JP2006334979A - Liquid droplet ejection apparatus, data creation apparatus, liquid droplet ejection method, and data creation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid droplet ejection apparatus, a data creation apparatus, a liquid droplet ejection method, and data creation method, wherein a white line generated by a poorly-ejected ejection means is made hardly seen without the need for a particular and complicated treatment only in a narrow range of the poorly-ejected ejection means, and its vicinity, and also a poor ejection is easily inspected. <P>SOLUTION: An inkjet recorder 10 is provided with a recording head 12 constituted of a plurality of head units 60 which have a plurality of arranged liquid droplet ejectors 62 (nozzles 62A) discharging ink droplets and, are arranged in an arrangement direction of the nozzles 62A. In this recorder 10, the liquid droplet ejection apparatus judges whether a poorly-ejected nozzle 62A which does not eject an ink droplet normally is included in every head unit 60, and, on the basis of image data input from an outside, creates recording data so that an ejection density of a head unit 60 which is judged as including a poorly-ejected nozzle 62A (a resolution of an image recorded with the head unit 60) is smaller than an arrangement density of the nozzles 62A. An image is formed by driving the nozzles 62A according to the created recording data. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a droplet discharge device including a head configured by arranging a plurality of units in which a plurality of discharge means for discharging droplets are arranged in a predetermined direction, and a droplet discharge method for discharging a droplet by the head The present invention also relates to a data generation apparatus and a data generation method for generating discharge data used in a droplet discharge apparatus.

  Currently, inkjet printers that have a recording head in which a plurality of nozzles are arranged as ejection means for ejecting liquid droplets and that record images by ejecting liquid droplets (in this case, ink droplets) from the nozzles are widely used. ing. An ink jet printer has a simple structure and a low printing sound, and can record a multi-tone image such as a photographic image with high image quality. Also, in recent years, high-density heads have become possible due to improvements in microfabrication technology.

  However, due to manufacturing variations of the recording head and troubles during use (bubbles generated in the liquid chamber communicating with the nozzles and dust), ink droplets can be ejected normally due to non-ejection or ejection failure of ink droplets. Difficult defective nozzles may occur. In particular, in recent years, the resolution has been increased, and the number of nozzles arranged in the recording head has been greatly increased as compared with the prior art. For this reason, the occurrence frequency of defective nozzles is also increasing.

  When a defective nozzle is generated, ink droplets are not applied to the portion corresponding to the defective nozzle portion of the recording paper, and white stripes are generated in the formed image.

  In a PWA (Partial Width Array) type ink jet printer that prints by moving the recording paper in the sub-scanning direction while scanning the recording head in the main scanning direction, white streaks are prevented by recording in the multi-pass recording method. Can do. In the multi-pass recording method, recording is performed with different nozzle groups by moving the recording medium minutely in the nozzle arrangement direction of the recording head and scanning the recording head a plurality of times (multi-pass) in a direction intersecting the nozzle arrangement direction. This is a method for completing an image by complementarily recording images thinned out in the same area of the medium. Therefore, even if a part of the nozzles of the recording head becomes defective in ejection, it is supplemented by other nozzles, and the occurrence of white stripes is prevented.

  On the other hand, in a so-called FWA (Full Width Array) type ink jet printer which has a long recording head having a width substantially equal to the width of the recording paper and performs recording while conveying the recording medium only with the recording head fixed. Although high-speed printing is possible, the occurrence of defective nozzles is a particularly serious problem because multi-pass printing cannot be performed. In many cases, long recording heads are usually manufactured by connecting a plurality of small units with a plurality of nozzles arranged in the main scanning direction, but all units are in a complete state with no defective nozzles. Manufacturing is costly, and even if it can be manufactured, it is difficult to prevent the generation of defective nozzles depending on the state of use.

Therefore, in response to the determination result that the nozzle is a defective nozzle, as a countermeasure, ink droplet ejection from the defective nozzle is stopped, and dots corresponding to two adjacent normal nozzles land approximately twice as large as in normal operation. An ink jet printer that controls the above is proposed (for example, see Patent Document 1). Also, by applying this to a multi-head line printer, if a part of the nozzles that make up the multi-head fails, a printer that switches the drive to increase the dot diameter of the nozzle adjacent to the failed nozzle is proposed. (For example, see Patent Document 2).
JP 11-348246 A JP 2002-86767 A

  However, in the conventional technology, white stripes are made difficult to see by increasing the density at the pixel adjacent to the defective nozzle, or ejecting large dots using a special drive circuit, and increasing the amount of ink to blur the dots. Therefore, there is a problem that special drive control is required only at a location adjacent to the defective nozzle, and the control becomes complicated. In addition, in order to increase the dot diameter, control for switching the drive waveform for the nozzles near the failed nozzle is performed, so that it is necessary to specify the defective nozzles in units of nozzles, which complicates the inspection of defective nozzles.

  The present invention has been made to solve the above-mentioned problems, and it is possible to achieve the above-described problem by using a discharge failure discharge means without requiring special and complicated processing only for a narrow area around the discharge failure discharge means and the discharge failure discharge means. It is an object of the present invention to provide a droplet discharge device, a data generation device, a droplet discharge method, and a data generation method that make it difficult to see generated white streaks and simplify discharge failure inspection.

  In order to achieve the above object, a droplet discharge device of the present invention includes a head configured by arranging a plurality of units in which a plurality of discharge means for discharging droplets are arranged in the arrangement direction of the discharge means, and each unit. A determination unit that determines whether or not there is a defective discharge unit that does not normally discharge droplets, and based on data input from the outside, it is determined that the discharge unit with the defective discharge is included. A generating unit that generates discharge data so that a discharge density of the unit formed is lower than an array density of the discharge units, and a driving unit that drives the discharge unit based on the generated discharge data. Has been.

  In this droplet discharge device, the determination unit determines whether or not a discharge failure discharge unit that does not normally discharge a droplet is included for each unit, and the generation unit includes a unit including the discharge failure discharge unit. The discharge data is generated so that the discharge density is lower than the arrangement density of the discharge means.

  Specifically, the generating unit includes a group of ejection units including the ejection unit having the ejection failure when the ejection unit of the unit determined to include the ejection unit having the ejection failure is divided into a plurality of groups. By generating the discharge data so that no liquid droplets are discharged from the liquid, the discharge density can be made lower than the arrangement density of the discharge means.

  A method for dividing the discharge means is not particularly limited, but it is preferable to divide the discharge means so as not to be included in the same group.

  In addition, the generating unit determines the discharge unit having the discharge failure when dividing every n−1 (n is an integer of 2 or more) of the plurality of discharge units into one group. By generating the discharge data so that droplets are not discharged from a group of discharge means, the discharge density can be reduced to 1 / n of the array density of the discharge means.

  For example, when generating discharge data so that the discharge density is ½ of the array density, every other discharge means is made into one group, and two groups (an odd-numbered group along the array direction). When divided into even-numbered groups), ejection data is generated so that droplets are not ejected from the ejection means of the group including the ejection means with defective ejection.

  And a drive means drives a discharge means based on the produced | generated discharge data.

  In this way, by lowering the discharge density of the unit including the discharge means with defective discharge, it is possible to prevent the generation of white stripes that are sensitively recognized by human vision and to obtain a high-quality output result. Simple discharge control can be performed on a unit-by-unit basis without performing special and complicated processing only for defective discharge means and a narrow area around the defective discharge means.

  Further, as described above, the discharge means is divided into a plurality of groups or every n−1 discharge means as one group and divided into n groups, and the droplets are discharged from the discharge means of the group including the discharge means having defective discharge. In order to generate discharge data so that no discharge occurs, it is necessary for the determination means to determine whether or not a discharge means with defective discharge is included in each group, but for each of the discharge means arranged in the unit It is not necessary to determine whether or not there is a discharge failure. Accordingly, it is very easy to inspect for ejection defects.

  In addition, since the discharge density can be controlled for each unit, the region in which the discharge density is changed is limited, and it is not necessary to lower the discharge density as a whole.

  Furthermore, the generation unit can generate the discharge data so that the size of the liquid droplets discharged from the unit having a low discharge density is larger than a predetermined size.

  When the discharge density is lowered as described above, the area corresponding to one ejection means in the medium to be ejected with droplets is wider than when the ejection density is not lowered. If this is left, droplets may not be sufficiently applied to the region. Accordingly, if the ejection data is generated so as to increase the size of the droplet, the droplet can be sufficiently applied.

  When the droplet size is increased as described above, for example, a control signal or information (for example, information on the discharge density) for driving to increase the droplet size is included in the discharge data. Alternatively, the ejection data itself may indicate the droplet size.

  In addition, the generation unit may generate the one dot when the size of the droplet discharged from the unit with the low discharge density is not sufficient for the discharge area for one dot when the discharge density is low. The ejection data can be generated so that a plurality of droplets are ejected to the ejection area for each minute.

  As a result, even when the driving method of the driving unit is limited, if a plurality of droplets are ejected to the ejection region for one dot, the droplets can be sufficiently ejected to the ejection medium.

  Further, the generating means is adapted so that at least one of the color and density of the image formed by the unit having a low discharge density is harmonized with at least one of the color and density of the image formed by the other units other than the unit. In addition, at least one of color conversion and density conversion of the ejection data can be performed. In addition, the generation unit performs halftone processing of the ejection data so that the density of the image formed by the unit having a low ejection density matches the density of the image formed by another unit other than the unit. be able to.

  For example, when the discharge density or droplet size of a unit is changed, the color and density may change compared to the case where droplets are discharged by a unit that does not change them. Therefore, by performing color change, density conversion, and halftone processing so as to harmonize with the output of other units, the output result can be made high quality.

  Note that the determination means includes information on the discharge state of the discharge means for each group in each unit obtained by the discharge inspection performed for each group when the discharge means of the unit is divided into a plurality of groups. Based on this, it can be determined whether or not the ejection failure means is included in each unit.

  Thereby, since the discharge inspection of the discharge means may be performed for each group when the discharge means of the unit is divided into a plurality of groups, the inspection becomes easy.

  Further, the data generating apparatus of the present invention drives a discharge unit based on a head configured by arranging a plurality of units in which a plurality of discharge units for discharging droplets are arranged in the arrangement direction of the discharge unit, and discharge data. A data generation device for generating discharge data used in a droplet discharge device provided with a driving means for performing whether or not a discharge failure unit that does not normally discharge droplets is included in each unit. Based on the judgment means for judging and the data inputted from the outside, the ejection data so that the ejection density of the unit judged to include the ejection means having the ejection failure is lower than the arrangement density of the ejection means. Generating means for generating.

  In this data generation device, the determination unit determines whether or not a discharge failure unit that does not normally discharge droplets is included for each unit, and the generation unit discharges the unit including the discharge unit having a discharge failure. The ejection data is generated so that the density is lower than the arrangement density of the ejection means. The droplet discharge device can drive the discharge means based on the discharge data generated in this way.

  This data generation device can also reduce the discharge density of the unit including the discharge means having the discharge failure, making it difficult to see the white stripes and obtaining a high-quality output result. This makes it possible to perform simple discharge control in units of units without performing special and complicated processing only in a narrow range.

  The droplet discharge method of the present invention is executed by a droplet discharge apparatus including a head configured by arranging a plurality of units in which a plurality of discharge means for discharging droplets are arranged in the arrangement direction of the discharge means. A method for determining whether or not each unit includes a discharge unit having a discharge failure that does not normally discharge a droplet, and the discharge based on data input from the outside. A generating step for generating discharge data such that a discharge density of a unit determined to include defective discharge means is lower than an array density of the discharge means; and the discharge means based on the generated discharge data And a driving process for driving.

  The droplet discharge method of the present invention can also reduce the discharge density of the unit including the discharge means having a defective discharge, as in the case of the droplet discharge apparatus of the present invention. In addition, it is possible to perform simple discharge control on a unit-by-unit basis without performing special and complicated processing only for the discharge means having a discharge failure and a narrow range around the discharge means.

  In the data generation method of the present invention, a head in which a plurality of units in which a plurality of ejection means for ejecting droplets are arranged are arranged in the arrangement direction of the ejection means, and the ejection means is driven based on ejection data. A data generation method for generating discharge data used in a droplet discharge apparatus having a driving unit for performing whether or not a discharge failure unit that does not normally discharge droplets is included in each unit. Based on the determination step of determining and the data input from the outside, the discharge data so that the discharge density of the unit determined to include the discharge means having the discharge failure is lower than the arrangement density of the discharge means. Generating step.

  In the data generation method of the present invention, similarly to the data generation apparatus of the present invention, the discharge density of the unit including the discharge means with defective discharge can be reduced, and white lines are difficult to see and high quality output results are obtained. In addition, simple discharge control can be performed on a unit-by-unit basis without performing special and complicated processing only for the discharge means having a discharge failure and a narrow range around the discharge means.

  As described above, the present invention makes it difficult to see white streaks generated by a discharge failure discharge means without requiring special and complicated processing only for a discharge failure discharge means and a narrow area around the discharge failure discharge means. In addition, it is possible to simplify the discharge defect inspection.

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

[First Embodiment]
As shown in FIG. 1, an inkjet recording apparatus 10 serving as a droplet discharge apparatus according to the present embodiment includes Y (yellow), M (magenta), and C arranged from the upstream side in the transport direction of paper P. (Sian) and K (black) color recording heads 12Y to 12K, and ink tanks 14Y to 14K for storing ink to be supplied to the recording heads 12Y to 12K for the respective colors. Hereinafter, when the recording heads 12Y to 12K and the ink tanks 14Y to 14K of the respective colors are described without particular distinction, the suffixes at the end of the reference numerals are omitted and referred to as the recording head 12 and the ink tank 14.

  In addition, the inkjet recording apparatus 10 includes a paper feed tray 16 that accommodates paper P as a recording medium, an endless belt-like transport body 24 that is disposed to face the recording head 12 and transports the paper P, and paper after printing. Are provided with a paper discharge tray 18 and maintenance units 26A and 26B for cleaning the nozzles of the recording head 12.

  Further, the inkjet recording apparatus 10 includes a first conveyance path constituted by a path 20A from the paper feed tray 16 to the conveyance body 24 and a path 20B from the conveyance body 24 to the paper discharge tray 18, and the first conveyance path. A plurality of transport rollers are provided so that a second transport path 22 extending from the path 20B to the transport body 24 in the opposite direction is formed.

  In the first conveyance path 20A, the paper P is conveyed from the paper feed tray 16 to the conveyance body 24 by a plurality of conveyance rollers one by one. Further, in the path 20B, the discharge tray 18 is conveyed by a plurality of conveyance rollers. To reach. In the present embodiment, the second transport path 22 is provided to enable double-sided printing by inverting the paper.

  Further, the transport body 24 includes a belt wound around two rolls. As a method of holding the paper P by the transport body 24, a power feeding suction force can be used. That is, the sheet is pressed against the belt by the charging roll, and the sheet P is charged to generate an adsorption force.

  The recording head 12 has a head bar (not shown) having a length corresponding to the width of the paper P and a direction in which the head unit 60 as shown in FIG. 3 is orthogonal to the paper transport direction (this is called a main scanning direction). And a print area corresponding to the maximum width of the paper P. In each head unit 60, a plurality of droplet ejectors 62 (nozzles 62 </ b> A) that eject ink droplets are arranged in the same direction as the arrangement direction of the head units 60. The ink jet recording apparatus 10 can print on the entire width of the paper P by performing recording while transporting only the paper P while the recording head 12 is fixed without performing main scanning.

  As shown in FIGS. 4B and 4D, the droplet ejector 62 includes an ink pressure chamber 62B communicating with a nozzle 62A for ejecting ink, and a piezoelectric element 62C provided in contact with the ink pressure chamber 62B. It is comprised including. As is well known, the piezoelectric element 62C has a property of changing its shape when a voltage is applied. By using this change in shape, pressure is applied to the ink pressure chamber 62B, and ink droplets are ejected from the nozzle 62A. Then, dots are recorded on the paper P. At this time, as shown in FIGS. 4A and 4C, by controlling the drive waveform applied to the piezoelectric element 62C, for example, a large ink droplet from the nozzle 62A (see FIG. 4B). A small ink droplet (see FIG. 4D) is ejected. In addition, when ink droplets are not ejected from the nozzle 62A (no droplets), it is possible to apply a waveform voltage that does not form dots.

  FIG. 2 is a block diagram showing the configuration of the control system of the inkjet recording apparatus 10 according to the present embodiment. As shown in FIG. 2, the inkjet recording apparatus 10 includes a resolution conversion unit 30 that converts image data into image data having a desired resolution for each head unit when image data is input from the outside. . A color conversion unit 32 is connected to the resolution conversion unit 30. The color conversion unit 32 performs color conversion processing on the image data from the resolution conversion unit 30 according to the characteristics of the paper P and ink.

  The color converter 32 performs color conversion according to a color conversion table (Look Up Table, hereinafter referred to as LUT) 46. The LUT 46 is separately created and stored so that the color characteristics expressed by the image data match the color characteristics expressed by the inkjet recording apparatus 10. The color conversion unit 32 performs not only color conversion but also density conversion. The density conversion is also performed according to the density conversion table, but the illustration of the density conversion table is omitted. By performing density conversion, it is possible to convert input image data into image data having gradation values that can be appropriately reproduced on an output image.

  A quantization unit 34 is connected to the color conversion unit 32. The quantization unit 34 performs halftone processing on the image data processed by the color conversion unit 32. Here, since 256-gradation image data is input, the quantization unit 34 can control the 256-gradation image data by an ejector driving unit 38 described later (that is, can be recorded by the inkjet recording apparatus 10). N) is converted into image data having the number of gradations. For example, if two-tone recording of “no drops / large drops” is possible with the inkjet recording apparatus 10, binary halftone processing is performed, and “no drops / small drops / medium drops / large drops” 4 If gradation recording is possible, four-value halftone processing is performed. In the present embodiment, halftone processing is performed by known error diffusion processing or dither processing. In the present embodiment, it is assumed that four gradation recording is possible.

  A recording data creation unit 36 is connected to the quantization unit 34. The recording data creation unit 36 converts the image data processed by the quantization unit 34 into a data structure that can be recorded by the ejector driving unit 38, rearranges the data in the recording order (transfer order), and sends the data to the ejector driving unit 38. Output. At this time, print data is created in consideration of the ejection timing and data arrangement mapped to the arrangement of the print head 12 and the nozzles 62A. Various control signals are applied and inserted as necessary.

  An ejector driving unit 38 is connected to the recording data creating unit 36. The ejector driving unit 38 ejects ink droplets from the nozzles 62 </ b> A of the droplet ejector 62 by outputting a driving signal having a predetermined driving waveform to the piezoelectric elements 62 </ b> C of the droplet ejectors 62 of the recording head 12.

  A controller 40 that controls these components is connected to the color converter 32, the quantizer 34, the recording data generator 36, and the ejector driver 38.

  The control unit 40 and the ejector driving unit 38 are based on the recording data generated by the recording data generating unit 36 while the control unit 40 controls the conveying system 42 to convey the sheet by the conveying body 24. Then, the droplet ejector 62 is driven to eject an ink droplet to form an image.

  In the inkjet recording apparatus 10, every third droplet ejector 62 out of a plurality of droplet ejectors 62 arranged in each head unit 60 is grouped for each head unit 60 of the recording head 12. Data indicating whether or not each group when divided into four groups includes defective nozzles (defective droplet ejectors) that are difficult to eject ink droplets normally due to non-ejection or defective ejection of ink droplets. A memory (not shown) for storing (hereinafter referred to as data relating to ejection failure) is provided. In accordance with the data relating to the ejection failure stored in the memory, processing such as reducing the resolution of the image area formed by the head unit 60 including the defective nozzle as shown in FIG. 5 is performed.

  The ejection failure inspection may be performed automatically at a predetermined timing (for example, at the start of use) or periodically. Moreover, you may make it perform manually by a user at arbitrary timings.

  Here, a specific inspection method will be described. In the present embodiment, every third droplet ejector 62 out of the plurality of droplet ejectors 62 arranged in the head unit 60 is taken as one group, and the first to fourth four in the arrangement direction of the nozzles 62A. As shown in FIG. 3, ink droplets are ejected from the nozzles 62A for each group, and a line having a predetermined length in the sub-scanning direction (paper transport direction) is recorded on the test paper.

  The number of divisions of the nozzles 62A is not limited to four, but it is preferable to divide the nozzles so that the line interval d in each group is an interval at which the presence / absence of lines (discharge state of each nozzle 62A) can be confirmed.

  Here, when the nozzle array density of each head unit 60 of the recording head 12 is 1200 npi in the main scanning direction (density at which 1200 nozzles 62A are arranged per inch), recording is performed for each of the four divided groups. The interval between the lines (interval d in FIG. 3) is 300 dpi.

  Then, the formed lines are visually confirmed, or the printing result is automatically read by a reading device, and the line intervals are obtained by causing the computer to calculate the line intervals from the reading results. The line intervals are different from 300 dpi. If there is an interval portion, it is determined that a defective nozzle is included in the group in which the line is formed. For example, if there is one 150 dpi line interval in the printing result, it can be determined that the group contains one non-ejection defective nozzle. This inspection is performed for each head unit 60, and the determination result (presence / absence of defective nozzles for each group) is stored in the memory for each head unit 60. By storing information on the presence / absence of defective nozzles for each group divided into four in the memory, the resolution can be reduced to ½ or ¼.

  Note that the ejection failure inspection may be performed at the time of shipment of the recording head 12 from the factory. In this case, the inspection result is stored not in the memory of the control unit 40 but in the memory of the recording head 12, for example, and when the recording head 12 is mounted on the inkjet recording apparatus 10, the control unit 40 records the data. It can be used by reading from the memory of the head 12.

  Next, the flow of processing when image data is input to the inkjet recording apparatus 10 from the outside will be described.

  When image data is input from an external computer or the like, first, the resolution conversion unit 30 executes a processing routine as shown in FIG.

  In step 100, image data is read in units of head units 60. In step 102, data relating to ejection failure stored in correspondence with the head unit 60 is read from the memory.

  In step 104, it is determined whether or not a defective nozzle is included in the head unit 60 that forms the image of the image data read in step 100, based on the read data relating to ejection failure.

  If it is determined in step 104 that a defective nozzle is included, the process proceeds to step 106, and the image data read in step 100 is converted into low-resolution image data. Specifically, the image data is converted into image data having a resolution lower than the highest resolution (that is, the arrangement density of the nozzles 62 </ b> A) that can be recorded by the inkjet recording apparatus 10.

  In the present embodiment, every third droplet ejector 62 out of the plurality of droplet ejectors 62 arranged in the head unit 60 is divided into four groups, and the divided four groups are divided. Data indicating whether or not a defective nozzle is included in each of these is stored in the aforementioned memory. Therefore, although it is possible to create image data with the resolution reduced to 1/2 or 1/4 of the maximum resolution, here, in order to simplify the explanation, even if a defective nozzle is included in the head unit 60. Assuming that the number is about one at most, image data with the resolution reduced to ½ of the maximum resolution is created. Specifically, when it is determined that the defective nozzle data read from the memory includes defective nozzles in any of the first to fourth groups divided into four, the nozzles 62A are alternately used. Image data is thinned out so that ink droplets are ejected.

  On the other hand, if it is determined in step 104 that the head unit 60 does not include a defective nozzle, the process proceeds to step 108 where the image data read in step 100 is converted into high-resolution image data. Here, the image data is converted into image data having the highest resolution (that is, the arrangement density of the nozzles 62A) that can be recorded by the inkjet recording apparatus 10. Here, when the image data input from the outside is equal to the maximum resolution, the resolution is maintained without being thinned, and when the input image data is higher than the maximum resolution, the image data Thin out and convert to the highest resolution.

  In step 110, it is determined whether or not resolution conversion processing has been completed for all image data input from the outside. If it is determined that the process has not been completed, the process returns to step 100, the image data corresponding to the next head unit 60 is read, and the same process as described above is repeated. If it is determined that the conversion process has been completed, this processing routine is ended, and the processed image data is output to the color conversion unit 32.

  The color conversion unit 32 performs color conversion of the image data whose resolution is converted by the resolution conversion unit 30 using the color conversion table 46. Further, density conversion is performed using a density conversion table (not shown).

  The image data processed by the color conversion unit 32 is halftone processed by the quantization unit 34. In the present embodiment, the image data of 255 gradations is “no drop (0) / small drop (85) / medium drop (170) / large drop (255)” by error diffusion processing using three threshold values. Are converted into image data having recording levels of four gradations.

  The image data that has undergone halftone processing by the quantization unit 34 is converted into recording data by a recording data creation unit 36. Specifically, first, the image data processed by the quantizing unit 34 is recorded in a data structure that can be recorded by the ejector driving unit 38 (for example, no droplet (00) / small droplet (01) / medium droplet (10) / Large droplets (11), etc.). Thereafter, the recording data is created by rearranging the data in the recording order (transfer order) while considering the arrangement of the recording head 12 and the nozzles 62A. Of the recording data, the portion used by the head unit 60 that is determined to include a defective nozzle is based on the data relating to the discharge failure from all the nozzles 62A in the group including the defective nozzle. In order to prevent ink droplets from being ejected, NULL is inserted every other one. Therefore, when the data regarding ejection failure indicates that the odd-numbered first or third group includes defective nozzles among the first to fourth groups divided into four, the odd number If the data for driving the droplet ejector 62 of the th group is NULL, indicating that the even-numbered second or fourth group includes a defective nozzle, the even-numbered group The data for driving the droplet ejector 62 is NULL.

  Based on the recording data generated by the recording data creation unit 36, the ejector driving unit 38 applies no droplet (00) / small droplet (01) / medium droplet (10) to the piezoelectric element 62C of each droplet ejector 62. ) / Voltage of drive waveform corresponding to each data of large droplet (11) is applied. In addition, for the droplet ejector 62 corresponding to the NULL data, the droplet ejector 62 is not driven so that ink droplets are not ejected. Thereby, an image can be formed without using a defective nozzle.

  Here, a specific example will be described. FIG. 5 shows a recording head 12 composed of three head units 60a, 60b, and 60c having a nozzle arrangement density of 1200 npi, and each head unit 60a, 60b, and the like in the recording head 12 capable of outputting 1200 dpi in one scan. It is the figure which showed typically the specific example of the discharge control with respect to 60c.

  In order to prevent the occurrence of white stripes in the recording head 12, as shown in FIG. 5A, the resolution of the image output by the head unit 60b including the defective nozzle (defective droplet ejector) is set to a normal resolution. The ink droplets are ejected at an ejection density that is half of the nozzle arrangement density by setting it to 1/2 (600 dpi). Specifically, the ink droplets are ejected only from the nozzles 62A of the group that does not include the defective nozzle (the odd-numbered group in FIG. 5), and the group that includes the defective nozzle (the even-numbered group in FIG. 5). The recording data is generated so that ink droplets are not ejected from the nozzles 62A of the (group).

  Although not described above, depending on the presence or absence of defective nozzles in each group, it is not possible to cope with the problem by reducing the resolution (for example, all groups include defective nozzles or only have a low resolution that is not acceptable. If it cannot be output, maintenance operations such as dummy jet discharge processing and wiping processing may be executed. Whether or not to perform the maintenance operation may be determined immediately after the discharge inspection.

  As described above, since the head unit 60 including defective nozzles reduces the discharge density and does not use the group including defective nozzles to form an image, the reaction to white streaks appearing in a flat image is Due to the human visual characteristic that it is sensitive but is not responsive to regular high-frequency grayscale images, white streaks that are sensitively perceived by human vision do not occur, and high-quality output results can be obtained. Note that, by reducing the resolution (discharge density), many white streaks may appear in a fine cycle. However, in the head unit 60 (recording head 12) in which the nozzles 62A are originally arranged at a high density, the resolution is reduced. Even if it is lowered somewhat, a high resolution can be ensured to some extent, so even if white stripes with a fine cycle occur, human visual ability does not matter. In particular, if a recording medium, such as plain paper, in which ink droplets easily bleed is used, a high-quality output result can be obtained with almost no problem.

  Further, in the above embodiment, n-1 (in the above, three) droplet ejectors 62 out of the plurality of droplet ejectors 62 arranged in the head unit 60 are grouped into n (in the above, the above). 4 groups), and whether or not each of the divided n groups includes a defective nozzle is stored in the memory so that which nozzle 62A is defective. Is not necessary (nozzle number or the like for identifying the nozzle 62A), and the inspection becomes very easy.

  Even if a plurality of nozzles 62A (droplet ejector 62) are defective in one head unit 60, in an extreme case, if all of them are included in one nozzle group, the group If the resolution is reduced so that it is not discharged at the same time, it can be output as it is without generating white streaks. Therefore, the maintenance operation (number of times) can be reduced.

  In addition, by controlling the resolution for each head unit 60 as described above, the area in which the resolution is reduced is limited. Therefore, the resolution of the entire output image is not reduced, and the deterioration of the image quality can be suppressed.

  Furthermore, the processing speed is not reduced by reducing the resolution, but rather the amount of data handled is reduced by reducing the resolution, so that an improvement in the processing speed can be expected.

  In the above embodiment, an example in which only the ejection density (resolution) in the main scanning direction (arrangement direction of the nozzles 62A) is reduced has been described. However, the resolution in the sub-scanning direction is also halved in accordance with the resolution in the main scanning direction. It may be made to become.

  In the above-described embodiment, the example in which the recording data is generated by reducing the resolution to 1/2 of the maximum resolution has been described. However, the present invention is not limited to this, and in the above, ejection failure when divided into four groups. Since the data related to this is stored, the resolution can be reduced to ¼ depending on the presence or absence of defective nozzles in each group.

  Further, in the above embodiment, it is inspected whether each of the four divided groups includes a defective nozzle, and the inspection result is stored in the memory for each group. If the array density of 62A is relatively low and the image quality deteriorates when the resolution is reduced to ¼, the resolution can always be reduced only to half the resolution. The data of the two groups of the odd-numbered group and the even-numbered group may be stored in the memory.

  In the above embodiment, every third droplet ejector 62 out of the plurality of droplet ejectors 62 arranged in the head unit 60 is divided into four groups, and the four divided segments are divided into four groups. Although an example of inspecting whether or not a defective nozzle is included in each of the groups has been described, the division method is not limited to this, and for example, it can be divided and inspected as shown below.

  For example, when an image is output at a discharge density (resolution) that is ½ of the nozzle arrangement density, the defective nozzle is included in either the even-numbered group or the odd-numbered group along the arrangement direction of the nozzles 62A. Therefore, it is only necessary to divide into even numbers such as 2, 4 and so on. Further, when an image is output at a discharge density (resolution) that is 1/3 of the nozzle arrangement density, it is determined which of the first to third groups the defective nozzle is included in the arrangement direction of the nozzles 62A. Therefore, it is sufficient to divide the inspection into 3 divisions, 6 divisions,... And 3k (k is an integer of 1 or more).

  For example, if the nozzle arrangement density of the head unit 60 is 1200 npi, at the time of inspection, when every other nozzle 62A is divided into two groups along the arrangement direction as two groups, an interval of 600 dpi is used. Each line is recorded. Further, when every second nozzle 62A is divided into three groups along the arrangement direction, each line is recorded at an interval of 400 dpi.

  Therefore, if the resolution is reduced to either 1/2 or 1/3, and output is divided into 6 groups every 5th, both resolutions can be obtained in one inspection. It is possible to group defective nozzles corresponding to. In that case, since the line interval d recorded on the test sheet is 200 dpi, it is possible to reasonably determine the ejection failure. Further, when the resolution is reduced to any one of 1/2, 1/3, and 1/4, and output is performed, the nozzles 62A may be divided into 12 portions every 11 along the arrangement direction.

  If the nozzle arrangement density of the head unit is high by performing the inspection in this way and there is no problem in image quality even if the resolution is 1/3, 1/4,..., Continuous 2 nozzles, 3 nozzles, Even if the nozzle is a defective nozzle, an image can be output without any problem.

  The present invention is not limited to this, and the plurality of nozzles 62A may be randomly divided into a plurality of groups, and the resolution may be changed by inspecting ejection defects for each group. At this time, it is more preferable that the two continuous nozzles 62A are divided so as not to be included in the same group.

  When the resolution of the image output by the head unit 60 including a defective nozzle is changed, depending on the type of image, continuity may not be ensured at the joint portion with the image output by the surrounding normal head unit 60. Therefore, the resolution of the image output from the head unit 60 around the head unit 60 including the defective nozzle may be changed. For example, when the normal resolution is 1200 dpi and the resolution of the image output by the head unit 60 including the defective nozzle is 600 dpi, the resolution is arranged on both sides of the head unit 60 including the defective nozzle. The resolution of the image output by the head unit 60 is reduced to an intermediate resolution of 900 dpi. Thereby, generation | occurrence | production of a discontinuous location can be prevented and continuity can be maintained.

[Second Embodiment]
When the resolution (discharge density) is changed as in the first embodiment, there may be a case where a sufficient density cannot be secured at the changed portion. This is because by reducing the resolution (discharge density), the area for one pixel becomes wider than in the case of high resolution, and the dot size becomes relatively smaller than the area for one pixel. Therefore, in the present embodiment, an example will be described in which not only the resolution is changed, but also the size of the dots formed by the head unit 60 with the changed resolution is changed according to the changed resolution. Note that the configuration of the ink jet recording apparatus 10 in the present embodiment is the same as that of the first embodiment, and a description thereof will be omitted.

  Hereinafter, the recording data creation process in the present embodiment will be described. In the present embodiment, the inkjet recording apparatus 10 can perform recording with four gradations of no droplet / small droplet / medium droplet / large droplet, and the resolution of an image output from the head unit 60 can be reduced. When lowering, control is performed so that the size of the medium and large droplets ejected by the head unit 60 is larger than in the case of high resolution, and the dot size of the small droplets is always the same regardless of the resolution. A case where the control is performed will be described as an example. The dot size of the medium droplet is adjusted to the size of the large droplet with the larger dot size and the small droplet with the dot size as it is.

  First, when image data is input from the outside, the resolution conversion unit 30 performs resolution conversion for each head unit 60, and the color conversion unit 32 performs color conversion and density conversion, as in the first embodiment. Done. Then, in the quantization unit 34, the image data of 255 gradations is divided into 4 gradations of “no drop (0) / small drop (85) / medium drop (170) / large drop (255)” by halftone processing. Are converted into image data of the recording level value.

  The halftone processed image data is converted into recording data by the recording data creation unit 36. In the present embodiment, the recording data is converted according to the processing flow shown in FIG.

  In step 200, image data of the pixel of interest is read. In step 202, it is determined whether or not the recording level value of the read image data is a recording level value of medium droplets or large droplets. If it is determined in step 202 that the recording level value of the image data is a recording level value of medium droplet or large droplet, the process proceeds to step 204.

  In step 204, it is determined whether or not the read image data is the image data of the portion converted to a low resolution by the resolution conversion unit 30. If an affirmative determination is made in step 204, the image data is converted into low-resolution recording data in step 206. If a negative determination is made in step 204, the image data is converted to a high-resolution image in step 208. Convert to recorded data.

  For example, when recording data of one pixel is represented by 3 bits, according to the dot size and resolution, no drop (000) / small drop (001) / medium drop at high resolution (010) / low resolution Medium droplet (011) / large droplet at high resolution (100) / large droplet at low resolution (101). The recording data creation unit 36 converts the image data into any of the recording data represented by the 3 bits according to the recording level value and the resolution indicated by the image data of the pixel of interest. For example, when the recording level value of the image data of the pixel of interest is 170 (medium droplet) or 255 (large droplet) and the resolution is low, in step 206, “011” (low) is set according to the recording level value. Medium resolution at the time of resolution) or “101” (large drop at the time of low resolution). If the resolution is high, in step 208, “010” (high resolution Medium droplet) or “100” (large droplet at high resolution).

  On the other hand, if it is determined in step 202 that the recording level value of the image data is no droplet or a recording level value of a small droplet, the process proceeds to step 208. As described above, since the dot size of the droplet is always the same regardless of the resolution, the image data is converted into high resolution recording data. That is, regardless of the resolution, it is converted into “000” (no droplet) or “001” (small droplet) according to the recording level value.

  After the process in step 206 or 208, it is determined in step 210 whether or not the recording data generation process has been completed for all image data. If it is determined that the processing has not been completed for all the image data, the process returns to step 200, the image data of the next pixel of interest is read, and the same processing as described above is performed. If it is determined in step 210 that the processing has been completed for all the image data, each data is rearranged in the recording order (transfer order) in step 212 (mapping). At this time, as in the first embodiment, for the portion output by the head unit 60 determined to include a defective nozzle, the group including the defective nozzle based on the data relating to the ejection failure. In order to prevent ink droplets from being discharged from the nozzle 62A, NULL is inserted every other nozzle.

  The drive waveform of the voltage applied to the piezoelectric element 62C is set in advance corresponding to each recording data, and the ejector driving unit 38 can apply the voltage of the driving waveform corresponding to the recording data.

  The drive waveform corresponding to the recording data “011” and the drive waveform corresponding to the recording data “010” are set so that the dot size of the medium droplet at the low resolution is larger than that of the medium droplet at the high resolution. Each is preset. Further, the drive waveform corresponding to the recording data “101” and the driving waveform corresponding to the recording data “100” are set so that the large droplet at the low resolution has a larger dot size than the large droplet at the high resolution. Each is preset.

  As a result, the dot size of the ink droplets ejected by the head unit 60 with reduced resolution (ejection density) is the same as that of the ink droplets ejected by the head unit 60 without reducing the resolution. It becomes larger than the dot size of the droplet (see FIG. 5B).

  Therefore, a sufficient concentration can be ensured even if the discharge density is lowered. Further, as described above, since the drive waveform is controlled not for each droplet ejector 62 but for each head unit 60, it can be controlled more easily than before.

  In the above embodiment, an example in which 3-bit recording data is generated from the dot size and resolution and output to the ejector driving unit 38 has been described. However, the present invention is not limited to this. Is used to create recording data indicating the type of dot (no droplet, small droplet, medium droplet, large droplet), and after mapping this, information on the resolution for each head unit 60 (1200 dpi) Alternatively, 600 dpi may be output to the ejector driving unit 38. In this case, the recording data indicating the dot type and the information relating to the resolution correspond to the ejection data of the present invention. The ejector driving unit 38 determines a driving waveform to be used from the recording data and information on the resolution of each head unit 60 and applies the driving waveform to the piezoelectric element 62C.

  Further, in the above embodiment, only the large and medium droplets are increased in size, and other cases (such as small droplets) are described as an example in which the size of the dots is not changed. For example, the size of the small droplet dot may be changed in accordance with the enlarged large droplet or medium droplet. Thereby, dots can be hit with a good balance. Further, the size of the large droplet may be increased and the size of the medium droplet and the small droplet may be left as they are. In addition, it can prevent that the granularity in a highlight part deteriorates by not changing the size of a droplet.

  In the above description, an example in which the dot size is increased has been described. However, it is also possible to create print data so that a plurality of dots are ejected in an area for one pixel.

  An example shown in FIG. 8 can be considered as a variation for changing the discharge density and the dot size.

  FIG. 8A is a diagram illustrating a printing state when the discharge density and the dot size are not reduced. The discharge density (resolution) is 1,200 dpi, one dot is printed with a dot size that fills a 1200 dpi * 1200 dpi pixel.

  FIG. 8B shows a printing state when the resolution is 600 * 600 dpi and printing is performed with a dot size in which pixels of 600 * 600 dpi are filled with one dot. That is, the resolution in both the main scanning direction and the sub-scanning direction is halved. As shown in the figure, every other droplet ejector 62 is used. As a result, white stripes do not occur and a high-quality image is obtained, and a sufficient density can be ensured by increasing the dots. Further, since the resolution in the sub-scanning direction as well as the main scanning direction is reduced, the amount of data handled can be greatly reduced, the processing efficiency can be increased, and the processing cost can be reduced.

  FIG. 8C shows a printing state when printing is performed with the same resolution (600 * 600 dpi) as in FIG. 8B and with a dot size in which pixels of 600 * 600 dpi are filled with 2 dots. That is, even if the dot size does not fill a pixel of 600 * 600 dpi with one dot, it is filled by hitting a plurality of dots. As a result, the modulation range of the drive waveform of the voltage applied to the piezoelectric element of the droplet ejector 62 can be made smaller than in FIG. 8B, and the design of the recording head 12 is facilitated. In addition, the load required to produce large dots can be reduced.

  FIG. 8D shows a printing state when the resolution is 600 * 1200dp and printing is performed with a dot size in which pixels of 600 * 1200 dpi are filled with one dot. That is, the resolution is reduced to ½ only in the main scanning direction. Compared to FIGS. 8B and 8C, the amount of data handled is increased and the processing cost is increased, but the resolution is small and a high-definition image is obtained compared to FIGS. 8B and 8C.

[Third Embodiment]
When the dot size is changed as in the second embodiment, the color and density change, and in the final output result, bands of different colors and densities may be formed in the width of the head unit 60 unit. . Therefore, in the present embodiment, when the resolution (discharge density) and the dot size are changed, the LUT 46 used in the color conversion unit 32 is matched with the LUT 46 as shown in FIG. An example to be changed will be described. Note that the configuration of the ink jet recording apparatus 10 in the present embodiment is the same as that of the first embodiment, and a description thereof will be omitted.

  FIG. 9 is a flowchart showing the flow of a color conversion processing routine executed by the color conversion unit 32 of the present embodiment. This processing routine starts after the resolution of the image data is converted by the resolution conversion unit 30.

In step 300, image data of the pixel of interest is read. In step 302, it is determined whether or not the read image data is image data of a portion converted to a low resolution by the resolution conversion unit 30. If an affirmative determination is made in step 302, the image data is color-converted using the low resolution LUT 46 in step 304. If a negative determination is made in step 302, the image data is converted to a high resolution in step 306. Color conversion is performed using the LUT 46.
These LUTs 46 are set so that the color of the high resolution image and the color of the low resolution image are in harmony, and an optimum LUT 46 corresponding to the resolution is prepared in advance.

  In step 308, it is determined whether or not the color conversion process has been completed for all image data. If it is determined that the processing has not been completed for all image data, the process returns to step 300, the image data of the next pixel of interest is read, and the same processing as described above is performed. When it is determined that the processing has been completed for all image data, this processing routine is terminated.

  As described above, since color conversion is performed using the LUT 46 that is optimal in accordance with the resolution, the overall color difference is suppressed, and the colors of the high-resolution image and the low-resolution image are harmonized.

  Here, an example in which color conversion processing is executed using different LUTs 46 according to resolutions has been described, but density conversion processing can also be performed using different conversion tables according to resolutions. If an LUT that takes into account the difference in color (density) caused by individual differences between the head units 60 is prepared, the overall color can be matched and high image quality can be realized.

  Note that the color (density) can be adjusted by changing the LUT for low resolution so that it matches the color (density) of high resolution, or by changing the LUT for high resolution so that it matches the color (density) of low resolution. There are two ways to change. The former method is more general, but the latter method is suitable, for example, when the density is not sufficient at a low resolution (color gamut is narrow). As a result, a high resolution LUT having a wide density range (wide color gamut) can be adapted to a low resolution having only a narrow density range (narrow color gamut).

  Here, one recording head 12 has been described as an example, but considering this as the full-color recording heads 12Y to 12K, the number of necessary LUTs is the simplest example as described above. Since two types of LUTs of low resolution and high resolution are used for each color, two types ^ 4 colors = 16 types. However, in the case where color matching between colors is performed more strictly as described below, more LUTs are required.

  (1) When printing all four colors at high resolution, one type of LUT is required.

  (2) When only one color out of the four colors is set to a low resolution, the following four patterns (1: a pattern for changing the resolution of C, 2: a pattern for changing the resolution of M, and 3: a resolution for changing the resolution of Y) A total of four types of LUTs are required in accordance with a pattern to be changed and a pattern to change the resolution of 4: K.

  (3) When two colors (for example, C color and M color) of the four colors are set to a low resolution (1/2 of the high resolution), the nozzles 62A of each head unit 60 are set to an even number group and an odd number. If the discharge is performed in either of the following groups, the following four patterns (1: C is an even group and M is an even group pattern, 2: C is an even group and M is an even group) An odd group pattern, 3: a pattern in which C is an odd group and M is an even group, and 4: a pattern in which C is an odd group and M is an odd group). In the patterns 4 and 4, the positions of the C and M dots overlap, and in the patterns 2 and 3, the positions of the C and M dots are shifted. Therefore, it is sufficient to prepare two types of LUTs in consideration of the difference in color between a pattern in which dot positions overlap and a pattern in which dot positions are shifted. Here, since there are 6 combinations for selecting 2 colors from among 4 colors, 2 × 6 = 12 types of LUTs are required in total.

  (4) When three of the four colors (for example, C, M, and Y) are set to a low resolution (1/2 of the high resolution), the same as in (3) above, There are 3 patterns, a pattern that deviates from Y, a pattern in which only M deviates from Y and C, a pattern in which only Y deviates from C and M, and there are 4C3 = 4 combinations to choose from 4 colors. 4 × 3 = 12 types of LUTs are required.

  (5) When all four colors are set to a low resolution (1/2 of the high resolution), a pattern in which only one of the remaining three colors and the position of the dot are shifted is considered in the same manner as in the above (3). There is a pattern in which the remaining two colors deviate from the dot position. In a pattern in which only one color has the remaining three colors and the position of the dot shifted, there are four ways to select that one color, and in a pattern in which the remaining two colors have the remaining two colors and the position of the dot shift, the selection of the two colors is 4C2 = 6. Because there are, 4 + 6 = 10 types of LUTs are required.

As described above, from (1) to (5), the LUT to be prepared is
1 + 4 + 12 + 12 + 10 = 37 types.

  If these types of LUTs are prepared, strict color matching is possible. However, in reality, even if the dots are slightly shifted, there is no problem and the image quality does not deteriorate significantly. Therefore, it is only necessary to consider two types of low resolution or high resolution for each color. Therefore, there is no problem if 16 types of LUTs are prepared as described above.

  In the above description, an example in which both the color conversion table and the density conversion table are selectively used according to the resolution has been described. However, only one of them may be used properly. Actually, if the density correction table (γ correction table) is used separately for low resolution and high resolution, approximate colors can be matched.

[Fourth Embodiment]
When the dot size is changed as in the second embodiment, the color and density change, and in the final output result, bands of different colors and densities may be formed in the width of the head unit 60 unit. . Therefore, in the present embodiment, when changing the resolution (ejection density) and the dot size in order to match the overall color tone, the threshold value used in the halftone process performed in the quantization unit 34 is adjusted accordingly. An example in which the color (density) is adjusted by changing the recording level value and controlling the ratio of large droplet / medium droplet / small droplet / no droplet will be described. Note that the configuration of the ink jet recording apparatus 10 in the present embodiment is the same as that of the first embodiment, and a description thereof will be omitted.

  FIG. 10 is a flowchart showing a flow of a processing routine executed by the quantization unit 34 of the present embodiment. This processing routine starts after color conversion / density conversion processing of image data is performed by the color conversion unit 32.

  In step 400, image data of the pixel of interest is read. In step 402, it is determined whether or not the read image data is image data of a portion converted to a low resolution by the resolution conversion unit 30. If an affirmative determination is made in step 402, a threshold for converting the image data into a low-resolution recording level value is set in step 404. If a negative determination is made in step 402, the image is A threshold is set for converting the data into a high-resolution recording level value. Hereinafter, a specific example of the recording level value and the threshold value will be described.

  For example, high resolution large droplets are made smaller than low resolution large droplets so as to match color and density, and the maximum recording level value (255) is assigned to the low resolution large droplets. The level value is assigned a value smaller than the maximum value, for example, 240. If medium droplets are considered in the same way as large droplets, and small droplets and no droplets are common to all resolutions, the recording level value in the case of high resolution is, for example, no droplet (0) / small droplet (85) / medium droplet. (160) / large drop (240), and the recording level value in the case of low resolution is, for example, no drop (0) / small drop (85) / medium drop (170) / large drop (255). it can. This value is set in advance in the apparatus according to the resolution. Thus, by setting the recording level value to a recording level value corresponding to each resolution, it becomes easy to create a smooth gradation (change in density).

  The threshold value used in the error diffusion process is set according to this recording level value. For example, the threshold value may be a value obtained by adding the preceding and following recording level values and dividing by two. That is, in the case of high resolution, the threshold for drawing large and medium drops is 205 (= (170 + 240) / 2), and the threshold for drawing medium and small drops is 120. (= (80 + 160) / 2), and the threshold for drawing a small droplet and no droplet can be 43 (= (0 + 85) / 2). In the case of low resolution, the threshold for drawing large and medium drops is 213 (= (170 + 255) / 2), and the threshold for drawing medium and small drops is 127 (= (85 + 170) / 2), the threshold for drawing a small droplet and no droplet can be 43 (= (0 + 85) / 2). In order to prevent the color and density of the image from being formed darker in the low resolution part (by increasing the dot size of large and medium drops) than in the high resolution part, the above calculated threshold value is used. May be further finely adjusted to further adjust the appearance ratio of each dot type.

  These threshold values may be calculated and stored in advance, and the threshold values stored as appropriate according to the resolution may be read and set.

  In step 408, error diffusion processing is performed with the threshold set in this way. Thereby, the image data is converted into one of the recording level values according to the resolution. In step 410, it is determined whether or not error diffusion processing has been completed for all image data. If it is determined that the error diffusion process has not been completed for all the image data, the process returns to step 400 and the same process as described above is repeated for the image data of the next pixel of interest. If it is determined that the error diffusion processing has been completed for all the image data, this processing routine is terminated.

  The recording data creation unit 36 at the subsequent stage creates recording data corresponding to the recording level value based on the image data subjected to the halftone processing in this way. The ejector driving unit 38 applies a voltage having a driving waveform corresponding to the recording data to each droplet ejector 62 to form an image.

  As described above, by processing the recording level value and the threshold value in the halftone process differently for the low resolution image data and the high resolution image data, bands of different colors and densities can be formed in the width of the head unit 60 unit. Can be prevented and the overall color can be adjusted. In addition, graininess can be reduced, and high image quality can be realized.

  Here, an example of adjusting the color (density) by changing the recording level value of high resolution and low resolution and the threshold value has been described, but the present invention is not limited to this. For example, the recording level value of high resolution and low resolution is used. May be made equal, and only the threshold value may be changed. By adjusting the threshold in this way, the ratio of ejecting large drops, medium drops, etc. can be adjusted, and the color (density) can be matched between the high resolution portion and the low resolution portion.

  In addition, in the error diffusion process, an error diffusion window (or error diffusion filter) used in the error diffusion process is prepared according to the resolution so that the range (distance) of the error to be diffused becomes almost equal regardless of the resolution change. You may make it use properly.

  Although the first to fourth embodiments have been described above, the present invention is not limited to the above-described embodiments, and various designs can be made within the scope of the invention described in the claims. Changes can be made.

  For example, the color / density conversion process according to the resolution described in the third embodiment and the halftone process according to the resolution described in the fourth embodiment may be combined. Thereby, an output image with higher image quality can be obtained.

  Furthermore, in the first to fourth embodiments, the case where the number of gradations that can be recorded by the recording head 12 is described as an example, but the present invention is limited to four gradations. Instead, for example, the number of gradations may be two, three, or five or more.

  In the above-described embodiment, the recording head 12 that discharges ink droplets using the piezoelectric element 62C has been described as an example. However, the present invention is not limited to such a configuration. For example, the recording head 12 in the ink pressure chamber 62B is used. The recording head may be a type of recording in which ink droplets are ejected by applying heat to the ink, and the size of the dots may be controlled according to the applied heat.

  In the above-described embodiment, an example is described in which image data is input, recording data is generated in the ink jet recording apparatus based on the input image data, and a droplet ejector is driven according to the recording data for recording. Although described above, the present invention is not limited to this. For example, the recording data may be generated by an external device, and the ink jet recording device may drive the droplet ejector to perform recording based on the recording data generated by the external device. . In detail, it can be configured as shown in FIG. A printer driver 54 provided with an application 52 for generating image data, the resolution conversion unit 30, the color conversion unit 32, the quantization unit 34, and the recording data creation unit 36 on the personal computer (personal computer) 50 side as an external device. And an output unit 48 that is an interface with the inkjet recording apparatus 10a. The ink jet recording apparatus 10 a is provided with an input unit 44 that is an interface with the personal computer 50, a control unit 40, an ejector driving unit 38, and a transport system 42 (illustration of the recording head 12 is omitted).

  Even in such a configuration, the same operations and effects as the above-described embodiment are obtained except that the process of creating the recording data based on the image data is performed on the personal computer 50 side.

  In addition, the resolution conversion unit 30, the color conversion unit 32, the quantization unit 34, and the recording data creation unit 36 are not provided in a single device, but operate as an ink jet recording system in which each (or some) is provided in different devices. It may be a device that performs.

  In the above description, the recording head 12 in which a plurality of head units 60 in which the nozzles 62A are arranged in a row in the main scanning direction is described as an example. However, the nozzles 62A may be arranged in a staggered manner. Moreover, as long as a plurality of head units 60 are arranged in the arrangement direction of the nozzles 62A, the configuration is not limited to the above embodiment.

1 is a schematic configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. 2 is a block diagram illustrating a configuration of a control system of the ink jet recording apparatus. FIG. FIG. 3 is an explanatory diagram for explaining a configuration of a recording head and a method for discharging inspection of a droplet ejector (nozzle). It is a figure which illustrates typically the structure of a droplet ejector, the drive waveform of the voltage applied to the piezoelectric element of a droplet ejector, and the size of the dot discharged corresponding to this drive waveform. It is a figure explaining the specific example of the processing content when a defective nozzle (defective droplet ejector) is included in a head unit. It is a flowchart which shows the process routine performed with the resolution conversion part of 1st Embodiment. It is a flowchart which shows the processing routine performed in the recording data preparation part of 2nd Embodiment. It is the figure which illustrated various variations in the case of changing dot size. It is a flowchart which shows the processing routine performed with the color conversion part of 3rd Embodiment. It is a flowchart which shows the process routine performed in the quantization part of 4th Embodiment. It is a block diagram which shows the structure of the control system of a personal computer and an inkjet recording device in a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 10a Inkjet recording device 12Y-12K Recording head 30 Resolution conversion part 32 Color conversion part 34 Quantization part 36 Recording data creation part 38 Ejector drive part 40 Control part 46 Color conversion table 50 Personal computer 54 Printer driver 60 Head unit 62 Droplet Ejector 62A Nozzle 62B Ink pressure chamber 62C Piezoelectric element

Claims (11)

A head configured by arranging a plurality of units in which a plurality of discharge means for discharging droplets are arranged in the arrangement direction of the discharge means;
A determination means for determining whether or not a discharge failure unit that does not normally discharge droplets is included for each unit;
Generating means for generating discharge data such that the discharge density of the unit determined to include the discharge means having the discharge failure is lower than the arrangement density of the discharge means based on data input from the outside;
Drive means for driving the discharge means based on the generated discharge data;
A liquid droplet ejection apparatus including:   The generating means may generate droplets from the discharge means of the group including the discharge failure discharge means when the discharge means of the unit determined to include the discharge failure discharge means is divided into a plurality of groups. The droplet discharge apparatus according to claim 1, wherein the discharge density is made lower than an array density of the discharge means by generating the discharge data so as not to be discharged.   The generating unit includes a discharge unit having the discharge failure when n-1 (n is an integer of 2 or more) of the plurality of discharge units is divided into n groups. 3. The droplet discharge device according to claim 1, wherein the discharge density is set to 1 / n of the array density of the discharge means by generating the discharge data so that the droplets are not discharged from the discharge means of the group. .   4. The apparatus according to claim 1, wherein the generation unit further generates the discharge data so that a size of a droplet discharged from a unit having a low discharge density is larger than a predetermined size. 2. A droplet discharge device according to item 1.   Further, the generation means is configured so that when the size of the droplets discharged from the unit with the lowered discharge density is not sufficient for the discharge area for one dot when the discharge density is lowered, 5. The droplet discharge device according to claim 1, wherein the discharge data is generated so that a plurality of droplets are discharged in a discharge region for dots.   The generation unit further harmonizes at least one of the color and density of an image formed by a unit having a low discharge density with at least one of the color and density of an image formed by another unit other than the unit. The liquid droplet ejection apparatus according to claim 1, wherein at least one of color conversion and density conversion of the ejection data is performed.   The generation means further performs halftone processing of the discharge data so that the density of an image formed by a unit having a low discharge density and the density of an image formed by another unit other than the unit are harmonized. The droplet discharge device according to claim 1, wherein the droplet discharge device is performed.   The determination means is based on information on the discharge state of the discharge means for each group in each unit obtained by the discharge inspection performed for each group when the discharge means of the unit is divided into a plurality of groups. The liquid droplet ejection apparatus according to claim 1, wherein it is determined whether or not the ejection failure unit is included in each unit. A liquid droplet ejection apparatus comprising: a head configured by arranging a plurality of units in which a plurality of ejection means for ejecting liquid droplets are arranged in the arrangement direction of the ejection means; and a driving means for driving the ejection means based on ejection data A data generation device for generating discharge data used in
A determination means for determining whether or not a discharge failure unit that does not normally discharge droplets is included for each unit;
Generating means for generating the discharge data so that the discharge density of the unit determined to include the discharge means having the discharge failure is lower than the arrangement density of the discharge means based on data input from the outside; ,
A data generation device including: A droplet discharge method executed by a droplet discharge apparatus including a head configured by arranging a plurality of units in which a plurality of discharge means for discharging droplets are arranged in the arrangement direction of the discharge means,
A determination step of determining whether or not a discharge failure unit that does not normally discharge droplets is included for each unit;
A generating step for generating discharge data so that a discharge density of a unit determined to include the discharge means having the discharge failure is lower than an array density of the discharge means based on data input from the outside;
A driving step of driving the discharge means based on the generated discharge data;
A droplet discharge method comprising: A liquid droplet ejection apparatus comprising: a head configured by arranging a plurality of units in which a plurality of ejection means for ejecting liquid droplets are arranged in the arrangement direction of the ejection means; and a driving means for driving the ejection means based on ejection data A data generation method for generating discharge data used in
A determination step of determining whether or not a discharge failure unit that does not normally discharge droplets is included for each unit;
A generating step for generating the discharge data so that a discharge density of a unit determined to include the discharge means having the discharge failure is lower than an array density of the discharge means based on data input from the outside; ,
Data generation method.

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