JP2003234888A - Image correction device, program, storage medium, and method for correcting image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize a change in a distance between the external form of each page after correcting a skew and the locus of an optical axis and to suitably correct three-dimensional distortion in a sub-scanning direction on the basis of the external shape of the page. <P>SOLUTION: The skew angle θ of a scanned image is detected by a binding part boundary TS corresponding to the page binding part of a book original which is detected on the basis of the external form of the page of the book original arranged on the upper and lower sides of the scanned image in a main scanning direction and the main scanning direction of image reading. The skew of the scanned image is corrected by rotating the whole scanned image only by the skew angle θ around an intersecting point O between the locus of the optical axis of an image reading means and the binding part boundary TS. Since the change in the distance between the external form of each page after skew correction and the locus of the optical axis can be minimized, the three- dimensional distortion in the sub-scanning direction on the basis of the external shape of the page can be suitably corrected. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image correction device, a program, a storage medium and an image correction method.

[0002]

2. Description of the Related Art Most of originals read by using a flat bed scanner are sheet-like originals. An openable / closable pressure plate is provided on a contact glass, and the original is placed on the contact glass and then closed to close the original. I try to scan. However, the originals are not limited to sheet-like ones, and book originals (books, booklets, etc.) may also be handled as originals. In such a case, place the book original on the contact glass and scan the original. Will be done.

However, when a book document is used as the document, the page binding portion 101 of the book document 100 is lifted from the contact glass 102 as shown in FIG. When the page binding portion 101 of the book original 100 floats above the contact glass 102 in this way, the page binding portion 101 moves away from the focal plane, so that the scan image of the floating portion has image distortion and shadow. , Image deterioration such as character blurring occurs. The page binding section 101 of the deteriorated image is difficult to read,
The recognition rate when performing character recognition processing by OCR is significantly reduced. Especially in thick bookbinding, the ratio is high. Also,
When the page binding portion 101 of the book original 100 is pressed so as not to be separated from the focal plane, the book original 100
It may damage itself.

In order to solve such a problem, there has been proposed a method of correcting image distortion by using a method of estimating a three-dimensional shape of an object from density information of the image. As a method for estimating the three-dimensional shape of an object from such density information of an image, T. Wada, H. Uchida and T. Matsuyama, “Sha
pe from Shading with Interreflections under a Prox
imal Light Source: Distortion-Free Copying of an U
nfolded Book ”, International Journal Computer Vis
Ion 24 (2), 125-135 (1997) Shape from
The method called Shading is a typical example.

However, the above-mentioned Shape from Shadi
According to the method called ng, the amount of calculation is large and the calculation time of the distortion correction processing is long, so that it is difficult to put it into practical use.

The method disclosed in Japanese Patent Laid-Open No. 5-160002 is not suitable because a special shape measuring device for measuring the shape of a book by the triangulation method is required.

Therefore, in recent years, in order to effectively correct the distortion with a small amount of calculation, an image correction apparatus has been proposed which estimates the three-dimensional shape of the book surface using the shape of the page outline of the read scan image ( For example, JP-A-11-414
(See Publication No. 55, etc.).

[0008]

By the way, when setting a book original on the contact glass, it is necessary to set the image of the book original face down, so that the operator can see only the back surface of the original. Has become. Therefore, as shown in FIG. 31, a scan image in which a page binding portion of a book document is inclined with respect to the main scanning direction, that is, a so-called skew may occur in the scan image.

However, since the conventional image correction method does not take these situations into consideration, if such distortion of the scanned image is corrected, not only the correction cannot be sufficiently performed, but also the image quality is deteriorated. There is.

An object of the present invention is to minimize the change in the distance between each page outline after skew correction and the optical axis locus, and to obtain a three-dimensional shape in the sub-scanning direction based on the page outline shape. An object of the present invention is to provide an image correction device, a program, a storage medium, and an image correction method capable of appropriately performing distortion correction.

An object of the present invention is to provide an image correction device, a program, and a program capable of avoiding deterioration of image quality due to distortion correction.
A storage medium and an image correction method are provided.

[0012]

An image correcting apparatus according to the present invention is a book document in which a page binding portion is substantially parallel to a main scanning direction of image reading and is brought into contact with an upper or lower portion of a contact glass. In an image correction device that corrects the scanned image read by the image reading means,
Based on the page outline extracting means for extracting the page outline of the book document located near the upper side and the lower side in the main scanning direction of the scan image from the scan image, and the page outline extracted by the page outline extracting means. The binding part boundary line detecting means for detecting the binding part boundary line corresponding to the page binding part, and the angle formed between the binding part boundary line detected by the binding part boundary line detecting means and the main scanning direction of the image reading, The skew angle detecting means for detecting the skew angle of the scanned image, and the scan for the skew angle detected by the skew angle detecting means around the intersection of the locus of the optical axis of the image reading means and the binding part boundary line. Skew correction means for rotating the entire image to correct the skew of the scanned image, and the shape of the page outer shape And an image distortion correcting means for correcting the three-dimensional shape distortion of the scanned image based.

Therefore, the binding part boundary line corresponding to the page binding part of the book document is detected based on the page outlines of the book document located near the upper side and the lower side of the scanned image in the main scanning direction. The skew angle of the scanned image is detected depending on the main scanning direction of image reading. Then, the skew of the scan image is corrected by rotating the entire scan image by the skew angle about the intersection of the locus of the optical axis of the image reading means and the binding part boundary line. In the scan image in which the skew is corrected in this way, the three-dimensional shape distortion is also corrected based on the shape of the page outline. As a result, in skew correction, since rotation is performed around the intersection of the optical axis trajectory of the image reading means and the binding part boundary line, the distance between each page outline after skew correction and the optical axis trajectory is corrected. Therefore, even if the detected skew angle is large, it is possible to appropriately perform the three-dimensional shape distortion correction in the sub-scanning direction based on the shape of the page outline. Become.

According to a second aspect of the present invention, in the image correction apparatus according to the first aspect, the page outer shape extracting means includes pages of the book document from within a certain range from a central position of the scan image in the sub-scanning direction. Extract the outline.

Therefore, it is considered that the position of the binding line boundary line of the scan image exists substantially at the center of the scan image in the sub-scanning direction, and thus the range to be searched in this way is constant from the center position of the scan image in the sub-scanning direction. By limiting the area to the range, the processing time can be shortened.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the image correction apparatus described above, the binding portion boundary line detecting unit determines a point having a minimum coordinate value in the main scanning direction for the page outer shape located on the upper side in the main scanning direction extracted by the page outer shape extracting unit. As one end point of the binding section boundary line, and for the page outer shape located on the lower side in the main scanning direction, the point having the maximum coordinate value in the main scanning direction is the other end point of the binding section boundary line, and a line connecting both end points The minute is regarded as the boundary line of the binding portion.

Therefore, since the binding portion boundary line corresponding to the page binding portion is a line segment that connects the two points that are most indented inside the page outline on the upper side and the lower side in the main scanning direction of the scanned image, the page binding portion is surely It is possible to detect the corresponding binding part boundary line.

The invention according to claim 4 is the invention according to claims 1 to 3.
In the image correction device described in any one of 1 to 3, the skew correction unit includes a linear interpolation unit that performs a linear interpolation process based on pixel values of four adjacent blocks for each pixel value of the scanned image after image rotation. .

Therefore, the coordinates of the pixels of the image corrected by rotating the entire scan image will not be decimal.
This makes it possible to maintain the image quality of the skew corrected image.

The present invention as defined in claim 5 is any one of claims 1 to 4.
In the image correction device according to any one of the items 1 to 5, a correction selection unit that selectively executes the skew correction unit and the image distortion correction unit according to an absolute value of the skew angle detected by the skew angle detection unit is provided. Prepare

Therefore, it becomes possible to selectively execute the skew correction means and the image distortion correction means according to the magnitude of the absolute value of the skew angle. For example, in an image in which the absolute value of the skew angle is very small. Even if the skew correction is not performed, the correction can be sufficiently performed by only the three-dimensional shape distortion correction. Therefore, the skew correction can be omitted to shorten the processing time, and the three-dimensional image can be processed in a very large absolute value of the skew angle. When the shape distortion correction is performed, the distortion may rather increase and the image quality may be deteriorated. Therefore, in this case, if the skew correction and the distortion correction are not performed, the deterioration of the image quality due to the distortion correction can be avoided. It becomes possible to do.

According to a sixth aspect of the present invention, in the image correction apparatus according to the fifth aspect, the correction selecting means is a first absolute value of the skew angle detected by the skew angle detecting means. When it is equal to or more than the threshold value, the skew correction by the skew correction means and the distortion correction by the image distortion correction means with respect to the scan image are not performed, and the absolute value of the skew angle detected by the skew angle detection means is the first value. Is less than the threshold value and is greater than or equal to a second threshold value that is set in advance, the three-dimensional shape distortion of the scan image whose skew has been corrected by the skew correction means is corrected by the image distortion correction means, and the skew is corrected. When the absolute value of the skew angle detected by the angle detection means is less than the second threshold value,
Only the three-dimensional shape distortion of the scan image is corrected by the image distortion correction means without performing the skew correction by the skew correction means.

Therefore, if the absolute value of the skew angle is less than the first threshold value, the process is continued, otherwise the process is interrupted. Then, even when the processing is continued, if the absolute value of the skew angle is equal to or larger than the second threshold value, the three-dimensional shape distortion correction processing is executed after the skew correction. This makes it possible to avoid deterioration of image quality due to distortion correction.

According to a seventh aspect of the invention, in the image correction apparatus according to the fifth aspect, the correction selecting means has an absolute value of the skew angle detected by the skew angle detecting means which is equal to or larger than a predetermined threshold value. In this case, the image distortion correction unit corrects the three-dimensional shape distortion of the scan image whose skew has been corrected by the skew correction unit, and the absolute value of the skew angle detected by the skew angle detection unit is predetermined. If it is less than the threshold value, the skew correction by the skew correction unit is not performed, and only the three-dimensional shape distortion of the scan image is corrected by the image distortion correction unit.

Therefore, if the absolute value of the skew angle is greater than or equal to the threshold value, the three-dimensional shape distortion correction processing is executed after the skew correction, and if not, only the three-dimensional shape distortion correction processing is executed without performing the skew correction. It This makes it possible to avoid deterioration of image quality due to distortion correction.

According to an eighth aspect of the present invention, in the image correction apparatus according to the fifth aspect, the correction selecting means has an absolute value of the skew angle detected by the skew angle detecting means which is equal to or larger than a predetermined threshold value. In this case, skew correction by the skew correction unit and distortion correction by the image distortion correction unit with respect to the scan image are not performed,
When the absolute value of the skew angle detected by the skew angle detecting means is less than a predetermined threshold value,
The image distortion correction unit corrects the three-dimensional shape distortion of the scan image whose skew has been corrected by the skew correction unit.

Therefore, if the absolute value of the skew angle is equal to or larger than the predetermined threshold value, the processing is interrupted, and if not, the three-dimensional shape distortion correction processing is executed after the skew correction. This makes it possible to avoid deterioration of image quality due to distortion correction.

According to a ninth aspect of the present invention, there is provided a program for scanning a book document, which is brought into contact with the top or bottom of a contact glass with the page binding portion substantially parallel to the main scanning direction of image reading, read by the image reading means. A program for causing a computer to perform image correction of an image, the page outline extracting function for causing the computer to extract the page outline of the book document located near the upper side and the lower side in the main scanning direction of the scan image from the scan image. And a binding part boundary line detecting function for detecting a binding part boundary line corresponding to the page binding part based on the page external shape extracted by the page external shape extracting function, and a binding part boundary line detecting function. The angle formed between the binding portion boundary line and the main scanning direction of image reading is the skew of the scanned image. Skew angle detection function for detecting the degree as a degree, and rotating the entire scan image by the skew angle detected by the skew angle detection function around the intersection of the locus of the optical axis of the image reading means and the binding part boundary line. Then, the skew correction function for correcting the skew of the scan image and the image distortion correction function for correcting the three-dimensional shape distortion of the scan image based on the shape of the page outer shape are executed.

Therefore, the binding part boundary line corresponding to the page binding part of the book document is detected based on the page outline of the book document located near the upper side and the lower side of the scanned image in the main scanning direction. The skew angle of the scanned image is detected depending on the main scanning direction of image reading. Then, the skew of the scan image is corrected by rotating the entire scan image by the skew angle about the intersection of the locus of the optical axis of the image reading means and the binding part boundary line. In the scan image in which the skew is corrected in this way, the three-dimensional shape distortion is also corrected based on the shape of the page outline. As a result, in skew correction, since rotation is performed around the intersection of the optical axis trajectory of the image reading means and the binding part boundary line, the distance between each page outline after skew correction and the optical axis trajectory is corrected. Therefore, even if the detected skew angle is large, it is possible to appropriately perform the three-dimensional shape distortion correction in the sub-scanning direction based on the shape of the page outline. Become.

In the storage medium according to the tenth aspect of the present invention, the book reading original which is brought into contact with the upper or lower side of the contact glass with the page binding portion substantially parallel to the main scanning direction of image reading is read by the image reading means. A computer-readable storage medium that stores a program for causing a computer to perform image correction of a scan image, the page outline of the book document being located in the computer near an upper side and a lower side in a main scanning direction of the scan image. A page outline extraction function for extracting from the scan image, and a binding part boundary line detection function for detecting a binding part boundary line corresponding to the page binding part based on the page outline extracted by the page external shape extraction function, The binding part boundary line detected by this binding part boundary line detection function and the main scanning of the image A skew angle detection function for detecting the angle formed by the direction as the skew angle of the scan image, and the skew angle detection function for detecting the skew angle of the optical axis of the image reading means and the boundary line of the binding portion as the center. A skew correction function of correcting the skew of the scan image by rotating the entire scan image by the skew angle, and an image distortion correction function of correcting three-dimensional shape distortion of the scan image based on the shape of the page outer shape. , A program for executing, is stored.

Therefore, the binding part boundary line corresponding to the page binding part of the book document is detected based on the page outlines of the book document located near the upper side and the lower side in the main scanning direction of the scanned image. The skew angle of the scanned image is detected depending on the main scanning direction of image reading. Then, the skew of the scan image is corrected by rotating the entire scan image by the skew angle about the intersection of the locus of the optical axis of the image reading means and the binding part boundary line. In the scan image in which the skew is corrected in this way, the three-dimensional shape distortion is also corrected based on the shape of the page outline. As a result, in skew correction, since rotation is performed around the intersection of the optical axis trajectory of the image reading means and the binding part boundary line, the distance between each page outline after skew correction and the optical axis trajectory is corrected. Therefore, even if the detected skew angle is large, it is possible to appropriately perform the three-dimensional shape distortion correction in the sub-scanning direction based on the shape of the page outline. Become.

The image correction method according to the invention of claim 11 is
An image correction method for a scan image obtained by reading a book document, which is brought into contact with the top or bottom of a contact glass with the page binding portion substantially parallel to the main scanning direction of image reading, by an image reading means. A page outline extraction step of extracting the page outline of the book document located near the upper side and the lower side in the main scanning direction from the scan image, and the page binding section based on the page outline extracted by the page outline extraction step. A binding portion boundary line detecting step of detecting a corresponding binding portion boundary line, and an angle formed between the binding portion boundary line detected by the binding portion boundary line detecting step and a main scanning direction of image reading is a skew of the scan image. The skew angle detecting step of detecting the angle, and the intersection point of the locus of the optical axis of the image reading means and the binding part boundary line A skew correction step of correcting the skew of the scan image by rotating the entire scan image by the skew angle detected by the skew angle detecting means as a core, and a three-dimensional image of the scan image based on the shape of the page outline. An image distortion correction step of correcting the shape distortion.

Therefore, the binding part boundary line corresponding to the page binding part of the book document is detected based on the page outlines of the book document located near the upper side and the lower side of the scanned image in the main scanning direction. The skew angle of the scanned image is detected depending on the main scanning direction of image reading. Then, the skew of the scan image is corrected by rotating the entire scan image by the skew angle about the intersection of the locus of the optical axis of the image reading means and the binding part boundary line. In the scan image in which the skew is corrected in this way, the three-dimensional shape distortion is also corrected based on the shape of the page outline. As a result, in skew correction, since rotation is performed around the intersection of the optical axis trajectory of the image reading means and the binding part boundary line, the distance between each page outline after skew correction and the optical axis trajectory is corrected. Therefore, even if the detected skew angle is large, it is possible to appropriately perform the three-dimensional shape distortion correction in the sub-scanning direction based on the shape of the page outline. Become.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention.
25 to 25 will be described. The image correction apparatus of the present embodiment is provided in a digital copying machine which is an image forming apparatus, and the scanner unit of the digital copying machine is applied as the image reading apparatus.

Here, FIG. 1 is a vertical sectional front view showing the configuration of the scanner unit 1. As shown in FIG. 1, the scanner unit 1
Is a contact glass 2 on which an original is placed, a first traveling body 5 including an exposure lamp 3 for exposing the original and a first reflecting mirror 4, and a second traveling mirror including a second reflecting mirror 6 and a third reflecting mirror 7. A running body 8, a CCD (Charge Coupled Device) 9 as an image pickup device for reading an image of an original, and a C
A lens unit 10 for forming an image on the CD 9, a document scale 11 that serves as a reference for placing a document and prevents the contact glass 2 from being displaced or dislocated, and for shading correction installed under the document scale 11. The white reference plate 12 and the frame 14 are provided. CCD9
Are formed on the sensor board 13.

When scanning the original, the first traveling body 5 and the second traveling body 8 are moved in the sub-scanning direction by the stepping motor 24 (see FIG. 3). That is, the first traveling body 5 and the second traveling body 8 travel under the contact glass 2 to expose and scan an original with the exposure lamp 3, and the reflected light thereof is reflected by the first reflection mirror 4, the second reflection mirror 6, and the second reflection mirror 6. The light is reflected by the third reflection mirror 7 and focused on the CCD 9 through the lens unit 10. The image reading means is realized here.

The scanner unit 1 as described above is a printer unit (a printer unit, which is an image printing device, which forms an image on a sheet by, for example, an electrophotographic method according to image data based on an image of a document read by the scanner unit 1 ( It is mounted on a digital copying machine 16 including an unillustrated device). FIG. 2 is a perspective view showing an upper portion of the digital copying machine 16 equipped with the scanner unit 1. As shown in FIG. 2, the scanner unit 1 is provided with a pressure plate 17 that can be opened and closed with respect to the contact glass 2 and an opening / closing sensor 18 that detects opening / closing of the pressure plate 17. The printer provided in the digital copying machine 16 includes an electrophotographic system, an inkjet system,
Sublimation type thermal transfer system, silver salt photography system, direct thermal recording system,
Various printing methods such as a fusion type thermal transfer method can be applied. Since its specific configuration is well known, detailed description thereof will be omitted.

FIG. 3 is a block diagram showing the electrical connection of the control system of the scanner section 1. As shown in FIG. 3, this control system includes a main control unit 19 that controls the entire scanner unit 1, an image processing unit 20 that is a circuit that performs various image processes on image data read by the CCD 9, and a first control unit 19. Traveling body 5
And a traveling body control unit 2 which is a circuit for controlling the second traveling body 8.
1, an operation panel 22 for receiving various operations to the digital copying machine 16 and displaying various messages, and a CC
The memory 23 that stores the image data read in D9, predetermined data, and the like is connected. The operation panel 2
2 is provided with a copy start key for declaring the start of copying. Further, the traveling body control unit 21 has
Exposure lamp 3, stepping motor 24 that drives first traveling body 5 and second traveling body 8, and scanner home position sensor that detects whether first traveling body 5 and second traveling body 8 are at home positions. (HP sensor) 25,
The open / close sensor 18 is connected.

FIG. 4 is a block diagram showing the basic internal structure of the image processing section 20. As shown in FIG.
The image processing unit 20 includes an analog video processing unit 26 that performs amplification processing and digital conversion processing of an analog image signal obtained by reading an original with the CCD 9, a shading correction processing unit 27 that performs shading correction processing, and a digital image signal after shading correction processing. Further, an image data processing unit 28 that performs various image data processing such as MTF correction, scaling processing, and γ correction to generate a scan image, and an image correction function of a scan image that is a characteristic function of the present embodiment are realized. It is composed of an image correction unit 29. The digital image signal after the above image processing is transmitted to the printer unit via the main control unit 19 and is used for image formation.

The main controller 19 is, as shown in FIG.
A CPU (Central Processing Unit) that centrally controls each unit
nit) 31 and the CPU 31 has a BIO
ROM (Read Only Memory that stores S etc.)
Only Memory) 32 and a RAM (Ra that functions as a work area of the CPU 31 by rewritably storing various data.
ndom Access Memory) 33 is connected by a bus 34 to form a microcomputer. Further, on the bus 34, an HDD 35 in which a control program is stored,
CD (Compact Disc) -CD-R that reads ROM 37
An OM drive 36 and an interface (I / F) 38 that controls communication with the printer unit and the like are connected.

The CD-ROM 37 shown in FIG. 5 embodies the storage medium of the present invention and stores a predetermined control program. The CPU 31 is a CD-ROM 37
The control program stored in is read by the CD-ROM drive 36 and installed in the HDD 35. As a result, the main control unit 19 enters a state in which it is possible to perform various types of processing described below.

The storage medium is a CD-ROM 3
In addition to 7, various types of media such as various optical discs such as DVD, various magneto-optical discs, various magnetic discs such as flexible discs, and semiconductor memories can be used. Alternatively, the program may be downloaded from a network such as the Internet and installed in the HDD 35. In this case, the storage device that stores the program in the server on the transmission side is also the storage medium of the present invention. The program is a specified OS
(Operating System) may be used, in which case some of the various processes described below may be executed by the OS, or predetermined application software such as word processing software or OS It may be included as a part of a group of program files configuring the above.

Next, the CP provided in the main controller 19
The contents of various processes executed by the U31 based on the control program will be described. Here, of the processing executed by the CPU 31, the image of the scan image in the image correction unit 29, which is an image correction apparatus that realizes the image correction function of the scan image, which is a characteristic function of the scanner unit 1 according to the present embodiment. Only the correction process will be described.

FIG. 6 is a flow chart schematically showing the flow of the image correction processing of the scanned image. Here, as shown in FIG. 7, the book binding 40 is positioned on the contact glass 2 by arranging the page binding section 41 of the book binding 40 and the main scanning direction of the image reading of the scanner section 1 to be substantially parallel to each other. The case where the device is intended to be placed downward will be described.

First, the book document 40 output from the image data processing unit 28 and placed on the contact glass 2 is placed.
The scan image of is input (step S1). here,
FIG. 8 shows an example of the input image. Then, as shown in FIG. 9, the scan image 41 of the page binding portion 41 is included in the scan image of the input book document 40.
Distortion occurs near ´.

Next, in step S2, image correction processing is executed.

In the image correction process, first, the page outline is extracted from the scan image (step S2-1).
Here, FIG. 10 is an explanatory diagram showing an example of a scan image having a page outline at the upper end, and FIG. 11 is a black pixel histogram on the left side of the binding portion boundary line of the scan image shown in FIG. The x-axis of the histogram shown in FIG. 11 indicates the main scanning direction of the scan image (vertical direction in FIG. 10), and the upper end of the scan image is associated with the left end of the histogram. In the case of a scan image whose page outer shape exists at the lower end, the lower end of the scan image is associated with the right end of the histogram. Therefore, as shown in FIG. 10, when the page outline exists at the upper end of the scan image, a black band appears at the top of the scan image,
A tall vertical bar appears at the left end of the histogram shown in FIG. In the present embodiment, using such a characteristic, it is determined whether or not the page outline exists in the scan image.

More specifically, as shown in FIG. 11, the distance AO from the scan image 41 'of the page binding portion 41 to the left end (the left end in FIG. 10) of the scan image, and the height BO of the histogram vertical bar, The ratio is calculated by the following formula (1),

[0049]

[Equation 1] When the calculated ratio k is larger than a predetermined threshold value, it is determined that the page outline exists in the scan image.

If there are page outlines above and below the scanned image, high vertical bars will appear at the left and right ends of the histogram. In such a case, the vertical bars at the left and right ends of the histogram will be high. Based on this, a determination is made as to whether or not a page outline exists in the scanned image.

The determination processing as to whether or not the page outline exists in the scan image is executed for each of the left and right pages with the binding portion boundary line of the scan image as a boundary.

When it is determined by the above processing that the page outline exists in the scan image, the page outline is extracted together with the information indicating which of the upper and lower sides of the left and right pages the page outline exists in, and the RAM 33 stores it. Store temporarily. Here, the function of the page outline extracting means is executed.

However, in the present embodiment, FIG.
As shown in, the sub-scanning direction of the scan image (in FIG. 12,
Upper and lower page outlines within a predetermined range from the center position in the x direction) are extracted. This is because it is considered that the position of the binding part boundary line of the scan image is present at substantially the center of the scan image in the sub-scanning direction. The range to be searched is set according to the characteristics of the scanner. By limiting the search range in this way, the processing time can be shortened.

The method for extracting the page outline from the scanned image is not limited to this, and it is not limited to this method.
The method described in Japanese Patent No. 1455 may be used.

Further, when it is known in advance that the page outline exists in the scan image, the determination as to whether or not the page outline exists may be omitted and only the page outline may be extracted.

When the page outline is extracted from the scan image, the flow advances to step S2-2 to detect the binding part boundary line of the scan image. Here, the function of the binding portion boundary line detecting means is executed. More specifically, as shown in FIG.
Regarding the page outline on the upper side, its main scanning direction (see FIG.
The point with the smallest coordinate value in the (m, y direction) and the point with the largest coordinate value in the main scanning direction for the page outline on the lower side are the end points of the binding section boundary line, and the line segment connecting both end points is bound. It is regarded as a division line. As a result, the binding portion boundary line corresponding to the page binding portion 41 is a line segment that connects the two points that are most indented inside the page outline on the upper side and the lower side in the main scanning direction of the scanned image, and thus the page binding portion 41 is reliably It is possible to detect the corresponding binding part boundary line.

When the boundary of the binding portion of the scan image is detected, the process proceeds to step S2-3, and the skew angle is detected based on the boundary of the binding portion of the scan image. More specifically, as shown in FIG. 14, the binding portion vertices of the binding portion boundary line are set to T and S, respectively. The angle θ formed by the line segment TS, which is the boundary line of the binding portion, and the main scanning direction is defined as the skew angle. There are various known methods for calculating θ, but as an example, tan is obtained from the difference between the coordinate values of the vertex T and the vertex S in the main scanning direction and the sub scanning direction, and the line segment TS and the main scanning direction are obtained. There is a method of calculating the angle θ formed by. Here, the function of the skew angle detecting means is executed.

Next, the image distortion correction of the scanned image in step S2-4 will be described with reference to FIG. In the image distortion correction process of the scan image, first, it is determined whether or not the absolute value of the skew angle θ detected in step S2-3 is larger than the predetermined thresholds ts1 and ts2 (steps S21 and S22). Note that threshold ts2 <threshold ts1. In this way, the absolute value of the detected skew angle θ is compared with the threshold values ts1 and ts2 only in the conventional distortion correction without skew correction in an image in which the absolute value of the skew angle θ is very small. It is desirable to omit skew correction in order to shorten the processing time because it can be sufficiently corrected. Conversely, if distortion correction is performed on an image with a very large absolute value of skew angle θ, the distortion is rather increased and the image quality deteriorates. This is because it may happen. Therefore, in the present embodiment, the skew angle θ will be described later in detail.
If the absolute value of is less than the predetermined threshold value ts1, the image distortion correction processing is continued, and if not, the image distortion correction processing is interrupted. Then, even when the image distortion correction process is continued, if the absolute value of the skew angle θ is equal to or larger than a predetermined threshold value ts2, the distortion correction process is executed after the skew correction. . Here, the correction selection means is realized.

That is, when the absolute value of the detected skew angle θ is less than the threshold value ts2 (N in step S21,
It progresses to N) of step S22 and step S23.

In step S23, shape correction in the main scanning direction is performed based on the page outer shape (upper side and lower side). The shape correction of the scan image in the main scanning direction in the present embodiment is a line (reference line) serving as a reference for distortion correction (expansion), and a correction rate (expansion rate) corresponding to the reference line. Based on the reference line for calculation, the scan image is expanded to correct the distortion in the main scanning direction. More specifically, as shown in FIG. 16, the page outline on the lower side of the scan image is used as a reference line, and the page outline on the upper side of the scan image is used as a reference line.

As shown in FIG. 16, the curved portion of the "page outline" located near the scanned image 41 'of the page binding portion 41 is the distortion occurrence portion, and x0 is the reference line located on the right page (on the lower side). The boundary point between the straight line portion and the curved portion of the page outline), and y0 is the boundary point between the straight line portion and the curved portion of the reference line (lower side page outline) located on the left page.
Various processing methods can be used for the determination processing of the boundary point between the straight line portion and the curved portion of the page outline. For example, it is possible to use the method described in JP-A-11-41455. In general,
An approximate straight line is obtained based on the extracted page outline, and a portion that becomes a curve apart from this straight line is determined as a boundary point between the linear portion and the curved portion of the page outline. Here, in FIG. 16, A is an image boundary line of the scan image.

As the shape correction processing in the main scanning direction, first, the virtual page outline VE as shown by the chain double-dashed line in FIG. 17 is obtained. The virtual page outline VE is a virtual page outline when it is considered that the page outline is located at the image boundary line A which is the boundary portion of the scan image. For example, the virtual page outline VE on the right page has a distance a0 between the reference line at the boundary point x0 and the image boundary line A, and a boundary point x0.
It can be calculated based on the distance b0 between the reference line and the reference line at. That is, if the distance b between the reference line and the reference line at the position x, which is closer to the scan image 41 ′ of the page binding unit 41 than the boundary point x0 and is an arbitrary position in the sub-scanning direction, is found, then a / b = Since it is a0 / b0, the distance a from the position x to the virtual page outline VE can be calculated. Therefore, the virtual page outline VE can be obtained by calculating the distance a at all positions x in the sub-scanning direction of the curved portion of the reference line (the page outline on the lower side) located on the right page. Here, the function of the virtual page outline calculating means is executed. Such processing is performed independently for the left and right pages.

The correction rate used in the shape correction in the main scanning direction is the reference line at the boundary point x0 and the image boundary line A.
A distance h0 (h0 = a0 + b0) obtained by adding the distance b0 between the reference line and the reference line at the boundary point x0
When the distance from the reference line at the position x to the virtual page outline VE is calculated as h (h = a + b), the distortion correction rate at the position x can be expressed as h0 / h. That is, the distortion correction rate is such that when the image is expanded and corrected in the main scanning direction, the distance between the reference line and the reference line becomes equal at all positions x in the sub scanning direction in the curved line portion. It is a value calculated for each x.

In actual correction, first, each pixel is shifted in the main scanning direction so that the virtual page outline VE (see FIG. 17) matches the image boundary line A as shown in FIG. In this case, since the virtual page outline VE is a curved portion (a portion located between y0 and x0) of the reference line (the page outline on the lower side), the shape correction process in the main scanning direction in the present embodiment is performed on the page. Curved part of external shape (distortion occurrence part)
Will be executed only for. As a result, the reference line becomes ED in FIG. 18, and the reference line becomes EU in FIG.

After that, the image is expanded to the upper side in the main scanning direction by h0 / h at all positions x in the sub scanning direction in the curved portion (distortion occurring portion) of the page outline. As a result, the reference line is RED in FIG. 18, and the reference line is REU in FIG.
Is corrected to a straight line.

As described above, the shape correction of the scan image in the main scanning direction is completed. The shape correction process in the main scanning direction in step S24 is not limited to the process described above, and various processing methods can be used.

When the shape correction in the main scanning direction of the scan image is completed, the shape correction in the sub-scanning direction is subsequently performed (step S2).
Execute 4).

The shape correction in the sub-scanning direction in step S24 is performed roughly so that the length of the detected image in the boundary direction (main scanning direction) of the page binding portion 41 after restoration is one pixel or more. The image expansion data is calculated as soon as the image density data of the line for an integer number of pixels is calculated and the data of the surrounding pixels for calculating the image of the restored unit line is obtained. Therefore, real-time correction processing is possible.

Specifically, the image is expanded according to the amount of change in the depth of the page binding portion 41. As shown in FIG. 19, the shape of the book original 40 is read to form a minute triangle for each line, and the image length L in one line for reading a page is read.
n is calculated by the following formula Ln = √ {1+ (Tn-Tn-1) ² }, and the accumulated image length Ln is taken as the page extension length. As a result, the hypotenuse of the approximated triangle becomes almost the same as the curved page shape, and the cumulative page length is used as the image length of the page to obtain an accurate page length.
Especially by shape approximation with the minimum pitch for each line,
The restoration accuracy of the length is high.

In the page binding portion 41 of the book original 40, the reading pixel pitch changes with respect to the book original 40 in the spread direction of the book original 40. That is, in the page binding portion 41 of the book original 40, the reading pixel pitch is not equal to the book original 40 in the spread direction of the book original 40. Therefore, the shape of the page binding portion 41 of the book document 40 is detected, and the pixel position restoration calculation is performed in accordance with the change in the sampling pitch.

That is, a restored image is calculated by the cubic function convolution method in the detected boundary direction (main scanning direction) of the page binding portion 41, and the pixel interval of the pixel of interest is calculated as the reference "1". While the reading line interval changes, that is, the sampling pixel interval changes sequentially for a document when it is flat,
Apply image expansion processing. Further, geometrically, the image projection double length in the main scanning direction and the depth of the page binding portion 41 are in a proportional relationship, and as shown in FIG. 20, the page binding portion of the book original 40 is determined from the boundary address A3 as described above. 41 depth T
The following equation T = focal plane distance * (A3-Ak) / {(Ak
-Ka)-(A3-Ak)}. Based on the difference between the depths of the adjacent main scanning lines calculated in this way, the page restoration position can be calculated by approximating with a straight line with a fine pitch for each pixel.

Book manuscript 40 calculated in this way
As shown in FIG. 19, the depth T of the page binding portion 41 of
It is used to calculate the image length Ln in the sub-scanning direction to be restored for each line. That is, the image length Ln in the sub-scanning direction to be restored for each line is calculated by the following equation Ln = √ {1+ (Tn-Tn-1) ² }. Therefore, the cumulative image length Ln becomes the page length in the sub-scanning direction. Note that image enlargement is performed by using inter-pixel interpolation by the cubic function convolution method as in the case of enlargement in the main scanning direction, and the calculation accuracy is sufficiently high.

Normally, the page binding portion 41 of the book document 40 is
As the depth of the depth increases, the amount of change in the depth increases. Therefore, in the present embodiment, the image expansion is limited according to the depth of the page binding portion 41 of the book document 40 at that position. Specifically, the difference between adjacent boundary addresses is limited to (depth [mm] / 5) [pixels] at that position to suppress an error in restoration in the sub-scanning direction due to erroneous detection of a boundary.

In the restoration in the sub-scanning direction, the image length Ln differs depending on the position, and the read image data are not at regular intervals as shown in FIG. In FIG. 21, the density data at the positions 2, 3, 4, and 5 in the read image data is used to obtain the density at the position 3'as the density of the restored data, but r1: (between the positions 3 to 3 ' Distance) / (distance between positions 3-4), r2: (1-r1), r3: (2-
3'position distance) / (distance between 3-4 positions), r4: (distance between 3'-5 positions) / (3-4
The distance between the positions 3) and 4) is set to 1. Then, by setting these as r, inter-pixel interpolation is executed by the cubic function convolution method.

FIG. 22 shows a sub-scanning direction restoration flow. In FIG. 21, the accumulation of the image length Ln becomes the page length in the sub-scanning direction, which is read by the original document (book original 4
0) position. Reference numerals 2, 3, 4, and 5 in FIG. 21 represent main scanning lines, and the respective positions are f4 [2] and f4.
Let [3], f4 [4], f4 [5]. w is the position of the line to be interpolated and is an integer between f4 [3] and f4 [4].

First, the integer part of the position f4 [3] is substituted for w (step 7-a). The position of w at this time is f4
It is between [2] and f4 [3].

Next, it is judged whether or not w + 1 is f4 [4] or less (step 7-b). If w + 1 is not f4 [4] or less (N in step 7-b), step 7- f
Proceed to.

In step 7-f, the interpolation is not performed, and the density data is shifted by the 4-line buffer in order to shift to the interpolation between the line 4 and the line 5. That is, the density data of line 3 is replaced with the density data of line 2, the density data of line 4 is replaced with the density data of line 3, the density data of line 5 is replaced with the density data of line 4, and the density data of the new line is replaced. Replaced with the density data of line 5, replaced position f4 [2] with position f4 [3], replaced position f4 [3] with position f4 [4], and replaced position f4 [4] with position f4 [5]. The new position f4 [5] is replaced with the new position f4 [5].

Next, it is judged whether or not it is the last line of the read image, and if it is the last line of the read image, the process proceeds to step 7-g and the process is ended. If it is not the final line of the read image, the process returns to step 7-a.

On the other hand, if w + 1 is equal to or less than f4 [4] (Y in step 7-b), the process proceeds to step 7-c, and the cubic function convolution method is used to obtain the density data at the position of w by interpolation. Find the required r1, r2, r3, r4. The data intervals of the read image are not equal. Therefore, as described below, the interval between the line positions of the read data sandwiching the position to be interpolated (3 to 4, that is, f4 [4]
-F4 [3]) is set to 1. That is, r1 = (distance of 3 to 3 ′) / (distance of 3 to 4) = (w−
f4 [3]) / (f4 [4] −f4 [3]) r2 = 1−r1 r3 = (distance of 2 to 3 ′) / (distance of 3 to 4) = (w−
f4 [2]) / (f4 [4] −f4 [3]) r4 = (distance of 3 ′ to 5) / (distance of 3 to 4) = (w−
f4 [5]) / (f4 [4] -f4 [3]) is calculated.

Then, in step 7-d, the density of the line at the position w is obtained by interpolating by the cubic function convolution method, and the process returns to step 7-a.

The shape correction processing in the sub-scanning direction (step S24) is completed by the above processing.

The shape correction process in the sub-scanning direction in step S24 is not limited to the process described above, and various processing methods can be used.

As described above, the functions of the image distortion correction means are executed by steps S23 to S24.

On the other hand, when the absolute value of the detected skew angle θ is less than the threshold value ts1 but not less than the threshold value ts2 (N in step S21, Y in step S22), step S
25, after performing skew correction based on the skew angle θ detected in step S2-3, step S23-
The processing of S24 is performed.

Here, the skew correction processing based on the skew angle θ will be described. Skew correction of the scan image is roughly performed by skewing the entire scan image by the skew angle θ.
Only by rotating. At that time, the center of rotation must be properly determined. This is because, when performing the shape correction in the sub-scanning direction (step S24) described above, the expansion rate in the sub-scanning direction is calculated from the height of floating from the scan surface of the book page. It is necessary to measure the distance between the page outline and the optical axis trajectory of the lens of the scanner, and the distance between the page outline and the optical axis trajectory after such skew correction will change depending on the rotation center position. is there.

Therefore, in the present embodiment, FIG.
As shown in, the line segment T that does not change the distance relationship between the center of rotation and the locus of the optical axis of the lens of the scanner as much as possible.
Intersection of the locus of S and the optical axis of the lens (O in FIG. 23) ",
Skew correction of the scan image is performed by rotating the entire scan image by the skew angle θ. The function of the skew correction means is executed here.

However, when skew correction is performed by rotating the entire scan image, if the entire scan image is simply rotated as it is, the pixel coordinates of the corrected image may become a decimal number, and the image quality of the skew correction image may be reduced. It may be dropped. Therefore, in the present embodiment, in order to solve this, linear interpolation processing of pixels is performed. Here, the function of the linear interpolation means is carried out.

FIG. 24 is an explanatory view showing how to obtain the pixel value by the linear interpolation processing. Coordinates (x, y) shown in FIG. 24
The pixel value f (x, y) at
j], [i + 1, j], [i, j + 1], [i + 1, j
Pixel values f (i, j), f (i +) after the smoothing processing of [+1]
1, j), f (i, j + 1), f (i + 1, j + 1) are calculated as linear interpolation values. More specifically, the pixel value f (x, y) after the linear interpolation processing at the coordinates (x, y)
Is

[0090]

[Equation 2] Is calculated by

With the above processing, the skew correction based on the skew angle θ detected in step S2-3 is completed. The scan image after skew correction is shown in FIG. Figure 2
As shown in FIG. 5, the line segment TS that is the binding portion boundary line of the scan image before the skew correction becomes the line segment T ′S ′ after the skew correction and is exactly parallel to the main scanning direction. .

If the absolute value of the detected skew angle θ is greater than or equal to the threshold value ts1 (Y in step S21), the process proceeds to step S26 and the image distortion correction process is interrupted. This makes it possible to avoid deterioration of image quality due to distortion correction.

Here, the binding portion boundary line corresponding to the page binding portion 41 of the book original 40 is detected based on the page outline of the book original 40 located near the upper side and the lower side in the main scanning direction of the scanned image, and this binding is performed. The skew angle θ of the scan image is detected from the boundary line and the main scanning direction of image reading. Then, the skew of the scan image is corrected by rotating the entire scan image by the skew angle θ around the intersection of the optical axis trajectory of the image reading means and the binding part boundary line. In the scan image in which the skew is corrected in this way, the three-dimensional shape distortion is also corrected based on the shape of the page outline. Accordingly, in skew correction, since the optical axis of the image reading means is rotated about the intersection of the boundary line of the binding portion,
Since it is possible to minimize the change in the distance between each page outline after skew correction and the optical axis trajectory, even if the detected skew angle θ is large, the page outline shape is Based on this, it becomes possible to appropriately perform three-dimensional shape distortion correction in the sub-scanning direction.

If the absolute value of the skew angle θ is less than the first threshold value, the processing is continued, and if not, the processing is interrupted. Then, even when the processing is continued, if the absolute value of the skew angle θ is equal to or larger than the second threshold value, the three-dimensional shape distortion correction processing is executed after the skew correction. This makes it possible to avoid deterioration of image quality due to distortion correction.

Next, FIG. 26 shows a second embodiment of the present invention.
It will be described based on. The same parts as those described in the first embodiment of the present invention are designated by the same reference numerals, and the description thereof will be omitted. The present embodiment is different from the above-described first embodiment in the image distortion correction processing (step S2-4 shown in FIG. 6).

In the image distortion correction processing of the scanned image of the present embodiment, first, it is judged whether or not the absolute value of the skew angle θ detected in step S2-3 is larger than a predetermined threshold value ts1 (step S31). . As described above, the absolute value of the detected skew angle θ is compared with the threshold value ts1. In the image in which the absolute value of the skew angle θ is very small, the conventional distortion correction can be sufficiently performed without performing the skew correction. Therefore, it is desirable to omit the skew correction in order to reduce the processing time. Therefore, in the present embodiment, details will be described later, but if the absolute value of the skew angle θ is less than a predetermined threshold value ts1, the image distortion correction process is continued, and if not, the distortion correction is performed after the skew correction. The processing is executed. Here, the correction selection means is realized.

That is, in the present embodiment, when the absolute value of the detected skew angle θ is less than the threshold value ts1 (N in step S31), shape correction in the main scanning direction (step S32) and sub-scanning are performed. The shape correction of the direction (step S33) is executed. Regarding the shape correction in the main scanning direction (step S32) and the shape correction in the sub-scanning direction (step S33), the shape correction in the main-scanning direction (step S23) and the sub-scanning described in the first embodiment. This is not different from the shape correction of the direction (step S24), and therefore the description thereof is omitted here.

On the other hand, when the absolute value of the detected skew angle θ is greater than or equal to the threshold value ts1 (Y in step S31), the process proceeds to step S34, and skew correction is performed based on the skew angle θ detected in step S2-3. After that, the processes of steps S32 to S33 are performed. Note that step S2-3
The skew correction (step S34) based on the skew angle θ detected in step S23 is no different from the skew correction (step S25) described in the first embodiment, and thus the description thereof is omitted here.

Here, if the skew angle θ is equal to or larger than the threshold value, the three-dimensional shape distortion correction processing is executed after the skew correction, and otherwise, the skew correction is not executed and only the three-dimensional shape distortion correction processing is executed. . This makes it possible to avoid deterioration of image quality due to distortion correction.

Next, FIG. 27 shows a third embodiment of the present invention.
It will be described based on. The same parts as those described in the first embodiment of the present invention are designated by the same reference numerals, and the description thereof will be omitted. The present embodiment is different from the above-described first embodiment in the image distortion correction processing (step S2-4 shown in FIG. 6).

In the image distortion correction processing of the scan image of the present embodiment, first, it is judged whether the absolute value of the skew angle θ detected in step S2-3 is larger than a predetermined threshold value ts1 (step S41). . In this way, the absolute value of the detected skew angle θ is compared with the threshold value ts1. When an image with a very large absolute value of the skew angle θ is subjected to distortion correction, the distortion is rather increased and the image quality deteriorates. This may be the case. Therefore, in the present embodiment, the details will be described later, but if the absolute value of the skew angle θ is less than a predetermined threshold value ts1, the distortion correction processing is executed after the skew correction, and if not, the image The distortion correction process is interrupted. here,
The correction selection means is realized.

That is, in the present embodiment, when the absolute value of the detected skew angle θ is less than the threshold value ts1 (N in step S41), the skew correction based on the skew angle θ detected in step S2-3 is performed. (Step S4
2), shape correction in the main scanning direction (step S43), and shape correction in the sub-scanning direction (step S44).
The skew correction based on the skew angle θ detected in step S2-3 (step S42) is the skew correction described in the first embodiment (step S2).
Since it is not different from 5), its description is omitted here. Further, the shape correction in the main scanning direction (step S4
3) and the shape correction in the sub-scanning direction (step S44) are also the same as the shape correction in the main-scanning direction (step S23) and the shape correction in the sub-scanning direction (step S24) described in the first embodiment. Since it does not change, the description here is omitted.

On the other hand, when the absolute value of the detected skew angle θ is equal to or larger than the threshold value ts1 (Y in step S41), the process proceeds to step S45 to interrupt the image distortion correction process. This makes it possible to avoid deterioration of image quality due to distortion correction.

If the absolute value of the skew angle θ is equal to or larger than the predetermined threshold value, the process is interrupted. If not, the three-dimensional shape distortion correction process is executed after the skew correction. This makes it possible to avoid deterioration of image quality due to distortion correction.

Next, FIG. 28 shows a fourth embodiment of the present invention.
It will be described based on. The same parts as those described in the first embodiment of the present invention are designated by the same reference numerals, and the description thereof will be omitted. The present embodiment is different from the above-described first embodiment in the image distortion correction processing (step S2-4 shown in FIG. 6).

Unlike the first to third embodiments of the present invention, the image distortion correction processing of the scanned image of the present embodiment does not depend on the absolute value of the skew angle θ detected in step S2-3, The distortion correction process is always executed after the skew correction. Here, the correction selection means is realized.

That is, in the present embodiment, the skew correction based on the skew angle θ detected in step S2-3 (step S51), the shape correction in the main scanning direction (step S52), and the shape correction in the sub-scanning direction ( Step S
53) is executed. Note that skew correction based on the skew angle θ detected in step S2-3 (step S5
Since 1) is not different from the skew correction (step S25) described in the first embodiment, description thereof will be omitted here. As for the shape correction in the main scanning direction (step S52) and the shape correction in the sub scanning direction (step S53), the shape correction in the main scanning direction (step S23) and the sub scanning described in the first embodiment are also performed. This is not different from the shape correction of the direction (step S24), and therefore the description thereof is omitted here.

In each of the embodiments, the scanner unit 1 of the digital copying machine is applied as the image reading device, but the present invention is not limited to this, and may be applied to, for example, a scanner equipped with an automatic page turning function. May be.

Further, in each of the embodiments, the book binding 40 is positioned on the contact glass 2 so that the page binding section 41 of the book binding 40 and the main scanning direction of the image reading of the scanner section 1 are parallel to each other. Although the case where the device is placed facing downward has been described, the present invention is not limited to this. For example, as shown in FIG. 29, the book document 40 facing upward may be pressed against the contact glass 2 from below the contact glass 2.

Further, in each of the embodiments, the image correction apparatus is provided in the digital copying machine 16 which is an image forming apparatus, and the image correction processing is performed on the scan image read by the scanner section 1 of the digital copying machine 16. I chose
It is not limited to this. For example, an image scanner having an image reading unit for reading a document image is connected to a personal computer having a system configuration equivalent to that of the main controller 19 shown in FIG. 5, and the HDD of the personal computer is a storage medium. CD-ROM
Even if the image correction apparatus is configured by installing the program stored in 37 and operating the CPU of the personal computer in accordance with this program, the same effects as the various effects described above can be obtained. Further, the program stored in the CD-ROM 37, which is a storage medium, is stored in the main control unit 19 shown in FIG.
Installed in the HDD of a personal computer having a system configuration equivalent to that of the above, and the CPU of the personal computer is operated according to this program to configure an image correction device, and image correction is performed on a scan image read in advance by the image reading means. You may make it process.

[0111]

According to the image correcting apparatus of the first aspect of the present invention, a book document which is in contact with the top or bottom of the contact glass with the page binding portion substantially parallel to the main scanning direction of image reading is imaged. In an image correction device that corrects a scan image read by a reading unit, a page outline extraction unit that extracts the page outline of the book document located near the upper side and the lower side in the main scanning direction of the scan image from the scan image, and Bounding part boundary line detecting means for detecting a binding part boundary line corresponding to the page binding part based on the page outer shape extracted by the page outer shape extracting means, and the binding part detected by the binding part boundary line detecting means Skew angle detection for detecting the angle between the boundary line and the main scanning direction of image reading as the skew angle of the scanned image Steps, the entire scan image is rotated by the skew angle detected by the skew angle detecting means about the intersection of the locus of the optical axis of the image reading means and the binding part boundary line, and the skew of the scan image is rotated. Skew correction means for correcting the three-dimensional shape distortion of the scanned image based on the shape of the page outer shape, and image distortion correction means for correcting three-dimensional shape distortion of the scanned image, which are located near the upper side and the lower side in the main scanning direction of the scanned image. The binding portion boundary line corresponding to the page binding portion of the book original document is detected based on the page outline of the book original document, and the skew angle of the scan image is detected by the binding portion boundary line and the main scanning direction of image reading. Then, the entire scan image is rotated by a skew angle around the intersection of the locus of the optical axis of the image reading means and the binding part boundary line, thereby correcting the skew of the scan image and three-dimensionally based on the outer shape of the page. By correcting the shape distortion as well, the skew is corrected by rotating around the intersection of the optical axis locus of the image reading means and the binding part boundary line. Therefore, each page outline after skew correction and the optical axis locus are corrected. Since the change in the distance between and can be minimized, even if the detected skew angle is large, the three-dimensional shape distortion correction in the sub-scanning direction based on the shape of the page outline is appropriately performed. You can

According to a second aspect of the invention, in the image correction apparatus according to the first aspect, the page outline extracting means is arranged to select the book document from a region within a certain range from a central position of the scan image in the sub-scanning direction. By extracting the page outline of, the position of the binding portion boundary line of the scan image is considered to be present substantially at the center of the scan image in the sub-scanning direction, and therefore the processing time can be shortened.

According to the third aspect of the invention, in the image correction apparatus according to the first or second aspect, the binding portion boundary line detecting means is located on the upper side in the main scanning direction extracted by the page outer shape extracting means. Regarding the page outer shape, the point having the smallest coordinate value in the main scanning direction is defined as one end point of the binding part boundary line, and the page outer shape located on the lower side in the main scanning direction has the largest coordinate value in the main scanning direction. By defining a point as the other end point of the binding part boundary line and regarding the line segment connecting both end points as the binding part boundary line, the binding part boundary line corresponding to the page binding part is the upper side and the lower side in the main scanning direction of the scan image. Since it is a line segment that connects the two points that are the most inside the page outer shape, it is possible to reliably detect the binding portion boundary line corresponding to the page binding portion.

According to a fourth aspect of the invention, in the image correction apparatus according to any one of the first to third aspects, the skew correction means are adjacent to each other for each pixel value of the scan image after image rotation. By providing a linear interpolation unit that performs a linear interpolation process based on each pixel value of the block,
Since the coordinates of the pixels of the image corrected by rotating the entire scan image are not decimal, the image quality of the skew corrected image can be maintained.

According to the fifth aspect of the invention, in the image correction apparatus according to any one of the first to fourth aspects, the skew correction is performed according to the absolute value of the skew angle detected by the skew angle detection means. By including the correction selecting unit that selectively executes the image correcting unit and the image distortion correcting unit, the skew correcting unit and the image distortion correcting unit can be selectively executed according to the magnitude of the absolute value of the skew angle. Therefore, for example, in an image in which the absolute value of the skew angle is very small, the skew correction can be sufficiently performed by only the three-dimensional shape distortion correction without performing the skew correction, and thus the skew correction can be omitted to shorten the processing time. If an image having a very large absolute value of the skew angle is subjected to the three-dimensional shape distortion correction, the distortion may rather increase and the image quality may deteriorate. If so does not perform the skew correction and distortion correction in this case, it is possible to avoid the deterioration of image quality caused by distortion correction.

According to a sixth aspect of the invention, in the image correction apparatus according to the fifth aspect, the correction selecting means is a first absolute value of the skew angle detected by the skew angle detecting means. When it is equal to or more than one threshold value, the skew correction by the skew correction unit and the distortion correction by the image distortion correction unit with respect to the scan image are not performed, and the absolute value of the skew angle detected by the skew angle detection unit is When it is less than the first threshold value and equal to or more than the predetermined second threshold value, the three-dimensional shape distortion of the scan image whose skew is corrected by the skew correction means is corrected by the image distortion correction means, If the absolute value of the skew angle detected by the skew angle detecting means is less than the second threshold value, the skew If the absolute value of the skew angle is less than the first threshold value by correcting only the three-dimensional shape distortion of the scan image by the image distortion correction means without performing skew correction by the corrector, the processing is continued, Otherwise, the process is interrupted. Then, even when the processing is continued, if the absolute value of the skew angle is equal to or larger than the second threshold value, the three-dimensional shape distortion correction processing is executed after the skew correction, so that the image quality is deteriorated due to the distortion correction. Can be avoided.

According to a seventh aspect of the invention, in the image correcting apparatus according to the fifth aspect, the correction selecting means is a threshold value in which the absolute value of the skew angle detected by the skew angle detecting means is predetermined. In the above case, the image distortion correction unit corrects the three-dimensional shape distortion of the scan image whose skew has been corrected by the skew correction unit, and the absolute value of the skew angle detected by the skew angle detection unit is If it is less than a predetermined threshold value, the image distortion correction unit corrects only the three-dimensional shape distortion of the scan image without performing the skew correction by the skew correction unit, so that the absolute value of the skew angle becomes the threshold value. If it is above, 3 after skew correction
Since the three-dimensional shape distortion correction processing is executed and otherwise the three-dimensional shape distortion correction processing is executed without performing skew correction, it is possible to avoid deterioration of image quality due to the distortion correction.

According to the invention described in claim 8, in the image correction apparatus according to claim 5, the correction selection means is a threshold value in which the absolute value of the skew angle detected by the skew angle detection means is predetermined. In the above case, the skew correction by the skew correction unit and the distortion correction by the image distortion correction unit with respect to the scan image are not performed, and the absolute value of the skew angle detected by the skew angle detection unit is predetermined. If it is less than the threshold value, the absolute value of the skew angle is equal to or greater than a predetermined threshold value by correcting the three-dimensional shape distortion of the scan image whose skew is corrected by the skew correction means by the image distortion correction means. If so, interrupt the process,
Otherwise, since the three-dimensional shape distortion correction process is executed after the skew correction, it is possible to avoid the deterioration of the image quality due to the distortion correction.

According to the program of the ninth aspect of the invention, the image reading means reads the book document which is brought into contact with the upper or lower side of the contact glass with the page binding portion substantially parallel to the main scanning direction of image reading. A program for causing a computer to perform image correction of the scanned image, the page contour extracting the page contour of the book document located near the upper side and the lower side of the scanned image in the main scanning direction from the scanned image. An extraction function, a binding part boundary line detection function that detects a binding part boundary line corresponding to the page binding part based on the page external shape extracted by the page external shape extraction function, and a binding part boundary line detection function The angle formed by the bound line of the bound portion and the main scanning direction of image reading is defined as the scan of the scanned image. The skew angle detection function for detecting as a skew angle, and the entire scan image by the skew angle detected by the skew angle detection function centered on the intersection of the locus of the optical axis of the image reading means and the binding part boundary line. The main scanning of the scan image is performed by rotating and performing a skew correction function of correcting the skew of the scan image and an image distortion correction function of correcting the three-dimensional shape distortion of the scan image based on the shape of the page outline. The binding part boundary line corresponding to the page binding part of the book document is detected based on the page outer shape of the book document located near the upper side and the lower side in the direction, and the scanned image is obtained by the binding part boundary line and the main scanning direction of image reading. The skew angle of is detected. Then, the entire scan image is rotated by a skew angle around the intersection of the locus of the optical axis of the image reading means and the binding part boundary line, thereby correcting the skew of the scan image and three-dimensionally based on the outer shape of the page. By correcting the shape distortion as well, the skew is corrected by rotating around the intersection of the optical axis locus of the image reading means and the binding part boundary line. Therefore, each page outline after skew correction and the optical axis locus are corrected. Since the change in the distance between and can be minimized, even if the detected skew angle is large, the three-dimensional shape distortion correction in the sub-scanning direction based on the shape of the page outline is appropriately performed. You can

According to the storage medium of the tenth aspect of the present invention, the book reading original brought into contact with the top or bottom of the contact glass with the page binding portion substantially parallel to the main scanning direction of image reading is brought into contact with the image reading means. A computer-readable storage medium that stores a program for causing a computer to perform image correction of a read scan image, wherein the computer stores the book document located near an upper side and a lower side in a main scanning direction of the scan image. A page outline extracting function for extracting a page outline from the scan image, and a binding part boundary line detecting function for detecting a binding part boundary line corresponding to the page binding part based on the page outline extracted by the page outline extracting function. And the binding part boundary line detected by this binding part boundary line detection function and image reading With a skew angle detection function for detecting an angle formed with the main scanning direction as a skew angle of the scan image, and the skew angle detection function with the intersection of the optical axis trajectory of the image reading means and the binding portion boundary line as the center. A skew correction function of rotating the entire scan image by the detected skew angle to correct the skew of the scan image, and an image distortion correction of correcting three-dimensional shape distortion of the scan image based on the shape of the page outline. And a program for executing the function, and detects the binding portion boundary line corresponding to the page binding portion of the book document based on the page outer shape of the book document located near the upper side and the lower side in the main scanning direction of the scan image, The skew angle of the scan image is detected based on the boundary line of the binding portion and the main scanning direction of image reading. Then, the entire scan image is rotated by a skew angle around the intersection of the locus of the optical axis of the image reading means and the binding part boundary line, thereby correcting the skew of the scan image and three-dimensionally based on the outer shape of the page. By correcting the shape distortion as well, the skew is corrected by rotating around the intersection of the optical axis locus of the image reading means and the binding part boundary line. Therefore, each page outline after skew correction and the optical axis locus are corrected. Since the change in the distance between and can be minimized, even if the detected skew angle is large, the three-dimensional shape distortion correction in the sub-scanning direction based on the shape of the page outline is appropriately performed. You can

According to the image correcting method of the eleventh aspect of the present invention, the image reading means is used for the book original which is brought into contact with the upper or lower side of the contact glass with the page binding portion substantially parallel to the main scanning direction of the image reading. An image correction method for a scan image read by the method, comprising: a page outline extraction step of extracting the page outline of the book document located near the upper side and the lower side in the main scanning direction of the scan image from the scan image; A binding part boundary line detecting step of detecting a binding part boundary line corresponding to the page binding part based on the page outline extracted by the extracting step, and the binding part boundary line detected by the binding part boundary line detecting step And a skew angle detection step of detecting an angle formed by the main scanning direction of image reading as a skew angle of the scan image, The entire scan image is rotated by the skew angle detected by the skew angle detection means around the intersection of the optical axis trajectory of the image reading means and the binding part boundary line, and the skew of the scan image is corrected. A skew correction step and an image distortion correction step of correcting the three-dimensional shape distortion of the scan image based on the shape of the page outer shape are included, and a book document located near the upper side and the lower side of the scan image in the main scanning direction is stored. The binding portion boundary line corresponding to the page binding portion of the book document is detected based on the page outer shape, and the skew angle of the scan image is detected based on the binding portion boundary line and the main scanning direction of image reading. Then, the entire scan image is rotated by a skew angle around the intersection of the locus of the optical axis of the image reading means and the binding part boundary line, thereby correcting the skew of the scan image and three-dimensionally based on the outer shape of the page. By correcting the shape distortion as well, the skew is corrected by rotating around the intersection of the optical axis locus of the image reading means and the binding part boundary line. Therefore, each page outline after skew correction and the optical axis locus are corrected. Since the change in the distance between and can be minimized, even if the detected skew angle is large, the three-dimensional shape distortion correction in the sub-scanning direction based on the shape of the page outline is appropriately performed. You can

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing a configuration of a scanner unit according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing an upper portion of a digital copying machine equipped with a scanner unit.

FIG. 3 is a block diagram showing electrical connection of a control system of a scanner unit.

FIG. 4 is a block diagram showing a basic internal configuration of an image processing unit.

FIG. 5 is a block diagram showing electrical connection of a main control unit.

FIG. 6 is a flowchart schematically showing the flow of a scan image correction process.

FIG. 7 is a perspective view showing a state where a book document is placed on the contact glass of the scanner unit.

FIG. 8 is a plan view showing an example of an input image.

FIG. 9 is an explanatory diagram showing distortion in the vicinity of a page binding portion of a scan image.

FIG. 10 is an explanatory diagram showing an example of a scan image having a page outline on the upper end.

11 is a black pixel histogram on the left side of the binding portion boundary line of the scan image shown in FIG.

FIG. 12 is an explanatory diagram showing a search range of a page outline of a scan image.

FIG. 13 is an explanatory diagram illustrating a method of detecting a binding part boundary line of a scan image.

FIG. 14 is an explanatory diagram showing a method of detecting a skew angle of a scan image.

FIG. 15 is a flowchart showing a flow of image distortion correction processing of a scan image.

FIG. 16 is an explanatory diagram showing boundary points of a distortion occurrence portion in a scan image.

17 is an explanatory diagram showing the outer shape of the virtual page in FIG.

FIG. 18 is an explanatory diagram showing a state in which FIG. 16 is pixel-shifted and then expanded and corrected by a predetermined distortion correction rate.

FIG. 19 is an explanatory diagram showing calculation of image length.

FIG. 20 is an explanatory diagram showing boundary distortion of a page binding portion.

FIG. 21 is an explanatory diagram showing interpolation between pixels in the main scanning direction.

FIG. 22 is a flowchart showing sub-scanning direction restoration.

FIG. 23 is an explanatory diagram showing how to determine a rotation center.

FIG. 24 is an explanatory diagram showing a method of obtaining a pixel value by linear interpolation processing.

FIG. 25 is an explanatory diagram showing a scan image after skew correction.

FIG. 26 is a flowchart showing a flow of image distortion correction processing for a scanned image according to the second embodiment of this invention.

FIG. 27 is a flowchart showing a flow of image distortion correction processing for a scanned image according to the third embodiment of this invention.

FIG. 28 is a flowchart showing the flow of image distortion correction processing for a scanned image according to the fourth embodiment of the present invention.

FIG. 29 is a front view showing a state where a book document is brought into contact with the contact glass.

FIG. 30 is a front view showing a state where a book document is placed on the contact glass.

FIG. 31 is an explanatory diagram showing a scan image in which skew has occurred.

[Explanation of symbols]

2 contact glass 29 Image correction device 37 storage media 40 book manuscripts 41 pages binding

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5B057 AA11 CA02 CA12 CA16 CB02                       CB12 CB16 CC01 CD03 CD12                       CH08                 5C072 AA01 DA02 DA05 EA05 LA03                       RA03 VA06                 5C076 AA23 AA24 BA06

Claims (11)

[Claims] 1. An image correction apparatus for correcting a scan image obtained by reading an image of a book document, which is brought into contact with the top or bottom of a contact glass, with a page binding portion substantially parallel to the main scanning direction of image reading. Based on the page contour extraction unit that extracts the page contour of the book document located near the upper side and the lower side of the scan image in the main scanning direction from the scan image, and the page contour extracted by the page contour extraction unit. A binding portion boundary line detecting unit that detects a binding portion boundary line corresponding to the page binding unit, and an angle formed between the binding portion boundary line detected by the binding portion boundary line detecting unit and the main scanning direction of image reading. Skew angle detecting means for detecting the skew angle of the scanned image, and a trajectory of the optical axis of the image reading means Skew correction means for correcting the skew of the scan image by rotating the entire scan image by the skew angle detected by the skew angle detection means around the intersection with the binding part boundary line, and forming the page outline shape. And an image distortion correction unit that corrects the three-dimensional shape distortion of the scan image based on the image correction apparatus. 2. The image correction according to claim 1, wherein the page outline extracting means extracts the page outline of the book document from an area within a certain range from a central position of the scan image in the sub-scanning direction. apparatus. 3. The binding section boundary line detecting unit determines, for the page outline located on the upper side in the main scanning direction extracted by the page outline extracting unit, a point having a minimum coordinate value in the main scanning direction as the binding unit. As one end point of the boundary line, with respect to the page outer shape located on the lower side in the main scanning direction, the point having the maximum coordinate value in the main scanning direction is set as the other end point of the binding section boundary line, and a line segment connecting both end points is formed. The image correction apparatus according to claim 1, wherein the image correction apparatus regards it as the boundary line of the binding portion. 4. The skew correction means comprises a linear interpolation means for performing linear interpolation processing on each pixel value of the scan image after image rotation based on each pixel value of four adjacent blocks. Item 4. The image correction device according to any one of items 1 to 3. 5. A correction selecting means for selectively executing the skew correcting means and the image distortion correcting means according to an absolute value of the skew angle detected by the skew angle detecting means. Claims 1 to 4
The image correction device according to any one of 1. 6. The correction selecting means, when the absolute value of the skew angle detected by the skew angle detecting means is greater than or equal to a predetermined first threshold value, the skew correcting means for the scan image. Skew correction and distortion correction by the image distortion correction means are not performed,
When the absolute value of the skew angle detected by the skew angle detecting means is less than the first threshold value and is equal to or more than a predetermined second threshold value, the skew is corrected by the skew correcting means. When the absolute value of the skew angle detected by the skew angle detecting unit is less than the second threshold value, the skew correcting unit corrects the three-dimensional shape distortion of the scan image by the image distortion correcting unit. The image correction apparatus according to claim 5, wherein only the three-dimensional shape distortion of the scan image is corrected by the image distortion correction unit without correction. 7. The scan in which the skew is corrected by the skew correction means when the absolute value of the skew angle detected by the skew angle detection means is equal to or greater than a predetermined threshold value. Image 3
If the absolute value of the skew angle detected by the skew angle detecting means is less than a predetermined threshold value, the skew correcting means does not perform the skew correction. The image correction apparatus according to claim 5, wherein only the three-dimensional shape distortion of the scan image is corrected by the image distortion correction unit. 8. The correction selecting means, when the absolute value of the skew angle detected by the skew angle detecting means is equal to or more than a predetermined threshold value, skew correction by the skew correcting means for the scan image and If the absolute value of the skew angle detected by the skew angle detecting means is less than a predetermined threshold value, the skew is corrected by the skew correcting means without performing the distortion correction by the image distortion correcting means. The image correction apparatus according to claim 5, wherein the three-dimensional shape distortion of the scanned image is corrected by the image distortion correction unit. 9. A computer executes image correction of a scan image obtained by reading a book document which is in contact with the top or bottom of a contact glass with the page binding portion substantially parallel to the main scanning direction of the image reading by the image reading means. A program for causing the computer to extract a page outline of the book document located near the upper side and the lower side in the main scanning direction of the scan image from the scan image, and a page outline extracting function. A binding portion boundary line detecting function for detecting a binding portion boundary line corresponding to the page binding portion based on the extracted page outer shape, and the binding portion boundary line and image reading detected by the binding portion boundary line detecting function. Skew angle detection for detecting the angle formed by the main scanning direction of the The output function, the entire scan image is rotated by the skew angle detected by the skew angle detection function around the intersection point of the locus of the optical axis of the image reading unit and the binding part boundary line, and the scan image A program for executing a skew correction function for correcting skew and an image distortion correction function for correcting three-dimensional shape distortion of the scan image based on the shape of the page outer shape. 10. A computer executes image correction of a scan image obtained by reading a book document which is brought into contact with the top or bottom of a contact glass with the page binding portion substantially parallel to the main scanning direction of the image reading by the image reading means. A computer-readable storage medium that stores a program for causing the computer to extract a page outline of the book document located near an upper side and a lower side in the main scanning direction of the scan image from the scan image. An extraction function, a binding part boundary line detection function that detects a binding part boundary line corresponding to the page binding part based on the page outline extracted by the page outline extraction function, and a binding part boundary line detection function The angle formed between the bound line of the bound portion and the main scanning direction of image reading is defined as the scan angle. Skew angle detection function for detecting the skew angle of the scanned image, and the scan for the skew angle detected by the skew angle detection function centered on the intersection of the optical axis trajectory of the image reading means and the binding portion boundary line. A skew correction function of rotating the entire image to correct the skew of the scan image, and 3 of the scan image based on the shape of the page outline.
A computer-readable storage medium characterized by storing a program for executing an image distortion correction function for correcting a three-dimensional shape distortion. 11. A method for correcting an image of a scan image obtained by reading, by an image reading means, a book document which is in contact with the top or bottom of a contact glass with a page binding portion substantially parallel to the main scanning direction of image reading. A page outline extracting step of extracting the page outline of the book document located near the upper side and the lower side in the main scanning direction of the scan image from the scan image, and based on the page outline extracted by the page outline extracting step. A binding part boundary line detecting step of detecting a binding part boundary line corresponding to the page binding part, and an angle formed between the binding part boundary line detected by the binding part boundary line detecting step and a main scanning direction of image reading. A skew angle detecting step of detecting as a skew angle of the scan image, a locus of an optical axis of the image reading means, and the binding A skew correction step of correcting the skew of the scan image by rotating the entire scan image by the skew angle detected by the skew angle detection means around an intersection with a boundary line, and based on the shape of the page outline. 3 of the scan image
An image distortion correction step of correcting a three-dimensional shape distortion.