JP6939918B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus that monitors a color tone at the time of image forming.

There is an image forming apparatus that connects a reading unit composed of an in-line sensor or the like to the downstream side of an image forming unit that forms an image on paper and reads an image on the image-formed paper. Further, there is an image forming system in which a reading device (output reading device) is connected to a subsequent stage of an image forming device that forms an image on paper, and the image on the image-formed paper is read by the reading device.

In such an image forming apparatus or an image forming system, a predetermined patch image (correction image) is periodically formed on the paper, and the patch image on the paper is read to change the color of the image forming apparatus. (Color difference) can be detected and corrected (calibrated).

However, since the patch image is formed on the paper, there are problems such as consumption of the paper for forming the patch image and a decrease in the productivity of normal image formation due to the output of the paper on which the patch image is formed.
Therefore, in order to suppress such paper waste and productivity decrease, a method has been proposed in which image data for image formation and output image read image data are compared on a pixel-by-pixel basis during normal image formation. According to this method, since the patch image is not formed on the paper, it is expected that the waste of paper and the decrease in productivity can be suppressed.

As this kind of technology, various related proposals have been made in the following patent documents.

Japanese Unexamined Patent Publication No. 2014-182353

An object of the present invention is to realize an image forming apparatus capable of appropriately monitoring a color tone without using a color patch or the like.

The image forming apparatus reflecting one aspect of the present invention is a timely of the image forming unit that forms an image on the paper based on the image data for image forming and the paper on which the image is formed by the image forming unit. A reading unit that reads each image on each paper formed before and after, a value based on the reading image data of a plurality of papers read by the reading unit, and a paper on which an image is formed after the plurality of papers. It is provided with a control unit that analyzes color reproduction by comparing with the value of the scanned image data and performs color correction of the image forming unit.

According to the present invention, it is possible to appropriately monitor the color tone without using a color patch or the like.

It is a block diagram which shows the structure of embodiment of this invention. It is a block diagram which shows the structure of embodiment of this invention. It is explanatory drawing which shows the processing block of embodiment of this invention. It is a flowchart which shows the operation of the Embodiment of this invention. It is explanatory drawing which shows the state of the process of embodiment of this invention. It is explanatory drawing which shows the state of the process of embodiment of this invention. It is explanatory drawing which shows the state of the process of embodiment of this invention.

Hereinafter, embodiments of an image forming apparatus capable of analyzing color reproduction without being affected by unstable factors and without using a color patch or the like will be described in detail with reference to the drawings.
[Structure of image forming apparatus]
A configuration example of the image forming apparatus 100 will be described in detail with reference to FIGS. 1 and 2. FIG. 1 is a functional block diagram showing the functions of each part of the image forming apparatus 100, and FIG. 2 is an explanatory diagram showing mechanical components of each part of the image forming apparatus 100.

The image forming apparatus 100 is connected to the PC 20 as an information processing terminal via a network 30. The PC 20 creates original image data (printing data other than the raster image) described in the PDL language, and transmits the original image data (printing data other than the raster image) to the image forming apparatus 100 via the network 30.
Here, the image forming apparatus 100 includes a control unit 101 that controls each unit in the image forming apparatus 100, a communication unit 102 for communicating with other connected devices, and an operation input and an image forming apparatus by a user. An operation display unit 103 for displaying the status of 100, a storage unit 104 for storing various settings, a paper feed unit 105 capable of feeding paper stored in a paper feed tray, and a transport unit for transporting paper in the apparatus. A unit 107, a printer controller 110 that RIP-processes the original image data described in PDL from the PC 20 to convert the original image data into image forming image data, and the image forming image data and the read image data with reference to the original image data. A monitoring setting unit 115 for setting a monitoring setting color for monitoring a color difference at a corresponding position and an ideal value of the monitoring setting color, a document reading unit 120 for reading a document, image data for image formation, and various types of images. An image data storage unit 130 for storing data, an image processing unit 140 for executing various image processing necessary for image formation, and an image forming unit 150 for forming an image on paper based on an image forming command and image data. The fixing unit 160 that stabilizes the image of the toner formed on the paper with heat and pressure, and the color tone monitoring unit 180 that analyzes the color reproduction by comparing the pixel values in the image forming image data and the read image data. It is configured to include an output reading unit 190 for reading an image formed on a paper.

As shown in FIG. 2, the image forming unit 150 develops an electrostatic latent image formed on the charged image carrier to form a toner image, and the toner images of each color are superimposed on the intermediate transfer body. This is a so-called electrophotographic image forming unit that is then transferred to paper. However, the specific configuration of the image forming unit 150 is not limited to that shown in FIG.

Further, the output material reading unit 190 reads an image formed on the paper, and is arranged on the downstream side of the image forming unit 150 and the fixing unit 160 so as to read the image during paper transportation. There is. The output reading unit 190 may be arranged in an intermediate processing device or a post-processing device (not shown) connected to the subsequent stage of the image forming device 100.

[Control and setting of each part of the image forming apparatus]
It is assumed that the color materials used for image formation in the image forming unit 150 are cyan C, magenta M, yellow Y, and black K. Further, in the present embodiment, the color tone means a color system divided by the lightness and saturation of the color. In the following description, L * a * b * is simply referred to as Lab.

The printer controller 110 constitutes a raster image processing unit that converts original image data other than the raster image into image data for image formation of the raster image.
The monitoring setting unit 115 is a primary color (C, M, Y, K) of any one of the CMYK color materials used for image formation, and a secondary color (R,) which is a combination of any two primary colors. G, B), a tertiary color (skin color, etc.) that is a combination of three chromatic colors of the primary color in a predetermined ratio, and a trichromatic color (C, M, Y) that is a primary color is combined in a predetermined ratio. The monitoring setting color is set so as to include at least one of the tertiary achromatic colors (gray).

The tertiary color such as skin color is not limited to the skin color of a specific ethnic group, and can be any skin color included in the image in the country or region where it is used.
The monitoring setting unit 115 refers to the original image data, and when monitoring the color tone difference at the corresponding position between the image forming image data and the read image data, the monitoring setting color and the ideal value of the monitoring setting color To set. Further, the monitoring setting unit 115 sets the monitoring setting color in the low frequency region of the spatial frequency and does not include the text data with reference to the original image data. Here, the low frequency region of the spatial frequency means an region or the like filled with a certain color without contours or patterns in the image, and the specific spatial frequency is manufactured by an image forming apparatus. Person or user can arbitrarily determine.

Further, the monitoring setting unit 115 can set a plurality of different colors as the monitoring setting colors. Further, the monitoring setting unit 115 converts the original image data as the monitoring setting color based on the ICC profile or the multidimensional LUT and sets the ideal value. Further, the monitoring setting unit 115 sets a loose threshold value or a strict threshold value according to a loose setting or a strict setting of the monitoring setting color according to the setting status of the monitoring setting color. Further, the monitoring setting unit 115 sets an appropriate threshold value according to the type of monitoring setting color. Further, the monitoring setting unit 115 sets the monitoring setting color by using the average value of the colors extracted from a plurality of places of the image.

Further, the monitoring setting unit 115 is not based on the original image data, but is based on the scanned image data obtained by reading the image-formed paper based on the image-forming image data or a plurality of average values of the scanned image data. It is also possible to set the ideal value based on this. The color tone monitoring unit 180 monitors the color tone difference between the value of the read image data of the monitor set color and the ideal value at the corresponding positions of the image forming image data and the read image data for the monitor set color. Further, the color tone monitoring unit 180 monitors the color tone difference by using at least one of the absolute value of the color tone difference due to the change with time or the degree of change in the color tone difference as a threshold value.

When a tertiary achromatic color is selected as the monitoring setting color, the color tone monitoring unit 180 monitors the change in hue as a color tone difference. Further, the color tone monitoring unit 180 determines the color in the face region recognized by the face recognition process as the tertiary color when the tertiary color is selected as the monitoring setting color, and determines the saturation of the tertiary color. Monitor changes as color differences. At this time, the image processing unit 140 executes image processing such as face recognition processing.

The color tone monitoring unit 180 monitors the color tone difference at one position corresponding to the read image data for one setting of the monitoring setting color.
When the spot color other than the color of the basic color material used for image formation is set as the monitoring set color, the color tone monitoring unit 180 makes a color tone difference in a region where only the spot color is included and other colors are not included. Monitor. Further, the control unit 101 controls to execute the color correction of the image forming unit 150 when the color tone difference is equal to or more than a predetermined threshold value in the monitoring of the color tone monitoring unit 180.

The control unit 101 performs color correction by adjusting the image forming unit 150 by using the reading correction image data obtained by reading the paper on which the correction image is formed in the margin of the paper. Further, the control unit 101 executes the color correction of the image forming unit 150 for a certain period or for each fixed number of image formations even when the color tone difference does not reach the threshold value. Further, the control unit 101 executes color correction of the image forming unit 150 for a certain period of time or for each fixed number of image forming sheets even when the monitoring set color does not appear.

〔motion〕
Hereinafter, the operation of the image forming apparatus of the present embodiment will be described with reference to the drawings. FIG. 3 is a processing block diagram showing a data flow when executing the color tone monitoring of the present embodiment. Further, FIG. 4 is a flowchart when executing the color tone monitoring of the present embodiment.

In the PC 20, the original image data (printing data other than the raster image) described in the PDL language is created by the user (step S101 in FIGS. 3 and 4). The original image data in the PDL language format is supplied to the image forming apparatus via the network 30.
The user operates the operation display unit 103 to instruct the printer controller 110 to form an image of the original image data. Upon receiving the instruction from the user, the printer controller 110 performs RIP processing on the original image data before RIP described in the page description language, and image data (image for image formation) for forming an image in the image forming unit 150. Data) is generated (step S102 in FIGS. 3 and 4). Then, the printer controller 110 stores the image data for image formation in the image data storage unit 130, and supplies the image data to the image processing unit 140 and the image forming unit 150 as needed.

The image forming unit 150 executes image forming using the image forming image data from the printer controller 110, forms an image on paper, and outputs a printed matter (step S103 in FIGS. 3 and 4). In this embodiment, the paper on which the image is formed by the image forming unit 150 is referred to as "printed matter". This printed matter is read by the output material reading unit 190 or the document reading unit 120, and the read image data is generated (step S104 in FIGS. 3 and 4). The output material reading unit 190 or the document reading unit 120 temporarily stores the scanned image data generated by reading the printed matter in the image data storage unit 130, and supplies the scanned image data to the image processing unit 140 or the like as needed.

The monitoring setting unit 115 refers to the original image data, and determines the monitoring setting color when monitoring the color difference at the corresponding position between the image forming image data and the read image data, and the ideal value of the monitoring setting color. Set (step S105 in FIGS. 3 and 4).
Here, the monitoring setting unit 115 refers to the input original image data, and refers to the primary color (C, M, Y, K) of any one of the color materials CMYK used for image formation. Secondary colors (R, G, B) that combine any two colors, tertiary colors that combine the three chromatic colors of the primary colors in a predetermined ratio (skin color, etc. (hereinafter, specific tertiary colors)), The monitoring setting color is set so as to include at least one of the tertiary achromatic color (gray), which is an achromatic color in which the tertiary chromatic colors (C, M, Y) of the primary color are combined in a predetermined ratio.

The tertiary achromatic color is sensitive to changes in hue (chromaticity), and when it changes, it is easy to confirm which color of CMY has changed. That is, if the color tone difference of the third-order achromatic color is monitored, it is possible to grasp the fluctuation of CMY, and it is possible to feed back to the correction of CMY in the image forming unit 150. Primary colors (CMY or CMYK) and secondary colors (RGB) are useful for monitoring the highest density areas. Specific tertiary colors such as flesh tones are sensitive to changes in hue and saturation, and it is easy to confirm changes in hue and saturation.

Further, the ideal value of the set monitoring setting color is set by any of the following three types. First, the monitoring set color (CMYK) is converted based on the ICC profile or the multidimensional LUT and set as an ideal value of Lab or RGB. Second, the measured value (read image data: RGB) of the first printed matter in which the monitoring set color appears is set as the ideal value. Third, the average value of the measured values (read image data: RGB) of several printed matter from the beginning when the monitoring set color appears is set as the ideal value.

In addition, in order to reduce the influence of the error, the monitoring setting unit 115 sets the monitoring setting color in the low frequency region of the spatial frequency that does not include the text data with reference to the original image data.
Further, the monitoring setting unit 115 does not set the ideal value based on the original image data (solid line in FIG. 3), but reads the paper obtained by reading the image-formed paper based on the image-forming image data. It is also possible to set an ideal value based on the image data or a plurality of average values of the read image data (broken line in FIG. 3).

Further, here, a plurality of different colors can be set as the monitoring setting colors. Further, the original image data is converted as the monitoring setting color based on the ICC profile or the multidimensional LUT, and the ideal value is set. In addition, a loose threshold value or a strict threshold value is set according to a loose setting or a strict setting of the monitoring setting color according to the setting status of the monitoring setting color. In addition, an appropriate threshold value is set according to the type of monitoring setting color. In addition, the monitoring setting color is set using the average value of the colors extracted from a plurality of places in the image.

Here, the image processing unit 140 converts the image forming image data and the read image data into data in a unified format that can be compared (step S106 in FIGS. 3 and 4). The image data for image formation is CMYK bitmap data, and the read image data is RGB bitmap data, which cannot be compared as they are. Therefore, the image processing unit 140 executes image processing so that the image forming image data and the read image data have the same data format as the RGB bitmap data and the Lab data. In FIG. 3, "image forming image data'" and "reading image data'" mean data in a state in which the data formats match.

The color tone monitoring unit 180 monitors the color tone difference between the value of the read image data of the monitor set color and the ideal value at the corresponding positions of the image forming image data and the read image data for the monitor set color (FIGS. 3 and 3). Step S107 in FIG. 4).
That is, the color tone monitoring unit 180 first extracts the pixels of the region belonging to the monitoring set color set by referring to the image forming image data and the read image data. Explaining this in detail, when the pixel of interest of the image forming image data matches the setting condition of the monitoring set color, the pixel of interest is extracted from the image data for image formation, and the pixel at the same position as the pixel of interest in the read image data. Is extracted as the corresponding pixel. Then, the corresponding pixels of the read image data are compared with the ideal values of the monitoring set colors, and the color tone difference between the two is extracted.

As the timing of monitoring the above color tone difference, when the analysis of the image for one page is completed, the read image data (actual measurement value) of the extracted monitoring set color and the color tone difference of the ideal value are calculated. Here, when the ideal value is set by the RGB value, the difference between the scanned image data obtained from the scanned image and the RGB value is compared, and if the difference is equal to or more than the threshold value, color correction is executed. When the ideal value is set as the Lab value, the RGB value of the scanned image data obtained from the scanned image is converted into the Lab value based on the scanner profile or the multidimensional LUT, and then compared, and the difference is equal to or larger than the threshold value. If, color correction is performed.

The color tone monitoring unit 180 monitors the color tone difference with at least one of the absolute value of the color tone difference due to the change over time or the degree of change in the color tone difference as a threshold value. When a tertiary achromatic color is selected as the monitoring setting color, the color tone monitoring unit 180 monitors the change in hue as a color tone difference. When a specific tertiary color such as a skin color is selected as the monitoring setting color, the color tone monitoring unit 180 defines the color in the face area recognized by the face recognition process as the specific tertiary color, and determines the specific tertiary color. The hue change and saturation change of are monitored as a color difference. At this time, the image processing unit 140 may perform image processing such as face recognition processing to extract the above-mentioned attention pixel and corresponding pixel. The color tone monitoring unit 180 monitors the color tone difference at one position corresponding to the read image data for one setting of the monitoring setting color. When the spot color other than the color of the basic color material used for image formation is set as the monitoring set color, the color tone monitoring unit 180 makes a color tone difference in a region where only the spot color is included and other colors are not included. Monitor.

A specific example of color tone monitoring will be described below. Here, absolute color tone monitoring and relative color tone monitoring will be described.
[Specific example of absolute color tone monitoring]
-Image data for image formation (CMYK) → Profile → Ideal value RGB,
-Image data for image formation (CMYK)-> Printed matter reading-> Measured value RGB,
In this case, the color tone difference is monitored by comparing the ideal value RGB and the measured value RGB, and when the color tone difference becomes equal to or more than a predetermined threshold value, the color correction described later is executed.

[Specific example of relative color tone monitoring]
・ First printed matter;
Image data for image formation # 1 (CMYK) → Printed matter # 1 → Printed matter # 1 reading (RGB) → Ideal value Lab # 1,
-Nth printed matter (n = 2, 3, 4, ...);
Image data for image formation #n (CMYK) → Printed matter #n → Printed matter #n reading (RGB) → Measured value Lab # n,
In this case, the ideal value Lab # 1 generated from the measured value is used as a reference, the ideal value Lab # 1 and the measured value Lab # n are compared, and the color tone difference for each n is monitored, and the color tone difference is predetermined. When the threshold value is exceeded, the color correction described later is executed.

Regarding the monitoring of the color tone difference by the color tone monitoring unit 180, when the color tone difference (absolute value) ΔE becomes a predetermined threshold value Th1 or more at a certain point, it is determined that the color tone monitoring result = the color tone difference threshold value or more. In FIG. 5, ΔE ≧ Th1 in the part (a1).
Regarding the monitoring of the color tone difference by the color tone monitoring unit 180, the color tone difference (absolute value) ΔE due to the change with time is sampled and integrated, and when the color tone difference integrated value ∫ΔE becomes a predetermined threshold Th2 or more. , It is judged that the color tone monitoring result = the color tone difference threshold value or more. In FIG. 6, ΔE ≧ Th2 in the part (a2). In this case, even if the color tone difference ΔE itself does not reach the threshold value Th1 described above, if a constant color tone difference continues for a certain period of time, the color correction is performed by the color tone difference integral value ∫ΔE. Can determine the need for execution.

Regarding the monitoring of the color tone difference by the color tone monitoring unit 180, the degree of sudden change in the color tone difference, that is, the color tone difference for each printed matter is monitored, and the color tone difference (relative value) δE for each printed matter is predetermined. When the change threshold value becomes thδ or higher, it is determined that the color tone monitoring result = the color tone difference threshold value or higher. In FIG. 7, in the part (b), the color tone difference (absolute value) ΔE <Th1, but the color tone difference (relative value) δE ≧ thδ.

That is, as described above, there are three types of cases in which "the color tone difference is equal to or higher than a predetermined threshold value". Further, as for the monitoring of these color tone differences, any one of the simple color tone monitoring over time, the integrated value monitoring of the color tone difference over time, and the sudden color tone monitoring may be performed, but it is desirable to perform a plurality of monitoring. In addition, when performing a plurality of monitoring, if it is determined that even one of them is equal to or higher than the threshold value, it is desirable to proceed to the color correction execution.

The control unit 101 executes color correction of the image forming unit 150 when the color tone difference is equal to or greater than a predetermined threshold value in the monitoring of the color tone monitoring unit 180 (YES in step S108 in FIG. 3 and step S108 in FIG. 4). (Step S109 in FIGS. 3 and 4). That is, the control unit 101 performs color correction by adjusting the image forming unit 150 by using the reading correction image data obtained by reading the paper on which the correction image is formed in the margin of the paper.

Then, the control unit 101 repeatedly executes the above processing for the images of all the papers for which the images are formed as a series of jobs (step S110 in FIG. 4). However, it can be arbitrarily determined whether the above color tone monitoring process is executed for every one sheet of all sheets or every few sheets. In the above embodiment, since it is not necessary to use a color patch or the like in the color tone monitoring, the productivity is not lowered even if the image is executed for each sheet of paper to be formed.

[Other operations (1)]
In the image data for image formation obtained by the RIP processing, there is a possibility that the secondary colors and the tertiary achromatic colors that are completely the same color are mixed in a certain range by the color management. Therefore, it is desirable to set a threshold value that allows color mixing in the monitoring set color within a range that does not affect the color tone monitoring in order to execute the process in the actual product.

For example, when extracting a tertiary achromatic color (gray) as a monitoring setting color, when the signal value of each YMC color is set to 256 steps of 0-255, (CM <± 3) and (MY < When the difference between the signal values of each CMY is smaller than 3, such as ± 3) and (Y−C <± 3), it is desirable to consider it as a tertiary achromatic color and extract it. Here, 256 steps of signal values and setting the difference between signal values to 3 are examples, and arbitrary numerical values can be determined. When a certain amount of color mixing is recognized in the monitoring set colors in this way, it is desirable to set a slightly looser threshold value for the color tone difference in the color tone monitoring in consideration of the color mixing.

Further, the tertiary achromatic color (gray) in the above embodiment means that it is not a gray made only from K. Therefore, even gray mixed with K in addition to CMY is treated as a tertiary achromatic color.
[Other operations (2)]
The images used by the user are various, and the color to be extracted may not appear as the monitoring setting color. In that case, data can be collected in a wider range by widening the threshold value (width) for extraction. However, when the threshold value for extraction is widened by this method, it is desirable to lower the threshold value for color difference. Further, when such a measure is taken, it is desirable to notify the user via the operation display unit 103.

[Specific example (3) of the embodiment]
When monitoring the color tone of the monitored set color for the scanned image data, the target image of the scanned image data is divided into a plurality of M × N areas, and the average value of the monitored set colors extracted from each of the multiple areas is obtained and this average is obtained. It is possible to monitor the value by comparing it with the ideal value. By doing so, it is possible to monitor the color tone difference on the entire surface of the printed matter.

[Specific example (4) of the embodiment]
Monitoring setting for scanned image data When monitoring the color tone of the set color, the target image of the scanned image data is divided into multiple areas of M × N, and the ideal value generated in each corresponding area is the same as the area to which the ideal value belongs. It is also desirable to perform color tone monitoring of the monitoring set color for the pixels of the scanned image data included in the area. By doing so, it becomes possible to perform color tone monitoring by eliminating the influence of in-plane unevenness that causes different densities at the center and edges of the paper.

[Specific example (5) of the embodiment]
Even when the color tone difference does not reach the threshold value, it is desirable that the control unit 101 executes the color correction of the image forming unit 150 for a certain period or for each fixed number of image formations. Here, the monitoring set color is any of a specific tertiary color such as a primary color (CMYK), a secondary color (RGB), and a skin color, and a tertiary achromatic color, and the color difference being monitored is equal to or less than the threshold value. In this case, it is desirable to feed back to the gamma correction from the difference between the measured data and the ideal value data.

[Specific example (6) of the embodiment]
The control unit 101 may execute the color correction of the image forming unit 150 for a certain period of time or for each fixed number of image forming sheets even when the state in which the monitoring set color does not appear is continuous over a plurality of sheets of paper. desirable.

[Specific example (7) of the embodiment]
When the color tone monitoring unit 180 uses a spot color other than the color of the basic color material used for image formation, this spot color can be used as the monitoring set color. When the spot color is set as the monitoring set color in this way, it is desirable to monitor the color tone difference in the area where only the spot color is included and other colors are not included.

For example, assuming that the fifth color other than CMYK is red (R) as the color of the coloring material used for image formation, the region composed only of red R not including CMYK can be monitored. It is possible to monitor the fluctuation of the five colors.
Further, when the fifth color is a transparent color (clear), the area including the clear is excluded from the monitoring target as the monitoring setting color even if it matches another monitoring setting color. This is to exclude the influence of clearing on the scanned image data.

[Other Embodiments (1)]
The image forming apparatus 100 shown in FIG. 1 shows a state in which the printer controller 110 is built in, but the present invention is not limited to this. That is, the printer controller 110 may exist outside the image forming apparatus 100, and the image forming apparatus 100 may receive the RIP-processed image forming image data from the outside.

[Other Embodiments (2)]
In the above image forming apparatus 100, an example in which the printer controller 110 and the monitoring setting unit 115 are separated has been shown, but the present invention is not limited to this. Since both the printer controller 110 and the monitoring setting unit 115 refer to the original image data, the printer controller 110 may be configured to include the monitoring setting unit 115.

[Other Embodiments (3)]
The above image forming apparatus 100 shows a configuration in which a color tone monitoring unit 180 is built. Here, it is also possible to configure a color tone monitoring device having a monitoring setting unit 115 and a color tone monitoring unit 180 outside the image forming device 100. In this case, the monitoring result by the color tone monitoring device is transmitted to the image forming apparatus 100, and the image forming apparatus executes color correction.

100 Image forming device 102 Communication unit 103 Operation display unit 104 Storage unit 105 Paper feeding unit 107 Transport unit 110 Printer controller 115 Monitoring setting unit 120 Document reading unit 130 Image data storage unit 140 Image processing unit 150 Image forming unit 160 Fixing unit 180 Color tone Monitoring unit 190 Output reading unit

Claims (6)

An image forming unit that forms an image on paper based on image data for image forming,
A reading unit that reads an image on paper on which an image is formed by the image forming unit,
Correction according to the comparison result when comparing the value based on the scanned image data of the plurality of papers read by the scanning unit and the value of the scanned image data of the paper on which the image is formed after the plurality of papers. A control unit that corrects the color of the image forming unit by the amount,
An image forming apparatus comprising. The control unit compares the average value of the scanned image data of the plurality of papers read by the scanning unit with the value of the scanned image data of the paper on which the image is formed after the plurality of papers to reproduce the color. The image forming apparatus according to claim 1, wherein the image forming apparatus is analyzed. Provided is provided with a color tone monitoring unit that monitors the color tone difference between the value based on the scanned image data of the plurality of sheets read by the scanning unit and the value of the scanned image data of the sheet on which the image is formed after the plurality of sheets. The image forming apparatus according to claim 1 or 2. The image forming apparatus according to claim 3, wherein the control unit performs color correction of the image forming unit when the color tone difference is equal to or more than a predetermined threshold value in the color tone monitoring unit. The color tone difference is predetermined to be a primary color of any one of the coloring materials used for image formation, a secondary color obtained by combining any two of the primary colors, and a trichromatic color of the primary color. The image according to claim 3 or 4, wherein at least one of a tertiary color combined in a ratio and a tertiary achromatic color in which the trichromatic colors of the primary color are combined in a predetermined ratio is monitored. Forming device. The image forming apparatus according to any one of claims 3 to 5, further comprising a monitoring setting unit for setting a monitoring setting color when monitoring the color tone difference.

Images