LIQUID DISCHARGE SYSTEM AND LIQUID DISCHARGE METHOD

Abstract

To secure efficiency of processing of making image abnormality generated by a discharge defective nozzle inconspicuous at a high level.SOLUTION: A liquid discharge system according to one aspect of the present invention includes a liquid discharge device for discharging a liquid on the basis of image data, and a processing device, wherein the processing device includes quantization means of quantizing the image data and transmission means of transmitting the image data quantized by the quantization means to the liquid discharge device; the liquid discharge device includes liquid discharge means that includes a plurality of nozzles and discharges the liquid from the plurality of nozzles, specification means for specifying a discharge defective nozzle out of the plurality of nozzles, and change means for changing the size of liquid droplets formed from the liquid discharged from the liquid discharge means on the basis of the quantized image data and a specification result by the specification means.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a liquid ejection system and a liquid ejection method. [Background technology]

[0002] Conventionally, in a liquid ejection device that ejects liquid from multiple nozzles onto a recording medium based on image data, a technique is known that makes image abnormalities caused by a nozzle with poor ejection characteristics less noticeable by controlling the ejection from nozzles surrounding the nozzle with the defective ejection.

[0003] As the above-mentioned technology, there is disclosed a technology in which after quantization processing, image abnormalities caused by ejection-defective nozzles are compensated for (for example, see Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology of Patent Document 1, the quantization process and the image abnormality compensation process are performed by the same processing device, so if the defective nozzle among the multiple nozzles changes, the quantization process must be repeated, reducing processing efficiency.

[0005] An object of the present invention is to ensure high efficiency in processing for making image abnormalities caused by ejection-failed nozzles less noticeable. [Means for solving the problem]

[0006] A liquid ejection system according to one aspect of the present invention is a liquid ejection system including a liquid ejection device that ejects liquid based on image data, and a processing device, wherein the processing device includes a quantization means for quantizing the image data, and a transmission means for transmitting the image data quantized by the quantization means to the liquid ejection device, and the liquid ejection device includes a plurality of nozzles, and includes liquid ejection means for ejecting the liquid from the plurality of nozzles, an identification means for identifying a nozzle having an ejection defect among the plurality of nozzles, and a change means for changing the size of droplets formed by the liquid ejected from the liquid ejection means, based on the quantized image data and the identification result by the identification means. In the image data, pixels corresponding to each of the plurality of nozzles are assigned in advance an allocation value corresponding to the size of the droplet, and the change means changes the size of the droplet when a sum obtained by adding a product of the allocation value assigned to the pixel corresponding to the discharge-failed nozzle and a predetermined distribution coefficient to the allocation value assigned to the pixel corresponding to the nozzle adjacent to the discharge-failed nozzle is greater than the allocation value. do. Effect of the Invention

[0007] According to the present invention, it is possible to ensure high efficiency in the process of making image abnormalities caused by ejection-failed nozzles less noticeable. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an example of the overall configuration of an image forming system according to an embodiment. [Diagram 2] 1 is a diagram illustrating an example of the overall configuration of an image forming apparatus according to an embodiment. [Diagram 3] 1 is a diagram illustrating an example of the configuration of an image forming unit of an image forming apparatus according to an embodiment. [Figure 4] 3 is a diagram illustrating an example of a nozzle row in a liquid ejection head. [Diagram 5] 2 is a diagram showing an example of the arrangement of an in-line sensor in an image forming apparatus according to an embodiment; [Figure 6] 2 is a diagram illustrating a hardware configuration of a control unit of the image forming apparatus according to the embodiment. [Figure 7] FIG. 2 is a diagram illustrating an example of a hardware configuration of a DFE according to an embodiment. [Figure 8] FIG. 2 is a diagram illustrating an example of a functional configuration of the image forming system according to the first embodiment. [Figure 9] FIG. 13 is a diagram showing an inspection image according to a comparative example. [Figure 10] FIG. 4 is a diagram showing an example of an inspection image according to the embodiment. [Figure 11] FIG. 4 is a diagram showing an example of a correspondence relationship between colors of an inspection image and a read image. [Figure 12] FIG. 4 is a flow diagram of an example of image forming processing by the image forming system. [Figure 13] FIG. 11 is a flow diagram of an example of a change process by the image forming system during image formation. [Figure 14] FIG. 11 is a detailed flow diagram of an example of a change process performed by the image forming system. [Figure 15] FIG. 11 is a diagram illustrating an example of a functional configuration of an image forming system according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same components are given the same reference numerals, and duplicated explanations will be omitted as appropriate. In the embodiments, the terms image formation, recording, printing, copying, and printing are all synonymous.

[0010] <Overall configuration example of image forming system 1> 1 is a diagram showing an example of the configuration of an image forming system 1. The image forming system 1 includes a DFE (Digital Front End) 102 and an image forming apparatus 103. These are connected to each other so as to be able to communicate with each other via the Internet or the like. The image forming system 1 is an example of a liquid ejection system. In addition, the image forming system 1 is further connected to a client PC (Personal Computer) 101 and a management server 104 so as to be able to communicate with each other.

[0011] The client PC 101 creates a print job for which a user wants to form an image, and transmits the print job to the DFE 102 or the management server 104. The client PC 101 is equipped with a display unit that is a liquid crystal display, and input devices such as a mouse and a keyboard.

[0012] The DFE 102 is an example of a processing device that receives a print job from the client PC 101 or the management server 104 and transmits image data generated based on the received print job to the image forming device 103 .

[0013] The image forming device 103 is an example of a liquid ejection device that forms an image on paper P, which is a recording medium serving as a sheet material, by ejecting ink, which is an example of a liquid, onto the recording medium based on image data received from the DFE 102.

[0014] The management server 104 manages print jobs received from the client PC 101. Furthermore, the management server 104 transmits print jobs to the DFE in response to a request from the DFE.

[0015] Note that a plurality of image forming apparatuses and a plurality of client PCs may be communicably connected to the image forming system 1.

[0016] <Example of configuration of image forming apparatus 103> The configuration of an image forming apparatus 103 according to an embodiment will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a diagram illustrating an example of the overall configuration of the image forming apparatus 103. Fig. 3 is a diagram illustrating an example of the configuration of an image forming unit 200 included in the image forming apparatus 103.

[0017] As shown in FIG. 2, the image forming apparatus 103 includes a paper feed section 100, an image forming section 200, a drying section 300, a paper discharge section 400, a control section 30, and an operation section .

[0018] In the image forming apparatus 103, ink for image formation is ejected and adhered by the image forming unit 200 onto the paper P fed from the paper feed unit 100, thereby forming an image on the paper P. Then, after the ink adhered onto the paper P is dried by the drying unit 300, the paper P is discharged by the paper discharge unit 400.

[0019] (Paper feed section) The paper feed section 100 includes a paper feed tray 110 on which a plurality of sheets P are stacked, a feed device 120 that separates and sends out the sheets P one by one from the paper feed tray 110, and a pair of registration rollers 130 that sends the sheets P to the image forming section 200. The feed device 120 can be any feed device, such as a device using rollers or a device using air suction. The paper P sent out from the paper feed tray 110 by the feed device 120 is conveyed along a conveying direction 20, and after the leading edge of the paper P reaches the pair of registration rollers 130, the pair of registration rollers 130 is driven at a predetermined timing to feed the paper P to the image forming section 200. In this embodiment, the paper feed section 100 is not limited in its configuration as long as it sends out the paper P to the image forming section 200.

[0020] (Image forming section) 2 and 3, the image forming unit 200 includes a receiving cylinder 201 that receives the paper P fed from the paper feeding unit 100, and a paper carrying drum 210 that carries and transports the paper P transported by the receiving cylinder 201 on its outer circumferential surface. The image forming unit 200 also includes a liquid ejection unit 220 that ejects ink toward the paper P carried on the paper carrying drum 210, a transfer cylinder 202 that delivers the paper P transported by the paper carrying drum 210 to the drying unit 300, and an in-line sensor 230.

[0021] The paper P transported from the paper supply unit 100 to the image forming unit 200 has its leading edge gripped by a paper gripper provided on the surface of the receiving cylinder 201, and is transported as the surface of the receiving cylinder 201 moves. The paper P transported by the receiving cylinder 201 is delivered to the paper carrying drum 210 at a position facing the paper carrying drum 210.

[0022] A paper gripper is provided on the surface of the paper carrying drum 210, and the leading edge of the paper P is gripped by the paper gripper. In addition, a plurality of suction holes are formed in a dispersed manner on the surface of the paper carrying drum 210, and a suction device 215 generates a suction air current in the direction toward the inside of the paper carrying drum 210 at each suction hole. The leading edge of the paper P transferred from the receiving cylinder 201 to the paper carrying drum 210 is gripped by the paper gripper, and the paper P is adsorbed to the surface of the paper carrying drum 210 by the suction air current, and is transported as the surface of the paper carrying drum 210 moves.

[0023] The liquid ejection unit 220 ejects ink of four colors, C (cyan), M (magenta), Y (yellow), and K (black), to form an image. In the following, cyan may be represented as C, magenta as M, yellow as Y, and black as K. The liquid ejection unit 220 includes liquid ejection heads 220C, 220M, 220Y, and 220K, each for a different ink color.

[0024] Each of the liquid ejection heads 220C, 220M, 220Y, and 220K is provided with a plurality of nozzles that eject ink across the entire width of the paper P so that an image can be formed across the entire width of the paper P in the width direction 10 of the paper P, which is approximately perpendicular to the transport direction 20. This configures the image forming apparatus 103 as a so-called line-type apparatus in which the liquid ejection section 220 is not moved. Note that each of the liquid ejection heads 220C, 220M, 220Y, and 220K may be provided in plurality along the width direction 10 so that an image can be formed across the entire width of the paper P.

[0025] The liquid ejection heads 220C, 220M, 220Y, and 220K are not limited in configuration and may be of any configuration as long as they eject ink. If necessary, a liquid ejection head that ejects special ink such as white, gold, or silver may be provided, or a liquid ejection head that ejects ink that does not form an image, such as a surface coating liquid, may be provided.

[0026] The liquid ejection heads 220C, 220M, 220Y, and 220K each have an ejection operation controlled by a drive signal corresponding to image data. When the paper P carried on the paper carrying drum 210 passes through an area facing the liquid ejection section 220, ink of each color is ejected from the liquid ejection heads 220C, 220M, 220Y, and 220K, and an image corresponding to the image data is formed on the paper P. In this embodiment, the image forming section 200 is not limited in configuration as long as it forms an image by depositing ink on the paper P.

[0027] An in-line sensor 230 is provided downstream of the liquid ejection unit 220 in the transport direction 20. The in-line sensor 230 reads an image formed on the paper P with ink ejected by the liquid ejection unit 220. Note that the transport direction 20 corresponds to the rotation direction of the paper carrying drum 210 in the image forming unit 200.

[0028] The in-line sensor 230 includes a plurality of reading pixels provided across the entire width of the paper P in the width direction 10. For example, the in-line sensor 230 includes an imaging element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), and the reading pixels are pixels of the imaging element that output an electrical signal according to the intensity of the received light.

[0029] In this embodiment, the inline sensor 230 has reading pixels that output electrical signals according to the light intensity of each of the received colors R (red), G (green), and B (blue), and outputs a color read image obtained by reading multiple patch images.

[0030] (Drying section) 2, the drying section 300 includes a heating mechanism 301 for drying the ink deposited on the paper P in the image forming section 200, and a transport mechanism 302 for transporting the paper P transported from the image forming section 200. The paper P transported from the image forming section 200 is received by the transport mechanism 302, then transported to pass through the heating mechanism 301, and delivered to the paper discharge section 400. When passing through the heating mechanism 301, the ink on the paper P is subjected to a heat treatment, which evaporates the liquid content in the ink, such as water, and the ink is fixed on the paper P, while curling of the paper P is suppressed.

[0031] (Paper ejection section) The paper discharge section 400 includes a paper discharge tray 410 on which a plurality of sheets of paper P are stacked. The sheets of paper P conveyed from the drying section 300 are sequentially stacked and held on the paper discharge tray 410. In this embodiment, the paper discharge section 400 is not limited in its configuration as long as it discharges the sheets of paper P.

[0032] (Control unit) The control unit 30 controls the overall operation of the image forming apparatus 103. The function of the control unit 30 will be described in detail separately. In FIG. 2, the control unit 30 is provided in the image forming unit 200, but the control unit 30 may be provided at any position inside or outside the image forming apparatus 103.

[0033] (Operation unit) Operation unit 40 includes a touch panel, a keyboard, and the like, and accepts operation input to image forming apparatus 103 by a user who operates image forming apparatus 103. In FIG. 2, operation unit 40 is provided in paper feed unit 100, but operation unit 40 may be provided at any position inside or outside image forming apparatus 103.

[0034] (Other functional parts) The image forming apparatus 103 includes a paper feed unit 100, an image forming unit 200, a drying unit 300, and a paper discharge unit 400, but other functional units may be added as appropriate. For example, a pre-processing unit that performs pre-processing of the image formation may be added between the paper feed unit 100 and the image forming unit 200, and a post-processing unit that performs post-processing of the image formation may be added between the drying unit 300 and the paper discharge unit 400.

[0035] An example of a pre-treatment section is one that performs a treatment liquid application process in which a treatment liquid that reacts with the ink to suppress bleeding is applied to the paper P, but there are no particular limitations on the content of the pre-treatment.

[0036] Examples of post-processing sections include a paper inversion and transport processing section, a binding processing section, a correction mechanism, and a cooling mechanism. The paper inversion and transport processing section inverts the paper P on which an image has been formed in the image forming section 200 and sends it back to the image forming section 200 to form images on both sides of the paper P. The binding processing section performs a process of binding multiple sheets of paper P on which images have been formed. The forcing mechanism corrects deformation of the paper P, and the cooling mechanism cools the paper P. However, there are no particular limitations on the content of the post-processing.

[0037] (Example of the configuration of nozzle rows in a liquid ejection head) 4 is a diagram illustrating nozzle rows in a liquid ejection head 220K provided in the image forming apparatus 103. The liquid ejection head 220K has four nozzle rows L1, L2, L3, and L4. Each of the four nozzle rows L1, L2, L3, and L4 has a plurality of nozzles N arranged along the width direction 10. In other words, the liquid ejection section 220 ejects ink onto the paper P transported along the transport direction 20, and the plurality of nozzles N are arranged side by side along the width direction 10 that is approximately perpendicular to the transport direction 20.

[0038] In the liquid ejection head 220K, the multiple nozzles N are arranged in a staggered pattern. Here, staggered pattern refers to a state in which, for example, a nozzle N included in a nozzle row L3 adjacent to the nozzle row L1 in the transport direction 20 is arranged between two nozzles N adjacent to each other in the width direction 10 in the nozzle row L1.

[0039] Ink is ejected from each of the multiple nozzles N. The ejected ink lands on the paper P to form dots on the paper P. In this embodiment, the dots formed on the paper P by the ink ejected from the nozzles N of the nozzle rows L2 and L4 are formed at positions on the paper P adjacent in the width direction 10 to the dots formed on the paper P by the ink ejected from the nozzles N of the nozzle row L1.

[0040] If the distance between two adjacent nozzles in the nozzle row is d, then by displacing the two liquid ejection heads 220K by d / 2 along the transport direction 20, it is possible to double the image formation resolution of the image forming apparatus 103 compared to the case where one liquid ejection head 220K is provided. Note that, although the nozzle row of the liquid ejection head 220K is illustrated in Fig. 4, the nozzle rows of the liquid ejection heads 220C, 220M and 220Y are also configured in the same manner as the liquid ejection head 220K.

[0041] (Example of arrangement of in-line sensor 230) 5 is a diagram illustrating an example of the arrangement of the inline sensor 230 provided in the image forming apparatus 103. The inline sensor 230 includes a first inline sensor 231 and a second inline sensor 232. The first inline sensor 231 is provided upstream of the second inline sensor 232 in the transport direction 20. The first inline sensor 231 and the second inline sensor 232 are provided at positions shifted from each other along the width direction 10 so as to be able to read the entire width of the paper P in the width direction 10. An overlapping region 233 represents a region in the width direction 10 where the reading ranges of the first inline sensor 231 and the second inline sensor 232 overlap each other.

[0042] If it is possible to read the entire width of the paper P in the width direction 10, the number of in-line sensors included in the in-line sensor 230 is not limited to two and may be any number. Also, in the present embodiment, the first in-line sensor 231 and the second in-line sensor 232 have the same configuration and function, but the configurations and functions of the first in-line sensor 231 and the second in-line sensor 232 do not necessarily have to be the same as long as the paper P can be read with equivalent quality.

[0043] <Configuration example of the control unit 30> (Hardware configuration) FIG. 6 is a block diagram showing an example of the hardware configuration of the control unit 30 provided in the image forming apparatus 103. The control unit 30 includes a CPU (Central Processing Unit) 301, a ROM (Read Only Memory) 302, a RAM (Random Access Memory) 303, an HDD (Hard Disk Drive) / SSD (Solid State Drive) 304, and an I / F (Interface) 305. These are electrically connected to each other via a system bus 306, and are also connected to each of the liquid ejection unit 220, the in-line sensor 230, and the operation unit 40 so as to be able to transmit and receive data and signals via the system bus 306.

[0044] The CPU 301 uses the RAM 303 as a work area and executes the programs stored in the ROM 302. The HDD / SSD 304 is used as a storage unit and stores preset setting values. The information stored in the HDD / SSD 204 may be read by the CPU 201 and used during program execution. The I / F 305 is an interface that enables the image forming apparatus 103 and a client PC (Personal Computer) 101 or the like to communicate with each other via the Internet or the like.

[0045] <Configuration example of the DFE 102> 7 is a block diagram illustrating an example of a hardware configuration of the DFE 102. The DFE 102 includes a central processing unit (CPU) 201, a read only memory (ROM) 202, a random access memory (RAM) 203, a hard disk (HDD) / solid state drive (SSD) 204, and an interface (I / F) 205.

[0046] Of these, the CPU 201 uses the RAM 203 as a working area and executes programs stored in the ROM 202 to control the overall operation of the DFE 102 .

[0047] The HDD / SSD 204 is used as a storage unit and stores preset setting values. The information stored in the HDD / SSD 204 may be read by the CPU 201 and used when executing a program.

[0048] The I / F 205 is an interface that enables the DFE 102 to communicate with the client PC 101, the image forming apparatus 103, and the management server 104 via the Internet or the like.

[0049] [First embodiment] (Example of functional configuration of image forming system 1) FIG. 8 is a block diagram showing an example of a functional configuration of the image forming system 1 according to the first embodiment.

[0050] The DFE 102 includes a RIP (Raster Image Processor) processing unit 211, a quantization processing unit 212, and a transmission unit 213. The DFE 102 realizes the functions of the RIP processing unit 211 and the quantization processing unit 212 by the CPU 201 executing a program loaded from the ROM 202 to the RAM 203, etc. The DFE 102 also realizes the function of the transmission unit 213 by the CPU 201 executing a program loaded from the ROM 202 to the RAM 203 and controlling the I / F 205, etc.

[0051] The control unit 30 of the image forming apparatus 103 includes a specification unit 311 , a reading control unit 312 , a storage unit 313 , a receiving unit 314 , a change unit 315 , and a discharge control unit 316 .

[0052] The control unit 30 realizes the functions of an identification unit 311, a reading control unit 312, a change unit 315, and an ejection control unit 316 by, for example, having the CPU 301 execute a program loaded from the ROM 302 to the RAM 303. The control unit 30 also realizes the function of a receiving unit 314 by having the CPU 301 execute a program loaded from the ROM 302 to the RAM 303 and controls the I / F 305, and realizes the function of a storage unit 313 by controlling the HDD / SSD 304.

[0053] FIG. 8 illustrates the main functional configurations of the DFE 102 and the control unit 30, but the DFE 102 and the control unit 30 may each have a functional configuration other than the functional configuration illustrated in FIG.

[0054] The RIP processor 211 outputs image data including 8-bit (256-value) pixels for each of C, M, Y, and K colors generated based on a print job received from the client PC 101 or management server 104 to a quantization processor 212 .

[0055] The quantization processing unit 212 is an example of a quantization means that quantizes the image data received from the RIP processing unit 211. The quantization processing unit 212 generates 1-bit (binary) data by performing a quantization process on the image data. Examples of the quantization processing method used by the quantization processing unit 212 include pseudo halftoning such as a dither method or an error diffusion method, and processing methods such as screen processing. Screen processing is a process that generates color gradations based on the number and density of color points or color lines.

[0056] The transmission unit 213 is an example of a transmission unit that transmits the image data quantized by the quantization processing unit 212 to the image forming apparatus 103 .

[0057] In the control unit 30, the identification unit 311 is an example of an identification means for identifying defective discharge noise among the multiple nozzles included in the liquid ejection unit 220 based on the image read by the in-line sensor 230 input via the reading control unit 312. A defective discharge nozzle refers to a nozzle in which a defective discharge occurs. The defective discharge includes non-ejection, in which ink is not ejected from the nozzle, and deflected ejection, in which ink is ejected from the nozzle in a direction different from the desired direction. The identification unit 311 outputs identification information indicating the defective discharge noise to the storage unit 313 to store it.

[0058] The change unit 315 is an example of a change means that changes the size of droplets formed by ink ejected from the liquid ejection unit 220, based on the quantized image data received via the receiving unit 314 and the identification result by the identification unit 311. Types of droplet sizes include, for example, small droplets, which are small droplets, large droplets, which are larger than small droplets, medium droplets, which are droplets between small droplets and large droplets, and no droplets, which are not ejected.

[0059] When ejection defects occur, image abnormalities occur in the image formed on the paper P. Image abnormalities are streaky or dotted areas in the image formed on the paper P where no ink has been applied.

[0060] The modification unit 315 modifies the quantized image data so as to increase the size of droplets formed by ink ejected from normal nozzles that are positioned around the ejection-failed nozzles in the liquid ejection unit 220 and are capable of ejecting ink normally. By increasing the size of the droplets, part of the ink ejected from the normal nozzles covers an image abnormality region, such as a region where no ink has been applied, in the image formed on the paper P. As a result, the area of ​​the image abnormality region becomes smaller, and the image abnormality becomes less noticeable.

[0061] The identifying unit 311 can identify the defective discharge nozzle based on the read image read by the in-line sensor 230 while the image forming device 103 is forming an image on the paper P, and can rewrite and update the identification information of the defective discharge noise stored in the storage unit 313. The changing unit 315 can change the size of the droplets based on the updated identification information of the defective discharge noise and the image data received from the quantization processing unit 212.

[0062] <Example of inspection image of a nozzle with ejection problems> 9 and 10 are diagrams showing an example of an inspection image formed on paper P and read by in-line sensor 230 in order to identify ejection-fault nozzles by identification unit 311. Fig. 9 shows an inspection image 70X according to a comparative example, and Fig. 10 shows an inspection image 70 according to this embodiment.

[0063] As shown in Figure 9, inspection image 70X includes a black linear image 70XK (solid line pattern), a cyan linear image 70XC (dashed line pattern), a magenta linear image 70XM (dotted line pattern), and a yellow linear image 70XY (dotted line pattern).

[0064] A linear image is not limited to an image of a straight line that extends in a straight line without interruption, and as long as the image is linear overall, it can be an image that is partially curved or interrupted.

[0065] The linear images 70XK, 70XC, 70XM, and 70XY each extend along the conveying direction 20 and are arranged along the width direction 10. All of these are images of the same pattern, and only the color of the image is different. The linear images 70XK, 70XC, 70XM, and 70XY are each arranged at different positions in the conveying direction 20. Different positions in the conveying direction 20 means that the positions of the linear images 70XK, 70XC, 70XM, and 70XY in the conveying direction 20 do not overlap.

[0066] 10, the inspection image 70 according to this embodiment includes a black linear image 70K (solid line pattern) and a linear image 70CMY composed of linear images of three colors, cyan, magenta, and yellow. The linear images 70K and 70CMY each extend along the conveying direction 20 and are arranged along the width direction 10.

[0067] The linear image 70CMY is composed of three linear images of cyan, magenta, and yellow. The linear images of cyan, magenta, and yellow are all images of the same pattern, and only the colors of the images are different.

[0068] The three linear images of cyan, magenta, and yellow are arranged at approximately the same position in the transport direction 20. Approximately the same position in the transport direction 20 means that the three linear images of cyan, magenta, and yellow in the linear image 70CMY extend in the transport direction 20 from approximately the same position in the transport direction 20 as the start point, and end the stretching at approximately the same position in the transport direction 20 as the end point.

[0069] The three color linear images in linear image 70CMY are arranged at approximately the same position in conveying direction 20, so that inspection image 70 has a shorter length in conveying direction 20 and is smaller than inspection image 70X.

[0070] 10 shows an example in which the linear images of three colors, cyan, magenta, and yellow, in the linear image 70CMY are arranged at approximately the same position in the transport direction 20, but they do not necessarily have to be at approximately the same position, and it is sufficient that their positions overlap in the transport direction 20. Furthermore, it is sufficient that the positions of the linear images of at least two colors of ink among the multiple colors of ink overlap in the transport direction 20.

[0071] The three color linear images in linear image 70CMY are arranged with their positions overlapping in conveying direction 20, so that inspection image 70 is smaller in length in conveying direction 20 than inspection image 70X by the amount of overlap.

[0072] Although an example has been shown in which the linear images of the three colors of cyan, magenta, and yellow in the linear image 70CMY are all images of the same pattern, they do not necessarily have to be images of the same pattern. For example, the length or thickness of the lines in the linear images may be different. Even in this case, by overlapping the positions of the linear images of at least two colors of ink in the transport direction 20, the length in the transport direction 20 is shortened by the overlap amount compared to when there is no overlap.

[0073] <Example of process for identifying nozzles with ejection defects by the identifying unit 311> The process of identifying a nozzle with ejection problems by the identifying unit 311 will be described with reference to Fig. 11. Fig. 11 is a diagram showing an example of the correspondence between an inspection image 70 on a sheet of paper P and the colors in the data read by the in-line sensor 230. A linear image 70CMY is a part of the inspection image formed on the sheet of paper with the colors C, M, and Y.

[0074] The read data 80 corresponds to a portion of the image of the linear image 70CMY read by the in-line sensor 230. The read data 80 shows the luminance distribution of a cross section of the linear image 70CMY along the width direction 10. The horizontal axis of the graph represents the position in the width direction 10, and the vertical axis represents the luminance. The luminance is pixel luminance, and is expressed in units of gradation.

[0075] In-line sensor 230 acquires read data of red (R), green (G), and blue (B). In read data 80, the solid line graph indicates the R read data, the dashed line graph indicates the G read data, and the dashed dot line graph indicates the B read data.

[0076] If the linear images of each color overlap in the transport direction 20, it may be difficult to extract linear images for each color in the overlapping areas, making it difficult to identify nozzles with ejection problems based on image processing of the linear images.

[0077] In this embodiment, by utilizing the fact that G is the complementary color of M, a linear image of M is extracted by extracting only the image of the G component in the read data 80. Similarly, by utilizing the fact that R is the complementary color of C and B is the complementary color of Y, a linear image of M is extracted from the read data of G, and a linear image of Y is extracted from the read data of B. The identification unit 311 identifies the nozzle with the defective ejection by detecting loss or bending of patterns in the extracted linear images of C, M, and Y through image processing.

[0078] The identifying unit 311 performs image processing on the color component data of R, G, and B, which correspond to the complementary colors of C, M, and Y, in the portion where the linear images of each color overlap in the transport direction 20. This makes it possible to identify the defective ejection nozzles in each of the liquid ejection heads 220C, 220M, and 220Y.

[0079] Since linear images can be easily extracted from the K linear images in Figures 9 and 10 and the C, M and Y linear images in parts where their positions do not overlap in the transport direction 20, the identification unit 311 can easily identify nozzles with poor ejection performance by image processing.

[0080] <Processing example by image forming system 1> 12 to 14, the processing by the image forming system 1 will be described. Fig. 12 is a flowchart showing an example of the image forming processing by the image forming system 1. The image forming system 1 starts image formation in response to either reception of a print job from the client PC 101 by the image forming apparatus 103, or operation input by a user using the operation unit 40 to start image formation.

[0081] First, in step S 121 , the image forming system 1 causes the quantization processing unit 212 to quantize the image data generated by the RIP processing unit 211 .

[0082] Next, in step S122, the image forming system 1 causes the change unit 315 to refer to the storage unit 313 and acquire identification information of the ejection-failed nozzle in the liquid ejection unit 220.

[0083] Next, in step S123, the image forming system 1 causes the modification unit 315 to modify the quantized image data so as to increase the size of droplets from normal nozzles located around the ejection-failure nozzle.

[0084] Next, in step S 124 , the image forming system 1 causes the image forming apparatus 103 to form an image based on the image data changed by the change unit 315 .

[0085] In this way, the image forming system 1 can form an image on the paper P while performing change processing to make the ejection-failed nozzle less noticeable.

[0086] 13 is a flowchart showing an example of a change process performed by the change unit 315 while the image forming apparatus 103 is forming an image. The image forming system 1 starts image formation in response to either the reception of a print job by the image forming apparatus 103 from the client PC 101 or an operation input for starting image formation by a user using the operation unit 40.

[0087] Note that the processing of step S131 in FIG. 13 is the same as the processing of step S121 in FIG. 12, and the processing of steps S133 to S135 in FIG. 13 is the same as the processing of steps S122 to S124 in FIG. 12. Therefore, duplicate explanations will be omitted here and the differences will be mainly described.

[0088] In step S132, the image forming system 1 causes the identification unit 311 to identify the defective discharge nozzle based on the read image read by the in-line sensor 230 while the image forming apparatus 103 is forming an image on the paper P. The identification unit 311 rewrites and updates the identification information of the defective discharge noise stored in the storage unit 313 to the identification information of the identified defective discharge nozzle.

[0089] In step S136, the image forming system 1 determines whether or not to end the image formation. For example, when the image formation is completed for the number of sheets P designated by the user, the image forming system 1 determines to end the image formation.

[0090] In step S136, if it is determined that the process is to be ended (step S136, Yes), the image forming system 1 ends the process. On the other hand, if it is determined that the process is not to be ended (step S136, No), the image forming system 1 performs the process from step S132 onwards again.

[0091] In this way, the image forming system 1 can perform change processing to make the ejection-failed nozzle less noticeable while the image forming apparatus 103 is forming an image.

[0092] Fig. 14 is a flowchart showing an example of the modification process by the modification unit 315 in more detail. In the process of Fig. 14, it is assumed that a streak-like image abnormality occurs in pixels from the upstream side to the downstream side in the transport direction corresponding to the defective nozzle in the image data. Also, in the image data, an allocation value corresponding to the size of the droplets ejected from the nozzle is assigned in advance to the pixels corresponding to each of the multiple nozzles. The modification unit 315 adds the product of the allocation value assigned to the pixel corresponding to the defective nozzle and a predetermined distribution coefficient to the allocation value assigned to the pixel corresponding to the nozzle adjacent to the defective nozzle along the width direction 10, and modifies the size of the droplets when the sum is greater than the allocation value.

[0093] The image forming system 1 starts the process of FIG. 14 at the timing of step S123 in FIG. 12 or at the timing of step S134 in FIG.

[0094] First, in step S141, the modification unit 315 obtains an allocation value a for a pixel corresponding to a discharge-failed nozzle in the image data by multiplying the allocation values ​​assigned to the adjacent pixels on both sides in the width direction 10 by a predetermined drop coefficient. The drop coefficient is a coefficient for optimizing the effect of the modification process by the modification unit 315 in accordance with differences in drop configuration. The drop coefficient can be set for each drop size and color. For example, the drop coefficient is set to 1.0 for no drops, small drops, and large drops, and to 2.0 for medium drops.

[0095] Next, in step S142, the change unit 315 obtains an integrated value b by multiplying the allocation value of the pixel corresponding to the discharge-failed nozzle in the image data by a predetermined distribution coefficient. The distribution coefficient is a coefficient that converts the droplets that were scheduled to be discharged by the discharge-failed nozzle into an error value for distribution. For example, the distribution coefficient is 0.7. The distribution coefficient can be set for each color.

[0096] Next, in step S143, the change unit 315 adds the allocation value a and the integrated value b to obtain an added value c.

[0097] Next, in step 144, the change unit 315 determines whether the added value c is equal to or greater than a predetermined large drop threshold value. The large drop threshold value is, for example, 3.0.

[0098] In step S144, if it is determined that the added value c is equal to or greater than the large drop threshold value (step S144, Yes), in step S145, the modification unit 315 assigns an allocation value corresponding to large drops to both pixels adjacent in the width direction 10 to the pixel corresponding to the discharge-failed nozzle in the image data. After that, the modification unit 315 proceeds to the process of step S150.

[0099] On the other hand, if it is determined in step S144 that the additional value c is not equal to or greater than the large drop threshold (step S144, No), in step S146, the change unit 315 determines whether the additional value c is equal to or greater than a predetermined medium drop threshold. The medium drop threshold is, for example, 2.0.

[0100] In step S146, if it is determined that the added value c is equal to or greater than the medium droplet threshold value (step S146, Yes), in step S147, the modification unit 315 assigns allocation values ​​corresponding to medium droplets to the pixels on both sides adjacent to the pixel corresponding to the discharge-failed nozzle in the image data along the width direction 10. Thereafter, the modification unit 315 proceeds to the process of step S150.

[0101] On the other hand, if it is determined in step S146 that the additional value c is not equal to or greater than the medium droplet threshold (step S146, No), in step S148, the change unit 315 determines whether the additional value c is equal to or greater than a predetermined small droplet threshold. The small droplet threshold is, for example, 1.0.

[0102] In step S148, if it is determined that the added value c is equal to or greater than the small droplet threshold value (step S148, Yes), in step S149, the modification unit 315 assigns allocation values ​​corresponding to small droplets to the pixels on both sides adjacent to the pixel corresponding to the discharge-failed nozzle in the image data in the width direction 10. Thereafter, the modification unit 315 proceeds to the process of step S150.

[0103] On the other hand, in step S148, if it is determined that the additional value c is not equal to or greater than the small droplet threshold value (step S148, No), the change unit 315 moves the process to step S150.

[0104] Next, in step S150, the change unit 315 subtracts a predetermined carryover value from the additional value c.

[0105] Next, in step S151, the modification unit 315 adds the difference between the additional value c and the carryover value to the allocation values ​​of the pixels on both sides of the ejection-failed nozzle in the width direction 10 on the downstream side in the transport direction 20 in the image data.

[0106] Next, in step S152, the modification unit 315 determines whether modification processing has been completed for all pixels corresponding to ejection-failure nozzles along the transport direction 20.

[0107] If it is determined in step S152 that the process has ended (Yes in step S152), the modification unit 315 ends the process. On the other hand, if it is determined that the process has not ended (No in step S152), the modification unit 315 shifts the positions of the pixels on both sides of the ejection-failed nozzle by one pixel downstream along the transport direction 20, and then performs the processes from step S141 onwards again. In other words, the modification unit 315 sequentially performs the process of changing the size of the droplets on the pixels located downstream along the transport direction 20 in the image data.

[0108] In this way, the modification unit 315 can perform the modification process. The modification unit 315 distributes and disperses the droplets that were to be discharged from the discharge-faulty nozzle to adjacent pixels on both sides in the width direction 10, or adjacent pixels on both sides in the width direction 10 downstream in the transport direction 20. In accordance with this distribution, the droplets discharged from the nozzles around the discharge-faulty nozzle become larger. As a result, the area on the paper P where ink is not applied due to the discharge-faulty nozzle is covered by the droplets discharged from the nozzles around the discharge-faulty nozzle, making the area where ink is not applied less noticeable.

[0109] <Functions and Effects of Image Forming System 1> Next, the effects of the image forming system 1 will be described.

[0110] There is a known technique for identifying a nozzle that is faulty in ejecting ink and making image abnormalities such as streaks caused by the faulty nozzle less noticeable by increasing the size of droplets ejected from normal nozzles around the faulty nozzle.

[0111] However, in the conventional technology, when the number of nozzles with poor ejection performance changes or increases during image formation by the image forming apparatus, the quantization process needs to be performed again, which increases the processing time. As a result, there is a concern that the processing efficiency will decrease. In addition, there is a method of applying different halftone masks to pixels surrounding a pixel corresponding to a nozzle with poor ejection performance in the image data, but with this method, there is a concern that artifacts such as local graininess differences will be visible at the boundary between different halftones.

[0112] The image forming system 1 (liquid ejection system) according to this embodiment includes an image forming device 103 (liquid ejection device) that ejects ink (liquid) based on image data, and a DFE2 (processing device). The DFE2 includes a quantization processing unit 212 (quantization means) that quantizes image data, and a transmission unit 213 (transmission means) that transmits the image data quantized by the quantization processing unit 212 to the image forming device 103. The image forming device 103 includes a liquid ejection unit 220 (liquid ejection means) that includes a plurality of nozzles N and ejects ink from the plurality of nozzles N, an identification unit 311 (identification means) that identifies nozzles that are defective in ejection from the plurality of nozzles, and a change unit 315 (change means) that changes the size of droplets formed by the ink ejected from the liquid ejection unit 220 based on the quantized image data and the identification result by the identification unit 311.

[0113] By increasing the size of the liquid droplets ejected from the normal nozzles located around the ejection-failed nozzle in the liquid ejection unit 220 through the change process, some of the ink ejected from the normal nozzles covers the image abnormality area in the image formed on the paper P. As a result, the area of ​​the image abnormality area becomes smaller, and the image forming system 1 can make the image abnormality less noticeable.

[0114] Furthermore, the image forming system 1 includes the quantization processing unit 212 in the DFE 102, and the change unit 315 in the control unit 30 in the image forming apparatus 103. For example, if the number of ejection-failed nozzles changes or increases during image formation by the image forming apparatus 103, the image forming system 1 does not need to perform the quantization process again, which takes a long time to process. This allows the image forming system 1 to suppress a decrease in efficiency of the process that makes image abnormalities caused by ejection-failed nozzles less noticeable, and ensure high processing efficiency. Furthermore, the change unit 315 executes the process without using a different halftone mask, so that it is possible to avoid the occurrence of artifacts and ensure high quality of the image formed on the paper P (recording medium).

[0115] Furthermore, in this embodiment, the liquid ejection unit 220 ejects ink onto the paper P transported along the transport direction 20, and the multiple nozzles N are arranged side by side along the width direction 10 intersecting with the transport direction 20. With this configuration, in a configuration including a so-called line-type image forming apparatus 103 in which the liquid ejection unit 220 does not move, the image forming system 1 can suppress a decrease in efficiency of a process that makes image abnormalities caused by ejection-failed nozzles less noticeable, and ensure high processing efficiency.

[0116] Furthermore, in this embodiment, the image forming apparatus 103 forms an image on the paper P by ejecting ink, and the identification unit 311 identifies the ejection-defective nozzle while the image forming apparatus 103 is forming the image on the paper P. This allows the image forming system 1 to execute the process by the change unit 315 without stopping the image formation during image formation, thereby ensuring high efficiency of image formation.

[0117] In this embodiment, in the image data, pixels corresponding to each of the multiple nozzles N are assigned in advance an allocation value corresponding to the size of the droplet. The change unit 315 changes the size of the droplet when the sum of the allocation value assigned to the pixel corresponding to the discharge-faulty nozzle and a predetermined distribution coefficient and the allocation value assigned to the pixel corresponding to the nozzle adjacent to the discharge-faulty nozzle is greater than the allocation value. Through this process, the image forming system 1 can diffuse the influence of the discharge-faulty nozzle to the nozzles surrounding the discharge-abnormal nozzle, thereby suppressing deterioration in the quality of the image formed on the paper P.

[0118] Furthermore, in this embodiment, the image forming system 1 ejects ink onto the paper P transported in the transport direction, and the change unit 315 executes the process of changing the size of the droplets sequentially for pixels located downstream in the transport direction 20 in the image data. Through this process, the image forming system 1 can diffuse the effects of the ejection-defective nozzle to pixels downstream in the transport direction 20 in the image data, and further suppress deterioration in the quality of the image formed on the paper P.

[0119] Note that the image forming apparatus 103 may have a quantization processing function if it does not execute quantization processing.

[0120] [Second embodiment] An image forming system 1a according to the second embodiment will be described. The same components as those in the first embodiment are given the same reference numerals, and duplicated descriptions will be omitted as appropriate.

[0121] 15 is a block diagram showing an example of a functional configuration of the image forming system 1a. In this embodiment, the image forming system 1a includes an image processing device 105 and an image forming device 103a. The image processing device 105, the image forming device 103a, and the DFE 102 are connected to each other so as to be able to communicate with each other via the Internet or the like.

[0122] The image processing device 105 includes a transmission / reception unit 510 and a change unit 315a. The control unit 30a included in the image forming device 103 includes a transmission / reception unit 317. The DFE2 is an example of a first processing device including a quantization unit. The image processing device 105 is an example of a second processing device including a change unit.

[0123] The transmitting / receiving unit 317 transmits the identification information of the ejection-faulty nozzle identified by the identifying unit 311 to the image processing device 105. The changing unit 315a performs processing to change the size of droplets based on the identification information of the ejection-faulty nozzle and the quantized image data acquired via the transmitting / receiving unit 501. The changing unit 315a transmits the changed image data to the image forming device 103a via the transmitting / receiving unit 501. The ejection control unit 316 causes the liquid ejection unit 220 to eject ink based on the image data changed by the changing unit 315a acquired via the transmitting / receiving unit 317.

[0124] In this way, even in a configuration in which the image processing device 105 includes the change unit 315a, the image forming system 1a does not need to repeat the quantization process, which takes a long time, when the number of ejection-failed nozzles changes or increases while the image forming device 103a is forming an image. As a result, the image forming system 1a can suppress a decrease in efficiency of the process that makes image abnormalities caused by ejection-failed nozzles less noticeable, and can ensure high processing efficiency. Other effects are the same as those of the first embodiment.

[0125] Although examples of embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims.

[0126] The liquid ejection device according to the embodiment is not limited to an image forming device that includes a liquid ejection unit that ejects ink toward a surface of a recording medium to be dried and visualizes meaningful images such as characters and figures using the ejected ink. For example, the liquid ejection device according to the embodiment also includes a device that forms a pattern that does not have any meaning in itself.

[0127] The recording medium is not limited in terms of material, and may be any material to which a liquid can be attached even temporarily, such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, etc. For example, the recording medium may be used for film products, cloth products such as clothing, building materials such as wallpaper and flooring, leather products, etc.

[0128] The "liquid" is not particularly limited as long as it has a viscosity and surface tension that allows it to be discharged from the head, but it is preferable that the viscosity is 30 mPa·s or less at room temperature and pressure, or by heating or cooling. More specifically, it is a solution, suspension, emulsion, etc. that contains a solvent such as water or an organic solvent, a colorant such as a dye or pigment, a functionalizing material such as a polymerizable compound, a resin, or a surfactant, a biocompatible material such as DNA, amino acids, proteins, or calcium, an edible material such as a natural dye, etc., and these can be used for applications such as inkjet inks and surface treatment liquids.

[0129] The term "image forming apparatus" includes serial type apparatuses in which the liquid ejection section is moved, line type apparatuses in which the liquid ejection section is not moved, and the like.

[0130] The liquid ejection unit is a functional component that ejects and sprays liquid from an ejection hole (nozzle). As an energy generation source for ejecting liquid, ejection energy generation means such as a piezoelectric actuator (a laminated piezoelectric element and a thin-film piezoelectric element), a thermal actuator using an electrothermal conversion element such as a heating resistor, and an electrostatic actuator consisting of a vibration plate and a counter electrode can be used, but the ejection energy generation means used is not limited.

[0131] The embodiment also includes a liquid ejection method. For example, the liquid ejection method is a liquid ejection method by a liquid ejection system including a liquid ejection device that ejects liquid based on image data and a processing device, in which the processing device quantizes the image data by a quantization means, transmits the image data quantized by the quantization means to the liquid ejection device by a transmission means, the liquid ejection device ejects the liquid from the multiple nozzles by a liquid ejection means including multiple nozzles, identifies a nozzle that is defective in ejection among the multiple nozzles by an identification means, and changes the size of the droplets formed by the liquid ejected by the liquid ejection means based on the quantized image data and the identification result by the identification means by a change means. Such a liquid ejection method can obtain the same effect as the image forming system described above.

[0132] The ordinal numbers, quantities, and other numbers used in the description of the embodiments are all provided as examples to specifically explain the technology of the present invention, and the present invention is not limited to the exemplified numbers. Furthermore, the connection relationships between the components are provided as examples to specifically explain the technology of the present invention, and do not limit the connection relationships that realize the functions of the present invention.

[0133] Each function of the embodiment can be realized by one or more processing circuits. Here, the term "processing circuit" in this specification includes a processor programmed to execute each function by software, such as a processor implemented by an electronic circuit, and a device such as an ASIC (Application Specific Integrated Circuit), a DSP (digital signal processor), an FPGA (field programmable gate array), or a conventional circuit module designed to execute each function described above. [Explanation of symbols]

[0134] 1. Image forming system (an example of a liquid ejection system) 10 Width direction 20 Conveying direction 30 Control section 40 Control section 101 Client PC 102 DFE (an example of a processing device, an example of a first processing device) 103 Image forming apparatus (an example of a liquid ejection apparatus) 104 Management Server 105 Image processing device (an example of a second processing device) 211 RIP processing unit 212 Quantization processing unit 213 Transmission unit (an example of a transmission means) 220 Liquid discharge part 230 Inline Sensor 311 Specific unit (an example of specific means) 312 Reading control unit 313 Storage Unit 314 Receiving section 315 Change section (an example of a change means) 316 Discharge control section 317, 501 Transmitter / Receiver [Prior art documents] [Patent documents]

[0135] [Patent Document 1] JP 2020-66177 A

Claims

1. A liquid ejection system including a liquid ejection device that ejects liquid based on image data and a processing device, The processing device includes: quantization means for quantizing the image data; a transmission unit that transmits the image data quantized by the quantization unit to the liquid ejection device, The liquid ejection device includes: a liquid ejection means including a plurality of nozzles and configured to eject the liquid from the plurality of nozzles; A means for identifying a nozzle having a discharge defect among the plurality of nozzles; a change unit that changes a size of a droplet formed by the liquid discharged from the liquid discharge unit based on the quantized image data and a result of the determination by the determination unit, In the image data, pixels corresponding to each of the plurality of nozzles are assigned in advance values ​​corresponding to the size of the droplets, The change means is a liquid ejection system that changes the size of the droplet when the sum of the allocation value assigned to the pixel corresponding to the faulty ejection nozzle and a predetermined distribution coefficient added to the allocation value assigned to the pixel corresponding to the nozzle adjacent to the faulty ejection nozzle is greater than the allocation value.

2. the liquid ejection means ejects the liquid onto a recording medium transported along a transport direction; The liquid ejection system according to claim 1 , wherein the plurality of nozzles are arranged side by side in a direction intersecting the transport direction.

3. A liquid ejection system including a liquid ejection device that ejects liquid based on image data, and a processing device, The processing device includes: quantization means for quantizing the image data; a transmission unit that transmits the image data quantized by the quantization unit to the liquid ejection device, The liquid ejection device includes: a liquid ejection means including a plurality of nozzles and configured to eject the liquid from the plurality of nozzles; and a determination unit for determining a nozzle having a discharge defect among the plurality of nozzles, the liquid ejection system includes a first processing device and a second processing device different from the first processing device; the first processing device comprises the quantization means, the second processing device includes a changer that changes a size of a droplet formed by the liquid discharged from the liquid discharger based on the quantized image data and a result of the identification by the identification device; In the image data, pixels corresponding to each of the plurality of nozzles are assigned in advance values ​​corresponding to the size of the droplets, The change means is a liquid ejection system that changes the size of the droplet when the sum of the allocation value assigned to the pixel corresponding to the faulty ejection nozzle and a predetermined distribution coefficient added to the allocation value assigned to the pixel corresponding to the nozzle adjacent to the faulty ejection nozzle is greater than the allocation value.

4. the liquid ejection device forms an image on a recording medium by ejecting the liquid; 4. The liquid ejection system according to claim 1, wherein the identifying unit identifies the ejection-defective nozzle while the liquid ejection device is forming an image on the recording medium.

5. the liquid ejection means ejects the liquid onto a recording medium transported along a transport direction; The liquid ejection system according to claim 1 , wherein the change unit sequentially executes the process of changing the size of the liquid droplets for the pixels located downstream in the transport direction in the image data.

6. A liquid ejection method using a liquid ejection system including a liquid ejection device that ejects liquid based on image data and a processing device, the processing device comprising: quantizing the image data by a quantization means; A transmitting unit transmits the image data quantized by the quantization unit to the liquid ejection device; The liquid ejection device, A liquid ejection means includes a plurality of nozzles, and ejects the liquid from the plurality of nozzles; Identifying a nozzle having a discharge defect among the plurality of nozzles by an identifying means; a changer changes the size of droplets formed by the liquid discharged by the liquid discharger based on the quantized image data and the identification result by the identification means; In the image data, pixels corresponding to each of the plurality of nozzles are assigned in advance values ​​corresponding to the size of the droplets, The change means is a liquid ejection method that changes the size of the droplet when the sum of the allocation value assigned to the pixel corresponding to the faulty ejection nozzle and a predetermined distribution coefficient and the allocation value assigned to the pixel corresponding to the nozzle adjacent to the faulty ejection nozzle is greater than the allocation value.

7. The liquid ejection means ejects the liquid onto a recording medium transported along a transport direction, The liquid ejection method according to claim 6 , wherein the change unit sequentially executes the process of changing the size of the liquid droplets for the pixels located downstream in the transport direction in the image data.

Images