JP2021160334A - Printing system and printing method - Google Patents

Abstract

To adequately reduce influence of an abnormal nozzle in an ink jet head.SOLUTION: A printing system 10 for performing printing comprises an ink jet head 102, an RIP processing part 14 which is a discharge data generation part, and a control part 110 which is a discharge control part. The RIP processing part 14 executes: density correction processing for gradation image data which is image data showing an image to be printed with a prescribed graduation that performs correction of a density of at least a part of the graduation image data on the basis of abnormal nozzle information indicating an abnormal nozzle; and quantization processing that performs processing for decreasing the number of graduation for the graduation image data after performance of the density correction processing, thereby generating discharge designation data.SELECTED DRAWING: Figure 1

Description

The present invention relates to a printing system and a printing method.

Conventionally, an inkjet printer, which is a printing apparatus that prints using an inkjet head, has been widely used. When printing using an inkjet head, it is required to reduce the influence of variations in nozzle characteristics in the inkjet head in order to print with high quality.

On the other hand, conventionally, as a method of reducing the influence of individual differences of the inkjet head, a method of adjusting the voltage of the waveform of the drive signal (head drive waveform) used for driving the inkjet head and a temperature of heating the ink (ink). A method of adjusting and stabilizing the heating temperature) is known. When such a method is used, for example, unevenness in print density can be reduced by reducing the influence of individual differences of the inkjet head on the diameter of the formed ink dots. Further, conventionally, regarding a method of controlling an inkjet head, a recovery process or the like in which another nozzle is used instead of an abnormal nozzle (defective nozzle) whose ejection characteristics are out of the normal range is also known (see, for example, Patent Document 1). .).

Japanese Unexamined Patent Publication No. 2014-172260

When trying to reduce the influence of individual differences in the inkjet head by stabilizing the voltage of the head drive waveform and the ink heating temperature, the cost of the device is due to the need for a configuration for adjusting the voltage and heating temperature. Is expected to rise. Further, depending on the model of the printing apparatus and the like, it may be difficult to use these configurations.

Further, when printing is performed using another nozzle instead of the abnormal nozzle, for example, the timing at which the ink lands on the medium to be printed is different from the normal time, so that the print result is recovered. The part where the above was performed may become more noticeable. In particular, when the recovery process is performed on a plurality of nozzles located close to each other, the influence on the print quality may be large. Therefore, conventionally, it has been desired to reduce the influence of variations in nozzle characteristics in an inkjet head by a more appropriate method. Therefore, an object of the present invention is to provide a printing system and a printing method that can solve the above problems.

The inventor of the present application has conducted diligent research on a method for reducing the influence of an abnormal nozzle on an inkjet head. Then, it was considered to reduce the influence of the abnormal nozzle by correcting the image used for generating the ejection designation data indicating the ejection position for ejecting the ink to the inkjet head. In addition, it was confirmed that the influence of the abnormal nozzle can be reduced by such a method by actually conducting an experiment or the like.

In addition, the inventor of the present application has found the features necessary for obtaining such an effect through further diligent research, and has reached the present invention. In order to solve the above problems, the present invention is a printing system that prints by an inkjet method, and indicates an inkjet head that ejects ink from a plurality of nozzles and an ejection position that ejects ink to the inkjet head. A discharge data generation unit that generates designated data and a discharge control unit that discharges ink to each of the plurality of nozzles in the inkjet head based on the discharge designated data are provided, and the discharge data generation unit should print. The gradation based on the abnormal nozzle information indicating the abnormal nozzle which is the nozzle whose amount of ink to be ejected is out of the predetermined normal range with respect to the gradation image data which is the image data showing the image with a predetermined gradation. The ejection designation data is obtained by performing a density correction process for correcting at least a part of the density of the image data and a process for reducing the number of gradations with respect to the gradation image data after the density correction process is performed. Performs the quantization process to be generated.

With such a configuration, for example, by correcting the gradation image data based on the abnormal nozzle information in the density correction processing, the gradation image data can be corrected so as to reduce the influence of the abnormal nozzle. .. Further, in the quantization process, by generating the ejection designation data based on the corrected gradation image data, it is possible to generate the ejection designation data in which the influence of the abnormal nozzle is reduced. Therefore, with such a configuration, for example, the influence of an abnormal nozzle on the inkjet head can be appropriately reduced.

In this configuration, as the abnormal nozzle information, for example, it is conceivable to use information indicating the position and characteristics of the abnormal nozzle. In this case, the position of the abnormal nozzle can be considered as, for example, the position of the abnormal nozzle in the inkjet head. More specifically, the inkjet head has, for example, a nozzle array in which a plurality of nozzles are arranged in a predetermined nozzle array direction. In this case, the position of the abnormal nozzle can be considered as, for example, the position of the abnormal nozzle in the nozzle row. Further, in the abnormal nozzle information, as the characteristic of the abnormal nozzle, for example, it is conceivable to use information indicating the magnitude relationship or difference between the amount of ink ejected by the abnormal nozzle and the predetermined reference amount.

Further, in this configuration, the ejection designation data can be considered as, for example, data indicating positions where ink should be ejected at a plurality of ejection positions set according to the print resolution. Further, regarding the correction of the density of at least a part of the gradation image data, for example, the gradation image data is corrected so that the density of at least a part of the image indicated by the gradation image data changes. I can think. Further, the density in the gradation image data can be considered as, for example, the color density in the image indicated by the gradation image data. Further, the color density can be considered as, for example, the color density specified by the pixel values of the pixels constituting the image. Further, in the density correction process, the ejection data generation unit changes, for example, the density of the image indicated by the gradation image data at the position corresponding to the position where the ink is ejected by the abnormal nozzle based on the abnormal nozzle information. Then, the density is corrected so that the influence of the abnormal nozzle is reduced. With this configuration, for example, the influence of the abnormal nozzle can be appropriately reduced.

Further, in this configuration, the printing system includes, for example, a plurality of inkjet heads that eject inks of different colors from each other. In this case, in the density correction process, for example, it is conceivable to correct the gradation image data generated in advance corresponding to each inkjet head. More specifically, in this case, in the density correction process, the ejection data generation unit is based on, for example, the abnormal nozzle information indicating the abnormal nozzle in each inkjet head for the gradation image data corresponding to each inkjet head. Correct the density. With this configuration, the influence of the abnormal nozzle can be appropriately reduced for each inkjet head.

Further, in this case, as the gradation image data corresponding to each inkjet head, for example, it is conceivable to use the grayscale image data generated corresponding to the color of the ink ejected from the inkjet head. More specifically, as the gradation image data corresponding to each inkjet head, for example, gray generated by performing plate separation processing on a color image indicating an image to be printed according to the color of the ink used for printing. It is conceivable to use data showing a scale image or the like. With this configuration, for example, in the density correction process, the density can be appropriately corrected to reduce the influence of the abnormal nozzle. Further, in this case, the density in the gradation image data can be considered as, for example, the density indicated by the pixel value in the gray scale image.

Further, in this configuration, the printing system further includes, for example, a main scanning drive unit and a sub-scanning drive unit. In this case, the main scanning drive unit is a drive unit that causes the inkjet head to perform the main scanning operation. The sub-scanning drive unit is a driving unit that causes the inkjet head to perform a sub-scanning operation. The main scanning operation can be considered, for example, an operation of ejecting ink while moving relative to the medium to be printed in a preset main scanning direction. The sub-scanning operation can be considered, for example, an operation of moving relative to the medium in the sub-scanning direction orthogonal to the main scanning direction.

Further, in the inkjet head, the plurality of nozzles are arranged so as to be displaced from each other in the sub-scanning direction, for example. In this case, the abnormal nozzle information indicates the influence of the abnormal nozzle for each nozzle range, which is a range including a plurality of nozzles continuously arranged in the sub-scanning direction, for example. Further, in the density correction process, the discharge data generation unit corrects the density, for example, in units of regions corresponding to the nozzle range. With this configuration, for example, correction for suppressing the influence of the abnormal nozzle can be appropriately performed on the gradation image data. Further, in this case, in the density correction process, the ejection data generation unit selects, for example, a region corresponding to the nozzle range including the abnormal nozzle for the gradation image data, and the density of the region is affected by the abnormal nozzle. Make corrections so that With this configuration, for example, the influence of the abnormal nozzle can be appropriately reduced.

Further, when the gradation image data is corrected in units of regions corresponding to a predetermined nozzle range in this way, the abnormal nozzle information also includes information indicating the position and characteristics of the abnormal nozzles in units of nozzle ranges. It is conceivable to use it. With this configuration, for example, it is not always necessary to identify which nozzle is the abnormal nozzle, but only the nozzle range including the abnormal nozzle is identified, and the correction for suppressing the influence of the abnormal nozzle is performed. Can be done properly. Further, as a result, for example, the influence of the abnormal nozzle can be easily and appropriately reduced. Further, as the nozzle range, for example, it is conceivable to use a range including only one nozzle.

Further, in this configuration, the ejection control unit controls the operation of the main scanning drive unit and the sub-scanning drive unit, for example, to cause the inkjet head to eject ink in a multipath system. In this case, the multi-pass method can be considered, for example, a method in which the number of passes, which is the number of main scanning operations in which the inkjet head passes through the same position on the medium and the position facing the same position, is a plurality of times. Then, in this case, in the density correction process, the ejection data generation unit corrects the density with respect to the region where the ink is ejected from the nozzle range including the abnormal nozzle in each main scanning operation, for example. With this configuration, for example, when printing in the multipath method, the influence of the abnormal nozzle can be appropriately reduced.

Further, in this configuration, as the abnormal nozzle information, for example, it is conceivable to use information obtained by printing a predetermined test pattern using a plurality of nozzles in the inkjet head. With this configuration, for example, the characteristics of the abnormal nozzle can be appropriately detected. Further, as a result, for example, abnormal nozzle information used for reducing the influence of the abnormal nozzle can be appropriately created.

Further, as the configuration of the present invention, it is conceivable to use a printing method or the like having the same characteristics as described above. In this case as well, for example, the same effect as described above can be obtained.

According to the present invention, for example, the influence of an abnormal nozzle on an inkjet head can be appropriately reduced.

It is a figure which shows an example of the structure of the printing system 10 which concerns on one Embodiment of this invention. FIG. 1A shows an example of the configuration of the printing system 10. FIG. 1B shows an example of the configuration of the print execution unit 12 in the print system 10. It is a figure explaining the influence of an abnormal nozzle. FIG. 2A simplifies the state of the inkjet head 102 in which the abnormal nozzle is present. FIG. 2B simplifies the result of ejecting ink using the inkjet head 102 in which the abnormal nozzle is present. It is a figure which shows the example of the nozzle range 204. It is a flowchart which shows an example of the process performed in order to suppress the influence of an abnormal nozzle. It is a figure which explains more concretely about the effect of the density correction performed in this example. FIG. 5A shows an example of a nozzle range 204 including an abnormal nozzle. FIG. 5B shows an example of the influence of the abnormal nozzle. FIG. 5C shows an example of the density correction performed in this example. It is a flowchart which shows an example of the operation which generates RIP generation data in RIP processing unit 14.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of the configuration of the printing system 10 according to the embodiment of the present invention. FIG. 1A shows an example of the configuration of the printing system 10. FIG. 1B shows an example of the configuration of the print execution unit 12 in the print system 10. Except as described below, the printing system 10 of this example may have the same or similar characteristics as a known printing system.

In this example, the printing system 10 is a printing system that prints on a medium (media) 50 to be printed by an inkjet method, and includes a print execution unit 12 and a RIP processing unit 14. The print execution unit 12 is a unit that executes a printing operation of ejecting ink to the medium 50. The print execution unit 12 can be considered, for example, a portion that functions as a printing device in the printing system 10. Further, the print execution unit 12 can be considered as, for example, a main body portion of an inkjet printer. In this example, the print execution unit 12 receives RIP generation data, which is data generated by performing RIP (Raster Image Processor) processing, from the RIP processing unit 14, and ejects ink according to the RIP generation data. The operation of printing on the medium 50 is executed. Further, the print execution unit 12 includes a plurality of inkjet heads 102, a platen 104, a main scan drive unit 106, a sub scan drive unit 108, and a control unit 110.

Each of the plurality of inkjet heads 102 is an ejection head that ejects ink by an inkjet method, and ejects ink of each color used for printing. In this case, it is conceivable that each of the plurality of inkjet heads 102 ejects inks of different colors. More specifically, each of the plurality of inkjet heads 102 ejects ink of each color of the process color, which is a basic color in color printing, for example. As the ink of each color of the process color, for example, it is conceivable to use inks of each color of cyan (C color), magenta color (M color), yellow color (Y color), and black color (K color). Further, each inkjet head 102 has a nozzle row in which a plurality of nozzles are arranged in a predetermined nozzle row direction, and ink is ejected from each nozzle in the nozzle row. In this example, the nozzle row direction is a direction parallel to the sub-scanning direction (X direction in the drawing) set in advance in the print execution unit 12. In this case, in each inkjet head 102, the plurality of nozzles are arranged in the nozzle row direction so that the positions in the sub-scanning direction are shifted from each other.

The platen 104 is a trapezoidal member on which the medium 50 is placed on the upper surface, and holds the medium 50 in a state of facing the plurality of inkjet heads 102. The main scanning drive unit 106 is a drive unit that causes a plurality of inkjet heads 102 to perform a main scanning operation. The main scanning operation is an operation of ejecting ink while moving relative to the medium 50 in a preset main scanning direction. Further, in this example, the main scanning direction is a direction orthogonal to the sub-scanning direction (Y direction in the drawing). During the main scanning operation, the main scanning drive unit 106 is applied to each nozzle of each of the plurality of inkjet heads 102 with respect to the ejection position set according to the print resolution, for example, according to the control of the control unit 110. Ink is ejected. The sub-scanning drive unit 108 is a driving unit that causes a plurality of inkjet heads 102 to perform a sub-scanning operation. The sub-scanning operation is an operation of moving in the sub-scanning direction relative to the medium 50. In this example, the sub-scanning operation can be considered as, for example, an operation of sending the medium 50 in the sub-scanning direction between the main scanning operations.

The control unit 110 is, for example, a part of the print execution unit 12 including a CPU and the like, and controls the operation of each part of the print execution unit 12. Further, as described above, in this example, the main scanning drive unit 106 ejects ink to each nozzle of each of the plurality of inkjet heads 102 according to the control of the control unit 110. In this case, it can be considered that the control unit 110 controls the ejection of ink from each nozzle. More specifically, the control unit 110 controls the operations of the main scanning drive unit 106, the sub-scanning drive unit 108, and the like to eject ink to the plurality of inkjet heads 102 in each main scanning operation. Let me. Further, in this example, the control unit 110 controls the operations of the main scanning drive unit 106, the sub-scanning drive unit 108, and the like to cause the plurality of inkjet heads 102 to eject ink in a multi-pass system. In this case, the multipath method can be considered, for example, a method in which the number of passes is a plurality of times. Further, the number of passes can be considered as, for example, the number of main scanning operations in which the inkjet head 102 passes through the same position on the medium 50 and the position facing the same position. Further, the multi-pass method can be considered as, for example, a method in which the pass width is less than the nozzle length. In this case, the pass width can be considered as, for example, a width corresponding to the relative movement amount (feed amount) of the inkjet head in one sub-scanning operation. The nozzle length can be considered, for example, as a range in which a plurality of nozzles are lined up in the inkjet head (a range in the sub-scanning direction). Further, in this case, the path width can be considered to be, for example, a width corresponding to the distance obtained by dividing the nozzle length by the number of passes.

Further, in this example, the control unit 110 is an example of the ejection control unit, and ejects ink to each nozzle of each inkjet head 102 based on the RIP generated data. Further, as a result, the control unit 110 ejects ink to each nozzle of each inkjet head 102 to an ejection position determined according to, for example, an image to be printed. With this configuration, for example, a printing operation based on RIP-generated data can be appropriately executed.

Further, as described above, in this example, the print execution unit 12 receives the RIP generation data from the RIP processing unit 14. In this case, the RIP processing unit 14 generates RIP generation data by performing the RIP processing according to, for example, the configuration of the print execution unit 12 and the setting of the printing operation executed by the print execution unit 12. More specifically, in this example, the RIP processing unit 14 generates, as RIP generation data, data indicating at least the positions where ink should be ejected at a plurality of ejection positions set according to the print resolution. In this case, the RIP generated data can be considered as an example of discharge designation data, for example. The ejection designation data can be considered, for example, data indicating positions at which ink should be ejected at a plurality of ejection positions set according to the print resolution.

Further, in this example, the RIP processing unit 14 is an example of a discharge data generation unit. As the RIP processing unit 14, for example, a computer or the like that executes software for RIP processing can be preferably used. Further, the RIP processing unit 14 can be considered as, for example, a computer that controls the operation of the print execution unit 12. Further, as described above, in this example, the plurality of inkjet heads 102 in the print execution unit 12 perform the main scanning operation to eject ink to the medium 50. In this case, the RIP processing unit 14 generates, as RIP generation data, data indicating at least the ejection position for ejecting ink from each nozzle of each inkjet head 102 in each main scanning operation.

Further, in this example, the RIP processing unit 14 generates RIP generation data in further considering the ejection characteristics of each nozzle in each inkjet head 102. More specifically, when any of the inkjet heads 102 in the print execution unit 12 has an abnormal nozzle that is a nozzle in which the amount of ink to be ejected is out of a predetermined normal range, the RIP processing unit 14 determines the abnormal nozzle. RIP generation data is generated by performing processing for reducing the influence of. Further, in this case, as such a process, the RIP processing unit 14 corrects the density of the image data indicating the image to be printed with a predetermined gradation based on the abnormal nozzle information indicating the abnormal nozzle.

Further, as described above, as the RIP processing unit 14, for example, a computer or the like that executes software for RIP processing or the like can be preferably used. In this case, it is conceivable that the abnormal nozzle information is stored in advance in a storage device (for example, HDD or the like) of the RIP processing unit 14, and is used when the RIP generation data is generated. According to this example, for example, printing on the medium 50 can be appropriately performed. Further, in this case, the influence of the abnormal nozzle can be appropriately reduced by generating the RIP generation data by performing a process for reducing the influence of the abnormal nozzle.

Subsequently, the process for reducing the influence of the abnormal nozzle will be described in more detail. First, the influence of the abnormal nozzle will be specifically described. FIG. 2 is a diagram illustrating the influence of the abnormal nozzle. FIG. 2A simplifies the state of the inkjet head 102 in which the abnormal nozzle is present. FIG. 2B simplifies the result of ejecting ink using the inkjet head 102 in which the abnormal nozzle is present.

As described above, in this example, the inkjet head 102 has a plurality of nozzles 202 arranged in a nozzle row direction parallel to the sub-scanning direction. Further, in FIG. 2A, abnormal nozzles are shown by making the shading pattern different, and the arrangement of a plurality of nozzles 202 in the inkjet head 102 is shown. More specifically, in FIG. 2A, the illustration is simplified by reducing the number of nozzles 202 in the inkjet head 102, and an example of a state in which some nozzles 202 are abnormal nozzles is shown. There is. Further, in the case shown in the figure, the third, fifth, and sixth nozzles 202 from the top in the figure are abnormal nozzles.

Further, when the inkjet head 102 in which the abnormal nozzle is present is subjected to the main scanning operation, the arrangement of the ink dots 302 formed by the ink ejected in the main scanning operation is, for example, as shown in FIG. 2 (b). It will reflect the characteristics of the abnormal nozzle. More specifically, in FIG. 2B, the dot 302 formed by the abnormal nozzle is shown with a shaded pattern different from that of the dot 302 formed by the normal nozzle 202. Then, in this case, it is considered that the size of the dots 302 deviates from the original size at the position where the dots 302 formed by the abnormal nozzles are lined up, so that the color density deviates. Further, as a result, uneven printing density may occur.

On the other hand, in this example, as described above, the influence of the abnormal nozzle is reduced by correcting the density of the image data using the abnormal nozzle information. Then, in this case, as the abnormal nozzle information, for example, a predetermined test pattern (hereinafter referred to as an adjustment pattern) is printed using a plurality of nozzles 202 in each inkjet head 102 in the print execution unit 12 (see FIG. 1). It is conceivable to use the information obtained by doing so. More specifically, in this case, for example, an adjustment pattern as shown in FIG. 2B is drawn on each inkjet head 102, the result is read by a camera, a scanner, or the like, and a position where the density is high or a position where the density is low, etc. It is conceivable to create abnormal nozzle information by detecting. With this configuration, for example, the characteristics of the abnormal nozzle can be appropriately detected.

Further, in this example, the abnormal nozzle information can be considered as, for example, information indicating the position and characteristics of the abnormal nozzle. In this case, the position of the abnormal nozzle can be considered, for example, the position of the abnormal nozzle in the inkjet head 102. The position of the abnormal nozzle in the inkjet head 102 can be considered, for example, the position of the abnormal nozzle in the nozzle array in the inkjet head 102. Further, in the abnormal nozzle information, as the characteristic of the abnormal nozzle, for example, it is conceivable to use information indicating the magnitude relationship or difference between the amount of ink ejected by the abnormal nozzle and the predetermined reference amount.

Here, it is conceivable that the printing of the adjustment pattern and the acquisition of the abnormal nozzle information are automatically performed, for example, between the printing operations corresponding to the job (print job) for printing the desired printed matter. .. In this case, for example, it is conceivable to generate abnormal nozzle information by automatically printing and scanning the adjustment pattern. Further, such an operation can be considered as, for example, an operation of automatically correcting the density of the image data.

Further, when trying to detect the influence of the abnormal nozzle more strictly, it is conceivable to identify the nozzle 202 that ejects ink to each position of the adjustment pattern in units of one nozzle 202. Then, in this case, it is conceivable that the process for reducing the influence of the abnormal nozzle is also performed in units of one nozzle 202. However, as described above, in this example, as the processing for reducing the influence of the abnormal nozzle, the density of the image data is corrected instead of performing the direct processing by designating the abnormal nozzle. By doing, so to speak, indirect processing is performed. Then, in this case, if the processing for correction is performed in units of one nozzle 202, it is conceivable that the position where the processing is performed becomes more conspicuous.

Therefore, in this example, for example, as shown in FIG. 3, a process for reducing the influence of abnormal nozzles is performed in units of nozzle range 204, which is a range including a plurality of nozzles 202 that are continuously arranged in the sub-scanning direction. I do. FIG. 3 is a diagram showing an example of the nozzle range 204. As the nozzle range 204, for example, it is conceivable to use a range in which about 2 to 20 nozzles 202 are continuously arranged. The number of nozzles 202 lined up in the nozzle range 204 is preferably about 2 to 10, and more preferably about 2 to 5. Further, in this case, as the abnormal nozzle information, information indicating the influence of the abnormal nozzle is used for each nozzle range 204. More specifically, in this case, it is conceivable to use information indicating the position and characteristics of the abnormal nozzle in units of the nozzle range 204 as the abnormal nozzle information.

According to this example, for example, it is not always necessary to identify which nozzle is the abnormal nozzle, but only the nozzle range 204 including the abnormal nozzle is identified, and the correction for suppressing the influence of the abnormal nozzle is performed. Can be done properly. Further, as a result, for example, the influence of the abnormal nozzle can be easily and appropriately reduced. Further, in this example, performing the process for reducing the influence of the abnormal nozzle in units of the nozzle range 204 is considered to be, for example, changing the density of the region corresponding to the nozzle range 204 in the image data. be able to.

Subsequently, the processing performed in this example in order to suppress the influence of the abnormal nozzle will be described more specifically. FIG. 4 is a flowchart showing an example of processing performed to suppress the influence of the abnormal nozzle. As described above, in this example, processing is performed in order to suppress the influence of the abnormal nozzles by using the abnormal nozzle information obtained by printing a predetermined adjustment pattern. Then, in this case, first, the print execution unit 12 prints the adjustment pattern (S102). In this case, the print execution unit 12 prints the adjustment pattern in response to the instruction of the RIP processing unit 14, for example. Further, in this example, the print execution unit 12 prints the adjustment pattern by the operation of one pass instead of the multi-pass method. The one-pass operation can be considered, for example, a printing operation performed with the number of passes set to 1. In addition, the print execution unit 12 prints the adjustment pattern so that the patterns drawn by the inkjet head 102 for each color can be distinguished. Such an operation can be considered, for example, an operation of drawing one adjustment pattern on one inkjet head 102.

Further, after drawing the adjustment pattern in step S102, the adjustment pattern is read (input) using a camera, a scanner, or the like, and based on the reading result, the range of nozzles to be corrected (correction target nozzle range). ) Is confirmed (S104). In this case, the correction target nozzle range can be considered as, for example, the nozzle range 204 (see FIG. 2) including the abnormal nozzle in the inkjet head 102.

Further, more specifically, it is conceivable that the adjustment pattern is read by using, for example, a camera installed in the print execution unit 12. Further, in this case, for example, it is conceivable to use a camera that moves together with the inkjet head 102 during the main scanning operation. With this configuration, for example, the adjustment pattern can be read without moving the medium on which the adjustment pattern is printed. Further, in this case, it is conceivable to read the adjustment pattern at the same time as the operation of printing the adjustment pattern. Further, the adjustment pattern may be read by using, for example, a camera, a scanner, or the like prepared separately from the print execution unit 12.

Further, for checking the correction target nozzle range, for example, it is conceivable to use software that associates the nozzle range 204 of the inkjet head 102 with each position of the adjustment pattern. Further, as such software, for example, it is conceivable to use software (RIP software) for performing RIP processing in the RIP processing unit 14. In this case, the operation of step S104 can be considered as, for example, an operation of inputting the result of reading the adjustment pattern with a camera, a scanner, or the like into the RIP software.

Further, in this example, the density of the image is corrected based on the correction target nozzle range confirmed in step S104. More specifically, in this case, the RIP processing unit 14 sets the correction unit area for the image data indicating the image to be printed (S106). In this case, the correction unit area can be considered as, for example, an area that is a unit of correction in the image indicated by the image data. Further, the operation of setting the correction unit area for the image data can be considered as, for example, an operation of dividing the image indicated by the image data into a plurality of correction unit areas. Further, in this example, the correction unit area is set so that the nozzle range 204 and the correction unit area in the inkjet head 102 are associated with each other in consideration of the operation in the multipath method. Regarding the association between the nozzle range 204 and the correction unit area in the inkjet head 102 in consideration of the operation in the multi-pass method, for example, ink is added to each correction unit area in each main scanning operation performed in the multi-pass method. It can be considered that the nozzle range 204 and the correction unit area are associated with each other so that it can be identified which is the nozzle range 204 including the nozzle that discharges the ink. Further, in this case, with respect to the nozzle for ejecting ink to the correction unit region, for example, ink is ejected to the correction unit region by any one of the main scanning operations for the number of passes in the multi-pass method. It can be thought of as a nozzle or the like. Further, the operation of setting the correction unit area in this way may be performed, for example, in the operation of dividing the image data (multi-pass print data) into each pass (every pass) on the RIP software. Conceivable.

Further, after the operation of step S106 is performed, the density of the image data is corrected so as to reduce the influence of the abnormal nozzle (S108). In this example, the operation of step S108 is performed in the operation of generating RIP generation data in the RIP processing unit 14. Further, in this case, the RIP processing unit 14 corrects the density of the correction unit region corresponding to the abnormal nozzle so that the influence of the abnormal nozzle becomes smaller. The correction unit area corresponding to the abnormal nozzle can be considered as, for example, a correction unit area in which ink is ejected by the abnormal nozzle in each main scanning operation. Further, in this case, the operation of step S108 can be considered as, for example, an operation of correcting the density for each main scanning operation (for each pass). The operation of correcting the density of the image data will be described in more detail later.

Further, in this case, the RIP processing unit 14 generates RIP generation data based on the image data after the density is corrected. Further, as a result, the RIP processing unit 14 reflects the result of the density correction in the control (print control) of the printing operation performed by the print execution unit 12 (S110). According to this example, for example, a process for appropriately suppressing the influence of an abnormal nozzle can be appropriately performed. Further, as a result, the print execution unit 12 can appropriately prevent the occurrence of, for example, density unevenness, and can appropriately perform high-quality printing. Further, in this case, for example, the influence of the abnormal nozzle can be appropriately suppressed by a method that does not depend on the model of the inkjet head 102 or the device configuration of the inkjet head 102.

Further, as can be understood from the above description and the like, in this example, the print execution unit 12 does not use another nozzle instead of the abnormal nozzle, but also uses the abnormal nozzle to perform printing. In this case, for example, as compared with the case where another nozzle is used instead of the abnormal nozzle, the influence of the abnormal nozzle can be reduced while suppressing the influence on the print quality. Therefore, according to this example, even when an abnormal nozzle is present among a plurality of nozzles in the inkjet head 102, the influence of the abnormal nozzle can be appropriately reduced.

FIG. 5 is a diagram for more specifically explaining the effect of the density correction performed in this example. FIG. 5A is a diagram showing an example of the nozzle range 204 including the abnormal nozzle, and shows the position of the nozzle range 204 including the abnormal nozzle with a shaded pattern in the inkjet head 102. In the case shown in the figure, the nozzle range 204 including the abnormal nozzle exists near the center of the inkjet head 102 in the sub-scanning direction. Then, in this case, when the printing operation is executed in the print execution unit 12 without performing the processing for reducing the influence of the abnormal nozzle, for example, as shown in FIG. 5B, the nozzle range 204 including the abnormal nozzle There will be a deviation in the concentration at the position. FIG. 5B is a diagram showing an example of the influence of the abnormal nozzle, and is an example of the printing result (printing result) when the printing operation is performed without performing the processing for reducing the influence of the abnormal nozzle. show.

More specifically, in FIG. 5B, printing by a multi-pass method in which the number of passes is 3 is based on image data showing an image in which a predetermined range is filled with a constant density as shown as the original image. An example of the operation when performing is shown in the figure. In this case, the original image can be considered, for example, an image to be printed without processing for reducing the influence of the abnormal nozzle. Further, the inkjet head 102 indicated by numbers 1 to 5 in the central portion of the drawing indicates the position of the inkjet head 102 in the sub-scanning direction for five consecutive main scanning operations. In the inkjet head 102 in the figure, the portion shown by the same shaded pattern as in FIG. 5A indicates the nozzle range 204 including the abnormal nozzle. The original images and print results shown on the left and right sides of the figure are illustrated by drawing straight lines (horizontal lines) at positions that serve as boundaries of the nozzle range 204. As for the print result, the difference in density caused by the influence of the abnormal nozzle is shown by the difference in the shaded pattern.

As can be understood from the above description and the like, when an abnormal nozzle is present in the inkjet head 102, the amount of ink ejected from the abnormal nozzle is deviated, so that the size of the ink dots formed on the medium is deviated. Will occur. In this case, the deviation of the dot size can be considered as, for example, a deviation exceeding a predetermined allowable range with respect to the design size. Further, as a result, as shown as a print result in the drawing, a deviation in density occurs in a portion where ink is ejected from the nozzle range 204 including the abnormal nozzle in any of the main scanning operations.

On the other hand, in this example, as shown in FIG. 5C, for example, the influence of the abnormal nozzle on the print result is reduced by correcting the image data showing the original image. FIG. 5C is a diagram showing an example of density correction performed in this example, and shows a printing result (printing result) when a printing operation is performed by performing a process for reducing the influence of an abnormal nozzle. An example is shown. As shown by differently shaded patterns in the figure, in this example, the density of a part of the image to be printed (original image) is corrected. Further, more specifically, in this case, the influence of the abnormal nozzle is reduced to the correction unit region corresponding to the portion where the ink is ejected from the nozzle range 204 including the abnormal nozzle in any of the main scanning operations. , Correct the density. In this case, it can be considered that the density is corrected so that the influence of the abnormal nozzle is reduced, for example, the density is corrected so as to compensate for the deviation of the discharge characteristics in the abnormal nozzle. More specifically, for example, it is conceivable to correct the density so as to reduce (thin) the density in the correction unit region corresponding to the abnormal nozzle in which the discharge amount is large. On the contrary, it is conceivable to correct the density so as to increase (dense) the density in the correction unit region corresponding to the abnormal nozzle in which the discharge amount is small.

Further, in this case, the RIP processing unit 14 generates RIP generation data in which the influence of the abnormal nozzle is reduced based on the corrected image data. Further, the control unit 110 (see FIG. 1) in the print execution unit 12 ejects ink to the inkjet head 102 in each main scanning operation based on such RIP generation data. Then, in this case, as shown in the figure as the print result when there is correction, it becomes possible to print at a more uniform density.

More specifically, in this case, the RIP processing unit 14 generates RIP generation data based on the corrected image data, so that the number of dots in the correction unit region corresponding to the abnormal nozzle in which the discharge amount is large is increased. RIP generation data is generated such that the number of dots (dot density) in the correction unit region corresponding to the abnormal nozzle having a small (dot density) and a small discharge amount is large. With this configuration, for example, the influence of the abnormal nozzle can be appropriately reduced. Further, when the inkjet head 102 in which the volume of the ink droplets to be ejected is variable in a plurality of steps is used, the RIP processing unit 14 generates RIP generation data based on the corrected image data, for example, the ejection amount. RIP generation data is generated such that the dot size in the correction unit region corresponding to the abnormal nozzle with a large amount is small and the dot size in the correction unit area corresponding to the abnormal nozzle with a small discharge amount is large.

Subsequently, the operation of the density correction performed in this example will be described more specifically. FIG. 6 is a flowchart showing an example of an operation of generating RIP generated data in the RIP processing unit 14 (see FIG. 1). The flowchart shown in FIG. 6 can be considered, for example, a flowchart showing the operation of density correction from a different viewpoint from the flowchart shown in FIG.

In the operation of generating the RIP generation data, the RIP processing unit 14 first inputs, for example, an image to be printed (printed image) (S202), and converts the resolution according to the print resolution (S204). .. The input of the printed image and the conversion of the resolution can be performed in the same manner or the same as the operation performed by the known RIP process, for example. More specifically, in step S202, the print image is input by, for example, inputting image data indicating a color image into the RIP processing unit 14. Further, in the resolution conversion performed in step S204, the RIP processing unit 14 converts the resolution according to the resolution of the print executed by the print execution unit 12 (see FIG. 1).

Further, following the operation in step S204, the RIP processing unit 14 performs a plate separation process (S206). The plate separation process can be considered, for example, a process of separating a color image indicating an image to be printed according to the color of the ink used for printing. The plate separation process can also be performed in the same manner or the same as the operation performed in the known RIP process, for example. Further, in the plate separation process, the RIP processing unit 14 generates a grayscale image corresponding to the ink of each color used for printing based on the image (color image) whose resolution is converted in step S204. Further, in this example, the data indicating the grayscale image generated by the plate separation process (hereinafter referred to as the plate separation data) is an example of gradation image data which is image data indicating an image to be printed with a predetermined gradation. Is. The separation data can be considered, for example, gradation image data corresponding to each inkjet head in the print execution unit 12. The gradation image data corresponding to each inkjet head can be considered as, for example, grayscale image data generated corresponding to the color of the ink ejected from each inkjet head.

Further, following the operation in step S206, the RIP processing unit 14 divides the separation data into data for each pass according to the operation in the multipath method performed by the print execution unit 12 (S208). Further, more specifically, in this example, the RIP processing unit 14 performs the same or the same operation as the operation performed by the known RIP processing on the plate separation data corresponding to the color of the ink of each color generated in step S206. Divide into data for each path. In this case, the separation data after division (hereinafter referred to as path division data) can also be considered as an example of gradation image data. Further, the correction process performed on the path-divided data described below can be considered as an example of the process performed on the gradation image data.

The operation in step S208 can be considered as an example of an operation of dividing the image data for each path on the RIP software, for example. Further, as described above, in this example, the operation of setting the correction unit area shown in step S106 of FIG. 4 is performed by dividing the image data for each path. More specifically, in step S208, the RIP processing unit 14 sets a correction unit area for the data after path division. Further, in the operation of setting the correction unit area, the RIP processing unit 14 can identify which nozzle range 204 (see FIG. 3) includes the nozzle for ejecting ink to each correction unit area. The range 204 is associated with the correction unit area.

Further, following the operation in step S208, the RIP processing unit 14 corrects (changes) at least a part of the density of the data after path division based on the abnormal nozzle information (S210). In this case, the RIP processing unit 14 corrects the density so that the influence of the abnormal nozzle is reduced, for example, as described above with reference to FIG. Further, in this example, regarding the density correction performed on the data after the path division, for example, the correction operation performed on the gradation image data generated in advance corresponding to each inkjet head in the print execution unit 12. Can be considered as an example of. Further, in this example, the operation of step S206 is an example of the operation of the density correction processing. The density correction process can be considered, for example, a process of correcting the density of at least a part of the gradation image data based on the abnormal nozzle information. Further, depending on how the density correction process is defined, for example, an operation that combines at least a part of the operations performed in step S208 and an operation performed in step S210 can be considered as an example of the operation of the density correction process.

Regarding the operation performed in step S210, regarding the correction of the density of at least a part of the data after the path division, for example, after the path division so that the density of at least a part of the image indicated by the data after the path division changes. It can be thought of as correcting the data. Further, the density in the data after the path division can be considered as, for example, the color density in the image indicated by the data after the path division. The color density can be considered, for example, the color density specified by the pixel values of the pixels constituting the image. Further, in this example, the density in the data after path division can be considered as, for example, the density indicated by the pixel value in the grayscale image.

Further, in this example, the RIP processing unit 14 changes the density of the image indicated by the data after path division by changing the density of the correction unit region corresponding to the nozzle range 204 including the abnormal nozzles based on the abnormal nozzle information. Correct the density so that the effect of the abnormal nozzle is reduced. In this case, the RIP processing unit 14 selects, for example, a correction unit region corresponding to the nozzle range 204 including the abnormal nozzle for the data after path division, and the influence of the abnormal nozzle is small on the density of the correction unit region. Make corrections so that Further, in this case, the RIP processing unit 14 corrects the density of the path-divided data corresponding to each inkjet head based on the abnormal nozzle information indicating the abnormal nozzle in each inkjet head. With this configuration, for example, the density can be appropriately corrected to reduce the influence of the abnormal nozzle. Further, as a result, for example, the influence of the abnormal nozzle can be appropriately reduced.

Further, as described above, in this example, the influence of the abnormal nozzle is small on the correction unit region corresponding to the portion where the ink is ejected from the nozzle range 204 including the abnormal nozzle in each main scanning operation. The density is corrected so as to be. Such a correction operation can be considered as an example of an operation of correcting the density in units of a region corresponding to a predetermined nozzle range 204, for example. Further, such a correction operation can be considered as, for example, an operation of correcting the density with respect to the correction unit region for ejecting ink from the nozzle range 204 including the abnormal nozzle in each main scanning operation.

Further, following the operation in step S210, the RIP processing unit 14 performs the quantization processing on the corrected path-divided data in the same manner as or in the same manner as the operation performed in the known RIP processing, and obtains the RIP generated data. Generate (S212). The quantization process can be considered, for example, a process of generating RIP-generated data by performing a process of reducing the number of gradations with respect to the corrected path-divided data. Further, the quantization process can be considered, for example, an operation of reducing the gradation to the number of gradations that can be expressed by the capacity of the droplets (ink droplets) that can be ejected by the inkjet head. Further, the quantization process can be considered as, for example, a halftone process performed according to the configuration of the inkjet head. More specifically, when an inkjet head that ejects only one type of capacitance is used, the quantization process can be considered as, for example, a process of binarizing an image. When an inkjet head that ejects droplets having a plurality of types of capacities is used, the quantization process can be considered as, for example, a process of reducing the number of gradations of an image to the number of gradations according to the type of droplet capacity. .. Further, the quantization process in the case of using an inkjet head that ejects droplets having a plurality of types of capacities can be considered as, for example, a process of binarizing an image for each droplet volume. Further, the concentration after the correction in step S210 can be considered as, for example, an example of an adjustment value for reducing the influence of the abnormal nozzle.

Further, in this example, the RIP processing unit 14 performs the quantization processing on the data after the path division whose density has been corrected as described above, so that the influence of the abnormal nozzle is more than that in the case where the correction is not performed. Generate smaller RIP generation data. Then, the RIP processing unit 14 supplies the RIP generation data generated in this manner to the print execution unit 12, and causes the print execution unit 12 to perform the printing operation. With this configuration, the result (adjustment value) of the density correction as described above can be appropriately reflected in the printing operation. Further, as a result, for example, the influence of the abnormal nozzle can be appropriately reduced.

Subsequently, supplementary explanations and the like regarding each configuration described above will be given. As described above, in this example, the processing for reducing the influence of the abnormal nozzle is performed in units of the correction unit area corresponding to the nozzle range 204, which is the range including the plurality of nozzles 202. Further, as such a process, for example, the density is corrected so that the influence of the abnormal nozzle is reduced on the correction unit area set in the data after the path division. In this case, the density may be further corrected for the correction unit region corresponding to the nozzle range 204 other than the nozzle range 204 including the abnormal nozzle. More specifically, for example, in addition to the correction unit area corresponding to the nozzle range 204 including the abnormal nozzle, the density can be corrected for the correction unit area adjacent to this correction unit area in the sub-scanning direction. Conceivable.

Further, in the above, the operation and the like when the range including a plurality of nozzles is used as the nozzle range 204 has been mainly described. However, in a modified example of the method of correcting the density, it is conceivable to use a range including only one nozzle as the nozzle range 204. In this case, the density can be corrected, for example, in units of nozzles. Further, when considering the use of a wider nozzle range 204, it is possible to consider, for example, using a range corresponding to the pass width in the multipath method as the nozzle range 204. In this case, it can be considered that the density correction is performed in units of, for example, the path width.

Further, in the above, the operation of correcting the density after dividing the separation data into the data after the path division for each path has been described with reference to FIG. 6 and the like. However, in the modified example of the method of correcting the density, it is conceivable to perform the correction of the density on the separation data before division. Further, in this case, it is conceivable that the division into the data for each path is performed after the quantization processing is performed, for example. Also in this case, the density can be appropriately corrected to suppress the influence of the abnormal nozzle by performing the quantization process or dividing into the data for each path based on the corrected plate separation data. Further, in a further modification of the method of correcting the density, for example, it is conceivable to correct the density based on the abnormal nozzle information on the color image before the plate separation processing. In this case, for example, the data indicating the color image to be corrected can be considered as an example of the gradation image data.

Further, as described above, in this example, the density is corrected based on the abnormal nozzle information obtained by printing a predetermined test pattern (adjustment pattern). On the other hand, for example, when the position of the nozzle where the ejection characteristics are likely to deviate is determined by the configuration and operation of the inkjet head 102, etc., the abnormal nozzle information created by a method other than printing the adjustment pattern should be used. Etc. are also conceivable. In this case, for example, it is conceivable to correct the density based on the abnormal nozzle information created based on the duty in the image data indicating the image to be printed. In this case, for example, it is conceivable to use the information indicating the duty as the abnormal nozzle information. Further, for example, it is conceivable to measure the temperature of each part of the inkjet head and correct the density according to the temperature unevenness occurring in the inkjet head. In this case, for example, the information indicating the temperature unevenness can be considered as an example of the abnormal nozzle information.

Further, as described above, in this example, the printing system 10 includes a printing execution unit 12 and a RIP processing unit 14. In this case, as the print execution unit 12 and the RIP processing unit 14, it is conceivable to use individual devices as described above with reference to, for example, FIG. Further, in this case, it can be considered that the printing system 10 is composed of, for example, a plurality of devices. On the other hand, in a modified example of the configuration of the printing system 10, for example, it is conceivable to configure the printing system 10 with one device. In this case, for example, it is conceivable to configure the printing system 10 with one inkjet printer having the functions of the print execution unit 12 and the RIP processing unit 14. Further, in this case, the inkjet printer constituting the printing system 10 can be considered as, for example, a printing device corresponding to the printing execution unit 12 having the function of the RIP processing unit 14 in the control unit 110. Further, in a further modification of the configuration of the printing system 10, it is conceivable that the printing system 10 is configured by three or more devices. In this case, for example, it is conceivable to configure the printing system 10 by a plurality of printing execution units 12 and RIP processing units 14. Further, for example, it is conceivable that the printing system 10 is configured by three or more devices by further using other devices having a part of the functions of the print execution unit 12 or the RIP processing unit 14.

Further, in the above description, the configuration of the printing system 10 mainly when ink is ejected to the medium has been described. In this case, the print execution unit 12 in the print system 10 can be thought of as an inkjet printer or the like that draws a two-dimensional image on the medium. Further, in the modified example of the printing system 10, it is conceivable to use a 3D printer (3D printing device) or the like for modeling a three-dimensional modeled object as the printing execution unit 12. Even in such a case, for example, the influence of the abnormal nozzle can be appropriately reduced by correcting the density in the same manner as or in the same manner as described above. Further, the density correction described above may be applied to other than the configuration of ejecting a liquid (ink or the like) using an inkjet head. In this case, for example, as a method for suppressing light emission unevenness in a display device such as an organic EL, it is conceivable to perform the same processing as the density correction described above.

The present invention can be suitably used for, for example, a printing system.

10 ... printing system, 12 ... printing execution unit, 14 ... RIP processing unit, 50 ... medium, 102 ... inkjet head, 104 ... platen, 106 ... main scanning drive unit , 108 ... Sub-scanning drive unit, 110 ... Control unit, 202 ... Nozzle, 204 ... Nozzle range, 302 ... Dot

Claims (8)

It is a printing system that prints by inkjet method.
An inkjet head that ejects ink from multiple nozzles,
An ejection data generation unit that generates ejection designation data indicating an ejection position for ejecting ink to the inkjet head, and an ejection data generator.
A discharge control unit for ejecting ink to each of the plurality of nozzles in the inkjet head based on the ejection designation data is provided.
The ejection data generation unit refers to gradation image data, which is image data indicating an image to be printed with a predetermined gradation.
Density correction processing that corrects the density of at least a part of the gradation image data based on the abnormal nozzle information indicating the abnormal nozzle that is the nozzle whose amount of ink to be ejected is out of the predetermined normal range.
A printing system characterized in that a quantization process for generating the ejection designation data is performed by performing a process of reducing the number of gradations on the gradation image data after the density correction process is performed. In the density correction process, the ejection data generation unit changes the density of the image indicated by the gradation image data at a position corresponding to the position where ink is ejected by the abnormal nozzle based on the abnormal nozzle information. The printing system according to claim 1, wherein the density is corrected so that the influence of the abnormal nozzle is reduced. A plurality of the inkjet heads that eject inks of different colors are provided.
In the density correction process, the ejection data generator has the density of the gradation image data corresponding to each of the inkjet heads based on the abnormal nozzle information indicating the abnormal nozzle in each of the inkjet heads. The printing system according to claim 1 or 2, wherein the correction is performed. The gradation image data corresponding to each of the inkjet heads is data indicating a grayscale image generated by performing plate separation processing on a color image indicating an image to be printed according to the color of the ink used for printing. The printing system according to claim 3, wherein the printing system is provided. A main scanning drive unit that causes the inkjet head to perform a main scanning operation of ejecting ink while moving relative to a medium to be printed in a preset main scanning direction.
Further provided with a sub-scanning drive unit that causes the inkjet head to perform a sub-scanning operation that moves relative to the medium in a sub-scanning direction orthogonal to the main scanning direction.
In the inkjet head, the plurality of nozzles are arranged so as to be displaced from each other in the sub-scanning direction.
The abnormal nozzle information indicates the influence of the abnormal nozzle for each nozzle range that includes a plurality of the nozzles that are continuously arranged in the sub-scanning direction.
The printing system according to any one of claims 1 to 4, wherein in the density correction process, the ejection data generation unit corrects the density in units of a region corresponding to the nozzle range. The ejection control unit controls the operations of the main scanning drive unit and the sub-scanning drive unit, so that the path is the number of times of the main scanning operation in which the inkjet head passes through a position facing the same position in the medium. The ink is ejected to the inkjet head by a multi-pass method in which the number is a plurality of times.
The claim is characterized in that, in the density correction process, the ejection data generation unit corrects the density in a region for ejecting ink from the nozzle range including the abnormal nozzle in each of the main scanning operations. 5. The printing system according to 5. The printing system according to any one of claims 1 to 6, wherein the abnormal nozzle information is information obtained by printing a predetermined test pattern using the plurality of nozzles in the inkjet head. It is a printing method that prints by the inkjet method.
Generates ejection designation data indicating the ejection position for ejecting ink to the inkjet head that ejects ink from multiple nozzles.
Ink is ejected to each of the plurality of nozzles in the inkjet head based on the ejection designation data.
In the operation of generating the ejection designation data, with respect to the gradation image data which is the image data indicating the image to be printed with a predetermined gradation.
Density correction processing that corrects the density of at least a part of the gradation image data based on the abnormal nozzle information indicating the abnormal nozzle that is the nozzle whose amount of ink to be ejected is out of the predetermined normal range.
A printing method characterized by performing a quantization process for generating the ejection designation data by performing a process of reducing the number of gradations on the gradation image data after performing the density correction process.

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