JP4507106B2 - Image processing apparatus and image processing method - Google Patents

Description

  The present invention relates to an image processing apparatus and an image processing method for correcting color unevenness in an image.

  By reading the image formed on the recording medium by the image forming apparatus, acquiring density data indicating the density unevenness generated in the image by the image forming apparatus and correcting the density unevenness generated in the image by the image forming apparatus It is known (see Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 06-003911 JP 05-227396 A

  The density data indicating the density unevenness (color unevenness) of the image increases in data amount according to the correction accuracy of the color unevenness. In addition, even when the amount or number of images whose color unevenness is to be corrected is large, the amount of density data increases, and a sufficient memory is required to store the density data of the read image for correction. . For example, when correcting color unevenness of a color image formed by an image forming apparatus, density data indicating color unevenness is required for each of a plurality of color images constituting the color image. Thus, an image showing a plurality of color unevenness is acquired. That is, a large-capacity memory is required to store an image showing a plurality of color unevenness by color-separating the image. In the above-described conventional example, when correcting color unevenness by color-separating an image, there is no disclosure about reducing a memory necessary for storing an image showing color unevenness.

  Therefore, the present invention provides an image processing apparatus and an image processing method capable of reducing a memory required for storing an image showing color unevenness when color separation is performed by correcting the color of the image. With the goal.

  In order to achieve the above object, a first feature of the present invention is that any one of color separation means for color-separating an image printed on a recording medium into a plurality of colors and an image obtained by color separation by the color separation means. An image selection means for selecting the image, a storage means for storing the image selected by the image selection means, a detection means for detecting color unevenness of the image stored by the storage means, and a correction for the color unevenness detected by the detection means The image processing apparatus includes a correction amount calculation unit that calculates the amount. That is, since the storage means does not store an image that is not selected by the image selection means, when correcting the color unevenness by color-separating the image, it is possible to reduce the memory required for storing the image showing the color unevenness. it can.

  The second feature of the present invention is that a printing unit that prints an image on a recording medium, a color separation unit that separates an image printed by the printing unit into a plurality of colors, and the color separation unit An image selection means for selecting any one of the decomposed images, a storage means for storing the image selected by the image selection means, a detection means for detecting color unevenness of the image stored by the storage means, and the detection means An image processing apparatus comprising: a correction amount calculating unit that calculates a correction amount for color unevenness to be detected; and a control unit that controls the printing unit to print an image according to the correction amount calculated by the correction amount calculating unit. It is in.

  Preferably, the image selection means selects a complementary color image of the correction target color. That is, since the reflection of light by the correction target color corresponds to the absorption of light by the complementary color of the correction target color, the correction amount for the color unevenness can be efficiently achieved by the image selecting means selecting the complementary color image of the correction target color. Can be calculated.

  Preferably, the color separation means individually separates at least each of cyan, magenta and yellow images. That is, the storage means serially stores the color images corresponding to the respective color images constituting the color image printed on the recording medium, and the memory required for storing the image showing the color unevenness is reduced. be able to.

  Preferably, the color separation means separates at least a gray image individually. That is, the color separation means performs color separation on an achromatic image in the same manner as a chromatic image.

  The third feature of the present invention is that an image printed on a recording medium is color-separated into a plurality of colors, one of the color-separated images is selected, the selected image is stored, and the stored image In this image processing method, the color unevenness is detected, and the correction amount for the detected color unevenness is calculated.

  The fourth feature of the present invention is that an image is printed on a recording medium by a printing unit, the printed image is color-separated into a plurality of colors, and one of the color-separated images is selected and selected. An image processing method for storing an image, detecting color unevenness of the stored image, calculating a correction amount for the detected color unevenness, and controlling the printing unit to print the image according to the calculated correction amount. is there.

  ADVANTAGE OF THE INVENTION According to this invention, when color-separating an image and correct | amending color nonuniformity, the memory required in order to memorize | store the image which shows color nonuniformity can be reduced.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an outline of an image processing apparatus 10 according to an embodiment of the present invention. The image processing apparatus 10 includes an image reading unit 11, an exposure device 13, a plurality of image forming units 14, an intermediate transfer belt 16, recording medium trays 17 a to 17 d, a recording medium conveyance path 18, a fixing device 19, and a control unit 20. In response to user operations, C (cyan), M (magenta), Y (yellow), and K (black) image data is acquired from a DFE (Digital Front End) such as a computer or server (not shown), and the paper Print an image on a recording medium. The image processing apparatus 10 may include a computer and other terminal devices connected via a network as a system, and the control unit 20 is disposed in any of the systems.

An image reading unit 11 is disposed on the upper part of the image processing apparatus 10. The image reading unit 11 is a scanner that separates and reads an image into R (red), G (green), and B (blue-violet). For example, the image reading unit 11 reads a test image printed by the image processing apparatus 10 and configures the RGB constituting the test image. Are output to the control unit 20.
An exposure device 13 is disposed below the image reading unit 11. The exposure device 13 includes a light source and a lens (not shown), and a plurality of image forming units arranged below the exposure device 13 with laser light modulated for each color of YMCK according to image data input from the control unit 20. 14 respectively.

  The plurality of image forming units 14 are arranged corresponding to the colors constituting the color image. In this example, the first image forming unit 14Y, the second image forming unit 14M, and the third image forming corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K). The unit 14C and the fourth image forming unit 14K are horizontally arranged along the intermediate transfer belt 16 with a certain interval. The intermediate transfer belt 16 rotates as an intermediate transfer member in the direction of arrow a in the figure. The four image forming units 14Y, 14M, 14C, and 14K sequentially form toner images of the respective colors based on the image data input from the control unit 20, and the intermediate transfer belt 16 so that the plurality of toner images are superimposed on each other. The toner image is transferred to (primary transfer). The order of the colors of the image forming units 14Y, 14M, 14C, and 14K is not limited and is arbitrary.

  The recording medium conveyance path 18 is disposed below the intermediate transfer belt 16. The recording medium supplied from any of the recording medium trays 17a to 17d is conveyed on the recording medium conveying path 18, and the toner images of each color transferred onto the intermediate transfer belt 16 are collectively transferred (secondary transfer). The transferred toner image is fixed by the fixing device 19 and discharged to the outside along the arrow b.

Next, each configuration of the image processing apparatus 10 will be described in detail.
The image reading unit 11 is formed on a platen glass 110 on which a document P such as a test image is placed, a platen cover 112 that presses the document P against the platen glass 110, and a document P placed on the platen glass 110. An image reading unit 120 that decomposes and reads an image into three RGB images and outputs each of the separated and read images to the control unit 20. The image reading unit 120 illuminates the original P placed on the platen glass 110 with the light source 122, and converts the reflected light image from the original P into three CCDs via a reduction optical system including a plurality of mirrors 124. A scanning exposure is performed on an image reading element 126 composed of, and the like, and an image formed on the original P is decomposed and read into three RGB images having a predetermined dot density (for example, 16 dots / mm) by the image reading element 126. It is configured.

  The first image forming unit 14Y, the second image forming unit 14M, the third image forming unit 14C, and the fourth image forming unit 14K are arranged and formed in parallel at a certain interval in the horizontal direction. The configuration is almost the same except that the color of the image is different. Accordingly, the first image forming unit 14Y will be described below. The configuration of each image forming unit 14 is distinguished by attaching Y, M, C, or K.

The image forming unit 14Y includes an optical scanning device 140Y and an image forming device 150Y.
The optical scanning device 140Y deflects and scans the laser beam corresponding to yellow (Y) input from the exposure device 13 by the rotary polygon mirror 142Y, and irradiates the photosensitive drum 152Y of the image forming device 150Y via the reflection mirror 144Y. To do.
The image forming apparatus 150Y includes a photosensitive drum 152Y as an image carrier that rotates at a predetermined rotation speed in the direction of arrow a, a charger 154Y that uniformly charges the surface of the photosensitive drum 152Y, and a photosensitive drum. The developing unit 156Y that develops the electrostatic latent image formed on the body drum 152Y, a cleaning device 158Y, and a charge removal device 159Y are included. The photosensitive drum 152Y is uniformly charged by the charger 154Y, and an electrostatic latent image is formed by the laser light irradiated by the optical scanning device 140Y. The electrostatic latent image formed on the photosensitive drum 152Y is developed with yellow toner by the developing unit 156Y and transferred to the intermediate transfer belt 16. Note that after the toner image transfer process, residual toner, paper dust, and the like adhering to the photoreceptor drum 152Y are removed by the cleaning device 158Y, and the photoreceptor drum 152Y is discharged by the charge removal device 159Y.
The other image forming units 14M, 14C, and 14K also form magenta (M), cyan (C), and black (K) toner images in the same manner as described above, and intermediately transfer the formed toner images of the respective colors. Transfer to belt 16.

The intermediate transfer belt 16 is wound around the drive roll 160, the idle roll 162, the steering roll 164, and the backup roll 166 with a constant tension. The drive roll 160 is driven by a drive motor (not shown). By being rotationally driven, it is circulated at a predetermined speed in the direction of arrow a. The intermediate transfer belt 16 is formed into an endless belt by, for example, forming a flexible synthetic resin film such as polyimide in a belt shape and connecting both ends of the synthetic resin film formed in a belt shape by welding or the like. It has been done.
The intermediate transfer belt 16 includes a first primary transfer roll 168Y, a second primary transfer roll 168M, a third primary transfer roll 168C, and a position facing the image forming units 14Y, 14M, 14C, and 14K, respectively. A fourth primary transfer roll 168K is provided, and the toner images of the respective colors formed on the photosensitive drums 152Y, 152M, 152C, 152K are transferred onto the intermediate transfer belt 16 in a multiple manner by these primary transfer rolls 168. The

In the recording medium conveyance path 18, a paper feed roller 180 for taking out the recording medium from each of the recording medium trays 17a to 17d, a pair of recording medium conveyance rollers 182 and the recording medium are conveyed to a secondary transfer position at a predetermined timing. A resist roll 184 is provided.
A secondary transfer roll 186 that is in pressure contact with the backup roll 166 is disposed at the secondary transfer position on the recording medium conveyance path 18, and the toner images of the respective colors that are transferred onto the intermediate transfer belt 16 in a multiple manner. The secondary transfer roll 186 is secondarily transferred onto the recording medium by the pressing force and electrostatic force. The recording medium on which the toner image of each color is transferred is conveyed to the fixing device 19.
The fixing device 19 fixes the toner to the recording medium by applying heat and pressure to the recording medium on which the toner images of the respective colors are transferred.

The control unit 20 includes an image signal conversion unit 200, a test image data generation circuit 202, a selector 204, a complementary color image selection unit 206, an image memory 208, and a correction calculation circuit 210.
The image signal conversion unit 200 includes a memory for storing a conversion table for each color, which will be described later, acquires image data of each color of CMYK from a DFE such as a computer or a server (not shown), and corrects the acquired image data of each color of CMYK Density conversion is performed using a conversion table for each color received from the arithmetic circuit 210 and the result is output to the selector 204.
The test image data generation circuit 202 generates test image data for forming a test image (see FIG. 3) for each color of CMYK and outputs the test image data to the selector 204.

  The selector 204 corrects a mode for printing an image (normal print mode) or color unevenness (color shading) of an image to be printed according to the image data of each color of CMYK acquired from the DFE by the image processing apparatus 10. A setting indicating which mode (test mode) should be operated is acquired through, for example, a user interface (not shown), and image data selected according to the acquired setting is output to the exposure apparatus 13. . That is, the selector 204 selects and outputs the image data input from the image signal conversion unit 200 when acquiring the setting to operate in the normal printing mode, and acquires the setting to operate in the test mode. The test image data input from the test image data generation circuit 202 is selected and output.

  The complementary color image selection unit 206 selects a complementary color image (an image of any RGB color) of the correction target color (any color of CMY) from the three RGB images (image data) output from the image reading unit 11. The image is selected and passed, and an image of one color is output to the image memory 208. Note that the complementary color image selection unit 206 may select a complementary color image of the correction target color using, for example, a color set by the user via a user interface (not shown) as a correction target color, or an image reading unit. 11 may select the complementary color image of the correction target color according to the density value of the RGB image acquired from No. 11 (for example, considering the image with the highest density value as the complementary color image of the correction target color). . In addition, when the correction target color is black, the complementary color image selection unit 206 is, for example, a G (green) image (an image of one of R and B colors) according to the user setting or the RGB image density value. May be selected) as an alternative to the complementary color image.

  The image memory 208 stores one color image (image data) input from the complementary color image selection unit 206, and outputs the image data to the correction calculation circuit 210 in response to access from the correction calculation circuit 210. The image memory 208 only needs to have a capacity capable of storing any one of the three RGB images obtained by color-separating the test image.

The correction calculation circuit 210 includes, for example, a CPU, acquires image data from the image memory 208, and detects color unevenness in the image selected by the complementary color image selection unit 206 (an image of any color of RGB). When the correction arithmetic circuit 210 detects color unevenness, it is assumed that color unevenness occurs in an image of a complementary color (any color of CMY) of the color of the image (any color of RGB) from which the color unevenness is detected. A correction amount (density conversion amount) to be corrected so that color non-uniformity does not occur in the complementary color image (any one of CMY images) of the image where color unevenness is detected is calculated, and color unevenness is calculated from the calculated correction amount. Is generated and output to the image signal converter 200. The conversion tables output by the correction arithmetic circuit 210 are four conversion tables for each color that respectively convert the density of each CMYK color so as to correct color unevenness with respect to the image data of each CMYK color.
Note that the CMY density values corresponding to the RGB density values are set in advance.

Next, a process in which the image processing apparatus 10 generates a conversion table for correcting color unevenness from a test image will be described in detail.
FIG. 2 is a flowchart illustrating a process (S10) in which the image processing apparatus 10 generates a conversion table for correcting color unevenness from a test image.
FIG. 3 is a conceptual diagram illustrating a process in which the image processing apparatus 10 generates a conversion table for correcting color unevenness from a test image.
In order to generate the conversion table, the image processing apparatus 10 prints a test image of each color of CMYK, for example, according to a user operation. Each of the CMYK test images is set to the same density in the main scanning direction, for example, in order to correct color unevenness in the main scanning direction, and the number of gradations gradually increases in the sub scanning direction. A pattern is formed.

  As shown in FIG. 2, in step 100 (S100), the image reading unit 11 color-separates one of the CMYK test images (see FIG. 3) into three RGB images in accordance with a user operation. .

  In step 102 (S102), the complementary color image selection unit 206 selects and passes the complementary color image of the correction target color, and outputs an image of one color to the image memory 208.

  In step 104 (S104), the image memory 208 stores a complementary color image of the correction target color.

  In step 106 (S106), the correction calculation circuit 210 acquires image data from the image memory 208 and detects color unevenness (color shading). For example, the correction arithmetic circuit 210 detects color unevenness for each pattern of the number of gradations increasing step by step in correspondence with the position of the image forming unit 14 in the main scanning direction (see FIG. 3).

  In step 108 (S108), the correction calculation circuit 210 considers that color unevenness has occurred in an image of a complementary color (any color of CMY) of the color of the image (any color of RGB) from which color unevenness has been detected, A correction amount (density conversion amount) to be corrected so as not to cause color unevenness in an image complementary to the color of the image in which the color unevenness is detected (any one of CMY images) is calculated.

  In step 110 (S110), the correction calculation circuit 210 generates a conversion table for correcting color unevenness from the calculated correction amount, and outputs the conversion table to the image signal conversion unit 200.

  In step 112 (S112), the image signal conversion unit 200 stores the conversion table input from the correction arithmetic circuit 210.

  The image processing apparatus 10 serially performs the processing of S10 on each of the CMYK color test images in accordance with the user's operation, and converts the colors for CMYK colors so that color unevenness does not occur when printing the color image. Remember the table.

Further, in the above-described embodiment, in order to correct color unevenness in the main scanning direction, the case where each test image is formed with a pattern set to the same density in the main scanning direction has been described as an example. Without limitation, in order to correct color unevenness in the sub-scanning direction, each test image may be formed with a pattern set to the same density in the sub-scanning direction.
In the above-described embodiment, the case where the image reading unit 11 reads the test image by the user setting the test image on the image reading unit 11 is described as an example. A reading device may be provided so as to read the test image after the test image is fixed on the recording medium by the device 19, and the test image may be discharged from the image processing device 10 after reading the test image.

1 is a side view showing an outline of an image processing apparatus according to an embodiment of the present invention. It is a flowchart which shows the process (S10) which an image processing apparatus produces | generates the conversion table for correcting color nonuniformity from a test image. It is a conceptual diagram which shows the process which the image processing apparatus produces | generates the conversion table for correcting color nonuniformity from a test image.

Explanation of symbols

10 Image Processing Device 11 Image Reading Unit (Scanner)
13 exposure device 14Y first image forming unit 14M second image forming unit 14C third image forming unit 14K fourth image forming unit 16 intermediate transfer belts 17a to 17d recording medium tray 18 recording medium transport path 19 fixing device 20 Control unit 200 Image signal conversion unit 202 Test image data generation circuit 204 Selector 206 Complementary color image selection unit 208 Image memory 210 Correction arithmetic circuit

Claims (6)

A first image relating to a correction target color expressed in a first color expression format printed on a recording medium is separated into a plurality of colors expressed in a second color expression format and read, and the second color expression Reading means for generating a plurality of second images for each of a plurality of colors represented in a format;
Image selecting means for selecting one second image relating to a color that is a complementary color of the correction target color expressed in the first color representation format among the plurality of second images generated by the reading means; ,
Storage means for storing one second image selected by said image selecting unit,
Detecting means for detecting the color unevenness of one second image stored by said storage means,
A correction amount for correcting such color unevenness does not occur in the first image for the color represented by the first color expression form uneven color becomes complementary color for the second image detected by said detecting means An image processing apparatus comprising: a correction amount calculating means for calculating. Printing means for printing an image on a recording medium;
Reading by decomposing the first image related to the correction target color represented in a first color expression form which is printed by the printing means into a plurality of color represented in a second color representation, the second color Reading means for generating a plurality of second images for each of a plurality of colors represented in an expression format;
Image selecting means for selecting one second image relating to a color that is a complementary color of the correction target color expressed in the first color representation format among the plurality of second images generated by the reading means; ,
Storage means for storing one second image selected by said image selecting unit,
Detecting means for detecting the color unevenness of one second image stored by said storage means,
A correction amount for correcting such color unevenness does not occur in the first image for the color represented by the first color expression form uneven color becomes complementary color for the second image detected by said detecting means Correction amount calculation means for calculating,
The correction amount calculated in accordance with the correction amount calculated by the means, the image processing apparatus and a control means for the printing means is controlled to print an image. It said reading means includes at least cyan, an image processing apparatus according to claim 1 or 2, decompose individually magenta and yellow each image. It said reading means is at least gray image processing apparatus according to any of claims 1 to 3 to decompose individually images. A first image relating to a correction target color expressed in a first color expression format printed on a recording medium is separated into a plurality of colors expressed in a second color expression format and read, and the second color expression Generating a plurality of second images for each of the plurality of colors represented in the format;
Selecting one second image related to a color that is a complementary color of the correction target color represented in the first color representation format from among the plurality of generated second images ;
Memorize one selected second image,
Detect color unevenness in one stored second image,
An image processing method for calculating a correction amount for correcting the first image related to the color represented in the first color expression format which is a complementary color of the color related to the detected second image so as not to cause color unevenness . Printing an image on a recording medium by printing means;
The first image relating to the correction target color expressed in the first color expression format printed is separated into a plurality of colors expressed in the second color expression format and read, and displayed in the second color expression format. Generating a plurality of second images for each of the plurality of colors obtained,
Selecting one second image related to a color that is a complementary color of the correction target color represented in the first color representation format from among the plurality of generated second images ;
Memorize one selected second image,
Detect color unevenness in one stored second image,
Calculating a correction amount for color unevenness that is corrected so as not to cause color unevenness in the first image related to the color represented in the first color representation format that is a complementary color of the color related to the detected second image ;
An image processing method for controlling the printing unit to print an image in accordance with a calculated correction amount.

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