JP2011042048A - Image processor, recording apparatus, and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image quality produced when a relationship between a pattern size for generating binary data in the density pattern method or the like and a feed amount is not a non-integer multiple when a feed amount in multipass recording is changed Prevent deterioration.
A multi-pass recording feed amount is determined, and a pattern size for generating binary data is determined according to the determined feed amount. Specifically, the pattern size is an integral multiple of the feed amount and equal to or less than the number of nozzles of the head. As a result, the image quality deterioration can be prevented while keeping the pattern size large.
[Selection] FIG.

Description

  The present invention relates to an image processing apparatus, a recording apparatus, and an image processing method. More specifically, the same area of a recording medium is scanned with a plurality of recording heads with an amount of recording medium conveyed corresponding to the area. This is related to the generation of recording data when recording is completed.

  With the spread of information processing equipment such as personal computers, recording devices as image forming terminals are also widely used. In particular, an ink jet recording apparatus that records on a recording medium such as paper by ejecting ink from an ejection port is a non-impact, low-noise recording method, capable of high-density and high-speed recording operations, It has the advantage that it can easily cope with color recording. In this respect, inkjet recording apparatuses are becoming mainstream as personal use recording apparatuses.

  In such a serial type apparatus in the ink jet recording apparatus, a multi-pass recording method is widely adopted. Note that “pass” and “scanning” used below have the same meaning. In this multi-pass printing, image data in a certain area is divided into data for each color and pass, and a mask is widely used for the division.

  FIG. 1 is a diagram for explaining multi-pass printing using a mask, and schematically shows a print head, a printed dot pattern, and the like when an image is completed by four scans. In the figure, P0001 indicates a recording head. Here, for simplification of illustration and description, it is expressed as having 16 discharge ports (hereinafter also referred to as nozzles). The nozzle row is divided into first to fourth four nozzle groups each including four nozzles as shown in the figure. P0002 indicates a mask pattern, and mask pixels (recording allowable pixels) that allow recording corresponding to each nozzle are indicated by black. The mask patterns corresponding to the four nozzle groups are complementary to each other, and when these four patterns are overlapped, all 4 × 4 pixels are print permitting pixels. That is, recording of a 4 × 4 area is completed using four patterns.

  P0003 to P0006 indicate the arrangement pattern of the dots to be formed, and show how the image is completed by repeating the recording scan. As shown in these patterns, in multi-pass printing, dots are formed based on binary print data (dot data) generated by a mask pattern corresponding to each nozzle group in each print scan. Each time the recording scan is completed, the recording medium is conveyed by the width of the nozzle group in the direction of the arrow in the figure. As described above, in the area corresponding to the width of each nozzle group of the recording medium, an image of each area is completed by four recording scans.

  According to the multi-pass printing as described above, variations in ink ejection direction and quantity between a plurality of nozzles that may occur in the manufacturing process and density unevenness due to an error in paper feeding performed between printing scans are made inconspicuous. be able to.

  FIG. 1 shows an example of four-pass printing, but two-pass printing that completes an image by two printing scans, three-pass printing that completes an image by three printing scans, and five or more printing scans. In the case of multi-pass printing with 5 or more passes to complete an image, the same operation is performed. That is, as described with reference to FIG. 1, the division of the ejection port group of the recording head and the conveyance amount are determined according to the number of passes.

  On the other hand, binary print data (dot data) used for multi-pass printing is generated using a pseudo gradation method such as a density pattern method or a dither method. In the case of the density pattern method, binary data is obtained by selecting a density pattern according to a density pattern selection matrix according to a density level to be input according to each density level, and having a plurality of density patterns with predetermined dot arrangements. Is generated. In the case of the dither method, binary data is generated using a dither pattern in which thresholds are arranged in a predetermined pattern.

  These density selection matrices and dither patterns are not prepared for the developed binary data, but the same size matrix or pattern as the developed data. Used repeatedly depending on the overall size.

  Conventionally, the matrix or pattern that is repeatedly used is one pattern that is fixed in size. Patent Document 1 describes that a density selection matrix (index pattern) is a single pattern that is fixed in multi-pass printing. Thus, conventionally, in a system that performs the above-described multi-pass printing, for example, even when the number of passes of multi-pass printing is changed by switching the printing mode, the matrix or pattern with the fixed size is repeated. Used.

  On the other hand, high-quality and high-speed recording is one of the requirements for recent recording apparatuses. For this purpose, there is a discharge thinning. This means thinning out the image resolution and recording at a resolution lower than the image resolution in one scan. For example, when the image resolution in the main scanning direction is 1200 dpi, a driving frequency for discharging once at an interval of 1200 dpi is required. However, if the ejection thinning is performed and each nozzle is driven at a driving frequency at which ejection is performed once at 600 dpi intervals and a 1200 dpi image is recorded by two scans, it is equivalent to driving at 1200 dpi intervals. Can be recorded without reducing the recording speed.

(Example of using AB column)
As an example of thinning out discharge, Japanese Patent Application Laid-Open No. 2004-151561 describes a method of performing recording by providing a plurality of nozzle rows for one color ink. FIG. 12A shows a recording head in the case of recording with one nozzle row for one color ink. On the other hand, FIG. 12B shows a recording head used in the case of recording with two nozzle rows for one color ink. In these drawings, for simplification of illustration, one nozzle row is illustrated as comprising 16 nozzles. When an image to be recorded with one nozzle row in FIG. 12 (a) is recorded with two nozzle rows in FIG. 12 (b), the drive frequency of each nozzle row is the same as when recording with one nozzle row, The scanning speed of the nozzle row can be doubled, and the recording speed can be doubled. In addition, when using the two nozzle rows in FIG. 12B as compared with the case of one row in FIG. 12A, a certain amount of area, for example, one half of an area for printing is recorded. Since the number of times of use is increased, the life of the recording head is extended.

  Such a process of distributing dot data to a plurality of nozzles in two rows or three or more rows is performed, for example, by the configuration shown in FIG. FIG. 13 shows a configuration from when image (dot) data is divided for so-called multi-pass printing and printing is performed by driving a print head based on the divided dot data. In FIG. 13, the image (dot) data input in step 201 is subjected to mask processing in step 202 to generate dot data for each of a plurality of scans. In step 203, the divided dot data for each scan is assigned to the nozzles of the respective nozzle rows. The assignment of dot data to the nozzle rows is performed according to a predetermined pattern. In this specification, this pattern is referred to as a “block pattern” or a “drive pattern”.

  FIG. 14A is a schematic diagram showing a block pattern (driving pattern), in particular, for allocating ejection data to two rows of nozzles. In the example shown in the figure, two nozzle arrays A and B that eject ink of the same color are arranged with 16 nozzles at an interval corresponding to 1200 dpi in the vertical direction of the figure. The image to be recorded is a so-called solid image (an image in which ink dots are recorded in all areas (unit areas for recording ink dots)) having a resolution of 1200 dpi. The drive frequency of each nozzle in the nozzle rows A and B is one discharge at an area interval corresponding to 600 dpi. In the case of multi-pass printing, the images assigned to the two nozzle rows are divided corresponding to a plurality of scans. In the above-described solid image, ink dots are recorded in an area of a division ratio corresponding to the number of scans in each scan. However, in the description with reference to FIG. A case where printing is performed by scanning will be described as an example.

  In FIG. 14A, dot data is assigned according to block pattern A for nozzle row A, and dot data is assigned according to block pattern B for nozzle row B. Specifically, when the column (vertical area row in the figure) 0 is recorded, in the nozzle row A, the nozzle numbers {1, 2}, {5, 6, 7}, {9, 10}, {14 }, And in nozzle row B, nozzle numbers {3, 4}, {8}, {11, 12, 13}, {15, 16} are used. When the column 1 is recorded, both the nozzle rows A and B are recorded using exclusive (complementary) nozzles used in the column 0. Of course, when three or more n nozzle rows are used, the pattern is complemented by n columns. Further, the example shown in FIG. 14A is an example in which a plurality of nozzle arrays of the same color ink are configured in one head. However, it is obvious that the above description applies also when each nozzle row is configured as one head and a plurality of recording heads are used for the same ink color.

  As described above, even if each nozzle is driven at a driving frequency of ejecting once at 600 dpi intervals, driving equivalent to the driving frequency of ejecting once at 1200 dpi intervals can be performed, so that the recording speed of a high-resolution image is reduced. It is possible to record without any error.

(Example of column thinning)
As a high-speed recording method, there is a printing method called column thinning in addition to the method using a plurality of nozzle rows as described above. Normally, when a 1200 dpi solid image is completed by two scans, it must be driven at 1200 dpi intervals. On the other hand, when recording by thinning out two columns, recording is performed as shown in FIG. Column number 0 is recorded in the first scan, and column number 1 is recorded in the second scan. By thinning out two columns, it is possible to record an image having a resolution of 1200 dpi without reducing the recording speed even when driven at a driving frequency of discharging once at an interval of 600 dpi. Data processing when column thinning is used is performed according to the flow shown in FIG. The image (dot) data input in step 501 is masked in step 502 to generate dot data for each of a plurality of scans. In step 503, column thinning processing is performed, and the divided dot data for each scan is assigned to the nozzles of the respective nozzle rows.

JP 2001-54956 A JP 2009-039944 A JP 2007-306549 A JP 2006-050596 A

  When a single pattern having a fixed size as in the prior art is used for a multi-pass printing system in which the number of passes is changed, there are the following problems. When a fixed pattern is used, the purpose of image recording such as the recording image quality intended by the pattern is not realized well due to the relationship with the conveyance amount (hereinafter also referred to as feed amount) of the recording medium performed during a plurality of scans. There is a case.

  That is, the binary data generated based on the density pattern selection matrix and the index pattern or dither pattern is generated with a repetition period corresponding to the size of these patterns. In this case, when the feed amount is not an integral multiple of the repetition cycle of the binary data, the pass mask pattern and the repetition cycle in the binary data (this is determined by the density selection matrix and the index pattern or dither pattern). Correspondence varies depending on the location.

  As described above, when the relationship between the “mask pattern period” and the “repetition period existing in the binary pattern” is different for each place, the dot pattern that is sequentially driven in each pass is greatly different for each place. Unevenness occurs in the occurrence of color unevenness and image quality degradation occurs.

  As means for solving this problem, there is means as disclosed in Patent Document 2. In the present invention, the recording head is scanned a plurality of times with respect to the unit area of the recording medium, and the recording medium is conveyed for each of the plurality of scannings, thereby sequentially completing the recording of the plurality of unit areas. An image processing apparatus for generating binary data, the binary data generating means for generating binary data using a pattern having information for generating binary data corresponding to a pixel area, and each scan A feed amount discriminating unit for discriminating a feed amount, which is the amount of recording medium transport, and a cycle in the recording medium transport direction of binary data generation by the pattern according to the feed amount discriminated by the feed amount discrimination unit Means for determining the period as a divisor of the feed amount. By using such control, it is possible to synchronize binary data and mask data.

  However, the problem with the above means is that the number of passes increases and the feed amount decreases, and at the same time the cycle of binary data in the recording medium conveyance direction decreases. In particular, when generating a binarized pattern by density pattern development (Patent Document 3) or dither (Patent Document 4) designed so that the binary data pattern does not have a non-periodic and low-frequency bias, A longer period in the recording medium conveyance direction is advantageous because the degree of freedom in size of the density pattern development table or dither matrix can be increased. Conversely, when the period is small, the degree of freedom is reduced.

  An object of the present invention is to synchronize the feed amount and mask pattern in multi-pass printing, and relatively increase the pattern size for binary data generation in the density pattern method or dither even if the feed amount becomes small. It is to provide an image processing apparatus, a recording apparatus, and an image processing method that can be performed.

  In order to achieve the above object, according to the present invention, the recording head scans the unit area of the recording medium a plurality of times, and the recording medium is conveyed for each of the plurality of scannings, thereby An image processing apparatus for generating binary data for sequentially completing recording, and generating binary data using a pattern having information for generating binary data corresponding to a pixel area Generation means, feed amount determination means for determining a feed amount that is the amount of recording medium transport for each scan, and recording of binary data generation by the pattern according to the feed amount determined by the feed amount determination means Means for determining a period in the medium conveying direction, wherein the period is a multiple of the feed amount and not more than the number of head nozzles.

  According to the above configuration, the pattern size for binary data generation in the density pattern method or dithering is relatively reduced even if the feed amount is reduced while synchronizing the feed amount and the mask pattern in multi-pass printing. Can be bigger.

FIG. 3 is a diagram schematically illustrating multi-pass printing using a print head, a recorded dot pattern, and the like. FIG. 6 is a diagram illustrating a relationship between a recording head and a recording medium when performing two-pass recording. (A) And (b) is a figure explaining the case where two-pass multipass printing is performed using C, M, and Y ink according to one embodiment of the present invention. 1 is a block diagram mainly illustrating hardware and software configurations of a personal computer as an image processing apparatus according to a first embodiment of the present invention. It is a flowchart which shows the procedure of the image processing which concerns on 1st embodiment of this invention. It is a figure which shows the density | concentration pattern used by one Embodiment of this invention. It is a figure explaining the relationship between the repetition period of binary data generation and feed amount concerning one Embodiment of this invention. FIG. 3 is a diagram schematically illustrating a relationship between a recording head and a recording medium in 3-pass multi-pass recording. It is a figure explaining the relationship between these feed amount and a repetition cycle when the repetition cycle of binary data generation is not a divisor of the feed amount. It is a figure which shows the relationship between the feed amount and repetition period in 3 pass recording of one Embodiment of this invention. It is a flowchart which shows the change process of the repetition period of binary data generation accompanying the change of the number of passes of multipass printing of one embodiment of the present invention. (A) shows a recording head having one nozzle row for one color ink, and (b) shows a recording head having two nozzle rows for one color ink. It is a flowchart which shows the process which distributes dot data to the nozzle of several rows. It is a figure which shows the relationship between a nozzle row and a block pattern (drive pattern). It is a flowchart which shows an example of the data processing using column thinning. FIG. 6 is a diagram illustrating a state where recording is performed using discharge thinning. FIG. 6 is a diagram specifically illustrating multi-pass printing using a mask. It is the figure shown about the relationship between column thinning and a mask pattern. It is a figure which shows the relationship between the feed amount and repetition period in 16 pass recording of one Embodiment of this invention. It is a figure which shows the relationship between the feed amount and repetition period in 16 pass recording of one Embodiment of this invention.

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

  A printer as an ink jet recording apparatus according to an embodiment of the present invention has a plurality of recording modes that differ in the number of passes required to complete recording in multipass recording, and executes recording by switching these modes. Then, as will be described later with reference to FIG. 11, when switching the recording mode, it is determined whether or not the number of passes is changed by the mode switching. In accordance with the above, the repetition cycle of binary data generation is changed.

  FIG. 2 is a diagram schematically illustrating the relationship between the print head and the print medium in a mode in which two-pass multi-pass printing is performed as an example among print modes executed by the printer of the present embodiment. In the case of two-pass recording, an image to be recorded in a predetermined unit area of the recording medium is completed by scanning the recording head twice.

  The cyan, magenta, and yellow color nozzle groups are divided into two groups, a first group and a second group, and each group includes 256 nozzles. Therefore, the number of nozzles for each color is 512. Each color nozzle group discharges ink to each unit area corresponding to the arrangement width of the nozzle group on the recording medium while scanning in a direction substantially perpendicular to the nozzle arrangement direction ("head scanning direction" indicated by an arrow in the drawing). In this example, based on binary image data of C, M, and Y, ink ejection of C, M, and Y is performed for each unit region. Each time scanning is completed, the recording medium has a width equal to the width of one group (here, the same 256 as the width of the unit area) in the direction orthogonal to the scanning direction (the “recording medium conveyance direction” indicated by the arrow in the figure). It is transported pixel by pixel). Thereby, the image of each unit region is completed by scanning twice. Hereinafter, the amount of recording medium conveyance performed during a plurality of scans for completing such recording is also referred to as a feed amount. As shown in FIG. 2, this feed amount is represented as Nf (= 256) pixels.

  More specifically, the above-described two-pass multi-pass printing will be described. In the first scan, the first group of the C nozzle group, the first group of the M nozzle group, and the first group of the Y nozzle group with respect to the area A on the printing medium. Recording is performed in the order of CMY using one group. Next, in the second scan, the second group of the C nozzle group, the second group of the M nozzle group, and the second group of the Y nozzle group are arranged in the order of YMC with respect to the area A where the printing in the first scan is completed. Used to record the rest. At the same time, in the unrecorded region B, recording is performed in the order of YMC using the first group of the C nozzle group, the first group of the M nozzle group, and the first group of the Y nozzle group. Furthermore, by continuing such an operation, each unit area (area A, area B) in the order of C1, M1, Y1, Y2, M2, C2, or in the order of Y1, M1, C1, C2, M2, Y2. Recording will continue.

  FIGS. 3A and 3B are diagrams for explaining the recording order with respect to the unit area when performing 2-pass multi-pass printing using C, M, and Y inks as shown in FIG. It is.

  FIG. 3A shows a state where an image of an area (area A in FIG. 2) recorded in the order of forward scanning and backward scanning is completed. In the forward scan (first pass), which is the first scan, a cyan image is first recorded based on cyan dot data for each pass generated using a mask as described later with reference to FIG. Subsequently, in the same scanning, magenta and yellow are similarly recorded based on dot data generated using a mask. That is, the magenta image is overlaid on the cyan image recorded before that, and the yellow image is overlaid on the preceding cyan and magenta images, and sequentially recorded. In the reverse scan (second pass), which is the second scan after the recording medium is transported by a predetermined amount, similarly, it is sequentially determined based on the yellow, magenta, and cyan dot data for each pass generated by the mask. Images are sequentially recorded on top of the previously recorded images.

  On the other hand, FIG. 3B shows a state where an image of an area (area B in FIG. 2) recorded in the order of backward scanning and forward scanning is completed. In the reverse scan (first pass), which is the first scan, first, a yellow image is recorded based on yellow dot data generated using a mask for each pass. Subsequently, in the same scan, printing is performed on magenta and cyan based on dot data generated using the same mask for each pass. That is, the magenta image is overlaid on the yellow image recorded earlier than that, and the cyan image is overlaid on the yellow and magenta images recorded earlier than the yellow image. In the forward scan (second pass), which is the second scan after the recording medium is conveyed by a predetermined amount, similarly, based on the dot data of cyan, magenta, and yellow that are generated in the same manner, before that, Record sequentially on the recorded image.

  FIG. 4 is a block diagram mainly showing hardware and software configurations of a personal computer (hereinafter also simply referred to as a PC) as an image processing apparatus (image data generation apparatus) according to the present embodiment.

  In FIG. 4, a PC 100 that is a host computer operates application software 101, a printer driver 103, and a monitor driver 105 by an operating system (OS) 102. The application software 101 performs processing related to a word processor, spreadsheet, internet browser, and the like. The monitor driver 104 executes processing such as creating image data to be displayed on the monitor 106.

  The printer driver 103 performs image processing on image data and the like issued from the application software 101 to the OS 102, and finally generates binary ejection (dot) data used by the printer 104. Specifically, binary image data of C, M, and Y used in the printer 104 is generated from multi-valued image data of C, M, and Y by executing processing that will be described later with reference to FIGS. To do. The binary image data generated in this way is transferred to the printer 104.

  The host computer 100 includes a CPU 108, a hard disk drive (HD) 107, a RAM 109, a ROM 110, and the like as various hardware for operating the above software. That is, the CPU 108 executes the process according to the software program stored in the hard disk 107 or the ROM 110, and the RAM 109 is used as a work area when the process is executed.

  The printer 104 of this embodiment is a so-called serial printer that performs recording by scanning a recording medium that ejects ink with respect to a recording medium and ejecting ink during that time, as described with reference to FIG. By mounting a recording head having each ejection port group corresponding to each of the C, M, and Y inks on the carriage, it is possible to scan a recording medium such as recording paper. A recording element such as an electrothermal conversion element or a piezoelectric element is provided in a flow path communicating with each ejection port of the recording head, and ink is ejected from the ejection port by driving these recording elements. The array density of each ejection port is 1200 dpi, and 3.0 picoliters of ink is ejected from each ejection port. The number of discharge ports in each color discharge port group is 512.

  The printer 104 includes a CPU, memory, and the like (not shown). The binary image data transferred from the host computer 100 is stored in the memory of the printer 104. Then, under the control of the CPU, the binary image data stored in the memory is read and sent to the drive circuit of the recording head. The drive circuit drives the recording element of the recording head based on the sent binary image data, and ejects ink from the ejection port.

  In one embodiment of the present invention, binary data of six planes distinguished by forward or backward scanning in multipass printing and three color inks of C, M, and Y is generated using a density pattern method. FIG. 5 is a flowchart showing binary data generation processing.

  In FIG. 5, first, color adjustment processing is performed on RGB 8-bit data (S401), then CMY 8-bit image data is obtained by color conversion processing (S402), and further gamma correction processing (S403) is performed. Is called.

  The CMY 8-bit 256-value image data subjected to the above processing is then quantized into 3-bit 5-value data by error diffusion (S404). Based on the quinary data, binary data development using the density pattern (dot arrangement pattern) shown in FIG. 6 is performed (S405). Here, the quinary data obtained in step S404 is one pixel having a resolution of 600 dpi. On the other hand, the density pattern (dot arrangement pattern) is a pattern having 2 pixels × 2 pixels as one unit with respect to the 600 dpi pixels, and therefore the resolution of the generated binary data is 1200 dpi × 1200 dpi. .

  FIG. 6 is a diagram showing the density pattern of the present embodiment. As shown in the figure, the density pattern of this embodiment has four types of patterns for each of five levels. In the binary data development, a pattern is selected according to the pattern type indicated by the density pattern selection matrix in accordance with the density level indicated by the quinary data, and this is used as binary data in units of 2 pixels × 2 pixels. For example, if the density level indicated by the quinary data is “1” and the value of the density pattern selection matrix is 0, one of the four density pattern levels 1 (= 2 × 2 pixels have one dot ON) Density pattern corresponding to the 0th is selected. By repeating this, a binary image having a resolution of 1200 dpi × 1200 dpi is generated.

  Here, the density pattern selection matrix of the present embodiment has a size of 32 pixels × 32 pixels, and each pixel stores four types of values from 0 to 3 without regularity. . Then, for each pixel of the density pattern selection matrix, a density pattern of 2 pixels × 2 pixels size is developed based on the values “0” to “3” of the pixel. That is, a binary data (dot) pattern having a resolution of 1200 dpi × 1200 dpi has a period of 64 pixels (main scanning direction) × 64 pixels (feed direction) according to the size of 32 pixels × 32 pixels of the density pattern selection matrix. It becomes a pattern. If the density pattern selection matrix has a size of 100 pixels × 100 pixels, the developed binary data pattern is developed as a pattern having a cycle of 200 pixels × 200 pixels. In changing the size or cycle of each embodiment to be described later, attention is paid to the pattern size after development by the density pattern selection matrix.

  Referring to FIG. 5 again, finally, with respect to the binary data obtained by the binary data expansion, binary data for each of the six planes is obtained using a mask (S406).

  It should be noted that the present invention can be similarly applied to the case of using four color inks to which black (Bk) is added, and further to the case of using a light ink having a low density or a special color ink such as red, blue, or green. Is clear from the following explanation.

(Embodiment 1)
The first embodiment of the present invention determines whether or not the feed amount in multi-pass recording has been changed when the recording mode is changed. When the feed amount is changed, the density pattern selection matrix is changed to a size corresponding to the changed feed amount.

  As described with reference to FIG. 2, in the two-pass printing mode of the present embodiment, the feed amount Nf is 256 pixels in relation to the number of nozzles of the printing head. Correspondingly, in 2-pass printing, the size of the density pattern selection matrix is 32 pixels in the feed direction, and therefore the repetition period Ng in the feed direction of binary data developed by the matrix is 64 pixels. . That is, the repetition period Ng (= 64 pixels) is a divisor of the feed amount Nf (= 256 pixels).

  FIG. 7 is a diagram for explaining the relationship between the repetition period and the feed amount. As shown in the figure, the upper ends of the areas A, B,... That are unit areas for completing recording are always started from the same repetition cycle.

  Next, a case will be described in which the number of multi-passes is changed to 3 by changing the recording mode or the like.

  FIG. 8 is a diagram for explaining 3-pass multi-pass printing, and schematically shows the relationship between the print head and the print medium. As will be described below, in the case of three-pass printing, an image to be recorded in a predetermined unit area of the recording medium is completed by three scans of the recording head.

  The cyan, magenta, and yellow color nozzle groups are divided into two groups, a first group, a second group, and a third group, and each group includes 168 nozzles. 2) At this time, 168 was selected, and a value close to 170 obtained by dividing 512 nozzles (corresponding to pixels in this case) by 3 was selected.

  Each color nozzle group discharges ink to each unit area corresponding to the arrangement width of the nozzle group on the recording medium while scanning in a direction substantially perpendicular to the nozzle arrangement direction ("head scanning direction" indicated by an arrow in the drawing). In this example, based on binary image data of C, M, and Y, ink ejection of C, M, and Y is performed for each unit region. Each time scanning is completed, the recording medium is conveyed by the width of one group, that is, feed amount = 168 pixels, in a direction orthogonal to the scanning direction (“feed direction” indicated by an arrow in the figure). . Further, the same operation is repeated once more, and each unit region completes an image by scanning three times.

  Here, consider a case where the repetition cycle Ng (= 64) of binary data generation is not a divisor of the feed amount Nf (= 168 pixels), that is, the repetition cycle is not changed. FIG. 9 is a diagram for explaining the relationship between the feed amount Hf and the repetition period Hg in this case.

  For example, it is assumed that the start position of the area A is 0, and this is the same as the start position in the repetition cycle. At this time, the head of the region B has feed direction coordinates 168 corresponding to the feed amount (168 pixels). The head coordinate 168 of the region B is not divisible by 64 when the repetition period Ng is 64 pixels, unlike the case of 2 passes. That is, in the case of the region A and the case of the region B, different binary data as a whole correspond to the two regions. Further, in the area C where the feed amount for 168 pixels is increased, the cycle of the binary data is shifted in the head coordinate 340, and similarly, different binary data as a whole corresponds to the two areas.

  Therefore, in the present embodiment, when the number of passes in multi-pass printing is changed, the binary data generation repetition cycle Ng is changed according to the feed amount that changes accordingly. In the present embodiment, in the case of 3 passes, it is 84 which is a divisor of Nf (= 168 pixels). 2) Specifically, in the case of three passes shown in this example, a new 42 pixel (main scanning direction) × 42 pixel (feed direction) matrix different from the two passes is used as the density pattern selection matrix. The density pattern is 2 pixels × 2 pixels. Thus, binary data for 84 pixels is generated in the scanning direction and the feed direction by density pattern development.

  Here, when selecting a divisor, it is desirable to select a value larger than at least 32. In other words, in the case of the density pattern method, it is effective to design a plurality of density patterns corresponding to each density level so that the selection cycle of the plurality of density patterns is not regular. This is because an irregular pattern can suppress a change in the degree of dot overlap when the dot recording position is shifted. In order to perform this irregular selection, it is necessary to increase the period or size of the density pattern selection matrix to some extent. According to the study by the present inventors, it has been found that this size is desirably at least 32 pixels or more.

  FIG. 10 is a diagram showing the relationship between the feed amount Nf and the repetition period Ng in the 3-pass printing of this embodiment. As shown in the figure, in accordance with the feed amount being changed to 168 pixels, the repetition period is also changed to 84 pixels.

  Thereby, it is possible to satisfactorily realize the purpose of image recording such as the recording image quality intended by the density pattern. That is, the density selection matrix is created so that a desired image quality objective is realized by determining the dot arrangement and pattern size in units of the size. On the other hand, an area completed by multi-pass printing is a unit in which various conditions for printing operation such as the order of use of nozzles of the printing head are defined. In this way, the unit for realizing the desired image quality purpose in the image processing and the unit for the recording operation are matched, so that the purpose for image recording intended by the pattern for generating binary data is improved. Can be realized.

  As described above, according to the present embodiment, a plurality of unit areas are obtained by scanning the recording head a plurality of times with respect to the unit area of the recording medium and conveying the recording medium for each of the plurality of scans. Binary data for multi-pass recording that sequentially completes the recording is generated. At this time, binary data is generated using a pattern of the density pattern selection matrix, which is a pattern having information for generating binary data corresponding to the pixel area. At this time, a feed amount for multi-pass recording is determined, and a cycle in the recording medium conveyance direction of binary data generation according to the pattern is determined according to the determined feed amount. The cycle is approximately equal to the feed amount. Determine the period to be a number.

  FIG. 11 is a flowchart showing processing associated with the recording operation of the present embodiment, and particularly shows processing for changing the repetition cycle of binary data generation associated with changing the number of passes in multi-pass recording.

  When there is a recording command from the host device, it is first determined whether or not the recording mode has been changed (S1201). If it is determined that the recording mode has been changed, it is further determined whether or not the number of passes, which is the number of times of scanning a plurality of times in multi-pass printing, has changed due to the change of the mode (S1202).

  Here, when it is determined that the number of passes has been changed, as described above with reference to FIGS. 7 to 10, the repetition cycle of binary data generation is changed according to the change in the feed amount accompanying the change in the number of passes ( S1203). That is, the density pattern selection matrix used for binary data generation by the density pattern is set to a size corresponding to the changed feed amount. Then, binary data is generated by repeatedly using this selection matrix. As a result, it is possible to avoid a mismatch between a unit that realizes a desired image quality purpose in image processing and a recording operation area, and to improve the purpose of image recording intended by a pattern for generating binary data. Can be realized. Finally, based on the generated binary data, a printing operation is executed using a mask corresponding to the number of passes (S1204).

  Next, consider a case where the number of multipaths increases. In the case of two passes, as shown in FIG. 7, the feed amount was 256, and 64 was selected as a divisor thereof. Increasing the number of multipaths decreases the throughput, but generally the image quality is often improved. For example, consider the case of printing in 16 passes. The figure in that case of FIG. 19 is shown. Since the feed amount is 32 in the case of 16 passes, the cycle of binary data in the recording medium conveyance direction is 32 at the maximum. As described above, a binary pattern is generated by density pattern development (Patent Document 3) or dither (Patent Document 4) designed so that the binary data pattern has no non-periodic and low-frequency bias. In this case, it is advantageous that the period in the recording medium conveyance direction is large because the degree of freedom in size of the density pattern development table or dither matrix can be increased. Conversely, when the period is small, the degree of freedom is reduced.

  In view of this, the present invention proposes a method capable of increasing the period of binary data in the recording medium conveyance direction in the case of an operation in which multipass mask control and “ejection thinning-out control” are used in combination. FIG. 16 shows a case where “discharge thinning control” is used. In this example, the above-described column thinning is selected as “discharge thinning control” (FIG. 14B). In reciprocal printing, column number 0 is selected for the forward direction and column number 1 is selected for the backward direction. In such column thinning control, when the band width is assumed to be the paper feed amount unit, each band starts with printing from the forward direction (= defined as band 1) and printing from the backward direction. Band (= defined as band 2) to be arranged alternately. In the figure, the first band and the third band start from forward printing (= defined as band 1), and in the figure, the second band and the fourth band start from backward printing ( = Band 2 defined).

  FIG. 17 is a diagram specifically illustrating multi-pass printing using a mask, and schematically shows a print head, a recorded dot pattern, and the like when an image is completed by four scans. It is a figure corresponding to FIG. In the figure, P0001 indicates a recording head. Here, for simplification of illustration and description, it is expressed as having 16 discharge ports (hereinafter also referred to as nozzles). The nozzle row is divided into first to fourth four nozzle groups each including four nozzles as shown in the figure. P0002 indicates a mask pattern, and mask pixels (recording allowable pixels) that allow recording corresponding to each nozzle are indicated by black. Here, the difference from FIG. 1 is that “column thinning control” is performed, so that the nozzles capable of discharging in the forward direction and the backward direction are skipped in the column direction regardless of the mask pattern. . For example, in the band 1 (= starting from forward printing), a part of the even-numbered columns is first turned ON. This is because, in forward printing, ink ejection is prohibited in odd-numbered columns by “column thinning control”. On the other hand, the second pass of band 1 is printed by backward scanning so that only odd columns are ON. In the case of band 2, on the contrary, printing is performed by backward scanning such that only odd columns are turned ON in the first pass, and printing is performed by forward scanning so that only even columns are turned ON in the second pass.

  Focusing on the mask pattern at this time, it can be seen that in the band 1 and the band 2, the column thinning is reversed for each pass, and therefore, a mask pattern that is completely different for each pass is used and ON dots are determined. This is shown in FIG. When the mask pattern used for printing band 1 is associated with the nozzle position, the column positions allowed in each band are shown in (a1) and (a2). When a 4-pass mask pattern is indicated by P0, a pattern allowed for each band (= logical product of a1 or a2 and P0) is indicated by P1 and P2. It can be seen that P1 and P2 are composed of completely exclusive patterns.

  By using this characteristic, the period in the recording medium conveyance direction can be increased. In the case of the 16 passes described above, the feed amount is 32. However, for example, by using column thinning 2, it is possible to synchronize with the mask even if the period is set to double 64. As a result, the binarization pattern period can be extended as shown in FIG.

100 Personal computer (PC)
103 Printer driver 104 Printer 107 HD
108 CPU
109 RAM
110 ROM

Claims (8)

Binary data for sequentially completing the recording of the plurality of unit areas by scanning the recording head a plurality of times with respect to the unit area of the recording medium and conveying the recording medium for each of the plurality of scans. An image processing device to generate,
Binary data generating means for generating binary data using a pattern having information for generating binary data corresponding to a pixel area;
Feed amount determination means for determining a feed amount that is an amount of recording medium transport for each scan;
Means for determining a cycle in the recording medium conveyance direction of binary data generation by the pattern according to the feed amount determined by the feed amount determination unit, wherein the cycle is a multiple of the feed amount and not more than the number of head nozzles A period determining means, and
An image processing apparatus comprising:   The image processing apparatus according to claim 1, wherein the pattern having information for generating the binary data is a pattern of a density pattern selection matrix for selecting a density pattern.   The image processing apparatus according to claim 1, wherein the pattern having information for generating binary data is a dither pattern.   The image processing apparatus according to claim 1, wherein the period determining unit sets the period to the same value as the feed amount. The generated binary data is divided into binary data for each of a plurality of scans for completing the recording of the unit area using a mask,
5. The mask according to claim 1, wherein the mask is created in consideration of an arrangement of the information in a pixel area in a pattern having information for generating binary data. Image processing apparatus.   The image processing apparatus according to claim 1, wherein the feed amount determination unit determines a feed amount in accordance with switching of the number of times of scanning for completing the recording of the unit area. . Binary data for sequentially completing the recording of the plurality of unit areas by scanning the recording head a plurality of times with respect to the unit area of the recording medium and conveying the recording medium for each of the plurality of scans. A recording device that generates and records on a recording medium based on the generated binary data,
Binary data generating means for generating binary data using a pattern having information for generating binary data corresponding to a pixel area;
Feed amount determination means for determining a feed amount that is an amount of recording medium transport for each scan;
Means for determining a cycle in the recording medium conveyance direction of binary data generation by the pattern according to the feed amount determined by the feed amount determination unit, wherein the cycle is a multiple of the feed amount and not more than the number of head nozzles A period determining means, and
A recording apparatus characterized by comprising: Binary data for sequentially completing recording of a plurality of unit areas by scanning the recording head a plurality of times with respect to the unit area of the recording medium and transporting the recording medium for each of the plurality of scans. An image processing method for generating,
A binary data generation step of generating binary data using a pattern having information for generating binary data corresponding to a pixel region;
A feed amount determination step of determining a feed amount that is an amount of recording medium transport for each scan;
A step of determining a cycle in the recording medium conveying direction of binary data generation by the pattern according to the feed amount determined by the feed amount determining means, wherein the cycle is a multiple of the feed amount and not more than the number of head nozzles A cycle determining step, and
An image processing method characterized by comprising:

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