JP2006027226A - Image recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To record an image of a high quality by reducing a variation of a discharged volume per unit area of a printing medium in an image recording apparatus using a multi-drop type inkjet recording head capable of changing the volume per one time by a nozzle. <P>SOLUTION: The image recording apparatus performs a recording on the recording medium using a recording head in which a plurality of recording elements are arranged. The image recording apparatus is equipped with a recording head part 23 in which one recording head is composed of at least two recording head units by connecting them so as to position in the perpendicular direction to the arrangement direction of the recording elements, recording head driving parts 58 and 59 recording the image on the recording medium by driving a plurality of the recording elements of the recording head part on every recording head unit in accordance with the image data, a head characteristic table 510 in which recording characteristics on every recording element of the recording head unit are recorded, and an image distributing processing part 85 distributing an input image recorded based on the head characteristic table to different head unit driving parts. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

    The present invention relates to an on-demand type image recording apparatus, for example.

    As an image recording apparatus, for example, an on-demand type inkjet recording apparatus is known.

  A conventional on-demand ink jet recording apparatus will be described with reference to FIG. In the figure, the head unit includes a recording element portion 2 provided with a number of ink chambers 1, a main body portion 4 provided with a common ink chamber 3 that supplies ink to each ink chamber 1, and ink in the common ink chamber 3. An ink supply path 5 is provided. Then, by applying a volume variation in the ink chamber 1, ink droplets are ejected from the recording element 6 in the ink chamber 1 to perform dot printing. The ink consumed in the ink chamber 1 is replenished from the common ink chamber 3.

  As a control method for giving a volume variation in the ink chamber 1, there are a piezoelectric control method using distortion deformation of a piezoelectric member, a thermal control method using heat generation of a heating element, and the like (for example, see Patent Document 1 and Patent Document 2). ). Printing can be performed on demand by arbitrarily giving a volume fluctuation to each ink chamber 1 by such a control method.

In such an ink jet recording apparatus, it is important to increase the speed. In order to increase the speed, it is better that the number of recording elements of the ink jet head is larger. As a technique for increasing the number of recording elements, there is a technique in which a plurality of head units having a large number of recording elements are integrally arranged so that the arrangement of the recording elements is substantially parallel to form one long recording head. is there. And, by making the length of the head correspond to the width of the recording paper, it becomes a line head, and high-speed printing can be realized.
JP 2003-127439 A JP-A-6-246933

  However, when a head unit having a large number of recording elements is used, it is ideal that the ink droplet capacities of each of the plurality of recording elements are uniform. However, manufacturing variations and ink discharge operations in the ink chamber 1 are not possible. Ink discharge capacity increases or decreases due to variations in propagation of pressure fluctuations. As the ink discharge capacity increases or decreases, the output characteristics vary, resulting in uneven density in the recorded image. In an image recording apparatus in which a plurality of such head units are arranged to form a line head, it is very difficult to correct image quality deterioration such as density unevenness and gradation deterioration for each recording element or each head unit.

  In the thermal control method using the heat generated by the heating element as in Patent Document 1 described above, ink of the same color is ejected on a virtual line in the main scanning direction of the recording head through the center of the first ejection port having a large ejection volume. The center of the second discharge port is arranged. The second ejection ports have a smaller volume of ink droplet ejection than the first ejection ports, and more than the first ejection ports. That is, the discharge volume variation is reduced by discharging the discharge volume variation of the first discharge port from the plurality of second discharge ports and landing on the same pixel of the print medium. At this time, since the first discharge ports, the plurality of second discharge ports, and a large number of nozzles are required, the manufacturing cost increases.

  Further, in an image recording apparatus using a multi-drop type ink jet recording head, there is a variation in ejection volume with one drop for each recording element. For this reason, when a plurality of drops are ejected onto one dot of the recording paper by the same recording element, the ejection volume between adjacent recording elements is varied by the number of drops, and the difference is only widening.

  Further, if a recording head having no discharge volume variation or extremely small variation between recording elements is required, there is no productivity and the manufacturing cost is increased several times.

  The present invention has been made in view of the above points, and an object of the present invention is to perform printing in an image recording apparatus using a multi-drop type ink jet recording head in which the volume ejected by one nozzle at a time can be changed. An object of the present invention is to provide an image recording apparatus capable of recording a high-quality image by reducing the discharge volume variation per unit area of the medium.

According to the first aspect of the present invention, in an image recording apparatus that performs recording on a recording medium using a recording head in which a plurality of recording elements are arranged, two or more recording head units are arranged perpendicular to the arrangement direction of the recording elements. A recording head unit that is connected so as to be positioned in a direction and constitutes one recording head, and a plurality of recording elements of the recording head unit are driven for each recording head unit according to image data, and an image is recorded on a recording medium. A recording head driving unit for recording
A head characteristic table in which recording characteristics of each recording element of the recording head unit are recorded; and an image distribution processing unit that distributes an input image recorded based on the head characteristic table to different recording head unit driving units. It is characterized by that.

  The invention according to claim 2 is characterized in that the recording head drive unit according to claim 1 can eject a plurality of inks to the same pixel, and eject ink from different recording head units to the same pixel. To do.

  According to a third aspect of the present invention, the image distribution processing unit according to the first aspect distributes an input image signal to each recording head driving unit based on the head unit characteristic table.

  According to a fourth aspect of the present invention, in an image recording apparatus that performs recording on a recording medium using a recording head in which a plurality of recording elements are arranged, two or more recording head units are arranged in a direction perpendicular to the arrangement direction of the recording elements. In addition, the recording head unit configured by shifting the position of the recording element of each head unit to form one recording head and a plurality of recording elements of the recording head unit according to image data are driven and recorded for each recording head unit. A recording head driving unit that records an image on a medium, a head characteristic table that records recording characteristics for each recording element of the recording head unit, and an image processing unit that processes an input image recorded based on the head characteristic table It was characterized by comprising.

  The invention described in claim 5 is characterized in that the recording head drive unit described in claim 4 ejects a plurality of inks to the same pixel.

  According to a sixth aspect of the present invention, the image distribution processing section according to the fourth aspect distributes the input image signal to the recording head driving section based on the head unit characteristic table.

  As described above in detail, according to the present invention, in an image recording apparatus that performs recording on a recording medium using a recording head in which a plurality of recording elements are arranged, two or more recording head units are connected to the recording elements. A recording head section is provided which is connected so as to be positioned in a direction perpendicular to the arrangement direction, and constitutes one recording head. The image distribution processing section is stored in a head characteristics table in which recording characteristics for each recording element of the recording head unit are recorded. Since the input image to be recorded is distributed to the different recording head unit driving units, the ejection volume variation between the recording elements in the recording head and the ejection volume between the recording elements between the recording heads, which are generated due to manufacturing. To provide an image recording apparatus capable of increasing the discharge frequency while reducing the density unevenness caused by the variation, and recording a high-speed and high-quality image. It can be.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. For example, an ink jet recording apparatus will be described as an example of the image recording apparatus.

  FIG. 1 is a diagram illustrating a configuration of the entire inkjet recording apparatus. In the figure, reference numeral 11 denotes a main body case 11. A drum 12 that rotates in a direction indicated by an arrow in the figure is provided in the case main body 11 and is a recording medium that is a recording medium fed to the drum 12 via paper feed rollers 13 and 14. The medium 15 is wound around.

  A paper feed cassette 16 is provided at the bottom of the main body case 11. The recording medium 15 placed on the placement plate 17 of the paper feed cassette 16 is taken out one by one by a feed roller 18 and fed to the paper feed rollers 13 and 14. Further, the recording medium 15 manually fed from the manual feed tray 19 attached to the side of the main body case 11 so as to be freely opened and closed is fed to the feeding rollers 13 and 14 via the feeding roller 20. Switching between feeding by the feeding roller 18 and feeding by the feeding roller 20 is performed by a feeding switching means 21.

  A charging roller 22 is disposed on the drum 12 so as to oppose the recording medium 15 fed from the paper feeding rollers 13 and 14 to the drum surface. In addition, an ink jet recording head (recording head portion) 23 in which a large number of recording elements are arranged in a line shape is movable on the drum 12 in the direction of the rotation axis of the drum 12, which is the direction in which the recording elements of the recording head 23 are arranged. The printing mechanism 24 arranged in the above is opposed to the printing mechanism 24. Accordingly, the recording medium 15 is conveyed in a direction substantially orthogonal to the arrangement direction of the recording elements of the ink jet recording head 23 by the rotation of the drum 12.

  As shown in FIG. 3, the ink jet recording head unit 23 includes three recording head units 231, 232, and 233 having substantially the same recording characteristics in which a large number of recording elements a are arranged at a predetermined pitch. The recording head unit 232 is bonded to both sides of the recording head unit 232 at the center on one side and the recording head units 231 and 233 are attached to the end sides on the other side. The positional relationship between the recording head unit 232 and the recording head units 231 and 233 is such that all the recording elements are arranged at equal distances. Here, the recording head unit is composed of three recording heads, but the present invention is not limited to this.

  The recording elements of the recording head units 231 and 233 and the recording element a of the recording head unit 232 do not line up in a straight line with respect to the line direction. By controlling the ink discharge timing, control is performed so that the same printing result as that when the recording elements a of the recording head units 231, 232, 233 are arranged on a straight line is obtained.

  Further, as shown in FIGS. 5A and 5B, each recording head unit 231, 232, 233 shown in FIG. 3 has the recording surface in the direction perpendicular to the arrangement direction of the recording elements a. The arrangement is such that the recording resolution in the arrangement direction of the recording elements increases.

  Returning to FIG. 1, the printing mechanism 24 includes a reciprocating mechanism 25 on which an ink jet recording head 23 is mounted, a motor unit 26 having a reciprocating rod and a linear motor, and advancing / retreating means 27. 27, the ink jet recording head 23 is moved back and forth with respect to the drum 12, and the motor unit 26 controls the reciprocation mechanism 25 to move in the direction of the rotation axis of the drum 12. It is designed to reciprocate in the direction.

  The drum 12 is provided with a peeling claw 28 that can be inserted between the drum surface and the recording medium 15, and the recording medium 15 peeled off by the peeling claw 28 is discharged by a recording medium discharge / conveyance mechanism 29. It has become. The recording medium discharging / conveying mechanism 29 includes a belt conveyor 30 that contacts the non-recording surface of the recording medium 15 and a pressing unit 31 that presses the recording medium 15 against the surface of the belt conveyor 30.

  A discharge roller 32 is disposed on the upper side of the main body case 11 so as to discharge the recording medium 15 conveyed by the belt conveyor 30 to the outside of the main body case 11. In the main body case 11, a main motor 33 that rotates and drives each part, an ink cassette 34 that serves as an ink supply source, an ink buffer 35 that temporarily stores ink from the ink cassette 34, and ink in the ink buffer 35 An ink supply tube 36 to be supplied to the ink jet recording head 23 is accommodated.

  In the ink jet recording apparatus, for example, the recording medium 15 is taken out from the paper feed cassette 16 by the paper feed roller 18 and sent to the paper feed rollers 13 and 14 at the time of printing. The recording medium 15 is fed and wound around the rotating drum 12 by the paper feed rollers 13 and 14. The recording medium 15 is attracted to the surface of the drum 12 by the charging roller 22.

  As the drum 12 rotates, the recording medium 15 moves in a direction (Y) perpendicular to the arrangement direction (X) of the recording elements of the recording head 23 as shown in FIG. Image recording is performed by selectively ejecting ink to the recording medium 15 at a predetermined timing based on the image signal.

  Next, a description will be given of a recording head driving unit that drives a plurality of recording elements of the recording head unit according to image data and records an image on a recording medium with different ink droplet amounts for each recording head unit. Conventionally, the amount of ink droplets is determined by the recording resolution, the properties of the ink, and the properties of the recording medium such as paper. In general, assuming that ink is ejected from all the recording elements, it is desirable that the dots formed on the recording surface are large enough to cover the recording surface. If it is smaller than that, there will be a problem of density reduction, and if it is larger than this, there is a possibility that bleeding will occur due to excessive ink amount. The present invention provides a recording element density (resolution) within a range that does not cause the above problem and an ink droplet amount that results in a dot shape, and an ink droplet amount that is ejected from the recording element of each recording head unit of the recording head unit. Are different amounts.

  Next, the arrangement of the recording heads will be described with reference to FIG. In this embodiment, there are two types of arrangement of the recording head, as shown in FIGS. 5 (a) and 5 (b). As shown in FIG. 5A, when the recording head units 231a, 232a, and 233a in the recording head units 23, 232, and 233 are ejected with the maximum number of drops, the recording surface is completely filled with dots without causing density reduction or blurring. As described above, the recording elements and the recording heads in the recording head are arranged. Further, the recording elements of the recording head units 231b, 232b, and 233b are arranged on an imaginary line extending in the paper feed direction Y of the recording elements of the recording head units 231a, 232a, and 233a.

  Further, as shown in FIG. 5B, the recording heads 231a, 232a, and 233a in the recording head units 231, 232, and 233 are such that the recording surface is completely filled with dots without causing the above-described density reduction or bleeding. Between the recording elements and between the recording head units are arranged. Further, the recording elements of the recording head units 231b, 232b, 233b are arranged on a virtual line extending in the paper feed direction Y from the center between the recording elements of the recording head units 231a, 232a, 233a. That is, the recording elements of the recording head units 231b, 232b, and 233b are shifted by a half of the pitch of the recording elements of the recording head units 231a, 232a, and 233a.

  According to FIGS. 5A and 5B, the distance between recording elements in one recording head unit appears to be a distance (resolution) at which the recording surface is completely filled with dots without causing the above-described density reduction or blurring. However, it is not always necessary to satisfy the resolution with a single recording head.

  Next, the size of the dots formed by the ink ejected from the recording elements of the recording head units 231a, 232a, and 233a will be described with reference to FIG. When the maximum recording resolution is D [dpi], the length d between adjacent pixels is d = 25.4 / D, and the dot size is a design value of d * √2. When ink is ejected from all the recording elements of the recording head at this size, the recording surface is completely filled with dots.

  On the other hand, it indicates the size of dots formed on the recording surface by the ink ejected from the recording elements of the recording head units 231b, 232b, 233b in the recording head units 231, 232, 233, and the dot size d ′ is d ′ = d is a design value. When ink is ejected from all the recording elements of the recording head with this size, the recording surface is fully filled with dots.

  Next, the control unit of the ink jet recording apparatus will be described with reference to FIG. In FIG. 7, 51 is a central processing unit. Connected to the central processing unit 51 are a ROM (read only memory) 52, a RAM (random access memory) 53, an input / output (I / O) port 54, and an interface (I / F) 55.

  The CPU 51 implements various operations such as a printing operation and a maintenance process by executing program data and the like for controlling each unit stored in the ROM 52.

  The RAM 53 is provided with a memory area and the like used for various data processing executed by the CPU 51.

  Each device described later is connected to the I / O port 54. A host computer 56 is connected to the I / F 55 via a communication cable.

  The CPU 51 and the ROM 52, RAM 53, I / O port 54, and I / F 55 are electrically connected by a bus line 57 such as a control bus, a system bus, and a data bus.

  In the RAM 53, an image processing parameter area 53a for temporarily storing a table and a program necessary for image processing for converting an input recording image into an image optimal for the image recording apparatus, and ejection of each recording head unit. A discharge characteristic area 53b for temporarily storing characteristics read from the discharge characteristic table of each recording head unit, a temporary storage of a correction area calculation program, and a recording element to be subjected to density correction based on the discharge characteristics are determined. A correction area 53c for storing the area, an input image for recording, an image processing program, and an input / output image area 53d for storing an output image converted into an image optimal for the image recording apparatus by the correction processing program; Receive buffer 53e for temporarily receiving print data from the host computer 56 It is provided.

  The I / O port 54 includes an a head driver (recording head driving unit) 58 that drives an ink chamber of the recording head units 231a, 232a, and 233a (hereinafter also collectively referred to as recording head unit a), and the recording. Drives the head driver (recording head drive unit) 58 that drives the ink chambers of the head units 231b, 232b, and 233b (hereinafter collectively referred to as the recording head unit b), the drum 12, the paper feed rollers 13 and 14, and the like. A motor driver 511d for controlling the conveyance motor 511, a power switch 512, a temperature / humidity sensor 515 for detecting the temperature / humidity in the vicinity of the inkjet recording head 23, and an input unit 517 for setting various flags are connected. The I / O port 54 is connected to a maintenance mechanism 514 that is driven during maintenance of the inkjet recording head 23 and a maintenance driver 513 that controls the maintenance mechanism 514.

  Connected to the bus line 57 are an ejection characteristic table 510 storing the ejection characteristics of each recording head unit and an image processing parameter table 514. For example, the ejection characteristic table 510 includes ejection characteristic tables Tbl1 and Tbl2 that store the ejection characteristics of the recording head units 231a and 231b, respectively. As the ejection characteristics, not only the ejection volume variation for each of the recording head units 231a and 231b, but also ejection volume variations Xi and Yi of a plurality of recording elements of the recording head units 231a and 231b are stored. Similarly, ejection characteristic tables are provided for the recording head units 232a, 232b, 233a, and 233b.

  Next, processing of the image processing program stored in the ROM 52 until input data is output as an output image will be described with reference to FIG. The image processing program includes a color conversion processing unit 81, a UCR processing unit 82, a gradation correction unit 83, a pseudo halftone processing unit 84, and a discharge distribution processing unit (image distribution processing unit) 85.

  First, in the color conversion processing unit 81, for example, a standard RGB color signal is converted into a CMY color of a color reproduction color in a printer, for example, on an input 8-bit monitor. Next, in the UCR processing unit 82, the black component is extracted from the CMY colors, the subsequent CMY colors are determined, and finally converted to CMYK colors. Next, the gradation correction processing unit 83 performs correction processing on the 8-bit image signal of each color, and the pseudo halftone processing unit 84 converts the image signal of one pixel to the printing capability of the inkjet recording device 72 for each color. The combined colors are converted into multi-value image signals having a smaller number of gradations of about 2 to 4 bits.

  Next, in the discharge distribution processing unit 85, which is a feature of the present invention, the recording element Xi of the recording head unit a or the recording head unit in the same unit area of the recording paper based on the data of the ejection characteristic table 510 of each recording head unit. It is determined which of the recording elements Yi of b ejects more, and a signal is output to each recording element. In this ink jet recording apparatus, the volume of ink ejected from each recording element of each of the head units 231, 232, 233 is changed by varying a voltage t that gives a volume fluctuation to the ink chamber, as shown in FIG. Can do. Then, the voltage between t1 and t2 in which the voltage and the discharge volume change in proportion is controlled by, for example, seven divisions to control 1 to 7 gradations, and this includes 0 gradations that do not eject ink. Eight gradation printing can be controlled.

  Next, the discharge data distribution determination process for the print head units 231b, 232b, and 233b of the print head units 231a, 232a, and 233a performed in the discharge distribution processing unit 85 will be described with four examples.

  First, the first example will be described. FIG. 10 shows the recording elements of the recording head unit b (231b, 232b, 233b) of the recording head unit 231, 232, 233 as shown in FIG. 5A, the recording element of the recording head unit a (231a, 232a, 233a). FIG. 6 is a flowchart showing processing when the discharge volume variation of one recording head unit having a plurality of recording elements arranged on an imaginary line extending in the paper feeding direction Y is σ.

  First, processing for the recording head units 231a and 231b will be described with reference to the flowchart of FIG.

  First, initialization is performed (ST1, ST2). Here, the argument i indicates the order of the recording elements of the input image signal in the arrangement direction, and the argument j indicates the arrangement of the recording elements of the input image signal and the order in the vertical direction (hereinafter, the coordinates are (i, j)). Will be shown). Next, the input image signal value at the coordinates (i, j) is input to the conversion D0 (ST3). Here, Img [i] [j] indicates an input image signal value at the coordinates (i, j). Next, at ST4, variations in ejection characteristics for each recording head unit obtained from the ejection characteristics tables Tbl1 and Tbl2 provided for the respective recording head units 231a and 231b are set as σ1 and σ2, and their sizes are compared. Performed (ST4). Here, the input image values transferred to the control units of the recording head units 231a and 231b are D1 and D2. In the determination of ST4, “YES” is determined, that is, when σ1> σ2, D1 = Da, D2 = Db (D0 = Da + Db, Da <Db) (ST5). On the other hand, when the determination of ST4 is “NO”, that is, when σ1 <σ2, D1 = Da, D2 = Db (D0 = Da + Db, Da> Db) is performed (ST4a).

  Then, i is incremented by 1 (ST8) while it is determined as “i ≦ N” in ST6, and the process returns to ST3. Further, j is incremented by 1 while it is determined that “j ≦ M” is determined in ST7 (ST9), and the process returns to ST2.

  Thus, when the discharge volume variation σ1 of the recording head unit a is larger than the discharge volume variation σ2 of the recording head unit b, Da <Db. That is, the recording head unit a having a larger ejection volume variation is adapted to eject ink having a smaller number of drops than the recording head unit b.

In this way, by reducing the discharge volume variation per unit volume of the print medium, it is possible to reduce the density unevenness caused by the discharge volume variation generated between the recording head units.

  Next, a second example will be described. In the second example, the recording elements of the recording head unit a (231a, 232a, 233a) and the recording head unit b (231b, 232b, 233b) are arranged in the same manner as in the first example, but a plurality of recording elements are used. The discharge volume variations Xi and Yi of the elements are compared one by one with the corresponding recording elements.

  First, processing for the recording head units 231a and 231b will be described as an example with reference to the flowchart of FIG. First, initialization is performed (ST8, ST9). Here, the argument i indicates the order of the recording elements of the input image signal in the arrangement direction, and the argument j indicates the arrangement of the recording elements of the input image signal and the order in the vertical direction (hereinafter referred to as coordinates (i, j)). .

  Next, the input image signal value at the coordinates (i, j) is input to the variable D0 (ST10). Here, Img [i] [j] indicates an input image signal value at the coordinates (i, j).

  Next, the variation in ejection characteristics for each recording head unit recording element obtained from the head characteristic tables Tbl1, Tbl2 provided in the recording head units 231a, 231b is represented by X1, X2,..., Xi, Y1, Y2,. And compare the sizes (ST11). Here, the input image values transferred to the control units of the recording head units 231a and 231b are D1 and D2. If “YES” in the determination of ST11, that is, if X1> Y1, D1 = Da, D2 = Db (D0 = Da + Db, Da <Db) are set (ST12). On the other hand, in the determination of ST11, “NO”, that is, when X1 <Y1, D1 = Da, D2 = Db (D0 = Da + Db, Da> Db) is set (ST11a).

  Here, i is incremented by 1 (ST15) while ST13 determines “i ≦ N”, and the process returns to ST10. Further, j is incremented by 1 while “j ≦ M” is determined in ST14 (ST16), and the process returns to ST9.

  Thus, when the ejection volume variation Xi of the recording elements of the recording head unit a is larger than the ejection volume variation Yi of the recording elements of the recording head unit b, Da <Db. In other words, the recording element of the recording head unit a having the larger ejection volume variation is adapted to eject ink having a smaller number of drops than the recording element of the recording head unit b.

  In this way, by reducing the discharge volume variation per unit volume of the print medium, it is possible to reduce the density unevenness caused by the discharge volume variation that occurs between the recording elements of the recording head unit.

  Next, a third example will be described. In FIG. 12, as shown in FIG. 5B, the recording head unit is arranged between the recording elements in the recording head and between the recording heads so that the recording surface is completely filled with dots without causing the above-described density reduction or bleeding. Further, the recording elements of the recording head unit b (231b, 232b, 233b) are arranged on an imaginary line extending in the paper feed direction Y from the center between the recording elements of the recording head unit a (231a, 232a, 233a). FIG. 5 is a flowchart when the discharge volume variation of one recording head unit having a plurality of recording elements is σ.

  The processing for the recording head units 231a and 231b will be described as an example with reference to the flowchart of FIG.

  First, initialization is performed (ST15, ST16). Here, the argument i represents the order of the recording elements of the input image signal in the arrangement direction, and the argument j represents the arrangement of the recording elements of the input image signal and the order in the vertical direction (hereinafter indicated by coordinates (i, j)). )

  Next, variables D0 and D0 ′ are input as input image signal values at coordinates (i, j) (ST17). Here, Img [i] [j] indicates an input image signal value at the coordinates (i, j).

  Next, variations in ejection characteristics for each recording head unit obtained from the head characteristic tables Tbl1 and Tbl2 provided in the recording head units 231a and 231b are set as σ1 and σ2, and the sizes are compared (ST18). Here, the input image values transferred to the control units of the recording head units 231a and 231b are D1 and D2. If “YES” in the determination of ST18, that is, σ1> σ2, it is determined that D1 = Da, D2 = Db (D0 + D0 ′ = Da + Db, Da <Db) (ST19). On the other hand, if “NO” in the determination of ST18, that is, if σ1 <σ2, D1 = Da, D2 = Db (D0 + D0 ′ = Da + Db, Da> Db) is set (ST18a).

  Here, i is incremented by 1 (ST22) while ST20 determines “i ≦ N”, and the process returns to ST17. Further, while it is determined that “j ≦ M” in the determination of ST21, j is incremented by 2 (ST16), and the process returns to ST16.

    Thus, when the discharge volume variation σ1 of the recording head unit a is larger than the discharge volume variation σ2 of the recording head unit b, Da <Db. That is, the recording head unit a having a larger ejection volume variation is adapted to eject ink having a smaller number of drops than the recording head unit b.

In this way, by reducing the discharge volume variation per unit volume of the print medium, it is possible to reduce the density unevenness caused by the discharge volume variation generated between the recording head units.

  Next, a fourth example will be described. In FIG. 13, the recording elements of the recording head unit a (231a, 232a, 233a) and the recording head unit b (231b, 232b, 233b) are arranged in the same manner as in the third example, but a plurality of recording elements are ejected. The flowchart in the case of comparing each of the recording elements corresponding to the volume variations Xi and Yi is shown.

  The operation for the recording head units 231a and 231b is taken as an example, and the operation will be described with reference to the flowchart of FIG.

    First, initialization is performed (ST22, ST23). Here, the argument i indicates the order of the recording elements of the input image signal in the arrangement direction, and the argument j indicates the arrangement of the recording elements of the input image signal and the order in the vertical direction (hereinafter, indicated by coordinates (i, j)). ) Next, the input image signal value at the coordinates (i, j) is input to the variables D0 and D0 ′ (ST24). Here, Img [i] [j] indicates an input image signal value at the coordinates (i, j). Next, X1, X2,... Xi, Y1, Y2,... Yi are variations in ejection characteristics for each recording head unit recording element obtained from the head characteristic tables Tbl1, Tbl2 provided in the recording head units 231a, 231b. The sizes are compared (ST25). Here, the input image values transferred to the control units of the recording head units 231a and 231b are D1 and D2. If “YES” is determined in ST25, that is, if Xi> Yi, D1 = Da, D2 = Db (D0 + D0 ′ = Da + Db, Da <Db) are set (ST26). On the other hand, if “NO” in ST25, that is, if Xi <Yi, D1 = Da, D2 = Db (D0 + D0 ′ = Da + Db, Da> Db) are set (ST25a).

  Here, i is incremented by 1 (ST29) while ST27 determines that “i ≦ N”, and the process returns to ST24. Further, while it is determined that “j ≦ M” in the determination of ST28, j is incremented by 2 (ST30), and the process returns to ST23.

  Thus, when the ejection volume variation Xi of the recording elements of the recording head unit a is larger than the ejection volume variation Yi of the recording elements of the recording head unit b, Da <Db. In other words, the recording element of the recording head unit a having the larger ejection volume variation is adapted to eject ink having a smaller number of drops than the recording element of the recording head unit b.

  In this way, by reducing the discharge volume variation per unit volume of the print medium, it is possible to reduce the density unevenness caused by the discharge volume variation that occurs between the recording elements of the recording head unit.

  By performing the processing in the discharge distribution processing unit 85 as described above, the discharge volume variation per unit area of the recording medium is reduced, and the density unevenness caused by the discharge volume variation generated between the recording elements or between the print heads can be reduced. it can.

  In the above embodiment, one recording head is configured by connecting two recording head units so as to be positioned in a direction perpendicular to the arrangement direction of the recording elements. However, three or more recording head units are provided. One recording head may be configured by being connected so as to be positioned in a direction perpendicular to the arrangement direction of the recording elements.

1 is a cross-sectional view of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 2 is a front view illustrating a schematic configuration of an inkjet head unit mounted on the inkjet recording apparatus. FIG. 3 is a perspective view of the ink jet recording head. FIG. 3 is a front view showing a positional relationship between the inkjet recording head and a recording medium. FIG. 5A is a diagram showing an example of the arrangement of the inkjet recording heads, and FIG. 5B is a diagram showing another example of the arrangement of the inkjet recording heads. FIG. 4 is a diagram illustrating an arrangement interval between recording elements and recording heads. 2 is a block diagram showing a system configuration of the inkjet recording apparatus. FIG. FIG. 3 is a block diagram for explaining image processing performed in the inkjet recording apparatus. FIG. 4 is a diagram illustrating a relationship between a voltage applied to an ink chamber and an ejection volume of ink ejected from the ink chamber. FIG. 10A is a configuration diagram of the head unit, and FIG. 10B is a flowchart for explaining a first example of the ejection data distribution method of the ink jet recording head. FIG. 11A is a configuration diagram of the head unit, and FIG. 11B is a flowchart for explaining a second example of the ejection data distribution method of the ink jet recording head. 12A is a configuration diagram of the head unit, and FIG. 12B is a flowchart for explaining a third example of the ejection data distribution method of the ink jet recording head. FIG. 13A is a configuration diagram of the head unit, and FIG. 13B is a flowchart for explaining a fourth example of the ejection data distribution method of the ink jet recording head.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 51 ... Central processing unit, 52 ... ROM, 510 ... Discharge characteristic table, 81 ... Color conversion process part, 82 ... UCR process part, 83 ... Tone correction part, 84 ... Pseudo halftone process part, 85 ... Discharge distribution process part 510: Discharge characteristic table.

Claims (6)

In an image recording apparatus for recording on a recording medium using a recording head in which a plurality of recording elements are arranged,
Two or more recording head units are connected so as to be positioned in a direction perpendicular to the arrangement direction of the recording elements, and a recording head unit constituting one recording head;
A plurality of recording elements of the recording head unit according to image data, a recording head driving unit that drives each recording head unit to record an image on a recording medium;
A head characteristic table in which recording characteristics for each recording element of the recording head unit are recorded;
An image recording apparatus comprising: an image distribution processing unit that distributes an input image recorded based on the head characteristic table to different recording head unit driving units. The image recording apparatus according to claim 1, wherein the recording head driving unit is capable of discharging a plurality of inks to the same pixel and discharging ink from different recording head units to the same pixel. The image recording apparatus according to claim 1, wherein the image distribution processing unit distributes each input image signal to the recording head driving unit based on the head unit characteristic table. In an image recording apparatus for recording on a recording medium using a recording head in which a plurality of recording elements are arranged,
Two or more recording head units, a recording head portion that constitutes one recording head by shifting the position of the recording element of each head unit in a direction perpendicular to the arrangement direction of the recording elements, and
A plurality of recording elements of the recording head unit according to image data, a recording head driving unit that drives each recording head unit to record an image on a recording medium;
A head characteristic table in which recording characteristics for each recording element of the recording head unit are recorded;
An image recording apparatus comprising: an image processing unit that processes an input image recorded based on the head characteristic table. The image recording apparatus according to claim 4, wherein the recording head driving unit discharges a plurality of inks to the same pixel. The image recording apparatus according to claim 4, wherein the image distribution processing unit distributes each input image signal to the recording head driving unit based on the head unit characteristic table.

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