JP2009095994A - Suppression of liquid jet irregularity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique of suppressing liquid jet irregularities caused by meandering in scanning of at least one of a liquid jet head and a liquid jet object. <P>SOLUTION: A liquid jet apparatus includes a dot data generating part which generates dot data representative of a formation state of a dot of each pixel set on the jet object, and a liquid jetting part which forms the dot by jetting a liquid onto the jet object while carrying out scanning in a scan direction of a nozzle array in a common printing region by a plurality of the number times. The liquid jet apparatus thins dots to suppress mutual contact of dot groups formed by every scanning of the nozzle array in a graphic region, and omits thinning in a text region and a photograph region when image data includes both an image region of at least one of the photograph region as an image region representative of an image and the text region as an image region representative of a text, and the graphic region as an image region representative of a graphic. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for ejecting liquid onto a liquid ejection target while performing at least one of scanning of a liquid ejection head and a liquid ejection target.

  2. Description of the Related Art Printing apparatuses that print ink by forming ink dots by scanning on a printing medium are widely used as output apparatuses for images created by a computer or images taken by a digital camera. In such a printing apparatus, it is common to print an image by forming dots on the print medium while scanning at least one of the print head and the print medium. In such printing, in a line printer that completes printing in one scan, the deterioration of the print image due to the meandering of the scan is ascertained, and paper feed scanning (scanning of the printing medium) is performed as a means for suppressing the deterioration. A technique for suppressing meandering caused by the above has been proposed (Patent Document 1).

JP-A-8-217302

  However, conventionally, it has not been studied to suppress such image quality deterioration by devising dot formation. Furthermore, the inventor of the present application has found that not only a line printer but also a serial printer that forms a print image by a plurality of scans causes deterioration of the print image due to the meandering of the scan. In addition, the present inventor has also found that such a problem is not limited to a printing apparatus, but is a problem common to apparatuses that eject liquid as a problem of liquid ejection unevenness.

  The present invention has been made to solve the above-described problems in the prior art, and provides a technique for suppressing liquid ejection unevenness caused by meandering of scanning of at least one of a liquid ejecting head and a liquid ejecting target. With the goal.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1]
A liquid ejecting apparatus that ejects liquid onto a liquid ejection target,
In accordance with the given image data, a dot data generation unit that generates dot data representing a dot formation state of each pixel set on the ejection target;
A nozzle row including a plurality of nozzles arranged in a direction substantially perpendicular to a scanning direction according to the dot data, and scanning the nozzle row in the scanning direction a plurality of times in a common print region A liquid ejecting unit that ejects the liquid onto an ejection target to form dots;
With
In the liquid ejecting apparatus, the image data includes at least one of an image area that is an image area that represents a photograph and a text area that is an image area that represents a text, and a graphic area that is an image area that represents a graphic. In some cases, the graphic area is a liquid ejecting apparatus in which dots are thinned out so as to suppress mutual contact of dot groups formed each time the nozzle row is scanned, and the thinning is omitted in the text area and the photographic area.

  In this liquid ejecting apparatus, in the graphic area, dots are thinned out so as to suppress mutual contact of dot groups formed every time the nozzle row is scanned, and thinning out is omitted in the text area and the photograph area. As a result, in the graphic area where the uneven ejection of the liquid due to the mutual contact of the dot groups is likely to be manifested, the manifestation of the uneven ejection is suppressed, while the uneven ejection of the liquid due to the mutual contact of the dot groups is relatively suppressed. It is possible to suppress missing dots due to thinning out in a text region where it is difficult to manifest.

  In this way, by switching processing according to images having different properties, it is possible to appropriately suppress the “emergence of ejection unevenness” and “dot missing due to thinning” in a liquid ejected while performing multiple scans. Can do. The cause of the ejection unevenness is mutual contact of dot groups formed every time the nozzle row is scanned. This contact is caused, for example, by a phase shift of vibration in a direction perpendicular to the scan of at least one of the nozzle row during scanning and the liquid ejection target. This mechanism will be described in detail in Examples.

  Such a plurality of scans are not necessarily limited to the configuration in which the same nozzle row scans the same region, and each of the plurality of nozzle rows when the plurality of nozzle rows relatively move together as follows. A configuration for performing the scanning is also included. Here, “relative movement” means relative movement by movement of at least one of the liquid jet head (nozzle row) and the liquid jet target.

[Application Example 2]
A liquid ejecting apparatus according to Application Example 1,
The liquid ejecting unit includes a liquid ejecting head in which a plurality of the nozzle rows are arranged at positions separated in the scanning direction,
The liquid ejecting apparatus is a liquid ejecting apparatus that completes the plurality of scans by one scan of the liquid ejecting head.

  In this configuration, for example, as shown in FIGS. 3 to 6, a plurality of nozzle arrays are arranged at positions separated in the scanning direction. Here, the “liquid ejecting head” corresponds to a combination of the two print heads 10A and 10B, and may be configured as a single body or may be configured as a separate body. “Multiple scanning” means scanning of each of the two black ink nozzle rows K, the two cyan ink nozzle rows C, the two magenta ink nozzle rows Mz, and the two yellow ink nozzle rows Y. In other words, it means eight scans by each nozzle row executed by one scan of the two print heads 10A and 10B corresponding to the “liquid ejecting head”.

[Application Example 3]
The liquid ejecting apparatus according to Application Example 1 or 2,
The plurality of scans includes a plurality of scans that eject liquids of the same color at positions that are staggered in a direction substantially perpendicular to the scan direction,
The liquid ejecting apparatus performs the thinning in at least one specific scan of the plurality of scans, and at least one of the scans other than the specific scan in the plurality of scans. A liquid ejecting apparatus that compensates for a decrease in the amount of ejection caused by the thinning by increasing the amount of ejection in scanning.

  With this configuration, it is possible to easily suppress a decrease in the injection amount due to thinning.

  The present invention relates to various forms such as a printing apparatus, other liquid ejecting apparatuses, a printing method, other liquid ejecting methods, and a printed matter generating method, or a computer program for causing a computer to realize the functions of these methods or apparatuses, The present invention can be realized in various forms such as a recording medium on which the computer program is recorded and a data signal that includes the computer program and is embodied in a carrier wave.

Below, in order to demonstrate the effect | action and effect of this invention more clearly, embodiment of this invention is described in the following orders.
A. Example of printing system configuration:
B. Halftone processing in the first embodiment of the present invention:
B-1. First modification of the first embodiment:
B-2. Second modification of the first embodiment:
B-3. Third modification of the first embodiment:
C. Halftone processing in the second embodiment of the present invention:
C-1. First modification of the second embodiment:
C-2. Second modification of the second embodiment:
C-3. Third modification of the second embodiment:
C-4. Fourth modification of the second embodiment:
D. Variations:

A. Example of printing system configuration:
FIG. 1 is a block diagram illustrating an example of a configuration of a printing system. This printing system includes a computer 90 as a printing control device and a color printer 20 as a printing unit. The combination of the color printer 20 and the computer 90 can be called a “printing apparatus” in a broad sense.

  In the computer 90, an application program 95 operates under a predetermined operating system. A video driver 91 and a printer driver 96 are incorporated in the operating system. The application program 95 supplies image data to the printer driver 96. The printer driver 96 processes the supplied image data and outputs print data PD for transfer to the color printer 20. The application program 95 performs desired processing on the image to be processed, and displays the image on the CRT 21 via the video driver 91.

  In the printer driver 96, an image data analysis module 80 that analyzes image data supplied from the application program 95 and determines the type of image for each image data or for each area of the image represented by the image data, A resolution conversion module 97 that converts the resolution of the input image into a print resolution, a color conversion module 98 that converts RGB into CMYK, and a dither matrix M generated in an embodiment to be described later are used to dot input gradation values. A halftone module 99 that reduces the number of output gradations that can be expressed by forming the print data, a print data generation module 100 that generates print data to be transmitted to the color printer 20 using the halftone data, and a color conversion module 98. Color conversion table LUT as a reference for color conversion and each for halftone processing And a recording rate table DT for determining recording rates of size dots, are provided.

  The printer driver 96 corresponds to a program for realizing a function for generating print data PD. A program for realizing the function of the printer driver 96 is supplied in a form recorded on a computer-readable recording medium. Examples of such a recording medium include a CD-ROM 126, a flexible disk, a magneto-optical disk, an IC card, a ROM cartridge, a punch card, a printed matter on which a code such as a bar code is printed, an internal storage device of a computer (RAM, ROM, etc. A variety of computer-readable media such as an external storage device and an external storage device.

  FIG. 2 is a schematic configuration diagram of the color printer 20. The color printer 20 includes an operation panel 32, a paper feed motor 22, a paper feed drive unit that transports the print medium P in the paper feed direction by the paper feed motor 22, and the print heads 10A and 10B. And a control circuit 40 for controlling dot formation. The control circuit 40 is connected to the computer 90 via the connector 56. In the color printer 20, the main scanning of the print heads 10A and 10B is not performed.

  The inventor of the present application generates vibration in the paper width direction when the print medium P is conveyed in the paper feed direction by the paper feed motor 22, that is, when scanned, thereby confirming that image quality degradation has occurred. In addition, the mechanism of image quality degradation was analyzed as described later.

  FIG. 3 corresponds to the arrow AA in FIG. 2 and is an explanatory diagram showing the nozzle arrangement on the lower surfaces of the print heads 10A and 10B. On the lower surface of each of the print heads 10A and 10B, a black ink nozzle row K for discharging black ink, a cyan ink nozzle row C for discharging cyan ink, and a magenta ink nozzle for discharging magenta ink. A row Mz and a yellow ink nozzle row Y for discharging yellow ink are formed.

  The plurality of nozzles Nz in each nozzle row are aligned at a constant nozzle pitch k · D along a direction (paper width direction) perpendicular to the paper feed. Here, k is an integer, and D is a pitch (referred to as “dot pitch”) corresponding to the printing resolution in the paper width direction. In this specification, it is also referred to as “nozzle pitch is k dots”. The unit [dot] at this time means the dot pitch of the printing resolution. Similarly, the unit of [dot] is used for the paper feed amount.

  In each nozzle row C, Mz, Y, and K provided in each of the two print heads 10A and 10B, the nozzle pitch k is 2. On the other hand, since the two print heads 10A and 10B are arranged (staggered arrangement) at positions shifted by the nozzle pitch k in the paper width direction, the two print heads 10A and 10B cause omission in each pixel. And ink of each color can be ejected. Such an arrangement corresponds to “a position where they stagger each other” in the claims. Here, the “positions that are staggered with respect to each other” include, for example, three positions where the nozzle pitch k is 3 or more and are shifted by the nozzle pitch k.

  FIG. 4 corresponds to the arrow BB in FIG. 2 and is an explanatory diagram showing the lateral surfaces of the print heads 10A and 10B. In FIG. 4, only the nozzle row that discharges yellow ink Y is shown for easy understanding. In FIG. 4, since the print medium P is fed in the paper feed direction indicated by the arrow, the print head 10A and the print head 10B eject ink droplets at positions shifted in this paper feed direction (scanning direction). .

  5 and 6 are explanatory diagrams showing a mechanism by which meandering in scanning in this embodiment causes image quality degradation. FIG. 5 shows a dot pattern Dy1 formed by the yellow ink nozzle row Y of the preceding head 10A and a dot pattern Dy2 formed by the yellow ink nozzle row Y of the subsequent head 10B. As can be seen from FIG. 5, both have the same waveform and are shifted in phase. The reason for having the same waveform is that the print medium P moves relatively with “the same paper feed” and “the same vibration” with respect to the two fixed print heads 10A and 10B. The phase is shifted because the yellow ink nozzle row Y mounted on each of the two print heads 10A and 10B is shifted in the paper feed direction. The shift amount in FIG. 5 matches the shift amount in FIG.

  FIG. 6 shows a virtual dot pattern Dy12h formed by combining two dot patterns Dy1 and Dy2 without shifting, and an actual dot pattern Dy12a formed by combining with shifting. As can be seen from FIG. 6, in the virtual dot pattern Dy12h, the relative positional relationship between the respective dot groups of the two dot patterns Dy1 and Dy2 is maintained, and the mutual contact is made uniform. In the actual dot pattern Dy12r, it is understood that the relative positional relationship between the dot groups of the two dot patterns Dy1 and Dy2 is not maintained, and the degree of mutual contact varies in the paper feed direction.

  Conventionally, as disclosed in JP-A-8-217302, it has been studied to suppress such image quality degradation by suppressing vibration. However, the present inventor is not a method of directly dealing with the cause of image quality deterioration called suppression of vibration, but is essentially the conventional approach of suppressing image quality deterioration by suppressing the causal relationship between vibration and image quality deterioration. Created a different method. This method is based on a completely different approach from the conventional one created by paying attention to the relationship between the type of image and image quality degradation.

  The inventor of the present application is unlikely to cause image quality deterioration due to meandering scanning in “an image with a narrow print area like a character” or “a photographic image with a high image frequency”, but on the other hand, “ We paid attention to the conspicuously conspicuous point in “image with low frequency”. Further, it has been noted that such an “image having a large print area and a small image quality frequency such as a solid image” has a small influence even if the print resolution is reduced because the image quality frequency is small. The inventor of the present application has created a technical idea for suppressing image quality degradation due to mutual interference between the two dot patterns Dy1 and Dy2 based on two points of interest that are completely different from each other.

  FIG. 7 is an explanatory diagram illustrating a print image G that is a target of image quality deterioration suppression processing in the first embodiment. The print image G includes two text areas Zt1 and Zt2 and a graphic area Zg. Each of these regions can be classified by analyzing the image data representing the print image G by the image data analysis module 80 (FIG. 1). In this classification, the two text areas Zt1 and Zt2 are both classified as “text images”, and the graphic area Zg is classified as “graphic area”.

  FIG. 8 is an explanatory diagram showing the thinning pattern Psk1 used in the image quality deterioration suppression process in the first embodiment and the two dot patterns Dy12a and Dy1 before and after thinning. The thinning pattern Psk1 is configured to leave the dots of the pixel rows with the odd row numbers (hatched pixel groups) and delete the dots of the pixel rows with the even row numbers (the pixel groups without hatching). It is. The dot pattern Dy12a and the dot pattern Dy1 are the same as the dot pattern Dy12a shown in FIG. 6 and the dot pattern Dy1 shown in FIG.

  In this embodiment, the thinning pattern Psk1 is applied to the dot pattern Dy12a so that the dot pattern Dy1 is formed in the pixel column with the odd row number and the dot pattern Dy2 is formed in the pixel column with the even row number. The In this manner, the dot pattern Dy2 is thinned out from the dot pattern Dy12a before thinning out and the dot pattern Dy1 remains, and it can be seen that image quality deterioration due to mutual interference between the dot pattern Dy1 and the dot pattern Dy2 can be eliminated. Specific processing is performed as follows.

B. Halftone processing in the first embodiment of the present invention:
FIG. 9 is a flowchart showing a routine of print data generation processing in the first embodiment of the present invention. The print data generation process is a process performed by the computer 90 to generate print data PD to be supplied to the color printer 20.

  In step S100, the printer driver 96 (FIG. 1) inputs image data from the application program 95. This input process is performed in response to a print command from the application program 95. The image data is image data representing the print image G (FIG. 7), and stores attribute information of each image area.

  In step S200, the image data analysis module 80 (FIG. 1) determines whether each image area of the image data is a “text area”, a “photo area”, or a “graphic area”. As a result of the determination, if the image area determined as “graphic area” is not included, the process proceeds to step S500. If the image area determined as “graphic area” is included, the process proceeds to step S400. It is advanced.

  In step S400, the image data analysis module 80 sets a predetermined flag for the image area determined as the “graphic area”. This flag is set for each image area and used in halftone processing described later.

  In step S500, the resolution conversion module 97 converts the input image data into RGB bitmap data, and converts the resolution (that is, the number of pixels per unit length) into a predetermined resolution.

  In step S600, the color conversion module 98 converts RGB bitmap data into multi-tone data of ink colors that can be used by the color printer 20 for each pixel while referring to the color conversion table LUT (FIG. 1). .

  In step S700, the halftone module 99 performs halftone processing. In the present embodiment, the halftone process is a process of reducing 256 gradations, which is the number of gradations of multi-gradation data, to the number of gradations that the color printer 20 can represent with each pixel, and performing a predetermined correction process (decimation). Process).

  FIG. 10 is a flowchart showing the flow of the halftone process of the first embodiment. In step S710, the halftone module 99 performs dot data generation processing. The dot data formation process is a process for generating data representing the dot formation state for each pixel. In this embodiment, the dot formation state for each pixel is expressed as two gradations of “no dot formation” and “dot formation”.

  In step S720, the halftone module 99 performs region selection processing. The area selection process is a process of sequentially selecting each area of dot data corresponding to each of the two text areas Zt1, Zt2 and graphic area Zg of the print image G (FIG. 7), for example.

  In step S730, the halftone module 99 determines whether the flag of each selected area is set (whether it is ON). As a result of the determination, when the flag is not “ON”, the process proceeds to step S750, and when the flag is “ON”, the process proceeds to step S740.

  In step S740, the halftone module 99 performs dot data correction processing. The dot data correction process is a process for applying the thinning pattern Psk1 (FIG. 8) to the dot data in a selected area.

  FIG. 11 is a flowchart showing the dot data correction processing routine of the first embodiment and the pixel group Dg of the selected region. In step S742, the halftone module 99 performs a column selection process. The column selection process is a process of selecting a set of pixels (pixel columns) parallel to the paper feed direction in order from the first row number in the pixel group Dg in the selected region.

  In step S744, the halftone module 99 determines whether or not the row number of the selected pixel column is an odd number. As a result of this determination, when the number is odd, the process proceeds to step S748. When the number is even, the process proceeds to step S746.

  In step S746, the halftone module 99 performs blanking processing. The blanking process is a process of correcting dot data and changing the dot data of all the pixels in the selected column to “no dot formation”.

  Such processing from step S742 to step S746 is repeatedly executed up to the last column of the selected region. In this way, as described above, the dot pattern Dy2 is thinned out from the dot pattern Dy12a before thinning, and the dot pattern Dy1 remains. As a result, it can be seen that image quality deterioration due to mutual interference between the dot pattern Dy1 and the dot pattern Dy2 can be eliminated. Note that it is not always necessary to perform processing for each region. For example, only image data of text or image data of only graphics may be processed collectively for the entire image.

B-1. First modification of the first embodiment:
FIG. 12 is an explanatory diagram showing the thinning pattern Psk2 of the first modification example of the first embodiment and the contents of the thinning process. The thinning pattern Psk2 is configured to thin out dots in a checkered pattern so that the dots do not continue in the vibration direction, and the dot pattern Dy12sk2 is formed by this thinning. As can be seen from the dot pattern Dy12sk2, since it is difficult for the dots to contact each other in the vibration direction by performing such thinning, it can be understood that mutual interference between the dot pattern Dy1 and the dot pattern Dy2 can be suppressed.

  FIG. 13 is a flowchart illustrating a routine of dot data correction processing according to the first modification. The dot data correction processing routine of the first modification is different from that of the first embodiment in that step S744 in FIG. 11 is replaced with step S744a. Step S744a is different from step S744 of the first embodiment in that the thinning pattern Psk2 (FIG. 13) is implemented instead of the thinning pattern Psk1 (FIG. 8).

  The function Mod (i, n) in the calculation formula in step S744a is a function for calculating the number of remainders obtained by dividing the line number i by the parameter n. Similarly, the function Mod (j, n) is a function for calculating the number of remainders by dividing the column number j by the parameter n.

  Thus, in order to suppress the mutual interference between the dot pattern Dy1 and the dot pattern Dy2, it is not always necessary to thin out either the dot pattern Dy1 or the dot pattern Dy2, and a dot pattern in which dots do not continue in the vibration direction is used. It can be seen that this should be realized. As such a thinning pattern, for example, a thinning pattern Psk3 as shown in FIG. 14 can be used. If the parameter n of the two functions Mod (i, n) and Mod (j, n) is set to 3, the thinning pattern Psk3 can be realized by the flowchart of FIG.

B-2. Second modification of the first embodiment:
FIG. 15 is a flowchart showing the dot data correction process routine of the second modification of the first embodiment. The dot data correction process routine of the second modification is different from the first modification in that step S735 is added. In step S735, the halftone module 99 performs density compensation processing. The density compensation process is a process for increasing the ink amount of dots that have not been thinned out in order to compensate for the ink density that has decreased as the dots are thinned out. The density compensation process has a remarkable effect when the thinning rate (ratio of the number of pixels to be thinned with respect to the total number of pixels) is large as in the thinning pattern Psk3 (FIG. 14).

B-3. Third modification of the first embodiment:
In the above-described embodiments and modifications, the dots are regularly thinned out according to a certain rule. For example, the dots may be thinned out randomly, or the dots may be substantially thinned out as in the embodiments described later. You may comprise as follows. In the present specification, “thinning” has a broad meaning, and a configuration in which the dot formation position is changed without reducing the ink density or the number of dots represented by the dots (for example, a second embodiment described later). ).

C. Halftone processing in the second embodiment of the present invention:
FIG. 16 is an explanatory diagram illustrating the principle of suppressing image quality degradation due to mutual interference between the two dot patterns Dy1 and Dy2 by the halftone process of the second embodiment. The second embodiment is different from the first embodiment in that it is configured not to perform thinning, but to adjust the dot formation order in the dither method to suppress mutual interference between the two dot patterns Dy1 and Dy2. Is different.

  FIG. 16 shows a dot arrangement allocation matrix AL and a dot number distribution table Dn. The dot arrangement allocation matrix AL includes a first pixel group having a pixel value “1” and a second pixel group having a pixel value “2”. These two pixel groups are pixel groups that are divided so that dots do not continue in the vibration direction. It can be seen that both the first pixel group and the second pixel group are configured such that the dots do not continue in the vibration direction by themselves. In other words, each pixel group is configured so that dots do not continue in the vibration direction unless dots are formed in both the first pixel group and the second pixel group. Mutual interference due to deviations in the vibration direction of the motor is suppressed.

  The dot number distribution table Dn is a table for determining the distribution of the dot-on target number to the first pixel group and the second pixel group at each input gradation value. The horizontal axis indicates the input gradation value in the range of 256 gradations from 0 to 255. The vertical axis indicates the dot formation rate for each pixel group (left vertical axis) and the number of dots formed for all pixels (right vertical axis). The relationship between the input gradation value and the dot formation rate for the first pixel group is indicated by a curve Td1. The relationship between the input gradation value and the dot formation rate for the second pixel group is indicated by a curve Td2. The number of dots formed on all pixels is indicated by a straight line Total.

  For example, when the input gradation value is 0, no dot is formed in any pixel group. When the input gradation value is 64, the dot formation rate for the first pixel group, the dot formation rate for the second pixel group, and the number of dot formations for all the pixels are 50%, 0%, and 16 pieces. That is, while dots are formed in 16 pixels, which are 50% of 32 pixels in the first pixel group, no dots are formed in the second pixel group, and the number of dots formed in all the pixels is 16. It becomes a piece.

  When the input gradation value is 128, the dot formation rate for the first pixel group, the dot formation rate for the second pixel group, and the number of dot formations for all pixels are 100%, 0%, and 32. is there. That is, while dots are formed in all 32 pixels, which are 100% of 32 pixels in the first pixel group, no dots are formed in the second pixel group, and the number of dots formed in all pixels is 32. It has become.

  Furthermore, when the input gradation value is 192, the dot formation rate for the first pixel group, the dot formation rate for the second pixel group, and the number of dot formations for all pixels are 100%, 50%, and 48. is there. That is, dots are formed in all 32 pixels, which are 100% of 32 pixels in the first pixel group, and dots are formed in 16 pixels, which are 50% of 32 pixels in the second pixel group. Therefore, the number of dots formed on all pixels is 48 as the total number of both dots.

  The dot formation rate is converted into level data having 256 stages from 0 to 255, for example, and the presence or absence of dot formation is determined by comparing the level data with the threshold value of the dither matrix M. In the second embodiment, since the dot formation rate is the ratio of dots formed as a whole regardless of the pixel group, the input gradation value having 256 gradation ranges from 0 to 255 is 256 in the range from 0 to 255. It is linearly converted into level data having stages.

  FIG. 17 is an explanatory diagram illustrating a state in which image quality deterioration due to mutual interference between the two dot patterns Dy1 and Dy2 is suppressed by the halftone process according to the second embodiment. The two dot patterns Dy12ha and Dy12ra are a set of a plurality of dots in which dots are formed on all the pixels corresponding to the dot arrangement allocation matrix AL (FIG. 16). In other words, the dot pattern Dy12ha is a dot pattern obtained by extracting dots formed in the pixels corresponding to the dot arrangement assignment matrix AL from the dot pattern Dy12h (FIG. 6). The dot pattern Dy12ra is a dot pattern obtained by extracting dots formed in pixels corresponding to the dot arrangement allocation matrix AL from the dot pattern Dy12r (FIG. 6).

  The dot pattern Dy12em2 is a set of dots (dot group) formed on all the pixels of the first pixel group. The hatched 16 dots are formed in pixels having a pixel value of “1” in the odd-numbered rows of the first to fourth columns of the dot arrangement assignment matrix AL. Twelve dots that are not hatched are pixels that have a pixel value of “1” in the even-numbered rows of the fifth to eighth columns of the dot arrangement assignment matrix AL. The dot pattern Dy12em2 is a dot formation state when the input gradation value is 128 in the dot number distribution table Dn. That is, 32 dots are formed in all the pixels of the first pixel group.

  In the second embodiment, such a halftone process uses a dither matrix Ms adjusted so as to realize a dot assignment process determined by the dot arrangement assignment matrix AL (FIG. 16) and the dot number distribution table Dn. It is realized by doing. In the following, first, a basic configuration of halftone processing using a dither matrix will be described.

  FIG. 18 is an explanatory diagram conceptually illustrating a part of the dither matrix M. In the illustrated matrix, 256 elements in the horizontal direction (main scanning direction), 64 elements in the vertical direction (sub-scanning direction), a total of 16384 elements, were selected uniformly from the range of gradation values 1 to 255. A threshold value is stored. The size of the dither matrix M is not limited to the size illustrated in FIG. 18, and can be various sizes including a matrix having the same number of vertical and horizontal elements.

  FIG. 19 is an explanatory diagram showing the concept of the presence / absence of dot formation using a dither matrix. For the sake of illustration, only some elements are shown. In the determination of the presence / absence of dot formation, as shown in FIG. 19, the gradation value of the image data is compared with the threshold value stored at the corresponding position in the dither matrix. If the gradation value of the image data is larger than the threshold value stored in the dither table, a dot is formed, and if the gradation value of the image data is smaller, no dot is formed. In FIG. 19, a hatched pixel means a pixel on which a dot is to be formed.

  Furthermore, when the gradation value of the image data is determined, whether or not dots are formed in each pixel is determined solely by the threshold value set in the dither matrix. It is possible to positively control the dot generation state by the threshold storage position set in the matrix. In the second embodiment, the dot assignment process determined by the dot arrangement assignment matrix AL (FIG. 16) and the dot number distribution table Dn is realized by utilizing such properties of the dither matrix.

  FIG. 20 is an explanatory diagram conceptually illustrating the spatial frequency characteristics of threshold values set for each pixel of a blue noise dither matrix having blue noise characteristics as a simple example of dither matrix adjustment. The spatial frequency characteristic of the blue noise matrix is a characteristic in which the length of one cycle has the largest frequency component in a high frequency region near two pixels. Such spatial frequency characteristics are set in consideration of human visual characteristics. That is, the blue noise dither matrix is a dither matrix M in which the threshold storage position is adjusted so that the largest frequency component is generated in the high frequency region in consideration of the human visual characteristic that the sensitivity is low in the high frequency region.

  FIG. 20 further illustrates the spatial frequency characteristics of the green noise matrix as a dashed curve. As shown in the figure, the spatial frequency characteristic of the green noise matrix is a characteristic having the largest frequency component in the intermediate frequency region in which the length of one cycle is from 2 pixels to several tens of pixels. Since the threshold value of the green noise matrix is set so as to have such a spatial frequency characteristic, when it is determined whether or not dots are formed in each pixel with reference to the dither matrix M having the green noise characteristic, a unit of several dots is obtained. While dots are formed adjacent to each other, the dots are formed in a dispersed state as a whole. In printers where it is difficult to stably form fine dots of about one pixel, such as so-called laser printers, it is possible to identify isolated dots by determining the presence or absence of dot formation with reference to such a green noise matrix. Occurrence can be suppressed. As a result, it is possible to quickly output an image with stable image quality. In other words, a dither matrix that is referred to when determining the presence or absence of dot formation by a laser printer or the like is set with a threshold value adjusted to have green noise characteristics.

  FIG. 21 is an explanatory diagram conceptually showing a visual spatial frequency characteristic VTF (Visual Transfer Function) which is a sensitivity characteristic with respect to the visual spatial frequency of a human. By using the visual spatial frequency characteristic VTF, the human visual sensitivity is modeled as a transfer function called the visual spatial frequency characteristic VTF, thereby quantifying the graininess of the dots after the halftone process appealing to the human visual sense. It becomes possible. The value quantified in this way is called the graininess index. Formula F1 shows a typical experimental formula representing the visual spatial frequency characteristic VTF. The variable L in the formula F1 represents the observation distance, and the variable u represents the spatial frequency. Formula F2 is a formula that defines the graininess index. The coefficient K in the formula F2 is a coefficient for matching the obtained value with the human sense.

  Such quantification of the granularity that appeals to human vision enables fine optimization of the dither matrix for the human visual system. Specifically, Fourier transform is performed on the dot pattern assumed when each input gradation value is input to the dither matrix to obtain the power spectrum FS, and all the inputs are obtained after multiplication with the visual spatial frequency characteristic VTF. The graininess index that can be obtained by integrating with the gradation value (formula F2) can be used as an evaluation function of the dither matrix. In this example, the optimization can be achieved by adjusting the threshold storage position so that the evaluation function of the dither matrix becomes small.

  What is common to dither matrices such as blue noise dither matrix and green noise matrix set in consideration of such human visual characteristics is the region of the spatial frequency with the highest human visual sensitivity on the print medium. This is that the average value of the components within a predetermined low frequency range from 0.5 millimeters per millimeter to 2 millimeters per cycle with a center frequency of 1 millimeter per cycle is set to be small. For example, the average value of the components in a predetermined low frequency range is at least 5 cycles per millimeter to 20 cycles per millimeter with a frequency of 10 cycles per millimeter at which human visual sensitivity is almost zero. By having a frequency characteristic that is smaller than the average value, graininess can be suppressed in a region where human visual sensitivity is high, so that effective image quality improvement focusing on human visual sensitivity is performed. The inventor has confirmed that this is possible.

  FIG. 22 is a flowchart showing the processing routine of the dither matrix generation method in the second embodiment. In this example, a small dither matrix of 8 rows and 8 columns corresponding to the dot arrangement assignment matrix AL (FIG. 16) is generated for easy understanding. The granularity index (formula F2, FIG. 21) is used as an evaluation representing the optimality of the dither matrix.

  In step S1100, a grouping process is performed. The grouping process is a process for dividing the small dither matrix M of 8 rows and 8 columns described above into two divided matrices M1 and M2 (FIG. 23). The division matrix M1 corresponds to a first pixel group (a group of pixels having a pixel value “1” in FIG. 16). The division matrix M2 corresponds to the second pixel group (a group of pixels having the pixel value “2” in FIG. 16).

  In step S1200, a target threshold value determination process is performed. The target threshold value determination process is a process for determining a threshold value to be a storage element determination target. In this embodiment, the threshold value is determined by selecting in order from a threshold value having a relatively small value, that is, a threshold value having a value at which dots are easily formed. Thus, if the dots are selected in order from the threshold at which dots are likely to be formed, the elements stored in order from the threshold for controlling the dot arrangement in the highlight area where the graininess of the dots is conspicuous are fixed. This is because a large degree of design freedom can be given to a highlight region where graininess is conspicuous.

  In step S1300, a storage element determination process is performed. The storage element determination process is a process for determining an element for storing a target threshold value. A dither matrix is generated by alternately repeating the threshold value determination process (step S1200) and the storage element determination process (step S1300).

  FIG. 24 is a flowchart showing the processing routine of the storage element determination process in the second embodiment. In step S1310, the corresponding dot of the determined threshold is turned on. The determined threshold means a threshold at which the storage element is determined. In this embodiment, since the threshold value is selected in order from the value at which dots are likely to be formed as described above, when a dot is formed as the threshold value of interest, the pixel corresponding to the element storing the determined threshold value is not used. Dots are always formed. Conversely, at the smallest input tone value at which dots are formed at the threshold value of interest, no dots are formed at pixels corresponding to elements other than the element storing the determined threshold value.

  FIG. 25 is a black circle showing how dots are formed in each of the seven pixels corresponding to each element of the matrix in which threshold values (0 to 6) in which the first to seventh dots are likely to be formed are stored in the matrix. It is explanatory drawing shown. The dot pattern Dpa1 configured in this way is used to determine which pixel should form the eighth dot. The * mark will be described later.

  In step S1320, a candidate storage element selection process is performed. The candidate storage element selection process is an element other than an element for which a threshold value to be stored has been determined (in the example of FIG. 25, an element in which a threshold value (0 to 6) at which dots are easily formed in the first to seventh positions is stored). Are sequentially selected as storage threshold value candidates. In the example of FIG. 25, the element storing the * mark in the first row and the first column is selected as the first storage candidate of the target threshold value.

  The storage candidate element selection process is selected so as to realize the dot allocation process determined by the dot arrangement allocation matrix AL (FIG. 16) and the dot number distribution table Dn. That is, for example, as can be seen from the dot number distribution table Dn (FIG. 16), the storage elements are only included from the 16 elements belonging to the divided matrix M1 until the thresholds are filled in all the elements (hatched elements) belonging to the divided matrix M1. Will be selected.

  In FIG. 26, black dots indicate how dots are formed in each of the 16 pixels corresponding to each element of the matrix in which threshold values (0 to 15) at which dots are easily formed in the matrix are 1 to 16th. It is explanatory drawing shown. The dot pattern Dpa2 configured in this way is used to determine in which pixel the 17th dot is to be formed.

  In step S1330, the corresponding dot of the storage candidate element is turned on. This process is performed in the form of being added to the dot group that was turned on as the corresponding dot of the determined threshold value in step S310.

  FIG. 27 shows a matrix in which the dot formation state (dot pattern Dpa1 in FIG. 25) in which the corresponding dot of the storage candidate element and the corresponding dot of the determined threshold value are turned on, that is, the dot density that quantitatively represents the dot density. It is explanatory drawing which shows matrix Dda1. The number 0 means that no dot is formed, and the number 1 means that a dot is formed (including the case where it is assumed that a dot is formed in a storage candidate element as described above). Means.

  In step S1340, an evaluation value determination process is performed. In this embodiment, the evaluation value determination process is calculated using the formulas F1 and F2 shown in FIG. 21 as an index representing the granularity of the image quality of each pixel group. Thereby, it is possible to realize an image quality with less graininess based on human visual sensitivity.

  In step S1350, the currently calculated evaluation value is compared with the previously calculated evaluation value (stored in a buffer (not shown)). As a result of the comparison, when the evaluation value calculated this time is small (preferably), the evaluation value calculated in this buffer is stored (updated) in association with the storage candidate element, and the current storage candidate element is stored as the storage element. Temporarily determined (step S1360).

  Such a process is performed for all candidate elements, and finally, the candidate storage elements stored in a buffer (not shown) are determined (step S1370). Further, such processing is performed for all threshold values or all threshold values in a preset range, and the generation of the dither matrix Ms is completed (step S1400, FIG. 22).

  Thus, in the second embodiment, by using the dither matrix Ms configured to realize the dot allocation process determined by the dot arrangement allocation matrix AL (FIG. 16) and the dot number allocation table Dn, Image quality deterioration due to mutual interference between the two dot patterns Dy1 and Dy2 can be suppressed.

C-1. First modification of the second embodiment:
FIG. 28 is an explanatory diagram showing an example in which the dither matrix M of the second embodiment is shifted and used. In this example, the shift amount of the dither matrix M is determined such that the relative positional relationship between the first pixel group and the second pixel group is maintained beyond the range of the individual dither matrix M. As described above, the dither matrix Ms of the second embodiment can be shifted and used.

  Such a shift of the dither matrix is performed in order to improve image quality by suppressing, for example, low-frequency noise generated in the arrangement cycle of the dither matrix. Low-frequency noise is generated in the dither matrix array period because dots are formed at the same position in the dither matrix when halftone processing is performed for the same gradation value using the same dither matrix. It is.

C-2. Second modification of the second embodiment:
FIG. 29 is an explanatory diagram showing the contents of the dot number distribution table Dnv of the second modification of the second embodiment. The dot number distribution table Dnv of the first modified example is a table that determines the distribution of the dot-on target number to the first pixel group and the second pixel group at each input gradation value. This is common with the number distribution table Dn (FIG. 16). However, the relationship between the dot formation rate for the first pixel group and the dot formation rate for the second pixel group corresponding to each input gradation value is changed from the curve Td1 and the curve Td2 to the curve Td1v and the curve Td2v, respectively. This is different from the dot number distribution table Dn (FIG. 16) of the second embodiment.

  For example, when the input gradation value is 128, the dot formation rate for the first pixel group, the dot formation rate for the second pixel group, and the number of dots formed for all pixels are the dot number distribution table Dn of the second embodiment. In FIG. 16, they are 100% (32), 0% (0), and 32, respectively, but in the dot number distribution table Dnv of the first modification of the second embodiment, 75% (24). , 25% (8), 32. Thus, in the second embodiment, the dot formation in the first pixel group is completely prioritized over the dot formation in the second pixel group. However, in the first modification of the second embodiment, Priority has been relaxed.

  Such priority adjustment (relaxation) makes it possible to adjust the trade-off between image quality degradation due to dot graininess and dot pattern mutual interference. In other words, in the dither matrix generation method of the second embodiment, since dot formation in the first pixel group is completely prioritized, the values belonging to the divided matrix M1 are maintained until the thresholds are filled in all the elements belonging to the divided matrix M1. It can be seen that there is room for selection only in the storage element, and the degree of freedom of selection is narrow. The priority adjustment (relaxation) described above has the effect of reducing the image quality deterioration due to mutual interference of the dot patterns and improving the granularity of the dots.

C-3. Third modification of the second embodiment:
FIG. 30 is an explanatory diagram showing a dot pattern of each pixel group in a third modification of the second embodiment. In the third modification of the second embodiment, the graininess is reduced not only in the dot pattern Dpa actually formed on the print medium but also in the dot patterns formed in each of the first pixel group and the second pixel group. Has been. In the second embodiment, the dot pattern Dpa1 formed in the first pixel group is substantially formed in the second pixel group because the dither matrix Ms is configured to reduce the granularity. The dot pattern Dpb1v is also different from the second embodiment in that the graininess is reduced.

  The graininess of the dot pattern formed in the second pixel group is manifested as density unevenness in combination with the mutual interference between dots caused by the meandering of scanning. There is an advantage that such density unevenness can be suppressed. In particular, a remarkable effect is obtained when dots are formed in both the first and second pixel groups from a relatively low gradation range as in the first modification of the second embodiment.

  FIG. 31 shows dot density matrices Dda1 and Dda2 corresponding to two pixel groups in the third modification of the second embodiment. FIG. 32 shows an evaluation value calculation formula for calculating an evaluation value using the two dot density matrices Dda1 and Dda2 of the third modification. This evaluation value calculation formula is configured as the sum of a first term for calculating the graininess index Ga with all the pixels being evaluated and a second term for calculating the graininess index Gg1 and Gg2a with each pixel group being evaluated. Has been.

  The first term calculates the graininess index Ga with all pixels as ratings. In this embodiment, the graininess index Ga is calculated using the formulas F1 and F2 shown in FIG. 21 as an index representing the graininess of the image quality as in the second embodiment. In the second term, the graininess indexes Gg1 and Gg2 with the respective pixel groups being evaluated are calculated in the same manner as the first term.

  Note that the weighting coefficients Wa and Wg are values representing weighting for the first term and the second term, respectively. Specifically, when importance is attached to the granularity of all pixels, the value of the weighting coefficient Wa may be increased. When importance is attached to the granularity of each pixel group, the value of the weighting coefficient Wg is increased. good. Further, the graininess index Gg1, Gg2 may be further multiplied by a weighting coefficient. In this case, it is preferable that the weighting coefficient of the graininess index Gg1 is larger than the weighting coefficient of the graininess index Gg2.

C-4. Fourth modification of the second embodiment:
FIG. 33 is an explanatory diagram showing the relationship between the input gradation value and the level data in the halftone process of the fourth modified example of the second embodiment. The third modification of the second embodiment uses a general dither matrix instead of performing halftone processing using a dither matrix Ms configured to suppress image quality deterioration due to meandering of scanning. The second embodiment is different from the second embodiment in that the image quality deterioration is suppressed by adjusting the level data LVL.

  The relationship between the input gradation value and the level data LVL is represented by a curve LVL1 for the first pixel group and by a curve LVL2 for the second pixel group. For example, when the input gradation value is 128, the level data LVL is converted to “128” for the pixels belonging to the first pixel group, and is converted to “0” for the pixels belonging to the second pixel group.

  Thus, in the present invention, the dither matrix may be adjusted as shown in the second embodiment, or the level data LVL determined according to the input gradation value may be adjusted. It is also possible to adjust both of them.

  Furthermore, the present invention can also be applied to halftones using the error diffusion method. Specifically, a threshold value (usually fixed to a constant value) that determines whether or not dots are formed may be adjusted. For example, it can be realized by making the threshold used for the pixels belonging to the second pixel group larger than the threshold used for the pixels belonging to the first pixel group.

D. Variations:
As mentioned above, although several embodiment of this invention was described, this invention is not limited to such embodiment at all, and implementation in a various aspect is possible within the range which does not deviate from the summary. It is. In particular, elements other than those described in common in all the independent claims in the constituent elements in each of the above embodiments can be omitted as appropriate because they are additional elements.

D-1. In the above-described embodiment, the line printer that completes printing by one scan of the two print heads 10A and 10B has been described as an example. However, the present invention also applies to a serial printer that completes printing by a plurality of scans. Can be applied. This is because if the scanning is different, the phases of the vibrations of the print head do not necessarily match each other. This mismatch is caused by, for example, fluctuations in the scanning direction and the vibration phase for each scanning.

D-2. In the above-described embodiment, halftone processing is performed by the dither method, but such halftone processing can also be realized by the error diffusion method. For example, by adjusting at least one of the threshold value of the error diffusion method and the input tone value, for example, a configuration for increasing the threshold value of the pixel or pixel group to be thinned or a configuration for reducing the input tone value by applying a bias is realized. Is possible. Here, if the bias is not included in the diffusion error, the density error due to the bias can be avoided.

D-3. In the above-described embodiment, the granularity index is used as the evaluation measure of the dither matrix. However, for example, RMS granularity as described later may be used. This evaluation scale can be determined by performing low-pass filter processing on the dot density value using a low-pass filter and calculating a standard deviation of the density value subjected to low-pass filter processing. Further, for example, as a simplified method, the storage element may be determined so that the threshold value of interest is stored in an element corresponding to a pixel in which dot formation is sparse.

  In addition, the method is not limited to the method of sequentially determining threshold values, and prepares a dither matrix as an initial state, and replaces a part of a plurality of threshold values stored in each element with threshold values stored in other elements. The dither matrix may be generated by determining the element in which the threshold value is stored. In this case, the evaluation function can be set by including in the evaluation function (punishment function) a difference in dot density formed in each of the predetermined element group elements. It should be noted that the dot density matrix that is the reference for evaluation may be generated based on the smallest input gradation value at which dots are formed at the threshold value of interest, or may be generated based on an input gradation value higher than that. good.

D-4. In the above-described embodiment, the nozzle arrays C, Mz, Y, and K included in each of the two print heads 10A and 10B are arranged in a staggered manner, and color unevenness due to contact between dots of the same color is suppressed. However, for example, only one of the two print heads 10A and 10B may be provided, and the contact between dots having different colors may be suppressed. For example, mutual contact between cyan dots and magenta dots. The present invention can also be applied to the suppression of such contact. Note that the hue variation due to the suppression can be suppressed, for example, by switching the thinning out at a period outside the human visual sensitivity in the high frequency region.

D-5. In the above-described embodiment, dots are thinned out by adjusting the dot data. For example, the control of the control circuit 40 (FIG. 2) that controls the ink ejection and dot formation by driving the print heads 10A and 10B. It is also possible to thin out by changing the contents. For example, the thinning shown in FIG. 8 can be realized by cutting the drive signal to the print head 10B during printing of the graphic area. Furthermore, for example, the ink amount can be compensated (FIG. 15) by changing the waveform of the drive signal without correcting the dot data.

D-6. In the above-described embodiments, the liquid ejecting apparatus is embodied as an ink jet recording apparatus. However, the liquid ejecting apparatus is not limited to this. Liquid other than ink (a liquid or gel in which functional material particles are dispersed in addition to liquid) And a fluid ejecting apparatus that ejects or ejects a fluid other than a liquid (such as a solid that can be ejected by flowing as a fluid). For example, a liquid material injection device for injecting a liquid material in the form of dispersion or dissolution of materials such as liquid crystal display, EL (electroluminescence) display, surface emitting display, electrode material and color material used for manufacturing color filters, It may be a liquid ejecting apparatus that ejects a bio-organic matter used for biochip production, or a liquid ejecting apparatus that ejects a liquid that is used as a precision pipette and serves as a sample.

  In addition, transparent resin liquids such as UV curable resins to form liquid injection devices that inject lubricating oil onto precision machines such as watches and cameras, and micro hemispherical lenses (optical lenses) used in optical communication elements. Examples include a liquid ejecting apparatus that ejects a liquid onto a substrate, a liquid ejecting apparatus that ejects an etching solution such as acid or alkali to etch the substrate, a fluid ejecting apparatus that ejects gel, and a powder such as toner. It may be a powder jet recording apparatus that jets a solid. The present invention can be applied to any one of these injection devices.

1 is a block diagram illustrating an example of a configuration of a printing system. 1 is a schematic configuration diagram of a color printer 20. FIG. Explanatory drawing which shows the nozzle arrangement | sequence in the lower surface of print head 10A, 10B. Explanatory drawing which shows the horizontal surface of print head 10A, 10B. Explanatory drawing which shows the mechanism in which meandering in the scanning of 1st Example causes image quality degradation. Explanatory drawing which shows the mechanism in which meandering in the scanning of 1st Example causes image quality degradation. Explanatory drawing which shows the print image G used as the object of the image quality degradation suppression process of 1st Example. Explanatory drawing which shows the thinning pattern used by the image quality degradation suppression process of 1st Example, and two dot patterns before and behind thinning. 3 is a flowchart illustrating a routine of print data generation processing according to the first embodiment. The flowchart which shows the flow of the halftone process of 1st Example. The flowchart which shows the routine of the dot data correction process of 1st Example, and the pixel group Dg of the selected area | region. Explanatory drawing which shows the content of the thinning pattern of the 1st modification of 1st Example, and the thinning process. The flowchart which shows the routine of the dot data correction process of the 1st modification of 1st Example. Explanatory drawing which shows the thinning pattern of the other example of the 1st modification of 1st Example. 10 is a flowchart illustrating a routine of dot data correction processing according to a second modification of the first embodiment. Explanatory drawing which shows the principle which suppresses image quality degradation by the mutual interference of two dot patterns by the halftone process of 2nd Example. Explanatory drawing which shows a mode that the image quality degradation by the mutual interference of two dot patterns is suppressed by the halftone process of 2nd Example. FIG. 3 is an explanatory diagram conceptually illustrating a part of the dither matrix M. Explanatory drawing which shows the idea of the presence or absence of the dot formation using a dither matrix. FIG. 4 is an explanatory diagram conceptually illustrating a spatial frequency characteristic of a threshold value set for each pixel of a blue noise dither matrix having a blue noise characteristic as a simple example of dither matrix adjustment. Explanatory drawing which showed notionally the visual spatial frequency characteristic VTF (Visual Transfer Function) which is a sensitivity characteristic with respect to the visual spatial frequency which a human has. The flowchart which shows the processing routine of the production | generation method of the dither matrix of 2nd Example. Explanatory drawing which shows the dither matrix M divided | segmented into two division | segmentation matrices in 2nd Example. The flowchart which shows the processing routine of the storage element determination process in 2nd Example. Explanatory drawing which shows a mode that the dot was formed in each of the seven pixels corresponding to each element of the matrix in which the threshold value (0 to 6) at which the first to seventh dots are likely to be formed is stored in the matrix. Explanatory drawing which shows a mode that the dot was formed in each of 16 pixels corresponding to each element of the matrix in which the threshold value (0-15) in which the 1st to 16th dot is easy to be formed is stored in the matrix. Explanatory drawing which shows the dot density matrix Dda1 which quantitatively represented the matrix which digitized the dot formation state in which the corresponding dot of the storage candidate element and the corresponding dot of the determined threshold value were turned on, ie, the dot density. Explanatory drawing which shows an example which shifts and uses the dither matrix M in the 1st modification of 2nd Example. Explanatory drawing which shows the content of the dot number distribution table Dnv of the 2nd modification of 2nd Example. Explanatory drawing which shows the dot pattern of each pixel group in the 3rd modification of 2nd Example. Explanatory drawing which shows the dot density matrix corresponding to two pixel groups in the 3rd modification of 2nd Example. Explanatory drawing which shows the evaluation value calculation formula which calculates an evaluation value using two dot density matrices in the 3rd modification of 2nd Example. Explanatory drawing which shows the relationship between the input gradation value and level data in the halftone process of the 4th modification of 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10A ... Preceding head 10B ... Subsequent head 10A, 10B ... Print head 20 ... Color printer 20a ... Color printer 22 ... Motor 24 ... Carriage motor 32 ... Operation panel 40 ... Control circuit 56 ... Connector 60 ... Print head unit 80 ... Image data analysis Module 90 ... Computer 91 ... Video driver 95 ... Application program 96 ... Printer driver 97 ... Resolution conversion module 98 ... Color conversion module 99 ... Halftone module 100 ... Print data generation module

Claims (5)

A liquid ejecting apparatus that ejects liquid onto a liquid ejection target,
In accordance with the given image data, a dot data generation unit that generates dot data representing a dot formation state of each pixel set on the ejection target;
A nozzle row including a plurality of nozzles arranged in a direction substantially perpendicular to a scanning direction according to the dot data, and scanning the nozzle row in the scanning direction a plurality of times in a common print region A liquid ejecting unit that ejects the liquid onto an ejection target to form dots;
With
In the liquid ejecting apparatus, the image data includes at least one of an image area that is an image area that represents a photograph and a text area that is an image area that represents a text, and a graphic area that is an image area that represents a graphic. In some cases, the graphic area is a liquid ejecting apparatus in which dots are thinned out so as to suppress mutual contact of dot groups formed each time the nozzle row is scanned, and the thinning is omitted in the text area and the photographic area. The liquid ejecting apparatus according to claim 1,
The liquid ejecting unit includes a liquid ejecting head in which a plurality of the nozzle rows are arranged at positions separated in the scanning direction,
The liquid ejecting apparatus is a liquid ejecting apparatus that completes the plurality of scans by one scan of the liquid ejecting head. The liquid ejecting apparatus according to claim 1 or 2,
The plurality of scans includes a plurality of scans that eject liquids of the same color at positions that are staggered in a direction substantially perpendicular to the scan direction,
The liquid ejecting apparatus performs the thinning in at least one specific scan of the plurality of scans, and at least one of the scans other than the specific scan in the plurality of scans. A liquid ejecting apparatus that compensates for a decrease in the amount of ejection caused by the thinning by increasing the amount of ejection in scanning. A liquid ejecting method for ejecting liquid onto the liquid ejection target,
In accordance with the given image data, a dot data generation step for generating dot data representing a dot formation state of each pixel set on the ejection target;
A nozzle row including a plurality of nozzles arranged in a direction substantially perpendicular to a scanning direction according to the dot data, and scanning the nozzle row in the scanning direction a plurality of times in a common print region A liquid ejecting step of ejecting the liquid onto an ejection target to form dots;
When the image data includes at least one image area of a photo area that is an image area that represents a photograph and a text area that is an image area that represents a text, and a graphic area that is an image area that represents a graphic, Is a step of thinning out dots so as to suppress mutual contact of dot groups formed for each scan of the nozzle row, omitting the thinning out in the text region and the photo region,
A liquid ejection method comprising: A nozzle row including a plurality of nozzles arranged in a direction substantially perpendicular to the scanning direction, and performing the scanning of the nozzle row in the scanning direction a plurality of times in a common print region, and applying a liquid to the liquid ejection target A computer program for causing a computer to generate ejection data to be supplied to a liquid ejecting unit that ejects upward to form dots,
In accordance with the given image data, a dot data generation function that generates dot data representing the dot formation state of each pixel set on the ejection target;
When the image data includes at least one image area of a photo area that is an image area that represents a photograph and a text area that is an image area that represents a text, and a graphic area that is an image area that represents a graphic, Is a function of thinning out dots so as to suppress mutual contact of dot groups formed for each scan of the nozzle row, and a function of omitting the thinning out in the text region and the photo region,
A computer program comprising a program for causing the computer to realize the above.

Images