JP2007272111A - Image forming apparatus and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that image quality happens to be deteriorated when the amount of developing material becomes larger on the downside in a transfer material advancing direction by a sweeping development, thereby recognizing that a color on a recording medium is different from image data. <P>SOLUTION: Contour information is extracted from image information including vector information (S5); an object area to be observed is extracted based on the extracted contour information (S6 to S9); a correction area is formed in the object area (S10 to S12), and image density in the correction area is set to density lowered in comparison with the density of the original image data (S13). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms a visible image on a predetermined recording medium based on input information and a control method therefor.

Conventionally, image forming apparatuses such as electrophotographic laser beam printers, copiers, multifunction machines, and printing machines use a powdery or liquid developer (toner, ink, etc.) to form a visible image on a recording medium. Forming. In an image forming apparatus using such an electrophotographic system, an electrostatic latent image is formed on the image carrier by charging the image carrier, scanning the charged image carrier with laser light, and exposing it. Form. Then, after developing the electrostatic latent image on the image carrier with a developer, the image is transferred to a recording medium and fixed, thereby forming a visible image on the recording medium. In such an image forming apparatus, the visible image is formed according to input image data.
JP 2003-345076 A

  When such an electrophotographic image is formed, unevenness in the density of the visible image may occur in an image area having a certain size or more.

  FIG. 10 is a diagram for explaining one of the causes of such density unevenness.

  As shown in FIG. 10, at the boundary from the latent image area 13 to the charged area on the photosensitive drum, the developer 10 adhering to the developing sleeve 12 at the position corresponding to the charging portion and the minute peripheral area is 14. As shown, it is thought to be caused by the flight to the latent image area side having a low potential (14).

  FIG. 11 is a diagram illustrating a cause of unevenness in the density of the visible image on the recording medium under such conditions.

  As shown in FIG. 11, there is a case where the amount of the developer 10 is increased on the lower side in the traveling direction of the transfer material 11. Density unevenness having this feature is particularly called sweeping.

  FIG. 12 is a diagram for explaining unevenness in the density of a visible image formed on a recording medium due to such sweeping development, and a developer near a contour line in a specific direction (for example, downstream in the transport direction). Development occurs such as the density of the toner increases.

  Such sweeping development increases the amount of the developer on the lower side with respect to the moving direction of the transfer material, so that it is recognized that the color on the recording medium is different from the image data, and the image quality may be lowered. . Also, because the amount of developer increases due to sweeping development, the developer overlaps with the image data to be visualized at the boundary where the areas having developer components of different colors touch each other. Will do. As a result, the color may change or the brightness may be different from that of the image data.

  An object of the present invention is to solve the above-mentioned problems of the prior art.

  A feature of the present invention resides in that a high-quality image is formed by suppressing deterioration in image quality due to the occurrence of the above-described sweeping development.

In order to achieve the above object, an image forming apparatus according to an aspect of the present invention has the following configuration. That is,
An image forming apparatus that develops an electrostatic latent image formed on an image carrier to form a visible image on a recording medium,
Contour extracting means for extracting contour information from image information including vector information;
Based on the contour information extracted by the contour extracting means, the recording medium has a predetermined width or more in the conveyance direction and has a predetermined lightness, and a predetermined color of an area to be noticed. Extraction means for extracting an area having an adjacent area as a target area;
Generating means for generating a correction area in the target area extracted by the extracting means;
Density setting means for setting the image density of the correction area to a density reduced with respect to the density of the original image data.

In order to achieve the above object, a method for controlling an image forming apparatus according to an aspect of the present invention includes the following steps. That is,
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  According to the present invention, it is possible to form a high-quality image while suppressing deterioration in image quality due to the occurrence of sweeping development.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments do not limit the present invention according to the claims, and all combinations of features described in the present embodiments are essential to the solution means of the present invention. Not exclusively.

  FIG. 1 is a block diagram showing a relationship between an image forming apparatus according to an embodiment of the present invention and related apparatuses.

  The CPU 1 is a central processing unit, and performs control of the entire image forming apparatus according to the present embodiment, processing such as calculation processing, and calculation. An interface (I / F) 2 is connected to a host computer 3 such as a workstation or a personal computer, and communicates image data and control signals to be processed. The ROM 4 provides a storage area for a control program executed by the CPU 1 and font data. The RAM 5 provides a storage area in which each program and data is loaded and executed for each process, and a buffer area for received image data. The program shown in this embodiment is also expanded in the ROM 4 or the RAM 5. The bitmap memory 6 provides a storage area for developing and processing image data for forming a visible image. The operation panel 7 provides various operation means for issuing various control instructions to the apparatus and displays information. The image processing engine 8 processes image data generated to form a visible image on the recording medium, and forms a visible image on the recording medium using the printer engine 9. The print engine 9 forms a visible image on the recording medium according to the control by the CPU 1. In this embodiment, the print engine 4 is the same as an image forming apparatus using an electrophotographic system.

  FIG. 2 is a diagram illustrating a printing system in which the image forming apparatus according to the present embodiment and the host computer 3 are connected.

  The host computer 3 includes an image processing apparatus and a technique. The host computer 3 prepares image data, generates PDL and other control information based on the image data, and transmits the PDL and other control information to the image forming apparatus. In the image forming apparatus, the PDL and control information are converted to obtain intermediate data, and various processes are performed. Thus, in order to form a visible image on the recording medium according to the intermediate data and the control information, raster data is generated and sent to the print engine 9 to obtain a visible image.

  Although the image forming apparatus according to the present embodiment can process arbitrary image data, here, for convenience of description, the image to be processed will be described by focusing on color image processing including vector data. In this embodiment, image data given for image formation is intermediate data obtained by converting a PDL command and data.

  In the present embodiment, intermediate data of smooth curve data such as a free curve is divided and stored into segmented straight line contour data. The region in the intermediate data is expressed by data surrounded by a closed contour formed by segmented straight line data.

  Some PDLs form an image whose color changes smoothly with a single drawing command, such as shading. In this embodiment, the intermediate data described here converts such a smoothly changing region into a state where it is subdivided into small regions painted in a single color so as to be indistinguishable visually. is doing.

  FIG. 3 is a flowchart for explaining the flow of image processing in the image forming apparatus according to the present embodiment under such conditions. Here, processing is performed to suppress degradation in the quality of the visible image formed on the recording medium due to sweeping. A program for executing this process is stored in the ROM 4 or the RAM 5 and is executed under the control of the CPU 1.

  First, in step S1, PDL intermediate data is received. In step S2, the paper (recording medium) transport direction is checked. This is to check which direction in the image data is the transport direction in the image forming apparatus of the recording medium for forming the visible image from the information included in the intermediate data. Next, in step S4, it is checked whether or not unprocessed intermediate data remains. If it remains, the process proceeds to step S5, and contour information is extracted from the intermediate data. Next, proceeding to step S6, it is determined whether or not the width of a unit for forming an image (this unit is referred to as an object) that defines an area color surrounded by the focused contour in the focused contour portion is a certain size or more. To do.

  FIG. 4 is a diagram illustrating the width in the transport direction.

  For example, as shown by Wi in FIG. 4, it is a distance from a certain outline of interest to a scan that is substantially parallel to the transport direction and scans inward of the area and goes out of the area of interest. When the width Wi in the transport direction is extremely short, sweeping does not become significant. In this case, since it is inappropriate to perform the process, the determination process in step S6 is necessary.

  Next, for example, if the color of the target portion is remarkably close to the paper color, even if sweeping development occurs, it is difficult to visually recognize a reduction in the quality of the visible image due to the sweeping development. Therefore, in step S7, the characteristics of the target image formation and developer are examined in advance, and based on this, the function or table is used to reduce the image quality due to the sweeping development from the brightness of the visible image. Whether or not can be recognized. Next, in steps S8 and S9, for example, it is determined whether there is a region adjacent to the target portion of the image and the color of the adjacent region has substantially the same color as that of the target region. If adjacent regions exist and the color of the adjacent region is almost the same as the color of the region of interest, it is considered that sweeping development between the regions is unlikely to occur. Therefore, in this case, the sweeping process is not performed. That is, since the same plate is shared if adjacent regions have substantially the same color, it is considered that there is no change in the density of the developer in each plate, or it is sufficiently small. Accordingly, it is considered that there is no difference in potential on the photosensitive drum that causes sweeping or the difference is small. Therefore, if the determination in steps S8 and S9 is “NO”, in this case, sweeping development is unlikely to occur, and there is no need to perform processing to suppress this. Thus, if the determination is “NO” in steps S6 to S9, sweeping development is unlikely to occur, so the process proceeds to step S3, and the process proceeds to the next intermediate data reading process.

  On the other hand, if all the determinations in steps S6 to S9 are “YES”, it is determined that a process for suppressing the sweeping phenomenon is necessary, and the process proceeds to step S10, in which the conveyance direction in the image data examined in step S2 is determined. And the angle formed by the target contour line.

  In the present embodiment, the direction of each contour that surrounds the region is the direction in which the region is rotated clockwise (see FIG. 5). Then, the vector in the conveyance direction is rotated clockwise until it becomes the same direction as the noticed contour. At this time, an angle required until the vector in the transport direction and the target contour are in the same direction is obtained.

  FIG. 5 is a diagram for explaining an angle formed by the conveyance direction of the recording medium and the target contour line according to the present embodiment.

  Next, the process proceeds to step S11, and the shape (in this case, width) of the region to be generated for suppressing density unevenness due to sweeping is determined from the angle obtained in step S10. By the way, under the above conditions, for example, if it is below the transport direction, a larger correction area is required. On the other hand, if it is upstream in the transport direction, the correction area is not necessary.

  FIG. 6 is a diagram showing an example of a table that associates the angle shown in FIG. 5 with the width of the correction area according to the present embodiment.

  This table is prepared based on a correction area having an appropriate size for each angle based on the characteristics of each model. This table is stored in the ROM 4, for example.

  In step S12, a correction area is generated in the given intermediate data based on the shape of the area obtained in step S11.

  FIG. 7 is a diagram for explaining such a correction region.

  Reference numeral 70 denotes an area including the target contour line, and reference numeral 71 denotes a correction area.

  In the present embodiment, the newly generated correction area 71 is in contact with the target outline 72 and is generated inside the area 70. However, the correction area 71 must be generated in the intermediate data so as not to protrude from the area 70 including the outline and above the area 70 including the target outline. Here, when the correction area is set on the downstream side in the transport direction, the arrow 73 indicates the transport direction.

  In step S13, the color of the correction area 71 generated in step S12 is determined, and this information is generated in the given intermediate data. In the present embodiment, the color information of the correction area 71 determined here is assigned with the color of the area 70 including the target outline 72 reduced. As the color reduction rate used for the color reduction calculation, an appropriate color reduction rate is obtained in advance based on the characteristics of each model, and based on this, the color of the area is reduced with reference to a table prepared in advance in the ROM 4 or the like.

  Thus, after step S13, or when the determination is “NO” in steps S6, S7, and S9, the process proceeds to step S3 to check whether there is any unprocessed intermediate data.

  In the flowchart shown in FIG. 3, the above-described processing related to sweeping suppression is repeated until there is no unprocessed intermediate data. As a result, it is determined whether or not it is necessary to suppress sweeping in all the contours, and a correction area necessary in the process is generated and inserted into intermediate data.

  FIG. 8 is a diagram for explaining target image data in the embodiment of the present invention.

  FIG. 9 is a diagram for explaining the intermediate data after the correction area according to the embodiment of the present invention is inserted into the intermediate data.

  As is clear from comparison between FIG. 12 and FIG. 9, in FIG. 9 according to the present embodiment, the developer density by the sweeping development is higher in the vicinity 90 of the outline in the transport direction than in the case of FIG. 12. It can be seen that this situation has not occurred.

[Other embodiments]
As described above, the image forming apparatus according to the present embodiment is not limited to a printing apparatus that obtains PDL or other control information from a host computer and prints, for example, an electrophotographic multifunction machine or a copying machine. As described above, an apparatus that obtains image data from its own apparatus and performs printing based on the image data may be used.

  The connection status for obtaining PDL and other control information from the host computer is the same as in the previous embodiment, but the system of the printing apparatus that obtains a visible image on the recording medium is external image processing other than the host computer. It may be a system having an apparatus and a computer having the method.

  In addition, the processing apparatus according to the present embodiment may be inside or outside the printing apparatus, and includes the case where the functions of the above-described embodiments are realized by the form.

  Another embodiment includes a case in which the functions of the above-described embodiments are realized by the processing in a system using information that can generate a visible image on another recording medium other than PDL. .

  As another embodiment, in step S3 of FIG. 3, the processing apparatus of this embodiment designates the transport direction, and control is performed so that a predetermined recording medium is transported to the print engine 9 in this transport direction. May be performed.

  As another embodiment, even if the given intermediate data is data that does not include color information in step S1 of FIG. 3, the function of the above-described embodiment is realized by the processing. It is.

(Other embodiments)
The embodiment of the present invention has been described in detail above. However, the present invention may be applied to a document search system including a plurality of devices or a document search apparatus including a single device. good.

  In the present invention, a software program that implements the functions of the above-described embodiments is supplied directly or remotely to a system or apparatus, and the computer of the system or apparatus reads and executes the supplied program. Can also be achieved. In that case, as long as it has the function of a program, the form does not need to be a program.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. That is, the claims of the present invention include the computer program itself for realizing the functional processing of the present invention. In this case, the program may be in any form as long as it has a program function, such as an object code, a program executed by an interpreter, or script data supplied to the OS.

  Various recording media for supplying the program can be used. For example, floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM, DVD (DVD-ROM, DVD- R).

  As another program supply method, the program can be supplied by connecting to a home page on the Internet using a browser of a client computer and downloading the program from the home page to a recording medium such as a hard disk. In this case, the computer program itself of the present invention or a compressed file including an automatic installation function may be downloaded. It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer is also included in the claims of the present invention.

  Further, the program of the present invention may be encrypted, stored in a storage medium such as a CD-ROM, and distributed to users. In that case, a user who has cleared a predetermined condition is allowed to download key information to be decrypted from a homepage via the Internet, and using the key information, the encrypted program can be executed on a computer in a format that can be executed. To be installed.

  Further, the present invention can be realized in a form other than the form in which the functions of the above-described embodiments are realized by the computer executing the read program. For example, based on the instructions of the program, an OS or the like running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments can also be realized by the processing.

  Furthermore, the program read from the recording medium may be written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. In this case, thereafter, based on the instructions of the program, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing. .

1 is a block diagram illustrating a relationship between an image forming apparatus according to an embodiment of the present invention and apparatuses related thereto. 1 is a diagram illustrating a printing system in which an image forming apparatus according to an exemplary embodiment and a host computer are connected. FIG. 4 is a flowchart illustrating a flow of image processing in the image forming apparatus according to the present embodiment. It is a figure explaining the width | variety with respect to the conveyance direction which concerns on this Embodiment. FIG. 4 is a diagram for explaining an angle formed by a conveyance direction of a recording medium according to the present embodiment and a target contour line. It is a figure which shows an example of the table which matches the distance from the outline of the correction | amendment area | region which concerns on this Embodiment, and an angle. It is a figure explaining the correction | amendment area | region which concerns on this Embodiment. In an embodiment of the present invention, it is a figure shown in order to explain object image data. It is the figure shown in order to demonstrate the intermediate data after inserting the correction | amendment area | region which concerns on embodiment of this invention in intermediate data. It is a figure explaining one of the causes of density nonuniformity. It is a figure explaining the cause of the nonuniformity of the density of the visible image on a recording medium. FIG. 6 is a schematic diagram showing how density unevenness occurs when sweeping development occurs. It is a figure explaining the memory map of ROM or RAM which concerns on this Embodiment.

Claims (12)

An image forming apparatus that develops an electrostatic latent image formed on an image carrier to form a visible image on a recording medium,
Contour extracting means for extracting contour information from image information including vector information;
Based on the contour information extracted by the contour extracting means, the recording medium has a predetermined width or more in the conveyance direction and has a predetermined lightness, and a predetermined color of an area to be noticed. Extraction means for extracting an area having an adjacent area as a target area;
Generating means for generating a correction area in the target area extracted by the extracting means;
Density setting means for setting the image density of the correction area to a density reduced with respect to the density of the original image data;
An image forming apparatus comprising:   The generation unit obtains an angle formed between a contour line defined by the contour information and a conveyance direction of the recording medium, and determines a width of the correction area with respect to the conveyance direction according to the angle. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the generation unit generates the correction area along a contour line on a downstream side in the conveyance direction of the recording medium in the target area. An angle-width table for storing a width of the correction area with respect to the transport direction according to an angle formed between the contour line and the transport direction of the recording medium;
The image forming apparatus according to claim 3, wherein the generation unit determines a width of the correction area with reference to the angle-width table.   The image forming apparatus according to claim 1, wherein the density setting unit sets the color of the correction area to a color obtained by subtracting the color of the original image data. A control method for an image forming apparatus for developing a latent image formed on an image carrier to form a visible image on a recording medium,
A contour extracting step for extracting contour information from image information including vector information;
Based on the contour information extracted in the contour extraction step, the recording medium has a predetermined width or more in the conveyance direction, has a predetermined brightness, and has a predetermined color for a region to be noticed. An extraction step of extracting a region having an adjacent region as a target region;
A generation step of generating a correction region in the target region extracted in the extraction step;
A density setting step for setting the image density of the correction area to a density reduced with respect to the density of the original image data;
A control method for an image forming apparatus, comprising:   In the generation step, an angle formed between a contour line defined by the contour information and a conveyance direction of the recording medium is obtained, and a width of the correction area with respect to the conveyance direction is determined according to the angle. A method for controlling the image processing apparatus according to claim 6.   8. The method of controlling an image forming apparatus according to claim 6, wherein, in the generation step, the correction area is generated along a contour line downstream in a conveyance direction of the recording medium in the target area. . An angle-width table for storing a width of the correction area with respect to the transport direction according to an angle formed between the contour line and the transport direction of the recording medium;
9. The method of controlling an image forming apparatus according to claim 8, wherein in the generation step, the width of the correction area is determined with reference to the angle-width table.   7. The method of controlling an image forming apparatus according to claim 6, wherein, in the density setting step, the color of the correction area is set to a color obtained by subtracting the color of the original image data.   The program which performs the control method of any one of Claims 6 thru | or 10.   A computer-readable storage medium storing the program according to claim 11.

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