JP3932076B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a digital system typified by a digital copying machine in which optically read image information is converted into an electrical signal, digitized, subjected to various image processing, and then optically written with a modulated laser beam. The present invention relates to an image forming apparatus.
[0002]
[Prior art]
The digital copier irradiates the document set on the contact glass with light from a lamp and forms an image of the reflected light on a CCD image sensor by an imaging lens, thereby converting the image information into an electrical signal. Get.
Thereafter, the analog signal is A / D converted by an A / D converter, and after various image processing such as shading correction, gamma correction, and gradation correction, the laser is modulated by the image signal.
Then, optical writing is performed on the photosensitive member by the modulated laser to form an electrostatic latent image on the photosensitive member, and the electrostatic latent image is developed with toner to obtain a visible image. The visible image is transferred to a sheet by a transfer unit and fixed by a fixing unit, so that an image is finally formed.
[0003]
By the way, when a document image is read by a scanner and a multi-valued image is output, the density of the background of the document is also reproduced, so that the background stain is conspicuous in the output image. Therefore, many techniques for removing dirt on the background of the document have been proposed.
[0004]
For example, in Japanese Patent Laid-Open No. Hei 6-197216, density conversion is performed only on color data located in the vicinity of white and white, and the color reduction is changed in accordance with the degree of whiteness to change the color image. There has been proposed a technique for removing background stains without causing a change in color tone of a picture when reproduced and output by an output device.
[0005]
[Problems to be solved by the invention]
By the way, in the conventional technology, when there is a dark color character or design on the back side and the back side design is transparent on the surface, if you want to erase the transparent part about the location of the image body Since it is not possible to distinguish between the front and back, this is done only by using the background removal function based on the shading of the surface, but with this method there is a risk of erasing even symbols that are not on the back side.
[0006]
In other words, with the prior art, there is only a method for erasing the transparent back side pattern that is not on the front side by simply distinguishing the shade by only reading the front side, and it is impossible to erase it by confirming the back side pattern. The erasure target was ambiguous against the show.
[0007]
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can extract an image of only a pure surface by comparing front and back images.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the present invention is a scanner unit for reading a document image, and a double-sided document feeder for causing the scanner unit to read the back side of the document after reading the surface of the document by the scanner unit. A digital image forming apparatus comprising: a density determination unit that determines density by dividing the density of a read image into a finite number of gradations; and a storage unit that stores the read image. When the reverse image is stored in the storage means and the back side of the same document is read, the stored front side reverse image and the back side image are compared, and the density of the front side reverse image is lower than that of the back side image at the same location. If, comprises a control means for erasing the image of the surface corresponding to the location output, the control means of the back surface image, searches the darkest range of concentration, corresponding to a range that the search surface The concentration of the thinnest portion of the image, is characterized in that it has a function of a threshold concentration to be erased.
[0009]
In order to achieve the above object, the invention according to claim 2 is the invention according to claim 1,
When the double-sided copy mode is selected, the control unit has a function of erasing and outputting an image corresponding to the back side when the density of the front side inverted image is higher than that of the back side image. It is what.
[0010]
To achieve the above object, an invention according to claim 3, wherein, in the invention of claim 1 or 2, wherein said control means has a function to change the criteria of the concentration as a reference of image erasure It is characterized by.
[0012]
To achieve the above object, an invention according to claim 4, wherein, prior Symbol storage means stores a first memory area for storing the front and back images for comparison, an image have been processed in comparison Clear second and a storage area, the process of comparison have one to one document is finished, those characterized by having a function to open the first storage area for comparison for the next document to be It is.
[0013]
In order to achieve the above object, the invention as set forth in claim 5 is characterized in that in the invention as set forth in claim 1, there is provided a function for facsimile transmission of an image that has been subjected to processing for erasing the back surface image. It is.
[0014]
In the first aspect of the present invention, the patterns of the reverse surface image and the reverse image are compared. At the time of reading, the shades of the colors of each part are assigned with different levels of gradation, and if the same pattern is detected on the front and back sides, the thin one is considered as a transmission image on the back side and erased from the image data In addition, the transparent back surface pattern can be removed. Also, by finding the part where there is no image on the reading side and the image on the back side, the density of the image on the reading side affected by the transparency of the image on the back side is used as the upper limit reference, and automatically It is possible to set a standard for
[0015]
According to the second aspect of the present invention, when copying both sides of the document, the invention according to the first aspect is used, and a portion determined to be an image on the front side is erased from the back side and output, so that both sides of the document are backside. It is also possible to cope with the case where the pattern of this is transparent.
[0016]
In the invention described in claim 3, there is an upper limit on the color density to be determined as an image on the back side of the scanned surface, there are actually designs on both sides of the document, and the design on one side is lighter than the design on the other side. In such a case, the problem that the pattern judged to be thin is erased is eliminated. As for the upper limit, gradation can be made within the range allowed by the gradation of light and shade, and it corresponds to each original.
[0018]
According to the fourth aspect of the present invention, the storage area for comparing the front and back images and the transfer storage area for which the post-comparison processing is completed are separated, so that the front and back of the next original can be performed while performing the transfer process. Compare images and increase productivity.
[0019]
According to the fifth aspect of the present invention, it is possible to prevent the back side image from being transmitted during FAX transmission, and to obtain a clear received original.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a block diagram of an image forming apparatus showing a first embodiment of the present invention.
The image forming apparatus includes a double-sided document feeding device 1, a scanner unit (reading unit) 2, an image processing unit 3, a plotter unit 4, and a system control unit 5. The system control unit 5 includes the double-sided document feeding device 1 and the scanner unit. 2, exchange of control signals with the image processing unit 3 and the plotter unit 4 is performed.
[0021]
The double-sided document feeder 1 is an existing device that realizes reading of both sides of a document in the scanner unit 2 by arranging the back side of the document on the scanner unit 2 after the scanner unit 2 reads the surface of the document. This is used to read the front and back of the document.
The image processing unit 3 includes not only various known image processing means but also a front / back image comparison memory 31. The memory 31 has a front image storage area 31-1 and a back image storage area 31-2.
[0022]
The plotter unit 4 is a part that actually performs copying (printing), and includes a photosensitive member, an image forming process unit around the photosensitive member, and a paper feeding / conveying system.
The system control unit 5 controls the double-sided document feeder 1, the scanner unit 2, the image processing unit 3, and the plotter unit 4.
[0023]
Hereinafter, each control operation example of the present invention will be described.
FIG. 2 is a flowchart of a first control operation example.
First, the document on the front side is read by the scanner unit 2 (S1), and then the scanned image is divided into shades of gray by the scanner unit 2 (S2).
Then, the image processing unit 3 inverts the left and right sides of the digital image on the surface with gradation of light and shade (hereinafter, the left and right inversion of the image is simply referred to as “inversion”) and is in the front / back image comparison memory 31. It is stored in the surface image storage area 31-1 (S3).
[0024]
Next, the original is turned over by the double-sided document feeder 1, and the back side of the document is read by the scanner unit 2 (S4). Then, the same image processing is performed on the back image (S5), and the back image data is stored in the back image storage area 31-2 (S6).
[0025]
Next, the front and back densities of the origin coordinates of the comparison image data are compared (S7). If the front side is thinner than the back side (y in S8), the front side image of the corresponding coordinate is erased (determined as white) (S9). Then, the next coordinate to be compared is set until the processing is completed for all the coordinates of the document (S10).
[0026]
FIG. 3 is a flowchart of the second control operation example.
After the process A of the first control operation example shown in FIG. 2, it is determined whether or not to copy the back side of the document, that is, whether or not the duplex copy mode is set (S11). In the double-sided copy mode, the front and back densities of the origin coordinates of the comparison image data are compared (S12). If the back side is thinner than the front side (y in S13), the back side image of the corresponding coordinate is erased ( (S14). Then, the next coordinate to be compared is set until the processing is completed for all the coordinates of the document (S15).
[0027]
4 and 5 are flowcharts of a third control operation example.
In this control example, the upper limit gradation of the density to be erased is determined, and for the density higher than that, the erasure process is not performed even in the portion determined as the erasure target in the first control example and the second control example. .
[0028]
FIG. 4 shows the case of processing the front side of the document. The front and back images are stored in the comparison memory 31 by the method (A) of the first control example (S21), and the front and back of the origin coordinates of the comparison image data are stored. The densities are compared (S22), and if the front side is thinner than the back side (y in S23), it is determined whether or not the front side is thinner than the set erasure upper limit (S24). If it is dark (n in S24), the image on the front side of the corresponding coordinate is deleted (determined to be white) (S25). Then, the next coordinate to be compared is set until the processing is completed for all the coordinates of the document (S26).
[0029]
FIG. 5 shows the case of processing on the back side of the document. After the entire process B shown in FIG. 4, the density of the front and back of the origin coordinates of the comparison image data is compared (S31). (Y in S32), it is determined whether or not the back surface is thinner than the set erasure upper limit (S33). If it is dark (n in S33), the image behind the corresponding coordinate is deleted (determined to be white) (S34). Then, the next coordinate to be compared is set until the processing is completed for all the coordinates of the document (S35).
[0030]
FIG. 6 is a flowchart of the fourth control operation example.
The flow shown in FIG. 6 is a flow for determining the document front side erasure, and the back side can be realized by the same processing by switching the front and back in the following flow.
In this control example, the darkest part of the gradation of light and shade is searched from the data of the document back side image stored in the back side image storage area 31-2. Next, the thinnest portion of the surface image data corresponding to the searched portion (limited range) is searched. The darkness on the front side of the portion obtained as a result is set as the upper limit of the gradation to be erased from the surface (the density below that gradation is erased). For the back side, the above operation is reversed, and the upper limit of erasure of the back side image is determined.
[0031]
First, storage is performed in the comparison memory 31 on the front and back surfaces by the method A of the first control example (S41). Next, the origin is set as coordinates for comparing the front and back images (S42). Next, the density of the back surface of the target coordinate is set in the buffer (1). Similarly, the surface density is set in the buffer (2) (S43). Next, the unchecked coordinates of the back surface data are changed to a check target (S44).
[0032]
If the density of the back surface of the target coordinates is higher than (1) (y in S45, y in S46), the back surface density of the target coordinates is set to (1) and the front surface density is set to (2) (S47). If the density of the back surface is thinner than (1) (n in S46), it is next determined whether the density of the target coordinate table is thinner than (2) (S48). If it is thin (y in S48), ( The value of 2) is rewritten to the density of the target coordinates (S49). If there are no unchecked coordinates in the back surface data (n in S50), (2) is set as the upper limit of the density of front surface erasure (S51).
[0033]
FIG. 7 is a block diagram of an image forming apparatus showing a second embodiment of the present invention.
In addition to the configuration of the image forming apparatus according to the first embodiment shown in FIG. 1, the image forming apparatus includes a front transfer image storage area 31-3 and a back transfer image storage area 31-4 in the image processing unit 3. It has.
[0034]
In this embodiment, the digital image data read by the scanner unit is input to the image processing unit 3 and stored in the storage areas 31-1 and 31-2 of the memory 31 that compares the density of the front and back. Then, the image that has been compared and determined to be transparent on the back side of the target surface is erased and stored in a transfer image storage area 31-3 (31-4) that stores the target surface. At the same time, the back side surface is also stored in the transfer image storage area 31-4 (31-3) storing the back side of the target surface by the same processing.
[0035]
The plotter 4 prints the image in the transfer image storage area on the transfer paper. During this period, the image of the next original captured by the scanner unit 2 is stored in the front / back image comparison memory 31.
[0036]
8 and 9 are flowcharts of a fifth control operation example.
First, the document on the front side is read by the scanner unit 2 (S61), and then the scanned image is divided into shades of gray by the scanner unit 2 (S62).
Then, the image processing unit 3 inverts the left and right sides of the digital image on the surface with gradation of light and shade, and stores it in the front surface image storage area (front side memory area) 31-1 in the front and back image comparison memory 31 ( S63).
[0037]
Next, the original is turned over by the double-sided document feeder 1 and the back side of the document is read by the scanner unit 2 (S64). Then, the same image processing is performed on the back side image (S65), and this back side image data is stored in the back side image storage area (back side memory area) 31-2 (S66).
[0038]
Next, the front and back densities of the origin coordinates of the comparison image data are compared (S67). If the front side is thinner than the back side (y in S68-1), an image from which the data on the front side of the corresponding coordinates has been deleted is obtained. It stores in the corresponding coordinates of the surface transfer image storage area 31-3 (S69-1). Further, the back side image of the corresponding coordinate is stored in the corresponding coordinate of the back side transfer image storage area 31-4 (S70-1). Then, the next coordinate to be compared is set until the processing is completed for all the coordinates of the document (S71).
[0039]
Also, as shown in FIG. 9, when the back side is thinner than the front side (y in S68-2), the image from which the data on the back side of the corresponding coordinate is erased is used as the corresponding coordinates in the back side transfer image storage area 31-4. (S69-2). Further, the surface image of the corresponding coordinate is stored in the corresponding coordinate of the surface transfer image storage area 31-3 (S70-2). Then, the next coordinate to be compared is set until the processing is completed for all the coordinates of the document (S71).
[0040]
FIG. 10 is a block diagram of an image forming apparatus showing a third embodiment of the present invention.
This image forming apparatus includes a FAX unit 6 in addition to the configuration of the image forming apparatus according to the second embodiment shown in FIG. 7, and receives image data (FAX data) that has been subjected to show-through removal processing at the time of image reading. It can be transmitted to the other party via the telephone line 7.
[0041]
【The invention's effect】
According to the first aspect of the present invention, when the reverse side image of the read original surface is stored in the storage means and the reverse side of the original is read, the stored reverse surface image and the reverse image are compared, and the same If the density of the reverse image of the front surface is lower than that of the back image, the image on the front surface corresponding to that location is erased and output so that the back image can be identified and the transparent design or print It is possible to clearly determine whether it is a design to be performed. Further, the density of the entire front surface image is searched by searching the darkest range of the back image and setting the density of the thinnest portion of the front image corresponding to the searched range as the threshold value of the density to be erased. Thus, it is possible to automatically obtain a density serving as a reference for erasing without detecting the above.
[0042]
According to the second aspect of the present invention, the same effect as described above can be obtained for the front and back sides of the document by performing the same process as described above on the back side of the document.
[0043]
According to the third aspect of the present invention, it is possible to set a limit to the darkness of the transparent symbol, and to obtain an effect of preventing erroneous erasure.
[0045]
According to the fourth aspect of the present invention, the storage area for comparing the front and back images and the storage area for transfer after the comparison processing are separated, so that the next original can be processed while performing the transfer process. The front and back images can be compared to increase productivity.
[0046]
According to the fifth aspect of the present invention, it is possible to prevent transmission of an image on the back side during FAX transmission and obtain a clear received document.
[Brief description of the drawings]
FIG. 1 is a block diagram of an image forming apparatus showing a first embodiment of the present invention.
FIG. 2 is a flowchart of a first control operation example.
FIG. 3 is a flowchart of a second control operation example.
FIG. 4 is a flowchart of a third control operation example.
FIG. 5 is a flowchart of a third control operation example.
FIG. 6 is a flowchart of a fourth control operation example.
FIG. 7 is a block diagram of an image forming apparatus showing a second embodiment of the present invention.
FIG. 8 is a flowchart of a fifth control operation example.
FIG. 9 is a flowchart of a fifth control operation example.
FIG. 10 is a block diagram of an image forming apparatus showing a third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Double-sided document feeder 2 Scanner part 3 Image processing part 31 Front and back image comparison memory 31-1 Front surface image storage area 31-2 Back surface image storage area 31-3 Front surface transfer image storage area 31-4 Back surface transfer image storage area 4 Plotter unit 5 System control unit 6 FAX unit 7 Telephone line

Claims (5)

A scanner unit that reads a document image, a double-sided document feeder that scans the back side of the document with the scanner unit after scanning the surface of the document, and a density of the scanned image divided into a finite number of gradations In a digital image forming apparatus including a density determination unit that determines a density and a storage unit that stores a read image.
When the reverse side image of the scanned original is stored in the storage unit and the back side of the original is scanned, the stored reverse side image and back side image are compared, and the reverse side image is the back side at the same location. When the density is lower than the image, it is equipped with a control means for erasing and outputting the surface image corresponding to the location ,
The control means has a function of searching for the darkest range in the back surface image, and setting the density of the thinnest portion of the front image corresponding to the searched range as a threshold value for the density to be erased. An image forming apparatus. 2. The image forming apparatus according to claim 1, wherein when the double-sided copy mode is selected, the control unit erases an image at a corresponding portion on the back side when the density of the front side inverted image is higher than that of the back side image. And an output function. The image forming apparatus according to claim 1 or 2, wherein the control means, the image forming apparatus characterized by having a function to change the criteria of the concentration as a reference for image erasing. The image forming apparatus according to claim 1 or 2, wherein said storage means, second storage area for storing an image after a first memory area for storing the front and back images for comparison, the process of comparison erasure And an image forming apparatus having a function of releasing the first storage area for comparison for the next original when the comparison process is completed for one original . The image forming apparatus according to claim 1 Symbol placement, the image forming apparatus characterized by having a function for transmitting a facsimile image processing is performed to erase the back side of the show-through.

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