JP2016215572A - Print control apparatus and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a print control apparatus which can deal with a head with low nozzle density and suppress density unevenness due to the impact time difference without lowering the printing speed.SOLUTION: A print control apparatus which controls an image formation device for forming an image on a recording sheet by discharging chromatic ink in a forward scan constituting one scan region and discharging achromatic ink in a backward scan comprises: detection means 201 which detects overprinting to the same pixel with the achromatic ink and the chromatic ink in the input image data; acquisition means 202 which acquires the impact time difference of overprinting in the same pixel on the recording sheet with the chromatic ink and the achromatic ink; and correction means 203 which performs density correction processing in accordance with the impact time difference so as to decrease the ratio of the chromatic ink and increase the ratio of the achromatic ink in comparison to normal processing in the scan region.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a print control device and a program.

  Conventionally, in color recording on plain paper or the like, bi-directional printing, in which ink is ejected while the head is moving in both the forward direction and the backward direction in the scanning direction of the recording head in order to improve the recording speed, is generally used Known.

  However, on the other hand, depending on the arrangement of the nozzle rows that eject ink, there is a problem of bi-directional color difference that occurs when ink is ejected in different color orders in forward scanning and backward scanning. Therefore, as a technique for correcting the bidirectional color difference, a method of printing chromatic color ink (color ink) and achromatic color ink (black ink) at different scan timings has been considered.

  However, in the scan area (band) of the recording head, for example, when an image is formed by ejecting chromatic ink in the forward scan and achromatic ink in the backward scan, it is present at both ends of the scan start position and end position in the band. There is a new problem that density unevenness occurs due to the difference in density due to the difference in landing time between the chromatic ink and the achromatic ink.

  In view of this, a technique for suppressing density unevenness at both ends in a band by providing a landing time difference longer than the ink permeation time has been proposed and is already known. However, according to such a conventional technique, there is a problem that the printing speed is slowed by providing a landing time difference longer than the ink penetration time.

  On the other hand, in Patent Document 1, for the purpose of suppressing density unevenness due to a difference in landing time during bidirectional printing, image formation is performed using a nozzle that records achromatic ink that is not in parallel with a nozzle that records chromatic color ink. By doing so, an image forming method is disclosed in which density unevenness is corrected without providing a difference in landing time more than the ink permeation time. According to the technology disclosed in Patent Document 1, density unevenness is reduced by detecting the landing time difference between chromatic ink and achromatic ink during bidirectional printing and correcting the ink adhesion amount according to the landing time difference. I try to let them.

  According to the technique disclosed in Patent Document 1, if the recording head has a high nozzle density, it is possible to select a nozzle that records chromatic ink that is not in parallel with a nozzle that records achromatic ink. However, in a head having a low nozzle density, it is general that an achromatic color recording head that discharges achromatic color ink and a chromatic color recording head that discharges chromatic color ink are in parallel, and in this case, the above technique cannot be applied.

  The present invention has been made in view of the above, and can be applied to a head having a low nozzle density. Further, the same pixel on the recording paper of the chromatic color ink and the achromatic color ink can be used without reducing the printing speed. An object of the present invention is to provide a printing control apparatus and program capable of suppressing density unevenness due to a difference in landing time of overstrike.

  In order to solve the above-described problems and achieve the object, the present invention discharges chromatic color ink with a chromatic recording head in the forward scan that constitutes one scanning area, and does not perform the backward scanning that constitutes the one scanning area. In a print control apparatus for controlling an image forming apparatus that forms an image on a recording sheet by ejecting achromatic ink by a chromatic recording head, the same color ink and chromatic ink in the input image data are applied to the same pixel. Detection means for detecting overstrike, acquisition means for acquiring a landing time difference of the chromatic color ink and the achromatic color ink at the same pixel on the recording paper, and comparison with normal processing in the scanning region A correction unit that performs density correction processing according to the landing time difference so as to reduce the ratio of the chromatic color ink and increase the ratio of the achromatic color ink. Characterized in that it comprises a and.

  According to the present invention, it is possible to cope with a head having a low nozzle density, and further, density unevenness due to a difference in landing time of overprinting of chromatic ink and achromatic ink on the same pixel on the recording paper without lowering the printing speed. There is an effect that it can be suppressed.

FIG. 1 is a perspective view schematically showing the ink jet recording apparatus according to the first embodiment. FIG. 2 is a plan view schematically showing the mounting structure of the recording head. FIG. 3 is a plan view showing the recording head. FIG. 4 is a diagram for explaining the colorant distribution inside the paper when the dye-based ink is driven into the same location. FIG. 5 is a diagram for explaining the colorant distribution inside the paper when the pigment-based ink is driven into the same location. FIG. 6 is a diagram for explaining the penetration depth into the sheet due to the landing time difference. FIG. 7 is a graph showing an example of the relationship between the landing time difference and the density. FIG. 8 is a diagram for explaining an example of density unevenness in a conventional ink jet recording apparatus. FIG. 9 is a block diagram schematically showing a hardware configuration of the ink jet recording apparatus. FIG. 10 is a block diagram schematically showing the hardware configuration of the host. FIG. 11 is a block diagram schematically showing a functional configuration relating to image processing. FIG. 12 is a flowchart showing a flow of image processing including density correction processing. FIG. 13 is a diagram illustrating an example of an LUT. FIG. 14 is a flowchart illustrating a flow of image processing including density correction processing according to the second embodiment. FIG. 15 is a diagram illustrating an example of the BG / UCR table. FIG. 16 is a diagram illustrating an example of BG / UCR table switching. FIG. 17 is a flowchart illustrating a flow of image processing including density correction processing according to the third embodiment. FIG. 18 is a flowchart illustrating a flow of image processing including density correction processing according to the fourth embodiment. FIG. 19 is a flowchart showing the flow of black density determination processing for an image data area. FIG. 20 is a flowchart illustrating a flow of image processing including density correction processing according to the fifth embodiment. FIG. 21 is a flowchart showing the flow of the droplet composition changing process. FIG. 22 is a diagram illustrating an example of a mask pattern. FIG. 23 is a diagram schematically showing the droplet configuration changing process. FIG. 24 is a diagram exemplarily showing a difference between mask patterns. FIG. 25 is a diagram for explaining a drive waveform change for increasing the appropriate amount of liquid K medium droplets.

  Embodiments of a print control apparatus and a program will be described below in detail with reference to the accompanying drawings. In the present embodiment, an ink jet recording apparatus is applied as an image forming apparatus, and a host such as a personal computer is applied as a print control apparatus.

(First embodiment)
FIG. 1 is a perspective view schematically showing the ink jet recording apparatus 1 according to the first embodiment. As shown in FIG. 1, an ink jet recording apparatus 1 that is an image forming apparatus includes an image forming unit 2 that is an ink jet head, a sheet conveying unit 3, and a recording paper storage unit 4. These units are included in the apparatus main body 1a. Arranged inside.

  The recording paper storage unit 4 sets a roll-shaped recording paper 30 as an image recording sheet. The recording paper storage unit 4 can set recording papers 30 having different sizes in the sheet width direction.

  The recording paper 30 is provided with flanges 31 from both sides with respect to a paper shaft (not shown). The recording paper 30 is stored in the recording paper storage unit 4 by placing the flange 31 on the flange receiver 32 provided in the recording paper storage unit 4. A support roller (not shown) is provided inside the flange receiver 32. The support roller and the outer periphery of the flange 31 placed on the flange receiver 32 come into contact with each other, whereby the flange 31 rotates and the recording paper 30 is sent out to the sheet conveyance path.

  The ink jet recording apparatus 1 forms an image while scanning the carriage 15 constituting the image forming unit 2 in the width direction of the recording paper 30. The ink jet recording apparatus 1 then transports the recording paper 30 after one or more scans of the carriage 15 are completed, and forms the next recording line. That is, the ink jet recording apparatus 1 is a so-called serial type ink jet recording apparatus.

  The image forming unit 2 includes a guide rod 13 and a guide rail 14 that are stretched over both side plates (not shown). The carriage 15 is held so as to be slidable in the direction of arrow A with respect to the guide rod 13 and the guide rail 14. The carriage 15 is mounted with a recording head 15a (see FIG. 2) that ejects ink droplets. The recording head 15a ejects ink droplets of each color of black (K), yellow (Y), magenta (M), and cyan (C).

  The image forming unit 2 includes a main scanning mechanism 10 including a carriage drive motor 21 disposed on one side in the width direction of the recording paper 30. The main scanning mechanism 10 includes a driving pulley 22, a driven pulley 23, and a belt member 24. The drive pulley 22 is rotationally driven by a carriage drive motor 21. The driven pulley 23 is disposed on the other side in the seat width direction. The driven pulley 23 is tensioned outward by a tension spring (not shown), that is, in a direction away from the drive pulley 22.

  The belt member 24 is wound around the driving pulley 22 and the driven pulley 23. The belt member 24 pulls the carriage 15 in the sheet width direction by being partly fixed and held by a belt fixing portion provided on the back side of the carriage 15.

  In addition, the image forming unit 2 includes an encoder sheet 40 (see FIG. 2) in order to detect the main scanning position of the carriage 15. The encoder sheet 40 is arranged along the width direction of the recording paper 30. That is, the main scanning position of the carriage 15 is detected by reading the encoder sheet 40 by an encoder sensor (not shown) provided on the carriage 15.

  In the recording area of the main scanning area of the carriage 15, the sheet conveying unit 3 moves the recording sheet 30 in a direction orthogonal to the width direction of the recording sheet 30, that is, in the sheet conveying direction (the direction indicated by arrow B in FIG. 1). Transport intermittently.

  In addition, the main cartridge 18 is located outside the moving area of the carriage 15 in the width direction of the recording paper 30 in the sheet conveying section 3 or in one end side area (left side in FIG. 1) of the main scanning area. It is detachably attached to 1a. The main cartridge 18 contains ink of each color supplied to the sub tank of the recording head 15a.

  Further, an idle discharge receiver (not shown) is also provided on one end side area of the movement area of the carriage 15 in the sheet conveying unit 3, that is, on the idle discharge position side (left side in FIG. 1). The idle ejection receiver receives the ejected ink droplets in the idle ejection operation for ejecting ink droplets that do not contribute to image recording in order to eject the thickened ink. Each recording head 15a performs idle ejection at the idle ejection position in order to maintain or restore ejection performance when a predetermined condition is satisfied.

  Further, a maintenance / recovery mechanism 19 that performs maintenance / recovery of the recording head 15a is arranged on the other end side of the movement area of the carriage 15, that is, on the carriage home position side (right side in FIG. 1). Although not shown, the maintenance / recovery mechanism 19 includes caps for capping the nozzle surfaces of the recording head 15a, wiper blades as blade members for wiping the nozzle surfaces, and the like.

  Depending on the specifications of the apparatus, for example, an empty discharge receptacle may be provided on the carriage home position side and included in the maintenance / recovery mechanism 19 in the same manner as the cap and wiper blade. Moreover, the structure which provides an idle discharge receptacle in both the carriage home position side and the idle discharge position side may be sufficient.

  Next, the recording head 15a will be described. Here, FIG. 2 is a plan view schematically showing the mounting structure of the recording head 15a, and FIG. 3 is a plan view showing the recording head 15a. As shown in FIG. 2, the recording head 15 a is mounted on the carriage 15 that is held by the guide rod 13 and the guide rail 14.

  As shown in FIG. 3, the recording head 15a includes nozzle rows K1 to K4, C1 to C2, M1 to M2, and Y1 to Y2 that discharge inks of KCMY colors. As shown in FIG. 3, the odd-numbered nozzle row and the even-numbered nozzle row are arranged at positions shifted by ½ of the nozzle pitch, thereby doubling the printing resolution per scan. .

  Here, two achromatic recording heads 15b having nozzle rows for discharging K ink (black ink) are arranged in a column in order to improve the printing speed of a monochrome image. One of the two rows is arranged in parallel with the chromatic recording head 15c having a nozzle row for discharging CMY ink (color ink), and the other row is provided with a nozzle row for discharging CMY ink. It is provided at a position not parallel to the color recording head.

  Further, the nozzle rows that discharge CMY inks are arranged symmetrically in the main scanning direction A in order to avoid bidirectional color differences due to the landing order of ink colors, which will be described later.

  The arrangement of the recording head 15a is not limited to this. For example, the nozzle rows K3 to K4 may be provided on the opposite side of the sub-scanning direction with respect to K1 to K2, and the color of the CMY ink may be used. If the order is also symmetrical, the arrangement of CMY may be changed.

  Here, the bidirectional color difference depending on the landing order of the ink colors will be described. As an ink colorant fixing characteristic, there is a characteristic that when ink droplets of different colors are ejected to the same location, the ink of the color that has landed on the paper surface first becomes dominant. FIG. 4 is a diagram for explaining the distribution of the colorant inside the paper when the dye-based ink is ejected at the same location, and FIG. 5 is a diagram for explaining the colorant distribution inside the paper when the pigment-based ink is ejected at the same location. is there.

  In the dye-based ink, when the A-color droplet and the B-color droplet are sequentially ejected onto the recording paper 30 as shown in FIG. 4A, first, the A color that is first ejected as shown in FIG. 4B. Drops permeate the recording paper 30. Next, when a B-color droplet is injected, the B-color droplet penetrates into the A-colored permeation region as shown in FIG. In the case of a dye-based ink, the A-colored droplets that are ejected first spread over a wider range than the B-colored droplets that are ejected later, and a difference occurs in the fixing range of the colorant. For this reason, in the secondary color (C + M, M + Y, etc.), the color of the previously ejected drop becomes a more dominant color component.

  In the pigment-based ink, when the A-color droplet and the B-color droplet are sequentially ejected onto the recording paper 30 as shown in FIG. 5A, first, the A color that is first ejected as shown in FIG. 5B. Drops permeate the recording paper 30. Next, when a B-color droplet is injected, the B-color droplet penetrates through the penetration region of the A color as shown in FIG. In the case of pigment-based ink, the colorant contained in the ink that has been ejected first remains on the surface of the paper, and the colorant that has been ejected later sinks inside the paper. As a result, in the case of pigment-based ink, the characteristics of the colorant on the side closer to the paper surface (the direction of the previously ejected droplet) become stronger and become a dominant color component.

  Although FIGS. 4 and 5 describe the recording object through which the liquid penetrates, the same phenomenon occurs in the recording object through which the liquid does not penetrate.

  When the nozzle rows for ejecting CMY ink are not symmetrically arranged and one band image is completed by one scan of the recording head, the order of CMY ink strikes is switched between forward scanning and backward scanning in the main scanning direction. The ink color that controls the color tone changes between bands, resulting in a color difference. However, even if the order of CMY ink is changed in units of one nozzle within one scan, it is not recognized as a color difference by human eyes.

  From the above, it is desirable that the nozzle rows for ejecting CMY inks be symmetrically arranged in the main scanning direction A (see FIG. 3) so that the order in which the nozzles are driven is not switched between bands.

  However, when the recording heads 15a are arranged in the order of the nozzle colors as shown in FIG. 3, the K ink and CMY inks are not symmetrically arranged, so the color of the shadow portion where the amount of K ink used is large. Bidirectional color difference occurs in the area. In order to avoid this, in the printing mode in which one band image is completed by one scan, only K3 to K4 of the recording head 15a shown in FIG. 3 can be used in order to always land K ink after CMY ink. More desirable.

  Next, a difference in density caused by a difference in landing time of ink droplets will be described. Here, FIG. 6 is a diagram for explaining the penetration depth into the paper due to the landing time difference. According to the experiments by the present inventors, it is known that a difference in penetration depth occurs in the landing time difference as shown in FIG.

  As shown in FIG. 6A, when the landing time difference is small, the dots of the achromatic ink (black ink) are landed when the dots of the chromatic ink (color ink) that land first are not completely dried. To do. For this reason, the achromatic ink tends to penetrate into the recording paper 30 and the density of the achromatic ink tends to decrease.

  On the other hand, as shown in FIG. 6B, when the landing time difference is large, the achromatic ink dots land while the chromatic ink dots that land first are dry. The density of the achromatic ink tends to be high because the ink does not easily penetrate into the interior 30.

  FIG. 7 is a graph showing an example of the relationship between the landing time difference and the density. The graph shown in FIG. 7 shows the relationship between the landing time difference and the density when the recording head 15a is scanned at the moving speed V [m / s]. As shown in FIG. 7, the relationship between the landing time difference and the concentration tends to increase as the landing time difference increases, and the concentration saturates when a certain landing time difference is exceeded.

The landing time difference is calculated from the moving speed of the carriage 15 of the inkjet recording apparatus 1 and the target pixel position as follows. For example, the target pixel position is the leading edge of the recording paper 30 and the forward recording start position (lower right position in FIG. 2), the distance from the target pixel position to the forward path end position is L1 [mm], and the backward path start position to the target pixel position The distance to is L2 [mm]. The moving speed of the carriage 15 is V [mm / S]. Then, the time difference between the forward recording timing and the backward recording timing at the target pixel position, that is, the landing time difference between the color ink and the black ink at the target pixel position is obtained by the following equation.
Landing time difference of target pixel position = (L1 + L2) / V [Sec]

If the landing time difference at the target pixel position can be calculated, the landing time difference between pixel positions that are N [pixels] apart can be obtained by the following equation using the recording resolution D [dpi].
Landing time difference between pixel positions separated by N pixels = {(L1−25.4 * N / D) + (L2−25.4 * N / D)} / V [Sec]

Note that the landing time difference at the target pixel position may be measured while scanning the carriage using a travel time measuring unit as described in Japanese Patent Application Laid-Open No. 2004-082449, which is a known technique. In this case, the landing time difference between the pixel positions separated by N pixels can be obtained from the recording frequency f [Hz] and the measured landing time difference t1 [S] by the following equation.
Landing time difference between pixel positions separated by N pixels = t1-2N / f [Sec]

  Here, the density unevenness generated according to the density difference as described above in the conventional ink jet recording apparatus will be described. Here, an example of an ink jet recording apparatus that employs a printing method for achieving high-speed printing that completes an image of one band region in one scan will be described.

  FIG. 8 is a diagram for explaining an example of density unevenness in a conventional ink jet recording apparatus. In FIG. 8, CMY ink is ejected while scanning the carriage in the forward direction in the first scan (first scan), and K ink is ejected while scanning the carriage in the backward direction in the second scan (second scan). Pay attention to (the lowermost band in the sheet conveying direction in FIG. 8). In this band, as shown in FIG. 8, the density is lower at the left end portion of FIG. 8, and the density is higher at the right end portion. Therefore, as shown in FIG. 8, there are “dark” and “thin” portions at the left and right ends of the band, and the arrangement of “dark” and “thin” portions is repeated while being reversed for each band. Is recognized as density unevenness.

  Next, the hardware configuration of the inkjet recording apparatus 1 will be described.

  FIG. 9 is a block diagram schematically showing a hardware configuration of the inkjet recording apparatus 1. As shown in FIG. 9, the ink jet recording apparatus 1 includes a control unit 100. The control unit 100 includes a CPU (Central Processing Unit) 101 that controls the entire inkjet recording apparatus 1, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, a nonvolatile memory (NVRAM) 104, An ASIC (Application Specific Integrated Circuit) 105 is provided.

  The ROM 102 stores programs executed by the CPU 101 and other fixed data. The RAM 103 temporarily stores image data and the like. The nonvolatile memory (NVRAM) 104 holds data even when the power supply of the inkjet recording apparatus 1 is shut off. The ASIC 105 processes image processing for performing various signal processing and rearrangement, and other input / output signals for controlling the entire apparatus.

  The ROM 102 also includes a landing time difference storage unit 102a that stores a landing time difference for each paper size. The landing time difference storage unit 102a schematically stores a difference in landing time of overprinting of the achromatic color ink (black ink) and the chromatic color ink (color ink) on the recording paper 30 in the same pixel. Since the distances L1 and L2 are values that vary depending on the size of the recording paper 30, the landing time difference storage unit 102a holds the landing time difference corresponding to the recording pixel position for each size of the recording paper 30 as table data. ing.

  In addition, the control unit 100 includes a host I / F 106, a head drive control unit 107, a head driver 108, a main scanning motor driving unit 111, a sub scanning motor driving unit 113, and an I / O 116. . In addition, the control unit 100 connects the AC bias supply unit 114 and the environment sensor 118.

  The host I / F 106 transmits and receives data and signals to and from the host 90 functioning as a print control device. The host 90 is a data processing apparatus that is an image processing apparatus such as a personal computer, an image reading apparatus such as an image scanner, and an imaging apparatus such as a digital camera. The head drive control unit 107 and the head driver 108 generate a drive waveform for driving and controlling the recording head 15a. The main scanning motor driving unit 111 drives a carriage driving motor 21 that is a main scanning motor. The sub-scanning motor driving unit 113 drives the sub-scanning motor 112 that drives the sheet conveying unit 3.

  The AC bias supply unit 114 supplies an AC bias to the charging roller 34. For example, when the recording paper 30 is in contact with the charging roller 34, the AC bias supply unit 114 applies an applied voltage to the charging roller 34 having a polarity opposite to the detected surface potential and the same potential. 30 surface charges are effectively removed. The environmental sensor 118 detects environmental temperature and / or environmental humidity. The I / O 116 inputs a detection signal from the environment sensor 118.

  In addition, an operation panel 117 for inputting and displaying information necessary for the inkjet recording apparatus 1 is connected to the control unit 100.

  Here, the control unit 100 receives print data including image data from the host 90 side by the host I / F 106 via a cable or a network. Note that print data is generated and output to the control unit 100 by the printer driver PD on the host 90 side. The printer driver PD is a program that generally transfers image data (print data) to the inkjet recording apparatus 1 in order to form an image.

  The CPU 101 of the control unit 100 reads and analyzes the print data in the reception buffer of the host I / F 106, performs data rearrangement processing by the ASIC 105, and transfers the image data to the head drive control unit 107.

  The print data for image output is converted into bitmap data by developing the image data into bitmap data by the printer driver PD on the host 90 side and transferring it to the inkjet recording apparatus 1 as described above. Yes. However, the present invention is not limited to this. For example, font data may be stored in the ROM 102.

  The head drive control unit 107 includes a D / A converter that performs D / A conversion on drive pulse pattern data. The head drive control unit 107 outputs a drive waveform composed of one drive pulse (drive signal) or a plurality of drive pulses (drive signal) to the head driver 108.

  The head driver 108 drives the recording head 15a based on image data (dot pattern data) corresponding to one line of the recording head 15a input serially. More specifically, the head driver 108 selectively applies a driving pulse constituting a driving waveform provided from the head driving control unit 107 to the pressure generating means (not shown) of the recording head 15a based on the image data.

  For example, the head driver 108 includes a shift register, a latch circuit, a level conversion circuit (level shifter), an analog switch array (switch means), and the like. The shift register inputs a clock signal and serial data. The latch circuit latches the register value of the shift register with a latch signal. The level conversion circuit (level shifter) changes the level of the output value of the latch circuit. The analog switch array (switch means) is controlled to be turned on / off by a level shifter.

  The head driver 108 controls the on / off of the analog switch array to selectively apply a required drive waveform included in the drive waveform from the head drive control unit 107 to the pressure generating unit to drive the recording head 15a. To do. Here, the drive waveform is composed of a plurality of drive pulses, and by giving one or a plurality of drive pulses, four types of gradations of large droplets, medium droplets, small droplets, and no droplets can be reproduced. .

  Next, the hardware configuration of the host 90 will be described.

  FIG. 10 is a block diagram schematically showing the hardware configuration of the host 90. As shown in FIG. 10, the host 90 includes a CPU (Central Processing Unit) 91 that is a computer that is a main body for controlling the operation of the host 90. The CPU 91 includes a ROM (Read Only Memory) 92 for storing a program executed when the CPU 91 is activated, necessary data, and the like, and a RAM (Random Access Memory) 93 for configuring a work area of the CPU 91 and the like. They are connected via an internal bus 94.

  Further, the CPU 91 includes a clock circuit 95, a network interface (I / F) circuit 96, a network transmission control unit 97, a magnetic disk device 98, a medium control device 99, a display control unit 89, and an input control unit 88, and an internal bus 94. Connected through. Data exchange between these elements is mainly performed through the internal bus 94.

  The clock circuit 95 is for outputting current date information.

  The network I / F circuit 96 is for connecting the host 90 to the inkjet recording apparatus 1 via a network (not shown) such as a LAN. The network transmission control unit 97 is for executing communication control processing of various predetermined protocol suites for exchanging various data with the ink jet recording apparatus 1 via the network. For example, the network I / F circuit 96 connects the ink jet recording apparatus 1 via the network and transmits print document information (print data) or the like to the ink jet recording apparatus 1 or the print processing state from the ink jet recording apparatus 1. It performs operations such as receiving.

  The magnetic disk device 98 is for storing various data such as an OS (Operating System), various application programs running on the OS, work data, file data, and image information data. In the present embodiment, a printer driver PD and the like are stored as application programs. The medium control device 99 is for reading data (various data such as various application programs, work data, file data, image information data) stored in the exchangeable recording medium 50 such as a CD-ROM. is there.

  In such a host 90, when the user turns on the power, the CPU 91 activates a program called a loader in the ROM 92, reads the OS from the magnetic disk device 98 into the RAM 93, and activates the OS. Such an OS activates an application program, reads information, or stores information in accordance with a user operation. The recording medium 50 is not limited to a CD-ROM, and may be any computer-readable recording medium such as a flexible disk (FD), a CD-R, a CD-RW, a DVD, or a semiconductor memory. In this case, it goes without saying that the medium control device 99 is changed to one that can read data in the storage medium. In addition, the application program is not limited to one that runs on a predetermined OS, but may be one that causes the OS to execute some of the various processes described below. Furthermore, the application program may be included as a part of a group of program files that constitute predetermined application software, OS, or the like.

  In general, an application program installed in the magnetic disk device 98 of the host 90 is recorded in the recording medium 50, and the application program recorded in the recording medium 50 is installed in the magnetic disk device 98. Therefore, the recording medium 50 can also be a storage medium that stores application programs. Further, the application program may be taken in from the outside via, for example, the network interface circuit 96 and installed in the magnetic disk device 98.

  A display device 87 such as a CRT is for displaying a screen for operating the host 90. The display control unit 89 controls the display content of the display device 87.

  The keyboard device 86 is for causing various instructions to the host 90 to be performed by various key operations. The pointing device 85 is for performing an operation such as pointing to an arbitrary point on the display device 87 (for example, a pointing device such as a mouse). Then, the input control unit 88 captures input information of the keyboard device 86 and the pointing device 85, for example.

  Print document information (print data) is generated by the activated application program (printer driver PD) and stored in the magnetic disk device 98 or output to the inkjet recording apparatus 1.

  Next, image processing among various types of processing executed by the CPU 91 of the host 90 according to the printer driver PD will be described below.

  FIG. 11 is a block diagram schematically showing a functional configuration relating to image processing. As shown in FIG. 11, the CPU 91 of the host 90 follows a printer driver PD, thereby a CMM (Color Management Module) processing unit 200, a color discrimination processing unit 201 that functions as a detection unit, a calling unit 202 that functions as an acquisition unit, It functions as a correction processing unit 203 that functions as a correction unit. Further, the CPU 91 of the host 90 functions as a total amount restriction processing unit 204, a γ correction unit 205, a halftone processing unit 206, a rendering processing unit 207, and an end determination processing unit 208 according to the printer driver PD.

  The CMM processing unit 200 converts image data given from application software or the like from a color space for monitor display to a color space for the inkjet recording apparatus 1 (RGB color system → CMYK color system).

  After the data conversion to CMYK by the CMM processing unit 200, the color discrimination processing unit 201 determines the color of the pixel based on the value of CMYK. That is, after the data conversion to CMYK by the CMM processing unit 200, the color determination processing unit 201 detects overstrike for the same pixel of achromatic ink (black ink) and chromatic color ink (CMY ink).

  As described above, the color discrimination processing unit 201 discriminates the presence of an achromatic color and a chromatic color in the same pixel because the density difference between the left and right ends occurs when the black ink and the color ink overlap. Is.

  The calling unit 202 refers to the landing time difference storage unit 102a of the ROM 102 of the inkjet recording apparatus 1 when detecting overstrike of the same pixel of the achromatic color ink (black ink) and the chromatic color ink (CMY ink). Then, the calling unit 202 calls the landing time difference information of the overlapping hits on the recording paper 30 of the black ink and the color ink that match the image size of the image data on the same pixel. The landing time difference storage unit 102a may be copied in advance to the magnetic disk device 98 of the host 90 or the like.

  The correction processing unit 203 performs density correction processing according to the landing time difference called by the calling unit 202 so that the ratio of the chromatic color ink is decreased and the ratio of the achromatic color ink is increased compared to the normal processing in the scanning region. Run.

  In the present embodiment, the correction processing unit 203 switches the LUT (Look Up Table) according to the landing time difference called by the calling unit 202 and executes the density correction processing. More specifically, when the color is an achromatic color, the correction processing unit 203 switches to a density correction LUT for the purpose of performing processing to decrease the CMY ratio and increase the K ratio. I do.

  The total amount restriction processing unit 204 performs a total amount restriction process that restricts the total number of ink adhesion amounts.

  The γ correction unit 205 performs γ correction reflecting the characteristics of the ink jet recording apparatus 1 and the user's preference.

  The halftone processing unit 206 performs halftone processing for replacing the image data with a pattern arrangement of dots ejected from the recording head 15 a of the inkjet recording apparatus 1.

  The rendering processing unit 207 performs a rendering process for generating an image.

  The end determination processing unit 208 determines whether predetermined processing for all pixels has been completed.

  Next, image processing including density correction processing among image processing executed by the CPU 91 of the host 90 according to the printer driver PD will be described with reference to a flowchart of FIG.

  As shown in FIG. 12, when image data (RGB data) is input, the CPU 91 of the host 90 stores the RGB values of the input image data (RGB data) in the RAM 93 (step S1).

  Next, the CPU 91 (CMM processing unit 200) of the host 90 performs color matching processing (step S2). More specifically, the CMM processing unit 200 converts the image data given from application software or the like from the color space for monitor display to the color space for the inkjet recording apparatus 1 (RGB color system → CMYK color system). System) is performed by a LUT (Look Up Table) for normal processing.

  Next, the CPU 91 (color discrimination processing unit 201) of the host 90 detects overstrike for the same pixel of the achromatic color ink (black ink) and the chromatic color ink (CMY ink) based on the result of the color matching process ( Steps S3 to S4).

  When it is determined that there is no overstrike for the same pixel of the achromatic color ink (black ink) and the chromatic color ink (CMY ink) (Yes in step S3 or Yes in step S4), the CPU 91 of the host 90 directly performs the process in step S9. Proceed to the total amount regulation process.

  On the other hand, when it is determined that there is an overstrike for the same pixel of achromatic ink (black ink) and chromatic ink (CMY ink) (No in step S3, No in step S4), the CPU 91 of the host 90 (calling unit 202). ) Refers to the landing time difference storage unit 102 a of the ROM 102 of the inkjet recording apparatus 1. Then, the CPU 91 (calling unit 202) of the host 90 performs overstrike for the pixels on the recording paper 30 with black ink and color ink corresponding to the size of the recording paper 30 matching the image size of the input image data. The landing time difference information is called (step S5).

  Next, the CPU 91 (correction processing unit 203) of the host 90 calls the RGB value of the image data (RGB data) stored in the RAM 93 (step S6). Further, the CPU 91 (correction processing unit 203) of the host 90 performs switching to a density correction processing LUT (Look Up Table) corresponding to the landing time difference (step S7).

  When density correction is executed, the LUT is switched to a LUT having a smaller CMY ratio and a larger K ratio than the LUT used in normal processing. The CPU 91 (correction processing unit 203) of the host 90 suppresses the density unevenness due to the landing time difference by reducing the CMY ratio as compared with the normal processing.

  Next, the CPU 91 (CMM processing unit 200) of the host 90 performs color matching processing (step S8). More specifically, the CMM processing unit 200 converts image data (RGB data) from a monitor display color space to a color space for the inkjet recording apparatus 1 (RGB color system → CMYK color system), Performed by the LUT switched in S7 That is, the CMM processing unit 200 calculates an output value (CMYK color system) corresponding to each input value (RGB color system) from the LUT.

  Here, FIG. 13 is a diagram illustrating an example of the LUT. In this embodiment, a density correction processing LUT corresponding to density correction is provided separately from the normal processing LUT. FIG. 13A shows an example of an LUT for normal processing, and FIG. 13B shows an example of an LUT for density correction processing.

  The LUT is an output value allocation table for input values. The table capacity (stored number) of the LUT exists for the gradation. For example, with 256 gradations, there are 256 data storage numbers. The LUT performs data conversion by referring to an output value with respect to a preset input value.

  For example, when pixel data having an R: G: B value of 10:10:10 is input, the normal processing LUT has a C: M: Y: K value as shown in FIG. Is output instantaneously as 50: 50: 50: 200. On the other hand, when pixel data having a R: G: B value of 10:10:10 is input, the LUT for density correction processing has a 10: 10: 10: 255 as shown in FIG. 13B. Is output instantaneously. By switching to the density correction processing LUT in this way, the ratio of chromatic ink can be reduced and the ratio of achromatic ink can be increased.

  Subsequently, total amount restriction processing (step S9) by the CPU 91 (total amount restriction processing unit 204) of the host 90 and γ correction processing (step S10) by the CPU 91 (γ correction unit 205) are executed. Further, halftone processing (step S11) by the CPU 91 (halftone processing unit 206) and rendering processing (step S12) by the CPU 91 (rendering processing unit 207) are executed.

  Then, the CPU 91 (total amount restriction processing unit 204) of the host 90 repeatedly executes the above-described processing (steps S1 to S12) for all pixels (step S13). If the CPU 91 (total amount restriction processing unit 204) of the host 90 determines that the processing for all the pixels has been completed (Yes in step S13), it sends the processed data to the inkjet recording apparatus 1 as image data.

  As described above, according to the present embodiment, when overprinting with respect to the same pixel of the achromatic color ink and the chromatic color ink in the input image data is detected, the same color ink and achromatic color ink on the recording paper are detected. Obtain the landing time difference of overstrike in the pixel. A table corresponding to the landing time difference is switched to a density correction processing LUT that reduces the ratio of the chromatic color ink and increases the ratio of the achromatic color ink in the scanning region as compared with the normal process. Accordingly, it is possible to cope with a head having a low nozzle density, and it is possible to suppress density unevenness due to a difference in landing time without lowering the printing speed.

(Second Embodiment)
Next, a second embodiment will be described. The same parts as those in the first embodiment described above are denoted by the same reference numerals, and description thereof is also omitted.

  In the first embodiment, density unevenness due to the landing time difference is suppressed by switching to the LUT for density correction processing corresponding to the landing time difference (step S7). In the present embodiment, the first implementation is that processing for reducing the CMY ratio and increasing the K ratio is performed by switching the BG / UCR (black plate generation / undercolor removal) table. The form is different.

  Here, image processing among various types of processing executed by the CPU 91 of the host 90 according to the printer driver PD will be described below. In the present embodiment, the correction processing unit 203 shown in FIG. 11 performs density correction processing by switching the BG / UCR table according to the landing time difference called by the calling unit 202.

  Next, image processing including processing for switching the BG / UCR table among image processing executed by the CPU 91 of the host 90 in accordance with the printer driver PD will be described with reference to the flowchart of FIG. Note that the processing excluding step S17 is not different from the processing described with reference to the flowchart of FIG.

  As shown in FIG. 14, the CPU 91 (correction processing unit 203) of the host 90 calls the RGB values of the image data (RGB data) stored in the RAM 93 (step S6). Then, the CPU 91 (correction processing unit 203) of the host 90 performs switching to the BG / UCR table for density correction processing according to the landing time difference (step S17). When density correction is executed, the BG / UCR table is switched to a BG / UCR table having a lower CMY ratio and a higher K ratio than the BG / UCR table used in normal processing. The CPU 91 (correction processing unit 203) of the host 90 suppresses the density unevenness due to the landing time difference by reducing the CMY ratio as compared with the normal processing.

  Here, FIG. 15 is a diagram showing an example of the BG / UCR table. Note that BG (Black Generation) represents “black generation processing” for generating K data from CMY data. UCR (Under Color Removal) represents “under color removal processing” for deleting color (CMY) data that can be replaced with K data. In the present embodiment, a BG / UCR table for density correction corresponding to density correction is provided separately from the BG / UCR table for normal processing. FIG. 15A shows an example of a BG / UCR table for normal processing, and FIG. 15B shows an example of a BG / UCR table for density correction processing. In the BG / UCR table for normal processing in FIG. 15A, when the input value is 100, BG = 30 and UCR = 10. In the BG / UCR table for density correction processing in FIG. 15B, when the input value is 100, BG = 50 and UCR = 20.

  Next, the CPU 91 (CMM processing unit 200) of the host 90 performs color matching processing (step S8). More specifically, the CMM processing unit 200 switches the image data (RGB data) from the color space for monitor display to the color space for the inkjet recording apparatus 1 (RGB color system → CMYK color system). BG / UCR table. That is, the CMM processing unit 200 calculates an output value (CMYK color system) corresponding to each input value (RGB color system) from the BG / UCR table.

  Here, an example of image processing in which the BG / UCR table is switched in the present embodiment will be described. Here, FIG. 16 is a diagram showing an example of switching of the BG / UCR table. FIG. 16A shows an example of image processing using a BG / UCR table for normal processing, and FIG. 16B shows an example of image processing using a BG / UCR table for density correction processing.

  As shown in FIG. 16A, for example, when the value of C: M: Y is 100: 200: 200 and the input value to the correction processing unit 203 is 100, the BG / UCR table of normal processing Then, BG = 30 and UCR = 10. In this case, the value of C: M: Y: K is 90: 190: 190: 30.

  As shown in FIG. 16B, for example, when the value of C: M: Y is 100: 200: 200 and the input value to the correction processing unit 203 is 100, the density correction processing BG / In the UCR table, BG = 50 and UCR = 20. In this case, the value of C: M: Y: K is 80: 180: 180: 50.

  By switching to the BG / UCR table for density correction processing in this way, the ratio of chromatic ink can be reduced and the ratio of achromatic ink can be increased.

  As described above, according to the present embodiment, when overprinting with respect to the same pixel of the achromatic color ink and the chromatic color ink in the input image data is detected, the same color ink and achromatic color ink on the recording paper are detected. Obtain the landing time difference of overstrike in the pixel. Then, a table corresponding to the landing time difference is switched to the density correction processing BG / UCR table in which the ratio of the chromatic color ink is decreased and the ratio of the achromatic color ink is increased in the scanning region as compared with the normal processing. Accordingly, it is possible to cope with a head having a low nozzle density, and it is possible to suppress density unevenness due to a difference in landing time without lowering the printing speed.

(Third embodiment)
Next, a third embodiment will be described. In addition, the same part as 1st Embodiment mentioned above or 2nd Embodiment is shown with the same code | symbol, and description is also abbreviate | omitted.

  In the second embodiment, density unevenness due to the landing time difference is suppressed by switching to the BG / UCR table for density correction processing according to the landing time difference. This embodiment is different from the second embodiment in that it is determined whether or not to execute density correction processing based on image density (tone value).

  Here, image processing among various types of processing executed by the CPU 91 of the host 90 according to the printer driver PD will be described below. In the present embodiment, the correction processing unit 203 shown in FIG. 11 determines whether to switch the BG / UCR table according to the landing time difference called by the calling unit 202 according to the gradation value.

  Next, image processing including processing for switching the BG / UCR table among image processing executed by the CPU 91 of the host 90 in accordance with the printer driver PD will be described with reference to the flowchart of FIG. Note that the processing excluding step S21 is not different from the processing described in the flowchart of FIG.

  As shown in FIG. 17, the CPU 91 (correction processing unit 203) of the host 90 calls the RGB value of the image data (RGB data) stored in the RAM 93 (step S6), and determines the density from the called RGB value. (Step S21).

  The reason for determining the density from the RGB values in this way is as follows. As described with reference to FIG. 8, the density difference between the left and right end portions in the band occurs particularly when black is printed. More specifically, the density difference between the left and right end portions in the band is particularly noticeable when black of gradation 255 is printed, and it is known that the density difference decreases as the gradation value decreases. . Therefore, the correction processing unit 203 according to the present embodiment executes switching to the density correction BG / UCR table only when it is determined to print black. In other words, if the correction processing unit 203 determines not to print black, the correction processing unit 203 performs processing using the BG / UCR table for normal processing and does not perform density correction.

  More specifically, the CPU 91 (correction processing unit 203) of the host 90 performs density unevenness at the left and right end portions in the band when the gradation value of R = G = B in the called RGB value is larger than the threshold value T. Assuming that (image density difference) is large, switching to the density correction BG / UCR table is executed. On the other hand, the CPU 91 (correction processing unit 203) of the host 90 has small density unevenness at the left and right end portions in the band when the gradation value of R = G = B in the called RGB value is smaller than the threshold value T. The processing result of the color matching process (step S2) using the BG / UCR table for normal processing is adopted, and density correction is not performed.

  As described above, according to the present embodiment, it is possible to efficiently reduce the burden on the image processing by controlling the density correction processing only when the density difference is large.

  In this embodiment, switching to the density correction BG / UCR table is executed only when it is determined to print black, but the present invention is not limited to this. For example, switching to the LUT for density correction processing may be executed only when it is determined to print black.

(Fourth embodiment)
Next, a fourth embodiment will be described. The same parts as those in the first to third embodiments described above are denoted by the same reference numerals, and description thereof is also omitted.

  In the second embodiment, density unevenness due to the landing time difference is suppressed by performing density correction processing by switching to the BG / UCR table for density correction processing according to the landing time difference. This embodiment is different from the second embodiment in that it is determined whether to execute density correction processing based on the density of black in a certain image data area obtained by dividing image data. It has become.

  Here, image processing among various types of processing executed by the CPU 91 of the host 90 according to the printer driver PD will be described below. In the present embodiment, whether or not the correction processing unit 203 shown in FIG. 11 performs switching of the BG / UCR table according to the landing time difference called by the calling unit 202 is a certain image obtained by dividing the image data. Judgment is made according to the density of black in the data area.

  Next, image processing including processing for switching the BG / UCR table among image processing executed by the CPU 91 of the host 90 in accordance with the printer driver PD will be described with reference to the flowchart of FIG. Note that the processing excluding steps S31 to S32 is not different from the processing described in the flowchart of FIG.

  As shown in FIG. 18, the CPU 91 (correction processing unit 203) of the host 90 calls the RGB values of the image data (RGB data) stored in the RAM 93 (step S6). Then, the CPU 91 (correction processing unit 203) of the host 90 determines the black density of a certain image data area obtained by dividing the image data (step S31).

  The reason for determining the black density of a certain image data area in this way is as follows. As described with reference to FIG. 8, the difference in density between the left and right end portions in the band occurs particularly when black is printed densely. Therefore, the correction processing unit 203 according to the present embodiment calculates the black density of a certain image data area from the image data, and switches to the density correction BG / UCR table only when it is determined that the black density is high. Is to be executed. That is, the correction processing unit 203 calculates the black density of a certain image data area from the image data, and when it is determined that the black density is low, the color matching using the BG / UCR table for normal processing It is assumed that the processing result of the processing (step S2) is adopted and density correction is not performed.

  Here, the determination process of the black density of the image data area will be described with reference to the flowchart of FIG.

  As shown in FIG. 19, the CPU 91 (correction processing unit 203) of the host 90 divides the input image data into N1 image areas (step S311).

  Next, the CPU 91 (correction processing unit 203) of the host 90 calculates the number of black (K) pixels where R = G = B in the divided area (step S312).

  Next, the CPU 91 (correction processing unit 203) of the host 90 determines whether or not the calculated number of black pixels exceeds the threshold (step S313). The CPU 91 (correction processing unit 203) of the host 90 assumes that density unevenness appears more noticeably when the number of black pixels in the divided area is larger than the threshold value, and sets a flag for executing density correction (step) S314). On the other hand, when the number of black pixels in the divided area is smaller than the threshold, the CPU 91 (correction processing unit 203) of the host 90 assumes that the influence of density unevenness at the left and right ends in the band is small, and density correction Is not raised (step S315).

  Subsequently, as a result of determining the image data area, the CPU 91 (correction processing unit 203) of the host 90 determines whether to execute density correction based on whether the flag is set (step S32). When the execution flag is set, the CPU 91 (correction processing unit 203) of the host 90 executes switching to the BG / UCR table for density correction. Further, when the execution flag is not set, the CPU 91 (correction processing unit 203) of the host 90 adopts the processing result of the color matching process (step S2) using the BG / UCR table for normal processing, and the density correction is performed. Shall not be performed.

  As described above, according to the present embodiment, it is possible to efficiently reduce the burden on image processing by controlling the density correction processing only when the density of black is high in a certain image data area. it can.

  In the present embodiment, the black density of a certain image data area is calculated from the image data, and switching to the BG / UCR table for density correction is executed only when it is determined that the black density is high. However, it is not limited to this. For example, the black density of a certain image data area may be calculated from the image data, and switching to the LUT for density correction processing may be executed only when it is determined that the black density is high.

(Fifth embodiment)
Next, a fifth embodiment will be described. The same parts as those in the first to fourth embodiments described above are denoted by the same reference numerals, and description thereof is also omitted.

  This embodiment is different from the first to fourth embodiments in that the CMY ratio is decreased and the K ratio is increased by changing the droplet configuration. It has become.

  Here, image processing among various types of processing executed by the CPU 91 of the host 90 according to the printer driver PD will be described below. In the present embodiment, the correction processing unit 203 shown in FIG. 11 further changes the droplet configuration.

  Next, image processing including density correction processing among image processing executed by the CPU 91 of the host 90 according to the printer driver PD will be described with reference to the flowchart of FIG. 20 and the flowchart of FIG. Note that the processing excluding steps S51 and S52 in FIG. 20 is not different from the processing described with reference to the flowchart of FIG.

  As shown in FIG. 20, the CPU 91 (correction processing unit 203) of the host 90 calls the RGB values of the image data (RGB data) stored in the RAM 93 after halftone processing by the halftone processing unit 206 (step S11). (Step S51). Further, the CPU 91 (correction processing unit 203) of the host 90 performs a droplet configuration change process (step S52).

  The droplet composition change process roughly determines the density of image data divided for each predetermined threshold based on RGB values. Then, the drop composition change process selects and applies a mask pattern that takes into account the dot dispersion ratio so that the appropriate CMY thinning amount and the number of K medium drop pixels to be large drops correspond to the determined density category. To do.

  FIG. 22 is a diagram illustrating an example of a mask pattern. The mask pattern defines the thinning amount of CMY and the number of pixels of K medium droplets that become large droplets. As shown in FIG. 22, in the droplet composition change process, for a composite Bk composed of four colors of KCMY, each color is divided into N1 pixels, and a mask process is performed for each. For example, in the case of K, some of the middle drops among the pixels in one group divided into N1 pixels are changed to large drops. In the case of CMY, some of the pixels in one group divided into N1 pixels are changed without a drop. As shown in FIG. 22, the pixels to be changed without droplets in CMY are determined according to different rules for each CMY in consideration of dot dispersibility. As a result, it is possible to prevent the concentration of droplets in a part and a decrease in the density of a part.

  Here, FIG. 23 is a diagram schematically showing the droplet configuration changing process. With regard to the composite Bk composed of the four colors of KCMY, originally, the four colors of KCMY are overprinted as shown in FIG. On the other hand, the correction processing unit 203 of the present embodiment applies a mask pattern of FIG. 23B to the composite Bk as described above, thereby making some of the medium droplets of K large and a part of CMY. As shown in FIG. 23C, four colors of KCMY are overlaid and printed.

  In this way, by selecting and applying a mask pattern in consideration of the dot dispersion rate so as to be an appropriate CMY thinning amount and a large number of K medium droplets corresponding to the density classification of the image data, The ratio of chromatic ink can be reduced and the ratio of achromatic ink can be increased.

  More specifically, as shown in the flowchart of FIG. 21, the CPU 91 (correction processing unit 203) of the host 90 selects a mask pattern to be applied from the RGB values of the image data (RGB data) stored in the RAM 93 (step S521 to S525).

  In this embodiment, the correction processing unit 203 determines that R = G = B in the called RGB value when the gradation value in which R = G = B is greater than the threshold T in the called RGB value (Yes in step S521). When the gradation value that becomes = B is larger than the threshold value U (U <T) (Yes in step S522), the gradation value that becomes R = G = B in the called RGB value becomes the threshold value U (U <T). The mask pattern is selected and applied separately in the case where it is smaller (No in step S522).

  When the gradation value at which R = G = B is larger than the threshold value T (Yes in step S521), the correction processing unit 203 applies the mask pattern 1 (step S523). Further, when the gradation value at which R = G = B is larger than the threshold value U (U <T) (Yes in step S522), the correction processing unit 203 applies the mask pattern 2 (step S524). Further, when the gradation value at which R = G = B is smaller than the threshold value U (U <T) (No in step S522), the correction processing unit 203 applies the mask pattern 3 (step S525).

  Here, the difference between the mask patterns will be described with reference to an example shown in FIG. As shown in FIG. 24, in the present embodiment, when the K medium droplet is made large, the mask pattern of K having a different ratio of the target K medium droplet and the non-target K medium droplet, and no droplet are used. There are a plurality of mask patterns obtained by combining CMY mask patterns having different ratios of CMY to be added and CMY to which no drop is added.

  As described above, the density can be appropriately corrected by changing the ratio of enlarging K medium droplets and the thinning rate of CMY for each mask pattern. The mask pattern is an example and is not limited to FIG. As the number of types of such mask patterns increases, the correction accuracy for density correction improves.

  Returning to FIG. 21, the correction processing unit 203 sets a flag for making K medium droplets large (step S526).

  Here, FIG. 25 is a diagram for explaining the drive waveform change for making the appropriate amount of the medium droplet of K large. As shown in FIG. 25, the droplet volume of the discharge liquid is determined by the height V of the drive waveform. That is, as the height V of the drive waveform increases, the droplet volume increases. Therefore, as shown in FIG. 25B, when the density correction process is performed, the height V of the drive waveform is changed from V1 to V2. Thus, it is possible to make the droplet volume of K medium droplets large.

  The correction processing unit 203 repeats the above processing until the mask pattern is applied to all the pixels (No in step S527).

  When the correction processing unit 203 determines that the mask pattern has been applied to all the pixels (Yes in step S527), the droplet configuration change process ends.

  When the droplet composition change processing is completed as described above, the rendering processing by the CPU 91 (rendering processing unit 207) is executed (step S12).

  Then, the CPU 91 (total amount restriction processing unit 204) of the host 90 repeatedly executes the above-described processing for all the pixels. If the CPU 91 (total amount restriction processing unit 204) of the host 90 determines that the processing for all the pixels has been completed (Yes in step S13), it sends the processed data to the inkjet recording apparatus 1 as image data.

  As described above, according to this embodiment, it is possible to cope with a head having a low nozzle density, and it is possible to suppress density unevenness due to a difference in landing time without lowering the printing speed.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 90 Print control apparatus 201 Detection means 202 Acquisition means 203 Correction means

JP 2009-73092 A

Claims (7)

A chromatic ink is ejected by the chromatic recording head in the forward scan constituting one scanning area, and an achromatic ink is ejected by the achromatic recording head in the backward scanning constituting the one scanning area to form an image on the recording paper. In a print control apparatus for controlling an image forming apparatus
Detecting means for detecting overstrike for the same pixel of the achromatic color ink and the chromatic color ink in the input image data;
An acquisition means for acquiring a landing time difference between the chromatic color ink and the achromatic color ink at the same pixel on the recording paper;
Correction means for performing density correction processing according to the landing time difference so as to reduce the ratio of the chromatic color ink and increase the ratio of the achromatic color ink in the scanning region as compared with the normal processing;
A printing control apparatus comprising: The correction means is an LUT (Look Up Table) that is an allocation table for color space conversion from the RGB color system to the CMYK color system, and is a table corresponding to the landing time difference, and is within a scanning area compared to normal processing. And switching to a density correction processing LUT that decreases the ratio of the chromatic color ink and increases the ratio of the achromatic color ink.
The print control apparatus according to claim 1. The correction means generates a BG / UCR table, which is a table used in black plate generation processing for generating K data from CMY data and undercolor removal processing for deleting CMY data corresponding to K data, in accordance with the landing time difference. Switching to a density correction processing BG / UCR table that reduces the ratio of the chromatic color ink and increases the ratio of the achromatic color ink in the scanning region as compared with the normal processing.
The print control apparatus according to claim 1. The correction unit performs density correction processing when it is determined that the gradation value of the image data is equal to or greater than a predetermined threshold and the image density difference is large.
The printing control apparatus according to claim 1, wherein the printing control apparatus is a printing control apparatus. The correction unit performs density correction processing when it is determined that the density of pixels that are black in the image area obtained by dividing the image data is equal to or higher than a predetermined threshold and an image density difference occurs.
The printing control apparatus according to claim 1, wherein the printing control apparatus is a printing control apparatus. The correction unit determines the density of the image data divided for each predetermined threshold based on the RGB value, and the CMY thinning amount and the number of K medium droplets to be large droplets corresponding to the determined density classification Perform density correction processing to apply a mask pattern that defines
The printing control apparatus according to claim 1, wherein the printing control apparatus is a printing apparatus. A chromatic ink is ejected by the chromatic recording head in the forward scan constituting one scanning area, and an achromatic ink is ejected by the achromatic recording head in the backward scanning constituting the one scanning area to form an image on the recording paper. A computer that is a main body of a print control device that controls the image forming apparatus,
Detecting means for detecting overstrike for the same pixel of the achromatic color ink and the chromatic color ink in the input image data;
An acquisition means for acquiring a landing time difference between the chromatic color ink and the achromatic color ink at the same pixel on the recording paper;
Correction means for performing density correction processing according to the landing time difference so as to reduce the ratio of the chromatic color ink and increase the ratio of the achromatic color ink in the scanning region as compared with the normal processing;
Program to function as.