JP2008284774A - Image processing method and inkjet recording apparatus - Google Patents

Abstract

In image processing for generating recording data of an ink jet recording apparatus, the deterioration of graininess is eliminated by changing the type of ink used according to the recording width.
A color separation table A is used when the width of a recording medium to be used is less than 44 inches. As a result, it is possible to record gray with good gradation while reducing the graininess of gray, particularly in the highlight portion. On the other hand, when the width of the recording medium to be used is 44 inches or more, the color separation table B is used. According to this color separation table B, since PM ink and PC ink are not used, when the recording time difference between passes becomes large, the ink ejected with the above time difference is connected to form a large lump. Can be suppressed. As a result, it is possible to prevent the deterioration of graininess and the occurrence of graininess unevenness.
[Selection] Figure 14

Description

  The present invention relates to an image processing method and an ink jet recording apparatus, and more particularly to reduction of graininess caused by beading of ink landed on a recording medium.

  Conventionally, in an ink jet recording apparatus, a serial method is often used in which recording is performed by scanning a recording head on a recording medium such as recording paper. In this type of device, the so-called multi-pass printing method, in which image recording is completed by scanning a plurality of times with different corresponding ink ejection openings in the same area on the recording medium, is widely executed in terms of improving image quality. This is the recording method used.

  FIG. 1 is a diagram for explaining a multi-pass printing method. As an example, two-pass multi-pass printing in which printing is completed by two main scans (hereinafter also referred to as scans) is shown. Specifically, FIG. 6 illustrates multi-pass printing based on the relationship between the position of the print head H and the print area of an image printed on the print medium P. In the figure, an image is recorded on the recording medium P by ejecting ink based on the recording data while the recording head H moves in the main scanning direction (arrow X1 direction). Thus, each time the recording head H scans once, a width (hereinafter referred to as 1/2) corresponding to 1/2 of the ejection opening array width in the recording head H (hereinafter also simply referred to as “width of the recording head H”). The recording medium P is conveyed in the sub-scanning direction (arrow Y direction) one by one. In FIG. 1, the position of the recording medium P is fixed, and the recording head H is shown as moving in the direction opposite to the sub-scanning direction with respect to the recording medium P. As is apparent from the above description of the two-pass recording method, the same can be executed with other numbers of passes. For example, in the case of four-pass recording in which the recording of the image is completed by scanning the recording head four times in the main scanning direction, the same area can be obtained by carrying an amount of 1/4 of the ejection opening array width for each scan. An image can be completed by four scans by changing the corresponding discharge ports.

  By the way, in the multipass printing method as described above, a problem of image quality deterioration due to an increase in the width (recording width) of the scanning area is particularly known. In other words, ink that is ejected in a plurality of scans that complete an image is ejected with a time interval corresponding to the recording width between the scans, and density unevenness may occur. This is a problem that the density unevenness becomes more conspicuous as the length becomes longer.

  2A to 2D and FIGS. 3A to 3D are diagrams for explaining the occurrence of density unevenness in accordance with such a time interval (hereinafter also referred to as a recording time difference).

  2A to 2D schematically show the state of ink permeation and fixing with respect to the recording medium 102 when the difference in recording time between the first pass and the second pass in two-pass printing is relatively short. It is a representation. As shown in FIG. 10A, the ink droplet 101a ejected in the first pass penetrates in a direction perpendicular to the surface of the recording medium 102 and a direction along the surface as shown in FIG. Thus, a pigment such as a dye that is an ink component physically and chemically binds to the recording medium 102. As shown in FIG. 8C, the ink droplets 101b ejected in the second pass are in a direction perpendicular to the surface of the recording medium 102 and a direction along the surface as shown in FIG. Although it penetrates, it does not penetrate so much into the area where the ink droplet 101a that has landed first is fixed. This may be because the ink droplet 101a that has landed first is still penetrating. Therefore, the ink droplet 101b that has landed later penetrates and fixes further below the region where the ink droplet 101a that has landed earlier penetrates, as shown in FIG. 2C and 2D, the landing position of the ink droplet 101b in the second pass or the fixing position thereof is the landing position of the ink droplet 101a in the first pass shown in FIGS. The fixing position is shifted due to multi-pass recording. That is, the ink ejection data of each scan that completes the image is complementary based on the thinning-out process for the pixels, and the pixels that land in the second pass of the first pass are not the same, but are adjacent, for example. The same applies to FIG. 3 described below.

  3A to 3D show the recording medium 102 when the difference in recording time between the first pass and the second pass in the two-pass recording method is longer than that shown in FIG. This is a schematic representation of ink penetration and fixing. As shown in FIG. 3A, the ink droplet 101a ejected in the first pass is perpendicular to the surface of the recording medium 102 as shown in FIG. 3B, as in the case shown in FIG. Permeates in direction and along the surface. Then, a pigment such as a dye that is an ink component physically and chemically binds to the recording medium 102. In contrast to the case shown in FIG. 3D, the ink droplet 101b ejected in the second pass and landed later is compared with the area where the first landed 101a penetrates and is fixed, as shown in FIG. Penetration (Figure 3 (d)). This is because the ink droplet 101a that has landed first penetrates sufficiently and spreads or its volatile components can evaporate due to the relatively long recording time difference between the first pass and the second pass. . Therefore, it is considered that the amount of ink droplets 101a per unit volume of the recording medium 102 decreases, and ink droplets 101b that have landed later can penetrate.

  As described above, the amount of ink fixed near the surface of the recording medium, that is, the amount of a pigment such as a dye may differ depending on the recording time difference between the first pass and the second pass. Since the recording density corresponds to the amount of light absorbed by the dye fixed near the surface of the recording medium, if the recording time difference between the first pass and the second pass is different, the recording density will be different accordingly. .

  FIG. 4 is a diagram illustrating an example of density unevenness due to the generation mechanism described above. This figure explains the relationship between the recording width, which is the length that the recording head scans during recording, and the recording time difference between the first pass and the second pass in multi-pass recording by bidirectional scanning. When recording is performed by scanning the recording head H from the left to the right in the figure at the first scan, and recording from the right to the left at the second scan, a region A and a right end of a predetermined size at the left end of the recorded image Focus on a region B of the same size. In the leftmost region A, the recording head H scans from the left to the right and performs the first pass recording at the initial stage, and then the recording head turns back at the right end and scans from the right to the left. Record the second pass at the last stage. For this reason, the recording time difference from recording the first pass to recording the second pass is relatively long. On the other hand, in the rightmost region B, the recording head scans from the left to the right and performs the first pass at the final stage, and then the recording head turns back at the right end and scans from the right to the left. The second pass is recorded in the initial stage of. For this reason, the recording time difference from recording the first pass to recording the second pass is relatively short. In the area where recording is performed at the last stage of scanning after the recording head is turned back as in the area A, the recording time difference is a time corresponding to the recording width. For this reason, the recording time difference varies depending on the length of the recording width, and as a result, the density difference between the region A and the region B increases as the recording width increases.

  FIG. 5 is a diagram for explaining density unevenness (time difference unevenness) that occurs in a recorded image due to the difference in recording time between the rightmost region and the leftmost region in scanning in bidirectional multipass recording as described above. In the figure, a region where the recording time difference from the first pass recording to the second pass recording is long is indicated by α, and a short region is indicated by Β. As can be seen from this, in the bi-directional recording, the α region and the wrinkle region occur alternately, and the density difference between these regions appears as repeated high and low density at both ends of the recorded image, and this is remarkably recognized as uneven time difference. It will be.

  In the above description, the case of 2-pass multi-pass printing has been described, but it is a matter of course that the same time difference unevenness can occur in multi-pass printing of 3 passes or more. In this case, for example, in m (3 or more) pass recording, not only the time difference from the (m-1) / m pass recording to the m / m pass recording when the recording is completed, but also the time difference due to the time difference in the intermediate recording. Causes unevenness. That is, the same time difference unevenness can be caused by the time difference of two consecutive scans from the k / m pass recording to the (k + 1) / m pass recording. That is, the regions that become the α region and the heel region in the (k + 1) / mth pass are the B region and the α region in the next (k + 2) / mth pass, respectively. In this case, the time difference unevenness described above occurs at that time due to the penetration and fixing of the ink in the (k + 1) / mth pass, and this density unevenness affects the final time difference unevenness of the region. In the case of multi-pass recording of three or more passes, there is a problem of final time difference unevenness when recording is completed by m passes including the influence of such time difference unevenness in the middle.

  The problem of uneven time difference described above is particularly noticeable in a large-format recording apparatus that records on a large-size recording medium. In recent years, large-format inkjet recording apparatuses capable of recording on a recording medium having a relatively large recording width such as a 36-inch width, a 42-inch width, and a 60-inch width as well as a plain paper size have been provided. In such a large format recording apparatus, as described above with reference to FIG. 4, since the density difference between the A area and the B area is in accordance with the recording width, the density difference between both areas becomes larger. As a result, the occurrence of unevenness in time difference becomes more prominent. Therefore, the time difference unevenness is a particularly serious problem in a large-format ink jet recording apparatus capable of recording a relatively large size.

  As a technique for suppressing the time difference unevenness caused by the recording time difference as described above, one described in Patent Document 1 is known. This document describes that the recording mode is switched from bidirectional recording to unidirectional recording when the possibility of uneven density is high. Specifically, the recording area is divided into a plurality of areas in the main scanning direction, and the number of dots of black ink and color ink applied to each area is counted. If there are areas where both black and color exceed the respective threshold values, the number of areas is counted, and if the number is greater than or equal to a predetermined number, there is a high possibility that time difference unevenness will occur, and switching to one-way recording is performed. This makes it possible to suppress the time difference unevenness occurring at both ends of the recorded image. The document also detects the width of image data to be recorded, that is, the width of the range scanned by the recording head, and if the width is small, the degree of unevenness in time difference is small, and the number of areas is not less than a predetermined value. It is also described that switching to one-way recording is not performed.

  As another technique for suppressing the time difference unevenness, Patent Document 2 describes that when the recording width is long, the time difference unevenness between the bands is made inconspicuous by increasing the number of multi-pass passes. Further, this document also describes that it is difficult to recognize the time difference unevenness by repeating the time difference unevenness at a high frequency. In addition, when the recording width is long, it is possible to shorten the multipass time difference by increasing the scanning speed of the recording head, or to reduce unevenness in time difference by switching to unidirectional recording and making the recording time in each band the same. Are listed.

JP 2003-34021 A JP 2005-144868 A

  However, in addition to the above-described non-uniformity in time difference, a problem in image quality caused by an increase in recording width has been found from recent examination results. That is, it has been confirmed that in multi-pass printing using ink containing a polymer, beading occurs as the recording time difference between passes increases. This beading forms a grain which is a large lump formed by connecting ink droplets and causes deterioration of the graininess of a recorded image. It has been found that this beading occurs more frequently as the ratio of the polymer in the ink composition increases.

  FIGS. 6A to 6E are schematic diagrams showing dot fixing states on the paper surface in the case of using ink with a low polymer ratio in two-pass printing. As shown in FIG. 6A, the ink droplets 601 ejected in the first pass land on the surface of the recording medium 602, and as shown in FIG. 6B, the ink-fixed portion 603 (referred to as an ink layer). ) Is formed on the recording medium 602. Next, as shown in FIG. 4C, the ink droplet 604 ejected in the second pass lands on the ink layer 603 formed in the first pass, and passes through the state shown in FIG. Finally, it is fixed on the ink layer 603 like the ink layer 606 in FIG.

  On the other hand, FIGS. 7A to 7E schematically show dot fixing states on the paper surface in the case of using an ink having a higher polymer ratio than an ink having a lower polymer ratio in two-pass printing. FIG. As shown in FIG. 7A, the ink droplets 701 ejected in the first pass land on the surface of the recording medium 702, and as shown in FIG. 7B, an ink fixing portion 703 (referred to as an ink layer). Are formed on the recording medium 702. Next, as shown in FIG. 4C, the ink droplet 704 ejected in the second pass lands on the ink layer 703 formed in the first pass, but the landed ink droplet 705 As shown in FIG. 6D, the dot diameter is greatly expanded as compared with the ink droplet 605 shown in FIG. Then, as shown in FIG. 5E, beading in which ink droplets are connected occurs. This is presumably because the surface ratio of the ink layer 703 is high because the polymer ratio in the ink is large, and the ink droplets in contact with this layer are likely to spread. Further, when the ink layer 703 is formed with ink having a high polymer ratio, the gap in the receiving layer of the glossy paper is filled with the polymer. As a result, absorption of the ink droplets 704 ejected in the second pass into the receiving layer is hindered, and the droplets tend to remain for a long time. As a result, the ink droplets can easily come into contact with each other, and the possibility of beading increases.

  The phenomenon described with reference to FIGS. 6 and 7 relates to the case where multi-pass printing is performed using the same color ink. However, the description also applies to the case where different color inks are ejected in a plurality of passes so that they contact each other with a time difference between passes.

  6 and 7 described above, the landing position or the fixing position is not shifted between the first pass and the second pass as described with reference to FIGS. 2 and 3. Because. In the case of multi-pass printing, the ink ejection data of each scan that completes an image is complementary based on the thinning-out process for pixels, and the pixels that land in the first pass and the second pass are not the same. Adjacent. In such a case, the ink droplet (layer) that has landed or fixed in the first pass may come into contact with the ink droplet that landed in the second pass. In this case, the phenomenon described above with reference to FIGS. Get up. Of course, as shown in FIGS. 6 and 7, there is a recording mode in which ink is ejected at overlapping positions. In this case, the recording mode is as described above.

  FIG. 8 is a diagram illustrating a change in the dot diameter of the second pass according to the time difference between the first pass and the second pass of the ink having a high polymer ratio and the ink having a low polymer ratio. As shown in the figure, in the ink with a small polymer ratio, the dot diameter hardly changes even if the time difference between the first pass and the second pass changes. On the other hand, in the case of ink having a high polymer ratio, the dot diameter changes greatly with the change in time difference. As a result, when the time difference is relatively large, there is a high possibility that beading will occur, and the resulting graininess may become noticeable. In addition to the deterioration of graininess itself, unevenness due to the difference in graininess depending on the recording position (graininess unevenness) may be conspicuous.

  As described above, when multi-pass printing is performed using ink containing a relatively large amount of polymer, the graininess becomes noticeable at a certain recording position or the graininess between the recording positions depends on the recording width. The difference appears as unevenness. In particular, it becomes a significant problem when the recording width is particularly large, such as a large-format ink jet printer. Further, in the case of normal color recording, the polymer ratio of each color ink is often different. Therefore, the problem of graininess due to beading as described above tends to occur due to the influence of ink having a high polymer ratio.

  The graininess due to the use of such a polymer-rich ink is not limited to the multi-pass printing bi-directional printing described with reference to FIGS. 4 and 5, but multi-pass printing is performed only in one-way scanning. It also occurs in some cases. Of course, the same region is not recorded by different ejection ports, but is also generated when scanning is performed a plurality of times using the same ejection port to complete an image. That is, when ink having a relatively large amount of polymer is ejected to adjacent positions or the same position with a certain time difference, beading in which ink droplets are connected may occur, and the resulting graininess may deteriorate image quality. The position where the graininess is observed is a position where a certain time difference or more occurs when ink is ejected to the adjacent position or the same position in the scanning region of the recording head.

  In addition, it is clear from the above explanation that even if the techniques described in Patent Document 1 and Patent Document 2 are applied to the above-described problem of graininess caused by beading, the deterioration of graininess itself cannot be solved. It is.

  Further, unlike the problem of beading with ink containing a large amount of polymer as described above, the present invention shows that the density unevenness at the end of the scanning region described in FIGS. 4 and 5 differs depending on the type of ink used. Have found headlines.

  An object of the present invention is to change the type of ink used according to the recording width or the like, thereby eliminating the deterioration of graininess itself and reducing the density unevenness at the end of the scanning region. And providing an ink jet recording apparatus.

  Therefore, in the present invention, an image processing method for generating recording data for performing recording by discharging ink from the recording head to the recording medium while scanning the recording head for discharging ink with respect to the recording medium. The print data is generated by performing a process of varying the amount of ink used for printing in accordance with information indicating the width of the print medium in the scanning direction of the print head or information indicating the print width. The process of having carried out.

  An ink jet recording apparatus that performs recording by ejecting ink from the recording head to the recording medium while scanning the recording head for ejecting ink on the recording medium, the recording in the scanning direction of the recording head It is characterized by comprising means for performing processing for varying the amount of ink used for recording in accordance with information indicating the width of the medium or information indicating the recording width.

  According to the above configuration, the amount of ink used for recording is varied according to the recording width information. For example, the recording width is long, and the graininess deteriorates due to the properties of the predetermined ink used. When there is a risk of this, the amount of the predetermined ink used can be reduced. Alternatively, for example, when the recording width is long and there is a risk of uneven density, the amount of ink that easily causes uneven density can be reduced.

  As a result, it is possible to eliminate the deterioration of the graininess itself and reduce the density unevenness at the end of the scanning region.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 9 is a block diagram mainly showing the configuration of the host computer of the recording system according to the embodiment of the present invention. The host computer 14 includes a CPU 202, a memory 203 such as a RAM and a ROM, and an external storage device 204 such as a hard disk. Furthermore, an input unit 205 to which input devices such as a keyboard and a mouse are connected, and an interface 206 to which peripheral devices such as a printer can be connected are provided. These units are connected to each other via a system bus. The CPU 202 executes a program stored in the memory 203, thereby executing processing described later with reference to FIG. 10, FIG. 12, and FIG. This program is stored in the external storage 204 or the like, and is supplied from the external device 204 to the memory 203 as necessary.

  The host computer 14 is connected to the printer 13 via the interface 206, sends image data subjected to image processing to the printer 13, and performs a recording operation.

  FIG. 10 is a block diagram showing the main functions of image processing executed in the host computer 14, and input R, G, B color image data of 8 bits (256 gradations) is converted into C, M, Y, A process of outputting as 1-bit recording data of each color of K, R, G, and B is shown. This process is realized as a printer driver that operates on the host computer 14.

The R, G, B 8-bit image data that is input data is corrected by the color correction processing unit 101 into 8-bit R, G, B color image data that can be reproduced by the printer 13. This process is performed by using a three-dimensional lookup table (LUT) and using an interpolation operation together. Specifically, in order to obtain a desired color reproduction such as color reproduction by an sRGB monitor, for example, the gamut mapping technique is used to set the color gamut of the printer 13 on a uniform color space such as L ^* a ^* b ^* . Perform color matching to connect to the appropriate color target. A known gamut mapping technique can be used. Note that the color correction process is not necessarily performed using a table, and the color correction process may be performed using an appropriate linear or non-linear color correction function.

  Next, the color conversion processing unit 102 performs color separation processing, which will be described later in the following embodiments, to convert RGB image signal values into 8-bit image signal values for each color such as C, M, Y, and K. Is done. This process is also performed by using an interpolation operation together with the three-dimensional LUT. By this processing, combinations of ink color signals C, M, Y, K, R, G, and B when an image represented by the color signals RGB is reproduced using a printer are determined.

  The 8-bit image data of each color such as C, M, Y, and K obtained by the color conversion process is subjected to output gamma correction by the output gamma correction unit 103 using a one-dimensional LUT. In many cases, output gamma correction corrects the relationship between the number of recorded dots per unit area that is not linear and the output characteristics (reflection density, etc.), and inputs 8 bits for each color such as C, M, Y, K, etc. This guarantees a linear relationship between the image data and the output characteristics of the formed image.

  Further, 8-bit image data of each color such as C, M, Y, and K is quantized by the quantization processing unit 104 according to the recording mechanism of the printer 13. For example, if the printer 13 is a binary printer, it is quantized (binarized) into 1-bit data for each color such as C, M, Y, and K. As this quantization method, a known error diffusion method or dither method can be used. In this quantization process, for example, quantization larger than a binary value such as a quaternary value is performed, and a dot pattern is developed based on the quaternary data in the printer, so that the recording head is finally driven. The binary data may be obtained.

  In the following, some embodiments of the color separation processing with the above-described configuration will be described. Embodiments of the present invention relate to information that changes the amount of ink used according to information indicating the width of a recording medium in the scanning direction of the recording head or information indicating the recording width. That is, as described above, inks containing a relatively large amount of polymer deal with the graininess caused by beading that may occur when they come into contact with each other with the time required for scanning the recording head.

  FIG. 11 is a diagram for explaining the graininess of an image that occurs as time elapses with the scan of the recording head. As shown in the figure, when the recording width is relatively large, graininess may be conspicuous at the center and the end of the recording width.

  That is, in the case of bidirectional multi-pass recording, there is a time difference (wait) for reciprocating half the recording width between the first pass and the second pass, for example, in the central portion of the recording width. When this time difference is the length that causes the beading (connection of ink droplets) described with reference to FIG. 7, the graininess due to the beading becomes noticeable in the center portion.

  In addition, at the end of the recording width, there is a time difference (large wait) for reciprocating the full length of the recording width every other scanning area (band) by the ejection port group divided by the recording head between certain passes. . In this case as well, the graininess becomes noticeable at each end, and the graininess is uneven between even and odd bands. And the graininess of this edge part becomes more remarkable than the graininess of the center part because the time difference is longer.

  Of course, depending on the recording width, the graininess may be noticeable only at the end portion, and the graininess may not be so much deteriorated at the center portion.

(First embodiment)
In the first embodiment of the present invention, cyan (C), magenta (M), yellow (Y), photocyan (PC), photomagenta (PM), gray (Gy), and black (K) are used as recording heads. A recording head having discharge ports for discharging the respective pigment inks is used. PC ink and PM ink are inks having a lighter pigment concentration than C ink and M ink, respectively. Further, the ratio of polymer to pigment is 0.5 for C ink and M ink, and the ratio is 2 for PC ink and PM ink. The discharge amount of ink of each color of the print head is 4.5 pl, and the moving speed of the carriage on which the print head is mounted is 33.3 inches. In the following description, a recording mode in which glossy paper is used as a recording medium and 16-pass multipass printing is performed will be described.

  In the first embodiment of the present invention, when the width of the recording medium used for recording is relatively large, the PM ink containing a relatively large amount of polymer as a table used in the color separation processing in step 102 shown in FIG. A color separation table that does not use PC ink is used. That is, a color separation table in which the usage amount of PM ink and PC ink is zero is used.

  FIG. 12 is a flowchart showing printer driver processing executed in the host computer 14 for recording according to the first embodiment of the present invention.

  In FIG. 12, first, in step 901, the width of the recording medium used for recording is determined. This determination can be made by the user in response to the selection input of the type of the recording medium via the user interface screen by the printer driver. That is, the width of the recording medium is known according to the type of the recording medium input by the user, and thereby recording width information that is the length of the scanning area of the recording head can be obtained. The recording width information may be width information directly input by the user, or may be acquired by detecting the width of the recording medium with a sensor.

  Next, in step 902, a color separation table corresponding to the width of the recording medium is determined. The color separation table is a table in which combinations of usage amounts of the respective color inks are associated as grid point data in accordance with combinations of the values of the color signals R, G, and B. In the color separation process of step 102 shown in FIG. 10, the grid point data is obtained by referring to this table, and the amount of use of each color ink corresponding to the color signals R, G, B is determined by using interpolation calculation together. Combinations can be determined. The amount of ink used as the grid point data is set to 100% when four 4.5 pl ink droplets are ejected into an area of 600 dpi × 600 dpi.

  FIG. 13 is a diagram illustrating the relationship between the width of the recording medium and the color separation table used according to the present embodiment. As shown in the figure, the color separation table A is used when the recording medium width determined in step 901 is 44 inches or less, and the color separation table B is used when the recording medium width is 44 inches or more. Represents.

  FIGS. 14A and 14B are diagrams showing part of the contents of the color separation table A and the color separation table B, respectively. That is, these drawings show color separation for gray in which the color represented by the R, G, and B signals changes from white (W) to black (K) as an example of a table.

  In the case of the color separation table A shown in FIG. 14 (a), when recording gray, a large amount of PM ink and PC ink having a basically low color material density are used over the entire range. Thereby, it is possible to reduce the graininess particularly in the gray highlight portion. On the other hand, as shown in FIG. 14B, the color separation table B represents gray without using PM ink and PC ink.

  In the present embodiment, as shown in FIG. 13, when the width of the recording medium to be used is less than 44 inches, the color separation table A is used. As a result, it is possible to record gray with good gradation while reducing the graininess of gray, particularly in the highlight portion. On the other hand, the color separation table B is used when the width of the recording medium to be used is a predetermined width of 44 inches or more. According to this color separation table B, since PM ink and PC ink are not used, when the recording time difference between passes becomes large, the ink ejected with the above time difference is connected to form a large lump. Can be suppressed. As a result, it is possible to prevent the deterioration of graininess and the unevenness of graininess described with reference to FIG.

  Note that the color separation table B expresses a gray particularly highlight portion mainly by Gy ink without using PM ink and PC ink, and therefore, the graininess may be deteriorated. However, this deterioration is less severe than the deterioration of the graininess described with reference to FIG. 11 that occurs when PM ink and PC ink are not used.

  Further, the contents of the tables shown in FIGS. 14A and 14B relate to gray, but it goes without saying that the same applies to colors other than gray. That is, when the color separation table A uses PM ink or PC ink for colors other than gray, the color separation table B is configured to represent the same color without using PM ink or PC ink. When the color separation table B is expressed without using PM ink or PC ink, the gradation characteristics are considered in relation to other colors so that image degradation such as pseudo gradation does not occur in the recorded image. The amount of each ink used is determined. The above description is the same for the embodiments described below.

  FIG. 15 is a diagram illustrating the evaluation of graininess in the recording result for each combination of the width of the recording medium and the color separation table to be used. Specifically, the graininess at the center of the recording width when the gray gradation image is recorded using the color separation table A or the color separation table B for the case where the width of the recording medium is 17 inches and 60 inches, respectively. It is the result of evaluating. When the width of the recording medium is 17 inches, comparing the graph 1101 of the color separation table A and the graph 1103 of the color separation table B, the case where the color separation table A is used rather than the case where the color separation table B is used. Graininess is improved. This is because, as described above, in particular, reduction of graininess is taken into consideration by using PM ink and PC ink in the highlight portion.

  On the other hand, when recording is performed using the color separation table A when the recording medium has a width of 60 inches, the graininess deteriorates as shown in the graph 1102. This is due to beading that occurs as the width of the recording medium increases as described above. On the other hand, when recording is performed using the color separation table B as in the present embodiment, deterioration of graininess can be reduced as in the graph 1104.

  Referring to FIG. 12 again, after the color separation process, print data is generated by performing gamma correction and quantization, and in step 903, the printer is instructed to start printing, and this processing is ended.

  As described above, by using different color separation tables depending on the width of the recording medium, a large-format printer corresponding to various recording medium widths can achieve high-quality recording with little graininess in any recording medium width. Can be done. That is, in this embodiment, a plurality of types of inks having different polymer content ratios are used. Specifically, the first pigment ink (PM, PC) having a relatively high polymer content and the second pigment ink (C, M) having a polymer content smaller than that of the first ink are used. When the recording width is the second recording width (the range of 44 inches or more) larger than the first recording width (the range of less than 44 inches), the usage amount of the first pigment ink is set to the first recording width. Less than the amount of the first pigment ink used. The first pigment ink and the second pigment ink have similar colors.

  Needless to say, the color separation table to be used differs depending on the recording mode conditions such as the type of recording medium used and the number of passes. Even in that case, as described above, a table using PM ink and PC ink and a table not using them are selectively used according to the width of the recording medium.

(Second Embodiment)
Unlike the first embodiment, the second embodiment of the present invention selectively uses three color separation tables according to the width of the recording medium.

  FIG. 16 is a diagram showing a table showing the correspondence between the width of the recording medium and the color separation table to be used. As shown in the figure, the color separation table D is used when the width of the recording medium is less than 33 inches, and the color separation table E is used when the width of the recording medium is 33 inches or more and less than 44 inches. Further, when the width of the recording medium is 44 inches or more, the color separation table F is used.

  FIGS. 17A to 17C are diagrams showing the contents of these color separation tables for gray color separation. The color separation table D shown in FIG. 17A uses a relatively large amount of PC ink and PM ink. In addition, the color separation table E shown in FIG. 17B is a table that uses less PC ink and PM ink than the color separation table D. Furthermore, the color separation table F shown in FIG. 17C is a table that does not use PC ink and PM ink.

  Thus, according to the present embodiment, the color separation table to be used (contents) can be determined more finely according to the degree of graininess that can occur according to the width of the recording medium. It is possible to perform high-quality recording in which is suppressed more.

(Third embodiment)
In the first and second embodiments, the color separation processing in the case where recording is performed using eight colors has been described. On the other hand, the third embodiment of the present invention relates to a color separation process when recording is performed using six pigment inks of cyan, magenta, yellow, photocyan, photomagenta, and black. In the following, a description will be given of a case where each color ink has a discharge amount of 4.5 pl, a carriage speed of 33.3 inches / sec, and a mode in which 6-pass multipass printing is performed on glossy paper.

  FIG. 18 is a diagram showing a table showing the correspondence between the width of the recording medium used for recording and the color separation table according to the present embodiment. In this embodiment, the color separation table G is used when the width of the recording medium is less than 44 inches. On the other hand, when the width of the recording medium is 44 inches or more, the color separation table H is used.

  FIG. 19A is a diagram illustrating the contents of the color separation table G by color separation of cyan colors that change from white (W) to primary cyan (C). The color separation table G is a highlight portion of cyan, and uses PC ink and C ink. This is because, as in the above embodiment, when the recording width is small, even when a PC ink containing a polymer is used, ink droplets are less likely to be connected due to this, so the graininess of the highlight portion is reduced. PC ink is used preferentially.

  On the other hand, the color separation table H expresses cyan using C ink without using PC ink. That is, as the width of the recording medium is larger, PC ink having a higher polymer ratio causes beading, and therefore, C ink is used to represent cyan without using PC ink.

  As described above, when a cyan color gradation is expressed, high image quality can be obtained for any width of the recording medium by using different color separation tables depending on the width of the recording medium.

(Fourth embodiment)
The fourth embodiment of the present invention relates to color separation when using a recording apparatus that performs a recording operation in which the width of the recording medium is different from the recording width that is actually the length scanned by the recording head. That is, in the present embodiment, the actual recording width is detected, and the same control as in the first embodiment is performed.

  The width of the recording medium used for recording is 60 inches. However, when the width of scanning by actual recording is 17 inches due to recording data or the like, it is preferable to use the color separation table A in the example shown in FIG. Therefore, in the present embodiment, processing related to recording is performed according to the flowchart shown in FIG.

  In FIG. 20, in step 1401, the width of the recording medium is determined as in the first embodiment. Next, in step 1402, the recording width is calculated from the image data to be recorded, and the recording width is determined. At this time, the recording width may be determined for each band (= vertical size is the paper feed amount) or the maximum recording width may be determined for each area. Next, in step 1403, a color separation table corresponding to the recording width is performed. In step 1404, recording is started. When the above flow ends, the recording width of the next band or area is calculated, and the subsequent processing is repeated.

  As described above, when the width of the recording medium is different from the actual recording width, the graininess can be satisfactorily reduced by performing the processing as in the present embodiment.

(Fifth embodiment)
The fifth embodiment of the present invention relates to a configuration for solving the density unevenness described above with reference to FIGS. That is, in the present embodiment, for example, cyan is used when the recording width is 17 inches in color separation for recording a high density of a blue line. If the recording width is 60 inches and time difference color unevenness is likely to occur, cyan ink is not used, but blue ink that makes it difficult to recognize density unevenness is used.

  In this embodiment, recording is performed using 12 colors of dye inks of cyan, magenta, yellow, photocyan, photomagenta, gray, photogrey, black, red (R), green (G), and blue (B). . In the following, an example will be described in which each color ink is discharged in an amount of 4.5 pl, a carriage speed of 40 inches / sec, and two-pass bidirectional recording mode.

  When a blue image (luminance value: RGB = 255, 255, 0) is formed with a total of 200% of cyan ink 100% and magenta ink 100%, when the recording width is 60 inches, color difference between bands occurs at the edge. To do.

  FIG. 21 is a diagram for explaining unevenness due to the color difference. In FIG. 21, the end region 1501 has a small time difference between the first pass and the second pass, but the end region 1502 has a large time difference. As shown in FIGS. 4 and 5, the degree of ink penetration varies depending on the difference in time, and a color difference occurs between bands. Accordingly, the color difference between the region 1501 and the region 1502 increases as the recording width such as the recording width of 60 inches increases.

  Therefore, in the present embodiment, when the image is recorded, when the recording width is 44 inches or more, a color separation table in which the amount of blue ink used is 100% is used to express blue. Thereby, the color difference between bands can be reduced by the blue ink which makes it difficult to recognize the color difference. On the other hand, when the recording width is less than 44 inches, a color separation table that uses the cyan ink 100% and the magenta ink 100% is used. As a result, the surface of the paper can be covered with more ink than when 100% of the blue ink is used, and a high image quality with less graininess can be obtained.

(Other embodiments)
In the embodiment described above, the example in which the color separation process and the related process are performed in the host computer has been described. However, the application of the present invention is not limited to such a form. For example, a similar color separation process may be executed in an inkjet recording apparatus such as a printer. In this case, this recording apparatus implements the image processing method of the present invention.

(Still another embodiment)
The present invention can also be realized by a program code that realizes the functions of the above-described embodiments and that realizes the procedures of the flowcharts shown in FIGS. 12 and 20 or a storage medium that stores the program code. It can also be achieved by reading and executing a program code stored in a storage medium that is read by a computer (or CPU or MPU) of the system or apparatus. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  As a storage medium for supplying the program code, for example, a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, or the like is used. be able to.

  In addition, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also the OS running on the computer performs an actual process based on the instruction of the program code. Part or all may be performed.

  Further, after the program code is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the CPU or the like may perform part of the actual processing or based on the instruction of the program code. You may do everything.

It is a figure explaining a multipass printing system. (A)-(d) is a figure explaining the generation | occurrence | production mechanism of the density nonuniformity in case a recording time difference is short. (A)-(d) is a figure explaining the generation | occurrence | production mechanism of the density nonuniformity in case a recording time difference is long. It is a figure explaining an example of the density nonuniformity by the said generation | occurrence | production mechanism. FIG. 6 is a diagram for explaining density unevenness caused by a difference in recording time between a right end region and a left end region in scanning in bidirectional multipass recording. (A)-(e) is a typical figure which shows the fixing state of the dot on the paper surface at the time of using the ink with few polymer ratios in 2-pass printing. (A)-(e) is a figure which shows typically the fixed state of the dot on the paper surface at the time of using the ink with a larger polymer ratio than the ink with a smaller ratio of the said polymer in 2-pass printing. It is a figure which shows the change of the dot diameter of the 2nd pass according to the time difference of the 1st pass and the 2nd pass of the ink with many polymer ratios and a small ink, respectively. 1 is a block diagram mainly showing a configuration of a host computer of a recording system according to an embodiment of the present invention. FIG. 3 is a block diagram illustrating main functions of image processing executed in a host computer 14. FIG. 4 is a diagram for explaining the graininess of an image that occurs with the passage of time associated with scanning of a recording head. 6 is a flowchart illustrating processing of a printer driver executed in a host computer 14 regarding recording according to the first embodiment of the present invention. FIG. 3 is a diagram illustrating a relationship between a width of a recording medium and a color separation table to be used according to the first embodiment. (A) And (b) is a figure which shows a part of content of the color separation table A and the color separation table B, respectively. It is a figure which shows the evaluation of the graininess in the recording result for every combination of the width | variety of a recording medium, and the color separation table to be used. It is a figure which shows the table which shows a response | compatibility with the width | variety of the recording medium which concerns on 2nd Embodiment, and the color separation table to be used. (A)-(c) is a figure which shows the content of the color separation table in the said correspondence about the color separation of gray. It is a figure which shows the table which shows a response | compatibility with the width | variety of the recording medium used for recording, and a color separation table based on 3rd embodiment of this invention. It is a figure which shows the content of the color separation table G based on color separation of the color of cyan which changes from white (W) to primary cyan (C) based on 3rd Embodiment. It is a flowchart which shows the process regarding the recording which concerns on 4th embodiment of this invention. It is a figure explaining the nonuniformity by a color difference based on 5th embodiment of this invention.

Explanation of symbols

13 Printer 14 Host computer 202 CPU
203 Memory 205 Input Unit 206 Interface

Claims (7)

An image processing method for generating recording data for performing recording by discharging ink from a recording head to a recording medium while scanning the recording head for discharging ink with respect to the recording medium,
A process of generating the recording data by performing a process of varying the amount of ink used for recording according to information indicating the width of the recording medium in the scanning direction of the recording head or information indicating the recording width. ,
An image processing method characterized by comprising: The ink includes a first pigment ink containing a polymer, and a second pigment ink having a lower polymer content than the first pigment ink,
In the processing step, when the recording width is a second recording width larger than the first recording width, the usage amount of the first pigment ink is set to be the amount of use of the first pigment ink when the recording width is the first recording width. The image processing method according to claim 1, wherein the processing is performed so that the amount is less than the amount.   3. The image processing method according to claim 2, wherein in the processing step, when the recording width is larger than a predetermined width, processing for reducing the amount of the first pigment ink to be used is performed.   4. The image processing method according to claim 1, wherein the first pigment ink and the second pigment ink have similar colors.   In the processing step, a color separation table in which the amount of ink used is determined according to the image signal value, and a plurality of color separation tables corresponding to a plurality of different recording medium widths or a plurality of different recording widths is used. The image processing method according to claim 1, wherein a process of varying the amount of ink used is performed. An inkjet recording apparatus that performs recording by discharging ink from the recording head to a recording medium while scanning a recording head for discharging ink.
Means for performing processing for varying the amount of ink used for recording in accordance with the information of the recording width, which is the length of the range scanned by the recording head during recording;
An ink jet recording apparatus comprising: By being read by the computer, the computer generates recording data for performing recording by ejecting ink from the recording head to the recording medium while scanning the recording head for ejecting ink with respect to the recording medium. A program for causing an image processing apparatus to function.
Means for generating the recording data by performing a process of varying the amount of ink used for recording according to information indicating the width of the recording medium in the scanning direction of the recording head or information indicating the recording width;
The program characterized by having.

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