JPH11115222A - Method and apparatus for dot recording employing submode for reproducing gradation in plural types, and recording medium having program for executing process therefor recorded therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make reproduction of gradations possible for images while utilizing usable ink in various kinds by a method wherein dot density modulation that modifies dot recording density to be defined as the rate of pixels discharged in a fixed quantity of ink to the whole pixels in accordance with image signals is executed. SOLUTION: Discharge quantity modulation is executed for the third kind gradation reproducing submode for reproducing the gradation for images in the same color with a fixed quantity of ink ejected for dot density recording at 100% and ink in the same color of one kind out of ink in the same color in a plurality of kinds. On the other hand, ink in the same color of another kind is selected out of the fourth kind gradation reproducing submode for reproducing the gradation for images in the same color with a fixed quantity of ink ejected for dot density recording at 100%. By using gradation reproducing submode in a plurality of kinds including at least one of the third kind and the fourth kind gradation reproducing submodes, gradations for images in the same color are reproduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for recording dots on a dot recording medium such as a sheet of paper by discharging ink, thereby reproducing an image.

[0002]

2. Description of the Related Art In recent years, as an output device of a computer,
2. Description of the Related Art A color printer of a type that discharges a plurality of colors of ink from a head has become widespread, and is widely used for printing an image processed by a computer or the like in multiple colors and multiple gradations. In such a color printer, inks of four primary colors of CMYK can usually be used. Some types of color printers use cyan and magenta light inks in addition to these four types of inks to improve image quality.

As a method of reproducing the gradation of an image in a printer, there are known a method using dot recording density modulation and a method using ejection amount modulation of ink for forming dots. In the method using dot recording density modulation, the size of each dot is constant, and the density gradation of the image is reproduced by adjusting the ratio of the positions where dots are formed (referred to as “dot recording density”). On the other hand, in the method using the ink ejection amount modulation, the density gradation of the image is reproduced by adjusting the size of each dot. Many ordinary printers reproduce the density gradation for each ink by applying dot recording density modulation for each ink. Also, in a printer that modulates the ejection amount of ink, ejection amount modulation is applied to each ink.

[0004]

As described above, conventionally,
Since simply applying dot recording density modulation and ink ejection amount modulation for each ink, the various inks available in dot recording devices such as color printers are not fully utilized for gradation representation of images. Was.

The present invention has been made to solve the above-mentioned problems in the prior art, and has a technique capable of reproducing the gradation of an image while utilizing various inks that can be used by a dot recording apparatus. The purpose is to provide.

[0006]

In order to solve at least a part of the above-mentioned problems, a first dot recording method according to the present invention is directed to a method of recording dots in at least one primary color with substantially the same color. Forming dots on an image recording medium using a plurality of types of same-color inks different from each other, thereby recording an image in accordance with an image signal. By performing dot recording density modulation that uses the same color ink and adjusts the dot recording density defined as the ratio of pixels from which a fixed amount of ink is ejected to all pixels in accordance with the image signal, the image related to the same color is obtained. And a first type of tone reproduction sub-mode for reproducing the same tone and one type of the same color ink among the plurality of types of the same color inks at a dot recording density of 100%. While ejecting the ink in Tsu door position,
A second type of gradation reproduction sub-mode for reproducing the gradation of an image related to the same color by performing a discharge amount modulation for adjusting an ink discharge amount at each dot position according to the image signal; The dot recording density modulation is performed for one type of the same color ink, while 100% for the other type of the same color ink.
% Of the same color by discharging a fixed amount of ink at a dot recording density of 3%.
The tone reproduction sub-mode and the ejection amount modulation are performed for one kind of the same color ink among the plurality of kinds of the same color inks, while 100% dots are used for the other one kind of the same color ink. A fourth type of gradation reproduction sub-mode for reproducing the gradation of the image related to the same color by ejecting a fixed amount of ink at a recording density;
By using a plurality of types of tone reproduction submodes including at least one of the third and fourth types of tone reproduction submodes, the tone of the image relating to the same color is reproduced. I do.

In the third and fourth types of tone reproduction sub-modes, the tone of an image is reproduced by using a combination of a plurality of types of the same color ink. In the first dot recording method, a plurality of types of tone reproduction sub-modes including at least one of these are used. Can be reproduced.

In the first dot recording method, the plurality of types of same-color inks include a first same-color ink having a relatively low density and a second same-color ink having a relatively high density. The entire gradation range of the image signal is (i) the first
A first gradation reproduction sub-mode area using the first same color ink in the kind of gradation reproduction sub-mode; and (ii)
A second tone reproduction submode area using the first same color ink in the second type tone reproduction submode;
(Iii) a third tone reproduction mode area using the second same color ink in the second tone reproduction submode, and (iv) the third tone reproduction submode in the third tone reproduction submode. A fourth gradation reproduction sub-mode area for performing the dot recording density modulation on the first same color ink, and discharging a fixed amount of ink at a dot recording density of 100% on the second same color ink; (V) In the fourth type of tone reproduction sub-mode, the ejection amount modulation is performed on the first same color ink, while the second same color ink is a fixed amount at a dot recording density of 100%. A fifth gradation reproduction sub-mode area for discharging
It is preferable to be divided into

This makes it possible to reproduce the entire gradation range of the image signal while utilizing the first and second same color inks.

In the first dot recording method, when a plurality of types of the same color ink are superimposed on the same dot position in the third or fourth type of tone reproduction sub-mode, It is preferable that the same type of the same color ink is ejected during the same main scan.

In this case, the ink ejected before is ejected before the ink ejected before is dried, so that the dot shape and color reproducibility can be improved.

According to a second dot recording method of the present invention, for at least one primary color, dots are formed on an image recording medium by using a plurality of types of same-color inks of substantially the same color and different densities. A method of recording an image according to an image signal, wherein a plurality of types of the same color dots formed by combining the type and the discharge amount of the same color ink discharged at the same dot position are used, A step of reproducing the gradation of an image relating to color, wherein the plurality of types of same-color dots are formed by discharging at least two types of same-color inks at the same dot positions in at least one type of the same color. It is characterized by including dots.

Since at least one kind of same color dot is formed by using at least two kinds of same color inks,
It is possible to reproduce the gradation of an image while utilizing a plurality of types of the same color ink available in the dot recording apparatus.

In the second dot recording method, it is preferable that the plurality of types of same-color dots have recording densities at substantially equal intervals.

In this case, smoother gradation reproduction is possible.

In the second dot recording method, the plurality of types of the same color inks include a relatively low density light ink and a relatively high density dark ink, and the plurality of types of the same color dots are The same color dot of light ink formed of only ink, the same color dot of dark ink formed of only the dark ink, and the same color of mixed ink formed by ejecting the light ink and the dark ink in an overlapping manner And a dot.

By using such three types of dots of the same color, a wide gradation range can be smoothly reproduced.

Further, in the second dot recording method, the light color dots of the same color of the light ink have a relative value of recording density close to an integer in the range of 1 to n (n is an integer of 1 or more). And the same color dot of the dark ink has a relative value of the recording density of (n + 1) to (n +
m) includes m types of dots each having a value close to an integer (m is an integer of 1 or more) in the range of m), and the mixed ink same-color dot has a mixed value in which the relative value of the recording density is close to (n + m + 1). The same color ink dots may be included.

In this case, at least 1 to (n + m +
In the range of 1), dots having recording densities at substantially equal intervals can be used.

In the second dot recording method, the ratio of the density of the light ink to the density of the dark ink is substantially 1: (n + 1).
It is preferred that

In this case, nozzles having the same specifications can be used for the light ink and the dark ink.

A third dot recording method according to the present invention is a method of reproducing a gray image corresponding to a gray image signal by forming dots by discharging inks of four colors of cyan, magenta, yellow and black. (I) a first-type gradation reproduction sub-mode in which only black ink is ejected to a dot position to be recorded; and (ii) a cyan ink, a magenta ink, and a yellow ink at a dot position to be recorded. A dot position at which cyan ink is ejected while ejecting the selected one type of ink;
A second type of tone reproduction sub-mode that determines the dot positions at which each ink is ejected such that the dot positions at which the magenta ink is ejected and the dot positions at which the yellow ink is ejected have substantially the same distribution. And (iii) at the dot position to be recorded, two types of ink selected from cyan ink, magenta ink and yellow ink are ejected in a superposed manner, and the dot position at which cyan ink is ejected and the magenta ink are A third type of tone reproduction sub-mode for determining the dot position at which each ink is ejected such that the dot position at which the ink is ejected and the dot position at which the yellow ink is ejected have a distribution substantially equivalent to each other; iV) At the dot position to be recorded, three types of inks of cyan ink, magenta ink and yellow ink are ejected in a superposed manner. Four and tone reproduction submode,
(V) At the dot position to be recorded, one selected from cyan ink, magenta ink and yellow ink
Two inks, one ink and the other black ink, are ejected in a superposed manner, and a dot position where the cyan ink is ejected, a dot position where the magenta ink is ejected,
A fifth type of gradation reproduction sub-mode for determining a dot position at which each ink is ejected such that the dot positions at which the yellow ink is ejected have a distribution substantially equivalent to each other;
i) At a dot position to be printed, two types of inks selected from cyan ink, magenta ink, and yellow ink, and three types of ink, black ink, are discharged in an overlapping manner, and cyan ink is discharged. Dot position, dot position where magenta ink is ejected,
A sixth type of gradation reproduction sub-mode for determining the dot positions at which the respective inks are ejected so that the dot positions at which the yellow ink is ejected have a distribution substantially equivalent to each other;
ii) At the dot positions to be recorded, four of cyan ink, magenta ink, yellow ink, and black ink
Reproduces the grayscale of a gray image by using a seventh type of tone reproduction sub-mode in which different types of ink are ejected in a superposed manner, and a plurality of types of tone reproduction sub-modes selected from among them. And

In this way, all the four color inks can be used to reproduce the gray scale of the gray image.
Moreover, a wide gradation range can be reproduced.

In the third dot recording method, the entire gradation range of the gray image signal is divided into a plurality of gradation reproduction regions, and each gradation reproduction region reproduces a partially overlapping gradation range. Each of the two types of tone reproduction sub-modes is reproduced using two possible tone reproduction sub-modes, and in each tone reproduction region other than the tone reproduction region existing at the head of the entire gradation range. By performing dot recording density modulation, which adjusts the dot recording density defined as the ratio of pixels from which a fixed amount of ink is ejected to all pixels in accordance with the gray image signal, for the dots formed respectively, The gradation of the image may be reproduced.

This makes it possible to smoothly reproduce the entire gradation range of the gray image signal.

In the third dot recording method, in each of the second to sixth tone reproduction sub-modes, a dot position at which cyan ink is ejected, a dot position at which magenta ink is ejected, It is also possible to determine which ink is to be ejected at each dot position by using a mask in which the dot positions at which yellow ink is ejected have a distribution equivalent to each other and repeatedly applying the mask on the image plane. Good.

This makes it possible to easily determine the ejection position of each ink.

A first dot recording apparatus according to the present invention is a dot recording apparatus for recording dots on the surface of a recording medium using a dot recording head, and comprises a plurality of sets of nozzles for discharging a plurality of types of ink. A dot recording head including an array, main scanning driving means for performing main scanning by driving at least one of the dot recording head and the recording medium, and a plurality of nozzles included in the dot recording head during the main scanning A head driving unit for driving at least a part of the head to form dots, and a sub-scanning driving unit for driving at least one of the dot recording head and the recording medium to perform sub-scanning each time the main scanning is completed. And control means for controlling each of the means, wherein the dot recording head has substantially the same color and different density for at least one primary color. A plurality of sets of same-color nozzle arrays for ejecting several kinds of same-color inks are provided, and the control means uses one kind of the same-color ink among the plurality of kinds of the same-color inks, and a fixed amount of ink for all pixels is used. By performing dot recording density modulation that adjusts the dot recording density defined as the ratio of ejected pixels in accordance with the image signal, a first type of gradation reproduction sub that reproduces the gradation of the image related to the same color The mode and the amount of ink ejected at each dot position while discharging ink at each dot position at a dot recording density of 100% by using one type of the same color ink among the plurality of types of the same color inks. The second type of gradation reproduction sub-mode for reproducing the gradation of the image related to the same color by performing the ejection amount modulation adjusted according to The above-described dot recording density modulation is performed for one kind of the same color ink, and a constant amount of ink is discharged at a dot recording density of 100% for the other one kind of the same color ink, thereby controlling the same color. The third type of gradation reproduction sub-mode for reproducing the gradation of an image and the ejection amount modulation are performed for one kind of the same color ink among the plurality of kinds of the same color inks, while the other one kind of the same kind of ink is used. 10 for the same color ink
A fourth type of gradation reproduction sub-mode for reproducing a gradation of an image relating to the same color by discharging a fixed amount of ink at a dot recording density of 0%; By using a plurality of types of tone reproduction sub-modes including one of the first and fourth types of tone reproduction sub-modes, the tone of the image relating to the same color is reproduced.

In the first dot recording apparatus, similarly to the above-described first dot recording method, it is possible to reproduce the gradation of an image while utilizing a plurality of types of the same color ink available in the dot recording apparatus. it can.

A second dot recording apparatus according to the present invention is a dot recording apparatus for recording dots on the surface of a recording medium using a dot recording head, and comprises a plurality of sets of nozzles for discharging a plurality of types of ink. A dot recording head including an array, main scanning driving means for performing main scanning by driving at least one of the dot recording head and the recording medium, and a plurality of nozzles included in the dot recording head during the main scanning A head driving means for driving at least a part of the head to form dots, and a sub-scan driving means for driving at least one of the dot recording head and the recording medium to perform sub-scanning each time the main scanning is completed. And control means for controlling each of the means, wherein the dot recording head has substantially the same color and different density for at least one primary color. A plurality of same-color nozzle arrays for ejecting several kinds of same-color inks, wherein the control means is configured to combine a plurality of kinds of same-color inks to be ejected at the same dot position with a plurality of kinds of same-color inks to be formed; Means for reproducing the gradation of the image relating to the same color using color dots, wherein the plurality of types of same color dots are
It is characterized by including at least one kind of same color dot created by discharging at least two kinds of same color ink at the same dot position.

Also in this second dot recording apparatus, similar to the above-described second dot recording method, it is possible to reproduce the gradation of an image while utilizing a plurality of types of the same color ink available in the dot recording apparatus. Can be.

A third dot recording apparatus according to the present invention is a dot recording apparatus for recording dots on the surface of a recording medium by using a dot recording head, and uses four color inks of cyan, magenta, yellow and black. A dot recording head including four sets of nozzle arrays for discharging, main scanning driving means for driving at least one of the dot recording head and the recording medium to perform main scanning, and the dot recording head during the main scanning A head driving unit for driving at least a part of the plurality of nozzles included in the nozzle to form dots, and driving the at least one of the dot recording head and the recording medium each time the main scanning is completed to perform sub-scanning. A sub-scanning driving unit for performing the above-mentioned operations, and a control unit for controlling each of the above-mentioned units. And (ii) ejecting one type of ink selected from cyan ink, magenta ink and yellow ink at a dot position to be recorded, and discharging cyan ink at a dot position to be recorded. A second dot position where each ink is ejected is determined such that the dot position where the ink is ejected, the dot position where the magenta ink is ejected, and the dot position where the yellow ink is ejected have a distribution substantially equivalent to each other. And two types of ink selected from cyan ink, magenta ink and yellow ink are ejected in a superposed manner at the dot position to be recorded and (iii) cyan ink is ejected at the dot position to be recorded. The dot position, the dot position at which magenta ink is ejected, and the dot position at which yellow ink is ejected are mutually different. A third type of gradation reproduction sub-mode for determining the dot positions at which each ink is ejected so as to have a substantially equivalent distribution, and (iv) the dot positions of cyan ink, magenta ink, and yellow ink at the dot positions to be recorded. Fourth, in which three types of ink are ejected in an overlapping manner
Two types of inks, one of cyan ink, magenta ink, and yellow ink, and the other black ink are ejected at the dot position to be recorded (V) at the dot position to be recorded, and two kinds of inks, namely, black ink. In addition, the dot positions at which the cyan ink is discharged, the dot positions at which the magenta ink is discharged, and the dot positions at which the yellow ink is discharged have a distribution substantially equivalent to each other. A fifth type of gradation reproduction sub-mode for determining the position; and (Vi) two types of ink selected from cyan ink, magenta ink and yellow ink, and black ink at the dot position to be recorded. In addition to ejecting different types of ink,
The dot positions at which the respective inks are ejected are determined so that the dot positions at which the cyan ink is ejected, the dot positions at which the magenta ink is ejected, and the dot positions at which the yellow ink is ejected have substantially equivalent distributions. A sixth type of gradation reproduction sub-mode, and (Vii) a seventh type of gradation reproduction in which four types of inks of cyan, magenta, yellow, and black are ejected at the dot position to be recorded. By using a sub-mode and a plurality of types of gradation reproduction sub-modes selected from among the sub-modes, the gradation of a gray image is reproduced.

According to the third dot recording apparatus, similarly to the above-described third dot recording method, all the four color inks can be used to reproduce the gray scale of the gray image. A wide gradation range can be reproduced.

A first recording medium according to the present invention is a dot recording head having a plurality of sets of nozzle arrays for ejecting a plurality of types of same-color inks of substantially the same color and different densities for at least one primary color. A computer-readable recording medium, which is used in a dot recording apparatus including a computer and records a computer program for recording dots on the surface of a dot recording medium using the dot recording head, wherein the computer The program uses one type of the same color ink among the plurality of types of the same color inks, and sets a dot recording density defined as a ratio of pixels from which a fixed amount of ink is ejected to all pixels according to the image signal. By performing dot recording density modulation for adjustment, a first type of gradation for reproducing the gradation of an image related to the same color Using a reproduction submode, one type of the same color inks in said plurality of types of the same color ink, 10
By performing ejection amount modulation for adjusting the ink ejection amount at each dot position according to the image signal while ejecting ink at each dot position at a dot recording density of 0%, the gradation of the image related to the same color can be adjusted. A second type of tone reproduction sub-mode to be reproduced and one of the plurality of types of same color inks
For the same type of same color ink, the dot recording density modulation is performed, while for the other type of same color ink, 1 dot is applied.
A third type of gradation reproduction sub-mode for reproducing the gradation of an image related to the same color by discharging a fixed amount of ink at a dot recording density of 00%, and one of the plurality of types of same-color inks The ejection amount modulation is performed for the same type of the same color ink, while the other type of the same color ink is ejected with a constant amount of ink at a dot recording density of 100%. And a plurality of types of tone reproduction sub-modes selected from a fourth type of tone reproduction sub-mode for reproducing tones and including at least one of the third and fourth types of tone reproduction sub-modes , The function of reproducing the gradation of the image relating to the same color is provided.

A second recording medium according to the present invention includes a dot recording head having a plurality of sets of nozzle arrays for discharging a plurality of types of same-color inks of substantially the same color and different densities for at least one primary color. A computer-readable recording medium that is used in a dot recording apparatus including a computer and that records a computer program for recording dots on the surface of a dot recording medium using the dot recording head. The program has a function of reproducing the gradation of an image related to the same color by using a plurality of types of same color dots formed by combining the type and the discharge amount of the same color ink discharged at the same dot position. The plurality of types of same-color dots include at least two types of same-color inks at the same dot position. Characterized in that it comprises at least one of the same color dots are created by discharging Te.

A third recording medium according to the present invention includes a dot recording head including four sets of nozzle arrays for ejecting four color inks of cyan, magenta, yellow, and black;
A computer-readable recording medium that is used in a dot recording apparatus including a computer and records a computer program for recording dots on the surface of a dot recording medium using the dot recording head. Is selected from (i) a first-type gradation reproduction sub-mode in which only black ink is ejected to a dot position to be recorded, and (ii) a selection from cyan ink, magenta ink, and yellow ink at the dot position to be recorded. While discharging one type of ink,
The dot positions at which the respective inks are ejected are determined so that the dot positions at which the cyan ink is ejected, the dot positions at which the magenta ink is ejected, and the dot positions at which the yellow ink is ejected have substantially equivalent distributions. And (iii) in a dot position to be recorded, two types of ink selected from cyan ink, magenta ink and yellow ink are ejected in a superposed manner, and the cyan ink is Thirdly, the dot positions at which the respective inks are ejected are determined so that the dot positions at which the magenta ink is ejected, the dot positions at which the magenta ink is ejected, and the dot positions at which the yellow ink is ejected have substantially equivalent distributions. And (iv) cyan ink, magenta ink, and yellow at the dot position to be recorded. And (V) one ink selected from cyan ink, magenta ink and yellow ink at the dot position to be recorded. The two types of ink, black and black, are ejected in a superposed manner, and the dot positions at which the cyan ink is ejected, the dot positions at which the magenta ink is ejected, and the dot positions at which the yellow ink is ejected are substantially equivalent to each other. A fifth type of gradation reproduction sub-mode for determining the dot position at which each ink is ejected so as to have a distribution, and (Vi) selecting from cyan ink, magenta ink and yellow ink at the dot position to be recorded The three types of ink, black ink and two types of ink, are ejected in a superposed manner, and the cyan ink is ejected. A sixth type of floor that determines the dot position at which each ink is ejected so that the dot position, the dot position at which the magenta ink is ejected, and the dot position at which the yellow ink is ejected have substantially equivalent distributions to each other. A tone reproduction sub-mode and (Vii) a seventh type gradation reproduction sub-mode in which four inks of cyan ink, magenta ink, yellow ink, and black ink are ejected in a dot position to be recorded in a superposed manner. And a function of reproducing the gray scale of a gray image by using a plurality of types of gray scale reproduction sub-modes selected from.

The above-mentioned first medium is also used by these recording media.
As in the third to third dot recording methods and the first to third dot recording apparatuses, it is possible to reproduce the gradation of an image while utilizing a plurality of types of inks that can be used by the dot recording apparatus.

As a recording medium, a flexible disk, CD-ROM, magneto-optical disk, IC card,
Various computer-readable media such as a ROM cartridge, a punched card, a printed matter on which a code such as a barcode is printed, an internal storage device (memory such as RAM and ROM) and an external storage device of the computer can be used.

[0039]

Other Embodiments of the Invention The present invention includes the following other embodiments. A first aspect is an aspect as a program supply device that supplies a computer program for realizing the functions of each step or each means of the above-described invention to a computer via a communication path. In such an embodiment, the above-described method and apparatus can be realized by placing the program on a server or the like on a network, downloading the necessary program to a computer via a communication path, and executing the program.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION

A. Device configuration: An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a printing apparatus as one embodiment of the present invention. As shown, the scanner 12 and the color printer 22 are connected to the computer 90, and a predetermined program is loaded and executed on the computer 90, so that the computer 90 functions as a printing apparatus as a whole. The hardware as the printing device is a normal computer 90. As shown
The computer 90 includes the following units interconnected by a bus 80, centering on a CPU 81 that executes various arithmetic processes for controlling operations related to image processing according to a program. The ROM 82 previously stores programs and data necessary for the CPU 81 to execute various arithmetic processes, and the RAM 83 temporarily reads and writes various programs and data necessary for the CPU 81 to execute various arithmetic processes. Memory. The input interface 84 controls input of signals from the scanner 12 and the keyboard 14, and the output interface 85 controls output of data to the printer 22. The CRTC 86 controls signal output to the CRT 21 capable of color display, and the disk controller (DDC) 87
Or a flexible drive 15 or a CD-not shown
Controls data transfer to and from the ROM drive. The hard disk 16 stores various programs loaded and executed in the RAM 83 and various programs provided in the form of device drivers. other than this,
The bus 80 has a serial input / output interface (SI
O) 88 is connected. The SIO 88 is connected to the modem 18, and is connected to the public telephone line PNT via the modem 48. The computer 90 is connected to an external network via the SIO 88 and the modem 18. By connecting to a specific server SV, it is also possible to download a program required for image processing to the hard disk 76. Necessary programs are stored on a flexible disk FD or C
It is also possible to load the data from the D-ROM and make the computer 90 execute the data.

FIG. 2 is a block diagram showing the configuration of software related to print processing. In the computer 90, an application program 95 operates under a predetermined operating system. A video driver 91 and a printer driver 96 are incorporated in the operating system, and the final color image data FNL is output from the application program 95 via these drivers. An application program 95 for performing image retouching and the like includes:
The image is read from the scanner, and the image is displayed on the CRT display 93 via the video driver 91 while performing predetermined processing on the image. When the application program 95 issues a print command, the printer driver 96 of the computer 90 receives the image information from the application program 95, and receives the image information from the application program 95 as a signal that can be printed by the printer 22 (here, a binary signal for each ink color). Signal). In the example shown in FIG. 2, a rasterizer 97 that converts color image data handled by the application program 95 into image data in dot units is provided inside the printer driver 96.
A color correction module 98 that performs color correction on the image data in units of dots in accordance with the characteristics of the ink colors and the colors used by the printer 22; a color correction table CT that the color correction module 98 refers to; And a halftone module 99 that generates so-called halftone image information from the image information. The functions of the color correction module 98 and the halftone module 99 will be further described later.

FIG. 3 is a schematic configuration diagram of the printer 22. As shown in the figure, the printer 22 includes a mechanism for transporting a sheet P by a paper feed motor 23, a mechanism for reciprocating a carriage 31 in the axial direction of a platen 26 by a carriage motor 24, and a print head mounted on the carriage 31. And a control circuit 40 for exchanging signals with the paper feed motor 23, the carriage motor 24, the print head assembly 60 and the operation panel 32. Have been.

The carriage 31 of the printer 22 includes
A black ink cartridge 71 and a color ink cartridge 72 can be mounted. At the bottom of the carriage 31, an introduction pipe 65 (see FIG. 4) for guiding ink from the ink tank to each ink head of the print head assembly 60 is provided upright. When the black ink cartridge 71 and the color ink cartridge 72 are mounted on the carriage 31 from above, an introduction tube is inserted into a connection hole provided in each cartridge, and ink is supplied from each ink cartridge to the print head assembly 60. Becomes possible.

The mechanism for ejecting ink will be briefly described. Ink cartridges 71 and 72 are carriage 31
The ink in the ink cartridge is sucked out through the introduction tube 65 by utilizing the capillary phenomenon, and is guided to the nozzles of each color of the print head assembly 60 provided below the carriage 31. When the ink cartridge is first mounted, the operation of sucking the ink into the print head assembly 60 is performed by a dedicated pump. In this embodiment, a pump for suction and covering the print head assembly 60 at the time of suction are provided. Illustration and description of the configuration of the cap and the like are omitted.

As shown in FIG. 4, the print head assembly 60 is provided with a plurality of nozzles n for each color. Each nozzle is one of the electrostrictive elements and has excellent responsiveness. A piezo element PE is arranged. FIG. 5 shows the structure of the piezo element PE and the nozzle n in detail. As shown in the drawing, the piezo element PE is provided at a position in contact with an ink passage 66 for guiding ink to the nozzle n. As is well known, the piezo element PE is an element that distorts the crystal structure due to the application of a voltage and converts electro-mechanical energy very quickly. In the present embodiment, by applying a voltage having a predetermined time width between the electrodes provided at both ends of the piezo element PE, the piezo element PE expands by the voltage application time as shown in the lower part of FIG. One side wall 66 is deformed. As a result, the volume of the ink passage 66 contracts in accordance with the expansion of the piezo element PE, and the ink corresponding to this contraction becomes particles Ip and is discharged from the tip of the nozzle n at a high speed. When the ink particles Ip soak into the paper P mounted on the platen 26, printing is performed.

In the printer 22 having the above-described hardware configuration, the carriage 31 is reciprocated by the carriage motor 24 while the paper P is conveyed by rotating the platen 26 and other rollers by the paper feed motor 23, and at the same time, the print head The piezo element PE of each ink nozzle of the assembly 60 is driven to eject each color ink, and a multicolor image is formed on the paper P. The specific arrangement of each ink nozzle will be further described later.

The mechanism for transporting the paper P is a paper feed motor 2
A gear train (not shown) for transmitting the rotation of No. 3 not only to the platen 26 but also to a paper transport roller (not shown) is provided. The mechanism for reciprocating the carriage 31 includes an endless drive belt 36 extending between the carriage motor 24 and a slide shaft 34 that is erected in parallel with the axis of the platen 26 and slidably holds the carriage 31. Pulley 38,
Position detection sensor 3 for detecting the origin position of carriage 31
9 and so on.

The control circuit 40 (FIG. 3) includes a programmable ROM (PROM) 42 as a rewritable nonvolatile memory in addition to a CPU and a main memory (ROM and RAM) not shown. PRO
M42 stores tone reproduction mode information including a plurality of tone reproduction mode parameters. Here, the “gradation reproduction mode” refers to the type of ink used to reproduce image densities of a plurality of colors and the method of forming dots (how to combine dot recording density modulation and ink ejection amount modulation). ) Means the reproduction method of the gradation defined by Various examples of the tone reproduction mode will be described later in detail. The PROM 42 further stores gradation reproduction mode designation information for designating a preferred mode from a plurality of gradation reproduction modes. For example, PROM
When four types of tone reproduction mode information can be stored in the register 42, the tone reproduction mode designation information is composed of 2-bit data.

The tone reproduction mode information is stored in the computer 90.
When the printer driver 96 (FIG. 2) is installed at the time of startup, the PROM is
42. That is, the printer driver 9
6 is a PROM which stores the tone reproduction mode information for the preferred tone reproduction mode designated by the tone reproduction mode designation information.
Read from 42. The processing in each module of the printer driver 96 (FIG. 2) and the main scanning and sub-scanning operations are executed according to the gradation reproduction mode information.

The PROM 42 may be a rewritable nonvolatile memory, and various nonvolatile memories such as an EEPROM and a flash memory can be used. Further, the tone reproduction mode designation information is preferably stored in a rewritable nonvolatile memory, but the tone reproduction mode information may be stored in a non-rewritable ROM. Also, a plurality of tone reproduction mode information is
The information may be stored in another storage means instead of the PROM 42, or may be registered in the printer driver 96.

B. First Embodiment: FIG. 6 is a diagram showing a configuration of a print head assembly used in a first embodiment of the present invention. The print head assembly 60 includes two print heads 61,
62. Two print heads 61 and 62
Are mutually fixed by fixing means such as screws.
It is assembled as one print head assembly 60.

[0052] The first print head 61, and the dark black ink nozzle group K _D, and light black ink nozzle group K _L is formed. On the other hand, the second print head 62 includes
A dark cyan ink nozzle group C _D, light cyan ink nozzle group C _L, and dark magenta ink nozzle group M _D, light magenta ink nozzle group M _L, dark yellow ink nozzle group Y
And _D, a light and a yellow ink nozzle group Y _L are formed. Each nozzle group of one ink includes 128 nozzles # 1 to # 128.

In this specification, the four primary colors (black, cyan, magenta, and yellow) of the printing ink are referred to as primary colors. The dark ink and the light ink mean relatively high-density ink and relatively low-density ink having substantially the same color. Strictly speaking, the dark ink and the light ink not only have different densities, but also have slightly different hues and saturations. However, in this specification, strictly speaking, two types of inks having different densities that are recognized as having substantially the same color even though the hue and saturation are slightly different are referred to as “dark inks”.
And "light ink".

The 128 nozzles of each ink group are aligned in a straight line along the sub-scanning direction SS. Eight nozzles assigned the same nozzle number in each nozzle group are arranged so as to be aligned on a straight line along the main scanning direction MS. As described above, the eight nozzles that eject different inks are aligned on a straight line along the main scanning direction MS mainly because the dots of different colors are shifted in the sub-scanning direction. This is for preventing the deterioration of the image quality that occurs. As described later, the two nozzles (e.g. nozzle K _D, K _L) of the eight nozzles arranged in a straight line along the main scanning direction MS from the ink at the same location during the same main scan By discharging the inks so as to overlap each other, dots formed by a plurality of types of ink can be formed.

FIG. 7 is a graph showing the division of the tone reproduction area in the first embodiment. The horizontal axis of the graph in FIG. 7 is the image signal level, and the vertical axis is the recording density (also referred to as “image density” or “density gradation”) for one primary color of cyan, magenta, yellow, and black. is there. Note that the graph shown in FIG. 7 is applied to each of the four primary colors of cyan, magenta, yellow, and black. The entire range of the image signal level is divided into the following five areas.

(1) Light ink recording density modulation area R1: an area where dot recording density modulation using only light ink is performed.

(2) Light ink ejection amount modulation region R2: A region where ink ejection amount modulation using only light ink is performed.

(3) Dark ink ejection amount modulation area R3: An area where ink ejection amount modulation using only dark ink is performed.

(4) Constant dark ink + light ink recording density modulation area R4: Dark ink discharges a fixed amount of ink at a recording density of 100%, while light ink performs dot recording density modulation.

(5) Constant dark ink + light ink discharge amount modulation area R5: A dark ink discharges a fixed amount of ink at a recording density of 100%, while a light ink modulates the ink discharge amount.

Here, "dot recording density modulation" is a method of reproducing the density of an image by maintaining the size of each dot (that is, the ink ejection amount) and adjusting the ratio of the positions where dots are formed. It is. The “ratio of the positions where dots are formed”, that is, “the ratio of the pixels that eject a fixed amount of ink to all the pixels in a certain area” is called “dot recording density”. “Ink ejection amount modulation” is a method of ejecting ink at a recording density of 100% (that is, at all dot positions), and reproducing the image density by adjusting the ink ejection amount.

The five tone reproduction areas R1 to R5 are:
Since tone reproduction methods are different from each other, these are different types of tone reproduction sub-modes. In this specification, the entire method of reproducing the gradation in the entire gradation range of the image signal is referred to as one gradation reproduction mode. The reproduction method is called a gradation reproduction sub-mode. As will be understood from other embodiments described later, the ranges of the plurality of gradation reproduction sub-modes may be set so as to partially overlap each other.

FIG. 8 shows the five gradation reproduction regions R1 to R1 of FIG.
It is a graph which shows the discharge amount of light ink and dark ink in each of R5. FIG. 9 shows each gradation reproduction region R1.
It is a graph which shows the diameter of the dot formed in -R5. In the light ink recording density modulation region R1 of FIG. 8, the discharge amount of the light ink at the dot position to be printed is constant at 5 ng, and the position where the dot is formed is selected according to the image signal value. As shown in the first tone reproduction area R1 in FIG. 9, dots having a diameter of 40 μm are formed by discharging 5 ng of light ink. The ink ejection amount and the dot diameter have the relationship shown in FIG. 5ng
The dot of 40 μm in diameter is formed by the ejection of the ink of 80 μm, and the dot of 80 μm by the ejection of the ink of 20 μm.
m dots are formed. In the first embodiment, each of the nozzles shown in FIG. 6 can adjust the ink ejection amount almost continuously in the range of 5 ng to 20 ng. The adjustment of the ink amount is realized by adjusting the waveform of the drive signal supplied to the piezo element of each nozzle. FIG.
Are applied to the eight types of inks shown in FIG.

In the light ink ejection amount modulation region R2 in FIG.
Light ink is ejected at the same ejection amount at all dot positions, and the ejection amount is adjusted so as to increase as the image signal value increases in the range of 5 ng to 20 ng. As a result, as shown in FIG. 9, in the second tone reproduction area R2, the diameter of the dot formed by the light ink is 40
It increases linearly from μm to 80 μm. Note that the relationship between the dot diameter and the recording density is substantially linear as shown in FIG. As described above, in the second tone reproduction area of FIG. 9, the dot diameter increases linearly with the increase of the image signal value, and therefore, as shown in FIG. It increases linearly as the signal value increases.

In the dark ink ejection amount modulation area R3 of FIG.
The dark ink is ejected at the same ejection amount at all dot positions, and the ejection amount is adjusted so as to increase as the image signal value increases in the range of 5 ng to 20 ng. As a result, as shown in FIG. 9, in the third tone reproduction area R3, the diameter of the dot formed by the dark ink is 40 μm.
It increases linearly from m to 80 μm.

In the constant dark ink + light ink recording density modulation area R4 in FIG. 8, dark ink is applied to all dot positions.
ng, and the light ink is ejected at a fixed ejection amount of 5 ng at a dot position selected according to the image signal value. As a result, as shown in FIG. 9, in the fourth gradation reproduction region R4, a dot having a diameter of 80 μm formed only with the dark ink and a dot having a diameter of 90 μm formed with the dark ink and the light ink.
μm mixed ink dots are recorded. Here, the diameter of the mixed ink dot becomes 90 μm because the total ejection amount becomes 25 ng (see FIG. 10).

In the constant dark ink + light ink discharge amount modulation area R5 in FIG. 8, the dark ink is 20 n at all dot positions.
g. On the other hand, the light ink is also discharged at the same discharge amount at all dot positions, and the discharge amount is adjusted so as to increase as the image signal value increases in the range of 5 ng to 20 ng. As a result, as shown in FIG.
In the tone reproduction region R5, a mixed ink dot having a diameter of 90 to 120 μm formed by dark ink and light ink is recorded.

FIGS. 12 (a-1), (a-2), (a-
3) to (e-1), (e-2), and (e-3) are explanatory diagrams showing various dots formed in each of the five tone reproduction regions R1 to R5 in FIG. In each of these figures, a square frame indicates dot positions (pixel positions) separated by one dot pitch. Circles indicate dots formed by ink ejection. A circle including many points is a dot including light ink, and a hatched circle is a dot including dark ink. The circle containing both the oblique lines and the multiple points are mixed ink dots.

FIGS. 12 (a-1) to 12 (a-3) show dots formed in the image portion of the light ink recording density modulation area R1. As shown in FIG.
No dot is formed in the image portion where the image signal value is S0 (= 0). As shown in FIG.
In an image portion having an intermediate image signal value in the tone reproduction region R1, light ink dots having a diameter of 40 μm are formed at several dot positions selected according to the image signal value. Further, as shown in FIG. 12A-3, in the image portion where the image signal value is S1, light ink dots having a diameter of 40 μm are formed at all dot positions.

FIGS. 12 (b-1) to 12 (b-3) show dots formed in the image portion of the light ink ejection amount modulation area R2. FIG. 12 (b-1) corresponds to FIG.
It is the same figure as 3), and has shown the image part whose image signal value is S1. As shown in FIG. 12 (b-2), in an image portion having an intermediate image signal value in the gradation reproduction region R2, light ink dots are formed at all dot positions, but light ink ejection is performed. Since the amount is adjusted according to the image signal value, the diameter of all dots is changed. Also,
As shown in FIG. 12B-3, in the image portion where the image signal value is S2, light ink dots having a diameter of 80 μm are formed at all dot positions.

FIGS. 12 (c-1) to 12 (c-3) show dots formed in the image portion of the dark ink ejection amount modulation area R3. FIG. 12 (c-1) corresponds to FIG.
Similarly to 3), the image portion whose image signal value is S2 is shown. In this image signal value S2, as shown in FIG. 12B-3, 20 ng of light ink may be ejected to form a light ink dot having a diameter of 80 μm, or as shown in FIG.
Even if 5 ng of dark ink is ejected as in 1), the diameter is 40 μm.
May be formed. FIG. 12 (c-2)
As shown in the figure, in the image portion having an intermediate image signal value in the gradation reproduction region R3, dark ink dots are formed at all dot positions, but the ejection amount of the dark ink depends on the image signal value. So that the diameter of all dots is changed. Also, as shown in FIG.
In the image portion where the image signal value is S3, 80 μm diameter dark ink dots are formed at all dot positions.

FIGS. 12 (d-1) to 12 (d-3) show dots formed in the image portion of the constant dark ink + light ink recording density modulation area R4. FIG. 12 (d-1)
Is the same as FIG. 12 (c-3), and the image signal value is S3
Is shown. As shown in FIG. 12D-2, in an image portion having an intermediate image signal value in the gradation reproduction region R4, a fixed amount (20 ng) of dark ink is ejected to all dot positions. Further, a fixed amount (5 ng) of light ink is ejected to the dot position selected according to the image signal value. In the example of FIG.
Relatively small dots (80 μm) are formed by ejecting only dark ink at four dot positions among the four dot positions, and dark ink and light ink are ejected at the other five dot positions. Relatively large mixed ink dots (9
0 μm). As shown in FIG. 12D-3, in the image portion where the image signal value is S4, 20 ng dark ink and 5 ng light ink are ejected to all dot positions, and as a result, all dot positions are ejected. Diameter 90
A mixed ink dot of μm is formed.

FIGS. 12 (e-1) to 12 (e-3) show dots formed in the image portion of the constant dark ink + light ink discharge amount modulation area R3. FIG. 12 (e-1) is the same as FIG. 12 (d-3), and shows an image portion whose image signal value is S4. As shown in FIG. 12E-2, in an image portion having an intermediate image signal value in the gradation reproduction region R5, dark ink and light ink are ejected at all dot positions. The ink ejection amount is 20n
While g is constant, the ejection amount of light ink is adjusted according to the image signal value. As shown in FIG. 12E-3, in the image portion where the image signal value is S5 (100%), mixed ink dots having a diameter of 120 μm are formed at all dot positions.

As can be understood from FIG. 6 described above, at the time of main scanning, eight nozzles for ejecting eight different inks sequentially pass on the same raster (main scanning line) on the printing paper. . That is, the same pixel position on the same raster, through a nozzle of the first light yellow ink nozzle group Y _L, then the nozzle of the dark yellow ink nozzle group Y _D, light nozzle of the magenta ink nozzle group M _L, conc. going through the nozzle ... order of the magenta ink nozzle group M _D. When ejecting dark ink and light ink of the same color to the same dot position, dark ink and light ink are ejected so as to overlap the same dot position during the same main scan. For example, when forming a yellow dot having a diameter of 120 μm using a light yellow ink and a dark yellow ink,
First pale 20n from the nozzle of the yellow ink nozzle group Y _L
ejecting pale yellow inks g, then the diameter by ejecting from a nozzle of dark yellow ink nozzle group Y _D conc yellow ink 20ng to the same dot position 120
A yellow dot of μm is formed.

A mixed ink dot formed by ejecting light ink and dark ink of the same color at the same position has an intermediate density between the light ink dot and the dark ink dot. Such a difference in dot density affects image processing (specifically, processing in the color correction module 98 and the halftone module 99 in FIG. 2). Therefore, when light ink and dark ink of the same color are ejected at the same position, the contents of these image processings are changed according to the color of the dots to be formed.

It is preferable that the light ink and the dark ink are ejected in the same order as in the first embodiment. The reason for this is that when the light ink is ejected later, the light ink spreads around the dark ink, so that the density change between the periphery and the center of the dot tends to be larger than when the dark ink is ejected first. It is.

In the above-described first embodiment, since the five gradation reproduction areas R1 to R5 are combined, the entire gradation range of the image signal is more smoothly compared to the case where only one type of ink is used. Can be reproduced. In particular, a relatively low gradation range (regions R1 and R2 in FIG. 8) and a relatively high gradation range (region R in FIG.
4 and R5) can be smoothly reproduced.

Although not used in FIG. 7, it is possible to use the recording density modulation of dark ink. In addition, constant light ink + dark ink recording density modulation area (area R
4 with the roles of dark ink and light ink swapped),
It is also possible to use a constant light ink + dark ink discharge amount modulation area (the role of the dark ink and light ink in the area R5 is switched). That is, generally, a plurality of tone reproduction areas selected from the following four types of tone reproduction areas (also referred to as “tone reproduction sub-modes”) (that is, a plurality of tone reproduction sub-modes) are selected. ) By combining them, the gradation of the image can be reproduced.

(1) First-type tone reproduction area: a sub-mode in which dot recording density modulation is performed for dark ink or light ink. (Region R1 in FIG. 8)

(2) Second type tone reproduction area: a sub-mode in which ejection amount modulation is performed for dark ink or light ink.
(Regions R2 and R3 in FIG. 8)

(3) Third-type tone reproduction area: For one of the dark ink and the light ink of the same color, a fixed amount of ink is ejected at a dot recording density of 100%.
A sub-mode in which dot recording density modulation is performed for the other ink. (Region R4 in FIG. 8)

(4) Fourth-type tone reproduction area: one of dark ink and light ink of the same color uses a certain amount of ink at 100%
Is a sub mode in which ejection is performed at a dot recording density of, and the other ink performs ejection amount modulation. (Region R5 in FIG. 8)

As the combination of the first to fourth types of tone reproduction regions for reproducing the entire tone of the image, various modes other than the first embodiment can be considered. At this time, if at least the third or fourth type of tone reproduction area is included, it is possible to use dark ink and light ink for tone reproduction successfully.

C. Second Embodiment: In the above-described first embodiment, it has been assumed that each nozzle can adjust the ink ejection amount almost continuously within a predetermined range. Is often difficult to adjust. Therefore, in the second embodiment described below, when each nozzle can discharge ink with a limited amount of discharge, the entire tone range is designed to be smoothly reproduced. The configuration of the hard wafer of the second embodiment is the same as that of the above-described first embodiment except for the ejection capability of the nozzles.

FIG. 13 is an explanatory diagram showing the relationship between the image signal level and the configuration of the dots to be recorded in the second embodiment. The horizontal axis in FIG. 13 is the relative value of the image signal level,
The vertical axis indicates the relative value of the recording density level. In the second embodiment, eight types of dots 101 to 108 corresponding to the recording density levels 1 to 8, respectively, are formed corresponding to the image signal levels 1 to 8, respectively. The eight types of dots 101 to 108 are respectively configured as follows.

(1) First dot 101: light ink 5n
g (40 μm diameter). (2) Second dot 102: 20 ng of light ink (diameter 8
0 μm). (3) Third dot 103: dark ink 5 ng (diameter 40)
μm). (4) Fourth dot 104: dark ink 8 ng (diameter 53)
μm). (5) Fifth dot 105: dark ink 13 ng (diameter 6
6 μm). (6) Sixth dot 106: dark ink 20 ng (diameter 8
0 μm). (7) Seventh dot 107: dark ink 20 ng + light ink 5 ng (diameter 90 μm). (8) Eighth dot 108: dark ink 20 ng + light ink 20 ng (diameter 120 μm).

FIG. 14 is a graph showing the relationship between the ink ejection amount and the dot diameter in the second embodiment. In the second embodiment, the light ink nozzle only needs to be capable of discharging light ink with two types of discharge amounts, 5 ng and 20 ng.
The dark ink nozzles are 5 ng, 8 ng, 13 ng,
It is only necessary to have a capability of discharging light ink with four types of discharge amounts of 20 ng. By using such a nozzle, as shown in FIG.
Kinds of light ink dots 101 and 102 and four kinds of dark ink dots 103 to 106 formed only by dark ink.
And two types of mixed ink dots 10 formed by discharging dark ink and light ink at the same dot position.
7, 108 can be formed respectively. In the second embodiment, since it is not necessary to adjust the ink ejection amount almost continuously, there is an advantage that the configuration for driving the nozzles can be realized more easily than in the first embodiment. In particular, in the second embodiment, since the two types of discharge amounts of the light ink are equal to two of the four types of discharge amounts of the dark ink, it is necessary to use the same nozzles for the dark ink and the light ink. Can be.

As shown in FIG. 13, light ink dots 101 of the minimum size formed by 5 ng of light ink
Is between 1: 3 and the recording density level of the dark ink dot 103 of the minimum size formed with 5 ng of deep ink. Similarly, the ratio between the recording density level of the maximum size light ink dot 102 formed with 20 ng light ink and the recording density level of the maximum size dark ink dot 106 formed with 20 ng dark ink is also 1: 3. is there. In other words, the ratio of the density of the light ink to the density of the dark ink is 1: 3, and the ratio of the recording density level for the same dot diameter is also 1: 3. Further, the ratio between the recording density level of the light ink dot 101 having the minimum size and the recording density level of the light ink dot 102 having the maximum size is 1: 2.
Therefore, the recording density level of the maximum size light ink dot 102 is a value exactly intermediate between the recording density level of the minimum size light ink dot 101 and the recording density level of the minimum size dark ink dot 103. As a result, it is possible to form a plurality of types of dots 101 to 108 having equally spaced recording density levels (relative values).

In general, when the ratio of the recording density level between the minimum size light ink dot and the maximum size light ink dot is 1: n, the density ratio between the light ink and the dark ink is set to 1: (n + 1). It is preferable to set. Where n
Is an integer of 1 or more. Also, the nozzle for light ink is 1
It is preferable to have the ability to form dots corresponding to each recording density level (relative value) in the range from n to n. In this case, as shown in FIG. 13, it is possible to form a plurality of types of dots having a plurality of recording density levels at substantially equal intervals. The dark ink nozzles are (n + 1) to (n +
It is preferable to have the ability to form dots corresponding to m recording density levels of m). Here, m is an integer of 1 or more. This makes it possible to form dots at recording density levels of 1 to (n + m) at equal intervals. Further, as a mixed ink dot (also referred to as a “mixed ink same color dot”) formed by overlapping the dark ink and the light ink at the same position, at least a dot corresponding to a recording density level of (n + m + 1) is used. Is preferred. This has the advantage that nozzles of the same specifications can be used for dark ink and light ink.
In the example of FIG. 13 described above, n = 2 and m = 4,
Dot 10 corresponding to (n + m + 2) recording density level
8 is also used.

FIGS. 15A and 15B are graphs showing a tone reproduction method in the second embodiment. FIG. 15 (a),
The horizontal axis of (b) indicates the relative value of the image signal level, and FIG.
The vertical axis in FIG. 15A indicates the dot recording density of each of the dots 101 to 108, and the vertical axis in FIG. 15B indicates the recording density of the image. Here, “dot recording density” means the ratio of pixel positions where dots are formed. For example, 1
When dots are formed at 40 pixel positions in an area including 00 pixels, the dot recording density is 40 pixels.
%.

As can be understood from the graph of FIG. 15A, when the image signal level is in the range of 0 to 1, the dot recording density of the first dot 101 monotonically increases from 0% to 100% as the image signal level increases. (More specifically, linearly). As a result, in the image portion where the image signal level is 1, the first dots 101 are formed at all dot positions. When the image signal level is in the range of 1 to 2, the dot recording density of the first dot 101 monotonously decreases from 100% to 0% as the image signal level increases, while the dot recording density of the second dot 102 increases. The dot recording density monotonically increases from 0% to 100%. The total dot recording density of the first and second dots is 100%. In the image portion where the image signal level is 2, the second dots 102 are formed at all dot positions. Thus, according to the image signal level of each image portion, the image portion is recorded with one or two types of dots, so that the recording density of the image is smoothly and linearly as shown in FIG. Will be reproduced.

As described above, in the second embodiment, the gradation of an image is reproduced by recording density modulation using a plurality of dots which reproduce recording density at substantially equal intervals. By doing so, it is possible to smoothly reproduce the gradation of an image using nozzles that eject ink with a limited ejection amount. In particular, since mixed ink dots formed by ejecting dark ink and light ink in a superimposed manner are used, a wider range of gradations can be reproduced than in the case of using one type of ink. It is.

FIGS. 16A and 16B are explanatory views showing a modification of the second embodiment, and correspond to FIG. 15A. FIG. 16A shows gradation of an image over the entire range of image signal levels by recording density modulation using four types of dots 201 to 204 whose recording density levels (relative values) are 1: 2: 3: 4. Is reproduced. FIG. 16B shows that the recording density level (relative value) is 2:
The case where the gradation of the image over the entire range of the image signal level is reproduced by the recording density modulation using the four types of dots 301 to 304 of 3: 6: 8.

In the example of FIG. 16B, in the image portion where the image signal level is slightly higher than 3, the dot 302 having the recording density level 3 occupies most of the image portion, and the recording density is included therein. Dots 303 with level 6 appear sparsely. However, these two types of dots 3
The recording density levels of 02 and 303 are 3 and 6, and there is a considerable difference. The small number of high-density dots 303 existing in the large number of low-density dots 302 are conspicuous, so that the graininess is increased and the image quality may be degraded. If the recording density levels of the dots are not at regular intervals, the image quality may be degraded as described above.
It is preferable to perform recording density modulation using dots corresponding to recording density levels at substantially equal intervals, as shown in FIG.

D. Third Embodiment: FIG. 17 shows a third embodiment of the present invention.
FIG. 3 is a diagram illustrating a configuration of a print head assembly according to the embodiment. The first print head 61 'are dark black ink nozzle group K _D of forming the second print head 62', the the dark cyan ink nozzle group C _D, and dark magenta ink nozzle group M _D, a dark yellow ink nozzle group Y _D, light cyan ink nozzle group C _L, and the light magenta ink nozzle group M _L is formed. Printhead assembly of Figure 17 is different from the print head assembly of FIG. 6 that light and yellow ink nozzle group Y _L and the light black nozzle group K _L is described above in that it is not provided. The nozzle of the dark yellow ink nozzle group Y _D has a larger diameter than the nozzles of the other ink, thus, is configured to be discharged more ink.

FIG. 18 is a graph showing the relationship between the ink ejection amount and the dot diameter in the third embodiment. The nozzles for ejecting cyan ink, magenta ink, and black ink are all 5 ng, 8 ng, 13 ng, and 20 ng.
g of ink can be ejected at one time. On the other hand, a nozzle that discharges yellow ink can discharge 10 ng, 20 ng, and 40 ng of ink at one time.

The reason why a nozzle for forming a large dot only with respect to the dark yellow ink is employed is that the yellow visual angle sensitivity is low, so that even if a large dot is formed, a granular feeling is not generated. Further, the reason why the light black ink is not used is that black having a low density (that is, gray) can be reproduced by using the three CMY inks. Therefore, in the third embodiment, the density gradation of each color is reproduced by using dark ink and light ink only for cyan and magenta.

Of the four primary colors CMYK, cyan and magenta are subjected to recording density modulation using a plurality of types of dots in the same manner as in the second embodiment.
The gradation of the image can be reproduced. For yellow and black (gray), the gradation is reproduced as follows.

FIGS. 19A and 19B are explanatory diagrams showing the structure of yellow dots and the content of recording density modulation in the third embodiment. As shown in FIG. 19A, as yellow dots, a first dot 401 having a diameter of 60 μm formed with 10 ng dark ink, a second dot 402 having a diameter of 80 μm formed with 20 ng dark ink, 4
A third dot 403 having a diameter of 120 μm and formed of 0 ng dark ink is used. These three types of dots 401 to 403 have relative recording density levels of 3, 4, 6
It is. Therefore, as shown in FIG. 19B, when the image signal level is in the range of 0 to 3, the dot recording density of the first dot 401 increases from 0% to 1 as the image signal level increases.
It increases monotonically (more specifically, linearly) to 00%. When the image signal level is in the range of 3 to 4, the first
The dot recording density of the dot 401 decreases monotonically from 100% to 0% as the image signal level increases, while the dot recording density of the second dot 402 decreases from 0% to 1%.
It increases monotonically to 00%. The other ranges are almost the same. In the case where the recording density levels of the three types of dots are not at equal intervals as described above, the granularity tends to occur in the reproduced image portion, but the yellow ink is not conspicuous and often causes no problem.

FIGS. 20A and 20B are explanatory diagrams showing the configuration of black dots and the content of recording density modulation in the third embodiment. As shown in FIG. 20A, as black dots, a first dot 501 having a diameter of 40 μm formed by 5 ng dark black ink and a second dot 502 having a diameter of 80 μm formed by 20 ng dark black ink are used. And a diameter 1 formed by mixing four types of inks
A third dot 503 of 20 μm is used. The third dot 503 is formed by ejecting 10 ng dark black ink and 8 ng dark cyan ink, dark magenta ink, and dark yellow ink respectively at the same position. These three types of dots 501-
503, the relative values of the recording density levels are 2, 4, and 6,
Evenly spaced. Therefore, as shown in FIG. 20B, recording density modulation can be performed at equal intervals. As a result, it is possible to prevent the occurrence of graininess in the reproduced image portion.

It is to be noted that a plurality of kinds of combinations can be used as the ejection amount of the ink for forming the third dot 503. For example, when about 13 ng each of dark cyan ink, dark magenta ink, and dark yellow ink is ejected, high density dots 50 are ejected without ejecting dark black ink.
3 can be formed. The ejection amounts of the dark cyan ink, the dark magenta ink, and the dark yellow ink are as follows.
The ejection amounts are not necessarily equal to each other, and the respective ejection amounts are determined so that a gray balance can be obtained (that is, gray is obtained when three color inks are mixed).

Even when nozzles for ejecting dark ink and light ink for at least cyan and magenta are provided as in the third embodiment, the gradation of the image can be smoothed for each color. is there. At this time, it is preferable that the yellow nozzle is configured so that a relatively large-sized dot can be formed by one ejection.

E. Fourth Embodiment: First to Third Embodiments
In the embodiment, the gradation for each of the CMYK primary colors is reproduced. However, in the fourth embodiment described below, a device is devised to reproduce the black gradation (that is, the gray image gradation). . The same hardware configuration as that of the first embodiment described above can be used as the hardware configuration of the fourth embodiment. However, in the fourth embodiment, since only four types of inks of YMCK are used for grayscale reproduction of a gray image, light ink of each color is unnecessary in this sense.

FIGS. 21A and 21B are explanatory diagrams showing the configuration of the first dot 601 and the second dot 602 for reproducing a gray image in the fourth embodiment. FIG.
As shown in (a), a first dot 601 of small size
Is formed by discharging the dark black ink once. On the other hand, as shown in FIG. 21B, the large-size second dot 602 first discharges one of cyan ink, magenta ink, and yellow ink, and discharges black ink at the same position. It is formed by doing. Therefore, as the second dot 602,
There are three different types of dots 602a, 602b, 602c of (K + C), (K + M), and (K + Y).
The ejection amounts of the cyan ink, the magenta ink, and the yellow ink are determined so that a gray balance can be obtained. In addition, a first dot position where cyan ink is ejected, a second dot position where magenta ink is ejected,
The third dot positions at which the yellow ink is ejected are arranged so as to have regular and mutually equivalent distributions. As a result, an area macroscopically recognized as gray can be recorded. Note that in order to achieve gray balance, the respective ejection amounts differ according to the density of each ink. For example, when the density of the yellow ink is relatively high, gray can be reproduced by making the amount of the yellow ink smaller than that of cyan or magenta. In this way, an appropriate amount of each of the three CMY inks is arranged so as to be macroscopically gray.

FIG. 22 is an explanatory view showing a mask used in the fourth embodiment. This mask has a 3 × 3 dot area, and defines which ink should be ejected at each dot position. For example, black ink and cyan ink are ejected at the upper left dot position. When such a mask is repeatedly applied to the gray area when printing a macro gray area, FIG.
Each ink can be ejected in the arrangement shown in FIG.

In the example shown in FIG. 21B, ink is ejected at all dot positions. However, when the gray density is low, ink is not ejected at some dot positions. Is also possible. For example, according to the gray density of the image portion, C is used for each 3 × 3 pixel area shown in FIG.
It is possible to determine whether or not to eject MY ink. In such a case, the regularity of the dot positions at which the cyan, magenta, and yellow inks are ejected as a whole image is somewhat impaired. However, also in this case, the ejection positions of the respective inks have distributions substantially equivalent to each other, and thus are recognized as gray areas.

FIG. 23 is an explanatory diagram showing the contents of the recording density modulation in the fourth embodiment. In this example, when the image signal level is in the range of 0 to 4, the gradation is reproduced by the recording density modulation of the first dot 601. When the image signal level is in the range of 4 to 6, the gradation is reproduced by the recording density modulation of the first dot 601 and the second dot 602.
Note that, when the image signal level is in the range of 4 to 6, FIG.
As shown in FIG. 1B, a fixed amount (for example, 20 ng) of black ink is ejected to all dot positions. Therefore, in actuality, when the image signal level is in the range of 4 to 6, the ejection amount and the ejection position of the black ink do not change, and C
The position where the MY ink is ejected increases as the image signal level increases. As a result, the gradation of the image portion macroscopically recognized as a gray color can be smoothly reproduced. The image signal level at which the recording density modulation using the second dot 602 is started can be changed by adjusting the ejection amount of each ink for forming the dot.

F. Fifth Embodiment FIGS. 24A and 24B and FIGS. 25A and 25B show first to fourth dots 701 for reproducing a gray image in the fifth embodiment.
FIG. 146 is an explanatory diagram illustrating a configuration of 704. As shown in FIG. 24A, the smallest first dot 701 is formed by discharging dark black ink once to each dot position. As shown in FIG. 24B, the second dot 7
No. 02 is formed by ejecting two kinds of inks of cyan ink, magenta ink and yellow ink so as to overlap at the same position. Therefore, as the second dot 702, (C + M), (M + Y) and (Y + C)
Dots 702a, 702b, 70 of three different colors
2c exists. As shown in FIG. 25A, the third dot 703 is formed by ejecting cyan ink, magenta ink, and yellow ink so as to overlap at the same position. Further, as shown in FIG.
Dot 704 is formed by ejecting cyan ink, magenta ink, yellow ink, and black ink so as to overlap at the same position. In addition, in each of the four types of dots 701 to 704, the ejection amounts of the cyan ink, the magenta ink, and the yellow ink are determined so as to achieve a gray balance.

FIGS. 26A and 26B are explanatory diagrams showing masks used for the first dot 701 and the second dot 702 of the fifth embodiment, respectively. Each of these masks has an area of 3 × 3 dots, and defines which ink should be ejected at each dot position. If such a mask is repeatedly applied to the gray area on the image plane, it is possible to discharge each ink in the arrangement as shown in FIGS. Note that the third dot 703 and the fourth dot 704 (FIG. 25A,
In (b), since three or four types of ink are ejected at the same position, no mask is required.

FIG. 27 is an explanatory diagram showing the contents of the recording density modulation in the fifth embodiment. In this example, four types of dots 701 to 704 correspond to image signal levels 1, 2, 3, 4
, And the recording density can be modulated at regular intervals. The image density level corresponding to each dot can be changed by adjusting the ejection amount of each ink for forming each dot.

In the above-described third to fifth embodiments, the dots formed by discharging a plurality of types of inks of different colors at the same position are used to reproduce the dots formed only by the black ink. It is possible to reproduce a difficult wide gradation range.

The gray-scale tone reproduction modes similar to those described in the third to fifth embodiments are generally selected from the following seven types of tone reproduction sub-modes. Can be used.

(I) First-type tone reproduction sub-mode: Only black ink is ejected to dot positions to be recorded (first and second dots 501 and 502 in FIG. 20 and FIG. 21A ) First dot 601).

(Ii) Second-type tone reproduction sub-mode: one type of ink selected from cyan, magenta, and yellow inks is ejected at dot positions to be recorded (FIG. 21A) Of the first dot 701).

(Iii) Third-type gradation reproduction sub-mode:
Two types of ink selected from cyan ink, magenta ink, and yellow ink are ejected at the dot position to be recorded in an overlapping manner (the second dot 70 in FIG. 24B).
2).

(IV) Fourth-type gradation reproduction sub-mode: three kinds of inks of cyan, magenta, and yellow inks are ejected at the dot positions to be recorded in a superposed manner (third in FIG. 25A). Dot 703).

(V) Fifth-type tone reproduction sub-mode: Two types of ink, one of cyan ink, magenta ink and yellow ink, and the black ink are provided at the dot positions to be recorded. The ink is ejected in a superposed manner (second dot 602 in FIG. 21B).

(Vi) Sixth type of tone reproduction sub-mode: three types of ink: two types of inks selected from cyan, magenta and yellow inks, and black ink at dot positions to be recorded Are ejected in an overlapping manner (not in the above-described embodiment).

(Vii) Seventh-type tone reproduction sub-mode:
Four types of inks, cyan ink, magenta ink, yellow ink, and black ink, are ejected at the dot positions to be recorded (the fourth dot 70 in FIG. 25B).
4).

In each of the above tone reproduction sub-modes, the dot positions at which the cyan ink is ejected, the dot positions at which the magenta ink is ejected, and the dot positions at which the yellow ink is ejected have substantially equivalent distributions. Thus, the dot position at which each ink is ejected is determined. In each of the tone reproduction sub-modes of the second to sixth types, a mask having a distribution in which the dot positions at which the respective CMY inks are ejected have an equivalent distribution (FIGS. 22 and 2).
It is preferable to determine which ink is to be ejected at each dot position by repeatedly applying this mask on the image plane using 6). This makes it easy to determine at which dot position each ink should be ejected.

When reproducing the gray scale of a gray image, as shown in the recording density modulations shown in FIGS. It is preferable to use two tone reproduction sub-modes in each tone reproduction region other than the first tone reproduction region. Here, the gradation ranges of the two gradation reproduction sub-modes used in each gradation reproduction area are as follows:
It is set to partially overlap. For example, in the example of FIG. 27, in the first tone reproduction area (area of level 0 to 1), the tone reproduction submode using the first dot 701 is used, but in the second tone reproduction area. In (areas of levels 1 and 2), a gradation reproduction sub-mode in which recording density modulation of the first dot 701 is performed and a gradation reproduction sub-mode in which recording density modulation of the second dot 702 is used.

G. FIG. 28 shows an example of an equivalent circuit of the functions of the color correction module 98 and the halftone module 99 (FIG. 2) used in the second to fifth embodiments. FIG. Color correction module 98
Has the function of a UCR section (under color removing section) 800. The halftone module 99 includes the error buffer unit 9
00, an adder 902, a subtractor 904, a threshold value setting unit 906, a comparator 908, a level determination unit 910,
It has functions of a subtractor 912, two selectors 914 and 916, and a recording signal generation unit 918. The error buffer unit 900 includes a plurality of buffers 922 and 924. Further, the recording signal generation unit 918 includes a mask reference unit 920.
It has the function of These units are realized by a printer driver which is a computer program, and FIG. 28 is an equivalent circuit of the function.

The UCR section 800 converts the color image signals RGB
Are converted into CMY signals, and undercolor removal processing is performed to generate density signals of four colors of CMYK, which are supplied to the halftone module 98. The grayscale image (multi-tone image representing the gray image) is supplied as it is to the halftone module 98 as a density signal. Since the processing relating to the density signal of each color in the halftone module 98 is substantially the same, the processing of the density signal for one color will be mainly described below.

FIG. 29 is an explanatory diagram showing an example of the processing by the equivalent circuit of FIG. Here, the first type shown in FIG.
The fourth to fourth dots 701 to 704 are referred to as “level 1 dot” to “level 4 dot”, respectively. Also,
The relative levels 1 to 4 of the image signal are respectively associated with specific signal values 63, 127, 191, 255, and it is assumed that the value of the density signal Sin to be processed is 80. I have.

[0125] The level determination unit 910 in FIG. 28, according to the value of the density signal Sin, and the level signal S _L, and the upper-level weight signal W _U, determines and outputs a low-level weight signal W _L. Level signal S _L indicates the relative levels in the upper than the value of the density signal Sin. In the graph of FIG. 29, the density signal Sin = 80 is at the intermediate level 1 and level 2, the value of the level signal S _L corresponding thereto is 2 (see (2) in FIG. 29). Higher level weight signal W _U is an image signal value corresponding to the relative level indicated by the level signal S _L, The lower level weight signal W _L is the image signal values corresponding to the level below one. FIG.
9 (3), as shown in (4), the value of the upper-level weight signal W _U in this example 127, the value of the lower level weight signal W _L is 63.

[0126] Threshold value setting unit 906 of FIG. 28 is a lookup table for outputting the threshold value Th in accordance with the level signal S _L and the concentration signal Sin. As the threshold value Th, an intermediate value between an image signal value corresponding to a relative level generally represented by the level signal _SL and an image signal value corresponding to a relative level immediately below the selected level is selected. In the example of (5) in FIG. 29, 120 is output as the threshold value Th. The contents of the look-up table of the threshold value setting unit 906 are set experimentally so that a desired image recording result is obtained.

The adder 902 shown in FIG.
And the error signal S read from the error buffer 900.
err and the density signal with error Sdot
Generate In the example of (6) in FIG. 29, the error signal Serr
Is assumed to be 5, and the value of the density signal with error Sdot is 85. This density signal with error Sdot is output to the comparator 90
At 8 the threshold value Th is compared. The value of the comparison result signal COMP, which is the output of the comparator 90, is determined as follows.

When Th <Sdot: COMP = 1 (select the upper level), when Sdot ≦ Th: COMP = 0 (select the lower level)

In the example of FIG. 29, Sdot = 85, Th = 12
Since it is 0, the value of the comparison result signal COMP becomes "0" as shown in (7) of FIG. This comparison result signal COM
P is supplied to two selectors 914 and 916. The first selector 914, a level signal S _L, the low-level signal indicating the relative level of the lower two thereof (S _L -1) is input. When the value of the comparison result signal COMP is 0 (indicating that the lower level is selected), the lower level signal (S _L -1) is selected, and the recording signal generator 918 is selected.
(See (8) in FIG. 29). The value of the lower level signal (S _L -1) is 1, indicating that the dot to be recorded is the level 1 dot 701. The recording signal generation unit 918 generates a recording signal indicating that the level 1 dot 701 is to be recorded in accordance with the signal output from the selector 914 (lower level signal (S _L -1) in this example). Control circuit 40 of printer 22 (FIG. 3)
To supply. The control circuit 40 (FIG. 3) of the printer generates a driving signal for the piezo element according to the recording signal.

In the fifth embodiment described above, the level 1 dot 701 and the level 2 dot 70 for the gray image are used.
26, a mask as shown in FIGS. 26A and 26B was used. Therefore, when a signal indicating the level 1 dot 701 or the level 2 dot 702 is given from the selector 914 to the recording signal generation unit 918, the mask reference unit 920 refers to the mask for that level and determines which ink Is to be ejected.

[0131] The second selector 916, and the upper-level weight signal W _U, and a lower level weight signal W _L is input. If the value of the comparison result signal COMP is 0 (indicating a selection of a lower level) is selected lower level weight signal W _L in the selector 916, subtracter 904
Supplied to The subtracter 904 outputs the density signal with error Sdot.
Subtracting the weight signal W _L from the to produce a new error signal Serr '(see (9) in FIG. 29). The new error signal Serr 'is diffused at a predetermined ratio to pixels around the pixel to be processed (indicated by *) in the error buffer unit 900.

When the density signals Sin of the pixels on the same line are all 80, a level 1 dot 701 is recorded as shown in FIG. 29, but since the error is diffused, several pixels are obtained. , A level 2 dot 702 is recorded. As a result, as shown in the graph of FIG. 29, about 68% of level 1 dots 701 are formed and about 32% of level 2 dots 702 are formed as shown in the graph of FIG. 29 in the entire image portion where the density signal Sin is 80. .

The present invention is not limited to the above Examples and Embodiments, but can be implemented in various modes without departing from the gist of the invention.
For example, the following modifications are possible.

(1) In the above embodiment, part of the configuration realized by hardware may be replaced by software, and conversely, part of the configuration realized by software may be replaced by hardware. You may do so. For example, part of the equivalent circuit illustrated in FIG. 28 can be realized by hardware.

[Brief description of the drawings]

FIG. 1 is an exemplary block diagram illustrating an example in which a printing apparatus according to an embodiment is configured around a computer.

FIG. 2 is a block diagram illustrating a configuration of software related to print processing.

FIG. 3 is a schematic configuration diagram illustrating a configuration of a color printer 22 as an example of an image output device 20.

FIG. 4 is an explanatory diagram showing a configuration for ejecting ink in each print head.

FIG. 5 is an explanatory diagram showing a state in which ink particles Ip are ejected by expansion of a piezo element PE.

FIG. 6 is a diagram illustrating a configuration of a print head assembly according to the first embodiment of the present invention.

FIG. 7 is a graph showing the division of a tone reproduction area in the first embodiment.

FIG. 8 is a graph showing ink ejection amounts in each of five regions R1 to R5 in FIG. 7;

FIG. 9 is a graph showing the diameter of dots formed in each of five regions R1 to R5 in FIG.

FIG. 10 is a graph showing a relationship between an ink ejection amount and a dot diameter.

FIG. 11 is a graph showing the relationship between dot diameter and recording density.

FIG. 12 is an explanatory diagram showing dots formed in each of five regions R1 to R5 in FIG. 7;

FIG. 13 is an explanatory diagram showing the relationship between the image signal level and the configuration of dots to be recorded in the second embodiment.

FIG. 14 is a graph showing the relationship between the ink ejection amount and the dot diameter in the second embodiment.

FIG. 15 is a graph showing a tone reproduction method according to the second embodiment.

FIG. 16 is an explanatory view showing a modification of the second embodiment.

FIG. 17 is a diagram illustrating a configuration of a print head assembly according to a third embodiment of the present invention.

FIG. 18 is a graph showing a relationship between an ink ejection amount and a dot diameter in a third embodiment.

FIG. 19 is an explanatory diagram showing a configuration of a yellow dot and contents of recording density modulation in a third embodiment.

FIG. 20 is an explanatory diagram showing the configuration of black dots and the contents of recording density modulation in the third embodiment.

FIG. 21 is an explanatory diagram showing a configuration of a first dot 601 and a second dot 602 for reproducing a gray image in the fourth embodiment.

FIG. 22 is an explanatory view showing a mask used in the fourth embodiment.

FIG. 23 is a graph showing the contents of recording density modulation in the fourth embodiment.

FIG. 24 is an explanatory diagram showing a configuration of first and second dots 701 and 702 for reproducing a gray image in the fifth embodiment.

FIG. 25 is an explanatory diagram showing a configuration of third and fourth dots 703 and 704 for reproducing a gray image in the fifth embodiment.

FIG. 26 is an explanatory diagram showing a mask used for a first dot 701 and a second dot 702 in the fifth embodiment.

FIG. 27 is an explanatory diagram showing the contents of recording density modulation in the fifth embodiment.

FIG. 28 is a block diagram showing an equivalent circuit of the functions of a color correction module 98 and a halftone module 99 used in the second to fifth embodiments.

FIG. 29 is an explanatory diagram showing an example of processing by the equivalent circuit of FIG. 28;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 ... Scanner 14 ... Keyboard 15 ... Flexible drive 16 ... Hard disk 18 ... Modem 21 ... CRT 22 ... Printer 23 ... Paper feed motor 24 ... Carriage motor 26 ... Platen 28 ... Print head 31 ... Carriage 32 ... Operation panel 34 ... Sliding axis 36 ... Drive belt 38 ... Pulley 39 ... Position detection sensor 40 ... Control circuit 42 ... PROM 48 ... Modem 60 ... Print head assembly 61,62 ... Print head 65 ... Introduction tube 66 ... Ink passage 71 ... Black ink cartridge 72 ... Color ink cartridge 76 ... Hard disk 80 ... Bus 81 ... CPU 82 ... ROM 83 ... RAM 84 ... Input interface 85 ... Output interface 86 ... CRTC 88 ... SIO 90 ... Computer 91 ... Video driver 93 ... CRT data Display 95 Application program 96 Printer driver 97 Rasterizer 98 Color correction module 99 Halftone module

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 1/60 H04N 1/40 D 1/46 1/46 Z

Claims (25)

[Claims] An image corresponding to an image signal is recorded by forming dots on an image recording medium using a plurality of types of same color inks of substantially the same color and different densities for at least one primary color. The method according to claim 1, wherein one of the plurality of types of the same color ink is used as the same color ink, and a dot recording density defined as a ratio of pixels from which a fixed amount of ink is ejected to all pixels is added to the image signal. By performing dot recording density modulation that is adjusted accordingly, the first tone that reproduces the gradation of the image related to the same color
A plurality of types of tone reproduction sub-modes, and using one type of the same color ink among the plurality of types of the same color inks, discharging ink at each dot position at a dot recording density of 100%, A second type of gradation reproduction sub-mode for reproducing the gradation of an image related to the same color by performing a discharge amount modulation for adjusting a discharge amount according to the image signal; The above-described dot recording density modulation is performed for one kind of the same color ink, and a constant amount of ink is discharged at a dot recording density of 100% for the other one kind of the same color ink, thereby controlling the same color. A third type of gradation reproduction sub-mode for reproducing the gradation of an image; and the ejection amount modulation is performed for one type of the same color ink among the plurality of types of the same color inks. For the same type of same color ink, select from a fourth type of gradation reproduction sub-mode for reproducing the gradation of the image related to the same color by discharging a fixed amount of ink at a dot recording density of 100%. And at least the third type and the fourth type
A dot recording method for reproducing a gradation of an image relating to the same color by using a plurality of gradation reproduction sub-modes including one of the kinds of gradation reproduction sub-modes. 2. The dot recording method according to claim 1, wherein the plurality of types of same-color inks have a relatively low density.
The same color ink and a second same color ink having a relatively high density, wherein the entire gradation range of the image signal is (i) the first same color reproduction in the first type gradation reproduction sub-mode. A first gradation reproduction sub-mode area using color ink; and (ii) the second gradation reproduction sub-mode area.
A second tone reproduction sub-mode area using the first same color ink in the kind of tone reproduction sub-mode; (ii)
i) In the second type gradation reproduction sub-mode, the second type
A third tone reproduction mode area using the same color ink of
(Iv) In the third type of gradation reproduction sub-mode, the dot recording density modulation is performed on the first same color ink, while 100% is performed on the second same color ink.
% Of the first same color ink in the fourth gradation reproduction sub-mode area, which discharges a fixed amount of ink at a dot recording density of%. A dot recording method, wherein the modulation is performed, and the second same color ink is divided into a fifth gradation reproduction sub-mode area in which a fixed amount of ink is ejected at a dot recording density of 100%. 3. The dot recording method according to claim 1, wherein a plurality of types of the same color ink are superimposed on the same dot position in the third type or the fourth type of gradation reproduction sub mode. In the dot recording method, the plurality of types of the same color inks are respectively ejected during the same main scan. 4. An image corresponding to an image signal is recorded by forming dots on an image recording medium using a plurality of types of same color inks of substantially the same color and different densities for at least one primary color. A method of reproducing a tone of an image related to the same color by using a plurality of types of same color dots formed by combining a type and an ejection amount of the same color ink ejected to the same dot position. Wherein the plurality of types of same-color dots include at least one type of same-color dots created by ejecting at least two types of same-color inks at the same dot position. Recording method. 5. The dot recording method according to claim 4, wherein the plurality of types of same-color dots have recording densities at substantially equal intervals. 6. The dot recording method according to claim 5, wherein the plurality of types of the same color inks include a relatively low density light ink and a relatively high density dark ink, and the plurality of types of the same color inks. The dots are formed by discharging the same color dot of the light ink formed only with the light ink, the same color dot of the dark ink formed only with the dark ink, and the light ink and the dark ink in a superposed manner. And a mixed ink dot of the same color. 7. The dot recording method according to claim 6, wherein the same color dot of light ink has a relative value of recording density of 1 to 1.
n includes n types of dots each having a value close to an integer in the range of n (n is an integer of 1 or more), and the same color dot of the dark ink has a relative value of (n
+1) to (n + m) (m is an integer of 1 or more)
A dot recording method, comprising m kinds of dots each having a value close to the same, and wherein the mixed ink same color dots include mixed ink same color dots having a recording density relative value close to (n + m + 1). 8. The dot recording method according to claim 7, wherein the ratio of the density of the light ink to the density of the dark ink is substantially 1: (n +
1) A dot recording method. 9. A method for reproducing a gray image corresponding to a gray image signal by discharging ink of four colors of cyan, magenta, yellow, and black to form dots, and (i) recording is performed. A first-type gradation reproduction sub-mode in which only black ink is ejected at the dot position;
i) At a dot position to be recorded, one type of ink selected from cyan ink, magenta ink and yellow ink is ejected, and a dot position at which cyan ink is ejected and a dot position at which magenta ink is ejected And a second type of tone reproduction sub-mode for determining the dot positions at which the respective inks are ejected so that the dot positions at which the yellow ink is ejected have substantially the same distribution as each other. At the dot position, two types of ink selected from cyan ink, magenta ink and yellow ink are ejected in a superposed manner, and a dot position at which cyan ink is ejected, a dot position at which magenta ink is ejected, and In order that the dot positions at which ink is ejected have a distribution substantially equivalent to each other,
A third type of gradation reproduction sub-mode that determines the dot position at which each ink is discharged, and (iv) three types of inks of cyan ink, magenta ink, and yellow ink are discharged at the dot position to be recorded. In the fourth type of gradation reproduction sub-mode and (V) dot position to be recorded,
One type of ink selected from cyan ink, magenta ink and yellow ink and two types of ink, black ink, are ejected in a superposed manner, and the dot position at which cyan ink is ejected and the magenta ink are ejected A fifth type of gradation reproduction sub-mode for determining a dot position at which each ink is ejected such that the dot position and the dot position at which the yellow ink is ejected have a distribution substantially equivalent to each other; and (Vi) recording At a dot position to be ejected, two types of inks selected from cyan ink, magenta ink, and yellow ink and three types of black ink are ejected in a superposed manner, and the dot position at which the cyan ink is ejected is determined. The dot positions at which the magenta ink is ejected and the dot positions at which the yellow ink is ejected are substantially equal to each other. Do distribution to have a, a sixth kind tone reproduction submode of determining dot positions each ink is ejected, the dot positions to be recorded (Vii),
Use of a seventh type of tone reproduction sub-mode in which four types of inks of cyan ink, magenta ink, yellow ink, and black ink are ejected in a superposed manner, and a plurality of types of tone reproduction sub-modes selected from among them A dot recording method for reproducing a gray scale of a gray image. 10. The dot recording method according to claim 9, wherein the entire gradation range of the gray image signal is divided into a plurality of gradation reproduction regions, and each gradation reproduction region partially overlaps. The tone reproduction range is reproduced using two tone reproduction sub-modes capable of reproducing the tone range, and in each tone reproduction region other than the tone reproduction region existing at the top of the entire tone range, the plurality of types of For the dots formed in the tone reproduction sub-mode, dot recording density modulation is performed to adjust the dot recording density defined as the ratio of pixels for which a fixed amount of ink is ejected to all pixels in accordance with the gray image signal. A dot recording method whereby the gray scale of the gray image is reproduced. 11. The dot recording method according to claim 9, wherein in each of the second to sixth tone reproduction sub-modes, a dot position at which cyan ink is ejected and a magenta ink are used. Which ink is to be ejected at each dot position by using a mask in which the dot positions to be ejected and the dot positions to which the yellow ink is ejected have a distribution equivalent to each other, and repeatedly applying the mask on the image plane. Determine the dot recording method. 12. A dot recording apparatus for recording dots on the surface of a recording medium using a dot recording head, comprising: a dot recording head including a plurality of sets of nozzle arrays for discharging a plurality of types of ink; Main scanning drive means for performing main scanning by driving at least one of a dot recording head and the recording medium; and driving at least a part of a plurality of nozzles included in the dot recording head during the main scanning to form a dot. A head drive unit for performing the formation of, a sub-scan drive unit for performing sub-scan by driving at least one of the dot recording head and the recording medium each time the main scan is completed, and a control unit for controlling each of the units. Control means, wherein the dot recording head ejects a plurality of types of same-color inks having substantially the same color and different densities for at least one primary color. A plurality of sets of the same color nozzle arrays, wherein the control means uses one kind of the same color ink among the plurality of kinds of the same color inks, and calculates a ratio of a pixel in which a fixed amount of ink is ejected to all pixels. By performing dot recording density modulation that adjusts a defined dot recording density according to the image signal, a first tone for reproducing the gradation of an image related to the same color is obtained.
A plurality of types of tone reproduction sub-modes, and using one type of the same color ink among the plurality of types of the same color inks, discharging ink at each dot position at a dot recording density of 100%, A second type of gradation reproduction sub-mode for reproducing the gradation of an image related to the same color by performing a discharge amount modulation for adjusting a discharge amount according to the image signal; The above-described dot recording density modulation is performed for one kind of the same color ink, and a constant amount of ink is discharged at a dot recording density of 100% for the other one kind of the same color ink, thereby controlling the same color. A third type of gradation reproduction sub-mode for reproducing the gradation of an image; and the ejection amount modulation is performed for one type of the same color ink among the plurality of types of the same color inks. For the same type of same color ink, select from a fourth type of gradation reproduction sub-mode for reproducing the gradation of the image related to the same color by discharging a fixed amount of ink at a dot recording density of 100%. And at least the third type and the fourth type
A dot recording apparatus that reproduces the gradation of an image related to the same color by using a plurality of kinds of gradation reproduction submodes including one of the kinds of gradation reproduction submodes. 13. The dot recording apparatus according to claim 12, wherein the plurality of types of the same color inks have a relatively low density.
The same color ink and a second same color ink having a relatively high density, wherein the entire gradation range of the image signal is (i) the first same color reproduction in the first type gradation reproduction sub-mode. A first gradation reproduction sub-mode area using color ink; and (ii) the second gradation reproduction sub-mode area.
A second tone reproduction sub-mode area using the first same color ink in the kind of tone reproduction sub-mode; (ii)
i) In the second type gradation reproduction sub-mode, the second type
A third tone reproduction mode area using the same color ink of
(Iv) In the third type of gradation reproduction sub-mode, the dot recording density modulation is performed on the first same color ink, while 100% is performed on the second same color ink.
% Of the first same color ink in the fourth gradation reproduction sub-mode area, which discharges a fixed amount of ink at a dot recording density of%. A dot recording apparatus which performs modulation and, on the other hand, is divided into a fifth gradation reproduction sub-mode area for discharging a fixed amount of ink at a dot recording density of 100% for the second same color ink. 14. The dot recording apparatus according to claim 12, wherein a plurality of types of ink of the same color are superimposed on the same dot position in the third or fourth type of gradation reproduction sub-mode. In this case, the dot recording apparatus is configured such that the plurality of types of the same color inks are respectively ejected during the same main scan. 15. A dot recording apparatus for recording dots on the surface of a recording medium using a dot recording head, comprising: a dot recording head including a plurality of sets of nozzle arrays for discharging a plurality of types of ink; Main scanning drive means for performing main scanning by driving at least one of a dot recording head and the recording medium; and driving at least a part of a plurality of nozzles included in the dot recording head during the main scanning to form a dot. A head drive unit for performing the formation of, a sub-scan drive unit for performing sub-scan by driving at least one of the dot recording head and the recording medium each time the main scan is completed, and a control unit for controlling each of the units. Control means, wherein the dot recording head ejects a plurality of types of same-color inks having substantially the same color and different densities for at least one primary color. A plurality of same-color nozzle arrays, wherein the control means uses a plurality of types of same-color dots formed by combining the types and discharge amounts of the same-color inks discharged at the same dot positions, Means for reproducing a gradation of an image relating to the same color, wherein the plurality of types of same color dots are formed by ejecting at least two types of same color inks at the same dot positions at least one type of the same color dots. A dot recording device comprising color dots. 16. The dot recording apparatus according to claim 15, wherein the plurality of types of same-color dots have recording densities at substantially equal intervals. 17. The dot recording apparatus according to claim 16, wherein the plurality of types of same-color inks include a relatively low-density light ink and a relatively high-density dark ink, and the plurality of types of the same color inks. The dots are formed by discharging the same color dot of the light ink formed only with the light ink, the same color dot of the dark ink formed only with the dark ink, and the light ink and the dark ink in a superposed manner. And a mixed ink dot of the same color. 18. The dot recording apparatus according to claim 17, wherein the same color dot of light ink has a relative value of recording density of 1 to 1.
n includes n types of dots each having a value close to an integer in the range of n (n is an integer of 1 or more), and the same color dot of the dark ink has a relative value of (n
+1) to (n + m) (m is an integer of 1 or more)
A dot recording apparatus, comprising m kinds of dots each having a value close to the same, and wherein the mixed ink same color dots include mixed ink same color dots having a recording density relative value close to (n + m + 1). 19. The dot recording apparatus according to claim 18, wherein the ratio of the density of the light ink to the density of the dark ink is substantially 1: (n +
1) A dot recording device. 20. A dot recording apparatus for recording dots on the surface of a recording medium by using a dot recording head, comprising four sets of nozzle arrays for ejecting four color inks of cyan, magenta, yellow, and black. A dot recording head; a main scanning driving unit that drives at least one of the dot recording head and the recording medium to perform main scanning; and at least one of a plurality of nozzles included in the dot recording head during the main scanning. A head driving unit for driving a unit to form dots; a sub-scanning driving unit for performing sub-scanning by driving at least one of the dot recording head and the recording medium each time the main scanning is completed; Control means for controlling the means, the control means comprising: (i) a first-type tone reproduction for discharging only black ink at a dot position to be recorded; In the sub-mode, (ii) at a dot position to be recorded, one type of ink selected from cyan ink, magenta ink, and yellow ink is ejected, and the dot position at which cyan ink is ejected and the magenta ink are ejected. A second type of tone reproduction sub-mode for determining a dot position at which each ink is ejected such that the dot position at which the ink is ejected and the dot position at which the yellow ink is ejected have a distribution substantially equivalent to each other; iii) At a dot position to be recorded, two types of ink selected from cyan ink, magenta ink and yellow ink are ejected in a superposed manner, and a dot position at which cyan ink is ejected and a magenta ink are ejected. The dot positions and the dot positions at which the yellow ink is ejected have distributions substantially equivalent to each other. A third type of gradation reproduction sub-mode that determines the dot position at which each ink is discharged, and (iv) three types of inks of cyan ink, magenta ink, and yellow ink are discharged at the dot position to be recorded. In the fourth type of gradation reproduction sub-mode, (V) two kinds of inks of one ink selected from cyan ink, magenta ink and yellow ink and black ink are overlapped at a dot position to be recorded. So that the dot positions at which the cyan ink is ejected, the dot positions at which the magenta ink is ejected, and the dot positions at which the yellow ink is ejected have substantially equivalent distributions to each other.
A fifth type of gradation reproduction sub-mode for determining the dot position at which each ink is ejected, and (Vi) two types of ink selected from cyan ink, magenta ink and yellow ink at the dot position to be recorded And the black ink and the three inks are ejected in a superposed manner, and the dot positions at which the cyan ink is ejected, the dot positions at which the magenta ink is ejected, and the dot positions at which the yellow ink is ejected are substantially equivalent to each other. To have an optimal distribution
Sixth type of tone reproduction sub-mode for determining the dot position where each ink is ejected, and (Vii) four types of inks of cyan ink, magenta ink, yellow ink and black ink at the dot position to be recorded A dot recording apparatus that reproduces the gray scale of a gray image by using a seventh type of gray scale reproduction sub-mode that discharges ink by using a plurality of types of gray scale reproduction sub-modes selected from among them. . 21. The dot recording apparatus according to claim 20, wherein the entire gradation range of the gray image signal is divided into a plurality of gradation reproduction regions, and each gradation reproduction region partially overlaps. The tone reproduction range is reproduced using two tone reproduction sub-modes capable of reproducing the tone range, and in each tone reproduction region other than the tone reproduction region existing at the top of the entire tone range, the plurality of types of For the dots formed in the tone reproduction sub-mode, dot recording density modulation is performed to adjust the dot recording density defined as the ratio of pixels for which a fixed amount of ink is ejected to all pixels in accordance with the gray image signal. A dot recording device that reproduces the gradation of the gray image. 22. The dot recording apparatus according to claim 20, wherein the control unit controls a dot position at which cyan ink is ejected in each of the second to sixth tone reproduction sub-modes. And a dot position at which magenta ink is ejected and a dot position at which yellow ink is ejected, using a mask having a distribution equivalent to each other, and by repeatedly applying the mask on the image plane, A dot recording device that determines whether to eject ink. 23. A dot recording apparatus comprising: a dot recording head having a plurality of sets of nozzle arrays for ejecting a plurality of types of same-color inks of substantially the same color and different densities for at least one primary color; and a computer. A computer-readable recording medium that is used in an apparatus and records a computer program for recording dots on a surface of a dot recording medium using the dot recording head, wherein the computer program is the same kind of the plurality of types. Using one kind of the same color ink among the color inks, dot recording density modulation is performed to adjust a dot recording density defined as a ratio of a pixel from which a fixed amount of ink is ejected to all pixels according to the image signal. By doing so, the first tone for reproducing the gradation of the image related to the same color
A plurality of types of tone reproduction sub-modes, and using one type of the same color ink among the plurality of types of the same color inks, discharging ink at each dot position at a dot recording density of 100%, A second type of gradation reproduction sub-mode for reproducing the gradation of an image related to the same color by performing a discharge amount modulation for adjusting a discharge amount according to the image signal; The above-described dot recording density modulation is performed for one kind of the same color ink, and a constant amount of ink is discharged at a dot recording density of 100% for the other one kind of the same color ink, thereby controlling the same color. A third type of gradation reproduction sub-mode for reproducing the gradation of an image; and the ejection amount modulation is performed for one type of the same color ink among the plurality of types of the same color inks. For the same type of same color ink, select from a fourth type of gradation reproduction sub-mode for reproducing the gradation of the image related to the same color by discharging a fixed amount of ink at a dot recording density of 100%. And at least the third type and the fourth type
A computer-readable function having a function of reproducing the gradation of an image related to the same color by using a plurality of gradation reproduction sub-modes including one of the kinds of gradation reproduction sub-modes. recoding media. 24. A dot recording apparatus comprising: a dot recording head having a plurality of sets of nozzle arrays for ejecting a plurality of types of same color inks of substantially the same color and different densities for at least one primary color; and a computer. A computer-readable recording medium that is used in an apparatus and records a computer program for recording dots on the surface of a dot recording medium using the dot recording head, wherein the computer program is located at the same dot position. A function of reproducing the gradation of an image related to the same color by using a plurality of types of same color dots formed by combining the type of the same color ink to be discharged and the discharge amount; Dots are formed by ejecting at least two types of ink of the same color at the same dot position. A computer-readable recording medium comprising at least one kind of same-color dot to be created. 25. A dot recording head that includes a dot recording head including four sets of nozzle arrays for ejecting four color inks of cyan, magenta, yellow, and black, and a computer, and uses the dot recording head. A computer program for recording a computer program for recording dots on the surface of a dot recording medium, the computer program comprising: (i) a computer program for ejecting only black ink at a dot position to be recorded; One type of gradation reproduction sub-mode, and (ii) one type of ink selected from cyan ink, magenta ink and yellow ink at a dot position to be recorded,
The dot positions at which the respective inks are ejected are determined so that the dot positions at which the cyan ink is ejected, the dot positions at which the magenta ink is ejected, and the dot positions at which the yellow ink is ejected have substantially equivalent distributions. And (iii) in a dot position to be recorded, two types of ink selected from cyan ink, magenta ink and yellow ink are ejected in a superposed manner, and the cyan ink is Thirdly, the dot positions at which the respective inks are ejected are determined so that the dot positions at which the magenta ink is ejected, the dot positions at which the magenta ink is ejected, and the dot positions at which the yellow ink is ejected have substantially equivalent distributions. And (iv) cyan ink, magenta ink, and yellow at the dot position to be recorded. And (V) one ink selected from cyan ink, magenta ink and yellow ink at the dot position to be recorded. The two types of ink, black and black, are ejected in a superposed manner, and the dot positions at which the cyan ink is ejected, the dot positions at which the magenta ink is ejected, and the dot positions at which the yellow ink is ejected are substantially equivalent to each other. A fifth type of gradation reproduction sub-mode for determining the dot position at which each ink is ejected so as to have a distribution, and (Vi) selecting from cyan ink, magenta ink and yellow ink at the dot position to be recorded The three types of ink, black ink and two types of ink, are ejected in a superposed manner, and the cyan ink is ejected. A sixth type of floor that determines the dot position at which each ink is ejected so that the dot position, the dot position at which the magenta ink is ejected, and the dot position at which the yellow ink is ejected have substantially equivalent distributions to each other. The tone reproduction sub-mode and (Vii) a seventh type tone reproduction sub-mode in which four types of inks of cyan ink, magenta ink, yellow ink, and black ink are ejected at the dot position to be recorded in a superposed manner. A computer-readable recording medium having a function of reproducing a grayscale of a gray image by using a plurality of types of grayscale reproduction submodes selected from the group consisting of: