JP2011161823A - Image processing method, image recording method, image processing apparatus, and image recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing method, an image recording method, an image processing apparatus and an image recording apparatus by which a correction process is immediately performed when a plurality of recording elements being close to each other become abnormal, and a visual sense effect by the approaching of abnormal recording elements is suppressed. <P>SOLUTION: Nozzle attribute information is imparted to a nozzle adjacent to a non-discharging nozzle satisfying conditions A which have been determined based on the generating characteristics of the non-discharging nozzle. The nozzle attribute information is imparted as well to a nozzle adjacent to a normal nozzle satisfying conditions B which are determined based on the attribute information of the non-discharging nozzle. The nozzle attribute information includes the interval quantity and the periodicity of the non-discharging nozzle. For the conditions A and the conditions B, the interval quantity is set to be from 4 to 6, and the periodicity is set to be 1 or higher. A correction factor for correcting a non-discharge correcting factor is stored in an index table for which the interval quantity and the periodicity are made indexes. When a new non-discharging nozzle is generated, the correcting factor is read, and the non-discharge correcting factor is corrected. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image processing method, an image recording method, an image processing apparatus, and an image recording apparatus, and more particularly, to an image correction technique when a recording element abnormality occurs.

  As a general-purpose image forming apparatus, an ink jet recording apparatus that forms a desired image on a recording medium using an ink jet method is known. In an ink jet recording apparatus, abnormalities such as non-ejection may occur in any of a large number of nozzles (recording elements) provided in the ink jet head, and some of the nozzles may have different ejection characteristics. is there. The occurrence of abnormal nozzles and the presence of nozzles with different ejection characteristics cause density unevenness in the output image, and the image quality is significantly degraded.

  In Patent Literature 1, when a failure occurs in any of a plurality of nozzles, driving of the adjacent nozzles is performed so that dots formed from normal nozzles adjacent to the failed nozzle are formed larger than a predetermined size. Disclosed is a switchable technology. In the technique disclosed in Patent Document 1, the density curve of a pixel corresponding to a failed (abnormal) nozzle is changed to increase the dot size, and the high density side where non-ejection is conspicuous is corrected to a higher density. .

JP 2002-86767 A

  However, with the technique disclosed in Patent Document 1, there is a possibility that image correction for the occurrence of a defective nozzle cannot be handled without delay. For example, when detecting a failed nozzle by reading a test chart formed using a head, it takes a predetermined time to analyze the read image, so that correction data is created during continuous printing and replaced with correction data. It is difficult to do. Also, when multiple failed nozzles occur, the density of failed nozzles (interval between failed nozzles) is not taken into account, so the visual effect due to the proximity of failed nozzles (corrected density interferes with each other as black streaks) To be visually recognized).

  The present invention has been made in view of such circumstances, and an image processing method in which correction processing is immediately executed when a plurality of adjacent recording elements become abnormal, and the visual effect due to the proximity of abnormal recording elements is suppressed. An object of the present invention is to provide an image recording method, an image processing apparatus, and an image recording apparatus.

  In order to achieve the above object, an image processing method according to the present invention includes an abnormal recording element information acquisition step for acquiring information on an abnormal recording element in a recording head including a plurality of recording elements, and an image in which image data is input. Data input step, abnormal correction coefficient storage step for storing an abnormal correction coefficient for each recording element when an adjacent recording element becomes abnormal, and generation of an abnormal recording element grasped from the acquired abnormal recording element information Adjacent to a normal recording element satisfying a second condition determined based on an abnormality correction coefficient of a recording element adjacent to an abnormal recording element satisfying a first condition determined based on characteristics and a generation characteristic of the abnormal recording element A correction coefficient for correcting an abnormality correction coefficient when the normal recording element becomes an abnormal recording element is stored in association with the occurrence characteristic of the abnormal recording element. A correction coefficient storing step, a recording element adjacent to the abnormal recording element satisfying the first condition, and a recording element adjacent to the normal recording element satisfying the second condition. If the recording element adjacent to the recording element corresponding to the processing target pixel is an abnormal recording element, the pixel value of the processing target pixel is corrected using the stored abnormality correction coefficient. And when the abnormal recording element adjacent to the recording element corresponding to the pixel to be processed is adjacent to another abnormal recording element, the information stored with reference to the information on the occurrence characteristics of the abnormal recording element is stored. And a correction step of correcting the abnormality correction coefficient of the pixel to be processed using the correction coefficient.

  According to the present invention, there is another abnormal recording element in a close position that satisfies the first condition determined based on the occurrence characteristic of the abnormal recording element based on the information about the abnormal recording element grasped in advance. When it is determined that there is a correction coefficient for correcting the abnormality correction coefficient for a recording element adjacent to the abnormal recording element, a correction coefficient is prepared and determined based on the generation characteristic of the abnormal recording element. A correction coefficient for correcting an abnormal correction coefficient when the normal recording element becomes an abnormal recording element is prepared for a recording element adjacent to the normal recording element satisfying the above condition.

  Therefore, when there is an abnormal recording element in the vicinity, the abnormality correction coefficient is corrected by the correction coefficient, and density unevenness that occurs when the abnormal recording element is in the vicinity is suppressed. In addition, when a new abnormal recording element is generated, the abnormal correction coefficient is corrected using a correction coefficient prepared in advance for the recording element adjacent to the normal recording element. It is possible to respond.

Conceptual diagram for explaining a high-speed processing technique applied to the non-ejection correction method according to the embodiment of the present invention The conceptual diagram explaining the optimization technique of the non-ejection nozzle correction which is applied to the non-ejection correction method which concerns on embodiment of this invention 6 is a flowchart showing a flow of an image processing method to which a non-ejection correction method according to an embodiment of the present invention is applied. Conceptual diagram showing a configuration example of correction coefficient switching and correction coefficient correction processing shown in FIG. The flowchart which shows the flow of the correction coefficient correction process shown in FIG. The figure explaining the nozzle attribute applied to correction coefficient correction processing Explanatory drawing of condition A and condition B shown in FIG. The figure which shows an example of the index table applied to the correction coefficient correction process shown in FIG. 1 is a block diagram showing a schematic configuration of an image processing apparatus according to an embodiment of the present invention. Flow chart showing the procedure for deriving the unevenness correction coefficient and the non-ejection correction coefficient The figure which shows the structural example of the test pattern applied for derivation | leading-out of a nonuniformity correction coefficient and a non-ejection correction coefficient Flowchart illustrating a method for deriving the unevenness correction coefficient and the non-ejection correction coefficient Illustration of dot drop rate table Explanatory drawing of the droplet ejection volume table Explanatory drawing which shows an example of a data storage cell Illustration of halftone processing Explanatory diagram of threshold table Illustration of error diffusion processing Explanatory drawing of end processing for one line 1 is an overall configuration diagram of an ink jet recording apparatus to which a non-ejection correction method according to an embodiment of the present invention is applied. Plane perspective view of an ink jet head applied to the ink jet recording apparatus shown in FIG. Enlarged view of the head module shown in FIG. Sectional drawing which shows the three-dimensional structure of the inkjet head shown in FIG. The block diagram which shows schematic structure of the control system of the inkjet recording device shown in FIG.

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

[Description of high-speed processing technology for non-ejection correction processing]
FIG. 1 is a conceptual diagram of a high-speed processing technique applied to an image recording method (non-ejection correction technique) according to an embodiment of the present invention. In an image forming apparatus such as an ink jet recording apparatus, sudden non-ejection due to dust clogging may occur. On the other hand, recovery of the non-ejection state due to maintenance of the inkjet head and sudden recovery of the non-ejection state over time can occur. In order to cope with such a change in the discharge state of the nozzle, the discharge state of each nozzle is regularly monitored, and as soon as it is understood that a certain nozzle is in a non-discharge state, the normal data is not used. It is necessary to prepare non-ejection correction data in advance so that switching to ejection correction data is executed.

  However, in order to obtain high correction accuracy by the non-ejection correction method using the droplet ejection position error of each nozzle, every time a new non-ejection nozzle is generated, the derivation calculation of correction data is performed again. Since the derivation calculation of the correction data requires a long processing time, there is a concern that the real-time property of the correction processing is impaired.

  The non-ejection correction method shown in this example is data for correction when one adjacent nozzle is non-ejection for all nozzles in an inkjet head having a structure in which a plurality of nozzles are arranged in a predetermined arrangement, and Data for correction when the other adjacent nozzle becomes non-ejecting is obtained in advance, and immediately after the non-ejecting nozzle occurs, data (density value) of the position (pixel) corresponding to the adjacent nozzle of the non-ejecting nozzle. ) Is replaced with correction data obtained in advance. With this configuration, it is possible to immediately correct the occurrence of non-ejection nozzles. The correction data obtained in advance is stored in an LUT (Look Up Table) using the nozzle number (x) and the density value as parameters.

  The unevenness correction LUT 10 shown in FIG. 1 is an LUT in which unevenness correction coefficients are stored for all nozzles, and nozzle numbers (x = 1, 2, 3,..., I,...) And density values (for example, , 0-255) as parameters. The “unevenness correction coefficient” is a correction coefficient for correcting density unevenness in the printed image that appears due to the ejection characteristics (nozzle locality) of each nozzle. If no non-ejection nozzles are known, unevenness correction is performed. The density value is corrected by the coefficient.

  The non-ejection correction LUT (i-1) 12 is an LUT in which the correction coefficient of the (i-1) -th nozzle when the target nozzle (nozzle number i) is recognized as a non-ejection nozzle. It is. The non-ejection correction LUT (i + 1) 14 is an LUT in which the correction coefficient of the (i + 1) th nozzle when the target nozzle (nozzle number i) is recognized as a non-ejection nozzle. The non-ejection correction LUT (i−1) 12 and the non-ejection correction LUT (i + 1) 14 are LUTs using the nozzle number i and the density value as parameters.

  That is, when the nozzle of nozzle number i is grasped as a non-ejection nozzle, the position corresponding to the nozzle of nozzle number (i-1) adjacent to the non-ejection nozzle and the position corresponding to the nozzle of nozzle number (i + 1) The nonuniformity correction coefficient is replaced with a non-ejection correction coefficient. With such a configuration, as soon as a non-ejection nozzle is generated, the position data corresponding to the nozzle adjacent to the non-ejection nozzle is corrected. As described above, the correction data when the adjacent nozzle is not ejected is obtained for each nozzle and for each density value, and stored in the LUT or the like, so that correction processing for occurrence of the non-ejection nozzle is performed. Real-time performance is ensured.

[Explanation of optimization technology for correction of adjacent non-ejection nozzles]
FIG. 2A is an explanatory diagram of a correction optimization technique when a plurality of adjacent nozzles are recognized as non-ejection nozzles. FIG. 2B is a diagram for explaining a problem in correction when a plurality of adjacent nozzles are grasped as non-ejection nozzles. A technique is known in which when an isolated nozzle becomes non-ejection, the density value at a position corresponding to a nozzle adjacent to both sides is increased to correct a density decrease at a position corresponding to the non-ejection nozzle. For example, in the head 20 shown in FIG. 2A, when the nozzle 22A becomes non-ejection, the density at the position corresponding to one adjacent nozzle 22C of the non-ejection nozzle 22A is increased and the other of the non-ejection nozzle 22A is increased. When the density at the position corresponding to the adjacent nozzle 22D is increased, a decrease in density at the position corresponding to the nozzle 22A can be suppressed.

  Even when there are multiple non-ejection nozzles, it is possible to suppress the density drop at positions corresponding to each non-ejection nozzle by correcting the density value at the position corresponding to the nozzle adjacent to each non-ejection nozzle. It is.

  On the other hand, in the head 20 shown in FIG. 2 (a), the plurality of nozzles 22A and 22B in the close position are both non-ejection. In such a case, when the density values at the positions corresponding to the nozzles 22C and 22D adjacent to the non-ejection nozzle 22A are corrected and the density values at the positions corresponding to the nozzles 22E and 22F adjacent to the non-ejection nozzle 22B are corrected, The correction corresponding to the non-ejection nozzle 22A and the correction corresponding to the non-ejection nozzle 22B interact, and density unevenness (black) between the position corresponding to the non-ejection nozzle 22A and the position corresponding to the non-ejection nozzle 22B. Can be seen. In particular, in the single-pass method in which the head and the drawing area of the recording medium are operated only once relatively and image recording is performed over the entire surface of the recording medium, it is visually recognized as streaky unevenness along the scanning direction of the head and the recording medium. Is done.

  As shown in FIG. 2B, the corrected densities at the positions corresponding to the nozzles 22C, 22D, 22E, and 22F shown in FIG. 2A are all the same value (in FIG. 2A, before correction). If this is about 1.5 times the density of the image, black streak 32 that can be visually recognized is generated in the output image 30 ′, and the image quality is significantly deteriorated. Therefore, when there is a non-ejection nozzle at a close position, the density correction value at the position corresponding to the adjacent nozzle 22D of the non-ejection nozzle 22A and the position corresponding to the adjacent nozzle 22E of the non-ejection nozzle 22B is corrected. The density unevenness between the position corresponding to the non-ejection nozzle 22A and the position corresponding to the non-ejection nozzle 22B can be suppressed.

  That is, as shown in FIG. 2A, the corrected density of the position corresponding to the nozzle 22D and the position corresponding to the nozzle 22E is the corrected density of the position corresponding to the nozzle 22C and the position corresponding to the nozzle 22F. The interaction between the corrected density at the position corresponding to the nozzle 22D and the corrected density at the position corresponding to the nozzle 22E is alleviated, and the output image 30 appears in the output image 30 ′. Such black stripes are not visible.

  Data for correction (correction coefficient) in the case where a plurality of non-ejection nozzles are present at close positions is prepared in advance so that the non-ejection nozzle can be grasped and another non-ejection nozzle in the vicinity of the non-ejection nozzle. As soon as it is grasped that the density is present, the density value is corrected at the position corresponding to the adjacent nozzle of the non-ejection nozzle.

  However, while achieving high-accuracy correction using the "Optimization technology for correction of adjacent non-ejection nozzles" described here, the above-mentioned "High-speed processing technology for non-ejection correction processing" increases the overall processing speed. In order to achieve this, it is necessary to analyze the interval between the non-ejection nozzles and the number of repetitions of the non-ejection nozzles each time a non-ejection nozzle occurs. On the other hand, the presence of such an analysis step can be an obstacle for executing processing in real time for the occurrence of a non-ejection nozzle. On the other hand, in place of such an analysis step, it is substantially possible to prepare correction value data for non-discharge correction coefficients for all combinations of non-discharge nozzle intervals and non-discharge nozzle repetition numbers for every density value for all nozzles. Is difficult.

  Therefore, the non-ejection correction method shown in this example grasps the non-ejection nozzles that have already occurred, and predicts normal nozzles that are likely to be non-ejection from the occurrence status of non-ejection nozzles (already non-ejection) Of the nozzles in the vicinity of the non-ejection nozzles that are likely to be non-ejection) and recognizes the normal nozzle as a temporary non-ejection nozzle and causes no ejection to the nozzle adjacent to the normal nozzle. Data for correcting the correction coefficient is assigned.

  That is, for a normal nozzle that satisfies a predetermined condition with the non-ejection nozzle ascertained from the non-ejection nozzle information, data for correcting the non-ejection correction coefficient similar to the non-ejection nozzle with respect to the adjacent nozzle of the normal nozzle Is assigned. Therefore, even if a new non-ejecting nozzle occurs, the non-ejecting correction coefficient can be immediately switched to correction data for correcting the non-ejecting correction coefficient assigned to the nozzle adjacent to the predetermined normal nozzle. It is possible to optimize the correction of adjacent non-ejection nozzles while ensuring.

[Description of image recording to which non-ejection correction is applied]
Next, an image recording method in which the above-described “high-speed processing technology for non-ejection correction processing” and “optimization technology for correction of adjacent non-ejection nozzles” is realized will be described with a specific example.

  FIG. 3 is a flowchart showing the flow of processing of the image recording method shown in this example. Here, a case will be described in which a color image is recorded by an ink jet method using each color ink of K (black), C (cyan), M (magenta), and Y (yellow).

  As shown in FIG. 3, image data is acquired in step S10. Such image data has 256 gradations for each color of R (red), G (green), and B (blue). Next, density conversion processing for converting RGB data into KCMY data is executed (step S12).

  On the other hand, non-ejection nozzle information is acquired in step 14, and the unevenness correction coefficient and non-ejection correction coefficient are switched for each nozzle based on the non-ejection nozzle information (step S16). Information on the non-ejection nozzles is stored in a predetermined memory and updated as appropriate. That is, if the nozzle number of the non-ejection nozzle is i, the adjacent nozzles of the non-ejection nozzles (nozzles with nozzle numbers i−1 and i + 1) are replaced from the unevenness correction coefficient to the non-ejection correction coefficient. The “non-ejection nozzle information” used here is the latest information updated every time the image is recorded.

  Predetermined nozzle attribute information is read (step S18), and the non-ejection correction coefficient is corrected based on the nozzle attribute information for nozzles to which the non-ejection correction coefficient is assigned (nozzles adjacent to the non-ejection nozzle). (Step S20). The “nozzle attribute information” in step S18 functions as a parameter for determining correction data when a non-ejection nozzle is present at an adjacent position.

  The nozzle attribute information includes information on the interval between the non-ejection nozzles (interval information) and information on the cycle of the non-ejection nozzles (period information). The relationship with the non-ejection nozzle is given to the nozzle adjacent to the normal nozzle that satisfies the predetermined condition. In addition, the nozzle attribute information is updated in response to the update of the non-ejection nozzle information.

  For example, if the non-ejection nozzle 22A in FIG. 2A is the i-th nozzle, the nozzle 22D is the (i + 1) -th nozzle and the non-ejection for correcting the non-ejection nozzle 22A. A correction factor is assigned. Further, since the non-ejection nozzle 22B exists in the vicinity of the non-ejection nozzle 22A, the non-ejection correction coefficient is corrected based on the nozzle attribute information of the nozzle 22D. The non-ejection correction coefficient correction process based on the nozzle attribute information is executed for the nozzle 22E in FIG. On the other hand, for the nozzle 22C, there is no other non-ejection nozzle on the nozzle 22C side of the non-ejection nozzle 22A, so the non-ejection correction coefficient assigned in step S16 in FIG. 3 is used. Similarly to the nozzle 22C, the non-ejection correction coefficient assigned in step S16 in FIG. 3 is used for the nozzle 22F.

  In this way, when any one of the non-uniformity correction coefficient, the non-discharge correction coefficient, or the corrected non-discharge correction coefficient (correction data) based on the nozzle attribute is assigned to all the nozzles, the process proceeds to step S22, and half Tone processing (quantization processing) is executed, and dot data is generated. The pressure element corresponding to each nozzle is driven by the drive signal generated based on this dot data, and ink droplets are ejected from each nozzle at a predetermined droplet ejection timing (step S24). In step S24, image output is executed, non-ejection nozzle information is updated, and nozzle attribute information is updated based on the updated non-ejection nozzle information.

  FIG. 4 is a conceptual diagram illustrating switching of the unevenness correction coefficient, non-ejection correction coefficient, and correction data (correction coefficient). The unevenness correction LUT 10 shown in the figure stores the unevenness correction coefficient of each nozzle when both adjacent nozzles are normal nozzles. The unevenness correction LUT 10 has data corresponding to the total number of nozzles × density value (number of gradations), the nozzle number (x) and the density value are parameters, and a unevenness correction coefficient is stored for each nozzle and for each density value. ing.

  The non-ejection correction LUT (i-1) 12 (see FIG. 1) stores the non-ejection correction coefficient of each nozzle when one of the adjacent nozzles (nozzle with the nozzle number one before) is non-ejection. The non-ejection correction LUT (i + 1) 14 stores a non-ejection correction coefficient for each nozzle when the other adjacent nozzle (for example, the nozzle with the next nozzle number) is non-ejection. The non-ejection correction LUT (i−1) 12 and the non-ejection correction LUT (i + 1) 14 have data corresponding to the total number of nozzles × density value, and the nozzle number (x) and density value are parameters. A non-ejection correction coefficient is stored for each density value and density value.

  The selection unit 40 illustrated in FIG. 4 includes a flag table 42, an LUT switching unit 44, and an index table 46. The flag table 42 stores lookup table selection information (flag data). In this example, “0” is set when the nozzles adjacent to the target nozzle are not non-ejection nozzles, “1” is set when the target nozzle is a non-ejection nozzle, and the nozzle having the nozzle number immediately before the target nozzle is non-ejection “2” is input in the case of a nozzle, and “3” is input in the case where the nozzle having the nozzle number immediately after the target nozzle is a non-ejection nozzle. The flag table 42 shown in FIG. 4 is created based on the non-ejection nozzle information.

  The LUT switching unit 44 reads the flag data (0 to 4) of the target nozzle from the flag table 42 based on the nozzle number (x), and reads the unevenness correction coefficient from the unevenness correction LUT10 according to the flag data, or the non-ejection Switching between reading the non-ejection correction coefficient from the correction LUT 12 or the non-ejection correction LUT 14 or reading the constant is executed.

  Further, the selection unit 40 includes an index table 46 in which correction coefficients corresponding to the nozzle attribute information are stored. Although details of the index table 46 will be described later, nozzle attribute information given to the target nozzle is read from the nozzle attribute information storage unit 48 using the nozzle number (x) as a parameter. Based on the read nozzle attribute information, the correction coefficient is read from the index table 46, and the non-ejection correction coefficient is corrected by the correction coefficient.

  As described above, since the nozzle attribute information stored in the nozzle attribute information storage unit 48 is updated in response to the update of the non-ejection nozzle information, when reading the correction coefficient from the index table 46, The latest nozzle attribute information is applied.

[Description of nozzle attribute information]
Next, nozzle attribute information applied to the non-ejection correction process in image recording shown in this example will be described. As described above, in order to perform an appropriate correction process when a plurality of non-ejection nozzles are present at close positions, the interval between non-ejection nozzles and the cycle of the non-ejection nozzles must be analyzed. Don't be. However, in order to perform high-speed processing as a whole image recording while correcting the occurrence of non-ejection nozzles in real time, the processing time of the step of analyzing the interval between non-ejection nozzles and the cycle of non-ejection nozzles It becomes a problem.

  Therefore, for normal nozzles that have not yet failed, if there is a possibility that they may become unejected and come close to other nozzles that are already known as non-ejection nozzles, the normal nozzle is recognized as a temporary non-ejection nozzle. Then, a correction coefficient is prepared in advance for the nozzle adjacent to the temporary non-ejection nozzle. When this correction coefficient is determined, nozzle attribute information given to each nozzle is used.

  FIG. 5 is a flowchart showing a procedure for generating nozzle attribute information. First, the latest non-ejection nozzle information is acquired (step S100), the interval between non-ejection nozzles is analyzed for the latest non-ejection nozzle information (step S102), and the period between non-ejection nozzles is analyzed. (Step S104). Based on the interval and period of the non-ejection nozzles obtained in step S102 and step S104, nozzle attribute information is given to the adjacent nozzles of the non-ejection nozzles that satisfy the condition A (step S106), and the non-ejections that satisfy the condition B Nozzle attribute information is given to the nozzle adjacent to the nozzle (step S108). The nozzle attribute information given to the target nozzle in step S106 and step S108 is stored (updated) in a predetermined memory (step S110).

  “Condition A” in step S106 indicates a specific interval number and cycle number condition set for the non-ejection nozzle, and “condition B” in step S108 is set for a normal nozzle. The conditions for the number of intervals with the non-ejection nozzle are shown.

  Here, the interval (number of intervals) between the non-ejection nozzles in “Condition A”, the cycle (number of cycles) between non-ejection nozzles, and the number of intervals with the non-ejection nozzles in “Condition B” will be described. FIG. 6A is an explanatory diagram of a non-ejection nozzle interval. In the figure, “◯” means a normal nozzle, and “x” means a non-ejection nozzle. As shown in the figure, the number of intervals means the number of nozzle pitches between non-ejection nozzles (a value obtained by adding 1 to the number of normal nozzles existing between non-ejection nozzles). That is, “the number of intervals = 4” means that the two non-ejection nozzles are at a position apart by a pitch between the four nozzles, and there are three normal nozzles between them.

  “Number of intervals = 5” means that the two non-ejection nozzles are located at a distance of 5 nozzle pitches, and there are four normal nozzles between them. “Number of intervals = 6” is 2 One non-ejecting nozzle is located at a position separated by 6 nozzle pitch, which means that there are five normal nozzles between them.

  FIG. 6B is an explanatory diagram of the number of cycles. As in FIG. 6A, “◯” represents a normal nozzle, and “X” represents a non-ejection nozzle. As shown in FIG. 6B, “period number = 0” means a case where a non-ejection nozzle exists alone and no other non-ejection nozzle does not exist in a close position. “Number of periods = 1” means a case where two non-ejection nozzles are present at close positions, and “Number of periods = 2” means a case where three non-ejection nozzles are present at close positions.

  That is, the “nozzle attribute information” is represented by using the “number of intervals” described with reference to FIG. 6A and the “number of periods” described with reference to FIG. For example, if there are three non-ejection nozzles with an interval number of 4, the number of intervals is 4, and the number of periods is 2, and if there are three non-ejection nozzles with an interval number of 5, the number of intervals is 5, and the number of periods is 2. It becomes.

  Next, “condition A” in step S106 and “condition B” in step S108 will be described in detail. FIG. 7A is a diagram schematically showing a non-ejection situation (non-ejection nozzle information). The upper part of the figure represents the presence or absence of non-ejection of each nozzle, where “◯” represents a normal nozzle and “x” represents a non-ejection nozzle.

  The numerical value shown in the middle of the figure is the number of intervals between the nozzles, and each nozzle has two left and right intervals. The interval number “N” means that the value of the interval number is outside the predetermined range. For example, the number of intervals of the seventh non-ejection nozzle from the left end is “N / 4”. This non-ejection nozzle has no non-ejection nozzle on the left side in the figure (the interval between adjacent non-ejection nozzles is infinite), and other non-ejection nozzles are located at the “number of intervals = 4” position on the right side. Existing. The number of intervals of the eleventh non-ejection nozzle from the left end is “4/4”, another non-ejection nozzle exists at the position of “number of intervals = 4” on the left side in the figure, and “number of intervals = There is another non-ejection nozzle at the position “4”.

  The numerical value in the lower part of FIG. 7A is the number of periods of each nozzle. Similar to the number of intervals, each nozzle has a period number on both the left and right sides. For example, the cycle number of the seventh non-ejection nozzle from the left end is “0/2”. This non-ejection nozzle has no non-ejection nozzle on the left side in the figure, and there are two other non-ejection nozzles close to the right side. The cycle number of the eleventh non-ejection nozzle from the left end is “½”, and there is one other non-ejection nozzle close to the left side in the figure, and two other non-ejection nozzles near the right side. There are two.

  In FIG. 7A, the nozzles surrounded by broken lines indicate non-ejecting nozzles that satisfy the condition A in relation to other non-ejecting nozzles. In this example, a non-ejection nozzle having an interval number of 4 to 6 and a cycle number of 1 or more falls under “non-ejection nozzle satisfying condition A”. In FIG. 7A, the number of intervals “N” indicates that the number of intervals is 3 or less, or 7 or more.

  FIG. 7B is an explanatory diagram of a normal nozzle whose relationship with the non-ejection nozzle satisfies the condition B. In the drawing, the nozzle surrounded by a broken line indicates that “the normal nozzle whose relationship with the non-ejection nozzle satisfies the condition B”. It corresponds to. For example, in the figure, the leftmost nozzle has a number of intervals from the leftmost 7th non-ejection nozzle (the number of rightsides) is 6, and the second nozzle from the leftmost is the number of intervals from the 7th nozzle from the left end. Is 5, and the third nozzle from the left end has a distance of 4 from the seventh nozzle from the left end.

  Further, the cycle number of the leftmost nozzle, the second nozzle from the left end, and the third nozzle from the left end is 3, which is obtained by adding 1 to the cycle number 2 of the seventh non-ejection nozzle from the left end.

  In the drawing, the rightmost nozzle has a number of intervals from the right end of the seventh non-ejection nozzle (the number of intervals on the left side) of 6, and the second nozzle from the right end has the number of intervals from the right end of the seventh non-ejection nozzle ( The number of intervals on the left side is 5 and the number of intervals between the third nozzle from the right end and the seventh non-ejection nozzle from the right end (number of intervals on the left side) is 4. The number of cycles of the right end nozzle, the second nozzle from the right end, and the third nozzle from the right end is 2, which is obtained by adding 1 to the seventh non-ejection nozzle cycle number 1 from the right end.

  In this example, the normal nozzle that satisfies the condition of the non-ejection nozzle and the interval number of 4 to 6 corresponds to the “normal nozzle that satisfies the condition B in relation to the non-ejection nozzle”.

  FIG. 7C is an explanatory diagram of nozzles to which nozzle attribute information is assigned. Nozzle attribute information is assigned to normal nozzles surrounded by a broken line in FIG. Since the eighth nozzle from the left end is adjacent to the right side of the non-ejection nozzle that satisfies the seventh condition A from the left end, the interval number 4 on the right side of the seventh non-ejection nozzle from the left end and the right cycle number 2 are nozzles. Assigned as attribute information.

  The tenth nozzle from the left end adjacent to the left side of the eleventh non-ejection nozzle from the left end is given the interval number 4 and the cycle number 1 on the left side of the eleventh non-ejection nozzle from the left end as nozzle attribute information, and the left end The 12th nozzle from the left end adjacent to the right side of the 11th non-ejection nozzle from the left is assigned the interval number 4 and the period number 2 as the nozzle attribute information on the right side of the 11th non-ejection nozzle from the left end.

  On the other hand, nozzle attribute information is also given to adjacent nozzles of normal nozzles that satisfy condition B. That is, the leftmost nozzle interval number 6 and the period number 3 are assigned as nozzle attribute information to the second nozzle from the left end, and the third nozzle number from the left end is the interval number 5 and period number of the second nozzle from the left end. 3 is assigned as nozzle information, and the number of intervals 4 and the number of periods 3 of the third nozzle from the left end are assigned to the fourth nozzle from the left end as nozzle information.

  In this way, the nozzle attribute information of the adjacent nozzles of the non-ejection nozzle satisfying the condition A obtained in step S108 in FIG. 5 and the nozzle information of the adjacent nozzles of the normal nozzle satisfying the condition B obtained in step S110. Is memorized. The nozzle attribute information is updated every time the non-ejection nozzle information is updated.

FIG. 8 is an explanatory diagram schematically showing a specific example of the index table 46 shown in FIG. The index table 46 shown in the figure stores the correction coefficient f _ij obtained in advance by experiments or the like using the number of intervals (i) and the number of periods (j) as indexes. The correction coefficient f _ij is a value between 1 and 2, and when the correction coefficient f _ij is 1, it is “no correction”, and the standard value of the correction coefficient f _ij is 1.5.

  That is, when there is a non-ejection nozzle, the standard pixel value of the normal nozzle position on both sides of the non-ejection nozzle is 1.5 times, and the non-ejection nozzle is adjacent to another non-ejection nozzle. In this case (in this example, the number of intervals is 4 to 6), the pixel value at the position of the normal nozzle adjacent to the non-ejection nozzle is adjusted within a range of 1 (no correction) to 2 times.

In this way, not only nozzles that are already known as non-ejection nozzles, but also normal nozzles that are likely to become non-ejection nozzles in the future are predicted based on the information on the number of intervals and the number of cycles of non-ejection nozzles. When the predicted normal nozzle is actually a non-ejection nozzle and is close to another known non-ejection nozzle, the non-ejection correction coefficient is switched to a correction coefficient f _ij prepared in advance. . By keeping obtained relation between correction coefficient f _ij a number of intervals and the number of cycles of the non-ejection nozzle, newly since faulty nozzle does not need to calculate the correction coefficient f _ij in each occurrence, adjacent non-ejection Nozzle correction optimization processing does not hinder high-speed processing of the entire image recording.

  In the non-ejection correction process shown in this example, when the number of intervals is 3 or less (when the number of nozzles existing between non-ejection nozzles is 0 to 2), it is not possible to perform the optimization process for correcting the neighboring non-ejection nozzles. Error processing is executed. When the number of intervals is 7 or more, the number of intervals is infinite (indicated as “N” in FIGS. 7A to 7C), and it is determined that the optimization process for correcting the adjacent non-ejection nozzles is unnecessary. Is done.

  FIG. 9 is a block diagram illustrating an apparatus configuration example to which the above-described image recording method is applied. The image processing apparatus 100 shown in the figure includes an image input unit 102 to which image data (for example, color image data of RGB 256 gradation) is input, a non-ejection nozzle information acquisition unit 104 from which non-ejection nozzle information is obtained, A density value conversion unit 106 that converts input image data into CMKY data, and a density value correction unit that corrects density values using the unevenness correction coefficient or non-ejection correction coefficient stored in the correction coefficient storage unit 108 110, a density value correction unit 116 that corrects the density value using the correction coefficient read from the correction coefficient storage unit 114 based on the nozzle attribute information stored in the nozzle attribute information storage unit 112, and an image A halftone processing unit 118 that performs halftone processing on data, and a data output unit 120 that outputs image data after halftone processing are provided. It is.

  When the inkjet head (see FIG. 2A) is driven using a drive signal formed based on output data (dot data) of the image processing apparatus 100 shown in FIG. 9, a desired color image is formed on the recording medium. Is formed.

  The density value correction unit 110 in FIG. 9 corresponds to the selection unit 40 in FIG. 4, and the nozzle attribute information storage unit 112 corresponds to the nozzle attribute information storage unit 48. 9 stores the unevenness correction LUT 10, non-ejection correction LUT (i-1) 12, and non-ejection correction LUT (i + 1) 14 shown in FIG. 4, and the correction coefficient storage unit 114 stores the correction coefficient storage unit 114 shown in FIG. An index table 46 is stored.

  In the image recording method configured as described above, in the image recording in which the coefficient for correcting the pixel value is switched from the unevenness correction coefficient to the non-ejection correction coefficient when an adjacent nozzle becomes a non-ejection nozzle, the condition A is set in advance. If the nozzle attribute information is assigned to the adjacent nozzle of the non-ejection nozzle satisfying the condition B and the adjacent nozzle of the normal nozzle satisfying the condition B and the nozzle adjacent to the nozzle to which the nozzle attribute is imparted is non-ejection, it is determined based on the nozzle attribute information. The non-ejection correction coefficient is corrected by the correction coefficient. Therefore, when a new non-ejection nozzle is newly generated, even when the non-ejection nozzle is adjacent to another non-ejection nozzle, it is possible to execute the optimization process for correcting the neighboring non-ejection nozzle.

  Further, by storing the correction coefficient in the index table with the number of intervals and the number of periods as indexes, there is no need to store the correction coefficient corresponding to the number of intervals and the number of periods for each nozzle and density value. It is possible to save the memory for storing the correction coefficient, and it is possible to immediately cope with the occurrence of a new non-ejection nozzle.

  In this example, color image formation by an ink jet method is exemplified as an example of image recording, but the present invention can also be applied to other image recording methods other than the ink jet method such as an LED method and an electrophotographic method.

[Explanation of unevenness correction coefficient and non-ejection correction coefficient]
Next, the above-described unevenness correction coefficient and non-ejection correction coefficient will be described in detail.

  FIG. 10 is a flowchart showing a procedure for deriving the unevenness correction coefficient and the non-ejection correction coefficient. First, in order to detect the characteristics of each nozzle, a test pattern is drawn by ejecting ink from all the nozzles of the inkjet head (see FIG. 2A) (step S202), and the test pattern is read by the reading device (scanner). Is read (step S204).

  Next, the landing position error is measured for all nozzles based on the test pattern reading result (step S206), the unevenness correction coefficient is derived based on the landing position error (step S208), and the non-ejection correction coefficient is calculated. Derived (step S210), the derivation of the unevenness correction coefficient and the non-ejection correction coefficient ends (step S212).

FIG. 11A is a schematic diagram showing an example of a test pattern formed in step S202 of FIG. 10, and FIG. 11B is a partially enlarged view of FIG. FIG. 11 (a), the test patterns shown in (b), to define a plurality of nozzles arranged in a row from one end _{A 1, A 2, A 3} ··· in this order, and _{A n,} a plurality of nozzles _{A 1} When the nozzle number of ~ _An is k, it is divided into four groups of 4k-3, 4k-2, 4k-1, 4k (k = 1, 2, 3,...), Medium and inkjet Ink droplets are continuously ejected from nozzles with a nozzle number of 4k-3 while moving the head relative to one direction to form a straight line (dot row) along the moving direction of the medium for each nozzle. Next, ink droplets are continuously ejected from the nozzle having the nozzle number 4k-2, a straight line is formed for each nozzle, and the nozzle number is 4k-1 and the nozzle number is 4k. Similarly, a straight line for each nozzle is formed.

  In this way, by grouping nozzles that are spaced apart by a certain distance, straight lines are formed without ejecting ink from adjacent nozzles, and adjacent straight lines are prevented from overlapping.

  As described above, as shown in FIGS. 11A and 11B, on the medium, four linear groups G1, G2, G3, and G4 corresponding to the four groups of nozzles are formed. A group is formed. In addition, since a plurality of types of droplet ejection points can be formed by changing the number of droplets dropped by each nozzle onto one droplet ejection point, a test pattern is also formed for each type of droplet ejection point. The test pattern may be recorded on all the test patterns on a single recording medium or on a plurality of test patterns. However, by recording on a single recording medium, the test pattern will be described later with higher accuracy. Recording characteristics can be measured.

  The scanner for reading the test pattern executed in step S204 in FIG. 10 only needs to have a reading resolution equal to or higher than 1/4 of the recording resolution of the inkjet head.

  As for the landing position measured in step S206 in FIG. 10, for example, as described in Japanese Patent Application Laid-Open No. 2006-264069, the density profile of each straight line is detected, and the center of each straight line is calculated from the detection result. Thus, the landing position of the ink droplet ejected from each nozzle can be calculated. Further, the calculation method of the center position is not particularly limited, and both ends of the ink droplet may be detected, and the middle point may be the center or the position having the highest density may be the center.

  This landing position is preferably calculated by calculating the center at a plurality of points on each straight line and connecting the centers to calculate an approximate straight line. By calculating the approximate line by connecting the centers of multiple points, the ink droplet landing position can be detected more accurately, and by further extending this approximate line, the relative positional relationship between each group Can also be detected accurately. Note that the relative positional relationship may be such that a reference nozzle is set when a test pattern is created, and straight lines formed by the nozzles are formed in all four groups. Based on the landing position of the landing point calculated in this way, a difference (landing position error) from the ideal landing position of the droplet landing point (a landing position of the assumed droplet landing point) is calculated.

  FIG. 12 is a flowchart showing a specific example of the unevenness correction coefficient shown in step S208 of FIG. 10 and the non-ejection correction coefficient shown in step S210. Here, an example of calculating the unevenness correction coefficient and the non-ejection correction coefficient for each density value in order to obtain the unevenness correction coefficient and the non-ejection correction coefficient corresponding to the density value will be described. The flowchart shown in FIG. 12 is for calculating the unevenness correction coefficient and the non-ejection correction coefficient for one nozzle. This procedure is repeated for all nozzles (nzl = 0 to N) and the density value “ For the range of 0.0 to 1.0, the process of calculating the correction coefficient for each density with a predetermined step size (for example, a step of “0.5”) is repeated.

  First, assuming that the selected nozzle (nozzle number nzl) is non-ejection, only the non-ejection information corresponding to that nozzle is turned ON, and the assumed non-ejection information is created assuming that the selected nozzle is non-ejection Then, the dot drop rate is calculated for the calculation target density (d) (step S222). In step S222, a dot ejection rate table (dp_buf [kind]) corresponding to the target pixel density (d) is used by using a dot ejection rate table indicating the existence ratio (droplet ejection type ratio) for each dot type for each density value. ) Is calculated.

  FIG. 13 is a diagram illustrating an example of a dot stagnation rate table (DP_buf [d] [kind]) indicating the relationship of the droplet ejection type ratio to the density value (pixel density). The dot stagnation rate table shown in FIG. 13 is a table having the pixel density [d] and the dot type [kind] as variables. The dot stagnation rate table shown in FIG. 13 exemplifies a case where there are four types of dots (kind = [1 drop, 2 drop, 3 drop, 4 drop]). In the figure, the horizontal axis represents pixel density [d], and the vertical axis represents droplet ejection type (dot type) ratio. For example, when looking at the ratio of each dot type when the pixel density is 0.8, the ratio of “3 drops” is the highest, about 0.72, then the ratio of “4 drops” is about 0.24, and “2 drops”. The ratio is about 0.04, and the ratio of “1 drop” is 0.0. Thus, the ratio of each dot type at a certain pixel density value is set as the value of dp_buf.

  A dot drop rate table having a relationship as shown in FIG. 13 is created and stored in advance. Note that the dot ejection rate table may be used after being interpolated as necessary. After determining the dot droplet ejection rate for the calculation target density as described above, next, an effective droplet ejection error is calculated (step S224 in FIG. 12). In the calculation of the effective droplet ejection error in step S224 of FIG. 12, the position error data measurement value (err_x [nzl] [kind]) for each dot type is the effective droplet ejection error (position: err_xx [nzl]) for each nozzle. An operation to be converted to is performed. The component of “position: err_xx [nzl]” in the effective droplet ejection error is obtained by the following equation [Formula 1].

すなわち、実行打滴誤差の「位置：ｅｒｒ＿ｘｘ［ｎｚｌ］」は、着弾位置誤差の測定値をドット打滴率（ｄｐ＿ｂｕｆ［ｋｉｎｄ］）と、打滴液量（ｖｏｌｕｍｅ［ｋｉｎｄ］）と、を用いて重み付けして加重平均をとったものである。なお、打滴液量（ｖｏｌｕｍｅ［ｋｉｎｄ］）のテーブルは、予めドット種類ごとの液量を測定して記憶しておくものとする。図１４に打滴液量のテーブルの一例を示す。

That is, the “position: err_xx [nzl]” of the effective droplet ejection error uses the measured value of the landing position error, the dot droplet deposition rate (dp_buf [kind]), and the droplet ejection volume (volume [kind]). And weighted average. Note that the droplet ejection volume (volume [kind]) table is measured and stored in advance for each dot type. FIG. 14 shows an example of a droplet ejection volume table.

  Returning to FIG. 12, when the calculation of the effective droplet ejection error is executed in step S224, the density correction coefficient (coef [nzl]) is calculated and corrected. For example, a case will be described in which the unevenness correction coefficient and the non-ejection correction coefficient are calculated using the correction target nozzle and three nozzles each of the right and left nozzles as a correction window (N = 3). In this case, the correction coefficient for the left nozzle in the correction window is stored in p [0], the correction coefficient for the center nozzle is stored in p [1], and the correction coefficient for the right nozzle is stored in p [2]. In the calculation, the number of non-ejection nozzles in the correction window and the position thereof are classified based on the non-ejection information (npn [nzl]) of the head.

  In this example, when there are two or more non-ejection nozzles in the correction window, the calculation is stopped. A specific calculation example is shown below. The calculation described below is repeated for all nozzles.

  First, a correction window to be calculated is determined and divided into the following three patterns according to the number and position of non-ejection nozzles in the correction window. That is, when there is no non-ejecting nozzle, the central nozzle is non-ejecting, the left or right nozzle is non-ejecting, the patterns are divided into three patterns and switched to the corresponding processing.

(When there is no non-ejection nozzle)
When there is no non-ejection nozzle, the ideal position interval value L is added to the position error of each nozzle (left: -L, center: 0, right: + L), and converted to an absolute position (a [3]). That is, the calculation shown in the following equation [Formula 2] is executed.

そして、当該位置誤差情報（ａ［３］）を用いて補正係数（ｐ［３］）が演算される。この演算の詳細は後述する。ここでは、表記の便宜上、補正ウインドウ内のノズル位置を表す［０］、［１］、［２］の３種類をまとめて［３］と表記している。なお、位置誤差情報（ａ［３］）の示す位置誤差が所定のしきい値（例えば、０．１μｍ）内であれば、実質的に補正不要であるとして位置補正を行わないものとする。補正を行うか否かの判断基準となるしきい値は、誤差を許容できる許容範囲の観点から定められる。当該補正ウインドウ内の各ノズルの補正係数は、次式〔数３〕によって求められる。

Then, a correction coefficient (p [3]) is calculated using the position error information (a [3]). Details of this calculation will be described later. Here, for convenience of description, three types of [0], [1], and [2] representing nozzle positions in the correction window are collectively expressed as [3]. If the position error indicated by the position error information (a [3]) is within a predetermined threshold value (for example, 0.1 μm), the position correction is not performed because it is substantially unnecessary. A threshold value that is a criterion for determining whether or not to perform correction is determined from the viewpoint of an allowable range in which an error can be allowed. The correction coefficient of each nozzle in the correction window is obtained by the following equation [Equation 3].

さらに、中央ノズル（ｐ［１］）に対しては、１を減ずる。すなわち、次式〔数４〕に示す演算が実行される。

Further, 1 is subtracted from the central nozzle (p [1]). That is, the calculation shown in the following equation [Equation 4] is executed.

次に、ムラ補正係数（ｃｏｅｆ［ｎｚｌ］）に上記のように求められた補正ウインドウ内補正係数が加算される。すなわち、次式〔数５〕に示す演算が実行される。

Next, the correction coefficient in the correction window obtained as described above is added to the unevenness correction coefficient (coef [nzl]). That is, the calculation shown in the following equation [Formula 5] is executed.

（中央ノズルが不吐出の場合）
一方、中央ノズルが不吐出の場合は、各ノズルの位置誤差に理想位置間隔値Ｌが合算され（左：−Ｌ、中央：０、左：＋Ｌ）、絶対位置（ａ［３］）に変換される（〔数２〕参照）。そして、当該位置誤差情報（ａ）［３］を用いて補正係数（ｐ［３］）の演算が実行される。この演算は、不吐出ノズルを除外して演算が行われる。つまり、不吐の中央ノズルは「ないもの」として演算される。当該補正ウインドウ内の各ノズルの補正係数は、次式〔数６〕によって求められる。

(When the central nozzle does not discharge)
On the other hand, when the center nozzle does not eject, the ideal position interval value L is added to the position error of each nozzle (left: -L, center: 0, left: + L), and converted to an absolute position (a [3]). (See [Equation 2]). Then, the correction coefficient (p [3]) is calculated using the position error information (a) [3]. This calculation is performed excluding non-ejection nozzles. That is, the undischarged central nozzle is calculated as “nothing”. The correction coefficient of each nozzle in the correction window is obtained by the following equation [Equation 6].

さらに、次式〔数７〕に示すように、中央ノズル（ｐ［１］）に対しては、−１が代入される。

Furthermore, as shown in the following equation [Expression 7], −1 is substituted for the central nozzle (p [1]).

そして、ムラ補正係数（ｃｏｅｆ［ｎｚｌ］）に上記求めた補正ウインドウ内補正係数が加算される。すなわち、次式〔数８〕に示す演算が実行される。

Then, the correction coefficient in the correction window obtained above is added to the unevenness correction coefficient (coef [nzl]). That is, the calculation shown in the following equation [Equation 8] is executed.

（左又は右ノズルが不吐出の場合）
他方、左又は右ノズルが不吐出の場合は、各ノズルの位置誤差に理想位置間隔値Ｌが合算され（左：−Ｌ、中央：０、右：＋Ｌ）、絶対位置（ａ［３］）に変換される（［数２］参照）。そして、当該位置誤差情報（ａ［３］）を用いて補正係数（ｐ［３］）の演算が実行される。この演算は、不吐出ノズルを除外して演算が行われる。つまり、不吐の左ノズル又は右ノズルは「ないもの」として演算される。左ノズルが不吐出のとき、当該補正ウインドウ内の各ノズルの補正係数は、次式〔数９〕によって求められる。

(When the left or right nozzle does not discharge)
On the other hand, when the left or right nozzle does not eject, the ideal position interval value L is added to the position error of each nozzle (left: -L, center: 0, right: + L), and absolute position (a [3]) (See [Equation 2]). Then, the correction coefficient (p [3]) is calculated using the position error information (a [3]). This calculation is performed excluding non-ejection nozzles. That is, the undischarged left nozzle or right nozzle is calculated as “nothing”. When the left nozzle does not eject, the correction coefficient of each nozzle in the correction window is obtained by the following equation [Equation 9].

さらに、次式〔数１０〕に示すように、中央ノズル（ｐ［１］）に対しては、１を減ずる。

Further, 1 is subtracted from the central nozzle (p [1]) as shown in the following equation (10).

また、次式〔数１１〕に示すように、左ノズル（ｐ［０］）には、０が代入される。

Also, as shown in the following equation [Equation 11], 0 is assigned to the left nozzle (p [0]).

また、右ノズルが不吐出のとき、当該補正ウインドウ内の各ノズルの補正係数は、次式〔数１２〕によって算出される。

When the right nozzle is not ejecting, the correction coefficient of each nozzle in the correction window is calculated by the following equation [Equation 12].

＜右ノズルが不吐出の時＞
さらに、次式〔数１３〕に示すように、中央ノズル（ｐ［１］）に対しては、１を減ずる。

<When the right nozzle does not discharge>
Further, 1 is subtracted from the central nozzle (p [1]) as shown in the following equation (13).

また、次式〔数１４〕に示すように、右ノズル（ｐ［２］）には０が代入される。

Further, as shown in the following equation [Equation 14], 0 is substituted into the right nozzle (p [2]).

そして、ムラ補正係数（ｃｏｅｆ［ｎｚｌ］）に上記したように求められた補正ウインドウ内補正係数が加算される。すなわち、次式〔数１５〕に示すように演算が実行される。

Then, the correction coefficient in the correction window obtained as described above is added to the unevenness correction coefficient (coef [nzl]). That is, the calculation is executed as shown in the following equation [Equation 15].

このようにして、すべてのノズルについて、上記の演算が繰り返される。濃度値ごとに、順次同様の処理を実行した後、各画素濃度での補正係数（ｃｏｅｆ［ｊ］）を、ムラ補正係数（ＣＯＥＦ［ｄ］［ｊ］）、不吐出左隣補正係数（Ｌ＿ＣＯＥＦ［ｄ］［ｊ］）、不吐出右隣補正係数（Ｒ＿ＣＯＥＦ［ｄ］［ｊ］）に移動させる。なお、このとき全データに１を加算する。

In this way, the above calculation is repeated for all nozzles. After the same processing is sequentially executed for each density value, the correction coefficient (coef [j]) at each pixel density is changed to the unevenness correction coefficient (COEF [d] [j]) and the non-ejection left adjacent correction coefficient (L_COEF). [D] [j]), the non-ejection right adjacent correction coefficient (R_COEF [d] [j]). At this time, 1 is added to all data.

  Here, as shown in the following equation, the correction coefficient of the nozzle (j = nzl) assumed to be non-ejection is not moved, and the correction coefficient of the nozzle (j = nzl + 1) adjacent to the left of the nozzle assumed to be non-ejection is , L_COEF [d] [j], and the correction coefficient of the nozzle (j = nzl−1) on the right side of the nozzle assumed to be non-ejection is moved to R_COEF [d] [j]. Further, the correction coefficients of the nozzles (j ≠ nzl, nzl-1, nzl + 1) which are not any of the above three are moved to COEF [d] [j].

  When the above processing is executed, the unevenness correction coefficient derivation step (step S226) and the non-ejection correction coefficient derivation step (step S228) shown in FIG. 9 is stored in the correction coefficient storage unit 108 in FIG. 9 (step S230 in FIG. 12), and the derivation of the unevenness correction coefficient and the non-ejection correction coefficient is ended (step S232).

  The unevenness correction coefficient (COEF [d] [j]), the non-ejection left neighbor correction coefficient (L_COEF [d] [j]), and the non-ejection right neighbor correction coefficient (R_COEF [d] [j]) If the position error fluctuation range of each nozzle is stable within a certain value and the ejection characteristics of each nozzle can be predicted, it can be easily obtained as follows without measuring the landing position error.

ここで、Ｃ［ｊ］は予め実験的に求めたノズルごとの定数であり、０＜Ｃ［ｊ］＜２が望ましい。また、Ｃ_Ｌ［ｄ］、Ｃ_Ｒ［ｄ］は予め実験的に求めた濃度ごとの定数であり、０＜Ｃ_Ｌ［ｄ］＜２、０＜Ｃ_Ｒ［ｄ］＜２が望ましい。

Here, C [j] is a constant for each nozzle obtained experimentally in advance, and 0 <C [j] <2 is desirable. Further, C _L [d] and C _R [d] are constants for each concentration obtained experimentally in advance, and 0 <C _L [d] <2 and 0 <C _R [d] <2 are desirable.

(Explanation of unevenness correction coefficient)
Next, an example of unevenness correction coefficient processing will be described.

  When the unevenness correction process is executed, first, the unevenness correction coefficient table for each density (COEF [Dmax] [Nnzl]), the non-ejection left adjacent correction coefficient table (L_COEF [Dmax] [Nnzl]), and the non-ejection right adjacent correction coefficient The table (R_COEF [Dmax] [Nnzl]) is read. The unevenness correction coefficient and the discharge correction coefficient are stored in the correction coefficient storage unit 108 in FIG.

  Next, actually measured non-discharge information (NPN [Nnzl]) is read. Here, as described above, the measurement non-ejection information is recorded as a test pattern in which a straight line is formed for each nozzle, detects whether or not a straight line corresponding to each nozzle is formed, and detects a non-ejection nozzle. Can be created. The measurement non-ejection information is information that the non-ejection nozzle is turned on and the normal nozzle (nozzle that ejects ink droplets) is turned off.

  Next, unevenness / non-ejection selection information (F_npn []) is created so that a table corresponding to each nozzle is selected based on the read measurement non-ejection information. Specifically, when the left and right nozzles of the target nozzle (nzl) are normal nozzles (NPN [nzl + 1] = OFF and NPN [nzl-1] = OFF), F_npn [nzl] = 0 is set, and the target nozzle When (nzl) is a non-ejection nozzle, F_npn [nzl] = 1, and when the right nozzle of the target nozzle (nzl) is non-ejection (NPN [nzl + 1] = ON), F_npn [nzl] = 2 When the right nozzle of the target nozzle (nzl) is not ejecting (NPN [nzl-1] = ON), F_npn [nzl] = 3.

  Then, the following processing is repeated for the entire range while sequentially changing the value y of the calculation target position in the image height direction (y direction, see FIG. 15). That is, the calculation target position (x value) is determined in the image width direction (x direction, see FIG. 15) in the y value of the calculation target position, and the nozzle number (nzl number) corresponding to the x position is determined for this x position. ) From the unevenness correction coefficient table, the non-ejection left adjacent correction coefficient table, and the non-ejection right adjacent correction coefficient table, the unevenness correction coefficient and the non-ejection correction coefficient according to the pixel density d [x] [y] and the nzl value. Is read for each concentration.

  When F_npn [nzl] = 0, the corresponding unevenness correction coefficient of nzl and image density d is read from the unevenness correction coefficient table (COEF [d] [nzl]) for each density, and the read unevenness correction coefficient Is the correction coefficient (f). When F_npn [nzl] = 1, the correction coefficient (f) is a fixed constant (for example, 0). When F_npn [nzl] = 2, the corresponding non-ejection correction coefficients of nzl and image density d are read from the non-ejection left adjacent correction coefficient table (L_COEF [Dmax] [Nnzl]), and the read non-ejection The correction coefficient (unevenness correction coefficient) is set as the correction coefficient (f).

  When F_npn [nzl] = 3, the corresponding non-ejection correction coefficients of nzl and image density d are read out from the non-ejection right side correction coefficient table (R_COEF [Dmax] [Nnzl]), and the read out non-ejection coefficient The correction coefficient (unevenness correction coefficient) is set as the correction coefficient (f). Then, using this correction coefficient (f), the correction calculation is executed by the following equation [Equation 17].

画像幅（ｘ方向）について、ｘの位置を順次変えながら、画像幅の全範囲について、上述した工程が繰り返される。すべての画素位置［ｘ］［ｙ］について、上記の補正演算が終了すると、本処理は終了される。

For the image width (x direction), the process described above is repeated for the entire range of the image width while sequentially changing the position of x. When the above correction calculation is completed for all pixel positions [x] [y], this processing is terminated.

  The method for deriving the unevenness correction coefficient and the non-ejection correction coefficient described above is merely an example, and the nonuniformity correction coefficient and the non-ejection correction coefficient derived by other methods (procedures) may be applied.

[Explanation of halftone processing]
Next, an error diffusion method will be described as an example of the halftone process shown in step S22 of FIG. In the error diffusion process, first, 0 is initialized in the error integration buffer. FIG. 15 shows a conceptual diagram of the error integration buffer. As shown in the figure, the error integration buffer has data storage cells corresponding to positions corresponding to the entire width of the image in the x direction, and can store data for two lines in the y direction. In the error accumulation buffer initialization process, all the data in each cell is set to zero. Thereafter, the following processing is repeated for the entire range while sequentially changing the position (y value) to be calculated in the height direction (y direction) of the image.

  N-value processing is performed in raster order for each x position belonging to the y value line of the pixel to be calculated. In the N-value conversion procedure, first, an integration error value is added to the density of image data for the target position x in the image width direction. FIG. 16 is an explanatory diagram thereof. Now, for the position of interest x, the accumulated error value at the same position in the error accumulation buffer is added to the image data density, and the density obtained by adding the accumulated error value is (modinp).

Next, a threshold value corresponding to the density value (modinp) is read from a threshold value table for N-value conversion. FIG. 17 is a diagram illustrating an example of the threshold value table. As shown in the figure, the threshold value table is an example in the case of using four types of droplet ejection (binarization), and the threshold values of “1 drop” to “4 drops” for each dot type are T _1. It is defined as ~T _4.

After appropriate noise is added to the threshold values read from the threshold value table shown in FIG. 17, the droplet ejection type is determined from the density value of the target point. In the case of this example, the droplet ejection type is determined as follows according to the value of “density value + error integrated value” and the magnitude relationship of T ₁ , T ₂ , T ₃ , T ₄ (see FIG. 14).

(When the value of “Density value + Error integrated value” is T ₄ or more)
When the value of “density value + error integrated value” is equal to or greater than T4, the output image (droplet spot density) at the pixel position [x] [y] is represented by a ₄ drop dot value (for example, “ 144 ”). The error value of the target point generated by the N-value conversion is a value obtained by subtracting the droplet drop point density from “density value + error integrated value”.

<If the value of "density value + Error integration value" is less than T ₃ or more T _4>
When the value of “density value + error integrated value” is T ₃ or more and less than T ₄ , the output image (droplet point density) at the pixel position [x] [y] is set to a ₃ drop dot value (for example, “112”). ). The error value of the target point generated by this N-value conversion is a value obtained by subtracting the 3 drop droplet ejection point density from “density value + error integrated value”.

(When the value of "density value ten error accumulated value" is smaller than T ₂ or T ₃₎
When the value of “density value + error integrated value” is T ₂ or more and less than T ₃ , the output image (droplet dot density) at the pixel position [x] [y] is set to a 2 drop dot value (for example, “80”). ). The error value of the target point generated by the N-value conversion is a value obtained by subtracting the 2 drop injection point concentration from “density value + error integrated value”.

(When the value of "density value + error integration value" is less than the above T ₁ T ₂₎
If the value of "density value + error integration value" is less than the above _{T 1 T 2,} the pixel position [x] output image (droplet ejection point density) dot value of 1drop of [y] (e.g., "48" ). The error value of the target point generated by the N-value conversion is a value obtained by subtracting the drop drop point density from “density value + error integrated value”.

(If the value of the "concentration value tens of error integrated value" is less than T ₁₎
The value of "density value + error integrated value" If there is less than T _1, droplets are ejected without for that pixel position [x] [y] and (droplet ejection point density 0). The error value of the target point generated by the N-value conversion is “density value + error integrated value” itself. Next, a process of diffusing the error value of the target point generated by the above five N-value conversions to unprocessed pixels adjacent to the target point is executed.

  FIG. 18A is a diagram showing a distribution constant (ratio at which an error is diffused) applied to the error diffusion processing, and FIG. 18B is a schematic diagram showing an example of error value diffusion processing. . In the error diffusion processing shown in the figure, error values generated at the target point [x] are distributed to the four adjacent unprocessed positions at the ratio (distribution constant) shown in FIG. When the above N-value conversion is completed for all x positions belonging to the target line, the target line (y) is changed. At this time, the error integration buffer is updated corresponding to the movement of the target line (y).

  That is, as shown in FIG. 19, the error accumulation buffer is scrolled up in the y direction, and 0 is assigned to each cell of the accumulation buffer for the new line. In this way, the above process is repeated for all lines for the image height (y direction), and when the droplet ejection type is determined for all pixels, the error diffusion process is terminated.

  Note that various known means such as an error diffusion method, a dither method, a threshold matrix method, and a density pattern method can be applied as the means for halftone processing.

[Application example to inkjet system]
Next, a case where the non-ejection correction technique (image recording method) described above is applied to an ink jet recording apparatus (ink jet system) will be described.

(Description of overall configuration of inkjet recording apparatus)
FIG. 20 is a configuration diagram showing the overall configuration of the ink jet recording apparatus according to the present embodiment. The ink jet recording apparatus 310 shown in the figure forms an image on a recording surface of a recording medium 314 based on predetermined image data using an ink containing a color material and an aggregating treatment liquid having a function of aggregating the ink. This is a two-liquid aggregation type recording apparatus.

  The ink jet recording apparatus 310 mainly includes a paper feeding unit 320, a processing liquid application unit 330, a drawing unit 340, a drying processing unit 350, a fixing processing unit 360, and a discharge unit 370. Transfer cylinders 332, 342, 352, and 362 are provided as means for delivering the recording medium 314 conveyed upstream of the processing liquid application unit 330, the drawing unit 340, the drying processing unit 350, and the fixing processing unit 360. As means for conveying the recording medium 314 while holding it in the coating unit 330, the drawing unit 340, the drying processing unit 350, and the fixing processing unit 360, impression cylinders 334, 344, 354, and 364 having drum shapes are provided. .

  The transfer cylinders 332, 342, 352, 362 and the impression cylinders 334, 344, 354, 364 are provided with grippers 380 A, 380 B that hold the front end (or rear end) of the recording medium 314 at predetermined positions on the outer peripheral surface. It has been. The structure for holding the tip of the recording medium 314 in the gripper 380A and the gripper 380B and the structure for transferring the recording medium 314 between the other impression cylinder or the gripper provided in the transfer cylinder are the same, and The gripper 380 </ b> A and the gripper 380 </ b> B are arranged at symmetrical positions that are moved 180 ° in the rotation direction of the pressure drum 334 on the outer peripheral surface of the pressure drum 334.

  When the transfer cylinders 332, 342, 352, 362 and the impression cylinders 334, 344, 354, 364 are rotated in a predetermined direction with the gripper 380 A, 380 B holding the leading end of the recording medium 314, the transfer cylinders 332, 342 are rotated. , 352, 362 and the impression cylinders 334, 344, 354, 364, the recording medium 314 is rotated and conveyed along the outer peripheral surface.

  In FIG. 20, only the grippers 380 </ b> A and 380 </ b> B provided in the impression cylinder 334 are denoted by reference numerals, and the other impression cylinders and the transfer cylinder grippers are omitted.

  When the recording medium (sheet) 14 accommodated in the paper supply unit 320 is fed to the treatment liquid application unit 330, the aggregation process is performed on the recording surface of the recording medium 314 held on the outer peripheral surface of the impression cylinder 334. A liquid (hereinafter simply referred to as “treatment liquid”) is applied. The “recording surface of the recording medium 314” is an outer surface in a state where the impression cylinders 334, 344, 354, and 364 are held, and is a surface opposite to a surface held by the impression cylinders 334, 344, 354, and 364. It is.

  Thereafter, the recording medium 314 to which the aggregation processing liquid has been applied is sent to the drawing unit 340, and color ink is applied to the area of the recording surface to which the aggregation processing liquid has been applied, thereby forming a desired image.

  Further, the recording medium 314 on which the image of the color ink is formed is sent to the drying processing unit 350, where the drying processing unit 350 performs the drying process, and after the drying process, the recording medium 314 is sent to the fixing processing unit 360 to perform the fixing process. Applied. By performing the drying process and the fixing process, the image formed on the recording medium 314 is hardened. In this manner, a desired image is formed on the recording surface of the recording medium 314. After the image is fixed on the recording surface of the recording medium 314, the image is conveyed from the discharge unit 370 to the outside of the apparatus.

  Hereinafter, each part (the paper feed unit 320, the processing liquid application unit 330, the drawing unit 340, the drying processing unit 350, the fixing processing unit 360, and the discharge unit 370) of the ink jet recording apparatus 310 will be described in detail.

(Paper Feeder)
The paper feed unit 320 is provided with a paper feed tray 322 and a feed mechanism (not shown), and the recording medium 314 is configured to be fed from the paper feed tray 322 one by one. The recording medium 314 sent out from the paper feed tray 322 is positioned by a guide member (not shown) so that the leading end is positioned at a gripper (not shown) of the transfer drum (paper feed drum) 332 and temporarily stops.

(Processing liquid application part)
The processing liquid coating unit 330 includes a pressure drum (processing liquid drum) 334 that holds the recording medium 314 delivered from the paper feed cylinder 332 on the outer peripheral surface and transports the recording medium 314 in a predetermined transport direction, and a processing liquid drum. And a processing liquid coating device 336 that applies the processing liquid to the recording surface of the recording medium 314 held on the outer peripheral surface of 334. When the processing liquid drum 334 is rotated counterclockwise in FIG. 20, the recording medium 314 is rotated and conveyed in the counterclockwise direction along the outer peripheral surface of the processing liquid drum 334.

  The processing liquid coating device 336 shown in FIG. 20 is provided at a position facing the outer peripheral surface (recording medium holding surface) of the processing liquid drum 334. As a configuration example of the processing liquid coating device 336, a processing liquid container in which the processing liquid is stored, a pumping roller that is partially immersed in the processing liquid in the processing liquid container, and pumps up the processing liquid in the processing liquid container, and a pumping roller An embodiment including an application roller (rubber roller) that moves the pumped processing liquid onto the recording medium 314 is exemplified.

  In addition, there is provided an application roller moving mechanism that moves the application roller in the vertical direction (the normal direction of the outer peripheral surface of the treatment liquid drum 334), and a configuration in which collision between the application roller and the grippers 380A and 380B can be avoided. preferable.

  The treatment liquid applied to the recording medium 314 by the treatment liquid application unit 330 contains a color material flocculant that aggregates the color material (pigment) in the ink applied by the drawing unit 340, and the treatment liquid is applied on the recording medium 314. And the ink come into contact with each other, the separation of the color material and the solvent in the ink is promoted.

  The treatment liquid application device 336 is preferably applied while measuring the amount of the treatment liquid applied to the recording medium 314, and the film thickness of the treatment liquid on the recording medium 314 is determined by the ink droplets ejected from the drawing unit 340. It is preferable to make it sufficiently smaller than the diameter.

(Drawing part)
The drawing unit 340 holds an impression cylinder (drawing drum) 344 that holds and conveys the recording medium 314, a sheet pressing roller 346 for bringing the recording medium 314 into close contact with the drawing drum 344, and an inkjet that applies ink to the recording medium 314. Heads 348M, 348K, 348C, and 348Y are provided. The basic structure of the drawing drum 344 is the same as that of the processing liquid drum 334 described above, and a description thereof is omitted here.

  The sheet pressing roller 346 is a guide member for bringing the recording medium 314 into close contact with the outer peripheral surface of the drawing drum 344, faces the outer peripheral surface of the drawing drum 344, and delivers the recording medium 314 between the transfer drum 342 and the drawing drum 344. The recording medium 314 is disposed on the downstream side in the conveyance direction of the recording medium 314 from the position, and further on the upstream side in the conveyance direction of the recording medium 314 than the inkjet heads 348M, 348K, 348C, and 348Y.

  The recording medium 314 transferred from the transfer drum 342 to the drawing drum 344 is pressed by the sheet pressing roller 346 when being rotated and conveyed with the leading end held by a gripper (reference number omitted), and the outer periphery of the drawing drum 344. Adhere to the surface. After the recording medium 314 is brought into close contact with the outer peripheral surface of the drawing drum 344 in this way, the recording medium 314 is sent to the print area immediately below the ink jet heads 348M, 348K, 348C, 348Y without being lifted from the outer peripheral surface of the drawing drum 344. It is done.

  The inkjet heads 348M, 348K, 348C, and 348Y correspond to inks of four colors, magenta (M), black (K), cyan (C), and yellow (Y), respectively, and the rotation direction of the drawing drum 344 (see FIG. 20 are arranged in order from the upstream side in the counterclockwise direction), and the ink discharge surfaces (nozzle surfaces, denoted by reference numeral 114A in FIG. 5) of the ink jet heads 348M, 348K, 348C, and 348Y are illustrated in the drawing drum. It is arranged so as to face the recording surface of the recording medium 314 held by 344. The “ink ejection surface (nozzle surface)” is a surface of the ink jet heads 348M, 348K, 348C, and 348Y that faces the recording surface of the recording medium 314. This is a surface on which is formed.

  In addition, in the inkjet heads 348M, 348K, 348C, and 348Y shown in FIG. 20, the recording surface of the recording medium 314 held on the outer peripheral surface of the drawing drum 344 and the nozzle surfaces of the inkjet heads 348M, 348K, 348C, and 348Y are substantially parallel. In such a manner, it is arranged to be inclined with respect to the horizontal plane.

  The inkjet heads 348M, 348K, 348C, and 348Y are full-line heads having a length corresponding to the maximum width of the image forming area in the recording medium 314 (the length in the direction orthogonal to the conveyance direction of the recording medium 314). The recording medium 314 is fixedly installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 314.

  On the nozzle surfaces of the inkjet heads 348M, 348K, 348C, and 348Y, nozzles for ejecting ink are formed in a matrix arrangement over the entire width of the image forming area of the recording medium 314.

  When the recording medium 314 is transported to the printing area immediately below the inkjet heads 348M, 348K, 348C, 348Y, the image data is converted into the area where the aggregation processing liquid of the recording medium 314 is applied from the inkjet heads 348M, 348K, 348C, 348Y. Based on this, ink of each color is ejected (droplet ejection).

  When ink droplets of the corresponding color ink are ejected from the inkjet heads 348M, 348K, 348C, 348Y toward the recording surface of the recording medium 314 held on the outer peripheral surface of the drawing drum 344, processing is performed on the recording medium 314. The liquid and the ink come into contact with each other, and an aggregation reaction of the color material (pigment-based color material) dispersed in the ink or the color material (dye-based color material) to be insolubilized appears, and a color material aggregate is formed. As a result, movement of the color material in the image formed on the recording medium 314 (dot misalignment, dot color unevenness) is prevented.

  Further, since the drawing drum 344 of the drawing unit 340 is structurally separated from the processing liquid drum 334 of the processing liquid application unit 330, the processing liquid does not adhere to the inkjet heads 348M, 348K, 348C, and 348Y. In addition, the cause of abnormal ink ejection can be reduced.

  In this example, the configuration of CMYK standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink, dark ink, and special colors are used as necessary. Ink may be added. For example, it is possible to add an inkjet head that discharges light-colored ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

(Dry processing part)
A drying processing unit 350 holds a recording medium 314 after image formation and conveys a pressure drum (drying drum) 354, and a solvent drying device 356 that performs a drying process for evaporating water (liquid component) on the recording medium 314. It has. The basic structure of the drying drum 354 is the same as that of the processing liquid drum 334 and the drawing drum 344 described above, and a description thereof is omitted here.

  The solvent drying device 356 is a processing unit that is disposed at a position facing the outer peripheral surface of the drying drum 354 and evaporates moisture present in the recording medium 314. When ink is applied to the recording medium 314 by the drawing unit 340, the liquid component (solvent component) of the ink and the liquid component (solvent component) of the processing liquid separated by the aggregation reaction between the processing liquid and the ink are placed on the recording medium 314. Since it remains, it is necessary to remove such a liquid component.

  The solvent drying device 356 performs a drying process for evaporating the liquid component existing on the recording medium 314 by heating with a heater, blowing with a fan, or a combination thereof, and a process for removing the liquid component on the recording medium 314. Part. The amount of heating and the amount of air supplied to the recording medium 314 are appropriately set according to parameters such as the amount of moisture remaining on the recording medium 314, the type of the recording medium 314, and the conveyance speed (interference processing time) of the recording medium 314. Is done.

  When the drying process is performed by the solvent drying device 356, the drying drum 354 of the drying processing unit 350 is structurally separated from the drawing drum 344 of the drawing unit 340. Therefore, the inkjet heads 348M, 348K, 348C, and 348Y. In this case, it is possible to reduce the cause of abnormal ink ejection due to drying of the head meniscus by heat or air blowing.

  In order to exhibit the cockling correction effect of the recording medium 314, the curvature of the drying drum 354 is preferably 0.002 (1 / mm) or more. In order to prevent the recording medium from being curved (curled) after the drying process, the curvature of the drying drum 354 is preferably set to 0.0033 (1 / mm) or less.

  In addition, a means (for example, a built-in heater) for adjusting the surface temperature of the drying drum 354 may be provided, and the surface temperature may be adjusted to 50 ° C. or higher. By performing heat treatment from the back surface of the recording medium 314, drying is promoted and image destruction during the subsequent fixing process is prevented. In such an embodiment, it is more effective to provide means for bringing the recording medium 314 into close contact with the outer peripheral surface of the drying drum 354. As an example of means for closely attaching the recording medium 314, vacuum adsorption, electrostatic adsorption, and the like can be given.

  The upper limit of the surface temperature of the drying drum 354 is not particularly limited, but from the viewpoint of safety of maintenance work such as cleaning ink adhering to the surface of the drying drum 354 (preventing burns due to high temperatures). It is preferably set to 75 ° C. or lower (more preferably 60 ° C. or lower).

  The recording medium 314 is held on the outer peripheral surface of the drying drum 354 configured as described above so that the recording surface of the recording medium 314 faces outward (that is, in a state where the recording surface of the recording medium 314 is convex). By performing the drying process while rotating and transporting, drying unevenness due to wrinkling and floating of the recording medium 314 is surely prevented.

(Fixing processing part)
The fixing processing unit 360 includes a pressure drum (fixing drum) 364 that holds and conveys the recording medium 314, a heater 366 that heats the recording medium 314 that has been subjected to image formation and from which the liquid has been removed, and the recording And a fixing roller 368 that presses the medium 314 from the recording surface side. The basic structure of the fixing drum 364 is the same as that of the processing liquid drum 334, the drawing drum 344, and the drying drum 354, and a description thereof is omitted here. The heater 366 and the fixing roller 368 are disposed at positions facing the outer peripheral surface of the fixing drum 364, and are sequentially disposed from the upstream side in the rotation direction of the fixing drum 364 (counterclockwise direction in FIG. 20).

  In the fixing processing unit 360, the recording surface of the recording medium 314 is subjected to preliminary heating processing by the heater 366 and fixing processing by the fixing roller 368. The heating temperature of the heater 366 is appropriately set according to the type of recording medium, the type of ink (the type of polymer fine particles contained in the ink), and the like. For example, a mode in which the glass transition temperature and the minimum film forming temperature of the polymer fine particles contained in the ink are considered.

  The fixing roller 368 is a roller member for heating and pressurizing the dried ink to weld the self-dispersing polymer fine particles in the ink to form a film of the ink, and is configured to heat and press the recording medium 314. The Specifically, the fixing roller 368 is disposed so as to be in pressure contact with the fixing drum 364 and constitutes a nip roller with the fixing drum 364. As a result, the recording medium 314 is sandwiched between the fixing roller 368 and the fixing drum 364 and nipped at a predetermined nip pressure, and the fixing process is performed.

  As an example of the configuration of the fixing roller 368, there is an embodiment in which the fixing roller 368 is configured by a heating roller in which a halogen lamp is incorporated in a metal pipe such as aluminum having good thermal conductivity. By heating the recording medium 314 with such a heating roller, when thermal energy equal to or higher than the glass transition temperature of the polymer fine particles contained in the ink is applied, the polymer fine particles are melted to form a transparent film on the surface of the image. Is done.

  When pressure is applied to the recording surface of the recording medium 314 in this state, the polymer fine particles melted into the unevenness of the recording medium 314 are pressed and fixed, and the unevenness of the image surface is leveled, so that preferable glossiness can be obtained. A configuration in which a plurality of fixing rollers 368 are provided in accordance with the thickness of the image layer and the glass transition temperature characteristics of the polymer particles is also preferable.

  The surface hardness of the fixing roller 368 is preferably 71 ° or less. By making the surface of the fixing roller 368 softer, a follow-up effect can be expected with respect to the unevenness of the recording medium 314 caused by cockling, and uneven fixing due to the unevenness of the recording medium 314 can be more effectively prevented. .

  In the inkjet recording apparatus 310 shown in FIG. 20, an inline sensor 382 is provided at the subsequent stage (downstream in the recording medium conveyance direction) of the processing area of the fixing processing unit 360. The inline sensor 382 is a sensor for reading an image formed on the recording medium 314 (or a check pattern formed in a blank area of the recording medium 314), and a CCD line sensor is preferably used.

  In the ink jet recording apparatus 310 shown in this example, the presence or absence of ejection abnormality of the ink jet heads 348M, 348K, 348C, and 348Y is determined based on the reading result of the inline sensor 382 (details will be described later). Further, the inline sensor 382 may include a measuring unit for measuring a moisture amount, a surface temperature, a glossiness, and the like. In such an embodiment, parameters such as the processing temperature of the drying processing unit 350, the heating temperature of the fixing processing unit 360, and the pressurizing pressure are appropriately adjusted based on the moisture content, surface temperature, and gloss reading result, and the temperature inside the apparatus. The control parameter is adjusted as appropriate in accordance with the change and the temperature change of each part.

(Discharge part)
As shown in FIG. 20, a discharge unit 370 is provided following the fixing processing unit 360. The discharge unit 370 includes an endless conveyance belt 374 wound around the stretching rollers 372A and 372B, and a discharge tray 376 that stores the recording medium 314 after image formation.

  The recording medium 314 after the fixing process sent out from the fixing processing unit 360 is transported by the transport belt 374 and discharged to the discharge tray 376.

(Description of structure of inkjet head)
FIG. 21 is a schematic configuration diagram of an ink jet head applied to the present invention. FIG. 21 is a view of the recording surface of the recording medium as viewed from the ink jet head (a plan perspective view of the head). In addition, since the inkjet heads 348M, 348K, 348C, and 348Y shown in FIG. Collectively, it is described as “inkjet head 348”.

  The ink-jet head 348 shown in the figure forms a multi-head by connecting n sub-heads 348-i (i is an integer from 1 to n) in a line. Each sub head 348-i is supported by head covers 349A and 349B from both sides of the inkjet head 348 in the short direction. It is also possible to configure a multi-head by arranging the sub-heads 348 in a staggered manner.

  As an application example of a multi-head configured by a plurality of sub-heads, a full-line head corresponding to the entire width of a recording medium can be given. The full-line head has a plurality of nozzles (corresponding to the length (width) in the main scanning direction of the recording medium along the direction (main scanning direction) orthogonal to the moving direction (sub-scanning direction) of the recording medium. In FIG. 23, a reference numeral 408 is attached for illustration. An image can be formed over the entire surface of the recording medium by a so-called single-pass image recording method in which the inkjet head 348 having such a structure and the recording medium are scanned only once relatively to perform image recording.

  FIG. 22 is a partially enlarged view of the inkjet head 348. As shown in the figure, the sub head 348 has a substantially parallelogram-shaped planar shape, and an overlap portion is provided between adjacent sub heads. The overlap portion is a connecting portion of the sub heads, and dots formed adjacent to the sub heads 348-i (horizontal direction in FIG. 21, main scanning direction X shown in FIG. 22) belong to different sub heads. The

  FIG. 23 is a plan view showing the nozzle arrangement of the sub head 348-i. As shown in the figure, each sub head 348-i has a structure in which nozzles 408 are arranged two-dimensionally, and a head provided with such a sub head 348-i is a so-called matrix head.

  In the sub head 348-i shown in FIG. 23, a large number of nozzles 408 are arranged along a column direction W that forms an angle α with respect to the sub scanning direction Y and a row direction V that forms an angle β with respect to the main scanning direction X. The substantial nozzle arrangement density in the main scanning direction X is increased. In FIG. 23, the nozzle group (nozzle row) arranged along the row direction V is denoted by reference numeral 408V, and the nozzle group (nozzle row) arranged along the column direction W is denoted by reference numeral 408W. ing.

  In this matrix arrangement, when the interval between adjacent nozzles in the sub-scanning direction is Ls, in the main scanning direction, each nozzle 408 is substantially equivalent to a linear arrangement with a constant pitch P = Ls / tan θ. It can be handled.

  The ink jet head 348 having the structure shown in FIG. 23 is arranged in a grid pattern with a fixed arrangement pattern along a row direction V that forms an angle β with the main scanning direction X and a column direction W that forms an angle α with respect to the sub-scanning direction Y. By arranging a large number, the high-density nozzle head of this example is realized.

  The main scanning direction X and the sub-scanning direction Y in FIG. 23 correspond to the x direction and the y direction in FIGS. 15, 16, 18, and 19, respectively.

  FIG. 23 is a cross-sectional view showing an example of the three-dimensional structure of the ink jet head 348, and illustrates a droplet ejecting element for one channel serving as a recording element unit. The inkjet head 348 shown in the figure operates a piezoelectric element 432 provided on the ceiling surface of the pressure chamber 416 to pressurize the liquid in the pressure chamber 416 and eject droplets from a nozzle 408 communicating with the pressure chamber 416. It is configured to let you. When a droplet is ejected from the nozzle 408, the liquid is supplied from a tank (not shown) serving as a liquid supply source to the pressure chamber 416 via a common channel 418 through a supply port 422 communicating with the pressure chamber 416. Filled.

  An inkjet head 348 shown in FIG. 23 includes a nozzle plate 414 having a nozzle 408 formed on a nozzle surface 414A, a flow path plate 420 having a pressure chamber 416, a supply port 422, a common flow path 418, and the like. It consists of a laminated structure. The nozzle plate 414 constitutes the nozzle surface 414A of the inkjet head 348, and a plurality of nozzles 408 communicating with the pressure chambers 416 are arranged in a predetermined arrangement pattern.

  The flow path plate 420 constitutes a side wall portion of the pressure chamber 416 and a flow in which a supply port 422 is formed as a constricted portion (most narrowed portion) of an individual supply path that guides ink from the common flow channel 418 to the pressure chamber 416. It is a path forming member. For convenience of explanation, the flow path plate 420 has a structure in which one or a plurality of substrates are stacked, although it is illustrated in FIG. 23 in a simplified manner. The nozzle plate 414 and the flow path plate 420 can be processed into a required shape by a semiconductor manufacturing process using silicon as a material.

  A diaphragm 424 constituting a part of the pressure chamber 416 (ceiling surface in FIG. 2) includes an upper electrode (individual electrode) 426 and a lower electrode 428, and a piezoelectric layer is provided between the upper electrode 4266 and the lower electrode 428. A piezoelectric element (piezo element) 432 having a structure in which the body 430 is sandwiched is joined. When the diaphragm 424 is formed of a metal thin film or a metal oxide film, it functions as a common electrode corresponding to the lower electrode 428 of the piezoelectric element 432. In the aspect in which the diaphragm is formed of a non-conductive material such as resin, a lower electrode layer made of a conductive material such as metal is formed on the surface of the diaphragm member.

  By applying a driving voltage to the upper electrode 4266, the piezoelectric element 432 is deformed and the diaphragm 424 is deformed to change the volume of the pressure chamber 416, and a droplet is ejected from the nozzle 408 by the pressure change accompanying this.

  The image recording method (non-ejection correction method) according to the present invention is particularly effective for image recording by a single-pass method using a full-line head. In such image recording, when a non-ejection nozzle is generated, a streak-like density unevenness along the moving direction of the recording medium at the drawing position by the non-ejection nozzle or a visual effect (black streaks) due to the proximity of a faulty nozzle occurs. The quality will be significantly reduced. Of course, the image recording method according to the present invention also has a certain effect in reducing the visibility of streaky irregularities along the scanning direction of the head, even for single-pass image recording in the serial system.

(Description of control system)
FIG. 24 is a block diagram illustrating a system configuration of the inkjet recording apparatus 310. As shown in FIG. 24, the ink jet recording apparatus 310 includes a communication interface 440 and a system control unit 442, and the system control unit 442 performs overall control of each part of the apparatus.

  The communication interface 440 is an interface unit (image input unit) that receives image data sent from the host computer 454. As the communication interface 440, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted.

  The system control unit 442 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 310 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. To do. Further, it generates control signals for controlling the conveyance control unit 444, the image processing unit 446, the head driving unit 448, and the like, and functions as a memory controller for the image memory 450 and the ROM 452.

  The image processing unit 446 is a processing block that performs predetermined processing on the image data, and includes a processor having an image processing function. The image data sent from the host computer 454 is taken into the inkjet recording apparatus 310 via the communication interface 440 and temporarily stored in the image memory 450. The image memory 450 is a storage unit that stores an image input via the communication interface 440, and data is read and written through the system control unit 442. The image memory 450 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The image memory 450 stores programs executed by the CPU of the system control unit 442 and various data necessary for control (including data for ejecting test charts, abnormal nozzle information, and the like). The image memory 450 may be a non-rewritable storage means or a rewritable storage means such as an EEPROM.

  A temporary storage unit (not shown) is used as a temporary storage area for image data and various data, and is also used as a program development area and a calculation work area for the CPU.

  The image processing unit 446 performs various processing and correction processes for generating a droplet ejection control signal from image data (multi-valued input image data) in the image memory, under the control of the system control unit 442. It functions as a signal processing means. A droplet ejection control signal (ink ejection data) generated by the image processing unit 446 is supplied to the head driving unit 448.

  That is, the image processing unit 446 includes functional blocks such as a density data generation unit, a correction processing unit, and an ink ejection data generation unit. Each of these functional blocks can be realized by ASIC, software, or an appropriate combination.

  The density data generation unit is a signal processing unit that generates initial density data for each ink color from input image data, and includes density conversion processing (including UCR processing and color conversion) and, if necessary, pixel number conversion processing. I do. The correction processing unit is a processing unit that performs density correction calculation using the density correction coefficient, and performs density data correction processing such as unevenness correction processing. That is, the correction processing unit corresponds to the density value correction unit 110 and the density value correction unit 116 in FIG.

  The ink ejection data generation unit is a signal processing unit including a halftoning processing unit that converts the corrected image data (density data) generated by the correction processing unit into binary or multivalued dot data. Multi-value processing is performed. Various known means such as an error diffusion method, a dither method, a threshold matrix method, and a density pattern method can be applied as the halftone processing means. In the halftone process, generally, gradation image data having an M value (M ≧ 3) is converted into binary or multi-value gradation image data smaller than M. In the simplest example, the image data is converted into binary (dot on / off) dot image data. However, in the halftone process, the dot size type (for example, 3 dots such as a large dot, a medium dot, a small dot, etc.) It is also possible to perform multi-level quantization corresponding to the type).

  The system control unit 442 functioning as the control unit of the image processing unit 446 and the image processing unit 446 illustrated in FIG. 24 has a configuration corresponding to the image processing apparatus 100 described above.

  The image processing unit 446 is provided with an image buffer memory (not shown), and image data, parameters, and other data are temporarily stored in the image buffer memory when the image processing unit 446 processes image data. Note that the image buffer memory may be attached to the image processing unit 446 or may be used as the image memory. Further, the image processing unit 446 may be integrated with the system control unit 442 and configured with one processor.

  The ink discharge data generated by the image processing unit 446 (ink discharge data generation unit) is given to the head drive unit 448, and the ink discharge operation of the inkjet head 348 is controlled.

  The head drive unit 448 functions as means for controlling the ejection drive of the inkjet head 348 and generates a drive signal waveform for driving the actuator (piezoelectric actuator 16 shown in FIG. 5) corresponding to each nozzle 408 of the inkjet head 348. A drive waveform generator for generating is included. The signal output from the drive waveform generation unit may be digital waveform data or an analog voltage signal. Such a drive waveform generation unit corresponds to the waveform generation unit 18 of FIG.

  An overview of the flow of processing from image input to print output is as follows. Image data to be printed is input from the outside via the communication interface 440 and stored in an image memory. At this stage, for example, RGB multi-valued image data is stored in the image memory.

  In the ink jet recording apparatus 310, a pseudo continuous tone image is formed by changing the droplet ejection density and dot size of fine dots with ink (coloring material) to the human eye. It is necessary to convert to a dot pattern that reproduces the gradation (shading of the image) as faithfully as possible. Therefore, the original image (RGB) data stored in the image memory is sent to the image processing unit 446 via the system control unit 442, and is processed by the density data generation unit, the correction processing unit, and the ink ejection data generation unit. Converted to dot data for each ink color.

  That is, the image processing unit 446 performs processing for converting the input RGB image data into dot data of four colors of M, K, C, and Y. The dot data thus generated by the image processing unit 446 is stored in the image buffer memory. This dot data for each color is converted into MKCY droplet ejection data for ejecting ink from the nozzles of the inkjet head 348 and printed, ink ejection data (dot timing for each nozzle and the dot size for each drive timing ( Discharge amount)) is confirmed.

  In FIG. 24, illustrations of configurations corresponding to the correction coefficient storage unit 108, the nozzle attribute information storage unit 112, and the correction coefficient storage unit 114 in FIG. 9 are omitted, but these are memories in which various parameters are stored. Or other memory can be used.

  The head drive unit 448 outputs a drive signal for driving the actuator 132 corresponding to each nozzle 408 of the inkjet head 348 in accordance with the print content based on the ink ejection data and the drive signal (drive waveform). The head drive unit 448 may include a feedback control system for keeping the head drive conditions constant.

  In this way, the drive signal output from the head drive unit 448 is applied to the inkjet head 348, whereby ink is ejected from the corresponding nozzle 408. An image is formed on the recording medium 314 by controlling ink ejection from the inkjet head 348 in synchronization with the conveyance speed of the recording medium 314.

  As described above, based on the ink ejection data generated through the required signal processing in the image processing unit 446 and the drive signal waveform generated by the waveform generation unit 445, the ink from each nozzle is passed through the head drive unit 448. Control of the discharge amount and discharge timing of the droplet is performed. Thereby, a desired dot size and dot arrangement are realized.

  The in-line detection unit 470 illustrated in FIG. 24 is a functional block that provides information regarding abnormal nozzles to the system control unit 442 through reading of nozzle detection patterns, processing of read data, and processing of determining abnormal nozzles. The inline detection unit 470 includes the inline sensor 382 illustrated in FIG. In the image recording method shown in this example, as a means for acquiring non-ejection nozzle information, a configuration in which a test pattern is read by the inline detection unit 470 and the read information is analyzed can be applied.

  The system control unit 442 performs various corrections on the ink jet head 348 based on information on the abnormal nozzle obtained from the inline detection unit 470 and other information, and also performs cleaning operations such as preliminary ejection, suction, and wiping as necessary ( Nozzle recovery operation) is performed.

  Although not shown, a maintenance processing unit including members necessary for head maintenance such as an ink receiver, a suction cap, a suction pump, and a wiper blade is provided as means for executing the cleaning operation.

  In addition, an operation unit as a user interface is provided, and the operation unit includes an input device 468 and a display unit (display) 466 for an operator (user) to perform various inputs. The input device 468 can employ various forms such as a keyboard, a mouse, a touch panel, and buttons. By operating the input device 468, the operator can input printing conditions, select an image quality mode, input / edit attached information, search for information, etc. This can be confirmed through display on the display unit 466. The display unit 466 also functions as means for displaying a warning such as an error message.

  In the image recording method shown in this example, a configuration in which non-ejection nozzle information is acquired via the input device 468 is also possible.

  Further, in this example, the correction of the non-ejection nozzle has been described, but the present invention is not limited to the non-ejection nozzle, but the landing position abnormal nozzle in which the error of the landing position of the droplet that is ejected exceeds the allowable range, The present invention is also applicable to correction of abnormal ejection nozzles, such as ejection abnormal nozzles whose droplet ejection amount error exceeds an allowable range.

[Example of application to other devices]
Other device configuration examples include, for example, a wiring drawing device for drawing a wiring pattern of an electronic circuit, a manufacturing device for various devices, a resist printing device that uses a resin liquid as a functional liquid for ejection, a color filter manufacturing device, a material deposition The present invention can be widely applied to an inkjet system that obtains various shapes and patterns using a liquid functional material, such as a fine structure forming apparatus that forms a fine structure using a material for use.

[Appendix]
As can be understood from the description of the embodiment described in detail above, the present specification includes disclosure of various technical ideas including the invention described below.

  (Invention 1): An abnormal recording element information acquisition step for acquiring information of an abnormal recording element in a recording head having a plurality of recording elements, an image data input step for inputting image data, and an adjacent recording element is abnormal An abnormality correction coefficient storing step for storing the abnormality correction coefficient for each recording element, and a first condition determined based on the occurrence characteristic of the abnormal recording element grasped from the acquired abnormal recording element information. The normal recording element of the recording element adjacent to the normal recording element satisfying the second condition determined based on the abnormality correction coefficient of the recording element adjacent to the abnormal recording element to be satisfied and the generation characteristic of the abnormal recording element is abnormal. A correction coefficient storing step of storing a correction coefficient for correcting an abnormal correction coefficient in the case of a recording element in association with a generation characteristic of the abnormal recording element; and the first condition A characteristic information providing step for providing information on the generation characteristics of the abnormal recording element to a recording element adjacent to the abnormal recording element and a recording element adjacent to the normal recording element satisfying the second condition; When the recording element adjacent to the recording element corresponding to the pixel is an abnormal recording element, the correction process for correcting the pixel value of the processing target pixel using the stored abnormality correction coefficient, and the recording corresponding to the processing target pixel When the abnormal recording element adjacent to the element is adjacent to another abnormal recording element, the abnormal correction of the processing target pixel is performed using the stored correction coefficient with reference to the information on the occurrence characteristic of the abnormal recording element A correction step of correcting the coefficient.

  According to the present invention, there is another abnormal recording element in a close position that satisfies the first condition determined based on the occurrence characteristic of the abnormal recording element based on the information about the abnormal recording element grasped in advance. When it is determined that there is a correction coefficient for correcting the abnormality correction coefficient for a recording element adjacent to the abnormal recording element, a correction coefficient is prepared and determined based on the generation characteristic of the abnormal recording element. A correction coefficient for correcting an abnormal correction coefficient when the normal recording element becomes an abnormal recording element is prepared for a recording element adjacent to the normal recording element satisfying the above condition.

  Therefore, when there is an abnormal recording element in the vicinity, the abnormality correction coefficient is corrected by the correction coefficient, and density unevenness that occurs when the abnormal recording element is in the vicinity is suppressed. In addition, when a new abnormal recording element is generated, the abnormal correction coefficient is corrected using a correction coefficient prepared in advance for the recording element adjacent to the normal recording element. It is possible to respond.

  The first condition and the second condition include the distance between the abnormal recording elements at the closest position (the number of pitches and the number of intervals of the arrangement pitch of the recording elements) and the number of repeated occurrences of the abnormal recording elements (number of periods). The aspect is this.

  The “recording element” is a concept encompassing nozzles in an inkjet head, LED elements in an electrophotographic system, and the like. Further, the “abnormal recording element” includes an element in which the position error of a formed pixel (dot) exceeds an allowable range, an element in which an error in the size of the formed pixel exceeds an allowable range, and the like.

  (Invention 2): In the image processing method according to Invention 1, the abnormal recording element satisfying the first condition is an abnormal recording element in which another abnormal recording element exists in a close position within a predetermined range. Features.

  According to this aspect, when another abnormal recording element exists in the predetermined interval range, the abnormality correction coefficient is corrected, so that density interference due to the proximity of the abnormal recording element is avoided.

  In this aspect, the predetermined range can be set to the number of intervals between abnormal recording elements (the number of recording element pitches between abnormal recording elements).

  (Invention 3): In the image processing method according to Invention 1 or 2, the abnormal recording element satisfying the first condition is an abnormal recording element in which other abnormal recording elements repeatedly appear at a cycle within a predetermined range. It is characterized by that.

  The first condition may be a combination of the number of intervals of the abnormal recording elements according to the second aspect and the number of periods of the abnormal recording elements according to the third aspect.

  (Invention 4): In the image processing method according to any one of Inventions 1 to 3, the normal recording element satisfying the second condition is a normal recording element in which an abnormal recording element exists at a close position within a predetermined range. It is characterized by being.

  According to this aspect, based on the occurrence state (occurrence distribution) of the abnormal recording element, a normal recording element that is highly likely to be abnormal is recognized as a temporary abnormal recording element, and the temporary abnormal recording element Is also assigned a correction coefficient for correcting the abnormality correction coefficient. Therefore, when the temporary abnormal recording element becomes abnormal newly, it is possible to immediately correct the abnormality correction coefficient.

  (Invention 5): In the image processing method according to any one of Inventions 1 to 3, the normal recording element satisfying the second condition is one of the abnormal recording elements repeatedly appearing at a cycle within a predetermined range. It is a normal recording element existing at a close position within the range.

  The second condition may be a combination of the number of intervals of the abnormal recording element according to the fourth aspect and the number of periods of the abnormal recording element according to the fifth aspect.

  (Invention 6): In the image processing method according to any one of Inventions 1 to 5, the characteristic information providing step includes a recording element adjacent to the abnormal recording element satisfying the first condition and normal recording satisfying the second condition. The recording element adjacent to the element is provided with at least one of an interval between the abnormal recording elements and an appearance period of the abnormal recording element as information on the generation characteristic of the abnormal recording element.

  In such an aspect, an aspect in which the characteristic information for the recording element adjacent to one and the characteristic information for the recording element adjacent to the other is separately provided is preferable.

  (Invention 7): In the image processing method according to any one of Inventions 1 to 6, the correction coefficient is stored in an index table format using at least one of an interval between abnormal recording elements and an appearance period of the abnormal recording elements as an index. It includes a correction coefficient storing step.

  According to this aspect, it is not necessary to store a correction coefficient for correcting the abnormal correction coefficient for each recording element, for each pixel value, for each interval between abnormal recording elements, for each occurrence period of the abnormal recording element, and for correction. The storage capacity for storing the coefficients can be saved.

  (Invention 8): An abnormal recording element information acquisition step of acquiring information of an abnormal recording element in a recording head having a plurality of recording elements, an image data input step of inputting image data, and an adjacent recording element being abnormal An abnormal correction coefficient storage step for storing the abnormal correction coefficient for each recording element and a first condition determined based on the occurrence characteristic of the abnormal recording element grasped from the acquired abnormal recording element information The normal recording element of the recording element adjacent to the normal recording element that satisfies the second condition determined based on the abnormality correction coefficient of the recording element adjacent to the abnormal recording element and the generation characteristic of the abnormal recording element is abnormally recorded. A correction coefficient storing step of storing a correction coefficient for correcting an abnormal correction coefficient in the case of an element in association with the occurrence characteristic of the abnormal recording element, and satisfying the first condition A characteristic information providing step for providing information on the generation characteristics of the abnormal recording element to a recording element adjacent to the abnormal recording element and a recording element adjacent to the normal recording element satisfying the second condition; When the recording element adjacent to the recording element corresponding to is an abnormal recording element, a correction process for correcting the pixel value of the processing target pixel using the stored abnormality correction coefficient, and the recording element corresponding to the processing target pixel When the abnormal recording element adjacent to the other abnormal recording element is adjacent to the abnormal recording element, the abnormal correction coefficient of the pixel to be processed is referred to by using the stored correction coefficient with reference to the information on the occurrence characteristic of the abnormal recording element A correction step for correcting the corrected pixel value, a halftone processing step for applying a halftone process to the corrected pixel value, and a data after the halftone process is performed. Image recording method which comprises a data output step of outputting.

  In the present invention, an aspect including a drive signal generation step of generating a drive signal for driving the recording element based on the output data output from the data output step is preferable.

  (Invention 9): In the image recording method according to Invention 8, when there is an abnormal recording element that is closer than the predetermined range in the first condition based on the acquired abnormal recording element information Includes an error information notification step of notifying that fact as error information.

  In this aspect, it is preferable that the image processing is interrupted when there is an abnormal recording element that is closer than the predetermined range in the first condition.

  The present invention includes a program invention for causing a computer to execute each step of the image processing method according to any one of the first to ninth aspects.

  (Invention 10): Abnormal recording element information acquisition means for acquiring abnormal recording element information in a recording head having a plurality of recording elements, image data input means for inputting image data, and adjacent recording elements are abnormal An abnormal correction coefficient storage means for storing the abnormal correction coefficient for each recording element, and a first condition determined based on the occurrence characteristic of the abnormal recording element grasped from the acquired abnormal recording element information The normal recording element of the recording element adjacent to the normal recording element that satisfies the second condition determined based on the abnormality correction coefficient of the recording element adjacent to the abnormal recording element and the generation characteristic of the abnormal recording element is abnormally recorded. A correction coefficient storing means for storing a correction coefficient for correcting an abnormality correction coefficient in the case of an element in association with the occurrence characteristic of the abnormal recording element, and the first condition A characteristic information providing means for providing information on the generation characteristics of the abnormal recording element to a recording element adjacent to the abnormal recording element and a recording element adjacent to the normal recording element satisfying the second condition; When the recording element adjacent to the recording element corresponding to the pixel is an abnormal recording element, the correction means for correcting the pixel value of the processing target pixel using the stored abnormality correction coefficient, and the recording corresponding to the processing target pixel When the abnormal recording element adjacent to the element is adjacent to another abnormal recording element, the abnormal correction of the processing target pixel is performed using the stored correction coefficient with reference to the information on the occurrence characteristic of the abnormal recording element An image processing apparatus comprising: correction means for correcting a coefficient.

  In the present invention, it is preferable that an output unit that outputs data after image processing is provided.

  (Invention 11): A recording head provided with a plurality of recording elements, an abnormal recording element information acquisition means for acquiring information on abnormal recording elements in the recording head provided with a plurality of recording elements, and image data to which image data is input An input means, an abnormality correction coefficient storage means for storing an abnormality correction coefficient when an adjacent recording element becomes abnormal for each recording element, and an occurrence characteristic of an abnormal recording element grasped from the acquired abnormal recording element information Adjacent to the normal recording element satisfying the second condition determined based on the abnormality correction coefficient of the recording element adjacent to the abnormal recording element satisfying the first condition determined based on A correction coefficient for correcting an abnormal correction coefficient of the recording element when the normal recording element becomes an abnormal recording element is stored in association with the generation characteristic of the abnormal recording element. Information on generation characteristics of the abnormal recording element with respect to a positive coefficient storage means, a recording element adjacent to the abnormal recording element satisfying the first condition, and a recording element adjacent to the normal recording element satisfying the second condition When the recording element adjacent to the recording element corresponding to the processing target pixel is an abnormal recording element, the pixel value of the processing target pixel is corrected using the stored abnormality correction coefficient. When the correction unit and the abnormal recording element adjacent to the recording element corresponding to the pixel to be processed are adjacent to another abnormal recording element, the stored correction is made with reference to the information on the occurrence characteristics of the abnormal recording element. Correction means for correcting an abnormality correction coefficient of the processing target pixel using a coefficient, halftone processing means for performing halftone processing on the corrected pixel value and the corrected pixel value, The image recording apparatus characterized by serial halftone process includes a recording control means for forming an image on the medium by operating the recording device on the basis of the data after having been subjected.

  As an example of an image recording apparatus, an inkjet including an inkjet head having a plurality of nozzles, a moving unit that relatively moves the recording medium and the inkjet head, and an ejection control unit that controls ejection of the inkjet head A recording device may be mentioned.

  DESCRIPTION OF SYMBOLS 10 ... Unevenness correction LUT, 12, 14 ... Non-ejection correction LUT, 20, 348 ... Head, 22, 408 ... Nozzle, 44 ... LUT switching part, 46 ... Index table, 48, 112 ... Nozzle attribute information storage part, 102 ... Image input unit 104 ... Non-ejection nozzle information acquisition unit 108 ... Correction coefficient storage unit 110 ... Density value correction unit 114 ... Correction coefficient storage unit 116 ... Density value correction unit 120 ... Data output unit 310 ... Inkjet Recording device, 442 ... system control unit, 446 ... image processing unit

Claims (11)

An abnormal recording element information acquisition step of acquiring information of an abnormal recording element in a recording head including a plurality of recording elements;
An image data input process in which image data is input;
An abnormality correction coefficient storing step for storing an abnormality correction coefficient for each recording element when an adjacent recording element becomes abnormal,
The abnormality correction coefficient of the recording element adjacent to the abnormal recording element that satisfies the first condition determined based on the generation characteristic of the abnormal recording element grasped from the acquired abnormal recording element information, and the occurrence of the abnormal recording element A correction coefficient for correcting an abnormal correction coefficient of a recording element adjacent to a normal recording element that satisfies the second condition determined based on the characteristics when the normal recording element becomes an abnormal recording element A correction coefficient storage step for storing the correlation with the occurrence characteristic;
Characteristic information provision for providing information on the occurrence characteristics of the abnormal recording element to a recording element adjacent to the abnormal recording element satisfying the first condition and a recording element adjacent to the normal recording element satisfying the second condition Process,
When the recording element adjacent to the recording element corresponding to the processing target pixel is an abnormal recording element, a correction step of correcting the pixel value of the processing target pixel using the stored abnormality correction coefficient;
When the abnormal recording element adjacent to the recording element corresponding to the pixel to be processed is adjacent to another abnormal recording element, the stored correction coefficient is used with reference to the information on the generation characteristic of the abnormal recording element. A correction step of correcting the abnormality correction coefficient of the processing target pixel;
An image processing method comprising: The image processing method according to claim 1,
The image processing method according to claim 1, wherein the abnormal recording element satisfying the first condition is an abnormal recording element in which another abnormal recording element exists at a close position within a predetermined range. The image processing method according to claim 1 or 2,
The abnormal recording element satisfying the first condition is an abnormal recording element in which other abnormal recording elements repeatedly appear at a cycle within a predetermined range. The image processing method according to any one of claims 1 to 3,
The normal recording element satisfying the second condition is a normal recording element in which an abnormal recording element exists in a close position within a predetermined range. The image processing method according to any one of claims 1 to 3,
The normal recording element that satisfies the second condition is a normal recording element in which one of the abnormal recording elements that repeatedly appears at a cycle within a predetermined range is present at a close position within the predetermined range. Method. The image processing method according to any one of claims 1 to 5,
The characteristic information providing step includes an interval between the abnormal recording elements and an abnormal recording element for a recording element adjacent to the abnormal recording element satisfying the first condition and a recording element adjacent to the normal recording element satisfying the second condition. An image processing method characterized in that at least one of the appearance periods is given as information on the occurrence characteristics of the abnormal recording element. The image processing method according to any one of claims 1 to 6,
An image processing method comprising: a correction coefficient storing step of storing the correction coefficient in an index table format using at least one of an interval between abnormal recording elements and an appearance period of abnormal recording elements as an index. An abnormal recording element information acquisition step of acquiring information of an abnormal recording element in a recording head including a plurality of recording elements;
An image data input process in which image data is input;
An abnormality correction coefficient storing step for storing an abnormality correction coefficient for each recording element when an adjacent recording element becomes abnormal,
The abnormality correction coefficient of the recording element adjacent to the abnormal recording element that satisfies the first condition determined based on the generation characteristic of the abnormal recording element grasped from the acquired abnormal recording element information, and the occurrence of the abnormal recording element A correction coefficient for correcting an abnormal correction coefficient of a recording element adjacent to a normal recording element that satisfies the second condition determined based on the characteristics when the normal recording element becomes an abnormal recording element A correction coefficient storage step for storing the correlation with the occurrence characteristic;
Characteristic information provision for providing information on the occurrence characteristics of the abnormal recording element to a recording element adjacent to the abnormal recording element satisfying the first condition and a recording element adjacent to the normal recording element satisfying the second condition Process,
When the recording element adjacent to the recording element corresponding to the processing target pixel is an abnormal recording element, a correction step of correcting the pixel value of the processing target pixel using the stored abnormality correction coefficient;
When the abnormal recording element adjacent to the recording element corresponding to the pixel to be processed is adjacent to another abnormal recording element, the stored correction coefficient is used with reference to the information on the generation characteristic of the abnormal recording element. A correction step of correcting the abnormality correction coefficient of the processing target pixel;
A halftone processing step of performing a halftone process on the corrected pixel value and the corrected pixel value;
A data output step of outputting the data after the halftone processing is performed;
An image recording method comprising: The image recording method according to claim 8, wherein
If there is an abnormal recording element that is closer than the predetermined range in the first condition based on the acquired abnormal recording element information, an error information notification step that notifies the fact as error information An image recording method comprising: An abnormal recording element information acquisition means for acquiring information of an abnormal recording element in a recording head including a plurality of recording elements;
Image data input means for inputting image data;
An abnormality correction coefficient storage means for storing an abnormality correction coefficient for each recording element when an adjacent recording element becomes abnormal;
The abnormality correction coefficient of the recording element adjacent to the abnormal recording element that satisfies the first condition determined based on the generation characteristic of the abnormal recording element grasped from the acquired abnormal recording element information, and the occurrence of the abnormal recording element A correction coefficient for correcting an abnormal correction coefficient of a recording element adjacent to a normal recording element that satisfies the second condition determined based on the characteristics when the normal recording element becomes an abnormal recording element Correction coefficient storage means for storing in association with occurrence characteristics;
Characteristic information provision for providing information on the occurrence characteristics of the abnormal recording element to a recording element adjacent to the abnormal recording element satisfying the first condition and a recording element adjacent to the normal recording element satisfying the second condition Means,
Correction means for correcting the pixel value of the processing target pixel using the stored abnormality correction coefficient when the recording element adjacent to the recording element corresponding to the processing target pixel is an abnormal recording element;
When the abnormal recording element adjacent to the recording element corresponding to the pixel to be processed is adjacent to another abnormal recording element, the stored correction coefficient is used with reference to the information on the generation characteristic of the abnormal recording element. Correction means for correcting the abnormality correction coefficient of the processing target pixel;
An image processing apparatus comprising: A recording head comprising a plurality of recording elements;
An abnormal recording element information acquisition means for acquiring information of an abnormal recording element in a recording head including a plurality of recording elements;
Image data input means for inputting image data;
An abnormality correction coefficient storage means for storing an abnormality correction coefficient for each recording element when an adjacent recording element becomes abnormal;
The abnormality correction coefficient of the recording element adjacent to the abnormal recording element that satisfies the first condition determined based on the generation characteristic of the abnormal recording element grasped from the acquired abnormal recording element information, and the occurrence of the abnormal recording element A correction coefficient for correcting an abnormal correction coefficient of a recording element adjacent to a normal recording element that satisfies the second condition determined based on the characteristics when the normal recording element becomes an abnormal recording element Correction coefficient storage means for storing in association with occurrence characteristics;
Characteristic information provision for providing information on the occurrence characteristics of the abnormal recording element to a recording element adjacent to the abnormal recording element satisfying the first condition and a recording element adjacent to the normal recording element satisfying the second condition Means,
Correction means for correcting the pixel value of the processing target pixel using the stored abnormality correction coefficient when the recording element adjacent to the recording element corresponding to the processing target pixel is an abnormal recording element;
When the abnormal recording element adjacent to the recording element corresponding to the pixel to be processed is adjacent to another abnormal recording element, the stored correction coefficient is used with reference to the information on the generation characteristic of the abnormal recording element. Correction means for correcting the abnormality correction coefficient of the processing target pixel;
Halftone processing means for performing halftone processing on the corrected pixel value and the corrected pixel value;
Recording control means for operating the recording element based on the data after the halftone processing to form an image on a medium;
An image recording apparatus comprising:

Images