JP2002211012A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printer in which a higher gray scale can be represented even if the number of ink liquid drops is limited and an image can be formed with a higher image quality by controlling ink ejection optimally. SOLUTION: When both light and dark color inks can be ejected less than three drops for one ink ejection region, only five gray scale of 0-4 can be represented. When the entire region of 2 row×2 column is regarded as one pixel and the gray scale is varied from region to region, mean gray scale of the entire pixels can be represented by 16 steps or more. Consequently, an image can be formed with a higher image quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer, and more particularly, to an ink jet printer by restricting an ink discharge amount.
The present invention relates to an ink jet printer capable of forming a higher quality image.

[0002]

2. Description of the Related Art In recent years, printers capable of receiving digital image data and performing full-color printing have been used. Digital image data is subjected to image processing by an internal CPU, and full-color printing is performed on recording paper from, for example, an inkjet head (hereinafter, referred to as a head). A resolution of 300 dpi or more has been used.

[0003]

By the way, it has been found that in an ink jet printer capable of full-color printing, a so-called banding phenomenon occurs, in which an image has uneven streaks. Such banding is caused by poor positional accuracy of the nozzles and poor feed accuracy in the sub-scanning direction.
There is a limit to improving the accuracy of parts of an ink jet printer or the like to solve the problem, because it involves a problem such as an increase in cost.

On the other hand, there has been an attempt to eliminate banding by adjusting the amount of ink ejected. That is, the idea is to make the unevenness less visible by optimally adjusting the ink absorption characteristics of the recording medium from which the ink is ejected and the ink ejection amount. However, in reality, it is not known what discharge amount is set to most effectively eliminate banding. Even when the number of ink droplets at the same point is limited due to the limitation of the ink absorption characteristics of the recording medium, it is convenient if higher gradations can be expressed.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and can express higher gradation and reduce the ink discharge amount even when the number of ink droplets is limited. An object of the present invention is to provide an ink jet printer capable of forming a higher quality image by performing optimal control.

[0006]

In order to achieve the above object, an ink jet printer according to a first aspect of the present invention is an ink jet printer which forms an image by discharging ink in a matrix on a recording medium. , N rows and M columns (N and M are integers equal to or greater than 2) so that ink droplets can be ejected for each region.
The area of N rows and M columns is regarded as one pixel unit, and the average gradation of each pixel unit is expressed in a plurality of stages by a combination of a region where ink is ejected and a region where ink is not ejected. .

According to a second aspect of the present invention, there is provided an ink jet printer for forming an image by ejecting ink on a recording medium in a matrix, wherein N rows and M columns (where N and M are 2 or more) are formed on the recording medium. ) Can be ejected in each of the regions arranged in a matrix, and the N rows and M columns are regarded as one pixel unit, and the highest density gradation is expressed in the pixel unit. In this case, no ink is ejected to at least one region.

A third aspect of the present invention is an ink jet printer for forming an image by ejecting ink in a matrix on a recording medium, wherein N rows and M columns (where N and M are 2 or more) are formed on the recording medium. ) Can be ejected in each of the regions arranged in a matrix, and the entire region of the N rows and M columns is regarded as one pixel unit, and the maximum ejection amount of the ink in each region is defined as C In this case, the amount of ink ejected to the entire pixel unit is limited to (C × N × M) / 2 or less.

[0009]

According to a first aspect of the present invention, there is provided an ink jet printer for forming an image by ejecting ink on a recording medium in a matrix, wherein N rows and M columns (N and M are 2 or more) are formed on the recording medium. Integer)
The ink droplets can be ejected for each of the regions arranged in a row, and the region of N rows and M columns is regarded as one pixel unit.
Since the average gradation of each pixel unit is expressed in a plurality of stages by a combination of a region where ink is ejected and a region where ink is not ejected, even when the type of the amount of ink droplet ejected to the same region is small. Thus, a higher quality image can be formed.

The principle of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a pattern in a case where ink is ejected to each region of two rows and two columns on a recording medium using an ink jet printer capable of ejecting inks of different colors, for example, of similar colors. It is. FIG. 2 is a diagram showing tone values of one area that can be expressed by using ink droplets in such an ink jet printer.

Here, if it is assumed that only two droplets can be ejected in one region in a combination of light and dark colors, as an example, five steps (up to six steps) as shown in FIG.
Can be represented only by However, as shown in FIG. 1, the entire area of two rows and two columns is regarded as one pixel, and the gray level is changed for each area, so that the average gray level of the entire pixel is expressed in 16 or more stages. Becomes possible. Thereby, a high-quality image can be formed. Figure 1
In (a) and (b), 10
The example which expressed the gradation of the stage is shown.

If N and M are increased, a higher gradation can be expressed in pixel units, but the pixels may be coarser. Therefore, the N rows and M columns are changed to 2 rows and 2 columns.
With columns, higher gradations can be expressed while maintaining the pixels to some extent finer. However, it is not limited to this.
Various configurations, such as rows and three columns, four rows and four columns, are possible.
Also, N and M need not be equal.

According to a second aspect of the present invention, there is provided an ink jet printer for forming an image by ejecting ink on a recording medium in a matrix, wherein N rows and M columns (N and M are 2 or more) are formed on the recording medium. ) Can be ejected in each of the regions arranged in a matrix, and the N rows and M columns are regarded as one pixel unit, and the highest density gradation is expressed in the pixel unit. Also in this case, since ink is not ejected to at least one region, a higher quality image can be formed.

The principle of the present invention will be described with reference to FIGS. According to the study of the present inventors, for example, when the maximum ejection amount in each area of two rows and two columns is two inks, the two inks are applied to all areas (here, one pixel unit). It was found that when the recording medium was ejected to four areas, the recording medium could not absorb the ink completely and overflowed with the ink, thereby deteriorating the image quality. Therefore, in the present invention, FIG.
In FIG. In FIG. 1B, the pixel unit of No. 6 is No.
Even in the case of expressing the highest density gradation in the pixel unit as in the pixel unit of 9, the ink ejection is restricted to at least one region so that the region where the ink is not ejected becomes another region. It becomes possible to absorb the ink in the area and form a higher quality image.

In the above case, the number of areas where ink is not ejected is set to one. However, the present invention is not limited to this. That is, whether or not the ink overflows depends on the recording medium and the appropriate amount of the ink ejected per time. Therefore, in the pixel unit, it is preferable that the number of areas where ink is not ejected is changed in accordance with at least one of the recording medium and an appropriate amount of ink ejected per time.

According to the research results of the present inventors, it has been confirmed that, in each pixel unit arranged in a line, if the area where ink is not ejected is located at the same position, the image quality deteriorates. Therefore, by controlling the ejection of ink from the nozzles so that the positions of areas where ink is not ejected in adjacent pixel units are different, a higher quality image can be obtained. FIG. 3 shows an example in which the position rotates clockwise.

As described above, the control in which the position of the region where ink is not ejected is different, for example, such that the position of the region where ink is not ejected is rotated around the center of the pixel unit with respect to adjacent pixel units. It is conceivable to control the driving of the nozzles, which can effectively improve the image quality, but is not limited to this.

According to a third aspect of the present invention, there is provided an ink jet printer for forming an image by ejecting ink on a recording medium in a matrix, wherein N rows and M columns (N and M are 2 or more) are formed on the recording medium. ) Can be ejected in each of the regions arranged in a matrix, and the entire region of the N rows and M columns is regarded as one pixel unit, and the maximum ejection amount of the ink in each region is defined as C In this case, the amount of ink ejected to the entire pixel unit is limited to (C × N × M) / 2 or less.
A higher quality image can be formed.

The principle of the present invention will be described with reference to FIGS. As described above, according to the study of the present inventors, for example, when the maximum ejection amount in each area of two rows and two columns is two drops of ink, two drops of this ink are used in one pixel unit. It was found that when the ink was ejected to all the areas (here, four areas), the recording medium could not absorb the ink and overflowed with the ink, thereby deteriorating the image quality. In the second aspect of the present invention, an area where ink is not ejected is provided to suppress ink overflow. On the other hand, in the third invention, for example, if N = M = 2 and the maximum ink ejection amount per area is two drops, the amount of ink ejected to the entire pixel unit is (2 × 2 × 2) / 2
By setting = 4 drops, the amount of ink is limited so that a high quality image can be formed. Since the maximum ink ejection amount per area is two, the combination of inks in such a case is as shown in FIG.
Here, the position of the area is not considered.

It is preferable that the area where the ink is ejected contacts at least two areas where the ink is not ejected. This state is shown in FIG. 9 and 10. That is, in FIG. 1 to No.
By expressing all gradations in units of 8 pixels, it is possible to suppress overflow of ink and to form a higher quality image.

Further, when an image is formed using a plurality of types of inks having similar lightness with respect to similar colors, if only the amount of ink on the light color side is limited to (C × N × M) / 2 or less, it becomes more difficult. The formation of a high-quality image has been found from the research results of the present inventors.

Further, the amount of the ink may be limited to at least the middle of the gradation expressed by the ink jet printer. In this case, the image up to the halftone must be of higher quality. Can be. This is due to the fact that stripes and the like are difficult to visually recognize in an image having a high density.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 5 is a diagram illustrating an example of a mechanical configuration near the head in the inkjet printer according to the present embodiment. The carriage 2 is a resin case housing the head 10 and a head driver (not shown). The head driver, which is a driving unit housed in the carriage 2, is composed of, for example, an IC including a later-described parasili 18, and is connected to the control board 9 by a flexible cable 5 pulled out from the carriage 2.

The carriage 2 is reciprocated by the carriage driving mechanism 6 in the main scanning direction (X direction) indicated by an arrow in the figure. The carriage drive mechanism 6 includes a motor 6a, a pulley 6b, a toothed belt 6c, and a guide rail 6d, and the carriage 2 is fixed to the toothed belt 6c.

When the pulley 6b is rotated by the motor 6a, the carriage 2 fixed to the toothed belt 6c is moved along the arrow X direction in the figure. Guide rail 6d
Are two columns parallel to each other and penetrate through the insertion hole of the carriage 2 so that the carriage 2 slides.

For this reason, the toothed belt 6c is
The carriage 2 does not bend under its own weight, and the direction of the reciprocating movement of the carriage 2 is on a straight line. The direction in which the carriage 2 moves can be changed by reversing the rotation direction of the motor 6a, and the moving speed of the carriage 2 can be changed by changing the number of rotations. The ink cartridge 4 (not shown) has an ink tank inside. The ink supply port of the ink tank is opened when the ink cartridge 4 is set on the carriage 2 and connected to the ink supply pipe. When the connection is released, the ink supply port is closed and the ink is supplied to the head 10.

A head 10 is provided on the carriage 2. On the back surface of the head 10, Y, M,
Ink cartridges containing inks of the respective colors C and K are detachably arranged. The illustration of the ink cartridge is omitted. Flexible cable 5
Is a data transfer means, in which a wiring pattern including a data signal line, a power supply line and the like is printed on a flexible film, and the data is transferred between the carriage 2 and the control board 9; Follow the movement.

The encoder 7 is provided with graduations at a predetermined interval on a transparent film of resin, and the graduations are detected by an optical sensor provided on the carriage 2 so that the carriage 2 can detect the graduations.
Detects the moving speed, position, and moving direction of. Paper transport mechanism 8
Is a mechanism for transporting the recording paper P in the sub-scanning direction indicated by the arrow Y in the figure, and includes a transport motor 8a and transport roller pairs 8b and 8c.
It is comprised including. The transport roller pair 8b and the transport roller pair 8c are driven by the transport motor 8a, and are a pair of rollers that are substantially equal by a gear train (not shown), but rotate at a slightly higher peripheral speed.

The recording paper P is sent out from a paper feeding mechanism (not shown) and is nipped by a pair of conveying rollers 8b rotated at a constant speed, and is conveyed in a sub-scanning direction by a paper feeding guide (not shown). Is corrected and then conveyed while being nipped by the conveying roller pair 8c.

Since the peripheral speed of the pair of conveying rollers 8c is slightly higher than that of the pair of conveying rollers 8b, the recording paper P passes through the recording section without causing slack. The speed at which the recording paper P moves in the sub-scanning direction is set to a constant speed.

The carriage 2 is moved at a constant speed in the main scanning direction while moving the recording paper P at a constant speed in the sub-scanning direction in this manner, and the ink ejected from the head 10 is adhered to one side of the recording paper P. The image is recorded in a predetermined range of the image.

FIG. 6 is a block diagram showing an outline of a circuit for processing image data in the ink jet printer according to the present embodiment. In the processing circuit of FIG. 6, after the image data is processed by the pre-processing unit 11 in which the error diffusion processing and the like are performed, 16 bits are input to the data input unit 12 serving as a reading unit, Are stored in the expansion memory 14.

The image data stored in the developing memory 14 is read out by the data control unit 13 in response to a request from the data read request unit 15 made via the SDRAM control unit 16, and is read by the data control unit 13. The data is input to the I / F unit 17. The image data is transmitted to the parallel I / F unit 17.
After the data shift is performed, the data is transmitted in 32 bits (16 bits × 2) to the parallel circuit 18 constituting the drive data generating means, and the head driver generates the drive data for driving the head 10 based on the data shift. It is supposed to.

According to the present embodiment, by performing address control of data in the parallel I / F unit 17, it is possible to perform rotation of an area where ink is not ejected as shown in FIG. On the other hand, in the parallel circuit 18, the ink ejection amount can be limited as described with reference to FIGS.

The present invention has been described with reference to the embodiments. However, the present invention should not be construed as being limited to the above embodiments, and it is needless to say that modifications and improvements can be made as appropriate. is there.

[0036]

According to the present invention, higher gradation can be expressed even when the number of ink droplets is limited.
In addition, by optimally controlling the ejection amount of the ink, it is possible to provide an ink jet printer capable of forming a higher quality image.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pattern in a case where ink is ejected to each area of two rows and two columns on a recording medium by using an ink jet printer capable of ejecting inks of different colors, for example, of similar colors; It is.

FIG. 2 is a diagram showing gradation values of one area that can be expressed by using ink droplets in the ink jet printer of the present invention.

FIG. 3 is a diagram illustrating an example of a rotation in a region where ink is not ejected.

FIG. 4 is a diagram illustrating an example of a combination of ink droplets when the amount of ink per pixel unit is limited.

FIG. 5 is a diagram illustrating an example of a mechanical configuration near a head in the ink jet printer according to the present embodiment.

FIG. 6 is a block diagram illustrating an outline of a circuit for processing image data in the ink jet printer according to the present embodiment.

[Explanation of symbols]

 2 Carriage 5 Flexible cable 6 Carriage drive mechanism 10 Head 12 Data input unit 13 Data control unit 14 Expansion memory 15 Data read request unit 17 Parallel I / F unit 18 Parallel

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tatsuro Oishi 1 Sakuracho, Hino-shi, Tokyo Konica Corporation F term (reference) 2C056 EA08 ED03 ED05 ED07 2C057 AF39 CA04 CA05 CA07

Claims (10)

[Claims] 1. An ink jet printer that forms an image by ejecting ink onto a recording medium in a matrix form, wherein each area on the recording medium is arranged in N rows and M columns (N and M are integers of 2 or more). Each of the N rows and M columns is regarded as one pixel unit, and the average of each pixel unit is determined by a combination of a region where the ink is discharged and a region where the ink is not discharged. An ink jet printer characterized by expressing a target gradation in a plurality of stages. 2. The ink jet printer according to claim 1, wherein the N rows and M columns are two rows and two columns. 3. An ink jet printer which forms an image by ejecting ink in a matrix on a recording medium, wherein each area arranged in N rows and M columns (N and M are integers of 2 or more) on the recording medium. Ink droplets can be ejected every time, the area of N rows and M columns is regarded as one pixel unit, and even when expressing the highest density gradation in the pixel unit, at least one An ink jet printer, characterized in that ink is not ejected to an area. 4. The apparatus according to claim 3, wherein, in the pixel unit, the number of areas where ink is not ejected varies according to at least one of a recording medium and an appropriate amount of ink ejected per time. The ink-jet printer as described. 5. The ink jet printer according to claim 3, wherein the positions of the areas where ink is not ejected in adjacent pixel units are different. 6. The ink-jet apparatus according to claim 3, wherein the position of a region where ink is not ejected is different from an adjacent pixel unit so as to rotate around the center of the pixel unit. Printer. 7. An ink jet printer which forms an image by ejecting ink on a recording medium in a matrix form, wherein each area arranged in N rows and M columns (N and M are integers of 2 or more) on the recording medium. Each of the N rows and M columns is regarded as one pixel unit, and the maximum ejection amount of ink in each area is defined as C.
Wherein the amount of ink ejected to the entire pixel unit is limited to (C × N × M) / 2 or less. 8. The ink jet printer according to claim 7, wherein the area where the ink is ejected contacts at least two areas where the ink is not ejected. 9. When an image is formed using a plurality of types of inks of different colors with similar colors, only the amount of ink on the light color side is limited to (C × N × M) / 2 or less. The ink jet printer according to claim 7 or 8, wherein 10. The ink jet printer according to claim 7, wherein the amount of the ink is limited to at least the middle of the gradation expressed by the ink jet printer.