JP4453371B2 - Color unevenness correction apparatus, color unevenness correction method, and color unevenness correction program - Google Patents

Description

  The present invention relates to a color unevenness correction device, a color unevenness correction method, and a color unevenness correction program for a printing result image formed on a sheet by an image forming apparatus.

  In general, the quality of a printed image formed on a sheet by an image forming apparatus such as a printing machine, a printer, or a copier is determined by visual inspection by a human. In particular, in the case of color printing, visual inspection is performed for colors determined by superimposing primary colors such as yellow (Y), cyan (C), and magenta (M) by comparison with reference products. By this visual inspection, color unevenness in the printed surface is determined, and the color is adjusted by adjusting the image forming conditions in the image forming apparatus.

On the other hand, a method of automatically inspecting color unevenness is also known. For example, an image of a print result is read by a CCD sensor or the like, and red (R), green (G), and blue (B) image signals are obtained as color signals for each pixel. It is converted to a color space in the CIEL ^* a ^* b ^* system recommended by the International Lighting Commission). Then, using the CIEL ^* a ^* b ^* color difference value Delta] E ^* ab in the color space, the color shift between the reference products, and evaluate the color unevenness in the surface, etc., by feeding back the evaluation result to the image inspection device Adjust the color.

  However, in actual color inspections, there are parts that humans easily perceive color deviation according to the pattern of the printed material, that is, parts that are important, and parts that humans hardly perceive color deviation, that is, parts that are not important. To do. However, in the conventional color determination method, the difference in the importance of the region is not taken into consideration, and the color determination suitable for human sense cannot be performed.

  For example, Japanese Patent Laid-Open No. 6-160298 (Patent Document 1) emphasizes a step-by-step color difference quantitatively in automatic color determination and is important in an inspection for each local region of a printing surface. For the purpose of making a determination close to human visual determination, a multi-stage comprehensive evaluation determination result by a visual inspector is input, and color difference values are measured for a plurality of color regions in the printing surface, A weight for each color region is calculated, and a quantitative value for each multistage evaluation is calculated. At the time of inspection, the evaluation value of the color as the inspection target printed matter is calculated by using the information on the important place and the degree of importance. It is disclosed that the quality of a printed matter is determined by comparing the result with a threshold value determined according to a quantitative value for multistage evaluation.

JP-A-6-160298

  However, in the method described in Patent Document 1, it is determined whether each area is regarded as important for each of a large number of local areas included in the printing surface, or is not considered important. It is necessary to set. This setting value has to be changed for each color, which makes the setting operation very complicated and problematic.

  The present invention provides a color unevenness correction apparatus, a color unevenness correction method, and a color unevenness correction program that can easily correct color unevenness of a print result image formed on a sheet by an image forming apparatus.

The present invention provides a color unevenness correction device that corrects color unevenness of a print image formed on a sheet based on original image data by an image forming apparatus, the means for acquiring the original image data, and the original image data Image display means for displaying the image, means for causing the user to select a reference color to be used for color unevenness correction based on the displayed original image data, and image formation based on the color information of the selected reference color and a control means for changing an image forming condition of the device, was closed, said control means sets in advance the size and shape, the image display means and the setting in the data to be displayed on the size and shape of the area Are detected in the order of the number of areas having the same color, and a single area having a uniform color included in the data displayed on the image display means is detected. Detecting a single area having a uniform color included in the order in which the areas of the detected areas are large and data displayed on the image display means, and detecting the same color among the detected areas The reference color is displayed on the image display means so that the reference color can be selected in any one of the order of the sum of the areas .

According to another aspect of the present invention, there is provided a color unevenness correction device for correcting color unevenness of a print image formed on paper based on original image data by an image forming apparatus, the means for acquiring the original image data, and the original Means for acquiring inspection image data read from a reference print image formed on a sheet by the image forming apparatus based on image data, and an image for displaying the original image data and comparison image data based on the inspection image data Display means; means for allowing a user to select a reference color to be used for color unevenness correction based on the displayed comparison image data; and image formation of the image forming apparatus based on color information of the selected reference color possess a control means for changing conditions, the said control means, a region of said inspection image data as the target region, the noted territory in the original image data By comparing the color space of the region corresponding to display on the image display unit to allow selection of the reference color in descending order of color difference.

According to another aspect of the present invention, there is provided a color unevenness correction device for correcting color unevenness of a print image formed on paper based on original image data by an image forming apparatus, the means for acquiring the original image data, and the original Control means for automatically selecting a reference color to be used for color unevenness correction based on image data, and changing image forming conditions of the image forming apparatus based on color information of the automatically selected reference color; , have a, wherein, in advance to set the size and shape, the original image data in the set size and shape of the region in the detecting area is a uniform color, areas having the same color A region having the largest area of a single region having a uniform color included in the original image data and the color of the region and the same color included in the original image data are detected. Detecting the sum of the area of the region having a color, select the color of the area, any one of the said reference color.

According to another aspect of the present invention, there is provided a color unevenness correction device for correcting color unevenness of a print image formed on paper based on original image data by an image forming apparatus, the means for acquiring the original image data, and the original Inspection image acquisition means for acquiring inspection image data read from a reference print image formed on a sheet by the image forming apparatus based on image data, and color unevenness correction based on the document image data and the inspection image data automatically selecting a reference color to be used for the automatically closed and control means on the basis of the selected reference color color information to change the image forming condition of said image forming apparatus, wherein the control means , the inspection to an area of the image data as a target region, the document image of the region corresponding to the region of interest in the data L ^* a ^* b ^* before the highest color chroma by comparing color space It is selected as the reference colors.

  In the color unevenness correction apparatus, the image forming apparatus is preferably an electrophotographic image forming apparatus.

According to another aspect of the present invention, there is provided a color unevenness correction method for correcting color unevenness of a print image formed on a sheet based on original image data by an image forming apparatus, wherein the control unit acquires the original image data. A step in which the control unit displays the original image data, a step in which the control unit causes the user to select a reference color to be used for color unevenness correction based on the displayed original image data, , it looks including the steps of: changing an image forming condition of said image forming apparatus based on the selected reference color color information, the control unit sets a pre-size and shape, the data to be the display In the region of the set size and shape, a region having a uniform color is detected, and the region having the same color is ordered in descending order, and the uniform color included in the displayed data is detected. A single region having a uniform color included in the displayed data, and in order of increasing area of the detected region, and detecting the single region. The reference colors are displayed so that the reference color can be selected in any one of the order in which the sum of the areas of the same colors is large .

According to another aspect of the present invention, there is provided a color unevenness correction method for correcting color unevenness of a print image formed on a sheet based on original image data by an image forming apparatus, wherein the control unit acquires the original image data. A control unit acquiring inspection image data read from a reference print image formed on a sheet by the image forming apparatus based on the original image data; and a control unit acquiring the original image data and the inspection A step of displaying comparison image data based on the image data, a step of causing the control unit to select a reference color to be used for color unevenness correction based on the displayed comparison image data, and a control unit comprising: see containing and changing an image forming condition of said image forming apparatus based on the selected reference color color information, and the control unit, in said inspection image data That the region as a target region, and displays the original image the inside data by comparing the color space of the region corresponding to the region of interest so as to select the reference color in descending order of color difference.

According to another aspect of the present invention, there is provided a color unevenness correction method for correcting color unevenness of a print image formed on a sheet based on original image data by an image forming apparatus, wherein the control unit acquires the original image data. And a step of automatically selecting a reference color to be used for color unevenness correction based on the document image data, and a control unit based on color information of the automatically selected reference color. look including the steps of: changing an image forming condition of said image forming apparatus, wherein the control unit sets a pre-size and shape, a uniform the set size and shape of the regions within the document image data A color area is detected, the color having the largest number of areas having the same color, and the area having the largest area of a single area having a uniform color included in the original image data are detected. , And detects the sum of the area of the region having the same color included in the original image data, to select the color of the area, any one of the said reference color.

According to another aspect of the present invention, there is provided a color unevenness correction method for correcting color unevenness of a print image formed on a sheet based on original image data by an image forming apparatus, wherein the control unit acquires the original image data. An inspection image acquisition step in which the control unit acquires inspection image data read from a reference print image formed on a sheet by the image forming apparatus based on the document image data; and the control unit includes the document image data And a step of automatically selecting a reference color used for color unevenness correction based on the comparison image data based on the inspection image data, and a control unit based on the color information of the automatically selected reference color wherein the step of changing an image forming condition of the image forming apparatus, seen including, said control unit, a region of said inspection image data as target region Te, the original image data The color difference by comparing L ^* a ^* b ^* color space of the region corresponding to the region of interest to select the highest color as the reference color.

According to another aspect of the present invention, there is provided a color unevenness correction program for correcting color unevenness of a printed image formed on a sheet based on original image data by an image forming apparatus, wherein the computer acquires the original image data. A means for displaying the original image data; a means for allowing the user to select a reference color to be used for color unevenness correction based on the displayed original image data; and based on the color information of the selected reference color. possess a control means for changing an image forming condition of said image forming apparatus, said control means sets in advance the size and shape, the set size and shape in the data to be displayed on said image display means Areas having a uniform color are detected, and the uniform colors included in the data displayed on the image display means are arranged in the order of the number of areas having the same color. Detecting a single region having a uniform color included in the data displayed on the image display means in the order in which the areas of the detected regions are large, and detecting the single region The color unevenness correcting device is displayed so that the reference color can be selected in any one of the areas in the order of the sum of the areas of the same color .

According to another aspect of the present invention, there is provided a color unevenness correction program for correcting color unevenness of a printed image formed on a sheet based on original image data by an image forming apparatus, wherein the computer acquires the original image data. Means for acquiring inspection image data read from a reference print image formed on a sheet by the image forming apparatus based on the original image data, and comparison image data based on the original image data and the inspection image data. Means for displaying, means for allowing a user to select a reference color to be used for color unevenness correction based on the displayed comparison image data, and an image of the image forming apparatus based on color information of the selected reference color possess control means for changing the forming conditions, wherein the control means, a region of said inspection image data as the target region, the document image data Wherein by comparing the color space of the focused region corresponding to the region to function as a color unevenness correction device to be displayed on the image display unit to allow selection of the reference color in descending order of color difference.

According to another aspect of the present invention, there is provided a color unevenness correction program for correcting color unevenness of a printed image formed on a sheet based on original image data by an image forming apparatus, wherein the computer acquires the original image data. Based on the original image data, a reference color used for color unevenness correction is automatically selected, and image forming conditions of the image forming apparatus are changed based on the color information of the automatically selected reference color. possess a control unit, wherein the control means is previously set the size and shape, the original image data in the set size and shape of the region in the detecting area is a uniform color, the same color A region having the largest area of a single region having a uniform color included in the original image data, the color of the region, and the original image Detecting the sum of the area of the region having the same color included in the data, the color of that area, any one to function as a color unevenness correction unit for selecting as said reference color of the.

Furthermore, the present invention provides a color unevenness correction program for correcting color unevenness of a print image formed on a sheet based on original image data by an image forming apparatus, and a computer for acquiring the original image data. Inspection image acquisition means for acquiring inspection image data read from a reference print image formed on a sheet by the image forming apparatus based on the document image data, and comparison based on the document image data and the inspection image data Control means for automatically selecting a reference color to be used for color unevenness correction based on image data, and changing image forming conditions of the image forming apparatus based on color information of the automatically selected reference color; , have a, said control means, a region of said inspection image data as the target region, L of the region corresponding to the region of interest in the original image data ^* a ^* b ^* Compare color spaces and function as a color unevenness correction device that selects the color with the largest color difference as the reference color .

  According to the present invention, it is possible to easily correct color unevenness in a printed image surface formed on a sheet by an image forming apparatus. In addition, color unevenness can be corrected based on a reference color designated by the user, not based on a dedicated chart, or based on individual user's original data, so that color unevenness can be corrected according to the color usage of the user original. .

  As shown in FIG. 1, the color unevenness correction system according to an embodiment of the present invention includes a color unevenness correction apparatus 10 and an image forming apparatus 20. In some embodiments, the image reading device 30 may be included. The image forming apparatus 20 receives image data to be printed from the outside and forms an image on a sheet based on the image data. The image forming apparatus 20 is, for example, various printers such as an electrophotographic system, an inkjet system, a thermal system, and a plotter system, a copying machine, a multifunction machine, or a printing machine. The image reading device 30 reads an image printed by the image forming device 20 and acquires it as inspection image data. The acquired inspection image data is transmitted to the color unevenness correction apparatus 10. The image reading device 30 is, for example, a scanner including an optical sensor and a data interface. Here, the paper means not only paper but also general printing objects such as OHP sheets.

  As illustrated in FIG. 1, the color unevenness correction apparatus 10 includes a control unit 100, a storage unit 120, a display unit 140, an input unit 160, and a data interface 180. Note that it is not necessary for all of these configurations to be included in one apparatus. For example, the control unit 100, the storage unit 120, the display unit 140, the input unit 160, and the data interface 180 may be configured as independent devices and combined as appropriate. The control unit 100 includes a control element such as a CPU, and has a function of controlling the color unevenness correction apparatus 10 in an integrated manner. The storage unit 120 includes a semiconductor memory, a hard disk, and the like, and stores and holds various data and programs used when correcting color unevenness. The display unit 140 includes a monitor and a touch panel, and is used to present information used for processing to the user. The input unit 160 includes a keyboard, a touch panel, and the like, and is used to acquire various types of information used for processing from the user. The color unevenness correction apparatus 10 uses the data interface 180 to exchange data with the image forming apparatus 20 and the image reading apparatus 30 via a network or the like.

  The color unevenness correction apparatus 10 executes a color unevenness correction program stored in the storage unit 120 to correct color misregistration and unevenness of a printed material on which an image is formed in the image forming apparatus 20. One embodiment of the uneven color correction method of the present invention is realized by executing each step of the flowchart shown in FIG.

  In step S500, the control unit 100 acquires the user's original image data from the host computer or the like using the data interface 180.

  The document image data is not limited to image data transmitted from a host computer or the like, but may be image data obtained by converting PDL data or the like transmitted from a host computer or the like by a print server or the like. The document image data may be read from a document such as paper by a document image data acquisition unit including a scanner or the like included in the image forming apparatus 20 and transmitted to the color unevenness correction apparatus 10 via a network or the like. Good.

  In step S520, the control unit 100 displays the acquired document image data on the display unit 140. Here, the display unit 140 is preferably displayed on a user interface (UI) screen as shown in FIGS. 3 and 4, for example.

  In step S540, referring to the user interface screen, the user arbitrarily selects a reference color as a reference for correcting the color unevenness in the color unevenness correction apparatus 10. Examples of the user interface screen display method include the following methods.

For example, as shown in FIG. 3, it is preferable that the area of a single region having a uniform color included in the document image data is detected and displayed in order of the regions having the largest area. . Also, as shown in FIG. 4, it is preferable that a plurality of regions regarded as the same color are displayed with the same number. Furthermore, colors may be displayed in order of increasing area. Here, “uniform color” and “same color” mean that the color difference value ΔE ^* ab in the CIEL ^* a ^* b ^* color space is within 3.0. Further, the range of ΔE ^* ab regarded as “uniform color” and “same color” may be arbitrarily set. The user can select a reference color with reference to the order displayed on the screen.

  It is also preferable that areas having uniform colors are detected in the document image data, and numbers are assigned in descending order of the sum of the areas of the areas having the same color among the detected areas. In addition, colors may be displayed in order of increasing total area.

  Further, an area having a uniform color within an area of a predetermined size and shape, for example, a 5 mm × 5 mm square area, is automatically detected in the original image data, and the same color is detected in the original image data. It is also preferable that the numbers are displayed in the order of the largest number of regions having. The shape of the area can be arbitrarily set according to the document.

  The display method of the user interface can be arbitrarily set in addition to the methods listed above. Moreover, it is preferable to set so that these display methods can be easily switched. By setting the display method of the user interface as described above, the user can select a reference color to be used for correction with reference to the order, so that the reference color specified by the user can be selected based on the user's preference. In addition, it is possible to correct color unevenness in the printed image plane.

  When the user selects the reference color, for example, on the screen on which the document image is displayed, when the areas of the uniform color areas are numbered and displayed in the order of large areas as shown in FIGS. Select the target with the cursor, mouse, etc., in the color area you want to use as the reference in the color area you want to use as the reference, and press the “Determination of reference color” button.

  In the example of FIG. 3, the center right side portion of the region 1 is selected as the reference color. Then, correction processing is performed so that the region 1 is made uniform based on the selected color. In the example of FIG. 4, the lower left portion of the second area from the top of the area 3 regarded as the same color is selected as the reference color. Then, a correction process is performed so that a plurality of regions 3 are made uniform based on the selected color. In the case of the example in FIG. 3, correction processing is performed based on the color of the region 1, and therefore when the primary color used in the region 1 is also used in the region 2 and the region 3, Color reproduction may change. Similarly, in the case of the example in FIG. 4, the color reproduction of the region 1 and the region 2 may change. However, since the correction process is performed based on the color most regarded by the user, the in-plane color uniformity that the user satisfies can be obtained as a whole.

  In step S560, the control unit 100 changes the image forming conditions of the image forming apparatus 20 based on the reference color selected by the user, and corrects the color unevenness. Here, for example, when the image forming apparatus 20 is an electrophotographic system, the image forming conditions are changed by adjusting the exposure amount of the photosensitive member by a light beam such as a laser. In addition, the ejection amount of each color ink is adjusted in the case of the ink jet method, the heat generation amount of the thermal head is adjusted in the case of the thermal method, and the ink amount is adjusted in the case of printing with a plate.

  Here, how to obtain the correction data will be described by taking an electrophotographic image forming apparatus as an example. In an electrophotographic image forming apparatus, a test pattern print image is output by the image forming apparatus, and the density of the image (RGB signal value of the output of the scanner or the like) is measured from the print image by a scanner or the like. Correction is performed by adjusting the exposure amount so as to be flat. However, the density distribution does not always have the same slope for all gradations. For example, one color image is printed on the entire surface of the paper with a gradation of 60% (Cin 60%), and the exposure amount is adjusted so that the density distribution in the main scanning direction of this image is uniform. Next, when the same image is printed with a gradation of 20% (Cin 20%) with the adjusted exposure amount, the density distribution in the main scanning direction is not uniform. Therefore, in order to prevent color unevenness from occurring in the main scanning direction even when exposure is performed with the same exposure amount for each of a plurality of gradations, it is preferable to correct as follows.

First, the relationship between the monochrome YMC density in the multiple color image and the L ^* a ^* b ^* color space of the multiple color corresponding to the density is obtained in advance. This relationship is obtained as follows. For a plurality of gradations (for example, Cin 20% and Cin 60%), a light beam is scanned based on image data of Y, C, M single color patches and YC, YM, CM, YCM multicolor patches. The photosensitive member is exposed, and a printed image is output using the exposed photosensitive member. The RGB density is measured by a scanner or the like at several points in each patch of the image formed in this way, and converted to YMC density. On the other hand, the L ^* a ^* b ^* color space at the same point is measured with a colorimeter or the like. From the YMC density of the single color in the multiple colors thus measured and the L ^* a ^* b ^* color space of the multiple colors corresponding to the density, A and B matrices satisfying the conversion equation (1) are obtained by a regression method.

  Next, the density distribution of the print image based on the correction document data formed by the image forming apparatus 20 is measured. The correction document data is preferably a pattern including a plurality of colors, for example, primary colors (colors formed by any one of yellow, magenta, cyan, and black), secondary colors (yellow, magenta, cyan, According to an image pattern including a plurality of colors selected from three colors selected from among three colors (yellow, magenta, cyan, black). Preferably, it is configured. The correction document data may have a pattern of a quaternary color (a color formed by superposing four colors of yellow, magenta, cyan, and black). Further, it is preferable that the correction document data has a plurality of patterns with different gradations for the same color.

FIG. 5 shows an example of a primary color bar chart used as correction document data. FIG. 6 shows an example of a bar chart of multiple colors (secondary colors and tertiary colors). In this manner, a pattern having a uniform color in a strip shape in the main scanning direction and the density and mixing ratio of the basic color (primary color) being changed in the sub scanning direction is formed. Here, a plurality of patterns (here, 20% and 60%) with different densities are formed for each color included in the bar chart. 5 and 6, Y represents yellow, M represents magenta, C represents cyan, K represents black, and W represents white. Here, “uniform” means that the color difference value ΔE ^* ab in the CIEL ^* a ^* b ^* color space is within 3.0 within the region. For example, a bar chart including a band-like single color and multiple color patterns having a uniform color region in the main scanning direction of the image forming apparatus 20 having a plurality of gradations (20% and 60%) as shown in FIGS. 5 and 6 is corrected. It is used as original document data, and a photosensitive member is exposed by scanning a light beam, and a printed image is output using the exposed photosensitive member.

  When the image forming apparatus 20 is an electrophotographic image forming apparatus, uneven exposure is likely to occur in the main scanning direction of a light beam such as a laser that exposes the photosensitive member. The pattern is preferably a bar chart including a band-like region having a uniform color in the main scanning direction. Here, the main scanning direction is a direction orthogonal to the paper transport direction during printing, and the sub-scanning direction is a direction parallel to the paper transport direction.

  The RGB density of each image thus formed is measured by a scanner or the like. Specifically, the RGB density at each point in the main scanning direction of the chart (for example, each point from the one end position (0 mm) to the other end position (300 mm) of the exposure surface of the photoreceptor) is sub-scanned in the same pattern. Measure several points in the direction. The average density of each point measured in the sub-scanning direction is obtained. When this RGB density is converted to YMC density, a YMC density distribution as shown in FIG. 7 is obtained for each color Y, M, and C. In the example of FIG. 7, the horizontal axis indicates the position in the main scanning direction, and the vertical axis indicates the measured density of yellow (Y).

Next, after converting into L ^* a ^* b ^* color space distribution information using the conversion formula (1) obtained from this YMC density distribution, the color difference ΔE ^* ab for the point with the lowest density is averaged. Find the distribution of. FIG. 8 shows the relationship between the position in the main scanning direction thus obtained and the color difference ΔE ^* ab. In FIG. 8, the horizontal axis indicates the position in the main scanning direction, and the vertical axis is obtained by averaging changes in color difference.

Next, with reference to the exposure amount R ₀ when the density distribution of FIG. 7 is obtained, the exposure amount at each point from one end to the other end along the main scanning direction of the photoreceptor is uniformly reduced to −9%. Then, a print image is output again based on the same document data. Similar to the above, the maximum in the main scanning direction density information of the print image L ^* a ^* b ^* after conversion to the color space information, obtains the color difference Delta] E ^* ab for the low point of lowest density, color-difference Delta] E ^* ab The difference between the value and the minimum value (here, 1.6) is taken (FIG. 9). The above processing is performed stepwise from −9% to + 6% of the exposure amount, and a graph showing the relationship between the exposure amount and the difference between the maximum value and the minimum value of the color difference ΔE ^* ab is obtained for each gradation of each color pattern ( FIG. 10).

Here, as shown in FIG. 10, the exposure value and the maximum value of the color difference ΔE ^* ab obtained for a plurality of gradations, for example, a gradation of 60% (Cin 60%) and a gradation of 20% (Cin 20%). As for the relationship between the difference between the maximum value and the minimum value, a value having a larger difference between the maximum value and the minimum value of the color difference ΔE ^* ab among the values for any gradation for each exposure amount is selected and set as a total value. . The exposure amount R0 = −2.5% at which the difference between the maximum value and the minimum value of the color difference ΔE ^* ab is minimum can be obtained as the optimum exposure value. At this time, instead of selecting a value having a larger difference between the maximum value and the minimum value of the color difference ΔE ^* ab, values for a plurality of gradations at each exposure amount may be simply added to obtain a total value. Moreover, the average value may be taken. Further, a total value may be obtained by weighting and calculating for each gradation, and an optimum exposure amount may be determined based on the total value. That is, for the side on which the value of the difference between the maximum value and the minimum value of the color difference ΔE ^* ab corresponding to the exposure distribution control value obtained for each of the 60% gradation and 20% gradation shown in FIG. To increase the weight. In this example, the optimum exposure amount is obtained for 60% and 20% gradations, but may be obtained in the same manner for more other gradations.

  The above processing is performed for each color of single color and multiple colors, and the optimum exposure amount condition can be obtained. Each data for correction may be made into a database.

  In the case of a full-color output device that superimposes colors, the density distribution in the main scanning direction may differ between when printing a single color image and when printing a multi-color image where two or more colors are superimposed. For example, when a G image is formed, a C image is superimposed on a Y image, but a phenomenon occurs in which an already existing Y color material interferes with the overlap of the C color material. In this case, even if the single color is corrected accurately, the single color density distribution is not flat in the multiple colors. Therefore, it is preferable to correct as follows.

  First, a relationship between the RGB density of each of a plurality of multiple color images and the YMC density of a single color image corresponding to the density is obtained in advance. This relationship is obtained as follows. For example, for a plurality of gradations (20% and 60%), a photoconductor is exposed by scanning a light beam on the basis of image data of multi-color patches of YC, YM, CM, and YCM. The printed image is output using the body. At the same time, print images of primary colors of Y, C, and M are also output. After measuring the RGB density of each image of a plurality of gradations formed in this way with a scanner or the like, it is converted into a YMC density, and the density of each YMC single color in multiple colors is obtained.

  Next, the RGB density distribution of the print image based on the correction document data formed by the image forming apparatus 20 is measured. For example, a bar chart including a strip-like single color and a multiple color pattern having a uniform color region in the main scanning direction of a plurality of gradations (20% and 60%) as shown in FIGS. 5 and 6 is used as document data. The photosensitive member is exposed by scanning the light beam, and a printed image is output using the exposed photosensitive member. The RGB density of each image thus formed is measured by a scanner or the like. Specifically, the RGB density at each point in the main scanning direction of the chart (for example, each point from the one end position (0 mm) to the other end position (300 mm) of the exposure surface of the photoconductor) is subtracted within the same pattern. Measure several points along the scanning direction. An average of the density of each point measured in the sub-scanning direction is obtained to obtain an RGB density distribution.

  From the combination of the density distribution, the various densities of the secondary color and the tertiary color obtained above, and the image density of the primary colors of Y, C, and M at that time, as shown in FIG. It is possible to estimate how much and where the monochromatic YMC density in the multiple colors changes. Then, a corrected exposure amount for flattening the YMC density distribution of each single color in the multiple colors can be calculated from the relationship between the light amount correction amount and the YMC density obtained in advance shown in FIG. The above processing is performed for each color of multiple colors, and the respective optimum exposure conditions can be obtained. Each data for correction may be made into a database.

  In the present embodiment, since the color unevenness is corrected based on the reference color selected by the user, it is possible to obtain a uniform color within the print surface that satisfies the user.

  FIG. 13 is a chart showing another embodiment of the uneven color correction method of the present invention.

  In step S <b> 600, the control unit 100 acquires the user's document image data from the host computer or the like using the data interface 180.

  In step S <b> 620, the image forming apparatus 20 outputs one reference printed material on which an image is formed on a sheet based on the document image data, and causes the image reading device 30 to read the image of the printed material. This reading is preferably performed automatically. For example, the inspection image data is automatically acquired by irradiating the image surface of the printed material conveyed in the image forming apparatus 20 with an irradiation lamp and detecting the reflected light with an imaging device such as a CCD. Can do. The inspection image data read by the image reading device 30 is sent to the color unevenness correction device 10.

  In step S640, control unit 100 compares the received document image data and inspection image data, and displays the comparison data on display unit 140. Here, the display unit 140 is preferably displayed on a user interface (UI) screen as shown in FIGS. 3 and 4 described above.

  In step S660, referring to the user interface screen, the user arbitrarily selects a reference color as a reference for correcting the color unevenness in the color unevenness correction apparatus 10.

As a display method of the user interface screen, in this embodiment, a certain area in the inspection image data, for example, an area having a predetermined size and shape is set as the attention area and corresponds to the attention area in the document image data. It is preferable that the L ^* a ^* b ^* color spaces of the areas are compared, and the colors are displayed in the order of the colors of the areas where the color difference ΔE ^* ab is large.

  In step S680, the control unit 100 changes the image forming conditions of the image forming apparatus 20 based on the reference color selected by the user, and corrects the color unevenness in the same manner as described above.

  FIG. 14 is a chart showing another embodiment of the color unevenness correction method of the present invention. FIG. 15 shows an example of a more specific procedure of the present embodiment.

  In step S <b> 700, the control unit 100 acquires user document image data using the data interface 180.

  In step S720, the control unit 100 automatically selects a reference color as a reference for correcting color unevenness in the acquired document image data. Here, as the selection method, for example, the document image data is divided into areas of a predetermined size and shape, for example, a square area of 5 mm × 5 mm, and the area has a uniform primary color, 2 A region that is the next color or tertiary color is searched, and if there is only one uniform color region in the document image data, the color of that region is set as the reference color. Further, when there are a plurality of such areas, it is preferable that the color having the largest number of areas having the same color in the document image data is used as the reference color. The size and shape of the area can be arbitrarily set according to the document.

  As a reference color selection method, it is also preferable that a region having the largest area is detected from a single region having a uniform color included in the document image data, and the color of the region is used as the reference color. In addition, it is also preferable that the reference color is the color having the largest total area of the areas having the same color.

  The reference color selection method can be arbitrarily set in addition to the methods listed above. Moreover, it is preferable to set so that the selection method can be easily switched.

  In step S740, based on the reference color selected by the user, the control unit 100 changes the image forming conditions of the image forming apparatus 20 as described above to make the reference color uniform, and corrects color unevenness. .

  FIG. 16 is a chart showing another embodiment of the color unevenness correction method of the present invention. FIG. 17 shows an example of a more specific procedure of the present embodiment.

  In step S800, the control unit 100 acquires the user's original image data using the data interface 180.

  First, in step S820, the image forming apparatus 20 outputs one reference printed material on which an image is formed on paper based on the original image data, and the image reading device 30 reads the image of the printed material. This reading is preferably performed automatically. The inspection image data read by the image reading device 30 is sent to the color unevenness correction device 10.

  Next, in step S840, the color irregularity correction apparatus 10 automatically selects a reference color as a reference for color irregularity correction. The control unit 100 compares the document image data and the inspection image data, and selects a reference color as a reference for correcting color unevenness in the image plane based on the comparison data. Here, the following method is mentioned as the selection method.

In this embodiment, a certain region in the inspection image data, for example, a region having a predetermined shape and size, is set as a target region, and L ^* a ^* b of a region corresponding to the target region in the document image data. ^* It is preferable to compare the color spaces and automatically select the color of the region having the largest color difference ΔE ^* ab as the reference color.

  The reference color selection method can be arbitrarily set in addition to the methods listed above. Moreover, it is preferable to set so that the selection method can be easily switched.

  In step S840, based on the reference color selected by the user, the control unit 100 changes the image forming conditions of the image forming apparatus 20 as described above to make the reference color uniform, and corrects color unevenness. .

  In the present embodiment, color unevenness is corrected based on the inspection image data of the reference printed material by the user original, or the user original data, instead of the dedicated chart. Therefore, it is possible to obtain a uniform color within the printing surface that satisfies the user. it can. In particular, when a large number of colors are used in a document, the in-plane uniformity of colors other than the reference color is improved as compared to correcting in-plane color unevenness based on an arbitrary color. .

  The color unevenness correcting method, color unevenness correcting apparatus, and color unevenness correcting program of the present invention are an electrophotographic method such as a copying machine, a laser printer, a facsimile machine, and a composite machine thereof; an ink jet method; Printed images formed on paper by image forming devices such as heat transfer methods such as mold thermal transfer; flat printing such as offset flat printing, intaglio printing such as gravure printing, relief printing, stencil printing such as screen printing, etc. However, the color of the printed image by the electrophotographic image forming apparatus in which it is difficult to print uniformly within the printing surface with the same color and local color unevenness is likely to occur. It can be suitably applied to unevenness correction.

  In accordance with the present invention, an electrophotographic system such as a copying machine, a laser printer, a facsimile machine, and a composite machine thereof; an ink jet system; a thermal system; a plotter system; and a printed image formed on a sheet by an image forming apparatus for general printing. Can be easily corrected. In addition, since color unevenness can be corrected based on original document data of each user instead of a dedicated chart, color unevenness can be corrected according to the color usage of the user original.

It is a block diagram which shows one Embodiment of the color nonuniformity correction apparatus of this invention. It is a chart figure which shows one Embodiment of the uneven color correction method of this invention. It is a figure which shows an example of the user interface screen of the color nonuniformity correction apparatus of this invention. It is a figure which shows an example of the user interface screen of the color nonuniformity correction apparatus of this invention. It is a figure which shows an example of the monochrome bar chart used in one Embodiment of this invention. It is a figure which shows an example of the multicolor bar chart used in one Embodiment of this invention. It is a graph which shows YMC density distribution of the main scanning direction in one Embodiment of this invention. It is a graph which shows the color difference distribution of the main scanning direction in one Embodiment of this invention. It is a graph which shows the color difference distribution of the main scanning direction in one Embodiment of this invention. It is a graph which shows the relationship between the exposure distribution control value and color difference in one Embodiment of this invention. It is a graph which shows the distribution of the main scanning direction of the monochrome YMC density | concentration in the multiple color in one Embodiment of this invention. It is a graph showing the relationship between the exposure amount and monochrome YMC density in one embodiment of the present invention. It is a chart figure which shows another embodiment of the uneven color correction method of this invention. It is a chart figure which shows another embodiment of the uneven color correction method of this invention. It is a chart figure which shows the specific example of another embodiment of the uneven color correction method of this invention. It is a chart figure which shows another embodiment of the uneven color correction method of this invention. It is a chart figure which shows another specific example of another embodiment of the uneven color correction method of this invention.

Explanation of symbols

  10 color unevenness correction device, 20 image forming device, 30 image reading device, 100 control unit, 120 storage unit, 140 display unit, 160 input unit, 180 data interface.

Claims (10)

An uneven color correction device that corrects uneven color of a printed image formed on a sheet based on original image data by an image forming apparatus,
Means for obtaining the document image data;
Image display means for displaying the document image data;
Means for allowing a user to select a reference color to be used for color unevenness correction based on the displayed document image data;
Control means for changing image forming conditions of the image forming apparatus based on color information of the selected reference color;
Have
The control means includes
An order in which the size and shape are set in advance, the region of the set size and shape is uniform in the data displayed on the image display means, and the number of regions having the same color is large ,
Detecting a single region having a uniform color included in the data displayed on the image display means, and in order of increasing area of the detected region; and
Detecting a single region having a uniform color included in the data displayed on the image display means, and in order of increasing the sum of areas of the same color among the detected regions;
An uneven color correction apparatus, wherein the reference color is displayed on the image display means so that any one of the reference colors can be selected. An uneven color correction device that corrects uneven color of a printed image formed on a sheet based on original image data by an image forming apparatus,
Means for obtaining the document image data;
Means for acquiring inspection image data read from a reference print image formed on a sheet by the image forming apparatus based on the document image data;
Image display means for displaying comparison image data based on the document image data and the inspection image data;
Means for allowing a user to select a reference color to be used for color unevenness correction based on the displayed comparison image data;
Control means for changing image forming conditions of the image forming apparatus based on color information of the selected reference color;
Have
The control means includes
The image display means can select a reference color in order of increasing color difference by comparing a color space of a region corresponding to the target region in the document image data as a region of interest in the inspection image data. A color unevenness correction device characterized by displaying on the screen. An uneven color correction device that corrects uneven color of a printed image formed on a sheet based on original image data by an image forming apparatus,
Means for obtaining the document image data;
Control for automatically selecting a reference color to be used for color unevenness correction based on the original image data and changing image forming conditions of the image forming apparatus based on color information of the automatically selected reference color Means,
Have
The control means includes
A size and shape are set in advance, a region having a uniform color within the region of the set size and shape is detected in the document image data, and the color having the largest number of regions having the same color,
A region having the largest area of a single region having a uniform color included in the document image data is detected, and the color of the region; and
Detecting the sum of the areas of the regions having the same color included in the document image data,
Any one of the color unevenness correction apparatuses is selected as the reference color. The uneven color correction device according to any one of claims 1 to 3 ,
The color unevenness correcting apparatus, wherein the image forming apparatus is an electrophotographic image forming apparatus. An uneven color correction method for correcting uneven color of a printed image formed on a sheet based on original image data by an image forming apparatus,
A control unit acquiring the document image data;
A control unit displaying the document image data;
A step of causing the user to select a reference color to be used for color unevenness correction based on the displayed document image data;
A control unit changing image forming conditions of the image forming apparatus based on color information of the selected reference color;
Including
The controller is
The size and shape are set in advance, the region of the set size and shape is detected as a uniform color in the displayed data, and the number of regions having the same color is large in order.
Detecting a single region having a uniform color included in the displayed data, in order of increasing area of the detected region; and
A single region having a uniform color included in the displayed data is detected, and the order of the sum of areas of the same color among the detected regions is large,
A method for correcting color unevenness, wherein the reference color is displayed so as to be selectable by any one of the methods. An uneven color correction method for correcting uneven color of a printed image formed on a sheet based on original image data by an image forming apparatus,
A control unit acquiring the document image data;
A step of acquiring inspection image data read from a reference print image formed on a sheet by the image forming apparatus based on the document image data;
A control unit displaying comparison image data based on the document image data and the inspection image data;
A step of causing the user to select a reference color used for color unevenness correction based on the displayed comparison image data;
A control unit changing image forming conditions of the image forming apparatus based on color information of the selected reference color;
Including
The controller is
A region in the inspection image data is set as a region of interest, and a color space of the region corresponding to the region of interest in the document image data is compared and displayed so that the reference color can be selected in order of increasing color difference. A characteristic color unevenness correction method. An uneven color correction method for correcting uneven color of a printed image formed on a sheet based on original image data by an image forming apparatus,
A control unit acquiring the document image data;
A step of automatically selecting a reference color to be used for color unevenness correction based on the document image data;
A control unit changing image forming conditions of the image forming apparatus based on color information of the automatically selected reference color;
Including
The controller is
A size and shape are set in advance, a region having a uniform color within the region of the set size and shape is detected in the document image data, and the color having the largest number of regions having the same color,
A region having the largest area of a single region having a uniform color included in the document image data is detected, and the color of the region; and
Detecting the sum of the areas of the regions having the same color included in the document image data,
Any one of the above is selected as the reference color. An uneven color correction program for correcting uneven color of a printed image formed on paper based on original image data by an image forming apparatus,
Computer
Means for obtaining the document image data;
Means for displaying the document image data;
Means for allowing a user to select a reference color to be used for color unevenness correction based on the displayed document image data;
Control means for changing image forming conditions of the image forming apparatus based on color information of the selected reference color;
Have
The control means is
An order in which the size and shape are set in advance, the region of the set size and shape is uniform in the data displayed on the image display means, and the number of regions having the same color is large ,
Detecting a single region having a uniform color included in the data displayed on the image display means, and in order of increasing area of the detected region; and
Detecting a single region having a uniform color included in the data displayed on the image display means, and in order of increasing the sum of areas of the same color among the detected regions;
A color unevenness correction program that functions as a color unevenness correction device that displays the reference color so that any one of the reference colors can be selected. An uneven color correction program for correcting uneven color of a printed image formed on paper based on original image data by an image forming apparatus,
Computer
Means for obtaining the document image data;
Means for acquiring inspection image data read from a reference print image formed on a sheet by the image forming apparatus based on the document image data;
Means for displaying comparison image data based on the original image data and the inspection image data;
Means for allowing a user to select a reference color to be used for color unevenness correction based on the displayed comparison image data;
Control means for changing image forming conditions of the image forming apparatus based on color information of the selected reference color;
Have
The control means is
The image display means can select a reference color in order of increasing color difference by comparing a color space of a region corresponding to the target region in the document image data as a region of interest in the inspection image data. A color unevenness correction program that functions as a color unevenness display device displayed on the screen. An uneven color correction program for correcting uneven color of a printed image formed on paper based on original image data by an image forming apparatus,
Computer
Means for obtaining the document image data;
Control for automatically selecting a reference color to be used for color unevenness correction based on the original image data and changing image forming conditions of the image forming apparatus based on color information of the automatically selected reference color Means,
Have
The control means is
A size and shape are set in advance, a region having a uniform color within the region of the set size and shape is detected in the document image data, and the color having the largest number of regions having the same color,
A region having the largest area of a single region having a uniform color included in the document image data is detected, and the color of the region; and
Detecting the sum of the areas of the regions having the same color included in the document image data,
A color unevenness correction program that functions as a color unevenness correction device that selects any one of them as the reference color.