KR102480007B1 - Method for improving density banding by masking - Google Patents

Abstract

The present invention provides a method for improving density banding using masking in an extremely simple manner, in which printing is performed by dividing one print head (PH) into two areas, wherein: in a first pass, a lower region (PB) of the print head prints only front parts (11,13, ... 82, 84) of an image by a first masking pattern; in a second pass, ("A") the lower region (PB) of the print head prints only rear parts (15, 17, ... 86, 88) of the image by the first masking pattern ("A") and an upper region (PA) of the print head prints a remaining area not printed in the first pass with a second masking pattern ("B") reversed from the first masking pattern; and in a third pass, the upper region (PA) of the print head prints all the remaining parts (16, 18, ... 85, 87) not printed in the second pass by filing the same with the second masking pattern ("B"), thereby allowing specific lines of the image to be printed by different nozzles to improve density banding.

Description

Method for improving density banding using a mask {METHOD FOR IMPROVING DENSITY BANDING BY MASKING}

The present invention relates to a method for improving density bending of a printer, and more particularly, to a method for improving density bending using a mask.

Generally, normal printing of a printer is performed as shown in FIG. 1 . That is, assuming that an image of 8 pixels in width and 8 pixels in height is printed, for example, as in (b) of FIG. 1, a normal printing method (a method of printing without masking), As the print head (PH) having 8 nozzles moves as indicated by the arrow, pixels 81 to 88 are printed at once in the order of pixels 11 to 18, pixels 21 to 28, and pixels 31 to 38.

In other words, all 8 pixels in width and 8 pixels in height are printed in one pass. In other words, the method of printing with 1 pass is the most common and fastest printing method.

However, when printing is performed with a low pass such as 1 pass, the banding caused by the profile of the print head cannot be hidden. The print head profile refers to a curve of drop velocity or drop volume of each nozzle. When the drop velocity is high, the drop volume is high, and conversely, when the drop velocity is low, the drop volume is also low.

2 shows a head profile graph and a printed image. If you look at the part where the injection speed is high in the graph, the magenta color looks darker, which is called density banding. Such density bending occurs due to the deviation of each nozzle itself and also to the difference in piezo characteristics that control the pressure of each nozzle. According to the first prior art, such fine density bending is unavoidable. .

On the other hand, as a first prior art to improve the "bleeding" problem in which ink flows from one printed dot to another in relation to an inkjet printer and thus a lot of ink is used, through a mask, Patent Publication No. 10-2005 -0068005 (name: image printing method of a printer) is disclosed.

According to the second prior art, as shown in FIG. 3, some pixels 50, 52, 54, 56, and 58 are simply skipped and printed without printing, and then pixels that are not printed again in the first pass. By printing (51,53,55,57,59) using a two-pass method, which then prints in the second pass, when two pixels are printed next to each other, two drops of ink are printed on the print medium. As the volume of ink is large, it is possible to solve the problem of bleeding and banding in which the ink droplets flow to different ink droplets before they dry.

However, the second prior art, such as the above document 1, is also the same as the first prior art in that a specific spray nozzle sprays to a pixel at a specific position, so density bending cannot be improved either.

On the other hand, techniques for improving banding that occurs for various reasons through a mask have been disclosed. As a third prior art for improving feed banding, Patent Publication No. 10-2013-0100336 (title : An inkjet printer and a printing method therefor) are disclosed.

Feed bending, as shown in FIG. 4, is a bending that repeatedly occurs in a cycle of one rotation due to the eccentricity of the conveying roller, and the eccentricity in the conveying roller is the same rotation angle of the print medium even when the conveying roller rotates. Since it causes a difference in conveying amount and makes it impossible to convey the desired amount of print media, eccentricity-derived unevenness occurs, which is sparsely formed at some locations and densely formed at other locations.

In the third prior art, the deviation of the dot formation position due to the insufficient conveying accuracy of the print medium due to the eccentricity of the conveying roller is suppressed, thereby making it difficult to recognize the unevenness.

On the other hand, among banding that occurs for various reasons, technologies to be improved through a mask are disclosed, as a fourth prior art for improving feed banding, Patent Publication No. 10-2013-0100336 ( Name: inkjet printer and its printing method) are disclosed.

According to the fourth prior art, as shown in FIG. 5, in order to eliminate banding between printed bands in a multi-pass inkjet printer, the print head is moved in the main scan direction (X) in each scan, , Printing is performed by moving the print head relative to the print medium in the sub-scan direction (Y) by the band width (BW) at a time. The print head has a nozzle array composed of a plurality of nozzles arranged in a line along the sub-scanning direction Y. The nozzle array is divided into pass arrays P (P1 to P4) respectively corresponding to a plurality of passes (e.g., first to fourth passes), and ink is not ejected between adjacent pass arrays P, respectively. It includes a skip row (S) (S1 to S3) composed of nozzles that do not. It is controlled so that the nozzles of each pass column P discharge ink droplets and the nozzles of each skip column S do not discharge ink droplets. In this way, the position of the end of the base band and the position of the end of the band formed thereon can be shifted.

That is, a print head having a nozzle array composed of a plurality of nozzles arranged along a sub-scanning direction orthogonal to the main scanning direction is provided, the print head is controlled to eject ink droplets by associating print data with the nozzles, and the print head At the same time as moving in the main scanning direction, the print head is moved relative to the print medium by a band width in the sub-scan direction for each scan to print a plurality of passes in one scan on the print medium, each scan Bands formed by the same pass are continuously formed on the same layer, and printing is performed so that the end of the band formed in the previous scan and the end of the band formed overlapping thereon are shifted, thereby improving band bending.

However, compared to the complexity, the effect of the fourth prior art is insignificant because it improves the density banding as in FIG. 2 .

Patent Document 1: Publication No. 10-2005-0068005 (Name: Image printing method of printer) Patent Document 2: Registered Patent Publication No. 10-1151267 (Name: Inkjet printing device and printing method) Patent Document 3: Publication No. 10-2013-0100336 (Name: Inkjet Printer and Printing Method) Patent Document 4: Registered Patent Publication No. 10-1565056 (Name: Inkjet Printer and Printing Method Thereof)

The present invention is to solve the above problems, and an object thereof is to provide a method for improving density bending using a mask in a very simple manner.

Additionally, in addition to density banding, it is possible to simultaneously improve banding caused by a feeding error or various other bandings by an extremely simple method.

The above object and other additional objects will be clearly recognized by those skilled in the art without departing from the spirit of the present invention by the appended claims.

A method for improving density bending using a mask according to an aspect of the present invention for solving the above problems is to divide one print head (PH) into two areas and perform printing, but in the first pass, the print head The sub-area PB prints only the front part (11,13, ... 82,84) of the image by the first masking pattern ("A"), and in the second pass, the print head sub-area PB Only the rear part of the image (15, 17, ... 86, 88) is printed by the first masking pattern ("A"), and the upper area (PA) of the print head is a second masking pattern inverted from the first masking pattern. The remaining area not printed in the first pass is printed with the pattern ("B"), and in the third pass, the print head upper area (PA) is the second masking pattern ("B") and the remaining portion (unprinted in the second pass) 16, 18, ... 85, 87) are filled in and printed, so that specific lines of the image are printed by different nozzles and density banding is improved.

Preferably, all pixel data of the image in the first pass is filtered by a filter matrix of Equation 1 below,

........................ (수학식1)

................... (Equation 1)

All pixel data of the image in the second pass is filtered by the following filter matrix (Equation 2),

........................ (수학식2)

................... (Equation 2)

All pixel data of the image in the third pass is filtered by the following filter matrix (Equation 3),

........................ (수학식3)

................... (Equation 3)

It is characterized by allowing the original image data to be printed as a whole.

On the other hand, a method for improving density bending using a mask according to another aspect of the present invention for solving the above problems is to divide one print head PH into two areas to print, but in the first pass, print The subarea PB of the head prints only the front part (11,13, ... 82,84) of the image by the first masking pattern ("A"), and in the second pass, the print head subarea PB prints only the rear part of the image (15, 17, ... 86, 88) by the third masking pattern ("C"), and the print head upper area (PA) is a second masking pattern inverted from the first masking pattern ("C"). The remaining area not printed in the first pass is printed with the masking pattern ("B"), and in the third pass, the upper area (PA) of the print head is printed with the fourth masking pattern ("D") inverted from the third masking pattern. By filling in and printing all the remaining parts (16, 18, ... 85, 87) not printed in the second pass, it is possible to improve density banding while allowing specific lines of the image to be printed by different nozzles. to be characterized

Preferably, the first masking pattern (“A”) and the third masking pattern (“C”) continuously form a gradient, and the fifth masking pattern (“B”) and the fourth masking pattern (“D ") is characterized in that a continuous gradient in an opposite direction to the gradient of the first masking pattern ("A") and the third masking pattern ("C") is formed.

On the other hand, in a method for improving density bending using a mask according to another aspect of the present invention for solving the above problems, one print head PH is provided with a first area P1 and a second area P2 ) and the third area P3, and printing is performed, but in the first pass, the third area P3 of the print head is the foremost 1/3 of the image by the first masking pattern "A". Only the part (M1) is printed, and in the second pass, the third area (P3) of the print head prints only the middle 1/3 part (M2) of the image by the first masking pattern ("A"), and printing The second area P2 of the head prints another partial area of the foremost 1/3 portion M1 of the image not printed in the first pass with the second masking pattern "B", and in the third pass, The third area P3 of the print head prints only the rearmost 1/3 of the image (M3) by the first masking pattern ("A"), and the second area P2 of the print head prints the second area P2 of the print head. Another partial area of the middle 1/3 portion (M2) of the image not printed in the second pass is printed with the masking pattern ("B"), and the first area (P1) of the print head is the third masking pattern ( "C"), all remaining areas of the foremost 1/3 portion (M1) of the image not printed in the first and second passes are printed, and in the fourth pass, the second area (P2) of the print head is Another partial area of the rearmost 1/3 portion (M3) of the image not printed in the third pass is printed with the second masking pattern ("B"), and the first area (P1) of the print head is the third pass. All remaining areas of the middle 1/3 portion (M2) of the image not printed in the second and third passes are printed with the masking pattern ("C"), and in the fifth pass, the first area (P1) of the print head ) is the third masking pattern ("C") by printing all the remaining areas of the rearmost 1/3 portion (M3) of the image that is not printed in the third and fourth passes, so that the specific line of the image is different 3 While being printed by two nozzles, It is characterized by improving density banding.

Most preferably, in the part where the drop velocity is particularly fast in the head profile, some dots are removed to lower the density, and in the part where the drop velocity is particularly slow, some dots are added to increase the density. It is characterized in that it allows.

According to the method for improving density bending using a mask according to the present invention, it is possible to improve density bending using a mask in a very simple manner, and by changing a mask pattern, additionally, in addition to density bending, an extremely simple Even with this method, it is possible to simultaneously improve bending caused by a feeding error or various other types of bending.

Meanwhile, additional features and advantages of the present invention will become more clear through the following description.

1 is a diagram explaining a 1-pass printing method of a first prior art;
2 is a diagram showing a relationship between a head profile and density bending in a first prior art;
3 is a diagram showing a 2-pass printing method of a second prior art;
4 is a view showing the generation of stains due to accumulated conveying errors due to eccentricity of a conveying roller of a third prior art;
5 is a diagram showing a multi-pass printing method for improving bending between each band of a fourth prior art;
6 is a conceptual diagram of divisional control of the printer head PH according to the first embodiment of the present invention.
7 is a diagram explaining the masking concept according to the first embodiment of the present invention.
Fig. 8 is a diagram explaining a multi-pass printing method according to the first embodiment of the present invention;
9 is a view for explaining a first modified example of a mask pattern corresponding to FIG. 7;
FIG. 10 is a view for explaining a second modified example of a mask pattern corresponding to FIG. 7;
Fig. 11 is a view of a printing state using actual masking according to the first embodiment of the present invention;
12A to 12C are partial enlarged views of FIGS. 11 (a) to (c), respectively.
Fig. 13 is a diagram explaining a masking concept according to a second embodiment of the present invention;
Fig. 14 is a diagram explaining a masking concept according to a third embodiment of the present invention;

The present invention will be described with reference to the accompanying drawings for preferred embodiments.

However, the embodiments of the present invention can be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described in detail below, and those of ordinary skill in the art can It is provided for complete explanation.

Hereinafter, with reference to the accompanying drawings will be described in detail according to the present invention.

Prior to the detailed description of the present invention, the same or corresponding components in the drawings are given the same reference numerals, and if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description will be omitted.

Also, in this specification, the examples and embodiments described below are to be considered as illustrative and not restrictive, and the present invention is not limited to the details given herein, but substitutions and equivalents within the scope and equivalents of the appended claims. can be changed to other embodiments

(First embodiment)

Now, referring to FIGS. 6 to 11 , a method of improving density banding using a mask according to the first embodiment of the present invention will be described.

6 is a conceptual diagram of division control of the printer head (PH) according to the first embodiment of the present invention, FIG. 7 is a diagram explaining the masking concept according to the first embodiment of the present invention, and FIG. It is a diagram explaining the multi-pass printing method according to the first embodiment.

FIG. 9 is a view for explaining a first modified example of the mask pattern corresponding to FIG. 7 , and FIG. 10 is a view for explaining a second modified example of the mask pattern corresponding to FIG. 7 .

Fig. 11 is a drawing of a printing state using actual masking according to the first embodiment of the present invention, and Figs. 12A to 12C are partially enlarged views of Figs. 11 (a) to (c), respectively.

There may be several methods to hide the density banding, but here, a method of solving the density banding using masking is described. When masking is used, the number of print passes is at least doubled. A higher print pass has the effect of hiding more of the banding.

One print head (PH) to two or more areas for masking. It is divided into two areas here. The upper 1/2 area of the print head PH is assumed to be the upper area PA, and the lower 1/2 area is assumed to be the lower area PB. That is, in FIG. 6 , the blue portion (nozzles 1 to 4) is the upper area PA, and the red portion (nozzles 5 to 8) is the lower area PB.

If the masking pattern used in the upper area (PA) of the print head (PH) is "A" and the inverted masking pattern used in the lower area (PB) of the print head (PH) is "B", "A" + B = original image”.

Alternatively, conversely, the masking pattern of "B" is printed by the upper area PA of the print head PH, and the unprinted area is filled with the inverted masking pattern "A" to print the lower area of the print head PH ( PB) may be printed. Whether A or B prints first may depend on the media feeding direction.

In either case, A and B are patterns of mutually inverted shapes. Adding two patterns always results in the original image.

7 shows the simplest mask pattern. In the first pass, pixels are printed while skipping one by one, and in the second pass, pixels not printed in the first pass are printed.

In FIG. 8, as an example, the number of nozzles of the print head (PH) is 8, and a state in which an image of 8 pixels in width x 8 pixels in height is printed is shown.

First, as shown in (a) of FIG. 8, in the first pass, the print head sub-region (red nozzle) (PB) is only partially (11,13, .. 82,84) to print. At this time, the upper area (blue nozzle) PA of the print head does not print anything.

Next, as shown in (b) of FIG. 8, in the second pass, the entire print head is divided into an upper area (PA) and a lower area (PB) for printing. Like the first pass, the lower area (PB) is printed in FIG. Only a part of the image (15,17, ... 86,88) is printed by the "A" masking pattern of "A", and the upper area (PA) is an inverted masking pattern ("B"), and the rest not printed in the first pass The area is printed, that is, the remaining parts 12, 14, ... 81, 83 (blue parts of the image) of the image are filled and printed by the "B" masking pattern of FIG. Thus, the front 4 pixels (11 to 14, ... 81 to 84) of the image are all printed.

Finally, as shown in (c) of FIG. 8, in the third pass, the print head lower area PB does not print anything, and the upper area PA does not print anything in the second pass (16, 18, ... 85, 87) are filled in and printed. Then, the back 4 pixels (15 to 18, ... 85 to 88) of the original image are all printed.

Therefore, when multi-scan is performed by dividing the print head PH into two parts (A and B), three multi-scans are eventually required. In the case of doing so, multi-scan (2n-1) times is eventually required.

A filter for masking of the print head in the three-pass method is expressed as a matrix as follows.

(1) Filter matrix in the first pass:

........................ (수학식1)

................... (Equation 1)

(2) Filter matrix in the second pass:

........................ (수학식2)

................... (Equation 2)

(3) Filter matrix in the third pass:

........................ (수학식3)

................... (Equation 3)

Depending on the shape of the mask pattern used, a difference in the type and effect of improved banding may occur.

9 and 10 show first and second modified examples of the mask pattern in which a change is made to the mask pattern of the first embodiment.

11 is an example of a masking pattern shape in actual use. In FIGS. 6 to 10, 8×8 pixels have been described for convenience of description, but in practice, usually hundreds to thousands of pixels form one image.

11(a) and 12a perform masking in a gradient shape. In this case, the masking pattern used for printing the front image and the masking pattern used for printing the rear image will be different from each other. As a result, In the first pass, the pixels in the front of the image are printed by the print head subregion (P5-P8) in the "A" masking pattern, and in the second pass, the pixels in the back of the image are printed in the "C" masking pattern by the print head subregion (P5). ~ P8), the front pixels of the image are printed by the print head upper areas (P1 to P4) with the “B” masking pattern, and in the third pass, the rear pixels of the image are printed with the “D” masking pattern by the print head By being printed by the upper regions (P1 to P4), since each line of the image is printed by different nozzles, it is possible to minimize density banding due to the inherent deviation of the nozzles, and at the same time, even bending due to feeding errors can be reduced to an extent. At this time, "A" and "B" are mutually inverted patterns, "C" and "D" are mutually inverted patterns, and "A" and "C" and "D" and "B" are respectively gradient patterns. is a mask pattern forming As a result, in the case of the gradient masking, there is an additional effect of improving even the banding caused by the feeding error.

11(b) and 12b make the image look soft, and FIGS. 11(c) and 12c are examples of masking patterns that enable printing at a frequency higher than the maximum print frequency of the print head.

(Second embodiment)

In FIG. 13, a masking concept related to the second embodiment for improving density banding is described.

The type of banding that can be improved is determined according to the shape of the masking pattern. Depending on the shape, several types of bending can be improved at the same time.

Density banding caused by a print head profile is improved to some extent by the masking method described above. To further improve the density banding, it is possible to modify the masking method.

13, “A + B = C”. According to the masking method described above, C should be the original image, but C does not become the original image here.

If you look at the horizontal line number 1, there is a gray filled pixel (green dot). This pixel is also in the "A" masking pattern, and also in the "B" masking pattern. That is, since it is printed in the first pass and also in the second pass, the first horizontal line has a darker color.

Conversely, if you look at the horizontal line number 4, there are pixels filled with white (red dots). This pixel is neither in the "A" masking pattern nor in the "B" masking pattern. That is, since it is not printed in the first pass and not printed at all in the second pass, the number 4 horizontal line has a lighter color.

Using this principle, the part where the drop velocity is particularly fast in the head profile can be reduced by removing some dots, and the part where the drop velocity is particularly slow can be increased by adding some dots. . Then, the effect of reducing the density banding is higher and the image quality is further improved.

(Third Embodiment)

In FIG. 14, a masking concept related to the third embodiment for density banding improvement is described.

In this third embodiment, when the print head (PH) is divided into three areas and the image projection medium is divided into three areas for printing, a total of five multi-passes are used while density banding is performed using a mask. A brief description of how to improve.

First, one print head (PH) is divided into three areas of a first area (P1), a second area (P2), and a third area (P3) to perform printing, and even in the case of a print medium, the front third It is divided into three zones: zone (M1), middle 1/3 zone (M2), and rearmost 1/3 zone (M3).

At this time, naturally, it is preferable that the original image is printed by combining three masks, the first mask (A), the second mask (M2), and the third mask (M3).

First, in the first pass, the third region P3 of the print head PH in FIG. 14 partially (preferably 1) only the foremost 1/3 part (M1) of the image by the first masking pattern (“A”). /3) is printed, and the other first area P1 and second area P2 do not operate.

Next, in the second pass, as the print medium moves, the third area P3 of the print head prints only the middle 1/3 portion (M2) of the image by the first masking pattern ("A"), and prints The second area P2 of the head prints another partial area of the foremost 1/3 portion M1 of the image not printed in the first pass with the second masking pattern "B", and the other first area ( P1) does not do anything.

Subsequently, in the third pass, the third area P3 of the print head prints only the rearmost 1/3 of the image (M3) by the first masking pattern ("A"), and the second area (P3) of the print head Area P2 prints another partial area of the middle 1/3 portion M2 of the image not printed in the second pass with the second masking pattern "B", and the first area P1 of the print head ) is the third masking pattern ("C") by printing all the remaining areas of the front 1/3 portion M1 of the image not printed in the first and second passes, thereby forming the front 1/3 portion of the image (M1) causes printing to be completed.

Continuing thereafter, in the fourth pass, the second area P2 of the print head is the second masking pattern ("B") of the rearmost 1/3 portion M3 of the image not printed in the third pass. Another partial area is printed, and the first area (P1) of the print head is the third masking pattern ("C") of the middle 1/3 portion (M2) of the image not printed in the second and third passes. By printing the rest of the area, the middle 1/3 of the image (M2) is also printed (at this time, the other third area (P3) of the print head does not operate).

Finally, in the fifth pass, the first area P1 of the print head is the third masking pattern "C", and the rearmost 1/3 portion (M3) of the image not printed in the third and fourth passes. ), so that the rearmost 1/3 of the image (M3) is also printed (At this time, the other second area (P2) and third area (P3) of the print head do not operate. not).

As a result, by having a specific line of an image printed 1/3 by three different nozzles, density banding due to deviation of each nozzle is further improved.

Although the present invention has been described by way of examples above, various modifications such as division of the printer head area or change of mask pattern are possible, and in addition, those skilled in the art to which the present technology belongs can perform the present invention It is natural that changes and modifications within the range not departing from the technical idea belong to the present invention.

PH: Printer head
PA: upper area of print head
PB: print head subarea
1 to 8: Nozzle
11 to 88: pixels
11 to 14, ... 81 to 84: front pixel image
15 to 18, ... 85 to 88: rear pixel image
A: Forward image masking pattern in 1st pass
B: Forward image masking pattern in 2nd pass
C: Backward image masking pattern in 2nd pass
D: Rear image masking pattern in 3rd pass

Claims (6)

Printing is performed by dividing one print head (PH) into two areas,
In the first pass, the subregion (PB) of the print head prints only the front part (11,13, ... 82,84) of the image by the first masking pattern ("A"),
In the second pass, the print head lower area PB prints only the rear part (15, 17, ... 86, 88) of the image by the first masking pattern "A", and the print head upper area PA ) prints the remaining area not printed in the first pass with the second masking pattern ("B") inverted from the first masking pattern,
In the third pass, the upper area PA of the print head is printed by filling all the remaining portions (16, 18, ... 85, 87) not printed in the second pass with the second masking pattern ("B"),
to improve Density banding, while allowing certain lines of the image to be printed by different nozzles;
In the part where the drop velocity is faster than the first predetermined reference value in the head profile, some dots are removed to lower the density, and in the part where the drop velocity is slower than the predetermined second reference value, some dots are added to A method of improving density banding using a mask characterized in that it allows to increase the density. Printing is performed by dividing one print head (PH) into two areas,
In the first pass, the subregion (PB) of the print head prints only the front part (11,13, ... 82,84) of the image by the first masking pattern ("A"),
In the second pass, the print head lower area PB prints only the rear part (15, 17, ... 86, 88) of the image by the first masking pattern "A", and the print head upper area PA ) prints the remaining area not printed in the first pass with the second masking pattern ("B") inverted from the first masking pattern,
In the third pass, the upper area PA of the print head is printed by filling all the remaining portions (16, 18, ... 85, 87) not printed in the second pass with the second masking pattern ("B"),
to improve Density banding, while allowing certain lines of the image to be printed by different nozzles;
All pixel data of the image in the first pass is filtered by the following filter matrix (Equation 1),

................... (Equation 1)
All pixel data of the image in the second pass is filtered by the following filter matrix (Equation 2),

................... (Equation 2)
All pixel data of the image in the third pass is filtered by the following filter matrix (Equation 3),

................... (Equation 3)
A method of improving density banding using a mask, characterized in that the original image data as a whole is printed. Printing is performed by dividing one print head (PH) into two areas,
In the first pass, the subregion (PB) of the print head prints only the front part (11,13, ... 82,84) of the image by the first masking pattern ("A"),
In the second pass, the print head lower area (PB) prints only the rear part (15,17, ... 86,88) of the image by the third masking pattern ("C"), and the print head upper area (PA) prints the remaining area not printed in the first pass with a second masking pattern ("B") inverted from the first masking pattern,
In the third pass, the upper area PA of the print head is a fourth masking pattern ("D") inverted from the third masking pattern, and the remaining portions (16, 18, ... 85, 87) not printed in the second pass By filling in all and printing,
to improve Density banding, while allowing certain lines of the image to be printed by different nozzles;
In the part where the drop velocity is faster than the first predetermined reference value in the head profile, some dots are removed to lower the density, and in the part where the drop velocity is slower than the predetermined second reference value, some dots are added to A method of improving density banding using a mask characterized in that it allows to increase the density. According to claim 3,
The first masking pattern ("A") and the third masking pattern ("C") continuously form a gradient,
The second masking pattern ("B") and the fourth masking pattern ("D") are continuous in opposite directions to the gradient of the first masking pattern ("A") and the third masking pattern ("C") A method of improving density banding using a mask characterized by forming a gradient. Printing is performed by dividing one print head PH into three areas: a first area P1, a second area P2, and a third area P3.
In the first pass, the third area (P3) of the print head prints only the foremost 1/3 portion (M1) of the image by the first masking pattern ("A");
In the second pass, the third area P3 of the print head prints only the middle 1/3 of the image (M2) by the first masking pattern ("A"), and the second area P2 of the print head prints another partial area of the foremost 1/3 portion (M1) of the image not printed in the first pass with a second masking pattern ("B");
In the third pass, the third area P3 of the print head prints only the rearmost 1/3 of the image (M3) by the first masking pattern ("A"), and the second area P2 of the print head ) prints another partial area of the middle 1/3 portion M2 of the image not printed in the second pass with the second masking pattern "B", and the first area P1 of the print head 3 Print all remaining areas of the foremost 1/3 portion (M1) of the image not printed in the first and second passes with a masking pattern ("C");
In the fourth pass, the second area P2 of the print head covers another partial area of the rearmost 1/3 portion M3 of the image not printed in the third pass with the second masking pattern "B". printing, and the first area P1 of the print head covers all remaining areas of the middle 1/3 portion M2 of the image not printed in the second and third passes with the third masking pattern "C". print,
In the fifth pass, the first area P1 of the printhead is the remainder of the rearmost one-third portion M3 of the image not printed in the third and fourth passes with the third masking pattern "C". By printing all areas,
A method for improving density banding using a mask, characterized in that a specific line of an image is printed by three different nozzles while improving density banding. The method of claim 5,
In the part where the drop velocity is faster than the first predetermined reference value in the head profile, some dots are removed to lower the density, and in the part where the drop velocity is slower than the predetermined second reference value, some dots are added to A method of improving density banding using a mask characterized in that it allows to increase the density.

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