JP2002271620A - Image reader and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device that can provide output of a proper read image, without causing a difference from read data between two modes of book reading and sheet-through reading, where an original face takes a different position to a read system. SOLUTION: A 2nd reference white board 13 is provided to an original guide plate of an ADF(automatic document feeder) corresponding to a sheet-through fixed read position C of a carriage 6, on which the read system is mounted. In the sheet-through read mode, before the start of reading of a 1st original of a set original bundle, a 1st reference white board 12 is read at a position B used in common to the book read mode, the 2nd reference white board 13 is re-read at the position C, the difference between the both, that is the difference of the read condition between the two modes is detected, the difference data are used for correction data to apply correction to the original read data, so that no difference is produced in outputs between the two modes. Only the data, by using the 2nd reference white board taken from the 2nd and succeeding originals, the correction data are obtained by applying correction to the data of the 2nd reference white board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital copying machine,
More specifically, the present invention relates to an image reading device provided in a scanner device or the like. More specifically, when reading is performed by two methods, a fixed original reading (book reading) and a transport original reading (sheet through reading), the difference between the read image data and BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus that corrects read image data so as not to cause a problem and an image forming apparatus including the image reading apparatus.

[0002]

2. Description of the Related Art As an image reading device provided in a digital copying machine, a scanner, or the like, a carriage on which a reading optical system (mirror, lamp, etc.) for transmitting a document image to a CCD line image sensor is mounted in a sub-scanning direction. (C
In the direction perpendicular to the main scanning line of the CD)
Reads image information of a fixed document (hereinafter, this fixed document reading mode is referred to as "book reading" mode)
It supports both the original scanning method and the automatic document feeder (ADF) that conveys the original on a fixed reading optical system and reads the moving original (hereinafter, this original reading mode is called “sheet-through reading” mode). 2. Description of the Related Art An image reading apparatus having equipment is conventionally known. By the way, in image reading using a CCD line image sensor (hereinafter simply referred to as “CCD”), the image data converted by the CCD is obtained. An incorrect value appears in the read data due to distortion due to the optical system, variation in each CCD pixel of the image sensor, and the like. To correct this incorrect value, a white reference plate is read, and so-called shading correction is performed using correction data generated from the read data as actual document reading data. When such shading correction is performed in an image reading apparatus having equipment corresponding to two methods of book reading and sheet through reading, correction data obtained from a common white reference plate is usually used for the two methods. That method is adopted.

[0003]

However, if a common white reference plate is used, the read data after correction differs between the two systems. This means that when reading a book, the position of the document surface and the white reference plate (the height from the light source)
It can be almost the same, and the same exposure condition will be obtained,
In sheet-through reading, it is difficult to make the document the same as the position of the white reference plate because the document is in the conveyance path on the ADF side (see FIGS. 1 and 2 described later). This is because it becomes more difficult to stabilize the surface of the document passing through the reading position due to variations or the like that occur in the state of attachment to the main body. As described above, since the position of the document surface is different in the two reading methods of the book and the sheet through, the read data of the document is different. Therefore, even if the same correction is performed on both the read data, it is natural. However, the data difference between the methods is not corrected, and the image data remains deteriorated (particularly, appears in halftone), so that a sufficient result cannot be obtained. The present invention has been made in view of the above-described problems of the related art in an image reading apparatus having equipment corresponding to the two methods of book reading and sheet-through reading. Even if reading is performed by a method with different reading conditions such as the position of the document surface being different, there is no difference between the read data of each method and an image that can output an appropriate read image An object of the present invention is to provide a reading device and an image forming apparatus provided with the image reading device.

[0004]

According to a first aspect of the present invention, there is provided a mode and a carriage for reading a fixed original by moving the carriage and including a carriage having a reading optical system, an original conveying means, and a carriage moving means. And fix
An image reading apparatus capable of operating in both modes of reading a document during transport by a document transport unit, wherein a first white reference body is provided at a moving position of a carriage over an entire reading area of a reading optical system, Means for providing a second white reference body at the fixed position of the carriage over the entire reading area of the reading optical system and performing shading correction based on read data of the first or second white reference body; An image reading apparatus comprising means for correcting a difference between read data in both modes based on read data of a second white reference body.

According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the second white reference body is a member common to an original guide provided in the original conveying means, and the second white reference body is used in a conveying original reading mode. The shading correction of the read data is performed based on the read data of the first white reference body.

According to a third aspect of the present invention, there is provided the image reading apparatus according to the second aspect, further comprising means for correcting abnormal data included in the read data of the second white reference body. It is.

According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising: the image reading apparatus according to any one of the first to third aspects; and means for forming an image based on image data. .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image reading apparatus according to the present invention will be described below with reference to the accompanying drawings.
The following embodiment can be applied as a component of an image forming apparatus such as a digital copying machine. FIG. 1 is a schematic diagram showing an overall configuration of an image reading apparatus equipped with an ADF according to an embodiment of the present invention. FIG. 2 is a view for explaining the operation of the sheet through (ADF) reading section in an enlarged manner. 1 and 2, S is a document, 1 is a platen platen (contact glass) on which the document S is placed, 2 is a light source for illuminating the document S, 3
Is a first reflection mirror, 4 is a second reflection mirror, 5 is a third reflection mirror, 6 is a first carriage on which the light source 2 and the first reflection mirror 3 are mounted, and 7 is a second reflection mirror 4 and a third reflection mirror. Reference numeral 5 denotes a second carriage, reference numeral 8 denotes a lens unit for forming an image on an exposed portion of the document, and reference numeral 9 denotes a CCD line image sensor (hereinafter simply referred to as "CCD") for photoelectrically converting the document image formed by the lens unit 8. 10) is a sensor board substrate, 11 is a signal processing board connected to the sensor board substrate 10, 12 is a first white reference plate used for correction of shading and the like, and 13 is a second white reference plate used for sheet-through correction.
A white reference plate, 14 is a document tray on which an ADF document is placed, 1
Reference numeral 5 denotes a conveying roller group for feeding the original, 16 a guide plate for guiding the original at the sheet through reading position, and 17 a discharge roller for discharging the conveyed original.

The image reading apparatus shown in FIG. 1 has a configuration in which the reading operation is performed in two modes. 1
First, as shown by arrows in FIG.
This is a sheet-through reading mode performed using the DF, and the other is a book reading mode performed by placing a document on the contact glass 1. In the sheet-through reading mode, the original placed on the original tray 14
5. The reading surface of the document, which is fed by the paper discharge roller 17 and comes into contact with and guides the guide plate 16 in the transport path, is exposed through the contact glass 1 and the reflected light is transmitted by the reading optical system. Therefore, the first carriage 6 is located at the position C shown in FIG.
Is fixed, and an image on the document surface can be read by passing the document over it (that is, in a sheet-through manner).

In the book reading mode, the original is placed on the contact glass 1 and the first carriage 6 and the second carriage 7 on which the reading system is mounted are stopped at the stop position C (the home position, which is also a fixed position in sheet-through reading). From the first reference white plate 1 provided at the position B shown in FIG.
2. The document is moved in the sub-scanning direction (indicated by an arrow A in FIG. 1) to the end of the document through the document reading start position at position A, during which the sheet-through reading mode is performed by a reading system provided on the carriage. In the same manner as described above, an image on the document surface is transmitted. In either of the above two modes, the light emitted from the light source 2 irradiates the original, and the reflected light is guided to the CCD 9 by the imaging optical system 8 via a group of mirrors, and forms an image thereon. Is converted to CCD
The image signal converted in 9 is subjected to analog processing such as sample hold and amplification in the sensor board
It is converted into a digital signal by the D converter. After conversion into a digital signal, various correction processes such as shading correction are performed by the signal processing board 11 and output via an I / F to an image processing unit (not shown) for generating print data and the like at the next stage. .

The shading correction using the reference white plate is performed in order to stabilize the output in response to the deterioration of the light source over time, the change in the illumination light amount due to the lighting time, the change in the ambient environment temperature, the variation in the sensitivity of the CCD, and the like. Do. The timing of shading correction is usually performed by reading a reference white plate provided over the entire reading area of the reading optical system every scan for reading a document, generating correction data based on the obtained read value, and generating the correction data. Basically, the data is continuously used throughout the scanning of one document as data for shading correction of document reading data performed for each main scanning line of the CCD. The reading of the reference white plate in this embodiment, which is performed for shading correction, is performed simultaneously with the scanning operation for reading the original in the book reading mode. That is, the reference white plate provided at the position B while the carriage 6 stopped at the home position C (see FIG. 2) is moved to the document reading start position at the position A is exposed, and the main scanning by the CCD 9 is performed. Read the white board. The reference white board provided at the position B, which is read at this time, is referred to as a first reference white board 12. In the book reading mode, the shading correction data generated based on the read data of the first reference white plate 12 is used until the first reference white plate 12 is read again when the next original is scanned and new shading correction data is generated. Basically, it continues to be used for each main scan line data.

In this embodiment, in the sheet-through reading mode, the first reference white plate 12 used in the book reading mode is commonly used for shading correction. When the first reference white plate 12 used in the book reading mode is commonly used, the reference white plate reading operation cannot be performed simultaneously with the original reading operation in the sheet-through reading mode. In the sheet-through reading mode, when reading a document, the position C shown in FIG.
This is because the carriage 6 is fixed and read.
The reading operation of the reference white plate 12 is performed separately. Therefore, in order to perform the shading correction, the carriage 6 fixed at the time of reading the original is moved to the first reference white plate 1.
2 It is necessary to move to the reading position B, and this operation imposes a load on the CPU that performs the reading control, and leads to prolonging the time required for reading.

Therefore, in the present invention, this load is reduced as much as possible, and the reading time is shortened. In addition, differences in reading conditions that can occur individually in sheet-through reading are detected for each read document, and the difference between book reading and book reading is detected. It is intended to correct the reading result so that there is no difference. For this reason, in the present invention, the second reference white plate 1 is placed on the AFD side corresponding to the fixed reading position C of the carriage 6.
3 (see FIG. 2) is provided over the entire reading area. The second reference white plate 13 enables a difference in reading conditions to be checked before reading each document. This check is performed when the plurality of document bundles are set on the document tray 14 and the first reference white plate 12 is read by moving to the position B before starting reading the first document of the set document bundle. The data of the obtained first reference white plate 12 is read out of the second reference white plate 13
By detecting a difference in the reading conditions for each document as compared with the data of the reference white plate 13. A document guide plate 16 on the ADF side provided at the sheet-through reading position C is used as the second reference white plate 13 used to carry out such a method.
Guide surface can be used. This makes it possible to take a more effective embodiment without increasing the number of parts.

Next, as an embodiment of the present invention, the reading of the first reference white plate 12 and the second reference white plate 13 and the correction operation in the sheet-through reading mode performed using the read data will be described below. Note that the correction operation of the embodiment described below is executed by the CPU in a control unit (not shown) that controls the entire reading operation such as the scanner operation, the document conveyance of the ADF, and the processing of the read signal in the image reading apparatus. . FIG. 3 shows a flow of an operation of correcting read data in the sheet-through read mode. The details of the correction operation will be described with reference to FIG. When the apparatus receives the bundle of originals set on the original tray 14 of the ADF and starts the operation, first, it is checked whether or not the original is the first read original (S1). In the case of the first sheet, since there is a stop period, it is highly possible that the reading condition has changed. Therefore, in order to obtain data for correction, the carriage 6 is moved to the position B and the first reference white plate 12 is moved. Is read by the CCD 9 (S2). The read data of the first reference white plate 12 read here represents a detection value for each pixel of the CCD 9 as a digital value of a predetermined number of gradations. An example of this is shown in a diagram in FIG. It becomes such data. In FIG. 4, the white level is on the vertical axis, and each pixel from 1 to 7500 is on the horizontal axis. The read data of the first reference white board 12 obtained in step S2 is stored in a storage unit (S3), and then shading correction data is generated based on the stored read data, and the generated correction data is stored in a subsequent stage. Is stored in the storage unit for use in the step (S4). The shading correction data is generated by obtaining a correction coefficient to be multiplied by each pixel data actually read from the first reference white plate 12 in order to equalize the white level as originally expected when the reference white plate is read. It can be carried out by the known arithmetic operation.

Thereafter, the carriage 6 is moved to return the reading position to the position C again. At this time, since the document has not been conveyed yet, the surface of the guide plate 16 functioning as the second reference white plate 13 is exposed at the reading position C. Then, the second reference white plate 13 is read by the CCD 9 (S
5). In the read data of the second reference white plate 13 that is read here, the reading conditions that are different from those of the first reference white plate 12 (that is, the difference in the document position in the book / sheet-through reading mode) are reflected in the detection value. That is, since the second reference white plate 13 at the reading position C is provided on the ADF side, compared with the case of the first reference white plate 12 provided on the same surface as the original surface for book reading, the reading system for the original surface The distance will be long,
The mounting state of the scanner and the ADF is not constant,
Variations in the attachment of the DF to the main body cause unevenness in the distance of the reading system from the document surface, and reflect such differences.

FIG. 5 shows an example of the mounting state of the scanner and the ADF. FIG. 5 shows a case where the ADF is attached to the scanner so that the depth of the ADF is high (A) and a case where the ADF is attached so that the front of the ADF is high (B). , The read values in the main scanning direction become non-uniform. Further, a difference due to a variation in mounting of the ADF may appear as a difference between the center and the periphery of the image and a difference between left and right. By reading the second reference white plate 13, the difference in the reading conditions can be checked as described above. On the other hand, as a condition different from that of the first reference white plate 12, the reading data of the second reference white plate 13 includes the document guide surface of the ADF. Since the guide surface is used as a reference white plate, the guide surface is contaminated and stained, and appears as noise in the read data.
FIG. 6 shows an example of read data in which the influence of the attached matter and dirt on the guide surface has occurred. As shown in FIG. 6, the level of a part of the pixel is reduced due to the attached matter, and appears as a black stripe.

As described above, the read data of the second reference white plate 13 reflects conditions different from those of the first reference white plate 12, and this difference is caused by the difference in white level between the first and second reference white plate read data. It can be extracted by taking. FIG. 7 shows the relationship between the first and second reference white board read data. FIG.
As shown in the figure, the second reference white board read data is usually
The level is lower than that of the first reference white board read data, and in the example shown in the figure, the ADF is in an improperly attached state, and the inclination in the main scanning direction occurs. By taking the white level difference shown in FIG. 7 from the first and second reference white board read data,
The sheet-through read data can be corrected using the difference data. That is, the difference data is generated as the sheet-through correction data, and the correction data is used to correct the document-reading data by the sheet-through, so that the same reading data as in the book reading mode can be output.

However, when generating the sheet-through correction data, it is necessary to correct data included as noise in the second reference white board read data. As a method of correction, since noise due to an adhered substance is an abnormal signal, it can be distinguished by threshold processing. If an abnormal signal is detected, the abnormal signal is eliminated and the vicinity of the abnormal signal is removed. In order to prevent the influence of the abnormal signal from appearing by adopting the normal signal described in FIG. The operation flow includes the first reference white board read data read in step S3,
Difference data (shown as a white level difference in FIG. 7) between the first and second reference white board read data is obtained from the second reference white board read data read in step S5, and this is used as white level correction data in the subsequent stage. (S6).

As a procedure in the operation flow, after reading the first and second reference white plates, the original conveyed by the ADF is read while the carriage is fixed at the position C (S7). Next, sheet through correction is performed on the document read data (S8). The sheet-through correction corrects the document read data in the sheet-through mode based on the white level correction data generated in step S6. Here, this is performed by adding the white level correction data to the original reading data. The read data obtained by this correction is a signal of the same level as read in the book mode. Thereafter, shading correction is performed on the read data processed in the previous step S8 (S9). The shading correction is a process usually performed on read data, and is similarly performed in the book reading mode. Here, the correction is performed by multiplying the document reading data subjected to the sheet-through correction in step S8 by the correction coefficient as the shading correction data generated in step S4. Next, it is checked whether or not the next document is present on the document tray 14 of the ADF (S10). If there is no next document as a result of the check, this flow is terminated.

On the other hand, as a result of the check in step S10,
If there is a next original, the process returns to the first step S1 of this flow, and it is checked whether or not the original to be read is the first original (S1). In the procedure described here, the first document has already been read, so the check result is
Since the determination is NO, the first reference white plate 12 is not read for the first document, and the second reference white plate 1 is immediately read.
Step S5 for reading 3 is performed. Thereafter, the processing performed when reading the first original document is similarly performed up to step S10. This process is performed for all the remaining originals, and the process is terminated. FIG. 8 is a chart showing the reading timing of the first and second reference white plates when a plurality of document bundles are processed in the sheet-through reading mode. As shown in FIG. 8, the first sheet of the document bundle reads both the first and second reference white plates.
The second reference white plate 13 provided at the sheet-through reading position
Only read of. Therefore, by reading the first reference white plate 12 only on the first sheet at a minimum, an operation of moving the carriage is required for the second and subsequent sheets.
It is possible to suppress the prolongation of the time required for reading, which leads to imposing a load on the PU, and to output appropriate read data by shading correction and sheet-through correction.

[0021]

According to the first aspect of the present invention, a first white reference body is provided at a moving position of the carriage, and a second white reference body is provided at the fixed position of the carriage. The shading correction is performed based on the read data of the white reference body, and the difference between the read data in both the book reading mode and the sheet through reading mode is corrected based on the read data of the first and second white reference bodies. This makes it possible to obtain appropriate image data with no difference in read output regardless of which mode is read.

(2) Effects corresponding to the second aspect of the invention In addition to the effects of the above (1), the second white reference body is made a common member with the original guide provided in the original conveying means, and the second white reference body is used in the sheet-through reading mode. By performing shading correction of the read data based on the read data of the first white reference body commonly used in the book read mode, it is possible to obtain appropriate read image data in the sheet-through read mode without increasing the number of parts. Becomes possible. (3) Effects corresponding to the third aspect of the invention In addition to the effects of the above (2), by correcting the abnormal data included in the read data of the second white reference body, there is a possibility that the correction will occur in the sheet-through read mode. Deterioration of certain image data can be prevented. (4) Effects corresponding to the fourth aspect of the invention: a copier equipped with the image reading device according to the first to third aspects,
In image forming apparatuses such as facsimile machines, the above (1)-
By realizing the effect (3), the performance of the image forming apparatus can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an overall configuration of an image reading apparatus equipped with an ADF according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a sheet-through reading (ADF reading) unit in the embodiment of FIG. 1 and illustrating its operation.

FIG. 3 shows a flow of an operation of correcting read data in a sheet-through read mode.

FIG. 4 illustrates an example of read output data of a CCD that reads a first reference white plate in the present embodiment.

FIG. 5 shows an example of an image reading apparatus scanner according to the present embodiment equipped with an ADF and an attached state of the ADF.

FIG. 6 illustrates an example of read output data of a CCD that reads a second reference white plate in the present embodiment.

FIG. 7 is a diagram illustrating an example of read output data of a CCD that reads first and second reference white boards in the present embodiment, and is a diagram for explaining a white level difference.

FIG. 8 shows the reading timing of the first and second reference white plates when a document bundle is processed in the sheet-through reading mode.

[Explanation of symbols]

1 ... platen platen (contact glass), 2 ... light source,
Reference numeral 3 denotes a first reflection mirror, 4 denotes a second reflection mirror, 5 denotes a third reflection mirror, 6 denotes a first carriage, 7 denotes a second carriage, 8 denotes a group of transport rollers, and 6 denotes a discharge roller.
... Guide plate (background plate), 8 ... Lens unit, 9 ... CCD line image sensor, 10 ... Sensor board substrate, 11 ... Signal processing substrate, 12
... first white reference plate, 13 ... second white reference plate,
14: document tray, 15: transport roller group,
16: guide plate, 17: discharge roller,
S: manuscript.

Claims (4)

[Claims] A carriage provided with a reading optical system;
An image reading apparatus that includes a document transport unit and a carriage moving unit, and that can move in the carriage and read a fixed document and a mode in which the carriage is fixed and a mode in which the document is read during transport by the document transport unit. An apparatus, wherein a first white reference body is provided at the moving position of the carriage over the entire reading area of the reading optical system, and a second white reference body is provided at the fixed position of the carriage, and the whole reading area of the reading optical system is provided. Means for performing shading correction based on the read data of the first or second white reference body, and correcting the difference between the read data of both modes based on the read data of the first and second white reference bodies. An image reading apparatus comprising: 2. The image reading apparatus according to claim 1, wherein the second white reference member is a member common to a document guide provided in the document conveying means, and shading correction of read data in a conveyance document reading mode. Image reading apparatus based on the read data of the first white reference body. 3. The image reading apparatus according to claim 2, further comprising: means for correcting abnormal data included in the read data of the second white reference body. 4. An image forming apparatus comprising: the image reading apparatus according to claim 1; and means for forming an image based on image data.