direction.

  As shown in FIGS. 7 and 8A, a document guide 67 is arranged above the glass plate 65, and a space between the glass plate 65 and the document guide 67 is a document passage area 66. The first reference white plate 59 is disposed on the lower surface of the glass plate 65, and the second reference white plate 61 is disposed on the upper surface of the glass plate 65.

  As shown in FIG. 8A, the document passage area 66 has a maximum document width (for example, A4 size width) that can be read by the image reading apparatus 101, and the maximum size document is the document passage area 66. Is passed to the right side of the room. Further, on the left side of the document passage area 66, a void area 68 through which the document does not pass and a document non-passage area 69 are provided.

  The first reference white plate 59 is set to have the same length as the width of the document passage area 66 and is arranged so as to overlap with the document passage area 66. However, as shown in FIG. 7, the first reference white plate 59 only overlaps one end portion of the glass plate 65, and the central portion of the glass plate 65 is opened so that reading of the document surface through the glass 65 is not hindered. Has been.

  The second reference white plate 61 is set to have the same length as the width of the document non-passing area 69 and is arranged so as to overlap with the document non-passing area 69.

  The reading area W by the CCD 48 is enlarged by the imaging lens 47 and set to the same length as the entire width of the document passage area 66, the void area 68, and the document non-passage area 69. The furniture overlaps. Accordingly, the CCD 48 can read a document passing through the document passage area 66 and can simultaneously read the first and second reference white plates 59 and 61.

  In the first reading unit 41 as described above, as apparent from FIG. 8A, the upper side of the glass plate 65 is the document passage area 66, and the first reference white plate 59 is disposed on the lower surface of the glass plate 65. Therefore, the position of the first reference white plate 59 is closer to the position of the document passage area 66 with respect to the CCD 48 or the exposure lamp 51 (shown in FIG. 2), and the white level of the first reference white plate 59 and the document passage area 66 Even if the white level of the original is the same, the output level of the CCD 48 corresponding to the white level of the first reference white plate 59 is higher than the output level of the CCD 48 corresponding to the white level of the original. For this reason, if the shading correction level is obtained using only the output level of the CCD 48 corresponding to the first reference white plate 59, an error occurs in the shading correction level.

  Therefore, simultaneously with reading the first reference white plate 59 by the CCD 48, the second reference white plate 61 of the document non-passing area 69 adjacent to the document passing area 66 is simultaneously read to output the output level of the CCD 48 corresponding to the second reference white board 61. The shading correction level is corrected based on the above.

  The second reference white plate 61 is provided in the document non-passing area 69 adjacent to the document passing area 66, provided at the same height as the document passing area 66, and provided on the upper surface of the glass plate 65. Accordingly, the position of the second reference white plate 61 with respect to the exposure lamp 51 or the CCD 48 and the position of the document passage area 66 are equal, and the output level of the CCD 48 corresponding to the second reference white plate 61 has the second reference white plate 61 and the document passage area. 66, the level rise due to the position shift with respect to 66 does not occur. Therefore, if the white level of the second reference white plate 61 and the white level of the document in the document passage area 66 are the same, the output level of the CCD 48 corresponding to the white level of the second reference white plate 61 becomes the white level of the document. It becomes equivalent to the output level of the corresponding CCD 48.

  For example, as shown in FIG. 8B, if the output level of the first to mth photoelectric conversion elements on the right side of the CCD 48, that is, the output level of the CCD 48 corresponding to the first reference white plate 59 is V1, this output level V1. If the output level of each of the n-th to p-th photoelectric conversion elements of the CCD 48, that is, the output level of the CCD 48 corresponding to the second reference white plate 61 is V2, this output level V2 becomes lower, and V1> V2 It becomes. This is because the position of the first reference white plate 59 is closer to the exposure lamp 51 or the CCD 48 than the position of the second reference white plate 61 adjacent to the document passage area 66.

  Since the output level V2 of the CCD 48 corresponding to the second reference white plate 61 indicates the white level of the document in the document passage area 66, the output level V2 corresponds to the first reference white plate 59 until it is substantially equal to the output level V2. If the output level V1 of the CCD 48 is lowered and obtained as a shading correction level, it is possible to eliminate the influence of an error caused by a positional deviation between the first reference white plate 59 and the document passage area 66.

  Specifically, as shown in FIG. 8C, the output levels of the n-th to p-th photoelectric conversion elements of the CCD 48 are averaged, and this average value is the average output of the CCD 48 corresponding to the second reference white plate 61. Let it be level v2. Further, the output levels of the same number of (m− (p−n)) th to mth photoelectric conversion elements as the nth to pth photoelectric conversion elements of the CCD 48 are averaged, and this average value is calculated as the first value. The average output level v1 of the CCD 48 corresponding to the reference white plate 59 is set. Then, the average output level v1 is subtracted from the average output level v2 to obtain a difference ΔA, and this difference ΔA is subtracted from the output levels of the first to mth photoelectric conversion elements on the right side of the CCD 48 one by one. Is calculated as the shading correction level of each of the first to m-th photoelectric conversion elements on the right side. As a result, a shading correction level that eliminates the influence of an error caused by the positional deviation between the first reference white plate 59 and the document passage area 66 is obtained.

  As the average output level v1 of the CCD 48 corresponding to the first reference white plate 59, the average value of the output levels of the (m− (pn)) th to mth photoelectric conversion elements in the vicinity of the second reference white plate 61 is obtained. Looking for. If this is specified in the vicinity of the second reference white plate 61, the illumination unevenness of the exposure lamp 51 between the second reference white plate 61 and the vicinity thereof is small, and the influence of this illumination unevenness is substantially eliminated, and the accuracy of the shading correction level is improved. This is because it can be improved.

  Such processing for obtaining and correcting the shading correction level of the CCD 48 is performed by the first image processing unit 111 in FIG. 3 when the image forming apparatus 100 is turned on. The first image processing unit 111 receives the output level of each photoelectric conversion element of the CCD 48 as a digital signal, processes the output level of each photoelectric conversion element indicated by this digital signal, and obtains and corrects the shading correction level. The processing by the first image processing unit 111 is substantially the same as the second image processing unit 211, and is performed according to the flowchart of FIG.

  First, when the image reading apparatus 101 is activated (step S301), the CPU 121 initializes the register of the LSI 117 and each AFE 116 through the SCAN ASIC 126 (step S302), and then sets the gain of each AFE 116 (step S303). .

  Then, the CPU 121 turns off the exposure lamp 51 through the SCAN ASIC 126 and performs reading by the CCD 48 in this state (step S304), and performs a second calculation on the output level of each of the first to mth photoelectric conversion elements on the right side of the CCD 48. The output level is stored in the flash memory 124 as each dark output correction level, and each dark output correction level already stored in the flash memory 124 is updated (step S305).

  Subsequently, the CPU 121 turns on the exposure lamp 51 through the SCAN ASIC 126 (step S306) and illuminates the first and second reference white plates 59 and 61. In this state, the CPU 121 performs reading with the right side 1 of the CCD 48. The output level of each of the nth to mth photoelectric conversion elements, that is, the output level V1 of the CCD 48 corresponding to the first reference white plate 59, and the output level of each of the nth to pth photoelectric conversion elements of the CCD 48, that is, the second reference white plate. The output level V2 of the CCD 48 corresponding to 61 is taken into the second calculation unit 114, and these output levels V1 and V2 are stored in the flash memory 124 (steps S307 to S312).

  Thereafter, the CPU 121 refers to the output levels V1 and V2 in the flash memory 124, averages the output levels of the nth to pth photoelectric conversion elements of the CCD 48, and the CCD 48 corresponding to the second reference white plate 61. And the average output level of the CCD 48 corresponding to the first reference white plate 59 is obtained by averaging the output levels of the (m- (pn))-th to m-th photoelectric conversion elements of the CCD 48. v1 is obtained, and the average output level v1 is subtracted from the average output level v2 to obtain the difference ΔA (step S313). Then, the CPU 121 subtracts this difference ΔA one by one from the output levels of the first to m-th photoelectric conversion elements on the right side of the CCD 48, and the respective differences are shaded correction levels for the first to m-th photoelectric conversion elements on the right side. (Step S314), these are stored in the flash memory 124 as respective shading correction levels, and the respective shading correction levels already stored in the flash memory 124 are updated (Step S315). Then, the CPU 121 turns off the exposure lamp 51 (step S316), and ends the process for obtaining the shading correction level of the CCD 48.

  The dark output correction level and the shading correction level of each of the first to m-th photoelectric conversion elements stored in the flash memory 124 are transferred from the flash memory 124 to the SCAN ASIC 126 and stored therein. When the document is read by the CCD 48, the SCAN ASIC 126 extracts the outputs of the first to mth photoelectric conversion elements on the right side as those indicating the document image in the document passage area 66, and outputs the output of each photoelectric conversion element indicating the document image. The dark output correction level of each photoelectric conversion element is subtracted one by one to eliminate the influence of the dark output, and the output of each photoelectric conversion element indicating a document image is normalized by each shading correction level. As a result, a digital image signal that eliminates uneven illumination of the original and uneven sensitivity of the CCD 48 can be obtained. This digital image signal is transmitted from the SCAN ASIC 126 to the laser exposure apparatus 1 of the image forming apparatus 100 via the bus switch 129 and the transmission unit 130, and the image is recorded on the recording paper in the image forming apparatus 100.

  As described above, in the image reading apparatus 101 according to the present embodiment, the second reference white plate is provided in the document non-passing region adjacent to the document passing region, and shading correction is performed based on the output levels of the CCD 48 and the CIS 73 corresponding to the second reference white plate. Since the level is corrected, it is possible to reduce an error of the shading correction level caused by the contamination of the glass plate or the positional deviation between the document passage area and the first reference white plate. In addition, the shading correction level of all the pixels can be corrected collectively, and the calculation process is simple.

  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, as shown in FIG. 9, a void area 92 and an original non-passing area 93 may be provided on both sides of the original passing area 91, respectively. Also in this case, the first reference white plate 94 is provided so as to overlap the document passage area 91, and the second reference white plate 95 is provided only on one side of the document non-passage area 93, and the CCD and CIS corresponding to the second reference white plate 95 are provided. The shading correction level may be corrected based on the output level.

  If there is no illumination unevenness with respect to the first and second reference white plates, the difference between the average value of all output levels corresponding to the first reference white plate and the average value of all output levels corresponding to the second reference white plate is obtained. The difference may be added to or subtracted from the shading correction level.

1 is a cross-sectional view illustrating an image forming apparatus to which an embodiment of an image reading apparatus of the present invention is applied. FIG. 2 is a cross-sectional view showing an image reading apparatus of the present embodiment mounted on the image forming apparatus of FIG. 1. It is a block diagram which shows the structure of the signal processing system of the image reading apparatus of this embodiment. FIG. 3 is a cross-sectional view showing a vicinity of a first glass plate in a second reading unit of the document conveying unit of FIG. (A) is a front view schematically showing the vicinity of the first glass plate in the second reading unit in the document transport direction, and (b) is a diagram illustrating the CIS read output in the second reading unit. (C) is a figure which illustrates the result of a shading correction | amendment. 4 is a flowchart showing a processing procedure for obtaining and correcting a shading correction level by the first and second image processing units in FIG. 3. FIG. 3 is a cross-sectional view showing a vicinity of a glass plate in a first reading unit of the document conveying unit in FIG. 2 as viewed from the side. (A) is a front view schematically showing the vicinity of the glass plate in the first reading unit in the document conveyance direction, and (b) is a diagram illustrating the reading output of the CCD in the first reading unit; c) is a diagram illustrating the result of shading correction. FIG. 6 is a diagram illustrating a modification example of a document passage area, a void area, and a document non-passage area.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser exposure apparatus 2 Developing apparatus 3 Photosensitive drum 4 Cleaner apparatus 5 Charger 8 Intermediate transfer belt apparatus 10 Paper feed tray 12 Fixing apparatus 15 Paper discharge tray 41 First reading part 42 Document conveying part 43 Second reading part 44 Platen glass 45 First scanning unit 46 Second scanning unit 47 Imaging lens 48 CCD (Charge Coupled Device)
49 Paper discharge tray 51 Exposure lamps 59, 77 First reference white plate 61, 78 Second reference white plate 65 Glass plate 66, 75 Document passage area 67 Document guide 68, 79 Void area 69, 81 Document non-pass area 71 LED array 72 cells Fock lens array 73 Contact Image Sensor (CIS)
73S line sensor 74 first glass plate 76 second glass plate 100 image forming apparatus 101 image reading apparatus 111 first image processing unit 113 first sensor unit 114 first calculation unit 115 scan driving unit 211 second image processing unit 213 second Sensor unit 214 Second calculation unit 215 Transport drive unit

Claims (9)

An original reading means for reading an original, an original passage area through which an original read by the original reading means, a translucent plate, and a first reference white plate are sequentially arranged, and the original passage area and the translucent plate are arranged by the original reading means. In the image reading apparatus that reads the first reference white plate via the first reference white plate and sets the shading correction level from the read output level of the document reading means corresponding to the first reference white plate.
A second reference white plate that is provided at a location where a document adjacent to the document passage area does not pass and is read by the document reading unit;
An image reading apparatus comprising: correction means for correcting the shading correction level based on a read output level of the document reading means corresponding to the second reference white plate.   The correction means obtains a difference between a reading output level of the original reading means corresponding to the second reference white plate and a reading output level of the original reading means corresponding to the first reference white plate, and uses the difference as a shading correction level. The image reading apparatus according to claim 1, wherein the shading correction level is corrected by addition.   The correction means includes an average value of the read output level of the original reading means corresponding to the second reference white plate and a read output level of the original reading means corresponding to the specified area of the first reference white plate near the second reference white plate. The image reading apparatus according to claim 1, wherein a difference from an average value is obtained, and the difference is added to the shading correction level to correct the shading correction level. An original passage area through which an original passes, a translucent plate, a first reference white board, and an original reading means for reading an original in the original passage area are sequentially arranged, and the first reference white board is read by the original reading means. In the image reading apparatus for setting the shading correction level from the reading output level of the document reading means corresponding to the reference white plate,
A second reference white plate that is provided at a location where a document adjacent to the document passage area does not pass and is read by the document reading unit;
An image reading apparatus comprising: correction means for correcting the shading correction level based on a read output level of the document reading means corresponding to the second reference white plate.   The correction unit obtains a difference between an output level of the document reading unit corresponding to the second reference white plate and a reading output level of the document reading unit corresponding to a specified area of the first reference white plate, and calculates the difference as the shading. The image reading apparatus according to claim 4, wherein the shading correction level is corrected by subtracting from the correction level.   The correction means includes an average value of the reading output level of the document reading means corresponding to the second reference white plate and a reading output level of the document reading means corresponding to the specified area of the first reference white plate near the second reference white plate. 5. The image reading apparatus according to claim 4, wherein a difference from the average value is obtained, and the difference is subtracted from the shading correction level to correct the shading correction level.   5. The image reading apparatus according to claim 1, wherein the second reference white plate is provided at one place where a document adjacent to one side of the document passage area does not pass.   The image reading apparatus according to claim 1, wherein the document reading unit is a contact image sensor.   An image forming apparatus comprising the image reading device according to claim 1.

Images