LIQUID EJECTION APPARATUS, LIQUID EJECTION METHOD, AND PROGRAM

Abstract

To improve an image quality further in executing superposition processing.SOLUTION: A liquid discharge device comprises: a liquid discharge head that discharges liquid from a plurality of nozzles onto a recording medium; a scanning part that scans at least either of the recording medium and the liquid discharge head; a first quantization processing part that creates dot data from image data; a second quantization processing part that imparts information on overlapping dots showing whether the dots are overlapped and recorded for each dot in the dot data on the basis of a pattern in the dot data; a select-punching processing part that creates scan data showing whether discharging of liquid is possible for each scanning by the nozzles in multi-pass recording processing in which the nozzles scans the same region on the recording medium plural times, using the information on overlapping dots imparted to each dot in the dot data and a select-punching mask; and a control part that controls the liquid discharge head and the scanning part on the basis of the scan data, so that the multi-pass recording processing is executed to the recording medium.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In inkjet liquid ejection devices (inkjet recording devices), a technology has been developed for creating data for each scan using multiple ejection masks for dot data after halftone processing in a multi-scan printing process (multi-scan recording process). In mask processing, masks are used as an overlap process in which ejected dots of the same color in an image formed by actual printing partially overlap, a gap process in which dots are not formed regardless of the presence or absence of dot data, or a combination process of overlap and gap processing. Such technology can suppress image defects such as banding and streaks caused by deviation in the landing position of dots, and can increase the amount of ink deposition beyond the number of dots in the data. Summary of the Invention [Problem to be solved by the invention]

[0003] However, mask processing in multi-scan printing is performed regardless of the print image data. For example, when using a printing mask that increases the number of overlapping dots to ensure high gradation density, the amount of ink applied increases in the image of the high gradation area, and the intended effect of improving density is achieved. However, in the image of the low gradation area, the dots overlap, so the dot size of the formed image becomes larger, the color of the dots becomes darker, and the graininess worsens.

[0004] The present invention has been made in view of the above, and has an object to provide a liquid ejection apparatus, a liquid ejection method, and a program that can further improve image quality. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems and achieve the object, the present invention comprises a liquid ejection head which ejects liquid from a plurality of nozzles onto a recording medium, a scanning unit which scans at least one of the recording medium and the liquid ejection head, a first quantization processing unit which creates dot data from image data, a second quantization processing unit which assigns overlapping dot information to each dot of the dot data based on a pattern of the dot data, indicating whether the dot is to be overlapped and recorded, a printing discrimination processing unit which uses the overlapping dot information assigned to each dot of the dot data and a printing discrimination mask to generate scan data which indicates whether or not liquid is to be ejected for each scan by the nozzle in a multi-pass recording process in which the nozzle scans the same area on the recording medium a plurality of times, and a control unit which controls the liquid ejection head and the scanning unit based on the scan data to perform the multi-pass recording process on the recording medium. The second quantization processing unit calculates the amount of liquid adhesion of the dot data, and assigns the overlapping dot information to each dot of the dot data so that the number of dots to be overlapped is reduced for small droplet dots having a small calculated adhesion amount, and assigns the overlapping dot information to each dot of the dot data so that the number of dots to be overlapped is increased for medium droplet and large droplet dots having a large calculated adhesion amount. Effect of the Invention

[0006] The present invention provides an advantage that image quality can be further improved. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of a schematic configuration of an inkjet recording apparatus according to the present embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of a hardware configuration of the inkjet recording apparatus according to the present embodiment. [Diagram 3] FIG. 3 is a diagram showing an example of the functional block configuration of the inkjet recording apparatus according to the present embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a multi-pass printing process in a serial type inkjet recording apparatus. [Diagram 5] FIG. 5 is a diagram showing an example of a flowchart of data processing during multi-pass printing processing. [Figure 6] FIG. 6 is a diagram for explaining the basic stroke-selection process. [Figure 7] FIG. 7 is a diagram showing an example of 2-pass 1 / 4 interlace. [Figure 8] FIG. 8 is a diagram for explaining the shot separation process when the overlap gap process is performed. [Figure 9] FIG. 9 is a diagram for explaining the effect of the overlapping process and the gap treatment on density unevenness. [Figure 10] FIG. 10 is a graph showing the overlap ratio versus gradation. [Figure 11] FIG. 11 is a diagram showing an example of a dot arrangement when overlapping processing is performed or not in a low gradation portion and when a landing deviation occurs. [Figure 12] FIG. 12 is a diagram for explaining an example of a process for providing overlapping dot information in the inkjet recording apparatus according to the present embodiment. [Figure 13] FIG. 13 is a diagram for explaining an example of a process for providing overlapping dot information in the inkjet recording apparatus according to the present embodiment. [Figure 14] FIG. 14 is a diagram for explaining an example of a process for providing overlapping dot information in the inkjet recording apparatus according to the present embodiment. [Figure 15] FIG. 15 is an example of a graph showing the overlap ratio versus gradation in overlap gap processing in the inkjet recording apparatus according to this embodiment. [Figure 16] FIG. 16 is a diagram for explaining an example of the printing process in the inkjet printing apparatus according to the present embodiment. [Figure 17] FIG. 17 is a diagram for explaining an example of printing process by 2-pass 1 / 4 interlace in the inkjet printing apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a liquid ejection device, a liquid ejection method, and a program will be described in detail with reference to the accompanying drawings.

[0009] An inkjet recording device, which is an example of a liquid ejection device according to the present embodiment, has a head unit (liquid ejection head) that ejects dye inks of four colors, black (K), cyan (C), magenta (M), and yellow (Y). It is also possible to eject water-based pigment inks, UV-curable inks, and the like, instead of dye inks. These head units are reciprocated in a direction (main scanning direction) perpendicular to the conveying direction (sub-scanning direction) of the recording medium to form an image. That is, the inkjet recording device according to the present embodiment forms an image using pigment inks and dye inks, at least one of which contains a specific color (black (K)). The specific color is a color that belongs to black (black (K)) that contains gray. The specific color is not limited to black (K) and is arbitrary.

[0010] 1 is a diagram showing an example of a schematic configuration of an inkjet recording apparatus according to the present embodiment. The schematic configuration of an inkjet recording apparatus 10 according to the present embodiment will be described with reference to FIG.

[0011] 1, an inkjet recording device 10, which is an example of a liquid ejection device, is a serial type inkjet printer capable of performing multi-pass printing, which performs printing by scanning a head unit 12 multiple times in a main scanning direction. The inkjet recording device 10 includes a carriage 11 that moves back and forth (bidirectional scanning) in both a forward direction 21 and a backward direction 22 (main scanning direction), and a transport stage 13 as a scanning unit that transports a recording medium 14. Note that the scanning unit may be one that scans the recording medium 14 in the main scanning direction and the sub-scanning direction without moving the head unit 12, or one that scans the head unit 12 in the main scanning direction and the sub-scanning direction without moving the recording medium 14.

[0012] The carriage 11 is equipped with a head unit 12 having a plurality of ejection heads that eject ink (one example of liquid). The carriage 11 also forms an image by scanning in a direction (main scanning direction) perpendicular to the transport direction (sub-scanning direction) of the recording medium 14. Note that the recording medium 14 is not limited to paper.

[0013] The head unit 12 includes one or more ejection heads (an example of a liquid ejection head) that eject ink droplets onto the recording medium 14 to form an image. Note that it is also possible to eject ink droplets from multiple nozzle rows of one ejection head. The ejection head included in the head unit 12 can be one that has a pressure generating function such as a piezoelectric element that generates pressure to eject ink droplets.

[0014] The transport stage 13 is a platform that is disposed below the movement area of ​​the carriage 11 and transports the placed recording medium 14 in the sub-scanning direction. The recording medium 14 placed on the transport stage 13 is transported in the sub-scanning direction by the transport stage 13, and an image is formed by the head unit 12. That is, the inkjet recording device 10 can form a desired image on the recording medium 14 by moving the carriage 11 and discharging ink droplets from the head unit 12 onto the recording medium 14.

[0015] 2 is a diagram showing an example of a hardware configuration of an inkjet recording apparatus according to the present embodiment. The hardware configuration of the inkjet recording apparatus 10 according to the present embodiment will be described with reference to FIG.

[0016] As shown in FIG. 2, the inkjet recording apparatus 10 includes a main control board 120, a carriage 11, a main scanning motor 16, and a sub-scanning motor 17.

[0017] The main control board 120 is a board that controls the operations of various devices within the inkjet recording apparatus 10. The main control board 120 includes a CPU (Central Processing Unit) 121, a ROM (Read Only Memory) 122, a RAM (Random Access Memory) 123, a recording head driving circuit 124, a main scanning driving circuit 125, a sub-scanning driving circuit 126, a communication I / F 127, and a control FPGA (Field Programmable Gate Array) 130.

[0018] The carriage 11 is a moving body that moves in the main scanning direction over the recording medium 14 and forms an image on the recording medium 14 by ejecting ink droplets from the head unit 12. The carriage 11 includes the head unit 12, an encoder sensor 15, and a print sensor 18.

[0019] The CPU 121 is a calculation device that controls the entire inkjet recording apparatus 10. For example, the CPU 121 uses the RAM 123 as a working area, executes various control programs stored in the ROM 122, and outputs control commands for controlling various operations in the inkjet recording apparatus 10.

[0020] The recording head drive circuit 124 is a drive circuit that drives the head unit 12 to perform a discharge operation. The main scanning drive circuit 125 is a drive circuit that moves the carriage 11 in the main scanning direction by rotating the main scanning motor 16. The sub-scanning drive circuit 126 is a drive circuit that transports the recording medium 14 on the transport stage 13 in the sub-scanning direction.

[0021] The communication I / F 127 is an interface for connecting the inkjet recording apparatus 10 to an external device 30 such as a PC (Personal Computer) for data communication. For example, the communication I / F 127 receives print data such as image data for forming (printing) an image by the inkjet recording apparatus 10 from the external device 30. Note that in FIG. 2, the communication I / F 127 of the inkjet recording apparatus 10 is directly connected to the external device 30, but is not limited thereto. For example, the communication I / F 127 may be connected to the external device 30 via a network, or data communication with the external device 30 may be performed by wireless communication.

[0022] The control FPGA 130 is an integrated circuit that cooperates with the CPU 121 to control various operations in the inkjet recording apparatus 10. The control FPGA 130 has, as functional components, for example, a CPU control unit 131, a memory control unit 132, and a sensor control unit 133.

[0023] The CPU control unit 131 communicates with the CPU 121 , transmits various pieces of information acquired by the control FPGA 130 to the CPU 121 , and also inputs control commands output from the CPU 121 .

[0024] The memory control unit 132 performs memory control for the CPU 121 to access the ROM 122 and the RAM 123 .

[0025] The sensor control unit 133 performs processing for inputting the encoder value output from the encoder sensor 15 and the image data read by the print sensor 18 .

[0026] The head unit 12 is driven by a recording head driving circuit 124 whose operation is controlled by a CPU 121 and a control FPGA 130, and is a unit that ejects ink droplets onto a recording medium 14 on a transport stage 13 to form an image.

[0027] The encoder sensor 15 is a sensor that detects marks on an encoder sheet (not shown) and outputs an encoder value obtained by the detection to the control FPGA 130. This encoder value is sent from the control FPGA 130 to the CPU 121 and is used, for example, to calculate the position and speed of the carriage 11. The CPU 121 generates and outputs a control command for controlling the main scanning motor 16 based on the position and speed of the carriage 11 calculated from this encoder value.

[0028] The print sensor 18 is, for example, a sensor that reads an image printed by the head unit 12 in order to detect the ejection state of each nozzle in the nozzle row.

[0029] It should be noted that the hardware configuration of the inkjet recording apparatus 10 shown in FIG. 2 is merely an example, and the inkjet recording apparatus 10 may include components other than those shown in FIG.

[0030] FIG. 3 is a diagram showing an example of the functional block configuration of the inkjet recording apparatus according to the present embodiment.

[0031] As shown in FIG. 3, the inkjet recording apparatus 10 includes an image acquisition unit 140, an image processing unit 141, a rendering processing unit 142, an image formation end determination unit 143, a motor control unit 144, an image forming unit 145, and a memory unit 146.

[0032] The image acquisition unit 140 is a functional unit that acquires image data received from the outside (e.g., external device 30, etc.) via the communication I / F 127. The image data acquired by the image acquisition unit 140 is composed of color information of three colors, RGB, for example. The image acquisition unit 140 is realized by the control FPGA 130 shown in FIG. 2, or by the CPU 121 executing a program.

[0033] The image processing unit 141 is a functional unit that converts the image data (RGB data) acquired by the image acquisition unit 140 into CMYK data that the inkjet recording device 10 handles. The image processing unit 141 also performs gamma correction to reflect the characteristics of the inkjet recording device 10 and the user's preferences. The image processing unit 141 also performs halftone processing. Here, halftone processing is processing that quantizes CMYK gradation data (generally 8 bits for each color) into data that the inkjet recording device 10 can handle (generally 1 to 3 bits). The image data after halftone processing becomes dot data. The image processing unit 141 is realized by the control FPGA 130 shown in FIG. 2, or by the CPU 121 executing a program.

[0034] The rendering processing unit 142 is a functional unit that performs rendering processing. Here, the rendering processing is processing that determines how to move the head unit 12 and the recording medium 14 and from which nozzle to eject ink droplets for dot data for which halftone processing and non-ejection complement processing have been completed. The rendering processing unit 142 is realized by the control FPGA 130 shown in FIG. 2, or by the CPU 121 executing a program.

[0035] The image formation end determination unit 143 is a functional unit that determines the end of the printing operation controlled by the image forming unit 145. The image formation end determination unit 143 is realized by the control FPGA 130 shown in FIG. 2, or by the CPU 121 executing a program.

[0036] The motor control unit 144 is a functional unit that controls the operation of the main scanning drive circuit 125 under the control of the image forming unit 145, thereby controlling the main scanning motor 16 driven by the main scanning drive circuit 125, and controls the movement of the carriage 11 in the main scanning direction. Also, under the control of the image forming unit 145, the motor control unit 144 controls the operation of the sub-scanning drive circuit 126, thereby controlling the sub-scanning motor 17 driven by the sub-scanning drive circuit 126, and controls the transport of the recording medium 14 on the transport stage 13 in the sub-scanning direction. The motor control unit 144 is realized by the control FPGA 130 shown in FIG. 2, or is realized by executing a program by the CPU 121.

[0037] The image forming unit 145 is a functional unit that sends the dot data rendered by the rendering processing unit 142 to the printer engine and controls the operation of the recording head driving circuit 124 to control the timing of ink droplet ejection from the head unit 12 driven by the recording head driving circuit 124, the amount of ink droplet ejection, etc. The image forming unit 145 is realized by the control FPGA 130 shown in FIG. 2, or by the CPU 121 executing a program.

[0038] The storage unit 146 is a functional unit that stores a plurality of mask patterns required for the print dot distribution process by the image processing unit 141. The plurality of mask patterns will be described later. The storage unit 146 is realized by a storage device such as the ROM 122 or the RAM 123 shown in FIG.

[0039] The image processing unit 141 includes a color-specific data generating unit 151 , a first quantization processing unit 152 , and a second quantization processing unit 153 .

[0040] The color-specific data generation processing unit 151 generates color-specific data for each CMYK by converting the image data (RGB data) acquired by the image acquisition unit 140 into CMYK data handled by the inkjet recording device 10. The first quantization processing unit 152 generates dot data that can be handled by the inkjet recording device 10 based on the CMYK gradation data. In other words, the first quantization processing unit 152 functions as an example of a first quantization processing unit that creates dot data from image data. The second quantization processing unit 153 functions as an example of a second quantization processing unit that, based on the pattern of the dot data generated by the first quantization processing unit 152, gives, for each dot of the dot data, overlapping dot information indicating whether or not the dot is to be overlapped (an example of overlapping recording).

[0041] The rendering processing unit 142 also has a discrimination processing unit 154. The discrimination processing unit 154 generates print data (an example of scan data) using overlapping dot information given to each dot of the dot data and a mask pattern (an example of a discrimination mask) for the discrimination processing. Here, the print data is an example of scan data indicating whether or not ink is discharged for each scan by the nozzle in the multi-pass print processing. The multi-pass print processing is an example of a multi-pass recording processing in which the nozzle scans the same area on the recording medium 14 multiple times. The CPU 121 is an example of a control unit that controls the carriage 11 (the transport stage 13 and the head unit 12) based on the print data generated by the discrimination processing unit 154 to execute the multi-pass print processing on the recording medium 14. The head unit 12 can discriminate one or more types of droplets with different volumes, such as large droplets, medium droplets, small droplets, and no discharge, by applying a drive waveform based on the scan data.

[0042] FIG. 4 is a diagram showing an example of a multi-pass print process in a serial type inkjet recording device, and FIG. 5 is a diagram showing an example of a flowchart of data processing during the multi-pass print process.

[0043] 4, an example of multi-pass printing processing in the serial type inkjet recording device 10 will be described here. Multi-scan printing processing is a printing method in which dots are arranged in a divided manner over multiple scans in the serial type inkjet recording device 10, and the relative positions of the media and the nozzles are shifted for each scan to form an image with a target resolution.

[0044] FIG. 4 is an example of 2-pass 1 / 4 interlace. In the case of 2-pass 1 / 4 interlace operation, one scan line is formed by two scans, and the dot data of the formed scan line is printed by printing separately in two scans. For example, the dots in the part surrounded by the thick line in FIG. 4 are located at the same scan line position by the nozzle 42 of the head 41 in the first scan and the fifth scan. Therefore, the dots to be printed in each of the first scan and the fifth scan are separated, and the scan line can be completed by printing the dots separately in each scan.

[0045] 3 and 5, when data is input in step S11, in step S12, the color-specific data generation processing unit 151 converts the image data acquired by the image acquisition unit 140 into CMYK data handled by the inkjet recording device 10, and generates color-specific data for each CMYK. In step S13, the first quantization processing unit 152 generates dot data for each generated color-specific data. Next, in step S14, the second quantization processing unit 153 adds overlapping dot information to each dot of the dot data based on the pattern of the dot data.

[0046] Next, in step S15, the printing process unit 154 executes a printing process to generate print data using the overlapping dot information assigned to each dot of the dot data and a printing mask. In step S15, the head unit 12 scans and prints (outputs) the print data generated in the printing process.

[0047] FIG. 6 is a diagram for explaining a basic printing process, and FIG. 7 is a diagram showing an example of 2-pass 1 / 4 interlace.

[0048] The basic ejection process is explained below, where the four values ​​of the dot data are for large droplets, medium droplets, small droplets, and no ejection. The ejection process obtains data corresponding to the nozzle position during each scan from the created dot data, and then performs the ejection process on the obtained data.

[0049] As shown in Figure 6, the printing process in Figure 6 is an example of 2-pass 1 / 4 interlace, where the nozzle positions overlap in the first and fifth scans. Therefore, printing process is performed in the first and fifth scans. Here, "0" represents no ink ejection, "1" represents small ink droplets, "2" represents medium ink droplets, and "3" represents large ink droplets.

[0050] As shown in FIG. 7, the printing process in FIG. 7 uses a printing process mask pattern to perform printing in the first half scan (first scan) and the second half scan (fifth scan). The mask patterns for conventional printing process are "0" for no ink ejection and "1" for ink ejection. Conventionally, these two mask patterns "0" and "1" are used to distribute dot data to each scan. In this case, the relationship between the mask pattern for the first scan and the mask pattern for the fifth scan is complementary. In other words, by performing two print scans, an arrangement of dots that is the same as the dot data is formed.

[0051] Table 1 below shows an example of printing process using a binary mask pattern. In this case, for example, it is a mask process that calculates the logical product (AND) of the mask value at the corresponding position with the dot data. The mask pattern is binary, and the pixels that do not eject "00" and the pixels that eject "11" are set for the dot data of no ejection "00", small droplet "01", medium droplet "10", and large droplet "11". The size of the ink droplet to be output is determined by calculating the logical product (AND) of the dot data and the mask pattern. That is, when the mask pattern is "00", the droplet size to be output is no ejection. On the other hand, when the mask pattern is "11", the dot data of the pixels to be ejected, small droplet "01", medium droplet "10", and large droplet "11", are output as is.

[0052] [Table 1]

[0053] FIG. 8 is a diagram for explaining the printing process when the overlapping process is performed.

[0054] As shown in FIG. 8, the printing process in FIG. 8 is an explanation of the printing process when overlapping processing is performed. In order to suppress uneven density caused by deviation in the landing position of ink droplets, there is a printing process called overlapping processing in which some dots are overlapped. In this case, FIG. 8 is an example of the printing process using this overlapping processing. Here, the overlapping processing uses a mask pattern for the printing process to perform printing in the first half scan (first scan) and the second half scan (fifth scan). The mask pattern for the printing process is "0" for no ink ejection and "1" for ink ejection.

[0055] In the separate printing process using overlapping processing in Figure 8, the mask pattern for separate printing process does not have a complementary relationship between the ejected "1" and non-ejected "0" between the first and fifth scans, and some pixel values ​​in the mask pattern overlap. In pixels where the values ​​of the mask pattern for separate printing process overlap, overlapping dots (thick "1") are formed. Alternatively, pixels where no dots are ejected (thick "0") occur. By performing overlapping processing, density unevenness is less likely to occur even if the landing position of the ink droplets is shifted. In other words, the multi-pass printed image that has undergone overlapping processing has parts where pixels are "4", "6", and "8" with the same droplet type overlapping.

[0056] FIG. 9 is a diagram for explaining the effect of the overlapping process on density unevenness.

[0057] As shown in Figure 9, in the separate printing process that includes overlap processing, separate printing was performed in the first half scan and the second half scan, and in the first half scan, there was no deviation in the landing of the ink droplets, but in the second half scan, there was deviation in the landing of the ink droplets. Figure 9 shows the dot arrangement with and without overlap processing at this time.

[0058] Fig. 9(1) is an example when overlapping processing is not performed, in which misalignment of the ink droplet landing positions causes dots in the first half scan to overlap with some dots in the second half scan, resulting in unintended blank spaces and leading to uneven density. On the other hand, Fig. 9(2) is an example when overlapping processing is performed, in which misalignment of the ink droplet landing positions causes blank spaces to occur due to the landing misalignment, but one side of the overlapping dots fills in the blank spaces caused by the landing position misalignment, so the difference in ink coverage area is smaller than when overlapping processing is not performed, which has the effect of suppressing uneven density.

[0059] FIG. 10 is a graph showing the overlap rate versus gradation, and FIG. 11 is a diagram showing an example of dot arrangement when overlap processing is performed in a low gradation portion and when landing deviation occurs.

[0060] As shown in FIG. 10, this graph shows the ratio of each droplet used in the gradation of image data and the overlapping rate of dots. Here, the solid line indicates the large droplet ratio, the dotted line indicates the medium droplet ratio, the thin line indicates the small droplet ratio, and the dashed line indicates the overlapping dot ratio. Conventional overlapping processes were performed by overlapping the values ​​of some pixels of a mask pattern in a separate printing process. Therefore, regardless of the type of droplet or the gradation, the overlapping rate of dots was constant for the gradation. In an inkjet recording device 10 equipped with droplet types of multiple sizes, small droplets are usually mainly used in low gradation areas. Also, the number of dots used is small, resulting in low data coverage.

[0061] As shown in Figure 11, in the separate printing process that includes overlap processing, separate printing was performed in the first half scan and the second half scan, and in the first half scan, there was no deviation in the landing of the ink droplets, but in the second half scan, there was deviation in the landing of the ink droplets. Figure 11 shows the dot arrangement with and without overlap processing in the low gradation area at this time.

[0062] Figure 11(1) is an example of a case where overlapping processing is not performed, and in the low gradation areas, the original dot coverage is low and small sized ink droplets are used, so when the landing position is shifted, overlapping of dots is unlikely to occur and density unevenness is unlikely to occur. On the other hand, Figure 11(2) is an example of a case where overlapping processing is performed, and in the low gradation areas, the position of overlapping dots is shifted, and the ink coverage area on one pixel becomes large, which may worsen the graininess.

[0063] 12 to 14 are diagrams for explaining an example of a process for providing overlapping dot information in the inkjet recording device according to the present embodiment. Next, an example of a process for providing overlapping dot information in the inkjet recording device 10 according to the present embodiment will be explained with reference to FIGS.

[0064] As shown in Fig. 12(1), first quantization processor 152 generates four-value dot data for large droplets, medium droplets, small droplets, and no ejection based on the color-specific data for each of CMYK. Next, second quantization processor 153 divides the dot data into a plurality of regions (e.g., regions 1 to 8) as shown in Fig. 12(2). Then, second quantization processor 153 calculates the amount of ink adhesion (hereinafter referred to as ink adhesion amount) M for each of the plurality of regions of the dot data.

[0065] 13, second quantization processor 153 adds overlapping dot information to each dot in each region based on the amount of ink adhesion M of each region of the dot data. In this embodiment, second quantization processor 153 adds overlapping dot information so that the number of overlapping dots decreases as the amount of ink adhesion M decreases.

[0066] For example, as shown in FIG. 13, the second quantization processing unit 153 selects a mask for imparting overlapping dot information to be used for imparting overlapping dot information to the dots in each region from among masks for imparting overlapping dot information 1 to 3 based on the amount of ink adhesion M in each region. Here, masks for imparting overlapping dot information 1 to 3 are masks that indicate whether or not each dot in the region is to be printed overlappingly. Mask for imparting overlapping dot information 1 is a mask that will produce the greatest number of dots that will be printed overlappingly. Mask for imparting overlapping dot information 2 is a mask that will produce the second greatest number of dots that will be printed overlappingly after mask for imparting overlapping dot information 1. Mask for imparting overlapping dot information 3 is a mask that will produce the least number of dots that will be printed overlappingly.

[0067] In this embodiment, as shown in Fig. 13, second quantization processing unit 153 selects overlapping dot information imparting mask 1 for areas where the ink adhesion amount M is 25 or more. Also, as shown in Fig. 13, second quantization processing unit 153 selects overlapping dot information imparting mask 2 for areas where the ink adhesion amount M is 15 or more and less than 25. Also, as shown in Fig. 13, second quantization processing unit 153 selects overlapping dot information imparting mask 3 for areas where the ink adhesion amount M is more than 10 and less than 15.

[0068] Then, second quantization processing unit 153 assigns overlapping dot information to the dots in each region using the overlapping dot information assignment mask selected for that region, as shown in Fig. 14. That is, second quantization processing unit 153 assigns overlapping dot information to the dots in each region so that the number of overlapping dots decreases as the ink adhesion amount M decreases.

[0069] Fig. 15 is an example of a graph showing the overlap ratio for gradation in overlap processing in the inkjet recording device according to this embodiment. Next, with reference to Fig. 15, an example of the overlap ratio for gradation in overlap gap processing according to print data generated using overlap dot information given to each dot of dot data by the second quantization processing unit 153 in the inkjet recording device 10 according to this embodiment will be described.

[0070] According to the inkjet recording device 10 of the present embodiment, as shown in FIG. 15, it is possible to reduce the number of overlapping dots (overlapped dot rate) for dots with low gradation (for example, dots of small droplets with a small amount of ink adhesion M) among the dot data. Also, according to the inkjet recording device 10 of the present embodiment, as shown in FIG. 15, it is possible to increase the number of overlapping dots (overlapped dot rate) for dots with high gradation (for example, dots of medium and large droplets with a large amount of ink adhesion M) among the dot data. That is, according to the inkjet recording device 10 of the present embodiment, when the overlapping process is performed, it is possible to suppress the position of the overlapping dots in the low gradation part from being shifted, causing the graininess to deteriorate. On the other hand, it is possible to perform the overlapping process that can suppress the density unevenness in the medium gradation part and the high gradation part. As a result, it is possible to further improve the image quality when the overlapping process is performed.

[0071] Fig. 16 is a diagram for explaining an example of the ejection process in the inkjet recording apparatus according to this embodiment. Fig. 17 is a diagram for explaining an example of the ejection process by 2-pass 1 / 4 interlace in the inkjet recording apparatus according to this embodiment. Here, the seven values ​​of dot data are when the droplets are large, medium, small, no ejection, small and small (overlapping dots of small droplets), medium and medium (overlapping dots of medium droplets), and large and large (overlapping dots of large droplets). The ejection process unit 154 obtains data corresponding to the nozzle position at each scan from the created dot data, and performs the ejection process on the obtained data.

[0072] As shown in Fig. 16, the ejection process in Fig. 16 is an example of 2-pass 1 / 4 interlace, where the nozzle positions overlap in the first and fifth scans. Therefore, the ejection process is performed in the first and fifth scans. Here, "0" represents no ink ejection, "1" represents small ink droplets, "2" represents medium ink droplets, "3" represents large ink droplets, "4" represents small and small ink droplets, "5" represents medium and medium ink droplets, and "6" represents large and large ink droplets.

[0073] As shown in FIG. 17, the print processing unit 154 uses a mask pattern for the print processing to perform print processing in the first half scan (first scan) and the second half scan (fifth scan). The mask pattern for the print processing is "0" for no ink ejection and "1" for ink ejection. In this embodiment, since the dot data before the print processing has seven values, the print processing unit 154 executes print processing of the dot data based on the following Table 2. Specifically, when the dot data is "3" or less, the print processing unit 154 uses a print mask to convert the dot data into print data. On the other hand, when the dot data is "4" or more, the print processing unit 154 converts "4" (011) into print data of "01", converts "5" (100) into print data of "10", and converts "6" (110) into print data of "11", regardless of the print mask.

[0074] [Table 2]

[0075] According to the inkjet recording device 10 of the present embodiment, when performing the overlapping process, it is possible to suppress the position of overlapping dots in low gradation areas from shifting, which causes the graininess to deteriorate. As a result, it is possible to further improve the image quality when performing the overlapping process.

[0076] In the above-described embodiment, an example has been described in which the liquid ejection device of the present invention is applied to an inkjet recording device 10, but the liquid ejection device can also be applied to any of multifunction peripherals, printers, scanner devices, facsimile devices, etc.

[0077] In the above-described embodiment, the recording medium 14 is a medium such as paper, recording paper, film, cloth, electronic board, electronic components such as piezoelectric elements, powder layers, organ models, test cells, etc., and includes anything to which liquid can adhere unless otherwise specified. The material of the recording medium 14 may be any material to which liquid can adhere even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc.

[0078] Furthermore, the liquid may be any liquid having a viscosity and surface tension that allows it to be ejected from a liquid ejection head, and may be, for example, an inkjet ink, a surface treatment liquid, a liquid for forming components of electronic elements or light-emitting elements or electronic circuit resist patterns, a material liquid for three-dimensional modeling, etc.

[0079] The program executed by the inkjet recording apparatus 10 of this embodiment is provided by being pre-installed in the ROM 122 or the like. The program executed by the inkjet recording apparatus 10 of this embodiment may be provided by being recorded in a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), a CD-R, or a digital versatile disk (DVD) in the form of an installable or executable file.

[0080] Furthermore, the program executed by the inkjet recording apparatus 10 of the present embodiment may be configured to be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Also, the program executed by the inkjet recording apparatus 10 of the present embodiment may be configured to be provided or distributed via a network such as the Internet.

[0081] The program executed by the inkjet recording device 10 of this embodiment has a modular configuration including the above-mentioned sections (image acquisition section 140, image processing section 141, rendering processing section 142, image formation end judgment section 143, motor control section 144, image forming section 145), and in terms of actual hardware, the CPU 121 (an example of a processor) reads out the program from the ROM 122 and executes it, thereby loading the above-mentioned sections onto the main memory device, and the image acquisition section 140, image processing section 141, rendering processing section 142, image formation end judgment section 143, motor control section 144, image forming section 145) are generated on the main memory device. [Explanation of symbols]

[0082] 10 Inkjet recording device 11 Carriage 12 Head Unit 120 Main control board 121 CPU 122 ROM 123 RAM 140 Image acquisition unit 141 Image processing section 142 Rendering Processor 143 Image formation completion determination unit 144 Motor control unit 145 Image forming section 146 Memory section [Prior art documents] [Patent documents]

[0083] [Patent Document 1] Patent No. 5328505

Claims

1. a liquid ejection head that ejects liquid from a plurality of nozzles onto a recording medium; a scanning unit that scans at least one of the recording medium and the liquid ejection head; A first quantization processing unit that creates dot data from image data; a second quantization processing unit that assigns overlapping dot information indicating whether or not the dot is to be overlappedly recorded for each dot of the dot data based on a pattern of the dot data; a print discrimination processing unit that generates scan data indicating whether or not liquid is to be ejected for each scan by the nozzle in a multi-pass printing process in which the nozzle scans the same area on the recording medium a plurality of times, using the overlapping dot information assigned to each dot of the dot data and a print discrimination mask; a control unit that controls the liquid ejection head and the scanning unit based on the scan data to execute the multi-pass printing process on the printing medium; Equipped with The second quantization processing unit calculates the amount of liquid adhesion of the dot data, and assigns the overlapping dot information to each dot of the dot data so that the number of dots that are overlapped is reduced for small droplet dots that have a small calculated adhesion amount, and assigns the overlapping dot information to each dot of the dot data so that the number of dots that are overlapped is increased for medium and large droplet dots that have a large calculated adhesion amount.

2. A liquid ejection method performed by a liquid ejection device, comprising: a first quantization process step of generating dot data from image data; a second quantization process step of providing overlapping dot information indicating whether or not the dot is to be overlapped for each dot of the dot data based on a pattern of the dot data; a printing process step of generating scan data indicating whether or not liquid is to be ejected for each scan by a nozzle of a liquid ejection head in a multi-pass recording process in which the nozzle scans the same area on a recording medium a plurality of times, using the overlapping dot information assigned to each dot of the dot data and a printing process mask; a control step of controlling a scanning unit that scans at least one of the recording medium and the liquid ejection head based on the scan data, and the liquid ejection head, to execute the multi-pass recording process on the recording medium; Including, The second quantization processing step calculates the amount of liquid adhesion of the dot data, and adds the overlapping dot information to each dot of the dot data so that the number of dots that are overlapped is reduced for small droplet dots having a small calculated adhesion amount, and adds the overlapping dot information to each dot of the dot data so that the number of dots that are overlapped is increased for medium and large droplet dots having a large calculated adhesion amount.

3. Computer, A first quantization processing unit that creates dot data from image data; a second quantization processing unit that assigns overlapping dot information indicating whether or not the dot is to be overlappedly recorded for each dot of the dot data based on a pattern of the dot data; a printing process unit that uses the overlapping dot information provided to each dot of the dot data and a printing process mask to generate scan data that indicates whether or not liquid is to be ejected for each scan by a nozzle of a liquid ejection head in a multi-pass recording process in which the nozzle scans the same area on a recording medium a plurality of times; and a scanning unit that scans at least one of the recording medium and the liquid ejection head based on the scan data, and a control unit that controls the liquid ejection head to execute the multi-pass recording process on the recording medium; Function as a The second quantization processing unit is a program that calculates the amount of liquid adhesion of the dot data, and assigns the overlapping dot information to each dot of the dot data so that the number of dots to be overlapped is reduced for small droplet dots having the calculated amount of adhesion small, and assigns the overlapping dot information to each dot of the dot data so that the number of dots to be overlapped is increased for medium droplet and large droplet dots having the calculated amount of adhesion large.

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