JPH11170539A - Apparatus and method for printing and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a color irregularity due to a hue difference of dots formed at a first half and a second half of a reciprocatory motion by arranging a means for controlling each raster record mode so that a recording cycle in a sub scan direction which is a combination of recording modes agrees with a pitch of nozzles. SOLUTION: In a method for recording dots, dots are formed at a first half of a reciprocatory motion at a third and a fourth recordings. In other words, a sub scan not forming dots is interposed between the third and fourth recordings. Specifically, in the method of the embodiment, images are formed in a cycle of three rasters, i.e., 'a first half motion recording mode → a second half motion recording mode → a first half motion recording mode → a second half motion without forming dots'. The cycle is coincident with a sub scan direction of a nozzle. Images obtained in the record method have a constant recording ratio 2:1 of the first half motion recording mode and second half motion recording mode at all areas (areas A, B, C).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus, a printing method, and a printing medium for printing an image on a printing medium by forming dots during both reciprocating movements in main scanning.

[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 that discharges several colors of ink from a head is widely used, and is widely used for printing an image processed by a computer or the like in multiple colors. In this type of printer, a technique has been proposed in which dots are formed not only at the time of forward movement but also at the time of backward movement in the main scanning in which the head reciprocates with respect to the recording medium (hereinafter, this technique forms dots). What to do (Bi-D)
Record).

[0003] As one of the bi-D (Bi-D) recordings, a dot is formed for each part of one raster during the forward movement of the head, and the remaining dots are formed by another nozzle during the backward movement. There is a dot recording technique in which all dots of one raster are completed in a reciprocating motion. According to this recording method, since one raster is recorded by different nozzles, a deviation in dot formation due to a mechanical error in nozzle production can be dispersed, and image quality can be improved.

Further, as a bi-D recording, a recording method in which all dots of one raster are formed when the head makes one forward movement, and all dots of another raster are formed by a subsequent backward movement. is there. According to this recording method, the dot formation efficiency is doubled as compared with the case where dots are formed only by the forward movement, so that the printing speed can be increased.
However, such a recording method has conventionally been mainly used in low-quality printing because dots formed during the forward movement and the backward movement are likely to be displaced in the main scanning direction and image quality is likely to be deteriorated.

[0005]

On the other hand, as the image quality of the output by the printer has been improved, the demand for achieving both high image quality and a high printing speed has been increased. From this viewpoint, in high-quality printing, all dots of one raster are formed in each of the forward movement and the backward movement to increase the printing speed.
i-D) Recording was attempted. However, it has been found that when such dots are recorded under certain conditions, color unevenness that cannot be overlooked from the viewpoint of high image quality occurs in the printed image. This phenomenon will be described with reference to FIG.

FIG. 11 is an explanatory view showing how dots are formed by a head having a plurality of nozzles. FIG.
The nozzle row is indicated by a circle “○” or a square “□” on the left side of 1, the circle “○” indicates the position of the nozzle during the forward movement, and the square “□” indicates the backward movement. The position of is shown.
"First time, second time ..." described along with the nozzle row
Indicates the number of main scans of the head. Also, a state is shown in which the sub-scan is performed with a constant paper feed amount for each main scan.

The right side of FIG. 11 shows the state of dots recorded by the above-described scanning of the head. The dotted line indicates a portion where the nozzles scan but do not record dots. Circles “○” and squares “□” mean dots formed during the forward movement and the backward movement of the head, respectively. As shown in FIG.
It can be seen that a complete image is formed at the points c to c. FIG. 11 shows a nozzle row including 11 nozzles, and the pitch of each nozzle in the sub-scanning direction is three times the recording density of an image. When an image is formed by the method described above, as is apparent from FIG. 11, the area where the recording rate of dots formed during the forward movement is high (area a and area c) and the area between the dots formed during the backward movement are different. It can be seen that the area where the recording rate is high (area b) alternates.

When a head in which the inks of the respective colors are arranged in a line in the main scanning direction is used, the order of ejecting the ink is different between the forward movement and the backward movement. For example, consider the head shown in FIG. FIG. 5 shows black (K), cyan (C), light cyan (LC),
FIG. 3 is a plan view of a head in which six colors of ink of magenta (M), light magenta (LM), and yellow (Y) are arranged in a line. When the head is moving rightward in FIG. 5 (during forward movement), “Y, LM,
Ink is ejected in the order of “M, LC, C, K”. When the head is moving to the left in FIG. 5 (during the backward movement), ink is ejected in the reverse order. If the order of ink ejection is different, the order in which ink permeates the paper will be different, so that even if the same amount of ink is ejected for each color, the resulting hue will be slightly different. As a result, the hue differs between the dots formed during the forward movement and the dots formed during the backward movement even if the same amount of ink is ejected.

As described above with reference to FIG. 11, in conventional bi-D (Bi-D) recording, the area (area a and area c) where the recording rate of dots formed during the forward movement is high, and Regions (regions b) where the recording rate of dots formed during the backward movement is high occur alternately. In a printer using a head in which the inks of each color are arranged in a line in the main scanning direction, the hues obtained by the two are slightly different, and this is recognized as color unevenness. Such a phenomenon is not limited to the number of nozzles shown in FIG. 11, but occurs as long as the nozzle pitch in the sub-scanning direction is an odd multiple of the image recording density. Since such color unevenness greatly impairs the image quality of a printed image, it cannot be overlooked from the viewpoint of obtaining high image quality while improving the printing speed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in a printing apparatus capable of performing bi-D (Bi-D) recording, the difference in hue of dots formed during forward movement and backward movement is considered. It is an object of the present invention to provide a technique for eliminating color unevenness based on the image and improving image quality.

[0011]

Means for Solving the Problems and Their Functions and Effects In order to solve the above problems, the present invention employs the following means. The printing apparatus of the present invention performs a main scan in which the head and the print medium reciprocate relatively and a sub-scan in which the head and the print medium are relatively moved in a direction intersecting with the main scan, and performs a predetermined scan in the sub-scan direction. A printing apparatus that can print an image by forming a plurality of dots having different hues on the print medium according to input image data using a plurality of nozzles arranged in the head at a pitch, As the head,
The predetermined pitch is an odd multiple of the image recording pitch in the sub-scanning direction, so that dots can be formed for each color during both reciprocating movements in the main scanning, and the forward movement and the backward movement can be performed. The head has a different order of ejecting ink of each color at the time, a forward movement recording mode in which all the dots of one raster are recorded at the time of the one-time movement in the main scanning, and all the dots of one raster at the time of the one-way movement. At least two types of recording modes are mixed, including a reverse motion recording mode for recording and a bidirectional recording mode for recording all dots of one raster by both reciprocating motions, and a combination of each recording mode And a raster recording control means for controlling a recording mode of each raster so that a recording cycle in the sub-scanning direction is equal to the pitch of the nozzles. .

According to the printing method of the present invention, the main scanning which reciprocates the head and the print medium relatively and the sub-scanning which relatively moves the head and the printing medium in a direction intersecting with the main scanning are performed while the sub-scanning is performed. A printing method capable of printing an image by forming a plurality of dots having different hues on the print medium in accordance with input image data using a plurality of nozzles arranged in the head at a predetermined pitch. In the head, the predetermined pitch is an odd multiple of the image recording pitch in the sub-scanning direction, and can form dots for each color during both reciprocating movements in the main scanning, and A head in which the order of ejecting ink of each color is different between the forward movement and the backward movement, and a forward movement recording mode in which all dots of one raster are recorded during the forward movement in the main scanning; Sometimes, at least two types of recording modes are mixed among three types of recording modes, a backward motion recording mode in which all dots of one raster are recorded and a bidirectional recording mode in which all dots of one raster are recorded by both reciprocating motions. In addition, the gist is that the recording mode of each raster is controlled and recorded so that the recording cycle in the sub-scanning direction, which is a combination of the recording modes, matches the pitch of the nozzles.

In the printing apparatus and the printing method, by controlling the raster printing method, at least two printing modes among the three printing modes of the forward movement printing mode, the backward movement printing mode, and the bidirectional printing mode are provided. And the printing cycle in the sub-scanning direction, which is a combination of the printing modes, can be matched with the pitch of the nozzles. The dots formed by the three printing modes described above form different rasters with different hues because the order of ejecting the inks of each color is different. In the above printing apparatus and printing method, the cycle of the recording mode used matches the pitch of the nozzles. Therefore, assuming that the nozzle pitch is equivalent to n rasters, the recording rate in each of the above recording modes will take a constant value regardless of where n consecutive rasters are selected from any part of the recorded image. As shown in FIG. 11, the recording rate in each recording mode does not change depending on the area. As a result, so-called color unevenness of the image can be eliminated, and the image quality can be improved.

Here, terms such as the nozzle pitch, the image recording pitch, and the period are defined. The nozzle pitch refers to the distance between the centers of two or more nozzles provided in the head, measured in the sub-scanning direction, of the nozzles adjacent in the sub-scanning direction. In this specification, this interval may be represented using the number of rasters. In addition to the case where the nozzles are arranged in a line in the sub-scanning direction as shown in FIG. 11, the same definition is applied to the case where the nozzles are arranged in a zigzag pattern as shown in FIG. The image recording pitch in the sub-scanning direction refers to the interval between each raster in the sub-scanning direction. For example, the interval corresponds to the recording pitch shown in FIG.

The term “cycle” generally means a time interval between repetitive events. In this specification, regardless of the time, the number of rasters required to complete the above-described recording combination in the recording mode is completely determined. Shall be referred to. For example, if an image is recorded in the repetition of “forward motion recording mode (forward) → reverse motion recording mode (reverse)”, “forward → return”,..., This recording cycle is 2 rasters. Further, when an image is recorded in a repetition of “forward → return → forward”, “forward → return → forward”, etc., the recording cycle is three rasters.

Various combinations of the recording modes in the printing apparatus, that is, control by the raster recording control means can be considered. For example, the raster recording control means may perform two of the forward movement recording mode and the backward movement recording mode.
Means for controlling the use of the recording mode so that the difference in the number of rasters recorded in the different recording modes becomes an odd number, so that the recording cycle in the sub-scanning direction, which is a combination of the respective recording modes, matches the nozzle pitch. You can also.

Specifically, the nozzle pitch is set to 3 of the image recording density.
In the case of double, the forward motion recording mode (forward) is used twice, and the reverse motion recording mode (back) is used once, and the image is repeated by repeating “forward → return → forward” and “forward → return → forward”. Can be recorded.
Of course, the repetition of “forward → forward → return” is substantially the same, and the reverse motion recording mode may be used twice. When the nozzle pitch is five times the image recording density, “forward → return → forward → return → forward” or “forward → return → return → return →
Various combinations such as "going" are possible. In such a recording method, there is at least one main scan in which dots are not formed.

The raster recording control means may be arranged such that the number of rasters recorded in the bidirectional recording mode is an odd number, and recording is performed in two types of recording modes, the forward motion recording mode and the backward motion recording mode. Means for controlling the use of the printing mode so that the difference in the number of rasters becomes 0 or an even number of 2 or more, so that the printing cycle in the sub-scanning direction, which is a combination of the printing modes, matches the pitch of the nozzles. Can also.

Specifically, the nozzle pitch is set to 3 of the image recording density.
In the case of double, the forward movement recording mode (forward), the backward movement recording mode (backward), and the bidirectional recording mode (bi
An image can be recorded by repeating “forward → return → bi” by using the image twice. When the nozzle pitch is five times the image recording density, various combinations such as “forward → return → forward → return → double” can be considered. From the standpoint of improving image quality only,
A recording method using the bidirectional recording mode an even number of times, such as “forward → return → forward → bi → bi”, is possible, but the dot formation efficiency is reduced and the printing speed is improved. The benefits will be lost.

On the other hand, in the above printing apparatus, dots are formed by the raster recording control means only in a predetermined raster area of the input image data which affects the image quality. It is desirable to have a recording method selecting means for forming dots by alternately using the reverse motion recording mode.

In the dot formation by the raster recording control means, although the image can be improved, there are always cases where dots are not formed in the main scanning and cases where one raster is formed by bidirectional main scanning. The dot formation efficiency is lower than when dots are formed in all main scans. In the above printing apparatus, recording is performed by raster recording control means having such characteristics only in a predetermined raster area of image data, and in other areas, dot recording is performed by alternately using the forward motion recording mode and the backward motion recording mode. I do. As a result, it is possible to minimize the recording of dots based on the raster control means that slightly lowers the dot formation efficiency, so that it is possible to improve the image quality and prevent the printing speed from lowering. The predetermined raster area includes an area where color unevenness in the sub-scanning direction is easily recognized, for example, a case where there is a solid area painted with a constant hue in the sub-scanning direction.

In the printing apparatus and the printing method described above, the relative movement amount of the print medium and the head in the sub-scan can be set variously. For example, all the movement amounts may be a fixed number of rasters, or may be changed at a predetermined cycle. In some cases, main scanning is performed without recording dots. In such a case, movement in the sub-scanning direction may or may not be performed.

The printing apparatus of the present invention described above can also be configured by realizing control of a head for recording dots by a computer.
The present invention can also take an aspect as a recording medium on which such a program is recorded.

The first recording medium of the present invention records a computer-readable program for printing an image by forming a plurality of dots on the printing medium in accordance with the image data input by the printing apparatus. The recording medium was recorded in a forward movement recording mode in which all dots of one raster were recorded during a single forward movement in the main scanning, and in a reverse movement recording mode in which all dots of one raster were recorded during a single backward movement. This is a recording medium on which a program for realizing the function of controlling the use of the recording mode by a computer so that the difference in the number of rasters becomes an odd number is recorded.

The second recording medium of the present invention records a computer-readable program for printing an image by forming a plurality of dots on the printing medium in accordance with image data input by a printing apparatus. The number of rasters recorded in the bidirectional recording mode in which all dots of one raster are recorded by both reciprocating movements in the main scanning is odd, and one raster is recorded in a single movement in the main scanning. So that the difference between the number of rasters recorded in the forward motion recording mode for recording all the dots and the number of rasters recorded in the reverse motion recording mode for recording all the dots in one raster during one backward motion is 0 or even or more even or more. It is a recording medium on which a program for realizing a function of controlling use of a recording mode by a computer is recorded.

The program recorded on the recording medium is
The printing apparatus of the present invention described above can be realized by being executed by the computer.

As storage media, flexible disks, CD-ROMs, magneto-optical disks, IC cards,
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. The present invention also includes an aspect as a program supply device that supplies a computer program for realizing the control function of the printing device to a computer via a communication path.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples. (1) Configuration of Apparatus FIG. 2 shows a schematic structure of the printer 22 of the present invention, and FIG. 1 shows a configuration of a color image processing system as an example of a system using the printer 22 of the present invention. In order to clarify the function of the printer 22, first, an outline of the color image processing system will be described with reference to FIG. This color image processing system includes a scanner 12, a personal computer 90,
And a color printer 22. The personal computer 90 includes a color display 21 and a keyboard,
An input unit 92 such as a mouse is provided. Scanner 1
2 reads color image data from a color original and supplies the computer 90 with original color image data ORG including three color components of red (R), green (G), and blue (B).

The computer 90 includes a CPU, a RAM, a ROM and the like (not shown), and an application program 95 runs under a predetermined operating system. The operating system incorporates a video driver 91 and a printer driver 96, and the application program 95 sends the final color image data F through these drivers.
NL will be output. An application program 95 for retouching an image reads an image from the scanner 12 and displays the image on the CRT display 21 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 sends the image information to a signal that can be printed by the printer 22 (here, each color of cyan, magenta, yellow, and black). (A binarized signal). In the example shown in FIG. 1, inside the printer driver 96, a rasterizer 97 that converts color image data handled by the application program 95 into image data in dot units, and a printer 22 for image data in dot units are provided. A color correction module 98 that performs color correction in accordance with the characteristics of the ink color and color used, a color correction table CT referred to by the color correction module 98, and the presence or absence of ink in dot units based on the color corrected image information And a halftone module 99 that generates so-called halftone image information expressing the density in a certain area. The printer 22 receives the printable signal and records image information on a recording sheet.

Next, a schematic configuration of the printer 22 will be described with reference to FIG. As shown in the drawing, the printer 22 includes a mechanism for transporting a sheet P by a paper feed motor 23 and a
6, a mechanism for driving a print head 28 mounted on a carriage 31 to control ink ejection and dot formation, and a paper feed motor 2
3, a control circuit 40 for exchanging signals with the carriage motor 24, the print head 28 and the operation panel 32.

The carriage 31 of the printer 22 includes
Black ink (Bk) cartridge 71 and cyan (C
1), light cyan (C2), magenta (M1), light magenta (M2), and yellow (Y) ink cartridges 72 containing six color inks can be mounted. For two colors, cyan and magenta, two types of inks are provided. The concentration of these inks will be described later. A total of six ink ejection heads 61 to 66 are formed on the print head 28 below the carriage 31, and at the bottom of the carriage 31,
An introduction pipe 67 (see FIG. 3) for leading the ink from the ink tank is provided upright for each color head. Carriage 3
When the cartridge 71 for black (Bk) ink and the cartridge 72 for color ink are mounted from above, the introduction pipe 67 is inserted into the connection hole provided in each cartridge, and from each ink cartridge to the ejection heads 61 to 66. Can be supplied.

The mechanism for discharging ink will be briefly described. FIG. 3 is an explanatory diagram showing a schematic configuration inside the ink discharge head 28. When the ink cartridges 71 and 72 are mounted on the carriage 31, the ink in the ink cartridge is sucked out through the introduction pipe 67 by utilizing the capillary phenomenon as shown in FIG. The print heads 28 are guided to the respective color heads 61 to 66 of the print head 28. When the ink cartridge is first mounted, the operation of sucking the ink into the heads 61 to 66 of the respective colors by a dedicated pump is performed. In this embodiment, a pump for suction and a cap for covering the print head 28 at the time of suction are provided. The illustration and description of such a configuration are omitted.

As will be described later, the heads 61 to 66 of each color are provided with 48 nozzles Nz for each color (see FIG. 6), and each nozzle is one of the electrostrictive elements. A piezo element PE having excellent responsiveness is provided. FIG. 4 shows the structure of the piezo element PE and the nozzle Nz in detail. As shown in the figure, the piezo element PE
It is installed at a position in contact with an ink passage 68 that guides ink to the nozzle Nz. 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 68 is deformed. As a result, the volume of the ink passage 68 contracts in accordance with the extension of the piezo element PE,
The ink corresponding to the contraction amount becomes the particles Ip and is ejected at a high speed from the tip of the nozzle Nz. Printing is performed by the ink particles Ip penetrating into the paper P mounted on the platen 26.

The printer 22 having the above-described hardware configuration rotates the platen 26 and other rollers by the paper feed motor 23 and conveys the paper P (hereinafter, referred to as sub-scanning) while moving the carriage 31 to the carriage motor 24.
(Hereinafter, referred to as main scanning), and at the same time, the piezo elements P of the respective color heads 61 to 66 of the print head 28.
By driving E, each color ink is ejected to form a dot to form a multicolor image on the paper P.

The mechanism for transporting the paper P is a paper feed motor 2
A gear train for transmitting the rotation of No. 3 not only to the platen 26 but also to the sheet transport roller is provided (not shown). The mechanism for reciprocating the carriage 31 includes an endless drive belt 36 extending between the carriage motor 24 and a slide shaft 34 erected in parallel with the axis of the platen 26 and slidably holding the carriage 31. Pulley 38 and carriage 31
And a position detection sensor 39 for detecting the origin position of the camera.

FIG. 5 is an explanatory diagram showing the arrangement of the ink jet nozzles Nz in the ink discharge heads 61 to 66. The arrangement of these nozzles is composed of six sets of nozzle arrays that eject ink for each color, and 48 nozzles Nz are arranged in a staggered manner at a constant nozzle pitch k. The positions of the nozzle arrays in the sub-scanning direction coincide with each other. The 48 nozzles Nz included in each nozzle array need not be arranged in a staggered manner, but may be arranged on a straight line. However, the arrangement in a staggered manner as shown in FIG. 5 has an advantage that the nozzle pitch k can be easily set small in manufacturing.

Each of the nozzle arrays has "black (K), cyan (C), light cyan (LC),
Magenta (M), light magenta (LM), yellow (Y) ”. Therefore, when the head moves to the right in FIG. 5, the printer 22 according to the present embodiment sets “Y → LM → M → LC → C →
(K) ", and when moving to the left, the ink is ejected in the reverse order. As a result of the ink ejection order, i.e., the order in which the ink permeates the paper when the head reciprocates, even if the ink of each color is ejected at a predetermined ratio, the dots recorded during the forward movement and the dots recorded during the backward movement are different. Will have a slightly different hue.

FIG. 6 shows an enlarged view of the nozzle array and the state of dots formed by the nozzle array. As shown in FIG. 6, in this embodiment, dots can be recorded at a pitch of 1/3 of the nozzle pitch by sub-scanning the nozzle array. That is, in the present embodiment, there is a relationship of nozzle pitch: recording pitch = 3: 1.

In this embodiment, as described above, the printer 22 having the head for discharging ink using the piezo element PE is used. However, the printer 22 for discharging ink by another method may be used. Good. For example, the present invention may be applied to a printer of a type in which a heater disposed in an ink passage is energized and ink is ejected by bubbles generated in the ink passage.

(2) Recording of Image Next, recording of an image by the printer 22 in this embodiment will be described. Hereinafter, the manner in which dots are formed by the main scanning of the head and the sub-scanning of the sheet will be specifically described. The main scanning and the sub-scanning are controlled by the control circuit 40 of the printer 22 shown in FIG. 2. However, since the control method is different for each printer 22 and is a well-known technique, the description using the flowchart is omitted. .

FIG. 7 is an explanatory diagram showing how dots are formed by the control used in this embodiment. Figure 5
As described above, the head of the printer 22 of the present embodiment has 48 nozzles. However, in order to avoid complexity, FIG. 7 shows how dots are formed by reducing the number of nozzles to 11. However, the nozzle pitch is equivalent to three rasters as in the present embodiment (see FIG. 6).

The nozzle row is indicated by a circle “○” or a square “□” on the left side of FIG. 7, and the circle “○” indicates the position of the nozzle during forward movement, and the square “□”. Indicates the position at the time of the backward movement. “First time, second time,...” Described together with the nozzle row indicates the number of times of main scanning of the head. In addition, a state is shown in which the sub-scan is performed with a constant paper feed amount of 11 rasters for each main scan. The right side of FIG. 7 shows the state of dots recorded by the above-described scanning of the head. The dotted line indicates a portion where the nozzles scan but do not record dots. Circles “○” and squares “□” mean dots formed during the forward movement and the backward movement of the head, respectively. In this case, the paper feed amount, that is, the movement amount in the sub-scanning direction has a constant value for 11 rasters.

In the dot recording method according to the present embodiment,
As shown in FIG. 7, dots are formed during the forward movement in both the third and fourth recordings. That is, the sub-scan is performed without forming a dot once during this time. In other words, FIG.
In the recording method shown in (1), an image is formed in a cycle consisting of three rasters, "forward movement recording mode (forward) → backward movement recording mode (backward) → forward movement recording mode (forward) → backward movement without forming dots". Will be. This cycle matches the pitch of the nozzles in the sub-scanning direction. The image obtained by this recording method has a constant recording ratio of 2: 1 in the forward motion recording mode and the backward motion recording mode in all regions (regions A, B, and C) as shown in FIG. .

FIG. 8 shows the number of nozzles in the printer 22 of this embodiment.
Shows how dots are printed when the number is adjusted to the number 48 provided in. As in FIG. 7, dots are formed during the forward movement in both the third and fourth recordings. That is, in FIG. 8 as well, the dot recording cycle in each recording mode matches the nozzle pitch. The paper feed amount is 4 for the second and third recordings.
The amount corresponds to 7 rasters, and is equal to 50 rasters at the time of the fourth recording. From the relationship between the nozzle pitch and the number of nozzles,
Since all rasters cannot be formed with a fixed paper feed amount, a slightly irregular paper feed is performed in this way. It can be seen that the image obtained by such a recording method has a constant recording rate in each mode in all regions as shown in FIG.

According to such a printing apparatus, the recording rates of the dots formed during the forward movement of the head and the dots formed during the backward movement are constant in all areas. As described above, in the printer 22 of the present embodiment, the dots formed during the forward movement and the dots formed during the backward movement have slightly different hues, but by controlling the dot recording mode,
In this way, rasters with different hues have very fine periods,
In addition, since it appears at a constant recording rate in any area of the image, a good image without color unevenness can be obtained.

In the above printing apparatus, the paper feed amount does not need to be maintained at a substantially constant value. FIG. 9 is an explanatory diagram showing a second pattern in which dots are formed by the control used in this embodiment. Here also, the state of dot formation is shown with the number of nozzles reduced to 11 to avoid complication. However, the nozzle pitch is equivalent to three rasters as in this embodiment (see FIG. 6).

In this pattern, the first to third dots are printed with the paper feed amount as one raster. As a result, the image corresponding to the area D in FIG. 9 is completed.
The recording of the area E immediately below is started. Even if the paper feed amount is set in this manner, dots are formed in a cycle of three rasters of “forward → return → forward”. Therefore, as is clear from FIG. Is constant, and a good image without color unevenness can be obtained. In addition, if such recording is performed, the sub-scan with a large paper feed amount can be performed at the time of the head re-movement of the head that does not form dots, so that there is an advantage that the printing time can be reduced.

In the above description, the case where three rasters are recorded in a cycle of “forward → return → forward” has been described, but another recording method in which three rasters are defined as one cycle may be employed. For example, "go->
It is conceivable that "go-to-go" or "go-to-go-to". Further, not only the combination of the forward motion recording mode and the backward motion recording mode but also the bidirectional recording mode may be used for recording three rasters in one cycle. The bidirectional printing mode is a mode in which only a part of dots are formed during a forward movement of a certain raster, and the remaining dots are formed during a backward movement, that is, printing in which one raster dot is completed by two reciprocating main scans. Mode.

FIG. 10 shows an example of dot formation using such a recording mode. FIG. 10 shows that in the third dot recording, the head forms a part of the raster dots while moving forward, and in the fourth dot recording, the head forms the remaining dots of the raster while moving backward. It shows how to do. That is, the third and fourth recordings are performed in the bidirectional recording mode together. Therefore,
In FIG. 10, three rasters of “forward → return → bidirectional recording (bi)” are defined as one cycle, and an image is recorded by repeating this.
Also in the case of such recording, as is clear from FIG. 10, the dot recording rate in each recording mode is constant in all the regions (regions F to H in FIG. 10), and a good image without color unevenness is obtained. be able to.

In the above description, the case where the nozzle pitch is 3 has been described as an example, but the nozzle pitch may be another odd number. For example, when the nozzle pitch is five times the image recording density, the forward motion recording mode and the reverse motion recording mode such as “forward → return → forward → return → forward” and “forward → return → return → return → forward”. And various recording methods in which five rasters are defined as one cycle. In this case, the difference between the number of times both are used in one cycle is set to be an odd number. In particular, it is necessary to alternately use the forward movement recording mode and the backward movement recording mode as much as possible. Preferred for efficiency. The same applies when the ratio between the nozzle pitch and the image recording density is another odd number.

When the bidirectional recording mode is used, for example, when the nozzle pitch is five times the image recording density,
Various combinations such as "going-to-go-to-go-to-go-to-bi" can be considered. In this case, the number of rasters recorded in the bidirectional recording mode is an odd number, and the difference between the number of rasters recorded in the two types of recording modes of the forward motion recording mode and the backward motion recording mode is 0 or It is preferable from the viewpoint of dot formation efficiency that dots are formed so that the number of dots becomes two or more even numbers. In particular, it is preferable to use the bidirectional recording mode once and use the other two recording modes in the same number. The same applies when the ratio between the nozzle pitch and the image recording density is another odd number.

Further, such a recording method may be used only in a certain image area. In the case where dots are formed using various recording modes at a period that matches the nozzle pitch, there are always rasters that do not form dots and rasters that are formed by bidirectional main scanning. Therefore, compared to a case where dots are formed in all main scans by simply repeatedly performing the forward movement recording mode and the backward movement recording mode, dot formation efficiency is reduced. Printing performed at a cycle that matches the nozzle pitch is used only in the area where color unevenness in the sub-scanning direction is easily visible, and in other areas, dot printing is performed by alternately using the forward movement recording mode and the backward movement recording mode. In this case, a decrease in dot formation efficiency can be minimized, so that a decrease in printing speed can be prevented while improving image quality.

The area where color unevenness in the sub-scanning direction is easily visible is, for example, a solid area painted with a constant hue in the sub-scanning direction, such as a blue sky in a landscape photograph or a bar graph created by graphics. Such cases may be mentioned. Such an area can be determined in image processing by the color correction module 98 or the halftone module 99 of the printer driver 96.

Further, in the printing apparatus, since the control of the head for performing dot recording includes processing by a computer, the embodiment as a recording medium on which a program for realizing such control is recorded is described. Can also be taken. Examples of such a storage medium include a flexible disk, a CD-ROM, a magneto-optical disk, an IC card, a ROM cartridge, a punched card, a printed matter on which a code such as a barcode is printed, and a computer internal storage device (such as a RAM or a ROM). Various computer readable media are available, such as memory and external storage. Further, an embodiment as a program supply device that supplies a computer program for realizing a head control function for performing the above-described dot recording on a computer via a communication path is also possible.

Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various embodiments can be implemented without departing from the gist of the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image processing system using a printer of the present invention.

FIG. 2 is a schematic configuration diagram of a printer of the present invention.

FIG. 3 is an explanatory diagram illustrating a schematic configuration of a dot recording head of the printer of the present invention.

FIG. 4 is an explanatory diagram showing a dot formation principle in the printer of the present invention.

FIG. 5 is an explanatory diagram showing an example of nozzle arrangement in the printer of the present invention.

FIG. 6 is an enlarged view of a nozzle arrangement in the printer of the present invention and an explanatory diagram showing a relationship with a formed dot.

FIG. 7 is an explanatory diagram showing a state in which dots are formed by bi-D recording according to the present invention.

FIG. 8 is an explanatory diagram showing a state of bi-D (Bi-D) recording in the present embodiment.

FIG. 9 is an explanatory diagram showing a pattern for forming second dots by bi-D (Bi-D) recording of the present invention.

FIG. 10 is an explanatory diagram showing a pattern for forming a third dot by bi-D (Bi-D) recording of the present invention.

FIG. 11 is an explanatory diagram showing how dots are formed by conventional bi-D (Bi-D) recording.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 12 ... Scanner 21 ... Color display 22 ... Color printer 23 ... Paper feed motor 24 ... Carriage motor 26 ... Platen 28 ... Print head 31 ... Carriage 32 ... Operation panel 34 ... Sliding shaft 36 ... Drive belt 38 ... Pulley 39 ... Position detection Sensor 40 Control circuit 61, 62, 63, 64, 65, 66 Ink ejection head 67 Inlet tube 68 Ink passage 71 Black ink cartridge 72 Color ink cartridge 90 Personal computer 91 Video driver 92 input unit 95 application program 96 printer driver 97 rasterizer 98 color correction module 99 halftone module

Claims (7)

[Claims] 1. A main scanning device that reciprocates a head and a print medium relatively and a sub-scanning device that relatively moves the head and a printing medium in a direction intersecting the main scanning, and performs a main scanning at a predetermined pitch in the sub-scanning direction. Using a plurality of nozzles arranged in the head,
A printing apparatus capable of printing an image by forming a plurality of dots having different hues on the print medium in accordance with input image data, wherein the predetermined pitch is an image in the sub-scanning direction. It is an odd multiple of the recording pitch, and can form dots for each color during both reciprocating movements in main scanning, and the order in which ink of each color is ejected differs between the forward movement and the backward movement. Having a head, a forward movement recording mode in which all dots of one raster are recorded during a single forward movement in the main scanning, a reverse movement recording mode in which all dots of one raster are recorded during a single backward movement, and both reciprocating movements. At least two types of printing modes are mixed among three types of printing modes of a bidirectional printing mode for printing all dots of one raster by movement, and each printing mode is set. Printing apparatus comprising a raster recording control means for controlling the recording mode for each raster so that the recording cycle in the sub-scanning direction comprising a combined coincides with the pitch of the nozzle. 2. The printing apparatus according to claim 1, wherein the raster recording control means sets an odd difference between the numbers of rasters recorded in the two types of recording modes, the forward motion recording mode and the backward motion recording mode. A printing apparatus which controls the use of the printing mode so that the printing cycle in the sub-scanning direction, which is a combination of the printing modes, matches the nozzle pitch. 3. The printing apparatus according to claim 1, wherein the raster recording control means is arranged such that the number of rasters recorded in the bidirectional recording mode is an odd number, and the forward motion recording mode and the backward motion recording. The use of the printing mode is controlled so that the difference between the numbers of rasters printed by the two printing modes is 0 or an even number of 2 or more, and the printing cycle in the sub-scanning direction, which is a combination of the printing modes, is A printing device that is a means for matching the nozzle pitch. 4. The printing apparatus according to claim 1, wherein the dots are formed by the raster recording control means only in a predetermined raster area of the input image data which affects the image quality, and in other areas, the dots are formed. A printing apparatus comprising a recording method selecting unit for forming dots by alternately using a forward motion recording mode and a backward motion recording mode. 5. While performing main scanning for reciprocating a head and a print medium relatively and sub-scanning for relatively moving in a direction intersecting with the main scanning, the main scanning is performed at a predetermined pitch in the sub-scanning direction. Using a plurality of nozzles arranged in the head,
A printing method capable of printing an image by forming a plurality of dots having different hues on the print medium in accordance with input image data, wherein the head is arranged such that the predetermined pitch is an image in the sub-scanning direction. It is an odd multiple of the recording pitch, can form dots for each color during both reciprocating movements in main scanning, and the order in which ink of each color is ejected differs between the forward movement and the backward movement. A head, a forward movement recording mode in which all dots of one raster are recorded during a one-time movement in the main scanning, a backward movement recording mode in which all dots of one raster are recorded during a one-way movement, and both reciprocating movements. , At least two of the three recording modes of the bidirectional recording mode for recording all the dots of one raster are mixed, and a combination of the recording modes is used. Printing method for recording by controlling the recording mode for each raster so that the recording period of the sub-scanning direction coincides with the pitch of the nozzle made of. 6. A computer-readable recording medium for recording a program for printing an image by forming a plurality of dots on the printing medium in accordance with image data input by a printing apparatus, comprising: The difference between the number of rasters recorded in the forward movement recording mode in which all dots of one raster are recorded during one forward movement in scanning and the number of rasters recorded in the backward movement recording mode in which all dots of one raster are recorded during one backward movement is an odd number. Recording a program for realizing the function of controlling the use of the recording mode by a computer as described above. 7. A computer-readable recording medium for recording a program for printing an image by forming a plurality of dots on the print medium in accordance with image data input by a printing apparatus, comprising: The number of rasters recorded in the bidirectional recording mode in which all dots of one raster are recorded by both reciprocating movements in scanning is an odd number, and all dots of one raster are recorded during a single movement in main scanning. A function for controlling the use of the recording mode so that the difference between the number of rasters recorded in the motion recording mode and the number of rasters recorded in the reverse motion recording mode in which all dots of one raster are recorded at the time of one reverse motion is 0 or even or more. Recording medium for recording a program for realizing the program by a computer.