Image forming device

Abstract

To improve image quality.SOLUTION: A color chart having a pattern image constituted by patches of different densities or luminance comprises: a first portion in which the patch is not formed; and a second portion in which the patch is formed. A reference patch indicating a color of the density or luminance to be a reference is formed on a spot that is adjacent to the first portion in the second portion. In the second portion, the patch according to any of the following A) to D) is arranged. A) The patches are arranged in ascending order of density from the density of the color indicated by the reference patch. B) The patches are arranged in descending order of density from the density of the color indicated by the reference patch. C) The patches are arranged in ascending order of luminance from the luminance of the color indicated by the reference patch. D) The patches are arranged in descending order of luminance from the luminance of the color indicated by the reference patch.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. Place Regarding. [Background technology]

[0002] There is a known technology for adjusting the quality of an image forming device, particularly adjusting the color reproduction density, by using a color chart. First, a color chart is configured by arranging color patches of colors that the image forming device can reproduce. Then, the image forming device forms an image of the color chart on a recording medium and outputs it. After that, the output color chart is measured by a colorimeter or the like. As a result of such color measurement, a color conversion profile is generated.

[0003] Specifically, the color patches are arranged so that the ratio of color reproduction density changes at a constant rate. In other words, the color patches are arranged so that color patches with similar gradations are adjacent to each other. In this way, a technology is known that makes the color reproduction density distribution a density distribution with a gradual change for the entire arrangement of color patches on a color chart (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional technology, the difference in gradation or brightness between the color patch and the background (e.g., the color of the recording medium) may be large. Therefore, there is a problem that the image quality is poor because the influence of flare cannot be sufficiently suppressed.

[0005] An object of the present invention is to provide a color chart or the like that can improve image quality. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the present invention is A pattern image consisting of patches of different densities or brightness An image forming apparatus for forming an image on a recording medium but, The pattern image is The portion where the patch is formed; 、 The patch is not formed portion Adjacent to A reference patch showing the reference density or brightness color forming the pattern image so as to include , Based on color information of the portion where the patch is not formed, the density or brightness of the reference patch, the arrangement of the patches of the pattern image, and the number of patches are determined. It is characterized by: Effect of the Invention

[0007] According to the present invention, image quality can be improved. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of a color chart. [Diagram 2] FIG. 13 is a diagram illustrating an example of patch arrangement. [Diagram 3] 13A to 13C are diagrams illustrating modified examples of patch arrangement. [Figure 4] FIG. 13 is a diagram showing an example in which the color of the recording medium is black. [Diagram 5] FIG. 13 is a diagram showing an example in which there are a plurality of second portions 102. [Figure 6] FIG. 2 is a diagram showing an example of the arrangement of a reference patch 201. [Figure 7] FIG. 2 is a diagram showing an example of the arrangement of reference patches 201 when the color of the recording medium is black. [Figure 8] FIG. 2 is a diagram showing an example of the arrangement of reference patches 201 when the color of a recording medium is an intermediate color. [Figure 9] FIG. 13 is a diagram illustrating an example of a gradation range. [Figure 10] FIG. 13 is a diagram showing a modified example of the gradation range. [Figure 11] FIG. 13 is a diagram showing a modified example of a patch. [Figure 12] FIG. 2 illustrates an example of a hardware configuration of an image forming apparatus. [Figure 13]FIG. 13 is a diagram illustrating a first modified example of the hardware configuration of an image forming apparatus. [Figure 14] FIG. 13 is a diagram illustrating a second modified example of the hardware configuration of the image forming apparatus. [Figure 15] FIG. 1 illustrates an example of the configuration of an image forming system. [Figure 16] FIG. 13 is a diagram illustrating an example of a configuration for performing calibration. [Figure 17] FIG. 13 is a diagram illustrating an example of the overall process. [Figure 18] FIG. 2 illustrates an example of a functional configuration of an image forming apparatus. [Figure 19] FIG. 1 is a diagram illustrating a first comparative example. [Figure 20] FIG. 11 is a diagram illustrating a second comparative example. [Figure 21] FIG. 13 is a diagram illustrating a third comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [First embodiment] Hereinafter, an example of a color chart (sometimes called a "calibration chart") will be described as an embodiment of the present invention with reference to the drawings.

[0010] The color chart is used, for example, for calibration to adjust the color reproduction density of an image formed by an image forming apparatus, etc. For example, the color chart has the following configuration.

[0011] 1 is a diagram showing an example of a color chart. For example, the color chart is created by forming an image (hereinafter referred to as a "pattern image") made up of a plurality of patches on a sheet of paper 100, which is an example of a recording medium.

[0012] A patch is an image of a predetermined color, density, and shape that is set in advance. That is, the image that becomes the patch is set according to the content of the calibration, and is not limited to a specific color, density, and shape. In addition, the combination, number, dimensions, etc. of the patches that make up the color chart are set in advance according to the content of the calibration.

[0013] Hereinafter, a portion other than where the pattern image is formed (hereinafter referred to as a "first portion 101") and a portion where the pattern image is formed (hereinafter referred to as a "second portion 102") will be described with reference to the example shown in FIG.

[0014] In the example described below, the paper 100 is white in color. Note that, for the sake of explanation, the drawings show divisions and the like as dotted lines, but there do not have to be any lines in the locations shown by the dotted lines.

[0015] 1, the first portion 101 is, for example, a portion that does not have a pattern image and is called a blank space, etc. Therefore, the color of the first portion 101 is the color of the paper 100, that is, the background color.

[0016] 1, the second portion 102 is a portion in which patches are arranged so that the densities increase in order from a patch (hereinafter referred to as a "reference patch 201") arranged at a location adjacent to the first portion 101. The reference patch 201 is one of the patches arranged at the outermost side in the second portion 102.

[0017] In this example, the reference patch 201 is the patch with the lowest density in the second portion 102. In this example, the patch with the highest density in the second portion 102 (hereinafter referred to as the "final patch 202") is placed at the center of the second portion 102.

[0018] For example, the patches are arranged so that the density increases from the reference patch 201 to the final patch 202 (in the order shown by the arrows in the figure). Therefore, in this example, the density is lower on the outside and higher on the inside and closer to the center. Therefore, if the color of the paper 100 is white, it is desirable for the reference patch 201 to be white, that is, a color with a density close to the color of the paper 100.

[0019] Moreover, the patches are arranged, for example, in a spiral shape toward the center, as shown by the arrows in Fig. 1. Specifically, the patches are arranged in the following order.

[0020] Fig. 2 is a diagram showing an example of patch arrangement. Below, an example of a color chart consisting of 16 patches will be explained. In the figure, the order in which the patches are arranged is indicated by numbers. Note that in the figure, the order of increasing density is also indicated by dotted arrows.

[0021] Specifically, the patches are arranged in increasing density starting from the location indicated by "1," with the patch with the highest density being arranged at the location indicated by "16." That is, the reference patch 201 is arranged at the location indicated by "1." Therefore, in this example, the color chart has the lightest patch arranged at the location indicated by "1," and the density of the patch increases as the number increases, with the patch arranged at the location indicated by "16" being the darkest.

[0022] The number of patches is not limited to 16, and may be increased by finely varying the density. On the other hand, the number of patches may be less than 16.

[0023] In this way, it is preferable to place patches of a color with a density close to the color of the paper 100 in the areas adjacent to the first portion 101, such as "1" to "4". It is also preferable to place patches with a density that increases toward the inside, such as "15" or "16".

[0024] Furthermore, with this arrangement, the difference in tone between adjacent patches such as "1" and "2" can be reduced.

[0025] The patch arrangement may be as follows, for example.

[0026] Fig. 3 is a diagram showing a modified example of the arrangement of the patches. Compared to the arrangement shown in Fig. 2, Fig. 3 differs in that the order of "10" and "11" is reversed. In other words, the patches do not have to be arranged in order of increasing density.

[0027] Specifically, for example, the difference in tone between adjacent patches such as the combination of "10" and "11", the combination of "10" and "12", and the combination of "11" and "9" should be small.

[0028] Whether or not the difference in gradation is small is determined, for example, by whether or not the difference in gradation is equal to or greater than a preset value. Therefore, it is sufficient that the color chart is composed of adjacent patches that have a small gradation difference less than a preset value.

[0029] The color chart arranged as above can reduce the gradation difference between the color of the patches arranged on the periphery of the reference patch 201 and the color of the paper 100. Therefore, the influence of flare and the like can be suppressed during calibration and the like. If the influence of flare and the like can be suppressed in this way, color reproducibility can be improved, and image quality during image formation can be improved. Furthermore, with such a configuration, there is no need to reduce the number of patches.

[0030] Flare occurs, for example, when a color chart is read in calibration, when the reading device captures reflected light from the periphery of the target patch. In addition, the greater the difference in gradation between the color of the patch and the color of the paper 100, the more likely the result is to deviate from the true value due to the influence of flare. Therefore, it is desirable that a patch (reference patch 201) placed in a location adjacent to a location that is the color of the paper 100 has the same density as the color of the paper 100 or a density close to the color of the paper 100. Also, when placing patches with increasing density starting from the reference patch 201, it is desirable to place a patch with a relatively low density in the entire color chart in a location that is close to the color of the paper 100. In other words, it is desirable that the density difference between the reference patch 201 and the color of the recording medium is equal to or less than a predetermined value.

[0031] [Second embodiment] The second embodiment is different from the first embodiment in that the color of the paper 100 is black. Therefore, in the second embodiment, the first portion 101 has a black color in the area where there is no pattern image.

[0032] It is desirable to switch the reference patch 201 according to the color of the recording medium. Specifically, when the color of the paper 100 is black as in the second embodiment, it is desirable to switch the reference patch 201 as follows.

[0033] FIG. 4 is a diagram showing an example in which the color of the recording medium is black. In this example, the patches are arranged so that the density increases toward the outside and decreases toward the inside. Therefore, when the color of the paper 100 is black, it is desirable that the reference patch 201 be black, that is, a color with a density close to the color of the paper 100. In this way, it is desirable that the reference patch 201 be switched to a color with the same density as the color of the paper 100 or a color with a density close to the color of the paper 100, depending on the color of the paper 100. The patches are arranged so that the density decreases in order from the reference patch 201 to the final patch 202.

[0034] As described above, the color of the paper 100 is not limited to white, and may be black, etc. Also, the color of the paper 100 may be an intermediate color, etc. An intermediate color is, for example, red, etc.

[0035] In addition, in the case of paper 100 of a neutral color, for example, there may be a plurality of second portions 102. Below, an example in which there are two second portions 102 will be described.

[0036] 5 is a diagram showing an example in which there are multiple second portions 102. In the following description, it is assumed that the color of the paper 100 is red. In the drawing, the first portions 101, i.e., the portions that are the background color, are shown by hatching.

[0037] For example, the two second portions are arranged one above the other (in the Y direction in the figure). Hereinafter, in this example, the second portion arranged on the top is referred to as the "upper portion 1022." Meanwhile, in this example, the second portion arranged on the bottom is referred to as the "lower portion 1021."

[0038] In the upper portion 1022, the patches are arranged in a spiral shape from the top left (hereinafter referred to as the "first reference patch 2011") to the center inward in such a way that the density decreases, with the patch at the center of the upper portion (hereinafter referred to as the "first final patch 2021") being the lightest patch. On the other hand, in the lower portion 1021, the patches are arranged in a spiral shape from the top left (hereinafter referred to as the "second reference patch 2012") to the center inward in such a way that the density decreases, with the patch at the center of the lower portion (hereinafter referred to as the "second final patch 2022") being the darkest patch.

[0039] For the sake of explanation, in FIG. 5, the first reference patch 2011, the second reference patch 2012, and the first portion 101 are depicted as being of different colors, but it is preferable that these colors have similar densities.

[0040] In this way, the color chart may have two second parts: a second part in which patches are arranged so that their density decreases from the first reference patch 2011 to the first final patch 2021, as in the upper part 1022, and a second part in which patches are arranged so that their density increases from the second reference patch 2012 to the second final patch 2022, as in the lower part 1021.

[0041] In particular, when using intermediate colors, both an arrangement of patches with increasing density and an arrangement of patches with decreasing density may be used for calibration. Therefore, when the recording medium is an intermediate color, the density of the reference patch is an intermediate value, so that only one of the arrangements of increasing density or decreasing density may result in some densities that cannot be obtained, resulting in a lack of data for calibration. On the other hand, as in the above example, if a configuration is used in which multiple second portions are arranged, data for calibration can be obtained and color reproduction can be improved by calibration, even if the recording medium is an intermediate color.

[0042] In the above example, the two second portions, that is, the upper portion and the lower portion, are equal. On the other hand, the upper portion and the lower portion do not have to be equal. Specifically, the ratio of the number of patches arranged in the upper portion and the lower portion in the above example is desirably adjusted according to the intermediate color. For example, when the paper 100 is an intermediate color and is a dark color, the number of patches arranged in the lower portion is smaller than the number of patches arranged in the upper portion. In this way, it is desirably to adjust the number of patches in the multiple second portions according to the density of the intermediate color.

[0043] [About standard patch 201] The reference patches 201 are arranged in the following locations:

[0044] FIG. 6 is a diagram showing an example of the arrangement of the reference patch 201. Note that the example described below is an example in which the paper 100 is white. For example, the reference patch 201 is arranged at one of the locations that form the outer periphery of the second portion 102 (for example, the "outermost periphery" in the figure). As in the example shown in the figure, the outermost periphery may be configured to be a pattern image. On the other hand, the location inside the outermost periphery (the location shown by hatching in FIG. 6; hereinafter simply referred to as the "inside") does not matter how the patch is arranged. In other words, the inside may not have a pattern image, and may be a blank space or any image. Note that, for the sake of explanation, the figure shows hatching, but the inside is configured without any description such as hatching.

[0045] As described above, when the reference patch 201 is arranged on the outermost periphery, the difference in gradation between the color of the patch and the color of the paper 100 can be reduced. Specifically, with the above-described configuration, the difference in gradation can be reduced to within about 30%. Therefore, the effects of flare can be suppressed.

[0046] As shown in the second embodiment, the color of the paper 100 may be black or a neutral color, as described below.

[0047] 7 is a diagram showing an example of the arrangement of the reference patch 201 when the color of the recording medium is black. In this way, if the paper 100 is black, the reference patch 201 is set to a color close to black. On the other hand, as in FIG. 6, the arrangement of the patches inside does not matter.

[0048] Fig. 8 is a diagram showing an example of the arrangement of the reference patch 201 when the color of the recording medium is an intermediate color. In this way, when the paper 100 is an intermediate color such as red, the color of the reference patch 201 is a color whose density (in the modified example described below, this is luminance) is close to the color of the background. On the other hand, as in Fig. 6, the arrangement of the patch inside does not matter.

[0049] [Patch placement] For example, the patches are arranged to achieve the following gradations:

[0050] 9 is a diagram showing an example of a gradation range. In the following, the second portion 102 will be described by dividing it into five regions from the outside, namely, a "first region," a "second region," a "third region," a "fourth region," and a "fifth region."

[0051] In the following explanation, the gradation is assumed to be in 100 stages from "0" to "99". The range of gradation to be used for the patch (hereinafter simply referred to as "gradation range") is set in advance for each area. Note that in the following example, the gradation becomes lighter as the value increases, and the color is closer to white. For example, the "gradation range" for an "area" is set as shown below (Table 1).

[0052] [Table 1] In the example shown in Table 1 above, patches with gradations between "71" and "99" are placed in the first region, i.e., in the location adjacent to the first portion 101. As shown in Table 1 above, patches with gradations smaller than the first region and larger than the third region are placed in the second region.

[0053] Similarly, in the third region, patches are placed with gradations whose numerical values ​​are smaller than those in the second region and larger than those in the fourth region. In addition, in the fourth region, patches are placed with gradations whose numerical values ​​are smaller than those in the third region and larger than those in the fifth region. Next, in the fifth region, patches with gradations whose numerical values ​​are smaller than those in the fourth region are placed. In this way, it is desirable to arrange patches whose density is higher (i.e., the value indicated in the "gradation range" is smaller) in the inner region than in the outer region.

[0054] It is desirable to arrange the patches in this way so that the difference in tone between the patch and the background, and the difference in tone between adjacent patches, are both small.

[0055] The arrangement of the patches is not limited to the example shown in Table 1 above, so long as the gradation difference between the patch and the background and the gradation difference between adjacent patches are within a certain range. For example, the following combinations of "gradation ranges" and "areas" are also acceptable.

[0056] Fig. 10 is a diagram showing modified examples of gradation range. As shown in Table 1 above, the gradation range of "71" to "99" is hereinafter referred to as "A" in the gradation range classification. The two gradation ranges of "51" to "70" and "31" to "50" are collectively referred to as "B" in the gradation range classification. Furthermore, the two gradation ranges of "11" to "30" and "0" to "10" are collectively referred to as "C" in the gradation range classification.

[0057] Compared to Fig. 9, Fig. 10 has a different "tone range" for the "area" in "tone range classification" "B." That is, when comparing Fig. 9 and Fig. 10, the "tone range" corresponding to the "second area" and the "third area" is reversed. Therefore, Fig. 10 has a configuration in which the third area, which has a higher density than the second area, is arranged on the outside. Specifically, the arrangement is as shown in Table 2 below.

[0058] [Table 2] Table 2 above differs from Table 1 above in that the "tone range" corresponding to the "second region" (second row from the top in the table) and the "tone range" corresponding to the "third region" (third row from the top in the table) are swapped. In this way, the arrangement may be such that the "tone ranges" are swapped in regions with the same "tone range classification."

[0059] Furthermore, the "gradation range classification" is not limited to the settings as shown above (Table 2). For example, three or more regions may belong to the "gradation range classification".

[0060] The method of setting the gradation range and the method of setting the regions are not limited to the example shown in Table 1 above. For example, the regions may be divided into six or more regions, or into less than five regions. In addition, the "gradation range classification" may not be set, or the "gradation range" may be interchanged between regions with different "gradation range classifications."

[0061] [Variations] The arrangement of the patches is not limited to the arrangement based on the density based on the CMYK standard. For example, the reference patch 201 and the order of the patches may be determined based on the color space of "L*a*b*" (hereinafter referred to as "Lab"), that is, based on the luminance based on the Lab standard.

[0062] "Lab" is a color space defined by the standards of the CIE (International Commission on Illumination).

[0063] The reference patch 201 and the like may be determined based on the luminance in such a Lab color space.

[0064] The patch (including the reference patch 201, hereinafter simply referred to as a "patch") is not limited to a square shape. For example, the patch may have the following shape.

[0065] Fig. 11 is a diagram showing modified examples of patches. First, for comparative explanation, Fig. 11(A) shows an example in which all patches have a square shape.

[0066] 11B shows an example including rectangular patches. Specifically, the patches may include vertically elongated patches (patches elongated in the Y-axis direction in the figure) or horizontally elongated patches (patches elongated in the X-axis direction in the figure).

[0067] The shape of the patch used for calibration does not matter as long as it has a certain area. Therefore, the patch is not limited to a square, and may be another shape such as a rectangle. Furthermore, the shape of the patch does not have to be uniform. However, it is desirable that the area of ​​the patches is as uniform as possible.

[0068] In this way, if the patch can be rectangular or the like, the degree of freedom in arranging the patches can be increased. For example, if the patch shape can be elongated, the number of patches arranged at the outer periphery can be reduced. Therefore, it is desirable that the reference patch 201 and the patch have the same area but different shapes.

[0069] [Examples of image forming devices] The image forming apparatus is, for example, an apparatus having the following hardware configuration.

[0070] 12 is a diagram showing an example of the hardware configuration of an image forming apparatus 10. For example, an image forming apparatus 10 includes a control device 11, a writing device 12, an image creating device 13, an intermediate transfer belt 14, a secondary transfer device 15, a fixing device 16, and a reading device 17.

[0071] The control device 11 is, for example, a calculation device and a storage device, etc. The control device 11 controls the writing device 12 and the like to control image formation.

[0072] The writing device 12, the image creating device 13, the intermediate transfer belt 14, the secondary transfer device 15, and the fixing device 16 form an image based on input image data, etc. Specifically, when an image indicated by the image data is formed on the paper 100, a latent image is generated based on the image data, and toner is transferred to the intermediate transfer belt 14. This toner is transferred to the paper 100 by the secondary transfer device 15. Next, the fixing device 16 heats the paper 100 to which the toner is attached, and fixes the image to the paper 100. When printing on both sides of the paper 100, images are formed on both the front and back sides.

[0073] The reading device 17 is, for example, an optical sensor. Therefore, the reading device 17 reads a pattern image for calibration that is written on the paper 100, and generates image data, etc. Calibration is performed based on the image data, etc., thus generated.

[0074] The reading device 17 may have the following configuration, for example.

[0075] Fig. 13 is a diagram showing a first modified example of the hardware configuration of the image forming apparatus. Compared to the hardware configuration shown in Fig. 12, this differs in that there are two reading devices 17. However, there may be three or more reading devices 17.

[0076] That is, the reader 17 may be provided for both the front and back sides.

[0077] The hardware configuration may be as follows:

[0078] 14 is a diagram showing a second modified example of the hardware configuration of the image forming apparatus 100. The reading device 17 may be located as shown in the figure.

[0079] In particular, high image quality is often required for printing such as production printing. Therefore, users perform calibration to improve the image quality of image formation depending on changes over time, changes in the environment, usage conditions, or a combination of these. In such cases, by performing calibration on an image forming device using the color chart according to this embodiment, the characteristics of the image forming device can be adjusted.

[0080] In the calibration, the gradation characteristics (for example, characteristics indicated by a gamma correction curve or the like) are adjusted based on the results of optically reading the color chart.

[0081] Furthermore, the embodiment may be an image forming system using an apparatus other than an image forming apparatus. For example, the image forming apparatus and the reading apparatus may be separate apparatuses as described below.

[0082] 15 is a diagram showing an example of the configuration of an image forming system. For example, an image forming system 20 is a system that combines an image forming apparatus 10 with a reading device 17 that is an external device independent of the image forming apparatus 10.

[0083] 13 and 14, the image forming apparatus 10 is different in that it does not have a reading device 17. The reading device 17 is a so-called colorimeter or the like, and has, for example, a sensor 21, a sensor control device 22, and the like.

[0084] In the image forming system 20, first, the image forming apparatus 10 forms a test chart on paper 100. Then, the reading device 17 reads the test chart. For example, paper discharged from the image forming apparatus 10 is manually inserted into the reading device 17. Then, the reading result by the reading device 17 is input to the image forming apparatus 10. In this manner, the calibration may be performed by a plurality of devices, such as by an external device. In other words, the number and type of devices are not important as long as the following configuration can be achieved.

[0085] 16 is a diagram showing an example of a configuration for performing calibration. For example, as shown in the figure, first, an image forming apparatus forms an image of a color chart or the like on paper 100 for calibration. Then, a reading device such as a colorimeter reads the color chart. Next, an information processing device such as a PC (Personal Computer) performs a process of calculating characteristic values ​​using the reading results by the reading device. Calibration may be performed by updating the settings of the image forming apparatus so as to obtain the characteristic values ​​obtained in this manner.

[0086] The image forming apparatus may be of a type other than the electrophotographic type. For example, the image forming apparatus may be of an inkjet type. Furthermore, the image forming apparatus may have a hardware configuration having hardware other than that shown above.

[0087] [Overall processing example] For example, the calibration is performed in the following manner.

[0088] Fig. 17 is a diagram showing an example of the overall process. The following takes as an example the case of the image forming apparatus shown in Fig. 12. That is, the explanation will be given on an example of a configuration in which the reading device and the like are all integrated in the image forming apparatus.

[0089] In step S1701, a recording medium is set in the image forming apparatus. That is, the user sets information about the paper 100 to be used for calibration in the image forming apparatus.

[0090] In step S1702, the image forming apparatus sets the patches. For example, the image forming apparatus determines the color of the reference patch 201, the arrangement of the patches, the number of patches, etc., according to the color of the recording medium. In this manner, the configuration of the color chart is determined. Note that the position of the reference patch 201, etc. may be set so that the image forming apparatus can determine, in the reading result, which data is based on the reference patch 201, etc.

[0091] In step S1703, the image forming apparatus generates a pattern image.

[0092] In step S1704, the image forming apparatus forms a pattern image. That is, the image forming apparatus forms the pattern image on a recording medium, and produces a color chart having the pattern image.

[0093] In step S1705, the image forming apparatus performs reading.

[0094] In step S1706, the image forming apparatus generates a reading result, that is, the image forming apparatus generates data of the reading result indicating patch information and the like, which serves as data for calibration.

[0095] In step S1707, the image forming apparatus updates and adjusts the characteristic values ​​etc. based on the reading result.

[0096] The overall process is not limited to the subject, content, and order described above. For example, a device other than those described above may perform the process. Furthermore, a process other than those described above may be performed.

[0097] [Example of functional configuration] 18 is a diagram showing an example of the functional configuration of an image forming apparatus 10. For example, the image forming apparatus 10 has a functional configuration including a reading unit 10F1, a control unit 10F2, an image forming unit 10F3, and a setting unit 10F4.

[0098] The reading unit 10F1 performs a reading procedure for reading the color chart. For example, the reading unit 10F1 is realized by a reading device 17 or the like.

[0099] The control unit 10F2 executes a control procedure for performing calibration based on the result of the reading. For example, the control unit 10F2 is realized by the control device 11 or the like.

[0100] The image forming unit 10F3 performs an image forming procedure to form an image in a state adjusted based on the calibration result. For example, the image forming unit 10F3 is realized by a writing device 12, an image creating device 13, an intermediate transfer belt 14, a secondary transfer device 15, a fixing device 16, etc.

[0101] The setting unit 10F4 performs a setting procedure for setting the positions of the reference patches 201, etc. For example, the setting unit 10F4 is realized by the reading device 17, an input device, or the like.

[0102] [Comparative Example] As comparative examples to the color chart according to this embodiment, for example, the following three color charts are considered.

[0103] 19 is a diagram showing a first comparative example. In this way, even if adjacent patches are arranged so that they have similar gradations, the difference in gradation with the skin color may be large.

[0104] 20 is a diagram showing a second comparative example. Even in the case where the area of ​​the patches arranged on the periphery is increased in this way, the difference in gradation with respect to the skin color may become large.

[0105] Fig. 21 is a diagram showing a third comparative example. The example in Fig. 21 is a chart in which images of various colors such as yellow, magenta, cyan, black, green, and brown are formed in a range from dark to light states.

[0106] When performing calibration using these color charts, the effects of flare and the like often occur when reading the color chart.

[0107] [Other embodiments] The colors, positions, sizes, shapes, and ratios of patches to blank spaces of the patches constituting the color chart are not limited to the examples described above.

[0108] The intermediate color may be a color other than red. In other words, the intermediate color is a color whose density is between the highest density color (such as black) and the lowest density color (such as white).

[0109] The recording medium is, for example, paper (also called "plain paper"). However, the recording medium may be coated paper, label paper, or an overhead projector sheet, film, or a flexible thin plate. That is, the material of the recording medium may be a material to which ink droplets can adhere, can adhere temporarily, adhere and stick, or adhere and penetrate. Specifically, the recording medium may be a recording medium such as paper, film, or cloth, an electronic board, an electronic component such as a piezoelectric element (also called "piezoelectric member"), a powder layer (also called "powder layer"), an organ model, or a test cell. In this way, the material of the recording medium may be a material to which liquid can adhere, such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, or a combination of these.

[0110] The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the technical gist of the present invention. The present invention covers all technical matters included in the technical ideas described in the claims. The above-described embodiments are preferred examples, but a person skilled in the art can realize various modifications from the disclosed contents. Such modifications are also included in the technical scope described in the claims. [Explanation of symbols]

[0111] 100 Paper 101 Part 1 102 Part 2 201 Baseline Patch 202 Final Patch 10F1 Reading unit 10F2 Control section 10F3 Image forming section 10F4 Setting section [Prior art documents] [Patent documents]

[0112] [Patent Document 1] JP 2012-147411 A

Claims

1. An image forming apparatus for forming a pattern image on a recording medium, the pattern image being made up of patches of different densities or luminances, The pattern image is A portion on which the patch is formed; forming the pattern image so as to include a reference patch indicating a color of a reference density or brightness adjacent to a portion where the patch is not formed; Based on color information of the portion where the patch is not formed, the density or brightness of the reference patch, the arrangement of the patches of the pattern image, and the number of patches are determined. Image forming device.

2. The portion in which the patches are formed is formed by arranging the reference patch and the patch in a spiral shape. The image forming apparatus according to claim 1 .

3. The patch is formed in a plurality of portions. The image forming apparatus according to claim 2 .

4. The reference patch and the patch are formed so as to have the same area. The image forming apparatus according to claim 1 .

5. The reference patch and the patch are formed so as to have different shapes. The image forming apparatus according to claim 1 .

6. The density is a value determined by the CMYK standard. The image forming apparatus according to claim 1 .

7. The brightness is a value determined by the Lab standard. The image forming apparatus according to claim 1 .

8. The reference patch is formed so that the density difference between the color of the reference patch and the color of the recording medium is equal to or less than a predetermined value. The image forming apparatus according to claim 1 .

9. 9. The image forming apparatus according to claim 1, A reading unit that reads the pattern image; A control unit that performs calibration based on a reading result by the reading unit; an image forming unit that forms an image based on a calibration result by the control unit; a setting unit that sets a position of the reference patch in the pattern image; An image forming apparatus comprising:

10. 9. The image forming apparatus according to claim 1, an image forming unit for forming the pattern image; A reading unit that reads the pattern image; a control unit that performs calibration based on a reading result by the reading unit; Equipped with The image forming unit includes: An image forming apparatus, comprising: an image forming unit that forms an image on a recording medium based on a calibration result by the control unit.

Images