JP2002152473A - Image input device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image input device capable of double-side reading, 'suppressing' or 'erasing' a part corresponding to back side copy unnecessary for front surface data and retaining information in an information area of the necessary front face. SOLUTION: The image input device comprises an exposure lamp 1a, a mirror 5a, image reader 3a and the like for reading image information recorded on a front surface of a medium, an exposure lamp 1b, a mirror 5b, image reader 3b and the like for reading the image information recorded on a rear surface of the medium, and an image processor 4 for suppressing a pixel area of the image information input from the reader 3b, and inhibiting the suppressing process for the pixel area of the image information input from the reader 3a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input device such as a scanner device for performing digital image processing, or a copying machine or a facsimile device equipped with the scanner device.

[0002]

2. Description of the Related Art In a conventional copying machine, for example, a document is input only from the front side. At that time, since show-through of the document is generally disliked by the user, there is an apparatus having a mechanism for removing show-through, including automatic and manual. However, only the information from the front side shows the information on the back side, but it is not possible for the machine to determine whether it is a highlight or a low contrast character of the picture, and we want to erase the show-through. That is, there has been a phenomenon that information such as a highlight portion of a picture or a low-contrast character is lost or thinned.

By the way, as for a higher-grade image input device, there is an image input device capable of reading both sides simultaneously, as described in, for example, Japanese Patent Application Laid-Open No. H8-125813. In the same apparatus, surface data is processed using double-sided information, but if the principle is briefly explained, information is left because positively subtracting surface information in an area that is likely to be affected from behind May or may not remain. In other words,
In the technique described in Japanese Patent Application Laid-Open No. 1-25813, the threshold value used is 0.5, but if this value is set to a somewhat large value (for example, 0.8), the information will be lost.
Even if the threshold value is not changed, low-contrast characters and the like will disappear. At present, there is also a pseudo halftone process such as an error diffusion method which has an advantage of preserving the density of an input document, instead of performing a binarization process with a fixed threshold.

[0004]

Problems to be Solved by the Invention
In the technique described in Japanese Patent Application Laid-Open No. 813, when pseudo halftone processing such as an error diffusion method is performed in post-processing of an input device output,
Obviously, the density value of the surface data may be reduced, and the highlight portion or the low-contrast character of the picture may disappear.

The present invention solves such a problem, and can suppress or erase a portion corresponding to show-through data which can be read on both sides and is not necessary in the surface data.
In addition, an object of the present invention is to propose an image input device capable of leaving information in a necessary information area on a surface.

[0006]

According to a first aspect of the present invention, a light source irradiates a medium on which an image is recorded with a light source and reads image information recorded on the medium surface from reflected light, and a light source. Back-side reading means for irradiating a medium on which an image is recorded and reading image information recorded on the back side of the medium from reflected light, and image processing means for processing image information input from the front-side reading means and the back-side reading means An image input device comprising:
A suppression process is performed on image data input from the front surface reading unit based on image information input from the back surface reading unit, and a suppression process on a pixel area of the image information input from the front surface reading unit is prohibited. There is.

In an image input apparatus capable of simultaneously reading both sides of a recording medium, by suppressing only the back side information, show-through on the front side information data is removed, and
It is avoided that the surface information data itself causes a decrease in density.

According to a second aspect of the present invention, in the first aspect, the pixel area of the image information input from the front surface reading means has a density value equal to or higher than a predetermined value.

The information area on the surface (excluding low-contrast characters such as pencils and picture printing portions) is simply determined by threshold processing of the surface information.

According to a third aspect of the present invention, in the first aspect, a pixel area of the image information input from the front surface reading means belongs to a print pattern.

The halftone print area on the front surface is simply determined by threshold processing or halftone area detection processing for the surface information.

According to a fourth aspect of the present invention, a medium on which an image is recorded is illuminated by a light source, and surface information reading means for reading image information recorded on the surface of the medium from the reflected light; Image reading means for irradiating the medium and reading image information recorded on the back surface of the medium from reflected light, and image processing means for processing image information input from the front surface reading means and the back surface reading means The image processing means performs threshold processing on image information input from the front surface reading means and the back surface reading means using respective preset threshold values, and as a result of the threshold processing, a medium If it is determined that the image on the front side is lighter than the predetermined density and the image on the back side of the medium is darker than the predetermined density, the front side reading is performed based on the image information input from the back side reading means. The suppression is performed with respect to image data input from the stage, it is characterized in that prohibiting suppression processing for the pixel area of the image information inputted from the side reading means.

The threshold value is appropriately set for each of the front and back surfaces, and the show-through removal processing is performed only when the pixel region of the front surface information is an unknown region and the pixel region of the back surface information is a show-through region. In addition, the surface information is corrected efficiently.

A fifth aspect of the present invention is characterized in that, in the fourth aspect, a plurality of the thresholds are set stepwise.

By performing threshold processing in multiple stages, smooth switching of image density is realized, and excessive information erasure in an unknown area is suppressed.

A sixth aspect of the present invention is characterized in that, in the fifth aspect, a mode setting means for setting a mode for performing a suppression process based on a result of the threshold value process is provided.

By providing the mode setting means, unnecessary suppression processing can be easily reduced according to the contents of mode setting by a user operation or the like.

[0018]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of an image input device (image reading device) according to an embodiment of the present invention.

The image reading apparatus includes an optical system such as a light source 1a and a mirror 5a, an image reading unit 3a including an A / D converter, an optical system such as a light source 1b and a mirror 5b, and an A / D converter. Image reading unit 3b, medium 2 such as a sheet (document) on which an image is recorded, and data A1 obtained by correcting surface information A based on image information A and B on the front and back surfaces of medium 2
Is provided. In addition, surface information A,
The back side information B is 8-bit density data (paper white = 0).

Here, image information obtained by reflection or transmission from the surface of the medium 2 by irradiation of the light source 1a such as an exposure lamp is converted into an electric signal by the image reading unit 3a, and the image information is processed as surface information A. It is input to the unit 4. On the other hand, image information obtained by reflection or transmission from the back surface of the medium 2 by irradiation of the light source 1b such as an exposure lamp
The signal b is converted into an electric signal, and is input to the image processing unit 4 as back surface information B. The image processing unit 4 receives the input surface information A
Based on the back surface information B, data A1 obtained by correcting the front surface information A is calculated.

As shown in FIG. 2, the image processing unit 4 includes a gamma conversion circuit 6, a gamma table generation circuit 7, a determination circuit 8
Is provided.

The determination circuit 8 compares the surface information A of the medium 2 with a preset threshold value THA, and determines whether the pixel area of the surface information A is an information area (having a density value equal to or higher than a predetermined value) or an unknown area. (It belongs to the print pattern), and the determination result is passed to the γ table generation circuit 7.

Further, the determination circuit 8 determines the back side information B of the medium 2.
Is compared with a predetermined threshold value THB to determine whether the pixel area of the back surface information B is a show-through area (area causing show-through) or a non-show-through area, and sends the determination result to the γ table generation circuit 7. hand over. Since the back surface information B is an 8-bit signal, for example, a pixel of B ≧ 200 (= THB) is set as a pixel in the show-through area.

Further, the γ table generation circuit 7 calculates the γ value (here, the ratio of the change in the brightness (density) of the surface image (surface information) A to the input / output voltage) according to the determination result of the determination circuit 8. A conversion table (γ table) for correction is generated. Specifically, when A <THA and B ≧ THB,
A .gamma. Table for obtaining correction data corresponding to the solid line shown in FIG. 2 is generated, and when A.gtoreq.THA and B <THB, a .gamma. Table with a gradient 1 (A = A1) is generated. Note that the actual γ table needs to be determined experimentally.

The γ conversion circuit 6 determines from the above-described determination result by the determination circuit 8 that the pixel area of the back side information B is a non-show-through area and the pixel area of the front side information A is an information area. In this case, the data A after the correction of the surface information A
1 (A = A1), and when it is determined from the determination result by the determination circuit 8 that the pixel region of the back surface information B is a show-through region and the pixel region of the front surface information A is an unknown region. The surface information A is converted to γ using the γ table described above.
After the correction, the corrected data A1 is output.

Next, referring to FIG.
The calculation method of the correction data A1 will be described.

In this embodiment, first, threshold processing is performed on the surface information A (s101). When the level of the surface information A is equal to or larger than the threshold value THA, the image area of the surface information A does not include a low-contrast character such as a pencil or a pattern highlight portion such as a photographic paper. If the information area is determined to be a normal information area, and the level of the surface information A is lower than the threshold value THA, the image area of the surface information A is a low-contrast character such as a pencil or a picture highlight portion such as a photographic paper. Is a density value for determining that the area is an unknown area.

If the level of the surface information A is equal to or greater than the threshold value THA (A ≧ THA),
The pixel area of the surface information A is determined as an information area, and if not (A <THA), the pixel area of the surface information A is determined as an unknown area.

Next, threshold processing is also performed on the back side information B (s102). Threshold THB used in this threshold processing
Is that when the level of the surface information B is equal to or greater than the threshold value THB, the pixel area of the surface information B is dense enough to cause show-through,
For example, when it is determined that a show-through area including a black character of printing is included and the signal level of the surface information B is lower than the threshold value THB, the pixel area of the surface information B is thin enough not to cause show-through. This is a density value for determining a non-show-through area that does not include printed black characters.

When the level of the input back surface information B is equal to or larger than the threshold value THB (B ≧ THB), the image processing section 4 determines that the pixel region of the back surface information B is a show-through region. In THB), the pixel region of the back surface information B is determined as a non-show-through region.

Based on the above determination result, when the pixel area of the surface information A is an information area or the pixel area of the back information B facing the front information A is a non-show-through area (s
In 103 yes), the surface information A is through, that is, A
Output as 1 = A (s106). On the other hand, surface information A
Is the unknown region, and the pixel region of the back surface information B facing the front surface information A is the show-through region (s10).
No. 3 and yes in s104), a one-dimensional conversion process as shown in FIG. 2 is performed on the surface information A, and a show-through removal process is performed (s105).

Note that the present invention is not limited to this embodiment, and the threshold value TH
B is set in a plurality of steps, and the determination is performed in a plurality of steps according to the density. For example, as the density is higher, a conversion table from the solid line a shown in FIG. 5 is selected. As a result, the conversion table from the solid line b shown in FIG. 5 may be selected. By this method, the surface information A
It is possible to suppress too much information from being erased in the unknown area, and smooth switching can be expected as an effect of the multi-stage determination.

Further, the present invention is not limited to this embodiment. Instead of the determination of the information area / unknown area by the threshold processing for the surface information A, a halftone dot area detection method described in Japanese Patent Application Laid-Open No. 2-112077 is used. May be. Of course, the area determined to be a halftone dot is the information area. This makes it possible to solve the following problems. That is, since the print pattern portion is basically formed by turning dots on and off, if a threshold determination is performed on image data that has been read, an unknown region frequently appears in the same region. ,
As a result, uneven or unnecessary show-through removal processing may be performed.

Further, as another embodiment, a mode for executing the processing shown in FIG. 4 on an operation unit (comprising a CPU, a RAM, a ROM, various button keys, a display, etc.) not shown in FIG. A mode key (mode button) for setting a show-through removal (or background removal) mode is provided. When the show-through removal (or background removal) mode is set by this mode key, the processing shown in FIG. 4 is performed. Run and if not set (default)
The processing shown in FIG. 4 may be prohibited. In this case, the contents of the user setting by the mode key are stored in the RAM or the like of the operation unit in an updatable manner.

As another embodiment, a prescan of the back surface of the medium is performed before the main scan (reading of the front and back surfaces of the medium 2), and a histogram of high-density pixels that can be the above-mentioned show-through area is obtained. If it is larger than the predetermined threshold value, the processing shown in FIG. 4 may be executed at the time of the main scan, and if not, the processing shown in FIG. 4 may be prohibited.

In another embodiment, the paper thickness is directly measured from the light transmittance before the main scan (see Japanese Patent Application Laid-Open No. H05-260, Heisei 5).
The processing shown in FIG. 4 may be executed / prohibited based on the paper thickness. That is, utilizing the fact that the light transmittance decreases as the paper thickness increases, and if it is determined that the original is thick enough to prevent show-through before the main scan, the processing shown in FIG. Otherwise, the processing shown in FIG. 4 is executed. Further, when the paper thickness can be measured directly and in multiple steps from the light transmittance, for example, in FIG. 5, the conversion table (γ table) from the solid line a is selected as the document becomes thinner than a predetermined value. Conversely, the conversion table (γ table) from the solid line b may be selected as the document becomes thicker than the predetermined value. According to this method, it is possible to prevent information from being overly erased in the unknown area.

Needless to say, if a conversion table is selected or calculated from both the paper thickness information and the back surface density information obtained from the light transmittance, higher precision control is possible. The rule in that case, that is, the conversion table can also be experimentally determined.

As another embodiment, the processing shown in FIG. 4 may be executed / prohibited according to the mode setting of the original in the image input device or the like. For example, in a color copier, when a mode such as a print mode, a photographic paper mode, and a generation mode can be set by a user operation, if the photographic paper mode is set, the paper thickness of the original is determined to be large enough not to show off. Then, the processing shown in FIG. 4 is prohibited.

Further, as another embodiment, the image input device is provided with a detecting means for detecting whether or not the document press (not shown) is tightened / not tightened, and the processing shown in FIG. Execution / prohibition may be performed. For example, if the document presser is not tightened, it is determined that the document is thick enough not to show off, and the processing shown in FIG. 4 is prohibited.

As described above, when the mode indicating the processing of FIG. 4 is set, when the prescanning of the back side of the original is possible, when the paper thickness of the original is directly measurable, and when the paper thickness of the original is indirectly measured. In cases where it is possible to judge the situation, the processing shown in FIG. 4 is not always executed, and only when there is a possibility that show-through may occur, unnecessary processing can be performed by selectively executing the processing shown in FIG. Suppression can be avoided.

The image reading section 3a and the like constitute the front side reading means, the image reading section 3b and the like constitute the back side reading means, the image processing section 4 and the like constitute the image processing means, and the operation section These constitute the mode setting means.

[0042]

According to the first aspect of the present invention, in an apparatus capable of reading both sides of a medium, an information area on the surface of the medium is detected, show-through is suppressed for the surface data, and the surface information data is suppressed. It is possible to prevent the concentration from decreasing.

According to the second aspect of the present invention, it is possible to easily determine the information area on the medium surface.

According to the third aspect of the present invention, it is possible to easily and accurately determine the halftone dot printing area on the medium surface.

According to the fourth aspect of the present invention, the show-through removal processing is performed only when the pixel region on the medium surface is an unknown region and the pixel region on the back surface of the medium is a show-through region. It is possible to efficiently correct the surface information.

According to the fifth aspect of the invention, by performing the threshold processing in multiple stages, it is possible to realize a smooth switching of the image density and to suppress excessive information deletion in an unknown area. is there.

According to the sixth aspect of the present invention, by providing the mode setting means, it is possible to easily reduce unnecessary suppression processing in accordance with the contents of mode setting by a user operation or the like.

As described above, according to the present invention, the part corresponding to the show-through data which is readable on both sides and which is unnecessary in the surface data can be "suppressed" or "erased".
In addition, it is possible to provide an image input device capable of leaving information in a necessary information area on the surface.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image input device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an image processing unit according to an embodiment of the present invention.

FIG. 3 shows a conversion table (γ) according to an embodiment of the present invention.
FIG.

FIG. 4 is a flowchart illustrating an image processing method according to an embodiment of the present invention.

FIG. 5 is a diagram showing a conversion table (γ table) according to another embodiment of the present invention.

[Explanation of symbols]

 1a, 1b Exposure lamp 3a, 3b Image reading unit 4 Image processing unit 5a, 5b Mirror 6 γ conversion circuit 7 γ table generation circuit 8 Judgment circuit

Claims (6)

[Claims] 1. A surface reading means for irradiating a medium on which an image is recorded with a light source and reading image information recorded on the surface of the medium from reflected light, and irradiating the medium on which the image is recorded with a light source to reflect the light. An image input apparatus comprising: a back surface reading unit that reads image information recorded on a back surface of a medium from light; and an image processing unit that processes image information input from the front surface reading unit and the back surface reading unit. The processing unit performs a suppression process on the image data input from the front surface reading unit based on the image information input from the back surface reading unit, and prohibits the suppression process on the pixel area of the image information input from the front surface reading unit. An image input device, comprising: 2. The image input device according to claim 1, wherein a pixel area of the image information input from the front surface reading means has a density value equal to or higher than a predetermined value. 3. The image input device according to claim 1, wherein a pixel area of the image information input from the front surface reading means belongs to a print pattern. 4. A surface reading means for irradiating a medium on which an image is recorded with a light source and reading image information recorded on the surface of the medium from reflected light, and irradiating a medium on which an image is recorded with a light source to reflect the light. An image input apparatus comprising: a back surface reading unit that reads image information recorded on a back surface of a medium from light; and an image processing unit that processes image information input from the front surface reading unit and the back surface reading unit. The processing unit performs threshold processing on the image information input from the front surface reading unit and the back surface reading unit using respective preset threshold values. As a result of the threshold processing, the image on the medium surface has a predetermined density. If it is determined that the image is thinner and the image on the back of the medium is darker than the predetermined density,
A suppression process is performed on image data input from the front surface reading unit based on image information input from the back surface reading unit, and a suppression process on a pixel area of the image information input from the front surface reading unit is prohibited. Image input device. 5. The image input device according to claim 4, wherein a plurality of the thresholds are set in a stepwise manner. 6. The image input apparatus according to claim 5, further comprising mode setting means for setting a mode for performing a suppression process based on a result of the threshold process.