JP5409541B2 - Image density adjusting method and image forming system using the same - Google Patents

Description

  The present invention relates to an image density adjustment method that is applied to an image forming apparatus or the like and adjusts so as to obtain an appropriate image density for a printed matter. The present invention also relates to an image forming system using this image density adjustment method.

  In an image forming apparatus typified by a copying machine or a scanner, image density adjustment for appropriately maintaining the gradation of image density is appropriately performed. This image density adjustment may be executed by measuring the density of a density adjustment patch formed on the surface of the image carrier or transfer body with a sensor and comparing the measured density with a target value.

  In particular, in a so-called multi-function machine having functions such as a copying machine and a scanner, a density adjustment chart may be used so that an appropriate image density is output for a printed matter. In this chart, a plurality of density adjustment patches are arranged in an orderly manner. The multifunction device scans the printed matter on which the density adjustment chart is printed, measures the image density, and sends the density adjustment data to the image forming unit so that the measured density approaches the target value, thereby adjusting the image density. Is running. An example of an image forming apparatus that performs image density adjustment using a chart in which a plurality of density adjustment patches are arranged can be seen in Patent Document 1.

JP 2007-189278 (page 9-10, FIG. 3)

  However, in the case of a so-called printer or the like that is not provided with an image reading unit for reading an image described and drawn on a printed matter, an image density adjustment method such as the image forming apparatus described in Patent Document 1 cannot be realized. In this case, it is possible to realize the above-described image density adjustment method by preparing a multifunction machine provided with a separate image reading unit and scanning a chart output as a printed matter by a printer with the multifunction machine.

  In such an image density adjustment method combining a printer and a multifunction peripheral, the multifunction peripheral needs to have a function corresponding to the density adjustment function employed in the printer. When a new model printer is developed and this printer is equipped with a new density adjustment function, a multifunction device equipped with a function corresponding to the old density adjustment function may not be used for adjusting the image density of this new printer. There is. As a result, there is a concern that in a multi-function peripheral, an update such as a software upgrade that is performed in the form of a function addition will be forced each time a printer having a new density adjustment function is developed.

  The present invention has been made in view of the above points. In an image density adjustment method combining an image forming apparatus not provided with an image reading unit and an image forming apparatus provided with an image reading unit, the image reading unit includes: An image that can cope with various types of density adjustment functions installed in an image forming apparatus that is not provided, and can continue to appropriately adjust the image density without executing update such as addition of functions. It is an object to provide a density adjustment method and an image forming system.

  In order to solve the above problems, an image density adjustment method of the present invention is a chart in which a plurality of density adjustment patches are arranged in a first image forming apparatus that is not provided with an image reading unit that reads an image written on a printed matter. A chart output step for outputting as a printed matter, a parameter output step for outputting the setting parameters specific to the chart in the first image forming apparatus by communication, and the parameters in the second image forming apparatus provided with the image reading unit. A parameter input step for receiving the setting parameter output in the output step by communication, a chart scan step for executing a scan of the chart in the second image forming device, and the chart scan step in the second image forming device Of the chart obtained by scanning with Density adjustment data based on the density measurement step for measuring the density of the patch, the setting parameter received in the parameter input step in the second image forming apparatus, and the density of the patch measured in the density measurement step A density adjustment data calculating step for calculating the density adjustment data obtained in the density adjustment data calculation step in the second image forming apparatus by communication, and the first adjustment data output step for outputting the density adjustment data by communication. In the image forming apparatus, the density adjustment data input step for receiving the density adjustment data output in the density adjustment data output step by communication and the density adjustment data input step in the first image forming apparatus are accepted. Density to perform image density adjustment based on the density adjustment data And integer processing step, was to have.

  In the image density adjustment method having the above-described configuration, the setting parameters include coordinates when performing density measurement in the chart, a target value of density at the coordinates, the number of patches included in the chart, and the density. And a calculation formula for calculating the adjustment data.

  In order to solve the above problems, an image forming system according to the present invention includes a first image forming apparatus that does not include an image reading unit that reads an image written on a printed matter, and a second image forming unit that includes the image reading unit. The image forming apparatus, and the first image forming apparatus outputs a chart in which a plurality of density adjustment patches are arranged as a printed matter and communicates the setting parameters unique to the chart to the second image forming apparatus. And the second image forming apparatus executes the scan of the chart and the density measurement of the patch and calculates the density adjustment data based on the setting parameter and the density of the patch. Is output to the first image forming apparatus by communication, and the first image forming apparatus further performs image density adjustment based on the density adjustment data. It was decided.

  According to these configurations, the second image forming apparatus provided with the image reading section includes the density adjustment chart obtained from the first image forming apparatus provided with no image reading section and the setting parameters unique to this chart. Based on the above, density adjustment data applicable to the first image forming apparatus is calculated.

  According to the configuration of the present invention, it is possible to cope with various types of density adjustment functions that are mounted on an image forming apparatus that is not provided with an image reading unit. It is possible to avoid the problem that the density cannot be adjusted. In this way, in an image density adjustment method that combines an image forming apparatus that is not provided with an image reading unit and an image forming apparatus that is provided with an image reading unit, an image is appropriately displayed without executing an update such as adding a function. It is possible to provide an image density adjustment method and an image forming system capable of continuing to perform density adjustment.

1 is a schematic configuration diagram showing an image forming system using an image density adjusting method according to an embodiment of the present invention. FIG. 2 is a schematic vertical sectional front view of the printer of the image forming system shown in FIG. 1. FIG. 3 is a block diagram illustrating a configuration of the printer in FIG. 2. FIG. 2 is a schematic vertical sectional front view of the multifunction peripheral of the image forming system shown in FIG. 1. FIG. 5 is a block diagram illustrating a configuration of the multifunction machine of FIG. 4. FIG. 6 is an explanatory diagram showing a flow of an image density adjustment method of a printer. It is a 1st example which shows the chart for image density adjustment. It is a 2nd example which shows the chart for image density adjustment.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  First, an image output operation of an image forming system using an image density adjusting method according to an embodiment of the present invention will be described while explaining the outline of the structure with reference to FIGS. 1 is a schematic configuration diagram showing an image forming system, FIG. 2 is a schematic vertical sectional front view of a printer of the image forming system, FIG. 3 is a block diagram showing the configuration of the printer, and FIG. 4 is a model of a multifunction device of the image forming system. FIG. 5 is a block diagram showing the configuration of the multifunction machine. These printers and multifunction machines are of the color printing type in which a toner image is transferred onto a sheet using an intermediate transfer belt.

  As illustrated in FIG. 1, the image forming system 1 includes a printer 100 that is a first image forming apparatus, and a multifunction peripheral 200 that is a second image forming apparatus. The printer 100 and the multifunction device 200 are each installed in a network environment, and can be used from each of a plurality of external computers.

  The printer 100 is an image forming apparatus that does not include an image reading unit that reads an image written on a printed matter such as a document and has only a printing function. As shown in FIG. 2, a paper feed cassette 102 is disposed below the inside of the main body 101 of the printer 100. The paper feed cassette 102 stores and accommodates paper P such as cut paper before printing. The sheets P are separated and sent one by one toward the upper left of the sheet feeding cassette 102 in FIG. The paper feed cassette 102 can be pulled out horizontally from the front side of the main body 101.

  A first paper conveyance unit 103 is provided inside the main body 101 and on the left side of the paper feed cassette 102. The first paper transport unit 103 is formed substantially vertically along the left side surface of the main body 101. Then, the first paper transport unit 103 receives the paper P sent out from the paper feed cassette 102 and transports it to the secondary transfer unit 104 vertically upward along the left side surface of the main body 101.

  A manual paper feed unit 105 is provided above the paper feed cassette 102 at a location on the right side, which is the side opposite to the left side of the main body 101 where the first paper transport unit 103 is formed. In the manual paper feed unit 105, paper of a size that is not in the paper feed cassette 102, paper that is to be manually fed, such as thick paper and an OHP sheet, is placed.

  A second paper transport unit 106 is provided on the left side of the manual paper feed unit 105. The second paper transport unit 106 is located immediately above the paper feed cassette 102, extends substantially horizontally from the manual paper feed unit 105 to the first paper transport unit 103, and joins the first paper transport unit 103. Then, the second paper transport unit 106 receives the paper sent out from the manual paper feed unit 105 and transports it to the first paper transport unit 103 substantially horizontally.

  On the other hand, the printer 100 receives document image data from an external computer. The image data information is subjected to image processing via a control unit and an image processing unit, which will be described later, and then sent to an exposure unit 107 disposed above the second paper transport unit 106. The exposure unit 107 irradiates the image forming unit 108 with laser light L controlled based on the image data.

  A total of four image forming units 108 are provided above the exposure unit 107, and an intermediate transfer belt 109 using an intermediate transfer member in the form of an endless belt is provided above each image forming unit 108. The intermediate transfer belt 109 is supported by being wound around a plurality of rollers, and is rotated clockwise in FIG. 2 by a driving device (not shown).

  The four image forming units 108 are of a so-called tandem type arranged in a line from the upstream side to the downstream side in the rotational direction along the rotational direction of the intermediate transfer belt 109 as shown in FIG. The four image forming units 108 are an image forming unit 108Y for yellow, an image forming unit 108M for magenta, an image forming unit 108C for cyan, and an image forming unit 108B for black in order from the upstream side. These image forming units 108 are replenished with a developer (toner) by a developer supply container and a conveying unit (not shown) corresponding to each color. In the following description, the identification symbols “Y”, “M”, “C”, and “B” are omitted unless particularly limited.

  In each image forming unit 108, an electrostatic latent image of a document image is formed by the laser light L emitted from the exposure unit 107, and a toner image is developed from the electrostatic latent image. The toner image is primarily transferred onto the surface of the intermediate transfer belt 109 by a primary transfer unit 110 provided above each image forming unit 108. The toner image of each image forming unit 108 is transferred to the intermediate transfer belt 109 at a predetermined timing along with the rotation of the intermediate transfer belt 109, so that the surface of the intermediate transfer belt 109 has four colors of yellow, magenta, cyan, and black. A color toner image is formed by superimposing the toner images.

  A secondary transfer unit 104 is disposed at a position where the intermediate transfer belt 109 is suspended on the sheet conveyance path. The color toner image on the surface of the intermediate transfer belt 109 is transferred to the paper P sent in synchronization by the first paper conveyance unit 103 at the secondary transfer nip portion formed in the secondary transfer unit 104.

  After the secondary transfer, deposits such as toner remaining on the surface of the intermediate transfer belt 109 are the cleaning device for the intermediate transfer belt 109 provided on the upstream side of the intermediate transfer belt 109 in the rotation direction of the image forming unit 108Y for yellow. It is cleaned by 111 and collected.

  A fixing unit 112 is provided above the secondary transfer unit 104. The sheet P carrying the unfixed toner image in the secondary transfer unit 104 is sent to the fixing unit 112, where the toner image is heated and pressed by a heat roller and a pressure roller to be fixed.

  A branch portion 113 is provided above the fixing portion 112. When the double-sided printing is not performed, the paper P discharged from the fixing unit 112 is discharged from the branching unit 113 to the paper discharge unit 114 provided at the upper part of the printer 100.

  The discharge port portion from which the paper P is discharged from the branch portion 113 toward the paper discharge portion 114 functions as a switchback portion 115. When performing duplex printing, the switchback unit 115 switches the transport direction of the paper P discharged from the fixing unit 112. Then, the paper P passes through the branching portion 113 and is sent downward through a double-sided printing paper conveyance path 116 provided on the left side of the fixing unit 112 and on the left side of the secondary transfer unit 104, and again the first paper conveyance. The image is sent to the secondary transfer unit 104 via the unit 103.

  Further, the printer 100 includes a control unit 117 composed of a CPU 118 and other electronic components (not shown) in the main body 101 as shown in FIG. The control unit 117 uses the central processing unit CPU 118 and the image processing unit 119, and the image forming unit 108, the intermediate transfer belt 109, the fixing unit 112, and the like based on the program and data stored and input in the storage unit 120. A series of image forming operations is realized by controlling the components. The control unit 117 receives image data and print condition settings related to the printing operation of the printer 100 by the user from the communication unit 121 described below.

  The printer 100 is connected to a network line for communicating with a plurality of external devices, and includes a communication unit 121 for exchanging image data with the external device using the network line. The communication unit 121 includes a network I / F (interface) unit 122 that communicates using a network line. Note that external devices include computers and servers used by a plurality of users, other image forming apparatuses, and the like.

  On the other hand, the multifunction device 200 is an image forming apparatus provided with a scanning function, a printing function, and a facsimile function. 4 and 5 has the same basic configuration as the printer 100, the description of the configuration common to the printer 100 will be omitted.

  The multifunction device 200 has a configuration different from that of the printer 100, and includes a document conveying device 223 on the upper surface of the main body 201, and an image reading unit 224 inside the main body 201 below. When a user copies an original, an original (printed material) on which an image such as a character, figure, or pattern is written is stacked on the original conveying device 223 or placed on the contact glass 224a on the upper surface of the image reading unit 224. To do. In the document conveying device 223, one or a plurality of documents are separated and sent one by one, and the image reading unit 224 reads the image. An image is read by scanning the original on the contact glass 224a with light in the image reading unit 224.

  The image reading unit 224 is provided with a lamp for irradiating the document with light, a mirror for guiding the reflected light to the lens, a lens for collecting the guided light, and an image sensor for receiving the light from the lens. The image sensor includes a plurality of light receiving elements arranged in a line and outputting a voltage corresponding to the amount of received light. Further, an amplifier and an A / D converter are provided in the image sensor and accompanying the image sensor. You may provide the correction process part which performs a shading correction | amendment etc. about the data after A / D conversion. Here, as the image sensor in the present embodiment, for example, a color-compatible one having a plurality of light receiving elements arranged in a line for each of R, G, and B colors can be used.

  The reading of the document image, that is, the start of image formation can be executed by using the operation panel 225 provided on the front side of the image reading unit 224 at the top of the main body 201. The operation panel 225 accepts not only the start of image formation by manual input by the user, but also print condition settings such as the type and size of paper used for printing, the number of copies, enlargement / reduction, and presence / absence of double-sided printing, and a transmission destination setting in a facsimile.

  Note that the multi-function device 200 can also execute the start of image formation, reception of print condition settings, and the like via the communication unit 221. The communication unit 221 includes a facsimile communication unit 226 that performs communication using a telephone line in addition to a network I / F (interface) unit 222 that performs communication using a network line.

  Next, an image density adjustment method of the printer 100 executed in the image forming system 1 will be described with reference to FIGS. 7 and 8 along the flow shown in FIG. FIG. 6 is an explanatory view showing the flow of the image density adjustment method of the printer, FIG. 7 is a first example showing a chart for image density adjustment, and FIG. 8 is a second example showing a chart for image density adjustment.

  When image density adjustment of the printer 100 is executed in the image forming system 1 (start of FIG. 6), first, the printer 100 outputs a density adjustment chart as a printed matter. The density adjustment chart is an array of a plurality of density adjustment patches, and the first example shown in FIG. 7 and the second example shown in FIG. 8 are listed as examples.

  In the first example of the density adjustment chart shown in FIG. 7, patches of 32 types of density are arranged for each of the four colors of black, cyan, magenta, and yellow. The 32 types of patches of each color are arranged in an orderly manner so that the shades change stepwise, with 16 types each in two rows. The data relating to the density adjustment is also designed to handle 32 colors.

  In the second example of the density adjustment chart shown in FIG. 8, patches of 64 types of density are arranged for each of the four colors of black, cyan, magenta, and yellow. The 64 types of patches of each color are arranged at random positions, and the design is designed to improve the accuracy of density adjustment. The data relating to the density adjustment is also designed to handle 64 colors, so that detailed adjustment can be expected.

  The chart output as a printed matter by the printer 100 is brought into the multifunction device 200 by the user's hand.

  Next, the printer 100 outputs the setting parameters specific to the chart to the multifunction device 200 via the communication unit 121. The setting parameters include, for example, a chart design, the number of data to be handled (the number of patches included in the chart), a calculation formula for calculating density adjustment data, and the like. Further, regarding the design of the chart, for example, coordinates at the time of executing density measurement and a target value of density at the coordinates are included. The setting parameters are stored in advance in the storage unit 120 of the printer 100, for example.

  The multifunction device 200 receives the setting parameters from the printer 100 via the communication unit 221. Then, in the multifunction device 200, a scan of the chart output as a printed matter by the printer 100 and brought in by the user's hand is executed. At this time, the control unit 217 of the multifunction device 200 causes the image reading unit 224 to read the image data of the chart. The image data of the chart is read by the image reading unit 224 by using the document conveying device 223 or placing the document on the contact glass 224a.

  Then, the control unit 217 of the multifunction device 200 causes the image processing unit 219 to perform density measurement of each density adjustment patch of the chart read by the image reading unit 224. In this density measurement, the measurement is performed using the coordinates when the density measurement is executed, the number of data to be handled (the number of patches included in the chart), etc., from the previously input setting parameters. By this density measurement, the density (pixel value) of each density adjustment patch is determined. In the following description, “density” may be referred to as “density value”.

  Subsequently, the image processing unit 219 of the multifunction device 200 calculates density adjustment data for performing density adjustment by the printer 100 based on the setting parameter and the density of each density adjustment patch. For calculating the density adjustment data, for example, the following processes (1) to (4) are executed.

  (1) Chart image data scanned using the image reading unit 224 is configured in an RGB representation format, and image data used for setting in the printer 100 (chart image data output by the printer 100 as printed matter) is CMY. It is structured in an expression format. Therefore, when calculating the density adjustment data, the image processing unit 219 first needs to convert the representation format of the chart image data from RGB to CMY.

  (2) The image processing unit 219 includes the density value (target value) of each patch in the image data of the chart output from the printer 100 and the density value of each patch actually read (a chart scanned using the image reading unit 224) And the difference between the target density value of each patch and the actually read density value.

  (3) The image processing unit 219 confirms the difference between the target density value of each patch and the actually read density value for each color, and confirms the overall density trend in printing by the printer 100. For example, while an image forming apparatus such as the printer 100 is being used, the density of the image forming unit 108 tends to decrease as a whole due to deterioration over time such as wear. Therefore, the image processing unit 219 obtains an average value of the difference between the target density value of each patch and the actually read density value, and obtains the overall density tendency as a numerical value. For example, the overall average value of the differences is output from the multifunction device 200 to the printer 100 as density adjustment data. Note that the value indicating the overall density tendency in printing by the printer 100 is not limited to the overall average value of the differences, and may be individual differences of each patch, for example.

  Accordingly, for example, the control unit 117 of the printer 100 may change the voltage (development bias) applied to the development roller by the development bias application unit of the image forming unit 108. As a result, the toner flying amount can be changed to adjust the overall density of the printed matter. For example, when the printed matter is darkened as a whole, the image forming unit 108 of the printer 100 increases the developing bias. Alternatively, the charge amount of the toner may be changed.

  Note that the content of the density adjustment data required by the printer 100 is included in the setting parameter in the form of a calculation formula or a sample point definition. Based on the setting parameters, the control unit 217 and the image processing unit 219 of the multifunction device 200 generate density adjustment data for overall density adjustment in the printer 100.

  (4) In the image data of a plurality of patches read from the chart, the density value increase / decrease must change linearly. If the image data includes data that deviates from the linear change of the density value, it is necessary to supplement the density value of the data. Furthermore, when the deviation is relatively large, it is necessary to detect it as an error. Therefore, the image processing unit 219 may output, as density adjustment data, the difference between the density value of the patch that deviates from a predetermined threshold and the target density value in order to determine whether or not to complement. Thereby, for example, the image processing unit 119 of the printer 100 can correct the density value of the density area corresponding to the patch outside the threshold value. Further, the image processing unit 219 may output, as density adjustment data, a difference between the density value of a patch that is outside a predetermined threshold and the target value of density in order to determine whether or not to detect as an error. Good. Thereby, for example, the control unit 117 of the printer 100 can display on the operation panel (not shown) that an error has occurred.

  The content of the density adjustment data required by the printer 100 is included in the setting parameters in the form of a calculation formula, a threshold for determining whether or not to complement, and a threshold for determining whether or not to detect as an error. Yes. Based on the setting parameters, the control unit 217 and the image processing unit 219 of the multifunction device 200 generate density adjustment data for density adjustment in a specific density range in the printer 100.

  Further, the calculation of the density adjustment data may be executed by the control unit 217.

  The multi-function device 200 outputs the calculated density adjustment data to the printer 100 via the communication unit 221. The printer 100 receives the density adjustment data from the multifunction device 200 via the communication unit 121. In the printer 100, the control unit 117 causes the image processing unit 119 and the image forming unit 108 to perform image density adjustment based on the density adjustment data. The density adjustment data is used for setting for executing conversion processing of the density value of each pixel such as error diffusion processing and gamma correction in the image processing unit 119. In this way, the image density adjustment of the printer 100 using the multifunction device 200 in the image forming system 1 is completed (end of FIG. 6).

  As described above, the MFP 200 provided with the image reading unit 224 is applied to the printer 100 based on the density adjustment chart obtained from the printer 100 provided with no image reading unit and the setting parameters unique to this chart. Possible density adjustment data is calculated.

  According to the configuration of the above-described embodiment, the printer without the image reading unit can cope with various types of installed density adjustment functions, so even when a new density adjustment function is installed. It is possible to avoid the problem that the image density cannot be adjusted. Therefore, in an image density adjustment method that combines a printer not provided with an image reading unit and a multi-function peripheral provided with an image reading unit, the image density is adjusted appropriately without executing an update such as adding a function. An image density adjustment method and an image forming system 1 that can be continued can be provided.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  For example, the printer 100 and the multifunction device 200 in the above-described embodiment are image forming apparatuses for color printing that transfer a toner image onto a sheet using an intermediate transfer belt, but the image forming apparatus to which the present invention is applied is this. The image forming apparatus is not limited to such a type, and may be an image forming apparatus that does not use an intermediate transfer belt or an image forming apparatus for monochrome printing.

  The present invention is applied to an image forming apparatus or the like, and can be used in an image density adjustment method for adjusting an image density suitable for a printed material.

DESCRIPTION OF SYMBOLS 1 Image forming system 100 Printer (1st image forming apparatus)
117 Control Unit 119 Image Processing Unit 200 Multifunction Device (Second Image Forming Apparatus)
217 Control unit 219 Image processing unit 224 Image reading unit

Claims (3)

A chart output step for outputting, as a printed matter, a chart in which a plurality of density adjustment patches are arranged in the first image forming apparatus that is not provided with an image reading unit for reading an image written on the printed matter;
A parameter output step of outputting setting parameters specific to the chart by communication in the first image forming apparatus;
A parameter input step of receiving the setting parameter output in the parameter output step by communication in the second image forming apparatus provided with the image reading unit;
A chart scanning step of performing scanning of the chart in the second image forming apparatus;
A density measuring step for measuring density of the patch of the chart obtained by scanning in the chart scanning step in the second image forming apparatus;
A step of calculating density adjustment data based on the set parameter received in the parameter input step and the density of the patch measured in the density measurement step in the second image forming apparatus ; A density adjustment data calculation step for including, as the density adjustment data, a difference between the density value of the patch and the density target value, in which the increase / decrease of the density value with respect to the setting parameter deviates from a linear change ,
A density adjustment data output step of outputting the density adjustment data obtained in the density adjustment data calculation step in the second image forming apparatus by communication;
A density adjustment data input step for receiving, via communication, the density adjustment data output in the density adjustment data output step in the first image forming apparatus;
A density adjustment processing step for adjusting image density based on the density adjustment data received in the density adjustment data input step in the first image forming apparatus;
I have a,
In the first image forming apparatus, the density adjustment data received in the density adjustment data input step includes a density value increase / decrease with respect to the setting parameter and a density value of the patch and a density target value that are out of a linear change. An image density adjustment method , wherein the density value of the patch is corrected when the difference exists . The setting parameter is
Coordinates for performing concentration measurement in the chart;
A target density value at the coordinates;
The number of patches of the chart;
A calculation formula for calculating the density adjustment data;
The image density adjustment method according to claim 1, further comprising: A first image forming apparatus not provided with an image reading unit for reading an image written on a printed material;
A second image forming apparatus provided with the image reading unit;
With
The first image forming apparatus outputs a chart in which a plurality of density adjustment patches are arranged as a printed matter and outputs setting parameters specific to the chart to the second image forming apparatus by communication.
The second image forming apparatus scans the chart and measures the density of the patch, calculates density adjustment data based on the setting parameter and the density of the patch, and adds a plurality of density adjustment data to the density adjustment data. The density adjustment data includes the difference between the density value of the patch whose density value increase / decrease with respect to the setting parameter out of the patch changes from the linear change and the density target value as the density adjustment data. Output to the first image forming apparatus;
Further, the first image forming apparatus executes image density adjustment based on the density adjustment data, and the density value of the patch whose density value increase / decrease with respect to the setting parameter deviates from a linear change, the density target value, and the like. An image forming system that corrects the density value of the patch when the difference exists .