JP6291733B2 - Image recording device - Google Patents

Description

  The present invention relates to an image recording apparatus for recording an image on a recording medium.

  When the size of the inkjet head is increased, a plurality of small units in which nozzle rows are formed may be arranged in order to reduce the cost. At this time, a technique is known in which the nozzle rows of each unit are partially overlapped to suppress deterioration in image quality due to an attachment error of each unit. For example, in an overlapping area of nozzle rows of units adjacent to each other, multi-value data of pixels is distributed to nozzles of nozzle rows corresponding to the same pixel, and halftone processing is performed on each of them. Yes (see Patent Document 1). Note that the multi-value data is distributed so that the distribution ratio decreases as it approaches the end of each nozzle row.

JP 2009-226904 A

  However, according to the above-described technique, when error diffusion accompanying quantization is accurately performed, an error that occurs with respect to a nozzle associated with one nozzle row and a nozzle associated with the other nozzle row are present in a region adjacent to the overlap region. It is conceivable to distribute both the errors that occur for. In this case, the processing becomes complicated and the hardware configuration becomes complicated.

  An object of the present invention is to provide an image recording apparatus capable of suppressing deterioration in image quality with a simple configuration.

The image recording apparatus of the present invention applies N (N: a natural number of 2 or more) nozzle rows in which a plurality of nozzles that discharge liquid are arranged in a predetermined direction, and a pressure for discharging liquid from the nozzles. A pressure applying unit that quantizes a sum of multi-value data related to each pixel of an image and a quantization error distributed to the pixel, and outputs quantization data obtained by the quantization and the quantization error A nozzle, an error buffer that stores the quantization error input from the quantization unit, and a control unit that controls the pressure applying unit, the quantization unit, and the error buffer, and the N nozzle rows Are provided such that the nozzle formation ranges in the predetermined direction are different from each other, and two nozzle rows adjacent to each other in the predetermined direction are on one side in the predetermined direction. When the nozzle row is the i-th (i: natural number from 1 to N−1) nozzle row and the other nozzle row is the i + 1-th nozzle row, at least one nozzle belonging to the i-th nozzle row and the The two adjacent nozzle rows partially overlap such that at least one of the nozzles belonging to the i + 1 nozzle row is the same in the predetermined direction, and the control unit belongs to the i-th nozzle row. For the nozzles and the nozzles that belong to the i + 1th nozzle row and have the same position in the predetermined direction as the nozzles, the multi-value data relating to the pixels corresponding to both the nozzles is distributed to both the nozzles. The quantized multi-value data obtained in this way is quantized by the quantization unit and belongs to the i-th nozzle row in the area partially overlapping with the i + 1-th nozzle row. For each nozzle, the distribution ratio of the distributed multi-value data gradually decreases from the one side toward the other side, and belongs to the i + 1th nozzle row in a region partially overlapping with the ith nozzle row. For each nozzle, the distribution ratio of the distributed multi-value data is gradually increased from the one side toward the other side, and the quantization unit is configured to quantize the multi-value data and the distributed multi-value data. When focusing on the nozzles belonging to the i-th nozzle row and the nozzles belonging to the i + 1-th nozzle row, the quantization relating to the pixels corresponding to these nozzles is: (1) belonging to the i-th nozzle row and The sum of the multi-value data relating to the pixels corresponding to the nozzles in a region that does not partially overlap with other nozzle rows and the quantization error distributed to the pixels, (2) Subsequently, the pixels corresponding to the nozzles that belong to the i + 1 nozzle row and partially overlap with the i-th nozzle row are quantized from the other side toward the other side And the quantization error distributed to the pixel is quantized in order from the one side toward the other side, and (3) further belongs to the (i + 1) th nozzle row and The sum of the multi-value data related to the pixels corresponding to the nozzles in the region that does not partially overlap with other nozzle rows and the quantization error distributed to the pixels is calculated from the one side to the other side. The multi-value data relating to the pixels corresponding to the nozzles in the region belonging to the i + 1th nozzle row and not partially overlapping with the other nozzle rows, Above (1 ), At least one of the quantization error accompanying quantization in (2) and the quantization error accompanying quantization in the multi-value data relating to the pixel corresponding to the nozzle in the region (4) Thereafter, the distribution multi-value data relating to the pixels corresponding to the nozzles belonging to the i-th nozzle row and partially overlapping the i + 1-th nozzle row and the distribution to the pixels The quantization error is quantized in order from the one side to the other side, and belongs to the i-th nozzle row and partially overlaps the i + 1-th nozzle row. The distribution multi-value data relating to the pixel corresponding to the nozzle includes the quantization error accompanying the quantization in (1) and the distribution multi-value relating to the pixel corresponding to the nozzle in the region. Value data To distribution only at least one of the quantization error with the quantization.

  According to the present invention, the distribution ratio of the pixel multi-value data to each nozzle is gradually decreased in the predetermined direction for the nozzles in the overlapping portion of the i-th nozzle row, and for the nozzles in the overlapping portion of the i + 1 nozzle row. Is gradually increased in a predetermined direction, and quantization with error diffusion is performed in the order of (1) to (4). As a result, the quantization can be continuously performed in units of multi-value data, and the hardware configuration is compared to the case of sequentially quantizing in the predetermined direction in the order of the i-th and i + 1-th nozzle rows. Be simple.

1 is a schematic side view showing the inside of an ink jet printer according to an embodiment of the present invention. It is a top view of the inkjet head shown in FIG. FIG. 2 is a functional block diagram of the printer shown in FIG. 1. FIG. 4 is a functional block diagram of an image processing circuit and a print control circuit shown in FIG. 3. It is a figure for demonstrating the function of the seam correction | amendment part shown in FIG. FIG. 5 is a diagram for explaining functions of the image processing circuit shown in FIG. 4.

  A schematic configuration of an ink jet printer 1 according to a preferred embodiment of the present invention will be described.

  As shown in FIG. 1, the printer 1 has an upper casing 11 and a lower casing 12 both having a rectangular parallelepiped shape. In addition, the left side surface in FIG. In addition, the right side surface in FIG. The upper housing 11 has an open bottom surface, and the lower housing 12 has an open top surface. The upper housing 11 is connected to the lower housing 12 so as to be rotatable about a rotation shaft 13. A paper discharge unit 15 is provided on the upper surface of the upper housing 11. The paper P that has been printed is sequentially discharged to the paper discharge unit 15.

  Further, an inkjet head 2, a paper tray 20, a paper transport mechanism 30, and a platen 9 are disposed in the internal space of the printer 1.

  As shown in FIGS. 1 and 2, the inkjet head 2 has a substantially rectangular parallelepiped shape, and has a discharge surface 2 a formed with a plurality of nozzles 8 for discharging ink droplets on the lower surface thereof. . Ink is supplied from an ink tank (not shown). The ink supplied to the inkjet head 2 reaches the nozzle 8 via a common ink chamber and a plurality of pressure chambers communicating with the common ink chamber. Inside the inkjet head 2, an actuator (not shown) that applies pressure to the ink stored in the pressure chamber is disposed. By driving the actuator, ink droplets are ejected from the nozzle 8.

  As shown in FIG. 2, four (u1 to u4) nozzle units 80 each including a plurality of nozzles 8 arranged in a matrix in a rectangular section are formed. In each nozzle unit 80, the plurality of nozzles 8 are arranged at different positions with respect to the main scanning direction. That is, nozzle rows arranged in the main scanning direction are formed in the nozzle unit 80. The four nozzle units 80 are arranged in a staggered pattern along the main scanning direction. Further, for two nozzle units 80 adjacent to each other in the main scanning direction, the nozzle unit 80 on one side in the main scanning direction (left side in FIG. 2; hereinafter, left) is ui, and the other side (in FIG. 2). When the nozzle unit 80 on the right side (hereinafter, right side) is u (i + 1) (in this embodiment, i is an integer from 1 to 3), a plurality of nozzles 8 and u (i + 1) nozzles belonging to the ui nozzle unit 80 Two nozzle units 80 adjacent to each other partially overlap so that the positions in the main scanning direction of the plurality of nozzles 8 belonging to the unit 80 are the same. As for the um nozzle unit 80 (in this embodiment, m is an integer of 1 to 4), the portion overlapping the nozzle unit 80 adjacent to the left is the nozzle group uml, and the nozzle unit 80 adjacent to the right is the nozzle unit 80. The overlapping portion is referred to as a nozzle group umr, and the portion not overlapping with any nozzle unit 80 is referred to as a nozzle group ui. However, when m is 1, that is, the left end nozzle unit 80 does not have uml, and when m is 4, that is, the right end nozzle unit 80 does not have umr. One actuator unit is used for each nozzle unit 80. The actuator unit includes the actuators by the number of nozzles 8 arranged in the nozzle unit 80. The actuator unit is provided with a driver IC (not shown) that controls the actuator unit.

  The sheet tray 20 can hold a plurality of stacked sheets P and is detachably disposed on the bottom surface of the lower housing 12.

  The platen 9 is a plate member for supporting paper, and is fixed to the lower housing 12 so as to face the ejection surface 2a of the inkjet head 2 when the upper housing 11 is in the closed position.

  The paper transport mechanism 30 constitutes a transport path for the paper P that passes from the paper tray 20 between the inkjet head 2 and the platen 9 to the paper discharge unit 15. The paper transport mechanism 30 includes a pickup roller 31, nip rollers 32a to 32e, and guides 33a to 33d. The pickup roller 31 sends out the sheets P stacked on the sheet tray 20 one by one from above. The nip rollers 32 a to 32 e are arranged along the conveyance path and apply a conveyance force to the paper P. The guides 33a to 33d are respectively disposed between the pickup roller 31 and the nip rollers 32a to 32e in the conveyance path, and the sheet P to which conveyance force is applied by the nip rollers 32a to 32e reaches the next nip rollers 32a to 32e. The paper P is guided. When the paper P transported by the paper transport mechanism 30 passes between the ink jet head 2 and the platen 9, an image is printed by ink droplets ejected from the nozzles 8 that open on the ejection surface 2 a of the ink jet head 2. The The paper P on which the image is printed is further transported by the paper transport mechanism 30 and discharged to the paper discharge unit 15.

  As shown in FIG. 3, the printer 1 includes a control unit 1p, an I / O control circuit 44, an image processing circuit 45, and a print control circuit 46. These are communicably connected by a bus. The control unit 1p includes a CPU (Central Processing Unit) 41, a ROM (Read Only Memory) 42, and a RAM (Random Access Memory) 43. The I / O control circuit 44 is electrically connected to the paper transport mechanism 30, and the print processing circuit 46 is electrically connected to the inkjet head 2.

  The ROM 42 stores a control program 42a (firmware) for controlling the printer 1, various settings, initial values, and the like. The RAM 43 is used as a work area from which the control program 42a is read or as a storage area (main memory) for temporarily storing data.

  The CPU 41 controls the printer 1 while storing the processing result in the RAM 43 in accordance with the control program 42 a read from the ROM 42 and signals sent from various sensors (not shown). At this time, the CPU 41 functions as a RIP (Raster image processor) by the control program 42a. The RIP prints image data (which may be stored in an internal memory or a main memory (not shown) or received from a host computer) indicated in a page description language indicating an image to be printed for print control. The data is converted into suitable raster data, developed as RIP data on the main memory, and output to the image processing circuit 45. The RIP data includes gradation values (multi-valued data) indicated by 256 gradations from 0 to 255 for each of the pixels arranged in a matrix in the main scanning direction and the sub-scanning direction.

  The I / O control circuit 44 has a plurality of input / output terminals, and performs ON / OFF control of output terminals according to instructions from the CPU 41 and outputs input signals to the input / output terminals to the CPU 41. Is. The I / O control circuit 44 is connected to the paper transport mechanism 30 and various devices (not shown). The CPU 41 controls the paper transport mechanism 30 and various devices via the I / O control circuit 44.

  As shown in FIG. 4, the image processing circuit 45 includes a RIP data receiving unit 51, a current line tone value line buffer 52, a peripheral line tone value line buffer 53, a tone value interpolation unit 54, and a seam correction unit 55. An error matrix calculation unit 56, an adder 57, a quaternary quantization unit 58, an error line buffer before one line 59, an error line buffer before two lines 60, an LVDS transmission unit 61, and an operation control state machine 62.

  The RIP data receiving unit 51 receives and stores RIP data output from the RIP. The RIP data receiving unit 51 converts the received RIP data from the plurality of pixel rows made up of a plurality of pixels arranged in the main scanning direction in the order of the pixel value (line) in order from the downstream side in the paper transport direction. Is output. The current line gradation value line buffer 52 stores the gradation value of the line to be processed output from the RIP data receiving unit 51. The peripheral line gradation value line buffer 53 stores the gradation values of other lines located around the line corresponding to the gradation value group stored in the current line gradation value line buffer 52. The gradation value group stored in the current line gradation value line buffer 52 is transferred to the peripheral line gradation value line buffer 53 immediately before being rewritten to the gradation value group in the next line unit. The gradation value interpolation unit 54 complements the gradation value of the received RIP data from surrounding pixels by a bilinear method or the like, and reduces the influence of the positional deviation of the head unit in the main scanning direction. The tone value interpolation unit 54 outputs the tone value group for each line subjected to the interpolation processing to the seam correction unit 55.

  The seam correction unit 55 is an overlapping portion of the nozzle units 80 among the tone value group in units of lines input from the tone value interpolation unit 54, that is, the nozzle group u1r, the nozzle group u2l, the nozzle group u2r, and the nozzle group. The gradation values of the pixels corresponding to u3l, nozzle group u3r, and nozzle group u4l are corrected. The seam correction unit 55 does not correct the gradation values for the portions where the nozzle units 80 do not overlap, that is, the pixels corresponding to the nozzle group uic.

  The positional accuracy of the nozzle unit 80 may vary due to manufacturing errors and the like. The misregistration in the sub-scanning direction can be dealt with by correcting the ink droplet landing position by controlling the ink droplet ejection timing, but it is difficult to correct the landing position in the main scanning direction. This causes a decrease in print image quality. Accordingly, the seam correction unit 55 causes the ink droplets to be ejected from the nozzles 8 belonging to different nozzle units 80 in the overlapping positions of the nozzle units 80 and located at the same position in the main scanning direction. Thereby, it is possible to reduce the visual influence caused by the positional deviation in the main scanning direction.

  For the nozzle 8 belonging to the nozzle group uir and the nozzle 8 belonging to the nozzle group u (i + 1) l having the same position in the main scanning direction as the nozzle 8, pixels corresponding to both the nozzles 8 Are distributed to both nozzles 8. Further, as shown in FIG. 5, the seam correction unit 55 gradually decreases the distribution ratio of the gradation value data from the left side to the right side for each nozzle 8 belonging to the nozzle group uir. For each nozzle 8 belonging to (i + 1) l, the distribution ratio of gradation value data is gradually increased from the left side to the right side. In the present embodiment, if the distribution ratio of the nozzles 8 belonging to the nozzle group uir is R (x) and the distribution ratio of the nozzles 8 belonging to the nozzle group u (i + 1) l is L (x), R (x ): L (x) = α: 1−α (α is a variable that takes 0 to 1), and the distribution ratio is determined. The seam correction unit 55 outputs the tone value of the tone value group for each corrected line to the adder 57 for each pixel. As a modification, R (x): L (x) = α: k−α may be used. (K may be a constant near 1 or a variable)

  Returning to FIG. 4, the error line buffer 59 before one line includes the gradation value data up to the number of pixels in one line including the gradation value data when the quaternary quantization unit 58 recently performed quantization. With regard to, the error value output when the quaternary quantization unit 58 performs quantization is stored. The two-line previous error line buffer 60 includes the gradation value from the gradation value data of the number of pixels one line before the gradation value data when the quaternary quantization unit 58 has recently performed quantization. Further, regarding the gradation value data up to the number of pixels of one line, the error value output when the quaternary quantization unit 58 performs quantization is stored. When the four-value quantization unit 58 performs four-quantization on the gradation value amount related to the target pixel to be processed (described later), the quantization error associated with the quantization is the one-line previous error line buffer 59 and the error matrix calculation. Input to the unit 56. The one-line-before error line buffer 59 and the two-line-before error line buffer 59 are shift registers having the number of stages corresponding to the number of pixels of one line, and are stored whenever a quantization error is input to the one-line-before error line buffer 59. The error value is shifted. Further, when an error value obtained when the quantization value of the target pixel to be processed by the value quantization unit 58 is four-quantized is input to the previous error line buffer 59, the previous line error buffer calculates an error matrix calculation. The error value corresponding to the position j is output to the error matrix calculation unit 56 in the unit 56. Similarly, the error buffer before two lines outputs an error value corresponding to the position e in the error matrix calculation unit 56 to the error matrix calculation unit 56.

  The error matrix calculation unit 56 includes a flip-flop circuit, a multiplier, and an adder. Quantization errors of peripheral pixels having a positional relationship of a to m with respect to the target pixel are held, and a total value obtained by multiplying these quantization pixels by a predetermined weighting coefficient (that is, the target pixel). The sum of the distributed quantization errors) is output to the adder 57. The peripheral pixels a to m are the current line (pixels k to m), a part of the line processed one time ago (pixels f to j), and a part of the line processed two times before (pixels a to e). Contains. The configuration of the peripheral pixels may be arbitrary. For example, it may be composed of only a few pixels on the current line. In this case, since the processing is simplified, the circuit configuration is simplified. The adder 57 adds the sum of the gradation value input from the seam correction unit 55 and the quantization error value input from the error matrix calculation unit 56 for each pixel and outputs the sum to the quaternary quantization unit 58. .

  The quaternary quantization unit 58 calculates the sum of the gradation value input from the adder 57 and the quantization error value input from the error matrix calculation unit 56 using three threshold values, 0, 4, 8, 12 pl ( A four-level quantized gradation value corresponding to the volume of the ink droplet) is generated. In the present embodiment, the quaternary quantization unit 58 uses the average error minimum method for determining the quantization gradation value so that the average of the difference before and after quantization is minimized for the peripheral pixels a to m. To do. Note that quantization may be performed using other methods such as an error diffusion method. The quaternary quantization unit 58 outputs the generated quantized gradation value to the LVDS transmission unit 61, and outputs an error value generated when the quantization is performed to the error line buffer and error matrix calculation unit before one line.

  The LVDS transmission unit 61 is a driver that converts input data into a differential signal and transmits the differential signal using LVDS (Low voltage differential signaling). The differential signal transmitted by the LVDS transmitter 61 is received by the LVDS receiver 71 of the print control circuit 46.

  The operation control state machine 62 determines the operation timing of the image processing circuit 45 by controlling the read or write timing of each buffer and the operation signal of the circuit according to the control of the CPU 41. Specifically, as shown in FIG. 6, the operation control state machine 62 includes pixels corresponding to the nozzle group u1c, the nozzle group u2l, the nozzle group u2c, the nozzle group u3l, the nozzle group u3c, the nozzle group u4l, and the nozzle group u4c. Are input to the quaternary quantization unit 58 in order from the left side to the right side in the main scanning direction, so that the current line gradation value line buffer 52, the peripheral line gradation value line buffer 53 and the read / write timing of the error matrix calculation unit 56 and the operation timings of the gradation value interpolation unit 54 and the seam correction unit 55 are controlled. At this time, the operation control state machine 62 corresponds to the nozzle 8 in the nozzle group u2l, the nozzle group u3l, and the nozzle group u4l in addition to the nozzle group for each of the illustrated nozzle group u2c, nozzle group u3c, and nozzle group u4c. Only the error value accompanying quantization with the gradation value relating to the pixel is distributed.

  Thereafter, the operation control state machine 62 determines the gradation values of the pixels corresponding to the nozzle group u1r, the nozzle group u2r, and the nozzle group u3r in order from the left side to the right side in the main scanning direction. 58, the read timing of the current line tone value line buffer 52, the peripheral line tone value line buffer 53 and the error matrix calculation unit 56, and the operation timing of the tone value interpolation unit 54 and the seam correction unit 55. To control. At this time, the operation control state machine 62, for each of the nozzle group u1r, the nozzle group u2r, and the nozzle group u3r, in addition to the nozzle group, the pixel corresponding to the nozzle 8 in the nozzle group u1c, the nozzle group u2c, and the nozzle group u3c. Only the error value accompanying quantization with the gradation value related to is distributed. However, at this time, the operation control state machine 62 outputs to the adder 57 the sum of only the error values associated with the quantization of the gradation values of the pixels in the positional relationship of k, l, m with respect to the target pixel. In addition, each buffer, the error matrix calculation unit 56, etc. are set so that the quantization error accompanying the quantization in the four-value quantization unit 58 is not input to the one-line-before error buffer and the two-line-before error buffer 60. Control.

  The operation control state machine 62 executes the storage timing of the gradation value group in units of lines of the current line gradation value line buffer and the peripheral line gradation value line buffer 53 in a cycle of 100 μsec, and one line in this cycle. Input to the quaternary quantization unit 58 of the gradation value of the.

  The print control circuit 46 includes an LVDS reception unit 71, a nozzle unevenness correction unit 72, and a rearrangement unit 73. The LVDS receiver 71 is an LVDS receiver that receives the differential signal transmitted from the LVDS transmitter 61. The LVDS reception unit 71 outputs the received differential signal to the nozzle unevenness correction unit 72. The nozzle unevenness correcting unit 72 corrects the received quantized gradation value according to the unique characteristics of the head 2. The nozzle unevenness correction unit 72 outputs the corrected data to the rearrangement unit 73. The rearrangement unit 73 rearranges the quantized gradation values so that ink droplets are ejected at the ejection timing corresponding to the position of the nozzle 8, generates head drive data, and outputs the generated drive data to the head 2. . The head 2 ejects ink droplets from the nozzles 8 in accordance with the output drive data.

  As described above in detail, according to the printer 1 of the present embodiment, the distribution ratio of the gradation value of the pixel to each nozzle 8 is set to the right in the main scanning direction for the nozzle 8 in the overlapping portion of the nozzle unit 80ui. The nozzles of the overlapping portion of the nozzle unit 80u (i + 1) are gradually increased toward the right side in the main scanning direction, and the nozzle group u1c, the nozzle group u2l, the nozzle group u2c, and the nozzle group Quantization with error diffusion is performed in the order of u3l, nozzle group u3c, nozzle group u4l, and nozzle group u4c, and then in order of nozzle group u1r, nozzle group u2r, and nozzle group u3r. As a result, the quantization can be continuously performed in units of gradation values, so that reception of gradation value data and processing of the gradation value data can be performed simultaneously. For this reason, in the configuration in which the received gradation value data is stored in the buffer, it is possible to prevent the gradation value stored in the buffer and the gradation value read from the buffer from corresponding to different pixels, thereby reducing the load on the buffer. be able to. Therefore, the hardware configuration is simplified as compared with the case where the quantization is sequentially performed in the order of the nozzle units 80 toward the right side in the main scanning direction.

  Note that the gradation values distributed to the nozzle group u1r, the nozzle group u2r, and the nozzle group u3r are quantized to the gradation values relating to the pixels corresponding to the nozzle group u2c, the nozzle group u3c, and the nozzle group u4c, respectively. The generated quantization error is not distributed. However, as can be seen from FIG. 5, in the vicinity of the nozzle group u2c, nozzle group u3c, and nozzle group u4c, the distribution ratios to the nozzle group u2l, nozzle group u3l, and nozzle group u4l are the nozzle group u1r, nozzle group u2r, and nozzle group. It can be seen that it is largely close to 1 compared with the distribution ratio to u3r. Therefore, the influence on the image quality of not distributing the quantization error generated by quantizing the gradation values distributed to the nozzle group u1r, the nozzle group u2r, and the nozzle group u3r is negligible.

  In addition, the storage timing of the gradation value group in units of lines of the current line gradation value line buffer 52 and the peripheral line gradation value line buffer 53 is executed at a cycle of 100 μsec, and the gradation value of one line within this cycle. Therefore, each line buffer does not need more capacity than the number of pixels in one line. Therefore, the hardware configuration is further simplified.

  Further, after quantizing the tone values of the pixels corresponding to the nozzle group u1c, nozzle group u2l, nozzle group u2c, nozzle group u3l, nozzle group u3c, nozzle group u4l, nozzle group u4c, the nozzle group u1r, nozzle group Since the gradation values of the pixels corresponding to u2r and nozzle group u3r are quantized, the above-described processes can be performed even when three or more nozzle units 80 are formed. .

  In addition, the seam correction unit 55 determines that the nozzles 8 belonging to the nozzle group uir and the nozzles 8 belonging to the nozzle group u (i + 1) l that have the same position in the main scanning direction as the nozzle 8 belong to both the nozzles 8. Since the gradation value relating to the corresponding pixel is configured to be distributed to both nozzles 8, it is possible to reduce the visual influence due to the positional deviation of the head unit in the main scanning direction.

  In addition, the quantization error generated with the quantization of the gradation values distributed to the nozzles 8 belonging to the nozzle group uir is not stored in the one-line-before error line buffer 59 and the two-line-before error line buffer 60. Therefore, a buffer having more stages than the number of pixels for two lines is not required, and the hardware configuration is simplified.

<Modification>
In this embodiment, when quantizing the gradation values of the pixels corresponding to the nozzle group u1r, the nozzle group u2r, and the nozzle group u3r, only the quantization error generated when the previous three gradation values are quantized. It is configured to be distributed, but includes a second error buffer for storing an error value generated when the nozzle group u1r, the nozzle group u2r, and the nozzle group u3r are quantized, and an error matrix when quantized. The configuration may be such that the error values stored in the calculation unit 56 and the second error buffer are added. According to this, since more accurate error diffusion can be performed, the image quality is improved.

  In addition, this embodiment is only a mere illustration and does not limit this invention at all. Therefore, the present invention can be variously improved and modified without departing from the scope of the invention. For example, in the above-described embodiment, the storage timing of the gradation value group for each line of the current line gradation value line buffer 52 and the peripheral line gradation value line buffer 53 is executed at a cycle of 100 μsec, and within this cycle. Although the configuration is such that the input of the gradation value of one line to the quaternary quantization unit 58 is completed, the gradation value group in line units of the current line gradation value line buffer 52 and the peripheral line gradation value line buffer 53. The storage timing may be arbitrary. In addition, the timing at which the input of the gradation value of one line to the quaternary quantization unit 58 may be independent of the period or may be longer than the period.

  Furthermore, in the above-described embodiment, for each of the nozzle group u1r, the nozzle group u2r, and the nozzle group u3r, in addition to the nozzle group, pixels corresponding to the nozzle 8 in the nozzle group u1c, the nozzle group u2c, and the nozzle group u3c In this configuration, only an error value accompanying quantization with such a gradation value is distributed, but the pixel corresponding to the nozzle group and the nozzle 8 in any one of the nozzle group u1c, the nozzle group u2c, and the nozzle group u3c. A configuration may be used in which only error values associated with quantization at the gradation values are distributed.

  In addition, in the above-described embodiment, the actuator is configured to eject ink droplets from the nozzle 8 by applying pressure to the ink stored in the pressure chamber, but is configured to eject ink droplets by thermal energy. May be.

  In addition, in the above-described embodiment, the quantization by the quaternary quantization unit is performed in one direction, but so-called bidirectional error diffusion in which the quantization direction is reversed for each line may be performed. .

  Furthermore, although an example in which the present invention is applied to an ink jet printer has been described, the present invention can be applied to any apparatus that records an image by discharging droplets onto a recording medium, such as a copying machine or a facsimile.

DESCRIPTION OF SYMBOLS 1 ... Inkjet printer 2 ... Inkjet head 2a ... Ejection surface 8 ... Nozzle 45 ... Image processing circuit 46 ... Print control circuit 51 ... RIP data receiving part 52 ... Current line gradation value line buffer 53 ... Peripheral line gradation value line buffer 54 ... gradation value interpolation section 55 ... seam correction section 56 ... error buffer 57 ... adder 58 ... quaternary quantization section 59 ... 1 line previous error line buffer 60 ... 2 line previous error line buffer 61 ... LVDS transmission section 62 ... Operation control state machine 71 ... LVDS receiver 72 ... Shading correction unit 73 ... Rearrangement unit 80 ... Nozzle unit

Claims (5)

N (N: a natural number of 2 or more) nozzle rows in which a plurality of nozzles that discharge liquid are arranged in a predetermined direction
Pressure applying means for applying pressure for discharging liquid from the nozzle;
A quantization unit that quantizes the sum of the multi-value data related to each pixel of the image and the quantization error distributed to the pixel, and outputs quantization data obtained by the quantization and the quantization error;
An error buffer for storing the quantization error input from the quantization unit;
A controller that controls the pressure applying means, the quantization unit, and the error buffer;
The N nozzle rows are provided so that the nozzle formation ranges in the predetermined direction are different from each other, and the two nozzle rows adjacent to each other in the predetermined direction are the nozzles on one side of the predetermined direction. When a row is an i-th (i: natural number from 1 to N−1) nozzle row and the other nozzle row is an i + 1-th nozzle row, at least one nozzle and i + 1-th nozzle belonging to the i-th nozzle row The two adjacent nozzle rows partially overlap so that the positions in the predetermined direction with the at least one nozzle belonging to the row are the same,
The controller is
For the nozzle belonging to the i-th nozzle row and the nozzle belonging to the i + 1 nozzle row having the same position in the predetermined direction as the nozzle, both the multi-value data relating to the pixels corresponding to both the nozzles are stored. The quantization multi-value data obtained by distributing to the nozzles is quantized by the quantization unit,
For each nozzle belonging to the i-th nozzle row in a region partially overlapping with the i + 1-th nozzle row, the distribution ratio of the distributed multi-value data is gradually decreased from the one side toward the other side, For each nozzle belonging to the (i + 1) th nozzle row in a region partially overlapping with the i nozzle row, the distribution ratio of the distributed multi-value data is gradually increased from the one side toward the other side,
When causing the quantization unit to quantize the multi-value data and the distributed multi-value data,
When attention is paid to the nozzles belonging to the i-th nozzle row and the nozzles belonging to the i + 1-th nozzle row, the quantization relating to the pixels corresponding to the nozzles is as follows.
(1) The multi-value data relating to the pixel corresponding to the nozzle in the region belonging to the i-th nozzle row and not partially overlapping with other nozzle rows and the quantization error distributed to the pixel The sum is quantized sequentially from the one side to the other side;
(2) Subsequently, the distributed multi-value data relating to the pixel corresponding to the nozzle belonging to the i + 1 nozzle row and partially overlapping the i-th nozzle row and the quantum distributed to the pixel The quantization error sum is sequentially quantized from the one side toward the other side,
(3) Further, the multi-value data relating to the pixel corresponding to the nozzle belonging to the i + 1 nozzle row and not partially overlapping with other nozzle rows, and the quantization distributed to the pixel Corresponds to the nozzles that are quantized in order from the one side toward the other side and that belong to the i + 1 nozzle row and do not partially overlap other nozzle rows. In the multi-value data related to the pixel, the quantization error associated with the quantization in the above (1) and (2) and the multi-value data related to the pixel corresponding to the nozzle in the region Distributing only at least one of the quantization errors associated with quantization at
(4) Thereafter, the distributed multi-value data relating to the pixels corresponding to the nozzles belonging to the i-th nozzle row and partially overlapping with the i + 1-th nozzle row, and the quantization distributed to the pixels The total error is quantized in order from the one side to the other side, and corresponds to the nozzle that belongs to the i-th nozzle row and partially overlaps the i + 1-th nozzle row. The distributed multi-value data related to the pixel includes the quantization error associated with the quantization in (1) above and the quantum in the distributed multi-value data related to the pixel corresponding to the nozzle in the region. An image recording apparatus that distributes at least one of the quantization errors associated with the conversion. A multi-value data buffer for storing the multi-value data relating to each pixel arranged in the predetermined direction;
The control unit stores the multi-value data in the multi-value data buffer in a pixel column unit composed of a plurality of the pixels arranged in the predetermined direction in the multi-value data for each predetermined cycle; and Within the period, the sum of each multi-value data stored in the multi-value data buffer and the quantization error distributed to the pixels of the multi-value data and the distributed multi-value obtained by distributing the multi-value data The image recording apparatus according to claim 1, wherein the quantization unit quantizes the sum of the data and the quantization error distributed to the distributed multilevel data.   The control unit includes nozzles that belong to an i-th nozzle row and partially overlap an i + 1-th nozzle row when three or more nozzle rows in which the nozzles are arranged in the predetermined direction are formed. The multi-value data related to the pixels corresponding to all the other nozzles is obtained by performing the total quantization of the distribution multi-value data related to the pixels corresponding to the pixel and the quantization error distributed to the distribution multi-value data. And the quantization unit that quantizes the sum of the quantization errors distributed to the pixels of the multi-value data and the sum of the quantization errors distributed to the distribution multi-value data and the distribution multi-value data. The image recording apparatus according to claim 1, wherein the image recording apparatus is performed. A multi-value data buffer for storing the multi-value data relating to each pixel arranged in the predetermined direction, and the multi-value data stored in the multi-value data buffer are distributed to the distributed multi-value data at a specified distribution ratio. A multi-value data distribution unit
The controller is
The distribution multi-value data relating to the pixels corresponding to the nozzles belonging to the i + 1 nozzle row and partially overlapping with the i-th nozzle row and the quantization error distributed to the distribution multi-value data The distributed multi-value data relating to the pixels corresponding to each nozzle belonging to the total and i-th nozzle row and partially overlapping with the i + 1-th nozzle row and the quantization distributed to the distributed multi-value data When the quantizing unit quantizes the sum of errors, the distribution multi-value data obtained by distributing the multi-value data stored in the multi-value data buffer to the multi-value data distribution unit is used. The image recording apparatus according to claim 1, wherein the image recording apparatus is an image recording apparatus.   The error buffer includes the multi-value data and the multi-value data related to the pixels corresponding to the nozzles other than the nozzles that belong to the i-th nozzle row and partially overlap with the i + 1-th nozzle row. The quantization unit calculates the sum of the quantization error distributed to the pixels and the distribution multi-value data obtained by distributing the multi-value data and the quantization error distributed to the distribution multi-value data. A first error buffer for storing the quantization error output by the quantization unit when quantized to the first nozzle, and the nozzle belonging to the i-th nozzle row and partially overlapping with the i + 1-th nozzle row The quantization unit outputs when the quantization unit quantizes the sum of the distribution multi-value data related to the pixel corresponding to the pixel and the quantization error distributed to the distribution multi-value data. Mistake The image recording apparatus according to claim 1, characterized in that it comprises a second error buffer for storing.

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