JP2001157052A - Image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processor, capable of nearly equalizing the brightness of a read original without regard to difference in respective original reading part by correcting data for shading correction in the different original reading parts. SOLUTION: This processor is provided with a first original read part 1, which can read an original, while carrying the original and execute shading correction for correcting the brightness of the read original and a second original read part 2 which can read the original, in a state of mounting the original and execute shading correction for correcting the brightness of the read original. The device is also provided with a correction circuit 3 for correcting the data for shading correction obtained by the respective original reading part, so as to nearly equalize the brightness of an output image obtained in the case of reading the same original between the part 1 and the part 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus such as a copying machine having an original reading means for optically reading an original, and more particularly to a reading method for reading an original while transporting the original, and an original fixed on a mounting table. The present invention relates to an image processing apparatus capable of executing a reading method for reading in a state.

[0002]

2. Description of the Related Art Conventionally, an image processing apparatus such as a copying machine has a scanner for optically reading a document image.

However, since the above-described scanner generally has a structure in which a plurality of light-emitting diodes are arranged in an array, the light amount varies depending on the reading position of the document. For this reason, shading correction for correcting variations in the amount of light depending on the reading position of the original is performed with reference to the reference white plate.

In order to output a document read by a scanner with good reproducibility, it is necessary to always perform optimal shading correction. For example, in an "image processing apparatus" disclosed in Japanese Patent Application Laid-Open No. 10-341337, optimal shading correction is always performed by automatically setting the shading correction accuracy.

In a copying machine, a first original reading mode for reading an original while the original is placed on an original platen, and a second original reading mode for reading the original while the original is conveyed by a conveying device or the like are provided. What can be executed is generally known, and usually, shading correction is executed for each document reading mode.

[0006]

By the way, when shading correction is performed for each document reading mode, in order to improve the reproducibility of the document, that is, to make the brightness of the read document image almost equal, It is necessary that the data after shading correction (shading data) obtained for each document reading mode be the same as much as possible.

[0007] However, the shading correction is a correction for making the brightness of a certain reference white plate constant and making the brightness of the document image to be read the same, but actually, if the document reading mode is different, the same document is not the same. However, the brightness of the read document image is not constant.

That is, if the document reading mode is different, the distance from the light source to the document and the distance from the document to the sensor for reading the document are different. For this reason, the brightness of the same document read in each document reading mode is different, and there is a problem that an output image faithful to the document cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to correct shading correction data obtained in different original reading modes to read data in each original reading mode. It is an object of the present invention to provide an image processing apparatus that can make the brightness of a document image to be almost equal.

[0010]

In order to solve the above-mentioned problems, an image processing apparatus according to the present invention has a light source, irradiates the original with light from the light source while reading the original while transporting the original, and reads the original. A first document reading unit for performing shading correction for correcting variations in the amount of reflected light of the document; and a light source. The light source irradiates the document with light from the light source while the document is placed, and reads the document. And a second document reading means for performing shading correction for correcting the variation of the document. An output image obtained by correcting the document image read by each document reading means based on the shading correction data obtained by the shading correction is provided. In the image processing apparatus, when the same document is read by the first document reading means and the second document reading means, the brightness of the output image is increased. So as to be substantially the same among the original reading means, it is characterized in that it comprises a correcting means for correcting the shading correction data obtained in the document reading unit.

According to the above arrangement, the brightness of the document read data corrected by the correction device based on the shading correction data obtained by the first document read device and the second document read device is substantially the same. Since each shading correction data is corrected, even if the distance from the light source to the original and the distance from the original to the sensor for reading the original are different due to the difference in the original reading mode, the reading is performed in each original reading mode. The brightness of the document image can be made the same, and as a result, an output image faithful to the document can be obtained.

The correction means may correct the shading correction data based on a preset correction value.

In this case, since the shading correction data is corrected based on a correction value set in advance, a large-scale processing is not required, so that a simple and inexpensive system can be provided.

The correction value may be set so as to be adjustable.

In this case, if the correction value is adjusted for each device constituting the document reading means, it is possible to eliminate variations in the brightness of the document read for each device.

When the first document reading means and the second document reading means as described above are used, the first document reading means and the second document reading means are used to read both sides of the document while conveying the document. A first reading method, a second reading method of reading a mounting surface of a document while the document is placed on a document mounting table using the second document reading means, and a document transport provided in the document reading means Using the means and the second document reading means, it is possible to execute three types of reading methods, namely, a third reading method for reading one surface of the document while conveying the document.

Therefore, the image processing apparatus of the present invention corrects the shading correction data according to the above three types of reading methods, thereby eliminating the difference in the brightness of the original due to the reading method. The brightness of the document read by any of the reading methods can be made substantially equal.

The correction means may correct the shading correction data based on two types of correction values.

That is, when an original is read by the above three reading methods, the brightness of the upper surface of the original by the first reading method is substantially equal to the brightness of the original by the second reading method, and the lower surface of the original by the first reading method is read. Since the brightness and the brightness of the document according to the third reading method tend to be substantially equal, in addition to the correction value for correcting the shading correction data due to the difference in the document reading means, the shading correction data due to the difference in the reading method is further added. By setting a correction value for correction, it is possible to prevent a change in the brightness of the document caused by a difference depending on the reading method.

The two kinds of correction values may be set based on shading correction data obtained by the second reading method.

In this case, in the second reading method, reading is performed in a state where the original is placed on the original placing table, that is, in a state where the original is fixed. The distance is constant. For this reason, the possibility that the brightness of the read document changes is the least.

Therefore, by setting two types of correction values for correcting the shading correction data with reference to the shading correction data obtained by the second reading method, the correction accuracy for correcting the shading correction data is improved. be able to.

The above two correction values may be set to be adjustable.

In this case, it is possible to prevent a change in the brightness of the read document caused by a difference in the reading method and a variation in a device constituting the document reading means.

Switching means for switching an image processing method for a document image after shading correction may be provided according to the above three types of reading methods.

In this case, even if the reading method is the same, it is possible to eliminate the problem caused by the difference in the image processing method of the document. For example, it is possible to prevent a change in the brightness of the read document and a change in the focus value caused by a difference in the distance from the document to the sensor that reads the document, which differs for each document reading method.

The switching means may switch the image processing method based on a density conversion table set for each of the three reading methods.

In this case, the entire brightness region, that is, the region from the bright portion to the dark portion can be appropriately corrected for each reading method.

The switching means may switch the image processing method based on a filter processing coefficient set for each of the three types of reading methods.

In this case, the MTF (focus level) of the read document can be appropriately corrected for each reading method.

The switching means may switch the image processing method based on an area separation parameter set for each of the three types of reading methods.

In this case, an area separation error can be prevented, and an image defect of a read document due to the area separation error can be prevented.

The switching means may switch the image processing method based on a combination of two or more of a density conversion table, a filter processing coefficient, and a region separation parameter set for each of the three types of reading methods.

In this case, since the shading correction data can be corrected with higher accuracy, not only the brightness of the read original due to the difference in the reading method but also the occurrence of image defects and the like due to a change in resolution or an incorrect area separation. Can be prevented.

The image processing apparatus according to the present invention further includes image processing means for switching an image processing mode in which image processing is performed for each document having different image characteristics such as a text document and a photo document. The image processing method is switched according to three types of reading methods and the image processing mode switched by the image processing means.

In this case, the correction value for correcting the shading correction data can be set to an optimum value regardless of the original reading method and the type of image processing mode.
It is possible to reliably correct the change in the brightness of the read document due to the difference in the image processing mode.

Further, in the case where there is a scaling processing means for performing a scaling processing of the read original image, the switching means is adapted to the three kinds of upper reading methods and the scaling processing mode by the scaling processing means. The image processing method may be switched.

In this case, the correction value for correcting the shading correction data can be set to an optimum value regardless of the original reading method and the magnification processing mode. Can be surely corrected.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
The following is a description based on FIGS. 1 to 25.

The image processing apparatus according to the present embodiment has the configuration shown in FIG.
As shown in FIG. 1, a first document reading section 1 and a second document reading section 2 as document reading means for optically scanning a document, a correction circuit 3 as correction means, and an image processing section as image processing means 4. An external device 5 is provided.

The first document reading section 1 is disposed on an upper surface of an image processing apparatus such as a copying machine, for example. As shown in FIG. 2, a light source 11 composed of a xenon lamp, a first mirror 12, and a second Mirror 13, third mirror 14, lens 1
5. A CCD 16 is provided to scan the original D transported from the transport tray 18 to the transport device 19.

That is, the reflected light obtained when the light source 11 irradiates the original D that has reached the opening 20a of the transport path 20 of the transport device 19 with the first mirror 1
2, through the second mirror 13 and the third mirror 14, the lens 1
5, a CCD (Charge Coupled) as a document reading sensor
Device 16). The CCD 16 converts the incident reflected light into an electric signal and transfers it as a CCD digital output signal to a signal processing circuit 64 (FIG. 4) described later.

As described above, the first document reading section 1 is a document reading apparatus in which the reading section that scans while transporting the document is fixed.

The second document reading section 2 is disposed inside an image processing apparatus such as a copying machine, for example. As shown in FIG. 2, a light source 21 composed of a xenon lamp, a first mirror 22, The apparatus includes a second mirror 23, a third mirror 24, a lens 25, and a CCD 26, and scans a document D placed on a document table 28. In the second document reading section 2, the movable reading section 29 composed of the light source 21 and the first mirror 22 can be moved in parallel to the upper surface of the document table 28 (double arrow in the drawing). The original D placed on the original table 28 is scanned while moving.

That is, the movable reading section 29 moves in parallel with the original D placed on the original placing table 28 while irradiating light from the light source 21. The reflected light from the document D at this time passes through a first mirror 22, a second mirror 23, and a third mirror 24, and is imaged by a lens 25 on a CCD 26 as a document reading sensor. This CCD
26 also converts the incident reflected light into an electric signal and transfers it as a CCD digital output signal to a signal processing circuit 64 (FIG. 4) described later, similarly to the CCD 16.

As described above, the second document reading section 2 is a movable document reading apparatus in which the reading section that scans the document in a fixed state is movable.

Normally, in an original reading apparatus for optically reading an original, the amount of reflected light from the original varies due to a difference in the reading position of the original and the like. Have been done. This shading correction is performed independently in the first document reading unit 1 and the second document reading unit 2.

In the first document reading section 1, a first reference white plate 17, which is a reference white plate, is disposed at a portion corresponding to the scanning position of the document D on the transport path 20 below the light source 11, and the first reference white plate 17 is provided. Shading correction is performed using the white plate 17.

The light reflecting surface of the first reference white plate 17 is located at substantially the same height as the light reflecting surface of the document D. The distance to 11 is almost the same. As a result, the light intensity applied to the first reference white plate 17 and the original D
Can be made the same in intensity.

Further, in the second document reading section 2, shading correction is performed by using a second reference white plate 27 which is a reference white plate located on the leading end side of the document on the document placing table 28. .

The light reflecting surface of the second reference white plate 27 is disposed in parallel with the light reflecting surface of the document D, and the distance from each surface to the light source 21 is substantially the same during shading correction and when scanning the document D. ing. Accordingly, the light intensity applied to the second reference white plate 27 and the light intensity applied to the document D can be made the same.

The details of the shading correction in the first document reading section 1 and the second document reading section 2 will be described later.

In the first document reading section 1, the path of the reflected light from the document D is fixed, whereas in the second document reading section 2, the path of the reflected light from the document D is not fixed. . That is, the distance from the light source 11 to the document D in the first document reading unit 1, the distance from the document D to the CCD 16, the distance from the light source 21 to the document D in the second document reading unit 2, and the distance from the document D to the CCD 26 The distance is different. Therefore, when the same document is read by both the first document reading unit 1 and the second document reading unit 2, the brightness of the read document image changes due to the difference in the distance. In addition,
The light source 11 and the light source 21 use a xenon lamp having the same light intensity.

Therefore, in the present invention, the shading correction data obtained by the first document reading section 1 and the second document reading section 2 are output to the correction circuit 3 shown in FIG.
The document images read by the document reading section 1 and the second document reading section 2 have the same brightness.

The correction circuit 3 receives shading correction data from the first document reading section 1 and the second document reading section 2 respectively, corrects the two shading correction data, and outputs a CCD digital output value. The first document reading unit 1 and the second document reading unit 2 are configured to be the same. This CCD digital output value is transferred to the image processing unit 4 as corrected image data.

The details of the correction of the shading correction data in the correction circuit 3 will be described later.

The image processing section 4, as shown in FIG.
It includes a density conversion circuit 41, a region separation circuit 42, a filter processing circuit 43, a scaling processing circuit 44, a gamma correction circuit 45, and an error diffusion processing circuit 46.

In the density conversion circuit 41, the input image data is converted into density data, and the image data converted into the density data is sent to the area separation circuit 42.

The area separation circuit 42 calculates various area separation parameters such as the total density of the sub-mask and the degree of complexity of the input image data, and calculates the area of the pixel of interest in the image data according to the calculation result. To determine. The determined area is sent to the filter processing circuit 43 as area data.

In the filter processing circuit 43, each area of the image data is subjected to the filter processing with a preset filter processing coefficient, and the filtered image data is sent to the scaling processing circuit 44.

The scaling processing circuit 44 performs a scaling process according to a preset scaling factor. The image data on which the scaling process has been performed is sent to the gamma correction circuit 45. The gamma correction circuit 45 performs a gamma conversion process on each area of the image data using a gamma correction table prepared in advance. The image data on which the gamma conversion has been performed is sent to the error diffusion processing circuit 46.

The error diffusion processing circuit 46 performs an error diffusion process on each area of the image data using an error diffusion parameter set in advance. The image data processed by the error diffusion processing circuit 46 is sent to the external device 5 (FIG. 1) as processed image data. Examples of the external device 5 include a storage device, a printer, and a personal computer.

Here, the shading correction in the first document reading section 1 and the second document reading section 2 will be described. Note that the first document reading unit 1 and the second document reading unit 2 use the same shading correction system.

The above shading correction system is shown in FIG.
As shown in FIG. 3, a control circuit 61, a flash memory 62, and a control circuit 61 for driving and controlling the CCD 16 (26).
It has a CD driving device 63 and a CCD 16 (26).
Processing circuit 6 for processing analog signals from
4, an A / D converter 65, a digital shading circuit 66, an SRAM 67, and a FIFO line memory 68.

That is, the analog signal output from the CCD 16 (26) is sent to the signal processing circuit 64, and the analog signal processing is performed by the clamp circuit, the sample hold circuit, and the amplifier circuit in the signal processing circuit 64. The processed analog signal is converted into a digital signal by the A / D converter 65.

The digital signal converted by the A / D converter 65 is output to a digital shading circuit 66, and digital shading (shading correction) is performed for each pixel of the image data. Actually, A / D
The digital signal converted by the converter 65 has its data stored in the FIFO line memory 68 for each pixel,
The digital shading circuit 66 performs shading correction while sequentially reading out the stored data.

Data subjected to shading correction by the digital shading circuit 66 is output to the correction circuit 3 shown in FIG.

The shading correction performed in the digital shading circuit 66 will be described below. As described above, the first document reading unit 1 and the second
Since the same shading correction is performed in the document reading unit 2, the shading correction in the first document reading unit 1 will be described here.

The shading correction is performed by adjusting the gain value and the black offset value required for the shading correction in the signal processing circuit 64, and then adjusting the gain value and the black offset value adjusted by the signal processing circuit 64 in the digital shading circuit 66. This is performed using

First, with respect to the adjustment of the gain value and the black offset value in the signal processing circuit 64, the following (I)
A description will be given based on the steps (III) to (III).

(I) Determine an initial provisional gain value. For this purpose, the light source 11 is turned on, the first reference white plate 17 is irradiated with light, and output data is obtained from the CCD 16. At this time, the signal processing circuit 64 shown in FIG. 4 uses the initial value or the previous set value as the gain value to be used, and also uses the initial value or the previous set value as the offset value.

Subsequently, output data obtained from the CCD 16 of the reference white board 17 for 7260 pixels from an arbitrary pixel position is stored in the SRAM 67.

Next, the average value and standard deviation value of the CCD digital output value of the first reference white plate 17 stored in the SRAM 67 are calculated from the data of 4096 pixels at the center. Then, the target value of the gain value is further calculated by the following equation (1).

Target value = average value + standard deviation × 2 (1) Here, the target value obtained by the above equation (1) is “24”.
The gain setting value is changed and adjusted so as to be "0".

When the target value becomes "240", the light source 11 is turned off.

(II) Subsequently, the black offset value is changed. In this case, the signal processing circuit 64 uses the provisional gain value determined as described above, and also uses the same offset value as when the above-described gain value is obtained.

Subsequently, black data obtained from the CCD 16 of the reference white plate 17 for 7260 pixels from an arbitrary pixel position is stored in the SRAM 67.

Next, the average value and the standard deviation value of the black data of the first reference white board 17 stored in the SRAM 67 are calculated from the data of 4096 pixels at the center. Then, the black offset value is adjusted so that the average value becomes “3”.

(III) Determine the final gain value. Here, the signal processing circuit 64 uses the provisional gain value determined in the above step (I), and the black offset value is
The offset value determined in the step (II) is used. Then, similarly to the step (I), the target value is “4”.
The gain value is adjusted to be "0", and this gain value is used as the final gain value.

Subsequently, the digital shading circuit 66
Will be described below.

First, in the signal processing circuit 64,
Since the output data from the CCD 16 of the first reference white board 17 in the state where the final gain value has been determined is stored in the SRAM 67, this data is transferred to the FIFO line memory 68 as it is. Here, the FIFO line memory 68
Is stored in the digital shading circuit 6
Lookup table (LU) used in the processing in FIG.
T) becomes the address data.

That is, in the digital shading circuit 66, by switching the address of the LUT for each pixel, actual image data is subjected to LUT conversion and shading correction is performed. Image data after shading correction (hereinafter referred to as corrected image data)
Is calculated by the following equation (2).

Corrected image data = image data before shading × LUT data (2) The data stored in the FIFO line memory 68 as the LUT data (address data) is shown in FIG.
Are stored as shown. Here, the LU shown in FIG.
The data of T has a 9-bit configuration, where the upper 2 bits are an integer part and the 7 bits are a decimal part.

The shading correction data obtained by the digital shading circuit 66 has the contents shown in Table 1 below. Here, since the shading correction in the first document reading unit 1 is described as described above, Table 1 below shows shading correction data obtained in the first document reading unit 1.

[0085]

[Table 1]

Since the shading correction is performed separately in the first document reading unit 1 and the second document reading unit 2, the shading data described in Table 1 is used in the first document reading unit 1
And the second document reading unit 2 are set to different values.

The above black offset value is determined by the black level (CCD
This is a value for controlling where to set (the level of 0 output from). Here, the black offset value is as shown in FIG.
Is obtained from the graph showing the relationship between the offset voltage and the set value. The set value in FIG. 6 is a black offset value included in the shading correction data, and is actually A / A
This is a reference voltage on one side of the D converter 65.

The above gain value is obtained from a graph showing the relationship between the gain and the set value shown in FIG. The set values in FIG. 7 are gain values included in the shading correction data.

As described above, the first document reading section 1 and the second document reading section 2 are respectively provided with the first reference white board 17 and the second
Since the shading correction is performed using the reference white plate 27, shading correction data obtained by reading the same document may be different between the first document reading unit 1 and the second document reading unit 2. In such a case, it is necessary to correct the shading correction data so that the CCD digital output value is substantially the same in the first document reading unit 1 and the second document reading unit 2.

Hereinafter, correction of shading correction data will be described.

First, in order to determine a correction value, a grayscale original is read by the first original reading unit 1 and the second original reading unit 2. FIG. 8 shows the relationship between the CCD digital output value and the document density in this case.

As shown in FIG. 8, the side where the document density is high is almost the same, but the side where the document density is low has a difference in the CCD digital output value. Here, the data for shading correction of the first document reading unit 1 and the data for shading correction of the second document reading unit 2 are shown in Table 2 below.

[0093]

[Table 2]

Here, by controlling the shading correction data shown in Table 2 as shown in Table 3 below, substantially the same CCD digital output values were obtained.

[0095]

[Table 3]

When the shading correction data was corrected as shown in Table 3 above, the relationship between the CCD digital output value and the document density was as shown in the graph of FIG. According to this graph, it is understood that the CCD digital output values of the first document reading unit 1 and the second document reading unit 2 are almost equal regardless of the document density.

In this case, based on Table 2 and Table 3, only the gain value of the shading correction data of the first original reading unit 1 is changed in the shading correction data. That is, if the gain value 128 of the shading correction data of the first document reading unit 1 is changed to 138, the CCD
It was found that the digital output values were almost equal.

Therefore, when the original is read, a correction value (+10) is added to the gain value of the shading correction data of the first original reading unit 1 so that the first original reading unit 1 and the second original reading unit 2 Can be made substantially equal.

Note that the above-mentioned correction value may need to be adjusted because there is a possibility that the correction value may slightly vary due to dimensional variations of the reading mechanism. In the present application, this adjusting function is provided.

More specifically, the above-mentioned correction value can be set and changed in a self-diagnosis mode. actually,
Grayscale is converted into a first document reading unit 1 and a second document reading unit 2
And changes the correction value that can be set in the self-diagnosis mode until there is no difference between the CCD digital output values. This processing is performed by the correction circuit 3.

If the correction value can be changed as described above, the shading correction data can be appropriately corrected even if the brightness changes due to dimensional variations of the reading mechanism.

The self-diagnosis mode is a special mode that is executed only during maintenance of the apparatus or only during the production process of the apparatus. The operation of the device in this self-diagnosis mode
The operation is almost the same as a normal copy operation, except that the copy is performed while changing the adjustment value of the adjustment mechanism.

Therefore, when making adjustments in the production process,
Alternatively, the self-diagnosis mode is executed when a difference occurs in the brightness of an image for each reading mechanism when replacing a part or a unit during maintenance of the apparatus.

As shown in FIG. 2, in the present embodiment, two document reading devices, a first document reading unit 1 and a second document reading unit 2, are provided. Can be read.

(I) First Reading Method A method in which the first document reading unit 1 reads the upper surface of a document and the second document reading unit 2 simultaneously reads the lower surface of the document.

(Ii) Second reading method A method in which only the second document reading section 2 is used, a document is placed on the document table 28, and the movable reading section 29 reads the document while moving.

(Iii) Third reading method A method of reading the lower surface of the original while using the second original reading section 2 to convey the original by the conveying device 19 of the first original reading section 1.

A method of reading the upper surface of the original using only the first original reading unit 1 is also conceivable. However, since only one of the lower surface of the original and the upper surface of the original need be read, in this embodiment, As shown in the second reading method (ii) above, the second reading method that uses the second document reading unit 2 and reads only the lower surface of the document is adopted.

By the way, in each of the above-described reading methods, the brightness, the resolution (focus), and the like are slightly shifted even when the same document reading section is used due to a difference in the document transport path. In order to solve this problem, it is conceivable to prevent a change in brightness by setting two types of correction values for the above-described shading correction data.

The correction of shading correction data based on two types of correction values will be described below.

First, as described above, the first original reading section 1
Is corrected as shown in Table 3 above. In this state, when the document (the same document on both the upper surface and the lower surface) is read by the above three types of reading methods,
The relationship between the CD digital output value and the document density is a graph shown in FIG.

From the graph shown in FIG. 10, since the gain value of the first original reading section 1 is corrected by +10 with the first correction value, the original in the first reading method using the first original reading section 1 is used. It can be seen that the CCD digital output value on the upper surface is almost the same as the CCD digital output value according to the second reading method. However, the CCD digital output value according to the second reading method is different from the CCD digital output value of the lower surface of the document in the first reading method, and is also different from the CCD digital output value according to the third reading method.

It can be seen that the CCD digital output value obtained by the third reading method is substantially equal to the CCD digital output value of the lower surface of the document obtained by the first reading method.

Here, considering the CCD digital output value of the second reading method as a reference, the CCD digital output value of the third reading method and the CC of the lower surface of the document of the second reading method are considered.
D digital output value and second correction value (second correction value)
, The CCD digital output values in all the methods can be made the same, and the brightness level of the document can be made equal.

The gain values when the brightness levels of the documents become equal in each reading method are set as shown in Table 4 below.

[0116]

[Table 4]

By setting the gain values as shown in Table 4, the CCD digital output value in each reading method can be changed as shown in FIG.
A graph as shown in FIG.

Here, the first correction value and the second correction value will be described.

As described above, the first document reading section 1 and the second
Since the gain value of the shading correction data when the grayscale document is read by the document reading unit 2 is corrected, the first correction value is +10.

As shown in Table 4, the gain value when reading the upper surface of the original in the first reading method, that is, when reading the upper surface of the original by the second original reading unit 2, and the reading of the original in the third reading method. The gain value at the time of reading, that is, when reading the document by the second document reading unit 2 is set to 12
Since it has been changed from 4 to 130, the second correction value is +6.

Since the original reading method of the first reading method is exactly the same as the original reading method of the third reading method, only one correction value is required.

This time, the gain value is corrected in accordance with another reading method based on the second reading method. The reason for this is that the second reading method, as shown in FIG.
Since the original is read by moving the movable reading unit 29 while the original is placed on the original placing table 28 using the original reading unit 2, the original is not conveyed and is fixed. Therefore, the original can be read most stably as compared with other reading methods.

The first correction value and the second correction value need to be adjusted because there is a possibility that the first correction value and the second correction value are slightly different due to variations in dimensions of the reading mechanism. In the present application, this adjusting function is provided. The adjustment of each correction value is also performed by the correction circuit 3.

More specifically, the first and second correction values can be set and changed in a self-diagnosis mode. Actually, the gray scale is read by the above-described first to third reading methods, and the first and second correction values that can be set in the self-diagnosis mode are changed until the difference between the CCD digital output values disappears.

As described above, if the first and second correction values can be changed, the shading correction data can be appropriately corrected even if the brightness changes due to dimensional variations of the reading mechanism. .

As described above, the CC using the three types of reading methods
The difference in the D digital output value was corrected by changing the gain value using the first correction value and the second correction value.
As described above, when correcting the gain value, it is possible to relatively easily correct the difference in brightness of a low density portion of the document, but it is often difficult to correct the halftone portion.

The reading device (first document reading unit 1, second document reading unit 1,
The presence of two types of document reading units 2) may cause variations in the reading sensors (CCD 16 and CCD 26) and their peripheral circuits to adversely affect the entire density region read.

Here, in the relationship between the CCD digital output value obtained by each of the above reading methods and the original density, if only the halftone portion changes, a graph as shown in FIG. 12 is obtained.

From the graph shown in FIG. 12, the CCD digital output value in each reading method is almost equal between the low density portion where the document density is low and the high density portion where the document density is high. It can be seen that only the CCD digital output value on the upper surface of the original in FIG.

As described above, when the brightness of only the halftone portion changes, it is not possible to properly correct only by changing the gain value as described above.

The values read by the CCD 16 and the CCD 26 in the first document reading section 1 and the second document reading section 2 show a substantially linear relationship with the brightness. The degree is expressed as a density. Therefore, the density conversion table for converting the RGB data of the reflected light from the original into the YMC density data is switched according to the reading method. Thereby, the brightness after the density conversion can be corrected in the entire area. For example, a density conversion table (LUT) before density data correction is as shown in FIG. 25A, and a density conversion table (LUT) after density data correction as shown in FIG. 25B. Become.

More specifically, in each of the above reading methods,
The reference is the second reading method, and the density conversion table corresponding to the second reading method is the first density conversion table. Also, the method of reading the upper surface of the original by the first reading method and the third method
A density conversion table corresponding to the reading method is prepared as a second density conversion table, and a density conversion table corresponding to the reading method of the lower surface of the document by the first reading method is prepared in advance as a third density conversion table. Then, by performing density conversion using one of the first to third density conversion tables according to the reading method when actually reading the original, the brightness level of the halftone portion (CCD digital output) Value) is prevented from being converted by the reading method.

Thus, when the brightness of the halftone portion changes due to the correction, in addition to the correction by adjusting the gain value, the CCD in each reading method can be obtained by using the density conversion table. Digital output values can be made substantially equal.

Since the density conversion table has a one-to-one relationship between input and output, switching the density conversion table in accordance with the method of reading the original is performed before the shading correction value is corrected. Either later or later.

When the original is read by placing the original on the original table 28 as in the second reading method described above, the scanning surface of the original may be shifted due to the wave of the original. A state in which the document is lifted up from 28, that is, a so-called document floating occurs. When the document floats, the focal point changes, and blur occurs on the scanning surface side of the document.

As described above, when the document is blurred on the scanning surface side, the resolution (focus) of the document to be read is changed, which causes a problem that the document becomes very difficult to read in the case of a character document. I will.

Normally, in order to solve the above-mentioned inconveniences, sharpening of an image called a filtering process is performed.
That is, by switching the filter processing coefficient used in the filter processing for each reading method, it is possible to obtain the same resolution by the above three types of reading methods.

As in the above-described density conversion table, the first to third filter processing coefficients are provided for each reading method. That is, the first filter processing coefficient corresponds to the reading method of the reference second reading method, and specifically, the one shown in FIG. 13A is used. The second filter processing coefficient corresponds to the reading method of the upper surface of the original in the first reading method and the reading method of the third reading method, and specifically, the one shown in FIG. Use Further, the third filtering coefficient is
The first reading method corresponds to the reading method of the lower surface of the document, and specifically, the method shown in FIG. 13C is used.

In the present embodiment, as shown in FIG. 3, when the area separation circuit 42 of the image processing unit 4 performs the area separation, the resolution at which the original is read is changed by the above-described correction. In this case, there is a possibility that the region separation result may change.

Here, the area separation will be described below. The area separation mainly detects states such as edges, non-edges, and halftone dots, and controls the filter processing coefficients, output conversion tables, error diffusion set values, and the like based on the detection results, and determines the state of each area. The purpose is to carry out image processing according to.

FIG. 14 shows the relationship between a main mask and a sub-mask (also referred to as a “sub-matrix”) used in the region separation processing. Here, the main masks as the main pixel groups are i0 to i27. The pixel of interest of the main mask is i10. On the other hand, the following four types of submasks are prepared for the submask as a subpixel group.

Two sub masks are prepared as sub masks in the main scanning direction. The first sub-mask in the main scanning direction is i0, i1, i2, i3, i4, i5, i6,
The second sub-mask in the main scanning direction is denoted by i21, i22, i
23, i24, i25, i26, and i27. The first and second sub-masks in the main scanning direction are set as one set.

Further, as a sub-mask in the sub-scanning direction,
Two submasks are provided. The first sub-mask in the sub-scanning direction is i0, i7, i14, i21, and the second sub-mask in the sub-scanning direction is i6, i13, i20, i
27. The first and second sub-masks in the sub-scanning direction are another set.

Next, the flow of the area separation processing will be described with reference to FIG.

First, a simple average density in the main mask is calculated (step S1). Here, the average density calculation of the 7 × 4 mask (total in the mask ÷ 32) is performed. Then, the average density is compared with the threshold ave (Step S)
2). If the average density is equal to or larger than the threshold value ave, it is determined that the area is a photograph area (non-edge area), and the result of this determination remains unchanged in the subsequent area determination (step S3).

On the other hand, if the average density is smaller than the threshold value ave in step S2, the sum of the above-described density differences of the sub-masks (sub-matrices) (hereinafter referred to as total density) is calculated (step S4), and the threshold value delta ( delta
= 150) (step S5). If the total density is greater than the threshold delta, the character area (edge area)
Is determined, and this determination result is not changed by the subsequent area determination (step S6). If it is determined in step S6 that the area is a character area, the feedback count is increased by "1". This feedback count is compared with the threshold value fb1 when the total density is equal to or smaller than the threshold value delta in step S5 (step S7). The threshold value fb1 is
This is a threshold for determining whether or not the occurrence frequency of a character area is high in a predetermined history state. In this area separation processing, the predetermined history state is set to 8 pixels in the previous history and the threshold fb1 is set to “2”. ing.

Therefore, when the edge determination result based on the total density is 3 or more pixels for the previous 8 pixels (that is,
(When the feedback count is larger than the threshold value fb1)
In addition, the value of the edge determination threshold delta is set to a predetermined amount fb.
2 (fb2 = 80), and the reduced threshold delta-fb2 is compared with the total density (step S8). If the total density is larger than the threshold value delta-fb2, it is determined that the area is a character area, and the result of this determination remains unchanged in the subsequent area determination (step S9).

As described above, by changing the threshold value of the edge determination according to the edge determination result of the previous history state and performing the feedback correction, it becomes possible to increase the edge determination accuracy according to the previous history state.

If it is determined in step S7 that the feedback count is equal to or less than the threshold value fb1, or if it is determined in step S8 that the total density is equal to or less than the threshold value delta-fb2, a region separation process based on the degree of complexity is performed.

The difference value busy-gap (difference between the main and sub-complexities) between the complexity in the main-scanning direction and the complexity in the sub-scanning direction, and the sum of the complexity in the main-scanning direction and the complexity in the sub-scanning direction Value busy-s
um (sum of primary and secondary complexity) is calculated (step S1)
After 0), the difference value busy-gap (complexity difference) of the degree of complexity is compared with a predetermined threshold value busy-g (busy-g = 120) (step S11).

If the difference value busy-gap of the degree of busyness is equal to or larger than the threshold value busy-g, it is determined that the area is a character area (edge area), and the result of this determination is unchanged by the subsequent area determination (step S12). When the difference value busy-gap of the busyness is smaller than the threshold busy-g, the total busyness-sum of the busyness (total busyness)
Is compared with a predetermined threshold value busy-s (busy-s = 180) (step S13). Busy-sum is the threshold value
If it is equal to or greater than busy-s, it is determined to be a halftone dot area (step S
14) If the total busy-sum value of the degree of busyness is smaller than the threshold value busy-s, it is determined that the area is a photograph area (step S15).

Step S3, Step S6, Step S
When the region is determined at the stage of step 9, step S12, step S14, or step S15, the process returns to the stage in FIG. 15, and the above-described region separation processing is performed again on the next pixel.

In this region separation processing, as described above, the determination based on the average density in the main mask, the determination based on the sum S of the total densities of the sub-masks, the determination based on feedback correction,
The determination based on the difference value busy-gap of the degree of complexity and the determination based on the total value busy-sum of the degree of complexity are performed in this order. In each determination, each of the above feature amounts (region separation parameters)
Is compared with each threshold value to determine a region. As a result, in this area separation processing, it is possible to detect three types of areas, that is, an edge area, a non-edge area, and a halftone dot area only by comparing with each threshold value without requiring a large memory.

In the case of a hardware configuration, instead of sequentially performing the processing using the above-described feature amounts, each feature amount (sum S of average density and total density, difference value busy-gap, total value busy
-sum) is calculated in parallel by so-called pipeline processing and processed in parallel, whereby a system with a higher speed and a simpler hardware configuration can be provided.

FIG. 16 is a block diagram showing the main area separation processing by the parallel processing. The processing of blocks 71 to 73 corresponds to steps S1 to S3, and the processing of blocks 74 to 7
7 corresponds to steps S4 to S9, and corresponds to block 78.
Processes to 82 correspond to steps S10 to S15. In this case, the processing of blocks 71 to 73, block 7
The processing of 4-77, and the processing of blocks 78-82,
Processed in parallel.

As described above, the region separation parameter is 4
Types of thresholds, each threshold being ave, delta,
busy-g and busy-s. Then, using the above-described area separation method, three kinds of area separation parameters as shown in Tables 5 to 7 below are prepared, and switched according to the reading method as described above.

Table 5 shows the area separation parameters corresponding to the reference second reading method. Table 6 shows the area separation parameters corresponding to the reading method of the upper surface of the original by the first reading method and the reading method by the third reading method. Table 7 shows the parameters.
Indicates an area separation parameter corresponding to the reading method of the lower surface of the document by the first reading method.

[0158]

[Table 5]

[0159]

[Table 6]

[0160]

[Table 7]

As described above, by switching the area separation parameter according to the reading method, it is possible to solve the problem that occurs in the area separation, that is, the problem that the area separation result changes when the resolution level of the original reading changes. Can be.

If any one of the above-described density conversion table, filter processing coefficient, and area separation parameter is switched according to the reading method, it is possible to prevent a change in brightness and a change in resolution of the read document. Become.

Furthermore, if two or more types of density conversion tables, filter processing coefficients, and area separation parameter switching means are used in combination, the accuracy for preventing a change in the brightness of the read original and a change in the resolution can be further improved. Can be improved.

More specifically, a case where the density conversion table and the filter processing coefficient are switched according to the reading method, a case where the density conversion table and the area separation parameter are switched according to the reading method, a case where the filtering processing coefficient and the area separation There is a case where the parameter and the parameter are switched according to the reading method.

It is to be noted that a change in the brightness of the read original,
In order to further improve the accuracy for preventing a change in resolution, all of the density conversion table, the filter processing coefficients, and the area separation parameters may be switched according to the reading method.

The present image processing apparatus has means (image processing means) for switching between two types of image processing modes, a character mode and a photograph mode.

In the character mode, image processing is performed so that characters can be clearly reproduced in a character original or the like. In the photo mode, image processing is performed so that an original having a photograph or a halftone dot can be optimally reproduced. I have.

Conventionally, in the above two image processing modes,
The filter processing coefficients as shown in FIGS. 17A and 17B are used. Here, FIG. 17A shows a filter processing coefficient corresponding to the character mode, and FIG. 17B shows a filter processing coefficient corresponding to the photograph mode.

However, if only the filter processing coefficients corresponding to the character mode and the photograph mode are set, it is not possible to perform the optimal image processing in all cases in the three types of reading methods as described above.

Therefore, it is conceivable that optimal image processing is performed in the two types of image processing modes of the character mode and the photo mode by setting filter processing coefficients according to the above-described three types of reading methods.

FIGS. 18A and 18B show filter processing coefficients corresponding to the reference second reading method. FIG. 18A shows a filter processing coefficient corresponding to the character mode,
FIG. 18B shows filter processing coefficients corresponding to the photograph mode.

FIGS. 19A and 19B show filter processing coefficients corresponding to the reading method of the upper surface of the original in the first reading method and the reading method of the third reading method. FIG. 19 (a)
19 is a filter processing coefficient corresponding to the character mode, and FIG.
(B) shows a filter processing coefficient corresponding to the photograph mode.

FIGS. 20A and 20B show filter processing coefficients corresponding to the original reading method of the lower surface of the original in the first reading method. FIG. 20A shows a filter processing coefficient corresponding to the character mode, and FIG. 20B shows a filter processing coefficient corresponding to the photograph mode.

As described above, by switching all six types of filter processing coefficients in accordance with the reading method and the image processing mode, it is possible to perform optimal image processing in each image processing mode and each reading method.

Therefore, as described above, the switching means for switching the image processing method for the original image after shading correction is provided in accordance with the three types of reading methods.
May be provided.

The image processing section 4 is provided with a register for setting a density conversion table, a filter coefficient, a region separation parameter, and the like.
CPU (central pr) provided in a control circuit (not shown)
ocessing unit) is stored. When information such as the state of the reading mechanism, the image mode, and the magnification is input, the CPU sets an appropriate value stored in a register in the image processing unit 4 according to the information.

Therefore, the image processing section 4 switches the image processing method by storing appropriate setting values in the registers for setting the density conversion table, the filter coefficient, the area separation parameter, and the like by the CPU.

In this case, even if the reading method is the same, it is possible to eliminate the problem caused by the difference in the image processing method of the original. For example, various effects such as a change in brightness of the read document and a change in focus value caused by a difference in the distance from the document to the sensor that reads the document depending on the document reading method can be achieved. .

Further, an example will be described in which the present image processing apparatus includes a scaling unit (scaling processing means) and switches the filter processing coefficient in accordance with the reading method and the scaling factor.

In general, three types of filter processing coefficients are prepared according to the magnification. For example, FIG. 21A shows filter processing coefficients corresponding to a scaling factor of 50% to 69%, and FIG. 21B shows filter processing coefficients corresponding to a scaling factor of 70% to 139%. , FIG. 21 (c)
Indicates a filter processing coefficient corresponding to a magnification of 140% to 200%.

In the present embodiment, it is conceivable that image processing at each magnification is appropriately performed by setting filter processing coefficients according to the above-described three types of reading methods.

FIGS. 22A to 22C show filter processing coefficients corresponding to the reference second reading method.
FIG. 22A shows the filter processing coefficients corresponding to the scaling factor of 50% to 69%, and FIG.
FIG. 22C shows the filter processing coefficients corresponding to 0% to 139%, and FIG. 22C shows the filter processing coefficients corresponding to the magnification of 140% to 200%.

FIGS. 23A to 23C show filter processing coefficients corresponding to the first reading method for reading the upper surface of the document and the third reading method. FIG.
FIG. 23A shows filter processing coefficients corresponding to a scaling factor of 50% to 69%, and FIG.
FIG. 2 shows filter processing coefficients corresponding to 139%.
3 (c) indicates a filter processing coefficient corresponding to a magnification of 140% to 200%.

FIGS. 24A to 24C show filter processing coefficients corresponding to the method of reading the lower surface of the original in the first reading method. FIG. 24A shows that the magnification is 50% to 69%.
FIG. 24B shows the filter processing coefficients corresponding to.
Shows the filter processing coefficients corresponding to the scaling factors from 70% to 139%, and FIG.
The filter processing coefficients corresponding to up to 200% are shown.

As described above, by switching all nine types of filter processing coefficients in accordance with the reading method and the magnification, it is possible to perform optimal image processing in each magnification and each reading method.

[0186]

As described above, the image processing apparatus of the present invention has a light source, irradiates the original with light from the light source while reading the original while reading the original, and corrects the variation in the reflected light amount of the original. A first document reading unit for performing shading correction, and irradiating the document with light from the light source in a state where the document is placed and reading the document, and correcting variations in the amount of reflected light of the obtained document. An image processing apparatus comprising: a second document reading means for performing shading correction; and obtaining an output image obtained by correcting a document image read by each document reading means based on shading correction data obtained by the shading correction. When the same document is read by the first document reading means and the second document reading means, the brightness of the output image is To be the same, a configuration in which a correction means for correcting the shading correction data obtained in the document reading unit.

Therefore, each of the original reading data corrected by the correcting means based on the shading correction data obtained by the first original reading means and the second original reading means has substantially the same brightness. Since the shading correction data is corrected, even if the distance from the light source to the document and the distance from the document to the sensor for reading the document are different due to the difference in the document reading mode, the brightness of the document image read in each document reading mode is different. As a result, it is possible to obtain an output image faithful to the original.

The correcting means may correct the shading correction data based on a preset correction value.

Therefore, since the shading correction data is corrected based on the correction value set in advance, a large-scale processing is not required, so that a simple and inexpensive system can be provided.

The correction value may be set to be adjustable.

Therefore, if the correction value is adjusted for each device constituting the document reading means, there is an effect that variations in the brightness of the document read for each device can be eliminated.

When the first document reading means and the second document reading means as described above are used, the first document reading means and the second document reading means are used to read both sides of the document while conveying the document. A first reading method, a second reading method of reading a mounting surface of a document while the document is placed on a document mounting table using the second document reading means, and a document transport provided in the document reading means Using the means and the second document reading means, it is possible to execute three types of reading methods, namely, a third reading method for reading one surface of the document while conveying the document.

Therefore, the image processing apparatus of the present invention corrects shading correction data in accordance with the above-described three types of reading methods, thereby eliminating the difference in brightness of the original due to the reading method. In this case, the brightness of the original read by any of the reading methods can be made substantially equal.

The correcting means may correct the shading correction data based on two types of correction values.

That is, when the original is read by the above three reading methods, the brightness of the upper surface of the original by the first reading method is substantially equal to the brightness of the original by the second reading method, and the lower surface of the original by the first reading method is read. Since the brightness and the brightness of the document according to the third reading method tend to be substantially equal, in addition to the correction value for correcting the shading correction data due to the difference in the document reading means, the shading correction data due to the difference in the reading method is further added. By setting a correction value for correction, there is an effect that it is possible to prevent a change in brightness of a document caused by a difference depending on a reading method.

The two types of correction values may be set based on shading correction data obtained by the second reading method.

Therefore, in the second reading method, reading is performed in a state where the original is placed on the original placing table, that is, in a state where the original is fixed. The distance is constant. For this reason, the possibility that the brightness of the read document changes is the least.

Therefore, by setting two types of correction values for correcting the shading correction data with reference to the shading correction data obtained by the second reading method, the correction accuracy for correcting the shading correction data is improved. It has the effect of being able to do so.

The two correction values may be set so as to be adjustable.

Therefore, it is possible to prevent a change in the brightness of the read document caused by a difference in the reading method and a variation in a device constituting the document reading means.

Switching means for switching the image processing method for the original image after shading correction may be provided according to the above three types of reading methods.

Therefore, even if the reading method is the same, it is possible to eliminate the problem caused by the difference in the image processing method of the original. For example, it is possible to prevent a change in brightness and a focus value of a read document caused by a difference in a distance from a document to a sensor that reads the document for each document reading method.

The switching means may switch the image processing method based on a density conversion table set for each of the three reading methods.

Therefore, there is an effect that the entire area of brightness, that is, an area from a bright place to a dark place can be appropriately corrected for each reading method.

The switching means may switch the image processing method based on a filter processing coefficient set for each of the three types of reading methods.

Therefore, there is an effect that the MTF (focus level) of the read document can be appropriately corrected for each reading method.

The switching means may switch the image processing method based on the area separation parameters set for each of the three types of reading methods.

Therefore, there is an effect that it is possible to prevent an area separation error and prevent an image defect of a read original due to an area separation error.

The switching means may switch the image processing method based on a combination of two or more of a density conversion table, a filter processing coefficient, and a region separation parameter set for each of the three types of reading methods.

[0210] Therefore, the shading correction data can be corrected with high accuracy, so that not only the brightness of the read original due to the difference in the reading method but also the occurrence of image defects and the like due to a change in resolution and an incorrect area separation. The effect that it can prevent is produced.

The image processing apparatus according to the present invention further includes image processing means for switching an image processing mode in which image processing is performed for each original having different image characteristics, such as a character original and a photo original. The image processing method is switched according to the three types of reading methods and the image processing mode switched by the image processing unit.

Therefore, the correction value for correcting the shading correction data can be set to an optimum value regardless of the original reading method and the type of image processing mode.
An advantage is provided in that a change in brightness of a read document due to a difference in image processing mode can be reliably corrected.

Further, in the case where there is a variable magnification processing means for performing a magnification processing of the read original image, the switching means is adapted in accordance with the upper three kinds of reading methods and the magnification processing mode by the variable magnification processing means. The image processing method may be switched.

Therefore, the correction value for correcting the shading correction data can be set to an optimum value regardless of the original reading method and the magnification processing mode. This has the effect that the change in brightness can be corrected without fail.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an image processing apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a document reading unit provided in the image processing apparatus shown in FIG.

FIG. 3 is a schematic block diagram of an image processing unit provided in the image processing apparatus shown in FIG.

FIG. 4 is a schematic block diagram illustrating a shading correction mechanism provided in a document reading unit provided in the image processing apparatus shown in FIG.

FIG. 5 is an explanatory diagram showing an example of a look-up table used in the shading correction mechanism shown in FIG.

FIG. 6 is a graph showing a relationship between an offset voltage and a set value.

FIG. 7 is a graph showing a relationship between a gain and a set value.

FIG. 8 is a graph showing a relationship between a CCD digital output value and document density before correcting shading correction data obtained by a first document reading unit and a second document reading unit.

FIG. 9 is a graph illustrating a relationship between a CCD digital output value and a document density after correcting shading correction data obtained by a first document reading unit and a second document reading unit.

FIG. 10 is a graph showing a relationship between a CCD digital output value and a document density before correcting shading correction data obtained for each document reading method.

FIG. 11 is a graph showing a relationship between a CCD digital output value and a document density after correcting shading correction data obtained for each document reading method.

FIG. 12 is a graph showing a state in which only a halftone portion is changed in a relationship between a CCD digital output value obtained by each reading method and a document density.

FIGS. 13A to 13C are explanatory diagrams showing filter processing coefficients set for each reading method.

FIG. 14 is an explanatory diagram showing a relationship between a main mask and a sub mask used for a region separation process.

15 is a flowchart showing a flow of a region separation process using the main mask and the sub mask shown in FIG.

FIG. 16 is a block diagram illustrating a flow of a region separation process shown in FIG.

17A and 17B are explanatory diagrams illustrating filter processing coefficients used in two image processing modes, wherein FIG. 17A illustrates a filter processing coefficient corresponding to a character mode, and FIG. 17B illustrates a filter processing coefficient corresponding to a photograph mode. .

FIGS. 18A and 18B are explanatory diagrams showing filter processing coefficients corresponding to a second reading method serving as a reference, in which FIG. 18A shows a filter processing coefficient corresponding to a character mode, and FIG. is there.

19A and 19B show filter processing coefficients corresponding to a reading method of an upper surface of a document in a first reading method and a reading method of a third reading method, wherein FIG. 19A shows a filter processing coefficient corresponding to a character mode, and FIG. FIG. 9 is an explanatory diagram showing filter processing coefficients corresponding to FIG.

FIGS. 20A and 20B show filter processing coefficients corresponding to the reading method of the lower surface of the original in the first reading method, wherein FIG. 20A shows the filter processing coefficients corresponding to the character mode, and FIG. FIG.

FIG. 21 shows filter processing coefficients for each scaling process;
(A) is a filter processing coefficient corresponding to a magnification of 50% to 69%, (b) is a filter processing coefficient corresponding to a magnification of 70% to 139%, and (c) is a magnification of 140%.
It is explanatory drawing which shows the filter processing coefficient corresponding to -200%.

FIGS. 22A and 22B show filter processing coefficients corresponding to a second reading method serving as a reference; FIG. 22A shows filter processing coefficients corresponding to a magnification of 50% to 69%; FIG.
FIG. 7C is an explanatory diagram illustrating filter processing coefficients corresponding to 139% to 139%, and FIG. 7C is an explanatory diagram illustrating filter processing coefficients corresponding to magnifications of 140% to 200%.

23A and 23B show filter processing coefficients corresponding to the original reading method of the first reading method and the reading method of the third reading method, and FIG. 23A shows filter processing coefficients corresponding to a magnification of 50% to 69%. , (B) show a magnification of 70% to 139.
FIG. 7C is an explanatory diagram showing a filter processing coefficient corresponding to up to%, and FIG.

24A and 24B show filter processing coefficients corresponding to a method of reading the lower surface of a document in the first reading method, and FIG.
% To 69%, a filter coefficient corresponding to a magnification of 70% to 139%, and (c) a filter coefficient corresponding to a magnification of 140% to 200%. FIG. 4 is an explanatory diagram showing coefficients.

FIG. 25 shows a density conversion table (LUT);
FIG. 4 is an explanatory diagram showing a state before correction of the LUT, and FIG. 4B is an explanatory diagram showing a state after correction of the LUT.

[Description of Signs] 1 First document reading unit (first document reading unit) 2 Second document reading unit (second document reading unit) 3 Correction circuit (correction unit) 4 Image processing unit (switching unit) 11 Light source 16 CCD Reference Signs List 21 light source 26 CCD 29 movable reading unit 61 control circuit 66 digital shading circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Mihoko Tanimura 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Noriyuki Yasuoka 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka (72) Inventor Masaaki Otsuki 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka F-term (reference) 5B047 AA01 AB02 BA01 BA02 BB02 DA04 DC01 5C072 AA01 BA08 EA05 FB12 LA18 RA16 UA02 VA06 XA01 5C077 LL02 MM03 MM27 NN02 NN11 PP06 PP27 PP28 PP44 PP46 PQ23 SS01 TT06

Claims (14)

[Claims] A first document reading means having a light source, irradiating the document with light from the light source while transporting the document, reading the document, and performing shading correction for correcting variations in the amount of reflected light of the document; A second original reading means for irradiating the original with light from the light source and reading the original while the original is placed, and performing shading correction for correcting variations in the amount of reflected light of the original. Means for obtaining an output image obtained by correcting the original image read by the means based on the shading correction data respectively obtained by the shading correction, wherein the same original is read by the first original reading means and the second original reading The brightness of the output image is substantially the same between the respective document reading means when read by the means. The image processing apparatus characterized by comprising a correction means for correcting the loading correction data. 2. An image processing apparatus according to claim 1, wherein said correction means corrects said shading correction data based on a preset correction value. 3. The image processing apparatus according to claim 2, wherein said correction value is set to be adjustable. 4. An image processing apparatus according to claim 1, wherein the first document reading means and the second document reading means use the first document reading means to read both sides of the document while transporting the document. (2) a second reading method for reading the mounting surface of the original while the original is placed on the original mounting table by using the original reading means; an original conveying means provided in the original reading means;
And a third reading method for reading one side of the document while transporting the document by using the document reading means. The correction means can perform three types of reading methods according to the three reading methods. An image processing apparatus that corrects shading correction data by using the image processing apparatus. 5. An image processing apparatus according to claim 4, wherein said correction means corrects the shading correction data based on two types of correction values. 6. An image processing apparatus according to claim 5, wherein said two kinds of correction values are set based on shading correction data obtained by said second reading method. 7. An image processing apparatus according to claim 5, wherein said two kinds of correction values are set so as to be adjustable. 8. An image processing apparatus according to claim 1, wherein said first document reading means and said second document reading means use a first reading method for reading both sides of the document while transporting the document. (2) a second reading method for reading the mounting surface of the original while the original is placed on the original mounting table by using the original reading means; an original conveying means provided in the original reading means;
And a third reading method for reading one side of the original while transporting the original by using the original reading means. The third reading method can be executed. An image processing apparatus provided with a switching unit that switches an image processing method for the original image. 9. An image processing apparatus according to claim 8, wherein said switching means switches an image processing method based on a density conversion table set for each of the three types of reading methods. 10. An image processing apparatus according to claim 8, wherein said switching means switches an image processing method based on a filter processing coefficient set for each of said three types of reading methods. 11. An image processing apparatus according to claim 8, wherein said switching means switches an image processing method based on an area separation parameter set for each of the three types of reading methods. 12. The switching means includes a density conversion table, a filter processing coefficient, and a density conversion table set for each of the three types of reading methods.
9. The image processing apparatus according to claim 8, wherein the image processing method is switched based on a combination of two or more segmentation parameters. 13. An image processing means for switching an image processing mode for performing image processing for each document having different image characteristics such as a text document and a photo document, wherein the switching means comprises: 13. The image processing apparatus according to claim 9, wherein an image processing method is switched according to the image processing mode switched by the image processing unit. 14. An image forming apparatus according to claim 11, further comprising: a scaling unit configured to perform a scaling process on the read document image, wherein the switching unit switches between the three types of reading methods and the scaling process mode by the scaling unit. 13. The image processing apparatus according to claim 9, wherein the image processing method is switched according to the image processing method.