JP3977089B2 - Data processing apparatus and data generation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a data processing apparatus and a data generation method , and more particularly to a recording apparatus that performs recording by expressing a gradation level by a combination of recording dots having different sizes, and creation of recording data used in such an apparatus. Is.
[0002]
[Prior art]
As a typical example of such an apparatus, an ink jet recording apparatus that records an image by applying ink of the same color with a plurality of different ejection amounts is known. The recording data used in this apparatus is obtained by finally converting image data in which gradation is expressed in a multi-value (for example, 8-bit 0-255) format for each pixel into binary ejection data. Is. For example, based on the value indicated by the image data, the image data is converted into multi-bit pattern data representing several levels of gradation, and an index indicating a predetermined dot arrangement relationship with respect to the level indicated by the pattern data. Based on the pattern, binary ejection data for forming dots of the pattern is obtained. Then, by appropriately determining this index pattern, it is possible to set the gradation and maximum density of the recorded image.
[0003]
For example, image data of 256 gradations from 0 to 255 is converted into 4-bit pattern data (represented as 0000 to 0101 by 4 bits) representing 9 values (levels 0 to 8), and an index corresponding thereto In the configuration in which binary data is converted according to the pattern, the index pattern determines the arrangement of large and small dots for each of the nine levels. Thereby, the multi-value image data is converted into ejection data (binary data) of each nozzle corresponding to the size of the ink droplets ejected by the recording head.
[0004]
Such an index pattern is one of the factors that determine the characteristics of a recorded image, such as gradation, but in general, when a relatively large amount of ink is used in a highlight portion of an image, graininess is felt. From the point of increase, for example, up to the level corresponding to the intermediate gradation region among the above nine levels, a pattern of only small dots is used, and large dots are arranged at a gradation value level higher than that. It is set as such a pattern.
[0005]
[Problems to be solved by the invention]
However, the index pattern defines the arrangement of large and small dots uniformly corresponding to the pattern data, and uniformly assigns the range of gradation values that can be represented by the image data to each level. For this reason, as described above, only small dots tend to be arranged exclusively at a level corresponding to a small gradation value.
[0006]
As a result, the following problems may occur in the highlight portion of an image expressed at a level where only such small dots are arranged or in an intermediate gradation portion having a higher density. A relatively small amount of ink (small droplet) that forms a small dot has a relatively small kinetic energy due to ejection, so the vibration of the mechanical part accompanying the recording operation and the movement of the recording head In some cases, the discharge state may be disturbed due to the influence of the air current generated on the surface, and the position of the formed dots may be shifted. This is recognized as a reduction in the quality of the recorded image. In particular, the dot density in the intermediate gradation portion is higher than that in the highlight portion, and streaks or the like are easily noticeable due to the deviation of the dot formation position.
[0007]
The present invention has been made to solve the above-described problems, and the object of the present invention is to display an image recorded by forming dots of a plurality of sizes, particularly a highlight portion or an intermediate floor. It is an object of the present invention to provide a data processing apparatus and a data generation method capable of reducing the recording quality deterioration in the key portion.
[0008]
[Means for Solving the Problems]
Therefore, in the present invention, a data processing device that generates a plurality of types of data for forming a plurality of types of dots, and a plurality of types of multivalues for forming a plurality of types of dots based on image data First generation means for generating data; and second generation means for generating a plurality of types of n-value data by converting each of a plurality of types of multi-value data generated by the first generation unit into n-values independently. The plurality of types of multi-value data generated by the first generation means have the same color and different sizes from the first multi-value data for forming at least the first type of dots and the first type of dots. and a second multi-level data for forming a second type of dot having the second generating means, said first multi-level data to generate the first n-value data by n value conversion , Converting the second multi-value data into n-values And generates a second n-value data Te.
[0009]
A data generation method for generating a plurality of types of data for forming a plurality of types of dots, wherein a plurality of types of multi-value data for forming a plurality of types of dots is generated based on image data. A first generation step, and a second generation step of generating a plurality of types of n-value data by independently converting each of a plurality of types of multi-value data generated in the first generation step into n-values. The plurality of types of multi-value data generated in the first type multi-value data for forming at least the first type of dots and the second type having the same color and different sizes from the first type of dots The second multi-value data for forming the dots, and in the second generation step, the first multi-value data is converted into n-values to generate first n-value data, and the second multi-value data is formed. The n-value of the multi-valued data is converted into the second n And generating the data.
[0010]
According to the above configuration, the dot arrangement can be determined independently for each large and small dot of the same color. As a result, the degree of freedom of arrangement of the same color large and small dots corresponding to each gradation value increases, and the dot arrangement design becomes easy .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0013]
1 to 3 are schematic views showing three examples of ejection port arrays in a recording head that can be used in an ink jet recording apparatus according to an embodiment of the present invention. As shown in these drawings, among the inks of cyan (C), magenta (M), and yellow (Y), each nozzle (ejection port) that ejects different amounts (volumes) of ink droplets of a predetermined color ink. ) Are provided on the same head chip or different head chips. For black (K) ink, nozzles are not provided to eject such different amounts of ink droplets, and all nozzles of ink K eject the same amount of ink. Each head chip is provided with a discharge heater (electrothermal converter) at its nozzle, and bubbles are generated in the ink by the thermal energy generated by the discharge heater, and the ink is discharged by the pressure of the bubbles. The amount of ink droplets to be ejected is such that a relatively large ejection heater is provided for a nozzle that ejects a large ink droplet, and a relatively small ejection heater is provided for a nozzle that ejects a small ink droplet. Is possible. Of course, any known configuration may be used as the configuration for varying the discharge amount.
[0014]
In the example shown in FIG. 1, two head chips are prepared for each of the C, M, and Y inks, and nozzles that eject different amounts of ink droplets are provided on the respective chips. More specifically, nozzles that eject different amounts of ink for each color ink (in the figure, a large circle ejects a relatively large ink droplet, and a small circle ejects a relatively small ink droplet. 2 and 3) are alternately arranged in each nozzle row. As described above, the K ink head chip includes only nozzles that eject relatively large ink droplets. This is because black is recorded at a high density. In addition, for each color ink head chip, the respective nozzles that eject different amounts of ink are arranged, but the heater board portion is common.
[0015]
In the example shown in FIG. 2, two head chips each having only nozzles for ejecting large or small ink droplets are prepared for each of C, M, and Y inks. The nozzle arrays in the two heads that discharge ink droplets of the same size for each color ink are arranged so as to be shifted from each other in the direction orthogonal to the scanning direction of the heads. Recording can be performed.
[0016]
Also, the head chips of the respective color inks shown in the figure are bonded together to form an integrated recording head.
[0017]
The example shown in FIG. 3 has the same nozzle and head configuration as that shown in FIG. 2, but differs from the example shown in FIG. 2 in that the yellow head has only nozzles that eject relatively large droplets. This is because yellow is not visually noticeable, and there is a case where there is little need to form small dots.
[0018]
The present embodiment uses the recording head provided with the nozzles for ejecting large and small ink droplets for the ink of the predetermined color as described above, and each nozzle as will be described later with reference to FIGS. Recording data is created.
[0019]
4 (a) to 4 (e) and FIGS. 5 (a) to 5 (d) are diagrams schematically showing nine-level index patterns according to the above-described conventional technology. As described above, for example, 8-bit multi-value image data for each pixel is divided into 9 levels based on a predetermined threshold value, and converted into 4-bit pattern data corresponding to each level. Specifically, for example, 8-bit image data is associated with 4-bit pattern data by each threshold value obtained by dividing the gradation value 0-255 into eight equal parts. The index pattern of level 0 to level 8 is specified by the 4-bit pattern data. Among these index patterns, the level 0 pattern has no dots (white background), and the level 8 pattern shows the highest density with large dots arranged at all positions.
[0020]
FIG. 6 shows an ink ejection rate (dots are pixels) with respect to input values indicated by the signals R ′, G ′, and B ′ when the dot pattern obtained using the index pattern shown in FIGS. 4 and 5 is used. It is the figure which showed the relationship with the ratio which coat | covers.
[0021]
As shown in FIGS. 4 and 5, in the case of using an index pattern, pixels are formed with only small dots up to level 4, that is, up to R′G′B ′ input value 128 shown in FIG. As a result, the strike rate can be changed substantially linearly from 0% to 50%, and smooth gradation can be obtained. However, even if the strike rate changes linearly in this way, as described above, the index pattern determines the arrangement of large and small dots uniformly corresponding to the pattern data between these dots, Since the range of gradation values that can be represented by the pattern data is uniformly assigned to each level, only small dots are arranged until the input level is 128. As a result, there arises a problem that the streak of the image is conspicuous at the intermediate gradation portion as described above.
[0022]
On the other hand, it is considered that the large dots are arranged even at an intermediate level by adjusting the contents of the index pattern. However, even if an attempt is made to place a large dot at a level where a large dot is not originally placed, the level corresponds to a relatively low gradation range in the state of the image data as described above. Large dots are arranged in the key range. In this case, if the ejection data is generated as an index pattern using all large dots without considering the gradation, problems such as increased graininess in the highlight portion are derived. In addition, if the threshold for determining the correspondence between image data and each level of the index pattern is changed in order to arrange large dots in a halftone range, density discontinuities may occur at the transition of the pattern. As a result, smooth gradation expression is not realized.
[0023]
In the present embodiment, the arrangement of dots can be changed relatively easily while maintaining smooth gradation, by the following configuration.
[0024]
FIG. 7 is a flowchart showing a recording data creation processing procedure executed by the ink jet recording apparatus of the present embodiment. It should be noted that all of the processes described below may be executed by the host device to obtain binary data and send this to the recording device.
[0025]
When processing relating to a predetermined color image is performed by the host computer, and as a result image data is sent to the apparatus, processing for inputting the image data RGB is performed in step S71. In step S72, a predetermined color correction process is performed on this signal to obtain 8-bit image data R'G'B '.
[0026]
In step S73, color conversion processing is performed. That is, for image data R′G′B ′, a color space based on C, M, Y, and K that matches the color of ink used in the recording apparatus of the present embodiment from the image data indicated by the R, G, and B color spaces. Convert to image data. This processing is performed with reference to an LUT (Look Up Table) in which the values of C, M, Y, and K corresponding to R ′, G ′, and B ′ input signals are stored in advance.
[0027]
FIG. 8 is a diagram schematically showing the contents of this LUТ. As shown in this figure, the LUT according to the present embodiment includes C, M, and Y data corresponding to large ink droplets, and data SC, SM, and SY corresponding to small ink droplets. Are also output as converted data. Specifically, each of the 8-bit image data K, C, M, SC, SM stored corresponding to the combination of the values of the data R ′, G ′, B ′ in the relationship described later in FIG. 10A. , SY data is output.
[0028]
Next, in step S74, an n-value conversion process is performed on 8-bit image data of K, C, M, SC, SM, and SY obtained by the color conversion process. In this embodiment, a quinary process is performed for each color image data. As a result, 4-bit (0000 to 0100) data can be obtained, and binary data used when ejecting from an index pattern corresponding to each of five levels can be obtained. Specifically, as described in detail in FIG. 9, ejection data of each nozzle for forming a 2 × 2 dot pattern by ejecting large and small ink droplets of each color ink for one pixel can be obtained. . The data obtained as described above is developed in the recording buffer in step S75. Note that the method of obtaining final binary ejection data from 8-bit image data of each color of K, C, M, SC, SM, and SY is not limited to the one using the index pattern described above. Any known method for obtaining binary data from 8-bit data can be used as long as the large and small dots are independently obtained.
[0029]
FIG. 9 is a diagram mainly showing a configuration of a recording buffer in the recording apparatus.
[0030]
The printer driver 211 shown in the figure is software that creates image data in the host device and transfers the created data to the recording device.
[0031]
The controller 200 in the recording apparatus of the present embodiment uses the swing circuit 207 to transfer the K, C, M, Y, SC, SM, and SY data for each pixel obtained by performing the processing in steps S71 to S74 described above. A process of writing data in each recording buffer 205 as 2-bit data for each color is performed (step S75).
[0032]
Specifically, for example, for cyan C data, 2-bit data is written for one pixel of 360 dpi. At this time, the present embodiment is configured to write a total of 4 bits, 2 bits each in the buffers C1 and C2 for the large ink droplet nozzles C1 and C2. Accordingly, 0 to 2 ink ejections can be set for each of the two nozzles C1 and C2 that eject large ink droplets corresponding to one pixel, and 0 to 4 large ink droplet ejections can be set in total. Similarly, the SC corresponding to the small cyan ink droplet is also configured to write 4 bits in total, 2 bits each in the buffers SC1 and SC2 for the small ink droplet nozzles SC1 and SC2. Four ink ejections can be set. Any one of the nozzle arrangements shown in FIGS. 1 to 3 can be used for ejecting large and small ink droplets, and two nozzles separated by one nozzle pitch for each large and small ink droplet in this arrangement are used for recording each pixel. Thus, it is possible to form a 2 × 2 dot pattern of large and small dots in one scan. Then, based on the recording data generated as described above, each head is driven by the head driver 240 to discharge each ink.
[0033]
That is, when each nozzle of the head reaches a pixel position where ink is actually ejected, data on each buffer is read into a register in each head, and each ink ejection operation is performed. Thereby, the dot arrangement from level 0 to level 4 shown in FIG. 4 can be realized independently of the size.
[0034]
10 (a) and 10 (b) show the relationship between the input level and the shot amount when the recording data for ejecting different amounts of ink of the same color is formed independently according to the size of the droplet. It represents.
[0035]
Specifically, FIG. 10A shows the conversion contents of the table shown in FIG. 8 with respect to C and SC among the conversion outputs for the color input indicated by the points on the CYAN-WHITE axis of the table. The conversion output will be described as an example. FIG. 10B is a diagram showing the ink deposition rate finally obtained corresponding to the input value.
[0036]
As shown in FIG. 10A, in the setting of LUТ, C data corresponding to a large ink droplet is set to an intermediate gradation value of 128 or more (in the figure, to the left of the center; 128 or less for density gradation). ) And the total of the SC data corresponding to the small ink droplets shows the linear gradation change shown in FIG. The contents of LUТ can be set in advance through simulations and experiments. As a result, large ink droplets can be used in a halftone area, and an image can be recorded by mixing large and small ink droplets in this area. As a result, even if the small ink droplet is distorted, the large ink droplet having a large kinetic energy is landed stably, thereby making it difficult to recognize streaks or the like.
[0037]
The 8-bit recording data for each of the large and small ink droplets obtained as described above is converted into 4-bit recording data corresponding to two nozzles for each pixel by the quinary processing as described above. The arrangement pattern of the large and small dots (in this embodiment, the contents of the index pattern) determined by this can be adjusted independently for each dot. Specifically, as described above, the color conversion table (LUТ) shown in FIG. 10 (a) is defined under the constraint that the total relationship shown in FIG. 10 (b) is linear. As long as the pattern satisfies the data values of K, C, M, Y, SC, SM, and SY, the size of the dot to be arranged and the position thereof are basically arbitrary. In other words, the n-value conversion processing in step S74 shown in FIG. 7 can be performed independently for each large and small ink droplet in each mode, and the dot arrangement obtained thereby can be determined independently. As a result, the dot arrangement corresponding to each gradation value of the image data can be easily adjusted, and recording can be performed using large dots at intermediate density gradation or less.
[0038]
Further, in this case, even when the relative balance of the ink droplet amount is changed by design, it is easy to cope with this by only changing the look-up table in the color conversion process and the aspect of the n-value conversion process. Can also be supported.
[0039]
FIG. 11 is a perspective view illustrating a schematic configuration of the ink jet recording apparatus according to the above-described embodiment. The recording apparatus 50 of this example is a serial scanning type recording apparatus, and a carriage 53 is guided by guide shafts 51 and 52 so as to be movable in the main scanning direction of an arrow A. The carriage 53 is reciprocated in the main scanning direction by a driving force transmission mechanism such as a carriage motor and a belt for transmitting the driving force. One of the recording heads shown in FIGS. 1 to 3 and an ink tank 54 for supplying ink to these recording heads are mounted on the carriage 53 for each ink color. The recording head and the ink tank 54 may constitute an integral ink jet cartridge. The paper P as the recording medium is inserted from the insertion port 55 provided at the front end of the apparatus, and then the transport direction is reversed, and then the transport is performed by the feed roller 56 in the sub-scanning direction indicated by the arrow B. The recording apparatus 50 moves the recording head in the main scanning direction, ejects ink toward the print area of the paper P on the platen 57, and moves the paper P in the sub-scanning direction by a distance corresponding to the recording width. The image is sequentially recorded on the paper P by repeating the transport operation for transporting to the paper P.
[0040]
At the left end in FIG. 11 in the movement area of the carriage 53, a recovery system unit 58 that faces the ejection port forming surface of the recording head mounted on the carriage 53 is provided. The recovery system unit 58 includes a cap capable of capping the discharge port of the recording head and a suction pump capable of introducing a negative pressure into the cap. The negative pressure is applied to the cap covering the discharge port. By introducing the ink, the ink is sucked and discharged from the ejection port, and a recovery process is performed to maintain a good ink ejection state of the recording head. Further, the recovery process can be performed to maintain a good ink discharge state of the recording head by discharging ink not contributing to an image from the discharge port toward the inside of the cap.
[0041]
In the above-described embodiment, the case where the head for ejecting ink is used has been described as an example, but the application of the present invention is not limited to this example. The present invention can be applied to any head that uses a recording element in which the size of the dots to be formed can be changed.
[0042]
<Other embodiments>
As described above, the present invention can be applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.) but also to an apparatus composed of a single device (for example, a copying machine, a facsimile machine). May be.
[0043]
In addition, a program code of software for realizing the functions of the embodiment is provided in an apparatus or a computer in the system connected to the various devices so as to operate the various devices so as to realize the functions of the above-described embodiments. What is implemented by operating the various devices in accordance with a program stored in a computer (CPU or MPU) of the system or apparatus supplied is also included in the scope of the present invention.
[0044]
Further, in this case, the program code itself of the processing shown in FIG. 7 realizes the functions of the above-described embodiment, and the program code itself and means for supplying the program code to the computer, for example, such program code The storage medium storing the above constitutes the present invention.
[0045]
As a storage medium for storing the program code, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
[0046]
Further, by executing the program code supplied by the computer, not only the functions of the above-described embodiments are realized, but also the OS (operating system) in which the program code is running on the computer, or other application software, etc. It goes without saying that the program code is also included in the embodiment of the present invention even when the functions of the above-described embodiment are realized in cooperation with the embodiment.
[0047]
Further, after the supplied program code is stored in the memory provided in the function expansion board of the computer or the function expansion unit connected to the computer, the CPU provided in the function expansion board or function extension unit based on the instruction of the program code Needless to say, the present invention includes a case where the functions of the above-described embodiments are realized by performing part or all of the actual processing.
[0048]
【The invention's effect】
As described above, according to the present invention, it is possible to independently determine the dot arrangement for each large and small dot of the same color. As a result, the degree of freedom of arrangement of the same color large and small dots corresponding to each gradation value increases, and the dot arrangement design becomes easy .
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a recording head used in an ink jet recording apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating another example of a recording head used in the ink jet recording apparatus according to the embodiment of the invention.
FIG. 3 is a diagram showing still another example of a recording head used in the ink jet recording apparatus according to the embodiment of the present invention.
FIGS. 4A to 4E are diagrams schematically showing index patterns used in conventional recording data creation. FIGS.
FIGS. 5A to 5D are diagrams schematically showing index patterns similarly used in conventional recording data creation. FIG.
FIG. 6 is a diagram illustrating a relationship between print data and ink printing rate when the index pattern is used.
FIG. 7 is a flowchart showing recording data creation processing according to an embodiment of the present invention.
FIG. 8 is a diagram schematically illustrating a look-up table used for color conversion in the above processing.
FIG. 9 is a diagram illustrating a process of storing data obtained by the data creation process in a buffer.
FIGS. 10A and 10B show the relationship between the input level and the shot amount when recording data for ejecting different amounts of ink of the same color is independently formed for each droplet size. FIG.
FIG. 11 is a perspective view showing a schematic configuration of an ink jet printer according to an embodiment of the present invention.
[Explanation of symbols]
200 Controller 205 Recording buffer 207 Swing circuit 211 Printer driver 240 Head driver

Claims (10)

A data processing device for generating a plurality of types of data for forming a plurality of types of dots,
First generation means for generating a plurality of types of multi-value data for forming a plurality of types of dots based on image data;
Second generation means for generating a plurality of types of n-value data by converting each of a plurality of types of multi-value data generated by the first generation means into n-values independently;
The plurality of types of multi-value data generated by the first generation means have the same color and different sizes from the first multi-value data for forming at least the first type of dots and the first type of dots. and a second multi-level data for forming a second type of dots having,
The second generation unit converts the first multi-value data into n-values to generate first n-value data, and converts the second multi-value data into n-values to generate second n-value data. A data processing apparatus. The first multi-value data is multi-value data for forming a first cyan dot as the first type of dot,
The second multi-value data is multi-value data for forming a second cyan dot smaller than the first cyan dot as the second type of dot. The data processing apparatus described. The first multi-value data is multi-value data for forming a first magenta dot as the first type of dot,
2. The second multi-value data is multi-value data for forming a second magenta dot smaller than the first magenta dot as the second type of dot. The data processing apparatus described. The plurality of types of multi-value data have the same color and different sizes as the third multi-value data and the third type dots for forming a third type dot having a color different from that of the first type dot. The data processing apparatus according to claim 1, further comprising fourth multi-value data for forming a fourth type dot having the following. The first multi-value data is multi-value data for forming a first cyan dot as the first type of dot,
The second multi-value data is multi-value data for forming a second cyan dot smaller than the first cyan dot as the second type of dot,
The third multi-value data is multi-value data for forming a first magenta dot as the third type of dot,
5. The fourth multi-value data is multi-value data for forming a second magenta dot smaller than the first magenta dot as the fourth type of dot. The data processing apparatus described.   6. The data processing apparatus according to claim 1, wherein the image data is RGB data. 7. The data processing apparatus according to claim 1, wherein the data processing apparatus is a recording apparatus for forming the dots on a recording medium using a recording head. 7. The data processing apparatus according to claim 1, wherein the data processing apparatus is a host apparatus connected to a recording apparatus for recording the dots on a recording medium using a recording head. . A data generation method for generating a plurality of types of data for forming a plurality of types of dots,
A first generation step of generating a plurality of types of multi-value data for forming a plurality of types of dots based on the image data;
A second generation step of generating a plurality of types of n-value data by independently converting each of a plurality of types of multi-value data generated in the first generation step into n-values,
The plurality of types of multi-value data generated in the first generation step have different sizes in the same color as the first multi-value data for forming at least the first type of dots and the first type of dots. Second multivalued data for forming a second type of dot having
In the second generation step, the first multi-value data is converted into n-values to generate first n-value data, and the second multi-value data is converted into n-values to generate second n-value data. A data generation method characterized by the above. A computer program for causing a computer to execute the data generation method according to claim 9.

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