JP2004284099A - Method for determining applied voltage value, image output device, applied voltage value determining program, and recording medium with the program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that a color space distance D0 cannot be obtained due to individual differences of inkjet heads unless a voltage of V1 is impressed although ink for the color space distance D0 between an ink color at a medium and the medium itself is printed when a voltage of a standard value V0 is impressed to the inkjet heads. <P>SOLUTION: According to the method provided, printing is carried out by impressing measurement voltages of V0+ΔV and V0-ΔV to the inkjet head, and color space distances D3 and D2 are measured. Linear interpolation is carried out, and at the same time a voltage corresponding to the color space distance D0 of the straight line is set to V1. The individual differences of the inkjet heads for discharging the ink by receiving the voltage can be solved accordingly. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to so-called calibration that eliminates individual differences between inkjet heads that eject ink by receiving a voltage.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, printers having an inkjet head have been widely used. The ink jet head discharges ink by receiving a voltage. The ejected ink adheres to a medium such as printing paper. As a result, printing on the medium is performed. Generally, as described in Patent Document 1 (see FIG. 2), the diameter of a dot formed on printing paper can be determined by a voltage applied to an inkjet head.
[0003]
[Patent Document 1]
Japanese Patent Publication No. 6-79853 (Fig. 2)
[Problems to be solved by the invention]
However, there are individual differences in ink jet heads. For example, it is assumed that an inkjet head is manufactured so as to obtain a dot diameter d when a voltage V is applied to the inkjet head. However, the dot diameter d cannot be obtained without applying the voltage V + ΔVa to the actually manufactured inkjet head A, and the dot diameter d cannot be obtained without applying the voltage V + ΔVb to the actually manufactured inkjet head B. Things can happen.
[0004]
If such an individual difference of the ink jet head is left, dots of a desired diameter are not printed on the printing paper. As a result, image quality is deteriorated such that a desired density cannot be obtained.
[0005]
In view of the above, an object of the present invention is to eliminate individual differences between inkjet heads that eject ink by receiving a voltage.
[0006]
[Means for Solving the Problems]
The invention according to claim 1 is a method for determining an applied voltage value for determining a value of a voltage to be applied to the ink discharging means in an image output apparatus having an ink discharging means for discharging an amount of ink corresponding to the applied voltage. A measurement voltage application step of applying a plurality of values of measurement voltage to the ink ejection unit, and a printing step of printing on a medium using ink ejected from the ink ejection unit by applying the measurement voltage, A color space distance measuring step of measuring a color space distance in a color space between the ink printed on the medium and the medium, and a predetermined color from the medium based on the value of the measurement voltage and the corresponding measured color space distance. And an applied voltage value determining step of determining a value of a voltage to be applied to the ink ejection unit when a color at a spatial distance is realized on the medium.
[0007]
According to the invention configured as described above, in an image output apparatus having an ink ejection unit that ejects an amount of ink corresponding to the applied voltage, the value of the voltage to be applied to the ink ejection unit can be determined. it can.
[0008]
That is, in the measuring voltage applying step, a plurality of values of the measuring voltage are applied to the ink ejection unit. In the printing step, printing is performed on the medium using the ink ejected from the ink ejection unit by applying the measurement voltage. The color space distance measuring step measures a color space distance in a color space between the ink printed on the medium and the medium. The applied voltage value determining step should be applied to the ink ejection means when realizing a color at a predetermined color space distance from the medium on the medium based on the value of the measurement voltage and the corresponding measured color space distance. Determine the value of the voltage.
[0009]
A second aspect of the present invention is the invention according to the first aspect, wherein the ink ejection means is provided when a color at a predetermined color space distance from the medium is realized on the medium between the values of the measurement voltage. It is configured so that there is a standard value of the voltage to be applied.
[0010]
The invention according to claim 3 is the invention according to claim 2, wherein the value of the measurement voltage is a value obtained by adding a predetermined difference to a standard value and subtracting the value.
[0011]
The invention according to claim 4 is the invention according to claim 1, wherein in the applied voltage value determining step, a difference between two measured voltage values and a corresponding difference between two measured color space distances. And the ratio is used.
[0012]
The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the color space is configured to be a Lab space or an xyz space.
[0013]
According to a sixth aspect of the present invention, there is provided an ink discharging means for discharging an amount of ink corresponding to the applied voltage, and a voltage to be applied determined by the invention according to any one of the first to fifth aspects. It is configured to include an applied voltage value recording means for recording a value, and an applied voltage value determining means for determining a voltage value to be applied to the ink discharging means based on the recorded contents of the applied voltage value recording means.
[0014]
The invention according to claim 7 is an image output apparatus having an ink ejection unit that ejects an amount of ink corresponding to the applied voltage, wherein a plurality of values of measurement voltages are applied to the ink ejection unit, and the measurement is performed. An image output device that prints on a medium using the ink ejected from the ink ejection unit by applying the application voltage and measures a color space distance in a color space between the ink printed on the medium and the medium is applied to the ink ejection unit. A program for causing a computer to execute an applied voltage value determination process for determining a value of a voltage to be applied, and a predetermined color space from a medium based on a measurement voltage value and a corresponding measured color space distance. When a color at a distance is realized on a medium, a computer executes an applied voltage value determination process for determining a value of a voltage to be applied to the ink ejection unit. It is because of the program.
[0015]
According to an eighth aspect of the present invention, there is provided a computer-readable recording medium storing the program according to the seventh aspect.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 is a block diagram illustrating a configuration of an image output device according to an embodiment of the present invention. The image output device 1 includes a control circuit 10, an interface circuit 20, a head drive circuit 30, and an inkjet head 40.
[0018]
The control circuit 10 has a CPU 102, a ROM 104, and a RAM 106. The CPU 102 determines the value of the voltage to be applied to the inkjet head 40 based on programs and data recorded in the ROM 104 and the RAM 106. Then, the signal is supplied to the head drive circuit 30 via the interface circuit 20. The ROM 104 is a read-only memory. The RAM 106 is a readable and writable memory.
[0019]
The interface circuit 20 is an interface between the control circuit 10 and the head drive circuit 30.
[0020]
The head drive circuit 30 receives the value of the voltage to be applied to the inkjet head 40 from the control circuit 10 via the interface circuit 20. Then, a voltage is applied to the inkjet head 40.
[0021]
The ink jet head 40 is deformed according to the applied voltage. The inkjet head 40 is, for example, a piezo element. The inkjet head 40 is for ejecting ink in accordance with the applied voltage.
[0022]
FIG. 2 is a cross-sectional view of an ink ejection mechanism for ejecting ink using the inkjet head 40. The ink ejection mechanism is a part of the image output device 1 and includes an inkjet head 40, an ink tank 52, an ink passage 54, and a nozzle 56.
[0023]
Ink is stored in the ink tank 52. There are six types of ink colors: C (cyan), M (magenta), Y (yellow), K (black), Lc (light cyan), and Lm (light magenta). Therefore, there are six ink ejection mechanisms corresponding to the types of colors.
[0024]
The ink passage 54 is a passage for guiding the ink stored in the ink tank 52.
[0025]
The nozzle 56 is a nozzle provided at the tip of the ink passage 54, and ejects ink.
[0026]
The ink jet head 40 is arranged near the nozzle 56 and above the ink passage 54. The portion of the ink passage 54 with which the inkjet head 40 contacts can bend according to the deformation of the inkjet head 40.
[0027]
FIG. 3 is an enlarged sectional view of the vicinity of the inkjet head 40 of the ink ejection mechanism. When no voltage is applied to the inkjet head 40, no ink is ejected, as shown in FIG. However, when a voltage is applied to the ink jet head 40, as shown in FIG. 3B, the ink jet head 40 is deformed in the direction of the arrow, causing the ink passage 54 to bend downward. This causes the ink in the ink passage 54 to be pressed and ejected from the nozzle 56. The ink ejected from the nozzle 56 becomes granular (ink particles) and reaches a medium (for example, printing paper) placed below the nozzle 56. Thereby, printing can be performed on the medium. As described above, since there are six colors of ink, color printing is possible.
[0028]
Note that the amount of deformation of the inkjet head 40 is determined by the voltage applied to the inkjet head 40. In addition, the amount of ink ejected from the nozzle 56 is determined by the amount of deformation of the inkjet head 40. The amount of ink ejected from the nozzles 56 determines the color density of the ink on the media. The density of the ink color in the medium determines a color space distance in a color space (for example, a Lab space or an xyz space) between the ink color in the medium and the medium itself. Therefore, the color space distance is determined by the voltage applied to the inkjet head 40. Note that the color space distance is obtained by taking the square root of the sum of squares of the difference between the coordinates of the ink color in the medium and the coordinates of the medium itself. For example, when considering the Lab space as the color space, the color coordinates of the ink in the media ^{(L *, a *, b} *), the coordinates of the media itself _{^{(L 0 *, a 0 *}} , b 0 *) and I do. At this time, the color space distance ^{becomes _{1/2 ((L * -L 0 *}} ) 2 + (a * -a 0 *) 2 + (b * -b 0 *) 2).
[0029]
As shown in FIG. 4, in the virtual standard device of the image output apparatus 1, when the voltage applied to the ink jet head 40 is the standard value V0, the color of the ink in the medium and the color of the medium itself in the color space The color space distance is set to a predetermined color space distance D0. However, it is assumed that a certain number N of dots are formed in a certain area A. Note that three types of dots, large, medium, and small, can be formed. However, there are two types of voltage patterns applied to the inkjet head 40, each corresponding to one of large, medium, and small dots. For example, one voltage pattern corresponds to a large dot and the other voltage pattern corresponds to a small dot. In this case, a medium dot is formed by combining one voltage pattern with the other voltage pattern.
[0030]
Incidentally, there is an error in the image output device 1 (actual machine) actually manufactured. Therefore, the color space distance D1 obtained when the voltage applied to the inkjet head 40 is V0 is different from D0 even if a certain number N of dots are formed in a certain area A. The error (= D1−D0) differs depending on each actual device, and is also called individual difference. Such individual differences have undesirable effects such as deteriorating image quality, and are therefore preferably eliminated. In the image output device 1 according to the embodiment of the present invention, the control circuit 10 eliminates individual differences. Note that the control circuit 10 can be provided outside the image output device 1.
[0031]
FIG. 5 is a block diagram showing the configuration of the image output apparatus 1 according to the embodiment of the present invention, and in particular, is a functional block diagram showing the functions of the control circuit 10 in detail. The image output device 1 includes a control circuit 10, an interface circuit 20, a head drive circuit 30, and an inkjet head 40. The control circuit 10 includes an image input unit 12, an image processing unit 14, an applied voltage value recording unit 16, and an applied voltage value determination unit 18. The interface circuit 20, the head drive circuit 30, and the inkjet head 40 are as described with reference to FIG.
[0032]
The image input unit 12 receives and outputs, from a host computer (not shown) connected to the image output device 1, image data composed of gradation data of each color of RGB for each pixel or dot. Note that RGB means R (red), G (green), and B (blue).
[0033]
The image processing unit 14 receives image data composed of RGB gradation data from the image input unit 12 and converts the image data into C, M, Y, K, Lc, and Lm gradation data.
[0034]
The applied voltage value recording unit 16 records the voltage to be applied to the inkjet head 40 for each of the colors C, M, Y, K, Lc, and Lm. A method of determining a voltage to be applied to the inkjet head 40 will be described with reference to FIGS. FIG. 6 is a diagram showing the correspondence between the voltage applied to the inkjet head 40 and the color space distance in the color space (the distance between the ink color on the medium and the medium itself) in the actual device of the image output apparatus 1. is there. FIG. 7 is a flowchart showing a method of determining a voltage to be applied to the inkjet head 40.
[0035]
First, values obtained by adding or subtracting a predetermined difference ΔV (for example, 2.5 [V]) from the standard value V0, and V0 + ΔV and V0−ΔV are applied to the inkjet head 40 for each color as measurement voltages (S10).
[0036]
When a voltage is applied to the inkjet head 40, the inkjet head 40 is deformed, and ink particles are ejected from the nozzles 56. Printing is performed by receiving the ink particles on the medium (S12). However, it is assumed that a certain number N of dots are formed in a certain area A. In addition, printing is performed by various kinds of dots (for example, large and small dots corresponding to the pattern of the voltage applied to the inkjet head 40) and one patch (C, M, Y, K) for each color. Is printed with a density of 25%, and Lc and Lm with a density of 50%). However, if a plurality of gradation (density) patches are printed, the voltage to be applied to the inkjet head 40 can be determined more accurately.
[0037]
Next, the color space distance between the color of the ink printed on the medium and the medium itself is measured for each color (S14). For example, as shown in FIG. 6, for a certain color, the color space distance when the voltage applied to the inkjet head 40 is V0 + ΔV is D3, and the color space distance when the voltage applied to the inkjet head 40 is V0−ΔV is D3. D2.
[0038]
Then, based on (V0 + ΔV, D3) and (V0−ΔV, D2), the voltage V1 to be applied to the inkjet head 40 to achieve the predetermined color space distance d0 in the medium is determined (S16).
[0039]
Specifically, as shown in FIG. 6, (V0 + ΔV, D3) and (V0−ΔV, D2) are interpolated by a straight line. Then, based on the interpolated straight line, a voltage V1 that can achieve a predetermined color space distance D0 is obtained. The voltage V1 is a voltage to be applied to the inkjet head 40 for each color of C, M, Y, K, Lc, and Lm.
[0040]
The voltage V1 for each color is recorded in the applied voltage value recording unit 16. However, the difference from the standard value V0 = V1-V0 may be recorded instead of the voltage V1.
[0041]
The applied voltage value determining unit 18 determines a voltage to be applied to the inkjet head 40 based on the recorded contents of the applied voltage value recording unit 16.
[0042]
When a predetermined number N of dots are formed in a certain area A, if the applied voltage V1 that can achieve the color space distance D0 is determined, the number of dots is adjusted to obtain another color space distance. Can also be achieved.
[0043]
According to the embodiments of the present invention, it is possible to eliminate individual differences between ink jet heads that eject ink by receiving a voltage. In addition, since the individual difference is eliminated by using the color space distance between the ink color in the medium and the medium itself, the difference in the color characteristics of the medium itself can be absorbed.
[0044]
If a program for realizing the image input unit 12, the image processing unit 14, the applied voltage value recording unit 16 and the applied voltage value determination unit 18 is recorded in the ROM 104 or the RAM 106, and the program is read and executed by the CPU 102, The function of each part is performed.
[0045]
In the above embodiment, the step of determining the voltage V1 to be applied to the ink jet head 40 in the media reading device of the computer including the CPU, the hard disk, and the medium (floppy disk, CD-ROM, etc.) (S16) Read the media on which the program that realizes the above is recorded and install it on the hard disk. Even in such a method, the voltage V1 to be applied to the inkjet head 40 can be determined.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an image output device according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of an ink ejection mechanism for ejecting ink using an inkjet head 40.
FIG. 3 is an enlarged cross-sectional view of the vicinity of the inkjet head 40 of the ink ejection mechanism. FIG. 3A illustrates a case where no voltage is applied to the inkjet head 40 (FIG. 3A) and a case where a voltage is applied to the inkjet head 40 (FIG. 3 (b)).
FIG. 4 is a diagram showing a correspondence between a voltage applied to an inkjet head 40 and a color space distance between an ink color on a medium and the medium itself in a virtual standard device and a real device of the image output apparatus 1.
FIG. 5 is a block diagram showing a configuration of the image output apparatus according to the embodiment of the present invention, and in particular, is a functional block diagram showing a function of the control circuit 10 in detail.
FIG. 6 is a diagram showing the correspondence between the voltage applied to the inkjet head 40 and the color space distance between the color of the ink on the medium and the medium itself in the actual machine of the image output apparatus 1.
FIG. 7 is a flowchart illustrating a method of determining a voltage to be applied to the inkjet head 40.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 image output device 10 control circuit 12 image input unit 14 image processing unit 16 applied voltage value recording unit 18 applied voltage value determination unit 20 interface circuit 30 head drive circuit 40 inkjet head

Claims (8)

In an image output apparatus having an ink ejection unit that ejects an amount of ink corresponding to an applied voltage, an application voltage value determination method for determining a value of a voltage to be applied to the ink ejection unit,
A measurement voltage application step of applying a measurement voltage of a plurality of values to the ink ejection unit,
A printing step of printing on a medium using ink ejected from the ink ejection unit by applying the measurement voltage,
A color space distance measuring step of measuring a color space distance in a color space between the ink printed on the medium and the medium,
Based on the value of the measurement voltage and the corresponding measured color space distance, a voltage to be applied to the ink ejection unit when a color at a predetermined color space distance from the medium is realized on the medium. An applied voltage value determining step of determining a value,
And a method for determining an applied voltage value. The method for determining an applied voltage value according to claim 1,
Between the value of the measurement voltage, there is a standard value of a voltage to be applied to the ink ejection unit when a color at the predetermined color space distance from the medium is realized on the medium.
How to determine the applied voltage value. The method for determining an applied voltage value according to claim 2,
The value of the measurement voltage is a value obtained by adding a predetermined difference to the standard value and a value obtained by subtracting the difference.
How to determine the applied voltage value. The method for determining an applied voltage value according to claim 1,
In the applied voltage value determination step, using a ratio of a difference between two measurement voltage values and a corresponding difference between two measured color space distances,
How to determine the applied voltage value. A method for determining an applied voltage value according to any one of claims 1 to 4, wherein
The color space is a Lab space or an xyz space.
How to determine the applied voltage value. An ink discharging means for discharging an amount of ink corresponding to the applied voltage,
An applied voltage value recording unit that records the value of the voltage to be applied determined by the applied voltage value determining method according to any one of claims 1 to 5,
An applied voltage value determining unit that determines a voltage value to be applied to the ink discharging unit based on the recorded content of the applied voltage value recording unit,
An image output device comprising: What is claimed is: 1. An image output apparatus comprising: an ink ejection unit that ejects an amount of ink corresponding to an applied voltage, wherein a plurality of measurement voltages are applied to the ink ejection unit, and the ink is applied by the measurement voltage. A voltage to be applied to the ink ejection unit for an image output apparatus that prints on a medium using the ink ejected from the ejection unit and measures a color space distance in a color space between the ink printed on the medium and the medium. A program for causing a computer to execute an applied voltage value determination process for determining the value of
Based on the value of the measurement voltage and the corresponding measured color space distance, a voltage to be applied to the ink ejection unit when a color at a predetermined color space distance from the medium is realized on the medium. A program for causing a computer to execute an applied voltage value determining process for determining a value. A computer-readable recording medium that stores the program according to claim 7.

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