JP6805593B2 - Inkjet printing machine, image density determination program and image density determination method - Google Patents

Description

The present invention relates to an inkjet printing machine, an image density determination program, and an image density determination method.

Conventionally, in a large-sized inkjet printing machine such as an inkjet continuous book machine, a line head in which a plurality of inkjet heads are connected is used. Since the individual inkjet heads (hereinafter, simply referred to as “heads”) and nozzles have variations in ejection characteristics, uneven printing density occurs between the heads and inside the heads.

A technique for correcting such a variation in density is called a uniformity adjustment technique. That is, if the target density for the adjustment is specified at the time of uniformity adjustment, the density difference between the devices can be corrected.
On the other hand, for uniformity adjustment, a test chart such as a gradation pattern is printed, the density characteristics for gradation are read by a reading device such as a scanner for each head or nozzle, the data is analyzed, and the correction value is calculated. The technique of finding and correcting is already known.

However, in the above-mentioned conventional uniformity adjustment technique, a test chart is output in a state where the density is considerably high, that is, the amount of ink adhered is large. This is because the gradation-density characteristics of the head and the nozzle are not linear over the entire gradation region, and therefore the uniformity beyond the gradation for which the uniformity adjustment is performed cannot be corrected.

If the test chart is printed with a large amount of ink adhered, cockling may occur depending on the paper. The scanner used for uniformity adjustment is often a CIS (Contact Image Sensor) scanner, but because the depth of field is shallow, the CIS scanner correctly adjusts the image density when cockling occurs. There is a problem that it cannot be read.

By the way, as a technique for correcting variations in print density, there is a technique disclosed in Patent Document 1 under the name of "image processing apparatus, image forming apparatus and program".
Each of the "image processing apparatus, image forming apparatus and program" disclosed in Patent Document 1 outputs a plurality of types of evaluation charts over a plurality of pages, and obtains a density correction value by reading the evaluation charts. I tried to do it.

Specifically, it is as follows.
That is, the number of output sheets of a plurality of types of evaluation charts over a plurality of pages is set, the output of the evaluation chart on the sheet is instructed according to the number of output sheets, and the chart pattern of each evaluation chart is stored.
Then, the reading of all the evaluation charts is instructed, the images of all the read evaluation charts are compared with the stored chart pattern of each evaluation chart, and the brightness of each gradation patch constituting each chart pattern is compared. Or find the average value of the concentration.
Then, the coefficient of density gradation conversion is calculated based on the average brightness or average density of the patch of each gradation in each evaluation chart, and the density gradation conversion table is updated based on the coefficient of density gradation conversion. It is said.
However, even in the configuration disclosed in Patent Document 1, if cockling occurs in the sheet from which the evaluation chart is output, the problem that the density of the image cannot be read correctly remains unsolved.

Therefore, an object of the present invention is to provide an inkjet printing machine capable of preventing the occurrence of cockling and correctly reading the density of an image.

The present invention described in claim 1 for solving the above problems is a first method of forming an image of a first test chart on a print medium in an inkjet printing machine that forms an image on a print medium by an ink jet head. Based on the test chart forming means of the above and the image of the first test chart formed on the printing medium, the ink adhesion reducing means for reducing the ink adhesion to the printing medium and the reduced ink adhesion. On the print medium, based on the second test chart forming means for forming the image of the second test chart on the print medium and the image of the second test chart formed on the print medium in quantity. It has an image density correction means for correcting the image density formed in.

According to the present invention, it is possible to prevent the occurrence of cockling and correctly read the density of the image.

It is a front view which shows the schematic structure of the whole inkjet printing machine which concerns on one Embodiment of this invention. It is a partially enlarged front view which shows the printing mechanism, the drying mechanism and the image inspection mechanism which form a part of the above-mentioned inkjet printing machine in an enlarged manner. It is a block diagram which shows the structure which connected the unwinder, the same inkjet continuous book machine main body, the separate continuous book machine main body, and a rewinder. (A) is a block diagram showing the electrical configuration of the control device of the above-mentioned inkjet printing machine, and (b) is a block diagram showing the functions of the control device. It is a flowchart which shows the conventional general uniformity adjustment. It is a gradation chart diagram which shows an example of a uniformity adjustment chart, (a) is a uniformity adjustment chart (input data), (b) is a print result of a uniformity adjustment chart, and (c) is a gradation correction. It is a print result after performing. It is a flowchart when the uniformity adjustment is performed after reducing the amount of ink adhering so that cock ring does not occur. (A) is an explanatory diagram showing an example of a test chart, and (b) is an explanatory diagram showing an example of a cockling test chart in which the amount of ink adhered is reduced. It is explanatory drawing which shows another example of a cock ring test chart. It is a flowchart when the uniformity adjustment is performed after reducing the adhesion amount of ink which does not generate cock ring by using the cock ring test chart shown in FIG. It is a flowchart when the operator makes a cockling judgment. It is a block diagram of the printing mechanism which concerns on another example.

The inkjet printing machine according to the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing a schematic configuration of an entire inkjet printing machine according to an embodiment of the present invention, and FIG. 2 shows a printing mechanism, a drying mechanism, and a drying mechanism that form a part of the inkjet printing machine according to an embodiment of the present invention. It is a partially enlarged front view which shows the image inspection mechanism enlarged. In the following, an inkjet continuous book machine will be described as an example of the inkjet printing machine.

As shown in FIG. 1, the inkjet continuous book machine A includes an unwinder 5, a continuous book machine main body 10, a continuous book machine main body 11 (not shown), and a rewinder 15.
The unwinder 5 unwinds the print medium (hereinafter, referred to as “paper”) P from the roll paper 6.
A first transfer mechanism 20, a printing mechanism 30, a drying mechanism 40, an image inspection mechanism 50, a reversing mechanism 60, and a second transfer mechanism 70 are arranged along a transfer path of paper P in the continuous book machine main body 10. It has a set structure.

The first transport mechanism 20 transports the paper P sent out from the unwinder 5, and specifically has the following configuration.
That is, the first transport mechanism 20 mainly includes a regulation guide 21, an in-feed unit 22, a dancer roller 23, an EPC (Edge Position Control) 24, a meandering amount detector 25, and the like.
The regulation guide 21 positions the paper P sent out from the unwinder 5 in the width direction, and the in-feed unit 22 is for keeping the tension of the paper P to be conveyed constant. Further, the dancer roller 23 outputs a position signal while moving up and down according to the tension of the paper P.
The EPC 24 controls the meandering of the paper P, and the meandering amount detector 25 has a function of feeding back the meandering amount. In addition, what is indicated by reference numeral 26 is a driven roller, a driving roller, or the like that stretches and forms a transport path for paper P.

The printing mechanism 30 prints on the surface (first surface) of the paper P unwound from the unwinder 5.
A head unit H composed of a single-pass type inkjet line head is installed in the printing mechanism 30. In this head unit H, the basic colors of black (K), cyan (C), magenta (M), and yellow (Y), the special colors orange and green, and the overcoat that imparts gloss and other treatments. The droplets are ejected to form an image on the paper P.
A coating mechanism may be provided in front of the printing mechanism 30 to apply, for example, a treatment liquid that controls the permeability of the ink to the recording surface of the paper P.

Since the head unit H needs to have a size equal to or larger than the paper width, it is often configured by connecting a plurality of heads H1 to H5. The individual heads H1 to H5 and nozzles have variations such as ejection characteristics, and the print density varies between the heads H1 to H5 and within each of these heads H1 to H5. Therefore, uniformity. Adjustment is needed.
The head unit H shown in the present embodiment can be retracted from the transport path of the paper P. This makes it possible to perform maintenance operations such as cleaning the nozzle surface and ejecting thickened ink.

The drying mechanism 40 dries the surface (first surface) of the paper P printed by the printing mechanism 30.
The drying mechanism 40 shown in the present embodiment employs a heat drum 41 that performs contact heating from the back surface of the above-mentioned paper P. The temperature of the heat drum 41 is set to about 50 to 100 ° C., although it depends on the printing speed and the drying property of the ink.
In the present embodiment, the heat drum 41 is described as an example, but other heating sources such as warm air, infrared rays, pressurization, and ultraviolet rays may be used, and these heating sources may be appropriately combined. You may use it.

The image inspection mechanism 50 performs inspection for detecting cockling and adjusting uniformity, and includes a device such as a scanner that reads an image. That is, an image is read for cock ring detection and uniformity adjustment, and the read image is processed by the control device C connected to the continuous book machine A.
As the reading device used in the image inspection mechanism 50, a CIS scanner is often used because it is necessary to read a large area and the cost is high.

The reversing mechanism 60 reverses the front and back sides of the above-mentioned paper P.
The second transfer mechanism 70 has an outfeed unit 71 that rotates at a constant speed to convey the paper P at a set speed, a puller 72 for discharging the paper P to the outside of the continuous book machine A, and the like. It is configured.
The continuous book machine main body 11 is arranged between the continuous book machine main body 10 and the rewinder 15 having the above-described configuration, and a schematic configuration thereof is shown in FIG.
The rewinder 15 winds up and collects the paper P discharged from the second transport mechanism 70. That is, the continuous paper P is unwound from the unwinder 5 at a high speed, wound up by the rewinder 15, and collected.

FIG. 3 is a block diagram showing a state in which the unwinder, the continuous book machine main body, the separate continuous book machine main body, and the rewinder are connected. In FIG. 3, the first transport mechanism 20 and the second transport mechanism 70 are not shown.
In the above-mentioned continuous book machine main body 11, a printing mechanism 30, a first conveying mechanism 20, a drying mechanism 40, an image inspection mechanism 50, and a second, which are equivalent to those arranged in the continuous book machine main body 10. Although the transport mechanism 70 is arranged, it differs in that the above-mentioned reversing mechanism 60 is not provided. With this configuration, the back surface (second surface) of the paper P is processed.

Next, the operation of the inkjet continuous book machine A having the above configuration will be described.
In the above-mentioned inkjet continuous book machine A, the paper P is unwound by the unwinder 5 and reaches the printing mechanism 30 in the continuous book machine main body 10 that prints the front surface (first surface).
After the surface of the paper P that has passed through the printing mechanism 30 is dried by the drying mechanism 40, the image inspection mechanism 50 inspects the paper P for cockling detection and uniformity adjustment.
The inspected paper P is turned upside down by the reversing mechanism 60 and then delivered to the continuous book machine main body 11.
Then, after the backside cockling is detected and the uniformity is adjusted by the printing mechanism 30 for printing the back surface (second surface) in the continuous book machine main body 11, the drying mechanism 40 for drying the back surface, and the image inspection mechanism 50. The paper P on which the printed image is formed is wound up by the rewinder 15.
Depending on the content of the processing after printing, the paper may be cut using a cutter instead of the rewinder.

A control device C, which is a control center of the continuous book machine A, is connected to the unwinder 5, the continuous book machine main body 10, the continuous book machine main body 11, and the rewinder 15 described above. FIG. 4A is a block diagram showing the electrical configuration of the continuous book machine A, and FIG. 4B is a block diagram showing the functions of the control device C.

The control device C has a CPU (Central Processing Unit) Ca, which is the control center of the continuous book machine A, and a memory Cb in which required programs, data tables, etc. are stored, via an interface circuit (not shown). , The above-mentioned unwinder 5, continuous book machine main body 10, continuous book machine main body 11, and rewinder 15 are connected.

The control device C described above exhibits the following functions by executing a required program.
-A function to form the first test chart on paper P. This function is referred to as "first test chart forming means C1".
The “first test chart” is indicated by reference numeral T1 in FIG. 8A, which will be described later.
-A function of reducing the amount of ink adhering to the paper (printing medium) P based on the image of the first test chart formed on the paper P. This function is referred to as "ink adhesion reducing means C2".
In this example, a function for determining the presence or absence of a cock ring (this function is referred to as "cock ring determination means C3") and a function for reducing the amount of ink adhered to the paper P when it is determined that there is a cock ring. (This function is referred to as "ink adhesion reducing means C4").
-A function of forming an image of a second test chart on paper P with a reduced amount of ink adhered. This function is referred to as "second test chart forming means C5".
The “second test chart” is indicated by reference numeral T2 in FIG. 8 (b) described later.
-A function of correcting the image density formed on the paper P based on the image of the second test chart formed on the paper P. This function is called "image density correction means C6".
The details of each of the above-mentioned functions will be described in detail below.

Here, the contents of the conventional general uniformity adjustment will be described. FIG. 5 is a flowchart showing a conventional general uniformity adjustment.
When the operator gives an instruction to start adjustment, the process proceeds to step 1.
Step 1 (Abbreviated as "Sa1" in the figure. The same shall apply hereinafter.): A state in which the uniformity adjustment chart for grasping the gradation-density characteristics of individual heads H1 to 5 and nozzles is loaded with ink to the maximum. Is printed on paper P.

Step 2: The printed uniformity adjustment chart is read by a reading device (not shown) such as a scanner of the image inspection mechanism 50 described above, and the reading information is passed to the control device C connected to the continuous book machine A.
Step 3: The read data is often in RGB format, which is converted to density data.
Step 4: The above data conversion is carried out for the entire print width, and the gradation-density characteristic for each print position is calculated.
Step 5: Based on the gradation-density characteristic for each printing position, a correction value that can achieve the target density at each gradation is calculated for each printing position. That is, in the test chart, the portion having a low density is shifted to a higher gradation, and the portion having a low density is shifted to a lower gradation.

In step 3, the RGB obtained by reading the uniformity adjustment chart is converted into density, but it may be converted into color information in another format such as L ^* a ^* b ^*. , RGB may be used for analysis. Further, although an example of correcting the gradation in order to make the in-plane uniform is given, the dot diameter may be controlled by changing the head drive voltage.

FIG. 6 is a gradation chart showing an example of a uniformity adjustment chart, (a) is a uniformity adjustment chart (input data), (b) is a print result of the uniformity adjustment chart, and (c) is a print result of the uniformity adjustment chart. , It is a print result after performing gradation correction. The horizontal axis direction indicates the arrangement direction of the head modules, and the vertical axis direction indicates the paper transport direction.

The gradation-density characteristics differ for each head and nozzle, and are often not linear for the entire gradation region. Therefore, it is necessary to print the uniformity adjustment chart with the full width of the head module and acquire data for a plurality of gradations. Generally, any image can be handled by setting adjustment points in about 10% steps.

In FIG. 3B, the reference numerals H1 to H5 correspond to the print areas of the heads H1 to H5, respectively. As is clear from FIG. 3B, since the gradation-density characteristics of the individual heads H1 to H5 vary, even if a uniform chart as shown in FIG. In the above figure, uneven shading occurs as shown in FIG. Therefore, the uniformity is adjusted and corrected.

As shown in FIG. 3B, in the example in which the density unevenness occurs, when the density of the head H1 is targeted, the gradation correction is performed so that the density of the heads H2 and H4 is lowered. The in-plane density becomes uniform. Gradation correction is performed so that the density of the heads H1, H3 and H5 is increased by setting the target to the density of the head H2, or the target density is set to the average value of the concentrations of the heads H1 to H5 and the gradation is applied to all the heads H1 to H5. A method of correction is also conceivable.
As shown in FIG. 3C, by performing the gradation correction as described above, it is possible to obtain a uniform output image with respect to the arrangement direction of the heads H1 to H5.

FIG. 7 is a flowchart when adjusting the uniformity after reducing the amount of ink adhering to which cock ring does not occur. 8 (a) is an explanatory diagram showing an example of a cock ring test chart, and FIG. 8 (b) is an explanatory diagram showing an example of a cock ring test chart in which the amount of ink adhered is reduced.

In the uniformity adjustment, the correction value is determined based on the result of printing and scanning the test chart. In other words, if you can't scan correctly, you can't make correct corrections.
Cock ring is one of the causes that cannot be scanned correctly. Cockling is often a problem in inkjet printing machines that use water-based inks, and is a phenomenon in which the paper undulates as the ink penetrates the paper.

If the amount of ink adhered to the uniformity adjustment chart is too large, the paper P will undulate due to the cock ring, and the distance from the scanner will not be kept uniform. In particular, in a CIS scanner with a shallow depth of field, the floating portion of the paper becomes darker than it actually is. Therefore, there arises a problem that an inaccurate correction value is calculated.

Therefore, the amount of ink that causes cockling is determined in advance, and the uniformity is adjusted in the area of the amount of ink that is less than the amount of adhesion.
The area where cockling occurs is also not used when printing the actual job. This is because the cockling causes the paper to undulate during job printing, which deteriorates the quality of the printed matter and also causes the paper to come into contact with the head and cause damage. Therefore, there is no problem even if the adhesion amount is reduced and the uniformity is adjusted.

The image density correction program used in the inkjet continuous book machine A has the following steps.
A first test chart forming step of forming an image of the first test chart on paper P.
-Ink adhesion reduction step of reducing the ink adhesion amount to the paper P based on the image of the first test chart formed on the paper P.
A second test chart forming step of forming an image of the second test chart on the paper P with a reduced amount of ink adhered.
An image density correction step of correcting the image density formed on the paper P based on the image of the second test chart formed on the paper P.

The image density correction method for correcting the image density formed on the paper P by the inkjet head H is as follows.
That is, an image of the first test chart is formed on the paper P, and the amount of ink adhered to the paper P is reduced based on the image of the first test chart formed on the paper P to reduce the ink. An image of the second test chart is formed on the paper P with the amount of adhesion, and the image density formed on the paper P is corrected based on the image of the second test chart formed on the paper P. Is the content.

The details of the processing contents will be described with reference to the flowchart shown in FIG.
When the operator gives an instruction to start adjustment, the process proceeds to step 1.
Step 1 (abbreviated as "Sb1" in the figure. The same shall apply hereinafter): The cockling test chart T1 shown in FIG. 8A is printed. In the present embodiment, the cockling test chart T1 shown in FIG. 8A is the first test chart.
The cockling test chart T1 printed first has an arbitrary pattern of the maximum amount of ink adhered. Since the cock ring tends to occur in a pattern in which the printed portion and the margin portion appear alternately, the pattern as shown in FIG. 8A is preferable.

Step 2: The cockling test chart T1 printed on the paper P is scanned by the image inspection mechanism 50, and the process proceeds to step 3.
Step 3: Based on the image of the cock ring test chart T1, the presence or absence of the cock ring is determined, and if it is determined that the cock ring is present, the process proceeds to step 4, and if it is determined that there is no cock ring, the process proceeds to step 5.
When cockling occurs, the scan result is such that the density changes in the head at a cycle of several mm pitch. In this way, the presence or absence of cockling can be determined by scanning the image and analyzing the state of density fluctuation.

Step 4: The process of reducing the amount of ink adhered is performed, and the process returns to step 1.
That is, as shown in FIG. 8B, the amount of ink adhered to the cockling test chart T2 is reduced, and the cockling test chart is printed again.
In the present embodiment, steps 1 to 4 are steps for reducing the amount of ink adhered to the paper P based on the image of the first test chart T1 formed on the paper P. There is. The cockling test chart T2 is the second test chart.
Step 5: Since cockling has not occurred, printing the uniformity adjustment chart is executed.
Step 6: Perform uniformity adjustment.
As described in detail above, the uniformity adjustment chart is such that when the presence or absence of the cock ring and the adjustment of the ink adhesion amount are repeated and the ink adhesion amount at which the cock ring does not occur is obtained, the adhesion amount becomes the maximum value. Is printed and adjustments are made.

FIG. 9 is an explanatory diagram showing another example of the cockling test chart, and FIG. 10 is a flowchart when the cockling test chart shown in FIG. 9 is used.
In the above example, the cockling test chart for one gradation was processed in the order of printing, judgment, and adjustment of the amount of ink adhered. However, in the case of the continuous book machine A having a long overall length, if the printing operation is repeated, the paper is damaged. The amount of ink will increase. Therefore, as shown in FIG. 9, the cockling test chart T1'with two gradations may be used.
The cockling test chart T1'is not limited to two gradations, and may have more gradations.

The uniformity adjustment using the cockling test chart shown in FIG. 9 will be described with reference to FIG. FIG. 10 is a flowchart when adjusting the uniformity after reducing the amount of ink adhering to which cock ring does not occur.
When the operator gives an adjustment instruction, the process proceeds to step 1.
Step 1 (Abbreviated as "Sc1" in the figure. The same shall apply hereinafter): A cockling test chart in which gradations are different from 100% as shown in FIG. 9 is printed by one printing operation.
The cock ring test chart is scanned in order to inspect the cock ring.
Step 2: Perform a cockling inspection.
Step 3: Detect the amount of ink that does not cause cockling.
Step 4: The uniformity adjustment chart is printed with the amount of ink adhered so that cock ring does not occur.
Step 5: Perform uniformity adjustment.

FIG. 11 is a flowchart when the operator determines the cock ring.
When the operator gives an adjustment instruction, the process proceeds to step 1.
Step 1 (Abbreviated as "Sd1" in the figure. The same shall apply hereinafter): A cockling test chart is printed.
Step 2: Perform a cockling inspection by the operator.
An erroneous determination of the cock ring is considered to be the cause of the uniformity adjustment being performed with an ink adhesion amount lower than expected. If the density unevenness in the head is severe or if it cannot be separated from the cock ring cycle, it may not be possible to make a correct judgment. In such a case, the operator determines the cock ring.
Step 3: The operator inputs and sets the amount of ink that does not cause cockling.
Step 4: Print the uniformity adjustment chart.
Step 5: Perform uniformity adjustment.

FIG. 12 is a block diagram of a printing mechanism according to another example. In addition, in FIG. 12, the same reference numerals as those described in FIG. 2 above are designated by the same reference numerals, and the description thereof will be omitted.
The printing mechanism 30A according to another example includes a detection sensor 31 for determining the presence or absence of cock ring, and in the present embodiment, the detection sensor 31 is used in the transport direction of the paper P of the image inspection mechanism 50. It is located near the upstream side. In this case, the cockling determining means determines the amount of ink adhering to which the cockling does not occur, based on the detection result of the detection sensor 31.

Judging from the scanned image of the cock ring, it may be erroneously judged as described above. Therefore, a method of directly observing the mutation of the paper P and determining the cockling can be considered. The detection sensor 31 shown in FIG. 12 is a laser displacement meter capable of detecting the waviness of the paper P. As a result, it is possible to detect the presence or absence of the cock ring and control the amount of ink adhered to the uniformity adjustment chart. Although a laser displacement meter has been exemplified as the detection sensor 31, the present invention is not limited to this.

In the above-described embodiment, an example of executing the program by the control device of the printing press A has been described, but the program is executed by a digital front end (DFE) (not shown) connected to the printing press A by a LAN cable. May be good. The digital front end (DFE) has a function of generating a raster image date (Raster data corresponding to a printing machine).
Further, in the above-described embodiment, paper has been described as an example of the printing medium, but it goes without saying that the present invention can be applied as long as it is affected by ink and undulates in addition to paper.

5 Unwinder 10 Continuously booked machine main body 11 Continuously booked machine main body 15 Rewinder 20 Conveyance mechanism 21 Regulation guide 23 Dancer roller 30 Printing mechanism 30A Printing mechanism 31 Detection sensor 40 Drying mechanism 41 Heat drum 50 Image inspection mechanism 60 Inversion mechanism 70 Conveyance mechanism 71 Out Feed section A Inkjet continuous book machine (inkjet printing machine)
C Control device Cb Memory H Head unit H1-5 Inkjet head P Paper (printing medium)

Japanese Unexamined Patent Publication No. 2011-199409

Claims (5)

In an inkjet printing machine that forms an image on a printing medium with an inkjet head.
A first test chart forming means for forming an image of a first test chart having a pattern in which print portions and margin portions alternate on the print medium.
Based on the image of the first test chart formed on the print medium, the ink adhesion amount reducing means for reducing the ink adhesion amount to the print medium and the ink adhesion amount reducing means.
A second test chart forming means for forming an image of the second test chart on the print medium with the reduced ink adhesion amount,
An inkjet printing machine comprising: an image density correction means for correcting an image density formed on the print medium based on an image of a second test chart formed on the print medium. It has a cock ring determination means for determining the presence or absence of a cock ring based on the image of the first test chart formed on the print medium.
The inkjet printing machine according to claim 1, wherein the cock ring determination means determines cock rings based on a first test chart composed of a plurality of gradations. A detection sensor that detects the waviness of the print medium is provided.
The inkjet printing machine according to claim 2, wherein the cockling determining means determines an amount of ink adhering to which cockling does not occur based on the detection result of the detection sensor. In an image density correction program used in an inkjet recorder that forms an image on a print medium with an inkjet head.
A first test chart forming step of forming an image of a first test chart of a pattern in which a printing portion and a margin portion alternate on the printing medium on a computer.
Based on the image of the first test chart formed on the print medium, the ink adhesion reduction step for reducing the ink adhesion amount to the print medium and the ink adhesion reduction step.
A second test chart forming step of forming an image of the second test chart on the print medium with the reduced ink adhesion amount.
An image density correction program comprising executing an image density correction step of correcting an image density formed on the print medium based on an image of a second test chart formed on the print medium. In an image density correction method for correcting the image density formed on a print medium by an inkjet head,
An image of the first test chart having a pattern in which the print portion and the margin portion alternate is formed on the print medium.
Based on the image of the first test chart formed on the print medium, the amount of ink adhered to the print medium is reduced.
With the reduced amount of ink adhered, an image of a second test chart is formed on the print medium.
An image density correction method characterized in that the image density formed on the print medium is corrected based on the image of the second test chart formed on the print medium.