JP5708908B2 - Image recording method and image recording apparatus - Google Patents

Description

  The present invention relates to an image recording method and an image recording apparatus for recording an image on a recording medium by discharging ink droplets.

  In offset printing or the like, CTP (Computer To Plate) that records an image directly on a printing plate using an inkjet printer is known. In this CTP, the gradation of an image is represented by various methods, and one of them is an AM (Amplitude Modulation) that represents the gradation by changing the area (size) of halftone dots arranged at a uniform pitch. ) A method using halftone dots (AM screening) is known.

  Ink jet printers used for CTP are equipped with an ink jet head in which a large number of nozzles are formed. However, since narrowing the nozzle pitch is limited, when an image is recorded at a higher resolution than the nozzle pitch, the image is recorded by multi-pass recording (see, for example, Patent Document 1). For example, when recording an image of 2400 dpi, which is a quadruple resolution, with an ink jet head having a nozzle pitch of 600 dpi, the recording medium is conveyed in 1/4 unit of the nozzle pitch, and the image is recorded by 4-pass multi-pass recording. Is going.

Republished Patent W2006 / 006595

  Incidentally, when a 2400 dpi image is recorded, the width of each pixel is 10.58 μm. On the other hand, when a 3 pl ink droplet is ejected from the nozzle, the diameter of the dot recorded in each pixel is 20 to 30 μm. For this reason, for example, when an image is recorded on a non-absorbing printing plate such as an aluminum plate or a plus chip plate that does not soak in ink, the dots recorded in adjacent pixels are mixed and beads that are pulled in directions close to each other. Bing occurs.

  For this reason, in the conventional image recording method, since dots are sequentially recorded on adjacent pixels, the dots in the second pass are mixed with the dots in the first pass and pulled by the dots in the first pass. The second dot is mixed with the second pass dot and pulled to the second pass dot, and the fourth pass dot is mixed with the third pass dot and pulled to the third pass dot. In this manner, regular dot deviation occurs for each nozzle pitch, and therefore a stripe extending in the main scanning direction called banding occurs in the recorded image.

  On the other hand, when an image of 2400 dpi is recorded, there is a problem in that the image recording speed becomes slow because the positions where dots are recorded increase. In particular, the problem occurs remarkably in the solid coating portion.

  Therefore, an object of the present invention is to provide an image recording method and an image recording apparatus capable of increasing the speed of image recording while suppressing the occurrence of banding when performing multipass recording.

The image recording method according to the present invention uses an ink jet printer equipped with an ink jet head having a plurality of nozzles to eject ink droplets from the nozzles while relatively moving the ink jet head and the recording medium in the main scanning direction. An image recording method for recording an image on a recording medium by multi-pass recording by causing the inkjet head and the recording medium to move relative to each other in the sub-scanning direction orthogonal to the main scanning direction. A unit area obtained by acquiring print data in which dot recording presence / absence is set for each pixel of the AM halftone dot, and comprising a plurality of pixels in the horizontal direction corresponding to the main scanning direction and a plurality of pixels in the vertical direction corresponding to the sub-scanning direction For each pixel group composed of two or more adjacent pixels in the left and right or up and down directions, the pixel sets adjacent in the left and right direction and the up and down direction are connected. Dot recording order setting step for setting the dot recording order of each pixel in the print data without making, have a, spaced dot recording order setting step, of the set of pixels in each unit region, one pixel set vertically and horizontally diagonal The first pixel group group composed of one or a plurality of pixel groups is set as the first rank in the dot recording order .

  According to the image recording method of the present invention, the dot of each pixel in the print data for each unit area composed of a plurality of pixels in the horizontal direction corresponding to the main scanning direction and a plurality of pixels in the vertical direction corresponding to the sub-scanning direction. In order to set the recording order, the dot recording order can be set two-dimensionally left and right and up and down. Then, since the dot recording order is set in units of pixel groups composed of two pixels that are adjacent to each other on the left and right or top and bottom, the image recording speed can be increased. In addition, by setting the dot recording order without causing the pixel groups adjacent in the horizontal direction and the vertical direction to continue, it is possible to prevent the dots from being regularly pulled in one direction for each unit region. The occurrence of banding can be suppressed.

In this case, it is preferable to further include a thinning-out step for deleting the dots of the target pixel when the dots of the four pixels above, below, left, and right of the target pixel are recorded. In this way, by deleting the dots of the target pixel where the four pixels on the top, bottom, left, and right record the dots, so-called solid coating dots are thinned out, so that it is possible to prevent the dots from overlapping too much and overflowing the ink. it can. In addition, as described above, since dots are recorded in the same order in two or more pixels that are adjacent to each other in the horizontal and vertical directions as described above, by thinning out dots in this way, even in the same pixel set, adjacent pixels are recorded. At the same time, dots can be prevented from being recorded. For this reason, generation | occurrence | production of banding can be suppressed more effectively.

In addition , when a first pixel group composed of one or a plurality of pixel groups that are separated from each other by one pixel group in the up, down, left, and right directions is a first rank in the dot recording order, when dots are recorded in the first pixel group Since dots have not yet been recorded in adjacent pixel groups that are diagonally up, down, left and right, dots can be recorded in each pixel group of the first pixel group without being pulled by other dots. And since the remaining pixel group becomes a pixel group sandwiched between the first pixel group group, the dots recorded in the first pixel group group are obtained by pulling the dots recorded in the remaining pixel group at least from both directions. The positions of dots recorded in the remaining pixel groups can be held. Thus, by recording dots in the first pixel group as the first order, the dots recorded in the first pixel group are kept at the positions of the dots recorded in the remaining pixel groups. It can function as an anchor.

  Further, in the dot recording order setting step, the second image pixel group group composed of one or a plurality of pixel groups arranged on the left and right sides of the first pixel group group and the first pixel group group arranged above and below the first pixel group group Either one of the third pixel group composed of a plurality of pixel groups is set as the second order in the dot recording order, and one of the second pixel group and the third pixel group is set as the third order in the dot recording order. It is preferable that the fourth pixel group composed of one or a plurality of pixel groups arranged obliquely in the first pixel group is the fourth order in the dot recording order. In this way, the second pixel group and the third pixel group that are in the second or third order are sandwiched between the first pixel group and the left and right or top and bottom, so the second pixel group and the third pixel group The dots recorded in the group are pulled in a balanced manner from the left and right or the top and bottom by the dots recorded in the first pixel group functioning as an anchor. Thereby, it can suppress that the position of the dot recorded on the 2nd pixel group group and the 3rd pixel group group shifts. Furthermore, the fourth pixel set group in the fourth order is sandwiched between the first pixel set group and the top and bottom and left and right sides between the second pixel set group and the third pixel set group. The dots recorded in the group are pulled in a balanced manner with equal force from the eight directions diagonally left and right, up and down by the dots recorded in the first pixel group, the second pixel group, and the third pixel group. Thereby, it is possible to prevent the positions of the dots recorded in the fourth pixel set group from shifting.

  In addition, as multi-pass printing with the same number of passes as the number of pixel sets constituting the unit area, a dot recording step for sequentially recording dots on the pixels of each pixel set for each pass in the order set in the dot recording order setting step. Furthermore, it is preferable to have. In this way, by performing multi-pass printing with the same number of passes as the number of pixel sets constituting the unit area, it is possible to appropriately suppress the occurrence of banding while increasing the speed of image recording.

  In the dot recording step, the inkjet head may be transported in the sub-scanning direction for each pass, and dots may be recorded with different nozzles for each pixel group in the same unit area. In this way, when the inkjet head is transported in the sub-scanning direction for each pass and dots are recorded with different nozzles for each pixel set, the dot recording start pixel set in the dot recording order varies depending on the pass position, Since the line position of the image set recorded by the ink jet head changes for each pass, the joint of the ink jet head can be made inconspicuous.

  On the other hand, the dot recording step may record dots with the same nozzle on each pixel group in the same unit area. In this way, dots are recorded from the first pixel group in the dot recording order set by the dot recording order setting step in all unit areas by recording dots in each pixel group in the same unit area. can do.

The image recording apparatus according to the present invention uses an ink jet printer equipped with an ink jet head having a plurality of nozzles to eject ink droplets from the nozzles while relatively moving the ink jet head and the recording medium in the main scanning direction. An image recording apparatus for recording an image on a recording medium by multipass recording by ejecting and relatively moving an inkjet head and a recording medium in a sub-scanning direction orthogonal to the main scanning direction. A unit area obtained by acquiring print data in which dot recording presence / absence is set for each pixel of the AM halftone dot, and comprising a plurality of pixels in the horizontal direction corresponding to the main scanning direction and a plurality of pixels in the vertical direction corresponding to the sub-scanning direction For each pixel group composed of two or more adjacent pixels in the left and right or up and down directions, the pixel sets adjacent in the left and right direction and the up and down direction are connected. Dot recording order setting unit that sets the dot recording order of each pixel in the print data without making, have a, spaced dot recording order setting unit, among the set of pixels in each unit region, one pixel set vertically and horizontally diagonal The first pixel group group composed of one or a plurality of pixel groups is set as the first rank in the dot recording order .

  According to the image recording apparatus of the present invention, the dot of each pixel in the print data for each unit area composed of a plurality of pixels in the horizontal direction corresponding to the main scanning direction and a plurality of pixels in the vertical direction corresponding to the sub-scanning direction. In order to set the recording order, the dot recording order can be set two-dimensionally left and right and up and down. Then, since the dot recording order is set in units of pixel groups composed of two pixels that are adjacent to each other on the left and right or top and bottom, the image recording speed can be increased. In addition, by setting the dot recording order without causing the pixel groups adjacent in the horizontal direction and the vertical direction to continue, it is possible to prevent the dots from being regularly pulled in one direction for each unit region. The occurrence of banding can be suppressed.

In this case, it is preferable to further include a thinning unit that deletes the dots of the target pixel when the dots of the upper, lower, left, and right pixels of the target pixel are recorded. In this way, by deleting the dots of the target pixel where the four pixels on the top, bottom, left, and right record the dots, so-called solid coating dots are thinned out, so that it is possible to prevent the dots from overlapping too much and overflowing the ink. it can. In addition, as described above, since dots are recorded in the same order in two or more pixels that are adjacent to each other in the horizontal and vertical directions as described above, by thinning out dots in this way, even in the same pixel set, adjacent pixels are recorded. At the same time, dots can be prevented from being recorded. For this reason, generation | occurrence | production of banding can be suppressed more effectively.

Also , assuming that the first pixel group group composed of one or a plurality of pixel groups that are spaced apart by one pixel group in the up, down, left, and right directions is the first rank, the dots are still in the up, down, left, and right directions when recording dots in the first pixel group group. Since dots are not recorded in adjacent pixel groups, dots can be recorded in each pixel group of the first pixel group group without being pulled by other dots. And since the remaining pixel group becomes a pixel group sandwiched between the first pixel group group, the dots recorded in the first pixel group group are obtained by pulling the dots recorded in the remaining pixel group at least from both directions. The positions of dots recorded in the remaining pixel groups can be held. Thus, by recording dots in the first pixel group as the first order, the dots recorded in the first pixel group are kept at the positions of the dots recorded in the remaining pixel groups. It can function as an anchor.

  Further, the dot recording order setting unit includes one or a plurality of second pixel groups that are composed of one or a plurality of pixel groups arranged on the left and right of the first pixel group group, and one or more that are arranged above and below the first pixel group group. Any one of the third pixel group composed of the pixel group is the second order in the dot recording order, and any one of the second pixel group and the third pixel group is the third order in the dot recording order. The fourth pixel group composed of one or a plurality of pixel groups arranged obliquely of the first pixel group is preferably set as the fourth order in the dot recording order. In this way, the second pixel group and the third pixel group that are in the second or third order are sandwiched between the first pixel group and the left and right or top and bottom, so the second pixel group and the third pixel group The dots recorded in the group are pulled in a balanced manner from the left and right or the top and bottom by the dots recorded in the first pixel group functioning as an anchor. Thereby, it can suppress that the position of the dot recorded on the 2nd pixel group group and the 3rd pixel group group shifts. Furthermore, the fourth pixel set group in the fourth order is sandwiched between the first pixel set group and the top and bottom and left and right sides between the second pixel set group and the third pixel set group. The dots recorded in the group are pulled in a balanced manner with equal force from the eight directions diagonally left and right, up and down by the dots recorded in the first pixel group, the second pixel group, and the third pixel group. Thereby, it is possible to prevent the positions of the dots recorded in the fourth pixel set group from shifting.

  In addition, as multi-pass printing with the same number of passes as the number of pixel sets constituting the unit area, a dot recording unit that records dots on the pixels of each pixel set sequentially for each pass in the order set by the dot recording order setting unit Furthermore, it is preferable to have. In this way, by performing multi-pass printing with the same number of passes as the number of pixel sets constituting the unit area, it is possible to appropriately suppress the occurrence of banding while increasing the speed of image recording.

  The dot recording unit may transport the inkjet head in the sub-scanning direction for each pass, and record dots with different nozzles for each pixel group in the same unit area. In this way, when the inkjet head is transported in the sub-scanning direction for each pass and dots are recorded with different nozzles for each pixel set, the dot recording start pixel set in the dot recording order varies depending on the pass position, Since the line position of the image set recorded by the ink jet head changes for each pass, the joint of the ink jet head can be made inconspicuous.

  On the other hand, the dot recording unit may record dots with the same nozzle in each pixel in the same unit area. In this way, dots are recorded from the first pixel group in the dot recording order set by the dot recording order setting unit in all unit areas by recording dots with the same nozzle in each pixel group in the same unit area. can do.

  According to the present invention, it is possible to increase the speed of image recording while suppressing the occurrence of banding when performing multipass recording.

1 is a schematic diagram illustrating a printer system according to an embodiment. It is the figure which illustrated the dot shape in AM network, (a) is the dot shape before correction | amendment, (b) is the dot shape which deleted both edges, (c) is the one edge deletion (Yes-> No) The dot shape is shown. It is the figure which showed the area occupation rate of the dot in AM net | network. It is a figure explaining the basic concept of a thinning-out process, (a) is the dot recorded, (b) has shown the dot recording presence or absence on print data. It is the figure which showed the case where a 3 * 3 pixel part is a solid coating, (a) shows the dot recorded, (b) has shown the dot recording presence or absence on print data. It is the figure which showed the case where a 4 * 4 pixel part is a solid coating, (a) shows the dot recorded, (b) has shown the dot recording presence or absence on print data. It is the figure which showed the case where the 8 * 8 pixel part is a solid coating, (a) shows the dot recorded, (b) has shown the dot recording presence or absence on print data. It is a schematic block diagram which shows the printing mechanism part of an inkjet printer. It is a figure for demonstrating the multipass recording of 16 passes. It is the figure which showed the mask pattern, (a) is a pixel group group, (b) has shown the dot recording order. It is the figure which showed the dot recording state for every pixel group group. It is the figure which showed the relationship between a nozzle arrangement | sequence and a recording pixel. It is the figure which showed the conveyance schedule of an inkjet head. FIG. 6 is a sequence diagram illustrating processing operations in the printer system. It is the flowchart which showed an example of the edge correction process by an edge correction part. It is the flowchart which showed an example of the thinning process by a thinning process part. FIG. 6 is a diagram illustrating a relationship between a transport position of an inkjet head and a dot recording position in a first pass. FIG. 6 is a diagram illustrating a relationship between a transport position of an inkjet head and a dot recording position in a second pass. FIG. 6 is a diagram illustrating a relationship between a transport position of an inkjet head and a dot recording position in a third pass. FIG. 6 is a diagram illustrating a relationship between a transport position of an inkjet head and a dot recording position in a fourth pass. FIG. 6 is a diagram illustrating a relationship between a conveyance position of an inkjet head and a dot recording position in a fifth pass. FIG. 6 is a diagram showing a relationship between an inkjet head conveyance position and a dot recording position in a sixth pass. FIG. 6 is a diagram illustrating a relationship between an inkjet head conveyance position and a dot recording position in an eighth pass. FIG. 10 is a diagram illustrating a relationship between a transport position of an inkjet head and a dot recording position in a ninth pass. It is the figure which showed the dot recording order in each block. It is a figure explaining the effect of the thinning process in a solid coating part, (a) shows the case where a thinning process is not performed, (b) shows the case where a thinning process is performed. It is the figure which showed the other example of the mask pattern, (a) is a pixel group group, (b) has shown the dot recording order.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of an image recording method and an image recording apparatus according to the present invention will be described in detail with reference to the drawings. In the present embodiment, the image recording method and the image recording apparatus according to the present invention are applied to a printer system including a workstation as an external device and an inkjet printer. This printer system records an image of 2400 dpi using an inkjet printer having a nozzle pitch of 600 dpi. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a schematic diagram illustrating a printer system according to the present embodiment. As shown in FIG. 1, the printer system 1 according to this embodiment includes a workstation 10 and an inkjet printer 20, and the workstation 10 and the inkjet printer 20 are electrically connected by a cable. .

  The workstation 10 generates an image to be recorded (printed) by the inkjet printer 20, converts the image into raster data, and transfers the raster data to the inkjet printer 20. Therefore, the workstation 10 includes a drawing application 11, a RIP (Raster Image Processor) 12, an edge correction unit 13, a thinning processing unit 14, and an I / F controller 15.

  The drawing application 11 generates PostScript data (original image data) represented by vector data using a Pezier curve by a user operation.

  The RIP 12 generates AM halftone dot data of binary bitmap data formed with an AM halftone dot pattern based on the PostScript data generated by the drawing application 11. First, the RIP 12 acquires the PostScript data generated by the drawing application 11 and analyzes the PostScript data. Next, the RIP 12 performs a rendering process and a rastering process, and images this PostScript data. Next, the RIP 12 performs a screening process, and generates AM halftone dot data that is binary bitmap data of 2400 dpi from the imaged data. Presence / absence of dot recording is set for each pixel of the AM halftone data. Next, the RIP 12 converts the AM halftone data into 1-bit TIFF format print data. This print data is composed of an AM halftone dot pattern of 2400 dpi, and whether or not dots are recorded is set for each pixel. If the original image data generated by the drawing application 11 is full-color data, print data is generated for each color.

  The edge correction unit 13 corrects the edge portion of the image in order to reduce the dot area of the AM halftone pattern in consideration of the spread of dots actually recorded. For example, when a dot is recorded with a 3 pl ink droplet, the dot diameter becomes 20 to 30 μm, so that the dot gain of the edge increases and the gradation is lowered. Therefore, the edge correction unit 13 detects an edge pixel (contour pixel) corresponding to an edge of the image (contour of the image) from each pixel of the AM halftone dot data generated by the RIP 12, and corrects the dot of the edge pixel. To do. As will be described later, there are three types of edge correction: both edge deletion, one edge deletion (Yes → No), and one edge deletion (No → Yes). Either method corrects the edge pixel dot. May be.

  Here, referring to FIG. 2 and FIG. 3, in the AM network of 2400 dpi and 175 lpi, the dot shape when both edges are deleted and the dot shape when one edge is deleted (Yes → No) explain. 2A and 2B are diagrams exemplifying dot shapes in an AM network, where FIG. 2A is a dot shape before correction, FIG. 2B is a dot shape in which both edges are deleted, and FIG. ) Shows the dot shape obtained. FIG. 3 is a diagram showing the area occupancy rate of dots in the AM network. In FIG. 2, pixels indicated by hatching are pixels from which dots have been deleted by edge correction.

  As shown in FIG. 2, when both edges are deleted from a dot shape with a dot area occupancy of 2.5%, the dots on both edges are deleted and the dot area occupancy becomes 0%. If one edge is deleted (Yes → No), one edge dot is deleted and the dot area occupation ratio becomes 0.5%. If both edges are deleted for a dot shape with a dot area occupancy rate of 3.0%, dots at both edges are deleted to a dot shape with a dot area occupancy rate of 0.5%, and one edge deletion ( When “Yes → No” is performed, a dot at one edge is deleted, and a dot area occupation ratio becomes 1.0%. If both edges are deleted from a dot shape with a dot area occupancy of 10.0%, the dots at both edges are deleted, resulting in a dot shape with a dot area occupancy of 4.0%. When “Yes → No” is performed, a dot at one edge is deleted, and a dot area occupation ratio becomes 6.5%. Similarly, when the dot area occupancy is 90.0%, if both edges are deleted, the dots at both edges are deleted to form a dot shape with a dot area occupancy of 82.0%, and one edge deletion ( When “Yes → No” is performed, the dot at one edge is deleted, and the dot area occupation ratio becomes 85.0%. These are summarized as shown in the graph of FIG.

  The thinning-out processing unit 14 thins out the dots in the solid coating portion, leaving the edge portion, in order to prevent the dots from overlapping in the solid coating portion and overflowing the ink (dots spread). For example, the size of each pixel with a resolution of 2400 dpi is 10.58 × 10.58 μm, whereas the diameter of a dot recorded with a 3 pl ink droplet is 20 to 30 μm. For this reason, if dots are recorded on adjacent pixels with 3 pl ink droplets, the two dots overlap and the ink overflows. Therefore, if the thinning processing unit 14 determines that dots are recorded in four pixels on the top, bottom, left, and right of the target pixel, the thinning processing unit 14 deletes (thinns out) the dot of the target pixel.

  Here, with reference to FIG. 4 to FIG. 7, a thinning process when a dot having a dot diameter of 21 μm is recorded with a resolution of 2400 dpi will be described. 4A and 4B are diagrams for explaining the basic concept of the thinning process. FIG. 4A shows dots to be recorded, and FIG. 4B shows whether dots are recorded on the print data. FIG. 5 is a diagram showing a case where the 3 × 3 pixel portion is solid, (a) shows dots to be recorded, and (b) shows whether dots are recorded on the print data. FIG. 6 is a diagram showing a case where the 4 × 4 pixel portion is solid, (a) shows dots to be recorded, and (b) shows whether dots are recorded on the print data. FIG. 7 is a diagram showing a case where the 8 × 8 pixel portion is solid, (a) shows dots to be recorded, and (b) shows whether dots are recorded on the print data. In FIGS. 4 to 7A, dots to be thinned are indicated by broken lines, and in FIG. 4B to FIG. 7B, target pixels to be thinned are indicated by grid-like hatching.

  As shown in FIG. 4, a case is considered in which dots are recorded in the upper, lower, left, and right pixels β of a certain target pixel α. In this case, since the size of each pixel is 10.58 × 10.58 μm, and the diameter of the dot recorded in each pixel is 21 μm, the dot recorded in the target pixel α and the upper, lower, left, and right pixels β Are overlapped with dots recorded on the left and right, and the target pixel α is filled with dots recorded on the upper, lower, left, and right pixels β. Therefore, by thinning out the dots of the target pixel α, the overlapping of dots at the target pixel α is reduced.

  Similarly, as shown in FIG. 5 to FIG. 7, when the 3 × 3, 4 × 4, and 8 × 8 pixel portions are solid, all the pixels on the top, bottom, left, and right are excluded except for the edge portion pixels. The pixel of interest where dots are recorded is thinned out. Accordingly, it is possible to prevent the ink from overflowing due to overlapping dots while preventing the outline of the image from becoming unclear.

  The I / F controller 15 controls the communication with the ink jet printer 20 to transfer the print data generated by the RIP 12 to the ink jet printer 20.

  As shown in FIG. 1, the inkjet printer 20 is an image recording apparatus that records an image on a recording medium by ejecting ink droplets, and therefore includes a buffer 21, a print mechanism unit 30, and a control device 40. I have.

  The buffer 21 is a temporary storage device that temporarily stores print data transferred from the I / F controller 15 of the workstation 10.

  FIG. 8 is a schematic configuration diagram illustrating a print mechanism unit of the inkjet printer. As shown in FIG. 8, the print mechanism unit 30 mainly includes a flat bed 31 on which the recording medium M is placed, an inkjet head 32 that ejects ink droplets, a carriage 33 on which the inkjet head 32 is mounted, and a carriage 33. And a Y bar 34 that is movably held in the scanning direction S and conveyed in the sub-scanning direction F perpendicular to the main scanning direction S. In the inkjet head 32, a large number of nozzles 35 for ejecting ink droplets are formed at a dot pitch corresponding to 600 dpi. Therefore, by moving the carriage 33 in the main scanning direction S, the ink jet head 32 can be moved in the main scanning direction S with respect to the recording medium M, and by transporting the Y bar 34 in the sub scanning direction F. The inkjet head 32 can be conveyed in the sub-scanning direction F with respect to the recording medium M.

  Then, the print mechanism unit 30 ejects ink droplets from the nozzles 35 while moving the carriage 33 in the main scanning direction S under the control of the control device 40, whereby pixels in the horizontal direction (horizontal direction) in the print data. In addition, by transporting the Y bar 34 by a predetermined width in the sub-scanning direction F, dots can be sequentially recorded on the pixels in the vertical direction (vertical direction) in the print data. Therefore, the left-right direction of the print data corresponds to the main scanning direction S, and the up-down direction of the print data corresponds to the sub-scanning direction F. The print mechanism unit 30 repeats such movement of the carriage 33 in the main scanning direction S and conveyance of the Y bar 34 in the sub-scanning direction F for each pass, thereby performing multi-pass printing with a predetermined number of passes. Images can be recorded on the recording medium M.

  The control device 40 controls the print mechanism unit 30 to record an image of 2400 dpi by 8-pass multi-pass printing. In addition, the control apparatus 40 is comprised mainly by the computer containing CPU, ROM, and RAM, for example. And each control of the control apparatus 40 mentioned later is implement | achieved by reading predetermined computer software on CPU or RAM, and making it operate | move under control of CPU. Therefore, a program for realizing each function of the control device 40 described later is incorporated in this computer software.

  Here, with reference to FIG. 9, the mechanism of multi-pass printing in the present embodiment will be described. FIG. 9 is a diagram for explaining 8-pass multi-pass printing. As shown in FIG. 9, the nozzle pitch of the nozzles 35 formed on the inkjet head 32 is 600 dpi, while the recording resolution of an image recorded on the recording medium M is 2400 dpi. For this reason, the printing resolution is four times the nozzle pitch.

  Therefore, conventionally, a 2400 dpi image is recorded by performing a 4-pass multi-pass recording. That is, dots are recorded on all pixels on the first line of the recording medium M in the first pass, dots are recorded on all pixels on the second line of the recording medium M in the second pass, and recording media are recorded on the third pass. Dots are recorded on all pixels on the third line of M, and dots are recorded on all pixels on the fourth line of the recording medium M in the fourth pass.

  On the other hand, in the present embodiment, a two-dimensional area composed of 4 lines in the vertical direction (vertical direction) corresponding to the sub-scanning direction F × 4 columns in the horizontal direction (horizontal direction) corresponding to the main scanning direction S. 16 pixels are set as one block (unit area) Z, and two pixels adjacent to the left and right are set as one set of pixels, and the number of passes which is the same as the number of pixel sets constituting the block Z, that is, 8-pass multi-pass printing. Print the image with. Then, dots are recorded on each pixel of the block Z sequentially for each pass by the conveyance control of the Y bar 34 and the carriage 33 and the ejection timing control of the ink droplets, so that the recording medium M is recorded. An image with a resolution of 2400 dpi is recorded.

  Therefore, as shown in FIG. 1, in order to enable the recording of such an image, the control device 40 has a mask pattern processing unit 41, a rearrangement processing unit 42, and ink droplets ejected from each nozzle 35. A discharge timing control unit 43 that controls the discharge timing of the Y bar 34, a carriage drive control unit 44 that controls the movement of the carriage 33 in the main scanning direction S, and a conveyance control unit that controls the conveyance of the Y bar 34 in the sub-scanning direction F. 45. As described above, by moving the carriage 33 in the main scanning direction S, the inkjet head 32 can be moved in the main scanning direction S, and by transporting the Y bar 34 in the sub-scanning direction F, inkjet is performed. The head 32 can be transported in the sub-scanning direction F.

  The mask pattern processing unit 41 divides the print data into blocks Z, and based on a predetermined mask pattern, sets the dot recording order of each pixel in each block Z in units of pixels composed of two pixels adjacent to the left and right. It is determined (set). The mask pattern is obtained by registering the dot recording order of each pixel in the block Z, and is stored in advance in a storage device of an ink jet printer. In the present embodiment, the numbers of the divided blocks are sequentially numbered from the first from the rear in the sub-scanning direction F to the front. For this reason, the last block in the sub-scanning direction F is the first block.

  Then, the mask pattern processing unit 41 reads the print data from the buffer 21 and divides the print data into blocks Z, and determines the dot recording order of each pixel in each block Z with reference to the mask pattern stored in the storage device. . Further, the mask pattern processing unit 41 arranges the pixels of the print data in the determined dot recording order.

  Here, the dot recording order registered in the mask pattern will be described with reference to FIG. 10A and 10B are diagrams showing mask patterns, where FIG. 10A shows a pixel group and FIG. 10B shows a dot recording order. As shown in FIG. 10, like the block Z, the mask pattern is 4 lines in the vertical direction (vertical direction) corresponding to the sub-scanning direction F × 4 columns in the horizontal direction (horizontal direction) corresponding to the main scanning direction S. 16 pixels.

  As shown in FIG. 10A, the mask pattern is composed of a total of 16 pixels, 4 pixels in the horizontal direction corresponding to the main scanning direction S and 4 pixels in the vertical direction corresponding to the sub-scanning direction F. Further, in this mask pattern, two pixels adjacent to the left and right constitute a set of pixels. Each pixel group of the mask pattern is divided into four pixel group groups, a first pixel group A, a second pixel group B, a third pixel group C, and a fourth pixel group D. The first pixel set group A is a two-pixel set arranged on the same column at positions spaced apart by one pixel set vertically (left and right apart) without being vertically adjacent to each other diagonally It is a pixel group composed of The second pixel group B is a pixel group composed of two pixel groups arranged on the left and right of the first pixel group A, and the third pixel group C is the first pixel group. It is a pixel group composed of two pixel groups arranged above and below A, and the fourth pixel group D is a pixel group composed of two pixel groups arranged diagonally to the first pixel group It is a group.

  As shown in FIG. 10B, the dot recording order of the mask pattern is an order in which adjacent pixel sets are not continuous on the left and right and top and bottom. More specifically, the dot recording order of the mask pattern is as follows. The first pixel group A is the first rank, the second pixel group B is the second rank, the third pixel group C is the third rank, and the fourth pixel. The group D is in the fourth rank. The dot recording order is the order of the first rank → second rank → third rank → fourth rank. The two pixels in the same pixel group have the same order. The two pixel groups in the same pixel group group have the pixel group arranged below in the previous order and the pixel group arranged in the upper part after. Has become a ranking. That is, 2 pixels in the 1st and 2nd columns of the 1st line are 1st, 2 pixels in the 1st and 2nd columns of the 3rd line are 2nd, 2 pixels in the 3rd and 4th columns of the 1st line are 3rd, 2nd pixel in the 3rd and 3rd rows of the 3rd line is 4th, 2nd pixel in the 1st and 2nd rows of the 2nd line is 5th, 2nd pixel in the 1st and 2nd rows of the 4th line is 6th and 2nd line The second pixel in the third and fourth columns is the seventh, and the second pixel in the third and fourth columns on the fourth line is the eighth.

  Here, with reference to FIG. 11, the effect by making a mask pattern into the dot recording order mentioned above is demonstrated. FIG. 11 is a diagram showing a dot recording state for each pixel group.

  First, as shown in FIG. 11A, when dots are recorded on each pixel group of the first pixel group A, the pixel groups adjacent to the pixel groups of the first pixel group A are diagonally adjacent to each other. In either case, no dot is recorded. For this reason, the dots recorded in each pixel group of the first pixel group A are not pulled by other dots, and the positions are not shifted.

  Next, as shown in FIG. 11B, when dots are recorded in each pixel group of the second pixel group B, dots are already recorded in each pixel group of the first pixel group A. However, since each pixel group of the second pixel group B is sandwiched from each side by each pixel group of the first pixel group A, the dots recorded in each pixel group of the second pixel group B are The dots recorded in each pixel group of the first pixel group A are pulled in a well-balanced manner with a uniform right and left force. For this reason, the dots recorded in each pixel group of the second pixel group B are difficult to shift.

  Next, as shown in FIG. 11C, when dots are recorded on each pixel group of the third pixel group C, dots are already formed on the pixel groups of the first pixel group A and the second pixel group B. Is recorded. However, each pixel group of the third pixel group C is sandwiched from above and below by each pixel group of the first pixel group A, and is obliquely sandwiched by each pixel group of the second pixel group B. Therefore, the dots recorded in each pixel group of the third pixel group C are equal forces from above and below and diagonally by the dots recorded in each pixel group of the first pixel group A and the second pixel group B. It is pulled with good balance. For this reason, the dots recorded in each pixel group of the third pixel group C are difficult to shift.

  Next, as shown in FIG. 11D, when dots are recorded on each pixel group of the fourth pixel group D, the first pixel group A, the second pixel group B, and the third pixel group are already recorded. A dot is recorded in each pixel group of group C. However, each pixel group of the fourth pixel group D is sandwiched obliquely by each pixel group of the first pixel group A, sandwiched from above and below by each pixel group of the second pixel group B, and further the third pixel Since the pixel group of the group C is sandwiched from the left and right, the dots recorded in each pixel group of the fourth pixel group D are the first pixel group A, the second pixel group B, and the third pixel. Each dot recorded in each pixel group of the group C is pulled in a balanced manner from eight directions that are diagonally up, down, left, and right. For this reason, the dots recorded in each pixel group of the fourth pixel group D are difficult to shift.

  The rearrangement processing unit 42 sets the nozzles based on the nozzle arrangement of the nozzles 35 recorded on the inkjet head 32 and the transport schedule in the sub-scanning direction F of the inkjet head 32 (Y bar 34) according to the recording resolution. The pixels arranged in the mask pattern processing unit 41 are rearranged in the order in which ink droplets are ejected from 35, that is, in the order in which dots are actually recorded. The nozzle arrangement and the conveyance schedule of the inkjet head 32 are stored in advance in a storage device of the inkjet printer. Therefore, the rearrangement processing unit 42 calculates the order in which dots are actually recorded by referring to the nozzle arrangement stored in the storage device and the conveyance schedule of the inkjet head 32 corresponding to the resolution of 2400 dpi. The pixels of the print data are rearranged in the order in which they are performed.

  Here, with reference to FIG. 12 and FIG. 13, the conveyance schedule and the dot recording position of the inkjet head 32 in the sub-scanning direction F will be specifically described.

  FIG. 12 is a diagram showing the relationship between the nozzle arrangement and the recording pixels. As shown in FIG. 12, 1260 nozzles 35 are recorded on the inkjet head 32 at a nozzle pitch of 600 dpi. Since each nozzle 35 records dots on four lines of pixels, the recording width of the inkjet head 32 is 5040 lines. In the present embodiment, the nozzle numbers of the nozzles 35 are numbered 1 to 1260 in order from the front to the rear in the sub-scanning direction F.

  FIG. 13 is a diagram showing a conveyance schedule of the inkjet head. As shown in FIG. 13, the conveyance schedule of the inkjet head 32 (Y bar 34) is represented by the feed amount in the sub-scanning direction F between each pass. This feed amount is also referred to as a transport amount. Specifically, as will be described later, the conveyance schedule is such that dots are recorded by only one nozzle 35 in the first pass, and the pass width formed by about 158 nozzles 35 in the second and subsequent passes. The dot is recorded sequentially. For this reason, the transport schedule is 630 lines for the first to third passes, 631 lines for the fourth pass, 630 lines for the fifth to seventh passes, and 629 lines for the eighth pass. The transport and transport amount in the first pass mean transport performed between the first pass and the second pass and the transport amount, and the same applies to the second pass to the eighth pass.

  Next, the processing operation of the printer system 1 will be described with reference to FIG. FIG. 14 is a sequence diagram showing processing operations in the printer system.

  As shown in FIG. 14, first, in the workstation 10, the drawing application 11 generates PostScript data based on an operation input from the user (step S1).

  Next, in the workstation 10, the RIP 12 performs AM halftone processing of the PostScript data generated in step S1 (step S2). In this AM halftone processing, PostScript data is analyzed and imaged to generate AM halftone data of AM halftone data. The generated AM halftone dot data is converted into 1-bit TIFF format print data.

  Next, in the workstation 10, the edge correction unit 13 performs edge correction processing of the AM halftone data generated in step S2 (step S3). As described above, the edge correction processing is performed by detecting edge pixels corresponding to the edges of the image and correcting the dots of the edge pixels. The edge correction may be performed by deleting both edges, deleting one edge (with or without), and deleting one edge, and the edge may be corrected by any method. Here, an example of edge correction processing will be described with reference to FIG.

  FIG. 15 is a flowchart illustrating an example of edge correction processing by the edge correction unit. As shown in FIG. 15, first, the edge correction unit 13 specifies a target pixel when starting the processing (step S <b> 301). In FIG. 15, Y indicates a position in the sub-scanning direction F, and X indicates a position in the main scanning direction S.

  Next, the edge correction unit 13 samples 8 pixels in the main scanning direction S (line direction) on the basis of 3 pixels of the target pixel, the pixel one line before the target pixel, and the pixel one line after the target pixel. (Step S302). Note that the sampling pixel corresponding to the target pixel is Y0, the sampling pixel corresponding to the pixel one line before the target pixel is Y-1, and the sampling pixel corresponding to the pixel one line after the target pixel is Y + 1.

  Next, the edge correction unit 13 performs AND (logical product) for each pixel of Y0 and Y-1, and stores the calculation result in & Y1 (step S303). Similarly, the edge correction unit 13 performs AND (logical product) for each pixel of Y0 and Y + 1, and stores the calculation result in & Y2 (step S304). Then, the edge correction unit 13 performs AND (logical product) for each pixel of & Y1 and & Y2, and stores the calculation result in & Y (step S305).

  Next, the edge correction unit 13 samples 8 pixels in the sub-scanning direction F (column direction) on the basis of 3 pixels of the target pixel, the pixel one column before the target pixel, and the pixel one column after the target pixel. (Step S306). Note that the sampling pixel corresponding to the target pixel is X0, the sampling pixel corresponding to the pixel one column before the target pixel is X-1, and the sampling pixel corresponding to the pixel one column after the target pixel is X + 1.

  Next, the edge correction unit 13 performs an AND (logical product) for each pixel of X0 and X-1, and stores the calculation result in & X1 (step S307). Similarly, the edge correction unit 13 performs AND (logical product) for each pixel of X0 and X + 1, and stores the calculation result in & X2 (step S308). Then, the edge correction unit 13 performs AND (logical product) for each pixel of & X1 and & X2, and stores the calculation result in & X (step S309).

  Next, the edge correction unit 13 determines whether the edge correction is deletion of both edges (step S310). Note that the determination in step S310 may be performed by a user operation input, or may be performed based on preset information.

  If it is determined in step S310 that the edge correction is deletion of both edges (step S310: YES), the edge correction unit 13 performs AND (logical product) for each pixel of & Y and & X, and stores the calculation result in & 1. (Step S311). And this & 1 is stored as a processing result, and it progresses to step S316 mentioned later.

  If it is determined in step S310 that the edge correction is not the deletion of both edges (step S310: NO), the edge correction unit 13 determines whether the edge correction is a one-edge deletion (no → present) (step S312). Note that the determination in step S312 may be performed by a user operation input, or may be performed based on preset information.

  If it is determined in step S312 that the edge correction is single-edge deletion (no → present) (step S312: YES), the edge correction unit 13 performs AND (logical product) for each pixel of & Y1 and & X1, and the calculation result Is stored in & 1 (step S313). And this & 1 is stored as a processing result, and it progresses to step S316 mentioned later.

  If it is determined in step S312 that the edge correction is not one-edge deletion (none → present) (step S312: NO), the edge correction unit 13 determines whether the edge correction is one-edge deletion (present → none). (Step S314). Note that the determination in step S314 may be performed by a user operation input, or may be performed based on preset information.

  If it is determined in step S314 that the edge correction is single-edge deletion (yes → no) (step S314: YES), the edge correction unit 13 performs AND (logical product) for each pixel of & Y2 and & X2, and the calculation result Is stored in & 2 (step S315). And this & 1 is stored as a processing result, and it progresses to step S316 mentioned later.

  If it is determined in step S314 that the edge correction is not single-edge deletion (yes → no) (step S314: NO), the edge correction unit 13 proceeds to step S316 without performing any processing.

  When the above processing is completed, the edge correction unit 13 moves the target pixel horizontally by one column (step S316).

  Then, the edge correction unit 13 determines whether or not one line has been completed (step S317). If it is determined that one line has not been completed (step S317: NO), the process returns to step S302, and the processing described above again. I do.

  On the other hand, if it is determined that one line has been completed (step S317: YES), the edge correction unit 13 moves the pixel of interest down one row (step S318).

  Then, the edge correction unit 13 determines whether or not all lines have been completed (step S319). If it is determined that all lines have not ended (step S319: NO), the process returns to step S301, and the above-described processing is performed again. I do.

  On the other hand, if it is determined that all lines have been completed (step S319: YES), the edge correction unit 13 ends the edge correction process.

  When the edge correction processing is completed in this way, next, in the workstation 10, the thinning processing unit 14 performs the thinning processing, and thins out dots in the solid portion of the AM halftone data subjected to edge correction in step S3. This thinning process is to delete the dots of the target pixel when it is determined that the dots are recorded in the upper, lower, left, and right four pixels of the target pixel, but any method can be used as long as the dots in the solid portion can be thinned out. A thinning process may be performed. Here, an example of the thinning process will be described with reference to FIG.

  FIG. 16 is a flowchart illustrating an example of the thinning process by the thinning processing unit. As shown in FIG. 16, first, the thinning-out processing unit 14 designates a target pixel when starting the processing (step S401).

  Next, the thinning processing unit 14 cuts out a 3 × 3 pixel region centered on the target pixel (step S402), and determines whether or not to record dots on the left, right, upper and lower pixels of the target pixel (step S402). S403).

  If it is determined in step S403 that dots are not recorded in at least one pixel on the left, right, top, and bottom of the target pixel (step S403: NO), the thinning processing unit 14 proceeds to step S406 without performing thinning.

  If it is determined in step S403 that dots are recorded in all the pixels on the left, right, top, and bottom of the target pixel (step S403: YES), the thinning processing unit 14 deletes the dot of the target pixel (step S405).

  Next, the thinning processing unit 14 moves the target pixel horizontally by one column (step S406).

  Then, the thinning processing unit 14 determines whether or not one line has been completed (step S407). If it is determined that one line has not been completed (step S407: NO), the process returns to step S402 and is again described above. Process.

  On the other hand, if it is determined that one line has been completed (step S407: YES), the thinning-out processing unit 14 moves the pixel of interest down one row (step S408).

  Then, the thinning processing unit 14 determines whether or not all lines have been completed (step S409), and if it is determined that all lines have not ended (step S409: NO), the process returns to step S402 and is again described above. Process.

  On the other hand, if it is determined that all lines have been completed (step S402: YES), the thinning processing unit 14 ends the thinning processing.

  In the above description, step S2 and steps S3 and S4 are described separately. However, in actuality, steps S3 and S4 are performed when step S2 is processed. That is, when AM halftone dot data is created based on PostScript data, first, edge correction processing and thinning processing are performed, and then print data is generated.

  Next, the I / F controller 15 of the workstation 10 performs a transfer process for transferring the print data to the inkjet printer 20 (step S15).

  The print data transferred from the workstation 10 to the inkjet printer 20 in this way is temporarily stored in the buffer 21 of the inkjet printer 20.

  Next, in the inkjet printer 20, the mask pattern processing unit 41 performs mask pattern processing, and determines the dot recording order for each block Z in the print data (step S5). In the mask pattern processing, as described above, first, the print data stored in the buffer 21 is read, and the read print data is divided into blocks Z. Then, with reference to a mask pattern (see FIG. 10) stored in a storage device or the like, the dot recording order of each pixel is determined for each block Z in units of pixel groups composed of two pixels adjacent to the left and right. The pixels of the print data are arranged in the determined dot recording order.

  Next, in the inkjet printer 20, the rearrangement processing unit 42 performs the rearrangement process, referring to the conveyance schedule of the inkjet head 32 and the nozzle arrangement of the inkjet head 32 according to the recording resolution stored in the storage device. The pixels of the print data arranged in step S5 are rearranged in the order in which dots are actually recorded. (Step S6). That is, in step S6, the rearrangement process is performed, so that the inkjet printer 20 is determined in step S5 for each pass by the 8-pass multi-pass printing in which the inkjet head 32 is conveyed in the sub-scanning direction F for each pass. In this order, dots can be recorded on each pixel.

  Next, in the inkjet printer 20, the ejection timing control unit 43, the carriage drive control unit 44, and the conveyance control unit 45 control the print mechanism unit 30 to form a 2400 dpi image on the recording medium M (step S7). In step S <b> 7, the carriage drive control unit 44 controls the movement of the carriage 33 in the main scanning direction S based on the print data in which the pixels are rearranged in step S <b> 6, and the ejection timing control unit 43 controls the ink jet head 32. The ejection control of the ink droplets ejected from each nozzle 35 is performed, and the conveyance control unit 45 performs the conveyance control of the Y bar 34 in the sub-scanning direction F. As a result, for each pass, the inkjet head 32 (Y bar 34) is conveyed in the sub-scanning direction F by the line shown in FIG. 13, and the ink liquid is ejected from each nozzle when the carriage 33 moves in the main scanning direction S. By ejecting the droplets, dots are sequentially recorded on the pixels of each block Z.

  Here, the relationship between the inkjet head 32 and the dot recording position in each pass will be described with reference to FIGS. FIG. 17 is a diagram illustrating the relationship between the transport position of the inkjet head and the dot recording position in the first pass, and FIG. 18 is a diagram illustrating the relationship between the transport position of the inkjet head and the dot recording position in the second pass. 19 is a diagram showing the relationship between the transport position of the inkjet head and the dot recording position in the third pass, FIG. 20 is a diagram showing the relationship between the transport position of the inkjet head and the dot recording position in the fourth pass, 21 is a diagram showing the relationship between the ink jet head transport position and the dot recording position in the fifth pass, and FIG. 22 is a diagram showing the relationship between the ink jet head transport position and the dot recording position in the sixth pass. FIG. 23 shows the relationship between the ink jet head transport position and the dot recording position in the eighth pass, and FIG. 24 shows the relationship in the ninth pass. That is a graph showing a relationship between a transport position and the dot recording position of the inkjet head.

  As shown in FIG. 17, when scanning the first pass, the first nozzle is associated with the first line of the first block by the conveyance control of the Y bar 34 in the sub-scanning direction F. Therefore, in the first pass, the ink jet head 32 (carriage 33) is moved in the main scanning direction S, and when the first nozzle comes to the first and second rows of the first block, the ink liquid from the first nozzle By ejecting the droplets, dots are recorded in the two pixels having the first dot recording number in the first block. Then, by controlling the Y bar 34 in the sub-scanning direction F, the inkjet head 32 is transported in the sub-scanning direction F by 630 lines (157 + 1/2 blocks), so that the 1st nozzle to the 158th nozzle are in the 158th block. -Corresponds to the third line of the first block.

  As shown in FIG. 18, in the second pass, the first nozzle to the 158th nozzle are associated with the third line of the 158th block to the first block, respectively. Therefore, in the second pass, the inkjet head 32 (carriage 33) is moved in the main scanning direction S, and the first nozzle to the 158th nozzle come to the first and second rows of the 158th block to the first block. Sometimes, by ejecting ink droplets from the 1st nozzle to the 158th nozzle, dots are recorded on the 2 pixels having the 2nd dot recording number in the 158th block to the 1st block. Thereby, in the first block, dots are recorded in the four pixels having the dot recording numbers No. 1 and No. 2, and in the second to 158th blocks, the dots are recorded in the two pixels having the dot recording number No. 2. Is done. Then, by controlling the Y bar 34 in the sub-scanning direction F, the inkjet head 32 is transported in the sub-scanning direction F by 630 lines (157 + 1/2 blocks), so that the 1st nozzle to the 316th nozzle are each in the 316th block. -Corresponds to the first line of the first block.

  As shown in FIG. 19, in the third pass, the first nozzle to the 316th nozzle are associated with the first line of the 316th block to the first block, respectively. For this reason, in the third pass, the inkjet head 32 (carriage 33) is moved in the main scanning direction S, and the nozzles No. 1 to No. 316 have come to the third and fourth rows of the 316th block to the first block. Sometimes, by ejecting ink droplets from the No. 1 nozzle to the No. 316 nozzle, dots are recorded on the pixels having the No. 3 dot recording number in the No. 316 block to the No. 1 block. Thereby, in the first block, dots are recorded in the 6 pixels having the dot recording numbers 1 to 3, and in the 2nd to 158 blocks, the dot recording numbers are the 4 pixels having the 2nd and 3rd dot recording numbers. Dots are recorded. The Y-bar 34 is transported in the sub-scanning direction F to transport the inkjet head 32 in the sub-scanning direction F for 630 lines (157 + 1/2 blocks). -Corresponds to the third line of the first block.

  As shown in FIG. 20, in the fourth pass, the first nozzle to the 473th nozzle are associated with the third line of the 473th block to the first block, respectively. Therefore, in the fourth pass, the inkjet head 32 (carriage 33) is moved in the main scanning direction S, and the first nozzle to the 473th nozzle come to the third and fourth rows of the 473th block to the first block. Sometimes, ink droplets are ejected from the No. 1 nozzle to the No. 473 nozzle, whereby dots are recorded in the pixels having the No. 473 dot recording number in the No. 473 block to the No. 1 block. Thereby, in the first block, dots are recorded in 8 pixels having dot recording numbers 1 to 4, and in the second block to 158 blocks, dots are recorded in 6 pixels having dot recording numbers 2 to 4. Is recorded. Then, by carrying the Y bar 34 in the sub-scanning direction F, the inkjet head 32 is carried in the 631 line (157 + 3/4 block) sub-scanning direction F, so that the 1st nozzle to the 631th nozzle are each in the 631th block. -Corresponds to the second line of the first block.

  As shown in FIG. 21, in the 5th pass, the 1st nozzle to the 631th nozzle are associated with the second line of the 631th block to the 1st block, respectively. Therefore, in the fifth pass, the inkjet head 32 (carriage 33) is moved in the main scanning direction S, and the first nozzle to the sixth nozzle come to the first and second rows of the 631th block to the first block. Sometimes, by ejecting ink droplets from the No. 1 nozzle to No. 631 nozzle, dots are recorded in the pixels having the No. 5 dot recording number in the 631th block to the 1st block. As a result, in the first block, dots are recorded in 10 pixels having dot recording numbers 1 to 5, and in the second block to 158 blocks, dots are recorded in 8 pixels having dot recording numbers 2 to 5. Is recorded. The Y-bar 34 is transported in the sub-scanning direction F so that the inkjet head 32 is transported in the sub-scanning direction F for 630 lines (157 + 1/2 blocks), so that the 1st nozzle to the 788th nozzle are in the 788th block. -Corresponds to the 4th line of the first block.

  As shown in FIG. 22, in the sixth pass, the 1st nozzle to the 788th nozzle are associated with the 4th line of the 788th block to the 1st block, respectively. For this reason, in the 6th pass, the inkjet head 32 (carriage 33) is moved in the main scanning direction S, and the 1st nozzle to the 788th nozzle come to the 1st and 2nd rows of the 788th block to the 1st block. Sometimes, ink droplets are ejected from the No. 1 nozzle to the No. 788 nozzle, whereby dots are recorded in the pixels having the No. 6 dot recording number in the No. 788 block to the No. 1 block. Thereby, in the first block, dots are recorded in 12 pixels having dot recording numbers 1 to 6, and in the second block to 158 blocks, dots are recorded in 10 pixels having dot recording numbers 2 to 6. Is recorded. Then, by controlling the Y bar 34 in the sub-scanning direction F, the inkjet head 32 is conveyed in the sub-scanning direction F by 630 lines (157 + 1/2 blocks), so that the 1st nozzle to the 946th nozzle are respectively in the 946th block. -Corresponds to the second line of the first block.

  As shown in FIG. 23, in the 8th pass, the 1st nozzle to the 1103rd nozzle are associated with the 4th line of the 1103th block to the 1st block, respectively. For this reason, in the 8th pass, the inkjet head 32 (carriage 33) is moved in the main scanning direction S, and the 1st nozzle to the 1103rd nozzle come to the 3rd and 4th rows of the 1103th block to the 1st block. Sometimes, ink droplets are ejected from the No. 1 nozzle to No. 1103 nozzle, whereby dots are recorded in the pixels having the dot recording numbers of No. 8 in the 1103rd block to the first block. As a result, dots are recorded in 16 pixels with dot recording numbers 1 to 8 in the first block, and dots are recorded in 14 pixels with dot recording numbers 2 to 8 in the second block to 158 blocks. Is recorded. The Y-bar 34 is transported in the sub-scanning direction F so that the inkjet head 32 is transported in the 629 line (157 + 1/4 block) sub-scanning direction F, so that the 1st nozzle to the 1260th nozzle are each in the 1261th block. -Corresponds to the first line of the second block.

  As shown in FIG. 24, in the 9th pass, the 1st nozzle to the 1260th nozzle are associated with the first line of the 1261st block to the 2nd block, respectively. For this reason, in the 9th pass, the inkjet head 32 (carriage 33) is moved in the main scanning direction S, and the 1st nozzle to the 1260th nozzle come to the 1st and 2nd rows of the 1261st block to the 2nd block. Sometimes, ink droplets are ejected from the No. 1 nozzle to No. 1260 nozzle, whereby dots are recorded in the pixels with the No. 1 dot recording number in the 1261st block to the 2nd block. As a result, in the second to 158th blocks, dots are recorded in 16 pixels having dot recording numbers 1 to 8. The Y-bar 34 is transported in the sub-scanning direction F so that the inkjet head 32 is transported in the sub-scanning direction F by 630 lines (157 + 1/2 blocks). -Corresponds to the 3rd line of the 159th block.

  Hereinafter, dots are sequentially recorded. When dots are recorded while the inkjet head 32 is conveyed in the sub-scanning direction F for each pass in this way, the order in which dots are recorded is changed for each block.

  FIG. 25 is a diagram showing the dot recording order in each block. As shown in FIG. 25, in the first block, dots are recorded from the two pixels (pixel set) having the first dot recording order, whereas in the second block to the 158th block, the dot recording order is the second. In the 159th to 316th blocks, dots are recorded from the second pixel (pixel set) having the third dot recording order. Further, in the 947th block to the 1103th block, dots are recorded from the pixel of the eighth dot recording order, and when the next 1104th block to the 1261st block are reached, the first two pixels (pixel group) of the dot recording order. Dots are recorded.

  Thus, when the inkjet head 32 is conveyed in the sub-scanning direction F for each pass, the dot recording start pixel changes for each block, but instead of recording dots continuously for each predetermined line as in the prior art, Overall, the dot recording order is non-uniform. For this reason, it is possible to prevent the dots recorded in each pixel from being regularly pulled in one direction, and to suppress the occurrence of banding.

  As described above, according to the printer system 1 according to the present embodiment, the block Z is configured by 16 pixels of 4 pixels in the horizontal direction corresponding to the main scanning direction S and 4 pixels in the vertical direction corresponding to the sub-scanning direction F. Since the dot recording order of each pixel in the print data is set every time, the dot recording order can be set two-dimensionally left and right and up and down. Then, since the dot recording order is set in units of pixel groups composed of two pixels that are adjacent to each other on the left and right or top and bottom, the image recording speed can be increased. In addition, by setting the dot recording order without consecutive pixel groups adjacent in the horizontal direction and the vertical direction, it is possible to prevent the dots from being regularly pulled in one direction for each block Z. The occurrence of banding can be suppressed.

  Then, by deleting the dots of the pixel of interest where the four pixels on the top, bottom, left, and right record the dots, so-called solid coating dots are thinned out, so that it is possible to prevent the dots from overlapping and overflowing. Moreover, as described above, in each pixel set, dots are recorded in the same order in two pixels that are adjacent to the left and right or up and down, so by thinning out dots in this way, even in the same pixel set, it is simultaneously applied to adjacent pixels. Dots can be prevented from being recorded. This will be specifically described with reference to FIG. 26A and 26B are diagrams for explaining the effect of the thinning process in the solid coating portion. FIG. 26A shows a case where the thinning process is not performed, and FIG. 26B shows a case where the thinning process is performed. As shown in FIG. 26 (a), if the thinning process is not performed in the solid coating portion, dots are not attracted to each other between the pixel groups because dots are simultaneously recorded in the two pixels constituting each pixel group. Dots constituting the pixel group are attracted to each other. On the other hand, as shown in FIG. 26B, when the thinning process is performed in the solid coating portion, no dot is recorded in one of the two pixels constituting each pixel set. It is possible to prevent the dots from attracting each other. For this reason, generation | occurrence | production of banding can be suppressed more effectively.

  Also, assuming that the first pixel group A, which is composed of two pixel groups that are spaced apart by one pixel group in the up, down, left, and right directions, is the first rank, when dots are recorded in the first pixel group, they are still adjacent in the up, down, left, and right directions. Since no dot is recorded in the pixel group, the dot can be recorded in each pixel group of the first pixel group group without being pulled by other dots. Since the remaining pixel groups are pixel groups sandwiched between the first pixel group A, the dots recorded in the first pixel group A pull the dots recorded in the remaining pixel groups at least from both directions. As a result, the positions of dots recorded in the remaining pixel groups can be held. Thus, by recording dots in the first pixel set group A as the first order, the dots recorded in the first pixel set group are kept at the positions of the dots recorded in the remaining pixel sets. It can function as an anchor.

  Further, since the second pixel group B and the third pixel group C that are in the second or third order are sandwiched between the first pixel group A and the left and right or top and bottom, the second pixel group B and the third pixel group C The dots recorded in the pixel group C are pulled in a balanced manner from the left and right or the top and bottom by the dots recorded in the first pixel group A that functions as an anchor. Thereby, it can suppress that the position of the dot recorded on the 2nd pixel group B and the 3rd pixel group C shifts. Furthermore, the fourth pixel group D, which is the fourth rank, is sandwiched between the first pixel group A and the top and bottom and left and right sides of the second pixel group B and the third pixel group C. The dots recorded in the fourth pixel group D are equal in force from eight directions diagonally up and down by the dots recorded in the first pixel group A, the second pixel group B, and the third pixel group C. Pulled in good balance. Thereby, it is possible to prevent the positions of the dots recorded in the fourth pixel set group D from shifting.

  Then, by performing multi-pass printing of 8 passes, which is the same as the number of pixel sets constituting the block Z, it is possible to appropriately suppress the occurrence of banding while increasing the speed of image recording.

  In addition, if the inkjet head 32 is conveyed in the sub-scanning direction F for each pass and dots are recorded by different nozzles 35 for each pixel set, the dot recording start pixel set in the dot recording order varies depending on the pass position. Since the line position of the image set recorded by the inkjet head 32 changes for each pass, the joint of the inkjet head 32 can be made inconspicuous.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, in the above-described embodiment, the mask pattern process and the rearrangement process are described as being performed by the control device 40 (the mask pattern processing unit 41 and the rearrangement process unit 42) of the inkjet printer 20, but are performed by the workstation 10. It is also good. In this case, the mask pattern process and the rearrangement process may be performed in the RIP 12.

  In the above embodiment, the inkjet head 32 is transported in the sub-scanning direction F for each pass, and the dots are recorded by the different nozzles 35 in each pixel set of the same block Z. However, for example, the same block The dots may be recorded by the same nozzle 35 on all the pixel groups of Z. In this way, by recording dots with the same nozzle 35 on all the pixel groups of the same block Z, dots are recorded from the first pixel group in the dot recording order determined by the mask pattern processing unit 41 in all the blocks Z. Can be recorded.

  In the above-described embodiment, the Y bar 34 (inkjet head 32) is transported in the sub-scanning direction F, so that the inkjet head 32 and the recording medium M are relatively moved in the sub-scanning direction F. The inkjet head 32 and the recording medium M may be relatively moved in the sub-scanning direction F by conveying the recording medium M in the sub-scanning direction F.

  In the above embodiment, the mask pattern and each block are described as being configured by 4 × 4 pixels. However, any pattern may be used as long as it is configured by even (line) × even (column) pixels. It may be a configuration. For example, in addition to 2 × 2 and 6 × 6, the pixel direction may be composed of different numbers of pixels such as 4 × 8 in the line direction and the column direction.

  Further, in the above-described embodiment, the description has been given on the assumption that two pixels constitute one set of pixels. However, as long as pixels are adjacent to each other on the left and right or top and bottom, one set of pixels may be formed by three or more pixels. good. However, when the dots are thinned out by the thinning process, it is preferable that the number of pixels constituting the pixel group is an even number so that the dots are not adjacent between the adjacent pixel groups.

  Moreover, although the said embodiment demonstrated as what each pixel group which comprises the 1st pixel group A is arrange | positioned on the same column, it is good also as what is arrange | positioned on another column. For example, as shown in FIG. 27, a pixel set composed of two pixels in the first and second columns of the first line, and a pixel composed of two pixels in the third and fourth columns of the third line. The group may be the first pixel group A. In this case, the second pixel group B is composed of a pixel group composed of two pixels in the third and fourth columns of the first line and two pixels in the first and second columns of the third line. And a pixel group. The third pixel group C is composed of a pixel group composed of two pixels in the first and second columns of the second line and two pixels in the third and fourth columns of the fourth line. It consists of a pixel set. The fourth pixel group D is composed of a pixel group composed of two pixels in the third and fourth columns of the second line and two pixels in the first and second columns of the fourth line. It consists of a pixel set.

  DESCRIPTION OF SYMBOLS 1 ... Printer system (image recording device), 10 ... Workstation, 11 ... Drawing application, 12 ... RIP, 13 ... Edge correction part, 14 ... Thinning process part (thinning part), 15 ... I / F controller, 20 DESCRIPTION OF SYMBOLS ... Inkjet printer, 21 ... Buffer, 30 ... Print mechanism part (dot recording part), 31 ... Flat bed, 32 ... Inkjet head, 33 ... Carriage, 34 ... Y bar, 35 ... Nozzle, 40 ... Control device, 41 ... Mask Pattern processing unit (dot recording order setting unit) 42. Rearrangement processing unit (dot recording unit) 43 43 Ejection timing control unit 44 Carriage drive control unit 45 Transport control unit A First pixel group , B ... second pixel group, C ... third pixel group, D ... fourth pixel group, S ... main scanning direction, F ... sub-scanning direction, M ... recording medium, Z ... Click (unit area), α ... pixel of interest.

Claims (12)

Using an inkjet printer equipped with an inkjet head having a plurality of nozzles, ink droplets are ejected from the nozzle while moving the inkjet head and the recording medium in the main scanning direction, and the main scanning direction An image recording method of recording an image on the recording medium by multi-pass recording by relatively moving the inkjet head and the recording medium in a sub-scanning direction orthogonal to
Print data in which dot recording presence / absence is set for each pixel of the AM halftone dot divided into the recording resolution is acquired, and a plurality of pixels in the horizontal direction corresponding to the main scanning direction and a plurality of pixels in the vertical direction corresponding to the sub scanning direction are obtained. For each unit area that is configured, a pixel set unit composed of two or more pixels that are adjacent in the left-right or up-down direction, and a dot of each pixel in the print data without consecutive pixel sets adjacent in the left-right direction and the up-down direction. Dot recording order setting step to set the recording order,
I have a,
In the dot recording order setting step, a first pixel group group composed of one or a plurality of pixel groups that are spaced apart from each other by one pixel group in the vertical and horizontal directions among the pixel groups of each unit region is defined in the dot recording order. An image recording method that ranks first . 2. The image recording method according to claim 1, further comprising: a thinning-out step of deleting the dots of the pixel of interest when dots of four pixels on the top, bottom, left, and right of the pixel of interest are recorded. The dot recording order setting step includes a second image pixel group composed of one or a plurality of pixel groups arranged on the left and right sides of the first pixel group, and 1 arranged above and below the first pixel group. Alternatively, any one of the third pixel set groups constituted by a plurality of pixel sets is set as the second order in the dot recording order, and any one of the second pixel set group and the third pixel set group is set in the dot recording order. 3. The fourth order according to claim 1, wherein a fourth order is a fourth order in the dot recording order, wherein the fourth order is a third order, and the fourth pixel group composed of one or a plurality of pixel sets arranged obliquely of the first pixel group. Image recording method. As multi-pass printing with the same number of passes as the number of pixel sets constituting the unit area, a dot recording step of sequentially recording dots on the pixels of each pixel set for each pass in the order set in the dot recording order setting step further comprising an image recording method according to any one of claims 1-3. 5. The image recording method according to claim 4 , wherein in the dot recording step, the inkjet head is transported in the sub-scanning direction for each pass, and dots are recorded by the different nozzles for each pixel group in the same unit area. The image recording method according to claim 4 , wherein in the dot recording step, dots are recorded by the same nozzle on each pixel group of the same unit region. Using an inkjet printer equipped with an inkjet head having a plurality of nozzles, ink droplets are ejected from the nozzle while moving the inkjet head and the recording medium in the main scanning direction, and the main scanning direction An image recording apparatus that records an image on the recording medium by multi-pass recording by relatively moving the inkjet head and the recording medium in a sub-scanning direction orthogonal to
Print data in which dot recording presence / absence is set for each pixel of the AM halftone dot divided into the recording resolution is acquired, and a plurality of pixels in the horizontal direction corresponding to the main scanning direction and a plurality of pixels in the vertical direction corresponding to the sub scanning direction are obtained. For each unit area that is configured, a pixel set unit composed of two or more pixels that are adjacent in the left-right or up-down direction, and a dot of each pixel in the print data without consecutive pixel sets adjacent in the left-right direction and the up-down direction. Dot recording order setting section for setting the recording order,
I have a,
The dot recording order setting unit sets a first pixel group group composed of one or a plurality of pixel groups that are spaced apart from each other by one pixel group in the upper, lower, left, and right directions among the pixel groups of each unit region. An image recording apparatus that is ranked first . The image recording apparatus according to claim 7 , further comprising: a thinning-out unit that deletes the dots of the pixel of interest when the dots of four pixels on the top, bottom, left, and right of the pixel of interest are recorded. The dot recording order setting unit includes a second pixel group composed of one or a plurality of pixel groups arranged on the left and right of the first pixel group group, and one or more arranged above and below the first pixel group group. Either one of the third pixel group composed of a plurality of pixel groups is set as the second order in the dot recording order, and one of the second pixel group and the third pixel group is set as the second order in the dot recording order. a three-order and fourth order in dot recording order of the fourth pixel pair group consisting in one or more sets of pixels are arranged diagonally of the first pixel set groups, according to claim 7 or 8 Image recording device. As a multi-pass printing with the same number of passes as the number of pixel sets constituting the unit area, a dot recording unit that records dots on the pixels of each pixel group sequentially for each pass in the order set by the dot recording order setting unit The image recording apparatus according to claim 7 , further comprising: The image recording apparatus according to claim 10 , wherein the dot recording unit conveys the inkjet head in a sub-scanning direction for each pass, and records dots with the nozzles that are different for each pixel group in the same unit area. The image recording apparatus according to claim 10 , wherein the dot recording unit records dots with the same nozzle in each pixel in the same unit area.