JP2018192644A - Recording apparatus and recording method - Google Patents

Abstract

To enable high-speed recording while inhibiting color unevenness of an image from being caused by the order of application of different inks to a recording medium.SOLUTION: A recording apparatus includes determination means for determining whether the previous scanning direction and the next scanning direction are set identical with each other or first and second scanning directions are set opposite to each other, in recording in a predetermined area, on the basis of shape information indicating an image shape formed in the predetermined area, and control means for controlling a recording head and scanning means so that the recording can be performed in the predetermined area according to determination.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a recording apparatus and a recording method.

  In general, an ink jet recording apparatus includes a carriage on which recording means (recording head) and an ink tank are mounted, a transport means for transporting a recording medium, and a control means for controlling them. A recording head that ejects ink droplets from a plurality of nozzles is serially scanned in the direction (main scanning direction) orthogonal to the conveyance direction (sub-scanning direction) of the recording paper, while the recording medium is recorded in the recording width during non-recording. Is intermittently conveyed by the same amount. This recording method performs recording by ejecting ink onto a recording sheet in accordance with a recording signal, and is widely used as a quiet recording method at a low running cost. In addition, many products using a plurality of colors of ink and applied to a color recording apparatus have been put into practical use.

  In recent years, recording speed has been increased in the ink jet recording method. If a head in which the heads of black and three colors (cyan, magenta, and yellow) to be used are arranged in the main scanning direction is used as the recording head, ink of all colors used in one scan can be ejected, and high-speed recording is performed. Convenient above. Furthermore, if an image is formed by alternately repeating the forward scanning and the backward scanning of the recording head, it is possible to further increase the speed. However, when a so-called secondary color such as blue is formed, for example, cyan and magenta are given in the forward scan, and magenta and cyan are given in the reverse scan. In this case, the blue color obtained due to the difference in the ink application order also appears, and there is a concern that color unevenness may occur in an image in which an area recorded in the forward scan and an area recorded in the backward scan are mixed. Is done. For this problem, there is a similar concern not only in the method of recording in a unit area by a single scan but also in the case of recording by a plurality of scans.

  In order to solve such a problem, the method described in Patent Document 1 acquires an index value for occurrence of color unevenness from the mixed state of ink in a predetermined area, and when the index value is larger than a threshold value, scanning is performed. A method for limiting the direction to a predetermined direction is disclosed. On the other hand, if the index value is not larger than the threshold value, printing is performed by scanning in the same direction as the previous scanning direction.

JP 2002-248798 A

  In this method, an index value for occurrence of color unevenness is obtained from the amount of ink applied.According to the inventor's study, the degree of color unevenness due to the ink application order is determined by the shape of the image to be formed. I know that it depends. In the method of Patent Document 1, for example, when the amount of ink applied is the same, a pattern in which white lines and white with high density such as hatching patterns are alternately arranged and a uniform halftone image are used. The scanning direction cannot be determined in a distinct manner. For this reason, in the method of Patent Document 1, even if it is not necessary to align the scanning direction depending on the shape of the image, it is assumed that printing is performed by scanning in the same direction, which hinders high-speed recording.

  The present invention has been made in view of the above, and an object of the present invention is to enable high-speed recording while suppressing occurrence of color unevenness in an image due to the order in which different inks are applied to a recording medium.

  The present invention provides a recording head comprising a first nozzle row for ejecting a first ink and a second nozzle row for ejecting a second ink having a different color from the first ink; A scanning unit that scans the recording head in a predetermined scanning direction; and a conveyance unit that conveys the recording medium in a conveyance direction that intersects the scanning direction. The first nozzle row and the second nozzle row Includes nozzles that discharge ink arranged in the scanning direction and in a direction intersecting the scanning direction, and alternately scanning the recording head by the scanning unit and conveying the recording medium by the conveying unit. A recording apparatus for recording an image on the recording medium, the first ink and the second ink being applied to record the image on a recording medium based on image data representing the image Appendices Based on the quantity information, a partial color difference caused by the scanning direction in the image to be recorded between the previous scanning of the recording head and the next scanning of the previous scanning is suppressed according to the applied amount. In accordance with the fact that the previous scanning and the next scanning are determined to have the same scanning direction, the shape information relating to the shape of the image to be recorded on the recording medium indicates a line drawing, Determining means for determining that the scanning direction is reversed between the previous scanning and the next scanning; and a control means for controlling the recording head and the scanning means to perform recording according to the determination by the determining means; It is a recording device characterized by having.

  An object of the present invention is to enable high-speed recording while suppressing occurrence of color unevenness in an image due to the order in which different inks are applied to a recording medium.

It is a schematic diagram which shows the mode of the recording by the recording device which concerns on 1st Embodiment. FIG. 3 is a schematic diagram illustrating a state of ink applied to a recording medium. 1 is a block diagram illustrating a concept of a control system of a recording apparatus and a PC according to a first embodiment. It is a figure which shows the flow of a process in the recording device which concerns on 1st Embodiment. It is a figure which shows the edge detection filter which concerns on 1st Embodiment. It is a figure for explanation about analysis of an image concerning a 1st embodiment. It is a figure for explanation about analysis of an image concerning a 1st embodiment. It is the graph which showed the relationship between line width and an identifiable color difference. It is a schematic diagram for description of shape reproducibility concerning a 2nd embodiment. 1 is a perspective view illustrating an appearance of a recording apparatus according to a first embodiment. FIG. 2 is a schematic diagram of a recording head according to the first embodiment. FIG. 5 is a schematic diagram for explaining processing in the recording apparatus according to the first embodiment. FIG. 5 is a schematic diagram for explaining processing in the recording apparatus according to the first embodiment. It is a schematic diagram which shows the mode of the recording by the recording device which concerns on 1st Embodiment.

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

(First embodiment)
FIG. 10 is a perspective view of the recording apparatus 308 according to the present embodiment, showing the appearance and a part of the inside. This is a so-called serial scanning type printer, which scans the recording head 9 (described later) in the X direction (scanning direction) so as to be substantially orthogonal to the Y direction (conveying direction) of the recording medium P, and prints an image. To record. FIG. 11 is a schematic view of the recording head 9 according to the present embodiment as viewed from the surface (discharge surface) side where the nozzles are open. FIG. 3 is a block diagram for explaining the configuration of the host PC 301, the recording apparatus, and the recording apparatus 308, which are image processing apparatuses according to the present embodiment.

  The configuration of the recording apparatus 308 and the outline of the operation during recording will be described with reference to FIGS. First, the recording medium P is conveyed in the Y direction from the spool 6 holding the recording medium P by a conveyance roller driven via a gear by a conveyance motor 318 (not shown). On the other hand, the carriage unit 2 is reciprocated (reciprocated) along the guide shaft 8 extending in the X direction by a carriage motor 319 (not shown) at a predetermined transport position. In this scanning process, the ejection operation is performed from the nozzles (ejection ports) of the recording head 9 that can be mounted on the carriage unit 2 at a timing based on the position signal obtained by the encoder 7, and corresponds to the nozzle arrangement range. Record a certain bandwidth.

  A carriage belt can be used to transmit the driving force from the carriage motor 319 to the carriage unit 2. However, instead of the carriage belt, for example, a lead screw that is rotationally driven by a carriage motor and extends in the X direction, and an engagement portion that is provided in the carriage unit 2 and engages with a groove of the lead screw, etc. Other driving methods can also be used.

  The fed recording medium P is nipped and conveyed by a paper feed roller and a pinch roller and guided to a recording position (scanning area of the recording head) on the platen 4. Since the face surface of the recording head is capped in the normal resting state, the cap is opened prior to recording, so that the recording head or carriage unit 2 can be scanned. After that, when data for one scan is accumulated in the buffer, the carriage unit 2 is scanned by the carriage motor, and recording is performed as described above. In the recording apparatus of the present embodiment, so-called multi-pass recording is performed, in which an image is recorded on a unit area (1 / n band) on the recording medium P by scanning the recording head a plurality of times (n times). Can do.

  FIG. 2 shows a recording head 9 according to this embodiment. The recording head 9 includes a nozzle row (K) that discharges black ink (K) as ink containing a color material, a nozzle row 22C that discharges cyan ink (C), a nozzle row 22M that discharges magenta ink (M), A nozzle row 22Y that discharges yellow ink (Y) is provided. These black ink (K), cyan ink (C), magenta ink (M), and yellow ink (Y) each contain a pigment as a coloring material. Also called ink. In addition, a nozzle array for discharging gray ink, light cyan ink, light magenta ink, red ink, blue ink, and the like may be included.

  In the recording head 9, these nozzle rows are arranged in the order of the nozzle rows 22K, 22C, 22M, and 22Y from the left side to the right side in the X direction. In the present embodiment, the nozzle row 22M is provided only on one side of the nozzle row 22C in the X direction, and the plurality of cyan ink nozzle rows and the magenta ink nozzle rows are not symmetrically arranged. These nozzle rows 22K, 22C, 22M, and 22Y are arranged in the Y direction (arrangement direction) at a density of 1200 per inch so that 1280 nozzles 30 that discharge the respective inks correspond to 1200 dpi. . Note that the amount of ink ejected from one nozzle 30 at a time in this embodiment is about 4.5 pl.

  These nozzle rows 22K, 22C, 22M, and 22Y are connected to ink tanks (not shown) that store the corresponding ink, respectively, and ink is supplied. Note that the recording head 9 and the ink tank used in the present embodiment may be configured integrally, or may be configured so as to be separable from each other.

  FIG. 3 is a block diagram for explaining the configuration of the host PC 301, the recording apparatus, and the recording apparatus 308 as image processing apparatuses usable in the present invention. The image processing apparatus includes a PC, a tablet PC, and the like. In this example, the description will be made on the PC. The CPU 302 executes various processes according to a program stored in the HDD 304 while using the RAM 303 as a work area. For example, the CPU 302 generates print data to be recorded by the recording device 308 based on a command received from the user via the keyboard / mouse I / F 306 or a program held in the HDD 304, and transfers this to the recording device 308. Further, the image data received from the recording device 308 via the data transfer I / F 307 is subjected to predetermined processing according to a program stored in the HDD, and the results and various information are displayed via the display I / F 305. Display on a display (not shown). Items that can be specified by the user on the display connected to the host PC 301 include the quality of recording, the type of recording medium, and the type of image to be recorded (line drawing, photograph). A line drawing is an image centered on a fine line, and a photograph includes many so-called flat portions in which a halftone is uniformly spread.

  On the other hand, in the recording device 308, the CPU 311 executes various processes according to a program held in the ROM 313 while using the RAM 312 as a work area. Further, the recording device 308 includes an image processing accelerator 309 for performing high-speed image processing.

  The image processing accelerator 309 is hardware that can execute image processing faster than the CPU 311. The image processing accelerator 309 is activated by writing parameters and data necessary for image processing for print data received from the host PC by the CPU 311 to a predetermined address in the RAM 312, and after reading the parameters and data, Predetermined image processing is executed. However, the image processing accelerator 309 is not an essential element, and equivalent processing can be executed by the CPU 311.

  Here, predetermined image processing performed by the CPU 311 or the image processing accelerator 309 will be described. The predetermined image processing is processing for processing the input print data to data indicating the dot formation position of ink in each scan. The CPU 311 or the image processing accelerator 309 performs color conversion and quantization of the input print data. The color conversion is a process of converting the color to the ink density handled by the printer. For example, the input print data includes image data indicating an image. When this image data indicates an image with color space coordinates such as sRGB which is an expression color of the monitor, the color coordinates (R, G, B) is converted into ink color data (CMYK) of the printing apparatus. The conversion method is realized by a known method such as matrix calculation processing or processing using a three-dimensional LUT. Since the printing apparatus 308 of the present embodiment uses black (K), cyan (C), magenta (M), and yellow (Y) ink, the image data of the RGB signals is K, C, M, and Y. It is converted into image data consisting of 8-bit color signals. The color signal of each color corresponds to the applied amount of each ink. In addition, although the four colors K, C, M, and Y are given as examples of the number of inks, light cyan (Lc), light magenta (Lm), and gray (Gy) inks with low density are used to improve image quality. When other inks are used, color signals corresponding to them are generated. Thereafter, a quantization process is performed on the image data having the ink color signal. This quantization process is a process of reducing the number of gradation levels of image data. In the present embodiment, quantization is performed using a dither matrix in which thresholds for comparison with image data values are arranged for each pixel. Through this process, binary data indicating whether or not to form dots at each dot formation position can be finally obtained. When performing multi-pass printing, which will be described later, in order to generate data for a thinned image corresponding to each scan, the image is thinned using a mask pattern or the like on the quantized data. . The use of the image processing accelerator 309 can speed up the processing.

  After completing the predetermined image processing, the recording data is transferred to the recording head by the recording head controller 314 in accordance with the recording direction determined by the CPU 311. Accordingly, the carriage controller 315 drives the carriage motor to scan the carriage unit 2. Further, the conveyance controller 316 moves the recording medium in the Y direction between each scan of the carriage unit in accordance with an instruction from the CPU 311. By doing so, a predetermined recording material is ejected onto the paper surface by the recording head to form an image.

  With reference to FIG. 13, the printing control according to the scanning direction will be described. The quantized image data is stored in the RAM 312 as shown in FIG. In the case of multi-pass recording, the data after the thinning process is used. The unit rectangles in the illustrated data layout correspond to pixels, and the arrangement corresponds to the arrangement of pixels formed on the recording medium. During forward scanning in the X direction, the print head controller 314 sequentially reads out the pixel data arranged in the direction 1302 and sequentially switches the pixel rows read in the X direction in units of data corresponding to the recording width of one scan. , Transfer. On the other hand, at the time of backward scanning in the X ′ direction, data of pixels arranged in the direction of 1301 are sequentially read out, and pixel rows to be read out in the X ′ direction are sequentially switched in units of data for the recording width of one scan. Go.

  FIG. 1 is a schematic diagram showing a state of recording by the recording apparatus 308 in the present embodiment. In both FIGS. 1A and 1B, a secondary blue solid image is recorded by a recording head 9 in which nozzles are arranged in the scanning direction in order to eject black ink, cyan ink, magenta ink, and yellow ink. An example will be described. The recording head 9 has a black ink nozzle row 22K (not shown in this figure), a cyan ink nozzle row 22C, a magenta ink nozzle row 22M, and a yellow ink nozzle row 22Y (this drawing) on the side facing the recording medium P. (Not shown) is provided. In each nozzle row, nozzles for ejecting ink are provided along the Y direction.

  Bidirectional recording is a method of recording in both forward scanning (scanning direction X) and backward scanning (scanning direction X ′), as shown in FIG. Can be recorded. The scanning direction X and the scanning direction X ′ are directions that intersect so as to be substantially perpendicular to the Y direction, which is the conveyance direction of the recording medium. The illustrated example is one-pass recording in which recording is performed in one scan in a unit area (here, an area corresponding to the recording width of the recording head 9) of the recording medium, and the recording medium records each time one scan is performed. It is conveyed in the Y direction by the recording width of the head. This recording width corresponds to a range where nozzles are provided. Adjacent unit areas are recorded in the reverse scanning direction. After the forward scan recording, the loopback is performed and the backward scan recording is performed, which is suitable for high-speed recording.

  One-way recording is a method of performing recording by only one of forward scanning and backward scanning as shown in FIG. The illustrated example is printing only in the forward scanning (scanning direction X), and is one-pass printing as in the example of FIG. After recording the forward scan, it is lifted once to the original position, and the forward scan is performed again, so that it takes time compared to recording in the reciprocating manner.

  In addition, there is a recording method by scanning a plurality of times. As shown in FIG. 14, this is a method called multi-pass printing in which the recording head scans the same area of the recording medium a plurality of times and records. In recording by a plurality of scans, ink dots to be finally formed on the recording medium are recorded by being shared by the plurality of scans, and by adjusting the transport amount of the recording medium, 2 dots can be applied to the same area. One or more recordings are possible. Since the nozzles used for recording in the unit area are different, there is an advantage that variations among the nozzles are not easily reflected in the recorded image. FIG. 14A shows an example of two-pass printing in which printing is performed by scanning twice in a unit area in bidirectional printing. After recording in the first scanning direction in the scanning direction X, the recording medium is transported in the Y direction by a distance corresponding to half the recording width of the recording head, and then recording is performed in the second scanning in the scanning direction X ′. Do it. The area recorded in the first scan, which is the previous scan, and the area recorded in the second scan, which is the next scan, partially overlap (here, halves). In this way, recording is performed so that the image to be recorded is complemented by two scans for each unit area (an area of half the recording width) of the recording medium. The point at which the conveyance of the recording medium is sandwiched between each scanning is the same as in the case of one-pass recording. FIG. 14B shows an example of two-pass printing in which printing is performed in a unit area by two scans in one-way printing. Here, as in FIG. 1B, only forward scanning (scanning direction X) is shown. The scanning direction is different from that in the case of the unidirectional recording described with reference to FIG. 14A, but the conveyance is the same.

(Recording direction and ink application order)
The factors that cause color unevenness depending on the recording direction will be described below. FIG. 2 is a diagram illustrating an example of recording a blue image with cyan ink and magenta ink in a region (regions a, b, c, and d) wider than the recording width of the recording head in FIG. In FIG. 1A, the recording head performs recording in the scanning direction X with respect to the area a. At this time, the cyan ink nozzle row 22C is the front side, and the magenta ink nozzle row 22M is the rear side. Ink droplets land on the recording medium P in the order of cyan and magenta. Then, after the recording medium P is conveyed in the Y direction by a length corresponding to the area b, the recording head scans in the scanning direction X ′, and recording is performed on the area b adjacent to the area a. At this time, ink droplets land in the order of magenta → cyan. In the region c, ink is applied in the order of cyan and magenta, and in the region d, ink is applied in the order of magenta and cyan. Regions a and c differ from regions b and d in the overlapping order of cyan ink and magenta ink during recording when forming a blue image. Similarly, in the bidirectional multi-pass printing shown in FIG. 14A, the ink overlapping order is different between the first and third scans and the second and fourth scans. Further, when the blue dots overlap, there are a region in which the double-scanning blue is formed on the forward-scanning blue and a region in which the forward-scanning blue is formed on the backward-scanning blue. On the other hand, in FIG. 1B, the unidirectional recording is performed, and the scanning direction is the same for the areas a, b, c, and d, and the ink application order is cyan and magenta. Similarly, in the bidirectional multi-pass printing shown in FIG. 14A, the ink application order from the first to the fourth scan is the same.

  FIG. 2 schematically shows a state where the applied ink droplets are fixed on the recording medium, and shows a cross section of the recording medium P. As shown in FIG. 2A, in the high density portion, the first applied ink 201 (black in the figure) is held in the ink receiving layer near the paper surface. The image of the high density portion is a so-called solid portion and a uniform image. The second ink 202 (gray in the figure) is less likely to be held on the surface layer because the first landed ink 201 occupies the upper part of the receiving layer. As a result, the ink 202 that has landed second permeates the lower part of the receiving layer and is held. The ink 201 is fixed on the upper part and the ink 202 is fixed on the lower part. On the surface of the recording medium, the color of the ink 201 held on the upper side of the receiving layer tends to appear stronger than the color of the ink 202 held on the lower side. On the contrary, if the applied order is the order of the ink 202 and the ink 201, the color of the ink 202 tends to appear stronger. In the embodiment described with reference to FIG. 1, the order in which cyan ink and magenta ink are applied is reversed between the scanning directions X and B, so that the colors that are likely to appear strongly differ between the region a and the region b. Become. As will be described in detail later, in this embodiment, the color in the case where the amount of applied ink is large and the recording density is high by aligning the scanning direction between regions by detecting the occurrence of color unevenness and determining the scanning direction based on the detection. Reduces unevenness.

  On the other hand, as shown in FIG. 2B, in the line portion, the previously applied ink 203 (black in the drawing) is held on the upper part of the receiving layer of the recording medium in the same manner as the high concentration portion. The receptive layer is free. As a result, the ink 204 applied next (gray color in the figure) is easily held in the empty portion of the upper ink receiving layer, and the ink 204 applied later than in the case illustrated in FIG. Colors are likely to appear. In the line portion, even if the ink application order is different between the scanning direction X and the scanning direction X ′ in FIG.

  With reference to FIG. 4, the flow of data processing for recording in the embodiment will be described.

  In step S401, the recording apparatus 308 receives print data from the host PC 301 serving as an image processing apparatus via the data transfer I / F 310. The received data is temporarily stored in the RAM 312. The received print data includes raster data such as bitmaps and vector data. Further, when the raster data is compressed by a compression algorithm or the like, a decoding process is performed. As the format of the compressed data, there are a compression method defined by JPEG (Joint Picture Expert Group) of irreversible compression and an RL (Run Length) compression method of lossless compression. Both compression methods can be used without particular limitation. When transferring uncompressed data, it can be transferred without image quality degradation. When vector data is transferred, what can be converted into vector data such as characters is limited, but it can be transferred with a smaller data amount than uncompressed data and without image quality deterioration. Vector data includes PDL (page description language) and printer control codes for drawings. In this case, information regarding the line width can be provided as data, and the CPU can determine whether or not the image is a line drawing based on the information included in the received data.

  Next, in step S402, the CPU 311 determines an analysis unit to be analyzed in steps S403 and S404. In the following embodiments, a method for analyzing RGB data in which pixel values of each pixel of an image are represented by RGB multi-value gradation values will be described as an example. If the print data received in S401 is vector data, it is necessary to rasterize and convert it to RGB data as necessary. The analysis unit includes a print data unit, a band unit divided at a predetermined height in conveyance of a recording medium, and a tile unit obtained by dividing an image into a plurality of areas of a predetermined size. The tile unit may be obtained by further dividing the band unit vertically and horizontally. The adjacent analysis regions may be overlapped in both the band unit and the tile unit. By overlapping, the effect of improving the analysis accuracy of the shape analysis performed in step S403 can be obtained. When performing analysis in units of bands, the areas a, b, c, and d in which recording is performed in the same scan shown in FIG. 1 may be used as each band, or as indicated by R1 and R2 in FIG. Each region corresponding to the amount of deviation between the regions to be recorded by continuous scanning can be set as each band.

  In the following, an example in which each area of an image corresponding to a plurality of rectangular areas of a predetermined size recognized when a recording medium is partitioned is analyzed and analyzed in units of tiles will be described.

  Next, in step S403, the CPU 311 executes processing for shape analysis of the image in the page. As processing for shape analysis, edge detection, Fourier transform, and reduction processing can be cited. Hereinafter, edge detection will be described as an example. The method of edge detection is not particularly limited, but in the embodiment, edge detection by filtering is described. This method is a method of obtaining an image in which only edges are extracted by changing pixel values of RGB image data using a filter that emphasizes edges. The CPU 311 extracts the edge by enhancing the edge by changing the pixel value of the image data using the filter shown in FIG. 5 to the image of the region of the analysis unit determined in step S402. FIG. 5 shows an edge emphasis filter, and the method of using each value arranged in this filter for edge emphasis can be performed using a known method. As a result of the processing, an image in which only edges are extracted is obtained, and information indicating the number of edge pixels, which is the total number of extracted edge pixels, is stored in the RAM 312 as shape information indicating the shape of the image formed on the recording medium.

  Next, in step S404, the CPU 311 performs a color analysis process related to occurrence of color unevenness due to a difference in scanning direction. In the present embodiment, a pixel having a predetermined RGB value is detected as a pixel having a predetermined color to which attention should be paid by analyzing the image data. One or a plurality of predetermined RGB values are determined as predetermined RGB values and stored in the ROM 313. This predetermined RGB value is determined in consideration of the extent to which a difference in color appears due to a difference in scanning direction when printing is performed with the applied amount of each ink determined based on RGB. It is determined whether or not the RGB values of the pixels are the predetermined RGB values stored in the ROM 313 for all the analysis unit pixels determined in step S402. The total number of pixels that match the predetermined RGB value is stored in the RAM 312 as color information. When the predetermined RGB values are stored in the ROM 313, if all the predetermined RGB values selected in advance are held in the ROM 313, the number of processes increases and the processing speed may decrease. In that case, a typical predetermined RGB value may be discretely defined using a 3DLUT or the like. For example, “1” is associated with a predetermined RGB value, and “0” is associated with a value that is not a predetermined RGB value. When processing is performed, values between lattice points of the 3DLUT can be easily calculated using tetrahedral interpolation. This will be specifically described with reference to FIG. The cube shown in FIG. 12A is a schematic diagram of a part of the 3DLUT. The intersection of each line in the cube is a lattice point. The white character “1” indicates that the value of the position of this vertex is “1”, and the black character “0” at the diagonal position indicates that the value of this position is “0”. ing. As shown in FIGS. 12B and 12C, when the values of the grid points of the tetrahedron are all 1 or 0, the output value of the interpolation result with respect to the input value to the region surrounded by this tetrahedron Becomes 1 or 0. When one of the tetrahedron grid points is 1 as shown in FIG. 12A, the interpolation result 1004 becomes 1 only when the input RGB value 1003 becomes the RGB value of the grid point. When two of the tetrahedral grid points are 1 as shown in FIG. 12D, the interpolation result 1006 is 1 only when the input RGB value 1005 is on the line connecting the grid points. When three of the tetrahedral grid points are 1 as shown in FIG. 12E, the interpolation result 1008 is 1 only when the input RGB value 1007 is on the plane constituted by the grid points. In this way, by combining 3DLUT and tetrahedral interpolation processing, determination of a color gamut in which color unevenness occurs can be performed with a small amount of memory and a small number of comparison processes. Furthermore, if the grid interval of the 3DLUT is widened, the determination can be made with a smaller amount of memory. When the grid interval is wide, the predetermined RGB value is 255, and the value that does not occur is 0. Then, if the threshold value is determined in advance, it can be determined whether or not color unevenness occurs by comparing the multi-value data and the threshold value, and the color unevenness occurrence pixel is accurately calculated even when the grid interval is wide. be able to.

  An example of a color having a predetermined RGB value is a color that is recorded using a plurality of different inks, and that is further added to each or more than a predetermined applied amount. For example, the signal value of the multi-value data of cyan ink is larger than 50% of the maximum value, and the signal value of the multi-value data of magenta ink is blue which is greater than 50% of the maximum value. For such a color, when obtaining a high-quality recorded image, it is a color to be aware of the difference in color between the image recorded by the forward scanning and the image recorded by the backward scanning. . For example, a dark color that increases the ink application amount may be set as a predetermined RGB value. On the other hand, for a color that uses only one color of ink, there is no difference in color depending on the scanning direction, and thus a predetermined RGB value is not used. Thus, the color information described above can also be referred to as application amount information regarding the application amounts of a plurality of inks.

  In this example, color determination is performed using RGB multi-value data in this example, but determination may be performed using CMYK multi-value data obtained from RGB data. Absent. Also, binary data representing the presence or absence of dot formation after quantization may be counted for each color.

  In the subsequent step S405, the influence on the color due to the different scanning direction of the recording head is evaluated from the shape information acquired in step S403 and the color information acquired in step S404, and the attention area is determined. A graph showing an example of the determination method is shown in FIG. In FIG. 6, the horizontal axis represents the number of pixels of the predetermined color detected in step S404, and the vertical axis represents the number of edge pixels acquired in S403. Lines extending from both axes indicate the respective threshold positions. When the number of edge pixels is equal to or smaller than a predetermined threshold and the number of pixels of a predetermined color is larger than the predetermined threshold, attention is paid to the difference in color due to the difference in scanning direction in the area of the analysis unit determined in step S402. Determine the area. When the number of edge pixels exceeds a predetermined threshold value, this analysis unit is regarded as a line drawing and is not regarded as a caution area. On the other hand, when the number of edge pixels is equal to or smaller than a predetermined threshold value, the analysis unit is a non-line image and is likely to be an image or a photograph.

  The threshold value for the edge pixel and the threshold value for the predetermined color are determined by the size of the analysis unit. As described with reference to FIG. 2, the thin line is unlikely to appear in the color in which the influence of the difference in the ink application order is recorded. For this reason, at 1200 dpi, fine lines with a width of 2 pixels or less are hardly visible even if the scanning directions of the respective parts are different. Based on this viewpoint, the threshold value for the edge pixel and the threshold value for the predetermined color may be determined in advance. For example, when the region corresponding to the image corresponding to the size of 9 × 9 pixels in the RGB data shown in FIG. 7 is used as the analysis unit, the threshold value of the edge pixel is 18, assuming that this image is recorded at a recording resolution of 1200 pixels per inch. The predetermined color threshold is set to 27. As shown in FIG. 7, two pixel columns formed by 18 black pixels correspond to thin lines having a width of 2 pixels. The determined result is stored in the RAM 312 as attention area information in association with the analysis unit.

  In step S406, it is determined whether or not the analysis of all analysis units of the CPU 311 print data has been completed. If not completed, the process proceeds to the next analysis unit and the processing is performed from step S403. If completed, the process proceeds to step S407. In this step, if all analysis units satisfying the predetermined area for determining the scanning direction in step S407 have been completed, the process may proceed to step S407. Then, scanning can be started during analysis, which leads to faster recording.

  In step S407, the CPU 311 determines the scanning direction of the recording head 9 for recording from the attention area information determined in step S405. This determination is performed in units of a predetermined area on the recording medium. For example, in the case of one-pass recording, the areas in which the recording head 9 passes in one scan are set as predetermined areas, and the tiles in the predetermined area are collected. Thus, the scanning direction for recording the area can be determined. For example, if all the tiles in the area for one scan are not the attention area, this area is recorded with a fine line center image such as a line drawing, or a flat image such as an image or a photograph but an ink It is determined that the applied amount is not so large as to align the scanning direction with the previous scan. In the case of an image or a photograph, even if the scanning direction must be aligned with that of the previous scanning, in the case of a line drawing, the color difference between different scannings is difficult to be visually recognized. In order to record such an area, a scanning direction opposite to the previous scanning direction is determined. Here, referring to FIG. 1A, it is assumed that an image whose scanning direction is determined in this way is formed in the region b in the scanning direction X ′. The images are continuous, and are formed from the region a formed in the scanning direction X to the region b or further across the region c. However, since the image to be recorded is a line drawing, or an image or photo that does not have a large ink application amount, the color difference between the regions is difficult to be visually recognized.

  On the other hand, if there is at least one tile of the attention area, the image to be recorded is an image, a flat image such as a photograph, and the amount of applied ink is the same in the scanning direction. It is desirable to suppress the difference. Therefore, the direction opposite to the previous scanning direction is determined as the scanning direction. For example, in the recording apparatus, when the scanning direction in the unidirectional recording mode is set as the forward direction (the direction of the arrow X in FIG. 9), each scanning after the second scanning on the recording medium is performed. The direction of forward scanning or the direction of backward scanning (arrow X ′ in FIG. 9) is determined. Referring now to FIG. 1B, it is assumed that an image whose scanning direction is determined is formed in the scanning direction X in the region b. The images are continuous and are formed from the region a formed in the scanning direction X to the region b, or further across the region c, but the scanning direction of each region is the same. The difference in color is difficult to see. In addition, as for the predetermined area to be determined in step S407, for example, when performing multipass printing, an area smaller than the recording width of the recording head in the Y direction as indicated by R1 and R2 in FIG. It is good.

  As the subsequent processing, the recording head controller 314 described above performs recording in accordance with the scanning direction as described with reference to FIG.

  By the way, in the above-described example, the analysis areas are grouped into one scanning area and the scanning direction is determined. However, the printing data corresponding to one page may be grouped. When the print data is collectively evaluated, the entire recording target can be captured and the scanning direction for recording can be determined, so that the effect of suppressing color unevenness can be sufficiently obtained. On the other hand, if it is necessary to determine in fine units when performing multi-pass printing, the determination may be performed in units indicated by R1 and R2 in FIG. R1 and R2 are areas in which the recorded image in the subsequent scan protrudes from the recorded image in the previous scan. For example, when there is a caution area in the R1 area, the direction of the second scan and the third scan in which the R1 area is recorded is determined to coincide.

  As described above, an optimal recording direction can be selected according to shape information and ink application amount information. High-speed recording can be performed while suppressing the occurrence of color unevenness in the image due to the order in which different inks are applied to the recording medium.

  In the example described above, edge detection is performed in step S403 to perform shape analysis, but reduction processing may be used. In step S402, the above is performed in units of tiles, but may be performed in units of print data. By doing so, the recording direction can be determined by a process lighter than the filter process. In the reduction process in this case, the average value reduction or the mode value reduction is most suitable for maintaining the shape. By doing so, it is possible to perform the reduction process while retaining the shape information, and there is an effect of improving the accuracy of the shape analysis in step S403.

  Moreover, although edge detection was performed in step S403, shape information may be determined according to the input format. When printing a drawing or the like, vector data is often used because transfer with vector data has a smaller transfer capacity and better quality. Therefore, when the input format is vector data, it may be indicated that the amount of edge pixels is larger than a predetermined threshold in the shape information for all analysis units. Alternatively, it is possible to omit the shape analysis and automatically determine to perform bidirectional recording. When printing a drawing or the like, bidirectional recording can be performed, and high-speed recording is possible.

  In addition, when the user recognizes that the image to be recorded is a line drawing, a recording mode for designating line drawing recording may be provided. For example, a recording target such as a photograph, Web, or line drawing can be designated on a driver screen on a display connected to a PC so that the user can select it. The recording device 308 that has received the information specifying the line drawing mode included in the print data from the PC uses this as shape information, and does not extract edge pixels from the print data image with the line drawing mode designation. Information that the edge always exceeds the threshold may be automatically acquired as a shape analysis result. By doing so, bidirectional recording is selected in the line drawing mode. Alternatively, when the line drawing mode is designated, S403 to S406 may be skipped, and it may be determined to perform bidirectional recording in S407. On the other hand, in a mode such as a photograph having a smaller number of lines than a line drawing, the flow from S401 to S406 can be executed to suppress the difference in color between regions caused by the scanning direction.

  In step S403, a thin line of 2 pixels (about 0.042 m) or less is detected at 1200 dpi in the above, but a line having a wider line width may be detected using visual characteristics. FIG. 8 is a graph showing the relationship between the identifiable color difference and the line width at an observation distance of 30 cm using Berten's visual characteristics. A color difference is identified in the area above the real curve in the graph. For example, when the color difference of the generated color unevenness is ΔE5.0, it can be seen that the maximum line width at which a person can identify the color unevenness is about 0.3 mm. Therefore, by setting the line width detected in step S403 to 0.3 mm or less, a more optimal recording method can be determined. As a result, more bidirectional recording is used, and the effect of improving the recording speed can be obtained.

  Note that the processing from step S401 to S407 described above and the predetermined image processing by the image processing accelerator 309 may all be performed using the CPU 302 of the host PC 301, the RAM 303, and the like. Alternatively, some of the upstream steps of steps S401 to S407 may be performed using the CPU 302 and the RAM 303 of the host PC 301, and the downstream steps may be performed on the recording apparatus side. it can.

(Second Embodiment)
In the first embodiment, various types of analysis are performed based on print data. However, when recording is actually performed on a recording medium, there is a corresponding gap between the original data and the recorded image. In the present embodiment, the state of the recorded image actually recorded based on the print data is reflected in the determination of the scanning direction. Other points are the same as those in the first embodiment unless otherwise specified.

The main factor of the gap between the shape surfaces of the print data and the recorded image is the reproducibility of the line width. The reproducibility of the line width is a recording condition such as the type of the recording medium and the ink ejection speed from the nozzles 30. In the present embodiment, the weight of the shape information and the color information is changed in the determination of the attention area in step S405. When the line width reproducibility is high, the shape information is emphasized, and when the line width reproducibility is low, the color information is emphasized. Specifically, it is defined that one pixel is recorded at 0.021 mm when an image indicated by print data is recorded at a recording resolution of 1200 dpi, and ink when recording from a recording apparatus to a recording medium is performed. Based on the size of one dot, the ratio is calculated using the following equation (1). The ratio is K, and the size L of one dot on the paper surface.
K = 0.021 / L (Formula 1)
Then, the number of edge pixels in each analysis unit obtained in S403 is multiplied by the calculated ratio K as a coefficient for correction. For example, when the diameter of one dot on a certain recording medium is 0.035 mm, K = 0.6. That is, 60% of the print data that are recognized as edge pixels are counted as edge pixels.

  Other than obtaining the line width reproducibility coefficient based on the dot diameter, other factors may be used. There are four main factors related to line width reproducibility: the amount of ink droplets ejected from the nozzles, the bleeding rate of the applied ink on the recording medium, the landing accuracy when the ink droplets land on the recording medium, and the unit This is the number of scans per area (hereinafter referred to as the number of passes).

  These factors will be described with reference to FIG. The right side shows a state in which the image indicated by the print data on the left side of the drawing is formed on the recording medium (the black portion of the print data is formed with dots). In order from the top, the recorded images are shown in comparison with the bleeding rate and the amount of discharge, the level of landing accuracy, and the number of passes. For each factor, the recorded image on the left side has higher shape reproducibility than the right side. The dot diameter is related to the ink ejection amount and the ink bleeding rate on the recording medium. When the ink droplet landing accuracy is low or the number of passes is large, the line width reproducibility deteriorates and the reliability of the shape information decreases. When the number of passes is large, the line width reproducibility tends to be low due to a recording position shift between passes. For example, when the number of paths is a predetermined number, the coefficient can be made larger than that of paths exceeding the predetermined number. Furthermore, the ink landing accuracy is affected by the scanning speed of the recording head, the distance between the recording head and the surface of the recording medium, the conveyance accuracy of the recording medium, and the like. As the scanning speed of the recording head increases, the ink landing accuracy tends to decrease. When the distance between the recording head and the surface of the recording medium is increased, the ink landing accuracy is deteriorated. If the paper feeding accuracy is degraded, the ink landing accuracy is degraded. Therefore. When the recording speed is a predetermined speed, the coefficient may be larger than when the recording speed is higher than the predetermined speed. Further, when the distance between the recording head and the surface of the recording medium is a predetermined distance, the coefficient may be set larger than when the distance is longer than the predetermined distance.

  As described above, in the attention area determination in step S405, the gap between the print data and the actual recording can be filled by changing the values of the shape information and the color information with the coefficients according to the line width reproducibility. As a result, the recording method can be changed to a more appropriate recording method, and the effect of improving the accuracy of color unevenness improvement can be obtained.

(Third embodiment)
In the first embodiment, a mode has been described in which bidirectional recording is performed when the user inputs that the image to be recorded is a line drawing. In the present embodiment, a mode in which the number of scans is further varied according to the print target selected by the user will be described.

  First, for example, it is the same as in the first embodiment in that a recording target such as a photograph, a web, a line drawing, and the like can be designated on the driver screen on the display and can be selected by the user. In addition, it is assumed that the quality of the recording selected by the user is the same in the first case and the second case.

  First, as a first case, when the user selects a line drawing as the type of recording image, the CPU 311 performs bidirectional recording and recording as shown in FIG. One-pass recording is determined, and each component of the recording apparatus performs recording based on the determination. The determination of the scanning direction based on the shape information and the ink application amount information described with reference to FIG. 4 is not performed.

  On the other hand, as the second case, when the user selects a mode in which the number of lines is smaller than that of the line drawing, for example, a mode for recording a photograph, the CPU 311 determines multi-pass recording as shown in FIG. Then, the flow of steps S401 to S407 described with reference to FIG. 4 is performed to determine the scanning direction. Further, without analyzing the shape of the image, it is determined whether the two consecutive scanning directions are the same or opposite depending on whether the applied amount indicated by the applied amount information of the ink is larger than a predetermined threshold value. You may make it do. For example, step S403 described with reference to FIG. 4 is omitted, and in step S405, the attention area is determined by the number of pixels of a predetermined color without using the number of edge pixels. Other points may be the same as in the first embodiment.

  In this way, it is possible to record a line drawing that is hardly affected by the difference in the scanning direction at a higher speed, and in the case of photographic recording that should be concerned about the occurrence of color unevenness, it is possible to change the color due to the difference in the scanning direction. The scanning direction is determined in consideration of the influence of the above, and high-quality recording can be performed.

Claims (12)

A recording head including a first nozzle row for discharging the first ink and a second nozzle row for discharging a second ink having a color different from that of the first ink; Scanning means for scanning in the scanning direction, and transporting means for transporting the recording medium in the transporting direction intersecting the scanning direction. The first nozzle array and the second nozzle array include the scanning And a nozzle that ejects ink arranged in a direction intersecting the scanning direction, and scanning the recording head by the scanning unit and conveying the recording medium by the conveying unit are alternately performed on the recording medium. A recording device for recording an image,
Based on the applied amount information on the applied amount of the first ink and the second ink applied to record the image on a recording medium based on the image data indicating the image, according to the applied amount, The previous scan and the next scan so as to suppress a partial color difference caused by the scan direction in the image to be recorded between the previous scan of the recording head and the next scan of the previous scan. And in accordance with the shape information relating to the shape of the image to be recorded on the recording medium, the previous scan and the next scan in accordance with Determining means for determining to reverse the direction of scanning;
And a control unit that controls the recording head and the scanning unit to perform recording in accordance with the determination by the determination unit.   The determining means determines that the previous scan and the next when the image is an image or a photograph and the first ink and the second ink for recording the image are larger than a first amount. When the scanning direction is determined to be the same, and the image is an image or a photograph, and the first ink and the second ink for recording the image are not larger than the first amount The printing apparatus according to claim 1, wherein the direction of scanning is determined to be reversed between the previous scan and the next scan.   In the case where the first ink and the second ink for recording the image are larger than the first amount, and the image is a line drawing, the determination unit determines whether the previous scan and the next scan are performed. It is determined that the direction of scanning between scans is reversed, and if the image is an image or a photograph, the scanning direction is determined to be the same between the previous scan and the next scan. The recording apparatus according to claim 1, wherein the recording apparatus is a recording apparatus.   When the shape information indicates a line drawing, the determining means determines whether the previous scan and the next scan are independent of the amounts of the first ink and the second ink indicated by the applied amount information. The recording apparatus according to claim 1, wherein the direction of scanning is determined to be reversed.   5. The apparatus according to claim 1, further comprising a determining unit that determines the shape information based on image data, wherein the determining unit determines the shape information by detecting a feature of the image. The recording device according to item.   The recording apparatus according to claim 1, wherein the shape information is based on a user input.   The recording apparatus according to claim 1, wherein the area to be recorded in the previous scan and the area to be recorded in the next scan are adjacent in the transport direction.   The recording apparatus according to claim 1, wherein an area recorded in the previous scan and an area recorded in the next scan partially overlap in the transport direction.   9. The nozzle row for ejecting the second ink in the scanning direction is provided only on one side of the first nozzle row. Recording device.   The recording apparatus according to claim 1, wherein the determination unit corrects the shape information using a coefficient set based on the reproducibility of a line shape on the recording medium. . A recording head including a first nozzle row for discharging the first ink and a second nozzle row for discharging a second ink having a color different from that of the first ink; Scanning means for scanning in the scanning direction, and transporting means for transporting the recording medium in the transporting direction intersecting the scanning direction. The first nozzle array and the second nozzle array include the scanning And a nozzle that ejects ink arranged in a direction intersecting the scanning direction, and scanning the recording head by the scanning unit and conveying the recording medium by the conveying unit are alternately performed on the recording medium. A recording device for recording an image,
In a recording mode for recording a line drawing, recording is performed by scanning the recording head once with respect to a unit area of the recording medium, and scanning of the previous recording head and subsequent scanning of the recording head are performed. The recording is performed with the scanning direction reversed between
In the recording mode for recording a photograph, the first ink is applied to record on the unit area of the recording medium by scanning the recording head a plurality of times and to record the image on the recording medium. In accordance with the application amount of the second ink, the scanning direction of the previous recording head and the subsequent scanning of the recording head for recording the image are the same. Or a recording apparatus that determines whether to reverse or not and performs recording according to the determination. A recording head provided with a first nozzle row for discharging the first ink and a second nozzle row for discharging a second ink having a different color from the first ink is scanned in a predetermined scanning direction. The recording medium is transported in a transport direction that intersects the scanning direction, and the first nozzle array and the second nozzle array are aligned in the scanning direction and aligned in the direction intersecting the scanning direction. A recording method for recording an image on the recording medium by alternately scanning the recording head and transporting the recording medium,
Based on the applied amount information on the applied amount of the first ink and the second ink applied to record the image on a recording medium, based on the image data indicating the image, and according to the applied amount information The previous scan and the next scan so as to suppress a partial color difference caused by the scan direction in the image to be recorded between the previous scan of the recording head and the next scan of the previous scan. The scanning direction is determined to be the same, and the shape information on the shape of the image to be recorded on the recording medium and the shape information indicate a line drawing based on the shape information. And deciding to reverse the scanning direction.

Images