JP6128826B2 - Recording apparatus and method for correcting recording density - Google Patents

Description

  The present invention relates to an ink jet recording apparatus that suppresses occurrence of recording density unevenness in the column direction of recording elements derived from head characteristics when recording using a recording head in which a plurality of recording elements are arranged in a line, and correction of recording density The present invention relates to a unit and a recording density correction method.

  As a recording method for discharging a liquid such as ink, an ink jet recording method is known in which the discharge of ink droplets is controlled using energy such as heat or pressure generated by applying an electrical signal to a recording element.

  In order to improve the recording speed and the recording image quality, generally, an ink discharge port or an ink flow path communicating with the ink discharge port and a discharge energy generating element that generates energy used for discharging the ink droplet (hereinafter collectively referred to as these). A multi-nozzle head having a plurality of recording elements) is used. Due to variations in manufacturing processes, characteristics of constituent materials, and the like, it is difficult to uniformly manufacture recording elements of a multi-nozzle head. Therefore, there is a certain degree of characteristic variation (manufacturing tolerance) between a plurality of recording elements of the multi-nozzle head. If the characteristics such as the shape of the ink ejection port and the ink liquid path are not uniform among the recording elements, the amount of ink ejected by each recording element is different. As a result, the size and positional relationship of the recorded dots are not uniform, and density unevenness occurs in the recorded image.

  In order to suppress the occurrence of such density unevenness, a so-called head shading method (HS method) is known in which density unevenness of a recorded test pattern is read and a signal for each recording element is corrected based on the read result. Yes. As a recording apparatus that employs the HS method, for example, there is an apparatus that performs signal correction using a test pattern recorded at a single density level. However, it is known that it is difficult to appropriately apply correction in all gradation representations from low density to high density by uniquely applying a correction formula for a single density level. As a countermeasure, Patent Document 1 discloses a first correction unit that selectively indicates recording characteristics of each recording element of the recording head for each of a plurality of density regions, and a recording characteristic instructed by the first correction unit. And a second correction means for correcting the signal. In this recording apparatus, the recording characteristic indicated by the first correction unit is selected according to the density region to which the signal corresponding to each recording element belongs.

  Further, in order to control the ejection amount of ink droplets that change with respect to the temperature distribution in the recording element substrate (hereinafter also referred to as ejection port chip), by performing separate head drive control within the ejection port chip, A technique for controlling density unevenness due to temperature distribution in the discharge port chip is known. For example, a plurality of temperature detection elements in the discharge port chip and a heater board configuration in which separate drive pulses and applied voltages can be set in the discharge port chip are adopted, and discharge is performed according to the output result of the temperature detection element. There are techniques for implementing separate head drive control within the outlet tip.

Japanese Patent Laid-Open No. 5-220977

  However, since the recording apparatus of Patent Document 1 performs correction using a plurality of density level test patterns, it is necessary to record the number of patterns corresponding to the number of density levels. Therefore, as compared with the case of using a test pattern of a single density level, the time required for pattern analysis and the amount of recording medium that becomes paper dust increase due to pattern recording.

  For example, in an ink jet recording apparatus equipped with a recording head for four color inks as shown in FIGS. 4A and 4B, patterns corresponding to a plurality of density levels are used as test patterns for detecting density unevenness. A total of four colors are required for each ink color. Although detailed description is omitted, in order to read the density unevenness of the recorded test pattern with a scanner or the like, the recording medium needs a blank space in addition to the recording analysis unit. It is assumed that the pattern length necessary for accurately detecting density unevenness is about 2.0 to 3.0 inches. At this time, if five levels of signals are input and five density level test patterns are recorded, the required length in the conveyance direction of the recording medium is a maximum of 60.0 inches (= 3.0 inches × 5 steps × 4 colors).

  Therefore, using a test pattern recorded at a single density level, a recording apparatus capable of suppressing density unevenness in all gradation representations from low density to high density, a recording density correction unit, and a recording density There is a need for a correction method.

In order to solve the above-described problems, a recording apparatus according to the present invention includes a recording head on which a discharge port chip in which a plurality of recording elements are arranged in an arrangement direction is mounted relative to a recording medium in a direction intersecting the arrangement direction. A recording apparatus that performs recording by ejecting ink by moving and driving the recording element,
Detection means for reading the recording density of the recorded pattern for each arbitrary unit of the plurality of recording elements in the arrangement direction with respect to the pattern recorded by ejecting ink by driving the plurality of recording elements under the same conditions; An acquisition means for acquiring image data corresponding to an image to be recorded; a range of ink discharge amounts corresponding to the recording density read by the detection means; and a recording duty indicated by the image data acquired by the acquisition means; Deciding means for determining the number of dots of ink per unit area according to the position of the arbitrary unit in the ejection port chip, and ejecting the ink of the number of dots determined by the deciding means. Control means for controlling, and the determining means is configured to control the ink based on the ink discharge amount range and the recording duty, respectively. (I) When the position of the arbitrary unit is the first position, the number of dots of the ink is determined using the first table. (Ii) When the position of the arbitrary unit is a second position farther from the end in the arrangement direction in the discharge port chip than the first position, the second table is used to The number of ink dots is determined, and when the range of the ink discharge amount is the same range, the first and second tables have the first table as the first duty increases as the recording duty increases. The number of ink dots is defined so that the number of ink dots defined is smaller than that of the table .

  According to the present invention, by using a test pattern of one type of density, it is possible to control the ink discharge amount for each of the plurality of printing elements and to suppress printing density unevenness with high accuracy.

FIG. 3 is a schematic diagram of a recording head according to the first embodiment. FIG. 2A is a schematic diagram illustrating a discharge port chip of the recording head of FIG. 1, and FIG. 2B is a diagram illustrating a relationship between a position in the discharge port chip and a temperature. It is a figure which shows the relationship between an input value and the number of output dots. (A) is a schematic perspective view of an inkjet recording device, (b) is a schematic sectional drawing in the recording medium conveyance direction of an inkjet recording device. It is a block diagram which shows the system configuration | structure of 1st Embodiment. It is a figure which shows the relationship between the scanning value and discharge amount rank of 1st Embodiment. (A) is a figure which shows the relationship between the position in a discharge outlet chip | tip, and temperature, (b) is a figure which shows the relationship between the position in a discharge outlet chip | tip, and a scanning value. It is a figure which shows the relationship between the input value which considered the temperature by the position in the discharge outlet chip | tip of 1st Embodiment, and the number of output dots. (A) is a figure which shows the relationship between the position in the discharge port chip | tip of 1st Embodiment, and temperature, (b) is the position in the discharge port chip | tip which considered the temperature by the position in a discharge port chip | tip. It is a figure which shows the relationship between a scan value. It is a block diagram explaining the image processing of 2nd Embodiment. It is a figure explaining the setting flow of the correction (gamma) value for every raster of 2nd Embodiment. It is a figure of the curve for amendment for every position in the discharge mouth tip of a 2nd embodiment. It is a schematic diagram explaining the relationship between the usage frequency of the nozzle of 3rd Embodiment, and the temperature distribution in a discharge outlet chip | tip. It is a figure which shows the example of the calculation formula of the temperature distribution coefficient for every position in the discharge outlet chip | tip of 3rd Embodiment. It is a figure explaining the setting flow of the gamma correction amount for every raster of 3rd Embodiment. It is a correspondence table of the temperature distribution coefficient of the third embodiment and the second correction γ value.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are application examples to an inkjet recording head and an inkjet recording apparatus equipped with the recording head.

(First embodiment)
<Sensor arrangement and temperature detection configuration in the discharge port chip>
FIG. 1 is a schematic view of a recording element substrate (hereinafter also referred to as an ejection port chip) and a temperature detection element of the recording head 2. The recording head 2 is a so-called multi-nozzle head having a plurality of ink discharge ports. Specifically, the recording head 2 is staggered so that the end portions overlap in the direction in which the supplied ink is circulated indicated by the arrow Y in the figure (hereinafter also referred to as the ink circulation direction or simply the Y direction). The discharge port tips N, N + 1, N + 2, and N + 3 are arranged in a shape. Each discharge port chip has nozzle rows A, B, C, and D in which a plurality of discharge ports are arranged along the ink circulation direction (Y direction) in this order so as to be arranged in a direction crossing the Y direction. Temperature sensors n_0, n_1, and n_2 as temperature detecting elements are arranged from the downstream side along the Y direction between the nozzle rows B and C, which are the central part of the discharge port chip in the direction crossing the Y direction. Arranged in order. In many cases, a diode sensor is used as the temperature detection element, and the temperature of the print head (hereinafter also simply referred to as the head temperature) is acquired from the detection result of the Vf value in a state where the sensor is connected to a constant current circuit.

<Main body configuration: recording unit and image reading unit>
FIG. 4A is a schematic diagram of an ink jet recording apparatus used in the present embodiment. When normal recording is performed with the ink jet recording apparatus 1, the recording medium 3 fed from the paper feed tray 4 is transported by the rotation of a plurality of transport rollers 5 arranged above and below. The recording medium 3 is moved from the left side to the right side in the direction indicated by the arrow X in the figure, and then recording is performed by the recording head 2 in the recording unit 20, which is then discharged onto the discharge tray 7.

  A recording head 2 shown in FIG. 1 is mounted on the recording unit 20 of the inkjet recording apparatus 1 for each ink color. As described in the background art, the amount of ink ejected from each ejection port in the ejection port chip of each recording head varies to some extent due to variations in characteristics of manufacturing processes and constituent materials. In order to detect the degree of variation in the amount of ejected ink (hereinafter also referred to as variation in ejection amount), a test pattern for detecting density unevenness is recorded.

  The density unevenness is detected by reading the recorded test pattern with the reading unit 6. In the present embodiment, the reading unit 6 is a CCD camera or a scanner described later.

  FIG. 4B is a schematic cross-sectional view of the ink jet recording apparatus shown in FIG. 4A taken along the conveyance direction of the recording medium.

  The reading unit 6 records 16 test nozzles as a single unit (hereinafter also simply referred to as a 16-nozzle unit) among a plurality of nozzles (discharge ports) in the Y direction of the discharge port chip. Read density as signal value. The read signal value is analyzed by a CPU which is a control unit of an image processing apparatus described later. Based on the analysis result, an increase / decrease in the number of dots of ink droplets recorded per unit area is determined with respect to an input signal of image data allocated to 16 nozzle units in the Y direction of the ejection port chip.

  The ink jet recording apparatus of the present embodiment can record four colors of ink of C (cyan), M (magenta), Y (yellow), and K (black), respectively, and four recording heads 2 (recording heads 2C, 2M, 2Y, and 2K).

  In this embodiment, a recording apparatus using four colors of C, M, Y, and K will be described as an example. However, the present invention is not limited to these ink colors, and light cyan, A form using a large number of inks such as light magenta, light gray, red, and green may be used. At this time, the number of recording heads corresponding to the number of ink colors may be provided. In the present embodiment, the recording head is described for each ink color. However, the present invention is not limited to this configuration. For example, a configuration may be adopted in which different colors of ink are ejected for each nozzle row in one recording head. At this time, the number of nozzle rows of one ejection port chip of the recording head is not limited to four.

  Processing to be described later is performed for each ink color, and the timing may be simultaneous or different. In addition, inspection patterns for all ink colors may be included in one test pattern at the same time.

  FIG. 5 is a block diagram showing the system configuration of this embodiment. The image processing apparatus 200 includes a video card 204 for connecting a CPU 201, a ROM 202, a RAM 203, and a monitor 213 (which may include a touch panel). The image processing apparatus 200 further includes a storage device 205 such as a hard disk drive or a memory card as a storage area. The image processing apparatus 200 also includes an interface 208 for a serial bus such as USB or IEEE1394 for connecting a pointing device 206 such as a mouse, stylus, and tablet, a keyboard 207, and the like. The image processing apparatus 200 further includes a network interface card (NIC) 215 that is connected to the network 214. These components are connected to each other via a system bus 209. A printer 210, a CCD camera 211, a scanner 212, and the like can be connected to the interface 208. Image data can also be input to the image processing apparatus 200 from a device that optically acquires image data such as a digital camera or digital video, or a portable medium such as a magnetic disk, an optical disk, or a memory card. The input image data may be in a form included in the image file. The CPU 201 loads a program (including an image processing program described below) stored in the ROM 202 or the storage device 205 into the RAM 203 as a work memory, and executes the program.

<Relationship between head temperature and discharge amount>
In the ejection phenomenon in which ink droplets are ejected from the ejection ports of the ejection port chips of the recording head, the viscosity of the ink changes depending on the temperature of the recording head (hereinafter also simply referred to as the head temperature). It is known that the viscosity decreases and the discharge rate increases.

  In this embodiment, a change in head temperature is detected by a temperature sensor arranged as shown in FIG. The detected temperature change is fed back to a signal for an ejection energy generating element (electrothermal conversion element (heater), piezoelectric element (piezo), etc.) in the recording element. Thereby, the ink discharge amount is controlled.

  FIG. 2A is a schematic diagram in which one discharge port chip of the recording head of FIG. 1 is extracted. FIG. 2B is a graph showing the head temperature detected in the discharge port chip shown in FIG.

  In this specification, the recording density condition for applying eight 3.0 ng ink droplets to a 600 dpi grid on one side is referred to as “recording duty 100%”. At this time, for example, “recording duty 50%” indicates a recording density condition in which four droplets of 3.0 ng are applied to a grid having a side of 600 dpi, and “recording duty 0%” does not apply ink droplets. Refers to the recording density condition. FIG. 2B shows the relationship between the position in the ejection port tip in the ink circulation direction Y and the head temperature detected when recording is performed at recording duty of 100%, 50%, and 0%. It is shown.

  As shown in FIG. 2B, the higher the recording duty, the greater the temperature difference depending on the position in the discharge port chip. Referring to the graphs for the recording duty of 50% and 100%, at the position B at the center of the ejection port tip in the ink circulation direction Y, the position A of the upstream end in the ink circulation direction Y and the downstream rear end The head temperature is higher than the position C of the part. In this phenomenon, the positions A and C at the front and rear end portions are more likely to conduct heat to the member adjacent to the discharge port chip than the position B at the central portion, and heat at the central portion B is relatively difficult to conduct. Therefore, it is thought that it has occurred. Further, in this recording head structure, since ink circulation is performed as a mode of supplying ink to the recording head, the temperature at the position A at the upstream end where the cold ink before heating flows first is one. The lowest result.

  Thus, a temperature distribution of the head temperature exists in the ink circulation direction in the ejection port chip, and the tendency of the temperature distribution depends on the recording duty. Since the ink discharge amount varies according to the temperature distribution of the head temperature, thereby causing density unevenness, the discharge amount variation is corrected to suppress the density unevenness.

<Discharge amount variation detection pattern and detection algorithm>
The ejection amount variation detection pattern refers to a test pattern for detecting variation in ejection amount. In this embodiment, the ejection amount variation detection pattern is a solid pattern in which the number of ink dots recorded per unit area is fixed to one type. In order to record the ejection amount variation detection pattern, an arbitrary value corresponding to the solid pattern to be recorded is used as an input value of a signal to the recording element of the ejection port chip. The density of the image recorded by the ink droplets output according to the input value of the signal is read every 16 nozzles. In accordance with the read density, an increase / decrease amount (correction amount) of the number of dots is set for each input value.

  First, an “input value-output dot number table” and a “scan value-discharge amount rank value table” are prepared in advance in the main body.

<Input value-Number of output dots table>
With reference to FIGS. 3A and 3B, the “input value-output dot number table” used in the present invention will be described.

  The “input value-output dot number table” shown in FIG. 3B is a unit area provided by a value (input value) of a recording signal input to the recording apparatus and an ink droplet output from the recording apparatus. 6 is a correspondence table showing a correspondence relationship with the number of hit dots (number of output dots). The correspondence table in FIG. 3B is derived from the relationship between the input value and the number of output dots for a plurality of ink ejection amounts (amount per ejected ink droplet) as shown in FIG. The

  In the graph of FIG. 3A, the horizontal axis represents the input value, the vertical axis represents the number of output dots, and examples of 3.5, 3.0, and 2.5 ng are shown as a plurality of ink ejection amounts. The input value at which the recording density (hereinafter also referred to as output density) reproducible by the recording apparatus is the highest is 0, the lowest input value is 255, and the signal input value is set between 0 and 255.

  A case where a solid pattern is recorded with an input value 127 that gives a recording density corresponding to a halftone with respect to an upper limit density that can be reproduced by the recording apparatus will be described. The number of dots of ink with the same recording density (hereinafter also referred to as scan value) read by the detection unit such as the scanner 212 in the reading unit 6 depends on the ink discharge amount. In this example, 4.0 dots were recorded when the ink discharge amount was 3.0 ng, 3.4 dots when 3.5 ng, and 4.8 dots when 2.5 ng, with respect to a 600 dpi grid. In some cases, equivalent scan values, i.e. recording densities, are obtained.

  As described above, the “input value-output dot number table” is a table showing correspondence in which the output dot number is adjusted so that the scan values are the same even with different ink discharge amounts for the respective input values of 0 to 255. . The ink discharge amount was divided into multi-stage ranges, and each range was ranked according to the discharge amount and defined as “discharge amount rank value”. In this example, the range where the discharge amount is minimum is set as the discharge amount rank value 0, the range where the discharge amount is maximum is set as the discharge amount rank value 127, and a total of 128 discharge amount rank values are set.

<Scan value-Discharge amount rank value table>
Next, the “scan value-discharge amount rank value table” for associating the scan value with the discharge amount rank value will be described.

  FIG. 6A shows the relationship between the scan value and the discharge amount rank value. The discharge amount rank value is assigned from the scan value every 16 nozzle units. In the illustrated example, the discharge amount rank is 63 when the scan value for a certain 16 nozzle unit is 127, and the discharge amount rank value is 93 when the scan value for another 16 nozzle unit is 101. is there.

  FIG. 6B shows an example of a “scan value-discharge amount rank value table” derived from the above result.

  By using the above-mentioned “input value-output dot number table” and “scan value-discharge amount rank value table”, the dot amount increase / decrease amount (correction amount) for each input value is set. Specifically, first, the discharge amount rank value corresponding to the scan value is determined from the scan value for every 16 nozzle units. Next, an input value-output dot number table corresponding to the discharge amount rank value is selected. In this way, the number of ink droplet dots per unit area corresponding to the input values 0 to 255 is determined every 16 nozzle units.

<Correction taking into account the temperature distribution in the discharge port tip>
Here, the correction in consideration of the temperature distribution of the head temperature in the discharge port chip will be described.

  FIG. 7A schematically shows the relationship between the position in the discharge port chip and the temperature distribution when recording is performed at a recording duty of 100%, 50%, and 10%.

  In FIG. 7B, when a solid pattern is recorded using signals of the input values 225, 127, and 0, the position in the ejection tip in the ink circulation direction and the scan value of the recorded image corresponding to that position The relationship between and is schematically shown. The recording duty corresponding to the input value 225 is 10%, the recording duty corresponding to the input value 127 is 50%, and the recording duty corresponding to the input value 0 is 100%. In the present embodiment, a value based on luminance is used as the input value, but the present invention is not limited to this, and a value of density or other image signal may be used.

  The scan value for the input value 127 (recording duty 50%) described so far is a substantially flat graph with almost no variation with respect to the position in the ejection port tip in the ink circulation direction. Therefore, when the solid pattern of the input value 127 is a density unevenness detection pattern, the same discharge amount rank value can be assigned to the position A and the center position B in the discharge port chip in the ink circulation direction. it can.

  On the other hand, when recording is performed with an input value of 0 (recording duty: 100%), the scanning of the center position B compared to the tip position A is caused by the influence of the temperature distribution in the discharge port chip. The value becomes smaller. Further, when recording is performed with the input value 225 (recording duty 10%), the scan value for the position of the central portion B is larger than the position of the tip portion A. This is because when the recording is performed with the input value 225 (recording duty 10%), the recording duty is low, so the influence of the above-described temperature distribution is very small, and the discharge amount variation at the position in the discharge port chip is reflected as it is. Conceivable. That is, in the illustrated discharge port chip, the discharge amount at the position B at the center portion is smaller than the position A at the tip portion due to variations in discharge amount due to manufacturing tolerances, and this is reflected.

  As described above, the temperature distribution depending on the position in the discharge port chip varies depending on the recording duty. Further, the discharge amount may vary due to manufacturing tolerances in the discharge port chip. Therefore, if the same discharge amount rank value is assigned regardless of the position in the discharge port chip, the density unevenness may not be completely corrected.

  Therefore, in the present invention, for each position in the discharge port chip, an “input value-output dot number table” corresponding to different discharge amount rank values considering the temperature distribution is prepared in advance, and the position and discharge amount rank value are set. The corresponding “input value-output dot number table” is selected.

  FIG. 8A shows the relationship between the input value and the number of output dots corresponding to the position A and the center position B in the discharge port chip in the ink circulation direction in consideration of the temperature distribution in the discharge port chip. Indicates.

  In the drawing, the graph for the position A at the tip is indicated by a broken line, and the graph for the position B at the center is indicated by a solid line. With the input value 127, as described above, the same scan value (recording density) can be obtained by using the same output dot number 4.0 for the position A of the front end portion and the position B of the central portion. When the input value approaches 0 and the recording duty becomes higher, the head temperature becomes higher at the central position B than at the front end position A, so that the amount of ink droplets to be ejected increases and recording is performed. The density increases and the scan value decreases. In order to obtain the same scan value (recording density) at the center position B as the tip position A using the same input value, the number of output dots is reduced by the increase in the ink discharge amount. Further, when the input value increases and the recording duty decreases, the recording density becomes lower and the scan value becomes larger at the central position B than at the leading edge position A. In order to obtain a scan value (recording density) comparable to that at the tip position A at the central position B using the same input value, the number of output dots is increased by that amount.

  FIG. 8B shows an “input value-output” corresponding to the discharge amount rank value selected at each of the position A of the tip and the position B of the center obtained in the same manner as the example shown in FIG. An example of a “dot number table” is shown.

  As described above, in the present invention, by using the "input value-output dot number table" and the "scan value-discharge amount rank value table" corresponding to different discharge amount rank values considering the temperature distribution, Set the number of dots for each input value.

  FIG. 9 shows the “scan value-discharge amount rank value table” shown in FIG. 6B and the position corresponding to the discharge amount rank value in consideration of the temperature distribution in the discharge port tip shown in FIG. 8B. The result of correcting the number of dots using the “input value-output dot number table” is shown. In the example of FIG. 9 to which the present invention is applied, similarly to the example of FIG. 7 to which the present invention is not applied, the temperature distribution in the discharge port chip varies depending on the recording duty (see each figure (a)). At this time, in the example of FIG. 7, the scan value varies depending on the recording duty and the position in the ejection port chip (see FIG. 7B). On the other hand, in the example of FIG. 9, it can be seen that a uniform scan value is obtained regardless of the recording duty and the position in the ejection port chip (see FIG. 9B).

  As described above, according to the present invention, it is possible to obtain the same scan value (recording density) at all the recording duty (input value) over all the positions (entire area) in the discharge port chip.

  In the present embodiment, the correction of the recording density unevenness in consideration of the manufacturing tolerance of one discharge port chip and the variation of the discharge amount due to the temperature distribution due to the position in the discharge port chip has been described. In the present invention, by applying this to the entire recording head, the occurrence of density unevenness over the entire recording head can be suppressed.

  In this embodiment, the scan value-discharge amount rank value table and the input value-output dot number table are prepared separately, but the present invention is not limited to this. That is, it is not essential to have two tables. For example, the scan value-discharge amount rank value table may be incorporated into the input value-output dot number table to form one table. The value column may be omitted.

(Second Embodiment)
In the second embodiment, a form different from the first embodiment will be described with respect to correction of recording density unevenness in consideration of variation in discharge amount due to manufacturing tolerances and temperature distribution due to position in the discharge port chip. Of the configurations of the second embodiment, those to which the configuration of the first embodiment can be applied will not be described.

  The image processing of this embodiment will be described with reference to FIG. This block diagram shows a processing flow for outputting input R, G, B color 8-bit image data (256 gradations) as C, M, Y, K color 1-bit data.

  Image data of 8 bits for each color of R, G, and B is first converted into data of 8 bits for each color of R ′, G ′, and B ′ by a three-dimensional lookup table (LUT). This processing is called color space conversion processing (previous color processing), and is performed to correct a difference between the color space of the input image (color space) and the reproduction color space of the output device.

  The 8-bit data of each color R ′, G ′, and B ′ subjected to the color space conversion process is converted into 8-bit data of each color C, M, Y, and K by the following three-dimensional LUT. This processing is called color conversion processing (post-stage color processing), and is performed to change the input RGB color to the output CMYK color. In many cases, input image data is data of three primary colors (RGB) of additive color mixture adopted in a light emitter such as a display. On the other hand, a subtractive mixed primary color (CMY) color material is used in a recording apparatus that expresses colors by reflecting light, such as a printer. Therefore, this conversion process is performed.

  The three-dimensional LUT used for the pre-stage color processing and the three-dimensional LUT used for the post-stage color processing hold data discretely, and the inter-holding data is obtained by interpolation processing. Since the interpolation process is a known technique, a detailed description thereof is omitted here.

  The 8-bit data of each color of C, M, Y, and K subjected to the subsequent color processing is subjected to output γ correction by a one-dimensional LUT. That is, a correction operation for obtaining a color expression closer to the original is performed by adjusting the correlation between the 8-bit data and the color actually output by recording. In many cases, the relationship between the number of recording dots per unit area and output characteristics (reflection density, etc.) is not a linear relationship. Therefore, by performing output γ correction, a linear relationship between the input level of C, M, Y, and K8 bits and the output characteristics at that time is guaranteed.

<Overview of setting correction γ value for each raster>
The output γ correction by the above-described one-dimensional LUT will be described. In this embodiment, output γ correction is performed by setting a correction γ value, which is a parameter necessary for gamma correction, for each raster.

  In this specification, a raster is a recording medium that moves relatively from a nozzle row of a nozzle array of a discharge port chip of a recording head in a direction orthogonal to the nozzle arrangement direction when recording is performed by a recording apparatus. This corresponds to a recording line formed by ejected ink. In this embodiment, the recording apparatus includes four (for each ink color of C, M, Y, and K) recording heads as shown in FIG. As shown in FIG. 2A, there are four nozzle rows A, B, C, and D. When recording is performed using one recording head, one recording line (identical to the same) is provided by nozzles arranged at corresponding positions in the recording medium conveyance direction orthogonal to the nozzle arrangement direction among the nozzles of these nozzle arrays. Raster). Similarly, when recording is performed using a plurality of recording heads, the nozzles of the nozzle arrays of the discharge port chips of the plurality of recording heads are arranged at corresponding positions in the recording medium direction orthogonal to the nozzle arrangement direction. The same raster can be formed by the nozzle.

<Flowchart>
The flowchart of FIG. 11 shows a method for setting a correction γ value for each raster in the second embodiment.

  In step S101, a setting mode for setting a correction γ value for each raster is selected on a user interface (UI) screen of a printer driver (not shown).

  In step S102, an arbitrary discharge amount variation detection pattern (solid pattern) built in the recording apparatus main body is used at a desired single recording density, that is, an arbitrary input value of a signal to the recording element of the discharge port chip. Record. Recording is performed by applying the same recording conditions to all rasters.

  In this embodiment, for each of the four recording heads for each of the four colors, one nozzle is arranged at a position corresponding to the recording medium conveyance direction among the nozzles of the four nozzle rows of the ejection port chip. Two recording lines (same raster) are recorded with a single color ink. The entire discharge amount variation detection pattern is recorded using all nozzles in the nozzle arrangement direction of each nozzle row.

  In step S103, with respect to the ejection amount variation detection pattern recorded in step S102, the reading unit 6 reads the recording density (scan value) for each raster by detection means such as the scanner 212. The recording density for each raster is obtained as an average value of the recording density of dots recorded in the area set as the raster scan range. In this example, recording is performed using a single color ink for each of the four recording heads, and the recording density is a single color ink ejected on the same raster from the nozzles of the four nozzle rows for each recording head. Is obtained as an average value for.

  In step S104, the recording density for each raster read in step S103 is associated with position information in the discharge port chip in order to consider the influence of the temperature distribution in the discharge port chip described above. Specifically, first, a correction curve diagram corresponding to the position in the discharge port tip for setting the correction γ value to be applied for each raster is prepared in advance. Then, when the recording density of the raster is read in step S103, a correction curve diagram corresponding to the position is selected based on information on the position in the discharge port chip where the nozzle used for the raster recording is positioned.

  FIG. 12A shows a correction curve for the position A (tip portion in the ink circulation direction) within the ejection port chip, and FIG. 12B shows the position B (ink circulation direction) within the ejection port chip. The figure of the curve for correction | amendment for the center part in FIG. In each figure, the horizontal axis indicates the input value of the signal to the recording element of the discharge port chip. Here, as an example, the input value is indicated by luminance. The brightness increases and the desired recording density decreases (lightens) as it goes to the right of the horizontal axis, and the desired recording density increases (darkens) as it goes to the left. The vertical axis represents the raster scan value read by the detecting means. The higher the vertical axis, the larger the scan value, and the smaller (lighter) recording density actually recorded (output), and the lower the scan value, the higher (higher) recording density.

  The graph of the correction curve for each position shows a plurality of correction curve graphs. The plurality of graphs correspond to the amount of ink droplets ejected from the nozzles (ink ejection amount). That is, since the tendency of the relationship between the input value and the scan value varies depending on the magnitude of the ink ejection amount, a plurality of correction curve graphs corresponding to the ink ejection amount are prepared for the same position in the ejection port chip. Here, five graphs corresponding to five types of ink ejection amounts a, b, c, d, and e are illustrated in each figure. In this example, the discharge amount is the smallest and the discharge amount is large in the order of a to e. For a discharge amount that is included between the discharge amounts a to e but is not illustrated, a correction curve graph can be calculated by, for example, interpolation processing.

  In step S105, a graph to be used for calculating a correction γ value is determined from among a plurality of correction curve graphs shown in the correction curve corresponding to the position in the ejection port tip selected in step S104. Specifically, the graph to be used is determined based on the recording conditions for recording the ejection amount variation detection pattern and the measurement result of the recording density. This will be described with reference to FIG. 12A, which is a diagram of a correction curve for the position A in the discharge port chip.

  First, as a recording condition for the ejection amount variation detection pattern, it is assumed that the ink ejection amount setting value is c, recording is performed with the input value In_o, and the scan value Out_o is obtained as the recording density. It is assumed that the measured value (scan value) of the recorded density of the recorded raster is Out_p. From FIG. 12A, the scan value Out_p is obtained for the input value In_o when the ink ejection amount is e. That is, in this example, recording is actually performed with the ink discharge amount e for the initial set value c. Therefore, in this example, in step S105, the graph of ink ejection amount c and the graph of e are determined as graphs used for calculating the corrected γ value.

  In step S106, the corrected γ value is calculated using the graph used for calculating the corrected γ value determined in step S105. With reference to FIG. 12A again, calculation of the corrected γ value will be specifically described. According to the determination in step S105, in this example, the corrected γ value is calculated using the graph of ink ejection amount c and the graph of e. It can be seen from the graph that the input value should be corrected from In_o to In_q in order to obtain the desired scan value Out_o when the ink ejection amount is e. This makes it possible to calculate a corrected γ value for the input value for obtaining a desired recording density. By repeating this, it is possible to set the correction γ value for each raster at each position in the discharge port chip.

  In the present embodiment, the corrected γ value for each raster set according to the flowchart shown in FIG. 11 is used in the one-dimensional LUT shown in FIG.

  According to the configuration of the present embodiment, it is possible to suppress the discharge amount variation due to the manufacturing tolerance of the discharge port chip and the influence of the temperature distribution due to the position in the discharge port chip. Recording with less unevenness than before is possible. In the present embodiment, since the correction γ value is set for each raster, it is possible to suppress the discharge amount variation with higher accuracy.

  In this embodiment, as described above, recording is performed using a single color ink in one ejection amount variation detection pattern, but the present invention is not limited to this. For example, one discharge amount variation detection pattern may be recorded for a plurality of colors of ink, that is, for a plurality of recording heads. Further, the recording head may be configured to eject different colors of ink for each nozzle row. In that case, one recording head uses a plurality of colors of ink to form one ejection amount variation detection pattern. It may be recorded.

(Third embodiment)
By the way, when recording is actually performed, the image to be recorded is not necessarily a solid pattern. The frequency of nozzle use varies depending on the pattern of the image to be recorded. The more frequently nozzles are used, the more likely the temperature will rise. Here, the usage frequency of the nozzles in this specification indicates the degree of nozzle driving, and the range and number of nozzles used for recording among the nozzles in the nozzle row, and the ejection of ink from the same nozzle. And the number of dots given per unit time.

  In the third embodiment, in addition to the variation in the discharge amount due to the temperature distribution due to the manufacturing tolerance and the position in the discharge port chip, the recording density considering the variation in the discharge amount due to the temperature change according to the use frequency of the nozzles Unevenness correction (dynamic HS correction) will be described. The description of the configuration of the third embodiment to which the configuration of the first or second embodiment can be applied is omitted.

<Effects of nozzle usage frequency on temperature distribution in discharge tip>
Below, the influence on the temperature distribution in the discharge outlet chip | tip by the usage frequency of a nozzle is demonstrated.

  FIG. 13 is a schematic diagram for explaining the relationship between the nozzle use frequency and the temperature distribution in the discharge port chip when the nozzle row in the discharge port chip is divided into three in the nozzle arrangement direction.

  FIG. 13A shows a state where the discharge port chip is divided into three in the nozzle arrangement direction of the nozzle row. The positions of the three regions obtained by dividing into three are referred to as positions A, B, and C in order from the upstream side in the ink circulation direction with respect to the recording head.

  In this example, it is assumed that each nozzle row includes 1020 nozzles. FIG. 13B shows an example in which ink is ejected using 1020 nozzles in each nozzle row and 340 nozzles in each of positions A, B, and C in the ejection port chip. More specifically, the inside of the ejection port chip when printing is performed by applying ink droplets of 2400 dots at a recording density of 1200 dpi in the conveyance direction of the recording medium orthogonal to the nozzle arrangement direction and 1020 dots in the nozzle arrangement direction. Shows the temperature distribution. Here, the number of dots in the transport direction corresponds to the recording time. In the upper graph of FIG. 13B, the horizontal axis corresponds to the position in the nozzle arrangement direction of the nozzle row in the discharge port chip, and the vertical axis represents the temperature of the discharge port chip at that position. In addition, the lower image in FIG. 13B shows a recorded image when recording is performed under the above-described recording conditions, and the horizontal axis also corresponds to the position of the nozzle row in the discharge port chip in the nozzle arrangement direction. The vertical axis corresponds to the position in the conveyance direction of the recording medium.

  Similarly, FIG. 13C-1 uses a total of 640 nozzles in the nozzle array, that is, 340 nozzles at position A and 340 nozzles at position B in the discharge port chip. The example which did not use a nozzle is shown. FIG. 13C-2 shows an example in which, in each nozzle row, a total of 640 nozzles of 340 nozzles at position A and 340 nozzles at position C are used, and nozzles at position B are not used. Show. In each nozzle row, FIG. 13 (d-1) shows an example in which only 340 nozzles at position A in the discharge port chip are used, and FIG. 13 (d-2) shows only 340 nozzles at position C. FIG. 13D-3 shows an example in which only 340 nozzles at position B are used.

  The temperature at each of the positions A to C in the discharge port chip is affected by the temperature rise caused by driving the nozzles belonging to the adjacent positions in addition to the temperature rise caused by driving the nozzles belonging to the position. The degree of the effect of temperature rise is the usage frequency of nozzles belonging to its own position in the discharge port tip, the usage frequency of nozzles belonging to other positions, and the relative positional relationship (distance) of these positions, Determined by.

  For example, in the example shown in FIG. 13C-1 and the example shown in FIG. 13C-2, the number of nozzles used is the same, and the entire nozzle array of the discharge port chips per unit time. The number of dots of ink droplets ejected from is the same. Nevertheless, in these examples, the temperature distribution in the discharge port tip is different. For example, paying attention to position A, the number of nozzles used and the number of ejected ink dots are the same in both examples, but the example of FIG. The degree of temperature rise at position A is greater than in the example of c-2), and the peak of temperature rise is biased.

  This is because the temperature distribution at each position in the discharge port chip is most affected by the driving of nozzles belonging to its own position, and is then influenced by the driving of nozzles belonging to adjacent positions, so that the nozzles belonging to separated positions are affected. The effect of driving is considered to be relatively small. For example, when attention is paid to the position B, the temperature distribution at the position B is greatly influenced by the driving of the nozzles belonging to the position B, that is, the usage frequency of the nozzles at the position B, but the nozzles belonging to the positions A and C with respect to the temperature distribution at the position B. The effect of driving is relatively small. Further, the temperature distribution at the position A is greatly affected by the frequency of use of the nozzle at the position A, and then the frequency of use of the nozzle at the adjacent position B. The distance is reduced by the distance between A and position C.

  By the way, since the usage frequency of the nozzle is determined according to the pattern of the image to be recorded, the temperature distribution in the discharge port tip can be dynamically changed depending on the pattern of the image to be actually recorded.

  The image pattern shown in the lower part of FIG. 13B is a pattern for recording using nozzles in the discharge port chip uniformly. It is assumed that a gamma correction amount of an input value (or the number of output dots) of a signal for each nozzle is determined using this as a discharge amount unevenness detection pattern. At this time, depending on the image pattern to be actually recorded, the density unevenness may not be sufficiently corrected with the determined correction amount due to the influence of the fluctuation of the temperature distribution.

  Therefore, the third embodiment proposes a correction method that further considers the dynamic fluctuation of the temperature distribution in the discharge port tip due to the different usage frequency of the nozzles depending on the pattern of the image to be recorded.

<Temperature distribution coefficient for each position in the discharge port tip>
In order to perform correction in consideration of the dynamic fluctuation of the temperature distribution in the discharge port chip, a temperature distribution coefficient for each position in the discharge port chip is obtained. FIG. 14 shows an example (expression 1) of a relational expression for calculating the temperature distribution coefficient. A temperature distribution coefficient is determined for each position in the discharge port chip. Since the number of ink droplets ejected from the nozzles belonging to its own position (hereinafter also referred to as dot count value) is used as it is, it is multiplied by a factor of 1/1. The number of ink droplets ejected from a nozzle belonging to a position adjacent to its own position is multiplied by a factor of 1/2. The number of ink droplets ejected from a nozzle belonging to a position one distance away from its own position is multiplied by a factor 1/3. By integrating each [dot count value × coefficient] obtained in this way, a temperature distribution coefficient for the position in the discharge port chip is obtained.

  Although the example in which the nozzles in the nozzle array in the discharge port chip are divided into three in the nozzle arrangement direction has been described above, the present embodiment can also be applied to the case where the nozzle array is divided into two or four or more. In other words, the dot count value for each position is multiplied by a coefficient according to the positional relationship with its own position, and the obtained value is integrated to calculate the temperature distribution coefficient for that position in the outlet tip. can do.

<Flowchart>
The flowchart of FIG. 15 shows a method for setting the gamma correction amount for each raster in the third embodiment.

  In step S201, a setting mode for setting a gamma correction amount for each raster based on the position in the ejection port chip and the dot count value is selected on a user interface (UI) screen of a printer driver (not shown).

  Since steps S202 to S205 of the third embodiment are the same as steps S102 to S105 of the second embodiment, the description thereof is omitted.

  Step S206 of the third embodiment is also substantially similar to step S106 of the second embodiment, and here, a correction γ value for each raster at each position in the discharge port tip is set. By the way, in 3rd Embodiment, the correction (gamma) value in each position in the discharge outlet chip | tip by a dot count value is set separately. Hereinafter, for the sake of clarity, the correction γ value for each raster based on the position in the discharge port chip set in step S206 is referred to as a first correction γ value, and is determined at each position in the discharge port chip based on a dot count value set separately. The corrected γ value is referred to as a second corrected γ value. In addition, the correction γ value of the present embodiment considering the first and second correction γ values is referred to as a gamma correction amount (Γ).

  In steps S201 to S206, the test pattern mode using the discharge amount variation detection pattern which is a solid pattern is terminated.

  Next, in step S207, recording of an image actually desired to be recorded (hereinafter simply referred to as actual recording) is started.

  In step S208, for each position in the ejection port chip, the number of ink droplets (dot count value) ejected from a nozzle belonging to that position within a predetermined time is acquired. In this example, the area (dot count area) on the recording medium from which the dot count value is acquired is 1020 nozzles (all nozzles) in the nozzle arrangement direction of the nozzle row and one nozzle in the recording medium conveyance direction. The recording density is 1200 dpi, and 2400 dots. Since there are four nozzle rows, the number of dots per nozzle row in the nozzle arrangement direction (1020) × {the number of dots per nozzle (2400) × the number of nozzle rows (4)} in the recording medium conveyance direction} The area indicated by is the dot count area of this embodiment. The recording apparatus main body has a configuration capable of acquiring a dot count value over the entire dot count area and a memory for storing the count value. Further, at this time, the recording apparatus main body is configured to be able to count the number of nozzles used at each position in the region obtained by dividing the discharge port chip into three as shown in FIG. That is, for each of the areas of the number of dots (1020 × 1/3) × {number of dots per nozzle (2400) × number of nozzle rows (4)} in each of the three divided areas of one nozzle row, A dot count value can be acquired.

  In step S209, first, based on the dot count value for each region corresponding to each position of the configuration obtained by dividing the nozzle row in the ejection port tip obtained in step S208, according to the relational expression illustrated in FIG. The temperature distribution coefficient at each position in the discharge port chip is obtained. Next, the second corrected γ value is obtained from the correspondence table between the temperature distribution coefficient and the second corrected γ value exemplified in FIG. For example, it is assumed that the temperature distribution coefficient calculated for the position A is 3000000. Since this value is 2618880 or more and less than 3928320, the second correction γ value is 32 from the correspondence table shown in FIG. Similarly, if the temperature distribution coefficient calculated for position B is, for example, 5500000, this value is 5237760 or more and less than 6547200, so the second correction γ value is 24 from the correspondence table shown in FIG. In this way, it is possible to calculate the second correction γ value according to the usage frequency of the nozzle.

  In step S210, the second correction γ value set in step S209 is subtracted from the first correction γ value set in step S206 to obtain the gamma correction amount (Γ) for each raster in the present embodiment. The gamma correction amount for each raster is used within the next predetermined time.

  In step S211, it is determined whether or not actual recording has ended. The determination is made every 2400 dots per nozzle at a recording density of 1200 dpi in the conveyance direction of the recording medium. If recording continues, that is, if there is still image data to be recorded, steps S208 to S211 are repeated. When the recording is finished, the setting mode of the gamma correction amount for each raster based on the position in the ejection port tip and the dot count value is finished.

  In the present embodiment, the correction γ value (gamma correction amount) for each raster based on the position in the ejection port tip and the dot count value set according to the flowchart shown in FIG. 15 is used in the one-dimensional LUT shown in FIG.

  In the first and second embodiments, the unevenness of density in consideration of the discharge amount variation due to the manufacturing tolerance of the discharge port chip, and the influence of the temperature distribution in the discharge port chip depending on the recording duty and the position in the discharge port chip. Correction was performed. On the other hand, in the third embodiment, the density unevenness is corrected by further taking into consideration the dynamic fluctuation of the temperature distribution due to the frequency of use of the nozzles at each position in the discharge port chip. That is, according to the present embodiment, it is possible to consider the influence of the temperature distribution in the discharge port chip due to the difference in the usage frequency of the nozzles in the discharge port chip per unit time, that is, the difference in the pattern of the image to be recorded. Therefore, recording with no unevenness is possible in all patterns.

Claims (9)

A recording head having a discharge port chip in which a plurality of recording elements are arranged in the arrangement direction is moved relative to the recording medium in a direction intersecting the arrangement direction, and ink is ejected by driving the recording elements. And a recording device for recording,
Detection means for reading the recording density of the recorded pattern for each arbitrary unit of the plurality of recording elements in the arrangement direction with respect to the pattern recorded by ejecting ink by driving the plurality of recording elements under the same conditions; ,
Acquisition means for acquiring image data corresponding to an image to be recorded;
And the range of ink ejection amount corresponding to the recording density read by said detecting means, and the print duty in which the image data indicates that obtained by the obtaining unit, the position of the discharge port chip of the arbitrary units, depending on the Determining means for determining the number of ink dots per unit area;
Control means for controlling to eject ink of the number of dots determined by the determination means;
Equipped with a,
In the first and second tables that define the number of dots of the ink based on the range of the ink discharge amount and the recording duty, respectively, (i) the position of the arbitrary unit is the first position The number of dots of the ink is determined using the first table, and (ii) the position of the arbitrary unit is the end in the arrangement direction in the discharge port chip rather than the first position. If the second position is far from the part, the number of dots of the ink is determined using the second table,
In the first and second tables, when the range of the ink ejection amount is the same range, the second table is more prescribed than the first table as the recording duty increases. A recording apparatus, wherein the number of dots of ink is defined so that the number of dots of the ink becomes smaller . In the first and second tables, (i) when the recording duty is a first value, the first and second tables define the same number of ink dots, and (ii) the recording 2. The number of dots of ink of the second table is smaller than that of the first table when the duty is a second value greater than the first value. The recording device described in 1. The recording apparatus according to claim 2, wherein the first value is a recording duty corresponding to a halftone among recording duties indicated by the image data.   The first position is an end in the arrangement direction in the discharge port chip,
  4. The recording apparatus according to claim 1, wherein the second position is a central portion in the arrangement direction in the discharge port chip. 5. The pattern, recording device according to claim 1, wherein in any one of the four that the number of dots ink applied per unit area is solid pattern is one. Wherein the discharge port chip A recording apparatus according to any one of claims 1 5, characterized in that the ink discharge amount is different recording elements arranged. Recording in which recording is performed by ejecting ink from the recording element by moving a recording head mounted with an ejection port chip in which a plurality of recording elements are arranged in the arrangement direction relative to the recording medium in a direction intersecting the arrangement direction. A method for correcting recording density in an apparatus, comprising:
For a pattern recorded by discharging ink from the plurality of recording elements, a detection step of reading a recording density for each arbitrary unit of the plurality of recording elements in the arrangement direction;
An acquisition step of acquiring image data corresponding to an image to be recorded;
According to the range of the ink discharge amount corresponding to the recording density read by the detection step, the recording duty indicated by the image data acquired by the acquisition step, and the position of the arbitrary unit in the discharge port chip A determination step for determining the number of dots of ink per unit area;
A control step of controlling to eject ink of the number of dots determined by the determination step;
Including
In the determining step, the first and second tables that define the number of dots of the ink based on the range of the ink discharge amount and the recording duty, respectively, (i) the position of the arbitrary unit is the first position The number of dots of the ink is determined using the first table, and (ii) the position of the arbitrary unit is the end in the arrangement direction in the discharge port chip rather than the first position. If the second position is far from the part, the number of dots of the ink is determined using the second table,
In the first and second tables, when the range of the ink ejection amount is the same range, the second table is more prescribed than the first table as the recording duty increases. A method for correcting a recording density, characterized in that the number of dots of ink is defined so that the number of dots is smaller . A recording head having a discharge port chip in which a plurality of recording elements are arranged in the arrangement direction is moved relative to the recording medium in a direction intersecting the arrangement direction, and ink is ejected by driving the recording elements. And a recording device for recording,
Detecting means for reading a recording density of a pattern recorded for each arbitrary unit of the plurality of recording elements in the arrangement direction with respect to a pattern recorded by ejecting ink by driving the plurality of recording elements under the same conditions;
Wherein a range in which the ink discharge amount corresponding to the recording density read by the detecting means, the position of the discharge port chip of the given organization number units, depending on the input signal used to drive the recording element A first correction unit that determines a correspondence between the value and the number of dots of ink per unit area, and corrects the number of dots per unit area to be recorded based on the determined correspondence;
Obtaining means for obtaining the use frequency of a plurality of the recording elements;
Second correction means for correcting the number of dots per unit area to be recorded based on the use frequency acquired by the acquisition means and a coefficient set in advance according to the use frequency of the recording element;
Equipped with a,
The frequency of use is represented by the number of ink droplets ejected per unit time from ejection ports belonging to each of a plurality of regions obtained by dividing the ejection port chip in the arrangement direction,
The preset coefficient is a value obtained by integrating a value calculated from the positional relationship with the area where the coefficient is set for each of the plurality of areas and the number of ink droplets with respect to all of the plurality of areas. recording apparatus, characterized in that the. A recording head having a discharge port chip in which a plurality of recording elements are arranged in the arrangement direction is moved relative to the recording medium in a direction intersecting the arrangement direction, and ink is ejected by driving the recording elements. A recording density correction method in a recording apparatus that performs recording,
A detection step of reading a recording density of a pattern recorded for each arbitrary unit of the plurality of recording elements in the arrangement direction for a pattern recorded by ejecting ink by driving the plurality of recording elements under the same conditions;
And the range of ink ejection amount corresponding to the recording density read by the detection step, a position of the discharge port chip of the arbitrary units, in accordance with an input value of the signal used to drive the recording element A first correction step of determining a correspondence relationship with the number of dots of ink per unit area and correcting the number of dots per unit area to be recorded based on the determined correspondence relationship;
An acquisition step of acquiring a use frequency of a plurality of the recording elements;
A second correction step of correcting the number of dots per unit area to be recorded based on the use frequency acquired by the acquisition step and a coefficient set in advance according to the use frequency of the recording element;
Including
The frequency of use is represented by the number of ink droplets ejected per unit time from ejection ports belonging to each of a plurality of regions obtained by dividing the ejection port chip in the arrangement direction,
The preset coefficient is a value obtained by integrating a value calculated from the positional relationship with the area where the coefficient is set for each of the plurality of areas and the number of ink droplets with respect to all of the plurality of areas. A method for correcting recording density, characterized in that:

Images