JP3902898B2 - Image forming method, image forming apparatus, and image processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-pass image forming method and apparatus for forming an image by completing a predetermined area by a plurality of scans, and further to an image processing method. In particular, the present invention relates to an image forming method and apparatus for reducing density unevenness and color unevenness of a recorded image in an image forming apparatus such as a copying machine, a facsimile machine, a printer, and a textile printing machine, and further to an image processing method.
[0002]
[Prior art]
Conventionally, in an image forming apparatus such as a copying machine or a textile printing machine, density unevenness of an image is reduced by completing a multi-pass method, that is, the same area by scanning a plurality of times. This multi-pass image forming apparatus will be described taking a textile printing machine as an example.
[0003]
FIG. 1 is a schematic diagram showing an outline of an image printing unit of a textile printing machine of an ink jet recording system that performs recording on a fabric applicable to the present invention. This printing apparatus is broadly divided into an ink jet head that feeds a print medium such as a roll-like cloth that has been pre-processed for textile printing, and precisely feeds the sent print medium. And a winding unit C that dries and winds the printed print medium. The main body A further includes a precision feeding portion A-1 and an ink jet printing portion A-2 for a print medium including a platen.
[0004]
Hereinafter, the operation of this apparatus will be described by taking as an example a case where printing is performed using a pre-processed print medium as a print medium.
[0005]
The pre-processed roll-shaped print medium 236 is sent out from the benefit part B and sent to the main body part. A thin endless belt 237 that is precisely step-driven is wound around a driving roller 247 and a winding roller 249 in the main body. The drive roller 247 is directly step-driven by a high-resolution stepping motor (not shown), and step-feeds the belt by the step amount. The fed cloth 236 is pressed and stuck on the surface of the belt 237 backed up by the winding roller 249 by the pressing roller 240.
[0006]
The print medium 236 that has been step-fed by the belt is localized by the platen 232 on the back surface of the belt in the first printing unit 602 and printed by the inkjet head 209 from the front side. Each time one line of printing is completed, the sheet is fed by a predetermined amount and then dried by the heating plate 234 from the back surface of the belt and the hot air from the surface supplied / discharged by the hot air duct 235. Subsequently, the second print unit 603 performs overprinting in the same manner as the first print unit.
[0007]
The print medium 236 that has been printed is peeled off, dried again by the post-drying unit 246 similar to the heating plate 234 and the hot air duct 235 described above, guided to the guide roll 241, and taken up on the take-up roll 248. . The wound print medium 236 is removed from the apparatus, and becomes a product through post-processing steps such as color development, washing, and drying by batch processing.
[0008]
Next, details in the vicinity of the inkjet print portion A-2 will be described with reference to FIG.
[0009]
Here, the information is printed by thinning out the number of dots by the head of the first printing unit, and the information thinned out by the head of the second printing unit is complemented by the head of the second printing unit through the drying process. Discharge drops.
[0010]
In FIG. 2, a print medium 236 is attached to a belt 237 and stepped upward in the figure. In the lower first print section 602 in the figure, there is a first carriage 244 on which four Y, M, C, and K inkjet heads are mounted. The ink jet head (print head) in this example uses an element having an element that generates thermal energy that causes film boiling in the ink as energy used to eject the ink.
[0011]
A drying unit 245 including a heating plate 234 for heating from the back surface of the belt and a hot air duct 235 for drying from the front side is provided on the downstream side of the first printing unit. The heat transfer surface of the heating plate 234 is pressed against a strongly tensioned endless belt 237, and the belt 237 is strongly heated from the back surface by high-temperature and high-pressure steam passing through a hollow inside. The belt 237 effectively heats the attached print medium 236 directly by heat conduction. Fins 234 'for collecting heat are provided inside the heating plate surface so that heat can be efficiently concentrated on the back surface of the belt. The side not in contact with the belt is covered with a heat insulating material 243 to prevent loss due to heat dissipation.
[0012]
On the front side, the drying hot air is blown from the supply duct 230 on the downstream side, so that the effect is enhanced by applying air with lower humidity to the print medium 236 being dried. The air that has flowed in the direction opposite to the conveyance direction of the print medium 236 and sufficiently contained water is sucked from the suction duct 233 on the upstream side by a much larger amount than the amount of spraying, so that the evaporated water leaks. Condensation is avoided on surrounding machinery. The hot air supply source is on the far side in FIG. 2, and suction is performed from the front side, and the pressure difference between the blowout port 238 facing the print medium 236 and the suction port 239 extends over the entire longitudinal direction. It is designed to be uniform. The air blowing / suction unit is offset downstream with respect to the center of the heating plate 234 on the back surface so that the air hits a sufficiently heated place. As a result, the first printing unit 602 strongly dries a large amount of water in the ink including the thinning liquid received by the print medium 236.
[0013]
Downstream (upward in the drawing) is a second print unit 603, and a second print unit 244 'having the same configuration as the first carriage forms the second print unit. A downstream dryer 46 having the same configuration as that of the hot air duct 235 is provided downstream thereof.
[0014]
Next, a specific example of inkjet textile printing will be described. As described above, FIG. 1 is a diagram showing a configuration of an ink jet printing apparatus suitable for textile printing. After the ink jet printing process using the ink jet printing apparatus as shown in FIG. 1, the print medium is dried (including natural drying). Subsequently, a step of diffusing the dye on the print medium fiber and reacting and fixing the dye on the fiber is performed. By this step, sufficient color development and fastness due to fixing of the dye can be obtained.
[0015]
This diffusion and reaction fixing step may be a conventionally known method, for example, a steaming method. In this case, the print medium may be subjected to alkali treatment in advance before the printing process.
[0016]
Thereafter, unreacted dye and substances used for the pretreatment are removed in the post-treatment step. Finally, the print is completed through a finishing process such as defect correction and ironing.
[0017]
FIG. 3 is a diagram showing the arrangement of the inkjet recording head units shown in FIGS. As described above, the printer forms an image with basic four-color CMYK inks. The recording head unit 601 is equipped with two ink-jet heads of each ink color. A head 603 (hereinafter referred to as a rear head) arranged in the upper part of the drawing and a head 602 (hereinafter referred to as a rear head) arranged in the lower part of the drawing. Front band) is arranged at a distance of 2.5 bands in the sub-scanning direction (the band is a unit of width in the nozzle row direction in which the inkjet head prints in one scan).
[0018]
FIG. 4 is a diagram showing a state in which printing is performed on the front head 602 and the rear head 603 in the printer. One sub-scan is performed for each main scan. The feed amount in the sub-scanning direction is one band, and an image is formed in a state where the front head 602 and the rear head 603 are shifted by a half band, that is, a half band overlap. Here, the half band 703 is formed by the upper half of the front head 602 in the figure and the lower half of the rear head 603, respectively, and the half band 704 is formed by the lower half of the front head 602 and the upper half of the rear head 603, respectively.
[0019]
FIG. 5 shows the processing contents from binarizing the multi-valued image data transferred to the printer, converting it into head drive data, ejecting ink from the nozzles, and printing. explain.
[0020]
(1) Multi-value image data transferred from the host computer is stored in the image data storage device 801. From here, data is read for each band.
[0021]
(2) In the palette conversion circuit 802, the image data is decomposed into multi-value data of each ink color. Hereinafter, the black ink Bk will be described as a representative.
[0022]
(3) In the γ conversion circuit 803-K, γ conversion is performed on multi-value data separated into ink colors.
[0023]
(4) The unevenness correction circuit 804 -K corrects unevenness due to the variation in nozzle characteristics using the unevenness correction table (multi-value → multi-value lookup table).
[0024]
(5) The binarization circuit 805-K converts multi-value data into binary data by the error diffusion method (ED).
[0025]
(6) An SMS (sequential multi-scan) circuit 806-K determines whether the binary data of each color is printed by the front head 602-K or the rear head 603-K. This SMS circuit-K is allocated alternately with front, rear, front, rear,... In order from the first dot appearing from the left end of the image when attention is paid to a certain raster. Each TMC (Timing Memory Controller) circuit 807- It is output to K1,807-K2. As a result, adjacent dots are not printed by the same head, and printing can be performed at a double speed of the head drive frequency. Furthermore, the dots that appear first in each raster are printed by the rear head 603-K for odd rasters and the front head 602-K for even rasters.
[0026]
(7) The TMC circuits 807-K1 and 807-K2 output one band of data to the heads 602-K and 603-K one by one in the nozzle row direction. The horizontal registration adjustment value adjusts the positional deviation in the head main scanning direction between the heads 807-K1 and 807-K2, but the output timing of data for one column differs depending on the horizontal registration adjustment value.
[0027]
(8) PHC (Printer Head Connector) boards 808-K1 and 808-K2 output binary data in the nozzle row direction in correspondence with the nozzles that actually perform printing. The vertical registration adjustment value adjusts the positional deviation in the nozzle row direction between the heads 807-K1 and 807-K2. In the head in this example, in addition to 1344 nozzles, the upper and lower 8 nozzles are print effective nozzles, so the vertical registration tone value is in the range of -8 to +8. When the vertical registration tone value is ± 0, the central 1344 nozzles are used. When the vertical registration tone value is ± 1 to 8, the actual 1344 nozzles are shifted from the center by 1 to 8 nozzles. With this vertical registration adjustment value, data for 1344 nozzles is output in correspondence with the nozzles that actually perform printing.
[0028]
(9) Finally, binary data of each nozzle is converted into head drive data by a print controller (Head CPU) 809, and printing is performed by ejecting ink.
[0029]
In particular, FIG. 7 specifically shows the processes (5) and (6). The multi-valued data (A in the figure) after being separated into each ink color and subjected to γ conversion and unevenness correction processing (802, 803, 804 in FIG. 5) is converted into an error diffusion matrix A (the error diffusion matrix shown in FIG. 6A). In FIG. 7B, error diffusion processing (FIG. 7B) is performed and binarization is performed (FIG. 7C). Note that * in FIG. 6 represents a target pixel. Then, it is determined by the SMS (806 in FIG. 5) whether to print with the front head or the rear head (FIG. 7D). The data shown in FIG. 7E is sent to the front head, and the data shown in FIG. 7F is sent to the rear head.
[0030]
According to the above-described method, since the image of the predetermined region is formed by the different nozzles of the two heads, it is possible to reduce the density unevenness caused by the characteristic variation of the plurality of nozzles. In addition, since the seam of the image is a half band unit, the banding period is halved, and the banding is less noticeable.
[0031]
[Problems to be solved by the invention]
However, the print image is easily affected by the registration adjustment error of the front head and rear head, the slant mounting of the head, the error of the feed amount in the sub-scanning direction of the recording medium, or the error of ink droplet landing due to carriage vibration. There is a problem that so-called half-band unevenness occurs. It has been found by the present inventors that the above method is caused by the fact that the “complementary relationship” between the print image of the front head and the print image of the rear head is complete.
[0032]
That is, in the above-described method, the half-band images completed by two scans are in a completely complementary relationship (hereinafter, the relationship in which dots printed in each pass are spatially complemented is referred to as “complementary”. Called "relationship"). For this reason, if an error occurs in registration for each band, for example, if the horizontal registration for a half dot shifts, complementation is performed with the horizontal registration shifted.
[0033]
Originally, if recording is performed by the above method using an ideal apparatus, the solid (uniform) image shown in FIG. 8 is evenly distributed without overlapping dots even if the images recorded by the respective scans are overlapped. Should be in line. In FIG. 8, 201 (black dot) indicates the one printed by the front head 602, 202 (white dot) indicates the one printed by the rear head 603, both of which eject ink of the same color, for example, the head 602. -K and 603-K are printed.
[0034]
However, in an actual apparatus, the registration changes slightly in each scan due to an error in physical accuracy. Therefore, when images recorded in each scan are overlapped, the dots are close or far away. They will leave or overlap. For example, when a horizontal registration shift of half a dot occurs in the front head 602, as shown in FIG. 9, coarse / dense between dots or dot overlap occurs. 201 (black dot) represents a print with the front head 602, and 202 (white dot) represents a print with the rear head 603. As a result, the recorded image differs from the original image density, causing density unevenness, which is a serious problem. That is, a band having a high density (a band is a unit of width in the direction of the nozzle array printed by the ink jet head in one scan) or a thin band is formed, and half-band unevenness occurs.
[0035]
Further, when multi-value data has the same value for a plurality of recording colors, if the registrations of the recording heads match each other, the recording color dots having the same value land at the same position. This is because, as shown in FIG. 10, binarization processing and the like are performed in the same manner for each of the Bk,..., Y colors.
[0036]
However, if an error occurs in the registration for each recording color for each band, the degree of dot overlap changes, the color of the secondary color changes, and half-band unevenness occurs.
[0037]
FIG. 11 shows a state where cyan and magenta dots are completely overlapped, and 401 indicates a dot where cyan and magenta overlap (blue dot). At this time, it is assumed that the multi-value data of cyan and magenta are the same, and the registration of the heads of the respective recording colors matches.
[0038]
On the other hand, FIG. 12 shows a state in which dots are shot when the registration of cyan and magenta does not match. In the figure, 501 (black dot) indicates a cyan dot, and 502 (white dot) indicates a magenta dot.
[0039]
Comparing FIG. 11 and FIG. 12, it is understood that the degree of dot overlap is different. As described above, an error occurs in registration for each band, so that a difference in dot overlap occurs, the color changes, and half-band unevenness occurs. Further, even if no registration error occurs, there arises a problem that the color reproduction range of the secondary color becomes narrow when all the dots overlap as shown in FIG.
[0040]
As described above, in conventional multi-pass printing, when an image is formed by a plurality of scans, an image completed by a plurality of scans has a complete complementary relationship, and each color has a correlation. It has been found by the present inventors that the change in the coloration appears as the density unevenness and color unevenness of the image as they are.
[0041]
The present invention has been made to solve the above problems, and even if the registration due to a physical accuracy error slightly changes, the image density and color are not greatly changed, and density unevenness and color unevenness are reduced. An object is to provide an image forming apparatus, an image forming method, and an image processing method capable of forming an image.
[0042]
[Means for Solving the Problems]
To achieve the above object, the present invention provides: Recording is possible with a single scan of the recording head. recoding media Up Multiple colors for a given area Respectively Multiple recording heads compatible with Each is scanned multiple times, By multiple scans Should be formed in the predetermined area the image Completed In the image forming apparatus, multi-value image data corresponding to the predetermined area is scanned for each of the plurality of times for each color. Share rate Distributing means for distributing differently, reducing gradation means for reducing gradation of multi-value image data for each color distributed by the distributing means, and reducing gradation by the reducing gradation means. Forming means for driving the plurality of recording heads to form an image in the plurality of scans based on the image data for each color.
[0043]
According to another aspect of the present invention, there is provided an image forming apparatus for forming an image on a predetermined area of a recording medium by a plurality of scans of a plurality of recording heads corresponding to a plurality of colors.
Distribution means for distributing multi-valued image data of each color corresponding to the predetermined region differently in the plurality of scans;
A gradation reduction means for reducing the gradation of multi-valued image data of each color distributed by the distribution means by different processing for each color;
Forming means for forming an image by driving the plurality of recording heads in the plurality of scans based on the image data of each color reduced in gradation by the gradation reduction means;
It is characterized by having.
[0044]
Furthermore, the present invention provides an image forming apparatus for forming an image on a predetermined area of a recording medium by a plurality of scans of a plurality of recording heads corresponding to a plurality of colors.
Distributing means for distributing multi-valued image data of each color corresponding to the predetermined region in correspondence with the plurality of scans;
A gradation reduction means for reducing gradation of each color and multi-value image data for each scan distributed by the distribution means by different processes;
Forming means for forming an image by driving the plurality of recording heads in the plurality of scans based on the image data of each color reduced in gradation by the gradation reduction means;
It is characterized by having.
[0045]
The present invention also provides: Recording is possible with a single scan of the recording head. recoding media Up Multiple colors for a given area Respectively Multiple recording heads compatible with Each is scanned multiple times, By multiple scans Should be formed in the predetermined area the image Completed In the image forming method, multi-value image data corresponding to the predetermined area is distributed for each color corresponding to the plurality of scans, each color distributed in the distribution step, and each color for each scan. Each value image data is different Error diffusion A plurality of recording heads are driven in the plurality of scans based on a gradation reduction step for reducing gradation by processing and image data for each color reduced in gradation by the gradation reduction step. And a forming step of forming an image.
[0046]
The present invention also provides: Recording is possible with a single scan of the recording head. recoding media Up Multiple colors for a given area Respectively Multiple recording heads compatible with Each is scanned multiple times, By multiple scans Should be formed in the predetermined area the image Completed In the image processing method for processing image data, a multi-valued image data corresponding to the predetermined area is distributed corresponding to the plurality of scans for each color, and distributed by the distributing step Different multi-value image data for each color and each scan Error diffusion And a gradation reduction step for reducing gradation by processing.
[0047]
According to the above configuration, even if the registration due to a physical accuracy error slightly changes, the dependency on the change in registration decreases, so the image density and color do not change greatly, and density unevenness and color unevenness Reduced images can be formed.
[0048]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Examples 1, 2, and 5 are examples in the case of having a plurality of heads of the same color, and Example 3 is an example in the case of performing quaternization processing instead of binarization as gradation reduction. Example 4 is an example in the case of having one head of the same color. The ink jet recording type textile printing machine that performs recording on the fabric shown in FIGS. 1 to 4 can also be applied to the present embodiment as described above, and the details thereof are omitted here.
[0049]
Example 1
In this embodiment, the multi-value data of each ink color is binarized, and the binary data is not distributed to the front head and the rear head, but the multi-value data before the binarization processing is used for the front head. Are distributed to the rear head, the converted multi-value data are converted by different coefficients, and different binarization processing is performed on the converted data. As a result, the “complementary relationship” of the printed image in each scan and each ink color can be reduced, or the “correlation” can be eliminated to prevent half-band unevenness.
[0050]
In this embodiment, the contents of processing from binarization of multi-valued image data, conversion to head drive data, ejection of ink from the nozzles, and printing are shown in FIG. 13, and the flow of processing will be described using the drawings. To do.
[0051]
(1) Multivalued image data transferred from the host computer is stored in the image data storage device 101. From here, data is read for each band.
[0052]
(2) In the palette conversion circuit 102, the image data is decomposed into multi-value data of each ink color. Hereinafter, the black ink Bk will be described as a representative.
[0053]
(3) In the γ conversion circuit 103-K, γ conversion is performed on multi-valued data separated into ink colors.
[0054]
(4) The unevenness correction circuit 104-K corrects unevenness due to the variation in nozzle characteristics using the unevenness correction table (multi-value → multi-value lookup table). Up to this point, the process is the same as the conventional process shown in FIG.
[0055]
(5) The distribution circuits 105-K1 and 105-K2 distribute data for the front head and the rear head.
[0056]
(6) The data conversion circuits 106-K1 and 106-K2 perform data conversion on the distributed data by a predetermined coefficient.
[0057]
(7) In the gradation reduction circuits 107-K1 and 107-K2, gradation reduction processing is performed by the error diffusion method for each head.
[0058]
(8) TMC (Timing Memory Controller) circuits 108-K1 and 108-K2 output one band of data in the nozzle row direction for each head for each head. The horizontal registration adjustment value adjusts the positional deviation of the head in the head main scanning direction, but the data output timing for one column differs depending on the horizontal registration adjustment value.
[0059]
(9) PHC (Printer Head Connector) boards 109-K1 and 109-K2 output binary data in the nozzle row direction in correspondence with the nozzles that actually perform printing. The vertical registration adjustment value adjusts the positional deviation of the head in the nozzle row direction. In the head in this example, in addition to 1344 nozzles, the upper and lower 8 nozzles are print effective nozzles, so the vertical registration tone value is in the range of -8 to +8. When the vertical registration tone value is ± 0, the central 1344 nozzles are used. When the vertical registration tone value is ± 1 to 8, the actual 1344 nozzles are shifted from the center by 1 to 8 nozzles. With this vertical registration adjustment value, data for 1344 nozzles is output in correspondence with the nozzles that actually perform printing.
[0060]
(10) Finally, the binary data of each nozzle is converted into head drive data by a print controller (Head CPU) 110, and printing is performed by ejecting ink.
[0061]
In this embodiment, the example in which the above-described processing is realized by the hardware configuration of the image processing apparatus has been described. However, it is also possible to appropriately realize the processing using software or the like.
[0062]
FIG. 14 shows a specific example of the processes 105, 106 and 107 in FIG. In FIG. 14, the image data for sending multi-value data (A in the figure) for each color to the front head 602 and the image data for sending to the rear head 603 (C in the figure) are divided into two. Distribute. Each distributed data is multiplied by the same coefficient (0.5) (D and E in the figure). Each data converted (F, G in the figure) is binarized by an error diffusion method (H, I in the same error distribution matrix) and binarized data (J, K in the figure) Print with the head. The error distribution matrix used in FIGS. 6A and 6B is the same as that shown in FIGS.
[0063]
The multi-valued data distributed and converted for the front head and rear head are the same, but the error distribution matrix for error diffusion is different from each other, so that the images printed by each head have a reduced "complementary relationship" It is possible to form an image with reduced half-band unevenness.
[0064]
In the above description, only black ink is described. In this embodiment, as shown in FIG. 15, not only the front and rear heads but also each ink color is binarized by an error diffusion method into different error distribution matrices. Binary data is printed by each head.
[0065]
That is, FIG. 15 also shows processing for a yellow (Y) head in addition to black (Bk). In FIGS. S and T, the respective data converted (Q and R in the figure) are binarized by the error diffusion method (C and D in FIG. 6) of different error distribution matrices (binary data) U and V) are printed by each head. Similarly, error diffusion methods using different error distribution matrices are used for cyan (C) and magenta (M) (not shown).
[0066]
As described above, even if the values of the multi-value data of the different ink colors are the same, the error distribution matrix is different from each other, so that there is no “correlation” between the respective colors. Therefore, as described below, even if the registration due to a physical error changes slightly, an image without color unevenness can be formed and the color reproduction range can be widened.
[0067]
FIG. 16 is a diagram in a case where overprinting is performed with the front head and the rear head using the image processing method according to the present invention, assuming that the physical accuracy is ideally suited. Reference numeral 601 (black dot) represents a print by the front head, and reference numeral 602 (white dot) represents a print by the rear head.
[0068]
FIG. 17 shows a case where the registration of the front head and the rear head is slightly shifted in FIG. Here, a case is shown where the registration of the front head is deviated by half a dot (to the right in the drawing). Even if FIG. 16 and FIG. 17 are compared, there is no significant change in the image density. That is, it can be seen that even if the registration in each scan changes slightly, the density hardly changes and half-band unevenness does not occur.
[0069]
16 and 17, 601 (black dot) is a cyan dot and 602 (white circle dot) is a magenta dot. In comparison, there is no significant change in dot overlap. That is, even if the registration of the head of each recording color changes slightly, the overlapping state of each color hardly changes, so that the color hardly changes and an image without half-band unevenness can be generated.
[0070]
Furthermore, since the dots for each recording color do not completely overlap and are appropriately dispersed, the color reproduction range becomes wider than before.
[0071]
Further, by performing data conversion by data conversion processing, printing with a duty of 100% or more can be performed.
[0072]
Here, although the present embodiment has been described based on the concept of “complementary relationship” in which images formed in a plurality of passes are macroscopically captured, they can also be microscopically captured. In this case, paying attention to dots recorded in a plurality of passes, and forming an image without the “correlation” that dots recorded in other passes exist next to dots recorded in a certain pass, It can also be captured.
[0073]
On the other hand, “correlation” between colors means that all dots forming a secondary color overlap.
[0074]
(Example 2)
FIG. 18 shows a specific example of the processing portions 105, 106, and 107 in FIG. In FIG. 18, multi-valued data (FIG. A) is divided into two parts: image data for sending to the front head (FIG. B) and image data for sending to the rear head (FIG. C). Each multivalued data is multiplied by the same coefficient (0.5) (D and E in the figure). The two converted data (F and G in the figure) are binarized by the error diffusion method (H and I in the figure) having different threshold values, and the binarized data (J and K in the figure). ) Is printed on each head.
[0075]
Although the multi-value data distributed and converted for the front head and rear head are the same, the error diffusion threshold values are different, so that the images printed by each head have a reduced "complementary relationship" It is possible to form an image with reduced band unevenness.
[0076]
In the above description, only black ink is described, but in this embodiment, as shown in FIG. 19, not only the front and rear heads but also each ink color is binarized by different threshold values and binarized data. Is printed with each head.
[0077]
That is, FIG. 19 also shows processing for a yellow (Y) head in addition to black (Bk). In FIGS. S and T, each data-converted data (Q and R in the figure) is binarized by an error diffusion method with different threshold values, and binarized data (U and V in the figure) is converted into each head. Print with. Similarly, error diffusion methods with different threshold values are used for cyan (C) and magenta (M) (not shown).
[0078]
In this way, even if the values of the multi-value data for different ink colors are the same, the threshold values are different from each other, so that there is no “correlation” between the colors. Therefore, even if the registration due to a physical error changes slightly, it is possible to form an image without color unevenness and widen the color reproduction range.
[0079]
The same effect can be obtained by combining the elements of the first embodiment and the second embodiment (error distribution error distribution matrix, binarization threshold value).
[0080]
(Example 3)
Next, in FIG. 13, a specific example of the process is shown in FIG. 20 for an example in which the quaternary processing is performed using dot diameter modulation as the gradation reduction. Except for performing quaternary processing as gradation reduction processing, the same as in the first embodiment, multi-value data (A in the figure) is distributed by the number of times the same area is scanned (B and C in the same figure), and distributed. Each multi-valued data is multiplied by the same coefficient (0.5) (D and E in the figure). The converted data (F and G in the figure) are converted into four values by the error diffusion method (H and I in the same figure) of different error distribution matrices, and the four-valued data (J and K in the figure) are converted into the respective heads. Print with.
[0081]
Even if the four-value processing is performed, when printing is performed by the conventional processing method, the images printed by the respective heads have a complete “complementary relationship”. An “complementary relationship” can be reduced and an image with reduced half-band unevenness can be formed.
[0082]
In the above description, only black ink is described. In this embodiment, as shown in FIG. 21, not only the front and rear heads but also each ink color is converted into four values by the error diffusion method of different error distribution matrices. Quaternary data is printed by each head.
[0083]
That is, FIG. 21 also shows processing for a yellow (Y) head in addition to black (Bk). In FIGS. S and T, the converted data (Q and R in the figure) are converted into four values by the error diffusion method (C and D in FIG. 6) of different error distribution matrices. U and V) are printed by each head. Similarly, error diffusion methods using different error distribution matrices are used for cyan (C) and magenta (M) (not shown).
[0084]
As described above, even if the values of the multi-value data of the different ink colors are the same, the error distribution matrix is different from each other, so that there is no “correlation” between the respective colors. Therefore, even if the registration due to a physical error changes slightly, it is possible to form an image without color unevenness and widen the color reproduction range.
[0085]
Similar to the second embodiment, the same effect can be obtained by using the error diffusion method having different threshold values or using the error distribution matrix and the threshold values different from each other.
[0086]
Example 4
Next, an embodiment of a printer having one head for each color will be described with reference to the drawings. In FIG. 13, when the F (front) head is replaced with the first scan and the R (rear) head is replaced with the second scan, the flow of the image processing of this embodiment is obtained.
[0087]
FIG. 22 shows the superimposed state of the print images of the first and second scans. The media feed amount is a half band, and an image is formed by a half band overlap of the first scan and the second scan.
[0088]
In this embodiment, similarly to Embodiments 1 and 2, data is distributed to the number of times the same area is scanned (here, 2), each data is converted by a predetermined coefficient, and the converted data is converted to a predetermined number. A process of binarization by the error diffusion method is performed.
[0089]
FIG. 23 shows a specific example of processing corresponding to FIG. In FIG. 23, similarly to the first to third embodiments, multi-valued data (A in the same figure) is distributed to (two) data (B and C in the same figure) for the number of times the same area is scanned. Are converted by the same coefficient (first scan: 0.5, second scan: 0.5) (D and E in the figure). The converted data (F, G in the figure) is binarized by an error diffusion method (H, I in the same error distribution matrix), and the binarized data (J, K in the figure) is subjected to the first scan. And printing in the second scan.
[0090]
The above description is for black (Bk), but the same is true for yellow (Y). In FIGS. S and T, each data converted (Q and R in the figure) is converted into a different error distribution matrix. The data is binarized by the error diffusion method (C and D in FIG. 6), and binarized data (U and V in the figure) is printed by the first scan and the second scan. Similarly, error diffusion methods using different error distribution matrices are used for cyan (C) and magenta (M) (not shown).
[0091]
Even if an error occurs in the feed amount of the media in the sub-scanning direction or the registration changes slightly, the error distribution matrix is different, so the “complementary relationship” is reduced for images printed in each scan. An image with reduced band unevenness can be formed.
[0092]
Even if the multi-value data values of different ink colors are the same, the error distribution matrices are different from each other, so that there is no “correlation” between the colors. Therefore, even if the registration due to a physical error changes slightly, it is possible to form an image without color unevenness and widen the color reproduction range.
[0093]
Similar to the second embodiment, the same effect can be obtained by using different threshold values in the error diffusion method, or using an error diffusion method in which both the error distribution matrix and the threshold value are different.
[0094]
(Example 5)
FIG. 24 shows a specific example of the processing portions 105, 106, and 107 in FIG. In FIG. 24, multi-valued data (FIG. A) is distributed into two parts, image data (FIG. B) for sending to the front head and image data (C) for sending to the rear head. Data conversion is performed using different coefficients for the front head and the rear head (D and E in the figure). Each data converted (F, G in the figure) is binarized by an error diffusion method (H, I in the same error distribution matrix), and binarized data (J, K in the figure) are converted into the respective data. Print with the head.
[0095]
Here, the difference from the first to fourth embodiments is that the sum of coefficients in the data conversion process is not 1 but 1 or more, and the data conversion coefficients for the front head and the rear head are different from each other. In the fifth embodiment, the sum of the coefficients is 1.2 (front: 0.65, rear: 0.55). This indicates that printing with a duty of 100% or more is possible.
[0096]
The above description is for black (Bk), but the same is true for yellow (Y). In FIGS. S and T, each data-converted data (Q and R in the figure) is different from Bk. Binarization is performed by the error diffusion method (B in FIG. 6) of the distribution matrix, and binarized data (U and V in the same figure) is printed in the first and second scans. Similarly, cyan (C) and magenta (M) (not shown) use different error diffusion matrix error diffusion methods.
[0097]
Since different data conversion coefficients are used for the front head multi-value data and the rear head multi-value data, the images printed by the respective heads are reduced in “complementary relationship” and form an image with reduced half-band unevenness. be able to. In the first to fourth embodiments as well, by using different data conversion coefficients for the front and rear, the first scan and the second scan, it is possible to reduce the “complementary relationship” in the mutual print images.
[0098]
Even if the multi-value data values of different ink colors are the same, the error distribution matrices are different from each other, so that there is no “correlation” between the colors. Therefore, even if the registration due to a physical error changes slightly, it is possible to form an image without color unevenness and widen the color reproduction range.
[0099]
In the fifth embodiment, the error distribution matrix is different, but the same effect can be obtained even if the error distribution matrix is different.
[0100]
Furthermore, since the sum of the data conversion coefficients during the data conversion process is 1 or more, printing with a duty of 100% or more is possible. Also in the first to fourth embodiments, printing with a duty of 100% or more is possible by using the data conversion coefficient having a sum of 1 or more.
[0101]
The present invention provides an excellent effect particularly in a recording apparatus using an ink jet recording head that performs recording by forming flying droplets using thermal energy among ink jet recording methods.
[0102]
As its typical configuration and principle, for example, those performed using the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 are preferable. This method can be applied to both the so-called on-demand type and continuous type. In particular, in the case of the on-demand type, it is arranged corresponding to the sheet or liquid path holding the liquid (ink). By applying at least one drive signal corresponding to the recording information and giving a rapid temperature rise exceeding nucleate boiling to the electrothermal transducer, the thermal energy is generated in the electrothermal transducer, and the recording head This is effective because film boiling occurs on the heat acting surface, and as a result, bubbles in the liquid (ink) corresponding to the drive signal can be formed. By the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection opening to form at least one droplet. It is more preferable that the drive signal has a pulse shape, since the bubble growth and contraction is performed immediately and appropriately, and thus it is possible to achieve discharge of a liquid (ink) having particularly excellent responsiveness. As this pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further excellent recording can be performed by employing the conditions described in US Pat. No. 4,313,124 of the invention relating to the temperature rise rate of the heat acting surface.
[0103]
As the configuration of the recording head, in addition to the combination configuration (straight liquid channel or right-angle liquid channel) of the discharge port, the liquid channel, and the electrothermal transducer as disclosed in each of the above-mentioned specifications, the thermal action A configuration using US Pat. No. 4,558,333 and US Pat. No. 4,459,600, which disclose a configuration in which the portion is arranged in a bent region, is also included in the present invention. In addition, for a plurality of electrothermal transducers, Japanese Patent Application Laid-Open No. Sho 59-123670 that discloses a configuration in which a common slit is used as a discharge portion of the electrothermal transducer or an aperture that absorbs pressure waves of thermal energy is provided. The effect of the present invention is also effective as a configuration based on Japanese Patent Application Laid-Open No. 59-138461 which discloses a configuration corresponding to the discharge unit. That is, whatever the form of the recording head is, according to the present invention, recording can be performed reliably and efficiently.
[0104]
In addition, the serial type as shown in the above example can be connected to the main body of the recording head or attached to the main body of the device so that it can be electrically connected to the main body of the device and ink can be supplied from the main body of the device. The present invention is also effective when a replaceable chip type recording head or a cartridge type recording head in which an ink tank is integrally provided in the recording head itself is used.
[0105]
In addition, it is preferable to add a recording head ejection recovery means, a preliminary auxiliary means, and the like as the configuration of the recording apparatus of the present invention, since the effects of the present invention can be further stabilized. Specifically, heating is performed using a capping unit, a cleaning unit, a pressurizing or suction unit, an electrothermal transducer, a heating element different from this, or a combination thereof. Examples thereof include a preliminary heating unit for performing the discharge and a preliminary discharge unit for performing discharge different from the recording.
[0106]
Also, regarding the type or number of mounted recording heads, two or more recording heads may be provided corresponding to a plurality of inks having different recording colors and densities. That is, for example, as a recording mode of the recording apparatus, not only a recording mode of only a mainstream color such as black, but also a recording head may be configured integrally or by a combination of a plurality of different colors, Alternatively, the present invention is extremely effective for an apparatus having at least one of full-color recording modes by color mixing.
[0107]
In addition, in the embodiments of the present invention described above, the ink is described as a liquid. However, ink that is solidified at room temperature or lower and that softens or liquefies at room temperature may be used. In the ink jet system, the temperature of the ink itself is adjusted within a range of 30 ° C. or higher and 70 ° C. or lower to control the temperature so that the viscosity of the ink is within the stable discharge range. A liquid material may be used. In addition, it is solidified and heated in an untreated state in order to actively prevent the temperature rise caused by thermal energy from being used as the energy for changing the state of the ink from the solid state to the liquid state, or to prevent the ink from evaporating. You may use the ink which liquefies by. In any case, by applying thermal energy according to the application of thermal energy according to the recording signal, the ink is liquefied and liquid ink is ejected, or when it reaches the recording medium, it already starts to solidify. The present invention can also be applied to the case of using ink having the property of being liquefied for the first time. The ink in such a case is in a state of being held as a liquid or a solid in a porous sheet recess or through-hole as described in JP-A-54-56847 or JP-A-60-71260. Alternatively, the electrothermal converter may be opposed to the electrothermal converter. In the present invention, the most effective one for each of the above-described inks is to execute the above-described film boiling method.
[0108]
In addition, the ink jet recording apparatus according to the present invention may be used as an image output terminal of an information processing device such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmission / reception function. The thing etc. may be sufficient.
[0109]
【The invention's effect】
According to the present invention, even if the registration due to a physical accuracy error changes slightly, the dependency on the change in registration decreases, so the image density and color do not change greatly, and density unevenness and color unevenness Reduced images can be formed.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an outline of an image printing unit of a textile printing machine of an ink jet recording system that performs recording on a fabric applicable to the present invention.
FIG. 2 is a perspective view showing details in the vicinity of an inkjet print section A-2 shown in FIG.
FIG. 3 is a diagram showing an arrangement state of heads applicable to the present invention.
FIG. 4 is a diagram illustrating a superimposed state of print images of a front head and a rear head.
FIG. 5 is a block diagram showing a flow of processing until data sent to a conventional printer is printed.
FIG. 6 is a diagram illustrating an example of an error distribution matrix;
FIG. 7 is a diagram illustrating a flow of a conventional image processing method.
FIG. 8 is a diagram showing the arrangement of dots when overprinting is performed with a conventional ideal front head and rear head.
FIG. 9 is a diagram showing the arrangement of dots when overprinting is performed with a conventional actual front head and rear head.
FIG. 10 is a diagram illustrating conventional image processing.
FIG. 11 is a diagram illustrating dot arrangement when cyan and magenta are overprinted in a conventional ideal state.
FIG. 12 is a diagram showing a dot arrangement when cyan and magenta are overprinted in a conventional actual state.
FIG. 13 is a block diagram showing a flow of processing until data sent to the printer in the present invention is printed.
FIG. 14 is a diagram showing a specific example of image processing in Embodiment 1 of the present invention.
FIG. 15 is a diagram showing a specific example of image processing in Embodiment 1 of the present invention.
FIG. 16 is a diagram showing an arrangement of dots when performing overprinting with an ideal front head and rear head according to the present invention.
FIG. 17 is a diagram showing an arrangement of dots when overprinting is performed with an actual front head and rear head according to the present invention.
FIG. 18 is a diagram illustrating a specific example of image processing according to the second embodiment of the present invention.
FIG. 19 is a diagram illustrating a specific example of image processing according to the second embodiment of the present invention.
FIG. 20 is a diagram illustrating a specific example of image processing in Embodiment 3 of the present invention.
FIG. 21 is a diagram showing a specific example of image processing in Embodiment 3 of the present invention.
FIG. 22 is a diagram illustrating a superimposed state of print images of each scan of a printer having one head per color applicable to the present invention.
FIG. 23 is a diagram showing a specific example of image processing in Embodiment 4 of the present invention.
FIG. 24 is a diagram showing a specific example of image processing in Embodiment 5 of the present invention.
[Explanation of symbols]
101 Image data storage device
102 Pallet conversion circuit
103 γ conversion circuit
104 Unevenness correction circuit
105 Distribution circuit
106 Data conversion circuit
107 gradation reduction circuit
108 TMC (Timing Memory Controller) circuit
109 PHC (Printer-Head Connector) board
110 Print control device
601 Recording head unit
602 Front head
603 Rear head

Claims (12)

A plurality of recording heads corresponding to a plurality of colors are scanned a plurality of times with respect to a predetermined area on the recording medium that can be recorded by one scanning of the recording head, and the plurality of scannings are formed in the predetermined area. in the image forming apparatus Ru to complete an image to,
Distribution means for distributing multi-valued image data corresponding to the predetermined area with different distribution ratios for the plurality of scans for each color;
A gradation reduction means for reducing gradation of the multi-value image data for each color distributed by the distribution means;
A forming unit that drives the plurality of recording heads to form an image in the plurality of scans based on the image data for each color that has been subjected to gradation reduction by the gradation reduction unit;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the gradation reduction unit is a binarization unit.   2. The image forming apparatus according to claim 1, wherein the gradation reduction means reduces gradation of multivalued image data by an error diffusion method.   4. The image forming apparatus according to claim 3, wherein the gradation reduction unit changes the error diffusion for each color and multi-value image data for each scan distributed by the distribution unit.   4. The image forming apparatus according to claim 3, wherein the gradation reduction means changes a gradation reduction threshold value for each color and multi-value image data for each scan distributed by the distribution means.   The image forming apparatus according to claim 1, wherein the recording head ejects ink.   2. The plurality of recording heads according to claim 1, wherein each of the plurality of recording heads includes first and second heads arranged to be shifted in a sub-scanning direction of the recording medium for each color, and the predetermined area is defined by the first and second heads. An image forming apparatus that forms the image.   The image forming apparatus according to claim 1, wherein the recording head includes a plurality of recording elements, and the predetermined area is formed by the plurality of different recording elements. A plurality of recording heads corresponding to a plurality of colors are scanned a plurality of times with respect to a predetermined area on the recording medium that can be recorded by one scanning of the recording head, and the plurality of scannings are formed in the predetermined area. in the image forming apparatus Ru to complete an image to,
And distribution means for distributing the image data of each color multi-valued corresponding to the prescribed region with different distribution rate against the plurality of scans,
A gradation reduction means for reducing the gradation of multi-valued image data of each color distributed by the distribution means by different error diffusion processing for each color;
Forming means for forming an image by driving the plurality of recording heads in the plurality of scans based on the image data of each color subjected to gradation reduction by the gradation reduction means. Image forming apparatus. A plurality of recording heads corresponding to a plurality of colors are scanned a plurality of times with respect to a predetermined area on the recording medium that can be recorded by one scanning of the recording head, and the plurality of scannings are formed in the predetermined area. in the image forming apparatus Ru to complete an image to,
Distributing means for distributing multi-valued image data of each color corresponding to the predetermined region in correspondence with the plurality of scans;
A gradation reduction means for reducing the gradation of each color and multi-value image data for each scan distributed by the distribution means by different error diffusion processes;
Forming means for forming an image by driving the plurality of recording heads in the plurality of scans based on the image data of each color subjected to gradation reduction by the gradation reduction means. Image forming apparatus. A plurality of recording heads corresponding to a plurality of colors are scanned a plurality of times with respect to a predetermined area on the recording medium that can be recorded by one scanning of the recording head, and the plurality of scannings are formed in the predetermined area. in the image forming method of Ru to complete an image to,
A distribution step of distributing multi-valued image data corresponding to the predetermined area corresponding to the plurality of scans for each color;
A gradation reduction step for reducing gradation by different error diffusion processing for each color and multivalued image data for each scan distributed in this distribution step;
A forming step of forming an image by driving the plurality of recording heads in the plurality of scans based on the image data for each color that has been reduced in gradation by the gradation reduction step;
An image forming method comprising: A plurality of recording heads corresponding to a plurality of colors are scanned a plurality of times with respect to a predetermined area on the recording medium that can be recorded by one scanning of the recording head, and the plurality of scannings are formed in the predetermined area. an image processing method for processing image data of order to complete an image to,
A distribution step of distributing multi-valued image data corresponding to the predetermined area corresponding to the plurality of scans for each color;
A gradation reduction step for reducing gradation by different error diffusion processing for each color and multivalued image data for each scan distributed in this distribution step;
An image processing method comprising:

Images