JP2022115165A - Density correction profile generation device - Google Patents

Abstract

To provide a density correction profile generation device which can generate a density correction profile that is not affected by wind ripple.SOLUTION: A density correction profile generation device comprises: an adjustment pattern acquisition unit 61 which acquires image data obtained by reading an adjustment pattern printed while relatively moving an ink jet head in which a plurality of nozzles are arrayed in the main-scanning direction in the sub-scanning direction orthogonal to the main-scanning direction with respect to a printing medium; a density profile acquisition unit 62 which acquires a density profile on the basis of image data acquired by the adjustment pattern acquisition unit 61; and a density correction profile generation unit 63 which removes a frequency component corresponding to wind ripple from the density profile and generates a density correction profile for correcting the density unevenness on the basis of the density profile from which the frequency component has been removed.SELECTED DRAWING: Figure 3

Description

The present invention relates to a density correction profile generating apparatus for generating a density correction profile for correcting density unevenness of an inkjet head.

2. Description of the Related Art Conventionally, there has been proposed an inkjet printing apparatus that performs print processing by ejecting ink from an inkjet head having a plurality of nozzles for ejecting ink onto a print medium transported on a transport path.

In such an inkjet printing apparatus, density unevenness occurs due to variations in the amount of ink ejected from each nozzle of the inkjet head.

Therefore, a solid image is printed by ejecting ink from all the nozzles of the inkjet head, a density profile is obtained from the image data obtained by reading the solid image with a scanner or the like, and density unevenness is corrected using the density profile. A method has been proposed (see Patent Document 1, for example).

JP 2013-115762 A

Here, in the inkjet printing apparatus described above, an air current is generated by conveying the print medium directly under the inkjet head.

Further, when ink is continuously ejected from the nozzles of the inkjet head, the ink droplets are ejected along with the self-airflow, and the self-airflow acts like a wall blocking the airflow caused by the transportation of the printing medium. Then, the airflow generated by the transportation of the print medium collides with the wall of the self-airflow, and the airflow may be complicatedly disturbed. Due to this turbulent air flow, the landing position of the ink ejected from the inkjet head may deviate from the desired position.

Therefore, in Japanese Patent Laid-Open No. 2002-200001, a solid image is used as a measurement chart for correcting the density unevenness of the inkjet head, but wind pattern unevenness may occur when printing this measurement chart. FIG. 9A is a schematic diagram of an example of a solid image with uneven wind ripples, and FIG. 9B is a diagram showing a density profile affected by the uneven wind ripples generated from the solid image shown in FIG. 9A.

However, when a desired print is actually printed, it is not always the case that the same unevenness in wind ripples occurs when the chart for measurement is printed. If density unevenness correction is performed using a measurement chart including wind pattern unevenness as shown in FIG. 9A in areas where continuous ejection is not performed, density unevenness will occur. The reason why uneven wind patterns are less likely to occur in low-density areas is that airflow due to ink ejection is less likely to occur. In high-density areas, the amount of ink ejected is large, so density unevenness due to uneven wind patterns is not noticeable due to dot gain. It is from

SUMMARY OF THE INVENTION It is an object of the present invention to provide a density correction profile generating apparatus capable of generating a density correction profile that is not affected by the above-described wind ripple unevenness.

The density correction profile generating apparatus of the present invention performs printing while relatively moving an inkjet head, in which a plurality of nozzles are arranged in the main scanning direction, in the sub-scanning direction perpendicular to the main scanning direction with respect to the printing medium. An adjustment pattern acquisition unit that acquires image data obtained by reading a pattern; a density profile acquisition unit that acquires a density profile based on the image data acquired by the adjustment pattern acquisition unit; and a density correction profile generation unit that removes the frequency component that causes the noise and generates a density correction profile for correcting density unevenness based on the density profile from which the frequency component has been removed.

According to the density correction profile generating apparatus of the present invention, the density profile is obtained based on the image data of the adjustment pattern, the frequency component corresponding to the uneven wind pattern is removed from the density profile, and the frequency component is removed. Since the density correction profile for correcting the density unevenness is generated based on the density profile, it is possible to generate the density correction profile that is not affected by the wind pattern unevenness.

1 is a diagram showing a schematic configuration of an inkjet printing apparatus using an embodiment of a density correction profile generating apparatus of the present invention; FIG. top view of head unit FIG. 2 is a block diagram showing a schematic configuration of a control system of the inkjet printing apparatus shown in FIG. 1; A diagram showing an example of an adjustment pattern A diagram showing an example of an adjustment pattern, a density profile, and a density correction profile that are not affected by wind ripple unevenness. A diagram showing an example of divided regions 4 is a flow chart for explaining an embodiment of a density correction profile generation method of the present invention; A diagram showing an example of the density profile of the divided regions R1 to R3 obtained based on the image data generating wind ripple unevenness as shown in FIG. A diagram showing an example of a solid image with uneven wind ripples and a density profile affected by uneven wind ripples.

Hereinafter, an inkjet printing apparatus using an embodiment of the density correction profile generating apparatus of the present invention will be described in detail with reference to the drawings. The inkjet printing apparatus of this embodiment is characterized by a method of generating a density correction profile for correcting density unevenness of the inkjet head. First, the overall configuration will be described. FIG. 1 is a diagram showing a schematic configuration of an inkjet printing apparatus 1 of this embodiment. Note that the up, down, left, and right directions shown in FIG. 1 are the up, down, left, and right directions of the inkjet printer 1 of the present embodiment. Further, the front side of the paper surface of FIG. 1 is the front direction, the back side of the paper surface is the rear direction, the front-back direction is the main scanning direction described later, and the horizontal direction is the sub-scanning direction described later.

As shown in FIG. 1, the inkjet printing apparatus 1 of the present embodiment includes a side paper feeding unit 10, an internal paper feeding unit 20, a print processing unit 30, a paper discharging unit 40, a reversing unit 50, and a control unit. 60 , an operation panel 70 and a reading unit 80 .

The print processing unit 30, the internal paper feeding unit 20, and the control unit 60 are housed and installed in a housing made of metal, resin, or the like. Further, the side paper feeding unit 10, the paper discharging unit 40, and the reversing unit 50 are installed in a state in which a part thereof is housed inside the housing and a part thereof protrudes outside the housing.

The side paper feed unit 10 includes a paper feed table 11 on which the print medium P is placed, and a primary paper feed unit that feeds out only the uppermost print medium P from the paper feed table 11 and conveys it onto the paper feed transport path FR. 12, and a secondary paper feeder 14 for transporting the print medium P transported by the primary paper feeder 12 onto the circulation transport path CR.

The internal paper feed unit 20 includes a paper feed table 21a on which the print medium P is placed, and a primary paper feed unit that feeds out only the uppermost print medium P from the paper feed table 21a and conveys it onto the paper feed transport path FR. 22a, a paper feed table 21b on which the print medium P is placed, a primary paper feed unit 22b that feeds out only the uppermost print medium P from the paper feed table 21b and conveys it onto the paper feed transport path FR, and a printing A paper feed table 21c on which the medium P is placed, a primary paper feed section 22c that feeds out only the uppermost print medium P from the paper feed table 21c and conveys it onto the paper feed transport path FR, and the print medium P is placed. and a primary paper feed section 22d that feeds out only the uppermost print medium P from the paper feed table 21d and conveys it onto the paper feed transport path FR.

In this manner, the printing medium P is conveyed to the secondary paper feeding section 14 from the side paper feeding section 10 or the internal paper feeding section 20, and the printing medium P is further conveyed from the reversing section 50, which will be described later.

Therefore, in front of the secondary paper feeder 14 in the transport direction, there are a transport path for the print medium P fed from the internal paper feeder 20 and a print medium P transported from the reversing unit 50 and having one surface printed thereon. There is a confluence point where the transport route of Based on this confluence point, the route on the side of the paper feed mechanism is called the paper feed transport route FR, and the other routes are called the circulatory transport route CR.

The print processing section 30 includes a head unit 31 and an annular conveying belt 133 provided facing the head unit 31 .

The conveying belt 133 is formed from an annular endless belt and has a large number of suction holes. The print medium P fed from the secondary paper feeding unit 14 is conveyed to the annular conveying belt 133 . The print medium P is sucked onto the conveying belt 133 by suction fans 131 and 132 installed on the back side of the conveying road surface of the conveying belt 133, and is conveyed at a predetermined conveying speed. While the print medium P is being transported by the transport belt 133, ink is ejected from the head unit 31 onto the print medium P, whereby the print medium P is subjected to print processing.

The head unit 31 includes four line heads 32a, 32b, 32c and 32d and a head holder 33 in which the four line heads 32a, 32b, 32c and 32d are installed. Each of the line heads 32 a to 32 d extends in a direction orthogonal to the transport direction of the print medium P, and ejects ink onto the print medium P transported by the transport belt 133 . The four line heads 32a to 32d are arranged at predetermined intervals along the transport path of the print medium P, as shown in FIG. The four line heads 32a to 32d eject inks of different colors (eg, black, cyan, magenta and yellow).

The head holder 33 is a member on which the inkjet heads 34 of the line heads 32a to 32d are installed. FIG. 2 is a top view showing a state in which the inkjet heads 34 of the line heads 32a to 32d are installed in the head holder 33. As shown in FIG.

The head holder 33 is composed of a box-shaped support member, and a plurality of installation holes are formed in the bottom surface of the head holder 33, into which the inkjet heads 34 are fitted and installed. The installation holes are through holes, and are formed so that the ink ejection surface of each inkjet head 34 is exposed to the outside of the bottom surface of the head holder 33 .

The dotted squares shown in FIG. 2 indicate the arrangement range of the six inkjet heads 34 of each of the line heads 32a to 32d.

Each of the line heads 32a to 32d, as shown in FIG. 2, has two rows of heads in which three inkjet heads 34 are arranged at equal intervals in a direction (main scanning direction) orthogonal to the transport direction of the print medium P. , are arranged in a staggered manner so that the two head rows overlap by a predetermined number of nozzles.

The print medium P printed by the print processing section 30 is transported on the circulation path CR by transport rollers or the like arranged on the circulation path CR. A switching mechanism 43 is provided on the circulation path CR to switch between guiding the print medium P transported on the circulation path CR to the paper discharge section 40 and recirculating it on the circulation path CR. there is Specifically, the switching mechanism 43 switches between the transport path on the paper discharge unit 40 side and the transport path on the reversing unit 50 side.

The paper discharge unit 40 includes a tray-shaped paper discharge table 41 protruding from the housing of the inkjet printing apparatus 1 and a pair of paper discharge rollers 42 for discharging the print medium P onto the paper discharge table 41 . Then, the print medium P guided by the switching mechanism 43 to the transport path on the side of the paper discharge unit 40 is discharged to the paper discharge table 41 by the paper discharge rollers 42 .

The reversing unit 50 has a reversing table 51 for reversing the print medium P, and transports the print medium P from the circulation conveying path CR to the reversing table 51, and transfers the printing medium P conveyed to the reversing table 51 onto the circulation conveying path CR. and a reversing roller 52 for returning to the original position.

The print medium P guided to the reversing section 50 by the switching mechanism 43 is transported from the circulating transport path CR to the reversing table 51 by the reversing rollers 52, and returned from the reversing table 51 to the circulating transport path CR, thereby being reversed. It is conveyed on the circulating conveying path CR in this state. Then, the print medium P whose front and back sides are reversed is transported again toward the print processing section 30 by a plurality of rollers such as the transport rollers 53 provided on the circulation transport path CR.

The operation panel 70 is composed of a touch panel having a liquid crystal display, displays various setting input screens, and accepts various setting inputs such as an instruction input to start printing.

The reading unit 80 is installed on a housing housing the print processing unit 30 and the like, and acquires image data by photoelectrically reading a document image. Image data acquired by the reading unit 80 is output to the control unit 60 . In particular, the reading unit 80 of this embodiment reads an adjustment pattern, which will be described later, and outputs the image data to the control unit 60 .

FIG. 3 is a block diagram showing a schematic configuration of the control system of the inkjet printer 1 of this embodiment.

The control unit 60 controls the entire inkjet printing apparatus 1, and includes a CPU (Central Processing Unit), a semiconductor memory, a hard disk, and the like. The control unit 60 executes a program pre-stored in a storage medium such as a semiconductor memory or a hard disk, and operates an electric circuit to control the operation of each unit of the inkjet printer 1 .

The control unit 60 also communicates with the control unit 90 of the print job output device 2 and receives print jobs output from the control unit 90 . Then, the control unit 60 controls the head unit 31 of the print processing unit 30 based on the print image data to be printed included in the input print job. apply.

Specifically, as shown in FIG. 3, the control unit 60 includes an adjustment pattern acquisition unit 61, a density profile acquisition unit 62, a density correction profile generation unit 63, a density correction profile storage unit 64, a density correction and a processing unit 65 .

The adjustment pattern acquisition unit 61 acquires image data of an adjustment pattern for correcting density unevenness caused by differences in the amount of ink ejected from each nozzle of the inkjet head 34 . In this embodiment, image data of a so-called solid image with uniform density is acquired as the image data of the adjustment pattern. The adjustment pattern is printed in advance by the inkjet printing apparatus 1, and the printed adjustment pattern is read by the reading unit 80, whereby the adjustment pattern acquisition unit 61 acquires the image data of the adjustment pattern. be done. The print image data representing the adjustment pattern used when printing the adjustment pattern described above may be stored in advance in the inkjet printing apparatus 1, or may be sent from the print job output apparatus 2 to the inkjet printing apparatus. 1 may be output.

FIG. 4 is a diagram showing an example of an adjustment pattern. The adjustment patterns shown in FIG. 4 are composed of a K adjustment pattern Pk, a C adjustment pattern Pc, an M adjustment pattern Pm, and a Y adjustment pattern Py. One rectangular pattern Pk1 shown in FIG. 4 is an adjustment pattern printed by one K inkjet head 34 . The length of the rectangular pattern Pk1 in the sub-scanning direction can be, for example, 2 cm to 3 cm, but is not limited to this.

In the present embodiment, as described above, each line head 32a to 32d has six inkjet heads 34 arranged in the main scanning direction. are placed in The configuration of the C adjustment pattern Pc, the M adjustment pattern Pm, and the Y adjustment pattern Py is the same.

The adjustment pattern acquisition unit 61 of the present embodiment acquires image data of adjustment patterns for each of the inkjet heads 34 of the line heads 32a to 32d. That is, image data of a rectangular pattern Pk1 is obtained for one K inkjet head 34, for example. For the other inkjet heads 34 , similarly, image data of rectangular patterns are acquired for each inkjet head 34 . That is, the image data of the adjustment pattern for each inkjet head 34 is obtained.

The density profile acquisition unit 62 acquires a density profile for each inkjet head 34 based on the image data of the adjustment pattern for each inkjet head 34 acquired by the adjustment pattern acquisition unit 61 .

Here, the density profile for each inkjet head 34 will be described. The density profile represents the density distribution for each nozzle of the inkjet head 34, and is used when generating a density correction profile, which will be described later. 5A is an example of image data of one rectangular pattern obtained for one inkjet head 34, FIG. 5B is a density profile obtained from the image data of the rectangular pattern shown in FIG. 5A, and FIG. 5B is a density correction profile generated from the density profile shown in FIG. 5B. It should be noted that the rectangular pattern shown in FIG. 5A is assumed to be unaffected by the above-described wind ripple unevenness for the sake of easy understanding.

The rectangular pattern image data shown in FIG. 5A is a set of line patterns L that are printed by the nozzles of the inkjet head 34 and extend in the sub-scanning direction. Therefore, the density profile acquisition unit 62 acquires the density profile shown in FIG. 5B by calculating the average density of the line pattern L corresponding to each nozzle of the inkjet head 34 shown in FIG. 5A.

The density correction profile shown in FIG. 5C is generated so that the average density of each nozzle becomes the same by canceling the variation in the average density of each nozzle shown in FIG. 5B. Specifically, the density correction profile is generated by obtaining a density correction coefficient for the target density of each nozzle based on the density profile. A method of generating the density correction profile will be described in detail later.

When generating the density profile for each inkjet head 34 as described above, the density profile acquisition unit 62 of the present embodiment acquires image data of one rectangular pattern corresponding to one inkjet head 34 in the sub-scanning direction. The image is divided into a plurality of divided areas, and a density profile is generated for each divided area based on the image data for each divided area.

Specifically, the density profile acquisition unit 62 of this embodiment divides the rectangular pattern image data into three divided areas R1, R2 and R3 as shown in FIG. Get each profile.

The reason why the three density profiles at different positions in the sub-scanning direction are obtained in this way is that when printing a rectangular pattern, the self-airflow caused by the ink droplets is not so strong at the beginning of the printing process, and the print medium This is because, as the printing process progresses, the self-airflow caused by the ink droplets becomes stronger, and the manner in which the wind pattern unevenness occurs changes depending on the direction of transportation.

FIG. 6 is a diagram schematically showing an example of image data of a rectangular pattern affected by uneven wind ripples. As shown in FIG. 6, no unevenness of wind ripples occurs in the divided area R1 on the most upstream side in the sub-scanning direction, but unevenness of wind ripples occurs in the divided areas R2 and R3 on the downstream side. In this embodiment, the side printed first is defined as the upstream side in the sub-scanning direction, and the side printed later is defined as the downstream side in the sub-scanning direction. That is, the conveying direction of the print medium P and the sub-scanning direction are opposite directions.

In addition, the influence of wind ripple unevenness is greater in the divided region R3 on the downstream side than in the divided region R2. That is, since the influence of wind pattern unevenness differs for each divided area, in this embodiment, the rectangular pattern image data is divided into three divided areas R1 to R3. This makes it possible to more appropriately remove the influence of wind ripple unevenness in the process of generating a density correction profile, which will be described later. Also, in the present embodiment, the screen is divided into three divided areas R1 to R3, but the present invention is not limited to this, and the screen may be divided into two divided areas or four or more divided areas.

Then, the density profile for each of the divided regions R1 to R3 acquired by the density profile acquisition section 62 is output to the density correction profile generation section 63. FIG.

The density correction profile generation unit 63 generates a density correction profile for each inkjet head 34 based on the density profiles of the divided regions R1 to R3 acquired by the density profile acquisition unit 62. FIG. A method of generating the density correction profile will be described in detail later.

The density correction profile storage unit 64 stores the density correction profile for each inkjet head 34 generated by the density correction profile generation unit 63 .

The density correction processing unit 65 uses the density correction profile for each inkjet head 34 stored in the density correction profile storage unit 64 to perform density correction processing on print image data to be printed. Specifically, the density correction processing unit 65 performs density correction processing by multiplying the print image data printed by each inkjet head 34 by the density correction profile of each inkjet head 34 .

Returning to FIG. 3, the print job output device 2 is composed of a computer. A document creation application for creating print image data to be printed and a printer driver for creating a print job including the print image data are installed in the print job output device 2 . The print job output device 2 generates a print job based on the print image data created by the document creation application and print conditions such as the number of copies set on the printer driver, and outputs the print job to the inkjet printer 1.

Next, a method of generating a density correction profile in the inkjet printing apparatus 1 of this embodiment will be described with reference to the flowchart shown in FIG.

First, in the inkjet printer 1, printing of the adjustment pattern described above is performed (S10).

Next, the adjustment pattern printed by the inkjet printer 1 is read by the reading unit 80, and image data of the adjustment pattern is obtained by the adjustment pattern obtaining unit 61 (S12).

Then, the image data of the adjustment pattern is acquired by the density profile acquisition unit 62, and the density profile acquisition unit 62 acquires the density profiles of the divided regions R1 to R3 based on the image data of the adjustment pattern for each inkjet head 34. and output to the density correction profile generator 63 (S14).

Next, the density correction profile generator 63 compares the density profiles of the divided regions R1 to R3, and determines whether or not the difference in the density profiles is smaller than a preset threshold value (S16). Regarding the difference in the density profile, for example, with reference to the density profile of the most upstream divided area R1 in the sub-scanning direction, the largest difference between the density profile of the divided area R1 and the density profile of the divided area R2 is obtained, Obtain the largest difference between the density profile of the divided region R1 and the density profile of the divided region R3. Then, the density correction profile generator 63 determines whether or not all the differences are smaller than the threshold.

If the density profile difference is equal to or greater than the threshold value in S16 (S16, NO), the density correction profile generation unit 63 adds a pattern corresponding to wind ripple unevenness to the profiles of the divided regions R2 and R3 on the further downstream side. It is checked whether or not the frequency component to be used is included (S18). Specifically, the density correction profile generation unit 63 performs Fourier transform on the density profiles of the divided regions R2 and R3 to extract frequency components. Check whether it is included or not. FIG. 8 is a diagram showing an example of the density profile of the divided regions R1 to R3 obtained based on the image data in which the wind pattern unevenness is generated as shown in FIG. The density profile of the divided region R1 does not contain the frequency component corresponding to the unevenness of the wind ripples, but the density profile of the divided region R2 contains the frequency component corresponding to the unevenness of the wind ripples, although the effect is small. The density profile of the divided region R3 on the most downstream side contains frequency components corresponding to wind ripple unevenness, which is more influential than that of the divided region R2.

Then, as shown in FIG. 8, if the profile of the divided region R2 or the divided region 3 contains a frequency component corresponding to wind ripple unevenness (S18, YES), the density correction profile generator 63 A band-pass filter process or the like is applied to the density profile including , thereby removing the frequency component corresponding to the wind pattern unevenness from the density profile (S20).

Subsequently, the density correction profile generation unit 63 averages the density profiles of all the divided areas R1 to R3, including the density profile of the divided area R2 or the divided area 3 from which the frequency component corresponding to the unevenness of the wind pattern has been removed (S22). , the averaged density profile is used to generate a density correction profile (S24).

On the other hand, if the density profile difference is less than the threshold value in S16 (S16, YES), the density correction profile generation unit 63 does not remove the frequency component corresponding to the wind ripple unevenness described above, and removes all of the frequency components. The density profiles of the divided regions R1 to R3 are averaged (S22), and a density correction profile is generated using the averaged density profiles (S24).

Further, if the profile of the divided region R2 or the divided region 3 does not include a frequency component corresponding to wind ripple unevenness in S18 (S18, NO), the density correction profile generation unit 63 Using the density profile of R1 (S26), a density correction profile is generated (S24).

According to the inkjet printing apparatus 1 of the above embodiment, the density profile is obtained based on the image data of the adjustment pattern, the frequency component corresponding to the wind pattern unevenness is removed from the density profile, and the frequency component is removed. Since the density correction profile for correcting the density unevenness is generated based on the density profile, it is possible to generate the density correction profile that is not affected by the wind pattern unevenness.

Further, in the inkjet printing apparatus 1 of the above-described embodiment, the image data of the adjustment pattern is divided into a plurality of divided regions R1 to R3, the density profile for each of the divided regions R1 to R3 is obtained, and the density profile for each of the divided regions R1 to R3 is obtained. out of the density profiles, the frequency component is removed from the density profile containing the frequency component corresponding to the wind pattern unevenness, and density correction is performed based on the density profiles of all the divided areas including the density profile from which the frequency component has been removed. Since the profile is generated, the frequency component corresponding to wind ripple unevenness can be removed more appropriately.

If you create a density correction profile using a density profile from which wind pattern unevenness frequency components (including various frequency components) have been removed without dividing it and apply it to the image data to be printed, it will affect the frequency components of the printed image, which is preferable. do not have. By dividing, the frequency components of uneven wind ripples in each divided area are limited, so that the unevenness of wind ripples can be removed from the density profile while suppressing the influence on the frequency components of the printed image.

Further, in the inkjet printing apparatus 1 of the above-described embodiment, when the difference in the density profile of each of the divided regions R1 to R3 is equal to or greater than a preset threshold value, the frequency component is removed, and the divided regions R1 to R3 are processed. If the difference between the density profiles of each divided area is less than a preset threshold value, the density correction profile is generated based on the density profiles of all the divided areas without performing the process of removing the frequency component. Therefore, the S/N ratio when calculating the average density of the line pattern L corresponding to each nozzle can be increased, and a density correction profile with less noise can be generated.

Further, in the inkjet printing apparatus 1 of the above-described embodiment, the difference in the density profile of each of the divided regions R1 to R3 is equal to or greater than a preset threshold, and the density profile of each of the divided regions R1 to R3 includes wind pattern unevenness. If there is no density profile containing a frequency component corresponding to Therefore, even if noise is generated in the density profile of the divided area R2 or the divided area R3 due to factors other than wind ripple unevenness, an appropriate density correction profile can be generated without being affected by this noise. can be generated.

Further, in the inkjet printing apparatus 1 of the above-described embodiment, since the image data of the adjustment pattern for each inkjet head 34 is acquired, the density unevenness for each inkjet head 34 can be removed more appropriately.

Regarding the density correction profile generating apparatus of the present invention, the following additional notes are disclosed.
(Appendix)

In the density correction profile generation apparatus of the present invention, the density profile acquisition section divides the image data acquired by the adjustment pattern acquisition section into a plurality of divided areas in the sub-scanning direction, and based on the image data for each divided area, , a density profile for each divided area can be obtained, and the density correction profile generation unit removes the frequency component from the density profile including the frequency component corresponding to the wind ripple unevenness among the density profiles for each divided area. A density correction profile can be generated based on density profiles of all divided regions, including density profiles from which frequency components have been removed.

In the density correction profile generation apparatus of the present invention, the density correction profile generation unit performs processing for removing frequency components corresponding to wind ripple unevenness when the difference in density profile between divided regions is equal to or greater than a preset threshold value. , if the difference in the density profile of each divided area is less than a preset threshold value, the density is calculated based on the density profiles of all the divided areas without performing the process of removing the frequency component corresponding to the unevenness of the wind pattern. A correction profile can be generated.

Further, in the density correction profile generation apparatus of the present invention, the density correction profile generation unit determines that the difference in the density profile of each divided area is equal to or greater than a preset threshold value and that the density profile of each divided area includes wind ripple unevenness. If there is no density profile containing a frequency component corresponding to can be generated.

Further, in the density correction profile generating apparatus of the present invention, the adjustment pattern acquisition section can acquire image data of the adjustment pattern for each inkjet head, and the density profile acquisition section subsumes the image data for each inkjet head. It is possible to divide the image into a plurality of divided regions in the scanning direction, and acquire the density profile for each divided region based on the image data for each divided region.

1 Inkjet printing device 2 Print job output device 10 Side paper feeder 11 Paper feeder 12 Primary paper feeder 14 Secondary paper feeder 20 Internal paper feeder 21a Paper feeder 21b Paper feeder 21c Paper feeder 21d Paper feed Bases 22a to 22d Primary paper feed section 30 Print processing section 31 Head units 32a to 32d Line head 33 Head holder 34 Ink jet head 40 Paper ejection section 41 Paper ejection table 42 Paper ejection roller 43 Switching mechanism 50 Reversing section 51 Reversing table 52 Reversing Roller 53 Conveyance roller 60 Control unit 61 Adjustment pattern acquisition unit 62 Density profile acquisition unit 63 Density correction profile generation unit 64 Density correction profile storage unit 65 Density correction processing unit 70 Operation panel 80 Reading unit 90 Control units 131 and 132 Suction fan 133 Conveying belt CR Circulating conveying path FR Paper feeding conveying path L Line pattern P Printing medium Pc C adjustment pattern Pk K adjustment pattern Pk1 Rectangular pattern Pm M adjustment pattern Py Y adjustment pattern R1 to R3 Divided area

Claims (5)

Acquiring image data obtained by reading an adjustment pattern printed while an inkjet head having a plurality of nozzles arranged in a main scanning direction is moved relative to a print medium in a sub-scanning direction perpendicular to the main scanning direction. an adjustment pattern acquisition unit;
a density profile acquisition unit that acquires a density profile based on the image data acquired by the adjustment pattern acquisition unit;
a density correction profile generation unit for removing frequency components corresponding to wind pattern unevenness from the density profile, and generating a density correction profile for correcting density unevenness based on the density profile from which the frequency components have been removed. Density correction profile generator. The density profile acquisition unit divides the image data acquired by the adjustment pattern acquisition unit into a plurality of divided regions in the sub-scanning direction, and calculates the density of each divided region based on the image data for each divided region. get profile,
The density correction profile generating unit removes the frequency component from the density profile including the frequency component corresponding to the wind ripple unevenness among the density profiles of the divided regions, and includes a density profile from which the frequency component is removed. 2. The density correction profile generation apparatus according to claim 1, wherein the density correction profile is generated based on the density profiles of all of the divided areas. The density correction profile generation unit performs a process of removing the frequency component corresponding to the wind pattern unevenness when the difference in the density profile of each of the divided areas is equal to or greater than a preset threshold, and calculates the density of each of the divided areas. If the profile difference is less than a preset threshold value, the density correction profile is calculated based on the density profiles of all the divided areas without performing the process of removing the frequency component corresponding to the wind ripple unevenness. 3. The density correction profile generation device according to claim 2, wherein the density correction profile generation device generates a density correction profile. The density correction profile generation unit generates a density in which a difference in the density profile of each of the divided areas is equal to or greater than a preset threshold value and the density profile of each of the divided areas includes a frequency component corresponding to the wind ripple unevenness. 2. If the profile does not exist, the density correction profile is generated using only the density profile of the divided area positioned most upstream in the sub-scanning direction among the density profiles of all the divided areas. 4. The density correction profile generation device according to 3. The adjustment pattern acquisition unit acquires image data of the adjustment pattern for each inkjet head,
wherein the density profile acquisition unit divides the image data for each inkjet head into a plurality of divided areas in the sub-scanning direction, and acquires the density profile for each divided area based on the image data for each divided area. 5. The density correction profile generating apparatus according to any one of items 2 to 4.

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