JP2002218225A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compute the resolution of a resolution original placed on an original platen and to correct file strength so as to attain a target resolution corresponding to the computed result. SOLUTION: This image reader is provided with the original platen 16, the resolution original 20 arranged on the original platen 16, original read means 10-15 for reading the resolution original 20 and an image processing board 2 provided with an image processing circuit for analyzing resolution original data read by the original read means. The image processing circuit generates the final image of the target resolution by changing a filter coefficient corresponding to the computed result of the resolution original data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus such as a digital copying machine, a facsimile or a scanner.

[0002]

2. Description of the Related Art When producing a scanner system, focus is adjusted at a production site or the like by using the principle of MTF (CTF) or the like. However, since the lens has aberrations, the formed image has a different focus (or resolution) between the center and the periphery of the lens. When the sub-scanning is performed, the slide mechanism is adjusted so as to move parallel to the document table, but it is difficult to move the slide mechanism completely parallel. For this reason, the focus (resolution) is set to a certain lower limit, and if it is equal to or higher than the lower limit, the product is manufactured as a non-defective product.

[0003] However, this does not correct the difference in image quality between the central part and the peripheral part of the lens and the parallelism of the lens, so that the resolution remains different depending on the location. Although there are individual differences, no special measures have been taken.

[0004] Conventionally, as a technique relating to an image processing filter, there is a technique of a multi-value image filter processing apparatus disclosed in, for example, Japanese Patent Application Laid-Open No. 3-185574. This multi-valued image filter processing device identifies the state of the density change of the multi-valued image data, specifies the noise appearing in the image from the result, and performs a filtering process applied to the noise with a filtering process different from other regions By doing so, the noise is made less noticeable.

[0005]

As described above, when a scanner system is produced, it has conventionally been shipped as a product while leaving a partial focus (resolution) difference generated by an image passing through a lens. . For this reason, there has been a problem that a document that has been resolved when placed on the center of the document table does not resolve when placed on the periphery of the document table by changing the placement of the document. The same can be said for the scanning accuracy of the scanner, but mechanical accuracy is required to be parallel to the platen.

On the production line, skilled adjustments and advanced adjustment jigs are required to increase the resolution over the entire surface as much as possible. Further, optical specifications of lenses and the like are strict in order to maintain the resolution, which has been one of the causes of cost increase.

Further, in the multi-value image filter processing apparatus disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 3-185574,
Although the content of the filter is adjusted for the density change, it is not intended to correct the reading resolution of the scanner.Therefore, the resolution of the scanner is partially determined, and the filtering is performed according to the area. There is a problem that the resolution cannot be corrected by the processing.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to calculate the resolution of a resolution original placed on a platen and to set a target resolution in accordance with the calculation result. It is an object of the present invention to provide an image reading apparatus capable of obtaining a stable image quality without variation among individuals by correcting the file strength as much as possible.

[0009]

In order to solve the above problems, an image reading apparatus according to the present invention comprises: a document table; a resolution document arranged on the document table; document reading means for reading the resolution document; Calculating means for analyzing the resolution document data read by the document reading means, wherein the calculation means generates a final image of a target resolution by changing a filter coefficient in accordance with a calculation result of the resolution document data It is characterized by doing.

That is, a document having a resolution placed on a document table is read by document reading means, and a filter coefficient for image processing is changed based on the resolution result of the read resolution document. As a result, it is possible to correct a difference in focus (resolution) between individuals due to assembling accuracy of the scanner or the like, and it is possible to obtain an image having no variation in resolution among individuals. Accordingly, it is possible to relax the mechanical accuracy of the document reading unit.

According to the image reading apparatus of the present invention, the image area read on the document table is divided into a plurality of areas along the main scanning direction, and resolution originals are arranged corresponding to the respective divided areas. The arithmetic means executes the arithmetic processing for each divided area.

For example, when a scanner captures an image with a CCD using a lens, the resolution of the peripheral portion of the lens is reduced due to the performance of the lens. Therefore, there is a difference in resolution between the central portion of the lens and the peripheral portion of the lens. By arranging a plurality of resolution originals in the main scanning direction at the leading end and changing the filter coefficient based on the read result, the difference in resolution can be corrected. Further, even in a reading apparatus such as a CIS in which the resolution (focus) changes uniformly in the main scanning direction, the filter coefficient can be changed, so that the resolution can be corrected and uniform image quality can be obtained. .

Further, according to the image reading apparatus of the present invention, the resolution original is formed in a striped pattern that is continuous in a direction orthogonal to the main scanning direction. As described above, by using a striped resolution original that is continuous in a direction orthogonal to the main scanning direction, it is not necessary to increase the positional accuracy of the scanner when reading the resolution original.

Further, according to the image reading apparatus of the present invention, in the processing of the data obtained by reading the resolution document, the arithmetic means reads the resolution document data a plurality of times while shifting the reading position of the resolution document data in the sub-scanning direction. The arithmetic processing is performed based on a plurality of times of data. As a result, the influence of irregular data such as dirt and scratches on the resolution document can be removed,
Accurate filter control can be performed.

According to the image reading apparatus of the present invention, the image area read by the document table is divided into a plurality of areas along the sub-scanning direction, and resolution originals are arranged corresponding to the respective divided areas. The arithmetic means executes the arithmetic processing for each divided area.

That is, a document having a resolution placed on a document table is read by document reading means, and a filter coefficient for image processing is changed based on the resolution result of the read resolution document. As a result, it is possible to correct a difference in focus (resolution) between individuals due to assembling accuracy of the scanner or the like, and it is possible to obtain an image having no variation in resolution among individuals. Accordingly, it is possible to relax the mechanical accuracy of the document reading unit.

Further, according to the image reading apparatus of the present invention, the resolution original is formed in a stripe pattern continuous in a direction orthogonal to the sub-scanning direction. As described above, by using a resolution original having a stripe pattern continuous in a direction orthogonal to the sub-scanning direction, it is not necessary to increase the position accuracy of the scanner when reading the resolution original.

Further, according to the image reading apparatus of the present invention, in the processing of the data obtained by reading the resolution original, the calculating means reads the resolution original data a plurality of times by shifting the reading position of the original data in the main scanning direction, and reads the data. The arithmetic processing is performed based on a plurality of times of data. As a result, the influence of irregular data such as dirt and scratches on the resolution document can be removed,
Accurate filter control can be performed.

Further, according to the image reading apparatus of the present invention, the shape of the filter for the image processing in the arithmetic means is the same mask shape. In this way, by using the same mask shape for the filter, discontinuity at the boundary between adjacent regions (divided regions) when the filter coefficient is changed can be suppressed.

Further, according to the image reading apparatus of the present invention, the calculating means changes the filter strength of another divided area so as to match the highest resolution part with respect to the calculated resolution result, or It is characterized in that the filter coefficients of all the divided areas are changed to the set target resolution.

As described above, after being adjusted as a mechanism, by compensating the filters of other areas (divided areas) in accordance with the area (divided area) having the highest resolution among them,
The entire scanner can be combined without deteriorating the mechanically superior resolution, and a high-level image reading device can be provided. In addition, by setting a preset resolution as a target, the resolution of the entire system can be improved by the filter even when the resolution of the system is slightly poor.

Further, according to the image reading apparatus of the present invention, the calculating means calculates a filter of all divided areas on the basis of an average resolution of measurement points with respect to a calculation result of resolution data measured on a plurality of resolution originals. The coefficient is changed.

When the resolution is measured for each area (divided area) and the filter of another area (divided area) is adjusted to the best resolution, the filter coefficient becomes too strong, so that the image quality has a poor graininess but is rough. May occur. Therefore, for a scanner that is mechanically adjusted to a certain level, by setting the average resolution for each divided area to the target resolution of that divided area, it is possible to prevent image quality deterioration due to excessive filter strength setting. Can be.

Further, according to the image reading apparatus of the present invention, the arithmetic means limits the intensity of the filter between the adjacent divided regions so that the difference in the value of the pixel of interest is 3 or less. I do. When correcting the filter coefficient for each divided area, if there is a large difference in the filter strength between adjacent divided areas, a discontinuity is generated in the image quality at the boundary between the divided areas in the final image. Therefore, in the present invention, in order to suppress such an adverse effect, a limitation is provided that the difference between the coefficients of the target pixel is 3 or less. Thus, it is possible to prevent a discontinuous line from being generated at the boundary between the divided regions.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram showing the periphery of the copying process of the image reading apparatus according to the present invention. Here, a digital copying machine is taken as an example.

That is, the scanner 1 includes, as main components, a document table 16, a light source 10 for exposing the image surface of a document (not shown) placed on the document table 16, and a reflected light image from the document. , The first to third mirrors 11 to 13 which are polarized in the directions
A lens 14 is provided for imaging the reflected light images polarized by 1 to 13 on the CCD 15. And CC
The image data read in D15 is guided to the image processing device.

The image processing apparatus includes, as main components, an image processing board 2 on which an image processing circuit is mounted, an exposure system 3 using a laser scanner, a photosensitive member 4, a main charger 5, a developing device 6, and a transfer charger 7. Have.

In the above configuration, in the present invention, the document table 1
A resolution original 20 for measuring the resolution is arranged in the non-image area at the front end of No. 6. That is, the resolution original 20 is adhered in a state of being in close contact with the upper surface of the glass surface serving as the original table 16.

FIG. 2 shows an example of the resolution original 20. FIG. 1A shows an example in which a white and black stripe pattern is formed that is continuous in a direction orthogonal to the sub-scanning direction Z (that is, a direction along the main scanning direction Y). (B) shows an example in which the center portion is formed in a donut shape with white and the periphery thereof in black.

Next, a series of procedures of image processing using the image reading apparatus having the above configuration will be described with reference to a flowchart shown in FIG. In this case, however, a document having a stripe pattern shown in FIG.

First, a rough flow of image processing will be described. The image data (analog signal) read by the CCD 15 is input to the image processing board 2. Various processing (A / D conversion, shading correction,
The image data subjected to density conversion, filter processing, electronic zoom resolution processing, gamma correction, error diffusion, etc.) is sent to an exposure system 3 using a laser scanner, and is set to a predetermined dark potential by a main charger 5. The charged photoconductor 4 is exposed. The latent image formed on the photoreceptor 4 is visualized by a developing device 6 and transferred to a transfer paper (not shown) via a transfer charger 7.
In the present embodiment, the writing resolution is 600 dpi (dot / inch), a 0.3 mW semiconductor laser is used as an exposure light source, and the resolution of the CCD 15 used for image input is 600 dpi. The above is the general flow of image processing.

Next, a procedure for reading image data from the resolution document 20 will be described.

First, the light source 10 is turned on, the reflected image from the resolution original 20 is read by the CCD 15 (steps S1 and S2), and the obtained multi-valued data (image data) is read by the image processing circuit of the image processing board 2. To send to. The image processing circuit performs A / D conversion, shading correction, and the like on the obtained image data (steps S3 to S5), and then measures the resolution of the read image data of the resolution document 20 (step S6).

FIG. 4 shows image data of the resolution original 20 read by the CCD 15. The image data of the A / D-converted digital signal is 256-gradation, that is, 8-bit data, and is represented by 255 on the vertical axis in the figure.
Is white and 0 is black.

The ideal read data is indicated by reference numeral 40 in the figure, which has the shape pattern of the resolution original 20 shown in FIG.
1, the read data having a shape different from the shape pattern of the resolution original 20 due to the resolution of the CCD 15, the aberration of the lenses 11 to 13 and the focus (resolution). Waveform data indicated by the middle code 402).

Here, FIG.
Is used, the degree of focus (resolution) is determined by CTF (Contrast Transfer).
Function). That is, CT
F = (max-min) / (max-min) was used. As a result of calculating the CTF for the resolution original 20 shown in FIG. 2A, CTF = 0.5 in the present embodiment. C
The larger the numerical value of TF, the better the resolving power.

On the other hand, the image processing circuit includes a filter processing circuit for emphasizing or weakening the image quality according to the purpose. In the present embodiment, a filter having a mask size of 5 × 5 is used as a basic shape of a filter of the filter processing circuit.

FIG. 5 shows this reference filter.

That is, it is composed of a pixel of interest (coefficient X is written) located at the center and 24 pixels around it. This reference filter may be set for each image quality mode (character mode, photo mode, etc.) or for each area obtained by separating the captured image into a specific area by the area separation function. However, for the sake of simplicity, here, the character mode is selected in image quality selection, and the same filter is used throughout without using the area separation function.

FIG. 6 shows the filter strength when the coefficient X is changed.

The filter strength is defined as F = X / Σfi (fi
Is the coefficient assigned to the filter mask, 25 in this embodiment), and the larger the value of f, the stronger the filter strength. That is, in the shape shown in FIG. 5, F increases as the value of X decreases, and the effect as a filter increases. The present invention is characterized in that the value (coefficient) of the target pixel can be arbitrarily changed based on the result of the above-described CTF with respect to this reference filter.

FIG. 7 shows the relationship between the calculation result of the CTF in the optical system used in this embodiment and the set value (coefficient value) of the target pixel of the filter.

In the present embodiment, the target resolution is CTF = 0.6, and the coefficient X at that time is 50. That is, C
When the TF is less than 0.6, a predetermined resolution is not obtained.
By increasing the filter strength by decreasing the value of X, the resolution is increased as the final output result.

For example, if the CTF obtained from the measurement is 0.5
If, the filter coefficient X is determined to be 47 from FIG. 7 based on the target CTF = 0.6 (step S7).
The filter coefficients thus determined are written in a memory (not shown) on the image processing board 2. Thereafter, when printing, the character mode is processed using the filter coefficients determined here.

After the filter coefficients are determined in this manner, a normal copy operation is performed (steps S8 to S8).
20). That is, the multi-valued image data captured by the scanner 1 is subjected to input γ correction and subjected to a filter process using the filter coefficients determined as described above (step S1).
5) Perform gamma correction according to the output device (step S1)
7). Then, after performing the binary error diffusion process (step S18), the image data is sent to a laser (not shown) of the exposure system 3 (step S19), and printing is executed through a printing process (step S20).

As described above, the resolution of the resolution document 20 placed on the document table 16 is calculated, and the filter strength is corrected in accordance with the calculation result to obtain the target resolution, thereby obtaining the final image quality. It is possible to obtain a stable image quality without variation between individuals.

The process of changing the filter coefficient (correcting the filter strength) in the above embodiment is performed at the site where the image reading apparatus is manufactured, and is adjusted by exchanging mechanical parts related to the scanner 1 at the user's site or the like. It is performed when you do. Although the original shown in FIG. 2A is used as the original 20 for the resolution, the original 20 having the shape shown in FIG. Similar results could be obtained even if the frequency of the part was adopted as a guideline for the resolution.

FIG. 8 shows an image reading apparatus having the above-described configuration, in which the resolution originals 20f, 20c, and 20r are placed on the original platen 16.
In the first embodiment, three positions are arranged along the main scanning direction Y: front (front) Rf, center (center) Rc, and rear (rear) Rr. FIG. 8 is a diagram of the document table 16 as viewed from above.

That is, the image area to be read on the document table 16 is divided into three areas along the main scanning direction Y,
The configuration is such that resolution originals 20f, 20c, and 20r are arranged corresponding to three locations of each of the divided areas 16f, 16c, and 16r. The image data Df, Dc, and Dr read from the resolution originals 20r, 20c, and 20f are different read data from all three locations as described above.

As a result of calculating the CTF for each of the image data Df, Dc, and Dr, in the first embodiment, for example, CTF (CTFf) of the image data Df = 0.4, CTF (CTFc) of the image data Dc = 0.6, and CTF of image data Dr (CTFr) = 0.5.
Since the larger the numerical value of CTF, the better the resolution, the above result shows that the resolution of the divided region 16c as the center Rc is the best and the resolution of the divided region 16r as the front Rf is the lowest.

Therefore, in the filter processing by the image processing circuit on the image processing board 2, each of the three divided areas 16
f, 16c, 16r, each resolution original 20f,
A corresponding to the resolutions of 20c and 20r
f, Ac, and Ar. Specifically, the target resolution is set to C
In order to make the center Rc value “0.6” indicating the maximum value of the TF, the front Rf side (divided area 16f) corresponds to the target pixel of the filter from the reading result of each resolution original 20f, 20c, 20r. 7 to 4
3 is determined. On the rear Rr side (divided region 16r), the coefficient X for the target pixel of the filter is calculated from FIG.
To decide.

Each of the divided areas 16f, 1
Filter coefficients “43, 50, 4” for 6c and 16r
7 ”is written in a memory on the image processing board 2 (not shown). Thereafter, when printing is performed, for the character mode, each divided area 16 is determined using the filter coefficient determined here.
Filter processing at f, 16c, 16r is performed.

As described above, the main scanning direction Y on the document table 16
Originals 20f, 20c, 2
0r is calculated, and according to the calculation result, for each of the divided areas 16f, 16c, and 16r, the filter strength is corrected to obtain the target resolution, and the final image quality is obtained. Image quality can be obtained.

In the first embodiment, the target value of the CTF is described as a preset value (here, 0.6). However, depending on the configuration of the scanner 1, the target value is set to each resolution original 20f, 20c. , 20r, it may be better to use the average value of the resolution indices obtained as the target value. That is,
When the resolution is measured for each of the divided regions 16f, 16c, and 16r, and the filters of the other divided regions are adjusted to the best resolution, the filter coefficient becomes too strong in the region with a low resolution (for example, the divided region 16f). The image quality is poor in graininess but may cause roughness. Therefore, by setting the average resolution of each divided region to the target resolution of the divided region, it is possible to prevent excessive filter correction from being applied. That is, it is possible to prevent the image quality from deteriorating.

In the first embodiment, the black line portions 201 of the resolution originals 20f, 20c, and 20r (FIG. 2A)
The length t is set to 7 mm or more, and when obtaining the CTF from the image data obtained by reading the resolution originals 20f, 20c, and 20r, the reading position is shifted by 40 pixels (about 1.69 mm) at five positions. And the maximum and minimum data were subtracted from the obtained data.
The number of CTFs may be used as the measurement value of the location. Thereby, when dust or the like is attached near the resolution originals 20f, 20c, and 20r, even if the value of the CTF at one location changes due to the influence, the change can be eliminated, thereby improving the reliability of the filter coefficient. be able to.

The processing of changing the filter coefficient (correcting the filter strength) in the first embodiment is also performed at the site where the image reading apparatus is manufactured, and by exchanging mechanical parts related to the scanner 1 at the user's site or the like. It is performed when making adjustments.

FIG. 9 shows an embodiment 2 in which the resolution originals 20l and 20h are arranged at two places, left Rl and right Rh, along the sub-scanning direction Z of the original table 16 in the image reading apparatus having the above-mentioned configuration. . FIG. 9 is a diagram of the document table 16 as viewed from above.

That is, the image area to be read on the document table 16 is divided into two areas along the sub-scanning direction Z,
The configuration is such that resolution originals 20l and 20h are arranged corresponding to two places of the divided areas 16l and 16h. FIG.
Indicates an example of the resolution originals 20l and 20h, and is formed in a white and black stripe pattern that is continuous in a direction orthogonal to the main scanning direction Y (that is, a direction along the sub scanning direction Z). I have. As described above, the image data Dl and Dh read from the resolution originals 20l and 20h are different from each other at two locations.

As a result of calculating the CTF for each of the image data Dl and Dh, in the second embodiment, the target C
For TF (= 0.6), for example, C of image data Dl
TF (CTFl) = 0.7, CTF of image data Dh
It is assumed that (CTFh) = 0.5. The larger the value of CTF, the better the resolving power.
It can be seen that the resolution of the divided region 16l that is 1 is larger than the target value, and the resolution of the divided region 16h that is right Rh is smaller than the target value.

Therefore, in the filter processing by the image processing circuit on the image processing board 2, each divided area 16
The resolutions of l and 16h are set to Al and Ah, respectively, in a form corresponding to the resolutions of the originals 20l and 20h. Specifically, in order to set the target resolution to the target value of CTF “0.6”, the left Rl (divided area 16l) corresponds to the target pixel of the filter from the reading result of each resolution original 20l, 20h. The coefficient X is determined from FIGS.
Also, for the right Rh (divided area 16h), the coefficient X for the target pixel of the filter is determined as shown in FIGS.

Each of the divided areas 16l, 1
The filter coefficients “52, 47” for 6h are written in a memory on the image processing board 2 (not shown). Thereafter, when printing, for the character mode, filter processing is performed in each of the divided areas 16l and 16h using the filter coefficient determined here.

As described above, the sub-scanning direction Z
The resolution of each of the resolution originals 20l and 20h arranged at the two positions is calculated, and according to the calculation result, each of the divided areas 16l and 20h is determined.
By correcting the filter strength to obtain the target resolution for each of l and 16h to obtain the final image quality, it is possible to obtain the image quality of uniform resolution over the entire surface. That is, in the related art, the scanner 1 is not set parallel to the document surface in the sub-scanning direction Z.
Since the difference in resolution between l) and the latter half (divided area 16h) can be reduced by adjusting the filter strength, it is possible to obtain an image with uniform resolution in the entire sub-scanning direction Z.

In the second embodiment, the filter is divided into two in the sub scanning direction Z. Near the boundary between the two regions (FIG. 9
In FIG. 2, the resolution of the input image has little difference. Here, in order to see the difference in image quality near the boundary, filter strength was changed, and confirmation experiments were performed for various filter shapes. The result is shown in FIG.
Shown in Filter shape (for example, 3 × 3, 5 × 5, 7 ×
7 and the like, and 3 × 5, 7 × 5 and the like rectangular types), and changes in filter coefficients, etc., cause differences in image quality. FIG.
This shows a case where the coefficient (intensity) of the pixel of interest is changed in two ways for three shape types A, B, and C.

That is, in the filter shape A, the difference in image quality between two cases where the intensity of the target pixel is changed is evaluated. The same evaluation was performed for the filter shapes B and C. As a result, as is clear from FIG. 11, if the difference in the intensity (coefficient value) of the pixel of interest is less than or equal to 3 at the boundary, it is found that the difference in image quality at the boundary portion 21 is acceptable. . Therefore, in the present embodiment, the first embodiment is used.
Also, including the second embodiment, a filter determination method in which a filter intensity difference (coefficient difference of a pixel of interest) between regions is limited to 3 or less is adopted. According to this determination method, even in the vicinity of the boundary between the regions where the filter strengths have been changed, it was possible to obtain a uniform resolution over the entire screen without a sense of incompatibility in image quality.

In the above embodiment, the resolution original 20
(20f, 20c, 20r, 20l, 20h) are described as being arranged in advance in the periphery of the document table 16, but when determining the filter coefficients, the resolution document 20 is placed at a predetermined location on the document table 16. May be set to determine the resolution.

Further, in the above embodiment, the image reading apparatus of the present invention is described as a digital copying machine for performing printing, but image data is discharged as a scanner output in a scanner function or the like having a multifunction machine. At times, it is possible to adopt a configuration in which the resolution is made uniform by a similar method.

[0068]

According to the image reading apparatus of the present invention, a document having a resolution placed on a document table is read by document reading means, and a filter coefficient for image processing is determined based on the resolution result of the read resolution document. Since the configuration is changed, it is possible to correct that the focus (resolution) differs between individuals due to the assembling accuracy of the scanner and the like, and it is possible to obtain an image quality in which the resolution does not vary among individuals. Also,
Along with this, the mechanical accuracy of the document reading means can be relaxed and the cost can be reduced.

Further, according to the image reading apparatus of the present invention, the image area read on the document table is divided into a plurality of areas along the main scanning direction, and resolution originals are arranged corresponding to the respective divided areas. The means is configured to execute arithmetic processing for each divided area. That is, a plurality of resolution originals are arranged in the main scanning direction at the end of the original platen,
By changing the filter coefficient based on the read result, the difference in resolution can be corrected. Also,
Even in a reading apparatus in which the resolution (focus) changes uniformly in the main scanning direction like the CIS, the filter coefficient can be changed, so that the resolution can be corrected and uniform image quality can be obtained.

Further, according to the image reading apparatus of the present invention, since the resolution original is formed in a stripe pattern continuous in the direction orthogonal to the main scanning direction, the position of the scanner when reading the resolution original is set. Since there is no need to increase the accuracy, it can be provided at a low cost.

According to the image reading apparatus of the present invention, in the processing of the data obtained by reading the resolution original, the calculating means reads the resolution original data a plurality of times while shifting the reading position in the sub-scanning direction, and reads the read plural times. Because the calculation processing is executed based on the data of the times,
The influence of irregular data such as dirt and scratches on the resolution document can be removed, and accurate filter control can be performed.

Further, according to the image reading apparatus of the present invention, the image area read on the document table is divided into a plurality of areas along the sub-scanning direction, and a resolution original is arranged corresponding to each divided area. The means is configured to execute arithmetic processing for each divided area. That is, by reading the resolution original placed on the platen by the original reading means, and changing the filter coefficient of the image processing based on the resolution result of the read resolution original, it is possible to focus on the assembling accuracy of the scanner or the like. (Resolution) differs between individuals, and image quality without variation in resolution among individuals can be obtained. Also, with this,
The mechanical accuracy of the document reading means can be reduced, and the cost can be reduced.

According to the image reading apparatus of the present invention, since the resolution original is formed in a striped pattern that is continuous in a direction orthogonal to the sub-scanning direction, the position of the scanner when reading the resolution original is set. Since there is no need to increase the accuracy, it can be provided at a low cost.

Further, according to the image reading apparatus of the present invention, in the processing of the data obtained by reading the resolution original, the calculating means reads the resolution original data a plurality of times by shifting the reading position of the original document in the main scanning direction, and reads the read plural times. Because the calculation processing is executed based on the data of the times,
The influence of irregular data such as dirt and scratches on the resolution document can be removed, and accurate filter control can be performed.

Further, according to the image reading apparatus of the present invention, since the shape of the filter for the image processing in the arithmetic means is the same mask shape, the shape of the filter in the adjacent area (divided area) when the coefficient of the filter is changed. The discontinuity at the boundary can be suppressed.

Further, according to the image reading apparatus of the present invention, the calculating means changes the filter strength of another divided area so as to match the highest resolution part with respect to the calculated result of the resolution, or sets it in advance. The filter coefficients of all the divided areas are changed to the target resolution set. In other words, by correcting the filters of other areas (divided areas) in accordance with the area (divided area) having the highest resolution, without impairing the mechanically highest resolution,
The entire scanner can be combined, and a high-level image reading device can be provided. In addition, by setting a preset resolution as a target, the resolution of the entire system can be improved by the filter even when the resolution of the system is slightly poor.

Further, according to the image reading apparatus of the present invention, the calculating means calculates the filter coefficients of all the divided areas on the basis of the average resolution of the measurement points with respect to the calculation result of the resolution data measured on the plurality of resolution originals. Is changed. In other words, mechanically, for a scanner that has been adjusted to a certain level, the average resolution for each divided area,
By setting the target resolution of the divided area, it is possible to prevent the image quality from deteriorating due to the excessive filter strength setting.

Further, according to the image reading apparatus of the present invention, the arithmetic means limits the intensity of the filter between the adjacent divided regions so that the difference in the value of the pixel of interest becomes 3 or less. That is, when the filter coefficient is corrected for each divided region, if there is a large difference in the filter strength between adjacent divided regions, a discontinuity is generated in the image quality at the boundary between the divided regions in the final image. By the configuration of
It is possible to prevent a discontinuous line from being generated at the boundary between the divided regions.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the periphery of a copying process of an image reading apparatus according to the present invention.

FIGS. 2A and 2B show an example of a resolution original, wherein FIG. 2A shows an example in which white and black stripes are formed in a direction perpendicular to the sub-scanning direction, and FIG. It is explanatory drawing which shows the example formed in the donut shape which made the circumference | surroundings black, respectively.

FIG. 3 is a flowchart illustrating a series of procedures of image processing using the image reading apparatus according to the embodiment.

FIG. 4 is a waveform diagram showing read data of a resolution original read by a CCD.

FIG. 5 is an explanatory diagram illustrating a configuration of a reference filter.

FIG. 6 is a graph showing a change in filter strength when a coefficient value of a pixel of interest is changed.

FIG. 7 is a graph showing a relationship between a calculation result of CTF in the optical system used in the present embodiment and a set value (coefficient value) of a target pixel of a filter.

FIG. 8 is an explanatory diagram showing Example 1 in which the resolution document is arranged at three places along the main scanning direction of the document table in the image reading apparatus of the embodiment.

FIG. 9 is an explanatory diagram showing Example 2 in which the resolution reading document is arranged at two places along the sub-scanning direction of the document table in the image reading apparatus of the embodiment.

FIG. 10 is an explanatory diagram illustrating an example of a resolution document formed in a white and black stripe pattern that is continuous in a direction orthogonal to the main scanning direction.

FIG. 11 is a table showing a result of experimentally determining a relationship between a filter intensity difference and an image quality.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scanner 2 Image processing board 3 Exposure system 4 Photoreceptor 5 Main charger 6 Developing device 7 Transfer charger 11 First mirror 12 Second mirror 13 Third mirror 14 Lens 15 CCD 16 Original table 20 Resolution original 16f, 16c , 16r, 16l, 16h Divided area 20f, 20c, 20r, 201, 20h Resolution original

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mihoko Tanimura 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Masaaki Otsuki 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside (72) Inventor Noriyasu Yasuoka 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Eiji Saiko 22-22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation F term (reference) 5B047 AA01 AB02 BB02 BC05 BC09 BC11 BC14 BC23 CA06 CB22 DB01 DC06 5B057 AA11 BA02 BA19 CA08 CA12 CA16 CB08 CB12 CB16 CC02 CE03 CE06 CH09 CH18 5C072 AA01 BA16 CA02 DA02 DA04 EA05 FB21A27 EB21 A27 FB21A 5C077 PP03 PP20 PP21 PP49 PP68 PP71 PQ08 PQ12 SS01 TT06

Claims (11)

[Claims] An original document, a resolution original document placed on the original document table, document reading means for reading the resolution document, and an arithmetic means for analyzing the resolution document data read by the document reading means; An image reading apparatus according to claim 1, wherein said calculating means generates a final image having a target resolution by changing a filter coefficient according to a calculation result of the resolution document data. 2. An image area to be read on the platen is divided into a plurality of areas along a main scanning direction, and a resolution document is arranged corresponding to each of the divided areas. The image reading device according to claim 1, wherein the arithmetic processing is performed. 3. The image reading apparatus according to claim 2, wherein the resolution original is formed in a striped pattern that is continuous in a direction orthogonal to the main scanning direction. 4. In the processing of data obtained by reading a resolution original, the arithmetic means reads a plurality of times by shifting a reading position of the resolution original data in the sub-scanning direction, and performs the arithmetic processing based on the read data a plurality of times. The image reading device according to claim 2, wherein the image reading device performs the following. 5. An image area to be read on the document table is divided into a plurality of areas along a sub-scanning direction, and a resolution document is arranged corresponding to each of the divided areas. The image reading device according to claim 1, wherein the arithmetic processing is performed. 6. The image reading apparatus according to claim 5, wherein the resolution original is formed in a stripe pattern that is continuous in a direction orthogonal to the sub-scanning direction. 7. In the processing of data read from a resolution document, the calculation means reads the resolution document data a plurality of times while shifting the reading position in the main scanning direction, and performs the calculation processing based on the read data a plurality of times. The image reading device according to claim 3, wherein the image reading device performs the following. 8. The image processing apparatus according to claim 1, wherein the shape of the filter for image processing in the calculation means is the same mask shape.
The image reading device according to claim 7. 9. The calculating means changes the filter strength of another divided area so as to match the highest resolution part with respect to the result of the calculated resolution, or changes all filter areas to a preset target resolution. 9. The image reading device according to claim 2, wherein the filter coefficient is changed. 10. The method according to claim 1, wherein the calculating means changes the filter coefficients of all the divided areas on the basis of the average resolution of the measurement points with respect to the calculation result of the resolution data measured on the plurality of resolution originals. The image reading device according to claim 2 or 5. 11. The method according to claim 2, wherein the calculation unit limits the filter strength between adjacent divided regions so that the difference between the values of the target pixels is 3 or less. Image reading device.