JP2009016915A - Manuscript reader and image forming apparatus equipped with the same, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manuscript reader which can obtain a correct reference value and can precisely make correction such as shading compensation. <P>SOLUTION: Second image processing section 220 in the image processing section 103 of a manuscript reader 100 reads a white reference sheet having dimensions smaller than those of the readable region S0 of a second document reading means 20 a plurality of times by the second document reading means 20, determines the reference value for all pixels in the readable region based on the pixel values of all pixels in the readable region and then correct the image of a manuscript being read out by the second document reading means 20 based on the reference value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an original reading apparatus that reads an original and corrects an original image of the read original, for example, shading correction, and an image forming apparatus including the original reading apparatus. The present invention also relates to an image processing method for correcting an original image of a read original, for example, shading correction.

  In the original reading apparatus, for example, in the adjustment process in the manufacturing process, a sheet-like white reference original (hereinafter referred to as “white reference sheet”) is read by the original reading unit, and the output value at that time, that is, the pixel value of each pixel Is stored as a reference value for shading correction. In the case of a document feed reading apparatus that performs so-called flow reading, in which the document reading unit is fixed and the document is moved to read the document image, in the adjustment process, the conveyance path covering the document reading unit is opened and the document reading unit has a white reference. Insert a sheet and have it read.

  The white reference sheet is inserted into the document reading unit by an operator, for example. When a white reference sheet is inserted by an operator, there is a problem that the adjustment process takes a long time. On the other hand, there is a document reading apparatus that inserts a white reference sheet without depending on an operator (see, for example, Patent Document 1). In the document reading device disclosed in Patent Document 1, the white reference sheet is transported to the document reading unit by the transport device and is read.

  The reading width of the document reading unit, that is, the size of the readable area that can be read by the document reading unit is the maximum size of the document that can be read in order to cope with the deviation in the width direction when the document is conveyed and the oblique feeding of the document. Is set larger in the width direction than a predetermined dimension in the width direction of the document (hereinafter referred to as “width direction dimension”). Also, when inserting the white reference sheet into the document reading unit, misalignment may occur. Therefore, the dimension of the white reference sheet in the width direction is larger than the reading width of the document reading unit in consideration of the misalignment at the time of insertion. It is necessary to select a larger value in the width direction.

  Therefore, as the white reference sheet, a dedicated white reference sheet having a special dimension is required as described in Patent Document 1. For example, when the maximum document that can be read by the document reading unit is a document in which an A4 size document stipulated in Japanese Industrial Standard (JIS) P0138 is vertically arranged, the reading width of the document reading unit is an A4 size document. Is set to a value larger than 297 mm, which is the length dimension of the long side portion, for example, 307 mm. Therefore, as a white reference sheet, the width direction dimension is a value larger than 307 mm, which is the reading width of the document reading portion, for example, A white reference sheet that is 310 mm is used.

Japanese Patent Laid-Open No. 7-46403 (page 3, FIGS. 1 and 3)

  The white reference sheet becomes dirty and difficult to use as it is repeatedly used in the adjustment process. If the adjustment process is performed using a dirty white reference sheet, an accurate reference value cannot be obtained, so that shading correction cannot be performed with high accuracy. Therefore, when the white reference sheet becomes dirty, it is necessary to replace it with a new white reference sheet that is not dirty.

  In the document reading apparatus disclosed in Patent Document 1, a dedicated white reference sheet is used, so the white reference sheet is expensive and the white reference sheet cannot be frequently replaced. Accordingly, the adjustment process may be performed using a dirty white reference sheet, an accurate reference value may not be obtained, and shading correction may not be performed with high accuracy. In this case, the reading of the document image becomes inaccurate, and the image quality of the read document image is deteriorated.

  An object of the present invention is to provide an original reading apparatus capable of obtaining an accurate reference value and capable of performing correction such as shading correction with high accuracy, an image forming apparatus including the original reading apparatus, and an image processing method.

The present invention includes a document reading unit that reads a document image of a document,
Based on the pixel values of all the pixels in the readable area obtained by reading a reference document having a size smaller than the readable area of the document reading section by the document reading section multiple times, And an image processing unit for correcting a document image of a document read by the document reading unit based on the reference value.

In the present invention, the image processing unit
Among the pixel values acquired by reading the reference document a plurality of times by the document reading unit, the pixel values of pixels included in a plurality of reference value acquisition ranges that are predetermined each time and divide the entire readable area are It includes a cut-out combining means for obtaining reference values of all the pixels in the readable area by respectively acquiring the reference values of the pixels and combining the acquired reference values of the respective pixels over the entire readable area. .

According to the present invention, the reference document is read a plurality of times by the document reading unit so that the pixel values of some of the pixels in the readable area are obtained in duplicate.
The image processor
A correction amount for correcting the pixel value of each pixel in the readable area is obtained based on a plurality of pixel values for each pixel in the overlapping area obtained by overlapping the pixel values in the readable area, and the correction Based on the amount, the pixel value of each pixel in the readable area is corrected, the corrected pixel value is acquired as the reference value of the pixel, and the acquired reference value of each pixel is synthesized over the entire readable area. Thus, a correction composition means for obtaining reference values of all the pixels in the readable area is included.

  Further, according to the present invention, the correction combining unit obtains a difference value between one pixel value of a plurality of pixel values for each pixel in the overlapping region and the remaining pixel value as the correction amount, and outputs the difference outside the overlapping region of the readable region. The pixel value of each pixel acquired together with the remaining pixel value in the region is corrected based on the correction amount.

The present invention further includes a document conveying unit that conveys the document to the readable area,
The readable area is composed of a plurality of pixels arranged in a predetermined main scanning direction,
The document reading unit reads a document image of a document conveyed in the sub-scanning direction orthogonal to the main scanning direction by the document conveying unit in the readable area,
The image processing unit conveys a reference document whose size in the main scanning direction is smaller than the size in the main scanning direction of the readable region in the readable region by the document conveying unit in the sub scanning direction, and reads the reference document a plurality of times by the document reading unit. Based on the acquired pixel values of all the pixels in the readable region, the reference values of all the pixels in the readable region are obtained.

In the present invention, the document conveying section
It includes a pair of restricting members that restrict the position of the document in the readable area in the main scanning direction so as to be displaceable over the entire main scanning direction of the readable area.

  According to the present invention, the document conveying unit is configured to be able to continuously convey a plurality of documents.

The present invention also provides a document reading apparatus according to the present invention,
An image forming apparatus comprising: an image forming unit that forms an output image based on a document image read by the document reading device.

The present invention also provides an image processing method for correcting a document image of a document read by a document reading unit,
A reference document having a size smaller than the readable area of the document reading unit is read a plurality of times by the document reading unit to obtain the pixel values of all the pixels in the readable area,
Based on the acquired pixel value, obtain a reference value for all pixels in the readable area,
In the image processing method, the document image is corrected based on the reference value.

  According to the present invention, an original image of an original is read by the original reading unit, and a reference value of all the pixels in the readable area is obtained by the image processing unit, and the original of the read original is read based on the reference value. The image is corrected. Based on the pixel values of all the pixels in the readable area obtained by reading the reference document having a size smaller than that of the readable area by the document reading section a plurality of times, all the pixels in the readable area Therefore, the reference values of all the pixels in the readable area can be obtained without using a reference document having the same size as or larger than the size of the readable area. Therefore, for example, a reference value of all the pixels in the readable area can be obtained by using a commercially available paper having a predetermined size as used for forming an output image of a document image as a reference document. The reference value can be obtained using a reference manuscript that is free or has as little dirt as possible and is suitable for obtaining the reference value. Since the image processing unit corrects the document image based on the reference value thus obtained, the document image can be corrected with high accuracy.

  According to the invention, the image processing unit includes a cut-out synthesis unit. Of the pixel values acquired by reading the reference document a plurality of times by the document reading unit by the cut-out combining means, the pixels included in the plurality of reference value acquisition ranges that are determined in advance each time and divide the entire readable area. The pixel values are acquired as the reference values of the pixels and synthesized over the entire readable area, whereby the reference values of all the pixels in the readable area are obtained. Thereby, the reference value of all the pixels in the readable area can be obtained with a simple configuration.

  Further, according to the present invention, the reference document is read a plurality of times by the document reading unit, so that the pixel values of the respective pixels are obtained in an overlapping area of the readable area. The image processing unit includes a correction combining unit, and the correction combining unit calculates a correction amount for correcting the pixel value of each pixel in the readable region based on a plurality of pixel values for each pixel in the overlapping region. Based on the correction amount, the pixel value of each pixel in the readable area is corrected and acquired as a reference value of the pixel, and the acquired reference value of each pixel is synthesized over the entire readable area, A reference value for all pixels in the readable area is obtained. The pixel values of all the pixels in the readable area are acquired in a plurality of times by reading the reference document a plurality of times. As described above, the pixel values are obtained based on the plurality of pixel values for each pixel in the overlapping area. Since the correction value is corrected by the correction combining unit based on the correction amount to be obtained and acquired as the reference value of each pixel, the influence of acquiring the pixel values of all the pixels in the readable area in a plurality of times is suppressed. be able to. For example, even when the reading condition by the document reading unit changes when the reference document is read a plurality of times, the influence of the change of the reading condition can be suppressed. Accordingly, as in the case where the pixel values of all the pixels in the readable area are acquired as the reference value by reading the reference document having the same size as or larger than that of the readable area once, a certain condition is set. Thus, the reference values of all the pixels in the readable area can be obtained. Since the document image is corrected based on the reference value obtained under certain conditions as described above, it is possible to suppress a change in image quality in the document image.

  Further, according to the present invention, the correction composition means obtains a difference value between one pixel value of a plurality of pixel values for each pixel in the overlapping region and the remaining pixel value as a correction amount, and based on this correction amount. Thus, the pixel value of each pixel acquired together with the remaining pixel value in the area outside the overlapping area of the readable area is corrected. Document reading that can determine the reference values of all the pixels in the readable area under certain conditions while suppressing the influence of the pixel values of all the pixels in the readable area being acquired in multiple steps. The apparatus can be realized with a simple configuration.

  According to the invention, in the readable area constituted by a plurality of pixels arranged in the main scanning direction, the document image of the document conveyed in the sub-scanning direction orthogonal to the main scanning direction by the document conveying unit is converted into the document reading unit. Read by. As a document, a reference document having a smaller dimension than the readable area, that is, a reference document having a dimension in the main scanning direction smaller than the dimension in the main scanning direction is scanned in the readable area in the sub-scanning direction by the document conveying unit. By transporting and reading multiple times by the document reading unit, the pixel values of all the pixels in the readable region are obtained, and based on this pixel value, the reference of all the pixels in the readable region by the image processing unit A value is determined. Therefore, a document reading apparatus capable of obtaining the reference values of all the pixels in the readable region without using a reference document having a size equal to or larger than the size of the readable region in the main scanning direction is realized. The

  According to the invention, the document is transported to the readable region with the position in the main scanning direction in the readable region regulated by the pair of regulating members of the document transport unit. The pair of restricting members restricts the position of the original in the readable area in the main scanning direction so as to be displaceable over the entire main scanning direction of the readable area. Therefore, when the reference document is read a plurality of times by the document reading unit, the position of the reference document in the readable area in the main scanning direction can be displaced over the entire main scanning direction. Can be obtained. As a result, a document reading apparatus capable of obtaining the reference value of each pixel throughout the main scanning direction of the readable area is realized.

  Further, according to the present invention, a plurality of documents can be continuously conveyed to the readable area by the document conveying unit. As a result, the operator can feed a plurality of reference documents to the readable area continuously by supplying a plurality of reference documents to the document conveying section at a time. Compared with the case of supplying to the section, the labor of the operator can be saved. Further, since the plurality of reference documents are continuously conveyed to the readable area, the plurality of reference documents are continuously read by the document reading unit, and the reference document is continuously read a plurality of times. Compared to the case where the reference document is not continuously conveyed, the time required to acquire the pixel values of all the pixels in the readable area can be shortened. Thereby, compared with the case where one reference document having the same size as or larger than the size of the readable area is read and the pixel values of all the pixels in the readable area are acquired as the reference value, the readable area It is possible to prevent the time required for obtaining the reference values of all the pixels from becoming excessively long. Therefore, the reference of all the pixels in the readable area can be obtained by using a reference document whose dimension in the main scanning direction is smaller than the dimension in the main scanning direction of the readable area without excessively increasing the time required to acquire the reference value. The value can be determined.

  According to the present invention, the image forming apparatus includes the excellent document reading apparatus and the image forming unit as described above. The image processing unit of the document reading apparatus is configured to read the reference document having a size smaller than the readable region based on the pixel values of all the pixels in the readable region obtained by reading the reference document by the document reading unit a plurality of times. Therefore, it is not necessary to use a reference document having the same size as or larger than the size of the readable area in order to obtain the reference value. Therefore, for example, since a standard value can be obtained using commercially available paper having a prescribed size as a standard document, a standard document that is not dirty or is as little as possible and suitable for obtaining the standard value is used. Thus, the reference value can be obtained. Since the image processing unit corrects the document image based on the reference value thus obtained, the document image can be corrected with high accuracy. Since the output image is formed by the image forming unit based on the original image corrected with accuracy as described above, an image forming apparatus capable of forming an output image faithfully matching the original is realized.

  According to the present invention, the reference document having a size smaller than the readable area of the document reading unit is read a plurality of times by the document reading unit, and the pixel values of all the pixels in the readable region are acquired. Based on the acquired pixel value, a reference value of all pixels in the readable area is obtained, and based on the reference value, the document image of the document read by the document reading unit is corrected. Since the reference values of all the pixels in the readable area are obtained based on the pixel values of all the pixels in the readable area acquired by reading the reference document a plurality of times in this way, the dimensions are the same as the dimensions of the readable area. Alternatively, the reference values of all the pixels in the readable area can be obtained without using a reference document having a size larger than that. Accordingly, for example, a standard value can be obtained by using a commercially available paper having a prescribed size as used for forming an output image of a manuscript image as a manuscript, so that there is no dirt or dirt is as little as possible. The reference value can be obtained using a reference document in a state suitable for obtaining the reference value. Since the original image is corrected based on the reference value thus obtained, the original image can be corrected with high accuracy.

  FIG. 1 is a block diagram showing an electrical configuration of a part of a document reading apparatus 100 according to the first embodiment of the present invention, and FIG. 2 is a block diagram showing an electrical configuration of the document reading apparatus 100. FIG. 2 shows a state where the external device 200 is connected to the document reading apparatus 100.

  As shown in FIG. 2, the document reading apparatus 100 generally includes a control unit 101, a scanner unit 102, an image processing unit 103, a storage unit 104, a communication unit 105, an operation panel unit 106, and a document. The scanning unit driver 107 for driving and controlling the scanning unit driving motor 107a and the conveyance roller driver 108 for driving and controlling the document conveyance roller driving motor 108a are configured.

The control unit 101 is a part that manages operation control of the entire document reading apparatus 100. More specifically, the above-described scanner unit 102, image processing unit 103, storage unit 104, communication unit 105, operation panel unit 106, scanning unit. It controls the operation of each part of the document reading apparatus 100 including the driver 107 and the conveyance roller driver 108. Although not shown, the control unit 101 includes a central processing unit (abbreviated as CPU), a ROM (Read Only Memory) that stores a control program executed by the CPU, and a RAM (Random) that provides a work area to the CPU.
Access Memory).

The scanner unit 102 includes a first image reading unit 10 and a second image reading unit 20. The first and second image reading means 10 and 20 read a document image of a document and output the read document image to the image processing unit 103. The first and second document reading means 10 reads a document image of a document as an analog signal. The second image reading unit 20 corresponds to a document reading unit. The first image reading unit 10 includes a first image sensor 14, and the second image reading unit 20 includes a second image sensor 24. The first and second image sensors 14 and 24 receive the reflected light from the document and output an electrical signal corresponding to the amount of received light. The first and second imaging devices 14 and 24 are, for example, charge coupled devices (Charge
It is realized by a coupled device (abbreviated as CCD). In the present embodiment, the first and second imaging elements 14 and 24 are realized by a CCD line sensor in which a plurality of pixels are arranged in a line in a predetermined main scanning direction X. The area where the plurality of pixels are arranged is a readable area S0 that can be read by the first and second image reading means 10 and 20. In the present embodiment, the readable area S0 of the first and second image reading means 10 and 20 is composed of a plurality of pixels arranged in the main scanning direction X.

  The image processing unit 103 processes the document image read by the first and second image reading units 10 and 20. For example, the image processing unit 103 processes the document image read by the first image reading unit 10 or the second image reading unit 20 in a predetermined unit, for example, a page unit.

  The storage unit 104 stores data under control controlled by the control unit 101 and various input instruction contents. The storage unit 104 includes an area that functions as an original image storage unit that stores an original image read by the scanner unit 102 and an area that functions as a document storage unit that stores a document including a converted character string code. The storage unit 104 includes, for example, a RAM, an EEPROM (Electrically Erasable Programmable Read Only Memory), a hard disk, and a magneto-optical disk (abbreviated as MO).

  The communication unit 105 is a communication unit that performs two-way communication with an external device 200 such as a computer or a printer. The communication unit 105 transmits data processed by the image processing unit 103 to the external device 200 and transmits the data from the external device 200. Received data. The communication unit 105 includes a memory for expanding data transmitted from the external device 200 into data that can be handled by the document reading apparatus 100.

  The operation panel unit 106 is used when the user inputs an operation mode of the document reading apparatus 100 when reading a document, for example, when the user inputs designation of one of the single-sided reading mode and the double-sided reading mode. Used for. Although not shown in FIG. 4 to be described later, the operation panel unit 106 is arranged on the front side of the document reading apparatus 100 toward the paper surface of FIG. Specifically, the housing 3 of the main scanning unit 2 is extended to the near side from the ADF 1 toward the paper surface of FIG. 4 and is disposed on the upper surface portion thereof.

  The document scanning unit drive motor 107a is a motor for moving the light source unit 15 and the mirror unit 16 of the first image reading unit 10 shown in FIG. 4 to be described later in the sub-scanning direction at an appropriate speed. Based on the control, the scanning unit driver 107 controls driving appropriately.

  The document transport roller drive motor 108a is a motor that drives each of the rollers such as a drawing roller 6, a transport roller 7, a registration roller 8, and a paper discharge roller 9 disposed in a document transport path F shown in FIG. Based on the control from the unit 101, the driving is appropriately controlled by the conveyance roller driver 108.

  FIG. 3 is a perspective view showing the document reading apparatus 100, and FIG. 4 is a cross-sectional view showing the document reading apparatus 100. FIG. 3 shows the overall appearance of the document reading apparatus 100 of the present embodiment. The document reading apparatus 100 of the present embodiment constitutes an upper part of an image forming apparatus 50 shown in FIG. The document reading apparatus 100 generally includes an automatic document feeder (abbreviated as ADF) 1 that automatically transports a document along a document transport path F, and a main scanning unit 2. The The ADF 1 and the main scanning unit 2 are connected by a hinge (not shown). The ADF 1 can be opened and closed with respect to the main scanning unit 2 by the rotation of the hinge.

  The ADF 1 includes the second image reading unit 20 described above, and the main scanning unit 2 includes the first image reading unit 10 described above. The first image reading means 10 reads an image of a first surface (hereinafter referred to as “front surface”) that is the surface on one side in the thickness direction of the document that has been conveyed by the ADF 1, and the second image reading means 20 is conveyed by the ADF 1. An image on the second surface (hereinafter referred to as “back surface”), which is the surface on the other side in the thickness direction of the document, is read.

  The main scanning unit 2 generally includes a housing 3, a platen plate 4 having a document placement surface on which a document is placed, and the first image reading means 10 housed in the housing 3. It is comprised including. The platen plate 4 has translucency, is realized by a transparent glass plate, for example, and is formed in a rectangular plate shape. The document placement surface constitutes one surface in the thickness direction of the platen plate 4. The first image reading unit 10 is disposed on the opposite side of the original placed on the original placement surface of the platen plate 4 with the platen plate 4 interposed therebetween.

  The first image reading unit 10 is a reduction optical system image reading unit that optically reduces and reads a document image of a document, and includes a light source 11, first to third mirrors 12a, 12b, and 12c, a lens 13, and the like. The first imaging element 14 described above is included. The light source 11 and the first mirror 12 a are included in the light source unit 15, and the second and third mirrors 12 b and 12 c are included in the mirror unit 16. That is, the first image reading unit 10 includes a light source unit 15 including a light source 11 and a first mirror 12a, a mirror unit 16 including a second mirror 12b and a third mirror 12c, a lens 13, and a first image sensor 14. Consists of including.

  The main scanning unit 2 reads an image by a document fixing method in which a user places a document on the platen plate 4 and reads a document image, and a document moving method by which a document image is read while the document is automatically conveyed by the ADF 1. This corresponds to both of the image reading method and the image reading method. That is, the main scanning unit 2 is used for an image reading operation by the document fixing method and an image reading operation by the document moving method. FIG. 4 shows a state in which a document image is read by the document movement method.

  When reading an original image by the original fixing method, when the image reading operation is started, the light source unit 15 and the mirror unit 16 move to home positions corresponding to the original fixing method, respectively. Thereafter, the light source unit 15 irradiates the original along the main scanning direction X while irradiating the original with the sub-scanning direction Y orthogonal to the main scanning direction X at a constant speed, in FIG. Move and scan the document image. Simultaneously with the movement of the light source unit 15, the mirror unit 16 moves in the sub-scanning direction Y in the same manner as the light source unit 15 at a movement speed that is ½ (½) of the movement speed of the light source unit 15.

  The light emitted from the light source unit 15 and reflected by the original is reflected by the first mirror 12a of the light source unit 15, and then sequentially reflected by the second and third mirrors 12b and 12c of the mirror unit 16 to change the optical path by 180 °. The The light reflected by the third mirror 12c forms an image on the first image sensor 14 via the lens 13 and is converted into electrical image data.

  When reading a document image by the document movement method, the light source unit 15 and the mirror unit 16 remain stationary at the home position corresponding to the document movement method, that is, the home position P1 shown in FIG. A document image conveyed by the ADF 1 so as to pass through a position facing the unit 15, specifically, above the light source unit 15 is irradiated with light from the light source 11 to scan the image of the document. . The document is transported so that the front side of the document faces the light source 11 of the first image reading means 10. The light reflected on the surface of the original is reflected by the first mirror 12a of the light source unit 15 and then the second and third mirrors 12b of the mirror unit 16 in the same manner as when reading the original image by the above-described original fixing method. , 12c, the optical path is changed by 180 °, and an image is formed on the first image sensor 14 via the lens 13 and converted into electrical image data.

  The ADF 1 generally includes the above-described second image reading unit 20, a document conveying unit 31, a casing 27 that houses the second image reading unit 20 and the document conveying unit 31, and a paper discharge tray 30. Consists of. The operation of each unit of the ADF 1 including the second image reading unit 20 and the document conveying unit 31 is controlled by the control unit 101. The document transport unit 31 is configured to be able to continuously transport a plurality of documents, and more specifically to be able to continuously feed a plurality of documents to the second image reading unit 20.

  The document transport unit 31 includes a document placing table 5 on which a document is placed, a first regulating member 32 that is a pair of regulating members that regulates the position of the document placed on the document placing table 5 in the main scanning direction X, and The second restricting member 33 is configured to include a transport unit 34 that transports the document placed on the document placing table 5 along a predetermined document transport path F and discharges the document onto the paper discharge tray 30. The first and second regulating members 32 and 33 are provided so as to be movable in the main scanning direction X, respectively. The first and second restricting members 32 and 33 are plate-like and are provided at both ends in the main scanning direction X of the document table 5. The first and second regulating members 32 and 33 move in the main scanning direction X, thereby reading the position of the document in the main scanning direction X in the readable area S0 of the first and second image reading means 10 and 20. It is restricted so that it can be displaced over the entire main scanning direction X of the possible region S0.

  Conveying means 34 includes an attracting roller 6 for attracting documents placed on the document placing table 5 one by one into the ADF 1, and a plurality of pairs of transport rollers 7 for transporting the attracted documents along the document conveying path F. And a registration roller 8 that adjusts the paper feed timing, and a paper discharge roller 9 that discharges an original whose image has been read to the paper discharge tray 30. The attracting roller 6, the transport roller 7, the registration roller 8, and the paper discharge roller 9 are arranged so that the unitized second image reading means 20 can be accommodated in the document transport path F that forms an arc in a substantially U shape. The

  The document conveying unit 31 regulates the document placed on the document placing table 5 by the first and second regulating members 31 and 32 and conveys the document along the document conveying path F by the conveying unit 34. The first and second image reading means 10 and 20 are conveyed to the readable area S0. In the readable area S0, the document is transported in the sub-scanning direction Y by the document transport unit 31, and the first and second image reading units 10 and 20 respectively read the document images of the document transported in the sub-scanning direction Y. .

  The second image reading unit 20 is a reduction optical system image reading unit, and includes a light source 21, a light source holder 25 that holds the light source 21, first to fourth mirrors 22 a, 22 b, 22 c, 22 d, and a lens 23. And the second image sensor 24 described above. The second image reading unit 20 includes a unit housing such that the light source 21, the light source holder 25, the first to fourth mirrors 22a, 22b, 22c, and 22d, the lens 23, and the second image sensor 24 form one aggregate. It is unitized by being accommodated in H.26. In the second image reading unit 20, the light source 21, the lens 23, and the second imaging element 24 held by the light source holder 25 are respectively the light source 11, the lens 13, or the first imaging element 14 that constitutes the first image reading unit 10. Realized by the same thing.

  The lower surface of the casing 27 constituting the ADF 1 functions as a pressing plate 28 that presses the document placed on the platen plate 4 of the main scanning unit 2 from above. The pressing plate 28 is a lid 29 that can be opened at a portion facing the light source holder 25 of the second image reading means 20.

  The second image reading unit 20 is used for an image reading operation by a document moving method. The second image reading unit 20 is configured such that the second image reading unit 20 receives a document reading path F when a double-sided scanning request is made by the user, that is, when a double-sided scanning request is input from the operation panel by the user. The image on the back side of the original conveyed is read. Specifically, after the image on the front side of the document is read by the first image reading unit 10, the second image reading is performed while the document is being transported along the document transport path F toward the discharge tray 30. The image on the back side of the document is read by the second image reading means 20 when passing the position facing the light source 21 of the means 10, specifically, below the light source holder 25. At this time, the light source 21 of the second image reading unit 20 emits light toward the back side of the document. The light reflected from the back side of the document is sequentially subjected to optical path conversion by the first to fourth mirrors 22a, 22b, 22c, and 22d, and then forms an image on the second image pickup device 24 through the lens 23 to be electrically Converted to image data.

  The document reading apparatus 100 further includes a white reference plate 200. The white reference plate 200 is a plate-like long member, and its main scanning portion is arranged such that its longitudinal direction is along the main scanning direction X and its one surface in the thickness direction is in contact with the document placement surface. 2 on the platen plate 4. The white reference plate 200 is provided at a predetermined position on the document placement surface of the platen plate 4, that is, at one end in the sub-scanning direction Y of the document placement surface of the platen plate 4 in this embodiment. The white reference plate 200 is used to acquire the first reference value stored in the first reference value storage means 215 shown in FIG.

  Returning to FIG. 1, the image processing unit 103 includes a first image processing unit 210 and a second image processing unit 220. The first image processing unit 210 includes a first amplifier 212, a first A / D (analog / digital) converter 213, a first shading correction unit 214, a first reference value storage unit 215, and a first output value conversion unit 216. . The operation of each part of the image processing unit 103 including the first amplifier 212, the first A / D converter 213, the first shading correction unit 214, the first reference value storage unit 215, and the first output value conversion unit 216 is controlled by the control unit 101. Controlled by.

  Image data representing the original image of the original read by the first image reading means 10 is output from the first image sensor 14 as an electrical signal corresponding to the amount of received light (hereinafter also referred to as “read signal”). The signal is supplied to one image processing unit 103, more specifically, to the first amplifier 212 of the first image processing unit 103. The first imaging element 14 is a signal representing the pixel value of each pixel of the document image of the document, and a reflectance signal representing the reflectance of the reflected light from the document at the portion corresponding to that pixel according to the amount of light received by that pixel. Is output.

  According to the first image processing unit 210, the read signal output from the first image sensor 14 and applied to the first amplifier 212 is amplified by the first amplifier 212 and converted into a digital signal by the first A / D converter 213. Then, it is given to the first shading correction means 214. When the read signal output from the first image sensor 14 is a read signal representing the image data of the document image of the document, that is, the image data supplied to the first image processing unit 210 is image data representing the document image of the document. In some cases, the control unit 101 controls the first shading correction unit 214 to perform shading correction on the image data given as a digital signal from the first A / D converter 213. The first shading correction unit 214 performs shading correction on the image data of the document image supplied from the first A / D converter 213 based on a command from the control unit 101.

  The first reference value storage unit 215 reads the reference value (hereinafter referred to as “first reference value”) for shading correction by the first shading correction unit 214 by the first image reading unit 10 and the first image sensor. The reference value for each pixel of the original image of the original given from 14 is stored. The first shading correction unit 214 performs shading correction on the document image of the document based on the first reference value stored in the first reference value storage unit 215.

  The document image subjected to the shading correction by the first shading correction unit 214 is given to the first output value conversion unit 216. The first output value conversion means 216 performs other image processing such as gamma correction on the original image subjected to the shading correction, and outputs the processed original image to the storage unit 104 and the control unit 101.

  The second image processing unit 220 includes a second amplifier 222, a second A / D converter 223, a second shading correction unit 224, a second reference value storage unit 225, a second output value conversion unit 226, and a cut-out synthesis unit 227. . Each part of the second image processing unit 220 including the second amplifier 222, the second A / D converter 223, the second shading correction unit 224, the second reference value storage unit 225, the second output value conversion unit 226, and the cutout synthesis unit 227. These operations are controlled by the control unit 101.

  Image data representing the original image of the original read by the second image reading means 20 is output from the second image sensor 24 as an electrical signal corresponding to the amount of received light (hereinafter also referred to as “read signal”). The two image processing unit 203 is supplied to the second amplifier 212 of the second image processing unit 203, more specifically. The second image sensor 24 is a reflectance signal representing the reflectance of the reflected light from the portion of the document corresponding to the pixel as a signal representing the pixel value of each pixel of the document image of the document according to the amount of light received by the pixel. Is output.

  According to the second image processing unit 220, the read signal output from the second image sensor 24 and applied to the second amplifier 222 is amplified by the second amplifier 222 and converted into a digital signal by the second A / D converter 223. Then, it is given to the second shading correction means 224. When the read signal output from the second image sensor 24 is a read signal representing image data of a document image of a document, that is, image data given to the second image processing unit 220 is image data representing a document image of a document. In some cases, the control unit 101 controls the second shading correction unit 224 so as to correct the shading of the image data given as a digital signal from the second A / D converter 223. The second shading correction unit 224 performs shading correction on the image data of the document image supplied from the second A / D converter 223 based on a command from the control unit 101.

  The second reference value storage unit 225 reads the second image reading unit 20 as a reference value for shading correction by the second shading correction unit 224 (hereinafter referred to as “second reference value”), and the second image sensor. The reference value for each pixel of the document image of the document given from 24 is stored. The second shading correction unit 224 performs shading correction on the document image of the document based on the second reference value stored in the second reference value storage unit 225.

  The document image subjected to the shading correction by the second shading correction unit 224 is given to the second output value conversion unit 226. The second output value conversion unit 226 performs other image processing such as gamma correction on the original image subjected to shading correction, and outputs the processed original image to the storage unit 104 and the control unit 101.

  The first and second reference values stored in the first and second reference value storage means 215 and 225 are stored in the corresponding reference value storage means 215 and 225 in the reference value storage step. The reference value storing step for the first reference value (hereinafter referred to as “first reference value storing step”) is an adjustment process in the manufacturing process of the document reading apparatus 100, before the start of the document reading operation, or after the end of the document reading operation. Implemented at an appropriate time.

  In the first reference value storing step, the first reference value is acquired using the reference white board 201 shown in FIG. Specifically, the control unit 101 controls the first image reading unit 10 and the first image processing unit 210 so as to acquire the first reference value from the reference white plate 201. The first image reading means 10 moves the light source unit 15 to a reference value reading position P0 facing the reference white plate 201, based on a command from the control unit 101, to a reference value reading position P0 below the reference white plate 201 in FIG. Then, at the reference value reading position P0, the reference white plate 201 is irradiated with reading light, the reflected light from the reference white plate 201 is imaged on the first image sensor 14, and the reflected light amount from the reference white plate 201 is reflected. An electrical signal based on the above is output as a read signal.

  The read signal output from the first image sensor 14 is supplied to the first amplifier 212 of the first image processing unit 210 in the same manner as the original image of the original, amplified by the first amplifier 212, and the first A / D converter 213. Is converted to a digital signal by the first shading correction means 224.

  When the image data given to the first image processing unit 210 is image data representing a document image obtained by reading the reference white plate 201, the control unit 101 is based on the image data given from the first A / D converter 213. Then, the first shading correction unit 214 is controlled so as to calculate the first reference value. The first shading correction unit 214 is based on the image data given from the first A / D converter 213 according to the command from the control unit 101, that is, based on the amount of reflected light from the reference white plate 201. The first reference value An for each pixel in the readable area S0 is calculated. The symbol “n” indicates a pixel number. The calculated first reference value An is given to the first reference value storage unit 215 and stored in the first reference value storage unit 215.

  A reference value storage step for the second reference value (hereinafter referred to as “second reference value storage step”) is performed, for example, in an adjustment process in the manufacturing process of the document reading apparatus 100. In the first reference value storing step described above, the light source unit 15 of the first image reading means 10 is moved to the reference value reading position P0 below the reference white plate 201, and the reference white plate 201 is read at the reference value reading position P0. To obtain the first reference value. On the other hand, in the second reference value storing step, the white reference sheet 202 as a reference document is conveyed to the readable area S0 of the second image reading unit 20 by the ADF 1 and is read to obtain the second reference value. . This is because the second image reading unit 20 cannot move unlike the first image reading unit 10, and therefore the light source 21 is moved to the reference value reading position P 0, which is a position facing the reference white plate 201. This is because the value cannot be read.

  Specifically, in the second reference value storing step, the control unit 101 controls the ADF 1, the second image reading unit 20, and the second image processing unit 220 so as to acquire the second reference value from the white reference sheet 202. . Based on the command from the control unit 101, the white reference sheet 202 is conveyed to the readable area S 0 by the ADF 1, and the second image reading is performed at the reading position where the white reference sheet 202 faces the light source 21 of the second image reading unit 20. Read by means 20. The second image reading unit 20 irradiates the white reference sheet 202 with reading light from the light source 21 and outputs an electric signal based on the reflected light from the second image sensor 24 as a reading signal.

  The read signal output from the second image sensor 24 is supplied to the second amplifier 222 of the second image processing unit 220 in the same manner as the original image of the original, amplified by the second amplifier 222, and the second A / D converter 223. Is converted to a digital signal by the second shading correction means 224 and supplied to the second shading correction means 224.

  When the image data given to the second image processing unit 220 is image data representing a document image (hereinafter, also referred to as “reference document image”) acquired by reading the white reference sheet 202, the control unit 101 The second shading correction unit 224 is controlled so that the image data supplied from the 2A / D converter 223 is supplied to the cropping and synthesizing unit 227. The second shading correction means 224 gives the image data given from the second A / D converter 223 to the cut-out synthesis means 227 based on a command from the control unit 101.

  Although the details will be described later, the cropping and synthesizing unit 227 is readable by the second image reading unit 20 based on the image data given from the second A / D converter 223, that is, based on the amount of reflected light from the white reference sheet 202. A second reference value Bn for each pixel in the region is obtained. The symbol “n” indicates a pixel number. The obtained second reference value Bn is given to the second reference value storage means 225 and stored in the second reference value storage means 225.

  FIG. 5 is a diagram illustrating an example of a reference value acquired by the first shading correction unit 214 or the cutout synthesis unit 227. In FIG. 5, the horizontal axis indicates the pixel number n, and the vertical axis indicates the first reference value An or the second reference value Bn. Pixel number 0 shown on the horizontal axis corresponds to a pixel at one end in the main scanning direction X of the first or second imaging element 14, 24, and pixel number 4000 is the main number of the first or second imaging element 14, 24. This corresponds to the pixel at the other end in the scanning direction X. The first reference value An or the second reference value Bn shown on the vertical axis corresponds to the luminance of light received by the corresponding imaging element, that is, the first or second imaging element 14, 24, and the higher the luminance, the more the pixel. The reference value of becomes larger.

  The white reference plate 201 and the white reference sheet 202 are formed in a uniform white color. The reference value obtained by reading the white reference plate 201 or the white reference sheet 202 is the main scan as shown in FIG. It is high near the center pixel between both ends in the direction X, and low at pixels near both ends in the main scanning direction X. That is, from a broad perspective, the luminance of the light received by the first or second image sensor 14 or 24 increases near the center pixel between both ends in the main scanning direction X, and decreases near the pixels at both ends. ing.

  This is because the light emitted from the light sources 11 and 21 that irradiate the reference white plate 201 or the white reference sheet 202 has a finite size. 201. Peripheral dimming has occurred based on the characteristics of the imaging lenses 13 and 23 for condensing the reflected light from the 201 or white reference sheet 202 onto the corresponding imaging devices 14 and 24, and the first or second imaging device. This is due to variations in the sensitivity of the pixels 14 and 24.

  In this way, at each position in the main scanning direction X of the readable area S0, even if the pixels have the same density value, the luminance varies depending on the position. A reference value of each pixel corresponding to this luminance is obtained from the reading result of the reference white plate 201 or the white reference sheet 202, and based on this reference value, the first and second shading correction means 214, 224 Shading correction is applied. Thereby, a difference in luminance depending on the position of each pixel in the main scanning direction X can be removed.

  In the present embodiment, the second reference value Bn, which is a reference value for shading correction by the second shading correction unit 224, is a white reference sheet having a smaller dimension than the readable area S0 of the second image reading unit 20. 202, more specifically, the white reference sheet 202 having a smaller dimension in the main scanning direction X than the dimension in the main scanning direction X of the readable area S0 is obtained. As the white reference sheet 202, specifically, an existing white paper that is used when an output image of a document image is formed, for example, a commercially available white paper having a prescribed size is used. Although there is no particular limitation on a commercially available white paper having a predetermined size that can be used as the white reference sheet 202, for example, A4 size paper is used.

  The white reference sheet 202 having a size smaller than that of the readable area S0 is read by the second image reading unit 20 to obtain the second reference value Bn in the second reference value storing step. The second reference value Bn is obtained by reading the white reference sheet 202 a plurality of times by the second image reading unit 20. The white reference sheet 202 is placed on the document placing table 5 of the ADF 1 shown in FIG. 3 and conveyed to the readable area S0 of the second image reading means 20 by the ADF 1 and read.

  As shown in FIG. 3 described above, the document table 5 is provided with a pair of restricting members 32 and 33 for restricting the position of the document in the main scanning direction X, that is, the first restricting member 32 and the second restricting member 33. . The first and second restricting members 32 and 33 have a rectangular plate shape, and are arranged such that the thickness direction is along the main scanning direction X and the long side portion is along the sub-scanning direction Y orthogonal to the main scanning direction. . The first and second regulating members 32 and 33 are arranged at different positions with respect to the main scanning direction X and at substantially equal positions with respect to the sub-scanning direction Y. The first and second regulating members 32 and 33 are provided so as to be movable in the main scanning direction X, respectively.

  FIG. 6 is a plan view schematically showing the positional relationship between the readable area S0 of the second image reading means 20 and the first and second restricting members 32 and 33. As shown in FIG. In the present embodiment, the second image reading unit 20 reads reflected light from the original by forming an image on the second image sensor 24. In the present embodiment, since the second image sensor 24 is a CCD line sensor in which a plurality of pixels are arranged in a line in the main scanning direction X, the readable area S0 is configured by a plurality of pixels arranged in the main scanning direction X. The In FIG. 6, the readable area S0 is indicated by a slanting line with a lower right.

  During normal document reading, that is, when reading a document image of a document, the distance from the front edge to the rear edge of the document 204 is equal to the center line 203 in the main scanning direction X of the document table 5, that is, The first and second distances so that the distance from the center line 203 to the end on the one X1 side of the document 204 in the main scanning direction is equal to the distance from the center line 203 to the end on the other X2 side of the document 204 in the main scanning direction. The regulating members 32 and 33 are positioned, and the document 204 is placed.

  In the document reading apparatus 100, due to variations in the operation of the document transport unit 31 of the ADF 1, there is a case where a document is obliquely fed, that is, a phenomenon in which the document is transported in the main scanning direction X from the position where the document 204 is placed may occur. . When the oblique feeding occurs, the document reading position, which is the position of the document when the document image is read by the second image reading unit 20, is set to the width direction of the document 204, that is, the main scanning direction, rather than the position where the document 204 is placed. Shift to X.

  Therefore, the dimension d0 in the main scanning direction X of the readable area S0, which is an area that can be read by the second image reading means 20, is readable so that the original image can be read even if the position of the original 204 is slightly shifted. It is set to be larger than the dimension d1 in the width direction of the original 204, that is, the main scanning direction X (hereinafter referred to as "width direction dimension"), which is predetermined as the maximum dimension original (hereinafter referred to as "maximum original"). For example, when the maximum readable document is a document in which an A4 size document stipulated in Japanese Industrial Standard (JIS) P0138 is arranged vertically, the width dimension of the document 204, that is, the long side portion of the A4 size document. Therefore, the dimension d0 in the main scanning direction X of the readable area S0 is set to a value larger than 297 mm, for example, 307 mm.

  Of the pair of restricting members 32 and 33, the first restricting member 32 provided on the X1 side in the main scanning direction has a position in the main scanning direction X1 of the surface portion facing the second restricting member 33 in the readable region S0. It is movably provided up to a position that is substantially equal to the end on the one X1 side in the main scanning direction. The second restricting member 33 provided on the other X2 side in the main scanning direction is such that the position of the surface portion facing the first restricting member 32 in the main scanning direction X is the end of the readable area S0 on the other X2 side in the main scanning direction. It is provided so as to be movable to a position that is substantially equal. Therefore, when the first and second restricting members 32 and 33 are arranged farthest from each other in the main scanning direction X, the distance dmax between the first restricting member 32 and the second restricting member 33 in the main scanning direction X can be read. It is substantially equal to the dimension d0 in the main scanning direction X of the region S0.

  Hereinafter, the first restricting member 32 arranged at the position farthest from the center line 203 in the main scanning direction one X1 is indicated by reference numeral 32a, and is arranged at the position farthest from the center line 203 in the other main scanning direction X2. The second restricting member 32 is indicated by reference numeral 33a.

  7 and 8 are plan views schematically showing the positional relationship between the readable area S0 of the second image reading means 20 and the white reference sheet 202. FIG. In FIGS. 7 and 8, the readable area S0 is indicated by a slanting line descending to the right as in FIG. In the present embodiment, the white reference sheet 202 has a rectangular sheet shape, more specifically, a rectangular sheet shape. As shown in FIGS. 7 and 8, the white reference sheet 202 is placed on the document placing table 5 so that one side thereof is along the first restriction member 32 or the second restriction member 33. The white reference sheet 202 may be arranged such that either the long side portion or the short side portion is along the regulating members 32 and 33, but in the present embodiment, the short side portion is the first regulating member 32 or the first side. 2 Arranged along the regulating member 33. That is, in the present embodiment, the white reference sheet 202 is arranged such that the width direction, which is the longitudinal direction along the long side portion, is along the main scanning direction X.

  When the white reference sheet 202 is placed on the document placing table 5, the first and second restricting members 32 and 33 are arranged farthest from each other in the main scanning direction X1 and the other X2. Therefore, when a commercially available paper having a prescribed size is used as the white reference sheet 202, the first restricting member 32 is disposed on the one X1 side in the main scanning direction as compared with the case of reading a document of that size, and the second restricting member. 33 is arranged on the other X2 side in the main scanning direction. The position of the first and second restricting members 32 and 33 is changed by an operator, for example.

  The number of readings of the white reference sheet 202 by the second image reading unit 20 is the dimension d1 in the main scanning direction X of the white reference sheet 202 in the state of being placed on the document placing table 5 shown in FIG. It is selected according to the dimension d0 in the main scanning direction X. For example, as the white reference sheet 202, a white reference sheet 202 having a side dimension that is 1/2 (1/2) or more of the dimension d0 in the main scanning direction X of the readable area S0 is used. When the one side portion 202 is arranged along the main scanning direction X, the number of readings of the white reference sheet 202 is selected to be twice.

  In this case, as shown in FIG. 7, as the first procedure, the first restricting member 32 further forwards, that is, one in the main scanning direction X1 from the normal position, that is, the position when reading the document having the same width direction dimension as the white reference sheet 202. And is arranged at a position farthest from the center line 203 in the main scanning direction X1. The white reference sheet 202 is placed close to the first restriction member 32a arranged in this way. By placing the white reference sheet 202 in this manner and carrying out reading by the second image reading means 20, a region closer to the front of the readable region S0, that is, an end portion on the X1 side in the main scanning direction is included. A pixel value of the pixel in the region S1 (hereinafter, also referred to as “one side pixel value”) is obtained.

  As the next procedure, as shown in FIG. 8, the second restricting member 33 moves further backward, that is, in the main scanning direction X2 from the normal position, that is, the position when reading the document having the same width direction dimension as the white reference sheet 202. It is arranged at a position farthest from the center line 203 in the other main scanning direction X2. The white reference sheet 202 is placed close to the second regulating member 33a arranged in this way. By placing the white reference sheet 202 in this manner and carrying out reading by the second image reading means 20, an area closer to the rear of the readable area S0, that is, an end portion on the other X2 side in the main scanning direction is included. A pixel value of the pixel in the region S2 (hereinafter, also referred to as “the other side pixel value”) is obtained.

  More specific description will be given with reference to FIGS. FIG. 9 is a plan view schematically showing the document reading apparatus 100 as viewed from the document table 5 side. 10 and 11 are plan views showing a state in which the white reference sheet 202 is placed on the document placing table 5 as viewed from the document placing table 5 side. 9-11, the 1st and 2nd control members 32 and 33 are shown by the slanting line of the lower left. As shown in FIG. 9, when the first and second restricting members 32, 33 are arranged farthest from each other in the main scanning direction X, the first restricting member 32 and the second restricting member 33 in the main scanning direction X The interval dmax is substantially equal to the dimension d0 in the main scanning direction X of the readable area S0.

  When the dimension d0 in the main scanning direction X of the readable area S0 is less than twice the dimension of the long side portion of the A4 size paper, the A4 size paper is used as the white reference sheet 202, and the long side portion Is arranged along the main scanning direction X, the number of readings of the white reference sheet 202 is selected to be two. In this case, as shown in FIG. 10, the operator moves the first restricting member 32 further from the position for reading the original image of the A4 size document to one side X1 in the main scanning direction, as shown in FIG. The reference sheet 202 is placed on the document placing table 5, and the second image reading unit 20 performs the first reading. As the next procedure, as shown in FIG. 11, the second regulating member 33 is further moved from the position for reading the original image of the A4 size original to the other X2 in the main scanning direction, and the white reference sheet 202 is placed on the original. The image is placed on the table 5 and the second image reading means 20 performs the second reading.

  The white reference sheet 202 may be read a plurality of times by repeatedly reading one white reference sheet 202 a plurality of times or by reading a plurality of white reference sheets 202.

  When using a plurality of white reference sheets 202, the operator may place the plurality of white reference sheets 202 on the document placement table 5 in an overlapping manner. In this case, the plurality of white reference sheets 202 are arranged at different positions with respect to the main scanning direction X. For example, when reading is performed using two A4 size white reference sheets 202 as described above, the first white reference sheet 202 from the top is placed closer to one X1 in the main scanning direction, that is, on the first regulating member 32. The second white reference sheet 202 from the top is placed near the other X2 in the main scanning direction, that is, placed along the second restricting member 33.

  In the present embodiment, the ADF 1 is configured so that a plurality of documents can be continuously conveyed to the second image reading unit 20, and can be continuously fed by controlling the ADF 1 by the control unit 101. As described above, by stacking the plurality of white reference sheets 202 and placing them on the document placing table 5, the plurality of white reference sheets 202 can be continuously conveyed to the readable area S0. Therefore, the work of placing the white reference sheet 202 on the document placing table 5 is only one time, which is efficient.

  As described above, the white reference sheet 202 is read a plurality of times by the second image reading unit 20, whereby the reference original image is read, and the pixel values of all the pixels in the readable area S0 are acquired. Image data representing the reference document image is given to the second image processing unit 220 of the image processing unit 103 from the second image sensor 24 of the second image reading unit 20 shown in FIG. In the present embodiment, the pixel values of all the pixels in the readable area S0 are acquired by reading the white reference sheet 202 twice. Image data representing the reference document image obtained by the two readings, that is, the one-side reference value B1 and the other-side reference value B2 are given to the second image processing unit 103.

  The second image processing unit 103 amplifies the image data of the reference document image given as an analog signal by the second amplifier 222, converts the image data into a digital signal by the second A / D converter 223, and then the second shading correction unit 224. To give. The second shading correction unit 224 cuts and combines the image data of the reference document image supplied from the second A / D converter 223, that is, the one-side reference value B1 and the other-side reference value B2, based on the command from the control unit 101. Provided to means 227.

  The cutting composition unit 227 includes a cutting range setting unit 228 and a cutting unit 229. The cropping unit 228 calculates pixel values of pixels included in a plurality of reference value acquisition ranges determined in advance for each time from among pixel values acquired by reading the white reference sheet 202 a plurality of times by the second document reading unit 20. This is given to the second reference value storage means 225. The readable area S0 is divided by a plurality of reference value acquisition ranges. That is, the plurality of reference value acquisition ranges constitute the readable area S0, and all the pixels of the plurality of reference value acquisition ranges are added to all the pixels of the readable area S0.

  In the present embodiment, the cropping unit 229 uses the image data of the reference original image obtained by the first reading, that is, the one-side pixel value, to detect pixels included in a predetermined reference value acquisition range as a reference on the one X1 side in the main scanning direction. A value (hereinafter referred to as “one-side reference value”) B1 is cut out and given to the second reference value storage means 215 for storage. Further, the cropping unit 229 extracts pixels included in a predetermined reference value acquisition range from the image data of the reference original image obtained by the second reading, that is, the pixel values on the rear side, as a reference value on the other X2 side in the main scanning direction (hereinafter, “ It is cut out as B2) (referred to as “the other side reference value”), and is given to the second reference value storage means 215 for storage. In the present embodiment, the clipping unit 229 determines the pixel value of the pixel on the X1 side in the main scanning direction from the center between both ends in the main scanning direction X of the first half pixel, that is, the readable region S0 from the one side pixel value. Cut out as the value B1, and cut out the second half pixel, that is, the pixel on the other X2 side in the main scanning direction from the center between both ends in the main scanning direction X as the other side reference value B2 from the other side pixel value.

  A reference value acquisition range that is a range to be cut by the cutting means 229 is set by the cutting range setting means 228 for the cutting means 229. The cut range setting unit 228 sets a reference value acquisition range by giving a start pulse and an end pulse to the cut unit 229. In the present embodiment, the first reference value acquisition range W1 is set as the reference value acquisition range for cutting the one-side reference value B1, and the first reference value acquisition range for cutting the other-side reference value B2 is the first reference value acquisition range. A reference value acquisition range of 2 is set.

  12 and 13 show pixel data output timing to the cutting means 229, pulse input timing from the cutting range setting means 228 to the cutting means 229, and image data output timing to the second reference value storage means 225. It is a figure for demonstrating the relationship. FIG. 12 shows a case where the one-side reference value B1 is cut off, and FIG. 13 shows a case where the other-side reference value B2 is cut off. 12 (a) and 13 (a) show the passage of time of the signal output from the second shading correction means 224 to the cutting means 229, and FIGS. 12 (b) and 13 (b) show the cutting setting means. FIG. 12C and FIG. 13C show the time lapse of the signal output from the cutting means 229 to the second reference value storage means 225. FIG. .

  When the start pulse 230 is input from the cut range setting unit 228, the cut unit 229 starts transfer of a reference value to the second reference value storage unit 225, that is, storage processing, and the cut range setting unit 228 starts the end pulse 231. Is input, the transfer of the reference value to the second reference value storage means 225, that is, the storage process is terminated.

  The output timing of the start pulse 230 and the end pulse 231 is determined by the leading edge adjustment amount V1 and the image length adjustment amount V2 given to the cutting range setting means 228 as a cutting range which is a reference value acquisition range. The leading end adjustment amount V1 and the image length adjustment amount V2 are given from the control unit 101 to the cutout range setting means 228.

  The leading edge adjustment amount V1 determines the number of pixels from the head output 232 of the signal representing the image data of the reference document image output from the second shading correction unit 224. As shown in FIG. 7, the second image reading unit 20 outputs the read signals of all the pixels in the readable area S0 even when the white reference sheet 202 to be read does not exist in a part of the readable area S0. Therefore, the head output 232 is an output of a pixel that is output first among all the pixels in the readable area S0 of the second image reading unit 20. When the leading output 232 is input to the cutting unit 229, a signal indicating that the leading output 232 has been input is input from the control unit 101 to the cutting setting unit 228. When receiving the signal indicating that the leading output 232 is input from the control unit 101, the cutting range setting unit 228 counts the number of pixels corresponding to the tip adjustment amount V1 and cuts out the subsequent pixels. A start pulse 230 is output.

  The image length adjustment amount V2 determines the number of pixels after the tip adjustment amount V1. The cutting range setting unit 228 counts the number of pixels corresponding to the image length adjustment amount V2 from the start pulse 230 and outputs an end pulse 231 to the cutting unit 229.

  As described above, the start pulse 230 and the end pulse 231 are output from the cutout range setting unit 228 to the cutout unit 229 in accordance with the leading end adjustment amount V1 and the image length adjustment amount V2. The number of pixels determined by the adjustment amount V2 is cut out, and image data for the pixels is output to the second reference value storage unit 225. In the present embodiment, the pixel values of the pixels included in the first reference value acquisition range W1 are given to the second reference value storage unit 225 as the one-side reference value B1, and the pixels included in the second reference value acquisition range W2 Is provided to the second reference value storage means 225 as the other-side reference value B2. Thus, the one-side reference value B1 and the other-side reference value B2 are combined and stored as the second reference value B in the second reference value storage means 225.

  The cutting range setting unit 228 sets different tip end adjustment amounts V1 and image length adjustment amounts V2 for the cutting unit 229 during the first reading and the second reading. Specifically, when the one-side reference value B1 is cut out from the image data obtained by the first reading as shown in FIG. 12, the cutting range setting means 228 uses the readable area as the image length adjustment amount V2. The number of pixels that is half the number of pixels that constitute S0 is set. In this case, the tip adjustment amount V1 is selected to be 10 pixels, for example. The pixel corresponding to the tip adjustment amount V1 is a portion where the output signal from the CCD line sensor, which is the second image sensor 24, is disturbed.

  As shown in FIG. 13, when the other side reference value B2 is cut out from the image data obtained by the second reading, the cutting range setting means 228 determines the leading end adjustment amount for determining the reference value acquisition range W2 of the other side reference value B2. As V1 ′, the number of pixels obtained by combining the leading end adjustment amount V1 for determining the reference value acquisition range W1 of the one-side reference value B1 and the image length adjustment amount V2 for determining the reference value acquisition range W1 of the one-side reference value B1. Set. The cutout range setting unit 228 sets the number of pixels that is a half of the number of pixels constituting the readable area S0 as the image length adjustment amount V2 ′ that determines the reference value acquisition range W2 of the other-side reference value B2. . Since the pixel input from the second shading correction means 224 after the pixel included in the image length adjustment amount V2 ′ is a portion where the output signal from the CCD line sensor as the second image sensor 24 is disturbed, the pixel Remove the minutes.

  FIG. 14 is a diagram for explaining how to synthesize a reference value by the cut-out synthesizing unit 227. FIG. 14A shows pixel values acquired by the first reading, FIG. 14B shows pixel values acquired by the second reading, and FIG. 14C shows the one-side reference. A reference value obtained by synthesizing the value B1 and the other-side reference value B2 is shown. As described above, the one-side reference value B1 is cut from the image data obtained by the first reading shown in FIG. 14A by the cutting means 229, and obtained by the second reading shown in FIG. 14B. By cutting out and synthesizing the other-side reference value B2 from the obtained image data, as shown in FIG. 14C, the second reference value B of all the pixels in the readable area S0 is obtained. In this way, in this embodiment, the cut-out and synthesizing unit 227 obtains the reference value by half by reading twice, and completes the final second reference value B.

  In this manner, the cut-out composition unit 227 determines a plurality of pixel values obtained by reading the white reference sheet 202 a plurality of times by the second document reading unit 20 and divides the entire readable region S0. The pixel values of the pixels included in the reference value acquisition ranges W1 and W2 are respectively acquired as the reference values of the pixels, and the acquired reference values of the respective pixels are synthesized over the entire readable area S0, and are read in the readable area S0. The reference values of all the pixels are obtained.

  FIG. 15 is a flowchart illustrating a processing procedure of the reference value acquisition operation of the control unit 101 in the second reference value storage step. The image processing method will also be described with reference to FIG. The reference value acquisition operation is executed by the control unit 101. When the operator places the white reference sheet 202 on the document table 5 and inputs a start command for the second reference value storage step from the operation panel unit 106, the reference value acquisition operation is started, and the process proceeds to step s2.

  In step s1, the control unit 101 controls the AFD 1 so as to start conveying the white reference sheet 202 placed in a state of being regulated by the first regulating member 32. The ADF 1 starts conveying the white reference sheet 202 to the readable area S <b> 0 based on a command from the control unit 101. When conveyance of the white reference sheet 202 is started in this way, the process proceeds to step s3.

  In step s3, the control unit 101 reads the white reference sheet 202, and acquires the second reference value B, which is the one-side reference value in the present embodiment, and the second image reading unit 20 and the second image processing unit 220. To control. The second image reading unit 20 reads the white reference sheet 202 at the reading position where the white reference sheet 202 faces the light source 21 of the second image reading unit 20 based on a command from the control unit 101, and reads the read reference document. The image is given to the second image processing unit 220. In the present embodiment, the second image reading means 20 reads the white reference sheet 202 at a plurality of positions in the sub-scanning direction Y, and calculates the average value of the read pixel values of each pixel of the reference document image. To the second image processing unit 220.

  The second image processing unit 220 cuts out the one-side reference value B1 from the reference document image data supplied from the second image reading unit 20 based on a command from the control unit 101, and supplies the cut value to the second reference value storage unit 225. , Remember. When the white reference sheet 202 is read in this way, the process proceeds to step s4.

  In step s4, the control unit 101 controls the AFD 1 so as to start transporting the white reference sheet 202 placed in a state of being regulated by the second regulating member 33. The ADF 1 starts conveying the white reference sheet 202 to the readable area S <b> 0 based on a command from the control unit 101. When the conveyance of the white reference sheet 202 is thus started, the process proceeds to step s5.

  In step s5, the control unit 101 reads the white reference sheet 202 and acquires the second reference value B, which is the other-side reference value in the present embodiment, and the second image reading unit 20 and the second image processing unit 220. To control. The second image reading unit 20 reads the white reference sheet 202 at the reading position where the white reference sheet 202 faces the light source 21 of the second image reading unit 20 based on a command from the control unit 101, and reads the read reference document. The image is given to the second image processing unit 220. The second image processing unit 220 cuts out the other-side reference value B2 from the reference document image data supplied from the second image reading unit 20 based on a command from the control unit 101, and supplies it to the second reference value storage unit 225. , Remember. Thereby, the second reference value B of all the pixels in the readable area S0 is acquired and stored in the second reference value storage unit 225. When the second reference value B of all the pixels in the readable area S0 is stored in the second reference value storage unit 225 in this way, the process proceeds to step s6, and the reference value acquisition operation ends.

  As described above, according to the present embodiment, the second image processing unit 220 can read the white reference sheet 202 having a size smaller than that of the readable area S0 by the second document reading unit 20 and obtain the readable area. Since the second reference value B of all the pixels in the readable area S0 is obtained based on the pixel values of all the pixels in S0, the white reference having the same dimension as or larger than the dimension of the readable area S0. Even without using the sheet 202, the second reference value B of all the pixels in the readable area S0 can be obtained. Accordingly, the second reference value B of all the pixels in the readable area S0 is obtained by using, as the white reference sheet 202, a commercially available paper having a predetermined size as used when forming an output image of a document image, for example. Therefore, the second reference value B can be obtained by using the white reference sheet 202 that is free of dirt or has as little dirt as possible and suitable for obtaining the second reference value B. Since the second shading correction means 224 of the second image processing unit 220 corrects the document image based on the second reference value B thus obtained, the document image can be corrected with high accuracy.

  Further, in the present embodiment, the second reference value B is the pixel value obtained by reading the white reference sheet 202 a plurality of times by the second document reading unit 20 by the cropping and synthesizing unit 227 of the second image processing unit 220. The pixel values of the pixels included in the plurality of reference value acquisition ranges W1 and W2 that are predetermined each time and divide the entire readable area S0 are respectively acquired as the second reference values B of the pixels, and the readable area S0 is acquired. It is determined by synthesizing over the whole. Therefore, the second reference value B of all the pixels in the readable area S0 can be obtained with a simple configuration.

  In the present embodiment, the document image of the document conveyed in the sub-scanning direction Y orthogonal to the main scanning direction X by the document conveying unit 31 in the readable area S0 composed of a plurality of pixels arranged in the main scanning direction X is also shown. Then, it is read by the second image reading means 20 which is a document reading unit. As a document, a reference document having a size smaller than that of the readable area S0, that is, a white reference sheet 202 that is a reference document having a dimension in the main scanning direction X smaller than that in the main scanning direction X can be read. In the area S0, the document is conveyed in the sub-scanning direction Y by the document conveying section 31, and read by the second image reading means 20 a plurality of times, whereby the pixel values of all the pixels in the readable area S0 are obtained. Based on this, the second image processing unit 220 obtains reference values for all the pixels in the readable area S0. Accordingly, a document in which the reference values of all the pixels in the readable area S0 can be obtained without using the white reference sheet 202 having the same dimension as or larger than the dimension in the main scanning direction X of the readable area S0. The reading device 100 is realized.

  In this embodiment, the document is transported to the readable area S <b> 0 with the position in the main scanning direction X in the readable area S <b> 0 regulated by the pair of regulating members 32 and 33 of the document transport unit 31. The pair of regulating members 31 and 32 regulates the position of the document in the readable area S0 in the main scanning direction X so that it can be displaced throughout the main scanning direction X of the readable area S0.

  Therefore, when the white reference sheet 202 is read a plurality of times by the second image reading means 20, the position of the white reference sheet 202 in the readable area S0 in the main scanning direction X can be displaced over the entire main scanning direction X, so that the reading is performed. The pixel value of each pixel can be obtained over the entire main scanning direction X of the possible area S0. As a result, the document reading apparatus 100 capable of obtaining the reference value of each pixel throughout the main scanning direction X of the readable area S0 is realized.

  In the present embodiment, the operator can continuously convey the plurality of white reference sheets 202 to the readable area S0 by supplying the plurality of white reference sheets 202 to the document conveying unit 31 at a time. Compared with the case where the plurality of white reference sheets 202 are separately supplied to the document conveying section 31, the labor of the operator can be saved.

  Further, the plurality of white reference sheets 202 are continuously conveyed to the readable area S0, whereby the plurality of white reference sheets 202 are continuously read by the second image reading unit 20, and the white reference sheet 202 is read a plurality of times. Since the reading is continuously performed, the time required to acquire the pixel values of all the pixels in the readable area S0 can be reduced as compared with the case where the white reference sheet 202 is not continuously conveyed. . As a result, as compared with the case where one white reference sheet 202 having a size equal to or larger than the size of the readable region S0 is read and the pixel values of all the pixels in the readable region S0 are acquired as the reference values. Therefore, it is possible to prevent the time required for obtaining the reference values of all the pixels in the readable area S0 from becoming excessively long. Therefore, the white reference sheet 202 whose dimension in the main scanning direction X is smaller than the dimension in the main scanning direction X of the readable area S0 is used in the readable area S0 without excessively increasing the time required to acquire the reference value. The reference values of all the pixels can be obtained.

  In the present embodiment described above, the first and second image reading units 10 and 20 are optical reduction type image reading units. However, the present invention is not limited to this. For example, the same magnification optical for reading a document image of a document at the same magnification. It may be a system image reading means. In this case, the first and second image sensors 14 and 24 are realized by, for example, a contact image sensor (abbreviated as CIS), and the first and second image reading units 10 and 20 are, for example, light emitting diode arrays. A light source, a lens such as a rod lens, and a CIS are included.

  FIG. 16 is a block diagram showing an electrical configuration of the document reading apparatus 300 according to the second embodiment of the present invention. In the document reading apparatus 300 according to the present embodiment, the configuration other than the cut-out synthesizing unit 227 in the document reading apparatus 100 according to the first embodiment is the same. Omitted.

  In the present embodiment, the second image processing unit 320 of the document reading apparatus 300 includes a correction combining unit 301 in place of the cut-out combining unit 227. The correction synthesis unit 301 includes a switching unit 302, a first temporary storage unit 303, a second temporary storage unit 304, and a synthesis processing unit 305.

  In the same manner as in the first embodiment, the correction combining unit 301 calculates pixel values of all the pixels in the readable area S0 acquired by reading the white reference sheet 202 a plurality of times, specifically, twice. The second reference value (hereinafter referred to as “front reference value”) C1 obtained at the first time, that is, the one-side pixel value C1 that is the pixel value of each pixel obtained by the first reading, and the second obtained at the second time. A difference value Δ with respect to a reference value (hereinafter referred to as “rear reference value”) B2, that is, the other-side pixel value C2 that is a pixel value of each pixel obtained by the second reading is obtained, and the first time based on the difference value Δ Alternatively, the reference value is synthesized after correcting the reference value B2 acquired by the second reading.

  FIG. 17 is a diagram for explaining how to synthesize reference values by the correction synthesis means 301. More specifically, the correction combining unit 301 receives the forward reference value C1 shown in FIG. 17A and the backward reference value C2 shown in FIG. 17B, and receives the forward reference value shown in FIG. A difference value Δ between C1 and the rear reference value C2 is obtained, and based on the difference value Δ, the front reference value C1 or the rear reference value C2, in this embodiment, the rear reference value C2 is corrected, and the two are combined. The second reference value B shown in FIG.

  More specifically, the correction combining unit 301 transmits an output closer to the front of the reference value obtained by the first reading, that is, the front reference value C1 to the first temporary storage unit 303 by the switching unit 302 and stores it. . Further, the correction synthesis unit 301 transmits the rearward output obtained by the second reading, that is, the rear reference value C2 to the second temporary storage unit by the switching unit 302 and stores it.

  FIG. 18 is a flowchart illustrating the processing procedure of the reference value acquisition operation of the control unit 101 in the second reference value storing step. The image processing method will also be described with reference to FIG. The reference value acquisition operation is executed by the control unit 101. When the operator places the white reference sheet 202 on the document placing table 5 and inputs a start command for the second reference value storage step from the operation panel unit 106, the reference value acquisition operation is started, and the process proceeds to step s12.

  In step s12, the control unit 101 controls the AFD 1 so as to start conveying the white reference sheet 202 placed in a state of being restricted by the first restriction member 32. The ADF 1 starts conveying the white reference sheet 202 to the readable area S <b> 0 based on a command from the control unit 101. When the conveyance of the white reference sheet 202 is thus started, the process proceeds to step s13.

  In step s13, the control unit 101 reads the white reference sheet 202 and acquires the second reference value B as in step s3 of the first embodiment shown in FIG. The second image reading unit 20 and the second image processing unit 220 are controlled so as to acquire the reference value C1. The second image reading unit 20 reads the white reference sheet 202 at the reading position where the white reference sheet 202 faces the light source 21 of the second image reading unit 20 based on a command from the control unit 101, and reads the read reference document. The image is given to the second image processing unit 220.

  The second image processing unit 220 gives reference document image data given from the second image reading unit 20 to the first temporary storage unit 303 based on a command from the control unit 101 and stores it. When the white reference sheet 202 is read in this way, the process proceeds to step s14.

  In step s14, the control unit 101 controls the AFD 1 so as to start conveying the white reference sheet 202 placed in a state of being restricted by the second restriction member 33. The ADF 1 starts conveying the white reference sheet 202 to the readable area S <b> 0 based on a command from the control unit 101. When conveyance of the white reference sheet 202 is started in this way, the process proceeds to step s15.

  In step s15, as in step s5 of the first embodiment, the control unit 101 reads the white reference sheet 202 and acquires the second reference value B, and acquires the rear reference value C2 in this embodiment. As described above, the second image reading unit 20 and the second image processing unit 220 are controlled. The second image reading unit 20 reads the white reference sheet 202 at the reading position where the white reference sheet 202 faces the light source 21 of the second image reading unit 20 based on a command from the control unit 101, and reads the read reference document. The image is given to the second image processing unit 220. The second image processing unit 220 gives the reference document image data given from the second image reading unit 20 to the second temporary storage unit 304 based on a command from the control unit 101 and stores it. When stored in this way, the process proceeds to step s16.

  In step s16, the control unit 101 controls the synthesis processing unit 305 to calculate the difference value Δ (n) of the reference values for each pixel n in the overlapping region T. The composition processing unit 305 calculates a difference value Δ (n) of the reference values for each pixel n in the overlapping region T based on a command from the control unit 101. The “overlapping area” is an area where the white reference sheet 202 is redundantly read in the first time and the second time.

In the first reading and the second reading, there is a possibility that the reading conditions may not be exactly the same, such as a slight change in the amount of light from the lamp. 305. The difference value Δ (n) at the pixel number n can be obtained from the value C1n of the front reference value C1 at the pixel number n and the value C2n of the rear reference value C2 at the pixel number n based on the following equation. When the difference value is obtained in this way, the process proceeds to step s17.
Δ (n) = front reference value C1n−rear reference value C2n

  In step s17, the control unit 101 controls the synthesis processing unit 305 to add the average value Δn of the difference values Δ to the rear reference value C2n. The synthesis processing unit 305 calculates an average value Δn of the difference value Δ based on a command from the control unit 101, adds the average value Δn of the difference value Δ to the rear reference value C2n, and corrects the rear reference value after correction. Get B2. The average value Δn of the difference values Δ is an average value of the difference values Δ (n) of all the pixels or an average value of the difference values Δ (n) of some pixels. In the present embodiment, an average value of the difference values Δ (n) of some pixels is used as the average value Δn of the difference values Δ. As a result, the amount of calculation can be reduced and the time required for calculation can be shortened.

  In step s18, the control unit 101 controls the synthesis processing unit 305 to synthesize the front reference value C1 and the corrected rear reference value C2α. The combining processing unit 305 combines the front reference value C1 and the corrected rear reference value C2α to obtain a final second reference value B. Specifically, for a non-overlapping area, that is, an area outside the overlapping area T of the readable area, the front area adopts the front reference value C1, and the rear area adopts the rear reference value C2. For the overlapping region T, the front reference value C1 is employed in the present embodiment, but the rear reference value C2 may be employed.

  The second reference value B thus obtained is given to the second reference value storage means 225 and stored. Thereby, the second reference value B of all the pixels in the readable area S0 is acquired and stored in the second reference value storage unit 225. When the second reference value B of all the pixels in the readable area S0 is stored in the second reference value storage unit 225 in this way, the process proceeds to step s19, and the reference value acquisition operation ends.

  As described above, according to the present embodiment, the correction composition unit 301 of the second image processing unit 320 calculates the pixel value of each pixel in the readable area S0 based on the plurality of pixel values for each pixel in the overlapping area T. A correction amount for correction is obtained, and based on the correction amount, the pixel value of each pixel in the readable area is corrected and acquired as a reference value of the pixel, and the acquired reference value of each pixel is read. By combining the entire possible area, a reference value of all the pixels in the readable area is obtained.

  The pixel values of all the pixels in the readable area are acquired in a plurality of times when the white reference sheet 202 is read a plurality of times, but as described above, the pixel values for each pixel in the overlapping area T are obtained. Since correction is performed by the correction combining unit 301 based on the correction amount obtained based on the pixel value and acquired as the reference value of each pixel, the pixel values of all the pixels in the readable region are acquired in multiple times. Can reduce the effects of.

  For example, even when the reading condition by the document reading unit changes when the reference document is read a plurality of times, the influence of the change of the reading condition can be suppressed. Accordingly, as in the case where the pixel values of all the pixels in the readable area are acquired as the reference value by reading the reference document having the same size as or larger than that of the readable area once, a certain condition is set. Thus, the reference values of all the pixels in the readable area can be obtained. Since the document image is corrected based on the reference value obtained under certain conditions as described above, it is possible to suppress a change in image quality in the document image.

  In the present embodiment, the correction composition unit obtains a difference value between one pixel value of the plurality of pixel values for each pixel in the overlapping region and the remaining pixel value as a correction amount, and based on this correction amount. The pixel value of each pixel acquired together with the remaining pixel value is corrected in an area outside the overlapping area of the readable area. Therefore, it is possible to read a document that can obtain the reference values of all the pixels in the readable area under a certain condition while suppressing the influence of the pixel values of all the pixels in the available area being acquired in a plurality of times. The apparatus can be realized with a simple configuration.

  In the above embodiment, the synthesis processing unit 305 is provided separately from the control unit 101, but the control unit 101 may be used as the synthesis processing unit 305.

  FIG. 19 is a cross-sectional view showing an image forming apparatus 50 including the document reading apparatus 100 according to the first embodiment shown in FIG. The image forming apparatus 50 generally includes the document reading apparatus 100 according to the first embodiment, the image forming unit 60, the paper feeding unit 80, the paper discharging unit 90, and the lower housing 72. Composed. The lower housing 72 accommodates an image forming unit 60 that is an image forming unit, a part of the paper feeding unit 80, and a part of the paper discharge unit 90. The document reading apparatus 100 is disposed vertically above the lower housing 72. The paper discharge unit 90 is provided at an intermediate portion between the document reading apparatus 100 and the paper supply unit 80 in the vertical direction.

  The image forming unit 60 includes a photoconductor 51 that is an image carrier that is rotatably provided around an axis, a charging unit 61 that is a charging unit, a laser scanner unit 62 that is an exposure unit, and a developing device 52 that is a developing unit. A transfer unit 63 serving as a transfer unit, a fixing device 64 serving as a fixing unit, a cleaning unit 65 serving as a cleaning unit, and a charge removal device 66 serving as a charge removal unit. The charging unit 61, the laser scanner unit 62, the developing device 52, the transfer unit 63, the cleaning unit 65, and the charge removal device 66 are arranged around the photoconductor 51 in this order from the upstream side to the downstream side in the rotation direction of the photoconductor 51. The In the present embodiment, the photoconductor 51 has a cylindrical shape. The shape of the photoreceptor 51 is not limited to a columnar shape, and may be a cylindrical shape, for example.

  The charging unit 61 charges the outer peripheral surface portion of the photoconductor 51. The laser scanner unit 62 exposes the charged photoreceptor 51. The developing device 52 develops the electrostatic latent image formed on the outer peripheral surface portion of the photoreceptor 51 by exposure. The transfer unit 63 transfers a toner image that is a visible image formed by development onto a recording sheet that is a recording medium. The transfer unit 63 is realized by a corona charger, for example.

  The fixing device 64 fixes the transferred toner image on the recording paper. Specifically, the fixing device 64 includes a heating roller 67 including a heater 69 inside, and a pressure roller 68 that elastically contacts the surface portion of the heating roller 67. The cleaning unit 65 includes a cleaning blade 70, and the toner remaining on the outer peripheral surface portion of the photoconductor 51 after the transfer operation by the transfer unit 63 is scraped off by the cleaning blade 70 to clean the outer peripheral surface portion of the photoconductor 51. The static eliminator 66 neutralizes the outer peripheral surface of the photoreceptor 51 after being cleaned by the cleaning unit 65.

  The paper feed unit 80 is provided inside the lower housing 72 and is provided to protrude from a side surface portion of the lower housing 72 and a paper feed cassette 81 that stores recording paper as a recording medium. A manual feed tray 82, a first paper feed roller 84 for feeding the recording paper stored in the paper feed cassette 81 to the first transport path 83, and a recording paper placed on the manual feed tray 82 in the second transport path. A second paper feed roller 86 that feeds the paper 85, and a registration roller 87 that temporarily holds the recording paper and feeds it to the image forming unit 60 in a timely manner.

  The paper discharge unit 90 stores a paper discharge roller 92 that discharges the recording paper on which the toner image has been fixed by the fixing device 64 of the image forming unit 60 to the paper discharge tray 91, and a recording paper discharged by the paper discharge roller 92. And a paper discharge tray 91.

  The image forming apparatus 50 has a copy mode (hereinafter sometimes referred to as “copier mode”), a printer mode, and a facsimile mode as image formation (hereinafter sometimes referred to as “print”) modes. In response to an operation input from an operation unit (not shown) or a print job received from an external host device such as a personal computer, the corresponding print mode is selected from the above-described print modes by a control unit (not shown) described later. Is done.

  When the copier mode is selected from among the print modes described above, an image is formed as follows. A user places a document on the platen plate 4 or the document placing table 5 of the document reading device 100, supplies recording paper to the paper feed cassette 81 or the manual feed tray 82 of the paper feed unit 80, and further controls the main of the document reading device 100. After the number of prints, the print magnification, and the like are input by a condition input key of an operation panel unit (not shown) arranged on the front side of the scanning unit 2 in FIG. 10, the start key of the operation panel unit is operated. Then, a copying operation is started.

  When the start key is operated, a main drive motor (not shown) starts and each drive gear (not shown) rotates. Next, the first paper supply roller 84 or the second paper supply roller 86 of the paper supply unit 80 rotates to feed (feed) the recording paper to the first conveyance path 83 or the second conveyance path 85, and a pair of registration rollers 87 is reached and captured. By this registration roller 87, the recording paper causes the leading end portion of the toner image formed on the surface portion of the photoreceptor 51, that is, the timing at which the image forming start portion reaches the position where the transfer unit 63 is provided, and the image formation scheduled area of the recording paper. Is temporarily stopped to synchronize with the timing of reaching the position where the transfer unit 63 is provided. At this time, the leading edge of the recording paper is uniformly pressed against the registration roller 31 to correct the leading edge of the recording paper.

  In the document reading apparatus 100, the first and second image reading means 10 and 20 read a document image as image information of the document and output it to the image processing unit 103 shown in FIG. As described above, the image processing unit 103 performs image processing on the input document image under the set conditions. The document image subjected to this image processing is transmitted as print data to the laser scanner unit 62 of the image forming unit 60.

  In the image forming unit 60, a part of the outer peripheral surface portion of the photoconductor 51 is charged to a predetermined potential over the entire axial direction of the photoconductor 51 by the charging unit 61, and further, the outer peripheral surface portion of the photoconductor 51 is rotated by the rotation of the photoconductor 51. The whole is charged to a predetermined potential. The outer peripheral surface portion of the charged photoconductor 51 sequentially moves to the next step by the rotation of the photoconductor 51.

  In the laser scanner unit 62, although not shown, laser light emitted from the semiconductor laser is input from the image processing unit by a polygon mirror (rotating polygonal mirror) having a plurality of reflecting surfaces in the rotation direction and various optical systems. The photosensitive member 51 is irradiated while being deflected according to the print data. As a result, the laser beam is scanned on the outer peripheral surface portion of the photoconductor 51 charged by the charging unit 61, and an electrostatic latent image is formed on the outer peripheral surface portion of the photoconductor 51.

  Thereafter, the toner in the developer accommodated in the developer accommodating container 54 is supplied to the outer peripheral surface portion of the rotating photoreceptor 51 by the magnet roller 53 in the developer accommodating container 54 of the developing device 52. The toner adheres to the outer peripheral surface portion of the photoreceptor 51 in accordance with the potential gap that forms the electrostatic latent image. As a result, the electrostatic latent image is visualized (developed), and a toner image as an output image is formed. As described above, in the image forming apparatus 50 of the present embodiment, an output image is formed based on the document image read by the document reading apparatus 100.

  Further, the recording paper on which an image is to be formed is fed to the transfer position between the photoconductor 51 and the transfer unit 63 by measuring the timing by the registration rollers 87 of the paper feed unit 80. At the transfer position, the toner image formed on the outer peripheral surface portion of the photoconductor 51 is transferred to the recording paper by the transfer unit 63.

  The recording sheet on which the toner image has been transferred is conveyed to the fixing device 64, and heat and pressure are applied when it passes between the heating roller 67 and the pressure roller 68 of the fixing device 64. As a result, the unfixed toner on the surface portion of the recording paper is melted, fixed to the recording paper, and fixed. The recording sheet on which the toner image is fixed is discharged to the discharge tray 91 by the discharge roller 92 of the discharge unit 90.

  Further, the toner that is not transferred onto the recording sheet and remains on the outer peripheral surface of the photoreceptor 51 is scraped off and collected by the cleaning blade 70 of the cleaner unit 65. The outer peripheral surface portion of the photoreceptor 51 from which the residual toner is scraped off by the cleaning blade 70 is neutralized by the neutralization device 66 while moving to the position where the charging unit 61 is disposed. The outer peripheral surface portion of the photoconductor 51 may not be neutralized by the neutralization device 66 when it is not necessary to neutralize.

  In the above-described printer mode, the image reading unit 40 does not operate, and an image is formed according to image information input from an external host device such as a personal computer. In the facsimile mode, an image is formed according to image information input via a communication line.

  The image forming apparatus 50 according to the present embodiment includes the document reading apparatus 100 according to the first embodiment described above. The second image processing unit 220 of the document reading apparatus 100 according to the first embodiment includes all the pixels in the readable area obtained by reading the reference document having a size smaller than the readable area by the document reading unit a plurality of times. Since the reference value of all the pixels in the readable area is obtained based on the value, it is not necessary to use a reference document having a size equal to or larger than the size of the readable area in order to obtain the reference value. Therefore, for example, since a standard value can be obtained using commercially available paper having a prescribed size as a standard document, a standard document that is not dirty or is as little as possible and suitable for obtaining the standard value is used. Thus, the reference value can be obtained.

  Since the second image processing unit 220 corrects the document image based on the reference value thus obtained, the document image can be corrected with high accuracy. Since the output image is formed by the image forming unit based on the document image corrected with accuracy as described above, the image forming apparatus 50 capable of forming an output image faithfully matching the document is realized.

1 is a block diagram illustrating an electrical configuration of a part of a document reading apparatus 100 according to a first embodiment of the present invention. 2 is a block diagram showing an electrical configuration of a document reading apparatus 100. FIG. 1 is a perspective view showing a document reading device 100. FIG. 1 is a cross-sectional view showing a document reading device 100. FIG. An example of the reference value acquired by the first shading correction unit 214 or the cut-out synthesis unit 227 is shown. 4 is a plan view schematically showing a positional relationship between a readable area S0 of the second image reading means 20 and first and second regulating members 32 and 33. FIG. 6 is a plan view schematically showing a positional relationship between a readable area S0 of the second image reading unit 20 and a white reference sheet 202. FIG. 6 is a plan view schematically showing a positional relationship between a readable area S0 of the second image reading unit 20 and a white reference sheet 202. FIG. FIG. 3 is a plan view schematically showing a state in which the document reading apparatus 100 is viewed from the document placing table 5 side. 6 is a plan view showing a state in which a white reference sheet 202 is placed on the document placing table 5 when viewed from the document placing table 5 side. FIG. 6 is a plan view showing a state where a white reference sheet 202 is placed on the document placing table 5 as viewed from the document placing table 5 side. In order to explain the relationship between the pixel data output timing to the cropping means 229, the pulse input timing from the cropping range setting means 228 to the cropping means 229, and the image data output timing to the second reference value storage means 225. FIG. In order to explain the relationship between the pixel data output timing to the cropping means 229, the pulse input timing from the cropping range setting means 228 to the cropping means 229, and the image data output timing to the second reference value storage means 225. FIG. It is a figure for demonstrating the method of the synthesis | combination of the reference value by the cutting composition means 227. FIG. It is a flowchart which shows the process sequence of the reference value acquisition operation | movement of the control part 101 in a 2nd reference value storage step. FIG. 6 is a block diagram illustrating an electrical configuration of a document reading apparatus 300 according to a second embodiment of the present invention. It is a figure for demonstrating the method of the synthesis | combination of the reference value by the correction | amendment synthetic | combination means. It is a flowchart which shows the process sequence of the reference value acquisition operation | movement of the control part 101 in a 2nd reference value storage step. FIG. 2 is a cross-sectional view illustrating an image forming apparatus 50 including the document reading apparatus 100 according to the first embodiment illustrated in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 1st image reading means 20 2nd image reading means 103 Image processing part 210 1st image processing part 220 2nd image processing part 222 2nd amplifier 223 2nd A / D converter 224 2nd shading correction means 225 2nd reference value Storage unit 226 Second output value conversion unit 227 Cutting composition unit 228 Cutting range setting unit 229 Cutting unit

Claims (9)

An original reading unit for reading an original image of an original;
Based on the pixel values of all the pixels in the readable area obtained by reading a reference document having a size smaller than the readable area of the document reading section by the document reading section multiple times, And an image processing unit for correcting a document image of a document read by the document reading unit based on the reference value. The image processor
Among the pixel values acquired by reading the reference document a plurality of times by the document reading unit, the pixel values of pixels included in a plurality of reference value acquisition ranges that are predetermined each time and divide the entire readable area are It includes a cutout combining means for obtaining reference values of all pixels in the readable area by respectively acquiring the reference values of the pixels and combining the acquired reference values of the respective pixels over the entire readable area. The document reading device according to claim 1. The reference document is read a plurality of times by the document reading unit so that the pixel values of some of the pixels in the readable area are obtained in duplicate.
The image processor
A correction amount for correcting the pixel value of each pixel in the readable area is obtained based on a plurality of pixel values for each pixel in the overlapping area obtained by overlapping the pixel values in the readable area, and the correction Based on the amount, the pixel value of each pixel in the readable area is corrected, the corrected pixel value is acquired as the reference value of the pixel, and the acquired reference value of each pixel is synthesized over the entire readable area. The document reading apparatus according to claim 1, further comprising: correction combining means for obtaining reference values of all pixels in the readable area.   The correction composition means obtains a difference value between one pixel value of a plurality of pixel values for each pixel in the overlap area and the remaining pixel value as the correction amount, and the remaining area in an area outside the overlap area of the readable area The document reading apparatus according to claim 3, wherein the pixel value of each pixel acquired together with the pixel value is corrected based on the correction amount. A document transport unit that transports the document to a readable area;
The readable area is composed of a plurality of pixels arranged in a predetermined main scanning direction,
The document reading unit reads a document image of a document conveyed in the sub-scanning direction orthogonal to the main scanning direction by the document conveying unit in the readable area,
The image processing unit conveys a reference document whose size in the main scanning direction is smaller than the size in the main scanning direction of the readable region in the readable region by the document conveying unit in the sub scanning direction, and reads the reference document a plurality of times by the document reading unit. 5. The document according to claim 1, wherein a reference value of all the pixels in the readable area is obtained based on the acquired pixel values of all the pixels in the readable area. Reader. The document transport section
6. The document reading apparatus according to claim 5, further comprising a pair of regulating members that regulate the position of the document in the readable area in the main scanning direction so as to be displaceable over the entire scanning direction of the readable area.   The document reading device according to claim 5 or 6, wherein the document transport unit is configured to be able to transport a plurality of documents continuously. A document reading device according to any one of claims 1 to 7,
An image forming apparatus comprising: an image forming unit that forms an output image based on a document image read by the document reading device. An image processing method for correcting a document image of a document read by a document reading unit,
A reference document having a size smaller than the readable area of the document reading unit is read a plurality of times by the document reading unit to obtain the pixel values of all the pixels in the readable area,
Based on the acquired pixel value, obtain a reference value for all pixels in the readable area,
An image processing method comprising correcting the original image based on the reference value.

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