Image recording device and its control method, information processing device, and program

Abstract

This invention provides a new technique for suppressing the influence of reading position-dependent variations in reading characteristics when evaluating the recording characteristics of an image recording device, which depend on the recording position, by reading images. [Solution] An image is recorded on a medium based on print data. The recorded chart image is read. Based on the reading results, recording characteristics dependent on the recording position are determined. Based on the reading results for the first density region, recording characteristics for the second density region are estimated.

Description

Technical Field

[0001] The present disclosure relates to an image recording apparatus, a control method thereof, an information processing apparatus, and a program, and particularly relates to a color adjustment technique of an image recording apparatus.

Background Art

[0002] An image recording apparatus can record an arbitrary image by attaching a coloring material to a medium. As an image recording apparatus, an inkjet (IJ) printer that records an image by ejecting ink droplets from a plurality of nozzles is widely used. On the other hand, the recording characteristics using the coloring material may vary depending on the recording position. For example, the landing position and ejection amount of ink from the nozzles aligned in the recording head may deviate from the target. As a result, band-shaped or streak-shaped density unevenness (banding) may occur on the recording object. Therefore, color adjustment (referred to as "head shading correction") is performed to correct the image data of the recording target so that density unevenness does not occur according to the deviation of the ink ejection amount or landing position depending on the recording position (for example, in units of nozzles or modules).

[0003] In head shading correction (HS correction), in order to acquire the recording characteristics of the recording head, a test chart is scanned. However, the sensor used for scanning may include variations in reading characteristics that depend on the reading position. For example, reading using a line sensor may be affected by factors such as illuminance unevenness in the main scanning direction and angle dependence of reading. In this case, the recording characteristics of the recording head determined based on the reading result are affected by the variations in the reading characteristics. And since the determination result of the recording characteristics of the recording head referred to for HS correction is affected by the variations in the reading characteristics, density unevenness may occur even after HS correction is performed.

[0004] Patent Document 1 discloses adjusting the image output parameters of an image forming apparatus using the reading results of a patch image by an inline sensor. In the method of Patent Document 1, the reading results are corrected using a color correction coefficient corresponding to the reading position. This color correction coefficient is calculated by comparing the reading results of the evaluation pattern by the inline sensor with the reading results of an external spectrophotometer.

[0005] Furthermore, Patent Document 2 proposes a technique for generating correction information used for banding correction to remove density unevenness. In the method of Patent Document 2, a density gradient is extracted for the density values ​​of the measured patch image. Then, the density values ​​of the measured patch image are corrected based on the density gradient. Correction information is generated based on these corrected density values. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-220828 [Patent Document 2] Japanese Patent Publication No. 2007-283750 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The method described in Patent Document 1 requires measuring the evaluation pattern using a spectrophotometer separate from the inline sensor in order to calculate the color correction coefficient. This increases the costs related to equipment, time, and effort. In particular, the reading characteristics of the sensor may differ depending on the surface characteristics or spectral characteristics of the medium. The problems of Patent Document 1 become more pronounced when dealing with the reading characteristics of various media. Furthermore, in the method described in Patent Document 2, the density gradient of the extracted sensor is affected by the recording characteristics of the recording head. In particular, when the variation in recording characteristics that depends on the recording position has a low-frequency component, it becomes difficult to correct the variation in recording characteristics. As a result, there were limitations to the accuracy of the obtained correction information, and furthermore, to the accuracy of banding correction.

[0008] The present invention provides a novel technique for suppressing the influence of fluctuations in reading characteristics that depend on the reading position when evaluating the recording characteristics of an image recording device that depend on the recording position by reading an image. [Means for solving the problem]

[0009] An image recording apparatus according to one embodiment has the following configuration: A recording means for recording an image onto a medium based on print data, A reading means for reading the chart image recorded by the recording means, The system includes a determination means that determines the recording characteristics of the recording means, which depend on the recording position, based on the reading result by the reading means. The determination means estimates the recording characteristics for the second concentration region based on the reading results for the first concentration region. [Effects of the Invention]

[0010] This invention provides a new technique for suppressing the influence of reading position-dependent variations in reading characteristics when evaluating the recording characteristics of an image recording device, which depend on the recording position, by reading images. [Brief explanation of the drawing]

[0011] [Figure 1] Figure showing an example of the hardware configuration of an image recording apparatus according to an embodiment. [Figure 2] Figure showing an example of the configuration of an image recording unit and an image acquisition unit. [Figure 3] Figure showing an example of the functional configuration of an image processing unit. [Figure 4] Figure showing an example of a HS correction table. [Figure 5] Figure showing an image recording flow according to an embodiment. [Figure 6] Figure showing a creation flow of a HS correction table according to an embodiment. [Figure 7] Figure showing an example of a HS chart. [Figure 8] Figure showing a correction parameter calculation flow for each nozzle. [Figure 9] Figure for explaining a method of calculating correction parameters. [Figure 10] Figure showing a nozzle characteristic estimation flow. [Figure 11] Figure showing an example of a recording characteristic model. [Figure 12] Figure showing an example of the relationship between a reading position and a reading signal value. [Figure 13] Figure showing a creation flow of a HS correction table according to an embodiment. [Figure 14] Figure showing an example of a HS chart. [Figure 15] Figure showing an example of the relationship between a reading position and a reading signal value. [Figure 16] Figure showing an example of an input-reading relationship. [Figure 17] Figure showing a nozzle characteristic estimation flow. [Figure 18] Figure showing a creation flow of a HS correction table according to an embodiment. [Figure 19] Figure for explaining a method of estimating reading characteristics.

Embodiments of the Invention

[0012] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0013] First, an outline of the processing performed by an information processing device according to one embodiment will be described. The information processing device first acquires read image data that shows the result of reading a chart image recorded on a medium (for example, S602). An image recording unit that records an image on a medium based on print data can record such a chart image. An image acquisition unit can read such a chart image. The information processing device may be provided inside an image recording device. In this case, the information processing device can acquire read image data obtained by an image acquisition unit of the image recording device reading an image recorded by an image recording unit of the image recording device. However, the image may be generated by an image forming device separate from the information processing device. Also, the read image data may be generated by an image reading device separate from the information processing device.

[0014] Next, the information processing device determines the recording characteristics of the image recording unit or image forming apparatus based on the above reading results (for example, S606). These recording characteristics are dependent on the recording position (for example, a position perpendicular to the transport direction of the medium). When the image recording unit records an image using an inkjet (IJ) method, the recording characteristics may indicate unevenness information caused by deviations in ink ejection amount or landing position at the nozzle level (or module level including piezoelectric elements or heater elements corresponding to each nozzle). In the embodiments described below, the recording characteristics can show the relationship between a color signal value (input signal value) for controlling the amount of colorant used for recording at each recording position (or each nozzle), and the recording density on the medium when recording is performed according to this input signal value.

[0015] Through the above processing, the information processing device can determine the recording characteristics. In this embodiment, when determining the recording characteristics, the recording characteristics in a region with a large difference in read characteristics are inferred from the reading results in a region with a small difference in read characteristics. Specifically, based on the reading results in a first density region, the recording characteristics in a second density region can be inferred using an existing model equation. As another example, based on the reading results of the first density region in the second region and the reading results of the second density region in the first region, the recording characteristics of the second density region in the second region can be inferred. In one embodiment, the first density region is a region with a lower density than the second density region. Through these processing, the influence of reading characteristic differences depending on the reading position, which are particularly likely to occur in high-density regions and are included in the determined recording characteristics, can be suppressed.

[0016] The determined recording characteristics can be used, for example, for color adjustment. In the following embodiment, the information processing device calculates correction parameters based on the determined recording characteristics to reduce the unevenness of the image recorded by the image recording unit (e.g., S607). In the following embodiment, the information processing device calculates parameters for head shading correction (HS correction) processing. By estimating the recording characteristics as in this embodiment, it is possible to suppress a decrease in the accuracy of correction based on the determined recording characteristics.

[0017] (Hardware configuration of the image recording device) An information processing device and an image recording device according to one embodiment can be realized using a combination of a processor and memory. For example, a processor such as the CPU 100 shown in Figure 1 can realize functions such as an image processing unit 106 by executing a program stored in memory such as RAM 101 or ROM 102.

[0018] Figure 1 shows an example of the hardware configuration of an image recording device according to one embodiment. The image recording device in this embodiment includes a CPU 100, RAM 101, ROM 102, operation unit 103, display unit 104, external storage device 105, image processing unit 106, image recording unit 107, image acquisition unit 108, I / F (interface) unit 109, and bus 110.

[0019] The Central Processing Unit (CPU) 100 controls the operation of the entire image recording device using the input data or computer programs stored in RAM or ROM, as described later. Alternatively, multiple hardware components sharing the processing may control the entire image recording device.

[0020] Random Access Memory (RAM) 101 has a storage area for temporarily storing computer programs or data read from the external storage device 105, or data received from an external source via the I / F unit 109. Furthermore, RAM 101 is used as a storage area when the CPU 100 performs various processes, or when the image processing unit 106 performs image processing.

[0021] The Read Only Memory (ROM) 102 has a storage area for storing setting parameters for each part of the image recording device, or boot programs, etc.

[0022] The control unit 103 is an input device such as a keyboard or mouse. The control unit 103 receives operations (instructions) from the operator. In this way, the operator can input various instructions to the CPU 100.

[0023] The display unit 104 is a display device such as a Cathode Ray Tube (CRT) or a liquid crystal screen. The display unit 104 can display the processing results of the CPU 100 as images or characters. If the display unit 104 is a touch panel capable of detecting touch operations, the display unit 104 may function as part of the operation unit 103.

[0024] The external storage device 105 is a large-capacity information storage device such as a hard disk drive. The external storage device 105 can store computer programs or data that cause the OS (operating system) or CPU 100 to execute various processes. The external storage device 105 can also store temporary data generated by the processing of each part (for example, input image data, recorded image data, or threshold values ​​used by the image processing unit 106). The computer programs or data stored in the external storage device 105 are read according to the control of the CPU 100. The read computer programs or data are stored in RAM 101 and become subject to processing by the CPU 100.

[0025] The image processing unit 106 performs various image processing operations to convert input image data, which indicates the image to be recorded and is input to the image recording device for image recording, into recording image data that controls the operation of the image recording unit 107, as described later. The image processing unit 106 can be implemented as a processor capable of executing computer programs or as a dedicated image processing circuit. The image processing unit 106 corresponds to an information processing device according to one embodiment. In addition, the CPU 100 may perform various image processing operations as the image processing unit 106.

[0026] The image recording unit 107 records images onto a medium based on print data. Based on recorded image data received directly from the image processing unit 106, or via the RAM 101 or external storage device 105, the image recording unit 107 can record images on a recording medium (e.g., paper) using recording material. The image recording unit 107 can record chart images such as HS charts, which will be described later. Details will be described later.

[0027] The image acquisition unit 108 reads images. The image acquisition unit 108 can read images recorded on a medium by the image recording unit 107. The image acquisition unit 108 can read chart images, such as HS charts. The image acquisition unit 108 can then generate read image data indicating the reading result. The image acquisition unit 108 is, for example, an image sensor that captures images (e.g., a line sensor or an area sensor). Hereafter, the image acquisition unit 108 may be referred to as a sensor. Further details will be described later.

[0028] The I / F unit 109 can function as an interface for connecting the image recording device to external devices. Furthermore, the I / F unit 109 can function as an interface for exchanging data with communication devices using infrared communication or wireless LAN (Local Area Network), etc. Additionally, the I / F unit 109 can function as an interface for connecting the image recording device to the internet. Through the I / F unit 109, the image recording device can exchange data such as input images with external devices.

[0029] Each of the above-mentioned components is connected to the bus 111, and can exchange data with each other via the bus 111. Alternatively, each of the above-mentioned components (for example, the image recording unit 107 or the image acquisition unit 108) may be connected via the I / F unit 109.

[0030] (Details of the image recording unit 107 and the image acquisition unit 108) Figure 2 is a schematic diagram showing the image recording unit 107 and the image acquisition unit 108 according to the embodiment. The image recording device in this embodiment is an inkjet (IJ) printer that records images by ejecting ink from nozzles onto the paper surface. The image recording unit 107 is equipped with a plurality of nozzles, each ejecting ink. The image recording unit 107 also has an ink head equipped with nozzles.

[0031] As shown in Figure 2(A), the image recording unit 107 has a plurality of recording heads 201 to 204, each corresponding to black (K), cyan (C), magenta (M), and yellow (Y). The recording heads 201 to 204 can have various configurations. In this embodiment, each of the recording heads 201 to 204 has a plurality of nozzles for ejecting ink, arranged along a predetermined direction within a range corresponding to the width of the recording paper 206, which is the medium. In one embodiment, the plurality of nozzles of the image recording unit 107 are arranged at different positions in a direction perpendicular to the transport direction of the medium. However, two or more rows of nozzles may be provided along the width direction of the medium. The recording heads 201 to 204 in this embodiment are so-called full-line type recording heads. That is, the nozzle rows composed of a plurality of nozzles are provided so as to cover the entire width of the printing area of ​​the medium. In the following description, the width direction of the medium will be referred to as the x direction, and the transport direction of the medium will be referred to as the y direction.

[0032] The recording heads 201-204 may be composed of multiple chip modules. In the example shown in Figure 2(B), the recording head 201 has multiple chip modules 201-1 to 201-5. Each chip module may be connected to an independent circuit board.

[0033] Figure 2(C) shows a chip module viewed from the paper side. The chip module has multiple nozzles. In the example shown in Figure 2(C), the chip module has 16 nozzles. Inside each nozzle, there is an element (not shown) for ejecting ink as a droplet. The element may be, for example, a heater element that converts electrical energy into thermal energy, or a piezoelectric element that converts electrical energy into kinetic energy. In this embodiment, the nozzle arrangement density for each ink color is 1200 dpi.

[0034] The recording paper 206 is transported in the direction indicated by arrow 207 in the figure by the rotation of the transport roller 205 (and other rollers not shown) driven by a motor (not shown). While the recording paper 206 is being transported, ink is ejected from each nozzle of the recording heads 201 to 204 according to the recorded image data, thereby recording one raster image corresponding to the nozzle row of each recording head onto the recording paper 206. In this way, by repeatedly ejecting ink from each recording head onto the transported recording paper 206, one page of image can be recorded.

[0035] Furthermore, an image acquisition unit 108 is positioned downstream of the recording heads 201-204. After images are recorded by the recording heads 201-204, the recording paper 206 is transported to the image acquisition unit 108. The image acquisition unit 108 may have a reading area extending in the x direction. This reading area is provided to encompass the entire width of the printing area of ​​the medium. The image acquisition unit 108 generates read image data by sequentially capturing images of the recording paper 206 as it is transported through the reading area. Therefore, in this embodiment, an image recorded at a specific x-direction position by a specific nozzle of the image recording unit 107 is read by the image acquisition unit 108 at the corresponding specific x-direction position.

[0036] For example, the image acquisition unit 108 can generate two-dimensional RGB image data and record it in the external storage device 105. In one embodiment, the resolution of the read image data is 600 dpi. However, the resolution is not particularly limited. For example, the resolution in the x-direction and the y-direction may be different. For example, the resolution in the x-direction may be 1200 dpi and the resolution in the y-direction may be 600 dpi.

[0037] (Details of the image processing unit 106) The configuration of the image processing unit 106 will be described below with reference to Figure 3. As shown in Figure 3, the image processing unit 106 includes a conversion unit 301, a correction unit 302, an HT (halftone) processing unit 304, a creation unit 305, and a determination unit 306. The image processing unit 106 also includes a correction table 303.

[0038] The conversion unit 301, the correction unit 302, and the HT processing unit 304 generate print data from the input image data to be supplied to the image recording unit 107. The print data is generated based on the recording characteristics determined by the determination unit 306, as described later, in order to reduce recording unevenness based on the recording characteristics of the image recording unit 107, which depend on the recording position.

[0039] Specifically, the conversion unit 301 converts the input image data into image data corresponding to the ink color. In this embodiment, the conversion unit 301 converts the input image data, which is RGB image data, into CMYK image data. In one embodiment, the signal value of each pixel in each image data is 8 bits for each color. The conversion unit 301 can perform such color conversion processing using 3D LUT (lookup table) processing.

[0040] Furthermore, the correction unit 302 performs HS (head shading) correction processing on the image data corresponding to the ink color. HS correction processing is a correction process performed for each nozzle in order to correct density unevenness in the recorded material caused by the recording characteristics of the recording heads 201 to 204. The correction unit 302 can perform HS correction processing by referring to the correction table 303. This correction table 303 is created by the creation unit 305 based on the recording characteristics determined by the determination unit 306. The image processing unit 106 can hold correction tables 303 for each CMYK color. In this embodiment, the image processing unit 106 has four types of correction tables.

[0041] The correction table 303 is a table that holds correction parameters corresponding to each input signal value for each nozzle number. The correction unit 302 corrects the input signal value of each pixel of the image data for each color using the correction parameters corresponding to this input signal value and the nozzle number used to record this pixel. Figure 4 shows an example of the correction table 303 in this embodiment. The input signal value 401 is an 8-bit signal value corresponding to the signal value of the image data of any one of the CMYK colors. The nozzle number 402 is a number assigned to each nozzle of the recording head.

[0042] In this embodiment, the correction unit 302 uses a combination of the correction table 303 and linear interpolation processing for HS correction processing. For example, in Figure 4, when the input signal value is 8 and the nozzle number is 0, the correction unit 302 calculates a correction value 14 by linear interpolation using a correction value (0) corresponding to the input value 0 and nozzle number 0, and a correction value (28) corresponding to the input value 16 and nozzle number 0.

[0043] The correction table 303 is created by the creation unit 305. Details of the process for creating the correction table 303 will be described later.

[0044] The HT processing unit 304 performs HT processing (quantization processing) on ​​the image data after HS correction processing. In this embodiment, the HT processing unit 304 converts 8-bit image data for each color into 1-bit HT image data for each color. The method of HT processing is not particularly limited. For example, the HT processing unit 304 can perform HT processing using the dithering method. On the other hand, the HT processing unit 304 may also use other methods such as the error diffusion method.

[0045] The image processing unit 106 transmits the HT-processed image data obtained by the HT processing to the image recording unit 107 as print image data. Such print image data can specify whether or not to eject ink from each nozzle at each timing. The image recording unit 107 controls the ejection of ink from the recording heads 201 to 204 based on the received print image data. In this way, the image recording unit 107 records the image on the recording paper 206.

[0046] As described above, the image acquisition unit 108 captures images recorded on a medium such as the recording paper 206. If an HS chart, which will be described later, is recorded on the medium, the image acquisition unit 108 transmits the read image data of the HS chart to the determination unit 306.

[0047] The determination unit 306 determines the recording characteristics of the image recording unit 107, which depend on the recording position, based on the reading result from the image acquisition unit 108. In this embodiment, the recording position represents the position relative to the image recording unit 107 where recording using colorants is performed. This recording position may be a position in a direction perpendicular to the transport direction of the medium (in this embodiment, the x-direction).

[0048] In this embodiment, ink ejection to each recording position is performed by a nozzle located at the corresponding position. For example, ink ejection to a specific position along the x-direction on the medium is performed by a specific nozzle among a plurality of nozzles on the recording head, each located at different positions in the x-direction. For example, the recording position may correspond to the target position for ink ejection from the nozzle. In the following description, recording characteristics dependent on the recording position mean the recording characteristics of each of the plurality of nozzles. Recording characteristics for a specific recording position are the recording characteristics of the nozzle used for recording to that recording position. In this specification, a nozzle corresponding to a recording position or area means a nozzle used for recording to that recording position or area.

[0049] The determination unit 306 determines the recording characteristics (hereinafter referred to as nozzle characteristics) of each nozzle of the image recording unit 107 based on the read image data. The determination unit 306 can determine the recording characteristics of the nozzle of interest based on the relationship between the input signal value and the read signal value for that nozzle. Here, the determination unit 306 can infer the recording characteristics for a second density region based on the reading results for a first density region. Details of this process will be described later.

[0050] (Image recording flow) The following describes the processing flow performed by the image recording device in this embodiment, with reference to the flowchart shown in Figure 5. Through the following processing, the image recording device records the image specified by the user onto the medium.

[0051] In S501, the image recording device acquires a recording job. For example, the user submits a recording job to the image recording device through the operation unit 103. The user can specify input image data through the operation unit 103. The user may also transmit input image data to the image recording device via the I / F unit 109 by operating an external device.

[0052] In S502, the conversion unit 301 performs color conversion processing on the input image data as described above. In this embodiment, the conversion unit 301 converts the input image data into CMYK image data.

[0053] In S503, the correction unit 302 determines whether or not it is necessary to create the correction table 303. In this embodiment, the correction unit 302 checks whether or not the correction table 303 has already been created. If the correction table 303 has not been created, the correction unit 302 determines that it is necessary to create the correction table 303.

[0054] If it is determined that the correction table 303 does not need to be created, the process proceeds to S504. If it is determined that the correction table 303 needs to be created, the process proceeds to S507. In S507, the creation unit 305 creates the correction table 303. After that, the process proceeds to S504. Details of the HS correction table creation process will be described later.

[0055] The method for determining whether or not to create the correction table 303 is not limited to the method described above. For example, the correction unit 302 may determine whether or not to create the correction table 303 based on the elapsed time since the correction table 303 was created. For example, the correction unit 302 may determine that it is necessary to create the correction table 303 if the elapsed time exceeds a threshold. Alternatively, the correction unit 302 may determine whether or not to create the correction table 303 based on the timing of the head cleaning process performed by the image recording device. For example, the correction unit 302 may determine that it is necessary to create the correction table 303 if the correction table 303 has not been created since the most recent head cleaning process.

[0056] In S505, the HT processing unit 304 generates print image data as described above. For example, the HT processing unit 304 can generate print image data by performing HT processing on the image data after HS correction processing.

[0057] In S506, the image recording unit 107 records an image on the medium based on the printed image data as described above.

[0058] By following the processes described in S501 to S507 above, the image recording device can record the image specified by the user onto the medium.

[0059] (Process for creating correction tables) The following describes the process of creating the correction table in S507, referring to the flowchart shown in Figure 6. The creation unit 305 calculates the correction parameters for the correction process based on the chart image reading results. The creation unit 305 creates a correction table 303 for each ink color. Therefore, the process shown in Figure 6 can be performed for each ink color.

[0060] In S601, the image recording unit 107 records an HS chart onto the medium. The HS chart is used to create a correction table. Figure 7 shows an example of an HS chart. Figure 7 shows the image data of the HS chart. The HS chart 700 includes multiple patch images, each having a different input signal value. Each patch image has a uniform input signal value. Each patch image extends in the width direction of the medium and can be called a band region. Recording of each patch image can be performed using all the nozzles of the recording head corresponding to one ink color. In the example in Figure 7, the HS chart 700 includes regions 701 to 704, each corresponding to a patch image. Regions 701 to 704 have a uniform input signal value of 4 levels. Regions 701 to 704 are sometimes called unevenness acquisition regions.

[0061] Furthermore, the HS chart 700 includes markers 710a to 710e for associating the nozzle positions of the recording head with positions on regions 701 to 704. As shown in Figure 7, in this embodiment, the markers are multiple straight lines extending in the y-direction and arranged at predetermined intervals in the x-direction. A nozzle for ejecting ink to record each of the multiple straight lines constituting the marker can be predetermined.

[0062] In this embodiment, each patch image has input signal values ​​included in a first density region. This first density region is set so that differences in reading characteristics depending on the reading position are less likely to occur. On the other hand, the creation unit 305 calculates correction parameters for the correction process for the second density region based on the chart image reading results for the first density region. Details will be described later.

[0063] In S602, the image acquisition unit 108 generates a read image of the HS chart recorded on the medium in S601. The image acquisition unit 108 can generate two-dimensional read image data by capturing images of the HS chart. The image acquisition unit 108 sends the read image data to the determination unit 306.

[0064] In S603, the determination unit 306 extracts patch images from the read image data. The determination unit 306 also calculates a line profile showing the read signal value corresponding to the position in the x-direction based on the extracted patch image. For example, the determination unit 306 can average the read signal value in the carrier direction (y-direction) for each position in the x-direction. In this case, the line profile shows the relationship between the position in the x-direction and the average value of the read signal. The line profile is represented as one-dimensional data corresponding to each patch image. In this embodiment, the determination unit 306 calculates four line profiles corresponding to each of the regions 701 to 704.

[0065] Figure 12 shows an example of such a line profile. If there are no variations based on recording characteristics or reading characteristics, the line profile will be a straight line. However, if recording or reading characteristics exist, the read signal value will vary depending on the position in the x-direction.

[0066] In S604, the determination unit 306 associates the x-direction position on the read image with the nozzle number. For example, the determination unit 306 can detect markers 710a to 710e from the read image. As described above, the straight lines that constitute the markers and the nozzles that record these straight lines can be associated in advance. According to this association, the determination unit 306 can associate the x-direction position of the straight line with the nozzle number that recorded this straight line. Furthermore, the determination unit 306 can, by interpolation, associate the nozzle number of a nozzle that does not record a straight line with the x-direction recording position of that nozzle.

[0067] In S605, the determination unit 306 initializes the nozzle number of interest. The nozzle number of interest indicates the nozzle of interest whose recording characteristics are to be determined. In the following process, the corrected signal value for the nozzle of interest is determined. In this embodiment, the processes in S606 and S607 are performed sequentially for all nozzles. In the following description, the nozzle number of the leftmost nozzle of the recording head is set to 0. In this case, in S605, the determination unit 306 initializes the nozzle number of interest to 0.

[0068] In S606, the determination unit 306 determines the recording characteristics of the nozzle of interest. In this embodiment, the determination unit 306 determines the recording characteristics of the nozzle of interest based on the read signal value at the position corresponding to the nozzle of interest, as indicated by the line profile obtained in S603. In this embodiment, the HS chart has a patch image included in the first density region. Therefore, in S602 to S604, the read signal value at the position corresponding to the nozzle of interest in the first density region is obtained. In this embodiment, the determination unit 306 infers the recording characteristics of a second density region, which is different from the first density region, based on the reading results for the first density region. The specific method for determining the recording characteristics will be described later.

[0069] In S607, the creation unit 305 determines the parameters for the HS correction process for the nozzle of interest based on the recording characteristics of the nozzle of interest determined in S606. The correction table 303 can store the parameters thus determined. In this embodiment, the creation unit 305 determines the signal value after the HS correction process for the nozzle of interest. Details of this process will also be described later.

[0070] In S608, the determination unit 306 determines whether the recording characteristics have been determined for all nozzles. If there are any nozzles that have not been determined, the determination unit 306 adds 1 to the nozzle number of interest, and the process then returns to S606. If the recording characteristics have been determined for all nozzles, the process proceeds to S609.

[0071] In S609, the creation unit 305 stores the parameters for the HS correction process determined for each nozzle in the correction table 303.

[0072] Through the above series of processes, the correction table 303 creation process in S307 is performed.

[0073] (Determination process for recording characteristics) Next, the recording characteristic determination process in S606 will be explained in detail with reference to the flowchart shown in Figure 10. In S606, the determination unit 306 determines the recording characteristics (nozzle characteristics) for each nozzle. In this embodiment, the recording characteristics represent the relationship between the input signal value and the recording density. That is, the nozzle characteristics show the relationship between the color signal value (input signal value) for controlling ink ejection from the nozzle of interest and the recording density on the medium due to ink ejection from the nozzle of interest according to this input signal value. In this embodiment, this input signal value refers to the color signal value in the image data before HT processing.

[0074] On the other hand, in this embodiment, the HS chart has patch images that are included in the first density region. For example, regions 701 to 704 shown in the example in Figure 7 are all low-density regions (regions with a small amount of ink), and the HS chart 700 does not include high-density regions (regions with a large amount of ink). Therefore, in S603, a line profile corresponding to the input signal value corresponding to low density (small value) is obtained, while a line profile corresponding to the input signal value corresponding to high density (large value) is not obtained.

[0075] The first density region is set so that differences in reading characteristics depending on the reading position are less likely to occur. Therefore, the reading signal value in the first density region is expected to represent the recording density with good accuracy. On the other hand, there is a possibility that the differences in reading characteristics in the second density region will be large depending on the reading position. Therefore, the reading signal value in the second density region may not represent the recording density with good accuracy. In this embodiment, the determination unit 306 estimates the recording characteristics for the second density region at the point of interest based on the reading result for the first density region at the point of interest. For example, the determination unit 306 determines the nozzle characteristics based on the reading signal value in the low density region shown by the line profile. At this time, the determination unit 306 estimates not only the nozzle characteristics in the low density region but also the nozzle characteristics in the high density region.

[0076] First, in steps S1001 to S1003, the determination unit 306 creates a recording characteristic model based on the reading results for the first density region at the position of interest. Specifically, in step S1001, the determination unit 306 acquires the recording characteristic model. The recording characteristic model is a model that shows the relationship between the input signal value and the recording density on the medium, and may include unknown parameters.

[0077] For example, the determination unit 306 can use the model shown in equation (1). α × I = -log 10 (S / S_max) ……(1) In equation (1), I is the input signal value, and S is the signal value read by the sensor. S_max is the maximum value of the read signal. For example, if the read signal value is represented by 8 bits, then S_max = 255. α is a parameter specific to each nozzle and represents the nozzle characteristics.

[0078] In S1002, the determination unit 306 acquires the reading signal value corresponding to each of the input signal values ​​measured for the nozzle of interest. Specifically, the determination unit 306 acquires the line profiles for each region 701 to 704 calculated in S603. Furthermore, the determination unit 306 identifies the x-direction position corresponding to the nozzle of interest based on the correspondence obtained in S604. Then, the determination unit 306 acquires the reading signal value at the identified position from each line profile. In this embodiment, four reading signal values ​​corresponding to each of the regions 701 to 704 are obtained.

[0079] In S1003, the determination unit 306 determines the parameters of the recording characteristic model based on the respective read signal values ​​acquired in S1002. In this embodiment, the determination unit 306 determines the parameter α in equation (1).

[0080] Refer to Figure 11 to explain the parameter determination method in more detail. Figure 11 shows the input signal value for the nozzle of interest and the right-hand side of equation (1) (D = -log 10This graph shows the relationship between (S / S_max)). Points 1101-1104 in Figure 11 show the plot results for regions 701-704 according to the read signal values ​​obtained in S1002. That is, points 1101-1104 represent the input signal value I for each of regions 701-704 and the right-hand side of equation (1) (D=-log 10 This shows the relationship with (S / S_max).

[0081] Here, the determination unit 306 can determine the parameters of the recording characteristic model to fit the reading result for the first density region at the position of interest. That is, the parameter α can be determined by any method so that the recording characteristic model approximates the relationship between the input signal value and the read signal value (hereinafter referred to as the input-read relationship). For example, determining the parameter α in equation (1) is equivalent to determining the slope of the line 1105 in Figure 11. Such a parameter α can be determined using the least squares method so as to minimize the error between points 1101 to 1104 and the line 1105.

[0082] In S1004, the determination unit 306 estimates the recording characteristics for the second density region at the position of interest based on the created recording characteristic model. Specifically, the determination unit 306 estimates the relationship between the input signal value and the recording density as the nozzle characteristics of the nozzle of interest. In this embodiment, the determination unit 306 estimates the recording density corresponding to each input signal value from 0 to I_max. In this embodiment, the determination unit 306 calculates the recording density corresponding to each input signal value according to the recording characteristic model acquired in S1001 and the parameters determined in S1003. More specifically, the determination unit 306 associates the input signal value I with the value S calculated using equation (2), which is obtained by rearranging equation (1). S = S_max × 10 -αI ...(2)

[0083] In this way, by determining the parameters of the recording characteristic model based on the read signal values ​​of each region 701 to 704, the relationship between input signal values ​​from 0 to I_max and the recording density can be calculated. In this embodiment, the color signal values ​​of regions 701 to 704 of the HS chart 700 are set to be within the first density region (for example, less than or equal to I_th, as described later). On the other hand, according to the method of this embodiment, it is possible to estimate the recording density corresponding to the input signal value in the second density region (for example, a color signal value greater than I_th).

[0084] As described above, the reading characteristics of the image acquisition unit 108 may differ depending on the position in the x-direction. This point will be explained with reference to Figure 12. Figure 12 shows the relationship between the reading signal value (vertical axis) obtained by the image acquisition unit 108 reading a uniform yellow (Ye) patch image and the reading position x on the image (horizontal axis). Position x represents the position in the x-direction as shown in Figure 2. The reading position x can represent the position within the reading area by the image acquisition unit 108. The reading position x can be called the sensor pixel position. The center of the image is the origin, and at this position x=0.

[0085] Curves 1201 to 1204 in Figure 12 represent the read signal values ​​obtained by reading a uniform pattern on the medium corresponding to different input signal values. These curves 1201 to 1204 correspond to line profiles. Since the number of dots per unit area differs in each pattern, the average read signal values ​​for each curve 1201 to 1204 are different. Curve 1201 represents the read signal value corresponding to 0 dots, i.e., white paper. On the other hand, curve 1204 represents the read signal value corresponding to a pattern formed with the maximum number of dots that the recording head 204 can eject.

[0086] When reading a uniform pattern in this way, ideally, approximately the same reading signal value should be obtained regardless of the position in the x-direction, as shown by curve 1201. However, due to differences in reading characteristics, the reading signal value may fluctuate depending on the position in the x-direction. For example, even when an image of uniform density is recorded, the reading signal value may be smaller at the edges in the x-direction compared to the center. Such fluctuations may be affected by illuminance unevenness and the angle dependence of the reading. Therefore, depending on the configuration of the image acquisition unit 108, the reading signal value may be smaller in the center than at the edges in the x-direction.

[0087] The inventors of this application have found that the magnitude of such reading position-dependent changes in reading characteristics (reading characteristic difference) varies depending on the input signal value. For example, in one embodiment, such reading characteristic difference becomes smaller in low-density regions and larger in high-density regions.

[0088] In the example in Figure 12, the greater the number of dots per unit area, the greater the decrease in the reading signal value at the edges compared to the reading signal value at the center of the sensor. Thus, the larger the input signal value (higher density), the greater the difference in reading characteristics depending on the position. Also, when the input signal value is large, the number of dots per unit area increases, so the average reading signal value becomes smaller. Therefore, the influence of the difference in reading characteristics on the reading signal value becomes larger.

[0089] On the other hand, in this embodiment, the parameters of the recording characteristics model are calculated based on the read signal value within a first density region set to minimize differences in readability. Therefore, it is possible to suppress the influence of differences in sensor readability on the recording density estimated according to the recording characteristics model. According to this embodiment, it is possible to suppress the influence of differences in readability in the high-density region, especially when determining the recording characteristics of the nozzle at the end of the sensor. Furthermore, by creating a correction table using the nozzle characteristics obtained in this way, it is possible to suppress unevenness caused by HS correction processing due to differences in readability, especially in the high-density region.

[0090] The type of recording characteristic model is not particularly limited. For example, equation (1) above may also include a constant term b. Alternatively, instead of equation (1), a function including a combination of polynomials of degree two or higher, exponential functions, or trigonometric functions may be used. For example, equation (3) below may be used as the recording characteristic model. Equation (3) is a model equation based on the Yule-Niele equation. In equation (3), the recording density Dt is expressed as Ds × (I / Imax), where Imax is the maximum value of the input signal. S = S_max × (1-10 -Dt / n ) / (1-10 -Ds / n ) ... (3) In this case, in S1003, the determination unit 306 determines the coefficient n and the solid concentration Ds in equation (3) as parameters.

[0091] Alternatively, a weighted sum of recording densities corresponding to heads, chip modules, or nozzles, each having different recording characteristics, may be used as a recording characteristic model. For example, the relationship between input signal values ​​and recording densities can be obtained in advance for multiple heads with different discharge volumes. Then, the nozzle characteristics of the nozzle of interest can be represented by the weighted sum of recording densities for each of the multiple heads. For example, nozzle characteristics can be represented by the weighted sum of functions that give recording densities to input signal values ​​for each of the multiple heads. In this case, in S1003, the determination unit 306 determines the weight for each head as a parameter.

[0092] In the above-described embodiment, the determination unit 306 estimated the recording characteristics for both the first and second concentration regions based on the recording characteristics model. However, the method for estimating the recording characteristics is not limited to this method. For example, while the determination unit 306 estimates the recording characteristics for the second concentration region using this method, it may also use the input-read relationship shown by the reading result as the recording characteristics for the first concentration region.

[0093] (HS correction processing parameter determination process) The process for determining the parameters of the HS correction process in S607 will be explained below with reference to Figures 8 and 9. Figure 8 is a flowchart of this process.

[0094] In S801, the creation unit 305 acquires the recording characteristics of the nozzle of interest obtained in S606. Curve 901 in Figure 9 shows an example of nozzle characteristics. In Figure 9, the horizontal axis is the input signal value for the nozzle of interest, and the vertical axis is the recording density. Curve 901 differs for each nozzle depending on the ink ejection amount or the deviation of the impact position. For example, the curve representing the nozzle characteristics of a nozzle with a small ejection amount shifts upward (towards a brighter direction).

[0095] In step S802, the creation unit 305 acquires the target characteristics that have been given in advance as design values. The curve 902 in Figure 9 shows an example of target characteristics. The method of determining the target characteristics is not particularly limited. For example, the creation unit 305 may create the target characteristics by averaging the curves representing the nozzle characteristics for all nozzles.

[0096] In S803, the creation unit 305 initializes the input signal value of interest. In the subsequent S804, the parameters corresponding to each input signal value subject to parameter determination processing are determined. It is not necessary to determine the parameters for HS correction processing for all input signal values. For example, when creating the correction table shown in Figure 4, parameters are determined for each input signal value shown in input signal value 401. The input signal value of interest represents the input signal value that is the target of processing in S804 among the input signal values ​​shown in input signal value 401. In this embodiment, the creation unit 305 initializes the input signal value of interest with 0, which is the first input signal value shown in input signal value 401.

[0097] In step S804, the creation unit 305 determines correction parameters for the input signal value of interest. The process of determining the correction parameters will be explained with reference to Figure 9. Figure 9 shows the input signal value 903 corresponding to the input signal value of interest. At this time, the creation unit 305 acquires the recording density shown by the curve 902 corresponding to the target characteristic, which corresponds to the input signal value 903, as the target value 904. Furthermore, the creation unit 305 acquires the input signal value shown by the curve 901 corresponding to the nozzle characteristic, which corresponds to the target value 904, as the corrected input signal value 905.

[0098] In the subsequent S609, the creation unit 305 records the corrected input signal value 905 in the correction table 303, corresponding to the input signal value 903. In this case, the correction unit 302 can correct the input signal value 903 to the input signal value 905 in HS correction. In this case, it is expected that the recording density based on the corrected input signal value 905, using a nozzle having nozzle characteristics corresponding to curve 901, will approach the recording density that follows the target characteristics corresponding to the input signal value 903.

[0099] In S805, the creation unit 305 determines whether processing has been performed on all input signal values ​​that are subject to parameter determination processing. If there are any unprocessed input signal values, the creation unit 305 selects the next input signal value of interest, and the process then returns to S804. If parameters have been determined for all input signal values, the process in S607 is completed. Through this series of processes, the creation unit 305 can calculate the parameters for the HS correction process for one nozzle, which will be stored in the correction table 303.

[0100] (Method for determining the concentration range) As mentioned above, the color signal values ​​in regions 701 to 704 of the HS chart 700 are set to fall within a first density region where differences in reading characteristics depending on the reading position are less likely to occur. The method for setting this first density region is described below.

[0101] As described above, the first density region is a region with a small difference in readability characteristics. The second density region is a region with a large difference in readability characteristics. The second density region can be any region within the entire density range other than the first density region. In one embodiment, the difference in readability characteristics in the first density region is smaller than the difference in readability characteristics in the second density region.

[0102] Such a first density region can be determined according to the reading characteristic difference. In this embodiment, the first density region is the region below the threshold I_th. In this case, the smallest color signal value at which the reading characteristic difference is below an acceptable value can be used as the threshold I_th. In this case, the HS chart 700 can be prepared so that the color signal values ​​in each region 701 to 704 are below the threshold I_th.

[0103] The threshold I_th will be described in detail below with reference to Figure 12. In this specification, the reading characteristic difference at a specific reading position is defined by the difference in reading signal values ​​between the center of the sensor (x=0) and the reading position. In this embodiment, the minimum color signal value at which the absolute value of the reading characteristic difference at the edge of the reading area is less than or equal to a predetermined tolerance value is used as the threshold I_th. The absolute value of the reading characteristic difference at the edge corresponds to the length of arrow 1205. Alternatively, the maximum value of the absolute value of the reading characteristic difference at each position may be used instead of the absolute value of the reading characteristic difference at the edge.

[0104] For example, if the absolute value of the reading characteristic difference at the edge shown by curve 1202 is less than or equal to the tolerance value, and the absolute value of the reading characteristic difference at the edge shown by curve 1203 is greater than the tolerance value, the color signal value corresponding to curve 1202 can be used as I_th. Alternatively, the color signal value corresponding to the tolerance value may be calculated by interpolation, and the calculated color signal value may be used as I_th. For example, the color signal value corresponding to the tolerance value may be determined using linear interpolation based on the absolute value of the reading characteristic difference at the edge shown by each curve and the color signal value corresponding to each curve.

[0105] However, the method for determining the first density region is not limited to the method described above. The first density region may be predetermined, or it may be set by the creation unit 305 according to the measurement results of the image acquisition unit 108. Furthermore, the method for determining the threshold I_th is not limited to the method described above. For example, the first density region may be set so that the color difference ΔE between the color measured at the center of the sensor and the color measured at the edge of the sensor is less than or equal to a predetermined value (e.g., 0.8). In this case, the color signal value corresponding to the color difference ΔE = 0.8 can be used as I_th. Alternatively, the first density region may be determined based on the reading error of the sensor, which is independent of position, or the magnitude of density fluctuations during recording. For example, a value obtained by multiplying the magnitude of these fluctuations by a constant may be used as the threshold I_th. Furthermore, the density region or threshold I_th may be determined based on the results of visual observation of the recorded material, or the results of color measurement using a colorimeter independent of the image recording device. For example, a correction table for HS correction processing may be created based on the reading signal value, which includes reading characteristic differences depending on the reading position. The threshold I_th may then be determined by recording to a medium using this correction table, and then visually inspecting or colorimetrically measuring the recording result.

[0106] Furthermore, there may be density ranges where differences in reading characteristics are less likely to occur, or the threshold I_th mentioned above may be unknown. For example, differences in reading characteristics may change depending on the medium. Therefore, when recording on an unknown type of paper, the threshold I_th is unknown. In this case, instead of setting a threshold I_th for the input signal value, a threshold related to the read signal value may be set. For example, the right-hand side D(-log) of equation (1) 10A threshold D_th of (S / S_max) can be set. In this case, the HS chart 700 can include patch images ranging from input signal value 0 to I_max. On the other hand, when calculating the parameters of the recording characteristic model for each nozzle, it is possible to determine whether to use the measured read signal value for each patch image to calculate the parameters based on a comparison with the threshold D_th. For example, the parameter α of the recording characteristic model can be calculated using read signal values ​​less than or equal to the threshold D_th and the corresponding input signal value. In this case, pairs of read signal values ​​exceeding the threshold D_th and the corresponding input signal values ​​are not used. The threshold D_th can be set in the same way as the threshold I_th.

[0107] (Modified method for determining recording characteristics) In the above embodiment, nozzle characteristics corresponding to each input signal value were estimated based on the input-read relationship and recording characteristics model in the first concentration region. Furthermore, the first concentration region in which reading characteristic differences are less likely to occur was defined according to the threshold I_th. On the other hand, the recording characteristics model or threshold may be dynamically created based on the reading results.

[0108] As shown in Figure 12, the reading characteristic difference can be expressed by the difference between the reading signal value at the reference position and the reading signal value at the reading position. This reading characteristic difference is small in low-density areas, i.e., areas with a small number of dots per unit area. On the other hand, even in high-density areas, the difference in reading signal values ​​at each reading position near the center is small. Therefore, when the center of the sensor (x=0) is taken as the reference position, it is possible to define a reading position (sensor area) in which the reading characteristic difference between the reference position and the reading position is acceptable.

[0109] Furthermore, the number of nozzles corresponding to the first region (e.g., the central region) where an acceptable difference in reading characteristics can be obtained is usually sufficiently large. Therefore, it can be expected that nozzles whose characteristics are substantially the same as those of nozzles corresponding to the second region (e.g., the edge region) outside the first region will be included in the group of nozzles corresponding to the first region. Specifically, nozzles whose reading signal values ​​are substantially the same in the first density region where differences in reading characteristics are unlikely to occur are likely to have substantially the same nozzle characteristics.

[0110] Therefore, in this modified example, the determination unit 306 estimates the recording characteristics of the second region based on the reading result in the first region. The first region is a region in which an acceptable difference in reading characteristics can be obtained. The second region is a different region from the first region. The second region may be a region at the end in the x-direction perpendicular to the transport direction of the medium (end region). The first region may be a region located closer to the center in the x-direction than the second region (central region). The first region can correspond to a part of the reading area by the image acquisition unit 108, and the second region can correspond to the remaining part of the reading area by the image acquisition unit 108.

[0111] Specifically, in this modified example, the nozzle characteristics of the nozzle corresponding to the first region are determined based on the reading result corresponding to the nozzle corresponding to the first region. In the first region, the difference in reading characteristics is small, so the reading density accurately represents the recording density. Therefore, the input-read relationship shown by the reading result can be used as the nozzle characteristics.

[0112] On the other hand, the nozzle characteristics of the nozzle corresponding to the second region are determined as follows. That is, the determination unit 306 selects a reading result at a position in the first region that corresponds to the reading result at the position of interest in the second region, based on the similarity of the reading results for the first concentration region. For example, the determination unit 306 selects a reading result corresponding to the nozzle corresponding to the first region such that the reading result corresponding to the nozzle of interest in the second region in the first concentration region substantially matches the reading result corresponding to the nozzle corresponding to the first region. Then, the determination unit 306 infers the recording characteristics for the second concentration region at the position of interest based on the reading results for the second concentration region indicated by the selected reading results. For example, the determination unit 306 creates the recording characteristics of the nozzle of interest corresponding to the second region based on the selected reading results. Specifically, the input-read relationship indicated by the selected reading results can be used as the nozzle characteristics of the nozzle of interest. The processing in this modified example corresponds to using the reading results corresponding to the nozzle corresponding to the first region as the recording characteristics model. In this modified example, when selecting the reading result, the reading result in the second region is not referenced. Therefore, it is possible to select the recording characteristic model while suppressing the influence of the reading characteristic difference in the second density region.

[0113] Through the processing described above, nozzle characteristics can be obtained in which the influence of differences in reading characteristics at each reading position is suppressed. According to this modified example, nozzle characteristics can be determined even when it is difficult to approximate the nozzle characteristics using a recording characteristics model due to the smoothness of the media surface, ease of wetting, or the presence of a coating layer. Furthermore, the accuracy of nozzle characteristic determination can be maintained even when the sensor's reading characteristics change over time.

[0114] The following describes the processing flow for realizing this modified example with reference to Figure 13. Figure 13 is a flowchart of the process for creating the correction table 303 (S507) in this modified example.

[0115] In S1301, the image recording unit 107 records the HS chart onto the medium. Figure 14 shows an example of an HS chart used in this modified example. The HS chart 1400 has multiple patch images, each having a different color signal value, similar to Figure 7. On the other hand, the HS chart 1400 includes band-shaped regions 1401 to 1409. Regions 1401 to 1409 have uniform color signal values ​​in 9 levels. Here, the HS chart 1400 includes regions 1401 to 1404 having color signal values ​​in a first density region (low density region), as well as regions 1405 to 1409 having color signal values ​​in a second density region (high density region). The HS chart 1400 may include regions such as region 1409 that correspond to the maximum input signal value. The HS chart 1400 also includes markers 1410a to 1410j, similar to the HS chart 700.

[0116] Steps S1302 to S1304 are performed in the same manner as steps S602 to S604. This process yields the read image data and line profile.

[0117] In S1305, the determination unit 306 determines the recording characteristics for each recording position based on the read image data. The determination unit 306 can record the input-read relationship for each nozzle, as shown in the line profile, as nozzle characteristics. In this way, the recording characteristics of the nozzles corresponding to the first region are determined. On the other hand, the recording characteristics of the nozzles corresponding to the second region (end region) are not used because they are updated in S1308. For this reason, in S1305, the determination unit 306 may determine the recording characteristics only for the nozzles corresponding to the first region. The recording characteristics of the nozzles corresponding to the first region are used as a recording characteristic model, as described above.

[0118] In S1306, the determination unit 306 initializes the nozzle number of interest, similar to S605. The subsequent processes S1307 to S1309 are performed sequentially for all nozzles.

[0119] In S1307, the determination unit 306 determines whether the target nozzle corresponds to the first region in the x direction. In this modification example, the first region is the central region in the x direction. The range of the central region can be defined as, for example, -3000 < x < 3000. The determination unit 306 can determine that the target nozzle corresponds to the first region when the recording position of the target nozzle in the x direction is included in the first region. Details of the first region will be described later. When it is determined that the target nozzle corresponds to the central region, the process proceeds to S1309. Otherwise, the process proceeds to S1308.

[0120] In S1308, the determination unit 306 determines the recording characteristics (nozzle characteristics) of the target nozzle. In S1308, the recording characteristics of the nozzle corresponding to the end region are determined. Details of the process will be described later.

[0121] In S1309, the creation unit 305 calculates the correction parameter for the target nozzle based on the nozzle characteristics in the same manner as S607. In this modification example, the recording characteristics are represented by the combination of the input signal value and the recording density. Therefore, when determining the parameters of the HS correction process by the method shown in FIG. 9, the creation unit 305 can calculate the input signal value corresponding to the target value 904 according to the recording characteristics by interpolation processing such as linear interpolation. Further, the creation unit 305 may calculate the input signal value corresponding to the target value 904 according to the function approximating the recording characteristics.

[0122] S1310 to S1311 are performed in the same manner as S608 to S609. Through the above series of processes, the correction table 303 creation process in S307 is performed.

[0123] Here, the first region will be explained in more detail with reference to Figure 15. In this modified example, the central region, which is the first region, is defined such that its reading characteristics can be considered to be approximately the same as those at the center of the sensor (x=0). In Figure 15, curve 1501 is an example showing the relationship between the read signal value (vertical axis) and the reading position x (horizontal axis) when the image acquisition unit 108 reads a uniform yellow (Ye) image recorded with the maximum number of dots that the recording head 204 can eject. As explained with reference to Figure 12, the read signal value may be smaller at the x-direction edge of the medium compared to the central part. The difference in reading characteristics for each reading position can be defined by the length of arrow 1205. That is, the difference in reading characteristics at each reading position can be defined by the difference between the read signal value at each reading position and the read signal value at reading position x=0.

[0124] In this modified example, the first region is the region in which the reading characteristic difference determined in this way is less than or equal to a predetermined tolerance value. For example, in Figure 15, the central region is between x1 and x2. In the example in Figure 15, arrow 1502 corresponds to this tolerance value. Such a tolerance value may be set, for example, so that the color difference ΔE between the color measured at position x=0 and the color measured at a position within the first region is less than or equal to a predetermined value (e.g., 0.8). As mentioned above, the reading characteristic difference varies depending on the patch image (or input signal value). Therefore, the first region can be defined so that the reading characteristic difference in the first region is less than or equal to a predetermined tolerance value for all patch images. Alternatively, the first region may be defined so that the reading characteristic difference in the first region is less than or equal to a predetermined tolerance value for the patch image corresponding to the maximum input signal value.

[0125] However, the method for determining the first region is not limited to the method described above. Furthermore, such a first region may be set in advance, or the creation unit 305 may set it according to the measurement results of the image acquisition unit 108. For example, in order to achieve a color difference ΔE < 0.8 or less that is difficult to perceive visually, in combination with errors other than the reading characteristic difference, a value corresponding to ΔE < 0.4 may be used as an acceptable value. In this case, the color difference ΔE between the color measured at x=0 and the color measured at x=x2 may be 0.4. In addition, the first region may be determined based on the reading error of the sensor that is independent of position or the magnitude of density fluctuations during recording. For example, a value obtained by multiplying the magnitude of these fluctuations by a constant may be used as an acceptable value. Furthermore, the first region may be set based on the results of visual observation of the recorded material or the results of color measurement using a colorimeter independent of the image recording device. For example, a correction table for HS correction processing may be created based on the reading signal value including the reading characteristic difference according to the reading position. Then, after recording to a medium using this correction table, the range of the first region (x1 to x2) may be set by visually inspecting or colorimetrically measuring the recording results.

[0126] The following describes the processing in S1308 in more detail. In S1308, the recording characteristics of multiple nozzles corresponding to the first region (central region) are used as the recording characteristic model. Then, for the nozzle of interest corresponding to the second region (edge ​​region), a recording characteristic model is searched for that shows the closest recording density (=read signal value) in the first density region (low density region). The recording characteristics shown by the recording characteristic model thus searched for are used as the recording characteristics of the nozzle of interest.

[0127] Hereinafter, for simplicity of explanation, the read signal values at the positions corresponding to nozzles A to C will be described. Nozzles A and B correspond to the central region, and nozzle C corresponds to the end region. FIG. 16 schematically shows the relationship between the input signal value and the read signal value (input-read relationship). In the figure, the horizontal axis represents the input signal value, and the vertical axis represents the read signal value by the image acquisition unit 108. The solid line 1601 corresponds to nozzle A, the solid line 1602 corresponds to nozzle B, and the dotted line 1603 corresponds to nozzle C, respectively. The black circles in the figure indicate the plot results of the combinations of the color signal values of regions 1401 to 1409 and the read signal values corresponding to each nozzle. Also, B_th represents a threshold value related to the read signal value.

[0128] As shown in FIG. 16, for nozzle A corresponding to the central region and nozzle C corresponding to the end region, in the region of the read signal value of B_th or more, the input-read relationship is substantially the same. On the other hand, in the region of the read signal value smaller than B_th, a difference occurs in the input-read relationship. In this modification, since the input-read relationships of nozzles A and C substantially coincide in the low density portion (≧B_th), it is presumed that the nozzle characteristics of nozzles A and C substantially coincide. And the difference in the high density portion (<B_th) between nozzle A and nozzle C is presumed to be due to the reading error of the sensor rather than the difference in nozzle characteristics. Therefore, in this modification, as the recording characteristics of nozzle C, the input-read relationship of nozzle A indicated by the solid line 1602 is used instead of the input-read relationship of nozzle C indicated by the dotted line 1603.

[0129] The threshold B_th can be defined as follows. As explained with reference to Figure 15, for each nozzle of interest, the read signal value and the reading characteristic difference corresponding to each input signal value can be obtained. Therefore, the input signal value corresponding to the largest reading characteristic difference that is less than or equal to the tolerance value used to define the first region described above can be used as the threshold B_th. In this way, the threshold B_th can be set for each nozzle based on the reading results. On the other hand, the method for setting the first concentration region with a small reading characteristic difference is not limited to the method described above. For example, the tolerance value used to define the first concentration region does not need to be the same as the tolerance value used to define the first region described above. Also, a common threshold B_th may be used for all nozzles. In this case, for the nozzle at the outermost end in the x direction, the input signal value corresponding to the largest reading characteristic difference that is less than or equal to the tolerance value described above may be used as the threshold B_th.

[0130] In S1308, the determination unit 306 selects a nozzle from among multiple nozzles corresponding to the central region that exhibits the input-read relationship most similar to that of the nozzle of interest. For example, from among the solid lines 1601 and 1602, the determination unit 306 selects the solid line 1601, which is more similar to the dotted line 1603. Specifically, the determination unit 306 can select a nozzle such that the sum of the absolute values ​​of the differences (i.e., the distance between the black circles) of the read signal values ​​corresponding to the same input signal value for each input signal value is minimized. In this modified example, when comparing the input-read relationships, only read signal values ​​greater than or equal to the threshold B_th are used. With this configuration, it is possible to select a nozzle in the central region that has substantially the same recording characteristics as the nozzle of interest while suppressing the influence of differences in reading characteristics.

[0131] The following describes the processing flow of S1308 with reference to the flowchart shown in Figure 17. In S1701, the determination unit 306 acquires the input-reading characteristics of the nozzle of interest based on the nozzle number of interest. For example, the determination unit 306 acquires the combination of the read signal value and the input signal value, indicated by the black circle on the dotted line 1603 in Figure 16.

[0132] Next, in S1702, the determination unit 306 initializes the model number of interest. As described above, in this modified example, the input-reading characteristics of the nozzle corresponding to the central region are used as the recording characteristic model. Furthermore, the processing in S1703 to S1704 is performed sequentially for all recording characteristic models (i.e., all nozzles corresponding to the central region). Therefore, the model number of interest can be initialized to the recording characteristic model number of the leftmost nozzle in the central region (for example, number 0).

[0133] In the subsequent S1703, the determination unit 306 acquires the input-read characteristics corresponding to the model number of interest. For example, the determination unit 306 acquires a combination of a read signal value and an input signal value, indicated by a black circle on either the solid line 1601 or 1602 in Figure 16.

[0134] In the following S1704, the determination unit 306 calculates the difference between the input-reading characteristics of the nozzle of interest acquired in S1701 and the input-reading characteristics corresponding to the model number of interest acquired in S1703. As described above, the determination unit 306 calculates the difference in a first concentration region that is determined to minimize the difference in reading characteristics. For example, if the model of interest corresponds to nozzle A, the determination unit 306 selects six pairs of black circles on the solid line 1601 and the dotted line 1603 where the reading signal values ​​are all greater than or equal to B_th. Then, the determination unit 306 calculates the absolute value of the difference in reading signal values ​​for each of these pairs of black circles. The sum of these calculated absolute values ​​is used as the difference between the input-reading characteristics of the nozzle of interest and the input-reading characteristics of the model of interest.

[0135] In the next step, S1705, the determination unit 306 determines whether or not a difference was calculated in S1704 for all recording characteristic models within the central region. If a difference has been calculated for all recording characteristic models within the central region, the process proceeds to S1706. Otherwise, the determination unit 306 updates the model number of interest. The process then returns to S1703, and the determination unit 306 continues the difference calculation process. The determination unit 306 can update the model number of interest by, for example, adding 1 to it.

[0136] In S1706, the determination unit 306 selects one recording characteristic model from multiple recording characteristic models based on the difference calculated in S1704 for each recording characteristic model. For example, the determination unit 306 can select a recording characteristic model such that the difference calculated in S1704 for the selected recording characteristic model is smaller than the difference calculated in S1704 for the other recording characteristic models. In this way, the determination unit 306 can select a recording characteristic model that is close to the input-reading characteristics of the nozzle of interest.

[0137] In S1707, the determination unit 306 replaces the recording characteristics of the nozzle of interest with the recording characteristics shown by the recording characteristics model selected in S1706. In this way, the estimated result of the recording characteristics of the nozzle of interest corresponding to the second region is obtained.

[0138] Through the above processing, nozzle characteristics can be obtained in which the influence of differences in reading characteristics for each reading position is suppressed. Note that it is not necessary to use the recording characteristics of all nozzles corresponding to the first region as the recording characteristic model. For example, the processing in S1703 to S1704 may be performed on only some of the recording characteristic models. Alternatively, a recording characteristic model may be generated based on the recording characteristics of the nozzles corresponding to the first region. For example, the recording characteristics of each nozzle can be classified based on similarity. In this case, the recording characteristics that represent each of the multiple classifications, or the average recording characteristics for each classification, can be used as the recording characteristic model. For example, if the nozzle characteristics are similar for each chip module, multiple recording characteristic models can be created by averaging the nozzle characteristics for each chip module.

[0139] Furthermore, in the above modified example, the first density region is defined by a threshold B_th for the read signal value. Alternatively, the first density region may be defined by a threshold I_th for the input signal value, as already described. In this case, when comparing the input-read relationship in S1308, only read signal values ​​corresponding to input signal values ​​greater than or equal to the threshold I_th can be used.

[0140] Furthermore, similar to the embodiments described above, the recording characteristics of the nozzle of interest may be estimated based on a weighted sum of multiple recording characteristics. For example, the weights of each recording characteristic can be set so that the input-reading characteristics of the nozzle of interest in a first concentration region are represented by a weighted sum of the recording characteristics of multiple nozzles corresponding to the first region. In this case, the recording characteristics of the nozzle of interest can be estimated as a weighted sum of each recording characteristic according to the set weights.

[0141] (Another variation of recording characteristic determination) In the embodiments and modifications described above, the nozzle characteristics in the high-density region were estimated based on the reading signal value corresponding to the nozzle of interest in the low-density region and the recording characteristics model. On the other hand, in the following modifications, instead of directly estimating the nozzle characteristics, the reading characteristics dependent on the reading position in the high-density region are first estimated. Then, the nozzle characteristics are estimated by removing the reading characteristic difference from the reading signal value. In the following modifications, it is expected that the accuracy of nozzle characteristic estimation will improve when the sensor's reading characteristic difference changes gradually with respect to the reading position.

[0142] The processing flow in this modified example will be described below with reference to Figure 18. Figure 18 is a flowchart of the process for creating the correction table 303 (S507) in this embodiment. In S1801 to S1809, the recording characteristics of each nozzle are estimated. The estimation of the nozzle recording characteristics can be performed based on the reading results of the HS chart, as described above. For example, this process can be performed in the same way as S1301 to S1308 and S1310. Alternatively, this process can be performed in the same way as S601 to S606 and S608.

[0143] In S1810, the determination unit 306 estimates the reading characteristics of the sensor. Specifically, the determination unit 306 can estimate the reading characteristics for each reading position based on the line profile corresponding to each patch image obtained in S1803 and the nozzle characteristics estimated in S1808.

[0144] The processing of S1810 will be explained in detail with reference to Figure 19. Curve 1901 in Figure 19(A) schematically shows the line profile corresponding to region 709. As shown by curve 1901, the line profile obtained from a patch image such as region 709 may contain high-frequency components. These high-frequency components are affected not only by differences in nozzle characteristics, but also by random fluctuations with each ink ejection, reading errors that are not dependent on position, or irregularities or dirt contained in the paper. Thus, the read signal value may contain high-frequency components originating from causes other than nozzle characteristics and differences in reading characteristics.

[0145] Curve 1902 in Figure 19(B) schematically shows the line profile for region 709, represented by the nozzle characteristics obtained in S1805 and S1808. The nozzle characteristics represent the relationship between the input signal value and the recording density for each recording position (nozzle). Meanwhile, the recording position and the reading position are associated as described above. Furthermore, the recording density corresponds to the reading signal value as described above. In this way, the line profile shown in Figure 19(B) can be obtained from the nozzle characteristics for each recording position.

[0146] The determination unit 306 determines a reading characteristic value representing the reading characteristics of the image acquisition unit 108 according to the reading position, based on the reading result by the image acquisition unit 108 as shown by curve 1901 and the recording characteristics of the image recording unit 107 as shown by curve 1902. The reading characteristic value can be the reading characteristic difference at each reading position. For example, curve 1903 in Figure 19(C) is a plot of the difference between curve 1901 and curve 1902. Curve 1903 schematically shows the reading characteristic difference of the sensor in region 709. That is, curve 1903 is obtained by removing the change in recording characteristics that depends on the recording position shown in curve 1902 from the reading signal values ​​at each position shown in curve 1901. In addition to the reading characteristic difference of the sensor, curve 1903 also includes the high-frequency components mentioned above. Furthermore, curve 1903 may be affected by the estimation error of the nozzle characteristics. It is assumed that such estimation errors also appear as high-frequency components.

[0147] On the other hand, the sensor's reading characteristics are expected to change smoothly depending on the reading position. Specifically, reading characteristics such as relative sensitivity may change depending on the distance from the sensor's center position (x=0). For example, if the image acquisition unit 108 has a reduction optical system, the angle of incidence of reflected light to the sensor changes smoothly depending on the reading position. Also, if there is illuminance unevenness in the light that the image acquisition unit 108 irradiates onto the medium, the illuminance distribution is likely to change smoothly. In such cases, the constraint that the sensor's reading characteristics change smoothly with respect to the reading position can be used.

[0148] To apply this constraint, the determination unit 306 can perform smoothing processing on the reading characteristic value of the image acquisition unit 108 according to the reading position. As smoothing processing, for example, function approximation processing or high-frequency suppression processing can be performed. Curve 1904 in Figure 19(D) is obtained by function approximation of curve 1903. This function is a function of the reading position (e.g., position x). Specifically, curve 1904 can be obtained by approximating curve 1903 using a cubic function of position x. Through such processing, the above high-frequency components are removed from curve 1903. Therefore, curve 1904 is expected to more accurately represent the difference in sensor reading characteristics. As described above, the influence of changes in recording characteristics that depend on the recording position is reduced from curve 1903. Therefore, even if the fluctuation in recording characteristics has low-frequency components, it becomes easier to more accurately evaluate the difference in sensor reading characteristics. Alternatively, instead of using function approximation, a curve 1904 with low-frequency components may be calculated by applying a low-pass filter to curve 1903.

[0149] In S1810, the determination unit 306 calculates the difference (curve 1902) between the reading signal value obtained by measurement and the reading signal value calculated according to the estimated nozzle characteristics for each reading position. Then, the determination unit 306 estimates the reading characteristics (curve 1904) for each reading position by performing a smoothing process on the difference for each reading position. By performing this process for each patch image, the determination unit 306 can obtain the reading characteristics corresponding to each input signal value.

[0150] In the subsequent S1811, the determination unit 306 corrects the reading result by the image acquisition unit 108 based on the reading characteristic value after smoothing obtained in S1810. The determination unit 306 can correct the reading result in a way that suppresses the influence of the reading characteristic difference. For example, the determination unit 306 can remove the sensor reading characteristic difference obtained in S1810 from the line profile obtained in S1803. In this modified example, the determination unit 306 subtracts the reading characteristic difference shown by curve 1904 from the line profile shown by curve 1901. This process reduces the influence of the sensor reading characteristic difference from the line profile. In this modified example, the determination unit 306 performs this process for each patch image. In this way, a total of nine line profiles with reduced influence of the reading characteristic difference are obtained. These line profiles show the recording characteristics for each recording position in both the first density region and the second density region. In this way, the determination unit 306 can re-determine the recording characteristics of the image recording unit 107, which depend on the recording position, based on the corrected reading result.

[0151] In the subsequent S1812, the creation unit 305 determines correction parameters for each recording position based on the recording characteristics of the image recording unit 107 determined based on the corrected reading results. For example, the creation unit 305 can determine correction parameters for each nozzle based on the line profile obtained in S1811. Specifically, the creation unit 305 can create combinations of input signal values ​​and recording density for each recording position based on the line profile obtained in S1811. Here again, the reading signal values ​​indicated by the line profile can be used as the recording density. The determination of the correction parameters can be performed in the same way as in S1309.

[0152] Finally, in S1813, the creation unit 305 stores the HS correction processing parameters determined for each nozzle in the correction table 303.

[0153] Through the above process, the parameters for the HS correction process can be determined based on nozzle characteristics in which the influence of reading characteristic differences has been reduced.

[0154] (Other variations) In the above explanation, HS correction was performed on a nozzle-by-nozzle basis. However, multiple nozzles may be grouped together as a block. The recording characteristics may then be determined for each block. Alternatively, the recording characteristics may be determined for each chip module on which the nozzles are mounted. Furthermore, the parameters for the HS correction process may be determined for each block or chip module. For example, let's assume that one block contains four nozzles and the recording characteristics are determined for each block. In this case, the correction table 303 shown in Figure 4 records the block number instead of the nozzle number. The determination unit 306 then estimates the average recording characteristics for each block.

[0155] Furthermore, the processing unit for HS correction and the processing unit for estimating nozzle characteristics may be different. For example, in the process shown in Figure 18, HS correction can be performed on a nozzle-by-nozzle basis or in a block-by-block basis including 4 nozzles. On the other hand, it can be used to determine the average recording characteristics for each chip and to calculate the difference in sensor reading characteristics.

[0156] Furthermore, the difference in reading characteristics depending on the reading position depends on the spectral distribution of the image. Therefore, depending on the ink color, it is possible to switch whether or not to perform the process of estimating the nozzle characteristics in the second density region based on the reading result in the first density region. For example, when reading yellow ink in the blue channel, the difference in reading characteristics in the high density region tends to be large. For this reason, this process (e.g., S1806~S1811) may be performed only when determining the parameters for the HS correction process for the ink head that ejects yellow ink. On the other hand, when determining the parameters for the HS correction process for a head that ejects a different ink, the nozzle characteristics determined in S1805 may be used for both the first and second density regions. In this way, by configuring the system to perform the above estimation process only when recording with a predetermined ink color or when the image contains a predetermined ink color, the computational load required for the HS correction process can be reduced.

[0157] (Other examples) The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0158] The disclosures herein include the following image recording devices and their control methods, information processing devices, and programs. (Item 1) A recording means for recording an image onto a medium based on print data, A reading means for reading the chart image recorded by the recording means, The system includes a determination means that determines the recording characteristics of the recording means, which depend on the recording position, based on the reading result by the reading means. The image recording device is characterized in that the determination means estimates the recording characteristics for a second density region based on the reading result for a first density region. (Item 2) The image recording apparatus according to item 1, characterized in that the change in the reading characteristics of the reading means, which depends on the reading position in the first density region, is smaller than the change in the reading characteristics of the reading means, which depends on the reading position in the second density region. (Item 3) The image recording device according to any one of items 1 to 2, characterized in that the first density region is a region with a lower density than the second density region. (Item 4) The image recording device according to any one of items 1 to 3, characterized in that the recording position is a position in a direction perpendicular to the transport direction of the medium. (Item 5) The recording means comprises a plurality of nozzles that eject ink, The image recording device according to any one of items 1 to 4, characterized in that the plurality of nozzles are arranged at different positions in a direction perpendicular to the transport direction of the medium. (Item 6) The image recording apparatus according to item 5, characterized in that the recording characteristics of the recording means, which depend on the recording position, are the recording characteristics of each of the plurality of nozzles. (Item 7) The image recording device according to any one of items 1 to 6, characterized in that the recording characteristics represent the relationship between the input signal value and the recording density. (Item 8) The image recording device according to any one of items 1 to 7, characterized in that the determination means estimates the recording characteristics for the second density region at the position of interest based on the reading result for the first density region at the position of interest. (Item 9) The image recording apparatus according to item 8, characterized in that the determination means creates a recording characteristic model based on the reading result for the first density region at the position of interest, and estimates the recording characteristics for the second density region at the position of interest based on the recording characteristic model. (Item 10) The image recording device according to any one of items 8 to 9, characterized in that the determination means determines the parameters of a recording characteristic model to fit with the reading result for the first density region at the position of interest, and estimates the recording characteristics for the second density region at the position of interest based on the recording characteristic model. (Item 11) The image recording device according to any one of items 1 to 10, characterized in that the determination means estimates the recording characteristics for a second region in a direction perpendicular to the transport direction of the medium based on the reading result in a first region in a direction perpendicular to the transport direction of the medium. (Item 12) The image recording apparatus according to item 11, characterized in that the determination means selects a reading result at a position in the first region that corresponds to the reading result at a position of interest in the second region, based on the similarity of the reading results for the first density region, and estimates the recording characteristics for the second density region at the position of interest based on the reading results for the second density region indicated by the selected reading result. (Item 13) The image recording device according to any one of items 11 to 12, characterized in that the second region is a region at the end in a direction perpendicular to the transport direction of the medium, and the first region is a region located closer to the center than the second region. (Item 14) The determination means is, Based on the reading result by the reading means and the determined recording characteristics of the recording means, the reading characteristic value of the reading means corresponding to the reading position is determined. Smoothing is performed on the reading characteristic value of the reading means according to the reading position. Based on the reading characteristic value after the smoothing process, the reading result by the reading means is corrected. An image recording device characterized by any one of items 1 to 13. (Item 15) The image recording device according to any one of items 1 to 14, further comprising a processing means for generating print data to be supplied to the recording means from input image data, in order to reduce recording unevenness based on the recording characteristics of the recording means which depend on the recording position, based on the recording characteristics determined by the determination means. (Item 16) The image recording device according to any one of items 1 to 15, characterized in that the recording means is an ink head that ejects yellow ink. (Item 17) A control method performed by an image recording device equipped with recording means for recording an image on a medium based on print data, The process of reading the chart image recorded by the recording means using the reading means provided by the image recording device, The process includes determining the recording characteristics of the recording means, which depend on the recording position, based on the reading results of the chart image, A control method characterized in that, in the determination step, the recording characteristics for a second concentration region are estimated based on the reading results for a first concentration region. (Item 18) An acquisition means for acquiring the reading result of a chart image recorded by a recording means provided in an image recording device that records an image on a medium based on print data, and the reading result of the reading means of the image recording device. The system includes a determination means for determining the recording characteristics of the recording means, which depend on the recording position, based on the reading result. The determination means is characterized by inferring the recording characteristics for a second concentration region based on the reading results for a first concentration region, and is an information processing device. (Item 19) A program that enables a computer to function as an information processing device as described in item 18. (Item 20) A recording means for recording an image onto a medium based on print data, A reading means for reading the chart image recorded by the recording means, A processing means that generates the print data to be supplied to the recording means from input image data by performing a correction process to reduce recording unevenness based on the recording characteristics of the recording means which depend on the recording position, A calculation means for calculating correction parameters for the correction process based on the reading results of the chart image, so as to calculate correction parameters for the correction process for the second density region based on the reading results of the chart image for the first density region, An image recording device characterized by comprising:

[0159] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of Symbols]

[0160] 106: Image processing unit, 107: Image recording unit, 108: Image acquisition unit, 301: Conversion unit, 302: Correction unit, 304: HT processing unit, 305: Creation unit, 306: Determination unit

Claims

1. A recording means for recording an image onto a medium based on print data, A reading means for reading the chart image recorded by the recording means, The system includes a determination means that determines the recording characteristics of the recording means, which depend on the recording position, based on the reading result by the reading means. The image recording device is characterized in that the determination means estimates the recording characteristics for a second density region based on the reading results for a first density region.

2. The image recording apparatus according to claim 1, characterized in that the change in the reading characteristics of the reading means, which depends on the reading position in the first density region, is smaller than the change in the reading characteristics of the reading means, which depends on the reading position in the second density region.

3. The image recording apparatus according to claim 1, characterized in that the first density region is a region with a lower density than the second density region.

4. The image recording apparatus according to claim 1, characterized in that the recording position is a position in a direction perpendicular to the transport direction of the medium.

5. The recording means comprises a plurality of nozzles that eject ink, The image recording apparatus according to claim 1, characterized in that the plurality of nozzles are arranged at different positions in a direction perpendicular to the conveying direction of the medium.

6. The image recording apparatus according to claim 5, characterized in that the recording characteristics of the recording means, which depend on the recording position, are the recording characteristics of each of the plurality of nozzles.

7. The image recording apparatus according to claim 1, characterized in that the recording characteristics represent the relationship between the input signal value and the recording density.

8. The image recording apparatus according to claim 1, characterized in that the determination means estimates the recording characteristics for the second density region at the position of interest based on the reading result for the first density region at the position of interest.

9. The image recording apparatus according to claim 8, characterized in that the determination means creates a recording characteristic model based on the reading result for the first density region at the position of interest, and estimates the recording characteristics for the second density region at the position of interest based on the recording characteristic model.

10. The image recording apparatus according to claim 8, characterized in that the determination means determines the parameters of a recording characteristic model so as to fit with the reading result for the first density region at the position of interest, and estimates the recording characteristics for the second density region at the position of interest based on the recording characteristic model.

11. The image recording apparatus according to claim 1, characterized in that the determination means estimates the recording characteristics for a second region in a direction perpendicular to the transport direction of the medium based on the reading result in a first region in a direction perpendicular to the transport direction of the medium.

12. The image recording apparatus according to claim 11, characterized in that the determination means selects a reading result at a position in the first region that corresponds to the reading result at a position of interest in the second region, based on the similarity of the reading results for the first density region, and estimates the recording characteristics for the second density region at the position of interest based on the reading results for the second density region indicated by the selected reading result.

13. The image recording apparatus according to claim 11, characterized in that the second region is a region at the end in a direction perpendicular to the transport direction of the medium, and the first region is a region located closer to the center than the second region.

14. The determination means is, Based on the reading result by the reading means and the determined recording characteristics of the recording means, the reading characteristic value of the reading means corresponding to the reading position is determined. Smoothing is performed on the reading characteristic value of the reading means according to the reading position. Based on the reading characteristic value after the smoothing process, the reading result by the reading means is corrected. The image recording device according to claim 1, characterized in that...

15. The image recording apparatus according to claim 1, further comprising a processing means for generating print data to be supplied to the recording means from input image data, based on the recording characteristics determined by the determination means, in order to reduce recording unevenness based on the recording characteristics of the recording means which depend on the recording position.

16. The image recording apparatus according to claim 1, characterized in that the recording means is an ink head that ejects yellow ink.

17. A control method performed by an image recording device equipped with recording means for recording an image on a medium based on print data, The process of reading the chart image recorded by the recording means using the reading means provided by the image recording device, The process includes determining the recording characteristics of the recording means, which depend on the recording position, based on the reading results of the chart image, A control method characterized in that, in the determination step, the recording characteristics for a second concentration region are estimated based on the reading results for a first concentration region.

18. An acquisition means for acquiring the reading result of a chart image recorded by a recording means provided in an image recording device that records an image on a medium based on print data, and the reading result of the reading means of the image recording device. The system includes a determination means for determining the recording characteristics of the recording means, which depend on the recording position, based on the reading result. The determination means is characterized by inferring the recording characteristics for a second concentration region based on the reading results for a first concentration region, and is an information processing device.

19. A program for causing a computer to function as an information processing device according to claim 18.

20. A recording means for recording an image onto a medium based on print data, A reading means for reading the chart image recorded by the recording means, A processing means that generates the print data to be supplied to the recording means from input image data by performing a correction process to reduce recording unevenness based on the recording characteristics of the recording means which depend on the recording position, A calculation means for calculating correction parameters for the correction process based on the reading results of the chart image, so as to calculate correction parameters for the correction process for the second density region based on the reading results of the chart image for the first density region, An image recording device characterized by comprising:

Images