JP2006197445A - Image processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a processing for eliminating wrong discrimination using a method different from a decision method for a show-through image targeted at only edge strength in the suppressing processing of the back-copying image and being capable of improving general-purpose properties and further reducing the processing load. <P>SOLUTION: An image Di read by a scanner and shading-corrected is input to a density decision section 111, an edge decision section 112 and a density-unevenness decision section 113 respectively. Whether an input image has the image quality of a back-copying is detected by threshold processing. Whether the input image is the show-through image (the back-copying image is decided, when all of them have the image quality of the show-through) by integrating each detecting result is decided by a back-copying image decision section 115. A back-copying suppressing processing section 117 conducts the processing erasing image data as the processing suppressing the input-image data value Di decided as the back-copying image by receiving the decision results, and obtains output-image data Do. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus that reads a document printed on both sides as a pixel signal by an image conversion means and then processes the data as data usable for image output. The present invention relates to an image processing apparatus provided with means for suppressing (erasing or the like) an image.

2. Description of the Related Art Conventionally, data input of document images has been performed by scanners, and scanners are widely used for data input in image forming apparatuses such as copiers, facsimiles, MFPs (multifunction or composite) machines, or image processing apparatuses such as computers connected to image scanners. It is used. Such a scanner employs a reading method in which an original image is photoelectrically scanned by a CCD line image sensor (hereinafter also simply referred to as “CCD”) and converted into a pixel signal.
In a scanner that employs this reading method, which is generally used in a copying machine, a book read method in which an original placed at a predetermined position on a contact glass is scanned by an exposure scanning unit and read, and a DF (original) A system called a sheet through (SDF) system is used in which an original fed by a transport device is read by an exposure scanning unit that is stopped at a reading position.
In today's diversified printing paper, thin paper is sometimes used, and when a document printed on such paper is read by a scanner, the back side is seen through the original paper, resulting in a “show-through”, which degrades the image quality. That is a problem. In particular, in the sheet-through (SDF) method, an apparatus having a double-sided reading function (a function of reading images on both sides at once from a document printed on both sides) has been developed, and this apparatus can simultaneously read both sides. Since the reading system (see FIG. 4) is configured, show-through tends to occur.

As conventional methods for suppressing show-through, a method for processing image information obtained by inputting a show-through image and a manuscript image including a show-through respectively, and a method for processing image information only for inputting a manuscript image including a show-through How to do is known.
As a document showing the former method, for example, the following Patent Document 1 can be cited. In the method described in Patent Document 1, only an image that causes show-through (backing image) is obtained in advance without a read document, and the show-through image (document transmittance is taken into account) from the read image of the document. This is a method of performing processing for obtaining an image of the original surface to be read without show-through.
Further, as a document showing the latter method, for example, the following Patent Document 2 can be cited. The method described in Patent Document 2 below pays attention to the edge portion of the image, determines the edge strength of the input document image, determines whether the edge of the show-through image by threshold processing for the calculated edge strength, A method of removing and restoring the show-through image according to the discrimination result is adopted.
JP-A-9-116753 JP 2002-314790 A

However, the method described in Patent Document 1 performs subtraction processing even on an image area that is not show-through or has a low show-through degree, and narrows the dynamic range of the image, so that a good image can be obtained. In some cases, there is a restriction that the images to be subjected to subtraction processing must be strictly aligned with each other, and there is a problem in versatility.
Further, the method described in Patent Document 2 is a method for removing a show-through image using only a document image, and thus does not cause the above-described problem that occurs in the method described in Patent Document 1. However, as a method for determining whether or not the image is a show-through image (pixel), a method is used in which a threshold value is set for the edge strength and determined based on whether or not the threshold value is exceeded. Even when a threshold value obtained in advance as an empirical value is applied, erroneous detection is unavoidable and it is difficult to guarantee versatility when document images having various image quality are targeted. For this reason, the method described in Patent Document 2 employs a method that guarantees versatility by using a variation threshold value that sets an optimum threshold value based on an edge intensity histogram. However, in order to obtain the variation threshold value set for adapting to the target image, it is necessary to obtain an edge intensity histogram and analyze the histogram. Although the processing load is reduced by processing such as taking a weighted average with the adjacent area, the processing load for obtaining the threshold and the effect on the processing speed are not small, and depending on the processing capability of the device, it may not be compatible. It will be.
The present invention has been made in view of the above-described problems in a conventional image processing apparatus that performs a process of determining a show-through image by threshold processing for edge strength, and removing and repairing the show-through image according to the determination result. By using an approach that is different from the discrimination method that focuses only on the image, it realizes suppression of show-through images that eliminates misclassification, is highly versatile, can reduce the processing burden, and can improve processing speed. This is a problem to be solved.

  The invention according to claim 1 is an image processing apparatus that reads a document and processes the obtained image data as data that can be used for image output. Data of density, edge strength, and density unevenness of the read document image are obtained. Image quality detection means for comparing with a reference value indicating the degree of the show-through image, and comprehensive judgment of the show-through image based on the image quality detection results for the density, edge strength and density unevenness data obtained by the image quality detection means An image processing apparatus comprising: a show-through determination unit that suppresses a show-through image according to a determination result of the show-through determination unit.

Invention of Claim 2 is a means using the reference value which obtains a detection result by the binary of whether the said image quality detection means has the image quality of show-through in the image processing apparatus described in Claim 1, The show-through determination means determines the show-through image on condition that the image quality detection results of the density, edge strength, and density unevenness data obtained by the image quality detection means are all show-through image quality. It is characterized by.
According to a third aspect of the present invention, in the image processing apparatus according to the second aspect, the means for suppressing the show-through image includes the determined show-through image when the show-through determining means determines the show-through image. It is characterized by erasing.

According to a fourth aspect of the present invention, in the image processing apparatus according to the first aspect, the image quality detecting means uses a reference value for detecting the degree of the show-through image at a plurality of levels. The means for determining the overall image quality of the show-through from the image quality detection results of the density, edge strength and density unevenness obtained by the image quality detection means, and means for suppressing the show-through image according to the determination result The strength of suppression of show-through is changed.
According to a fifth aspect of the present invention, in the image processing apparatus according to any one of the first to fourth aspects, the means for suppressing the show-through image has an operation unit that enables an input for setting a processing condition. According to the document thickness information input from the operation unit, at least one of the reference value, the determination method, and the strength of suppression of show-through is changed.

According to the present invention, the density, edge strength, and density unevenness data of the original image are compared with a reference value indicating the degree of the show-through image, and the show-through image is determined comprehensively based on the obtained result. By determining the show-through by simple processing and suppressing the show-through according to the determination result, it is possible to eliminate the erroneous determination that occurs in the conventional method of determining the show-through image based on the edge strength. In the conventional method for discriminating show-through images based on edge strength, the edge strength histogram required to guarantee versatility is obtained, and high versatility can be obtained without processing the obtained histogram. In addition, the processing load can be reduced, and the processing speed can be improved.
In addition, for each of the density, edge strength, and density unevenness of the original image, the degree of the show-through image is detected at a plurality of levels, and the degree of overall show-through image quality is determined from these detection results. Therefore, it is possible to optimize the suppression of show-through.
Further, it is possible to appropriately suppress the show-through according to the thickness information of the document.

An image processing apparatus according to an embodiment of the present invention will be described below.
First, the components of the image processing apparatus and the outline of the control system according to the present embodiment will be described. This embodiment shows a form applied to an image reading apparatus as an image processing apparatus of the present invention. The present invention is an image processing apparatus characterized by means for performing processing for suppressing the show-through image included in the read data of the original image, and the following image reading apparatus is also an object of the present invention. Is one of the devices. In addition to the image reading apparatus described below, as an image processing apparatus that requires processing means for suppressing a show-through image, for example, an image forming apparatus such as a copying machine, a facsimile machine, an MFP (multifunctional or composite) machine, or an image Computers to which a scanner is connected are included in the application target.
FIG. 1 is a diagram illustrating a configuration of an image reading apparatus according to the present embodiment. FIG. 1 shows a device configuration of a mechanical operation unit centering on a document reading optical system (this component unit is referred to as “image scanner” or simply “scanner” in a narrow sense). It consists of a main body 1, a document conveying device 2 and a document reading table 3.
In FIG. 1, inside the reader main body 1, a first traveling body 4 having a light source 4a and a mirror 4b made of a xenon lamp or a fluorescent lamp, and a second traveling having mirrors 5a and 5b. An exposure scanning optical system 9 comprising a body 5, a lens 6, a one-dimensional photoelectric conversion element (for example, a CCD line image sensor) 7, and a stepping motor 8 that drives the first and second traveling bodies 4 and 5. Is provided.
The document feeder 2 is provided with a sheet-through document feeder (SDF) unit 10 and a document table 11. A stepping motor 12 is provided in the SDF unit 10.
Further, a document pressing plate 14 is rotatably attached to the upper portion of the document reading table 3, and the document 13 is set under the document pressing plate 14. A white reference plate 15 for shading correction is disposed at the end of the document reading table 3.

FIG. 2 is a block diagram showing the configuration of the control system of the image reading apparatus shown in FIG.
The control system shown in FIG. 2 includes a light source 4a, a light source driver 17, a CCD 7, a CCD drive unit 18, stepping motors 8 and 12, motor drivers 20 and 28, a CPU (ROM and RAM attached) 16, an image processing unit 19, and a scan. A buffer 25, a buffer controller 27, and an I / F controller 26 are provided.
Further, in order to place the light source driver 17, motor drivers 20 and 28, the image processing unit 19, the buffer controller 27, and the I / F controller 26 under the control of the CPU 16 that controls the entire system, these are connected by a bus. The ROM under the control of the CPU 3 stores a program for controlling the processing flow from the input of the document image to the output to the user side through the image processing process, and calls a program necessary for operation from the ROM. A predetermined process is executed by driving. During processing, the CPU 16 uses the managed RAM as a work area, that is, a temporary storage location for data such as parameters necessary for processing image data and controlling each unit.

The image reading apparatus of the present embodiment performs a book mode in which image data is read using the document reading table 3 and an SDF mode operation in which image data is read using the document conveying device 2.
FIG. 3 shows the configuration of the scanner unit (see FIG. 1) for explaining the document reading operation in the book mode.
First, referring to FIG. 3, the basic operation of reading image data in the book mode (scanning and reading a document placed at a predetermined position on the document reading table by the exposure scanning unit) will be described below.
After setting the document 13 on the document reading table 3 below the document pressing plate 14, the CPU 16 operates the light source driver 17 to turn on the light source 4a. Next, the CCD 7 driven by the CCD drive unit 18 reads the white reference plate 15, performs analog-digital conversion with an A / D converter (not shown) in the image processing unit 19, and performs shading correction for the change data. The reference data is stored in a RAM (not shown) in the image processing unit 19.
The CPU 16 drives a motor driver (driving device) 20 to operate the stepping motor 8, whereby the first traveling body 4 moves in a direction (arrow direction in FIG. 3) of the document 13. As the first traveling body 4 scans the document surface at a constant speed, the image data of the document 13 is photoelectrically converted by the CCD 7.

Next, the basic operation of image data reading in the SDF mode (DF: reading a document sent by a document conveying device by an exposure scanning unit stopped at a reading position) will be described below.
FIG. 4 shows the configuration of the scanner unit (see FIG. 1) for explaining the document reading operation in the SDF mode.
Referring to FIG. 4, in the case of reading image data in the SDF mode, first, the CPU 16 reads the white reference plate 15 (at this time, it needs to move to the white reference plate reading position), and then the stepping motor 12 is moved to the motor. By driving with a driver (driving device) 28, the document 13 set on the document table 11 is transported by the separation roller 29 and the transport roller 30, and is read by the first traveling body 4 at a predetermined position. Transport to. At this time, the document 13 is conveyed at a constant speed, and the first traveling body 4 reads the image data on the document surface with the CCD 7 while stopped.
In addition, in the configuration that enables the SDF mode, a configuration for performing both-sided simultaneous reading can be provided, and the apparatus shown in FIG. 4 shows this example. As shown in FIG. 4, the apparatus having the configuration capable of simultaneous reading on both sides irradiates the back side of the document 13 with light from the back side reading lamp 101, reads the reflected light by the contact sensor 100, and outputs image data. Get. As a result, the image data of the front and back sides of the document can be obtained simultaneously. In the case of performing double-sided simultaneous reading with the configuration shown in FIG. 4, if a thin original sheet is used, show-through tends to occur, and a show-through suppression process described later is required.

In both the book mode and the SDF mode described above, the image photoelectrically converted by the CCD 7 by exposure scanning is processed by the image processing unit 19 as data that can be used by the image output device for output.
FIG. 5 is a block diagram showing a basic configuration of the image processing unit 19 shown in FIG.
An image processing unit 19 shown in FIG. 5 includes an analog video processing unit 21, a shading correction processing unit 22, in order from the input side (receiving the signal a from the CCD 7) to the output side (outputting data b to the scan buffer 25). An image data processing unit 23 and a binarization processing unit 24 are provided.
The analog video signal a photoelectrically converted by the CCD 7 is processed up to digital conversion by the analog video processing unit 21 (refer to the description of FIG. 6 described later), and then the shading correction processing unit 22 and the image data processing unit 23. When a binary image is desired after performing various data processing required for shading correction and output image data, binarization processing unit 24 creates binary data, and multi-value When data is desired, the binarization processing unit 24 is passed through to output 8-bit data as data b to the next stage. In this embodiment, the output binarized or multivalued data b is sequentially stored in the scan buffer 25.
The I / F controller 26 performs control to output data in the scan buffer 25 to a device that uses an output image such as an external host computer (not shown). The buffer controller 27 performs input / output management of image data to the scan buffer 25.

FIG. 6 is a block diagram showing the image processing unit 19 shown in FIG. 5 in more detail.
The analog video processing unit 21 illustrated in FIG. 5 includes a preamplifier circuit 31 and a variable amplifier circuit 32. The shading correction processing unit 22 includes an A / D converter 33, a black arithmetic circuit 34, a shading correction arithmetic circuit 35, and a line buffer 36.
The reflected light irradiated on the document 13 on the document reading table 3 by the light source 4 a is condensed by the lens 6 through the shading adjustment plate 37 and imaged on the CCD 7. In FIG. 6, a mirror for folding the reflected light is omitted for the sake of simplicity. The shading adjustment plate 37 plays a role of adjusting the amount of light for eliminating the difference in the amount of reflected light between the central portion and the end portion of the CCD 7. This is because, in the shading calculation process, if there is too much difference in the amount of reflected light at the center and end of the CCD, only the calculation result including distortion is obtained. This is for performing arithmetic processing.
As described above, the image signal photoelectrically converted by the CCD 7 is processed by the analog video processing unit 21 and the shading correction processing unit 22 shown in FIG. 6, and the document read image data to be outputted is subjected to correction processing such as shading correction. Variations in characteristics of the are corrected and normalized. The analog video processing unit 21 and the shading correction processing unit 22 can be implemented by applying an existing technique, and detailed description thereof is omitted.

As described above, since the variation due to the characteristics of the apparatus is corrected by the shading correction processing unit 22 or the like, the image data input to the image data processing unit 23 is normalized data.
However, when the original image is read, if the original is thin, a show-through image may be input together with an image on the surface of the original to be read, and the show-through image mixed in the read signal converted by the CCD 7 may be input. However, in the course of the correction process up to the shading correction processing unit 22, the show-through image cannot be processed. Therefore, the image data processing unit 23 performs a show-through image suppression process on the normalized read image data.
In order to suppress the show-through image, a determination unit for the show-through image mixed in the read image and a unit for suppressing the show-through image according to the determination result are required.
The present invention is characterized in the show-through image determination means, and as shown in the embodiment of the present invention described below, the original image density, edge strength, and density unevenness data are used to indicate the degree of the show-through image. Compared with the value, a means for comprehensively determining the show-through image based on the obtained result is used.

In the following, as “Embodiment 1” to “Embodiment 3”, three embodiments in which the show-through image suppression processing is performed by different methods are shown.
“Embodiment 1”
In this embodiment, whether or not the data of density, edge strength, and density unevenness has a show-through image quality is detected in binary, and the detection results of density, edge strength, and density non-uniformity are all show-through image quality. A process of determining that the image is a show-through image under certain conditions and deleting the image determined to be show-through is performed.
FIG. 7 shows a configuration of a processing unit for suppressing a show-through image according to the present embodiment. As shown in the figure, in order to determine a show-through image with respect to a read image, a density determination unit 111, an edge determination unit 112, a density unevenness determination unit 113, and a show-through image determination unit 115 are provided. In order to suppress the show-through image of the input image according to the determination result, a show-through suppression processing unit 117 is provided.
The read image data Di read by the scanner and processed by the shading correction processing unit 22 or the like is input to the density determination unit 111, the edge determination unit 112, and the density unevenness determination unit 113, and processed.
The density determination unit 111 compares the input image data value Di with a preset threshold value Thd1, and determines whether or not the input image has a show-through image quality based on the comparison result. That is, if the density of the input image represented by the size of the Di value is thinner than the density set by the threshold Thd1, the back image may be a show-through image that has passed through the original paper. And On the other hand, if the density is higher than the set density, the surface image is determined to be read.

The edge determination unit 112 performs edge detection processing of the input image data value Di, compares the detected edge intensity with a preset threshold value The1, and determines whether the edge portion has a show-through image quality based on the comparison result. . In other words, the show-through image has a sharpness that decreases in the process of passing through the original paper, and the edge strength becomes weak.Therefore, if the detected edge strength is smaller than the threshold value The1, there is a possibility of a show-through image. A candidate for a captured image On the other hand, if the edge strength is greater than the set edge strength, the surface image is determined to be read.
As an edge detection method, a detection method using a matrix filter can be applied.
FIG. 8 is a diagram for explaining an example of an edge detection method using a matrix filter. The example of FIG. 8 applies to an image region (a to i are pixels constituting a matrix) with a matrix size of “3 × 3” as shown in FIG. Edge detection filters for horizontal edge detection, vertical edge detection, left diagonal edge detection, and right diagonal edge detection are prepared in the order of (E) to (E). When edge detection processing is performed on the image area shown in FIG. 8A by the edge detection filters having the configurations shown in FIGS. 8B to 8E, the arithmetic processing shown in Expression (1) in FIG. 8 is performed. (In the equation (1), a to i indicate the pixel values of the pixels a to i), edge strengths (Ey, Et, Ehn) of the horizontal edge, vertical edge, left diagonal edge, and right diagonal edge , Emn). In the example of FIG. 8, the matrix size is “3 × 3”, but any size may be used.
For the usage of edge strength (Ey, Et, Ehn, Emn), it is possible to adopt a method of determining whether or not the edge portion has a show-through image quality by threshold processing for the maximum strength of each edge strength. It is.

The density unevenness determination unit 113 calculates a dispersion value of the image data around the target pixel in the input image data value Di, compares the calculated image density unevenness (variation) around the target pixel with a preset threshold value Thv1, It is determined whether the density unevenness has a show-through image quality based on the comparison result. That is, in the show-through image, since an image having a certain density or more passes through the original paper, the density unevenness is considered to be small. Therefore, if the variance value is smaller than the threshold value Thv1, it is determined as a show-through image candidate. On the other hand, when the variance value is larger than the threshold value Thv1, it is determined that the surface image is to be read.
FIG. 9 is a diagram for explaining an example of the density unevenness detection processing method. The example of FIG. 9 shows variations in peripheral pixels a to i for an image region (pixels a to i) having a matrix size of “3 × 3” around the pixel of interest e as shown in the figure. The variance value var is calculated, and this is set as the degree of density unevenness. The variance value var is obtained by calculating equation (3) in FIG. In Equation (3), ave is an average value of the pixel values shown in Equation (2) (in Equations (2) and (3), a to i represent the respective pixels a to i). Indicates pixel value). In the example of FIG. 9, the matrix size is “3 × 3”, but any size may be used.

In the density determination unit 111, the edge determination unit 112, and the density unevenness determination unit 113, whether or not the data of density, edge strength, and density unevenness has a show-through image quality, that is, whether or not it is a show-through image candidate. The binary detection is performed, and the result is passed to the show-through image determination unit 115.
The show-through image determination unit 115 comprehensively determines whether or not the input image data value Di is a show-through image based on each received detection result.
In the present embodiment, it is determined that the image is a show-through image on the condition that all the density, edge strength, and density unevenness data have a show-through image quality.
When the show-through image determination unit 115 determines that the image is a show-through image, the determination result is transmitted to the show-through suppression processing unit 117.
The show-through suppression processing unit 117 performs a process of erasing the image data as a process of suppressing the input image data value Di according to the determination result that it is the received show-through image, and sets the output image data Do.

“Embodiment 2”
In the first embodiment, whether or not each data of density, edge strength, and density unevenness has a show-through image quality is detected in binary, but in this embodiment, the show-through of density, edge strength, and density unevenness is detected. Performs processing to detect the nature of the image at multiple levels, determine the degree of overall show-through image quality from each detection result, and change the intensity of show-through suppression according to this determination result .
FIG. 10 shows a configuration of a processing unit for suppressing a show-through image according to the present embodiment. As shown in the figure, in order to determine the degree of show-through image quality, a density determination unit 121, an edge determination unit 122, a density unevenness determination unit 123, and a show-through image determination unit 125 are provided. In order to suppress the show-through image of the input image according to the determination result, a show-through suppression processing unit 127 is provided.
The read image data Di that has been read by the scanner and processed by the shading correction processing unit 22 or the like is input to the density determination unit 121, the edge determination unit 122, and the density unevenness determination unit 123, and processed. At this time, in the present embodiment, the characteristics as the show-through image of the density, edge strength, and density unevenness are detected based on three levels, that is, in relation to two threshold values.
In the density determination unit 121, the input image data value Di is compared with two threshold values Thd1 (high density side) and Thd2 (low density side) set in advance. Judgment is made (see equation (4) in FIG. 10). That is, when the density of the input image represented by the magnitude of the Di value is higher than the threshold value Thd1 (high density side) (Di> Thd1), it has no property as a show-through image, so it is determined as a surface image. When the density of the input image is not more than the threshold Thd1 (high density side) and not less than Thd2 (low density side) (Thd2 ≦ Di ≦ Thd1), it is determined to be a middle density portion and a quasi-back image. When the density of the input image is lighter than Thd2 (low density side) (Di <Thd2), it has a property as a show-through image, so it is determined as a show-through image.

The edge determination unit 122 performs edge detection processing on the input image data value Di, and sets two threshold values The1 (strong edge side) and The2 (weak edge) in which the detected edge strength Ex (Ey, Et, Ehn, Emn) is set in advance. 3), the characteristics as a show-through of the input image are determined at three levels according to the comparison result (see equation (5) in FIG. 10). That is, when the edge intensity Ex of the input image is larger than the threshold value The1 (strong edge side) (Ex> The1), it is determined as a surface image because it has no property as a show-through image. If the edge strength Ex of the input image is less than the threshold The1 (strong edge side) and greater than The2 (weak edge side) (The2 ≦ Ex ≦ The1), it is a weak edge part and is determined to be a quasi-back image To do. When the edge strength Ex of the input image is weaker than The2 (weak edge side) (Ex <The2), it has a property as a show-through image, so it is determined as a show-through image.
Note that the detection method using the matrix filter described in the first embodiment can be applied to the detection method of the edge intensity Ex (Ey, Et, Ehn, Emn).

The density unevenness determination unit 123 calculates the dispersion value var of the image data around the target pixel in the input image data value Di, and sets two threshold values Thv1 (preliminary values) for the calculated image density unevenness (variation) around the target pixel. Compared with Thv2 (high dispersion side) and Thv2 (low dispersion side), the nature of the show-through of the input image is determined at three levels according to the comparison result (see equation (6) in FIG. 10). That is, in the show-through image, since an image having a certain density or more passes through the original paper, the density unevenness is considered to be small. Therefore, when the variance value var of the input image is larger than the threshold value Thv1 (high dispersion side) (var> Thv1), the image is not a show-through image and is determined to be a front image. When the variance value var of the input image is smaller than the threshold Thv1 (high dispersion side) and larger than Thv2 (low dispersion side) (Thv2 ≦ var ≦ Thv1), the density unevenness is moderate and the quasi-rear surface Judged as an image. When the variance value var of the input image is smaller than Thv2 (low dispersion side) (var <Thv2), it has a property as a show-through image, so it is determined as a show-through image.
As a method for calculating the variance value var of the image data, it is possible to apply the method of calculating from the image data in the peripheral matrix region of the pixel of interest described in Embodiment 1 using the equation (3) in FIG. .

The density determination unit 121, the edge determination unit 122, and the density unevenness determination unit 123 detect the characteristics of the show-through included in the input image data of density, edge strength, and density unevenness at three levels, and the result is the show-through image determination. Passed to section 125.
The show-through image determination unit 125 comprehensively determines the degree of show-through image quality of the input image data value Di based on each received detection result. That is, the case where the determination results of the density, edge strength and density unevenness are all determined to be the front image is minimized, and the case where the determination results of the density, edge strength and density unevenness are all determined to be the show-through image, Ranks the degree of image quality of the show-through image in association with variations when the determination results of density, edge strength, and density unevenness are combined. This ranking needs to be determined by experimental confirmation.
The result determined by ranking the degree of image quality of the show-through image by the show-through image determination unit 125 is transmitted to the show-through suppression processing unit 127.
The show-through suppression processing unit 127 performs a process of suppressing the show-through image in the input image data value Di with an intensity corresponding to the degree of image quality of the received show-through image (ranked determination result). In other words, if all the determination results of density, edge strength, and density unevenness are determined to be the front image, the show-through image suppression process is not performed, and the determination results of density, edge strength, and density unevenness are all determined to be the show-through image. If it is, the process of deleting the image data is performed to obtain output image data Do.
In the case of an intermediate rank, the suppression strength (pixel density) of the show-through image in the input image data value Di is changed stepwise according to the determination result, the image data suppression processing is performed, and the output image data Do To do. For example, it is possible to use a method of adjusting the erasure of image data (pixels) in an image portion (having a region of a predetermined size) for which the same rank is determined according to the rank.
In this embodiment, two threshold values Th1 and Th2 are used to determine density, edge strength, and density unevenness, and detection is performed at three levels. The suppression process of the show-through image according to the number may be performed.

“Embodiment 3”
In the second embodiment, it is detected at three levels whether or not the data of density, edge strength, and density unevenness have a show-through image quality, and the degree of the image having an intermediate image quality of the show-through image is determined. (Ranking), and an example of a configuration that performs a process of suppressing a show-through image in an input image with an intensity according to the determination result has been shown. Absent. Therefore, a case where proper suppression processing is not performed occurs.
In view of this, the present embodiment adds a means for enabling appropriate show-through image suppression processing in accordance with the difference in thickness of the original paper. In the following, an example in which means for adapting to the thickness of the original paper is added to the second embodiment is shown, but the same can be applied to the first embodiment.
In the present embodiment, as means for adapting to the thickness of the manuscript paper, means for switching the strength of the show-through image suppression processing according to the manuscript paper thickness set as the processing condition is provided. The thickness of the manuscript paper is set from an operation unit that is usually provided in this type of apparatus and for a user to input processing conditions.
FIG. 11 shows a configuration of a processing unit for suppressing a show-through image according to the present embodiment. As shown in the figure, in order to determine the degree of show-through image quality, a density determination unit 131, an edge determination unit 132, a density unevenness determination unit 133, and a show-through image determination unit 135 are provided. In order to suppress the show-through image of the input image according to the determination result, a show-through suppression processing unit 137 is provided.
As shown in FIG. 11, the configuration of the processing unit for suppressing the show-through image according to the present embodiment is the thickness of the original paper set in the show-through suppression processing unit 137 by the operation unit (not shown). Data is input, and an adjustment is made by switching the intensity of the show-through image suppression process corresponding to the difference in thickness of the original paper. The show-through image determination processing unit for the input image other than the adjustment corresponding to the thickness of the original paper in the show-through suppression processing unit 137 is the same as the processing unit of the second embodiment. Therefore, for the show-through image determination processing unit, the description of the second embodiment is referred to, and the description is omitted here.

The adjustment of the intensity of the suppression process in the show-through suppression processing unit 137 reduces the intensity of the show-through suppression process because the possibility of show-through is low when the thickness of the original paper input as the setting condition is a certain value or more. When the direction is reversed, the direction is switched to a direction to increase the strength of the show-through suppression processing, and the show-through suppression processing is performed in accordance with the set thickness of the original paper.
As in the second embodiment, the show-through image determination unit 135 ranks the degree of image quality of the show-through image and outputs a determination result. Therefore, if the thickness of the manuscript paper input as the setting condition is greater than or less than the reference thickness, the suppression strength determined corresponding to the rank in the reference thickness Does not fit. Therefore, in this case, appropriate suppression is applied by using the suppression strength determined corresponding to the rank in the reference thickness by shifting it according to the deviation from the reference thickness.
In the present embodiment, an example is shown in which the adjustment corresponding to the thickness of the document paper is performed by switching the correspondence between the determination result (ranking) of the show-through image by the show-through image determination unit 135 and the suppression strength. As an adjustment method, it is also possible to adopt a method of performing adjustment in the process until obtaining a show-through image determination result (ranking).

1 shows a configuration of an image reading apparatus according to an image processing apparatus of the present invention. FIG. 2 is a block diagram illustrating a configuration of a control system for the image reading apparatus illustrated in FIG. 1. 1 shows a configuration of a scanner unit (see FIG. 1) for explaining an original reading operation in a book mode. 1 shows a configuration of a scanner unit (see FIG. 1) for explaining an original reading operation in a sheet through mode. FIG. 3 is a block diagram illustrating a basic configuration of an image processing unit illustrated in FIG. 2. FIG. 6 is a block diagram showing in more detail an image processing unit up to shading correction shown in FIG. 5. 3 illustrates a configuration of a processing unit for suppressing a show-through image according to the first exemplary embodiment. The figure for demonstrating an example of the edge detection method using a matrix filter is shown. The figure for demonstrating an example of a density nonuniformity detection processing method is shown. The structure of the process part for suppressing the show-through image of Embodiment 2 is shown. The structure of the process part for suppressing the show-through image of Embodiment 3 is shown.

Explanation of symbols

1. Image reading device main body, 2. Document feeder,
3. Document reading table 7. CCD line image sensor,
13 .... Original, 19 .... Image processing section,
21 .. Analog video processing unit 22.. Shading correction processing unit
23. Image data processing section,
111, 121, 131 .. density determination unit,
112, 122, 132 .. edge determination unit,
113, 123, 133.. Density unevenness determination unit,
115, 125, 135, .. show-through image determination unit,
117, 127, 137 .. The show-through suppression processing unit.

Claims (5)

An image processing apparatus that reads a document and processes the obtained image data as data usable for image output,
An image quality detecting means for comparing the density, edge strength and density unevenness data of the read document image with a reference value indicating the degree of the show-through image;
Show-through determination means for comprehensively determining a show-through image based on image quality detection results for the density, edge strength and density unevenness data obtained by the image quality detection means;
An image processing apparatus comprising: means for suppressing a show-through image according to a result of determination by the show-through determination means. The image processing apparatus according to claim 1, wherein the image quality detection means uses a reference value for obtaining a detection result with binary values as to whether or not the image has a show-through image quality.
The show-through determination means determines the show-through image on condition that the image quality detection results of the density, edge strength, and density unevenness data obtained by the image quality detection means are all show-through image quality. An image processing apparatus.   The image processing apparatus according to claim 2, wherein the show-through image suppression unit deletes the determined show-through image when the show-through determination unit determines the show-through image. Image processing device. The image processing apparatus according to claim 1, wherein the image quality detection means uses a reference value for detecting the degree of a show-through image at a plurality of levels.
The show-through determination means determines the degree of overall show-through image quality from the image quality detection results of the density, edge strength and density unevenness obtained by the image quality detection means,
The image processing apparatus characterized in that the means for suppressing the show-through image changes the strength of suppression of the show-through according to the determination result.   5. The image processing apparatus according to claim 1, further comprising an operation unit that enables input for setting a processing condition, wherein the means for suppressing the show-through image is input from the operation unit. An image processing apparatus comprising: changing at least one of a reference value, a determination method, and an intensity of suppression of show-through according to document thickness information.

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