JP2007081989A - Image reading apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an improvement in robust performance of an image reading apparatus and maintenance-free by detecting an abnormality of correction data caused by factors such as device deterioration and changing or correcting a correction value or a correction value calculation parameter.
A 4-channel CCD image sensor 301 and the output from each output unit of the CCD image sensor 301 are digitalized and combined for each output direction of the first half and the second half, and the first half or the second half is also synthesized. In an image reading apparatus having a linearity unit 305 that corrects linearity for each output direction and a storage device that stores a correction value or correction value calculation parameter for correcting linearity, an abnormality detection correction amount calculation unit 309 and a CPU 311. Thus, the corrected data of the first half and the second half are compared and collated, and when the comparison and collation result is out of the set standard value, it is detected as an abnormality.
[Selection] Figure 3

Description

  The present invention relates to an image reading apparatus that reads an original image using a CCD line sensor having a plurality of output channels per line, and an image forming apparatus including the image reading apparatus.

  In image forming apparatuses such as a digital copying machine, a scanner, and a facsimile, an image reading apparatus that optically reads a document image is provided. In such an image reading device, a CCD line sensor having a plurality of shift registers is used. In this CCD line sensor, a two-channel output line sensor that divides the output by odd / even pixels is used. However, according to the recent demand for high speed, one line is divided from the center into the first half and the second half. A 4-channel output CCD line sensor that divides and outputs even-numbered pixels and odd-numbered pixels for each of the first half and the second half has been proposed.

This 4-channel CCD has a difference in CCD characteristics depending on the difference between the devices in the first half and the latter half. In particular, there is a problem that a density difference occurs between the first half and the second half due to a difference in linearity. As a countermeasure against this problem, for example, Patent Document 1 proposes a method of correcting the other read data with reference to the read data of the first half or the second half of one line. Patent Document 2 proposes a method in which correction data serving as a reference is previously stored in the apparatus and correction is performed on the first half and the second half.
JP 2000-188686 A JP 2002-218186 A

  In the case of the above-described conventional technology, the correction value or correction value calculation parameter for correcting the linearity of the first half and the second half has a unique value for each image reading device, and the correction value or correction value calculation adjusted once is calculated. When the parameters are stored in the image reading device circuit, they are not rewritten thereafter. However, if the correction value or the correction value calculation parameter does not match the actual CCD characteristics due to aging of the device, environmental change, or other factors, a correct correction result cannot be obtained.

  The present invention has been made in view of such a state of the art, and an object of the present invention is to easily detect an abnormality when an expected correction cannot be performed for some reason after shipment from the factory. There is in doing so.

  To achieve the above object, the first means is an image reading apparatus comprising a CCD image sensor in which a shift register for transferring charges accumulated in a photodiode is divided and output from the central part to the first half part and the second half part. The first half and the second half of the corrected data are compared and collated, and an abnormality detecting means is provided for detecting an abnormality when a result of the comparison and collation is out of a preset standard value. And

  The second means is the first means for combining the output from the CCD image sensor with the output of the first half and the latter half, and linearity for each output direction of the first half or the second half. It is characterized by comprising correction means for performing correction, and storage means for storing a correction value or correction value calculation parameter for correcting linearity by the correction means.

  The third means includes a reference density member that represents a reference density in the first or second means, and the data to be compared and collated reads the reference member every predetermined period or when requested. It is characterized by acquiring by.

  The fourth means is a correcting means for correcting the stored contents of the correction value or the correction value calculation parameter when any abnormality of the data after correction is detected by the abnormality detecting means in any of the first to third means. It is characterized by having.

  According to a fifth means, in the fourth means, when the correction means corrects the correction value or the correction value calculation parameter, the correction value at the time of shipment from the factory or the value of the correction value calculation parameter is retained and corrected. A correction amount for the value or correction value calculation parameter is calculated.

  A sixth means is characterized in that, in the fifth means, the calculated correction amount is calculated with the correction value or the correction value calculation parameter to obtain a new correction value or correction value calculation parameter.

  A seventh means is characterized in that, in the sixth means, the new correction value or correction value calculation parameter is overwritten and stored in the storage means.

  An eighth means is characterized in that, in any one of the first to seventh means, the CCD image sensor has a 4-channel output end.

  The ninth means is characterized in that the image forming apparatus includes any one of the first to eighth image reading apparatuses.

  In the embodiment described later, the photodiode is denoted by reference numeral 100, the shift register is denoted by numerals 103 to 106, the CCD image sensor is denoted by reference numeral 301, the abnormality detecting means is combined with the abnormality detection correction amount calculating unit 309 and the CPU 311, and the combining means. Is the first half data synthesis unit 303a and second half data synthesis unit 303b, the correction means is the linearity correction part 305, the storage means is the storage device 306, the reference density member is the reference white plate 3, and the correction means is an abnormality detection correction amount calculation. This corresponds to the unit 309, the CPU 311, and the calculator 312.

  According to the present invention, the corrected data of the first half and the second half of the CCD image sensor are compared and collated, and when the comparison and collation results deviate from a preset standard value, an abnormality is detected. An abnormality can be easily detected when the expected correction cannot be performed for some reason later.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an image reading apparatus according to an embodiment of the present invention. This image reading apparatus includes a contact glass 1 for placing a document, a reference white plate 3 for white level adjustment and shading data generation, a light source 7 for illuminating the document 5, and a first carriage 9 on which a first mirror 8 is mounted, The second carriage 12 on which the second mirror 10 and the third mirror 11 are mounted, the lens unit 13 for reducing and forming an image on the CCD image sensor 14a, the image reading circuit board 14 on which the CCD image sensor is mounted, and not shown. And a scanner driving motor for driving the first and second carriages 9 and 12, a home position sensor, a document detection sensor, and the like.

  In the above configuration, when the document 5 is placed on the contact glass 1, the light source 7 is turned on, and the document 5 is read by moving the first carriage 9 and the second carriage 12 to the right by the scanner motor. The light source 7 is turned on while the flatbed reading and the first carriage 9 and the second carriage 12 are stopped, and the sheet is conveyed by the conveying roller 4 of the document conveying device via the sheet-through reading contact glass 2. So-called sheet-through reading can be selected by irradiating the original 6 for reading.

  When the original 5 is read by the flatbed method, prior to reading the original 5, the data of the reference white plate 3 is acquired to generate shading correction data, the correction data is stored in a memory, and the shading correction is performed. By normalizing the image data of the document 5 based on the data, the light amount distribution unevenness and the CCD sensitivity unevenness in the image reading apparatus are corrected. Thereby, it is possible to read the image information of the original with high quality. On the other hand, when reading by the sheet-through method, before reading the document 6, first, the first carriage 9 is moved below the reference white plate 3 to generate shading correction data, and after returning to the sheet-through reading position. Then, the original is conveyed and the original reading operation is started.

  FIG. 2 is a diagram for explaining the configuration of the CCD image sensor 301 (see FIG. 3) on the image reading circuit board 14. The CCD image sensor 301 used here is a 4-channel output CCD line sensor, which includes a plurality of photodiodes 100 arranged in a pixel, and first and second two shift gates 101 and 102 (in the figure, shift gates 1 and 102). 2), first to fourth four CCD analog registers 103 to 106 (indicated by CCD analog registers 1, 2, 3, and 4 in the figure), two output buffers 107 that output odd components OS1 and OS3, 108, and two output buffers 109 and 110 for outputting even-numbered components OS2 and OS4. Since the output order is from the end of the pixel array due to the structure of the CCD, the output order is different between the first half and the second half, and a time-series conversion process is required later.

  As described above, the 4-channel output CCD image sensor 301 further divides the even component and the odd component into the left and right, respectively, to form a four-system output configuration, and includes four CCD analog registers 103 to 106. Accordingly, the first CCD analog register 103 sequentially transfers and outputs the signal from the leftmost photodiode of the odd component, and the second CCD analog register 104 sequentially transfers and outputs the signal from the even component of the leftmost photodiode. The third CCD analog register 105 sequentially transfers and outputs the signal from the right-end photodiode of the odd component, and the fourth CCD analog register 106 sequentially transfers and outputs the signal from the right-end photodiode of the even component. In the CCD image sensor 301, an RS terminal, a CP terminal, φ2B, φ1, and φ2 terminals are provided in the first half and the second half. In general, a signal is generated by a dedicated timing generation circuit for these drives, and one output is provided for each signal, and the signal is supplied to the terminals of the first half and the second half by two drivers (buffers). ing.

  FIG. 3 is a diagram showing the configuration of the image reading circuit board 14, the correction unit and the image processing unit, and the data flow. The image reading circuit board 14 includes a 4-channel output CCD image sensor 301 shown in FIG. 2, and a signal processing A / D conversion unit 302a that processes signals of odd pixels in the first half of the CCD image sensor 301 and performs A / D conversion. The signal processing A / D converter 302b that processes the signals of the even pixels in the first half of the CCD image sensor 301 and A / D converts them, and processes the signals from these two signal processing A / D converters 302a and 302b. The first half data synthesizer 303 a that synthesizes the data in the first half, the signal processing A / D converter 302 c that processes the signals of the odd-numbered pixels in the second half of the CCD image sensor 301 and performs A / D conversion, and the second half of the CCD image sensor 301. A signal processing A / D conversion unit 302d that processes and A / D-converts the signals of even-numbered pixels, and these two signal processing A / D conversion units 302c, And a front half portion data synthesis section 303b that performs data synthesis of first half processes the signals from 02d.

  In such a configuration, the CCD line sensor 301 outputs data consisting of a total of four channels, that is, even pixels and odd pixels in the first half, and even pixels and odd pixels in the second half for each line. In FIG. 3, the data flow for one line is shown. However, in the case of a color CCD, there are generally three lines of R (red), G (green), and B (blue), and 3 lines × 4 channels. Will have 12 channels. Each analog data divided from the CCD line sensor 301 is subjected to signal processing such as signal amplification by the respective signal processing A / D converters 302a to 302d and gain adjustment of the even pixel level and odd pixel level to perform A / D. Converted. From the A / D converted signal, the data of the even-numbered pixels and the odd-numbered pixels in the first half or the second half are synthesized by the data synthesis processing units 303a to 303b.

  The correction unit includes a shading correction unit 304, a linearity correction unit 305, a storage device 306, an abnormality detection correction amount calculation unit 309, a CPU 311 and a calculator 312. In such a correction unit composed of each element, first, shading correction of data in which even-numbered pixels and odd-numbered pixels are combined is performed in the shading correction unit 304. In this case, in the shading correction, the pixels of the reference white plate data and the data pixels correspond one-to-one, and therefore it is not always necessary to divide the first half data and the second half data and perform shading. For example, the result is the same even if shading correction is performed in a data format divided into even pixels and odd pixels.

  The linearity correction unit 305 sets a γ table from the correction value or the correction value calculation parameter 307 in the storage device 306 when the image reading apparatus in FIG. 1 is turned on, and the arithmetic unit 312 refers to the γ table to perform correction processing. Done. Here, the storage device 306 is a nonvolatile readable / writable memory, and for example, NVRAM or EEPROM is used. There are several methods for correcting the difference in linearity between the first half data and the second half data depending on the type of the correction value or the correction value calculation parameter 307. As an example, there is a correction value or correction value calculation parameter for the latter half (or the first half) relative to the linearity correction for the first half (or the second half), and a method for adjusting the latter half (or the first half) to the linearity correction of the first half, This is a method of having correction values or correction value calculation parameters for the first half and the second half for a certain ideal linearity, and adjusting the linearity so that the first half and the second half are ideal. The data after the linearity correction is transferred to the image processing unit 308 directly or after being converted into an appropriate data format.

  FIG. 4 is a diagram showing the configuration and data flow of the image reading circuit board 14, the correction unit, and the image processing unit when there is no means for detecting data abnormality after linearity correction. In this case, the change in CCD characteristics In such a case, data is passed to the image processing unit 306 without performing the intended correction. Therefore, in the present embodiment, as shown in FIG. 3, as a countermeasure when a change in CCD characteristics occurs, an abnormality detection correction amount calculation unit 309 that compares the first half and the second half of the correction data to detect an abnormality, An arithmetic unit 312 that calculates a correction value or a correction amount for the correction value calculation parameter is included, and a storage unit 306 has a correction amount storage unit 310 that stores a correction amount separately from the correction value or the correction value calculation parameter. .

  The correction data comparison and abnormality detection method and the correction amount calculation method may be realized by controlling all of or a part of the functions including the CPU 311 by software or by hardware. As data to be compared, a member serving as a reference of density installed in the reading apparatus is read, and examples of the member include a reference white plate 3 and a patch having at least one gradation and having different densities. When setting correction values or correction value calculation parameters at the time of factory adjustment, a document having a plurality of gradations (for example, a gray scale chart) is read. Therefore, in creating correction data, it is desirable to read the comparison data using a document similar to the gray scale or a patch having a plurality of gradations as the comparison data. However, if it is difficult due to the configuration of the image reading device, the correction data is created by reading the comparison data limited to patches with different densities having one or more gradations. When the comparison data is read only for patches with different densities and having one or more gradations, the correction value calculation of the density without comparison data assumes the ratio from the read patch density or the coefficient of the γ curve. To calculate.

  The comparison of the correction data may be executed automatically by the apparatus every predetermined period, or may be arbitrarily executed by a user or a serviceman through a panel operation. The correction amount 310 is preferably a parameter that can compensate for the difference between the first half and the latter half of the corrected data by adding or subtracting the correction value or the correction value calculation parameter. When an abnormality of correction data is detected in this comparison step, a correction amount 310 is calculated, and the calculated correction amount 310 is stored in the storage device 306. If the previous correction amount 310 is in the storage device 306, the new correction amount 310 is overwritten. It is desirable that the correction amount at the time of factory adjustment is set to a NULL value. The correction value or correction value calculation parameter 307 is corrected by adding or subtracting the correction amount 310 to or from the correction value or correction value calculation parameter 307 by the calculator 312 to obtain a new correction value or correction value calculation parameter 307. Input to the correction unit 305. As described above, addition / subtraction is desirable in correcting the correction value or the correction value calculation parameter 307. The calculation may be executed by software as a configuration including the CPU 311 or may be executed by hardware.

  As described above, with the configuration of FIG. 3, there is a difference between the first half and the second half of the correction data compared by the abnormality detection correction amount calculation unit 309, and the difference is outside a predetermined value (standard value). The abnormality detection correction amount calculation unit 309 calculates the correction amount, stores the correction amount 310 in the storage device 306, and uses the correction value or the correction value calculation parameter 307 and the correction amount 310 for data correction for subsequent reading. A γ table is set based on the result calculated by the calculator 312, and linearity correction is performed by the linearity correction unit 305.

  FIG. 5 is a flowchart showing a processing procedure when an abnormality detection request for a correction value or a correction value calculation parameter is generated every predetermined period or arbitrarily. That is, in this processing procedure, first, the reference density is read (step S501), shading correction is performed by the shading correction unit 304, and linearity correction is performed by the linearity correction unit 305 (step S502). The abnormality detection correction amount calculation unit 309 checks whether or not there is an abnormality (step S503). This process is complete | finished when there is no abnormality. On the other hand, if an abnormality is detected, a correction amount is calculated from the correction value or correction value calculation parameter 307 in the storage device 306 or the correction amount 310 (step S504), and a rewriting process of the correction amount 310 is performed (step S505). . Next, the correction value is calculated based on the correction value or the correction value calculation parameter 307 and the correction amount 310 (step S506), and finally the γ table is reset (step S507).

  FIG. 6 is a flowchart illustrating a processing procedure of the γ table setting process when the image reading apparatus is powered on. First, a correction value is calculated based on the correction value or correction value calculation parameter 307 and the correction amount 310 in the storage device 306 (step S601), and a γ table is set based on the calculation result (step S602).

  FIG. 7 is a diagram showing an outline of the mechanical configuration of a digital copying machine as an image forming apparatus provided with an image reading apparatus. In the figure, a digital copying machine is for monochrome image formation, and includes a main body 400, an image reading device 500 installed on the upper portion of the image forming apparatus main body 400, and an automatic document feeder (hereinafter referred to as an automatic document feeder) mounted thereon. , “A / DF”) 550, a large-capacity paper feeding device 700 disposed on the right side of the image forming apparatus main body 400, and a rear side of the paper disposed on the left side of the image forming apparatus main body 400 in FIG. The processing apparatus 800 is basically configured. The image reading apparatus shown in FIG. 1 and the image reading apparatus 500 shown in FIG. 7 are the same in the mechanism part for reading an image, except that the document feeding apparatus (document pressure plate) set on the contact glass 1 is different.

  The image forming apparatus main body 400 includes an image writing unit 410, an image forming unit 420, a fixing unit 430, a duplex conveying unit 440, a paper feeding unit 450, a vertical conveying unit 460, and a manual feeding unit 470.

  The image writing unit 410 modulates the LD, which is a light source, based on the image information of the document read by the image reading device 500, and writes laser on the photosensitive drum 421 by a scanning optical system such as a polygon mirror and an fθ lens. is there. The image forming unit 420 includes a photosensitive drum 421 and known electrophotographic imaging elements such as a developing unit 422, a transfer unit 423, a cleaning unit 424, and a charge eliminating unit provided along the outer periphery of the photosensitive drum 421. Consists of.

  The fixing unit 430 fixes the image transferred by the transfer unit 423 on the transfer paper. The double-sided conveyance unit 440 is provided downstream of the fixing unit 420 in the transfer sheet conveyance direction, and includes a first switching claw 441 that switches the transfer sheet conveyance direction to the sheet post-processing device 800 side or the double-side conveyance unit 440 side, , The reverse conveying path 442 guided by the switching claw 441, the image forming side conveying path 443 that conveys the transfer paper reversed by the reverse conveying path 442 to the transfer unit 423 again, and the reverse transfer paper after the sheet post-processing device 800. A second switching claw 445 is disposed at a branch portion between the image forming side conveying path 443 and the post processing side conveying path 444.

  The sheet feeding unit 450 includes four sheet feeding stages, and the transfer sheets stored in the sheet feeding stages selected by the pickup roller and the sheet feeding roller are drawn out and guided to the vertical conveyance unit 460. The vertical conveyance unit 460 conveys the transfer paper fed from each paper feed stage to the registration roller 461 immediately upstream in the paper conveyance direction of the transfer unit 423, and the registration roller 461 provides a visible image on the photosensitive drum 421. The transfer paper is fed into the transfer unit 423 in time with the leading edge. The manual feed portion 470 includes an openable and closable manual feed tray 471, and opens the manual feed tray 471 as needed to supply transfer paper manually. Also in this case, the transfer timing of the transfer paper is taken by the registration roller 461 and is transported.

  The large-capacity paper feeding device 700 supplies a large amount of transfer paper of the same size, and the bottom plate 702 rises as the transfer paper is consumed, so that the paper can always be picked up from the pickup roller 701. ing. The transfer paper fed from the pickup roller 701 is conveyed from the vertical conveyance unit 460 to the nip of the registration roller 461.

  The sheet post-processing apparatus 800 performs predetermined processing such as punching, alignment, stapling, and sorting. In this embodiment, the punch 801, the staple tray (alignment) 802, the stapler 803, and the shift tray 804 are used for the above functions. I have. In other words, the transfer paper carried from the image forming apparatus 400 to the paper post-processing apparatus 800 is punched one by one with the punch 801 when punching, and then if there is no particular processing, the proofing is performed. When sorting, stacking, and sorting to the tray 805, the sheets are discharged to the shift tray 804, respectively. In this embodiment, the sorting is performed by the reciprocating movement of the shift tray 804 by a predetermined amount in a direction orthogonal to the sheet conveyance direction. In addition, sorting can be performed by moving the paper in a direction orthogonal to the paper transport direction on the paper transport path.

  In the case of alignment, the transfer paper that has been punched or not punched is guided to the lower transport path 806, and the staple tray 804 is aligned in the direction perpendicular to the paper transport direction by the rear end fence. In the jogger fence, alignment in the direction parallel to the paper transport direction is performed. Here, when binding is performed, a predetermined position of the aligned sheet bundle, for example, a predetermined position such as a corner portion or two central positions is bound by the stapler 803 and discharged to the shift tray 804 by the discharge belt. In this embodiment, a pre-stack conveyance path 807 is provided in the lower conveyance path 806, and a plurality of sheets are stacked at the time of conveyance to avoid interruption of the image forming operation on the image forming apparatus main body 400 side during post-processing. Be able to.

  The image reading device 500 is guided onto the contact glass 510 by the A / DF 600, optically scans the stopped document, and the read image formed by the imaging lens through the first to third mirrors is read by the CCD or the like. Reading is performed by a photoelectric conversion element such as a CMOS. The read image data is subjected to predetermined image processing by an image processing circuit (not shown) and temporarily stored in a storage device. Then, it is read from the storage device by the image writing unit 410 during image formation, modulated according to the image data, and optical writing is performed.

  The A / DF 550 has a double-sided reading function, and is attached to the contact glass 510 installation surface of the image reading apparatus 500 so as to be freely opened and closed. In the A / DF 550, the document placed on the document placement table 551 is automatically sent onto the contact glass 510 when the document is read.

  This image reading apparatus can be applied to a digital copying machine, a digital multifunction machine, a FAX, a scanner, and the like.

As described above, according to this embodiment,
1) If there is a difference between the first half and the second half of the corrected data due to factors such as aging of the device after shipment from the factory, it is possible to detect an abnormality in the correction data.
2) Since correction data abnormalities are detected at regular intervals or every request by reading the density reference member installed inside the reading device, it is possible to promptly notify the maintenance time and increase the efficiency of maintenance work. Can be realized.
3) Since abnormal correction data is automatically corrected, the reliability of the read image quality can be improved.
4) Maintenance costs can be reduced because parts replacement and service work are not involved. 5) Since correction can be performed while maintaining the factory adjustment value of the correction value or the correction value calculation parameter, even if it is necessary to return to the correction value or correction value calculation parameter at the time of shipment from the factory for some reason, It can correspond to.
6) If the correction is not completed due to an accident such as a power failure during maintenance operation, it can be restored immediately and the correction amount can be stored in the storage device. It is possible to refer to the correction amount once calculated any number of times without executing the amount calculation.
7) By using this image reading apparatus in an image forming apparatus such as a digital copying machine, a digital multi-function peripheral, a scanner, or a FAX, the occurrence of an abnormality in the read image data can be prevented and the robust performance of image reading can be improved. Can do. In addition, the efficiency of maintenance work can be improved.

1 is a diagram illustrating a schematic configuration of an image reading apparatus according to an embodiment of the present invention. It is a figure for demonstrating the structure of a CCD image sensor. It is a figure which shows the structure of the image reading circuit board 14, the correction | amendment part, and an image process part, and the flow of data. It is a figure which shows the structure and data flow of an image reading circuit board, a correction | amendment part, and image processing part when there is no means to detect the data abnormality after linearity correction | amendment. It is a flowchart for demonstrating the process when the abnormality detection request | requirement of a correction value or a correction value calculation parameter occurs. 6 is a flowchart for explaining γ table setting processing when the image reading apparatus is powered on. It is a figure which shows the mechanical structure of an example of the image forming apparatus provided with the image reading apparatus of FIG.

Explanation of symbols

3 Reference white plate 7 Light source 9 First carriage 12 Second carriage 14 Image reading circuit board,
301 CCD image sensors 302a to 302d Signal processing A / D converter 303a First half data synthesizer 303b Second half data synthesizer 305 Linearity corrector 306 Storage device 309 Abnormality detection correction amount calculator 311 CPU
312 Calculator 400 Image Forming Device Main Body 500 Image Reading Device

Claims (9)

In an image reading apparatus including a CCD image sensor in which a shift register for transferring charges accumulated in a photodiode is divided and output from a central part to a first half part and a second half part.
Comparing the corrected data of the first half and the second half, and having an abnormality detecting means for detecting as an abnormality when a result of the comparison and collation is out of a preset standard value Image reading device. Combining means for combining the output from the CCD image sensor with the output from the first half and the second half;
Correction means for correcting linearity for each output direction of the first half or the second half,
Storage means for storing correction values or correction value calculation parameters for correcting linearity by the correction means;
The image reading apparatus according to claim 1, further comprising:   The reference density member representing a density as a reference is provided, and the data to be compared and collated is acquired by reading the reference member every predetermined period or when requested. Image reading device.   4. The apparatus according to claim 1, further comprising a correction unit that corrects a stored value of a correction value or a correction value calculation parameter when the abnormality of the corrected data is detected by the abnormality detection unit. The image reading apparatus according to item.   When the correction unit corrects the correction value or the correction value calculation parameter, the correction value or correction value calculation parameter value at the time of shipment from the factory is held, and a correction amount for the correction value or the correction value calculation parameter is calculated. The image reading apparatus according to claim 4.   The image reading apparatus according to claim 5, wherein the calculated correction amount is calculated with the correction value or the correction value calculation parameter to obtain a new correction value or correction value calculation parameter.   The image reading apparatus according to claim 6, wherein the new correction value or the correction value calculation parameter is overwritten and stored in the storage unit.   8. The image reading apparatus according to claim 1, wherein the CCD image sensor has a 4-channel output end.   An image forming apparatus comprising the image reading apparatus according to claim 1.

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