JP2005277886A - Image scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image scanner capable of suppressing show-through by a simple configuration. <P>SOLUTION: The image scanner includes a reading mode setting means that can set a show-through prevention mode, and an image processing means that determines the level of show-through based on pixel density distribution information about an original which is read in the show-through prevention mode, and binalizes to eliminate the pixel component of the density equal to or less than the determined level of show-through. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image reading apparatus that suppresses show-through of image data read from a document.

When reading an original image with an image reading device such as a copier, if the original paper is thin, the image on the back side of the original is read together with the image on the front side, and the image quality of the read image may deteriorate. . In order to suppress the show-through, in the following patent document, an image processing apparatus configured to read both the front and back images, invert the back image and offset the show-through portion in addition to the front image. Disclosure.
JP-A-10-304204

However, in the image processing apparatus of the above-mentioned patent document, since it is necessary to read both the front surface and the back surface of the document, the structure of the apparatus is complicated and the price is high.
On the other hand, an object of the present invention is to provide an image reading apparatus that suppresses show-through with a simpler configuration.

In order to solve the above-mentioned problem, according to a first aspect of the present invention, there is provided a reading mode setting means capable of setting a show-through prevention mode, and a pixel density distribution for a read original when the show-through prevention mode is executed. An image reading apparatus comprising: an image processing unit that determines a show-through level based on information and performs binarization processing so that pixel components having a density equal to or less than the determined show-through level are erased. is suggesting.
According to a second aspect of the present invention, there is proposed an image reading device in which the image processing means is configured to change the threshold value of the binarization process according to the determined show-through level.
According to a third aspect of the present invention, there is proposed an image processing apparatus in which the image processing means is configured to change a γ correction characteristic according to the determined show-through level.
According to a fourth aspect of the present invention, the reading mode setting means that can set the show-through prevention mode, and a preset threshold value is applied to the binarization process when the show-through prevention mode is executed, An image reading apparatus is proposed that includes image processing means that applies a set characteristic to γ correction and performs binarization processing so that pixel components having a density equal to or lower than a predetermined level are erased. .

According to the first to third aspects, since the show-through level is determined based on the pixel density distribution information about the read document, the show-through prevention process is executed according to the image of the document.
In claim 4, a manual operation is accepted, and a preset threshold value is applied to the binarization process, or a preset characteristic is applied to the γ correction to perform the binarization process. The user can set the show-through prevention process as necessary.

  In the present invention, an image reading apparatus that reads only one side of an original, that is, a scanner, a facsimile machine, a copier, and a so-called multi-function machine that integrates these functions is an optimal embodiment. Hereinafter, the present invention will be described in detail using such a copying machine as an example.

FIG. 1 is a block diagram illustrating a basic configuration of a copier M that is an embodiment of an image reading apparatus according to the present invention.
The copier M is configured by an MPU or the like, and stores a control unit 11 that controls each unit of the copier M by software processing, a program memory 12 that stores programs constituting the software, and various data. A data memory 13, a liquid crystal panel, and the like. The display unit 14 displays information according to the user's operation and the state of the apparatus, the operation unit 15 for the user to operate, A scanner unit 16 for reading, an image memory 17 for storing image data read by the scanner unit, and a printer unit 18 for printing out the image data stored in the image memory 17 on paper are provided.

  The present invention is characterized in that an image of a document is read together with an image on the back side thereof and is prevented from being printed out in a so-called show-through state. Then, a show-through prevention mode for performing a process to prevent show-through can be set with a special key.

  That is, the operation unit 15 includes a show-through prevention mode setting key 15a for setting a show-through prevention mode in addition to the operation keys of a known copier, and exhibits a function as a reading mode setting means. In addition, an automatic show-through prevention mode setting key 15b for setting an automatic show-through prevention mode for judging an image of a document and automatically executing a process for preventing show-through, or only characters according to an image of a document. A reading mode setting key 15c for setting a black and white mode suitable for a document or a halftone mode suitable for a document such as a photograph may be provided.

Further, the scanner unit 16 is provided with a read image processing circuit 16a for performing image processing corresponding to each of the above modes as shown in the block diagram of FIG. 2, and exhibits a function as image processing means.
FIG. 2 is a more detailed block for explaining the basic configuration of the read image processing circuit 16a. In this block, the read image processing circuit 16a indicated by the broken line block reads the pixel unit by the CCD element 161. An analog signal indicating the density of the original image is converted into a digital signal by the A / D converter 162 and input.

  The read image processing circuit 16a has an image correction circuit 163 for making the input image data easy to view, and each pixel of the image data corrected by the image correction circuit 163 in a predetermined level corresponding to the monochrome mode. And a comparator 164 for dividing the data into white and black binary data and corresponding to the halftone mode, each pixel of the image data corrected by the image correction circuit 163 is binarized based on an error diffusion method or a dither method. A gradation processing circuit 165 for converting the data into a digitized data and a selector 166 for selecting either the output of the comparator 164 or the output of the gradation processing circuit 165 are provided.

  The image correction circuit 163 performs γ correction as one of the image corrections, and the γ correction table 167 defining the correction characteristics can be rewritten by the control unit 11. Similarly, the threshold value register 168 that defines the level for dividing white and black in the comparator 164 can also be rewritten by the control unit 11. These values are rewritten according to the user's shade specification or execution of the show-through prevention mode.

  Next, the show-through phenomenon of the read image will be described qualitatively. In the show-through phenomenon, the light beam irradiated for reading the document by the scanner unit 16 is transmitted through the paper of the document, reflected by the reflective plate attached to the back surface of the suppression lid, and the reflected light is transmitted through the paper again. When the light enters the CCD element 161, a part of the reflected light is absorbed by the black portion on the back surface and becomes weak (blacker).

  FIG. 3 is a histogram of the density distribution of the read image. When there is no show-through, steep peaks of white and black appear corresponding to white and black on the surface image of the document. On the other hand, when there is show-through, a peak corresponding to the image on the back surface appears in the middle portion. This peak corresponds to the black portion on the back surface, but since the reflection of the white portion on the front surface is superimposed, it appears somewhat white and appears in the middle portion. Note that in a manuscript such as a photograph, many pixels are distributed in the middle portion, and the show-through peak is mixed with it, so it is difficult to identify.

  Therefore, in the copying machine M, if the pixel corresponding to the peak of the intermediate portion is processed to become white by the binarization process, the show-through is effectively suppressed. For this purpose, as illustrated in FIG. 4, the threshold value defining the white and black level of the comparator 164 of the read image processing circuit 16 a is made closer to black than the peak of the intermediate portion, or Although the threshold value is not changed, the γ correction in the image correction circuit 163 may be made to have a characteristic in which the peak of the intermediate portion is close to white.

FIG. 4A shows white and black classification when the threshold value defining the level for classifying white and black in the comparator 164 is changed. Here, the horizontal axis indicates pixels and the vertical axis indicates density, but the pixels VZ are not printed out in the show-through prevention mode.
FIG. 4B shows characteristics of the image correction circuit 163 in γ correction. Here, the input density and the vertical axis indicate the output density, but the density B is corrected to a level determined as white in the show-through prevention mode.

Here, the control of the copying machine M configured as described above will be described in detail according to a flowchart.
FIG. 5 is a flowchart for explaining basic control of the copier M. When starting the reading operation, the control unit 11 determines whether the monochrome mode or the halftone mode is set (step 201). In the case of the halftone mode, the shade processing circuit 165 is selected as an output by the selector 166, the image is read, the image data is encoded and stored in the image memory 17 (steps 202 to 203). On the other hand, if the mode is black and white, the selector 166 selects the comparator 164, and then determines whether the show-through prevention mode is set (204-205). Here, if the show-through prevention mode is set, a predetermined threshold for preventing show-through (closer to black) is set in the threshold register 168 (step 206), but if the show-through prevention mode is not set. The normal threshold value is set in the threshold value register 168 (step 207). Thereafter, the image is read, and the image data is encoded and stored in the image memory 17 (step 203).

  FIG. 6 is a flowchart for explaining basic control when the automatic show-through prevention mode is set. When the reading operation is started, the control unit 11 reads a predetermined line (here, it is not limited to this) of the image data, creates a histogram as shown in FIG. The peak is determined based on the read pixel density distribution information, and the show-through level is determined (steps 301-303). Here, when the show-through is determined, a threshold for preventing show-through (closer to black) is set in the threshold register 168 so that pixel components below the show-through level are deleted (step 304). When the show-through peak is not determined, a normal threshold is set in the threshold register 168 (step 305). Thereafter, the image is read, and the image data is encoded and stored in the image memory 17 (step 306).

In the flowcharts of FIG. 5 and FIG. 6, the threshold value that defines the level for distinguishing white and black of the comparator 164 is changed to prevent show-through, but γ correction by the image correction circuit 163 is performed at the intermediate portion. Processing may be performed to prevent show-through by making the peak close to white.
In the automatic show-through prevention mode, the show-through prevention threshold or γ correction characteristics can be set to be variable according to the show-through level based on the pixel density distribution information. Can be prevented.

1 is a block diagram illustrating a basic configuration of a copier M that is an embodiment of an image reading apparatus of the present invention. It is a block for explaining a basic configuration of a read image processing circuit (image processing means). It is a histogram figure of the light and shade distribution of the read image. It is drawing explaining a monochrome determination level. 3 is a flowchart illustrating basic control of the image reading apparatus. 10 is a flowchart illustrating another control of the image reading apparatus.

Explanation of symbols

15 Operation unit (reading mode setting means)
16 Scanner unit 16a Read image processing circuit (image processing means)
167 γ correction table 168 Threshold register

Claims (4)

  Reading mode setting means that enables setting of the show-through prevention mode, and when executing the show-through prevention mode, the show-through level is determined on the basis of the pixel density distribution information about the read document, and is less than the determined show-through level. An image reading apparatus comprising: an image processing unit configured to perform binarization processing so that density pixel components are erased.   The image reading apparatus according to claim 1, wherein the image processing unit is configured to change a threshold value of the binarization process according to the determined show-through level.   The image processing apparatus according to claim 1, wherein the image processing unit is configured to change a γ correction characteristic according to the determined show-through level. The reading mode setting means that can set the show-through prevention mode, and when executing the show-through prevention mode, apply a preset threshold value to the binarization process, or apply a preset characteristic to the γ correction, An image reading apparatus comprising: an image processing unit configured to perform binarization processing so that pixel components having a density equal to or lower than a predetermined level are erased.

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