JP2005217914A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently perform attachment detection processing and shading correction processing and to enhance the accuracy of the respective processing. <P>SOLUTION: Received light quantity of reflected light of a reference plate from a monochromatic reference plate, which is received by an optical system light receiving means, is used to apply attachment detection processing to originals that are sequentially carried by an original carrying means of an ADF (automatic document feeder) or the like, and the shading correction processing is performed on the basis of the received light quantity of the reflected light of the reference plate which is used in the attachment detection processing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is directed to a CCD or the like in which light from a light source is irradiated onto a document whose document reading position on a contact glass is moved in the sub-scanning direction by an automatic document feeder (ADF) or the like, and reflected light from the document is fixed. The above-described contact glass is executed when reading the image data of the document sequentially conveyed by the automatic document conveying device. The present invention relates to an image reading apparatus capable of efficiently performing an adhering matter detection process for detecting an adhering substance adhering to a surface and a shading correction process for the optical system light receiving means for correcting image unevenness of a read image.

  Conventionally, in the image reading apparatus A provided with the automatic document feeder (ADF) 60 shown in FIG. 4, in order to speed up the reading process of the image data of the document S, the document reading on the contact glass 66 by the ADF 60 is performed. A plurality of documents are sequentially moved in the sub-scanning direction between the position 67 and the document presser 64, and when the document S passes the document reading position 67, the light L1 is transmitted from the exposure device 71 to the moving document S. Is used, and the reflected light L2 from the document S is received by optical system light receiving means 72 to 76 such as a CCD 76 which is fixed. 4 is a schematic cross-sectional view showing a schematic configuration of a conventional image reading apparatus A, in which 61 is a document setting unit, 62 is a document discharge unit, and 64a is a monochrome reference plate provided on the document holder 64. , 65 is a position detection sensor for detecting the position of the conveyed document, 68 is an operation display unit, 72 to 74 are mirrors for guiding reflected light from the document or the monochrome reference plate 64a to the CCD 76 via the optical lens 75. , 10 are image processing control units that execute predetermined image processing based on the amount of light received by the CCD 76.

  However, when the original S is read with the above-described original reading method in a state where dirt or dust adhering to a predetermined size or more adheres to the original reading position 67 on the contact glass 66, the adhering matter is removed. It is read as a so-called black stripe image, and the quality of the read image is deteriorated. In order to prevent such black streak images from occurring, the image processing control unit 10 of the image reading apparatus A has a well-known deposit that detects deposits at the document reading position 67 on the contact glass 66. A detection function (attachment detection means) is provided. The adhering matter detection function is configured to detect the amount of reflected light from the conveyed document (hereinafter referred to as “document reflected light”), and the document at the document reading position 67 at the front part of the front and rear of the document. Each of the received light amounts of the reflected light from the monochrome reference plate 64a (hereinafter referred to as “reference plate reflected light”) received by the portion having no color (hereinafter referred to as “non-document portion”) is predetermined at the same position in the main scanning direction. By determining whether or not there is a pixel having the above density, the deposit on the contact glass 66 is detected. Patent Document 1 proposes a technique related to the attached matter detection function.

On the other hand, as shown in FIG. 5, the light source such as a straight tube lamp and a halogen lamp used in the exposure apparatus 71 gradually decreases in exposure amount with time after lighting and varies for several minutes (depending on the type of light source). Has an exposure characteristic (lamp characteristic) that the exposure amount becomes stable after a lapse of about 2 to 10 minutes). Therefore, when images of tens or hundreds of originals are read continuously, the first original image read immediately after the start of exposure and the tens of original images read several minutes after the exposure However, since a difference occurs in the amount of received light to be read, there is a disadvantage that the color tone and brightness of the read image differ between documents. In order to avoid such inconvenience, the image processing control unit 10 of the image reading apparatus A corrects image unevenness or the like of the read image data based on the received light amount read by the optical system light receiving means. A known shading correction function (shading correction means) is provided. In this shading correction function, the reference plate reflected light from the monochromatic reference plate 64a is reflected at a portion where there is no document at the document reading position 67 (no document portion) before the first document reaches the document reading position 67. Then, the reference plate reflected light from the monochrome reference plate 64a received at the non-document portion in the gap (between paper sheets) between the conveyed document and the document conveyed in the next order is appropriately received, Thus, using the correction data created based on the difference between the received light amounts, the light amount correction of the exposure device 71 or the brightness and color tone of the read image is performed. Patent Document 2 proposes a technique related to the shading correction function.
JP 2000-196814 A JP 2000-270171 A

However, in the image reading apparatus A having both the conventionally known adhered matter detection function and the shading correction function, the attached matter detection process and the shading correction process based on each function are sequentially conveyed by the ADF 60. It was executed alternately or intermittently on the original document. That is, when the processing which has been conventionally carried out will be described with reference to the schematic diagram of FIG. 3, first, the first sheet free document portions of the front of the document S _1, and the original S ₁ and the document S ₂ of the next order received light amount of the reference plate reflected light from the light-receiving criteria plate 64a between the paper and the said deposit detection process based on the amount of received document reflected light from the original S ₁ is executed, the next, the original S The shading correction processing is executed based on the received light amount of the reference plate reflected light received between the sheets before and after the _second original S2 conveyed in the next order of ₁ . Further, the adhering matter detection process is executed on the _third original S ₃ conveyed in the next order in the same manner as the original S ₁ . As described above, conventionally, in the image reading apparatus A, the attached matter detection process and the shading correction process are separately performed based on the received light amounts of the different reference plate reflected lights read at different timings. , The processing efficiency was not good. Furthermore, since the above processes are performed separately as described above, the following problems may occur.
That is, while the attached matter detection process is being performed on the first document, the shading correction process is performed on the second and subsequent documents. There is a problem that the color tone difference and brightness difference generated between the original images after the eyes are not corrected.
In addition, since the attached matter detection process is not executed while the shading correction process is being performed, for example, when an adherent such as dirt adheres to the contact glass during the shading correction process (for example, attached to a document). In this case, the dirt and dust transferred and attached) cannot be detected, and the attached matter appears in the read image as a so-called black streak image, resulting in a problem that the image quality is deteriorated. Further, in this case, since the black streak image is included in the received light amount of the reference plate reflected light used for the shading correction process, there is a problem that the shading correction accuracy is lowered.
Accordingly, the present invention has been made in view of the above circumstances. The object of the present invention is to efficiently execute the deposit detection process by the deposit detection function and the shading correction process by the shading correction function, and An object of the present invention is to provide an image reading apparatus capable of improving processing accuracy.

In order to achieve the above object, the present invention provides an original conveying means for sequentially conveying an original so as to pass the original reading position on the contact glass in the sub-scanning direction, and a reflection from a predetermined monochrome reference plate at least at the original reading position. A fixed optical system light receiving means for receiving reflected light of the reference plate in the main scanning direction, an attached matter detecting means for performing an attached matter detection process for detecting an attached matter at the document reading position on the contact glass, and An image reading apparatus comprising: a shading correction unit that performs a shading correction process on the optical system light receiving unit; and the adhering matter detection unit using the received light amount of the reference plate reflected light received by the optical system light receiving unit. The shading correction unit is configured to execute an adhering matter detection process and based on a received light amount of the reference plate reflected light used for the adhering matter detection process. And it is configured as an image reading apparatus characterized by comprising by executing the shading correction process by.
This eliminates the need to individually receive the reflected light from the reference plate used in the adhering matter detection process and the shading correction process, so that each process can be executed efficiently.
In addition, since each of the above processes is performed using the same reference plate reflected light, it is possible to execute the attached matter detection process and the shading correction process for each of a plurality of documents sequentially conveyed by the document conveying unit. It becomes possible. Thereby, the deposit is detected without overlooking the deposit adhering to the contact glass, and the accuracy of the deposit detection process is improved. Furthermore, since the deposit is almost completely removed by the deposit detection process, the reference plate reflected light used for the shading correction process does not include the black stripe image, and the accuracy of the shading correction process is improved. Is done. In addition, since it is possible to perform light amount correction and image correction of an exposure device or the like for each original, the accuracy of shading correction processing is further improved.

Incidentally, the exposure apparatus has exposure characteristics (see FIG. 5) as described above. Usually, it is considered that the reflected light that does not conform to the exposure characteristics includes a so-called black streak image due to dust, dirt or the like, or an extra image other than that. Therefore, the shading correction means is used in the exposure apparatus that irradiates light on the original or the monochrome reference plate in order to execute the shading correction process by excluding the received light amount of the non-conforming reflected light from the object of the shading correction process. It is preferable that the shading correction process is executed based on the received light amount of the reference plate reflected light according to the exposure characteristics. Thereby, the accuracy of the shading correction process is improved, and the image quality of the read image is improved.
In this case, the image reading apparatus includes characteristic adaptability determining means for determining whether or not the received light amount of the reference plate reflected light received by the optical system light receiving means conforms to the exposure characteristics of the exposure apparatus, and the characteristic adaptability. It is desirable that the apparatus further comprises an alarm display output means for outputting an alarm display indicating that there is a deposit on the single color reference plate or the contact glass based on the determination result by the determination means.

Further, it further comprises an averaging processing means for averaging the received light amount of the reflected light from the reference plate, and the shading correction means performs the shading correction processing based on the average received light amount averaged by the averaging processing means. It may be. In this case, it is desirable that the averaging processing means averages the received light amount obtained by removing the received light amount exceeding a certain density value from the received light amount of the reference plate reflected light.
As a result, shading correction processing is performed using the averaged monotonous amount of received light, so that the processing speed can be improved and the processing time can be shortened. Further, since the received light amount corresponding to the black streak image due to dust or the like exceeding a certain density value is removed from the received light amount of the reference plate reflected light, the accuracy of the shading correction processing is further improved, and the better A read image can be obtained.

As described above, according to the present invention, the received light amount of the reference plate reflected light from the monochrome reference plate received by the optical system light receiving means is used for the originals sequentially conveyed by the original conveying means such as ADF. The attached matter detection process is executed, and the shading correction process is executed based on the received light amount of the reference plate reflected light used for the attached matter detection process. That is, the attached matter detection process and the shading correction process are executed using the same received light amount of the reference plate reflected light. Therefore, it is not necessary to individually receive the reference plate reflected light used for the adhering matter detection process and the shading correction process, and the respective processes can be executed efficiently.
Furthermore, it is possible to execute the adhering matter detection process and the shading correction process for each of a plurality of documents sequentially conveyed by the document conveying means. As a result, the deposit is detected without overlooking the deposit adhering to the contact glass, so that the accuracy of the deposit detection process is improved. In addition, since the attached matter is almost completely removed by the attached matter detection process, the received light amount of the reference plate reflected light used for the shading correction process does not include the black streak image, and the shading correction process is performed. Accuracy is improved. Further, since the light amount correction and image correction of the exposure device and the like are performed for each original, the accuracy of the shading correction process is further improved, and a good read image can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a block diagram showing a schematic configuration of the image processing control unit 10 of the image reading apparatus X according to the embodiment of the present invention, and FIG. 2 shows an attached matter detection process executed by the image processing control unit 10. FIG. 3 is a schematic diagram for explaining an operation of reading an image of a moving document (S _{1 to} S ₃ ), and FIG. 4 is a schematic cross-sectional view showing a schematic configuration of the image reading apparatus. FIG. 5 is a graph showing the exposure characteristics of the exposure apparatus. FIG. 3 shows a state in which the document (S _{1 to} S ₃ ) moves horizontally in the direction of arrow P (the right direction on the paper) for the sake of simplicity. Move through the transport path.

Here, a schematic configuration of the image reading apparatus X according to the embodiment of the present invention will be described with reference to FIG. 4A is a schematic cross-sectional view seen from the side of the image reading device X, and FIG. 4B is a front view of the image reading device X seen from the arrow A shown in FIG. The image reading apparatus X is merely an example of an image reading apparatus according to an embodiment of the present invention. As another example, a copying machine, a facsimile apparatus, a scanner apparatus, or a plurality of these apparatuses including an automatic document feeder. This corresponds to a multi-function machine that has both functions.
The image reading apparatus X is roughly divided into an apparatus main body 50 and an automatic document feeder (ADF) 60 disposed above the apparatus main body 50 in the same manner as the conventional image reading apparatus A described above. ing.

  The ADF 60 sequentially transports one or more documents S set on the document setting unit 61 and moves the document S so as to pass through a document reading position 67 on the contact glass 66 in the sub-scanning direction. Inside the ADF 60, a document presser 64 for pressing the moving document S is disposed adjacent to the contact glass 66 at a position corresponding to the document reading position 67. A position detection sensor 65 for detecting the position of the conveyed document S is disposed in the vicinity of the side where the document S is fed of the document presser 64. Further, a monochromatic reference plate 64a such as white or gray is attached to the surface of the original presser 64 on the side of the contact glass 66 (the surface on which light is irradiated).

A contact glass 66 is provided on the upper surface of the apparatus main body 50, and an operation display section 68 having an operation section including operation keys such as a keyboard and a display section such as a liquid crystal display is disposed on the front side surface.
Inside the apparatus main body 50, an exposure device (light source) 71 for irradiating light to the original S or the monochrome reference plate 64a, and reflected light from the original S or the monochrome reference plate 64a through the contact glass 66. The optical system light receiving means 70 including the mirrors 72 to 74, the optical lens 75, the CCD 76, etc., and the reflected light from the monochrome reference plate 64a and the reflected light from the document S moving at the document reading position 67 are the CCD 76. Image processing that executes the adhering matter detection processing (achieved by the adhering matter detection means) and the shading correction processing (achieved by the shading correction means), which will be described later, using the received light data (the amount of received light) that has been received and converted into an electrical signal. A controller 10 is disposed as appropriate.

  The exposure device 71 and the mirror 72 (also referred to as a carriage) of the optical system light receiving means 70, when reading an image of a stationary document placed on the contact glass 66, in the sub-scanning direction along the stationary document. While moving, the reflected light from the original is received. However, when the reflected light from the moving original S moving at the original reading position 67 and the monochrome reference plate 64a is received as in the present invention, the exposure device 71 irradiates the original reading position 67 with light. The mirror 72 is fixed at a position where the reflected light from the moving original S and the monochrome reference plate 64a can be received at the original reading position 67.

Here, a schematic configuration of the image processing control unit 10 that executes the attached matter detection process and the shading correction process will be described with reference to the block diagram of FIG.
As shown in FIG. 1, the image processing control unit 10 is connected to a CPU 11, a RAM 12, a ROM 13, an ASIC 20, an optical light receiving means 70 such as an external CCD 76, the operation display unit 68, etc. An external terminal 14 for inputting and outputting signals is connected to each other.
The ASIC 20 (Application Specific Integrated Circuit) is an IC designed to provide the image reading apparatus X with a deposit detection function and a shading correction function, and internally includes the document reading on the contact glass 66. An adhering matter detection circuit 23 (an example of adhering matter detection means) that performs an adhering matter detection process for detecting an adhering matter at the position 67, and a received light amount (light receiving data) processed by the adhering matter detection circuit 23 is temporarily stored. A buffer 21; a shading correction circuit 24 (an example of a shading correction means) that performs a shading correction process on the optical system light receiving means 70; and a buffer 22 that temporarily stores a received light amount (light reception data) processed by the shading correction circuit 24. Etc. are provided.
The ROM 13 stores a program for causing the adhering matter detection circuit 23 and the shading correction circuit 24 to execute predetermined processing, and data relating to the exposure characteristics (FIG. 5) of the exposure device 71. The program is read from the ROM 13 by the CPU 12 that controls the respective components in an integrated manner, and processing according to the program is performed, whereby the deposit detection circuit 23 and the shading correction circuit 24 are operated. Thus, the adhering matter detection process and the shading correction process are realized.

Next, referring to the schematic diagram of FIG. 3, the attached matter detection process and the shading correction process executed by the CPU 11 and the ASIC 20 in the image processing control unit 10 of the image reading apparatus X will be described with reference to the flowchart of FIG. 2. An example of the procedure will be described. In the figure, S10, S20,... Indicate processing procedure (step) numbers. The process starts from step S10. FIG. 3 is a schematic diagram showing a moving state of the document (S _{1 to} S ₃ ) moving in the sub-scanning direction between the document presser 64 and the contact glass 66.

The documents (S _{1 to} S ₃ ) placed on the document setting unit 61 (FIG. 4) are sequentially conveyed from the document S ₁ by the ADF 60 (FIG. 4), and the leading edge of the document S ₁ conveyed to the first sheet. When the portion Sa (FIG. 3) is detected by the position sensor 65 (S10), the CPU 11 starts exposure by the exposure device 71 before the leading end portion Sa reaches the document reading position 67. Thus, the optical light receiving means 70 (FIG. 1) receives the reflected light L1 (hereinafter referred to as the reference plate reflected light L1) from the entire area in the main scanning direction of the monochrome reference plate 64a provided on the document holder 64 (see FIG. 1). S20).
Then, the received light amount of the reference plate reflected light L1 received by the optical system light receiving means 70 (hereinafter referred to as received light data D1) is stored in the buffer 21 in the ASIC 20 (S30).

Subsequently, when the front end portion Sa of the original S ₁ is to reach the document reading position 67, the reflected light from the original S ₁ (original S ₁ reflected light) is received by the optical system light receiving means, the document S ₁ The amount of received light (received data) of the reflected light is stored in the buffer 21 (S40).
When the original S ₁ is further conveyed and the rear end Sb (FIG. 3) of the original S ₁ is detected by the position sensor 65, the distance between the position sensor 65 and the original reading position 67 and the conveyance of the original are detected. Based on the speed, the exposure by the exposure device 71 is completed at the timing when the trailing edge Sb of the document S ₁ passes through the document reading position 67. At this time, even after the trailing end Sb reaches the document reading position 67, the exposure device 71 is exposed for a short time, and the optical system light receiving means receives the light. Accordingly, at this time, the reflected light from the entire area in the main scanning direction of the monochrome reference plate 64a (hereinafter referred to as the reference plate reflected light L2) is received again by the optical system light receiving means (S50). Thereafter, the received light amount of the reference plate reflected light L2 (hereinafter referred to as received light data D2) is stored in the buffer 21 by the CPU 11 (S60). The reference plate reflected light L2 (see S50) received at this time is somewhat lighter than the reference plate reflected light L1 (see S20) due to the exposure characteristics of the exposure device 71 (see FIG. 5). Has fallen.

In step S60, when the received light data D2 of the reference plate reflected light L2 is stored in the buffer 21, the received light data D1 (S30) of the reference plate reflected light L1 stored in the buffer 21 and the reference data are subsequently stored. receiving data D2 of the plate reflected light L2 (S60), the received light data of the document S ₁ reflected light (S40) is fed to the deposit sensing circuit 23 of the ASIC20 by the CPU 11. On the other hand, in the ASIC 20, the light reception data D1 and D2 are compared to determine whether or not there is a common black pixel (referred to as a black peak value) having a certain density or more at the same position in the main scanning direction. (S70). In addition, the process performed by S70 is a deposit | attachment detection process.
If it is determined that the black peak value does not exist in common, the process proceeds to S100. On the other hand, if it is determined that the black peak value is present in common, the adhering matter detection circuit 23 detects dust presence information (the adhering matter such as dust or dirt adheres to the contact glass 66 or the monochrome reference plate 64a). The information indicating that there is dust is sent out and displayed on the operation display unit 68 (FIG. 1) provided in the image reading apparatus X by the CPU 11 (S80). Thereafter, the CPU 11 performs a process of removing the black peak value from the received light data D1 and D2 of the reference plate reflected light L1 and L2 (S90).

Next, in S100, it is determined whether or not the received light data D2 of the received reference plate reflected light L2 matches the exposure characteristics of the exposure device 71 (FIG. 5). This determination is made by reading out the exposure characteristics stored in a storage device such as the ROM 13 and determining whether the received light data D2 substantially matches the read exposure characteristics. Note that the process in S100 is a characteristic conformity determination process by the characteristic conformity determination means.
If it is determined that the light reception data D3 matches the exposure characteristics, then the light reception data D1 and D2 stored in the buffer 21 are developed on the RAM 12, and the light reception data D1 and D2 are stored in the RAM 12. Averaged (averaged) by the CPU 11 (S110), and then averaged received light data D1 averaged (hereinafter referred to as average received light data D3) and averaged received light data D2 average received light amount (Hereinafter referred to as average received light data D4) is stored in the buffer 22 (S120).
On the other hand, if it is determined that the received light data D2 does not conform to the exposure characteristics (No side of S100), the received light data D2 of the reference plate reflected light L2 that does not conform to the exposure characteristics, Since other extra images are expected to be included, in step S101, as in step S80, the CPU 11 alerts or displays the dust presence information on the operation display unit 68 (FIG. 1) or the like. Is output. Note that the processing in S101 is alarm display output processing by the alarm display output means.
After that, the shading process using the light reception data D2 is not performed, and the processes of S10 to S100 are repeatedly performed on the documents conveyed in the next order. As described above, since the received light data that does not match the exposure characteristics is excluded from the object of the shading correction process, the accuracy of the shading correction process is improved and the image quality of the read image is improved.

When the average light reception data D3 and the average light reception data D4 are stored in the buffer 22 (S120), the CPU 11 subsequently converts the average light reception data D3 and D4 stored in the buffer 22 into the shading correction. The difference between the average light reception data D3 and the average light reception data D4 is calculated by the shading correction circuit 24, and correction data used for a light amount correction process or an image correction process described later is created based on the difference. (S130). Thereafter, a light amount correction process or an image correction process based on the correction data is executed (S140). In this way, since the light amount correction process or the image correction process (shading correction process) is performed using the averaged monotonous light reception data, the processing speed can be improved and the processing time can be shortened. The light amount correction process is a well-known process for adjusting the exposure amount uniformly by controlling the power supplied to the exposure device 71, and the image correction process is performed for each document generated based on the received light amount. This is a known process for correcting the brightness, color tone, and the like between the image data so as to be equal to each other.
When the light quantity correction processing or image correction processing (S140) is completed, the document S ₂ which is transported to the next order, and further the following order for the document S ₃ to be conveyed to the processing of S10~S140 described above is repeatedly executed The
As described above, according to the present invention, since the attached matter detection process and the shading correction process are executed when one original image is read, the reference plate reflected light is received for each process. There is no need, and each process is executed efficiently.

1 is a block diagram showing a schematic configuration of an image processing control unit 10 of an image reading apparatus X according to an embodiment of the present invention. 7 is a flowchart for explaining a procedure of attached matter detection processing and shading correction processing executed by the image processing control unit 10. Schematic diagram for explaining an operation of reading an image of a document to move (S ₁ ~S _3). 1 is a schematic cross-sectional view illustrating a schematic configuration of an image reading apparatus. The graph which shows the exposure characteristic of exposure apparatus.

Explanation of symbols

10 Image processing control unit 11 CPU
12 ... RAM
13 ... ROM
14 ... Input / output terminal 20 ... ASIC
21, 22, buffer 23, attached matter detection circuit 24, shading correction circuit 60, automatic document feeder 61, document setting unit 64, document holder 64 a, monochrome reference plate 65, position detection sensor 66, contact glass 67, document reading position 68 ... Operation display unit 75 ... Optical lens 76 ... CCD
71 ... Exposure devices 72 to 74 ... Mirror

Claims (5)

Document conveying means for sequentially conveying the document so as to pass the document reading position on the contact glass in the sub-scanning direction;
A fixed optical system light receiving means for receiving the reference plate reflected light in the main scanning direction reflected from a predetermined single color reference plate at least at the document reading position;
An adhering matter detection means for performing adhering matter detection processing for detecting an adhering matter at the document reading position on the contact glass;
Shading correction means for performing shading correction processing on the optical system light receiving means;
In an image reading apparatus comprising:
Using the received light amount of the reference plate reflected light received by the optical system light receiving means, the attached matter detecting means executes the attached matter detecting process, and receiving the reference plate reflected light used for the attached matter detecting process. An image reading apparatus, wherein the shading correction processing by the shading correction means is executed based on a quantity.   2. The shading correction means for executing the shading correction processing based on an amount of received reflected light of the reference plate corresponding to an exposure characteristic of an exposure apparatus that irradiates light to the original or the monochrome reference plate. The image reading apparatus described. Characteristic suitability judging means for judging whether or not the received light amount of the reference plate reflected light received by the optical system light receiving means matches the exposure characteristics of the exposure apparatus;
3. An alarm display output means for outputting an alarm display indicating that there is a deposit on the single color reference plate or the contact glass based on a determination result by the characteristic conformity determination means. Image reading apparatus. And further comprising an averaging processing means for averaging the amount of received light of the reference plate reflected light,
The image reading apparatus according to claim 1, wherein the shading correction unit performs the shading correction process based on an average received light amount averaged by the averaging processing unit.   5. The image reading apparatus according to claim 4, wherein the averaging processing means averages the received light amount from which the received light amount exceeding a certain density value is removed from the received light amount of the reference plate reflected light.

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