JP2003333327A - Image reader and copying machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deviation in a density balance between read image data caused by a difference between read density characteristics between two read means in the case that the two read means are used to read an image on both sides of an original respectively. <P>SOLUTION: An image reader applies shading correction to read image data on the basis of white reference data acquired by using two kinds of read means 10, 11 to read white reference areas 8a, 9a of two kinds of white reference members 8, 9 respectively and corrects the density balance of the read image data by the two kinds of different read means 10, 11 on the basis of medium density reference data acquired by using two kinds of the read means 10, 11 to read medium density reference areas 8b to 8f, 9b to 9f of two kinds of medium density reference members 8, 9 respectively. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device and a copying machine.

[0002]

2. Description of the Related Art For example, an ADF (Auto Document Feeder) that conveys a document in a document conveyance path is used to image both sides of a document while the document is conveyed in the document conveyance path. There is an image reading device for reading. Such an image reading device includes a light source that emits light,
There is an apparatus in which an image of a document is read by a reading unit such as a reading optical system configured by a reading sensor or the like that receives light emitted from a light source and reflected from the document.
Examples of the reading sensor include a plurality of sensor chips arranged on a line in the sub-scanning direction.

When reading an original having images formed on both sides, if the intensity of light applied to the original exceeds the light transmittance of the original, the image on the back side of the original to be read is also printed. I will read it. For this reason, the read image data is in a state in which the image on the back side is the show-through on the image on the document side.

In order to prevent such a problem, for example, Japanese Patent Laid-Open No. 11-187268 discloses that when the intensity of light emitted from a light source exceeds the light transmittance of the original when reading a double-sided original, A technique is disclosed in which the density of read image data of a document is calculated to correct the read image data. Further, in the technique disclosed in the publication, when the intensity of light emitted from the light source exceeds the light transmittance of the document, the read image data on the back side of the target document surface is calculated and offset as noise. By doing so, it is possible to correct the read image data on the document surface.

[0005]

By the way, in order to read the images on both sides of the original while the original is being conveyed once in the original conveying path, a reading means for reading the images on the front side of the original is provided. It is necessary to arrange the reading means for reading the image on the back side in the document conveyance path. In such an image reading apparatus, a contact sensor of an equal-magnification optical system is used for one of the reading means and a CCD of the reduction optical system is used for the other reading means in view of downsizing of the image reading apparatus and cost reduction. Charge
Coupled Device) Image sensors are often used.

However, in the contact sensor and the CCD image sensor, for example, MTF (Modulation Transfer Fun) is used.
function, and the reading characteristics such as the reading density characteristics have a considerable gap. Therefore, as in the technique disclosed in Japanese Patent Laid-Open No. 11-187268, correction of read image data on the document surface is performed by calculating read image data on the back surface of the target document surface and canceling it out as noise. Such as processing
In an image forming apparatus that performs correction processing by using the correlation between the read image data on the front side and the read image data on the back side, the quality of the obtained read image data is greatly affected by the reading characteristics of the reading unit. For this reason, there is a case in which the quality of the front side and the back side of the document are greatly different even though the image data is the read image data read from a single document.

As a countermeasure against this, a correction process is required after the reading characteristics of two types of reading means having different reading characteristics such as a contact sensor and a CCD image sensor are matched.

Of the reading characteristics of the reading optical system, M
Regarding the TF, by tuning each reading means or performing processing such as an MTF filter or a smoothing filter on the read image data read by one reading means It is possible to eliminate variations in the quality of read image data due to differences in MTF to some extent.

However, since the reading density characteristic of the reading characteristics of the reading means changes with time, it is difficult to eliminate the variation in the quality of the read image data due to the difference in the reading density characteristics of the two types of reading means. Is. Also, for example, in a single image, continuous or halftone image,
If the original has different density reproduction methods,
Even if the MTF shift is slight, the difference in image density appears remarkably. Therefore, it is desirable to match the read density characteristics as much as possible.

It is an object of the present invention, when the images on both sides of the original are read using two reading means, the density balance between the read image data is deviated due to the difference in the read density characteristics between the reading means. It is to suppress the occurrence.

An object of the present invention is to provide a reading density characteristic between reading means due to a change with time of the reading density characteristic even when the reading density characteristics between two reading means for reading images on both sides of an original change with time. This is to prevent the density balance between the read image data from being deviated due to the difference between

[0012]

According to another aspect of the present invention, there is provided an image reading apparatus, which is provided at a first reading unit for reading an image on one side of a document and at a position readable by the first reading unit. The white reference area of the first white reference member is read by the first reading unit to obtain white reference data, and shading is performed on the read image data read by the first reading unit based on the white reference data. The first shading correction means for performing correction, the second reading means for reading the image on the other surface side of the document, and the second white reference member provided at a position readable by the second reading means. White reference data is obtained by reading the white reference area by the first reading means, and based on the white reference data, the white reference data is read from the read image data read by the second reading means. A second shading correction means for performing the bleeding correction and a plurality of different density areas of the first intermediate density reference member provided at a position readable by the first reading means are read by the first reading means. The first intermediate density data acquisition means for acquiring the first intermediate density data, and the plurality of different density areas included in the second intermediate density reference member provided at a position readable by the second reading means. A second intermediate density data acquisition means for acquiring second intermediate density data by reading the second intermediate density data by the second reading means, and the first and second intermediate density data acquisition means acquired by the first and second intermediate density data acquisition means. Intermediate density data adjusting means for adjusting at least one of the second intermediate density data to match the read density characteristics of the first and second reading means, and the intermediate density data adjusting means. It said first means is adjusted based on the second intermediate density data, wherein the first,
A second shading correction means for adjusting the density balance of the read image data after shading correction by the second shading correction means.

Therefore, based on the white reference data obtained by reading the white reference regions of the first and second white reference members by the first and second reading means, respectively, the first and second reading means. Shading correction is performed on the read image data read by the first and second shading correction means, respectively, and a plurality of different density areas of the first and second intermediate density reference members are provided by the first and second reading means. The at least one of the first and second intermediate density data acquired by the first and second intermediate density data acquisition means has the same read density characteristics of the first and second reading means. Is adjusted by the intermediate density data adjusting means, and the first and second shading corrections are performed based on the adjusted first and second intermediate density data. Density balance of the read image data after the shading correction by stages is adjusted by the density correction means.

According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the first and second intermediate density data acquisition means are configured to perform the first and second intermediate density data at predetermined timings. To get.

Therefore, at least one of the first and second intermediate density data acquired at every predetermined timing by the first and second intermediate density data acquisition means is adjusted by the intermediate density data adjustment means.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the image reading apparatus described above, the first and second intermediate density data acquisition means acquires the first and second intermediate density data each time the original image is read by the first and second reading means. .

Therefore, at least one of the first and second intermediate density data acquired by the second intermediate density data acquisition means each time the original image is read by the first and second reading means is adjusted to the intermediate density data. Adjusted by means.

According to a fourth aspect of the present invention, in the image reading apparatus according to the first, second or third aspect, the intermediate density data adjusting means acquires the first and second intermediate density data acquiring means. The first and second intermediate density data are adjusted so as to match the intermediate value between the first intermediate density data and the second intermediate density data.

Therefore, the first and second intermediate density data obtained by the first and second intermediate density data acquisition means are adjusted to the intermediate value between the first intermediate density data and the second intermediate density data. Are adjusted by the intermediate density data adjusting means.

According to a fifth aspect of the present invention, in the image reading apparatus according to the first, second or third aspect, the intermediate density data adjusting means is the first and second intermediate density data acquiring means. The first and second intermediate density data are adjusted to match the specified intermediate density data.

Therefore, the first and second intermediate density data obtained by the first and second intermediate density data obtaining means are adjusted by the intermediate density data adjusting means so as to match the prescribed intermediate density data. .

A copying machine according to a sixth aspect of the present invention forms an image on a recording material based on the image reading device according to the first, second, third, fourth or fifth aspect and the read image data read by the image reading device. And an image forming apparatus for forming the image.

Therefore, an image based on the read image data whose density balance has been corrected is formed on the recording material by the action of the invention described in claim 1, 2, 3, 4 or 5.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described with reference to FIGS. The present embodiment shows an application example to an image reading apparatus that automatically reads a set original.

FIG. 1 is a schematic view showing a part of the image reading apparatus of this embodiment. Image reading apparatus 1 of the present embodiment
Is an ADF (Auto Do
cument Feeder: Automatic document feeder 3). A
The DF 3 conveys the document from the position indicated by A in FIG. 1 to the position indicated by D in the document conveyance path 2.

A first reading optical system 4 for reading an image of an original document conveyed in the original document conveyance path 2 is provided in the original document conveyance path 2.
And a second reading optical system 5 is provided. The image reading apparatus 1 according to the present embodiment has an operation unit 26 (see FIG. 5) that accepts scanning by an operator, and when reading an original set at a position A of the ADF 3,
It is possible to set either a single-sided mode for reading an image on one side of the original or a double-sided mode for reading images on both sides of the original. After that, the symbol B is added to the reading position of the first reading optical system 4.
Will be described, and the reading position by the second reading optical system 5 will be described with reference numeral C.

Further, a contact glass 6 which constitutes a part of the document transport path 2 is provided in the document transport path 2. In addition, although not shown in FIG. 1, a contact glass on which a document is placed is provided on the right side of the reading position C in FIG. These contact glasses 6
Is formed of a transparent member such as glass.

Although not shown in detail because it is a known technique, the first reading optical system 4 of the present embodiment has a first traveling body 4 having a light source 4a for emitting light and a mirror 4b.
c and the second traveling body 4 equipped with the two mirrors 4d and 4e.
f and a CCD (Charge Coupled) that receives the light guided by the mirrors 4b, 4d, and 4e through the imaging lens 4g.
Device) A reduction optical system including an image sensor 4h and the like. The CCD image sensor 4h photoelectrically converts the reflected light from the original image formed on the CCD image sensor 4h into digital read image data. The first and second traveling bodies 4c and 4f are reciprocally provided so as to travel along the contact glass at a speed ratio of 2: 1 by a driving unit such as a motor (not shown). first,
The second traveling bodies 4c, 4f are on standby at the home position shown in FIG. 2A when the image reading device 1 is in an idle state, and are driven by the driving means to be described later when reading an original image. The density reference plate 8 is reciprocated to a reference reading position for exposure scanning (see FIG. 2B).

Similarly, although not shown in detail because it is a known technique, the second reading optical system 5 is a light source that emits light, and an original that is emitted from the light source and is conveyed in the original conveying path 2. A contact sensor 5a for receiving reflected light from, and
The unity magnification optical system is configured by a unity magnification lens or the like that corresponds to each pixel of the contact sensor 5a and forms an image of reflected light from a document on the corresponding pixel. The contact sensor 5a has a width equal to or larger than the width of the document in the main scanning direction, and is a linear sensor in which the plurality of contact sensors 5a are arranged in a line along the main scanning direction. Further, the equal-magnification lens also has an array shape in which a plurality of equal-magnification lenses are arranged in a line along the main scanning direction in accordance with the contact sensor 5a. On the contact sensor 5a, the reflected light from the document imaged on the contact sensor 5a is photoelectrically converted into digital read image data.

When reading the original image, C
It is assumed that the CD image sensor 4h and the contact sensor 5a treat each line of data read at once as one unit, and handle each unit.

The operation of reading the original image by the first and second optical systems 4 and 5 will now be described. The operation of reading the original image is started by declaring the execution of the image reading operation in a state where the reading mode is set to one of the double-sided / single-sided by the operation of the operation unit 26.

When reading a document placed on the contact glass 53, the first reading optical system 4 is used.
The light source is turned on, and the first and second traveling bodies 4c and 4f are caused to travel along a contact glass (not shown) at a speed ratio of 2: 1 to expose and scan an original placed on the contact glass, Reflected light from the document is reflected by mirrors 4b, 4d, 4
CCD image sensor 4h via e and the imaging lens
The image is read by receiving light at.

When reading a document set at the position A of the ADF 3, the set document is read by the ADF 3
Conveys to the position D via the reading positions B and C,
When a document transported in the document transport path 2 passes through the reading position B, the first reading optical system 4 reads an image on one side of the document via the contact glass 6. At this time, when the double-sided mode is set by the operation of the operation unit 26, when the document conveyed in the document conveyance path 2 passes through the reading position C, the other surface of the document is read by the second reading optical system 5. Read the image on the side. Hereinafter, the surface read by the first reading optical system 4 will be described as the front surface, and the surface read by the second reading optical system 5 will be described as the back surface.

A density reference plate 8 is provided downstream of the contact glass 6 in the document transport direction in the document transport path 2. As shown in FIG. 3, the density reference plate 8 is a rectangular plate-shaped member, and is arranged with its longitudinal direction aligned with the main scanning direction (the front and back direction of the paper surface in FIG. 1). Further, as shown in FIG. 3, the density reference plate 8 is divided into a plurality of areas along the main scanning direction, and a white level reference at the time of shading correction, which will be described later, is provided on the most upstream side in the document conveyance direction. The white density portion 8a is provided. Next to the white density portion 8a, a plurality of types of intermediate density portions 8b, 8c, 8d, 8 which provide a plurality of intermediate density data which are used as a reference of a reading density characteristic used in a reading operation of a document image described later.
e, 8f are provided. Intermediate density parts 8b, 8c, 8
d, 8e, and 8f are the downstream side in the document conveying direction (right side in FIG. 3)
The higher the density, the higher the density. In the present embodiment, the density reference plate 8 realizes the first white reference member and the first intermediate density reference member.

A density reference roller 9 is provided at a position facing the second reading optical system 5 with the document conveying path 2 in between. The density reference roller 9 has a cylindrical or columnar shape, is arranged with its axial direction aligned with the main scanning direction, and is rotatably provided around the axial center. The rotation of the density reference roller 9 is drive-controlled by a rotation driving means (not shown). The outer peripheral surface of the density reference roller 9 is divided into a plurality of regions along the rotation direction. Here, FIG.
Shows a development view in which the outer peripheral surface of the density reference roller 9 is cut open along the axial direction. As can be seen from FIG. 4, on the outer peripheral surface of the density reference roller 9, a white density portion 9a serving as a white level reference, and a plurality of types of intermediate density portions serving as a reference for the read density characteristics adjacent to the white density portion 9a. 9b, 9c, 9d, 9
e, 9f are provided. In the present embodiment, the white density portion 9a is used as a reference, and the density is increased on the downstream side of the density reference roller 9 in the rotation direction. That is, the density reference roller 9 rotates in the direction of arrow R in FIG. In the present embodiment, the density reference roller 9 realizes the second white reference member and the second intermediate density reference member.

Next, the electrical connection of each section of the image reading apparatus 1 will be described with reference to FIG. FIG. 5 is a block diagram schematically showing the electrical connection of each part of the image reading device 1. In the image reading apparatus 1, the document transport path 2
While the original is conveyed once inside, the first reading unit 10 (first reading optical system 4, the first reading unit 10 including the driving unit for driving the first and second traveling bodies 4c and 4f) (first reading optical system 4) (Reading unit) and a second reading unit 11 (second reading unit) including a driving unit that rotationally drives the second reading optical system 5 and the density reference roller 9 described above. Scan both front and back images.

The first reading unit 10 includes an image data bus 12
Also, it is electrically connected to the first shading correction unit 14 via the shading data bus 13.
The first shading correction unit 14 is provided with a line memory (not shown) that stores white reference data for several lines transferred from the first reading unit 10 in the image reading operation described later. Shading correction is performed on the read image data read by the reading unit 10 based on the white reference data stored in the line memory. In addition, the first reading unit 10 includes the reading characteristic data bus 1
It is electrically connected to the image density adjusting unit 16 via 5. The image density adjusting unit 16 includes an image data bus 17
The first shading correction unit 14 is electrically connected via.

The second reading unit 11 includes an image data bus 18
Also, it is electrically connected to the second shading correction section 20 via the shading data bus 19.
The second shading correction unit 20 is provided with a line memory (not shown) that stores white reference data for several lines transferred from the second reading unit 11 in the image reading operation described later. Shading correction is performed on the read image data read by the reading unit 11 based on the white reference data stored in the line memory. In addition, the second reading unit 11 uses the reading characteristic data bus 2
1 is electrically connected to the image density adjusting unit 16. The image density adjusting unit 16 includes an image data bus 22.
The second shading correction unit 20 is electrically connected via.

The first and second reading units 10 and 11, the first and second shading correction units 14 and 20, and the image density adjusting unit 16 are connected to the image reading apparatus 1 via the address bus 23 and the CPU bus 24. It is connected to a CPU 25 that centrally controls the drive of each part of the. Although not particularly shown, C
The PU 25 is connected to various memory means such as a ROM for storing a control program and the like, and a RAM for rewritably storing variable data.

The CPU bus 24 has an operating section 26 for receiving an operation by an operator via the address bus 23.
Also, an external connection unit 27 to which an external device (not shown) such as an image storage device or an image output device is electrically connected is electrically connected. Although not shown in particular, the operation unit 26 is provided with various operation keys such as an execution key for declaring execution of the image reading operation and a mode setting key for setting the reading mode to double-sided / single-sided. The operation unit 26 outputs a signal corresponding to the operated operation key to the CPU 25. To the external connection unit 27, the read image data after being subjected to a predetermined correction process by the image correction unit 29, which will be described later, is transferred, and the transferred read image data is electrically connected to an image storage device or an image output device. Transfer to an external device such as a device.

In addition, the CPU bus 24 is electrically connected via the address bus 23 to the image correction unit 29 connected to the image density adjusting unit 16 via the image data bus 28. The image correction unit 29 performs predetermined correction on the read image data transferred from the image density adjustment unit 16, such as MTF correction of the read image data or density correction processing of read image data called γ conversion. Perform processing. In addition, M
Since the density correction processing of the read image data such as TF correction and γ conversion is a known technique, description thereof will be omitted. The read image data subjected to the predetermined correction processing by the image density adjustment unit 16 is transferred to the external connection unit 27 via the image data bus 30.

Next, the reading operation of the original image by the drive control by the CPU 25 will be described in detail. CPU
As described above, the reference numeral 25 outputs a reading instruction when execution of the image reading operation is declared in a state where the reading mode is set to either one of double-sided / single-sided by the operation of the operation unit 26, The first and second reading units 10 and 11 are operated. At this time, when the reading mode is set to single-sided, only the first reading unit 10 is operated, and when the reading mode is set to double-sided, the first and second reading units 10, Both 11 are activated. In this embodiment,
A case where the reading mode is set to both sides will be described.

When an instruction to read a document image is output from the CPU 25, first, the first reading unit 10 first moves from the home position shown in FIG. 2 (a) to the reference reading position shown in FIG. 2 (b). The second traveling bodies 4c and 4f are moved. The light source 4a is turned on at the timing when the first and second traveling bodies 4c and 4f have reached the reading reference position, and the first and second traveling bodies 4 are kept as they are.
By moving c and 4f toward the second reading position C, the density reference plate 8 is exposed and scanned. Of the read data read by exposing and scanning the density reference plate 8,
White reference data obtained by reading the white density portion 8a is transferred to the first shading correction portion 14 for several lines via the shading data bus 13.

The first shading correction unit 14 performs an averaging process for each pixel on the white reference data for several lines transferred from the first reading unit 10 to obtain one line in the main scanning direction. Minute white level correction data is generated. The generated shading correction data is stored in a line memory (not shown). For example, if the image data is 8
In the case of the bit, as shown in FIG. 6, the shading correction data is generated by performing a simple averaging process on white reference data for any N lines for each pixel in the main scanning direction.

The method of generating shading correction data illustrated with reference to FIG. 6 is merely an example, and the present invention is not limited to this.

The intermediate density portions 8b to 8 of the density reference plate 8 are also provided.
The first intermediate density data obtained by exposing and scanning f is transferred to the image density adjusting unit 16 for several lines via the reading characteristic data bus 15. Here, the function as the first intermediate density data acquisition means is realized.

Subsequently, the first and second traveling bodies 4c and 4f are moved to the reading position B shown in FIG. 2C, and the document conveyance by the ADF 3 is started. In addition, in the present embodiment, FIG.
The home positions of the first and second traveling bodies 4c and 4f shown in (a) and the reading position B of the first and second traveling bodies 4c and 4f shown in FIG. 2 (c) are the same position. The light source 4a is turned on in synchronization with the timing when the leading edge of the document conveyed in the document conveyance path 2 by the ADF 3 passes the reading position B.
As a result, in the state where the original conveying path 2 is irradiated with light through the contact glass 6, the originals conveyed in the original conveying path 2 by the ADF 3 sequentially pass through the reading position B, and the original is exposed and scanned. It By this exposure scan,
As shown in FIG. 7, the end of the leading edge (first line) of the document is set as the document reference point P, and the main scanning direction is a single “line” with respect to this document reference point P. Images are sequentially read in the scanning direction. The read image data that has been read is transferred to the first shading correction unit 14 via the image data bus 12.

The first shading correction unit 14 performs a shading correction process for each line on the read image data transferred from the first reading unit 10 based on the shading correction data stored in the line memory. To do.

The shading correction processing performed by the first shading correction unit 14 is, for example, the pixel located at the document reference point P as the head pixel of the CCD image sensor, and 0, 1, 2 from the head pixel in the main scanning direction. ，
, K, ..., N are numbered in order, and among the read image data corresponding to each pixel, read image data before shading correction processing is Xk, and shading correction data corresponding to each pixel is Sk. In addition, the read image data Xk ′ after the shading correction processing is performed by executing the calculation of the following expression (1) is performed. Here, the function as the first shading correction means is realized. Xk ′ = (Xk / Sk) × 255 (1) (k = 0, 1, 2, ..., K, ..., N) However, when Sk = 0, Xk ′ = 255.

In the present embodiment, the shading correction processing is performed by executing the calculation of equation (1), but the present invention is not limited to this, and various known methods can be used.

The read image data for which the shading correction processing in the first shading correction unit 14 is completed is
It is transferred to the image density adjusting unit 16 via the image data bus 17.

On the other hand, when the instruction to read the original image is output from the CPU 25, the second reading section 11 turns on the light source and rotates the density reference roller 9. As a result, a plurality of regions provided on the outer peripheral surface of the density reference roller 9 are sequentially exposed and scanned, and among the read data read by this exposure scanning, the white reference data obtained by reading the white density portion 9a is A few lines are transferred to the second shading correction section 20 via the shading data bus 19.

The second shading correction unit 20 is similar to the first shading correction unit 14 in that the second reading unit 1
For several lines of white reference data transferred from 1,
By performing the averaging process for each pixel, white level correction data for one line in the main scanning direction is generated. The generated shading correction data is stored in a line memory (not shown).

Similarly to the first shading correction unit 14, the second shading correction unit 20 converts the read image data transferred from the second reading unit 11 based on the shading correction data stored in the line memory. for,
The shading correction processing is performed for each line by executing the calculation of the equation (1), and the read image data for which the shading correction processing has been completed is transferred to the image density adjusting unit 16 via the image data bus 22. Here, the function as the second shading correction means is realized.

The intermediate density portion 9b of the density reference roller 9
The second intermediate density data obtained by exposing and scanning 9f to 9f are transferred to the image density adjusting unit 16 for several lines via the reading characteristic data bus 21. Here, the function as the second intermediate density data acquisition means is realized.

The image density adjusting section 16 first processes the first intermediate density data transferred from the first reading section 10 and the second intermediate density data transferred from the second reading section 11. Based on this, the density conversion table T1 (see FIG. 9) is created. When creating the density conversion table T1, values obtained by averaging the intermediate density data of several lines in each of the intermediate density portions 8b to 8f and 9b to 9f were used as the first and second intermediate density data, respectively.

Here, a case where the dynamic range is 8 bits will be described as an example. In FIG. 3 and FIG. 4, the intermediate density portions 8b to 8f, 9 of five different densities
Although b-9f are illustrated, here, the density reference plate 8
The density reference roller 9 and the density reference roller 9 will be described on the assumption that each of the density reference rollers 9 has eight types of intermediate density portions having different densities in stages.

The first and second intermediate density data obtained by reading the intermediate density portions of the density reference plate 8 and the density reference roller 9 by the first and second reading units 10 and 11 are shown in FIG.
If the second intermediate density data is adjusted so that the second intermediate density data matches the first intermediate density data when the values are t1 and t2 shown in Table T1 of FIG. The conversion table T1 'can be obtained.

Here, the gradation of the read image data transferred from the first and second shading correction units 14 and 20 is
Since 256 gradations from 0 to 255 are assumed, the created conversion table T1 ′ has 256 gradations from 0 to 255 for continuously converting the second intermediate density data into the first intermediate density data. Must have. Conversion table T1 ′ having conversion data of 256 gradations from 0 to 255
In order to create, the conversion data Z for converting the intermediate density data between the eight intermediate density data included in the first and second intermediate density data are required.

In this embodiment, the adjacent intermediate density data among the first intermediate density data are Y1 and Y2, and the second intermediate density data corresponding to these intermediate density data Y1 and Y2 are X1 and X2, respectively. Then, the conversion data Z continuous during this period is acquired by calculating the following equation (2). Here, the function as the intermediate density data adjusting means is realized. Z = [(Y2-Y1) / (X2-X1)] * (X-X1) + Y1 (2) where X1≤X <X2 and Y1≤Z <Y2

In the calculation of the equation (2), the conversion data Z corresponding to the intermediate density data smaller than the smallest intermediate density data (the intermediate density part of the lightest density) acquired from the reading of the intermediate density part is converted into the intermediate density data. It is assumed that the smallest intermediate density data acquired from reading a copy is X2 and Y2, X1 and Y1 are "0", and interpolation is performed with 0. The conversion data Z corresponding to the intermediate density data larger than the largest intermediate density data obtained from the reading of the intermediate density portion (the intermediate density portion having the highest density) is the largest obtained from the reading of the intermediate density portion. The intermediate density data is X1, Y1, and X2, Y2
Is set to “255”, and interpolation is performed with 255.

When the converted data Z obtained by the calculation of the equation (2) has a fractional value below the decimal point, all the converted data are made integers by a unified method such as rounding up or down.

In the present embodiment, the second reading unit 1
Although the conversion table T1 ′ for converting the intermediate density data of No. 1 into the intermediate density data of the first reading unit 10 is created, the present invention is not limited to this, and the intermediate density data of the first reading unit 10 is read by the second reading. A conversion table for converting the intermediate density data of the unit 11 may be created to convert the intermediate density data of the first reading unit 10 into the intermediate density data of the second reading unit 11.

The image density adjusting unit 16 reads each pixel of the read image data after shading correction transferred from the second reading unit 11 based on each value of the conversion table T1 'obtained as described above. The density characteristics are corrected line by line so that they match the converted data Z. Here, the function as the density correction means is realized.

When reading images on both sides of the original, the white density portions 8a and 9a of the density reference plate 8 and the density reference roller 9 are read by the first and second reading units 10 and 11.
Is read to obtain white reference data, and the first and second reading units 10 and 11 are read based on the white reference data.
Shading correction is performed on the read image data read by. In addition, the first and second reading units 10 and 11 allow a plurality of different intermediate density portions 8b to 8 in the density reference plate 8 and the density reference roller 9.
f and 9b to 9f are read to obtain the first and second intermediate density data. Then, at least one of the first and second intermediate density data is stored in the first and second reading units 1.
The read density characteristics of 0 and 11 are adjusted to match, and the density balance of each read image data after shading correction is corrected based on the adjusted intermediate density data.

As a result, even when the images on both sides of the original are read using the first and second reading units 10 and 11 having different reading density characteristics, the reading densities of the first and second reading units 10 and 11 are read. It is possible to prevent the density balance between the read image data from being deviated due to the difference in characteristics.

In the present embodiment, the intermediate density portions of the density reference member 8 and the density reference roller 9 are read every time the operation of reading images on both sides of the original is performed by the first and second reading portions 11. The intermediate density data is acquired by the method, and the density balance of each read image data is corrected based on the intermediate density data.

As a result, the first and second reading units 10,
Even when the reading density characteristics of the first and second reading units 10 and 11 change with time and the reading density characteristics of the first and second reading units 10 and 11 change with time, the first and second reading units 10 due to the changes of the reading density characteristics with time. , 11 can prevent the deviation of the density balance between the read image data due to the difference in the read density characteristics.

In the present embodiment, a conversion table T1 'for converting the second intermediate density data into the first intermediate density data is created, and the second reading unit 11 uses the conversion table T1' based on the conversion table T1 '. Although the density balance of the read read image data is corrected, a conversion table (not shown) for converting the first intermediate density data into the second intermediate density data is created, and the first reading is performed based on this conversion table. The density balance of the read image data read by the unit 11 may be corrected.

Next, a second embodiment of the present invention will be described with reference to FIGS. The present embodiment is an application example to an image reading apparatus, and the acquisition method of the conversion table T2 ′ is different from that of the first embodiment.
The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. The same applies hereinafter.

The image density adjusting unit 16 of the image reading apparatus 1 of the present embodiment transfers the read image transferred from the first and second reading units 10 and 11 to the first and second shading correction units 14 and 20. Corresponding to the data, the first and second reading unit 1
A value obtained by averaging the first and second intermediate density data transferred from 0 and 11 through the read density characteristic data buses 15 and 21 for each pixel (see t3 in FIG. 10) is used as the conversion data Z.

The image density adjusting unit 16 adjusts the intermediate density data between the read image data transferred from the first shading correction unit 14 and the read image data transferred from the second shading correction unit 20, and then the image Data bus 2
Then, the data is transferred to the image correction unit 29 in the interleaved format via 8.

When reading the original image, the respective intermediate density data when the density reference plate 8 or the density reference roller 9 is read by the first and second reading units 10 and 11 are values as shown in FIG. 9, for example. If it is, the acquired conversion data Z has a value indicated by t3 in FIG.

A conversion table T for correcting the first intermediate density data into the conversion data Z as shown in FIG. 11 based on the conversion data Z indicated by t3 in FIG. 10 in the same manner as described above.
Create 2 '. Here, the function as the intermediate density data adjusting means is realized.

Although not shown in particular, similarly, t3 in FIG.
A conversion table for correcting the second intermediate density data to the conversion data Z is created based on the conversion data Z shown in FIG.

Based on the corresponding conversion table T2 'acquired as described above, the first and second reading units 10 and 11 are
Read density characteristics of the read image data transferred from the first to second shading correction units 14 and 20 from
It is corrected line by line so as to match the converted data Z. Here, the function as the density correction means is realized.

Here, in the operation of reading the original image, each of the two kinds of intermediate density data transferred from the first and second reading units 10 and 11 is adjusted so as to match the intermediate value of each other. The density balance of each read image data after shading correction is corrected based on the adjusted intermediate density data.

As a result, the first and second reading units 10,
The density balance of the two types of intermediate density data transferred from 11 is evenly distributed, and due to the adjustment of the intermediate density data, the first and second shading correction units 14,
It is possible to suppress the occurrence of a difference in the image quality of each read image data transferred to 20.

Next, a third embodiment of the present invention will be described with reference to FIGS. The present embodiment is an application example to an image reading apparatus. In this embodiment,
The acquisition method of the conversion table T3 ′ is different from that of the first embodiment.

The image density adjusting unit 16 of the present embodiment corresponds to the read image data transferred from the first and second reading units 10 and 11 to the first and second shading correction units 14 and 20. , A preset value (see t4 in FIG. 12) is used as the conversion data Z, and the first and second shading correction units 1
The read density characteristics of the read image data transferred from Nos. 4 and 20 are corrected.

In the present embodiment, the conversion data Z can be set to an arbitrary value by operating the operation unit 26. The conversion data Z of an arbitrary value set by the operation of the operation unit 26 is defined as the intermediate density data. Further, the conversion data Z of 256 gradations acquired based on the conversion data Z of an arbitrary value set by the operation of the operation unit 26.
Is also specified intermediate concentration data.

Therefore, the operation unit 26 is provided with various setting keys for setting arbitrary conversion data Z, a display unit for guiding the contents of the setting, and the like. The operator
It is possible to set arbitrary conversion data Z according to the display screen displayed on the display unit. However, the range of conversion data Z that can be set is the density reference plate 8
Also, it is limited within a certain range so that the magnitude relationship of each intermediate density data in the intermediate density portion of the density reference roller 9 does not change.

Further, the CPU 25 is provided with a conversion data memory (not shown) for storing the conversion data Z set by the setting of the operation unit 26.

In addition, the image density adjusting unit 16 adjusts the read density characteristics of the read image data transferred from the first shading correction unit 14 and the read image data transferred from the second shading correction unit 20. After that, similarly to the second embodiment, the image data is transferred to the image correction unit 29 in the interleaved format via the image data bus 28.

When reading the original image by the image reading apparatus 1 having such a configuration, the first reading section 11 is used.
When the first intermediate density data when the density reference plate 8 is read with the value t1 in FIG. 12, the first intermediate density data is converted into the conversion data stored in the conversion data memory. A conversion table T3 ′ for converting according to Z (see t4 in FIG. 12) is created (see FIG. 13).

Although not shown in particular, similarly, when the second intermediate density data when the density reading roller 9 is read by the second reading unit 10 has a value as shown by t2 in FIG. The second intermediate density data is converted into the converted data Z stored in the converted data memory as shown by t4 in FIG.
A conversion table (not shown) for conversion is created according to the above.
Here, the function as the intermediate density data adjusting means is realized.

Then, based on the corresponding conversion table T3 'obtained as described above, the first and second reading units 1
0, 11 to the first and second shading correction units 14,
The read density characteristics of the read image data transferred to 20 are corrected line by line so that they match the converted data Z. Here, the function as the density correction means is realized.

Here, during the reading operation of the original image, each of the two kinds of intermediate density data transferred from the first and second reading units 10 and 11 is adjusted so as to match the specified intermediate density data. The density balance of each read image data after shading correction is corrected based on the adjusted intermediate density data.

As a result, for example, by allowing the operator or the like to arbitrarily set the prescribed intermediate density data, the intermediate density data of the first and second reading units 10 and 11 can be changed advantageously in design. it can.

Next, a fourth embodiment of the present invention will be described with reference to FIG. This embodiment shows an application example to a copying machine.

FIG. 14 is a schematic diagram showing the copying machine of this embodiment. The copying machine 50 includes an image reading device 51 that reads an image of a document and an image forming device 52 that forms an image on a recording material based on the read image data read by the image reading device 51.

The image reading device 51 includes an ADF 3, a first reading optical system 4 for reading an image of an original document placed on the contact glass 53 and an image of the surface of the original document conveyed in the original document conveyance path 2. It has a second reading optical system 5 for reading an image on the back surface of a document transported in the document transport path 2. In the present embodiment, the reading position C by the second reading optical system 5 is provided between the density reference plate 8 and the contact glass 53 along the document conveyance path 2.

The image forming apparatus 52 is provided with a recording material path L from a paper feed tray 61 for stacking and holding sheet-like recording materials to a paper discharge tray 63 via an electrophotographic printer engine 62. The printer engine 62 according to the present embodiment transfers a toner image formed around the photoconductor 69 to a recording material by using a charger 64, an exposure device 65, a developing device 66, a transfer device 67, a cleaner 68, and the like, and transfers the toner image. The formed toner image is fixed on the recording material by the fixing device 70.

In addition, although not shown in particular, the copying machine 50
Has a control system for driving and controlling each unit included in the copying machine 50. The control system includes, in addition to the CPU for driving and controlling each unit included in the copying machine 50, the first and second reading units 1 described above.
0, 11, first and second shading correction units 14, 2
0, an image density adjusting unit 16, an image correcting unit 29, and the like. The CPU included in the control system functions similarly to the CPU 25 described above. Further, the control system drives and controls the printer engine 62 and the like based on the density-corrected read image data output from the image correction unit 29.

With such a configuration, when the images on both sides of the original are read by the reading / scanning optical system 54 and the second reading optical system 5, as in the above-described embodiment,
Prior to reading the image of the original, the density reference plate 8 and the density reference roller 9 are read. Then, the printer engine 62 is driven based on the read image data on which the shading correction and the read density characteristic correction have been performed, and an image is formed on the recording material.

As a result, in addition to shading correction, an image based on the read image data in which the density balance between the front and back sides of the document is corrected can be obtained, so that the quality of the image formed on the recording material can be improved. You can

In this embodiment, the printer engine 62 for forming an image on the recording material by the electrophotographic method is used, but the image forming method for forming the read image data on the recording material is the ink jet method. Any known method such as sublimation transfer method may be used.

Further, although an example of application to the copying machine 50 has been shown in the present embodiment, the present invention is not limited to this, and for example,
It is applied to a facsimile machine that forms read image data obtained by reading an image of a document on a recording medium such as paper and outputs the read image data, and sends the read image data read by an image reading device to an external device via a public line network. Good.

[0099]

According to the image reading apparatus of the present invention, the white reference acquired by reading the white reference areas of the first and second white reference members by the first and second reading means, respectively. Based on the data, shading correction is performed on the read image data read by the first and second reading means, respectively, and a plurality of different values of the first and second intermediate density reference members are provided by the first and second reading means. At least one of the first and second intermediate density data obtained by reading the density regions, respectively, is adjusted so that the read density characteristics of the first and second reading means match, and the first after this adjustment, Since the density balance of the read image data after shading correction is adjusted based on the second intermediate density data, the images on both sides of the original are read using two reading means. When taking the deviation in density balance between images due to the difference of the read density characteristics between reading means read data can be prevented from being generated.

According to the second aspect of the present invention, in the image reading apparatus according to the first aspect, the read image after the shading correction is performed based on the first and second intermediate density data obtained at every predetermined timing. Since the density balance of the data is adjusted, even if the reading density characteristics between the two reading means for reading the images on both sides of the document change over time, the reading density characteristics between the reading means due to the change over time of the reading density characteristics It is possible to suppress the occurrence of deviation in the density balance between the read image data due to the difference in

According to the third aspect of the present invention, in the image reading apparatus according to the first or second aspect, the first and second intermediate images obtained each time the original image is read by the first and second reading means. Since the density balance of the read image data after shading correction is adjusted based on the density data, the read density characteristics differ between the first and second reading means, and
Even when the read density characteristics of the respective reading means change with time, the density balance between the read image data is caused by the difference in the read density characteristics of the first and second reading means due to the change of the read density characteristics with time. It is possible to always favorably prevent the occurrence of the deviation in the timing of reading the document image.

According to the invention of claim 4, claim 1,
In the image reading device described in 2 or 3, by adjusting the first and second intermediate density data so as to match the intermediate value between the first intermediate density data and the second intermediate density data, The density balance of the second intermediate density data is evenly distributed, and it is possible to suppress the difference in the quality of the read image data due to the adjustment of the intermediate density data.

According to the invention of claim 5, claim 1,
In the image reading device described in 2 or 3, by adjusting the first and second intermediate density data so as to match the specified intermediate density data, for example, the operator can arbitrarily set the specified intermediate density data. By
The reading density characteristics of the first and second reading means can be changed advantageously in design.

According to the copying machine of the sixth aspect, an image based on the read image data whose density balance is corrected is formed on the recording material. Therefore, the copying machine according to the first aspect is described. An image of high quality can be formed with the effect of the invention.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a part of an image reading apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating an operation of reading a document image.

FIG. 3 is a plan view showing a density reference plate.

FIG. 4 is a development view in which the outer peripheral surface of the density reference roller is cut open along the axial direction.

FIG. 5 is a block diagram schematically showing electrical connection of each unit included in the image reading apparatus.

FIG. 6 is an explanatory diagram showing generation of shading correction data.

FIG. 7 is a plan view showing a relationship between document reading positions.

FIG. 8 is an explanatory diagram showing intermediate read densities read by the first and second reading units.

FIG. 9 is an explanatory diagram showing a conversion table.

FIG. 10 is an explanatory diagram showing intermediate read darkness and converted data read by the first and second reading units according to the second embodiment of the present invention.

FIG. 11 is an explanatory diagram showing a conversion table.

FIG. 12 is an explanatory diagram showing intermediate read density and converted data read by the first and second reading units according to the second embodiment of the present invention.

FIG. 13 is an explanatory diagram showing a conversion table.

FIG. 14 is a schematic view showing a copying machine according to a fourth embodiment of the present invention.

[Explanation of symbols]

1 Image reading device 8 First white reference member, first intermediate density reference member 9 Second white reference member, second intermediate density reference member 10 First reading means 11 Second reading means 50 copiers 51 image reading device 52 image forming apparatus

Continued front page    F term (reference) 5B047 AA01 AB02 BA01 BA07 BB02                       BC05 BC09 BC11 BC14 CB22                       DA03 DC06                 5C072 AA01 BA07 CA02 DA02 DA04                       DA25 EA05 EA07 FB12 LA15                       RA16 UA01 UA17 WA02 XA01                 5C077 LL04 PP02 PP06 PQ18 PQ22                       PQ24 SS01 TT06

Claims (6)

[Claims] 1. A first reading means for reading an image on one side of a document, and a white reference area of a first white reference member provided at a position where the first reading means can read the first reference area. First shading correction means for obtaining white reference data by reading with the reading means, and performing shading correction on the read image data read by the first reading means based on the white reference data; A second reading means for reading the image on the side, and a white reference area by reading the white reference area of the second white reference member provided at a position readable by the second reading means by the first reading means. Second shading correction means that acquires data and performs shading correction on the read image data read by the second reading means based on the white reference data And the first intermediate density data is obtained by reading a plurality of different density regions of the first intermediate density reference member provided at a position readable by the first reading means by the first reading means. And a plurality of different density areas of the second intermediate density reference member provided at a position readable by the second reading means, which are read by the second reading means. A second intermediate density data acquisition means for acquiring second intermediate density data, and adjusting at least one of the first and second intermediate density data acquired by the first and second intermediate density data acquisition means. The intermediate density data adjusting means for matching the read density characteristics of the first and second reading means with the first and second intermediate density data adjusted by the intermediate density data adjusting means. An image reading apparatus comprising: a density correction unit that corrects the density balance of the read image data after the shading correction by the first and second shading correction units. 2. The image reading apparatus according to claim 1, wherein the first and second intermediate density data acquisition means acquires the first and second intermediate density data at predetermined timings. 3. The first and second intermediate density data acquisition means acquires the first and second intermediate density data each time the original image is read by the first and second reading means. The image reading device described in 1 or 2. 4. The intermediate density data adjusting means converts the first and second intermediate density data acquired by the first and second intermediate density data acquiring means into the first intermediate density data and the first intermediate density data. The image reading apparatus according to claim 1, wherein the image reading apparatus is adjusted so as to match an intermediate value with the second intermediate density data. 5. The intermediate density data adjusting means adjusts the first and second intermediate density data acquired by the first and second intermediate density data acquiring means so as to match prescribed intermediate density data. The image reading device according to claim 1, 2 or 3. 6. An image reading apparatus according to claim 1, 2, 3, 4, or 5, and an image forming apparatus for forming an image on a recording material based on read image data read by the image reading apparatus. Copier to do.