JP2012158155A - Image forming apparatus, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve image quality in double-sided printing on performing double-sided printing.SOLUTION: The image forming apparatus includes: an image forming means for forming images on one or both sides of a recording medium by ejecting a developer on the basis of image data; a detecting means for detecting characteristics of the image data; a determination means for determining whether the image forming means forms the images on both sides of the recording medium; and a changing means configured to, when determined by the determination means that the image forming means forms the images on both sides of the recording medium, reduce the amount of the developer to be ejected from the image forming means in accordance with the characteristics.

Description

  The present invention relates to an image forming apparatus and an image forming method.

  In general, when an image is formed with ink on a sheet, depending on the type of the sheet, the water content of the ink expands and deforms, which may cause a problem that a high-quality image cannot be formed. In addition, when an image is formed with toner on a sheet, the thickness increases due to the overlapping of toner, and the sheet curls or the toner is peeled off, which may cause a problem that a high-quality image cannot be formed.

  In order to solve such a problem, a technique for improving the image quality by limiting the amount of ink and toner attached to the paper has been proposed (see, for example, Patent Documents 1 and 2).

  However, since the technique described in Patent Document 1 reduces the number of dots per unit area, there is a problem that color reproduction is poor and image quality is lowered.

  Further, the technique described in Patent Document 2 only determines whether or not double-sided printing is performed, and multiplies a certain coefficient to the adhesion amount of the output ink. Therefore, the ink adhesion amount for the image data on the opposite surface is also determined. There is a problem that the image quality is limited.

  Accordingly, in view of such a problem, an object of the present invention is to improve double-sided image quality when performing double-sided printing.

  In order to achieve the above object, an image forming unit that forms an image on one or both sides of a recording medium by discharging a developer based on image data, a detecting unit that detects a feature amount of the image data, and the image A determination unit configured to determine whether or not the forming unit forms an image on both sides of the recording medium; and the determination unit determines that the image forming unit forms an image on both sides of the recording medium. Accordingly, there is provided an image forming apparatus comprising: changing means for reducing the discharge amount of the developer discharged from the image forming means.

  According to the image forming apparatus of the present invention, double-sided image quality can be improved in the case of duplex printing.

1 is a diagram illustrating a functional configuration example of an image forming apparatus according to an embodiment. The figure which showed the function structural examples, such as an image processing means of a present Example. The figure which showed an example of the image data of the surface of a present Example. The figure which showed an example of the image data of the back surface of a present Example. FIG. 6 is a process flow diagram for obtaining the total number of pixels in the main scanning direction according to the present exemplary embodiment. The figure which showed an example of the memory | storage form of a present Example (the 1). FIG. 6 is a process flow diagram for obtaining the total number of pixels in the sub-scanning direction according to the present exemplary embodiment. The figure which showed an example of the memory | storage form of a present Example (the 2). The figure which showed the example of the 1st area | region of a present Example. The figure which showed the example of the 2nd area | region of a present Example. The figure which showed the example of the overlap area | region of a present Example. The figure which showed the image data of the surface of another embodiment. The figure which showed the image data of the back surface of another embodiment. The figure which showed the example which divided | segmented image data into several blocks.

  Examples of the image forming apparatus include a copying machine such as a printer, a facsimile, and an ink jet recording apparatus, a plotter, and a complex machine of these. The recording medium is, for example, a substrate, paper, continuous paper, thread, fiber, leather, metal, plastic, glass, wood, ceramics, or the like. The developer is used for forming an image on a recording medium, and refers to, for example, toner or ink. In the following description, it is assumed that the recording medium is paper and the developer is ink.

Each embodiment will be described below. In addition, the same number is given to the component having the same function and the process of performing the same process, and the duplicate description is omitted.
[Embodiment 1]
First, the hardware configuration of the first embodiment will be described. FIG. 1 is a diagram illustrating an example of a hardware configuration of an image forming apparatus 10 according to the present invention. As shown in FIG. 1, the image forming apparatus 10 includes a control unit 11, a main storage unit 12, an auxiliary storage unit 13, an external storage device I / F unit 14, a network interface unit 16, an input unit 17, a display unit 18, an engine. Part 19 is included.

  The control unit 11 is a CPU that controls each device, calculates data, and processes in a computer. The control unit 11 is an arithmetic device that executes a program stored in the main storage unit 12, receives data from the input device or the storage device, calculates and processes the data, and outputs the data to the output device or the storage device.

  The main storage unit 12 is a ROM (Read Only Memory), a RAM (Random Access Memory), or the like, and stores or temporarily stores programs such as an OS and application software that are basic software executed by the control unit 11 and image data. Device.

  The auxiliary storage unit 13 is an HDD (Hard Disk Drive) or the like, and is a storage device that stores data related to application software or the like.

  The external storage device I / F unit 14 is an interface between the image forming apparatus 10 and a storage medium 15 (for example, a flash memory, an SD card, etc.) connected via a data transmission path such as USB (Universal Serial Bus). . The main storage unit 12 and the auxiliary storage unit 13 are collectively referred to as a storage unit 30.

  A predetermined program is stored in the storage medium 15, and the program stored in the storage medium 15 is installed in the image forming apparatus 10 via the external storage device I / F unit 14, and the installed predetermined program is It can be executed by the image forming apparatus 10.

  The network interface unit 16 includes peripheral devices having a communication function connected via a network such as a LAN (Local Area Network) or a WAN (Wide Area Network) constructed by a data transmission path such as a wired and / or wireless line. It is an interface with the image forming apparatus 10 and acquires information from components in the image forming apparatus.

  The input unit 17 and the display unit 18 include a key switch (hard key) and an LCD (Liquid Crystal Display) having a touch panel function (including GUI software key: Graphical User Interface), and the image forming apparatus 10 has. It is a display and / or input device that functions as a UI (User Interface) when using the function.

The engine unit 19 drives, for example, the image forming unit 20 and the reading unit 21. The reading unit 21 acquires image data of a document by reading the document set by the user. The image forming unit 20 forms an image on a sheet by ejecting ink on the sheet based on the image data acquired by the reading unit 21.
[Image processing flow]
Next, the flow of image processing will be described. In this example, the control unit 11 is described as performing image processing. However, an image processing unit may be provided separately from the control unit 11, and the image processing unit may perform image processing.

  FIG. 2 shows a functional configuration example of the control unit 11. In the example of FIG. 2, a detection unit 128, a determination unit 130, and an image processing unit 140 are included. The image processing unit 140 performs image processing. A simple flow of image processing by the image processing means 140 will be described. The image data acquired by the reading unit 21 is converted into image data for each processing unit by the input control unit 112. Since the image data transferred to the image processing unit 140 may be different from the processing unit for performing image processing, such as being packed into data of several pixels in accordance with the transfer speed or the like, the input control unit 112 performs processing. Unit.

  The image data input from the input control unit 112 is filtered by the filter unit 114. The filtered image data is color-corrected by the color correcting means 116. The image data subjected to color correction is subjected to a scaling process by a scaling unit 118. Based on the image data that has undergone the scaling process, the changing unit 120 regulates the total amount of developer. Specifically, the developer discharge amount is limited (decreased) with respect to the image data of the image printed on the paper, and each color of the image to be printed with respect to the input one-dot image data. The developer discharge amount (for example, CMYK) is limited. The reduction in the discharge amount of the changing unit 120 will be described later. Note that the discharge rate reduction rate is predetermined and stored in the storage unit 30.

  The image data whose total amount is regulated by the changing unit 120 is subjected to gradation correction by the gradation correcting unit 122. Then, the tone-corrected image data is edited by the editing processing unit 124 and output as printing image data. Then, the output control means 126 converts the print image data into an output format.

  Next, further processing of the image forming apparatus according to the first embodiment will be described. The detection unit 128 detects the feature amount of the image data by measuring the image data acquired by the reading unit 21.

  Here, the feature amount of image data refers to (i) the area of a continuous (or substantially continuous) single-color pixel (hereinafter referred to as “continuous region”) or the number of the continuous regions, and (ii) an image. An area where the density value of data is equal to or greater than a second threshold (to be described later) (hereinafter referred to as “high density area”), and (iii) “an image formed on the front side of the paper and an image formed on the back side , And the like (referred to as “overlapping area”).

  Here, the single color pixel means a pixel having a color (for example, CMYK). Further, among all the pixels, pixels other than the single color pixel are referred to as non-monochromatic pixels. Non-monochromatic pixels refer to, for example, colorless pixels.

In the first embodiment, the feature amount of image data is (i) the area or number of continuous regions (hereinafter referred to as “the area of continuous regions”), or (ii) the area or number of high concentration regions (hereinafter referred to as “areas”). An example of “the area of the high concentration region” will be described. An example in which the feature amount is (iii) whether or not there is an overlapping region will be described in the second embodiment.
[Detection of features]
Next, a method for detecting a continuous area and a high density area of image data by the detection unit 128 will be described. FIG. 3 schematically shows image data for an image printed on the front side of the paper (that is, an image on the front side of the document set by the user), and FIG. 4 shows image data for an image printed on the back side of the paper (that is, the image). An image on the back side of a document set by a user is schematically shown. Hereinafter, the image data for the image formed on the front surface is simply referred to as “front surface image data”, and the image data for the image formed on the back surface is simply referred to as “back surface image data”.

  Also, the direction in which the image forming unit 20 prints on the paper is the main scanning direction, and the direction in which the paper is conveyed when the image forming unit 20 prints on the paper is the sub-scanning direction.

  The surface image data shown in FIG. 3 includes a pattern / photograph part A and a character part B. Further, the back side image data shown in FIG. Further, D in FIG. 3 schematically shows the total value of the number of single color pixels in the main scanning direction of the surface image data or the total value of the density values of the image data in the main scanning direction of the surface image data. 3E schematically shows the total value of the number of monochrome pixels in the sub-scanning direction of the surface image data or the total value of the density values of the image data in the sub-scanning direction of the surface image data. Further, F in FIG. 4 schematically shows the total value of the number of monochrome pixels in the main scanning direction of the back side image data or the total value of the density of the image data in the main scanning direction of the back side image data. 4 schematically shows the total value of the number of monochrome pixels in the sub-scanning direction of the back side image data or the total value of the density of the image data in the sub-scanning direction of the back side image data.

  Next, the total number of monochrome pixels in the main scanning direction or the total density value (D in FIG. 3 and F in FIG. 4) of the image data or the number of monochrome pixels in the sub-scanning direction of the image data by the detection unit 128. A method for obtaining the total value or the total value of density values (E in FIG. 3 and G in FIG. 4) will be described.

  First, how to obtain the total value of the number of monochrome pixels or the total value of the density values in the main scanning direction will be described. FIG. 5 shows a flow of processing for calculating the total value of the monochrome pixels or the total value of the density values in the main scanning direction by the detection unit 128.

  In the following description, it is assumed that there are pixels of M (M is a natural number) lines in the unit image data, and there are N pixels in one line. In the description of FIG. 5, m = 1... M and n = 1. That is, m and n indicate the order of lines and pixels, respectively. FIG. 5 shows the calculation process of the number of monochrome pixels in the m-th line and / or the calculation process of the density total value. Unit image data is, for example, image data for one page of a document.

  First, when the reading unit 21 acquires image data, the image data is temporarily stored in the storage unit 30. Then, the detection unit 128 sets n = 1 as an initial setting (step S11). Then, the n-th pixel (n = 1 in this case) of the m-th line is input to the detection means 128 (step S12).

  Next, the detection unit 128 reads the number of monochromatic pixels from the 1st to the (n-1) th in the m-th line and / or the density total value from the storage unit 30 (step S16). Here, since n = 1, the memory unit 30 does not store the number of monochromatic pixels from the 1st to (n-1) th and / or the total density value of the m-th line, so that the reading process is performed. There is no need.

  Next, the detection means 128 calculates the number of monochromatic pixels from the 1st to the nth of the m-th line and / or the density total value (step S18). First, a method for calculating the number of monochrome pixels will be described. First, the detection means 128 determines whether or not the nth pixel is a monochrome pixel. In this determination method, it is determined whether or not the density of the nth pixel is equal to or higher than a predetermined density threshold. If the density of the nth pixel is equal to or higher than the density threshold, it is determined that this pixel is a monochrome pixel. On the other hand, if the density of the nth pixel is less than the density threshold, it is determined that this pixel is a non-monochromatic pixel.

  Then, when the nth pixel is a monochrome pixel, the detection unit 128 increases the number of monochrome pixels from the 1st to the (n−1) th line of the Mth line read out in step S16 by “1”. Then, the storage unit 30 updates / stores the first to nth monochrome pixels in the storage unit 30. On the other hand, when the n-th pixel is not a monochrome pixel (when it is a non-monochromatic pixel), the detection unit 128 does not update the number of monochrome pixels from the 1st to (n-1) th in the m-th line read in step S16. .

  Next, a method for calculating the total density value in step S18 will be described. The detecting means 128 calculates the density value of the nth pixel. Then, the calculated nth density value is added to the 1st to (n-1) th density total values of the mth line read out in step S16. Then, the storage means 30 updates and stores the 1st to nth density total values in the storage means 30.

  Next, in step S18, the detection unit 128 determines whether or not the pixel for which the number of monochrome pixels or / and the total density value has been calculated most recently is the Nth pixel (final pixel) on the m-th line. (Step S20). The final pixel is a pixel located on the rightmost side of the m-th line. If the detection unit 128 determines that the pixel is not the final pixel (No in step S20), N is incremented by “1” (step S24).

  If the detection unit 128 determines that the nth pixel is the final pixel (that is, n = N) (Yes in step S20), the process proceeds to step S26. The answer of Yes in step S20 means that the number of monochrome pixels from the 1st to Nth pixels of the m-th line and / or the total density value has been calculated. Accordingly, the density total value and / or the number of monochrome pixels for the m-th line is stored in the storage means 30 (step S26).

  Further, for example, the processing of FIG. 5 is performed for all pixels from 1 to M lines in the unit image data. Here, the unit image data refers to image data for one page, for example.

In this way, the detection unit 128 calculates the total density value and / or the number of monochrome pixels of all the M lines of the image data. Then, the detection unit 128 causes the storage unit 30 to store the total density value and / or the number of monochrome pixels for each line. FIG. 6 shows an example of storage in the storage unit 30. As shown in FIG. 6, the total density value and / or the number of monochrome pixels are stored in association with 1 to M lines. In the example of FIG. 6, for example, the number of lines 1 is the number of monochromatic pixels a ₁ and the density total value b ₁ .

  Next, FIG. 7 shows the flow of processing for calculating the number of monochrome pixels or / and the density total value in the sub-scanning direction by the detection means 128. In addition, the arrangement of pixels in the sub-scanning direction is referred to as a “column”. In the following description, it is assumed that there are P (P is a natural number) columns of pixels in the unit image data, and there are Q pixels in one column. In the description of FIG. 7, p = 1... P and q = 1. That is, p and q indicate the order of columns and pixels, respectively. FIG. 7 shows the calculation process for the number of monochrome pixels in the p-th column and / or the calculation process for the density total value.

  First, when the reading unit 21 acquires image data, the image data is temporarily stored in the storage unit 30. Then, the detection means 128 sets q = 1 as an initial setting (step S11). Then, the q-th pixel (here, q = 1) -th pixel in the p-th column is input to the detection unit 128 (step S32).

  Next, the detection unit 128 reads the number of monochromatic pixels from the 1st to the q−1th in the q-th column and / or the density total value from the storage unit 30 (step S16). Here, since q = 1, the storage unit 30 does not store the number of monochromatic pixels from the 1st to q−1th in the p-th column and / or the total density value, and therefore performs the reading process. There is no need.

  Next, the detection unit 128 calculates the number of monochrome pixels up to q-th in the p-th column and / or the density total value. First, a method for calculating the number of monochrome pixels will be described. First, the detection unit 128 determines whether or not the qth pixel is a monochrome pixel. This determination method determines whether or not the density of the qth pixel is equal to or higher than a predetermined density threshold. If the density of the q-th pixel is equal to or higher than the density threshold, it is determined that this pixel is a monochrome pixel. On the other hand, if the density of the qth pixel is less than the density threshold, it is determined that this pixel is a non-monochromatic pixel. When the detection unit 128 calculates the number of monochrome pixels, the detection unit 128 determines that the 1st to q−1th columns in the P-th column read out in step S16 when the qth pixel is a monochrome pixel. The number of monochrome pixels up to 1 is increased by “1”. Then, the storage unit 30 updates and stores the 1st to qth monochromatic pixel numbers in the storage unit 30.

  Next, a method for calculating the total density value will be described. The detection means 128 calculates the density value of the qth pixel. Then, the calculated qth density value is added to the 1st to q-1th density total values in the Pth column read out in step S16. Then, the storage unit 30 updates and stores the 1st to qth density total values in the storage unit 30.

  Next, in step S38, the detection unit 128 determines whether or not the pixel for which the number of monochrome pixels or / and the total density value has been calculated most recently is the last pixel in the p-th column (step S40). The last pixel in the P column refers to the pixel located on the lowest side in the p column. When the detection unit 128 determines that the pixel is not the final pixel (No in step S40), q is incremented by “1” (step S44).

  If the detection unit 128 determines that the qth pixel is the final pixel (Yes in step S20), the process proceeds to step S46. The answer of Yes in step S40 means that the number of monochrome pixels from the first pixel to the last pixel in the p-th column and / or the total density value has been calculated. Therefore, the density total value and / or the number of monochrome pixels in the Pth column are stored in the storage means 30 (step S46).

  Further, for example, the processing in FIG. 7 is performed for all the pixels from the first column to the P column in the image data of one page.

In this way, the detection means 128 calculates the total density value and / or the number of monochrome pixels for all P columns of the image data. Then, the detection unit 128 causes the storage unit 30 to store the total density value and / or the number of monochrome pixels for each column. FIG. 8 shows an example of storage in the storage unit 30. As shown in FIG. 8, the density total value and / or the number of monochrome pixels are stored in association with the 1st to pth columns. In the example of FIG. 8, for the first column, the number of monochrome pixels is c ₁ and the density total value is d ₁ . As for the p-th column, a single color pixel number c _P, is the concentration total value d _P.

  5 and 7 are used to calculate the number of monochromatic pixels in the main scanning direction and the sub-scanning direction and / or the density total value for the image data on the front surface and the image data on the back surface.

  Next, the determination unit 130 determines whether the image forming unit 20 forms an image on both sides of the sheet. Whether or not to form an image on both sides of the paper is determined by the user. The user inputs whether or not to form an image on both sides of the sheet from an external PC terminal, or inputs whether or not to form an image on both sides of the sheet from the operation unit 17. Then, the determination unit 130 acquires information on whether or not to input an image.

  When printing on both sides of paper, reduce the amount of developer discharged to form double-sided images or the amount of developer discharged to form single-sided images to improve image quality on both sides. Let Hereinafter, the developer discharge amount for forming a double-sided image is simply referred to as “double-side discharge amount”, and the developer discharge amount for forming a single-sided image is simply referred to as “single-side discharge amount”.

[Change Method by Change Unit 120]
Next, a changing method by the changing unit 120 will be described. When the determination unit 130 determines that the image forming unit 20 forms an image on both sides of the sheet, the changing unit 120 reduces the amount of developer discharged from the image forming unit 20 according to the feature amount. The changing unit 120 performs any of the processes of (i) reducing the discharge amount on both sides (ii) reducing the discharge amount on one side (iii) not reducing the discharge amount on both sides.

First, the case where the feature amount is the area or the number of regions where the monochrome pixels are continuous or the area or the number of regions where the monochrome pixels of the image data are substantially continuous will be described.
<< When the feature amount is the area or the number of areas in which monochromatic pixels are continuous, or the area or the number of areas in which monochromatic pixels of image data are substantially continuous >>
“Continuous” in a region where monochromatic pixels are continuous means that monochromatic pixels are continuous in the main scanning direction or the sub-scanning direction. In the example of FIG. 3, it is an area constituting the “mountain” image A ₁ . In addition, the region where the monochrome pixels of the image data are “substantially continuous” is that the monochrome pixels are continuous, there are a small number (for example, 1 or 2) of non-monochromatic pixels, and the monochrome pixels are again A continuous area.

The changing unit 120 acquires the area of a region (hereinafter referred to as “continuous region”) in which single-color pixels of image data on both surfaces (front and back surfaces) detected by the detecting unit 128 are continuous. An example of a method for acquiring the area of the continuous region will be described. For example, for a pixel in which m _1st line and p _1st column are orthogonal, the sum of the number of monochrome pixels in m _1st line and the sum of the number of monochrome pixels in p _1st column What is necessary is just to judge whether a pixel is a monochrome pixel. In this manner, for all the pixels, the area of a continuous region on both surfaces it is determined whether the monochrome pixel, determines whether a first threshold value E ₁ or more. Here, the first threshold value E ₁ is a predetermined value and is stored in the storage means 30. Further, another method may be used as a method for acquiring the area of the continuous region.

The changing unit 120 reduces the discharge amount of the developer discharged when an image is formed on a surface of the both sides of the sheet where the area of continuous regions or the number of continuous regions is equal to or more than a first threshold. it is changing means 120, when the area of both sides of the continuous area is first threshold value E ₁ or both reduces the discharge amount when both sides of the image forming. Moreover, the change unit 120, the area of the continuous region of one surface and the first threshold E ₁ above, when the area of the other surface of the continuous area is first less than the threshold value E _1, at the time of image formation of the first surface Reduce the discharge amount. Moreover, the change unit 120, if the area of both sides of the continuous area is first less than the threshold value E ₁ together does not reduce the discharge amount when both sides of the image forming (hence, the discharge amount is unchanged).

In the example of FIG. 3, for the image data of the surface, the area of a continuous region "region of the image A ₁ of the" mountain "," is the first threshold value E ₁ or more. Further, there is no continuous area for the back side image data shown in FIG. Therefore, in the case of the image data of FIGS. 3 and 4, the discharge amount on both sides is not reduced.

Further, using the “number of continuous areas” instead of the “area of continuous areas”, the changing unit 120 may determine whether or not to reduce the discharge amount on both sides. In this case, the change unit 120, when the number of surfaces of the continuous region is the first threshold value E ₁ or both reduces the discharge amount when both sides of the image forming. Further, when the number of continuous areas on one side is equal to or greater than the first threshold value E ₁ and the area of the continuous areas on the other side is less than the first threshold value E ₁ , the changing unit 120 forms an image on the one side. Reduce the discharge amount. Moreover, the change unit 120, if the area of both sides of the continuous area is first less than the threshold value E ₁ together does not reduce the discharge amount when both sides of the image forming (hence, the discharge amount is unchanged).

3 will be described as an example. Further, the first threshold value _{E 1} and "2". There are _three continuous regions: “region A ₁ of“ mountain ”image”, “region A ₂ of“ cloud ”image”, and “region A ₃ of“ sun ”image. Accordingly, since the number of continuous regions (= 3) is larger than the first threshold value E ₁ (= 2), the discharge amount of the developer when forming the surface image is reduced. On the other hand, for the back side image data in FIG. 4, the number of continuous regions (= 0) is smaller than the first threshold value E ₁ (= 2). Do not decrease. Therefore, in the case of the image data of FIGS. 3 and 4, the ejection amount for the surface image data is reduced.

Next, a case where the feature amount is a density value of image data will be described.
≪When the feature value is the density value of the image data≫
Changing means 120, the density value is the number of areas or regions of a region is a second threshold value E ₂ or on the surface is the third threshold value E ₃ or more, reducing the discharge amount of the developer. The density value of the image data is detected by the detecting means 128. Hereinafter, the area density value is a second threshold value E ₂ or more as "density-high region".

The changing unit 120 acquires the area of the high density area of the image data on both sides (front and back sides). An example of a technique for acquiring the area of the high density region will be described. For example, the _first and the line m, and p ₁ th column, the pixels are orthogonal, the sum of the total concentration value of m ₁ th line, the sum of the total concentration value of p ₁ th row, the The density value of the pixel is obtained. In this way, the density value is obtained for all the pixels, and further, the area of the high density region is obtained. Area of density-high area of each surface is, determines whether a first threshold value E ₁ or more. Here, the third threshold value E ₃ is a predetermined value and is stored in the storage means 30. In addition, another method may be used as a method for acquiring the area of the high concentration region.

Changing means 120 of both sides of the paper, the surface number of the area or density-high area of density-high region is the third threshold value E ₃ or more, reducing the discharge amount of the developer discharged when imaged Let

Specifically, the change unit 120, if the area of both sides of density-high region are both third threshold E ₃ or more, reduces the discharge amount when both sides of the image forming. Moreover, the change unit 120, the area of density-high area of the one surface and the third threshold value E ₁ or more, when the area of the other surface of density-high region is less than the third threshold value E _3, the image formation of the first surface Reduce the discharge amount. Moreover, the change unit 120, if the area of both sides of density-high region are both less than the third threshold value E ₃ does not reduce the discharge amount when both sides of the image forming (hence, the discharge amount is unchanged) .

In the example of FIG. 3, for the image data of the surface, the area of a density-high region "," region of the image A ₁ of the mountain "," is the third threshold value E ₁ or more. Further, there is no high density region for the back side image data shown in FIG. Therefore, in the case of the image data of FIGS. 3 and 4, the discharge amount on the front surface is decreased and the discharge amount on the back surface is not decreased.

In addition, using the “number of high density areas” instead of the “area of high density areas”, the changing unit 120 may determine whether or not to reduce the ejection amount on both sides. In this case, the change unit 120, when the number of surfaces of density-high region is both the third threshold value E ₃ or more, reduces the discharge amount when both sides of the image forming. Moreover, the change unit 120, the number of density-high area of the one surface is a third threshold value E ₃ above, when the area of the other surface of density-high region is less than the third threshold value E _3, the image formation of the first surface Reduce the discharge amount. Moreover, the change unit 120, if the area of both sides of density-high region are both less than the third threshold value E ₃ does not reduce the discharge amount when both sides of the image forming (hence, the discharge amount is unchanged) .

3 will be described as an example. Further, the third threshold value _{E 3} and "2". Density-high area "," area A ₁ of an image of a mountain, "", "" area A ₂ of the image of cloud "," 3 "," region A ₃ of the image of the sun, "" There. Accordingly, the number of high density regions (= 3) is larger than the third threshold value E ₃ (= 2), so that the amount of developer discharged when forming an image on the surface is reduced. On the other hand, with respect to the back side image data in FIG. 4, the number of high density regions (= 0) is smaller than the third threshold value E ₃ (= 2). Therefore, the developer discharge amount when forming the back side image Does not decrease. Therefore, in the case of the image data of FIGS. 3 and 4, the ejection amount for the surface image data is reduced.

Also, the third threshold value E _3, may be employed a number of a plurality of pixels, it can also be a number of one pixel. When the third threshold value E ₃ and the "number of one pixel," on the surface or the back surface of the image data, if the concentration is even one higher pixel than the second threshold value E _2, the development of the surface of the Write pixel The discharge amount of the agent can be reduced. Further, the third threshold value E ₃ when a plurality of number of pixels, the third threshold value E _3, the area of density-high region, can be treated.

The feature amount may be a “continuous region” and a “high density region”. In this case, the feature amount used for the front surface and the back surface can be made different. For example, changing means 120 for surface area or the number of consecutive regions, judges whether a first threshold value E ₁ or more, the area or number of density-high area for back side, the third threshold value E ₃ You may make it judge whether it is above. Conversely, changing means 120 for surface area or the number of density-high region, determines whether a third threshold value E ₃ or more, the area or number of consecutive regions for the rear surface, the first it may be determined whether the threshold value E ₁ or more.

According to the first embodiment, when duplex printing is performed on a sheet, if the area and number of continuous regions and the area and number of high density regions are higher than a threshold, the amount of developer discharged on the surface higher than the threshold is set. Decrease. The fact that the area and number of continuous regions and the area and number of high density regions are higher than the threshold means that when the developer is ink, a show-through phenomenon occurs and image quality deteriorates. Further, when the developer is toner, the amount of the toner increases, the paper after image formation becomes thick, and the image quality deteriorates. Therefore, when the area and number of continuous regions and the area and number of high density regions are higher than the threshold value, it is possible to improve the image quality on both sides by reducing the developer discharge amount.
[Embodiment 2]
Next, the image forming apparatus according to the second embodiment will be described. The feature amount according to the second embodiment is an area in which an image formed on one side (front surface) of a sheet overlaps with an image formed on the other side (back side) of the sheet (hereinafter referred to as “overlapping area”). Or not)). Here, the overlapping area is an area where images overlap when viewed through the paper printed on the front and back surfaces. If there is this overlapping area, the show-through of the paper tends to occur.

  A method for determining whether or not there is an overlapping area will be described. As shown in FIGS. 3 and 4, the detecting means 128 detects the number of monochrome pixels or the total density value. Here, a case where the detection unit 128 detects the number of monochrome pixels will be described.

  Then, the changing unit 120 detects a region where the front and back pixels exist. The area where the pixels on the surface are present is the first area, and the coordinate width is the first coordinate width. In addition, a region where the pixels on the back surface exist is a second region, and a coordinate width is a second coordinate width. 9 shows the first region H, and FIG. 10 shows the second region I.

As the detection method of the first region H, changing means 120, the width H ₁ of the main scanning direction of the monochromatic pixel detecting unit 128 detects a first coordinate width in the main scanning direction, the width H of the single-color pixels in the subscanning direction Let _{2 be} the second coordinate width in the sub-scanning direction. A region having the first coordinate width and the second coordinate width as the coordinate width is defined as a first region H.

Similarly, as the detection method of the second area I, changing means 120, the width I ₁ of the main scanning direction of the monochromatic pixel detecting unit 128 detects a first coordinate width in the main scanning direction, the sub-scanning direction monochromatic pixels the width I ₂ and the second coordinate width in the sub-scanning direction. A region having the first coordinate width and the second coordinate width as the coordinate width is defined as a second region I.

And the detection means 128 detects the area | region J (overlapping area | region J) where the 1st area | region H and the 2nd area | region I overlap. As the detection method of a specific overlapping area J, the first coordinate width H ₁ in the main scanning direction of the surface, the main scanning of overlapping the by that width overlapping region J of the first coordinate width I ₁ of the rear surface of the main scanning direction the direction of the coordinate width _{J 1.} Further, a second coordinate width of H ₂ subscanning direction of the surface, the coordinate width J ₂ in the sub-scanning direction of the second coordinate width I ₂ overlapping the width and overlap region J of the back surface of the sub-scanning direction. Then, an area of the coordinate width J ₁ and coordinate width J ₂ and width coordinates and overlap region J.

  When the overlapping region J exists, a show-through phenomenon or the like is likely to occur. Therefore, it is necessary to reduce the discharge amount of developer on both sides or one side (one of the front and back sides). The method described in the first embodiment may be used to determine which developer discharge amount is to be reduced.

  On the other hand, if the overlapping region J does not exist, even if the conditions described in the first embodiment (the area and number of continuous regions and the area and number of high-density regions are higher than a threshold value), the paper Therefore, the developer discharge amount may not be reduced.

As described above, in the image forming apparatus according to the second embodiment, whether or not the changing unit 118 decreases the discharge amount of the developer using the single color pixel or / and the density value after it is determined that the overlapping region exists. Determine whether. Therefore, compared with the image forming apparatus of the first embodiment, the changing unit 118 can more accurately determine whether or not to reduce the developer discharge amount.
[Embodiment 3]
Next, the image forming apparatus of Embodiment 3 will be described. In the image forming apparatus according to the second embodiment, the overlapping area J is detected at a time. However, in the image forming apparatus according to the third embodiment, the overlapping area J is detected in a plurality of blocks. For example, the case where the image data on the front and back surfaces is the image data K shown in FIG. 12 will be described. That is, it is assumed that the image data on the front surface and the back surface are the same and there is no overlapping area.

As described above, the change unit 120, the _first and the line m, and p ₁ th column, the pixels are orthogonal, the sum of the number monochromatic pixels of m ₁ th line, the p ₁ th column From the total number of monochrome pixels, it is determined whether or not the pixel is a monochrome pixel. Therefore, in the case of the image data as shown in FIG. 12, it is determined that an image exists in the area N shown in FIG. As a result, the overlap area does not actually exist, but the area N is regarded as an overlap area, and the changing unit 120 makes an erroneous determination.

  Therefore, in the image forming apparatus according to the third embodiment, as shown in FIG. 14, the image data K may be divided into a plurality of blocks, and it may be determined whether or not there is an overlapping area for each block. The example of FIG. 14 shows an example in which the image data K is divided into 9 blocks. The line T is detected when there is a monochrome pixel for the upper left block, and the column where the monochrome pixel is detected in the sub-scanning direction. U is shown. Then, the line T and the column U are detected in all the blocks.

  Also, the same number of block divisions as the front surface are performed on the back surface, and the line T and the column U are detected. Then, the changing unit 120 determines whether there is an overlapping area for each block on the front surface and the back surface. By performing this block division processing, it is possible to prevent detection of an erroneous overlapping area for any image data.

  According to the image forming apparatus of the third embodiment, the image data is divided into a plurality of blocks, and an overlapping area is detected for each block. Therefore, it is possible to prevent detection of an erroneous overlapping area for any image data.

112 Input Control Unit 114 Filter Unit 116 Color Correction Unit 118 Scaling Unit 120 Change Unit 122 Gradation Correction Unit 124 Editing Processing Unit 126 Output Control Unit 128 Detection Unit 130 Determination Unit

JP 2002-036528 A JP 2007-118238 A

Claims (7)

Image forming means for forming an image on one or both sides of a recording medium by discharging a developer based on image data;
Detecting means for detecting a feature amount of the image data;
Determining means for determining whether or not the image forming means forms an image on both sides of the recording medium;
When the determination unit determines that the image forming unit forms an image on both sides of the recording medium, the changing unit decreases the discharge amount of the developer discharged from the image forming unit according to the feature amount. And an image forming apparatus.   The feature amount includes the area or the number of continuous regions in which the monochrome pixels of the image data are continuous, or the area or the number of continuous regions in which the monochrome pixels of the image data are substantially continuous. The image forming apparatus according to claim 1, further comprising: The changing means is
A discharge amount of the developer discharged when an image is formed is reduced on a surface of the recording medium on which the area of the continuous region or the number of the continuous regions is equal to or more than a first threshold. The image forming apparatus according to claim 2.   The image forming apparatus according to claim 1, wherein the feature amount includes an area of a high density region or a number of high density regions having a density value equal to or greater than a second threshold value. The changing means is
Reducing the discharge amount of the developer that is discharged when an image is formed on a surface of the recording medium where the area of the high density region or the number of high density regions is equal to or greater than a third threshold value. The image forming apparatus according to claim 4.   The feature amount includes whether or not there is an overlapping area where an image formed on one surface of the recording medium and an image formed on the other surface of the recording medium overlap. Item 6. The image forming apparatus according to any one of Items 1 to 5. The changing means is
The image forming apparatus according to claim 6, wherein when there is the overlapping area, the discharge amount of the developer when forming an image on one side or the other side of the recording medium is reduced.

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