JP2002300393A - Shading correction data generator, white shading correction device, image reader, image formation device, shading correction data generating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set an optimum arithmetic coefficient so as to reduce the effect of noise on white reference data such as flaw and dirt or so as to generate shading correction data on small numbers of lines. SOLUTION: An averaging circuit 34 obtains a weighted mean of image data between lines data obtained by reading a white reference board to obtain shading correction data of each pixel. The arithmetic coefficient to obtain the weighted mean is set to coefficient setting registers 27-29 for each of areas 1-n resulting from dividing a read range of image data into a plurality in the subscanning direction. The arithmetic coefficient is selected so as to be smaller when the area resides toward the backside in the subscanning direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shading correction data generating apparatus for generating shading correction data from a white reference, a white shading correction apparatus having the shading correction data generating apparatus, an image reading apparatus and an image forming apparatus, and a white reference. The present invention relates to a shading correction data creating method, a program, and a storage medium for creating shading correction data from a program.

[0002]

2. Description of the Related Art In general, in a digital image reading apparatus, unevenness in sensitivity of each pixel of a CCD line sensor constituting a reading scanning optical system, variation in transmitted light amount in a lens, and unevenness and deterioration of an illumination light source and an optical system are caused. The output from the light receiving element corresponding to each pixel is not always uniform.

[0003] As a means for correcting these, white shading correction is known. In the white shading correction, a white reference (a white reference plate or the like is used) is illuminated prior to actual document reading processing, the reflected light is read, and shading correction data for shading correction of each pixel is obtained. Then, based on the shading correction data, white shading correction of the read image data of the document is performed.

In order to accurately perform white shading correction, it is necessary to reduce noise from read data based on white. For example, in a system having a large amount of noise in read data, accurate shading correction data cannot be generated, and a read image corrected by the shading correction data becomes an output image affected by noise.

In order to solve such a problem, in the technique disclosed in Japanese Patent Application Laid-Open No. H11-289432, shading correction data is generated by performing simple averaging on a plurality of lines based on white, thereby reducing the influence of noise. It is designed to minimize

Further, since the simple averaging has a complicated circuit configuration and is costly, the technique disclosed in Japanese Patent Application Laid-Open No. H11-289432 discloses a weighted average (multiple averaging) that can be realized by a simple and low-cost circuit. It is also conceivable to perform

[0007]

However, the effects of noise cannot be completely eliminated in any averaging process. In particular, when shading correction data is generated from multiple averaging of multiple lines, the effect of the last line is the most affected.Therefore, if there is noise in the last line, the effect of noise on the shading correction data is large. become.

[0008] When the arithmetic coefficient of the weighted averaging is increased, the influence on the shading correction data when noise is present in the last line increases. On the other hand, when the arithmetic coefficient is reduced, a value that can be reliably used as an average value is reduced. Although a large number of lines are required, the member serving as a white reference cannot be increased in size, so that there is a problem that the number of read lines cannot be increased.

An object of the present invention is to make it possible to set an operation coefficient to an optimum one so that the influence of noise can be reduced or shading correction data can be created with a small number of lines. .

SUMMARY OF THE INVENTION It is an object of the present invention to enable an optimal operation coefficient to be set for each white reference reading area.

An object of the present invention is to make the system configuration simple and low-cost.

An object of the present invention is to make it possible to create optimal shading correction data by multiple averaging.

An object of the present invention is to enable shading correction data to be created with a relatively small number of lines while reducing the influence of noise on the last line on the shading correction data.

[0014] An object of the present invention is to provide an image processing method that can be used even when the total number of lines available for generating shading correction data fluctuates.
That is, it is possible to set an optimal operation coefficient.

An object of the present invention is to enable automatic change to an optimum operation coefficient in accordance with the total number of lines of image data obtained by reading the white reference.

An object of the present invention is to provide an optimum method capable of achieving a balance between the reduction of the influence of noise and the generation of shading correction data with a small number of lines in accordance with the total number of lines of image data obtained by reading the white reference. That is, the number of areas can be selected.

An object of the present invention is to reduce the influence of noise and generate shading correction data with a small number of lines in accordance with the total number of lines of image data obtained by reading the white reference for the operation coefficient used for the first line. Is to be able to select the optimal value that can achieve the harmony of

An object of the present invention is to enable an operation coefficient and the number of areas to be optimally set according to an image reading speed based on white.

An object of the present invention is to make it possible to create shading correction data in which the influence of noise such as dust, dirt, and scratches on a white reference plate has been sufficiently removed.

It is an object of the present invention to obtain accurate shading correction data without reducing the number of pixels that can be used for generating shading correction data.

An object of the present invention is to enable accurate creation of shading correction data from which the influence of noise has been sufficiently removed.

[0022]

According to a first aspect of the present invention, there is provided a shading correction data generating apparatus for generating shading correction data used for white shading correction from image data obtained by reading a white reference. Averaging means for obtaining the shading correction data of each pixel by calculating an average of the pixel data, and an arithmetic coefficient used for obtaining the average is set for each position in the sub-scanning direction of the image data. This is a shading correction data creation device.

Therefore, the influence of noise can be reduced or the shading correction can be performed with a small number of lines by setting the operation coefficient used for obtaining the average for each position in the sub-scanning direction of the image data read from the white reference. The operation coefficient can be set to an optimum value so that data can be created.

According to a second aspect of the present invention, in the shading correction data creating apparatus according to the first aspect, the operation coefficient is set for each of a plurality of areas obtained by dividing the read range of the image data in the sub-scanning direction. The present invention is characterized in that it comprises a calculation coefficient setting means.

Therefore, it is possible to set an optimum operation coefficient for each area.

According to a third aspect of the present invention, in the shading correction data creating apparatus according to the second aspect, the operation coefficient setting means sets the operation coefficient to 1/2 ⁿ (n =
1, 2, 3,...) Are set.

Therefore, the operation coefficient of each area can be realized only by the bit shift on the digital circuit, and the system configuration can be simplified and the cost can be reduced.

The invention according to claim 4 is the invention according to claim 2 or 3
In the shading correction data creation device described in the above,
The averaging means is for obtaining a multiple averaging between lines of the image data.

Therefore, optimum shading correction data can be created by multiple averaging.

According to a fifth aspect of the present invention, in the shading correction data creating apparatus according to the fourth aspect, the operation coefficient setting means sets the value such that the value becomes smaller as the area is located rearward in the sub-scanning direction. It is characterized in that an operation coefficient is set.

Therefore, the shading correction data can be generated with a relatively small number of lines while reducing the influence of the noise of the last line on the shading correction data.

According to a sixth aspect of the present invention, in the shading correction data creating apparatus according to any one of the second to fifth aspects, the first operation coefficient set by the operation coefficient setting means is varied. Is provided.

Therefore, even when the total number of lines usable for shading correction data generation fluctuates, it is possible to set an optimum operation coefficient.

According to a seventh aspect of the present invention, in the shading correction data creating apparatus according to any one of the second to fifth aspects, the calculation coefficient setting means is provided in accordance with information indicating a total number of lines of the image data. And a first variable means for varying the operation coefficient set in step (1).

Therefore, it is possible to automatically change the operation coefficient to the optimum calculation coefficient according to the information indicating the total number of lines of the image data obtained by reading the white reference.

According to an eighth aspect of the present invention, in the shading correction data creating apparatus according to any one of the second to seventh aspects, the number of areas is variable according to information indicating the total number of lines of the image data. A second variable means for performing the operation.

Therefore, according to the information indicating the total number of lines of the image data obtained by reading the white reference, an optimal area in which the effect of noise can be reduced and the shading correction data can be created with a small number of lines. You can choose the number.

According to a ninth aspect of the present invention, in the shading correction data creating apparatus according to any one of the second to eighth aspects, the multiple averaging is performed in accordance with information indicating a total number of lines of the image data. A third variable means for varying the operation coefficient used for the first line to be performed is provided.

Therefore, for the operation coefficient used for the first line, it is possible to reduce the influence of noise and generate shading correction data with a small number of lines according to the information indicating the total number of lines of the image data obtained by reading the white reference. It is possible to select an optimal value that can achieve harmony.

The invention according to claim 10 is the invention according to claims 7 to 9
In the shading correction data creation device according to any one of the above, the first, second, or third variable means may use information indicating the total number of lines as information of an image reading speed of the image data. Features.

Therefore, the operation coefficient and the number of areas can be set to optimum values according to the image reading speed based on white.

The eleventh aspect of the present invention relates to the first to first aspects.
0, a shading correction data generating apparatus according to any one of claims 1 to 4, wherein reference data generating means for performing statistical processing on a plurality of lines at the head of the image data in the sub-scanning direction to generate reference data; Comparing means for performing a comparison operation on the image data after the reference data and the reference data; and exclusion for excluding image data after the reference data from a target for generating the shading correction data based on a result of the comparison operation. Means, wherein the averaging means creates the shading correction data based on the image data after the exclusion of the reference data.

Accordingly, it is possible to create shading correction data in which the influence of noise such as dust, dirt, and scratches on the white reference plate has been sufficiently removed.

According to a twelfth aspect of the present invention, in the shading correction data creating apparatus according to the eleventh aspect, the reference data corresponding to the pixel to be excluded is replaced by the reference data instead of the image data excluded. It is characterized in that it comprises a replacement means for creating shading correction data.

Therefore, accurate shading correction data can be obtained without reducing the number of pixels that can be used for shading correction data generation.

According to a thirteenth aspect of the present invention, in the shading correction data creating device according to the eleventh or twelfth aspect, the comparing means subtracts a value obtained by subtracting a preset value from the reference data and the reference data. Wherein the exclusion means performs the exclusion when the image data after the reference data is smaller in the comparison.

Therefore, by comparing a value obtained by subtracting a preset value from the reference data with image data after the reference data, shading correction data from which the influence of noise has been sufficiently removed can be accurately generated. .

The invention according to claim 14 is the invention according to claims 1 to 1.
3. A shading correction data creation device according to any one of the above 3, and white shading correction means for performing white shading correction on image data of a read image of a document using the shading correction data created by the shading correction data creation device. And a white shading correction device.

Therefore, the same operation and effect as the invention according to any one of the first to thirteenth aspects can be obtained.

According to a fifteenth aspect of the present invention, there is provided a photoelectric conversion element for reading an image of a document, and a white shading correction device for performing a white shading correction on the image data of the read image. An image reading apparatus characterized in that:

Therefore, the same operation and effect as the invention according to any one of the first to thirteenth aspects can be obtained.

According to a sixteenth aspect of the present invention, there is provided the image reading apparatus according to the fifteenth aspect, which reads an image of a document, and forms an image on a recording medium based on the read image of the document. Image forming apparatus.

Therefore, the same operation and effect as the invention according to any one of the first to thirteenth aspects can be obtained.

According to a seventeenth aspect of the present invention, in a shading correction data creating method for creating shading correction data used for white shading correction from image data obtained by reading a white reference, an average between lines of the image data is obtained. An averaging step of obtaining the shading correction data of each pixel, wherein an arithmetic coefficient used for obtaining the average is set for each position of the image data in the sub-scanning direction. This is a shading correction data creation method.

Therefore, the effect of noise can be reduced or the shading correction can be performed with a small number of lines by setting the operation coefficient used for obtaining the average for each position in the sub-scanning direction of the image data obtained by reading the white reference. The operation coefficient can be set to an optimum value so that data can be created.

According to an eighteenth aspect of the present invention, in the shading correction data creating method according to the seventeenth aspect, in the averaging step, the read range of the image data is divided into a plurality in the sub-scanning direction as the operation coefficient. It is characterized in that one set for each area is used.

Therefore, it is possible to set an optimum operation coefficient for each area.

According to a nineteenth aspect of the present invention, in the shading correction data creating method according to the eighteenth aspect, the averaging step includes a step of calculating the operation coefficient as 1/2 ⁿ (n =
It is characterized in that a value set as a numerical value represented by (1, 2, 3,...) Is used.

Therefore, the operation coefficient of each area can be realized only by the bit shift on the digital circuit, and the system configuration can be made simple and low cost.

According to a twentieth aspect of the present invention, in the shading correction data creating method according to the eighteenth or nineteenth aspect, the averaging step is for obtaining a multiple averaging between lines of the image data. Features.

Therefore, optimum shading correction data can be created by multiple averaging.

According to a twenty-first aspect of the present invention, in the shading correction data creating method according to the twentieth aspect, in the averaging step, the value of the arithmetic coefficient becomes smaller as the area is located rearward in the sub-scanning direction. It is characterized by using one set as described above.

Therefore, the shading correction data can be generated with a relatively small number of lines while reducing the influence of the noise of the last line on the shading correction data.

The invention according to claim 22 is the invention according to claims 18 to
21. The method for creating shading correction data according to any one of 21., further comprising a first variable step of varying the setting of the operation coefficient prior to the averaging step.

Therefore, even when the total number of lines usable for generating shading correction data fluctuates, it is possible to set an optimum operation coefficient.

According to the twenty-third aspect of the present invention,
21. The shading correction data creation method according to any one of 21., further comprising, prior to the averaging step, a first variable step of varying a setting of the operation coefficient in accordance with information indicating a total number of lines of the image data. It is characterized by comprising.

Therefore, it is possible to automatically change the operation coefficient to the optimum operation coefficient according to the information indicating the total number of lines of the image data obtained by reading the white reference.

The invention according to claim 24 is the invention according to claims 18 to
23. The shading correction data creating method according to any one of 23, further comprising a second variable step of varying the number of areas in accordance with information indicating a total number of lines of the image data prior to the averaging step. It is characterized by becoming.

Therefore, according to the information indicating the total number of lines of the image data obtained by reading the white reference, an optimal area in which the effect of noise can be reduced and the shading correction data can be created with a small number of lines. You can choose the number.

The invention according to claim 25 is the invention according to claims 18 to
24. The shading correction data generating method according to any one of the above 24, wherein the arithmetic coefficient used for a first line on which the multiple averaging is performed in accordance with information indicating a total number of lines of the image data prior to the averaging step Is varied.

Therefore, for the operation coefficient used for the first line, the effect of noise can be reduced and the shading correction data can be generated with a small number of lines in accordance with the information indicating the total number of lines of image data obtained by reading the white reference. It is possible to select an optimal value that can achieve harmony.

The invention according to claim 26 is the invention according to claims 23 to
25. In the shading correction data creation method according to any one of 25, the first, second or third variable step uses information indicating the total number of lines as information on an image reading speed of the image data. It is characterized by.

Therefore, the operation coefficient and the number of areas can be set to the optimum values according to the image reading speed based on white.

According to a twenty-seventh aspect of the present invention, in the computer readable program for causing a computer to execute shading correction data for use in white shading correction from image data obtained by reading a white reference, The computer calculates and executes an averaging process of obtaining the shading correction data of each pixel by calculating an average between the pixels, and an arithmetic coefficient used in obtaining the average is set for each position in the sub-scanning direction of the image data. It is a program characterized by using what has been done.

Therefore, the effect of noise can be reduced or the shading correction can be performed with a small number of lines by setting the operation coefficient used for obtaining the average for each position in the sub-scanning direction of the image data obtained by reading the white reference. The operation coefficient can be set to an optimum value so that data can be created.

According to a twenty-eighth aspect of the present invention, in the program according to the twenty-seventh aspect, in the averaging process, the reading range of the image data is set as the operation coefficient for each of a plurality of divided areas in the sub-scanning direction. It is characterized by using what has been done.

Therefore, it is possible to set an optimum operation coefficient for each area.

According to a twenty-ninth aspect of the present invention, in the program according to the twenty-eighth aspect, the averaging process is performed by using a numerical value represented by 1/2 ⁿ (n = 1, 2, 3,...) As the operation coefficient. It is characterized by using what is set as.

Therefore, the operation coefficient of each area can be realized only by the bit shift on the digital circuit, and the system configuration can be simplified and the cost can be reduced.

According to a thirtieth aspect of the present invention, in the program according to the twenty-eighth or twenty-ninth aspect, the averaging process is for obtaining a multiple averaging between the lines of the image data.

Therefore, optimal shading correction data can be created by multiple averaging.

According to a thirty-first aspect of the present invention, in the program according to the thirty-third aspect, the averaging process is set such that the value of the operation coefficient is smaller as the area is located rearward in the sub scanning direction. Is used.

Therefore, shading correction data can be generated with a relatively small number of lines while reducing the influence of the noise of the last line on the shading correction data.

The invention according to claim 32 is the invention according to claims 28 to
31. The program according to claim 31, wherein a setting of the operation coefficient is changed prior to the averaging process.
Characterized by causing a computer to execute the variable processing.

Therefore, even when the total number of lines that can be used for generating shading correction data fluctuates, it is possible to set an optimum operation coefficient.

The invention according to claim 33 is the invention according to claims 28 to
31. The program according to any one of 31), further comprising causing a computer to execute a first variable process of changing a setting of the operation coefficient in accordance with information indicating a total number of lines of the image data before the averaging process. It is characterized by the following.

Therefore, it is possible to automatically change the operation coefficient to the optimum operation coefficient according to the information indicating the total number of lines of the image data obtained by reading the white reference.

The invention according to claim 34 is the invention according to claims 28 to
33. The program according to any one of 33, wherein the program causes a computer to execute a second variable process of changing the number of areas according to information indicating a total number of lines of the image data before the averaging process. I do.

Therefore, according to the information indicating the total number of lines of the image data obtained by reading the white reference, the optimum area in which the influence of noise can be reduced and the shading correction data can be created with a small number of lines can be harmonized. You can choose the number.

The invention according to claim 35 is the invention according to claims 28 to
34. The program according to any one of 34, wherein, prior to the averaging processing, the calculation coefficient used for a first line on which the multiple averaging is performed is varied according to information indicating a total number of lines of the image data. A third feature is that the variable processing is executed by a computer.

Therefore, as for the operation coefficient used for the first line, it is possible to reduce the influence of noise and generate shading correction data with a small number of lines according to the information indicating the total number of lines of the image data obtained by reading the white reference. It is possible to select an optimal value that can achieve harmony.

The invention according to claim 36 is the invention according to claims 33 to
35. The program according to any one of 35, wherein the first, second, or third variable processing uses information indicating the total number of lines as information on an image reading speed of the image data. .

Therefore, the operation coefficient and the number of areas can be set to the optimum values according to the image reading speed based on white.

The invention according to claim 37 is the invention according to claims 33 to
35. A storage medium storing the program according to any one of 35.

Therefore, the same operations and effects as those of the invention according to any one of claims 33 to 35 are obtained.

[0096]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment of the Invention] One embodiment of the present invention will be described as a first embodiment of the present invention.

FIG. 1 is a longitudinal sectional view showing the entire configuration of the image reading apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the image reading apparatus 1 is of a flat bed type, and includes a contact glass 3 on which an original 2 is placed, a halogen lamp 4 for exposing the original 2 and a first reflection mirror 5. 1 carriage 6, a second carriage 9 including a second reflection mirror 7 and a third reflection mirror 8, and a CCD linear image sensor (hereinafter simply referred to as C
A lens unit 11 for forming an image on the CCD 10, a white reference plate 12 serving as a white reference for white shading correction, and a stepping motor 14 for driving the first carriage 6 and the second carriage 9. Have. The CCD 10 is provided on a sensor board substrate 13. The halogen lamp 4, the first, second, and third reflecting mirrors 5, 7, 8 and the lens unit 11 constitute a scanning optical system.

The halogen lamp 4 irradiates light at a certain angle with respect to the reading surface of the white reference plate 12 and the contact glass 3, and the light reflected by the white reference plate 12 or the document 2 is first and second.
Second and third reflection mirrors 5, 7, 8 and lens unit 1
The light enters the CCD 10 via 1. The CCD 10 outputs a voltage corresponding to the amount of incident light as analog image data. The first and second carriages 6 and 9 are moved in the sub-scanning direction by the driving of the stepping motor 14 while keeping the distance between the reading surface of the document 2 and the CCD 10 constant, and expose and scan the document 2.

FIG. 2 is a timing chart for explaining gate signals used in the image reading operation of the image reading apparatus 1. That is, the shading gate is connected to the white reference plate 1.
2 reading range (shading correction data generation area)
When the shading gate is at the L level, the image data output from the CCD 10 is fetched. The gate signal XFGATE indicates the reading range of the document 2 (document reading area), and the gate signal XFGATE
Is at the L level, the image data output from the CCD 10 is captured. Whether the output image data of the CCD 10 is that of the white reference plate 12 or that of the original 2 is also determined from the state of the shading gate and the gate signal XFGATE.

FIG. 3 is a block diagram of the white shading correction device 21 provided in the image reading device 1. The white shading correction device 21 is configured in a predetermined ASIC. As shown in FIG. 3, the analog image data output from the CCD 10 is subjected to signal processing such as waveform shaping, sample hold, and amplification by a signal processing circuit 22, and A
After being converted into digital image data by the / D converter 23, the digital image data is output to the white shading correction device 21.

In the shading correction device 21,
A data input path 24, an input path for digital image data after A / D conversion, a shading correction data input path 25, and a reference data input path 38 are provided. The selector 39 includes a shading gate and a gate signal XFGA.
The TE and the count value (described later) output from the line number counter 32 are input, and the digital image data output from the A / D converter 23 is selectively transmitted to each path 2 as described later.
4, 25, 38.

Further, there are provided coefficient setting registers 27 to 29, an area number setting register 30, and an initial value setting register 31 which can set a calculation coefficient of a multiple averaging and a number of areas to be described later. A line synchronization signal is input to the line number counter 32, and counts the number of the current line. The set values of the registers 27 to 31 and the count value of the line number counter 32 are input to a coefficient selection circuit 33. The averaging circuit 34 performs shading correction data in accordance with the output from the coefficient selection circuit 33, as described below, to generate shading correction data. This implements an averaging means and an averaging step. The above registers 27 to 31, line number counter 32, coefficient selection circuit 33, and averaging circuit 34
Thus, a shading correction data creation device 35 is configured.

This shading correction data creation device 3
5 will be described.

The reading range of the white reference plate 12 is divided into n areas in advance, as shown in FIG. White reference plate 1
The position of each of the reading ranges 2 in each of the areas 1 to n is determined by the count value output from the line number counter 32,
The coefficient selection circuit 33 determines from the number of areas set in the area number setting register 30. Further, the coefficient selection circuit 33 determines which area the current area is, selects an operation coefficient corresponding to the area from the values set in the coefficient setting registers 27 to 29, and outputs it to the averaging circuit 34. I do. Area number setting register 30, coefficient setting register 2
7 to 29, the setting of each value in the initial value setting register 31 is C
PU26 performs this. Arithmetic coefficient setting means is realized by coefficient setting registers 27 to 29, and first variable means and first variable process are realized by setting numerical values in coefficient setting registers 27 to 29 by CPU 26. The second variable means and the second variable step are realized by setting the numerical value in the area number setting register 30 by the CPU 26. CPU26
The third variable means and the third variable step are realized by setting a numerical value in the initial value setting register 31 according to (3).

When the shading gate goes low, reading of the white reference plate 12 is started in the first area 1, and the read image data of the white reference plate 12 is input to the averaging circuit 34 from the shading correction data input path 25 by the selector 39. Is entered. The averaging circuit 34 calculates the first line by the following equation for each pixel. The initial value m for determining the operation coefficient “(m−1) / m” at this time refers to the value of the initial value setting register 31.

Current shading correction data = ((m−
1) / m) × Current read image data In this example, the initial value m = 4, and the result is as follows.

Current shading correction data = (3/4)
× Current read image data From the second line, multiple addition averaging processing is performed for each pixel by the following formula (operation coefficient k1 = 1/4).

Current shading correction data = (3/4)
X previous shading correction data + (1/4) x current read image data Next, reading of the area 2 is started, and the image data from the shading correction data input path 25 is
In step 4, the multiple addition averaging process (operation coefficient k2
= 1/8).

Current shading correction data = (7/8)
X previous shading correction data + (1/8) x current read image data The same multiple addition and averaging processing as in area 2 is also performed in the intermediate area below area 2, and after this intermediate area up to the last area n For the area, the following multiple addition averaging processing (operation coefficient k3 = 1/16) is performed.

Current shading correction data = (15/1)
6) × previous shading correction data + (1/16) × current read image data As described above, the average value of each pixel when the averaging process of the last line of area n is completed is the FIFO (shading correction data Dsh). (First-in first-out circuit) 36.

In the section where the gate signal XFGATE in FIG. 2 is at the L level, when the image of the original 2 is read, the read image data Di of the original 2 from the data input path 24 by the selector 39 and the pixel data from the FIFO 36 The shading correction data Dsh is output, and is processed by a look-up table method based on an algorithm of an arithmetic expression for shading correction stored in the ROM 37 in advance, and the read image data Di is converted to shading correction data Dsh. Based on the white shading correction, the image data Do of the corrected document 2 is generated. This implements white shading correction means.

The image data Do after the white shading correction is subjected to image processing such as black shading correction, MTF correction, filter processing, scaling processing, γ conversion, and background removal processing of the original 2. The processed image data is output from the image reading device 1. Since the specific contents of these processes are well known, detailed description will be omitted.

As is clear from the above description, the magnitude of each value of the operation coefficients k1 to k3 is set so as to be smaller in the areas 1 to n as they are located rearward in the sub-scanning direction.

That is, in the first area 1 in the shading correction data generation area, a period in which a large arithmetic coefficient is used to perform multiple averaging and the reliability of the average value is increased with a small number of lines.

In an intermediate area from area 2, area 1
The calculation coefficient is smaller than the calculation coefficient of the weighted averaging, and the influence on the shading correction data when the noise is present in the last line is set to be less than the calculation in the area 1.

From the area after the intermediate area to the area n, an operation coefficient smaller than the operation coefficient of the double averaging of the area 2 is used to determine the influence on the shading correction data when there is noise in the last line. The period is set to be less than the calculation of.

Therefore, the optimum shading correction data Dsh can be generated with a relatively small number of lines while reducing the influence of the noise of the last line on the shading correction data Dsh. The operation coefficients k1 to k3 can be set.

Each value of the operation coefficients k1 to k3 is 1 /
2 ⁿ (n = 1, 2, 3,...), Whereby the operation coefficients k1 to k3 of the areas 1 to n can be set only by the bit shift on the coefficient setting registers 27 to 29. It is also possible to make the system configuration simple and low-cost.

The CPU 26 calculates the operation coefficients k1 and k set in the coefficient setting registers 27 to 29 in accordance with the image scanning speed currently set by the image reading apparatus 1.
2. Change the value of k3. The reading scanning speed is information indicating how many lines the white reference plate 12 is read.

When the scanning speed is high, the number of lines is small.
To increase the reliability of the average value with a small number of lines above,
The setting is made so that multiple averaging is performed with large operation coefficients k1 to k3. When the scanning speed is low, the number of lines is large. To minimize the influence on the shading correction data when there is noise in the last line, the multiple averaging is performed with small arithmetic coefficients k1 to k3. Set.

For example, the reading scanning speed mode can be set in the image reading device 1 in two stages of “high speed” and “low speed”, and in the above-mentioned example (the calculation coefficients k1, k2, and k3 are each 1).
/ 4, 1/8, 1/16) in the “high-speed” mode, the operation coefficients k1, k2,
It is conceivable that k3 is set to 1/8, 1/16, and 1/32, respectively.

The CPU 26 operates in the image reading device 1.
The value of the number of areas to be set in the area number setting register 30 is changed in accordance with the reading scanning speed of the image which is currently set. That is, when the reading scanning speed is high, the number of lines is small, and when the number of lines in each area is equal, it is not possible to take many areas, so a small number of areas is set. When the scanning speed is low, the number of lines is large, so that a large area can be taken. Therefore, a large area number is set.

Therefore, it is possible to select the optimum number of areas in which the influence of noise can be reduced and the shading correction data Dsh can be created with a small number of lines in accordance with the scanning speed.

Further, the CPU 26 controls the image reading speed of the image currently set by the image reading apparatus 1 in accordance with the scanning speed.
The value of the initial value m set in the initial value setting register 31 is changed. That is, when the scanning speed is high, the number of lines is small, and the initial value m is reduced so that the operation coefficient “(m−1) / m” is reduced so as not to be strongly affected by the noise of the first line. . When the scanning speed is low, the number of lines is large, and the initial value m is increased so that the operation coefficient “(m−1) / m” is increased so as to quickly approach a reliable average value.

By the way, the coefficient selection circuit 33 determines the predetermined number of lines L (L = 1, 2, 2) from the point in time when the shading gate becomes L level and reading of the white reference plate 12 starts.
3,...), That is, the first L lines of the read image data of the white reference plate 12 in the sub-scanning direction. In this example,
When the multiple averaging is obtained as described above up to the last line of the range of the area 1 (reference data generation area) (the range of the area 1 can be determined by, for example, the count value output from the line number counter 32). The output value is output to the FIFO 40 as reference data and stored. Therefore, area 1
The statistical processing is performed by calculating the multiple averaging up to the last line in the range, thereby realizing the reference data generating means.

The selector 39 outputs the read image data of the white reference plate 12 only to the shading correction data input path 25 up to the area 1 (reference data generation area). Not only the input path 25 but also the reference data input path 3
The read image data of the white reference plate 12 is also output to the subtraction / comparison circuit 41 via the reference numeral 8.

In the subtraction / comparison circuit 41, the reference data stored in the FIFO 40 and the reference data input path 38
Based on the image data (data for generating shading correction data) of area 2 and subsequent areas input from, the following comparison operation processing is performed. This implements comparison means.

That is, a value set in advance from the reference data
NOREF is subtracted, and this “reference data−NOREF” is compared with shading correction data generation data for each pixel.

If the relationship of shading correction data generation data <reference data−NOREF (1) is satisfied, the corresponding shading correction data generation data input to the averaging circuit 34 is excluded for each pixel. I do. As a result, the data of the excluded pixels are not subjected to the calculation for obtaining the multiple averaging as described above. Therefore, an exclusion unit is realized.

At this time, because of the relationship of the expression (1), for the excluded pixels, the reference data obtained by the comparison of the expression (1) is output to the averaging circuit 34 instead. Replace with This implements replacement means.

As described above, with respect to the read image data of the white reference plate 12, a plurality of (L) lines at the head (the range of area 1 as described above) are statistically created, and the reference data after the reference data (area 2), the pixels affected by dust, dirt, flaws, etc. can be excluded, so that noise can be sufficiently removed from the white shading correction data Dsh.

In this case, pixels for which shading correction data generation data is not output are replaced with reference data instead, so that the number of pixels that can be used to generate shading correction data Dsh is not reduced.
Accurate shading correction data can be obtained.

When comparison is made between the reference data and the image data after the reference data, a predetermined value NOREF is subtracted from the reference data in advance, and the comparison is performed. The shading correction data Dsh can be accurately obtained by performing the adjustment.

[Second Embodiment of the Invention] Another embodiment will be described as a second embodiment of the present invention.

The image reading apparatus 1 according to the second embodiment is different from the image reading apparatus according to the first embodiment in that
1 is not provided, and instead, white shading correction having the same contents as in the first embodiment is performed by the CPU 2.
6 is based on a predetermined white shading correction program, thereby realizing a shading correction data creation device and a white shading correction device. Other points are the same as those in the first embodiment,
The same reference numerals as those in FIGS. 1 to 3 are used, and the detailed description is omitted.

In the following, the contents of the white shading correction processing performed by CPU 26 based on the white shading correction program will be described.

First, FIG. 7 is a block diagram showing the electrical connection of the control system of the image reading apparatus 1. As shown in FIG. 7, the RA connected to the CPU 26 via the bus 76.
The MPU controls the IPU (Image Pr
storing the shading correction data obtained by the result of the later-described calculation by the operating unit (74). The ROM 71 serving as a storage medium is a nonvolatile memory such as a flash memory, and stores a shading correction data creation program, a white shading correction program, and the like. In addition,
The program stored in the ROM 71 is the CPU 26
Can be rewritten into a program downloaded from an external device (not shown) via the I / O port 73. In addition to the above restrictions, the CPU 26 obtains information indicating the degree of deterioration of the scanning optical system and calculates the value of NOREF.

The sensor board substrate (SBU: Sensor Proce
The ssing unit 13 is a board on which the CCD 10, the signal processing circuit 22, and the A / D converter 23 are mounted.
Reference numeral 4 denotes a ROM as a storage medium under the control of the CPU 26.
A shading correction data creation program and a white shading sig correction program are called from the (flash memory) 71 to perform shading correction data creation and white shading correction calculations. When shading correction data is created, the value of NOREF is set by the CPU 26.

FIG. 4 is a flowchart for explaining the processing procedure of the white shading correction processing. As shown in FIG. 4, when a series of image reading operations is started (Y in step S1), the CPU 26 determines whether the reading scan speed mode setting is the “high speed” mode or the “low speed” mode (step S2). ), Operation coefficients k1 to k3, number of areas n and initial value m
Are switched in the same manner as in the first embodiment, and R
AM 72 is set (steps S3 and S4). Steps S2, S3, and S4 realize first, second, and third variable means, first, second, and third variable steps, first, second, and third variable processing, and operation coefficient setting means. are doing.

Then, shading correction data is created as follows. That is, by using the set operation coefficient k1, similarly to the above, until the last line of the area 1 (reference data generation area) (the initial value m set as described above is applied to the first line). A multiple averaging is obtained and used as reference data (step S5). Step S
5 implements reference data creation means. Note that the range of each area is determined by the CPU 26 based on the count value of the line synchronization signal and the count value.

Next, a comparison operation based on the above equation (1) is performed on the reference data obtained in step S5 and the image data of each line after area 2 (step S5).
6), shading correction data generation data <reference data−
If NOREF is satisfied (Y in step S6), area 2
The subsequent image data of each line is excluded for each pixel (step S7), and replaced with the reference data that has been subjected to the comparison operation (step S8). Step S6 implements comparison means, step S7 implements exclusion means, and step S8 implements replacement means. Then, according to the area of the line, the set operation coefficient k2 or k3 is selected (step S9), and the multiple averaging is obtained using the operation coefficient k2 or k3 as described above (step S10). The averaging means, the averaging process, and the averaging process are realized by step S10.

When the multiple averaging is obtained up to the last line of the area n (Y in step S11),
The finally obtained multiple averaging value is stored as shading correction data in a predetermined RAM or the like (step S
12).

When reading of the original 2 is started (Y in step S13), the read image data of the original 2 is read line by line using the shading correction data in the same manner as in the first embodiment. White shading correction is performed (step S14). When the white shading correction is completed up to the last line of the document 2 (step S1
(5) Y), a series of processing ends.

According to the image reading apparatus 1 described above, the shading correction is performed with a relatively small number of lines while reducing the influence of the noise of the last line on the shading correction data Dsh, as in the first embodiment. It is possible to set the optimal operation coefficients k1 to k3 for each of the areas 1 to n so that the data Dsh can be created.

Further, it is possible to set the operation coefficients k1 to k3 of the optimal size according to the reading scanning speed (steps S3 and S4).

Further, it is possible to select the optimum number n of areas in which the influence of noise can be reduced and the shading correction data Dsh can be created with a small number of lines in accordance with the scanning speed (step). S3, S4).

Further, the value of the initial value m can be changed in accordance with the scanning speed for reading the image (steps S3 and S3).
4).

Regarding the read image data of the white reference plate 12,
A comparison is made between the reference data created by statisticizing the plurality of (L) lines at the top (the range of area 1 as described above) and the image data subsequent to the reference data (area 2 and subsequent), and dust, dirt, Since pixels affected by flaws or the like can be excluded (steps S5, S6, S7), noise can be sufficiently removed from the white shading correction data Dsh.

In this case, pixels for which shading correction data generation data is not output are replaced with reference data instead (step S8), so that the accuracy can be reduced without reducing the number of pixels that can be used for generating shading correction data Dsh. Good shading correction data can be obtained.

When the reference data is compared with the image data after the reference data (step S6), the reference data is subtracted from the reference data by a predetermined value NOREF in advance, and the comparison is performed. Adjust to an appropriate value,
Accurate shading correction data Dsh can be obtained accurately.

The shading correction data creation program may be stored in the ROM 71 in advance,
At the time of product shipment, the conventional shading correction data creation program that creates shading correction data from the average value of data for multiple lines reading the white reference
Stored in M71.
A shading data creation program according to this embodiment, which is stored in a storage medium such as a D-ROM,
A program such as a (Personal Computer) may be read once by a readable external device, and the read program may be downloaded to the ROM 71 under the control of the CPU 26 via the I / O port 73.

[Embodiment 3] Another embodiment will be described as Embodiment 3 of the present invention.

FIG. 5 is a block diagram showing a schematic configuration of a digital copying machine 51 according to the third embodiment. As shown in FIG. 5, the digital copying machine 51 implements the image forming apparatus of the present invention, and includes an image reading device 1, a printer engine 52, a microcomputer for controlling the entire digital copying machine 51, and the like. And a control unit 53.

Since the configuration of the image reading apparatus 1 is the same as that of the first or second embodiment, the same reference numerals as those of the first and second embodiments are used below, and the detailed description is omitted.

The printer engine 52 forms an image on a recording medium such as paper. The printing method is an electrophotographic method, an ink jet method, a sublimation type thermal transfer method, a silver halide photographic method, a direct thermal recording method. Various types of well-known methods such as a method and a fusion-type thermal transfer method can be used.

The control section 53 controls the image reading device 1 and the printer engine 52 to read the original 2 with the image reading device 1 and forms an image with the printer engine 52 based on the read image data.

Therefore, according to the digital copying machine 51, the same operation and effect as those of the first and second embodiments can be obtained for the white shading correction of the image data.

[Embodiment 4] Another embodiment will be described as Embodiment 4 of the present invention.

FIG. 6 is a block diagram showing a schematic configuration of a printing system 61 according to the fourth embodiment. As shown in FIG. 6, the printing system 61 implements the image forming apparatus of the present invention. The printing system 61 is connected to the image reading apparatus 1 and a PC (Pers) capable of performing various types of information processing based on a given program.
The image reading apparatus 1 and the printer 63 are connected to the information processing apparatus 62 via a predetermined interface.

Since the configuration of the image reading apparatus 1 is the same as that of the first or second embodiment, the same reference numerals as those of the first and second embodiments are used below, and the detailed description is omitted.

The printer 63 forms an image on a recording medium such as paper. The printing method is an electrophotographic method, an ink jet method, a sublimation type thermal transfer method, a silver halide photographic method, a direct thermal recording method. Various known methods such as a fusion-type thermal transfer method can be used.

The information processing device 62 stores driver software for driving the image reading device 1 and the printer 63, and controls the image reading device 1 and the printer 63 based on the driver software by operating the information processing device 62. Then, the document 2 can be read by the image reading device 1 and an image can be formed by the printer engine 52 based on the read image data.

Therefore, according to the printing system 61, the same operation and effect as those of the first and second embodiments can be achieved for the white shading correction of the image data.

[0164]

According to the first aspect of the present invention, the influence of noise is reduced by setting an arithmetic coefficient used for obtaining an average for each position in the sub-scanning direction of image data obtained by reading the white reference. Alternatively, the operation coefficient can be set to an optimum value so that shading correction data can be created with a small number of lines.

According to a second aspect of the present invention, in the shading correction data creating apparatus according to the first aspect, it is possible to set an optimal operation coefficient for each area.

According to a third aspect of the present invention, in the shading correction data creating apparatus according to the second aspect, the operation coefficient of each area can be realized only by the bit shift on the digital circuit, and the system configuration is simplified. The cost can be reduced.

The invention according to claim 4 is the invention according to claim 2 or 3
In the shading correction data creation device described in the above,
Optimum shading correction data can be created by multiple averaging.

According to a fifth aspect of the present invention, in the shading correction data generating apparatus according to the fourth aspect, the shading correction data is generated with a relatively small number of lines while reducing the influence of the noise of the last line on the shading correction data. Can be created.

According to a sixth aspect of the present invention, in the shading correction data generating apparatus according to any one of the second to fifth aspects, even when the total number of lines usable for shading correction data generation changes. It is possible to set an optimal operation coefficient.

According to a seventh aspect of the present invention, in the shading correction data creating apparatus according to any one of the second to fifth aspects, according to the information indicating the total number of lines of image data obtained by reading the white reference, It can be automatically changed to the optimal calculation coefficient.

According to an eighth aspect of the present invention, in the shading correction data generating apparatus according to any one of the second to seventh aspects, according to the information indicating the total number of lines of image data obtained by reading the white reference. It is possible to select an optimal number of areas in which the effect of noise can be reduced and the generation of shading correction data with a small number of lines can be harmonized.

According to a ninth aspect of the present invention, in the shading correction data creating apparatus according to any one of the second to eighth aspects, the calculation coefficient used for the first line is calculated based on the total of the image data obtained by reading the white reference. According to the information indicating the number of lines, it is possible to select an optimal value that can achieve a balance between the reduction of the influence of noise and the generation of shading correction data with a small number of lines.

The invention according to claim 10 is the invention according to claims 7 to 9
In the shading correction data creation device according to any one of the above, the calculation coefficient and the number of areas can be set to be optimum according to the image reading speed based on white.

The eleventh aspect of the present invention relates to the first to first aspects.
0, the shading correction data generating apparatus according to any one of the above aspects can generate shading correction data from which the influence of noise such as dust, dirt, and scratches on the white reference plate has been sufficiently removed.

According to the twelfth aspect of the present invention, in the shading correction data generating apparatus according to the eleventh aspect, accurate shading correction data can be obtained without reducing the number of pixels usable for shading correction data generation. .

According to a thirteenth aspect of the present invention, in the shading correction data creating apparatus according to the eleventh or twelfth aspect, a value obtained by subtracting a preset value from the reference data is compared with image data after the reference data. This makes it possible to accurately create shading correction data from which the influence of noise has been sufficiently removed.

The invention according to claim 14 is the invention according to claims 1-1.
The same operation and effect as the invention described in any one of the third aspect can be obtained.

The invention according to claim 15 provides the invention according to claims 1 to 1
The same operation and effect as the invention described in any one of the third aspect can be obtained.

The invention according to claim 16 is the invention according to claims 1-1.
The same operation and effect as the invention described in any one of the third aspect can be obtained.

According to the seventeenth aspect of the present invention, the effect of noise is reduced by setting the operation coefficient used for obtaining the average for each position in the sub-scanning direction of the image data obtained by reading the white reference. In addition, it is possible to set the operation coefficient to an optimum value so that shading correction data can be created with a small number of lines.

According to the eighteenth aspect of the present invention, in the shading correction data creating method according to the seventeenth aspect, it is possible to set an optimal operation coefficient for each area.

According to a nineteenth aspect of the present invention, in the shading correction data creating method according to the eighteenth aspect, the operation coefficient of each area can be realized only by the bit shift on the digital circuit, and the system configuration is simplified. The cost can be reduced.

According to the twentieth aspect, optimal shading correction data can be created by multiple averaging.

According to a twenty-first aspect of the present invention, in the shading correction data creation method according to the twentieth aspect, the shading correction data is generated with a relatively small number of lines while reducing the influence of noise of the last line on the shading correction data. Can be created.

The invention according to claim 22 is the invention according to claims 18 to
21. In the shading correction data creation method according to any one of 21., even when the total number of lines that can be used for shading correction data generation fluctuates, it is possible to set an optimal calculation coefficient.

The invention according to claim 23 is the invention according to claims 18 to
21. The shading correction data creation method according to any one of 21., wherein the calculation coefficient can be automatically changed to an optimal calculation coefficient in accordance with information indicating the total number of lines of image data obtained by reading the white reference.

The invention according to claim 24 is the invention according to claims 18 to
23. The method of generating shading correction data according to any one of 23, wherein the effect of noise is reduced and the shading correction data is generated with a small number of lines in accordance with the information indicating the total number of lines of the image data obtained by reading the white reference. It is possible to select the optimal number of areas that can achieve harmony with the above.

The twenty-fifth aspect of the present invention relates to the eighteenth aspect.
24. In the shading correction data creation method according to any one of 24, the effect of noise is reduced and reduced for the operation coefficient used for the first line in accordance with information indicating the total number of lines of image data obtained by reading the white reference. It is possible to select an optimal value that can be harmonized with the generation of shading correction data based on the number of lines.

The invention according to claim 26 is the invention according to claims 23 to
In the shading correction data creation method according to any one of the twenty-fifth, the calculation coefficient and the number of areas can be set to optimum values in accordance with the white-based image reading speed.

According to the twenty-seventh aspect of the present invention, the effect of noise is reduced by setting the operation coefficient used for obtaining the average for each position in the sub-scanning direction of the image data obtained by reading the white reference. In addition, it is possible to set the operation coefficient to an optimum value so that shading correction data can be created with a small number of lines.

According to a twenty-eighth aspect of the present invention, in the program according to the twenty-seventh aspect, it is possible to set an optimal operation coefficient for each area.

According to a twenty-ninth aspect of the present invention, in the program according to the twenty-eighth aspect, the operation coefficient of each area can be realized only by a bit shift on a digital circuit.
The system configuration can be made simple and low-cost.

According to a thirtieth aspect of the present invention, in the program according to the twenty-eighth or twenty-ninth aspect, optimal shading correction data can be created by multiple averaging.

According to a thirty-first aspect of the present invention, in the program according to the thirty-third aspect, the shading correction data is created with a relatively small number of lines while reducing the influence of noise of the last line on the shading correction data. Can be.

The invention according to claim 32 is the invention according to claims 28 to
In the program according to any one of the items 31, even when the total number of lines that can be used for generating shading correction data changes, it is possible to set an optimal operation coefficient.

The invention according to claim 33 is the invention according to claims 28 to
In the program according to any one of the first to third aspects, it is possible to automatically change the operation coefficient to an optimal operation coefficient in accordance with the information indicating the total number of lines of the image data obtained by reading the white reference.

The invention according to claim 34 is the invention according to claims 28 to
33. The program according to any one of 33, wherein the effect of noise is reduced and the shading correction data is created with a small number of lines in accordance with the information indicating the total number of lines of the image data obtained by reading the white reference. It is possible to select the optimal number of areas that can be used.

The invention according to claim 35 is the invention according to claims 28 to
34, the calculation coefficient used for the first line is reduced according to the information indicating the total number of lines of the image data obtained by reading the white reference, reducing the influence of noise and reducing the number of lines. It is possible to select an optimal value that can be harmonized with the creation of the shading correction data.

The invention according to claim 36 is the invention according to claims 33 to
35. The program according to any one of 35, wherein the calculation coefficient and the number of areas can be set to optimum values according to the image reading speed based on white.

The invention according to claim 37 is the invention according to claims 33 to
According to the thirty-fifth aspect, the same operation and effect as those of the invention described in any one of the thirty-fifth aspects are exerted.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing the entire configuration of an image reading apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a timing chart illustrating a gate signal used in an image reading operation by the image forming apparatus.

FIG. 3 is a block diagram illustrating a circuit configuration of a white shading correction device of the image forming apparatus.

FIG. 4 is a flowchart illustrating a white shading correction process performed by an image reading apparatus according to a second embodiment of the present invention;

FIG. 5 is an explanatory diagram illustrating an overall configuration of a digital copying machine according to a third embodiment of the present invention;

FIG. 6 is an explanatory diagram illustrating an overall configuration of a printing system according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram illustrating electrical connection of a control system of the image reading apparatus according to the second embodiment of the present invention;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image reading device 2 document 10 photoelectric conversion element 12 white reference 21 white shading correction device 27 calculation coefficient setting device 28 calculation coefficient setting device 29 calculation coefficient setting device 35 shading correction data creation device 51 image forming device 61 image forming device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Eie Kisara 3-1 Shinmei-do, Meiji, Shimada-cho, Shibata-cho, Shibata-gun, Miyagi F-term in Tohoku Ricoh Co., Ltd. 5B047 AA01 BA02 CA07 CB07 CB09 CB11 CB16 DA04 DC01 DC20 5C072 AA01 BA08 FB12 RA16 UA03 UA12 UA14 UA20 XA01 5C077 LL02 LL04 MM27 PP06 PP44 PP46 PP48 PP62 PP68 PQ08 PQ17 PQ20 SS01 TT01

Claims (37)

[Claims] 1. A shading correction data generating apparatus for generating shading correction data used for white shading correction from image data obtained by reading a white reference, wherein the shading correction data of each pixel is obtained by obtaining an average between lines of the image data. The shading correction data generating apparatus is characterized in that an averaging means for obtaining the average is provided, and an arithmetic coefficient used for obtaining the average is set for each position of the image data in the sub-scanning direction. 2. The image processing apparatus according to claim 1, further comprising an operation coefficient setting unit configured to set the operation coefficient for each of a plurality of areas obtained by dividing the reading range of the image data in a sub-scanning direction. Shading correction data creation device. 3. The arithmetic coefficient setting unit according to claim 2, wherein the arithmetic coefficient setting unit sets a numerical value represented by 1/2 ⁿ (n = 1, 2, 3,...) As the arithmetic coefficient. Shading correction data creation device. 4. The shading correction data generating apparatus according to claim 2, wherein the averaging means calculates a multiple averaging between the lines of the image data. 5. The shading correction according to claim 4, wherein the calculation coefficient setting means sets the calculation coefficient such that the value becomes smaller as the area is located rearward in the sub-scanning direction. Data creation device. 6. The shading correction according to claim 2, further comprising a first variable unit that varies the operation coefficient set by the operation coefficient setting unit. Data creation device. 7. The image processing apparatus according to claim 1, further comprising a first variable unit configured to vary the operation coefficient set by the operation coefficient setting unit according to information indicating a total number of lines of the image data. 7. The shading correction data creation device according to any one of 2 to 6. 8. The apparatus according to claim 2, further comprising a second variable unit that varies the number of areas according to information indicating a total number of lines of the image data. Shading correction data creation device. 9. The image processing apparatus according to claim 1, further comprising: third variable means for varying the operation coefficient used for the first line on which the multiple averaging is performed according to information indicating the total number of lines of the image data. Item 9. The shading correction data creation device according to any one of Items 2 to 8. 10. The apparatus according to claim 7, wherein said first, second, or third variable means uses information indicating the total number of lines as information on an image reading speed of said image data.
10. The shading correction data creating device according to any one of 9 above. 11. Reference data creating means for creating reference data by performing statistical processing on a plurality of lines at the head of the image data in the sub-scanning direction, and the image data and the reference after the reference data in the sub-scanning direction. A comparison unit that performs a comparison operation with respect to data, and an exclusion unit that excludes image data subsequent to the reference data from a target for generating the shading correction data based on a result of the comparison operation. 11. The shading correction data creation device according to claim 1, wherein the shading correction data is created based on image data after the reference data after the exclusion. 12. The image processing apparatus according to claim 1, further comprising a replacement unit that sets the reference data corresponding to the pixel to be excluded instead of the excluded image data as an object of generating the shading correction data. The shading correction data creation device according to claim 11. 13. The comparison means for comparing the magnitude of a value obtained by subtracting a preset value from the reference data with image data after the reference data, and the exclusion means performs the comparison in the comparison. 13. The shading correction data creating device according to claim 11, wherein the exclusion is performed when image data after the reference data is smaller. 14. A shading correction data creating device according to claim 1, wherein said shading correction data created by said shading correction data creating device is used for image data of a read image of a document. A white shading correction device comprising: white shading correction means for performing white shading correction. 15. A photoelectric conversion device for reading an image of a document, and a white shading correction device according to claim 14 for performing white shading correction on image data of the read image. Image reading device. 16. An image forming apparatus comprising the image reading device according to claim 15, which reads an image of a document, and forms an image on a recording medium based on the read image of the document. 17. A shading correction data generating method for generating shading correction data used for white shading correction from image data obtained by reading a white reference. Wherein the calculation coefficient used for obtaining the average is set for each position in the sub-scanning direction of the image data. 18. The method according to claim 17, wherein the averaging step uses, as the operation coefficient, a value set for each of a plurality of areas obtained by dividing the reading range of the image data in the sub-scanning direction. How to create shading correction data. 19. The method according to claim 18, wherein the averaging step uses a value set as a numerical value represented by 1/2 ⁿ (n = 1, 2, 3,...) As the operation coefficient. The shading correction data creation method described in 1. 20. The shading correction data generating method according to claim 18, wherein the averaging step is for obtaining a multiple averaging between lines of the image data. 21. The averaging step according to claim 20, wherein, as the operation coefficient, a value that is set so that the value becomes smaller as the area is located later in the sub-scanning direction. How to create shading correction data. 22. The shading correction data according to claim 18, further comprising a first variable step of varying the setting of the operation coefficient prior to the averaging step. How to make. 23. The method according to claim 18, further comprising a first changing step of changing a setting of the operation coefficient in accordance with information indicating a total number of lines of the image data, prior to the averaging step. 22. The shading correction data creation method according to any one of items 21 to 21. 24. The method according to claim 18, further comprising a second variable step of varying the number of areas in accordance with information indicating a total number of lines of the image data, prior to the averaging step. The shading correction data creation method according to any one of the above. 25. A method according to claim 25, further comprising the step of: varying the operation coefficient used for the first line on which the multiple averaging is performed in accordance with information indicating the total number of lines of the image data prior to the averaging step. 19. The method of claim 18, wherein
25. The shading correction data generation method according to any one of the above items. 26. The method according to claim 23, wherein the first, second, or third variable step uses information indicating the total number of lines as information on an image reading speed of the image data.
26. The shading correction data creation method according to any one of items 25 to 25. 27. A computer-readable program for causing a computer to execute shading correction data for use in white shading correction from image data obtained by reading a white reference, wherein an average between lines of the image data is obtained. The computer is configured to execute an averaging process for obtaining the shading correction data of each pixel, and a calculation coefficient used for obtaining the average is set for each position in the sub-scanning direction of the image data. A program characterized by: 28. The averaging process according to claim 27, wherein the arithmetic coefficient uses a value set for each of a plurality of areas obtained by dividing the reading range of the image data in a sub-scanning direction. Program. 29. The averaging process according to claim 28, wherein a value set as a value represented by 1/2 ⁿ (n = 1, 2, 3,...) Is used as the operation coefficient. The program described in. 30. The program according to claim 28, wherein the averaging process is for obtaining a multiple averaging between lines of the image data. 31. The averaging process according to claim 30, wherein a value set as the operation coefficient is set to be smaller as the area is located rearward in the sub-scanning direction. program. 32. The non-transitory computer-readable storage medium according to claim 28, wherein the program causes a computer to execute a first variable process for changing a setting of the operation coefficient before the averaging process. 33. A computer according to claim 33, wherein a first variable process for changing a setting of said operation coefficient is performed prior to said averaging process in accordance with information indicating a total number of lines of said image data. 32. The program according to any one of 28 to 31. 34. The method according to claim 28, further comprising, before the averaging process, causing a computer to execute a second variable process of changing the number of areas according to information indicating the total number of lines of the image data. 33. Program in any one of 33. 35. A computer which performs a third variable process of varying the arithmetic coefficient used for the first line on which the multiple averaging is performed in accordance with information indicating the total number of lines of the image data prior to the averaging process. The program according to any one of claims 28 to 34, wherein the program is executed. 36. The method according to claim 33, wherein the first, second, or third variable processing uses information indicating the total number of lines as information on an image reading speed of the image data.
36. The program according to any one of -35. 37. A storage medium storing the program according to any one of claims 33 to 35.