JP7451038B2 - Printing system and printing method - Google Patents

Description

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

Conventionally, inkjet printers, which are printing devices that perform printing using inkjet heads, have been widely used. When printing using an inkjet head, in order to print with high quality, it is required to reduce the influence of variations in the characteristics of nozzles in the inkjet head.

In contrast, conventional methods for reducing the effects of individual differences in inkjet heads include methods for adjusting the voltage of the drive signal waveform (head drive waveform) used to drive the inkjet head, and methods for adjusting the voltage at which the ink is heated (the ink There are known methods of adjusting and stabilizing the heating temperature (heating temperature). When such a method is used, for example, by reducing the influence of individual differences among inkjet heads on the diameter of formed ink dots, unevenness in print density can be reduced. Conventionally, regarding the method of controlling inkjet heads, recovery processing is also known in which another nozzle is used in place of an abnormal nozzle (defective nozzle) whose ejection characteristics are out of the normal range (for example, see Patent Document 1). ).

JP2014-172260A

When trying to reduce the effects of individual differences in inkjet heads by stabilizing the voltage of the head drive waveform and the ink heating temperature, a configuration for adjusting the voltage and heating temperature is required, which reduces the cost of the device. is likely to increase. Furthermore, depending on the model of the printing device, it may be difficult to use these configurations.

In addition, when printing using another nozzle instead of the abnormal nozzle, for example, the timing at which the ink lands on the printing target medium (media) may differ from normal times, resulting in recovery processing being performed on the print result. The areas where this has been done may become more noticeable. In particular, when recovery processing is performed on a plurality of nozzles located close to each other, there is a risk that the print quality will be greatly affected. Therefore, it has conventionally 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 extensive research on methods for reducing the effects of abnormal nozzles on inkjet heads. The inventors also considered reducing the influence of abnormal nozzles by correcting the image used to generate ejection designation data indicating the ejection position at which ink is to be ejected from the inkjet head. Furthermore, through actual experiments, we confirmed that this method can reduce the effects of abnormal nozzles.

In addition, the inventor of the present application further conducted extensive research and discovered the features necessary to obtain such effects, leading to the present invention. In order to solve the above problems, the present invention provides a printing system that performs printing using an inkjet method, which includes an inkjet head that ejects ink from a plurality of nozzles, and an ejection head that indicates the ejection position where the ink is ejected from the inkjet head. an ejection data generation section that generates specification data; and an ejection control section that causes each of the plurality of nozzles in the inkjet head to eject ink based on the ejection specification data; With respect to gradation image data, which is image data that indicates an image at a predetermined gradation, the gradation is determined based on abnormal nozzle information indicating an abnormal nozzle, which is the nozzle whose ejected amount of ink is outside a predetermined normal range. The ejection designation data is corrected by performing a density correction process that corrects the density of at least a part of the image data, and a process that reduces the number of gradations for the gradation image data after the density correction process. Performs quantization processing to generate.

With this configuration, for example, by correcting the gradation image data based on the abnormal nozzle information in the density correction process, it is possible to correct the gradation image data so as to reduce the influence of the abnormal nozzle. . Furthermore, in the quantization process, by generating ejection designation data based on the corrected gradation image data, it is possible to generate ejection designation data that is less affected by abnormal nozzles. Therefore, with this configuration, for example, the influence of abnormal nozzles on the inkjet head can be appropriately reduced.

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

Further, in this configuration, the ejection designation data can be considered to be, for example, data indicating the position at which ink should be ejected among a plurality of ejection positions set according to the printing resolution. Furthermore, correction of the density of at least a part of the gradation image data may include, for example, correcting the gradation image data so that the density of at least a part of the image represented by the gradation image data changes. I can think. Further, the density in the gradation image data can be considered, for example, as the color density in the image represented by the gradation image data. Further, the color density can be considered as, for example, the color density specified by the pixel values of pixels forming an image. In addition, in the density correction process, the ejection data generation unit may, for example, change 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. Then, the density is corrected so that the influence of the abnormal nozzle is reduced. With this configuration, for example, the influence of an abnormal nozzle can be appropriately reduced.

Furthermore, in this configuration, the printing system includes, for example, a plurality of inkjet heads that eject ink of different colors. In this case, in the density correction process, for example, it is possible to correct gradation image data that is generated in advance for each inkjet head. More specifically, in this case, in the density correction process, the ejection data generation unit, for example, based on the abnormal nozzle information indicating the abnormal nozzle in each inkjet head, for the gradation image data corresponding to each inkjet head, Perform density correction. With this configuration, it is possible to appropriately reduce the influence of abnormal nozzles on each inkjet head.

Further, in this case, as the gradation image data corresponding to each inkjet head, it is conceivable to use, for example, data of a grayscale image generated corresponding to the color of ink ejected from that inkjet head. More specifically, the gradation image data corresponding to each inkjet head includes, for example, grayscale image data generated by performing color separation processing on a color image indicating the image to be printed according to the color of the ink used for printing. It is conceivable to use data indicating a scale image. With this configuration, for example, in the density correction process, it is possible to appropriately correct the density in order 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 pixel values in a grayscale image.

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

In addition, in the inkjet head, the plurality of nozzles are aligned with their positions shifted from each other in the sub-scanning direction, for example. In this case, the abnormal nozzle information indicates, for example, the influence of the abnormal nozzle for each nozzle range, which is a range that includes a plurality of consecutive nozzles in the sub-scanning direction. Furthermore, in the density correction process, the ejection data generation section corrects the density in units of areas corresponding to the nozzle range, for example. With this configuration, for example, correction for suppressing the influence of an abnormal nozzle can be appropriately performed on the gradation image data. In this case, in the density correction process, the ejection data generation unit selects, for example, an area corresponding to the nozzle range including the abnormal nozzle in the gradation image data, and calculates the influence of the abnormal nozzle on the density of the area. Make corrections so that it becomes smaller. With this configuration, for example, the influence of an abnormal nozzle can be appropriately reduced.

In addition, when correcting gradation image data in units of areas corresponding to a predetermined nozzle range in this way, information indicating the position and characteristics of the abnormal nozzle in units of nozzle ranges is also used as abnormal nozzle information. It is possible to use it. With this configuration, for example, without necessarily identifying which nozzle is an abnormal nozzle, it is possible to simply identify the nozzle range that includes the abnormal nozzle and perform corrections to suppress the effects of the abnormal nozzle. Can be done properly. Moreover, thereby, for example, the influence of an abnormal nozzle can be easily and appropriately reduced. Further, as the nozzle range, for example, a range including only one nozzle may be used.

Furthermore, in this configuration, the ejection control section causes the inkjet head to eject ink in a multi-pass method by, for example, controlling the operations of the main scanning drive section and the sub-scanning drive section. In this case, the multi-pass method can be considered, for example, as 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 and opposite positions on the medium, is multiple times. In this case, in the density correction process, the ejection data generation section corrects the density of, for example, the area where ink is ejected from the nozzle range including the abnormal nozzle in each main scanning operation. With this configuration, for example, when performing multi-pass printing, the influence of abnormal nozzles can be appropriately reduced.

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

Further, as a configuration of the present invention, it is also possible to use a printing method or the like having characteristics similar to those described above. Also in this case, for example, the same effects as above can be obtained.

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

1 is a diagram illustrating an example of the configuration of a printing system 10 according to an embodiment of the present invention. FIG. 1A shows an example of the configuration of the printing system 10. As shown in FIG. FIG. 1B shows an example of the configuration of the print execution unit 12 in the printing system 10. It is a figure explaining the influence of an abnormal nozzle. FIG. 2A shows a simplified state of the inkjet head 102 in which an abnormal nozzle exists. FIG. 2B shows a simplified result of ejecting ink using the inkjet head 102 in which an abnormal nozzle exists. 3 is a diagram showing an example of a nozzle range 204. FIG. 12 is a flowchart illustrating an example of processing performed to suppress the influence of an abnormal nozzle. FIG. 7 is a diagram illustrating in more detail the effect of density correction performed in this example. FIG. 5A shows an example of a nozzle range 204 that includes abnormal nozzles. FIG. 5(b) shows an example of the influence of an abnormal nozzle. FIG. 5C shows an example of density correction performed in this example. 3 is a flowchart showing an example of an operation for generating RIP generation data in the RIP processing unit 14. FIG.

Embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 shows an example of the configuration of a printing system 10 according to an embodiment of the present invention. FIG. 1A shows an example of the configuration of the printing system 10. As shown in FIG. FIG. 1B shows an example of the configuration of the print execution unit 12 in the printing system 10. The printing system 10 of this example may have the same or similar features as known printing systems, except as described below.

In this example, the printing system 10 is a printing system that prints on a printing target medium 50 using an inkjet method, and includes a printing execution section 12 and a RIP processing section 14. The printing execution section 12 is a section that executes a printing operation of ejecting ink onto the medium 50. The print execution unit 12 can be considered, for example, as a part of the printing system 10 that functions as a printing device. Further, the print execution unit 12 can be considered as, for example, a main body part 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. A printing operation is executed on the medium 50. Further, the printing execution unit 12 includes a plurality of inkjet heads 102 , a platen 104 , a main scanning drive unit 106 , a sub-scanning drive unit 108 , and a control unit 110 .

Each of the plurality of inkjet heads 102 is an ejection head that ejects ink using 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 ink of a mutually different color. More specifically, each of the plurality of inkjet heads 102 ejects ink of each process color, which is a basic color in color printing, for example. As the process color inks, for example, cyan (C), magenta (M), yellow (Y), and black (K) inks may be used. Further, each inkjet head 102 has a nozzle row in which a plurality of nozzles are lined up 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 figure) set in advance in the printing execution unit 12. In this case, in each inkjet head 102, the plurality of nozzles are lined up in the nozzle row direction so that their positions in the sub-scanning direction are shifted from each other.

The platen 104 is a table-like member on which the medium 50 is placed, and holds the medium 50 in a state facing the plurality of inkjet heads 102 . The main scanning drive unit 106 is a drive unit that causes the 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 perpendicular to the sub-scanning direction (Y direction in the figure). During the main scanning operation, the main scanning drive unit 106, for example, controls each nozzle in each of the plurality of inkjet heads 102 to a discharge position that is set according to the printing resolution under the control of the control unit 110. Discharge ink. The sub-scanning drive unit 108 is a drive unit that causes the 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 feeding the medium 50 in the sub-scanning direction between main scanning operations.

The control unit 110 is a part that includes, for example, a CPU in the print execution unit 12, and controls the operation of each unit of the print execution unit 12. Further, as explained above, in this example, the main scanning drive unit 106 causes each nozzle in each of the plurality of inkjet heads 102 to eject ink under the control of the control unit 110. In this case, the control unit 110 can be considered to control 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, etc. to eject ink to the plurality of inkjet heads 102 in each main scanning operation. let Furthermore, in this example, the control unit 110 causes the plurality of inkjet heads 102 to eject ink in a multi-pass method by controlling the operations of the main scanning drive unit 106, the sub-scanning drive unit 108, and the like. In this case, the multi-pass method can be considered, for example, as a method in which the number of passes is multiple 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 positions opposite to the same position on the medium 50. Furthermore, 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 to be, 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 an inkjet head (range in the sub-scanning direction). Further, in this case, the pass 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 an ejection control unit, and causes each nozzle in each inkjet head 102 to eject ink based on RIP generated data. Further, thereby, the control unit 110 causes each nozzle in each inkjet head 102 to eject ink to an ejection position determined depending on the image to be printed, for example. With this configuration, for example, printing operations based on RIP generated data can be appropriately executed.

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

Further, in this example, the RIP processing section 14 is an example of an ejection data generation section. As the RIP processing unit 14, for example, a computer that executes software for RIP processing can be suitably used. Further, the RIP processing section 14 can be considered as, for example, a computer that controls the operation of the printing execution section 12. Further, as explained above, in this example, the plurality of inkjet heads 102 in the print execution section 12 eject ink onto the medium 50 by performing a main scanning operation. In this case, the RIP processing unit 14 generates, as RIP generation data, data indicating at least the ejection position at which ink is ejected 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 by further considering the ejection characteristics of each nozzle in each inkjet head 102. More specifically, if there is an abnormal nozzle in which the amount of ink ejected is outside a predetermined normal range in any of the inkjet heads 102 in the print execution unit 12, the RIP processing unit 14 determines whether the abnormal nozzle The RIP generated data is generated by performing processing to reduce the influence of. Further, in this case, as such processing, the RIP processing unit 14 performs density correction on image data indicating an image to be printed at a predetermined gradation based on abnormal nozzle information indicating an abnormal nozzle.

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

Next, processing for reducing the influence of abnormal nozzles will be explained in more detail. First, the influence of abnormal nozzles will be specifically explained. FIG. 2 is a diagram illustrating the influence of an abnormal nozzle. FIG. 2A shows a simplified state of the inkjet head 102 in which an abnormal nozzle exists. FIG. 2B shows a simplified result of ejecting ink using the inkjet head 102 in which an abnormal nozzle exists.

As explained above, in this example, the inkjet head 102 has a plurality of nozzles 202 lined up in the nozzle row direction parallel to the sub-scanning direction. Further, in FIG. 2A, abnormal nozzles are indicated by different hatching patterns, and the arrangement of a plurality of nozzles 202 in the inkjet head 102 is illustrated. More specifically, in FIG. 2A, the illustration is simplified by reducing the number of nozzles 202 in the inkjet head 102, and an example is shown in which some of the nozzles 202 are abnormal nozzles. There is. Further, in the illustrated case, 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 exists performs a main scanning operation, the arrangement of ink dots 302 formed by ink ejected during the main scanning operation is, for example, as shown in FIG. 2(b). This will reflect the characteristics of the abnormal nozzle. More specifically, in FIG. 2B, the dots 302 formed by the abnormal nozzle are illustrated with a different hatching pattern from the dots 302 formed by the normal nozzle 202. 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 nozzle are lined up, causing a deviation in color density. Furthermore, as a result, unevenness in print density may occur.

In contrast, in this example, as explained above, the influence of the abnormal nozzle is reduced by correcting the density of the image data using the abnormal nozzle information. In this case, the abnormal nozzle information includes, for example, printing a predetermined test pattern (hereinafter referred to as an adjustment pattern) using a plurality of nozzles 202 in each inkjet head 102 in the printing execution unit 12 (see FIG. 1). It is possible to use the information obtained by doing so. More specifically, in this case, for example, each inkjet head 102 draws an adjustment pattern as shown in FIG. It is possible to create abnormal nozzle information by detecting this. With this configuration, for example, the characteristics of an abnormal nozzle can be appropriately detected.

Further, in this example, the abnormal nozzle information can be considered as information indicating the position, characteristics, etc. of the abnormal nozzle, for example. In this case, the position of the abnormal nozzle can be considered, for example, as the position of the abnormal nozzle within the inkjet head 102. The position of the abnormal nozzle within the inkjet head 102 can be considered, for example, as the position of the abnormal nozzle within the nozzle row of the inkjet head 102. Further, in the abnormal nozzle information, as the characteristic of the abnormal nozzle, for example, information indicating the magnitude relationship or difference between the amount of ink ejected by the abnormal nozzle and a predetermined reference amount may be used.

Here, printing the adjustment pattern and acquiring abnormal nozzle information may be automatically performed between printing operations corresponding to a job (print job) for printing a desired printed material, for example. . In this case, for example, abnormal nozzle information may be generated by automatically printing and scanning adjustment patterns. Furthermore, such an operation can be considered as, for example, an operation that automatically corrects the density of image data.

Furthermore, in order to more precisely detect the influence of abnormal nozzles, it is conceivable to identify the nozzles 202 that ejected ink to each position of the adjustment pattern in units of one nozzle 202. In this case, it is conceivable that processing for reducing the influence of the abnormal nozzle may be performed for each nozzle 202. However, as explained above, in this example, the processing to reduce the effects of abnormal nozzles does not involve direct processing by specifying abnormal nozzles, but rather correction of the density of image data. By doing so, indirect processing is performed. In this case, if an attempt is made to perform correction processing on one nozzle 202 as a unit, the position where the processing has been performed may become more noticeable.

Therefore, in this example, as shown in FIG. 3, for example, the process for reducing the influence of abnormal nozzles is performed in units of nozzle ranges 204, which are ranges that include a plurality of nozzles 202 that are consecutively lined up 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, it is conceivable to use, for example, a range in which about 2 to 20 nozzles 202 are consecutively lined up. The number of nozzles 202 arranged in the nozzle range 204 is preferably about 2 to 10, more preferably about 2 to 5. Furthermore, in this case, information indicating the influence of the abnormal nozzle for each nozzle range 204 is used as the abnormal nozzle information. 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, without necessarily identifying which nozzle is an abnormal nozzle, by simply identifying the nozzle range 204 that includes the abnormal nozzle, correction can be performed to suppress the influence of the abnormal nozzle. Can be done properly. Moreover, thereby, for example, the influence of an abnormal nozzle can be easily and appropriately reduced. Furthermore, in this example, processing for reducing the influence of abnormal nozzles in units of nozzle range 204 may be considered, for example, as changing the density of the area corresponding to nozzle range 204 in the image data. be able to.

Next, the processing performed in this example to suppress the influence of abnormal nozzles will be explained in more detail. FIG. 4 is a flowchart illustrating an example of processing performed to suppress the influence of abnormal nozzles. As explained above, in this example, processing is performed to suppress the influence of abnormal nozzles using abnormal nozzle information obtained by printing a predetermined adjustment pattern. In this case, first, the printing execution unit 12 prints the adjustment pattern (S102). In this case, the printing execution section 12 prints the adjustment pattern in response to an instruction from the RIP processing section 14, for example. Further, in this example, the printing execution unit 12 prints the adjustment pattern by a single-pass operation rather than by a multi-pass method. The one-pass operation can be considered, for example, as a printing operation performed with one pass. The printing execution unit 12 also prints adjustment patterns so that the patterns drawn by the inkjet heads 102 for each color can be distinguished. Such an operation can be considered, for example, as an operation of causing one inkjet head 102 to draw one adjustment pattern.

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

Further, more specifically, reading the adjustment pattern may be performed using, for example, a camera installed in the print execution unit 12. Further, in this case, for example, it is possible 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. In this case, it is also conceivable that the adjustment pattern be read at the same time as the adjustment pattern is printed. Further, the adjustment pattern may be read using, for example, a camera, scanner, or the like prepared separately from the print execution unit 12.

Further, confirmation of the nozzle range to be corrected may be performed using software that associates the nozzle range 204 in the inkjet head 102 with each position of the adjustment pattern, for example. Further, as such software, for example, software for performing RIP processing in the RIP processing section 14 (RIP software) may be used. In this case, the operation in step S104 can be considered as, for example, an operation of reading the adjustment pattern with a camera, scanner, or the like and inputting the result to the RIP software.

Further, in this example, the image density is corrected based on the correction target nozzle range confirmed in step S104. More specifically, in this case, the RIP processing unit 14 sets a correction unit area for image data indicating an 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 a correction unit area for image data can be considered, for example, as an operation of dividing an image indicated by 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 in the inkjet head 102 and the correction unit area are associated with each other in consideration of the multi-pass operation. Regarding the correspondence between the nozzle range 204 in the inkjet head 102 and the correction unit area in consideration of the operation in the multi-pass method, for example, ink is applied to each correction unit area in each main scanning operation performed in the multi-pass method. This can be thought of as correlating the nozzle range 204 with the correction unit area so that it can be identified which nozzle range 204 includes the nozzle that ejects the nozzle. Further, in this case, for the nozzle that ejects ink to the correction unit area, for example, ink is ejected to the correction unit area in one of the main scanning operations for the number of passes in the multi-pass method. It can be thought of as a nozzle, etc. Furthermore, the operation of setting the correction unit area in this way can be performed, for example, during the operation of dividing image data (multi-pass print data) into each pass (each pass) on the RIP software. Conceivable.

Further, after performing the operation in step S106, density correction is performed on the image data so as to reduce the influence of the abnormal nozzle (S108). In this example, the operation of step S108 is performed in the RIP processing unit 14 during the operation of generating RIP generation data. Furthermore, in this case, the RIP processing unit 14 performs density correction on the correction unit area corresponding to the abnormal nozzle so that the influence of the abnormal nozzle is further reduced. The correction unit area corresponding to the abnormal nozzle can be considered, for example, as a correction unit area where ink is ejected by the abnormal nozzle in each main scanning operation. Further, in this case, the operation in 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 image data will be explained in more detail later.

Further, in this case, the RIP processing unit 14 generates RIP generation data based on the image data after performing density correction. Furthermore, the RIP processing section 14 reflects the density correction results in the control of the printing operation (printing control) performed by the printing execution section 12 (S110). According to this example, for example, processing for appropriately suppressing the influence of an abnormal nozzle can be appropriately performed. Furthermore, this allows the print execution unit 12 to appropriately prevent, for example, density unevenness from occurring, and to 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.

Furthermore, as can be understood from the above description and the like, in this example, the printing execution unit 12 does not use another nozzle in place of the abnormal nozzle, but also uses the abnormal nozzle to perform printing. In this case, for example, compared to the case where another nozzle is used in place of the abnormal nozzle, the influence of the abnormal nozzle can be reduced while suppressing the influence on printing quality. Therefore, according to this example, even if an abnormal nozzle exists 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 illustrating in more detail the effect of density correction performed in this example. FIG. 5A is a diagram showing an example of a nozzle range 204 including an abnormal nozzle, and the position of the nozzle range 204 including an abnormal nozzle is shown with a hatched 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. In this case, if the print execution unit 12 executes the printing operation without performing any processing to reduce the influence of the abnormal nozzle, for example, as shown in FIG. 5(b), the nozzle range 204 including the abnormal nozzle This results in a difference in density at certain positions. FIG. 5(b) is a diagram showing an example of the influence of an abnormal nozzle, and shows an example of a printing result (print result) when a printing operation is performed without performing processing to reduce the influence of an abnormal nozzle. show.

More specifically, in FIG. 5(b), printing is performed using a multi-pass method with three passes based on image data showing an image in which a predetermined range is filled with a constant density as shown as the original image. This figure shows an example of the operation when performing the following. In this case, the original image can be considered, for example, as an image to be printed without performing any processing to reduce the influence of the abnormal nozzle. Further, the inkjet heads 102 shown with numbers 1 to 5 in the center of the figure indicate the positions of the inkjet heads 102 in the sub-scanning direction for five consecutive main scanning operations. In the inkjet head 102 in the figure, the portion indicated by the same hatching pattern as in FIG. 5(a) indicates a nozzle range 204 including abnormal nozzles. Further, the original image and the print result shown on the left and right sides of the figure are illustrated by drawing straight lines (horizontal lines) at positions that are the boundaries of the nozzle range 204. Furthermore, regarding the print results, differences in density caused by the influence of abnormal nozzles are indicated by differences in hatching patterns.

As can be understood from the above explanation, when there is an abnormal nozzle in the inkjet head 102, a deviation occurs in the amount of ink ejected from the abnormal nozzle, resulting in a deviation in the size of the ink dots formed on the medium. will occur. In this case, the deviation in dot size can be considered to be, for example, a deviation that exceeds a predetermined allowable range for the designed size. Further, as a result, as shown in the print result in the figure, a density deviation occurs in a portion where ink is ejected from the nozzle range 204 including the abnormal nozzle in any one of the main scanning operations.

In contrast, 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 representing the original image. FIG. 5(c) is a diagram showing an example of the density correction performed in this example, and shows the printing result (print result) when the printing operation is performed after performing processing to reduce the influence of abnormal nozzles. Give an example. In this example, the density is corrected for a part of the image to be printed (original image), as shown with different hatching patterns in the drawings. More specifically, in this case, the influence of the abnormal nozzle is reduced on the correction unit area corresponding to the part where ink is ejected from the nozzle range 204 including the abnormal nozzle in any main scanning operation. , perform density correction. In this case, correcting the density so as to reduce the influence of the abnormal nozzle can be thought of as, for example, correcting the density so as to compensate for deviations in the ejection characteristics of the abnormal nozzle. More specifically, for example, it is conceivable to correct the density so as to reduce (thin) the density for a correction unit area corresponding to an abnormal nozzle with a large ejection amount. On the other hand, it is conceivable to perform density correction to increase (darker) the density for a correction unit area corresponding to an abnormal nozzle with a reduced ejection amount.

Furthermore, 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 causes the inkjet head 102 to eject ink in each main scanning operation based on such RIP generation data. In this case, as shown in the figure as a print result with correction, it becomes possible to print with a more uniform density.

More specifically, in this case, the RIP processing unit 14 generates RIP generation data based on the corrected image data, thereby determining the number of dots in the correction unit area corresponding to the abnormal nozzle with a large ejection amount. RIP generation data is generated such that the number of dots (density of dots) in a correction unit area corresponding to an abnormal nozzle whose ejection amount is decreased and the number of dots (density of dots) is increased. With this configuration, for example, the influence of an abnormal nozzle can be appropriately reduced. Furthermore, when using an inkjet head 102 that can vary the volume of ink droplets to be ejected in multiple stages, the RIP processing unit 14 generates RIP generation data based on the corrected image data, so that, for example, the ejection amount is RIP generation data is generated such that the dot size in a correction unit area corresponding to an abnormal nozzle with a large amount of discharge becomes small, and the dot size in a correction unit area corresponding to an abnormal nozzle with a small ejection amount becomes large.

Next, the density correction operation performed in this example will be explained in more detail. FIG. 6 is a flowchart showing an example of the operation of generating RIP generation data in the RIP processing unit 14 (see FIG. 1). The flowchart shown in FIG. 6 can be considered, for example, as a flowchart showing the density correction operation from a different perspective from the flowchart shown in FIG. 4.

In the operation of generating RIP generation data, the RIP processing unit 14 first inputs, for example, an image to be printed (print image) (S202), and converts the resolution in accordance with the printing resolution (S204). . Input of a print image and conversion of resolution can be performed in the same or similar manner to, for example, operations performed in known RIP processing. More specifically, the input of the print image in step S202 is performed by inputting image data representing a color image to the RIP processing unit 14, for example. Furthermore, in the resolution conversion performed in step S204, the RIP processing unit 14 performs resolution conversion in accordance with the resolution of printing executed by the print execution unit 12 (see FIG. 1).

Further, following the operation in step S204, the RIP processing unit 14 performs color separation processing (S206). The color separation process can be thought of as, for example, a process in which a color image representing an image to be printed is separated according to the color of ink used for printing. The color separation process can also be performed in the same or similar manner to, for example, the operations performed in the known RIP process. In addition, in the color separation process, the RIP processing unit 14 generates a grayscale image corresponding to each color of ink used for printing, based on the image (color image) whose resolution was converted in step S204. In addition, in this example, data indicating a grayscale image generated by separation processing (hereinafter referred to as separation data) is an example of gradation image data, which is image data indicating an image to be printed at a predetermined gradation. It is. The separation data can also be considered, for example, as gradation image data corresponding to each inkjet head in the printing execution unit 12. The gradation image data corresponding to each inkjet head can be considered, for example, as grayscale image data generated corresponding to the color of 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 in accordance with the multi-pass operation performed by the print execution unit 12 (S208). More specifically, in this example, the RIP processing unit 14 performs the same or similar operations as those performed in known RIP processing on the color separation data corresponding to each color of ink generated in step S206. Divide data into each pass. In this case, the separation data after division (hereinafter referred to as post-pass division data) can also be considered as an example of gradation image data. Further, the correction processing performed on the pass-divided data, which will be described below, can be considered as an example of the processing performed on gradation image data.

The operation in step S208 can be considered, for example, as an example of an operation in which image data is divided into passes on RIP software. Further, as explained above, in this example, the operation of setting the correction unit area shown in step S106 in FIG. 4 is performed by dividing the image data for each pass. More specifically, in step S208, the RIP processing unit 14 sets a correction unit area for the pass-divided data. In addition, in the operation of setting the correction unit area, the RIP processing unit 14 sets the nozzle range 204 (see FIG. 3) that includes the nozzles that eject ink to each correction unit area. The range 204 and the correction unit area are associated with each other.

Further, following the operation in step S208, the RIP processing unit 14 corrects (changes) the density of at least a portion of the pass-divided data 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, as described above with reference to FIG. 5, for example. Further, in this example, regarding the density correction performed on the data after pass division, for example, the correction operation performed on the gradation image data generated in advance corresponding to each inkjet head in the printing execution unit 12. This can be considered as an example of Furthermore, in this example, the operation in step S206 is an example of the operation of the density correction process. The density correction process can be considered, for example, as a process of correcting the density of at least a portion of gradation image data based on abnormal nozzle information. Furthermore, depending on how the density correction process is defined, for example, the combination of at least part of the operations performed in step S208 and the operation performed in step S210 may be considered as an example of the operation of the density correction process.

Regarding the operation performed in step S210, correction of the density of at least a part of the data after pass division is performed, for example, after the pass division so that the density of at least a part of the image indicated by the data after pass division changes. This can be thought of as correcting data. Further, the density in the pass-divided data can be considered, for example, as the color density in the image indicated by the pass-divided data. The color density can be considered, for example, as the color density specified by the pixel values of pixels forming an image. Further, in this example, the density in the pass-divided data can be considered as, for example, the density indicated by pixel values in a grayscale image.

Further, in this example, the RIP processing unit 14 changes the density of the image indicated by the post-pass division data in the correction unit area corresponding to the nozzle range 204 including the abnormal nozzle based on the abnormal nozzle information. The density is corrected to reduce the influence of the abnormal nozzle. In this case, the RIP processing unit 14 selects, for example, a correction unit area corresponding to the nozzle range 204 including the abnormal nozzle for the pass-divided data, and the density of the correction unit area is less affected by the abnormal nozzle. Make corrections so that Furthermore, in this case, the RIP processing unit 14 corrects the density of the pass-divided data corresponding to each inkjet head based on abnormal nozzle information indicating an abnormal nozzle in each inkjet head. With this configuration, for example, density correction can be appropriately performed to reduce the influence of an abnormal nozzle. Moreover, thereby, for example, the influence of an abnormal nozzle can be appropriately reduced.

Furthermore, as explained above, in this example, the influence of the abnormal nozzle is small on the correction unit area corresponding to the part where ink is ejected from the nozzle range 204 including the abnormal nozzle in each main scanning operation. Correct the density so that Such a correction operation can be considered as an example of an operation in which the density is corrected in units of areas corresponding to the predetermined nozzle range 204, for example. Further, such a correction operation can be considered as, for example, an operation of correcting the density for a correction unit area in which ink is ejected 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 a quantization process on the corrected pass-divided data in the same or similar manner to the operation performed in a known RIP process, and converts the RIP generated data into Generate (S212). The quantization process can be considered, for example, as a process of generating RIP generated data by performing a process of reducing the number of gradations on the corrected pass-divided data. Further, the quantization process can be considered as, for example, an operation of reducing the number of gradations to the number of gradations that can be expressed by the volume of droplets (ink droplets) that can be ejected from an inkjet head. Further, the quantization process can also be considered as, for example, a halftone process that is performed in accordance with the configuration of the inkjet head. More specifically, when using an inkjet head that ejects droplets of only one type of volume, the quantization process can be thought of as, for example, a process of binarizing an image. When using an inkjet head that ejects droplets of multiple types of capacities, quantization processing can be thought of as, for example, processing that reduces the number of gradations of an image to the number of gradations depending on the type of capacity of the droplets. . Further, the quantization process when using an inkjet head that ejects droplets of a plurality of different capacities can be considered as, for example, a process of binarizing an image for each droplet capacity. Further, the density after correction in step S210 can be considered as an example of an adjustment value for reducing the influence of an abnormal nozzle, for example.

Furthermore, in this example, the RIP processing unit 14 performs quantization processing on the pass-divided data whose density has been corrected as described above, thereby reducing the influence of abnormal nozzles more than when no correction is performed. Generate smaller RIP generation data. Then, the RIP processing section 14 supplies the RIP generation data generated in this manner to the printing execution section 12, and causes the printing execution section 12 to perform a printing operation. With this configuration, the result of the density correction (adjustment value) as described above can be appropriately reflected in the printing operation. Moreover, thereby, for example, the influence of an abnormal nozzle can be appropriately reduced.

Next, supplementary explanations regarding each of the configurations explained above will be given. As explained above, in this example, processing for reducing the influence of abnormal nozzles is performed in units of correction unit areas corresponding to the nozzle range 204, which is a range including a plurality of nozzles 202. Further, as such processing, for example, density correction is performed on the correction unit area set in the post-pass division data so that the influence of the abnormal nozzle is reduced. In this case, density correction may be further performed on correction unit areas corresponding to nozzle ranges 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, density correction may also be performed 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 a range including a plurality of nozzles is used as the nozzle range 204 has been mainly explained. However, in a modification of the density correction method, it is also possible to use a range that includes only one nozzle as the nozzle range 204. In this case, density correction can be considered to be performed in units of nozzles, for example. Furthermore, when considering the use of a wider nozzle range 204, it is also possible to consider using, for example, a range corresponding to the pass width in a multi-pass method as the nozzle range 204. In this case, density correction can be considered to be performed in units of pass width, for example.

Further, in the above, the operation of correcting the density after dividing the separation data into pass-divided data for each pass has been explained using FIG. 6 and the like. However, in a modified example of the density correction method, density correction may be performed on the separation data before division. Further, in this case, division into data for each pass may be performed, for example, after performing quantization processing. In this case as well, by performing quantization processing and dividing into data for each pass based on the corrected color separation data, it is possible to appropriately correct the density to suppress the influence of the abnormal nozzle. Further, in a further modification of the density correction method, for example, density correction may be performed on a color image before performing separation processing based on abnormal nozzle information. In this case, for example, data indicating a color image to be corrected can be considered as an example of gradation image data.

Furthermore, as explained above, in this example, the density is corrected based on abnormal nozzle information obtained by printing a predetermined test pattern (adjustment pattern). On the other hand, for example, when determining the position of a nozzle where deviations in ejection characteristics are likely to occur due to the configuration or operation of the inkjet head 102, abnormal nozzle information created by a method other than printing an adjustment pattern may be used. etc. can also be considered. In this case, for example, it may be possible to correct the density based on 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 information indicating duty as abnormal nozzle information. Further, for example, it is also possible to measure the temperature of each part of the inkjet head and correct the density depending on the temperature unevenness that occurs within the inkjet head. In this case, for example, information indicating temperature unevenness can be considered as an example of abnormal nozzle information.

Further, as explained above, in this example, the printing system 10 includes the print execution unit 12 and the RIP processing unit 14. In this case, as the print execution section 12 and the RIP processing section 14, it is conceivable to use separate devices as explained above using, for example, FIG. 1 and the like. Further, in this case, the printing system 10 can be considered to be composed of a plurality of devices, for example. On the other hand, in a modification of the configuration of the printing system 10, for example, the printing system 10 may be configured with one device. In this case, for example, the printing system 10 may be configured with one inkjet printer having the functions of the print execution section 12 and the RIP processing section 14. Further, in this case, the inkjet printer constituting the printing system 10 can be considered, for example, as a printing device corresponding to the print execution section 12 in which the control section 110 has the function of the RIP processing section 14. Further, in a further modification of the configuration of the printing system 10, it is conceivable that the printing system 10 is configured with three or more devices. In this case, for example, the printing system 10 may be configured by a plurality of print execution units 12 and RIP processing units 14. Furthermore, for example, it is also conceivable to configure the printing system 10 with three or more devices by further using another device having a part of the function of the print execution section 12 or the RIP processing section 14.

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

INDUSTRIAL APPLICATION This invention can be conveniently utilized for a printing system etc., for example.

DESCRIPTION OF SYMBOLS 10... Printing system, 12... Print 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)

A printing system that prints using an 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 at which ink is to be ejected to the inkjet head;
an ejection control unit that causes each of the plurality of nozzles in the inkjet head to eject ink based on the ejection designation data,
The ejection control unit ejects ink to the inkjet head while moving relative to the printing target medium in a preset main scanning direction, and the number of passes, which is the number of main scanning operations, is a plurality of times. Print using multi-pass method,
The ejection data generation unit generates gradation image data, which is image data indicating an image to be printed at a predetermined gradation,
a density correction process of correcting the density of at least a portion of the gradation image data based on abnormal nozzle information indicating an abnormal nozzle in which the amount of ink ejected is outside a predetermined normal range;
performing quantization processing to generate the ejection designation data by performing processing to reduce the number of gradations on the gradation image data after performing the density correction processing ;
In the density correction process,
The density is corrected by setting a range corresponding to the pass width in the multi-pass method as a correction unit area, which is a correction unit area, and the correction unit area is adjacent to the correction unit area including the abnormal nozzle. A printing system characterized in that it also performs density correction . 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 a position where ink is ejected by the abnormal nozzle based on the abnormal nozzle information. 2. The printing system according to claim 1, wherein the density is corrected so that the influence of the abnormal nozzle is reduced. comprising a plurality of the inkjet heads that eject ink of mutually different colors,
In the density correction process, the ejection data generation unit calculates the density of the gradation image data corresponding to each inkjet head based on the abnormal nozzle information indicating the abnormal nozzle in each inkjet head. 3. The printing system according to claim 1, wherein the printing system performs correction. The gradation image data corresponding to each of the inkjet heads is data representing a grayscale image generated by performing separation processing on a color image representing an image to be printed in accordance with the color of ink used for printing. The printing system according to claim 3, characterized in that: a main scanning drive unit that causes the inkjet head to perform the main scanning operation;
further comprising a sub-scanning drive unit that causes the inkjet head to perform a sub-scanning operation of moving relatively to the medium in a sub-scanning direction perpendicular to the main-scanning direction,
In the inkjet head, the plurality of nozzles are arranged with their positions shifted 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 consecutively arranged in the sub-scanning direction;
The nozzle range is an area corresponding to the correction unit area,
5. The printing system according to claim 1, wherein in the density correction process, the ejection data generation unit corrects the density in units of areas corresponding to the nozzle range. The ejection control unit causes the inkjet head to eject the ink in the multi-pass method by controlling operations of the main scanning drive unit and the sub-scanning drive unit,
In the density correction process, the ejection data generation unit performs the density correction on a region where ink is ejected from the nozzle range including the abnormal nozzle in each main scanning operation. 5. The printing system according to 5. 7. The printing system according to claim 1, wherein the abnormal nozzle information is information obtained by printing a predetermined test pattern using the plurality of nozzles in the inkjet head. A printing method that prints using an inkjet method,
Generate ejection specification data that indicates ejection positions at which ink is to be ejected from an inkjet head that ejects ink from multiple nozzles;
causing each of the plurality of nozzles in the inkjet head to eject ink based on the ejection designation data;
Printing is performed using a multi-pass method in which the inkjet head performs a plurality of passes, which is the number of main scanning operations in which ink is ejected while moving relative to a printing target medium in a preset main scanning direction. conduct,
In the operation of generating the ejection designation data, for gradation image data that is image data indicating an image to be printed at a predetermined gradation,
a density correction process of correcting the density of at least a portion of the gradation image data based on abnormal nozzle information indicating an abnormal nozzle in which the amount of ink ejected is out of a predetermined normal range;
performing quantization processing to generate the ejection designation data by performing processing to reduce the number of gradations on the gradation image data after performing the density correction processing ;
In the density correction process,
The density is corrected by setting a range corresponding to the pass width in the multi-pass method as a correction unit area as a correction unit area, and the correction unit area is adjacent to the correction unit area including the abnormal nozzle. A printing method characterized in that density correction is also carried out .

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