JP2004130545A - Inkjet recorder and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a recording image having a high image quality by suppressing occurrence of a joint streak effectively on the boundary of bands. <P>SOLUTION: In the inkjet recorder recording in units of a specified area by scanning an inkjet recording head ejecting ink drops having different volumes relatively with a recording medium, number of ink drops being ejected to each unit area of a specified size, obtained by dividing a joint part including the boundary of specified adjacent areas, is counted for respective ink drops of different volume (S402), the color region of an image being recorded in the unit area is judged based on the count (S403), a decimation rank of ink drops being ejected to an area in the vicinity of the boundary is determined based on the color region thus judged and the count (S404), and then the ink drops being ejected to an area in the vicinity of the boundary are decimated based on the decimation rank (S405). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink jet recording apparatus and an ink jet recording method, and more particularly to an ink jet recording apparatus that performs recording in a predetermined area by scanning an ink jet recording head that ejects ink droplets having different volumes relative to a recording medium. The present invention relates to a reduction in connecting streaks.
[0002]
[Prior art]
2. Description of the Related Art As an information recording apparatus in a word processor, a personal computer, a facsimile, or the like, a printer that records desired information such as characters and images on a sheet-shaped recording medium such as paper or film is widely used.
[0003]
Various methods are known as recording methods for printers. Ink jet methods have recently been used because non-contact recording is possible on recording media such as paper, colorization is easy, and quietness is high. It has attracted special attention, and its configuration includes a serial head that mounts a recording head that ejects ink in accordance with desired recording information and performs recording while performing reciprocal scanning in a direction that intersects the feed direction of a recording medium such as paper. The recording method is generally widely used because of its low cost and easy downsizing.
[0004]
In recent years, there has been a great demand for high-speed and high-quality inkjet printers. In order to achieve high image quality, it is common to reduce the ink volume (ejection amount) by minimizing the diameter of the ejection port (nozzle) and the foaming energy to enable recording of minute dots. It is. When printing with fine dots, granularity (roughness in highlights and the like) is suppressed, and the dot arrangement (dot pattern) in the region corresponding to the pixel is diversified, so that the overall gradation is improved. be able to.
[0005]
However, simply reducing the ink ejection amount of all nozzles greatly increases the recording resolution in each of the main scanning direction and the sub-scanning direction, so that the number of main scans increases and the feed amount in the sub-scanning direction increases. The recording speed decreases.
[0006]
In order to avoid such a decrease in printing speed, it has been practically used to print using two types of dots, a small dot and a large dot having a larger size. According to this, the granularity can be reduced by using small dots in the highlight portion, and a decrease in recording speed can be prevented by using large dots in the high density portion.
[0007]
To perform high-speed printing, it is effective to reduce the number of passes in multi-pass printing used for realizing high image quality. Here, the number of printing passes refers to the number of carriage scans required to complete printing in each area. For example, if printing can be performed in one pass while printing is currently being performed in two passes, the speed can be simply doubled.
[0008]
When a print head having a plurality of nozzles for ejecting ink scans in a direction intersecting the nozzle arrangement direction and performs printing in one pass, a band-like image area (band) is formed by one scan. It is formed.
[0009]
FIG. 15 is a diagram illustrating a state where printing is performed on the printing medium 8 by three scans in one pass. In the drawing, reference numerals 801 to 803 indicate bands recorded in each scan, reference numerals 811 and 812 indicate boundary portions which are boundary portions of the bands, and reference numerals 821 and 822 indicate connecting stripes appearing at the boundary portions.
[0010]
In one-pass printing, the amount of ink ejected onto the print medium at one time is larger than in multi-pass printing in which an image is formed by performing multiple scans. For this reason, although the degree differs depending on the printing medium and the properties of the ink, the bleeding of the ink on the printing medium in a portion where the printing duty is high (high-density portion) in one-pass printing is higher than when multi-pass printing is performed. And the extent of the connecting streak generated at the boundary between the bands becomes worse. That is, as the number of recording passes is reduced, the occurrence of a connecting streak between bands becomes more remarkable.
[0011]
In addition, a connecting streak between the bands is such that a plurality of ejection opening arrays (or recording heads) for ejecting inks of different colors (cyan, magenta, yellow, etc.) are arranged in parallel so as to intersect the main scanning direction. In a printer having a head configuration in a so-called side-by-side configuration, it becomes more noticeable. This is because the connection position of each color occurs in the same place.
[0012]
FIG. 16 is a diagram schematically illustrating an example of the recording head 1 in which seven ejection opening arrays are arranged side by side. In the X direction (scanning direction) from the left in the figure, a discharge port array 31 for cyan (C), a discharge port row 32 for magenta (M), and a discharge port row 33 for yellow (Y) are formed as Y discharge ports. Direction (sub-scanning direction), the discharge ports are shifted to the right by half the pitch in the Y direction, and the discharge port array 34 for cyan (C) and the discharge port for magenta (M) are displaced. An outlet row 35 and a discharge port row 36 for yellow (Y) are arranged. At the right end, a discharge port array 37 for black (BK) having about twice the number of discharge ports is arranged so that the discharge port rows 34 to 36 and the discharge ports are aligned in the Y direction.
[0013]
In the configuration of the recording head 1 shown in FIG. 16, the ejection ports of the three ejection port arrays 31 to 33 are aligned in the Y direction, and the ejection ports of the four ejection port arrays 34 to 37 are also aligned in the Y direction. I have. Therefore, when ink is ejected from all the ejection opening arrays in the recording scan by the recording head unit having such a configuration, three or four ink droplets (dots) are ejected at the same position.
[0014]
As described above, the connecting streak generated at the boundary between the bunts significantly lowers the recording quality, and the recorded image may be at a level that cannot withstand practical use.
[0015]
As a method of reducing such a connecting streak, recording data necessary for creating recording data for one band is read, an area near a connecting portion is divided, and the number of recording data is counted in each of the divided areas. A method has been proposed in which thinning processing is performed on print data in the vicinity of a connection portion in accordance with the count value (see, for example, JP-A-2002-96460).
[0016]
[Problems to be solved by the invention]
However, the above method is based on the premise that ink droplets are ejected from the recording head at the same ejection amount, and an ink jet printer that performs recording using ink droplets having different ejection amounts to record two types of large and small dots. It is not intended to be applied to Therefore, even if the above method is applied to an ink jet printer that performs recording using two types of dots, large and small, the connecting streak is not sufficiently reduced.
[0017]
On the other hand, as described above, it is very effective to perform recording using two types of dots, large and small, in order to improve image quality. For this reason, in a serial type printer that records using dots of different sizes, it is required to effectively suppress the occurrence of connecting streaks.
[0018]
This is not limited to the serial type ink jet printer, but is a problem common to ink jet recording apparatuses that perform recording by moving the recording head relative to the recording medium using ink droplets (dots) having different sizes (volumes). is there.
[0019]
The present invention has been made in view of the above-described circumstances, and effectively suppresses occurrence of a connecting streak at a boundary of a recording area, and can obtain a high-quality recorded image. The aim is to provide a method.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, an inkjet recording apparatus according to the present invention is an inkjet recording apparatus that performs recording in a predetermined area by scanning an inkjet recording head that ejects ink droplets having different volumes relative to a recording medium. So,
Counting means for counting the number of ink droplets ejected to the unit region for each ink droplet having a different volume, for each unit region of a predetermined size obtained by dividing a connecting portion including a boundary between the predetermined regions adjacent to each other,
Information obtaining means for obtaining relative information about an image recorded in the unit area based on a count result by the counting means;
Level determining means for determining a reduction level of ink droplets ejected to an area near the boundary based on the relative information and the count result;
A reduction unit configured to reduce ink droplets ejected to a region near the boundary based on the reduction level.
[0021]
In addition, the inkjet recording method of the present invention for achieving the above object is an inkjet recording method in which an inkjet recording head that ejects ink droplets having different volumes is relatively scanned with respect to a recording medium to perform recording in a predetermined area as a unit. So,
A counting step of counting the number of ink droplets ejected to the unit region for each ink droplet having a different volume, for each unit region of a predetermined size obtained by dividing a connecting portion including a boundary between the predetermined regions adjacent to each other,
An information obtaining step of obtaining relative information on an image recorded in the unit area based on a count result in the counting step;
Based on the relative information and the count result, a level determining step of determining a reduction level of ink droplets ejected to an area near the boundary,
A reduction step of reducing ink droplets discharged to a region near the boundary based on the reduction level.
[0022]
That is, according to the present invention, in an ink jet recording apparatus that performs recording in a predetermined area as a unit by relatively scanning an ink jet recording head that ejects ink droplets having different volumes with respect to a recording medium, a boundary between predetermined adjacent areas is determined. The number of ink droplets ejected to the unit area is counted for each ink droplet having a different volume for each unit area of a predetermined size obtained by dividing the connecting portion including the recording medium, and is recorded in the unit area based on the count result. Based on the relative information and the count result, a reduction level of the ink droplet ejected to the region near the boundary is determined, and the ink droplet ejected to the region near the boundary is determined based on the reduction level. Reduce.
[0023]
In this way, the relative information on the image recorded in the unit area and the number of ink droplets of different volumes ejected to the unit area are used to cause ink bleeding or inflow near the boundary in the unit area. It is appropriately determined whether or not a connecting streak is likely to occur, and it is possible to reduce the number of ink droplets discharged to a region near the boundary according to the determination result.
[0024]
Therefore, when printing is performed using ink droplets of different volumes, it is possible to effectively suppress the occurrence of connecting streaks at the boundary and obtain a high-quality recorded image.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In each drawing, the same or corresponding parts are represented by the same reference numerals.
[0026]
In the embodiment described below, a serial type printer will be described as an example of a recording apparatus using an inkjet recording method.
[0027]
In the present specification, “recording” (sometimes referred to as “printing”) refers not only to forming significant information such as characters and figures, but also to meaningless or insignificant human perception. Regardless of whether or not the image is exposed, a case where an image, a pattern, a pattern, or the like is widely formed on a recording medium or a case where the medium is processed is also described.
[0028]
In addition, the term “recording medium” refers to not only paper used in general recording devices, but also a wide range of materials that can accept ink, such as cloth, plastic films, metal plates, glass, ceramics, wood, and leather. Shall be.
[0029]
Further, “ink” (sometimes referred to as “liquid”) is to be interpreted broadly as in the definition of “recording (printing)”, and when applied on a recording medium, an image or pattern , Or a liquid that can be used for forming a pattern or the like, processing a recording medium, or processing ink (for example, coagulation or insolubilization of a colorant in ink applied to a recording medium).
[0030]
(Configuration of recording device)
FIG. 1 is a schematic perspective view showing a main part configuration of an ink jet printer as one embodiment according to the present invention.
[0031]
In FIG. 1, a plurality of (four) head cartridges 1A, 1B, 1C, 1D each including an ink tank for storing ink and a recording head for discharging ink supplied from the ink tank are exchangeable with a carriage 2. It is installed. Each of the cartridges 1A to 1D corresponds to a different color (for example, cyan, magenta, yellow, and black) used for color recording, and is provided with a connector for receiving a signal for driving a recording head. In the following description, when referring to the entirety or any one of these head cartridges 1A to 1D, they will be simply indicated by recording means (recording head or head cartridge) 1.
[0032]
Each recording means 1 is configured to be removably attached to a predetermined position of a carriage 2, and a connector holder (electric connection unit) for transmitting a drive signal or the like via a connector of the recording means 1 to the carriage 2. ) Is provided. The carriage 2 is movable by being guided by a guide shaft 3 installed in the main body of the apparatus along the main scanning direction. The carriage 2 is driven by a main scanning motor 4 via a timing belt 7 wound around a motor pulley 5 and a driven pulley 6, and its position and movement are controlled.
[0033]
The recording medium 8 such as a sheet of paper or a thin plastic plate is conveyed (paper-fed) through a position (recording section) facing the discharge port surface of the recording head 1 by rotation of two pairs of conveying rollers 9 and 10 and 11 and 12. You. The recording medium 8 has its back surface supported by a platen (not shown) so that a flat recording surface can be formed in the recording section. In this case, each of the cartridges 1 mounted on the carriage 2 is held such that their discharge port surfaces protrude downward from the carriage 2 and face the recording medium 8 substantially in parallel between the two pairs of transport rollers. ing.
[0034]
A recovery device 14 for the recording head 1 is provided near the home position of the carriage 2. The recovery device 14 includes a blade 18 for cleaning the ejection surface of the recording head 1, a mounting table 18 for mounting the blade, four caps 15 provided to cover each recording head, and a recording head 1. When the cover is covered with a cap, the suction pump 16 sucks concentrated ink in which water in the vicinity of the discharge port surface has evaporated, and a pipe member 27 connecting the suction pump 16 and each cap 15.
[0035]
(Configuration of recording head)
The recording head 1 is an ink jet recording unit that ejects ink using thermal energy, and includes an electrothermal converter for generating thermal energy. The recording head 1 performs recording by ejecting ink from ejection ports by utilizing pressure changes caused by growth and contraction of bubbles caused by film boiling caused by thermal energy applied by the electrothermal transducer.
[0036]
FIG. 2 is a partial perspective view schematically illustrating a part of the main structure of the ink ejection unit 13 of the recording head 1. In FIG. 2, a plurality of discharge ports (nozzles) 22 are formed at a predetermined pitch on a discharge port surface 21 facing the recording medium 8 with a predetermined gap (about 0.5 to 2 mm). An electrothermal converter 25 such as a heating resistor is disposed along a wall surface of each flow path 24 connecting the chamber 23 with each discharge port 22 to generate energy of an ink discharge amount.
[0037]
In the present embodiment, the recording head 1 is mounted on the carriage 2 in a positional relationship such that the ejection ports 22 are arranged in a direction intersecting the scanning direction of the carriage 2. In this way, the corresponding electrothermal transducer 25 is driven (energized) based on the image signal or the ejection signal to cause the ink in the flow path 24 to boil, and the ink generated from the ejection port 22 is ejected by the pressure generated at that time. The recording head 1 is configured.
[0038]
The nozzle configuration of the recording head 1 used in the present embodiment is the same as that shown in FIG. 16 described above with respect to the conventional example. However, from two ejection port arrays provided corresponding to each color of CMY, a small-sized (for example, 2 ng) ink droplet for recording a small-sized dot and a large-sized dot for recording a large-sized dot are recorded. A large-volume (for example, 4 ng) ink droplet is selectively ejected by, for example, changing the shape of a drive signal applied to the electrothermal transducer.
[0039]
(Configuration of control circuit)
FIG. 3 is a block diagram showing a schematic configuration of a control circuit in the ink jet printer shown in FIG.
[0040]
In FIG. 3, a controller 100 is a main control unit and includes, for example, a CPU 101 in the form of a microcomputer, a ROM 103 storing programs and necessary tables and other fixed data, an area for developing image data, an area for work, and the like. It has a RAM 105.
[0041]
The host device 110 is a supply source of image data (in addition to being a computer that creates and processes data such as images related to printing, it may be in the form of a reader unit for reading images). Image data, other commands, status signals, and the like are transmitted and received to and from the controller 100 via the interface (I / F) 112.
[0042]
The operation unit 120 is a group of switches that receive an instruction input by the operator, and includes a power switch 122, a switch 124 for instructing the start of printing, a recovery switch 126 for instructing activation of suction recovery, and the like.
[0043]
The head driver 140 is a driver that drives the electrothermal transducer 25 provided in the print head 1 according to print data or the like. The head driver 140 includes a shift register that aligns print data in accordance with the position of the electrothermal converter 25, a latch circuit that latches at appropriate timing, and a logic circuit that energizes the electrothermal converter 25 in synchronization with a drive timing signal In addition to the elements, it has a timing setting unit and the like for appropriately setting the drive timing (ejection timing) for dot formation alignment.
[0044]
The recording head 1 may be provided with a spare sub-heater in addition to the electrothermal transducer 25 for discharging ink. The sub-heater adjusts the temperature for stabilizing the ink ejection characteristics, and is formed on the substrate of the recording head 1 and / or attached to the recording head body or the head cartridge simultaneously with the electrothermal transducer 25. It can be in the form.
[0045]
The motor driver 150 is a driver for driving the main scanning motor 4 that moves the carriage 2, the sub-scanning motor 162 is a motor used to convey (sub-scan) the recording medium 8, and the motor driver 160 is a sub-scanning The driver of the motor 162.
[0046]
(Connection processing)
In the following, a description will be given of a bridging process that suppresses bridging streaks that occur at the boundary between bands in the inkjet printer having the above configuration.
[0047]
FIG. 4 is a flowchart of a process executed from reception of recording data for one band to recording in this embodiment. As will be described later, it is not possible to correctly determine whether or not a streak is likely to occur at the boundary of a band without referring to the recording data of the two adjacent bands. And then start.
[0048]
First, when print data for one band is received from the host device (step S401), a portion of the print data near the boundary with the band from which the print data was previously received is divided into a predetermined unit area, and The number of print data (the number of dots) for each color is counted for each area (step S402), and information on the hue and saturation of the area of interest is determined as a color gamut from the dot count value for each color (step S403). .
[0049]
Then, in this color gamut, thinning-out is performed by referring to a graph (or table) showing the relationship between the dot count value (or print duty) for each unit area obtained by the sum of the dot count values for each color and the thinning-out rank. The thinning rank of the processing area is determined for each ink (step S404), and the SMS thinning processing is executed according to the determined thinning rank (step S405).
[0050]
Thereafter, it is determined whether or not all the processing for the recording data of one band has been completed (step S406). For example, the connection processing from steps S402 to S405 is similarly performed on the unit area that has not been processed. Do. On the other hand, if it is determined in step S406 that the processing for the recording data of one band has been completed, the recording of the band for which the recording data has been received first is executed (step S407).
[0051]
In the present embodiment, in the dot count process of step S402, a color gamut determination process for determining a color gamut is performed so that a seamless process can be effectively performed when printing is performed using dots of different sizes. And the dot count for thinning used in the thinning processing are separately performed.
[0052]
By performing the above-described processing, even when printing is performed using dots of different sizes, it is possible to obtain a high-quality print image by suppressing the occurrence of connecting streaks.
[0053]
The processing executed in each step in the connection processing of the present embodiment described above will be described in more detail below.
[0054]
(Dot count)
The dot count is performed for all the inks used for recording, that is, for the color, cyan, magenta, and yellow recording data, and the sum of the dot counts obtained from each is calculated as the dot count value (or total dot count). Dot count value). The dot count value of each color and the total dot count value obtained here are stored in a predetermined storage area for use in processing described later.
[0055]
Here, supplementing the dot count value, "the dot count value is 1" means that one dot exists in one pixel, and if it is 2, it means that two dots exist in one pixel. Is shown.
[0056]
The dot count is performed in a divided area near the boundary of the band, and the size of one area is 16 rasters in the recording medium transport direction (sub-scanning direction) and 16 dots (pixels) in the carriage scanning direction. An area having a size of a minute is defined as a unit (hereinafter also referred to as “dot count area”).
[0057]
FIG. 11 is a diagram illustrating a dot count area, a link portion, and a thinning area according to the present embodiment. As shown in (a), a dot count of 16 rasters in the direction in which the recording medium is conveyed (Y direction) and 16 dots in the carriage scanning direction (X direction) near the boundary between the bands 801 and 802 is counted. The dot count area is continuous from the left side to the right side in the figure, such as 841, 842,..., 84n-1, 84n.
[0058]
Further, a portion composed of the four lowermost rasters of the band 801 in the dot count area is referred to as a connecting portion 840. The connecting portion is a portion that actually connects the two bands, and since a streak easily occurs at this portion, the connecting portion is subjected to a thinning process described later. The connecting portion 840 is composed of a plurality of thinning regions 841 corresponding to the respective dot count regions from left to right in the drawing.
[0059]
FIG. 14B is an enlarged view of one thinning region 841. As shown, the thinning area 841 is made up of 16 dots in the four lowermost rasters of the band 801, with the upper two rasters being called upper and the lower two rasters being called lower.
[0060]
Here, the total dot count value is simply the sum of the dot count values of cyan, magenta, and yellow. However, if the influence on the occurrence of the connecting streak differs depending on the color, the value of each color is A weighted calculation may be performed. In addition, when conditions such as a different discharge amount for each color (for example, a certain color has a larger discharge amount), it is preferable to calculate the total dot count value in consideration of such conditions.
[0061]
As described above, in the dot count processing of the present embodiment, since only a small area near the boundary is targeted as the dot count area in the print data of one band, the processing load is small. Thus, even when the time allocated to the processing is short, the processing can be sufficiently performed.
[0062]
In addition, not only the connecting portion where a streak easily occurs but also a region including the connecting portion and being larger in the vertical direction (sub-scanning direction) than the connecting portion is used as a dot count region, so that the state of recording dots above and below the connecting portion can be grasped. I can do it. In other words, it is possible to more accurately determine whether or not the dot arrangement is likely to cause a connecting streak, and it is possible to perform a more efficient connecting process.
[0063]
When the dot count is performed only for one band of print data, the amount of ink bleeding that causes a connecting streak in the area can be assumed. The degree of the influence of can not be grasped. The occurrence of the connecting streak varies depending on the amount of ink near the connecting portion in the adjacent band. For example, if there is a certain amount of ink at the joint of the band to be recorded next, the streaks are likely to occur due to mutual ink bleeding, but if the amount of ink is small, the band recorded first Although there is a possibility that ink bleeding may occur, it is unlikely that it will become a connecting streak.
[0064]
Here, the generation mechanism of the connecting streak will be described with reference to FIG. In the figure, the dots of the upper four rasters belong to the band recorded earlier, and the dots of the lower four rasters belong to the band recorded later. (A) shows a state where the connection processing is not performed, and (b) shows a state where the connection processing of the present embodiment is performed.
[0065]
Where the fixation is promoted with the ink of the previously recorded band slightly blurred, the next band is recorded. Here, it is considered that, in the process in which the ink in the next band permeates into the inside or the surface of the recording medium, it is drawn and flows into the band region previously recorded. At this time, as shown in (a), if no processing is performed on the joint portion, the amount of ink at the boundary between the bands increases, and the density of the joint portion becomes higher than that of the other portions, resulting in a streak. It is assumed to be visible.
[0066]
Therefore, in order to suppress the occurrence of the connecting streak, it is effective to reduce the amount of ink at the boundary portion between the band to be recorded first and the band to be recorded later, that is, to thin out the recording data. In this case, the thinning may be performed in only one of the bands, or the thinning processing may be performed in both the bands. (B) shows an example of a case where the linking process for thinning out the recording data of the band recorded earlier is performed. In this case, the ink of the band recorded later flows into the band recorded earlier. However, the density is appropriate, and no streaking occurs.
[0067]
As described above, since the cause of the occurrence of the connecting streak is caused by the ink amount of the band on both sides of the boundary, the connecting line is generated by setting the dot count area including the connecting portion as the target of the dot count as described above. It is possible to more accurately determine whether or not it is easy, and it is possible to efficiently suppress the connecting streak.
[0068]
Further, for the two bands adjacent to the boundary, at the time of dot counting, one of the band recorded first and the band recorded later may be weighted. For example, if there is a high tendency that the occurrence of streaks at the connection is caused by the ink amount of the band to be recorded first, the dot count value of the band to be recorded first is increased by 1.2 times, and the band of the band to be recorded first is increased. It is also considered effective to consider the effect of the ink amount.
[0069]
(Color gamut judgment)
In this specification, hue and saturation are collectively referred to as a color gamut. FIG. 6 is a diagram showing the division of the color gamut in the present embodiment, FIG. 7 is a diagram showing an example of the dot count value of each ink in a certain dot count region, and FIG. 8 is a diagram showing the dot count value, hue and saturation. FIG. Hereinafter, an example of the color gamut determination method of the present embodiment will be described with reference to these drawings.
[0070]
In this specification, a color represented by only one ink is expressed as a primary color, a color expressed by two inks is expressed as a secondary color, and a color expressed by three inks is expressed as UC.
[0071]
First, referring to FIG. 7, the primary color dot count value used for color gamut determination is calculated from the dot count value of each ink obtained in each dot count area by the dot count process described above. A method for obtaining the color dot count value and the UC dot count value will be described.
[0072]
If the dot count value for each color is as shown in FIG. 7, the count value of the ink with the smallest value, that is, the count value common to the three inks, is taken as the UC dot count value (UC). A value obtained by subtracting the UC dot count value from the count value of the ink having the second lowest value, that is, the count value common to only the two inks is set as the secondary color dot count value (D2). Then, a value obtained by subtracting the secondary color dot count value from the count value of the ink having the largest value, that is, the count value of only one ink is set as the primary color dot count value (D1).
[0073]
Next, a method of determining the hue direction will be described. Here, the hue direction is determined on the outermost circumference in FIG. 6, that is, whether it is a primary color, a secondary color, or an intermediate color.
[0074]
In the present embodiment, the hue is, as shown in FIG. 8A, the dot count value of the primary color (D1) shown on the horizontal axis and the dot count value (D2) of the secondary color shown on the vertical axis. Determined by the ratio.
[0075]
Specifically, a value (D1 / 2) obtained by dividing the dot count value of the primary color by 2 and a value (D2 / 2) obtained by dividing the dot count value of the secondary color by 2 are obtained. The dot count value of the next color (D2) and the dot count value of the primary color (D1) are compared. If the value (D1 / 2) obtained by dividing the primary color dot count value by 2 is larger than the secondary color dot count value (D2), it is determined that the hue is the primary color. On the other hand, when the value (D2 / 2) obtained by dividing the dot count value of the secondary color by 2 is larger than the dot count value (D1) of the primary color, it is determined that the hue is the secondary color. Otherwise, it is determined that the hue is intermediate.
[0076]
Next, the determination of the saturation direction will be described. Here, it is determined whether the saturation direction is near the center of FIG. 6, near the circumference, or in the middle.
[0077]
In this embodiment, the saturation is determined by the ratio between the sum of the dot count values of the primary color and the secondary color shown on the horizontal axis and the dot count value of UC shown on the vertical axis, as shown in FIG. It is determined.
[0078]
Specifically, a value {(D1 + D2) / 2} obtained by dividing the sum of the dot count values of the primary color and the secondary color by 2 and a value (UC / 2) obtained by dividing the dot count value of UC by 2 Are compared with the UC dot count value (UC) and the sum of the dot count values of the primary color and the secondary color (D1 + D2). If the value obtained by dividing the sum of the dot count values of the primary color and the secondary color by 2 {(D1 + D2) / 2} is larger than the UC dot count value, the saturation is high saturation close to the circumference. Is determined. On the other hand, when the value (UC / 2) obtained by dividing the dot count value of UC by 2 (UC / 2) is larger than the sum (D1 + D2) of the dot count values of the primary color and the secondary color, the saturation is low saturation close to the center of the circle. It is determined to be a degree. In other cases, it is determined that the saturation is intermediate.
[0079]
As described above, the color gamut of the dot count area is determined. Here, the method of determining hue and saturation is simply expressed as
Hue:
If D1 / 2> D2, primary color area
If D2 / 2> D1, the secondary color area
Other than the above, the intermediate hue area
saturation:
If (D1 + D2) / 2> UC, the high saturation area
If UC / 2> (D1 + D2), low saturation area
Other than the above, the middle saturation area
It becomes.
[0080]
As described above, in the present embodiment, the color gamut is finely divided, so that it is easy to cope with differences in the appearance and behavior of the connecting streaks caused by the number and characteristics of the ink used.
[0081]
(Decimation rank decision)
In the present embodiment, the relationship between the dot count value and the thinning rank is shown for each of the inks used in seven areas (cyan, magenta, yellow, blue, green, red, and UC) of the color gamut shown in FIG. A graph (or table) is prepared, and for the other intermediate regions, thinning ranks are calculated from the graphs of these seven regions. For this reason, the data amount of the graph showing the thinning rank can be reduced.
[0082]
As an example of a method of calculating a thinning rank in each graph, an average rank of a primary color and a secondary color is set for an intermediate region in a hue direction, and high saturation and low saturation are set for an intermediate region in a saturation direction. There is a method of adopting a high degree of thinning rank.
[0083]
What is the area where the thinning process is performed in the present embodiment? As described with reference to FIG. 11, this is a thinned area 841 composed of 16 dots in the four rasters at the bottom of the band 801. Furthermore, the four rasters to be processed are divided into two areas of two rasters (also referred to as upper) on the paper discharge side and two rasters (also referred to as lower) on the paper feed side, and a thinning rank is determined for each of them. Prepare different thinning rank graphs so that they can be determined.
[0084]
Therefore, the number of thinning rank graphs prepared in the present embodiment specifies the thinning rank for each type of ink (cyan, magenta, yellow) and divides the thinning region into two.
7 (color gamut) × 3 (the number of inks) × 2 (the number of divisions of the thinning region) = 42
It becomes.
[0085]
From the 42 graphs prepared in this way, the thinning rank is determined using six graphs corresponding to the color gamut of the focused dot count region determined by the above color gamut determination. FIG. 9 shows an example of a thinning rank graph in which the color gamut corresponds to blue, and FIG. 10 shows an example of a thinning rank graph in which the color gamut corresponds to red. Note that the values of the decimation ranks in FIGS. 9 and 10 indicate how many of the eight significant data are decimated, and the decimation rank 1 is one of the eight significant data. Is thinned out, and a thinning rank 8 indicates that all data is thinned out.
[0086]
With reference to such a thinning rank graph, a thinning rank used in the following SMS thinning processing is determined based on the total dot count.
[0087]
(SMS thinning process)
The SMS thinning process will be briefly described. Each time there is significant recorded data, the counter value (specific bit, here, MSB; most significant bit) designated by the counter (register) is read, and if the value is 1, the recorded data is recorded and the counter is shifted to the right. Move (shift) one. On the other hand, if the counter value is 0, the recording data is decimated and the counter is moved right by one. When the counter moves to the rightmost, it returns to the leftmost again. This is a processing method in which thinning dots are determined by repeating this processing each time print data arrives.
[0088]
The SMS thinning process will be described more specifically with reference to FIGS. In FIGS. 12 and 13, in the recording data, a portion where data exists is indicated by ○, and a portion where no data exists is indicated by ×. The data of interest is indicated by arrows. Regarding the counter value, the place where recording is performed is indicated by 1, the place where recording data is thinned is indicated by 0, and the counter value designated by the counter is indicated by an arrow.
[0089]
FIG. 12A shows the original print data and the counter value. In (b) showing the processing of the first print data, the first print data is ○ and the counter value is 0, so the first print data is thinned out. Therefore, the first print data after the processing becomes x, and the counter moves one position to the right. Since there is no recording data at the next position, it remains as is, and the counter also remains at the position without moving. Since the third print data shown in (c) is ○ and the counter value is 1, the print data remains as it is, and the counter is shifted by one to the right. In this way, the recording data is thinned out at a rate of one out of four (thinning rank 2), and the data after processing the original data is as shown in (d).
[0090]
In FIG. 13, since the thinning-out processing area is 4 rasters, an area of 8 dots in the main scanning direction and 4 rasters in the sub-scanning direction (an area where the thinning-out processing area in the present embodiment is halved in the main scanning direction) 2) shows the state of the SMS thinning process, and here, the case where the thinning rank is set to the discharge side 2 and the feed side 4 is shown.
[0091]
In FIG. 13, as shown in FIG. 13A, the first raster, the second raster, the third raster, and the fourth raster are referred to from the discharge side. The SMS thinning process according to the present embodiment is performed for each raster from the raster on the paper discharge side, and when the processing of one raster is completed, the process proceeds to the processing of the next raster.
[0092]
In the example shown here, it is assumed that the counter position does not return to the initial position even if the thinning level changes. Further, the counter is not returned to the initial position even if the thinning region moves to an adjacent region in the same band, and the counter position is stored in the same band. On the other hand, when the processing has shifted to a different band, the counter position is returned to the initial position. Also, it is assumed that the counter initial position in the first processing area of one band is randomly specified.
[0093]
As a result of such processing, the first to fourth rasters are processed as shown in FIGS. 8B to 8E, and as a whole, as shown in FIG.
[0094]
As described above, the thinning rank is determined from the dot count value in the vicinity of the connecting portion, and the SMS thinning process is performed to suppress the connecting streak.
[0095]
(Processing for different dot sizes)
The connection processing described above does not consider the case where there are a plurality of dot sizes. Even if the connection processing is directly applied to an ink jet printer that records using two types of large and small dots having different sizes, the effect of suppressing the connection streaks can be obtained. Not enough. In view of this point, the present embodiment performs processing as described below, and effectively suppresses a continuous line when printing is performed using two types of large and small dots having different sizes.
[0096]
In the present embodiment, when printing is performed using large and small dots having different sizes, the dot count for color gamut determination for color gamut determination and the dot count for thinning used for thinning processing are separately provided as dot counts. It is configured to perform. The following describes each dot count.
The color gamut determination dot count is performed by taking into account the dot size for each color (cyan, magenta, yellow). Specifically, for a certain ink, the number of large dots and the number of small dots are counted, and a value obtained by adding a value obtained by multiplying the number of large dots and the number of small dots by ２ is added. Is the dot count value of the ink. The reason why the number of small dots is multiplied by か ら is that the ratio of the volume (ejection amount) of large and small dots is 2 to 1 in this embodiment, and the volume ratio of small dots to large dots is large. The value to be multiplied may be set in accordance with. In the subsequent color gamut determination, the hue direction and the saturation direction are determined in the same manner as described above, and the color gamut is determined.
[0097]
On the other hand, the thinning dot count does not perform the small dot count for each color, but performs only the large dot count, and calculates the total dot count that is the sum of cyan, magenta, and yellow. A thinning rank is determined from the total dot count value and a thinning rank graph obtained from the previously determined color gamut, and thinning processing is performed on large dots.
[0098]
Normally, printing using both large and small dots is a mode for printing with higher image quality.Therefore, multi-pass printing is performed to prevent so-called banding such as uneven ejection amount of each printing nozzle and dot landing error. Is performed. When multi-pass printing is performed, the amount of ink ejected in one scan is reduced, so that the possibility of ink flowing into a band printed earlier from a small dot is further reduced. Originally, the ejection amount of a small dot is half that of a large dot, so the fixing time on a recording medium is short. However, by performing multi-pass printing, the number of dots ejected in one scan is reduced. It hardly affects the occurrence of connecting streaks. For the reasons described above, in the present embodiment, the thinning process is executed only for large dots.
[0099]
On the other hand, in the color gamut determination, not only the large dots but also the small dots are counted. This is because the color gamut cannot be accurately determined by the dot count of only the large dots. That is, when an image is printed using both large and small dots, small dots are usually used in order to reduce the graininess caused by the use of large dots in a low density portion. The number of large dots increases and the density of large dots becomes inconspicuous.The use of large dots is started, and the ratio of large and small dots is controlled to change for each color and for each input density. This is because it is highly likely to affect the determination.
[0100]
FIG. 14 shows six graphs in the case where the color gamut is determined to be blue as an example of a graph showing the thinning rank when printing is performed using large and small dots in the present embodiment. As is clear from this figure, the thinning rank used when printing using large and small dots in the present embodiment is shifted in the direction of less thinning as a whole compared to the thinning rank shown in FIG. ing. This is because the thinning rate can be set lower in consideration of the fact that the occurrence of a connecting streak is suppressed by performing multi-pass printing.
[0101]
As described above, according to the present embodiment, even when printing is performed using ink droplets having different volumes, the occurrence of connecting streaks at band boundaries is effectively suppressed, and a high-quality printed image is obtained. be able to.
[0102]
[Modification]
In the above-described embodiment, an ink jet printer that performs printing by ejecting two types of ink droplets as ink droplets having different volumes has been described as an example. However, a printing apparatus that uses three or more types of ink droplets having different volumes is also described. The invention is of course applicable.
[0103]
Further, the volumes (ejection amounts) of the two types of large and small dots (ink droplets) and their ratios are not limited to the values described in the above embodiment, but may be various values. Further, the arrangement and arrangement of the ejection ports of the recording head and the arrangement of the plurality of recording heads are not limited to those described in the above embodiment, and various types of recording heads can be used.
[0104]
In addition, in order to reduce the amount of ink ejected to the thinning region, in the above-described embodiment, the color gamut determination, the thinning rank determination, and the SMS thinning process are performed. May be reduced. In particular, various methods other than the method using the above-described graph and the SMS thinning processing can be applied to the method of determining the thinning rank and the method of the thinning processing.
[0105]
[Other embodiments]
The above-described embodiment includes a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for causing ink to be ejected, particularly in an ink jet recording system. By using a method that causes a change in the state, it is possible to achieve higher density and higher definition of recording.
[0106]
Regarding the typical configuration and principle, it is preferable to use the basic principle disclosed in, for example, US Pat. Nos. 4,723,129 and 4,740,796. This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, it is arranged corresponding to the sheet or liquid path holding the liquid (ink). Applying at least one drive signal corresponding to the recording information and providing a rapid temperature rise exceeding the nucleate boiling, to generate heat energy in the electrothermal transducer, thereby causing the recording head to emit heat energy. This is effective in that film boiling occurs on the heat-acting surface of the liquid, and as a result, air bubbles in the liquid (ink) corresponding to the drive signal on a one-to-one basis can be formed.
[0107]
By discharging the liquid (ink) through the discharge opening by the growth and contraction of the bubble, at least one droplet is formed. When the drive signal is in a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable.
[0108]
As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further, if the conditions described in US Pat. No. 4,313,124 of the invention relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.
[0109]
As the configuration of the recording head, in addition to the combination of the discharge port, the liquid path, and the electrothermal converter (the linear liquid flow path or the right-angled liquid flow path) as disclosed in each of the above-mentioned specifications, a heat acting surface The configurations described in U.S. Pat. No. 4,558,333 and U.S. Pat. No. 4,459,600, which disclose the configuration in which the is bent, are also included in the present invention. In addition, Japanese Unexamined Patent Publication No. 59-123670 discloses a configuration in which a common slot is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters, or an opening for absorbing a pressure wave of thermal energy is discharged. A configuration based on JP-A-59-138461, which discloses a configuration corresponding to each unit, may be adopted.
[0110]
In addition, not only the cartridge-type recording head in which the ink tank is provided integrally with the recording head itself described in the above embodiment, but also the electrical connection with the apparatus main body by being mounted on the apparatus main body. A replaceable chip-type recording head that can supply ink from the apparatus main body may be used.
[0111]
Further, it is preferable to add recovery means for the printhead, preliminary auxiliary means, and the like to the configuration of the printing apparatus described above, since the printing operation can be further stabilized. Specific examples thereof include capping means for the recording head, cleaning means, pressurizing or sucking means, preheating means using an electrothermal transducer or another heating element or a combination thereof. It is also effective to provide a preliminary ejection mode for performing ejection that is different from printing, in order to perform stable printing.
[0112]
Further, the printing mode of the printing apparatus is not limited to a printing mode of only a mainstream color such as black, and may be a printing head integrally formed or a combination of a plurality of printing heads. The device may be provided with at least one of the full colors.
[0113]
In the above-described embodiment, the description has been made on the assumption that the ink is a liquid.However, even if the ink solidifies at room temperature or below, an ink that softens or liquefies at room temperature may be used. Alternatively, in the ink jet system, the temperature of the ink itself is controlled within a range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is in a stable ejection range. It is sufficient if the ink is sometimes in a liquid state.
[0114]
In addition, to prevent the temperature rise due to thermal energy from being used as the energy of the state change of the ink from the solid state to the liquid state, or to prevent the ink from evaporating, the ink solidifies in a standing state. Alternatively, ink that liquefies by heating may be used. In any case, the application of heat energy causes the ink to be liquefied by application of the heat energy according to the recording signal and the liquid ink to be ejected, or to start to solidify when reaching the recording medium. The present invention is also applicable to a case where an ink having a property of liquefying for the first time is used.
[0115]
In such a case, as described in JP-A-54-56847 or JP-A-60-71260, the ink is held in a liquid state or a solid state in the concave portion or through hole of the porous sheet. It is good also as a form which opposes an electrothermal transducer. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.
[0116]
The present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, and the like), but can be applied to an apparatus (for example, a copying machine and a facsimile device) including one device. May be applied. Further, an object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and a computer (or CPU or MPU) of the system or apparatus to store the storage medium. It is needless to say that the present invention can also be achieved by reading and executing the program code stored in the program.
[0117]
In this case, the program code itself read from the storage medium realizes the function of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.
[0118]
As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, and the like can be used.
[0119]
When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also an OS (Operating System) running on the computer based on the instruction of the program code. It goes without saying that a part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing.
[0120]
Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that a CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.
[0121]
【The invention's effect】
As described above, according to the present invention, based on relative information about an image recorded in a unit area and the number of ink droplets of different volumes ejected to the unit area, the amount of ink in the vicinity of a boundary in the unit area is determined. It is appropriately determined whether or not a bridging streak due to bleeding or inflow is likely to occur, and it is possible to reduce the number of ink droplets ejected to a region near the boundary according to the determination result.
[0122]
Therefore, when printing is performed using ink droplets of different volumes, it is possible to effectively suppress the occurrence of connecting streaks at the boundary and obtain a high-quality recorded image.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a schematic configuration of an inkjet printer according to an embodiment of the present invention, partially cut away.
FIG. 2 is a partial perspective view schematically showing a structure near an ejection port of the recording head shown in FIG.
FIG. 3 is a block diagram illustrating a schematic configuration of a control circuit of the inkjet printer of FIG. 1;
FIG. 4 is a flowchart illustrating a connection processing procedure according to the embodiment of the present invention.
FIG. 5 is a diagram illustrating a mechanism in which a streak occurs at a joint portion of a band.
FIG. 6 is a diagram illustrating an example of a color gamut division according to the embodiment of the present invention.
FIG. 7 is a diagram illustrating an example of a dot count value in a certain unit area according to the embodiment of the present invention.
FIG. 8 is a diagram for explaining an example of a method for determining hue and saturation in the embodiment of the present invention.
FIG. 9 is an example of a thinning rank graph according to the embodiment of the present invention.
FIG. 10 is an example of a thinning rank graph according to the embodiment of the present invention.
FIG. 11 is a diagram illustrating an area where dot count of print data is performed and an area where thinning is performed in the embodiment of the present invention.
FIG. 12 is a diagram for explaining processing of recording data by SMS thinning according to the embodiment of the present invention.
FIG. 13 is a diagram for explaining processing of recording data by SMS thinning according to the embodiment of the present invention.
FIG. 14 is an example of a thinning rank graph when two dots, large and small, are used.
FIG. 15 is a diagram for explaining bands and boundaries in an image recorded by a serial printer.
FIG. 16 is a schematic diagram illustrating a configuration of a recording head for color recording.
[Explanation of symbols]
1, 1A, 1B, 1C, 1D head cartridge
2 carriage
3 Guide shaft
4 Main scanning motor
5 Motor pulley
6 driven pulley
7 Timing belt
8 Recording media
9-12 Conveyance roller
21 Discharge port surface
22 outlet
23 Common liquid chamber
24 fluid paths
25 Electrothermal converter
100 controller
101 CPU
103 ROM
105 RAM
110 Host device
112 I / F
120 Operation unit
122 Power switch
124 print switch
126 Recovery switch
140 Head Driver
150, 160 Motor driver
162 Sub-scanning motor

Claims (18)

An inkjet recording apparatus that performs recording in a predetermined area by scanning an inkjet recording head that ejects ink droplets having different volumes relative to a recording medium,
Counting means for counting the number of ink droplets ejected to the unit region for each ink droplet having a different volume, for each unit region of a predetermined size obtained by dividing a connecting portion including a boundary between the predetermined regions adjacent to each other,
Information obtaining means for obtaining relative information about an image recorded in the unit area based on a count result by the counting means;
Level determining means for determining a reduction level of ink droplets ejected to an area near the boundary based on the relative information and the count result;
An ink jet recording apparatus comprising: a reduction unit configured to reduce ink droplets discharged to a region near the boundary based on the reduction level. The recording head ejects ink droplets having different volumes for each of a plurality of color inks,
The counting means counts the number of the ink droplets for each ink,
2. The ink jet recording apparatus according to claim 1, wherein the level determination unit obtains the reduction level for each ink. The inkjet recording apparatus according to claim 2, wherein the plurality of colors include cyan, magenta, and yellow. 4. The ink jet recording apparatus according to claim 2, wherein the information obtaining unit obtains relative information on hue and saturation as the relative information from the count result and information on the volume of the ink droplet. 5. 5. The ink jet recording apparatus according to claim 1, wherein the reducing unit reduces the number of ink droplets having a large volume. 6. The ink jet recording apparatus according to claim 1, wherein the level determination unit determines the reduction level stepwise according to the number of ink droplets having a large volume. 7. The method according to claim 1, wherein the reducing unit thins out print data corresponding to the ink droplet having a large volume according to a predetermined method to reduce the number of ink droplets having a large volume. 8. The inkjet recording apparatus according to any one of the preceding claims. The ink jet recording apparatus according to any one of claims 1 to 7, wherein the unit area includes an area near the boundary, and is larger in a direction intersecting a scanning direction than the area near the boundary. 9. The recording head according to claim 1, wherein the recording head is a recording head that ejects ink by using thermal energy, and includes a thermal energy converter for generating thermal energy to be applied to the ink. An ink jet recording apparatus according to any one of the preceding claims. An inkjet recording method for performing recording in a predetermined area by scanning an inkjet recording head that ejects ink droplets having different volumes relative to a recording medium,
A counting step of counting the number of ink droplets ejected to the unit region for each ink droplet having a different volume, for each unit region of a predetermined size obtained by dividing a connecting portion including a boundary between the predetermined regions adjacent to each other,
An information obtaining step of obtaining relative information on an image recorded in the unit area based on a count result in the counting step;
Based on the relative information and the count result, a level determining step of determining a reduction level of ink droplets ejected to an area near the boundary,
A reduction step of reducing ink droplets discharged to a region near the boundary based on the reduction level. The recording head ejects ink droplets having different volumes for each of a plurality of color inks,
In the counting step, counting the number of the ink droplets for each ink,
11. The ink jet recording method according to claim 10, wherein in the level determining step, the reduction level is obtained for each ink. The inkjet recording method according to claim 11, wherein the plurality of colors include cyan, magenta, and yellow. 12. The ink jet recording method according to claim 10, wherein, in the information obtaining step, relative information on hue and saturation is obtained as the relative information from the count result and information on the volume of the ink droplet. 14. The ink jet recording method according to claim 10, wherein the number of ink droplets having a large volume is reduced in the reducing step. 15. The ink jet recording method according to claim 10, wherein in the level determining step, the reduction level is determined stepwise according to the number of ink droplets having a large volume. 16. The method according to claim 10, wherein, in the reducing step, print data corresponding to a large-volume ink droplet is thinned out according to a predetermined method to reduce the number of the large-volume ink droplet. The ink-jet recording method described in the above. A computer program for causing a computer device to execute the inkjet recording method according to any one of claims 10 to 16. A storage medium storing the computer program according to claim 17.

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