JP2005280276A - Ink-jet recording method and ink-jet recording system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize the density more emphasized in a high-density part with the state of a granular feeling not being spoiled in a highlight-area while making a density data of multiple value of each pixel have a meaning, for an ink-jet recording system performing a dot-arrangement patterning processing operation. <P>SOLUTION: The system is composed of a mask pattern and a dot arrangement pattern for which the total of dot number recorded by multi-pass at one pixel becomes equal to a designated dot number exceeding the area number defined as a record of dot at the dot-arrangement patterning processing and, simultaneously, a relationship, such that the designated dot number may increase the more for the pixel having the higher tone level, exists. Thereby, since the dot for making an emphasis with the multi-pass can be given only to the pixel with high tone level, it becomes possible to realize the maximum density and broader tone nature which can be expressed in the whole density area ranging from a high density to a low density with the state of the granular feeling of the pixel not being spoiled. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention uses matrix expansion for determining dot recording / non-recording of density data quantized into multiple values in an area composed of L (horizontal) × M (vertical) areas. The present invention relates to an ink jet recording method and an ink jet recording system for expressing a predetermined density on a recording medium.

  Currently known recording methods include a thermal transfer method in which ink ribbon ink is transferred to a recording medium by thermal energy and recorded, or ink droplets are ejected from a plurality of recording elements and attached to a recording medium such as paper. Examples include an ink jet recording method for performing recording. In particular, the inkjet recording method is a non-impact method, so there is no noise during recording, high-speed recording is possible, and it is possible to record on plain paper without requiring special fixing processing. It attracts attention because of its advantages.

  Advances in ink-jet recording technology will promote higher image quality, higher speed, and lower cost of recorded images, and will contribute to the effect of popularizing recording devices to personal users in conjunction with the popularization of personal computers and digital cameras. It was very big. However, due to such widespread use, further improvement in image quality has been demanded. Particularly, in recent years, a high-quality output image suitable for silver salt photography has been demanded.

  Compared with so-called general silver salt photographs, the inkjet recording apparatus has been regarded as a problem for a long time because of its unique graininess. Along with this, various measures for reducing the graininess have been proposed in recent years, and many recording apparatuses incorporating such measures have been provided. For example, there is an ink jet recording apparatus including an ink system in which light cyan or light magenta having a lower density is added in addition to normal cyan, magenta, yellow, and black. With such an ink system, graininess can be reduced by using light cyan or light magenta in a low density region. Further, in a high density region, it is possible to realize wider color reproduction and smooth gradation by recording with normal cyan and magenta.

  Furthermore, there is a method for reducing the graininess by designing the size of the dots that land on the recording medium to be smaller, and for this purpose, there is also a technique for reducing the amount of ink droplets ejected from each recording element arranged in the recording head. It has been advanced. In this case, it is possible to obtain a high-resolution image without impairing the recording speed by configuring not only a small amount of ink droplets but also a larger number of recording elements with a higher arrangement density.

  By the way, many methods have already been proposed when performing so-called binarization processing for converting multi-value density data indicating the density of an image to be recorded into binary data indicating whether or not ink droplets are to be recorded on a recording medium. Basically, any method can be adopted. However, as the recording resolution and ink color types of recording apparatuses tend to increase as in recent years, the amount of data to be processed is enormous, so the burden of image processing is too great and throughput is reduced. There were problems such as a significant drop.

  Thus, for example, after a quantization process is first performed to reduce the gradation to several levels by a printer driver installed in a host device connected to the recording apparatus, a final binarization process is performed inside the recording apparatus. In recent years, many recording systems that perform binarization processing with a two-stage configuration, such as performing the above, have been provided. In this case, color conversion and multi-value quantization processing with a relatively heavy processing load can be executed in a state lower than the actual recording resolution, thereby reducing the processing load on the host device. On the other hand, the recording apparatus expresses gradation of the input pixel having multi-value information by a plurality of levels of density.

  Several proposals and implementations have already been made for a method of converting multi-level density data in several stages into binary data. For example, in the case of a recording head that cannot modulate the amount of ejected ink droplets, the density value n of one pixel output from the host device can be expressed in binary by dot recording / non-recording. A method of expressing the density in a region where a plurality of images are collected is employed. In this case, specifically, a plurality of types of dot arrangement patterns corresponding to a plurality of density values are prepared in advance in the memory in the printing apparatus, and a plurality of types of dot arrangement patterns are prepared according to the input density values. One of them is selected and output as binary data. Hereinafter, such processing is referred to as dot arrangement patterning processing.

  The dot arrangement patterning process has already been disclosed in Patent Document 1 and the like. According to Japanese Patent Laid-Open No. 2004-228561, a method of expressing gradation by recording / non-recording four dots in a 2 × 2 area for one input pixel having five levels of density values is disclosed. Furthermore, according to the same document, a plurality of patterns are prepared for the same density value for dot arrangement in a 2 × 2 area, and these dot arrangement patterns are arranged sequentially or randomly. A method is also disclosed. Doing so does not fix the dot arrangement pattern for each density value, so it reduces the pseudo contour and the so-called “fraying phenomenon” that appears at the edge of the image when pseudo halftone processing is performed, and recording. It is stated that there is also an effect on use averaging of a plurality of recording elements arranged in the head.

  By the way, in the ink jet recording apparatus, a serial type and a full line type are known in the recording operation mode. In particular, a serial type recording apparatus alternately repeats a recording main scan for ejecting ink onto a recording medium while moving the recording head and a sub-scan for conveying the recording medium in a direction crossing the recording main scan. This is a configuration in which images are sequentially formed on a recording medium, and since it can be provided in a small size at a low price, it is widely used in the market.

  However, in a serial type ink jet recording apparatus, image defects such as density unevenness and streaks are likely to occur due to slight variations in ink droplets ejected from the recording elements and variations in conveyance of the recording medium. Therefore, in the serial type ink jet recording apparatus, the same image area of the recording medium is scanned a plurality of times, and the image area is sequentially completed by a plurality of areas in the recording head. In many cases, a pass recording method is employed.

  FIG. 1 is a diagram showing a mask pattern for explaining the multipass printing method. Here, FIG. 1A shows a mask pattern that can be applied by the first recording scan and FIG. 1B shows a mask that can be applied by the second recording scan for recording data included in the same image area of the recording medium. Show. In the figure, each grid indicated by 1 or 0 indicates one area in which the recording apparatus can record one dot, and an area indicated by “1” is recorded by the recording scan. An area that can be performed, an area indicated by “0” indicates an area that cannot be recorded by the recording scan. The binary print data is subjected to an AND process using the mask shown in the figure, and the result finally becomes discharge data to be printed in each print scan.

  FIG. 1C shows the result of superimposing FIG. 1A and FIG. 1B, and shows that the two mask patterns are interpolated. In the figure, a mask pattern of an area of 6 horizontal areas × 8 vertical areas is shown, but a larger mask pattern is actually prepared according to the number of recording elements and the recording scanning width of the recording head.

  When the multi-pass printing method is performed using such a mask pattern, print data thinned out according to the mask pattern of FIG. 1A by the first area of the print head is recorded in a predetermined image area. The In the subsequent sub-scanning, a transport operation for a distance shorter than the width of the recording head is performed. In the subsequent recording scan, the recording data thinned out according to the mask pattern of FIG. 1B is recorded by the second area of the recording head. At this time, in the predetermined image area, 100% recording is completed by different recording areas (recording elements) of the recording head in the first recording scan and the second recording scan. Therefore, the variation in ejection and the variation in the conveyance amount unique to the printing element are dispersed, and a smooth image without unevenness can be obtained.

  In the above description, two-pass multi-pass printing in which an image is completed with two printing scans for the same image area has been described as an example. However, the number of divisions in the multi-pass printing method is not limited to this. Even if the image data is divided into three or more divisions and an image is formed by three or more recording scans, as a result, a 100% image is interpolated by a plurality of recording scans for the same image area. Therefore, the multi-pass recording method is established if the configuration is completed.

  Furthermore, the multipass printing method can be used as a means for increasing the density (see, for example, Patent Document 2). Normally, only one ink droplet is applied to one area from one recording head, and the recording system performs image processing so that a desired density can be expressed with this determined amount. However, even if the same amount of ink droplets is applied, the expressed image density varies depending on the type of the recording medium. Even in this case, it is possible to increase the density by using the multi-pass printing method, particularly for the ink color whose image density is desired to be increased.

  FIG. 2 is a diagram showing an example of a mask pattern when performing a multipass printing method for increasing the density. As in FIG. 1, FIG. 2A shows a mask pattern applied in the first recording scan, and FIG. 2B shows a mask applied in the second recording scan. Each mask has a recording rate equivalent to 60% with respect to the entire area. In FIG. 2C in which both are superimposed, a recording rate of about 120% is obtained. Here, the area indicated by “2” is an area in which recording is performed by each of the first-pass mask and the second-pass mask, and as a result, two dots are recorded.

  When the multipass printing method is performed using such a mask pattern, 120% printing is completed by different printing elements in the printing head in the first printing scan and the second printing scan in a predetermined image area. Going to be. Therefore, the discharge variation and the conveyance amount variation inherent to the printing element are dispersed, and the image density can be enhanced simultaneously while obtaining a smooth image without unevenness.

  As described above, in recent inkjet recording apparatuses, the resolution of the recorded image is increased, the recording head density is increased and the ink droplets are reduced, a plurality of types of ink are mounted, and the dot arrangement patterning process is performed. It is possible to express high-quality images by developing various technologies such as high-gradation density expression and the use of a multi-pass recording method.

JP-A-9-46522 JP-A-5-278232

  However, when the conventional density emphasis method represented by Patent Document 2 is adopted, in the configuration in which the binarization process is performed by the above-described dot arrangement patterning process, appropriate density expression may not be performed. That is, in the mask pattern for emphasis, since the dot arrangement pattern included therein is not conscious, the number of dots added for emphasis with respect to the dot arrangement pattern having the same density value is It will be mixed. This makes the multi-value density data of each pixel meaningless.

  Furthermore, when the conventional density emphasis method represented by Patent Document 2 is adopted, there arises a situation in which the graininess, which is particularly problematic when trying to realize photographic image quality, is further deteriorated.

  FIG. 3 is a schematic diagram for explaining how the graininess deteriorates. Graininess is a phenomenon that is particularly confirmed in highlights. In the highlight portion, the density data after quantization is at a low level, and dots are often scattered and recorded as shown in FIG. In this situation, when the conventional density emphasis method is adopted, since some of the scattered dots are provided with ink droplets for two times, they are formed more conspicuously than necessary as shown in FIG. The overall graininess is impaired.

  Many of the purposes of density enhancement are mainly to increase the density of the high gradation part. Further, if the density of only the high gradation part can be increased while maintaining the density of the low gradation part, gradation expression in a wider range can be performed, and a more preferable result can be obtained. However, the conventional density enhancement method as described in Patent Document 2 has a configuration in which dots for enhancement are uniformly added in all gradations from the highlight portion to the high density portion. Therefore, the density of the high density portion increases, but the graininess of the low density portion deteriorates and the gradation area does not widen.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to give meaning to multi-value density data of each pixel in an ink jet recording system that performs dot arrangement patterning processing. On the other hand, it is an object to provide an ink jet recording system and an ink jet recording method which can obtain a more emphasized density in a high density area while maintaining a graininess in a highlight area.

  Therefore, the present invention provides an ink jet recording method for forming an image on a recording medium by ejecting ink from the recording head while causing the recording head that ejects a plurality of colors of ink to scan the recording medium a plurality of times. Assigning a dot arrangement pattern composed of a plurality of areas in which dot recording / non-recording is determined corresponding to each of the gradation levels to each pixel represented by a multi-value gradation level; A step of assigning recording to an area determined to perform dot recording according to the dot arrangement pattern to the plurality of scans using a mask pattern, and creating recording data corresponding to each of the plurality of scans; And ejecting ink from the recording head based on the recording data to form dots on the recording medium, The total number of dots recorded in the plurality of scans with respect to the pixels represented by the number of dots becomes a predetermined number of dots that is equal to or greater than the number of areas defined as dot recording in the assignment step, and the gradation The mask pattern and the dot arrangement pattern are configured such that the higher the level, the larger the predetermined number of dots, and the predetermined number of dots differs from the others for at least one of the plurality of colors of ink. It is characterized by.

  In addition, an ink is ejected from the recording head while the recording head for forming ink dots having different densities or diameters that can express the same hue is scanned a plurality of times to form an image on the recording medium. Ink-jet recording method, wherein each pixel represented by a multi-level gradation level is a dot composed of a plurality of areas in which dot recording / non-recording is determined corresponding to each gradation level The step of assigning the arrangement pattern and the recording in the area determined to perform the dot recording according to the dot arrangement pattern are divided into the plurality of scans using the mask pattern, and the recording corresponding to each of the plurality of scans A step of creating data, and a step of forming dots on the recording medium by ejecting ink from the recording head based on the recording data And when the ink dots having a relatively high density or the ink dots having a relatively large diameter are recorded, the pixel expressed by at least a predetermined gradation level among the multi-value gradation levels. Using the mask pattern and the dot arrangement pattern configured such that the total number of dots recorded in the plurality of scans is larger than the number of areas determined as dot recording in the assignment step. In the case where the ink dots having a relatively low density or the ink dots having a relatively small diameter are recorded, the number of dots recorded by the plurality of scans with respect to the pixel represented by the multi-value gradation level Using the mask pattern and the dot arrangement pattern configured to be the same as the number of areas defined as dot recording in the allocation step. And wherein the door.

  An ink jet recording method for forming an image on the recording medium by ejecting ink from the recording head while causing the recording head to eject ink to scan the recording medium a plurality of times. A step of assigning a dot arrangement pattern composed of a plurality of areas in which dot recording / non-recording is determined corresponding to each gradation level to each pixel to be expressed, and dot recording according to the dot arrangement pattern Allocating the recording in the defined area to the plurality of scans using a mask pattern, creating recording data corresponding to each of the plurality of scans, and ink from the recording head based on the recording data Forming dots on the recording medium by discharging the plurality of pixels for the pixels represented by the multilevel gradation levels. The total number of dots recorded in the scanning is a predetermined number of dots that is equal to or greater than the number of areas defined as dot recording in the assignment step, and the higher the gradation level, the larger the predetermined number of dots. Thus, the mask pattern and the dot arrangement pattern are configured, and the predetermined number of dots differs according to the type of the recording medium.

  An inkjet recording system that forms an image on the recording medium by ejecting ink from the recording head while causing the recording head that discharges a plurality of colors to scan the recording medium a plurality of times. Means for allocating a dot arrangement pattern composed of a plurality of areas in which dot recording / non-recording is determined corresponding to each gradation level to each pixel represented by a tone level, and according to the dot arrangement pattern The recording in the area defined as dot recording is divided into the plurality of scans using a mask pattern, and the recording data corresponding to each of the plurality of scans is created, and the recording based on the recording data Means for ejecting ink from the head to form dots on the recording medium, and for the pixels represented by the multi-level gradation levels. The total number of dots recorded by the plurality of scans is a predetermined number of dots equal to or greater than the number of areas determined to be recorded by the assigning unit, and the higher the gradation level, the higher the predetermined dot. The mask pattern and the dot arrangement pattern are configured so as to increase in number, and the predetermined number of dots is different from the others for at least one of the plurality of colors of ink.

  Furthermore, an ink jet recording system that forms an image on the recording medium by ejecting ink from the recording head while causing the recording head to eject ink to scan the recording medium a plurality of times. Means for allocating a dot arrangement pattern composed of a plurality of areas in which dot recording / non-recording is determined corresponding to each gradation level to each pixel to be expressed; and dot recording according to the dot arrangement pattern And recording means to distribute the recording to the plurality of scans using a mask pattern and create recording data corresponding to each of the plurality of scannings, and from the recording head based on the recording data Means for forming dots on the recording medium by discharging the ink, and for the pixels represented by the multi-level gradation levels, The total number of dots recorded in several scans is a predetermined number of dots that is equal to or greater than the number of areas determined as dot recording by the assigning unit, and the higher the gradation level, the higher the predetermined number of dots. The mask pattern and the dot arrangement pattern are configured so as to increase, and the predetermined number of dots differs depending on the type of the recording medium.

  According to the present invention, dots for emphasis can be given only to pixels with high gradation levels by multipass. As a result, it is possible to realize the maximum density that can be expressed and a wider gradation in an entire density region ranging from a low density to a high density without impairing the granularity of the image.

(First embodiment)
The first embodiment of the present invention will be described in detail below.
FIG. 4 is a block diagram showing a flow of image data conversion processing in the ink jet recording system of this embodiment. The ink jet recording apparatus applied in the present embodiment performs recording by light cyan and light magenta in addition to the basic colors of cyan, magenta, yellow, and black. For this purpose, a recording head that discharges these six colors of ink is used. It is prepared. As shown in FIG. 4, each process shown here is assumed to be performed by a recording device and a personal computer (PC) as a host device.

  There are an application and a printer driver as programs that operate in the operating system of the host device, and the application J0001 executes processing for creating image data to be recorded by the recording device. At the time of actual recording, image data created by the application is passed to the printer driver.

  Assume that the printer driver according to the present embodiment includes pre-processing J0002, post-processing J0003, γ correction J0004, halftoning J0005 that is multi-level quantization, and print data creation J0006. Here, each process will be briefly described. The pre-stage process J0002 performs color gamut mapping. Then, data conversion is performed to map the color gamut reproduced by the image data R, G, B of the sRGB standard into the color gamut reproduced by the recording apparatus. Specifically, data in which R, G, and B are each expressed in 8 bits is converted into 8-bit data of R, G, and B having different contents by using a three-dimensional LUT.

  The post-processing J0003 is based on the data R, G, and B in which the color gamut is mapped, and the color separation data Y, M, C, K, Lc, and Lm corresponding to the combination of inks that reproduce the color represented by the data. The process which calculates | requires is performed. Here, similarly to the pre-processing, it is assumed that interpolation calculation is performed in combination with a three-dimensional LUT.

  The γ correction J0004 performs gradation value conversion for each color data of the color separation data obtained by the post-processing J0003. Specifically, by using a one-dimensional LUT corresponding to the gradation characteristics of each color ink of the recording apparatus, conversion is performed so that the color separation data is linearly associated with the gradation characteristics of the recording apparatus.

  Halftoning J0005 performs quantization that converts 8-bit color separation data Y, M, C, K, Lc, and Lm into 2-bit data. In this embodiment, multi-level error diffusion is used to convert 256-gradation 8-bit data into 3-gradation 2-bit data. This 2-bit data is data serving as an index for indicating an arrangement pattern in the dot arrangement patterning process performed in the printing apparatus.

  At the end of the process performed by the printer driver, print data is created by adding print control information to the print image data containing the 2-bit index data by print data creation process J0006.

  The printing apparatus performs a dot arrangement patterning process J0007 and a mask data conversion process J0008 on the input print data.

  The dot arrangement patterning process J0007 in the present embodiment will be described below. In the halftone process described above, the number of levels is reduced from 256-value multi-value density information (8-bit data) to ternary tone value information (2-bit data). However, information that can be actually recorded by the ink jet recording apparatus of the present embodiment is binary information indicating whether or not to record ink. In the dot arrangement patterning process, it plays a role of reducing the ternary level from 0 to 2 to the binary level that determines the presence or absence of dots. Specifically, in this dot arrangement patterning process J0007, for each pixel represented by 2-bit data of level 0 to 2 that is an output value from the halftone processing unit, the gradation value (level 0 to 0) of that pixel is represented. A dot arrangement pattern corresponding to 2) is assigned, whereby dot on / off is defined in each of a plurality of areas in one pixel, and ejection of 1 bit of “1” or “0” in each area in one pixel Arrange the data.

  FIG. 5 shows output patterns for input levels 0 to 2 that are converted by the dot arrangement patterning processing of this embodiment. Each level value shown on the right side of the drawing corresponds to level 0 to level 2 which are output values from the halftone processing unit. An area composed of 2 vertical areas × 1 horizontal area arranged on the left side corresponds to an area of one pixel (pixel) output by halftone processing, and is 600 ppi (pixels / inch; reference value) in both vertical and horizontal directions. The size corresponds to the pixel density. Each area in one pixel corresponds to a minimum unit in which dot ON / OFF is defined, and corresponds to a recording density of 1200 dpi (dot / inch; reference value) in the vertical direction and 600 dpi in the horizontal direction. In the recording apparatus of this embodiment, a predetermined amount of ink droplets is recorded in one area represented by about 20 μm in length and about 40 μm in width corresponding to the above recording density to obtain a desired density. It is designed to be In the figure, the filled area indicates an area where dots are recorded, and the number of dots to be recorded increases by one as the number of levels increases.

  When the input data is level 1, two types of patterns are prepared. That is, a pattern for recording the upper area and a pattern for recording the lower area among the two areas arranged vertically. As described above, when there are a plurality of patterns capable of expressing the same density, if the density expression is performed only with the fixed pattern, a texture or a pseudo contour may be generated on the image. Therefore, in the present embodiment, a configuration is adopted in which a plurality of patterns are mixedly arranged even when expressing the same density.

  FIGS. 6A to 6C are diagrams showing a matrix corresponding to each level value for arranging a plurality of patterns in a mixed manner. Here, one matrix is composed of 16 vertical areas × 8 horizontal areas. FIG. 6A is a matrix corresponding to level 0. Since there is only one type of pattern corresponding to level 0, all areas of the mother matrix are not recorded. FIG. 6B is a matrix corresponding to level 1. Since there are two types of dot arrangement patterns corresponding to level 1, inside the mother matrix, the pattern in which the upper area is recorded and the pattern in which the lower area is recorded are evenly mixed and arranged. ing. As will be described in detail later, the arrangement configuration here is related to the mask pattern in the mask data conversion process J0008. FIG. 6C shows a mother matrix corresponding to level 2. Since there is only one type of pattern corresponding to level 2, the mother matrix is in a state where dots are recorded in all areas.

  FIG. 7 is a diagram showing a configuration in which the mother matrix shown in FIG. 6 is arranged over the entire image. FIG. 7C shows a plurality of mother matrices prepared corresponding to the number of levels, and FIG. 7A shows a mother matrix corresponding to an arbitrary level value. As shown in FIG. 7B, the mother matrix is arranged in the vertical and horizontal directions of the image, whereby the dot arrangement pattern of each level is determined in all image areas on the recording medium. In the density data input to the dot arrangement patterning process J0007, dot recording / non-recording is finally determined by the dot arrangement pattern corresponding to the recording position on the recording medium.

  As described in the background art section, such a configuration can be achieved by distributing the number of ejections between the recording elements located in the upper part and the lower part of the dot arrangement pattern. It is possible to obtain various effects such as dispersion of various noises and reduction of the so-called “break-off phenomenon” appearing at the edge of the image or the pseudo contour when the pseudo halftone process is performed.

  Referring to FIG. 4 again, the binary data of each color that has been subjected to the dot arrangement patterning process is then input to the mask data conversion process J0008.

  FIG. 8 is a diagram for explaining the relationship between the mask pattern applied in the mask data conversion process J0008 of the present embodiment and the dot arrangement pattern described above. FIG. 8A shows a mask pattern that is applied to the recording data recorded in a predetermined image area in the first recording scan. FIG. 8B shows a mask to be applied in the second printing scan. Each mask has a recording rate equivalent to 60% with respect to the entire area, and in FIG. 8C where both are superimposed, a recording rate of about 120% is obtained. Here, the area indicated by “2” is an area in which recording is performed by each of the first-pass mask and the second-pass mask, and as a result, two dots are recorded.

  FIG. 8D is a matrix corresponding to level 1 already described with reference to FIG. Here, comparing FIG. 8C and FIG. 8D, all of the areas indicated by “2” in FIG. 8C correspond to areas where no dots are recorded in FIG. 8D. Can be confirmed. As shown in the figure, the mask pattern and the dot arrangement pattern are arranged in such a manner that a predetermined pattern is repeated both vertically and horizontally, so that the above rule holds in all image areas. That is, for the density data of level 1, overstrike for emphasis is not performed in all image areas.

  With the above configuration, since the enhancement is not performed in the low density region expressed by the level 0 to the level 1, it is possible to suppress deterioration of graininess due to enhancement, which has been regarded as a problem in the past. Conversely, in the high density region of level 2, dot emphasis is positively performed. As described above, since the maximum density is increased without changing the density in the highlight portion, the gradation region that can be expressed in the entire image is expanded.

  FIG. 9 is a graph showing the recording rate in the image area with respect to the digital count of the density data. Note that the digital count can be regarded as density data of 0 to 255 that is input to the halftoning J0005 in FIG. 4 and represented by an 8-bit signal.

  FIG. 9A shows a case where the 100% mask described in FIG. 1 is used. The recording rate rises to 100% linearly with respect to the input value. FIG. 9B shows a case where a 120% mask according to the conventional enhancement method described in FIG. 2 is used. Although the maximum recording rate is 120%, as in FIG. 9A, the recording rate increases linearly, and it can be seen that the emphasis is uniformly applied even at low and medium densities. .

  FIG. 9C shows a case where the 120% mask of the present embodiment described in FIG. 8 is used. According to the figure, the locus is the same as that in FIG. 9A until the input value is about 128, but emphasis is performed in the region after 128, that is, the region where the pixel converted to level 2 exists, and the input value 255. The maximum recording rate is 120%.

  In the present embodiment, the mask shown in FIG. 8 is applied only to dark ink (cyan, magenta, yellow, and black) of the six colors of ink. The light cyan and light magenta light inks apply the 100% mask shown in FIG.

  FIG. 10 is a diagram for explaining the recording rate of each ink with respect to the input image density when a grayscale image is recorded in an ink jet recording apparatus in which a plurality of types of inks having different densities are simultaneously mounted. According to the figure, in the low density region, a gray image is formed using three colors of light cyan (Lc), light magenta (Lm), and yellow (Y). In the process in which the density gradually increases from the low density to the high density, dots tend to be recorded discretely, and therefore, the graininess is reduced by using ink having a lower density. Ink dots formed with light-colored ink are not noticeable on the recording medium, and are used.

  In the area around the medium density, the output values of Lm and Lc are close to the maximum values, and it becomes difficult to express a density higher than this with the combination of these inks. On the other hand, since a large number of dots are filled on the recording medium, the granularity of single dots due to the dark ink is less noticeable. Therefore, from this stage, by gradually adding cyan (C), magenta (M), and further black (K), it is possible to increase the density while reducing the graininess. I can do it. At the same time, for Lc, Lm and Y, the output value is gradually decreased. Ultimately, when the output value of K is higher than any of the other inks, it is possible to express black having a high hue and a suitable hue.

  Here, description has been made taking an example of expressing gray scale, but the relationship between the recording rate of dark ink and the recording rate of light ink is almost the same in any hue. That is, the light ink is mainly used in the low density region in order to reduce graininess, and the dark ink is replaced with this in the region expressing a higher density. Therefore, the present inventors have determined that it is not necessary to realize a recording rate as high as 100% or more for light ink. Conversely, applying ink more than necessary not only consumes ink wastefully, but also raises concerns that new problems will occur on the recording medium, such as blurring and a decrease in saturation.

  By the way, if the graininess in the highlight portion is suppressed by the light ink, even if the conventional mask shown in FIG. 2 is applied to the dark ink, it is considered that the graininess in the highlight portion is not affected. . However, in the middle density portion where the light ink is gradually replaced with the dark ink, the dark ink dots are emphasized. In this case, the graininess in the middle density portion is also conspicuous. Therefore, in this embodiment, the mask shown in FIG. 8 is applied only to dark ink, and the normal 100% mask shown in FIG. 1 is applied to light ink.

  As described above, according to the present embodiment, a high maximum density and a wide gradation are applied to each ink to be applied in a state where the granularity of the image is not impaired in all density regions ranging from a low density to a high density. It became possible to realize it in response.

(Second Embodiment)
The second embodiment of the present invention will be described below. In the first embodiment, the mask pattern to be applied is different according to the color of the ink. However, in this embodiment, the mask pattern is different according to the type of the recording medium.

  In general, even when the same amount of ink is applied, the output density value expressed is often different depending on the type of the recording medium. Further, the change in the output density value with the amount of ink applied is also characterized by the recording medium. For example, when recording is performed on glossy paper with an arbitrary ink, it is assumed that the density increases smoothly until the recording rate reaches 150%. However, even if the same recording is performed on plain paper, the same effect is often not obtained. In the case of plain paper, not only the same density cannot be obtained, but also the situation that the density hardly changes when the recording rate is about 120%, for example. In such a case, if a 150% mask pattern is used in accordance with glossy paper, there is a concern about image defects such as fixing failure and blurring on plain paper. Therefore, it can be said that the degree of emphasis is preferably adjusted according to the recording medium.

  Further, the appropriate degree of emphasis may differ depending on the ink even for the same recording medium. That is, for example, on plain paper, even if cyan, magenta, and black have no significance for enhancement of 120% or more, a certain increase in density may be confirmed for yellow, up to 150%. Therefore, it is preferable that an appropriate mask pattern is prepared in accordance with the type of ink and the type of recording medium, and this embodiment has a configuration that realizes such a demand.

  Also in the present embodiment, the block diagram of FIG. 4 is applied as in the first embodiment. However, in the recording system of the present embodiment, the user can select the recording mode from the printer driver according to the type of the recording medium. Here, it is assumed that at least two recording media of plain paper and glossy paper can be selected, and that each process after the printer driver is independently handled according to the recording medium.

  In the following, processing when plain paper is selected by the printer driver will be described first. In the recording system of this embodiment, the dot arrangement patterning process is the same as that of the first embodiment. That is, the dot arrangement of the density data quantized into three values from level 0 to level 2 is determined according to the patterns described with reference to FIGS.

  In this embodiment, the maximum recording rate of each ink color on plain paper is 100% for light cyan and light magenta, 120% for cyan, magenta and black, and 130% for yellow. For light cyan and light magenta, the normal mask shown in FIG. 1 is used as in the first embodiment. For cyan, magenta, and black, a mask with a maximum recording rate of 120% shown in FIG. 8 can be applied.

  FIG. 11 is a diagram for explaining the relationship between the mask pattern applied to yellow and the dot arrangement pattern when plain paper is selected in the mask data conversion process J0008 of this embodiment. FIG. 11A shows a mask pattern to be applied to the recording data recorded in a predetermined image area by the first recording scan. FIG. 11B shows a mask pattern to be applied in the second printing scan. Each mask pattern has a recording rate equivalent to 65% with respect to the entire area. In FIG. 11C in which both are superimposed, a recording rate of about 130% is obtained. It is confirmed that the area indicated by “2” is slightly larger than the 120% enhancement described with reference to FIG.

  FIG. 11D shows a matrix corresponding to level 1. As in the case of 120% recording, all of the areas indicated by “2” in FIG. 11C correspond to areas in which dots are not recorded in FIG. Therefore, as in the case of FIG. 8, overwriting for emphasis is not performed on the density data of level 1 in all image areas. That is, in the yellow of the present embodiment, since the enhancement is not performed in the low density region, the effect of suppressing the deterioration of the graininess can be obtained similarly to the enhancement of 120% described in FIG. On the other hand, in the high density region, dots are more actively emphasized, and a higher maximum density can be realized.

  Next, processing when glossy paper is selected by the printer driver will be described. Also for glossy paper, the dot arrangement patterning process is the same as in the first embodiment. That is, the dot arrangement of the density data quantized into three values from level 0 to level 2 is determined according to the patterns described with reference to FIGS.

  In this embodiment, the maximum recording rate of each ink color on glossy paper is 100% for light cyan and light magenta, 130% for cyan and magenta, 140% for black, and 150% for yellow. For light cyan and light magenta, the normal mask shown in FIG. 1 is used as in the first embodiment. For cyan and magenta, the mask pattern having the maximum recording rate of 130% described in FIG. 11 can be applied.

  FIG. 12 is a diagram for explaining a relationship between a mask pattern applied to black and a dot arrangement pattern when glossy paper is selected in the mask data conversion process J0008 of the present embodiment. FIG. 12A shows a mask pattern to be applied by the first recording scan with respect to recording data recorded in a predetermined image area. FIG. 12B shows a mask pattern to be applied in the second printing scan. Each mask pattern has a recording rate equivalent to 70% with respect to the entire area, and in FIG. 12 (c) where both are superimposed, a recording rate of about 140% is obtained. The area indicated by “2” is further larger than the case where the 130% emphasis described in FIG. 11 is performed.

  FIG. 12D is a mother matrix corresponding to level 1. As in the case of 120% recording, all of the areas indicated by “2” in FIG. 12C correspond to the areas in which dots are not recorded in FIG. Therefore, as in the case of FIG. 8, overwriting for emphasis is not performed on the density data of level 1 in all image areas.

  FIG. 13 is a diagram for explaining the relationship between the mask pattern applied to yellow and the dot arrangement pattern when glossy paper is selected in the mask data conversion process J0008 of the present embodiment. FIG. 13A shows a mask pattern that is applied to the recording data recorded in a predetermined image area in the first recording scan. FIG. 13B shows a mask pattern applied in the second recording scan. Each mask pattern has a recording rate equivalent to 75% with respect to the entire area, and in FIG. 13C in which both are superimposed, a recording rate of about 150% is obtained. The area indicated by “2” is larger than in the case of performing the 140% enhancement described with reference to FIG.

  FIG. 13D is a mother matrix corresponding to level 1. As in the case of recording at 120%, all of the areas indicated by “2” in FIG. 13C correspond to areas in which dots are not recorded in FIG. Therefore, as in the case of FIG. 8, overwriting for emphasis is not performed on the density data of level 1 in all image areas.

  In the black and yellow of the present embodiment, since the enhancement is not performed in the low density region, the effect of suppressing the deterioration of the graininess can be obtained in the same manner as the 120% enhancement described with reference to FIG. On the other hand, in the high density region, dots are more actively emphasized, and a higher maximum density can be realized.

  As described above, according to the present embodiment, in an inkjet recording system capable of recording on a plurality of types of recording media, in the entire density region from low density to high density, the granularity of the image is not impaired, It has become possible to achieve the maximum density and wider gradation that can be expressed on each recording medium.

(Other embodiments)
In the above embodiment, the description has been given by taking as an example two-pass multi-pass printing in which an image is completed by two printing scans. However, the present invention is realized if there are multiple passes of two or more passes. I can do it. At this time, for example, if the ternary dot arrangement matrix pattern as described with reference to FIG. 5 is applied, a configuration in which dots are recorded in a non-recorded area in level 1 as in the above-described embodiment may be used. That's fine. In this case, the degree of emphasis can be further increased to 3 dots for 3 passes and 4 dots for 4 passes.

  In the above embodiment, the dot arrangement patterning process that expresses three levels of density by associating two areas with one pixel has been described as an example. However, two or more areas are used. The present invention can be realized as long as the dot arrangement patterning process is performed.

  FIG. 14 is a diagram showing the level value and the dot arrangement pattern in the same manner as FIG. 5 in an example in which one pixel corresponds to a 2 × 2 area and the density is expressed by five levels (5 values). is there. As in FIG. 5, the filled area indicates the area where dots are recorded, and the number of dots to be recorded increases by one as the number of levels increases.

  When the input data is level 1, four types of patterns are prepared. This is because there are four methods for selecting the recording area among the four areas. Similarly, six types of level 2 patterns and four types of levels 3 are prepared. As described above, even when more patterns capable of expressing the same density are applied, the consistency between the dot arrangement based on the dot arrangement matrix pattern and the mask pattern used in multi-pass printing is the same as in the above-described embodiment. The present invention is established if the value is removed.

  In the above-described two embodiments, the dot arrangement at level 1 and the position to be emphasized using the mask pattern are configured to be exclusive, thereby preventing the enhancement at level 1. On the other hand, in the configuration having a larger number of levels as in the case of FIG. 14, it is possible to control “up to which level no emphasis is performed”. Furthermore, by setting a large number of multi-passes, it becomes possible to control “how many dots are to be emphasized at which level”.

  In the case of recording an image represented by the density in the dot arrangement matrix pattern of FIG. 14 by four-pass multipass, for example, no enhancement is performed up to level 2, and one dot is added in one pixel at level 3. At emphasis, level 4 can be emphasis by adding 2 dots. Further, it is possible to perform emphasis by adding 3 dots at level 4 without emphasizing up to level 3. That is, according to the present invention, it is also possible to perform systematic emphasis while making the number of dots to be recorded correspond one-to-one for each of the multi-value density levels (0 to 4). It can be said that it is completely different from the conventional enhancement method as described in Document 2.

  In the above description, at a level where a plurality of dot arrangement patterns can be prepared, a description is given of a configuration in which a plurality of dot arrangement patterns are sequentially arranged by using all of the plurality of dot arrangement patterns, for example, using a matrix matrix configuration. However, the present invention is not limited to such a configuration. The arrangement method does not need to use a mother matrix, and may be configured to be randomly arranged instead of sequential.

  Furthermore, even if the present invention is at a level where a plurality of dot arrangement patterns can be prepared, it is not always necessary to apply a plurality of dot arrangement patterns. As described above, the use of a plurality of dot arrangement patterns has an effect of suppressing the generation of textures and pseudo contours on an image, but a configuration in which one kind of dot arrangement pattern is fixedly used at all levels. Even so, if the matching between the mask pattern and the dot arrangement pattern is achieved, an effect specific to the present invention can be obtained.

  Further, in the two embodiments described above, the inkjet recording system including the host device and the recording device as shown in FIG. 4 has been described, but the present invention is not limited to such a configuration. For example, the mask data conversion processing may be performed by the host device, and the recording device may have a function of only ejecting ink according to the input binary data, or all functions may be integrated. It may be an inkjet recording system.

  In the above embodiment, when using a plurality of types of inks (dark ink, light ink, etc.) having different densities that express the same hue, a mask pattern having a maximum recording rate of more than 100% is applied to the dark ink. In the above description, the mask pattern having the maximum recording rate of 100% is applied to the light ink. However, the maximum recording rate of the mask pattern applied to the light ink is not limited to 100%. The maximum recording rate of the mask pattern applied to the light ink may be lower than the maximum recording rate of the mask pattern applied to the dark ink.

  Further, the present invention is not limited to the application of two types of dark ink (dark magenta, dark cyan) and light ink (light magenta, light cyan) as inks having different densities that express the same hue. Alternatively, three or more types of inks having different densities may be applied.

  In this case, the normal 100% mask pattern is applied only to the ink with the lowest density among the inks having different densities expressing the same hue, and the mask pattern exceeding 100% is applied to the other inks. It is good also as a form. For example, when dark ink, medium ink, and light ink are present, a 100% mask pattern is applied only to light ink, and a mask pattern exceeding 100% is applied to medium ink and dark ink. Further, the maximum recording rate of the mask pattern of dark ink may be set higher than that of medium ink. As another form, a mask pattern exceeding 100% is applied only to the ink with the highest density among the inks having different densities expressing the same hue, and a mask pattern of 100% is applied to the other inks. It is good to do.

  Further, in the above-described embodiment, an embodiment using inks (dark magenta, light magenta, dark cyan, and light cyan) with different densities expressing the same hue has been described, but the present invention is not limited to this embodiment. The present invention is also applicable to a mode in which the same ink is ejected with different ejection amounts. In this case, the same 100% mask pattern for light ink is applied to small dots with a relatively small discharge amount, and the same 100% mask pattern for dark ink is applied to large dots with a relatively large discharge amount. Should be applied.

  The large dots and the small dots do not need to be applied to all of the plurality of colors of ink used, and may be applied to at least one color of the plurality of colors of ink. For example, when four colors of black, yellow, cyan, and magenta are used, black and yellow may be recorded with a single dot diameter, and only cyan and magenta may be recorded with different dot diameters. Good. In this case, the maximum recording rate of the mask pattern applied to recording of small cyan dots and small magenta dots is set to 100%, and the mask pattern applied to recording of large cyan dots, large magenta dots, yellow dots and black dots. It is preferable to set the maximum recording rate of 100% or more.

  Further, the types of dot diameters of the same ink are not limited to applying two types, and may be three or more types. For example, when there are three types of small dots, medium dots, and large dots, a 100% mask pattern is applied only to small dots, and a mask pattern exceeding 100% is applied to medium dots and large dots. Also good. Furthermore, the maximum recording rate of the mask pattern for larger dots than for medium dots may be set higher. As another form, a mask pattern of more than 100% may be applied only to large dots, and a mask pattern of 100% may be applied to other medium dots and small dots.

(A)-(c) is the figure which showed the mask pattern for demonstrating a multipass printing method. (A)-(c) is the figure which showed the example of the mask pattern at the time of performing the multipass printing method aiming at the density increase. (A) And (b) is a schematic diagram for demonstrating a mode that a granular feeling deteriorates. It is a block diagram for demonstrating the flow of the image data conversion process in embodiment of this invention. It is a figure which shows the output pattern with respect to the input levels 0-2. (A)-(c) is the figure which showed the mother matrix corresponding to each level value for arrange | positioning a some pattern mixedly. (A)-(c) is the figure which showed the structure which arrange | positions a mother matrix in the whole image. (A)-(d) is a figure for demonstrating the relationship between the mask pattern applied by mask data conversion process, and a dot arrangement pattern. (A)-(c) is the figure which showed the recording rate to the image area | region with respect to the digital count of density data. FIG. 5 is a diagram for explaining the recording rate of each ink with respect to an input image density when a grayscale image is recorded in an inkjet recording apparatus in which a plurality of types of ink having different densities are simultaneously mounted. (A)-(d) is a figure for demonstrating the relationship between the mask pattern applied to yellow, and a dot arrangement pattern, when a plain paper is selected in the 2nd Embodiment of this invention. (A)-(d) is a figure for demonstrating the relationship between the mask pattern applied to black when a glossy paper is selected in the 2nd Embodiment of this invention, and a dot arrangement pattern. (A)-(d) is a figure for demonstrating the relationship between the mask pattern applied to yellow, when a glossy paper is selected in the 2nd Embodiment of this invention, and a dot arrangement pattern. It is the figure which showed the mode of the level value and the dot arrangement pattern of the example which expresses density with five levels (5 values).

Claims (7)

An ink jet recording method for forming an image on the recording medium by ejecting ink from the recording head while causing the recording head to eject a plurality of colors of ink to scan the recording medium a plurality of times.
Assigning a dot arrangement pattern composed of a plurality of areas in which dot recording / non-recording is determined corresponding to each of the gradation levels to each pixel represented by a multi-value gradation level;
A step of assigning recording to an area determined to perform dot recording according to the dot arrangement pattern to the plurality of scans using a mask pattern, and creating recording data corresponding to each of the plurality of scans;
A step of ejecting ink from the recording head based on the recording data to form dots on the recording medium,
For the pixels represented by the multi-level gradation levels, the total number of dots recorded by the plurality of scans becomes a predetermined number of dots that is equal to or more than the number of areas defined as dot recording in the assignment step. In addition, the mask pattern and the dot arrangement pattern are configured such that the higher the gradation level, the larger the predetermined number of dots.
An ink jet recording method, wherein the predetermined number of dots is different from that of at least one of the plurality of colors of ink.   The plurality of color inks include a plurality of inks having different densities expressing the same hue, and the ink having a relatively high density has the predetermined number of dots compared to the ink having a relatively low density. The ink jet recording method according to claim 1, wherein the number is large. Inkjet that ejects ink from the recording head and forms an image on the recording medium while scanning the recording head a plurality of times with respect to the recording medium to form ink dots that can express the same hue and have different densities or diameters A recording method,
Assigning a dot arrangement pattern composed of a plurality of areas in which dot recording / non-recording is determined corresponding to each of the gradation levels to each pixel represented by a multi-value gradation level;
A step of assigning recording to an area determined to perform dot recording according to the dot arrangement pattern to the plurality of scans using a mask pattern, and creating recording data corresponding to each of the plurality of scans;
A step of ejecting ink from the recording head based on the recording data to form dots on the recording medium,
When recording ink dots having a relatively high density or ink dots having a relatively large diameter, the plurality of times are applied to a pixel expressed by at least a predetermined gradation level among the multi-value gradation levels. Using the mask pattern and the dot arrangement pattern configured such that the total number of dots recorded by scanning is larger than the number of areas determined as dot recording in the allocation step,
When printing the ink dots having a relatively low density or the ink dots having a relatively small diameter, the number of dots recorded by the plurality of scans with respect to the pixel represented by the multi-value gradation level. An ink jet recording method using the mask pattern and the dot arrangement pattern configured so that the total number is the same as the number of areas determined as dot recording in the assigning step. An ink jet recording method for forming an image on a recording medium by ejecting ink from the recording head while causing the recording head to eject ink to scan the recording medium a plurality of times. Assigning to each pixel a dot arrangement pattern composed of a plurality of areas in which dot recording / non-recording is determined corresponding to each of the gradation levels;
The step of assigning the recording to the area defined as dot recording according to the dot arrangement pattern to the plurality of scans using a mask pattern, and creating the recording data corresponding to each of the plurality of scans;
A step of ejecting ink from the recording head based on the recording data to form dots on the recording medium,
For the pixels represented by the multi-level gradation levels, the total number of dots recorded by the plurality of scans becomes a predetermined number of dots that is equal to or more than the number of areas defined as dot recording in the assignment step. In addition, the mask pattern and the dot arrangement pattern are configured such that the higher the gradation level, the larger the predetermined number of dots.
The inkjet recording method, wherein the predetermined number of dots varies depending on the type of the recording medium.   The inkjet recording method according to claim 4, wherein the recording head ejects a plurality of colors of ink, and the predetermined number of dots is different from that of other inks for at least one of the plurality of colors of ink. . An ink jet recording system that forms an image on the recording medium by ejecting ink from the recording head while causing the recording head to eject ink of a plurality of colors to scan the recording medium a plurality of times.
Means for allocating a dot arrangement pattern composed of a plurality of areas in which dot recording / non-recording is determined corresponding to each of the gradation levels for each pixel represented by a multi-value gradation level;
Means for creating a recording data corresponding to each of the plurality of scans, and allocating the recording to an area defined as dot recording according to the dot arrangement pattern, to the plurality of scans using a mask pattern;
Means for ejecting ink from the recording head based on the recording data to form dots on the recording medium;
For the pixels represented by the multi-value gradation levels, the total number of dots recorded by the plurality of scans becomes a predetermined number of dots equal to or greater than the number of areas determined as dot recording by the assigning means. In addition, the mask pattern and the dot arrangement pattern are configured such that the higher the gradation level, the larger the predetermined number of dots.
An ink jet recording system, wherein the predetermined number of dots is different from that of at least one of the plurality of colors of ink. An ink jet recording system that forms an image on the recording medium by ejecting ink from the recording head while causing the recording head that ejects ink to scan the recording medium a plurality of times.
Means for allocating a dot arrangement pattern composed of a plurality of areas in which dot recording / non-recording is determined corresponding to each of the gradation levels for each pixel represented by a multi-value gradation level;
Means for creating a recording data corresponding to each of the plurality of scans, and allocating the recording to an area defined as dot recording according to the dot arrangement pattern, to the plurality of scans using a mask pattern;
Means for ejecting ink from the recording head based on the recording data to form dots on the recording medium;
For the pixels represented by the multi-level gradation levels, the total number of dots recorded by the plurality of scans becomes a predetermined number of dots that is equal to or more than the number of areas determined as dot recording by the assigning means. In addition, the mask pattern and the dot arrangement pattern are configured such that the higher the gradation level, the larger the predetermined number of dots.
The inkjet recording system, wherein the predetermined number of dots varies depending on the type of the recording medium.

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