JP4576288B2 - Image recording apparatus and image data correction method - Google Patents

Description

  The present invention relates to an image recording apparatus that records an image based on input image data using a recording head having a large number of ink ejection nozzles.

  2. Description of the Related Art Image recording apparatuses such as ink jet recording, thermal recording system, and thermal transfer recording system are used for image recording apparatuses such as printers and copying machines. Among these, the ink jet recording method uses a recording head in which a large number of ink discharge nozzles for forming recording dots are arranged substantially linearly.

As a format of the image recording apparatus, there are a carriage scan type as shown in FIG. 8 and a full line type as shown in FIG.
In the following description, the conveyance direction of the recording material is the sub-scanning direction, and the direction orthogonal to the sub-scanning direction is the main scanning direction.

First, the carriage scan type image recording apparatus shown in FIG. 8 will be described.
In the image recording apparatus of FIG. 8, the recording medium 11 on the conveyance path is intermittently conveyed in the direction of the arrow 14 by a distance corresponding to the recording width of the recording head 16a by the roller 13 driven by the first motor 12. Then, sub-scanning is performed. In addition, the carriage 15a on which the recording head 16a is mounted is driven along the rail 17 by the second motor 18 via the wire 19 stretched between the pulley 20 and the pulley 21. The main scan is performed in a reciprocating direction. By this main scanning and sub-scanning, an image is divided and recorded for each recording width of the recording head 16 a and an image is formed on the recording medium 11.

Next, the full line type image recording apparatus shown in FIG. 9 will be described.
In the image recording apparatus of FIG. 9, the recording heads 16b-1 to 16b-6 are fixedly disposed on the carriage 15b at positions where the respective image forming ranges are in contact with each other (or partially overlap each other). . The recording medium 11 on the conveyance path is conveyed in the direction of the arrow 14 by a roller 13 driven by a motor 12, and an image is divided and recorded on the recording medium 11 by the recording heads 16b-1 to 16b-6. The

Next, the recording head of the image recording apparatus shown in FIGS. 8 and 9 will be described.
FIG. 10 is a view of the recording head of the ink jet recording type image recording apparatus as viewed from the direction of the ink ejection surface.

In the figure, the recording head has a large number of ink discharge nozzles 32 formed on the ink discharge surface 31 in a substantially straight line over a distribution width 33.
By the way, in an image recording apparatus, density unevenness caused by characteristics unique to each apparatus, particularly physical characteristics of the recording head, may occur in a recorded image.

  For example, the ink jet recording type recording head used in the carriage scan type image recording apparatus shown in FIG. 8 or the full line type image recording apparatus shown in FIG. When the amount of ink discharged from several ink discharge nozzles at both ends of the discharge nozzle increases or decreases, and the recording density of the ink discharge nozzles is higher or lower than the recording dots of other ink discharge nozzles There is. This is a cause of uneven density of the recorded image.

FIG. 11 schematically shows the distribution of ink ejection amounts when image data having the same density is input to each ink ejection nozzle provided in the recording head and recorded.
The abscissa of the drawing represents the position of the ink discharge nozzle, and the range 35 corresponds to the distribution width 33 of the ink discharge nozzle of FIG. The vertical axis indicates the amount of ink discharged from each ink discharge nozzle.

  As shown by the curve 34 in FIG. 11, in the ink discharge nozzles configured on the recording head, the ink discharge amounts by the several ink discharge nozzles configured at both ends of the straight line are different from each other. May be more than part.

  The degree to which the ejection amount increases has a characteristic that it differs depending on the gradation of the recording density. Therefore, in the case of a structure that divides and records an image, such as a carriage scan type that records an image in a plurality of times, or a configuration that the image recording apparatus divides and records an image by arranging a plurality of recording heads in series, the recording head Density unevenness occurs at the joints, and the image quality of the recorded image decreases.

FIG. 12 schematically shows an example of the distribution of the ink discharge amount as shown in FIG. 11, and shows only the portions corresponding to both ends of the recording head 37 in an enlarged manner.
In the ink jet type recording head 37, the ink discharge amount gradually increases in the end region of the recording head 37 as indicated by 36 a and 36 d in FIG. There is a characteristic of decreasing (increasing in FIG. 12). The degree of increase or decrease of the ink discharge amount varies depending on the individual heads, but the width of the end region where the ink discharge amount increases or decreases is substantially constant regardless of the individual recording heads, and the distribution of the ink discharge amount is Each recording head exhibits characteristics such as 39a and 39b.

FIG. 13 schematically shows a part of the divided and recorded image when image data having the same gradation value is input to all the ink discharge nozzles.
The range of widths 41 and 42 in the figure corresponds to the range recorded by one scan in the carriage scan type image recording apparatus, and the range recorded by one recording head in the full line type image recording apparatus. Correspond.

Due to the difference in the ink discharge amount shown in FIG. 12, the density of the portion 43 recorded in the end region of each recording head is higher than that in the portion of the non-end region.
On the other hand, Patent Document 1 discloses an ink jet recording apparatus that improves density unevenness generated in an end region.

In Patent Document 1, in order to reduce density unevenness generated at the end of the recording head, density correction is performed to such an extent that there is almost no density difference between the non-end area and the end area.
JP 2003-320647 A (FIG. 7, paragraphs [0030] to [0040])

  However, the ink jet recording apparatus described in the above-mentioned patent document 1 eliminates the density difference that occurs at the boundary between the end region and the non-end region of the recording head, and the problem of uneven density caused by the end region portion. There is no disclosure about the solution and its solution.

  Conventionally, in order to correct density unevenness, it has been necessary to measure the recording characteristics of each recording element. However, since the structure of the recording head and the recorded image have a very fine structure, the ink in the edge region is used. It was difficult to measure the recording characteristics for each discharge nozzle.

  In view of the above problems, an object of the present invention is to provide an image recording apparatus capable of eliminating density unevenness caused by an end region portion of a recording head.

  An image recording apparatus according to the present invention is based on the assumption that an image is recorded on a recording material by a recording head having a plurality of ink ejection nozzles based on image data. A coefficient calculation unit and an image data correction unit are provided.

The correction parameter setting unit sets correction parameters corresponding to one or more ink ejection nozzles located in each end region of the recording head.
The correction coefficient calculation unit obtains a correction coefficient corresponding to the ink ejection nozzle located in the end area based on the correction parameter.

The image data correction unit corrects the image data based on the correction coefficient obtained by the correction coefficient calculation unit.
The present invention includes not only the image recording apparatus but also a method for correcting image data by the image recording apparatus.

According to the present invention, it is possible to correct the density unevenness generated in the end region and record a high-quality image in which the density unevenness is not noticeable.
Further, at this time, appropriate correction can be performed without measuring the density of the dots to be formed and obtaining the correction value for each of the ink discharge nozzles in the end region.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram for explaining the image recording apparatus of the present embodiment.
An image recording apparatus 50 illustrated in FIG. 1 includes a correction processing unit 51, a control unit 52, a transport mechanism 53, and an image recording unit 54.

  The correction processing unit 51 is a part that corrects image data to correct density unevenness, a correction parameter setting unit 55 that sets a correction parameter used for correction, a correction coefficient calculation unit 56 that calculates a correction coefficient from the correction parameter, and An image data correction unit 57 that corrects image data using the correction coefficient is provided.

  The control unit 52 controls the entire image recording apparatus 50. The CPU executes a program stored in a memory such as a ROM or a RAM provided therein, thereby constituting each image recording apparatus 50. Provides control instructions for the components.

The transport mechanism 53 transports a recording material for recording an image based on an instruction from the control unit 52.
The image recording unit 54 includes a recording head driving unit 58 and a recording head 59, controls the recording head 59 in accordance with an instruction from the control unit 52, and uses the image data corrected by the correction processing unit 51 to record a recording material. Then, image formation is performed.

  In the image recording apparatus 50 of FIG. 1, image data for performing image recording is received from the outside such as a computer 60 connected to the image recording apparatus 50, and correction processing is added to the image data by the correction processing unit 51. An image is recorded on the recording material by the image recording unit 54 using the image data.

Next, a first embodiment of the image recording apparatus in the present embodiment will be described.
FIG. 2 is a block diagram illustrating a configuration example of the image recording apparatus according to the first embodiment. 2 that have basically the same functions as those shown in FIG. 1 are denoted by the same reference numerals.

The image recording apparatus 50a of FIG. 2 has a user interface 71 that allows the operator to input correction parameters to the correction parameters 55a.
Then, the correction coefficient calculation unit 56 calculates a correction coefficient corresponding to each ink ejection nozzle provided at the end of the recording head from the correction parameter value set in the correction parameter setting unit 55a, and this is calculated as an image data correction unit 57. Output to. Using this correction coefficient, the image data correction unit 57 applies the image data received from the control unit 52 to the data corresponding to the ink ejection nozzles located at the end of the recording head. Correction is performed, and the corrected image data is returned to the control unit 52. Details of the correction method will be described later.

  When the corrected image data is received from the image data correction unit 57, the control unit 52 sends the image data to the image recording unit 54 and controls the conveyance mechanism 53 to convey the recording material. The recording head drive unit 58 drives the recording head 59 based on the image data from the control unit 52 to record an image on the recording material conveyed by the conveyance mechanism 53.

  As shown in FIG. 10, a plurality of, for example, 600 ink discharge nozzles are arranged in parallel on the recording head 59 of the image recording unit 54. In the following description, these ink discharge nozzles are arranged in the order # 1, # 1. It is represented by the numbers # 2, # 3,. An area corresponding to the end of the recording head in which ink discharge nozzles # 1 to # 3 and # 598 to # 600 are arranged in parallel is called an end area, and ink discharge nozzles from # 4 to # 597 are arranged in parallel. The other area is referred to as a non-end area.

  The ink discharge amount from the ink discharge nozzle in the non-end region is almost stable, but the ink discharge amount increases or decreases in the ink discharge nozzle in the end region as compared with the non-end region as shown in FIG. Tend. The increase / decrease method is monotonous, and the ink discharge amount gradually changes as the position of the ink discharge nozzle reaches the end. Therefore, the change in the ink discharge amount can be approximated by a straight line.

  The image data correction performed by the image data correction unit 57 is performed by using the correction coefficient obtained from the correction coefficient calculation unit 56 as input image data input from the outside of the image recording apparatus 50a such as the host computer 60.

  This correction coefficient is a coefficient to be corrected by multiplying the input image data, for example. When this value is 1, the density after correction is the same as the density before correction, and when it is greater than 1, the density after correction is corrected. Is higher than the density before correction, and when smaller than 1, the density after correction becomes lower than the density before correction.

Since the ink discharge amount of the ink discharge nozzles in the end region can be approximated by a straight line as described above, the corresponding correction parameter value can also be obtained from a simple calculation.
The correction coefficient corresponding to each ink discharge nozzle is set to the values of the correction parameter # 1 and the correction parameter # 600 for the ink discharge nozzles # 1 and # 600 as shown in the graph of FIG. The ink discharge nozzles in the adjacent non-end region, that is, the ink discharge nozzles of # 4 and # 597 have a value of 1, and the ink discharge nozzles # 2 to # 3 and # 598 to # 599 in the meantime The correction coefficient of each ink ejection nozzle is calculated so that the value changes linearly.

From the correction parameter values of the ink discharge nozzles # 1 and # 600 in the end region set and input by the operator from the user interface 71, the correction parameter values of the ink discharge nozzles # 2, # 3, # 598, and # 599 are internally divided. It can be obtained from the following formula using the calculation of
(# 1 correction coefficient) = (# 1 correction parameter value)
(# 2 correction coefficient) = ((# 1 correction parameter value) * 2 + 1 * 1) / 3
(# 3 correction coefficient) = ((# 1 correction parameter value) * 1 + 1 * 2) / 3
(Correction coefficient of # 598) = ((Correction parameter value of # 600) * 1 + 1 * 2) / 3
(Correction coefficient of # 599) = ((Correction parameter value of # 600) * 2 + 1 * 1) / 3
(Correction coefficient of # 600) = (Correction parameter value of # 600)
In this way, since the correction coefficient values (correction coefficients) of the ink discharge nozzles at both ends (# 1, # 600) can be obtained, the correction coefficient of the ink discharge nozzles at the other end areas can be obtained. For each of the ink ejection nozzles, there is no need to measure and correct the ink density.

Next, operation processing during image formation by the image recording apparatus 50a of the first embodiment will be described in more detail.
FIG. 4 is a flowchart showing an operation process at the time of image recording by the image recording apparatus 50a of the first embodiment.

  In the figure, first, in step S1, the image recording apparatus 50a prompts the operator from the user interface 71 to set two correction parameter values corresponding to the end regions at both ends of each recording head, that is, the correction parameter # 1 and the correction # 600. Lets you set and input parameters.

  These correction parameters are used as correction coefficients for adjusting the ink discharge amounts of the ink discharge nozzles # 1 and # 600, respectively, and as described above, the ink discharge nozzles # 2, # 3, It is also used to determine correction coefficient values corresponding to # 598 and # 599.

  The operator reduces the ink discharge amount when the ink discharge amount increases as the position of the ink discharge nozzle reaches the end in the end region as shown in 39a and 39b in FIG. Therefore, a value smaller than 1 is set and input. Conversely, if the ink discharge amount decreases as the position of the ink discharge nozzle reaches the end in the end region, a value greater than 1 is set and input to increase the ink discharge amount.

  These correction parameters are directly input and set by the operator using the user interface 71 provided in the correction parameter setting unit 55a, and these values are temporarily stored as correction parameters in a memory (not shown) of the correction parameter setting unit 55a. Is done.

FIG. 5 is a diagram illustrating correction parameter values stored in the memory of the correction parameter setting unit 55a.
This figure shows an example when the operator inputs 0.94 as the value of the correction parameter # 1 and 0.91 as the value of the correction parameter # 600. By storing the correction parameters in the memory as shown in FIG. 5, the correction parameters input by the operator are set in the correction parameter setting section 55a.

  Next, in step S2, in the image recording apparatus 50a, the correction coefficient calculation unit 56 refers to the correction parameter set in the correction parameter setting unit 55a and calculates a correction coefficient corresponding to each ink ejection nozzle in the edge region.

  As described above, the correction coefficient of each ink discharge nozzle is set to the correction parameter value of the ink discharge nozzles # 1 and # 600 for the ink discharge nozzles # 1 and # 600, and the non-end portion adjacent to the end region. It is assumed that the value is 1 for the ink discharge nozzles in the region, that is, the ink discharge nozzles of # 4 and # 597, and the correction coefficient of each ink discharge nozzle is assumed to change linearly for each ink discharge nozzle in the meantime. Calculate

  If the correction parameter of # 1 is 0.94 and the correction parameter of # 600 is 0.91, the correction coefficient value of the ink ejection nozzle # 1 is 0.94 from the above-described equation using the calculation of the inner part. The correction coefficient value of # 2 is 0.96, the correction coefficient value of # 3 is 0.98, the correction coefficient value of # 598 is 0.97, the correction coefficient value of # 599 is 0.94, # The correction coefficient value of 600 is 0.91. These values are stored in a memory (not shown) included in the correction coefficient calculation unit 56.

FIG. 6 shows an example of the correction coefficient corresponding to each ink ejection nozzle stored in the memory of the correction coefficient calculation unit 56.
In the example shown in the figure, the calculated # 1 to # 3 and # 598 to # 600 are calculated when 0.94 and 0.97 are given as correction values corresponding to the ink ejection nozzles # 1 and # 600. Each correction coefficient corresponding to each ink ejection nozzle is recorded.

In step S <b> 3, in the image recording apparatus 50 a, the control unit 52 receives image data from the host computer 60 and outputs it to the image data correction unit 57.
In step S4, the image data correction unit 57 reads the correction coefficient stored in the memory shown in FIG. 6 from the correction coefficient calculation unit 56, and uses this correction coefficient for the image data input from the control unit 52. The image data corresponding to the ink ejection nozzles in the end area is corrected. That is, the value of the image data is corrected by multiplying the value of the corresponding correction coefficient for each image data corresponding to the ink ejection nozzles in the end region.

  When this correction is completed, in step S5, the control unit 52 outputs the corrected image data to the image recording unit 54 and controls the transport mechanism 53 to transport the recording material onto the recording head 59. The recording head driving unit 58 is controlled to form an image on the recording material. At this time, the image data corrected by the image data correction unit 57 is input to the image recording unit 54 via the control unit 52, and the recording head driving unit 58 drives the recording head 59 based on the image data to be covered. An image is formed on the recording material.

Accordingly, image formation is performed in which density unevenness caused by the difference in the ink discharge amount of the ink discharge nozzles in the end region and the non-end region is corrected.
As described above, in the image recording apparatus according to the first embodiment, it is possible to perform image recording in which density unevenness caused by a difference in ink discharge amount between the end region and the non-end region of the recording head 59 is prevented.

  At this time, the density of the ink ejection nozzles at both ends can be obtained from the operator's input without measuring the density of the formed dots for each of the ink ejection nozzles in the end region and obtaining the correction value. Thus, appropriate correction can be performed.

Next, a second embodiment of the image recording apparatus in this embodiment will be described.
FIG. 7 is a block diagram illustrating a configuration example of the image recording apparatus according to the second embodiment. In addition, each component shown in FIG. 7 is also given the same reference numeral for the component that basically performs the same function as that shown in FIG.

  In the image recording apparatus according to the first embodiment, the user interface 71 is provided, and the operator sets and inputs correction parameters from the user interface 71. However, in the image recording apparatus 50b according to the second embodiment, a correction parameter setting unit is provided. 55b is provided with a densitometer 72 for measuring the density of an image formed on the recording material instead of the user interface 71. The density meter 72 is used to measure the density difference between the edge area and the non-edge area when image formation is performed with image data corresponding to the recording density of the same gradation, and the correction is made from this difference. Set parameters automatically.

  The method of setting the correction parameter using the image recording apparatus 50b of the second embodiment shown in FIG. 7 will be described by taking the method of setting the correction parameter for the left end region 36a of the recording head 38 shown in FIG. 12 as an example. To do.

  First, image data corresponding to the recording density of the same gradation is input to the image recording unit 54 in the end region 36a and the non-end region 36b, and an image for density measurement is recorded on the recording material. For this image, the density of the formed image by the end region and the non-end region of the recording head 59 is measured using the densitometer 72.

  Here, it is assumed that the density of the image formed in the end region indicated by 36a in FIG. 12 is d1, and the density of the image formed in the non-end region 36b adjacent thereto is d2. In the second embodiment, a value (d2 / d1) * k1 obtained by multiplying the density ratio d2 / d1 by a constant k1 is set as a correction parameter for the ink discharge nozzle # 1. Alternatively, the correction parameter of the ink ejection nozzle # 1 may be defined and set as 1+ (d1−d2) * k2 from the difference between the densities d1 and d2 and the constant k2.

The values of the constants k1 and k2 are selected as adjustments with reference to the correction result of the recorded image so that the density unevenness is least noticeable.
The same calculation can be made for the end region 36d on the right side of the recording head shown in FIG. 12 for the end region 36d and the non-end region 36c adjacent thereto.

  As described above, in the image recording apparatus of the second embodiment, an image is formed for determining the correction coefficient, and the density of this image is measured by the densitometer 72, so that the end of the recording head is the same as in the first embodiment. It is possible to perform image recording in which density unevenness caused by a difference in ink discharge amount between the partial area and the non-end area is prevented.

  At this time, by measuring the density of the ink discharge nozzles at both ends, it is appropriate to measure the density of the dots formed for each of the ink discharge nozzles in the end region and not calculate the correction value. Correction can be performed.

  In the second embodiment, the density of the recorded image is measured by providing a densitometer. However, instead of the densitometer, a sensor that measures the amount of ink discharged from one ink ejection nozzle in each end region. The ink discharge amount measured by this sensor is used instead of the density, for example, in the difference or ratio between the ink discharge amount of the ink discharge nozzle in the end region and the ink discharge amount of the ink discharge nozzle in the non-end region. The correction parameter may be set on the basis of this.

As a result, even when the ink ejection amount is used, the image data can be corrected as in the case where the image density is measured.
Each of the image recording apparatuses described above is realized by hardware as shown in FIG. 1, but a part of the image recording apparatus is executed by the control unit 52 or individual controller executing software on the memory. You may implement | achieve using the method of software to implement | achieve.

  As a method for setting the correction parameter, the correction parameter is changed, image recording is performed to create a plurality of correction samples, and the correction parameter value is determined by selecting the most corrected sample among them. You may do it.

  Further, in the above embodiment, the correction coefficients for the other ink discharge nozzles are obtained on the assumption that the correction coefficient for each ink discharge nozzle in the end region changes linearly, that is, in a linear function. As long as it is an increase function or a function that performs monotonic decrease, other functions such as an n-order function and an exponential function may be used instead of a linear function.

  In the above description of the embodiment, the three ink discharge nozzles in the end region have been described on the premise that the ink discharge amount is different from other ink discharge noises. The number of ink ejection nozzles is not limited to three, and the recording head varies depending on various conditions such as the size of the recording head, the number of ink ejection nozzles to be formed, the pitch width, and the value is not necessarily limited to a specific value such as three. Since there is no limitation, correction may be performed by selecting an appropriate number based on conditions such as the shape of the recording head.

  Furthermore, although the above description has been made on the assumption of an ink jet type image recording apparatus, the image recording apparatus of the present embodiment is not limited to the ink jet type, and a line head in which the recording density changes at the end depending on temperature characteristics. The present invention can also be applied to a thermal type image recording apparatus using the

  In FIG. 1 and the like, the image recording apparatus of the present embodiment is configured to include the correction processing unit 51 in the image recording apparatus 50. However, the image recording apparatus 50 of the present embodiment is limited to such a configuration. Instead, the correction processing unit 51 may be provided outside the image recording apparatus 50, for example, in the host computer 60, and the image recording apparatus 50 may receive the image data corrected by the correction processing unit 51 and perform image recording. .

It is a block diagram which shows the structure of the image recording device of this embodiment. 1 is a block diagram illustrating a configuration of an image recording apparatus according to a first embodiment. It is a conceptual diagram which shows the example of the correction coefficient corresponding to the ink discharge nozzle of an edge part area | region. 3 is a flowchart illustrating processing performed by the image recording apparatus according to the first embodiment. It is a figure which shows the content of the memory which a correction parameter setting part has. It is a figure which shows the content of the memory which a correction coefficient calculation part has. It is a block diagram which shows the structure of the image recording device of 2nd Embodiment of this invention. 1 is a diagram illustrating a carriage scan type image recording apparatus. FIG. 1 is a diagram illustrating a full line type image recording apparatus. FIG. FIG. 3 is a diagram of a recording head of an inkjet recording type image recording apparatus as viewed from the direction of an ink ejection surface. FIG. 6 is a diagram schematically illustrating a distribution of ink discharge amounts by a recording head. FIG. 6 is a diagram illustrating a distribution of ink discharge amounts at portions corresponding to both ends of a recording head. FIG. 6 is a diagram schematically illustrating divided and recorded images when image data having the same gradation is input to all ink discharge nozzles.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Recording medium 12 1st motor 13 Roller 15a, 15b Carriage 16a, 16b-1-16b-6 Recording head 17 Rail 18 2nd motor 19 Wire 20, 21 Pulley 50, 50a, 50b Image recording apparatus 51, 51a, 51b Correction processing unit 52 Control unit 53 Conveying mechanism 54 Image recording unit 55, 55a, 55b Correction parameter setting unit 56 Correction coefficient calculation unit 57 Image data correction unit 58 Recording head drive unit 59 Recording head 60 Host computer 71 User interface 72 Densitometer

Claims (11)

In an image recording apparatus for recording an image on a recording material by a recording head having a plurality of ink discharge nozzles based on image data,
A correction parameter setting unit that sets correction parameters corresponding to one or more of the ink ejection nozzles located in each end region of the recording head;
A correction coefficient calculation unit for obtaining a correction coefficient corresponding to the ink ejection nozzle located in the end region based on the correction parameter;
An image data correction unit that corrects the image data based on the correction coefficient obtained by the correction coefficient calculation unit;
An image recording apparatus comprising:   The image recording apparatus according to claim 1, wherein the correction coefficient calculation unit calculates correction coefficients for a plurality of ink ejection nozzles in the end region using a monotonically changing function.   The image recording apparatus according to claim 2, wherein the monotonically changing function is a linear function. The previous period correction parameter setting unit sets a correction parameter corresponding to the ink discharge nozzle at the end of the end region,
The linear function passes through the value of the correction parameter at the endmost ink discharge nozzle, and passes through a value corresponding to no correction at the ink discharge nozzle in the non-end region closest to the end region. The image recording apparatus according to claim 3.   The correction parameter setting unit sets the correction parameter based on the difference or ratio between the density of the image recorded by the ink discharge nozzles in the end region and the density of the ink discharge nozzle in the non-end region. The image recording apparatus according to claim 1.   The correction parameter setting unit sets the correction parameter based on a difference or ratio between an ink discharge amount of an ink discharge nozzle in an end region and an ink discharge amount of an ink discharge nozzle in a non-end region. The image recording apparatus according to claim 1.   The correction parameter setting unit has a user interface for setting a correction parameter value, and the correction parameter setting unit sets the correction parameter based on a value input by an operator from the user interface. The image recording apparatus according to claim 1.   The correction parameter setting unit includes a densitometer that measures the density of an image recorded on the recording material, and the correction parameter setting unit sets the correction parameter based on a measurement result by the densitometer. The image recording apparatus according to claim 1, wherein:   The image recording apparatus according to claim 1, wherein the image recording apparatus is a carriage scan type image recording apparatus.   The image recording apparatus according to claim 1, wherein the image recording apparatus is a full-line type image recording apparatus. A method for correcting image data in an image recording apparatus for recording an image on a recording material by a recording head having a plurality of ink ejection nozzles based on the image data,
Setting correction parameters corresponding to one or more of the ink ejection nozzles located in each end region of the recording head;
Based on the correction parameter, a correction coefficient corresponding to the ink ejection nozzle located in the end region is obtained,
The image data correction method, wherein the image data is corrected based on the correction coefficient obtained by the correction coefficient calculator.

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